1101
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Abstract
Ferroportin1 is a newly discovered molecule that may play a role in iron export. It is expressed on the basolateral surfaces of mature enterocytes within the duodenum and in macrophages of the spleen and liver. Furthermore, this protein was found to be expressed in placental syncytiotrophoblasts and may be involved in the supply of maternal iron to the fetus. Sequence analysis of ferroportin1 predicts it has ten transmembrane domains, a reductase site and a basolateral localization signal. In addition, the ferroportin1 mRNA transcript contains an iron response element in its 5' untranslated region. This review is focused on the current state of knowledge on ferroportin1 and the medical implications of this discovery.
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Affiliation(s)
- Nghia T V Le
- The Iron Metabolism and Chelation Group, The Heart Research Institute, 145 Missenden Road, Camperdown, Sydney, NSW 2050, Australia
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1102
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Abstract
Organs are specialized tissues used for enhanced physiology and environmental adaptation. The cells of the embryo are genetically programmed to establish organ form and function through conserved developmental modules. The zebrafish is a powerful model system that is poised to contribute to our basic understanding of vertebrate organogenesis. This review develops the theme of modules and illustrates how zebrafish have been particularly useful for understanding heart and blood formation.
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Affiliation(s)
- Christine Thisse
- Institut de Biologie Moléculaire et Cellulaire, CNRS, INSERM, Université Louis Pasteur, 1 rue Laurent Fries, BP 163, 67404 Illkirch Cedex, C. U. de Strasbourg, France
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1103
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Wardrop SL, Wells C, Ravasi T, Hume DA, Richardson DR. Induction of Nramp2 in activated mouse macrophages is dissociated from regulation of the Nramp1, classical inflammatory genes, and genes involved in iron metabolism. J Leukoc Biol 2002. [DOI: 10.1189/jlb.71.1.99] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- S. L. Wardrop
- Institute of Molecular Biosciences and ARC Special Research Centre for Functional and Applied Genomics, University of Queensland, Brisbane, Australia
| | - C. Wells
- Institute of Molecular Biosciences and ARC Special Research Centre for Functional and Applied Genomics, University of Queensland, Brisbane, Australia
| | - T. Ravasi
- Institute of Molecular Biosciences and ARC Special Research Centre for Functional and Applied Genomics, University of Queensland, Brisbane, Australia
| | - D. A. Hume
- Institute of Molecular Biosciences and ARC Special Research Centre for Functional and Applied Genomics, University of Queensland, Brisbane, Australia
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1104
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Abstract
BACKGROUND/AIMS The recovery from iron overload is hampered by the limited number of pathways and therapeutic agents available for the augmentation of iron secretion/excretion. The present study was aimed to investigate the process of iron storage and release by cultured human hepatoma cells, the role of transferrin receptors and ferritin in this process as well as the effect of iron chelators. METHODS We followed the acquisition, storage and release of iron by cultured cells HepG2 and Hep3B by biochemical means and electron microscopy. RESULTS The uptake of iron from diferric transferrin (Trf) was extremely low, while iron as ferric-ammonium-citrate (FAC) was taken up readily, especially by Hep3B cells. Up to 80% of the iron taken up by hepatoma cells was released to the medium. The rate of spontaneous iron release depended on the extent of iron loading. ApoTrf and deferoxamine facilitated release after 1- and 7-day iron-exposure. Up to a third of the radio-iron released from the cells was associated with ferritin. The release of ferritin-iron was not enhanced by either deferoxamine or Trf. CONCLUSIONS Ferritin-iron release appeared to be an important mechanism of iron discarding in cultured human hepatoma cells, independent of the activity of chelating agents.
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Affiliation(s)
- Mark Hirsh
- The Pediatric Research and Electron Microscopy Unit, B Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, P.O. Box 9649, Haifa 31096, Israel
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1105
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Abstract
Like other organisms, insects must balance two properties of ionic iron, that of an essential nutrient and a potent toxin. Iron must be acquired to provide catalysis for oxidative metabolism, but it must be controlled to avoid destructive oxidative reactions. Insects have evolved distinctive forms of the serum iron transport protein, transferrin, and the storage protein, ferritin. These proteins may serve different functions in insects than they do in other organisms. A form of translational control of protein synthesis by iron in insects is similar to that of vertebrates. The Drosophila melanogaster genome contains many genes that may encode other proteins involved in iron metabolism.
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Affiliation(s)
- Helen Nichol
- Department of Nutritional Science, University of Arizona, Shantz 309, P.O. Box 210038, Tucson, Arizona 85721-0038, USA.
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1106
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1107
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Burdo JR, Menzies SL, Simpson IA, Garrick LM, Garrick MD, Dolan KG, Haile DJ, Beard JL, Connor JR. Distribution of divalent metal transporter 1 and metal transport protein 1 in the normal and Belgrade rat. J Neurosci Res 2001; 66:1198-207. [PMID: 11746453 DOI: 10.1002/jnr.1256] [Citation(s) in RCA: 214] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Iron accumulation in the brain occurs in a number of neurodegenerative diseases. Two new iron transport proteins have been identified that may help elucidate the mechanism of abnormal iron accumulation. The Divalent Metal Transporter 1 (DMT1), is responsible for iron uptake from the gut and transport from endosomes. The Metal Transport Protein 1 (MTP1) promotes iron export. In this study we determined the cellular and regional expression of these two transporters in the brains of normal adult and Belgrade rats. Belgrade rats have a defect in DMT1 that is associated with lower levels of iron in the brain. In the normal rat, DMT1 expression is highest in neurons in the striatum, cerebellum, thalamus, ependymal cells lining the third ventricle, and vascular cells throughout the brain. The staining in the ependymal cells and endothelial cells suggests that DMT1 has an important role in iron transport into the brain. In Belgrade rats, there is generalized decrease in immunodetectable DMT1 compared to normal rats except in the ependymal cells. This decrease in immunoreactivity, however, was absent on immunoblots. The immunoblot analysis indicates that this protein did not upregulate to compensate for the chronic defect in iron transport. MTP1 staining is found in most brain regions. MTP1 expression in the brain is robust in pyramidal neurons of the cerebral cortex but is not detected in the vascular endothelial cells and ependymal cells. MTP1 staining in Belgrade rats was decreased compared to normal, but similar to DMT1 this decrease was not corroborated by immunoblotting. These results indicate that DMT1 and MTP1 are involved in brain iron transport and this involvement is regionally and cellularly specific.
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Affiliation(s)
- J R Burdo
- Department of Neuroscience and Anatomy, Hershey Medical Center, Pennsylvania State College of Medicine, 500 University Drive, Hershey, PA 17036, USA
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1108
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Gunshin H, Allerson CR, Polycarpou-Schwarz M, Rofts A, Rogers JT, Kishi F, Hentze MW, Rouault TA, Andrews NC, Hediger MA. Iron-dependent regulation of the divalent metal ion transporter. FEBS Lett 2001; 509:309-16. [PMID: 11741608 DOI: 10.1016/s0014-5793(01)03189-1] [Citation(s) in RCA: 224] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The first step in intestinal iron absorption is mediated by the H(+)-coupled Fe(2+) transporter called divalent cation transporter 1/divalent metal ion transporter 1 (DCT1/DMT1) (also known as natural resistance-associated macrophage protein 2). DCT1/DMT1 mRNA levels in the duodenum strongly increase in response to iron depletion. To study the mechanism of iron-dependent DCT1/DMT1 mRNA regulation, we investigated the endogenous expression of DCT1/DMT1 mRNA in various cell types. We found that only the iron responsive element (IRE)-containing form, which corresponds to one of two splice forms of DCT1/DMT1, is responsive to iron treatment and this responsiveness was cell type specific. We also examined the interaction of the putative 3'-UTR IRE with iron responsive binding proteins (IRP1 and IRP2), and found that IRP1 binds to the DCT1/DMT1-IRE with higher affinity compared to IRP2. This differential binding of IRP1 and IRP2 was also reported for the IREs of transferrin receptors, erythroid 5-aminolevulinate synthase and mitochondrial aconitase. We propose that regulation of DCT1/DMT1 mRNA by iron involves post-transcriptional regulation through the binding of IRP1 to the transporter's IRE, as well as other as yet unknown factors.
