Enhanced caspase activity during ethanol-induced apoptosis in rat cerebellar granule cells

The effects of ethanol on cerebellar granule cell death were examined in cultures maintained for either 5 days in vitro (immature) or 8 and 12 days in vitro (mature). Ethanol did not alter cell survival under the usual growth conditions (i.e., 10% serum and 25 mM KCl). However, in mature cultures ethanol enhanced apoptosis induced by either serum withdrawal or incubation in non-depolarizing media. In immature cultures, serum deprivation, but not non-depolarizing media, resulted in granule cell death that was enhanced by ethanol. Serum removal increased both cleavage of the caspase-specific substrate N-acetyl-Asp-Glu-Val-Asp-7 amino-4-methylcoumarin (Ac-DEVD-amc) and the amount of active caspase-3. Inclusion of ethanol during the serum deprivation augmented Ac-DEVD-amc cleavage without further increasing the amount of active caspase-3. This study demonstrates that when neurotrophic factors are limiting, ethanol is toxic to cerebellar granule cells regardless of maturation status. The ability of ethanol to promote apoptosis involves an increase in caspase activity, but this does not entail an increase in the proteolytic activation of caspase-3.