Early-onset pediatric atopic dermatitis is T H 2 but also T H 17 polarized in skin

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.

Atopic dermatitis and IgE-mediated food allergy: Common biologic targets for therapy and prevention

OBJECTIVE

To highlight common mechanistic targets for the treatment of atopic dermatitis (AD) and IgE-mediated food allergy (IgE-FA) with potential to be effective for both diseases and prevent atopic progression.

DATA SOURCES

Data sources were PubMed searches or National Clinical Trials (NCT)-registered clinical trials related to AD, IgE-FA, and other atopic conditions, especially focused on the pediatric population.

STUDY SELECTIONS

Human seminal studies and/or articles published in the past decade were emphasized with reference to preclinical models when relevant. NCT-registered clinical trials were filtered by inclusion of pediatric subjects younger than 18 years with special focus on children younger than 12 years as a critical period when AD and IgE-FA diseases may often be concurrent.

RESULTS

AD and IgE-FA share several pathophysiologic features, including epithelial barrier dysfunction, innate and adaptive immune abnormalities, and microbial dysbiosis, which may be critical for the clinical progression between these diseases. Revolutionary advances in targeted biologic therapies have shown the benefit of inhibiting type 2 immune responses, using dupilumab (anti-interleukin-4Rα) or omalizumab (anti-IgE), to potentially reduce symptom burden for both diseases in pediatric populations. Although the potential for biologics to promote disease remission (AD) or sustained unresponsiveness (IgE-FA) remains unclear, the refinement of biomarkers to predict infants at risk for atopic disorders provides promise for prevention through timely intervention.

CONCLUSION

AD and IgE-FA exhibit common features that may be leveraged to develop biologic therapeutic strategies to treat both conditions and even prevent atopic progression. Future studies should be designed with consistent age stratification in the pediatric population and standardized regimens of adjuvant oral immunotherapy or dose escalation (IgE-FA) to improve cross-study interpretation.

RNA-sequencing of paired tape-strips and skin biopsies in atopic dermatitis reveals key differences

BACKGROUND

Skin tape-strips and biopsies are widely used methods for investigating the skin in atopic dermatitis (AD). Biopsies are more commonly used but can cause scarring and pain, whereas tape-strips are noninvasive but sample less tissue. The study evaluated the performance of skin tape-strips and biopsies for studying AD.

METHODS

Whole-transcriptome RNA-sequencing was performed on paired tape-strips and biopsies collected from lesional and non-lesional skin from AD patients (n = 7) and non-AD controls (n = 5). RNA yield, mapping efficiency, and differentially expressed genes (DEGs) for the two methods (tape-strip/biopsy) and presence of AD (AD/non-AD) were compared.

RESULTS

Tape-strips demonstrated a lower RNA yield (22 vs. 4596 ng) and mapping efficiency to known genes (28% vs. 93%) than biopsies. Gene-expression profiles of paired tape-strips and biopsies demonstrated a medium correlation (R2 = 0.431). Tape-strips and biopsies demonstrated systematic differences in measured expression levels of 6483 genes across both AD and non-AD samples. Tape-strips preferentially detected many itch (CCL3/CCL4/OSM) and immune-response (CXCL8/IL4/IL5/IL22) genes as well as markers of epidermal dendritic cells (CD1a/CD207), while certain cytokines (IL18/IL37), skin-barrier genes (KRT2/FLG2), and dermal fibroblasts markers (COL1A/COL3A) were preferentially detected by biopsies. Tape-strips identified more DEGs between AD and non-AD (3157 DEGs) then biopsies (44 DEGs). Tape-strips also detected higher levels of bacterial mRNA than biopsies.

CONCLUSIONS

This study concludes that tape-strips and biopsies each demonstrate respective advantages for measuring gene-expression changes in AD. Thus, the specific skin layers and genes of interest should be considered before selecting either method.

Atopic dermatitis phenotype affects expression of atopic diseases despite similar mononuclear cell cytokine response

BACKGROUND

The atopic march refers to the coexpression and progression of atopic diseases in childhood, often beginning with atopic dermatitis (AD), although children may not progress through each atopic disease.

OBJECTIVE

We hypothesized that future atopic disease expression is modified by AD phenotype and that these differences result from underlying dysregulation of cytokine signaling.

METHODS

Children (n = 285) were enrolled into the Childhood Origins of Asthma (COAST) birth cohort and followed prospectively. Rates of AD, food allergy, allergic rhinitis, and asthma were assessed longitudinally from birth to 18 years of age. Associations between AD phenotype and food allergy, allergic rhinitis, asthma, allergic sensitization, exhaled nitric oxide, and lung function were determined. Peripheral blood mononuclear cell responses (IL-5, IL-10, IL-13, IFN-γ) to dust mite, phytohemagglutinin, Staphylococcus aureus Cowan I, and tetanus toxoid were compared among AD phenotypes.

RESULTS

AD at year 1 was associated with an increased risk of food allergy (P = .004). Both persistent and late-onset AD were associated with an increased risk of asthma (P < .001), rhinitis (P < .001), elevated total IgE (P < .001), percentage of aeroallergens with detectable IgE (P < .001), and elevated exhaled nitric oxide (P = .002). Longitudinal analyses did not reveal consistent differences in peripheral blood mononuclear cell responses among dermatitis phenotypes.

CONCLUSION

AD phenotype is associated with differential expression of other atopic diseases. Our findings suggest that peripheral blood cytokine dysregulation is not a mechanism underlying this process, and immune dysregulation may be mediated at mucosal surfaces or in secondary lymphoid organs.

Monoclonal antibodies for moderate-to-severe atopic dermatitis: a look at phase III and beyond

INTRODUCTION

The understanding of atopic dermatitis (AD) pathogenesis has rapidly expanded in recent years, catalyzing the development of new targeted monoclonal antibody treatments for AD.

AREAS COVERED

This review aims to summarize the latest clinical and molecular data about monoclonal antibodies that are in later stages of development for AD, either in Phase 3 trials or in the pharmacopoeia for up to 5 years, highlighting the biologic underpinning of each drug's mechanism of action and the potential modulation of the AD immune profile.

EXPERT OPINION

The therapeutic pipeline of AD treatments is speedily progressing, introducing the potential for a personalized medical approach in the near future. Understanding how targeting pathogenic players in AD modifies disease progression and symptomatology is key in improving therapeutic choices for patients and identifying ideal patient candidates.

Effects and mechanisms of polycyclic aromatic hydrocarbons in inflammatory skin diseases

Polycyclic aromatic hydrocarbons (PAHs) are hydrocarbons characterized by the presence of multiple benzene rings. They are ubiquitously found in the natural environment, especially in environmental pollutants, including atmospheric particulate matter, cigarette smoke, barbecue smoke, among others. PAHs can influence human health through several mechanisms, including the aryl hydrocarbon receptor (AhR) pathway, oxidative stress pathway, and epigenetic pathway. In recent years, the impact of PAHs on inflammatory skin diseases has garnered significant attention, yet many of their underlying mechanisms remain poorly understood. We conducted a comprehensive review of articles focusing on the link between PAHs and several inflammatory skin diseases, including psoriasis, atopic dermatitis, lupus erythematosus, and acne. This review summarizes the effects and mechanisms of PAHs in these diseases and discusses the prospects and potential therapeutic implications of PAHs for inflammatory skin diseases.

Bilateral Association Between Atopic Dermatitis® and Alopecia Areata: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis aimed to explore the association between atopic Dermatitis® (AD) and alopecia areata (AA). A comprehensive search was conducted in PubMed, Embase, Cochrane, and Web of Science from the inception of each database to November 10, 2022 for relevant studies. As there is a potential bilateral association between the 2 diseases, we assessed the prevalence/incidence of AA in patients with AD and the prevalence/incidence of AD in patients with AA. A total of 29 studies involving 11,233,448 participants were included in this analysis. AA was the exposure factor in 23 studies, AD in 7 studies, and both in 1 study. The meta-analysis revealed that the prevalence of AD was 11.2% (7.7%-15.1%) in patients with AA, and the prevalence of AA was 3.2% (95% confidence interval [CI]: 0.0%-11.5%) in patients with AD. The incidence of AD in AA patients was found to vary with age (P = 0.07). Based on 7 studies, there was a significant association between AD and AA when AA was the exposure factor [odds ratio, OR, = 4.537 (95% CI: 2.409-8.544)]; based on 10 studies, there was also a significant association between AD and AA when AD was the exposure factor [OR = 2.643 (95% CI: 1.737-3.995)]. In conclusion, this meta-analysis demonstrated the 2-way association between AD and AA, providing a clinical reference for disease prevention and control.

