DNA lesions and cytogenetic changes induced by N-nitrosomorpholine in HepG2, V79 and VH10 cells: the protective effects of Vitamins A, C and E.
BACKGROUND
N-Nitrosomorpholine (NMOR), present in the workplace of tyre chemical factories, is a known hepatocarcinogen. This compound belongs to the group of N-nitrosamines, which are indirect-acting and require metabolic activation. However, the mechanism of its carcinogenic effect is not completely clear.


OBJECTIVE
The objective of this study was (i) to compare the DNA-damaging and clastogenic effects of NMOR in three cell lines (HepG2, V79 and VH10) with different levels of metabolizing enzymes and (ii) to determine the protective effects of Vitamins A, C and E against deleterious effects of NMOR.


METHODS
The exponentially growing cells were pre-treated with Vitamins A, C and E and treated with NMOR. Genotoxic effects of NMOR were evaluated by single-cell gel electrophoresis (SCGE, comet assay), while the chromosomal aberration assay was used for the study of clastogenic effects.


RESULTS
NMOR-induced a significant dose-dependent increase of DNA damage as analyzed by SCGE, but the extent of DNA migration in the electric field was unequal in the different cell lines. Although the results obtained by SCGE confirmed the genotoxicity of NMOR in all cell lines studied, the number of chromosomal aberrations was significantly increased only in HepG2 and V79 cells, while no changes were observed in VH10 cells. In HepG2 cells pre-treated with Vitamins A, C and E we found a significant decrease of the percentage of tail DNA induced by NMOR. The reduction of the clastogenic effects of NMOR was observed only after pretreatment with Vitamins A and E; Vitamin C did not alter the frequency of NMOR-induced chromosomal aberrations under the experimental conditions of this study.


CONCLUSIONS
The fat-soluble Vitamins A and E, which are dietary constituents, reduce the harmful effects of N-nitrosomorpholine in human hepatoma cells HepG2, which are endowed with the maximal capacity for metabolic activation of several drugs.
Robichová
Sona
S
Laboratory of Mutagenesis and Carcinogenesis, Cancer Research Institute, Slovak Academy of Sciences, Vlárska 7, 833 91 Bratislava, Slovak Republic. sona.robichova@savba.sk
Slamenová
Darina
D
Chalupa
Ivan
I
Sebová
Lívia
L
D000818:Animals; D016587:Antimutagenic Agents / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology*; D002460:Cell Line; D002869:Chromosome Aberrations; D006224:Cricetinae; D004249:DNA Damage; D006801:Humans; D009153:Mutagens / Q000633:toxicity*; D009602:Nitrosamines / Q000633:toxicity*; D014801:Vitamin A / Q000494:pharmacology*; D014810:Vitamin E / Q000494:pharmacology*
D016587:Antimutagenic Agents; D009153:Mutagens; D009602:Nitrosamines; D014801:Vitamin A; D014810:Vitamin E; C002741:N-nitrosomorpholine; D001205:Ascorbic Acid