酰基辅酶A胆固醇酰基转移酶1基因过表达对泡沫细胞形成的影响

目的研究在三种不同细胞中过表达酰基辅酶A胆固醇酰基转移酶1基因对泡沫细胞形成的影响。方法构建携带酰基辅酶A胆固醇酰基转移酶1全长cDNA的pCDNA3.1质粒载体并稳定转染体外培养的人THP-1单核细胞、小鼠RAW264.7单核巨噬细胞和人胚肾293上皮细胞,以油红O染色法检测在乙酰化低密度脂蛋白作用下转染前后三种细胞形成泡沫细胞的情况。结果在相同的脂质负荷条件下,转染酰基辅酶A胆固醇酰基转移酶1基因的THP-1单核细胞和RAW264.7巨噬细胞同未转染的细胞相比泡沫细胞的形成数量增加,而人胚肾293上皮细胞无论是否转染酰基辅酶A胆固醇酰基转移酶1基因均不易形成泡沫细胞。结论单核巨噬细胞中过表达酰基辅酶A胆固醇酰基转移酶1基因可促进泡沫细胞的形成。     

巨噬细胞荷脂过程中脂肪分化相关蛋白与酰基辅酶A:胆固醇酰基转移酶1及中性胆固醇酯水解酶相互结合

目的探讨脂肪分化相关蛋白是否与酰基辅酶A:胆固醇酰基转移酶1或中性胆固醇酯水解酶相互结合。方法50mg/L氧化型低密度脂蛋白孵育RAW264.7细胞0、0.5、1、3、6h,使用逆转录-聚合酶链反应及蛋白免疫印迹分析技术检测脂肪分化相关蛋白、酰基辅酶A:胆固醇酰基转移酶1和中性胆固醇酯水解酶的mRNA及蛋白的表达;应用免疫共沉淀技术检测脂肪分化相关蛋白与酰基辅酶A:胆固醇酰基转移酶1或中性胆固醇酯水解酶是否相互结合。结果随着氧化型低密度脂蛋白与RAW264.7细胞孵育时间的延长,逆转录-聚合酶链反应和蛋白免疫印迹分析显示,脂肪分化相关蛋白、酰基辅酶A:胆固醇酰基转移酶1和中性胆固醇酯水解酶的mRNA和蛋白质随着时间的延长而增多,与0h相比,差异有显著性（P<0.05,n＝3）。免疫共沉淀实验显示,RAW264.7细胞与氧化型低密度脂蛋白孵育0、0.5、1、3h时脂肪分化相关蛋白与酰基辅酶A:胆固醇酰基转移酶1结合,6h时脂肪分化相关蛋白与酰基辅酶A:胆固醇酰基转移酶1不结合;孵育0、0.5、1h时脂肪分化相关蛋白与中性胆固醇酯水解酶不结合,3、6h时与中性胆固醇酯水解酶结合。结论在荷脂的RAW264.7细胞中脂肪分化相关蛋白与中性胆固醇酯水解酶及酰基辅酶A:胆固醇酰基转移酶1相互结合。脂肪分化相关蛋白与酰基辅酶A:胆固醇酰基转移酶1和中性胆固醇酯水解酶在细胞内脂质代谢中可能协同作用。     

胆固醇诱导未折叠蛋白反应及其调节酰基辅酶A胆固醇酰基转移酶2基因的表达

目的探讨胆固醇对肝细胞和小肠粘膜上皮细胞中未折叠蛋白反应及其调节酰基辅酶A胆固醇酰基转移酶2基因表达的影响。方法以不同浓度(10mg/L和20mg/L)的游离胆固醇和氧化胆固醇温育肝癌细胞系HepG2细胞和小肠粘膜上皮细胞系Caco2细胞,应用半定量逆转录聚合酶链反应法检测两种细胞中X盒结合蛋白1和酰基辅酶A胆固醇酰基转移酶2mRNA的表达水平。结果随着游离胆固醇和氧化胆固醇温育浓度的升高,HepG2细胞和Caco2细胞中的X盒结合蛋白1和酰基辅酶A胆固醇酰基转移酶2mRNA表达均上调,呈现浓度依赖性。结论胆固醇和氧化胆固醇均可诱导未折叠蛋白反应中标记分子X盒结合蛋白1的表达,并上调酰基辅酶A胆固醇酰基转移酶2的表达,提示酰基辅酶A胆固醇酰基转移酶2的表达可能受未折叠蛋白反应的调控;鉴于酰基辅酶A胆固醇酰基转移酶2在胆固醇吸收的酯化过程中具有重要作用,未折叠蛋白反应可能在胆固醇吸收调控中具有重要意义。     

