Rhynchophylline attenuates LPS-induced pro-inflammatory responses through down-regulation of MAPK/NF-κB signaling pathways in primary microglia.

Excessive activation of microglial cells has been implicated in various types of neuroinflammation. Suppression of microglial activation would have therapeutic benefits, leading to the alleviation of the progression of neurodegeneration. In this study, the inhibitory effects of rhynchophylline (RIN), a tetracyclic oxindole alkaloid component isolated from Uncaria rhynchophylla (Miq.) Jacks., on the production of pro-inflammatory mediators were investigated in lipopolysaccharide (LPS)-stimulated microglia. The results showed that RIN markedly reduced the production of nitric oxide (NO), prostaglandins E(2) (PGE(2) ), monocyte chemoattractant protein (MCP-1), tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in LPS-activated microglia. The mRNA expression levels of iNOS and COX-2 were also depressed by RIN in a concentration-dependent manner. Further studies revealed that RIN blocked IκBα phosphorylation and degradation, inhibited the phosphorylation of mitogen-activated protein kinases (MAPKs). In summary, these data suggest that RIN suppresses inflammatory responses of microglia and may act as a potential therapeutic agent for various neurodegenerative diseases involving neuroinflammation.