Distinct Roles of IL-4, IL-13, and IL-22 in Human Skin Barrier Dysfunction and Atopic Dermatitis

Atopic dermatitis (AD) is a chronic type-2 inflammatory skin disease characterized by epithelial barrier dysfunction. IL-4, IL-13, and IL-22 represent major cytokines contributing to AD-pathogenesis. Models using reconstructed keratinocytes have been used in previous studies, however, did not represent the real skin situation. Here, we report the distinct effects of IL-4, IL-13, and IL-22 on bio-stabilized human skins with intact barriers and resident immune cells. Spatial transcriptomics on AD-lesions and non-lesional skin of patients, and RNA-sequencing, and proteomics were performed in IL-4-, IL-13- and IL-22-treated native skins. Skin barrier integrity was evaluated using electrical impedance spectroscopy. Spatial transcriptomics demonstrated that CLDN1, FLG, and FLG2 were significantly downregulated in the epidermis of AD lesions. IL-4, IL-13, and IL-22 disrupted the skin barrier in the ex vivo human skin by downregulation of the genes and proteins critical for barrier function and keratinization. IL-4 and IL-13 suppressed, whereas IL-22 upregulated the antimicrobial peptides. Interestingly, IL-4 and IL-13 showed a cross-regulation with IL-22, by downregulation of IL-22Rα1 with IL-4 and IL-13 and upregulation of IL-4Rα with IL-22. Three months of dupilumab treatment in AD patients restored the IL-4 and IL-13-dysregulated genes, whereas genes co-regulated or only regulated by IL-22 remained unaltered. In conclusion, this study comprehensively provides insights into the distinct immune profiles following IL-4, IL-13, and IL-22 stimulation in human skin, highlighting their complex interplay in the pathogenesis of AD modulating keratinocyte and immune responses.