Background and Purpose-Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that degrade the extracellular matrix and are implicated in numerous pathological conditions including atherosclerosis, inflammation, and tumor growth and metastasis. In the brain, the endothelial cell wall, strengthened by tight junctions, defines the blood-brain barrier (BBB). The extracellular matrix molecules constitute the basement membrane underlying the vasculature and play a critical role in maintaining the integrity of the BBB. After focal stroke, there is a breakdown of the BBB with an associated increase in vascular permeability, inflammatory cell influx, and neuronal cell death. The present study was designed to investigate the effects of MMP expression after stroke. Methods-Focal stroke was produced by permanent middle cerebral artery occlusion (MCAO) in the rat, and MMP protein expression was measured by Western blot and zymogram analysis over a time course ranging from 6 hours to 30 days (nϭ32). Immunohistochemistry at 1 and 5 days (nϭ8 and 6, respectively) was also utilized to characterize the expression of several MMPs and related proteins after stroke, including their cellular source. To test the hypothesis that early increased MMP-9 expression is involved in ischemic brain injury, a neutralizing monoclonal antibody directed against MMP-9 was administered intravenously (nϭ7 per group) 1 hour before MCAO, and infarct size was measured 24 hours later. Results-MMP expression increased progressively over time after stroke. After 12 hours, significant (PϽ0.05) MMP-9 activity was observed that reached maximum levels by 24 hours (PϽ0.001), then persisted for 5 days at this level and returned to basal (zero) levels by 15 days. On the basis of morphological criteria, MMP-9 appeared to stain with endothelial cells and neutrophils identified both within and at the periphery of the infarct within 24 hours of focal ischemia. After 5 days, MMP-9 appeared to stain with macrophages present within the infarcted brain. MMP-2 activity was significantly (PϽ0.001) increased by 24 hours and was maximum after 5 days following MCAO. MMP-2 appeared to stain with macrophages present within the infarcted region. Unlike MMP-9 and MMP-2, tissue inhibitor of metalloproteinase-1 was identified at comparable levels in both control and ischemic tissue after MCAO. MMP-1 and MMP-3 could not be detected in the brain after focal stroke. When an MMP-9 -neutralizing monoclonal antibody was administered systemically, animals exhibited significantly reduced infarct size (ie, a 30% reduction compared with non-immune antibody controls; PϽ0.05). Conclusions-These results demonstrate that early increased MMP-9 expression in endothelial cells and infiltrating neutrophils is a significant response to cerebral focal ischemia and that selective inhibition of MMP-9 activity can significantly reduce brain injury after stroke.

Carvedilol is a cardiovascular drug currently used for the treatment of hypertension. Clinical studies have recently demonstrated efficacy in angina and congestive heart failure. Recently, carvedilol has been shown to attenuate oxygen free radical-initiated lipid peroxidation and to inhibit vascular smooth muscle mitogenesis induced by a wide variety of growth factors. These rmdings are of interest since smooth muscle proliferation and abnormal lipid metabolism are proposed to play an important role in the pathogenesis of atherosclerotic plaque formation and in development of stenotic lesions following vascular iD,ury by balloon angioplasty and coronary artery bypass grafting. On the basis of these observations, the antiproliferative actions of carvedilol have been explored in detail. In human cultured pulmonary artery vascular smooth muscle cells, carvedilol (0.1-10 FM) produced a concentration-dependent inhibition of the mitogenesis stimulated by platelet-derived growth factor, epidermal growth factor, thrombin, and serum, with ICso values ranging from 0.3 to 2.0 #sM. Carvedilol also produced a concentrationdependent inhibition of vascular smooth muscle cell migration induced by platelet-derived growth factor, with an IC5. value of 3 FM. The extensive neointimal formation that occurs following balloon angioplasty of rat carotid arteries was markedly attenuated by carvedilol (1 mg/kg, i.p.; twice daily starting 3 days before angioplasty and continuing until 14 days after angioplasty). Quantitative image analysis demonstrated that carvedilol reduced the neointimal growth following angioplasty by 84% without altering either medial or adventitial cross-sectional areas. These observations indicate that carvedilol may also be effective in the treatment of pathological disorders principally associated with abnormal vascular smooth muscle growth, such as atherosclerosis and acute vascular wail injury induced by angioplasty or coronary artery bypass gng.

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Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that degrade the extracellular matrix (ECM). The membrane-type matrix metalloproteinases (MT-MMPs) are a new family of MMPs that differ from other MMPs in that they have a transmembrane domain that anchors them to the cell surface. MT-MMPs have been shown to function as receptors and activators for other MMPs and to localize extracellular matrix proteolysis at the pericellular region. Here we report on mRNA and protein expression of the fifth human MT-MMP (MT5-MMP), a 64-kDa protein that is capable of converting pro-MMP-2 to its active form, in human kidney as well as its upregulation in diabetes. We also demonstrate upregulation of the active form of MMP-2 in kidney samples from patients with diabetes. Through immunohistochemistry, MT5-MMP expression was localized to the epithelial cells of the proximal and distal tubules, the collecting duct, and the loop of Henle. Furthermore, the tubular epithelial cells that expressed MT5-MMP were associated with tubular atrophy. Because renal tubular atrophy is a significant factor in the pathogenesis of diabetic nephropathy and renal failure and the molecular mechanisms regulating this process remain unknown, it is hypothesized that the elevated expression of MT5-MMP contributes to the activation of pro-MMP-2, which participates in the remodeling of the proximal and distal tubules as well as in the collecting duct. These results provide the first evidence of the expression of a MT-MMP in diabetes and suggest a novel role for MT5-MMP in the pathogenesis of renal tubular atrophy and end-stage renal disease.