The Relationship Between Cathepsin B And P-Akt In Cerebral Ischemia Reperfusion

Background and ObjectiveIt is known that the pathophysiological process of cerebral ischemic penumbra zone isischemia reperfusion injuruy，so preventing penumbra’s neuronal cell from apoptosis is akey to control the progression of cerebral infarction. Previous studies show that the releaseof Cathepsin B (CB) and the activation of PI3K-Akt signaling pathway are both participatein the penumbra’s cells’apoptosis.But the study between Cathepsin B and the activation ofPI3K-Akt signaling pathway is little. The aim of my study is to explore the relationship ofCB and p-Akt in rat models given brain ischemia-reperfusion through the observation ofpenumbra’s (ischemic rat preoptic area) lysosome’s activation and protein CB and p-Akt’sdynamic expression.At the same time we investigate the impact of CB and p-Akt on cas-pase3.May be the study will provide a new theoretical foundation and treatment forischemic stroke.MethodsEighty healthy male Sprague-Dawley (SD) rats (280±20g,10~12weeks) were ran-domly divided into four groups:sham-operated group; injury reperfusion injury(IRI) group;LY294002group; Cathepsin B inhibition CA-074(CBI) group. The rat models with focalcerebral ischemia-reperfusion were established to make middle cerebral artery occlu-sion(MCAO) by method of reversibly inserting a nylon thread. LY294002(25μg,5μlDMSO), CA-074(20μg/1μl*5μl) or DMSO（10ml/L*5μl）was injected intracerebro-ventricularly (icv.) before ischemia30minutes. The neurological deficit scores were eva-luated with long’s five-point scale stardard scoring method.The morphologic variations oflysosome in cerebral ischemia penumbra was used electron microscope to observe and theprotein expression of Cathepsin B, p-Akt and caspase3were measured by western blot- ting.Results1. Middle cerebral artery occlusion models were achived in74.23%. Compared withIRI group, CA-074can decrease neurological deficit scores，LY294002can aggravate thesymptoms of cerebral ischemia and increase neurological deficit score(P<0.05).2. Through the electron microscope,we found that the number of lysosomes in IRIgroup’s is more and the value of lysosomes is bigger than the sham group’s at various timepoints in penumbra.The secondary lysosomes were activated. The difference is statisticallysignificant(P<0.05). In the late ischemic injury, cells gradually appeared to be apoptosis ornecrosis.3. The protein expression of caspase3is consistent with the severity of each group’sneurological deficit scores. LY group is the first,IRI group is the second, CA-074group isthe third.They are all more than sham group’s.4. In the sham group, Cathepsin B and p-Akt weren’t obviously expressed. In IRIgroup, there were both obvious expression at each time，peaked at3h,3-12h on a down-ward trend, but they are still more than sham group,12-24h compared with the previousupward trend(P<0.05). In LY group, the expression of CB is less than IRI group at0-6h,While it is more than IRI group at12h and24h(P<0.05). It is a upward trend from0hto24h. While the expression of CBI group’s p-Akt has the same trend with the expressionof LY group’s CB.Conclusions1. Lysosomes in rat models with cerebral ischemia reperfusion injury were activated.2. Early in cerebral ischemia and reperfusion injury(0-6h), the expression of Cathep-sin B and p-Akt in penumbra may have a relationship.3. In cerebral ischemia and reperfusion penumbra，it can partly prevent cell fromapoptosis with only use CA-074to inhibit lysosomes to release cathepsin B.