脂肪分化相关蛋白促进RAW 264.7细胞内酰基辅酶A:胆固醇酰基转移酶1高表达

目的 观察高表达脂肪分化相关蛋白细胞内酰基辅酶A∶胆固醇酰基转移酶1表达的变化,阐明脂肪分化相关蛋白促进细胞内脂质蓄积的机制.方法 构建的pQCXIP-HA-Adi逆转录病毒载体转染PA317包装细胞,获得pQCXIP-HA-Adi逆转录病毒.用病毒感染RAW 264.7细胞, Puromycin筛选后获得稳定高表达脂肪分化相关蛋白的RAW264.7细胞株.应用逆转录聚合酶链反应和免疫印迹法检测经感染后细胞内脂肪分化相关蛋白和酰基辅酶A∶胆固醇酰基转移酶1的表达.并应用阿托伐他汀处理高表达脂肪分化相关蛋白的RAW 264.7细胞,观察酰基辅酶A∶胆固醇酰基转移酶1表达的改变.结果 用pQCXIP-HA-Adi逆转录病毒感染RAW 264.7细胞后,脂肪分化相关蛋白和酰基辅酶A∶胆固醇酰基转移酶1 mRNA和蛋白表达明显升高,而对照组表达无明显变化.加入阿托伐他汀后,即在去除底物对酰基辅酶A∶胆固醇酰基转移酶1表达影响的情况下,高表达脂肪分化相关蛋白细胞内酰基辅酶A∶胆固醇酰基转移酶1表达仍升高.结论 高表达脂肪分化相关蛋白可明显上调RAW 264.7细胞酰基辅酶A∶胆固醇酰基转移酶1的表达.     

脂肪分化相关蛋白通过酰基辅酶A∶胆固醇酰基转移酶1促进巨噬细胞脂质蓄积

目的观察高表达脂肪分化相关蛋白对酰基辅酶A∶胆固醇酰基转移酶1表达及脂质蓄积的影响。方法构建表达载体pcDNA3.1-HA-脂肪分化相关蛋白,使用THP-1巨噬细胞,通过瞬时转染使之高表达脂肪分化相关蛋白,依次用氧化型低密度脂蛋白和(或)丙泮尼地处理。逆转录聚合酶链反应和Western blot检测酰基辅酶A∶胆固醇酰基转移酶1及脂肪分化相关蛋白的表达,油红O染色和高效液相色谱检测细胞内脂质的蓄积。结果随着氧化型低密度脂蛋白浓度的增加,巨噬细胞脂肪分化相关蛋白及酰基辅酶A∶胆固醇酰基转移酶1表达明显增强,两者呈伴行关系。丙泮尼地能抑制酰基辅酶A∶胆固醇酰基转移酶1表达上调,且随处理时间延长,其表达逐渐减少,并且能减少细胞内脂滴生成。与对照组相比,瞬时转染pcDNA3.1-HA-脂肪分化相关蛋白能使脂肪分化相关蛋白表达明显升高。高表达脂肪分化相关蛋白的巨噬细胞能使酰基辅酶A∶胆固醇酰基转移酶1表达增加,促进细胞内胆固醇酯蓄积,并协同增强氧化型低密度脂蛋白的作用。加入丙泮尼地后,高表达脂肪分化相关蛋白的作用被减弱。结论高表达脂肪分化相关蛋白能上调THP-1巨噬细胞酰基辅酶A∶胆固醇酰基转移酶1表达,促进细胞内脂质蓄积。脂肪分化相关蛋白可能通过酰基辅酶A∶胆固醇酰基转移酶1促进细胞内胆固醇酯的蓄积。     

