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Sze SCW, Zhang L, Zhang S, Lin K, Ng TB, Ng ML, Lee KF, Lam JKW, Zhang Z, Yung KKL. Aberrant Transferrin and Ferritin Upregulation Elicits Iron Accumulation and Oxidative Inflammaging Causing Ferroptosis and Undermines Estradiol Biosynthesis in Aging Rat Ovaries by Upregulating NF-Κb-Activated Inducible Nitric Oxide Synthase: First Demonstration of an Intricate Mechanism. Int J Mol Sci 2022; 23:ijms232012689. [PMID: 36293552 PMCID: PMC9604315 DOI: 10.3390/ijms232012689] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 10/12/2022] [Accepted: 10/13/2022] [Indexed: 11/07/2022] Open
Abstract
We report herein a novel mechanism, unraveled by proteomics and validated by in vitro and in vivo studies, of the aberrant aging-associated upregulation of ovarian transferrin and ferritin in rat ovaries. The ovarian mass and serum estradiol titer plummeted while the ovarian labile ferrous iron and total iron levels escalated with age in rats. Oxidative stress markers, such as nitrite/nitrate, 3-nitrotyrosine, and 4-hydroxy-2-nonenal, accumulated in the aging ovaries due to an aberrant upregulation of the ovarian transferrin, ferritin light/heavy chains, and iron regulatory protein 2(IRP2)-mediated transferrin receptor 1 (TfR1). Ferritin inhibited estradiol biosynthesis in ovarian granulosa cells in vitro via the upregulation of a nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and p65/p50-induced oxidative and inflammatory factor inducible nitric oxide synthase (iNOS). An in vivo study demonstrated how the age-associated activation of NF-κB induced the upregulation of iNOS and the tumor necrosis factor α (TNFα). The downregulation of the keap1-mediated nuclear factor erythroid 2-related factor 2 (Nrf2), that induced a decrease in glutathione peroxidase 4 (GPX4), was observed. The aberrant transferrin and ferritin upregulation triggered an iron accumulation via the upregulation of an IRP2-induced TfR1. This culminates in NF-κB-iNOS-mediated ovarian oxi-inflamm-aging and serum estradiol decrement in naturally aging rats. The iron accumulation and the effect on ferroptosis-related proteins including the GPX4, TfR1, Nrf2, Keap1, and ferritin heavy chain, as in testicular ferroptosis, indicated the triggering of ferroptosis. In young rats, an intraovarian injection of an adenovirus, which expressed iron regulatory proteins, upregulated the ovarian NF-κB/iNOS and downregulated the GPX4. These novel findings have contributed to a prompt translational research on the ovarian aging-associated iron metabolism and aging-associated ovarian diseases.
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Affiliation(s)
- Stephen Cho Wing Sze
- Department of Biology, Faculty of Science, Hong Kong Baptist University, Kowloon, Hong Kong SAR 999077, China
- Golden Meditech Center for NeuroRegeneration Sciences, Hong Kong Baptist University, Kowloon, Hong Kong SAR 999077, China
- Correspondence: (S.C.W.S.); (K.K.L.Y.); Tel.: +852-34112318 (S.C.W.S.); Tel.: +852-34117060 (K.K.L.Y.)
| | - Liang Zhang
- School of Chinese Medicine, LKS Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR 999077, China
| | - Shiqing Zhang
- Department of Biology, Faculty of Science, Hong Kong Baptist University, Kowloon, Hong Kong SAR 999077, China
- Golden Meditech Center for NeuroRegeneration Sciences, Hong Kong Baptist University, Kowloon, Hong Kong SAR 999077, China
- JNU-HKUST Joint Laboratory for Neuroscience and Innovative Drug Research, College of Pharmacy, Jinan University, Guangzhou 999077, China
| | - Kaili Lin
- Department of Biology, Faculty of Science, Hong Kong Baptist University, Kowloon, Hong Kong SAR 999077, China
- Golden Meditech Center for NeuroRegeneration Sciences, Hong Kong Baptist University, Kowloon, Hong Kong SAR 999077, China
- School of Public Health, Guangzhou Medical University, Guangzhou 999077, China
| | - Tzi Bun Ng
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR 999077, China
| | - Man Ling Ng
- Department of Biology, Faculty of Science, Hong Kong Baptist University, Kowloon, Hong Kong SAR 999077, China
- Golden Meditech Center for NeuroRegeneration Sciences, Hong Kong Baptist University, Kowloon, Hong Kong SAR 999077, China
| | - Kai-Fai Lee
- Department of Obstetrics and Gynaecology, LKS Faculty of Medicine, HKU, Pokfulam, Hong Kong SAR 999077, China
| | - Jenny Ka Wing Lam
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
- Department of Pharmacology & Pharmacy, LKS Faculty of Medicine, HKU, Pokfulam, Hong Kong SAR 999077, China
| | - Zhang Zhang
- Department of Biology, Faculty of Science, Hong Kong Baptist University, Kowloon, Hong Kong SAR 999077, China
- Golden Meditech Center for NeuroRegeneration Sciences, Hong Kong Baptist University, Kowloon, Hong Kong SAR 999077, China
| | - Ken Kin Lam Yung
- Department of Biology, Faculty of Science, Hong Kong Baptist University, Kowloon, Hong Kong SAR 999077, China
- Golden Meditech Center for NeuroRegeneration Sciences, Hong Kong Baptist University, Kowloon, Hong Kong SAR 999077, China
- Correspondence: (S.C.W.S.); (K.K.L.Y.); Tel.: +852-34112318 (S.C.W.S.); Tel.: +852-34117060 (K.K.L.Y.)
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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: 69] [Impact Index Per Article: 17.3] [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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Burkitt MJ. Chemical, Biological and Medical Controversies Surrounding the Fenton Reaction. PROGRESS IN REACTION KINETICS AND MECHANISM 2019. [DOI: 10.3184/007967403103165468] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A critical evaluation is made of the role of the Fenton reaction (Fe2+ + H2O2 → Fe3+ + •OH + OH-) in the promotion of oxidative damage in mammalian systems. Following a brief, historical overview of the Fenton reaction, including the formulation of the Haber–Weiss cycle as a mechanism for the catalysis of hydroxyl radical production, an appraisal is made of the biological relevance of the reaction today, following recognition of the important role played by nitric oxide and its congers in the promotion of biomolecular damage. In depth coverage is then given of the evidence (largely from EPR studies) for and against the hydroxyl radical as the active oxidant produced in the Fenton reaction and the role of metal chelating agents (including those of biological importance) and ascorbic acid in the modulation of its generation. This is followed by a description of the important developments that have occurred recently in the molecular and cellular biology of iron, including evidence for the presence of ‘free’ iron that is available in vivo for the Fenton reaction. Particular attention here is given to the role of the iron-regulatory proteins in the modulation of cellular iron status and how their functioning may become dysregulated during oxidative and nitrosative stress, as well as in hereditary haemochromatosis, a common disorder of iron metabolism. Finally, an assessment is made of the biological relevance of ascorbic acid in the promotion of hydroxyl radical generation by the Fenton reaction in health and disease.
