Abstract 14745: Acute Post-ischemic GPER1 Activation Protects the Myocardium Against Ischemia/Reperfusion Injury by Reducing Mitochondrial Protein Ubiquitination, Histone Acetylation and Calpain10 levels and Inhibition of the mPTP Opening

Abstract

Introduction: We recently found that acute pre-ischemic estrogen-induced cardioprotection against ischemia/reperfusion injury was mainly mediated via G protein-coupled estrogen receptor1 (GPER1) activation but not through classical estrogen receptors: alpha (ERα) and beta (ERβ). Hypothesis: We investigated whether acute post-ischemic estrogen (PI-E2) treatment can also induce cardioprotective effect via GPER1 activation in the intact animal subjected to ischemia/reperfusion injury. Methods: Male and ovarectomized female Sprague-Dawley rats were anesthetized with ketamine (80 mg/kg i.p.) and xylazine (8 mg/kg i.p.). Hearts were subjected to 35 min of the left anterior descending (LAD) artery occlusion, followed by 180 min reperfusion. An E2 bolus (50 mg/kg body weight) or PBS (same volume) was applied via the femoral vein 5 min before reperfusion and a GPER1 antagonist, G15, was given 10 min before E2. Area at risk (AAR) was identified using Evans Blue dye and myocardial infarct size assessed by TTC staining method. Mitochondria calcium retention capacity (CRC) required to induce mitochondrial permeability transition pore (mPTP) opening was assessed after 10 min reperfusion. Expression levels of ubiquitinated; histone acetylated; calpains 1 and 10 proteins were measured by Western Blot in mitochondrial and cytosolic fractions. Results: We found that PI-E2 treatment reduced myocardial infarct size normalized to the AAR or the whole LV and improved mitochondrial CRC. PI-E2 treatment reduced protein histone acetylation in mitochondrial but not in cytosolic fractions, decreased mitochondrial proteins ubiquitination and also decreased calpain1 and calpain10 levels in cytosolic and mitochondrial fractions as compared to control, respectively. Interestingly, all these of E2 effects were abolished by addition of G15. Conclusion: Acute post-ischemic GPER1 activation by estrogen induces cardioprotection against ischemia/reperfusion injury. PI-E2 effects through GPER1 involve the reduction of the level of mitochondrial protein histone acetylation, ubiquitination, calpain1 and calpain10. This PI-E2-GPER1 effect is associated with the inhibition of the mPTP opening.