Local hepcidin in the anterior segment: Physiological and pathological implications

眼前节局部铁调素：生理和病理学意义

基本信息

批准号：
10546487
负责人：
Neena Singh
金额：
$ 24.15万
依托单位：
CASE WESTERN RESERVE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2022
资助国家：
美国
起止时间：
2022-02-01 至 2025-01-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10546487
关键词：
Anterior Anterior eyeball segment structure Antioxidants Aqueous Humor Blood-Aqueous Barrier Blood-Retinal Barrier Carnosine Cataract Cattle Cells Chemistry Ciliary epithelium Clinical Trials Contralateral Cornea Corneal Endothelium Data Disease Down-Regulation Endothelial Cells Environment Epithelial Cells Epithelium Eye FDA approved Ferritin Generations Glaucoma Harvest Heparin Hepatic Homeostasis Human In Transferrin Inbred BALB C Mice Interleukin-6 Iron Iron Overload Knock-out Laboratories Length Lipopolysaccharides Measures Mediating Metabolic Modeling Monitor Mus Nature Ocular Pathology Operative Surgical Procedures Organ Culture Techniques Pathologic Patients Perfusion Physiologic Intraocular Pressure Physiological Primary Open Angle Glaucoma Probability Protein Export Pathway ROS1 gene Reaction Reactive Oxygen Species Regulation Reporting Retina Role Sampling Serum Signal Transduction Stabilizing Agents Structure Testing Therapeutic Time Toxic effect Trabecular meshwork structure Trace Elements Transfection Transferrin Transforming Growth Factor beta Up-Regulation Vitreous humor antagonist anterior chamber clinically relevant cytokine efficacy evaluation experimental study hepcidin in vivo lens metal transporting protein 1 mouse model overexpression peptide hormone prevent stem

项目摘要

ABSTRACT Iron is an essential bio-metal, but requires tight regulation to minimize the generation of iron-catalyzed reactive oxygen species (ROS). This is accomplished by hepcidin, a mainly hepatic peptide hormone that regulates serum transferrin iron (Tf-iron) by downregulating ferroportin (Fpn), an iron export protein. The synthesis of local hepcidin in the ciliary epithelial, corneal endothelial, and trabecular meshwork (TM) cells suggests autonomous regulation of iron in the anterior segment, independent of the retina. However, hepcidin is upregulated by cytokines as well, the latter signal superseding the signal from Tf-iron. This raises the concern of cytokine- mediated upregulation of hepcidin, creating a toxic environment by increasing intracellular iron and ROS, known contributors of toxicity in primary open angle glaucoma (POAG) and other ocular conditions. Pertinent to this application is TGFβ2, a cytokine implicated in POAG. Data from my laboratory show that biologically active TGFβ2 upregulates hepcidin in primary human TM cells and ex-vivo human organ culture perfusion model of POAG. Remarkably, hepcidin upregulates full-length (FL) and biologically active TGFβ2, the latter probably through ROS, forming a self-sustained feed-forward loop that is disrupted by heparin, a hepcidin antagonist, and N-acetyl carnosine, an antioxidant. Based on these observations, we hypothesize that the anterior segment maintains autonomous regulation of iron by locally synthesized hepcidin, and cytokine-mediated upregulation of local hepcidin forms a self-sustained feed-forward loop that is disrupted by hepcidin antagonists and Fpn stabilizing agents. This hypothesis will be tested in three specific aims. In Aim 1,autonomous regulation of iron by the anterior segment will be explored in wild-type (wt) C57BL/6 and Balb/c mice at steady state and after systemic iron overload that is known to cause retinal iron accumulation. Transport of serum iron across the blood- aqueous barrier, and from the retina to the aqueous humor (AH) will be determinedin the absence or presence of exogenous synthetic hepcidin in the AH. The role of local hepcidin in corneal endothelial cells in regulating iron exchange between the AH and the cornea will be determined in the human corneal cup ex-vivo model. In Aim 2, levels of FL and bioactive TGFβ2 will be determined in hepcidin knock-out (hepc-/-) and littermate hepc+/+ controls at steady state, and after over-expressing FL TGFβ2 to evaluate whether absence of hepcidin and iron- mediated ROS decreases bioactive TGFβ2 and IOP . In addition, levels of hepcidin, Tf-iron, and TGFβ2 will be determined in the human AH of POAG cases and cataract controls collected at surgery. In Aim 3, ex-vivo human anterior segment organ culture perfusion model will be used to evaluate the efficacy of FDA approved Fpn stabilizing agent fursultiamine in reducing intracellular iron, ROS, and bioactive TGFβ2-mediated increase in IOP . Successful completion of these studies will clarify the role of local hepcidin in regulating iron in the anterior segment, and its contribution to ocular pathology through iron-mediated ROS. Clinical relevance of these studies stems from the potential of disrupting this loop with available hepcidin antagonists and Fpn stabilizing agents.

