特应性皮炎和紧密连接

Skin barrier dysfunction, a defining feature of atopic dermatitis (AD), arises from multiple interacting systems. In AD, skin inflammation is caused by host-environment interactions involving keratinocytes as well as tissue-resident immune cells such as type 2 innate lymphoid cells, basophils, mast cells, and T helper type 2 cells, which produce type 2 cytokines, including IL-4, IL-5, IL-13, and IL-31. Type 2 inflammation broadly impacts the expression of genes relevant for barrier function, such as intracellular structural proteins, extracellular lipids, and junctional proteins, and enhances

Human β-defensin-3 (hBD-3) exhibits antimicrobial and immunomodulatory activities; however, its contribution to autophagy regulation remains unclear, and the role of autophagy in the regulation of the epidermal barrier in atopic dermatitis (AD) is poorly understood. Here, keratinocyte autophagy was restrained in the skin lesions of patients with AD and murine models of AD. Interestingly, hBD-3 alleviated the IL-4- and IL-13-mediated impairment of the tight junction (TJ) barrier through keratinocyte autophagy activation, which involved aryl hydrocarbon receptor (AhR) signaling. While autophagy deficiency impaired the epidermal barrier and exacerbated inflammation, hBD-3 attenuated skin inflammation and enhanced the TJ barrier in AD. Importantly, hBD-3-mediated improvement of the TJ barrier was abolished in autophagy-deficient AD mice and in AhR-suppressed AD mice, suggesting a role for hBD-3-mediated autophagy in the regulation of the epidermal barrier and inflammation in AD. Thus, autophagy contributes to the pathogenesis of AD, and hBD-3 could be used for therapeutic purposes.

Tight junctions are involved in skin barrier functions. In this study, the expression of CLDN1, CLDN4, and OCLN was found to decrease in skin lesions of atopic dermatitis by bioinformatics analysis. Immunohistochemistry staining in skin specimens from 12 patients with atopic dermatitis and 12 healthy controls also showed decreased CLDN1, CLDN4, and OCLN expression in atopic dermatitis lesions. In vitro studies showed that IL-4 and IL-13 downregulated CLDN1, CLDN4, and OCLN expression in HaCaT cells as well as CLDN4 and OCLN expression in human primary keratinocytes. This effect, which was mediated through the Jak-signal transducer and activator of transcription 6 signaling pathway, increased paracellular flux of 4-kDa dextran. Benvitimod, a new drug for atopic dermatitis, upregulated CLDN4 and OCLN through the aryl hydrocarbon receptor/aryl hydrocarbon receptor nuclear translocator pathway. Benvitimod induced nuclear translocation of NRF2 and reduced production of ROS in keratinocytes, thus inhibiting IL-4-/IL-13-induced CLDN1 downregulation and signal transducer and activator of transcription 6 phosphorylation. These results indicate that T helper 2 cytokines are involved in tight junction impairment, and benvitimod can inhibit these effects.

Atopic dermatitis (AD) is a chronic inflammatory skin disorder characterised by itching, erythema, and epidermal barrier dysfunction. The pathogenesis of AD is complex and multifactorial; however,mast cell (MC) activation has been reported to be one of the crucial mechanisms in the pathogenesis of AD. The MC receptor Mas related G protein-coupled receptor-X2 (MRGPRX2) has been identified as a prominent alternative receptor to the IgE receptor in causing MC activation and the subsequent release of inflammatory mediators. The current study aimed to evaluate the therapeutic effect of a novel small molecule MRGPRX2 antagonist GE1111 in AD using in vitro and in vivo approaches. We developed an in vitro cell culture disease model by using LAD-2 MC, HaCaT keratinocytes and RAW 264.7 macrophage cell lines. We challenged keratinocytes and macrophage cells with CST-14 treated MC supernatant in the presence and absence of GE1111 and measured the expression of tight junction protein claudin 1, inflammatory cytokines and macrophage phagocytosis activity through immunohistochemistry, western blotting, RT-qPCR and fluorescence imaging techniques. In addition to this, we developed a DFNB-induced AD model in mice and evaluated the protective effect and underlying mechanism of GE1111. Our in vitro findings demonstrated a potential therapeutic effect of GE1111, which inhibits the expression of TSLP, IL-13, MCP-1, TNF-a, and IL-1ß in MC and keratinocytes. In addition to this, GE1111 was able to preserve the expression of claudin 1 in keratinocytes and the phagocytotic activity of macrophage cells. The in vivo results demonstrated that GE1111 treatment significantly reduced phenotypic changes associated with AD (skin thickening, scaling, erythema and epidermal thickness). Furthermore, immunohistochemical analysis demonstrated that GE1111 treatment preserved the expression of the tight junction protein Involucrin and reduced the expression of the inflammatory mediator periostin in the mouse model of AD. These findings were supported by gene and protein expression analysis, where GE1111 treatment reduced the expression of TSLP, IL-13, and IL-1ß, as well as downstream signalling pathways of MRGPRX2 in AD skin lesions. In conclusion, our findings provide compelling in vitro and in vivo evidence supporting the contribution of MRGPRX2-MC interaction with keratinocytes and macrophages in the pathogenesis of AD.

Our current understanding of atopic dermatitis (AD) and psoriasis pathophysiology is largely derived from skin biopsy studies that cause scarring and may be impractical in large-scale clinical trials. Although tape strips show promise as a minimally invasive technique in these common diseases, a comprehensive molecular profiling characterizing and differentiating the 2 diseases in tape strips is unavailable. Our aim was to construct a global transcriptome of tape strips from lesional and nonlesional skin of adults with moderate-to-severe AD and psoriasis. A total of 20 tape strips were obtained from lesional and nonlesional skin of patients with AD and psoriasis and skin from controls (n = 20 each); the strips were subjected to RNA sequencing (RNA-seq), with quantitative RT-PCR validation of immune and barrier biomarkers. We detected RNA-seq profiles in 96 of 100 of samples (96%), with 4123 and 5390 genes differentially expressed in AD and psoriasis lesions versus in controls, respectively (fold change ≥ 2; false discovery rate [FDR] < 0.05). Nonlesional tape-stripped skin from patients with AD was more similar to lesional skin than to nonlesional skin of patients with psoriasis, which showed larger differentiation from lesions. AD and psoriasis tissues shared increases in levels of dendritic cell and T-cell markers (CD3, ITGAX/CD11c, and CD83), but AD tissues showed preferential T RNA-seq tape strip profiling detected distinct immune and barrier signatures in lesional and nonlesional AD and psoriasis skin, suggesting their utility as a minimally invasive alternative to biopsies for detecting disease biomarkers.

Atopic march refers to the phenomenon wherein the occurrence of asthma and food allergy tends to increase after atopic dermatitis. The mechanism underlying the progression of allergic inflammation from the skin to gastrointestinal (GI) tract and airways has still remained elusive. Impaired skin barrier was proposed as a risk factor for allergic sensitization. Claudin-1 protein forms tight junctions and is highly expressed in the epithelium of the skin, airways, and GI tract, thus, the downregulation of claudin-1 expression level caused by CLDN-1 gene polymorphism can mediate common dysregulation of epithelial barrier function in these organs, potentially leading to allergic sensitization at various sites. Importantly, in patients with atopic dermatitis, asthma, and food allergy, claudin-1 expression level was significantly downregulated in the skin, bronchial and intestinal epithelium, respectively. Knockdown of claudin-1 expression level in mouse models of atopic dermatitis and allergic asthma exacerbated allergic inflammation, proving that downregulation of claudin-1 expression level contributes to the pathogenesis of allergic diseases. Therefore, we hypothesized that the tight junction dysfunction mediated by downregulation of claudin-1 expression level contributes to atopic march. Further validation with clinical data from patients with atopic march or mouse models of atopic march is needed. If this hypothesis can be fully confirmed, impaired claudin-1 expression level may be a risk factor and likely a diagnostic marker for atopic march. Claudin-1 may serve as a valuable target to slowdown or block the progression of atopic march.

Interleukin (IL)-13 is a key driver of inflammation and barrier dysfunction in atopic dermatitis (AD). While there is robust evidence that tralokinumab - a monoclonal antibody that neutralizes IL-13 - reduces inflammation and clinical disease activity, less is known about its effects on barrier function. To characterize the effects of tralokinumab treatment on skin barrier function. Transepidermal water loss (TEWL), stratum corneum hydration (SCH), natural moisturizing factor content, histopathological characteristics, biomarker expression and microbiome composition were evaluated in lesional, nonlesional and sodium lauryl sulfate-irritated skin of 16 patients with AD over the course of 16 weeks of tralokinumab treatment. All clinical severity scores decreased significantly over time. At week 16, mean TEWL in target lesions decreased by 33% (P = 0.01) and SCH increased by 58% (P = 0.004), along with a histological reduction in spongiosis (P = 0.003), keratin 16 expression and epidermal thickness (P = 0.001). In parallel, there was a significant decrease in several barrier dysfunction-associated and proinflammatory proteins such as fibronectin (P = 0.006), CCL17/TARC (P = 0.03) and IL-8 (P = 0.01), with significant changes seen as early as week 8. Total bacterial load and Staphylococcus aureus abundance were significantly reduced from week 2. Tralokinumab treatment improved skin physiology, epidermal pathology and dysbiosis, further highlighting the pleiotropic role of IL-13 in AD pathogenesis. Atopic dermatitis (AD) is a common chronic inflammatory skin disease characterized by a marked skin barrier impairment. The skin barrier deficiency is characterized by an imbalance of organisms naturally found on the skin, including a reduction in the diversity of organisms and an increased amount of bacteria called Staphylococcus aureus. Further, there are reduced structural proteins, problems with ‘tight junctions’ (which maintain skin integrity) and abnormalities in the make-up/organization of skin lipids. As a result, the skin cannot keep itself hydrated or moisturized, and there is an increased likelihood of ‘irritant contact dermatitis’ (for example, rashes, dry skin and itching). ‘Interleukin (IL)-13’ is a signalling protein found in the immune system that is increased in AD and causes inflammation. Tralokinumab is a drug that neutralizes IL-13 and reduces inflammation and the severity of AD; however, less is known about its effect on the skin barrier. This study aimed to investigate the effects of tralokinumab on skin barrier function by looking at levels of water loss, hydration, natural moisturizing factor content, histopathological characteristics (how it looks under a microscope), the expression of biomarkers (indicators of a particular condition) and composition of the microbiome (organisms living together) in the upper skin layer of 16 people with AD who were treated with tralokinumab for 16 weeks. We found that blocking IL-13 leads to a better skin barrier with less water loss and better hydration, as well as the normalization of skin bacteria. The skin was also less irritable, and its microscopic appearance was similar to normal skin after 16 weeks of treatment. Finally, the drug appeared to be effective and safe. Overall, our findings suggest that by neutralizing IL-13, tralokinumab could help to restore the skin barrier function of people with AD.

Atopic dermatitis (AD) is characterized by both IgE- and non-IgE-mediated immune responses, as well as skin barrier dysfunction. Ginsenoside Rg1, tetrandrine, and icariin each exhibit distinct properties that may contribute to the management of AD. Ginsenoside Rg1 has demonstrated efficacy in mitigating IgE-mediated allergic rhinitis, while tetrandrine is known to suppress abnormal T-cell activation. Icariin has been shown to improve intestinal barrier function, which is crucial in conditions like AD. However, the potential effectiveness of the combined formula of these compounds, referred to as GTI, in treating AD remains unexplored. This study aimed to investigate the anti-AD effects and mechanisms of GTI in a mouse model. A calcipotriol (MC903)-induced AD-like dermatitis mouse model was used to evaluate the anti-AD effects of GTI. Dermatitis scores and mouse ear thickness were recorded to assess disease severity. Ear tissues, ear-draining lymph nodes, spleens and sera were collected for use in the investigation of the effects and mechanisms of action of GTI. Topical application of GTI significantly alleviated AD-like dermatitis in mice, as evidenced by decreased dermatitis scores, reduced ear thickening, and diminished epidermal and dermal thickness, along with lower levels of the inflammatory cytokines IL-1β and IL-4 in ear tissues. Unlike the positive dexamethasone, GTI had no significant toxicity in the model mice. Topical GTI lowered serum IgE levels and diminished the accumulation of eosinophils and mast cells in ear tissues of model mice, suggesting that GTI mitigates IgE-mediated allergic reactions. GTI significantly decreased the numbers of CD4 This study, for the first time, demonstrated that the topical application of GTI alleviates symptoms of AD without overt toxicity in a calcipotriol-induced AD mouse model. The anti-AD effects of GTI are associated with the suppression of allergic reactions, reduction of hyperactive immune responses, improvement of skin barrier function, and inhibition of MAPK activation. These findings suggest that GTI has the potential to be developed into a safe and effective treatment for AD.

The strong association between epidermal barrier gene variants and Atopic Dermatitis (AD) highlights that impaired skin barrier is a key feature in the pathogenesis of AD. Although the filaggrin (FLG) gene is the major AD risk gene in European and Asian populations, disease-associated variants remain elusive in African populations. A previous study has reported that variants in the tight junction gene CLDN1 have been associated with AD susceptibility and disease severity in African-Americans. Our aim was therefore to investigate the association of CLDN1 with AD in the Ethiopian population. To investigate how CLDN1 variants may be involved in increasing the risk of AD in the Ethiopian population, we analysed whole exome sequencing (WES) data for all exons in CLDN1, and in addition, assayed four SNPs (rs17501010, rs9290927, rs9290929 and rs893051) which had previously showed association in African-American AD patients. No damaging variants were detected through WES in 22 Ethiopian samples. Genotyping of disease-associated CLDN1 SNPs in Ethiopian cases and control material showed no overall association. However, significant association was seen for rs893051 in patients who developed AD before the age of 5 years (P < 0.03). Taken together, we demonstrate that tight junction genes and, in particular, CLDN1 rather than variants in FLG may be involved in the susceptibility of AD in the Ethiopian population.

Atopic dermatitis (AD) is characterized by dry skin and a hyperactive immune response to allergens, 2 cardinal features that are caused in part by epidermal barrier defects. Tight junctions (TJs) reside immediately below the stratum corneum and regulate the selective permeability of the paracellular pathway. We evaluated the expression/function of the TJ protein claudin-1 in epithelium from AD and nonatopic subjects and screened 2 American populations for single nucleotide polymorphisms in the claudin-1 gene (CLDN1). Expression profiles of nonlesional epithelium from patients with extrinsic AD, nonatopic subjects, and patients with psoriasis were generated using Illumina's BeadChips. Dysregulated intercellular proteins were validated by means of tissue staining and quantitative PCR. Bioelectric properties of epithelium were measured in Ussing chambers. Functional relevance of claudin-1 was assessed by using a knockdown approach in primary human keratinocytes. Twenty-seven haplotype-tagging SNPs in CLDN1 were screened in 2 independent populations with AD. We observed strikingly reduced expression of the TJ proteins claudin-1 and claudin-23 only in patients with AD, which were validated at the mRNA and protein levels. Claudin-1 expression inversely correlated with T(H)2 biomarkers. We observed a remarkable impairment of the bioelectric barrier function in AD epidermis. In vitro we confirmed that silencing claudin-1 expression in human keratinocytes diminishes TJ function while enhancing keratinocyte proliferation. Finally, CLDN1 haplotype-tagging SNPs revealed associations with AD in 2 North American populations. Collectively, these data suggest that an impairment in tight junctions contributes to the barrier dysfunction and immune dysregulation observed in AD subjects and that this may be mediated in part by reductions in claudin-1.

The fruit of Gardenia jasminoides Ellis, which belongs to the plant family Rubiaceae, was first recorded in Shennong's Herbal Medicine and has been used in traditional Chinese medicine. Pharmacological studies have shown that Gardenia has certain liver- and gallbladder-protecting, blood sugar-lowering, pancreatic secretion-promoting, gastric function-protective, blood pressure-lowering, lipid-regulating, neuroprotective, anti-inflammatory, antioxidant, anti-fatigue, and anti-thrombotic activities. Moreover, G. jasminoides fruit extract (GJFE) can ameliorate symptoms of atopic dermatitis, but the specific mechanisms involved remain unclear. The aim of this study was to investigate the potential mechanisms and signalling pathways through which GJFE alleviates atopic dermatitis (AD) in keratinocytes, three-dimensional (3D) epidermal models and mouse models. We established a model of IL-4- and IL-13-induced atopic dermatitis using keratinocytes and 3D epidermal models. Additionally, an atopic dermatitis model was induced by applying MC903 (calcipotriol) to mouse ears for 8 consecutive days. The effects of GJFE and gardenoside on inflammation and skin barrier damage were verified through western blotting, quantitative polymerase chain reaction, immunofluorescence and network pharmacology. To further elucidate the molecular mechanisms involved, we employed small interfering RNA and small molecule inhibitors to investigate the relationships among OVOL1, signal transducer and activator of transcription 6 (STAT6), and tight junctions. Our findings provide convincing evidence that GJFE may alleviate atopic dermatitis by inhibiting inflammation and repairing the barrier in human keratinocytes, 3D epidermal models and AD mouse model. Specifically, it was found to suppress the expression of key inflammatory cytokines and chemokines, including IL-24, IL-33, and CCL26. Simultaneously, it promoted the expression of proteins essential for preserving skin barrier integrity, such as CLDN1, CLDN4, and OVOL1. We discovered that these effects are mediated via the JAK-STAT6 signalling pathway. Furthermore, we revealed that STAT6 phosphorylation is crucial for the regulation of downstream tight junction proteins and that OVOL1 can affect the expression of CLDN1 and CLDN4. Our study demonstrates that Gardenia jasminoides fruit extract alleviates MC903-induced atopic dermatitis and reduces IL-4/IL-13-induced tight junction disruption and inflammation by regulating the phosphorylation of STAT6. Our findings provide preliminary experimental evidence supporting the potential application value of GJFE in the treatment of atopic dermatitis, particularly in terms of its anti-inflammatory and barrier-repairing functions.

Atopic dermatitis is a common chronic inflammatory skin disease characterized by relapsing eczema and intense itch. DGT is a novel synthetic heterocyclic diterpenoid derived from plants. Its therapeutic potential and mechanism(s) of action are poorly understood. We investigated the potent therapeutic effect of DGT on atopic dermatitis, exploring the underlying mechanisms and determining whether DGT is a safe and well-tolerated topical treatment. We observed anti-inflammatory effects of DGT on tumor necrosis factor-α/interferon-γ-treated human keratinocytes, and anti-allergic effects on immunoglobulin E-sensitized bone marrow-derived mast cells. In vivo, DGT was topically applied to two experimental mouse models of atopic dermatitis: oxazolone-induced sensitization and topically applied calcipotriol. Then the therapeutic effects of DGT were evaluated physiologically and morphologically. Moreover, we performed nonclinical toxicology and safety pharmacology research, including general toxicity, pharmacokinetics, and safety pharmacology on the cardiovascular, respiratory, and central nervous systems. In keratinocytes, DGT reduced the expression of inflammatory factors, promoting the expression of barrier functional proteins and tight junctions and maintaining the steady state of barrier function. DGT also inhibited the activation and degranulation of mast cells induced by immunoglobulin E. Moreover, we found that interleukin-4 receptor-α was the possible target of DGT. Meanwhile, DGT had therapeutic effects on oxazolone/calcipotriol-treated mice. Notably, our pharmacology results demonstrated that DGT was safe and nontoxic in our studies. DGT's potent anti-inflammatory effects and good safety profile suggest that it is a potential candidate for the treatment of atopic dermatitis.

Small interfering RNA (siRNA) has been proposed as a novel treatment for atopic dermatitis (AD) because it suppresses sequence-specific mRNA expression. Indeed siRNA-based therapy achieves an almost complete cure with fewer side effects than currently available treatments. However, the tight junctions in the granular layer of the epidermis in the atopic skin are barriers to siRNA delivery. We previously reported the potential clinical utility of AT1002, a peptide that opens tight junctions. In the present study, we evaluated a topical siRNA-based therapy for AD using AT1002 in combination with a flexible liposome. The 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE)/cholesteryl hemisuccinate (CHEMS) liposome was chosen as a carrier for siRNA because of its highly flexible structure and permeability. We prepared siRNA-encapsulated DOPE/CHEMS liposomes and examined their physical properties, safety, uptake into RAW264.7 cells, and topical application in healthy and AD-affected skin. We then assessed the efficacy of anti-nuclear factor-kappa B (NF-κB) (RelA) siRNA (siRelA)-encapsulated DOPE/CHEMS liposomes with AT1002 in AD model mice. The siRNA-DOPE/CHEMS liposomes were absorbed significantly better than siRNA alone and they enhanced siRNA skin penetration without toxicity. Moreover, siRelA-DOPE/CHEMS liposomes with AT1002 alleviated AD symptoms and reduced the levels of inflammatory cytokines in AD model mice. Therefore, the combination of AT1002 and DOPE/CHEMS liposomes could be a dermally applied RNA interference therapeutic system for effective RNA delivery and AD treatment.

Atopic dermatitis (AD) is a common allergic inflammatory skin disease, concomitant with a high relapse rate. Yu-Ping-Feng-San (YPFS), a well-known Chinese herbal decoction, reduces the AD relapse rate and recurring severity incidence. However, the underlying mechanism of YPFS on resisting AD recurrence is still unknown and further study is needed. To evaluate the effects of YPFS on recurrent allergic inflammation of AD in a murine model and to investigate the underlying mechanisms in vivo and ex vivo. A fluorescein isothiocyanate (FITC)-induced AD relapsing mouse model was established to study the effects of YPFS and three active components, claycosin, formononetin, and cimifugin, on recurrent allergic inflammation in vivo. Histological analyses of ear tissue inflammation were evaluated by hematoxylin and eosin staining. Production of interleukin (IL)-4, IL-5, IL-13, and interferon-gamma in mice ear tissues, IgE in serum, and thymic stromal lymphopoietin (TSLP) in cell cultures were measured by ELISAs. Tight junction (TJ) expression was detected by immunohistochemistry and western blots. Epithelial barrier integrity was observed with electron microscopy, transepithelial electric resistance (TER), and paracellular flux measurements. HaCaT cells were utilized for ex vivo cellular analyses. In the recurrent phase of AD, YPFS exhibited both short- and long-term anti-allergic inflammatory efficacy with reduced ear tissue inflammation and decreased IL-4, IL-5, IL-13, and IgE production. The three active components, claycosin, formononetin, and cimifugin, showed similar effects as YPFS. Stimulus-induced decreased TER and increased FITC-dextran flux in air-liquid interface cultures of HaCaT cells were significantly repaired by YPFS and the three active components. Notably, the upregulated TJ (CLDN-1 and occludin) expression of epithelium was observed only with YPFS and the three components-treated mice as opposed to the result using conventional anti-allergy medicines. Restored TJ expression by YPFS three components was also detectable in the remission phase of AD. Moreover, decreased TJ expression influenced the effects of YPFS on epithelial cells-derived TSLP production. YPFS ameliorated recurrent allergic inflammation of AD by repairing TJ defects of epithelial barriers. Intervening epithelial barrier functions could be a preventive and therapeutic approach for recurrent allergic inflammation of AD.

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by impaired skin barrier function and immune dysregulation. Autophagy, a lysosome-dependent degradation pathway essential for removing unnecessary components, plays a crucial role in maintaining cellular homeostasis. Defective autophagy has been implicated in AD pathogenesis, and enhancing autophagic activity represents a viable therapeutic strategy. This study investigated the potential of the natural saponin escin to ameliorate AD through autophagy activation. We demonstrated that escin induced autophagy in HaCaT keratinocytes and mitigated tight junction (TJ) barrier disruption in an AD-like cell model stimulated with IL-4 and IL-13. Notably, silencing ATG7, an essential autophagy-related protein, abrogated the barrier-restorative effects of escin. Furthermore, in a 2,4-dinitrochlorobenzene (DNCB)-induced murine model of AD, escin treatment ameliorated AD-like skin lesions, reduced mast cell infiltration, and decreased cutaneous levels of the pro-inflammatory cytokines IL-4, IL-13, and IFN-γ. Escin administration also restored the epidermal expression of key TJ proteins, Claudin-1 and ZO-1. Mechanistically, escin promoted the nuclear translocation of transcription factor EB (TFEB) and upregulated the expression of genes involved in autophagy and lysosome biogenesis. These protective effects were associated with the activation of the AMPK-mTORC1-TFEB signaling pathway. Collectively, our findings indicate that escin enhances autophagy and restores skin barrier function, highlighting its potential as a novel therapeutic agent for AD treatment.

Few studies have explored the intricate connections between vitamin D receptor (VDR) gene polymorphisms, VDR, tight junction (TJ) protein expression and clinical features of atopic dermatitis (AD). From 43 adult AD patients, VDR polymorphisms were genotyped from peripheral blood samples using polymerase chain reaction-restriction fragment length polymorphism. VDR, occludin, claudin-1 and ZO-1 protein expression from skin lesion biopsies were assessed by immunohistochemistry. The A1012G heterozygous VDR polymorphism exhibited a lower odds ratio (OR) for juvenile AD onset (OR: 0.046, 95% CI 0.004-0.51, p=0.012). In contrast, the presence of ≥2 homozygous VDR polymorphisms were significantly associated with positive skin prick test (SPT) (10/20, 50%) vs. negative SPT (1/23, 4.3%; p=0.0003). The most highly expressed TJ proteins in lesions of AD patients were claudin-1 and zonulin-1 (ZO-1), while VDR and occludin were less prevalent. A significant correlation was observed between ZO-1 expression and a body mass index ≥30 kg/m This study provides novel insights into the relationship between VDR gene polymorphisms, VDR, TJ protein expression, and clinical features in adult AD patients, highlighting a significant role of vitamin D in the pathophysiology of this disease.

Tight junctions are important for skin barrier function. The tight junction protein claudin 1 (Cldn-1) has been reported to be down-regulated in nonlesional skin of atopic dermatitis (AD) patients. In contrast, we did not observe a significant down-regulation of Cldn-1 in nonlesional skin of the AD cohort used in this study. However, for the first time, a significant down-regulation of Cldn-1 in the upper and lower epidermal layers of lesional skin was detected. In addition, there was a significant up-regulation of Cldn-4 in nonlesional, but not lesional, AD skin. For occludin, no significant alterations were observed. In an AD-like allergic dermatitis mouse model, Cldn-1 down-regulation in eczema was significantly influenced by dermal inflammation, and significantly correlated with hallmarks of eczema (ie, increased keratinocyte proliferation, altered keratinocyte differentiation, increased epidermal thickness, and impaired barrier function). In human epidermal equivalents, the addition of IL-4, IL-13, and IL-31 resulted in a down-regulation of Cldn-1, and Cldn1 knockdown in keratinocytes resulted in abnormal differentiation. In summary, we provide the first evidence that Cldn-1 and Cldn-4 are differentially involved in AD pathogenesis. Our data suggest a role of Cldn-1 in AD eczema formation triggered by inflammation.

Tight junctions (TJs) play important roles in epidermal barrier function and their dysfunction is involved in the pathogenesis of various skin diseases, including atopic dermatitis (AD). Mucopolysaccharide polysulphate (MPS) is the active ingredient of a moisturizing agent used to treat xerosis in patients with AD; however, its mechanism of action on TJ barrier function remains unclear. To elucidate the effects of MPS on TJs, adult human epidermal keratinocyte (HEKa) cells were exposed to MPS, subjected to Western blotting and quantitative PCR analyses for the investigation of TJ-related factors. MPS treatment significantly increased the mRNA and protein expression of claudin-1 (CLDN1) and zonula occludens-1, and significantly increased transepithelial electrical resistance (TEER), which indicates TJ integrity. Conversely, the sulphated and non-sulphated glycosaminoglycans, chondroitin sulphate and hyaluronic acid, respectively, had little effect on TEER or the expression of mRNAs or TJ-related proteins. Interestingly, MPS treatment also inactivated the extracellular signal-regulated kinase signalling pathway, which is known to negatively regulate CLDN1 expression. Furthermore, MPS notably improved the reduction in CLDN1 expression and TEER caused by histamine, which is upregulated in the skin of patients with AD and is known to disrupt the TJ barrier function. Taken together, these findings demonstrate that treatment with the moisturizing agent, MPS, can repair TJ dysfunction and could therefore represent a new therapeutic option for treating patients with AD.

The transmembrane protein claudin-1 is a major component of epidermal tight junctions (TJs), which create a dynamic paracellular barrier in the epidermis. Claudin-1 downregulation has been linked to atopic dermatitis (AD) pathogenesis but variable levels of claudin-1 have also been observed in healthy skin. To elucidate the impact of different levels of claudin-1 in healthy and diseased skin we determined claudin-1 levels in AD patients and controls and correlated them to TJ and skin barrier function. We observed a strikingly broad range of claudin-1 levels with stable TJ and overall skin barrier function in healthy and non-lesional skin. However, a significant decrease in TJ barrier function was detected in lesional AD skin where claudin-1 levels were further reduced. Investigations on reconstructed human epidermis expressing different levels of claudin-1 revealed that claudin-1 levels correlated with inside-out and outside-in barrier function, with a higher coherence for smaller molecular tracers. Claudin-1 decrease induced keratinocyte-autonomous IL-1β expression and fostered inflammatory epidermal responses to non-pathogenic Staphylococci. In conclusion, claudin-1 decrease beyond a threshold level results in TJ and epidermal barrier function impairment and induces inflammation in human epidermis. Increasing claudin-1 levels might improve barrier function and decrease inflammation and therefore be a target for AD treatment.

The tight junction (TJ) barrier is located in the granular layer of the epidermis. Filaggrin deficiency predisposes patients to atopic dermatitis (AD) by impairing stratum corneum (SC) barrier function. Altered TJ barrier function has been observed in the skin of patients with AD; however, it remains unclear whether TJ function is influenced by filaggrin deficiency directly or secondarily via skin inflammation. To investigate the in vivo effects of filaggrin deficiency and skin inflammation on epidermal TJ function. Morphological changes in the TJ were investigated in filaggrin knockout mice and mice with hapten-induced dermatitis using en face visualization of epidermal sheets, and functional changes in the TJ were assessed with an in vivo permeation assay using tracers of various sizes. In filaggrin knockout mice, there was no apparent change in the honeycomb morphology of the TJ, TJ component mRNA expression, or TJ barrier function in neonates and adults, indicating that filaggrin-deficiency had no direct effects on the TJ. By contrast, in mice with hapten-induced dermatitis, the mRNA expression of TJ components was decreased markedly and the TJ barrier function was size-dependently impaired: the TJ leaked small tracers (<5 kDa), but not large tracers (>30 kDa). Filaggrin deficiency did not affect the epidermal TJ barrier directly, but once dermatitis occurred, the skin inflammation induced TJ dysfunction. Since TJ dysfunction induces the SC barrier impairment, skin inflammation will enhance skin permeability to external antigens and result in a vicious cycle of barrier dysfunction and skin inflammation.

The epidermal barrier is thought to protect sensory nerves from overexposure to environmental stimuli, and barrier impairment leads to pathological conditions associated with itch, such as atopic dermatitis (AD). However, it is not known how the epidermal barrier continuously protects nerves for the sensory homeostasis during turnover of the epidermis. Here we show that epidermal nerves are contained underneath keratinocyte tight junctions (TJs) in normal human and mouse skin, but not in human AD samples or mouse models of chronic itch caused by epidermal barrier impairment. By intravital imaging of the mouse skin, we found that epidermal nerve endings were frequently extended and retracted, and occasionally underwent local pruning. Importantly, the epidermal nerve pruning took place rapidly at intersections with newly forming TJs in the normal skin, whereas this process was disturbed during chronic itch development. Furthermore, aberrant Ca

The long-term use of topical corticosteroids (TCS) is associated with side effects such as skin atrophy and barrier deterioration. Moisturizers, such as mucopolysaccharide polysulfate (MPS), have been reported to prevent relapses in atopic dermatitis (AD) when used in combination with TCS. However, the mechanisms underlying the positive effects of MPS in combination with TCS in AD are poorly understood. In the present study, we investigated the effects of MPS in combination with clobetasol 17-propionate (CP) on tight junction (TJ) barrier function in human epidermal keratinocytes (HEKa) and 3D skin models. The expression of claudin-1, which is crucial for TJ barrier function in keratinocytes, and transepithelial electrical resistance (TEER) was measured in CP-treated human keratinocytes incubated with and without MPS. A TJ permeability assay, using Sulfo-NHS-Biotin as a tracer, was also conducted in a 3D skin model. CP reduced claudin-1 expression and TEER in human keratinocytes, whereas MPS inhibited these CP-induced effects. Moreover, MPS inhibited the increase in CP-induced TJ permeability in a 3D skin model. The present study demonstrated that MPS improved TJ barrier impairment induced by CP. The improvement of TJ barrier function may partially be responsible for the delayed relapse of AD induced by the combination of MPS and TCS.

Atopic dermatitis (AD) is characterized by epidermal tight junction (TJ) defects and a propensity for Staphylococcus aureus skin infections. S. aureus is sensed by many pattern recognition receptors, including Toll-like receptor 2 (TLR2). We hypothesized that an effective innate immune response will include skin barrier repair, and that this response is impaired in AD subjects. S. aureus-derived peptidoglycan (PGN) and synthetic TLR2 agonists enhanced TJ barrier and increased expression of TJ proteins, claudin-1 (CLDN1), claudin-23 (CLDN23), occludin, and Zonulae occludens 1 (ZO-1) in primary human keratinocytes. A TLR2 agonist enhanced skin barrier recovery in human epidermis wounded by tape stripping. Tlr2(-/-) mice had a delayed and incomplete barrier recovery following tape stripping. AD subjects had reduced epidermal TLR2 expression as compared with nonatopic subjects, which inversely correlated (r=-0.654, P=0.0004) with transepidermal water loss (TEWL). These observations indicate that TLR2 activation enhances skin barrier in murine and human skin and is an important part of a wound repair response. Reduced epidermal TLR2 expression observed in AD patients may have a role in their incompetent skin barrier.

Atopic dermatitis (AD) is the most prevalent chronic inflammatory skin condition and significantly reduces quality of life. Tight junction (TJ), which is located directly beneath the stratum corneum, maintains skin barrier function and aids in the identification of the cell's "territory". We evaluated seventeen TJ related genes to explore AD related alterations of TJ. Remarkably, we found that the expression of ZO-3, a gene that had not been linked to the development of TJ in AD, was significantly down-regulated in the skin of AD mice and patients. siRNA mediated knock-down of ZO-3 significantly decreased transepithelial electrical resistance in HaCaT cells, demonstrating that ZO-3 is essential to epidermal barrier function. In addition to ZO-3 downregulation, protein kinase B (Akt) phosphorylation was increased in the skin of AD mice. We further confirmed an inverse relationship between Akt phosphorylation and ZO-3 expression in AD using HaCaT cells and mouse model. Finally, we tested the efficacy of osthole as a treatment for AD in mice and HaCaT cells. Osthole inhibits Akt phosphorylation, and thereby enhances ZO-3 expression in mouse models of AD, resulting in greatly lessened AD associated skin damage and chronic itch, and osthole also increased the expression of ZO-3 in HaCaT cells by inhibiting the phosphorylation of Akt. Together, we established that ZO-3 is essential for the development of TJ in AD skin and HaCaT cells, and our findings provide fresh support for osthole's ability to protect ZO-3 expression and the epidermal barrier in AD.

The antimicrobial peptide derived from insulin-like growth factor-binding protein 5 (AMP-IBP5) exhibits antimicrobial activities and immunomodulatory functions in keratinocytes and fibroblasts. However, its role in regulating skin barrier function remains unclear. Here, we investigated the effects of AMP-IBP5 on the skin barrier and its role in the pathogenesis of atopic dermatitis (AD). 2,4-Dinitrochlorobenzene was used to induce AD-like skin inflammation. Transepithelial electrical resistance and permeability assays were used to investigate tight junction (TJ) barrier function in normal human epidermal keratinocytes and mice. AMP-IBP5 increased the expression of TJ-related proteins and their distribution along the intercellular borders. AMP-IBP5 also improved TJ barrier function through activation of the atypical protein kinase C and Rac1 pathways. In AD mice, AMP-IBP5 ameliorated dermatitis-like symptoms restored the expression of TJ-related proteins, suppressed the expression of inflammatory and pruritic cytokines, and improved skin barrier function. Interestingly, the ability of AMP-IBP5 to alleviate inflammation and improve skin barrier function in AD mice was abolished in mice treated with an antagonist of the low-density lipoprotein receptor-related protein-1 (LRP1) receptor. Collectively, these findings indicate that AMP-IBP5 may ameliorate AD-like inflammation and enhance skin barrier function through LRP1, suggesting a possible role for AMP-IBP5 in the treatment of AD.

