G Protein-Coupled Estrogen Receptor 1 Mediates Acute Estrogen-Induced Cardioprotection via MEK/ERK/GSK-3β Pathway after Ischemia/Reperfusion

Three types of estrogen receptors (ER) exist in the heart, Esr1, Esr2 and the G protein-coupled estrogen receptor 1, Gper1. However, their relative importance in mediating estrogen protective action is unknown. We found that, in the male mouse ventricle, Gper1 transcripts are three- and seventeen-fold more abundant than Esr1 and Esr2 mRNAs, respectively. Analysis of the three ER knockouts (Esr1(-/-), Esr2(-/-) and Gper1(-/-)) showed that only the Gper1(-/-) hearts lost their ability to be protected by 40 nM estrogen as measured by heart function, infarct size and mitochondrial Ca(2+) overload, an index of mitochondrial permeability transition pore (mPTP) activity. Analysis of Akt, ERK(1/2) and GSK-3β salvage kinases uncovered Akt and ERK(1/2) transient activation by estrogen whose phosphorylation increased during the first 5 min of non-ischemic perfusion. All these increase in phosphorylation effects were abrogated in Gper1(-/-). Inhibition of MEK(1/2)/ERK(1/2) (1 μM U0126) and PI-3K/Akt (10 μM LY294002) signaling showed that the MEK(1/2)/ERK(1/2) pathway via GSK-3β exclusively was responsible for cardioprotection as an addition of U0126 prevented estrogen-induced GSK-3β increased phosphorylation, resistance to mitochondrial Ca(2+)-overload, functional recovery and protection against infarction. Further, inhibiting PKC translocation (1 μM chelerythrin-chloride) abolished estrogen-induced cardioprotection. These data indicate that estrogen-Gper1 acute coupling plays a key role in cardioprotection against ischemia/reperfusion injury in male mouse via a cascade involving PKC translocation, ERK(1/2)/GSK-3β phosphorylation leading to the inhibition of the mPTP opening.