Regulation of FGF23 in Chronic Kidney Disease (CKD) by iron and inflammation

铁和炎症对慢性肾脏病 (CKD) 中 FGF23 的调节

基本信息

批准号：
9333342
负责人：
Nicolae Valentin David
金额：
$ 36.4万
依托单位：
NORTHWESTERN UNIVERSITY AT CHICAGO
依托单位国家：
美国
项目类别：
财政年份：
2015
资助国家：
美国
起止时间：
2015-08-01 至 2020-07-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9333342
关键词：
Binding Biological Blocking Antibodies Brucella abortus C-terminal Cardiovascular Diseases Cessation of life Chronic Chronic Kidney Failure Clinical Coupled Couples Data Data Reporting Diet Disease Progression Elements Enterobacteria phage P1 Cre recombinase Genes Genetic Genetic Transcription Goals HIF1A gene Health Homeostasis Hormones Hypoxia Hypoxia Inducible Factor Inflammation Inflammatory Injury Injury to Kidney Interleukin-1 Iron Kidney Kidney Diseases Knockout Mice LCN2 gene Link Lipopolysaccharides Mediating Mediator of activation protein Metabolism Minerals Modeling Molecular Monoclonal Antibodies Mus Osteoblasts Osteocalcin Osteocytes Outcome Oxygen Pathway interactions Patients Pharmacology Phosphorus Production Proteins Recombinants Regulation Renal function Reporting Resistance Risk Role Serum Site-Directed Mutagenesis Stimulus System Testing Therapeutic Vitamin D Wild Type Mouse base bone bone cell chromatin immunoprecipitation clinically relevant cohort cytokine design fibroblast growth factor 23 genetic approach hypoxia inducible factor 1 improved improved outcome inhibitor/antagonist innovation inorganic phosphate insight interest iron deficiency mortality mouse model mutant novel novel therapeutic intervention overexpression promoter public health relevance response therapy design transcription factor

项目摘要

DESCRIPTION (provided by applicant): Fibroblast growth factor 23 (FGF23) is secreted by osteocytes and regulates phosphate and vitamin D homeostasis. Serum FGF23 levels rise early in the course of chronic kidney disease (CKD), and high levels are independently associated with greater risks of CKD progression, cardiovascular disease and death. These findings have stimulated interest in designing therapies to lower FGF23 levels, but the approach is limited by poor understanding of the molecular mechanisms that stimulate FGF23 production beginning in early CKD. Iron deficiency is a novel stimulator of FGF23 transcription and may be a critical contributor to elevated FGF23 levels in CKD. Although overt iron deficiency is uncommon in early CKD, functional iron deficiency due to reticuloendothelial iron sequestration as a result of chronic inflammation is highly prevalent. In preliminary data presented in this application, we demonstrate that high levels of the iron sequestering protein, neutrophil gelatinase associated lipocalin (NGAL), reduce intracellular iron concentrations in osteocytes and stimulate FGF23 production. In further preliminary data, we report that NGAL-mediated reductions in cellular iron stabilize hypoxia inducible factor (HIF)1a, which initiates FGF23 transcription by binding the FGF23 promoter. Since NGAL expression is increased in response to kidney injury and inflammation, and serum levels are chronically elevated in CKD, we propose that kidney injury stimulates NGAL production, which induces iron efflux from osteocytes, creating intracellular iron deficiency that stabilizes HIF1a and promotes FGF23 production. In this innovative proposal, we will examine the regulatory effects of inflammation, NGAL, and true and functional iron deficiency on FGF23 production in health and in CKD. In Aim 1, we will define the regulatory effects of inflammation and NGAL on FGF23 production by exposing wild type and NGALko mice to three models of systemic inflammation, and we will show that endogenous and exogenous NGAL increases FGF23 production. In Aim 2, we will investigate HIF1a as a molecular mediator of FGF23 regulation that underlies the mechanistic crosstalk between NGAL, iron, inflammation and FGF23. We will perform CHIP assays and site-directed mutagenesis to test whether HIF1a binds the FGF23 promoter, and we will delete HIF1a in osteocytes to demonstrate that HIF1aOc-cko mice are resistant to NGAL and iron deficiency-induced increases in FGF23. In Aim 3, we will determine the clinical relevance and therapeutic potential of the NGAL and HIF1a pathways in CKD by studying the impact of NGAL and HIF1a deletion in the Col4a3ko mouse model of progressive CKD. We will investigate if Col4a3ko/NGALko and Col4a3ko/HIF1aOc-cko compound mutants display blunted increases in FGF23 production relative to Col4a3ko mice with intact NGAL and HIF1a systems, and we will also test the effects on FGF23 production of NGAL blocking antibodies and HIF1 inhibitors in Col4a3ko mice. The project will contribute new insights into the molecular regulation of FGF23 in health and in CKD, and support our ultimate goal of developing novel therapeutic approaches to improve outcomes in CKD.

