Dysregulation of the inflammatory response by Francisella tularensis

土拉弗朗西斯菌引起的炎症反应失调

• 批准号: 8803366
• 负责人: Lee-Ann H Allen
• 金额: --
• 依托单位: IOWA CITY VA MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-04-01 至 2017-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8803366
• 关键词: Accounting; Acute; Affect; Alveolus; Animals; Apoptosis; Apoptotic; BAX gene; BIRC4 gene; Bacteria; Bacterial Genes; Biological Warfare; Breathing; Bronchioles; Calpain; Caspase; Cells; Cessation of life; Characteristics; Chronic Obstructive Airway Disease; Cytosol; Data; Defect; Development; Disease; Down-Regulation; Event; Francisella tularensis; Gene Expression; Gene Expression Profile; Genes; Goals; Granuloma; Health; Host Defense; Human; Immune; Immunoglobulin M; Infection; Infection prevention; Inflammatory Response; Inhibition of Apoptosis; Leukocytes; Libraries; Life; Longevity; Lung; Lung diseases; Macaca mulatta; Manuscripts; Mediating; Microbe; Mitochondria; Molecular; Molecular Mechanisms of Action; Mus; NADPH Oxidase; Necrosis; Organism; Oryctolagus cuniculus; Pathogenesis; Pathway interactions; Phagocytes; Phagocytosis; Phagosomes; Play; Pneumonia; Process; Rattus; Regulation; Resolution; Role; Surface; Symptoms; Testing; Therapeutic; Tissues; Tularemia; Veterans; Virulence; Virulence Factors; Virulent; Zoonoses; antimicrobial; calpastatin; insight; interest; macrophage; microbicide; mutant; neutrophil; particle; pathogen; prevent; programs; receptor; screening

DESCRIPTION (provided by applicant): Tularemia is a potentially fatal zoonosis of humans caused by the facultative intracellular bacterium, Francisella tularensis, and inhalation of as few as ten organisms is sufficient to cause severe pneumonic disease, tissue necrosis, and death. Accumulation of neutrophils (polymorphonuclear leukocytes, PMNs) in the lungs is essential for development of severe disease in animals infected with this pathogen, and tissue destruction progresses steadily as more alveoli and bronchioles become clogged with infected PMNs and debris. Direct evidence that neutrophils contribute to tularemia progression and pathogenesis rather than effective host defense is demonstrated by the fact that blockade of PMN influx into the lung is protective, and animals survive what would otherwise be a lethal infection. Nevertheless, most studies of F. tularensis have focused on the fate of this organism in macrophages. Our long-term goal is to define in detail the role of human neutrophils in the pathogenesis of tularemia. To this end we have made several important discoveries. We have shown that natural IgM is required for opsonization of F. tularensis and identified receptors that mediate infection of both neutrophils and macrophages. We discovered that evasion of oxidative host defense is achieved via the ability of F. tularensis to act at multiple levels to disrupt NADPH oxidase assembly and activity, and identified relevant virulence factors. We were also the first to show that F. tularensis can escape the phagosome and replicate in neutrophil cytosol, confirming its ability to successfully infect multiple phagocytes types. Particularly relevant here is our discovery of PMN-specific aspects of virulence. Neutrophils are short-lived cells that are preprogrammed to die by constitutive apoptosis, a process that is typically accelerated by phagocytosis and is essential for resolution of the inflammatory response. In marked contrast, we find that F. tularensis inhibits PMN apoptosis and significantly prolongs cell lifespan, and this is achieved, in part, via effects on neutrophil gene expression. These data are noteworthy as defects in PMN turnover are indicative of an ineffective and dysregulated inflammatory response. Timely clearance of dying PMNs by macrophages is essential to prevent necrosis and tissue damage, and our preliminary data suggest that this process may also be impaired. In view of these data we hypothesize that F. tularensis inhibits PMN apoptosis by affecting expression of a specific subset of anti- and proapoptotic genes and pro-survival factors, and that defects in clearance of infected PMNs by macrophages favors cell necrosis, sustains infection, and prevents the reprogramming of macrophages that is required for termination of the inflammatory response. To test this, we propose the following Specific Aims: 1. To elucidate the molecular mechanisms of apoptosis inhibition by F. tularensis with a focus on the BAX, XIAP and calpastatin. 2. To identify bacterial genes required for PMN apoptosis inhibition. 3. To elucidate the functional consequences of prolonged neutrophil lifespan. We expect that completion of the proposed studies will provide fundamental insight into the molecular mechanisms that account for the dysregulated inflammatory response that is characteristic of tularemia, and that our findings will also inform studies of other diseases that are also characterized by defects in PMN turnover, and affect Veterans more frequently, such as chromic obstructive pulmonary disease.

