A Role Of TLRs Mediated NFκB Activation Signaling Pathway In The Development Of Cardiac Hyerptrohy In Vivo

BACKGROUND:Cardiac hypertrophy is an adaptive response to various intrinsic and extrinsic stimuli. Initially, hypertrophy of the heart beneficially increases work output, but prolonged hypertrophy will result in dilated cardiomyopathy, heart failure, and sudden death. Using in vitro cultured candiomyocytes and transgenic mice models, several signaling pathways have been implicated in cardiac hypertrophy. These include G-protein coupled receptors (GPCRs), mitogen-activated protein kinase (MAPK), calcium/calmodulin dependent protein kinase (CaMK), calcineurin/NFAD (13), gpl30-LIF (leukemia inhibitory foctor), and PBK/Akt signaling pathways. There are excellent reviewed literatures about role of these signaling pathways in cardiac hypertrophy. Although those are wealth of intriguing data, it is still unclear which signaling pathways and what transcription factors are critical for the development of cardiac hypertrophy in vivo.We have previously reported that myocardial ischemia/reperfusion (T/R) and pressure overload resulted in NFkB activation in vivo. Since cardiac hypertrophy is an adaptive response to various stimuli, including myocardial 1/R and pressure overload stimulation, we hypothesized that NFkB activation plays a critical role in the development of cardiac hypertrophy in vivo. NFkB is a transcription factor in the downstream of Toll-like receptor (TLR) mediated signaling pathways. We prospected that TLRs might contribute to the development of cardiac hypertrophy in vivo. To define the role of TLRs mediated NFkB activation signaling pathways in development of cardiac hypertrophy in vivo, we designed aseries of experiments as following.SPECIFIC AIMS1. To determine whether NFkB activation pathway plays a critical role in the development of cardiac hypertrophy in vivo.2. To explore whether NFkB activation participates in the activated PDK/Akt signaling induced cardiac hypertrophy in vivo.3. To investigate whether simultaneous inhibiting NFkB activation and PDK/Akt signaling pathway could result in a maximal reduction of the development of cardiac hypertrophy in vivo.4 To define a role ofTLR4 mediated MyD88-dependent NFkB activation signaling pathway in the development of cardiac hypertrophy in vivo.MATERIALS AND METHODS: L Animal modds:1. To elucidate whether NFkB activation pathway plays a critical role in the development of cardiac hypertrophy in vivo, Sprague-Dawley rats were employed and cardiac hypertrophy was induced by banding the aorta for 1,3,5 days and 1-6 weeks. The NFkB binding activity was examined in the hearts subjected to aortic banding. In a separate experiment, adenovirus- expressing IkBcc mutant (Ad5-lKBaM), a super-repressor for NFkB activation, was transfected into the hearts immediately followed by aortic banding for three weeks in order to determine the effect of inhibiting NFkB activation on the development of cardiac hypertrophy.2. To explore whether NFkB activation participates in the activated PDK/Akt signaling induced cardiac hypertrophy, transgenic mice with cardiac specific expression ofconstitutively active PDK (caPDK) or caAkt induced cardiac hypertrophy were employed and NFkB binding activity in the hypertrophic hearts were examined NFkB binding activity was also examined in the hypertrophic hearts induced by aortic banding for 2 weeks of dominant negative PI3K (dnPBK) or kinase defective-Akt (kdAkt) transgenic mice.3. To investigate whether simultaneous inhibiting NFkB activation and PBK/Akt signaling pathway could result in a maximal reduction of the development of cardiac hypertrophy in vivo, Rapamycin (2mg/kg/day), a specific inhibitor of target of rapamycin down stream of Akt pathway, or PDTC (120 mg/kg/day), an antioxidant which can inhibit NFkB activity, or both Rapamycin and PDTC were administered into caPBK or caAkt transgenic mice for 2 weeks. Rapamycin or PDTC was also administered into dnPBK or kdAkt transgenic mice subjected to aortic banding for 2 weeks. Effects ofRapamycin or PDTC on the development of cardiac hypertroph...