Preclinical Atopic Dermatitis Skin in Infants: An Emerging Research Area

Whereas clinically apparent atopic dermatitis (AD) can be confirmed by validated diagnostic criteria, the preclinical phenotype of infants who eventually develop AD is less well-characterized. Analogous to unaffected or nonlesional skin in established AD, clinically normal-appearing skin in infants who will develop clinical AD has distinct changes. Prospective studies have revealed insights into this preclinical AD phenotype. In this study, we review the structural, immunologic, and microbiome nature of the preclinical AD phenotype. Determination of markers that predict the development of AD will facilitate targeting of interventions to prevent the development or reduce the severity of AD in infants.

Biomarkers for phenotype-endotype relationship in atopic dermatitis: a critical review

Atopic dermatitis (AD) is the most common form of chronic skin inflammation with diverse clinical variants. Historically, various AD phenotypes have been grouped together without considering their heterogeneity. This approach has resulted in a lack of phenotype- and endotype-adapted therapeutic strategies. Comprehensive insights into AD pathogenesis have enabled precise medicinal approach for AD. These efforts aimed to redefine the endophenotype of AD and develop various biomarkers for diverse purposes. Among these endeavours, efforts are underway to elucidate the mechanisms (and related biomarkers) that lead to the emergence and progression of atopic diseases originating from AD (e.g., atopic march). This review focuses on diverse AD phenotypes and calls for a definition of endophenotypes. While awaiting scientific validation, these biomarkers ensure predicting disease onset and trajectory and tailoring therapeutic strategies for the future.

Genetic and Immunological Pathogenesis of Atopic Dermatitis

Type 2 immune-mediated diseases give a clear answer to the issue of nature (genetics) versus nurture (environment). Both genetics and environment play vital complementary roles in the development of atopic dermatitis (AD). As a key component of the atopic march, AD demonstrates the interactive nature of genetic and environmental contributions to atopy. From sequence variants in the epithelial barrier gene encoding FLG to the hygiene hypothesis, AD combines a broad array of contributions into a single syndrome. This review will focus on the genetic contribution to AD and where genetics facilitates the elicitation or enhancement of AD pathogenesis.

Proteomic alterations in patients with atopic dermatitis

INTRODUCTION

Atopic Dermatitis (AD) is the most common inflammatory skin disease with a complex and multifactorial pathogenesis. The use of proteomics in understanding AD has yielded the discovery of novel biomarkers and may further expand therapeutic options.

AREAS COVERED

This review summarizes the most recent proteomic studies and the methodologies used in AD. It describes novel biomarkers that may monitor disease course and therapeutic response. The review also highlights skin and blood biomarkers characterizing different AD phenotypes and differentiates AD from other inflammatory skin disorders. A literature search was conducted by querying Scopus, Google Scholar, Pubmed/Medline, and Clinicaltrials.gov up to June 2023.

EXPERT OPINION

The integration of proteomics into research efforts in atopic dermatitis has broadened our understanding of the molecular profile of AD through the discovery of new biomarkers. In addition, proteomics may contribute to the development of targeted treatments ultimately improving personalized medicine. An increasing number of studies are utilizing proteomics to explore this heterogeneous disease.

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.

Differentiation of keratinocytes or exposure to type 2 cytokines diminishes S. aureus internalization

Staphylococcus aureus is a leading cause of skin and soft tissue infections. Colonization by this bacterium is increased in individuals with chronic cutaneous diseases such as atopic dermatitis, psoriasis, and bullous pemphigoid. The greater abundance of S. aureus on the skin of subjects with atopic dermatitis in particular has been linked to recurrent cutaneous infections. The primary cell type of the epidermal layer of the skin is the keratinocyte, and it is thought that S. aureus internalized in keratinocytes associates with an increased incidence of skin infections. This study addresses whether keratinocyte differentiation and/or inflammation, two important characteristics altered in cutaneous diseases, influence bacterial internalization. To do this, S. aureus internalization was measured in immortalized and primary keratinocytes that were differentiated using high Ca2+-containing media and/or exposed to cytokines characteristic of atopic dermatitis (IL-4 and IL-13) or psoriasis (IL-17A and IL-22) skin. Our results indicate that S. aureus internalization is uniquely decreased upon keratinocyte differentiation, since this was not observed with another skin-resident bacterium, S. epidermidis. Additionally, treatment with IL-4 + IL-13 diminished bacterial internalization. We interpret this decrease as a mechanism of keratinocyte-based bacterial killing since a similar number of bacterial genomes were detected in cytokine-treated cells, but less viable internalized S. aureus was recovered. Finally, of the receptors reported for S. aureus binding/internalizing into keratinocytes, expression of the α5 component of the α5β1 integrin was in greatest accordance with the number of internalized bacteria in the context of keratinocyte differentiation.IMPORTANCEIndividuals with chronic cutaneous diseases demonstrate heightened susceptibility for severe and recurrent infections from Staphylococcus aureus. What drives this altered susceptibility remains poorly understood. Previous publications have detected S. aureus as deep as the dermal layer of skin in subjects with atopic dermatitis, suggesting that the cutaneous environment of this disease enables deeper bacterial infiltration than occurs in healthy individuals. This observation indicates that S. aureus has greater opportunity to interact with multiple skin cell types in individuals with chronic inflammatory skin diseases. Identifying the characteristics of the skin that influence bacterial internalization, a common method to establish reservoirs and evade the immune response, is critical for our understanding of S. aureus pathogenesis. The significance of this research is the novel identification of epidermal characteristics that influence S. aureus internalization. With this knowledge, methods can be developed to identify patient populations at greater risk for cutaneous infections.

Circadian Rhythms in Skin Barrier Function in Atopic Dermatitis: A Pilot Study

Atopic dermatitis (AD) is symptomatically worse in the evening, but the mechanism driving nocturnal eczema remains elusive. Our objective was to determine the circadian rhythm of skin barrier function measured by transepidermal water loss (TEWL) in AD patients and explore the molecular underpinnings. A pilot study was performed on a diverse group of AD (n = 4) and control (n = 2) young patients. We used an inpatient tightly controlled, modified, constant routine protocol. TEWL was measured at least every 90 min in the antecubital fossa (lesional) and forearm, while whole blood samples were collected every 4 h. Results show a significant difference in the antecubital fossa TEWL in the AD group versus controls. TEWL in control skin decreases starting a few hours prior to bedtime, both in the antecubital fossa and in the forearm, while in the AD forearm skin, pre-bedtime TEWL increases. We identified 1576 differentially expressed genes using a time-dependent model. The top 20 upregulated gene ontology pathways included neuronal pathways, while the downregulated functional terms included innate immune signaling and viral response. Similar pathways positively correlated with forearm TEWL in controls and inversely with the AD group. Upregulation in sensory perception pathways correlated with increases in lesional (antecubital fossa) TEWL in the evening. Results show skin barrier function worsens in the evening in the AD group, at a time when barrier is normally rejuvenating in healthy skin. This timing and the detection of transcriptomic signatures of sensory perception and diminished viral response might correspond to the nocturnal itch. Larger studies are needed to evaluate these associations in the skin.

