Activation of Matrix Metalloproteinase-3 and Agrin Cleavage in Cerebral Ischemia/Reperfusion

Abstract

Matrix metalloproteinase-3 (MMP-3) degrades components of the extracellular matrix and may participate in the pathogenesis of stroke. Here we examine the expression, activation, and cellular location of MMP-3 and the cleavage of agrin, an MMP-3 substrate, following transient middle cerebral artery occlusion in the rat. MMP-3 was activated by ischemia/reperfusion, which was revealed by the appearance of a cleaved form and increased degradation of a substrate. MMP-3 was observed in ischemic neurons, oligodendrocytes, microvasculature, and reactive microglia/macrophages. In cell cultures, MMP-3 expression was observed in neurons and, to a lesser extent, in mature oligodendrocytes, but not in oligodendrocyte progenitors, astrocytes, or microglia. Casein zymography revealed MMP-3 in cultured neurons. Agrin was expressed in cultured neurons and cultured astrocytes. In brain tissue, agrin was detected in neurons, and following ischemia it was also detected in reactive astrocytes. Addition of MMP-3 to protein extracts from control brain caused neuronal agrin degradation. Following ischemia/reperfusion, agrin disappeared from the tissue membrane fraction and a cleaved agrin fragment was found in tissue protein extracts. The present results show MMP-3 activation and neuronal transmembrane agrin cleavage after ischemia/reperfusion. In addition, the finding that MMP-3 cleaves brain agrin strongly suggests that ischemia-induced MMP-3 activation causes agrin cleavage.

Cerebral Ischemia Causes Dysregulation of Synaptic Adhesion in Mouse Synaptosomes

“…Furthermore, Solé et al (2004) observed Agrn staining in glia after cerebral ischemia. Incidentally, we did not observe the ischemia-induced 135 kDa Agrn fragment reported by Solé et al (2004) in ISC synaptosomes. This may be due to a lack of MMP3 degradation of synaptic Agrn in the 3 to 20 h time frame or loss of the nonmembrane-associated Agrn fragment during the synaptosomal isolation procedure.…”

Matrix metalloproteinases in the brain and blood–brain barrier: Versatile breakers and makers

“…Various studies in human and rat brains show that protein and activity levels of MMPs-2, -3, and -9 are increased after stroke and MCAO compared to control tissue. 173,174 These changes in MMP protein and activity levels result in aberrant proteolysis that contributes to blood-brain barrier dysfunction and in part determines the extent of the infarct. 132,[173][174][175][176][177] In addition, studies using rat stroke models suggest that by degrading the basal lamina, MMPs predispose brain capillaries to rupture and hemorrhagic transformations after stroke.…”

“…173,174 These changes in MMP protein and activity levels result in aberrant proteolysis that contributes to blood-brain barrier dysfunction and in part determines the extent of the infarct. 132,[173][174][175][176][177] In addition, studies using rat stroke models suggest that by degrading the basal lamina, MMPs predispose brain capillaries to rupture and hemorrhagic transformations after stroke. [178][179][180] Other examples of detrimental MMP effects in stroke were shown in studies using rodent models of focal cerebral ischemia.…”

Matrix metalloproteinases at key junctions in the pathomechanism of stroke

“…Collagen degradation after cerebral ischemia might be in part caused by MMP-13 [43]. Another matrix metalloproteinase, MMP-3 can also be activated after ischemia in rat brain, causing cleavage of the cerebral matrix agrin [82]. MMP-3 can contribute to BBB opening during neuroinflammation after intra-cerebral lipopolysaccharide injection in mice.…”