Neuroendocrine control of TLR4-dependent inflammation in influenza

总结 流感是一种高度传染性的呼吸道疾病，CDC估计约有4750万人感染 从2019年10月1日至2020年4月4日，美国人死亡人数高达62，00人。在缺乏“普遍性”的情况下， 流感疫苗，“每年接种疫苗，强烈建议;然而，每种疫苗的组成， 基于对哪种菌株将在下一年占主导地位的预测， 不正确.批准的抗病毒药物可以通过限制病毒复制来改善疾病，但必须在 在感染早期要有效，耐药流感病毒株已经出现。流感引起的疾病 是由病毒复制引发的，导致气道上皮损伤，严重的炎症反应， 作为先天免疫细胞中代谢应激的结果（例如，巨噬细胞）最终释放出“细胞因子 风暴”，可能导致急性呼吸窘迫综合征（ARDS）和死亡。因此，一种新的方法， 靶向宿主先天性免疫反应将代表流感治疗的一个非常重要的进展 以及其他导致ARDS的呼吸道病毒，例如，SARS-CoV-2.我们已经鉴定出Toll样受体 4（TLR 4），一种模式识别受体，以其感知革兰氏阴性脂多糖的能力而闻名 (LPS)作为宿主对流感的炎症反应的关键。这最初令人惊讶，因为流感病毒 不表达任何通过TLR 4引发炎症的“病原体相关分子模式”。 尽管如此，使用TLR 4-/-小鼠和多种TLR 4拮抗剂在小鼠流感模型中， 感染，以及对非适应菌株敏感的棉鼠（Sigmodon hispidus; CR） 在人类流感中，我们严格证明了TLR 4信号传导是肺生成的中心， 全身炎症反应感染。我们鉴定了一种宿主衍生蛋白，高迁移率族蛋白1 （HMGB 1），在感染过程中从垂死细胞释放，作为一种“与癌症相关的分子模式”， 从而通过其共受体MD 2触发TLR 4。最近，我们发现了第二种宿主衍生蛋白， 胃泌素释放肽（GRP），作为流感介导的疾病的贡献，使用三种不同的抑制剂， GRP或GRP受体信号传导显著减弱细胞因子的产生、肺病理学和致死性， 给小鼠进行治疗。我们发表的和初步的数据支持中心假设， 这两种介质是相互关联的，并且在宿主对流感感染的反应期间会聚。在两 具体的目的，我们建议（1）描绘流感介导的相互作用之间的GRP受体（GRPR）- 和TLR 4/MD 2介导的信号传导，以及（2）将GRP和HMGB 1水平与两种疾病的严重程度相关联。 流感诱导疾病和流感感染患者的不同实验模型。在这个探索性的 R21的应用，我们将寻求确定这两者之间关系的机制基础 信号通路，具有确定治疗策略以改善疾病的潜力。

SUMMARY Influenza is a highly contagious respiratory illness that the CDC has estimated to afflict ~47.5 million Americans with up to 62,00 deaths from October 1, 2019 to April 4, 2020. In the absence of a “universal influenza vaccine,” yearly vaccination is strongly recommended; however, the composition of each vaccine is based on predictions of which strains will predominate in the following year and such predictions may be incorrect. Approved antivirals can ameliorate disease by limiting viral replication, but they must be administered early in infection to be effective, and resistant influenza strains have emerged. While influenza-induced disease is initiated by viral replication resulting in airway epithelial damage, the severe inflammatory response that follows as a result of metabolic stress in innate immune cells (e.g., macrophages) ultimately elicits a “cytokine storm” that may lead to acute respiratory distress syndrome (ARDS) and death. Thus, a new approach that targets the host innate immune response would represent a highly significant therapeutic advance for influenza as well as other respiratory viruses that lead to ARDS, e.g., SARS-CoV-2. We have identified Toll-like receptor 4 (TLR4), a pattern recognition receptor best known for its ability to sense Gram-negative lipopolysaccharide (LPS), as key to the host inflammatory response to influenza. This was initially surprising since influenza virus does not express any “pathogen-associated molecular patterns” that trigger inflammation via TLR4. Nonetheless, using both TLR4-/- mice and multiple TLR4 antagonists in both a mouse model of influenza infection, as well as in cotton rats (Sigmodon hispidus; CR) that are susceptible to non-adapted strains of human influenza, we rigorously demonstrated that TLR4 signaling is central to the generation of lung and systemic inflammation in response to infection. We identified a host-derived protein, High Mobility Group Box-1 (HMGB1), released from dying cells during infection, that acts as a “danger-associated molecular pattern,” thereby triggering TLR4 through its co-receptor, MD2. Recently, we identified a second host-derived protein, gastrin-releasing peptide (GRP), as contributory to influenza-mediated disease, using three distinct inhibitors of GRP or GRP receptor signaling to significantly blunt cytokine production, lung pathology, and lethality when administered to mice therapeutically. Our published and preliminary data support the central hypothesis that these two mediators are interrelated and converge during the host response to influenza infection. In two Specific Aims, we propose to (1) delineate influenza-mediated interactions between GRP receptor (GRPR)- and TLR4/MD2-mediated signaling, and (2) correlate GRP and HMGB1 levels with disease severity in two distinct experimental models of influenza-induced disease and in influenza-infected patients. In this exploratory R21 application, we shall seek to identify the mechanistic underpinnings of the relationship between these two signaling pathways with the potential of identifying therapeutic strategies to ameliorate disease.