Mechanisms of Heme and Non-heme Iron Absorption in Murine Models of Iron Overload

铁过载小鼠模型中血红素和非血红素铁吸收的机制

基本信息

批准号：
10701227
负责人：
James F. Collins
金额：
$ 10万
依托单位：
UNIVERSITY OF FLORIDA
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：
2022-09-25 至 2023-12-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10701227
关键词：
3&apos Untranslated Regions Adult Anemia Assimilations Binding Blood Transfusion Cardiomyopathies Coupled Development Diabetes Mellitus Diet Dietary Iron Disease Duodenum Elements Enteral Enterocytes Erythropoiesis European Excretory function Experimental Models Folic Acid Gene Mutation Gene Silencing Genes Genetic Diseases Genetic Transcription Ginger Heme Heme Iron Hepatocyte Hereditary hemochromatosis Homeostasis Hormones Human Hydroxyl Radical Impairment Impotence Intestines Investigation Ions Iron Iron Metabolism Disorders Iron Overload Iron-Regulatory Proteins Lipids Liver Liver diseases Mediating Membrane Messenger RNA Metabolic Pathway Micronutrients Modeling Molecular Mus Mutate Mutation Nutrient Nutritional Oral Administration Osteoporosis Oxides Pathway interactions Physiological Process Production Protein Isoforms Proteins Rattus Reaction Regulation Repression Risk Role Serum Small Interfering RNA Sprague-Dawley Rats System Testing Therapeutic Intervention Tissues Transcript Transferrin Transfusion Translations Up-Regulation Variant absorption apical membrane arthropathies beta Globin beta Thalassemia cytotoxic dietary dietary heme divalent metal hepcidin in vivo in vivo evaluation iron absorption iron deficiency iron metabolism knock-down macrophage metal transporting protein 1 mouse model mutant nanoparticle oxidative damage peptide hormone pre-clinical prevent promoter siRNA delivery thalassemia intermedia therapeutic development vector

项目摘要

Project Summary Iron is an essential nutrient for rats, mice, and humans, yet iron in excess is toxic. Iron deficiency (ID) and iron overload (IO) thus result in severe homeostatic perturbations. Since iron excretion is inefficient and unregulated, intestinal iron absorption dictates overall body iron levels. Dietary iron exists mainly as non-heme and heme iron, and both contribute significantly to iron nutriture. Non-heme iron absorption by duodenal enterocytes critically relies on the iron importer divalent metal-ion transporter 1 (DMT1) and the iron exporter ferroportin (FPN). Mechanisms of heme-iron absorption have not been clarified. Inappropriately elevated absorption of heme and non-heme iron underlies iron loading in the genetic disorders hereditary hemochromatosis (HH) and β- thalassemia (βthal). Iron overload can cause liver disease, arthropathies, osteoporosis, cardiomyopathy, diabetes mellitus and impotence. HH is caused by mutations in genes that regulate transcription of the Hamp gene in hepatocytes. Hamp encodes the iron-regulatory hormone hepcidin, which regulates serum iron content by modulating FPN levels in duodenal enterocytes and reticuloendothelial macrophages (which store iron). The most common gene mutated in HH is homeostatic iron regulator (HFE). In the U.S., ~1:300 adults of Northern European descent is homozygous for HFE mutations1, significantly increasing risk for severe liver disease2. HH can also be caused by mutations in Hamp which impair production of the functional hormone. βthal is an iron- loading anemia, typified by ineffective erythropoiesis, due to β-globin gene mutations, and disordered iron metabolism. Elevated iron absorption (due to low hepcidin) and frequent blood transfusion both contribute to iron loading. In a transfusion-independent form of the disease, βthal intermedia (βTI), excessive iron absorption is the main contributor to iron loading. In HH and βTI, increased FPN activity (due to low hepcidin) depletes intracellular iron from duodenal enterocytes, which upregulates DMT1. The mechanism of DMT1 induction involves a transcript variant that contains an iron-responsive element (+IRE) in the 3’ UTR. When iron is low, this +IRE variant is stabilized by binding of an iron-regulatory protein (IRP) to the IRE motif thus stabilizing the transcript and increasing translation. High DMT1 and FPN thus precipitate excessive iron absorption. In Aim 1, we seek to mitigate iron loading in Hamp KO and Th3/+ mice by targeting the +IRE DMT1 mRNA using our Folic Acid-coupled Ginger Nanoparticle-derived Lipid Vector (FA-GDLV) siRNA delivery system. We further seek to ascertain if non-heme and heme-iron absorption are coordinately regulated to maintain iron homeostasis under physiological conditions and to clarify whether this regulation goes awry in ID and IO (in Aim 2). Additional experimentation will elucidate whether DMT1 and FPN modulate heme-iron absorption and contribute to iron loading in HH (in Aim 3). Ambiguities in mechanisms and regulation of heme-iron absorption cannot be resolved using mouse models, since mice inefficiently absorb heme iron. We thus developed Sprague-Dawley (SD) rat models of heme-iron absorption and HH (Hamp KO), thus allowing this investigation to proceed in this direction.

