Effects of mustard sprouts and allylisothiocyanate on benzo(a)pyrene-induced DNA damage in human-derived cells: a model study with the single cell gel electrophoresis/Hep G2 assay.

The aim of this study was to investigate the chemoprotective effects of mustard sprouts on benzo(a)pyrene [B(a)P]-induced DNA damage in the single cell gel electrophoresis (SCGE)/Hep G2 assay. This model combines the advantages of the SCGE assay with that of human-derived cells that possess inducible phase I and phase II enzymes. Treatment of the cells with small amounts of mustard juice (0.1-1.25 microl/ml) and B(a)P reduced the genotoxic effect of the carcinogen in a dose-dependent manner. Contrary to the results with the juice, unexpected synergistic effects were observed with allyl isothiocyanate (AITC, 0.3 microM), a breakdown product of sinigrin, which is contained in black mustard and many other cruciferous vegetables. Although these concentrations of AITC did not cause DNA damage per se, pronounced dose-dependent DNA damage was seen with higher concentrations of AITC (>or= 25 microM). In parallel with the comet assays, also enzyme measurements were carried out which showed that exposure of the cells to mustard juice (2.0 microl/ml) causes a moderate induction of ethoxyresorufin-O-deethylase, and more pronounced (approximately 2-fold) increase of the activity of glutathione-S-transferase. In conclusion, our findings indicate that i) mustard juice is highly protective against B(a)P-induced DNA damage in human derived cells and ii) that induction of detoxifying enzymes may account for its chemoprotective properties. iii) Furthermore, our findings show that the effects of crude juice can not be explained by its allyl isothiocyanate contents.

Effects of garden and water cress juices and their constituents, benzyl and phenethyl isothiocyanates, towards benzo(a)pyrene-induced DNA damage: a model study with the single cell gel electrophoresis/Hep G2 assay.

The aim of this study was to investigate the chemoprotective effects of water and garden cress juices towards benzo(a)pyrene (B(a)P)-induced DNA damage using the single cell gel electrophoresis (SCGE)/Hep G2 test system. This experimental model combines the advantages of the SCGE assay with that of human derived cells possessing inducible phase I and phase II enzymes. Treatment of Hep G2 cells with small amounts of water cress or garden cress juice (0.1-1.25 microl/ml) and B(a)P reduced the genotoxic effect of the latter in a dose-dependent manner. Contrary to the results with the juices, unexpected synergistic effects were observed with benzyl isothiocyanate (BITC, 0.6 microM), a breakdown product of glucotropaeolin contained abundantly in garden cress. Although these concentrations of BITC did not cause DNA damage per se, at higher concentrations (> or = 2.5 microM), the compound caused a pronounced dose-dependent DNA damage by itself. With phenethyl isothiocyanate (PEITC), the breakdown product of gluconasturtin contained in water cress, no synergistic effects with B(a)P were seen; however, significant induction of DNA damage was observed when the cells were exposed to the pure compound at concentrations > or = 5 microM. In experiments with (+/-)-anti-benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE, 5.0 microM), the ultimate genotoxic metabolite of B(a)P, and the juices, only moderate protective effects were seen indicating that detoxification of BPDE is not the main mechanism behind the protective effect of the juices against B(a)P-induced DNA damage. In conclusion, our findings show that garden and water cress juices are highly protective against B(a)P-induced DNA damage in human derived cells and that their effects can not be explained by their isothiocyanate contents.