Singlet oxygen involvement in ultraviolet (254 nm) radiation-induced formation of 8-hydroxy-deoxyguanosine in DNA

Huachen Wei, Qiuyin Cai, Ronald Rahn, Xueshu Zhang

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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 for 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.

Original languageEnglish
Pages (from-to)148-154
Number of pages7
JournalFree Radical Biology and Medicine
Volume23
Issue number1
DOIs
StatePublished - 1997

Keywords

  • 8-Hydroxy-2'-deoxyguanosine
  • Fenton Reaction
  • Ionizing radiation
  • Oxidative DNA damage
  • Reactive oxygen species
  • Singlet oxygen
  • UV radiation

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