Intestinal Inflammation Induced by Pathogens

描述（由申请人提供）：炎症性肠病（IBDs）包括克罗恩病（CD）和溃疡性结肠炎（UC）是一种慢性疾病，其特征是中性粒细胞（pmn）明显浸润到结肠粘膜病变，伴有上皮细胞坏死和溃疡。疾病活动性和患者症状也与粘膜和表面上皮内PMN浸润的组织学发现相关。在由肠炎沙门氏菌血清型鼠伤寒沙门氏菌（沙门氏菌病）引起的胃肠炎急性期，pmn大量经上皮迁移的组织学事件也同样发生。因此，了解病原体引起的肠道活动性炎症将作为一个重要的模型，为IBD的活动性炎症提供有价值的信息。利用肠道病原体鼠伤寒沙门氏菌作为研究PMN在肠道上皮内募集机制的工具，我们已经证明了二十烷类hepoxilin A3 （HXA3）的一种新的核心作用。HXA3是花生四烯酸的衍生物，由12-脂氧合酶（12-LO）途径的酶促作用形成。这一观察揭示了先前未被探索的现象，从机制上解释了肠道炎症活跃状态的主要组织病理学特征。此外，我们最近发现HXA3是通过位于肠上皮顶端表面的外排运输系统分泌的，该系统涉及ABC转运蛋白MRP2。我们还发现，肠道炎症的诱导与MRP2的顶端表达的显著上调相对应。这种MRP2的上调在体内进一步在IBD慢性小鼠模型和活动性CD或UC患者的人肠道活检组织中得到证实。因此，该项目的主要目标是了解HXA3合成的分子机制（Specific Aim 1），以及确定HXA3的生产是如何调节的（Specific Aim 2）。为了实现这些目标，我们计划将互补的体外和体内模型与最先进的细胞、分子和生化技术相结合。我们假设，理解基于HXA3/MRP2的信号传导，它指导PMNs在肠上皮中的运动，将导致重要的治疗方法的发展，旨在帮助控制感染性、过敏性和特发性（IBD）结肠炎患者的炎症事件。

DESCRIPTION (provided by applicant): Inflammatory bowel diseases (IBDs) including Crohn's disease (CD) and ulcerative colitis (UC) are chronic diseases characterized by a pronounced infiltration of neutrophils (PMNs) into colonic mucosal lesions, accompanied by epithelial cell necrosis and ulceration. Disease activity and patient symptoms also correlate with the histologic finding of PMN infiltrates within the mucosa and surface epithelium. This same histological event of massive transepithelial migration of PMNs occurs in the acute phase of gastroenteritis induced by Salmonella enterica serovar Typhimurium (salmonellosis). Thus, insight into pathogen elicited active inflammation of the intestine will serve as an important model to provide valuable information relating to active inflammation in IBD. Using the enteric pathogen S. typhimurium as a tool to investigate mechanisms underlying PMN recruitment across the intestinal epithelia, we have demonstrated a novel and central role for the eicosanoid hepoxilin A3 (HXA3). HXA3 is a derivative of arachidonic acid formed from the enzymatic action of the 12-lipoxygenase (12-LO) pathway. This observation has unlocked a previous unexplored phenomenon that mechanistically explains a primary histopathologic feature of active states of intestinal inflammation. Moreover, we have recently shown that HXA3 is secreted through an efflux transport system located at the apical surface of the intestinal epithelia that involves the ABC transporter MRP2. We also revealed that induction of intestinal inflammation corresponds to a profound up-regulation of the apical expression of MRP2. Such up-regulation of MRP2 was further demonstrated in vivo in chronic murine models of IBD and human intestinal biopsy tissues from patients with active CD or UC. Thus, the primary objectives of this project are to understand the molecular mechanisms underlying HXA3 synthesis (Specific Aim 1), as well as to determine how HXA3 production is regulated (Specific Aim 2). To accomplish these aims we plan to use a combination of complementary in vitro and in vivo models coupled with state of the art cellular, molecular, and biochemical techniques. We hypothesize that understanding HXA3/MRP2 based signaling, which directs the movement of PMNs across the intestinal epithelium, will lead to the development of important therapeutics designed to help control this inflammatory event in patients with infectious, allergic, and idiopathic (IBD) colitis. PUBLIC HEALTH RELEVANCE: It is estimated that as many as one million Americans have inflammatory bowel disease (IBD) with that number evenly split between Crohn's disease and ulcerative colitis. Males and females appear to be affected equally. IBDs including Crohn's disease and ulcerative colitis are chronic recurrent inflammatory disorders of the gastrointestinal tract that are of unkown etiology. Although the exact pathogenesis of IBDs is poorly understood, evidence indicates that it involves interaction between the immune system, genetic susceptibility, and the environment. These diseases are characterized by a pronounced infiltration of neutrophils (PMNs) into colon mucosal lesions, accompanied by epithelial cell necrosis and ulceration. Moreover, disease activity and patient symptoms correlate with the histologic finding of PMN infiltrates within the mucosa and surface epithelium. Curiously, this same histological event of massive transepithelial migration of PMNs occurs in the acute phase of gastroenteritis induced by Salmonella enteritis serovar Typhimurium (salmonellosis). Thus, while the evolution of these responses most likely initially targeted pathogens such as S. typhimurium, perhaps aberrant activation of such pathways also occurs, leading to inappropriate states of active intestinal inflammation. The goal of this proposal is to understand the molecular mechanisms by which S. typhimurium triggers and controls the directed movement of PMN across the epithelial surface so that novel targets for therapeutic intervention in such inflammatory bowel diseases can be identified.