Alcohol consumption produces a variety of pathological effects, including fetal alcohol syndrome, liver and brain damage and an increased risk of cancer of the upper GI tract. The association between ethanol consumption and cancer suggests that alcohol intake results in effects on genomic DNA. Mechanisms by which ethanol can produce DNA damage are: 1) direct adduction of DNA by acetaldehyde, the major metabolite of ethanol; 2) the generation of DNA damaging oxygen radicals by cytochrome P450 2E1 (CYP2E1), which is induced by ethanol in liver and brain. To test the hypothesis that alcohol metabolism results in DNA damage, we have created CHO cell lines which express biologically relevant levels of CYP 2E1, ADH4 (the form of ADH specifically prodecued in upper GI tract) or both enzymes. The cells contain a mutational target (the APRT gene) which makes them highly sensitive for detecting mutations produced by cross linking agents and oxygen radicals. Our prediction is that growing these cells in presence of EtOH will increase mutation frequency. The level of DNA repair activity in target tissues is expected to be a crucial determinant of alcohol-induced DNA toxicity. Therefore, we have also placed the EtOH metabolizing enzymes in CHO cells which lack specific DNA repair pathways. This will allow us to identify which of the several DNA repair pathways play a role in protecting cellular DNA from genomic damage to EtOH metabolites. Analogous studies are being carried out in mice to assess whether the lack of specific DNA repair pathways makes them more susceptible to EtOH related tissue pathologies. We are also studying N2-ethyl deoxyguanosine, the major DNA adduct produced by acetaldehyde. This adduct is undetectable in normal liver but accumulates in the DNA of mice fed alcohol. We are assessing whether the adduct is a substrate for DNA repair and what type of repair is involved, and are also assessing the mutagenicity of this adduct in mammalian cells. We are also focusing on the generation and repair of a specific type of oxidative DNA lesion called cyclo-dA. We have shown that cyclo-dA is a substrate for repair by the nucleotide excision repair pathway, and is a strong block to gene expression in mammalian cells. We are developing sensitive assays for detecting this lesion in DNA obtained from tissue samples, to study the relationship bewteen the formation of this lesion and neurodegenerative disease.
Showing the most recent 10 out of 19 publications
