A novel calpain inhibitor, ((1S)-1((((1S)-1-benzyl-3-cyclopropylamino-2,3-di-oxopropyl)amino)carbonyl)-3-methylbutyl) carbamic acid 5-methoxy-3-oxapentyl ester, protects neuronal cells from cerebral ischemia-induced damage in mice

Abstract Cerebral ischemia induces Ca2+ influx into neuronal cells, and activates several proteases including calpains. Since calpains play important roles in neuronal cell death, calpain inhibitors may have potential as drugs for cerebral infarction. ((1S)-1(((1S)-1-Benzyl-3- cyclopropylamino-2,3-di-oxopropyl)amino)carbonyl)-3-methylbutyl) carbamic acid 5-methoxy-3-oxapentyl ester (SNJ-1945) is a novel calpain inhibitor that has good membrane permeability and water solubility. We evaluated the effect of SNJ-1945 on the focal brain ischemia induced by middle cerebral artery occlusion (MCAO) in mice. Brain damage was evaluated by assessing neurological deficits at 24 h or 72 h after MCAO and also by examining 2,3,5-triphenyltetrazolium chloride (TTC) staining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining of brain sections. When injected at 1 h after MCAO, SNJ-1945 at 30 and 100 mg/kg, i.p. decreased the infarction volume and improved the neurological deficits each assessed at 24 h. SNJ-1945 at 100 mg/kg, i.p. also showed neuroprotective effects at 72 h and reduced the number of TUNEL-positive cells at 24 h. SNJ-1945 was able to prevent neuronal cell death even when it was injected at up to 6 h, but not at 8 h, after MCAO. In addition, SNJ-1945 decreased cleaved α-spectrin at 6 h and 12 h, and active caspase-3 at 12 h and 24 h in ischemic brain hemisphere. These findings indicate that SNJ-1945 inhibits the activation of calpain, and offers neuroprotection against the effects of acute cerebral ischemia in mice even when given up to 6 h after MCAO. SNJ-1945 may therefore be a potential drug for stroke.