Certain Forms of Matrix Metalloproteinase-9 Accumulate in the Extracellular Space After Microdialysis Probe Implantation and Middle Cerebral Artery Occlusion/Reperfusion

• Published in: Journal of cerebral blood flow and metabolism Vol. 22; no. 8; pp. 918 - 925
• Main Authors: Planas, Anna M., Justicia, Carles, Solé, Sònia, Friguls, Bibiana, Cervera, Álvaro, Adell, Albert, Chamorro, Ángel
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.08.2002; Lippincott Williams & Wilkins; Sage Publications Ltd
• Subjects: Animals; Biological and medical sciences; Brain - enzymology; Brain - pathology; Brain Ischemia - enzymology; Brain Ischemia - pathology; Extracellular Space - enzymology; Isoenzymes - metabolism; Male; Matrix Metalloproteinase 9 - metabolism; Medical sciences; Microdialysis; Middle Cerebral Artery; Neurology; Neutrophil Infiltration; Peroxidase - metabolism; Rats; Rats, Sprague-Dawley; Reperfusion; Vascular diseases and vascular malformations of the nervous system; Focal ischemia; Brain; Stroke; In vivo microdialysis; Injury; Neutrophils; Immunohistochemistry; Focal lesion; Rat; Cardiovascular disease; Metalloendopeptidases; Vascular disease; Reperfusion; Ischemia; Immunoblotting assay; Cerebrovascular disease; Nervous system diseases; Enzyme; Rodentia; Exploration; Gelatinase B; Cerebral disorder; Pathology; Peptidases; In vivo; Vertebrata; Experimental disease; Mammalia; Microdialysis; Animal; Central nervous system disease; Hydrolases; Brain (vertebrata)
• ISSN: 0271-678X; 1559-7016
• DOI: 10.1097/00004647-200208000-00003

Matrix metalloproteinases (MMPs) are activated in focal cerebral ischemia. The activation of MMP-9 is involved in blood—brain barrier breakdown and tissue remodeling. The MMPs are released to the extracellular space, but the form and fate of secreted enzymes in brain are unknown. Using microdialysis in vivo, the authors studied whether ischemia-induced MMP-9 in brain tissue was related to free MMP-9 in the extracellular fluid. A microdialysis probe was placed into the right striatum and microdialysis was initiated 24 hours later in controls (n = 7). One hour prior to microdialysis, a group of rats (n = 7) was subjected to 1-hour occlusion of the right middle cerebral artery, followed by reperfusion. Dialysates were collected at discrete time points up to 24 hours, and subjected to zymography and Western blot analysis. The MMP-9 was released after ischemia and accumulated in the extracellular space at 24 hours (P < 0.05). Free MMP-9 forms include mainly the 95-kd proform, and, to a lesser extent, dimers and cleaved active forms (70 kd), but not the 88-kd form found in tissue. Probe implantation and microdialysis increased free MMP-9 in the dialysate. This increase was concomitant with neutrophil infiltration after the mechanical lesion, as myeloperoxidase was found by means of Western blot analysis in the brain hemisphere subjected to microdialysis (P < 0.005), and immunohistochemistry revealed the presence of myeloperoxidase stain surrounding the site of probe implantation. The results suggest that certain forms of MMP-9 are released and accumulate in the extracellular space after brain injury, and that vascular alterations and neutrophil recruitment elicit MMP-9 activation in the brain after focal ischemia and trauma.