描述（由适用提供）：成纤维细胞生长因子23（FGF23）由骨细胞分泌，并调节磷酸盐和维生素D稳态。血清FGF23水平在慢性肾脏疾病（CKD）的早期升高，高水平与CKD进展，心血管疾病和死亡的风险更大。这些发现激发了对降低FGF23水平设计疗法的兴趣，但是该方法受到对刺激从CKD早期开始刺激FGF23产生的分子机制的理解不良的限制。铁缺乏症是FGF23转录的新型刺激剂，可能是CKD中FGF23水平升高的关键因素。尽管早期CKD中明显的铁缺乏症并不常见，但由于慢性炎症而导致的网状内皮铁隔离引起的功能性铁缺乏症非常普遍。在本应用中介绍的初步数据中，我们证明了高水平的铁隔离蛋白，中性粒细胞明胶酶相关的脂肪蛋白（NGAL），降低骨细胞中的细胞内铁浓度并刺激FGF23产生。在进一步的初步数据中，我们报告说，NGAL介导的细胞铁稳定缺氧诱导因子（HIF）1a的减少，该因子通过结合FGF23启动子来启动FGF23转录。由于NGAL表达因肾脏损伤和感染而增加，并且CKD的血清水平长期升高，因此我们建议肾脏损伤刺激NGAL产生，从而诱导骨细胞的铁外排出，从而产生细胞内铁缺乏症，从而稳定HIF1A并促进FGF23的产生。在这项创新的建议中，我们将研究感染，NGAL以及真实和功能性铁缺乏对健康和CKD中FGF23产生的调节作用。在AIM 1中，我们将通过将野生型和Ngalko小鼠暴露于三种全身感染模型中来定义感染和NGAL对FGF23产生的调节作用，我们将表明内源性和外源性NGAL会增加FGF23的产生。在AIM 2中，我们将研究HIF1A作为FGF23调节的分子介质，该调节是NGAL，铁，炎症和FGF23之间机械串扰的基础。我们将执行CHIP分析和定点诱变，以测试HIF1A是否结合FGF23启动子，我们将删除骨细胞细胞中的HIF1A，以证明HIF1AOC-CKO小鼠对FGF23中的NGAL和铁缺乏症引起的抗性抗性。在AIM 3中，我们将通过研究NGAL和HIF1A缺失在渐进式CKD的COL4A3KO小鼠模型中的影响，确定CKD中NGAL和HIF1A途径的临床相关性和治疗潜力。我们将研究COL4A3KO/NGALKO和COL4A3KO/HIF1AOC-CKO化合物突变体在FGF23的产生中显示出钝化的增加，相对于具有完整的NGAL和HIF1A系统的COL4A3KO小鼠，我们还将测试对NGAL阻断抗体抗体和HIF1的FGF23生产的影响。该项目将为健康和CKD中FGF23的分子调节提供新的见解，并支持我们开发新型治疗方法以改善CKD结果的最终目标。