Barrier Function In Atopic Dermatitis Research Articles

Toll-like receptors: their roles in pathomechanisms of atopic dermatitis.

The skin functions as a physical barrier and represents the first line of the innate immune system. There is increasing evidence that toll-like receptors (TLRs) are involved in the pathomechanisms of not only infectious diseases, but also non-infectious inflammatory diseases. Interestingly, it has been demonstrated that TLRs recognize both exogenous threats, e.g. bacteria and viruses, and endogenous danger signals related to inflammation, cell necrosis, or tissue damage. Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disease, which is associated with impaired skin barrier function, increased skin irritability to non-specific stimuli, and percutaneous sensitization. The impairment of skin barrier function in AD allows various stimuli, such as potential allergens and pathogens, to penetrate the skin and activate the innate immune system, including TLR signaling, which can lead to the development of adaptive immune reactions. In this review, I summarize the current understanding of the roles of TLR signaling in the pathogenesis of AD, with special emphasis on skin barrier function and inflammation.

Targeting Skin Barrier Function in Atopic Dermatitis

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease in the general population. Skin barrier dysfunction is the central abnormality leading to AD. The cause of skin barrier dysfunction is complex and rooted in genetic mutations, interactions between the immune pathway activation and epithelial cells, altered host defense mechanisms, as well as environmental influences that cause epithelial cell activation and release of alarmins (such as thymic stromal lymphopoietin) that can activate the type 2 immune pathway, including generation of interleukins 4 and 13, which induces defects in the skin barrier and increased allergic inflammation. These inflammatory pathways are further influenced by environmental factors including the microbiome (especially Staphylococcus aureus), air pollution, stress, and other factors. As such, AD is a syndrome involving multiple phenotypes, all of which have in common skin barrier dysfunction as a key contributing factor. Understanding mechanisms leading to skin barrier dysfunction in AD is pointing to the development of new topical and systemic treatments in AD that helps keep skin borders secure and effectively treat the disease.

Dupilumab inhibits vascular leakage of blood proteins into atopic dermatitis skin

Atopic dermatitis (AD) skin lesions are associated with oozing, bleeding, and erythema that are primarily driven by polarized type 2 immune responses. These suggest vascular changes in AD. Dupilumab is an antibody to the alpha-subunit of interleukin (IL)-4 receptor that demonstrates robust efficacy in the treatment of moderate-to-severe AD. IL-4 is known to reduce the permeability barrier function of vascular endothelium. The effect of dupilumab on vascular barrier function in AD is unknown.

New Potential of Roxatidine Acetate Hydrochloride on Atopic Dermatitis Mouse Model, Human Keratinocytes, and Human Skin Equivalent Model.

Atopic dermatitis (AD) is a complex inflammatory skin disorder, characterized by a complicated pathophysiology and a wide range of clinical phenotypes. Roxatidine acetate chloride (RXA) is a precursor of Roxatidine and a histamine H2 receptor antagonist, used for the treatment of gastric ulcers. In this study, we aimed to examine whether RXA had anti-AD effects and determine the underlying molecular mechanism of RXA. The anti-AD effects were examined in Dermatophagoides farinae body (Dfb)-induced AD mouse model, tumor necrosis factor (TNF)-α/interferon (IFN)-γ-stimulated HaCaT keratinocytes, and human skin equivalent model using ELISA, histological analysis, immunohistochemistry, Western blot, and immunofluorescence. Results showed that RXA treatment significantly alleviated Dfb-induced AD skin symptoms and clinical severity in mice by decreasing the levels of immunoglobulin E, histamine, and inflammatory cytokines. RXA effectively inhibited the expression of adhesive molecules and recovered the filaggrin expression in Dfb-induced AD skin lesions and TNF-α/IFN-γ-stimulated HaCaT keratinocytes. Additionally, RXA significantly upregulated the expression of aryl hydrocarbon receptor and sirtuin1. The anti-AD effects of RXA were associated with suppressed nuclear factor kappa cascade. Overall, our results suggest that RXA may be a potential anti-AD candidate owing to its inhibitory effect against skin inflammation and protection of the skin barrier function in AD.

