ZIP8-dependent Zinc Metabolic Regulation in Alveolar Progenitor Cell Aging and Fibrosis

摘要 随着全球老龄化人口的快速增长，与老龄化相关的肺部疾病的年发病率 如特发性肺纤维化(IPF)，正在增加。因此，非常需要全面地 研究复杂的肺部衰老过程并制定干预措施以延长老年人的健康寿命 人口。2型肺泡上皮细胞(AEC2s)作为祖细胞维持上皮细胞的功能 动态平衡和肺损伤后的修复。肺老化的一个特征是祖细胞耗尽， 反过来，会损害肺泡再生。持续性上皮细胞损伤伴肺泡上皮功能不全 祖细胞衰竭引起的修复导致了年龄相关性肺疾病的原型，IPF。事实上，它一直是 认为IPF是一种AEC2过早衰老的疾病。因此，专注于重新激活和/或 在肺老化中需要扩增AEC2祖细胞。 正如我们所报道的，AEC2祖细胞在人的IPF肺中耗尽。IPF AEC2无法在中重新生成 相对于正常AEC2的有机物检测。在我们对这一应用程序的初步研究中，我们发现 AEC2的更新能力和AEC2种群的丧失发生在肺老化过程中。我们的目标是揭开 在衰老过程中导致AEC2更新受损的分子机制，长期目标是 可以使衰老的AEC2恢复活力的新干预措施的方法。我们发现：1)更新能力 18-20个月龄小鼠肺的AEC2减少，就像我们在IPF肺观察到的一样；2)使用 单细胞rna-seq和流式细胞术，我们发现了特异性锌转运蛋白SLC39A8的缺陷 (编码ZIP8)在18-20年龄小鼠肺和IPF肺的AEC2中；3)Sirtuin信号通路 在博莱霉素损伤的老年小鼠肺和IPF肺的AEC2中表达下调；4)ZIP8调节AEC2 AEC2更新需要通过SIRT1和ZIP8/SIRT1轴的祖细胞功能。此外，我们还有 在AEC2细胞中建立了一种新的ZIP8缺陷小鼠模型，揭示了早产儿AEC2的表型 衰老。基于这些新的发现，我们假设ZIP8缺乏发生在AEC2中随着年龄的增长和 下调SIRT1，从而损害AEC2祖细胞的更新。此外，我们建议 恢复ZIP8/锌/SIRT1途径的关键成分将改善AEC2前体活性，从而 保持肺上皮细胞完整性，预防与年龄相关的肺部疾病。

Abstract With the rapid growth of an aging population worldwide, the annual incidences of aging-associated lung diseases such as idiopathic pulmonary fibrosis (IPF), are increasing. Therefore, there is a great need to comprehensively investigate the complex process of lung aging and develop interventions to extend the health span of the elderly population. Type 2 alveolar epithelial cells (AEC2s) function as progenitor cells that maintain epithelium homeostasis and repair the lung after injury. A characteristic of the aging lung is progenitor cell exhaustion and, in turn, impairs alveolar regeneration. Persistent epithelial cell injury coupled with inadequate alveolar epithelial repair due to progenitor cell failure results in a prototype of age-associated lung disease, IPF. In fact, it has been argued that IPF is a disease of premature aging of AEC2s. Hence, studies focusing on re-activating and/or expanding AEC2 progenitor cells in lung aging are needed. As we reported, AEC2 progenitor cells are exhausted in human IPF lungs. IPF AEC2s fail to regenerate in organoid assays relative to normal AEC2s. In our preliminary studies for this application, we found a decrease in AEC2 renewal capacity and a loss of AEC2 population occur during lung aging. We aimed to uncover the molecular mechanisms that contribute to impaired AEC2 renewal during aging, with the long-term goal of pointing the way to novel interventions that can rejuvenate aged AEC2s. We have found that: 1) The renewal capacity of AEC2s in 18-20 months old aged mouse lungs are reduced just as what we observed with IPF lungs; 2) Using single cell RNA-seq and flow cytometry, we identified a deficiency of a specific zinc transporter SLC39A8 (encoding ZIP8) in AEC2s from 18-20 months old aged mouse lungs and IPF lungs; 3) Sirtuin signaling pathway was downregulated in AEC2s from bleomycin-injured old mouse lungs and IPF lungs; 4) ZIP8 regulates AEC2 progenitor function through SIRT1 and ZIP8/SIRT1 axis is required for AEC2 renewal. In addition, we have generated a novel mouse model of Zip8 deficiency in AEC2 cells that reveals phenotypes of premature AEC2 aging. Based on these novel findings, we hypothesize that ZIP8 deficiency occurs in AEC2s with aging and downregulates SIRT1, thereby impairing AEC2 progenitor cell renewal. Furthermore, we propose that restoring critical components of the ZIP8/zinc/SIRT1 pathway will improve AEC2 progenitor activity and, thus maintain lung epithelial integrity and prevent age-associated lung diseases.