Differentiative Signals for Macrophage Activation

描述(申请人提供)：单核细胞和巨噬细胞在其环境中感知病原体、肿瘤、组织损伤和宿主衍生的介质，并通过分化为不同的功能表型来调节宿主的先天性免疫反应。然而，巨噬细胞的分化过程被描述为“可塑性”，这意味着这些细胞可以通过分化来可逆地调节其功能，以应对环境的快速变化。例如，“经典激活的”巨噬细胞(CA-MX)具有很强的杀菌活性，但它们产生的炎性细胞因子和一氧化氮可能会损害宿主组织。在功能谱的另一端，由IL-4和IL-13诱导的“交替激活的”巨噬细胞(AA-MX)通过清除受损组织和其他抗炎机制来调节“伤口愈合”。在过去的26年里，我的实验室一直试图更全面地了解巨噬细胞分化的复杂分子基础，以及这如何影响宿主防御和疾病结局。在这个资金周期中，我们的工作主要集中在保守的微生物结构(如细菌脂多糖(LPS)或呼吸道合胞病毒(RSV)融合蛋白(F))和细胞衍生细胞因子(如干扰素(IFN))诱导的Toll样受体(TLR)信号转导机制。在拟议的应用中，需要检验的总体假设是，TLR和/或细胞因子受体参与的特定细胞内信号通路的激活编程了促炎症和抗炎基因的离散盒表达，这些基因决定了宿主对感染的反应方式。提出了三个特定的目标来在体外和体内验证这一假说，最终目标是确定需要巨噬细胞来遏制入侵的病原体或预防或修复病原体造成的组织损伤的疾病的新的治疗干预措施。这项建议详细介绍了创新的实验方法，这些方法将：(1)定义MyD88，IRAK1和IRAK4与TRAF6之间最早的相互作用，介导TLR依赖的信号转导，并确定将防止IRAK4缺乏对细菌和病毒感染做出反应的补偿信号通路；(2)阐明TLR信号被负调控的新机制，无论是通过耗尽膜相关的TIRAP还是通过先前未知的内毒素耐受机制，以及(3)研究TLR4和干扰素-b在诱导AA-MX作为预防或修复RSV感染所致肺损伤的机制中的作用。在这些综合研究的结论中，我们将明确控制TLR激动剂和/或干扰素的初始相互作用导致巨噬细胞激活变化的过程，期望这些知识将转化为控制肿瘤或入侵病原体或对抗病原体引起的组织炎症损伤的合理治疗方法。 与公共卫生相关：巨噬细胞是白细胞，是抵御许多病原体的前线。这个项目的目标是深入了解巨噬细胞如何感知和响应入侵的微生物，这是通过分析调节其功能的分子过程获得的。我们的发现将导致开发新的药物，这些药物将提高巨噬细胞更有效地杀灭细菌和病毒的能力，或者预防或修复细菌或病毒感染对组织造成的损害。

DESCRIPTION (provided by applicant): Monocytes and macrophages sense pathogens, tumors, tissue damage, and host-derived mediators in their environment and respond by differentiating into distinct functional phenotypes that mediate host innate immune responses. However, the process of macrophage differentiation has been described in terms of its "plasticity," implying that these cells can modulate their functions reversibly through differentiation in response to rapid changes in the environment. For example, "classically activated" macrophages (CA-MX) are highly microbicidal, yet their production of inflammatory cytokines and nitric oxide may damage host tissue. At the other end of the functional spectrum, "alternatively activated" macrophages (AA-MX), induced by IL-4 and IL- 13, mediate "wound healing" through elimination of damaged tissue and other anti-inflammatory mechanisms. For the past 26 years of this grant, my laboratory has sought to understand more fully the complex molecular underpinnings of macrophage differentiation and how this impacts host defenses and disease outcome. Our work in this funding cycle has focused primarily on the mechanisms by which Toll-like receptor (TLR) signaling induced by conserved microbial structures, such as bacterial lipopolysaccharide (LPS) or Respiratory Syncytial Virus (RSV) fusion (F) protein, and cell-derived cytokines, such as interferons (IFNs), drive this complex process. In the proposed application, the overarching hypothesis to be tested is that activation of specific intracellular signaling pathways distal to TLR and/or cytokine receptor engagement programs expression of discrete cassettes of pro- and anti-inflammatory genes that dictate the manner in which the host responds to infection. Three Specific Aims are proposed to test this hypothesis in vitro and in vivo, with the ultimate goal of identifying novel therapeutic interventions for diseases where macrophages are required for containing the invading pathogen or preventing or repairing tissue damage caused by pathogens. This proposal details innovative experimental approaches that will: (1) define the earliest interactions between MyD88, IRAK1 and IRAK4, and TRAF6 that mediate TLR-dependent signaling and identify compensatory signaling pathways that will protect against IRAK4 deficiency in response to bacterial and viral infections; (2) elucidate novel mechanisms through which TLR signaling is negatively regulated, either through depletion of membrane- associated TIRAP or through previously unrecognized mechanisms of endotoxin tolerance, and (3) examine the roles of TLR4 and IFN-b in the induction of AA-MX as a mechanism for prevention or repair of lung damage induced by RSV infection. At the conclusion of these comprehensive studies, we will have defined processes that govern the initial interaction of TLR agonists and/or IFN that lead to changes in macrophage activation with the expectation that this knowledge will translate into reasonable therapeutic approaches for controlling tumors or invading pathogens or counteracting inflammatory damage to tissues induced by pathogens. PUBLIC HEALTH RELEVANCE: Macrophages are white blood cells that are the front line of defense against many pathogens. An in- depth understanding of how macrophages sense and respond to invading microbes, obtained by analyzing the molecular processes that mediate their functions, is the goal of this project. Our findings will lead to development of new drugs that will increase the capacity of macrophages to kill bacteria and viruses more effectively or to prevent or repair damage to tissues caused by bacterial or viral infection.