Lipopolysaccharide (LPS) can cause increased level of TNFα through TLR4/CD14 – NFκB/IκB pathway, contributing to cardiomyocyte apoptosis. To explore the cardioprotective effects of 17b-estradiol (E2) and estrogen receptor a (ERa) on cariomyocytes, we established a Tet-On system, using doxycycline (Dox) to induce ER-a overexpression in H9c2 cardiomyoblast cells. Using TUNEL assay and western blot analysis, LPS-treated Tet-On/ ERa H9C2 cells show not only up-regulated TNFα protein expression and apoptosis, but also increased levels of pro-apoptotic proteins such as cleaved caspase 8, tBid, cytosol cytochrome c and cleaved caspase 3, which was inhibited by the addition of E2, Dox, E2 plus Dox or BSA-E2. The same treatments also efficiently inhibited LPS-induced IκBα degradation and consolidated the complex of NFκBp65 and IκBα, which further inhibiting downstream TNFα gene expression. The data indicated that E2, ERα overespression and impermeable BSA-E2 efficiently inhibited LPS-induce TNFα gene expression which causes cell apoptosis through NFkB/IkB-dependent pathway in H9c2 cardiomyoblast cells.
