Anti-inflammatory effects of Polygala tenuifolia root through inhibition of NF-κB activation in lipopolysaccharide-induced BV2 microglial cells

Ethnopharmacological relevance: The root of Polygala tenuifolia Willd is a well-known traditional Oriental medicine and has been prescribed for treatment of dysfunction in memorial systems and various brain inflammatory diseases. The present study was designed to validate the anti-inflammatory effects of the water extract of Polygala tenuifolia root (WEPT). Materials and methods: The anti-inflammatory properties of WEPT were studied using lipopolysaccharide (LPS)-stimulated murine BV2 microglia model. As inflammatory parameters, the production of nitric oxide (NO), inducible NO synthase (iNOS), cyclooxygenase (COX)-2, prostaglandin E-2 (PGE(2)), tumor necrosis factor (TNF)-alpha, and interleukin (IL)-1 beta were evaluated. We also examined the extract's effect on the activity of nuclear factor-kappaB (NF-kappa B), and toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (Myd-88) expression. Results: WEPT suppressed LPS-induced production of NO, PGE(2), and expression of iNOS and COX-2 in a dose-dependent manner, without causing cytotoxicity. It also significantly reduced generation of proinflammatory cytokines, including IL-1 beta and TNF-alpha. In addition, WEPT suppressed NF-kappa B translocation by blockade of IkappaB-alpha (I kappa B-alpha) degradation and inhibited TLR4 and Myd-88 expression in LPS-stimulated BV2 cells. Conclusions: These results indicate that the inhibitory effects of WEPT on LPS-stimulated inflammatory mediator production in BV2 microglia are associated with suppression of the NF-kappa B and toll-like receptor signaling pathways. Therefore, Polygala tenuifolia extracts may be useful in treatment of neurodegenerative diseases by inhibition of inflammatory mediator production in activated microglia. (C) 2011 Elsevier Ireland Ltd. All rights reserved.