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: 8599191
• 负责人: DANA M MCTIGUE
• 金额: $ 35.94万
• 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/8599191
• 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(申请人提供)：这项建议将测试新的假设，即小胶质细胞/巨噬细胞或星形胶质细胞中异常的铁稳态导致抑制脊髓损伤(SCI)后的恢复。铁是所有基本细胞功能所必需的，但过量的铁或损害铁的新陈代谢是剧毒的。因此，哺乳动物进化出复杂的调节机制来维持铁的动态平衡。脊髓损伤后，出血和细胞死亡引发慢性炎症反应，这与脊髓内铁的长期积聚有关。大多数铁与激活的小胶质细胞/巨噬细胞共定位。我们的新数据显示，铁代谢和铁调节蛋白在损伤的脊髓中持续数周的失调，当高度保守的巨噬细胞激活机制受损时，这种失调加剧。具体地说，通过Toll样受体4(TLR4)受损的信号会加剧脊髓损伤的恢复，并与增强脊髓内铁的积累有关。此外，脊髓损伤后两种关键蛋白--海普西丁和铁门蛋白(FP)的表达受到不成比例的调节，尤其是在TLR4信号缺陷(TLR4KO)的小鼠中。TLR4KO小鼠脊髓中FP表达的显著增加有利于从激活的小胶质细胞/巨噬细胞输出隔离的铁。这项提议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髓损伤后的脊髓内铁平衡和促进恢复。首先(目标1)，标准的和合成的TLR4激动剂将被注射到脊髓损伤小鼠体内，目的是增加小胶质细胞/巨噬细胞产生海普西丁，这是一种通过导致FP降解来限制铁外流的蛋白质。其次(目标2)，海普西丁将被注入损伤部位，从而绕过TLR4激活的需要。最后，在目标3中，条件基因敲除小鼠(星形胶质细胞、小胶质细胞或单核细胞来源的巨噬细胞中的FP基因敲除)将被用来确定这些不同的细胞亚群对脊髓损伤后过量铁释放的相对贡献；这将使未来的治疗能够针对特定的细胞群。同时，当我们评估脊髓内铁的变化时，我们还将检查全身铁的调节。新的初步数据显示，在脊髓损伤后的几周内，肝脏中的铁相关蛋白发生了变化。由于脊髓损伤患者通常是贫血的(尽管脊髓内铁水平很高)，了解全身和脊髓内铁是如何受到影响的很重要。通过这样做，可以定制新的药物或遗传干预措施，以促进有效的神经恢复，而不会导致全身病理。