CORTICOSTEROID INDUCED APOPTOSIS IN AIRWAY EPITHELIUM

气道上皮在维持气道稳态中起着重要作用，在哮喘等炎症性疾病中可能受到广泛损伤。环境暴露于过敏原可能加重哮喘，部分原因是引起上皮细胞脱落和细胞死亡。虽然支气管上皮剥落是哮喘病理的主要特征，但这一现象的机制尚不清楚。作为其在气道中有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淋巴细胞凋亡。我们实验室的新数据表明，在培养细胞和动物模型中，皮质类固醇也可以诱导气道上皮细胞凋亡。因此，皮质类固醇可能具有迄今未被认识到的不良后果：诱导上皮细胞凋亡和延长支气管上皮脱落。持续的上皮损伤可能导致亚上皮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存活，即使它促进气道炎症的解决。我们的目标是回答两个特定的假设：1)皮质类固醇是否会引起上皮细胞凋亡，并在过敏原攻击时加重上皮细胞凋亡；2)上皮细胞分化因子是否对抗皮质类固醇诱导的细胞凋亡。将使用特定的测定方法来确定培养和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 blot、荧光检测和RT-PCR进行研究。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和顺式维甲酸）是否会减弱细胞凋亡和加速修复。小鼠模型将用于证明皮质类固醇和分化因子处理对体内上皮细胞凋亡、修复和完整性的影响。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。这些实验将揭示上皮细胞凋亡导致气道黏膜损伤后修复受损的机制。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表现可能是该疾病治疗的结果。这些数据将有助于为哮喘治疗提供新的治疗思路和模式，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.