Both psoriasis and atopic dermatitis (AD) are not only associated with an impaired stratum corneum barrier, but also with abnormal expression of the tight junction (TJ) proteins. Because host defense peptides, including LL-37, are overexpressed in lesional psoriatic skin but are downregulated in lesional AD skin, we hypothesized that LL-37 might regulate the TJ function in keratinocytes. We demonstrated that LL-37 selectively increased the expression of several claudins and occludin, and enhanced their membrane distribution. Furthermore, LL-37 elevated the transepithelial electrical resistance while reducing the paracellular permeability of keratinocyte layers, and this activity was weakened by the claudin inhibitor ochratoxin A. A characterization of the molecular mechanism underlying the regulation of the TJ barrier by LL-37 revealed that LL-37 induced the activation of the Rac1, atypical PKC, glycogen synthase kinase-3 and PI3K pathways, and the specific inhibition of these pathways reversed the LL-37-mediated regulation of TJ function. In addition, LL-37 enhanced the expression of differentiation markers under the control of ochratoxin A, suggesting an association between LL-37-induced TJ function and keratinocyte differentiation. These data provide novel evidence that, in addition to its antimicrobial and other immunoregulatory functions, LL-37 contributes to cutaneous immunity by strengthening the skin's barrier function.

Atopic dermatitis (AD) is a chronic, recurrent eczematous disorder with a complex pathophysiology caused by skin barrier abnormalities. Rosacea is a common chronic immune-mediated inflammatory disorder that results in diminished skin barrier function. Reflectance confocal microscopy (RCM) is a non-invasive method for visualizing the dynamic status of epidermal and upper dermal structures. In this study, we compared skin barrier permeability among normal, AD and rosacea groups. To assess skin barrier permeability, zinc was applied to lesional skin and the RCM reflectance intensity of zinc penetration was measured. Reflectance confocal microscopy revealed that the intensity in patients with rosacea and AD was higher than that in the normal group at depths of 8-24 μm in both the face and forearm, which were considered as the stratum corneum (SC) and tight junction (TJ) level (p < 0.0001). When comparing AD and rosacea, the intensity of rosacea was higher than that of AD at a depth of 8 μm in the face (p < 0.0001). The intensity of AD was higher than that of rosacea at a depth of 24 μm (p = 0.009). This suggests that skin barrier permeability is increased in the upper epidermis of patients with AD and rosacea. On the face, patients with rosacea had more SC weakness than did those with AD, whereas patients with AD had more TJ weakness than those with rosacea.

Although atopic dermatitis (AD) has been reported to be a typical type 2 immune response disease, it is also an inflammatory skin disease that involves cytokines, such as Th1, Th17 and Th22. However, little is known about the mechanism by which the candidate cytokines, alone or in combination, are involved in AD pathology. Differences in cytokine balance, which contribute to the complexity of AD pathology, may influence the stratum corneum barrier function through tight junction (TJ) functional stability and contribute to disease severity. To confirm the regulatory mechanism of TJ protein expression in AD, we investigated the Th1 and Th17 pathways, which are the initiation factors of chronic AD pathology. We examined the effects of these cytokines on TJ protein expression in normal human epidermal keratinocytes in vitro, and also examined their function in a human skin equivalent model. We observed a time- and dose-dependent inhibitory effect of IFN-γ on claudin-1 expression via the IFN-γ receptor/JAK/STAT signalling pathway. IFN-γ impaired TJ function in a human skin equivalent model. Moreover, we investigated co-stimulation with IL-17A, which is highly expressed in AD skin lesions and found that IL-17A restores IFN-γ-induced TJ dysfunction. This restoration of TJ function was mediated by atypical protein kinase C zeta activation without recovery of TJ protein expression. These results are informative for personalized AD treatment via systemic therapies using anti-cytokine antibodies and/or JAK inhibitors.

Kochiae Fructus is a traditional herbal medicine used to treat a variety of skin conditions. Momordin Ic, the main bioactive pentacyclic triterpenoid saponin component of Kochiae Fructus, is known for its broad pharmacological effects, including antioxidative and anti-inflammatory. However, its therapeutic potential and underlying pharmacological mechanisms in atopic dermatitis (AD) remain poorly understood, especially its role in epidermal barrier function, which still awaits further research. The research aims to clarify the skin barrier protection and anti-inflammatory mechanisms of Momordin Ic in AD. The effects of Momordin Ic on scratch behavior, ear swelling, dermatitis scores, and inflammation were evaluated using an AD mouse model. The expressions of JAK1/STAT3, TRPA1, ZO-1 and occludin were analyzed through western blotting analysis and immunofluorescence techniques. HaCaT cells with TNF-α/IFN-γ stimulation were used to further explore the anti-inflammatory and barrier protective properties of Momordin Ic. Momordin Ic significantly reduced AD-like clinical symptoms caused by MC903 and also reduced the level of pro-inflammatory factors. In addition, Momordin Ic significantly suppressed the phosphorylation of JAK1/STAT3 as well as the level of TRPA1, and increased the levels of ZO-1 and occludin. In vitro experiments further demonstrated that Momordin Ic inhibited the inflammation in HaCaT cells and modulated the JAK1/STAT3 pathway and TJ proteins. The results showed that Momordin Ic can effectively reduce inflammation and skin barrier damage associated with AD, suggesting that it may be an option for AD treatment.

Recent epidemiological studies have demonstrated that air pollution is associated with the inflammatory response and may aggravate inflammatory skin diseases such as atopic dermatitis (AD). However, it is unclear whether particulate matter (PM) aggravates AD symptoms. The aim of this study was to investigate whether PM exposure affects the skin barrier dysfunction and aggravates AD symptoms using human keratinocytes (HaCaT) cells and a mouse model of oxazolone-induced AD-like skin. Standard reference material (SRM) 1649b, which mainly comprises polycyclic aromatic hydrocarbons, was used as the reference PM. HaCaT cells and mouse model of oxazolone-induced AD-like skin were treated with PM. The mRNA or protein expression levels of stratum corneum (SC) and tight junction (TJ) proteins, inflammatory cytokines, as well as clinical and histological changes of the AD-like skin of mouse model were evaluated. The expression of genes and proteins was analyzed by real-time polymerase chain reaction and Western blotting. Levels of inflammatory cytokines were measured by enzyme-linked immunosorbent assay. The results revealed that PM downregulates the expression levels of several SC and TJ-related proteins in the mouse model with AD-like skin. Clinically, epidermal and dermal thickness was significantly increased and dermal inflammation was prominent in PM treated AD-like skin. In conclusion, we found that PM aggravates skin barrier dysfunction, clinically augmenting epidermal and dermal thickening with dermal inflammation in AD-like skin. These results suggest that PM may trigger the exacerbation of AD symptoms via skin barrier dysfunction-related mechanisms.

Tight junction (TJ) dysfunction in the stratum granulosum leads to aberrant barrier function of the stratum corneum (SC) in the epidermis. However, it is unclear whether TJs are perturbed in atopic dermatitis (AD), a representative aberrant SC-related skin disease, and whether some factors related to AD pathogenesis induce TJ dysfunction. To address these issues, we investigated the alterations of TJs in AD skin and the effects of Th2 and Th17 cytokines on TJs in a skin-equivalent model. The levels of TJ proteins were determined in the epidermis of nonlesional and lesional skin sites of AD. Western blot and immunohistochemical analyses revealed that the levels of zonula occludens 1 were decreased in the nonlesional sites of AD, and the levels of zonula occludens 1 and claudin-1 were decreased in the lesional sites relative to the levels in skin from healthy subjects. Next, we examined the effects of interleukin (IL)-4, tumor necrosis factor-α, IL-17, and IL-22 on the TJ barrier in a skin-equivalent model. Only IL-17 impaired the TJ barrier. Furthermore, we observed a defect in filaggrin monomer degradation in the IL-17-treated skin model. Thus, TJs are dysfunctional in AD, at least partly, due to the effect of IL-17, which may result in an aberrant SC barrier.

In the epidermis, tight junction (TJ) structure is specifically located in the stratum granulosum, where the expression of ΔNp63, a p53 family transcription factor, is attenuated. Since the relationship between ΔNp63 and barrier function has not been fully uncovered, we assessed expression profiles of TJ proteins in skin tissues and cultured keratinocytes. The results showed that expression of ΔNp63 and that of claudin-4 were inversely correlated in healthy human epidermis. In vitro studies using HaCaT keratinocytes revealed functional relevance of ΔNp63 and claudin-4. Curiously, Toll-like receptor (TLR)-3 ligand, which is known to be liberated from damaged cells, suppressed ΔNp63 expression and concomitantly upregulated claudin-4 expression in primary keratinocytes. More interestingly, a broad expression pattern of claudin-4 was found in the epidermis of atopic dermatitis (AD), a barrier defect disorder, which contains ΔNp63-lacking keratinocytes as we reported previously. Therefore, upregulation of claudin-4 expression regulated by ΔNp63 might be associated with complementary or repair responses of damaged keratinocytes with AD.

Atopic dermatitis (AD) is a common skin disease characterized by recurrent pruritic inflammatory skin lesions and defects of the skin barrier. Bacterial infection with Staphylococcus aureus contributes to increased severity of AD by compromising the barrier further. A microorganism component of Avène Thermal Spring Water, Aquaphilus dolomiae, is thought to contribute to some of its beneficial effects to skin, eg AD alleviation. Here, we have investigated the effects of an extract of A. dolomiae, A. dolomiae extract-G1 (ADE-G1), on the structural barrier function of keratinocytes, tight junction (TJ) protein expression and the expression of several genes altered in AD patients. An epidermal cell culture model mimicking the AD environment and phenotype was used, in which S. aureus-infected cell cultures of normal human epidermal keratinocytes were exposed to a proinflammatory environment. Endpoints measured included the transepithelial electrical resistance (TER) and immunohistological staining of the epidermal TJ proteins, claudin and occludin. Additional analysis was made of several genes known to be differentially regulated in skin from AD patients (C-C motif chemokine ligand 20 (CCL20), interleukin-8 (IL-8), S100 calcium binding protein A7 (S100A7), defensin beta 4 (DEFB4) and filaggrin). Aquaphilus dolomiae extract-G1 strongly increased TER in non-infected cells and provided protection against infection by overcoming the decrease in TER induced by the infection with S. aureus. In infected cells exposed to a pro-inflammatory environment - depicting AD-like conditions - TER protection by ADE-G1 was still observed. Gene expression analysis of infected and pro-inflammatory stimulated cells indicated that ADE-G1 modulated the inflammatory response (induced IL-8 and attenuated CCL20 expression), increased antimicrobial activities (induced DEFB4 and A100A7) and strengthened barrier function (restored filaggrin expression). ADE-G1 reinforces barrier function and strongly protects TJ barrier disruption induced by bacterial infection and inflammation.

Delgocitinib ointment 0.5% is the world's first topical Janus kinase inhibitor product and was approved for treatment of atopic dermatitis (AD) in Japan. Although topical corticosteroids (TCSs) have been the mainstay of pharmacotherapy in AD over the past decades, long-term use of TCSs causes skin atrophy and alteration of the epidermal tight junction (TJ) leading to epidermal barrier dysfunction. In this study, delgocitinib ointment 0.5% or representative TCSs of different potencies were applied dermally once daily to the ear pinna of normal ICR mice for 14 days, and ear pinna thickness, histopathology, and immunohistochemistry for epidermal TJ proteins claudin-1 and -4 were evaluated. All the TCSs caused decreases in ear pinna thickness with epidermal thinning, sebaceous gland atrophy, and atrophy/decreased number of the subcutaneous adipocytes and decreased immunohistochemical staining intensity for epidermal claudins. In contrast, delgocitinib ointment 0.5% did not cause any of those changes. In conclusion, once daily topical delgocitinib ointment 0.5% for 14 days did not cause skin atrophy or decreased immunohistochemical staining of epidermal claudins, which are common safety concerns associated with TCSs. These characteristics suggest that delgocitinib ointment 0.5% has an improved safety profile over currently available TCS therapies particular for the long-term AD treatment.

Tight junctions (TJ) are important for skin barrier function and could be relevant in modulating allergen penetration in atopic dermatitis (AD). Humans with AD have been described to have decreased expressions of some TJ proteins in the skin. This study aimed to investigate TJ protein expression using an experimental AD model in dogs. Skin biopsies from six atopic (nonlesional skin) and five normal beagle dogs were stained for TJ proteins [zonula occludens 1 (ZO-1), occludin, claudin-1] by immunohistochemistry. Staining intensity was evaluated both objectively using imaging software and subjectively. Six images/sections were randomized and blindly scored by six investigators for intensity, distribution, integrity and staining pattern. The intensity of ZO-1 was significantly decreased in the atopic group objectively (P = 0.010) and subjectively (P = 0.002) relative to the normal group. Occludin was decreased significantly subjectively (P = 0.027) but not objectively. Claudin was not significantly different between groups by either quantification. Additionally, only ZO-1 demonstrated a significantly patchier staining pattern in the atopic group. There was no consistent staining pattern in this study. ZO-1 and occludin, which have not been described to be associated with the development of AD in humans, could play a role in this atopic dog model. Further investigation on the expression and modulation of TJ proteins and their clinical relevance is needed.

Recent studies have demonstrated that microRNA-155-5p (miR-155-5p) plays an essential role in the regulation of allergen-induced inflammation and is overexpressed in the skin of patients with atopic dermatitis (AD), although the mechanism is unknown. In this study, silencing miR-155-5p attenuated the thickening of the epidermis in AD model and reduced the infiltration of inflammatory cells and the secretion of Th2 cytokines. Protein kinase inhibitor α (PKIα) was identified as a direct target of miR-155-5p and correlated negatively with miR-155-5p in our AD model. Fluorescence in situ hybridization showed that miR-155-5p-expressing cells were predominantly present in the epidermis. When epithelial cells were transfected with an miR-155-5p inhibitor, the expression of PKIα, occludin, and CLDN16 increased and that of TSLP decreased significantly, whereas the overexpression of miR-155-5p resulted in the opposite changes. The increased expression of PKIα and tight junction (TJ) proteins, with reduced TSLP and IL-33, was also detected in miR-155-5p-blocked mice, in both the initial and elicitation stages of AD. The expression of TJ proteins also decreased when cells were transfected with PKIα siRNA. TJ proteins increased and TSLP and IL-33 decreased significantly after the overexpression of PKIα. Our data provide the first evidence that miR-155-5p is critical for the allergic inflammation in a mouse model of AD by directly regulating PKIα and thus epithelial TJ expression. These findings suggest new therapeutic strategies that target miR-155-5p in patients with allergic disorders.

Tight junctions (TJs) have important roles in skin barrier function. The TJ protein claudin-1 (CLDN1) is decreased in atopic dermatitis (AD). However, little is known about the mechanism of CLDN1 down-expression. To elucidate the effect of IL-33 on CLDN1 expression in keratinocytes. Normal human epidermal keratinocytes (NHEKs) and human skin equivalent models (HSEMs) were cultured in vitro in the presence of IL-33. Production of CLDN1, signal transducer and activator of transcription 3 (STAT3) and Mitogen-activated protein kinases (MAPK) expression were measured by real-time PCR, western blot and immunofluorescence assay. MAPK inhibitors and small interfering RNA were used to confirm the signal pathway of STAT3 and CLDN1. Barrier function was measured by transepithelial electric resistance (TEER) and FITC-dextran flux assays. Electrophoretic Mobility Shift Assay was used to detect STAT3 transcriptional activity. Levels of CLDN1 expression were reduced in the epidermis of AD-model mice overexpressing IL-33. IL-33 down-regulated the expression of CLDN1 mRNA and protein in NHEKs and HSEMs. IL-33 attenuated transepithelial electric resistance and induced FITC-dextran flux in NHEKs. The IL-33 suppressed CLDN1 expression was regulated by an extracellular signal-regulated kinase (ERK) and signal transducer and activator of transcription 3 (STAT3). STAT3 suppressed CLDN1 expression by direct binding to the promoters. IL-33 may down-regulate CLDN1 expression through the ERK/STAT3 pathway in keratinocytes.

Human β-defensin (hBD)-3 is an antimicrobial peptide that exhibits both antimicrobial and immunomodulatory activities, but its role in autophagy regulation remains unclear. Additionally, the role of autophagy in skin barrier regulation in atopic dermatitis (AD) is not well understood. This study aimed to investigate the role of autophagy in the skin lesions of AD patients and mouse models, as well as the effects of hBD-3 on autophagy and skin barrier function. We assessed autophagy in epidermal keratinocytes from skin lesions of AD patients and an AD mouse model. We also examined the effects of hBD-3 on autophagy activation in epidermal keratinocytes and its ability to mitigate IL-4 and IL-13-induced tight junction (TJ) barrier disruption. Autophagy was suppressed in epidermal keratinocytes from both AD patients and the AD mouse model (in vivo). Interestingly, hBD-3 activated autophagy in these keratinocytes in vitro and alleviated IL-4 and IL-13-mediated TJ barrier disruption. Autophagy deficiency led to impaired skin barrier function and exacerbated inflammation in vivo. However, hBD-3 ameliorated skin inflammation and strengthened the TJ barrier in AD. Notably, hBD-3-mediated TJ barrier improvement was absent in autophagy-deficient AD mice (in vivo), highlighting the essential role of autophagy in the regulation of skin barrier function and inflammation by hBD-3 in AD. This study suggests that hBD-3 plays a critical role in regulating the skin barrier and inflammation in AD through autophagy. hBD-3 holds potential as a therapeutic agent for skin diseases associated with autophagy dysfunction and skin barrier impairment, including AD.

Atopic dermatitis (AD) is a chronic inflammatory skin condition with evidence of defects in the barrier properties of the epidermis. Changes in the permeability properties of the tight junction have been reported in AD, and reversing this leaky tight junction may be a potential treatment for AD. This study aimed to determine the effect of larazotide, an antagonist of the protease-activated receptor 2, on the permeability and barrier properties of the tight junctions in keratinocyte monolayers. Normal human epithelial keratinocytes were grown in culture on permeable supports. The effects of larazotide on transepithelial resistance and permeability properties of keratinocyte monolayers were studied before and after histamine challenge. Larazotide mitigated the disruptive effect of histamine on epithelial permeability by increasing the electrical resistance and decreasing epithelial permeability. Larazotide may be beneficial as a topical therapeutic for AD; however, the permeability properties of the short-peptide larazotide through the uppers layers of the epidermis is currently unknown. In conclusion, the protease-activated receptor 2 antagonist larazotide has a protective effect on keratinocyte monolayers and may be useful as an adjunct therapeutic agent to enhance barrier function and promote epidermal healing in AD.

Although it is widely accepted that filaggrin (FLG) deficiency contributes to an abnormal barrier function in ichthyosis vulgaris and atopic dermatitis, the pathomechanism of how FLG deficiency provokes a barrier abnormality in humans is unknown. We report here that the presence of FLG mutations in Caucasians predicts dose-dependent alterations in epidermal permeability barrier function. Although FLG is an intracellular protein, the barrier abnormality occurred solely via a paracellular route in affected stratum corneum. Abnormal barrier function correlated with alterations in keratin filament organization (perinuclear retraction), impaired loading of lamellar body contents, followed by nonuniform extracellular distribution of secreted organelle contents, and abnormalities in lamellar bilayer architecture. In addition, we observed reductions in corneodesmosome density and tight junction protein expression. Thus, FLG deficiency provokes alterations in keratinocyte architecture that influence epidermal functions localizing to the extracellular matrix. These results clarify how FLG mutations impair epidermal permeability barrier function.

Human β-defensins (hBDs) are host defense peptides that not only exhibit microbicidal properties but also stimulate various cellular activities, including keratinocyte proliferation, migration, and wound healing. hBDs are overexpressed in the skin in cases of psoriasis but are downregulated in atopic dermatitis skin, although both diseases are associated with stratum corneum barrier defects. Because the tight-junction (TJ) barrier is also dysfunctional in both atopic dermatitis and psoriasis patients, we hypothesized that hBDs may regulate the TJ barrier function in keratinocytes. We observed that, among the hBDs tested, only hBD-3 increased the expression of several claudins and their localization along the cell-cell borders. In addition, hBD-3 elevated the transepithelial electrical resistance and reduced the paracellular permeability of keratinocyte layers, and this effect was reversed by the claudin inhibitor ochratoxin A, CCR6 antibody, and CCR6 small interfering RNA. Moreover, hBD-3 enhanced the activation of Rac1, atypical protein kinase C, glycogen synthase kinase-3, and phosphatidylinositol 3 kinase, which are required for the hBD-3-mediated regulation of the TJ barrier function, as evidenced by the effects of their respective inhibitors. Collectively, our findings provide evidence regarding the contribution of host defense peptides to the innate immunity of skin by regulating TJ barrier function, in addition to their antimicrobial and other immunomodulatory activities.

Defects in epidermal barrier function and/or vesicular transport underlie severe skin diseases including ichthyosis and atopic dermatitis. Tight junctions (TJs) form a single layered network in simple epithelia. TJs are important for both barrier functions and vesicular transport. Epidermis is stratified epithelia and lamellar granules (LGs) are secreted from the stratum granulosum (SG) in a sequential manner. Previously, continuous TJs and paracellular permeability barriers were found in the second layer (SG2) of SG in mice, but their fate and correlation with LG secretion have been poorly understood. We studied epidermal TJ-related structures in humans and in mice and found occludin/ZO-1 immunoreactive multilayered networks spanning the first layer of SG (SG1) and SG2. Paracellular penetration tracer passed through some TJs in SG2, but not in SG1. LG secretion into the paracellular tracer positive spaces started below the level of TJs of SG1. Our study suggests that LG-secretion starts before the establishment of TJ barrier in the mammalian epidermis.

Treatment of inflammatory skin diseases, including atopic dermatitis (AD) and psoriasis, is undergoing transformative changes, highlighting the need to develop experimental models of skin inflammation in humans to predict treatment responses. We topically or intradermally administered four common sensitizers (dust mite (DM), diphencyprone (DPCP), nickel (Ni), and purified protein derivative (PPD)) to the backs of 40 healthy patients and the skin hypersensitivity response was biopsied and evaluated using immunohistochemistry, RNA-seq, and RT-PCR. All agents induced strong increases in cellular infiltrates (T-cells and dendritic cells) as compared to untreated skin (p < .05), with variable T helper polarization. Overall, DPCP induced the strongest immune responses across all pathways, including innate immunity (IL-1α, IL-8), Th1 (IFNγ, CXCL10), Th2 (IL-5, CCL11), and Th17 (CAMP/LL37) products, as well as the highest regulatory tone (FOXP3, IL-34, IL-37) (FDR <0.01). Nickel induced Th17 (IL-17A), Th1 (CXCL10) and Th2 (IL-4R) immune responses to a lesser extent than DPCP (p < .05). PPD induced predominantly Th1 (IFNγ, CXCL10, STAT1) and Th17 inflammation (IL-17A) (p < .05). DM induced modulation of Th2 (IL-13, CCL17, CCL18), Th22 (IL-22), and Th17/Th22 (S100A7/9/12) pathways (p < .05). Barrier defects that characterize both AD and psoriasis were best modeled by DPCP and Ni, followed by PPD, including downregulation of terminal differentiation (FLG, FLG2, LOR, LCEs), tight junction (CLDN1/CLDN8), and lipid metabolism (FA2H, FABP7)-related markers. Our data imply that DPCP induced the strongest immune response across all pathways, and barrier defects characteristic of AD and psoriasis.

Atopic dermatitis (AD), a prevalent chronic inflammatory skin disorder, is characterized by compromised skin barrier and heightened immune responses. The study investigates the therapeutic efficacy of catestatin (CST), a chromogranin A-derived antimicrobial peptide, in mitigating AD-like symptoms. Utilizing both keratinocyte cultures and a C57BL/6 mouse model, we examined CST's impact on skin barrier proteins, tight junction (TJ) integrity, inflammatory cytokines, and AD-like symptoms. CST administration led to a significant upregulation of skin barrier proteins and improved TJ function, counteracting the negative effects of Th2 cytokines on these parameters. In a 2,4-dinitrochlorobenzene-induced AD mouse model, CST treatment markedly reduced AD-like symptoms, including ear thickness, transepidermal water loss, and scratching behavior, and normalized barrier protein expression and TJ barrier function. Furthermore, CST was found to interact with the Notch1 receptor, activating the Notch1/PKC pathway, which may underlie its skin barrier-enhancing properties. Collectively, these findings suggest CST as a promising therapeutic agent for AD, capable of enhancing skin barrier function, modulating immune responses, and targeting the Notch1/PKC pathway, offering a novel approach to AD treatment focusing on barrier restoration and immune modulation.

Mast cells play a critical role in the pathogenesis of atopic dermatitis (AD), a chronic inflammatory skin disease characterized by itch, eczema, and barrier dysfunction. These immune cells are abundant in the skin and are activated in response to allergens, irritants, and microbial products. Upon activation, mast cells release a variety of mediators, including histamine, proteases, cytokines, and chemokines, which contribute to the inflammation and pruritus observed in AD. Recent studies have highlighted the importance of mast cell-derived IL-4, IL-13, and IL-31 in promoting Th2-type immune responses and itch sensation. Moreover, interactions between mast cells and sensory neurons may further exacerbate neuroimmune inflammation. Mast cells also influence skin barrier integrity by modulating keratinocyte function and disrupting tight junctions. Their numbers and activation state are often elevated in AD lesions, correlating with disease severity. Targeting mast cell activation or blocking their mediators has shown promise in preclinical models, offering potential therapeutic strategies. Overall, mast cells are increasingly recognized as key contributors to the initiation and amplification of AD, making them an important focus for understanding disease mechanisms and developing new treatments.

This review presents recent evidence of impaired Notch signalling in atopic dermatitis (AD), which is proposed to represent the "a-topic" defect linking both epidermal and immunological barrier dysfunctions in AD. AD epidermis exhibits a marked deficiency of Notch receptors. Mouse models with genetically suppressed Notch signalling exhibit dry skin, signs of scratching, skin barrier abnormalities, increased transepidermal water loss and TH2 cell-mediated immunological changes closely resembling human AD. Notch signals are critically involved in the differentiation of regulatory T cells, in the feedback inhibition of activated innate immunity, in late epidermal differentiation associated with filaggrin- and stratum corneum barrier lipid processing. Most importantly, Notch deficiency induces keratinocyte-mediated release of thymic stromal lymphopoietin (TSLP). TSLP promotes TH2 cell-driven immune responses associated with enhanced production of interleukin (IL)-4 and IL-31. Both TSLP and IL-31 stimulate sensory cutaneous neurons involved in the induction of itch. Notably, Notch1 is a repressor of activator protein-1 (AP-1), which is upregulated in AD epidermis. Without Notch-mediated suppression of AP-1 this transcription factor promotes excess expression of TH2 cell-related cytokines. Impaired Notch signalling negatively affects the homeostasis of aquaporin 3 and of the tight junction component claudin-1, thus explains disturbed skin barrier function with increased transepidermal water loss and Staphylococcus aureus colonisation as well as increased cutaneous susceptibility for viral infections. Thus, accumulating evidence links deficient Notch signalling to key pathological features of AD.

Although atopic dermatitis (AD) often starts in early childhood, detailed tissue profiling of early-onset AD in children is lacking, hindering therapeutic development for this patient population with a particularly high unmet need for better treatments. We sought to globally profile the skin of infants with AD compared with that of adults with AD and healthy control subjects. We performed microarray, RT-PCR, and fluorescence microscopy studies in infants and young children (<5 years old) with early-onset AD (<6 months disease duration) compared with age-matched control subjects and adults with longstanding AD. Transcriptomic analyses revealed profound differences between pediatric patients with early-onset versus adult patients with longstanding AD in not only lesional but also nonlesional tissues. Although both patient populations harbored T Skin samples from children and adult patients with AD share lipid metabolism and tight junction alterations, but epidermal differentiation complex defects are only present in adult AD, potentially resulting from chronic immune aberration that is not yet present in early-onset disease.

(1) Background: Atopic dermatitis is one of the most common inflammatory skin diseases characterized by T helper (Th) 2 and Th22 cells producing interleukin (IL)-4/IL-13 and IL-22, respectively. The specific contribution of each cytokine to the impairment of the physical and the immune barrier via Toll-like receptors (TLRs) is poorly addressed concerning the epidermal compartment of the skin. (2) Methods: The effect of IL-4, IL-13, IL-22, and the master cytokine IL-23 is evaluated in a 3D model of normal human skin biopsies (n = 7) at the air-liquid interface for 24 and 48 h. We investigated by immunofluorescence the expressions of (i) claudin-1, zonula occludens (ZO)-1 filaggrin, involucrin for the physical barrier and (ii) TLR2, 4, 7, 9, human beta-defensin 2 (hBD-2) for the immune barrier. (3) Results: Th2 cytokines induce spongiosis and fail in impairing tight junction composition, while IL-22 reduces and IL-23 induces claudin-1 expression. IL-4 and IL-13 affect the TLR-mediated barrier largely than IL-22 and IL-23. IL-4 early inhibits hBD-2 expression, while IL-22 and IL-23 induce its distribution. (4) Conclusions: This experimental approach looks to the pathogenesis of AD through molecular epidermal proteins rather than cytokines only and paves the way for tailored patient therapy.

Atopic dermatitis (AD) is the most common chronic and relapsing inflammatory skin disease. AD is typically characterized by skewed T helper (Th) 2 inflammation, yet other inflammatory profiles (Th1, Th17, Th22) have been observed in human patients. How cytokines from these different Th subsets impact barrier function in this disease is not well understood. As such, we investigated the impact of the canonical Th17 cytokine, IL-17A, on barrier function and protein composition in primary human keratinocytes and human skin explants. These studies demonstrated that IL-17A enhanced tight junction formation and function in both systems, with a dependence on STAT3 signaling. Importantly, the Th2 cytokine, IL-4 inhibited the barrier-enhancing effect of IL-17A treatment. These observations propose that IL-17A helps to restore skin barrier function, but this action is antagonized by Th2 cytokines. This suggests that restoration of IL-17/IL-4 ratio in the skin of AD patients may improve barrier function and in so doing improve disease severity.

To investigate the effect of emollient on atopic march in a murine model of atopic dermatitis (AD). Following induction of AD with topical calcipotriol (MC903) and ovalbumin (OVA), one group of mice was treated topically with a linoleic acid-ceramide-containing emollient, while mice without emollient treatment served as disease controls. After 28 days, clinical, histological and transcriptomic analyses were performed in the skin lesions and the lung as well as serum cytokine levels. Treatments of mice with MC903 and OVA induced a typical phenotype of AD, accompanied by increased expression levels of Th2 and basophil-related genes in the lung. Topical emollients markedly decreased the severity of skin lesions and inflammatory cell infiltration. Moreover, emollient treatments significantly downregulated expression levels of AD-related genes (286 of 1450 differentially expressed genes), including those related to innate inflammation (S100a8/a9, Il1b, Defb3/6, Mmp12), chemokines (Cxcl1/3, Ccl3/4) and epidermal permeability barrier (Krt2/6b/80, Serpinb12, Lce3e, Sprr2), etc. Downregulated genes were enriched in mitochondrial OXPHOS-related pathways, while upregulated genes were mainly enriched in axon guidance and tight junctions. Moreover, topical emollient treatments decreased total serum levels of IL-4, along with substantial reductions in IgE and thymic stromal lymphopoietin (TSLP) levels. Furthermore, 187 of 275 upregulated genes in lung tissue were also significantly downregulated, including those involved in leucocyte chemotaxis (Ccl9, Ccr2, Retnlg, Ccl3, Cxcl10, Il1r2, etc.) and basophil activation (Mcpt8, Cd200r3, Fcer1a, Ms4a2). In conclusion, topical emollient not only reduces skin inflammation, but also mitigates systemic inflammation by decreasing TSLP and IgE levels. Moreover, topical emollient reduces chemokine production and basophil infiltration and activation in the lung.

The aryl hydrocarbon receptor (AhR) is widely expressed in the skin. It controls immune-mediated skin responses to various external environmental signals, promote terminal differentiation of epidermal keratinocytes and participates the maintenance of the skin barrier function. As a therapeutic target, AhR activation modulates many diseases progression driven by immune/inflammatory processes such as atopic dermatitis (AD) and psoriasis. In this study, we revealed that GDU-952 is a novel AhR agonist, which is able to decreases IgE serum levels, to inhibit pro-inflammatory cytokines such as IL-6 and TNF-α and to induce immunoregulatory effects through restoring Th1/Th2 immune balance and promoting CD4

Betacellulin (BTC) is a peptide ligand that belongs to the epidermal growth factor family, the members of which have been implicated in skin morphogenesis, homeostasis, repair, and angiogenesis; however, the role of BTC in the regulation of the skin barrier remains unknown. To examine the role of BTC in skin barrier function, we analyzed atopic dermatitis (AD) transcriptomic data from Gene Expression Omnibus (GEO) datasets, performed BTC immunohistochemistry using human skin tissues, and evaluated the effects of BTC on primary human keratinocytes by real-time PCR, Western blotting, and assay of the transepidermal electrical resistance (TER), a functional parameter to monitor the tight junction barrier. We found that the gene expression of BTC was downregulated in skin lesions from patients with AD, and this downregulated expression recovered following biological treatments. Consistently, the BTC protein levels were downregulated in the lesional skin of AD patients compared with the normal skin of healthy participants, suggesting that the BTC levels in skin might be a biomarker for the diagnosis and therapy of AD. Furthermore, in human keratinocytes, BTC knockdown reduced the levels of skin-derived antimicrobial peptides and skin barrier-related genes, whereas BTC addition enhanced their levels. Importantly, in human skin equivalents, BTC restored the increased tight junction permeability induced by Th2 cytokine IL-4/IL-13 treatment. In addition, specific inhibitors of epidermal growth factor receptor (EGFR) and protein kinase C (PKC) abolished the BTC-mediated improvement in skin barrier-related proteins in keratinocyte monolayers. Collectively, our findings suggest that treatment with BTC might improve the Th2-type cytokine-mediated impairment of skin barrier function through the EGFR/PKC axis and that BTC might be a novel potential biomarker and therapeutic target for the treatment of skin conditions characterized by the overproduction of Th2 cytokines and dysfunctional skin barriers, such as AD.

Qing-Re-Chu-Shi Decoction (QRCSD), a traditional Chinese herbal formula, has been employed as a complementary and alternative therapy for inflammatory skin diseases. However, its active constituents and the mechanistic basis of its action on atopic dermatitis remain in adequately understood. Atopic dermatitis (AD) is an allergic dermatitis marked by eczematous lesions and pruritus. The study aimed to elucidate the underlying effects of QRCSD on AD and to identify the components responsible for its therapeutic efficacy in a mouse model. Network pharmacology and UPLC-mass analysis were used to anticipate the pharmacological mechanisms and to identify active components of QRCSD, respectively. A DNCB-induced AD-like model was established in NC/Nga mice. QRCSD or prednisolone (as a positive control) was administered via gavage every other day from day14 to day 21. Dermatitis severity score, scratching behavior, skin barrier function, spleen index, Th1/Th2 lymphocyte ratio, and serum IgE levels were evaluated. Protein arrays, including 40 inflammatory cytokines, were performed on skin lesions, followed by confirmation experiments of Western blotting in dorsal skin lesions. The construction of a QRCSD-AD-Network and topological analysis firstly proposed potential targets of QRCSD acting on AD. Animal experiments demonstrated that oral administration of QRCSD ameliorated AD-like lesions, reduced epidermal thickness and mast cell count, decreased serum IgE levels, augmented tight junction protein (Claudin 1, Occludin) levels, and regulated the Th1/Th2 balance in the spleen, as well as spleen index. Elevated levels of interleukin (IL)-4, IL-5, IL-6, IL-17, and Eotaxin were revealed in AD-like skin lesions by protein arrays. Western blotting confirmed that the phosphorylation levels of ERK, P38, JNK, STAT3 and P65 were downregulated, and IL-6 expression was also reduced following QRCSD treatment. The study enhances the understanding of the anti-inflammatory and immunomodulatory effects of QRCSD, showcasing its significant protective role against atopic dermatitis. Treatment with QRCSD may be considered as a viable candidate for complementary and alternative therapy in managing atopic dermatitis.

Calycosin, a bioactive component derived from Astragali Radix (AR; Huang Qi), has been shown to have an effect of anti-allergic dermatitis with unknown mechanism. This study aims to investigate the mechanism of calycosin related to tight junctions (TJs) and HIF-1α both in FITC-induced mice allergic contact dermatitis and in IL-1β stimulated HaCaT keratinocytes. Th2 cytokines (IL-4, IL-5 and IL-13) were detected by ELISA. The epithelial TJ proteins (occludin, CLDN1 and ZO-1), initiative key cytokines (TSLP and IL-33) and HIF-1α were assessed by Western blot, real-time PCR, immunohistochemistry or immunofluorescence. Herein, we have demonstrated that allergic inflammation and the Th2 cytokines in ACD mice were reduced significantly by calycosin treatment. Meanwhile, calycosin obviously decreased the expression of HIF-1α and repaired TJs both in vivo and in vitro. In HaCaT keratinocytes, we noted that IL-1β induced the deterioration of TJs, as well as the increased levels of TSLP and IL-33, which could be reversed by silencing HIF-1α. In addition, administration of 2-methoxyestradiolin (2-ME), a HIF-1α inhibitor,significantly repaired the TJs and alleviated the allergic inflammation in vivo. Furthermore, TJs were destroyed by DMOG or by overexpressing HIF-1α in HaCaT keratinocytes, and simultaneously, calycosin down-regulated the expression of HIF-1α and repaired the TJs in this process. These results revealed that calycosin may act as a potential anti-allergy and barrier-repair agent via regulating HIF-1α in AD and suggested that HIF-1α and TJs might be possible therapy targets for allergic dermatitis.

