Innate immune defense against community associated methicillin-resistant S.aureus

描述(由申请人提供)：这项竞争性更新申请将测试三个关于人多形核白细胞(PMN)和摄入的金黄色葡萄球菌(SA)之间相互作用的新假设，以及它们对人类PMN、SA感染和炎症命运的影响。大量摄入的SA存活在PMN中，促使PMN启动细胞命运程序，导致非典型细胞凋亡。这些凋亡的、携带SA的PMN与巨噬细胞(MF)结合，扭曲MF的细胞因子谱，并通过不完全明确的机制阻止吞噬作用。携带SA的PMN没有被MF内化，会发生细胞坏死和裂解，从而释放出通过PMN后更具毒力的活性SA。在我们对PMN中杀菌事件的新的、综合的观点的框架内，我们将确定SA在PMN中介导它们生存的转录反应，定义由PMN启动的信号通路，以响应活性的细胞内SA，触发在SA感染的PMN中看到的非典型和最终的坏死性细胞死亡。最后，我们将确定MF未能清除PMN-SA的机制基础和后果，以及MF摄取PMN的扭曲的细胞因子谱，在PMN中存活的SA持续存在。后一项研究将为SA如何破坏细胞事件提供重要的见解，这些事件通常最终导致炎症的消退和组织内稳态的恢复。每个相互关联但又相互独立的目标都得到了强有力的初步数据的支持。目的1确定SA在人PMN吞噬小体中存活的机制和后果我们将确定SA上调msrA1/B、YjiE和其他转录反应如何促进SA存活(1.A.i-III)以及对PMN和Mf的功能影响(1.B.)。目的2确定金黄色葡萄球菌感染中性粒细胞和中性粒细胞功能改变的机制我们将确定信号转导途径，并确定PMN-SA(2.A.)“非典型”凋亡的分子基础--重点是Mc1-1(2.A.i)、IL-1b(2.A.ii)和HIF-1a(2.A.iii)--MF减少PMN-SA的吞噬作用及其促进炎症的作用(2.b)，以及PMN-SA最终的坏死性细胞死亡(2.c)。我们的研究将确定导致PMN非典型凋亡和坏死性死亡的机制，从而为吞噬细胞控制炎症反应的基本方面提供新的见解。从微生物的角度，我们将确定PMN暴露诱导的存活SA转录适应的功能后果，从而为SA脆弱性提供洞察，可作为治疗攻击的新靶点。

DESCRIPTION (provided by applicant): This competitive renewal application will test three novel hypotheses about the interactions between human polymorphonuclear leukocytes (PMN) and ingested Staphylococcus aureus (SA) and their implications for the fate of human PMN, SA infection and inflammation. A significant fraction of ingested SA survives in PMN and prompts PMN to initiate cell fate programs that result in atypical apoptosis. These apoptotic, SA-laden PMN bind to macrophages (Mf), skew Mf cytokine profiles, and block efferocytosis, by incompletely defined mechanisms. SA-laden PMN not internalized by Mf undergo necrotic cell death and lysis, thereby releasing viable SA that are more virulent after passage through PMN. Within the framework of our novel, integrated view of microbicidal events in PMN, we will determine the transcriptional responses of SA that mediate their survival in PMN, define signaling pathways initiated by PMN in response to viable intracellular SA that trigger the atypical and eventual necrotic cell death seen in SA-infected PMN. Lastly, we will determine the mechanistic basis for and consequences of the failure of Mf to clear PMN-SA and the skewed cytokine profile of Mf that ingest PMN in which viable SA persist. The latter studies will provide important insight into how SA undermine cellular events that normally culminate in resolution of inflammation and return to tissue homeostasis. Each of the inter-related but independent aims is supported by strong preliminary data. Aim 1 Determine the mechanisms and consequences of survival of SA in human PMN phagosomes We will determine how SA upregulation of msrA1/B, YjiE, and other transcriptional responses to HOCl and other PMN- generated toxins promote SA survival (1.A.i-iii) and the functional consequences to PMN and Mf (1.B.). Aim 2 Determine mechanisms for functional changes in PMN and Mf during SA infection We will identify the signalling pathways and determine the molecular basis for "atypical" apoptosis of PMN-SA (2.A.) -- focusing on Mcl-1 (2.A.i), IL-1b (2.A.ii), and HIF-1a (2.A.iii) -- the decreased efferocytosis of PMN-SA by Mf and its impact on promoting inflammation (2.B), and the eventual necrotic cell death of PMN-SA (2.C). Our studies will identify mechanisms responsible for the atypical apoptosis and necrotic death of PMN, thereby providing novel insights into fundamental aspects of phagocyte control of the inflammatory response. From the microbial perspective, we will identify the functional consequences of transcriptional adaptations of surviving SA that were induced by PMN exposure, thus providing insight into SA vulnerability that could be exploited as novel targets for therapeutic attack.