Gper Activation Inhibits Mitochondria Permeability Transition Pore Opening Via Erk Phosphorylation and Provides Cardioprotection after Ischemia-Reperfusion

Abstract

Recently, several studies have demonstrated G protein coupled receptor 30 (GPER) can directly bind to estrogen and mediate its action. We investigated the role and the mechanism of estrogen-induced cardioprotection after ischemia-reperfusion using a specific GPER agonist G1. Isolated hearts from male mice were perfused using Langendorff technique with oxygenated (95% O2 and 5% CO2) Krebs Henseleit buffer (control), with addition of G1 (1μM), and G1 (1μM)+PD98059 (10μM) to investigate the involvement of Erk pathway. After 20 min of perfusion, hearts were subjected to 20 min global normothermic (37°C) ischemia followed by 40min reperfusion. During the course of experiment cardiac function was measured and myocardial necrosis was evaluated by triphenyltetrazolium chloride (TTC) staining at the end of the reperfusion. Mitochondria were isolated after 10 minutes of reperfusion to assess the calcium load required to induce mPTP opening. G1 treated hearts developed better functional recovery with higher rate pressure product (RPP, 6140±264 vs. 2640±334 mmHgxbeats/min, p<0.05). The infarct size decreased significantly in G1 treated hearts (21±2% vs. 46±3% p<0.001) and the Ca2+ load required to induce mPTP opening increased (2.4±0.06 vs. 1.6±0.11 μM/mg mitochondrial protein, p<0.05) as compared to the controls. The addition of PD 98059 significantly prevents G1 effect on heart function RPP (4120±46 mmHgxbeats/min, p<0.05), infarct size (53±2%) and calcium retention capacity (1.4±0.11μM/mg mitochondrial protein p<0.05) These results suggest that GPER activation inhibits the mPTP opening and provide a cardioprotective effect after ischemia-reperfusion and this effect is mediated by Erk pathway. Supported by NIH and AHA.