Restoring Iron Homeostasis to Promote Recovery after Spinal Cord Injury

恢复铁稳态以促进脊髓损伤后的恢复

• 批准号: 8703831
• 负责人: DANA M MCTIGUE
• 金额: $ 35.69万
• 依托单位: OHIO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8703831
• 关键词: Adult; Affect; Agonist; Anti-Bacterial Agents; Astrocytes; Binding; Bone Marrow; Bypass; Cell Death; Cell physiology; Cells; Cessation of life; Chimera organism; Chronic; Data; Defense Mechanisms; Development; Extracellular Space; Ferritin; Functional disorder; Future; Genetic Polymorphism; Genetic Screening; Goals; Grant; Healthcare; Hemorrhage; Homeostasis; Human; Inflammation; Inflammatory; Inflammatory Response; Injury; Integral Membrane Protein; Iron; Iron-Regulatory Proteins; Knock-out; Knockout Mice; Lead; Life; Liver; Macrophage Activation; Mammals; Mediating; Metals; Microglia; Molecular; Movement; Mus; Myeloid Cells; Oligodendroglia; Oxidative Stress; Paralysed; Pathologic Processes; Pathology; Pathway interactions; Population; Production; Proteins; Radiation; Recovery; Recovery of Function; Regulation; Relative (related person); Signal Transduction; Site; Spinal; Spinal Cord; Spinal cord injury; Spinal cord injury patients; Stream; Techniques; Testing; Time; Tissues; antimicrobial; base; extracellular; gene therapy; hepcidin; improved; injured; iron metabolism; macrophage; metal transporting protein 1; mimetics; monocyte; nervous system disorder; neurological recovery; neuroprotection; neurotoxicity; novel; pathogen; peptide hormone; progenitor; prognostic; public health relevance; receptor; repaired; research study; response; therapeutic target; tissue repair; toll-like receptor 4; uptake

DESCRIPTION (provided by applicant): This proposal will test the novel hypothesis that aberrant iron homeostasis in microglia/macrophages or astrocytes causes inhibits recovery after spinal cord injury (SCI). Iron is essential for all basic cell functions but excess iron or impaire iron metabolism is highly toxic. Accordingly, mammals have evolved sophisticated regulatory mechanisms to maintain iron homeostasis. After SCI, hemorrhage and cell death elicit a chronic inflammatory response that is associated with prolonged accumulation of intraspinal iron. Most of this iron co- localizes with activated microglia/macrophages. Our new data show that iron metabolism and iron regulatory proteins are dysregulated in the injured spinal cord for several weeks and this dysregulation is exacerbated when highly conserved mechanisms of macrophage activation are impaired. Specifically, impaired signaling via toll-like receptor 4 (TLR4) exacerbates recovery from SCI and is associated with enhanced accumulation of intraspinal iron. Also, expression of two key proteins, hepcidin and ferroportin (FP), is disproportionately regulated after SCI, most notably in mice with deficient TLR4 signaling (TLR4KO). A significant increase in FP expression in spinal cords of TLR4KO mice favors export of sequestered iron from activated microglia/macrophages. Experiments in this proposal will determine if macrophage and astrocyte iron-related proteins can be manipulated to restore intraspinal iron homeostasis and promote recovery after SCI. First (Aim 1), canonical and synthetic TLR4 agonists will be injected into SCI mice with the goal of enhancing microglia/macrophage production of hepcidin, a protein that limits iron efflux by causing FP degradation. Second (Aim 2), hepcidin will be infused to the injury site thereby bypassing the need for TLR4 activation. Finally, in Aim 3, conditional knock-out mice (FP knockout in astrocytes, microglia or monocyte-derived macrophages) will be used to determine the relative contribution of these distinct cellular subsets to excess iron release after SCI; this will allow future therapies to be targeted to specific cell populations. In parallel, as we evaluate changes i intraspinal iron, we will also examine systemic iron regulation. Novel preliminary data show that iron-related proteins are altered for several weeks post-SCI in the liver. Since SCI patients are often anemic (despite high intraspinal iron levels), it is important to understand how systemic and intraspinal irons are affected. By doing so, new pharmacologic or genetic interventions can be customized to promote efficient neurological recovery without causing systemic pathology.

描述（由申请人提供）：该提案将检验以下新假设：小胶质细胞/巨噬细胞或星形胶质细胞中异常的铁稳态会导致脊髓损伤（SCI）抑制恢复。铁对于所有基本细胞功能都是必不可少的，但是过量的铁或障碍铁代谢是有毒的。因此，哺乳动物已经发展出复杂的调节机制以维持铁稳态。 SCI后，出血和细胞死亡引起了慢性炎症反应，该反应与长期积累的脊柱内铁的积累有关。大多数铁与活化的小胶质细胞/巨噬细胞共同定位。我们的新数据表明，铁代谢和铁调节蛋白在受伤的脊髓中失调数周，当高度保守的巨噬细胞激活机制受损时，这种失调会加剧。具体而言，通过Toll样受体4（TLR4）通过Toll样受体4（TLR4）的信号传导加剧了从SCI中恢复，并且与载体内铁的积累增强有关。同样，在SCI之后，两种关键蛋白（Hepcidin和Ferroportin（FP））的表达受到了不成比例的调节，最著名的是在缺乏TLR4信号传导（TLR4KO）的小鼠中。 TLR4KO小鼠的脊髓中FP表达的显着增加，有利于从活化的小胶质细胞/巨噬细胞中导出隔离的铁。该提案中的实验将确定是否可以操纵巨噬细胞和星形胶质细胞铁相关蛋白来恢复脊柱内铁稳态并在SCI后促进恢复。首先（AIM 1），典型和合成的TLR4激动剂将被注入Sci小鼠中，其目的是增强肝素的小胶质细胞/巨噬细胞产生，这是一种蛋白质，该蛋白质通过导致FP降解来限制铁外排。第二（AIM 2），肝素将被注入损伤部位，从而绕开了对TLR4激活的需求。最后，在AIM 3中，有条件的敲除小鼠（星形胶质细胞，小胶质细胞或单核细胞衍生的巨噬细胞中的FP敲除）将用于确定这些不同细胞子集对SCI后过量铁释放的相对贡献；这将允许将来的疗法针对特定的细胞群体。同时，随着我们评估I次级铁的变化，我们还将检查全身铁调节。新的初步数据表明，与铁相关的蛋白质在肝脏中SCI后几周改变。由于SCI患者通常是贫血的（尽管脊柱内铁水平较高），因此了解系统性和脊柱内铁如何受到影响很重要。通过这样做，可以定制新的药理学或遗传干预措施，以促进有效的神经恢复而不会引起全身病理。