MiR-3926 inhibits synovial fibroblasts proliferation and inflammatory cytokines secretion through targeting toll like receptor 5

Rheumatoid arthritis synovial fibroblasts (RASFs) play a key role in the pathogenesis of rheumatoid arthritis (RA). This study was aimed to investigate the effects of miR-3926 on the biological activities of RASFs. The results showed that miR-3926 was significantly down-regulated in RASFs and RA synovial tissue. Overexpression of miR-3926 significantly inhibited RASFs proliferation and decreased the secretion of inflammatory cytokines including TNF-alpha, IL-1 beta and IL-6 in RASFs. TLR5 was identified to be a direct target of miR-3926. TLR5 showed an opposite expression trends with miR-3926 in RASFs and RA synovial tissue. Overexpression of miR-3926 led to a reduction of endogenous TLR5 in RASFs, whereas down-regulation of miR-3926 increased TLR5 expression. Knocking down of TLR5 significantly inhibited RASFs proliferation and inflammatory cytokines secretion. Rescue experiments with a miR-3926-resistant variant of TLR5 showed that overexpression of TLR5 restored RASFs proliferation and inflammatory cytokines secretion in miR-3926-overexpressing RASFs. In conclusion, miR-3926 is downregulated in RA synovial tissues and its overexpression caused the inhibitory effects on RASF proliferation and inflammatory cytokines secretion by targeting TLR5. The miR-3926/TLR5 pathway may represent a novel target for prevention and treatment of RA.