Inhibition of Rho-kinase by fasudil attenuated angiotensin II-induced cardiac hypertrophy in apolipoprotein E deficient mice

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Abstract

Recent evidence indicates that the GTPase activated Rho/Rho-kinase pathway contributes angiotensin II-induced cardiac hypertrophy and vascular remodeling. We tested this hypothesis in vivo by determining the effects of fasudil, a Rho-kinase inhibitor, on angiotensin II-induced cardiac hypertrophy, coronary vascular remodeling, and ventricular dysfunction. Six-month-old apolipoprotein E deficient (apoE-KO) mice were subcutaneously infused with angiotensin II (1.44 mg/kg/day) using an osmotic mini-pump. Mice were randomly assigned to either vehicle or fasudil (136 or 213 mg/kg/day in drinking water) group. Infusion of angiotensin II for 4 weeks resulted in cardiac enlargement, myocyte hypertrophy, and myocardial interstitial and coronary artery perivascular fibrosis. These changes were accompanied by reduced aortic flow velocity and acceleration rate. Cardiac gene expression levels of atrial natriuretic peptide (ANP) and collagen type III detected by real-time reverse transcriptase polymerase chain reaction were significantly increased in angiotensin II-infused mice. Treatment with fasudil dose-dependently attenuated angiotensin II-induced cardiac hypertrophy, prevented perivascular fibrosis, blunted the increase in ANP and collagen type III expression, and improved cardiac function, without changing blood pressure. These data are consistent with a role for Rho-kinase activation in angiotensin II-induced cardiac remodeling and vascular wall fibrosis.

Introduction

Cardiac hypertrophy occurs in response to sustained increases in afterload, wall stress, and neurohumornal stimulation, eventually leading to ventricular dysfunction and heart failure. Angiotensin II induces cardiac hypertrophy, by directly stimulating cardiomyocyte growth and by increasing ventricular afterload. Rho-kinase, a target protein of the small GTP-binding protein Rho, can affect cell growth and motility, focal adhesions and cytokinesis (Amano et al., 1997), and has been implicated in cardiovascular disease (see review (Shimokawa, 2002)). Data suggest that some of the cardiac effects of angiotensin II be mediated by Rho/Rho-kinase signaling. Activation of angiotensin 1 (AT1) receptors by angiotensin II has been shown to activate Rho, which, in turn, induces protein synthesis in cardiomyocytes, leading to hypertrophy (Aikawa et al., 2000, Aoki et al., 1998). Angiotensin II also promotes inflammation by up-regulating the expression monocyte chemotactic protein (MCP-1), macrophage colony-stimulating factor (M-CSF), vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1) and E-selectin, and by promoting monocyte/macrophage migration (Tham et al., 2002b). Rho-kinase has been shown to mediate angiotensin II-induced MCP-1 expression, macrophage infiltration (Aikawa et al., 2000, Aoki et al., 1998, Funakoshi et al., 2001, Miyata et al., 2000), and connective tissue growth factor production, thus contributing to fibrosis (Iwanciw et al., 2003). Recent data indicate that inhibition of Rho-kinase can prevent angiotensin II-induced expression of plasminogen activator inhibitor-1, and attenuate cardiac remodeling in the rat (Kobayashi et al., 2002a, Kobayashi et al., 2002b). In the present study, we used a Rho-kinase inhibitor, fasudil, to test the hypothesis that Rho-kinase mediates angiotensin II-induced cardiac hypertrophy and coronary vascular remodeling in apolipoprotein E deficient (apoE-KO) mice.

Section snippets

Animal preparation

The Institutional Animal Care and Use Committee approved all animal protocols. Osmotic mini-pumps (model 2004, Alzet, Palo Alto, CA) containing either phosphate buffered saline (PBS) or angiotensin II (1.44 mg/kg/day in PBS, Calbiochem, CA) were implanted subcutaneously in 6-month-old apoE-KO male mice (Jackson Lab, Bar Harbor, ME). Two days prior to pump implantation, mice were provided with either tap water (vehicle group) or tap water dissolved with fasudil at a concentration of 0.5 (L) or

Effects of fasudil on angiotensin II-induced cardiac hypertrophy

Infusion of angiotensin II in apoE-KO mice for 1 month significantly increased heart weight by 44% and heart/body weight ratio by 50% (Fig. 1). Treatment with fasudil attenuated angiotensin II-induced increases in heart weight and heart/body weight ratio. Angiotensin II resulted in an increase in cardiomyocyte size, which was significantly reduced by treatment with fasudil (Fig. 2). Histological examination revealed myocardial interstitial fibrosis in the mice receiving angiotensin II, but not

Discussion

In the present study, a 30-day infusion of angiotensin II in apoE-KO mice resulted in cardiac hypertrophy, and myocardial interstitial and coronary artery perivascular fibrosis. These morphological changes were associated with increased expression of ANP and collagen type III as well as impaired left ventricular ejection phase indices. Without significant effect on systemic blood pressure, treatment with fasudil attenuated cardiac hypertrophy, prevented perivascular fibrosis, and restored left

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