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

Highly DNA-reactive alpha,beta-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 micromol/mol guanine in smokers versus 0.46 +/- 0.26 micromol/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 micromol/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 micromol/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.

Salivary levels of N-nitrosamines and some metabolites after IP injection of N-nitrosamines in rats.

The carcinogens N-nitrosodimethylamine (DMN) and N-nitrosodiethylamine (DEN) were detected in rat saliva by gas liquid chromatography or HPLC after their ip injections. Salivary levels were equal to or greater than blood levels. A fairly linear dose response in salivary levels was observed in the range of 1-50 mg/kg. Salivary levels of DMN and DEN decreased between 0.5 and 1.0 hr after administration with the decrease becoming more prominent at lower doses. Formaldehyde and bicarbonate, metabolites of DMN, were also detected in rat saliva.

Mutagenesis induced by oral carcinogens in lacZ mouse (MutaMouse) tongue and other oral tissues.

Animal models for carcinogenesis of the oral cavity are limited, although this disease is often fatal or disfiguring and its incidence in the USA is approximately 30 000 cases/year. Short-term whole-animal models for this disease should prove valuable in the investigation of factors affecting oral carcinogenesis. In this study we observed that a group of oral carcinogens are clearly mutagenic in the lacZ transgenic mouse oral cavity. The carcinogens 4-nitroquinoline-N-oxide (4-NQO), benzo[a]pyrene (B[a]P), N-nitroso-N-methylurea (NMU), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), nitrosonornicotine (NNN) and 7,12-dimethylbenzanthracene (DMBA) were all mutagenic in a mixture of pooled oral tissues (gingival, buccal, pharyngeal and sublingual) and in the tongue. All agents except DMBA (which was swabbed in the oral cavity) and B[a]P (by gavage) were given in drinking water for 2-4 weeks followed by a 2 week expression period before killing. With one exception, groups of 4-5 female mice were treated. The doses and mutant fractions (MF) in DNA isolated from pooled oral tissues (in mutants/10(5) p.f.u. +/- SD) were: 4-NQO (20-80 microg/ml, over 4 weeks) 78 +/- 16; B[a]P (five doses of 125 mg/ml) 33.2 +/- 10.9; NMU (20-80 microg/ml over 4 weeks) 7.8 +/- 2.6; NNK (0.1 mg/ml, weeks 1-2, 0.2 mg/ml, weeks 3-4) 9.1 +/- 3.0; NNN (same dose as NNK) 9.2 +/- 1.6 and DMBA (0.5 mg/ml in corn oil, 3 weeks) 7.1 +/- 2.7. The corresponding value for untreated controls was 3.2 +/- 1.8. Values for induced mutagenesis in tongue from the same animals were similar except for 4-NQO which was about twice as potent in tongue. Mutagenesis by several compounds was compared in other organs. B[a]P was assayed in lung and kidney and was about twice as mutagenic in oral tissues as in lung, but several times less mutagenic in kidney. Lung, but not kidney is a target organ for B[a]P-induced carcinogenesis in the mouse. NNK was somewhat more mutagenic in lung (MF of 15.0 +/- 5.5) than in oral tissues, corresponding with previous reports on carcinogenesis by NNK. Mutagenesis induced by NNN was also assayed in esophagus, a target organ in rodents, and was similar to that in oral tissue. In all cases the MF in untreated control group was about 3-4. These results suggest that: (i) the oral cavity has a significant capacity for metabolic activation of carcinogens; (ii) DNA damage in the oral cavity can be converted to mutations; and (iii) there is significant target organ specificity. The results also tend to support the concept that the anatomical components of the upper aerodigestive tract, in general, behave similarly with respect to genotoxicity. As carcinogenesis is believed to involve mutagenesis, this study demonstrates the utility of the lacZ mouse for investigations involving initiation of carcinogenesis of the oral cavity.