Abstract 188: Rapid Estrogen-Induced Cardioprotection Effect is Mediated by Glycogen Synthase Kinase Independently of Akt Phosphorylation Pathway
Introduction: In this study, we investigated the role of Glycogen Synthase Kinase (GSK-3b) and of PI-3K-Akt as mechanisms of the rapid cardio-protective effect of 17β-estradiol (E2) during ischemia/reperfusion injury.
Methods: Isolated heart mice were retrograde-perfused using the Langendorff system at 37oC. After 20 min perfusion, hearts were subjected to 20 min global normothermic ischemia followed by 40 min of reperfusion. Hearts were perfused with Krebs-Henseleit (KH) solution or KH+E2 (40 nM) and oxygenated with 95% O2 and 5% CO2. Cardiac function was continuously recorded and infarct size was evaluated by TTC staining after 40 min after reperfusion. In other groups of experiments after 10 min of reperfusion, mitochondria were isolated to measure calcium retention capacity (CRC), ROS production by stimulation of complexes I and II; or whole cell lysates were immunoblotted to detect pGSK-3b/GSK-3b, pErk/Erk, pAkt/Akt and vinculin protein levels.
Results: The E2-treated group had increased mitochondrial CRC (0.73±0.11μM vs. 1.3±0.06, p< 0.01), reduced infarct size (43±3% vs. 68±5%, p< 0.001) and improved heart functional recovery compared to control group. The ROS production by complex I stimulation (glutamate/malate) was similar in all groups but the ROS production when complex II was stimulated with succinate was significantly increased in the E2 treated group compared to control. pGSK-3b/GSK-3b and pErk/Erk ratios increased with E2 treatment while pAkt/Akt remained.
Conclusions: These results indicate that rapid E2 exposure inhibits the mPTP opening resulting in a reduction of the infarct size, improvement of heart function recovery and respiratory chain preservation via GSK-3b and Erk phosphorylation independently of Akt phosphorylation.
- © 2010 by American Heart Association, Inc.