Hepatic Cholesteryl Ester Metabolism and Cholesterol Elimination

肝脏胆固醇酯代谢和胆固醇消除

• 批准号: 8253720
• 负责人: SHOBHA GHOSH
• 金额: $ 37万
• 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/8253720
• 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）是胆固醇从外周组织（包括与动脉壁相关的巨噬细胞）转运至肝脏并最终转化为胆汁酸或直接分泌到胆汁中的主要机制。在细胞内或在与脂蛋白相关的血流中运输时，胆固醇主要以胆固醇酯（CE）的形式存在。因此，RCT 的强制性第一步和限速步骤是外周组织（例如巨噬细胞泡沫细胞）中储存的细胞内 CE 的细胞内水解，并且该反应由中性胆固醇酯水解酶（CEH）催化。被细胞外胆固醇受体（例如 HDL）去除的游离或未酯化胆固醇 (FC) 被血清 LCAT 重新酯化，并作为 CE 携带到肝脏，在肝脏中通过清道夫受体 BI (SR-BI) 选择性摄取进行递送。 CE 的水解对于随后释放的 FC 转化为胆汁酸或直接分泌到胆汁中是必须的。在确定了人巨噬细胞CEH在调节FC、RCT流出从而减轻LDLR-/-小鼠饮食诱导的动脉粥样硬化中的作用后，PI最近报道了人肝脏CEH的克隆和表征。该酶的过度表达导致细胞内 CE 动员和胆汁酸合成增加。小鼠体内腺病毒介导的CEH过度表达导致体内RCT显着增加，并增加分泌胆汁酸形式的胆固醇消除，并且该过程需要HDL受体SR-BI的存在。因此，CEH 介导的 CE 水解代表了调节 RCT 第一步（巨噬细胞中产生游离胆固醇用于流出）以及最后一步（产生游离胆固醇用于胆汁酸合成或胆汁胆固醇分泌）的关键事件。该研究项目的中心假设是：肝脏CEH通过调节细胞内胆固醇酯（内源合成或通过SR-BI选择性摄取HDL传递）的水解来影响RCT，从而提供游离胆固醇以胆汁酸形式消除或直接分泌到胆汁中，因此具有潜在的抗动脉粥样硬化作用。该假设将通过以下四个具体目标进行检验： 目标 1：通过开发肝脏特异性 CEH 转基因小鼠来确定肝脏 CEH 的抗动脉粥样硬化作用。目标 2：描绘肝脏 CEH 介导的 RCT 调节的潜在机制：CEH 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 摄取传递到肝脏。目标 3：确定肝脏 CEH 在调节胆汁酸合成中性或酸性途径的 FC 可用性中的作用。目标 4：通过小鼠肝脏特异性靶向破坏 CEH 获得体内“概念验证”，并确定其对细胞内 CE 代谢和动脉粥样硬化的影响。 公众健康相关性：肝脏是唯一负责将胆固醇以游离胆固醇 (FC) 或胆汁酸形式从粪便中排出体外的器官。与过量未修饰的低密度脂蛋白相关的胆固醇以及通过高密度脂蛋白从外周器官（包括动脉壁相关的巨噬细胞泡沫细胞）去除的胆固醇被肝脏吸收。这两种脂蛋白都以胆固醇酯 (CE) 的形式传递胆固醇，并且这些 CE 在肝脏内水解对于为胆汁酸合成或直接消除到胆汁中提供 FC 至关重要。这种水解是在溶酶体外区室中由中性胆固醇酯水解酶 (CEH) 进行的。我们已经鉴定了人类肝脏CEH，并证明了其在增加胆汁酸分泌以及增强胆固醇从巨噬细胞到胆汁的通量方面的作用，表明肝脏CEH具有抗动脉粥样硬化功能。拟议的研究将在此基础上建立，并确定肝脏 CEH 的作用，不仅可以增加体内胆固醇以胆汁酸的形式排出，而且可以减轻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普遍存在，目前的研究结果可能具有重要的临床意义。