CHOLESTEROL TRANSPORT IN GALLBLADDER EPITHELIAL CELLS

胆囊上皮细胞中的胆固醇转运

• 批准号: 6620298
• 负责人: RAHUL P KUVER
• 金额: $ 6.3万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-03-01 至 2004-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6620298
• 关键词: apolipoproteins; cellular polarity; cholesterol; cyclic AMP; epithelium; gallbladder; high density lipoproteins; hormone receptor; intracellular transport; lipid transport; receptor; tissue /cell culture; transport proteins

Gallbladder epithelial cells and cholangiocytes are exposed to high concentrations of cholesterol because the major pathway of cholesterol excretion from the body is through bile. Oxidized forms of cholesterol, called oxysterols, are also found in bile. The effects of oxysterols on the biliary system are not understood. Cholesterol handling biliary epithelial cells is therefore an important are of investigation, as an understanding of the mechanisms involved in cholesterol transport and of the effects of oxysterols at the cellular and molecular level has potential implications for therapy of cholesterol gallstone disease, cholesterolosis of the gallbladder, and inflammatory states affecting the biliary system such as cholecystitis and cholangitis. An understanding of biliary epithelial cell cholesterol transport may also provide insights into cholesterol handling by other polarized epithelial cells such as villous enterocytes. We propose to use gallbladder epithelial cells, cultured in a polarized fashion, to study cholesterol transport, with a focus on the interactive roles of the cholesterol transporter ABCA1 and the HDL receptor, SR-B1. Key questions to be addressed are the polarity of expression of these molecules and their functional interactions. We hypothesize that ABCA1 and SR-B1 are expressed on opposing sides of polarized gallbladder epithelial cells. Cholesterol influx is mediated by SR-B1from the apical surface, and cholesterol efflux from the basolateral surface by ABCA1. This mechanism allows cholesterol concentrations in bile to be regulated, and a set-point for cholesterol concentration maintained based on the relative activities of these proteins. We postulate a key role for apolipoprotein A1 in this process. We also postulate that oxysterosis modulate ABCA1 activity via transport mechanisms involving the nuclear hormone receptors LXR alpha and RXR. The Specific Aims are to: 1. Demonstrate the functional expression of ABCA1activity via transcriptional mechanisms involving the nuclear hormone receptors LXR alpha and RXR. 2. Determine the mechanisms of apolipoprotein A1-mediated cholesterol efflux in polarized gallbladder epithelial cells. 3. Compare and contrast the mechanisms of activation of ABCA1 via the cAMP responsive and the LXRalpha/RXR- responsive pathways.

胆囊上皮细胞和胆管细胞暴露于高浓度的胆固醇，因为体内胆固醇排泄的主要途径是通过胆汁。胆汁中还发现了氧化形式的胆固醇，称为氧甾醇。 氧甾醇对胆道系统的影响尚不清楚。 因此，处理胆道上皮细胞的胆固醇是一个重要的研究领域，因为了解胆固醇转运的机制以及氧甾醇在细胞和分子水平上的作用对于胆固醇胆结石疾病、胆囊胆固醇中毒以及影响胆道系统的炎症状态（例如胆囊炎和胆管炎）的治疗具有潜在的意义。 对胆道上皮细胞胆固醇转运的了解还可以为其他极化上皮细胞（例如绒毛肠细胞）处理胆固醇提供见解。 我们建议使用以极化方式培养的胆囊上皮细胞来研究胆固醇转运，重点是胆固醇转运蛋白 ABCA1 和 HDL 受体 SR-B1 的相互作用。 要解决的关键问题是这些分子表达的极性及其功能相互作用。 我们假设 ABCA1 和 SR-B1 在极化胆囊上皮细胞的相对侧表达。 胆固醇流入由顶端表面的 SR-B1 介导，胆固醇从基底外侧表面的流出由 ABCA1 介导。 这种机制可以调节胆汁中的胆固醇浓度，并根据这些蛋白质的相对活性维持胆固醇浓度的设定点。 我们假设载脂蛋白 A1 在此过程中发挥关键作用。 我们还假设氧固醇通过涉及核激素受体 LXR α 和 RXR 的转运机制调节 ABCA1 活性。具体目标是： 1. 通过涉及核激素受体 LXR α 和 RXR 的转录机制展示 ABCA1 活性的功能表达。 2.确定极化胆囊上皮细胞中载脂蛋白A1介导的胆固醇流出的机制。 3. 比较和对比通过 cAMP 响应途径和 LXRalpha/RXR 响应途径激活 ABCA1 的机制。