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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、小鼠和人类的必需营养素，但过量的铁是有毒的。缺铁（ID）和铁因此，过载（IO）导致严重的稳态扰动。由于铁的排泄效率低且不受调节，肠道铁吸收决定了全身铁水平。膳食铁主要以非血红素铁和血红素铁的形式存在，两者都对铁营养有显着贡献。十二指肠上皮细胞对非血红素铁的吸收依赖于铁输入者二价金属离子转运蛋白1（DMT 1）和铁输出者铁转运蛋白（FPN）。血红素铁吸收的机制尚未阐明。血红素吸收不适当增加，非血红素铁是遗传性血色素沉着症（HH）和β- 地中海贫血（β塔尔）。铁超负荷可导致肝脏疾病、关节病、骨质疏松症、心肌病，糖尿病和阳痿。HH是由调节Hamp转录的基因突变引起的。肝细胞中的基因。Hamp编码铁调节激素hepcidin，其调节血清铁含量通过调节十二指肠上皮细胞和网状内皮巨噬细胞（储存铁）中的FPN水平。的 HH中最常见的突变基因是稳态铁调节因子（HFE）。在美国，~1：300北方成年人欧洲血统是HFE突变的纯合子1，显著增加严重肝病的风险2。HH 也可由Hamp突变引起，其损害功能性激素的产生。β-塔尔是一种铁- 由于β-珠蛋白基因突变和铁紊乱，以无效红细胞生成为典型的负荷性贫血新陈代谢.铁吸收增加（由于低铁调素）和频繁输血都有助于铁加载中在一种不依赖输血的中间型β塔尔贫血（βTI）中，铁负荷的主要贡献者。在HH和βTI中，FPN活性增加（由于低铁调素）来自十二指肠上皮细胞的细胞内铁，其上调DMT 1。DMT 1诱导机制涉及在3' UTR中含有铁响应元件（+IRE）的转录物变体。当铁含量低时， +IRE变体通过铁调节蛋白（IRP）与IRE基序的结合而稳定，从而稳定IRE变体。翻译和增加翻译。高DMT 1和FPN因此沉淀过量的铁吸收。在目标1中，我们试图通过使用我们的叶酸靶向+IRE DMT 1 mRNA来减轻Hamp KO和Th 3/+小鼠的铁负荷。酸偶联姜纳米粒衍生脂质载体（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吸收是否协调调节，以维持铁稳态，生理条件下，并澄清这种调节是否在ID和IO中出错（目标2中）。额外实验将阐明DMT 1和FPN是否调节血红素铁的吸收，并有助于铁在HH中加载（在目标3中）。血红素铁吸收的机制和调节的模糊性无法解决使用小鼠模型，因为小鼠不能有效地吸收血红素铁。因此，我们开发了SD大鼠血红素铁吸收和HH（Hamp KO）的模型，从而使这项调查在这个方向上进行。