Hepatic Cholesteryl Ester Metabolism and Cholesterol Elimination

肝脏胆固醇酯代谢和胆固醇消除

• 批准号: 8092766
• 负责人: SHOBHA GHOSH
• 金额: $ 37.38万
• 依托单位: VIRGINIA COMMONWEALTH UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2014-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8092766
• 关键词: Adenoviruses; Affect; Albumins; Arterial Fatty Streak; Arteries; Atherosclerosis; Attenuated; Bile Acid Biosynthesis Pathway; Bile Acids; Bile fluid; Biliary; Blood; CYP7A1 gene; Cell Culture System; Cells; Characteristics; Chenodeoxycholic Acid; Cholesterol; Cholesterol 7-alpha-Monooxygenase; Cholesterol Esters; Cholesterol Homeostasis; Cholic Acids; Cloning; Coronary Arteriosclerosis; Diet; Endocytosis; Enzymes; Esters; Event; Excision; Excretory function; Feces; Foam Cells; Foundations; Gallbladder; Generations; HDL cholesteryl ester; HDL receptor; Hepatic; Hepatocyte; High Density Lipoproteins; Human; Hydrolysis; Knockout Mice; Laboratories; Lesion; Link; Lipid-Laden Macrophage; Lipoproteins; Liver; Low Density Lipoprotein Receptor; Low-Density Lipoproteins; Mediating; Metabolism; Modeling; Monitor; Movement; Mus; Organ; Output; Oxidoreductase; Pathway interactions; Peripheral; Phosphatidylcholine-Sterol O-Acyltransferase; Plasma; Play; Prevalence; Prevention; Process; Proteins; Reaction; Regulation; Reporting; Research Project Grants; Role; Route; SR-BI receptor; Serum; Stream; Testing; Tissues; Tracer; Transgenic Mice; Transgenic Organisms; adenoviral-mediated; clinically relevant; esterase; in vivo; lipoprotein cholesterol; macrophage; muricholic acid; operation; public health relevance; recombinase; reverse cholesterol transport; sterol O-acyltransferase 2; uptake; vitamin D3 25-hydroxylase

DESCRIPTION (provided by applicant): Reverse cholesterol transport (RCT) is the major mechanism by which cholesterol is transported from the peripheral tissues including macrophages associated with the artery wall, to liver for the ultimate conversion into bile acids or direct secretion into the bile. Within the cells or while being transported in the blood stream associated with the lipoproteins, cholesterol is mainly present as cholesteryl esters (CE). Thus, the obligatory first and rate-limiting step of RCT is the intracellular hydrolysis of the stored intracellular CE in the peripheral tissues, e.g., macrophage foam cells, and this reaction is catalyzed by a neutral cholesteryl ester hydrolase (CEH). Free or unesterified cholesterol (FC) that is removed by extra-cellular cholesterol acceptors such as HDL is re-esterified by serum LCAT and carried as CE to the liver where it is delivered by selective uptake via scavenger receptor BI (SR-BI). Hydrolysis of CE once again is obligatory to subsequent conversion of released FC to bile acids or direct secretion into bile. Having established the role of human macrophage CEH in regulating the efflux of FC, RCT and thus attenuating diet-induced atherosclerosis in LDLR-/- mice, the PI has recently reported the cloning and characterization of human liver CEH. Over-expression of this enzyme results in intracellular CE mobilization and an increase in bile acid synthesis. Adenovirus- mediated over-expression of CEH in mice led to significant increase in in vivo RCT and increased elimination of cholesterol as secreted bile acids, and this process required the presence of HDL- receptor SR-BI. CEH-mediated CE hydrolysis, therefore, represents a key event regulating the first step in RCT (generation of free cholesterol in macrophage for efflux) as well as the final step (generating free cholesterol for bile acid synthesis or biliary cholesterol secretion). The central hypothesis of this research project is: Hepatic CEH affects RCT by regulating the hydrolysis of intracellular cholesterol esters (endogenously synthesized or delivered via selective uptake from HDL through SR-BI) thereby providing free cholesterol for elimination as bile acids or direct secretion into the bile and is, therefore, potentially anti-atherosclerotic. This hypothesis will be tested by the following four specific aims: Aim 1: To establish the anti-atherosclerotic role of hepatic CEH by developing liver specific CEH transgenic mice. Aim 2: To delineate the mechanism(s) underlying hepatic CEH-mediated regulation of RCT: role of CEH in hydrolyzing CE delivered to liver by scavenger receptor BI (SR-BI) or SR-BII mediated uptake of HDL-associated CE. Aim 3: To determine the role of hepatic CEH in regulating FC availability for neutral or acidic pathways for bile acid synthesis. Aim 4: To obtain in vivo "proof of concept" by liver-specific targeted disruption of CEH in mice and to determine its effect on intracellular CE metabolism and atherosclerosis. PUBLIC HEALTH RELEVANCE: Liver is the only organ responsible for the ultimate elimination of cholesterol from the body as free cholesterol (FC) or bile acids that are excreted in the feces. Cholesterol associated with excess unmodified LDL as well as the cholesterol removed from the peripheral organs including artery wall- associated macrophage foam cells by HDL is taken up by the liver. Both these lipoproteins deliver cholesterol in the form of cholesterol esters (CE) and within liver hydrolysis of these CEs is essential to provide FC for bile acid synthesis or for direct elimination into the bile. This hydrolysis is carried out in the extra-lysosomal compartment by a neutral cholesteryl ester hydrolase (CEH). We have identified the human hepatic CEH and demonstrated its role in increasing bile acid secretion as well as in enhancing the flux of cholesterol from macrophages to bile suggesting an anti-atherosclerotic function of hepatic CEH. The proposed studies will build on this foundation and establish the role of hepatic CEH in not only increasing cholesterol elimination from the body as bile acids but also in attenuating diet-induced atherosclerosis. Given the prevalence of atherosclerosis and coronary artery disease, the current findings are likely to have important clinical relevance.

