Functional Interplay between IL-9 and Peptide YY Contributes to Chronic Skin Inflammation

Immune cells in the epithelial immune microenvironment of psoriasis: emerging therapeutic targets

Psoriasis is a chronic autoimmune inflammatory disease characterized by erroneous metabolism of keratinocytes. The development of psoriasis is closely related to abnormal activation and disorders of the immune system. Dysregulated skin protective mechanisms can activate inflammatory pathways within the epithelial immune microenvironment (EIME), leading to the development of autoimmune-related and inflammatory skin diseases. In this review, we initially emphasized the pathogenesis of psoriasis, paying particular attention to the interactions between the abnormal activation of immune cells and the production of cytokines in psoriasis. Subsequently, we delved into the significance of the interactions between EIME and immune cells in the emergence of psoriasis. A thorough understanding of these immune processes is crucial to the development of targeted therapies for psoriasis. Finally, we discussed the potential novel targeted therapies aimed at modulating the EIME in psoriasis. This comprehensive examination sheds light on the intricate underlying immune mechanisms and provides insights into potential therapeutic avenues of immune-mediated inflammatory diseases.

Keratinocytes activated by IL-4/IL-13 express IL-2Rγ with consequences on epidermal barrier function

Atopic dermatitis (AD) is a Th2-type inflammatory disease characterized by an alteration of epidermal barrier following the release of IL-4 and IL-13. These cytokines activate type II IL-4Rα/IL-13Rα1 receptors in the keratinocyte. Whilst IL-2Rγ, that forms type I receptor for IL-4, is only expressed in haematopoietic cells, recent studies suggest its induction in keratinocytes, which questions about its role. We studied expression of IL-2Rγ in keratinocytes and its role in alteration of keratinocyte function and epidermal barrier. IL-2Rγ expression in keratinocytes was studied using both reconstructed human epidermis (RHE) exposed to IL-4/IL-13 and AD skin. IL-2Rγ induction by type II receptor has been analyzed using JAK inhibitors and RHE knockout (KO) for IL13RA1. IL-2Rγ function was investigated in RHE KO for IL2RG. In RHE, IL-4/IL-13 induce expression of IL-2Rγ at the mRNA and protein levels. Its mRNA expression is also visualized in keratinocytes of lesional AD skin. IL-2Rγ expression is low in RHE treated with JAK inhibitors and absent in RHE KO for IL13RA1. Exposure to IL-4/IL-13 alters epidermal barrier, but this alteration is absent in RHE KO for IL2RG. A more important induction of IL-13Rα2 is reported in RHE KO for IL2RG than in not edited RHE. These results demonstrate IL-2Rγ induction in keratinocytes through activation of type II receptor. IL-2Rγ is involved in the alteration of the epidermal barrier and in the regulation of IL-13Rα2 expression. Observation of IL-2Rγ expression by keratinocytes inside AD lesional skin suggests a role for this receptor subunit in the disease.