The effects of acetaldehyde exposure on histone modifications and chromatin structure in human lung bronchial epithelial cells.

As the primary metabolite of alcohol and the most abundant carcinogen in tobacco smoke, acetaldehyde is linked to a number of human diseases associated with chronic alcohol consumption and smoking including cancers. In addition to direct DNA damage as a result of the formation of acetaldehyde-DNA adducts, acetaldehyde may also indirectly impact proper genome function through the formation of protein adducts. Histone proteins are the major component of the chromatin. Post-translational histone modifications (PTMs) are critically important for the maintenance of genetic and epigenetic stability. However, little is known about how acetaldehyde-histone adducts affect histone modifications and chromatin structure. The results of protein carbonyl assays suggest that acetaldehyde forms adducts with histone proteins in human bronchial epithelial BEAS-2B cells. The level of acetylation for N-terminal tails of cytosolic histones H3 and H4, an important modification for histone nuclear import and chromatin assembly, is significantly downregulated following acetaldehyde exposure in BEAS-2B cells, possibly due to the formation of histone adducts and/or the decrease in the expression of histone acetyltransferases. Notably, the level of nucleosomal histones in the chromatin fraction and at most of the genomic loci we tested are low in acetaldehyde-treated cells as compared with the control cells, which is suggestive of inhibition of chromatin assembly. Moreover, acetaldehyde exposure perturbs chromatin structure as evidenced by the increase in general chromatin accessibility and the decrease in nucleosome occupancy at genomic loci following acetaldehyde treatment. Our results indicate that regulation of histone modifications and chromatin accessibility may play important roles in acetaldehyde-induced pathogenesis. Environ. Mol. Mutagen. 59:375-385, 2018.