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

Background and purpose: Traditionally, the stem and root bark of Ulmus davidiana var. japonica (Ulmaceae) have been known to be anti-inflammatory in Korea [1]. Anti-inflammatory effects of torilin, isolated from this plant [2] and the underlying mechanisms were examined by using lipopolysaccharide (LPS)-stimulated microglial BV2 cells.

Experimental approach: 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-1beta (IL-1beta) 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-kappaB (NF-kappaB) and cyclic AMP-responsive element (CRE)-binding protein (CREB).

Key results: Torilin significantly reduced the LPS-induced expression of iNOS, COX-2 and IL-1beta, and the subsequent release of NO, prostaglandin E₂ and IL-1beta 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-kappaB and CREB was shown by torilin-mediated recovery of LPS-induced degradation of inhibitor kappaB-alpha and suppression of LPS-induced phosphorylation of CREB respectively.

Conclusion and implications: This study indicates that torilin inhibited LPS-induced iNOS, COX-2 and IL-1beta via down-regulation of ERK1/2, p38 MAPK, NF-kappaB and CREB and suggests that torilin has a potential as an anti-inflammatory drug candidate.

References: [1] Lee, S.J. (1966) Korean Folk Medicine. Seoul National University Press. Seoul.

[2] Kim, Y.C. et al. (2007) Fitoterapia 78:196–199.