The Rho-kinase inhibitor, fasudil, attenuates diabetic nephropathy in streptozotocin-induced diabetic rats
Introduction
Diabetic nephropathy is the leading cause of end stage renal disease in the world. The development of strategies for treatment of diabetic nephropathy is an urgent issue; however, a clear cut strategy has not been established. Various factors are known to be involved in the progression of diabetic nephropathy, including hyperglycemia, hypertension, dyslipidemia, production of inflammatory cytokines and oxidative stress. Since all of these appear simultaneously in diabetic subjects, therapeutic strategies should be integrated appropriately, based on the precise impact of each therapy on the pathogenesis of diabetic nephropathy.
The small GTPase proteins (small G proteins), Ras, Rho, Rab, and Ran, are monomeric proteins with a low molecular mass of 20–40 kDa and elicit a variety of pivotal intracellular signals (Takai et al., 2001). 3-Hydroxy-methylglutaryl coenzyme A (HMG-Co A) reductase inhibitors or statins, are potent inhibitors of cholesterol biosynthesis. Recently, these agents have been recognized to exert protective effects on cardiovascular and kidney disease by suppressing activation of small G proteins, independently of their lipid-lowering effect (Miida et al., 2004, Kasiske et al., 1988, Kurata, 1994). On the other hand, these pleiotropic effects of statins indicate that signaling pathways mediated by small G proteins could play an important role in the pathogenesis of cardiovascular and kidney diseases. In particular, a series of recent investigations has revealed a novel contribution of Rho and its effector molecule, Rho-kinase, to cardiovascular disease via modulation of cell motility, proliferation and apoptosis (Shimokawa and Takeshita, 2005, Kamiyama et al., 2003).
Rho-kinase, a serine/threonine kinase of molecular mass ∼ 160 kDa, phosphorylates the myosin-binding subunit (MBS) of myosin light-chain phosphatase (Kimura et al., 1996), ERM (ezrin, radixin, moesin), adductin (Bernhard et al., 2005) and LIM (Lin11, Isl1 and Mec3) kinase as substrates (Sumi et al., 2001), and regulates stress fiber formation, focal adhesion, migration and gene expression in vascular lineage cells. On the other hand, fasudil, which is already available for the treatment of angiospasm after subarachnoid hemorrhage, has been proven to act as a specific inhibitor of Rho-kinase (Asano et al., 1987). Fasudil reportedly suppresses the progression of atherosclerotic lesions in animal models (Shimokawa and Takeshita, 2005, Hattori et al., 2004, Matsumoto et al., 2004). With these points in mind, this study aimed to investigate the effect of statin and fasudil on diabetic nephropathy and clarify the possibility that the Rho/Rho-kinase pathway could be a target in the treatment of diabetic nephropathy.
Section snippets
Materials
Sprague–Dawley (SD) rats weighing 180–200 g were purchased from Charles River Japan (Yokohama, Japan). The following items were also purchased; streptozotocin from Sigma Chemical Co. (St Louis, MO, USA), Rho pull down assay kit from Cell Signaling (Bevelrly, MA, USA), γ-[32P]dCTP from Perkin Elmer (Wellesy, MA, USA), and random primer labeling kit from Takara (Otsu, Shiga, Japan). Fasudil (Rho-kinase inhibitor) was obtained from Asahi Kasei Pharmaceutical Co. (Tokyo, Japan). Fluvastatin
Effects of fasudil and statin on blood pressure and metabolic parameters
Metabolic parameters for all animal groups are presented in Table 1. Plasma glucose concentrations in diabetic rats exceeded 300 mg/dl. Body weights were significantly decreased and kidney weights were significantly increased in diabetic rats compared to controls. Administration of fasudil and fluvastatin did not affect plasma glucose levels, body weights and kidney weights in the diabetic rats. Plasma cholesterol levels tended to be elevated in the diabetic rats, and were decreased
Discussion
Statins, which are potent inhibitors of cholesterol biosynthesis, suppress synthesis of isoprenoids including farnesyl pyrophosphate and geranylgeranyl pyrophosphate, which bind to the C-terminus of small G proteins and increase their hydrophobicity (prenylation). Prenylation is believed to be a critical step in activation of small G proteins, facilitating their anchoring to the plasma membrane where GTPase activation occurs (Takai et al., 2001). Statins modulate intracellular signaling
References (24)
- et al.
Effect of fasudil on Rho-kinase and nephropathy in subtotally nephrectomized spontaneously hypertensive rats
Kidney Int.
(2003) - et al.
Fasudil attenuates interstitial fibrosis in rat kidney with unilateral ureteral obstruction
Eur. J. Pharmacol.
(2002) - et al.
Specific activation LIM kinase 2 via phosphorylation of threonine 505 by ROCK, a Rho-dependent protein kinase
J. Biol. Chem.
(2001) - et al.
Mechanism of action of a novel antivasospasm drug, HA1077
J. Pharmacol. Exp. Ther.
(1987) - et al.
Rho kinase, a promising drug targeting for neurological disorders
Nat. Rev.
(2005) - et al.
Increased expression of NAD(P)H oxidase subunits, NOX 4 and p22phox, in the kidney of streptozotocin-induced diabetic rats and its reversibility by intensive insulin treatment
Diabetologia
(2003) - et al.
Long-term treatment with a specific Rho-kinase inhibitor suppresses cardiac allograft vasculopathy in mice
Circ. Res.
(2004) - et al.
Contribution of Rho A and Rho kinase to platelet-derived growth factor-BB-induced proliferation of vascular smooth muscle cells
J. Atheroscler. Thromb.
(2003) - et al.
Pharmacologic treatment of hyperlipidemia reduces glomelular injury in rat 5/6 nephrectomy model of chronic renal failure
Circ. Res.
(1988) - et al.
Regulation of myosin phosphatase by Rho and Rho-associated kinase
Science
(1996)