Altered innate leukocyte programming dynamics in sepsis

项目总结 脓毒症造成严重的健康问题，没有有效的预防或治疗方法。关键的绊脚石是 先天性白细胞动态平衡被破坏的高度复杂性质。败血症单核细胞动态平衡紊乱 反映在炎症过程的早期戏剧性上升，随后是晚期代偿性 宽容。脓毒症患者中性粒细胞动态平衡紊乱主要表现为“迁移性瘫痪” 败血症的中性粒细胞失去了对细菌产物的迁移能力，同时保持了对细菌产品的迁移 无菌组织，由于优先减少FPR2和诱导CCR5。败血症的中性粒细胞也有 减少产生中性粒细胞胞外陷阱(NET)的可能性。总的来说，这些颠覆了先天的 白细胞动态平衡可能损害宿主防御，加剧多器官炎症。然而， 单核细胞启动和中性粒细胞麻痹的机制尚不清楚。由于他们的高度 动态的性质，目前的体外实验系统或体内的动物模型都不能正确地捕捉到 破坏了白细胞的稳态。PI过去的系统分析与实验和计算 方法揭示了一种模型系统，该模型系统在体外和在 体内应用亚临床超低剂量脂多糖(LPS)。与广泛的影响形成鲜明对比 使用更高剂量的内毒素，优先促进单核细胞耐受，李博士的实验室证明，超 低剂量的内毒素“激活”单核细胞，缓解长期的“失控”炎症。此外，李实验室观察到，超级- 低剂量的脂多糖使中性粒细胞进入瘫痪状态，模拟FPR2减少的败血症中性粒细胞， 细菌杀灭潜力降低，CCR5升高。单核细胞启动与中性粒细胞麻痹 体外培养的人血白细胞中可观察到低剂量的内毒素。盲肠结扎术和脓毒症穿刺术 LI实验室发现，在超低剂量脂多糖预处理的小鼠中，脓毒症死亡率加剧。 从机制上讲，LI实验室观察到，超低剂量的内毒素通过以下方式有效地重新编程单核细胞和中性粒细胞 扰乱关键的动态平衡事件和分子。基于这些耐人寻味的观察，长期目标是 是为了了解先天免疫紊乱导致的发病率和死亡率升高的原因 败血症。作为关键的第一步，我们的关键目标是更好地了解导致 破坏单核细胞和中性粒细胞的动态平衡。该项目计划测试以下中心假设 脓毒症时单核细胞启动和中性粒细胞瘫痪是由关键动态平衡的破坏引起的 分子和过程。目标1将检验这样一个假设，即动态平衡分子的破坏 RelB负责单核细胞启动，有助于增加脓毒症死亡率。《目标2》将揭示 中性粒细胞麻痹的基本细胞和分子机制。目标3将测试这一点是否 白细胞动力学的改变可能会加剧，而白细胞稳态的恢复可能会减弱 脓毒症的发病机制。

PROJECT SUMMARY Sepsis poses grave health concerns with no effective prevention or cure. The key stumbling block is the highly complex nature of the disrupted innate leukocyte homeostasis. Disrupted sepsis monocyte homeostasis is reflected in a dramatic early upswing of inflammatory processes followed by a late-phase compensatory tolerance. Disrupted neutrophil homeostasis in sepsis patients is cardinally represented by “migratory paralysis” in which septic neutrophils lose migratory potential toward bacterial products while retaining migration toward sterile tissues, due to preferential reduction of FPR2 and induction of CCR5. Septic neutrophils also have reduced potential for generating neutrophil extra-cellular trap (NET). Collectively, these disrupted innate leukocyte homeostasis may compromise host defense and exacerbate multi-organ inflammation. However, mechanisms underlying monocyte priming and neutrophil paralysis are poorly understood. Due to their highly dynamic natures, current experimental systems in vitro or animal models in vivo fail to properly capture the disrupted leukocyte homeostasis. The PI’s past systems analyses with experimental and computational approaches reveal a model system that recapitulates the disrupted human leukocyte homeostasis in vitro and in vivo by applying subclinical super-low dose lipopolysaccharide (LPS). In sharp contrast to the effects of widely used higher dosages LPS which preferentially facilitate monocyte tolerance, Dr. Li’s lab documented that super- low dose LPS “primes” monocytes for prolonged “run-away” inflammation. In addition, Li lab observed that super- low dose LPS “programs” neutrophils into a paralytic state, mimicking septic neutrophils with reduced FPR2, reduced potential of bacterial killing and elevated CCR5. Monocyte priming and neutrophil paralysis by super- low dose LPS can be observed in human blood leukocyte ex vivo. With the cecal ligation and puncture sepsis model, Li lab demonstrated exacerbated sepsis mortality in mice pre-conditioned with super-low dose LPS. Mechanistically, Li lab observed that super-low dose LPS potently reprograms monocytes and neutrophils by disrupting key homeostatic events and molecules. Based on these intriguing observations, the long-term goal is to understand the disrupted innate immune dynamics responsible for the elevated morbidity and mortality of sepsis. As a crucial first step, our key objective is to better understand the mechanisms responsible for the disrupted homeostasis in monocytes and neutrophils. This project plans to test the central hypothesis that monocyte priming and neutrophil paralysis during sepsis are caused by the disruption of key homeostatic molecules and processes. Aim 1 will test the hypothesis that the disruption of homeostatic molecules such as RelB is responsible for the monocyte priming conducive for increased sepsis mortality. Aim 2 will reveal the fundamental cellular and molecular mechanisms responsible for neutrophil paralysis. Aim 3 will test whether that alteration of leukocyte dynamics may exacerbate, while restoration of leukocyte homeostasis may attenuate sepsis pathogenesis.