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Affiliation(s)
- H Gunshin
- Membrane Biology Program and Renal Division, Brigham and Women's Hospital and Harvard Medical School, Harvard Institutes of Medicine, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.
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1109
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Parkkila S, Niemelä O, Britton RS, Fleming RE, Waheed A, Bacon BR, Sly WS. Molecular aspects of iron absorption and HFE expression. Gastroenterology 2001; 121:1489-96. [PMID: 11729128 DOI: 10.1053/gast.2001.29617] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Hereditary hemochromatosis, a disease of iron overload, occurs in about 1 in 200-400 Caucasians. The gene mutated in this disorder is termed HFE. The product of this gene, HFE protein, is homologous to major histocompatibility complex class I proteins, but HFE does not present peptides to T cells. Based on recent structural, biochemical, and cell biological studies, transferrin receptor (TfR) is a ligand for HFE. This association directly links HFE protein to the TfR-mediated regulation of iron homeostasis. Although evidence is accumulating that binding of HFE to TfR is critical for the effects of HFE, the final pieces in the HFE puzzle have not been established. This review focuses on recent advances in HFE research and presents a hypothetical model of HFE function.
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Affiliation(s)
- S Parkkila
- Department of Anatomy and Cell Biology, University of Oulu, Oulu, Finland
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1110
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Abstract
Inventive genetic screens in zebrafish are revealing new genetic pathways that control vertebrate development, disease and behaviour. By exploiting the versatility of zebrafish, biological processes that had been previously obscured can be visualized and many of the responsible genes can be isolated. Coupled with gene knockdown and overexpression technologies, and small-molecule-induced phenotypes, genetic screens in zebrafish provide a powerful system by which to dissect vertebrate gene function and gene networks.
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Affiliation(s)
- E E Patton
- Howard Hughes Medical Institute, Children's Hospital of Boston, 300 Longwood Avenue, Enders 750, Boston, Massachusetts 02115, USA.
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1111
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Lieschke GJ, Oates AC, Crowhurst MO, Ward AC, Layton JE. Morphologic and functional characterization of granulocytes and macrophages in embryonic and adult zebrafish. Blood 2001; 98:3087-96. [PMID: 11698295 DOI: 10.1182/blood.v98.10.3087] [Citation(s) in RCA: 347] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The zebrafish is a useful model organism for developmental and genetic studies. The morphology and function of zebrafish myeloid cells were characterized. Adult zebrafish contain 2 distinct granulocytes, a heterophil and a rarer eosinophil, both of which circulate and are generated in the kidney, the adult hematopoietic organ. Heterophils show strong histochemical myeloperoxidasic activity, although weaker peroxidase activity was observed under some conditions in eosinophils and erythrocytes. Embryonic zebrafish have circulating immature heterophils by 48 hours after fertilization (hpf). A zebrafish myeloperoxidase homologue (myeloid-specific peroxidase; mpx) was isolated. Phylogenetic analysis suggested it represented a gene ancestral to the mammalian myeloperoxidase gene family. It was expressed in adult granulocytes and in embryos from 18 hpf, first diffusely in the axial intermediate cell mass and then discretely in a dispersed cell population. Comparison of hemoglobinized cell distribution, mpx gene expression, and myeloperoxidase histochemistry in wild-type and mutant embryos confirmed that the latter reliably identified a population of myeloid cells. Studies in embryos after tail transection demonstrated that mpx- and peroxidase-expressing cells were mobile and localized to a site of inflammation, indicating functional capability of these embryonic granulocytes. Embryonic macrophages removed carbon particles from the circulation by phagocytosis. Collectively, these observations have demonstrated the early onset of zebrafish granulopoiesis, have proved that granulocytes circulate by 48 hpf, and have demonstrated the functional activity of embryonic granulocytes and macrophages. These observations will facilitate the application of this genetically tractable organism to the study of myelopoiesis.
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Affiliation(s)
- G J Lieschke
- Ludwig Institute for Cancer Research, The Royal Melbourne Hospital, Parkville, Victoria, Australia.
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1112
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Abstract
The zebrafish is a useful model organism for developmental and genetic studies. The morphology and function of zebrafish myeloid cells were characterized. Adult zebrafish contain 2 distinct granulocytes, a heterophil and a rarer eosinophil, both of which circulate and are generated in the kidney, the adult hematopoietic organ. Heterophils show strong histochemical myeloperoxidasic activity, although weaker peroxidase activity was observed under some conditions in eosinophils and erythrocytes. Embryonic zebrafish have circulating immature heterophils by 48 hours after fertilization (hpf). A zebrafish myeloperoxidase homologue (myeloid-specificperoxidase; mpx) was isolated. Phylogenetic analysis suggested it represented a gene ancestral to the mammalian myeloperoxidase gene family. It was expressed in adult granulocytes and in embryos from 18 hpf, first diffusely in the axial intermediate cell mass and then discretely in a dispersed cell population. Comparison of hemoglobinized cell distribution,mpx gene expression, and myeloperoxidase histochemistry in wild-type and mutant embryos confirmed that the latter reliably identified a population of myeloid cells. Studies in embryos after tail transection demonstrated that mpx- and peroxidase-expressing cells were mobile and localized to a site of inflammation, indicating functional capability of these embryonic granulocytes. Embryonic macrophages removed carbon particles from the circulation by phagocytosis. Collectively, these observations have demonstrated the early onset of zebrafish granulopoiesis, have proved that granulocytes circulate by 48 hpf, and have demonstrated the functional activity of embryonic granulocytes and macrophages. These observations will facilitate the application of this genetically tractable organism to the study of myelopoiesis.
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1113
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Abstract
An African American male infant with sickle cell disease has a devastating stroke; an African American soldier is surprised when he is informed that he has sickle cell disease. They are both homozygous for the same mutation. An Ashkenazi Jewish woman with Gaucher disease has a huge spleen and severe thrombocytopenia; her older brother, homozygous for the same 1226G glucocerebrosidase mutation, is found on routine examination to have a barely palpable spleen tip. The fact that clinical manifestations of genetic diseases can vary widely among patients has been recognized for many decades. In the past, however, it could often be attributed to the pleomorphic nature of mutations of the same gene: the patient with severe disease, it was averred, must have a different mutation than the one with mild disease. Even before a precise definition of mutations could be achieved at the DNA level, such an explanation did not serve to clarify the differences that existed between siblings with the same autosomal recessive disease. Such siblings must surely be carrying the same 2 disease-producing alleles. With the advent of sequence analysis of genes, the great extent of phenotype variation in patients with the same genotype has come to be more fully appreciated, but understanding of why it occurs continues to be meager. It is the purpose of this review to explore some of the variations in phenotype seen by hematologists in patients with identical mutations, to indicate where some progress has been made, and to suggest how understanding in this important area may be expanded.
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Affiliation(s)
- E Beutler
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
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1114
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Bury NR, Grosell M, Wood CM, Hogstrand C, Wilson RW, Rankin JC, Busk M, Lecklin T, Jensen FB. Intestinal iron uptake in the European flounder (Platichthys flesus). J Exp Biol 2001; 204:3779-87. [PMID: 11719541 DOI: 10.1242/jeb.204.21.3779] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Iron is an essential element because it is a key constituent of the metalloproteins involved in cellular respiration and oxygen transport. There is no known regulated excretory mechanism for iron, and homeostasis is tightly controlled via its uptake from the diet. This study assessed in vivo intestinal iron uptake and in vitro iron absorption in a marine teleost, the European flounder Platichthys flesus. Ferric iron, in the form 59FeCl3, was reduced to Fe2+ by ascorbate, and the bioavailability of Fe3+ and Fe2+ were compared. In vivo Fe2+ uptake was significantly greater than Fe3+ uptake and was reduced by the iron chelator desferrioxamine. Fe2+ was also more bioavailable than Fe3+ in in vitro studies that assessed the temporal pattern and concentration-dependency of iron absorption. The posterior region, when compared with the anterior and mid regions of the intestine, was the preferential site for Fe2+ uptake in vivo. In vitro iron absorption was upregulated in the posterior intestine in response to prior haemoglobin depletion of the fish, and the transport showed a Q10 value of 1.94. Iron absorption in the other segments of the intestine did not correlate with haematocrit, and Q10 values were lower. Manipulation of the luminal pH had no effect on in vitro iron absorption. The present study demonstrates that a marine teleost absorbs Fe2+ preferentially in the posterior intestine. This occurs in spite of extremely high luminal bicarbonate concentrations recorded in vivo, which may be expected to reduce the bioavailability of divalent cations as a result of the precipitation as carbonates (e.g. FeCO3).
