Regulation of airway epithelial repair

描述（由申请人提供）：气道上皮的持续损伤是慢性、重度哮喘的主要特征，而这种受损上皮的修复通常不会发生在哮喘气道中。我们提出了一种新的范式，可以解释为什么哮喘气道的上皮修复不能正常工作。在正常气道中，损伤诱导“促炎”细胞因子如TNFa和IL-1¿的产生。这两种细胞因子激活特定的信号通路，激活丝裂原活化蛋白激酶（MAPKs），如p38 MARK和JNK，进而启动气道上皮细胞迁移的早期步骤，以覆盖受损的气道。然而，哮喘气道的环境减缓了这一修复过程，通过严重和持续的支气管收缩反复拉伸和压缩气道，这将损害mapk介导的迁移。为了解决这个范例，我们提出以下具体目标：目标#1。确定p38 MARK和JNK是否调节气道上皮细胞损伤后的迁移。我们假设，在损伤后几分钟到几小时内，通过MAPK信号通路整合了许多促进修复的局部和区域刺激，通过转录因子如ATF-2和AP-1激活基因表达，并通过p38 MAPK介导的热休克蛋白-27激活启动肌动蛋白重塑。目标# 2。通过下调p38 MAPK和JNK的激活，特别是通过抑制通常导致其激活的上游途径，确定循环拉伸和压缩是否会损害气道上皮细胞的迁移。我们假设，循环拉伸和压缩抵消了预处理信号，部分通过下调p38 MAPK和/或JNK的激活来抑制修复，部分通过抑制上游激活途径的激活来发生。目标# 3。确定支气管肺泡灌洗液、IL-1¿和TNFa是否通过p38 MAPK和JNK加速气道上皮细胞的迁移，以及IL-1¿和TNFa在循环拉伸和压缩条件下是否不能加速修复。我们假设TNFa和IL-13通过激活MAPKs来加速损伤后上皮细胞的修复过程，但当被循环拉伸和压缩时却无法做到这一点。在哮喘气道内发现的其他产物，如支气管肺泡灌洗液，也能刺激修复，但不能克服循环变形对气道上皮细胞迁移的抑制作用。了解早期细胞迁移信号通路的步骤，细胞因子在启动迁移中的作用，以及损害早期所需信号从而减缓迁移的物理力量，将有助于我们理解慢性哮喘气道上皮如何无法充分修复。

DESCRIPTION (provided by applicant): Persistent damage to airway epithelium is a cardinal feature in chronic, severe asthma, and repair of this damaged epithelium frequently does not occur in asthmatic airways. We suggest a new paradigm that may explain why epithelial repair in asthmatic airways does not function properly. In normal airways, injury induces the production of "pro-inflammatory" cytokines such as TNFa and IL-1¿. Both cytokines activate specific signaling pathways that activate the mitogen-activated protein kinases (MAPKs), such as p38 MARK and JNK, that in turn initiate early steps in the migration of airway epithelial cells to cover damaged airways. However, the milieu of the asthmatic airway acts to slow this repair process, by repeated stretching and compressing airways via severe and continued bronchoconstriction that will impair MAPK-mediated migration. To address this paradigm we propose the following specific aims: Aim #1. Determine whether or not p38 MARK and JNK regulate the migration of airway epithelial cells after injury. We hypothesize that signaling via MAPK pathways within minutes to hours of injury integrates a number of local and regional stimuli that are pro-reparative, by activating gene expression via transcription factors such as ATF-2 and AP-1, and by initiating actin remodeling via p38 MAPK mediated activation of heat shock protein-27. Aim #2. Determine whether or not cyclic stretch and compression impairs airway epithelial cell migration by down-regulating activation of p38 MAPK and JNK, specifically by suppressing upstream pathways that ordinarily lead to their activation. We hypothesize that cyclic stretch and compression counter the proreparative signals and inhibit repair in part by down-regulating activation of p38 MAPK and/or JNK, and that this occurs in part by suppressing activation of upstream activating pathways. Aim #3. Determine whether or not bronchoalveolar lavage fluid, IL-1¿ and TNFa accelerate airway epithelial cell migration via p38 MAPK and JNK, and whether IL-1¿ and TNFa fail to accelerate repair under conditions of cyclic stretch and compression. We hypothesize that TNFa and IL-13 accelerate the process of epithelial repair after injury via activation of MAPKs, but fail to do so when countered by cyclic stretch and compression. Other products found within asthmatic airways, as can be collected in bronchoalveolar lavage fluid, also stimulate repair but will not be able to overcome the inhibitory effects of cyclic deformation on airway epithelial cell migration. Understanding the steps in the signaling pathway in early cell migration, the role of cytokines in initiating migration, and the physical forces that impair early, required signaling and thereby slow migration will help us to understand how the airway epithelium may fail to repair adequately in chronic asthma.