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Epidermal keratinocytes form the outermost layer of the skin and serve as a pivotal barrier against external insults. This barrier, however, can be compromised in conditions such as atopic dermatitis (AD), where both genetic and environmental factors contribute to its disruption. Recent studies have indicated that macropinocytosis, a non-selective endocytic process, is involved in the internalization of barrier proteins. In this study, we explored the role of macropinocytosis in differentiated keratinocytes and its potential impact on skin barrier integrity in AD. Our results demonstrated that epidermal growth factor (EGF), but not the type 2 cytokines IL-4 and IL-13, significantly promoted macropinocytosis in differentiated HaCaT keratinocytes. EGF stimulation increased the uptake of 70 kDa dextran and induced the internalization of occludin, a component of tight junction proteins. Furthermore, enhanced macropinocytosis was observed in the epidermis of a mouse model of AD, accompanied by elevated EGF expression in the skin, indicating that the AD skin microenvironment may drive this process. NAV1 was identified as a critical regulator of EGF-induced macropinocytosis, as its knockdown significantly impaired this process. Transcriptome analysis of NAV1-knockdown cells further revealed changes in the expression of Rho family GTPases, including CDC42 and MMP14, suggesting that NAV1 modulates macropinocytosis through Rho-dependent pathways. These findings provide new insights into the regulation of macropinocytosis in keratinocytes and its potential contribution to the barrier dysfunction observed in AD.

Atopic dermatitis (AD) is a chronic inflammatory skin disease. Many studies investigating AD pathogenesis and its therapy have been conducted but none have been successful. One of the causes of AD is dysfunction of tight junctions through reduction of claudin 1 expression in the epidermal barrier of the skin. In the present study, we investigated the role of bortezomib (BTZ) in the restoration of the reduced expression of claudin 1. Immunoblot and immunofluorescence analyses revealed that BTZ increased the protein expression level of claudin 1 in the human keratinocyte cell line HaCaT, thereby forming paracellular barriers. Furthermore, repeated application of BTZ alleviated atopic symptoms on the backs and ears of 2, 4-dinitrochlorobenzene (DNCB)-induced AD mice, and led to the formation of normal tight junctions in the epidermal barrier of DNCB-induced mice skin. Taken together, these results demonstrate that BTZ-induced claudin 1 expression may be a valuable therapeutic approach for AD.

Atopic dermatitis (AD) is a common inflammatory skin disorder that affects children and adults. Despite the pathology of AD involves in immune dysfunction and epidermal barrier function destruction has been found, the mechanism of immune activation and barrier damage remain largely unknown. In the present study, The TNF-α/IFN-γ-stimulated HaCaTs, organotypic AD-like 3D skin equivalents and AD-like mouse model were constructed. The mRNA, histological morphology, protein levels, cytokines were detected by real-time quantitative polymerasechain reaction (RT-qPCR), hematoxylin and eosin (H & E) staining, Immunohistochemistry (IHC), immunoblotting, immunofluorescence (IF) staining, and enzyme linked immunosorbent assay (ELISA), respectively. Cell viability, cell cycle, and apoptosis were respectively calculated using a Methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay and flow cytometry. A dual-luciferase reporter gene system was used to investigate the relationship between miR-1294 and STAT3. Compared with the control group, the expression of miR-1294 decreased in TNF-α/IFN-γ-stimulated HaCaTs (P < 0.001), AD-like skin model, and AD-like mouse model (P < 0.001). Moreover, STAT3 was documented as a direct target of miR-1294. Inflammation (P < 0.05) and epidermal barrier function destruction (P < 0.05) in AD was suppressed by overexpression of miR-1294 but enhanced by STAT3 upregulation and its downstream NF-κB pathway. We also found miR-1294 upregulation inhibited inflammation and epidermal barrier function destruction via targeting STAT3 to suppress NF-κB pathway activation in AD.

The epidermis, the most superficial layer of the human skin, serves a critical barrier function, protecting the body from external pathogens and allergens. Dysregulation of epidermal differentiation contributes to barrier dysfunction and has been implicated in the pathology of various dermatological diseases, including atopic dermatitis (AD). Mucopolysaccharide polysulphate (MPS) is a moisturising agent used to treat xerosis in patients with AD. However, its mechanism of action on keratinocytes, the main constituents of the epidermis, remains unclear. In this study, we investigated the effect of MPS on keratinocytes by subjecting adult human epidermal and three-dimensional cultured keratinocytes to MPS treatment, followed by transcriptome analysis. The analysis revealed that MPS treatment enhances keratinocyte differentiation and suppresses proliferation. We focused on amphiregulin (AREG), a membrane protein that belongs to the epidermal growth factor (EGF) family and possesses a heparin-binding domain, as a significant target among the genes altered by MPS. MPS exerted an inhibitory effect directly on AREG, rather than on EGF receptors or other members of the EGF family. Furthermore, AREG leads to a reduction in epidermal barrier function, whereas MPS contributes to barrier enhancement via AREG inhibition. Collectively, these findings suggest that MPS modulates barrier function through AREG inhibition, offering insights into potential therapeutic strategies for skin barrier restoration.

Atopic dermatitis (AD) is a common chronic inflammatory skin disease that results in significant morbidity. A hallmark of AD is disruption of the critical barrier function of upper epidermal layers, causatively linked to environmental stimuli, genetics, and infection, and a critical current target for the development of new therapeutic and prophylactic interventions. Staphylococcus aureus is an AD-associated pathogen producing virulence factors that induce skin barrier disruption in vivo and contribute to AD pathogenesis. We show, using immortalized and primary keratinocytes, that S. aureus protease SspA/V8 is the dominant secreted factor (in laboratory and AD clinical strains of S. aureus) inducing barrier integrity impairment and tight junction damage. V8-induced integrity damage was inhibited by an IL-1β-mediated mechanism, independent of effects on claudin-1. Induction of keratinocyte expression of the antimicrobial/host defense peptide human β-defensin 2 (hBD2) was found to be the mechanism underpinning this protective effect. Endogenous hBD2 expression was required and sufficient for protection against V8 protease-mediated integrity damage, and exogenous application of hBD2 was protective. This modulatory property of hBD2, unrelated to antibacterial effects, gives new significance to the defective induction of hBD2 in the barrier-defective skin lesions of AD and indicates therapeutic potential.

Previous studies have shown that enolase-1 (ENO1) in the stratum corneum (SC) is more highly expressed in patients with atopic dermatitis (AD) than in healthy individuals, suggesting that it is a novel biomarker for evaluating skin condition in patients with AD. However, the mechanism underlying high ENO1 expression in the SC and its pathological relevance in AD are unclear. In this study, the relationship between ENO1 expression and keratinization of epidermis was investigated, and the role of high ENO1 expression in keratinocytes was characterized. ENO1 expression and morphological characteristics were examined in SC from the cheeks of 24 patients with AD. Additionally, the localization of ENO1 in the excised human epidermis was observed. Moreover, to analyse the role of ENO1 in cellular barrier function, tight junction proteins (TJs) and transepithelial electrical resistance (TEER) in keratinocytes with ENO1 overexpression were evaluated. Furthermore, the localization of ENO1 and plasminogen in keratinocytes was evaluated by immunostaining, and the cellular barrier function in keratinocytes was examined after treatment with tranexamic acid (TXA). ENO1 expression was substantially correlated with the rate of nucleated corneocytes in AD. In addition, ENO1 localized in the basal to spinous layers, but was its expression dramatically decreased in healthy human SC. ENO1 overexpression in human epidermal keratinocytes reduced the expression of TJs (claudin-4, E-cadherin, tricellulin, and occludin) and TEER, and treatment with anti-ENO1 IgG reversed these effects. ENO1 colocalized with plasminogen in keratinocytes. Treatment with TXA rescued the ENO1-induced reductions in TJ and TEER expression. We found a substantial correlation between ENO1 expression and the rate of nucleated corneocytes in AD and decreased ENO1 expression with nuclear disappearance. These results suggest that high ENO1 expression in the SC of AD is caused by deficient keratinization, which is an AD characteristic. Moreover, ENO1 overexpression in keratinocytes promoted dysfunction of TJ dynamics, leading to reduced integrity of the cellular barrier, and these effects might be mediated by plasmin activity. We propose that ENO1 is a useful indicator of parakeratosis and might have a potential role in cellular TJ barrier function in the epidermis.

Atopic dermatitis (AD) is a common inflammatory skin disorder, characterized by skin barrier defects and enhanced allergen priming. Null mutations in the filaggrin gene (FLG) are strongly associated with moderate to severe AD, but the pathways linking barrier dysfunction and cutaneous inflammation are still largely unknown. To assess alteration of endogenous cysteine protease activity in FLG-deficient keratinocytes, and to determine whether the alteration in cysteine protease activity affects epidermal barrier function and associated gene and protein expression. We established a stable FLG knockdown cell line, and reconstructed epidermal equivalents in vitro. Barrier function of the reconstructed epidermis, the barrier-associated genes and proteins, and the activity of endogenous cysteine proteases were tested. Inhibitors of cysteine proteases were used to further evaluate the role of endogenous cysteine proteases in epidermal barrier function. FLG knockdown induced impaired epidermal barrier function. Microarray, western blotting and fluorescence staining showed reduced expression of K10, ZO-1, E-cadherin, claudin-1 and occludin in FLG knockdown keratinocytes. Compared with cysteine protease activity in control cells, protease activity was dramatically enhanced in FLG knockdown keratinocytes. Furthermore, administration of cysteine protease inhibitors significantly recovered expression of K10 and tight junction proteins, and the barrier defect induced by FLG deficiency. This is the first observation of elevated endogenous cysteine protease activity in FLG-deficient keratinocytes, which may play an important role in impaired barrier function in AD skin. Modulation of cysteine protease activity might be a novel therapeutic approach for AD treatment.

BACKGROUND AND OBJECTIVE Atopic dermatitis (AD) is a chronic inflammatory itchy skin condition. Genomic- and epigenetic wide association studies provide insights into the genetic susceptibility and potential underlying disease pathogenesis. This study sought to functionally characterise an AD-associated single nucleotide polymorphism (SNP) located deep intronic of the tight junction protein 2 (TJP2) gene (9q21.11 locus), identified through a genome-wide association study (GWAS). METHODS The association between the 9q21.11 locus (rs7872806) and AD was identified through a GWAS of 956 cases and 723 controls. TJP2 expression in peripheral blood mononuclear cells (PBMCs) was assessed against the rs7872806 genotypes. Allele-specific methylation was evaluated at CpG sites 10kb up- and down-stream of the 9q21.11 locus. Effects of DNA methylation on TJP2 expression was validated via in vitro methylation and 5-aza-2'-deoxycytidine-induced transcriptional activation studies. Trans-epidermal water loss measurements were used to determine skin barrier function. RESULTS The major allele of rs7872806 was determined to increase AD risk by 2.64-fold (adjusted p-value=2.40 x 10-18, OR=0.38), associated with increased methylation levels at cg13920460 site (p<0.001) and lower TJP2 expression in PBMCs (Pearson's p=1.09 x 10-6, Pearson's R=-0.313, p<0.001). Methylation inhibition by 5-aza-2'-deoxycytidine increased TJP2 promoter activity by up to 85%. Elimination of the cg13920460 methylation site increased expression by approximately 25%. The rs7872806 major allele was also found to be associated with increased trans-epidermal water loss (p<0.001). CONCLUSION Epigenetic influence at CpG site cg13920460 is associated with rs7872806 located deep intronic at 9q21.11. The SNP confers susceptibility to AD through altering TJP2 expression and promoting trans-epidermal water loss.

Topical probiotic formulations containing Lactobacillus plantarum have emerged as a promising intervention for enhancing skin barrier repair in atopic dermatitis (AD), a chronic inflammatory condition characterized by disrupted epidermal barrier function and heightened susceptibility to irritants and allergens. Lactobacillus plantarum exerts its therapeutic effects through multiple mechanisms, including modulation of the skin microbiome, suppression of pro-inflammatory cytokines, and promotion of epidermal barrier integrity. By rebalancing microbial diversity, L. plantarum reduces the overgrowth of pathogenic species such as Staphylococcus aureus, which are known to exacerbate inflammation and compromise barrier function in AD. Furthermore, L. plantarum enhances the production of key structural components of the epidermis, including ceramides and tight junction proteins, which are critical for maintaining barrier strength and preventing transepidermal water loss (TEWL). Preclinical and clinical studies have demonstrated significant improvements in key metrics of AD severity, such as reductions in erythema, pruritus, and TEWL, following the application of L. plantarum-enriched formulations. The probiotic also attenuates immune responses by downregulating Th2-mediated inflammation, thereby reducing the cycle of barrier disruption and inflammation that typifies AD. Emerging research suggests synergistic effects when L. plantarum is combined with conventional therapies such as corticosteroids and calcineurin inhibitors, providing a multifaceted approach to disease management. L. plantarum has been found to have tremendous potential as a non-invasive, adjunctive therapy that addresses both microbial and barrier dysfunctions in AD, paving the way for innovative treatment paradigms that target the

Atopic dermatitis is a chronic, inflammatory, and pruritic skin disease affecting both humans and animals. The pathogenesis of Canine Atopic Dermatitis (CAD) involves a complex interplay of genetic factors, such as skin barrier defects and immune dysregulation, as well as environmental triggers. Identifying the role of individual factors in CAD progression through clinical observational studies in atopic dogs remains challenging. This study aimed to develop an in vitro organoid model that accurately recapitulates the morphological and molecular characteristics of CAD. Canine Primary Epidermal Organoids (cPEOs) were cultured from normal canine keratinocytes and treated with Th2 cytokines (IL-4, IL-13) and TNF-α to mimic atopic skin. Morphological changes in the organoids were assessed through histological analysis and transmission electron microscopy. Molecular markers, including keratins 5 and 10, filaggrin, involucrin, loricrin, tight junction proteins, Ki67 (proliferation), and caspase-3 (apoptosis), were evaluated via RT-qPCR and/or immunostaining. Cytokine treatment induced morphological and molecular characteristics in cPEOs reminiscent of CAD, including epidermal spongiosis and reduced suprabasal keratinocyte differentiation. Th2 cytokines increased keratinocyte proliferation while TNF-α appeared to induce cellular apoptosis within the organoid model. Since these organoids effectively mimic CAD characteristics, they can serve as a valuable model system to delineate the effects of multiple factors involved in the pathogenesis of this condition. Furthermore, this organoid platform could be utilized to identify novel therapeutic approaches and test the efficacy of potential novel treatments.

Colonization of Staphylococcus aureus (S. aureus) is a crucial factor aggravating atopic dermatitis (AD). Berberine (BBR) is the main effective component of Coptis chinensis against bacteria. To explore the potential mechanism by which BBR inhibits the progression of AD caused by S. aureus. S. aureus was cultured with a BBR-added medium to verify the bacteriostatic effect of BBR. Effects of BBR on the expressions of TTC39A-AS1, hsa-miR-3936, and RNASE3 were detected by qPCR, and the dual luciferase assay and overexpression assay were used to demonstrate the regulation among them. The roles of them in S. aureus-induced injury of human primary epidermal keratinocytes (HEKs) were evaluated by their exogenous expressions. The growth, inflammation, and tight junction were evaluated by CCK-8 assay, detection of inflammatory factors, and measurement of transepithelial electrical resistance (TEER) value, to evaluate the impairment of HEKs. BBR significantly inhibited the reproduction of S. aureus and improved the damage to HEKs function caused by it. The stimulation of S. aureus significantly inhibited the growth and tight junction function of HEKs and induced the inflammatory response. These changes were exacerbated by overexpression of TTC39A-AS1 or RNASE3, and reversed by upregulation of hsa-miR-3936. TTC39A-AS1 promoted RNASE3 expression by targeting hsa-miR-3936. Moreover, BBR visibly inhibited the expressions of TTC39A-AS1 and RNASE3 and up-regulated hsa-miR-3936. In conclusion, BBR has the potential to alleviate AD by modulating the TTC39A-AS1/hsa-miR-3936/RNASE3 axis.

Atopic dermatitis (AD) is a chronic inflammatory skin disease. A hallmark of AD is dry itchy skin that results from defects in the epidermal barrier function. Aloe vera is used widely to promote general health and is administered topically to treat skin conditions such as eczema, burns and wounds. However, effects of A vera on AD were not fully elucidated. In this study, we investigated the oral administration of processed A vera gel (PAG) containing low molecular weight Aloe polysaccharides to treat ovalbumin (OVA)‐induced AD in mice. Oral administration of PAG suppressed total and OVA‐specific IgE production in sera and decreased the epidermal thickness of skin. Numbers of Ki‐67‐positive cells were reduced by PAG treatment. Expression levels of tight junction genes, including those that encode ZO‐1, Claudin‐1 and Claudin‐8, were decreased in AD skin lesions, whereas oral administration of PAG partially restored the expression levels of tight junction genes. In addition, IL‐4 and IL‐17A mRNA transcript levels were reduced in skin lesions after PAG treatment. Taken together, our findings suggest that oral administration of PAG ameliorated AD, normalized tight junction gene expression and suppressed inflammatory cytokines in AD skin.

BACKGROUND The aberrant expression of tight junction (TJ) proteins play an important role in several diseases with impaired skin barriers, including atopic dermatitis, psoriasis, and chronic wounds. The evidence provided thus far suggests an important role of calcitriol in skin homeostasis. However, it is not known whether calcitriol improves the impaired skin barrier. OBJECTIVE To investigate the effect of calcitriol on TJ barrier function in human primary keratinocytes. METHODS Normal human primary keratinocytes were stimulated with calcitriol, and the expression of TJ-related proteins was measured by real-time PCR and Western blotting. Immunofluorescence was used to examine the intercellular distribution of TJ-related proteins. TJ barrier function was assessed by the transepithelial electrical resistance (TER) assay. RESULTS We demonstrated that calcitriol increased the expression levels of TJ-related proteins, including claudin-4, claudin-7, occludin, and zonula occludens (ZO)- 1. Calcitriol enhanced the distribution of TJ-related proteins at cellcell borders and induced the phosphorylation of pathways involved in the regulation of TJ barrier function, such as atypical protein kinase C (aPKC), Ras-related C3 botulinum toxin substrate 1 (Rac1), phosphoinositide 3-kinase (PI3K), and protein kinase B (Akt), as evidenced by the effects of specific inhibitors on the above pathways. Indeed, we confirmed that calcitriol enhanced TER in keratinocyte monolayers. CONCLUSION These findings showed that calcitriol could modify the expression of keratinocyte TJ proteins, contributing to the maintenance of homeostatic barrier function.

Skin barrier dysfunction and thin epidermis are hallmarks of sensitive skin and contribute to premature aging. Avenanthramides are the primary bioactive components of colloidal oatmeal, a commonly used treatment to enhance skin barrier function. This study investigated the relationship between skin barrier function and epidermal characteristics and explored the potential of dihydroavenanthramide D (dhAvD), a synthetic avenanthramide, to improve the skin barrier. We observed a significant correlation between impaired skin barrier function and decreased epidermal thickness, suggesting that a weakened barrier contributes to increased sensitivity. Our in vitro results in HaCaT cells demonstrated that dhAvD enhances keratinocyte proliferation, migration, and tight junction protein expression, thereby strengthening the skin barrier. To mimic skin barrier dysfunction, we treated keratinocytes and full-thickness skin equivalents with IL-4 and IL-13, cytokines that are implicated in atopic dermatitis, and confirmed the downregulation of tight junction and differentiation markers. Furthermore, dhAvD treatment restored the barrier function and normalized the expression of key epidermal components, such as tight junction proteins and natural moisturizing factors, in keratinocytes treated with inflammatory cytokines. In the reconstructed human skin model, dhAvD promoted both epidermal and dermal restoration. These findings suggest that dhAvD has the potential to alleviate skin sensitivity and improve skin barrier function.

Tight junctions (TJs) are important factors constituting the physical barriers of the skin, and their suppression has been described in various conditions, such as aged skin and atopic dermatitis lesions. However, the methods for improving skin TJ function remain insufficient. Therefore, to obtain compounds that can improve TJ function, we developed a novel high-throughput screening system termed live-cell immunostaining to evaluate cell surface-localized claudin-1 (CLDN1) with high selectivity using normal human epidermal keratinocytes (NHEKs). Heparinoid and phospho-pyridoxal (p-Pyr), a metabolite of pyridoxine, were identified as hit compounds. In addition, heparinoid was strongly suggested to increase CLDN1 expression by inhibiting epidermal growth factor receptor signaling. By contrast, p-Pyr did not enhance CLDN1 expression, but it accelerated the translocation of CLDN1 to the cell surface. Finally, we confirmed that heparinoid and p-Pyr improved barrier function in NHEKs in a transepithelial electrical resistance assay. In conclusion, heparinoid and p-Pyr could potentially ameliorate skin conditions by improving TJ function.

Atopic dermatitis (AD) is a non-infectious inflammatory skin disease characterized by persistent itching of the skin, and it has become a global health problem with increasing incidence and complex pathogenesis. Momordin Ic (MMI) is a triterpenoid saponin that has anti-inflammatory effect and may play an effective role in the treatment of AD. To explore the molecular mechanism of MMI in relieving AD, and to provide some experimental data for the clinical application of MMI in AD. The mRNA levels of IL-33, IL-4 and NF-κB were detected by RT-qPCR. The protein expressions of Filaggrin, Claudin-1, MyD88 and NLRP3 were detected by western blotting. Transepithelial/transendothelial electrical resistance (TEER) method was used to detect the tight-junction function of HaCaT cells. Molecular docking experiment was performed on CB-DOCK2 to predict the binding of MMI and NLRP3. MMI reversed the decrease of filaggrin protein expression and intercellular resistance in HaCaT cells induced by TNF-α and IFN-γ. In addition, MMI reversed the increase in IL-33 and IL-4 mRNA levels in HaCaT cells treated with TNF-α and IFN-γ. In addition, MMI promoted the expression of Claudin-1 and inhibited the expression of MyD88 and NLRP3. In addition, the molecular docking results showed that MMI and NLRP3 had interaction sites. MMI improved the inflammatory response of HaCaT cells by regulating the expression of Claudin-1/MyD88 and targeting NLRP3, which may act a positive role in relieving AD.

Atopic dermatitis and psoriasis are prevalent chronic inflammatory skin diseases that are characterized by dysfunctional skin barriers and substantially impact patients’ quality of life. Vitamin D3 regulates immune responses and keratinocyte differentiation and improves psoriasis symptoms; however, its effects on atopic dermatitis remain unclear. Here, we investigated the effects of calcitriol, an active form of vitamin D3, on an NC/Nga mouse model of atopic dermatitis. We observed that the topical application of calcitriol decreased the dermatitis scores and epidermal thickness of NC/Nga mice with atopic dermatitis compared to untreated mice. In addition, both stratum corneum barrier function as assessed by the measurement of transepidermal water loss and tight junction barrier function as evaluated by biotin tracer permeability assay were improved following calcitriol treatment. Moreover, calcitriol treatment reversed the decrease in the expression of skin barrier-related proteins and decreased the expression of inflammatory cytokines such as interleukin (IL)-13 and IL-33 in mice with atopic dermatitis. These findings suggest that the topical application of calcitriol might improve the symptoms of atopic dermatitis by repairing the dysfunctional epidermal and tight junction barriers. Our results suggest that calcitriol might be a viable therapeutic agent for the treatment of atopic dermatitis in addition to psoriasis.

Atopic dermatitis is a chronic inflammatory skin condition characterized by immune dysregulation and dysfunction of the epidermal barrier. Although occludin, a vital tight junction protein, is essential for preserving barrier integrity, very little is known about its potential as a serum biomarker in atopic dermatitis. This pilot case-control study measured serum occludin levels in 30 adult atopic dermatitis patients and 30 age- and sex-matched healthy controls between May and August 2025, using a commercially available sandwich enzyme-linked immunosorbent assay (ELISA) kit. Findings showed serum occludin levels were significantly higher in atopic dermatitis patients (mean: 2.50 ± 1.10 ng/mL) compared to healthy controls (mean: 0.68 ± 0.69 ng/mL; p < 0.001), with levels showing a decreasing trend with age. Serum occludin exhibited high diagnostic performance [area under the curve (AUC) = 0.92] and represents a sensitive and specific, non-invasive biomarker for atopic dermatitis. These preliminary findings lay the groundwork for future studies exploring serum occludin as a potential biomarker for atopic dermatitis assessment.

Individuals with underlying chronic skin conditions, notably atopic dermatitis (AD), are disproportionately affected by infections from members of the herpesviridae, papovaviridae, and poxviridae families. Many patients with AD experience recurrent, widespread cutaneous viral infections that can lead to viremia, serious organ complications, and even death. Little is known about how the type 2 inflammatory environment observed in the skin of AD patients impacts the susceptibility of epidermal cells (keratinocytes) to viral pathogens. Herein, we studied the susceptibility of keratinocytes to the prototypical poxvirus, vaccinia virus (VV)—the causative agent of eczema vaccinatum—under conditions that simulate the epidermal environment observed in AD. Treatment of keratinocytes with type 2 cytokines (IL-4 and -13) to simulate the inflammatory environment or a tight junction disrupting peptide to mirror the barrier disruption observed in AD patients, resulted in a differentiation-dependent increase in susceptibility to VV. Furthermore, pan JAK inhibition was able to diminish the VV susceptibility occurring in keratinocytes exposed to type 2 cytokines. We propose that in AD, the increased viral susceptibility of keratinocytes leads to enhanced virus production in the skin, which contributes to the rampant dissemination and pathology seen within patients.

Three integral membrane proteins, clau- din-1, -2, and occludin, are known to be components of tight junction (TJ) strands. To examine their ability to form TJ strands, their cDNAs were introduced into mouse L fibroblasts lacking TJs. Immunofluorescence microscopy revealed that both FLAG-tagged claudin-1 and -2 were highly concentrated at cell contact sites as planes through a homophilic interaction. In freeze-fracture replicas of these contact sites, well-developed networks of strands were identified that were similar to TJ strand networks in situ and were specifically labeled with anti-FLAG mAb. In glutaraldehyde-fixed samples, claudin-1–induced strands were largely associated with the protoplasmic (P) face as mostly continuous structures, whereas claudin-2–induced strands were discontinuous at the P face with complementary grooves at the extracellular (E) face which were occupied by chains of particles. Although occludin was also concentrated at cell contact sites as dots through its homophilic interaction, freeze-fracture replicas identified only a small number of short strands that were labeled with anti-occludin mAb. However, when occludin was cotransfected with claudin-1, it was concentrated at cell contact sites as planes to be incorporated into well- developed claudin-1–based strands. These findings suggested that claudin-1 and -2 are mainly responsible for TJ strand formation, and that occludin is an accessory protein in some function of TJ strands.

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Atopic dermatitis (AD) is featured with impaired skin barrier. The stratum corneum (SC) and the intercellular tight junctions (TJs) constitute the permeability barrier, which is essential to protect the host water loss and pathogen entrance. The epidermal barrier is constantly renewed by differentiating keratinocytes through cornification, during which autophagy contributes to organelles and nucleus elimination. The human GSDMA and its mouse homologs Gsdma1-3 are expressed in the suprabasal epidermis. Although a pyroptotic role for GSDMA/Gsdma1 in host defense against Streptococcus pyogenes has been reported, the physiological function of Gsdma1/a2/a3 in epidermal homeostasis remains elusive. Herein, through repeated epidermal barrier disruption, we found that TJ formation and SC maturation were defective in the Gsdma1/a3-deficient epidermis. Using comparative gene profiling analysis, mitochondrial respiration measurement, and in vivo tracing of mitophagy, our data indicate that Gsdma1/a3 activation leads to mitochondrial dysfunction and subsequently facilitates mitochondrial turnover and epidermal cornification. In calcipotriol (MC903)-induced AD-like animal model, we demonstrated that Gsdma1/a3-deficiency selectively enhanced the Th2 response. Remarkably, the GSDMA expression is reduced in the epidermis of patients with AD compared to normal individuals. Gsdma1/a3-deficiency might be involved in AD pathogenesis, likely through GSDMA-mediated epidermal differentiation and cornification.

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Although modulation of claudin-1-based tight junction (TJ) in stratum granulosum is an option for transdermal absorption of drugs, granular permeation enhancers have never been developed. We previously found that homoharringtonine (HHT), a natural alkanoid, weakened intestinal epithelial barrier with changing expression and cellular localization of TJ components such as claudin-1 and claudin-4. In the present study, we investigated whether HHT is an epidermal granular permeation enhancer. Treatment of normal human epidermal keratinocytes (NHEK) cells with HHT decreased claudin-1 and claudin-4 but not zonula occludens-1 and E-cadherin. HHT lowered TJ-integrity in NHEK cells, accompanied by permeation-enhancement of dextran (4 kDa) in a dose-dependent manner. Transdermal treatment of mice with HHT weakened epidermal barrier. HHT treatment enhanced transdermal absorption of dextran with a molecular mass of up to 10 kDa. Together, HHT may be a transdermal absorption enhancer.

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ABSTRACT Epidermal permeability barrier defects are associated with several skin diseases, including atopic dermatitis (AD). Using an AD mouse model, we previously demonstrated that topically administered small extracellular vesicles (sEVs) (prepared following the International Society of Extracellular Vesicles recommendations) from human adipose tissue‐derived mesenchymal stem cells (ASC) ameliorate skin inflammation and normalize barrier function in parallel with increased ceramide (a key barrier lipid) production. To elucidate how ASC‐sEVs alleviate these AD skin abnormalities, we characterized lipids and ceramide metabolic enzymes in ASC‐sEVs versus donor ASCs. Our study revealed that free fatty acid, ceramide, and sphingomyelin are enriched in ASC‐sEVs versus donor ASCs, while the synthetic enzymes of ceramide (and acidic sphingomyelinase), and sphingosine‐1‐phosphate (sphingosine kinase) are significantly higher in ASC‐sEVs versus donor ASCs. Conversely, ceramide (ceramidase), and sphingosine‐1‐phosphate hydrolytic enzymes (sphingosine‐1‐phosphate lyase and sphingosine‐1‐phosphate phosphatase) are lower in ASC‐sEVs, suggesting that ceramide and sphingosine‐1‐phosphate levels could elevate in cells that receive ASC‐sEVs. ASC‐sEV‐mediated increases in sphingosine‐1‐phosphate suppress pro‐inflammatory cytokine production in AD‐model human keratinocytes. Additionally, keratinocyte differentiation, which is required for a competent epidermal permeability barrier, was restored in AD‐model human keratinocytes treated with ASC‐sEVs. Taken together, cells that endocytose ASC‐sEVs can normalize epidermal permeability barrier function as well as alleviate inflammation by stimulating a sphingosine‐1‐phosphate signalling pathway.

Atopic dermatitis (AD) is a Th2‐type inflammatory disease characterized by an alteration of epidermal barrier following the release of IL‐4 and IL‐13. These cytokines activate type II IL‐4Rα/IL‐13Rα1 receptors in the keratinocyte. Whilst IL‐2Rγ, that forms type I receptor for IL‐4, is only expressed in haematopoietic cells, recent studies suggest its induction in keratinocytes, which questions about its role. We studied expression of IL‐2Rγ in keratinocytes and its role in alteration of keratinocyte function and epidermal barrier. IL‐2Rγ expression in keratinocytes was studied using both reconstructed human epidermis (RHE) exposed to IL‐4/IL‐13 and AD skin. IL‐2Rγ induction by type II receptor has been analyzed using JAK inhibitors and RHE knockout (KO) for IL13RA1. IL‐2Rγ function was investigated in RHE KO for IL2RG. In RHE, IL‐4/IL‐13 induce expression of IL‐2Rγ at the mRNA and protein levels. Its mRNA expression is also visualized in keratinocytes of lesional AD skin. IL‐2Rγ expression is low in RHE treated with JAK inhibitors and absent in RHE KO for IL13RA1. Exposure to IL‐4/IL‐13 alters epidermal barrier, but this alteration is absent in RHE KO for IL2RG. A more important induction of IL‐13Rα2 is reported in RHE KO for IL2RG than in not edited RHE. These results demonstrate IL‐2Rγ induction in keratinocytes through activation of type II receptor. IL‐2Rγ is involved in the alteration of the epidermal barrier and in the regulation of IL‐13Rα2 expression. Observation of IL‐2Rγ expression by keratinocytes inside AD lesional skin suggests a role for this receptor subunit in the disease.

Atopic dermatitis (AD) is a common chronic inflammatory skin disorder characterized by disrupted epidermal barrier function and aberrant immune responses. Despite recent developments in new therapeutics for AD, there is still a large unmet medical need for disease management due to the complex and multifactorial nature of AD. Recent genome-wide association studies (GWAS) have identified NLRP10 as a susceptible gene for AD but the physiological role of NLRP10 in skin homeostasis and AD remains unknown. Here we show that NLRP10 is downregulated in AD skin samples. Using an air-lift human skin equivalent culture, we demonstrate that NLRP10 promotes keratinocyte survival and is required for epidermal differentiation and barrier function. Mechanistically, NLRP10 limits cell death by preventing the recruitment of caspase-8 to the death inducing signaling complex (DISC) and by inhibiting its subsequent activation. NLRP10 also stabilizes p63, the master regulator of keratinocyte differentiation, to drive proper keratinocyte differentiation and to reinforce the barrier function. Our findings underscore NLRP10 as a key player in atopic dermatitis pathogenesis, highlighting NLRP10 as a potential target for therapeutic intervention to restore skin barrier function and homeostasis in AD.

Skin diseases affect the quality of life of people who suffer from it. Atopic dermatitis (AD) and psoriasis (PS) are part of the most common causes of dermatological consultation in Mexico. Diagnosing AD can be challenging due to its multifactorial etiology and similarity of lesions from other dermatoses. Therefore, characterizing AD in an integral manner could lead to better understanding of the disease by creating a cellular and molecular hallmark for AD. In this study, 39 AD patients, 25 PS patients and 15 healthy controls were analyzed by immunofluorescence to identify the main markers that differentiate AD from PS. Results showed higher MFI for filaggrin (FL) and and involucrin (IV) proteins for PS patients than AD patients. While tight junctions, claudin 1 and 4 had no MFI differences in the 3 groups, AD patients showed major presence of occludin in keratinocytes and dermis cell infiltrate. Subsets of T CD4+ cells were quantified, obtaining a larger proportion of Th2, Th17, Th22 and Treg infiltrate in AD showing a greater activity of T CD4+ in this disease. Innervation, Substance P and CGRP neuropeptides presence were evaluated, finding significant increase for these makers in AD. Finally, a PCA was made to identify the main markers of AD, were the infiltrate of CD4+ T cells (Th2, Th22, Th17), along with the high presence of nerve endings and cells with the neuropeptides CGRP, seems to play an important role in the differentiation of atopic dermatitis samples. Conahcyt CVU: 1225279 SEDENA Translational and Interventional Immunology (TI)

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SCOPE Supplementing Limosilactobacillus reuteri Fn041, a breast milk-derived probiotic from agricultural and pastoral areas, to maternal mice during late pregnancy and lactation prevents atopic dermatitis (AD) in offspring. This study aims to elucidate the molecular mechanism of Fn041-mediated immune regulation. METHODS AND RESULTS Fn041 is administered prenatal and postnatal to maternal mice, and to offspring after weaning. The ears are administered with calcipotriol to induce AD. Fn041 treatment significantly alleviates ear inflammation, and reduces mast cell infiltration. Fn041 treatment upregulates and downregulates intestinal ZO-1 and Claudin-2 mRNA expression, respectively. Transcriptome analysis of Peyer's patches reveals that pathways related to DNA damage repair are activated in AD mice, which is inhibited by Fn041 treatment. Fn041 activates pathways related to retinol absorption and metabolism. Untargeted metabolomic analysis reveals that Fn041 treatment increases plasma retinol and kynurenine. Fn041 treatment does not significantly alter the overall cecal microbiota profile, only increases the relative abundances of Ligilactobacillus apodemi, Ligilactobacillus murinus, Akkermansia muciniphila, and Bacteroides thetaiotaomicron. CONCLUSIONS Fn041 induces anti-AD immune responses directly by promoting the absorption and metabolism of retinol in Peyer's patches, and plays an indirect role by strengthening the mucosal barrier and increasing the abundance of specific anti-AD bacteria in the cecum.