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Affiliation(s)
- N R Bury
- Division of Health and Life Sciences, King's College London, 150 Stamford Street, London SE1 9NN, UK.
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1115
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Sordino P, Belluzzi L, De Santis R, Smith WC. Developmental genetics in primitive chordates. Philos Trans R Soc Lond B Biol Sci 2001; 356:1573-82. [PMID: 11604124 PMCID: PMC1088537 DOI: 10.1098/rstb.2001.0919] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Recent advances in the study of the genetics and genomics of urochordates testify to a renewed interest in this chordate subphylum, believed to be the most primitive extant chordate relatives of the vertebrates. In addition to their primitive nature, many features of their reproduction and early development make the urochordates ideal model chordates for developmental genetics. Many urochordates spawn large numbers of transparent and externally developing embryos on a daily basis. Additionally, the embryos have a defined and well-characterized cell lineage until the end of gastrulation. Furthermore, the genomes of the urochordates have been estimated to be only 5-10% of the size of the vertebrates and to have fewer genes and less genetic redundancy than vertebrates. Genetic screens, which are powerful tools for investigating developmental mechanisms, have recently become feasible due to new culturing techniques in ascidians. Because hermaphrodite ascidians are able to self-fertilize, recessive mutations can be detected in a single generation. Several recent studies have demonstrated the feasibility of applying modern genetic techniques to the study of ascidian biology.
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Affiliation(s)
- P Sordino
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK.
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1116
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Yamaji S, Tennant J, Tandy S, Williams M, Singh Srai SK, Sharp P. Zinc regulates the function and expression of the iron transporters DMT1 and IREG1 in human intestinal Caco-2 cells. FEBS Lett 2001; 507:137-41. [PMID: 11684086 DOI: 10.1016/s0014-5793(01)02953-2] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Trace metals influence the absorption of each other from the diet and it has been suggested that the divalent metal transporter (DMT1) represents a common uptake pathway for these important micronutrients. However, compelling evidence from our laboratory suggests that DMT1 is predominantly an iron transporter, with lower affinity for other metals. Several studies have shown that increasing dietary iron downregulates DMT1. Interestingly, our current data indicate that zinc upregulates DMT1 protein and mRNA expression and also pH-dependent iron uptake. Transepithelial flux of iron was also increased and was associated with a rise in IREG1 mRNA expression.
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Affiliation(s)
- S Yamaji
- Department of Biochemistry and Molecular Biology, Royal Free and University College Medical School, London, UK
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1117
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Loyevsky M, LaVaute T, Allerson CR, Stearman R, Kassim OO, Cooperman S, Gordeuk VR, Rouault TA. An IRP-like protein from Plasmodium falciparum binds to a mammalian iron-responsive element. Blood 2001; 98:2555-62. [PMID: 11588054 DOI: 10.1182/blood.v98.8.2555] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This study cloned and sequenced the complementary DNA (cDNA) encoding of a putative malarial iron responsive element-binding protein (PfIRPa) and confirmed its identity to the previously identified iron-regulatory protein (IRP)-like cDNA from Plasmodium falciparum. Sequence alignment showed that the plasmodial sequence has 47% identity with human IRP1. Hemoglobin-free lysates obtained from erythrocyte-stage P falciparum contain a protein that binds a consensus mammalian iron-responsive element (IRE), indicating that a protein(s) with iron-regulatory activity was present in the lysates. IRE-binding activity was found to be iron regulated in the electrophoretic mobility shift assays. Western blot analysis showed a 2-fold increase in the level of PfIRPa in the desferrioxamine-treated cultures versus control or iron-supplemented cells. Malarial IRP was detected by anti-PfIRPa antibody in the IRE-protein complex from P falciparum lysates. Immunofluorescence studies confirmed the presence of PfIRPa in the infected red blood cells. These findings demonstrate that erythrocyte P falciparum contains an iron-regulated IRP that binds a mammalian consensus IRE sequence, raising the possibility that the malaria parasite expresses transcripts that contain IREs and are iron-dependently regulated.
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1118
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Frazer DM, Vulpe CD, McKie AT, Wilkins SJ, Trinder D, Cleghorn GJ, Anderson GJ. Cloning and gastrointestinal expression of rat hephaestin: relationship to other iron transport proteins. Am J Physiol Gastrointest Liver Physiol 2001; 281:G931-9. [PMID: 11557513 DOI: 10.1152/ajpgi.2001.281.4.g931] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The membrane-bound ceruloplasmin homolog hephaestin plays a critical role in intestinal iron absorption. The aims of this study were to clone the rat hephaestin gene and to examine its expression in the gastrointestinal tract in relation to other genes encoding iron transport proteins. The rat hephaestin gene was isolated from intestinal mRNA and was found to encode a protein 96% identical to mouse hephaestin. Analysis by ribonuclease protection assay and Western blotting showed that hephaestin was expressed at high levels throughout the small intestine and colon. Immunofluorescence localized the hephaestin protein to the mature villus enterocytes with little or no expression in the crypts. Variations in iron status had a small but nonsignificant effect on hephaestin expression in the duodenum. The high sequence conservation between rat and mouse hephaestin is consistent with this protein playing a central role in intestinal iron absorption, although its precise function remains to be determined.
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Affiliation(s)
- D M Frazer
- Joint Clinical Sciences Program, The Queensland Institute of Medical Research and The University of Queensland, PO Royal Brisbane Hospital, Brisbane, Queensland 4029, Australia
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1119
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Barañano DE, Snyder SH. Neural roles for heme oxygenase: contrasts to nitric oxide synthase. Proc Natl Acad Sci U S A 2001; 98:10996-1002. [PMID: 11572959 PMCID: PMC58673 DOI: 10.1073/pnas.191351298] [Citation(s) in RCA: 232] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The heme oxygenase (HO) and nitric oxide (NO) synthase (NOS) systems display notable similarities as well as differences. HO and NOS are both oxidative enzymes using NADPH as an electron donor. The constitutive forms of the enzyme are differentially activated, with calcium entry stimulating NOS by binding to calmodulin, whereas calcium entry activates protein kinase C to phosphorylate and activate HO2. Although both NO and carbon monoxide (CO) stimulate soluble guanylyl cyclase to form cGMP, NO also S-nitrosylates selected protein targets. Both involve constitutive and inducible biosynthetic enzymes. However, functions of the inducible forms are virtual opposites. Macrophage-inducible NOS generates NO to kill other cells, whereas HO1 generates bilirubin to exert antioxidant cytoprotective effects and also provides cytoprotection by facilitating iron extrusion from cells. The neuronal form of HO, HO2, is also cytoprotective. Normally, neural NO in the brain seems to exert some sort of behavioral inhibition. However, excess release of NO in response to glutamate's N-methyl-d-aspartate receptor activation leads to stroke damage. On the other hand, massive neuronal firing during a stroke presumably activates HO2, leading to neuroprotective actions of bilirubin. Loss of this neuroprotection after HO inhibition by mutant forms of amyloid precursor protein may mediate neurotoxicity in Familial Alzheimer's Disease. NO and CO both appear to be neurotransmitters in the brain and peripheral autonomic nervous system. They also are physiologic endothelial-derived relaxing factors for blood vessels. In the gastrointestinal pathway, NO and CO appear to function as coneurotransmitters, both stimulating soluble guanylyl cyclase to cause smooth muscle relaxation.
