Immunologic Dysfunction in Biliary Atresia

描述（由申请人提供）：胆道闭锁是儿童终末期肝硬化最常见的原因，也是儿童肝移植的首要适应症。它是由肝外胆管炎症性纤维化梗阻引起的，表现为新生儿黄疸。尽管及时诊断和手术治疗，疾病仍会进展并导致大量发病率和死亡率。尽管病因学在很大程度上仍不明确，但追求该奖项先前目标的研究已经掌握了疾病致病机制的先进知识。具体来说，我们发现树突状、NK和CD8+细胞的顺序激活会破坏胆管粘膜并促进管腔阻塞。与疾病的多因素基础一致，我们还发现Th2信号的激活在实验和人体组织中发生在胆道损伤期间。综上所述，这些研究将免疫系统置于发病机制的中心点，并开始确定潜在的治疗靶点。在这个竞争性的更新应用中，我们提出了一个统一的假设，即肝炎症细胞具有双重作用，作为胆管损伤的效应器和作为恢复上皮完整性的生存信号的提供者。这一假设将在三个密切相关但独立的目标中得到检验。在Aim 1中，我们将定义淋巴细胞可溶性配体诱导上皮损伤的机制。这将通过应用体外和强大的动物模型系统来检查TNFα信号传导和颗粒酶如何作为胆管细胞裂解的分子执行者来完成。在Aim 2中，我们将确定巨噬细胞和中性粒细胞作为胆道损伤促进因子的作用。这一目的是建立在初步实验表明，新生儿肝脏表达巨噬细胞和中性粒细胞的化学引诱物。因此，我们将使用基因工程小鼠来探索单个细胞类型在调节产生疾病表型的炎症反应中的作用。在Aim 3中，我们将研究Th2细胞因子作为恢复上皮完整性的生存信号。我们产生了初步的证据，肝基髓细胞产生Th2生存信号，对胆管细胞具有强大的有丝分裂特性。在这里，我们建议通过研究警示蛋白IL33和IL13-IL4Rα-STAT6轴在实验性胆道闭锁中胆管细胞增殖和上皮完整性恢复中的特性来解剖这些信号。一旦完成，我们提出的实验将促进我们对疾病致病机制的理解，并发现促进损伤组织修复的新生长信号。这些结果将确定一系列新疗法的靶点，以阻止疾病进展，恢复胆道上皮，并促进胆道闭锁患者的长期生存。

DESCRIPTION (provided by applicant): Biliary atresia is the most common cause of end-stage cirrhosis in children and the number one indication for pediatric liver transplantation. It results from an inflammatory and fibrosing obstruction of extrahepatic bile ducts that presents as neonatal jaundice. Despite prompt diagnosis and surgical treatment, the disease progresses and causes substantial morbidity and mortality. Although the etiology remains largely undefined, studies pursuing the previous aims of this award have advanced knowledge of pathogenic mechanisms of disease. Specifically, we uncovered a sequential activation of dendritic, NK and CD8+ cells that disrupts the bile duct mucosa and promotes lumenal obstruction. Consistent with a multifactorial basis of disease, we also found that the activation of Th2 signals occurs during biliary injury experimentally and in human tissues. Combined, these studies placed the immune system in a central point of pathogenesis and began to identify potential therapeutic targets. In this competing renewal application, we propose a unifying hypothesis that hepatic inflammatory cells have a dual role as effectors of bile duct injury and as suppliers of survival signals to restore epithelial integrity. This hypothesis will be tested in three closely related bu independent aims. In Aim 1, we will define the mechanisms used by lymphocyte soluble ligands to induce epithelial injury. This will be done by applying in vitro and powerful animal model systems to examine how TNFα signaling and granzymes serve as molecular executors of cholangiocyte lysis. In Aim 2, we will determine the roles of macrophages and neutrophils as promoters of biliary injury. This aim is built on initial experiments showing that the neonatal livr expresses macrophage and neutrophil chemoattractants. Thus, we will use genetically engineered mice to explore the role of individual cell types in modulating the inflammatory response that produces the disease phenotype. And in Aim 3, we will investigate Th2 cytokines as survival signals to restore epithelial integrity. We generated preliminary evidence that liver-based myeloid cells produce Th2 survival signals with potent mitogenic properties to cholangiocytes. Here, we propose to dissect these signals by investigating the properties of the alarmin IL33 and the IL13-IL4Rα-STAT6 axis in cholangiocyte proliferation and restoration of epithelial integrity in experimental biliary atresia. Upon completion, the proposed experiments will advance our understanding of the pathogenic mechanisms of disease and uncover new growth signals that promote repair of the injured tissue. These results will identify an array of targets for new therapies that block progression of disease, restore the biliary epithelium, and foster long-term survival of patients with biliary atresia.