α,β-unsaturated carbonyl compounds:: induction of oxidative DNA damage in mammalian cells

alpha,beta-Unsaturated carbonyl compounds occur in food and other environmental media. Due to their reactivity with cellular nucleophiles (e.g. Michael adduct formation with DNA bases and with glutathione) they might represent a potential health risk. In this study, induction of oxidative DNA damage was investigated in mammalian cells, as a consequence of glutathione depletion induced by selected food relevant 2-alkenals, including E-(2)-hexenal (HEX), (2E,4E)-2,4-hexadienal (HEXDI) and (E)-2-cinnamaldehyde (CA) and the cyclic analogue 2-cyclohexen-1-one (CHX). Oxidative DNA breakage was monitored with the Comet assay, using treatment with formamidopyrimidine-DNA glycosylase (FPG). Total cellular glutathione (tGSH) was determined in a kinetic, photometric assay. After 1 h incubation of V79 cells with HEX (100 muM) and CHX (300 muM), HEXDI and CA (300 muM each), tGSH was depleted down to <20% of control (viability >85%). Under these conditions, FPG-sensitive sites were not observed; moderate direct DNA breakage, however, was detectable. During 3 h post-incubation (without test compound) distinct oxidative DNA breakage occurred in HEX- and CA-, but not in CHX- and HEXDI-pretreated cells. Direct DNA breakage was markedly diminished, most probably by repair processes, and tGSH concentrations were observed to increase again within 3 h post-treatment. The results give strong evidence for alkenal-mediated oxidative stress contributing to cytotoxic/genotoxic cell damage. The extent of oxidative stress appears to be influenced by structure-specific properties of the alkenals.