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Jain C, Parimi S, Huang W, Hannifin S, Singhal R, Das NK, Lee KE, Shah YM. Myeloid Hif2α is not essential to maintain systemic iron homeostasis. Exp Hematol 2023; 125-126:25-36.e1. [PMID: 37562670 PMCID: PMC11046397 DOI: 10.1016/j.exphem.2023.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 08/02/2023] [Accepted: 08/03/2023] [Indexed: 08/12/2023]
Abstract
Dietary consumption serves as the primary source of iron uptake, and erythropoiesis acts as a major regulator of systemic iron demand. In addition to intestinal iron absorption, macrophages play a crucial role in recycling iron from senescent red blood cells. The kidneys are responsible for the production of erythropoietin (Epo), which stimulates erythropoiesis, whereas the liver plays a central role in producing the iron-regulatory hormone hepcidin. The transcriptional regulator hypoxia-inducible factor (HIF)2α has a central role in the regulation of Epo, hepcidin, and intestinal iron absorption and therefore plays a crucial role in coordinating the tissue crosstalk to maintain systemic iron demands. However, the precise involvement of Hif2α in macrophages in terms of iron homeostasis remains uncertain. Our study demonstrates that deleting Hif2α in macrophages does not disrupt the expression of iron transporters or basal erythropoiesis. Mice lacking Hif2α in myeloid cells exhibited no discernible differences in hemodynamic parameters, including hemoglobin concentrations and erythrocyte count, when compared with littermate controls. This similarity was observed under conditions of both dietary iron deficiency and acute erythropoietic demand. Notably, we observed a significant increase in the expression of iron transporters in the duodenum during iron deficiency, indicating heightened iron absorption. Therefore, our findings suggest that the disruption of Hif2α in myeloid cells does not significantly impact systemic iron homeostasis under normal physiologic conditions. However, its disruption induces adaptive physiologic changes in response to elevated iron demand, potentially serving as a mechanism to sustain increased erythropoietic demand.
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Affiliation(s)
- Chesta Jain
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI
| | - Sanjana Parimi
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI
| | - Wesley Huang
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI; Department of Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI; Department of Medical Scientist Training Program, University of Michigan, Ann Arbor, MI
| | - Sean Hannifin
- Program in Immunology, University of Michigan, Ann Arbor, MI
| | - Rashi Singhal
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI
| | - Nupur K Das
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI
| | - Kyoung Eun Lee
- Department of Pharmacology, University of Michigan, Ann Arbor, MI; Rogel Cancer Center, University of Michigan, Ann Arbor, MI
| | - Yatrik M Shah
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI; Rogel Cancer Center, University of Michigan, Ann Arbor, MI; Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, MI.
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Banerjee A, Dey T, Majumder R, Bhattacharya T, Dey S, Bandyopadhyay D, Chattopadhyay A. Oleic acid prevents erythrocyte death by preserving haemoglobin and erythrocyte membrane proteins. Free Radic Biol Med 2023; 202:17-33. [PMID: 36965537 DOI: 10.1016/j.freeradbiomed.2023.03.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Revised: 03/11/2023] [Accepted: 03/20/2023] [Indexed: 03/27/2023]
Abstract
Haemolysis of erythrocytes upon exposure to haemato-toxic phenylhydrazine (PHZ), makes it an experimental model of anaemia and a partial model of β-thalassaemia, where oxidative stress (OS) was identified as principal causative factor. Oleic acid (OA) was evidenced to ameliorate such stress with antioxidative potential. Erythrocytes were incubated in vitro using 1 mM PHZ, 0.06 nM OA. Erythrocyte membrane protein densities and haemoglobin (Hb) status were examined. Any interaction of Hb with PHZ/OA was checked by calorimetric and spectroscopic analysis using pure molecules. Occurrence of erythrocyte apoptosis and involvement of free iron in all groups were evaluated. PHZ exposure to erythrocytes results in OS with subsequent apoptosis as evidenced from increased lipid peroxidation and translocation of phosphatidylserine in outer membrane. Preservations of erythrocyte cytoskeletal architecture and membrane bound enzyme activity were found in presence of OA. Moreover, both heme and globin of Hb was examined to be conserved by OA. Presence of OA, impeded apoptosis also, possibly by thwarting Hb breakdown followed by free iron release and consequent free radical generation. Additionally, direct sequential binding of OA with PHZ endorsed another protective mechanism of OA toward erythrocytes. OA affords protection to erythrocytes by conserving its major components and prevents haemolysis which projects OA as a haemato-protective agent. Apart from combating PHZ toxicity, anti-apoptotic action of OA strongly suggests its usage in anaemia and β-thalassaemia patients to curb irreversible erythrocyte breakdown. This research strongly recommends OA in pure form or from dietary sources as a therapeutic against haemolytic disorders.
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Affiliation(s)
- Adrita Banerjee
- Department of Physiology, Vidyasagar College, 39, Sankar Ghosh Lane, Kolkata, 700006, India; Oxidative Stress and Free Radical Biology Laboratory, Department of Physiology, University of Calcutta, 92, APC Road, Kolkata, 700009, India
| | - Tiyasa Dey
- Oxidative Stress and Free Radical Biology Laboratory, Department of Physiology, University of Calcutta, 92, APC Road, Kolkata, 700009, India
| | - Romit Majumder
- Department of Physiology, Vidyasagar College, 39, Sankar Ghosh Lane, Kolkata, 700006, India; Oxidative Stress and Free Radical Biology Laboratory, Department of Physiology, University of Calcutta, 92, APC Road, Kolkata, 700009, India
| | - Tuhin Bhattacharya
- Department of Physiology, University of Calcutta, 92, APC Road, Kolkata, 700009, India
| | - Sanjit Dey
- Department of Physiology, University of Calcutta, 92, APC Road, Kolkata, 700009, India
| | - Debasish Bandyopadhyay
- Oxidative Stress and Free Radical Biology Laboratory, Department of Physiology, University of Calcutta, 92, APC Road, Kolkata, 700009, India.
| | - Aindrila Chattopadhyay
- Department of Physiology, Vidyasagar College, 39, Sankar Ghosh Lane, Kolkata, 700006, India.
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IRE-dependent Regulation of Intestinal Dmt1 Prevails During Chronic Dietary Iron Deficiency but is Dispensable in Conditions of Acute Erythropoietic Stress. Hemasphere 2022; 6:e693. [PMID: 35187408 PMCID: PMC8853625 DOI: 10.1097/hs9.0000000000000693] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 01/28/2022] [Indexed: 01/01/2023] Open
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Valente de Souza L, Hoffmann A, Weiss G. Impact of bacterial infections on erythropoiesis. Expert Rev Anti Infect Ther 2020; 19:619-633. [PMID: 33092423 DOI: 10.1080/14787210.2021.1841636] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
INTRODUCTION The importance of iron is highlighted by the many complex metabolic pathways in which it is involved. A sufficient supply is essential for the effective production of 200 billion erythrocytes daily, a process called erythropoiesis. AREAS COVERED During infection, the human body can withhold iron from pathogens, mechanism termed nutritional immunity. The subsequent disturbances in iron homeostasis not only impact on immune function and infection control, but also negatively affect erythropoiesis. The complex interplay between iron, immunity, erythropoiesis and infection control on the molecular and clinical level are highlighted in this review. Diagnostic algorithms for correct interpretation and diagnosis of the iron status in the setting of infection are presented. Therapeutic concepts are discussed regarding effects on anemia correction, but also toward their role on the course of infection. EXPERT OPINION In the setting of infection, anemia is often neglected and its impact on the course of diseases is incompletely understood. Clinical expertise can be improved in correct diagnosing of anemia and disturbances of iron homeostasis. Systemic studies are needed to evaluate the impact of specific therapeutic interventions on anemia correction on the course of infection, but also on patients' cardiovascular performance and quality of life.
