Estrogen: The Current Status and the Future Role in Postconditioning Protection to the Heart

Ischemic Heart Disease (IHD) is one of the leading causes of worldwide morbidity and mortality. Reperfusion was the first procedure used to rescue the ischemic heart; however, this procedure is associated with subsequent reperfusion injury. Ischemic Preconditioning (IPC) was introduced as an intervention to protect against the potential injury before the insult occurred. Yet, the application of IPC in the clinic was limited because the onset of ischemia is not predictable and neither was the amount of damage caused by the event. Thus, Ischemic Postcondtioning (IPOC) was introduced as an intervention immediately following reperfusion in order to surpass the shortcomings of preconditioning translation in the clinic. Several methods and procedures were used in postconditioning, among them are postconditioning with estrogen (17-β estradiol (E2)) and Selective E2 Receptors Modulators (SERMs). However, the role of E2 is controversial and its research was challenged by the unexpected outcomes of two large clinical trials (heart and Oestrogen/progestin Replacement Study (HERS) and Women's Health Initiative (WHI). Controversy still exists regarding the results of the experiments using E2; however, many scientists still believe that the potentials of E2 are yet to be unraveled. The aim of this review is to highlight the use and effects of E2 in postconditioning, as well as its possible use in future clinical research.