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.