Abstract: AIM: To explore the possible mechanism of Radix Tetrastigma (RT) on anti-rheumatoid arthritis (RA).  METHODS: The rat model of RA was established by intradermal injection of complete Freund's adjuvant into the right hind foot of SD rats. RT Extract with different dosage was continuous intragastric administration for 3 weeks, then, the degree of foot swelling, arthritis index score, joint heat and grip of each rat was measured respectively. ELISA was used to detect the expression levels of Interleukin (IL) 6, IL-17, IL-10, tumor necrosis factor-α, and rheumatoid factor. Fully automatic hemorheometer was applied to measure hemorheology indexes. The number of CD4+IL-17+T cells and CD4+CD25+Foxp3+T cells in peripheral blood were measured by flow cytometry. HE staining was used to observe the pathological changes of ankle joints. Western blot was used to measure expressions of IL-6, RORγt, Foxp3, STAT3 and p-STAT3 proteins in synovial tissues of joints. RESULTS: RT could significantly decrease swelling degree, arthritis index scores and joint heat of rats with RA. Grasping power of rats was improved and the serum levels of IL-6, IL-17, TNF-α and RF were significantly decreased, levels of IL-10 was increased significantly. Th17/Treg ratio in whole blood was decreased. Protein expressions of IL-6, STAT3, p-STAT3, and RORγt were down-regulated and Foxp3 protein was up-regulated in synovial tissues of joints. Functional morphology of the ankle joint of the plantar of rats with RA were significantly improved. CONCLUSION: RT has obvious anti-rheumatoid arthritis effect, and its mechanism may be related to regulating Th17/Treg balance by regulating IL-6/STAT3 axis.

Key words: radix tetrastigma, IL-6/STAT3 axis, Th17/Treg balance, rheumatoid arthritis