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Matsuoka T, Abe M, Kobayashi H. Iron Metabolism and Inflammatory Mediators in Patients with Renal Dysfunction. Int J Mol Sci 2024; 25:3745. [PMID: 38612557 PMCID: PMC11012052 DOI: 10.3390/ijms25073745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 03/23/2024] [Accepted: 03/25/2024] [Indexed: 04/14/2024] Open
Abstract
Chronic kidney disease (CKD) affects around 850 million people worldwide, posing significant challenges in healthcare due to complications like renal anemia, end-stage kidney disease, and cardiovascular diseases. This review focuses on the intricate interplay between iron metabolism, inflammation, and renal dysfunction in CKD. Renal anemia, prevalent in CKD, arises primarily from diminished erythropoietin (EPO) production and iron dysregulation, which worsens with disease progression. Functional and absolute iron deficiencies due to impaired absorption and chronic inflammation are key factors exacerbating erythropoiesis. A notable aspect of CKD is the accumulation of uremic toxins, such as indoxyl sulfate (IS), which hinder iron metabolism and worsen anemia. These toxins directly affect renal EPO synthesis and contribute to renal hypoxia, thus playing a critical role in the pathophysiology of renal anemia. Inflammatory cytokines, especially TNF-α and IL-6, further exacerbate CKD progression and disrupt iron homeostasis, thereby influencing anemia severity. Treatment approaches have evolved to address both iron and EPO deficiencies, with emerging therapies targeting hepcidin and employing hypoxia-inducible factor (HIF) stabilizers showing potential. This review underscores the importance of integrated treatment strategies in CKD, focusing on the complex relationship between iron metabolism, inflammation, and renal dysfunction to improve patient outcomes.
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Affiliation(s)
| | | | - Hiroki Kobayashi
- Division of Nephrology, Hypertension and Endocrinology, Department of Medicine, Nihon University School of Medicine, Tokyo 173-8610, Japan
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2
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Arora EK, Sharma V. Iron metabolism: pathways and proteins in homeostasis. REV INORG CHEM 2022. [DOI: 10.1515/revic-2022-0031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Iron is essential to human survival. The biological role and trafficking of this trace essential inorganic element which is also a potential toxin is constantly being researched and unfolded. Vital for oxygen transport, DNA synthesis, electron transport, neurotransmitter biosynthesis and present in numerous other heme and non-heme enzymes the physiological roles are immense. Understanding the molecules and pathways that regulate this essential element at systemic and cellular levels are of importance in improving therapeutic strategies for iron related disorders. This review highlights the progress in understanding the metabolism and trafficking of iron along with the pathophysiology of iron related disorders.
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Affiliation(s)
- Ekta Kundra Arora
- Chemistry Department, St. Stephen’s College , University of Delhi , Delhi 110007 , India
| | - Vibha Sharma
- Chemistry Department, St. Stephen’s College , University of Delhi , Delhi 110007 , India
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3
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Abou-Hamdan A, Mahler R, Grossenbacher P, Biner O, Sjöstrand D, Lochner M, Högbom M, von Ballmoos C. Functional design of bacterial superoxide:quinone oxidoreductase. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148583. [PMID: 35671795 DOI: 10.1016/j.bbabio.2022.148583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 05/10/2022] [Accepted: 05/31/2022] [Indexed: 06/15/2023]
Abstract
The superoxide anion - molecular oxygen reduced by a single electron - is produced in large amounts by enzymatic and adventitious reactions. It can perform a range of cellular functions, including bacterial warfare and iron uptake, signalling and host immune response in eukaryotes. However, it also serves as precursor for more deleterious species such as the hydroxyl anion or peroxynitrite and defense mechanisms to neutralize superoxide are important for cellular health. In addition to the soluble proteins superoxide dismutase and superoxide reductase, recently the membrane embedded diheme cytochrome b561 (CybB) from E. coli has been proposed to act as a superoxide:quinone oxidoreductase. Here, we confirm superoxide and cellular ubiquinones or menaquinones as natural substrates and show that quinone binding to the enzyme accelerates the reaction with superoxide. The reactivity of the substrates is in accordance with the here determined midpoint potentials of the two b hemes (+48 and -23 mV / NHE). Our data suggest that the enzyme can work near the diffusion limit in the forward direction and can also catalyse the reverse reaction efficiently under physiological conditions. The data is discussed in the context of described cytochrome b561 proteins and potential physiological roles of CybB.
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Affiliation(s)
- Abbas Abou-Hamdan
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, 3012 Bern, Switzerland
| | - Roman Mahler
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, 3012 Bern, Switzerland
| | - Philipp Grossenbacher
- Institute of Biochemistry and Molecular Medicine, University of Bern, 3012 Bern, Switzerland
| | - Olivier Biner
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, 3012 Bern, Switzerland; Department of Plant and Microbial Biology, University of Zürich, 8008 Zürich, Switzerland
| | - Dan Sjöstrand
- Stockholm center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden
| | - Martin Lochner
- Institute of Biochemistry and Molecular Medicine, University of Bern, 3012 Bern, Switzerland
| | - Martin Högbom
- Stockholm center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden
| | - Christoph von Ballmoos
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, 3012 Bern, Switzerland.
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4
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Roth-Walter F. Iron-Deficiency in Atopic Diseases: Innate Immune Priming by Allergens and Siderophores. FRONTIERS IN ALLERGY 2022; 3:859922. [PMID: 35769558 PMCID: PMC9234869 DOI: 10.3389/falgy.2022.859922] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 03/03/2022] [Indexed: 12/12/2022] Open
Abstract
Although iron is one of the most abundant elements on earth, about a third of the world's population are affected by iron deficiency. Main drivers of iron deficiency are beside the chronic lack of dietary iron, a hampered uptake machinery as a result of immune activation. Macrophages are the principal cells distributing iron in the human body with their iron restriction skewing these cells to a more pro-inflammatory state. Consequently, iron deficiency has a pronounced impact on immune cells, favoring Th2-cell survival, immunoglobulin class switching and primes mast cells for degranulation. Iron deficiency during pregnancy increases the risk of atopic diseases in children, while both children and adults with allergy are more likely to have anemia. In contrast, an improved iron status seems to protect against allergy development. Here, the most important interconnections between iron metabolism and allergies, the effect of iron deprivation on distinct immune cell types, as well as the pathophysiology in atopic diseases are summarized. Although the main focus will be humans, we also compare them with innate defense and iron sequestration strategies of microbes, given, particularly, attention to catechol-siderophores. Similarly, the defense and nutritional strategies in plants with their inducible systemic acquired resistance by salicylic acid, which further leads to synthesis of flavonoids as well as pathogenesis-related proteins, will be elaborated as both are very important for understanding the etiology of allergic diseases. Many allergens, such as lipocalins and the pathogenesis-related proteins, are able to bind iron and either deprive or supply iron to immune cells. Thus, a locally induced iron deficiency will result in immune activation and allergic sensitization. However, the same proteins such as the whey protein beta-lactoglobulin can also transport this precious micronutrient to the host immune cells (holoBLG) and hinder their activation, promoting tolerance and protecting against allergy. Since 2019, several clinical trials have also been conducted in allergic subjects using holoBLG as a food for special medical purposes, leading to a reduction in the allergic symptom burden. Supplementation with nutrient-carrying lipocalin proteins can circumvent the mucosal block and nourish selectively immune cells, therefore representing a new dietary and causative approach to compensate for functional iron deficiency in allergy sufferers.
