Early appearance of activated matrix metalloproteinase-9 and blood-brain barrier disruption in mice after focal cerebral ischemia and reperfusion

Blood-brain barrier (BBB) disruption is thought to play a critical role in the pathophysiology of ischemia/reperfusion. Matrix metalloproteinases (MMP s) are a family of proteolytic enzymes that can degrade all the components of the extracellular matrix when they are activated. Gelatinase A (MMP-2) a nd gelatinase B (MMP-9) are able to digest the endothelial basal lamina, wh ich plays a major role in maintaining BBB impermeability. The present study examined the expression and activation of gelatinases before and after tra nsient focal cerebral ischemia (FCI) in mice. Adult male CD1 mice were subj ected to 60 min FCI and reperfusion. Zymography was performed from 1 to 23 h after reperfusion using the protein extraction method with detergent extr action and affinity-support purification. MMP-9 expression was also examine d by both immunohistochemistry and Western blot analysis, and tissue inhibi tors to metalloproteinase-1 was measured by reverse zymography. The BBB ope ning was evaluated by the Evans blue extravasation method. The 88-kDa activ ated MMP-9 was absent from the control specimens, while it appeared 3 h aft er transient ischemia by zymography. At this time point, the BBB permeabili ty alteration was detected in the ischemic brain. Both pro-MMP-9 (96 kDa) a nd pro-MMP-2 (72 kDa) were seen in the: control specimens, and were markedl y increased after FCI. A significant induction of MMP-9 was confirmed by bo th immunohistochemistry and Western blot analysis. The early appearance of activated MMP-9, associated with evidence of BBB permeability alteration, s uggests that activation of MMP-9 contributes to the early formation of vaso genic edema after transient FCI. (C) 1999 Elsevier Science B.V. All rights reserved.