RSV-induced M2 macrophage differentiation: role of TLR4/PPARg/RXR signaling axis (80)

项目总结/摘要 单核细胞和巨噬细胞（Mf）感测病原体、组织损伤和宿主源性免疫缺陷的存在。 介质在他们的环境和响应分化成不同的功能表型，介导 宿主先天免疫反应。例如，“经典活化”（M1）巨噬细胞具有高度杀微生物性， 但是它们产生的炎症介质也可能损害宿主组织。在函数的另一端， 由IL-4和IL-13诱导的“交替激活”（M2）巨噬细胞介导“伤口愈合” 通过消除受损组织和其他抗炎机制。 布兰科和沃格尔实验室密切合作，研究宿主对呼吸道感染的反应。 合胞病毒（RSV）是婴儿、老年人严重下呼吸道感染的最重要原因， 和免疫抑制的个体。在野生型（WT）小鼠中，RSV感染导致早期、短暂的M1 Mf再表达， 在肺中发生反应，随后是更持续的M2 Mf优势期和炎症消退期， 炎性肺病理学我们报道了IL-4 Ra-/-小鼠，这些小鼠对RSV感染没有反应， 表现出极大增强的肺病理学，这可以通过过继转移WT Mf来克服，WT Mf 在RSV感染后分化为M2 Mf。重要的是，RSV诱导的TLR 4信号被证明是一个前 这是诱导转录因子过氧化物酶体增殖物激活受体γ（PPARg）所必需的。 PPARg与类维生素A X受体（RXR）形成异二聚体，所述RXR结合M2 Mf基因启动子并激活跨膜转运。 M2 Mf基因的转录。我们在此R21应用程序中的主要目标是更详细地定义机制 控制TLR 4诱导的PPARg/RXR信号轴和M2 Mf在解决 RSV感染。待检验的总体假设是RSV感染期间M1和M2 Mf的平衡 决定了RSV疾病的程度。通过比较WT小鼠和PPARg缺陷型Mf小鼠的反应， 在体内和体外，我们将确定TLR 4诱导的PPARg/RXR轴在调节M2 Mf中的作用。 RSV（Specific Aim 1）。在具体目标2中，靶向TLR 4诱导的PPARg/RXR信号- 在RSV的棉鼠模型中，我们将使用棉鼠来扩展我们的发现，棉鼠是RSV的金标准。 RSV疗法的开发，以检验PPARg和RXR激动剂的治疗性施用 将导致协同的M2 Mf分化，这反过来将减轻炎症性肺 通常由RSV感染引起的损伤。这两个目标是基于我们强大的出版和初步的 数据，并支持M1 MF介导的炎性肺损伤和M2 MF介导的炎性肺损伤之间的平衡的概念。 PPARg/RXR驱动的M2 Mf基因转录导致组织修复，决定了最终结果。在 根据这些探索性研究的结论，导致Mf激活变化的关键过程将是 定义，反过来，预计将转化为合理和实用的治疗方法， 作用于由RSV诱导的炎性肺损伤，以及可能的其它试剂（例如，流感，SARS-CoV-2）。

PROJECT SUMMARY/ABSTRACT Monocytes and macrophages (Mf) sense the presence of pathogens, tissue damage, and host-derived mediators in their environment and respond by differentiating into distinct functional phenotypes that mediate host innate immune responses. For example, “classically activated” (M1) macrophages are highly microbicidal, yet their production of inflammatory mediators may also damage host tissue. At the other end of a functional spectrum, “alternatively activated” (M2) macrophages, induced by IL-4 and IL-13, mediate “wound healing” through elimination of damaged tissue and other anti-inflammatory mechanisms. The Blanco and Vogel laboratories have worked closely together to study the host response to Respiratory Syncytial Virus (RSV), the most significant cause of severe lower respiratory tract infection in infants, the elderly, and immunosuppressed individuals. In wild-type (WT) mice, RSV infection elicits an early, transient M1 Mf re- sponse in the lung that is followed by a more sustained period of M2 Mf predominance and resolution of inflam- matory lung pathology. We reported that IL-4Ra-/- mice, that fail to respond to RSV infection with the development of M2 Mf, exhibit greatly enhanced lung pathology that can be overcome by adoptive transfer of WT Mf that differentiate into M2 Mf upon RSV infection. Importantly, RSV-induced TLR4 signaling was shown to be a pre- requisite for induction of the transcription factor peroxisome proliferator-activated receptor gamma (PPARg). PPARg forms heterodimers with retinoid X receptor (RXR) that bind to M2 Mf gene promoters and activate tran- scription of M2 Mf genes. Our primary objective in this R21 application is to define in greater detail mechanisms governing the TLR4-induced PPARg/RXR signaling axis and the consequences of M2 Mf in the resolution of RSV infection. The overarching hypothesis to be tested is that the balance of M1 and M2 Mf during RSV infection dictates the extent of RSV disease. By comparing the responses of WT mice and mice with PPARg-deficient Mf in vivo and in vitro, we will determine the role of TLR4-induced PPARg/RXR axis in the regulation of M2 Mf development in RSV (Specific Aim 1). In Specific Aim 2, Targeting the TLR4-induced PPARg/RXR signal- ing axis in the cotton rat model of RSV, we will extend our findings using cotton rats, the gold standard for development of RSV therapies, to test the hypothesis that therapeutic administration of PPARg and RXR agonists to infected cotton rats will result in synergistic M2 Mf differentiation that, in turn, will mitigate inflammatory lung damage normally caused by RSV infection. These two aims are based on our strong published and preliminary data, and support the concept that the balance between M1 Mf-mediated inflammatory lung damage and PPARg/RXR-driven transcription of M2 Mf genes, leading to tissue repair, dictates the ultimate outcome. At the conclusion of these exploratory studies, key processes that lead to changes in Mf activation will have been defined that, in turn, are expected to translate into reasonable and practical therapeutic approaches for counter- acting inflammatory lung damage induced by RSV, and possibly other agents (e.g., influenza, SARS-CoV-2).