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BackgroundAlthough multiple studies have assessed molecular changes in chronic atopic dermatitis (AD) lesions, little is known about the transition from acute to chronic disease stages, and the factors and mechanisms that shape chronic inflammatory activity.ObjectivesWe sought to assess the global transcriptome changes that characterize the progression from acute to chronic stages of AD.MethodsWe analyzed transcriptome changes in paired nonlesional skin, acute and chronic AD lesions from 11 patients and 38 healthy controls by RNA-sequencing, and conducted in vivo and histological assays to evaluate findings.ResultsOur data demonstrate that approximately 74% of the genes dysregulated in acute lesions remain or are further dysregulated in chronic lesions, whereas only 34% of the genes dysregulated in chronic lesions are altered already in the acute stage. Nonlesional AD skin exhibited enrichment of TNF, TH1, TH2, and TH17 response genes. Acute lesions showed marked dendritic-cell signatures and a prominent enrichment of TH1, TH2, and TH17 responses, along with increased IL-36 and thymic stromal lymphopoietin expression, which were further heightened in chronic lesions. In addition, genes involved in skin barrier repair, keratinocyte proliferation, wound healing, and negative regulation of T-cell activation showed a significant dysregulation in the chronic versus acute comparison. Furthermore, our data show progressive changes in vasculature and maturation of dendritic-cell subsets with chronicity, with FOXK1 acting as immune regulator.ConclusionsOur results show that the changes accompanying the transition from nonlesional to acute to chronic inflammation in AD are quantitative rather than qualitative, with chronic AD having heightened TH2, TH1, TH17, and IL36 responses and skin barrier repair mechanisms. These findings provide novel insights and highlight underappreciated pathways in AD pathogenesis that may be amenable to therapeutic targeting.

Background Interleukin (IL)-13 is a key driver of inflammation and barrier dysfunction in atopic dermatitis (AD). While there is robust evidence that tralokinumab – a monoclonal antibody that neutralizes IL-13 – reduces inflammation and clinical disease activity, less is known about its effects on barrier function. Objectives To characterize the effects of tralokinumab treatment on skin barrier function. Methods Transepidermal water loss (TEWL), stratum corneum hydration (SCH), natural moisturizing factor content, histopathological characteristics, biomarker expression and microbiome composition were evaluated in lesional, nonlesional and sodium lauryl sulfate-irritated skin of 16 patients with AD over the course of 16 weeks of tralokinumab treatment. Results All clinical severity scores decreased significantly over time. At week 16, mean TEWL in target lesions decreased by 33% (P = 0.01) and SCH increased by 58% (P = 0.004), along with a histological reduction in spongiosis (P = 0.003), keratin 16 expression and epidermal thickness (P = 0.001). In parallel, there was a significant decrease in several barrier dysfunction-associated and proinflammatory proteins such as fibronectin (P = 0.006), CCL17/TARC (P = 0.03) and IL-8 (P = 0.01), with significant changes seen as early as week 8. Total bacterial load and Staphylococcus aureus abundance were significantly reduced from week 2. Conclusions Tralokinumab treatment improved skin physiology, epidermal pathology and dysbiosis, further highlighting the pleiotropic role of IL-13 in AD pathogenesis. [ABSTRACT FROM AUTHOR]

Background: Atopic dermatitis (AD) is the most common paediatric inflammatory skin disease. There are currently no robust biomarkers that could reliably predict its manifestation, and on the molecular level, it is less well characterized than adult AD. Objectives: This study aimed to extend previous findings and provide evidence for distinct changes of the epidermal proteome and microbiome preceding the onset of AD as well as characterizing early AD. Methods: We longitudinally analysed epidermal biomarker levels and microbial profiles in a cohort of 50 neonates at high risk for AD, who had participated in a randomized controlled trial on early emollient use for AD prevention. Results: About 26% of the infants developed AD until month 24 with an average age of 10 month at disease onset. In children with later AD, IL‐1Ra, TNFβ, IL‐8, IL‐18, IL‐22, CCL2, TARC, TSLP and VEGFa showed increased levels prior to disease manifestation with levels of IL‐1Ra, TNFβ and VEGFa already increased shortly after birth. Further, children with later AD displayed a delayed maturation and differentially composed skin microbiome prior to AD onset. At manifestation, levels of multiple Th2, Th17/22 and Th1‐associated biomarkers as well as innate immunity markers were elevated, and abundances of commensal Streptococcus species were reduced in favour of Staphylococcus epidermidis. Conclusions: Our results indicate that elevations of proinflammatory stratum corneum biomarkers and alterations of the skin microbiome precede paediatric AD and characterize the disease at onset. [ABSTRACT FROM AUTHOR]

