In utero ethanol exposure causes mitochondrial dysfunction, which can result in apoptotic cell death in fetal brain: A potential role for 4-hydroxynonenal

Background: In utero ethanol exposure causes abnormal fetal brain developme nt that may partly be due to enhanced cell death. The mechanisms underlying this remain to be defined, but ethanol-induced oxidative stress may play a role. The following studies investigated the effects of short-term in uter o ethanol exposure on fetal brain mitochondrial events that are known to el icit apoptotic cell death. Evidence is presented suggesting that 4-hydroxyn onenal (HNE), a toxic product of lipid oxidation, is a causal factor in the observed mitochondrial damage. Methods: Mitochondria were isolated from control and ethanol-exposed fetal brains (days 17 and 18 of gestation). Permeability transition was determine d spectrophotometrically, and cytochrome c and apoptosis-inducing factor (A IF) release were assessed by Western blotting. Caspase-3 activity and DNA f ragmentation were determined both as markers for mitochondrially mediated a poptosis and as consequences of cytochrome c and AIF release. Results: Maternal ethanol intake caused an increase in mitochondrial permea bility transition, and this was accompanied by cytochrome c and AIF release from fetal brain mitochondria that exceeded control values by 62 and 25%, respectively (p < 0.05). In utero ethanol exposure resulted in a 30% increa se in caspase-3 activity and a 25% increase in DNA fragmentation (p < 0.05) in the fetal brain. HNE levels were increased by 23% (p < 0.05) in mitocho ndria by in vivo ethanol exposure. In vitro treatment of fetal brain mitoch ondria with HNE (25-100 muM) also caused increases in mitochondrial permeab ility transition, as well as dose-dependent releases of cytochrome c and AI F. Conclusions: These studies illustrate that in utero ethanol exposure can el icit a cascade of events in the fetal brain that are consistent with mitoch ondrially mediated apoptotic cell death. Additionally, the increase in mito chondrial content of HNE after ethanol intake and the ability of HNE added to fetal brain mitochondria to mimic these effects of in vive ethanol expos ure support a potential role for HNE in the proapoptotic responses to ethan ol.