Neuroprotection with a calpain inhibitor in a model of focal cerebral ischemia.

Abstract

Background and Purpose Excessive elevation of intracellular calcium and uncontrolled activation of calcium-sensitive events are believed to play a central role in ischemic neuronal damage. Calcium-activated proteolysis by calpain is a candidate to participate in this form of pathology because it is activated under ischemic conditions and its activation results in the degradation of crucial cytoskeletal and regulatory proteins. The present studies examined the effects of a cellpenetrating inhibitor of calpain on the pathological outcome after transient focal ischemia in the brain.Methods Twenty-five male Sprague-Dawley rats were divided into four groups: a saline-treated group, a vehicletreated group, and two calpain inhibitor-treated groups (CbzVal-Phe-H; 30-mg/kg and 60-mg/kg cumulative doses). Ischemia was induced by occluding the left middle cerebral artery and both common carotid arteries for 3 hours followed by reperfusion. Animals were killed 72 hours after surgery, and quantitative measurements of infarction volumes were performed using histological techniques. Eight additional rats were killed 30 minutes after ischemia and examined for the

Excitotoxicity and focal cerebral ischemia induce truncation of the NR2A and NR2B subunits of the NMDA receptor and cleavage of the scaffolding protein PSD-95

“…Previous results demonstrating a requirement for Ca 2 þ (Figure 3c) and reports showing calpain as a major effector in excitotoxicity and ischemia [35][36][37] suggested that activation of this protease might be responsible for the NR2A cleavage induced by NMDA, as shown before for NR2B. 19 We first confirmed the activation of calpain in the in vitro model of excitotoxicity used in these experiments.…”

“…Considering that calpain is activated very early during the ischemic process 36,37 and the results previously obtained in the in vitro model of excitotoxicity, it is very likely that this protease is responsible for the proteolytic processing of the NR2A and NR2B subunits occurring in ischemia. We confirmed calpain activation by the production of brain spectrin BDPs, paying special attention to the kinetics of the process (Figure 6b).…”

“…Calpains are important mediators of cellular toxicity and pathology 48 and are activated in processes of brain ischemia and excitotoxic degeneration, among others. [35][36][37] In order to understand the process of neuronal degeneration associated to these pathologies, it is important to characterize the substrates of this protease and the way calpain cleavage modifies their functions. One of them is the Na þ / Ca 2 þ exchanger (NCX), 49 the major plasma membrane Ca 2 þ extruding system in neurons.…”

“…These results strongly suggest that this protease is responsible for the coordinated cleavage of subunits NR2A and NR2B and their associated proteins, spectrin and PSD-95, in the infarcted region during cerebral ischemia. The neuroprotective role of calpain inhibition found in a model of transient focal cerebral ischemia 36 can be explained in the light of the important functions in neuronal survival of substrates of this protease.…”

Local Cerebral Glucose Utilization and Cytoskeletal Proteolysis as Indices of Evolving Focal Ischemic Injury in Core and Penumbra

“…Calpain inhibitors have been reported to improve posthypoxic synaptic recovery in both neocortical (Hiramatsu et al, 1993) and hippocampal (Arling haus et al, 199 1) slices and to protect neurons both in the context of cytotoxic hypoxia in vitro and fol lowing transient global ischemia in vivo (Rami and Krieglstein, 1993). In recent studies, cell-pene trating calpain inhibitors have been reported to re duce the volume of infarction and to attenuate the increase in SBPs in models of focal ischemia (Bar tus et al, 1994;Hong et al, 1994). These results suggest that calcium-activated proteolysis is close ly involved in the process of ischemic neuronal damage and may offer a crucial target for achiev ing pharmacological neuroprotection in ischemic stroke.…”