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Zurawska G, Jończy A, Niklewicz M, Sas Z, Rumieńczyk I, Kulecka M, Piwocka K, Rygiel TP, Mikula M, Mleczko-Sanecka K. Iron-triggered signaling via ETS1 and the p38/JNK MAPK pathway regulates Bmp6 expression. Am J Hematol 2024; 99:543-554. [PMID: 38293789 DOI: 10.1002/ajh.27223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 12/13/2023] [Accepted: 01/01/2024] [Indexed: 02/01/2024]
Abstract
BMP6 is an iron-sensing cytokine whose transcription in liver sinusoidal endothelial cells (LSECs) is enhanced by high iron levels, a step that precedes the induction of the iron-regulatory hormone hepcidin. While several reports suggested a cell-autonomous induction of Bmp6 by iron-triggered signals, likely via sensing of oxidative stress by the transcription factor NRF2, other studies proposed the dominant role of a paracrine yet unidentified signal released by iron-loaded hepatocytes. To further explore the mechanisms of Bmp6 transcriptional regulation, we used female mice aged 10-11 months, which are characterized by hepatocytic but not LSEC iron accumulation, and no evidence of systemic iron overload. We found that LSECs of aged mice exhibit increased Bmp6 mRNA levels as compared to young controls, but do not show a transcriptional signature characteristic of activated NFR2-mediated signaling in FACS-sorted LSECs. We further observed that primary murine LSECs derived from both wild-type and NRF2 knock-out mice induce Bmp6 expression in response to iron exposure. By analyzing transcriptomic data of FACS-sorted LSECs from aged versus young mice, as well as early after iron citrate injections, we identified ETS1 as a candidate transcription factor involved in Bmp6 transcriptional regulation. By performing siRNA-mediated knockdown, small-molecule treatments, and chromatin immunoprecipitation in primary LSECs, we show that Bmp6 transcription is regulated by iron via ETS1 and p38/JNK MAP kinase-mediated signaling, at least in part independently of NRF2. Thereby, these findings identify the new components of LSEC iron sensing machinery broadly associated with cellular stress responses.
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Affiliation(s)
- Gabriela Zurawska
- International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Aneta Jończy
- International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Marta Niklewicz
- International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Zuzanna Sas
- Medical University of Warsaw, Warsaw, Poland
| | - Izabela Rumieńczyk
- Maria Sklodowska-Curie National Research Institute of Oncology, Warsaw, Poland
| | - Maria Kulecka
- Maria Sklodowska-Curie National Research Institute of Oncology, Warsaw, Poland
| | | | - Tomasz P Rygiel
- Mossakowski Medical Research Institute, Polish Academy of Sciences, Warsaw, Poland
| | - Michal Mikula
- Maria Sklodowska-Curie National Research Institute of Oncology, Warsaw, Poland
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2
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Ledesma-Colunga MG, Passin V, Vujic Spasic M, Hofbauer LC, Baschant U, Rauner M. Comparison of the effects of high dietary iron levels on bone microarchitecture responses in the mouse strains 129/Sv and C57BL/6J. Sci Rep 2024; 14:4887. [PMID: 38418857 PMCID: PMC10902348 DOI: 10.1038/s41598-024-55303-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 02/22/2024] [Indexed: 03/02/2024] Open
Abstract
Iron is an essential nutrient for all living organisms. Both iron deficiency and excess can be harmful. Bone, a highly metabolic active organ, is particularly sensitive to fluctuations in iron levels. In this study, we investigated the effects of dietary iron overload on bone homeostasis with a specific focus on two frequently utilized mouse strains: 129/Sv and C57BL/6J. Our findings revealed that after 6 weeks on an iron-rich diet, 129/Sv mice exhibited a decrease in trabecular and cortical bone density in both vertebral and femoral bones, which was linked to reduced bone turnover. In contrast, there was no evidence of bone changes associated with iron overload in age-matched C57BL/6J mice. Interestingly, 129/Sv mice exposed to an iron-rich diet during their prenatal development were protected from iron-induced bone loss, suggesting the presence of potential adaptive mechanisms. Overall, our study underscores the critical role of genetic background in modulating the effects of iron overload on bone health. This should be considered when studying effects of iron on bone.
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Affiliation(s)
- Maria G Ledesma-Colunga
- Department of Medicine III & Center for Healthy Aging, Medical Faculty and University Hospital Carl Gustav Carus, Dresden University of Technology, Dresden, Germany
| | - Vanessa Passin
- Department of Medicine III & Center for Healthy Aging, Medical Faculty and University Hospital Carl Gustav Carus, Dresden University of Technology, Dresden, Germany
| | - Maja Vujic Spasic
- Institute of Comparative Molecular Endocrinology, Ulm University, Ulm, Germany
| | - Lorenz C Hofbauer
- Department of Medicine III & Center for Healthy Aging, Medical Faculty and University Hospital Carl Gustav Carus, Dresden University of Technology, Dresden, Germany
| | - Ulrike Baschant
- Department of Medicine III & Center for Healthy Aging, Medical Faculty and University Hospital Carl Gustav Carus, Dresden University of Technology, Dresden, Germany
| | - Martina Rauner
- Department of Medicine III & Center for Healthy Aging, Medical Faculty and University Hospital Carl Gustav Carus, Dresden University of Technology, Dresden, Germany.
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3
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Wang Y, Protchenko O, Huber KD, Shakoury-Elizeh M, Ghosh MC, Philpott CC. The iron chaperone poly(rC)-binding protein 1 regulates iron efflux through intestinal ferroportin in mice. Blood 2023; 142:1658-1671. [PMID: 37624904 PMCID: PMC10656723 DOI: 10.1182/blood.2023020504] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 07/28/2023] [Accepted: 08/13/2023] [Indexed: 08/27/2023] Open
Abstract
Iron is an essential nutrient required by all cells but used primarily for red blood cell production. Because humans have no effective mechanism for ridding the body of excess iron, the absorption of dietary iron must be precisely regulated. The critical site of regulation is the transfer of iron from the absorptive enterocyte to the portal circulation via the sole iron efflux transporter, ferroportin. Here, we report that poly(rC)-binding protein 1 (PCBP1), the major cytosolic iron chaperone, is necessary for the regulation of iron flux through ferroportin in the intestine of mice. Mice lacking PCBP1 in the intestinal epithelium exhibit low levels of enterocyte iron, poor retention of dietary iron in enterocyte ferritin, and excess efflux of iron through ferroportin. Excess iron efflux occurred despite lower levels of ferroportin protein in enterocytes and upregulation of the iron regulatory hormone hepcidin. PCBP1 deletion and the resulting unregulated dietary iron absorption led to poor growth, severe anemia on a low-iron diet, and liver oxidative stress with iron loading on a high-iron diet. Ex vivo culture of PCBP1-depleted enteroids demonstrated no defects in hepcidin-mediated ferroportin turnover. However, measurement of kinetically labile iron pools in enteroids competent or blocked for iron efflux indicated that PCBP1 functioned to bind and retain cytosolic iron and limit its availability for ferroportin-mediated efflux. Thus, PCBP1 coordinates enterocyte iron and reduces the concentration of unchaperoned "free" iron to a low level that is necessary for hepcidin-mediated regulation of ferroportin activity.
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Affiliation(s)
- Yubo Wang
- Genetics and Metabolism Section, Liver Diseases Branch, National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
| | - Olga Protchenko
- Genetics and Metabolism Section, Liver Diseases Branch, National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
| | - Kari D. Huber
- Genetics and Metabolism Section, Liver Diseases Branch, National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
| | - Minoo Shakoury-Elizeh
- Genetics and Metabolism Section, Liver Diseases Branch, National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
| | - Manik C. Ghosh
- Section on Human Iron Metabolism, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD
| | - Caroline C. Philpott
- Genetics and Metabolism Section, Liver Diseases Branch, National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
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4
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Enns CA, Weiskopf T, Zhang RH, Wu J, Jue S, Kawaguchi M, Kataoka H, Zhang AS. Matriptase-2 regulates iron homeostasis primarily by setting the basal levels of hepatic hepcidin expression through a nonproteolytic mechanism. J Biol Chem 2023; 299:105238. [PMID: 37690687 PMCID: PMC10551898 DOI: 10.1016/j.jbc.2023.105238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 08/07/2023] [Accepted: 08/23/2023] [Indexed: 09/12/2023] Open
Abstract
Matriptase-2 (MT2), encoded by TMPRSS6, is a membrane-anchored serine protease. It plays a key role in iron homeostasis by suppressing the iron-regulatory hormone, hepcidin. Lack of functional MT2 results in an inappropriately high hepcidin and iron-refractory iron-deficiency anemia. Mt2 cleaves multiple components of the hepcidin-induction pathway in vitro. It is inhibited by the membrane-anchored serine protease inhibitor, Hai-2. Earlier in vivo studies show that Mt2 can suppress hepcidin expression independently of its proteolytic activity. In this study, our data indicate that hepatic Mt2 was a limiting factor in suppressing hepcidin. Studies in Tmprss6-/- mice revealed that increases in dietary iron to ∼0.5% were sufficient to overcome the high hepcidin barrier and to correct iron-deficiency anemia. Interestingly, the increased iron in Tmprss6-/- mice was able to further upregulate hepcidin expression to a similar magnitude as in wild-type mice. These results suggest that a lack of Mt2 does not impact the iron induction of hepcidin. Additional studies of wild-type Mt2 and the proteolytic-dead form, fMt2S762A, indicated that the function of Mt2 is to lower the basal levels of hepcidin expression in a manner that primarily relies on its nonproteolytic role. This idea is supported by the studies in mice with the hepatocyte-specific ablation of Hai-2, which showed a marginal impact on iron homeostasis and no significant effects on iron regulation of hepcidin. Together, these observations suggest that the function of Mt2 is to set the basal levels of hepcidin expression and that this process is primarily accomplished through a nonproteolytic mechanism.
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Affiliation(s)
- Caroline A Enns
- Department of Cell, Developmental, and Cancer Biology, Oregon Health & Science University, Portland, Oregon, USA
| | - Tyler Weiskopf
- Department of Cell, Developmental, and Cancer Biology, Oregon Health & Science University, Portland, Oregon, USA
| | - Richard H Zhang
- Department of Cell, Developmental, and Cancer Biology, Oregon Health & Science University, Portland, Oregon, USA
| | - Jeffrey Wu
- Department of Cell, Developmental, and Cancer Biology, Oregon Health & Science University, Portland, Oregon, USA
| | - Shall Jue
- Department of Cell, Developmental, and Cancer Biology, Oregon Health & Science University, Portland, Oregon, USA
| | - Makiko Kawaguchi
- Faculty of Medicine, Section of Oncopathology and Regenerative Biology, Department of Pathology, University of Miyazaki, Miyazaki, Japan
| | - Hiroaki Kataoka
- Faculty of Medicine, Section of Oncopathology and Regenerative Biology, Department of Pathology, University of Miyazaki, Miyazaki, Japan
| | - An-Sheng Zhang
- Department of Cell, Developmental, and Cancer Biology, Oregon Health & Science University, Portland, Oregon, USA.
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Woźniak M, Borkowska A, Jastrzębska M, Sochal M, Małecka-Wojciesko E, Talar-Wojnarowska R. Clinical Significance of Erythroferrone and Bone Morphogenetic Protein-6 in Patients with Anemia in the Course of Inflammatory Bowel Disease. Metabolites 2023; 13:1006. [PMID: 37755286 PMCID: PMC10537870 DOI: 10.3390/metabo13091006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 09/04/2023] [Accepted: 09/08/2023] [Indexed: 09/28/2023] Open
Abstract
In recent years, a steady increase in the incidence of inflammatory bowel diseases (IBD) has been observed with anemia as their most common extraintestinal symptom. Erythroferrone and Bone Morphogenetic Protein 6 (BMP-6) are recently identified cytokines involved in the process of increased erythropoiesis in anemia of various pathomechanisms. The aim of this study was to analyze the concentration of erythroferrone and BMP-6 in IBD patients in relation to clinical and laboratory data. The study comprised 148 patients: 118 with IBD, including 73 (61.85%) diagnosed with anemia (42 with Crohn's disease (CD) (66.7%) and 31 (56.4%) with ulcerative colitis (UC)) and 30 as a control group. The erythroferrone concentration was significantly higher in IBD patients with anemia (p = 0.009) and higher in UC patients both with and without anemia (p = 0.018), compared to the control group. In CD, no similar difference was observed between patients with and without anemia. Regarding BMP-6, higher levels were found in CD patients with anemia compared to the control group (p = 0.021). The positive correlation between BMP-6 and iron concentration in UC was also noticed. In conclusion, we confirm an increase in erythroferrone concentration in the entire group of IBD patients with anemia, while BMP-6 levels were higher only in anemic CD patients. Due to the clinical importance of anemia in IBD, this problem is worth further analysis and research projects.
