Dysregulation of the inflammatory response by Francisella tularensis

土拉菌病是一种潜在的致命性疾病，其病原体土拉弗朗西斯菌（Ft）是少数几种 可感染中性粒细胞（多形核白细胞，PMN）和巨噬细胞的细菌病原体。 值得注意的是，巨噬细胞和中性粒细胞似乎在兔热病发病机制中发挥明显不同的作用， 巨噬细胞作为细菌生长和传播的主要载体，而中性粒细胞发挥核心作用 破坏宿主组织中性粒细胞寿命短，与其他白细胞不同， 在释放到循环中后24小时经历细胞凋亡。对这一过程进行严格的时空控制， 对于消除感染和缓解炎症至关重要，因此PMN周转缺陷 炎症反应失调和无效，促进组织破坏和疾病。 与此相一致，我们发现Ft抑制人中性粒细胞凋亡，并显著抑制细胞凋亡。 寿命，并证明这是通过对内在和外在凋亡途径的影响实现的， 以及中性粒细胞转录组的变化，包括365个独特的 与细胞凋亡和细胞命运相关的基因。然而，细胞寿命的延长只是部分原因， 明白在此，我们提出了突破性的研究，基于我们发现的中性粒细胞代谢 重编程作为细胞凋亡抑制的新机制。我们提出的研究得到了广泛的支持。 初步数据，并具有高度创新性，因为糖酵解和细胞器功能的综合操纵 以前没有被记录为感染期间PMN寿命的调节机制。潜在 这些变化对细菌生长的影响以及PMN代谢产物对巨噬细胞极化的影响 也将被确定。此外，我们最近确定了细菌脂蛋白（BLP）作为Ft的活性因子， 条件培养基（CM），通过依赖于共同的单一细胞因子的机制延长PMN的寿命。 人类TLR 1（rs 5743618，T1805 G）中的一种核苷酸多态性（SNP），显著影响了 以及许多感染性和炎症性疾病的结果，包括但不限于 局限于肺结核、肾盂肾炎、动脉粥样硬化、关节炎、狼疮、结肠炎和癌症。阐明 BLP和TLR 2/1驱动的细胞凋亡抑制的机制是本研究的第二个目的。我们 实验设计还将利用特异性靶向HIF-1 α和TLR 2、线粒体自噬、糖酵解或 其他相关的信号传导中间体，以确定治疗干预的点， 与许多影响退伍军人的疾病有关。我们的具体目标是：1）阐明机制， 中性粒细胞代谢重编程的功能后果。2)为了阐明BLP的机制， TLR 2/1介导的细胞凋亡抑制和治疗干预的潜力。

Tularemia is a potentially fatal disease and the causative agent, Francisella tularensis (Ft), is one of few bacterial pathogens that can infect both neutrophils (polymorphonuclear leukocytes, PMNs) and macrophages. Notably, macrophages and neutrophils appear to play distinctly different roles in tularemia pathogenesis, with macrophages acting as major vehicles for bacterial growth and dissemination, and PMNs playing a central role in host tissue destruction. Neutrophils are short lived, and unlike other leukocytes are preprogrammed to undergo apoptosis 24 h after release into the circulation. Tight spatial and temporal control of this process is critical for elimination of infection and resolution of inflammation, and for this reason defects in PMN turnover exemplify a dysregulated and ineffective inflammatory response that promotes tissue destruction and disease. In keeping with this, we discovered that Ft inhibits human neutrophil apoptosis and markedly prolongs cell lifespan, and demonstrated that this is achieved via effects on the intrinsic and extrinsic apoptosis pathways, as well as changes in the neutrophil transcriptome that include significant differential expression of 365 unique genes linked to apoptosis and cell fate. Nevertheless, how cell lifespan is prolonged is only partially understood. Herein, we propose groundbreaking studies based on our discovery of neutrophil metabolic reprogramming as a new mechanism for apoptosis inhibition. Our proposed studies are supported by extensive preliminary data, and are highly innovative, as integrated manipulation of glycolysis and organelle function has not been previously documented as a mechanism for regulation of PMN lifespan during infection. Potential effects of these changes on bacterial growth and the influence of PMN metabolites on macrophage polarization will also be determined. In addition, we recently identified bacterial lipoproteins (BLPs) as active factors in Ft conditioned medium (CM) that extend PMN lifespan via a mechanism that is dependent on a common single nucleotide polymorphism (SNP) in human TLR1 (rs5743618, T1805G) that significantly influences the severity and lethality of sepsis as well as the outcomes of many infectious and inflammatory diseases, including but not limited to tuberculosis, pyelonephritis, atherosclerosis, arthritis, lupus, colitis, and cancer. Elucidating the mechanism(s) of BLP and TLR2/1-driven apoptosis inhibition is a second objective of this study. Our experimental design will also utilize drugs that specifically target HIF-1 and TLR2, mitophagy, glycolysis or other relevant signaling intermediates to identify points for therapeutic intervention that are expected to be relevant to many diseases that affect Veterans. Our specific aims are: 1) To elucidate the mechanisms and functional consequences of neutrophil metabolic reprogramming. 2) To elucidate the mechanisms of BLP and TLR2/1-mediated apoptosis inhibition and potential for theraputic intervention.