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Affiliation(s)
- Lara Valente de Souza
- Department of Internal Medicine II, Infectious Diseases, Immunology, Rheumatology, Medical University ofI nnsbruck, Innsbruck, Austria.,Christian Doppler Laboratory for Iron Metabolism and Anemia Research, Medical University of Innsbruck, Innsbruck, Austria
| | - Alexander Hoffmann
- Department of Internal Medicine II, Infectious Diseases, Immunology, Rheumatology, Medical University ofI nnsbruck, Innsbruck, Austria.,Christian Doppler Laboratory for Iron Metabolism and Anemia Research, Medical University of Innsbruck, Innsbruck, Austria
| | - Günter Weiss
- Department of Internal Medicine II, Infectious Diseases, Immunology, Rheumatology, Medical University ofI nnsbruck, Innsbruck, Austria.,Christian Doppler Laboratory for Iron Metabolism and Anemia Research, Medical University of Innsbruck, Innsbruck, Austria
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Magliulo L, Bondi D, Pietrangelo T, Fulle S, Piccinelli R, Jandova T, Blasio GD, Taraborrelli M, Verratti V. Serum ferritin and vitamin D evaluation in response to high altitude comparing Italians trekkers vs Nepalese porters. Eur J Sport Sci 2020; 21:994-1002. [PMID: 32627691 DOI: 10.1080/17461391.2020.1792559] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Altitude hypoxia induces changes in iron homeostasis with serum ferritin (sFER) response being recently linked to erythropoiesis. The main aim of this study was to investigate sFER and Vitamin D (Vit D) response to hypobaric hypoxia, taking into account factors including nutrition and ethnic origin. As part of a "Kanchenjunga Exploration & Physiology" project, 6 Italian trekkers and 6 Nepalese porters took part in a 19-days long altitude trek in the Himalayas self-recording daily food consumption. Blood samples were collected and analyzed before and after the trek for sFER and Vit D. A web-based system calculated the dietary intake, generating reports that were used for later statistical analyses. sFER decreased after the trek (on average by 26% p = 0.013, partial η2 = 0.479) in both groups, whereas Vit D did not change in both groups. Nepalese tended to have lower sFER, but this difference was reduced when corrected for the dietary intake. Mean Cell Volume (MCV) and Hematocrit (HCT), in respect to baseline, remained higher 10 days after the trek (respectively, 87.37-88.85 fL with p = 0.044, and 43.05-44.63% with p = 0.065) in Italian trekkers. The observed reduction of sFER levels was related to altitude per se as inflammation or anemia were medically excluded. sFER, therefore, may act as a primary factor in the examination of hypobaric hypoxia in field studies. The results of this study open a new door into the mechanisms of iron homeostasis in specific tissues related to hypoxia adaptations, taking into account dietary intake and ethnic origin.
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Affiliation(s)
- Laura Magliulo
- Department of Neuroscience, Imaging and Clinical Sciences, University "G. d'Annunzio" of Chieti - Pescara, Chieti, Italy
| | - Danilo Bondi
- Department of Neuroscience, Imaging and Clinical Sciences, University "G. d'Annunzio" of Chieti - Pescara, Chieti, Italy
| | - Tiziana Pietrangelo
- Department of Neuroscience, Imaging and Clinical Sciences, University "G. d'Annunzio" of Chieti - Pescara, Chieti, Italy
| | - Stefania Fulle
- Department of Neuroscience, Imaging and Clinical Sciences, University "G. d'Annunzio" of Chieti - Pescara, Chieti, Italy
| | - Raffaela Piccinelli
- Council for Agricultural Research and Economics, Research Centre for Food and Nutrition, Rome, Italy
| | - Tereza Jandova
- Department of Neuroscience, Imaging and Clinical Sciences, University "G. d'Annunzio" of Chieti - Pescara, Chieti, Italy
| | | | - Mattia Taraborrelli
- Department of Medical, Oral and Biotechnological Sciences, University "G. d'Annunzio" of Chieti - Pescara, Chieti, Italy
| | - Vittore Verratti
- Department of Psychological, Health and Territorial Sciences, University "G. d'Annunzio" of Chieti - Pescara, Chieti, Italy
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MCCORMICK RACHEL, MORETTI DIEGO, MCKAY ALANNAHKA, LAARAKKERS COBYM, VANSWELM RACHEL, TRINDER DEBBIE, COX GREGORYR, ZIMMERMAN MICHAELB, SIM MARC, GOODMAN CARMEL, DAWSON BRIAN, PEELING PETER. The Impact of Morning versus Afternoon Exercise on Iron Absorption in Athletes. Med Sci Sports Exerc 2019; 51:2147-2155. [DOI: 10.1249/mss.0000000000002026] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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7
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McAllister M, Phillips N, Belosevic M. Trypanosoma carassii infection in goldfish (Carassius auratus L.): changes in the expression of erythropoiesis and anemia regulatory genes. Parasitol Res 2019; 118:1147-1158. [PMID: 30747294 DOI: 10.1007/s00436-019-06246-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Accepted: 02/01/2019] [Indexed: 12/12/2022]
Abstract
Trypanosoma carassii is a flagellated bloodstream parasite of cyprinid fish with pathogenesis manifesting primarily as anemia in experimentally infected fish. This anemia is characterized by decreases in the number of circulating red blood cells (RBCs) during peak parasitemia. We examined changes in the key blood metrics and expression of genes known to be important in the regulation of erythropoiesis. Increasing parasitemia was strongly correlated with an overall decrease in the total number of circulating RBCs. Gene expression of key erythropoiesis regulators (EPO, EPOR, GATA1, Lmo2, and HIFα) and proinflammatory cytokines (IFNγ and TNFα) were measured and their expressions differed from those in fish made anemic by injections of phenylhydrazine (PHZ). Significant upregulation of pro-erythropoietic genes was observed in PHZ-induced anemia, but not during peak parasitic infection. Previously, we reported on functional characterization of goldfish erythropoietin (rgEPO) and its ability to induce survival and differentiation of erythroid progenitor cells in vitro. Treatment of goldfish during the infection with rgEPO reduced the severity of anemia but failed to fully prevent the onset of the anemic state in infected fish. Proinflammatory cytokines have been implicated in the suppression of erythropoiesis during trypanosomiasis, specifically the cytokines TNFα, IFNγ, and IL-1β. Analysis of key proinflammatory cytokines revealed that mRNA levels of IFNγ and TNFα were upregulated in response to infection, but only TNFα increased in response to PHZ treatment. Synergistic activity of the proinflammatory cytokines may be required to sustain prolonged anemia. These findings provide insight into the relationship between T. carassii and host anemia and suggest that T. carassii may directly or indirectly suppress host erythropoiesis.
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Affiliation(s)
- Mark McAllister
- Department of Biological Sciences, CW-405 Biological Sciences Building, University of Alberta, Edmonton, AB, T6G 2E9, Canada
| | - Nicole Phillips
- Department of Biological Sciences, CW-405 Biological Sciences Building, University of Alberta, Edmonton, AB, T6G 2E9, Canada
| | - Miodrag Belosevic
- Department of Biological Sciences, CW-405 Biological Sciences Building, University of Alberta, Edmonton, AB, T6G 2E9, Canada.
