title: Biochemical identification of a hydroperoxide derivative of the free 8-oxo-7,8-dihydroguanine base.
abstract: 8-Oxo-7,8-dihydroguanine is one the most abundant base lesions in pro- and eukaryotic DNA. In mammalian cells, it is excised by the 8-oxoguanine DNA glycosylase (OGG1) during DNA base-excision repair, and the generated free 8-oxoG base is one of the DNA-derived biomarkers of oxidative stress in biological samples. The modification of 8-oxoG in the context of nucleoside and DNA has been the subject of many studies; however, the oxidative transformation of the free 8-oxoG base has not been described. By using biochemical and cell biological assays, we show that in the presence of molecular oxygen, the free 8-oxoG base transforms to a highly reactive hydroperoxide (8-oxoG*). Specifically, 8-oxoG* oxidizes Amplex red to resorufin, H(2)DCF to DCF, Fe(2+) to Fe(3+), and GSH to GSSG. This property of 8-oxoG* was diminished by treatment with catalase and glutathione peroxidase, but not superoxide dismutase. 8-OxoG* formation was prevented by reducing agents or nitrogen atmosphere. Its addition to CM-H(2)DCF-DA-loaded cells rapidly increased intracellular DCF fluorescence. There were no such properties observed for 8-oxodeoxyguanosine, 2,6-diamino-4-hydroxy-5-formamidopyrimidine, 2'-deoxyguanosine, guanine, adenine, guanosine, and 8-hydroxyadenine. These data imply that a free 8-oxoG base is more susceptible to oxidation than is its nucleoside form and, consequently, it stands as unique among intact and oxidatively modified purines.
authors.affiliation: Department of Microbiology and Immunology, University of Texas Medical Branch at Galveston, Galveston, TX 77555, USA.
authors.forename: Gyorgy
authors.initials: G
authors.lastname: Hajas
authors.forename: Attila
authors.initials: A
authors.lastname: Bacsi
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Aguilerra-Aguirre
authors.forename: Peter
authors.initials: P
authors.lastname: German
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Radak
authors.forename: Sanjiv
authors.initials: S
authors.lastname: Sur
authors.forename: Tapas K
authors.initials: TK
authors.lastname: Hazra
authors.forename: Istvan
authors.initials: I
authors.lastname: Boldogh
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000737:chemistry; D002374:Catalase / Q000737:chemistry; D002460:Cell Line; D005452:Fluoresceins / Q000737:chemistry; D005978:Glutathione / Q000737:chemistry; D005979:Glutathione Peroxidase / Q000737:chemistry; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D051379:Mice; D010078:Oxazines / Q000737:chemistry; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010100:Oxygen / Q000737:chemistry; D010545:Peroxides / Q000737:chemistry* / Q000378:metabolism; D013482:Superoxide Dismutase / Q000737:chemistry
chemical_list: D015415:Biomarkers; D005452:Fluoresceins; D010078:Oxazines; D016877:Oxidants; D010545:Peroxides; C470430:Amplex Red; C024829:8-hydroxyguanine; C037631:2',7'-dichlorofluorescein; D006147:Guanine; D007501:Iron; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D005978:Glutathione; D010100:Oxygen