Endothelial estrogen receptor α plays an essential role in the coronary and myocardial protective effects of estradiol in ischemia/reperfusion

Abstract

Objective- To assess the coronary endothelial protective effects of 17β-estradiol (E2) and the role of estrogen receptor (ER) α in ischemia/reperfusion (I/R). Methods and Results- E2 exerts protective effects in cardiac I/R. However, the implication in vivo of the endothelium and the cellular targets of the anti-ischemic effects of E2 are unknown. Mice were subjected to I/R (30 minutes of I and 1 hour of R) in vivo, after which acetylcholine-induced relaxation of isolated coronary segments was assessed ex vivo. I/R induced a coronary endothelial dysfunction in untreated ovariectomized mice that was prevented by long-term treatment with E2 in wild-type, but not in ERα, mice. Chimeric mice inactivated for ERα in the hematopoietic compartment remained protected by E2. Further inactivation of endothelial ERα abolished the protective action of E2 on coronary endothelial function in Tie2-Cre(+) ERα mice. More importantly, E2 significantly limited infarct size in wild-type mice but not in mice deficient in endothelial ERα, even in the presence of hematopoietic ERα. Conclusion- Endothelial ERα plays a crucial role in the E2-induced prevention of endothelial dysfunction after I/R. To our knowledge, we demonstrate for the first time, by using unique genetically modified mice, that targeting endothelial protection per se can confer cardiomyocyte protection in I/R. © 2010 American Heart Association. All rights reserved.