Arvelexin from Brassica rapa suppresses NF-κB-regulated pro-inflammatory gene expression by inhibiting activation of IκB kinase

Abstract

BACKGROUND AND PURPOSE Brassica rapa species constitute one of the major sources of food. In the present study, we investigated the anti-inflammatory effects and the underlying molecular mechanism of arvelexin, isolated from B. rapa, on lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages and on a model of septic shock induced by LPS. EXPERIMENTAL APPROACH The expression of Inducible nitric oxide synthase (iNOS) and COX-2, TNF-α, IL-6 and IL-1β were determined by Western blot and/or RT-PCR respectively. To elucidate the underlying mechanism(s), activation of NF-κB activation and its pathways were investigated by electrophoretic mobility shift assay, reporter gene and Western blot assays. In addition, the in vivo anti-inflammatory effects of arvelexin were evaluated in endotoxaemia induced with LPS. KEY RESULTS Promoter assays for iNOS and COX-2 revealed that arvelexin inhibited LPS-induced NO and prostaglandin E 2 production through the suppression of iNOS and COX-2 at the level of gene transcription. In addition, arvelexin inhibited NF-κB-dependent inflammatory responses by modulating a series of intracellular events of IκB kinase (IKK)-inhibitor κBα (IκBα)-NF-κB signalling. Moreover, arvelexin inhibited IKKβ-elicited NF-κB activation as well as iNOS and COX-2 expression. Serum levels of NO and inflammatory cytokines and mortality in mice challenged injected with LPS were significantly reduced by arvelexin. CONCLUSION AND IMPLICATIONS Arvelexin down-regulated inflammatory iNOS, COX-2, TNF-α, IL-6 and IL-1β gene expression in macrophages interfering with the activation of IKKβ and p38 mitogen-activated protein kinase, and thus, preventing NF-κB activation. © 2011 The British Pharmacological Society.