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的最常见原因，也是小儿肝移植的头号适应症。它是由于肝外胆管的炎症和纤维化阻塞引起的，表现为新生儿黄疸。尽管及时诊断和手术治疗，疾病的进展，并导致大量的发病率和死亡率。虽然病因仍然在很大程度上不确定，追求这个奖项的先前目标的研究已经先进的疾病的致病机制的知识。具体而言，我们发现了树突状细胞、NK细胞和CD 8+细胞的顺序激活，其破坏胆管粘膜并促进管腔阻塞。与疾病的多因素基础相一致，我们还发现，在实验性胆道损伤和人体组织中，Th 2信号的激活发生。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，即肝脏炎症细胞具有双重作用，即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供应者。这一假设将在三个密切相关但独立的目标进行检验。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检查TNFα信号传导和颗粒酶如何作为胆管细胞溶解的分子执行器来完成。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。这一目标是建立在初步实验表明，新生儿livr表达巨噬细胞和中性粒细胞趋化因子。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Th 2细胞因子作为恢复上皮完整性的生存信号。我们产生的初步证据表明，肝为基础的髓系细胞产生的Th 2细胞的生存信号与有效的促有丝分裂特性的胆管细胞。在这里，我们建议通过研究alarmin IL 33和IL 13-IL 4 R α-STAT 6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剖析这些信号。完成后，拟议的实验将推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生长信号。这些结果将为阻断疾病进展、恢复胆管上皮和促进胆道闭锁患者长期生存的新疗法确定一系列靶点。

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.