Mitochondrial dysfunction in mechanisms of ethanol toxicity in the spinal neural crest

Prenatal exposure to ethanol causes a range of anatomical defects in humans and animals termed fetal alcohol syndrome. Defects are linked to perturbations in neural crest cell (NCC) migration and differentiation during embryogenesis. This dissertation tests the hypothesis that ethanol inhibits NCC migration and differentiation through mechanisms involving induction of the mitochondrial permeability transition (MPT). Two- or seven-day cultured spinal NCCs contained mixtures of polarized and unpolarized mitochondria. Migration of NCCs was enhanced following establishment of mitochondrial potentials. Most control NCCs either remained undifferentiated or expressed Schwann cell markers. Differentiated cells exhibited greater mitochondrial polarization but lower migration rates than their undifferentiated counterparts. Ethanol (3 or 18 mg/ml) decreased mitochondrial transmembrane potential of 2-day NCCs within 24 or 0.5 h respectively. Exposure of 7-day NCCs to 18 mg/ml ethanol caused marked decreases in mitochondrial transmembrane potential after 15 min. Ethanol (18 mg/ml) transiently increased, then inhibited NCC migration. Death of NCCs and loss of mitochondrial membrane potential by low or high-dose ethanol was prevented by the MPT inhibitor, bongkrekic acid (BKA), regardless of day in culture, but BKA-pretreatment did not alter ethanol-induced changes in 2-day NCC migration. In utero exposure to 4.5 g/kg ethanol decreased embryonic mitochondrial glutathione but increased embryonic ATP content. These data indicate that mitochondria in 2-day cultures are less mature and more sensitive to ethanol exposure than their 7-day counterparts. These studies also suggest that the MPT is unrelated to ethanol-induced perturbation of migration. However, MPT pore opening mediates death of undifferentiated NCCs in vitro, and depletion of mitochondrial glutathione may initiate opening of the pore in vivo. The high degree of correlation between mitochondrial polarization states and NCC migration and differentiation requires further investigation, but suggests that genetic and environmental factors that coordinate NCC function also play a central role in mitochondrial maturation.