Aciculatin inhibits lipopolysaccharide-mediated inducible nitric oxide synthase and cyclooxygenase-2 expression via suppressing NF-B and JNK/p38 MAPK activation pathways

Abstract

Objectives. Natural products have played a significant role in drug discovery and development. Inflammatory mediators such as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) have been suggested to connect with various inflammatory diseases. In this study, we explored the anti-inflammatory potential of aciculatin (8-((2R,4S,5S,6R)-tetrahydro-4,5- dihydroxy-6-methyl-2H-pyran-2-yl)-5-hydroxy-2-(4-hydroxyphenyl) -7-methoxy-4H-chromen-4-one), one of main components of Chrysopogon aciculatis, by examining its effects on the expression and activity of iNOS and COX-2 in lipopolysaccharide (LPS)-activated macrophages. Methods. We used nitrate and prostaglandin E2(PGE2) assays to examine inhibitory effect of aciculatin on nitric oxide (NO) and PGE2levels in LPS-activated mouse RAW264.7 macrophages and further investigated the mechanisms of aciculatin suppressed LPS-mediated iNOS/COX-2 expression by western blot, RT-PCR, reporter gene assay and confocal microscope analysis. Results: Aciculatin remarkably decreased the LPS (1 g/mL)-induced mRNA and protein expression of iNOS and COX-2 as well as their downstream products, NO and PGE2respectively, in a concentration-dependent manner (1-10 M). Such inhibition was found, via immunoblot analyses, reporter gene assays, and confocal microscope observations that aciculatin not only acts through significant suppression of LPS-induced NF-B activation, an effect highly correlated with its inhibitory effect on LPS-induced IB kinase (IKK) activation, IB degradation, NF-B phosphorylation, nuclear translocation and binding of NF-B to the B motif of the iNOS and COX-2 promoters, but also suppressed phosphorylation of JNK/p38 mitogen-activated protein kinases (MAPKs). Conclusion: Our results demonstrated that aciculatin exerts potent anti-inflammatory activity through its dual inhibitory effects on iNOS and COX-2 by regulating NF-B and JNK/p38 MAPK pathways. © 2011 Hsieh et al; licensee BioMed Central Ltd.