Reduction of genotoxic effects of N-nitrosomorpholine in human hepatoma cells and hamster lung cells by carboxymethyl chitin-glucan.

N-nitrosomorpholine (NMOR) belongs to the group of N-nitrosamines and represents a known hepatocarcinogen. Exposure to this compound is considered to be a potential health hazard to humans. There is, however, considerable evidence that the effect of many carcinogenic agents can be markedly influenced or altered by various natural substances. The objective of this study was to assess the DNA-protective and anticlastogenic effects of the derivative of a natural compound, carboxymethyl chitin-glucan (CM-CG), against genotoxicity of N-nitrosomorpholine (NMOR) in human hepatoma cells HepG2 and hamster lung cells V79 cultured in vitro. The exponentially growing cells were pre-treated during 24 h with three different concentrations of CM-CG (150, 750 and 1500 mg/ml) and then treated with different concentrations of NMOR. DNAprotective effects of CM-CG were evaluated by single-cell gel electrophoresis (SCGE, comet assay) and anticlastogenic effects by chromosomal aberration assay. At the SCGE assay a short-term (30 min) and at the chromosomal aberration assay a continuous treatment with NMOR was used. In both HepG2 and V79 cells pre-treated with CM-CG, a significant decrease of the percentage of DNA lesions induced by NMOR was observed along with a reduction of NMOR-induced chromosomal aberrations. We did not find any substantial differences between the genotoxic effects of NMOR on HepG2 and V79 cells, which have different histopathological origins and different levels of metabolizing enzymes. Three different concentrations of CM-CG exerted a similar protective effect against NMOR-induced DNA lesions and chromosomal aberrations in both HepG2 and V79 cells.