Myocardial Riveting Set Repeat Sequence Protein (carp) Protection Function And Molecular Mechanisms Of Cardiac Hypertrophy

Cardiac hypertrophy is an adaptive enlargement of the myocardium in response to increased workload. Although cardiac hypertrophy may initially be compensatory, sustained pathologic hypertrophy is deleterious and may lead to dilated cardiomyopathy, sudden death and heart failure. Therefore it is important to inhibit the hypertrophy for preventing the heart failure happening or improving the heart function in heart failure patients.Cardiac Ankyrin Repeat Protein (CARP) is one of the negative regulators of heart development. CARP expression can be detected at least as early as at E8.5, the expression decreases and is detectable at relatively low levels in the El1.0heart. However in neonatal and adult heart, CARP expression displays a relatively low level in cardiac muscle compared with embryo. Various hypertrophic chemicals, cardiac ischemia, stretch stimulus and pressure overload can induce CARP expression, suggesting that up-regulation of CARP expression is a common feature of the adaptive response of ventricular myocardium to various stimuli. From the previous published work, it is possible that CARP can regulate the hypertrophy in vitro. But it is still unknown whether CARP could inhibit hypertrophy in vivo, and the precise relationship between CARP and hypertrophy is still obscure.In order to investigate CARP function in hypertrophy, we over-expressed CARP protein in neonatal cardiac myocytes by using adenovirus, and then induced cells with100μM PE for24hours. By measuring the cell area and the hypertrophic marker genes expression, we found CARP could partially inhibit PE induced hypertrophy. Based on the in vitro results, we had generated transgenic (TG) mice with cardiac-specific expression of CARP gene. We had found that under normal growth condition, there was no obvious difference in HW/BW value between CARP-Tg and WT mouse. Also we could not observe any significiant difference from echocardiography data. However by inducing heart hypertrophy in the wild type and CARP transgenic mice with isoproterenol infusion or pressure overload (transverse aortic constriction, TAC), we found CARP could partially inhibit ISO infusion or TAC surgery induced hypertrophy. The increasing of HW/BW and HW/TL values were partially inhibited in CARP-Tg mice compared with WT mice, so do for the echocardiography results of LVPW;d and LV mass. In addition, our data also have demonstrated that the hypertrophic marker genes expression and fibrosis were partially inhibited in CARP-Tg mouse.In order to explore the molecular mechanism underlying CARP function for inhibiting hypertrophy, we analyzed the genes expression profiling of CARP-Tg and WT mouse after TAC surgery by microarray assay. We found the expression of genes associatied with chemokines, extracellular matrix, inflammation factors, and transporters had been altered in CARP-Tg mice compared with wild type mouse. Also the genes from signaling pathways of fatty acid and glucose metabolism, TGF-β signaling pathway, MAPK signaling pathway and G-protein signaling pathway had been changed in CARP-Tg mice. Most inportantly the genes expression of TGF-β1, TGF-β2and TGF-β3were inhibited in CARP-Tg mouse compared with wild type mouse. Further biochemical analysis showed that levels of phospho-Smad3was decreased in the heart of CARP transgenic mice after TAC treatment. Our results imply that CARP inhibits heart hypertrophy through repressing TGF-β/Smad signaling pathway.