Role of titin in the pathophysiology of diaphragm weakness during mechanical vent

肌联蛋白在机械通气期间膈肌无力病理生理学中的作用

• 批准号: 9199443
• 负责人: Coen Ottenheijm
• 金额: $ 37.12万
• 依托单位: UNIVERSITY OF ARIZONA
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9199443
• 关键词: Affect; Animal Model; Animals; Antibodies; Applications Grants; Atrophic; Binding Proteins; Biophysics; Biopsy; Breathing; Clinical; Data; Denervation; Development; Environmental air flow; Failure; Fiber; Functional disorder; Gene Targeting; Genetic Engineering; Goals; Growth; Hour; Human; Hypertrophy; Impairment; Intensive Care Units; Knockout Mice; Lead; Link; Location; Lung; Lung diseases; Mechanical Stress; Mechanical ventilation; Mechanics; Mediating; Microfilaments; Modeling; Molecular; Morphology; Mus; Muscle; Mutation; Oxygen; Patients; Periodicity; Pilot Projects; Play; Property; Proteins; RNA Recognition Motif; RNA Splicing; Rattus; Research; Respiration; Respiratory Diaphragm; Roentgen Rays; Role; Signal Pathway; Signal Transduction; Stretching; Structure; Testing; Time; Vent; Weaning; Work; X ray diffraction analysis; X-Ray Diffraction; base; clinically relevant; connectin; innovation; mechanical load; mechanotransduction; mortality; mouse model; muscle form; novel; novel therapeutics; preconditioning; protein degradation; public health relevance; response; sensor; tool; uptake

DESCRIPTION (provided by applicant): The long-term goal of this proposal is to gain detailed understanding of how the diaphragm - the main muscle of respiration - rapidly weakens in response to mechanical unloading and of the mechanisms whereby the giant elastic protein titin influences this response. The diaphragm is a unique muscle in that it is constantly subjected to mechanical loading. Recent work suggests that diaphragm strength is remarkably sensitive to mechanical unloading, as occurs during mechanical ventilation in the ICU. How unloading affects diaphragm strength is poorly understood. Increasing this understanding is critically important: within hours, diaphragm unloading during mechanical ventilation causes diaphragm weakness in ICU patients, which leads to difficulties in weaning patients from ventilatory support and contributes to mortality. Th search for the molecular triggers for the development of diaphragm weakness during mechanical unloading is ongoing. The potential role of mechano-sensor proteins, that link diaphragm unloading to protein turnover, is unexplored but is an exciting and novel concept that needs to be studied. A candidate mechano-sensor is titin, a giant elastic protein that has been suggested to sense mechanical stress and link this to trophic signalling pathways. The elucidation of titin's role in diaphragm trophicity and in diaphragm weakness during mechanical ventilation is central to this grant proposal. Aim 1 will critically test whether titin affects musle trophicity. I will use unilateral diaphragm denervation (UDD), a condition that is clinically important and that presents itself as a great tool for this work as it induces rapid hypertrophy of the denervated hemidiaphragm due to cyclic passive stretch. I will study UDD in two novel titin KO mouse models: one in which titin stiffness is increased through deletion of Ig domains (Ig KO) and another in which titin stiffness is decreased through deletion of the titin splice factor rbm20 (Rbm20 KO). I anticipate that the hypertrophic response following UDD is exaggerated in Ig KO mice and blunted in Rmb20 KO mice, and that this response is mediated by altered titin signaling. Aim 2 will study whether low titin stiffness protects the diaphragm from weakening during mechanical ventilation-induced unloading and will use a rat model with low titin stiffness. If titin-based mechano-sensing mediates the response of the diaphragm to mechanical unloading, then I anticipate that low titin stiffness, by preconditioning the diaphragm to reduced mechanosensing, blunts this response. Aim 3 will study the mechanistic basis for diaphragm weakness in mechanically ventilated ICU patients using, for the first time, diaphragm fibers isolated from biopsies of mechanically ventilated ICU patients. The goal is to investigate whether the findings of animal studies extrapolate to patients. The innovation of this proposal lies in the novel research foci with innovative guiding hypotheses, its novel mouse models, unique diaphragm biopsies from mechanically ventilated ICU patients, and its novel experimental tools. The proposal's integrative approach is expected to lead to a significant step forward in our understanding of diaphragm function and the role of titin therein.

描述（由申请人提供）：该提案的长期目标是详细了解隔膜如何 - 呼吸的主要肌肉 - 响应机械卸载以及巨大的弹性蛋白titin会影响这种反应的机制而迅速削弱。 隔膜是一种独特的肌肉，因为它不断受到机械负荷的影响。最近的工作表明，隔膜强度对机械卸载非常敏感，就像ICU中的机械通气一样。卸载如何影响隔膜强度的理解很少。提高这种理解至关重要：在几个小时内，机械通气过程中的隔膜卸载会导致ICU患者的隔膜无力，这导致断奶患者无法获得通气支持的困难，并导致死亡率。在机械卸载过程中，寻找用于发展膜片弱点的分子触发器的搜索正在进行中。机械传感器蛋白的潜在作用是将隔膜卸载与蛋白质更新的链接的潜在作用，这是没有探索的，但这是一个令人兴奋且新颖的概念，需要研究。候选机械传感器是Titin，这是一种巨大的弹性蛋白，已被建议以感知机械应力并将其与营养信号通路联系起来。在机械通气期间，泰丁在隔膜营养和隔膜无力中的作用阐明了这项赠款提案的核心。 AIM 1将批判性地测试TITIN是否影响肌肉的营养。我将使用单侧隔膜神经保护（UDD），这种疾病在临床上很重要，并且将自己作为这项工作的重要工具，因为它会引起快速的肥大 由于循环被动拉伸而导致的半脑膜。我将在两个新型的Titin KO小鼠模型中研究UDD：一种通过删除Ig域（IG KO）而增加的titin刚度，另一个通过删除Titin Splice splice rbm20（RBM20 KO）而降低了TITIN刚度。我预计UDD后的肥厚反应在IG KO小鼠中被夸大并在RMB20 KO小鼠中钝化，并且这种反应是通过改变的Titin信号传导介导的。 AIM 2将研究低滴定刚度是否可以保护隔膜在机械通气引起的卸载过程中弱化，并将使用具有低滴定刚度的大鼠模型。如果基于TITIN的机械感应会介导隔膜对机械卸载的响应，那么我预计通过对隔膜减少机械感应的预处理，我预计较低的Titin刚度会钝化这种响应。 AIM 3将首次研究机械通风的ICU患者的隔膜弱点的机理基础，首次使用机动通风的ICU患者活检分离出的隔膜纤维。目的是研究动物研究的发现是否推断出患者。 该提案的创新在于具有创新的指导假设，其新型小鼠模型，来自机械通风的ICU患者的独特隔膜活检以及其新型实验工具的新型研究焦点。该提案的综合方法有望在我们对膜片功能和titin的作用方面迈出重要的一步。