The Influence of Microbiome Dysbiosis and Bacterial Biofilms on Epidermal Barrier Function in Atopic Dermatitis-An Update.

Atopic dermatitis (AD) is a common inflammatory dermatosis affecting up to 30% of children and 10% of adults worldwide. AD is primarily driven by an epidermal barrier defect which triggers immune dysregulation within the skin. According to recent research such phenomena are closely related to the microbial dysbiosis of the skin. There is growing evidence that cutaneous microbiota and bacterial biofilms negatively affect skin barrier function, contributing to the onset and exacerbation of AD. This review summarizes the latest data on the mechanisms leading to microbiome dysbiosis and biofilm formation in AD, and the influence of these phenomena on skin barrier function.

Validation of a novel patient-operated device for measuring skin barrier function in atopic dermatitis.

Transepidermal water loss (TEWL) and capacitance are used in atopic dermatitis (AD) trials to provide objective data on clinical change and response to therapy. Many barrier devices are costly, limiting their utility. GPSkin is a novel low-cost, patient-operable device that measures both TEWL and capacitance via smartphone application. This validation study investigated the correlation of GPSkin with the AquaFlux and Corneometer, and the reliability of these devices, in patients with AD. Fifty AD patients with varying disease severity performed self-measurements with GPSkin, while investigators collected data with all 3 devices, on both nonlesional and lesional skin. GPSkin and AquaFlux demonstrated strong correlation for TEWL on nonlesional and lesional skin by Spearman's correlation (rs ), independent of device user. For capacitance, GPSkin and the Corneometer showed moderate correlation when obtained by patients, yet a strong correlation when obtained by a clinician. Despite good correlation, GPSkin showed poor agreement with both the AquaFlux and Corneometer in Bland-Altman plots. GPSkin underestimated both TEWL and capacitance. Overall, the devices had good test-retest reliability. None of the devices could discriminate between AD severity states. While GPSkin marks an exciting advancement in barrier technology, further study is needed for validation on AD skin.

16437 Effects of cleansing on skin barrier function in atopic dermatitis and healthy skin: A pilot study

Introduction: Cleansers and bathing are known to worsen skin barrier function (SBF), especially in intrinsically barrier-compromised atopic dermatitis (AD). Many commercially-available cleansers are marketed for AD, but guidance for optimal product selection and direct comparison are lacking.

The Suppressive Effect of Leucine-Rich Glioma Inactivated 3 (LGI3) Peptide on Impaired Skin Barrier Function in a Murine Model Atopic Dermatitis.

This study aimed to restore the skin barrier function from atopic dermatitis (AD) via treatment with leucine-rich glioma inactivated 3 (LGI3) peptide. Male NC/Nga mice (7 weeks, 20 g) were randomly allocated into three groups (control, AD, and LGI3 group). After induction of AD skin lesions with Dermatophagoides farinae ointment, mice were treated with LGI3. The clinical score of AD was the highest and the dorsal skin thickness was the thickest in the AD group. In contrast, LGI3 treatment improved the clinical score and the dorsal skin thickness compared to the AD model. LGI3 treatment suppressed histopathological thickness of the epithelial cell layer of the dorsal skin. LGI3 treatment could indirectly reduce mast cell infiltration through restoring the barrier function of the skin. Additionally, the filaggrin expression was increased in immunohistochemical evaluation. In conclusion, the ameliorating effect and maintaining skin barrier homeostasis in the AD murine model treated with LGI3 could be attributed to complete re-epithelialization of keratinocytes. Hence, LGI3 might be considered as a new potential therapeutic target for restoring skin barrier function in AD.

Changes in nano-mechanical properties of human epidermal cornified cells in children with atopic dermatitis.

