Acute alcohol exposure induces apoptosis and increases histone H3K9/18 acetylation in the mid-gestation mouse lung

Alcohol consumption causes cellular injury and excessive cell death. Recent studies indicate that ethanol can induce epigenetic alterations, particularly acetylation and methylation of histones and hypomethylation and hypermethylation of DNA. In the current study, we tested the hypothesis that acute exposure of pregnant mice to alcohol during mid-gestation can induce apoptosis and increase histone H3K9/18 acetylation in the fetal lung. The increased expression of histone H3K9/18 acetylation could alter the expression of genes that induce apoptosis.

C57BL/6J mice at day 13.5 of gestation were injected intraperitoneally with 2 doses of 25% ethanol (experimental) or Ringer solution (control) at 4-hour intervals. The fetuses were retrieved at 1, 3, 12, and 24 hours after alcohol exposure. The lungs were processed for detection of apoptosis by the terminal deoxynucleotidyl transferase biotin- deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) assay and for levels of acetylated histone H3K9/18 by immunohistochemistry.

In the control lungs, apoptosis was observed in 0.22% and 0.25% of the mesenchymal and epithelial cells, respectively. In contrast, at 24 hours after alcohol injection at E13.5, 3.4% of the mesenchymal and 4.0% of the epithelial cells in the lung were undergoing apoptosis (TUNEL-positive; P < .005). The number of positively stained cells and levels of acetylated histone H3K9/18 staining significantly increased 1 hour after alcohol injection (P < .05) and returned to basal levels after 12 hours.

Acute alcohol exposure of pregnant mice at mid-gestation results in increased apoptosis in the fetal lung, and elevated levels of acetylated histone H3K9/18 precede the observation of apoptosis.