Shikonin alleviates collagen-induced arthritis mice by inhibiting M1 macrophage polarization

OBJECTIVE: To investigate the effects of shikonin(SKN) on M1 and M2 polarization of macrophages both in vitro and in vivo. METHODS: Collagen-induced arthritis(CIA) in male DBA/1 mice were treated with a dose of 4 mg/kg/day of SKN for 23 d(n = 6/group). The histopathology of inflamed joints in CIA mice was evaluated to test the antiarthritic effect of SKN. M1/M2 polarization of macrophages induced by lipopolysaccharide(LPS) and interferon(IFN)-γ or interleukin(IL)-4 and IL-13, were used to assess the effect of SKN(0.05, 0.1, and 0.2 μM). The effect of SKN on the protein expression of nitric oxide synthase, arginase, CD68, and CD206 was evaluated using western blot analysis. RESULTS: The results of this study revealed that SKN delayed the arthritis feet symptom score, reduced the incidence rate of arthritis, and relieved the inflammation of joints in CIA mice. SKN inhibited M1 macrophage polarization but did not affect M2 macrophage polarization in the joints of CIA mice. Moreover, SKN inhibited M1 polarization induced by LPS and IFN-γ, but did not affect M2 polarization induced by IL-4 and IL-13. CONCLUSION: These findings suggest that SKN alleviated CIA through inhibiting M1 macrophage polarization and has great potential as a new drug for RA treatment.