Background: The antimicrobial ribonuclease RNase 7 is abundantly expressed in the epidermis of lesional skin of atopic dermatitis (AD). Host RNase inhibitor (RI) binds to RNase 7 and blocks its ribonuclease activity. This study aimed to evaluate the impact of RNase 7–RI interactions on AD. Methods: Cultured human primary keratinocytes, with siRNA‐mediated downregulation of RNase 7 and RI, were stimulated with the synthetic RNA polyinosinic‐polycytidylic acid (poly I:C). Induction of proinflammatory mediators was analyzed by real‐time PCR and ELISA. RI expression in AD non‐lesional and lesional skin biopsies and healthy controls was analyzed by real‐time PCR and immunostaining. RI protein release in vivo on the AD skin surface was determined by western blot. Antimicrobial and ribonuclease assays were used to investigate the functional role of RI. Results: RNase 7 inhibited the RNA‐induced expression of proinflammatory mediators in keratinocytes. Accordingly, downregulation of RNase 7 in keratinocytes enhanced RNA‐mediated induction of proinflammatory mediators, whereas downregulation of RI had the opposite effect. RI was released by damaged keratinocytes and epidermis. In vivo expression and release of RI on the skin surface were enhanced in lesional AD skin. Rinsing solution from the surface of lesional AD skin blocked the ribonuclease activity of RNase 7. The anti‐Staphylococcus aureus activity of RNase 7 was abrogated by RI. Conclusions: Our data suggest a novel role of RI as a trigger factor of inflammation in AD by blocking the ribonuclease and antimicrobial activity of RNase 7, thereby enhancing RNA‐mediated inflammation and S. aureus growth. [ABSTRACT FROM AUTHOR]

Introduction/Background Growing evidence suggests that blocking the OX40 ligand (OX40L)/OX40 costimulatory pathway could have therapeutic effects in inflammatory diseases such as atopic dermatitis (AD). Amlitelimab (SAR445229; KY1005) is a potential first-in-class, fully human, non-depleting anti-OX40L monoclonal antibody that blocks OX40L-OX40 interactions. We report OX40L and OX40 expression from skin biopsies collected in two studies: an amlitelimab Phase 2a (Ph2a) study in patients with moderate-to-severe AD, and a small-scale study of patients with mild AD and healthy volunteers. Objectives: Assess OX40L and OX40 expression in AD skin (lesional and non-lesional) and healthy control skin. Methods: As part of a Ph2a randomized, double-blind, placebo-controlled study (NCT03754309) of amlitelimab in moderate-to-severe AD, 174 baseline-paired lesional/non-lesional skin biopsies were collected from all patients (n=87). In a separate small-scale study, 24 skin biopsies were collected, including healthy control skin from healthy volunteers (n=6) and paired lesional/non-lesional skin from patients with mild AD (n=9). Each biopsy underwent immunohistochemical (IHC; formalin-fixed paraffin-embedded) analyses using various antibodies (OX40L: rabbit IgG antibody from Cell Signaling Technology for Ph2a biopsies, proprietary mouse IgG2a KY1005 for small-scale study biopsies; OX40: clone Ber-ACT35 from BioLegend for all biopsies). A trained pathologist assessed IHC staining in the dermis and/or epidermis using semi-quantitative scoring (0 [no stained cells] to 10 [all cells stained]) or quantitative methods (cells/mm2, Tissue Studio 4.0, and HALO link image analysis software). Wilcoxon matched-pairs signed-rank test was used to assess IHC staining of Ph2a biopsies. Ph2a biopsies also underwent transcriptomic analyses (stored in RNALater) for OX40L (TNFSF4) and OX40 (TNFRSF4) on sequenced RNA using a linear mixed model with Benjamini-Hochberg adjustment. Results: In baseline Ph2a biopsies, IHC analysis revealed elevated OX40L and OX40 staining in lesional versus non-lesional AD skin (P <0.0001 for both markers). For OX40L, the median score was 3 (lesional) versus 1 (non-lesional) and the Wilcoxon matched-pairs signed-rank test found P<0.0001. For OX40+ cells, the median expression was 179.8 cells/mm2 in lesional AD skin versus 54.45 cells/mm2 in non-lesional AD skin (P<0.0001 using the Wilcoxon matched-pairs signedrank test). These findings were confirmed by RNA sequencing analysis, with TNFSF4 (OX40L) and TNFRSF4 (OX40) differentially expressed in lesional and non-lesional AD skin (P<0.01 and P<0.0001, respectively). A larger scale study is ongoing that may further support this finding. In the smallscale study including patients with mild AD and healthy volunteers, there was a trend for an increase of mean OX40L+ and OX40+ cells/mm2 in lesional skin versus non-lesional skin and healthy control skin in the dermis and epidermis (OX40L+ dermal lesional, non-lesional, healthy, respectively: 17.6, 11.2, 11.5; OX40L+ epidermal: 5.8, 2.1, 1.9; OX40+ dermal: 5.7, 2.1, 0.4; OX40+ epidermal: 10.9, 9.0, 1.8); the increase was significant for lesional versus healthy control skin for dermal OX40+ cells/mm2 (P<0.001). Conclusions: We confirm with IHC and RNA sequencing that OX40L and OX40 expression is elevated in skin lesions of patients with moderate-to-severe AD. We also demonstrate a trend to elevated OX40L and elevated OX40 in mild AD skin versus healthy volunteers. A potential explanation for the lower levels of OX40L and OX40 in patients with mild AD in this study may be their lower disease severity versus Ph2a study patients. These findings support the OX40L/OX40 pathway as a relevant target in T cell immune dysregulation; its blockade may represent a novel treatment approach for moderate-to-severe AD. [ABSTRACT FROM AUTHOR]