Dear Editor, Atopic dermatitis (AD) is a chronic skin disease with a prevalence of 10%– 20% in children and 1%– 3% in adults.1 We investigated the expression patterns of interleukin (IL)1α, IL1β and IL18 in AD and their interplay with the expression of profilaggrin, loricrin and claudin1. We performed analyses by RTqPCR and immunohistochemistry using skin samples from AD patients (n = 6) and healthy controls (HC) (n = 6), but also human skin explants (n = 4– 8). Nonatopic, HCs were defined as having no personal or family history of allergic diseases, no personal history of chronic systemic or skin diseases and a serum total IgE that was ≤2 SD of agedependent norms. SCORAD and three item severity scores were used to evaluate the severity of AD. Punch biopsies were obtained from forearm of six AD patients and six HC. Innate immune responses derived from keratinocytes are important initiators of skin inflammation, for example after skin irritation.2 The role of IL1 cytokines including IL1α, IL1β and IL18 in skin inflammation has been established for a long time.3 We observed enhanced IL1α and IL1β positive cells in lesional— compared to nonlesional skin (Figure 1a,b). Also, IL1βand IL18positive cells were upregulated in lesional AD compared to HC (Figure 1b,c). Among the tight junction proteins, claudin1 has been shown to play a key role in the function of the skin barrier Received: 4 November 2022 | Accepted: 18 April 2023

Itch is the dominant symptom in atopic dermatitis (AD). Cutaneous neuronal alterations underlying this symptom are still poorly understood. Therefore, we aimed at deciphering cutaneous neuronal alterations during AD treatment with dupilumab. Skin biopsies and blood from 49 adult patients with severe AD receiving dupilumab 300mg subcutaneously every two weeks over a period of 16 weeks were analyzed at initial assessment (IA) and at follow-up (FU) for intraepidermal nerve fiber density (IENFD), alloknesis and biomarker. Decreased IENFD and increased alloknesis in pruritic lesional (PL) and non-pruritic non-lesional (NPNL) skin at IA improved following dupilumab treatment. Formation of tight junctions (claudin-1 staining) was correlated to the epidermal level of IENF growth. Expression of targeted interleukin receptors (IL4R, IL13RA1, IL13RA2) and mediators related to innervation density (NGF, SEMA3A) were increased in IA-PL compared to IA-NPNL and FU-FPL (former pruritic lesional/healed). Blood CD8+ central memory T-cells and CD4+ CD25+ CD127- cells including regulatory T-cells increased at FU, CD8 T-effector cells and CLA+ activated CD4+ cells decreased. In conclusion, treatment with an IL4Rα-antibody is paralleled by an improvement of neuroanatomy and reduction of neuronal sensitization paralleled by relevant biomarker improvement.

Atopic dermatitis (AD) is a chronic inflammatory skin condition with a high prevalence worldwide and multifaceted pathogenesis. In general, patients with moderate to severe AD often experience relapse after discontinuing treatment. Therefore, to understand the possible factors of chronic relapse of AD and to look for biological markers that predict the relapse or poor prognosis of AD will be helpful for clinical treatment. Mutations in genes such as FLG, SPINK5, STAT, KIF3A, claudin-1, Ovol1, and HLA-DRB1 offer new insights into the genetic basis of AD. Routine factors may help improve patient lifestyle, highlight the importance of environmental influences (including psychological stress), and support clinicians in optimizing anti-infective treatment strategies. The inflammatory axis (CD30–CD30L axis, IL-9-IL-18 axis) provides new insights into the inflammatory pathways of AD and may be a target for future therapies. Low NKG2D expression may have adverse effects on prognosis. Prognostic biomarkers can play an important role in treatment monitoring, disease progression and recurrence, and provide the possibility for more personalized treatment.

Atopic dermatitis (AD) is a chronic inflammatory skin disorder influenced by proteins involved in skin barrier maintenance and vitamin D metabolism. Using an intra-patient design, this study compared protein expression in intra-lesional (IL) and peri-lesional (PL) skin biopsies from AD patients and examined associations between protein levels, vitamin D status, and clinical features. Forty-four biopsies from twenty-two AD patients were analyzed using antibody microarrays targeting twelve proteins. IL samples had significantly higher total protein levels than PL samples, with a mean difference of 77.7% (p < 0.001). Several proteins, including cathelicidin, cingulin, occludin, filaggrin, and the vitamin D receptor, were upregulated in IL samples. Patients with vitamin D levels below 30 ng/mL showed higher expression of CYP24A (p = 0.054), alpha-catenin (p = 0.043), and haptoglobin (p = 0.033). Increased EASI scores (≥16) were associated with elevated expression of CYP24A (p = 0.024), CYP27B (p = 0.044), filaggrin (p = 0.027), occludin (p = 0.049), and claudin-1 (p = 0.052). Multivariate regression analysis identified significant correlations between protein expression, skin prick test positivity, and low vitamin D levels. These findings suggest that proteins related to epithelial barrier function and vitamin D metabolism are highly upregulated in IL skin regions, offering potential therapeutic targets for improving both skin barrier function and overall disease severity in AD patients.

This study aimed to investigate the effects of scallop oil (SCO) on atopic dermatitis (AD)-like symptoms induced by mite allergens in the dorsal and ear skins of NC/Nga mice compared to those of refined corn oil and krill oil (KO). SCO, rich in n-3 polyunsaturated fatty acids and phospholipids, was prepared from the internal organs of Japanese giant scallop, an underutilized fishery resource in Japan. Results showed that SCO intake improved AD-like symptoms, including ear edema, ear thickness, and transepidermal water loss of dorsal skin, and tended to decrease the scratching behavior, whereas KO intake did not. Further, SCO intake decreased the degranulated mast cell count and increased the tight junction protein claudin-1 expression, which is important for the barrier function, in the dorsal skin compared to refined corn oil intake. SCO improved the AD-like symptoms by suppressing mast cell degranulation and strengthening the barrier function of dorsal skin in NC/Nga mice.

Neuroimmune interaction is crucial to inducing pruritic sensations in atopic dermatitis (AD). In this study, we examine the neuroimmune pathways involved in children with AD. HumanMethylation450 BeadChip and GeneChip Human Transcriptome Array 2.0 from 24 children with ad and 24 healthy controls were cross‐referenced with gene expression data from GSE116486. SEMA7A, which encodes for semaphorin 7a and is associated with neuron development and immune response and was identified on pathway analysis as a crucial gene in children with ad. In addition, we found that SEMA7A cytosine‐phosphate‐guanine sites (CpG sites) cg13557411 and cg17917837 were hypomethylated, and mRNA expression of SEMA7A was higher in children with ad. Vectors containing SEMA7A were then transfected into Jurkat T cells, which increased the protein excretion of interleukin 4 (IL‐4) and the mRNA expression of interleukin 1 receptor‐like 1 (IL1RL1, receptor for the cytokine IL‐33). Furthermore, stimulation of HaCaT keratinocytes with SEMA7A protein resulted in increased mRNA expression of the genes interleukin 33 (IL33) and IL1RL1, but suppressed mRNA expression of the tight junction protein ZO‐1(TJP1). In conclusion, in this study, we found that SEMA7A is overexpressed in patients with AD and is a central gene on pathway analysis. Results of our study suggest that overexpression of SEMA7A is associated with increased expression of IL4, IL33 and its receptor IL1RL1, which are associated with pruritic sensation in AD. SEMA7A also appears to suppress the expression of TJP1 in keratinocytes, thereby possibly increasing the permeability of the skin barrier. SEMA7A may be an alternative therapeutic target in AD, especially for neuroimmune‐related pruritis.

Petroselinum crispum (Mill.) Fuss (parsley), a traditional botanical drug used for treating skin conditions including atopic dermatitis (AD), has unclear effects on epidermal keratinocytes. This study investigated the antioxidant and anti-inflammatory properties of parsley extracts in human keratinocytes and evaluated their therapeutic potential in an experimental AD model. The aqueous, ethanolic, and hydro-ethanolic (HE) extracts of parsley were evaluated for total polyphenol and flavonoid metabolites (TPC, TFC) and antioxidant activity using DPPH and FRAP assays. In vitro, HaCaT cells were treated with tert-butyl hydroperoxide (t-BHP) and TNF-α/IFN-γ to induce oxidative stress and inflammation. Therapeutic efficacy was further evaluated in 2,4-dinitrofluorobenzene (DNFB)-induced AD-like mouse model. The results showed that HE extracts of parsley (HEP) contained the highest TPC and TFC and exhibited the strongest antioxidant activity, significantly improving cell viability and reducing ROS levels in t-BHP-treated cells. Mechanistically, HEP alleviated oxidative stress by activating Nrf2 pathway and enhancing the expression of antioxidant enzymes, such as superoxide dismutase (SOD) and catalase (CAT). In addition, HEP suppressed inflammatory cytokines IL-33, IL-6, and IL-8 expression by inhibiting JAK1/STAT1 and NF-κB signaling, and simultaneously increased the expression of skin barrier proteins, including filaggrin and claudin-1 in TNF-α/IFN-γ-stimulated HaCaT cells. Moreover, HEP application could alleviate AD-like symptoms in DNFB-induced mouse model, including reduced skin hyperplasia and decreased immune cells infiltration. These findings suggest that HEP modulates oxidative stress and inflammation through multiple signaling pathways, offering promising natural therapeutic agent for AD management.

Permeability barrier disruption has been shown to induce immunological alterations (i.e., an “outside-to-inside” pathogenic mechanism). Conversely, several inflammatory and immunological mechanisms reportedly interrupt permeability barrier homeostasis (i.e., an “inside-to-outside” pathogenic mechanism). It is now widely recognized that alterations of even a single molecule in keratinocytes can lead to not only permeability barrier dysfunction but also to immunological alterations. Such a simultaneous, bidirectional functional change by keratinocytes is herein named an “intrinsic” pathogenic mechanism. Molecules and/or pathways involved in this mechanism could be important not only as factors in disease pathogenesis but also as potential therapeutic targets for inflammatory cutaneous diseases, such as atopic dermatitis, psoriasis, and prurigo nodularis. Elevation of skin surface pH following permeability barrier abrogation comprises one of the key pathogenic phenomena of the “outside-to-inside” mechanism. Not only type 2 cytokines (e.g., IL-4, IL-13, IL-31) but also type 1 (e.g. IFN-γ), and type 3 (e.g., IL-17, IL-22) as well as several other inflammatory factors (e.g. histamine) can disrupt permeability barrier homeostasis and are all considered part of the “inside-to-outside” mechanism. Finally, examples of molecules relevant to the “intrinsic” pathogenic mechanism include keratin 1, filaggrin, and peroxisome proliferator-activated receptor-α (PPARα).

The skin is our outer permeability and immune defense barrier against myriad external assaults. Aryl hydrocarbon receptor (AhR) senses environmental factors and regulates barrier robustness and immune homeostasis. AhR agonists have been approved by the FDA for psoriasis treatment and are in clinical trials for the treatment of atopic dermatitis (AD), but the underlying mechanism of action remains poorly defined. Here, we report that OVOL1/Ovol1 is a conserved and direct transcriptional target of AhR in epidermal keratinocytes. We show that OVOL1/Ovol1 influences AhR-mediated regulation of keratinocyte gene expression and that OVOL1/Ovol1 ablation in keratinocytes impairs the barrier-promoting function of AhR, exacerbating AD-like inflammation. Mechanistically, we have identified Ovol1’s direct downstream targets genome-wide and provided in vivo evidence supporting the role of Id1 as a functional target in barrier maintenance, disease suppression, and neutrophil accumulation. Furthermore, our findings reveal that an IL-1/dermal γδT cell axis exacerbates type 2 and 3 immune responses downstream of barrier perturbation in Ovol1-deficient AD skin. Finally, we present data suggesting the clinical relevance of OVOL1 and ID1 functions in human AD skin. Our study highlights a keratinocyte-intrinsic AhR-Ovol1-Id1 regulatory axis that promotes both epidermal and immune homeostasis in the context of skin inflammation, identifying new therapeutic targets.

BACKGROUND Atopic dermatitis (AD), a widespread inflammatory skin disease, is characterized by disease recurrence, even after successful treatment. Past clinical research has mainly focused on understanding the active disease state as opposed to what drives and triggers AD relapses in the first place. OBJECTIVE To elucidate the unknown molecular mechanisms behind AD relapses. METHODS An observational clinical study with patients in remission was conducted, comparing biopsies from skin that would relapse within the next weeks with skin that stayed in remission using single-cell-RNA sequencing and immunohistochemistry analyses. RESULTS Signs of subclinical inflammation were present in the clinically healthy appearing pre-relapse state. On the one hand, we detected molecular signals reminiscent of active AD, such as epidermal barrier dysregulation, chemokine signaling, increased vascular permeability and first signs of T cell activity and infiltration. On the other hand, we also observed signals for processes specific to the pre-relapse state, including epidermal growth factor receptor (EGFR) signaling and macrophage phagocytosis. CONCLUSION Taken together, this work uncovers novel aspects of AD development, and putatively paves the way for new therapeutic approaches that are specifically designed to prevent AD recurrence.

Atopic dermatitis (AD) is a chronic skin disease characterized by inflammation and intense pruritus. Although the efficacy of Lactobacillus in AD management has been well-documented, the direct impact on skin remains unclear due to the limitations imposed by the intestinal barrier. Extracellular vesicles (EVs) derived from Lactobacillus exhibit superior membrane permeability, enabling them to potentially bypass gastrointestinal barriers and reach distant tissues. Through integrated murine model experiments and HaCaT cell analysis, we systematically evaluate the therapeutic potential of extracellular vesicles derived from Limosilactobacillus reuteri CCFM1040 (Lr1040-EVs) in AD pathophysiology. Our findings reveal that Lr1040-EVs significantly accelerate HaCaT cell migration while exerting potent anti-inflammatory and antipruritic effects through modulation of the signal transducer and activator of transcription 3 (STAT3) pathway. These effects were specifically manifested in the upregulation of barrier proteins (Occludin, Claudin7, filaggrin (FLG), loricrin (LOR)), enhancement of IL-10, and suppression of TNF-α and Th2-associated immune mediators. Proteomic analysis revealed that the bioactivity of Lr1040-EVs primarily originates from proteins associated with aminoacyl tRNA and biosynthesis. Histidyl tRNA synthetase has been verified to be one of the functional cargoes. Collectively, these results underscore the therapeutic efficacy of Lr1040-EVs in AD and elucidate their underlying molecular mechanisms, paving the way for clinical use and further study of their immunomodulatory effects.

Atopic dermatitis (AD) is a chronic inflammatory skin disease, its pathogenesis is associated with immunological disorders and genetically determined defects of the epidermal barrier. Exposure to aeroallergens, including pollen, plays a crucial role in the exacerbations and progression of AD. When individuals sensitized to pollen allergens come into contact with these allergens, a T2 immune response is activated, characterized by the release of cytokines IL-4, IL-13, and IL-31, which stimulate the production of IgE. This leads to enhanced inflammation, improved penetration of allergens through the compromised epidermal barrier, and activation of keratinocytes and dendritic cells, further impairing the skin barrier function and exacerbating AD symptoms. Previous studies have shown that pollen allergens can directly affect the epidermal barrier by activating proteolytic enzymes that break down intercellular connections in the epidermis, increasing its permeability to allergens and pathogens. This study analyzes the impact of sensitization to birch pollen allergens on the AD exacerbation in adult patients living in Moscow and the Moscow region. Birch pollen is a significant allergen capable of triggering exacerbations of allergic diseases, especially in the Northern Hemisphere countries where birch is widely spread. The study included 30 adult AD patients sensitized to birch pollen, and the SCORAD index was used to assess the severity of the disease, combining both objective skin condition indicators and subjective patient complaints (itching, sleep disturbance). Allergological examination was conducted using the ISAC ImmunoCAP allergochip, allowing for the determination of specific IgE levels to more than 100 allergens, including the main birch pollen allergen – Bet v 1. The analysis showed that most patients experienced a significant increase in AD symptoms during the birch flowering period, correlating with the levels of specific IgE to Bet v 1. The study highlights the clinical significance of sensitization to birch pollen as a trigger factor for AD exacerbation, confirming the need to analyze sensitization to pollen allergens to develop personalized approaches to the diagnosis and treatment of AD patients.

Atopic dermatitis (AD) is a chronic cutaneous disease with a complex underlying mechanism, and it cannot be completely cured. Thus, most treatment strategies for AD aim at relieving the symptoms. Although corticosteroids are topically applied to alleviate AD, adverse side effects frequently lead to the withdrawal of AD therapy. Tacrolimus (TAC), a calcineurin inhibitor, has been used to treat AD, but its high molecular weight and insolubility in water hinder its skin permeability. Herein, we developed and optimized TAC-loaded chitosan-based nanoparticles (TAC@CNPs) to improve the skin permeability of TAC by breaking the tight junctions in the skin. The prepared nanoparticles were highly loadable and efficient and exhibited appropriate characteristics for percutaneous drug delivery. TAC@CNP was stable for 4 weeks under physiological conditions. CNP released TAC in a controlled manner, with enhanced skin penetration observed. In-vitro experiments showed that CNP was non-toxic to keratinocyte (HaCaT) cells, and TAC@CNP dispersed in an aqueous solution was as anti-proliferative as TAC solubilized in a good organic solvent. Importantly, an in-vivo AD mouse model revealed that topical TAC@CNP containing ~1/10 of the dose of TAC found in commercially used Protopic® Ointment exhibited similar anti-inflammatory activity to that of the commercial product. TAC@CNP represents a potential therapeutic strategy for the management of AD.

No abstract available

No abstract available

Inflammatory diseases like atopic dermatitis have shown a correlation between changes in immune responses and variations in the TLR2 gene, with a specific focus on how TLR2 polymorphisms influence IL- 10 and IL-6 levels in individuals with AD. Fifty eight patients with atopic dermatitis and 32 healthy controls provided blood samples for analysis. IL-10 and IL-6 levels were measured using Elisa assay, and TLR2 gene variants were identified with Sanger sequencing. The results revealed that TLR2 polymorphisms, particular¬ly (T-6686-A), were not significantly associated with AD patients compared to healthy controls. There was a significant increase in the IL-6 and IL-10 levels between atopic dermatitis patients and healthy control. Otherwise, the result showed a significant increase in the IL-6 level and no significant increase in the IL- 10 level between AD patients’ men and women. These results suggest a potential link between TLR2 genetic variations and altered IL-10 or IL-6 levels in AD patients, highlighting the influence of TLR2 polymorphisms on immune responses in this condition. Studying TLR2 polymorphisms’ effect on cytokine profiles could of¬fer insights into AD pathogenesis and guide personalized immune-targeted therapies for affected individuals. The absence of significant differences in the distribution of genotypes among various allele variants may be due to the small size of the sample or the variant TLR2 (rs4696480). Individuals with AD often exhibit ele¬vated levels of IL-6 and IL-10, highlighting the complex immune dysfunction associated with this condition.

Skin barrier dysfunction plays a pivotal role in the pathogenesis of inflammatory skin diseases such as atopic dermatitis and psoriasis. This review provides a comprehensive analysis of recent advances in the transcriptional and post-transcriptional regulation of key skin barrier-related genes, including FLG, LOR, CLDN1, AQP3 and IVL. We detail how intrinsic genetic variations and immune-mediated cytokine pathways-particularly the T helper 2 and T helper 17 axes-disrupt the epidermal defense system. Emerging therapeutic strategies targeting skin barrier restoration through natural compounds, biologic agents, and gene modulation technologies-such as small interfering RNA, antisense oligonucleotides, and histone deacetylase inhibitors-are critically reviewed. Moreover, the impact of the gut-skin axis and microbial metabolites on epidermal gene expression is discussed. Finally, we highlight the role of artificial intelligence and multi-omic integration in driving biomarker discovery and enabling precision dermatology. These insights underscore the potential of barrier-centric, gene-targeted approaches as a transformative strategy in managing chronic dermatoses.

Toll-like receptors (TLR), the key players of the innate immune system, contribute to the pathogenesis of atopic dermatitis (AD) through multiple pathways. TLRs play a crucial role in delaying barrier repair, promoting Th2-mediated dermatitis, shifting the response toward Th1 in the chronic phase, and contributing to the establishment of the itch-scratch cycle, as well as mediating the effects of UV radiation. The dysregulation of proinflammatory and immunomodulatory effects of TLRs can be attributed to their ligand structures, receptor heterodimerization, the relative frequency of each TLR, interactions with other receptors/signalling pathways, cytokine milieu, and genetic polymorphisms. Current AD treatments like vitamin-D analogs, tacrolimus, and cyclosporine partially work through TLR modulation. Direct TLR stimulation using different compounds has shown therapeutic benefits in preclinical studies. However, significant challenges exist, including off-target effects due to ubiquitous TLR expression and complex roles in immune responses. Future directions include CRISPR-based gene editing to understand TLR functions, development of specific TLR modulators for targeted therapy, and machine learning applications to predict drug responses and identify novel ligands. Patient heterogeneity, including the presence or absence of polymorphisms, variations in TLR expression levels, and differences in immune responses, underscores the need for personalized therapeutic approaches.

Atopic dermatitis (AD) is a disease with a complex genetic background, in which only the predisposition to atopy is inherited. Genetic, environmental, and psychosomatic factors contribute to the development of this allergic inflammatory disease. The patient’s age and population affiliation also play a significant role. Gene groups associated with AD are primarily: genes responsible for the epidermal barrier, interaction with the environment and related to the immune response. In turn, polymorphisms in these genes can affect the severity of atopic dermatitis through mechanisms such as excessive stimulation of the immune system or increased synthesis of immunoglobulin E (IgE). Among the genes related to the immune system that play an important role in the development of atopic dermatitis, we can distinguish: Chitinase-3-like protein 1 (CHI3L1), FcεRI (Fc epsilon RI, ligand-binding subunit of the high-affinity IgE receptor), toll-like receptors (TLRs), and cytokine encoding genes.

Background: The etiopathogenesis of atopic dermatitis is complicated, and it includes aspects such as dysfunction of the skin barrier, changes in immune responses, IgE-mediated hypersensitivity, and many characteristics of the environment. Regarding skin barrier dysfunction, a number of genetic changes have been described. This genetic predisposition could be related to the phenotypes of atopic dermatitis. Aim: In this study, several polymorphisms in five proinflammatory genes were associated with certain phenotypes of AD patients (genotype–phenotype study). Methods: In total, 89 unrelated AD Czech (Caucasian) patients were genotyped regarding five proinflammatory gene polymorphisms (angiotensinogen AGT M235T, AGT-6 G/A, TNF-α-238 G/A, TNF-β Fok1, IL-6-174 C/G and IL-6-596 G/A). Genotyping was performed using PCR and restriction analysis. For phenotypes, patients’ sex, age and personal and family history of atopy, aero- and food allergies and other complex diseases were evaluated. Results: A significant association with transepidermal water loss (TEWL) measured on the forearm was found with the AGT M235T polymorphism (p = 0.02). For the AG genotype of TNF-α-238 G/A, a six-times higher risk for a family history of diabetes mellitus compared to other examined aspects of family history was found (p = 0.02). A family history of thyreopathy was associated with the IL-6-174 G/C polymorphism when compared to a family history of other complex diseases. The GG genotype had a ten-times higher risk for a family history of thyreopathy compared to the other genotypes (p = 0.004). This result was highly specific (0.914). The GG genotype of IL-6-596 G/A was associated with a family history of thyreopathy, with the same result (p = 0.004). Moreover, the G allele of IL-6-174 G/C was associated with a family history of thyreopathy compared to AD patients without a positive family history of complex diseases (p = 0.03). In AD men, the MM genotype of the AGT M235T gene was found to be associated with food allergies (p = 0.004). This result was highly sensitive (0.833). A family history of cardiovascular disease in AD men was associated with AGT-6 G/A variability. The A allele was found to be six times more frequent in patients with a positive family history of cardiovascular disease (p = 0.02, with high sensitivity and specificity (0.700 and 0.735, respectively)). A family history of diabetes mellitus was associated with the TNF-β Fok1 polymorphism, where the B1 allele was almost six times more frequent in AD men with a positive family history of diabetes mellitus (p = 0.02), with high sensitivity (0.85). A significant association between TEWL measured on the forearm and the AGT M235T polymorphism was found when AD women were carriers of the MM genotype, with a median of 25 and range 4–61; those patients with the MT genotype had a median of 10 and range of 0.3–39; and patients with the TT genotype had a median of 5 and range of 3–40, p = 0.003. The polymorphism AGT-6 G/A was associated with different ages of eczema onset. The AG genotype was almost nine times more risky for the youngest group (0–7 years) compared to the oldest group (more than 18 years) (p = 0.02), with high specificity for this result. Conclusions: Our results in the field of cytokine signaling in the immune system in patients with atopic dermatitis are in agreement with those of GWASs. We suggest that cost-effective and simple PCR tests may be the best approach for the rapid and optimal collection of valid genetic information in clinical practice.

Abstract Background: This study aimed to investigate the role of serine protease inhibitor Kazal-type 5 (SPINK5) polymorphisms (Asn368Ser, Asp386Asn and Glu420Lys) and the risk of atopic dermatitis (AD). Methods: Studies associated with SPINK5 mutations and AD risk were searched from three databases, including PubMed, Embase, and Cochrane library, with a retrieval deadline of April 22, 2019. An odds ratio (OR) with a 95% confidence interval (95% CI) was chosen as the effect size. Egger's linear regression test was enrolled to assess the level of publication bias. Results: Overall, 6 studies met the inclusion criteria for meta-analysis. Significantly statistical differences were calculated between patients with AD and healthy individuals on Asn368Ser polymorphism in the allele model (G vs A: OR = 1.2643, 95% CI = 1.0666–1.4987, P = .0069), co-dominant model (GG vs AA: OR = 1.6609, 95% CI = 1.1736–2.3505, P = .0042; GA vs AA: OR = 1.5448, 95% CI = 1.1263–2.1189, P = .0070), and dominant model (GG+GA vs AA: OR = 1.5700, 95% CI = 1.1656–2.1146, P = .0030). However, no statistically significant difference was found in the recessive model for Asn368Ser and other genetic models for Asp386Asn and Glu420Lys (all P > .05). No significant publication bias was found. Conclusion: The SPINK5 Asn368Ser polymorphism may be a risk factor for AD.

Atopic dermatitis is a relapsing inflammatory skin condition, in which bacteria, fungi and viruses may colonize the skin and aggravate the condition. Mannose-binding lectin is part of the innate immune system. Polymorphism in the mannose-binding lectin gene can result in deficiency of mannose-binding lectin, which may affect defence against microbes. The aim of this study was to investigate whether polymorphisms in the mannose-binding lectin gene affect the extent of sensitization to common skin microbes, the skin barrier function, or the severity of the disease in a cohort of patients with atopic dermatitis. Genetic testing of mannose-binding lectin polymorphism was performed in 60 patients with atopic dermatitis. The disease severity, skin barrier function, and serum levels of specific immunoglobulin E against skin microbes were measured. In patients with low mannose-binding lectin genotype (group 1) 6 of 8 (75%) were sensitized to Candida albicans, compared to 14 of 22 (63.6%) patients with intermediate mannose-binding genotype (group 2) and 10 of 30 (33.3%) patients with high mannose-binding genotype (group 3). Group 1 (low mannose-binding lectin) was more likely to be sensitized to Candida albicans compared with group 3 (high mannose-binding lectin) (odds ratio 6.34, p-value 0.045). In this cohort of patients with atopic dermatitis, mannose-binding lectin deficiency was associated with increased sensitization to Candida albicans.

Introduction: This paper reports the study of a combined genetic and biomarker panel for assessing the risk of development of different phenotypes of atopic dermatitis (AD) in children: alone and combined with other atopic disorders (AtD) – allergic rhinitis/rhino-conjunctivitis (AR/ARC) and bronchial asthma (BA). The aim was to establish a personalized diagnostic multi-marker panel for assessing the developmental risk of different AD phenotypes in children combining single nucleotide polymorphism (SNP) rs_7927894 filaggrin (FLG) genotype variants, serum levels of total immune globulin E (IgE), cutaneous T-cell attracting chemokine (CTACK/CCL27) and thymus and activation regulated chemokine (TARC/CCL17). Material and methods: The study recruited patients aged 3–18 years old: 39 atopic patients to the main group and 47 non-atopic patients to the control group. All the patients were tested for SNP variants of rs_7927894 FLG and serum concentrations of total IgE, CTACK/CCL27 and TARC/CCL17. Results: Within AD alone phenotype patients we detected the following significant risk ratios: cytosine\thymine (C/T) rs_7927894 FLG [odds ratio (OR) = 4.14, p < 0.05], total IgE > 173 IU/ml (OR = 8.98, p < 0.001), CTACK/ CCL27 > 3658.5 pg/ml (OR = 5.64, p < 0.01). Atopic disorders combined with other AtD phenotype: C/T rs_7927894 FLG (OR = 2.88, p < 0.05), total IgE > 213 IU/ml (OR = 136.7, p < 0.001), CTACK/CCL27 > 4308.8 pg/ml (OR = 7.40, p < 0.001). With AD combined with other AtD collated to AD alone – total IgE > 1001 IU/ml (OR = 16.0, p < 0.001). TARC/CCL17 had no significant differences among main and control groups. Conclusions: Cytosine\thymine rs_7927894 FLG variant combined with cut-off serum IgE and CTACK/ CCL27 levels is a novel significant personalized multi-marker panel for assessing the risk of development of the different AD phenotypes in children.

INTRODUCTION Atopic Dermatitis (AD) is a recurrent chronic condition associated with microorganism and their interaction with the susceptible host. Malassezia yeast is a known commensal which is thought to provoke the recurrent episodes of symptoms in atopic dermatitis patients. Malassezia immunomodulatory properties along with defective skin barrier in such host, results in disease manifestation. Here, we studied Single Nucleotide Polymorphism (SNP) in IL10 and IFN γ genes of the host and its relation with susceptibility to Malassezia infection. AIM To isolate Malassezia yeast from AD patients and compare the genetic susceptibility of the host by correlating the cytokine gene polymorphism with the control subjects. MATERIALS AND METHODS Study was conducted from January 2012 to January 2013. It was a prospective observational study done in Department of Microbiology and Department of Dermatology and Venereology in University College of Medical Sciences and GTB Hospital, Delhi. Sample size comprised of 38 cases each of AD. Skin scrapings were used for fungal culture on Sabouraud Dextrose Agar (SDA) and Modified Dixon Agar (MDA) and isolated were identified as per conventional phenotypic methods. Genomic DNA was extracted from blood samples collected from all study subjects. Cytokine genotyping was carried out by Amplification Refractory Mutations System- Polymerase Chain Reaction (ARMS-PCR) with sequence specific primers. Three SNPs (IL10-1082A/G; IL10-819/592C/T; IFN-γ+874A/T) in two cytokine genes were assessed in all the patients and healthy controls. STATISTICAL ANALYSIS Chi-Square Test or Fisher's-Exact Test and Bonferroni's correction. RESULTS In AD group, Malassezia yeasts were cultured in 24 out of 38 samples and thus the identification rate was 63.1 percent as compared to healthy group, 52.6 percent (20/38). Significant difference in allele, or genotype distribution were observed in IL10-819/592C/T and IFN-γ+874A/T gene polymorphism in AD group. CONCLUSION Higher isolation rate in cases as compared to control group highlights the implication of Malassezia in AD. Association between specific cytokine gene polymorphism and clinical outcome was found to be significant in study group. The result of cytokine gene polymorphism in the present study demonstrated susceptibility of host to Malassezia infection.

Atopic dermatitis is a chronic condition where epidermal barrier dysfunction and cytokine production by infiltrating immune cells exacerbate skin inflammation and damage. A total lipid extract from Macrocystis pyrifera, a brown seaweed, was previously reported to suppress inflammatory responses in monocytes. Here, treatment of human HaCaT keratinocytes with M. pyrifera lipids inhibited tumour necrosis factor (TNF)-α induced TNF receptor-associated factor 2 and monocyte chemoattractant protein (MCP)-1 protein production. HaCaT cells stimulated with TNF-α, interleukin (IL)-4, and IL-13 showed loss of claudin-1 tight junctions, but little improvement was observed following lipid pre-treatment. Three-dimensional cultures of HaCaT cells differentiated at the air–liquid interface showed increased MCP-1 production, loss of claudin-1 tight junctions, and trans-epidermal leakage with TNF-α, IL-4, and IL-13 stimulation, with all parameters reduced by lipid pre-treatment. These findings suggest that M. pyrifera lipids have anti-inflammatory and barrier-protective effects on keratinocytes, which may be beneficial for the treatment of atopic dermatitis or other skin conditions.

The epidermal growth factor receptor (EGFR) signaling pathway is crucial for skin barrier integrity and immune response. This study explores the impact of EGFR inhibitors, osimertinib and afatinib, on keratinocyte function, focusing on keratin (KRT1, KRT17) and tight junction protein (CLDN1, CLDN2, CLDN4) expression in HaCaT cells. Osimertinib significantly increased the mRNA and protein levels of keratins and inflammatory markers, IL-6 and TNF-α, via activation of the EGFR-STAT3 signaling pathway. Co-treatment with recombinant human EGF reversed these changes, suggesting the pathway's modulatory role. These findings underscore the potential therapeutic applications of targeting the EGFR-STAT3 axis in skin barrier dysfunction and inflammatory skin disorders.

Atopic dermatitis (AD) is a prevalent inflammatory skin disorder with limited treatment options, highlighting the need for alternative therapeutic strategies. Traditionally, black soybean oil, prepared from Glycine max through high-temperature dry distillation, has been used in Asian medicine to relieve AD symptoms. However, this preparation method poses safety concerns due to the potential formation of carcinogenic by-products. To address these limitations, we prepared black soybean extract (BSE) using supercritical CO2 extraction and investigated its pharmacological effects and underlying mechanisms in AD-related cell models. Gas chromatography-mass spectrometry analysis identified five major fatty acids in BSE. In LPS-stimulated RAW264.7 macrophages, BSE reduced the production of pro-inflammatory mediators. In TNF-α/IFN-γ-stimulated HaCaT keratinocytes, BSE downregulated the mRNA levels of AD-associated alarmins, decreased apoptosis, and increased junction protein expression, suggesting its skin barrier-protective effects. Integrated network pharmacology and RNA sequencing analyses predicted that TNF signaling and its downstream MAPK and NF-κB pathways play key roles in BSE's effects. RT-qPCR validated that BSE downregulated the mRNA levels of genes involved in pro-inflammatory responses, immune activation, and skin barrier impairment. Western blotting results demonstrated that BSE inactivated MAPK and NF-κB signaling molecules, including ERK, p38, JNK, p65, and IκBα. Collectively, our findings demonstrate, for the first time, that BSE has anti-inflammatory and skin barrier-protective potential, with the inhibition of TNF-MAPK/NF-κB signaling pathways involved in BSE's effects. This study suggests that BSE has the potential to be used for managing AD-related inflammation and skin barrier dysfunction.

BACKGROUND Epithelial barrier dysfunction is a pivotal feature of asthma, and it also commonly occurs in other inflammatory conditions such as atopic dermatitis (AD) and ulcerative colitis (UC). However, the core regulatory mechanisms underlying epithelial barrier dysfunction-especially whether shared mechanisms exist across these diseases-remain unclear. METHODS Gene expression profiles of patients with asthma, AD, and UC were retrieved from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were identified using the limma package. Common DEGs among the three diseases were identified via a Venn diagram, followed by correlation analysis with junction molecules to screen for key genes. Interaction networks (protein-protein, transcription factor-gene, miRNA-gene, chemical-gene) of the key genes were constructed, and their correlations with asthma clinical features [Asthma Control Questionnaire (ACQ) score, Inhaled Corticosteroid (ICS) dose, lung function parameters] were analyzed. The effects of the key genes on epithelial barrier function were assessed in airway, epidermal, and intestinal epithelial cells. RESULTS A total of eight common DEGs exhibited consistent upregulation in the epithelial tissues of patients with asthma, AD, and UC. Four key genes-CDC7, PXDN, TCN1, and TIMP1-were identified; they were upregulated in the epithelium of all three diseases, significantly elevated in IL-13-stimulated airway epithelial cells, and negatively correlated with junction molecules that were downregulated in the three diseases. Furthermore, the expression of these key genes was associated with the severity of asthma. Correlation analysis between key gene expression and asthma clinical features revealed that PXDN expression was significantly negatively correlated with the lung function parameter FEV1 (forced expiratory volume in 1 s), while TCN1 expression showed a significant negative correlation with FEV1/FVC (forced expiratory volume in 1 s/forced vital capacity). Chemical-gene interaction analysis revealed that benzo[a]pyrene could induce the expression of these four key genes. Subsequent experiments confirmed that stimulation of airway epithelial cells with benzo[a]pyrene significantly upregulated the expression of these key genes. Finally, targeting these key molecules was found to alleviate the IL-13-induced reduction in CLDN1 expression in airway epithelial cells. In in vitro collagen-coated transwell assays, knocking down either CDC7 or TCN1 significantly attenuated IL-13-induced epithelial barrier disruption in airway, epidermal, and intestinal epithelia. CONCLUSION Our findings confirm that targeting CDC7 and TCN1 facilitates the improvement of barrier function in airway epithelial cells, epidermal keratinocytes, and intestinal epithelial cells in vitro, thereby providing promising therapeutic targets for diseases characterized by epithelial barrier dysfunction.

The pathophysiology of atopic dermatitis is complex and multifactorial, involving elements of barrier dysfunction, alterations in cell mediated immune responses, IgE mediated hypersensitivity, and environmental factors. Loss of function mutations in filaggrin have been implicated in severe atopic dermatitis due to a potential increase in trans-epidermal water loss, pH alterations, and dehydration. Other genetic changes have also been identified which may alter the skin's barrier function, resulting in an atopic dermatitis phenotype. The imbalance of Th2 to Th1 cytokines observed in atopic dermatitis can create alterations in the cell mediated immune responses and can promote IgE mediated hypersensitivity, both of which appear to play a role in the development of atopic dermatitis. One must additionally take into consideration the role of the environment on the causation of atopic dermatitis and the impact of chemicals such as airborne formaldehyde, harsh detergents, fragrances, and preservatives. Use of harsh alkaline detergents in skin care products may also unfavorably alter the skin's pH causing downstream changes in enzyme activity and triggering inflammation. Environmental pollutants can trigger responses from both the innate and adaptive immune pathways. This chapter will discuss the multifaceted etiology of atopic dermatitis which will help us to elucidate potential therapeutic targets. We will also review existing treatment options and their interaction with the complex inflammatory and molecular triggers of atopic dermatitis.