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8
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Tangudu NK, Alan B, Vinchi F, Wörle K, Lai D, Vettorazzi S, Leopold K, Vujić Spasić M. Scavenging Reactive Oxygen Species Production Normalizes Ferroportin Expression and Ameliorates Cellular and Systemic Iron Disbalances in Hemolytic Mouse Model. Antioxid Redox Signal 2018; 29:484-499. [PMID: 29212341 PMCID: PMC6034398 DOI: 10.1089/ars.2017.7089] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
AIMS Release of large amounts of free heme into circulation, overproduction of reactive oxygen species (ROS), and activation of toll-like receptor-4-dependent responses are considered critical for the ability of heme to promote oxidative stress and to initiate proinflammatory responses, posing a serious threat to the body. A deep understanding of the consequences of heme overload on the regulation of cellular and systemic iron homeostasis is, however, still lacking. RESULTS The effects of heme on iron metabolism were studied in primary macrophages and in mouse models of acute and chronic hemolysis. We demonstrated that hemolysis was associated with a significant depletion of intracellular iron levels and increased expression of the sole iron exporter protein, ferroportin. The pathophysiological relevance of this mechanism was further demonstrated in sickle cell anemia mice, which, despite chronic hemolysis, maintained high ferroportin expression and increased iron export. We identified a redox active iron species and superoxide as regulators for ferroportin induction by heme. Scavenging the ROS production, by use of a pharmacological antioxidant N-acetylcysteine, prevented ferroportin induction and normalized intracellular iron levels in macrophages and in experimentally induced hemolysis in mice. INNOVATION Our data propose that scavenging ROS levels may be a novel therapeutic strategy to balance intracellular iron levels and systemic iron influx in conditions associated with heme overload. CONCLUSION This study identifies that the pro-oxidant, and not the proinflammatory, actions of heme profoundly impact on iron homeostasis by critically regulating the expression of ferroportin and iron export in hemolytic conditions. Antioxid. Redox Signal. 29, 484-499.
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Affiliation(s)
- Naveen Kumar Tangudu
- 1 Institute of Comparative Molecular Endocrinology, University of Ulm , Ulm, Germany
| | - Betül Alan
- 1 Institute of Comparative Molecular Endocrinology, University of Ulm , Ulm, Germany
| | | | - Katharina Wörle
- 3 Institute of Analytical and Bioanalytical Chemistry, University of Ulm , Ulm, Germany
| | - Dilay Lai
- 1 Institute of Comparative Molecular Endocrinology, University of Ulm , Ulm, Germany
| | - Sabine Vettorazzi
- 1 Institute of Comparative Molecular Endocrinology, University of Ulm , Ulm, Germany
| | - Kerstin Leopold
- 3 Institute of Analytical and Bioanalytical Chemistry, University of Ulm , Ulm, Germany
| | - Maja Vujić Spasić
- 1 Institute of Comparative Molecular Endocrinology, University of Ulm , Ulm, Germany
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9
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Intestinal hephaestin potentiates iron absorption in weanling, adult, and pregnant mice under physiological conditions. Blood Adv 2017; 1:1335-1346. [PMID: 29296776 DOI: 10.1182/bloodadvances.2017008359] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 06/14/2017] [Indexed: 12/17/2022] Open
Abstract
Regulation of intestinal iron absorption is crucial to maintain body iron levels because humans have no regulated iron-excretory system. Elucidating molecular events that mediate intestinal iron transport is thus important for the development of therapeutic approaches to modify iron absorption in pathological states. The process of iron uptake into duodenal enterocytes is relatively well understood, but less is known about the functional coupling between the iron exporter ferroportin 1 and the basolateral membrane iron oxidase hephaestin (Heph). Initial characterization of intestine-specific Heph knockout (Hephint) mice demonstrated that adult male mice were mildly iron deficient; however, the specific role of intestinal Heph has not been determined in weanling mice, in female mice, or during physiological states which stimulate iron absorption. Furthermore, because ferroportin 1-mediated iron export from some tissues (eg, liver) is impaired in the absence of the Heph homolog, ceruloplasmin, we hypothesized that Heph is rate limiting for intestinal iron absorption, especially when iron demands increase. Our experimental approach was to assess various physiological parameters and iron (59Fe) absorption and tissue distribution in weanling, adult, and pregnant Hephint mice (and controls) under physiological conditions and in adult Hephint mice after dietary iron deprivation or acute hemolysis. Results demonstrate that intestinal Heph is essential for optimal iron transport in weanlings and adults of both sexes and during pregnancy, but not in adult mice with iron-deficiency or hemolytic anemia. Moreover, activation of unidentified, intestinal ferroxidases was noted, which may explain why intestinal Heph is not always required for optimal iron absorption.
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10
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EPO-dependent induction of erythroferrone drives hepcidin suppression and systematic iron absorption under phenylhydrazine-induced hemolytic anemia. Blood Cells Mol Dis 2016; 58:45-51. [PMID: 27067488 DOI: 10.1016/j.bcmd.2016.02.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 02/16/2016] [Accepted: 02/17/2016] [Indexed: 02/07/2023]
Abstract
Hemolytic anemia is a common form of anemia due to hemolysis, resulting in disordered iron homeostasis. In this study, a dose of 40mg/kg phenylhydrazine (PHZ) was injected into mice to successfully establish a pronounced anemia animal model, which resulted in stress erythropoiesis and iron absorption. We found that serum erythropoietin (EPO) concentration was dramatically elevated by nearly 5000-fold for the first 2days, and then drop to the basal level on day 6 after PHZ injection. Mirrored with serum EPO concentration, the mRNA expression of erythroferrone (ERFE) was rapidly increased in the bone marrow and spleen 3days after injection of PHZ, and then gradually decreased but was still higher than baseline on day 6. In addition, we also found that the hepcidin mRNA levels were gradually reduced almost up to 8-fold on day 5, and then was ameliorated compared to the untreated control. Mechanistic investigation manifested that the increase of serum EPO essentially determined the induction of ERFE expression particular at the first 3days after PHZ treatment. Lentiviral mediated ERFE knockdown significantly restrained hepcidin suppression under PHZ treatment. Thus, our data unearthed EPO-dependent ERFE expression acts as an erythropoiesis-driven regulator of iron metabolism under PHZ-induced hemolytic anemia.
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Dürrenberger F, Abbate V, Ma Y, Arno MC, Jaiash D, Parmar A, Marshall V, Latunde-Dada GO, Zimmermann T, Senn D, Altermatt P, Manolova V, Hider RC, Bansal SS. Functional characterization of fluorescent hepcidin. Bioconjug Chem 2013; 24:1527-32. [PMID: 23888876 DOI: 10.1021/bc400121x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Hepcidin is a peptide hormone that regulates homeostasis in iron metabolism. It binds to the sole known cellular iron exporter ferroportin (Fpn), triggers its internalization, and thereby modulates the efflux of iron from cells. This functional property has been adopted in this study to assess the bioactivity and potency of a range of novel fluorescent hepcidin analogues. Hepcidin was selectively labeled with 6-carboxyfluorescein (CF) and 6-carboxytetramethylrhodamine (TMR) using Fmoc solid phase peptide chemistry. Internalization of Fpn by hepcidin was assessed by high-content microscopic analysis. Both K18- and M21K-labeled hepcidin with TMR and CF exhibited measurable potency when tested in cultured MDCK and T47D cells expressing human ferroportin. The bioactivity of the labeled hepcidin varies with the type of fluorophore and site of attachment of the fluorophores on the hepcidin molecule.
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Affiliation(s)
- Franz Dürrenberger
- Chemical Biology Group, Institute of Pharmaceutical Sciences, and ‡Nutrition and Diabetes Research Group, King's College London , Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, U.K
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12
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Abstract
Although earlier, seminal studies demonstrated that the gut per se has the intrinsic ability to regulate the rates of iron absorption, the spotlight in the past decade has been placed on the systemic regulation of iron homeostasis by the hepatic hormone hepcidin and the molecular mechanisms that regulate its expression. Recently, however, attention has returned to the gut based on the finding that hypoxia inducible factor-2 (HIF-2α) regulates the expression of key genes that contribute to iron absorption. Here we review the current understanding of the molecular mechanisms that regulate iron homeostasis in the gut by focusing on the role of HIF-2 under physiological steady-state conditions and in the pathogenesis of iron-related diseases. We also discuss implications for adapting HIF-2-based therapeutic strategies in iron-related pathological conditions.