Interplay of cytokines in the pathophysiology of atopic dermatitis: insights from Murin models and human

The pathogenesis of atopic dermatitis (AD) is understood to be crucially influenced by three main factors: dysregulation of the immune response, barrier dysfunction, and pruritus. In the lesional skin of AD, various innate immune cells, including Th2 cells, type 2 innate lymphoid cells (ILC2s), and basophils, produce Th2 cytokines [interleukin (IL)-4, IL-5, IL-13, IL-31]. Alarmins such as TSLP, IL-25, and IL-33 are also produced by epidermal keratinocytes, amplifying type 2 inflammation. In the chronic phase, not only Th2 cells but also Th22 and Th17 cells increase in number, leading to suppression of filaggrin expression by IL-4, IL-13, and IL-22, which further deteriorates the epidermal barrier function. Dupilumab, which targets IL-4 and IL-13, has shown efficacy in treating moderate to severe AD. Nemolizumab, targeting IL-31RA, effectively reduces pruritus in AD patients. In addition, clinical trials with fezakinumab, targeting IL-22, have demonstrated promising results, particularly in severe AD cases. Conversely, in murine models of AD, several cytokines, initially regarded as promising therapeutic targets, have not demonstrated sufficient efficacy in clinical trials. IL-33 has been identified as a potent activator of immune cells, exacerbating AD in murine models and correlating with disease severity in human patients. However, treatments targeting IL-33 have not shown sufficient efficacy in clinical trials. Similarly, thymic stromal lymphopoietin (TSLP), integral to type 2 immune responses, induces dermatitis in animal models and is elevated in human AD, yet clinical treatments like tezepelumab exhibit limited efficacy. Therapies targeting IL-1α, IL-5, and IL-17 also failed to achieve sufficient efficacy in clinical trials. It has become clear that for treating AD, IL-4, IL-13, and IL-31 are relevant therapeutic targets during the acute phase, while IL-22 emerges as a target in more severe cases. This delineation underscores the necessity of considering distinct pathophysiological aspects and therapeutic targets in AD between mouse models and humans. Consequently, this review delineates the distinct roles of cytokines in the pathogenesis of AD, juxtaposing their significance in human AD from clinical trials against insights gleaned from AD mouse models. This approach will improve our understanding of interspecies variation and facilitate a deeper insight into the pathogenesis of AD in humans.

N-benzyl-N-methyldecan-1-amine, derived from garlic, and its derivative alleviate 2,4-dinitrochlorobenzene-induced atopic dermatitis-like skin lesions in mice

Given the intricate etiology and pathogenesis of atopic dermatitis (AD), the complete cure of AD remains challenging. This study aimed to investigate if topically applying N-benzyl-N-methyldecan-1-amine (BMDA), derived from garlic, and its derivative [decyl-(4-methoxy-benzyl)-methyl-1-amine] (DMMA) could effectively alleviate AD-like skin lesions in 2,4-dinitrochlorobenzene (DNCB)-treated mice. Administering these compounds to the irritated skin of DNCB-treated mice significantly reduced swelling, rash, and excoriation severity, alongside a corresponding decrease in inflamed epidermis and dermis. Moreover, they inhibited spleen and lymph node enlargement and showed fewer infiltrated mast cells in the epidermis and dermis through toluidine-blue staining. Additionally, they led to a lower IgE titer in mouse sera as determined by ELISA, compared to vehicle treatment. Analyzing skin tissue from the mice revealed decreased transcript levels of inflammatory cytokines (TNF-α, IL-1β, and IL-6), IL-4, iNOS, and COX-2, compared to control mice. Simultaneously, the compounds impeded the activation of inflammation-related signaling molecules such as JNK, p38 MAPK, and NF-κB in the mouse skin. In summary, these findings suggest that BMDA and DMMA hold the potential to be developed as a novel treatment for healing inflammatory AD.

Psoriasis dermatitis, a common phenotype of early forms of both psoriasis and atopic dermatitis in children: A prospective multicenter study

BACKGROUND

Psoriasis (Ps) and atopic dermatitis (AD) are chronic systemic immune-mediated diseases that can coexist in an overlapping condition called psoriasis dermatitis (PD). PD patients have intermediate lesions with characteristics of both Ps and AD. PD is very rare in adults but much more frequent in children. Little is known, however, about the course of PD in the pediatric population. The aim of this study was to evaluate the percentage of PD cases in children that evolved to a definite form of Ps or AD and to identify any clinical or epidemiological variables that could predict the course of the disease.

METHODS

We performed a prospective multicenter cohort study of children diagnosed with PD between January 2018 and December 2020. We collected participants' clinical and epidemiological characteristics, and pediatric dermatologists determined the percentage of participants who developed Ps or AD.

RESULTS

The study included 24 children with PD, with a median age of 7.0 years. After a median follow-up period of 31 months, 83.3% of cases had evolved to a definite form of Ps or AD (44.4% to Ps and 38.9% to AD). Younger age and family history of Ps were associated with progression to AD. Participants who progressed to AD or Ps had a longer follow-up than those with an unchanged PD diagnosis.

CONCLUSIONS

Given sufficient time, a large percentage of PD cases in children will evolve into Ps or AD. Long-term clinical follow-up is necessary for a correct diagnosis.

Sclerotic-Type Cutaneous Chronic Graft-Versus-Host Disease Exhibits Activation of T Helper 1 and OX40 Cytokines

Sclerotic-type cutaneous chronic graft-versus-host disease is a severe complication of allogeneic hematopoietic stem cell transplantation, with profound morbidity. A dearth of effective, targeted treatment options necessitates further investigation into the molecular mechanisms underlying this T-cell-mediated disease. In this study, we compared the transcriptome in skin biopsies from pediatric and young adult (aged <25 years) patients with sclerotic-type cutaneous chronic graft-versus-host disease (n = 7) with that in demographically matched healthy controls (n = 8) and patients with atopic dermatitis (n = 10) using RNA sequencing with RT-PCR and immunohistochemistry validation. Differential expression was defined as fold change > 1.5 and false discovery rate < 0.05. Sclerotic-type cutaneous chronic graft-versus-host disease exhibited strong and significant T helper (Th)1 skewing through key related cytokines and chemokines (CXCL9/10/11, IFNG/IFN-γ, STAT1/signal transducer and activator of transcription 1). Several markers related to the TSLP-OX40 axis were significantly upregulated relative to those in both controls and lesional atopic dermatitis, including TNFSF4/OX40L, TSLP, and IL33, as well as fibroinflammatory signatures characterized in a prior study in systemic sclerosis. Gene set variation analysis reflected marker-level findings, showing the greatest enrichment of the Th1 and fibroinflammatory pathways, with no global activation identified in Th2 or Th17/Th22. Cell-type deconvolution revealed a significant representation of macrophages and vascular endothelial cells. Sclerotic-type cutaneous chronic graft-versus-host disease in young patients may therefore be characterized by strong Th1-related upregulation with a unique TSLP-OX40 signature, suggesting new therapeutic avenues for this devastating disease.

Identification of the major immune differences in severe asthmatic children according to their atopic dermatitis status

Severe asthma (SA) affects 2% to 5% of asthmatic children. Atopic dermatitis can affect up to 34% of children with SA (cwSA). Atopic dermatitis and asthma share common genetic and immunological features. However, not all children with SA suffer from AD, and it remains unclear whether the overall immune profiles of these children are similar. In this study, seventeen cwSA (9.8 [7.1-13.2] years; seven with and ten without AD) were enrolled. Bronchoalveolar lavage (BAL) and blood samples were collected from these patients. Seventy-three cytokines/chemokines and distinct immune T cell populations were evaluated in blood and BAL. We found that BAL and blood immune profiles of cwSA with and without AD were globally similar. However, specific differences were observed, namely lower frequency of Tc2, Th17 and IL-17-producing mucosal associated invariant T (MAIT-17) cells and higher CD8/CD4 ratio and IL-22 concentrations in BAL and of CCL19 concentrations in plasma from cwSA with AD. Further, in contrast with cwSA without AD, we found a positive correlation between a set of plasma cytokines and almost all cytokines in BAL in cwSA with AD. In conclusion, this study shows the major immune differences between cwSA with and without AD in BAL and blood suggesting that distinct endotypes may be implicated in the inflammatory responses observed in these pediatric patients.

Ethnic endotypes in paediatric atopic dermatitis depend on immunotype, lipid composition and microbiota of the skin

BACKGROUND

Atopic dermatitis (AD) endotypes differ with ethnicity. We examined the skin microbiota, cytokine and lipid profiles in Greenlandic Inuit and Danish children with AD.

METHODS

Twenty-five Inuit children with AD and 25 Inuit control children were clinically examined and compared to previously collected data from 25 Danish children with AD. Skin tape strips and skin swabs were collected from lesional and non-lesional skin. Levels of cutaneous immune biomarkers, free sphingoid bases and their (glycosyl)ceramides were analysed. Skin swabs were analysed with 16S rRNA and tuf gene for characterization of bacterial species communities.

