Phenotypic Determinants of Murine Cholelithiasis

描述（由申请人提供）：在了解近交系小鼠胆固醇胆石形成方面的进展导致了新的和持续的特定目标，这些目标主要是先前拨款的延伸。主要的实验目标是鉴定、表征和量化小鼠胆结石形成的分子病理生理和表型，特别是那些由胆固醇胆结石（Lith）基因引起的。目的1：在遗传多样性的自交系小鼠中，确定新发现的数量性状位点（QTL）遗传易感性诱导的关键病理生理变化。这些信息对于确定QTL的位置候选基因至关重要。目的2将确定近端胆道树是否在Lith1位点诱导的胆汁成石性和胆固醇胆结石易感性中起决定性作用，并确定阻断胆盐的胆肝分流是否可阻止胆石形成。目的3将检查外排转运蛋白及其在肠细胞水平上的调节，作为胆囊结石易感近交系小鼠肠道胆固醇吸收增加的原因。目的4将研究靶向破坏胆囊收缩素(CCK)-A受体和羧肽酶E（后一种细胞内酶将前CCK转化为CCK）的小鼠胆固醇胆石形成的发病机制；预计除了胆道运动障碍外，还会有小肠运动障碍导致管腔胆固醇吸收增加。目的5阐明小鼠囊性纤维化模型中色素胆结石的发病机制。该假说预测肝内胆道树和胆囊内的胆汁碱性较低，并伴有胆盐吸收不良引起的非共轭胆红素肠肝循环，后者推测是继发于根尖钠-胆盐共转运体（ASBT）功能障碍。由于胆汁酸性较强，内源性？-葡萄糖醛酸酶在肝内和胆囊内的活性增加，胆红素偶联物的水解增加，导致胆红素钙沉淀，从而导致“黑色”色素胆结石，以及肝内微沉淀物引起机械性胆管阻塞。由于哺乳动物基因组之间的密切遗传对应关系，这些病理生理学研究应该导致对这些常见的以及具有经济意义的人类消化系统疾病有更基本的了解。

DESCRIPTION (provided by applicant): Progress in understanding cholesterol gallstone formation in inbred mice has led to new and continuing specific aims, which are mostly extensions of the previous grant. The principal experimental goals are to identify, characterize and quantify the molecular pathophysiologies and phenotypes involved in murine gallstone formation, particularly those caused by cholesterol gallstone (Lith) genes. Aim I proposes to determine the critical pathophysiological changes that are induced by genetic susceptibility within newly-identified quantitative trait loci (QTL) in genetically-diverse inbred mouse strains. This information will be crucial for identifying positional candidate genes for selected QTL's. Aim 2 will determine whether the proximal biliary tree plays a decisive role in bile lithogenicity and cholesterol gallstone susceptibility induced by the Lith1 locus and establish whether blocking cholehepatic shunting of bile salts prevents cholelithogenesis. Aim 3 will examine efflux transporters and their regulation at the enterocyte level as causes of the augmented cholesterol absorption from the intestine of gallstone-susceptible inbred mice. Aim 4 will investigate the pathogenesis of cholesterol cholelithogenesis in mice with targeted disruption of the cholecystokinin (CCK)-A receptor and carboxypeptidase E, the latter intracellular enzyme processing pro-CCK to CCK; it is anticipated that in addition to biliary dysmotility, there will be small intestinal hypomotility leading to augmented lumenal cholesterol absorption. Aim 5 will elucidate the pathogenesis of pigment gallstones in murine models of cystic fibrosis. The hypothesis predicts a less alkaline bile within the intrahepatic biliary tree and gallbladder with enterohepatic cycling of unconjugated bilirubin from bile salt malabsorption, the latter speculated to be secondary to apical sodium-bile salt co-transporter (ASBT) dysfunction. As a result of a more acidic bile, there will be increased endogenous ?-glucuronidase activity intrahepatically, as well as in the gallbladder, with augmented hydrolysis of bilirubin conjugates resulting in calcium bilirubinate precipitation, thereby leading to "black" pigment gallstones, as well as intrahepatic microprecipitates causing mechanical bile duct obstruction. Because of the close genetic correspondence between mammalian genomes, these pathophysiological studies should lead to more fundamental understanding of these common, as well as economically-significant digestive diseases in human beings.