Which Way Do We Go? Complex Interactions in Atopic Dermatitis Pathogenesis

Zinc gluconate improves atopic dermatitis by modulating CXCL10 release of keratinocytes via PPARα activation

Atopic dermatitis (AD) is a chronic inflammatory skin condition with complex causes involving immune factors. The presence of essential trace elements that support immune system function can influence the development of this condition. This study investigated how serum trace elements impact the pathogenesis of atopic dermatitis. Upon analyzing serum microelements in AD patients and control subjects, it was observed that patients with AD had notably lower zinc levels. Genomic analysis of AD skin revealed distinct gene expression patterns, specifically the increased expression of CXCL10 in the epidermis. The heightened levels of CXCL10 in AD skin lesions were found to correlate with reduced serum zinc levels. Treatment with zinc gluconate showed reduced chemotactic response and CXCL10 release, suggesting its potential to regulate CXCL10 expression of keratinocytes in AD. The mechanism behind this involved the downregulation of STAT phosphorylation through activating PPARα. In the AD-like dermatitis mouse model, zinc gluconate therapy decreased serum IgE levels, alleviated skin lesion severity, reduced skin thickness, and lowered CXCL10 expression, demonstrating its efficacy in managing AD-like skin conditions. These findings indicate that zinc gluconate can reduce inflammation in keratinocytes by activating PPARα, inhibiting STAT signaling, and decreasing CXCL10 release, thus highlighting its potential as a therapeutic target for AD.

Yu-Ping-Feng-San alleviates inflammation in atopic dermatitis mice by TLR4/MyD88/NF-κB pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Yu-Ping-Feng-San (YPF) is a traditional Chinese medicine formula that has therapeutic effects on allergic diseases such as allergic rhinitis and asthma. However, its potential efficacy and mechanism in the treatment of atopic dermatitis (AD) has not been extensively illustrated.

AIM OF THE STUDY

The purpose of this study was to investigate the efficacy and possible mechanisms of YPF in AD pathogenesis.

METHODS

Network pharmacology and GEO data mining were adopted to firstly identify the potential mechanisms of YPF on AD. Then DNCB induced-AD murine model was established to test the efficacy of YPF and verify its effects on inflammatory cytokines and NF-κB pathway. In addition, molecular docking was performed to detect the binding affinity of YPF's active components with NF-κB pathway related molecules.

RESULTS

Network pharmacology and human data mining suggested that YPF may act on the NF-κB pathway in AD pathogenesis. With DNCB mice model, we found that YPF significantly improved AD symptoms, reduced SCORAD scores, and alleviated skin tissue inflammation in mice. At the same time, the expression of inflammatory cytokines, TNF-α, sPLA2-IIA and IL-6, was down-regulated. Moreover, YPF suppressed TLR4/MyD88/NF-κB pathway in situ in a dose-dependent manner. Molecular docking further confirmed that seven compounds in YPF had exceptional binding properties with TNF-α, IL-6 and TLR4.

CONCLUSION

YPF may help the recovery of AD by inhibiting the TLR4/MyD88/NF-κB pathway, which provides novel insights for the treatment of AD by YPF.

Biologic and small-molecule therapy for treating moderate to severe atopic dermatitis: Mechanistic considerations

Atopic dermatitis (AD) is a complex and heterogeneous skin disease for which achieving complete clinical clearance for most patients has proven challenging through single cytokine inhibition. Current studies integrate biomarkers and evaluate their role in AD, aiming to advance our understanding of the diverse molecular profiles implicated. Although traditionally characterized as a TH2-driven disease, extensive research has recently revealed the involvement of TH1, TH17, and TH22 immune pathways as well as the interplay of pivotal immune molecules, such as OX40, OX40 ligand (OX40L), thymic stromal lymphopoietin, and IL-33. This review explores the mechanistic effects of treatments for AD, focusing on mAbs and Janus kinase inhibitors. It describes how these treatments modulate immune pathways and examines their impact on key inflammatory and barrier biomarkers.

Ursodeoxycholic acid alleviates atopic dermatitis-associated inflammatory responses in HaCaT and RBL-2H3 cells and DNCB/DFE-treated mice

AIMS

Ursodeoxycholic acid (UDCA) is a hydrophilic dihydroxy bile acid used for cholestatic liver disease and exhibits antioxidant, antitumor, and anti-inflammatory effects. However, its potential effects on atopic dermatitis (AD) have not been elucidated. This study aimed to evaluate the efficacy of UDCA in inhibiting the inflammatory response and alleviating lesions in AD-like mice.

MAIN METHODS

To investigate the efficacy of UDCA in AD-like inflammatory responses, tumor necrosis factor-alpha (TNF-α)- and interferon-gamma (IFN-γ)-stimulated HaCaT cells and anti-dinitrophenyl immunoglobulin E (DNP-IgE)- and human serum albumin (HSA)-stimulated RBL-2H3 cells were used to investigate the levels of inflammatory factors and their mechanisms. AD-like lesions were induced by applying DNCB/DFE to mice. The effect of UDCA administration in AD-like mice was analyzed by assessing organ weight, serum IgE and inflammatory cytokine levels, and histopathological changes using immunohistochemical and immunofluorescent staining.

KEY FINDINGS

In HaCaT cells, UDCA significantly diminished TARC, MDC, MCP-1, and IL-6 expression by inhibiting the phosphorylation of nuclear NF-κB and cytoplasmic IκB, and also increased the levels of skin barrier protein. In RBL-2H3 cells, UDCA reduced β-hexosaminidase and IL-4 levels. In AD-like mice, UDCA suppressed organ hypertrophy, ear edema, SCORAD index, DFE-specific IgE levels, inflammatory cytokine levels, skin hypertrophy, mast cell invasion, skin barrier loss, and thymic stromal lymphopoietin-positive areas.

