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Anderson GJ, Bardou-Jacquet E. Revisiting hemochromatosis: genetic vs. phenotypic manifestations. ANNALS OF TRANSLATIONAL MEDICINE 2021; 9:731. [PMID: 33987429 PMCID: PMC8106074 DOI: 10.21037/atm-20-5512] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Iron overload disorders represent an important class of human diseases. Of the primary iron overload conditions, by far the most common and best studied is HFE-related hemochromatosis, which results from homozygosity for a mutation leading to the C282Y substitution in the HFE protein. This disease is characterized by reduced expression of the iron-regulatory hormone hepcidin, leading to increased dietary iron absorption and iron deposition in multiple tissues including the liver, pancreas, joints, heart and pituitary. The phenotype of HFE-related hemochromatosis is quite variable, with some individuals showing little or no evidence of increased body iron, yet others showing severe iron loading, tissue damage and clinical sequelae. The majority of genetically predisposed individuals show at least some evidence of iron loading (increased transferrin saturation and serum ferritin), but a minority show clinical symptoms and severe consequences are rare. Thus, the disorder has a high biochemical penetrance, but a low clinical prevalence. Nevertheless, it is such a common condition in Caucasian populations (1:100–200) that it remains an important clinical entity. The phenotypic variability can largely be explained by a range of environmental, genetic and physiological factors. Men are far more likely to manifest significant disease than women, with the latter losing iron through menstrual blood loss and childbirth. Other forms of blood loss, immune system influences, the amount of bioavailable iron in the diet and lifestyle factors such as high alcohol intake can also contribute to iron loading and disease expression. Polymorphisms in a range of genes have been linked to variations in body iron levels, both in the general population and in hemochromatosis. Some of the genes identified play well known roles in iron homeostasis, yet others are novel. Other factors, including both co-morbidities and genetic polymorphisms, do not affect iron levels per se, but determine the propensity for tissue pathology.
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Affiliation(s)
- Gregory J Anderson
- Iron Metabolism Laboratory, QIMR Berghofer Medical Research Institute and School of Chemistry and Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
| | - Edouard Bardou-Jacquet
- Liver Disease Department, University of Rennes and French Reference Center for Hemochromatosis and Iron Metabolism Disease, Rennes, France
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2
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HFE Related Hemochromatosis: Uncovering the Inextricable Link between Iron Homeostasis and the Immunological System. Pharmaceuticals (Basel) 2019; 12:ph12030122. [PMID: 31443397 PMCID: PMC6789554 DOI: 10.3390/ph12030122] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 08/14/2019] [Accepted: 08/15/2019] [Indexed: 02/07/2023] Open
Abstract
The HFE gene (OMIM 235200), most commonly associated with the genetic iron overload disorder Hemochromatosis, was identified by Feder et al. in 1996, as a major histocompatibilty complex (MHC) class I like gene, first designated human leukocyte antigen-H (HLA-H). This discovery was thus accomplished 20 years after the realization of the first link between the then "idiopathic" hemochromatosis and the human leukocyte antigens (HLA). The availability of a good genetic marker in subjects homozygous for the C282Y variant in HFE (hereditary Fe), the reliability in serum markers such as transferrin saturation and serum ferritin, plus the establishment of noninvasive methods for the estimation of hepatic iron overload, all transformed hemochromatosis into a unique age related disease where prevention became the major goal. We were challenged by the finding of iron overload in a 9-year-old boy homozygous for the C282Y HFE variant, with two brothers aged 11 and 5 also homozygous for the mutation. We report a 20 year follow-up during which the three boys were seen yearly with serial determinations of iron parameters and lymphocyte counts. This paper is divided in three sections: Learning, applying, and questioning. The result is the illustration of hemochromatosis as an age related disease in the transition from childhood to adult life and the confirmation of the inextricable link between iron overload and the cells of the immune system.
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Sottile R, Federico G, Garofalo C, Tallerico R, Faniello MC, Quaresima B, Cristiani CM, Di Sanzo M, Cuda G, Ventura V, Wagner AK, Contrò G, Perrotti N, Gulletta E, Ferrone S, Kärre K, Costanzo FS, Carlomagno F, Carbone E. Iron and Ferritin Modulate MHC Class I Expression and NK Cell Recognition. Front Immunol 2019; 10:224. [PMID: 30873154 PMCID: PMC6404638 DOI: 10.3389/fimmu.2019.00224] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 01/25/2019] [Indexed: 12/30/2022] Open
Abstract
The ability of pathogens to sequester iron from their host cells and proteins affects their virulence. Moreover, iron is required for various innate host defense mechanisms as well as for acquired immune responses. Therefore, intracellular iron concentration may influence the interplay between pathogens and immune system. Here, we investigated whether changes in iron concentrations and intracellular ferritin heavy chain (FTH) abundance may modulate the expression of Major Histocompatibility Complex molecules (MHC), and susceptibility to Natural Killer (NK) cell cytotoxicity. FTH downregulation, either by shRNA transfection or iron chelation, led to MHC surface reduction in primary cancer cells and macrophages. On the contrary, mouse embryonic fibroblasts (MEFs) from NCOA4 null mice accumulated FTH for ferritinophagy impairment and displayed MHC class I cell surface overexpression. Low iron concentration, but not FTH, interfered with IFN-γ receptor signaling, preventing the increase of MHC-class I molecules on the membrane by obstructing STAT1 phosphorylation and nuclear translocation. Finally, iron depletion and FTH downregulation increased the target susceptibility of both primary cancer cells and macrophages to NK cell recognition. In conclusion, the reduction of iron and FTH may influence the expression of MHC class I molecules leading to NK cells activation.
