Acute ethanol inhibits extracellular signal-regulated kinase, protein kinase B, and adenosine 3':5'-cyclic monophosphate response element binding protein activity in an age- and brain region-specific manner.
BACKGROUND
As little as a single episode of exposure of the developing brain to ethanol can result in developmental neuropathology and mental retardation. Extracellular signal-regulated kinases (ERKs), protein kinase B (PKB), and adenosine 3':5'-cyclic monophosphate response element binding protein (CREB) are messenger molecules that play important roles in neuronal plasticity and survival. This study was undertaken to examine the effects of acute ethanol on ERK, PKB, and CREB activation in the brain.


METHODS
Immunoblot analysis was used to determine the effects of a 1-hr exposure of ethanol on levels of phospho-ERC in primary cortical cultures and in the cerebral cortex, hippocampus, and cerebellum of postnatal day 5 (PN5), postnatal day 21 (PN21), and adult rats.


RESULTS
In cortical cultures, ethanol (100 mM) significantly reduced activity-dependent activation of phospho-ERK, phospho-PKB, and phospho-CREB by approximately 50%. In PN5 rats, ethanol (3.5 g/kg) inhibited both phospho-ERK and phospho-PKB in the cerebral cortex and hippocampus but was without effect in the cerebellum. A similar brain region-specific inhibition of phospho-ERK was observed in PN21 rats, whereas in adult rats, ethanol inhibited phospho-ERK in all three brain regions. In contrast, ethanol had no effect on phospho-PKB in either PN21 or adult rats. Without exception, ethanol inhibited phospho-CREB in an identical brain region- and age-dependent manner as was observed for phospho-ERK. Finally, administration of the NMDA antagonist MK-801 (0.5 mg/kg) to PN5 rats had no effect on phospho-ERK or phospho-PKB levels in any brain region.


CONCLUSIONS
The results demonstrate that acute ethanol inhibits ERK/PKB/CREB signaling in brain. This inhibition occurs in an age- and brain region-specific manner, with inhibition of PKB restricted to a time during the brain growth-spurt period. Furthermore, the lack of effect of MK-801 suggests that inhibition of NMDA receptors is unlikely to play a major role in binge ethanol inhibition of ERK/PKB/CREB signaling in vivo.
Chandler
L Judson
LJ
Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina 29425, USA. chandj@musc.edu
Sutton
Greg
G
D000375:Aging / Q000502:physiology*; D000818:Animals; D015153:Blotting, Western; D001923:Brain Chemistry / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002492:Central Nervous System Depressants / Q000097:blood / Q000494:pharmacology*; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D000431:Ethanol / Q000097:blood / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors*; D005260:Female; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D000090204:Mesothelin; D009473:Neuronal Plasticity / Q000187:drug effects; D010766:Phosphorylation; D011247:Pregnancy; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley
D002492:Central Nervous System Depressants; D017362:Cyclic AMP Response Element-Binding Protein; D018691:Excitatory Amino Acid Antagonists; C000715529:Msln protein, rat; D011518:Proto-Oncogene Proteins; D000431:Ethanol; D016291:Dizocilpine Maleate; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D000090204:Mesothelin