SIGNIFICANCE

UDCA suppressed the expression of pro-inflammatory cytokines by keratinocytes and mast cells. It also alleviated atopy by suppressing symptoms without organ toxicity in AD-like mice. UDCA may be an effective and safe treatment for AD.

Comparison of Old and New Systemic Treatments for Moderate to Severe Atopic Dermatitis

PURPOSE OF REVIEW

Historically, systemic treatments for atopic dermatitis (AD) primarily consisted of immunosuppressive agents such as corticosteroids and Disease Modifying Antirheumatic Drugs (DMARDS), which provided symptomatic relief but often had long-term adverse effects. Newer treatments have shown significant efficacy with less side effects in clinical trials. This review discusses and compares conventional and newer systemic treatments for AD.

RECENT FINDINGS

Newer medications for AD including dupilumab, tralokinumab, lebrikizumab, and oral JAK inhibitors have been shown to be safe and efficacious. High dose cyclosporine and dupilumab were more effective than methotrexate and azathioprine in improving clinical signs of AD. High-dose upadacitinib was shown in another meta-analysis to be most effective in the measured outcomes but had the highest frequency of adverse events. Targeted biologic treatments are increasingly favored over traditional immunosuppressive treatments of AD. Treatment can be individualized based on potency, adverse side effects, mechanism of action, and administration preference. Ongoing research continues to expand treatment options for AD.

Identifying Atopic Dermatitis Risk Loci in 1,094,060 Individuals with Subanalysis of Disease Severity and Onset

Atopic dermatitis (AD) is a common inflammatory skin disease highly attributable to genetic factors. In this study, we report results from a genome-wide meta-analysis of AD in 37,541 cases and 1,056,519 controls with data from the FinnGen project, the Estonian Biobank, the UK Biobank, the EAGLE Consortium, and the BioBank Japan. We detected 77 independent AD-associated loci, of which 10 were, to our knowledge, previously unreported. The associated loci showed enrichment in various immune regulatory processes. We further performed subgroup analyses of mild and severe AD and of early- and late-onset AD, with data from the FinnGen project. Fifty-five of the 79 tested variants in the associated loci showed larger effect estimates for severe than for mild AD as determined through administered treatment. The age of onset, as determined by the first hospital visit with AD diagnosis, was lower in patients with particular AD-risk alleles. Our findings add to the knowledge of the genetic background of AD and may underlie the development of new therapeutic strategies.

Investigating dysregulation of TGF-β1/SMAD3 signaling in atopic dermatitis: a molecular and immunohistochemical analysis

Atopic dermatitis (AD) is a persistent and recurring inflammatory condition affecting the skin. An expanding corpus of evidence indicates the potential participation of transforming growth factor-β1 (TGF-β1) in the modulation of inflammation and tissue remodeling in AD. The primary objective of this study was to examine the aberrant modulation of TGF-β1/small mothers against decapentaplegic homolog 3 (SMAD3) signaling through a comprehensive analysis of their molecular and protein expression profiles. The study encompassed an aggregate of 37 participants, which included 25 AD patients and 12 controls. The assessment of mRNA and protein levels of TGF-β1 and SMAD3 was conducted utilizing quantitative real-time PCR and immunohistochemistry (IHC), whereas serum IgE and vitamin D levels were estimated by ELISA and chemiluminescence, respectively. Quantitative analysis demonstrated a 2.5-fold upregulation of TGF-β1 mRNA expression in the lesional AD skin (P < 0.0001). IHC also exhibited a comparable augmented pattern, characterized by moderate to strong staining intensities. In addition, TGF-β1 mRNA showed an association with vitamin D deficiency in serum (P < 0.02), and its protein expression was linked with the disease severity (P < 0.01) Furthermore, a significant decrease in the expression of the SMAD3 gene was observed in the affected skin (P = 0.0004). This finding was further confirmed by evaluating the protein expression and phosphorylation of SMAD3, both of which exhibited a decrease. These findings suggest that there is a dysregulation in the TGF-β1/SMAD3 signaling pathway in AD. Furthermore, the observed augmentation in mRNA and protein expression of TGF-β1, along with its correlation with the disease severity, holds considerable clinical significance and emphasizes its potential role in AD pathogenesis.

Time-dependent risk of atopic dermatitis following nontyphoidal Salmonella infection

BACKGROUND

The pathogenesis of atopic dermatitis (AD) remains unclear. Nontyphoidal Salmonella (NTS) infection might trigger immune-mediated reactions. We aimed to examine NTS and the risk of subsequent AD.

METHODS

From 2002 to 2015, eligible patients (aged 0-100 years) with NTS were identified. NTS and non-NTS groups were matched at a 1:10 ratio on age and sex. We utilized conditional multivariable Cox proportional hazard models to estimate the adjusted hazard ratio (aHR) and 95% confidence interval (CI) for AD development. Subgroup analyses were conducted based on age, sex, and severity of NTS infection. We utilized landmark analysis to explore the time-dependent hazard of AD following NTS.

