title: Antioxidant effect of a nitrated cyclic nucleotide functioning as an endogenous electrophile.
abstract: We describe here physiological formation of a unique nitrated cyclic nucleotide, 8-nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP) and its potent antioxidant activity. Our earlier studies revealed the NO-dependent guanine nitration in several types of cells. In fact, we identified physiological formation and functions of 8-nitro-cGMP, which is the first demonstration of a new second messenger derived from cGMP in mammals since the discovery of cGMP more than 40 years ago. Using immunocytochemical methods, we confirmed 8-nitro-cGMP formation in cultured macrophages, hepatocyte-like cells, adipocytes, and endothelial cells, depending on NO production. We further verified 8-nitro-cGMP formation via HPLC plus electrochemical detection and tandem mass spectrometry. 8-Nitro-cGMP as an electrophile reacts efficiently with sulfhydryls of proteins to generate a novel post-translational modification, which we call protein S-guanylation. Particular intracellular proteins can readily undergo S-guanylation by 8-nitro-cGMP. 8-Nitro-cGMP regulates the redox-sensor signaling protein Keap1, via S-guanylation of the highly nucleophilic cysteine sulfhydryls of Keap1. More importantly, we clarified that S-guanylation of Keap1 is involved in potent antioxidant effects mediated by 8-nitro-cGMP, by inducing oxidative stress-response genes such as heme oxygenase-1. Our discovery of 8-nitro-cGMP and its unique antioxidant effects thus shed light on new areas of oxidative stress research. Protein S-guanylation induced by 8-nitro-cGMP thus may have important implications in pharmaceutical chemistry and development of therapeutics for many diseases.
authors.affiliation: Department of Microbiology, Graduate School of Medical Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto 860-8556, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Sawa
authors.forename: Hideshi
authors.initials: H
authors.lastname: Ihara
authors.forename: Takaaki
authors.initials: T
authors.lastname: Akaike
mesh_terms: D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism; D004583:Electrons; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D051547:Heme Oxygenase-1 / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D000072019:Kelch-Like ECH-Associated Protein 1; D051379:Mice; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology; D011499:Protein Processing, Post-Translational; D015398:Signal Transduction / Q000502:physiology*; D053719:Tandem Mass Spectrometry; D015854:Up-Regulation
chemical_list: C525106:8-nitroguanosine 3',5'-cyclic monophosphate; D000975:Antioxidants; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; D009566:Nitrates; D009569:Nitric Oxide; D051547:Heme Oxygenase-1; D006152:Cyclic GMP; D003545:Cysteine