Formation of 8-nitroguanine in tobacco cigarette smokers and in tobacco smoke-exposed Wistar rats

Our previous studies have shown that 8-nitroguanine (8-NO2-G) could serve as a specific biomarker of DNA damage induced by gaseous nitrogen oxides (NOx) exposure. To evaluate the effect of tobacco cigarette smoking on the DNA damage in peripheral lymphocytes of cigarette smoke ones, we randomly collected and determined the level of 8-NO2-G in DNA extracted from peripheral lymphocyte of 15 each of light-smoking healthy volunteer (L-S, less than one pack per day), moderate-smoking healthy volunteers (M-S, one to two pack per day for 5-10 years), heavy-smoking healthy volunteers (H-S, over two packs per day for 10 years), lung cancer patients with heavy smoking (cancer H-S) and non-smoking healthy controls. Both of the mean level of the 8-NO2-G levels in peripheral lymphocyte (0.90±1.0, 1.23±1.14, 1.43±0.79, 3.62±1.38 ng per μg DNA) and serum nitrite (38.99±9.58, 46.70±9.38, 55.46±10.45, 70.1±18.54 μM) of L-S, M-S, H-S and cancer H-S groups were higher than that of non-smoking healthy controls (0.02±0.04 and 18.96±4.31 for 8-NO2-G level and serum nitrite, respectively). Furthermore, in animal experiment, a dose-dependent increase in 8-NO2-G was observed in rat lung and peripheral lymphocyte DNA of Wistar rats after tobacco cigarette smoke exposure twice a day, for 1 month. The level of 8-NO2-G is 0.17±0.41, 1.65±3.15, 23.50±20.75 and 37.58±17.55 ng per μg lung DNA for rat exposed with tobacco cigarette smoke from 0, 5, 10, 15 cigarettes per day, respectively. It was also found that count of peripheral lymphocytes and nitrite concentration in serum of rat increased after the tobacco smoke exposure. It is postulated that tobacco cigarette smoking could induce DNA damage (8-NO2-G formation) by exo- and endogenous NOx.