The skin forms an effective barrier between the organism and the environment preventing invasion of pathogens and fending off chemical and physical assaults, as well as the unregulated loss of water and solutes. In this review we provide an overview of several components of the physical barrier, explaining how barrier function is regulated and altered in dermatoses. The physical barrier is mainly localized in the stratum corneum (SC) and consists of protein-enriched cells (corneocytes with cornified envelope and cytoskeletal elements, as well as corneodesmosomes) and lipid-enriched intercellular domains. The nucleated epidermis also contributes to the barrier through tight, gap and adherens junctions, as well as through desmosomes and cytoskeletal elements. During epidermal differentiation lipids are synthesized in the keratinocytes and extruded into the extracellular domains, where they form extracellular lipid-enriched layers. The cornified cell envelope, a tough protein/lipid polymer structure, resides below the cytoplasmic membrane on the exterior of the corneocytes. Ceramides A and B are covalently bound to cornified envelope proteins and form the backbone for the subsequent addition of free ceramides, free fatty acids and cholesterol in the SC. Filaggrin is cross-linked to the cornified envelope and aggregates keratin filaments into macrofibrils. Formation and maintenance of barrier function is influenced by cytokines, 3',5'-cyclic adenosine monophosphate and calcium. Changes in epidermal differentiation and lipid composition lead to a disturbed skin barrier, which allows the entry of environmental allergens, immunological reaction and inflammation in atopic dermatitis. A disturbed skin barrier is important for the pathogenesis of contact dermatitis, ichthyosis, psoriasis and atopic dermatitis.

There has been extensive progress in understanding the cellular and molecular mechanisms of inflammation and immune regulation in allergic diseases of the skin and lungs during the last few years. Asthma and atopic dermatitis (AD) are typical diseases of type 2 immune responses. interleukin (IL)-25, IL-33, and thymic stromal lymphopoietin are essential cytokines of epithelial cells that are activated by allergens, pollutants, viruses, bacteria, and toxins that derive type 2 responses. Th2 cells and innate lymphoid cells (ILC) produce and secrete type 2 cytokines such as IL-4, IL-5, IL-9, and IL-13. IL-4 and IL-13 activate B cells to class-switch to IgE and also play a role in T-cell and eosinophil migration to allergic inflammatory tissues. IL-13 contributes to maturation, activation, nitric oxide production and differentiation of epithelia, production of mucus as well as smooth muscle contraction, and extracellular matrix generation. IL-4 and IL-13 open tight junction barrier and cause barrier leakiness in the skin and lungs. IL-5 acts on activation, recruitment, and survival of eosinophils. IL-9 contributes to general allergic phenotype by enhancing all of the aspects, such as IgE and eosinophilia. Type 2 ILC contribute to inflammation in AD and asthma by enhancing the activity of Th2 cells, eosinophils, and their cytokines. Currently, five biologics are licensed to suppress type 2 inflammation via IgE, IL-5 and its receptor, and IL-4 receptor alpha. Some patients with severe atopic disease have little evidence of type 2 hyperactivity and do not respond to biologics which target this pathway. Studies in responder and nonresponder patients demonstrate the complexity of these diseases. In addition, primary immune deficiency diseases related to T-cell maturation, regulatory T-cell development, and T-cell signaling, such as Omenn syndrome, severe combined immune deficiencies, immunodysregulation, polyendocrinopathy, enteropathy, X-linked syndrome, and DOCK8, STAT3, and CARD11 deficiencies, help in our understanding of the importance and redundancy of various type 2 immune components. The present review aims to highlight recent advances in type 2 immunity and discuss the cellular sources, targets, and roles of type 2 mechanisms in asthma and AD.

The main interfaces controlling and attempting to homeostatically balance communications between the host and the environment are the epithelial barriers of the skin, gastrointestinal system, and airways. The epithelial barrier constitutes the first line of physical, chemical, and immunologic defenses and provides a protective wall against environmental factors. Following the industrial revolution in the 19th century, urbanization and socioeconomic development have led to an increase in energy consumption, and waste discharge, leading to increased exposure to air pollution and chemical hazards. Particularly after the 1960s, biological and chemical insults from the surrounding environment-the exposome-have been disrupting the physical integrity of the barrier by degrading the intercellular barrier proteins at tight and adherens junctions, triggering epithelial alarmin cytokine responses such as IL-25, IL-33, and thymic stromal lymphopoietin, and increasing the epithelial barrier permeability. A typical type 2 immune response develops in affected organs in asthma, rhinitis, chronic rhinosinusitis, eosinophilic esophagitis, food allergy, and atopic dermatitis. The aim of this article was to discuss the effects of environmental factors such as protease enzymes of allergens, detergents, tobacco, ozone, particulate matter, diesel exhaust, nanoparticles, and microplastic on the integrity of the epithelial barriers in the context of epithelial barrier hypothesis.

The skin provides an effective barrier between the organism and the environment, preventing the invasion of pathogens and fending off chemical and physical assaults, as well as the unregulated loss of water and solutes. In this review we provide an overview of several components of the physical barrier, as well as how barrier function is regulated and altered in association with dermatoses. The physical barrier localized primarily in the stratum corneum (SC) and consists of protein-enriched cells (corneocytes with cornified envelope and cytoskeletal elements, as well as corneodesmosomes) and lipid-enriched intercellular domains. The nucleated epidermis, with its tight, gap and adherens junctions, additional desmosomes and cytoskeletal elements, also contributes to the barrier. Lipids are synthesized in the keratinocytes during epidermal differentiation and are then extruded into the extracellular domains, where they form lipid-enriched extracellular layers. The cornified cell envelope, a robust protein/lipid polymer structure, is located below the cytoplasmic membrane on the exterior of the corneocytes. Ceramides A and B, forming the backbone for the subsequent addition of free ceramides, free fatty acids and cholesterol in the SC, are covalently bound to cornified envelope proteins. Filaggrin is cross-linked to the cornified envelope and aggregates keratin filaments into macrofibrils. Cytokines, cAMP and calcium influence the formation and maintenance of barrier function. Changes in lipid composition and epidermal differentiation lead to a disturbed skin barrier, which allows the entry of environmental allergens, immunological reaction and inflammation in atopic dermatitis. A disturbed skin barrier is an important component in the pathogenesis of contact dermatitis, ichthyosis, psoriasis, and atopic dermatitis.

House dust mites are an unsurpassed cause of atopic sensitization and allergic illness throughout the world. The major allergenic dust mites Dermatophagoides pteronyssinus, Dermatophagoides farinae, Euroglyphus maynei, and Blomia tropicalis are eight-legged members of the Arachnid class. Their approximately 3-month lifespan comprises egg, larval, protonymph, tritonymph, and adult stages, with adults, about one fourth to one third of a millimeter in size, being at the threshold of visibility. The geographic and seasonal distributions of dust mites are determined by their need for adequate humidity, while their distribution within substrates is further determined by their avoidance of light. By contacting the epithelium of the eyes, nose, lower airways, skin, and gut, the allergen-containing particles of dust mites can induce sensitization and atopic symptoms in those organs. Various mite allergens, contained primarily in mite fecal particles but also in shed mite exoskeletons and decaying mite body fragments, have properties that include proteolytic activity, homology with the lipopolysaccharide-binding component of Toll-like receptor 4, homology with other invertebrate tropomyosins, and chitin-cleaving and chitin-binding activity. Mite proteases have direct epithelial effects including the breaching of tight junctions and the stimulation of protease-activated receptors, the latter inducing pruritus, epithelial dysfunction, and cytokine release. Other components, including chitin, unmethylated mite and bacterial DNA, and endotoxin, activate pattern recognition receptors of the innate immune system and act as adjuvants promoting sensitization to mite and other allergens. Clinical conditions resulting from mite sensitization and exposure include rhinitis, sinusitis, conjunctivitis, asthma, and atopic dermatitis. Systemic allergy symptoms can also occur from the ingestion of cross-reacting invertebrates, such as shrimp or snail, or from the accidental ingestion of mite-contaminated foods. Beyond their direct importance as a major allergen source, an understanding of dust mites leads to insights into the nature of atopy and of allergic sensitization in general.

Transepidermal water loss (TEWL) is the most widely used objective measurement for assessing the barrier function of skin in healthy individuals but also patients with skin diseases that are associated with skin barrier dysfunction, such as atopic dermatitis. TEWL is the quantity of condensed water that diffuses across a fixed area of stratum corneum to the skin surface per unit time. The water evaporating from the skin is measured using a probe that is placed in contact with the skin surface and contains sensors that detect changes in water vapor density. TEWL can be measured using an open-chamber, unventilated-chamber, or condenser-chamber device. It is a sensitive measure that is affected by properties of the surrounding microclimate such as environmental humidity, temperature, and airflow and should be measured under controlled conditions. TEWL varies significantly across different anatomical sites and also depends on sweat gland activity, skin temperature, and corneocyte properties. Here we describe how to optimally use TEWL measurements as a skin research tool in vivo and in vitro.

Tight junctions are transmembrane proteins that regulate the permeability of water, solutes including ions, and water-soluble molecules. The objective of this systematic review is to focus on the current knowledge regarding the role of tight junctions in atopic dermatitis and the possible impact on their therapeutic potential. A literature search was performed in PubMed, Google Scholar, and Cochrane library between 2009 and 2022. After evaluation of the literature and taking into consideration their content, 55 articles were finally included. TJs' role in atopic dermatitis extends from a microscopic scale to having macroscopic effects, such as increased susceptibility to pathogens and infections and worsening of atopic dermatitis features. Impaired TJ barrier function and skin permeability in AD lesions is correlated with cldn-1 levels. Th2 inflammation inhibits the expression of cldn-1 and cldn-23. Scratching has also been reported to decrease cldn-1 expression. Dysfunctional TJs' interaction with Langerhans cells could increase allergen penetration. Susceptibility to cutaneous infections in AD patients could also be affected by TJ cohesion. Dysfunction of TJs and their components, especially claudins, have a significant role in the pathogenesis and vicious circle of inflammation in AD. Discovering more basic science data regarding TJ functionality may be the key for the use of specific/targeted therapies in order to improve epidermal barrier function in AD.

The primary function of the epidermis is to produce the protective, semi-permeable stratum corneum that permits terrestrial life. The barrier function of the stratum corneum is provided by patterned lipid lamellae localized to the extracellular spaces between corneocytes. Anucleate corneocytes contain keratin filaments bound to a peripheral cornified envelope composed of cross-linked proteins. The many layers of these specialized cells in the stratum corneum provide a tough and resilient framework for the intercellular lipid lamellae. The lamellae are derived from disk-like lipid membranes extruded from lamellar granules into the intercellular spaces of the upper granular layer. Lysosomal and other enzymes present in the extracellular compartment are responsible for the lipid remodeling required to generate the barrier lamellae as well as for the reactions that result in desquamation. Lamellar granules likely originate from the Golgi apparatus and are currently thought to be elements of the tubulo-vesicular trans-Golgi network. The regulation of barrier lipid synthesis has been studied in a variety of models, with induction of several enzymes demonstrated during fetal development and keratinocyte differentiation, but an understanding of this process at the molecular genetic level awaits further study. Certain genetic defects in lipid metabolism or in the protein components of the stratum corneum produce scaly or ichthyotic skin with abnormal barrier lipid structure and function. The inflammatory skin diseases psoriasis and atopic dermatitis also show decreased barrier function, but the underlying mechanisms remain under investigation. Topically applied "moisturizers" work by acting as humectants or by providing an artificial barrier to trans-epidermal water loss; current work has focused on developing a more physiologic mix of lipids for topical application to skin. Recent studies in genetically engineered mice have suggested an unexpected role for tight junctions in epidermal barrier function and further developments in this area are expected. Ultimately, more sophisticated understanding of epidermal barrier function will lead to more rational therapy of a host of skin conditions in which the barrier is impaired.

The epithelial barriers of the skin, gut, and respiratory tract are critical interfaces between the environment and the host, and they orchestrate both homeostatic and pathogenic immune responses. The mechanisms underlying epithelial barrier dysfunction in allergic and inflammatory conditions, such as atopic dermatitis, food allergy, eosinophilic oesophagitis, allergic rhinitis, chronic rhinosinusitis, and asthma, are complex and influenced by the exposome, microbiome, individual genetics, and epigenetics. Here, we review the role of the epithelial barriers of the skin, digestive tract, and airways in maintaining homeostasis, how they influence the occurrence and progression of allergic and inflammatory conditions, how current treatments target the epithelium to improve symptoms of these disorders, and what the unmet needs are in the identification and treatment of epithelial disorders.

This review focuses on recent developments related to asthma, chronic rhinosinusitis, atopic dermatitis (AD), eosinophilic esophagitis, and inflammatory bowel diseases (IBD), with a particular focus on tight junctions (TJs) and their role in the pathogenetic mechanisms of these diseases. Lung, skin, and intestinal surfaces are lined by epithelial cells that interact with environmental factors and immune cells. Therefore, together with the cellular immune system, the epithelium performs a pivotal role as the first line physical barrier against external antigens. Paracellular space is almost exclusively sealed by TJs and is maintained by complex protein-protein interactions. Thus, TJ dysfunction increases paracellular permeability, resulting in enhanced flux across TJs. Epithelial TJ dysfunction also causes immune cell activation and contributes to the pathogenesis of chronic lung, skin, and intestinal inflammation. Characterization of TJ protein alteration is one of the key factors for enhancing our understanding of allergic diseases as well as IBDs. Furthermore, TJ-based epithelial disturbance can promote immune cell behaviors, such as those in dendritic cells, Th2 cells, Th17 cells, and innate lymphoid cells (ILCs), thereby offering new insights into TJ-based targets. The purpose of this review is to illustrate how TJ dysfunction can lead to the disruption of the immune homeostasis in barrier tissues and subsequent inflammation. This review also highlights the various TJ barrier dysfunctions across different organ sites, which would help to develop future drugs to target allergic diseases and IBD.

Sweat is a transparent hypotonic body fluid made from eccrine sweat glands. Various ingredients contained in sweat are involved in a broad sense in skin homeostasis including temperature regulation, skin moisture, and immune functions. Thus, sweat plays a major role in maintaining skin homeostasis. Therefore, abnormal sweating easily compromises human health. For example, in atopic dermatitis (AD), perspiration stagnation accompanying sweat tube or sweat pore blockage, leakage of perspiration from the sweat gland to the outside tissue, and impaired secretion of sweat from the sweat gland are confirmed. In recent years, the hypothesis that atopic dermatitis is a sweat stasis syndrome has been clarified by the establishment of a sweat and sweat gland dynamic analysis technique. Secretion of sweat and leakage into tissues is caused by dermatitis and is thought to promote itching. Furthermore, from the metabolomic analysis of sweat of patients with atopic dermatitis, it was confirmed that the glucose concentration in AD sweat increased according to severity and skin phenotype, suggesting that elevated glucose affected the homeostasis of the skin. Multifaceted analyses of sweat from subjects with AD have revealed new aspects of the pathology, and appropriate measures to treat sweat can be expected to contribute to long-term control of AD.

Atopic dermatitis (AD) is a chronic inflammatory skin disease that may be linked to changes in the gut microbiome. Acupuncture has been proven to be effective in reducing AD symptoms without serious adverse events, but its underlying mechanism is not completely understood. The purpose of this study was to investigate whether the potential effect of acupuncture on AD is gut microbiota-dependent. AD-like skin lesions were induced by applying MC903 topically to the cheek of the mouse. Acupuncture was done at the Gok-Ji (LI11) acupoints. AD-like symptoms were assessed by lesion scores, scratching behavior, and histopathological changes; intestinal barrier function was measured by fecal output, serum lipopolysaccharide levels, histopathological changes, and mRNA expression of markers involved in intestinal permeability and inflammation. Gut microbiota was profiled using 16S rRNA gene sequencing from fecal samples. Acupuncture effectively improved chronic itch as well as the AD-like skin lesions with epidermal thickening, and also significantly altered gut microbiota structure as revealed by β-diversity indices and analysis of similarities. These beneficial effects were eliminated by antibiotic depletion of gut microbiota, but were reproduced in gut microbiota-depleted mice that received a fecal microbiota transplant from acupuncture-treated mice. Interestingly, AD mice had intestinal barrier dysfunction as indicated by increased intestinal permeability, atrophy of the mucosal structure (reduced villus height and crypt depth), decreased expression of tight junctions and mucus synthesis genes, and increased expression of inflammatory mediators in the ileum. Acupuncture attenuated these abnormalities, which was gut microbiota-dependent. Acupuncture ameliorates AD-like phenotypes in a gut microbiota-dependent manner and some of these positive benefits are explained by modulation of the intestinal barrier, providing new perspective for non-pharmacological strategies for modulating gut microbiota to prevent and treat AD. Please cite this article as: Yeom M, Ahn S, Hahm DH, Jang SY, Jang SH, Park SY, Jang JH, Park J, Oh JY, Lee IS, Kim K, Kwon SK, Park HJ. Acupuncture ameliorates atopic dermatitis by modulating gut barrier function in a gut microbiota-dependent manner in mice. J Integr Med. 2024; 22(5): 600-613.

Atopic dermatitis is a chronic inflammatory skin disease with a complex pathogenesis, where changes in skin barrier and imbalance of the immune system are relevant factors. The skin forms a mechanic and immune barrier, regulating water loss from the internal to the external environment, and protecting the individual from external aggressions, such as microorganisms, ultraviolet radiation and physical trauma. Main components of the skin barrier are located in the outer layers of the epidermis (such as filaggrin), the proteins that form the tight junction (TJ) and components of the innate immune system. Recent data involving skin barrier reveal new information regarding its structure and its role in the mechanic-immunological defense; atopic dermatitis (AD) is an example of a disease related to dysfunctions associated with this complex.

After spinal cord injury (SCI), disruption of blood-spinal cord barrier (BSCB) elicits blood cell infiltration such as neutrophils and macrophages, contributing to permanent neurological disability. Previous studies show that epidermal growth factor (EGF) produces potent neuroprotective effects in SCI models. However, little is known that whether EGF contributes to the integrity of BSCB. The present study is performed to explore the mechanism of BSCB permeability changes which are induced by EGF treatment after SCI in rats. In this study, we demonstrate that EGF administration inhibits the disruption of BSCB permeability and improves the locomotor activity in SCI model rats. Inhibition of the PI3K/Akt pathways by a specific inhibitor, LY294002, suppresses EGF-induced Rac1 activation as well as tight junction (TJ) and adherens junction (AJ) expression. Furthermore, the protective effect of EGF on BSCB is related to the activation of Rac1 both in vivo and in vitro. Blockade of Rac1 activation with Rac1 siRNA downregulates EGF-induced TJ and AJ proteins expression in endothelial cells. Taken together, our results indicate that EGF treatment preserves BSCB integrity and improves functional recovery after SCI via PI3K-Akt-Rac1 signalling pathway.

The skin, the largest organ of the body, is an essential barrier that under homeostatic conditions efficiently protects and/or minimizes damage from both environmental (e.g. microorganisms, physical trauma, ultraviolet radiation) and endogenous (e.g., cancers, inflammation) factors. This formidable barrier function resides mainly in the epidermis, a dynamic, highly-stratified epithelium. The epidermis has 2 major barrier structures: stratum corneum, the outmost layer and tight junctions, intercellular junctions that seal adjacent keratinocytes in the stratum granulosum, found below the stratum corneum. In recent years there have been significant advances in our understanding of tight junction function, composition and regulation. Herein we review what is known about tight junctions in healthy skin and keratinocyte culture systems and highlight the dynamic crosstalk observed between tight junctions and the cutaneous immune system. Finally we discuss the preliminary observations suggesting that tight junction function or protein expression may be relevant for the pathogenesis of a number of common cutaneous inflammatory and neoplastic conditions.

Epidermal growth factor (EGF) and glucagon-like peptides (GLP) modulate the tight junctions (TJ) of the intestinal epithelial barrier (EB) of monogastric animals. This work tried to elucidate whether GLP-1, GLP-2 and EGF can affect the EB of the rumen. Ovine ruminal epithelia were incubated in Ussing chambers for 7 hr with 25 or 250 nM of either GLP-1 or GLP-2 on the serosal side, with 2.5 nM of EGF on the serosal side or with 0.25 or 2.5 nM EGF on the mucosal side. No treatment affected tissue conductance. Short-circuit current (I

The selection of skin is crucial for the in vitro permeation test (IVPT). The purpose of this study was to investigate the influence of different freezing-thawing processes on the barrier function of skin and the transdermal permeability of granisetron and lidocaine. Rat and hairless mouse skins were thawed at three different conditions after being frozen at -20℃ for 9 days: thawed at 4℃, room temperature (RT), and 32℃. There were no significant differences in the steady-state fluxes of drugs between fresh and thawed samples, but compared with fresh skin there were significant differences in lag time for the permeation of granisetron in rat skins thawed at RT and 32℃. Histological research and scanning electron microscopy images showed no obvious structural damage on frozen/thawed skin, while immunohistochemical staining and enzyme-linked immunosorbent assay for the tight junction (TJ) protein Cldn-1 showed significantly impaired epidermal barrier. It was concluded that the freezing-thawing process increases the diffusion rate of hydrophilic drugs partly due to the functional degradation of TJs. It's recommended that hairless, inbred strains and identical animal donors should be used, and the selected thawing method of skin should be validated prior to IVPT, especially for hydrophilic drugs.

Prior studies have revealed the key roles played by Th1/Th2 cell dysregulation, IgE production, mast cell hyperactivity, and dendritic cell signaling in the evolution of the chronic, pruritic, inflammatory dermatosis that characterizes atopic dermatitis (AD). We review here increasing evidence that the inflammation in AD results primarily from inherited abnormalities in epidermal structural and enzymatic proteins that impact permeability barrier function. We also will show that the barrier defect can be attributed to a paracellular abnormality due to a variety of abnormalities in lipid composition, transport and extracellular organization. Accordingly, we also review the therapeutic implications of this emerging pathogenic paradigm, including several current and potentially novel, lipid-based approaches to corrective therapy. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.

Mutations in the human filaggrin gene (FLG) are associated with atopic dermatitis (AD) and are presumed to provoke a barrier abnormality. Yet additional acquired stressors might be necessary because the same mutations can result in a noninflammatory disorder, ichthyosis vulgaris. We examined here whether FLG deficiency alone suffices to produce a barrier abnormality, the basis for the putative abnormality, and its proinflammatory consequences. By using the flaky-tail mouse, which lacks processed murine filaggrin because of a frameshift mutation in the gene encoding profilaggrin that mimics some mutations in human AD, we assessed whether FLG deficiency provokes a barrier abnormality, further localized the defect, identified its subcellular basis, and assessed thresholds to irritant- and hapten-induced dermatitis. Flaky-tail mice exhibit low-grade inflammation with increased bidirectional, paracellular permeability of water-soluble xenobiotes caused by impaired lamellar body secretion and altered stratum corneum extracellular membranes. This barrier abnormality correlates with reduced inflammatory thresholds to both topical irritants and haptens. Moreover, when exposed repeatedly to topical haptens at doses that produce no inflammation in wild-type mice, flaky-tail mice experience a severe AD-like dermatosis with a further deterioration in barrier function and features of a T(H)2 immunophenotype (increased CRTH levels plus inflammation, increased serum IgE levels, and reduced antimicrobial peptide [mBD3] expression). FLG deficiency alone provokes a paracellular barrier abnormality in mice that reduces inflammatory thresholds to topical irritants/haptens, likely accounting for enhanced antigen penetration in FLG-associated AD.

Although keratosis pilaris (KP) is common, its etiopathogenesis remains unknown. KP is associated clinically with ichthyosis vulgaris and atopic dermatitis and molecular genetically with filaggrin-null mutations. In 20 KP patients and 20 matched controls, we assessed the filaggrin and claudin 1 genotypes, the phenotypes by dermatoscopy, and the morphology by light and transmission electron microscopy. Thirty-five percent of KP patients displayed filaggrin mutations, demonstrating that filaggrin mutations only partially account for the KP phenotype. Major histologic and dermatoscopic findings of KP were hyperkeratosis, hypergranulosis, mild T helper cell type 1-dominant lymphocytic inflammation, plugging of follicular orifices, striking absence of sebaceous glands, and hair shaft abnormalities in KP lesions but not in unaffected skin sites. Changes in barrier function and abnormal paracellular permeability were found in both interfollicular and follicular stratum corneum of lesional KP, which correlated ultrastructurally with impaired extracellular lamellar bilayer maturation and organization. All these features were independent of filaggrin genotype. Moreover, ultrastructure of corneodesmosomes and tight junctions appeared normal, immunohistochemistry for claudin 1 showed no reduction in protein amounts, and molecular analysis of claudin 1 was unremarkable. Our findings suggest that absence of sebaceous glands is an early step in KP pathogenesis, resulting in downstream hair shaft and epithelial barrier abnormalities.

Hosting millions of microorganisms, the digestive tract is the primary and most important part of bacterial colonization. On one side, in cases of opportunistic invasion, the abundant bacterial population inside intestinal tissues may face potential health problems such as inflammation and infections. Therefore, the immune system has evolved to sustain the host-microbiota symbiotic relationship. On the other hand, to maintain host immune homeostasis, the intestinal microflora often exerts an immunoregulatory function that cannot be ignored. A field of great interest is the association of either microbiota or probiotics with the immune system concerning clinical uses. This microbial community regulates some of the host's metabolic and physiological functions and drives early-life immune system maturation, contributing to their homeostasis throughout life. Changes in gut microbiota can occur through modification in function, composition (dysbiosis), or microbiota-host interplays. Studies on animals and humans show that probiotics can have a pivotal effect on the modulation of immune and inflammatory mechanisms; however, the precise mechanisms have not yet been well defined. Diet, age, BMI (body mass index), medications, and stress may confound the benefits of probiotic intake. In addition to host gut functions (permeability and physiology), all these agents have profound implications for the gut microbiome composition. The use of probiotics could improve the gut microbial population, increase mucus-secretion, and prevent the destruction of tight junction proteins by decreasing the number of lipopolysaccharides (LPSs). When LPS binds endothelial cells to toll-like receptors (TLR 2, 4), dendritic cells and macrophage cells are activated, and inflammatory markers are increased. Furthermore, a decrease in gut dysbiosis and intestinal leakage after probiotic therapy may minimize the development of inflammatory biomarkers and blunt unnecessary activation of the immune system. In turn, probiotics improve the differentiation of T-cells against Th2 and development of Th2 cytokines such as IL-4 and IL-10. The present narrative review explores the interactions between gut microflora/probiotics and the immune system starting from the general perspective of a biological plausibility to get to the

Inflammatory bowel disease (IBD) is defined as an immune dysregulation disease with poor prognosis. Various therapies based on gut microbe modulation have been proposed. In this study, we aim to explore the therapeutic effect of

Yuzhi Zhixue (YZZX) granules, a classic Chinese herbal remedy, have demonstrated efficacy in managing hemorrhagic and inflammatory conditions, and are clinically used to treat uterine bleeding. Building upon their documented clinical applications and phytochemical composition, we hypothesized that YZZX may also possess therapeutic potential against ulcerative colitis (UC). This research aimed to examine the immunomodulatory effects of YZZX granules on Th1/Th17-mediated immune reactions in a murine UC model induced by dextran sulfate sodium (DSS). The major small-molecule constituents and macromolecular nano-components, specifically carbon dots (CDs), in YZZX were identified using UHPLC-QE-MS and other modern analytical techniques. UC was induced in mice via ad libitum access to a 2.5 % DSS solution, with YZZX administered orally. Anti-inflammatory effects were assessed by monitoring disease activity index (DAI) scores, body weight, colon length, ulcer area, and histopathological features. To uncover the mechanistic pathways of YZZX in UC treatment, transcriptomic sequencing, Flow cytometry, ELISA, RT-qPCR and Western blotting were conducted on colon tissue samples. YZZX significantly mitigated body weight loss, reduced DAI scores, ameliorated histopathological damage, and prevented colon shortening in UC mice. It improved the intestinal barrier function by promoting the upregulation of mucin MUC-2 and tight junction proteins (e.g., claudin, occludin, and ZO-1). Additionally, YZZX restored immune balance by modulating Th17/Treg and Th1/Th2 cell responses through the normalization of cytokine secretion and transcription factor expression. Transcriptomic analysis revealed that YZZX modulates the immune-inflammatory responses in colitis primarily via the JAK/STAT signaling pathway. These findings were further validated by Western blotting and RT-qPCR, which showed that YZZX suppressed the activation of this pathway by downregulating phosphorylated JAK/STAT protein expression. YZZX granules exert immunomodulatory effects primarily by rebalancing Th1/Th2 and Th17/Treg cell populations in the colon via inhibition of the JAK/STAT signaling pathway, thereby alleviating mucosal inflammation. This is the first study to systematically demonstrate the synergistic protective effects of both small-molecule compounds and carbon dot nano-components, derived from a traditional Chinese medicine formula in a DSS-induced murine model of UC.

Atopic dermatitis (AD), an inflammatory skin disorder with chronic course and characterized by intense pruritus, is a dermatosis of high prevalence of childhood. However, persistence of the disease in adolescents and adults may occur, and more studies regarding the interactions of the complex triggering factors, especially between the adaptive and innate immune alterations and skin barrier defects are needed. In this review the authors summarize the major novel findings of a dysfunctional skin barrier in AD, with emphasis on tight junction components, such as claudins and on proteins of the keratinocyte differentiation, such as filaggrin. This review also provides an update on the characterization of immune response in adults with atopic dermatitis. The adaptive immune dysfunction in AD, classically known as a Th2/Th1 model, has changed its profile, with recent reported cytokines such as interleukins 17, 22, and 31; as for the innate immune system scenario in AD, the characterization of skin microbiome opens new frontiers for the understanding of such a complex inflammatory disease.

Huanglian-ejiao decoction (HED) is a Chinese traditional medicinal formula evolved from the Shanghan Lun (Treatise on Febrile Diseases). However, HED ultimate mechanism of action remained indistinct. Therefore, this study aimed to investigate whether HED could exert anti-inflammatory effects on 2,4,6-Trinitrobenzenesulfonic acid (TNBS)-induced colitis (UC) model through the regulation of CD4 Fifty-eight major compounds in HED were identified by UPLC-Q-TOF/MS. The therapeutic efficacy of HED on UC was assessed by evaluating survival rate and so on. Flow cytometry was employed to assay the percentages of CD4 The administration of HED enhanced the survival rate of colitis mice, significantly restored body weight, DAI score, colon weight and index, spleen weight and index. HED effectively reshaped intestinal barrier dysfunction, inhibited the ratio of Th1 to Th2 cells, and preserved Th2/Th1 and Tregs/Th17 balance. Moreover, HED notably decreased the secretion of transcription factors and related cytokines. Interestingly, HED also exerts regulatory effects on gut dysbiosis by cumulative the plenteous of beneficial probiotics like Lactobacillus and Bacteroides, while inhibiting the overgrowth of opportunistic pathogens such as Helicobacter. The regulation of Th2/Th1 and Tregs/Th17 cell balance, as well as the modulation of gut microbiota by HED, provides further experimental evidence for the feasibility of its treatment of UC.

Allergic rhinitis (AR) is a chronic inflammatory disease primarily mediated by T

C-type lectin (CTL) plays an important act in parasite adhesion, host's cell invasion and immune escape. Our previous studies showed that recombinant Trichinella spiralis C-type lectin (rTsCTL) mediated larval invasion of enteral mucosal epithelium. The aim of this study was to investigate protective immunity produced by vaccination with rTsCTL and its effect on gut epithelial barrier function in a mouse model. The ELISA results showed that subcutaneous vaccination of mice with rTsCTL elicited a systemic humoral response (high levels of serum IgG, IgG1/IgG2a and IgA) and significant gut mucosal sIgA responses. The levels of Th1/Th2 cytokines (IFN-γ/IL-4) secreted from spleen, mesenteric lymph nodes and Peyer's patches were distinctly increased at 6 weeks following vaccination (P < 0.05). At one week after challenge, the numbers of goblet cells and expression level of Muc2, Muc5ac and pro-inflammatory cytokines (TNF-α and IL-1β) in gut tissues of vaccinated mice were obviously decreased, while expression of anti-inflammatory cytokines (IL-4 and IL-10) was evidently increased, compared to the infected PBS group. It is interesting that expression levels of gut epithelial tight junctions (TJs; occludin, claudin-1 and E-cad) were prominently elevated and intestinal permeability was interestingly declined in vaccinated mice. The rTsCTL-vaccinated mice exhibited a 51.69 and 48.19% reduction of intestinal adult and muscle larva burdens, respectively. The female fecundity in rTsCTL vaccinated mice was reduced by 40.51%. These findings indicated that rTsCTL vaccination impeded larval invasion and improved gut epithelial integrity and barrier function, reduced worm burdens, and relieved gut and muscle inflammation. Vaccination of mice with rTsCTL elicited an obvious protective immunity against larval challenge, impeded larval invasion of gut mucosa, enhanced gut epithelial integrity and barrier function, reduced worm burdens; it also alleviated gut and muscle inflammation. TsCTL might be a novel candidate target molecule for anti-Trichinella vaccines.

To infect its human host, herpes simplex virus 1 (HSV-1) must overcome the protective barriers of skin and mucosa. Here, we addressed whether pathological skin conditions can facilitate viral entry via the skin surface and used

Atopic dermatitis (AD) is a chronic inflammatory skin disorder characterized by defective skin barrier and Th2 immune responses. Chitinase 3-like 1 (CHI3L1), also known as breast regression protein 39 (BRP-39) in mice and human homologue YKL-40, plays important roles in Th2 inflammation and allergen sensitization. CHI3L1 has been implicated in a variety of diseases including asthma characterized by inflammation, apoptosis and tissue remodelling, but its role in AD remains elusive. The aim of this study was to investigate the role of CHI3L1 in the development and progression of AD. We investigated YKL-40 levels in the serum and skin of AD patients by ELISA and immunofluorescence, respectively. Using a murine model of AD induced by ovalbumin (OVA), we investigated Th2 immune responses, M2 macrophage activation and skin barrier gene expression using wild-type (WT) and BRP-39 null mutant (BRP-39 These findings demonstrate that CHI3L1 mediates the development of AD induced by OVA, affecting Th2 inflammation, M2 macrophage activation and skin barrier function.

Food allergy (FA) is acknowledged as a significant public health and food safety issue, due to its manifestation as an amplified immune reaction to food antigens. Recently, probiotics within Lactobacillus and Bifidobacterium have been highlighted as a promising strategy against allergic disease by modulating the balance of Th1/Th2 responses. However, the allergy-alleviating effects of probiotic Leuconostoc mesenteroides strains are unknown. Therefore, this study investigated the potentials of eleven L. mesenteroides strains on the Th1/Th2 balance in vitro by evaluating the expression patterns of interferon-gamma (IFN-γ) (Th1 cytokine) and interleukin-4 (IL-4) (Th2 cytokine) in mesenteric lymph node-derived lymphocytes from ovalbumin (OVA)-sensitized mice. Among strains, WHH1141 incubation caused the highest IFN-γ/IL-4 ratio. Oral administration of WHH1141 (1 × 10

Protease allergens are known to enhance allergic inflammation but their exact role in initiation of allergic reactions at mucosal surfaces still remains elusive. This study was aimed at deciphering the role of serine protease activity of Per a 10, a major cockroach allergen in initiation of allergic inflammation at mucosal surfaces. We demonstrate that Per a 10 increases epithelial permeability by disruption of tight junction proteins, ZO-1 and occludin, and enhances the migration of Monocyte derived dendritic cell precursors towards epithelial layer as exhibited by trans-well studies. Per a 10 exposure also leads to secretion of IL-33, TSLP and intracellular Ca

The discrepancy in drug absorption between healthy and diseased skins is an issue that needs to be elucidated. The present study attempted to explore the percutaneous absorption of drugs via lesional skin by using atopic dermatitis (AD) as a model. Tape-stripping and ovalbumin (OVA) sensitization induced AD-like skin. The lesions were evaluated by physiological parameters, histology, cytokines, and differentiation proteins. The permeants of tacrolimus, 8-methoxypsoralen, methotrexate, and dextran were used to examine in vitro and in vivo cutaneous permeation. Transepidermal water loss (TEWL) increased from 5.2 to 27.4 g/m(2)/h by OVA treatment. AD-like lesions were characterized by hyperplasia, skin redness, desquamation, and infiltration of inflammatory cells. Repeated OVA challenge produced a T-helper 2 (Th2) hypersensitivity accompanied by downregulation of filaggrin, involucrin, and integrin β. Tacrolimus, the most lipophilic permeant, revealed an increase of cutaneous deposition by 2.7-fold in AD-like skin compared to intact skin. The transdermal flux of methotrexate and dextran, the hydrophilic permeants, across AD-like skin increased about 18 times compared to the control skin. Surprisingly, AD-like skin showed less skin deposition of 8-methoxypsoralen than intact skin. This may be because the deficient lipids in the atopic-affected stratum corneum (SC) diminished drug partitioning into the superficial skin layer. The fluorescence and confocal microscopic images demonstrated a broad and deep passage of small-molecular and macromolecular dyes into AD-like skin. The results obtained from this report were advantageous for showing how the lesional skin influenced percutaneous absorption.

