CORTICOSTEROID INDUCED APOPTOSIS IN AIRWAY EPITHELIUM

气道上皮细胞在维持气道内环境稳定方面具有重要作用，并且在炎症性疾病如哮喘中可能被广泛损伤。 环境暴露于过敏原可能会恶化哮喘，部分原因是导致上皮细胞脱落和细胞死亡。 虽然支气管上皮剥脱是哮喘病理学的主要特征，但这种现象的机制仍不清楚。 作为其在气道中的强效炎症作用的一部分，皮质类固醇诱导迁移性嗜酸性粒细胞和T淋巴细胞的凋亡。 我们实验室的新数据表明，皮质类固醇也可以诱导气道上皮细胞凋亡，无论是在培养细胞和动物模型中。 因此，皮质类固醇可能具有迄今未认识到的不良后果：诱导上皮细胞凋亡和延长支气管上皮剥脱。持续的上皮损伤可能导致上皮下纤维化和慢性气道重塑的发展。 我们的建议的中心假设是，皮质类固醇治疗是有害的支气管上皮细胞的生存，即使它促进气道炎症的决议。 我们的目标是回答两个特定的假设：1）皮质类固醇是否引起上皮细胞凋亡，并在过敏原攻击过程中加重上皮细胞凋亡; 2）上皮细胞的分化因子是否对抗皮质类固醇诱导的凋亡。将使用特定测定法来确定培养物以及气道和肺组织切片中的细胞凋亡。 皮质类固醇引发细胞凋亡的信号机制将通过Western印迹、荧光测定和RT-PCR进行检查。 使用转染的人气道上皮细胞将确定分化因子，如转化生长因子-β和顺式-视黄酸，是否减弱细胞凋亡和加速修复。 将使用小鼠模型来证明皮质类固醇和分化因子治疗对上皮细胞凋亡、修复和体内完整性的影响。 该模型将有助于确定气道炎症和皮质类固醇治疗对上皮损伤发生的相互作用。这些实验将证明上皮细胞凋亡导致损伤后气道粘膜修复受损的机制。 皮质类固醇加重上皮细胞凋亡、脱落和死亡的证据表明，慢性哮喘中至少有一种病理学发现可能是治疗该疾病的结果。 这些数据将有助于在哮喘治疗中产生新的治疗理念和模式，以抑制炎症，同时防止粘膜损伤。

The airway epithelium has a major role in maintaining airway homeostasis and may be damaged extensively in inflammatory diseases such as asthma. Environmental exposure to allergen may worsen asthma in part by causing epithelial cell shedding and cell death. Although denudation of bronchial epithelium is a cardinal feature of the pathology of asthma, the mechanisms underlying this phenomenon remain unknown. As part of their potent inflammatory effects in airways, corticosteroids induce apoptosis in migratory eosinophils and T-lymphocytes. New data from our laboratory suggest that corticosteroids can also induce apoptosis in airway epithelium, both in cultured cells and in animal models. As such, corticosteroids may possess a heretofore unrecognized adverse consequence: induction of epithelial cell apoptosis and prolongation of bronchial epithelial denudation. Continued epithelial damage may lead to the development of sub- epithelial fibrosis and chronic airway remodeling. The central hypothesis of our proposal is that corticosteroid treatment is deleterious to bronchial epithelial survival, even though it promotes resolution of airway inflammation. Our goal is to answer two specific hypotheses: 1) whether corticosteroids elicit epithelial cell apoptosis, and worsen epithelial cell apoptosis during allergen challenge; and 2) whether differentiation factors for epithelial cells counter corticosteroid-induced apoptosis. Specific assays to determine apoptosis both in culture and in airway and lung tissue sections will be used. Signaling mechanisms for initiation of apoptosis by corticosteroids will be examined by Western blot, fluorescent assays, and RT-PCR. The use of transfected human airway epithelial cells will determine whether differentiation factors, such as transforming growth factor-beta and cis-retinoic acid, attenuate apoptosis and speed repair. A mouse model will be used to demonstrate the effect of corticosteroid and differentiation factor treatment on epithelial cell apoptosis, repair and integrity in vivo. This model will help determine the interplay between airway inflammation and corticosteroid treatment on the genesis of epithelial damage. These experiments will demonstrate mechanisms by which epithelial cell apoptosis leads to impaired repair of the airway mucosa after injury. Demonstration that corticosteroids worsen epithelial cell apoptosis, shedding and death would suggest that at least one of the pathologic findings in chronic asthma may be a result of treatment for the disease. These data would help lead to new therapeutic ideas and modalities in the treatment of asthma to suppress inflammation while preventing mucosal damage.