Abstract 323: G-Protein Coupled Estrogen Receptor 1 Activation Protects the Heart Against Ischemia/Reperfusion Injury by Inhibiting the mPTP Opening via PKC/ERK/GSK-3? Pathway

Abstract

Estrogen effect can be mediated by three receptors: Classical estrogen receptors: alpha (ERα) and beta (ERβ), and recently identified G protein-coupled estrogen receptor1 (GPER1). We investigated the role of ERα, ERβ and GPER1 in mediating rapid estrogen-induced cardioprotection in male mice hearts subjected to ischemia/reperfusion using wild type (WT) and gene specific knockout animals. 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 estrogen (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 (mPTP) opening was assessed after 10 min reperfusion. Protein levels were measured by Western Blot in whole heart lysates after 5 min treatment just before ischemia, and after 10 min reperfusion. LY294002, U0126 and Chelerythrin-Cl were used as inhibitor of PI-3K/Akt, MAPK/ERK and PKC translocation, respectively. In WT, ERα -/- and ERβ -/- , estrogen treatment significantly improved cardiac functional recovery, reduced infarct size and improved mitochondrial CRC. However, estrogen effects were completely absent in GPER1 -/- . Estrogen treatment during 5 min before ischemia induced up-regulation of Akt, GSK-3β, and ERK 1/2 phosphorylation in WT mouse as compared with control but not in GPER1 -/- . However, after 10 min reperfusion estrogen effect was still oserved on GSK-3β, but not on Akt and ERK 1/2 . Chelerythrin-Cl, and U126, inhibitors of MEK and PKC translocation, respectively abolished estrogen-induced cardioprotection while LY294002, a PI-3K inhibitor, did not prevent estrogen-induced cardioprotection in observed in WT. P<0.05 and n=4-7. Rapid activation of GPER1 induces cardioprotection effect against ischemia/reperfusion injury. Estrogen effects through GPER1 are mediated by phosphorylation of GSK-3β and ERK 1/2 , PKC translocation, and inhibition of the mPTP opening.