Targeting of RhoA/ROCK Signaling Ameliorates Progression of Diabetic Nephropathy Independent of Glucose Control

Abstract

OBJECTIVE-RhoA, a small GTPase protein, and its immediate downstream target, Rho kinase (ROCK), control a wide variety of signal transduction pathways. Recent studies have shown that fasudil, a selective ROCK inhibitor, may play a pivotal role in a number of pathological conditions, ranging from cardiovascular diseases to pulmonary hypertension and erectile dysfunction. Considerable evidence suggests that some of the beneficial effects of statins may also stem from their modulatory effects on RhoA/ROCK signaling. In the current study, we hypothesized that pharmacological blockade of the RhoA/ROCK pathway with either fasudil or simvastatin would ameliorate progression of diabetic nephropathy. RESULTS-The kidney cortices of untreated db/db mice displayed increased ROCK activity compared with db/m mice. The fasudil-treated mice exhibited a significant reduction in ROCK activity, albuminuria, glomerular collagen IV accumulation, and urinary collagen IV excretion compared with untreated db/db mice. Interestingly, blood glucose was unaffected by fasudil administration. Treatment with simvastatin significantly attenuated RhoA activation in the kidney cortices of db/db mice and resulted in a significant reduction of albuminuria and mesangial matrix expansion. RESEARCH DESIGN AND METHODS-InCONCLUSIONS-Based on these results, we propose that RhoA/ROCK blockade constitutes a novel approach to the treatment of diabetic nephropathy. Our data also suggest a critical role for RhoA/ROCK activation in the pathogenesis of diabetic nephropathy. Diabetes 57:714-723, 2008 T he Rho family of small GTPases are 20-to 40-kDa monomeric G proteins that regulate a number of cell functions, including cytoskeletal reorganization, cell motility, and gene expression (1). They cycle between two conformational states: an active GTPbound state and an inactive GDP-bound state (2). One of the best recognized members of the Rho GTPase family is RhoA. Rho kinase (ROCK), a downstream effector of RhoA, is a serine/threonine kinase of ϳ160 kDa that exists in two isoforms in mammals: ROCK1 and ROCK2 (3). ROCK is comprised of an amino-terminal kinase domain, followed by a coiled-coil region that contains the -binding domain. The carboxy-terminal consists of a plexstrinhomology domain, which contains an internal cysteinerich domain. ROCK1 and ROCK2 are highly homologous, sharing an identity of 65% in their overall amino acid sequences and 92% in their kinase domains.The RhoA/ROCK pathway has recently received considerable attention for its involvement in a wide variety of pathological states ranging from cardiovascular disease and pulmonary hypertension to Alzheimer's disease and glaucoma (4 -7). A growing body of evidence also suggests that the RhoA/ROCK pathway may have renomodulatory effects. Indeed, several recent studies have proposed that RhoA/ROCK may play an important role in renal fibrosis by enhancing signaling pathways involving transforming growth factor-␤, angiotensin II, and nuclear factor-B (8 -10). Furthermore, since the discovery of fasudi...

Blocking VEGF/Caveolin-1 signaling contributes to renal protection of fasudil in streptozotocin-induced diabetic rats

“…Our data indicated that fasudil may improve the enhanced GFR during the very early stage of nephropathy. No difference in serum creatinine or creatinine clearance was observed between groups at month 3 or 8, which agrees with previous studies [5,27] .…”

“…Further studies are required to determine whether fasudil has specific role in the control of blood pressure. Low-dose (10 mg/kg) fasudil had no effect in this study, which is different from previous studies [4,27] , and may be related to the differences in animal models, treatment periods and protocols.…”

“…Recent studies have demonstrated that treatment with fasudil, a ROCK inhibitor, prevents the development of experimental diabetic nephropathy by inhibiting the signaling pathways involving angiotensin II, TGF-β, and ECM accumulation [9,10,27] . However, whether fasudil blocks VEGF signaling has not been addressed yet.…”

Involvement of RhoA/ROCK in myocardial fibrosis in a rat model of type 2 diabetes

“…It has been reported that ROCK can directly activate JNK to stimulate c-Jun expression, the activity of which is independent of the ability of ROCK to promote actin polymerization [40] . Fasudil (10-30 mg·kg -1 ·d -1 ) can suppress renal interstitial fibrosis in insulin-resistant diabetic rats [7,8] . ROCK inhibition also improves pressure overload-induced cardiac hypertrophy and dysfunction [41] .…”

“…There is growing evidence that RhoA/ROCK signaling mediates the glomerular matrix accumulation of proteins in diabetic nephropathy. The ROCK inhibitor fasudil can suppress renal fibrosis and can reduce proteinuria [7,8] . The inhibition of ROCK attenuates cardiac fibrosis in angiotensin II-induced cardiac hypertrophy in vivo [9,10] .…”