MECHANICAL VENTILATION AND RESPIRATORY MUSCLES

说明(申请人摘要)：使用机械通风(MV) 在临床上为无能力的患者维持呼吸机 独立维持足够的肺泡通气量。不幸的是， 在许多情况下，撤除MV或断奶可能是困难的。 有强有力的证据表明，MV引起的呼吸肌无力是 对这些断奶困难的影响很大。事实上，我们最近 显示延长的机械通气会导致横隔膜萎缩和 横隔肌最大作用力明显减少。此外，我们 已经观察到长时间的MV会导致氧化损伤(即蛋白质 氧化)到隔膜；这一点很重要，因为被氧化的蛋白质 成为蛋白酶的靶子。MV诱导的致病机制 萎缩和蛋白质氧化是未知的，并构成了我们 拟议的实验。确定影响横隔膜的因素 延长MV期间的萎缩，我们将检验以下假设：1) MV诱导的横隔膜萎缩是由于合成减少的 肌肉蛋白质和蛋白质水解率增加；1)蛋白质水解率 延长MV期间横隔膜蛋白损失的主要原因；2a) 钙蛋白酶、溶酶体和三磷酸腺苷泛素依赖的活性增加 蛋白水解酶是蛋白质降解的共同原因。 来自MV动物的横隔膜；以及2b)尽管钙蛋白、溶酶体和 三磷酸腺苷-泛素依赖的蛋白水解酶都会导致横隔膜蛋白的丢失 在MV过程中，依赖于ATP泛素和钙蛋白的蛋白分解途径是 占主导地位。以确定哪些化学途径对横隔膜负责 MV期间的蛋白质氧化我们将检验MV诱导蛋白质的假设 隔膜中的氧化是由几种活性化学物质引起的 包括次氯酸、酪氨酸自由基和羟基自由基。为了测试 这些假设，我们将进行体外和体内研究使用一个 建立动物模型，并利用分子生物学、生物化学和生物化学等工具 生理学。这些实验将提高我们对机制的理解。 与MV诱导的横隔膜萎缩有关。我们的长期目标是 实验是为了提供制定临床策略所需的知识。 反对MV对呼吸肌的有害影响。

DESCRIPTION (Applicant's abstract): Mechanical ventilation (MV) is used clinically to sustain ventilation in patients who are incapable of independently maintaining adequate alveolar ventilation. Unfortunately, the withdrawal of MV, or weaning, can be difficult in a large number of cases. Strong evidence exists that MV-induced respiratory muscle weakness contributes significantly to these difficulties in weaning. Indeed, we have recently demonstrated that prolonged MV results in diaphragmatic atrophy and a significant reduction in diaphragmatic maximal force production. Further, we have observed that prolonged MV results in oxidative injury (i.e. protein oxidation) to the diaphragm; this is significant because oxidized proteins become targets for proteases. The mechanisms responsible for this MV-induced atrophy and protein oxidation are unknown and comprise the focus of our proposed experiments. To determine the factors that contribute to diaphragmatic atrophy during prolonged MV, we will test the following hypotheses: 1a) MV-induced diaphragmatic atrophy occurs due to a decrease in synthesis of muscle proteins as well as an increased rate of proteolysis; 1b) proteolysis is the major contributor to diaphragmatic protein loss during prolonged MV; 2a) The increased activity of calpain, lysosomal, and ATP ubiquitin-dependent proteases are collectively responsible for the protein degradation observed in diaphragms from MV animals; and 2b) Although calpain, lysosomal, and ATP-ubiquitin-dependent proteases all contribute to diaphragmatic protein loss during MV, the ATP-ubiquitin-dependent and calpain proteolytic pathways are dominant. To resolve which chemical pathways are responsible for diaphragmatic protein oxidation during MV we will test the hypothesis that MV-induced protein oxidation in the diaphragm is caused by several reactive chemical species including hypochlorous acid, tyrosyl radicals and hydroxyl radicals. To test these postulates, we will perform both in vitro and in vivo studies using an animal model and utilize the tools of molecular biology, biochemistry, and physiology. These experiments will improve our understanding of the mechanisms associated with MV-induced diaphragmatic atrophy. The long-term goal of our experiments is to provide the knowledge required to develop clinical strategies to oppose the deleterious effects of MV on respiratory muscles.