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13
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Latunde-Dada GO. Iron metabolism in athletes - achieving a gold standard. Eur J Haematol 2012; 90:10-5. [DOI: 10.1111/ejh.12026] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/09/2012] [Indexed: 01/01/2023]
Affiliation(s)
- Gladys O. Latunde-Dada
- Diabetes and Nutritional Sciences Division; School of Medicine; King's College London; London; UK
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14
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Choi J, Masaratana P, Latunde-Dada GO, Arno M, Simpson RJ, McKie AT. Duodenal reductase activity and spleen iron stores are reduced and erythropoiesis is abnormal in Dcytb knockout mice exposed to hypoxic conditions. J Nutr 2012; 142:1929-34. [PMID: 22990466 DOI: 10.3945/jn.112.160358] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Duodenal cytochrome b (Dcytb, Cybrd1) is a ferric reductase localized in the duodenum that is highly upregulated in circumstances of increased iron absorption. To address the contribution of Dcytb to total duodenal ferric reductase activity as well as its wider role in iron metabolism, we first measured duodenal ferric reductase activity in wild-type (WT) and Dcytb knockout (Dcytb(-/-)) mice under 3 conditions known to induce gut ferric reductase: dietary iron deficiency, hypoxia, and pregnancy. Dcytb(-/-) and WT mice were randomly assigned to control (iron deficiency experiment, 48 mg/kg dietary iron; hypoxia experiment, normal atmospheric pressure; pregnancy experiment, nonpregnant animals) or treatment (iron deficiency experiment, 2-3 mg/kg dietary iron; hypoxia experiment, 53.3 kPa pressure; pregnancy experiment, d 20 of pregnancy) groups and duodenal reductase activity measured. We found no induction of ferric reductase activity in Dcytb(-/-) mice under any of these conditions, indicating there are no other inducible ferric reductases present in the duodenum. To test whether Dcytb was required for iron absorption in conditions with increased erythropoietic demand, we also measured tissue nonheme iron levels and hematological indices in WT and Dcytb(-/-) mice exposed to hypoxia. There was no evidence of gross alterations in iron absorption, hemoglobin, or total liver nonheme iron in Dcytb(-/-) mice exposed to hypoxia compared with WT mice. However, spleen nonheme iron was significantly less (6.7 ± 1.0 vs. 12.7 ± 0.9 nmol · mg tissue(-1); P < 0.01, n = 7-8) in hypoxic Dcytb(-/-) compared with hypoxic WT mice and there was evidence of impaired reticulocyte hemoglobinization with a lower reticulocyte mean corpuscular hemoglobin (276 ± 1 vs. 283 ± 2 g · L(-1); P < 0.05, n = 7-8) in normoxic Dcytb(-/-) compared with normoxic WT mice. We therefore conclude that DCYTB is the primary iron-regulated duodenal ferric reductase in the gut and that Dcytb is necessary for optimal iron metabolism.
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Affiliation(s)
- Jeehyea Choi
- Diabetes and Nutritional Sciences Division, School of Biomedical and Health Sciences, King’s College, London, UK
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15
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Masaratana P, Latunde-Dada GO, Patel N, Simpson RJ, Vaulont S, McKie AT. Iron metabolism in hepcidin1 knockout mice in response to phenylhydrazine-induced hemolysis. Blood Cells Mol Dis 2012; 49:85-91. [PMID: 22609087 DOI: 10.1016/j.bcmd.2012.04.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Accepted: 03/27/2012] [Indexed: 11/26/2022]
Abstract
Hepcidin, an iron regulatory peptide, plays a central role in the maintenance of systemic iron homeostasis by inducing the internalization and degradation of the iron exporter, ferroportin. Hepcidin expression in the liver is regulated in response to several stimuli including iron status, erythropoietic activity, hypoxia and inflammation. Hepcidin expression has been shown to be reduced in phenylhydrazine-treated mice, a mouse model of acute hemolysis. In this mouse model, hepcidin suppression was associated with increased expression of molecules involved in iron transport and recycling. The present study aims to explore whether the response to phenylhydrazine treatment is affected by hepcidin deficiency and/or the subsequently altered iron metabolism. Hepcidin1 knockout (Hamp(-/-)) and wild type mice were treated with phenylhydrazine or saline and parameters of iron homeostasis were determined 3 days after the treatment. In wild type mice, phenylhydrazine administration resulted in significantly reduced serum iron, increased tissue non-heme iron levels and suppressed hepcidin expression. The treatment was also associated with increases in membrane ferroportin protein levels and spleen heme oxygenase 1 mRNA expression. In addition, trends toward increased mRNA expression of duodenal iron transporters were also observed. In contrast, serum iron and tissue non-heme iron levels in Hamp(-/-) mice were unaffected by the treatment. Moreover, the effects of phenylhydrazine on the expression of ferroportin and duodenal iron transporters were not observed in Hamp(-/-) mice. Interestingly, mRNA levels of molecules involved in splenic heme uptake and degradation were significantly induced by Hamp disruption. In summary, our study demonstrates that the response to phenylhydrazine-induced hemolysis differs between wild type and Hamp(-/-) mice. This observation may be caused by the absence of hepcidin per se or the altered iron homeostasis induced by the lack of hepcidin in these mice.
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Affiliation(s)
- Patarabutr Masaratana
- Diabetes and Nutritional Sciences Division, School of Medicine, King's College London, 150 Stamford Street, London SE1 9NH, UK
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16
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Anderson ER, Xue X, Shah YM. Intestinal hypoxia-inducible factor-2alpha (HIF-2alpha) is critical for efficient erythropoiesis. J Biol Chem 2011; 286:19533-40. [PMID: 21498508 DOI: 10.1074/jbc.m111.238667] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Erythropoiesis is a coordinated process by which RBCs are produced. Erythropoietin, a kidney-derived hormone, and iron are critical for the production of oxygen-carrying mature RBCs. To meet the high demands of iron during erythropoiesis, small intestinal iron absorption is increased through an undefined mechanism. In this study, erythropoietic induction of iron absorption was further investigated. Hypoxia-inducible factor-2α (HIF-2α) signaling was activated in the small intestine during erythropoiesis. Genetic disruption of HIF-2α in the intestine abolished the increase in iron absorption genes as assessed by quantitative real-time reverse transcription-PCR and Western blot analyses. Moreover, the increase in serum iron following induction of erythropoiesis was entirely dependent on intestinal HIF-2α expression. Complete blood count analysis demonstrated that disruption of intestinal HIF-2α inhibited efficient erythropoiesis; mice disrupted for HIF-2α demonstrated lower hematocrit, RBCs, and Hb compared with wild-type mice. These data further cement the essential role of HIF-2α in regulating iron absorption and also demonstrate that hypoxia sensing in the intestine, as well as in the kidney, is essential for regulation of erythropoiesis by HIF-2α.
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Affiliation(s)
- Erik R Anderson
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48108, USA
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Kell DB. Towards a unifying, systems biology understanding of large-scale cellular death and destruction caused by poorly liganded iron: Parkinson's, Huntington's, Alzheimer's, prions, bactericides, chemical toxicology and others as examples. Arch Toxicol 2010; 84:825-89. [PMID: 20967426 PMCID: PMC2988997 DOI: 10.1007/s00204-010-0577-x] [Citation(s) in RCA: 286] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Accepted: 07/14/2010] [Indexed: 12/11/2022]
Abstract
Exposure to a variety of toxins and/or infectious agents leads to disease, degeneration and death, often characterised by circumstances in which cells or tissues do not merely die and cease to function but may be more or less entirely obliterated. It is then legitimate to ask the question as to whether, despite the many kinds of agent involved, there may be at least some unifying mechanisms of such cell death and destruction. I summarise the evidence that in a great many cases, one underlying mechanism, providing major stresses of this type, entails continuing and autocatalytic production (based on positive feedback mechanisms) of hydroxyl radicals via Fenton chemistry involving poorly liganded iron, leading to cell death via apoptosis (probably including via pathways induced by changes in the NF-κB system). While every pathway is in some sense connected to every other one, I highlight the literature evidence suggesting that the degenerative effects of many diseases and toxicological insults converge on iron dysregulation. This highlights specifically the role of iron metabolism, and the detailed speciation of iron, in chemical and other toxicology, and has significant implications for the use of iron chelating substances (probably in partnership with appropriate anti-oxidants) as nutritional or therapeutic agents in inhibiting both the progression of these mainly degenerative diseases and the sequelae of both chronic and acute toxin exposure. The complexity of biochemical networks, especially those involving autocatalytic behaviour and positive feedbacks, means that multiple interventions (e.g. of iron chelators plus antioxidants) are likely to prove most effective. A variety of systems biology approaches, that I summarise, can predict both the mechanisms involved in these cell death pathways and the optimal sites of action for nutritional or pharmacological interventions.
