ABCA1基因调控与动脉粥样硬化的关系

ATP结合盒转运体A1(ABCA1)足一种整合膜蛋白,它以ATP为能源,转运细胞内的游离胆固醇、磷脂至细胞外并与载脂蛋白A1结合,形成高密度脂蛋白.ABCA1基因是胆固醇逆转运和高密度脂蛋白(HDL)生成起始步骤的关键基因.ABCA1的表达在转录和转录后水平受肝X受体/视黄醇X受体(LXR/RXR)等多种因子调控.ABCA1功能障碍将导致动脉粥样硬化的发生、发展,与心脑血管疾病密切相关.     

ABCA1与早发冠状动脉粥样硬化性心脏病

ATP结合盒转运蛋白A1（ATP binding cassette transport protein A1，ABCA1）是一种膜转运蛋白，广泛分布于体内各种组织内。ABCAl参与胆固醇的逆转运（reverse cholesterol transport，RCT），可减少动脉粥样硬化处巨噬细胞内胆固醇及泡沫细胞的生成，减缓动脉硬化发生发展。在与冠心病相关的ABCA1基因突变位点中，部分位点的突变能够使冠心病（CHD）发病年龄前移。现就ABCA1与早发CHD的研究进展做一综述。     

Preβ-1高密度脂蛋白与心血管疾病关系的研究进展

动脉粥样硬化是心血管疾病重要的病理生理基础,延缓和防治动脉粥样硬化对于减少和降低心血管疾病的发病率及死亡率具有重要意义。HDL(high density lipoprotein,HDL)通过参与介导胆固醇逆向转运(reverse cholesterol transport,RCT）在抗动脉粥样硬化的形成和进展中发挥了重要作用。Preβ-1高密度脂蛋白（Prebeta-1 high density lipoprotein,preβ1-HDL）作为HDL的一种亚类,是外周细胞移出胆固醇的最初接受体,直接参与了胆固醇逆向转运的起始步骤,并在随后胆固醇酯化及转运中起着重要作用。本文就preβ1-HDL的结构、代谢及其与心血管病的关系作一简要综述。     

膜转运蛋白ABCA1的表达调控、信号传导与脂质运输功能

ABCA1是一种介导细胞内过量胆固醇外流到载脂蛋白并将其包装成高密度脂蛋白(HDL)的膜转运蛋白,是调节血浆HDL及细胞内胆固醇水平的重要受体；然而,其具体的作用机制尚未明了。近期研究逐步揭示,ABCA1有可能通过特殊的信号传导通路诱发胆同醇外流；其信号传导作用还体现在抗凋亡、影响细胞骨架蛋白的相互作用等其它方面,本文对ABCA1的脂质调节、表达调控和信号传导等方面的最新研究进行了综述。     

脂联素对泡沫细胞三磷酸腺苷结合盒转运体A1表达及细胞内胆固醇含量的影响

目的通过研究脂联素对细胞内胆固醇外流的影响以及三磷酸腺苷结合盒转运子A1的功能变化,探讨其抗动脉粥样硬化作用的可能机制。方法以THP-1来源的泡沫细胞模型为研究对象,用脂联素进行体外干预;采用逆转录聚合酶链反应、酶联免疫吸附试验和高效液相色谱等方法测定干预前后三磷酸腺苷结合盒转运子A1表达和细胞内胆固醇含量的变化。结果脂联素在体外上调泡沫细胞三磷酸腺苷结合盒转运子A1mRNA和蛋白的表达,与载脂蛋白A1联合作用还能进一步增加细胞内胆固醇的流出。脂联素单独作用促进细胞内胆固醇酯转化为游离胆固醇。结论脂联素上调泡沫细胞三磷酸腺苷结合盒转运子A1表达,并促进其介导的细胞内游离胆固醇的外流;脂联素还能促进细胞内胆固醇酯的水解。     

ATP结合盒转运子调节细胞内胆固醇流出及对动脉粥样硬化的影响

ATP结合盒转运子是细胞内胆固醇流出至贫脂或无脂的高密度脂蛋白前体载脂蛋白AⅠ的调节子，在高密度脂蛋白合成和胆固醇逆转运过程中起重要作用。ATP结合盒转运子基因表达受核受体的高度调节。通过对ATP结合盒转运子调节，增加高密度脂蛋白浓度和胆固醇的逆转运，为预防和治疗动脉粥样硬化提供新思路和新方法。     