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Affiliation(s)
- D E Barañano
- Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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1120
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Montosi G, Donovan A, Totaro A, Garuti C, Pignatti E, Cassanelli S, Trenor CC, Gasparini P, Andrews NC, Pietrangelo A. Autosomal-dominant hemochromatosis is associated with a mutation in the ferroportin (SLC11A3) gene. J Clin Invest 2001. [PMID: 11518736 DOI: 10.1172/jci200113468] [Citation(s) in RCA: 398] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Hemochromatosis is a progressive iron overload disorder that is prevalent among individuals of European descent. It is usually inherited in an autosomal-recessive pattern and associated with missense mutations in HFE, an atypical major histocompatibility class I gene. Recently, we described a large family with autosomal-dominant hemochromatosis not linked to HFE and distinguished by early iron accumulation in reticuloendothelial cells. Through analysis of a large pedigree, we have determined that this disease maps to 2q32. The gene encoding ferroportin (SLC11A3), a transmembrane iron export protein, lies within a candidate interval defined by highly significant lod scores. We show that the iron-loading phenotype in autosomal-dominant hemochromatosis is associated with a nonconservative missense mutation in the ferroportin gene. This missense mutation, converting alanine to aspartic acid at residue 77 (A77D), was not seen in samples from 100 unaffected control individuals. We propose that partial loss of ferroportin function leads to an imbalance in iron distribution and a consequent increase in tissue iron accumulation.
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Affiliation(s)
- G Montosi
- Department of Internal Medicine, University of Modena, Modena, Italy
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1121
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Oates AC, Pratt SJ, Vail B, Ho RK, Johnson SL, Postlethwait JH, Zon LI. The zebrafish klf gene family. Blood 2001; 98:1792-801. [PMID: 11535513 DOI: 10.1182/blood.v98.6.1792] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Krüppel-like factor (KLF) family of genes encodes transcriptional regulatory proteins that play roles in differentiation of a diverse set of cells in mammals. For instance, the founding member KLF1 (also known as EKLF) is required for normal globin production in mammals. Five new KLF genes have been isolated from the zebrafish, Danio rerio, and the structure of their products, their genetic map positions, and their expression during development of the zebrafish have been characterized. Three genes closely related to mammalian KLF2 and KLF4 were found, as was an ortholog of mammalian KLF12. A fifth gene, apparently missing from the genome of mammals and closely related to KLF1 and KLF2, was also identified. Analysis demonstrated the existence of novel conserved domains in the N-termini of these proteins. Developmental expression patterns suggest potential roles for these zebrafish genes in diverse processes, including hematopoiesis, blood vessel function, and fin and epidermal development. The studies imply a high degree of functional conservation of the zebrafish genes with their mammalian homologs. These findings further the understanding of the KLF genes in vertebrate development and indicate an ancient role in hematopoiesis for the Krüppel-like factor gene family.
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Affiliation(s)
- A C Oates
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Victoria, Australia
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1122
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Lieschke GJ. Zebrafish--an emerging genetic model for the study of cytokines and hematopoiesis in the era of functional genomics. Int J Hematol 2001; 73:23-31. [PMID: 11372751 DOI: 10.1007/bf02981899] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Now that whole genomes are sequenced, the identification of gene function rather than gene discovery is a major challenge. Saturation mutagenesis and screening for mutant phenotypes are methods that allow sampling of the genome for lesions in genes critical for particular physiological processes. This approach promises to provide new insights into gene function, even for molecularly well-characterized processes such as hematopoiesis and cytokine signaling. Animal models for such genetic approaches have traditionally included Drosophila and the mouse. Recently, the zebrafish (Danio rerio) has emerged as a flexible and informative vertebrate for genetic studies. Zebrafish hematopoiesis has a morphological and molecular complexity closer to that of mammals than does Drosophila, providing scope for recognizing mutant zebrafish phenotypes representing finely tuned lesions in these processes. Compared to mice, zebrafish represent an economical, flexible, and genetically tractable animal model for mutagenesis studies. The structure of the teleost genome creates several phylogenetic issues in assessing zebrafish and piscine orthologues and paralogues of known mammalian genes, here exemplified by a cytokine ligand (interleukin-1beta), kinase receptors (c-kit and c-fins), and a family of intracellular signaling molecules (JAK kinases). Several anemic zebrafish mutants are now genetically characterized, and others present hematopoietic phenotypes that promise novel insights into the regulation of hematopoiesis.
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Affiliation(s)
- G J Lieschke
- Cytokine Biology Laboratory, Ludwig Institute for Cancer Research, Melbourne Tumor Biology Branch, The Royal Melbourne Hospital, Victoria, Australia.
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1123
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Debnam ES, Grimble GK. Methods for assessing intestinal absorptive function in relation to enteral nutrition. Curr Opin Clin Nutr Metab Care 2001; 4:355-67. [PMID: 11568496 DOI: 10.1097/00075197-200109000-00005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The success of nasoenteral nutrition support can be limited by intestinal impairment. In particular, reduced absorptive area, mucosal atrophy and abnormal motility may reduce absorption of macronutrients and micronutrients, and diarrhoea remains a commonly encountered complication. We review how basic physiological techniques can be used to investigate such pathophysiology. Lumenal nutrients control mucosal growth, expression of mucosal transporters and regional gut motility. Cell biology techniques now complement classical intestinal perfusion methods in determining the 'safety factor' of excess absorptive capacity. The controversial role of the sodium-glucose linked transporter in dietary glucose assimilation is described in terms of its control, its true function and its role in uptake of other solutes. Techniques that involve brush-border membrane vesicles, Caco-2 cells, mucosal immunohistochemistry and gene expression probes are described. Together, these techniques describe a picture of an organ with remarkable ability to maintain digestive and absorptive function in response to a wide variety of nutritional intakes, often in the face of inflammatory illness.
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Affiliation(s)
- E S Debnam
- Department of Physiology, University College, London, UK.
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1124
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Brissot P. Hemochromatosis at the intersection of classical medicine and molecular biology. COMPTES RENDUS DE L'ACADEMIE DES SCIENCES. SERIE III, SCIENCES DE LA VIE 2001; 324:795-804. [PMID: 11558326 DOI: 10.1016/s0764-4469(01)01354-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Hemochromatosis is a genetic disease of iron overload due to intestinal hyperabsorption of iron. It is one of the most prevalent autosomal recessive diseases in Caucasian populations. Hemochromatosis causes severe visceral and metabolic complications at adulthood, which include cirrhosis, diabetes, arthropathy and cardiac failure. A major breakthrough has been the discovery, in 1996, of the HFE gene which is strongly associated with the phenotypic expression of the disease. This discovery has, very quickly, provided a powerful genetic blood test which permits, in most cases, to establish the diagnosis in a non invasive way (i.e. without a liver biopsy). Hemochromatosis can be cured by repeated venesections provided the diagnosis has been detected sufficiently early. Moreover, an efficient preventive strategy can be applied to family members and should now be proposed to the general population. Finally, the identification of the HFE gene has paved the way for the identification of new iron overload entities.
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Affiliation(s)
- P Brissot
- Service des maladies du foie et unité Inserm U-522, hôpital universitaire Pontchaillou, 35033 Rennes, France.
