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Genotoxicity of versicolorins and 5-methoxysterigmatocystin assessed by micronucleus and comet-assay on A549 cells

Aflatoxin B1 (AFB1) is a well known human carcinogen and the most potent genotoxic agent produced by some Aspergillus species. The formation of covalent bond between furofurane epoxide of AFB1 and nucleophilic regions in DNA leads to genotoxicity. The purpose of our study was to determine genotoxicity of AFB1 precursors, versicolorin A (VER A, 20 and 50 μM) and versicolorin B (VER B, 20 and 50 μM) and derivative of sterigmatocystin produced by A. versicolor, 5-methoxysterigmatocystin (5-MET-ST, 45 and 90 μM), in human adenocarcinoma lung cells A549 using micronucleus test and alkaline comet assay. Tested compounds were applied at concentrations that correspond to ½ and ¼ of their IC50 in comparison with AFB1 and ST applied at concentrations that correspond to ½ of IC50, which were all previously determined in A549 cells. Cells were treated for 24 h both in comet assay and micronucleus test. The level of DNA damage in micronucleus test was evaluated by the number of formed micronuclei (MN), nuclear buds (NB) and nucleoplasmic bridges (NPB) in 1000 binucleated cells and DNA parameters of damage assessed by comet assay were tail length, tail intensity and tail moment. All toxins provoked statistically significant increase of MN, and slightly lower formation of the NB and NPB. AFB1, ST and 20 μM VER A showed statistically significant increase in all three micronucleus parameters compared to the control, and the highest increase in the number of MN occurred in cells treated with 50 μM of VER A. The DNA damage assessed by alkaline comet-assay is best represented by tail intensity that indicates % of DNA in the tail. Considering all three comet parameters all applied toxins exert significant DNA damage compared to control, while ST and VER B produced the highest damage of DNA. The differences between results obtained by micronucleus and comet assay could be explained by the fact that micronucleus detects irreversible DNA damage which usually correlates whit previously assessed cytotoxic potential of the AF precursors. To our knowledge this is a first report on genotoxicity of these compounds assessed by micronucleus and comet assay.

5-methoxysterigmatocystin; versicolorin A; versicolorin B; genotoxicity; A549 cells; comet-assay; micronucleus test

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