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Affiliation(s)
- Małgorzata Woźniak
- Department of Digestive Tract Diseases, Medical University of Lodz, 90-419 Lodz, Poland; (A.B.); (E.M.-W.); (R.T.-W.)
| | - Anna Borkowska
- Department of Digestive Tract Diseases, Medical University of Lodz, 90-419 Lodz, Poland; (A.B.); (E.M.-W.); (R.T.-W.)
| | - Marta Jastrzębska
- Department of Gastroenterology, Health Care Center, 26-200 Konskie, Poland;
| | - Marcin Sochal
- Department of Sleep Medicine and Metabolic Disorders, Medical University of Lodz, 90-419 Lodz, Poland;
| | - Ewa Małecka-Wojciesko
- Department of Digestive Tract Diseases, Medical University of Lodz, 90-419 Lodz, Poland; (A.B.); (E.M.-W.); (R.T.-W.)
| | - Renata Talar-Wojnarowska
- Department of Digestive Tract Diseases, Medical University of Lodz, 90-419 Lodz, Poland; (A.B.); (E.M.-W.); (R.T.-W.)
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6
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Ginzburg Y, An X, Rivella S, Goldfarb A. Normal and dysregulated crosstalk between iron metabolism and erythropoiesis. eLife 2023; 12:e90189. [PMID: 37578340 PMCID: PMC10425177 DOI: 10.7554/elife.90189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 08/06/2023] [Indexed: 08/15/2023] Open
Abstract
Erythroblasts possess unique characteristics as they undergo differentiation from hematopoietic stem cells. During terminal erythropoiesis, these cells incorporate large amounts of iron in order to generate hemoglobin and ultimately undergo enucleation to become mature red blood cells, ultimately delivering oxygen in the circulation. Thus, erythropoiesis is a finely tuned, multifaceted process requiring numerous properly timed physiological events to maintain efficient production of 2 million red blood cells per second in steady state. Iron is required for normal functioning in all human cells, the erythropoietic compartment consuming the majority in light of the high iron requirements for hemoglobin synthesis. Recent evidence regarding the crosstalk between erythropoiesis and iron metabolism sheds light on the regulation of iron availability by erythroblasts and the consequences of insufficient as well as excess iron on erythroid lineage proliferation and differentiation. In addition, significant progress has been made in our understanding of dysregulated iron metabolism in various congenital and acquired malignant and non-malignant diseases. Finally, we report several actual as well as theoretical opportunities for translating the recently acquired robust mechanistic understanding of iron metabolism regulation to improve management of patients with disordered erythropoiesis, such as anemia of chronic inflammation, β-thalassemia, polycythemia vera, and myelodysplastic syndromes.
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Affiliation(s)
- Yelena Ginzburg
- Division of Hematology and Medical Oncology, The Tisch Cancer Institute, Icahn School of Medicine at Mount SinaiNew YorkUnited States
| | - Xiuli An
- LFKRI, New York Blood CenterNew YorkUnited States
| | - Stefano Rivella
- Department of Pediatrics, Division of Hematology, The Children’s Hospital of PhiladelphiaPhiladelphiaUnited States
- Cell and Molecular Biology affinity group (CAMB), University of PennsylvaniaPhiladelphiaUnited States
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics at the Children’s Hospital of PhiladelphiaPhiladelphiaUnited States
- Penn Center for Musculoskeletal Disorders at the Children’s Hospital of PhiladelphiaPhiladelphiaUnited States
- Perelman School of Medicine, University of PennsylvaniaPhiladelphiaUnited States
- Institute for Regenerative Medicine at University of PennsylvaniaPhiladelphiaUnited States
- RNA Institute at University of PennsylvaniaPhiladelphiaUnited States
| | - Adam Goldfarb
- Department of Pathology, University of VirginiaCharlottesvilleUnited States
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7
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Baratz E, Protchenko O, Jadhav S, Zhang D, Violet PC, Grounds S, Shakoury-Elizeh M, Levine M, Philpott CC. Vitamin E Induces Liver Iron Depletion and Alters Iron Regulation in Mice. J Nutr 2023; 153:1866-1876. [PMID: 37127137 PMCID: PMC10375508 DOI: 10.1016/j.tjnut.2023.04.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 04/14/2023] [Accepted: 04/27/2023] [Indexed: 05/03/2023] Open
Abstract
BACKGROUND Vitamin E (vit E) is an essential nutrient that functions as a lipophilic antioxidant and is used clinically to treat nonalcoholic fatty liver disease, where it suppresses oxidative damage and impedes the progression of steatosis and fibrosis. Mice lacking a critical liver iron-trafficking protein also manifest steatosis because of iron-mediated oxidative damage and are protected from liver disease by oral vit E supplements. OBJECTIVES We aimed to examine the role of dietary vit E supplementation in modulating iron-sensing regulatory systems and nonheme iron levels in mouse liver. METHODS C57Bl/6 male mice, aged 6 wk, were fed purified diets containing normal amounts of iron and either control (45 mg/kg) or elevated (450 mg/kg) levels of 2R-α-tocopherol (vit E) for 18 d. Mouse plasma and liver were analyzed for nonheme iron, levels and activity of iron homeostatic proteins, and markers of oxidative stress. We compared means ± SD for iron and oxidative stress parameters between mice fed the control diet and those fed the vit E diet. RESULTS The Vit E-fed mice exhibited lower levels of liver nonheme iron (38% reduction, P < 0.0001) and ferritin (74% reduction, P < 0.01) than control-fed mice. The levels of liver mRNA for transferrin receptor 1 and divalent metal transporter 1 were reduced to 42% and 57% of the control, respectively. The mRNA levels for targets of nuclear factor erythroid 2-related factor (Nrf2), a major regulator of the oxidative stress response and iron-responsive genes, were also suppressed in vit E livers. Hepcidin, an iron regulatory hormone, levels were lower in the plasma (P < 0.05), and ferroportin (FPN), the iron exporter regulated by hepcidin, was expressed at higher levels in the liver (P < 0.05). CONCLUSIONS Oral vit E supplementation in mice can lead to depletion of liver iron stores by suppressing the iron- and redox-sensing transcription factor Nrf2, leading to enhanced iron efflux through liver FPN. Iron depletion may indirectly enhance the antioxidative effects of vit E.
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Affiliation(s)
- Ethan Baratz
- Genetics and Metabolism Section, NIDDK, NIH, Bethesda, MD, United States
| | - Olga Protchenko
- Genetics and Metabolism Section, NIDDK, NIH, Bethesda, MD, United States
| | | | - Deliang Zhang
- Section on Human Iron Metabolism, NICHD, NIH, Bethesda, MD, United States
| | | | - Samantha Grounds
- Genetics and Metabolism Section, NIDDK, NIH, Bethesda, MD, United States
| | | | - Mark Levine
- Molecular and Clinical Nutrition Section, NIDDK, NIH, Bethesda, MD, United States
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8
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Ginzburg YZ. Hepcidin and its multiple partners: Complex regulation of iron metabolism in health and disease. VITAMINS AND HORMONES 2023; 123:249-284. [PMID: 37717987 DOI: 10.1016/bs.vh.2023.03.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/19/2023]
Abstract
The peptide hormone hepcidin is central to the regulation of iron metabolism, influencing the movement of iron into the circulation and determining total body iron stores. Its effect on a cellular level involves binding ferroportin, the main iron export protein, preventing iron egress and leading to iron sequestration within ferroportin-expressing cells. Hepcidin expression is enhanced by iron loading and inflammation and suppressed by erythropoietic stimulation. Aberrantly increased hepcidin leads to systemic iron deficiency and/or iron restricted erythropoiesis as occurs in anemia of chronic inflammation. Furthermore, insufficiently elevated hepcidin occurs in multiple diseases associated with iron overload such as hereditary hemochromatosis and iron loading anemias. Abnormal iron metabolism as a consequence of hepcidin dysregulation is an underlying factor resulting in pathophysiology of multiple diseases and several agents aimed at manipulating this pathway have been designed, with some already in clinical trials. In this chapter, we assess the complex regulation of hepcidin, delineate the many binding partners involved in its regulation, and present an update on the development of hepcidin agonists and antagonists in various clinical scenarios.
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Affiliation(s)
- Yelena Z Ginzburg
- Tisch Cancer Institute, Division of Hematology and Medical Oncology, Icahn School of Medicine at Mount Sinai, New York, NY, United Sates.
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9
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Handa S, Ginzburg Y, Hoffman R, Kremyanskaya M. Hepcidin mimetics in polycythemia vera: resolving the irony of iron deficiency and erythrocytosis. Curr Opin Hematol 2023; 30:45-52. [PMID: 36728649 PMCID: PMC9908837 DOI: 10.1097/moh.0000000000000747] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
PURPOSE OF REVIEW Development of hepcidin therapeutics has been a ground-breaking discovery in restoring iron homeostasis in several haematological disorders. The hepcidin mimetic, rusfertide, is in late-stage clinical development for treating polycythemia vera patients with a global phase 3 trial [NCT05210790] currently underway. Rusfertide serves as the first possible noncytoreductive therapeutic option to maintain haematocrit control and avoid phlebotomy in polycythemia vera patients. In this comprehensive review, we discuss the pathobiology of dysregulated iron metabolism in polycythemia vera, provide the rationale for targeting the hepcidin-ferroportin axis and elaborate on the preclinical and clinical trial evidence supporting the role of hepcidin mimetics in polycythemia vera. RECENT FINDINGS Recently, updated results from two phase 2 clinical trials [NCT04057040 & NCT04767802] of rusfertide (PTG300) demonstrate that the drug is highly effective in eliminating the need for therapeutic phlebotomies, normalizing haematological parameters, repleting iron stores and relieving constitutional symptoms in patients with polycythemia vera. In light of these findings, additional hepcidin mimetic agents are also being evaluated in polycythemia vera patients. SUMMARY Hepcidin agonists essentially serve as a 'chemical phlebotomy' and are poised to vastly improve the quality of life for phlebotomy requiring polycythemia vera patients.
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Affiliation(s)
- Shivani Handa
- Tisch Cancer Institute, Division of Hematology-Oncology, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Yelena Ginzburg
- Tisch Cancer Institute, Division of Hematology-Oncology, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Ronald Hoffman
- Tisch Cancer Institute, Division of Hematology-Oncology, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Marina Kremyanskaya
- Tisch Cancer Institute, Division of Hematology-Oncology, Icahn School of Medicine at Mount Sinai, New York, NY
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10
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Jadhav S, Protchenko O, Li F, Baratz E, Shakoury-Elizeh M, Maschek A, Cox J, Philpott CC. Mitochondrial dysfunction in mouse livers depleted of iron chaperone PCBP1. Free Radic Biol Med 2021; 175:18-27. [PMID: 34455040 PMCID: PMC9137418 DOI: 10.1016/j.freeradbiomed.2021.08.232] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 08/05/2021] [Accepted: 08/25/2021] [Indexed: 12/20/2022]
Abstract
Iron is an essential nutrient that forms cofactors required for the activity of hundreds of cellular proteins. However, iron can be toxic and must be precisely managed. Poly r(C) binding protein 1 (PCBP1) is an essential, multifunctional protein that binds both iron and nucleic acids, regulating the fate of both. As an iron chaperone, PCBP1 binds cytosolic iron and delivers it to iron enzymes for activation and to ferritin for storage. Mice deleted for PCBP1 in the liver exhibit dysregulated iron balance, with lower levels of liver iron stores and iron enzymes, but higher levels of chemically-reactive iron. Unchaperoned iron triggers the formation of reactive oxygen species, leading to lipid peroxidation and ferroptotic cell death. Hepatic PCBP1 deletion produces chronic liver disease in mice, with steatosis, triglyceride accumulation, and elevated plasma ALT levels. Human and mouse models of fatty liver disease are associated with mitochondrial dysfunction. Here we show that, although deletion of PCBP1 does not affect mitochondrial iron balance, it does affect mitochondrial function. PCBP1 deletion affected mitochondrial morphology and reduced levels of respiratory complexes II and IV, oxygen consumption, and ATP production. Depletion of mitochondrial lipids cardiolipin and coenzyme Q, along with reduction of mitochondrial oxygen consumption, were the first manifestations of mitochondrial dysfunction. Although dietary supplementation with vitamin E ameliorated the liver disease in mice with hepatic PCBP1 deletion, supplementation with coenzyme Q was required to fully restore mitochondrial lipids and function. In conclusion, our studies indicate that mitochondrial function can be restored in livers subjected to ongoing oxidative damage from unchaperoned iron by supplementation with coenzyme Q, a mitochondrial lipid essential for respiration that also functions as a lipophilic radical-trapping agent.