高密度脂蛋白及其亚类与冠心病

血清高密度脂蛋白（HDL）是迄今唯一具有抗动脉粥样硬化（AS）作用的心脏保护性因子,HDL的水平与冠心病的发病率呈明显的负相关。HDL通过多种机制发挥其抗AS的作用,其中最为重要的是参与胆固醇的逆向转运,将胆固醇从外周血管壁等组织细胞中转运至肝脏并被清除,从而发挥其调节血胆固醇的水平、阻止巨噬细胞转化为泡沫细胞,以及防止胆固醇在血管壁中沉积的作用。本文主要综述了HDL及其亚类与冠心病的关系及以其为冠心病治疗靶点的相关进展。     

ABCA1基因转录调节与胆固醇代谢及动脉粥样硬化的关系

ABCA1（ATP-binding cassette transporter A1）可利用ATP参与胆固醇和磷脂从细胞内转运至贫脂或无脂的apoA1，促进高密度脂蛋白（HDL）生成，并在胆固醇逆转运（RCT）中起重要作用。ABCA1受多种因素调节，其中以核受体超家族的转录调节最为重要。上调ABCA1表达增加RCT、提高HDL血浆浓度是防治动脉粥样硬化（AS）的一个新方向，特异性肝X受体（LXR）激动剂可能是抗AS新药的希望所在。     

淋巴管参与胆固醇逆向转运

细胞需要胆固醇才能生存,但过量的胆固醇对细胞具有毒性,因此细胞需要调节胆固醇的稳态。细胞内胆固醇被转运到高密度脂蛋白载脂蛋白AI,会以胆固醇逆向转运的方式返回肝脏代谢。胆固醇逆向转运不仅是维持细胞胆固醇稳态所需的生理过程,而且对动脉粥样硬化发展起到潜在的抑制作用。目前的研究主要集中在细胞胆固醇流出的最初途径和最终代谢上,但关于胆固醇是如何离开血液却知之甚少。越来越多的研究表明,在胆固醇逆向转运过程中高密度脂蛋白需要通过淋巴管转运以返回到肝脏代谢。因此,研究高密度脂蛋白从血液流入外周组织的过程,以及它是怎样通过淋巴管转运对治疗动脉粥样硬化具有重要意义。本综述主要介绍淋巴管与胆固醇逆向转运之间的联系,为治疗动脉粥样硬化性心血管疾病提供新的策略。     

三磷酸腺苷结合盒转运子1和动脉粥样硬化

三磷酸腺苷结合盒转运子1(ABCA1)的一个重要生物功能是介导细胞内脂质外流.早期研究发现的相关证据支持这个结论.在巨噬细胞中,胆固醇外流是主动转运过程,ABCA1高度表达.在血清减少、增加细胞胆固醇含量和环腺苷酸处理的孵育条件下,载脂蛋白介导的细胞脂质外流升高,也诱导ABCA1的表达和细胞表面的出现,说明ABCA1与细胞脂质相关.相关的药物能抑制ABCA1阴离子和蛋白转运活性,也抑制脂质外流.应用反义寡核苷酸降低ABCA1表达或通过互补DNA转染提高ABCA1表达,能分别抑制或提高载脂蛋白A1(ApoA1)介导的细胞胆固醇外流.ABCA1参与此通路的最有力证据是识别引起丹吉尔病(TD)和家族性高密度脂蛋白(HDL)缺乏的人类基因突变所致的遗传缺陷,ABCA1存在不同程度的异常和功能障碍.研究也证实,ABCA1介导胆固醇和磷脂协同转运.     

