Genotoxicity of nicotine in cell culture of Caenorhabditis elegans evaluated by the comet assay

To assess the genotoxicity of nicotine, its DNA-damaging effect on Caenorhabditis elegans cells was tested with the alkaline single-cell microgel electrophoresis (comet) assay. The degree of DNA migration (a measure of possible DNA single-strand breaks, alkali-labile sites, and incomplete excision repair sites) was expressed as the head DNA%, tail length, and Olive tail moment. Large differences were found between experimental variants: 0, 1, 10, and 100 mu M (-)-nicotine. At concentrations of 1 and 10 mu M, no damages were detected by the comet assay, and the Olive tail moment and tail length were significantly lower than in the control (P<0.001). The highest head DNA% and the lowest tail length and Olive tail moment were observed in the presence of 1 mu M of nicotine. At 100 mu M of nicotine, a significant increase (P<0.001) was observed in Olive tail moment and tail length (up to 2.7- and 3-fold, respectively, compared to the control). The results are consistent with the lowest head DNA% among the three tested variants. This study demonstrated that nicotine treatment had dose-dependent effects on the level of DNA damage. Generally, a high dose of nicotine (100 mu M) is genotoxic, while a reasonably low concentration has a protective effect. The possible participation of reactive oxygen species in the DNA-damaging potential of nicotine in C. elegans is discussed.