NLRP1 activation induces deletion of hematopoietic progenitor cells

描述（由申请方提供）：全身性感染患者的外周血细胞减少是公认的致死性结局预测因子，尽管进行了抗菌治疗。本计画旨在探讨脓毒症引起血细胞减少的分子机制.我们已经确定了感染诱导的血细胞减少症中造血干细胞和祖细胞的Caspase-1依赖性死亡（称为焦亡）的核心作用。我们已经产生了两种NLRP 1突变小鼠模型，第一种是ENU诱导的NLRP 1a功能获得性突变（NLRP 1aQ 593 P），第二种是NLRP 1的所有三种亚型（NLRP 1a，NLRP 1b和NLRP 1c）的缺陷。NLRPlaQ 593 P突变发生在核苷酸结合（NACHT，NB）结构域和富含亮氨酸的重复序列（LRR）之间的柔性接头区域中，其中发现了降低植物NB-LRR先天防御蛋白激活阈值的激活突变JlrplaQ 593 P/Q593 P小鼠发生致死性脑膜脑炎、肺炎和心肌炎。这种疾病依赖于IL-1和Caspase-1，但不依赖于ASC或Caspase-11，并且出乎意料地受到IL-18的负调控。当Nlrp 1aQ 593 P/Q593 P小鼠缺乏IL-1受体时，不发生多器官炎性疾病，但小鼠是白细胞减少的，并且它们在稳态时表现出造血干细胞和祖细胞的显著缺乏（表1）。Nlrp 1aQ 593 P/Q593 P小鼠对淋巴细胞性脉络丛脑膜炎病毒（LCMV）感染或化疗诱导的造血应激的反应是不能使髓系、淋巴系和红系细胞再生。相反，NLRP 1缺陷型小鼠从LCMV感染和化疗中的恢复增强。基于我们的初步数据，我们提出：（1）在感染过程中，造血祖细胞中的NLRP 1的系统激活可诱导血细胞减少，导致免疫抑制。我们还提出（2）NLRP 1的生理作用之一是诱导受感染的造血干细胞和祖细胞的Caspase-1依赖性死亡，以防止感染传播到后代细胞。本研究旨在：A.研究NLRP 1的生化调节剂的作用，包括Bcl-2和SREBP-1 a，以确定体内B调节NLRP 1的新途径。使用竞争性骨髓移植、连续骨髓移植和离体克隆培养和活力测定来确定受NLRP 1影响的特定造血干细胞和祖细胞群体。C.探讨NLRP 1在感染和化疗诱导的造血应激过程中对造血干细胞和祖细胞的作用，了解NLRP 1激活的有益作用和病理作用

DESCRIPTION (provided by applicant): Peripheral blood cytopenias in patients with systemic infection are well-established predictors of fatal outcome despite antimicrobial therapy. This project proposal seeks to explain the molecular mechanism of sepsis- induced cytopenias. We have identified a central role for Caspase-1-dependent death, known as pyroptosis, of hematopoietic stem and progenitor cells in infection-induced cytopenias. We have generated two NLRP1 mutant mouse models, the first an ENU-induced gain-of-function mutation in NLRP1a (NLRP1aQ593P), and the second a deficiency in all three isoforms of NLRP1 (NLRP1a, NLRP1b and NLRP1c). The NLRP1aQ593P mutation occurs in the flexible linker region between the nucleotide-binding (NACHT, NB) domain and leucine- rich repeats (LRR), where activating mutations that reduce the threshold for activation of plant NB-LRR innate defense proteins are found. Nlrp1aQ593P/Q593P mice develop lethal meningoencephalitis, pneumonitis and myocarditis. This disease is dependent on IL-1¿ and Caspase-1 but not ASC or Caspase-11 and is unexpectedly, negatively regulated by IL-18. When Nlrp1aQ593P/Q593P mice are deficient in the IL-1 receptor, the multi-organ inflammatory disease does not develop but the mice are leukopenic and they display significant deficiencies in hematopoietic stem and progenitor cells at the steady state (Table 1). In response to hematopoietic stress induced by lymphocytic choriomeningitis virus (LCMV) infection or chemotherapy, Nlrp1aQ593P/Q593P mice fail to repopulate myeloid, lymphoid and erythroid cells. Conversely, NLRP1-deficient mice show enhanced recovery from LCMV infection and chemotherapy. Based on our preliminary data, we propose (1) that systemic activation of NLRP1 in hematopoietic progenitor cells during infection can induce cytopenia resulting in immunosuppression. We also propose that (2) one of the physiological roles of NLRP1 is to induce Caspase-1-dependent death of infected hematopoietic stem and progenitor cells to prevent dissemination of infection to progeny cells. This research seeks to: A. examine the role of biochemical regulators of NLRP1 including Bcl-2 and SREBP-1a to identify new avenues to modulate NLRP1 in vivo B. define specific hematopoietic stem and progenitor cell populations affected by NLRP1 using competitive bone marrow transplant, serial bone marrow transplant, and ex vivo clonal culture and viability assays. C. characterise the role of NLRP1 in hematopoietic stem and progenitor cells during hematopoietic stress induced by infection and chemotherapy, to understand beneficial and pathological roles for NLRP1 activation