Targeting chitin in fibrotic lung disease

摘要 健康的肺功能是由上皮细胞维持的，上皮细胞构成了环境与肺组织之间的屏障。 成分和宿主组织。这些细胞在慢性炎症和纤维化肺中变得失调 疾病，反映了遗传和环境的贡献。我们发现了一种新的关联 丰富的环境多糖和肺纤维化的发展之间的联系。这种多糖， 几丁质在患有特发性肺纤维化（IPF）的人的气道中异常积聚， 不可逆的、致命的间质性肺病，尚未完全了解。IPF与肺泡 上皮细胞功能障碍和未知的环境因素。甲壳素通常被酸性降解 哺乳动物几丁质酶（AMCase），一种在小鼠和人类中保守的几丁质分解酶，由肺分泌 上皮细胞介导几丁质从气道中清除。我们的研究结果表明，AMCase是由 可能直接参与肺纤维化发病机制的上皮细胞。环境衍生甲壳素 在缺乏AMCase或携带IPF相关遗传基因的小鼠的气道中自发积累 突变，与两种菌株中年龄相关的肺纤维化的发展一致。此外，虽然 野生型小鼠在急性上皮损伤后解决纤维化，AMCase缺陷小鼠进展为严重的间质性纤维化， 与死亡率增加相关的肺纤维化，类似于人类纤维化肺病的关键方面， 很难在动物模型中重现。总之，这些数据表明， 降解气道中的不溶性几丁质颗粒在肺纤维化中失调， 疾病的环境驱动因素。我们已经产生了几个基因敲除，转基因和报告小鼠 其使得能够对相关肺上皮细胞群体进行跟踪和功能评估。这些不同 小鼠品系将被用来解剖哺乳动物几丁质分解系统和相关的贡献。 上皮细胞对肺纤维化的发展。我们将描述几丁质的分子机制 使用在复合物上掺入常见的人类和小鼠酶变体的新测定的降解 印刷受体.这些测定与体内方法相结合，其将允许快速测试治疗药物。 可以靶向肺纤维化环境中的天然底物的候选物。因此，在本项目中，我们建议 将治疗性几丁质酶的开发与几丁质如何在三个国家驱动纤维化肺病的研究相结合， 目标：1.探讨环境几丁质对肺纤维化的影响。2.为了定义细胞和 纤维化疾病中几丁质酶活性的分子基础。3.为了表征几丁质的作用机制， 通过人几丁质酶介导的降解和测试体内新的治疗方法。理解 在纤维化肺病的背景下有效靶向和降解几丁质的方法可能会推动新的治疗方法 目前缺乏有效治疗的一组相关疾病。

ABSTRACT Healthy lung function is maintained by epithelial cells that comprise the barrier between environmental constituents and host tissues. These cells become dysregulated in chronic inflammatory and fibrotic lung disease, reflecting both genetic and environmental contributions. We have identified a novel association between an abundant environmental polysaccharide and the progression of lung fibrosis. This polysaccharide, chitin, accumulates abnormally in the airways of humans with idiopathic pulmonary fibrosis (IPF), an irreversible, fatal interstitial lung disease that is not completely understood. IPF has been linked to alveolar epithelial cell dysfunction and unknown environmental factors. Chitin is normally degraded by acidic mammalian chitinase (AMCase), a chitinolytic enzyme conserved in mice and humans that is secreted by lung epithelial cells to mediate chitin clearance from the airways. Our results indicate that AMCase is produced by epithelial cells that may be directly involved in the pathogenesis of lung fibrosis. Environmentally-derived chitin spontaneously accumulates in the airways of mice lacking AMCase or bearing IPF-associated genetic mutations, coincident with the development of age-related lung fibrosis in both strains. Additionally, whereas wild-type mice resolve fibrosis after acute epithelial injury, AMCase-deficient mice progress to severe interstitial lung fibrosis associated with increased mortality, resembling key aspects of human fibrotic lung disease that have been difficult to recapitulate in animal models. Together, these data suggest that the routine process of degrading insoluble chitin particles in the airways is dysregulated in lung fibrosis and may be a relevant environmental driver of disease. We have generated several genetic knockout, transgenic, and reporter mice that enable the tracking and functional assessment of relevant lung epithelial cell populations. These different mouse strains will be used to dissect the contributions of the mammalian chitinolytic system and associated epithelial cells to the development of lung fibrosis. We will characterize the molecular mechanisms of chitin degradation using novel assays incorporating common human and mouse enzyme variants on complex substrates. These assays are coupled with in vivo approaches that will allow for rapid testing of therapeutic candidates that can target natural substrates in a lung fibrosis setting. Thus, in this project, we propose coupling therapeutic chitinase development with the study of how chitin drives fibrotic lung disease in three aims: 1. To determine the contribution of environmental chitin to lung fibrosis. 2. To define the cellular and molecular basis for chitinase activity in fibrotic disease. 3. To characterize the mechanisms of chitin degradation mediated by human chitinases and test novel therapeutic approaches in vivo. Understanding ways to efficiently target and degrade chitin in the context of fibrotic lung disease may advance new therapies for a group of related diseases that currently lacks effective treatments.