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Affiliation(s)
- Rosa Sottile
- Tumor Immunology and Immunopathology Laboratory, Department of Experimental and Clinical Medicine, University Magna Graecia of Catanzaro, Catanzaro, Italy.,Department of Microbiology, Cell and Tumor Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Giorgia Federico
- Department of Molecular Medicine and Medical Biotechnologies Federico II University, Naples, Italy
| | - Cinzia Garofalo
- Tumor Immunology and Immunopathology Laboratory, Department of Experimental and Clinical Medicine, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Rossana Tallerico
- Tumor Immunology and Immunopathology Laboratory, Department of Experimental and Clinical Medicine, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Maria Concetta Faniello
- Research Center of Advanced Biochemistry and Molecular Biology, Department of Experimental and Clinical Medicine, Magna Græcia University of Catanzaro, Catanzaro, Italy
| | - Barbara Quaresima
- Research Center of Advanced Biochemistry and Molecular Biology, Department of Experimental and Clinical Medicine, Magna Græcia University of Catanzaro, Catanzaro, Italy
| | - Costanza Maria Cristiani
- Tumor Immunology and Immunopathology Laboratory, Department of Experimental and Clinical Medicine, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Maddalena Di Sanzo
- Research Center of Advanced Biochemistry and Molecular Biology, Department of Experimental and Clinical Medicine, Magna Græcia University of Catanzaro, Catanzaro, Italy
| | - Gianni Cuda
- Laboratory of Proteomics, Research Center of Advanced Biochemistry and Molecular Biology, Department of Experimental and Clinical Medicine, Magna Græcia University of Catanzaro, Catanzaro, Italy
| | - Valeria Ventura
- Tumor Immunology and Immunopathology Laboratory, Department of Experimental and Clinical Medicine, University Magna Graecia of Catanzaro, Catanzaro, Italy.,Division of Clinical Pathology, Department of Health Sciences, Magna Graecia University, Catanzaro, Italy
| | - Arnika Kathleen Wagner
- Department of Microbiology, Cell and Tumor Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Gianluca Contrò
- Department of Health Sciences, University of Catanzaro Magna Graecia, Catanzaro, Italy
| | - Nicola Perrotti
- Department of Health Sciences, University of Catanzaro Magna Graecia, Catanzaro, Italy
| | - Elio Gulletta
- Division of Clinical Pathology, Department of Health Sciences, Magna Graecia University, Catanzaro, Italy
| | - Soldano Ferrone
- Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
| | - Klas Kärre
- Department of Microbiology, Cell and Tumor Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Francesco Saverio Costanzo
- Research Center of Advanced Biochemistry and Molecular Biology, Department of Experimental and Clinical Medicine, Magna Græcia University of Catanzaro, Catanzaro, Italy.,CIS for Genomics and Molecular Pathology, Magna Graecia University of Catanzaro, Catanzaro, Italy
| | - Francesca Carlomagno
- Department of Molecular Medicine and Medical Biotechnologies Federico II University, Naples, Italy
| | - Ennio Carbone
- Tumor Immunology and Immunopathology Laboratory, Department of Experimental and Clinical Medicine, University Magna Graecia of Catanzaro, Catanzaro, Italy.,Department of Microbiology, Cell and Tumor Biology (MTC), Karolinska Institutet, Stockholm, Sweden
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4
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Costa M, Cruz E, Oliveira S, Benes V, Ivacevic T, Silva MJ, Vieira I, Dias F, Fonseca S, Gonçalves M, Lima M, Leitão C, Muckenthaler MU, Pinto J, Porto G. Lymphocyte gene expression signatures from patients and mouse models of hereditary hemochromatosis reveal a function of HFE as a negative regulator of CD8+ T-lymphocyte activation and differentiation in vivo. PLoS One 2015; 10:e0124246. [PMID: 25880808 PMCID: PMC4399836 DOI: 10.1371/journal.pone.0124246] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2015] [Accepted: 02/27/2015] [Indexed: 12/22/2022] Open
Abstract
Abnormally low CD8+ T-lymphocyte numbers is characteristic of some patients with hereditary hemochromatosis (HH), a MHC-linked disorder of iron overload. Both environmental and genetic components are known to influence CD8+ T-lymphocyte homeostasis but the role of the HH associated protein HFE is still insufficiently understood. Genome-wide expression profiling was performed in peripheral blood CD8+ T lymphocytes from HH patients selected according to CD8+ T-lymphocyte numbers and from Hfe-/- mice maintained either under normal or high iron diet conditions. In addition, T-lymphocyte apoptosis and cell cycle progression were analyzed by flow cytometry in HH patients. HH patients with low CD8+ T-lymphocyte numbers show a differential expression of genes related to lymphocyte differentiation and maturation namely CCR7, LEF1, ACTN1, NAA50, P2RY8 and FOSL2, whose expression correlates with the relative proportions of naïve, central and effector memory subsets. In addition, expression levels of LEF1 and P2RY8 in memory cells as well as the proportions of CD8+ T cells in G2/M cell cycle phase are significantly different in HH patients compared to controls. Hfe-/- mice do not show alterations in CD8+ T-lymphocyte numbers but differential gene response patterns. We found an increased expression of S100a8 and S100a9 that is most pronounced in high iron diet conditions. Similarly, CD8+ T lymphocytes from HH patients display higher S100a9 expression both at the mRNA and protein level. Altogether, our results support a role for HFE as a negative regulator of CD8+ T-lymphocyte activation. While the activation markers S100a8 and S100a9 are strongly increased in CD8+ T cells from both, Hfe-/- mice and HH patients, a differential profile of genes related to differentiation/maturation of CD8+ T memory cells is evident in HH patients only. This supports the notion that HFE contributes, at least in part, to the generation of low peripheral blood CD8+ T lymphocytes in HH.