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1125
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Montosi G, Donovan A, Totaro A, Garuti C, Pignatti E, Cassanelli S, Trenor CC, Gasparini P, Andrews NC, Pietrangelo A. Autosomal-dominant hemochromatosis is associated with a mutation in the ferroportin (SLC11A3) gene. J Clin Invest 2001; 108:619-23. [PMID: 11518736 PMCID: PMC209405 DOI: 10.1172/jci13468] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Hemochromatosis is a progressive iron overload disorder that is prevalent among individuals of European descent. It is usually inherited in an autosomal-recessive pattern and associated with missense mutations in HFE, an atypical major histocompatibility class I gene. Recently, we described a large family with autosomal-dominant hemochromatosis not linked to HFE and distinguished by early iron accumulation in reticuloendothelial cells. Through analysis of a large pedigree, we have determined that this disease maps to 2q32. The gene encoding ferroportin (SLC11A3), a transmembrane iron export protein, lies within a candidate interval defined by highly significant lod scores. We show that the iron-loading phenotype in autosomal-dominant hemochromatosis is associated with a nonconservative missense mutation in the ferroportin gene. This missense mutation, converting alanine to aspartic acid at residue 77 (A77D), was not seen in samples from 100 unaffected control individuals. We propose that partial loss of ferroportin function leads to an imbalance in iron distribution and a consequent increase in tissue iron accumulation.
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Affiliation(s)
- G Montosi
- Department of Internal Medicine, University of Modena, Modena, Italy
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1126
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Fleming RE, Sly WS. Ferroportin mutation in autosomal dominant hemochromatosis: loss of function, gain in understanding. J Clin Invest 2001; 108:521-2. [PMID: 11518724 PMCID: PMC209411 DOI: 10.1172/jci13739] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Affiliation(s)
- R E Fleming
- Department of Pediatrics, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA.
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1127
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Abstract
Mammalian cells and organisms coordinate to regulate expression of numerous proteins involved in the uptake, sequestration, and export of iron. When cells in the systemic circulation are depleted of iron, they increase synthesis of the transferrin receptor and decrease synthesis of the iron sequestration protein, ferritin. In iron-depleted animals, expression of duodenal iron transporters markedly increases and intestinal iron uptake increases accordingly. The major proteins of iron metabolism in the systemic circulation are also expressed in the central nervous system. However, the mechanisms by which iron is transported and distributed throughout the central nervous system are not well understood. Iron accumulation in specific regions of the brain is observed in several neurodegenerative diseases. It is likely that misregulation of iron metabolism is important in the pathophysiology of several human neurodegenerative diseases.
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Affiliation(s)
- T A Rouault
- Section on Human Iron Metabolism, Cell Biology and Metabolism Branch, National Institute of Child Health and Human Disease, Bethesda, Maryland 20892, USA
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1128
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Bennett CM, Kanki JP, Rhodes J, Liu TX, Paw BH, Kieran MW, Langenau DM, Delahaye-Brown A, Zon LI, Fleming MD, Look AT. Myelopoiesis in the zebrafish, Danio rerio. Blood 2001; 98:643-51. [PMID: 11468162 DOI: 10.1182/blood.v98.3.643] [Citation(s) in RCA: 342] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Genome-wide chemical mutagenesis screens in the zebrafish (Danio rerio) have led to the identification of novel genes affecting vertebrate erythropoiesis. In determining if this approach could also be used to clarify the molecular genetics of myelopoiesis, it was found that the developmental hierarchy of myeloid precursors in the zebrafish kidney is similar to that in human bone marrow. Zebrafish neutrophils resembled human neutrophils, possessing segmented nuclei and myeloperoxidase-positive cytoplasmic granules. The zebrafish homologue of the human myeloperoxidase (MPO) gene, which is specific to cells of the neutrophil lineage, was cloned and used to synthesize antisense RNA probes for in situ hybridization analyses of zebrafish embryos. Granulocytic cells expressing zebrafish mpo were first evident at 18 hours after fertilization (hpf) in the posterior intermediate cell mass (ICM) and on the anterior yolk sac by 20 hpf. By 24 hpf, mpo-expressing cells were observed along the ICM and within the developing vascular system. Thus, the mpo gene should provide a useful molecular probe for identifying zebrafish mutants with defects in granulopoiesis. The expression of zebrafish homologues was also examined in 2 other mammalian hematopoietic genes, Pu.1, which appears to initiate a commitment step in normal mammalian myeloid development, and L-Plastin, a gene expressed by human monocytes and macrophages. The results demonstrate a high level of conservation of the spatio-temporal expression patterns of these genes between zebrafish and mammals. The morphologic and molecular genetic evidence presented here supports the zebrafish as an informative model system for the study of normal and aberrant human myelopoiesis. (Blood. 2001;98:643-651)
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Affiliation(s)
- C M Bennett
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, 44 Binney Street, Boston, MA 02115, USA
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1129
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Nicolas G, Bennoun M, Devaux I, Beaumont C, Grandchamp B, Kahn A, Vaulont S. Lack of hepcidin gene expression and severe tissue iron overload in upstream stimulatory factor 2 (USF2) knockout mice. Proc Natl Acad Sci U S A 2001; 98:8780-5. [PMID: 11447267 PMCID: PMC37512 DOI: 10.1073/pnas.151179498] [Citation(s) in RCA: 888] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2001] [Indexed: 12/12/2022] Open
Abstract
We previously reported the disruption of the murine gene encoding the transcription factor USF2 and its consequences on glucose-dependent gene regulation in the liver. We report here a peculiar phenotype of Usf2(-/-) mice that progressively develop multivisceral iron overload; plasma iron overcomes transferrin binding capacity, and nontransferrin-bound iron accumulates in various tissues including pancreas and heart. In contrast, the splenic iron content is strikingly lower in knockout animals than in controls. To identify genes that may account for the abnormalities of iron homeostasis in Usf2(-/-) mice, we used suppressive subtractive hybridization between livers from Usf2(-/-) and wild-type mice. We isolated a cDNA encoding a peptide, hepcidin (also referred to as LEAP-1, for liver-expressed antimicrobial peptide), that was very recently purified from human blood ultrafiltrate and from urine as a disulfide-bonded peptide exhibiting antimicrobial activity. Accumulation of iron in the liver has been recently reported to up-regulate hepcidin expression, whereas our data clearly show that a complete defect in hepcidin expression is responsible for progressive tissue iron overload. The striking similarity of the alterations in iron metabolism between HFE knockout mice, a murine model of hereditary hemochromatosis, and the Usf2(-/-) hepcidin-deficient mice suggests that hepcidin may function in the same regulatory pathway as HFE. We propose that hepcidin acts as a signaling molecule that is required in conjunction with HFE to regulate both intestinal iron absorption and iron storage in macrophages.
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Affiliation(s)
- G Nicolas
- Institut National de la Santé et de la Recherche Médicale 129, Departement Genetique Developpement et Pathologie Moléculaire, Institut Cochin de Genetique Moléculaire, Faculté de Médecine Cochin-Port Royal, 75014 Paris, France
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1130
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Fleming RE, Sly WS. Hepcidin: a putative iron-regulatory hormone relevant to hereditary hemochromatosis and the anemia of chronic disease. Proc Natl Acad Sci U S A 2001; 98:8160-2. [PMID: 11459944 PMCID: PMC37412 DOI: 10.1073/pnas.161296298] [Citation(s) in RCA: 182] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Affiliation(s)
- R E Fleming
- Department of Pediatrics, Saint Louis University School of Medicine, St. Louis, MO 63014, USA
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1131
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Affiliation(s)
- S E Brockerhoff
- Department of Biochemistry, Box 357350, University of Washington, Seattle, WA 98195, USA.
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1132
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Njajou OT, Vaessen N, Joosse M, Berghuis B, van Dongen JW, Breuning MH, Snijders PJ, Rutten WP, Sandkuijl LA, Oostra BA, van Duijn CM, Heutink P. A mutation in SLC11A3 is associated with autosomal dominant hemochromatosis. Nat Genet 2001; 28:213-4. [PMID: 11431687 DOI: 10.1038/90038] [Citation(s) in RCA: 307] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Hereditary hemochromatosis (HH) is a very common disorder characterized by iron overload and multi-organ damage. Several genes involved in iron metabolism have been implicated in the pathology of HH (refs. 1-4). We report that a mutation in the gene encoding Solute Carrier family 11, member A3 (SLC11A3), also known as ferroportin, is associated with autosomal dominant hemochromatosis.
