Role Of CD36 In Obesity-mediated Endoplasmic Reticulum Stress And Vascular Injury

Objective Obesity is a global epidemic that can cause many chronic diseases.Cardiovascular diseases caused by obesity have become one of the main causes of death and disability in the world.However,there is still a lack of effective treatment for cardiovascular diseases caused by obesity.Vascular endothelial injury is an early manifestation of vascular damage and is considered to be a reliable predictor of obesity-related cardiovascular disease development.CD36 belongs to Class B scavenger receptor,also known as fatty acid transporter,which is involved in lipid transport,regulation and metabolism.In addition,it can bind various lipids to form signal complexes and induce a series of cell signal transduction effects.Endoplasmic reticulum stress(ERS)is a self-protective response,but strong and persistent ERS can lead to cell apoptosis in the organism and eventually lead to cardiovascular diseases.Although obesity,CD36 and endoplasmic reticulum stress are all closely related to the development of cardiovascular diseases,it remains unclear whether free fatty acids or obesity can cause vascular endothelial injury by binding to CD36 and activating the CD36 signaling pathway,and ultimately lead to cardiovascular diseases.The purpose of this study was to explore the role and mechanism of CD36 in the vascular injury of obese mice by silencing PA-induced human umbilical vein endothelial cells with siRNA transfection and using adenovirus to silence the CD36 gene induced by high fat diet,and to provide a theoretical basis for clarifying the pathogenesis of cardiovascular diseases caused by obesity.Methods In vivo,40 6-week-old C57BL/6 male mice were randomly divided into normal diet group.High-fat diet group;High fat diet + gene silencing control group,high fat diet + CD36 gene silencing group.Mice were fed normal diet and high-fat diet until the end of the 8th week,and adenovirus silenced target gene was injected into the tail vein of mice,and continued feeding until the end of the 12 th week.Changes in body weight and blood glucose of animals in each group were monitored,blood was collected to detect serum total cholesterol and triglyceride levels,paraffin embedded sections of aortic vessels were taken for Masson staining and HE staining to detect vascular structural damage.Intracellular and vascular reactive oxygen species were detected by immunofluorescence staining.Western blot was used to detect the expression of endoplasmic reticulum stress marker protein and inflammatory factor protein.In cell experiments,CD36 gene was silenced by transfection with si-RNA,and palmitic acid(100 μM)was added 12 h later.The cells were divided into scramb gene silencing group,CD36 gene silencing group,scramb gene silencing + palmitic acid group,and CD36 gene silencing + palmitic acid group.The cells were cultured for 24 h for follow-up experiments.Secondly,cells were pretreated with endoplasmic reticulum stress inhibitor taurursodeoxycholic acid(TUDCA)for 1 h,the final TUDCA concentration was 100 μM,and palmitic acid was added 1 h later.The cells were divided into normal control group,TUDCA group,palmitic acid group,palmitic acid +TUDCA group,and the follow-up operation was carried out after cell culture continued for 24 h.Results In obese animal models,obese mice induced by a high fat diet showed significant weight gain compared to mice fed a normal diet(P < 0.01);Increased blood glucose,serum total cholesterol(TC)and triglyceride(TG)levels(P < 0.05);CD36 enhanced immunofluorescence intensity(P < 0.01);The relative fluorescence expression of reactive oxygen species labeled by DHE probe was enhanced(P < 0.01);The expression levels of endoplasmic reticulum stress signature proteins GRP78 and CHOP were increased(P < 0.05);Increased vascular thickness(P < 0.01);The relative area of positive collagen fibers increased(P < 0.01),silence of CD36 gene can reverse the above results,indicating that high-fat diet-induced obese mice can cause excessive oxidative stress,endoplasmic reticulum stress,vascular inflammation,vascular hypertrophy and fibrosis,and eventually lead to vascular injury through up-regulation of CD36 expression.Silencing CD36 gene reduced palmitic acid-induced reactive oxygen generation in HUVEC cells(P < 0.01),decreased the level of intracellular oxidative stress;Down-regulating the expression of endoplasmic reticulum stress signature proteins GRP78 and CHOP improved endoplasmic reticulum stress(P < 0.05)and the inflammatory related proteins ICAM-1 and TNFα improved the inflammation of vascular endothelial cells(P < 0.05);Compared with the PA group,TUDCA significantly inhibited PA-induced HUVEC cell GRP78,CHOP and P-IRE1(P < 0.05)and the expression of inflammatory cytokines ICAM-1 and TNFα protein increased,suggesting that PA may promote the inflammation of vascular endothelial cells by increasing endoplasmic reticulum stress(P < 0.05).Conclusions1.Activation of CD36 signaling pathway by obesity or palmitic acid can affect the generation of reactive oxygen species and cause excessive oxidative stress and plasmic reticulum stress in vessels,leading to vascular endothelial cells and vascular inflammation and vascular injury.2.Obesity or palmitic acid activates CD36 signaling pathway by promoting endoplasmic reticulum stress of vascular endothelial cells,causing vascular endothelial cells and vascular inflammation leading to vascular damage.