Inhibition of Cathepsin B Ameliorates Murine Cognitive Dysfunction and Neuronal Damage in Ischemic Stroke by Inhibiting Mitochondrial Apoptosis and Drp1-Mediated Mitochondrial Fission

The surviving brain tissue undergoes secondary degeneration long after an ischemic stroke. Cathepsin B plays dual roles as both a scavenger and an executor. Using a mouse model of ischemic stroke, we specifically investigated the mechanism by which inhibiting Cathepsin B with CA074 methyl ester (CA-074Me) during the chronic phase of stroke exerts a protective effect. In the intervention group, CA-074Me (20 mu g CA-074Me/1 mu l DMSO) was stereotaxically injected in the right ventricle, and, 30 min later, the animals were subjected to develop transient middle cerebral artery occlusion and reperfusion (tMCAO/R) stroke model with modified Longa method. In the model group, 1 mu l DMSO was given in the right ventricle instead and the sham-operated group received 1 mu l DMSO in the right ventricle without arterial occlusion. We evaluated the effects of inhibition of Cathepsin B on the nervous system after tMCAO/R injury by combined use behavioral tests, neurological deficit scoring, Western blot and other pharmacological methods and explored the underlying mechanism. After tMCAO/R, sustained upregulation and activation of Cathepsin B was noticed in the ipsilateral hippocampus CA1 zone and CA-074Me ameliorated the parallel lysosome-mitochondria damage, decreased apoptosis, improved the cognitive dysfunction, but had no effects on levels of mouse anxiety or depression. Furthermore, CA-074Me reduced neuroinflammation, levels of oxidative stress and mitochondria fission. Inhibition of Cathepsin B alleviates mitochondrial abnormalities in the ipsilateral hippocampus CA1 zone 28 days after tMCAO/R by suppressing Drp-1mediated excessive mitochondrial fission. This, in turn, reduces neuronal apoptosis, ameliorates neuroinflammation, and mitigates oxidative stress and neuronal damage, indicating Cathepsin B may serve as a potential therapeutic target for remote secondary degeneration following acute ischemic stroke.