Gsk Mediates Rapid Estrogen-Induced Cardioprotection Without Akt Activation After Ischemia/Reperfusion

Abstract

We investigated the role of Glycogen Synthase Kinase (GSK-3β), Erk and Akt activation in rapid 17ß-estradiol (E2)-induced cardioprotection after ischemia/reperfusion. Isolated mice hearts were retrograde-perfused using the Langendorff system at 37oC. Hearts were perfused with oxygenated (95% O2 and 5% CO2) Krebs Henseleit solution (control) or with E2 (40 nM). After 20 min perfusion, hearts were subjected to 20 min global normothermic ischemia followed by 40 min reperfusion. Cardiac function was recorded throughout the experiment and at the end of the reperfusion (60 min) infarct size was evaluated by TTC staining. After 10 min of reperfusion, mitochondria were isolated to assess the calcium load required to induce the opening of mitochondria permeability transition pore (mPTP) referred as Calcium Retention Capacity (CRC), and whole heart lysates were prepared for Western blot analysis of pGSK-3β, pErk, pAkt and vinculin. The E2-treated group had significantly increased CRC (287±17 vs. 180±12 nM/mg mitochondrial protein p<0.05), reduced infarct size (26±3% vs. 54±2.8% p<0.001) and improved heart functional recovery (RPP, 11900±467 vs. 5911±318 mmHgxbeats/min, p<0.001) when compared to control. GSK-3β and Erk1/2 phosphorylation levels were significantly increased in E2-treated hearts (∼3 and ∼2 fold, respectively) without significant changes in Akt phosphorylation. These results indicate that rapid E2-induced cardioprotection inhibits the mPTP opening resulting in a reduction of the infarct size and improvement of heart function recovery via GSK-3β and Erk phosphorylation independently of Akt phosphorylation. Supported by NIH.