RESULTS

Bacterial β-diversity was significantly different between Inuit and Danish AD skin, in both lesional (p < 0.001) and non-lesional (p < 0.001) AD skin, and there was a higher relative abundance of Staphylococcus aureus in Danish compared to Inuit lesional (53% vs. 8%, p < 0.01) and non-lesional skin (55% vs. 5%, p < 0.001). Danish AD children had a higher α-diversity than Inuit children in non-lesional (p < 0.05) but not in lesional skin. Significantly higher levels of type 2 immunity cytokine interleukin (IL)-4 (p < 0.05) and IL-5 (p < 0.01) were identified in Inuit compared to Danish AD children. In contrast, IL-33 (p < 0.01) was higher in Danish lesional and non-lesional AD skin. Higher levels of long-chain glucosylceramide (GlcCER)[S](d26:1) were found in lesional (p < 0.001) and non-lesional (p < 0.001) Inuit skin compared with Danish AD skin. NMF levels were similar in Inuit and Danish AD skin.

CONCLUSION

Skin microbiota, cytokine and lipid composition differed significantly between Inuit and Danish children with AD and showed a stronger type 2 immune signature in Inuit children.

Phase 2b randomized trial of OX40 inhibitor telazorlimab for moderate-to-severe atopic dermatitis

Background

Telazorlimab is a humanized anti-OX40 monoclonal antibody being studied for treatment of T-cell-mediated diseases.

Objective

This randomized, placebo-controlled, phase 2b dose-range finding study investigated efficacy, safety, pharmacokinetics, and immunogenicity of telazorlimab in subjects with atopic dermatitis.

Methods

In this 2-part study (NCT03568162), adults (≥18 years) with moderate-to-severe disease were randomized to various regimens of subcutaneous telazorlimab or placebo for 16 weeks' blinded treatment, followed by 38 weeks' open-label treatment and 12 weeks' drug-free follow-up. Telazorlimab treatment groups (following a loading dose) in part 1 were 300 mg every 2 weeks; 300 mg every 4 weeks; or 75 mg every 4 weeks. Part 2 evaluated telazorlimab 600 mg every 2 weeks. The primary end point was percentage change from baseline in Eczema Area and Severity Index (EASI) at week 16. Safety assessments included incidence of treatment-emergent adverse events.

Results

The study randomized 313 subjects in part 1 and 149 in part 2. At 16 weeks, the least squares mean percentage change from baseline in EASI was significantly greater in subjects receiving telazorlimab 300 mg every 2 weeks (part 1) and 600 mg every 2 weeks (part 2) versus placebo (-54.4% vs -34.2% for part 1 and -59.0% vs -41.8% for part 2, P = .008 for both). Telazorlimab was well tolerated, with similar distribution of adverse events between telazorlimab- and placebo-treated subjects in both part 1 and part 2.

Conclusion

Telazorlimab, administered subcutaneously at 300 mg every 2 weeks or 600 mg every 2 weeks following a loading dose, was well tolerated and induced significant and progressive clinical improvement in adults with moderate-to-severe atopic dermatitis.

Diversity of atopic dermatitis and selection of immune targets

Atopic dermatitis (AD) is a heterogeneous immune-mediated skin disorder affecting people of all ages and ethnicities. Despite the development of targeted therapeutics such as biologics and Janus kinase inhibitors, attaining complete clinical efficacy remains difficult. This therapeutic challenge may be attributed to the complex pathogenesis of AD. Although the TH2 axis has been extensively studied, recent advancements have started to reveal the involvement of additional immune pathways including TH1, TH17, and TH22. Understanding the interplay of these immune axes may contribute to a more personalized therapeutic approach based on patients' molecular profile, with the prospect of improving clinical outcome. This review will discuss studies exploring the molecular profile of AD in both skin and blood across age, ethnicity/race, disease chronicity, IgE levels, filaggrin mutation status, and AD association with other atopic conditions. Moreover, it will explore the potential of personalized treatment strategies based on a patient's distinct immune signature.

Emerging Role of the IL-36/IL-36R Axis in Multiple Inflammatory Skin Diseases

IL-36 is a most recent member of the IL-1 cytokine family, primarily expressed at barrier sites of the body such as the skin, lungs, and intestine. It plays a vital role in inflammation and is implicated in the development of various cutaneous; intestinal; and pulmonary disorders, including psoriasis, inflammatory bowel disease, and chronic obstructive pulmonary disease. IL-36 comprises 4 isoforms: the proinflammatory IL-36α, IL-36β, and IL-36γ and the anti-inflammatory IL-36R antagonist. An imbalance between proinflammatory and anti-inflammatory IL-36 isoforms can contribute to the inflammatory fate of cells and tissues. IL-36 cytokines signal through an IL-36R heterodimer mediating their function through canonical signaling cacade, including the NF-B pathway. Prominent for its role in psoriasis, IL-36 has recently been associated with disease mechanisms in atopic dermatitis, hidradenitis suppurativa, neutrophilic dermatoses, autoimmune blistering disease, and Netherton syndrome. The major cutaneous source of IL-36 cytokines is keratinocytes, pointing to its role in the communication between the epidermis, innate (neutrophils, dendritic cells) immune system, and adaptive (T helper [Th]1 cells, Th17) immune system. Thus, cutaneous IL-36 signaling is crucial for the immunopathological outcome of various skin diseases. Consequently, the IL-36/IL-36R axis has recently been recognized as a promising drug target for the treatment of inflammatory disorders beyond psoriasis. This review summarizes the current update on IL-36 cytokines in inflammatory skin diseases.

Atopic dermatitis-associated genetic variants regulate LOC100294145 expression implicating interleukin-27 production and type 1 interferon signaling

Background

Atopic dermatitis (AD) is a complex inflammatory disease with a strong genetic component. A singular approach of genome wide association studies (GWAS) can identify AD-associated genetic variants, but is unable to explain their functional relevance in AD. This study aims to characterize AD-associated genetic variants and elucidate the mechanisms leading to AD through a multi-omics approach.

Methods

GWAS identified an association between genetic variants at 6p21.32 locus and AD. Genotypes of 6p21.32 locus variants were evaluated against LOC100294145 expression in peripheral blood mononuclear cells (PBMCs). Their influence on LOC100294145 promoter activity was measured in vitro via a dual-luciferase assay. The function of LOC100294145 was then elucidated through a combination of co-expression analyses and gene enrichment with g:Profiler. Mendelian randomization was further used to assess the causal regulatory effect of LOC100294145 on its co-expressed genes.

Results

Minor alleles of rs116160149 and rs115388857 at 6p21.32 locus were associated with increased AD risk (p = 2.175 × 10-8, OR = 1.552; p = 2.805 × 10-9, OR = 1.55) and higher LOC100294145 expression in PBMCs (adjusted p = 0.182; 8.267 × 10-12). LOC100294145 expression was also found to be increased in those with AD (adjusted p = 3.653 × 10-2). The genotype effect of 6p21.32 locus on LOC100294145 promoter activity was further validated in vitro. Co-expression analyses predicted LOC100294145 protein's involvement in interleukin-27 and type 1 interferon signaling, which was further substantiated through mendelian randomization.

Conclusion

Genetic variants at 6p21.32 locus increase AD susceptibility through raising LOC100294145 expression. A multi-omics approach enabled the deduction of its pathogenesis model comprising dysregulation of hub genes involved in type 1 interferon and interleukin 27 signaling.

Interferon-γ signaling in eosinophilic esophagitis has implications for epithelial barrier function and programmed cell death

Objective

Eosinophilic esophagitis (EoE) is a chronic esophageal inflammatory disorder characterized by eosinophil-rich mucosal inflammation and tissue remodeling. Transcriptional profiling of esophageal biopsies has previously revealed upregulation of type I and II interferon (IFN) response genes. We aim to unravel interactions between immune and epithelial cells and examine functional significance in esophageal epithelial cells.

Design

We investigated epithelial gene expression from EoE patients using single-cell RNA sequencing and a confirmatory bulk RNA-sequencing experiment of isolated epithelial cells. The functional impact of interferon signaling on epithelial cells was investigated using in vitro organoid models.

Results

We observe upregulation of interferon response signature genes (ISGs) in the esophageal epithelium during active EoE compared to other cell types, single-cell data, and pathway analyses, identified upregulation in ISGs in epithelial cells isolated from EoE patients. Using an esophageal organoid and air-liquid interface models, we demonstrate that IFN-γ stimulation triggered disruption of esophageal epithelial differentiation, barrier integrity, and induced apoptosis via caspase upregulation. We show that an increase in cleaved caspase-3 is seen in EoE tissue and identify interferon gamma (IFNG) expression predominantly in a cluster of majority-CD8+ T cells with high expression of CD69 and FOS.