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Affiliation(s)
- Mónica Costa
- I3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Basic and Clinical Research on Iron Biology, IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
- Doctoral Program in Biomedicine, Faculdade de Medicina, Universidade do Porto, Porto, Portugal
| | - Eugénia Cruz
- I3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Basic and Clinical Research on Iron Biology, IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
- Clinical Hematology, Santo António Hospital—Centro Hospitalar do Porto, Porto, Portugal
| | - Susana Oliveira
- I3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Basic and Clinical Research on Iron Biology, IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Vladimir Benes
- Genomics Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Tomi Ivacevic
- Genomics Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Maria João Silva
- Clinical Hematology, Santo António Hospital—Centro Hospitalar do Porto, Porto, Portugal
| | - Inês Vieira
- I3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Basic and Clinical Research on Iron Biology, IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Francisco Dias
- Clinical Hematology, Santo António Hospital—Centro Hospitalar do Porto, Porto, Portugal
| | - Sónia Fonseca
- Clinical Hematology, Santo António Hospital—Centro Hospitalar do Porto, Porto, Portugal
| | - Marta Gonçalves
- Clinical Hematology, Santo António Hospital—Centro Hospitalar do Porto, Porto, Portugal
| | - Margarida Lima
- Clinical Hematology, Santo António Hospital—Centro Hospitalar do Porto, Porto, Portugal
| | - Catarina Leitão
- Advanced Flow Cytometry Unit, IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Martina U. Muckenthaler
- Departments of Pediatric Hematology, Oncology and Immunology, University of Heidelberg and Molecular Medicine Partnership Unit, Heidelberg, Germany
| | - Jorge Pinto
- I3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Basic and Clinical Research on Iron Biology, IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Graça Porto
- I3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Basic and Clinical Research on Iron Biology, IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
- Clinical Hematology, Santo António Hospital—Centro Hospitalar do Porto, Porto, Portugal
- Molecular Immunology and Pathology, ICBAS—Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
- * E-mail:
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5
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Pinto JP, Arezes J, Dias V, Oliveira S, Vieira I, Costa M, Vos M, Carlsson A, Rikers Y, Rangel M, Porto G. Physiological implications of NTBI uptake by T lymphocytes. Front Pharmacol 2014; 5:24. [PMID: 24616700 PMCID: PMC3935319 DOI: 10.3389/fphar.2014.00024] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 02/11/2014] [Indexed: 12/29/2022] Open
Abstract
In iron overload disorders a significant fraction of the total iron circulates in the plasma as low molecular weight complexes not bound to transferrin, known as non-transferrin-bound iron (NTBI). By catalyzing the formation of free radicals, NTBI accumulation results in oxidative stress and cellular damage, being a major cause of organ toxicity. NTBI is rapidly and preferentially cleared from circulation by the liver and the myocardium, the main disease targets in iron overload conditions. We have recently demonstrated that human peripheral blood T lymphocytes take up NTBI in vitro, with a pattern that resembles that of hepatocytes. Since T lymphocytes constitute a numerically important component of the circulating cell pool, these findings support a putative role for this cell type in the systemic protection against iron toxicity. Here we tested the hypothesis that the circulating peripheral blood T lymphocyte pool constitutes an important storage compartment for NTBI and is thus a modifier of NTBI deposition in target organs. First we show that NTBI uptake by human T lymphocytes increases the expression of the iron-storage protein ferritin and of the iron exporter ferroportin via an IRE-dependent mechanism. NTBI retention by T lymphocytes is shown to be critically controlled by the hepcidin-mediated modulation of ferroportin both in vitro and in vivo. Finally, the protective effect of T lymphocytes was tested by analyzing the patterns of iron accumulation in the T lymphocyte-deficient mouse model Foxn1nu before and after reconstitution with T lymphocytes by adoptive transfer. The results confirmed a significant increase of liver and pancreas iron accumulation in T lymphocyte-deficient mice. NTBI accumulation in the liver and spleen was prevented by reconstitution with syngeneic T lymphocytes. Altogether, our results demonstrate that T lymphocytes are important components of a circulating “NTBI storage compartment” and show its physiological relevance as a modifier of tissue iron overload.
