Matrix metalloproteinase-inhibitor causes an activation of urokinase after experimental cerebral ischemia

Matrix metalloproteinases -2 and -9 (MMP-2/-9) are critically involved in the degradation of the basal lamina after experimental cerebral ischemia. Hemorrhages are closly related to microvascular basal lamina damage. The MMP activity is tightly regulated by exogenous and endogenous inhibitors. We investigated the effects of a synthetic inhibitor of MMP-2 and -9 (Calbiochemâ No. 444241) on the damage of the basal membrane, the occurred cerebral hemorrhages and the interference with the plasminogen/plasmin system.

Experimental cerebral ischemia in rats was induced for 3h and followed by 24h reperfusion (suture model). At the end of ischemia the inhibitor was administered (single bolus 5mg/kg. 2 groups, each 6 animals, received either treatment (MMP-I) or saline (control). The damage of the micravasculature was measured by the loss of collagen type IV, a main component of the microvessels.This quanitfication was done by western blot analysis.Zymography was used to detect MMP-2, MMP-9 and t-PA, u-PA activities. Cerebral hemorrhage was quantified by hemoglobin western blot.

The loss of the basal lamina antigen collagen type IV was significantly reduced in the MMP-I group: controls versus MMP-I: cortex: 46%±7% vs. 19±8% p<0.05 and basal ganglia 57±9% vs. 35±7%, p<0.05. The hemoglobin content of MMP-Inhibitor rats was less than in the controls: control versus MMP-I: cortex: 191%±23% vs. 158%±27%, p<0.05 and basal ganglia 442%±28% vs. 304%±32%; p<0.05. The proteolytic activities of u-PA were significantly increased in the basal ganglia in the MMP-I group: control versus MMP-I: 1019±22%/1767±15%; p<0.05).

A protective effect of the MMP inhibitor on the microvascular basal lamina could be established. Additionally the MMP inhibitor caused a reduction of the infarction size. The bleeding complications were reduced by treatment with the MMP inhibitor compared to control rats. Thus, a protective effect of the MMP inhibitor on the microvascular basal lamina was established. The significant increase of uPA might be understood as proteolytic compensation during MMP inhibition. However the mechanism of his compensative uPA increase are not revealed yet.