title: Singlet oxygen involvement in ultraviolet (254 nm) radiation-induced formation of 8-hydroxy-deoxyguanosine in DNA.
abstract: In the present article, we report that ultraviolet (UV 254 nm) radiation substantially induced the formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in purified DNA. The formation of 8-OHdG, a hallmarker of oxidative DNA damage, increased linearly up to 25 kJ/m2 and was dependent on the presence of oxygen in the solution. Deoxygenation by nitrogen significantly reduced the yield of 8-OHdG by UV radiation, whereas oxygenation with 100% oxygen substantially enhanced the yield. The hydroxyl radical (HO.) scavenger dimethysulfoxide (DMSO) dramatically quenched the formation of 8-OHdG by the ionizing radiation and Fenton reaction, but enhanced the formation of UV-induced 8-OHdG. Further studies showed that DMSO and mannitol, two predominant HO. scavengers, enhanced the levels of UV-induced 8-OHdG in a dose-dependent fashion, suggesting that UV-induced 8-OHdG is independent of the generation of HO.. The use of deuterium oxide (D2O), which prolongs the half life of singlet oxygen (1O2), substantially enhanced the yield of 8-OHdG by UV radiation, but not that by Fenton reaction. In contrast, sodium azide, a more and less specific 1O2 quencher, substantially reduced the levels of 8-OHdG by both UV radiation and Fenton reaction, indicating that sodium azide lacks the quenching specificity of 1O2 and HO.. It is proposed that UV induced 8-OHdG proceeds through a singlet oxygen involvement mechanism, rather than the generation of hydroxyl radicals.
authors.affiliation: Department of Dermatology, Mount Sinai School of Medicine, New York, NY 10029, USA.
authors.forename: H
authors.initials: H
authors.lastname: Wei
authors.forename: Q
authors.initials: Q
authors.lastname: Cai
authors.forename: R
authors.initials: R
authors.lastname: Rahn
authors.forename: X
authors.initials: X
authors.lastname: Zhang
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D001386:Azides / Q000494:pharmacology; D002417:Cattle; D004247:DNA / Q000378:metabolism / Q000528:radiation effects*; D004249:DNA Damage; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000378:metabolism; D017666:Deuterium Oxide / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism; D017665:Hydroxyl Radical / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D008353:Mannitol / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism*; D026082:Singlet Oxygen; D019810:Sodium Azide; D013950:Thymus Gland / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D001386:Azides; C045076:Fenton's reagent; D026082:Singlet Oxygen; D017665:Hydroxyl Radical; D008353:Mannitol; D000080242:8-Hydroxy-2'-Deoxyguanosine; D004247:DNA; D019810:Sodium Azide; D006861:Hydrogen Peroxide; D007501:Iron; D003849:Deoxyguanosine; D017666:Deuterium Oxide; D010100:Oxygen; D004121:Dimethyl Sulfoxide