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Affiliation(s)
- Jorge P Pinto
- Molecular and Cellular Biology Division, Basic and Clinical Research on Iron Biology, Instituto de Biologia Molecular e Celular, Universidade do Porto Porto, Portugal
| | - João Arezes
- Molecular and Cellular Biology Division, Basic and Clinical Research on Iron Biology, Instituto de Biologia Molecular e Celular, Universidade do Porto Porto, Portugal
| | - Vera Dias
- Molecular and Cellular Biology Division, Basic and Clinical Research on Iron Biology, Instituto de Biologia Molecular e Celular, Universidade do Porto Porto, Portugal
| | - Susana Oliveira
- Molecular and Cellular Biology Division, Basic and Clinical Research on Iron Biology, Instituto de Biologia Molecular e Celular, Universidade do Porto Porto, Portugal
| | - Inês Vieira
- Molecular and Cellular Biology Division, Basic and Clinical Research on Iron Biology, Instituto de Biologia Molecular e Celular, Universidade do Porto Porto, Portugal
| | - Mónica Costa
- Molecular and Cellular Biology Division, Basic and Clinical Research on Iron Biology, Instituto de Biologia Molecular e Celular, Universidade do Porto Porto, Portugal ; Faculdade de Medicina, Universidade do Porto Porto, Portugal
| | | | | | | | - Maria Rangel
- Chemistry Department, REQUIMTE, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto Porto, Portugal
| | - Graça Porto
- Molecular and Cellular Biology Division, Basic and Clinical Research on Iron Biology, Instituto de Biologia Molecular e Celular, Universidade do Porto Porto, Portugal ; Clinical Hematology, CHP-HSA - Santo António General Hospital Porto, Portugal ; Molecular Immunology and Pathology, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto Porto, Portugal
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6
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Arezes J, Costa M, Vieira I, Dias V, Kong XL, Fernandes R, Vos M, Carlsson A, Rikers Y, Porto G, Rangel M, Hider RC, Pinto JP. Non-transferrin-bound iron (NTBI) uptake by T lymphocytes: evidence for the selective acquisition of oligomeric ferric citrate species. PLoS One 2013; 8:e79870. [PMID: 24278199 PMCID: PMC3836815 DOI: 10.1371/journal.pone.0079870] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 09/27/2013] [Indexed: 02/06/2023] Open
Abstract
Iron is an essential nutrient in several biological processes such as oxygen transport, DNA replication and erythropoiesis. Plasma iron normally circulates bound to transferrin. In iron overload disorders, however, iron concentrations exceed transferrin binding capacity and iron appears complexed with low molecular weight molecules, known as non-transferrin-bound iron (NTBI). NTBI is responsible for the toxicity associated with iron-overload pathologies but the mechanisms leading to NTBI uptake are not fully understood. Here we show for the first time that T lymphocytes are able to take up and accumulate NTBI in a manner that resembles that of hepatocytes. Moreover, we show that both hepatocytes and T lymphocytes take up the oligomeric Fe3Cit3 preferentially to other iron-citrate species, suggesting the existence of a selective NTBI carrier. These results provide a tool for the identification of the still elusive ferric-citrate cellular carrier and may also open a new pathway towards the design of more efficient iron chelators for the treatment of iron overload disorders.
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Affiliation(s)
- Joao Arezes
- Basic and Clinical Research on Iron Biology, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
- * E-mail:
| | - Monica Costa
- Basic and Clinical Research on Iron Biology, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Ines Vieira
- Basic and Clinical Research on Iron Biology, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Vera Dias
- Basic and Clinical Research on Iron Biology, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Xiao L. Kong
- Pharmaceutical Sciences Research Division, King's College London, London, United Kingdom
| | - Rui Fernandes
- ATAF, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Matthijn Vos
- Europe NanoPort, FEI, Eindhoven, The Netherlands
| | | | - Yuri Rikers
- Europe NanoPort, FEI, Eindhoven, The Netherlands
| | - Graça Porto
- Basic and Clinical Research on Iron Biology, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
- Clinical Hematology, CHP-HSA - Santo António General Hospital, Porto, Portugal
- Molecular Immunology and Pathology, ICBAS - Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Maria Rangel
- REQUIMTE, ICBAS - Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Robert C. Hider
- Pharmaceutical Sciences Research Division, King's College London, London, United Kingdom
| | - Jorge P. Pinto
- Basic and Clinical Research on Iron Biology, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
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ER Stress and Iron Homeostasis: A New Frontier for the UPR. Biochem Res Int 2010; 2011:896474. [PMID: 21197476 PMCID: PMC3010616 DOI: 10.1155/2011/896474] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Accepted: 10/01/2010] [Indexed: 02/07/2023] Open
Abstract
The C282Y mutation of HFE accounts for the majority of cases of the iron overload disease Hereditary Hemochromatosis (HH).
The conformational changes introduced by this mutation impair the HFE association with β2-microglobulin
(β2m) and the cell surface expression of the protein: with two major consequences. From a functional perspective,
the ability of HFE to bind to transferrin receptors 1 and 2 is lost in the C282Y mutant, thus affecting hepcidin regulation. Also due to the faulty
assembly with β2m, HFE-C282Y molecules remain in the endoplasmic reticulum (ER) as aggregates that undergo
proteasomal degradation and activate an Unfolded Protein Response (UPR). UPR activation, regardless of the ER stress stimuli, was shown
to reshape the expression profile of iron-related genes and to decrease MHC-I cell surface expression. The possibility of a HFE-C282Y-mediated
interplay between the UPR and iron homeostasis influencing disease progression and the clinical heterogeneity among C282Y carriers is
discussed. The responsiveness of the ER chaperone calreticulin to both ER and iron-induced oxidative stresses, and its correlation with HH
patients' phenotype, reinforce the interest of dissecting the UPR signaling/iron metabolism crosstalk and points to the potential
clinical value of use of pharmacological chaperones in HFE-HH.
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Pinto JP, Dias V, Zoller H, Porto G, Carmo H, Carvalho F, de Sousa M. Hepcidin messenger RNA expression in human lymphocytes. Immunology 2010; 130:217-30. [PMID: 20102409 DOI: 10.1111/j.1365-2567.2009.03226.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Hepcidin regulates intracellular iron levels by interacting with and promoting the degradation of ferroportin, a membrane protein and the only known cellular iron exporter. Studies of hepcidin expression and regulation have focused on its effects in innate immunity and as a regulator of systemic iron metabolism. In the present study we characterized the expression of hepcidin messenger RNA (mRNA) in human peripheral blood mononuclear cells (PBMCs) with a focus on peripheral blood lymphocytes (PBLs). We found that (1) all human PBMCs analyzed express basal hepcidin mRNA levels; (2) hepcidin mRNA expression increases after T-lymphocyte activation; (3) expression by PBLs increases in response to challenge by holotransferrin (Fe-TF) and by ferric citrate in vitro; (4) the Fe-TF-mediated up-regulation of hepcidin decreases ferroportin expression at the cytoplasmic membrane of PBLs; and (5) silencing of tumour necrosis factor-alpha (TNF-alpha) abrogates the effect of Fe-TF. In summary, we show that hepcidin expression determines intracellular iron levels by regulating the expression of ferroportin, as described in other cells, and that inappropriately low expression of hepcidin impairs normal lymphocyte proliferation. The results establish hepcidin as a new player in lymphocyte biology.
