Abstract 271: Rapid Estrogen-Induced Cardioprotection Is Mainly Mediated by G-Protein--Coupled Estrogen Receptor 1 During Ischemia/Reperfusion

Abstract

Introduction: Numerous basic and clinical studies have demonstrated that 17β-estradiol (E2) has a protective effect on cardiovascular function. The long-term effects of E2 are mediated via classical estrogen receptors: alpha (ERα) and beta (ERβ) through genomic and non-genomic targets while rapid E2-induced protection seems to be mediated by the recent identified G-protein coupled estrogen receptor1 (GPER1). Hypothesis: We investigated the role of ERα, ERβ and GPER1 in mediating rapid E2-induced cardioprotection in male mice hearts subjected to ischemia/reperfusion (I/R) using wild type (WT) and specific knockout animals. Methods: Ventricles possess GPER1>ERα>ERβ mRNA levels quantified in absolute values with quantitative Real Time PCR. Isolated hearts from wild type (WT: C57BL/6NCrL), ERα -/- , ERβ -/- and GPER1 -/- were perfused using Langendorff apparatus with Krebs Henseleit buffer (control) or with the addition of E2 (40 nM). Hearts were subjected to 18 min global ischemia followed by 60 min reperfusion. Cardiac function was recorded during the entire experiment and myocardial infarct size measured by TTC staining at the end of the reperfusion. Mitochondria calcium retention capacity (CRC) required to induce the mitochondrial permeability transition pore opening (mPTP) opening was assessed and protein levels were measured by Western Blot in whole heart lysates after 10 min reperfusion. Results: In WT, ERα -/- and ERβ -/- , E2 treatment significantly improved cardiac functional recovery, reduced infarct size and improved mitochondrial CRC. However, E2-induced cardioprotective effects were completely absent in GPER1 -/- . Rapid E2 treatment induced up-regulation of GSK-3β, ERK 1/2 and PKC β II phosphorylation in WT mouse compared to control but not in GPER1 -/- . The reported results were statistically significant different with P<0.05 and n=3-6. Conclusion: These results suggest that GPER1 plays a major role in mediating rapid E2-induced cardioprotection after I/R. E2 effects through GPER1 are associated with phosphorylation of GSK-3β, ERK 1/2 and PKC βII and inhibition of the mPTP opening.