描述（由申请人提供）：反向胆固醇转运（RCT）是将胆固醇从包括与动脉壁相关的巨噬细胞在内的外周组织转运到肝脏的主要机制，以最终转化为胆汁酸或直接分泌到胆汁。在细胞内或在与脂蛋白有关的血液中运输时，胆固醇主要以胆固醇酯（CE）为单位。因此，RCT的强制性第一和限制步骤是外围组织中储存的细胞内CE的细胞内水解，例如巨噬细胞泡沫细胞，该反应由中性胆汁胆料酯（CEH）催化。由HDL等细胞外胆固醇受体去除的自由或未酯化的胆固醇（FC）被血清LCAT重新层置，并作为CE携带到肝脏中，并通过Savavenger受体BI（SR-BI）通过选择性摄取摄取。 CE的水解再次是强制性的，随后释放的FC转化为胆汁酸或直接分泌为胆汁。在确定了人类巨噬细胞CEH在调节FC，RCT的外排的作用，从而减弱了饮食诱导的LDLR - / - 小鼠的动脉粥样硬化，PI最近报道了人肝脏CEH的克隆和表征。这种酶的过表达导致细胞内CE动员和胆汁酸合成的增加。腺病毒介导的CEH在小鼠中的过表达导致体内RCT的显着增加，并增加了胆固醇作为分泌的胆汁酸，并且此过程需要存在HDL-受体SR-BI。因此，CEH介导的CE水解代表了调节RCT的第一步（巨噬细胞中的游离胆固醇的第一步）以及最后一步（产生免费的胆固醇胆固醇用于胆汁酸合成或胆固醇胆固醇分泌）。该研究项目的中心假设是：CEH肝CEH通过调节细胞内胆固醇酯的水解（通过从HDL到SR-BI的选择性吸收，通过选择性吸收到SR-BI到SR-BI）的水解对RCT，从而影响RCT，从而提供自由胆固醇，以消除自由胆固醇，以消除胆汁酸，从而使胆汁酸或直接分泌到Bile Isscore，并潜在地抗衡。该假设将通过以下四个特定目的来检验：目标1：通过开发特定于肝的CEH转基因小鼠来确定肝CEH的抗震颤性作用。目的2：描述CEH介导的RCT的基础机制：CEH在CEH中的作用在水解CE中的作用，通过清道夫受体BI（SR-BI）或SR-BII介导的HDL相关CE摄取。 AIM 3：确定肝CEH在调节FC可用性中的作用中，用于胆汁酸合成中中性或酸性途径。目标4：通过小鼠中CEH的肝脏特异性靶向破坏获得体内“概念证明”，并确定其对细胞内CE代谢和动脉粥样硬化的影响。 公共卫生相关性：肝脏是唯一一种导致胆固醇（FC）或粪便中胆汁酸最终消除胆固醇的器官。肝脏从HDL中吸收了与从外围器官中取出的胆固醇以及从外围器官中取出的胆固醇以及包括动脉壁相关的巨噬细胞泡沫细胞的胆固醇。这两种脂蛋白均以胆固醇酯（CE）的形式和这些CE的肝脏水解内递送胆固醇对于提供胆汁酸合成或直接消除胆汁至关重要。这种水解是由中性胆固醇酯水解酶（CEH）在散热体室中进行的。我们已经确定了人类肝脏CEH，并展示了其在增加胆汁酸分泌方面的作用，以及增强胆固醇从巨噬细胞到胆汁的通量，这表明肝CEH具有抗动脉粥样硬化功能。拟议的研究将基于这一基础，并确定CEH肝的作用，不仅在增加体内消除胆固醇作为胆汁酸，而且还可以减弱饮食引起的动脉粥样硬化。鉴于动脉粥样硬化和冠状动脉疾病的患病率，目前的发现可能具有重要的临床相关性。