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Affiliation(s)
- Jorge P Pinto
- Iron Genes and Immune System, IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
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9
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Abstract
Hereditary hemochromatosis (HH) is caused by chronic hyperabsorption of dietary iron. Progressive accumulation of excess iron within tissue parenchymal cells may lead to severe organ damage. The most prevalent type of HH is linked to mutations in the HFE gene, encoding an atypical major histocompatibility complex classImolecule. Shortly after its discovery in 1996, the hemochromatosis protein HFE was shown to physically interact with transferrin receptor 1 (TfR1) and impair the uptake of transferrin-bound iron in cells. However, these findings provided no clue why HFE mutations associate with systemic iron overload. It was later established that all forms of HH result from misregulation of hepcidin expression. This liver-derived circulating peptide hormone controls iron efflux from duodenal enterocytes and reticuloendothelial macrophages by promoting the degradation of the iron exporter ferroportin. Recent studies with animal models of HH uncover a crucial role of HFE as a hepatocyte iron sensor and upstream regulator of hepcidin. Thus, hepatocyte HFE is indispensable for signaling to hepcidin, presumably as a constituent of a larger iron-sensing complex. A working model postulates that the signaling activity of HFE is silenced when the protein is bound to TfR1. An increase in the iron saturation of plasma transferrin leads to displacement of TfR1 from HFE and assembly of the putative iron-sensing complex. In this way, iron uptake by the hepatocyte is translated into upregulation of hepcidin, reinforcing the concept that the liver is the major regulatory site for systemic iron homeostasis, and not merely an iron storage depot.
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11
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Schmidt PJ, Toran PT, Giannetti AM, Bjorkman PJ, Andrews NC. The transferrin receptor modulates Hfe-dependent regulation of hepcidin expression. Cell Metab 2008; 7:205-14. [PMID: 18316026 PMCID: PMC2292811 DOI: 10.1016/j.cmet.2007.11.016] [Citation(s) in RCA: 253] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Revised: 11/10/2007] [Accepted: 11/30/2007] [Indexed: 12/21/2022]
Abstract
Hemochromatosis is caused by mutations in HFE, a protein that competes with transferrin (TF) for binding to transferrin receptor 1 (TFR1). We developed mutant mouse strains to gain insight into the role of the Hfe/Tfr1 complex in regulating iron homeostasis. We introduced mutations into a ubiquitously expressed Tfr1 transgene or the endogenous Tfr1 locus to promote or prevent the Hfe/Tfr1 interaction. Under conditions favoring a constitutive Hfe/Tfr1 interaction, mice developed iron overload attributable to inappropriately low expression of the hormone hepcidin. In contrast, mice carrying a mutation that interferes with the Hfe/Tfr1 interaction developed iron deficiency associated with inappropriately high hepcidin expression. High-level expression of a liver-specific Hfe transgene in Hfe-/- mice was also associated with increased hepcidin production and iron deficiency. Together, these models suggest that Hfe induces hepcidin expression when it is not in complex with Tfr1.
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Affiliation(s)
- Paul J Schmidt
- Division of Hematology/Oncology, Children's Hospital Boston, Boston, MA 02115, USA
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12
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Abstract
Progress in the characterization of genes involved in the control of iron homeostasis in humans and in mice has improved the definition of iron overload and of the cells affected by it. The cell involved in iron overload with the greatest effect on immunity is the macrophage. Intriguing evidence has emerged, however, in the last 12 years indicating that parenchymal iron overload is linked to genes classically associated with the immune system. This review offers an update of the genes and proteins relevant to iron metabolism expressed in cells of the innate immune system, and addresses the question of how this system is affected in clinical situations of iron overload. The relationship between iron and the major cells of adaptive immunity, the T lymphocytes, will also be reviewed. Most studies addressing this last question in humans were performed in the clinical model of Hereditary Hemochromatosis. Data will also be reviewed demonstrating how the disruption of molecules essentially involved in adaptive immune responses result in the spontaneous development of iron overload and how they act as modifiers of iron overload.
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Affiliation(s)
- Graça Porto
- Institute of Molecular and Cellular Biology, Rua do Campo Alegre, Porto 8234150, Portugal.
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13
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Rodrigues P, Lopes C, Mascarenhas C, Arosio P, Porto G, De Sousa M. Comparative study between Hfe-/- and beta2m-/- mice: progression with age of iron status and liver pathology. Int J Exp Pathol 2006; 87:317-24. [PMID: 16875497 PMCID: PMC2517374 DOI: 10.1111/j.1365-2613.2006.00491.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Hepatic iron overload in hemochomatosis patients can be highly variable but in general it develops in older patients. The purpose of this study was to compare development of iron load in of beta2m-/- and Hfe-/- mice paying special attention to liver pathology in older age groups. Liver iron content of beta2m-/-, Hfe-/- and control B6 mice of different ages (varying from 3 weeks to 18 months) was examined. Additional parameters (haematology indices, histopathology, lipid content and ferritin expression) were also studied in 18-month-old mice. The beta2m-/- strain presents higher hepatic iron content, hepatocyte nuclear iron inclusions, mitochondria abnormalities. In addition, hepatic steatosis was a common observation in this strain. In the liver of Hfe-/- mice, large mononuclear infiltrates positive for ferritin staining were commonly observed. The steatosis commonly observed the beta2m-/- mice may be a reflection of its higher hepatic iron content. The large hepatic mononuclear cell infiltrates seen in Hfe-/- stained for ferritin, may point to the iron sequestration capacity of lymphocytes and contribute to the clarification of the differences found in the progression of hepatic iron overload and steatosis in older animals from the two strains.