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Affiliation(s)
- Franziska Roth-Walter
- Comparative Medicine, The Interuniversity Messerli Research Institute, University of Veterinary Medicine Vienna, Medical University Vienna, University of Vienna, Vienna, Austria
- Institute of Pathophysiology and Allergy Research, Center of Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria
- *Correspondence: Franziska Roth-Walter ;
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5
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Zhou Y, Liao J, Mei Z, Liu X, Ge J. Insight into Crosstalk between Ferroptosis and Necroptosis: Novel Therapeutics in Ischemic Stroke. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2021; 2021:9991001. [PMID: 34257829 PMCID: PMC8257382 DOI: 10.1155/2021/9991001] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 04/30/2021] [Accepted: 06/14/2021] [Indexed: 12/16/2022]
Abstract
Ferroptosis is a nonapoptotic form of cell death characterized by iron-dependent accumulation of lipid hydroperoxides to lethal levels. Necroptosis, an alternative form of programmed necrosis, is regulated by receptor-interacting protein (RIP) 1 activation and by RIP3 and mixed-lineage kinase domain-like (MLKL) phosphorylation. Ferroptosis and necroptosis both play important roles in the pathological progress in ischemic stroke, which is a complex brain disease regulated by several cell death pathways. In the past few years, increasing evidence has suggested that the crosstalk occurs between necroptosis and ferroptosis in ischemic stroke. However, the potential links between ferroptosis and necroptosis in ischemic stroke have not been elucidated yet. Hence, in this review, we overview and analyze the mechanism underlying the crosstalk between necroptosis and ferroptosis in ischemic stroke. And we find that iron overload, one mechanism of ferroptosis, leads to mitochondrial permeability transition pore (MPTP) opening, which aggravates RIP1 phosphorylation and contributes to necroptosis. In addition, heat shock protein 90 (HSP90) induces necroptosis and ferroptosis by promoting RIP1 phosphorylation and suppressing glutathione peroxidase 4 (GPX4) activation. In this work, we try to deliver a new perspective in the exploration of novel therapeutic targets for the treatment of ischemic stroke.
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Affiliation(s)
- Yue Zhou
- College of Integrated Traditional Chinese and Western Medicine, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China
| | - Jun Liao
- Medical School, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China
| | - Zhigang Mei
- College of Integrated Traditional Chinese and Western Medicine, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China
- Third-Grade Pharmacological Laboratory on Chinese Medicine Approved by State Administration of Traditional Chinese Medicine, Medical College of China Three Gorges University, Yichang, Hubei 443002, China
| | - Xun Liu
- College of Integrated Traditional Chinese and Western Medicine, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China
| | - Jinwen Ge
- College of Integrated Traditional Chinese and Western Medicine, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China
- School of Medicine, Shaoyang University, Shaoyang, Hunan 422000, China
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6
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Functional Assembly of Caenorhabditis elegans Cytochrome b-2 (Cecytb-2) into Phospholipid Bilayer Nanodisc with Enhanced Iron Reductase Activity. Biomolecules 2021; 11:biom11010096. [PMID: 33451048 PMCID: PMC7828500 DOI: 10.3390/biom11010096] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 01/07/2021] [Accepted: 01/12/2021] [Indexed: 12/14/2022] Open
Abstract
Among seven homologs of cytochrome b561 in a model organism C. elegans, Cecytb-2 was confirmed to be expressed in digestive organs and was considered as a homolog of human Dcytb functioning as a ferric reductase. Cecytb-2 protein was expressed in Pichia pastoris cells, purified, and reconstituted into a phospholipid bilayer nanodisc. The reconstituted Cecytb-2 in nanodisc environments was extremely stable and more reducible with ascorbate than in a detergent-micelle state. We confirmed the ferric reductase activity of Cecytb-2 by analyzing the oxidation of ferrous heme upon addition of ferric substrate under anaerobic conditions, where clear and saturable dependencies on the substrate concentrations following the Michaelis–Menten equation were observed. Further, we confirmed that the ferric substrate was converted to a ferrous state by using a nitroso-PSAP assay. Importantly, we observed that the ferric reductase activity of Cecytb-2 became enhanced in the phospholipid bilayer nanodisc.
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7
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Liu Z, Han K, Huo X, Yan B, Gao M, Lv X, Yu P, Gao G, Chang YZ. Nrf2 knockout dysregulates iron metabolism and increases the hemolysis through ROS in aging mice. Life Sci 2020; 255:117838. [DOI: 10.1016/j.lfs.2020.117838] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 05/13/2020] [Accepted: 05/20/2020] [Indexed: 02/06/2023]
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8
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Chen W, Yan X, Tian T, Yan R, Wang X, Yu Z, Li Y, Zhang L, Han S. Integrated analysis of a lncRNA‑mRNA network reveals a potential mechanism underlying necrotizing enterocolitis. Mol Med Rep 2020; 22:423-435. [PMID: 32319640 PMCID: PMC7248486 DOI: 10.3892/mmr.2020.11083] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 03/25/2020] [Indexed: 02/02/2023] Open
Abstract
Previous studies have shown that long non-coding RNAs (lncRNAs) serve important roles in necrotizing enterocolitis (NEC). However, the underlying mechanisms remain largely unknown. In order to examine the potential role of lncRNAs in NEC, the present study investigated lncRNA and mRNA expression profiles in NEC lesions and adjacent intestinal tissues using Next Generation Sequencing. A total of 4,202 differentially expressed lncRNAs (fold-change >2; P<0.05) and 7,860 differentially expressed mRNAs (fold-change >2; P<0.05) were identified. Moreover, 5 dysregulated lncRNAs and 5 mRNAs were randomly selected, and further assessed by reverse transcription-quantitative PCR in vitro. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses demonstrated that the differentially expressed lncRNAs were closely associated with NEC, and were enriched in ‘inflammatory response’, ‘Toll-like receptor binding’, ‘PPAR signaling pathway’, ‘PI3K-Akt signaling pathway’, ‘transforming growth factor-β signaling pathway’ and ‘hypoxia-inducible factor 1 signaling pathway’. In addition, co-expression analysis demonstrated that these lncRNAs, including lncRNA ENST00000623580, lncRNA NONHSAT180418.1, lncRNA NONHSAT125636.2 and NONHSAT087855.2, may mediate the pathogenesis and development of NEC via lncRNA-mRNA network interactions. Therefore, the present study provided a novel insight into the role of lncRNAs in NEC.
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Affiliation(s)
- Wenjuan Chen
- Department of Neonatology, Wuxi Children's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Xiangyun Yan
- Department of Neonatology, Wuxi Children's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Tian Tian
- Department of Neonatology, Wuxi Children's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Ru Yan
- Department of Neonatology, Wuxi Children's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Xingyun Wang
- Department of Neonatology, Wuxi Children's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Zhangbin Yu
- Department of Neonatology, Wuxi Children's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Yingzheng Li
- Department of Neonatology, Wuxi Children's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Le Zhang
- Department of Neonatology, Wuxi Children's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
| | - Shuping Han
- Department of Neonatology, Wuxi Children's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214023, P.R. China
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9
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Zimmerman SM, Dimori M, Heard-Lipsmeyer ME, Morello R. The Osteocyte Transcriptome Is Extensively Dysregulated in Mouse Models of Osteogenesis Imperfecta. JBMR Plus 2019; 3:e10171. [PMID: 31372585 PMCID: PMC6659450 DOI: 10.1002/jbm4.10171] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 12/19/2018] [Accepted: 01/13/2019] [Indexed: 12/14/2022] Open
Abstract
Osteocytes are long‐lived, highly interconnected, terminally differentiated osteoblasts that reside within mineralized bone matrix. They constitute about 95% of adult bone cells and play important functions including in the regulation of bone remodeling, phosphate homeostasis, and mechanical stimuli sensing and response. However, the role of osteocytes in the pathogenesis of congenital diseases of abnormal bone matrix is poorly understood. This study characterized in vivo transcriptional changes in osteocytes from CrtapKO and oim/oim mouse models of osteogenesis imperfecta (OI) compared with wild‐type (WT) control mice. To do this, RNA was extracted from osteocyte‐enriched cortical femurs and tibias, sequenced and subsequently analyzed to identify differentially expressed transcripts. These models were chosen because they mimic two types of OI with different genetic mutations that result in distinct type I collagen defects. A large number of transcripts were dysregulated in either model of OI, but 281 of them were similarly up‐ or downregulated in both compared with WT controls. Conversely, very few transcripts were differentially expressed between the CrtapKO and oim/oim mice, indicating that distinct alterations in type I collagen can lead to shared pathogenic processes and similar phenotypic outcomes. Bioinformatics analyses identified several critical hubs of dysregulation that were enriched in annotation terms such as development and differentiation, ECM and collagen fibril organization, cell adhesion, signaling, regulatory processes, pattern binding, chemotaxis, and cell projections. The data further indicated alterations in important signaling pathways such as WNT and TGF‐β but also highlighted new candidate genes to pursue in future studies. Overall, our study suggested that the osteocyte transcriptome is broadly dysregulated in OI with potential long‐term consequences at the cellular level, which deserve further investigations. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.
