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Antioxidant Effect of a Nitrated Cyclic Nucleotide Functioning as an Endogenous Electrophile

[ Vol. 11 , Issue. 14 ]


Tomohiro Sawa, Hideshi Ihara and Takaaki Akaike   Pages 1854 - 1860 ( 7 )


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-NitrocGMP 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-nitrocGMP 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.


Oxidative stress, antioxidant, reactive oxygen species, nitric oxide, adaptive response, electrophile, nitrated cyclic nucleotide, signal transduction, tandem mass spectrometry, redox-sensor signaling protein Keap1, heme oxygenase-1, diabetes, cancer, inflammatory diseases, flavonoids


Department of Microbiology, Graduate School of Medical Sciences, Kumamoto University, 1-1-1 Honjo,Kumamoto 860-8556, Japan.

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