Partial rescue of ethanol-induced neuronal apoptosis by growth factor activation of phosphoinositol-3-kinase

Background: Ethanol inhibition of insulin signaling pathways may contribute to impaired central nervous system (CNS) development in the fetal alcohol syndrome and brain atrophy associated with alcoholic neurodegeneration. Pre vious studies demonstrated ethanol inhibition of insulin-stimulated growth in PNET2 CNS-derived proliferative (immature) neuronal cells. We now provid e evidence that the growth-inhibitory effect of ethanol in insulin-stimulat ed PNET2 cells is partly due to apoptosis. Methods: Control and ethanol-treated PNET2 cells were stimulated with insul in and analyzed for viability, apoptosis, activation of pro-apoptosis and s urvival gene expression and signaling pathways, and evidence of caspase act ivation. Results: Ethanol-treated PNET2 neuronal cells exhibited increased apoptosis mediated by increased levels of p53 and phospho-amino-terminal c-jun kinas e (phospho-JNK), and reduced levels of Bcl-2, phosphoinositol 3-kinase (PI3 K), and intact (similar to 116 kD) poly (ADP ribose) polymerase (PARP), a deoxyribonucleic acid repair enzyme and important substrate for caspase 3. Partial rescue from ethanol-induced neuronal cell death was effected by cul turing the cells in medium that contained 2% fetal calf serum instead of in sulin, or insulin plus either insulin-like growth factor type I or nerve gr owth factor. The resulting enhanced viability was associated with reduced l evels of p53 and phospho-JNK and increased levels of PI3 K and intact PARP. Conclusions: The findings suggest that ethanol-induced apoptosis of insulin -stimulated neuronal cells can be reduced by activating PI3 K and inhibitin g pro-apoptosis gene expression and intracellular signaling through non-ins ulin-dependent pathways.