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

描述（由申请人提供）：本竞争性更新申请将测试关于人多形核白细胞（PMN）和摄入的金黄色葡萄球菌（SA）之间相互作用及其对人PMN、SA感染和炎症结局的影响的三种新假设。摄入的SA的一个显着的分数在PMN中存活，并提示PMN启动导致非典型凋亡的细胞命运程序。这些凋亡的SA负载的PMN通过不完全定义的机制与巨噬细胞（Mf）结合，扭曲Mf细胞因子谱，并阻断巨噬细胞增多。未被Mf内化的载有SA的PMN经历坏死性细胞死亡和溶解，从而释放出在通过PMN后更具毒性的活SA。在我们的新的框架内，在PMN中的杀微生物事件的综合观点，我们将确定SA的转录反应，介导他们的生存在PMN中，定义由PMN启动的信号通路，在响应于激活的细胞内SA，触发非典型的和最终的坏死性细胞死亡看到SA感染的PMN。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摄取其中存活SA持续存在的PMN的偏斜细胞因子谱。后者的研究将提供重要的洞察SA如何破坏细胞事件，通常最终在炎症的解决和恢复组织稳态。每一个相互关联但又相互独立的目标都得到了有力的初步数据的支持。目的1确定SA在人PMN吞噬体中存活的机制和结果我们将确定SA上调msrA 1/B、YjiE和其它对HOCl和其它PMN产生的毒素的转录应答如何促进SA存活（1.A.i-iii）以及对PMN和Mf的功能结果（1.B.）。目的2确定SA感染过程中PMN和Mf功能变化的机制我们将确定信号通路并确定PMN-SA“非典型”凋亡的分子基础（2.A.）--关注Mcl-1（2.A.i）、IL-1b（2.A.ii）和HIF-1a（2.A.iii）--Mf降低PMN-SA的胞浆细胞增多作用及其对促进炎症的影响（2.B），以及PMN-SA最终的坏死细胞死亡（2.C）。我们的研究将确定机制负责非典型凋亡和坏死性死亡的中性粒细胞，从而提供新的见解吞噬细胞控制炎症反应的基本方面。从微生物的角度来看，我们将确定由PMN暴露诱导的存活SA的转录适应的功能后果，从而提供对SA脆弱性的深入了解，可以利用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.