Cofilin Rods Facilitate The Hippocampal Synaptic Loss In Rats With Cognitive Deficits Following Chronic Cerebral Hypoperfusion

Objective:Chronic cerebral hypoperfusion(CCH)has been associated with cognitive decline in patients after stroke.However,the mechanism remains elusive.Permanent,bilateral occlusion of thecommon carotid arteries in rats has been established as a procedure to investigate the effects of chronic cerebral hypoperfusion on cognitive dysfunction and cofilin rods formation and synaptic plasticity.Material and method:190 male Sprague-Dawley rats were randomy divided into Sham group and BCCAO group,and then divided into 1 week,4weeks,12 weeks and 24 weeks group by the same method.The rats were subjected to per manent bilateral common carotid artery occlusion to reproduce CCH.The memory and learning effects of CCH were evaluated in Morris water maze,followed by Golgi-Cox staining to observe dendritic spine density,transmission electron microscopy to observe synaptic ultrastructure,immunofluorescent confocal microscopy to detect cofilin rods colocalized with synaptophysin,western blot to measurement the realative levels of cofilin and synaptophysin protein.Results:1.BCCAO rats surviving 4weeks ? 12 weeks and 24 weeks after surgery showed impairment of reference memory performance,as compared to sham groups.BCCAO groups had significantly greater latencies to reach the platform position from 1 week persisted to 24 weeks.Performance on the working memory task showed deficit from1 week to 24 weeks.2.Golgi staining was used to quantify the density of dendritic spines.Compared to sham groups,dendritic spine density of BCCAO groups significantly decreased(12.55±1.75 vs.10.39±1.94,P=0.018;12.37±2.55 vs.8.62±1.49,P=0.001;12.65±2.76 vs.6.94±1.86,P=0.001;12.87±2.38 vs.7.03±2.09,P=0.001).Dendritic spine density progressively decreased from 1 week to 12 weeks of BCCAO groups(1weekvs.4weeks,P =0.001,4weeks vs.12 weeks,P=0.001)and stabilized from 12 weeks to 24weeks(12 weeks vs.24 weeks,P=0.837).3.We used transmission electron microscopy to observe the change of synaptic ultrastructure.Compared to sham groups,synaptic density in hippocampal CA 1 of BCCAO groups significantly decreased.Syanptic density progressively decreased from1 week to 12 weeks after surgery.Compared to sham groups,the width of synaptic cleft significantly increased.The thickness of PSD of BCCAO groups progressively decreased from 1 week to 12 weeks compared to sham groups.Compared to sham groups,the length of synaptic active zone was no significant difference between 1 week and 4 weeks of BCCAO groups,however,significantly decreased from 12 weeks to 24 weeks.Compared to sham groups,the curvature of synaptic interface significantly from4 weeks to 24 weeks of BCCAO groups.This observation suggested that synaptic transmission was significantly disrupted under CCH.4.We used immunofluorescent confocal microscopy to detect cofilin rods.We discovered that cofilin rods were detectable in hippocampal CA1 of BCCAO groups from 1 weeks to 24 weeks(9.65±3.87,11.05±4.38,21.60±6.98,and18.20±6.30 at time points of 1,4,12,and 24 weeks).Cofilin rods progressively increased from 4 week to 12 weeks after surgery,and stabilized from 12 weeks to 24 weeks(12 weeks vs.24 weeks P=0.056).There were no cofilin rods in hippocampal CA 1 of sham groups.The percentage of SYN fluorescence indensity decreased by 23.99%-50.93%.Compared to sham groups,SYN fluorescence indensity in hippocampal CA1 of BCCAO groups significantlydecreased(99.52±29.87 vs.75.64±25.54,P=0.010,97.50±15.89 vs.63.16±18.49,P=0.001,100.26±23.87 vs.52.36±13.72,P(27)0.001,102.25±23.39 vs.50.17±14.15,P(27)0.001).SYN fluorescence indensity progressively increased from 4 week to 12 weeks after surgery,and stabilized from 12 weeks to 24 weeks(12 weeks vs.24 weeks P=0.710).Correlation analysis of cofilin rod indensity and SYN indensity is negative(r=-0.52,P(27)0.0001).5.western blot was used to measurement the realative levels of cofilin and synaptophysin protein.Correlation analysis of cofilin congtent and SYN content is negative(r=-0.789,P(27)0.0001).Conclusion:CCH can ficilitate lasting spacial learning and memory impairments,which accompanied by the change of synaptic ultrastructure,and the decrease in dendritic spine density,as well as the increase in the number of cofilin rods is correlated with the decrease of the SYN density.The results suggest a potential mechanism by which CCH can ficilitate synaptic loss,which may be an important pathophysiological basis of lasting learning and memory impairment.