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Affiliation(s)
| | - Olga Protchenko
- Genetics and Metabolism Section, NIDDK, NIH, Bethesda, MD, USA
| | - Fengmin Li
- Genetics and Metabolism Section, NIDDK, NIH, Bethesda, MD, USA
| | - Ethan Baratz
- Genetics and Metabolism Section, NIDDK, NIH, Bethesda, MD, USA
| | | | - Alan Maschek
- Dept. of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - James Cox
- Dept. of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
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11
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Colucci S, Marques O, Altamura S. 20 years of Hepcidin: How far we have come. Semin Hematol 2021; 58:132-144. [PMID: 34389105 DOI: 10.1053/j.seminhematol.2021.05.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 05/12/2021] [Accepted: 05/31/2021] [Indexed: 12/20/2022]
Abstract
Twenty years ago the discovery of hepcidin deeply changed our understanding of the regulation of systemic iron homeostasis. It is now clear that hepcidin orchestrates systemic iron levels by controlling the amount of iron exported into the bloodstream through ferroportin. Hepcidin expression is increased in situations where systemic iron levels should be reduced, such as in iron overload and infection. Conversely, hepcidin is repressed during iron deficiency, hypoxia or expanded erythropoiesis, to increase systemic iron availability and sustain erythropoiesis. In this review, we will focus on molecular mechanisms of hepcidin regulation and on the pathological consequences of their disruption.
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Affiliation(s)
- Silvia Colucci
- Department of Pediatric Hematology, Oncology and Immunology - University of Heidelberg, Heidelberg, Germany.; Molecular Medicine Partnership Unit, EMBL and University of Heidelberg, Heidelberg, Germany
| | - Oriana Marques
- Department of Pediatric Hematology, Oncology and Immunology - University of Heidelberg, Heidelberg, Germany.; Molecular Medicine Partnership Unit, EMBL and University of Heidelberg, Heidelberg, Germany
| | - Sandro Altamura
- Department of Pediatric Hematology, Oncology and Immunology - University of Heidelberg, Heidelberg, Germany.; Molecular Medicine Partnership Unit, EMBL and University of Heidelberg, Heidelberg, Germany..
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12
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Bloomer SA, Brown KE. Hepcidin and Iron Metabolism in Experimental Liver Injury. THE AMERICAN JOURNAL OF PATHOLOGY 2021; 191:1165-1179. [PMID: 33891874 DOI: 10.1016/j.ajpath.2021.04.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 02/25/2021] [Accepted: 04/06/2021] [Indexed: 11/18/2022]
Abstract
The liver plays a pivotal role in the regulation of iron metabolism through its ability to sense and respond to iron stores by release of the hormone hepcidin. Under physiologic conditions, regulation of hepcidin expression in response to iron status maintains iron homeostasis. In response to tissue injury, hepcidin expression can be modulated by other factors, such as inflammation and oxidative stress. The resulting dysregulation of hepcidin is proposed to account for alterations in iron homeostasis that are sometimes observed in patients with liver disease. This review describes the effects of experimental forms of liver injury on iron metabolism and hepcidin expression. In general, models of acute liver injury demonstrate increases in hepcidin mRNA and hypoferremia, consistent with hepcidin's role as an acute-phase reactant. Conversely, diverse models of chronic liver injury are associated with decreased hepcidin mRNA but with variable effects on iron status. Elucidating the reasons for the disparate impact of different chronic injuries on iron metabolism is an important research priority, as is a deeper understanding of the interplay among various stimuli, both positive and negative, on hepcidin regulation. Future studies should provide a clearer picture of how dysregulation of hepcidin expression and altered iron homeostasis impact the progression of liver diseases and whether they are a cause or consequence of these pathologies.
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Affiliation(s)
- Steven A Bloomer
- Division of Science and Engineering, Penn State Abington, Abington, Pennsylvania
| | - Kyle E Brown
- Iowa City Veterans Administration Medical Center, Iowa City, Iowa; Division of Gastroenterology-Hepatology, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa; Program in Free Radical and Radiation Biology, Department of Radiation Oncology, University of Iowa Carver College of Medicine, Iowa City, Iowa.
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13
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Urrutia PJ, Bórquez DA, Núñez MT. Inflaming the Brain with Iron. Antioxidants (Basel) 2021; 10:antiox10010061. [PMID: 33419006 PMCID: PMC7825317 DOI: 10.3390/antiox10010061] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 12/31/2020] [Accepted: 12/31/2020] [Indexed: 02/06/2023] Open
Abstract
Iron accumulation and neuroinflammation are pathological conditions found in several neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD). Iron and inflammation are intertwined in a bidirectional relationship, where iron modifies the inflammatory phenotype of microglia and infiltrating macrophages, and in turn, these cells secrete diffusible mediators that reshape neuronal iron homeostasis and regulate iron entry into the brain. Secreted inflammatory mediators include cytokines and reactive oxygen/nitrogen species (ROS/RNS), notably hepcidin and nitric oxide (·NO). Hepcidin is a small cationic peptide with a central role in regulating systemic iron homeostasis. Also present in the cerebrospinal fluid (CSF), hepcidin can reduce iron export from neurons and decreases iron entry through the blood-brain barrier (BBB) by binding to the iron exporter ferroportin 1 (Fpn1). Likewise, ·NO selectively converts cytosolic aconitase (c-aconitase) into the iron regulatory protein 1 (IRP1), which regulates cellular iron homeostasis through its binding to iron response elements (IRE) located in the mRNAs of iron-related proteins. Nitric oxide-activated IRP1 can impair cellular iron homeostasis during neuroinflammation, triggering iron accumulation, especially in the mitochondria, leading to neuronal death. In this review, we will summarize findings that connect neuroinflammation and iron accumulation, which support their causal association in the neurodegenerative processes observed in AD and PD.
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Affiliation(s)
- Pamela J. Urrutia
- Department of Biology, Faculty of Sciences, Universidad de Chile, 7800024 Santiago, Chile;
| | - Daniel A. Bórquez
- Center for Biomedical Research, Faculty of Medicine, Universidad Diego Portales, 8370007 Santiago, Chile;
| | - Marco Tulio Núñez
- Department of Biology, Faculty of Sciences, Universidad de Chile, 7800024 Santiago, Chile;
- Correspondence: ; Tel.: +56-2-29787360
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14
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Mleczko‐Sanecka K, Silvestri L. Cell-type-specific insights into iron regulatory processes. Am J Hematol 2021; 96:110-127. [PMID: 32945012 DOI: 10.1002/ajh.26001] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 08/20/2020] [Accepted: 09/14/2020] [Indexed: 12/16/2022]
Abstract
Despite its essential role in many biological processes, iron is toxic when in excess due to its propensity to generate reactive oxygen species. To prevent diseases associated with iron deficiency or iron loading, iron homeostasis must be tightly controlled. Intracellular iron content is regulated by the Iron Regulatory Element-Iron Regulatory Protein (IRE-IRP) system, whereas systemic iron availability is adjusted to body iron needs chiefly by the hepcidin-ferroportin (FPN) axis. Here, we aimed to review advances in the field that shed light on cell-type-specific regulatory mechanisms that control or modify systemic and local iron balance, and how shifts in cellular iron levels may affect specialized cell functions.
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Affiliation(s)
| | - Laura Silvestri
- Regulation of Iron Metabolism Unit, Division of Genetics and Cell Biology IRCCS San Raffaele Scientific Institute Milan Italy
- Vita‐Salute San Raffaele University Milan Italy
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15
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Cheng Z, Yan M, Lu Y, Pan XT. Expression of serum BMP6 and hepcidin in cancer-related anemia. ACTA ACUST UNITED AC 2020; 25:134-138. [PMID: 32153255 DOI: 10.1080/16078454.2020.1738098] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Objective: To study the function of human bone morphogenetic protein-6 (BMP6) and hepcidin in cancer-related anemia.Methods: The levels of Hemoglobin (Hb), serum C-reactive protein (CRP), BMP6, hepcidin and ferritin (SF) were measured in 115 patients with solid tumors, who were divided into elevated CRP group and normal CRP group, and further divided into anemia subgroup and non-anemia subgroup according to the CRP level.Results: The prevalence of anemia was 53.9% in all patients. In the elevated CRP group, the levels of CRP, hepcidin and SF of the anemia subgroup were higher than the non-anemia subgroup (P < 0.05); the BMP6 levels had no difference between the subgroups (P > 0.05). In the normal CRP group, the BMP6 level in the anemia subgroup was higher than the non-anemia subgroup (P < 0.01); the CRP, hepcidin and SF levels showed no difference between the subgroups (P > 0.05). Among the 115 patients, CRP and SF were both positively correlated with hepcidin (P < 0.05), and CRP and hepcidin were negatively correlated with Hb (P < 0.05), while SF had no correlation with Hb (P > 0.05); BMP6 was negatively correlated with Hb (P < 0.05) while had no correlation with CRP, hepcidin and SF (P < 0.05).Conclusions: The occurrence of anemia in patients with elevated CRP is associated with hepcidin over-expression, while in patients with normal CRP is associated with BMP6 over-expression. We speculate BMP6 and hepcidin likely play different roles in the occurrence of cancer-related anemia.
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Affiliation(s)
- Zhen Cheng
- Department of Hematology, Taicang Hospital of Soochow University, Taicang, People's Republic of China
| | - Min Yan
- Department of Hematology, Taicang Hospital of Soochow University, Taicang, People's Republic of China
| | - Ye Lu
- Department of Hematology, Taicang Hospital of Soochow University, Taicang, People's Republic of China
| | - Xiang-Tao Pan
- Department of Hematology, Taicang Hospital of Soochow University, Taicang, People's Republic of China
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16
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Orphan Nuclear Receptor ERRγ Is a Novel Transcriptional Regulator of IL-6 Mediated Hepatic BMP6 Gene Expression in Mice. Int J Mol Sci 2020; 21:ijms21197148. [PMID: 32998264 PMCID: PMC7582774 DOI: 10.3390/ijms21197148] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 09/24/2020] [Accepted: 09/24/2020] [Indexed: 12/23/2022] Open
Abstract
Bone morphogenetic protein 6 (BMP6) is a multifunctional growth factor involved in organ development and homeostasis. BMP6 controls expression of the liver hormone, hepcidin, and thereby plays a crucial role in regulating iron homeostasis. BMP6 gene transcriptional regulation in liver is largely unknown, but would be of great help to externally modulate iron load in pathologic conditions. Here, we describe a detailed molecular mechanism of hepatic BMP6 gene expression by an orphan nuclear receptor, estrogen-related receptor γ (ERRγ), in response to the pro-inflammatory cytokine interleukin 6 (IL-6). Recombinant IL-6 treatment increases hepatic ERRγ and BMP6 expression. Overexpression of ERRγ is sufficient to increase BMP6 gene expression in hepatocytes, suggesting that IL-6 is upstream of ERRγ. In line, knock-down of ERRγ in cell lines or a hepatocyte specific knock-out of ERRγ in mice significantly decreases IL-6 mediated BMP6 expression. Promoter studies show that ERRγ directly binds to the ERR response element (ERRE) in the mouse BMP6 gene promoter and positively regulates BMP6 gene transcription in IL-6 treatment conditions, which is further confirmed by ERRE mutated mBMP6-luciferase reporter assays. Finally, an inverse agonist of ERRγ, GSK5182, markedly inhibits IL-6 induced hepatic BMP6 expression in vitro and in vivo. Taken together, these results reveal a novel molecular mechanism on ERRγ mediated transcriptional regulation of hepatic BMP6 gene expression in response to IL-6.
