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

International audienceThe 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 mul/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 muM), 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 ( greater than or equal to 2.5 muM), 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 greater than or equal to 5 muM. In experiments with (+/-)-anti-benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE, 5.0 muM), 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. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved

Protective effects of Brussels sprouts towards B[a]P-induced DNA damage: a model study with the single-cell gel electrophpresis (SCGE)/Hep G2 assay

The aim of this study was to investigate the chemoprotective effects of Brussels sprouts juice towards benzo[a]pyrene (B(a)P)-induced DNA damage in the single-cell gel electrophoresis (SCGE)/Hep G2 test system. This assay combines the advantages of the SCGE assay with that of the use of human-derived cells possessing inducible phase I and phase 11 enzymes. Co-treatment of Hep G2 cells with small amounts of Brussels sprouts juice (0.25-2.0 mul/ml) and B(a)P reduced the genotoxic effect of the latter in a dose-dependent manner. Contrary to the results with the crude juice, unexpected synergistic effects were observed with allyl isothiocyanate (AITC, 1.0-6.0 muM), a breakdown product of sinigrin, which is the most abundant glucosinolate in Brussels sprouts. Although these concentrations of AITC did not cause DNA damage per se, at higher concentrations (greater than or equal to 25 muM), the compound caused a pronounced dose-dependent DNA damage by itself. Mechanistic studies showed that Brussels sprouts juice causes induction of activities of ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST) at dose levels which were protective towards B(a)P. In combined treatment experiments with (+/-)-anti-benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE, 5.0 muM), the main genotoxic metabolite of B(a)P, and Brussels sprouts juice, only weak protection was found indicating that the mechanism of chemoprotection of Brussels sprouts is not mediated through inactivation of this metabolite. In conclusion, our findings show that Brussels sprouts are highly protective against B(a)P-induced DNA damage in human-derived cells. (C) 2002 Elsevier Science Ltd. All rights reserved