Abstract
Adolescent intermittent ethanol (AIE) exposure diminishes neurogenesis and dendritic spine density in the dentate gyrus. The cholinesterase inhibitor, donepezil (Aricept), reverses AIE effects on dendritic spines, possibly by interacting with inflammatory and/or epigenetic mediators after AIE exposure. This study tests the hypothesis that donepezil reverses AIE-induced neuroimmune, and epigenetic changes in the adult dentate gyrus. Adolescent Sprague-Dawley male rats (PD30-43) were given 10 intermittent, intragastric doses of ethanol (5.0 g/kg) or isovolumetric water (AIW). Twenty-one days later half of the animals from each group were treated with either donepezil or isovolumetric water (i.g.) once daily for four days. Two hours after the last donepezil or water dose animals were sacrificed and brains prepared for immunohistochemical analyses. AIE reduced immunoreactivity for doublecortin (DCX) and increased immunoreactivity for activated caspase-3 and death receptor-3 in adulthood, suggesting an enduring attenuation of neurogenesis and an increase in progenitor death. These effects were reversed by donepezil treatment in adulthood. AIE also increased immunoreactivity for the inflammatory signaling molecules HMGB1 and RAGE, as well as the activated phosphorylated transcription factor pNFκB p65, and the gene silencing marker dimethylated histone H3K9. All of these AIE effects were also reversed by donepezil, with the exception of HMGB1.
Highlights
Www.nature.com/scientificreports a robust indicator of neuron formation and is greater in adolescence and declines in middle age
Adolescent intermittent ethanol (AIE) exposure reduces hippocampal dentate gyrus neurogenesis and the AIE deficit is reversed by Donepezil
A protein only expressed in developing neuroprogenitor cells, but not mature neurons, as a marker for neurogenesis in AIE exposed animals compared to controls in adulthood, as has been reported previously[34,49]
Summary
Www.nature.com/scientificreports a robust indicator of neuron formation and is greater in adolescence and declines in middle age. Most studies have found no marked effects of AIE on simple spatial learning tasks in the absence of acute ethanol or other challenges29,31,32 – we have shown modest but significant deficits on an object recognition task that simultaneously assesses both spatial and temporal object recognition[33] These deficits may be attributed to the changes induced by AIE in hippocampal structure and function. Histone deacetylase inhibitors alter epigenetic gene silencing, are anti-inflammatory and have been found to reverse AIE induced inhibition of neurogenesis and restore brain-derived neurotropic factor (BDNF) expression[14] For these reasons the present experiments were designed to assess the effects of AIE on neurogenesis and neural survival in the dentate gyrus and to determine if changes in those parameters are accompanied by changes in the expression of inflammatory and epigenetic markers and/or reversed by sub-chronic systemic treatment with donepezil
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