Brucine inhibits TNF-α-induced HFLS-RA cell proliferation by activating the JNK signaling pathway.

Rheumatoid arthritis (RA) is a diffuse connective tissue disease. Brucine selectively inhibits cell immunity, immune hypersensitivity and induces apoptosis. The current study aimed to investigate effects of brucine on human fibroblast-like synoviocytes (HFLS) of RA and to clarify associated molecular mechanisms. HFLS-RA were treated with tumor necrosis factor (TNF)-α prior to treatment with brucine at carrying concentrations. Cell Counting Kit-8 assays were performed to evaluate HFLS-RA proliferation. Western blot assays were employed to examine c-Jun N-terminal kinase (JNK) expression and phosphorylation in TNF-α-induced HFLS-RA. An association between brucine treatment and JNK phosphorylation was assessed by employing a linear regression analysis. The results suggested that low doses of brucine (0.125 and 0.25 mg/ml) significantly reversed proliferation effects induced by TNF-α, however, final cell viabilities were increased compared with the untreated control (P>0.05 and P<0.05, respectively). High brucine doses (≥0.5 mg/ml) significantly reversed TNF-α-induced proliferation and further inhibited viability compared with the untreated control (P<0.05). Regarding JNK expression, there were no significant differences among the brucine treatment, and between the Control and the TNF-α groups (P>0.05). Brucine treatment significantly decreased JNK phosphorylation compared with the TNF-α group (P<0.05). JNK specific inhibitor, SP600125, significantly inhibited brucine-induced cell viability enhancement compared with the brucine-treated groups without inhibitor (P<0.05). A linear regression analysis suggested that brucine was associated with JNK phosphorylation in TNF-α-treated HFLS-RA. In conclusion, brucine significantly inhibited TNF-α-induced HFLS-RA proliferation by activating the JNK signaling pathway. Therefore, brucine may have potential clinical applications in the treatment of RA.