Long-Term Treatment With a Rho-Kinase Inhibitor Improves Monocrotaline-Induced Fatal Pulmonary Hypertension in Rats

Abstract

Abstract-Primary pulmonary hypertension is a fatal disease characterized by endothelial dysfunction, hypercontraction and proliferation of vascular smooth muscle cells (VSMCs), and migration of inflammatory cells, for which no satisfactory treatment has yet been developed. We have recently demonstrated that intracellular signaling pathway mediated by Rho-kinase, an effector of the small GTPase Rho, is involved in the pathogenesis of arteriosclerosis. In the present study, we examined whether the Rho-kinase-mediated pathway is also involved in the pathogenesis of fatal pulmonary hypertension in rats. Animals received a subcutaneous injection of monocrotaline, which resulted in the development of severe pulmonary hypertension, right ventricular hypertrophy, and pulmonary vascular lesions in 3 weeks associated with subsequent high mortality rate. The long-term blockade of Rho-kinase with fasudil, which is metabolized to a specific Rho-kinase inhibitor hydroxyfasudil after oral administration, markedly improved survival when started concomitantly with monocrotaline and even when started after development of pulmonary hypertension. The fasudil treatment improved pulmonary hypertension, right ventricular hypertrophy, and pulmonary vascular lesions with suppression of VSMC proliferation and macrophage infiltration, enhanced VSMC apoptosis, and amelioration of endothelial dysfunction and VSMC hypercontraction. These results indicate that Rho-kinase-mediated pathway is substantially involved in the pathogenesis of pulmonary hypertension, suggesting that the molecule could be a novel therapeutic target for the fatal disorder. Key Words: pulmonary hypertension Ⅲ Rho-kinase Ⅲ vascular smooth muscle cells Ⅲ endothelial nitric oxide synthase Ⅲ macrophages P rimary pulmonary hypertension (PPH) is a lifethreatening disease characterized by a marked and sustained elevation of pulmonary artery pressure. The disease has no obvious causes and ultimately results in right ventricular (RV) failure and death. The pathological changes of hypertensive pulmonary arteries include endothelial injury, proliferation and hypercontraction of vascular smooth muscle cells (VSMCs), and migration of macrophages. 1-3 PPH continues to be a serious clinical problem with high morbidity and mortality. 4 In 1990s, Rho-kinase/ROK/ROCK was identified as an effector of the small GTPase Rho, 5-7 which plays an important role in various cellular functions, including smooth muscle contraction, actin cytoskeleton organization, cell adhesion and motility, cytokinesis, and gene expression. 8 -10 In a series of experimental and clinical studies, we have demonstrated that Rho-kinase-mediated pathway is substantially involved in the pathogenesis of arteriosclerosis. 11-17 These Rho-kinase-mediated alterations in blood vessels also may be involved in the pathogenesis of pulmonary hypertension (PH). In this study, we examined whether Rho-kinasemediated pathway is involved in the pathogenesis of rat model of fatal PH in vivo. Materials and MethodsThe present study was...

Rho kinase in the regulation of cell death and survival

“…Consistent with this finding, the inhibition of ROCK with fasudil enhances smooth muscle cell apoptosis in the neointima after stent implantation in the porcine coronary artery, and this increased apoptosis is associated with down-regulation of the anti-apoptotic protein Bcl-2 [84]. Moreover, inhibition of ROCK with fasudil significantly enhances smooth muscle cell apoptosis in autologous vein grafts in rabbits [40] and in pulmonary hypertension in rats [1], further supporting a pro-survival role of ROCK in smooth muscle cells. Increased smooth muscle cell apoptosis along with inhibition of smooth muscle cell proliferation, inflammatory cell infiltration and/or extracellular matrix protein production contribute to the inhibition of neointima formation via ROCK inhibition [40,84,120].…”

Defective endothelial nitric oxide synthase signaling is mediated by rho-kinase activation in rats with secondary biliary cirrhosis

“…Thereafter, MAP and PVP were measured every 5 minutes for 60 minutes from the beginning of intravenous infusion of saline (control), 0.3 mg/kg/hour, 1.0 mg/kg/ hour, or 2 mg/kg/hour fasudil (Eril; Asahi Kasei Corporation, Tokyo, Japan). 34,35 HTBF was also measured using a laser Doppler flow meter (Omega flow type II; Omega Flow Company Ltd., Tokyo, Japan) every 5 minutes for 60 minutes from the beginning of drug infusion. 36,37 Sixty minutes after intravenous infusion of a graded dose of fasudil, the livers and abdominal aortas were isolated and snap-frozen in liquid nitrogen.…”

“…Eighteen BDL rats received saline (control), 10 mg/kg/ day, or 30 mg/kg/day fasudil by oral administration for 4 weeks from 3 weeks after the BDL, as previously described. 34,49 Rats were anesthetized with sodium pentobarbital (40 mg/kg, intraperitoneally), and MAP, PVP, and HTBF were measured. After hemodynamic measurement for 15 minutes, blood samples were obtained from the inferior vena cava to assess hepatic and renal functions.…”

ROCKs as therapeutic targets in cardiovascular diseases

“…Thus, understanding the pathologic mechanism underlying pulmonary hypertension is of great clinical importance in the development of effective therapies to improve survival. Recent studies indicate that treatment with ROCK inhibitors improves monocrotaline-induced pulmonary hypertension in rats [82] and hypoxia-induced pulmonary hypertension in mice [83]. Furthermore, oral administration of fasudil improved survival of monocrotaline-injected rats even when therapy was initiated after the development of pulmonary hypertension.…”