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Affiliation(s)
- Douglas B Kell
- School of Chemistry and the Manchester Interdisciplinary Biocentre, The University of Manchester, Manchester M1 7DN, UK.
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Marro S, Chiabrando D, Messana E, Stolte J, Turco E, Tolosano E, Muckenthaler MU. Heme controls ferroportin1 (FPN1) transcription involving Bach1, Nrf2 and a MARE/ARE sequence motif at position -7007 of the FPN1 promoter. Haematologica 2010; 95:1261-8. [PMID: 20179090 DOI: 10.3324/haematol.2009.020123] [Citation(s) in RCA: 216] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Macrophages of the reticuloendothelial system play a key role in recycling iron from hemoglobin of senescent or damaged erythrocytes. Heme oxygenase 1 degrades the heme moiety and releases inorganic iron that is stored in ferritin or exported to the plasma via the iron export protein ferroportin. In the plasma, iron binds to transferrin and is made available for de novo red cell synthesis. The aim of this study was to gain insight into the regulatory mechanisms that control the transcriptional response of iron export protein ferroportin to hemoglobin in macrophages. DESIGN AND METHODS Iron export protein ferroportin mRNA expression was analyzed in RAW264.7 mouse macrophages in response to hemoglobin, heme, ferric ammonium citrate or protoporphyrin treatment or to siRNA mediated knockdown or overexpression of Btb And Cnc Homology 1 or nuclear accumulation of Nuclear Factor Erythroid 2-like. Iron export protein ferroportin promoter activity was analyzed using reporter constructs that contain specific truncations of the iron export protein ferroportin promoter or mutations in a newly identified MARE/ARE element. RESULTS We show that iron export protein ferroportin is transcriptionally co-regulated with heme oxygenase 1 by heme, a degradation product of hemoglobin. The protoporphyrin ring of heme is sufficient to increase iron export protein ferroportin transcriptional activity while the iron released from the heme moiety controls iron export protein ferroportin translation involving the IRE in the 5'untranslated region. Transcription of iron export protein ferroportin is inhibited by Btb and Cnc Homology 1 and activated by Nuclear Factor Erythroid 2-like involving a MARE/ARE element located at position -7007/-7016 of the iron export protein ferroportin promoter. CONCLUSIONS This finding suggests that heme controls a macrophage iron recycling regulon involving Btb and Cnc Homology 1 and Nuclear Factor Erythroid 2-like to assure the coordinated degradation of heme by heme oxygenase 1, iron storage and detoxification by ferritin, and iron export by iron export protein ferroportin.
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Affiliation(s)
- Samuele Marro
- Department of Pediatric Oncology, University of Heidelberg, Im Neuenheimer Feld 153, 69120 Heidelberg, Germany
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Abstract
Hereditary forms of iron-deficiency anemia, including animal models, have taught us much about the normal physiologic control of iron metabolism. However, the discovery of new informative mutants is limited by the natural mutation frequency. To address this limitation, we have developed a screen for heritable abnormalities of red blood cell morphology in mice with single-nucleotide changes induced by the chemical mutagen ethylnitrosourea (ENU). We now describe the first strain, fragile-red, with hypochromic microcytic anemia resulting from a Y228H substitution in the ferrireductase Steap3 (Steap3(Y288H)). Analysis of the Steap3(Y288H) mutant identifies a conserved motif required for targeting Steap3 to internal compartments and highlights how phenotypic screens linked to mutagenesis can identify new functional variants in erythropoiesis and ascribe function to previously unidentified motifs.
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20
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D'Anna MC, Veuthey TV, Roque ME. Immunolocalization of ferroportin in healthy and anemic mice. J Histochem Cytochem 2008; 57:9-16. [PMID: 18796409 DOI: 10.1369/jhc.2008.951616] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Ferroportin (FPN), the only iron exporter identified to date, participates in iron release from enterocytes and macrophages, regulating its absorption and recycling. We used a murine model of experimental hemolytic anemia to study adaptive changes in the localization of FPN in duodenum, liver, and spleen. FPN was assessed by IHC in healthy and anemic mice using rabbit anti-mouse FPN polyclonal antibodies. Goat-labeled polymer-horseradish peroxidase anti-rabbit Envision+System (DAB) was used as secondary antibody. Tissue iron was studied by Prussian blue iron staining. Anemia evolution and erythropoietic recovery was assessed using conventional hematological tests. Healthy mice showed mainly supranuclear expression of FPN in enterocytes and a weak basolateral expression, whereas in anemic mice, the expression was detected mainly at the basolateral membrane (days 4 and 5). Red pulp macrophages of healthy mice showed FPN-hemosiderin colocalization. In the liver of healthy mice, FPN was mainly cytoplasmic, whereas in anemic mice, it was redistributed to the cell membrane. Our findings clearly show that anemia induces adaptive changes in FPN expression, contributing to anemia restoration by increasing available iron. FPN expression in the membrane is the main pathway of iron release. Our data indicate that iron homeostasis in vivo is maintained through the coordinated expression of this iron exporter in both intestinal and phagocytic cells.
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Affiliation(s)
- María Cecilia D'Anna
- Laboratory of Human Physiology, Department of Biology, Biochemistry, and Pharmacy, Universidad Nacional del Sur, San Juan 670, Bahía Blanca, Argentina.
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Veuthey T, D'Anna MC, Roque ME. Role of the kidney in iron homeostasis: renal expression of Prohepcidin, Ferroportin, and DMT1 in anemic mice. Am J Physiol Renal Physiol 2008; 295:F1213-21. [PMID: 18653481 DOI: 10.1152/ajprenal.90216.2008] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It is known that renal tissue plays a role in normal iron homeostasis. The current study examines kidney function in iron metabolism under hemolytic anemia studying renal expression of Prohepcidin, Ferroportin (MTP1), and divalent metal transporter 1 (DMT1). The relationship between these proteins and iron pigments was also investigated. Immunohistochemical procedures to study renal expression of Prohepcidin, MTP1, and DMT1 were performed in healthy and anemic mice. Renal tissue iron was determined by Prussian blue iron staining. To assess anemia evolution and erythropoietic recovery, we used conventional tests. In healthy mice, Prohepcidin expression was marked in proximal tubules and inner medulla and absent in outer medulla. Cortical tissue of healthy mice also showed MTP1 immunostaining, mainly in the S2 segment of proximal tubules. Medullar tissue showed MTP1 expression in the inner zone. In addition, S2 segments showed intense DMT1 immunoreactivity with homogeneous DMT1 distribution throughout renal medulla. The main cortical findings in hemolytic anemia were in S2 segments of proximal tubules where we found that decreased Prohepcidin expression coincided with an increment in Ferroportin and DMT1 expression. This expression pattern was concomitant with increased iron in the same tubular zone. However, in medullar tissue both Prohepcidin and MTP1 decreased and DMT1 was detected mainly in larger diameter tubules. Our findings clearly demonstrate that in hemolytic anemia, renal Prohepcidin acts in coordination with renal Ferroportin and DMT1, indicating the key involvement of kidney in iron homeostasis when iron demand is high. Further research is required to learn more about these regulatory mechanisms.
