Genipin Inhibits LPS-Induced Inflammatory Response in BV2 Microglial Cells

Genipin, an aglycon of geniposide, has been reported to have anti-inflammatory effect. However, the anti-inflammatory activity of genipin on LPS-stimulated BV2 microglial cells has not been reported. In this study, we investigated the molecular mechanisms responsible for the anti-inflammatory activity of genipin both in vivo and in vitro. The levels of TNF-α, IL-1β, NO and PGE₂ were detected by ELISA. The expression of Nrf2, HO-1, and NF-κB were detected by western blot analysis. In vivo, genipin significantly attenuated LPS-induced memory deficit in the Morris water maze and passive avoidance tasks. Genipin also inhibited LPS-induced TNF-α and IL-1β expression in brain tissues. In vitro, our results showed that genipin inhibited LPS-induced TNF-α, IL-1β, NO and PGE₂ production in a concentration-dependent manner. Genipin also suppressed LPS-induced NF-κB activation. In addition, the expression of Nrf2 and HO-1 were up-regulated by treatment of genipin. Furthermore, the inhibition of genipin on inflammatory mediator production was attenuated by transfection with Nrf2 siRNA. In conclusion, genipin inhibited LPS-induced inflammatory response by activating Nrf2 signaling pathway in BV2 microglia.