A multi-biomarker approach to study the effects of smoking on oxidative DNA damage and repair and antioxidative defense mechanisms

Abstract

We investigated the effects of smoking-induced oxidative stress in healthy volunteers (21 smokers versus 24 non-smokers) by quantifying various markers of oxidative DNA damage and repair, and antioxidative defense mechanisms. Lymphocytic 7-hydroxy-8-oxo-2′-deoxyguanosine (8-oxo-dG) levels measured by high performance liquid chromatography with electrochemical detection, were significantly lower in smokers as compared with non-smokers (38.6 ± 5.2 versus 50.9 ± 4.6/106 dG, P = 0.05). The levels of oxidized pyrimidine bases in lymphocytes of smokers quantified by the endonuclease III-modified comet assay were non-significantly lower than those of non-smokers (% DNA in tail: 13 ± 3 versus 14 ± 2; tail length: 69 ± 13 versus 96 ± 10; tail moment: 6416 ± 1220 versus 7545 ± 1234). Urinary excretion levels of 8-hydroxy-2′-deoxyguanosine (8-OH-dG) assessed by enzyme-linked immunosorbent assay did not differ significantly between smokers and non-smokers (197 ± 31 versus 240 ± 33 ng/body mass index, P = 0.3). Overall DNA repair activity expressed as unscheduled DNA synthesis in blood leukocytes, was not significantly different between smokers and non-smokers (2.9 ± 0.3 versus 3.3 ± 0.3, P = 0.4). Plasma antioxidative capacity measured by the Trolox equivalent antioxidant capacity assay was slightly higher in smokers as compared with non-smokers (440 ± 16 versus 400 ± 15 μM Trolox equivalent, P = 0.09), and it was significantly related to lymphocytic 8-oxo-dG levels (r = 0.4, P = 0.001). Genotyping of human 8-OH-dG glycosylase/apurinic lyase and glutathione S-transferase M1 showed that a polymorphism in either or both of the two genes does not affect any of the quantified biomarkers. We conclude that oxidative stress imposed by cigarette smoking has a low impact upon certain pathways involved in DNA damage and the antioxidative defense system.