Lung Macrophage Memory Development and Responses in Secondary Pneumonia and Sepsis

项目摘要 对继发性细菌性肺炎的易感性增加是肺病毒性肺炎的重要临床并发症 感染.留下免疫疤痕/记忆的分子参与者的表征 从病毒感染临床恢复后的时期对于预防继发性肺炎感染至关重要。我们 目前在这方面的知识非常有限，迄今为止的研究主要集中在“免疫学”上， 免疫抑制微环境导致的“耐受化”树突状细胞和巨噬细胞的发育 在原发性感染消退后建立。在这个应用程序中，基于我们强大的支持数据， （与《自然免疫学》交流）显示，在肺部流感感染期间产生IFNγ， 在肺泡巨噬细胞（AM）中留下免疫记忆，驱动病理性先天记忆 响应随后的细菌病原体，我们建议确定新的转录机制， 在这些经过免疫训练的AM中进行重编程。在这方面，RNA聚合酶II（Pol II）在 大多数哺乳动物基因的转录起始位点，并释放到基因体上进行快速转录 是确定转录激活的关键步骤。通过使用最先进的 利用全基因组技术，我们发现巨噬细胞中IFNγ应答基因获得Pol II富集， 在启动子近端区域的转录诱导期， 延伸和随后的基因表达。我们将这种新机制称为获得性启动子近端Pol II富集（APPe），并提出APPe负责流感中IFN诱导的记忆表型 感染此外，我们发现染色质修饰蛋白精氨酸甲基转移酶8（PRMT 8）参与了 IFN诱导的记忆反应通过在训练的巨噬细胞中早期建立APPe。根据这些数据，我们 将确定：（目标1）PRMT 8如何控制IFN诱导的记忆转录重编程， 在这些训练过的AM中，IFN应答基因在再激活后的转录更早，更大， 继发性细菌感染，以及PRMT 8缺陷是否改善病理学并恢复 对革兰氏阴性菌（肺炎克雷伯菌）继发性细菌感染的适当免疫应答 和革兰氏阳性菌（金黄色葡萄球菌和肺炎链球菌/肺炎球菌）;（目标2） 继发性细菌性肺炎期间AM中的转录记忆结果如何通过 通过PRMT 8介导的APPe发生的APPe速率限制步骤，用于靶基因的早期、不受控制的转录 与细胞因子风暴和后来的严重败血症有关的基因。圆满完成拟议工作 将解决我们对流感期间巨噬细胞功能机制的认识中的一个主要空白， 随后的细菌感染，这将对未来的治疗措施产生影响。

Project Summary Increased susceptibility to secondary bacterial pneumonia is a significant clinical complication of pulmonary viral infections. The characterization of molecular players that leave immunological scars/memory for sustained periods after clinical recovery from viral infections is vital for preventing secondary pneumonic infections. Our current knowledge in this regard is vastly limited, and the studies so far have mainly focused on “immunologically tolerized” dendritic cells and macrophages developing as a result of immunosuppressive microenvironment established upon resolution of primary infection. In this application, based on our strong supportive data (communicated to Nature Immunology) showing that IFNγ produced during pulmonary influenza infection imprints an immunological memory in alveolar macrophages (AMs) that drive a pathologic innate memory response to a subsequent bacterial pathogen, we propose to identify the novel mechanism of transcriptional reprogramming in these immunologically trained AMs. In this regard, pausing of RNA polymerase II (Pol II) at the transcriptional start site of most mammalian genes and its release onto the gene body for rapid transcription upon cellular activation is a key step in determination of transcriptional activation. By using state-of-the art genome-wide techniques, we have found that IFNγ responsive genes in macrophages acquire Pol II enrichment at the promotor-proximal regions during their transcriptional induction phase that controls simultaneous elongation and subsequent gene expression. We termed this novel mechanism Acquired Promoter-proximal Pol II enrichment (APPe), and propose that APPe is responsible for IFN-induced memory phenotype in influenza infection. Further, we found that chromatin modifier Protein Arginine Methyltransferase 8 (PRMT8) is involved in IFN-induced memory response by establishing APPe early in trained-macrophages. Based on these data, we will determine: (Aim 1) how PRMT8 controls IFN-induced memory transcriptional reprogramming responsible for an earlier and greater transcription of IFN-responsive genes in these trained AMs upon reactivation during secondary bacterial infection, and whether PRMT8 deficiency ameliorates pathology and reinstates an appropriate immune response to secondary bacterial infection by both Gram-negative (Klebsiella pneumoniae) and Gram-positive bacteria (Staphylococcus aureus, and Streptococcus pneumoniae/ pneumococcus); (Aim 2) how transcriptional memory outcomes in AMs during secondary bacterial pneumonia are regulated through the rate-liming step of APPe via PRMT8 mediated APPe occurrence for an early, uncontrolled transcription of target genes that are involved in cytokine storm and later severe sepsis. The successful completion of proposed work will address a major gap in our knowledge of mechanisms dictating macrophage functions during influenza and subsequent bacterial infections, which will have implications for future therapeutic measures.