Regulation of airway epithelial repair

描述(由申请人提供)：持续的呼吸道上皮损伤是慢性重度哮喘的主要特征，而这种受损的上皮修复通常不会发生在哮喘的呼吸道中。我们提出了一种新的范式，可以解释为什么哮喘呼吸道上皮修复不能正常发挥作用。在正常的呼吸道中，损伤诱导产生“促炎”细胞因子，如TNFa和IL-1？这两种细胞因子都激活特定的信号通路，激活丝裂原激活的蛋白激酶(MAPK)，如p38Mark和JNK，进而启动呼吸道上皮细胞迁移的早期步骤，以覆盖受损的呼吸道。然而，哮喘呼吸道的环境通过严重和持续的支气管收缩反复拉伸和压缩呼吸道，从而减缓了这种修复过程，这将损害MAPK介导的迁移。为了应对这一范式，我们提出了以下具体目标：目的1.确定p38Mark和JNK是否调节损伤后呼吸道上皮细胞的迁移。我们假设，在损伤后几分钟到几小时内，通过MAPK通路的信号整合了许多局部和局部的修复刺激，通过转录因子ATF-2和AP-1激活基因表达，并通过p38MAPK介导的热休克蛋白-27的激活启动肌动蛋白重塑。目的#2.确定周期性拉伸和压迫是否通过下调p38MAPK和JNK的激活，特别是通过抑制通常导致它们激活的上游途径来损害呼吸道上皮细胞的迁移。我们假设，循环拉伸和压缩对抗修复信号，部分是通过下调p38MAPK和/或JNK的激活来抑制修复，这部分是通过抑制上游激活通路的激活而发生的。目的#3.确定肺泡灌洗液、IL-1β和TNFa是否通过p38MAPK和JNK促进气道上皮细胞迁移，以及在周期性拉伸和挤压条件下IL-1β和TNFa是否不能促进修复。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，但当被循环拉伸和压缩所抵消时，这一过程并不能实现。哮喘呼吸道内发现的其他产物，如可在支气管肺泡灌洗液中收集的，也可刺激修复，但无法克服周期性变形对呼吸道上皮细胞迁移的抑制作用。了解早期细胞迁移中信号通路的步骤，细胞因子在启动迁移中的作用，以及破坏早期所需信号从而减缓迁移的物理作用力，将有助于我们理解慢性哮喘时呼吸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.