201. Dioscoreanone suppresses LPS‐induced nitric oxide production and inflammatory cytokine expression in RAW 264.7 macrophages by NF‐κB and ERK1/2 signaling transduction
- Author
-
Poonsit Hiransai and Arunporn Itharat
- Subjects
Lipopolysaccharides ,MAP Kinase Signaling System ,Interleukin-1beta ,Nitric Oxide Synthase Type II ,Inflammation ,Biology ,Nitric Oxide ,Biochemistry ,Cell Line ,Nitric oxide ,Proinflammatory cytokine ,Inhibitory Concentration 50 ,Mice ,chemistry.chemical_compound ,Genes, Reporter ,medicine ,Animals ,Luciferases ,Molecular Biology ,RAW 264.7 Cells ,Mitogen-Activated Protein Kinase 1 ,Mitogen-Activated Protein Kinase 3 ,Dose-Response Relationship, Drug ,Interleukin-6 ,Macrophages ,NF-kappa B ,Quinones ,NF-κB ,Cell Biology ,Phenanthrenes ,Dicoumarol ,Antineoplastic Agents, Phytogenic ,Acetylcysteine ,Cell biology ,IκBα ,Gene Expression Regulation ,chemistry ,medicine.symptom ,Signal transduction ,medicine.drug - Abstract
Dioscoreanone, a 1,4-phenanthraquinone isolated from an ethanolic extract of the rhizome of Dioscorea membranacea, Pierre ex Prain & Burkill, a plant which has been used to treat inflammation and cancer in Thai Traditional Medicine. In this study, the mechanisms of dioscoreanone on LPS-induced NO production and cytokine expression through the activation of NF-κB and ERK1/2 are demonstrated in RAW 264.7 cells. Through measurement with Griess reagent, dioscoreanone was found to reduce NO levels with an IC(50) value of 2.50 ± 0.64 µM, due to the significant suppression of LPS-induced iNOS mRNA expression, as well as IL-1β and IL-6 levels at a concentration of 6 µM. At the signal transduction level, using the pNFκB-Luciferase reporter system, dioscoreanone significantly inhibited NF-κB transcriptional activity, which resulted from the prevention of IκBα degradation. In addition, dioscoreanone in the range of 1.2-5 µM significantly enhanced LPS-induced ERK1/2 activation and dioscoreanone alone induced the activation of ERK1/2 proteins in a concentration- and time-dependent response. The activation of ERK1/2 proteins by dioscoreanone was due to both an arylating reaction, which was suppressed by N-acetyl cysteine, and a redox cycling reaction of NQOR, which was inhibited by dicoumarol. In conclusion, the mechanisms of dioscoreanone on the inhibition of NO production and mRNA expression of iNOS, IL-1β, and IL-6 were due to both the inhibition of NF-κB activation and the activation of ERK1/2 proteins. The activation of dioscoreanone may in turn inhibit the binding of NF-κB to pro-inflammatory gene promoters in LPS-induced RAW264.7 macrophage cells.
- Published
- 2012