Functional mechanisms of apoptosis-related proteins in neonatal rat cerebellum are differentially influenced by ethanol at postnatal days 4 and 7.

Exposure of the developing nervous system to ethanol (EtOH) produces neurological aberrations associated with fetal alcohol syndrome. During a well-defined period, cerebellar neurons are highly susceptible to EtOH-induced death, primarily through apoptosis. Neonatal rodent cerebellum is exquisitely sensitive to EtOH on postnatal days 4-6 (P4-6); however, at slightly later developmental ages (P7 and later), EtOH effects are minimal. We have previously shown that EtOH differentially influences expression of apoptosis-related proteins of the Bcl-2 survival-regulatory gene family in P4 and P7 cerebellum. In the present study, the effects of EtOH on multiple functional mechanisms of Bcl-2, Bcl-xL, and Bax were investigated to characterize further the processes underlying these disparate EtOH sensitivities. For these analyses, we addressed the following questions, by using P4 and P7 cerebellar tissue following in vivo exposure: 1) Are there differential patterns of expression of antiapoptotic Bcl-2 or proapoptotic Bax in EtOH-vulnerable Purkinje cells that could contribute to the different degrees of temporal EtOH vulnerability? 2) How does EtOH affect intracellular localization of apoptosis-related proteins? 3) Does cleavage of Bax contribute to EtOH sensitivity? 4) Does EtOH differentially modulate cerebellar protein-protein interactions of Bcl-2, Bcl-xL, and Bax at the vulnerable vs. the resistant ages? Overall, we show that, at P4, the EtOH-mediated effects on Bcl-2, Bcl-xL, and Bax favor a prodeath response, whereas most of the intracellular responses to EtOH exposure at P7 promote survival. Such differential responsiveness likely plays a major role in the disparate ethanol vulnerability at these two postnatal ages.