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Objectives: Calpains are intracellular proteases, which are activated in various cerebral injuries. We studied the expression of mu-calpain in a model of focal cerebral ischemia/reperfusion and the efficacy of the calpain inhibitor A-558693., Methods: A transient occlusion of the middle cerebral artery was produced in male Wistar rats by using the suture model with 3 hours of ischemia and 24 hours of reperfusion. Six animals were given the calpain inhibitor and six animals were treated with placebo. The infarct size was determined by the loss of the calpain substrate microtubule-associated protein-2 (MAP-2) immunohistochemistry using volumetry in serial slices of the brains. Furthermore mu-calpain positive-stained cells were detected by immunohistochemistry and western blotting., Results: In placebo-treated animals the mu-calpain expression was significantly increased in the ischemic hemisphere compared with the contralateral non-ischemic hemisphere (88.6 versus 10.5% in the basal ganglia, 60.7 versus 10.7% in the cortex, p < 0.001, respectively) with a subsequent loss its substrate MAP-2. However, the use of the calpain inhibitor A-558693 did not significantly change the mu-calpain expression, nor significantly reduce the infarct volume., Discussion: The present data indicate that mu-calpain proteolysis plays an important role in the chain of events following cerebral ischemia. However, the calpain inhibitor A-558693 failed to prevent these changes.

Calpains, intracellular proteases, are involved in various cerebral disorders. To determine the effect of moderate hypothermia on calpain activity, transient middle cerebral artery occlusion in rats was performed. For the reperfusion period normothermic temperature was compared to post-ischemic hypothermia (32 degrees C). Calpain expression was measured by Western blot analysis and immunohistochemistry. The loss of calpain substrate was determined by immunohistochemistry against the anti-microtubule-associated protein-2 (MAP-2). The increase of calpains in the ischemic as compared to the non-ischemic contralateral hemisphere and the loss of MAP-2 were reduced by hypothermia. These data indicate that calpain activity and calpain-induced proteolysis play an important role in the network of events following cerebral ischemia and can be reduced by hypothermia. Moderate hypothermia may be a useful tool to limit secondary injury induced by intracellular calpain degradation.

Introduction: Calpains are intracellular proteases that are activated by increased intracellular calcium with proteolytic activity mainly against the cytoskeleton. We tested the expression of calpains and their substrates in an animal model of experimental cerebral venous thrombosis., Materials and Methods: Cerebral venous thrombosis was induced in seven male rats by rostral and caudal ligation of the superior sagittal sinus and injection of a thrombogenic cephalin suspension. Each animal survived 3 h of thrombosis. Using a polyclonal antibody against the 80 kD subunit of micro-calpain, immunohistochemistry of the region of interest (venous infarction) showed a loss of microtubule-associated protein-2. The micro-calpain-positive cells in the region of interest and normal tissue were measured using a video-imaging microscopy unit with magnification power of 400x. A cell was considered calpain positive when the nucleus and the periplasma were stained by the micro-calpain antibody., Results: The mean infarct size was 13.4+/-3.7% of one whole coronal section. A total of 57+/-14% of the cells were found to be calpain positive in the region of interest, whereas 5+/-2% of all cellular elements in unaffected tissue were calpain positive (p<0.001)., Conclusions: In conclusion, cerebral venous thrombosis causes an increase in calpain expression in affected tissue which is manifested by a loss of microtubule-associated protein-2. This increase might mediate secondary neuronal injury.