BACKGROUND - We have previously shown that cyclooxygenase-2 (COX-2) expression is low in the renal cortex of adult rats, but is increased in macula densa/cortical thick ascending limb and in glomerular podocytes after subtotal renal ablation.
METHODS - To evaluate the functional consequences of this increased COX-2 expression, male rats were subjected to subtotal renal ablation and divided into four groups: (1) treatment with the selective COX-2 inhibitor SC58236, (2) treatment with vehicle, (3) treatment with the angiotensin-converting enzyme inhibitor enalapril, and (4) treatment with enalapril + SC58236. The administration of drugs was begun on the third day after ablation and continued for 6 to 10 weeks.
RESULTS - Within one week after ablation, vehicle-treated rats developed hypertension. Although enalapril led to significant reductions in blood pressure, either alone or in combination with the COX-2 inhibitor, SC58236 alone did not significantly alter ablation-induced hypertension. However, the SC58236-treated animals exhibited levels of proteinuria at six weeks after ablation that were comparable to those seen with enalapril (vehicle, 47 +/- 4; enalapril, 27 +/- 2; SC58236, 30 +/- 2 mg/day; N = 7, P < 0.01, each group compared with vehicle), and continued SC58236 treatment led to persistent reductions in proteinuria at 10 weeks after renal ablation (vehicle, 77 +/- 4; SC58236, 50 +/- 4 mg/day; N = 6, P < 0. 01). SC58236 treatment also significantly reduced the percentage of glomeruli exhibiting segmental or global sclerosis at 10 weeks (32.6 +/- 7.8% vs. 10.9 +/- 2.8%, N = 6, P < 0.03). Furthermore, SC58236 treatment partially inhibited increases in transforming growth factor-beta1 mRNA expression and increases in collagen III and collagen IV mRNA expression.
CONCLUSIONS - These studies indicate that chronic treatment with a specific COX-2 inhibitor may retard the progression of progressive renal injury, and suggest that such compounds can be used in combination with angiotensin-converting enzyme inhibitors. Further studies are required to determine the mechanism by which COX-2 inhibition is renoprotective.