The Effects And Mechanisms Of PPAR? On Regulating Vascular Smooth Muscle–derived Foam Cells Formation

Background and Objectives:Atherosclerosis(AS)is the major cause of myocardial infarction and cerebral infarction.The formation and accumulation of fat-laden foam cells is the critical process in AS.Vascular smooth muscle cells(VSMCs)derived foam cells play an important role in AS,but the specific mechanism is still unclear.Normally,Lipid especially the oxidative modification of LDL deposition in the subendothelium of arterial walls,stimulates VSMCs to secrete a variety of extracellular matrix,undergo phenotype transformation,promote lipoprotein retention,modify and increase lipoprotein receptor and reduce cholesterol efflux,which increase the formation of foam cells and ultimately lead to cardiovascular and cerebrovascular diseases.Therefore,exploring the specific mechanisms of VSMC-derived foam cells formation has important signification for the prevention and treatment of AS.The peroxisome proliferator-activated receptor ?(PPAR?)is the ligand-activated transcription factor belonging to the nuclear receptor superfamily.Recently more and more attention has been focused on the role of PPAR? in the development of AS.PPAR? is widely expressed in all body tissues.PPAR? targets the promotor of downstream molecule,control gene transcription,and then regulates cell metabolism,inflammation and proliferation.A pervious study found that PPAR? could inhibit macrophage(Mo)foaming.Moreover PPAR? has an important regulatory role in multiple physiological and pathological process of VSMCs.But the mechanisms of the PPAR? for VSMCs-derived foam cell formation remain unclear.Therefore,the present study focuses on identifying the role of PPAR? during VSMCs foam cell formation.Acyl-coenzyme A: cholesterol acyltransferase 1(ACAT1)is a multi-transmembrane membrane protein,which catalyses the esterification of free cholesterol.ACAT1 play an important role in the maintenance of intracellular cholesterol homeostasis,becoming a targets for new pharmacological interventions in AS.Numerous studies show that inhibition of ACAT1 can play a positive role in anti-AS.We speculate activated PPAR? affect the formation of VSMC-derived foam cells by down-regulating the expression of ACAT1.This study is divided into two parts: 1.Observe the effects of PPAR? on VSMC-derived foam cell formation.2.Investigate the underlying mechanisms of PPAR? on VSMC-derived foam cell formation.Materials and Methods:1.Cultivation of primary VSMCs from C57BL/6J using tissue attached methods and identified by immunofluorescence.2.The protein expressions of PPAR? and ACAT1 were detected by Western Blot and immunofluorescence.3.Intracellular lipid deposition was detected by Oil Red O staining and integrated optical density of Oil Red O.Results:1.We cultured and identified the primary VSMCs from male C57BL/6J.2.In vitro,we confirmed that the protein expression level of PPAR? were reduced in a time-dependent manner during oxidized low-density lipoprotein(oxLDL)-induced VSMCs foam cell formation with a peak effect at 48 h and maintained at a low level3.PPAR? agonist GW0742 and antagonist GSK0660 are used to regulate the process of VSMCs foam cell formation.We found that activation of PPAR? correlated with reduction of the amount of lipid accumulation in VSMCs and inhibition of PPAR? correlated with increase of the amount of lipid accumulation.The differences were both statistically significant(P<0.05).4.We confirmed that the protein expression level of ACAT1 were increased during oxLDL-induced VSMCs foam cell formation.5.In addition,we also found that treatment of GW0742 decreased ACAT1 protein expression,while GSK0660 elevated ACAT1 protein expression.The difference was statistically significant(P<0.05).Conclusions:Activation of PPAR? suppresses VSMCs foam cell formation by down-regulating the expression of ACAT1.