项目摘要铁是大鼠，小鼠和人类的必不可少的营养素，但过量铁是有毒的。铁缺乏（ID）和铁因此，超载（IO）导致严重的稳态扰动。由于铁极端效率低下且不受监管，因此肠道抽象决定了体内铁的整体水平。饮食铁主要存在于非血红素和血红素铁，两者都对铁营养产生了重大贡献。十二指肠肠细胞滥用非血红素铁依靠铁进口商二价金属离子转运蛋白1（DMT1）和铁出口国铁蛋白（FPN）。血红素铁的遗憾机制尚未澄清。不适当地提高了血红素和非血红素铁构成遗传疾病中的铁负荷遗传性血色素沉着症（HH）和β- 地中海贫血（βthal）。铁超负荷会导致肝病，关节炎，骨质疏松症，心肌病，糖尿病和阳ot。 HH是由调节HAMP转录的基因突变引起的肝细胞中的基因。汉普编码铁调节马肠肝素，该马肝素调节血清铁含量通过调节十二指肠肠上皮细胞和网状内皮巨噬细胞（储存铁）的FPN水平。这 HH中最常见的基因是稳态铁调节剂（HFE）。在美国，北部〜1：300成人欧洲下降是HFE突变纯合1，大大增加了严重肝病的风险2。 hh 也可能是由汉普突变引起的，汉普的突变会损害功能马酮的产生。 βThal是铁由于β-珠蛋白基因突变和铁无效的铁，加载贫血，以无效的红细胞生成为代表代谢。升高铁滥用（由于肝素低），并且经常输血都导致铁加载中。在疾病的非依赖性形式中，βthalIntermedia（βTI），过度的铁滥用是铁负荷的主要贡献者。在HH和βTI中，FPN活性增加（由于肝素较低）的耗竭十二指肠肠细胞的细胞内铁，上调DMT1。 DMT1诱导的机制涉及一个转录物变体，该变体包含3’UTR中的铁响应元件（+ire）。当铁很低时，这个 +ire变体通过结合铁调节蛋白（IRP）与IRE基序结合稳定，从而稳定笔录和翻译的增加。因此，高DMT1和FPN沉淀了过量的铁滥用。在AIM 1中，我们试图通过使用我们的叶子靶向 + ire dmt1 mRNA来减轻汉普ko和th3/ +小鼠的铁载酸偶联的生姜纳米粒子衍生的脂质载体（FA-GDLV）siRNA递送系统。我们进一步寻求确定非血红素和血红素铁的受苦是否受到协调调节以维持铁稳态下生理条件，并阐明该法规是否在ID和IO中出现问题（在AIM 2中）。额外的实验将阐明DMT1和FPN是否调节滥用血红素铁并有助于铁在HH中加载（在AIM 3中）。机制的歧义和血红素滥用的调节无法解决使用小鼠模型，因为小鼠效率低下吸收血红素铁。因此，我们开发了Sprague-Dawley（SD）大鼠血红素滥用和HH（HAMP KO）的模型，从而允许这项投资朝这个方向进行。