低HDL-C者外周血白细胞胆固醇流出调节基因表达及相关研究

目的 研究低HDL-C患者外周血白细胞ABCA1和ABCG1 mRNA的表达状态.方法 采用实时荧光定量PCR方法,测定外周血白细胞ABCA1和ABCG1 mRNA表达水平.结果 低HDL-C患者ABCA1表达水平较对照组显著降低（0.23±0.09比1.18±0.49,P=0.042）,ABCG1 mRNA表达差异无统计学意义（3.09±1.08比3.94±1.48,P=0.355）;低HDL-C者高敏CRP（hs-CR P）水平明显高于对照组（2.34±1.68比1.15±0.48,P=0.008）;血清hsCRP水平与ABCA1 mRNA表达呈负相关（r=-0.330,P=0.043）,与血清HDL-C水平无相关性（r=0.19,P=0.254）.多因素线性回归分析表明,ABCA1mRNA表达水平与血清hs-CRP水平呈边缘性相关（β=-0.330,P=0.079）.结论 低HDL-C患者外周血ABCA1 mRNA表达水平降低,炎症因素或许是其机制之一.这可能是低HDL-C者心血管病风险增高的一个因素.     

Tissue-specific induction of intestinal ABCA1 expression with a liver X receptor agonist raises plasma HDL cholesterol levels

ABCA1 controls the rate-limiting step in HDL particle formation and is therefore an attractive molecular target for raising HDL levels and protecting against atherosclerosis. Intestinal ABCA1 significantly and independently contributes to plasma HDL cholesterol levels in mice, suggesting that induction of intestinal ABCA1 expression may raise plasma HDL cholesterol levels. We evaluated the ability of a synthetic Liver X Receptor (LXR) agonist, GW3965, to raise plasma HDL cholesterol levels in control mice and mice with liver- or intestinal-specific deletion of the Abca1 gene. Oral treatment with GW3965 increased the expression of ABCA1 by approximately 6-fold (P=0.004) as well as other LXR target genes in the intestines of mice, with no change in the hepatic expression of these genes. This resulted in a significant approximately 48% elevation of plasma HDL cholesterol levels in wild-type mice (P<0.01) with no change in plasma triglycerides. A similar increase in HDL cholesterol was observed in mice lacking hepatic ABCA1, indicating that the increase in plasma HDL cholesterol was independent of hepatic ABCA1. This effect was completely abrogated in mice lacking intestinal ABCA1. These data indicate that intestinal ABCA1 may be an attractive therapeutic target for raising HDL levels while avoiding the hepatic lipogenesis and hypertriglyceridemia typical of systemic LXR activation.     

ABCA1 and atherosclerosis

ATP binding cassette transporter A1 (ABCA1) mediates the cellular efflux of phospholipids and cholesterol to lipid-poor apolipoprotein A1 (apoA1) and plays a significant role in high density lipoprotein (HDL) metabolism. ABCA1's role in the causation of Tangier disease, characterized by absent HDL and premature atherosclerosis, has implicated this transporter and its regulators liver-X-receptoralpha (LXRalpha) and peroxisome proliferator activated receptorgamma (PPARgamma) as new candidates potentially influencing the progression of atherosclerosis. In addition to lipid regulation, these genes are involved in apoptosis and inflammation, processes thought to be central to atherosclerotic plaque progression. A Medline-based review of the literature was carried out. Tangier disease and human heterozygotes with ABCA1 mutations provide good evidence that ABCA1 is a major candidate influencing atherosclerosis. Animal and in vitro experiments suggest that ABCA1 not only mediates cholesterol and phospholipid efflux, but is also involved in the regulation of apoptosis and inflammation. The complex and beneficial interactions between apoA1 and ABCA1 seem to be pivotal for cholesterol efflux. The expression of the ABCA1 is tightly regulated. Furthermore the plaque microenvironment could potentially promote ABCA1 protein degradation thus compromising cholesterol efflux. PPAR-LXR-ABCA1 interactions are integral to cholesterol homeostasis and these nuclear receptors have proven anti-inflammatory and anti-matrix metalloproteinase activity. Therapeutic manipulation of the ABCA1 transporter is feasible using PPAR and LXR agonists. PPAR agonists like glitazones and ABCA1 protein stabilization could potentially modify the clinical progression of atherosclerotic lesions.     