Asthma development and pathogenesis are influenced by the interactions of airway epithelial cells and innate and adaptive immune cells in response to allergens. Oxidative stress is an important mediator of asthmatic phenotypes in these cell types. Nuclear erythroid 2-related factor 2 (Nrf2) is a redox-sensitive transcription factor that is the key regulator of the response to oxidative and environmental stress. We previously demonstrated that Nrf2-deficient mice have heightened susceptibility to asthma, including elevated oxidative stress, inflammation, mucus, and airway hyperresponsiveness (AHR) (Rangasamy T, Guo J, Mitzner WA, Roman J, Singh A, Fryer AD, Yamamoto M, Kensler TW, Tuder RM, Georas SN, Biswal S. J Exp Med 202: 47-59, 2005). Here we dissected the role of Nrf2 in lung epithelial cells and tested whether genetic or pharmacological activation of Nrf2 reduces allergic asthma in mice. Cell-specific activation of Nrf2 in club cells of the airway epithelium significantly reduced allergen-induced AHR, inflammation, mucus, Th2 cytokine secretion, oxidative stress, and airway leakiness and increased airway levels of tight junction proteins zonula occludens-1 and E-cadherin. In isolated airway epithelial cells, Nrf2 enhanced epithelial barrier function and increased localization of zonula occludens-1 to the cell surface. Pharmacological activation of Nrf2 by 2-trifluoromethyl-2'-methoxychalone during the allergen challenge was sufficient to reduce allergic inflammation and AHR. New therapeutic options are needed for asthma, and this study demonstrates that activation of Nrf2 in lung epithelial cells is a novel potential therapeutic target to reduce asthma susceptibility.

Mutations in the gene encoding for filaggrin (FLG) are major predisposing factors for atopic dermatitis (AD). Besides genetic predisposition, immunological dysregulations considerably contribute to its pathophysiology. For example, thymic stromal lymphopoietin (TSLP) is highly expressed in lesional atopic skin and significantly contributes to the pathogenesis of AD by activating dendritic cells that then initiate downstream effects on, for example, T cells. However, little is known about the direct interplay between TSLP, filaggrin-deficient skin and other immune cells such as T lymphocytes. In the present study, FLG knockdown skin equivalents, characterised by intrinsically high TSLP levels, were exposed to activated CD4

Atopic dermatitis (AD) is a chronic inflammatory skin disease caused by a combination of genetic and environmental factors. Genetic evidences depict a complex network comprising by epidermal barrier dysfunctions and dysregulation of innate and adaptive immunity in the pathogenesis of AD. Mutations in the human filaggrin gene (FLG) are the most significant and well-replicated genetic mutation associated with AD, and other mutations associated with epidermal barriers such as SPINK5, FLG-2, SPRR3, and CLDN1 have all been linked to AD. Gene variants may also contribute to the abnormal innate and adaptive responses found in AD, including mutations in PRRs and AMPs, TSLP and TSLPR, IL-1 family cytokines and receptors genes, vitamin D pathway genes, FCER1A, and Th2 and other cytokines genes. GWAS and Immunochip analysis have identified a total of 19 susceptibility loci for AD. Candidate genes at these susceptibility loci identified by GWAS and Immunochip analysis also suggest roles for epidermal barrier functions, innate and adaptive immunity, interleukin-1 family signaling, regulatory T cells, the vitamin D pathway, and the nerve growth factor pathway in the pathogenesis of AD. Increasing evidences show the modern lifestyle (i.e., the hygiene hypothesis, Western diet) and other environmental factors such as pollution and environmental tobacco smoke (ETS) lead to the increasing prevalence of AD with the development of industrialization. Epigenetic alterations in response to these environmental factors, including DNA methylation and microRNA related to immune system and skin barriers, have been found to contribute to the pathogenesis of AD. Genetic variants and epigenetic alteration might be the key tools for the molecular taxonomy of AD and provide the background for the personalized management.

Recent studies have shown that activated pyroptosis in atopic dermatitis (AD) switches inflammatory processes and causes abnormal cornification and epidermal barrier dysfunction. Little research has focused on the interaction mechanism between pyroptosis-related genes and human keratinocyte differentiation. The AD dataset from the Gene Expression Omnibus (GEO) was used to identify differently expressed pyroptosis-related genes (DEPRGs). Hub genes were identified and an enrichment analysis was performed to select epithelial development-related genes. Lesions of AD patients were detected A total of 27 DEPRGs were identified between either atopic dermatitis non-lesional skin (ANL) and healthy control (HC) or atopic dermatitis lesional skin (AL) and HC. The enrichment analysis showed that these DEPRGs were primarily enriched in the inflammatory response and keratinocytes differentiation. Of the 10 hub genes identified This study revealed that GSDMD was upregulated in AD lesions and that GSDMD regulated keratinocytes

Atopic dermatitis (AD) is an important chronic or relapsing inflammatory skin disease that often precedes asthma and allergic disorders. New insights into the genetics and pathophysiology of AD point to an important role of structural abnormalities in the epidermis as well as immune dysregulation not only for this skin disease but also for the development of asthma and allergies. Patients with AD have a unique predisposition to colonization or infection by microbial organisms, most notably Staphylococcus aureus and herpes simplex virus. Measures directed at healing and protecting the skin barrier and addressing the immune dysregulation are essential in the treatment of patients with AD, and early intervention may improve outcomes for both the skin disease as well as other target organs.

Diabetes causes skin complications, including xerosis and foot ulcers. Ulcers complicated by infections exacerbate skin conditions, and in severe cases, limb/toe amputations are required to prevent the development of sepsis. Here, we hypothesize that hyperglycemia induces skin barrier dysfunction with alterations of epidermal integrity. The effects of hyperglycemia on the epidermis were examined in streptozotocin-induced diabetic mice with/without insulin therapy. The results showed that dye leakages were prominent, and transepidermal water loss after tape stripping was exacerbated in diabetic mice. These data indicate that hyperglycemia impaired skin barrier functions. Additionally, the distribution of the protein associated with the tight junction structure, tight junction protein-1 (ZO-1), was characterized by diffuse and significantly wider expression in the diabetic mice compared to that in the control mice. In turn, epidermal cell number was significantly reduced and basal cells were irregularly aligned with ultrastructural alterations in diabetic mice. In contrast, the number of corneocytes, namely, denucleated and terminally differentiated keratinocytes significantly increased, while their sensitivity to mechanical stress was enhanced in the diabetic mice. We found that cell proliferation was significantly decreased, while apoptotic cells were comparable in the skin of diabetic mice, compared to those in the control mice. In the epidermis, Keratin 5 and keratin 14 expressions were reduced, while keratin 10 and loricrin were ectopically induced in diabetic mice. These data suggest that hyperglycemia altered keratinocyte proliferation/differentiation. Finally, these phenotypes observed in diabetic mice were mitigated by insulin treatment. Reduction in basal cell number and perturbation of the proliferation/differentiation process could be the underlying mechanisms for impaired skin barrier functions in diabetic mice.

Background Tight junction abnormalities are a common feature of inflammatory skin diseases such as psoriasis and atopic dermatitis and contribute to systemic immune responses. Evidence provided to date suggests that Heat shock protein 105 kDa (HSP105) exhibits significant protective effects in response to destructive external stimuli. However, its role in UV-induced skin tight junction remains to be fully understood. Objective To investigate the role and underlying mechanisms of HSP105 in acute UVB-induced tight junction damage. Methods By utilizing bioinformatics analysis, together with an in vitro UVB-induced tight junction injury model in HaCaT cells, we investigated the expression and localization of HSP105 and the tight junction proteins CLDN1, CLDN4, and OCLN. The role of HSP105 was further explored through shRNA-mediated silencing and lentiviral overexpression in HaCaT cells. Potential pathways by which HSP105 regulates tight junction were analyzed using the GSEA algorithm and validated through in vitro experiments. Results Acute UVB irradiation mainly disrupted the distribution of CLDN1, CLDN4, and OCLN in HaCaT cells, while gene expression remained largely unaffected. Acute UVB irradiation also caused a reduction in HSP105 protein levels in HaCaT cells. Inhibition of HSP105 expression worsened tight junction fragmentation. GSEA analysis showed that Store-operated calcium entry (SOCE) was significantly correlated with HSP105 expression. Silencing HSP105 downregulated STIM1 transcription and inhibited SOCE, leading to further fragmentation of tight junction proteins. Overexpression of HSP105 partially mitigated the damage to tight junction integrity caused by UVB and SOCE inhibition. Conclusion HSP105 protects against acute UVB-induced tight junction damage through the regulation of SOCE. Our findings offer new insights into the treatment of skin barrier injury.

Atopic dermatitis (AD) is a common chronic inflammatory skin disease that exhibits a complex interplay of skin barrier disruption and immune dysregulation. Patients with AD are susceptible to cutaneous infections that may progress to complications, including staphylococcal septicemia. Although most studies have focused on filaggrin mutations, the physical barrier and antimicrobial barrier also play critical roles in the pathogenesis of AD. Within the physical barrier, the stratum corneum and tight junctions play the most important roles. The tight junction barrier is involved in the pathogenesis of AD, as structural and functional defects in tight junctions not only disrupt the physical barrier but also contribute to immunological impairments. Furthermore, antimicrobial peptides, such as LL-37, human β-defensins, and S100A7, improve tight junction barrier function. Recent studies elucidating the pathogenesis of AD have led to the development of barrier repair therapy for skin barrier defects in patients with this disease. This review analyzes the association between skin barrier disruption in patients with AD and antimicrobial peptides to determine the effect of these peptides on skin barrier repair and to consider employing antimicrobial peptides in barrier repair strategies as an additional approach for AD management.

Background: Inflammatory bowel disease is a chronic immunoinflammatory disease of the gastrointestinal tract. Piperine, an alkaloid, has been reported to possess antioxidant, anti-inflammatory, antiapoptotic, and antiulcer potential. Aim: To elucidate the plausible mechanisms of action of piperine on experimental trinitrobenzenesufonic acid (TNBS)-induced colitis by assessing various biochemical, molecular, histological, and ultrastructural modifications. Methods: Colitis was induced in male Sprague–Dawley rats via intrarectal instillation of TNBS. Then, the rats were treated with piperine (10, 20, and 40 mg/kg, p.o.) for 14 days. Results: TNBS induced significant (p < 0.05) colonic damage, which was assessed by disease activity index, macroscopic score, and stool consistency. The administration of piperine (20 and 40 mg/kg) significantly inhibited (p < 0.05) these damages. Treatments with piperine (20 and 40 mg/kg) notably inhibited (p < 0.05) the TNBS-induced elevation of oxido-nitrosative stress (superoxide dismutase, glutathione, malondialdehyde, and nitric oxide), 5-hydroxytryptamine, and hydroxyproline content in the colon. Furthermore, colonic inducible nitric oxide synthase (iNOs), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, IL-6, interferon-gamma, and cyclooxygenase-2 (COX-2) messenger RNA (mRNA) expressions were upregulated after TNBS instillation and piperine (20 and 40 mg/kg) significantly attenuated (p < 0.05) these elevated mRNA expressions. TNBS decreased the expressions of tight junction (TJ) protein (claudin-1, occludin, and zonula occludens-1 (ZO-1)) and increased the expressions of proapoptotic (caspase-1) protein. These expressions were markedly inhibited (p < 0.05) by piperine treatment. Histological and ultrastructural studies of transmission electron microscopy suggested that piperine significantly ameliorated (p < 0.05) TNBS-induced colonic aberrations. Conclusion: Piperine ameliorated the progression of TNBS-induced colitis by modulating the nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor-alpha/nuclear factor-kappa B signaling pathway, thus inhibiting the overexpression of proinflammatory cytokines (TNF-α and IL’s), COX-2, iNOs, oxido-nitrosative stress, and proapoptotic proteins (caspase-1) that may improve the expression of TJ protein (claudin-1, occludin, and ZO-1).

Objective To investigate the protective effect and mechanism of curcumin on intestinal barrier function in rats with enterogenic sepsis. Methods Rats were divided into Sham group (Sham), Model group (Model), low-dose curcumin group (100 mg/kg), and high-dose curcumin group (200 mg/kg), with 10 rats in each group. Sepsis model was established in model group, low-dose curcumin group, and high-dose curcumin group. After drug intervention, hematoxylin-eosin (HE) staining was used to observe the histopathological changes of small intestine in each group. The levels of TNF-α, IL-1β, and IL-6 in serum and intestinal tissues of rats were determined by ELISA. The expression of ZO-1, occludin, and claudin-1 in ileum was detected by QRT-PCR and Western blot. Western blotting was used to detect the expression of ERK/JNK signaling pathway, NF-κB p65, apoptosis-related proteins Caspase-3, and TNF-α in rat intestinal tissues. Results HE staining showed that curcumin treatment reduced epithelial cell shedding, interstitial edema, and apoptosis. Compared with model group, DAO activity, serum intestinal fatty acid binding protein (I-FABP), TNF-α, IL-6, and IL-1β expression in curcumin group were decreased in a dose-dependent manner. Curcumin can upregulate the mRNA and protein expression levels of ZO-1, occludin, and claudin-1 in ileum of CLP-induced rats. In addition, curcumin inhibits NF-κB p65 activation and apoptosis by regulating ERK/JNK signaling pathway. Conclusion Curcumin can reduce inflammatory response and upregulate the expression of intestinal tight junction proteins ZO-1, occludin, and claudin-1 in rats with enterogenic sepsis, and protect intestinal barrier function.

Tong-fu-li-fei (TFL) prescription has already used to treat sepsis in clinic but its mechanism remains unclear. Here, we aimed to investigate the effect and mechanism of Tong-fu-li-fei (TFL) prescription on sepsis in rats. The Sprague-Dawley rats were divided into the sham group, model group, the TFL 3.6 g/kg and 7.2 g/kg-treated group. The sepsis model was induced by cecal ligation and puncture (CLP). After 7 days, TFL treatment improved the survival rate of CLP rats and alleviated sepsis-induced intestinal mucosal injury. The ELISA assay showed that inflammatory cytokine expressions including TNF-α and IL-1β in serum from TFL-treated rats were lower than that in the model. And TNF-α, IL-1β and IL-6 from intestinal tissues were also decreased and IL-10 was increased in TFL-treated rats. Meanwhile the expression levels of the tight junction molecules occludin, claudin-1, and zonula occludens-1 (ZO-1) mRNA and protein expressions examined by RT-PCR, western blot and immunohistochemistry, were also restored in rats that received TFL treatment. Our data showed that TFL mitigates the inflammatory response and maintains intestinal barrier function in sepsis through upregulating ZO-1/occludin/claudin-1 expression, providing a good experimental basis for its clinical treatment of sepsis.

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The blood-tumor barrier (BTB) hinders delivery of chemotherapeutic drugs to tumors in the brain; previous studies have shown that the BTB can be selectively opened by endothelial monocyte activating polypeptide-II (EMAP-II), but the specific mechanism involved remains elusive. In this study, we found that microRNA-429 (miR-429) expression in glioma vascular endothelial cells (GECs) was far lower than in human brain microvascular endothelial cells (ECs). miR-429 had lower expression in GECs and glioma tissues compared to ECs or normal tissues of the brain. Furthermore, miR-429 had lower expression in high grade glioma (HGG) than in low grade glioma (LGG). In in vitro BTB models, we also found that EMAP-II significantly increased BTB permeability, decreased expression of ZO-1, occludin and claudin-5 in GECs, in a time- and dose-dependent manner. EMAP-II greatly increased miR-429 expression in GECs of the BTB models in vitro. Overexpression of miR-429 in GECs significantly decreased the transepithelial electric resistance (TEER) values in BTB models, and led to enhanced horseradish peroxidase (HRP) flux. Overexpression of miR-429 in GECs significantly decreased the expression of tight junction (TJ)-associated proteins (ZO-1, occludin and claudin-5), and decreased the distribution continuity. Silencing of miR-429 in GECs increased the expression of TJ-associated proteins and the distribution continuity. The dual-luciferase reporter assay revealed that ZO-1 and occludin were target genes of miR-429, and we demonstrated that miR-429 overexpression markedly down-regulated protein expression of p70S6K, as well as its phosphorylation levels. The dual-luciferase reporter assay also showed that p70S6K was a target gene of miR-429; miR-429 overexpression down-regulated expression and phosphorylation levels of p70S6K, and also decreased phosphorylation levels of S6 and increased BTB permeability. Conversely, silencing of miR-429 increased the expression and phosphorylation levels of p70S6K, and increased phosphorylation levels of S6, while decreasing BTB permeability. In conclusion, the results indicated that EMAP-II caused an increase in miR-429 expression that directly targeted TJ-associated proteins, which were negatively regulated; on the other hand, miR-429 down-regulated the expression of TJ-associated proteins by targeting p70S6K, also negatively regulated. As a result, the BTB permeability increased.

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Background The intestinal epithelial barrier, which works as the first line of defense between the luminal environment and the host, once destroyed, it will cause serious inflammation or other intestinal diseases. Tight junctions (TJs) play a vital role to maintain the integrity of the epithelial barrier. Lipopolysaccharide (LPS), one of the most important inflammatory factors will downregulate specific TJ proteins including Occludin and Claudin-1 and impair integrity of the epithelial barrier. Betaine has excellent anti-inflammatory activity but whether betaine has any effect on TJ proteins, particularly on LPS-induced dysfunction of epithelial barriers remains unknown. The purpose of this study is to explore the pharmacological effect of betaine on improving intestinal barrier function represented by TJ proteins. Intestinal porcine epithelial cells (IPEC-J2) were used as an in vitro model. Results The results demonstrated that betaine enhanced the expression of TJ proteins while LPS (1 μg/mL) downregulates the expression of these proteins. Furthermore, betaine attenuates LPS-induced decreases of TJ proteins both shown by Western blot (WB) and Reverse transcription-polymerase chain reaction (RT-PCR). The immunofluorescent images consistently revealed that LPS induced the disruption of TJ protein Claudin-1 and reduced its expression while betaine could reverse these alterations. Similar protective role of betaine on intestinal barrier function was observed by transepithelial electrical resistance (TEER) approach. Conclusion In conclusion, our research demonstrated that betaine attenuated LPS-induced downregulation of Occludin and Claudin-1 and restored the intestinal barrier function.

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Entry of hepatitis C virus (HCV) into hepatocytes is a complex process that involves numerous cellular factors, including the scavenger receptor class B type 1 (SR-B1), the tetraspanin CD81, and the tight junction (TJ) proteins claudin-1 (CLDN1) and occludin (OCLN). Despite expression of all known HCV-entry factors, in vitro models based on hepatoma cell lines do not fully reproduce the in vivo susceptibility of liver cells to primary HCV isolates, implying the existence of additional host factors which are critical for HCV entry and/or replication. Likewise, HCV replication is severely impaired within hepatocellular carcinoma (HCC) tissue in vivo, but the mechanisms responsible for this restriction are presently unknown. Here, we identify tumor-associated calcium signal transducer 2 (TACSTD2), one of the most downregulated genes in primary HCC tissue, as a host factor that interacts with CLDN1 and OCLN and regulates their cellular localization. TACSTD2 gene silencing disrupts the typical linear distribution of CLDN1 and OCLN along the cellular membrane in both hepatoma cells and primary human hepatocytes, recapitulating the pattern observed in vivo in primary HCC tissue. Mechanistic studies suggest that TACSTD2 is involved in the phosphorylation of CLDN1 and OCLN, which is required for their proper cellular localization. Silencing of TACSTD2 dramatically inhibits HCV infection with a pan-genotype effect that occurs at the level of viral entry. Our study identifies TACSTD2 as a novel regulator of two major HCV-entry factors, CLDN1 and OCLN, which is strongly downregulated in malignant hepatocytes. These results provide new insights into the complex process of HCV entry into hepatocytes and may assist in the development of more efficient cellular systems for HCV propagation in vitro.

Occludin is the only known integral membrane protein localizing at tight junctions (TJ), but recent targeted disruption analysis of the occludin gene indicated the existence of as yet unidentified integral membrane proteins in TJ. We therefore re-examined the isolated junction fraction from chicken liver, from which occludin was first identified. Among numerous components of this fraction, only a broad silver-stained band ∼22 kD was detected with the occludin band through 4 M guanidine-HCl extraction as well as sonication followed by stepwise sucrose density gradient centrifugation. Two distinct peptide sequences were obtained from the lower and upper halves of the broad band, and similarity searches of databases allowed us to isolate two full-length cDNAs encoding related mouse 22-kD proteins consisting of 211 and 230 amino acids, respectively. Hydrophilicity analysis suggested that both bore four transmembrane domains, although they did not show any sequence similarity to occludin. Immunofluorescence and immunoelectron microscopy revealed that both proteins tagged with FLAG or GFP were targeted to and incorporated into the TJ strand itself. We designated them as “claudin-1” and “claudin-2”, respectively. Although the precise structure/function relationship of the claudins to TJ still remains elusive, these findings indicated that multiple integral membrane proteins with four putative transmembrane domains, occludin and claudins, constitute TJ strands.

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AIMS Defective tight junctions (TJs) can induce intestinal epithelial dysfunction, which participates in various diseases such as irritable bowel syndrome. However, the mechanisms of TJ defects remain unclear. Our study revealed the role of Piezo1 in regulating intestinal epithelial function and TJs. MATERIALS AND METHODS The human colonic adenocarcinoma cell line Caco-2 were cultured on Transwell plate to form an epithelial barrier in vitro, and Piezo1 expression was manipulated using a lentivirus vector. Epithelial function was evaluated by measuring transepithelial electronic resistance (TEER) and 4-kDa FITC-dextran (FD4) transmission. TJ proteins (claudin-1, occludin, ZO-1) were evaluated by RT-PCR, western blot, and immunostaining analysis. Potential signal pathways, including the ROCK and Erk pathways, were detected. Moreover, to explore the regulatory effect of Piezo1 activity on epithelial function, inhibitors (ruthenium red, GsMTx4) and an agonist (Yoda1) were introduced both ex vivo and in vitro. KEY FINDINGS Alteration of Piezo1 expression altered epithelial function and the expression of the tight junction protein claudin-1. Piezo1 expression regulated phosphorylated ROCK1/2 expression, whereas interference on ROCK1/2 prevented the regulation of claudin-1 by Piezo1. In both Caco-2 monolayer and mouse colon epithelium, Piezo1 activity directly modulated epithelial function and permeability. SIGNIFICANCE Piezo1 negatively regulates epithelial barrier function by affecting the expression of claudin-1. Such regulation may be achieved partially via the ROCK1/2 pathway. Moreover, activating Piezo1 can induce epithelial dysfunction.

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Background: Considering the increasing worldwide prevalence of inflammatory bowel disease (IBD), the early diagnosis of this disease is extremely important. However, non-invasive diagnostic methods remain limited, while invasive techniques are the most commonly used in daily practice. Therefore, there is a serious need to find new non-invasive biomarkers of IBD. Methods: The serum profiles of occludin, claudin-2, and zonulin were assessed in IBD patients using the ELISA method. The levels of the analyzed biomarkers were measured before and after a year of anti-inflammatory treatment, which was a tumor necrosis factor α (TNF-α) inhibitor (adalimumab) in patients with ulcerative colitis (UC) and conventional therapy in patients with Crohn’s disease (CD). Results: In IBD patients, the serum level of occludin (p < 0.001) decreased compared to healthy individuals, while the level of claudin-2 (p < 0.001) increased. Additionally, zonulin (p < 0.01) concentration increased in CD patients compared to the control group. The highest diagnostic ability was presented by occludin measurements with the area under the curve (AUC) of 0.959 (95% CI 0.907–1) in UC and 0.948 (95% CI 0.879–1) in CD. Claudin-2 also demonstrated very good ability in diagnosing UC and CD with AUC values of 0.864 (95% CI 0.776–0.952) and 0.896 (95% CI 0.792–0.999), respectively. The ability of zonulin to diagnose CD was estimated as good with an AUC of 0.74 (95% CI 0.598–0.881). Moreover, a significant correlation was identified between C-reactive protein (CRP), claudin-2 (r = −0.37; p < 0.05), and zonulin (r = −0.44; p < 0.05) in UC patients. Treatment with adalimumab improved the level of occludin, claudin-2, and zonulin in UC patients, while anti-inflammatory conventional therapy decreased the concentration of zonulin in CD. Conclusions: Occludin and claudin-2 measurements present significant utility in diagnosing both UC and CD, while zonulin assessments may be useful in CD diagnosis. Additionally, claudin-2 and zonulin measurements may be helpful in evaluating the intensity of the inflammatory process. Anti-TNF-α treatment improved the value of occludin, claudin-2, and zonulin, indicating its beneficial effect on the integrity of tight junctions in UC.

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Background & Aims The circadian clock drives daily rhythms in behavior and physiology. A recent study suggests that intestinal permeability is also under control of the circadian clock. However, the precise mechanisms remain largely unknown. Because intestinal permeability depends on tight junction (TJ) that regulates the epithelial paracellular pathway, this study investigated whether the circadian clock regulates the expression levels of TJ proteins in the intestine. Methods The expression levels of TJ proteins in the large intestinal epithelium and colonic permeability were analyzed every 4, 6, or 12 hours between wild-type mice and mice with a mutation of a key clock gene Period2 (Per2; mPer2m/m). In addition, the susceptibility to dextran sodium sulfate (DSS)-induced colitis was compared between wild-type mice and mPer2m/m mice. Results The mRNA and protein expression levels of Occludin and Claudin-1 exhibited daily variations in the colonic epithelium in wild-type mice, whereas they were constitutively high in mPer2m/m mice. Colonic permeability in wild-type mice exhibited daily variations, which was inversely associated with the expression levels of Occludin and Claudin-1 proteins, whereas it was constitutively low in mPer2m/m mice. mPer2m/m mice were more resistant to the colonic injury induced by DSS than wild-type mice. Conclusions Occludin and Claudin-1 expressions in the large intestine are under the circadian control, which is associated with temporal regulation of colonic permeability and also susceptibility to colitis.

Entamoeba histolytica, the protozoan responsible for human amoebiasis, causes between 30,000 and 100,000 deaths per year worldwide. Amoebiasis is characterized by intestinal epithelial damage provoking severe diarrhea. However, the molecular mechanisms by which this protozoan causes epithelial damage are poorly understood. Here, we studied the initial molecular interactions between the E. histolytica EhCPADH112 virulence complex and epithelial MDCK and Caco-2 cells. By confocal microscopy, we discovered that after contact with trophozoites or trophozoite extracts (TE), EhCPADH112 and proteins forming this complex (EhCP112 and EhADH112) co-localize with occludin and claudin-1 at tight junctions (TJ). Immunoprecipitation assays revealed interaction between EhCPADH112 and occludin, claudin-1, ZO-1 and ZO-2. Overlay assays confirmed an interaction of EhCP112 and EhADH112 with occludin and claudin-1, whereas only EhADH112 interacted also with ZO-2. We observed degradation of all mentioned TJ proteins after incubation with TE. Importantly, inhibiting proteolytic activity or blocking the complex with a specific antibody not only prevented TJ protein degradation but also epithelial barrier disruption. Furthermore, we discovered that TE treatment induces autophagy and apoptosis in MDCK cells that could contribute to the observed barrier disruption. Our results suggest a model in which epithelial damage caused by E. histolytica is initiated by the interaction of EhCP112 and EhADH112 with TJ proteins followed by their degradation. Disruption of TJs then induces increased paracellular permeability, thus facilitating the entry of more proteases and other parasite molecules leading eventually to tissue destruction.

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During intestinal invasion, Entamoeba histolytica opens tight junctions (TJs) reflected by transepithelial electrical resistance (TEER) dropping. To explore the molecular mechanisms underlying this, we studied in vitro and in vivo the damage produced by the recombinant E. histolytica cysteine protease (rEhCP112) on TJ functions and proteins. rEhCP112 reduced TEER in Caco-2 cells in a dose- and time-dependent manner; and EhCP112-overexpressing trophozoites provoked major epithelial injury compared to control trophozoites. rEhCP112 penetrated through the intercellular space, and consequently the ion flux increased and the TJs fence function was disturbed. However, macromolecular flux was not altered. Functional in vitro assays revealed specific association of rEhCP112 with claudin-1 and claudin-2, that are both involved in regulating ion flux and fence function. Of note, rEhCP112 did not interact with occludin that is responsible for regulating macromolecular flux. Moreover, rEhCP112 degraded and delocalized claudin-1, thus affecting interepithelial adhesion. Concomitantly, expression of the leaky claudin-2 at TJ, first increased and then it was degraded. In vivo, rEhCP112 increased intestinal epithelial permeability in the mouse colon, likely due to apical erosion and claudin-1 and claudin-2 degradation. In conclusion, we provide evidence that EhCP112 causes epithelial dysfunction by specifically altering claudins at TJ. Thus, EhCP112 could be a potential target for therapeutic approaches against amoebiasis.

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Sleep deprivation is a prevalent issue that disrupts the circadian rhythm of estrogen, particularly estradiol, thereby significantly affecting women’s skin health and appearance. These disruptions can impair skin barrier functionality and decrease dermal collagen synthesis. In this study, our results demonstrate that topical taurine supplementation promotes the expression of tight junction (TJ)-related proteins and enhances collagen production, effectively restoring skin homeostasis in sleep-deprived female mice. Mechanistically, taurine upregulates the expression of TMEM38B, a gene encoding the TRIC-B trimeric cation channel, resulting in increased intracellular calcium ion levels. This, in turn, promotes the upregulation of TJ-related proteins, such as ZO-1, occludin, and claudin-11 in epidermal cells, while also enhancing the expression of type III collagen in fibroblasts, thus restoring skin homeostasis. These findings suggest that taurine may serve as an alternative to estradiol, effectively improving skin homeostasis disrupted by sleep deprivation while mitigating the potential risks associated with exogenous estrogen supplementation. Collectively, these results provide preliminary insights into the protective mechanisms of taurine against sleep deprivation-induced skin impairments and establish a foundation for its potential application in treating skin conditions related to estrogen imbalances, such as skin aging in menopausal women.

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Glioblastoma stem cells (GSCs) are subpopulations of tumor-initiating cells responsible for glioblastoma (GBM) tumorigenesis and recurrence. Dual inhibition of vascular endothelium and GSCs is still a challenge due to their different pathological features. Here we present a combined all-in-control strategy to realize a local photothermal therapy (PTT). We designed T-cell-mimic nanoparticles with aggregation-induced emission (AIE) characteristics by coating the genetically engineered T cell membrane (CM) onto AIE nanoparticles (CM@AIE NPs). The CM shell was designed against CD133 and epidermal growth factor receptor (EGFR) which provides the possibility to target both GBM cells and GSCs for cancer therapy. CM@AIE NPs can serve as the tight junction (TJ) modulators to trigger an intracellular signaling cascade, causing TJ disruption and actin cytoskeleton reorganization to allow CM@AIE NPs to cross the blood-brain barrier (BBB) silently. The 980 nm excitation-triggered PTT can completely inhibit tumorigenesis and recurrence. The combination of CM-coating nanotechnology and genetic editing technique can inspire further development of synergetic techniques for preventing GBM recurrence.

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BackgroundDespite the fact that morphological and physiological observations suggest that the tight junction (TJ)-based permeability barrier is modified/disrupted in tumorigenesis, the role of members of the Claudin (Cldn) family of TJ proteins is not well-understood. Using a well-established two-stage chemical carcinogenesis model, we investigated the temporal and spatial changes in expression of those Cldns that we have previously demonstrated to be important in epidermal differentiation and the formation of the epidermal permeability barrier, i.e., Cldn1, Cldn6, Cldn11, Cldn12 and Cldn18.MethodsThe lower dorsal backskin of mice was treated topically with 7,12-dimethylbenz(a)anthracene (DMBA; 0.25 mg/ml in acetone) and following a 10-day incubation period, 12-O-tetradecanoyl-phorbol-13-acetate (TPA; 25 μg/ml in acetone) was applied three times a week to the same area. Backskin samples were dissected 2, 4, 6, 8 and 12 weeks after the initiation of the experimental protocol and immunohistochemistry was performed on sections using antibodies against the following: Cldn1, Cldn6, Cldn11, Cldn12, Cldn18, Ki67 and CD3.ResultsOur data indicate that along with the changes in epidermal cell morphology and differentiation that occur during tumor formation, there is a dramatic change in Cldn distribution consistent with cell polarity and barrier selectivity changes. Specifically, in the early stages of DMBA/TPA treatment, the suprabasal-specific Cldns occupy an expanded zone of expression corresponding to an increased number of suprabasal epidermal cell layers. As tumorigenesis progressed, the number of suprabasal epidermal layers positive for Cldn6, Cldn11, Cldn12 and Cldn18 was reduced, especially in the lower strata of the expanded suprabasal zone. In addition, a variably reduced cell membrane association of those differentiation-specific Cldns was observed, especially within the infiltrating epidermal structures. In contrast, Cldn1 (which is normally expressed in all the living layers of the epidermis) remained restricted to the cell membrane throughout the tumorigenesis protocol. However commencing 2 weeks after treatment there was a marked decrease in the number of Cldn1-positive basal cells, and the zone of Cldn1-null epidermal cells was expanded up into the lower stratified epidermis throughout the progression of DMBA/TPA treatment. In addition, there was no Cldn1 localization in the infiltrating epidermal structures of the tumorigenic epidermis.ConclusionThis is the first demonstration of the changes in Cldn expression in the progression of DMBA/TPA-induced skin tumors; however further investigation into the molecular mechanisms regulating the observed changes in barrier selectivity during tumorigenesis is required.

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by a compromised epidermal barrier and heightened immunoglobulin E (IgE) levels, often associated with filaggrin (FLG) gene mutations. Genetic factors like FLG mutations and environmental influences, including microbial exposure and pollutants, contribute to the disease’s progression, leading to itchy, inflamed skin. AD frequently coexists with allergic conditions, severely affecting the quality of life. The disease’s pathogenesis involves complex interactions between genetic predispositions, immune responses, and environmental triggers. Despite advances, the development of effective treatments remains challenging due to an incomplete understanding of how FLG mutations influence immune pathways and the variability in AD presentation. Current biomarkers are insufficient to fully capture disease complexity or predict therapeutic responses, highlighting the need for novel biomarkers and personalized approaches. Emerging therapies such as chimeric antigen receptor (CAR)-T cell therapy, stem cell therapy, and regenerative medicine show promise in addressing AD’s root causes. This review explores key aspects of AD pathogenesis, focusing on epidermal barrier dysfunction, immune mechanisms, and the need for innovative therapeutic strategies to improve patient outcomes.

The skin serves as a fundamental protective barrier against environmental insults, with the epidermis, particularly the stratum corneum and tight junctions (TJs) connecting keratinocytes, playing a crucial role. Chronic hyperglycemia can impair these TJs, leading to compromised epidermal barrier function and diabetic skin complications. This study aimed to investigate the effects of umbelliferone on epidermal barrier function under type 2 diabetic conditions. HaCaT keratinocytes were cultured under hyperglycemic conditions induced by 33 mM glucose with or without 1–20 μM umbelliferone to evaluate cellular protection and barrier-related protein regulation. Type 2 diabetic db/db mice were administered umbelliferone orally at 10 mg/kg per day for 10 weeks. The expression of epidermal barrier-related proteins in HaCaT cells and skin tissues was quantified by Western blot analysis. Umbelliferone enhanced multiple components essential for maintaining the skin barrier. It upregulated filaggrin, increased the expression of the TJ proteins ZO-1 and Occludin, and elevated AQP3 and HAS2 levels to support epidermal hydration, while reducing HYAL1 expression. Under impaired wound healing conditions induced by hyperglycemia, umbelliferone promoted cell migration via modulation of F-actin organization, Rho GTPase signaling, and integrin β1 expression. Additionally, it reduced ROS accumulation and alleviated high glucose–induced apoptosis. Umbelliferone preserves epidermal barrier integrity by strengthening cell–cell junctions, enhancing hydration, promoting cell migration, and providing protection against oxidative stress and apoptosis. These findings suggest the therapeutic potential of umbelliferone in managing and preventing diabetic skin complications.

The skin barrier is vital for protection against environmental threats including insults caused by skin‐resident microbes. Dysregulation of this barrier is a hallmark of atopic dermatitis (AD) and ichthyosis, with variable consequences for host immune control of colonizing commensals and opportunistic pathogens. While Malassezia is the most abundant commensal fungus of the skin, little is known about the host control of this fungus in inflammatory skin diseases.

