Objectives Cardiac apoptosis was found in ovariectomized rats without ischemia. Limited information regarding the protective effects of 17b-estradiol (E2) on cardiac Fas-dependent and mitochondria-dependent apoptotic pathways after post-menopause or bilateral oophorectomy in women was available. Methods Forty-eight female Wistar rats at 6-7 months of age were divided into sham-operated group (Sham, n?16) and bilateral ovariectomized group (n?32). After 4 weeks of operation, rats in ovariectomized group were injected intraperitoneally with either saline (OVX, n?16) or 10mg/kg/day 17b-estradiol (E2) for 10 weeks (OVX-E2, n?16). The excised hearts were measured by Hematoxylin-eosin staining, DAPI staining, positive TUNEL assays, and Western Blotting. Results 17b-estradiol (E2) decreased OVX-induced cardiac widely dispersed TUNEL-positive apoptotic cells. 17b-estradiol (E2) decreased OVX-induced TNF-alpha, Fas ligand (Fas L), Fas death receptors (Fas), Fas-associated death domain (FADD), activated caspase 8, and activated caspase 3 (Fas pathways). 17b-estradiol (E2) decreased OVX-induced proapoptotic t-Bid, Bax, Bax-to-Bcl2 ratio, Bax-to- BclXL ratio, activated caspase 9, and activated caspase 3 as well as increased anti-apoptotic Bcl2 and Bcl-XL relative to OVX (mitochondria pathway). Conclusions Our findings suggest that chronic 17b-estradiol (E2) treatment can prevent ovariectomy-induced cardiac Fas-dependent and mitochondria-dependent apoptotic pathways in rat models. The findings may provide one of possible mechenisms of 17b-estradiol (E2) for potentially preventing cardiac apoptosis after bilateral ovariectomy or menopause.