RESULTS

In the NTS group (N = 6624), 403 developed AD. After full adjustment of demographics and comorbidities, the NTS group had a higher risk of AD than the reference group (aHR = 1.217, 95% CI = 1.096-1.352). Age-stratified analysis revealed that NTS group exhibited an elevated risk compared to the reference group, particularly among those aged 13-30 years (aHR = 1.25, 95% CI = 1.017-1.559), individuals aged 31-50 years (aHR = 1.388, 95% CI = 1.112-1.733), those aged 51-70 years (aHR = 1.301, 95% CI = 1.008-1.679), and individuals aged 71 years and over (aHR = 1.791, 95% CI = 1.260-2.545). Severe NTS was associated with a higher risk of AD than the reference group (aHR = 2.411, 95% CI = 1.577-3.685). Landmark analysis showed generally consistent findings.

CONCLUSIONS

Minimizing exposure to NTS infection may represent a prospective strategy for averting the onset and progression of atopic dermatitis.

Nanotechnology strategies to address challenges in topical and cellular delivery of siRNAs in skin disease therapy

Gene therapy is one of the most advanced therapies in current medicine. In particular, interference RNA-based therapy by small interfering RNA (siRNA) has gained attention in recent years as it is a highly versatile, selective and specific therapy. In dermatological conditions, topical delivery of siRNA offers numerous therapeutic advantages, mainly by inhibiting the expression of target transcripts directly in the skin. However, crossing the stratum corneum and overcoming intracellular barriers is an inherent challenge. Substantial efforts by scientists have moved towards the use of multimodal and multifunctional nanoparticles to overcome these barriers and achieve greater bioavailability in their site of action, the cytoplasm. In this review the most innovative strategies based on nanoparticle and physical methods are presented, as well as the design principles and the main factors that contribute to the performance of these systems. This review also highlights the synergistic contributions of medicine, nanotechnology, and molecular biology to advancing translational research into siRNA-based therapeutics for skin diseases.

No Evidence of Causal Association Between Atopic Dermatitis and Primary Open-Angle Glaucoma: A Bidirectional Two-Sample Mendelian Randomization Study

Background: Atopic dermatitis (AD) can present with open-angle glaucoma, but powerful evidence to support their causal relationship is absent. Objective: To investigate the causal association of AD with primary open-angle glaucoma (POAG). Methods: A bidirectional 2-sample Mendelian randomization (MR) study was performed with the software R. Results: Eighteen single nucleotide polymorphisms (SNPs) were used in the forward MR analysis with AD as exposure. The inverse-variance weighted (IVW) method produced a result that genetically predicted AD was not associated with POAG (odds ratio [OR] = 1.10, 95% confidence interval [CI]: 0.95-1.27, P = 0.215). Fifty-one SNPs were used in the reverse MR analysis with POAG as exposure. The IVW method yielded a result that genetically predicted POAG was not correlated with AD (OR = 0.98, 95% CI: 0.95-1.01, P = 0.191). The bidirectional causal effect estimates were consistent with supplementary MR methods (MR-Egger, weighted median, simple mode, and weighted mode). The sensitivity analysis showed stable results. Conclusions: This bidirectional 2-sample MR study did not give evidence of causal association between AD and POAG.

Polygonum perfoliatum L. ethanol extract ameliorates 2,4-dinitrochlorobenzene-induced atopic dermatitis-like skin inflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Polygonum perfoliatum L. (PP) is classified as a heat-clearing and detoxifying agent in traditional Chinese medicine, and is believed to possess therapeutic properties for treating eczema, furuncles, and venomous snake bites. Previous studies have demonstrated that PP extract exhibits multiple bioactivities, including antibacterial, anti-inflammatory, antitumor, antioxidation, and antiviral properties. However, no existing studies have evaluated the effects of PP on animal models of atopic dermatitis (AD)-like skin symptoms, which are closely associated with traditional ethnic usage.

AIM OF THE STUDY

In present study, therefore, we aimed to explore the potential anti-atopic effect of Polygonum perfoliatum L. ethanol extract (PPE) in 2,4-Dinitrochlorobenzene (DNCB)-induced dermatitis-like skin lesions.

MATERIALS AND METHODS

For reaching this aim, DNCB-induced mice with AD-like skin inflammation were subjected to topical administration of PPE gels for a period of 21 days, and subsequently, the biological impacts of PPE were evaluated.

RESULTS

PPE gels effectively mitigated AD-like skin symptoms induced by DNCB in mice, as demonstrated by a marked reduction in epidermal thickness and dermatitis severity. Moreover, PPE significantly decreased the production of various cytokines, including TNF-α, IL-6, IL-1β, IL-4, IL-5, IL-13 and IgE, in addition to suppressed the production of key inflammation-related enzymes (iNOS and COX-2) and decreased the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-κB in AD-like skin samples. Furthermore, PPE treatment inhibited the abnormally elevated CD4+/CD8+ ratio in DNCB-induced AD mice. The results of the skin irritation test revealed that PPE exhibited no adverse toxicity in mice at dose of 10 mg/day.

CONCLUSIONS

PPE exhibits potential as a safe therapeutic agent for atopic dermatitis by efficiently mitigating DNCB-induced atopic symptoms and diminishing inflammation, and does not carry the risk of over-immunosuppression or treatment-associated adverse effects.

Skin repair and immunoregulatory effects of myeloid suppressor cells from human cord blood in atopic dermatitis

Introduction

Previously, we achieved large-scale expansion of bone marrow-derived suppressor cells (MDSCs) derived from cluster of differentiation (CD)34+ cells cultured in human umbilical cord blood (hUCB) and demonstrated their immunomodulatory properties. In the present study, we assessed the therapeutic efficacy of hUCB-MDSCs in atopic dermatitis (AD).

