Study On Mechanism Of BAG3 Mitigates The Progression Of Atherosclerosis Via The Improvement Of Vascular Endothelium Damage

Objective:Atherosclerosis is the main cause of coronary heart disease,cerebral infraction and peripheral vascular disease,and vascular endothelium damage is the main pathological basis for the occurrence and development of atherosclerosis.In the vasculature,partial inhibition of autophagy leads to endothelial dysfunction,suggesting that endothelial autophagy is critical for maintaining vascular endothelial function.Studies have reported that B cell lymphoma 2-associated anthanogene（BAG3）is a new participant in vascular homeostasis that plays a key role in regulating the pathological process of various cancers,myopathy and neurodegenerative diseases by mediating the activation of autophagy,but its role in atherosclerosis remains unclear.The purpose of this study was to investigate whether BAG3 is involved in the progression of atherosclerosis by regulating vascular endothelial autophagy,so as to provide a new theoretical basis for the study of endothelial function and a new strategy for the effective prevention and treatment of atherosclerosis.Methods:1.Apo E^-/-mice were fed a high-fat diet for 12 weeks to establish a mouse model of atherosclerosis.After a tail-vein injection of BAG3-overexpressing lentivirus,the lipid-related biochemical and pathological indicators of aortic lipids of mice in each group were detected to calrify the effect of BAG3 on atherosclerosis.2.The degree of vascular endothelium damage was evaluated by q RT-PCR,Western blot,immunofluorescence staining and Transwell assay to determine the effect of BAG3 on vascular endothelium damage.3.For the purpose of exploring the mechanism of BAG3 on atherosclerosis through regulation of vascular endothelium,human umbilical vein endothelial cell line（HUVEC）was respectively transfected with BAG3 si RNA and BAG3 pc DNA3.1 to detect the expression of autophagy-related proteins,and to examine the number of autophagosomes and autophagic flux.4.To further investigate the underlying molecular mechanism of BAG3 on vascular endothelial autophagy,the interaction of BAG3 and its molecular chaperones in endothelial cells was verified by co-immunoprecipitation,and the expressions of BAG3-mediated chaperone-assisted selective autophagy（CASA）complex-related proteins were also detected.Results:Compared with the control group,Apo E^-/-mice with high fat diet had higher blood lipid level,increased lipid deposition and plaque area of aortic root and aggravated injury of vascular endothelium,while the injection of BAG3-overexpressing-lentivirus significantly improved abnormal blood lipids,reduced lipid deposition and plaque area,and alleviated atherosclerotic endothelium damage.In oxidized low-density lipoprotein（ox-LDL）-induced HUVECs,overexpression of BAG3 reversed ox-LDL-induced decreased expression of endothelial marker CD31 and reduction in the conversion of autophagy-related protein LC3-I to LC3-II.Similarly,in HUVECs,the autophagy inducer Rapamycin ameliorated defective autophagy and endothelium damage induced by transfection of BAG3 si RNA.Furthermore,BAG3 promoted autophagy by binding to HSP70 and HSPB8 to form a CASA complex and inhibited ox-LDL-induced endothelium damage.Conclusion:By interacting with its molecular chaperone HSP70 and HSPB8,BAG3 forms a CASA complex,which induces elevated levels of endothelial autophagy and reduces injury of vascular endothelial cells,thereby improving the progression of atherosclerosis.