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Affiliation(s)
- Sarah M Zimmerman
- Department of Physiology and Biophysics University of Arkansas for Medical Sciences Little Rock AR USA
| | - Milena Dimori
- Department of Physiology and Biophysics University of Arkansas for Medical Sciences Little Rock AR USA
| | - Melissa E Heard-Lipsmeyer
- Department of Physiology and Biophysics University of Arkansas for Medical Sciences Little Rock AR USA
| | - Roy Morello
- Department of Physiology and Biophysics University of Arkansas for Medical Sciences Little Rock AR USA.,Department of Orthopaedic Surgery University of Arkansas for Medical Sciences Little Rock AR USA.,Division of Genetics University of Arkansas for Medical Sciences Little Rock AR USA
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10
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Sherman HG, Jovanovic C, Stolnik S, Baronian K, Downard AJ, Rawson FJ. New Perspectives on Iron Uptake in Eukaryotes. Front Mol Biosci 2018; 5:97. [PMID: 30510932 PMCID: PMC6254016 DOI: 10.3389/fmolb.2018.00097] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 10/23/2018] [Indexed: 12/20/2022] Open
Abstract
All eukaryotic organisms require iron to function. Malfunctions within iron homeostasis have a range of physiological consequences, and can lead to the development of pathological conditions that can result in an excess of non-transferrin bound iron (NTBI). Despite extensive understanding of iron homeostasis, the links between the “macroscopic” transport of iron across biological barriers (cellular membranes) and the chemistry of redox changes that drive these processes still needs elucidating. This review draws conclusions from the current literature, and describes some of the underlying biophysical and biochemical processes that occur in iron homeostasis. By first taking a broad view of iron uptake within the gut and subsequent delivery to tissues, in addition to describing the transferrin and non-transferrin mediated components of these processes, we provide a base of knowledge from which we further explore NTBI uptake. We provide concise up-to-date information of the transplasma electron transport systems (tPMETSs) involved within NTBI uptake, and highlight how these systems are not only involved within NTBI uptake for detoxification but also may play a role within the reduction of metabolic stress through regeneration of intracellular NAD(P)H/NAD(P)+ levels. Furthermore, we illuminate the thermodynamics that governs iron transport, namely the redox potential cascade and electrochemical behavior of key components of the electron transport systems that facilitate the movement of electrons across the plasma membrane to the extracellular compartment. We also take account of kinetic changes that occur to transport iron into the cell, namely membrane dipole change and their consequent effects within membrane structure that act to facilitate transport of ions.
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Affiliation(s)
- Harry G Sherman
- Division of Regenerative Medicine and Cellular Therapies, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom
| | | | - Snow Stolnik
- Division of Molecular Therapeutics and Formulation, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom
| | - Kim Baronian
- School of Biological Sciences, University of Canterbury, Christchurch, New Zealand
| | - Alison J Downard
- MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Physical and Chemical Sciences, University of Canterbury, Christchurch, New Zealand
| | - Frankie J Rawson
- Division of Regenerative Medicine and Cellular Therapies, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom
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11
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Ganasen M, Togashi H, Takeda H, Asakura H, Tosha T, Yamashita K, Hirata K, Nariai Y, Urano T, Yuan X, Hamza I, Mauk AG, Shiro Y, Sugimoto H, Sawai H. Structural basis for promotion of duodenal iron absorption by enteric ferric reductase with ascorbate. Commun Biol 2018; 1:120. [PMID: 30272000 PMCID: PMC6123691 DOI: 10.1038/s42003-018-0121-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 07/25/2018] [Indexed: 12/16/2022] Open
Abstract
Dietary iron absorption is regulated by duodenal cytochrome b (Dcytb), an integral membrane protein that catalyzes reduction of nonheme Fe3+ by electron transfer from ascorbate across the membrane. This step is essential to enable iron uptake by the divalent metal transporter. Here we report the crystallographic structures of human Dcytb and its complex with ascorbate and Zn2+. Each monomer of the homodimeric protein possesses cytoplasmic and apical heme groups, as well as cytoplasmic and apical ascorbate-binding sites located adjacent to each heme. Zn2+ coordinates to two hydroxyl groups of the apical ascorbate and to a histidine residue. Biochemical analysis indicates that Fe3+ competes with Zn2+ for this binding site. These results provide a structural basis for the mechanism by which Fe3+ uptake is promoted by reducing agents and should facilitate structure-based development of improved agents for absorption of orally administered iron.
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Affiliation(s)
- Menega Ganasen
- Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako, Hyogo, 678-1297, Japan
| | - Hiromi Togashi
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan
| | - Hanae Takeda
- Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako, Hyogo, 678-1297, Japan.,RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan
| | - Honami Asakura
- Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako, Hyogo, 678-1297, Japan
| | - Takehiko Tosha
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan
| | | | - Kunio Hirata
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan
| | - Yuko Nariai
- Department of Biochemistry, Shimane University School of Medicine, 89-1 Enya, Izumo, Shimane, 693-8501, Japan
| | - Takeshi Urano
- Department of Biochemistry, Shimane University School of Medicine, 89-1 Enya, Izumo, Shimane, 693-8501, Japan
| | - Xiaojing Yuan
- Department of Animal and Avian Sciences, University of Maryland, 8127 Regents Drive, College Park, MD, 20742, USA
| | - Iqbal Hamza
- Department of Animal and Avian Sciences, University of Maryland, 8127 Regents Drive, College Park, MD, 20742, USA
| | - A Grant Mauk
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Yoshitsugu Shiro
- Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako, Hyogo, 678-1297, Japan
| | - Hiroshi Sugimoto
- Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako, Hyogo, 678-1297, Japan. .,RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan.
| | - Hitomi Sawai
- Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako, Hyogo, 678-1297, Japan. .,RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan.