Background:Impaired skin barrier is an important etiological factor in atopic dermatitis (AD). The structural protein filaggrin (FLG) plays a major role in maintenance of the competent skin barrier and its deficiency is associated with enhanced susceptibility to mechanical injury. Here we examined biomechanical characteristics of the corneocytes in children with AD and healthy controls. Methods:We recruited 20 children with AD and 7 healthy children. They were genotyped for filaggrin gene ( FLG) loss-of-function mutations. Stratum corneum was collected from clinically unaffected skin by adhesive tapes. Cell stiffness (apparent elastic modulus, Ea) was determined by atomic force microscopy and filaggrin degradation products (NMF) by liquid chromatography. Skin barrier function was assessed through trans-epidermal water loss (TEWL) and disease severity by the SCORing Atopic Dermatitis (SCORAD) tool. Results: Corneocytes collected from AD patients showed a decreased elastic modulus which was strongly correlated with NMF and TEWL, but not with SCORAD. As compared with healthy controls, AD patients had reduced TEWL and NMF levels regardless of FLG mutations. NMF was strongly correlated with TEWL. Conclusion:Our findings demonstrate that AD patients have decreased corneocyte stiffness which correlates with reduced levels of filaggrin degradation products, NMF and skin barrier function. Altered mechanical properties of the corneocytes likely contribute to the loss of mechanical integrity of the SC and to reduced skin barrier function in AD.

Changes in nano-mechanical properties of human epidermal cornified cells in children with atopic dermatitis

Background: Impaired skin barrier is an important etiological factor in atopic dermatitis (AD). The structural protein filaggrin (FLG) plays a major role in maintenance of the competent skin barrier and its deficiency is associated with enhanced susceptibility to mechanical injury. Here we examined biomechanical characteristics of the corneocytes in children with AD and healthy controls. Methods: We recruited 20 children with AD and 7 healthy children. They were genotyped for filaggrin gene ( FLG) loss-of-function mutations. Stratum corneum was collected from clinically unaffected skin by adhesive tapes. Cell stiffness (apparent elastic modulus, Ea) was determined by atomic force microscopy and filaggrin degradation products (NMF) by liquid chromatography. Skin barrier function was assessed through trans-epidermal water loss (TEWL) and disease severity by the SCORing Atopic Dermatitis (SCORAD) tool. Results: Corneocytes collected from AD patients showed a decreased elastic modulus which was strongly correlated with NMF and TEWL, but not with SCORAD. As compared with healthy controls, AD patients had reduced TEWL and NMF levels regardless of FLG mutations. NMF was strongly correlated with TEWL. Conclusion: Our findings demonstrate that AD patients have decreased corneocyte stiffness which correlates with reduced levels of filaggrin degradation products, NMF and skin barrier function. Altered mechanical properties of the corneocytes likely contribute to the loss of mechanical integrity of the SC and to reduced skin barrier function in AD.

Changes in nano-mechanical properties of human epidermal cornified cells in children with atopic dermatitis.

Background:Impaired skin barrier is an important etiological factor in atopic dermatitis (AD). The structural protein filaggrin (FLG) plays a major role in maintenance of the competent skin barrier and its deficiency is associated with enhanced susceptibility to mechanical injury. Here we examined biomechanical characteristics of the corneocytes in children with AD and healthy controls. Methods:We recruited 20 children with AD and 7 healthy children. They were genotyped for filaggrin gene ( FLG) loss-of-function mutations. Stratum corneum was collected from clinically unaffected skin by adhesive tapes. Cell stiffness (apparent elastic modulus, Ea) was determined by atomic force microscopy and filaggrin degradation products (NMF) by liquid chromatography. Skin barrier function was assessed through trans-epidermal water loss (TEWL) and disease severity by the SCORing Atopic Dermatitis (SCORAD) tool. Results: Corneocytes collected from AD patients showed a decreased elastic modulus which was strongly correlated with NMF and TEWL, but not with SCORAD. As compared with healthy controls, AD patients had reduced TEWL and NMF levels regardless of FLG mutations. NMF was strongly correlated with TEWL. Conclusion:Our findings demonstrate that AD patients have decreased corneocyte stiffness which correlates with reduced levels of filaggrin degradation products, NMF and skin barrier function. Altered mechanical properties of the corneocytes likely contribute to the loss of mechanical integrity of the SC and to reduced skin barrier function in AD.