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Affiliation(s)
- O T Njajou
- Genetic-Epidemiology Unit: Department of Epidemiology & Biostatistics and Department of Clinical Genetics, Erasmus University Rotterdam, The Netherlands
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1133
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Abstract
Iron has the capacity to accept and donate electrons readily. This capability makes it physiologically essential, as a useful component of cytochromes and oxygen-binding molecules. However, iron is also biochemically dangerous; it can damage tissues by catalyzing the conversion of hydrogen peroxide to free-radical ions that attack cellular membranes, protein and DNA. This threat is reduced in the healthy state where, because of the fine iron metabolism regulation, there is never appreciable concentration of 'free iron'. Under pathological conditions, iron metabolism and superoxide metabolism are clearly interactive. Each can exacerbate the toxicity of the other. Iron overload may amplify the damaging effects of superoxide overproduction in a very broad spectrum of inflammatory, both acute and chronic, conditions. Furthermore, chronic oxidative stress may modulate iron uptake and storage, leading to a self-sustained and ever-increasing spiral of cytotoxic and mutagenic events. The iron chelator deferroxamine is able to chelate 'free iron' even inside the cell. Its regular clinical use is to promote the excretion of an iron overload, when phlebotomy is harmful, and the dosage varies between 2-10 g/d. In conditions where deferroxamine is used to prevent the iron-driven oxygen toxicity, i.e., acute or chronic inflammatory diseases with oxidative stress, the dosage can be extremely reduced and the addition of antioxidants could be useful.
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Affiliation(s)
- J Emerit
- Service de Biochimie, Hĵpital Saint-Joseph, Paris, France.
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1134
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Qian ZM, Ke Y. Rethinking the role of ceruloplasmin in brain iron metabolism. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 2001; 35:287-94. [PMID: 11423158 DOI: 10.1016/s0165-0173(01)00056-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
For more than three decades, it has been widely accepted that ceruloplasmin plays an important role in iron efflux from mammalian cells, including brain cells, via the activity of ferroxidase. However, in light of recent findings, this view might not be completely accurate and the role of ceruloplasmin in brain iron metabolism may need to be re-evaluated. Based on recent studies, we propose in this article that the role of ceruloplasmin in iron uptake by brain neuronal cells might be more important than its role in iron release from the cells. A possible explanation of why the absence of ceruloplasmin induces excessive iron accumulation in neurons in aceruloplasminemia (ceruloplasmin gene mutations) was also discussed.
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Affiliation(s)
- Z M Qian
- Laboratory of Brain Iron Metabolism, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Kowloon, Hong Kong.
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1135
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Biggs TE, Baker ST, Botham MS, Dhital A, Barton CH, Perry VH. Nramp1 modulates iron homoeostasis in vivo and in vitro: evidence for a role in cellular iron release involving de-acidification of intracellular vesicles. Eur J Immunol 2001; 31:2060-70. [PMID: 11449359 DOI: 10.1002/1521-4141(200107)31:7<2060::aid-immu2060>3.0.co;2-l] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Nramp1 controls responses to infection and encodes a biallelic (G169D) macrophage-restricted divalent-cation transporter. Nramp1(D169) is phenotypically null. We demonstrate Nramp1 is implicated in iron regulation in vivo. In spleen, expression is exclusive to Nramp1(G169) strains within the red pulp. By morphometric analysis, the distribution of splenic iron, following systemic overload, correlates with Nramp1 genotype. More iron is located within the red pulp in Nramp1(D169) strains, whereas in Nramp1(G169) strains iron deposits are localized within the marginal-zone metallophilic cells. Nramp1 immunoreactive protein is not present in control brain, but inducible within a hemorrhagic lesion model in Nramp1(G169) strains. Nramp1 protein expression demonstrates an inverse correlation to the presence of iron. Nramp1(G169) strains show no Perl's stain-reactive iron within the lesion. In contrast, Nramp1(D169) strains display iron-staining cells. The process of cellular iron regulation was investigated in vitro in Nramp1(G169) transfectant Raw264.7 macrophages. Greater (30-50%) iron efflux from Nramp1(G169) compared with Nramp1(D169) cells was determined. The extent of Nramp1-dependent iron-release was influenced by bafilomycin A1, and endogenous nitric oxide synthesis, both inhibitors of vacuolar-ATPase. This study demonstrates that Nramp1 regulates macrophage iron handling, and probably facilitates iron release from macrophages undergoing erythrophagocytosis in vivo.
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Affiliation(s)
- T E Biggs
- Biochemistry and Molecular Biology, School of Biological Sciences, Southampton, GB, UK
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1136
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Abstract
The zebrafish (Danio rerio) animal model offers a unique opportunity to discover novel genes required for the control of normal vertebrate myeloid cell development. It is well suited for both developmental and genetic analyses: eg, genome-wide chemical mutagenesis screens have led to the identification of specific new genes affecting vertebrate erythropoiesis. Mutants defective in one or more hematopoietic functions will be useful as models of human disease and will assist in the elucidation of lineage-specific developmental programs. By using a combination of forward genetic mutagenesis screens and emerging strategies based on transgenic and antisense knockdown approaches, it should be possible to dissect the genetic programs that lead to myeloproliferative/myelodysplastic syndromes and to acute myeloid leukemia.
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Affiliation(s)
- K Hsu
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, 44 Binney Street, Boston, MA 02115, USA
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1137
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Gambling L, Danzeisen R, Gair S, Lea RG, Charania Z, Solanky N, Joory KD, Srai SK, McArdle HJ. Effect of iron deficiency on placental transfer of iron and expression of iron transport proteins in vivo and in vitro. Biochem J 2001; 356:883-9. [PMID: 11389698 PMCID: PMC1221917 DOI: 10.1042/0264-6021:3560883] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Maternal iron deficiency during pregnancy induces anaemia in the developing fetus; however, the severity tends to be less than in the mother. The mechanism underlying this resistance has not been determined. We have measured placental expression of proteins involved in iron transfer in pregnant rats given diets with decreasing levels of iron and examined the effect of iron deficiency on iron transfer across BeWo cell layers, a model for placental iron transfer. Transferrin receptor expression was increased at both mRNA and protein levels. Similarly, expression of the iron-responsive element (IRE)-regulated form of the divalent metal transporter 1 (DMT1) was also increased. In contrast, the non-IRE regulated isoform showed no change in mRNA levels. Protein levels of DMT1 increased significantly. Iron efflux is thought to be mediated by the metal transporter protein, IREG1/ferroportin1/MTP1, and oxidation of Fe(II) to Fe(III) prior to incorporation into fetal transferrin is carried out by the placental copper oxidase. Expression of IREG1 was not altered by iron deficiency, whereas copper oxidase activity was increased. In BeWo cells made iron deficient by treatment with desferrioxamine ('deferioxamine'), iron accumulation from iron-transferrin increased, in parallel with increased expression of the transferrin receptor. At the same time, iron efflux also increased, showing a higher flux of iron from the apical to the basolateral side. The data show that expression of placental proteins of iron transport are up-regulated in maternal iron deficiency, resulting in an increased efficiency of iron flux and a consequent minimization of the severity of fetal anaemia.
