Glial-derived neurotrophic factor (GDNF) prevents ethanol-induced apoptosis and JUN kinase phosphorylation

Ethanol exposure during neural development leads to substantial neuronal lo ss in multiple brain regions. Our previous research indicated that exogenou s glial-derived neurotrophic factor (GDNF) attenuated ethanol-induced cereb ellar Purkinje cell loss. Additionally, ethanol decreased GDNF release sugg esting that ethanol disrupts GDNF-signaling pathways. The present experimen ts utilized a homogeneous GDNF-responsive neuroblastoma cell line (SK-N-SH) to test the hypothesis that exogenous GDNF could attenuate ethanol-induced cell loss by suppressing cytotoxic signaling pathways and cell suicide. We measured two independently regulated markers of apoptosis, DNA fragmentati on and the externalization of phosphatidylserine to the outer cell membrane leaflet. Ethanol induced a dose-related increase in both apoptosis and nec rosis. Lower concentrations of ethanol (34 and 68 mM) specifically increase d DNA fragmentation, while all concentrations (up to 137 mM) increased phos phatidylserine translocation, suggesting that ethanol induction of apoptosi s is not a unitary process. Furthermore, only higher concentrations of etha nol (103 and 137 mM) induced necrosis. Additionally, ethanol specifically i nduced phosphorylation of c-jun N-terminal-kinase (JNK), a mitogen-activate d protein (MAP) kinase selectively associated with apoptosis. In contrast, ethanol did not alter the phosphorylation of another MAP kinase, the extrac ellular signal-regulated kinases (ERK) that mediate cell survival. Thus, et hanol activated specific intracellular cell death-associated pathways and i nduced cell death. GDNF, in turn, prevented both ethanol-induced apoptosis and the activation of the death-associated JNK cascade. Therefore, GDNF may regulate multiple pathways to prevent ethanol-induced cell loss. (C) 2000 Elsevier Science B.V. All rights reserved.