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、严重哮喘的主要特征，并且这种受损上皮的修复通常不会在哮喘气道中发生。我们提出了一种新的范例，可以解释为什么哮喘气道的上皮修复不能正常发挥作用。在正常气道中，损伤会诱导产生“促炎”细胞因子，例如 TNFa 和 IL-1¿。这两种细胞因子都会激活特定的信号通路，从而激活丝裂原激活蛋白激酶 (MAPK)，例如 p38 MARK 和 JNK，进而启动气道上皮细胞迁移以覆盖受损气道的早期步骤。然而，哮喘气道的环境会通过严重且持续的支气管收缩来反复拉伸和压缩气道，从而损害 MAPK 介导的迁移，从而减缓这一修复过程。为了解决这一范式，我们提出以下具体目标：目标#1。确定 p38 MARK 和 JNK 是否调节损伤后气道上皮细胞的迁移。我们假设损伤后几分钟到几小时内通过 MAPK 途径的信号传导整合了许多局部和区域性刺激，这些刺激是通过转录因子（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。确定周期性拉伸和压缩是否通过下调 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）来损害气道上皮细胞迁移。我们假设循环拉伸和压缩部分地通过下调 p38 MAPK 和/或 JNK 的激活来抵消预修复信号并抑制修复，而这部分是通过抑制上游激活途径的激活而发生的。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 加速气道上皮细胞迁移，以及 IL-1¿ 和 TNFa 在循环拉伸和压缩条件下是否无法加速修复。我们假设 TNFa 和 IL-13 通过激活 MAPK 来加速损伤后的上皮修复过程，但在循环拉伸和压缩的对抗下却无法做到这一点。哮喘气道内发现的其他产物（可在支气管肺泡灌洗液中收集）也能刺激修复，但无法克服周期性变形对气道上皮细胞迁移的抑制作用。了解早期细胞迁移中信号传导途径的步骤、细胞因子在启动迁移中的作用以及损害早期所需信号传导从而减缓迁移的物理力将有助于我们了解慢性哮喘中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.