Ventilator-induced diaphragmatic atrophy: role of FoxO signaling

描述(由申请人提供)：机械通气(MV)是一种临床工具，用于维持无法维持足够肺泡通气量的患者的肺气体交换。虽然机械通气通常是一种挽救生命的干预措施，但延长机械通气时间会导致患者在脱离呼吸机后出现问题。虽然有几个因素可能会导致脱机困难，但吸气肌无力是一个主要因素。在这一点上，MV导致横隔肌缺乏活动，从而促进由于横隔肌萎缩和收缩功能障碍(称为呼吸机诱导的横隔膜功能障碍(VIDD))而导致的吸气肌无力的快速发作。虽然MV诱导的横隔膜萎缩是由于蛋白质分解增加和蛋白质合成减少引起的，但调节这些过程的机制(S)尚不清楚，因此，临床上还没有治疗方法。因此，我们的长期目标是确定生物靶点，以帮助制定预防VIDD的治疗策略，从而防止断奶困难。虽然许多信号事件可能导致VIDD，但我们预测叉头盒O(FoxO)转录因子家族是重要的，因为它们调节参与泛素-蛋白酶体和自噬蛋白分解途径的基因的表达。此外，FOXO的基因靶点也可能参与蛋白质合成的抑制。假设：我们将验证一个假设，即在MV期间，蛋白质合成减少，蛋白酶体/自噬基因表达增加，以及横隔膜发生纤维萎缩，需要激活FoxO依赖的转录。方法：我们的假设将在建立良好的MV大鼠模型中进行验证。因果关系将通过使用腺相关病毒载体进行基因传递来确定，以表达显性的负性FoxO，以防止延长MV期间FoxO靶基因在横隔膜中的激活。具体目的：Aim 1将确定FoxO依赖的转录是否是在延长MV期间观察到的横隔膜蛋白质合成迅速减少的关键因素。目的2将确定蛋白酶体和自噬基因在MV诱导的蛋白酶体和自噬基因表达增加是否需要FoxO依赖的转录，并伴随着横隔萎缩。意义：总的来说，这项工作可以为预防VIDD的新治疗策略提供基础，VIDD是导致患者无法脱离呼吸机的主要原因。 公共卫生相关性：虽然机械通气是急性呼吸衰竭患者的救命干预措施，但长时间的机械通气会导致呼吸肌无力，从而导致患者脱离呼吸机时出现问题。该项目的长期目标是确定有助于制定治疗策略的生物靶点，以防止MV引起的呼吸肌无力和防止断奶困难。这项研究的结果将为预防MV引起的横隔肌无力的新治疗策略提供基础，横隔肌无力是导致患者无法脱离呼吸机的主要原因。

DESCRIPTION (provided by applicant): Mechanical ventilation (MV) is a clinical tool to sustain pulmonary gas exchange in patients that are incapable of maintaining adequate alveolar ventilation. Although MV is often a life-saving intervention, prolonged MV promotes problems in "weaning" patients from the ventilator. While several factors can contribute to difficult weaning, weak inspiratory muscles are a major factor. In this regard, MV results in diaphragmatic inactivity that promotes the rapid onset of inspiratory muscle weakness due to diaphragmatic atrophy and contractile dysfunction (known as ventilator-induced diaphragm dysfunction (VIDD)). Although MV-induced diaphragmatic atrophy occurs due to both increased protein breakdown and decreased protein synthesis, the mechanism(s) that regulate these processes are poorly understood and thus, no clinical therapy exists. Hence, our long-term goal is to identify biological targets that will assist in the development of a therapeutic strategy to preven VIDD and therefore, protect against weaning difficulties. Although numerous signaling events can contribute to VIDD, we predict that the forkhead boxO (FoxO) family of transcription factors are important because they regulate the expression of genes involved in both the ubiquitin-proteasome and the autophagy pathway of proteolysis. Moreover, gene targets of FoxO may also contribute to the depression of protein synthesis. HYPOTHESIS: We will test the hypothesis that activation of FoxO-dependent transcription is required for the decreased protein synthesis, increased expression of proteasome/autophagy genes, and fiber atrophy that occurs in the diaphragm during MV. APPROACH: Our hypothesis will be tested in a well-established rat model of MV. Cause and effect will be determined by using an adeno-associated virus vector for gene delivery to express a dominant negative FoxO to prevent activation of FoxO target genes in the diaphragm during prolonged MV. SPECIFIC AIMS: Aim 1 will establish if FoxO-dependent transcription is essential for the rapid decrease in diaphragmatic protein synthesis that is observed during prolonged MV. Aim 2 will determine if FoxO-dependent transcription is required for the MV-induced increase in the expression of proteasome and autophagy genes along with diaphragmatic atrophy. SIGNIFICANCE: Collectively, this work can provide the foundation for new therapeutic strategies in the prevention of VIDD, a major contributor to the inability to wean patients from the ventilator. PUBLIC HEALTH RELEVANCE: Although mechanical ventilation is a life-saving intervention in patients with acute respiratory failure, prolonged mechanical ventilation promotes weakness in respiratory muscles that can lead to problems in weaning patients from the ventilator. The long-term goal of this project is to identify biological targets that will assist in the development of therapeutic strategy to prevent MV-induced respiratory muscle weakness and protect against weaning difficulties. The results of this study will provide the foundation for new therapeutic strategies for the prevention of MV-induced diaphragmatic weakness, a major contributor to the inability to wean patients from the ventilator.