内脂素通过过氧化体增殖物激活型受体γ信号转导通路上调酰基辅酶A∶胆固醇酰基转移酶1的表达

目的观察过氧化体增殖物激活型受体γ信号转导通路在内脂素调控人THP-1单核细胞源性巨噬细胞酰基辅酶A∶胆固醇酰基转移酶1表达中的作用,探讨内脂素诱导泡沫细胞形成的机制和途径。方法 THP-1单核细胞诱导分化为巨噬细胞,随机分组,给予不同浓度的内脂素和过氧化体增殖物激活型受体γ激动剂罗格列酮进行干预,分别运用油红O染色法观察细胞内脂滴形成情况,逆转录聚合酶链反应法和免疫印迹法检测细胞过氧化体增殖物激活型受体γ和酰基辅酶A∶胆固醇酰基转移酶1mRNA和蛋白的表达,酶荧光学法检测细胞内总胆固醇和游离胆固醇含量,总胆固醇与游离胆固醇之差为胆固醇酯含量。结果与对照组比较,内脂素组细胞内脂滴形成增加,过氧化体增殖物激活型受体γmRNA和蛋白表达水平降低(P0.05),酰基辅酶A∶胆固醇酰基转移酶1mRNA和蛋白表达水平升高(P0.05),细胞内胆固醇酯含量升高(P0.05);随着内脂素浓度(10-7mol/L、10-6mol/L和10-5mol/L)升高,过氧化体增殖物激活型受体γmRNA和蛋白表达水平逐渐降低(r值分别为-0.73和-0.83,P0.05),酰基辅酶A∶胆固醇酰基转移酶1mRNA和蛋白表达水平逐渐升高(r值分别为0.91和0.72,P0.05)。与内脂素组比较,罗格列酮组酰基辅酶A∶胆固醇酰基转移酶1mRNA和蛋白表达水平降低(P0.05),细胞内胆固醇酯含量降低(P0.05);随着罗格列酮浓度(10μmol/L、15μmol/L和20μmol/L)升高,酰基辅酶A∶胆固醇酰基转移酶1mRNA和蛋白表达水平逐渐降低(r值分别为-0.69和-0.84,P0.05)。结论内脂素呈浓度依赖性下调THP-1单核细胞源性巨噬细胞过氧化体增殖物激活型受体γ的表达,上调酰基辅酶A∶胆固醇酰基转移酶1的表达,而罗格列酮呈浓度依赖性抑制内脂素所诱导的上述效应。提示内脂素可能通过过氧化体增殖物激活型受体γ信号转导通路上调酰基辅酶A∶胆固醇酰基转移酶1表达,使细胞内胆固醇酯合成增加,从而诱导泡沫细胞形成。     

胰岛素对单核/巨噬源性泡沫细胞ACAT-1表达的影响

研究胰岛素对单核/巨噬细胞转分化和泡沫细胞形成过程中酰基辅酶A:胆固醇酰基转移酶-1(ACAT-1)表达的影响,发现胰岛素对ACAT-1酶的活性、蛋白、mRNA表达均有增强作用。     

葡萄糖对THP-1源性巨噬细胞酰基辅酶A:胆固醇酰基转移酶1表达的影响

研究葡萄糖对人THP-1单核分化巨噬细胞酰基辅酶A：胆固醇酰基转移酶1（ACAT-1）表达的影响。发现高糖作用下，巨噬细胞ACAT-1的mRNA及蛋白表达增加，这可能是糖尿病血管病变机制之一。     

溶血磷脂酸代谢途径及在炎症中的作用

溶血磷脂酸在溶血磷脂酸:酰基辅酶A酰基转移酶作用下生成磷脂酸是新近发现的磷脂代谢途径,作为细胞内第二信使系统发挥作用。现已证明溶血磷脂酸:酰基辅酶A酰基转移酶抑制剂能明显减轻内毒素休克,缺血、缺氧的病变程度,提示此途径在炎症反应中起重要作用。     

