Retinal Iron Transport in Health and Disease

项目摘要 铁在健康和患病的视网膜中都起着关键作用。的长期目标 提出的研究是为了了解视网膜铁通量的调节，确定为什么铁 在视网膜疾病中积累，并发现如何防止视网膜铁毒性。铁是 在视网膜中必需的氧化磷酸化，膜生物发生和视黄醇 异构化，但成为一个中央生产商的氧化应激时，调节不当。 铁毒性在视网膜疾病中是明显的，如下：1）铁引起快速视网膜变性 眼内异物进入眼内。2)人类AMD视网膜具有 铁含量高于年龄匹配的对照组，表明铁超载可能在AMD中发挥作用 发病机制3)与这一假设相一致，在遗传性疾病aceroplasminemia中， 铁氧化酶铜蓝蛋白（Cp）的缺失导致视网膜铁蓄积和早发性 黄斑变性4)敲除Cp及其同源物Hephaestin（Heph）的小鼠具有 年龄依赖性视网膜铁超载和AMD的退化共享特征，包括 补体激活和视网膜下新生血管形成。后两点表明，Cp 和Heph对视网膜健康很重要。其他器官的证据表明，Cp或Heph 可以与质膜铁转运蛋白（Fpn）合作， 细胞上一个供资期的进展情况表明，Fpn是以绝对营养水平表示的， 视网膜血管内皮细胞、Muller细胞和RPE的基底外侧膜。 由于Fpn是唯一已知的细胞铁输出蛋白，这种表达模式表明铁的转运途径。 铁助熔剂具有突变的Fpn的小鼠，其对由铁调节蛋白引发的降解具有抗性。 激素Hepc，具有视网膜铁积累。这些结果表明，当地的铁调节 Fpn和Hepc介导的视网膜内轴。本文提出的实验将利用视网膜 Fpn和Hepc的细胞类型特异性敲除，以确定Fpn介导的视网膜铁的途径 并评价Hepc对其的调节作用。将分析AMD和对照视网膜以确定 Hepc/Fpn失调是否有助于AMD中记录的铁积累 视网膜血清铁水平与局部控制铁流入视网膜的作用将是 测定该结果将有助于将AMD铁临床研究集中在血清铁水平或 视网膜内的局部铁调节机制。

PROJECT SUMMARY Iron plays a critical role in both the healthy and diseased retina. The long term goals of the proposed studies are to understand regulation of retinal iron flux, determine why iron accumulates in retinal disease, and discover how to protect against retina iron toxicity. Iron is necessary in the retina for oxidative phosphorylation, membrane biogenesis and retinol isomerization, but becomes a central producer of oxidative stress when improperly regulated. Iron toxicity is evident in retinal disease as follows: 1) Iron causes rapid retinal degeneration following entry into the eye carried by an intraocular foreign body. 2) Human AMD retinas have more iron than age-matched controls, suggesting that iron overload may play a role in AMD pathogenesis. 3) Consistent with this hypothesis, in the inherited disease aceruloplasminemia, loss of the ferroxidase ceruloplasmin (Cp) results in retinal iron accumulation and early onset macular degeneration. 4) Mice with knockout for Cp and its homolog hephaestin (Heph) have an age-dependent retinal iron overload and degeneration sharing features of AMD, including complement activation and subretinal neovascularization. The latter two points indicate that Cp and Heph are important for retinal health. Evidence from other organs suggests that Cp or Heph can cooperate with the plasma membrane iron transporter ferroportin (Fpn) to export iron from cells. Progress from the prior funding period indicates that Fpn is expressed on the ablumenal side of retinal vascular endothelial cells, Muller cells, and the basolateral membrane of the RPE. Since Fpn is the only known cellular iron exporter, this expression pattern suggests the route of iron flux. Mice with a mutated Fpn that is resistant to degradation triggered by the iron regulatory hormone Hepc, have retinal iron accumulation. These results suggest a local iron-regulatory axis within the retina mediated by Fpn and Hepc. Experiments proposed herein will utilize retinal cell type specific knockouts of Fpn and Hepc to determine the route of Fpn-mediated retinal iron flux and evaluate its regulation by Hepc. AMD and control retinas will be analyzed to determine whether Hepc/Fpn dysregulation contributes to the documented iron accumulation in AMD retinas. The role of serum iron levels versus local control of iron influx into the retina will be determined. The outcome will help focus AMD-iron clinical studies on either serum iron levels or local iron regulatory mechanisms within the retina.