Chronic Unpredictable Mild Stress Promotes Atherosclerosis Via HMGB1/TLR4-mediated Downregulation Of PPAR?/LXR?/ABCA1 In ApoE^-/-mice

[Background and Objective]Atherosclerosis?As?is the main pathological basis of cardiovascular and cerebrovascular diseases.In recent years,coronary heart disease,stroke,myocardial infarction and other cardio-cerebrovascular diseases caused by atherosclerosis seriously endanger the physical and mental health and the quality of life of human beings,it has become a serious social problem.Researches show that chronic stress has become an important independent risk factor for As cardiovascular disease.Therefore,it is a great of significance to elucidate the molecular biological mechanism of chronic stress affecting As lesions to prevent and treat As.In this study,we will explore the role of the high mobility group protein B1?HMGB1?/Toll-like receptor 4?TLR4?pathway in chronic stress induced As lesions and its mechanism.[Methods]Sixty ApoE^-/-male mice were randomly divided into 4 groups:control group,chronic stress group,chronic stress+Ethyl pyruvate?EP,an inhibitor of HMGB1?group,chronic stress+TAK242?TLR4 inhibitor?group.First,the level of serum corticosterone were measured to determine whether the stress model was established in ApoE^-/-mice.In order to clarify the effect of chronic stress on the release of HMGB1 and activation of TLR4,Elisa and Western Blot were used to detect the release of HMGB1 in serum and the expression of HMGB1 and TLR4 in vascular tissue of chronic stress ApoE^-/-mice.Then,HMGB1 selective inhibitor EP and TLR4 specific inhibitor TAK-242 were used to investigate the effects of inhibition of HMGB1release and activation of TLR4 on As pathological changes in chronic stress ApoE^-/-mice.HE,oil red O and Masson staining were used to evaluate the pathological changes of aortic sinus,the size of atherosclerotic plaque and the changes of collagen content.The migration level of smooth muscle cells in aortic sinuses and the expression and distribution of macrophages in atherosclerotic plaques were detected by immunofluorescence staining.The expressions of corticosterone,HMGB1,IL-1?and TNF-?in serum of mice were detected by ELISA method.The expression of HMGB1,TLR4,PPAR?,LXR?,ABCA1 and other proteins in aortic vascular tissue of mice was detected by Western Blot method.In chronic stress cell model in vitro,mouse Raw 264.7 macrophages incubated with glucocorticoid?corticosterone?were treated with HMGB1 inhibitor EP,TLR4 inhibitor TAK-242 and PPAR?agonist Rosiglitazone?RSG?,respectively.Observation the effects of blocking HMGB1/TLR4-PPAR?signaling pathway on lipid accumulation,HMGB1 release,LXR?and ABCA1expression to further clarify the role and mechanism of HMGB1/TLR4pathway under the chronic stress.The lipid content of Raw 264.7macrophages was evaluated by oil red O staining.The expression of HMGB1 in the supernatant of macrophages was detected by ELISA,and the expression of TLR4,PPAR?,LXR?and ABCA1 proteins in macrophages was detected by Western Blot method.[Results]1.Our results indicated that the serum corticosterone,inflammatory factors IL-1?and TNF-?levels were elevated with the development of atherosclerosis in CUMS ApoE^-/-mice,the protein levels of HMGB1,TLR4,IL-1?in aorta were significantly increased compared with the control group,while the expressions of PPAR?,LXR?,and ABCA1 decreased significantly.2.HMGB1 inhibition by EP reversed CUMS induced atherosclerotic development,pro-inflammatory cytokines level and the number of macrophages up-regulation,the content of collagen and smooth muscle cells down-regulation.The same trend was observed in the stressed mice treatment with TAK-242.3.HMGB1 inhibition by EP reversed CUMS-induced atherosclerotic development and PPAR?/LXR?-ABCA1 down-regulation.The same trend was observed in the stressed mice treatment with TAK-242.4.CORT promotes HMGB1 release,and increases TLR4 expression and foam cell formation,and decreases the expression of PPAR?/LXR?-ABCA1in Raw 264.7 macrophages.While these effects of CORT can be significantly abolished by EP,TAK-242 and rosiglitazone treatment,respectively.[conclusion]1.CUMS exacerbates atherosclerosis is likely via HMGB1-mediated drown-regulation of PPAR?/LXR?-ABCA1 through TLR4.which can induce chronic inflammation of vascular wall and promote the development of As in ApoE^-/-mice.