Conclusion

These findings offer insight into the interplay between immune and epithelial cells in EoE. Our data illustrate the relevance of several IFN-γ-mediated mechanisms on epithelial function in the esophagus, which have the potential to impact epithelial function during inflammatory conditions.

Adipokines in atopic dermatitis: the link between obesity and atopic dermatitis

Atopic dermatitis (AD) is a chronic skin condition with intense pruritus, eczema, and dry skin. The recurrent intense pruritus and numerous complications in patients with AD can profoundly affect their quality of life. Obesity is one of its comorbidities that has been confirmed to be the hazard factor of AD and also worsen its severity. Nevertheless, the specific mechanisms that explain the connection between obesity and AD remain incompletely recognized. Recent studies have built hopes on various adipokines to explain this connection. Adipokines, which are disturbed by an obese state, may lead to immune system imbalances in people with AD and promote the development of the disease. This review focuses on the abnormal expression patterns of adipokines in patients with AD and their potential regulatory molecular mechanisms associated with AD. The connection between AD and obesity is elucidated through the involvement of adipokines. This conduces to the in-depth exploration of AD pathogenesis and provides a new perspective to develop therapeutic targets.

Atopic Dermatitis Severity and Risk for Psoriasis: A Nationwide Population-Based Study

INTRODUCTION

As research on the role of the Th17/IL-23 pathway gains importance, the relationship between atopic dermatitis (AD) and psoriasis is becoming elucidated.

OBJECTIVE

The objective of this study wasto evaluate whether AD and its severity affect the risk for psoriasis.

METHODS

This retrospective population-based study used the database from the 2009 National Health Insurance Services-Health Screening Cohort in Korea. A total of 3,957,922 adult subjects were included and observed until 2018. The primary outcome was newly diagnosed psoriasis.

RESULTS

After adjusting for possible confounding factors, the moderate-to-severe AD group had the highest hazard ratio (HR) for psoriasis (HR = 2.50; 95% confidence interval (CI), 2.40-2.61), followed by the mild AD group (HR = 2.31; 95% CI: 2.19-2.44) compared with the non-AD group during a median 8.11 ± 1.19 years of follow-up.

LIMITATIONS

It is difficult to define AD, which is not standardized, using a claims database and exclude patients who were misdiagnosed with AD.

CONCLUSION

Patients with severe AD showed an increased risk for psoriasis compared to controls, and the risk for psoriasis was increased according to AD severity. This suggests that psoriasis and AD could share inflammatory, immune, and genetic features.

Development of a clinical algorithm to predict phenotypic switches between atopic dermatitis and psoriasis (the "Flip-Flop" phenomenon)

BACKGROUND

Atopic dermatitis (AD) and psoriasis vulgaris (PV) are almost mutually exclusive diseases with different immune polarizations, mechanisms and therapeutic targets. Switches to the other disease ("Flip-Flop" [FF] phenomenon) can occur with or without systemic treatment and are often referred to as paradoxical reactions under biological therapy.

METHODS

The objective was to develop a diagnostic algorithm by combining clinical criteria of AD and PV to identify FF patients. The algorithm was prospectively validated in patients enrolled in the CK-CARE registry in Bonn, Germany. Afterward, algorithm refinements were implemented based on machine learning.

RESULTS

Three hundred adult Caucasian patients were included in the validation study (n = 238 with AD, n = 49 with PV, n = 13 with FF; mean age 41.2 years; n = 161 [53.7%] female). The total FF scores of the PV and AD groups differed significantly from the FF group in the validation data (p < .001). The predictive mean generalized Youden-Index of the initial model was 78.9% [95% confidence interval 72.0%-85.6%] and the accuracy was 89.7%. Disease group-specific sensitivity was 100% (FF), 95.0% (AD), and 61.2% (PV). The specificity was 89.2% (FF), 100% (AD), and 100% (PV), respectively.

CONCLUSION

The FF algorithm represents the first validated tool to identify FF patients.

Intrapatient comparison of atopic dermatitis skin transcriptome shows differences between tape-strips and biopsies

BACKGROUND

Our knowledge of etiopathogenesis of atopic dermatitis (AD) is largely derived from skin biopsies, which are associated with pain, scarring and infection. In contrast, tape-stripping is a minimally invasive, nonscarring technique to collect skin samples.

METHODS

To construct a global AD skin transcriptomic profile comparing tape-strips to whole-skin biopsies, we performed RNA-seq on tape-strips and biopsies taken from the lesional skin of 20 moderate-to-severe AD patients and the skin of 20 controls. Differentially expressed genes (DEGs) were defined by fold-change (FCH) ≥2.0 and false discovery rate <0.05.

RESULTS

We detected 4104 (2513 Up; 1591 Down) and 1273 (546 Up; 727 Down) DEGs in AD versus controls, in tape-strips and biopsies, respectively. Although both techniques captured dysregulation of key immune genes, tape-strips showed higher FCHs for innate immunity (IL-1B, IL-8), dendritic cell (ITGAX/CD11C, FCER1A), Th2 (IL-13, CCL17, TNFRSF4/OX40), and Th17 (CCL20, CXCL1) products, while biopsies showed higher upregulation of Th22 associated genes (IL-22, S100As) and dermal cytokines (IFN-γ, CCL26). Itch-related genes (IL-31, TRPV3) were preferentially captured by tape-strips. Epidermal barrier abnormalities were detected in both techniques, with terminal differentiation defects (FLG2, PSORS1C2) better represented by tape-strips and epidermal hyperplasia changes (KRT16, MKI67) better detected by biopsies.

CONCLUSIONS

Tape-strips and biopsies capture overlapping but distinct features of the AD molecular signature, suggesting their respective utility for monitoring specific AD-related immune, itch, and barrier abnormalities in clinical trials and longitudinal studies.

Biofunctional Inorganic Layered Double Hydroxide Nanohybrid Enhances Immunotherapeutic Effect on Atopic Dermatitis Treatment

Atopic dermatitis (AD) is a widespread, recurrent, and chronic inflammatory skin condition that imposes a major burden on patients. Conventional treatments, such as corticosteroids, are associated with various side effects, underscoring the need for innovative therapeutic approaches. In this study, the possibility of using indole-3-acetic acid-loaded layered double hydroxides (IAA-LDHs) is evaluated as a novel treatment for AD. IAA is an auxin-class plant hormone with antioxidant and anti-inflammatory effects. Following the synthesis of IAA-LDH nanohybrids, their ability to induce M2-like macrophage polarization in macrophages obtained from mouse bone marrow is assessed. The antioxidant activity of IAA-LDH is quantified by assessing the decrease in intracellular reactive oxygen species levels. The anti-inflammatory and anti-atopic characteristics of IAA-LDH are evaluated in a mouse model of AD by examining the cutaneous tissues, immunological organs, and cells. The findings suggest that IAA-LDH has great therapeutic potential as a candidate for AD treatment based on its in vitro and in vivo modulation of AD immunology, enhancement of macrophage polarization, and antioxidant activity. This inorganic drug delivery technology represents a promising new avenue for the development of safe and effective AD treatments.

A single-centre prospective study comparing efficacy and safety of apremilast with cyclosporine in moderate to severe atopic dermatitis

BACKGROUND

Apremilast regulates several pro-inflammatory signals involved in atopic dermatitis (AD).

METHODS

A randomized, open-labelled study was conducted at a tertiary care centre in India. Fifty patients with AD of >1 year duration were randomly assigned in a 1:1 ratio to receive either apremilast (30 mg twice daily after initial titration) or cyclosporine (5 mg/kg/day) for 24 weeks, followed by a 12-week follow-up period. Primary outcome was mean percentage change in Eczema Area and Severity Index (EASI) from baseline to week 24. Secondary outcome measures were proportion of patients achieving EASI 75, EASI 90, ≥2-point improvement in Investigator's Global Assessment (IGA), SCORing Atopic Dermatitis (SCORAD) 75 at week 24 and percentage of patients experiencing ≥1 adverse effect (AEs).

