Determination of cytotoxic and genotoxic effects of naphthalene, 1-naphthol and 2-naphthol on human lymphocyte culture

Naphthalene, a bicyclic aromatic hydrocarbon, has toxic effects on animals and humans. Although recent studies stressed on the genotoxic and cytotoxic effects of naphthalene and its metabolites on eukaryotic cells, there is a big controversy among the results of these studies. The aim of this study is to investigate the effects of naphthalene and its metabolites on the cytotoxicity and genotoxicity in the human lymphocytes in the culture. The genotoxic and cytotoxic effects of naphthalene and its metabolites, 1-naphthol and 2-naphthol, were studied using cytotoxicity test (lactate dehydrogenase and cell proliferation (WST-1) assays) and DNA fragmentation assay (terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay). Naphthalene and its metabolites had no significant cytotoxic effect on treated samples when compared with untreated ones. This result was also confirmed by WST-1 assay. In the TUNEL assay, DNA fragmentation was induced significantly by all concentrations of naphthalene and 2-naphthol and 50 and 100 µM concentrations of 1-naphthol (p < 0.05 or 0.001). In the DNA fragmentation, the most effective dose of 2-naphthol (63%) was 100 µM, when compared with negative control group (13%). These results suggest that naphthalene and its metabolites, 1-naphthol and 2-naphthol, may cause DNA damage on human lymphocytes.