batimastat and Infarction--Middle-Cerebral-Artery

Intravenous recombinant tissue plasminogen activator (rtPA) can be beneficial in ischemic stroke despite an increased risk of hemorrhage and potential neurotoxic effects. We hypothesized that rtPA-mediated adverse effects depend on the timing of reperfusion and injury to the blood-brain barrier (BBB).. Male Wistar rats had middle cerebral artery occlusion (MCAO) by intraluminal thread placement. Intervals of ischemia/reperfusion, respectively, in hours were 0/18, 1.5/16.5, 3/15, 6/12, 18/0, and 6/1. Animals received either rtPA or saline for 1 hour at the time of reperfusion or, for the 18/0 trial, starting 1 hour after MCAO. Outcome parameters were mortality, matrix metalloproteinase-2 and -9 (MMP-2 and -9) concentrations, tissue hemoglobin, and brain water content. We analyzed the permeability of the BBB by using the brain 14C[sucrose] uptake method. Effects of the MMP inhibitor BB-94 on the BBB without rtPA treatment and on mortality with rtPA were tested in animals with 6/1 and 6/12, respectively.. In delayed reperfusion (6/12), rtPA increased mortality from 17% to 83% (P<0.01) without significantly affecting other outcome parameters. In 6/1, sucrose uptake in the ischemic hemisphere was markedly increased (8.80+/-1.14% vs 2.15+/-0.26%; P<0.01). This uptake was reduced by treatment with BB-94 (3.95+/-1.48%, P<0.01). Furthermore, BB-94 reduced rtPA-mediated mortality in 6/12 to 33% (P<0.05).. rtPA-mediated mortality in delayed reperfusion is associated with early opening of the BBB. Closure of the BBB with BB-94 given before rtPA treatment reduced mortality, suggesting that treatment with MMP inhibitors might reduce the risk associated with thrombolysis.

Topics: Animals; Blood-Brain Barrier; Brain; Brain Ischemia; Disease Models, Animal; Drug Administration Schedule; Enzyme Inhibitors; Infarction, Middle Cerebral Artery; Male; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Matrix Metalloproteinase Inhibitors; Matrix Metalloproteinases; Phenylalanine; Rats; Rats, Wistar; Recombinant Proteins; Reperfusion; Sucrose; Survival Rate; Thiophenes; Time Factors; Tissue Plasminogen Activator; Treatment Outcome; Water

Topics: Animals; Brain; Cerebrovascular Circulation; Disease Models, Animal; Enzyme Inhibitors; Extracellular Matrix; Female; Glycine; Hemodynamics; Humans; Hydroxamic Acids; Infarction, Middle Cerebral Artery; Intracranial Arteriosclerosis; Male; Matrix Metalloproteinase 1; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Matrix Metalloproteinase Inhibitors; Matrix Metalloproteinases; Mice; Phenylalanine; Thiophenes; Treatment Outcome

Fractalkine is a recently identified chemokine that exhibits cell adhesion and chemoattractive properties. It represents a unique member of the chemokine superfamily because it is located predominantly in the brain in which it is expressed constitutively on specific subsets of neurons. To elucidate the possible role of neuronally expressed fractalkine in the inflammatory response to neuronal injury, we have analyzed the regulation of fractalkine mRNA expression and protein cleavage under conditions of neurotoxicity. We observed that mRNA encoding fractalkine is unaffected by experimental ischemic stroke (permanent middle cerebral artery occlusion) in the rat. Similarly, in vitro, levels of fractalkine mRNA were unaffected by ensuing excitotoxicity. However, when analyzed at the protein level, we found that fractalkine is rapidly cleaved from cultured neurons in response to an excitotoxic stimulus. More specifically, fractalkine cleavage preceded actual neuronal death by 2-3 hr, and, when evaluated functionally, fractalkine represented the principal chemokine released from the neurons into the culture medium upon an excitotoxic stimulus to promote chemotaxis of primary microglial and monocytic cells. We further demonstrate that cleavage of neuron-derived, chemoattractive fractalkine can be prevented by inhibition of matrix metalloproteases. These data strongly suggest that dynamic proteolytic cleavage of fractalkine from neuronal membranes in response to a neurotoxic insult, and subsequent chemoattraction of reactive immune cells, may represent an early event in the inflammatory response to neuronal injury.

Topics: Animals; Animals, Newborn; Brain; Cell Membrane; Cells, Cultured; Chemokine CX3CL1; Chemokines, CX3C; Chemotaxis; Culture Media, Conditioned; Disease Models, Animal; Encephalitis; Endothelium, Vascular; Glutamic Acid; Infarction, Middle Cerebral Artery; Interleukin-1; Matrix Metalloproteinase Inhibitors; Matrix Metalloproteinases; Membrane Proteins; Microglia; Monocytes; Neurons; Phenylalanine; Protease Inhibitors; Rats; RNA, Messenger; Thiophenes; Transfection; Tumor Necrosis Factor-alpha