Female Adult Mouse Cardiomyocytes Are Protected Against Oxidative Stress

Premenopausal women have less cardiovascular disease and lower cardiovascular morbidity and mortality than men the same age. Our previous studies showed that female mice have lower mortality and better preserved cardiac function after myocardial infarction. However, the precise cellular and molecular mechanisms responsible for such a sex difference are not well established. Using cultured adult mouse cardiomyocytes, we tested the hypothesis that the survival advantage of females stems from activated estrogen receptors and Akt survival signaling pathways. Adult mouse cardiomyocytes were isolated from male and female C57BL/6J mice and treated with hydrogen peroxide (100 micromol/L) for 30 minutes. Cell survival was indicated by rod ratio (rod shaped cells:total cells), cell death by lactate dehydrogenase release, and positive staining of annexin-V (a marker for apoptosis) and propidium iodide (a marker for necrosis). In response to hydrogen peroxide(,) female adult mouse cardiomyocytes exhibited a higher rod ratio, lower lactate dehydrogenase release, and fewer Annexin-V-positive and propidium iodide-positive cells compared with males. Phospho-Akt was greater in females both at baseline and after hydrogen peroxide stimulation. The downstream molecule of Akt, phosphor-GSK-3beta (inactivation), was also higher, whereas caspase 3 activity was lower in females in response to hydrogen peroxide. Bcl-2 did not differ between sexes. Estrogen receptor-alpha was the dominant isoform in females, whereas estrogen receptor-beta was low but similar in both sexes. Our findings demonstrate that female adult mouse cardiomyocytes have a greater survival advantage when challenged with oxidative stress-induced cell death. This may be attributable to activation of Akt and inhibition of GSK-3beta and caspase 3 through an estrogen receptor-alpha-mediated mechanism.