人ACAT1基因P1启动子的克隆及意义

目的克隆人酰基辅酶A:胆固醇酰基转移酶1(ACAT 1)基因P 1启动子。方法应用PCR方法从人单核细胞系THP-1扩增分离出ACAT 1基因P 1启动子全长片段,将PCR产物克隆入T载体,并对所获得的序列进行生物信息学分析。结果经琼脂糖凝胶电泳及直接测序鉴定,克隆的ACAT 1基因P 1启动子片段碱基序列与G enB ank数据库一致,未发现突变。结论人ACAT 1基因P 1启动子克隆成功,此为动脉粥样硬化(A S)过程中ACAT 1基因转录调控机制的研究奠定了基础。     

The role of neutral cholesterol ester hydrolysis in macrophage foam cells

Cholesterol ester-laden macrophage foam cells are a hallmark of atherosclerosis. The cycle of esterification and hydrolysis of cholesterol esters is one of the key steps in macrophage cholesterol trafficking. In the process of foam cell formation, excess free cholesterol undergoes esterification by acyl coenzyme A: acylcholesterol transferase 1 (ACAT-1), and fatty acid sterol esters are stored in cytoplasmic lipid droplets. The actions of ACAT-1 are opposed by neutral cholesterol ester hydrolase (nCEH), which generates free cholesterol and fatty acids. The resulting free cholesterol is a preferential source for cholesterol efflux into the extracellular space. Despite the important role of nCEH in protection against foam cell formation and atherosclerosis, the molecular identity of nCEH has long been debated. Although hormone-sensitive lipase (LIPE) has been proposed to be the nCEH in macrophages, recent evidence suggested the existence of other nCEH(s). We have recently identified a novel nCEH, neutral cholesterol ester hydrolase 1 (NCEH1), and demonstrated that NCEH1, in addition to LIPE, primarily mediates the hydrolysis of CE in macrophages. This review focuses on the protective roles of nCEHs in atherosclerosis, with special emphasis on the role of NCEH1.     

A selective ACAT-1 inhibitor, K-604, suppresses fatty streak lesions in fat-fed hamsters without affecting plasma cholesterol levels

BACKGROUND: Acyl-coenzyme A:cholesterol O-acyltransferase-1 (ACAT-1), a major ACAT isozyme in macrophages, plays an essential role in foam cell formation in atherosclerotic lesions. However, whether pharmacological inhibition of macrophage ACAT-1 causes exacerbation or suppression of atherosclerosis is controversial. METHODS AND RESULTS: We developed and characterized a novel ACAT inhibitor, K-604. The IC(50) values of K-604 for human ACAT-1 and ACAT-2 were 0.45 and 102.85 micromol/L, respectively, indicating that K-604 is 229-fold more selective for ACAT-1. Kinetic analysis indicated that the inhibition was competitive with respect to oleoyl-coenzyme A with a K(i) value of 0.378 micromol/L. Exposure of human monocyte-derived macrophages to K-604 inhibited cholesterol esterification with IC(50) of 68.0 nmol/L. Furthermore, cholesterol efflux from THP-1 macrophages to HDL(3) or apolipoprotein A-I was enhanced by K-604. Interestingly, administration of K-604 to F1B hamsters on a high-fat diet at a dose of >or=1mg/kg suppressed fatty streak lesions without affecting plasma cholesterol levels. CONCLUSIONS: K-604, a potent and selective inhibitor of ACAT-1, suppressed the development of atherosclerosis in an animal model without affecting plasma cholesterol levels, providing direct evidence that pharmacological inhibition of ACAT-1 in the arterial walls leads to suppression of atherosclerosis.     