Methods

Dermatophagoides farinae (Df)-induced NC/Nga mice (clinical score of 7) were treated with hUCB-MDSCs or a control drug. The mechanisms underlying the therapeutic effects of hUCB-MDSCs were evaluated.

Results and discussion

hUCB-MDSCs demonstrated immunosuppressive effects in both human and mouse CD4+ T cells. hUCB-MDSCs significantly reduced the clinical severity scores, which were associated with histopathological changes, and reduced inflammatory cell infiltration, epidermal hyperplasia, and fibrosis. Furthermore, hUCB-MDSCs decreased the serum levels of immunoglobulin E, interleukin (IL)-4, IL-5, IL-13, IL-17, thymus- and activation-regulated chemokines, and thymic stromal lymphopoietin. Additionally, they altered the expression of the skin barrier function-related proteins filaggrin, involucrin, loricrin, cytokeratin 10, and cytokeratin 14 and suppressed the activation of Df-restimulated T-cells via cell-cell interactions. hUCB-MDSCs promoted skin recovery and maintained their therapeutic effect even after recurrence. Consequently, hUCB-MDSC administration improved Df-induced AD-like skin lesions and restored skin barrier function. Our findings support the potential of hUCB-MDSCs as a novel treatment strategy for AD.

Electrical impedance spectroscopy detects skin barrier dysfunction in childhood atopic dermatitis

BACKGROUND

Skin barrier dysfunction is associated with the development of atopic dermatitis (AD), however methods to assess skin barrier function are limited. We investigated the use of electrical impedance spectroscopy (EIS) to detect skin barrier dysfunction in children with AD of the CARE (Childhood AlleRgy, nutrition, and Environment) cohort.

METHODS

EIS measurements taken at multiple time points from 4 months to 3-year-old children, who developed AD (n = 66) and those who did not (n = 49) were investigated. Using only the EIS measurement and the AD status, we developed a machine learning algorithm that produces a score (EIS/AD score) which reflects the probability that a given measurement is from a child with active AD. We investigated the diagnostic ability of this score and its association with clinical characteristics and age.

RESULTS

Based on the EIS/AD score, the EIS algorithm was able to clearly discriminate between healthy skin and clinically unaffected skin of children with active AD (area under the curve 0.92, 95% CI 0.85-0.99). It was also able to detect a difference between healthy skin and AD skin when the child did not have active AD. There was no clear association between the EIS/AD score and the severity of AD or sensitisation to the tested allergens. The performance of the algorithm was not affected by age.

CONCLUSIONS

This study shows that EIS can detect skin barrier dysfunction and differentiate skin of children with AD from healthy skin and suggests that EIS may have the ability to predict future AD development.

Identification of potential miR‑155 target genes in epidermal immune microenvironment of atopic dermatitis patients and their inflammatory effects on HaCaT cells

Atopic dermatitis (AD) is a common inflammatory skin condition and the leading cause of morbidity associated with skin conditions worldwide. For the majority of patients, AD is a lifelong disease that cannot be cured completely. Therefore, in the present study, differentially expressed genes (DEGs) in the epidermal immune microenvironment were screened using bioinformatic techniques. Subsequently, an in vitro cellular model was constructed to investigate the role of microRNA (miR)-155 in immune infiltration during AD. In the present study, two datasets (GSE121212 and GSE157194) were downloaded from Gene Expression Omnibus, before the DEGs were screened and subjected to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes functional enrichment analyses. miRNet was used to predict the possible target genes of miR-155 among the differentially expressed genes found. Consequently, peptidase inhibitor 3 (PI3), FOS-like 1, AP-1 transcription factor subunit (FOSL1), C-X-C motif chemokine ligand (CXCL)1 and CXCL8 were selected to be the potential target genes of miR-155 in the epidermal immune microenvironment of patients with AD. Concurrently, an inflammatory cell model using HaCaT cells was constructed by TNF-α and IFN-γ treatment. The effects of miR-155 on HaCaT cell proliferation and secretion of IL-1β, IL-6, IL-10, IL-15, PI3, FOSL1, CXCL1 and CXCL8 under inflammatory and non-inflammatory conditions were then analyzed. The results showed that after the HaCaT cells were transfected with miR-155, miR-155 inhibited HaCaT cell proliferation and decreased the mRNA expression levels of PI3 and CXCL8, increased the mRNA levels of FOSL1 and secretion levels of IL-1β, IL-6, IL-15 and CXCL1. By contrast, miR-155 decreased the secretion levels of IL-10 and CXCL8. In the inflammatory cell model of HaCaT cells, miR-155 was found to significantly inhibit the proliferation of HaCaT cells during inflammation whilst significantly increasing the secretion of IL-1β, IL-6, IL-10 and IL-15. In addition, miR-155 increased the mRNA expression and secretion levels of CXCL1 and CXCL8, whilst also increasing the mRNA expression levels of PI3. Results from the current study suggest that miR-155 can stimulate keratinocytes to produce inflammatory cytokines and proteins to enhance the inflammatory response in AD.

Bidirectional Mendelian randomization analysis did not indicate a causal relationship between atopic dermatitis and COVID-19

The threat of COVID-19 infection imposes an additional psychological burden on patients with AD. Whether there is an association between AD and COVID-19 remains unclear as observational studies are susceptible to confounding factors and reverse causality. This study did not indicate a causal relationship between AD and susceptibility, hospitalization and severity of COVID-19.