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17
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A Short Review of Iron Metabolism and Pathophysiology of Iron Disorders. MEDICINES 2019; 6:medicines6030085. [PMID: 31387234 PMCID: PMC6789448 DOI: 10.3390/medicines6030085] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 08/01/2019] [Accepted: 08/02/2019] [Indexed: 12/11/2022]
Abstract
Iron is a vital trace element for humans, as it plays a crucial role in oxygen transport, oxidative metabolism, cellular proliferation, and many catalytic reactions. To be beneficial, the amount of iron in the human body needs to be maintained within the ideal range. Iron metabolism is one of the most complex processes involving many organs and tissues, the interaction of which is critical for iron homeostasis. No active mechanism for iron excretion exists. Therefore, the amount of iron absorbed by the intestine is tightly controlled to balance the daily losses. The bone marrow is the prime iron consumer in the body, being the site for erythropoiesis, while the reticuloendothelial system is responsible for iron recycling through erythrocyte phagocytosis. The liver has important synthetic, storing, and regulatory functions in iron homeostasis. Among the numerous proteins involved in iron metabolism, hepcidin is a liver-derived peptide hormone, which is the master regulator of iron metabolism. This hormone acts in many target tissues and regulates systemic iron levels through a negative feedback mechanism. Hepcidin synthesis is controlled by several factors such as iron levels, anaemia, infection, inflammation, and erythropoietic activity. In addition to systemic control, iron balance mechanisms also exist at the cellular level and include the interaction between iron-regulatory proteins and iron-responsive elements. Genetic and acquired diseases of the tissues involved in iron metabolism cause a dysregulation of the iron cycle. Consequently, iron deficiency or excess can result, both of which have detrimental effects on the organism.
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18
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Frýdlová J, Rogalsky DW, Truksa J, Nečas E, Vokurka M, Krijt J. Effect of stimulated erythropoiesis on liver SMAD signaling pathway in iron-overloaded and iron-deficient mice. PLoS One 2019; 14:e0215028. [PMID: 30958854 PMCID: PMC6453526 DOI: 10.1371/journal.pone.0215028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 03/25/2019] [Indexed: 12/21/2022] Open
Abstract
Expression of hepcidin, the hormone regulating iron homeostasis, is increased by iron overload and decreased by accelerated erythropoiesis or iron deficiency. The purpose of the study was to examine the effect of these stimuli, either alone or in combination, on the main signaling pathway controlling hepcidin biosynthesis in the liver, and on the expression of splenic modulators of hepcidin biosynthesis. Liver phosphorylated SMAD 1 and 5 proteins were determined by immunoblotting in male mice treated with iron dextran, kept on an iron deficient diet, or administered recombinant erythropoietin for four consecutive days. Administration of iron increased liver phosphorylated SMAD protein content and hepcidin mRNA content; subsequent administration of erythropoietin significantly decreased both the iron-induced phosphorylated SMAD proteins and hepcidin mRNA. These results are in agreement with the recent observation that erythroferrone binds and inactivates the BMP6 protein. Administration of erythropoietin substantially increased the amount of erythroferrone and transferrin receptor 2 proteins in the spleen; pretreatment with iron did not influence the erythropoietin-induced content of these proteins. Erythropoietin-treated iron-deficient mice displayed smaller spleen size in comparison with erythropoietin-treated mice kept on a control diet. While the erythropoietin-induced increase in splenic erythroferrone protein content was not significantly affected by iron deficiency, the content of transferrin receptor 2 protein was lower in the spleens of erythropoietin-treated mice kept on iron-deficient diet, suggesting posttranscriptional regulation of transferrin receptor 2. Interestingly, iron deficiency and erythropoietin administration had additive effect on hepcidin gene downregulation in the liver. In mice subjected both to iron deficiency and erythropoietin administration, the decrease of hepcidin expression was much more pronounced than the decrease in phosphorylated SMAD protein content or the decrease in the expression of the SMAD target genes Id1 and Smad7. These results suggest the existence of another, SMAD-independent pathway of hepcidin gene downregulation.
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Affiliation(s)
- Jana Frýdlová
- Institute of Pathological Physiology, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Daniel W. Rogalsky
- Institute of Pathological Physiology, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Jaroslav Truksa
- Laboratory of Tumour Resistance, Institute of Biotechnology, BIOCEV Research Center, Czech Academy of Sciences, Vestec, Czech Republic
| | - Emanuel Nečas
- Institute of Pathological Physiology, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Martin Vokurka
- Institute of Pathological Physiology, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Jan Krijt
- Institute of Pathological Physiology, First Faculty of Medicine, Charles University, Prague, Czech Republic
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19
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Abstract
Hepcidin, the main regulator of iron metabolism, is synthesized and released by hepatocytes in response to increased body iron concentration and inflammation. Deregulation of hepcidin expression is a common feature of genetic and acquired iron disorders: in Hereditary Hemochromatosis (HH) and iron-loading anemias low hepcidin causes iron overload, while in Iron Refractory Iron Deficiency Anemia (IRIDA) and anemia of inflammation (AI), high hepcidin levels induce iron-restricted erythropoiesis. Hepcidin expression in the liver is mainly controlled by the BMP-SMAD pathway, activated in a paracrine manner by BMP2 and BMP6 produced by liver sinusoidal endothelial cells. The BMP type I receptors ALK2 and ALK3 are responsible for iron-dependent hepcidin upregulation and basal hepcidin expression, respectively. Characterization of animal models with genetic inactivation of the key components of the pathway has suggested the existence of two BMP/SMAD pathway branches: the first ALK3 and HH proteins dependent, responsive to BMP2 for basal hepcidin activation, and the second ALK2 dependent, activated by BMP6 in response to increased tissue iron. The erythroid inhibitor of hepcidin Erythroferrone also impacts on the liver BMP-SMAD pathway although its effect is blunted by pathway hyper-activation. The liver BMP-SMAD pathway is required also in inflammation to cooperate with JAK2/STAT3 signaling for full hepcidin activation. Pharmacologic targeting of BMP-SMAD pathway components or regulators may improve the outcome of both genetic and acquired disorders of iron overload and deficiency by increasing or inhibiting hepcidin expression.
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20
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Abstract
Hepcidin is central to regulation of iron metabolism. Its effect on a cellular level involves binding ferroportin, the main iron export protein, resulting in its internalization and degradation and leading to iron sequestration within ferroportin-expressing cells. Aberrantly increased hepcidin leads to systemic iron deficiency and/or iron restricted erythropoiesis. Furthermore, insufficiently elevated hepcidin occurs in multiple diseases associated with iron overload. Abnormal iron metabolism as a consequence of hepcidin dysregulation is an underlying factor resulting in pathophysiology of multiple diseases and several agents aimed at manipulating this pathway have been designed, with some already in clinical trials. In this chapter, we present an overview of and rationale for exploring the development of hepcidin agonists and antagonists in various clinical scenarios.
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Affiliation(s)
- Yelena Z Ginzburg
- Tisch Cancer Institute, Division of Hematology and Medical Oncology, Icahn School of Medicine at Mount Sinai, New York, NY, United States.
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21
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Abstract
Since its discovery in 2001, there have been a number of important discoveries and findings that have increased our knowledge about the functioning of hepcidin. Hepcidin, the master iron regulator has been shown to be regulated by a number of physiological stimuli and their associated signaling pathways. This chapter will summarize our current understanding of how these physiological stimuli and downstream signaling molecules are involved in hepcidin modulation and ultimately contribute to the regulation of systemic or local iron homeostasis. The signaling pathways and molecules described here have been shown to primarily affect hepcidin at a transcriptional level, but these transcriptional changes correlate with changes in systemic iron levels as well, supporting the functional effects of hepcidin regulation by these signaling pathways.
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Affiliation(s)
- Gautam Rishi
- The Liver Disease and Iron Disorders Research Group, Institute of Health and Biomedical Innovation and School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD, Australia
| | - V Nathan Subramaniam
- The Liver Disease and Iron Disorders Research Group, Institute of Health and Biomedical Innovation and School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD, Australia.
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22
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Abstract
Iron, an essential nutrient, is required for many biological processes but is also toxic in excess. The lack of a mechanism to excrete excess iron makes it crucial for the body to regulate the amount of iron absorbed from the diet. This regulation is mediated by the hepatic hormone hepcidin. Hepcidin also controls iron release from macrophages that recycle iron and from hepatocytes that store iron. Hepcidin binds to the only known iron export protein, ferroportin, inducing its internalization and degradation and thus limiting the amount of iron released into the plasma. Important regulators of hepcidin, and therefore of systemic iron homeostasis, include plasma iron concentrations, body iron stores, infection and inflammation, hypoxia and erythropoiesis, and, to a lesser extent, testosterone. Dysregulation of hepcidin production contributes to the pathogenesis of many iron disorders: hepcidin deficiency causes iron overload in hereditary hemochromatosis and non-transfused β-thalassemia, whereas overproduction of hepcidin is associated with iron-restricted anemias seen in patients with chronic inflammatory diseases and inherited iron-refractory iron-deficiency anemia. The present review summarizes our current understanding of the molecular mechanisms and signaling pathways contributing to hepcidin regulation by these factors and highlights the issues that still need clarification.
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Affiliation(s)
- Marie-Paule Roth
- Institut de Recherche en Santé Digestive (IRSD), Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France.
| | - Delphine Meynard
- Institut de Recherche en Santé Digestive (IRSD), Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France
| | - Hélène Coppin
- Institut de Recherche en Santé Digestive (IRSD), Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France
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23
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Mao P, Wortham AM, Enns CA, Zhang AS. The catalytic, stem, and transmembrane portions of matriptase-2 are required for suppressing the expression of the iron-regulatory hormone hepcidin. J Biol Chem 2018; 294:2060-2073. [PMID: 30559294 DOI: 10.1074/jbc.ra118.006468] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 12/13/2018] [Indexed: 12/21/2022] Open
Abstract
Matriptase-2 (MT2) is a type-II transmembrane, trypsin-like serine protease that is predominantly expressed in the liver. It is a key suppressor for the expression of hepatic hepcidin, an iron-regulatory hormone that is induced via the bone morphogenetic protein signaling pathway. A current model predicts that MT2 suppresses hepcidin expression by cleaving multiple components of the induction pathway. MT2 is synthesized as a zymogen that undergoes autocleavage for activation and shedding. However, the biologically active form of MT2 and, importantly, the contributions of different MT2 domains to its function are largely unknown. Here we examined the activities of truncated MT2 that were generated by site-directed mutagenesis or Gibson assembly master mix, and found that the stem region of MT2 determines the specificity and efficacy for substrate cleavage. The transmembrane domain allowed MT2 activation after reaching the plasma membrane, and the cytoplasmic domain facilitated these processes. Further in vivo rescue studies indicated that the entire extracellular and transmembrane domains of MT2 are required to correct the low-hemoglobin, low-serum iron, and high-hepcidin status in MT2 -/- mice. Unlike in cell lines, no autocleavage of MT2 was detected in vivo in the liver, implying that MT2 may also function independently of its proteolytic activity. In conjunction with our previous studies implicating the cytoplasmic domain as an intracellular iron sensor, these observations reveal the importance of each MT2 domain for MT2-mediated substrate cleavage and for its biological function.
