Ethanol impairs activation of retinoic acid receptors in cerebellar granule cells in a rodent model of fetal alcohol spectrum disorders.
BACKGROUND
Ethanol is the main addictive and neurotoxic constituent of alcohol. Ethanol exposure during embryonic development causes dysfunction of the central nervous system (CNS) and leads to fetal alcohol spectrum disorders. The cerebellum is one of the CNS regions that are particularly vulnerable to ethanol toxic effects. Retinoic acid (RA) is a physiologically active metabolite of vitamin A that is locally synthesized in the cerebellum. Studies have shown that RA is required for neuronal development, but it remains unknown if ethanol impairs RA signaling and thus induces neuronal malformations. In this study, we tested the hypothesis that ethanol impairs the expression and activation of RA receptors in cerebellum and in cerebellar granule cells.


METHODS
The cerebellum of ethanol unexposed and exposed pups was used to study the expression of retinoic acid receptors (RARs or RXRs) by immunohistochemistry and by Western blot analysis. We also studied the effect of ethanol on expression of RA receptors in the cerebellar granule cells. Activation of RA receptors (DNA-binding activities) in response to high-dose ethanol was determined by electrophoretic mobility shift and supershift assays.


RESULTS
Findings from these studies demonstrated that ethanol exposure reduced the expression of RARalpha/gamma while it increased the expression of RXRalpha/gamma in the cerebellum and in cerebellar granule neurons. Immuno-histological studies further strengthened the expression pattern of RA receptors in response to ethanol. The DNA-binding activity of RARs was reduced, while DNA-binding activity of RXRs was increased in response to ethanol exposure.


CONCLUSIONS
For the first time, our studies have demonstrated that high-dose ethanol affects the expression and activation of RA receptors, which could impair the signaling events and induce harmful effects on the survival and differentiation of cerebellar granule cells. Taken together, these findings could provide insight into the treatment options for brain defects caused by excessive ethanol exposure, such as in Fetal Alcohol Spectrum Disorders.
Kumar
Ambrish
A
Department of Pathology, Microbiology, and Immunology, University of South Carolina School of Medicine, Columbia, 29209, USA.
Singh
Chandra K
CK
DiPette
Donald D
DD
Singh
Ugra S
US
D000428:Alcohol Drinking / Q000009:adverse effects / Q000378:metabolism / Q000473:pathology; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D002531:Cerebellum / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000378:metabolism; D004195:Disease Models, Animal; D000431:Ethanol / Q000008:administration & dosage*; D005260:Female; D063647:Fetal Alcohol Spectrum Disorders / Q000378:metabolism* / Q000473:pathology; D011247:Pregnancy; D011897:Random Allocation; D051381:Rats; D020318:Rats, Long-Evans; D018168:Receptors, Retinoic Acid / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D000072482:Retinoic Acid Receptor alpha; D000097768:Retinoic Acid Receptor gamma
D000431:Ethanol; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D000097768:Retinoic Acid Receptor gamma; C000607073:Rara protein, rat