Therapeutic effect of syringin on adjuvant arthritis in rats and its mechanisms

ABSTRACT

This study is to investigate the therapeutic effect of syringin on adjuvant arthritis (AA) in rats and its mechanisms. Complete Freund's adjuvant (FCA) was used to induce AA in rats. Secondary paw swelling of AA rats was measured with volume meter. Pain response and polyarthritis index were scored. Meanwhile, splenic lymphocyte proliferation response induced by concanavalin A (ConA) or lipopolysaccharide (LPS) was examined with MTT assay. IL-2 production of splenic lymphocytes and IL-1 beta, TNF-alpha production of peritoneal macrophage (PM phi) were estimated by enzyme linked immunosorbent assay (ELISA). The secondary inflammation of AA rats appeared on the 14th day after injection of FCA. Syringin and tripterygium glycosides (TG) were given by intragastric administration for 16 days from the 14th day. Treatment of AA rats with syringin and TG from the 22th day significantly attenuated the secondary hind paw swelling, as well as relieved the pain response and the polyarthritic symptoms of the whole body as compared with that of the AA model group. The suppressed lymphocyte proliferation and IL-2 production of splenic lymphocytes in AA rats were reversed by treatment with syringin. Meanwhile, syringin remarkably down-regulated IL-1 beta, TNF-alpha productions from PM phi. These results indicate that anti-inflammatory effects of syringin on AA rats are mediated by modulating the immune function of abnormal cells and the balance of cytokines.