Absence of gelatinase (MMP-9) or collagenase (MMP-13) attenuates adriamycin-induced albuminuria and glomerulosclerosis.

BACKGROUND/AIMS: The role of matrix metalloproteinases (MMPs) in the pathogenesis of glomerular injury appears to be complex. To investigate the role of individual MMPs, we examined the course of Adriamycin-induced albuminuria and glomerulosclerosis in mice lacking either a gelatinase (MMP-9) or a collagenase (MMP-13). METHODS: Adriamycin was administered to MMP-9 or MMP-13 knockout (KO) mice. Glomerular injury was assessed by the quantification of albuminuria, the glomerular injury score and type IV collagen immunostaining. RESULTS: Treatment of mice with Adriamycin (18 mg/kg i.v.) resulted in marked albuminuria and glomerulosclerosis reaching a peak at 4-8 weeks. The albuminuria and glomerulosclerosis were significantly (p < 0.05) attenuated in both the MMP-9 KO and MMP-13 KO mice compared to controls. In contrast, treatment of wild-type mice with the broad-spectrum MMP inhibitor doxycycline did not have a beneficial effect on the albuminuria and glomerulosclerosis. CONCLUSION: These results support a role for both gelatinase (MMP-9) and collagenase (MMP-13) in the pathogenesis of glomerular injury in the Adriamycin-induced glomerulosclerosis model. MMP inhibitors with high specificity towards MMP-9 and/or MMP-13 may be potential future candidates to provide more effective therapies to inhibit the development of glomerulosclerosis.

"Pulse" treatment with high-dose angiotensin blocker reverses renal arteriolar hypertrophy and regresses hypertension.

One ultimate goal of hypertension therapy is to cause permanent reversal ("regression") of already established hypertension. Our aim was to examine whether high-dose "pulse" treatment with a renin-angiotensin system inhibitor could cause regression of established hypertension and to link this action to reversal of arteriolar hypertrophy and changes in vascular matrix metalloproteinase activities. First, 16-week-old male spontaneously hypertensive rats (n=60) were pulse treated for 2 weeks with high-dose angiotensin-converting enzyme inhibitor (enalapril), angiotensin receptor blocker (candesartan), calcium channel blocker (nifedipine), or vasodilator (hydralazine) with or without salt restriction, and the long-term effects on blood pressure were examined. Second, spontaneously hypertensive rats were treated with angiotensin receptor blocker or calcium channel blocker, and the effects on renal gene expressions, arteriolar structure, and vascular matrix metalloproteinase were compared. Treatment of spontaneously hypertensive rats with different antihypertensive agents caused apparently similar reductions in blood pressure during the course of the pulse treatment, within the limitations of the tail-cuff method. After cessation of medications, blood pressure in the rats treated with renin-angiotensin system inhibitor remained reduced by >30 to 40 mm Hg for 4 months. No such effect was seen with calcium channel blocker or vasodilator. The 2-week angiotensin receptor blocker treatment induced a marked reversal of the arteriolar hypertrophy specifically in the small (30 to 100 microm) renal arterioles, together with increased expression and activity of matrix metalloproteinase-13. In conclusion, transient high-dose pulse treatment with angiotensin receptor blocker caused changes in vascular matrix metalloproteinase activity, specific reversal of renal arteriolar hypertrophy, and regression of hypertension in spontaneously hypertensive rats.