Dioscoreanone suppresses LPS-induced nitric oxide production and inflammatory cytokine expression in RAW 264.7 macrophages by NF-κB and ERK1/2 signaling transduction.
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.
Department of Applied Thai Traditional Medicine, Thammasat University, Klongluang, Pathumtani 12121, Thailand. iarunporn@yahoo.com
Arunporn
A
Itharat
Poonsit
P
Hiransai
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects; D017930:Genes, Reporter; D020128:Inhibitory Concentration 50; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008156:Luciferases; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D009569:Nitric Oxide / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D010616:Phenanthrenes / Q000494:pharmacology*; D011809:Quinones / Q000494:pharmacology*
D000972:Antineoplastic Agents, Phytogenic; D053583:Interleukin-1beta; D015850:Interleukin-6; D008070:Lipopolysaccharides; D016328:NF-kappa B; D010616:Phenanthrenes; D011809:Quinones; C516707:dioscoreanone; D009569:Nitric Oxide; D008156:Luciferases; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000111:Acetylcysteine