Research About The Mechanism Of The Role Of Activating Perivascular Brown Adipocyte In Protecting The Vasculature

Background:Cardiovascular and cerebrovascular diseases based on atherosclerosis are the leading cause of morbidity and mortality around the world.Endothelial dysfunction is hypothesized to be the critical initiating step in the development of atherogenesis.If not quelled,circulating inflammatory cells will finally migrate into the vessel wall and lipid will deposit beneath the endothelium.The direction of development of atherosclerosis is from inside to outside.While the endothelium remains the major cause of the development of atherosclerotic lesion,there is increasing evidence of important roles played by the adventitia.The direction of atherogenesis could be opposite,that is from outside to inside and initiated by adventitia inflammation.Most arteries throughout the body are directly enveloped by adipose tissue which is called perivascular adipose tissue(PVAT).Historically,it has long been accepted that adipose tissue offers mechanical protection of the vessels and maintains temperatures.Now,adipose tissue is widely accepted to be an active endocrine organ that produces a variety of cytokines that influence physiological function.Like other adipose tissues,PVAT acts as an endocrine organ,secreting a wide range of bioactive molecules with possible autocrine or paracrine effects that regulate vascular tone.Traditionally,adipose tissue was classified into two types: white adipose tissue(WAT)and brown adipose tissue(BAT).One area of relative promise centers on targeting brown adipose tissue(BAT)to increase energy expenditure.BAT is a thermogenic organ,metabolizing both fatty acids and glucose to produce heat to maintain homeothermy.Thus,developing BAT may provide an attractive new target for treatment of hyperglycemia,dyslipidemia and obesity.Recently,a better understanding of BAT development and function has made the BAT a potential treatment target to improve the patients affected by certain disorders.Objective : In this study,we aimed to explore the role of activation of BAT in atherosclerosis plaque,contractile regulation and the related mechanism via ?3-adrenergic receptor agonist(CL-316243)or transgenic expression of PRDM16.We prompt differentiation of adipogenic precursor cells(3T3-L1)into brown adipocyte via ectopic expression of PRDM16 and then investigate its mechanical role in mediating the functions of endothelia and macrophages.Finally,we aim to study the functional role of PGC-1? in the regulation of eNOS dysfunction and the underlying mechanisms.Methods:C57BL/6J mice were randomly divided into 3 groups: normal diet(ND),high-fat diet(HFD)and HFD+CL-316243.Apo E-/-mice were randomly divided into 3 groups and injected with normal saline,pAdenoG empty vector and PRDM16-pAdenoG vector.Weights were recorded every week.Total plasma levels of lipid and glucose were tested using commercial agents.HE staining on the abdominal aorta atherosclerosis plaque and adipose surrounding artery of rats was performed.Vascular reactivity of abdominal aorta rings was assessed with wire myography.The mRNA levels of Leptin,Adiponectin,MCP-1,IL-8,TNF-?,IL-6 and IL-10 in adipose rounding abdominal aorta were determined by RT-PCR.Adipocytes 3T3-L1 was transfected with PRDM16-pAdenoG vector and the differentiation was studied.PRDM16-induced brown adipose cells were co-cultured with endothelia and macrophages.The level of NO,eNOS,ET-1 of endothelia and the mRNA levels of LOX-1 and CD36 on the surface of macrophages were determined.The M1 and M2 macrophages were also identified.After overexpression of PGC-1? with adenovirus in human aortic endothelial cells with or without Angiotensin?(Ang?),NO generation,mRNA and protein expression of eNOS,PI3 K and Akt were determined by cellular,molecular and biochemical approach.Results: HFD mice gained more weight and higher levels of blood pressure,blood lipid and glucose.Fat accumulation in PVAT was obvious in HFD group.In contrast to ND group,the levels of leptin and several inflammatory factors were elevated in HFD group and the level of adiponectin was downregulated.The administration of ?3 adrenergic agonist CL-316243 in abdominal PVAT had no effects on weight,levels of plasm lipid and glucose,inflammatory state and endocrine function of PVAT.CL-316243 prompted activation of BAT in PVAT and elevated the levels of UCP-1 and mitochondria in PVAT.More atherosclerosis plaques were observed in empty virus vector(EV)and control group in contrast to PRDM16 group.White adipocyte occupied the main status of PVAT in EV and control group,while in PRDM16 group,brown adipocyte was found the most.PE/KCl-mediated vasoconstriction was significantly attenuated and ACh mediated vasorelaxation was increased in abdominal aorta vessel ring enveloped by PVAT transfected with PRDM16.mRNA levels of Leptin,Adiponectin and IL-8 in PRDM16 group increased markedly,while the values of MCP-1,TNF-?,IL-6 and IL-10 decreased significantly.PRDM16-induced brown adipocytes downregulated the expression of LOX-1 and CD36 on the surface of macrophages.The expressions of MCP-1,IL-6 and TNF-? in macrophages decreased,while the values of IL-10 increased.PGC-1? expression paralleled with the decrease in NO generation in human aortic endothelial cells after incubated with Ang?.The Ang?-induced decrease of NO generation was restored by overexpression of PGC-1?,as evidenced by elevated level of cGMP concentration and total nitrite production.PGC-1? inhibited Ang?-induced eNOS dephosphorylation,as well as in(phosphoinositide-3 kinase)PI3K and AKT dephosphorylation.Conclusion:High-fat diet causes perivascular adipose tissue dysfunctional in mice and dysfunctional PVAT is responsible for the enhanced arterial contractile response and atherosclerosis formation.Transfection of PRDM16 into PVAT can induce the formation of BAT,reduce the vasoconstriction and inhibit the occurrence of atherosclerosis plaque in abdominal aorta.Ectopic expression of PRDM16 in 3T3-L1 induced the differentiation into BAT cells.PRDM16-induced brown adipocyte suppressed the inflammation state of macrophage.PGC-1? overexpression in endothelia attenuates AngII-induced eNOS dysfunction through PI3K/Akt-dependent phosphorylation of eNOS.