Expression Of MiR-155 In Carotid Atherosclerotic Plaques Of Apolipoprotein E Knockout(ApoE^-/-)mice And The Interventional Effect Of Rapamycin

Objective: Carotid atherosclerosis(AS)is an inflammatory process and is the primary pathogenesis of cerebrovascular disease.Many factors are responsible for development of atherosclerosis such as inflammation and autophagy.It is reported that micro RNAs(mi Rs)could regulate the development of atherosclerosis through targeting autophagy-related genes.Many studies have demonstrated that micro RNA-155(mi R-155)might be involved in autophagy in macrophages or tumor cells.However,the role of mi R-155 on autophagy in carotid plaques is not yet known.In this study,we To explore the expression of micro RNA-155(mi R-155)and autophagy-related proteins in carotid plaques of Apo E-/-mice and the interventional effect of rapamycin.Methods: 36 male Apo E-/-mice(8 weeks old)were randomly divided into three groups: control group,model group,rapamycin group.control group(the carotid wound was closed in one layer with interrupted silk sutures,0.5 mg/kg/d;PBS,gastric injection),model group(silastic collars were placed bilaterally around the common carotid arteries,0.5 mg/kg/d;PBS,gastric injection)and the rapamycin group(silastic collars were placed bilaterally around the common carotid arteries,0.5 mg/kg/d;rapamycin,gastric injection).All the mice were fed with a western-type diet(0.25% cholesterol and 15% fat)and free access to water for 8 weeks.After treatment,all the mice were sacrificed by exsanguination.8 weeks after administration,we tested the level of total cholesterol(TC),triglycerides(TG),low-density lipoprotein cholesterol(LDL-c),high-density lipoprotein cholesterol(HDL-c)in the plasma.Histopathologic morphology of these atherosclerotic plaques were observed via hematoxylin and eosin(HE)staining.The ultrastructural change of macrophage in these atherosclerotic plaques was observed via transmission electron microscopy(TEM),the expression of autophage-related protein(microtubule?associated protein 2 light chain 3,LC3-Ⅱ)and mi R-155 were assayed by real-time fluorescence quantitative PCR(q RT-PCR)and the expression of LC3-Ⅱ and expression ratio of phosphorylated mammalian target of rapamycin to total mammalian target of rapamycin(p-m TOR/m TOR)were detected by western blotting.Results: Compared with control group,the level of TC,TG,LDL-c were elevated in the plasma(P<0.05);HDL-c were elevated in the plasma(P>0.05),HE showed atherosclerotic plaque areas were aggravated,some autophagosomes were detected by TEM;mi R-155 and m RNA of LC3-Ⅱ expression was up-regulated(P<0.05),p-m TOR/m TOR was down-regulated in model group(P<0.05).These results following rapamycin group indicated that the level of TC,TG,and LDL-c was reduced(P<0.05),but the level of HDL-c was update(P>0.05);atherosclerotic plaque areas were reduced,much more autophagosomes were detected by TEM;mi R-155 and m RNA of LC3-Ⅱ expression were significantly up-regulated(P<0.05),expression ratio of p-m TOR/m TOR was significantly down-regulated(P<0.05).Conclusions: Our results showed in the early stages of atherosclerotic plaques development,effective autophagy could attenuate atherosclerosis in Apo E-/-mice.Furthermore,our results also showed that,in the early stages of AS development,after rapamycin treatment,the level of mi RNA-155 expression was significantly up-regulated,autophagy levels was also up-regulated.our results also demonstrated that rapamycin might promote the activation of the autophagy by enhancing the expression of mi R-155 in the early stages of atherosclerotic plaques development,,which delays the development of atherosclerotic plaques.