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Affiliation(s)
- Peizhong Mao
- From the Department of Cell, Developmental, and Cancer Biology, Oregon Health & Science University, Portland, Oregon 97239
| | - Aaron M Wortham
- From the Department of Cell, Developmental, and Cancer Biology, Oregon Health & Science University, Portland, Oregon 97239
| | - Caroline A Enns
- From the Department of Cell, Developmental, and Cancer Biology, Oregon Health & Science University, Portland, Oregon 97239
| | - An-Sheng Zhang
- From the Department of Cell, Developmental, and Cancer Biology, Oregon Health & Science University, Portland, Oregon 97239
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24
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Frýdlová J, Rogalsky DW, Truksa J, Traeger L, Steinbicker AU, Vokurka M, Krijt J. Liver HFE protein content is posttranscriptionally decreased in iron-deficient mice and rats. Am J Physiol Gastrointest Liver Physiol 2018; 315:G560-G568. [PMID: 29927322 DOI: 10.1152/ajpgi.00070.2018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Although the relationship between hereditary hemochromatosis and mutations in the HFE gene was discovered more than 20 years ago, information on the in vivo regulation of HFE protein expression is still limited. The purpose of the study was to determine the response of liver HFE protein content to iron deficiency in mice and rats by immunoblotting. Attempts to visualize the HFE protein in whole liver homogenates were unsuccessful; however, HFE could be detected in liver microsomes or in plasma membrane-enriched fractions. Five-week-old male C57BL/6 mice fed an iron-deficient diet for 4 wk presented with a significant decrease in liver iron content and liver Hamp expression, as well as with a significant decrease in liver HFE protein content. Rats fed an iron-deficient diet for 4 wk also displayed significant decrease in liver Hamp expression and liver HFE protein content. These results suggest that the downregulation of HFE-dependent signaling may contribute to decreased Hamp gene expression in states of prolonged iron deficiency. It has recently been proposed that HFE protein could be a potential target of matriptase-2, a hepatocyte protease mutated in iron-refractory iron deficiency anemia. However, immunoblot analysis of HFE protein in the livers from Tmprss6-mutated mask mice did not show evidence of matriptase-2-dependent HFE protein cleavage. In addition, no indication of HFE protein cleavage was seen in iron-deficient rats, whereas the full-length matriptase-2 protein content in the same animals was significantly increased. These results suggest that HFE is probably not a major physiological target of matriptase-2. NEW & NOTEWORTHY Feeding of iron-deficient diet for 4 wk decreased liver HFE protein content in both mice and rats, suggesting that decreased HFE-dependent signaling may contribute to hepcidin downregulation in iron deficiency. There was no difference in HFE protein band appearance between matriptase-2-mutated mask mice and wild-type mice, indicating that HFE is probably not a major physiological substrate of matriptase-2-mediated protease activity in vivo.
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Affiliation(s)
- Jana Frýdlová
- Institute of Pathological Physiology, First Faculty of Medicine, Charles University , Prague , Czech Republic
| | - Daniel W Rogalsky
- Institute of Pathological Physiology, First Faculty of Medicine, Charles University , Prague , Czech Republic
| | - Jaroslav Truksa
- Laboratory of Tumour Resistance, Institute of Biotechnology, Biotechnology and Biomedicine Center of the Academy of Sciences and Charles University in Vestec Research Center, Czech Academy of Sciences, Vestec, Czech Republic
| | - Lisa Traeger
- Department of Anesthesiology, Intensive Care, and Pain Medicine, University Hospital Muenster, Muenster University , Muenster , Germany
| | - Andrea U Steinbicker
- Department of Anesthesiology, Intensive Care, and Pain Medicine, University Hospital Muenster, Muenster University , Muenster , Germany
| | - Martin Vokurka
- Institute of Pathological Physiology, First Faculty of Medicine, Charles University , Prague , Czech Republic
| | - Jan Krijt
- Institute of Pathological Physiology, First Faculty of Medicine, Charles University , Prague , Czech Republic
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25
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Camaschella C, Pagani A. Advances in understanding iron metabolism and its crosstalk with erythropoiesis. Br J Haematol 2018; 182:481-494. [PMID: 29938779 DOI: 10.1111/bjh.15403] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Recent years have witnessed impressive advances in our understanding of iron metabolism. A number of studies of iron disorders and of their animal models have provided landmark insights into the mechanisms of iron trafficking, distribution and homeostatic regulation, the latter essential to prevent both iron deficiency and iron excess. Our perception of iron metabolism has been completely changed by an improved definition of cellular and systemic iron homeostasis, of the molecular pathogenesis of iron disorders, the fine tuning of the iron hormone hepcidin by activators and inhibitors and the dissection of the components of the hepcidin regulatory pathway. Important for haematology, the crosstalk of erythropoiesis, the most important iron consumer, and the hepcidin pathway has been at least partially clarified. Novel potential biomarkers are available and novel therapeutic targets for iron-related disorders have been tested in murine models. These preclinical studies provided proofs of principle and are laying the ground for clinical trials. Understanding iron control in tissues other than erythropoiesis remains a challenge for the future.
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Affiliation(s)
- Clara Camaschella
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute and Vita Salute University, Milano, Italy
| | - Alessia Pagani
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute and Vita Salute University, Milano, Italy
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26
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Mirciov CSG, Wilkins SJ, Hung GCC, Helman SL, Anderson GJ, Frazer DM. Circulating iron levels influence the regulation of hepcidin following stimulated erythropoiesis. Haematologica 2018; 103:1616-1626. [PMID: 29903760 PMCID: PMC6165793 DOI: 10.3324/haematol.2017.187245] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 06/11/2018] [Indexed: 01/01/2023] Open
Abstract
The stimulation of erythrocyte formation increases the demand for iron by the bone marrow and this in turn may affect the levels of circulating diferric transferrin. As this molecule influences the production of the iron regulatory hormone hepcidin, we hypothesized that erythropoiesis-driven changes in diferric transferrin levels could contribute to the decrease in hepcidin observed following the administration of erythropoietin. To examine this, we treated mice with erythropoietin and examined diferric transferrin at various time points up to 18 hours. We also investigated the effect of altering diferric transferrin levels on erythropoietin-induced inhibition of Hamp1, the gene encoding hepcidin. We detected a decrease in diferric transferrin levels 5 hours after erythropoietin injection and prior to any inhibition of the hepatic Hamp1 message. Diferric transferrin returned to control levels 12 hours after erythropoietin injection and had increased beyond control levels by 18 hours. Increasing diferric transferrin levels via intravenous iron injection prevented the inhibition of Hamp1 expression by erythropoietin without altering hepatic iron concentration or the expression of Erfe, the gene encoding erythroferrone. These results suggest that diferric transferrin likely contributes to the inhibition of hepcidin production in the period shortly after injection of erythropoietin and that, under the conditions examined, increasing diferric transferrin levels can overcome the inhibitory effect of erythroferrone on hepcidin production. They also imply that the decrease in Hamp1 expression in response to an erythropoietic stimulus is likely to be mediated by multiple signals.
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Affiliation(s)
- Cornel S G Mirciov
- Iron Metabolism Laboratory, QIMR Berghofer Medical Research Institute, Herston, Australia.,School of Medicine, The University of Queensland, St Lucia, Australia
| | - Sarah J Wilkins
- Iron Metabolism Laboratory, QIMR Berghofer Medical Research Institute, Herston, Australia
| | - Grace C C Hung
- Iron Metabolism Laboratory, QIMR Berghofer Medical Research Institute, Herston, Australia
| | - Sheridan L Helman
- Iron Metabolism Laboratory, QIMR Berghofer Medical Research Institute, Herston, Australia.,School of Biomedical Sciences, Queensland University of Technology, Gardens Point, Australia
| | - Gregory J Anderson
- Iron Metabolism Laboratory, QIMR Berghofer Medical Research Institute, Herston, Australia.,School of Medicine, The University of Queensland, St Lucia, Australia.,School of Chemistry and Molecular Bioscience, The University of Queensland, St Lucia, Australia
| | - David M Frazer
- Iron Metabolism Laboratory, QIMR Berghofer Medical Research Institute, Herston, Australia .,School of Medicine, The University of Queensland, St Lucia, Australia
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Rishi G, Subramaniam VN. The liver in regulation of iron homeostasis. Am J Physiol Gastrointest Liver Physiol 2017; 313:G157-G165. [PMID: 28596277 DOI: 10.1152/ajpgi.00004.2017] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 05/31/2017] [Accepted: 05/31/2017] [Indexed: 01/31/2023]
Abstract
The liver is one of the largest and most functionally diverse organs in the human body. In addition to roles in detoxification of xenobiotics, digestion, synthesis of important plasma proteins, gluconeogenesis, lipid metabolism, and storage, the liver also plays a significant role in iron homeostasis. Apart from being the storage site for excess body iron, it also plays a vital role in regulating the amount of iron released into the blood by enterocytes and macrophages. Since iron is essential for many important physiological and molecular processes, it increases the importance of liver in the proper functioning of the body's metabolism. This hepatic iron-regulatory function can be attributed to the expression of many liver-specific or liver-enriched proteins, all of which play an important role in the regulation of iron homeostasis. This review focuses on these proteins and their known roles in the regulation of body iron metabolism.
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Affiliation(s)
- Gautam Rishi
- Liver Disease and Iron Disorders Research Group, Institute of Health and Biomedical Innovation and School of Biomedical Sciences, Queensland University of Technology, Brisbane, Australia
| | - V Nathan Subramaniam
- Liver Disease and Iron Disorders Research Group, Institute of Health and Biomedical Innovation and School of Biomedical Sciences, Queensland University of Technology, Brisbane, Australia
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Abstract
The regulation of iron metabolism in biological systems centers on providing adequate iron for cellular function while limiting iron toxicity. Because mammals cannot excrete iron, mechanisms have evolved to control iron acquisition, storage, and distribution at both systemic and cellular levels. Hepcidin, the master regulator of iron homeostasis, controls iron flows into plasma through inhibition of the only known mammalian cellular iron exporter ferroportin. Hepcidin is feedback-regulated by iron status and strongly modulated by inflammation and erythropoietic demand. This review highlights recent advances that have changed our understanding of iron metabolism and its regulation.
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Affiliation(s)
- Richard Coffey
- Departments of Medicine and Pathology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-1690
| | - Tomas Ganz
- Departments of Medicine and Pathology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-1690.
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Bone morphogenetic protein-binding endothelial regulator of liver sinusoidal endothelial cells induces iron overload in a fatty liver mouse model. J Gastroenterol 2017; 52:341-351. [PMID: 27364348 PMCID: PMC5323480 DOI: 10.1007/s00535-016-1237-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Accepted: 06/19/2016] [Indexed: 02/06/2023]
Abstract
BACKGROUND Non-alcoholic fatty liver disease (NAFLD) is frequently accompanied by iron overload. However, because of the complex hepcidin-regulating molecules, the molecular mechanism underlying iron overload remains unknown. To identify the key molecule involved in NAFLD-associated iron dysregulation, we performed whole-RNA sequencing on the livers of obese mice. METHODS Male C57BL/6 mice were fed a regular or high-fat diet for 16 or 48 weeks. Internal iron was evaluated by plasma iron, ferritin or hepatic iron content. Whole-RNA sequencing was performed by transcriptome analysis using semiconductor high-throughput sequencer. Mouse liver tissues or isolated hepatocytes and sinusoidal endothelial cells were used to assess the expression of iron-regulating molecules. RESULTS Mice fed a high-fat diet for 16 weeks showed excess iron accumulation. Longer exposure to a high-fat diet increased hepatic fibrosis and intrahepatic iron accumulation. A pathway analysis of the sequencing data showed that several inflammatory pathways, including bone morphogenetic protein (BMP)-SMAD signaling, were significantly affected. Sequencing analysis showed 2314 altered genes, including decreased mRNA expression of the hepcidin-coding gene Hamp. Hepcidin protein expression and SMAD phosphorylation, which induces Hamp, were found to be reduced. The expression of BMP-binding endothelial regulator (BMPER), which inhibits BMP-SMAD signaling by binding BMP extracellularly, was up-regulated in fatty livers. In addition, immunohistochemical and cell isolation analyses showed that BMPER was primarily expressed in the liver sinusoidal endothelial cells (LSECs) rather than hepatocytes. CONCLUSIONS BMPER secretion by LSECs inhibits BMP-SMAD signaling in hepatocytes and further reduces hepcidin protein expression. These intrahepatic molecular interactions suggest a novel molecular basis of iron overload in NAFLD.