Atopic dermatitis (AD) is a common, chronic and relapsing inflammatory skin disease with various clinical presentations and combinations of symptoms. The pathophysiology of AD is complex and multifactorial. There are several factors involved in the etiopathogenesis of AD including structural and immunological epidermal barrier defect, imbalance of the skin microbiome, genetic background and environmental factors. Alterations in structural proteins, lipids, proteases, and their inhibitors, lead to the impairment of the stratum corneum which is associated with the increased skin penetration and transepidermal water loss. The elevated serum immunoglobulin E levels and blood eosinophilia have been shown in the majority of AD patients. Type 2 T-helper cell immune pathway with increased expression of interleukin (IL)-4, IL-5, and IL-13, has an important role in the etiopathogenesis of AD. Both T cells and keratinocytes contribute to epidermal barrier impairment in AD via a dynamic interaction of cytokines and chemokines. The skin microbiome is another factor of relevance in the etiopathogenesis of AD. It has been shown that during AD flares, Staphylococcus aureus (S. aureus) colonization increased, while Staphylococcus epidermidis (S. epidermidis) decreased. On the contrary, S. epidermidis and species of Streptococcus, Corynebacterium and Propionibacterium increased during the remision phases. However, it is not clear whether skin dysbiosis is one of the symptoms or one of the causes of AD. There are several therapeutic options, targeting these pathways which play a critical role in the etiopathogenesis of AD. Although topical steroids are the mainstay of the treatment of AD, new biological therapies including IL-4, IL-13, and IL-31 inhibitors, as well as Janus kinase inhibitors (JAKi), increasingly gain more importance with new advances in the therapy of AD. In this review, we summarize the role of immunological and structural epidermal barrier dysfunction, immune abnormalities, impairment of lipids, filaggrin mutation and skin microbiome in the etiopathogenesis of AD, as well as the therapeutic options for AD and their effects on these abnormalities in AD skin.

Staphylococcus aureus is the most common cause of bacterial skin infections in humans, including patients with atopic dermatitis (AD). Polymorphonuclear neutrophils (PMNs) are the first cells to infiltrate an infection site, where they usually provide an effective first line of defense, including neutrophil extracellular trap (NET) formation. Here, we show that infiltrating PMNs in inflamed human and mouse skin enhance S. aureus skin colonization and persistence. Mechanistically, we demonstrate that a crosstalk between keratinocytes and PMNs results in enhanced NET formation upon S. aureus infection, which in turn induces oxidative stress and expression of danger-associated molecular patterns such as high-mobility-group-protein B1 (HMGB1) in keratinocytes. In turn, HMGB1 enhances S. aureus skin colonization and persistence by promoting skin barrier dysfunctions by the downregulation of epidermal barrier genes. Using patient material, we show that patients with AD exhibit enhanced presence of PMNs, NETs, and HMGB1 in the skin, demonstrating the clinical relevance of our finding.

Skin is damaged in atopic dermatitis (AD) patients. Age is also believed to have a negative effect on epidermal barrier function. The aim of this study was to investigate skin barrier function changes with age in AD patients. A cross-sectional study was conducted including 162 participants, 81 AD patients and 81 healthy volunteers. Skin barrier function parameters, such as transepidermal water loss (TEWL), erythema, temperature, stratum corneum hydration (SCH), pH, and elasticity, were evaluated. Healthy volunteers were evaluated on the volar forearm. AD patients were measured on two regions: on an eczematous lesion on the volar forearm and on a non-involved area 5 cm from the affected area. TEWL was lower on healthy skin than uninvolved AD skin (9.98 vs. 25.51 g·m−2·h−1, p < 0.001) and AD eczematous lesions (9.98 vs. 28.38 g·m−2·h−1, p < 0.001). SCH was lower on AD eczematous lesions than uninvolved AD skin (24.23 vs. 39.36 AU, p < 0.001) and healthy skin (24.23 vs. 44.36 AU, p < 0.001). Elasticity was lower on AD eczematous lesions than uninvolved AD skin (0.69 vs. 0.74, p = 0.038) and healthy skin (0.69 vs. 0.77, p = 0.014). A negative correlation was found between age and elasticity in all the population (r = −0.383, p < 0.001). This correlation was stronger in AD patients (r = −0.494, p < 0.001) than in controls (r = −0.266, p = 0.092). After conducting a linear regression model in AD patients adjusted by age, sex, and SCORing Atopic Dermatitis (SCORAD), it was found that elasticity was impaired by an increasing age (β = −0.004, p < 0.001) and a higher SCORAD (β = −0.003, p < 0.001). The skin barrier function is impaired by age and AD, reflected mainly in poor elasticity values in older AD patients.

Atopic dermatitis (AD) is an immune-mediated inflammatory dermatosis characterized by epidermal barrier dysfunction, immune dysregulation, and cutaneous microbial dysbiosis. Existing therapeutic modalities for AD are limited in efficacy and durability, highlighting an unmet clinical need for novel, safe, and effective treatment strategies. Peroxisome proliferator-activated receptor gamma (PPARγ), a pivotal nuclear receptor involved in metabolic and inflammatory regulation, has emerged as a promising therapeutic target for AD. Its pleiotropic mechanisms encompass the restoration of stratum corneum integrity, modulation of aberrant immunoinflammatory signaling, normalization of cutaneous lipid metabolism, and regulation of the cutaneous microbiome and neuroimmune circuitry. This review comprehensively synthesizes the mechanistic evidence linking PPARγ to AD pathogenesis and critically appraises its potential as a novel therapeutic.

Staphylococcus (S) aureus colonization is known to cause skin barrier disruption in atopic dermatitis (AD) patients. However, it has not been studied how S. aureus induces aberrant epidermal lipid composition and skin barrier dysfunction.

Psoriasis (PsO) and atopic dermatitis (AD) are chronic, inflammatory skin diseases with distinct, yet occasionally overlapping, immunological profiles. PsO is characterized by T helper (Th) 1/Th17 immune pathways, while AD predominantly involves Th2 responses. However, a subset of patients exhibit features of both conditions, presenting a diagnostic and therapeutic challenge. This review aims to comprehensively assess the pathogenesis, clinical presentation, and therapeutic considerations of the PsO-AD overlap phenotype. This unique clinical entity is characterized by mixed Th17/Th2 immune responses, including elevated levels of interleukin (IL)-17A, IL-23, IL-4, and IL-13, complicating diagnosis and treatment strategies. Recent insights into the genetic, immunological, and environmental contributors to this phenotype, alongside emerging biomarker-guided therapies, offer potential for more precise management.

BACKGROUND Asthma and atopic dermatitis are common allergic conditions that contribute to substantial health loss, economic burden, and pain across individuals of all ages worldwide. Therefore, as a component of the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021, we present updated estimates of the prevalence, disability-adjusted life-years (DALYs), incidence, and deaths due to asthma and atopic dermatitis and the burden attributable to modifiable risk factors, with forecasted prevalence up to 2050. METHODS Asthma and atopic dermatitis prevalence, incidence, DALYs, and mortality, with corresponding 95% uncertainty intervals (UIs), were estimated for 204 countries and territories from 1990 to 2021. A systematic review identified data from 389 sources for asthma and 316 for atopic dermatitis, which were further pooled using the Bayesian meta-regression tool. We also described the age-standardised DALY rates of asthma attributable to four modifiable risk factors: high BMI, occupational asthmagens, smoking, and nitrogen dioxide pollution. Furthermore, as a secondary analysis, prevalence was forecasted to 2050 using the Socio-demographic Index (SDI), air pollution, and smoking as predictors for asthma and atopic dermatitis. To assess trends in the burden of asthma and atopic dermatitis before (2010-19) and during (2019-21) the COVID-19 pandemic, we compared their average annual percentage changes (AAPCs). FINDINGS In 2021, there were an estimated 260 million (95% UI 227-298) individuals with asthma and 129 million (124-134) individuals with atopic dermatitis worldwide. Asthma cases declined from 287 million (250-331) in 1990 to 238 million (209-272) in 2005 but increased to 260 million in 2021. Atopic dermatitis cases consistently rose from 107 million (103-112) in 1990 to 129 million (124-134) in 2021. However, age-standardised prevalence rates decreased-by 40·0% (from 5568·3 per 100 000 to 3340·1 per 100 000) for asthma and 8·3% (from 1885·4 per 100 000 to 1728·5 per 100 000) for atopic dermatitis. In 2021, there were substantial variations in the burden of asthma and atopic dermatitis across different SDI groups, with the highest age-standardised DALY rate found in south Asia for asthma (465·0 [357·2-648·9] per 100 000) and the high-income super-region for atopic dermatitis (3552·5 [3407·2-3706·1] per 100 000). During the COVID-19 pandemic, the decline in asthma prevalence had stagnated (AAPC pre-pandemic -1·39% [-2·07 to -0·71] and during the pandemic 0·47% [-1·86 to 2·79]; p=0·020); however, there was no significant difference in atopic dermatitis prevalence in the same period (pre-pandemic -0·28% [-0·33 to -0·22] and during the pandemic -0·35% [-0·78 to 0·08]; p=0·20). Modifiable risk factors were responsible for 29·9% of the global asthma DALY burden; among them, high BMI was the greatest contributor (39·4 [19·6-60·2] per 100 000), followed by occupational asthmagens (20·8 [16·7-26·5] per 100 000) across all regions. The age-standardised DALY rate of asthma attributable to high BMI was highest in high-SDI settings, whereas the contribution of occupational asthmagens was highest in low-SDI settings. According to our forecasting models, we expect 275 million (224-330) asthma cases and 148 million (140-158) atopic dermatitis cases in 2050, with population growth driving this increase. However, age-standardised prevalence rates are expected to remain stable (-23·2% [-44·4 to 5·3] for asthma and -1·4% [-9·1 to 7·0] for atopic dermatitis) from 2021 to 2050. INTERPRETATION Although the increases in the total number of asthma and atopic dermatitis cases will probably continue until 2050, age-standardised prevalence rates are expected to remain stable. A considerable portion of the global burden could be managed through efforts to address modifiable risk factors. Additionally, the contribution of risk factors to the burden substantially varied by SDI, which suggests the need for tailored initiatives for specific SDI settings. The growing number of individuals expected to be affected by asthma and atopic dermatitis in the future suggests that it is essential to improve our understanding of risk factors for asthma and atopic dermatitis and collect disease prevalence data that are globally generalisable. FUNDING Gates Foundation.

Atopic dermatitis, psoriasis, alopecia areata, and vitiligo have been associated with comorbid conditions, including infections, malignancies, and cardiovascular diseases. This study evaluated the prevalence and incidence rates of these comorbidities in patients from Japan. This retrospective cohort study used data collected from the JMDC claims database between June 2013 and December 2020. Patients with a diagnosis of atopic dermatitis, psoriasis, alopecia areata, or vitiligo were matched (1:1) by age, sex, and index month with individuals with no claims records for atopic dermatitis, psoriasis, alopecia areata, or vitiligo diagnosis. Data included 691 338, 51 988, 43 692, and 8912 patients in the atopic dermatitis, psoriasis, alopecia areata, and vitiligo cohorts, respectively, and matched controls. The most prevalent comorbidities in the atopic dermatitis cohort versus matched controls included allergic rhinitis (47% vs 37%), conjunctivitis (33% vs 23%), asthma (27% vs 20%), viral infection (22% vs 15%), and acne (11% vs 3%). Incidence rates per 100 000 person‐years of comorbidities in the atopic dermatitis cohort versus matched controls were: venous thromboembolism, 51.4 (95% confidence interval [CI], 48.3–54.7) versus 31.7 (95% CI, 29.2–34.2); lymphoma, 13.8 (95% CI,12.2–15.6) versus 5.7 (95% CI, 4.7–6.8); cutaneous T‐cell lymphoma, 1.6 (95% CI, 1.1–2.2) versus 0.1 (95% CI, 0.0–0.4); and herpes zoster, 740.9 (95% CI, 728.8–753.1) versus 397.6 (95% CI, 388.9–406.6). Similar trends were observed in the psoriasis versus nonpsoriasis cohorts, with 95% CIs mostly overlapping for alopecia areata and vitiligo cohorts versus controls. Overall, patients from Japan with dermatologic diseases have a higher prevalence and incidence of certain health conditions, particularly venous thromboembolism, lymphoma, and infections in patients with atopic dermatitis and psoriasis, compared with individuals without these dermatologic diseases.

Background: Although itch is the universal symptom of atopic dermatitis (AD), little is known about its clinical phenotypes in AD. Objective: To examine the relationships of itch characteristics and patterns with AD severity, mental health, sleep, and quality of life (QOL). Methods: We conducted a prospective study of 456 adult patients with AD using validated questionnaires and skin examinations. Thirteen itch characteristics were assessed with the Patient-Reported Outcomes Measurement Information System Itch-Quality. Multivariable regression models evaluated the associations of itch characteristics, severity, or patterns with outcomes. Results: A total of 283 (62%) patients described their itch with ≥1 descriptor-most commonly, stinging (29%), tingling (24%), burning (23%), and painful (23%). The number of itch characteristics reported and endorsement of at least one itch quality were associated with greater AD and itch severity, history of anxiety and depression, active symptoms of clinical depression, sleep impairment, and QOL decrement. Reporting ≥1 itch characteristic remained associated with anxiety, active depression, sleep disturbance, and QOL impact independent of itch severity. All 13 itch descriptors were associated with worse sleep and QOL even after controlling for itch severity. Dermatitis affecting the face, eyelids, hands, or feet was each associated with distinct patterns of itch qualities. Latent class analysis identified three phenotypes of itch, which correlated with AD and itch severity, active symptoms of depression, and QOL decrement. Conclusion: Adults with AD commonly describe their itch heterogeneously using pain-related sensory descriptors. The quality of itch may independently predict mental health outcomes, sleep impairment, and QOL impact.

Background Interleukin -17 (IL-17), particularly IL-17A, thymic stromal lymphopoietin (TSLP), interferon gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), IL-2, IL-6, IL-23, and IL-31 play a significant role in the pathogenesis of various chronic inflammatory and autoimmune skin diseases. Method We conducted an assessment of plasma levels of interleukins IL-17A, TSLP, IFN-γ TNF-α, IL-2, IL-6, IL-23, and IL-31 in 89 atopic dermatitis (AD) patients and in 34 healthy individuals as a control group. The group of AD patients consisted of 27 patients treated with dupilumab for moderate and severe form (15 men, 12 women, mean age of 44.8 years) and 62 AD patients suffering from moderate and severe form without any systemic treatment (35 women,27 men, mean age of 46.3 years). The control group consisted of 34 healthy subjects (22 men, 12 women, mean age of 43.3 years). For screening analysis of plasma levels of cytokines the performance assay Human cytokine Luminex was used. Blood samples were unstimulated and stimulated with phorbol myristate acetate and ionomycin. The levels of IL-17A, TSLP, IFN-γ, TNF-α, IL-2, IL-6, IL-23, and IL-31 were compared in AD patients with the results in control group. Nonparametric Kruskal-Wallis analysis of variance with post-hoc Dunn’s test with Bonferroni modification of significance level was used for statistical analysis. Results Under unstimulated conditions we found these significant differences:1) Higher IL-17A and TNF-α in dupilumab-treated AD patients vs. healthy controls, suggesting residual Th17 and pro-inflammatory activity despite Th2 blockade. 2) TSLP elevated in both groups of AD patients indicating persistent epithelial barrier stress. 3) Low IFN-γ in both groups of AD patients is consistent with Th2 dominance. Under stimulated conditions we found these significant differences: 1) Lower IL-23 in both groups of AD patients vs. healthy controls suggesting possible impaired Th17 axis activation. 2) Lower IL-2 in patients without systemic treatment vs. healthy controls indicating reduced T-cell activation capacity without biologic therapy. 3) Higher IL-6 in both groups of AD patients vs. healthy controls reflecting ongoing innate/inflammatory activation under both conditions. Conclusion Dupilumab effectively suppresses Th2 signaling but does not fully normalize immune balance; residual Th17 and innate activity persists. Elevated TSLP and IL-6 suggest that epithelial stress and innate immune activation remain key drivers. Reduced IL-23 and IL-2 under stimulation indicate altered adaptive immune responsiveness in AD patients.

Background Atopic dermatitis (AD) burden increases with disease severity. Objective Characterize the real-world burden of AD in Brazil, Mexico, and Argentina. Methods MEASURE-AD enrolled patients (≥12-years old) with moderate to severe AD receiving or candidates for systemic therapy between December 2019-December 2020. Patient characteristics, treatments, and outcomes were recorded during one office visit. Primary outcome measures included worst itch/past 24 hours (Worst Pruritus Numerical Rating Scale [WP-NRS]), quality of life (QoL, Dermatology Life Quality Index [DLQI] and Children's DLQI [CDLQI]). Results Of 180 patients (adults, n = 157; adolescents, n = 23), 52.2% were male, the mean (SD) age was 33.8 (17.0) years, and all were receiving AD treatment (65.6% systemic therapy). Severe pruritus (WP-NRS ≥ 7) was reported by 54.4% (adults, 57.3%; adolescents, 34.8%). A very/extremely large effect on QoL (DLQI/CDLQI ≥ 11) was reported among 50.0% of patients ≥ 16 years old and 42.9% of patients 12–15 years old. The mean Eczema Area Severity Index (EASI) was 17.0 (adults, 17.7; adolescents, 12.4); 3.9% of patients had clear skin (EASI 0) and 26.7% had severe AD (EASI 23–72). Over the previous 6 months, 0, 1–2, 3–4, 5–6, and > 6 flares were reported by 8.3%, 27.2%, 31.1%, 11.7%, and 15.6% of patients, respectively. On average, flares lasted 15.2 days (adults, 15.9 days; adolescents, 11.1 days). Study limitations Patient self-reported information and recall during one office visit. Conclusions Despite treatment, disease severity and impact on QoL were high, suggesting that AD is not adequately controlled in all patients, highlighting a considerable unmet need for effective treatments to reduce AD burden.

Introduction: Psoriasis (PSO) and atopic dermatitis (AD) have traditionally been considered distinct diseases, respectively, mediated by T-helper 1 (Th1) and the T-helper 2 (Th2) immune pathway. In recent years, there has been a growing body of evidence highlighting an overlap between the two conditions, such as Asian AD, pediatric PSO, or “psoriasis dermatitis/PSOREMA”. Moreover, psoriasis dermatitis can be induced by therapeutic interventions. For instance, anti-IL-4/IL-13 monoclonal antibodies, commonly used to treat AD, can induce psoriasiform reactions by inhibiting the Th2 pathway, thereby unmasking Th1/Th17-driven PSO. Conversely, anti-TNFα and anti-IL-17 therapies, effective for PSO, may induce eczematous reactions promoting a switch toward Th2-driven inflammation. Janus Kinase Inhibitors (JAK-i) and IL-23 antagonists may represent valid therapeutic options for managing psoriasis dermatitis. JAK-i exert broader immunomodulatory effects, inhibiting both Th1 and Th2 pathways; however, they require careful monitoring due to potential adverse events. In contrast, IL-23 antagonists specifically suppress the IL-23/IL-17 axis inhibiting the p19 subunit of IL-23 and could represent a safer option for patients with psoriasis dermatitis. Materials and Methods/Results: We present a series of five cases of psoriasis dermatitis, including both patients who had the condition from the onset and those who developed it during treatment, with tailored therapeutic strategies based on individual patient profiles, comorbidities, and the specific characteristics of their overlapping disease presentation. Conclusion: JAK-i and IL-23 antagonists are both valid therapeutic options for managing psoriasis dermatitis, but with different immunomodulatory effects and safety profiles. Future research should focus on a better understanding of the immune pathway and identifying specific biomarkers of psoriasis dermatitis, to optimize therapeutic strategies.

The aim of the study was to evaluate the clinical significance of zinc deficiency in children with atopic dermatitis and its correction. Materials and Methods: The study was conducted at the multidisciplinary clinic of Tashkent Medical Academy in the department of pediatric allergology on 38 children aged 2-7 years with atopic dermatitis (AD). The children were divided into 3 groups: the main group - children with AD diagnosis receiving the main treatment + zinc, n=15 (39.5%); the comparison group - children with AD receiving only the main treatment, n=23 (60.5%); and the control group - almost healthy children, n=15. The clinical manifestations of AD were assessed using the SCORAD index. Clinical examination included anamnesis collection and objective examination. All children underwent standard laboratory tests and evaluation of zinc levels in blood serum (using X-ray fluorescence analysis). Results: All children with AD were divided into 2 groups based on the Zn content in their blood serum. The first group (main group) included children with serum Zn concentrations below 9.5 µmol/L. The second group (comparison group) included children with serum Zn concentrations above 10 µmol/L. In the main group, nail hyperkeratosis was observed in 7 children (46.7%), perioral dermatitis in 11 children (73.3%), and perianal dermatitis in 7 children (46.7%). In the comparison group, nail hyperkeratosis was observed in 2 children (8.7%), perioral dermatitis in 6 children (26.1%), and perianal dermatitis in 3 children (13.4%). Children in the main group received the main treatment and additionally took a zinc-containing preparation for 1 month. In the comparison group, children received only the main treatment. After treatment, a positive dynamic of AD symptoms was observed in the main group. The introduction of zinc-containing preparation not only significantly improved the SCORAD index but also helped to moisturize the skin. In the main group, an increase in blood zinc levels was recorded, and further treatment with zinc-containing preparation was recommended. For children with normal zinc levels, zinc-containing preparations were added to their diet. Conclusion: Thus, zinc deficiency in serum was found in 39.5% of children in the study group. Zinc deficiency in children with AD was accompanied by clinical manifestations such as nail hyperkeratosis, perioral and perianal dermatitis. It is recommended to prescribe zinc-containing preparations for correcting zinc deficiency in patients with AD.

Abstract Background/objective Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disease that typically occurs in childhood/infancy and is associated with complications like extracutaneous atopic morbidity. Providing systemic treatment for pediatric AD patients with unmet comprehensive medical needs remains challenging. We present a cohort study describing the efficacy and safety of dupilumab combined with topical calcineurin inhibitors (TCI) in children with moderate-to-severe atopic dermatitis under the age of 6 years. Methods A retrospective cohort study was conducted at a single center to analyze the use of dupilumab in combination with topical calcineurin inhibitors (TCI) in children aged 6 years and under moderate-to-severe AD that was inadequately controlled with topical therapy. Results Overall, 23 preschool children (mean [SD] age, 4.78 [1.278] years); 10 boys (43.5%) and 13 girls (56.5%) received 300 mg dupilumab every four weeks and TCI. The primary outcome, the average Eczema Area and Severity Index (EASI) percentage reduction from baseline, was −70.85%. Significant improvement was also observed in secondary outcomes: caregiver-reported Peak Pruritus numerical rating scale (P-NRS) (−77.73%), Body Surface Area (BSA) (−62.11%), and Investigators Global Assessment (IGA) (−36.23%) at week 16. A 1–2 grade decrease in IGA after 16 weeks of treatment was achieved by 91.3% of patients. There was a significant improvement in P-NRS and EASI scores from baseline to week 16. Injection-site reaction (one patient) and facial redness (two patients) were recorded. No severe drug-related adverse events were observed. Conclusion This study demonstrated that the combination of dupilumab and TCIs improved symptoms and quality of life in preschoolers with moderate-to-severe AD.

Background Neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) are systemic inflammation markers, but their association with adult atopic dermatitis (AD) remains underexplored. Methods This cross-sectional study analyzed 2001–2006 NHANES data from 10,890 US adults. AD was defined by self-reported physician diagnosis. Cutoffs for NLR (1. 81×109/L) and PLR (136. 13×109/L) were determined via ROC analysis. Multivariable models adjusted for sociodemographic and clinical covariates. Results Elevated NLR (≥1. 81×109/L) and PLR (≥136. 13×109/L) were independently associated with higher AD prevalence after full adjustment (NLR: OR=1. 23, 95%CI:1. 08–1. 40; PLR: OR=1. 24, 95%CI:1. 10–1. 41). Subgroup analyses revealed stronger associations in males, normal-BMI individuals, and asthmatics (PLR: OR=1. 84), but inverse correlations in nonsmokers (NLR: OR=0. 33; PLR: OR=0. 34). Significant interactions occurred with BMI and asthma (PLR-interaction P=0. 0077). Conclusion NLR and PLR are accessible systemic inflammatory biomarkers for AD, with subgroup heterogeneity suggesting roles for lymphocyte depletion (skin homing), neutrophilic (Th17), and platelet-mediated (Th2) inflammation pathways.

Background: Recent advances in understanding the molecular mechanisms underlying atopic dermatitis (AD) have led to the development and FDA approval of multiple targeted therapies. Molecular heterogeneity of AD contributes to inconsistent clinical presentation and therapeutic response, which can lead to delays in diagnosis and initiation of appropriate treatment for patients. Adding complexity to the decision-making process, newer targeted systemic treatments are also associated with varied efficacy, safety profiles, and monitoring requirements. More information is needed on patient perspectives of current systemic treatment options to support joint treatment decision-making.   Objectives: To 1) better understand patient attitudes about contemporary AD treatments and experiences and 2) evaluate patient perception of a molecular test to predict treatment response.    Methods: A 31-question survey (IRB-exempt) made available to attendees of the 2024 National Eczema Association Eczema Expo was designed to assess patient perspectives on their treatment for AD, including treatment attributes and experiences. Participation was voluntary and not associated with data presentation.   Results: Of 43 eligible respondents, 74% were 18 to 64 years old and 21% were <18 years of age, with the remaining participants ≥65 years (5%). Approximately 40% (16) of participants reported their AD was previously misdiagnosed and 28% (12) of the participants were biopsied to confirm their AD diagnosis. The top three factors most important to respondents using topical-only or systemic (±topical) medications were itch control (70%), skin clearance (58%), and safety/side effects (50%). For the 22 respondents who used targeted systemics, 23% switched or added another systemic and 32% added topicals. The top two reasons for switching or modifying systemic treatment were insufficient skin clearance and itch control. Patient ratings of how well current therapy met their treatment goals varied extensively. Scaled from 1% (goals not met) to 100% (goals met), patient rankings ranged from 26% - 100% with a median of 68% progress toward goals for those using systemic therapies (± skin-directed therapies). Over 80% of respondents would want, or may consider, taking a test informing them of which targeted systemic would work best for them, thus highlighting a clinical need for personalized therapeutic guidance in AD.   Conclusion: A substantial number of AD patients experience delayed diagnosis. Itch was the most important symptom that respondents desired their medication to address. While topicals and systemic therapies can be effective, AD patients had a wide variety of treatment responses regardless of treatment modality, suggesting a need for a more personalized approach to treatment selection. The majority (80%) of patients would want, or would consider, a test that would direct them towards a more effective therapy for their AD.

Importance The association of diet with atopic dermatitis (AD) remains poorly understood and could help explain heterogeneity in disease course. Objective To determine the extent to which a higher level of dietary sodium intake, estimated using urine sodium as a biomarker, is associated with AD in a large, population-based cohort. Design, Setting, and Participants This cross-sectional study of adult participants (aged 37-73 years) from the UK Biobank examined 24-hour urine sodium excretion, which was estimated using a single spot urine sample collected between March 31, 2006, and October 1, 2010, and calculations from the sex-specific International Cooperative Study on Salt, Other Factors, and Blood Pressure equation, incorporating body mass index; age; and urine concentrations of potassium, sodium, and creatinine. The data were analyzed between February 23, 2022, and March 20, 2024. Exposure The primary exposure was 24-hour urinary sodium excretion. Main Outcome and Measure The primary outcome was AD or active AD based on diagnostic and prescription codes from linked electronic medical records. Multivariable logistic regression models adjusted for age, sex, race and ethnicity, Townsend Deprivation Index, and education were used to measure the association. Results The analytic sample comprised 215 832 participants (mean [SD] age, 56.52 [8.06] years; 54.3% female). Mean (SD) estimated 24-hour urine sodium excretion was 3.01 (0.82) g per day, and 10 839 participants (5.0%) had a diagnosis of AD. Multivariable logistic regression revealed that a 1-g increase in estimated 24-hour urine sodium excretion was associated with increased odds of AD (adjusted odds ratio [AOR], 1.11; 95% CI, 1.07-1.14), increased odds of active AD (AOR, 1.16; 95% CI, 1.05-1.28), and increased odds of increasing severity of AD (AOR, 1.11; 95% CI, 1.07-1.15). In a validation cohort of 13 014 participants from the National Health and Nutrition Examination Survey, a 1 g per day higher dietary sodium intake estimated using dietary recall questionnaires was associated with a higher risk of current AD (AOR, 1.22; 95% CI, 1.01-1.47). Conclusions and Relevance These findings suggest that restriction of dietary sodium intake may be a cost-effective and low-risk intervention for AD.

Celastrol, a bioactive molecule extracted from the plant Tripterygium wilfordii Hook F., possesses anti‐inflammatory, anti‐obesity and anti‐tumour properties. Despite its efficacy in improving erythema and scaling in psoriatic mice, the specific therapeutic mechanism of celastrol in atopic dermatitis (AD) remains unknown. This study aims to examine the role and mechanism of celastrol in AD using TNF‐α‐stimulated HaCaT cells and DNCB‐induced Balb/c mice as in vitro and in vivo AD models, respectively. Celastrol was found to inhibit the increased epidermal thickness, reduce spleen and lymph node weights, attenuate inflammatory cell infiltration and mast cell degranulation and decrease thymic stromal lymphopoietin (TSLP) as well as various inflammatory factors (IL‐4, IL‐13, TNF‐α, IL‐5, IL‐31, IL‐33, IgE, TSLP, IL‐17, IL‐23, IL‐1β, CCL11 and CCL17) in AD mice. Additionally, celastrol inhibited Ezrin phosphorylation at Thr567, restored mitochondrial network structure, promoted translocation of Drp1 to the cytoplasm and reduced TNF‐α‐induced cellular reactive oxygen species (ROS), mitochondrial ROS (mtROS) and mitochondrial membrane potential (MMP) production. Interestingly, Mdivi‐1 (a mitochondrial fission inhibitor) and Ezrin‐specific siRNAs lowered inflammatory factor levels and restored mitochondrial reticular formation, as well as ROS, mtROS and MMP production. Co‐immunoprecipitation revealed that Ezrin interacted with Drp1. Knocking down Ezrin reduced mitochondrial fission protein Drp1 phosphorylation and Fis1 expression while increasing the expression of fusion proteins Mfn1 and Mfn2. The regulation of mitochondrial fission and fusion by Ezrin was confirmed. Overall, celastrol may alleviate AD by regulating Ezrin‐mediated mitochondrial fission and fusion, which may become a novel therapeutic reagent for alleviating AD.

No abstract available

Bosakitug (BSI-045B) is a humanized monoclonal antibody targeting thymic stromal lymphopoietin (TSLP) which is a master regulator of type 2 (Th2) immune responses at the barrier surfaces of skin and the respiratory/gastrointestinal tract. The expression of TSLP is elevated in individuals with atopic diseases such as atopic dermatitis (AD). Herein, we describe the clinical efficacy, safety, and pharmacokinetic results of bosakitug from a phase 2a study in moderate to severe AD subjects (ADAMANT). To evaluate the safety, clinical efficacy, pharmacokinetic characteristics, and immunogenicity (ADA) of monotherapy bosakitug injection in AD subjects. Each enrolled AD subject received 300 mg of bosakitug subcutaneous injection weekly for 4 weeks and then every 2 weeks thereafter through 23 weeks of treatment. Following the treatment phase, subjects are followed for 12 weeks. Eczema Area and Severity Index (EASI), Investigator’s Global Assessment (IGA), and Peak Pruritus Numerical Rating Scale (PPNRS) score were measured at baseline and at each study visit to assess clinical efficacy. Pharmacokinetic, pharmacodynamic, and ADA samples were collected at pre-dose, at each study visit and, if necessary, at the time of early withdrawal of study drug. Twenty-two subjects with moderate and severe disease were enrolled into the trial. Baseline mean scores for the cohort were EASI of 17.5, IGA of 3.05, and PP-NRS of 6.5. At week 23, with 18 evaluable participants completing the dosing phase of the study, 79% of the AD subjects achieved an IGA 0/1, 89% achieved an EASI-75, 44% achieved an EASI-90 and 28% achieved an EASI-100. The mean PP-NRS score decreased by ∼3 points through the end of the dosing period. The mean percentage change from baseline in EASI score showed continual improvement beyond week 23. By week 31, the five subjects who had reached eight weeks following their last dose, exhibited an EASI score reduction of 93% from baseline. One subject became pregnant after 7 doses at which time drug treatment was discontinued. The individual had already attained a 98% response in EASI score at that time. After 6 months post treatment the individual continues to maintain bosakitug exposure and an EASI response of 82%. A summary of the safety profile of bosakitug includes 19 AEs in 9 subjects during study treatment, all were of grade 1 except one of vertigo (grade 2); 16 subjects reported injection site reactions; and headache was the most common AE (4 cases in 4 subjects). No SAEs occurred. None of the 22 subjects exhibited a positive ADA response. The efficacy profile exhibited by bosakitug, with 79% of AD subjects achieving an IGA 0 or 1 and almost 90% of subjects showing 75% skin clearance is quite striking, especially as monotherapy. The 44 and 28% of subjects that achieved EASI-90 and EASI-100, respectively, also shows the high efficacious potential of bosakitug. In this phase 2a proof-of-concept study the dosing regimen was chosen to mimic the dupilumab dosing regimen in AD subjects to be able to compare efficacy and safety directly. Bosakitug’s substantially higher efficacy, as exhibited by 78% of subjects achieving an IGA 0/1, underscore its competitiveness to dupilumab and its potential as a first-in-class treatment for AD. The sustained concentration of bosakitug, due to its long half-life, and the continued efficacy after the last dose provides a good possibility that bosakitug could be administered at extended dosing intervals. Bosakitug’s impressive efficacy and safety profile, in conjunction with the opportunity for much longer dosing intervals than established therapies support further clinical development of bosakitug in a phase 2b, randomized, blinded, dose-finding trial in moderate to severe AD subjects.

Currently approved dosing regimens of upadacitinib (UPA) for moderate-to-severe atopic dermatitis (AD) are 15 mg (UPA15) once daily (QD) and 30 mg (UPA30) QD based on clinical trial data. However, dose alterations may be required in the context of inadequate efficacy, adverse events (AEs), and patient preference. Our multicenter retrospective study evaluated the effect of upadacitinib dose alterations on real-world effectiveness and safety outcomes in patients with AD at three practices in Canada. Among 119 patients with AD initiated on UPA with >23-week follow-up, we identified patients undergoing dose alteration (escalation or reduction). Reasons for dose alteration were collected along with effects of dose alteration on effectiveness outcomes including Investigator Global Assessment (IGA), mean Eczema Area and Severity Index (EASI), body surface area (BSA), Dermatology Life Quality Index (DLQI)/Children’s DLQI (CDLQI), and IGAxBSA. Impact of dose alteration on incidence and outcomes of AEs was additionally analyzed. From 119 total patients with AD initiated on UPA (>23-week follow-up), 26.9% (32/119) underwent dose alteration: 40.6% (13/32) with dose escalation and 59.4% (19/32) with dose reduction. The mean age of patients who underwent dose alteration was 44.8 (range: 12-79) years; 62.5% (20/32) were female and 15.6% (5/32) were adolescents. Initial doses were UPA15 (43.8%, 14/32) and UPA30 (56.3%, 18/32). The mean time from UPA initiation to dose alteration was 228.3 (range: 9-520) days. Thirteen patients underwent dose escalation: 69.2% (9/13) from UPA15 QD to UPA30 QD and 30.8% (4/13) from UPA30 QD to 45 mg (UPA45) QD. At the time of dose escalation: mean EASI score was 2.8 (mean EASI improvement from baseline: 57.4%), with 53.8% (7/13) and 7.7% (1/13) having achieved 75% and 90% improvements in baseline EASI scores (EASI75 and EASI90), respectively, while IGA scores were 1 (n=5) and 2 (n=8). At follow-up (mean duration: 83.3 days) after dose escalation: mean EASI score was 1.6 (mean EASI improvement: 84.4% [from baseline] and 54% [from date of dose escalation]), with 69.2% (9/13), 61.5% (8/13), 38.5% (5/13), and 61.5% (8/13) of patients achieving EASI75, EASI90, 100% improvement in EASI (EASI100), and IGA 0/1, respectively. Two patients (15.4%) discontinued UPA due to lack of efficacy despite dose escalation. Only 2 AEs were noted with dose escalation: transaminitis (n=1) and elevated creatine phosphokinase (n=1); the patient with transaminitis subsequently discontinued UPA. Nineteen patients underwent dose reduction: UPA30 QD to UPA15 QD (63.1%, 12/19), UPA30 QD to UPA30 every other day (QOD) (10.5%, 2/19), and UPA15 QD to UPA15 QOD (26.3%, 7/19). Reasons for dose reduction included AEs (57.9%, 11/19) and patient preference following clearance or near-clearance (42.1%, 8/19). EASI/IGA responses were maintained in 78.9% (15/19) patients. Following dose reduction, 21.1% (4/19) of patients flared and required re-escalation (mean duration: 147.3 days). AEs requiring dose reduction included acne (36.4%, 4/11), herpes simplex (18.2%, 2/11), transaminitis (18.2%, 2/11), folliculitis (9.1%, 1/11), and recurrent respiratory tract infections (18.2%, 2/11). AEs improved in 54.5% (6/11) patients with dose reduction (mean follow-up: 164.1 days). Our real-world data suggests dose escalation from UPA15 to UPA30 and UPA30 to UPA45 (off-label) can result in higher skin clearance without any short-term safety concerns. Comparable to a Japanese real-world study (n=23), we noted incremental benefits with dose escalation, including comparable and superior achievement of EASI75 (69.2% vs. 66.7%) and EASI90 (61.5% vs. 38.1%), respectively. Furthermore, we identified AEs at higher UPA doses can improve through dose reduction with majority of patients (78.9%) maintaining initial effectiveness response. Study limitations include its small sample size and retrospective nature.

