Dehydroepiandrosterone administration improves memory deficits following transient brain ischemia through sigma-1 receptor stimulation

Dehydroepiandrosterone (DHEA) is the most abundant neurosteroid synthesized de novo in the central nervous system. Oral DHEA administration elicits neuroprotection and cognitive improvement, but mechanisms underlying these functions in cerebral ischemia have remained unclear. Since DHEA is the endogenous ligand for the sigma-1 receptor (sigma 1R), we determined whether oral DHEA administration prevents neuronal cell death and improves cognition via sigma 1R stimulation in brain ischemia using a 20-min bilateral common carotid artery occlusion (BCCAO) mouse model. Twenty-four hours after BCCAO ischemia, mice were administered DHEA (15 or 30 mg/kg p.o.) daily for 11 consecutive days. Memory deficits following brain ischemia were improved by DHEA administration dose-dependently. Accordingly, DHEA administration significantly prevented neuronal cell death in the hippocampal CA1 region in BCCAO mice. Interestingly, DHEA administration rescued decreases in Ca2+/calmodulin-dependent protein kinase II (CaMKII) autophosphorylation and phosphorylation of extracellular signal-regulated kinase (ERK) and protein kinase B (Akt) in the CA1 region. Moreover, DHEA administration significantly ameliorated decreases in adenosine 5'-triphosphate (ATP) levels and decreased sigma 1R expression levels in CA1 following BCCAO ischemia. Finally, co-treatment of mice with the sigma 1R antagonist NE-100 (1 mg/kg, p.o.) blocked DHEA effects on memory improvement and neuroprotection in ischemic mice. Taken together, DHEA prevents neuronal cell death and activates CaMKII via sigma 1R stimulation, thereby improving cognitive deficits following brain ischemia. (C) 2015 Elsevier B.V. All rights reserved.