Abstract 192: Activation of Kidney Renin-angiotensin System (RAS) and Renoprotective Effects of Direct Renin Inhibition (DRI) in Glomerulonephritis

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The development of glomerulonephritis causes glomerular injury and reduced renal function and is associated with increased renin release. The aims of this study were to demonstrate activation of intrarenal RAS in glomerulonephritis and determine the effects of DRI with aliskiren on progression of glomerulonephritis associated renal injury induced by administration of an anti-Thy1.1 antibody. We divided rats into 3 groups; control group, anti-Thy1.1 glomerulonephritis group and anti-Thy1.1 glomerulonephritis treated with aliskiren (30 mg/kg/day) group. In the anti-Thy1.1 rats, protein excretion and micro albumin excretion levels increased markedly after anti-Thy1.1 antibody injection. The increases in protein (94.7 ± 13.0 mg/day) and micro albumin (7.5 ± 2.6 mg/day) excretions were attenuated by aliskiren treatment (43.6 ± 4.5 mg/day of protein and 2.6 ± 0.7 mg/day of micro albumin). The glomerular expansion score was significantly higher in the anti-Thy1.1 group compared to the control group. The anti-Thy1.1 group also showed elevation of intrarenal TGF-β and PAI-1 mRNA levels compared with control rats. The progression of glomerular expansion and elevation of these mRNA levels was prevented by aliskiren. Importantly, the anti-Thy1.1 group had markedly increased urinary angiotensinogen (AGT) excretion at days 3 (3102.9 ± 683.8 ng/day), but these changes were markedly suppressed by aliskiren treatment (441.3 ± 104.8 ng/day). AGT protein expression in the kidney was significantly lower in the aliskiren treatment group compared with anti-Thy1.1 group (western blot, 0.8 ± 0.04 and immunohistochemistry, 0.7 ± 0.11 relative to anti-Thy1.1 group). Furthermore, plasma renin activity (PRA) and plasma angiotensin (Ang) II levels were significantly increased in the anti-Thy1.1 group and aliskiren treatment prevented the elevation of PRA and plasma Ang II. Anti-Thy1.1 antibody also elicited left ventricular hypertrophy and fibrosis, which were not ameliorated by aliskiren. These results demonstrate that DRI prevents or reduces intrarenal RAS activation and glomerular injury in progressive glomerulonephritis. Accordingly, DRI may be an effective approach to treat glomerulonephritis as well as other intrarenal RAS associated kidney diseases.

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