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Affiliation(s)
- Mark J. Burkitt
- Cancer Research UK Free Radicals Research Group, Gray Cancer Institute, PO Box 100, Mount Vernon Hospital, Northwood, Middlesex HA6 2JR, UK
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Chungopast S, Duangkhet M, Tajima S, Ma JF, Nomura M. Iron-induced nitric oxide leads to an increase in the expression of ferritin during the senescence of Lotus japonicus nodules. JOURNAL OF PLANT PHYSIOLOGY 2017; 208:40-46. [PMID: 27889519 DOI: 10.1016/j.jplph.2016.11.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2016] [Revised: 08/25/2016] [Accepted: 11/14/2016] [Indexed: 06/06/2023]
Abstract
Iron is an essential nutrient for legume-rhizobium symbiosis and accumulates abundantly in the nodules. However, the concentration of free iron in the cells is strictly controlled to avoid toxicity. It is known that ferritin accumulates in the cells as an iron storage protein. During nodule senescence, the expression of the ferritin gene, Ljfer1, was induced in Lotus japonicus. We investigated a signal transduction pathway leading to the increase of Ljfer1 in the nodule. The Ljfer1 promoter of L. japonicus contains a conserved Iron-Dependent Regulatory Sequence (IDRS). The expression of Ljfer1 was induced by the application of iron or sodium nitroprusside, which is a nitric oxide (NO) donor. The application of iron to the nodule increased the level of NO. These data strongly suggest that iron-induced NO leads to increased expression of Ljfer1 during the senescence of L. japonicus nodules.
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Affiliation(s)
- Sirinapa Chungopast
- Faculty of Agriculture, Kagawa University, Miki-cho, Kita-gun, Kagawa 761-0795, Japan; Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Nakorn Pathom 73140, Thailand
| | - Mallika Duangkhet
- Faculty of Agriculture, Kagawa University, Miki-cho, Kita-gun, Kagawa 761-0795, Japan
| | - Shigeyuki Tajima
- Faculty of Agriculture, Kagawa University, Miki-cho, Kita-gun, Kagawa 761-0795, Japan
| | - Jian Feng Ma
- Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan
| | - Mika Nomura
- Faculty of Agriculture, Kagawa University, Miki-cho, Kita-gun, Kagawa 761-0795, Japan.
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White RS, Bhattacharya AK, Chen Y, Byrd M, McMullen MF, Siegel SJ, Carlson GC, Kim SF. Lysosomal iron modulates NMDA receptor-mediated excitation via small GTPase, Dexras1. Mol Brain 2016; 9:38. [PMID: 27080392 PMCID: PMC4832449 DOI: 10.1186/s13041-016-0220-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 04/08/2016] [Indexed: 12/23/2022] Open
Abstract
Background Activation of NMDA receptors can induce iron movement into neurons by the small GTPase Dexras1 via the divalent metal transporter 1 (DMT1). This pathway under pathological conditions such as NMDA excitotoxicity contributes to metal-catalyzed reactive oxygen species (ROS) generation and neuronal cell death, and yet its physiological role is not well understood. Results We found that genetic and pharmacological ablation of this neuronal iron pathway in the mice increased glutamatergic transmission. Voltage sensitive dye imaging of hippocampal slices and whole-cell patch clamping of synaptic currents, indicated that the increase in excitability was due to synaptic modification of NMDA receptor activity via modulation of the PKC/Src/NR2A pathway. Moreover, we identified that lysosomal iron serves as a main source for intracellular iron signaling modulating glutamatergic excitability. Conclusions Our data indicates that intracellular iron is dynamically regulated in the neurons and robustly modulate synaptic excitability under physiological condition. Since NMDA receptors play a central role in synaptic neurophysiology, plasticity, neuronal homeostasis, neurodevelopment as well as in the neurobiology of many diseases, endogenous iron is therefore likely to have functional relevance to each of these areas.
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Affiliation(s)
- Rachel S White
- Department of Psychiatry, Center for Neurobiology and Behavior, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Anup K Bhattacharya
- Department of Psychiatry, Center for Neurobiology and Behavior, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Yong Chen
- Department of Psychiatry, Center for Neurobiology and Behavior, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Madeleine Byrd
- Department of Psychiatry, Center for Neurobiology and Behavior, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Mary F McMullen
- Department of Psychiatry, Center for Neurobiology and Behavior, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Steven J Siegel
- Department of Psychiatry, Center for Neurobiology and Behavior, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Gregory C Carlson
- Department of Psychiatry, Center for Neurobiology and Behavior, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Sangwon F Kim
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania, 125 S 31st, TRL RM 2207, Philadelphia, PA, 19104, USA.
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Chen Y, Mathias L, Falero-Perez JM, Kim SF. PKA-mediated phosphorylation of Dexras1 suppresses iron trafficking by inhibiting S-nitrosylation. FEBS Lett 2015; 589:3212-9. [PMID: 26358293 DOI: 10.1016/j.febslet.2015.08.041] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 08/21/2015] [Accepted: 08/26/2015] [Indexed: 01/26/2023]
Abstract
Dexras1 is a small GTPase and plays a central role in neuronal iron trafficking. We have shown that stimulation of glutamate receptors activates neuronal nitric oxide synthase, leading to S-nitrosylation of Dexras1 and a physiological increase in iron uptake. Here we report that Dexras1 is phosphorylated by protein kinase A (PKA) on serine 253, leading to a suppression of iron influx. These effects were directly associated with the levels of S-nitrosylated Dexras1, whereby PKA activation reduced Dexras1 S-nitrosylation in a dose dependent manner. Moreover, we found that adiponectin modulates Dexras1 via PKA. Hence these findings suggest the involvement of the PKA pathway in modulating glutamate-mediated ROS in neurons, and hint to a functional crosstalk between S-nitrosylation and phosphorylation.
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Affiliation(s)
- Yong Chen
- Department of Psychiatry, and Systems Pharmacology and Translational Therapeutics, Center for Neurobiology and Behavior, The Perlman School of Medicine at the University of Pennsylvania, 125 S 31st St. TRL Rm 2207, Philadelphia, PA 19104, United States
| | - Lauren Mathias
- Department of Psychiatry, and Systems Pharmacology and Translational Therapeutics, Center for Neurobiology and Behavior, The Perlman School of Medicine at the University of Pennsylvania, 125 S 31st St. TRL Rm 2207, Philadelphia, PA 19104, United States
| | - Juliana M Falero-Perez
- Department of Psychiatry, and Systems Pharmacology and Translational Therapeutics, Center for Neurobiology and Behavior, The Perlman School of Medicine at the University of Pennsylvania, 125 S 31st St. TRL Rm 2207, Philadelphia, PA 19104, United States
| | - Sangwon F Kim
- Department of Psychiatry, and Systems Pharmacology and Translational Therapeutics, Center for Neurobiology and Behavior, The Perlman School of Medicine at the University of Pennsylvania, 125 S 31st St. TRL Rm 2207, Philadelphia, PA 19104, United States.
