| 摘要: | Evidence shows that females have lower TNFα levels and lower incidences of heart dysfunction and sepsis-related morbidity and mortality. To identify the cardioprotective effects and precise cellular/molecular mechanisms behind estrogen (E2) and estrogen receptors (ERs), we investigated the effects of 17β-estradiol (E2) and estrogen receptor α (ERα) on LPS-induced apoptosis by analyzing the activation of survival and death signaling pathways in doxycycline (Dox)-inducible Tet-On/ERα H9c2 myocardial cells and ERα-transfected primary cardiomyocytes overexpressing ERα. We found that LPS challenge activated JNK1/2, and then induced IκB degradation, NFκB activation, TNFα upregulation and subsequent myocardial apoptotic responses. In addition, treatments involving E2, membrane-impermeable BSA-E2 and/or Dox, which induces ERα overexpression, significantly inhibited LPS-induced apoptosis by suppressing LPS-upregulated JNK1/2 activity, IκB degradation, NFκB activation and pro-apoptotic proteins (e.g. TNFα, active caspases-8, t-Bid, Bax, released cytochrome c, active caspase-9, active caspase-3) in myocardial cells. However, the cardioprotective properties of E2, BSA-E2 and ERα overexpression to inhibit LPS-induced apoptosis and promote cell survival were attenuated by applying LY294002 (PI3K inhibitor) and PI3K siRNA. These findings suggest that E2, BSA-E2 and ERa expression exert their cardioprotective effects by inhibiting JNK1/2-mediated LPS-induced TNFα expression and cardiomyocyte apoptosis through activation of Akt. |
