ROLE OF B.FRAGILIS OXYGEN STRESS RESPONSE IN INFECTION

描述(由申请人提供)：破坏宿主与其本土微生物群之间的防御屏障可导致机会性感染，对人类健康造成严重影响。腹内脓肿是由于阑尾炎、憩室炎、癌症或手术导致肠穿孔后形成的。这些感染是由肠道混合菌群组成的，本土肠道厌氧菌脆弱类杆菌是主要成分。我们假设，对氧化应激的抵抗是这些感染发展的一个重要因素。这是因为相对于结肠，腹膜腔是一个充氧环境，中性粒细胞重新聚集到感染部位会导致脆弱芽孢杆菌暴露在活性氧物种中。在目前的筹资期间，我们记录了急性氧化应激反应，旨在最大限度地减少氧自由基的直接影响。这是由OxyR调节因子介导的，OxyR是小鼠最佳脓肿形成所必需的。我们还表明，存在一种与新陈代谢相关的新的、广泛的基因诱导，当长期暴露在氧化应激中时会发生这种情况。对于目前的应用，我们假设这种延长的阶段和伴随的代谢基因的扩张诱导对于延长对氧化应激的抵抗和体内肠外部位的存活至关重要。我们将学习这种长期的氧化应激(POST)反应如何促进对长期氧化应激的适应，确定是否有必要保持有机体处于抵抗状态，并阐明控制它的一些机制。最终，我们将发现它是否增强了在坏死性细胞碎片、存活的中性粒细胞和宿主血清因素的脓肿环境中的持久性。三个目标将解决这一核心假设。三个具体目标将解决这一核心假设。在特定的目标1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。在特定的目标2中，我们将证明强大的硫醇代谢是POST反应的一个组成部分，并确定它是否是在体内生存所必需的。最后，在具体目标3中，我们将检查铁存储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有助于铁硫蛋白的修复，并将测量它们的同源基因在体内的表达，以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.