Inhibition of inducible NO synthase, cyclooxygenase-2 and interleukin-1β by torilin is mediated by mitogen-activated protein kinases in microglial BV2 cells

Traditionally, the stem and root bark of Ulmus davidiana var. japonica (Ulmaceae) have been known to be anti-inflammatory in Korea. Anti-inflammatory effects of torilin, isolated from this plant and the underlying mechanisms were examined by using lipopolysaccharide (LPS)-stimulated microglial BV2 cells. The cells were treated with torilin prior to LPS exposure and the effects on pro-inflammatory enzymes, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), and a pro-inflammatory cytokine, interleukin-1 beta (IL-1 beta) were analysed by RT-PCR, Western blot or elisa. To reveal the mechanism of action of torilin we investigated the involvement of mitogen-activated protein kinase (MAPK) cascades and their downstream transcription factors, nuclear factor-kappa B (NF-kappa B) and cyclic AMP-responsive element (CRE)-binding protein (CREB). Torilin significantly reduced the LPS-induced expression of iNOS, COX-2 and IL-1 beta, and the subsequent release of NO, prostaglandin E-2 and IL-1 beta into culture medium. LPS stimulation of extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 MAPK was inhibited by torilin. In addition, the inhibitory effect of torilin on NF-kappa B and CREB was shown by torilin-mediated recovery of LPS-induced degradation of inhibitor kappa B-alpha and suppression of LPS-induced phosphorylation of CREB respectively. This study indicates that torilin inhibited LPS-induced iNOS, COX-2 and IL-1 beta via down-regulation of ERK1/2, p38 MAPK, NF-kappa B and CREB and suggests that torilin has a potential as an anti-inflammatory drug candidate.