INCREASED METALLOPROTEINASE ACTIVITY IN C RITICAL STENOSIS ZONES OF CAROTID ENDARTERECTOMY PLAQUES

Background: The presence of metalloproteinases in atherosclerotic plaq ues has been described but their role is not well understood. An incre ased secretion of these proteolytic enzymes could explain plaque insta bility and distal embolization. Aim: To measure metalloproteinase acti vity in atheroesclerotic plaques obtained after carotid endarterectomy . Material and methods: Plaques were divided in one segment with and o ne segment without stenosis, the latter being used as control. Both se gments were incubated in culture media for 48 h or were fixed for hist ology. The conditioned medium was studied using gelatin zimography and digital densitometry. Metalloproteinases were identified by their mol ecular weight, inhibition with EDTA or Western Blot. Standard histolog ic study and immunohistochemistry were done. Results: In stenotic area s, metalloproteinase 9 (92kD) secretion was 260% higher than in regula r plaques (191 and 73 Kilopixels/mu g protein respectively p < 0.02). The histological study of stenotic areas showed macrophage infiltratio n and neoformation of blood vessels. Conclusions: The increased secret ion of cellular matrix degrading enzyme metalloproteinase 9 in stenoti c areas of atheroesclerotic plaques, could explain plaque instability and subsequent embolization.