Molecular Pathways of Iron Detoxification in the Lung

描述(由申请人提供)： 铁是生物体中含量最丰富的过渡金属，在损伤过程中可以从组织中释放出来。在一些疾病的肺部，例如ARDS和囊性纤维化，已经证实了释放的催化活性铁的积累。相反，以一种催化活性较低的形式隔离铁在肺防御中至关重要。不会对健康组织造成损害的更好、更有效的铁螯合药物还没有开发出来。缺乏对肺部铁代谢的了解阻碍了对其在正常和疾病状态下的作用的全面了解，并阻碍了针对肺的治疗干预的发展。我们的长期目标是了解维持肺内正常铁稳态的分子机制。我们的中心假设是最近发现的两个跨膜铁转运蛋白，DMT1(二价金属转运蛋白1)和MTP1(金属转运蛋白1)，是一种新的肺中铁解毒机制的关键成分。在这个过程中，铁通过DMT1介导的转移被肺细胞摄取，并通过MTP1介导的途径以较少有害的蛋白结合形式被相同的细胞重新输出。这一假说基于我们实验室的数据，包括1)在呼吸道上皮细胞和肺泡巨噬细胞中，DMT1和MTP1基因被铁激活；2)内毒素暴露后和在一些病变肺中，DMT1和MTP1水平升高；3)MTP1蛋白仅定位于呼吸道上皮细胞的顶膜；4)在培养在多孔膜上的人支气管上皮细胞中，这些细胞跨顶面吸收的元素铁后来以蛋白结合的形式重新释放到相同的顶面。我们将使用培养的呼吸道上皮细胞和DMT1/MTP1介导的铁转运缺陷的突变小鼠来验证我们的假设。这项研究将有助于更好地了解患病肺部的铁功能障碍。

DESCRIPTION (provided by applicant): Iron the most abundant transition metal in living organisms can be released from tissues during injury. Accumulation of released catalytic reactive iron has been demonstrated in a number of diseased lungs, for examples, ARDS and cystic fibrosis. Conversely, sequestration of iron in a catalytically less reactive form is fundamentally important in lung defense. Better and more effective iron-chelating drugs, which do not inflict damage on healthy tissues, have not been developed. A lack of knowledge of iron metabolism in the lung hampers a complete understanding of its role in both normal and diseased states, and precludes the development of a lung-specific therapeutic intervention. Our long-term goal is to understand the molecular mechanisms involved in the maintenance of normal iron homeostasis in the lung. Our central hypothesis is that two recently identified transmembrane iron transporters, DMT1 (divalent metal transporter 1) and MTP1 (metal transporter protein 1), are key constituents of a novel mechanism for the detoxification of iron in the lung. In this process, iron is taken up by lung cells via DMT1-mediated transfer and re-exported by the same cells in less harmful protein-bound forms via MTP1-mediated pathway. This hypothesis is formulated based on the data from our laboratories that include 1) DMT1 and MTP1 genes are activated by iron in airway epithelial cells and alveolar macrophages, 2) the levels of DMT1 and MTP1 are elevated after endotoxin exposure and in some diseased lungs, 3) MTP1 protein is localized uniquely to the apical membrane in airway epithelial cells, and 4) in human bronchial epithelial cells cultured on a porous membrane, elemental iron taken up across the apical surface by these cells is later re-released across the same apical surface in protein-bound forms. We will test our hypothesis using cultured airway epithelial cells and mutant mice defective in DMT1/MTP1 mediated iron transport. This study will lead to a better understanding of iron dysfunction in diseased lungs.