miR-22 inhibits synovial fibroblasts proliferation and proinflammatory cytokine production in RASF via targeting SIRT1

Background/aims: Rheumatoid arthritis synovial fibroblasts (RASF) play an essential role in the pathogenesis of rheumatoid arthritis (RA). This study aimed to investigate the biological effects of miR-22 on RASFs. Methods: RT-qPCR was used to detect the expressions of miR-22 and SIRT1 in RA synovial tissue. The results of miR-22 on the proliferation of RASF were examined by MTT assay. The effects of miR-22 on the secretion of TNF-α, IL-1β, and IL-6 in RASF were measured by ELISA. Target gene prediction and screening, and luciferase reporter assay were used to testify downstream target genes of miR-22. RT-qPCR and western blotting were used to detect the mRNA and protein expression of SIRT1. Results: miR-22 was significantly decreased in RA synovial tissue, while SIRT1 was significantly increased in RA synovial tissue. Over-expression of miR-22 significantly inhibited the proliferation of RASFs and the secretions of inflammatory cytokines (TNF-α, IL-1β, and IL-6) in RASFs. SIRT1 was identified as a direct target of miR-22. Over-expression of miR-22 reduced the expression level of SIRT1 in RASFs. Over-expression of SIRT1 reversed the effect of miR-22 on the proliferation of RASFs and the secretion of inflammatory cytokines. Conclusion: MIR-22 was significantly down-regulated in RASF cells, which affected the secretions of inflammatory cytokines and cell proliferation by regulating SIRT1.