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.
Research design and methods: In two separate experiments, diabetic db/db mice received fasudil (10 mg x kg(-) x day(-) i.p.) or simvastatin (40 mg x kg(-) x day(-) p.o.) for 16 weeks. Untreated db/db and db/m mice served as controls.
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.
Conclusions: 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.