Study On Mechanisms Of PCBs Accelerating Atherosclerosis By Upregulating CD36 And Promoting Macrophage-Derived Foam Cells Formation

Polychlorinated biphenyls(PCBs)are persistent organic environmental pollutants.According to previous epidemiological reports,it is generally believed that PCBs exposure is highly related to atherosclerosis,but the underlying mechanism is unclear and corresponding mechanism studies are lacking.Although PCBs are easily metabolized,little information is available on the effects of their metabolites on atherosclerosis.In this study,we investigated a quinoid PCB metabolite,2,3,5-trichloro-6-phenyl-[1,4]-benzoquinone(PCB29-pQ),which promotes atherosclerosis Like hardening plays an important role.Atherosclerosis(atherosclerosis,AS)is a systemic disease related to lipid metabolism.Cardio-cerebrovascular diseases caused by it seriously endanger human health.In some European and American countries,it has become the number one killer of human health.Its main pathological feature is that the lipids in the blood enter the wall of the arterial artery and deposit in the intima of the blood vessel to form atheromatous plaque,which causes the artery to thicken and harden,and finally causes the plaque to rupture.Therefore,it is very important to study the specific mechanism of the occurrence and development of AS.In this study,we investigated the specific mechanism of the PCB metabolite,PCB29-pQ,which accelerates the formation of atherosclerosis by promoting macrophage foaming and up-regulating CD36-induced endoplasmic reticulum stress response.Part I:This part aims to investigate the formation of foaming of macrophages by PCB29-pQ.Polychlorinated biphenyls(PCB s)are organic environmental pollutants that are accused of various toxic effects.PCBs exposure are widely believed to be associated with atherosclerosis,but the underlying mechanisms are unclear.Although PCBs are easily metabolized,there is a rarely information on the effects of their metabolites on atherosclerosis.Currently,we evaluated the effect of 2,3,5-trichloro-6-phenyl-[1,4]-benzoquinone(PCB29-pQ)on the critical phase of atherosclerosis development,that is,the formation of macrophage-derived foam cells.We exposed Ox-LDL-induced RAW264.7 cells with 2.5μM and 5μM PCB29-pQ.Variety of evidences have demonstrated that PCB29-pQ promotes foam cells formation,develops pro-inflammatory cascade and cell necroptosis.In detail,we observed that PCB29-pQ increased levels of total cholesterol(TC),free cholesterol(FC),triglyceride(TG)and cholesteryl ester(CE)by increasing cholesterol influx and reducing cholesterol efflux.Moreover,we found that PCB29-pQ induces inflammatory cytokines,such as tumor necrosis factor(TNF-α),interleukin 6(IL-6)and IL-1β,release by activating the mitogen-activated protein kinase(MAPK)-nuclear factor kappa B(NF-κB)inflammatory pathway.In addition,we demonstrated that PCB29-pQ induces cell necroptosis via the receptor interacting protein kinase 1 and 3(RIPK1/3)and mixed lineage kinase domain-like(MLKL)pathway.Finally,the overproduction of reactive oxygen species(ROS)by PCB29-pQ play significant roles in these processes,which can be reversed with antioxidant.Overall,our results indicated that PCB29-pQ promotes macrophage formation of foam cells,inflammation,and cell necroptosis.Part II:This part discusses the effect of PCB29-pQ on the formation of atherosclerosis by promoting the expression of CD36 and participating in the endoplasmic reticulum stress response.Studies have shown that PCB29-pQ induces the activation of three branches of the endoplasmic reticulum(ER)stress response,namely phosphorylated protein kinase R-like ER kinase(p-PERK),eukaryotic translation initiation factor 2a(eIF2α)and transcription Factor 6(ATF6).It is worth noting that Caspase 12 activation means that endoplasmic reticulum stress promotes apoptosis,and macrophage apoptosis is also an important sign of the progression of atherosclerotic plaques.In the later stages of injury,apoptosis of macrophages can increase the formation of necrotic core,which in turn leads to plaque rupture.In the early stage of atherosclerosis,macrophages engulf a large amount of oxidatively modified low-density lipoprotein(Ox-LDL),which in turn promotes macrophages to foam cells.With the inactivation of acyl-CoA cholesterol acyltransferase(ACAT)and the imbalance of cholesterol outflow pathways,a large amount of free cholesterol has accumulated in the endoplasmic reticulum to activate the endoplasmic reticulum stress response.In the process of forming foam cells,CD36,as a key molecule in this process,we linked the lipid accumulation caused by CD36 to intranet stress,and we found that we found that the silence of CD36 can reverse the RAW264.7 cells caused by PCB29-pQ Medium lipid accumulation,endoplasmic reticulum stress response,promote apoptosis and necrosis and release of inflammatory factors.Overall,our results indicate that PCB29-pQ achieves lipid accumulation through CD36,induces endoplasmic reticulum stress response,and thereby promotes necroptosis and proinflammatory cytokine release.Part III:This part aims to study the effect of PCB29-pQ on atherosclerosis at animal level.Aortic plaques were increased in PCB29-pQ-treated ApoE-/-mice[5 mg/kg body weight,intraperitoneally(i.p.)injection once a week for twelve continuously weeks,high-fat feeding].We observed lipids accumulation and the release of pro-inflammatory factors,interleukin-1 beta(IL-1β),tumor necrosis factor alpha(TNF-α)and interleukin-6(IL-6)in ApoE-/-mice.Therefore,the exposure of PCB29-pQ promoted the formation of atherosclerosis in ApoE-/-mice.