Background: Atopic dermatitis (AD) is driven by the interplay between a dysfunctional epidermal barrier and a skewed cutaneous immune dysregulation. As part of the complex skin barrier dysfunction, abnormalities in lipid organization and microbiome composition have been described. We set out to systematically investigate the composition of the stratum corneum lipidome, skin microbiome and skin physiology parameters at three different body sites in patients with AD and healthy volunteers. Methods: We analysed tape strips from different body areas obtained from 10 adults with AD and 10 healthy volunteers matched for FLG mutation status for 361 skin lipid species using the Metabolon mass spectrometry platform. 16S rRNA data were available from all probands. Results: Our study showed that the lipid composition differs significantly between body sites and between AD patients and healthy individuals. Ceramide species NS was significantly higher in AD patients compared to healthy volunteers and was also higher in AD patients with a FLG mutation compared to AD patients without a FLG mutation. The correlation analysis of skin lipid alterations with the microbiome showed that Staphylococcus colonization in AD is positively correlated with ceramide subspecies AS, ADS, NS and NDS. Conclusion: This is the first study to reveal site‐specific lipid alterations and correlations with the skin microbiome in AD. [ABSTRACT FROM AUTHOR]

The study in Clinical & Experimental Allergy found that the Type 2 immune-dominant endotype is not linked to increased responsiveness to dupilumab treatment in adult atopic dermatitis patients. The research did not identify any biological evidence to exclude atopic dermatitis patients from considering dupilumab treatment based on their endotype. The study suggests that all atopic dermatitis patients should be considered for dupilumab treatment regardless of their Type 2 endotype. [Extracted from the article]

Atopic dermatitis (AD) is a chronic, pruritic skin disease characterized by type 2 immune-mediated inflammation and skin barrier dysfunction (1). The impaired skin barrier in AD is related to decreased expression of epidermal barrier proteins and to changes in lipid composition in the stratum corneum. AD lesions are characterized by increased expression of pro-inflammatory mediators, such as chemokines, leading to recruitment of immune cells, which may further exacerbate the inflammation. Interleukin (IL)-13 and IL-4 are the signature type 2 cytokines involved in AD. These cytokines both signal through the type II receptor, composed of IL-4Ra and IL-13Ra1, and display functional redundancy in cells harbouring this receptor, including keratinocytes and fibroblasts. This is in contrast to cells, such as T lymphocytes, containing the type I receptor (IL-4Ra combined with the common gamma chain), which is only used by IL-4 for signalling. Monoclonal antibodies targeting IL-4Ra (dupilumab) or IL-13 (tralokinumab and lebrikizumab) have demonstrated clinical efficacy in AD (2-4). Interestingly, protein levels of IL-13, but not IL-4, are consistently detected and shown to be increased in AD skin across studies (5, 6). Furthermore, 3 recently published studies using RNA-sequencing of AD biopsies found increased levels of IL13 in lesional and non-lesional AD skin, whereas expression of IL4 was undetectable or very low (7-9). Independent studies also found a correlation between expression levels of IL-13 at mRNA or protein level in lesional AD skin and disease severity (6, 7). The aim of the current study is to further investigate effects of IL-13 on AD-associated genes in human skin cells and to provide molecular insights into the mechanism of action of tralokinumab, a fully human IgG4 monoclonal antibody that specifically neutralizes IL-13. [ABSTRACT FROM AUTHOR]