Endoplasmic Reticulum Stress Signaling in Allergen-induced Airway Remodeling

 描述（由申请人提供）：已知上皮层的不可逆损伤和缺乏有序的上皮再生是肺重塑的标志。内质网（ER）应激在上皮细胞凋亡和随后的肺重塑病理中起着关键作用。哮喘患者表现出以胶原沉积和平滑肌细胞肥大为标志的气道结构重塑增加，这与肺功能降低、发病率、死亡率和医疗保健费用增加相关。然而，调节哮喘气道纤维化重塑的关键步骤的机制尚不清楚。我们的新的初步结果表明，过敏原屋尘螨（HDM），导致严重的ER应激，激活ER应激转导转录因子，ATF 6，二硫键异构酶ERp 57和二硫键在促凋亡巴克，导致气道上皮细胞凋亡和生长因子的生产从受损的气道上皮细胞，这是与小鼠气道纤维化重塑。重要的是，我们还观察到ATF 6a和ERp 57的缺失或用化学伴侣牛磺熊去氧胆酸（TUDCA）治疗可减弱过敏原诱导的小鼠气道纤维化。本文要解决的中心假设是过敏原暴露诱导ER应激介导的气道上皮细胞凋亡和损伤，随后产生纤维化介质，导致通过ATF 6-ERp 57-巴克信号传导轴的气道结构重塑。在具体目标#1中，我们将确定ER应激转导子ATF 6在调节变应原诱导的二硫键异构酶ERp 57表达以及随后诱导上皮细胞死亡和气道结构重塑发展中的功能作用。具体目标#2旨在探索变应原诱导的蛋白质二硫键异构酶ERp 57在二硫键介导的促凋亡巴克寡聚化中的功能需求，以引起上皮损伤和随后的气道重塑发展。在具体目标#3中，我们将评估化学分子伴侣TUDCA在缓解ER应激和减少随后的上皮细胞死亡，最终导致过敏原诱导的气道重塑消退方面的功效。我们将使用互补的人原代上皮细胞培养和小鼠转基因方法，再加上详细的生化分析，这些过程在小鼠肺组织。完成拟议的实验可能会传授一个重要的知识过敏原诱导的上皮ER压力，其转换器，可能是有针对性的，在未来使用小分子抑制剂，以减轻气道纤维化。此外，我们的项目将评估天然存在的胆汁酸（TUDCA）在减轻气道纤维化方面的疗效。鉴于慢性哮喘和纤维化缺乏治疗选择，TUDCA可能被证明是治疗气道重塑的替代疗法。

 DESCRIPTION (provided by applicant): Incessant damage of epithelial layer and lack of ordered epithelial regeneration are known to be the hallmarks of lung remodeling. The endoplasmic reticulum (ER) stress plays a critical role in epithelial apoptosis, and the subsequent pathology of lung remodeling. Patients with asthma exhibit increased airway structural remodeling marked by collagen deposition and smooth muscle cell hypertrophy, which correlates with decreased lung function, morbidity, mortality and increased health care costs. However, the mechanisms regulating the key steps leading to airway fibrotic remodeling in asthma are unknown. Our novel preliminary results demonstrate that allergen house dust mite (HDM), causes severe ER stress, activation of ER stress transducer-transcription factor, ATF6, disulfide isomerase ERp57 and disulfide bridges in proapoptotic Bak, leading to apoptosis of airway epithelial cells and production of growth factors from the injured airway epithelium, which is associated with airway fibrotic remodeling in mice. Importantly, we also observed that deletion of ATF6a and ERp57 or treatment with a chemical chaperone; tauroursodeoxycholic acid (TUDCA) attenuated allergen induced airway fibrosis in mice. The central hypothesis to be addressed herein is that allergen exposure induces ER stress mediated apoptosis and injury to airway epithelial cells and subsequent production of fibrotic mediators leading to airway structural remodeling via the ATF6-ERp57-Bak signaling axis. In Specific Aim #1 we will determine the functional roles of ER stress transducer ATF6 in regulating allergen- induced expression of disulfide isomerase, ERp57, and subsequent induction of epithelial cell death and development of airway structural remodeling. The specific Aim #2 seeks to explore the functional requirement of allergen-induced protein disulfide isomerase ERp57 in disulfide mediated oligomerization of proapototic Bak to cause epithelial injury and subsequent development of airway remodeling. In Specific Aim #3 we will assess the efficacy of a chemical chaperone, TUDCA in alleviating ER stress and decreasing subsequent epithelial cell death, ultimately resulting in resolution of allergen-induced airway remodeling. We will use complementary human primary epithelial cell culture and mouse transgenic approaches, coupled with detailed biochemical analysis of these processes in mouse lung tissues. Completion of proposed experiments is likely to impart a significant knowledge on allergen-induced epithelial ER stress, and its transducers which may be targeted in the future using small molecule inhibitors to attenuate airway fibrosis. Furthermore, our project will evaluate the efficacy of a naturally occurring bile acid (TUDCA) in attenuating airway fibrosis. Given the dearth of treatment options in chronic asthma and fibrosis, TUDCA may prove to be an alternative therapeutic for treatment of airway remodeling.