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

Abstract

BACKGROUND AND PURPOSEBrassica 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 APPROACHThe expression of Inducible nitric oxide synthase (iNOS) and COX-2, TNF-a, IL-6 and IL-1b were determined by Western blot and/or RT-PCR respectively. To elucidate the underlying mechanism(s), activation of NF-kB 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 RESULTSPromoter assays for iNOS and COX-2 revealed that arvelexin inhibited LPS-induced NO and prostaglandin E2 production through the suppression of iNOS and COX-2 at the level of gene transcription. In addition, arvelexin inhibited NF-kBdependent inflammatory responses by modulating a series of intracellular events of IkB kinase (IKK)-inhibitor kBa (IkBa)-NF-kB signalling. Moreover, arvelexin inhibited IKKb-elicited NF-kB 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 IMPLICATIONSArvelexin down-regulated inflammatory iNOS, COX-2, TNF-a, IL-6 and IL-1b gene expression in macrophages interfering with the activation of IKKb and p38 mitogen-activated protein kinase, and thus, preventing NF-kB activation. AbbreviationsIkBa, inhibitor of NF-kB-a; IKKs, IkB kinases; iNOS, inducible nitric oxide synthase; LPS, lipopolysaccharide; MAPK, mitogen-activated protein kinase; PBS, phosphate-buffered saline; PGE2, prostaglandin E2

Anti-inflammatory effects of 7-hydroxyl-1-methylindole-3-acetonitrile, a synthetic arvelexin derivative, on the macrophages through destabilizing mPGES-1 mRNA and suppressing NF-κB activation

“…NF-jB-dependent reporter gene assay and Western blotting revealed that 7-HMIA inhibited the transcriptional activity of NF-jB and the level of p65, subunits of NF-jB, in nuclear fractions. These results are in agreement with our previous finding that arvelexin down-regulated the LPS-induced inflammatory NO and cytokines via inhibition of NF-jB in RAW 264.7 macrophages [19]. Furthermore, Western blotting revealed that 7-HMIA significantly decreased the LPS-induced phosphorylation of Akt.…”

“…Unfortunately, the molecular factors leading mPGES-1 mRNA stabilization are poorly known. Several reports have demonstrated that MAPKs (JNK, p38 kinase, and ERK) signaling regulates inflammatory genes through alterations in transcriptional efficiency [19,32] and also via the mRNA decay system [33][34][35]. The JNK1/2 inhibitor, SP600125, abrogated the increases in mPGES-1 mRNA stability, mPGES-1 protein synthesis, and PGE 2 release induced by IL-1b or LPS in cardiomyocytes [36].…”

“…Arvelexin significantly inhibited the LPS-induced production of NO, PGE 2 , and cytokines in macrophages. Arvelexin also reduced mortality due to sepsis in mice challenged with LPS, and showed anti-colitis properties in dextran sulfate sodium (DSS)-induced mice and colon epithelial cells via NF-jB inactivation [18,19]. A series of arvelexin analogs possessing methoxy, benzyloxy, or hydroxyl substitutes at the benzene ring of the indole structure, and introduction of methyl or several acyl substitutes at nitrogen, were synthesized in order to explore the preliminary structure-activity relationship and obtain more potent inhibitors [20].…”

Fucosterol isolated from Undaria pinnatifida inhibits lipopolysaccharide-induced production of nitric oxide and pro-inflammatory cytokines via the inactivation of nuclear factor-κB and p38 mitogen-activated protein kinase in RAW264.7 macrophages

“…Our previous study also indicated that MAPKs indeed participated in regulating LPS-induced pro-inflammatory mediators, and some natural compounds can possess anti-inflammatory activity by modulating MAPK activation (Kim et al, 2009;Shin et al, 2011). Similarly, fucosterol was found to inhibit the LPS-induced phosphorylations of p38 MAPK and MKK3/6, the latter of which is upstream of p38 MAPK.…”

16α, 17α-epoxypregnenolone-20-oxime inhibits NO and IL-6 production in LPS-treated RAW264.7 cells

“…In macrophages, the MAPK signaling pathway is one of the most extensively investigated intracellular signaling cascades involved in the LPS-induced inflammatory response (5)(6)(7)(8). The MAPK pathway is comprised of at least three signaling components: Extracellular signal-regulated kinases 1/2 (ERK 1/2); c-Jun N-terminal kinase (JNK); and p38 MAPK, all of which have been demonstrated to induce the release of immune-related cytotoxic factors and proinflammatory cytokines (9)(10)(11).…”