Abstract 19034: Activation of GPER1 at the Reperfusion Protects the Ischemic Myocardium Against Injury by Decreasing Mitophagy and Delaying the mPTP Opening
Introduction: We recently showed that pre-ischemic estrogen (17 β-estradiol) treatment induces cardioprotective effects against ischemia/reperfusion (I/R) injury via G-protein coupled estrogen receptor1 (GPER1) activation by preserving mitochondrial integrity and function via MEK/ERK/GSK-3β pathway.
Hypothesis: We investigated whether post-ischemic estrogen (PI-E2) treatment can also induce cardioprotective effects via GPER1 activation and determine whether PI-E2 action involves the reduction of mitophagy and the mitochondrial permeability transition pore (mPTP) opening.
Methods: Male and ovariectomized female Sprague-Dawley rats were used. Hearts were subjected to 35 min of the left anterior descending artery occlusion followed by 180 min reperfusion. An estrogen bolus (50 mg/kg body weight) or PBS (same volume) was applied via the femoral vein 5 min before reperfusion, and GPER1 antagonist, G15, given 10 min before estrogen. Area at risk (AAR) was identified using Evans Blue dye and myocardial infarct size assessed by TTC staining. Mitochondrial calcium retention capacity (CRC) required to induce mPTP opening was assessed after 20 min reperfusion. Expression of LC3I, LC3II, p62, and pERK was detected by western blot in whole cell lysates. Total Parkin and ubiquitinated proteins were measured by Western blot in cytosolic and mitochondrial fractions.
Results: We found that PI-E2 treatment reduced myocardial infarct size normalized to the AAR or to the whole left ventricle and increased mitochondrial CRC compared to untreated. We also found that PI-E2 treatment decreased the level of LC3I and LC3II, and increased the level of p62 and pERK1/2. PI-E2 inhibited the translocation of Parkin from the cytosol to mitochondria and decreased mitochondrial ubiquitinated proteins as compared to control. Interestingly, all these PI-E2 effects were abolished by co-treatment with G15.
Conclusion: PI-E2 treatment induces cardioprotective effects against I/R injury via GPER1 activation. PI-E2 effects via GPER1 involve inhibition of mitophagy and reduction of mitochondrial protein ubiquitination. Together, these E2-GPER1 effects lead to inhibition of the mPTP opening, and subsequently cardioprotection.
Author Disclosures: Y. Feng: None. M. Lie: None. N. Madungwe: None. M. Kabir: None. J. Bopassa: None.
- © 2016 by American Heart Association, Inc.