Intestinal Inflammation Induced by Pathogens

描述(申请人提供)：炎症性肠病(IBD)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)明显渗入结肠粘膜病变，并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中性粒细胞浸润的组织学发现有关。在沙门氏菌肠炎(沙门氏菌病)引起的胃肠炎急性期，中性粒细胞大量跨上皮迁移的组织学事件也会发生。因此，深入了解病原体引起的肠道活动性炎症将成为提供与IBD活动性炎症相关的有价值信息的重要模型。使用肠道病原体鼠伤寒沙门氏菌作为工具来研究PMN在肠道上皮细胞中募集的机制，我们已经证明了二十烷类肝素A3(HXA3)的一个新的核心作用。HXA3是12-脂氧合酶(12-LO)途径的酶促作用下形成的花生四烯酸的衍生物。这一观察揭示了一个先前未被探索的现象，该现象从机械上解释了肠道炎症活动状态的主要组织病理学特征。此外，我们最近发现，HXA3是通过位于肠上皮细胞顶端的外流运输系统分泌的，该系统涉及ABC转运蛋白MRP2。我们还发现，肠道炎症的诱导对应于MRP2顶端表达的深刻上调。在慢性IBD小鼠模型和活动性CD或UC患者的人类肠道活检组织中，进一步证实了MRP2的这种上调。因此，该项目的主要目标是了解HXA3合成的分子机制(特定目标1)，以及确定HXA3生产是如何调节的(特定目标2)。为了实现这些目标，我们计划使用互补的体外和体内模型的组合，结合最先进的细胞、分子和生化技术。我们假设，了解基于HXA3/MRP2的信号，指导PMN在肠道上皮细胞的移动，将导致重要治疗药物的开发，旨在帮助控制感染性、过敏性和特发性(IBD)结肠炎患者的这种炎症事件。 公共卫生相关性：据估计，多达100万美国人患有炎症性肠病(IBD)，这一数字平均分为克罗恩病和溃疡性结肠炎。男性和女性似乎同样受到影响。IBDS包括克罗恩病和溃疡性结肠炎，是一种病因不明的慢性复发性胃肠道炎症性疾病。虽然IBD的确切发病机制尚不清楚，但有证据表明，它涉及免疫系统、遗传易感性和环境之间的相互作用。这些疾病的特点是中性粒细胞(PMN)明显渗入结肠粘膜病变，并伴有上皮细胞坏死和溃疡。此外，疾病活动性和患者症状与组织学发现的PMN在粘膜和表面上皮内的浸润性相关。奇怪的是，在沙门氏菌肠炎血清鼠伤寒沙门氏菌(沙门氏菌病)引起的胃肠炎的急性期，同样发生了中性粒细胞大量跨上皮迁移的组织学事件。因此，虽然这些反应的进化很可能最初针对的是病原体，如鼠伤寒沙门氏菌，但可能也会发生这些途径的异常激活，导致不适当的活动性肠道炎症状态。这项建议的目的是了解鼠伤寒沙门氏菌触发和控制PMN在上皮表面定向移动的分子机制，以便为此类炎症性肠道疾病的治疗干预确定新的靶点。

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.