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Affiliation(s)
- L Gambling
- The Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, Scotland, UK
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1138
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Caltagirone A, Weiss G, Pantopoulos K. Modulation of cellular iron metabolism by hydrogen peroxide. Effects of H2O2 on the expression and function of iron-responsive element-containing mRNAs in B6 fibroblasts. J Biol Chem 2001; 276:19738-45. [PMID: 11264285 DOI: 10.1074/jbc.m100245200] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Cellular iron uptake and storage are coordinately controlled by binding of iron-regulatory proteins (IRP), IRP1 and IRP2, to iron-responsive elements (IREs) within the mRNAs encoding transferrin receptor (TfR) and ferritin. Under conditions of iron starvation, both IRP1 and IRP2 bind with high affinity to cognate IREs, thus stabilizing TfR and inhibiting translation of ferritin mRNAs. The IRE/IRP regulatory system receives additional input by oxidative stress in the form of H(2)O(2) that leads to rapid activation of IRP1. Here we show that treating murine B6 fibroblasts with a pulse of 100 microm H(2)O(2) for 1 h is sufficient to alter critical parameters of iron homeostasis in a time-dependent manner. First, this stimulus inhibits ferritin synthesis for at least 8 h, leading to a significant (50%) reduction of cellular ferritin content. Second, treatment with H(2)O(2) induces a approximately 4-fold increase in TfR mRNA levels within 2-6 h, and subsequent accumulation of newly synthesized protein after 4 h. This is associated with a profound increase in the cell surface expression of TfR, enhanced binding to fluorescein-tagged transferrin, and stimulation of transferrin-mediated iron uptake into cells. Under these conditions, no significant alterations are observed in the levels of mitochondrial aconitase and the Divalent Metal Transporter DMT1, although both are encoded by two as yet lesser characterized IRE-containing mRNAs. Finally, H(2)O(2)-treated cells display an increased capacity to sequester (59)Fe in ferritin, despite a reduction in the ferritin pool, which results in a rearrangement of (59)Fe intracellular distribution. Our data suggest that H(2)O(2) regulates cellular iron acquisition and intracellular iron distribution by both IRP1-dependent and -independent mechanisms.
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Affiliation(s)
- A Caltagirone
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, 3755 Cote-Ste-Catherine Road, Montreal, Quebec H3T 1E2, Canada
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1139
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Abstract
Thymic organogenesis and T-cell lymphopoiesis are crucial interdependent processes that establish a functional vertebrate immune system. The current understanding of vertebrate thymic development during embryogenesis remains incomplete and would benefit from novel approaches. The zebrafish Danio rerio is a powerful developmental and genetic system for the dissection of early events in the ontogeny of the immune system. Forward genetic screens have uncovered genes involved in hematopoiesis, and specific screens are being designed to examine the genes that regulate T-cell development and the origin of the thymus. Studies of the zebrafish should improve our understanding of lymphoid development in vertebrates.
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Affiliation(s)
- N S Trede
- Division of Hematology, Children's Hospital and Howard Hughes Medical Institute, 320 Longwood Avenue, Boston, MA 02115, USA.
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1140
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Barisani D, Parafioriti A, Armiraglio E, Meneveri R, Conte D. Duodenal expression of a putative stimulator of Fe transport and transferrin receptor in anemia and hemochromatosis. Gastroenterology 2001; 120:1404-11. [PMID: 11313310 DOI: 10.1053/gast.2001.23946] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Stimulator of Fe Transport (SFT) and transferrin receptor (TfR) are proteins involved in iron transport. This study evaluated iron metabolism protein expression in duodenal biopsy specimens from controls and patients with abnormal iron metabolism. METHODS Twelve controls, 8 patients with iron deficiency anemia, 7 with HFE-related hemochromatosis, and 6 with non-HFE-related iron overload were studied. Immunohistochemistry was performed on duodenal biopsy specimens with anti-TfR and anti-SFT antibodies which recognize a putative stimulator of Fe transport of ~80 kilodaltons. RESULTS In controls, the putative stimulator of Fe transport was expressed in the middle and distal part of the villi in the subapical cytoplasmatic region. Its expression increased in anemics and, to a lesser degree, in HFE-related hemochromatotics, whereas it was reduced in patients with non-HFE-related iron overload. TfR expression showed a crypt-to-tip gradient in controls, but not in anemics, in whom it was uniformly overexpressed. TfR expression was intermediate in HFE-related hemochromatotics and similar to controls in non-HFE-related iron overload. CONCLUSIONS Expression of the putative stimulator of Fe transport and TfR increases in iron deficiency. Increased expression of both proteins is present only in HFE-related hemochromatotics suggesting that other factors may be involved in determining non-HFE-related iron overload phenotype.
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Affiliation(s)
- D Barisani
- Cattedra di Gastroenterologia, Dipartimento di Scienze Mediche, IRCCS-Ospedale Maggiore, Milan, Italy
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1141
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Zoller H, Koch RO, Theurl I, Obrist P, Pietrangelo A, Montosi G, Haile DJ, Vogel W, Weiss G. Expression of the duodenal iron transporters divalent-metal transporter 1 and ferroportin 1 in iron deficiency and iron overload. Gastroenterology 2001; 120:1412-9. [PMID: 11313311 DOI: 10.1053/gast.2001.24033] [Citation(s) in RCA: 211] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND & AIMS Imbalances of iron homeostasis are accompanied by alterations of intestinal iron absorption. The identification of divalent-metal transporter 1 (DMT1) and ferroportin 1 (FP1) has improved our understanding of transmembrane iron trafficking. To gain insight into the regulatory properties of these transporters in the duodenum, we studied their expression in patients with hereditary hemochromatosis (HFE-associated and non-HFE-associated), secondary iron overload, and iron deficiency. METHODS DMT1, FP1 messenger RNA (mRNA), and protein expression were analyzed in duodenal biopsy specimens from patients by means of TaqMan real-time polymerase chain reaction, Western blotting technique, and immunohistochemistry. RESULTS DMT1 and FP1 mRNA levels are positively correlated with each other in all patient groups (P < 0.001). Moreover, DMT1 and FP1 mRNA levels were significantly increased in patients with iron deficiency, HFE and non-HFE hemochromatosis, whereas they were unchanged in patients with secondary iron overload. Alterations in DMT1 and FP1 mRNA levels were paralleled by comparable changes in the duodenal expression of these proteins. In patients with normal iron status or iron deficiency, significant negative correlations between DMT1, FP1 mRNA, and serum iron parameters were found, which were absent in subjects with primary hemochromatosis. CONCLUSIONS DMT1 and FP1 are centrally involved in iron uptake/transfer in the duodenum and in the adaptive changes of iron homeostasis to iron deficiency and overload.
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Affiliation(s)
- H Zoller
- Department of Internal Medicine, Innsbruck, Austria
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1142
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Abstract
The discovery of novel metabolic pathways and the genetic basis for diseases of the liver continues to yield new insights into the pathogenesis of inherited metabolic diseases of the liver, whereas the application of new technologies to their treatment continues to advance therapeutic options. This review of selected articles covers a wide range of subjects, from the identification of novel proteins and transport pathways to disease diagnosis and treatment of acute liver failure. Four selected topics, Wilson disease, hemochromatosis and iron overload disorders, alpha-1 antitrypsin disease, and exciting new therapeutic options for lysosomal storage diseases are the focus of this review.
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Affiliation(s)
- M L Schilsky
- Department of Medicine and Genetics, The Mount Sinai Medical Center, New York, New York 10029, USA.
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1143
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Ferguson CJ, Wareing M, Ward DT, Green R, Smith CP, Riccardi D. Cellular localization of divalent metal transporter DMT-1 in rat kidney. Am J Physiol Renal Physiol 2001; 280:F803-14. [PMID: 11292622 DOI: 10.1152/ajprenal.2001.280.5.f803] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
We have demonstrated that the kidney plays an important role in iron balance and that metabolically significant reabsorption of this ion occurs in the loop of Henle and the collecting ducts [Wareing M, Ferguson CJ, Green R, Riccardi D, and Smith CP. J Physiol (Lond) 524: 581-586, 2000]. To test the possibility that the divalent metal transporter DMT1 (Gunshin H, Mackenzie B, Berger UV, Gunshin Y, Romero MF, Boron WF, Nussberger S, Gollan JL, and Hediger MA. Nature 388: 482-488, 1997) could represent the apical route for iron entry in the kidney, we raised and affinity-purified an anti-DMT-1 polyclonal antibody and determined DMT-1 distribution in rat kidney by Western analysis, immunofluorescence, and confocal microscopy. The strongest DMT1-specific (i.e., peptide-protectable) immunoreactivity was found in the collecting ducts, in both principal and intercalated cells. Thick ascending limbs of Henle's loop and, more intensely, distal convoluted tubules exhibited apical immunostaining. Considerable intracellular DMT-1 immunoreactivity was seen throughout the nephron, particularly in S3 segments. The described distribution of DMT-1 protein is in agreement with our previous identification of nephron sites of iron reabsorption, suggesting that DMT-1 provides the molecular mechanism for apical iron entry in the distal nephron but not in the proximal tubule. Basolateral iron exit may be facilitated by a different system.
