Loss of Rapid Estrogen-Induced Cardioprotection in GPER -/- Mice After Ischemia and Reperfusion

Abstract

Several studies have demonstrated that G protein coupled receptor 30 (GPER) can directly bind to 17ß-estradiol (E2) mediating its action. Using pharmacological tools, we previously identified GPER as possible mediator of E2-mediated cardioprotection in male wild type (WT) mice subjected to ischemia/reperfusion. Here, we investigate this point further using GPER-/- mice.Isolated hearts from male WT (C57BL/6NCrL) or GPER-/- mice were perfused using the Langendorff technique with oxygenated (95% O2 and 5% CO2) Krebs Henseleit buffer (control) containing or not 40 nM E2. After 20 min of perfusion, hearts were subjected to 18 min global normothermic ischemia followed by 60 min reperfusion. Heart function was continuously recorded and myocardial necrosis was evaluated by TTC staining after the reperfusion. Mitochondria were isolated after 10 minutes of reperfusion to assess the calcium load required to induce opening of mitochondria permeability transition pore referred as Calcium Retention Capacity (CRC). In WT mice, E2 treatment induced a much better recovery of heart function when compared with untreated hearts (RPP, 11900±467 vs. 5911±318 mmHgxbeats/min, p<0.001). In contrast, E2 treatment had no beneficial action in GPER-/- mice. No functional differences between E2-treated and control were found (RPP, 6370±655 vs. 6200±380 mmHgxbeats/min). Similarly, the infarct size decreased significantly in WT hearts after E2-treatment (26±3% vs. 54±2.8% p<0.001) but this protective infarct reduction by E2 treatment was not observed in GPER-/- hearts (46±5% vs. 50±4%). A similar pattern was found with CRC. E2 treatment in WT hearts significantly increased the mitochondria CRC (287±17 vs. 180±12 nM/mg mitochondrial protein, p<0.05), but it had no effect on CRC from mitochondria of GPER-/- hearts (170±33 vs. 167±7 nM/mg mitochondrial protein). These results conclusively demonstrate that GPER plays an important role in mediating rapid E2-induced cardioprotection after ischemia/reperfusion. Supported by NIH.