Effects Of Rosuvastatin On Apoptosis And Autophagy In The Hippocampus Of Rats With Vascular Dementia

Background and objectiveVascular dementia(VD)is the most common non-degenerative dementia,caused by cerebrovascular diseases and accounting for 15% to 20% of total dementia,following Alzheimer's Disease(AD).Chronic cerebral hypoperfusion(CCH)is considered a significant risk factor for dementia onset in patients with cerebrovascular diseases.CCH can cause critical areas,particularly the hippocampal CA1 area,to suffer from hypoxia-ischemia,which induces delayed-neuronal damage to develop into VD.Therefore,it's beneficial to find the potential therapy target by exploring the pathophysiologic changes of VD brain tissue.There is a large loss of neurons,and apoptosis and autophagy coexist in the pathological condition.Apoptosis is a type of initiative cell death.Bcl-2 protein has the anti-apoptosis effect and Bax protein has the opposite effect in Bcl-2 family proteins,which control apoptosis course depending on regulating the ratio of Bcl-2/Bax.Autophagy is the course of cell "self-eating".CCH can induce autophagy activation,and long-term excessive activation of autophagy causes neuronal damage.Beclin-1 protein is universal biological indicator for detecting autophagy onset.Statins have been konwn as primary prevention drugs after ischemic stroke.The main functions include lipid-decreasing,preventing platelet aggregation,anti-apoptosis,anti-inflammatory,anti-oxidative stress,autophagy regulation,etc.Different statins plays completely different roles in autophagy regulation of different tissue.A study showed rosuvastatin(ROS)could improve the abilities of learning and memory in VD rats,but the mechanism is still uncertain.It has not yet been confirmed whether the mechanism is related to modulation the effects of ROS on apoptosis and autophagy activation that CCH induced.This experiment aimed at providing experimental evidence for optimizing clinical drugs by exploring the protective effects and pathological mechanisms of ROS on VD rats.Method11-12 week-old male SD rats,weighing 250-270 g,were randomly divided into four groups: Sham group,Sham+ROS group,VD group,VD+ROS group.Bilateral common carotid artery occlusion(BCCAO)was used to establish VD model.2 weeks later,Sham+ROS group and VD+ROS group were treated with lavage with a dose of 5mg/kg /d for 3 weeks,while Sham and VD groups were provided with the equal volume of normal saline.The changes of learning and memory abilities were examed by Morris water maze,and the morphology changes of hippocampal CA1 area were detected by HE staining.The values of Bcl-2 / Bax ratio were detected by measure of Western Blotting.The expression of Beclin-1 protein and Bcl-2 protein in hippocampal CA1 area of rats were detected by measure of immunohistochemistry.Results1.The effects of ROS on the spatial learning and memory abilities of VD ratsThe escape latencies and time ratios that rats spent in the target quadrant had statistical difference among four experimental groups(P<0.01),but there was no statistical difference between the Sham and Sham+ROS groups(P>0.01).Compared with the former two groups,the escape latencies of rats in the VD group were significantly prolonged,and the rats spent less time in the target quadrant than the former two groups(P<0.01).The escape latencies of rats in the VD+ROS group were shorten compared with the VD group,and the rats spent more time in the target quadrant than in the VD group(P<0.01).2.The effect of ROS on the morphological structure of the hippocampal CA1 areas of VD ratsThe neurons in hippocampal CA1 areas of the Sham and Sham+ROS groups arranged orderly and densely,the nucleolus and cytoplasm were clear,and the morphological structure of cells was integral.Compared with the former two groups,there was a significant loss of neurons in the VD group rats.The neurons arranged loosely and irregularly.The Karyopyknosis and cytoplasm hyperchromatism appeared.After the intervention of rosuvastatin,the above-described morphological changes were improved.Compared the VD group,the loss of neurons in the hippocampal CA1 areas of rats were reduced at a certain degree.3.The effect of ROS on the ratio of Bcl-2/Bax in the hippocampal CA1 areas of VD ratsThe ratio of Bcl-2/Bax in the hippocampal CA1 areas of rats among four groups had statistical difference(P=0.003).There was no statistical difference between the Sham group and Sham+ROS group(P=0.966).The ratio was lower in the VD rats than in the former two groups(P<0.01),while the ratio was higher in the VD+ROS group than in the VD group(P=0.026).4.The effects of ROS on Bcl-2 protein and Beclin-1 protein positive expression in the hippocampal CA1 areas of VD ratsThe hippocampal CA1 areas of rats between the Sham group and Sham+ROS group had a small amount of Bcl-2 and Beclin-1 protein positive cells with minimal hyperchromatism,and had statistical difference(P>0.01).The number of Bcl-2 and Beclin-1 protein positive cells of rats in the VD group was more than the former two groups(P<0.05).The number of Bcl-2 protein positive cells was more,but the number of Beclin-1 protein positive cells was less in the VD+ROS group than the VD group(P<0.05).Conclusions1.BCCAO rat model is the useful model for studying cognitive dysfunction related to VD.After ROS intervention,the abilities of spatial learning and memory were improved to some extent.2.CCH after BCCAO caused pathological changes in the hippocampus.ROS intervention can alleviate neuron damage of the hippocampus CA1 areas in a certain degree.3.CCH induced neurons apoptosis and autophagy excessive activation,which led to hippocampal CA1 area neuronal death.Application of ROS can play the neuroprotective role in the hippocampus,by regulating the levels of neuron apoptosis and autophagy.