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Affiliation(s)
- Pedro Rodrigues
- Iron Genes and Immune System (IRIS), Institute for Molecular and Cell Biology (IBMC), Porto, Portugal.
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14
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Constante M, Jiang W, Wang D, Raymond VA, Bilodeau M, Santos MM. Distinct requirements for Hfe in basal and induced hepcidin levels in iron overload and inflammation. Am J Physiol Gastrointest Liver Physiol 2006; 291:G229-37. [PMID: 16565419 PMCID: PMC2891007 DOI: 10.1152/ajpgi.00092.2006] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Hepcidin is a negative regulator of iron absorption produced mainly by the liver in response to changes in iron stores and inflammation, and its levels have been shown to regulate the intestinal basolateral iron transporter ferroportin1 (Fp1). Hereditary hemochromatosis patients and Hfe-deficient mice show inappropriate expression of hepcidin but, in apparent contradiction, still retain the ability to regulate iron absorption in response to alterations of iron metabolism. To further understand the molecular relationships among Hfe, hepcidin, and Fp1, we investigated hepcidin and Fp1 regulation in Hfe-deficient mice (Hfe-/- and beta2m-/-) in response to iron deprivation, iron loading, and acute inflammation. We found that whereas basal hepcidin levels were manifestly dependent on the presence of Hfe and on the mouse background, all Hfe-deficient mice were still able to regulate hepcidin in situations of altered iron homeostasis. In the liver, Fp1 was modulated in opposite directions by iron and LPS, and its regulation in Hfe-deficient mice was similar to that observed in wild-type mice. In addition, we found that iron-deprived mice were able to mount a robust response after LPS challenge and that Toll-like receptor 4 (TLR-4)-deficient mice fail to regulate hepcidin expression in response to LPS. In conclusion, these results suggest that although Hfe is necessary for the establishment of hepcidin basal levels, it is dispensable for hepcidin regulation through both the iron-sensing and inflammatory pathways, and hepatic Fp1 regulation is largely independent of hepcidin and Hfe. The inflammatory pathway overrides the iron-sensing pathway and is TLR-4 dependent.
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Affiliation(s)
- Marco Constante
- Centre de recherche, Centre hospitalier de l'Université de Montréal, Hôpital Notre-Dame, Canada
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15
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Macedo MF, Cruz E, Lacerda R, Porto G, de Sousa M. Low serum transferrin levels in HFE C282Y homozygous subjects are associated with low CD8+ T lymphocyte numbers. Blood Cells Mol Dis 2005; 35:319-25. [PMID: 16140024 DOI: 10.1016/j.bcmd.2005.08.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2005] [Accepted: 08/02/2005] [Indexed: 12/23/2022]
Abstract
Hereditary hemochromatosis (HH) is a genetic iron overload disease, in the majority of cases associated with homozygosity for the C282Y mutation of the HFE gene. In spite of this genetic homogeneity, there is a great clinical heterogeneity among HH patients. Low CD8(+) lymphocyte numbers have been associated with a more severe expression of iron overload in HH patients, and in experimental models of iron overload. HH patients present low serum transferrin levels. Transferrin is an indispensable resource for lymphopoiesis. Lymphocyte homeostasis follows general ecology rules of population dynamics that involve competition for limiting resources. In the present study, we questioned whether transferrin levels could be associated with the anomalies seen previously in lymphocyte subset numbers in HH patients. Transferrin levels, total and subset T lymphocyte counts were done in 426 apparently healthy subjects genotyped for HFE. All HFE C282Y carriers presented significantly lower serum transferrin levels than the wild type group, a difference that could not be explained solely by the degree of iron overload. Significant differences were also seen in transferrin levels between males and females, with females presenting higher average serum Transferrin levels. In the population of subjects with Transferrin levels lower than 248 mg/dl, a positive correlation was seen between the peripheral CD8(+) lymphocyte numbers and serum transferrin levels (R(2) = 2.41; r = 0.16; P = 0.018). To test the possible limiting resource effect of transferrin, the correlation between transferrin levels and CD8(+) lymphocyte numbers was scrutinized in 34 HH patients, homozygous for the C282Y mutation. In the homozygous males, where the lowest average transferrin levels were seen, another highly significant correlation was observed between Transferrin levels and CD8(+) numbers. This correlation points to a possible role of transferrin as a limiting resource for MHC class I dependent lymphocyte proliferation, an effect that was not observed in C282Y homozygous female patients.
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Affiliation(s)
- M Fatima Macedo
- Division of Human Genetics and Genetic Disorders, Iron Genes and the Immune System Laboratory, Institute for Molecular and Cell Biology (IBMC), Oporto, Portugal
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16
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Rohrlich PS, Fazilleau N, Ginhoux F, Firat H, Michel F, Cochet M, Laham N, Roth MP, Pascolo S, Nato F, Coppin H, Charneau P, Danos O, Acuto O, Ehrlich R, Kanellopoulos J, Lemonnier FA. Direct recognition by alphabeta cytolytic T cells of Hfe, a MHC class Ib molecule without antigen-presenting function. Proc Natl Acad Sci U S A 2005; 102:12855-60. [PMID: 16123136 PMCID: PMC1200262 DOI: 10.1073/pnas.0502309102] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2005] [Indexed: 12/17/2022] Open
Abstract
Crystallographic analysis of human Hfe has documented an overall structure similar to classical (class Ia) MHC molecules with a peptide binding groove deprived of ligand. Thus, to address the question of whether alphabeta T cells could recognize MHC molecules independently of bound ligands, we studied human and mouse Hfe interactions with T lymphocytes. We provide formal evidence of direct cytolytic recognition of human Hfe by mouse alphabeta T cell receptors (TCR) in HLA-A*0201 transgenic mice and that this interaction results in ZAP-70 phosphorylation. Furthermore, direct recognition of mouse Hfe molecules by cytotoxic T lymphocytes (CTLs) was demonstrated in DBA/2 Hfe knockout mice. These CTLs express predominantly two T cell antigen receptor alpha variable gene segments (AV6.1 and AV6.6). Interestingly, in wild-type mice we identified a subset of CD8+ T cells positively selected by Hfe that expresses the AV6.1/AV6.6 gene segments. T cell antigen receptor recognition of MHC molecules independently of bound ligand has potential general implications in alloreactivity and identifies in the Hfe case a cognitive link supporting the concept that the immune system could be involved in the control of iron metabolism.