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Abstract
Iron is required for many biological processes but is also toxic in excess; thus, body iron balance is maintained through sophisticated regulatory mechanisms. The lack of a regulated iron excretory mechanism means that body iron balance is controlled at the level of absorption from the diet. Iron absorption is regulated by the hepatic peptide hormone hepcidin. Hepcidin also controls iron release from cells that recycle or store iron, thus regulating plasma iron concentrations. Hepcidin exerts its effects through its receptor, the cellular iron exporter ferroportin. Important regulators of hepcidin, and therefore of systemic iron homeostasis, include plasma iron concentrations, body iron stores, infection and inflammation, and erythropoiesis. Disturbances in the regulation of hepcidin contribute to the pathogenesis of many iron disorders: hepcidin deficiency causes iron overload in hereditary hemochromatosis and nontransfused β-thalassemia, whereas overproduction of hepcidin is associated with iron-restricted anemias seen in patients with chronic kidney disease, chronic inflammatory diseases, some cancers, and inherited iron-refractory iron deficiency anemia. This review summarizes our current understanding of the molecular mechanisms and signaling pathways involved in the control of hepcidin synthesis in the liver, a principal determinant of plasma hepcidin concentrations.
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Affiliation(s)
- Veena Sangkhae
- Center for Iron Disorders, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Elizabeta Nemeth
- Center for Iron Disorders, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
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32
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Endothelial cells produce bone morphogenetic protein 6 required for iron homeostasis in mice. Blood 2016; 129:405-414. [PMID: 27864295 DOI: 10.1182/blood-2016-06-721571] [Citation(s) in RCA: 153] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 11/14/2016] [Indexed: 02/06/2023] Open
Abstract
Bone morphogenetic protein 6 (BMP6) signaling in hepatocytes is a central transcriptional regulator of the iron hormone hepcidin that controls systemic iron balance. How iron levels are sensed to regulate hepcidin production is not known, but local induction of liver BMP6 expression by iron is proposed to have a critical role. To identify the cellular source of BMP6 responsible for hepcidin and iron homeostasis regulation, we generated mice with tissue-specific ablation of Bmp6 in different liver cell populations and evaluated their iron phenotype. Efficiency and specificity of Cre-mediated recombination was assessed by using Cre-reporter mice, polymerase chain reaction of genomic DNA, and quantitation of Bmp6 messenger RNA expression from isolated liver cell populations. Localization of the BMP co-receptor hemojuvelin was visualized by immunofluorescence microscopy. Analysis of the Bmp6 conditional knockout mice revealed that liver endothelial cells (ECs) expressed Bmp6, whereas resident liver macrophages (Kupffer cells) and hepatocytes did not. Loss of Bmp6 in ECs recapitulated the hemochromatosis phenotype of global Bmp6 knockout mice, whereas hepatocyte and macrophage Bmp6 conditional knockout mice exhibited no iron phenotype. Hemojuvelin was localized on the hepatocyte sinusoidal membrane immediately adjacent to Bmp6-producing sinusoidal ECs. Together, these data demonstrate that ECs are the predominant source of BMP6 in the liver and support a model in which EC BMP6 has paracrine actions on hepatocyte hemojuvelin to regulate hepcidin transcription and maintain systemic iron homeostasis.
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Kim DK, Kim YH, Jung YS, Kim KS, Jeong JH, Lee YS, Yuk JM, Oh BC, Choy HE, Dooley S, Muckenthaler MU, Lee CH, Choi HS. Orphan nuclear receptor SHP regulates iron metabolism through inhibition of BMP6-mediated hepcidin expression. Sci Rep 2016; 6:34630. [PMID: 27688041 PMCID: PMC5043349 DOI: 10.1038/srep34630] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 09/12/2016] [Indexed: 02/08/2023] Open
Abstract
Small heterodimer partner (SHP) is a transcriptional corepressor regulating diverse metabolic processes. Here, we show that SHP acts as an intrinsic negative regulator of iron homeostasis. SHP-deficient mice maintained on a high-iron diet showed increased serum hepcidin levels, decreased expression of the iron exporter ferroportin as well as iron accumulation compared to WT mice. Conversely, overexpression of either SHP or AMP-activated protein kinase (AMPK), a metabolic sensor inducing SHP expression, suppressed BMP6-induced hepcidin expression. In addition, an inhibitory effect of AMPK activators metformin and AICAR on BMP6-mediated hepcidin gene expression was significantly attenuated by ablation of SHP expression. Interestingly, SHP physically interacted with SMAD1 and suppressed BMP6-mediated recruitment of the SMAD complex to the hepcidin gene promoter by inhibiting the formation of SMAD1 and SMAD4 complex. Finally, overexpression of SHP and metformin treatment of BMP6 stimulated mice substantially restored hepcidin expression and serum iron to baseline levels. These results reveal a previously unrecognized role for SHP in the transcriptional control of iron homeostasis.
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Affiliation(s)
- Don-Kyu Kim
- National Creative Research Initiatives Center for Nuclear Receptor Signals and Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
| | - Yong-Hoon Kim
- Korea Research Institute of Bioscience and Biotechnology, University of Science and Technology (UST), Yuseong-gu, Daejeon, Republic of Korea
| | - Yoon Seok Jung
- National Creative Research Initiatives Center for Nuclear Receptor Signals and Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
| | - Ki-Sun Kim
- National Creative Research Initiatives Center for Nuclear Receptor Signals and Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
| | - Jae-Ho Jeong
- Department of Microbiology, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Yong-Soo Lee
- National Creative Research Initiatives Center for Nuclear Receptor Signals and Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
| | - Jae-Min Yuk
- Department of Medical Science and Infection Biology, Chungnam National University School of Medicine, Daegeon, Republic of Korea
| | - Byung-Chul Oh
- Lee Gil Ya Cancer and Diabetes Institute, Gachon University Graduate School of Medicine, Incheon, Republic of Korea
| | - Hyon E Choy
- Department of Microbiology, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Steven Dooley
- Department of Medicine II, Section Molecular Hepatology, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Martina U Muckenthaler
- Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg, Heidelberg, Germany.,Molecular Medicine Partnership Unit, University of Heidelberg, Heidelberg, Germany
| | - Chul-Ho Lee
- Korea Research Institute of Bioscience and Biotechnology, University of Science and Technology (UST), Yuseong-gu, Daejeon, Republic of Korea
| | - Hueng-Sik Choi
- National Creative Research Initiatives Center for Nuclear Receptor Signals and Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
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34
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Iron deficiency or anemia of inflammation? : Differential diagnosis and mechanisms of anemia of inflammation. Wien Med Wochenschr 2016; 166:411-423. [PMID: 27557596 PMCID: PMC5065583 DOI: 10.1007/s10354-016-0505-7] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 05/30/2016] [Indexed: 02/08/2023]
Abstract
Iron deficiency and immune activation are the two most frequent causes of anemia, both of which are based on disturbances of iron homeostasis. Iron deficiency anemia results from a reduction of the body’s iron content due to blood loss, inadequate dietary iron intake, its malabsorption, or increased iron demand. Immune activation drives a diversion of iron fluxes from the erythropoietic bone marrow, where hemoglobinization takes place, to storage sites, particularly the mononuclear phagocytes system in liver and spleen. This results in iron-limited erythropoiesis and anemia. This review summarizes current diagnostic and pathophysiological concepts of iron deficiency anemia and anemia of inflammation, as well as combined conditions, and provides a brief outlook on novel therapeutic options.
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35
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Chung H, Wu D, Smith D, Meydani SN, Han SN. Lower hepatic iron storage associated with obesity in mice can be restored by decreasing body fat mass through feeding a low-fat diet. Nutr Res 2016; 36:955-963. [PMID: 27632915 DOI: 10.1016/j.nutres.2016.06.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 04/29/2016] [Accepted: 06/01/2016] [Indexed: 12/20/2022]
Abstract
High-fat diet (HFD)-induced obesity has been reported to result in low hepatic iron storage. In the current study, we tested the hypothesis that these obesity-related changes in hepatic iron status could be reversed by decreasing adiposity by feeding a low-fat diet. Five-week-old C57BL/6 mice were assigned to 3 groups: the LL group was fed a control diet for 31 weeks, the HH group was fed a HFD for 31 weeks, and the HL group was fed the HFD for 15 weeks and then switched to the control diet for 16 weeks. The fat mass of the HL group decreased by 3.2 g from the 14th to the 30th weeks. Fat mass was significantly different among the groups (11.4, 15.8, and 37.5 g in the LL, HH, and HL groups, respectively; P< .001). The liver iron concentration of the HL group was similar to that of the LL group, which was about 30% higher than that of the HH group (74.2, 72.7, and 55.7 μg/g in the LL, HL, and HH groups, respectively; P< .05). Duodenal cytochrome b messenger RNA (mRNA) levels were higher in the HL group than in the HH group. Although bone morphogenetic protein 6 (Bmp6) mRNA levels showed no significant differences in the liver, duodenal Bmp6 mRNA levels were significantly lower in the HH group compared with the LL and HL groups. Liver Smad1/5 proteins were differentially activated: the HH group had significantly less phosphorylated Smads than did the LL and HL groups. Our data demonstrate that hepatic iron storage levels are closely related to body adiposity, and reducing body fat mass through feeding a lower-fat diet to HFD-induced obese mice restores liver iron storage.
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Affiliation(s)
- Hak Chung
- Department of Food and Nutrition, College of Human Ecology, Seoul National University, Seoul, Korea
| | - Dayong Wu
- JM USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA
| | - Donald Smith
- JM USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA
| | - Simin Nikbin Meydani
- JM USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA
| | - Sung Nim Han
- Department of Food and Nutrition, College of Human Ecology, Seoul National University, Seoul, Korea; Research Institute of Human Ecology, College of Human Ecology, Seoul National University, Seoul, Korea.
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36
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Wallace DF. The Regulation of Iron Absorption and Homeostasis. Clin Biochem Rev 2016; 37:51-62. [PMID: 28303071 PMCID: PMC5198508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Iron is an essential element in biology, required for numerous cellular processes. Either too much or too little iron can be detrimental, and organisms have developed mechanisms for balancing iron within safe limits. In mammals there are no controlled mechanisms for the excretion of excess iron, hence body iron homeostasis is regulated at the sites of absorption, utilisation and recycling. This review will discuss the discoveries that have been made in the past 20 years into advancing our understanding of iron homeostasis and its regulation. The study of iron-associated disorders, such as the iron overload condition hereditary haemochromatosis and various forms of anaemia have been instrumental in increasing our knowledge in this area, as have cellular and animal model studies. The liver has emerged as the major site of systemic iron regulation, being the location where the iron regulatory hormone hepcidin is produced. Hepcidin is a negative regulator of iron absorption and recycling, achieving this by binding to the only known cellular iron exporter ferroportin and causing its internalisation and degradation, thereby reducing iron efflux from target cells and reducing serum iron levels. Much of the research in the iron metabolism field has focussed on the regulation of hepcidin and its interaction with ferroportin. The advances in this area have greatly increased our knowledge of iron metabolism and its regulation and have led to the development of novel diagnostics and therapeutics for iron-associated disorders.
