Targeting chitin in fibrotic lung disease

摘要 健康的肺功能是由构成环境之间屏障的上皮细胞维持的 成分和寄主组织。这些细胞在慢性炎症和纤维化肺中变得失调。 疾病，反映了遗传和环境两方面的贡献。我们已经确定了一种新的联系 丰富的环境多糖与肺纤维化的进展之间的关系。这种多糖， 甲壳素在特发性肺纤维化(IPF)患者的呼吸道中异常蓄积， 不可逆的、致命的间质性肺病，目前还不完全清楚。肺间质纤维化与肺泡发育有关 上皮细胞功能障碍和未知的环境因素。甲壳素通常被酸性物质降解。 哺乳动物几丁质酶(AMCase)，一种保存在小鼠和人类体内的几丁质分解酶，由肺分泌 上皮细胞介导几丁质从呼吸道中清除。我们的结果表明AMCase是由 上皮细胞可能直接参与肺纤维化的发病机制。环保型甲壳素 在缺乏AMCase或携带IPF相关基因的小鼠的呼吸道中自发积聚 突变，与两个菌株的年龄相关性肺纤维化的发展相一致。此外，鉴于 野生型小鼠解决急性上皮损伤后的纤维化，AMCase缺陷小鼠进展为严重的间质 肺纤维化与死亡率增加有关，类似于人类纤维性肺病的关键方面 在动物模型中很难概括。总而言之，这些数据表明， 在肺纤维化中，降解不溶性甲壳素颗粒在肺纤维化中调节失调，可能是一种相关的 环境因素是疾病的驱动因素。我们已经产生了几种基因敲除、转基因和报告小鼠 这使得能够跟踪和功能评估相关的肺上皮细胞群体。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的贡献和相关 上皮细胞参与肺纤维化的发展。我们将研究甲壳素的分子机制。 结合人类和小鼠常见酶变体的复合体降解新方法 底物。这些分析与体内方法相结合，将允许快速测试治疗性 可以针对肺纤维化环境中的天然底物的候选药物。因此，在这个项目中，我们建议 将治疗性几丁质酶的开发与几丁质如何在三个月内导致纤维化肺疾病的研究结合起来 目的：1.探讨环境甲壳素在肺纤维化中的作用。2.定义蜂窝和 纤维性疾病中几丁质酶活性的分子基础。3.甲壳素的作用机制 人几丁质酶介导的降解，并在体内测试新的治疗方法。理解 在纤维化肺疾病背景下有效靶向和降解甲壳素的方法可能会推进新的治疗方法 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.