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Affiliation(s)
- Tania Veuthey
- Laboratory of Human Physiology, Departament of Biology, Biochemistry and Pharmacy, Universidad Nacional del Sur, San Juan 670, 8000 Bahía Blanca, Argentina
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22
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Latunde-Dada GO, Simpson RJ, McKie AT. Duodenal cytochrome B expression stimulates iron uptake by human intestinal epithelial cells. J Nutr 2008; 138:991-5. [PMID: 18492824 DOI: 10.1093/jn/138.6.991] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Duodenal cytochrome B (Dcytb) is localized principally in the apical membrane of the enterocyte. It is thought to act as a ferric reductase that furnishes Fe(II), the specific and selective iron species transported by divalent metal transporter 1 (DMT1) in the duodenal enterocytes. Expression of both genes is strongly iron regulated and is thought to be required for transcellular iron trafficking in concert in response to physiological requirements. We tested this hypothesis by expressing Dcytb in Caco-2 cells, a human cell line model often used to mimic intestinal enterocytes. Iron uptake (59Fe) was significantly higher in Dcytb-transfected Caco-2 cells than in cells transfected with empty vector as a control. Fe(III) reductase activity of Dcytb was measured with ferrozine, a strong chelator of Fe(II) species. Cells expressing Dcytb exhibited enhanced ferric reductase activity as well as increased 59Fe uptake compared with cells transfected with empty vector as a control. Ferrozine blocked iron uptake and preincubation of cells with dehydroascorbate (to increase cellular ascorbate levels) stimulated iron uptake. Cotransfection of Dcytb and DMT1 resulted in an additive increase in iron uptake by the cells. The results confirm Dcytb can act as a ferric reductase that stimulates iron uptake in Caco-2 cells.
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Affiliation(s)
- Gladys O Latunde-Dada
- Nutritional Sciences Division, School of Biomedical and Health Sciences, King's College London, London, SE1 9HN, UK.
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23
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Yoo CB, Chuang JC, Byun HM, Egger G, Yang AS, Dubeau L, Long T, Laird PW, Marquez VE, Jones PA. Long-term epigenetic therapy with oral zebularine has minimal side effects and prevents intestinal tumors in mice. Cancer Prev Res (Phila) 2008; 1:233-40. [PMID: 19138966 DOI: 10.1158/1940-6207.capr-07-0008] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Recent successes in the application of epigenetic drugs for the treatment of myelodysplastic syndrome have raised questions on the safety of long-term administration of DNA methylation inhibitors. We treated preweaned cancer prone Apc(Min/+) (Min) mice continuously with the DNA methylation inhibitor zebularine in their drinking water to determine the effects of the drug on normal mouse development as well as cancer prevention. Zebularine caused a tissue-specific reduction in DNA methylation at B1 short interspersed nucleotide elements in the small and large intestines of female Min mice but not in other organs examined after chronic oral treatment. No significant difference in the average weights of mice was observed during the treatment. In addition, analysis of global gene expression of colonic epithelial cells from the females indicated that only 3% to 6% of the genes were affected in their expression. We did not detect toxicity and abnormalities from the histopathologic analysis of liver and intestinal tissues. Lastly, we tested whether prevention of tumorigenesis can be achieved with chronic oral administration of zebularine in Min mice. The average number of polyps in Min females decreased from 58 to 1, whereas the average polyp number remained unaffected in Min males possibly due to differential activity of aldehyde oxidase. Taken together, our results show for the first time that long-term oral administration of zebularine causes a gender-specific abrogation of intestinal tumors while causing a tissue-specific DNA demethylation. Importantly, prolonged treatment of mice with epigenetic drugs resulted in only minor developmental and histologic changes.
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Affiliation(s)
- Christine B Yoo
- Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033-9181, USA
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24
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Oakhill JS, Marritt SJ, Gareta EG, Cammack R, McKie AT. Functional characterization of human duodenal cytochrome b (Cybrd1): Redox properties in relation to iron and ascorbate metabolism. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:260-8. [DOI: 10.1016/j.bbabio.2007.12.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Revised: 12/11/2007] [Accepted: 12/12/2007] [Indexed: 10/22/2022]
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Xu Q, Cheng CHC, Hu P, Ye H, Chen Z, Cao L, Chen L, Shen Y, Chen L. Adaptive evolution of hepcidin genes in antarctic notothenioid fishes. Mol Biol Evol 2008; 25:1099-112. [PMID: 18310660 DOI: 10.1093/molbev/msn056] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Hepcidin is a small bioactive peptide with dual roles as an antimicrobial peptide and as the principal hormonal regulator of iron homeostasis in human and mouse. Hepcidin homologs of very similar structures are found in lower vertebrates, all comprise approximately 20-25 amino acids with 8 highly conserved cysteines forming 4 intramolecular disulfide bonds, giving hepcidin a hairpin structure. Hepcidins are particularly diverse in teleost fishes, which may be related to the diversity of aquatic environments with varying degree of pathogen challenge, oxygenation, and iron concentration, factors known to alter hepcidin expression in mammals. We characterized the diversity of hepcidin genes of the Antarctic notothenioid fishes that are endemic to the world's coldest and most oxygen-rich marine water. Notothenioid fishes have at least 4 hepcidin variants, in 2 distinctive structural types. Type I hepcidins comprise 3 distinct variants that are homologs of the widespread 8-cysteine hepcidins. Type II is a novel 4-cysteine variant and therefore only 2 possible disulfide bonds, highly expressed in hematopoietic tissues. Analyses of d(N)/d(S) substitution rate ratios and likelihood ratio test under site-specific models detected significant signal of positive Darwinian selection on the mature hepcidin-coding sequence, suggesting adaptive evolution of notothenioid hepcidins. Genomic polymerase chain reaction and Southern hybridization showed that the novel type II hepcidin occurs exclusively in lineages of the Antarctic notothenioid radiation but not in the basal non-Antarctic taxa, and lineage-specific positive selection was detected on the branch leading to the type II hepcidin clade under branch-site models, suggesting adaptive evolution of the reduced cysteine variant in response to the polar environment. We also isolated a structurally distinct 4-cysteine (4cys) hepcidin from an Antarctic eelpout that is unrelated to the notothenioids but inhabits the same freezing water. Neighbor-Joining (NJ) analyses of teleost hepcidins showed that the eelpout 4cys variant arose independently from the notothenioid version, which lends support to adaptive evolution of reduced cysteine hepcidin variants on cold selection. The NJ tree also showed taxonomic-specific expansions of hepcidin variants, indicating that duplication and diversification of hepcidin genes play important roles in evolutionary response to diverse ecological conditions.
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Affiliation(s)
- Qianghua Xu
- Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, People's Republic of China
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26
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Oates PS. The relevance of the intestinal crypt and enterocyte in regulating iron absorption. Pflugers Arch 2007; 455:201-13. [PMID: 17473933 DOI: 10.1007/s00424-007-0264-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2007] [Accepted: 03/28/2007] [Indexed: 12/27/2022]
Abstract
Rigorous regulation of iron absorption is required to meet the requirements of the body and to limit excess iron accumulation that can produce oxidative stress. Regulation of iron absorption is controlled by hepcidin and probably by the crypt program. Hepcidin is a humoral mediator of iron absorption that interacts with the basolateral transporter, ferroportin. High levels of hepcidin reduce iron absorption by targeting ferroportin to lysosomes for destruction. It is also proposed that ferroportin is expressed on the apical membrane and coordinates with ferroportin-hepcidin derived from the basal surface to modulate the uptake phase of iron absorption. The crypt program suggests that as crypt cells differentiate and migrate into the absorptive zone they absorb iron from the diet at levels inverse to the amount of iron taken up from transferrin. Under most circumstances, intestinal iron absorption is controlled at multiple levels that lead to hepcidin/ferroportin modulation of the enterocyte labile iron pool (LIP). It is likely that transcription of iron transport proteins involved in the apical and basolateral transport of iron are differentially regulated by separate LIPs. Iron-responsive protein (IRP) 1 and IRP2 do not appear to play a significant role in the expression of iron transport proteins, although IRP2 regulates L- and H-ferritin expression. Despite the importance of hepcidin, there is evidence of hepcidin-independent regulation of iron absorption possibly involving haemojuvelin (HJV) and neogenin, which may be up-regulated during ineffective erythropoiesis.
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Affiliation(s)
- Phillip S Oates
- School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, 35 Stirling Highway, Nedlands 6009, Australia.