RESULTS

Mean percentage change in EASI (standard deviation) was -67.79% [22.44] in the apremilast treatment group and -83.06% [21.20] in the cyclosporine treatment group (p < 0.05). At week 24, 52.38% of patients in the apremilast group and 78.26% in the cyclosporine group achieved EASI 75 (p < 0.05); 14.29% in the apremilast group and 52.17% in the cyclosporine group achieved EASI 90 (p < 0.05) and 80.95% in the apremilast group and 82.60% patients achieved ≥2 point reduction in IGA (p > 0.05). 57.14% of patients achieved SCORAD 75 in the apremilast group and 69.56% in the cyclosporine group (p > 0.05). Mean time taken to achieve EASI 75 in the apremilast group was 4.50 ± 4.62 weeks, while it was 3.96 ± 3.43 weeks in the cyclosporine group (p > 0.05). Incidence of AEs was 28.57% in the apremilast group and 21.74%) in the cyclosporine group.

CONCLUSIONS

Apremilast demonstrated lesser efficacy in comparison to cyclosporine; it has the advantage of a favourable safety profile and requires no laboratory monitoring.

S100 Proteins in the Pathogenesis of Psoriasis and Atopic Dermatitis

The skin, the outermost layer of the human body, is exposed to various external stimuli that cause inflammatory skin reactions. These external stimulants trigger external epithelial cell damage and the release of intracellular substances. Following cellular damage or death, intracellular molecules are released that enhance tissue inflammation. As an important substance released from damaged cells, the S100 protein is a low-molecular-weight acidic protein with two calcium-binding sites and EF-hand motif domains. S100 proteins are widely present in systemic organs and interact with other proteins. Recent studies revealed the involvement of S100 in cutaneous inflammatory disorders, psoriasis, and atopic dermatitis. This review provides detailed information on the interactions among various S100 proteins in inflammatory diseases.

The pathogenetic role of Th17 immune response in atopic dermatitis

PURPOSE OF REVIEW

As we continue to unravel the pathophysiology and immune mechanisms underlying atopic dermatitis (AD), the emergence of targeted treatments has provided new options for management. Although there are available therapies targeting various immune pathways in AD, the precise pathogenic role of interleukin (IL)-17 in AD pathogenesis remains unclear. The objective of this review is to examine the existing data pertaining to the role of IL-17 in AD and shed light on the potential of targeting this pathway as a therapeutic approach in AD treatment.

RECENT FINDINGS

IL-17 has a dual role of pro-inflammatory and immune protective function, making it an important player in several autoimmune and inflammatory conditions. The extent of IL-17 axis involvement in AD pathogenesis is still debatable. Emerging data show that Th17-related cytokines/chemokines are elevated in skin and sera samples of AD patients, with some articles reporting correlations with disease severity. Particularly increased Th17 signature in specific AD patient subsets, such as Asian-origin or pediatric patients, suggests that certain patients' disease presentations are more predominantly influenced by Th17, and, thus, they may benefit more from Th17 therapeutic targeting approaches. Lack of clinical efficacy with anti-Th17 biologics in AD patients, underscores the need to better elucidate the role of Th17 in AD pathogenesis, along with its utility in therapy.

SUMMARY

The well established role of IL-17 in autoimmune disorders hints for its possible participation in AD disease pathogenesis. Subsequent investigations are needed to assess whether the targeting of specific IL-17 isoforms, homodimers, or heterodimers in specific subpopulations of AD can modify treatment outcomes.

Efficacy and safety profile of dupilumab for the treatment of atopic dermatitis in children and adolescents: A systematic review and meta-analysis

BACKGROUND

Dupilumab is the first biologic approved for the treatment of moderate-to-severe atopic dermatitis (AD) in children and adolescents. Previous systematic reviews explored the effectiveness and safety of dupilumab in adults with AD. However, the underlying mechanisms of AD can vary among different age groups, emphasizing the need for separate investigation into the use of dupilumab in children and adolescents with AD.

OBJECTIVE

To evaluate the efficacy and safety of dupilumab in children and adolescents with AD based on evidence from clinical trials and observational studies.

METHODS

The process of meta-analysis was conducted according to preferred reporting items for systematic reviews and meta-analyses guidelines.

RESULTS

Seven clinical trials and 11 observational studies involving 1275 children and adolescents with AD were eligible for quantitative analysis. Overall, the pooled percentages of eczema area and severity index (EASI) 50, EASI 75, EASI 90, EASI 100, and investigator's global assessment (IGA) 0/1 were 72.9% (95% CI: 61.6%-81.9%), 57.4% (48.1%-66.2%), 31.3% (24.0%-39.7%), 29.7% (23.3%-37.0%), and 35.2% (29.3%-41.5%). With prolonged treatment time, an increase was seen in the pooled rate of EASI response, indicating that dupilumab may provide sustained benefits for children and adolescents over the long term. The reported adverse events were primarily mild and manageable, with an overall incidence rate of 7.2% across clinical trials and 7.6% across observational studies.

CONCLUSION

Dupilumab was an effective and safe treatment option for children and adolescents with AD, with positive results observed from long-term use and an acceptable safety profile. More long-term, high-quality, controlled studies in different regions are needed for further verification.

Disease modification in inflammatory skin disorders: opportunities and challenges

Progress in understanding of the mechanisms underlying chronic inflammatory skin disorders, such as atopic dermatitis and psoriasis vulgaris, has led to new treatment options with the primary goal of alleviating symptoms. In addition, this knowledge has the potential to inform on new strategies aimed at inducing deep and therapy-free remission, that is, disease modification, potentially impacting on associated comorbidities. However, to reach this goal, key areas require further exploration, including the definitions of disease modification and disease activity index, further understanding of disease mechanisms and systemic spillover effects, potential windows of opportunity, biomarkers for patient stratification and successful intervention, as well as appropriate study design. This Perspective article assesses the opportunities and challenges in the discovery and development of disease-modifying therapies for chronic inflammatory skin disorders.

Spatial transcriptomics combined with single-cell RNA-sequencing unravels the complex inflammatory cell network in atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease with complex pathogenesis for which the cellular and molecular crosstalk in AD skin has not been fully understood.

METHODS

Skin tissues examined for spatial gene expression were derived from the upper arm of 6 healthy control (HC) donors and 7 AD patients (lesion and nonlesion). We performed spatial transcriptomics sequencing to characterize the cellular infiltrate in lesional skin. For single-cell analysis, we analyzed the single-cell data from suction blister material from AD lesions and HC skin at the antecubital fossa skin (4 ADs and 5 HCs) and full-thickness skin biopsies (4 ADs and 2 HCs). The multiple proximity extension assays were performed in the serum samples from 36 AD patients and 28 HCs.

RESULTS

The single-cell analysis identified unique clusters of fibroblasts, dendritic cells, and macrophages in the lesional AD skin. Spatial transcriptomics analysis showed the upregulation of COL6A5, COL4A1, TNC, and CCL19 in COL18A1-expressing fibroblasts in the leukocyte-infiltrated areas in AD skin. CCR7-expressing dendritic cells (DCs) showed a similar distribution in the lesions. Additionally, M2 macrophages expressed CCL13 and CCL18 in this area. Ligand-receptor interaction analysis of the spatial transcriptome identified neighboring infiltration and interaction between activated COL18A1-expressing fibroblasts, CCL13- and CCL18-expressing M2 macrophages, CCR7- and LAMP3-expressing DCs, and T cells. As observed in skin lesions, serum levels of TNC and CCL18 were significantly elevated in AD, and correlated with clinical disease severity.

CONCLUSION

In this study, we show the unknown cellular crosstalk in leukocyte-infiltrated area in lesional skin. Our findings provide a comprehensive in-depth knowledge of the nature of AD skin lesions to guide the development of better treatments.

