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，用于无法维持足够肺泡通气的患者维持肺气体交换。虽然中压通气通常是一种挽救生命的干预措施，但延长中压通气会增加患者“脱离”呼吸机的问题。虽然有几个因素会导致断奶困难，但吸气肌无力是主要因素。在这方面，中压导致膈肌不活动，促使膈肌萎缩和收缩功能障碍（称为呼吸机诱发的膈肌功能障碍（VIDD））引起的吸气肌无力快速发作。虽然mv诱导的膈肌萎缩是由于蛋白质分解增加和蛋白质合成减少引起的，但调控这些过程的机制尚不清楚，因此尚无临床治疗方法。因此，我们的长期目标是确定生物学靶点，以帮助制定预防VIDD的治疗策略，从而防止断奶困难。尽管许多信号事件都可能导致VIDD，但我们预测叉头盒（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蛋白水解自噬途径的基因的表达。此外，FoxO的基因靶点也可能导致蛋白质合成的抑制。假设：我们将验证foxo依赖性转录的激活是MV期间蛋白合成减少、蛋白酶体/自噬基因表达增加和横膈膜纤维萎缩所必需的假设。方法：我们的假设将在一个成熟的大鼠MV模型中得到验证。通过使用腺相关病毒载体进行基因传递来表达显性阴性FoxO，以防止在长时间MV期间隔膜中FoxO靶基因的激活，从而确定因果关系。特异性目的：目的1将确定foxo依赖性转录是否对长时间MV期间观察到的膈蛋白合成的快速下降至关重要。目标2将决定是否需要FoxO-dependent转录MV-induced增加蛋白酶体和自噬基因的表达随着膈萎缩。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。

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.