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27
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Raja KB, Jafri SE, Peters TJ, Simpson RJ. Iron and cadmium uptake by duodenum of hypotransferrinaemic mice. Biometals 2007; 19:547-53. [PMID: 16937261 DOI: 10.1007/s10534-005-5919-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2005] [Accepted: 12/14/2005] [Indexed: 11/25/2022]
Abstract
Absorption from food is an important route for entry of the toxic metal, cadmium, into the body. Both cadmium and iron are believed to be taken up by duodenal enterocytes via the iron regulated, proton-coupled transporter, DMT1. This means that cadmium uptake could be enhanced in conditions where iron absorption is increased. We measured pH dependent uptake of (109)Cd and (59)Fe by duodenum from mice with an in vitro method. Mice with experimental (hypoxia, iron deficiency) or hereditary (hypotransferrinaemia) increased iron absorption were studied. All three groups of mice showed increased (59)Fe uptake (p<0.05) compared to their respective controls. Hypotransferrinaemic and iron deficient mice exhibited an increase in (109)Cd uptake (p<0.05). Cadmium uptake was not, however, increased by lowering the medium pH from 7.4 to 6. In contrast, (59)Fe uptake (from (59)FeNTA(2)) and ferric reductase activity was increased by lowering medium pH in control and iron deficient mice (p<0.05). The data show that duodenal cadmium uptake can be increased by hereditary iron overload conditions. The uptake is not, however, altered by lowering medium pH suggesting that DMT1-independent uptake pathways may operate.
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Affiliation(s)
- Kishor B Raja
- Department of Clinical Biochemistry, King's College London, London, UK
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28
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Abstract
Hepcidin, a peptide hormone made in the liver, is the principal regulator of systemic iron homeostasis. Hepcidin controls plasma iron concentration and tissue distribution of iron by inhibiting intestinal iron absorption, iron recycling by macrophages, and iron mobilization from hepatic stores. Hepcidin acts by inhibiting cellular iron efflux through binding to and inducing the degradation of ferroportin, the sole known cellular iron exporter. Synthesis of hepcidin is homeostatically increased by iron loading and decreased by anemia and hypoxia. Hepcidin is also elevated during infections and inflammation, causing a decrease in serum iron levels and contributing to the development of anemia of inflammation, probably as a host defense mechanism to limit the availability of iron to invading microorganisms. At the opposite side of the spectrum, hepcidin deficiency appears to be the ultimate cause of most forms of hemochromatosis, either due to mutations in the hepcidin gene itself or due to mutations in the regulators of hepcidin synthesis. The emergence of hepcidin as the pathogenic factor in most systemic iron disorders should provide important opportunities for improving their diagnosis and treatment.
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Affiliation(s)
- Elizabeta Nemeth
- Departments of Medicine and Pathology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90095, USA.
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29
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Rachmilewitz EA, Weizer-Stern O, Adamsky K, Amariglio N, Rechavi G, Breda L, Rivella S, Cabantchik ZI. Role of iron in inducing oxidative stress in thalassemia: Can it be prevented by inhibition of absorption and by antioxidants? Ann N Y Acad Sci 2006; 1054:118-23. [PMID: 16339657 DOI: 10.1196/annals.1345.014] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The pathophysiology of thalassemia is, to a certain extent, associated with the generation of labile iron in the pathological red blood cell (RBC). The appearance of such forms of iron at the inner and outer cell surfaces exposes the cell to conditions whereby the labile metal promotes the formation of reactive oxygen species (ROS) leading to cumulative cell damage. Another source of iron accumulation results from increased absorption due to decreased expression of hepcidin. The presence of labile plasma iron (LPI) was carried out using fluorescent probes in the FACS. RNA expression of hepcidin was measured in two models of thalassemic mice. Hepcidin expression was also measured in human hepatoma HepG2 cells following incubation with thalassemic sera. LPI was identified and could be quantitatively measured and correlated with other parameters of iron overload. Hepcidin expression was downregulated in the livers of thalassemic mice, in major more than in intermedia. Thalassemic sera down regulated hepcidin expression in HepG2 liver cells. A possible way to decrease iron absorption could be by modulating hepcidin expression pharmacologically, by gene therapy or by its administration. Treatment with combination of antioxidants such as N-acetylcysteine for proteins and vitamin E for lipids in addition to iron chelators could neutralize the deleterious effects of ROS and monitored by quantitation of LPI.
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Affiliation(s)
- Eliezer A Rachmilewitz
- Department of Hematology, The Edith Wolfson Medical Center, P.O. Box 5, 58100 Holon, Israel.
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30
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Ganz T, Nemeth E. Regulation of iron acquisition and iron distribution in mammals. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:690-9. [PMID: 16790283 DOI: 10.1016/j.bbamcr.2006.03.014] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2005] [Revised: 03/03/2006] [Accepted: 03/05/2006] [Indexed: 02/08/2023]
Abstract
Both cellular iron deficiency and excess have adverse consequences. To maintain iron homeostasis, complex mechanisms have evolved to regulate cellular and extracellular iron concentrations. Extracellular iron concentrations are controlled by a peptide hormone hepcidin, which inhibits the supply of iron into plasma. Hepcidin acts by binding to and inducing the degradation of the cellular iron exporter, ferroportin, found in sites of major iron flows: duodenal enterocytes involved in iron absorption, macrophages that recycle iron from senescent erythrocytes, and hepatocytes that store iron. Hepcidin synthesis is in turn controlled by iron concentrations, hypoxia, anemia and inflammatory cytokines. The molecular mechanisms that regulate hepcidin production are only beginning to be understood, but its dysregulation is involved in the pathogenesis of a spectrum of iron disorders. Deficiency of hepcidin is the unifying cause of hereditary hemochromatoses, and excessive cytokine-stimulated hepcidin production causes hypoferremia and contributes to anemia of inflammation.
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Affiliation(s)
- Tomas Ganz
- Department of Medicine and Pathology, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA 90095-1690, USA.
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31
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Abstract
Hepcidin evolves as a potent hepatocyte-derived regulator of the body's iron distribution piloting the flow of iron via, and directly binding, to the cellular iron exporter ferroportin. The hepcidin-ferroportin axis dominates the iron egress from all cellular compartments that are critical to iron homeostasis, namely placental syncytiotrophoblasts, duodenal enterocytes, hepatocytes and macrophages of the reticuloendothelial system. The gene that encodes hepcidin expression (HAMP) is subject to regulation by proinflammatory cytokines, such as IL-6 and IL-1; excessive hepcidin production explains the relative deficiency of iron during inflammatory states, eventually resulting in the anaemia of inflammation. The haemochromatosis genes HFE, TfR2 and HJV potentially facilitate the transcription of HAMP. Disruption of each of the four genes leads to a diminished hepatic release of hepcidin consistent with both a dominant role of hepcidin in hereditary haemochromatosis and an upstream regulatory role of HFE, TfR2 and HJV on HAMP expression. The engineered generation of hepcidin agonists, mimetics or antagonists could largely broaden current therapeutic strategies to redirect the flow of iron.
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Affiliation(s)
- R Deicher
- Department of Medicine III, Medical University of Vienna, Vienna, Austria
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Latunde-Dada GO, McKie AT, Simpson RJ. Animal models with enhanced erythropoiesis and iron absorption. Biochim Biophys Acta Mol Basis Dis 2006; 1762:414-23. [PMID: 16459059 DOI: 10.1016/j.bbadis.2005.12.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2005] [Revised: 11/22/2005] [Accepted: 12/16/2005] [Indexed: 12/19/2022]
Abstract
The regulation of iron absorption is of considerable interest in mammals since excretion is minimal. Recent advances in iron metabolism have expounded the molecular mechanisms by which iron absorption is attuned to the physiological demands of the body. The pinnacle was the discovery and identification of hepcidin, a hepatic antimicrobial peptide that regulates absorption to maintain iron homeostasis. While the intricacies of its expression and regulation by HFE, transferrin receptor 2 and hemojuvelin are still speculative, hepcidin responsiveness has correlated negatively with iron absorption in different models and disorders of iron metabolism. Consequently, hepcidin expression is repressed to enhance iron absorption during stimulated erythropoiesis even in situations of elevated iron stores. Animal models have been crucial to the advances in understanding iron metabolism and the present review focuses on phenylhydrazine treated and hypotransferrinaemic rodents. These, respectively, experimental and genetic models of enhanced erythropoiesis highlight the shifting focus of iron absorption regulation from the marrow to the liver.