232 Identifying the mechanisms underlying the negative feedback loop between tight junction proteins and cutaneous microbial dysbiosis in atopic dermatitis

Reduced skin barrier function and dysbiosis of the skin microbiota are hallmarks of atopic dermatitis (AD). Both, reduced cutaneous barrier and dominance of Staphylococcus aureus (S. aureus) are believed to represent entry points of inflammation in AD, but how they regulate each other is not known. Tight junctions (TJs) in the skin are close contacts between plasma membranes of neighboring cells and important for barrier functioning. TJs have also been indicated to be essential for skin barrier function in AD, yet little is known about their interplay with S. aureus. Here, we investigated how skin barrier impairment contributes to the development of AD, focusing on the microbial shift towards S. aureus dominance in a mouse model. We found that barrier impairment induced by repeated tape stripping of the back skin leads to a significant downregulation of several TJ proteins (e.g. claudin-1, occludin) detected by RT-PCR ex vivo. Furthermore, an upregulation of S. aureus-associated pro inflammatory cytokines (e.g. IL-1ß, TNF-α, IL-6) was detected. Analyses of the skin microbiome affirm this finding by pointing to a shift within the microbial homeostasis characterized by a predominance of staphylococci after tape stripping. We applied the FITC dermatitis model to induce AD-like inflammation. As a result, sensitization of the mice at tape stripped skin resulted in a significant increase in ear swelling upon challenge one week later compared to non-tape stripped mice, as well as a more pronounced Th2-dominated immune response associated by an increased CD3+CD4+ cell population and higher levels of IL-4 and IL-13. These findings establish a model of skin barrier disruption which can be applied to study molecular mechanisms of AD pathophysiology. They also indicate an important role of the downregulation of TJs contributing to a staphylococci-dominated dysbiosis of the skin and AD development. To conclude, this model and findings should be used to develop treatment strategies for patients suffer from this disease.

355 Validation of a novel patient-operated device for measuring skin barrier function in atopic dermatitis

355 Validation of a novel patient-operated device for measuring skin barrier function in atopic dermatitis

Measurement of trihydroxy-linoleic acids in stratum corneum by tape-stripping: Possible biomarker of barrier function in atopic dermatitis.

Epidermal ceramides are indispensable lipids that maintain the functions of the stratum corneum. Esterified omega-hydroxyacyl-sphingosine (EOS) ceramide with a linoleate moiety is one of the most important ceramide species for forming cornified lipid envelopes. This linoleate moiety is eventually metabolized to trihydroxy-linoleic acid (triol, 9,10,13-trihydroxy-11E-octadecenoic acid). Thus, we assumed that a decrease of triols might reflect skin barrier dysfunction. Against this background, the purposes of this study were to measure the triols by a simple tape-stripping method and to determine the correlation between the amount of triols and transepidermal water loss (TEWL) as an indicator of barrier dysfunction in atopic dermatitis patients. Twenty Japanese subjects with normal skin and 20 atopic dermatitis patients were enrolled in this study. TEWL was measured and triols of the stratum corneum were analyzed by tape-stripping. The results showed for the first time that triols in the stratum corneum could be simply measured using the tape-stripping method. The triol levels in atopic dermatitis patients were much higher than those in healthy subjects. Moreover, the triol levels correlated with TEWL of non-lesional forearm skin in patients with atopic dermatitis. The results suggest that the assaying of triol levels via non-invasive tape-stripping could be beneficial for monitoring barrier function in atopic dermatitis.

