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，用于维持无法维持充分肺泡通气的患者的肺部气体交换。虽然MV通常是一种挽救生命的干预措施，但长时间的MV会导致患者“脱机”呼吸机的问题。虽然有几个因素可能导致脱机困难，但吸气肌无力是一个主要因素。在这方面，MV导致膈肌不活动，其促进由于膈肌萎缩和收缩功能障碍（称为呼吸机诱导的膈肌功能障碍（VIDD））引起的吸气肌无力的快速发作。尽管MV诱导的脑萎缩是由于蛋白质分解增加和蛋白质合成减少而发生的，但调节这些过程的机制知之甚少，因此不存在临床治疗。因此，我们的长期目标是确定生物学靶点，这将有助于开发预防VIDD的治疗策略，从而防止断奶困难。虽然许多信号事件可以有助于VIDD，我们预测，叉头boxO（FoxO）家族的转录因子是重要的，因为它们调节参与泛素-蛋白酶体和自噬途径的蛋白水解的基因的表达。此外，FoxO的基因靶点也可能有助于抑制蛋白质合成。假设：我们将测试的假设，FoxO依赖的转录激活所需的蛋白质合成减少，蛋白酶体/自噬基因的表达增加，纤维萎缩，发生在隔膜在MV。方法：我们的假设将在一个完善的MV大鼠模型中进行测试。将通过使用腺相关病毒载体进行基因递送以表达显性阴性FoxO来确定因果关系，以防止在延长的MV期间膈肌中FoxO靶基因的激活。具体目标：目的1将确定FoxO依赖性转录是否是在长时间MV期间观察到的促炎蛋白合成快速减少所必需的。目的2将确定是否需要FoxO依赖性转录的MV诱导的蛋白酶体和自噬基因的表达增加沿着脑萎缩。重要性：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是无法使患者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.