Acute postischemic treatment with estrogen receptor-α agonist or estrogen receptor-β agonist improves myocardial recovery

Background: After ischemia/reperfusion (I/R) injury, female hearts demonstrate improved functional recovery compared with male, which suggests a protective role for estrogen. Acute postischemic treatment with 17-β-estradiol (E2) attenuates myocardial dysfunction. However, it is unknown by which estrogen receptor (ER) E2 mediates this acute cardioprotection during I/R. Therefore, we hypothesize that postischemic infusion of the selective ER-α agonist (4,4',4''-[4-propyl-(1H)-pyrazole-1,3,5-triyl]tris-phenol [PPT]) or the selective ER-β agonist (2,3-bis(4-hydroxyphenyl)-propionitrile [DPN]) will improve myocardial function after I/R injury. Methods: Isolated, perfused hearts (Langendorff) from adult male rats were subjected to 25 minutes of ischemia followed by 40 minutes of reperfusion. Hearts (n = 4-6 per group) were randomly infused with either perfusate, PPT or DPN at 1, 10, or 100 nmol/L throughout reperfusion. After I/R, heart tissue was analyzed for tumor necrosis factor (TNF)-α, interleukin (IL)-1β, vascular endothelial growth factor (VEGF), and lactate dehydrogenase (LDH). Results: Postischemic treatment with 10 nmol/L of PPT significantly improved myocardial function. Additionally, 10 or 100 nmol/L of DPN significantly increased myocardial functional recovery after I/R injury, with maximum benefit at the 10 nmol/L dose. A trend toward lower levels of LDH was noted in DPN- and PPT-treated groups after I/R injury. Neither PPT nor DPN affected myocardial production of TNF-α or IL-1β. However, higher levels of myocardial VEGF were noted in the PPT-treated group compared with controls. Conclusion: Both ER-α and ER-β are involved in mediating E2-induced rapid cardioprotection after I/R injury. Advancing our understanding of both ER subtypes may be useful for the development of novel strategies that may benefit both males and females in response to myocardial ischemia.