Atopic dermatitis (AD) is a chronic relapsing dermatitis characterized by intense itching. Hanifin and Rajka criteria are the most commonly used diagnostic criteria in hospital setup, consisting of 4 major and 23 minor criteria. The objective of the study was to estimate the frequency of distribution of Hanifin and Rajka minor criteria in the pediatric age group, to assess the association of age with minor criteria of AD, and to assess the association of gender with minor criteria of AD. A cross-sectional study of 150 pediatric patients (≤16 years) was conducted in the department of dermatology, who were diagnosed with AD based on history and clinical and ophthalmological examination. Serum immunoglobulin E (IgE) was also assessed. The age and gender analysis were done using a Chi-square test. The most common clinical features were orbital darkening 133 (88.7%), Dennie–Morgan infraorbital fold 126 (84%), xerosis 102 (68%), keratosis pilaris 101 (67.3%), and hyperlinear palm 98 (65%). Serum IgE was elevated in 26%. The majority presented with high readings with no obvious keratoconus. Male children (88%) presented predominantly with orbital darkening (90.9%) and had an exacerbation in winters (18.2%) in comparison to females (62%) P ≤ 0.05. Children >1 year (141%) presented mostly with keratosis pilaris (71.6%), nonspecific hand-foot dermatitis (49.6%), and facial erythema (34.8%) than in infants (9%) P ≤ 0.05. Minor criteria are useful for the diagnosis of AD. Male children are more affected and manifest with orbital darkening with Dennie–Morgan infraorbital fold as the chief clinical finding in both the groups. Factors such as ethnic/racial, environmental, and diet have a role in AD.

Atopic dermatitis (AD) is a chronic inflammatory skin disorder characterized by eczematous lesions, dry skin and persistent itch. AD may worsen due to psychological stress. However, little is known about the neural correlates that mediate the interaction between psychological stress and AD.To identify the possible difference in brain activation during arithmetic‐task induced stress in patients with AD versus healthy controls (HC) as well as the link between the brain response and clinical and psychodemographic parameters.A cohort of 29 AD female patients and 23 matched HC were recruited to investigate the potential difference in functional magnetic resonance imaging (fMRI) response to a block‐designed arithmetic paradigm. Both the HC and AD subjects were evaluated regarding their psychological traits, and for the AD subjects also their clinical characteristics, including stress indicators such as heart rate and salivary cortisol. We employed both univariate and multivariate statistical methods to analyse the blood oxygen level dependent (BOLD) fMRI response of the subjects to the block‐designed arithmetic paradigm.(1) Compared with HC subjects, the AD patients depict less deactivation in the default mode network including right angular gyrus, bilateral temporal pole and temporal lobe in response to the arithmetic task. (2) The BOLD fMRI response amplitude in the right postcentral gyrus and inferior parietal lobule is positively correlated with the stress susceptibility scores in the AD subjects, whereas the trend was the opposite of this for the HC subjects. (3) The activation in the postcentral gyrus also shows a correlation with the degree of itch in the AD patients.The BOLD fMRI measurements based on an arithmetic paradigm can provide useful insight into altered brain processing and its association with psychological traits and clinical characteristics in subjects with AD. Psychological stress exacerbates brain activities for the AD subjects in the motor, somatosensory association cortex, perception and sensory integration processing. The postcentral gyrus might be of particular interest for itch and stress.

BACKGROUND Rocatinlimab is a T cell rebalancing therapy that inhibits and reduces the number of pathogenic T cells by targeting the OX40 receptor expressed on the surface of activated T cells. Two global phase 3 studies were performed to assess the efficacy and safety of rocatinlimab for the treatment of moderate-to-severe atopic dermatitis in adults. METHODS ROCKET-IGNITE (IGNITE) and ROCKET-HORIZON (HORIZON) were 24-week randomised, double-blind, placebo-controlled phase 3 trials conducted in 19 countries each. Eligible patients were 18 years and older with confirmed atopic dermatitis (American Academy of Dermatology Consensus Criteria) diagnosed 1 year or longer before study entry with moderate-to-severe disease activity, defined by an Eczema Area and Severity Index (EASI) score of 16 and over, validated Investigator's Global Assessment for Atopic Dermatitis (vIGA-AD) score of 3 (moderate) or 4 (severe), and affected body surface area of 10% and above. In IGNITE, patients were randomly allocated in a 3:2:2 ratio to receive subcutaneous 300 mg rocatinlimab, 150 mg rocatinlimab, or placebo; in HORIZON, patients were randomised 3:1 to receive subcutaneous 300 mg rocatinlimab or placebo. Randomisation was stratified by baseline disease severity (vIGA-AD score of 3 vs 4) and geographical region (Japan vs non-Japan Asian countries vs rest of world). Across both trials, 24-week treatment was administered at weeks 0, 2, and 4 and then every 4 weeks thereafter with the last dose at week 20. The coprimary endpoints for both trials were EASI-75 response (≥75% improvement in EASI score from baseline) at week 24 and vIGA-AD score of 0 or 1 (defined as a score of 0 [clear skin] or 1 [almost clear skin], representing a ≥2-point improvement from baseline) at week 24. Rescue therapy use, including topical therapy, phototherapy, and systemic therapy, was permitted from day 1; all patients who received rescue therapy were considered non-responders for all visits after the first use of rescue therapy but could generally continue study treatment unless prohibited per protocol. Efficacy analyses were conducted in all randomised patients; safety analyses were conducted in all patients who received one or more dose of study treatment, with patients grouped according to actual treatment received. The trials were registered at ClinicalTrials.gov: ROCKET-IGNITE (NCT05398445) and ROCKET-HORIZON (NCT05651711). FINDINGS Between May 31, 2022, and June 12, 2024, 769 patients were randomised in IGNITE (two patients were enrolled under an earlier protocol before study re-design and excluded from the analysis; after the protocol update, 328 were included in the 300 mg rocatinlimab group; 217 in the 150 mg rocatinlimab group; and 222 in the placebo group) and between Dec 14, 2022, and Dec 12, 2023, 726 patients were randomised in HORIZON (543 in 300 mg rocatinlimab and 183 in placebo). Both trials met their coprimary endpoints. Rocatinlimab treatment resulted in statistically significant improvements in EASI-75 response in comparison with placebo at week 24 in IGNITE (138 [42%] of 326 patients on 300 mg rocatinlimab; 78 [36%] of 215 on 150 mg rocatinlimab; and 28 [13%] of 219 on placebo; percentage difference vs placebo: 300 mg rocatinlimab 29·5% [95% CI 22·3-36·1], p<0·001 and 150 mg rocatinlimab 23·4% [15·4-30·9], p<0·001) and HORIZON (rocatinlimab, 178 [33%] of 543 vs placebo, 25 [14%] of 183; percentage difference 19·1% [95% CI 12·4-25·2], p<0·001). Statistically significant improvements with rocatinlimab treatment in comparison with placebo were also observed at week 24 for vIGA-AD score of 0 or 1 response in IGNITE (77 [24%] of 326 patients on 300 mg rocatinlimab; 41 [19%] of 215 patients on 150 mg rocatinlimab; and 19 [9%] of 219 patients on placebo; percentage difference vs placebo 14·9% [95% CI 8·8-20·6], p<0·001 for 300 mg rocatinlimab and 10·3% [3·8-16·6], p=0·002 for 150 mg rocatinlimab) and HORIZON (105 [19%] of 543 for 300 mg rocatinlimab vs 12 [7%] of 183 for placebo; percentage difference 12·8% [95% CI 7·6-17·3], p<0·001). The incidences of treatment-emergent adverse events were generally similar across rocatinlimab and placebo treatment groups in IGNITE and HORIZON. The most frequently reported adverse events in patients receiving rocatinlimab (defined as occurring in ≥4% of patients in any rocatinlimab treatment group and at a rate ≥2 times that of placebo) included pyrexia (105 [12%] of 870 for 300 mg rocatinlimab and 26 [12%] of 214 for 150 mg rocatinlimab), chills (48 [6%] of 870 and five [2%] of 214 for the 300 mg and 150 mg doses, respectively), and aphthous ulcers (38 [4%] of 870 and six [3%] of 214, respectively). Most events of pyrexia and chills were considered injection-related reactions; events were generally mild or moderate in severity and primarily occurred after the first dose. Serious adverse events were reported in 2% to 5% of patients in the rocatinlimab groups and 4% to 6% of patients in the placebo groups. No deaths were reported. INTERPRETATION Rocatinlimab treatment resulted in statistically significant and clinically meaningful improvements across clinical endpoints, including the coprimary endpoints of EASI-75 response and vIGA-AD score of 0 or 1, in comparison with placebo and had a clinically acceptable safety profile in adult patients with moderate-to-severe atopic dermatitis. FUNDING Amgen and Kyowa Kirin.

The treat-to-target concept established goals to guide treatment with systemic therapies in atopic dermatitis (AD), including goals for itch improvement, reported as the most burdensome symptom. The aim of this study is to assess optimal itch response onset and long-term maintenance using treat-to-target criteria in dupilumab-treated patients. This post hoc analysis assessed patients ≥ 18 years with moderate-to-severe AD in two phase 3, randomized, double-blind, placebo-controlled studies. Patients received dupilumab 300 mg every 2 weeks or placebo with concomitant topical corticosteroids (TCS) for 52 weeks (CHRONOS); or dupilumab monotherapy 300 mg every week/every 2 weeks/every 4 weeks/every 8 weeks or placebo for 36 weeks after achieving Eczema Area and Severity Index improvement of 75% or Investigator’s Global Assessment 0/1 with dupilumab in SOLO1/2 (SOLO-CONTINUE). Optimal itch response was defined as Peak Pruritus Numeric Rating Scale ≤ 4. Patients receiving dupilumab + TCS achieved optimal itch response faster and in higher proportion than those receiving placebo + TCS (P < 0.0001) and maintained optimal response longer (median [Q1–Q3] 40 [11–50] vs 3 [0–23] weeks; P < 0.0001). Patients achieving optimal itch response with dupilumab monotherapy who continued treatment maintained response longer compared with those transitioned to placebo, although duration decreased with less frequent dosing (P < 0.0001 for all dupilumab regimens vs placebo). Optimal itch response was achieved rapidly and maintained long term in adult patients treated with dupilumab with or without concomitant TCS therapy. NCT02395133 and NCT02260986. Atopic dermatitis (AD), the most common skin disorder, presents mainly with skin lesions that can be intensely itchy. Itch deeply impacts patients with AD and their quality of life; scratching due to itching can also worsen the lesions. An increasing number of “systemic therapies” (working through the whole body as opposed to, for example, treatments applied on the skin) have recently been approved for the treatment of AD. To help physicians decide between systemic treatment options, a guidance called “treat-to-target concept” defines specific treatment goals to be reached within a certain time, including specific improvements in itch. In this work, we analyzed itch improvement in patients with moderate-to-severe AD treated with the systemic therapy dupilumab. Patients treated with dupilumab achieved the intended itch improvement significantly faster compared to those receiving placebo (a saline solution without active treatment). Most importantly, patients treated with dupilumab maintained this improvement significantly longer than those receiving placebo. When patients who had achieved improvement in AD signs and symptoms (including itch) were assigned to continue dupilumab (in the same dose or less frequently) or placebo, those patients continuing dupilumab maintained itch improvement significantly longer than those switched to placebo, although the duration of improvement decreased in those receiving dupilumab less frequently. It should be noted that these analyses were decided upon and performed only after the data became available (“post hoc analyses”), which is a limitation. In conclusion, patients with AD treated with dupilumab achieved improvement of their itch rapidly, and this improvement was maintained long term.

Background: Activin A is involved in the inflammatory response, wound repair, and skin fibrosis. Serum activin A concentrations change during the menstrual cycle, and this can lead to periodic exacerbation of atopic dermatitis. Objective: To determine the effect of activin A on the cytokine expression profiles of human fibroblasts and keratinocytes under atopic dermatitis-like conditions. Methods: Cultured human fibroblasts and keratinocytes were treated with activin A in combination with interleukin (IL)-4 and IL-13 to determine the changes in cytokine concentrations. Results: Activin A decreased the expression of IL-1 β and IL-23 mRNA in fibroblasts. IL-4 and IL-13 increased the expression of IL-6 and IL-16 and decreased the expression of IL-1 α , IL-1 β , IL-8, IL-10, and IL-23 in fibroblasts. In keratinocytes, IL-4 and IL-13 increased the expression of IL-1 α and IL-1 β and decreased the expression of IL-8. Activin A treatment in combination with IL-4 and IL-13 significantly increased the expression of IL-1 α , IL-6, IL-8, IL-10, IL-16, and IL-23 and decreased the expression of IL-1 β in fibroblasts. In keratinocytes, only IL-8 expression was significantly increased following treatment with activin A, IL-4, and IL-13. Conclusion: Activin A modulates cytokine expression in a cell type dependent manner under conditions mimicking atopic dermatitis, suggesting its potential involvement in cutaneous inflammatory regulation.

Lebrikizumab is approved to treat patients with moderate‐to‐severe atopic dermatitis (AD). This study evaluated the 16‐week efficacy outcomes of lebrikizumab in adults and adolescents with severe AD in ADvocate trials who would be eligible for treatment based on South Korean reimbursement‐like criteria. This was a post‐hoc analysis of pooled data from ADvocate1 (NCT04146363) and ADvocate2 (NCT04178967). Patients were randomised 2:1 to receive lebrikizumab or placebo every 2 weeks. Two non‐mutually exclusive subgroups were selected based on South Korean reimbursement‐like criteria: Eczema Area and Severity Index (EASI) score ≥ 23, AD duration ≥ 3 years, and previous use of any systemic treatment (ST subgroup) or previous treatment with cyclosporine or methotrexate (CM subgroup). Week‐16 outcomes were Investigator's Global Assessment score of 0 or 1 (IGA [0,1]) with ≥ 2‐point improvement, ≥ 50%/75%/90% improvement in EASI score (EASI 50/75/90), Pruritus Numeric Rating Scale (NRS) ≥  4‐point improvement, and Dermatology Life Quality Index (DLQI) ≥ 4‐point improvement. Response rates to lebrikizumab and placebo were analysed using Cochran–Mantel–Haenszel tests. Common risk differences and 95% confidence intervals were reported. The ST subgroup included 322 patients, and the CM subgroup included 111 patients. More lebrikizumab‐treated than placebo‐treated patients achieved outcome responses. Percentage differences in favour of lebrikizumab ( p  < 0.01) were: IGA (0,1): ST = 25.7% (18.2%–33.1%), CM = 20.8% (7.9%–33.7%); EASI 50: ST = 42.7% (32.5%–52.9%), CM = 36.9% (19.8%–54.0%); EASI 75: ST = 40.2% (31.4%–49.1%), CM = 33.3% (19.1%–47.5%); EASI 90: ST = 27.4% (20.3%–34.5%), CM = 22.1% (11.3%–32.8%); Pruritus NRS ≥ 4‐point improvement: ST = 34.7% (26.7%–42.7%), CM = 26.7% (14.9%–38.4%); and DLQI ≥ 4‐point improvement: ST = 44.2% (33.2%–55.2%), CM = 39.5% (20.2%–58.8%). In this post‐hoc, exploratory subgroup analysis, lebrikizumab improved AD skin and pruritus at week 16 in adults and adolescents who would be eligible for treatment based on South Korean reimbursement‐like criteria.

Although the pathogenesis of atopic dermatitis (AD) remains to be fully deciphered, skin barrier abnormality and immune dysregulation are known to be involved. Recently, the vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) system has also been implicated in the pathogenesis of this multifactorial chronic inflammatory skin disorder. Previously, we showed that a novel tetrapeptide, N-acetyl-Arg-Leu-Tyr-Glu (Ac-RLYE), inhibits angiogenesis and vascular permeability effectively by selectively antagonizing VEGFR-2. The current study aimed to investigate the pharmacological effect of Ac-RLYE on AD in vitro and in vivo. The in vitro experiments demonstrated that Ac-RLYE inhibited VEGF-induced vascular permeability in endothelial cells. Moreover, in an in vivo animal model of AD, Ac-RLYE relieved AD-like symptoms such as ear thickness and dermatitis severity scores and infiltration of immune cells, including mast cells and eosinophils. Ac-RLYE inhibited IgE secretion, restored the skin barrier protein filaggrin level, and markedly downregulated gene expression of AD-related Th1, Th2, and Th17 cytokines. Collectively, these findings suggest that Ac-RLYE would be useful for the treatment of AD and associated inflammatory skin disorders.

BACKGROUND People with atopic dermatitis (AD) suffer from dry, itchy skin with reduced skin barrier function that leaves it prone to irritant and allergen penetration. Alterations in the composition and structure of the stratum corneum (SC) lipid lamellae underpin this increase in permeability. A wide range of emollients are used to ameliorate the skin of AD patients, but the majority have unclear effects on the lipid lamellae and barrier function. OBJECTIVES To compare the effects of a multivesicular emulsion containing physiologic lipids and glycerine (MVE+GL) to a commonly prescribed oil-in-water emulsion containing glycerine without physiologic lipids (OW+G). METHODS A double-blind, intra-participant-controlled study was undertaken in adults with a history of eczema. Participants applied MVE+GL to one forearm and lower leg and OW+G to contralateral sites twice daily for 28 days. Skin properties were assessed before and after treatment. A detailed lipidomic profile was generated from SC samples, alongside in vivo ATR-FTIR spectroscopic analysis of its molecular composition. RESULTS Fifty-eight people were included in the study (aged 46±21 years). At sites treated with MVE+GL skin barrier integrity improved significantly (38.02±18.64 g/m2/h TEWL20 before vs 29.79±13.47 after treatment, p=0.0002) whereas O/W+G had no effect (35.6±18.39 g/m2/h versus 37.4±16.69 g/m2/h). Concordantly skin sensitivity to sodium lauryl sulphate (SLS) was significantly reduced by MVE+GL treatment (Post-SLS TEWL was 35.58±15.43 before treatment and 29.54±11.64 g/m2/h after treatment, p=0.0008; erythema was also reduced). Skin moisture increased more rapidly at sites treated with MVE+GL compared to OW+G, leading to a more rapid reduction in visual skin dryness. Over 1600 lipid species were detected in the SC. Ceramide species NP and AP with 18 carbon sphingoid bases, both ingredients of MVE+GL, increased significantly by 24 and 19% respectively following MVE+GL treatment. In contrast changes of 9% for NP(18) and 6% for AP(18) were non-significant at sites treated with O/W+G. Increased abundance of NP(18) species relative to NdS species were related to improvements in skin barrier integrity. CONCLUSIONS Whilst the glycerine-containing emollient reduced skin dryness, it had no impact on barrier function. In contrast, MVE+GL improved the physical integrity of the barrier and reduced the sensitivity of the skin.

No abstract available

The skin, as the outermost layer of the body, serves as a crucial protective barrier against environmental insults while maintaining homeostasis. Atopic dermatitis (AD), a chronic inflammatory skin disorder characterized by recurrent eczema and type 2 inflammation, affects a significant global population. The pathophysiology of AD is closely linked to skin barrier dysfunction, which contributes to increased permeability, immune dysregulation, and microbial imbalances. Historically, skin barrier research has centered on the stratum corneum (SC) and intercellular lipids within the epidermis, primarily conceptualized through the "brick-and-mortar" model. However, recent advancements have revealed a more intricate interplay among various barrier components. Two key determinants of skin barrier-SC pH and SC ceramides-have gained substantial attention. Elevated SC pH leads to enhanced serine protease activity, impaired lipid metabolism, and microbiome dysbiosis, all of which exacerbate barrier dysfunction and inflammation in AD. Concurrently, alterations in SC ceramide profiles and structures compromise skin barrier function. Emerging evidence underscores the potential of SC pH and ceramides as biomarkers for disease progression and as therapeutic targets for barrier restoration. Advances in lipid analyses and non-invasive pH assessment offer promising prospects for personalized dermatologic interventions. This review explores the complex interactions of SC pH and ceramides in AD pathogenesis, discussing their implications for predicting disease flares, guiding treatment strategies, and identifying novel drug targets. A deeper understanding of these mechanisms could pave the way for next-generation therapeutic approaches in AD and other skin barrier-related disorders.

A compromised permeability barrier is a hallmark of atopic dermatitis (AD). Localized to the outermost skin layer, the stratum corneum (SC) is critically dependent on terminal differentiation of epidermal keratinocytes, which transform into protein-rich corneocytes surrounded by extracellular lamellae of unique epidermal lipids, conferring permeability barrier function. These structures are disrupted in AD. A leaky barrier is prone to environmental insult, which in AD elicits type 2-dominant inflammation, in turn resulting in a vicious cycle further impairing the SC structure. Therapies directed at enforcing SC structure and anti-inflammatory strategies administered by topical and systemic route as well as UV therapy have differential effects on the permeability barrier. The expanding armamentarium of therapeutic modalities for AD treatment warrants optimization of their effects on permeability barrier function.

Atopic dermatitis (AD) is a prevalent skin disorder affecting individuals globally, with many patients experiencing a range of symptoms. A pronounced clinical phenomenon associated with AD is the cyclic alternation of two distinct phases in time: inflammation and remission, depending on patients' immune response and skin permeability. Frequent and relatively long inflammatory times lead to symptoms that can severely deteriorate the quality of life for the patient. Through mathematical modeling, we find that patients with similar AD symptoms can be categorized into two phases depending on the skin permeability and immune response that constitute the most clinically relevant parameter plane: the inflammatory time is shorter or longer than the remission time, respectively and the transition between the two phases is of the second-order type. In the parameter plane, a critical threshold curve emerges, which separates the two phases. Computing the frequency and duration of the inflammatory response, we uncover a logarithmic scaling law governing the inflammatory and remission times and discuss its clinical implications. In particular, when the skin condition is managed to be near the phase transition point, the benefits of treatment are more pronounced. However, at this stage, the effectiveness of skincare in reducing flare-ups tends to be less noticeable, making it difficult to evaluate the success of the treatment, largely due to the nature of logarithmic decay in the remission time. Our study provides insights into the mechanisms of AD that can enhance diagnostic accuracy and treatment by understanding the alternation between inflammation and remission periods.

Ethanol is widely used in cosmetic formulations as a solvent, preservative, and penetration enhancer, yet its effects on atopic skin remain controversial. This study explores the impact of ethanol in skin care products on skin physiology, microbiome composition and subjective perception. A two-part investigation was conducted: (I) ex vivo analysis using porcine skin models exposed to varying ethanol concentrations, and (II) a double blinded, placebo controlled, randomized clinical pilot study on 9 patients with Atopic Dermatitis (AD) comparing creams with and without 12% ethanol. The ex vivo study revealed that ethanol concentrations above 15% negatively affected epidermal barrier integrity, increasing stratum corneum (SC) permeability and transepidermal water loss (TEWL). In the clinical trial, 12% ethanol demonstrated no significant adverse effects on SC hydration, erythema, pH, or TEWL over 30 days. Microbiome analysis revealed a localized increase in Xanthomonas species associated with ethanol use, while no significant community-wide changes were observed. The implications of increased Xanthomonas abundance in response to the application of a 12% ethanol cream for atopic dermatitis remain unclear. Subjective evaluations reported similar perceptions for both formulations, with no notable exacerbations in non-lesional AD skin. These findings indicate that ethanol in concentrations ≤ 12% is safe for atopic skin.

Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin condition marked by immune dysregulation, pruritus, and impaired skin barrier function. Effective transdermal drug delivery is essential for therapeutic success but remains hindered by stratum corneum (SC) dysfunction and variable skin permeability. This review examines recent advancements in vehicle formulations designed to enhance transdermal drug delivery, specifically in the context of AD. Peer-reviewed studies published within the last two decades were reviewed using PubMed and Google Scholar (Google LLC, Mountain View, California, United States), focusing on innovations in drug delivery systems, vehicle composition, and clinical applications. Novel delivery platforms such as liposomes, ethosomes, nanoemulsions, polymeric nanoparticles, solid lipid nanoparticles (SLNs), and nanostructured lipid carriers (NLCs) have demonstrated improved percutaneous absorption, increased drug stability, and reduced skin irritation. Additional breakthroughs include biomimetic formulations, occlusive enhancers, and pH-sensitive carriers tailored to the disrupted skin barrier in AD. Despite these advancements, significant challenges remain, including variability in skin hydration, interindividual differences in barrier function, and concerns about long-term safety. Continued research and clinical trials are necessary to validate the efficacy and tolerability of these technologies. Future advances may lie in personalizing transdermal therapies through skin barrier phenotyping, enabling more targeted, tolerable, and effective treatment strategies.

The circadian rhythm is a 24-hour periodic cycle driven by the Earth's rotation that modulates the behavior, physiology, and metabolism of all living organisms on Earth. The circadian rhythm controlled by a system called the circadian clock. The circadian clock mechanism is critical to the development and functioning of the body. In the skin, circadian rhythms manifest themselves in daily changes of transepidermal water loss, skin permeability and microcirculatory system function, itching intensity, sleep rhythm, the functioning of the innate and adaptive immune system. At the cellular level, the mitotic cycle of cell division, the time of differentiation of keratinocytes, and much more are subject to the circadian rhythm. With atopic dermatitis, there is a vicious circle - itching impairs sleep, leads to chronic stress, thereby disrupting the circadian sleep-wake rhythm, and lack and poor quality of sleep and chronic stress increase itching. In turn, the above processes provoke an exacerbation of atopic dermatitis, in which both itching and poor quality of sleep intensify, and the rhythmic functioning of the entire body in general and the skin in particular worsens. Understanding the importance of skin circadian functions and the consequences of their disruption allows physicians to improve therapy and maximize the effectiveness of prescribed treatments. Perhaps many topical preparations will be able to bring more benefits when used in the evening, when skin permeability is higher and the products used may be weaker or less concentrated. Perhaps many topical drugs can be more beneficial if circadian rhythms are taken into account, and the drugs used may be weaker or less concentrated.

Mycophenolate mofetil (MMF) shows significant potential for precision immunotherapy in moderate to severe atopic dermatitis (AD). However, its clinical application is limited by inadequate delivery efficiency and dose related toxicities. Herein, we propose a straightforward and effective drug delivery strategy that involves coating MMF with polydopamine (PDA) to fabricate MMF nanoparticles (MMF NPs). A systematic investigation of their therapeutic efficacy and mechanism of action was also conducted in the AD model mice. Due to surface hydrophilicity and nanoscale effects mediated by PDA, MMF NPs demonstrate excellent stability, high drug loading capacity, and optimized pharmacokinetics. The prolonged circulation time and enhanced permeability retention effect reduce both toxicity and susceptibility to infections associated with MMF, which leads to a marked improvement in the therapeutic efficacy of AD. Finally, MMF NPs achieve precise immunotherapy through the synergistic effect by balancing systemic immunity and precisely targeting the local inflammatory microenvironment. This study not only presents a safe and effective treatment strategy for AD but also introduces a novel delivery approach for the clinical application of MMF in immune-mediated disorders.

No abstract available

Atopic dermatitis (AD) is a composite disease presenting disruption of the skin permeability barrier (SPB) in the stratum corneum (SC). Recent evidence supports derangement of the sebaceous gland (SG) activity in the AD pathomechanisms. The objective of this study was to delineate profiles of both sebaceous and epidermal lipids and of aminoacids from SG‐rich (SGR) and SG‐poor (SGP) areas in AD. Both sebum and SC were sampled from SGR areas, while SC was sampled also from SGP areas in 54 adult patients with AD, consisting of 34 and 20 subjects, respectively with and without clinical involvement of face, and in 44 age and sex‐matched controls. Skin biophysics were assessed in all sampling sites. Disruption of the SBP was found to be associated with dysregulated lipidome. Abundance of sapienate and lignocerate, representing, respectively, sebum and the SC type lipids, were decreased in sebum and SC from both SGR and SGP areas. Analogously, squalene was significantly diminished in AD, regardless the site. Extent of lipid derangement in SGR areas was correlated with the AD severity. The abundance of aminoacids in the SC from SGR areas was altered more than that determined in SGP areas. Several gender‐related differences were found in both controls and AD subgroups. In conclusion, the SG activity was differently compromised in adult females and males with AD, in both SGR and SGP areas. In AD, alterations in the aminoacidome profiles were apparent in the SGR areas. Lipid signatures in association with aminoacidome and skin physical properties may serve the definition of phenotype clusters that associate with AD severity and gender.

Emerging evidence suggests a link between atopic dermatitis (AD) and gastrointestinal disorders, particularly in relation to gut microbial dysbiosis. This study explored the potential exacerbation of AD by gut inflammation and microbial imbalances using an irritable bowel syndrome (IBS) mouse model. Chronic gut inflammation was induced in the model by intrarectal injection of 2,4,6-trinitrobenzene sulfonic acid (TNBS), followed by a 4-week development period. We noted significant upregulation of proinflammatory cytokines in the colon and evident gut microbial dysbiosis in the IBS mice. Additionally, these mice exhibited impaired gut barrier function, increased permeability, and elevated systemic inflammation markers such as IL-6 and LPS. A subsequent MC903 challenge on the right cheek lasting for 7 days revealed more severe AD symptoms in IBS mice compared to controls. Further, fecal microbial transplantation (FMT) from IBS mice resulted in aggravated AD symptoms, a result similarly observed with FMT from an IBS patient. Notably, an increased abundance of Alistipes in the feces of IBS mice correlated with heightened systemic and localized inflammation in both the gut and skin. These findings collectively indicate that chronic gut inflammation and microbial dysbiosis in IBS are critical factors exacerbating AD, highlighting the integral relationship between gut and skin health.

As the relationship between the gut microbiome and allergies becomes better understood, targeted strategies to prevent and treat allergies through gut microbiome modulation are being increasingly developed. In the study presented herein, we screened various probiotics for their ability to inhibit mast cell degranulation and identified Lactiplatibacillus plantarum HD02 and MD159 as effective candidates. The two strains significantly attenuated vascular permeability induced by mast cell degranulation in a passive cutaneous anaphylaxis (PCA) model and, in the MC903-induced murine atopic dermatitis (AD) model, demonstrated comparable preventive effects against allergies, reducing blood levels of MCPT-1 (mast cell protease-1) and total IgE. In the house dust mite (HDM)-induced murine AD model, both L. plantarum HD02 and MD159 showed therapeutic effects, with L. plantarum HD02 demonstrating superior efficacy. Nevertheless, L. plantarum MD159 better suppressed transepidermal water loss (TEWL). Furthermore, L. plantarum HD02 and MD159 significantly increased the number of splenic Foxp3+ regulatory T cells, with L. plantarum MD159 having a more pronounced effect. However, only L. plantarum HD02 achieved a reduction in immune cells in the draining lymph nodes. Our findings highlight L. plantarum HD02 and MD159 as promising candidates for the prevention and treatment of allergies, demonstrating significant efficacy in suppressing mast cell degranulation, reducing the number of allergy biomarkers, and modulating immune responses in experimental models of AD. Their distinct mechanisms of action suggest potential complementary roles in addressing allergic diseases, underscoring their therapeutic promise in clinical applications.

Psychological stress and intestinal leakage are key factors in atopic dermatitis (AD) recurrence and exacerbation. Here, we demonstrate the mechanism underlying bacterial translocation across intestinal epithelial barrier damaged due to stress and further aggravation of trimellitic anhydride (TMA)–induced itch, which remain unclear, in AD mice. Immobilization (IMO) stress exacerbated scratching bouts and colon histological damage, and increased serum corticosterone and lipopolysaccharide (LPS). Orally administered fluorescein isothiocyanate (FITC)-dextran and surgically injected (into the colon) Cy5.5-conjugated LPS were detected in the serum and skin after IMO stress, respectively. The relative abundance of aerobic or facultative anaerobic bacteria was increased in the colon mucus layer, and Lactobacillus murinus, E. coli, Staphylococcus nepalensis, and several strains of Bacillus sp. were isolated from the spleens and mesenteric lymph nodes. Oral antibiotics or intestinal permeability blockers, such as lubiprostone (Lu), 2,4,6-triaminopyrimidine (TAP) and ML-7, inhibited IMO stress-associated itch; however, it was reinduced through intradermal or i.p. injection of LPS without IMO stress. I.p. injection of TAK-242 (resatorvid), a TLR4 inhibitor, abrogated IMO stress-associated itch, which was also confirmed in TLR4-KO mice. IMO stress alone did not cause itch in naïve mice. IMO stress-induced itch aggravation in TMA-treated AD mice might be attributed to the translocation of gut-derived bacterial cells and LPS, which activates peripheral TLR4 signaling.

Patchouli oil (PO) is a natural substance famous for its immune-enhancing and anti-inflammatory effects. Atopic dermatitis (AD) is characterized by epidermal gene mutations, skin barrier dysfunction, and immune dysregulation, making patchouli volatile oil a potential candidate for AD treatment. Initially, PO was mixed with ethyl oleate (EO), castor oil ethoxylated ether-40 (EL-40), anhydrous ethanol, and water to form a patchouli oil microemulsion (PO-ME) system. The formulation ratios were optimized using the Box–Behnken design-effect surface method, and their products were characterized for type, particle size, polydispersity index (PDI), and appearance. Additionally, patchouli oil microemulsion gel (PO-MEG) was developed with a specified concentration of 1.5% carbomer-940 as the matrix, and its pH, stability, viscosity, and permeability were evaluated. We assessed the irritation tests of PO-MEG using a rat self-control model and the Cell Counting Kit-8 (CCK-8) assay. The results demonstrated that should be attributed to non-irritating. This study also assessed the efficacy of optimized PO-MEG on AD-like symptoms using a 2,4-dinitrochlorobenzene (DNCB)-induced BALB/c mouse model. Compared with the model group, the in vivo efficacy studies have shown the PO-MEG group significantly reduces dermatitis scores, mast cell counts, epidermal thickness, and levels of pro-inflammatory cytokines and immune factors in skin homogenates. This suggests that PO-MEG would become a safer topical formulation for treating atopic dermatitis.

Abstract Introduction: Increased skin pH values in patients with atopic dermatitis (AD) contribute to poor antimicrobial and permeability barrier functions of the skin. In practice, the majority of topical preparations available for dry skin conditions do not provide sufficient pH and buffering capacity for maintaining optimum skin surface conditions. To address this issue, we tested a novel zinc lactobionate preparation to determine whether the regular application would lower skin surface pH, and in doing so improve the condition of lesional skin. Methods: The assessment for local severity of AD was done with the Scoring Atopic Dermatitis Index (SCORAD) and skin dryness was assessed by capacitance measurement. Results: The results showed that the test product lowered skin pH and improved AD skin lesions from moderate to mild during 2 weeks of application. In the treated area a lowered pH of about 0.85 units was found. Together with the lowering of pH, the local SCORAD significantly improved from 8.3 on average down to 4.0, while in the untreated area, only a slight improvement (from 8.2 to 6.4) was found. Conclusion: Synergistic effects of the test product’s pH lowering and emollient properties might explain the observed improvements in clinical signs of AD and further research against a comparator would allow the specific contribution of pH modulation to these improvements to be unambiguously isolated.

Atopic dermatitis (AD) is a chronic inflammatory skin condition. Natural products have gained traction in AD treatment due to their accessibility, low toxicity, and favorable pharmacological properties. However, their application is primarily constrained by poor solubility, instability, and limited permeability. The transdermal drug delivery system (TDDS) offers potential solutions for transdermal delivery, enhanced penetration, improved efficacy, and reduced toxicity of natural drugs, aligning with the requirements of modern AD treatment. This review examines the application of hydrogels, microneedles (MNs), liposomes, nanoemulsions, and other TDDS-carrying natural products in AD treatment, with a primary focus on their effects on penetration and accumulation in the skin. The aim is to provide valuable insights into the treatment of AD and other dermatological conditions.

Nanoformulation have been widely used in skin and transdermal drug delivery. However, the differences in integral nanoparticles absorption in healthy and diseased skin have not yet fully analyzed. The present study attempted to explore the percutaneous absorption of drugs via lesional skin by using atopic dermatitis (AD) as a model, dinitrochlorobenzene (DNCB) induced AD-like skin. In here, the small molecules of insoluble Licoricchalcone A (LA) and macromolecules glycyrrhizin polysaccharide were used to prepare LA-polysaccharide self-assembled nanoparticles (GPA-SANs) by micro-precipitation. An environment-responsive dye, P4, was loaded into SAN to track the transdermal translocation of the nanoparticles, while the drug marked with coumarin 6 (C6). Compared to healthy skin, the permeability of GPA-SANs on AD-like skin is stronger, which may be due to damage to the stratum corneum of the AD-like skin and increased intercellular spaces, resulting in an increased permeability coefficient. Therefore, the storage of nanoparticles and their diffusion at the lesion site also increased accordingly. CLSM shown that the fluorescence of P4 and C6 is observed to concentrate around the hair follicles and disseminate in the surrounding area in both AD-affected and healthy skin. It can be clearly seen that fluorescence signal of C6 in the intercellular spaces of the dermis and epidermis of AD-like skin, indicating that nano-drug on the disease skin can penetrate through the intercellular pathway to achieve therapeutic. The focus of the present study is to assess the permeability of healthy and disease skin, discuss their characteristics and discrepancy, aiming to provide a reference for the further study of nano-formulations in transdermal delivery.