Hydroxyl radicals and DNA base damage

Modified purine and pyrimidine bases constitute one of the major classes of hydroxyl-radical-mediated DNA damage together with oligonucleotide strand breaks, DNA-protein cross-links and abasic sites. A comprehensive survey of the main available data on both structural and mechanistic aspects of (OH) -O-.-induced decomposition pathways of both purine and pyrimidine bases of isolated DNA and model compounds is presented. In this respect, detailed in formation is provided on both thymine and guanine whereas data are not as c omplete for adenine and cytosine. The second part of the overview is dedica ted to the formation of (OH)-O-.-induced base lesions within cellular DNA a nd in vivo situations. Before addressing this major point, the main availab le methods aimed at singling out (OH)-O-.-mediated base modifications are c ritically reviewed. Unfortunately, it is clear that the bulk of the chemica l and biochemical assays with the exception of the high performance liquid chromatographic-electrochemical detection (HPLC/ECD) method have suffered f rom major drawbacks. This explains why there are only a few available accur ate data concerning both the qualitative and quantitative aspects of the (O H)-O-.-induced formation of base damage within cellular DNA. Therefore, maj or efforts should be devoted to the reassessment of the level of oxidative base damage in cellular DNA using appropriate assays including suitable con ditions of DNA extraction. (C) 1999 Elsevier Science B.V. All rights reserv ed.