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Bresgen N, Eckl PM. Oxidative stress and the homeodynamics of iron metabolism. Biomolecules 2015; 5:808-47. [PMID: 25970586 PMCID: PMC4496698 DOI: 10.3390/biom5020808] [Citation(s) in RCA: 165] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Revised: 04/21/2015] [Accepted: 04/22/2015] [Indexed: 12/12/2022] Open
Abstract
Iron and oxygen share a delicate partnership since both are indispensable for survival, but if the partnership becomes inadequate, this may rapidly terminate life. Virtually all cell components are directly or indirectly affected by cellular iron metabolism, which represents a complex, redox-based machinery that is controlled by, and essential to, metabolic requirements. Under conditions of increased oxidative stress—i.e., enhanced formation of reactive oxygen species (ROS)—however, this machinery may turn into a potential threat, the continued requirement for iron promoting adverse reactions such as the iron/H2O2-based formation of hydroxyl radicals, which exacerbate the initial pro-oxidant condition. This review will discuss the multifaceted homeodynamics of cellular iron management under normal conditions as well as in the context of oxidative stress.
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Affiliation(s)
- Nikolaus Bresgen
- Department of Cell Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg, Austria.
| | - Peter M Eckl
- Department of Cell Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg, Austria.
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Silva-Gomes S, Bouton C, Silva T, Santambrogio P, Rodrigues P, Appelberg R, Gomes MS. Mycobacterium avium infection induces H-ferritin expression in mouse primary macrophages by activating Toll-like receptor 2. PLoS One 2013; 8:e82874. [PMID: 24349383 PMCID: PMC3857292 DOI: 10.1371/journal.pone.0082874] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 11/06/2013] [Indexed: 11/18/2022] Open
Abstract
Important for both host and pathogen survivals, iron is a key factor in determining the outcome of an infectious process. Iron with-holding, including sequestration inside tissue macrophages, is considered an important strategy to fight infection. However, for intra-macrophagic pathogens, such as Mycobacterium avium, host defence may depend on intracellular iron sequestration mechanisms. Ferritin, the major intracellular iron storage protein, plays a critical role in this process. In the current study, we studied ferritin expression in mouse bone marrow-derived macrophages upon infection with M. avium. We found that H-ferritin is selectively increased in infected macrophages, through an up-regulation of gene transcription. This increase was mediated by the engagement of Toll like receptor-2, and was independent of TNF-alpha or nitric oxide production. The formation of H-rich ferritin proteins and the consequent iron sequestration may be an important part of the panoply of antimicrobial mechanisms of macrophages.
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Affiliation(s)
- Sandro Silva-Gomes
- IBMC, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
- ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Cécile Bouton
- Institut de Chimie des Substances Naturelles, UPR2301 CNRS, Centre de Recherche de Gif, Gif-sur-Yvette, France
| | - Tânia Silva
- IBMC, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
- ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | | | - Pedro Rodrigues
- IBMC, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
- ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Rui Appelberg
- IBMC, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
- ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Maria Salomé Gomes
- IBMC, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
- ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
- * E-mail:
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Lewinska A, Bartosz G. Yeast flavohemoglobin protects against nitrosative stress and controls ferric reductase activity. Redox Rep 2013; 11:231-9. [PMID: 17132272 DOI: 10.1179/135100006x154987] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The role of Saccharomyces cerevisiae flavohemoglobin (Yhb1) is controversial and far from understood. This study compares the effects of nitrosative and oxidative challenge on the yeast mutant lacking the YHB1 gene. Growth of the mutant was impaired by nitrosoglutathione and peroxynitrite, whereas increased sensitivity to reactive oxygen species was not observed. Increased levels of intracellular NO(*) after incubation with NO(*) donors were found in the mutants cells as compared to the wild-type cells. Deletion of the YHB1 gene was found to augment the reduction of Fe(3+) by yeast cells which suggests that flavohemoglobin participates in regulation of the activity of plasma membrane ferric reductase(s).
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Affiliation(s)
- Anna Lewinska
- Department of Biochemistry and Cell Biology, University of Rzeszow, Rzeszow, Poland.
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Li H, Song JB, Zhao WT, Yang ZM. AtHO1 is Involved in Iron Homeostasis in an NO-Dependent Manner. ACTA ACUST UNITED AC 2013; 54:1105-17. [DOI: 10.1093/pcp/pct063] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Toll-like receptor signal adaptor protein MyD88 is required for sustained endotoxin-induced acute hypoferremic response in mice. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 180:2340-50. [PMID: 22497726 DOI: 10.1016/j.ajpath.2012.01.046] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Revised: 01/24/2012] [Accepted: 01/30/2012] [Indexed: 12/24/2022]
Abstract
Hypoferremia, associated with immune system activation, involves a marked reduction in the levels of circulating iron, coupled with iron sequestration within macrophages. Toll-like receptor (TLR) signaling plays an important role in the development of the hypoferremic response, but how downstream signaling events affect genes involved in iron metabolism is incompletely understood. We investigated the involvement of MyD88-dependent (MyD88) and MyD88-independent (TRIF) TLR signaling in the development of hypoferremia. Using MyD88-deficient and TRIF-deficient mice, we show that MyD88 and TRIF signaling pathways are critical for up-regulation by lipopolysaccharide (LPS) of the iron regulator hepcidin. In addition, MyD88 signaling is required for the induction of lipocalin 2 secretion and iron sequestration in the spleen. Activation of TLR4 and TLR3 signaling through LPS and polyinosinic:polycytidylic acid [poly(I:C)] treatments resulted in rapid down-regulation of HFE protein [encoded by the hemochromatosis gene (Hfe)] and ferroportin [encoded by solute carrier family 40 (iron-regulated transporter), member 1 (Slc40a1)] expression in the spleen, independent of MyD88 or TRIF signaling and proinflammatory cytokine production. However, lack of MyD88 signaling significantly impaired the hypoferremic response triggered by LPS, indicating that ferroportin and HFE protein down-regulation alone are insufficient to maintain hypoferremia. The extent of the hypoferremic response was found to be limited by initial, basal iron levels. Together, these results suggest that targeting specific TLR signaling pathways by affecting the function of adaptor molecules may provide new strategies to counteract iron sequestration within macrophages during inflammation.