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37
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Kleven MD, Enns CA, Zhang AS. Bone Morphogenetic Protein-6 Mutations Take Their Place in Iron Overload Diseases. Gastroenterology 2016; 150:556-9. [PMID: 26820052 DOI: 10.1053/j.gastro.2016.01.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Mark D Kleven
- Department of Cell, Developmental and Cancer Biology, Oregon Health & Science University, Portland, Oregon
| | - Caroline A Enns
- Department of Cell, Developmental and Cancer Biology, Oregon Health & Science University, Portland, Oregon.
| | - An-Sheng Zhang
- Department of Cell, Developmental and Cancer Biology, Oregon Health & Science University, Portland, Oregon
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Chen H, Choesang T, Li H, Sun S, Pham P, Bao W, Feola M, Westerman M, Li G, Follenzi A, Blanc L, Rivella S, Fleming RE, Ginzburg YZ. Increased hepcidin in transferrin-treated thalassemic mice correlates with increased liver BMP2 expression and decreased hepatocyte ERK activation. Haematologica 2015; 101:297-308. [PMID: 26635037 DOI: 10.3324/haematol.2015.127902] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 12/01/2015] [Indexed: 12/13/2022] Open
Abstract
Iron overload results in significant morbidity and mortality in β-thalassemic patients. Insufficient hepcidin is implicated in parenchymal iron overload in β-thalassemia and approaches to increase hepcidin have therapeutic potential. We have previously shown that exogenous apo-transferrin markedly ameliorates ineffective erythropoiesis and increases hepcidin expression in Hbb(th1/th1) (thalassemic) mice. We utilize in vivo and in vitro systems to investigate effects of exogenous apo-transferrin on Smad and ERK1/2 signaling, pathways that participate in hepcidin regulation. Our results demonstrate that apo-transferrin increases hepcidin expression in vivo despite decreased circulating and parenchymal iron concentrations and unchanged liver Bmp6 mRNA expression in thalassemic mice. Hepatocytes from apo-transferrin-treated mice demonstrate decreased ERK1/2 pathway and increased serum BMP2 concentration and hepatocyte BMP2 expression. Furthermore, hepatocyte ERK1/2 phosphorylation is enhanced by neutralizing anti-BMP2/4 antibodies and suppressed in vitro in a dose-dependent manner by BMP2, resulting in converse effects on hepcidin expression, and hepatocytes treated with MEK/ERK1/2 inhibitor U0126 in combination with BMP2 exhibit an additive increase in hepcidin expression. Lastly, bone marrow erythroferrone expression is normalized in apo-transferrin treated thalassemic mice but increased in apo-transferrin injected wild-type mice. These findings suggest that increased hepcidin expression after exogenous apo-transferrin is in part independent of erythroferrone and support a model in which apo-transferrin treatment in thalassemic mice increases BMP2 expression in the liver and other organs, decreases hepatocellular ERK1/2 activation, and increases nuclear Smad to increase hepcidin expression in hepatocytes.
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Affiliation(s)
- Huiyong Chen
- Erythropoiesis Laboratory, LFKRI, New York Blood Center, NY, USA
| | - Tenzin Choesang
- Erythropoiesis Laboratory, LFKRI, New York Blood Center, NY, USA
| | - Huihui Li
- Erythropoiesis Laboratory, LFKRI, New York Blood Center, NY, USA Central South University, Changsha, PR China
| | - Shuming Sun
- Erythropoiesis Laboratory, LFKRI, New York Blood Center, NY, USA
| | - Petra Pham
- Flow Cytometry Core Laboratory, LFKRI, New York Blood Center, NY, USA
| | - Weili Bao
- Erythropoiesis Laboratory, LFKRI, New York Blood Center, NY, USA
| | - Maria Feola
- Erythropoiesis Laboratory, LFKRI, New York Blood Center, NY, USA University of Piemonte Orientale, Amedeo Avogadro, Novara, Italy
| | | | - Guiyuan Li
- Central South University, Changsha, PR China
| | - Antonia Follenzi
- University of Piemonte Orientale, Amedeo Avogadro, Novara, Italy
| | - Lionel Blanc
- The Feinstein Institute for Medical Research, Manhasset, NY, USA
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Camaschella C, Nai A. Ineffective erythropoiesis and regulation of iron status in iron loading anaemias. Br J Haematol 2015; 172:512-23. [PMID: 26491866 DOI: 10.1111/bjh.13820] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The definition 'iron loading anaemias' encompasses a group of inherited and acquired anaemias characterized by ineffective erythropoiesis, low hepcidin levels, excessive iron absorption and secondary iron overload. Non-transfusion-dependent β-thalassaemia is the paradigmatic example of these conditions that include dyserythropoietic and sideroblastic anaemias and some forms of myelodysplasia. Interrupting the vicious cycle between ineffective erythropoiesis and iron overload may be of therapeutic benefit in all these diseases. Induction of iron restriction by means of transferrin infusions, minihepcidins or manipulation of the hepcidin pathway prevents iron overload, redistributes iron from parenchymal cells to macrophage stores and partially controls anaemia in β-thalassaemic mice. Inhibition of ineffective erythropoiesis by activin ligand traps improves anaemia and iron overload in the same models. Targeting iron loading or ineffective erythropoiesis shows promise in preclinical studies; activin ligand traps are in clinical trials with promising results and may be useful in patients with ineffective erythropoiesis.
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Affiliation(s)
- Clara Camaschella
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Vita Salute University, Milano, Italy
| | - Antonella Nai
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Vita Salute University, Milano, Italy
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40
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Jenkitkasemwong S, Wang CY, Coffey R, Zhang W, Chan A, Biel T, Kim JS, Hojyo S, Fukada T, Knutson MD. SLC39A14 Is Required for the Development of Hepatocellular Iron Overload in Murine Models of Hereditary Hemochromatosis. Cell Metab 2015; 22:138-50. [PMID: 26028554 PMCID: PMC4497937 DOI: 10.1016/j.cmet.2015.05.002] [Citation(s) in RCA: 158] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 03/04/2015] [Accepted: 04/24/2015] [Indexed: 01/07/2023]
Abstract
Nearly all forms of hereditary hemochromatosis are characterized by pathological iron accumulation in the liver, pancreas, and heart. These tissues preferentially load iron because they take up non-transferrin-bound iron (NTBI), which appears in the plasma during iron overload. Yet, how tissues take up NTBI is largely unknown. We report that ablation of Slc39a14, the gene coding for solute carrier SLC39A14 (also called ZIP14), in mice markedly reduced the uptake of plasma NTBI by the liver and pancreas. To test the role of SLC39A14 in tissue iron loading, we crossed Slc39a14(-/-) mice with Hfe(-/-) and Hfe2(-/-) mice, animal models of type 1 and type 2 (juvenile) hemochromatosis, respectively. Slc39a14 deficiency in hemochromatotic mice greatly diminished iron loading of the liver and prevented iron deposition in hepatocytes and pancreatic acinar cells. The data suggest that inhibition of SLC39A14 may mitigate hepatic and pancreatic iron loading and associated pathologies in iron overload disorders.
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Affiliation(s)
- Supak Jenkitkasemwong
- Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611, USA
| | - Chia-Yu Wang
- Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611, USA
| | - Richard Coffey
- Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611, USA
| | - Wei Zhang
- Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611, USA
| | - Alan Chan
- Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611, USA
| | - Thomas Biel
- Department of Surgery, University of Florida, Gainesville, FL 32611, USA
| | - Jae-Sung Kim
- Department of Surgery, University of Florida, Gainesville, FL 32611, USA
| | - Shintaro Hojyo
- RIKEN Center for Integrative Medical Sciences, Yokohama 230-0045, Japan; Deutsches Rheuma-Forschungszentrum Berlin, Osteoimmunology, Charitéplatz, 10117 Berlin, Germany
| | - Toshiyuki Fukada
- RIKEN Center for Integrative Medical Sciences, Yokohama 230-0045, Japan; Division of Pathology, Department of Oral Diagnostic Sciences, School of Dentistry, Showa University, Shinagawa 142-8666, Japan; Molecular and Cellular Physiology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Tokushima 770-8055, Japan
| | - Mitchell D Knutson
- Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611, USA.
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41
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Rausa M, Pagani A, Nai A, Campanella A, Gilberti ME, Apostoli P, Camaschella C, Silvestri L. Bmp6 expression in murine liver non parenchymal cells: a mechanism to control their high iron exporter activity and protect hepatocytes from iron overload? PLoS One 2015; 10:e0122696. [PMID: 25860887 PMCID: PMC4393274 DOI: 10.1371/journal.pone.0122696] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 02/12/2015] [Indexed: 02/06/2023] Open
Abstract
Bmp6 is the main activator of hepcidin, the liver hormone that negatively regulates plasma iron influx by degrading the sole iron exporter ferroportin in enterocytes and macrophages. Bmp6 expression is modulated by iron but the molecular mechanisms are unknown. Although hepcidin is expressed almost exclusively by hepatocytes (HCs), Bmp6 is produced also by non-parenchymal cells (NPCs), mainly sinusoidal endothelial cells (LSECs). To investigate the regulation of Bmp6 in HCs and NPCs, liver cells were isolated from adult wild type mice whose diet was modified in iron content in acute or chronic manner and in disease models of iron deficiency (Tmprss6 KO mouse) and overload (Hjv KO mouse). With manipulation of dietary iron in wild-type mice, Bmp6 and Tfr1 expression in both HCs and NPCs was inversely related, as expected. When hepcidin expression is abnormal in murine models of iron overload (Hjv KO mice) and deficiency (Tmprss6 KO mice), Bmp6 expression in NPCs was not related to Tfr1. Despite the low Bmp6 in NPCs from Tmprss6 KO mice, Tfr1 mRNA was also low. Conversely, despite body iron overload and high expression of Bmp6 in NPCs from Hjv KO mice, Tfr1 mRNA and protein were increased. However, in the same cells ferritin L was only slightly increased, but the iron content was not, suggesting that Bmp6 in these cells reflects the high intracellular iron import and export. We propose that NPCs, sensing the iron flux, not only increase hepcidin through Bmp6 with a paracrine mechanism to control systemic iron homeostasis but, controlling hepcidin, they regulate their own ferroportin, inducing iron retention or release and further modulating Bmp6 production in an autocrine manner. This mechanism, that contributes to protect HC from iron loading or deficiency, is lost in disease models of hepcidin production.
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MESH Headings
- Anemia, Iron-Deficiency/metabolism
- Anemia, Iron-Deficiency/pathology
- Animals
- Apoferritins/metabolism
- Bone Morphogenetic Protein 6/genetics
- Bone Morphogenetic Protein 6/metabolism
- Cells, Cultured
- Disease Models, Animal
- GPI-Linked Proteins
- Hemochromatosis Protein
- Hepatocytes/cytology
- Hepatocytes/drug effects
- Hepatocytes/metabolism
- Hepcidins/metabolism
- Iron/metabolism
- Iron Deficiencies
- Iron Overload/metabolism
- Iron Overload/pathology
- Iron, Dietary/pharmacology
- Male
- Membrane Proteins/deficiency
- Membrane Proteins/genetics
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- RNA, Messenger/metabolism
- Receptors, Transferrin/genetics
- Receptors, Transferrin/metabolism
- Serine Endopeptidases/deficiency
- Serine Endopeptidases/genetics
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Affiliation(s)
- Marco Rausa
- Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
- Vita Salute University, Milan, Italy
| | - Alessia Pagani
- Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
- Vita Salute University, Milan, Italy
| | - Antonella Nai
- Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
- Vita Salute University, Milan, Italy
| | - Alessandro Campanella
- Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
- Vita Salute University, Milan, Italy
| | - Maria Enrica Gilberti
- Unit of Occupational Health and Industrial Hygiene, Department of Medical and Surgical Specialties, Radiological Sciences and Public Health, University of Brescia, Brescia, Italy
| | - Pietro Apostoli
- Unit of Occupational Health and Industrial Hygiene, Department of Medical and Surgical Specialties, Radiological Sciences and Public Health, University of Brescia, Brescia, Italy
| | - Clara Camaschella
- Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
- Vita Salute University, Milan, Italy
- * E-mail: (LS); (CC)
| | - Laura Silvestri
- Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
- Vita Salute University, Milan, Italy
- * E-mail: (LS); (CC)
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42
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Silva B, Faustino P. An overview of molecular basis of iron metabolism regulation and the associated pathologies. Biochim Biophys Acta Mol Basis Dis 2015; 1852:1347-59. [PMID: 25843914 DOI: 10.1016/j.bbadis.2015.03.011] [Citation(s) in RCA: 182] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 03/05/2015] [Accepted: 03/27/2015] [Indexed: 12/18/2022]
Abstract
Iron is essential for several vital biological processes. Its deficiency or overload drives to the development of several pathologies. To maintain iron homeostasis, the organism controls the dietary iron absorption by enterocytes, its recycling by macrophages and storage in hepatocytes. These processes are mainly controlled by hepcidin, a liver-derived hormone which synthesis is regulated by iron levels, inflammation, infection, anemia and erythropoiesis. Besides the systemic regulation of iron metabolism mediated by hepcidin, cellular regulatory processes also occur. Cells are able to regulate themselves the expression of the iron metabolism-related genes through different post-transcriptional mechanisms, such as the alternative splicing, microRNAs, the IRP/IRE system and the proteolytic cleavage. Whenever those mechanisms are disturbed, due to genetic or environmental factors, iron homeostasis is disrupted and iron related pathologies may arise.
