Trans-4-hydroxy-2-nonenal inhibits nucleotide excision repair in human cells: a possible mechanism for lipid peroxidation-induced carcinogenesis.

Lipid peroxidation (LPO) is a cellular process that commonly takes place under normal physiological conditions. Under excessive oxidative stress, the level of LPO becomes very significant, and a growing body of evidence has shown that excessive LPO may be involved in carcinogenesis. Trans-4-hydroxy-2-nonenal (4-HNE) is a major product of LPO, and its level becomes relatively high in cells under oxidative stress. 4-HNE is able to react readily with various cellular components, including DNA and proteins. We previously found that the 4-HNE-DNA adduct is a potent mutagen in human cells and is preferentially formed at codon 249 of the p53 gene, a mutational hotspot in human cancers. To further understand the role of 4-HNE in carcinogenesis, we addressed the question of whether 4-HNE affects DNA repair in human cells. We found that the repair capacity for benzo[a]pyrene diol epoxide and UV light-induced DNA damage was greatly compromised in human cells or human cell extracts treated with 4-HNE, which is mainly through interaction of 4-HNE with cellular repair proteins. We also found that 4-HNE greatly sensitizes cells to benzo[a]pyrene diol epoxide- and UV-induced killing. Together these results strongly suggest that this LPO metabolite damages not only DNA but also DNA repair mechanisms in human cells. We propose that these two detrimental effects of LPO may contribute synergistically to human carcinogenesis.