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Affiliation(s)
- Gladys O Latunde-Dada
- Department of Biochemistry and Nutrition Sciences Research Division, King's College London, Franklin Wilkin's Building, 150 Stamford Street, London SE1 9NH, UK
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Mok H, Mlodnicka AE, Hentze MW, Muckenthaler M, Schumacher A. The Molecular Circuitry Regulating the Switch between Iron Deficiency and Overload in Mice. J Biol Chem 2006; 281:7946-51. [PMID: 16418170 DOI: 10.1074/jbc.m509857200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recent positional cloning of the radiation-induced polycythaemia (Pcm) mutation revealed a 58-bp microdeletion in the promoter region of ferroportin 1 (Fpn1), the sole cellular iron exporter identified to date. Here we report a molecular definition of the regulatory mechanisms governing the dynamic changes in iron balance in Pcm heterozygous mice between 3 and 12 weeks of age. Hepatic and/or duodenal response patterns of iron metabolism genes, such as Trfr, cybrd1, and Slc11a2, explained the transition from early postnatal iron deficiency to iron overload by 12 weeks of age. A significant delay in developmental up-regulation of hepcidin (Hamp), the pivotal hormonal regulator of iron homeostasis, correlated with high levels of Fpn1 expression in hepatic Kupffer cells and duodenal epithelial cells at 7 weeks of age. Conversely, upon up-regulation of Hamp expression at 12 weeks of age, Fpn1 expression decreased, indicative of a Hamp-mediated homeostatic loop. Hamp regulation due to iron did not appear dependent on transcription-level changes of the murine homolog of Hemojuvelin (Rgmc). Aged cohorts of Pcm mice exhibited low levels of Fpn1 expression in the context of an iron-deficient erythropoiesis and profound iron sequestration in reticuloendothelial macrophages, duodenum, and other tissues. Thus, similar to the anemia of chronic disease, these findings demonstrate decreased iron bioavailability due to sustained down-regulation of Fpn1 levels by Hamp. We conclude that regulatory alleles, such as Pcm, with highly dynamic changes in iron balance are ideally suited to interrogate the genetic circuitry regulating iron metabolism.
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Affiliation(s)
- Henry Mok
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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Salazar J, Mena N, Núñez MT. Iron dyshomeostasis in Parkinson's disease. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 2006:205-13. [PMID: 17447431 DOI: 10.1007/978-3-211-33328-0_22] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Owing to its ability to undergo one-electron reactions, iron transforms the mild oxidant hydrogen peroxide into hydroxyl radical, one of the most reactive species in nature. Deleterious effects of iron accumulation are dramatically evidenced in several neurodegenerative diseases. The work of Youdim and collaborators has been fundamental in describing the accumulation of iron confined to the substantia nigra (SN) in Parkinson's disease (PD) and to clarify iron toxicity pathways and oxidative damage in dopaminergic neurons. Nevertheless, how the mechanisms involved in normal neuronal iron homeostasis are surpassed, remain largely undetermined. How nigral neurons survive or succumb to iron-induced oxidative stress are relevant questions both to know about the etiology of the disease and to design neuroprotective strategies. In this work, we review the components of neural iron homeostasis and we summarize evidence from recent studies aimed to unravel the molecular basis of iron accumulation and dyshomeostasis in PD.
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Affiliation(s)
- J Salazar
- Department of Biology, and Cell Dynamic and Biotechnology Research Center, Faculty of Sciences, University of Chile, Santiago, Chile
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Galy B, Ferring D, Minana B, Bell O, Janser HG, Muckenthaler M, Schümann K, Hentze MW. Altered body iron distribution and microcytosis in mice deficient in iron regulatory protein 2 (IRP2). Blood 2005; 106:2580-9. [PMID: 15956281 DOI: 10.1182/blood-2005-04-1365] [Citation(s) in RCA: 178] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
AbstractIron regulatory protein 2 (IRP2)-deficient mice have been reported to suffer from late-onset neurodegeneration by an unknown mechanism. We report that young adult Irp2-/- mice display signs of iron mismanagement within the central iron recycling pathway in the mammalian body, the liver-bone marrow-spleen axis, with altered body iron distribution and compromised hematopoiesis. In comparison with wild-type littermates, Irp2-/- mice are mildly microcytic with reduced serum hemoglobin levels and hematocrit. Serum iron and transferrin saturation are unchanged, and hence microcytosis is not due to an overt decrease in systemic iron availability. The liver and duodenum are iron loaded, while the spleen is iron deficient, associated with a reduced expression of the iron exporter ferroportin. A reduction in transferrin receptor 1 (TfR1) mRNA levels in the bone marrow of Irp2-/- mice can plausibly explain the microcytosis by an intrinsic defect in erythropoiesis due to a failure to adequately protect TfR1 mRNA against degradation. This study links a classic regulator of cellular iron metabolism to systemic iron homeostasis and erythropoietic TfR1 expression. Furthermore, this work uncovers aspects of mammalian iron metabolism that can or cannot be compensated for by the expression of IRP1. (Blood. 2005;106: 2580-2589)
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Affiliation(s)
- Bruno Galy
- European Molecular Biology Laboratory, Heidelberg, Germany
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Gunshin H, Starr CN, Direnzo C, Fleming MD, Jin J, Greer EL, Sellers VM, Galica SM, Andrews NC. Cybrd1 (duodenal cytochrome b) is not necessary for dietary iron absorption in mice. Blood 2005; 106:2879-83. [PMID: 15961514 PMCID: PMC1895297 DOI: 10.1182/blood-2005-02-0716] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Mammalian nonheme iron absorption requires reduction of dietary iron for uptake by the divalent metal ion transport system in the intestine. This was thought to be mediated by duodenal cytochrome b (Cybrd1), a ferric reductase enzyme resident on the luminal surface of intestinal absorptive cells. To test its importance in vivo, we inactivated the murine Cybrd1 gene and assessed tissue iron stores in Cybrd1-null mice. We found that loss of Cybrd1 had little or no impact on body iron stores, even in the setting of iron deficiency. We conclude that other mechanisms must be available for the reduction of dietary iron.
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Affiliation(s)
- Hiromi Gunshin
- Children's Hospital, Karp Family Research Laboratories RM 8-125, Boston, MA 02115-5737, USA
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Abstract
PURPOSE OF REVIEW The number of newly identified genes participating in the regulation of iron homeostasis has continued to expand at a remarkable pace. The roles for many have begun to be elucidated and there is an increasing indication that hepatocytes play a central role in determining the level of intestinal iron absorption. Total body iron homeostasis is dependent upon carefully regulated absorption of dietary iron, thus these genes are of fundamental importance in understanding of pathophysiology of such common disorders as hereditary hemochromatosis (HH) and the anaemia of chronic diseases. RECENT FINDINGS The hepatic peptide hepcidin plays a key role as a circulating hormone that regulates the absorption of dietary iron from the duodenum. Hepcidin expression is inappropriately decreased in hereditary hemochromatosis and is abnormally increased in the anaemia of chronic diseases. Other hepatic proteins essential for normal iron homeostasis, including HFE, transferrin receptor 2 (TfR2), and hemojuvelin, function at least in part, by modulating the expression of hepcidin. SUMMARY New insights into the pathophysiology of hereditary hemochromatosis and the anaemia of chronic diseases have been achieved with the recognition of the central role for hepcidin as an iron regulatory hormone. Investigations into the biologic control of this hormone and its mechanism of action offer the possibility of new therapeutic approaches to disorders of iron metabolism.
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Affiliation(s)
- Robert E Fleming
- Saint Louis University School of Medicine, 1465 South Grand Avenue, Saint Louis, Missouri 63104, USA.
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