8-Hydroxyguanine, an Oxidative DNA and RNA Modification

Reactive oxygen species (ROS), produced by ionizing radiation and many other environmental agents, damage DNA and RNA. They are also endogenously generated in cells by oxygen metabolism. 8-Hydroxy-2′-deoxyguanine (8-OHdG) was first reported in 1983, as a major form of oxidative DNA damage produced by heated sugar, Fenton-type reagents, and ionizing radiation in vitro. 8-OHdG has been detected in cellular DNA by HPLC-ECD and LC/MS/MS methods in many laboratories. The increase in the 8-OHdG level in cellular DNA, detected by these chromatographic methods, is supported by its immunochemical detection and enhanced repair activity. Its analysis in human leukocyte DNA, and in urine and saliva, is a promising approach toward the assessment of an individual's oxidative stress level. The ribonucleoside 8-hydroxyguanosine (8-OHGuo), in tissue RNA and urine, is also a good marker of oxidative stress in vivo. The free 8-hydroxyguanine (8-OHGua) base is also detectable in biological samples, such as urine, serum, and saliva. In this chapter, the validity of the general use of 8-OHdG, 8-OHGuo, and 8-OHGua as markers of cellular oxidative stress is discussed.