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Affiliation(s)
- C J Ferguson
- School of Biological Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
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Griffiths WJ, Sly WS, Cox TM. Intestinal iron uptake determined by divalent metal transporter is enhanced in HFE-deficient mice with hemochromatosis. Gastroenterology 2001; 120:1420-9. [PMID: 11313312 DOI: 10.1053/gast.2001.24050] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
BACKGROUND & AIMS Overexpression of duodenal divalent metal transporter (DMT1) messenger RNA occurs in hemochromatosis and HFE-knockout mice, suggesting that DMT1 mediates enhanced absorption of iron; however, increased expression of functional DMT1 protein has yet to be substantiated. We examined the role of DMT1 and the mucosal iron uptake defect in HFE-knockout mice. METHODS Unidirectional iron uptake of 59Fe by small intestinal mucosa in vitro was compared between matched pairs of HFE-knockout and wild-type mice. DMT1-specific antibodies were used to block iron transport and to quantify duodenal protein expression. RESULTS Ferrous iron uptake at 3.5-450 micromol/L was greatly enhanced in HFE-knockouts compared with wild-type, the apparent V(max) for Fe2+ transport being doubled (P < 0.01). Supplied as Fe3+, uptake was only enhanced in HFE-knockouts at < or =18 micromol/L, when the iron was almost completely converted to Fe2+ by mucosal ferrireductases. DMT1 antibody reduced the apparent Vmax for mucosal Fe2+ transport in HFE-knockouts to below wild-type control values (P < 0.02); immunoreactive mucosal DMT1 protein was increased nearly 2-fold in HFE-knockouts (P < 0.01). CONCLUSIONS Disruption of the HFE gene up-regulates functional DMT1 transporters and enhances uptake of ferrous iron by this mechanism; DMT1 also mediates increased uptake after reduction of ferric iron presented at physiological concentrations.
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Affiliation(s)
- W J Griffiths
- University of Cambridge Department of Medicine, Addenbrooke's Hospital, Cambridge, England
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1145
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Abstract
Recent biophysical studies on the interactions between lead and recombinant proteins and peptides that naturally bind zinc or calcium have provided unparalleled insights into the biological chemistry and molecular toxicology of lead. These studies lay the foundation for the rational design of improved methods for detecting and treating lead poisoning.
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Affiliation(s)
- H A Godwin
- Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA.
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1146
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Kwok JC, Richardson DR. The cardioprotective effect of the iron chelator dexrazoxane (ICRF-187) on anthracycline-mediated cardiotoxicity. Redox Rep 2001; 5:317-24. [PMID: 11140743 DOI: 10.1179/135100000101535898] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The cardiotoxic effect of anthracyclines limits their use in the treatment of a variety of cancers. The reason for the high susceptibility of cardiac muscle to anthracyclines remains unclear, but it appears to be due, at least in part, to the interaction of these drugs with intracellular iron (Fe). The suggestion that Fe plays an important role in anthracycline cardiotoxicity has been strengthened by observation that the chelator, dexrazoxane (ICRF-187), has a potent cardioprotective effect. In the present review, the role of Fe in the cardiotoxicity of anthracyclines is discussed together with the possible role of Fe chelation therapy as a cardioprotective strategy that may also result in enhanced antitumour activity.
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Affiliation(s)
- J C Kwok
- The Iron Metabolism and Chelation Group, The Heart Research Institute, Sydney, New South Wales, Australia
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1147
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Rötig A, Chantrel-Groussard K, Munnich A, Rustin P. Expression study of genes involved in iron metabolism in human tissues. Biochem Biophys Res Commun 2001; 281:804-9. [PMID: 11237730 DOI: 10.1006/bbrc.2001.4426] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Iron is required in all organisms for crucial functions, as a number of proteins need iron for activity. Mutations of the genes encoding proteins involved in iron uptake, transport, and utilization result in various human disorders or animal models with very different clinical presentations and organ involvement. However, little is known concerning the expression of iron metabolism genes in various human tissues and their eventual concerted regulation. We therefore examined the expression levels of various genes involved in iron uptake, reduction, and storage, in Fe-S protein biogenesis, in mitochondrial electron transport chain, plus the two SOD genes, in human adult tissues by Northern blot analysis. We observed that most of these genes were ubiquitously expressed, but that their transcript showed strongly different levels in the various tissues investigated denoting different mechanisms for iron utilization in various organs. However, surprisingly, no correlation could be made between expression pattern of these genes and the clinical presentation resulting in their mutations.
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Affiliation(s)
- A Rötig
- INSERM U393, Hôpital Necker-Enfants Malades, 149 rue de Sèvres, Paris, 75015, France.
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1148
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Abstract
Some interesting advances in mechanisms and regulation of nutrient absorption were reported last year. Further evidence was obtained that the rate-limiting step in triacylglycerol absorption, especially with large doses of lipid, is transport of prechylomicrons from the endoplasmic reticulum to the Golgi apparatus. Targeted disruption of the adenosine triphosphate-binding cassette transporter in mice produced changes similar to human Tangier disease and suggested that this mouse may be a model for studying intestinal high-density lipoprotein assembly and secretion. A new mechanism for carbohydrate malabsorption was discovered: in sucrase-isomaltase deficiency, the enzyme fails to anchor in the brush border membrane and so is secreted into the lumen, where it is ineffective. Glycosylating insulin at B1 phenylalanine permitted it to bind to the brush border membrane and greatly enhanced its hypoglycemic activity when given orally. CaCo-2 cells and normal human enterocytes were shown to have two variants of the human sodium-dependent vitamin C transporter, hSVCT1; one is active and the other is an inactive splice variant. In rats, the divalent metal ion transporter, DMT1, appeared to be important for regulation of both absorption of iron and its movement into the liver.
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Affiliation(s)
- Shadab A. Siddiqi
- Department of Medicine, Division of Gastroenterology and Department of Physiology, The University of Tennessee Health Science Center, Memphis, Tennessee, USA
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Enns CA. Pumping iron: the strange partnership of the hemochromatosis protein, a class I MHC homolog, with the transferrin receptor. Traffic 2001; 2:167-74. [PMID: 11260522 DOI: 10.1034/j.1600-0854.2001.020303.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
People suffering from hereditary hemochromatosis (HH) can not regulate the uptake of iron properly and gradually accumulate iron in their body over their lifetime. The protein involved in HH, HFE, has been recently identified as a class I major histocompatibility complex (MHC) homolog. The wild-type HFE associates and co-traffics with the transferrin receptor (TfR). The mutation responsible for 83% of HH (C260Y) results in the failure of HFE to form a critical disulfide bond, bind beta2 microglobulin, bind TfR, and traffic to the cell surface. In non-polarized cells, the partnership of HFE and TfR results in decreased iron uptake into cells. The mechanism whereby a class I MHC homolog modifies the function of a membrane receptor and how this dynamic complex of molecules regulates iron transport across intestinal epithelial cells is the subject of this review.
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Affiliation(s)
- C A Enns
- Department of Cell and Developmental Biology, L-215, Oregon Health Sciences University, Portland, OR 97201, USA.
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1150
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Abstract
Despite years of investigation, it is still not known why iron levels are abnormally high in some regions of the brain in neurodegenerative disorders. Also, it is not clear whether iron accumulation in the brain is an initial event that causes neuronal death or is a consequence of the disease process. Here, we propose that iron and iron-induced oxidative stress constitute a common mechanism that is involved in the development of neurodegeneration. Also, we suggest that, at least in some neurodegenerative disorders, brain iron misregulation is an initial cause of neuronal death and that this misregulation might be the result of either genetic or non-genetic factors.
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Affiliation(s)
- Z M Qian
- Laboratory of Brain Iron Metabolism, Dept of Applied Biology & Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, Kowloon, People's Republic of China.
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