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12
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Sherman HG, Jovanovic C, Stolnik S, Rawson FJ. Electrochemical System for the Study of Trans-Plasma Membrane Electron Transport in Whole Eukaryotic Cells. Anal Chem 2018; 90:2780-2786. [DOI: 10.1021/acs.analchem.7b04853] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Harry G. Sherman
- Division
of Regenerative Medicine and Cellular Therapies, School of Pharmacy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | | | - Snow Stolnik
- Division
of Molecular Therapeutics and Formulation, School of Pharmacy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Frankie J. Rawson
- Division
of Regenerative Medicine and Cellular Therapies, School of Pharmacy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
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13
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Roth-Walter F, Pacios LF, Bianchini R, Jensen-Jarolim E. Linking iron-deficiency with allergy: role of molecular allergens and the microbiome. Metallomics 2017; 9:1676-1692. [PMID: 29120476 DOI: 10.1039/c7mt00241f] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Atopic individuals tend to develop a Th2 dominant immune response, resulting in hyperresponsiveness to harmless antigens, termed allergens. In the last decade, epidemiological studies have emerged that connected allergy with a deficient iron-status. Immune activation under iron-deficient conditions results in the expansion of Th2-, but not Th1 cells, can induce class-switching in B-cells and hampers the proper activation of M2, but not M1 macrophages. Moreover, many allergens, in particular with the lipocalin and lipocalin-like folds, seem to be capable of binding iron indirectly via siderophores harboring catechol moieties. The resulting locally restricted iron-deficiency may then lead during immune activation to the generation of Th2-cells and thus prepare for allergic sensitization. Moreover, iron-chelators seem to also influence clinical reactivity: mast cells accumulate iron before degranulation and seem to respond differently depending on the type of the encountered siderophore. Whereas deferoxamine triggers degranulation of connective tissue-type mast cells, catechol-based siderophores reduce activation and degranulation and improve clinical symptoms. Considering the complex interplay of iron, siderophores and immune molecules, it remains to be determined whether iron-deficiencies are the cause or the result of allergy.
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Affiliation(s)
- Franziska Roth-Walter
- Department of Comparative Medicine, at the Interuniversity Messerli Research Institute, University of Veterinary Medicine Vienna, Medical University of Vienna and University of Vienna, Vienna, Austria.
| | - Luis F Pacios
- Centro de Biotecnología y Genómica de Plantas (CBGP, UPM-INIA), Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Campus de Montegancedo-UPM, 28223 Pozuelo de Alarcón, Madrid, Spain
| | - Rodolfo Bianchini
- Department of Comparative Medicine, at the Interuniversity Messerli Research Institute, University of Veterinary Medicine Vienna, Medical University of Vienna and University of Vienna, Vienna, Austria.
| | - Erika Jensen-Jarolim
- Department of Comparative Medicine, at the Interuniversity Messerli Research Institute, University of Veterinary Medicine Vienna, Medical University of Vienna and University of Vienna, Vienna, Austria. and Institute of Pathophysiology and Allergy Research, Center of Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria
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Inherent Oxidative Stress in the Lewis Rat Is Associated with Resistance to Toxoplasmosis. Infect Immun 2017; 85:IAI.00289-17. [PMID: 28739829 DOI: 10.1128/iai.00289-17] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 07/17/2017] [Indexed: 01/11/2023] Open
Abstract
The course of Toxoplasma gondii infection in rats closely resembles that in humans. However, compared to the Brown Norway (BN) rat, the Lewis (LEW) rat is extremely resistant to T. gondii infection. Thus, we performed RNA sequencing analysis of the LEW rat versus the BN rat, with or without T. gondii infection, in order to unravel molecular factors directing robust and rapid early T. gondii-killing mechanisms in the LEW rat. We found that compared to the uninfected BN rat, the uninfected LEW rat has inherently higher transcript levels of cytochrome enzymes (Cyp2d3, Cyp2d5, and Cybrd1, which catalyze generation of reactive oxygen species [ROS]), with concomitant higher levels of ROS. Interestingly, despite having higher levels of ROS, the LEW rat had lower transcript levels for antioxidant enzymes (lactoperoxidase, microsomal glutathione S-transferase 2 and 3, glutathione S-transferase peroxidase kappa 1, and glutathione peroxidase) than the BN rat, suggesting that the LEW rat maintains cellular oxidative stress that it tolerates. Corroboratively, we found that scavenging of superoxide anion by Mn(III) tetrakis (4-benzoic acid) porphyrin (MnTBAP) decreased the refractoriness of LEW rat peritoneal cells to T. gondii infection, resulting in proliferation of parasites in LEW rat peritoneal cells which, in turn, led to augmented cell death in the infected cells. Together, our results indicate that the LEW rat maintains inherent cellular oxidative stress that contributes to resistance to invading T. gondii, and they thus unveil new avenues for developing therapeutic agents targeting induction of host cell oxidative stress as a mechanism for killing T. gondii.
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Lemler DJ, Lynch ML, Tesfay L, Deng Z, Paul BT, Wang X, Hegde P, Manz DH, Torti SV, Torti FM. DCYTB is a predictor of outcome in breast cancer that functions via iron-independent mechanisms. Breast Cancer Res 2017; 19:25. [PMID: 28270217 PMCID: PMC5341190 DOI: 10.1186/s13058-017-0814-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 02/09/2017] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Duodenal cytochrome b (DCYTB) is a ferrireductase that functions together with divalent metal transporter 1 (DMT1) to mediate dietary iron reduction and uptake in the duodenum. DCYTB is also a member of a 16-gene iron regulatory gene signature (IRGS) that predicts metastasis-free survival in breast cancer patients. To better understand the relationship between DCYTB and breast cancer, we explored in detail the prognostic significance and molecular function of DCYTB in breast cancer. METHODS The prognostic significance of DCYTB expression was evaluated using publicly available microarray data. Signaling Pathway Impact Analysis (SPIA) of microarray data was used to identify potential novel functions of DCYTB. The role of DCYTB was assessed using immunohistochemistry and measurements of iron uptake, iron metabolism, and FAK signaling. RESULTS High DCYTB expression was associated with prolonged survival in two large independent cohorts, together totaling 1610 patients (cohort #1, p = 1.6e-11, n = 741; cohort #2, p = 1.2e-05, n = 869; log-rank test) as well as in the Gene expression-based Outcome for Breast cancer Online (GOBO) cohort (p < 1.0e-05, n = 1379). High DCYTB expression was also associated with increased survival in homogeneously treated groups of patients who received either tamoxifen or chemotherapy. Immunohistochemistry revealed that DCYTB is localized on the plasma membrane of breast epithelial cells, and that expression is dramatically reduced in high-grade tumors. Surprisingly, neither overexpression nor knockdown of DCYTB affected levels of ferritin H, transferrin receptor, labile iron or total cellular iron in breast cancer cells. Because SPIA pathway analysis of patient microarray data revealed an association between DCYTB and the focal adhesion pathway, we examined the influence of DCYTB on FAK activation in breast cancer cells. These experiments reveal that DCYTB reduces adhesion and activation of focal adhesion kinase (FAK) and its adapter protein paxillin. CONCLUSIONS DCYTB is an important predictor of outcome and is associated with response to therapy in breast cancer patients. DCYTB does not affect intracellular iron in breast cancer cells. Instead, DCYTB may retard cancer progression by reducing activation of FAK, a kinase that plays a central role in tumor cell adhesion and metastasis.
