Genotoxic and antiapoptotic effect of nicotine on human gingival fibroblasts

Growing evidence suggests that nicotine, the addictive component of cigarettes, can have a direct role in tumor development by enhancing cell proliferation and impairing apoptotic process in certain types of human cancer cell lines. Since the correlation between apoptosis and DNA damage is already well documented, we investigated the response of human gingival fibroblasts (HGFs) to nicotine exposure by examining its effect on DNA damage induction and apoptotic process in parallel. To assess the genotoxicity of this drug, the cytokinesis-block micronucleus (CBMN) test was performed. Treatment of HGFs with nicotine, at a concentration of 1 microM, caused a statistically significant increase of micronucleus (MN) frequency at the tested time intervals, while no change was detected in cell growth under the same conditions. Furthermore, we found that preincubation of HGFs with 1 microM nicotine strongly attenuated staurosporine (STP)-induced apoptosis. Finally, we found that cultures exposed to nicotine showed an increase of reactive oxygen species, as determined by increased levels of 2,7-dichlorofluorescein (DCF). When cells were prelabeled with N-acetyl-cysteine (NAC), a substrate for glutathione synthesis, and catalase (CAT), the oxygen free radical scavenger, a significant reduction in cytogenetic damage was observed. Thus, for the first time, we report a concomitant genotoxic and antiapoptotic effect of nicotine in HGFs.