Mechanical Ventilation and Diaphragmatic Oxidant Injury

描述（由申请人提供）：机械通气（MV）用于维持无法维持充分肺泡通气的患者的肺部气体交换。从患者体内撤出MV被称为“撤机”，撤机过程中经常出现问题。研究表明，肌肉无力是导致断奶困难的关键因素。重要的是，我们发现MV诱导的膈肌无力与膈肌的氧化损伤有关。此外，我们最近的工作表明，MV诱导的氧化应激抑制了海马特异性力的产生，促进了蛋白水解，导致海马萎缩。目前，MV诱导细胞氧化剂产生的机制尚不清楚。因此，这些实验将确定导致隔膜中MV诱导的氧化损伤的氧化剂途径。基于初步实验，我们的工作假设是MV诱导的细胞氧化应激是由于4种氧化剂产生途径之间的相互作用而发生的：1）NAD（P）H氧化酶产生超氧自由基; 2）黄嘌呤氧化酶途径产生超氧自由基; 3）一氧化氮合成酶产生一氧化氮;以及4）细胞活性铁水平增加形成羟基自由基。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，我们将使用一组已建立的技术来测量MV诱导的膈肌氧化损伤。其次，我们将研究每个氧化剂产生途径的关键要素，以确定这些成分是否在MV动物的横膈膜中升高。此外，我们将采用每种氧化剂途径的已证实的药理学抑制剂来确定MV诱导的血管氧化损伤和收缩功能障碍中该途径的相对重要性。描绘负责MV诱导的隔膜中的氧化剂产生的生物化学途径对于开发有效的方法来对抗这种破坏性过程是至关重要的。这些实验将提供新的和重要的机械信息的来源，在隔膜中的氧化剂，可用于开发最佳的临床策略，以延缓MV诱导的心肌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.