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Sheftel AD, Mason AB, Ponka P. The long history of iron in the Universe and in health and disease. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1820:161-87. [PMID: 21856378 PMCID: PMC3258305 DOI: 10.1016/j.bbagen.2011.08.002] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Revised: 07/19/2011] [Accepted: 08/01/2011] [Indexed: 12/21/2022]
Abstract
BACKGROUND Not long after the Big Bang, iron began to play a central role in the Universe and soon became mired in the tangle of biochemistry that is the prima essentia of life. Since life's addiction to iron transcends the oxygenation of the Earth's atmosphere, living things must be protected from the potentially dangerous mix of iron and oxygen. The human being possesses grams of this potentially toxic transition metal, which is shuttling through his oxygen-rich humor. Since long before the birth of modern medicine, the blood-vibrant red from a massive abundance of hemoglobin iron-has been a focus for health experts. SCOPE OF REVIEW We describe the current understanding of iron metabolism, highlight the many important discoveries that accreted this knowledge, and describe the perils of dysfunctional iron handling. GENERAL SIGNIFICANCE Isaac Newton famously penned, "If I have seen further than others, it is by standing upon the shoulders of giants". We hope that this review will inspire future scientists to develop intellectual pursuits by understanding the research and ideas from many remarkable thinkers of the past. MAJOR CONCLUSIONS The history of iron research is a long, rich story with early beginnings, and is far from being finished. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.
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Affiliation(s)
- Alex D. Sheftel
- University of Ottawa Heart Institute, 40 Ruskin St., Ottawa, ON K1Y 4W7, Canada
| | - Anne B. Mason
- Department of Biochemistry, College of Medicine, University of Vermont, 89 Beaumont Avenue, Burlington, VT 05405-0068, USA
| | - Prem Ponka
- Lady Davis Institute for Medical Research, Jewish General Hospital, 3755 Côte-Ste.-Catherine Rd., Montréal, QC H3T 1E2, and Departments of Physiology and Medicine, McGill University, Montréal, QC, Canada
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Styś A, Galy B, Starzyński RR, Smuda E, Drapier JC, Lipiński P, Bouton C. Iron regulatory protein 1 outcompetes iron regulatory protein 2 in regulating cellular iron homeostasis in response to nitric oxide. J Biol Chem 2011; 286:22846-54. [PMID: 21566147 DOI: 10.1074/jbc.m111.231902] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
In mammals, iron regulatory proteins (IRPs) 1 and 2 posttranscriptionally regulate expression of genes involved in iron metabolism, including transferrin receptor 1, the ferritin (Ft) H and L subunits, and ferroportin by binding mRNA motifs called iron responsive elements (IREs). IRP1 is a bifunctional protein that mostly exists in a non-IRE-binding, [4Fe-4S] cluster aconitase form, whereas IRP2, which does not assemble an Fe-S cluster, spontaneously binds IREs. Although both IRPs fulfill a trans-regulatory function, only mice lacking IRP2 misregulate iron metabolism. NO stimulates the IRE-binding activity of IRP1 by targeting its Fe-S cluster. IRP2 has also been reported to sense NO, but the intrinsic function of IRP1 and IRP2 in NO-mediated regulation of cellular iron metabolism is controversial. In this study, we exposed bone marrow macrophages from Irp1(-/-) and Irp2(-/-) mice to NO and showed that the generated apo-IRP1 was entirely responsible for the posttranscriptional regulation of transferrin receptor 1, H-Ft, L-Ft, and ferroportin. The powerful action of NO on IRP1 also remedies the defects of iron storage found in IRP2-null bone marrow macrophages by efficiently reducing Ft overexpression. We also found that NO-dependent IRP1 activation, resulting in increased iron uptake and reduced iron sequestration and export, maintains enough intracellular iron to fuel the Fe-S cluster biosynthetic pathway for efficient restoration of the citric acid cycle aconitase in mitochondria. Thus, IRP1 is the dominant sensor and transducer of NO for posttranscriptional regulation of iron metabolism and participates in Fe-S cluster repair after exposure to NO.
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Affiliation(s)
- Agnieszka Styś
- Institute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzębiec, 05-552 Wólka Kosowska, Poland
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Abstract
Iron is essential for all life, yet can be dangerous under certain conditions. Iron storage by the 24-subunit protein ferritin renders excess amounts of the metal non-reactive and, consequentially, ferritin is crucial for life. Although the mechanism detailing the storage of iron in ferritin has been well characterized, little is known about the fate of ferritin-stored iron and whether it can be released and reutilized for metabolic use within a single cell. Virtually nothing is known about the use of ferritin-derived iron in non-erythroid cells. We therefore attempted to answer the question of whether iron from ferritin can be used for haem synthesis in the murine macrophage cell line RAW 264.7 cells. Cells treated with ALA (5-aminolaevulinic acid; a precursor of haem synthesis) show increased haem production as determined by enhanced incorporation of transferrin-bound 59Fe into haem. However, the present study shows that, upon the addition of ALA, 59Fe from ferritin cannot be incorporated into haem. Additionally, little 59Fe is liberated from ferritin when haem synthesis is increased upon addition of ALA. In conclusion, ferritin in cultivated macrophages is not a significant source of iron for the cell's own metabolic functions.
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15
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Kumar P, Tewari RK, Sharma PN. Sodium nitroprusside-mediated alleviation of iron deficiency and modulation of antioxidant responses in maize plants. AOB PLANTS 2010; 2010:plq002. [PMID: 22476060 PMCID: PMC2965042 DOI: 10.1093/aobpla/plq002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 12/19/2009] [Accepted: 01/09/2010] [Indexed: 05/29/2023]
Abstract
BACKGROUND AND AIMS Nitric oxide (NO) has been reported to alleviate Fe-deficiency effects, possibly by enhancing the functional Fe status of plants. This study examines changes in tissue Fe status and oxidative metabolism in Fe-deficient maize (Zea mays L.) plants enriched with NO using sodium nitroprusside (SNP) as a source. METHODOLOGY Measurements included changes in concentrations of H(2)O(2), non-protein thiols, levels of lipid peroxidation and activities of superoxide dismutase (SOD) and of the Fe-requiring antioxidant haem enzymes catalase, peroxidase and ascorbate peroxidases. Internal NO in Fe-deficient maize plants was manipulated with SNP and the NO scavenger, methylene blue (MB). A key control was treatment with sodium ferrocyanide (SF), a non-NO-supplying analogue of SNP. PRINCIPAL RESULTS SNP but not SF caused re-greening of leaves in Fe-deficient maize plants over 10-20 days, increased in vivo NO content, raised chlorophyll and carotenoid concentrations, promoted growth in dry weight, increased the activities of H(2)O(2)-scavenging haem enzymes and enhanced lipid peroxidation, while decreasing SOD activity and H(2)O(2) concentrations. The NO scavenger, MB, blocked the effects of the SNP. Although SNP and SF each donated Fe and increased active Fe, only SNP increased leaf chlorophyll. CONCLUSIONS NO plays a role in Fe nutrition, independently of its effect on total or active Fe status. The most probable mechanism of NO involvement is to increase the intracellular availability of Fe by means of modulating redox. This is likely to be achieved by enhancing the chemical reduction of foliar Fe(III) to Fe(II).
