IDENTIFICATION OF POSSIBLE REACTIVE OXYGEN SPECIES INVOLVED IN ULTRAVIOLET RADIATION-INDUCED OXIDATIVE DNA-DAMAGE

We have previously demonstrated that each region of the ultraviolet (U V) spectrum (UVA, UVB, and UVC) induces the formation of 8-oxo-7,8-dih ydro-2'-deoxyguanosine (8-oxodGuo) in purified calf thymus DNA and HeL a cells in a fluence-dependent manner. In the present study, we furthe r characterize the possible reactive oxygen species (ROS) that are inv olved in the induction of 8-oxodGuo by UV radiation. Sodium azide, a s inglet oxygen (O-1(2)) scavenger though its quenching effect on HO . w as also reported, inhibited 8-oxodGuo production in calf thymus DNA ex posed to UVA, UVB, or UVC in a concentration-dependent fashion with ma ximal quenching effect of over 90% at a concentration of 10 mM. Catala se, at a concentration of 50 U/ml, reduced the yields of UVA-and UVB-i nduced 8-oxodGuo formation by approximately 50%, but had little effect on UVC-induced 8-oxodGuo production. In contrast, 50 U/ml of superoxi de dismutase (SOD) did nor affect induction of 8-oxodGuo by any portio n of the UV spectrum. Hydroxyl radical (HO .) scavengers mannitol and dimethylsulfoxide (DMSO) moderately reduced the levels of 8-oxodGuo in duced by UVA and UVB, but not those by UVC. instead, mannitol and DMSO enhanced the formation of 8-oxodGuo induced by UVC. These results sug gest that certain types of ROS are involved in UV-induced 8-oxodGuo fo rmation with O-1(2) playing the predominant role throughout the UV spe ctrum. Except for UVC, other ROS such as hydrogen peroxide (H2O2) and HO . may also be involved in UVA- and UVB-induced oxidative DNA damage . Superoxide anion appears not to participate in UV-induced oxidation of guanosine in calf thymus DNA, as SOD did not display any quenching effects. (C) 1997 Elsevier Science Inc.