Mechanisms of lung macrophage programming by MUC5B during health and disease

项目摘要 每天，肺部都暴露在数十亿颗粒物中，这些颗粒物的积累可能会导致感染， 损害虽然防范这些风险至关重要，但同样重要的是， 由炎症引起的最小生理破坏或损伤。粘液和巨噬细胞清除率是 标志性的非炎症防御存款在气道的颗粒和病原体被困在粘液 并通过纤毛和咳嗽力消除，而肺泡中的那些被肺泡巨噬细胞（AM）摄取。 使用Muc 5 b基因敲除小鼠，我们先前表明Muc 5 b是有效的粘膜纤毛清除所必需的 以及用于维持健康的驻留AM池。本提案的主要目的是确定 Muc 5 b在体内平衡和急性和急性期调节AM功能的特定机制， 消除炎症。我们已经确定了一种新的机制，通过以下途径将Muc 5 b与AM功能直接联系起来 唾液酸结合免疫球蛋白型凝集素受体-F（Siglec-F），一种抑制性免疫受体， 由常驻AM选择性表达，已知可结合含α 2，3-连接唾液酸的糖缀合物。 Muc 5 b是α 2，3-唾液酸化的，是一种内源性Siglec-F配体。我们提出，通过刺激Siglec-F， Muc 5 b校准静息肺中的AM炎症反应。因此，在健康状态下， AM发挥保护作用，同时限制潜在的有害炎症反应， 通过由Muc 5 b刺激Siglec-F介导的稳态编程机制发生。当 体内平衡被诸如细菌的刺激物破坏，暂时诱导AM炎性 需要作出反应。此外，常驻AM还加入了由以下来源产生的招募的巨噬细胞： 循环单核细胞这些募集的单核细胞来源的AM（MPAM）缺乏Siglec-F，并且高度亲脂。 煽动性在招募MDAM的同时，驻地AM下调其Siglec-F 表达并成为促炎症。随着炎症消退，招募的MADAM发生细胞凋亡， 被消除，而驻留AM恢复Siglec-F表达并恢复到其非炎症状态。 我们假设MUC 5 B：Siglec-F信号传导的短暂减少允许炎症反应， MUC 5 B的恢复：需要Siglec F信号传导来解决它。我们假设， Muc 5 b的Siglec-F是在炎症过程中控制巨噬细胞炎症反应的主要机制。 稳态和炎症。我们将使用野生型和基因工程小鼠，急性 炎症和免疫学读数，以在以下三个具体目的中测试该假设：1.测试 假设在体内平衡期间，保护性AM活性由MUC 5 B唾液酸聚糖维持， 依赖性Siglec-F刺激。2.检验MUC 5 B：Siglec-F依赖性抑制性 在急性炎症过程中失去了机制。3.检验MUC 5 B与MUC 5 B的重新接合的假设。 AM上的Siglec-F驱动炎症的消退。

PROJECT SUMMARY Each day, the lungs are exposed to billions of particles whose accumulation can potentially cause infection and damage. While it is crucial to defend against these exposures, it is equally important that protection occurs with minimal physiological disruption or injury caused by inflammation. Mucus and macrophage clearance are hallmark non-inflammatory defenses. Particles and pathogens that deposit in the airways are trapped in mucus and eliminated by ciliary and cough forces, while those in alveoli are ingested by alveolar macrophages (AMs). Using Muc5b knockout mice, we previously showed that Muc5b is required for effective mucociliary clearance and for maintaining healthy pools of resident AMs. The primary objective of this proposal is to determine specific mechanisms by which Muc5b regulates AM function during homeostasis and during acute and resolving inflammation. We have identified a novel mechanism that directly links Muc5b to AM function via sialic acid-binding immunoglobulin-type lectin receptor-F (Siglec-F), an inhibitory immunoreceptor that is expressed selectively by resident AMs and is known to bind α2,3-linked sialic acid-containing glycoconjugates. Muc5b is α2,3-sialylated and is an endogenous Siglec-F ligand. We propose that stimulation of Siglec-F by Muc5b calibrates AM inflammatory responses in the resting lung. Thus, in healthy states, the ability of resident AMs to serve protective roles while simultaneously limiting potentially injurious inflammatory responses may occur by a homeostatic programming mechanism mediated by stimulation of Siglec-F by Muc5b. When homeostasis is disrupted by stimuli such as bacteria, a temporary induction of AM inflammatory responsiveness is required. Furthermore, resident AMs are joined by recruited macrophages that arise from circulating monocytes. These recruited monocyte-derived AMs (MDAMs) lack Siglec-F and are highly pro- inflammatory. At the same time that MDAMs are recruited, resident AMs down-regulate their Siglec-F expression and become pro-inflammatory. As inflammation resolves, recruited MDAMs undergo apoptosis and are eliminated, whereas resident AMs restore Siglec-F expression and return to their non-inflammatory states. We postulate that transient reduction of MUC5B:Siglec-F signaling permits an inflammatory response and that restoration of MUC5B:Siglec F signaling is required for its resolution. We hypothesize that stimulation of Siglec-F by Muc5b is a major mechanism for controlling macrophage inflammatory responses during homeostasis and inflammation. We will use wild type and genetically engineered mice, models of acute inflammation, and immunological readouts to test this hypothesis in the following three Specific Aims: 1. Test the hypothesis that during homeostasis, protective AM activities are maintained by MUC5B sialyl glycan- dependent Siglec-F stimulation. 2. Test the hypothesis that MUC5B:Siglec-F dependent inhibitory mechanisms are lost during acute inflammation. 3. Test the hypothesis that re-engagement of MUC5B with Siglec-F on AMs drives the resolution of inflammation.