Longitudinal course of cognitive impairment in patients with atopic dermatitis

Atopic dermatitis (AD) is a common inflammatory skin disease. Cognitive dysfunction was recently demonstrated to be increased in adults and children with AD. However, little is known about the longitudinal course of cognitive impairment in AD and its relationship with pruritus. To investigate the longitudinal course and predictors of cognitive impairment in AD a prospective dermatology practice-based study was performed using questionnaires and evaluation by a dermatologist (n = 210). Patients with ≥ 2 visits were included (mean follow-up time: 318 days). Cognitive function was assessed using the Patient-Reported Outcomes Measurement Information System (PROMIS) Cognitive Function 8-item Short-Form. At baseline, 20.85% of patients had PROMIS T scores ≤ 45, indicating cognitive impairment (CI). Among patients with CI at baseline, 34.09% had persistent CI, 47.72% had a fluctuating course, and 18.18% had sustained improvement of cognitive function. In repeated-measures regression models, cognitive function scores declined overtime in patients with worse AD severity [SCORing Atopic Dermatitis (SCORAD): p = 0.01, Atopic Dermatitis Severity Index: p = 0.001], increased itch (p = 0.01), skin pain (p = 0.001), and sleep disturbance (p = 0.001). In multivariable logistic regression models, persistent CI was associated with female gender and depressive symptoms [moderate-to-severe Patient Health Questionnaire-9 score (PHQ9)]. Latent class analysis identified two classes of cognitive dysfunction: normal cognition (77.23%), moderate dysfunction (16.21%) and severe impairment (6.55%). Black/African-American race (p = 0.02), moderate-to-severe SCORAD (p = 0.03), dermatology life quality index (p < 0.0001), PHQ9 (p < 0.0001), itch (p = 0.02) and skin pain (p < 0.0001) were more likely to experience moderate dysfunction or severe cognitive impairment. AD is associated with a heterogeneous longitudinal course of cognitive function in adults, with some patients experiencing persistent CI over time.

Update on Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disorder with a lifetime prevalence of up to 20% which can occur at any age but is most common among children. There is a significant burden of pediatric AD in the primary care setting; thus, the ability to recognize and manage AD is of utmost importance to pediatricians. Treatment of AD requires a multifaceted approach based on a patient's severity including behavioral modifications, topical and systemic pharmacologic therapies, and phototherapy.

Assessment of Treatment-Relevant Immune Biomarkers in Psoriasis and Atopic Dermatitis: Toward Personalized Medicine in Dermatology

Immunologically targeted therapies have revolutionized the treatment of inflammatory dermatoses, including atopic dermatitis and psoriasis. Although immunologic biomarkers hold great promise for personalized classification of skin disease and tailored therapy selection, there are no approved or widely used approaches for this in dermatology. This review summarizes the translational immunologic approaches to measuring treatment-relevant biomarkers in inflammatory skin conditions. Tape strip profiling, microneedle-based biomarker patches, molecular profiling from epidermal curettage, RNA in situ hybridization tissue staining, and single-cell RNA sequencing have been described. We discuss the advantages and limitations of each and open questions for the future of personalized medicine in inflammatory skin disease.

Age of onset defines two distinct profiles of atopic dermatitis in adults

BACKGROUND

The incidence of adult-onset atopic dermatitis (AOAD) is increasing. However, the unique characteristics of AOAD compared to pediatric-onset AD persisting into adulthood (POAD) are underexplored, hampering the development of targeted-therapeutics for this growing population. We thus assessed the profile of AOAD in skin and blood compared to that of POAD.

METHODS

We collected skin biopsies and blood from adults with AOAD, POAD, and healthy controls (n = 15 in each group). Skin samples were analyzed by RNA sequencing, qRT-PCR, and immunohistochemistry, and Olink Proseek multiplex assay was used to identify the serum proteomic profile.

RESULTS

Compared to healthy controls, both AOAD and POAD showed cutaneous immune and barrier dysregulations with a shared Th2/Th22 hyperactivation. Overall, POAD showed greater inflammation in lesional skin, with more prominent expression of Th2/Th17/Th22 markers (CCL17/22, S100A8/9, IL-36A, PI3/Elafin, DEFB4) in POAD compared to AOAD (p-value < .05). In contrast, higher Th1-(IFN-γ, IL-2, IL-15, CCL5) upregulation and Th1-skewing were seen in AOAD. The epidermal barrier was also more compromised in POAD, with greater epidermal hyperplasia and lower expression of markers related to terminal differentiation, lipids, and cell adhesion. In parallel with increased rates of cardiovascular comorbidities, AOAD demonstrated many more significantly dysregulated proteins in serum (n = 148) compared to POAD (n = 86), including pro-inflammatory and cardiovascular-risk markers. Th1-related products showed significant correlations between their skin and blood expressions only in AOAD subjects.

CONCLUSION

Age-of-onset delineates two distinct endophenotypes in adult AD potentially suggesting the need for broader (beyond Th2) therapeutic targeting in AOAD.

Challenges and Future Trends in Atopic Dermatitis

Atopic dermatitis represents a complex and multidimensional interaction that represents potential fields of preventive and therapeutic management. In addition to the treatment armamentarium available for atopic dermatitis, novel drugs targeting significant molecular pathways in atopic dermatitis biologics and small molecules are also being developed given the condition's complex pathophysiology. While most of the patients are expecting better efficacy and long-term control, the response to these drugs would still depend on numerous factors such as complex genotype, diverse environmental triggers and microbiome-derived signals, and, most importantly, dynamic immune responses. This review article highlights the challenges and the recently developed pharmacological agents in atopic dermatitis based on the molecular pathogenesis of this condition, creating a specific therapeutic approach toward a more personalized medicine.

Thymic stromal lymphopoietin rather than IL-33 drives food allergy after epicutaneous sensitization to food allergen

BACKGROUND

A major route of sensitization to food allergen is through an impaired skin barrier. IL-33 and thymic stromal lymphopoietin (TSLP) have both been implicated in epicutaneous sensitization and food allergy, albeit in different murine models.

OBJECTIVE

We assessed the respective contributions of TSLP and IL-33 to the development of atopic dermatitis (AD) and subsequent food allergy in TSLP and IL-33 receptor (ST2)-deficient mice using an AD model that does not require tape stripping.

METHOD

TSLP receptor (TSLPR)-/-, ST2-/-, and BALB/cJ control mice were exposed to 3 weekly epicutaneous skin patches of one of saline, ovalbumin (OVA), or a combination of OVA and Aspergillus fumigatus (ASP), followed by repeated intragastric OVA challenges and development of food allergy.

RESULTS

ASP and/or OVA patched, but not OVA-alone patched, BALB/cJ mice developed an AD-like skin phenotype. However, epicutaneous OVA sensitization occurred in OVA patched mice and was decreased in ST2-/- mice, resulting in lower intestinal mast cell degranulation and accumulation, as well as OVA-induced diarrhea occurrences on intragastric OVA challenges. In TSLPR-/- mice, intestinal mast cell accumulation was abrogated, and no diarrhea was observed. AD was significantly milder in OVA + ASP patched TSLPR-/- mice compared to wild type and ST2-/- mice. Accordingly, intestinal mast cell accumulation and degranulation were impaired in OVA + ASP patched TSLPR-/- mice compared to wild type and ST2-/- mice, protecting TSLPR-/- mice from developing allergic diarrhea.

CONCLUSION

Epicutaneous sensitization to food allergen and development of food allergy can occur without skin inflammation and is partly mediated by TSLP, suggesting that prophylactic targeting of TSLP may be useful in mitigating the development of AD and food allergy early in life in at-risk infants.

JAK Signaling Is Critically Important in Cytokine-Induced Viral Susceptibility of Keratinocytes

Little is known about whether type 1 (IFNγ), 2 (IL-4/IL-13), or 3 (IL-17A/IL-22) cytokines affect the susceptibility of keratinocytes (KC) to viruses. These immune pathways predominate in various skin diseases: lupus, atopic dermatitis (AD), and psoriasis, respectively. Janus kinase inhibitors (JAKi) are approved to treat both AD and psoriasis, and are in clinical development for lupus. We evaluated whether these cytokines alter viral susceptibility of KC and determined if this effect is modulated by treatment with JAKi. Viral susceptibility to vaccinia virus (VV) or herpes simplex virus-1 (HSV-1) ± JAKi was assessed in immortalized and primary human KC pretreated with cytokines. Exposure to type 2 (IL-4 + IL-13) or the type 3 (IL-22) cytokines significantly increased KC viral susceptibility. Specifically, there was a peak increase of 12.2 ± 3.1-fold (IL-4 + IL-13) or 7.7 ± 2.8-fold (IL-22) in VV infection as measured by plaque number. Conversely, IFNγ significantly reduced susceptibility to VV (63.1 ± 64.4-fold). The IL-4 + IL-13-induced viral susceptibility was reduced (44 ± 16%) by JAK1 inhibition, while the IL-22-enhanced viral susceptibility was diminished (76 ± 19%) by TYK2 inhibition. IFNγ-mediated resistance to viral infection was reversed by JAK2 inhibition (366 ± 294% increase in infection). Cytokines expressed in AD skin (IL-4, IL-13, IL-22) increase KC viral susceptibility while IFNγ is protective. JAKi that target JAK1 or TYK2 reversed cytokine-enhanced viral susceptibility, while JAK2 inhibition reduced the protective effects of IFNγ.

