Mechanical Ventilation and Diaphragmatic Oxidant Injury

描述(申请人提供)：机械通气法(MV)用于维持肺泡通气量不足的患者的肺气体交换。从患者体内撤除MV的行为被称为“脱机”，脱机过程中出现的问题屡见不鲜。研究表明，横隔膜无力是导致脱机困难的关键因素。重要的是，我们发现MV引起的横隔膜无力与对横隔膜的氧化损伤有关。此外，我们最近的工作表明，MV诱导的氧化应激抑制了横隔膜比力的产生，并促进了蛋白分解，导致了横隔膜的萎缩。目前，MV诱导细胞产生氧化剂的机制(S)尚不清楚。因此，这些实验将确定导致MV诱导的横隔膜氧化损伤的氧化途径(S)。在初步实验的基础上，我们的工作假设是，MV诱导的隔膜氧化应激是由于4条氧化剂产生途径之间的相互作用：1)NAD(P)H氧化酶产生超氧阴离子自由基；2)黄嘌呤氧化酶途径产生超氧阴离子自由基；3)一氧化氮合酶产生一氧化氮；以及4)通过增加细胞内活性铁水平形成羟基自由基。这一假设将在MV的大鼠模型中使用创新和全面的实验方法进行测试。首先，我们将使用一组成熟的技术来测量MV诱导的横隔膜的氧化损伤。其次，我们将研究每条氧化剂产生途径的关键成分，以确定这些成分是否在MV动物的横隔膜中升高。此外，我们将使用已证实的每种氧化剂途径的药物抑制剂来确定该途径在MV诱导的横隔膜氧化损伤和收缩功能障碍中的相对重要性。阐明MV诱导隔膜产生氧化剂的生化途径对于开发有效的方法来对抗这一损害过程是至关重要的。这些实验将提供有关横隔膜氧化剂来源的新的和重要的机制信息，可用于开发最佳的临床策略来延缓MV诱导的横隔膜氧化应激和收缩功能障碍。

DESCRIPTION (provided by applicant): Mechanical ventilation (MV) is used to sustain pulmonary gas exchange in patients incapable of maintaining adequate alveolar ventilation. The withdrawal of MV from patients is called "weaning" and problems in weaning are frequent. Studies reveal that diaphragmatic weakness is a key contributor to weaning difficulties. Importantly, we have discovered that MV-induced diaphragmatic weakness is associated with oxidative damage to the diaphragm. Moreover, our recent work reveals that MV-induced oxidative stress depresses diaphragmatic specific force production and promotes proteolysis leading to diaphragmatic atrophy. At present, the mechanism(s) responsible for MV-induced production of cellular oxidants are unknown. Therefore, these experiments will determine the oxidant pathway(s) responsible for MV-induced oxidative injury in the diaphragm. Based upon preliminary experiments, our working hypothesis is that MVinduced diaphragmatic oxidative stress occurs due to interactions between 4 oxidant-producing pathways: 1) production of superoxide radicals by NAD(P)H oxidase; 2) generation of superoxide radicals by the xanthine oxidase pathway; 3) nitric oxide production via nitric oxide synthase; and 4) formation of hydroxyl radicals by increased cellular levels of reactive iron. This hypothesis will be tested in a rat model of MV using an innovative and comprehensive experimental approach. First, we will measure MV-induced oxidative injury in the diaphragm using a panel of established techniques. Secondly, we will investigate critical elements of each oxidant production pathway to determine if these components are elevated in diaphragms from MV animals. Further, we will employ proven pharmacological inhibitors of each oxidant pathway to determine the relative importance of the pathway in MV-induced diaphragmatic oxidative injury and contractile dysfunction. Delineating the biochemical pathways responsible for MV-induced oxidant production in the diaphragm is essential to developing an effective approach to oppose this damaging process. These experiments will provide new and important mechanistic information about the source of oxidants in the diaphragm that can be used to develop optimal clinical strategies to retard MV-induced diaphragmatic oxidant stress and contractile dysfunction.