Increase of a type of oxidative DNA damage, 8-hydroxyguanine, and its repair activity in human leukocytes by cigarette smoking.

To investigate the oxidative stress induced by cigarette smoking, the levels of a form of oxidative DNA damage, 8-hydroxyguanine (8-OH-Gua), and its repair activity in the leukocytes of current smokers, ex-smokers, and complete nonsmokers were measured. The mean level of 8-OH-Gua was 1.88-fold higher in smokers as compared to complete nonsmokers (the difference was statistically significant, P = 0.013). The mean 8-OH-Gua repair activity was 1.6-fold higher in smokers than complete nonsmokers (the difference was statistically significant, P = 0.0053). A positive association was observed for the 8-OH-Gua levels and its repair activity. Considerable interindividual variations in the 8-OH-Gua levels (current smokers, 3.5-fold; nonsmokers, 7.2-fold) and in its repair activity (current smokers, 7.5-fold; nonsmokers. 5.5-fold) were observed. These results demonstrate that not only smoking status but also life-style, environment, and genetic differences might have effects on the level of 8-OH-Gua and its repair activity in human leukocytes.