Endothelial Estrogen Receptor α Plays an Essential Role in the Coronary and Myocardial Protective Effects of Estradiol in Ischemia/Reperfusion
2010
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(+) ERαf/f 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.
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