The immunological and structural epidermal barrier dysfunction and skin microbiome in atopic dermatitis-an update

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.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

Modelling of indirect cell-cell interaction networks mediated by IFNγ/IL-4 cytokine involved in atopic dermatitis

Atopic dermatitis (AD) is an immune-driven inflammatory skin disease that is known to have a significantly high life-time prevalence in the human population. T-helper (Th) immune cells play a key role in the pathogenesis of AD which is marked by defects in the skin barrier function along with a significant increase in the population of either Th1 or Th2 sub-types of Th cells. The progression of AD from the acute to chronic phase is still poorly understood, and here we explore the mechanism of this transition through the study of a mathematical model for indirect cell-cell interactions among Th and skin cells via the secreted cytokines IFNγ and IL-4, both known to have therapeutic potential. An increase in the level of cytokine IFN γ can catalyse the transition of AD from an acute to a chronic stage, while an increase in the level of cytokine IL-4 has the reverse effect. In our model, the transition of AD from the acute to chronic stage and vice versa can be abrupt (switch-like) with hysteresis: this bistable behaviour can potentially be used to keep AD in the acute phase since therapy based on suppression of IFNγ can retard the transition to the chronic phase.

Anti-inflammatory and immunomodulatory effects of polysaccharide extracted from Wuguchong (maggot) on 2,4-dinitrochlorobenzene-induced atopic dermatitis in mice

Atopic dermatitis (AD) is an inflammatory, heterogeneous, chronic skin disorder characterized by recurrent eczematous lesions and intense pruritus, and the pathophysiology mechanism of AD is known for immune dysregulation and inflammatory responses. Wuguchong (maggot) has been widely used in the wound field and found with pharmacological properties of the anti-inflammatory and immunomodulatory function. Recently, some polysaccharides were proven to have beneficial effects on AD skin lesions in mice and humans. However, the effect of the polysaccharide extracted from Wuguchong (PEW) on AD remains to be investigated. In the present study, we examined the anti-inflammatory and immunomodulatory effects of PEW on AD and explored the potential mechanisms. Balb/c mice were orally administrated with PEW to evaluate the therapeutic effect of PEW on 2,4-dinitrochlorobenzene (DNCB)-induced AD. Oral PEW administration significantly ameliorated the lesions and symptoms in AD mice, such as the ear thickness and ear swelling degree, epidermal and dermal thickness, and the infiltration of mast cells. In addition, PEW treatment decreased the levels of serum IgE and histamine, the frequencies of Th1 and Th17 cells, as well as the mRNA expression levels of Th1 and Th17 cytokines and nuclear transcript factors (IFN-γ, T-bet, IL-17A, and ROR-rt). Furthermore, the activation of the NF-κB pathway and the phosphorylation of MAPKs (p38, ERK, and JNK) were significantly suppressed by PEW treatment. Taken together, our study suggests that PEW exerts anti-inflammatory and immunomodulatory effects through inhibition of Th1 and Th17 responses and downregulation of NF-κB and MAPK pathways, PEW would be developed as a promising immune therapy for AD.

Dietary Elimination for the Treatment of Atopic Dermatitis: A Systematic Review and Meta-Analysis

BACKGROUND

The influence of diet on atopic dermatitis (AD) is complex, and the use of dietary elimination as a treatment has conflicting views.

OBJECTIVE

To systematically review the benefits and harms of dietary elimination for the treatment of AD.

METHODS

We searched MEDLINE, Embase, AMED, PsycINFO, and the Cochrane Central Register of Controlled Trials from inception to January 18, 2022, without language restrictions, for randomized controlled trials (RCTs) and observational studies comparing dietary elimination and no dietary elimination for the treatment of AD. We conducted random-effects meta-analyses of eczema outcomes. We used the grading of recommendations, assessment, development, and evaluation approach to assess certainty of evidence (CRD42021237953).

RESULTS

Ten RCT (n = 599; baseline median of study mean age, 1.5 years; median of study mean SCOring Atopic Dermatitis index, 20.7, range, 3.5-37.6) were included in the meta-analysis. Compared with no dietary elimination, low-certainty evidence showed that dietary elimination may slightly improve eczema severity (50% with vs 41% without dietary elimination improved the SCOring Atopic Dermatitis index by a minimally important difference of 8.7 points, risk difference of 9% [95% CI, 0-17]), pruritus (daytime itch score [range, 0-3] mean difference, -0.21 [95% CI, -0.57 to 0.15]), and sleeplessness (sleeplessness score [range, 0-3] mean difference, -0.47 [95% CI, -0.80 to -0.13]). There were no credible subgroup differences based on elimination strategy (empiric vs guided by testing) or food-specific sensitization. Insufficient data addressed harms of elimination diets among included RCTs, although indirect evidence suggests that elimination diets may increase the risk for developing IgE-mediated food allergy.

CONCLUSIONS

Dietary elimination may lead to a slight, potentially unimportant improvement in eczema severity, pruritus, and sleeplessness in patients with mild to moderate AD. This must be balanced against potential risks for indiscriminate elimination diets including developing IgE-mediated food allergy and withholding more effective treatment options for AD.

Plasma Exosomes from Children with Atopic Dermatitis May Promote Apoptosis of Keratinocytes and Secretion of Inflammatory Factors in vitro

Purpose

Exosomes are important regulators of keratinocytes (KCs) that have been implicated in a variety of skin disorders. The effect of circulatory exosomes on KCs in pediatric atopic dermatitis (AD) has not been well studied. This study aims to explore the effect of plasma exosomes on KC activation, apoptosis and inflammation in pediatric AD patients.