Regulation of plasma high-density lipoprotein levels by the ABCA1 transporter and the emerging role of high-density lipoprotein in the treatment of cardiovascular disease

High-density lipoproteins (HDL) protect against cardiovascular disease. HDL removes and transports excess cholesterol from peripheral cells to the liver for removal from the body. HDL also protects low-density lipoproteins (LDL) from oxidation and inhibits expression of adhesion molecules in endothelial cells, preventing monocyte movement into the vessel wall. The ABCA1 transporter regulates intracellular cholesterol levels in the liver and in peripheral cells by effluxing excess cholesterol to lipid-poor apoA-I to form nascent HDL, which is converted to mature alpha-HDL by esterification of cholesterol to cholesteryl esters (CE) by lecithin cholesterol acyltransferase. The hepatic ABCA1 transporter and apoA-I are major determinants of levels of plasma alpha-HDL cholesterol as well as poorly lipidated apoA-I, which interact with ABCA1 transporters on peripheral cells in the process of reverse cholesterol transport. Cholesterol in HDL is transported directly back to the liver by HDL or after transfer of CE by the cholesteryl ester transfer protein (CETP) by the apoB lipoproteins. Current approaches to increasing HDL to determine the efficacy of HDL in reducing atherosclerosis involve acute HDL therapy with infusions of apoA-I or apoA-I mimetic peptides and chronic long-term therapy with selective agents to increase HDL, including CETP inhibitors.     

ATP-binding cassette A1 protein and HDL homeostasis

For three decades, low-density lipoprotein (LDL) dominated research into cholesterol metabolism and atherosclerosis, whereas scant attention was paid to high-density lipoprotein (HDL), an equally important risk factor for cardiovascular disease. This low interest reflected the lack of knowledge about physiological HDL receptors. As a result, our understanding of HDL-cell interactions failed to develop alongside that of LDL, and mechanisms through which atheroprotective HDL promoted clearance of cholesterol from peripheral cells remained poorly-defined. Interest was kindled with the recognition that scavenger receptor class B, type I is the cell-surface protein in hepatocytes and steroidogenic tissues which selectively extracts cholesteryl esters from HDL. Greater impetus still was given by the discovery that mutations in the gene encoding the ATP-binding cassette transporter, class A1 (ABCA1) are the cause of Tangier disease, a rare recessive disorder with near-absent plasma HDL. The ABCA1 transmembrane protein is crucial for efficient efflux of cellular cholesterol and HDL maturation and has emerged as a promising therapeutic target for cardiovascular disease. The hope is that new drugs, regulating ABCA1 activity and HDL homeostasis, will accelerate cholesterol efflux from lipid-laden foam cells and thus promote regression of atherosclerotic lesions.     

The ATP binding cassette transporter A1 (ABCA1) modulates the development of aortic atherosclerosis in C57BL/6 and apoE-knockout mice

Identification of mutations in the ABCA1 transporter (ABCA1) as the genetic defect in Tangier disease has generated interest in modulating atherogenic risk by enhancing ABCA1 gene expression. To investigate the role of ABCA1 in atherogenesis, we analyzed diet-induced atherosclerosis in transgenic mice overexpressing human ABCA1 (hABCA1-Tg) and spontaneous lesion formation in hABCA1-Tg x apoE-knockout (KO) mice. Overexpression of hABCA1 in C57BL/6 mice resulted in a unique anti-atherogenic profile characterized by decreased plasma cholesterol (63%), cholesteryl ester (63%), free cholesterol (67%), non-high density lipoprotein (HDL)-cholesterol (53%), and apolipoprotein (apo) B (64%) but markedly increased HDL-cholesterol (2.8-fold), apoA-I (2.2-fold), and apoE (2.8-fold) levels. These beneficial changes in the lipid profile led to significantly lower (65%) aortic atherosclerosis in hABCA1-Tg mice. In marked contrast, ABCA1 overexpression had a minimal effect on the plasma lipid profile of apoE-KO mice and resulted in a 2- to 2.6-fold increase in aortic lesion area. These combined results indicate that overexpression of ABCA1 in C57BL/6 mice on a high cholesterol diet results in an atheroprotective lipoprotein profile and decreased atherosclerosis, and thus provide previously undocumented in vivo evidence of an anti-atherogenic role for the ABCA1 transporter. In contrast, overexpression of ABCA1 in an apoE-KO background led to increased atherosclerosis, further substantiating the important role of apoE in macrophage cholesterol metabolism and atherogenesis. In summary, these results establish that, in the presence of apoE, overexpression of ABCA1 modulates HDL as well as apoB-containing lipoprotein metabolism and reduces atherosclerosis in vivo, and indicate that pharmacological agents that will increase ABCA1 expression may reduce atherogenic risk in humans.