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Affiliation(s)
- David J. Lemler
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT 06030 USA
- Present address: Department of Molecular Biomedical Sciences, North Carolina State University, CVM Research Building 474, Raleigh, NC 27695 USA
| | - Miranda L. Lynch
- Center for Quantitative Medicine, University of Connecticut Health Center, Farmington, CT 06030 USA
- Present address: Statistical Sciences Group CCS-6, Los Alamos National Laboratory, Los Alamos, NM 87545 USA
| | - Lia Tesfay
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT 06030 USA
| | - Zhiyong Deng
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT 06030 USA
| | - Bibbin T. Paul
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT 06030 USA
| | - Xiaohong Wang
- Department of Pathology, University of Connecticut Health Center, Farmington, CT 06030 USA
| | - Poornima Hegde
- Department of Pathology, University of Connecticut Health Center, Farmington, CT 06030 USA
| | - David H. Manz
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT 06030 USA
- School of Dental Medicine, University of Connecticut Health Center, Farmington, CT 06030 USA
| | - Suzy V. Torti
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT 06030 USA
| | - Frank M. Torti
- Department of Medicine, University of Connecticut Health Center, Farmington, CT 06030 USA
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Duodenal cytochrome b (DCYTB) in iron metabolism: an update on function and regulation. Nutrients 2015; 7:2274-96. [PMID: 25835049 PMCID: PMC4425144 DOI: 10.3390/nu7042274] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Revised: 03/03/2015] [Accepted: 03/05/2015] [Indexed: 01/01/2023] Open
Abstract
Iron and ascorbate are vital cellular constituents in mammalian systems. The bulk-requirement for iron is during erythropoiesis leading to the generation of hemoglobin-containing erythrocytes. Additionally, both iron and ascorbate are required as co-factors in numerous metabolic reactions. Iron homeostasis is controlled at the level of uptake, rather than excretion. Accumulating evidence strongly suggests that in addition to the known ability of dietary ascorbate to enhance non-heme iron absorption in the gut, ascorbate regulates iron homeostasis. The involvement of ascorbate in dietary iron absorption extends beyond the direct chemical reduction of non-heme iron by dietary ascorbate. Among other activities, intra-enterocyte ascorbate appears to be involved in the provision of electrons to a family of trans-membrane redox enzymes, namely those of the cytochrome b561 class. These hemoproteins oxidize a pool of ascorbate on one side of the membrane in order to reduce an electron acceptor (e.g., non-heme iron) on the opposite side of the membrane. One member of this family, duodenal cytochrome b (DCYTB), may play an important role in ascorbate-dependent reduction of non-heme iron in the gut prior to uptake by ferrous-iron transporters. This review discusses the emerging relationship between cellular iron homeostasis, the emergent “IRP1-HIF2α axis”, DCYTB and ascorbate in relation to iron metabolism.
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Ji C, Kosman DJ. Molecular mechanisms of non-transferrin-bound and transferring-bound iron uptake in primary hippocampal neurons. J Neurochem 2015; 133:668-83. [PMID: 25649872 DOI: 10.1111/jnc.13040] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 01/08/2015] [Accepted: 01/14/2015] [Indexed: 12/16/2022]
Abstract
The molecular mechanisms of iron trafficking in neurons have not been elucidated. In this study, we characterized the expression and localization of ferrous iron transporters Zip8, Zip14 and divalent metal transporter 1 (DMT1), and ferrireductases Steap2 and stromal cell-derived receptor 2 in primary rat hippocampal neurons. Steap2 and Zip8 partially co-localize, indicating these two proteins may function in Fe(3+) reduction prior to Fe(2+) permeation. Zip8, DMT1, and Steap2 co-localize with the transferrin receptor/transferrin complex, suggesting they may be involved in transferrin receptor/transferrin-mediated iron assimilation. In brain interstitial fluid, transferring-bound iron (TBI) and non-transferrin-bound iron (NTBI) exist as potential iron sources. Primary hippocampal neurons exhibit significant iron uptake from TBI (Transferrin-(59) Fe(3+)) and NTBI, whether presented as (59) Fe(2+) -citrate or (59) Fe(3+) -citrate; reductase-independent (59) Fe(2+) uptake was the most efficient uptake pathway of the three. Kinetic analysis of Zn(2+) inhibition of Fe(2+) uptake indicated that DMT1 plays only a minor role in the uptake of NTBI. In contrast, localization and knockdown data indicate that Zip8 makes a major contribution. Data suggest also that cell accumulation of (59) Fe from TBI relies at least in part on an endocytosis-independent pathway. These data suggest that Zip8 and Steap2 play a major role in iron accumulation from NTBI and TBI by hippocampal neurons. Analysis of the expression and localization of known iron uptake transporters demonstrated that Zip8 makes a major contribution to iron accumulation in primary cultures of rat embryonic hippocampal neurons. These cells exhibit uptake pathways for ferrous and ferric iron (non-transferrin-bound iron, NTBI in figure) and for transferrin-bound iron; the ferrireductases Steap2 and SDR2 support the uptake of ferric iron substrates. Zip8 and Steap2 are strongly expressed in the plasma membrane of both soma and processes, implying a crucial role in iron accumulation from NTBI and transferrin-bound iron (TBI) by hippocampal neurons.
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Affiliation(s)
- Changyi Ji
- Department of Biochemistry, State University of New York, School of Medicine and Biomedical Sciences Buffalo, Buffalo, New York, USA
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18
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Lane DJR, Richardson DR. The active role of vitamin C in mammalian iron metabolism: much more than just enhanced iron absorption! Free Radic Biol Med 2014; 75:69-83. [PMID: 25048971 DOI: 10.1016/j.freeradbiomed.2014.07.007] [Citation(s) in RCA: 143] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 07/04/2014] [Accepted: 07/08/2014] [Indexed: 01/18/2023]
Abstract
Ascorbate is a cofactor in numerous metabolic reactions. Humans cannot synthesize ascorbate owing to inactivation of the gene encoding the enzyme l-gulono-γ-lactone oxidase, which is essential for ascorbate synthesis. Accumulating evidence strongly suggests that in addition to the known ability of dietary ascorbate to enhance nonheme iron absorption in the gut, ascorbate within mammalian systems can regulate cellular iron uptake and metabolism. Ascorbate modulates iron metabolism by stimulating ferritin synthesis, inhibiting lysosomal ferritin degradation, and decreasing cellular iron efflux. Furthermore, ascorbate cycling across the plasma membrane is responsible for ascorbate-stimulated iron uptake from low-molecular-weight iron-citrate complexes, which are prominent in the plasma of individuals with iron-overload disorders. Importantly, this iron-uptake pathway is of particular relevance to astrocyte brain iron metabolism and tissue iron loading in disorders such as hereditary hemochromatosis and β-thalassemia. Recent evidence also indicates that ascorbate is a novel modulator of the classical transferrin-iron uptake pathway, which provides almost all iron for cellular demands and erythropoiesis under physiological conditions. Ascorbate acts to stimulate transferrin-dependent iron uptake by an intracellular reductive mechanism, strongly suggesting that it may act to stimulate iron mobilization from the endosome. The ability of ascorbate to regulate transferrin iron uptake could help explain the metabolic defect that contributes to ascorbate-deficiency-induced anemia.
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Affiliation(s)
- Darius J R Lane
- Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, University of Sydney, Sydney, NSW 2006, Australia.
| | - Des R Richardson
- Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, University of Sydney, Sydney, NSW 2006, Australia.
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A systems biology approach to iron metabolism. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 844:201-25. [PMID: 25480643 DOI: 10.1007/978-1-4939-2095-2_10] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Iron is critical to the survival of almost all living organisms. However, inappropriately low or high levels of iron are detrimental and contribute to a wide range of diseases. Recent advances in the study of iron metabolism have revealed multiple intricate pathways that are essential to the maintenance of iron homeostasis. Further, iron regulation involves processes at several scales, ranging from the subcellular to the organismal. This complexity makes a systems biology approach crucial, with its enabling technology of computational models based on a mathematical description of regulatory systems. Systems biology may represent a new strategy for understanding imbalances in iron metabolism and their underlying causes.