抽象的铁是一种重要的生物金属，但需要严格调节以尽量减少铁催化活性物质的产生这是由铁调素（一种主要调节肝肽激素）完成的。通过下调铁转运蛋白 (Fpn)（一种铁输出蛋白）的血清转铁蛋白 (Tf-铁) 的合成。睫状上皮、角膜内皮和小梁网 (TM) 细胞中的铁调素表明自主眼前段铁的调节，独立于视网膜。然而，铁调素被上调。细胞因子也是如此，后者的信号取代了 Tf-铁的信号，这引起了细胞因子的关注。介导铁调素的上调，通过增加细胞内铁和活性氧来创造有毒环境，已知原发性开角型青光眼（POAG）和其他与此相关的眼部疾病的毒性因素。应用程序是 TGFβ2，一种与 POAG 相关的细胞因子。我的实验室数据显示其具有生物活性。 TGFβ2上调原代人TM细胞和离体人体器官培养灌注模型中的铁调素值得注意的是，hepcidin 上调全长 (FL) 和具有生物活性的 TGFβ2，后者可能是。通过 ROS，形成一个自我维持的前馈循环，该循环被肝素（一种铁调素拮抗剂）破坏，并且 N-乙酰肌肽，一种抗氧化剂根据这些观察，我们发现眼前节。通过局部合成的铁调素维持对铁的自主调节，以及细胞因子介导的上调局部铁调素形成一个自我维持的前馈环，该环路被铁调素拮抗剂和 Fpn 破坏该假设将在三个具体目标中进行检验，即铁的自主调节。将在野生型 (wt) C57BL/6 和 Balb/c 小鼠中在稳态和稳态后探索眼前节的变化已知铁超载会导致视网膜铁积累，从而导致血清铁通过血液运输。水屏障，以及从视网膜到房水（AH）的存在或不存在将被确定外源性合成铁调素在 AH 中局部铁调素对角膜内皮细胞的调节作用。 AH 和角膜之间的铁交换将在人角膜杯离体模型中确定。目标2， FL 和生物活性 TGFβ2 的水平将在铁调素敲除 (hepc-/-) 和同窝仔猪 hepc+/+ 中测定控制稳态，并在过表达 FL TGFβ2 后评估是否缺乏铁调素和铁- ROS 介导降低生物活性 TGFβ2 和 IOP 此外，铁调素、Tf-铁和 TGFβ2 的水平也会升高。在目的 3 中，在 POAG 病例和白内障对照的人类 AH 中确定。眼前段器官培养灌注模型将用于评估 FDA 批准的 Fpn 的疗效稳定剂呋喃硫胺减少细胞内铁、ROS 和生物活性 TGFβ2 介导的作用增加眼压这些研究的成功完成将阐明局部铁调素在调节前部铁中的作用部分，及其通过铁介导的 ROS 对眼部病理学的贡献。源于可用的铁调素拮抗剂和 Fpn 稳定剂破坏该环的潜力。