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Affiliation(s)
- Pierre S Rohrlich
- Unité d'Immunité Cellulaire Antivirale, Département d'Immunologie, Institut Pasteur, 75724 Paris, France
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17
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Makui H, Soares RJ, Jiang W, Constante M, Santos MM. Contribution of Hfe expression in macrophages to the regulation of hepatic hepcidin levels and iron loading. Blood 2005; 106:2189-95. [PMID: 15914561 PMCID: PMC2891009 DOI: 10.1182/blood-2005-02-0629] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Hereditary hemochromatosis (HH), an iron overload disease associated with mutations in the HFE gene, is characterized by increased intestinal iron absorption and consequent deposition of excess iron, primarily in the liver. Patients with HH and Hfe-deficient (Hfe-/-) mice manifest inappropriate expression of the iron absorption regulator hepcidin, a peptide hormone produced by the liver in response to iron loading. In this study, we investigated the contribution of Hfe expression in macrophages to the regulation of liver hepcidin levels and iron loading. We used bone marrow transplantation to generate wild-type (wt) and Hfe-/- mice chimeric for macrophage Hfe gene expression. Reconstitution of Hfe-deficient mice with wt bone marrow resulted in augmented capacity of the spleen to store iron and in significantly decreased liver iron loading, accompanied by a significant increase of hepatic hepcidin mRNA levels. Conversely, wt mice reconstituted with Hfe-deficient bone marrow had a diminished capacity to store iron in the spleen but no significant alterations of liver iron stores or hepcidin mRNA levels. Our results suggest that macrophage Hfe participates in the regulation of splenic and liver iron concentrations and liver hepcidin expression.
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Affiliation(s)
- Hortence Makui
- Centre de recherche, CHUM-Hôpital Notre-Dame, Pav. De Sève Y5625, 1560 Sherbrooke est, Montréal, Québec H2L 4M1, Canada
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18
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Muckenthaler MU, Rodrigues P, Macedo MG, Minana B, Brennan K, Cardoso EM, Hentze MW, de Sousa M. Molecular analysis of iron overload in beta2-microglobulin-deficient mice. Blood Cells Mol Dis 2005; 33:125-31. [PMID: 15315790 DOI: 10.1016/j.bcmd.2004.05.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2004] [Revised: 05/13/2004] [Indexed: 12/20/2022]
Abstract
Beta2-microglobulin knockout (beta2m-/-) mice represent an instructive model of spontaneous iron overload resembling genetic hemochromatosis. The mechanism of iron accumulation in this mouse model may be more complex than involving the MHC class I-like protein HFE. We report that beta2m-deficient mice, like Hfe-/- mice, lack the adaptive hepatic hepcidin mRNA increase to iron overload. The inverse correlation of hepatic iron levels and hepcidin mRNA expression in six beta2m-/- mice underlines the importance of hepcidin in regulating body iron stores. In contrast to Hfe-/- mice, beta2m-deficient mice display increased expression of the duodenal iron transporters DMT1 and ferroportin 1. This result implicates a broader role of beta2m in mammalian iron metabolism, suggesting that (an) additional beta2m-interacting protein(s) could be involved in controlling iron homeostasis, and highlighting the emerging connection of iron metabolism with the immune system.
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19
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Cabrita M, Pereira CF, Rodrigues P, Cardoso EM, Arosa FA. Altered expression of CD1d molecules and lipid accumulation in the human hepatoma cell line HepG2 after iron loading. FEBS J 2005; 272:152-65. [PMID: 15634340 DOI: 10.1111/j.1432-1033.2004.04387.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Iron overload in the liver may occur in clinical conditions such as hemochromatosis and nonalcoholic steatohepatitis, and may lead to the deterioration of the normal liver architecture by mechanisms not well understood. Although a relationship between the expression of ICAM-1, and classical major histocompatibility complex (MHC) class I molecules, and iron overload has been reported, no relationship has been identified between iron overload and the expression of unconventional MHC class I molecules. Herein, we report that parameters of iron metabolism were regulated in a coordinated-fashion in a human hepatoma cell line (HepG2 cells) after iron loading, leading to increased cellular oxidative stress and growth retardation. Iron loading of HepG2 cells resulted in increased expression of Nor3.2-reactive CD1d molecules at the plasma membrane. Expression of classical MHC class I and II molecules, ICAM-1 and the epithelial CD8 ligand, gp180 was not significantly affected by iron. Considering that intracellular lipids regulate expression of CD1d at the cell surface, we examined parameters of lipid metabolism in iron-loaded HepG2 cells. Interestingly, increased expression of CD1d molecules by iron-loaded HepG2 cells was associated with increased phosphatidylserine expression in the outer leaflet of the plasma membrane and the presence of many intracellular lipid droplets. These data describe a new relationship between iron loading, lipid accumulation and altered expression of CD1d, an unconventional MHC class I molecule reported to monitor intracellular and plasma membrane lipid metabolism, in the human hepatoma cell line HepG2.
