Mitochondrial estrogen receptors as a vulnerability factor of chronic stress and mediator of fluoxetine treatment in female and male rat hippocampus

Abstract

Depression is a disease of an abnormal brain energy metabolism also marked with increased apoptosis in specific brain regions. Mounting evidence indicates that the mitochondrial oxidative phosphorylation and apoptosis are novel targets for the actions of estrogen receptors (ERs). In this study, we examined the effects of antidepressant (AD) fluoxetine (FLU) treatment on the mitochondria] ER alpha (ER alpha), ER beta (total and phospho-pER(beta) and their association with cytochrome c (cyt oxidase activity and apoptotic Bcl2/Bax-molecules in the hippocampal mitochondria of chronically isolated (CPSI) female and male rats depicting depression. Impaired behaviour induced by CPSI was followed by decreased corticosterone (CORT) in both sexes and downregulation of cyt c oxidase in males. CPSI did not affect the ERa in either of sexes, but it decreased mitochondrial ER beta and increased pER beta in both sexes. Stress-reduced ER beta is associated with a decrease in mitochondrial energetic processes in males and with apoptotic mechanisms in females. FLU normalized behaviour in both sexes and increased cyt c oxidase in females. FLU elevated ERa in males, increased ER beta and decreased pERB in both sexes. The AD-induced alterations of ER beta paralleled with bioenergetics and pro-survival pathways in females. In conclusion, sex-unspecific regulation of ER beta by the stress and by AD and its differential convergence with bioenergetics and apoptotic pathways in females and males implies its role as a vulnerability factor in the stress response and emphasizes mitochondrial ER beta-dependent pathways as an important gateway of ADs action, at least in females. (C) 2017 Elsevier B.V. All rights reserved.