Involvement of ceramide in ethanol‐induced apoptotic neurodegeneration in the neonatal mouse brain

Abstract

J. Neurochem. (2010) 115, 168–177. Abstract Acute administration of ethanol to 7‐day‐old mice is known to cause robust apoptotic neurodegeneration in the brain. Our previous studies have shown that such ethanol‐induced neurodegeneration is accompanied by increases in lipids, including ceramide, triglyceride (TG), cholesterol ester (ChE), and N‐acylphosphatidylethanolamine (NAPE) in the brain. In this study, the effects of ethanol on lipid profiles as well as caspase 3 activation were examined in the cortex, hippocampus, cerebellum, and inferior colliculus of the postnatal day 7 mouse brain. We found that the cortex, hippocampus, and inferior colliculus, which showed substantial caspase 3 activation by ethanol, manifested significant elevations in ceramide, TG, and NAPE. In contrast, the cerebellum, with the least caspase 3 activation, failed to show significant changes in ceramide and TG, and exhibits much smaller increases in NAPE than other brain regions. Ethanol‐induced increases in ChE were observed in all brain regions tested. Inhibitors of serine palmitoyltransferase effectively blocked ethanol‐induced caspase 3 activation as well as elevations in ceramide, ChE, and NAPE. Immunohistochemical studies indicated that the expression of serine palmitoyltransferase was mainly localized in neurons and was enhanced in activated caspase 3‐positive neurons generated by ethanol. These results indicate that de novo ceramide synthesis has a vital role in ethanol‐induced apoptotic neurodegeneration in the developing brain.

Ganglioside accumulation in activated glia in the developing brain: comparison between WT and GalNAcT KO mice

“…The KO mice may need to eliminate a higher number of degenerating neurons than WT mice, or the endosomal/ lysosomal pathway may be disrupted in the KO mice because of the lack of GM2/GD2 or downstream gangliosides. In addition, the accumulation of GM2 or GD3/GM3 may be promoted by enhanced lipogenesis and augmented de novo ceramide/ganglioside synthesis by ethanol, as we have shown previously in C57BL/6By mice ( 15,17 ) and in cultured neurons ( 47 ). While mechanisms of preferential elevation of GM2 in phagocytic microglia in WT mice remain to be elucidated, accumulation of simple gangliosides, such as GM3 and GM2, have often been reported in lysosomal storage diseases, neurodegenerative diseases, and neuroinjury models ( 23, 27-29, 34-36, 50, 51 ).…”

“…Our previous studies using cultured neurons ( 47 ) or P7 mice ( 15,17 ) also suggest that the elevation of these lipids is partially due to enhanced lipogenesis and de novo ceramide synthesis by ethanol treatment. While we are not able to eliminate the possibility that ethanol increases the entry of serum lipids into the brain, our previous studies showing brain region-specifi c accumulation of TG, ChE, and NAPE ( 17 ), different accumulation kinetics among these lipids ( 15 ), and the different effects of neuroprotective agents on each lipid content ( 17,48 ) suggest that the entry of serum lipids is not a major cause of the observed lipid elevation in the brain. Table 1 shows that ceramide, ChE, and NAPE also increased in KO mice treated with ethanol, although the elevation of TG did not reach a statistically signifi cant level.…”

“…This dose of DMSO has been shown to induce widespread caspase-3 activation in the P7 brain ( 39 ). In addition to the increase in GM2, there were highly signifi cant increases in NAPE and ChE, as observed in ethanol-induced neurodegeneration ( Table 1 ) ( 15,17 ). Immunohistochemical studies ( Fig.…”

“…GD3, GM3, and 9-Oacetyl GD3 were major gangliosides in the KO brain because of the deletion of GalNAcT, as previously reported ( 37,38,46 ), and ethanol treatment further increased amounts of these gangliosides. We have shown previously not only GM2, but also other lipids, specifi cally ceramide, TG, ChE, and NAPE, increased in the ethanol-treated P7 mouse brain, and the elevation of these lipids appeared to be correlated with the severity of neural cell damage/ death ( 15,17 ). Our previous studies using cultured neurons ( 47 ) or P7 mice ( 15,17 ) also suggest that the elevation of these lipids is partially due to enhanced lipogenesis and de novo ceramide synthesis by ethanol treatment.…”

“…We have shown previously not only GM2, but also other lipids, specifi cally ceramide, TG, ChE, and NAPE, increased in the ethanol-treated P7 mouse brain, and the elevation of these lipids appeared to be correlated with the severity of neural cell damage/ death ( 15,17 ). Our previous studies using cultured neurons ( 47 ) or P7 mice ( 15,17 ) also suggest that the elevation of these lipids is partially due to enhanced lipogenesis and de novo ceramide synthesis by ethanol treatment. While we are not able to eliminate the possibility that ethanol increases the entry of serum lipids into the brain, our previous studies showing brain region-specifi c accumulation of TG, ChE, and NAPE ( 17 ), different accumulation kinetics among these lipids ( 15 ), and the different effects of neuroprotective agents on each lipid content ( 17,48 ) suggest that the entry of serum lipids is not a major cause of the observed lipid elevation in the brain.…”