Rho-Kinase Inhibitor Attenuates Kidney Injury Via iNOS Mediated Mechanisms During Chronic Metabolic Acidosis

Abstract ID 97683 Poster Board 268 The interactions between pathways involving Rho-kinase, angiotensin II, and reactive oxygen species (ROS) have demonstrated their role during chronic metabolic acidosis (CMA) and in genesis of hypertension. CMA has been recently reported as a potential cause of hypertension. Here we investigate the magnitude of renal injury associated with CMA and evaluate the role of Rho-kinase, angiotensin II, and ROS independently. Male Sprague Dawley rats (100-150g) were divided into five groups: Control (vehicle treated), CMA (acidotic), CMA+fasudil (Rho-kinase inhibitor), CMA+captopril (Ang II reducer), and CMA+tempol (free radical scavenger). CMA was induced in rats by providing a weak acid solution of 0.28 M ammonium chloride (NH₄Cl) in drinking water for 8 weeks. At the end of experiment, microdialysis probes were implanted into the rat's renal compartments in each group to collect the interstitial fluid. ELISA was performed to analyze NGAL (Neutrophil gelatinase-associated lipocalin) and iNOS (Inducible nitric oxide synthase) in all the dialysate samples collected. Kidneys were harvested and sectioned. Hematoxylin and eosin (H&E) and periodic acid Schiff (PAS) staining were used to examine histological details. The iNOS expression is increased significantly in the fasudil treated group vs CMA group, conversely NGAL levels decreased. The captopril and tempol treated acidotic groups showed no significant changes in iNOS compared to the CMA, however the NGAL increases in all latter four groups compared to the control. Mean arterial pressure (MAP) was reduced significantly in fasudil treated group vs CMA group. Histopathology also suggests the fasudil treated group has intact glomerulus and no sign of necrosis. Interestingly, the tempol treated group showed significantly reduced tissue necrosis compared to the captopril treated group. Taken together, inhibition of Rho-kinase increases the intrarenal iNOS and may increase the vasodilator, nitric oxide (NO), eventually reducing MAP. Targeting Rho-kinase may provide reno-protective effect during chronic acidosis conditions and potentially regulate vascular tone to attenuate hypertension.