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16
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Briat JF, Duc C, Ravet K, Gaymard F. Ferritins and iron storage in plants. Biochim Biophys Acta Gen Subj 2009; 1800:806-14. [PMID: 20026187 DOI: 10.1016/j.bbagen.2009.12.003] [Citation(s) in RCA: 196] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Revised: 12/07/2009] [Accepted: 12/08/2009] [Indexed: 10/20/2022]
Abstract
Iron is essential for both plant productivity and nutritional quality. Improving plant iron content was attempted through genetic engineering of plants overexpressing ferritins. However, both the roles of these proteins in the plant physiology, and the mechanisms involved in the regulation of their expression are largely unknown. Although the structure of ferritins is highly conserved between plants and animals, their cellular localization differ. Furthermore, regulation of ferritin gene expression in response to iron excess occurs at the transcriptional level in plants, in contrast to animals which regulate ferritin expression at the translational level. In this review, our knowledge of the specific features of plant ferritins is presented, at the level of their (i) structure/function relationships, (ii) cellular localization, and (iii) synthesis regulation during development and in response to various environmental cues. A special emphasis is given to their function in plant physiology, in particular concerning their respective roles in iron storage and in protection against oxidative stress. Indeed, the use of reverse genetics in Arabidopsis recently enabled to produce various knock-out ferritin mutants, revealing strong links between these proteins and protection against oxidative stress. In contrast, their putative iron storage function to furnish iron during various development processes is unlikely to be essential. Ferritins, by buffering iron, exert a fine tuning of the quantity of metal required for metabolic purposes, and help plants to cope with adverse situations, the deleterious effects of which would be amplified if no system had evolved to take care of free reactive iron.
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Affiliation(s)
- Jean-François Briat
- Biochimie et Physiologie Moleculaire des Plantes, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Montpellier 2, SupAgro. Bat 7, 2 place Viala, 34060 Montpellier cedex 1, France.
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17
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Husić-Selimović A, Huskić J, Vukobrat-Bijedić Z, Mesihović R, Gribajcević M. The role of nitric oxide and ferritin in the pathogenesis of alcoholic liver disease: a controlled clinical study. Bosn J Basic Med Sci 2009; 9:204-9. [PMID: 19754474 DOI: 10.17305/bjbms.2009.2807] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The role of ferritin in fibrogenesis of liver parenchyma in patients with alcoholic liver disease has been investigated in previous studies. Ferritin was shown to be an indirect marker of ferum deposition in liver parenchyma in alcohol liver disease. The aim of the present study was to examine the role of nitric oxide (NO) in the pathogenesis of alcoholic liver disease as well as the influence of NO on iron (ferritin) metabolism in patients with alcoholic liver disease. Serum concentrations of NO and iron markers (iron, total iron binding capacity, ferritin) were measured in 30 male patients (aged 20-60 years) with alcoholic liver disease, as well as from a control group (30 male patients (aged 20-60 years) without liver disease). NO concentration was detected by measuring production of nitrates and nitrites using classical colorimetric Griess reactions. There was a statistically significant increase in serum NO concentration in patients with alcoholic liver disease compared to the control group (mean +/- SEM; 41,2 +/- 25,3 vs. 28,9 +/- 12,3 mmol/dm3, respectively; p<0,03). Similarly, serum iron levels (18,7 +/- 8,2 vs. 13,2 +/- 10,2 g/100 cm3, respectively; p<0,03) and serum total iron binding capacity (51,3 +/- 13,9 vs. 41,4 +/- 11,4 micromol/dm3, respectively; p<0,005) were also significantly higher in patients with alcoholic liver disease compared to control patients. The serum concentration of ferritin was 27% higher in patients with alcoholic liver disease than in the control group; however this was not statistically significant (283,2 +/- 291,0 vs. 222,9 +/- 252,0 g, respectively; p<0,4). There was no correlation between NO and ferritin in the investigated groups. These results suggest a possible role of NO and iron in the pathogenesis of alcoholic liver disease. NO and iron may be used as non-invasive predictors of liver damage. Also the role of iron in sera, and its deposition in liver parenchyma, could be used in clinical practice, especially in regards to assessing the fibrogenesis of liver parenchyma induced by ferritin.
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Affiliation(s)
- Azra Husić-Selimović
- Gastroenterohepatology Clinic, University of Sarajevo Clinics Centre, Bosnia and Herzegovina
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18
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Lichten LA, Liuzzi JP, Cousins RJ. Interleukin-1beta contributes via nitric oxide to the upregulation and functional activity of the zinc transporter Zip14 (Slc39a14) in murine hepatocytes. Am J Physiol Gastrointest Liver Physiol 2009; 296:G860-7. [PMID: 19179618 PMCID: PMC2670674 DOI: 10.1152/ajpgi.90676.2008] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Zinc metabolism during chronic disease is dysregulated by inflammatory cytokines. Experiments with IL-6 knockout mice show that LPS regulates expression of the zinc transporter, Zip14, by a mechanism that is partially independent of IL-6. The LPS-induced model of sepsis may occur by a mechanism signaled by nitric oxide (NO) as a secondary messenger. To address the hypothesis that NO can modulate Zip14 expression, we treated primary hepatocytes from wild-type mice with the NO donor S-nitroso N-acetyl penicillamine (SNAP). After treatment with SNAP, steady-state Zip14 mRNA levels displayed a maximal increase after 8 h and a concomitant increase in the transcriptional activity of the gene. Chromatin immunoprecipitation documented the kinetics of activator protein (AP)-1 and RNA polymerase II association with the Zip14 promoter after NO exposure, indicating a role of AP-1 in transcription of Zip14. We then stimulated the primary murine hepatocytes with IL-1beta, an LPS-induced proinflammatory cytokine and a potent activator of inducible NO synthase (iNOS) and NO production. In support of our hypothesis, IL-1beta treatment led to a threefold increase in Zip14 mRNA and enhanced zinc transport, as measured with a zinc fluorophore, in wild-type but not iNOS-/- hepatocytes. These data suggest that signaling pathways activated by NO are factors in the upregulation of Zip14, which in turn mediates hepatic zinc accumulation and hypozincemia during inflammation and sepsis.