Macrophages, inflammation, and atherosclerosis

The macrophage plays a diverse array of roles in atherogenesis and lipoprotein metabolism. The macrophage functions as a scavenger cell, an immune mediator cell, and as a source of chemotactic molecules and cytokines. Chemokines have been implicated in promoting migration of monocytes into the arterial intima. Monocyte chemoattractant protein-1 (MCP-1) attracts monocytes bearing the chemokine receptor CCR-2. Macrophage expression of cyclooxygenase-2, a key enzyme in inflammation, promotes atherosclerotic lesion formation in low-density lipoprotein receptor (LDLR)-deficient mice. In the arterial intima, monocytes differentiate into macrophages, which accumulate cholesterol esters to form lipid-laden foam cells. Foam cell formation can be viewed as an imbalance in cholesterol homeostasis. The uptake of atherogenic lipoproteins is mediated by scavenger receptors, including SR-A and CD36. In the macrophage, ACAT-1 is responsible for esterifying free cholesterol with fatty acids to form cholesterol esters. Surprisingly, deficiency of macrophage ACAT-1 promotes atherosclerosis in LDLR-deficient mice. A number of proteins have been implicated in the process of promoting the efflux of free cholesterol from the macrophage, including apoE, ABCA1, and SRB-1. Macrophage-derived foam cells express the adipocyte fatty acid-binding protein (FABP), aP2, a cytoplasmic FABP that plays an important role in regulating systemic insulin resistance in the setting of obesity. ApoE-deficient mice null for macrophage aP2 expression develop significantly less atherosclerosis than controls wild type for macrophage aP2 expression. These results demonstrate a significant role for macrophage aP2 in the formation of atherosclerotic lesions independent of its role in systemic glucose and lipid metabolism. Furthermore, macrophages deficient in aP2 display alterations in inflammatory cytokine production. Through its distinct actions in adipocytes and macrophages, aP2 links features of the metabolic syndrome including insulin resistance, obesity, inflammation, and atherosclerosis.     

脑肠肽Ghrelin通过生长激素促分泌素受体下调人源单核细胞株THP-1源性泡沫细胞酰基辅酶A:胆固醇酰基转移酶1表达的实验研究

目的 探讨脑肠肽Ghrelin对人源单核细胞株THP-1源性泡沫细胞酰基辅酶A:胆固醇酰基转移酶1(ACAT-1)表达的调控作用及其调控途径.方法 体外培养人源单核细胞株THP-1,由佛波酯(PMA)作用使其分化为巨噬细胞,继而在氧化低密度脂蛋白(ox-LDL)存在条件下进一步转变为泡沫细胞,油红O染色法鉴定泡沫细胞形成.运用PT-PCR法和Western blot法分别检测Ghrelin干预后及拮抗生长激素促分泌素受体(GHS-R)后ACAT-1 mRNA水平与ACAT-1蛋白表达,采用酶法,通过荧光分光光度计检测细胞内胆固醇含量并计算胆固醇酯含量.结果 Ghrelin可明显减少细胞内胆固醇酯的含量,并能显著降低单核/巨噬细胞泡沫化过程中ACAT-1 mRNA水平和蛋白表达(P均<0.01).拈抗GHS-R后,Ghrelin抑制泡沫细胞形成的效应被阻断,且GHS-R特异性拮抗剂浓度越高,该阻断作用越明显.浓度为10~(-5)、5×10~(-5)、10~(-4)mol/L的GHS-R特异性拈抗剂组ACAT-1mRNA水平与蛋白表达分别为1.14±0.04、1.58±0.03、2.40±0.16和1.25±0.09、1.77±0.11、2.30±0.09,明显高于Ghrelin组0.89±0.05和0.86±0.08(P均<0.05).结论 Ghrelin可能通过ACAT-1转录翻译水平的下调抑制泡沫细胞的形成,从而延缓动脉粥样硬化的发生,且该效应通过GHS-R途径发挥作用.     