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Affiliation(s)
- Marisa Cabrita
- Institute for Molecular and Cell Biology, Porto, Portugal
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20
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Miranda CJ, Makui H, Andrews NC, Santos MM. Contributions of beta2-microglobulin-dependent molecules and lymphocytes to iron regulation: insights from HfeRag1(-/-) and beta2mRag1(-/-) double knock-out mice. Blood 2003; 103:2847-9. [PMID: 14656877 PMCID: PMC2891006 DOI: 10.1182/blood-2003-09-3300] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Genetic causes of hereditary hemochromatosis (HH) include mutations in the HFE gene, coding for a beta2-microglobulin (beta2m)-associated major histocompatibility complex class I-like protein. However, iron accumulation in patients with HH can be highly variable. Previously, analysis of beta2mRag1(-/-) double-deficient mice, lacking all beta2m-dependent molecules and lymphocytes, demonstrated increased iron accumulation in the pancreas and heart compared with beta2m single knock-out mice. To evaluate whether the observed phenotype in beta2mRag1(-/-) mice was due solely to the absence of Hfe or to other beta2m-dependent molecules, we generated HfeRag1(-/-) double-deficient mice. Our studies revealed that introduction of Rag1 deficiency in Hfe knock-out mice leads to heightened iron overload, mainly in the liver, whereas the heart and pancreas are relatively spared compared with beta2mRag1(-/-) mice. These results suggest that other beta2m-interacting protein(s) may be involved in iron regulation and that in the absence of functional Hfe molecules lymphocyte numbers may influence iron overload severity.
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Affiliation(s)
- Carlos J Miranda
- Centre de recherche, Centre Hospitalier de l'Université de Montréal, QC, Canada
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21
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Feder JN, Gnirke A, Thomas W, Tsuchihashi Z, Ruddy DA, Basava A. The discovery of the new haemochromatosis gene. 1996. J Hepatol 2003; 38:704-9. [PMID: 12763361 DOI: 10.1016/s0168-8278(03)00142-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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22
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Cardoso CS, de Sousa M. HFE, the MHC and hemochromatosis: paradigm for an extended function for MHC class I. TISSUE ANTIGENS 2003; 61:263-75. [PMID: 12753664 DOI: 10.1034/j.1399-0039.2003.00065.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
HFE was discovered as the hereditary hemochromatosis (HH) gene. It is located on chromosome 6 (6p21.3), 4Mb telomeric to the HLA-A locus, and its product has a structure similar to MHC class I molecules. HFE encodes two frequent mutations: C282Y and H63D. One of these (C282Y) is present in a large proportion of Caucasian HH patients. HFE has a tissue distribution compatible with a role in iron absorption (intestine), recycling (macrophages) and transport to the fetus (placenta).
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Affiliation(s)
- C S Cardoso
- Molecular Immunology, Institute for Molecular and Cell Biology, Oporto, Portugal Molecular Pathology and Immunology, Instituto de Ciências Biomédicas Abel Salazar, OPorto, Portugal
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Bridle KR, Frazer DM, Wilkins SJ, Dixon JL, Purdie DM, Crawford DHG, Subramaniam VN, Powell LW, Anderson GJ, Ramm GA. Disrupted hepcidin regulation in HFE-associated haemochromatosis and the liver as a regulator of body iron homoeostasis. Lancet 2003; 361:669-73. [PMID: 12606179 DOI: 10.1016/s0140-6736(03)12602-5] [Citation(s) in RCA: 434] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND The mechanisms responsible for disturbed iron homoeostasis in hereditary haemochromatosis are poorly understood. However, results of some studies indicate a link between hepcidin, a liver-derived peptide, and intestinal iron absorption, suggesting that this molecule could play a part in hepatic iron overload. To investigate this possible association, we studied the hepatic expression of the gene for hepcidin (HAMP) and a gene important in iron transport (IREG1) in patients with haemochromatosis, in normal controls, and in Hfe-knockout mice. METHODS We extracted total RNA from the liver tissue of 27 patients with HFE-associated haemochromatosis, seven transplant donors (controls), and Hfe-knockout mice. HAMP and IREG1 mRNA concentrations were examined by ribonuclease protection assays and expressed relative to the housekeeping gene GAPD. FINDINGS There was a significant decrease in HAMP expression in untreated patients compared with controls (5.4-fold, 95% CI 3.3-7.5; p<0.0001) despite significantly increased iron loading. Similarly, we noted a decrease in Hamp expression in iron-loaded Hfe-knockout mice. Hepatic IREG1 expression was greatly upregulated in patients with haemochromatosis (1.8-fold, 95% CI 1.5-2.2; p=0.002). There was a significant correlation between hepatic iron concentration and expression of HAMP (r=0.59, p=0.02) and IREG1 (r=0.67, p=0.007) in untreated patients. INTERPRETATION Lack of HAMP upregulation in HFE-associated haemochromatosis despite significant hepatic iron loading indicates that HFE plays an important part in the regulation of hepcidin expression in response to iron overload. Our results imply that the liver is important in the pathophysiology of HFE-associated haemochromatosis. Furthermore, the increase in hepatic IREG1 expression in haemochromatosis suggests that IREG1 could function to facilitate the removal of excess iron from the liver.
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Affiliation(s)
- Kim R Bridle
- Hepatic Fibrosis Group, Queensland Institute of Medical Research, Royal Brisbane Hospital, Queensland, Herston, Australia
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