IL-1beta in the Development of Hypoxemia in Acute Lung Injury

描述（由申请人提供）：急性呼吸窘迫综合征（ARDS）是一种急性肺损伤的临床综合征，其特征为突然发作和肺严重不能吸收血液（低氧血症）。ARDS的死亡率为30%，尽管进行了广泛的研究，但在美国每年仍有75，000人死亡。脓毒症加机械通气的组合显著增加发展为ARDS的风险。因此，急性肺损伤的二次打击模型引起了极大的兴趣，并且已经在动物模型中进行了广泛的研究。然而，脓毒症和机械通气（MV）协同作用导致急性肺损伤的具体机制仍不清楚。白细胞介素1β（IL-1β）参与了ARDS的发病机制，其分泌受称为NLRP 3炎性体的细胞内复合物调节，我们最近证实，NLRP 3炎性体在巨噬细胞中被线粒体功能障碍激活，并与细胞死亡相关。我们开发了一种小鼠模型，其中MV触发巨噬细胞线粒体功能障碍和细胞死亡，吸入脂多糖（LPS）和MV共同导致IL-1β分泌和急性肺损伤的发展，如中性粒细胞浸润、肺泡水肿、趋化因子分泌和低氧血症所示。有趣的是，当IL-1β信号被caspase-1或NLRP 3的缺失或IL-1 R拮抗剂Anakinra的给药破坏时，我们观察到低氧血症的发展显著改善，而对中性粒细胞浸润或肺泡渗漏没有显著影响，表明在肺损伤中引起低氧血症的机制与肺部炎症无关，但依赖于IL-1β信号。这些数据表明IL-1β和NLRP 3炎性体的新作用，特别是在与急性肺损伤和ARDS相关的低氧血症中。我们假设，缺氧性肺血管收缩，其中血液从气体交换差的区域转移，可以帮助解释低氧血症的发展如何在机制上不同于炎症。文献表明，IL-1β可能通过影响肺中一氧化氮的产生来调节缺氧性肺血管收缩。事实上，我们发现MV增加了肺中一氧化氮合酶2（NOS 2）的表达和一氧化氮的产生，并且NOS 2缺陷小鼠被保护免于急性肺损伤相关低氧血症的发展。基于这些数据，该指导K 08资助申请的中心假设是，急性肺损伤中低氧血症的发展需要NLRP 3炎性体活化和IL-1β分泌，低氧血症的机制主要是通过IL-1β对缺氧性肺血管收缩的作用。我们现在提出通过以下目的来验证我们的假设：目的1是确定肺泡巨噬细胞在急性肺损伤低氧血症发展中的作用;目的2是确定一氧化氮在急性肺损伤IL-1β依赖性低氧血症中的作用;目的3是确定急性肺损伤中NLRP 3和IL-1β信号传导是否破坏缺氧性肺血管收缩。

DESCRIPTION (provided by applicant): Acute Respiratory Distress Syndrome (ARDS) is a clinical syndrome of acute lung injury characterized by a sudden onset and a profound inability of the lungs to oxygenate the blood (hypoxemia). ARDS has a mortality rate of 30% and is responsible for 75,000 deaths annually in the United States despite extensive research efforts. The combination of sepsis plus mechanical ventilation significantly increases the risk for developing ARDS. Therefore, a two-hit model of acute lung injury is of great interest and has been studied extensively in animal models. However, the specific mechanisms underlying the development of acute lung injury through synergy of sepsis and mechanical ventilation (MV) remain unknown. Interleukin 1β (IL-1β) is implicated in the pathogenesis of ARDS, and its secretion is regulated by an intracellular complex termed the NLRP3 inflammasome, which we recently demonstrated is activated in macrophages by mitochondrial dysfunction and is associated with cell death. We developed a mouse model in which MV triggers macrophage mitochondrial dysfunction and cell death, and inhaled lipopolysaccharide (LPS) and MV together lead to IL-1β secretion and the development of acute lung injury, as demonstrated by neutrophil infiltration, alveolar edema, chemokine secretion, and hypoxemia. Interestingly, when IL-1β signaling was disrupted by the absence of caspase-1 or NLRP3, or by the administration of IL-1R antagonist Anakinra, we observed significant improvement in the development of hypoxemia without significant effects on neutrophil infiltration or alveolar leakage, indicating that the mechanism causing hypoxemia in lung injury is independent of lung inflammation but dependent on IL-1β signaling. These data suggest a novel role for IL-1β and the NLRP3 inflammasome, specifically in the hypoxemia associated with acute lung injury and ARDS. We hypothesize that hypoxic pulmonary vasoconstriction, in which blood is diverted away from areas of poor gas exchange, can help to explain how the development of hypoxemia can be mechanistically distinct from inflammation. Literature suggests that IL-1β may modulate hypoxic pulmonary vasoconstriction by affecting nitric oxide production in the lung. Indeed, we found that MV increases expression of nitric oxide synthase 2 (NOS2) and nitric oxide production in the lung, and that Nos2-deficient mice were protected from the development of acute lung injury-related hypoxemia. Based on these data, the central hypothesis for this mentored K08 grant application is that the development of hypoxemia in acute lung injury requires NLRP3 inflammasome activation and IL-1β secretion, and that the mechanism of hypoxemia is primarily through IL-1β effects on hypoxic pulmonary vasoconstriction. We now propose to test our hypothesis through the following aims: Aim 1 is to determine the role of alveolar macrophages in the development of hypoxemia in acute lung injury; Aim 2 is to determine the role of nitric oxide in IL-1β-dependent hypoxemia in acute lung injury; and Aim 3 is to determine if NLRP3 and IL-1β signaling in acute lung injury disrupts hypoxic pulmonary vasoconstriction.