Quercetin suppresses inflammatory cytokine production in rheumatoid arthritis fibroblast‑like synoviocytes

Rheumatoid arthritis (RA) is a chronic, progressive and systemic autoimmune disease mainly characterized by symmetric multijoint synovitis. Quercetin has anti-inflammatory, anti-oxidation and immune regulation activities, and therefore shows high medicinal value. The present study aimed to observe the effect of quercetin on fibroblast-like synoviocytes (FLSs) in RA. Rheumatoid arthritis fibroblast-like synoviocytes (RAFLSs) were pretreated with 50 nmol/l quercetin for 2 h and were then stimulated using TNF-α for 24 h for subsequent experiments. RAFLSs were transfected with short interfering (si)-X-inactive specific transcript (XIST), microRNA (miR)-485 mimic, miR-485 inhibitor or si-PSMB8 or combination. ELISA, PCR and western blotting was used to evaluate the effect of quercetin on RAFLSs treated with TNF-α. It was revealed that quercetin inhibited the production of inflammatory cytokines and the expression of XIST in RAFLSs induced by TNF-α. Bioinformatics analysis indicated that XIST acted as a sponge for miR-485 and that proteasome subunit β type-8 (PSMB8) was a direct target of miR-485. Moreover, PSMB8 functioned as a suppressor in inflammatory cytokine production of RAFLSs induced by TNF-α. Overall, quercetin was observed to inhibit the production of inflammatory cytokines and the expression of XIST in RAFLSs induced by TNF-α. Moreover, XIST-silencing could suppress the inflammatory reaction by sponging miR-485 in cells treated with TNF-α. Altogether, quercetin could suppress the development of RA