miR‐34a Mediates IL‐23/IL‐17 Immune Inflammation and Promotes Cell Proliferation in HaCaT Cells by Targeting SIRT1/NLRP3

Psoriasis is a common immune‐mediated skin disorder. miR‐34a, as a significant regulatory component, has been involved in the regulation of immune‐inflammatory responses. Previous studies have shown that miR‐34a is abnormally expressed in psoriasis cell models. However, the role of miR‐34a in psoriasis remains unvalidated by any existing studies. We co‐stimulated HaCaT cells with IL‐17A, IL‐22, TNF‐α, IL‐1α, and M5 to establish an in vitro model of psoriasis. qPCR was used to detect the expression of miR‐34a; ELISA was performed to measure the secretion levels of pro‐inflammatory cytokines IL‐1β, IL‐6, IL‐17, and IL‐23 in HaCaT cells; CCK‐8 and EdU staining assays were used to assess cell growth and proliferation; Western blot analysis was employed to assess the expression levels of relevant proteins, including SIRT1, NLRP3, ASC, pro‐Caspase‐1, and Caspase‐1; dual‐luciferase reporter gene assays and RNA immunoprecipitation (RIP) were conducted to investigate the interaction between miR‐34a and SIRT1. Additionally, a mouse psoriasis model was induced by imiquimod (IMQ) to validate the role of miR‐34a in vivo. qPCR results found that miR‐34a was upregulated in HaCaT cells. ELISA results indicated that the levels of IL‐1β, IL‐6, IL‐17, and IL‐23 were significantly elevated in the M5‐treated group. CCK‐8 and EdU staining assays revealed that M5 treatment notably increased the proliferation and viability of HaCaT cells. After treatment with the miR‐34a inhibitor, the levels of cytokines and cell proliferation were significantly reduced. Western blot analysis showed that M5 treatment resulted in a significant decrease in SIRT1 protein levels, while the expression levels of NLRP3, ASC, pro‐Caspase‐1, and Caspase‐1 were increased. In contrast, miR‐34a‐inhibitor treatment showed the opposite results. Dual‐luciferase reporter and RIP assays indicated a negative feedback interaction between miR‐34a and SIRT1. Rescue experiments showed that overexpression of SIRT1 effectively inhibited NLRP3 expression, significantly reduced IL‐23/IL‐17 immune‐inflammatory responses, and suppressed HaCaT cell proliferation, while overexpression of NLRP3 had the opposite effects. In the IMQ‐induced mouse psoriasis model, the IMQ group showed severe psoriasis‐like phenotypes, obvious skin pathological changes, upregulated miR‐34a expression, and increased skin cytokine levels; all these abnormalities were alleviated by miR‐34a inhibitor treatment. miR‐34a mediates the IL‐23/IL‐17 immune‐inflammatory response and promotes HaCaT cell proliferation by regulating the SIRT1/NLRP3 pathway.