ROLE OF B.FRAGILIS OXYGEN STRESS RESPONSE IN INFECTION

描述（由申请人提供）：破坏宿主与其本地微生物群之间的防御屏障可导致机会性感染，对人类健康产生严重影响。腹内脓肿通常是由阑尾炎、憩室炎、癌或手术引起的肠穿孔后形成的。这些感染是由混合肠道菌群组成的，本地肠道厌氧菌，脆弱拟杆菌为主要成分。我们假设抗氧化应激是这些感染发生的一个重要因素。这是因为相对于结肠，腹膜腔是一个含氧环境，pmn在感染部位的招募将导致脆弱杆菌暴露于活性氧。在目前的资助期内，我们已经证明存在急性氧化应激反应，其目的是尽量减少氧自由基的直接影响。这是由调节氧合受体介导的，氧合受体是小鼠最佳脓肿形成所必需的。我们还表明，当长期暴露于氧化应激时，存在一种新的、广泛的与代谢相关的基因诱导。对于目前的应用，我们假设这个延长的阶段和伴随的代谢基因的广泛诱导对于延长氧化应激的抗性和在肠外部位的体内存活是至关重要的。我们将了解这种延长氧化应激（POST）反应如何促进对延长氧化应激的适应，确定是否有必要维持生物体处于抵抗状态，并阐明控制它的一些机制。最终，我们将发现它是否增强了脓肿环境中坏死细胞碎片、活pmn和宿主血清因子的持久性。三个目标将解决这一中心假设。三个具体目标将解决这一中心假设。在特定的目的中，我们将阐明调节POST反应的机制，确定它是如何被应激刺激控制的，以及它是否导致多重应激抵抗。在具体的目标2中，我们将展示一个强大的硫醇代谢是POST反应的一个组成部分，并确定它是否需要在体内生存。最后，在特定的Aim 3中，我们将研究铁储存的机制以及它们如何帮助防止POST期间的氧化损伤。我们将确定铁储存蛋白是否可以促进铁硫蛋白的修复，并测量其同源基因的体内表达，以深入了解它们在感染过程中的作用。

DESCRIPTION (provided by applicant): Disruption of the defense barriers between the host and its indigenous microflora can lead to opportunistic infections which have a serious impact on human health. Intra-abdominal abscesses are formed following perforation of the bowel often due to appendicitis, diverticulitis, carcinoma, or surgery. These infections are composed of mixed intestinal flora with the indigenous intestinal anaerobe, Bacteroides fragilis as the predominant component. We hypothesized that resistance to oxidative stress is an important factor in the development of these infections. This is because relative to the colon, the peritoneal cavity is an oxygenated environment, and the recruitment of PMNs to the site of infection will result in exposure of B. fragilis to reactive oxygen species. In the current funding period we have documented that there is an acute oxidative stress response which is designed to minimize the immediate affects of oxygen radicals. This is mediated by the regulator OxyR which is necessary for optimal abscess formation in mice. We also have shown that there is a novel, widespread induction of genes associated with metabolism, which occurs when there is extended exposure to oxidative stress. For the current application, we hypothesize that this extended phase and the accompanying expansive induction of metabolic genes is critical for prolonged resistance to oxidative stress and for in vivo survival in extra-intestinal sites. We will learn how this Prolonged Oxidative STress (POST) response promotes adaptation to extended oxidative stress, determine if it is necessary to maintain the organism in a resistant state and elucidate some of the mechanisms that control it. Ultimately we will discover if it enhances persistence in the abscess milieu of necrotic cell debris, viable PMNs, and host serum factors. Three aims will address this central hypothesis. Three specific aims will address this central hypothesis. In specific aim1 we will elucidate the mechanisms that regulate the POST response, determine how it is controlled by stress stimuli, and if it leads to multiple stress resistance. In specific aim 2 we will show that a robust thiol metabolism is an integral component of the POST response and determine if it is needed to survive in vivo. Finally in specific Aim 3 we will examine mechanisms of iron storage and how they help prevent oxidative damage during POST. We will determine if the iron storage proteins can contribute to the repair of iron sulfur proteins and the in vivo expression of their cognate genes will be measured to gain insight into their role during infection. PUBLIC HEALTH RELEVANCE: Every mucosal surface of the human body is inhabited by bacteria that have developed a commensal relationship with their host. Bacteroides fragilis is part of this indigenous, "normal", flora in the colon and the primary goal of this research is learn how it causes intra-abdominal infections after being translocated from the colon due to disease or trauma. The successful completion of this research could lead to the discovery innovative new treatment strategies based on intervention in the pathogenic process or unique properties of the organism.