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20
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Asard H, Barbaro R, Trost P, Bérczi A. Cytochromes b561: ascorbate-mediated trans-membrane electron transport. Antioxid Redox Signal 2013; 19:1026-35. [PMID: 23249217 PMCID: PMC3763232 DOI: 10.1089/ars.2012.5065] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
SIGNIFICANCE Cytochromes b561 (CYB561s) constitute a family of trans-membrane (TM), di-heme proteins, occurring in a variety of organs and cell types, in plants and animals, and using ascorbate (ASC) as an electron donor. CYB561s function as monodehydroascorbate reductase, regenerating ASC, and as Fe³⁺-reductases, providing reduced iron for TM transport. A CYB561-core domain is also associated with dopamine β-monooxygenase redox domains (DOMON) in ubiquitous CYBDOM proteins. In plants, CYBDOMs form large protein families. Physiological functions supported by CYB561s and CYBDOMs include stress defense, cell wall modifications, iron metabolism, tumor suppression, and various neurological processes, including memory retention. CYB561s, therefore, significantly broaden our view on the physiological roles of ASC. RECENT ADVANCES The ubiquitous nature of CYB561s is only recently being recognized. Significant advances have been made through the study of recombinant CYB561s, revealing structural and functional properties of a unique "two-heme four-helix" protein configuration. In addition, the DOMON domains of CYBDOMs are suggested to contain another heme b. CRITICAL ISSUES New CYB561 proteins are still being identified, and there is a need to provide an insight and overview on the various roles of these proteins and their structural properties. FUTURE DIRECTIONS Mutant studies will reveal in greater detail the mechanisms by which CYB561s and CYBDOMs participate in cell metabolism in plants and animals. Moreover, the availability of efficient heterologous expression systems should allow protein crystallization, more detailed (atomic-level) structural information, and insights into the intra-molecular mechanism of electron transport.
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Affiliation(s)
- Han Asard
- Department of Biology, University of Antwerp, Antwerp, Belgium.
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21
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Montalbetti N, Simonin A, Kovacs G, Hediger MA. Mammalian iron transporters: families SLC11 and SLC40. Mol Aspects Med 2013; 34:270-87. [PMID: 23506870 DOI: 10.1016/j.mam.2013.01.002] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 12/14/2012] [Indexed: 01/13/2023]
Abstract
This review is focused on the mammalian SLC11 and SLC40 families and their roles in iron homeostasis. The SLC11 family is composed of two members, SLC11A1 and SLC11A2. SLC11A1 is expressed in the lysosomal compartment of macrophages and in the tertiary granules of neutrophils, playing a key role in innate resistance against infection by intracellular microbes. SLC11A2 is a key player in iron metabolism and is ubiquitously expressed, most notably in the proximal duodenum, immature erythroid cells, brain, placenta and kidney. Intestinal iron absorption is mediated by SLC11A2 at the apical membrane of enterocytes, followed by basolateral exit via SLC40A1. To meet the daily requirement for iron, approximately 80% of the iron comes from the breakdown of hemoglobin following macrophage phagocytosis of senescent erythrocytes (iron recycling). Both SLC11A1 and SLC11A2 play an important role in macrophage iron recycling. SLC11A2 also transports iron into the cytosol across the membrane of endocytotic vesicles of the transferrin receptor-cycle. SLC40A1 is the sole member of the SLC40 family and is involved in the only cellular iron efflux mechanism described. SLC40A1 is highly expressed in several tissues and cells that play a critical role in body iron homeostasis. The signaling pathways that regulate SLC11A2 and SLC40A1 expression at transcriptional, post-transcriptional and post-translational levels are discussed. The roles of SLC11A2 and/or SLC40A1 in iron-associated disorders such as hemochromatosis, neurodegenerative diseases, and breast cancer are also summarized.
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Affiliation(s)
- Nicolas Montalbetti
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
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22
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Luo X, Hill M, Johnson A, Latunde-Dada GO. Modulation of Dcytb (Cybrd 1) expression and function by iron, dehydroascorbate and Hif-2α in cultured cells. Biochim Biophys Acta Gen Subj 2013; 1840:106-12. [PMID: 23981688 DOI: 10.1016/j.bbagen.2013.08.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 07/24/2013] [Accepted: 08/17/2013] [Indexed: 01/25/2023]
Abstract
BACKGROUND Duodenal cytochrome b (Dcytb) is a mammalian plasma ferric reductase enzyme that catalyses the reduction of ferric to ferrous ion in the process of iron absorption. The current study investigates the relationship between Dcytb, iron, dehydroascorbate (DHA) and Hif-2α in cultured cell lines. METHODS Dcytb and Hif-2α protein expression was analysed by Western blot technique while gene regulation was determined by quantitative PCR. Functional analyses were carried out by ferric reductase and (59)Fe uptake assays. RESULTS Iron and dehydroascorbic acid treatment of cells inhibited Dcytb mRNA and protein expression. Desferrioxamine also enhanced Dcytb mRNA level after cells were treated overnight. Dcytb knockdown in HuTu cells resulted in reduced mRNA expression and lowered reductase activity. Preloading cells with DHA (to enhance intracellular ascorbate levels) did not stimulate reductase activity fully in Dcytb-silenced cells, implying a Dcytb-dependence of ascorbate-mediated ferrireduction. Moreover, Hif-2α knockdown in HuTu cells led to a reduction in reductase activity and iron uptake. CONCLUSIONS Taken together, this study shows the functional regulation of Dcytb reductase activity by DHA and Hif-2α. GENERAL SIGNIFICANCE Dcytb is a plasma membrane protein that accepts electrons intracellularly from DHA/ascorbic acid for ferrireduction at the apical surface of cultured cells and enterocytes.
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Affiliation(s)
- Xiaomin Luo
- Diabetes and Nutritional Sciences Division, King's College London, London, UK
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23
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Recuenco MC, Rahman MM, Sakamoto Y, Takeuchi F, Hori H, Tsubaki M. Functional characterization of the recombinant human tumour suppressor 101F6 protein, a cytochrome b(561) homologue. J Biochem 2012; 153:233-42. [PMID: 23235316 DOI: 10.1093/jb/mvs139] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Candidate human tumour suppressor gene product, 101F6 protein, is a highly hydrophobic transmembrane protein and a member of cytochrome b(561) family. Purified 101F6 protein expressed in Pichia pastoris cells showed visible absorption spectra similar but distinct from those of cytochrome b(561). Haem content analysis indicated presence of two haems B per molecule. Midpoint potentials of the purified protein were found as +109 and +26 mV for two haems, slightly lower than those for bovine chromaffin granule or plant Zea mays cytochromes b(561). Electron paramagnetic resonance (EPR) spectra in oxidized state at 5 K showed only a highly anisotropic low-spin (HALS) signal at g(z) = 3.75. However, at 15 and 20 K, another HALS-type signal appeared at g(z) = 3.65 being overlapped with that of g(z) = 3.75. The rhombic EPR signal at g(z) = 3.16 previously seen in other cytochromes b(561) was not observed, suggesting distinct haem environments. Absence of the inhibition in the electron transfer from ascorbate by a treatment of 101F6 protein with diethylpyrocarbonate showed a remarkable contrast from those of other cytochromes b(561) where the 'concerted H(+)/e(-) transfer mechanism' at the cytosolic haem centre was blocked by specific Nε-carbethoxylation of haem-coordinating imidazole, suggesting that 101F6 protein might accept electrons via a mechanism distinct from other cytochromes b(561).