描述（由申请人提供）： 土拉热病是一种潜在致命的人类人畜共患病，由兼性细胞内细菌土拉弗朗西斯菌引起，吸入少至 10 种生物体就足以引起严重的肺炎疾病、组织坏死和死亡。肺部中性粒细胞（多形核白细胞，PMN）的积累对于感染这种病原体的动物发展为严重疾病至关重要，并且随着更多的肺泡和细支气管被感染的 PMN 和碎片堵塞，组织破坏稳步进展。中性粒细胞促进土拉菌病的进展和发病机制而不是有效的宿主防御的直接证据是，阻断中性粒细胞流入肺部具有保护作用，并且动物在原本致命的感染中存活下来。然而，大多数关于土拉弗朗西斯菌的研究都集中在该生物体在巨噬细胞中的命运。我们的长期目标是详细确定人类中性粒细胞在兔热病发病机制中的作用。为此，我们取得了几项重要发现。我们已经证明，土拉弗朗西斯菌的调理作用需要天然 IgM，并鉴定了介导中性粒细胞和巨噬细胞感染的受体。我们发现，土拉弗朗西斯菌能够在多个水平上破坏 NADPH 氧化酶的组装和活性，从而逃避宿主的氧化防御，并确定了相关的毒力因子。我们还首次证明土拉弗朗西斯菌可以逃脱吞噬体并在中性粒细胞胞质中复制，证实了其成功感染多种吞噬细胞类型的能力。与此特别相关的是我们对 PMN 毒力特异性方面的发现。中性粒细胞是寿命较短的细胞，被预先编程为通过组成性细胞凋亡而死亡，这一过程通常通过吞噬作用加速，对于解决炎症反应至关重要。与此形成鲜明对比的是，我们发现 F. tularensis 抑制 PMN 凋亡并显着延长细胞寿命，这部分是通过 对中性粒细胞基因表达的影响。这些数据值得注意，因为中性粒细胞更新的缺陷表明炎症反应无效且失调。巨噬细胞及时清除垂死的中性粒细胞对于防止坏死和组织损伤至关重要，我们的初步数据表明这一过程也可能受到损害。鉴于这些数据，我们假设土拉弗朗西斯通过影响抗凋亡基因和促凋亡基因以及促生存因子的特定子集的表达来抑制中性粒细胞凋亡，并且巨噬细胞清除受感染中性粒细胞的缺陷有利于细胞坏死，维持感染，并阻止终止炎症反应所需的巨噬细胞重新编程。为了测试这一点，我们提出以下具体目标： 1. 阐明 F. tularensis 抑制细胞凋亡的分子机制，重点关注 BAX、XIAP 和 calpastatin。 2. 鉴定抑制PMN凋亡所需的细菌基因。 3. 阐明中性粒细胞寿命延长的功能后果。我们预计，拟议研究的完成将为兔热病特征性炎症反应失调的分子机制提供基本见解，并且我们的研究结果还将为其他也以中性粒细胞周转缺陷为特征的疾病的研究提供信息，并更频繁地影响退伍军人，例如慢性阻塞性肺病。