LAUSR

&NA; Tenuigenin (TGN), a major active component of polygala tenuifolia root, has been reported to have anti‐inflammatory effect. In this study, we investigated the anti‐neuroinflammatory effects of TGN on LPS‐induced inflammation both in vitro and in vivo. The levels of tumor necrosis factor ‐&agr; (TNF‐&agr;), Interleukin‐1&bgr; (IL‐1&bgr;), Interleukin‐6 (IL‐6), and prostaglandin E2 (PGE2) were measured by ELISA. The expression of Nuclear factor E2–related factor 2 (Nrf2) and heme oxygenase 1 (HO‐1) were detected by western blot analysis. The results showed that TGN strongly inhibited LPS‐induced TNF‐&agr;, IL‐1&bgr;, IL‐6, and PGE2 production. The expression of Nrf2 and HO‐1 were up‐regulated by TGN in a dose‐dependent manner. Furthermore, the anti‐inflammatory effects of TGN were significantly inhibited by transfection with Nrf2 siRNA or protoporphyrin (SnPP), an HO‐1 activity inhibitor. In vivo, TGN attenuated LPS‐induced memory deficit in the Morris water maze and passive avoidance tasks. Also, TGN inhibited LPS‐induced TNF‐&agr; and IL‐1&bgr; expression in brain tissues. In conclusion, the results of this study indicated that TGN inhibited LPS‐induced inflammatory responses in microglia via activating the Nrf2‐mediated HO‐1 signaling pathway.