Sulfuretin isolated from heartwood of Rhus verniciflua inhibits LPS-induced inducible nitric oxide synthase, cyclooxygenase-2, and pro-inflammatory cytokines expression via the down-regulation of NF-kappaB in RAW 264.7 murine macrophage cells

Abstract

It has been reported that Rhusverniciflua exhibits anti-inflammatory, anti-oxidant and anti-cancer activities. However, little is known about biological activity of sulfuretin, a flavonoid isolated from R.verniciflua. In the present study, we investigated the anti-inflammatory effect and the underlying molecular mechanisms of sulfuretin in lipopolysaccharide (LPS)-induced RAW 264.7 cells. Sulfuretin dose-dependently reduced the productions of nitric oxide (NO), prostaglandin E(2) (PGE(2)), tumor necrosis factor-alpha (TNF-alpha), and interleukin-1 beta (IL-1 beta) induced by LPS. Consistent with these findings, sulfuretin significantly suppressed the LPS-induced expressions of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), TNF-alpha, and IL-1 beta. In addition, sulfuretin attenuated LPS-induced DNA binding and the transcriptional activities of nuclear factor-kappa B (NF-kappaB), which was accompanied by a parallel reduction of degradation and phosphorylation of inhibitory kappa B-alpha (I kappaB-alpha) and consequently by decreased nuclear translocation of p65 subunit of NF-kappaB. Furthermore, pretreatment with sulfuretin significantly inhibited the LPS-stimulated activation of I kappaB kinase beta (IKK beta). Taken together, these results suggest that the anti-inflammatory effect of sulfuretin in LPS-treated RAW 264.7 macrophages is associated with the suppression of NF-kappaB transcriptional activity via the inhibitory regulation of IKKbeta phosphorylation.