Inhibitory effects of the root extract of Litsea cubeba (lour.) pers. on adjuvant arthritis in rats

The dried root of Litsea cubeba (Lour.) Pers. (Family Lauraceae) has long been used as a folk remedy in Traditional Chinese Medicine (TCM) and Dai Ethnopharmacy for the treatment of rheumatic diseases in southwestern China.This study investigated the preventive efficacy of Litsea cubeba root in treating rheumatoid arthritis using Freund's complete adjuvant (CFA) induced arthritis (AA) in rat model.Arthritis was induced in male Wistar rats by immunization with CFA. Ethanol extract (EELC) and water extract (WELC) of Litsea cubeba root both at 50mg/kg and 200mg/kg were orally administered from a day after the induction of arthritis. Paw swelling, arthritic score, body weight growth rate, index of thymus and spleen were observed, and the production of TNF-α, IL-1β, IL-6 and IL-10 in serum were measured by enzyme-linked immunosorbent assay. The expression levels of inflammatory enzymes like cyclooxygenase and lipoxygenase were also measured by enzyme-linked immunosorbent assay. Moreover, histological changes in the ankle joint were analyzed in AA rats.Both EELC and WELC significantly suppressed paw swelling and arthritic score, increased the loss in body weight and decreased the index of thymus. Histopathological improvement in joint architecture was also observed in EELC, WELC-treated AA rats. The expression levels of cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) were decreased on treatment with EELC and WELC. Furthermore, the overproduction of TNF-α, IL-1β and IL-6 were remarkably attenuated in serum of all Litsea cubeba-treated rats, however, IL-10 was markedly increased at doses of 50mg/kg of EELC and WELC.These results indicate that extract of Litsea cubeba root significantly attenuates adjuvant arthritis in rats by decreasing the levels of TNF-α, IL-1β and IL-6 and increasing of IL-10 in serum as well as down-regulate the levels of inflammatory enzymes such as COX-2 and 5-LOX. This suggests that Litsea cubeba root might be used as a therapeutic agent for the treatment of human arthritis.