Abstract 672: Long-Term Inhibition of Rho-kinase Ameliorates Diastolic Heart Failure in Hypertensive Rats

Abstract

Background: Diastolic heart failure (DHF) is a major cardiovascular disorder with poor prognosis; however, its molecular mechanism remains to be fully elucidated. We have previously demonstrated that activation of Rho-kinase pathway is substantially involved in the pathogenesis of oxidative stress and cardiac remodeling. In this study, we thus examined whether Rho-kinase pathway is also involved in the pathogenesis of DHF. Methods: We maintained male Dahl salt-sensitive rats for 10 weeks, starting from 7 weeks of age, with either 0.5% NaCl (control) or 8% NaCl (DHF) with or without oral treatment with fasudil, a selective Rho-kinase inhibitor (30 and 100 mg/kg/day) (n=13–31). We serially measured hemodynamic variables and cardiac function by echocardiography, followed by histological analysis. Results: At week 17, the untreated DHF group exhibited overt heart failure (e.g. lung edema) associated with diastolic dysfunction but with preserved systolic function, characterized by increased myocardial stiffness, cardiomyocyte hypertrophy, and enhanced cardiac fibrosis and superoxide production (all P<0.01 vs. control). By contrast, in the fasudil-treated group, those myocardial changes associated with DHF were significantly and dose-dependently ameliorated, independent of the changes in blood pressure, with a resultant inhibition of the transition to decompensated heart failure. Western blot analysis showed that cardiac Rho-kinase activity, as evaluated by the extent of phosphorylation of ERM, a downstream substrate of Rho-kinase, was significantly increased in the untreated DHF group and was dose-dependently inhibited in the fasudil-treated group. Importantly, there was a highly significant correlation between the extent of myocardial stiffness and that of cardiac Rho-kinase activity (R=0.74 for the posterior wall and R=0.63 for the septum, both P<0.001). Cardiac Rho-kinase activity also significantly correlated with cardiac superoxide production. Conclusions: These results indicate that activation of Rho-kinase pathway plays an important role in the pathogenesis of DHF through cardiomyocyte hypertrophy and interstitial fibrosis, suggesting the therapeutic importance of Rho-kinase for the treatment of DHF in humans.