Investigating the anoxic protective effects of sex hormones and EphrinA1

Abstract

Cardiovascular disease is the most prevalent and debilitating disease in the US and globally. There is no cure, and its devastating socioeconomic impact continues to progress. Studies have shown that the occurrence of myocardial infarction (MI) differs by age, sex, and physical well-being, but little is known about the specific mechanism behind these discrepancies. Researchers hypothesize that these differences may be partly due to the varying expression of the predominant sex hormones estradiol (E2) in females and testosterone (T) in males, which change with age. Both hormones are linked to cardioprotection, and the decreased expression of them in elderly and obese populations likely contributes to their increased risk of MI. Our lab has shown that healthy mouse and human heart cells (cardiomyocytes) express ephrinA1. Administration of recombinant ephrinA1-Fc to the ischemic heart during injury onset reduces tissue damage and preserves cardiac function in acute and chronic mouse models of MI. In vitro treatment of human inducible pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) with ephrinA1-Fc preserved 84% of cells subjected to 24 hours of anoxia. One mechanism by which sex hormones may influence cardioprotective outcomes is by modulating the expression of the protein EphrinA1 and its cognate EphA receptors in cardiomyocytes. To test this hypothesis, we investigated the effects of varying levels of testosterone or estradiol on ephrinA1/EphA expression to determine if they have a role in modulating ephrinA1-Fc-induced protection from anoxic injury. Specifically, human inducible pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) will undergo anoxia by treatment with Oxyrase to remove all oxygen, simulating an ischemic event. These cells were treated with ephrinA1-Fc in the presence of either 0, 0.1, 1.0, 10, 100, or 1,000 M of T or E2, respectively. Cell survival and Western blotting for proteins involved in protective response (anti-apoptosis, autophagy, and metabolism) were used to determine the effects of the varying sex hormone concentrations on the molecular mediators of apoptosis, metabolism, and autophagy.