The Essential Role of microRNAs in Inflammatory and Autoimmune Skin Diseases-A Review

The etiopathogenesis of autoimmune skin diseases is complex and still not fully understood. The role of epigenetic factors is emphasized in the development of such diseases. MicroRNAs (miRNAs), a group of non-coding RNAs (ncRNAs-non-coding RNAs), are one of the important post-transcriptional epigenetic factors. miRNAs have a significant role in the regulation of the immune response by participating in the process of the differentiation and activation of B and T lymphocytes, macrophages, and dendritic cells. Recent advances in research on epigenetic factors have provided new insights into the pathogenesis and potential diagnostic and therapeutic targets of many pathologies. Numerous studies revealed a change in the expression of some microRNAs in inflammatory skin disorders, and the regulation of miRNA expression is a promising therapeutic goal. This review presents the state of the art regarding changes in the expression and role of miRNAs in inflammatory and autoimmune skin diseases, including psoriasis, atopic dermatitis, vitiligo, lichen planus, hidradenitis suppurativa, and autoimmune blistering diseases.

Impaired expression of metallothioneins contributes to allergen-induced inflammation in patients with atopic dermatitis

Regulation of cutaneous immunity is severely compromised in inflammatory skin disease. To investigate the molecular crosstalk underpinning tolerance versus inflammation in atopic dermatitis, we utilise a human in vivo allergen challenge study, exposing atopic dermatitis patients to house dust mite. Here we analyse transcriptional programmes at the population and single cell levels in parallel with immunophenotyping of cutaneous immunocytes revealed a distinct dichotomy in atopic dermatitis patient responsiveness to house dust mite challenge. Our study shows that reactivity to house dust mite was associated with high basal levels of TNF-expressing cutaneous Th17 T cells, and documents the presence of hub structures where Langerhans cells and T cells co-localised. Mechanistically, we identify expression of metallothioneins and transcriptional programmes encoding antioxidant defences across all skin cell types, that appear to protect against allergen-induced inflammation. Furthermore, single nucleotide polymorphisms in the MTIX gene are associated with patients who did not react to house dust mite, opening up possibilities for therapeutic interventions modulating metallothionein expression in atopic dermatitis.

Gamma-delta (γδ) T cell-derived cytokines (IL-4, IL-17, IFN-γ and IL-10) and their possible implications for atopic dermatitis development

Atopic dermatitis (AD) is a chronic disease related to skin disorders that affect individuals in their childhood and can persist or start in adulthood. Patients affected by this disease commonly show skin lesions on the body surface (mainly on the upper and lower limbs) and allergic rhinitis or asthma crises. Looking at the disease from a molecular perspective, the major cytokines involved in inflammatory skin diseases, not only AD, include IL-4, IL-17, IFN-γ and IL-10. Although they can produce these cytokines and infiltrate the affected epithelia in patients with AD, γδ T cells are still almost unexplored. In this update, we briefly discuss the involvement of IL-4, IL-17, IFN-γ and IL-10 in the pathophysiology of AD and the possible role of γδ T cells during the inflammatory process.

RELEVANCE OF CODING VARIATION IN FILAGGRIN AND DOCK8 IN FINNISH PEDIATRIC PATIENTS WITH EARLY-ONSET MODERATE-TO-SEVERE ATOPIC DERMATITIS

Early-onset, persistent atopic dermatitis (AD) is proposed as a distinct subgroup that may have specific genotypic features. FLG gene loss-of-function variants are the best known genetic factors contributing to epidermal barrier impairment and eczema severity. In a cohort of 140 Finnish children with early-onset moderate-to-severe AD, we investigated the effect of coding variation in FLG and 13 other genes with epidermal barrier or immune function through the use of targeted amplicon sequencing and genotyping. A FLG loss-of-function variant (Arg501Ter, Ser761fs, Arg2447Ter, or Ser3247Ter) was identified in 20 of 140 patients showing higher transepidermal water loss values than patients without these variants. Total FLG loss-of-function variant frequency (7.14%) was significantly higher than in the general Finnish population (2.34%). When tested separately, only Arg2447Ter showed a significant association with AD (P = 0.003104). In addition, a modest association with moderate-to-severe pediatric AD was seen for rs12730241 and rs6587667 (FLG2:Gly137Glu). Loss-of-function variants, previously reported pathogenic variants, or statistically significant enrichment of nonsynonymous coding region variants were not found in the 13 candidate genes studied by amplicon sequencing. However, higher IgE and eosinophil counts were found in carriers of potentially pathogenic DOCK8 missense variants, suggesting that the role of DOCK8 variation in AD should be further investigated in larger cohorts.

The translational revolution in atopic dermatitis: the paradigm shift from pathogenesis to treatment

Atopic dermatitis (AD) is the most common inflammatory skin disease, and it is considered a complex and heterogeneous condition. Different phenotypes of AD, defined according to the patient age at onset, race, and ethnic background; disease duration; and other disease characteristics, have been recently described, underlying the need for a personalized treatment approach. Recent advancements in understanding AD pathogenesis resulted in a real translational revolution and led to the exponential expansion of the therapeutic pipeline. The study of biomarkers in clinical studies of emerging treatments is helping clarify the role of each cytokine and immune pathway in AD and will allow addressing the unique immune fingerprints of each AD subset. Personalized medicine will be the ultimate goal of this targeted translational research. In this review, we discuss the changes in the concepts of both the pathogenesis of and treatment approach to AD, highlight the scientific rationale behind each targeted treatment and report the most recent clinical efficacy data.

T cell co-stimulatory and co-inhibitory pathways in atopic dermatitis

The use of immune checkpoint inhibitors (ICIs) targeting the T cell inhibitory pathways has revolutionized cancer treatment. However, ICIs might induce progressive atopic dermatitis (AD) by affecting T cell reactivation. The critical role of T cells in AD pathogenesis is widely known. T cell co-signaling pathways regulate T cell activation, where co-signaling molecules are essential for determining the magnitude of the T cell response to antigens. Given the increasing use of ICIs in cancer treatment, a timely overview of the role of T cell co-signaling molecules in AD is required. In this review, we emphasize the importance of these molecules involved in AD pathogenesis. We also discuss the potential of targeting T cell co-signaling pathways to treat AD and present the unresolved issues and existing limitations. A better understanding of the T cell co-signaling pathways would aid investigation of the mechanism, prognosis evaluation, and treatment of AD.

Peripheral Blood Gene Expression Profile of Infants with Atopic Dermatitis

To enhance the understanding of molecular mechanisms and mine previously unidentified biomarkers of pediatric atopic dermatitis, PBMC gene expression profiles were generated by RNA sequencing in infants with atopic dermatitis and age-matched controls. A total of 178 significantly differentially expressed genes (DEGs) (115 upregulations and 63 downregulations) were seen, compared with those in healthy controls. The DEGs identified included IL1β, TNF, TREM1, IL18R1, and IL18RAP. DEGs were validated by real-time RT- qPCR in a larger number of samples from PBMCs of infants with atopic dermatitis aged <12 months. Using the DAVID (Database for Annotation, Visualization and Integrated Discovery) database, functional and pathway enrichment analyses of DEGs were performed. Gene ontology enrichment analysis showed that DEGs were associated with immune responses, inflammatory responses, regulation of immune responses, and platelet activation. Pathway analysis indicated that DEGs were enriched in cytokine‒cytokine receptor interaction, immunoregulatory interactions between lymphoid and nonlymphoid cells, hematopoietic cell lineage, phosphoinositide 3-kinase‒protein kinase B signaling pathway, NK cell‒mediated cytotoxicity, and platelet activation. Furthermore, the protein‒protein interaction network was predicted using the STRING (Search Tool for the Retrieval of Interacting Genes/Proteins) database and visualized with Cytoscape software. Finally, on the basis of the protein‒protein interaction network, 18 hub genes were selected, and two significant modules were obtained. In conclusion, this study sheds light on the molecular mechanisms of pediatric atopic dermatitis and may provide diagnostic biomarkers and therapeutic targets.