Oxidation of DNA bases, deoxyribonucleosides and homopolymers by peroxyl radicals

DNA base oxidation is considered to be a key event associated with disease initiation and progression in humans. Peroxyl radicals (ROO^•) are important oxidants found in cells whose ability to react with the DNA bases has not been characterized extensively. In this paper, the products resulting from ROO^• oxidation of the DNA bases are determined by gas chromatography/MS in comparison with authentic standards. ROO^• radicals oxidize adenine and guanine to their 8-hydroxy derivatives, which are considered biomarkers of hydroxyl radical (HO^•) oxidations in cells. ROO^• radicals also oxidize adenine to its hydroxylamine, a previously unidentified product. ROO^• radicals oxidize cytosine and thymine to the monohydroxy and dihydroxy derivatives that are formed by oxidative damage in cells. Identical ROO^• oxidation profiles are observed for each base when exposed as deoxyribonucleosides, monohomopolymers and base-paired dihomopolymers. These results have significance for the development, utilization and interpretation of DNA base-derived biomarkers of oxidative damage associated with disease initiation and propagation, and support the idea that the mutagenic potential of N-oxidized bases, when generated in cellular DNA, will require careful evaluation. Adenine hydroxylamine is proposed as a specific molecular probe for the activity of ROO^• in cellular systems.