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Affiliation(s)
- Louis A. Lichten
- Food Science and Human Nutrition Department, Center for Nutritional Sciences, University of Florida, Gainesville, Florida
| | - Juan P. Liuzzi
- Food Science and Human Nutrition Department, Center for Nutritional Sciences, University of Florida, Gainesville, Florida
| | - Robert J. Cousins
- Food Science and Human Nutrition Department, Center for Nutritional Sciences, University of Florida, Gainesville, Florida
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19
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Tsai FT, Kuo TS, Liaw WF. Dinitrosyl Iron Complexes (DNICs) Bearing O-Bound Nitrito Ligand: Reversible Transformation between the Six-Coordinate {Fe(NO)2}9 [(1-MeIm)2(η2-ONO)Fe(NO)2] (g = 2.013) and Four-Coordinate {Fe(NO)2}9 [(1-MeIm)(ONO)Fe(NO)2] (g = 2.03). J Am Chem Soc 2009; 131:3426-7. [DOI: 10.1021/ja808743g] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Fu-Te Tsai
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, and Department of Chemistry, National Taiwan Normal University, Taipei, Taiwan
| | - Ting-Shen Kuo
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, and Department of Chemistry, National Taiwan Normal University, Taipei, Taiwan
| | - Wen-Feng Liaw
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, and Department of Chemistry, National Taiwan Normal University, Taipei, Taiwan
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20
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NS398 protects cells from sodium nitroprusside-mediated cytotoxicity through enhancing HO-1 induction independent of COX-2 inhibition. Arch Pharm Res 2009; 32:99-107. [DOI: 10.1007/s12272-009-1123-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Revised: 11/26/2008] [Accepted: 12/02/2008] [Indexed: 01/16/2023]
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21
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Doherty SP, Prophete C, Maciejczyk P, Salnikow K, Gould T, Larson T, Koenig J, Jaques P, Sioutas C, Zelikoff JT, Lippmann M, Cohen MD. Detection of Changes in Alveolar Macrophage Iron Status Induced by Select PM2.5-Associated Components Using Iron-Response Protein Binding Activity. Inhal Toxicol 2008; 19:553-62. [PMID: 17497533 DOI: 10.1080/08958370701280481] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The extent of adverse health effects, including induction/exacerbation of infectious lung disease, arising from entrainment of equivalent amounts (or exposure to a fixed increment) of fine particulate matter (PM2.5) can vary from region to region or city to city in a region. To begin to explain how differing effects on host resistance might arise after exposure to PM2.5 from various sites, we hypothesized that select metals (e.g., V, Al, and Mn) in each PM2.5 caused changes in alveolar macrophage (AM) Fe status that, ultimately, would lead to altered antibacterial function. To test this, iron-response protein (IRP) binding activity in a rat AM cell line was assessed after exposure to Fe alone and in conjunction with V, Mn, and/or Al at ratios of V:Fe, Al:Fe, or Mn:Fe encountered in PM2.5 samples from New York City, Los Angeles, and Seattle. Results indicated that V and Al each significantly altered IRP activity, though effects were not consistently ratio-(i.e., dose-) dependent; Mn had little impact on activity. We conclude that the reductions in Fe status detected here via the IRP assay arose, in part, from effects on transferrin-mediated Fe3+ delivery to the AM. Ongoing studies using this assay are allowing us to better determine: (1) whether mass (and/or molar) relationships between Fe and V, Al, and/or Mn in any PM2.5 sample consistently govern the extent of change in AM Fe status; (2) how much any specified PM2.5 constituent (metal or nonmetal) contributes to the overall disruption of Fe status found induced by an intact parent sample; and (3) whether induced changes in binding activity are relatable to other changes expected to occur in the AM, that is, in IRP-dependent mRNA/levels of ferritin/transferrin receptor and Fe-dependent functions. These studies demonstrate that pollutant-induced effects on lung cell Fe status can be assessed in a reproducible manner using an assay that can be readily performed by investigators who might otherwise have no access to other very costly analytical equipment, such as graphite atomic absorption or x-ray fluorescence spectro(photo)meters.
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Affiliation(s)
- S P Doherty
- NYU-EPA Particulate Matter Health Research Center, Nelson Institute, New York University School of Medicine Tuxedo, New York 10987, USA
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22
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Zhang F, Wang W, Tsuji Y, Torti SV, Torti FM. Post-transcriptional modulation of iron homeostasis during p53-dependent growth arrest. J Biol Chem 2008; 283:33911-8. [PMID: 18819919 DOI: 10.1074/jbc.m806432200] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Iron plays an essential role in cell proliferation and is a required cofactor for a number of critical cellular enzymes. In this report we investigate changes in proteins of iron metabolism during p53-mediated replicative arrest. Following the induction of p53 in H1299 lung cancer cells containing a doxycycline-inducible p53, an increase in both H and L subunits of ferritin protein was observed. To determine the mechanism of this effect, we investigated the ability of p53 to regulate ferritin. Real time reverse transcription-PCR demonstrated no difference in levels of ferritin H mRNA in the presence and absence of p53. Because these results suggested that transcriptional mechanisms were not responsible for the p53-dependent increase in ferritin, we tested whether a post-transcriptional mechanism was involved. RNA bandshift assays revealed that induction of p53 decreased iron regulatory protein binding. Consistent with this observation, Western blot analysis revealed a decline in transferrin receptor 1 protein levels following induction of p53. Collectively, these results suggest that p53 may induce cell cycle arrest not only by well described mechanisms involving the induction of cyclin-dependent kinase inhibitors but also by the recruitment of pathways that reduce the availability of intracellular iron.
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Affiliation(s)
- Fan Zhang
- Department of Cancer Biology, Wake Forest University, Winston-Salem, NC 27157, USA
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23
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Tacchini L, Gammella E, De Ponti C, Recalcati S, Cairo G. Role of HIF-1 and NF-kappaB transcription factors in the modulation of transferrin receptor by inflammatory and anti-inflammatory signals. J Biol Chem 2008; 283:20674-86. [PMID: 18519569 DOI: 10.1074/jbc.m800365200] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Inflammation generates various changes in body iron homeostasis, including iron sequestration in the reticuloendothelial system with ensuing hypoferremia and anemia of chronic disease. Increased iron accumulation is caused by hepcidin-mediated down-regulation of the iron export protein ferroportin and higher iron uptake. However, enhanced iron acquisition by macrophages cannot be accounted for by the previously reported transferrin receptor (TfR1) down-regulation in macrophages exposed to lipopolysaccharide (LPS)/interferon gamma (IFNgamma) because it impairs a major iron uptake mechanism. Because TfR1 is up-regulated by the hypoxia-inducible factor (HIF-1), we investigated the effect of inflammatory and anti-inflammatory signals on HIF-1-mediated TfR1 gene expression. Exposure of mouse macrophages (RAW 264.7 and J774A.1 cells or peritoneal macrophages) to LPS/IFNgamma up-regulated NF-kappaB, which in turn rapidly and transiently activated HIF-1-dependent TfR1 expression and iron uptake. Activation of an anti-inflammatory pathway by pre-exposure to the adenosine A(2A) receptor agonist CGS21680 prevented the inducing effect of LPS/IFNgamma on HIF-1 and TfR1 expression by inhibiting NF-kappaB activity, whereas treatment with CGS21680 alone increased HIF-1-mediated TfR1 expression by means of an NF-kappaB-independent signaling pathway. In conclusion, an interplay of the HIF-1 and NF-kappaB pathways controls TfR1 transcription in inflammation. The consequent changes in TfR1 expression may be involved in modulating iron retention in inflammatory macrophages, thus possibly contributing to the development of hypoferremia in the early phases preceding the down-regulation of macrophage ferroportin by hepcidin.
