Estradiol in vivo regulation of brain mitochondrial proteome

We used a combined proteomic and functional biochemical approach to determine the overall impact of 17β-estradiol (E₂) on mitochondrial protein expression and function. To elucidate mitochondrial pathways activated by E₂ in brain, two-dimensional (2D) gel electrophoresis was conducted to screen the mitoproteome. Ovariectomized adult female rats were treated with a single injection of E₂. After 24 h of E₂ exposure, mitochondria were purified from brain and 2D analysis and liquid chromatography-tandem mass spectrometry protein identification were conducted. Results of proteomic analyses indicated that of the 499 protein spots detected by image analysis, a total of 66 protein spots had a twofold or greater change in expression. Of these, 28 proteins were increased in expression after E₂ treatment whereas 38 proteins were decreased in expression relative to control. E2 regulated key metabolic enzymes including pyruvate dehydrogenase, aconitase, and ATP-synthase. To confirm that E ₂-inducible changes in protein expression translated into functional consequences, we determined the impact of E₂ on the enzymatic activity of the mitochondrial electron transport chain. In vivo, E₂ treatment enhanced brain mitochondrial efficiency as evidenced by increased respiratory control ratio, elevated cytochrome-c oxidase activity and expression while simultaneously reducing free radical generation in brain. Results of these analyses provide insights into E₂ mechanisms of regulating brain mitochondria, which have the potential for sustaining neurological health and prevention of neurodegenerative diseases associated with mitochondrial dysfunction such as Alzheimer's disease.