Abstract: Objective　To explore the protective effect of paeonol on IL-1β induced inflammatory response of human fibroblast-like synoviocytes and rheumatoid arthritis (HFLS-RA) and its possible mechanism. Methods　The HFLS-RA cells were divided into control group, 10 μmol/L paeonol group and 0.1, 1, 10 and 100 μmol/L HFLS-RA groups. The effect of paeonol on the proliferation of HFLS-RA was detected by MTT. The levels of TNF-α and IL-6 in HFLS-RA were detected by enzyme linked immunosorbent assay (ELISA). The nuclear translocation of NF-κB p65 was observed by immuno-fluorescence in blank control group, 10 μg/L IL-1β group and 10 μmol/L paeonol group. The expressions of MMP-1, MMP-3 and TLR4 groups in blank control group, 10 μg/L IL-1β group, 0.1, 1, 10 μmol/L paeonol and negative control group (only treated with 10 μmol/L paeonol) were detected by Western blot assay. Twenty-four male DBA/1 mice were randomly divided into control group, CIA group and treatment group. The limb cumulative score was evaluated. The pathological changes of joint tissues were observed by HE staining. The contents of TNF -α and IL-1β in synovial tissue were detected by ELISA. Results　Paeonol showed no inhibitory effect on IL-1β induced HFLS-RA proliferation. Compared with the blank control group, the expression levels of TNF-α, IL-6, NF-κB p65 nuclear translocation, MMP-1, MMP-3 and TLR4 protein were increased in 10 μg/L IL-1β group, and these changes could be reversed by paeonol intervention (P＜0.05). Compared with the CIA group, the limb cumulative score decreased significantly in the treatment group (P＜0.05). HE observation showed that the pathological changes of ankle joint were improved after 48 days of paeonol treatment, in which the inflammatory cells decreased significantly and the cartilage damage was alleviated. The levels of TNF-α and IL-1β in synovial tissue were lower in treatment group than those of CIA group. Conclusion　Paeonol can reduce the IL-1β induced expression levels of inflammatory factors in HFLS-RA and relieve arthritis symptoms in CIA mice, which may be related to the down regulation of TLR4-NF-κB p65 pathway.

Key words: arthritis, rheumatoid, cortex moutan, interleukin-1beta, NF-kappa B, matrix metalloproteinases, paeonol, human fibroblast like synoviocytes