Basic Research for Gene Therapy of Heart Failure by Transcoronay Gene Transfer

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We performed basic experiments to investigate changes in the regulatory mechanisms of cardiac contractility through the GTP binding protein-related pathways in heart failure. The main purpose of this project was to determine possible target genes to prevent the process by which normal hearts develop heart failure. We obtained the following findings.(A) In canine failing hearts, 1) GTP-binding protein Gq-RhoA-Rho kinase signaling was upregulated in association with an increase in the phosphorylation level of myosin light chain, which caused an increase in myofibrillar Ca^<2+> sensitivity, 2) β-adrenergicstimulation-induced decreasein the myofibrillar Ca^<2+> sensitivity was attenuated. These abnormal regulation of the myofibrillar Ca^<2+> sensitivity may be related to decreased contractile function in the failing hearts.(B) In cardiacmuscle, as in smooth muscle, the phosphorylation of myosin light chain was modulatedby calmodulin and cyclic GMP, both of which were able to regulate the cardiacmyofibrillar Ca^<2+> sensitivity.(C) Using a selective Rho kinase inhibitor Y-27632, we tested the hypothesis that chronic inhibition of Rho kinase might be able to prevent the process of myocardial hypertrophy resulting in heart failure. We found that chronic inhibition of Rho kinase prevented myocardial hypertrophy induced by hypertension and thereby preserved myocardial contractile function. Rho kinase may be an important target in treatment of heart failure.(D) We are performing another experiment to investigate the function of the transient receptor potential (TRP) proteins in cardiac cells. The TRP protein superfamily consists of a diverse group of receptor-operated Ca^<2+> channels activated by Gq-dependent mechanisms. The hypothesis is that cultured cardiomyocytes transfected with the TRP gene, incorporated into adenovirus vector, develop hypertrophy when stimulated by angiotensin II.