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Affiliation(s)
- Bruno Silva
- Departamento de Genética Humana, Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisboa, Portugal
| | - Paula Faustino
- Departamento de Genética Humana, Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisboa, Portugal.
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43
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Abstract
Iron, an essential nutrient, is required for many diverse biological processes. The absence of a defined pathway to excrete excess iron makes it essential for the body to regulate the amount of iron absorbed; a deficiency could lead to iron deficiency and an excess to iron overload and associated disorders such as anaemia and haemochromatosis respectively. This regulation is mediated by the iron-regulatory hormone hepcidin. Hepcidin binds to the only known iron export protein, ferroportin (FPN), inducing its internalization and degradation, thus limiting the amount of iron released into the blood. The major factors that are implicated in hepcidin regulation include iron stores, hypoxia, inflammation and erythropoiesis. The present review summarizes our present knowledge about the molecular mechanisms and signalling pathways contributing to hepcidin regulation by these factors.
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44
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Zou J, Wang X, Zhang L, Wang J. Iron Nanoparticles Significantly Affect the In Vitro and In Vivo Expression of Id Genes. Chem Res Toxicol 2015; 28:373-83. [DOI: 10.1021/tx500333q] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Jinglu Zou
- State Key
Laboratory of Bioelectronics, Southeast University, Nanjing 210096, China
| | - Xin Wang
- State Key
Laboratory of Bioelectronics, Southeast University, Nanjing 210096, China
| | - Ling Zhang
- State Key
Laboratory of Bioelectronics, Southeast University, Nanjing 210096, China
| | - Jinke Wang
- State Key
Laboratory of Bioelectronics, Southeast University, Nanjing 210096, China
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45
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Zhao N, Nizzi CP, Anderson SA, Wang J, Ueno A, Tsukamoto H, Eisenstein RS, Enns CA, Zhang AS. Low intracellular iron increases the stability of matriptase-2. J Biol Chem 2014; 290:4432-46. [PMID: 25550162 DOI: 10.1074/jbc.m114.611913] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Matriptase-2 (MT2) is a type II transmembrane serine protease that is predominantly expressed in hepatocytes. It suppresses the expression of hepatic hepcidin, an iron regulatory hormone, by cleaving membrane hemojuvelin into an inactive form. Hemojuvelin is a bone morphogenetic protein (BMP) co-receptor. Here, we report that MT2 is up-regulated under iron deprivation. In HepG2 cells stably expressing the coding sequence of the MT2 gene, TMPRSS6, incubation with apo-transferrin or the membrane-impermeable iron chelator, deferoxamine mesylate salt, was able to increase MT2 levels. This increase did not result from the inhibition of MT2 shedding from the cells. Rather, studies using a membrane-permeable iron chelator, salicylaldehyde isonicotinoyl hydrazone, revealed that depletion of cellular iron was able to decrease the degradation of MT2 independently of internalization. We found that lack of the putative endocytosis motif in its cytoplasmic domain largely abolished the sensitivity of MT2 to iron depletion. Neither acute nor chronic iron deficiency was able to alter the association of Tmprss6 mRNA with polyribosomes in the liver of rats indicating a lack of translational regulation by low iron levels. Studies in mice showed that Tmprss6 mRNA was not regulated by iron nor the BMP-mediated signaling with no evident correlation with either Bmp6 mRNA or Id1 mRNA, a target of BMP signaling. These results suggest that regulation of MT2 occurs at the level of protein degradation rather than by changes in the rate of internalization and translational or transcriptional mechanisms and that the cytoplasmic domain of MT2 is necessary for its regulation.
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Affiliation(s)
- Ningning Zhao
- From the Department of Cell and Developmental Biology, Oregon Health and Science University, Portland, Oregon 97239
| | - Christopher P Nizzi
- the Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Sheila A Anderson
- the Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Jiaohong Wang
- the Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, and
| | - Akiko Ueno
- the Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, and
| | - Hidekazu Tsukamoto
- the Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, and the Department of Veteran Affairs, Greater Los Angeles Healthcare System, Los Angeles, California 90073
| | - Richard S Eisenstein
- the Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Caroline A Enns
- From the Department of Cell and Developmental Biology, Oregon Health and Science University, Portland, Oregon 97239
| | - An-Sheng Zhang
- From the Department of Cell and Developmental Biology, Oregon Health and Science University, Portland, Oregon 97239,
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46
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Abstract
Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta (TGF-β) superfamily of signaling molecules. In addition to protean roles in embryonic development, germ-line specification, and cellular differentiation, a central role in iron homeostasis has recently been demonstrated for certain BMPs. Specifically, BMP6 serves to relate hepatic iron stores to the hepatocellular expression of the iron-regulatory hormone hepcidin. This regulation occurs via cellular SMAD-signaling molecules and is strongly modulated by the BMP coreceptor hemojuvelin (HJV). Mutations in certain genes influencing signaling to hepcidin via the BMP/SMAD pathway are associated with human disorders of iron metabolism, such as hereditary hemochromatosis and iron-refractory iron-deficiency anemia. Evidence suggests that signals in addition to iron stores influence hepcidin expression via the BMP/SMAD pathway. This review summarizes the details of BMP/SMAD signaling, with a particular focus on its role in iron homeostasis and iron-related diseases.
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Affiliation(s)
- Nermi L Parrow
- Division of Molecular and Clinical Nutrition, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
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47
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Core AB, Canali S, Babitt JL. Hemojuvelin and bone morphogenetic protein (BMP) signaling in iron homeostasis. Front Pharmacol 2014; 5:104. [PMID: 24860505 PMCID: PMC4026703 DOI: 10.3389/fphar.2014.00104] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 04/21/2014] [Indexed: 12/13/2022] Open
Abstract
Mutations in hemojuvelin (HJV) are the most common cause of the juvenile-onset form of the iron overload disorder hereditary hemochromatosis. The discovery that HJV functions as a co-receptor for the bone morphogenetic protein (BMP) family of signaling molecules helped to identify this signaling pathway as a central regulator of the key iron hormone hepcidin in the control of systemic iron homeostasis. This review highlights recent work uncovering the mechanism of action of HJV and the BMP-SMAD signaling pathway in regulating hepcidin expression in the liver, as well as additional studies investigating possible extra-hepatic functions of HJV. This review also explores the interaction between HJV, the BMP-SMAD signaling pathway and other regulators of hepcidin expression in systemic iron balance.
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Affiliation(s)
- Amanda B Core
- Division of Nephrology, Program in Membrane Biology, Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Program in Anemia Signaling Research Boston, MA, USA
| | - Susanna Canali
- Division of Nephrology, Program in Membrane Biology, Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Program in Anemia Signaling Research Boston, MA, USA
| | - Jodie L Babitt
- Division of Nephrology, Program in Membrane Biology, Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Program in Anemia Signaling Research Boston, MA, USA
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48
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Worthen CA, Enns CA. The role of hepatic transferrin receptor 2 in the regulation of iron homeostasis in the body. Front Pharmacol 2014; 5:34. [PMID: 24639653 PMCID: PMC3944196 DOI: 10.3389/fphar.2014.00034] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Accepted: 02/18/2014] [Indexed: 12/22/2022] Open
Abstract
Fine-tuning of body iron is required to prevent diseases such as iron-overload and anemia. The putative iron sensor, transferrin receptor 2 (TfR2), is expressed in the liver and mutations in this protein result in the iron-overload disease Type III hereditary hemochromatosis (HH). With the loss of functional TfR2, the liver produces about 2-fold less of the peptide hormone hepcidin, which is responsible for negatively regulating iron uptake from the diet. This reduction in hepcidin expression leads to the slow accumulation of iron in the liver, heart, joints, and pancreas and subsequent cirrhosis, heart disease, arthritis, and diabetes. TfR2 can bind iron-loaded transferrin (Tf) in the bloodstream, and hepatocytes treated with Tf respond with a 2-fold increase in hepcidin expression through stimulation of the bone morphogenetic protein (BMP)-signaling pathway. Loss of functional TfR2 or its binding partner, the original HH protein, results in a loss of this transferrin-sensitivity. While much is known about the trafficking and regulation of TfR2, the mechanism of its transferrin-sensitivity through the BMP-signaling pathway is still not known.
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Affiliation(s)
- Christal A Worthen
- Department of Cell and Developmental Biology, Oregon Health and Science University Portland, OR, USA
| | - Caroline A Enns
- Department of Cell and Developmental Biology, Oregon Health and Science University Portland, OR, USA
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49
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Abstract
A classic Girl Scout song says, "Make new friends/but keep the old/One is silver/and the other gold." This review focuses on the past decade of discovery in the field of iron homeostasis, which has identified "new friends" or key modifiers of the critical systemic iron regulator, hepcidin antimicrobial peptide. The foundation for these discoveries has been the identification of mutated genes in well-characterized cohorts of patients with inherited hemochromatosis from across the globe. Transgenic mouse models of iron overload and iron-restricted anemia have also contributed to understanding molecular pathophysiology in ways that could never be accomplished in human subjects alone. The majority of these newly discovered molecules coordinate signaling through the bone morphogenetic protein pathway of ligands, receptors and coreceptors, intracellular signaling and transcription. The discovery of these proteins and their interactions with "old friends," such as the 1st known hereditary hemochromatosis gene product, HFE and transferrin receptor, has opened the field of iron homeostasis to include regulatory networks involving signal transduction pathways, in particular, the mitogen-activated protein kinase and Smad pathways. These newly discovered partnerships have also made way for opportunities to develop novel therapeutics for the treatment of iron regulatory disorders, including hemochromatosis.
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50
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McDonald CJ, Wallace DF, Ostini L, Subramaniam VN. Parenteral vs. oral iron: influence on hepcidin signaling pathways through analysis of Hfe/Tfr2-null mice. Am J Physiol Gastrointest Liver Physiol 2014; 306:G132-9. [PMID: 24284962 DOI: 10.1152/ajpgi.00256.2013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Treatment for iron deficiency anemia can involve iron supplementation via dietary or parenteral routes that result in different cellular iron distributions. The effect of the administered iron on the iron regulatory system and hepcidin in the liver has not been well studied. Hepcidin, the liver-expressed central iron-regulatory peptide, is itself regulated through the bone morphogenetic protein (BMP)/SMAD signaling pathway. Specifically, Bmp6 expression is upregulated in response to iron and induces hepcidin through phosphorylation of Smad1/5/8. The hemochromatosis-associated proteins Hfe and transferrin receptor 2 (Tfr2) are known upstream regulators of hepcidin, although their precise roles are still unclear. To investigate the mechanisms of this regulation and the roles of the Hfe and Tfr2, we subjected wild-type, Hfe(-/-), Tfr2(-/-), and Hfe(-/-)/Tfr2(-/-) mice to iron loading via dietary or parenteral routes. Systematic analysis demonstrated that Tfr2 is required for effective upregulation of Bmp6 in response to hepatocyte iron, but not nonparenchymal iron. Hfe is not required for Bmp6 upregulation, regardless of iron localization, but rather, is required for efficient downstream transmission of the regulatory signal. Our results demonstrate that Hfe and Tfr2 play separate roles in the regulatory responses to iron compartmentalized in different cell types and further elucidates the regulatory mechanisms controlling iron homeostasis.
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Affiliation(s)
- Cameron J McDonald
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, 300 Herston Rd., Herston, Brisbane, QLD 4006, Australia.
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