乙酰化低密度脂蛋白促进胆固醇酰基转移酶活性升高的机制研究

目的 :研究乙酰化低密度脂蛋白 (Ac LDL)对人THP 1单核细胞 (MC)分化的巨噬细胞 (MP)酰基辅酶A、胆固醇酰基转移酶 1(ACAT 1)活性的影响及其机制。方法 :体外培养人THP 1单核细胞系 ,由佛波酯 (PMA)作用使其分化为MP ,后者再由乙酰化低密度脂蛋白Ac LDL进行脂质负荷转变为泡沫细胞。该过程中以放射性同位素标记底物法检测ACAT 1酶活性的变化 ,并用Westernblot法检测ACAT 1酶蛋白的表达及RT PCR法检测A CAT 1mRNA的水平。结果 :在MC分化为MP的过程中ACAT 1酶活性升高了 2倍 ,差异有统计学意义 (P <0 .0 5 ) ,酶蛋白及mRNA水平呈现类似变化趋势 ;Ac LDL作用于巨噬细胞 ,使ACAT1酶活性、酶蛋白及mRNA进一步升高 ,差异有统计学意义 (P <0 .0 5 )。结论 :MC分化为MP的过程中ACAT 1表达上调 ,使ACAT 1活性增强 ,而Ac LDL可进一步促进ACAT 1基因表达增加 ,升高ACAT 1活性。     

Is there a genetic basis for resistance to atherosclerosis?

Atherosclerosis and its major clinical manifestation, coronary heart disease, is and will remain the main cause of mortality. Reviews on this subject dealt with factors that enhance development of atherosclerosis. This review deals with a new facet, that some individuals are less prone to develop atherosclerosis: (1) despite high cholesterol intake or (2) despite hypercholesterolemia with elevated low-density lipoprotein cholesterol (LDL-C) levels. The variability of response of plasma cholesterol to dietary intake was shown to be regulated by liver x receptor (LXR) that determines the rate of intestinal cholesterol absorption through the ATP-binding cassette (ABC) gene family. Other gene products, such as apolipoprotein-E (apo-E), scavenger receptor-B1 (SR-B1) and acyl coenzyme: cholesterol acyltransferase-2 (ACAT-2) affect cholesterol absorption also. The role of a genetic background for relative resistance to atherosclerosis is highlighted by subjects with familial hypercholesterolemia in whom high plasma cholesterol levels has not curtailed their expected life span. Studies in animals have shown that resistance to atherosclerosis in spite of hypercholesterolemia is affected by factors such as high-density lipoprotein (HDL) phospholipids that enhance reverse cholesterol transport, non-responsiveness to induction or lack of monocyte chemotactic protein-1 (MCP-1), C-C chemokine receptor 2 (CCR2), macrophage colony stimulating factor (MCSF), or vascular cell adhesion molecule-1 (VCAM-1). Since macrophages have been regarded as pro- or anti-atherogenic, evidence was collated that the high activity of scavenger receptors may contribute towards resistance to atherosclerosis if accompanied by adequate amounts of apo-E for cholesterol removal.     

Effects of a new single-nucleotide polymorphism in the Acyl-CoA:cholesterol acyltransferase-2 gene on plasma lipids and apolipoproteins in patients with hyperlipidemia

Acyl-CoA:cholesterol acyltransferase (ACAT) catalyzes cholesterol esterification in mammalian cells. Two isoforms of ACAT have been reported to date (ACAT-1 and ACAT-2). ACAT-1 protein is ubiquitously expressed in tissues, including macrophages, hepatocytes, adrenal glands, and intestines. In contrast, ACAT-2 is expressed mainly in the intestine in humans. However, the roles of ACAT-1 and ACAT-2 in lipoprotein metabolism in humans have not yet been reported. This study was carried out to clarify the relationship between ACAT-2 gene mutations and hyperlipidemia in humans. To identify gene mutations, we screened 30 subjects with hyperlipidemia (TC > 220 mg/dl or TG >150 mg/dl) by direct sequencing. As a result, we found a new single-nucleotide polymorphism (SNP; a point mutation in intron 1, IVS1 -8 G-->C) in the ACAT-2 gene. To investigate the relationship between this SNP and both plasma lipids and apolipoproteins, 91 unrelated hyperlipidemic subjects (40 males and 51 females), and 92 unrelated normolipidemic subjects (46 males and 46 females) were screened by direct sequencing. The frequencies of the IVS1 - 8G-->C allele in normolipidemic and hyperlipidemic subjects were 0.131 and 0.125, respectively. IVS1 -8 G-->C did not affect plasma concentrations of lipids or apolipoproteins in either normolipidemic or hyperlipidemic subjects. Although further studies are needed, our data suggest that the ACAT-2 gene may not affect lipid levels in humans.