A physiologically based in silico model for trans-2-hexenal detoxification and DNA adduct formation in rat

Trans-2-Hexenal (2-hexenal) is an a,ß-unsaturated aldehyde that occurs naturally in a wide range of fruits, vegetables, and spices. 2-Hexenal as well as other a,ß-unsaturated aldehydes that are natural food constituents or flavoring agents may raise a concern for genotoxicity due to the ability of the a,ß-unsaturated aldehyde moiety to react with DNA. Controversy remains, however, on whether a,ß-unsaturated aldehydes result in significant DNA adduct formation in vivo at realistic dietary exposure. In this study, a rat physiologically based in silico model was developed for 2-hexenal as a model compound to examine the time- and dose-dependent detoxification and DNA adduct formation of this selected a,ß-unsaturated aldehyde. The model was developed based on in vitro and literature-derived parameters, and its adequacy was evaluated by comparing predicted DNA adduct formation in the liver of rats exposed to 2-hexenal with reported in vivo data. The model revealed that at an exposure level of 0.04 mg/kg body weight, a value reflecting estimated daily human dietary intake, 2-hexenal is rapidly detoxified predominantly by conjugation with glutathione (GSH) by glutathione S-transferases. At higher dose levels, depletion of GSH results in a shift to 2-hexenal oxidation and reduction as the major pathways for detoxification. The level of DNA adduct formation at current levels of human dietary intake was predicted to be more than 3 orders of magnitude lower than endogenous DNA adduct levels. These results support that rapid detoxification of 2-hexenal reduces the risk arising from 2-hexenal exposure and that at current dietary exposure levels, DNA adduct formation is negligible