Immunologic Dysfunction in Biliary Atresia

描述(申请人提供)：胆道闭锁是儿童终末期肝硬变最常见的原因，也是儿童肝移植的头号适应症。它是由炎性和肝外胆管纤维化阻塞引起的，表现为新生儿黄疸。尽管及时诊断和手术治疗，该病仍在发展，并导致相当大的发病率和死亡率。尽管病因学在很大程度上仍未确定，但追求该奖项先前目标的研究已经推进了对疾病致病机制的了解。具体地说，我们发现了树突状细胞、NK细胞和CD8细胞的顺序激活，破坏了胆管黏膜并促进了管腔阻塞。与疾病的多因素基础一致，我们还发现Th2信号的激活在胆道损伤实验中和在人体组织中发生。总而言之，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。在这个相互竞争的更新应用中，我们提出了一个统一的假设，即肝炎性细胞具有双重作用，既是胆管损伤的效应者，又是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的独立目标中得到检验。在目标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研究肿瘤坏死因子α信号和颗粒酶如何作为胆管细胞溶解的分子执行者来完成。在目标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剂的作用。这一目标建立在最初的实验表明新生儿LIVR表达巨噬细胞和中性粒细胞趋化物质的基础上。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。在目标3中，我们将研究Th2细胞因子作为生存信号来恢复上皮完整性。我们产生了基于肝脏的髓系细胞产生Th2生存信号的初步证据，该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ALARMIN IL33和IL13-IL4Rα-STAT6轴在实验性胆道闭锁的胆管细胞增殖和上皮完整性恢复中的特性来剖析这些信号。完成后，拟议的实验将促进我们对疾病致病机制的理解，并发现促进受损组织修复的新的生长信号。这些结果将确定一系列新疗法的靶点，以阻止疾病的进展，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.