Ceramide pathways modulate ethanol-induced cell death in astrocytes

We showed previously that alcohol exposure during in vivo brain development induced astroglial damage and caused cell death. Because ceramide modulates a number of biochemical and cellular responses to stress, including apoptosis, we now investigate whether ethanol-induced cell death in astrocytes is mediated by ceramide signalling pathways triggering apoptosis. Here we show that both ethanol and ceramide are able to induce apoptotic death in cultured astrocytes, in a dose-dependent manner, and that C-2-ceramide addition potentiates the apoptotic effects of ethanol. Cell death induced by ethanol is associated with stimulation of neutral and acidic sphingomyelinase (SMase) and ceramide generation, as well as with activation of stress-related kinases, c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (p38) and extracellular signal-regulated kinase (ERK) pathways. We also provide evidence for the participation of JNK and p38 in ethanol-induced cell death, because pharmacological inhibitors of these kinases largely prevent the apoptosis induced by ethanol or by ethanol and C-2-ceramide. Furthermore, we show that ethanol-induced ERK activation triggers the stimulation of cyclo-oxygenase-2 (COX-2) and the release of prostaglandin E-2, and that blockade of the mitogen-activated protein kinase kinase (MEK)/ERK pathway by PD98059 abolishes the up-regulation of COX-2 induced by ethanol plus ceramide, and decreases the ethanol-induced apoptosis. These results strongly suggest that ethanol is able to stimulate the SMase-ceramide pathway, leading to the activation of signalling pathways implicated in cell death. These findings provide an insight into the mechanisms involved in ethanol-induced astroglial cell death during brain development.