Retinal Disease Promoted by Iron-Induced Bisretinoid Oxidation

视网膜色素上皮 (RPE) 细胞会随着年龄的增长以及威胁视力的疾病而积累铁，包括 年龄相关性黄斑变性 (AMD)、隐性 Stargardt 病 (STGD1) 和铜蓝蛋白血症。 由于铁催化形成高反应性羟基，不受限制的游离铁会导致氧化还原失衡 过氧化氢产生的自由基。 RPE 所承受的氧化负担也源自 视黄醛加合物（双视黄醇）的混合物，随着年龄的增长以脂褐质的形式积累。的破坏性影响 RPE 细胞上的这些化合物与许多与年龄相关和早发性视网膜病变有关 疾病包括 STGD1 和 AMD。这些颜料的不利影响可能至少部分是由于 它们倾向于光产生活性氧并光降解为破坏性的二羰基和 含醛的片段。拟议研究的主要目标是了解铁是否可以 与 RPE 中的双维A酸相互作用，促进 RPE 细胞损伤和死亡。这个假设的中心假设 提议认为，细胞内铁失调部分通过促进双维A酸介导不良反应 氧化和降解。如果铁和双维A酸的组合加剧了氧化还原失衡 光氧化、铁螯合可能对涉及双维A酸毒性的疾病具有视网膜保护作用，包括 STGD1。在具体目标 1 中，我们将确定去铁酮 (DFP) 治疗对 Abca4-/- 小鼠的影响。 DFP 是一种临床上重要的铁螯合剂，可降低铁水平。我们将使用 DFP 广告管理系统进行保护测试 对抗 Abca4-/- 小鼠中铁介导的双维A酸氧化和感光细胞损失。氧化应激会 使用一组氧化还原指示剂进行评估，并且将采用基于细胞和无细胞的测定。具体来说 目标 2，我们建议确定补充铁是否有助于光氧化/氧化和 双维A酸的降解。这一目标将通过小鼠、细胞和无细胞检测来实现。我们将确定 铁介导毒性的途径之一是否是通过促进双维A酸氧化。我们还将 确定 STGD1 模型 Abca4-/- 小鼠的细胞内铁是否升高。在实验中提出 具体目标 3 我们将研究缺乏铜蓝蛋白 (Cp) 和铁黄蛋白 (Heph)、铁氧化酶的小鼠 将二价铁 (Fe2) 转化为三价铁 (Fe3) 的蛋白质，以促进细胞铁输出。对的影响 当使用双维A酸形成抑制剂时，将评估 Cp-/-;Heph-/- 小鼠的表型 管理；在 Abca4-/- 中； Cp-/-;Heph-/- 小鼠的 RPE 中铁和双维A酸含量较高， 当Rpe6rd12中没有RPE双维A酸(Rpe6rd12)和Cp-/-;Heph-/-缺陷组合时； Cp-/-;Heph-/- 老鼠。这项研究的完成将加深我们对铁、光和双维A酸如何结合的理解 促进与年龄相关和单基因视网膜疾病的疾病过程。

Retinal pigment epithelial (RPE) cells accumulate iron with age, and in diseases that threaten vision including age-related macular degeneration (AMD), recessive Stargardt disease (STGD1) and aceruloplasminemia. Unrestrained free iron can cause redox imbalance due to iron-catalyzed formation of highly reactive hydroxyl free radical from hydrogen peroxide. The oxidative burden to which RPE is subjected also originates from a mixture of retinaldehyde-adducts (bisretinoids) that accumulate with age as lipofuscin. The damaging effects of these compounds on RPE cells are implicated in a number of age-associated and early-onset forms of retinal disease including STGD1 and AMD. The adverse effects of these pigments are likely due, at least in part, to their propensity to photogenerate reactive oxygen species and to photodegrade into damaging dicarbonyl and aldehyde-bearing fragments. The broad objectives of the proposed studies are to understand whether iron can interact with bisretinoids in the RPE to promote RPE cell damage and death. The central hypothesis of this proposal is that dysregulated intracellular iron mediates adverse effects in part by promoting bisretinoid oxidation and degradation. If redox imbalance is potentiated by a combination or iron and bisretinoid photooxidation, iron chelation may be retina-protective in diseases involving bisretinoid toxicity including STGD1. In Specific Aim 1, we will determine the effects of deferiprone (DFP)-treatment in Abca4-/- mice. DFP is a clinically important iron chelator that serves to reduce iron levels. Using DFP we will test for protection against iron-mediated bisretinoid oxidation and photoreceptor cell loss in Abca4-/- mice. Oxidative stress will be assessed using a panel of redox indicators and cell-based and cell-free assays will be employed. In Specific Aim 2, we propose to determine whether supplemental iron contributes to the photooxidation/oxidation and degradation of bisretinoid. This aim will be achieved using mouse, cell and cell-free assays. We will ascertain whether one of the pathways by which iron mediates toxicity is by promoting bisretinoid oxidation. We will also establish whether intracellular iron is elevated in Abca4-/- mice, a model of STGD1. In experiments presented in Specific Aim 3 we will study mice that are deficient in ceruloplasmin (Cp) and hephaestin (Heph), ferroxidase proteins that convert ferrous (Fe2+) to ferric (Fe3+) iron so as to promote cellular iron export. Effects on the phenotype of the Cp-/-;Heph-/- mouse will be assessed when an inhibitor of bisretinoid formation is administered; in Abca4-/-; Cp-/-;Heph-/- mice which will have high levels of both iron and bisretinoids in the RPE, and when no RPE bisretinoid (Rpe6rd12) and deficiency in Cp-/-;Heph-/- are combined in Rpe6rd12; Cp-/-;Heph-/- mice. Completion of this research will advance our understanding of how, iron, light and bisretinoids combine to contribute to disease processes in age-related and monogenic retinal disorders.