Biochemical identification of a hydroperoxide derivative of the free 8-oxo-7,8-dihydroguanine base

Gyorgy Hajas, Attila Bacsi, Leopoldo Aguilerra-Aguirre, Peter German, Zsolt Radak, Sanjiv Sur, Tapas Hazra, Istvan Boldogh

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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 2DCF 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 2DCF-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.

Original languageEnglish (US)
Pages (from-to)749-756
Number of pages8
JournalFree Radical Biology and Medicine
Volume52
Issue number4
DOIs
StatePublished - Feb 15 2012

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Keywords

  • Free 8-oxoguanine base
  • Free radicals
  • Oxidative stress

ASJC Scopus subject areas

  • Biochemistry
  • Physiology (medical)

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