Downregulation of SHANK-associated RH domain-interacting protein elevates interleukin-33 expression by stimulating the Janus kinase 2/signal transducer and activator of transcription signaling pathway in HaCaT cells.

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Atopic dermatitis (AD) is a chronic inflammatory skin disease in which T-helper type 2 (Th2 ) immune responses are dominant. SHANK-associated RH domain interacting protein (SHARPIN) is expressed at low levels in AD, resulting in the upregulation of signal transducer and activator of transcription3 (STAT3) and the Th2 cytokine, interleukin (IL)-33. However, the roles of SHARPIN in AD have not been fully elucidated.Here, we aimed to evaluate the signaling interactions of SHARPIN and IL-33 to improve our understanding of the pathogenesis of AD.Western blotting was used to detect the Janus kinase (JAK)/STAT signaling proteins and IL-33 protein in HaCaT cells to determine the key proteins mediating the interaction between SHARPIN and IL-33. The findings were validated by immunofluorescence and immunohistochemical staining. Chromatin immunoprecipitation assays were employed to evaluate the activity of STAT3 at the IL-33 promoter.We found that phospho-JAK2 and phospho-STAT3 were upregulated in SHARPIN-knockdown HaCaT cells. Subsequent chromatin immunoprecipitation assays revealed that STAT3 bound to the IL-33 promoter to mediate IL-33 expression. Moreover, SHARPIN-mediated expression of IL-33 was reduced after treatment of HaCaT cells with the JAK/STAT inhibitor ruxolitinib. STAT3 and IL-33 expression levels were higher in AD skin lesion tissues than in normal skin tissues.These findings suggested that SHARPIN modulated inflammation in HaCaT cells by inhibiting JAK/STAT signaling, supporting the application of SHARPIN as a potential therapeutic target for AD.

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