Nemolizumab and Atopic Dermatitis: the Interaction Between Interleukin-31 and Interleukin-31 Receptor as a Potential Therapeutic Target for Pruritus in Patients With Atopic Dermatitis

Atopic dermatitis (AD) is a chronic eczematous skin disease associated with intense pruritus and skin barrier dysfunction. Interleukin-31 (IL-31), which is preferentially produced by T helper 2 (Th2) cells, has attracted attention as a pruritogen in patients with AD. To understand the mechanism of action, production, and roles of IL-31, we reviewed recent advances of the knowledge of IL-31, its receptor as well as results of recent clinical trials targeting IL-31/IL-31R signaling for pruritus in patients with AD. Activation of many cytokine pathways has been reported in AD, suggesting potential therapeutic targets with novel biologics. Most notably, the lesional skin of AD exhibits Th2-deviated immune reactions. Recently reported striking efficacy of dupilumab, a monoclonal antibody targeting the IL-4 receptor α subunit reconfirms the importance of Th2-deviated immune reactions in the pathogenesis of AD. A systemic and local administration of IL-31 induces scratching behavior in mice, dogs, and monkeys. In addition, serum levels of IL-31 have been correlated with severity of AD. Finally, an anti-interleukin (IL)-31 receptor α antibody (nemolizumab) has been shown to significantly alleviate pruritus in AD patients. The interaction between IL-31 and IL-31R has a role not only in the induction of intense pruritus, but also in the regulation of inflammation and barrier function in AD. In clinical trials, nemolizumab significantly improved pruritus in patients with moderate-to-severe AD. Targeting the IL-31/IL-31R interaction might be a promising therapeutic target to improve the burdensome pruritus experienced by patients with AD.

S100A7 (psoriasin) inhibits human epidermal differentiation by enhanced IL-6 secretion through IκB/NF-κB signalling.

Psoriasin (S100A7), a member of the S100 protein family, is a well-known antimicrobial peptide and a signalling molecule which regulates cellular function and is highly expressed in hyperproliferative skin conditions such as atopic dermatitis (AD) and psoriasis with disrupted skin barrier function. However, its role in epidermal differentiation remains unknown. We examined the effect of S100A7 on epidermal differentiation in normal human keratinocytes (NHKs) and on a reconstituted human epidermis model. When NHKs were exposed to disruptive stimuli such as Staphylococcus aureus, ultraviolet irradiation and retinoic acid, the secretion of S100A7 into the culture medium increased and the expression of epidermal differentiation markers decreased. Treatment of NHKs with S100A7 significantly inhibited epidermal differentiation by reducing the expression of keratin 1, keratin 10, involucrin and loricrin and by increasing the expression of abnormal differentiation markers (keratin 6 and keratin 16). We verified that the MyD88-IκB/NF-κB signal cascade was activated via RAGE after S100A7 treatment, resulting in the upregulation of interleukin-6. Finally, we confirmed that S100A7 is a negative regulator of epidermal differentiation using a reconstituted human epidermis model. This study suggests that S100A7-related signalling molecules could be potent targets for recovering skin barrier function in AD and psoriasis where S100A7 is accumulated excessively.

Effects of sphingolipid extracts on the morphological structure and lipid profile in an in vitro model of canine skin

Ceramides (CER) are essential sphingolipids of the stratum corneum (SC) that play an important role in maintaining cutaneous barrier function. Skin barrier defects occur in both human beings and dogs affected with atopic dermatitis, and have been associated with decreased CER concentrations and morphological alterations in the SC. The aim of the present study was to investigate the changes induced by three different sphingolipid extracts (SPE-1, SPE-2 and SPE-3) on the morphological structure and lipid composition of canine skin, using an in vitro model, whereby keratinocytes were seeded onto fibroblast-embedded collagen type I matrix at the air–liquid interface. Cell cultures were supplemented with SPE-1, SPE-2, SPE-3 or vehicle (control) for 14 days. The relative concentrations of lipids were determined by ultra-performance liquid chromatography coupled to mass spectrometry. The ultrastructural morphology of samples was examined by transmission electron microscopy. SPE-1 induced significant elevation in total CERs, CER[NS], CER[NDS], CER[NP], CER[AS], CER[AP], CER[EOS] and CER[EOP] subclasses, whereas SPE-2 induced a significant elevation in total CER, CER[AP] and CER[EOS] compared with control conditions. Ultrastructural analysis revealed an increase in lamellar-lipid structures in the SC of SPE-1-treated samples. The findings demonstrated that SPE-1 stimulates production of CERs, as shown by changes in lipid composition and ultrastructural morphology. Thus, SPE-1 contributes to the formation of a well-organised SC and represents a potential therapeutic target for improving skin barrier function in atopic dermatitis.

