Lack of mutagenicity of acrolein-induced DNA adducts in mouse and human cells

Acrolein is an endogenous metabolite and a ubiquitous environmental pollutant. Recently, it has been suggested that acrolein is a major etiologic agent for tobacco smoking-related lung cancer. Despite the known DNA-damaging effects of acrolein, its mutagenicity to mammalian cells remains uncertain. We have investigated acrolein-induced DNA damage in relation to mutagenesis, with special focus on DNA repair, in mouse and human cells. We mapped the formation of acrolein-induced DNA adducts and the kinetics of repair of the induced lesions in the W transgene, the mutational target, in acrolein-treated transgenic mouse fibroblasts. Acrolein-DNA adducts were formed preferentially at specific nucleotide positions, mainly at G:C base pairs, along the W transgene. The induced acrolein-DNA adducts were moderately resistant to DNA repair. Quantification of W mutant frequency in acrolein-treated cells, however, revealed that acrolein was not mutagenic to these cells at doses sufficient to produce DNA adducts. Determination of supF mutant frequency in DNA repair-proficient and DNA repair-deficient human fibroblasts transfected with acrolein-treated plasmids confirmed a lack of acrolein mutagenicity. Because CpG methylation may intensify acrolein-DNA adduction, we examined whether the extent of CpG methylation in the sapF gene can determine acrolein-induced mutagenesis in human cells. Enhancement of acrolein-DNA adduction by methylating CpGs in the supF sequence did not elicit a mutagenic response in human fibroblasts, however. We conclude that acrolein is not mutagenic to mouse and human fibroblasts, regardless of DNA repair capacity or methylation status of CpGs, possibly because of a highly accurate replication bypass of the induced lesions.