1,N²-propanodeoxyguanosine adducts: Potential new biomarkers of smoking-induced DNA damage in human oral tissue

Highly DNA-reactive α,β-unsaturated aldehydes such as acrolein and crotonaldehyde are common environmental pollutants present in cigarette smoke and automobile exhaust and are also released endogenously by lipid peroxidation. Acrolein- and crotonaldehyde-derived 1,N²- propanodeoxyguanosine (AdG and CdG, respectively) have been detected in the tissues of carcinogen-treated rodents and as background lesions in DNA from humans and untreated rodents. To determine whether cigarette smoking increases the levels of AdG and CdG, gingival tissue DNA from 11 smokers (4 males and 7 females; 30-58 years old) and 12 nonsmokers (8 males and 4 females; 21-66 years old) was analyzed using a previously described ³²P- postlabeling high-performance liquid chromatography method. The results showed that the mean AdG levels in smokers were significantly higher than those in nonsmokers (1.36 ± 0.90 μmol/mol guanine in smokers versus 0.46 ± 0.26 μmol/mol guanine in nonsmokers; P = 0.003). The mean CdG 1 levels in smokers and nonsmokers were 0.53 ± 0.44 and 0.06 ± 0.07 μmol/mol guanine, respectively, corresponding to an 8.8-fold increase for smokers (P = 0.0015). Similar to CdG 1, levels of CdG 2 were increased 5.5-fold in smokers as compared to nonsmokers, from 0.31 ± 0.40 to 1.72 ± 1.26 μmol/mol guanine (P = 0.0014). Furthermore, the total levels of cyclic adduct (AdG and CdG) in smokers were 4.4-fold greater than those in nonsmokers (P = 0.0003). This study shows the detection of the potentially promutagenic 1,N²- propanoguanine adducts in human oral tissues and demonstrates for the first time an increase of structurally identified adducts in oral tissue DNA by cigarette smoking.