Embryonic cerebral cortical progenitors are resistant to apoptosis, but increase expression of suicide receptor DISC-complex genes and suppress autophagy following ethanol exposure.
BACKGROUND
In utero exposure to ethanol can result in severe fetal brain defects. Previous studies showed that ethanol induces apoptosis in differentiated cortical neurons. However, we know little about ethanol's effects on proliferating embryonic cortical progenitors. This study investigated the impact of ethanol exposure on the Fas/Apo-1/CD95 suicide receptor pathway, and on the survival of proliferating cortical neuroepithelial progenitors.


METHODS
Murine embryonic-derived primary cortical neuroepithelial cells were maintained as neurosphere cultures and exposed to a dose range of ethanol for periods ranging from 1 to 5 days. Programmed cell death was measured by 4 independent means (Annexin-V staining, caspase activation, DNA fragmentation, and autophagic vacuole formation). Surface Fas/Apo-1 suicide receptor expression was measured by flow cytometry. Expression of Fas/Apo-1-associated DISC-complex genes was measured by quantitative polymerase chain reaction.


RESULTS
Ethanol exposure did not substantially increase apoptosis, necrosis, or surface Fas/Apo-1 expression. Moreover, ethanol significantly decreased caspase activation and autophagic activity. Finally, ethanol exposure induced mRNA expression of genes that constitute the death receptor complex.


CONCLUSIONS
This study provides surprising evidence that ethanol does not induce either programmed cell death or necrosis of immature progenitors during neurogenesis, although ethanol may render neural progenitors susceptible to future apoptotic insults. Furthermore, our novel observation that ethanol suppresses autophagy is consistent with a hypothesis that ethanol promotes premature neural progenitor maturation. Taken together with our previous data regarding the role of the Fas/Apo-1 receptor in neural development, we conclude that ethanol disrupts basic proliferation and differentiation machinery rather than initiating cell death per se.
Prock
Terasa L
TL
Department of Neuroscience and Experimental Therapeutics, Texas A&M University, Health Science Center College of Medicine, College Station, Texas 77843, USA.
Miranda
Rajesh C
RC
D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002492:Central Nervous System Depressants / Q000633:toxicity*; D002540:Cerebral Cortex / Q000166:cytology* / Q000196:embryology*; D053938:DNA Fragmentation; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000235:genetics*; D004789:Enzyme Activation / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000187:drug effects; D000431:Ethanol / Q000633:toxicity*; D005260:Female; D005434:Flow Cytometry; D005470:Fluorometry; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects; D011247:Pregnancy; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013234:Stem Cells / Q000187:drug effects*; D019014:fas Receptor / Q000378:metabolism
D017304:Annexin A5; D002492:Central Nervous System Depressants; D053418:Death Domain Receptor Signaling Adaptor Proteins; D019014:fas Receptor; D000431:Ethanol; D020169:Caspases