Patients and Methods

Exosomes were extracted from plasma collected from 20 pediatric AD patients and 20 age-matched healthy controls. AD-exosomes were added with KCs at concentrations of 0 g/L, 10 g/L, 20 g/L and 30 g/L. Proliferation of KCs in each group was measured using Ki67 staining flow cytometry. Apoptosis was measured using Annexin V-FITC/PI double staining flow cytometry. KCs were divided into three groups according to the source of the exosomes they were cultured with: patients with AD, healthy controls and blank controls. Q-PCR was used to detect the activation (K6) and differentiation (K10) of cells, as well as inflammatory indicators (thymic stromal lymphopoietin (TSLP) and IL-33).

Results

The proliferation rate of KCs treated with 20 g/L exosomes from AD patients was significantly lower than that of other groups, while the apoptosis rate was significantly increased. Additionally, expression levels of K6, K10, TSLP and IL-33 were all up-regulated compared to keratinocytes treated with exosomes from healthy controls.

Conclusion

Exosomes from the peripheral blood of pediatric AD patients can regulate the activation, apoptosis and inflammatory cytokine secretion of KCs in vivo, which may participate in the pathogenesis of AD.

Herpes Simplex Virus 1 Can Bypass Impaired Epidermal Barriers upon Ex Vivo Infection of Skin from Atopic Dermatitis Patients

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 ex vivo infection studies to explore viral invasion in atopic dermatitis (AD) skin characterized by disturbed barrier functions. Our focus was on the visualization of the onset of infection in single cells to determine the primary entry portals in the epidermis. After ex vivo infection of lesional AD skin, we observed infected cells in suprabasal layers indicating successful invasion in the epidermis via the skin surface which was never detected in control skin where only sample edges allowed viral access. The redistribution of filaggrin, loricrin, and tight-junction components in the lesional skin samples suggested multiple defective mechanical barriers. To dissect the parameters that contribute to HSV-1 invasion, we induced an AD-like phenotype by adding the Th2 cytokines interleukin 4 (IL-4) and IL-13 to healthy human skin samples. Strikingly, we detected infected cells in the epidermis, implying that the IL-4/IL-13-driven inflammation is sufficient to induce modifications allowing HSV-1 to penetrate the skin surface. In summary, not only did lesional AD skin facilitate HSV-1 penetration but IL-4/IL-13 responses alone allowed virus invasion. Our results suggest that the defective epidermal barriers of AD skin and the inflammation-induced altered barriers in healthy skin can make receptors accessible for HSV-1.

IMPORTANCE Herpes simplex virus 1 (HSV-1) can target skin to establish primary infection in the epithelium. While the human skin provides effective barriers against viral invasion under healthy conditions, a prominent example of successful invasion is the disseminated HSV-1 infection in the skin of atopic dermatitis (AD) patients. AD is characterized by impaired epidermal barrier functions, chronic inflammation, and dysbiosis of skin microbiota. We addressed the initial invasion process of HSV-1 in atopic dermatitis skin to understand whether the physical barrier functions are sufficiently disturbed to allow the virus to invade skin and reach its receptors on skin cells. Our results demonstrate that HSV-1 can indeed penetrate and initiate infection in atopic dermatitis skin. Since treatment of skin with IL-4 and IL-13 already resulted in successful invasion, we assume that inflammation-induced barrier defects play an important role for the facilitated access of HSV-1 to its target cells.

Post-Translational Modifications in Atopic Dermatitis: Current Research and Clinical Relevance

Atopic dermatitis (AD) is a chronic and relapsing cutaneous disorder characterized by compromised immune system, excessive inflammation, and skin barrier disruption. Post-translational modifications (PTMs) are covalent and enzymatic modifications of proteins after their translation, which have been reported to play roles in inflammatory and allergic diseases. However, less attention has been paid to the effect of PTMs on AD. This review summarized the knowledge of six major classes (including phosphorylation, acetylation, ubiquitination, SUMOylation, glycosylation, o-glycosylation, and glycation) of PTMs in AD pathogenesis and discussed the opportunities for disease management.

An Atopic Dermatitis-Like Mouse Model by Alternate Epicutaneous Application of Dinitrofluorobenzene and an Extract of Dermatophagoides Farinae

Several studies have tried to establish mice models of atopic dermatitis (AD) through the allergen of Dermatophagoides farinae (Df). However, there are no typical skin lesions after epicutaneous application of an extract of Df (DfE) on BALB/c mice. Dinitrofluorobenzene (DNFB) is a common hapten that brings about contact dermatitis. Skin dysfunction induced by DNFB may be a way to enhance the effects of DfE on mice skin. Thus, we hypothesized that alternate epicutaneous application of DNFB and DfE could induce AD-like skin lesions on BALB/c mice. To test this hypothesis, we alternately applied the DNFB and DfE to the back skin of BALB/c mice for 8 weeks. Changes in mice skin lesions and the frequency of scratching behavior were recorded. The variation of Th1-related cytokines (interferon-γ [IFN-γ] and interleukin two [IL-2]) and Th2-related cytokines (IL-4 and IL-13) was detected in serum and lesional skin. Eventually, the BALB/c mice developed severe erythema, erosion, scarring, and excoriation on the entire back, showing a high frequency of scratching behavior. In addition, Th2 cells' dominant cytokines appeared in both serum and lesional skin. Those results indicate that alternating epicutaneous exposure to DNFB and DfE can produce AD-like models with typical clinical features and Th2-type immune responses in BALB/c mice. This model could be valuable for studying the pathogenesis of AD and developing novel therapeutic agents for it.