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Affiliation(s)
- Lorenza Tacchini
- Institute of General Pathology, University of Milan, Via Mangiagalli 31, 20133 Milan, Italy
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24
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Chua ACG, Graham RM, Trinder D, Olynyk JK. The regulation of cellular iron metabolism. Crit Rev Clin Lab Sci 2008; 44:413-59. [PMID: 17943492 DOI: 10.1080/10408360701428257] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
While iron is an essential trace element required by nearly all living organisms, deficiencies or excesses can lead to pathological conditions such as iron deficiency anemia or hemochromatosis, respectively. A decade has passed since the discovery of the hemochromatosis gene, HFE, and our understanding of hereditary hemochromatosis (HH) and iron metabolism in health and a variety of diseases has progressed considerably. Although HFE-related hemochromatosis is the most widespread, other forms of HH have subsequently been identified. These forms are not attributed to mutations in the HFE gene but rather to mutations in genes involved in the transport, storage, and regulation of iron. This review is an overview of cellular iron metabolism and regulation, describing the function of key proteins involved in these processes, with particular emphasis on the liver's role in iron homeostasis, as it is the main target of iron deposition in pathological iron overload. Current knowledge on their roles in maintaining iron homeostasis and how their dysregulation leads to the pathogenesis of HH are discussed.
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Affiliation(s)
- Anita C G Chua
- School of Medicine and Pharmacology, University of Western Australia, Fremantle, Western Australia, Australia
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25
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Wang W, Di X, D'Agostino RB, Torti SV, Torti FM. Excess capacity of the iron regulatory protein system. J Biol Chem 2007; 282:24650-9. [PMID: 17604281 DOI: 10.1074/jbc.m703167200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Iron regulatory proteins (IRP1 and IRP2) are master regulators of cellular iron metabolism. IRPs bind to iron-responsive elements (IREs) present in the untranslated regions of mRNAs encoding proteins of iron storage, uptake, transport, and export. Because simultaneous knockout of IRP1 and IRP2 is embryonically lethal, it has not been possible to use dual knockouts to explore the consequences of loss of both IRP1 and IRP2 in mammalian cells. In this report, we describe the use of small interfering RNA to assess the relative contributions of IRP1 and IRP2 in epithelial cells. Stable cell lines were created in which either IRP1, IRP2, or both were knocked down. Knockdown of IRP1 decreased IRE binding activity but did not affect ferritin H and transferrin receptor 1 (TfR1) expression, whereas knockdown of IRP2 marginally affected IRE binding activity but caused an increase in ferritin H and a decrease in TfR1. Knockdown of both IRPs resulted in a greater reduction of IRE binding activity and more severe perturbation of ferritin H and TfR1 expression compared with single IRP knockdown. Even though the knockdown of IRP-1, IRP-2, or both was efficient, resulting in nondetectable protein and under 5% of wild type levels of mRNA, all stable knockdowns retained an ability to modulate ferritin H and TfR1 appropriately in response to iron challenge. However, further knockdown of IRPs accomplished by transient transfection of small interfering RNA in stable knockdown cells completely abolished the response of ferritin H and TfR1 to iron challenge, demonstrating an extensive excess capacity of the IRP system.
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Affiliation(s)
- Wei Wang
- Department of Cancer Biology, Public Health Sciences, Wake Forest University Health Sciences, Winston-Salem, North Carolina 27157, USA
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26
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Popovic Z, Templeton DM. Inhibition of an iron-responsive element/iron regulatory protein-1 complex by ATP binding and hydrolysis. FEBS J 2007; 274:3108-19. [PMID: 17521334 DOI: 10.1111/j.1742-4658.2007.05843.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Iron regulatory protein-1 binding to the iron-responsive element of mRNA is sensitive to iron, oxidative stress, NO, and hypoxia. Each of these agents changes the level of intracellular ATP, suggesting a link between iron levels and cellular energy metabolism. Furthermore, restoration of iron regulatory protein-1 aconitase activity after NO removal has been shown to require mitochondrial ATP. We demonstrate here that the iron-responsive element-binding activity of iron regulatory protein is ATP-dependent in HepG2 cells. Iron cannot decrease iron regulatory protein binding activity in cell extracts if they are simultaneously treated with an uncoupler of oxidative phosphorylation. Physiologic concentrations of ATP inhibit iron-responsive element/iron regulatory protein binding in cell extracts and binding of iron-responsive element to recombinant iron regulatory protein-1. ADP has the same effect, in contrast to the nonhydrolyzable analog adenosine 5'-(beta,gamma-imido)triphosphate, indicating that in order to inhibit iron regulatory protein-1 binding activity, ATP must be hydrolyzed. Indeed, recombinant iron regulatory protein-1 binds ATP with a Kd of 86+/-17 microM in a filter-binding assay, and can be photo-crosslinked to azido-ATP. Upon binding, ATP is hydrolyzed. The kinetic parameters [Km=5.3 microM, Vmax=3.4 nmol.min(-1).(mg protein)(-1)] are consistent with those of a number of other ATP-hydrolyzing proteins, including the RNA-binding helicases. Although the iron-responsive element does not itself hydrolyze ATP, its presence enhances iron regulatory protein-1's ATPase activity, and ATP hydrolysis results in loss of the complex in gel shift assays.
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Affiliation(s)
- Zvezdana Popovic
- Laboratory Medicine and Pathobiology, University of Toronto, Canada
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27
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Balla J, Jeney V, Varga Z, Komódi E, Nagy E, Balla G. Iron homeostasis in chronic inflammation. ACTA ACUST UNITED AC 2007; 94:95-106. [PMID: 17444278 DOI: 10.1556/aphysiol.94.2007.1-2.9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Inflammation induced anemia and resistance to erythropoietin are common features in patients with chronic kidney disease (CKD). Elevated levels of cytokines and enhanced oxidative stress, conditions associated with inflammatory states, are implicated in the development of anemia. Accumulating evidence suggests that activation of cytokine cascade and the associated acute-phase response, as it often occurs in patients with CKD, divert iron from erythropoiesis to storage sites within the reticuloendothelial system leading to functional iron deficiency and subsequently to anemia or resistance to erythropoietin. Other processes have also been shown to be involved in the pathogenesis of anemia provoked by the activated immune system including an inhibition of erythroid progenitor proliferation and differentiation, a suppression of erythropoietin production and a blunted response to erythropoietin. The present review concerns the underlying alterations in iron metabolism induced by chronic inflammation that result in anemia.