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Affiliation(s)
- Mariam C Recuenco
- Department of Chemistry, Graduate School of Science, Kobe University, Kobe, Hyogo, Japan
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24
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Dihydrolipoic acid reduces cytochrome b561 proteins. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2012; 42:159-68. [DOI: 10.1007/s00249-012-0812-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 03/22/2012] [Accepted: 03/27/2012] [Indexed: 12/11/2022]
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Lu Y, Fröbom R, Lagergren J. Incidence patterns of small bowel cancer in a population-based study in Sweden: increase in duodenal adenocarcinoma. Cancer Epidemiol 2012; 36:e158-63. [PMID: 22405637 DOI: 10.1016/j.canep.2012.01.008] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 11/30/2011] [Accepted: 01/30/2012] [Indexed: 12/14/2022]
Abstract
BACKGROUND Increasing incidences of malignant small bowel tumours have been reported, but data from European populations are limited. This study aimed to clarify the incidence patterns of malignant small bowel tumours in Sweden. METHODS Patients with a first and primary malignant small bowel tumour were identified from the Swedish Cancer Register during the study period 1960-2009. Sex-specific and age-standardised incidence rates of these tumours were calculated by their anatomical location and histological type in different time periods. Figures were plotted to show the proportions and incidence rates over time, and joinpoint loglinear regression models were estimated to assess any time trends. RESULTS A total of 6604 patients with malignant small bowel tumours were identified. The age-standardised incidence of all malignant small bowel tumours increased from 14.2 to 19.7 per 1,000,000 person-years during the study period. The incidence of duodenal cancer increased more than 3-fold (from 1.6 to 5.4 per 1,000,000 person-years), which was mainly expained by a dramatical rising trend of adenocarcinoma of the duodenum (from 0.7 to 4.2 per 1,000,000 person-years). Malignant tumours of small bowel with unspecified anatomical locations showed a slight increase (from 7.0 to 7.9 per 1,000,000). The incidence of small bowel tumours in other locations or of other histological types was more stable. CONCLUSIONS The incidence of small bowel malignancies has increased during the period 1960-2009. Among the specific types of small bowel cancer, a particularly rapid increase was found for duodenal adenocarcinoma.
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Affiliation(s)
- Yunxia Lu
- Upper Gastrointestinal Research, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
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26
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Cenacchi L, Busch M, Schleidt PG, Müller FG, Stumpp TVM, Mäntele W, Trost P, Lancaster CRD. Heterologous production and characterisation of two distinct dihaem-containing membrane integral cytochrome b(561) enzymes from Arabidopsis thaliana in Pichia pastoris and Escherichia coli cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:679-88. [PMID: 22085541 DOI: 10.1016/j.bbamem.2011.10.030] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Revised: 10/29/2011] [Accepted: 10/31/2011] [Indexed: 01/07/2023]
Abstract
Cytochrome (cyt) b(561) proteins are dihaem-containing membrane proteins, belonging to the CYBASC (cytochrome-b(561)-ascorbate-reducible) family, and are proposed to be involved in ascorbate recycling and/or the facilitation of iron absorption. Here, we present the heterologous production of two cyt b(561) paralogs from Arabidopsis thaliana (Acytb(561)-A, Acytb(561)-B) in Escherichia coli and Pichia pastoris, their purification, and initial characterisation. Spectra indicated that Acytb(561)-A resembles the best characterised member of the CYBASC family, the cytochrome b(561) from adrenomedullary chromaffin vesicles, and that Acytb(561)-B is atypical compared to other CYBASC proteins. Haem oxidation-reduction midpoint potential (E(M)) values were found to be fully consistent with ascorbate oxidation activities and Fe(3+)-chelates reductase activities. The ascorbate dependent reduction and protein stability of both paralogs were found to be sensitive to alkaline pH values as reported for the cytochrome b(561) from chromaffin vesicles. For both paralogs, ascorbate-dependent reduction was inhibited and the low-potential haem E(M) values were affected significantly by incubation with diethyl pyrocarbonate (DEPC) in the absence of ascorbate. Modification with DEPC in the presence of ascorbate left the haem E(M) values unaltered compared to the unmodified proteins. However, ascorbate reduction was inhibited. We concluded that the ascorbate-binding site is located near the low-potential haem with the Fe(3+)-chelates reduction-site close to the high-potential haem. Furthermore, inhibition of ascorbate oxidation by DEPC treatment occurs not only by lowering the haem E(M) values but also by an additional modification affecting ascorbate binding and/or electron transfer. Analytical gel filtration experiments suggest that both cyt b(561) paralogs exist as homodimers.
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Affiliation(s)
- Lucia Cenacchi
- Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Frankfurt, Germany
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Del Principe D, Avigliano L, Savini I, Catani MV. Trans-plasma membrane electron transport in mammals: functional significance in health and disease. Antioxid Redox Signal 2011; 14:2289-318. [PMID: 20812784 DOI: 10.1089/ars.2010.3247] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Trans-plasma membrane electron transport (t-PMET) has been established since the 1960s, but it has only been subject to more intensive research in the last decade. The discovery and characterization at the molecular level of its novel components has increased our understanding of how t-PMET regulates distinct cellular functions. This review will give an update on t-PMET, with particular emphasis on how its malfunction relates to some diseases, such as cancer, abnormal cell death, cardiovascular diseases, aging, obesity, neurodegenerative diseases, pulmonary fibrosis, asthma, and genetically linked pathologies. Understanding these relationships may provide novel therapeutic approaches for pathologies associated with unbalanced redox state.
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Affiliation(s)
- Domenico Del Principe
- Department of Experimental Medicine and Biochemical Sciences, University of Rome Tor Vergata, Rome, Italy.
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Liu W, Wu G, Tsai AL, Kulmacz RJ. High-yield production, purification and characterization of functional human duodenal cytochrome b in an Escherichia coli system. Protein Expr Purif 2011; 79:115-21. [PMID: 21501687 DOI: 10.1016/j.pep.2011.04.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Revised: 03/29/2011] [Accepted: 04/01/2011] [Indexed: 11/15/2022]
Abstract
Human duodenal cytochrome b (Dcytb) is a transmembrane hemoprotein found in the duodenal brush border membrane and in erythrocytes. Dcytb has been linked to uptake of dietary iron and to ascorbate recycling in erythrocytes. Detailed biophysical and biochemical characterization of Dcytb has been limited by difficulties in expressing sufficient amounts of functional recombinant protein in yeast and insect cell systems. We have developed an Escherichia coli Rosetta-gami B(DE3) cell system for production of recombinant His-tagged human Dcytb with a yield of ∼26 mg of purified, ascorbate-reducible cytochrome per liter of culture. The recombinant protein is readily solubilized with n-dodecyl-β-D-maltoside and purified to electrophoretic homogeneity by one-step chromatography on cobalt affinity resin. The purified recombinant Dcytb has a heme to protein ratio very close to the theoretical value of 2 and retains functional reactivity with ascorbate, as assessed by spectroscopic and kinetic measurements. Ascorbate showed a marked kinetic selectivity for the high-potential heme center over the low-potential heme center in purified Dcytb. This new E. coli expression system for Dcytb offers ∼7-fold improvement in yield and other substantial advantages over existing expression systems for reliable production of functional Dcytb at levels suitable for biochemical, biophysical and structural characterization.
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Affiliation(s)
- Wen Liu
- Department of Internal Medicine, University of Texas Health Science Center, Houston, TX 77030, United States.
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Abstract
Iron is an essential trace metal in the human diet because of its role in a number of metabolic processes including oxygen transport. In the diet, iron is present in two fundamental forms, heme and non-heme iron. This article presents a brief overview of the molecular mechanisms of intestinal iron absorption and its regulation. While many proteins that orchestrate iron transport pathway have been identified, a number of key factors that control the regulation of iron absorption still remain to be elucidated. This review also summarizes new and emerging information about iron metabolic regulators that coordinate regulation of intestinal iron absorption.
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Affiliation(s)
- Okhee Han
- Department of Nutritional Sciences, The Pennsylvania State University, 110 Chandlee Laboratory, University Park, PA 16802, USA.