Moderate to severe atopic dermatitis in adolescents treated with dupilumab: a multicenter Italian real-world experience

Background

Moderate‐to‐severe atopic dermatitis (AD) in the adolescence is a high burden disease, and its treatment can be very challenging due to paucity of approved systemic drugs for this age and their side‐effects. Dupilumab was recently approved for treatment of adolescent AD.

Objectives

A multicentre, prospective, real‐world study on the effectiveness and safety of dupilumab in adolescents (aged from ≥12 to <18 years) with moderate‐to‐severe AD was conducted. The main AD clinical phenotypes were also examined.

Methods

Data of adolescents with moderate‐to‐severe AD treated with dupilumab at label dosage for 16 weeks were collected. Treatment outcome was assessed by EASI, NRS itch, NRS sleep loss and CDLQI scores at baseline and after 16 weeks of treatment. The clinical scores were also evaluated according to clinical phenotypes.

Results

One hundred and thirty‐nine adolescents were enrolled in the study. Flexural eczema and head and neck eczema were the most frequent clinical phenotypes, followed by hand eczema and portrait‐like dermatitis. Coexistence of more than 1 phenotype was documented in 126/139 (88.5%) adolescents. Three patients (2.1%) contracted asymptomatic SARS‐CoV‐2 infection and 1 of the discontinued dupilumab treatment before the target treatment period. A significant improvement in EASI, NRS itch, NRS sleep loss and CDLQI was observed after 16 weeks of treatment with dupilumab. This outcome was better than that observed in clinical trials. Dupilumab resulted effective in all AD phenotypes, especially in diffuse eczema. Twenty‐eight (20.1%) patients reported adverse events, conjunctivitis and flushing being the most frequent. None of patients discontinued dupilumab due to adverse event.

Conclusions

Dupilumab in adolescent AD showed excellent effectiveness at week 16 with consistent improvement of all clinical scores. Moreover, dupilumab showed a good safety profile also in this COVID‐19 pandemic era.

Role of Aryl Hydrocarbon Receptor Activation in Inflammatory Chronic Skin Diseases

Aryl Hydrocarbon Receptor (AhR) is an evolutionary transcription factor which acts as a crucial sensor of different exogenous and endogenous molecules Recent data indicate that AhR is implicated in several physiological processes such as cell physiology, host defense, proliferation and differentiation of immune cells, and detoxification. Moreover, AhR involvement has been reported in the development and maintenance of several pathological conditions. In recent years, an increasing number of studies have accumulated highlighting the regulatory role of AhR in the physiology of the skin. However, there is evidence of both beneficial and harmful effects of AHR signaling. At present, most of the evidence concerns inflammatory skin diseases, in particular atopic dermatitis, psoriasis, acne, and hidradenitis suppurativa. This review exam-ines the role of AhR in skin homeostasis and the therapeutic implication of its pharmacological modulation in these cutaneous inflammatory diseases.

Five Functional Aspects of the Epidermal Barrier

The epidermis is a living, multilayered barrier with five functional levels, including a physical, a chemical, a microbial, a neuronal, and an immune level. Altogether, this complex organ contributes to protect the host from external aggression and to preserve its integrity. In this review, we focused on the different functional aspects.

The Keratinocyte as a Crucial Cell in the Predisposition, Onset, Progression, Therapy and Study of the Atopic Dermatitis

The keratinocyte (KC) is the main functional and structural component of the epidermis, the most external layer of the skin that is highly specialized in defense against external agents, prevention of leakage of body fluids and retention of internal water within the cells. Altered epidermal barrier and aberrant KC differentiation are involved in the pathophysiology of several skin diseases, such as atopic dermatitis (AD). AD is a chronic inflammatory disease characterized by cutaneous and systemic immune dysregulation and skin microbiota dysbiosis. Nevertheless, the pathological mechanisms of this complex disease remain largely unknown. In this review, we summarize current knowledge about the participation of the KC in different aspects of the AD. We provide an overview of the genetic predisposing and environmental factors, inflammatory molecules and signaling pathways of the KC that participate in the physiopathology of the AD. We also analyze the link among the KC, the microbiota and the inflammatory response underlying acute and chronic skin AD lesions.

Alarmins/stressorins and immune dysregulation in intractable skin disorders

Unlike other barrier epithelia of internal organs, the stratified squamous epithelium of the skin is always exposed to the external environment. However, the robust barrier structure and function of the skin are highly resistant against external insults so as to not easily allow foreign invasions. Upon sensing danger signals, the innate immunity system is promptly activated. This process is mediated by alarmins, which are released passively from damaged cells. Nuclear alarmins or stressorins are actively released from intact cells in response to various cellular stresses. Alarmins/stressorins are deeply involved in the disease processes of chronic skin disorders of an unknown cause, such as rosacea, psoriasis, and atopic dermatitis. Furthermore, alarmins/stressorins are also induced in the congenital skin disorders of ichthyosis and keratoderma due to defective keratinization. Studies on alarmin activation and its downstream pathways may help develop novel therapeutic agents for intractable skin disorders.

Comparison of Gut Microbiota Between Infants with Atopic Dermatitis and Healthy Controls in Guangzhou, China

Purpose

Evidence on the role of the gut microbiota in atopic dermatitis is inconsistent as human intestinal microbiota is influenced by geography. This cross-sectional study therefore aimed to compare differences in the gut microbiota of infants with atopic dermatitis and healthy infants in Guangzhou, China, by analyzing their stool.

