Novel Insights into Post-Ischemic Estrogen Cardioprotection Against I/R Injury

Project: Research


  • Jean C. Bopassa (PI)


Long-term estrogen (E2) effects are mediated via classical estrogen receptors alpha (ERa) and beta (ERb). Conversely, rapid E2 actions are mediated by G protein-coupled estrogen receptor 1 (GPER1). We have discovered that acute (~1 hour) pre-ischemic E2 treatment induces similar cardioprotection in WT, ERa-/- and ERb-/- mice, but not in GPER1-/- mice, indicating a key role for GPER1 in pre-ischemic E2 actions. Here, we will define the efficacy and molecular mechanisms underlying post-ischemic (PI) GPER1 cardioprotection. Our preliminary data indicate that PI-E2 treatment of male or ovarectomized (OVX) female WT mice hearts subjected to ischemia-reperfusion (I/R) improved cardiac functional recovery, reduced myocardial infarct size, delayed mitochondrial permeability transition pore (mPTP) opening, and up-regulated phosphorylation of ERK1/2 and GSK-3b. In isolated cardiomyocytes, E2 treatment reduced apoptosis while PI-E2 administration to intact male or OVX female mice reduced myocardial infarct size vs. saline. Of importance, all these PI-E2 effects were prevented by the GPER1 antagonist G15, and were absent in GPER1-/- mice, suggesting a GPER1-dependent mechanism. Using 2D-DIGE and mass spectrometry, we identified mitofilin, a key regulator of mitochondrial cristae integrity, as a protein up-regulated during E2-GPER1 action. Initial data reveal that mitofilin structurally links with cyclophilin D (CypD), a component of mPTP, and the mitofilin-CypD interaction is reduced after I/R. We found that the mechanism of reduction of mitofilin loss involves a decrease in mitochondrial protein ubiquitination, and reduction of mitophagy and mitochondrial calpain10 activity. We thus hypothesize that PI-GPER1 activation confers cardioprotection by activating MEK/ERK/GSK-3b; pathway leading to reduced mitochondrial protein ubiquitination, mitophagy and calpain10 cleavage of mitofilin, which interacts with CypD to delay the mPTP opening and thus improve mitochondrial function. To test this hypothesis, we will: 1. Define the impact of mitofilin in PI-GPER1 cardioprotection, define whether GPER1 activation reduces myocardial inflammation, and define the specific role of cardiac GPER1 in cell death. 2. Define the molecular mechanisms underlying PI-GPER1 inhibition of the mPTP opening, and determine whether PI-GPER1 reduction of mitophagy and calpain10 cleavage of mitofilin protects the mitofilin-CypD link leading to improved mitochondrial structural integrity and fun
Award amount$231,000.00
Award date01/01/2017
Program typeScientist Development Grant
Award ID17SDG33100000
Effective start/end date01/01/201712/31/2019