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Nakanishi N, Rahman MM, Sakamoto Y, Takigami T, Kobayashi K, Hori H, Hase T, Park SY, Tsubaki M. Importance of the conserved lysine 83 residue of Zea mays cytochrome b(561) for ascorbate-specific transmembrane electron transfer as revealed by site-directed mutagenesis studies. Biochemistry 2009; 48:10665-78. [PMID: 19803484 DOI: 10.1021/bi9010682] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cytochromes b(561), a novel class of transmembrane electron transport proteins residing in a large variety of eukaryotic cells, have a number of common structural features including six hydrophobic transmembrane alpha-helices and two heme ligation sites. We found that recombinant Zea mays cytochrome b(561) obtained by a heterologous expression system using yeast Pichia pastoris cells could utilize the ascorbate/mondehydroascorbate radical as a physiological electron donor/acceptor. We found further that a concerted proton/electron transfer mechanism might be operative in Z. mays cytochrome b(561) as well upon the electron acceptance from ascorbate to the cytosolic heme center. The well-conserved Lys(83) residue in a cytosolic loop was found to have a very important role(s) for the binding of ascorbate and the succeeding electron transfer via electrostatic interactions based on the analyses of three site-specific mutants, K83A, K83E, and K83D. Further, unusual behavior of the K83A mutant in pulse radiolysis experiments indicated that Lys(83) might also be responsible for the intramolecular electron transfer to the intravesicular heme. On the other hand, pulse radiolysis experiments on two site-specific mutants, S118A and W122A, for the well-conserved residues in the putative monodehydroascorbate radical binding site showed that their electron transfer activities to the monodehydroascorbate radical were very similar to those of the wild-type protein, indicating that Ser(118) and Trp(122) do not have major roles for the redox events on the intravesicular side.
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Affiliation(s)
- Nobuyuki Nakanishi
- Department of Molecular Science and Material Engineering, Graduate School of Science and Technology, Graduate School of Science, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
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Hower V, Mendes P, Torti FM, Laubenbacher R, Akman S, Shulaev V, Torti SV. A general map of iron metabolism and tissue-specific subnetworks. MOLECULAR BIOSYSTEMS 2009; 5:422-43. [PMID: 19381358 PMCID: PMC2680238 DOI: 10.1039/b816714c] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Iron is required for survival of mammalian cells. Recently, understanding of iron metabolism and trafficking has increased dramatically, revealing a complex, interacting network largely unknown just a few years ago. This provides an excellent model for systems biology development and analysis. The first step in such an analysis is the construction of a structural network of iron metabolism, which we present here. This network was created using CellDesigner version 3.5.2 and includes reactions occurring in mammalian cells of numerous tissue types. The iron metabolic network contains 151 chemical species and 107 reactions and transport steps. Starting from this general model, we construct iron networks for specific tissues and cells that are fundamental to maintaining body iron homeostasis. We include subnetworks for cells of the intestine and liver, tissues important in iron uptake and storage, respectively, as well as the reticulocyte and macrophage, key cells in iron utilization and recycling. The addition of kinetic information to our structural network will permit the simulation of iron metabolism in different tissues as well as in health and disease.
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Affiliation(s)
- Valerie Hower
- Department of Cancer Biology, Wake Forest University School of Medicine, Medical Center Blvd, Winston Salem, NC 27157, USA
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32
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Abstract
Dcytb (duodenal cytochrome b) is an iron-regulated ferric reductase highly expressed in duodenal enterocytes. Its location and strong regulation by iron has indicated it plays an important role in iron absorption. Expression of Dcytb in cells (Caco-2 and MDCK) was found to increase both ferric reductase activity and stimulate uptake of 59Fe. An additional increase in cupric reductase activity was found in MDCK (Madin–Darby canine kidney) cells expressing Dcytb. Expression and purification of Dcytb in insect cells reveals that Dcytb is a di-haem protein and that the haems are reducible by ascorbate, indicating that ascorbate is the likely intracelluar electron donor. Studies underway in Dcytb-knockout mice reveal that Dcytb is the only iron-regulated ferric reductase in the duodenal mucosa and that loss of Dcytb affects iron absorption.
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Moriya M, Ho YH, Grana A, Nguyen L, Alvarez A, Jamil R, Ackland ML, Michalczyk A, Hamer P, Ramos D, Kim S, Mercer JFB, Linder MC. Copper is taken up efficiently from albumin and alpha2-macroglobulin by cultured human cells by more than one mechanism. Am J Physiol Cell Physiol 2008; 295:C708-21. [PMID: 18579803 PMCID: PMC2544443 DOI: 10.1152/ajpcell.00029.2008] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Accepted: 06/19/2008] [Indexed: 11/22/2022]
Abstract
Ionic copper entering blood plasma binds tightly to albumin and the macroglobulin transcuprein. It then goes primarily to the liver and kidney except in lactation, where a large portion goes directly to the mammary gland. Little is known about how this copper is taken up from these plasma proteins. To examine this, the kinetics of uptake from purified human albumin and alpha(2)-macroglobulin, and the effects of inhibitors, were measured using human hepatic (HepG2) and mammary epithelial (PMC42) cell lines. At physiological concentrations (3-6 muM), both cell types took up copper from these proteins independently and at rates similar to each other and to those for Cu-dihistidine or Cu-nitrilotriacetate (NTA). Uptakes from alpha(2)-macroglobulin indicated a single saturable system in each cell type, but with different kinetics, and 65-80% inhibition by Ag(I) in HepG2 cells but not PMC42 cells. Uptake kinetics for Cu-albumin were more complex and also differed with cell type (as was the case for Cu-histidine and NTA), and there was little or no inhibition by Ag(I). High Fe(II) concentrations (100-500 microM) inhibited copper uptake from albumin by 20-30% in both cell types and that from alpha(2)-macroglobulin by 0-30%, and there was no inhibition of the latter by Mn(II) or Zn(II). We conclude that the proteins mainly responsible for the plasma-exchangeable copper pool deliver the metal to mammalian cells efficiently and by several different mechanisms. alpha(2)-Macroglobulin delivers it primarily to copper transporter 1 in hepatic cells but not mammary epithelial cells, and additional as-yet-unidentified copper transporters or systems for uptake from these proteins remain to be identified.
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Affiliation(s)
- Mizue Moriya
- Department of Chemistry and Biochemistry and Institute for Molecular Biology and Nutrition, California State University, Fullerton, California 92834-6866, USA
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Lane DJR, Lawen A. Non-transferrin iron reduction and uptake are regulated by transmembrane ascorbate cycling in K562 cells. J Biol Chem 2008; 283:12701-8. [PMID: 18347019 DOI: 10.1074/jbc.m800713200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
K562 erythroleukemia cells import non-transferrin-bound iron (NTBI) by an incompletely understood process that requires initial iron reduction. The mechanism of NTBI ferrireduction remains unknown but probably involves transplasma membrane electron transport. We here provide evidence for a novel mechanism of NTBI reduction and uptake by K562 cells that utilizes transplasma membrane ascorbate cycling. Incubation of cells with dehydroascorbic acid, but not ascorbate, resulted in (i) accumulation of intracellular ascorbate that was blocked by the glucose transporter inhibitor, cytochalasin B, and (ii) subsequent release of micromolar concentrations of ascorbate into the external medium via a route that was sensitive to the anion channel inhibitor, 4,4'-diisothiocyanatostilbene-2,2'-disulfonate. Ascorbate-deficient control cells demonstrated low levels of ferric citrate reduction. However, incubation of the cells with dehydroascorbic acid resulted in a dose-dependent stimulation of both iron reduction and uptake from radiolabeled [(55)Fe]ferric citrate. This stimulation was abrogated by ascorbate oxidase treatment, suggesting dependence on direct chemical reduction by ascorbate. These results support a novel model of NTBI reduction and uptake by K562 cells in which uptake is preceded by reduction of iron by extracellular ascorbate, the latter of which is subsequently regenerated by transplasma membrane ascorbate cycling.
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Affiliation(s)
- Darius J R Lane
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Melbourne, Victoria 3800, Australia
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