Patients and Methods

The composition of the intestinal microbiota was analyzed from the stool samples of 20 infants with atopic dermatitis (AD group) and 25 healthy infants (non-AD group) (1-6 months old), using full-length 16S rRNA gene sequencing. The Wilcoxon test was used to analyze the relative abundance of bacteria by phylum, family, genus, and species between groups; microbial community richness and diversity were compared between the two groups.

Results

There were no significant differences in the microbial community richness and diversity between the two groups. At the phylum level, 11 bacterial phyla were found; most sequences belonged to one of the three dominant bacterial phyla - Firmicutes, Proteobacteria, and Bacteroidetes. The top 10 microbes at the phylum, family, and genus levels showed no significant changes in their composition within the gut microbiota between the AD and non-AD groups. A decrease in the ratio of the Streptococcus genus was found in atopic dermatitis group when compared with healthy controls (p=0.048).

Conclusion

A decrease in the abundance of Streptococcus was found in children with AD. The role of Streptococcus in the development of AD needs to be confirmed in a large cohort study.

Sequestosome 1/p62 enhances chronic skin inflammation

BACKGROUND

The molecular control of inflammation and epidermal thickening in skin lesions of patients with atopic dermatitis (AD) is not known. Sequestosome 1/p62 is a multifunctional adapter protein implicated in the control of key regulators of cellular homeostasis, such as proinflammatory and mechanistic target of rapamycin signaling.

OBJECTIVE

We sought to determine whether p62 plays a role in the cutaneous and systemic manifestations of an AD-like mouse model.

METHODS

AD-like skin lesions were induced by deletion of JunB/AP-1, specifically in epidermal keratinocytes (JunB^Δep). The contribution of p62 to pathological changes was determined by inactivation of p62 in JunB^Δepp62^-/- double knockout mice.

RESULTS

Expression of p62 was elevated in skin lesions of JunB^Δep mice, resembling upregulation of p62 in AD and psoriasis. When p62 was inactivated, JunB^Δep-associated defects in the differentiation of keratinocytes, epidermal thickening, skin infiltration by mast cells and neutrophils, and the development of macroscopic skin lesions were significantly reduced. p62 inactivation had little effect on circulating cytokines, but decreased serum IgE. Signaling through mechanistic target of rapamycin and natural factor kappa B was increased in JunB^Δep but not in JunB^Δepp62^-/- double knockout skin, indicating an important role of p62 in enhancing these signaling pathways in the skin during AD-like inflammation.

CONCLUSIONS

Our results provide the first in vivo evidence for a proinflammatory role of p62 in skin and suggest that p62-dependent signaling pathways may be promising therapeutic targets to ameliorate the skin manifestations of AD and possibly psoriasis.

Murine Models for Staphylococcal Infection

Staphylococcus aureus is a Gram-positive bacterium that colonizes almost every organ in humans and mice and is a leading cause of diseases worldwide. S. aureus infections can be challenging to treat due to widespread antibiotic resistance and their ability to cause tissue damage. The primary modes of transmission of S. aureus are via direct contact with a colonized or infected individual or invasive spread from a colonization niche in the same individual. S. aureus can cause a myriad of diseases, including skin and soft tissue infections (SSTIs), osteomyelitis, pneumonia, endocarditis, and sepsis. S. aureus infection is characterized by the formation of purulent lesions known as abscesses, which are rich in live and dead neutrophils, macrophages, and surrounded by a capsule containing fibrin and collagen. Different strains of S. aureus produce varying amounts of toxins that evade and/or elicit immune responses. Therefore, animal models of S. aureus infection provide a unique opportunity to understand the dynamics of organ-specific immune responses and modifications in the pathogen that could favor the establishment of the pathogen. With advances in in vivo imaging of fluorescent transgenic mice, combined with fluorescent/bioluminescent bacteria, we can use mouse models to better understand the immune response to these types of infections. By understanding the host and bacterial dynamics within various organ systems, we can develop therapeutics to eliminate these pathogens. This module describes in vivo mouse models of both local and systemic S. aureus infection. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Murine model of Staphylococcus aureus subcutaneous infection Alternate Protocol: Murine tape stripping skin infection model Basic Protocol 2: Sample collection to determine skin structure, production of inflammatory mediators, and bacterial load Basic Protocol 3: Murine model of post-traumatic Staphylococcus aureus osteomyelitis Basic Protocol 4: Intravenous infection of the retro-orbital sinus Support Protocol: Preparation of the bacterial inoculum.

Atopic Dermatitis as a Multifactorial Skin Disorder. Can the Analysis of Pathophysiological Targets Represent the Winning Therapeutic Strategy?

Atopic dermatitis (AD) is a pathological skin condition with complex aetiological mechanisms that are difficult to fully understand. Scientific evidence suggests that of all the causes, the impairment of the skin barrier and cutaneous dysbiosis together with immunological dysfunction can be considered as the two main factors involved in this pathological skin condition. The loss of the skin barrier function is often linked to dysbiosis and immunological dysfunction, with an imbalance in the ratio between the pathogen Staphylococcus aureus and/or other microorganisms residing in the skin. The bibliographic research was conducted on PubMed, using the following keywords: 'atopic dermatitis', 'bacterial therapy', 'drug delivery system' and 'alternative therapy'. The main studies concerning microbial therapy, such as the use of bacteria and/or part thereof with microbiota transplantation, and drug delivery systems to recover skin barrier function have been summarized. The studies examined show great potential in the development of effective therapeutic strategies for AD and AD-like symptoms. Despite this promise, however, future investigative efforts should focus both on the replication of some of these studies on a larger scale, with clinical and demographic characteristics that reflect the general AD population, and on the process of standardisation, in order to produce reliable data.