Longitudinal Evaluation of the Skin Microbiome and Association with Microenvironment and Treatment in Canine Atopic Dermatitis

Host-microbe interactions may play a fundamental role in the pathogenesis of atopic dermatitis, a chronic relapsing inflammatory skin disorder characterized by universal colonization with Staphylococcus species. Toexamine the relationship between epidermal barrier function and the cutaneous microbiota in atopic dermatitis, this study used a spontaneous model of canine atopic dermatitis. In a cohort of 14 dogs with canineatopic dermatitis, the skin microbiota were longitudinally evaluated with parallel assessment of skin barrier function at disease flare, during antimicrobial therapy, and post-therapy. Sequencing of the bacterial 16S ribosomal RNA gene showed decreased bacterial diversity and increased proportions of Staphylococcus (S.pseudintermedius in particular) and Corynebacterium species compared with a cohort of healthy control dogs (n= 16). Treatment restored bacterial diversity with decreased proportions of Staphylococcus species, concurrent with decreased canine atopic dermatitis severity. Skin barrier function, as measured by corneometry, pH, and transepidermal water loss also normalized with treatment. Bacterial diversity correlated with transepidermal water loss and pH level but not with corneometry results. These findings provide insights intothe relationship between the cutaneous microbiome and skin barrier function in atopic dermatitis, show the impact of antimicrobial therapy on the skin microbiome, and highlight the utility of canine atopic dermatitis as a spontaneous nonrodent model of atopic dermatitis.

Effect of Herbs Grown in Korea on Recovery of Skin Barrier Function in Atopic Dermatitis

Effect of Herbs Grown in Korea on Recovery of Skin Barrier Function in Atopic Dermatitis

Short-Term Effect of Airborne Formaldehyde on Skin Barrier Function in Atopic Dermatitis

E S D A Y 848 Evaluation of Gene Expression Using a Skin Tape Stripping Method Byung Eui Kim, MD, PhD, Un Ha Lee, Peter Sang Kim, Donald Y. M. Leung, MD, PhD, FAAAAI; National Jewish Health, Denver, CO, Inje University, Paik Hospital, National Jewish Health. RATIONALE: Skin tape stripping is a non-invasive method used to evaluate epidermal protein expression. However, this technique has not been verified whether this skill is reliable to evaluate gene expression. METHODS: Skin tape stripping samples and skin punch biopsies were collected from 10 normal subjects and 10 patients with atopic dermatitis (AD). Total RNAwas isolated from the same donors for skin tape stripping samples and skin biopsies, and then real time RT-PCR was performed for filaggrin (FLG), thymic stromal lymphopoietin (TSLP) and loricrin (LOR). RESULTS: FLG gene expression was significantly decreased in lesional AD skin compared with skin from normal subjects in both tape stripping samples (P<0.05) and skin biopsies (P<0.05). LOR gene expression was also significantly decreased in lesional AD skin compared with skin from normal subjects in skin tape stripping samples (P<0.01) and skin biopsies (P<0.05). Additionally, LOR gene expression was significantly decreased (P<0.05) in nonlesional AD skin compared with normal subjects in tape stripping samples. TSLP gene expression from tape stripped samples was significantly increased in lesional AD skin compared with skin from normal subjects (P<0.05) and nonlesional AD (P<0.05). CONCLUSIONS: Using PCR data from both tape stripping samples and skin biopsies, we have found reduced filaggrin and loricrin, but increased TSLP, gene expression in AD. Skin tape stripping method may be used to examine gene expression in the skin since it is a non-invasive, and can be used for serial evaluation of the skin and protein expression. However, further study is required to validate this method.