Tetrandrine suppresses articular inflammatory response by inhibiting pro-inflammatory factors via NF-κB inactivation.

Targeting activated macrophages using anti-inflammatory phytopharmaceuticals has been proposed as general therapeutic approaches for rheumatic diseases. Besides macrophages, chondrocytes are another promising target of anti-inflammatory agents. Tetrandrine is a major bisbenzylisoquinoline alkaloid isolated from Stephania tetrandrae S. Moore which has been used for 2,000 years as an antirheumatic herbal drug in China. Although, the anti-inflammatory effect of tetrandrine has been demonstrated, the mechanism has not been clearly clarified. In this study, we designed a comprehensive anti-inflammatory evaluation system for tetrandrine, including complete Freund's adjuvant (CFA)-induced arthritis rat, LPS-induced macrophage RAW 264.7 cells, and chondrogenic ATDC5 cells. The results showed that tetrandrine alleviated CFA-induced foot swelling, synovial inflammation, and pro-inflammatory cytokines secretion. Tetrandrine could inhibit IL-6, IL-1β, and TNF-α expression via blocking the nuclear translocation of nuclear factor (NF)-κB p65 in LPS-induced RAW 264.7 cells. Moreover, ATDC5 cells well responded to LPS induced pro-inflammatory mediators secretion and tissue degradation, and tetrandrine could also inhibit the production of nitric oxide and prostaglandin E2 , as well as the expression of matrix metalloproteinase (MMP)-3 and tissue inhibitor of metalloproteinase (TIMP)-1 via inhibiting IκBα phosphorylation and degradation. In conclusion, the results showed that one of the anti-inflammatory mechanisms of tetrandrine was inhibiting IκBα and NF-κB p65 phosphorylation in LPS-induced macrophage RAW 264.7 cells and chondrogenic ATDC5 cells. Moreover, we introduce a vigorous in vitro cell screening system, LPS-induced murine macrophage RAW 264.7 cells coupling chondrogenic ADTC5 cells, for screening anti-rheumatic drugs.