Enhancing neutrophil function in neutropenia-related pneumonia

项目摘要 中性粒细胞减少和相关感染是造血细胞最重要的剂量限制性毒性 移植（HCT）和抗癌化疗和放疗，影响生活质量和临床 结果，有可能导致死亡。40%的感染涉及中性粒细胞减少症相关肺炎， 除了血液以外的部位，通常用广谱抗生素治疗和G-CSF治疗。 然而，并非所有患者都对这些治疗有反应。该项目的长期目标是探索一种 治疗/预防血小板减少性肺炎的替代策略，即通过增强中性粒细胞 在贫血患者中的功能。我们试图通过提高细胞内PtdIns（3，4，5）P3信号来实现这一点 这条通路与各种中性粒细胞功能有关。我们证实了这一概念， 通过破坏PTEN增强PtdIns（3，4，5）P3信号传导增强了中性粒细胞功能和细菌 清除率和降低的死亡率。然而，PTEN 破坏与肿瘤发生有关，这使其不适合作为治疗靶点。最近我们 报道，中性粒细胞中的PtdIns（3，4，5）P3信号也可以通过破坏IP6K1（一种酶）而升高。 负责合成IP7，IP7是一种负调节PtdIns（3，4，5）P3信号传导的胞质分子。 重要的是，纯合子IP6K1 KO小鼠是存活的，并且没有表现出任何大体的身体或行为变化。 异常在这些小鼠中没有发现任何类型的肿瘤。基于这些有趣的结果，我们 假设IP6K1破坏应该是治疗 肺炎相关的肺炎。在上一个融资期，我们研究了IP6K1的作用是调节 中性粒细胞在细菌性肺炎中的功能与IP6K1中PtdIns（3，4，5）P3信号的升高一致 中性粒细胞缺陷，破坏IP6K1基因（全身KO）或抑制IP6K1活性 使用特异性抑制剂TNP高效且有效地增强宿主细菌杀灭能力， 由革兰氏阳性和革兰氏阴性细菌肺炎引起的肺损伤。出乎意料的是， IP6K1降低肺中性粒细胞积聚。我们发现，IP6K1介导的无机 血小板产生聚磷酸盐（polyP）是感染诱导的嗜血小板聚集所必需的 (NPA)在细菌性肺炎期间，促进嗜中性粒细胞在肺泡腔中积聚。作为 我们的总体目标之一是进一步了解IP6K1的作用，并设计针对IP6K1的最佳战略 在与支原体相关的肺炎中，我们将继续研究嗜衣原体特异性IP6K1破坏是否 足以诱导宿主防御的提高（目的1）。此外，我们将阐明血小板IP6K1在 调节血小板相关性肺炎中的肺中性粒细胞积聚（目的2）。最后我们将 直接研究用IP6K1抑制剂TNP治疗是否可以减轻血小板相关性肺炎 以及聚P或血小板输注是否能增强TNP的抗肺炎作用（目的3）。

Project Summary Neutropenia and related infection are the most important dose limiting toxicities in hematopoietic cell transplantation (HCT) and anti-cancer chemo- and radiotherapy, impacting on quality of life and clinical outcomes, with the potential to cause death. Neutropenia-related pneumonias are involved in 40% infections at a site other than blood alone and usually treated with broad-spectrum antibiotic therapy and G-CSF therapy. However, not all patients respond to these treatments. The long-term goal of this project is to explore an alternative strategy for treating/preventing neutropenia-related pneumonia, namely by enhancing neutrophil function in neutropenic patients. We tried to achieve this by elevating intracellular PtdIns(3,4,5)P3 signaling pathway which has been implicated in various neutrophil functions. We confirmed this concept by showing that augmenting PtdIns(3,4,5)P3 signal by disrupting PTEN enhanced neutrophil function and bacterial clearance, and reduced mortality rate in a murine model of neutropenia-related pneumonia. However, PTEN disruption is associated with tumorigenesis, which rendered it unsuitable as a therapeutic target. Recently we reported that PtdIns(3,4,5)P3 signal in neutrophils can also be elevated by disrupting IP6K1, an enzyme responsible for the synthesis of IP7, a cytosolic molecule that negatively regulates PtdIns(3,4,5)P3 signaling. Importantly, homozygous IP6K1 KO mice were viable and did not display any gross physical or behavioral abnormalities. No tumors of any kind were discovered in these mice. Based on these intriguing results, we hypothesize that disruption of IP6K1 should be a legitimate therapeutic strategy for the treatment of neutropenia-related pneumonia. In the last funding period, we investigated the role of IP6K1 is regulating neutrophil function in bacterial pneumonia. Consistent with the elevated PtdIns(3,4,5)P3 signaling in IP6K1 deficient neutrophils, disrupting the Ip6k1 gene (whole-body KO) or pharmacologically inhibiting IP6K1 activity using a specific inhibitor TNP efficiently and effectively enhanced host bacterial killing capability, minimizing the lung damage caused by both Gram-positive and Gram-negative bacterial pneumonia. Unexpectedly, inhibition of IP6K1 reduced pulmonary neutrophil accumulation. We revealed that IP6K1-mediated inorganic polyphosphate (polyP) production by platelets was essential for infection-induced neutrophil-platelet aggregate (NPA) formation which facilitates neutrophil accumulation in alveolar spaces during bacterial pneumonia. As part of our overall goal to further understand the role of IP6K1 and to design the best strategy to target IP6K1 in neutropenia-related pneumonia, we will continue to examine whether neutrophil-specific IP6K1 disruption is sufficient to induce the elevated host defense (Aim 1). In addition, we will elucidate the role of platelet IP6K1 in regulating pulmonary neutrophil accumulation in neutropenia-related pneumonia (Aim 2). Finally, we will directly investigate whether treatment with IP6K1 inhibitor TNP can alleviate neutropenia-related pneumonia and whether polyP or platelet transfusion can enhance the anti-pneumonia effect of TNP (Aim 3).