TRPM7 facilitates fibroblast-like synoviocyte proliferation, metastasis and inflammation through increasing IL-6 stability via the PKCα-HuR axis in rheumatoid arthritis.

Transient receptor potential melastatin 7 (TRPM7) is a cation channel that plays a role in the progression of rheumatoid arthritis (RA), yet its involvement in synovial hyperplasia and inflammation has not been determined. We previously reported that TRPM7 affects the destruction of articular cartilage in RA. Herein, we further confirmed the involvement of TRPM7 in fibroblast-like synoviocyte (FLS) proliferation, metastasis and inflammation. We observed increased TRPM7 expression in FLSs derived from human RA patients. Pharmacological inhibition of TRPM7 protected primary RA-FLSs from proliferation, metastasis and inflammation. Furthermore, we found that TRPM7 contributes to RA-FLS proliferation, metastasis and inflammation by increasing the intracellular Ca2+ concentration. Mechanistically, the PKCα-HuR axis was demonstrated to respond to Ca2+ influx, leading to TRPM7-mediated RA-FLS proliferation, metastasis and inflammation. Moreover, HuR was shown to bind to IL-6 mRNA after nuclear translocation, which could be weakened by TRPM7 channel inhibition. Additionally, adeno-associated virus 9-mediated TRPM7 silencing is highly effective at alleviating synovial hyperplasia and inflammation in adjuvant-induced arthritis rats. In conclusion, our findings unveil a novel regulatory mechanism involved in the pathogenesis of RA and suggest that targeting TRPM7 might be a potential strategy for the prevention and treatment of RA.