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Affiliation(s)
- J Balla
- Department of Medicine, Division of Nephrology and Hemodialysis Unit, Medical and Health Science Center, University of Debrecen, Nagyerdei krt. 98, H-4012 Debercen, Hungary.
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28
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Irace C, Esposito G, Maffettone C, Rossi A, Festa M, Iuvone T, Santamaria R, Sautebin L, Carnuccio R, Colonna A. Oxalomalate affects the inducible nitric oxide synthase expression and activity. Life Sci 2006; 80:1282-91. [PMID: 17257628 DOI: 10.1016/j.lfs.2006.12.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2006] [Revised: 12/07/2006] [Accepted: 12/15/2006] [Indexed: 11/30/2022]
Abstract
Inducible nitric oxide synthase (iNOS) is an homodimeric enzyme which produces large amounts of nitric oxide (NO) in response to inflammatory stimuli. Several factors affect the synthesis and catalytic activity of iNOS. Particularly, dimerization of NOS monomers is promoted by heme, whereas an intracellular depletion of heme and/or L-arginine considerably decreases NOS resistance to proteolysis. In this study, we found that oxalomalate (OMA, oxalomalic acid, alpha-hydroxy-beta-oxalosuccinic acid), an inhibitor of both aconitase and NADP-dependent isocitrate dehydrogenase, inhibited nitrite production and iNOS protein expression in lipopolysaccharide (LPS)-activated J774 macrophages, without affecting iNOS mRNA content. Furthermore, injection of OMA precursors to LPS-stimulated rats also decreased nitrite production and iNOS expression in isolated peritoneal macrophages. Interestingly, alpha-ketoglutarate or succinyl-CoA administration reversed OMA effect on NO production, thus correlating NO biosynthesis with the anabolic capacity of Krebs cycle. When protein synthesis was blocked by cycloheximide in LPS-activated J774 cells treated with OMA, iNOS protein levels, evaluated by Western blot analysis and (35)S-metabolic labelling, were decreased, suggesting that OMA reduces iNOS biosynthesis and induces an increase in the degradation rate of iNOS protein. Moreover, we showed that OMA inhibits the activity of the iNOS from lung of LPS-treated rats by enzymatic assay. Our results, demonstrating that OMA acts regulating synthesis, catalytic activity and degradation of iNOS, suggest that this compound might have a potential role in reducing the NO overproduction occurring in some pathological conditions.
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Affiliation(s)
- Carlo Irace
- Dipartimento di Farmacologia Sperimentale, Università di Napoli Federico II, via D. Montesano 49, 80131-Napoli, Italy
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29
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Abstract
Activation-induced cell death (AICD) of immune cells is widely believed to be crucial for the regulation of immune responses. Although macrophage apoptosis has been observed under a variety of pathological conditions, questions as to whether there is AICD of macrophages and how macrophage life span is regulated have not been well addressed. AICD in macrophages requires two signals. One is cell activation triggered by LPS or other bacterial components. The other is an event that exists in AICD-susceptible (primed) but not unsusceptible (resting) macrophages. Here we show that RAW264.7 cell is susceptible to LPS stimulation when it is primed with Salmonella typhimurium, type 5 adenovirus (Ad5) or IFN-gamma. We found that the stability of the transcription factor MEF2C is increased in primed RAW264.7 cell. Transfection of a dominant negative form of MEF2C protects primed macrophage from cell death triggered by LPS. Our data demonstrate that the increase of MEF2C protein stability is a key factor in the AICD of macrophage.
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Affiliation(s)
- Wenxia Fu
- National Key Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Science, Peking University, Beijing 100871, China
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30
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Mikhael M, Kim SF, Schranzhofer M, Soe-Lin S, Lin SS, Sheftel AD, Mullner EW, Ponka P. Iron regulatory protein-independent regulation of ferritin synthesis by nitrogen monoxide. FEBS J 2006; 273:3828-36. [PMID: 16911529 DOI: 10.1111/j.1742-4658.2006.05390.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The discovery of iron-responsive elements (IREs), along with the identification of iron regulatory proteins (IRP1, IRP2), has provided a molecular basis for our current understanding of the remarkable post-transcriptional regulation of intracellular iron homeostasis. In iron-depleted conditions, IRPs bind to IREs present in the 5'-UTR of ferritin mRNA and the 3'-UTR of transferrin receptor (TfR) mRNA. Such binding blocks the translation of ferritin, the iron storage protein, and stabilizes TfR mRNA, whereas the opposite scenario develops when iron in the intracellular transit pool is plentiful. Nitrogen monoxide (commonly designated nitric oxide; NO), a gaseous molecule involved in numerous functions, is known to affect cellular iron metabolism via the IRP/IRE system. We previously demonstrated that the oxidized form of NO, NO(+), causes IRP2 degradation that is associated with an increase in ferritin synthesis [Kim, S & Ponka, P (2002) Proc Natl Acad Sci USA99, 12214-12219]. Here we report that sodium nitroprusside (SNP), an NO(+) donor, causes a dramatic and rapid increase in ferritin synthesis that initially occurs without changes in the RNA-binding activities of IRPs. Moreover, we demonstrate that the translational efficiency of ferritin mRNA is significantly higher in cells treated with SNP compared with those incubated with ferric ammonium citrate, an iron donor. Importantly, we also provide definitive evidence that the iron moiety of SNP is not responsible for such changes. These results indicate that SNP-mediated increase in ferritin synthesis is, in part, due to an IRP-independent and NO(+)-dependent post-transcriptional, regulatory mechanism.
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Affiliation(s)
- Marc Mikhael
- Department of Physiology, McGill University, Montreal, Canada
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31
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Cheah JH, Kim SF, Hester LD, Clancy KW, Patterson SE, Papadopoulos V, Snyder SH. NMDA receptor-nitric oxide transmission mediates neuronal iron homeostasis via the GTPase Dexras1. Neuron 2006; 51:431-40. [PMID: 16908409 PMCID: PMC3150500 DOI: 10.1016/j.neuron.2006.07.011] [Citation(s) in RCA: 217] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2005] [Revised: 06/21/2006] [Accepted: 07/13/2006] [Indexed: 01/24/2023]
Abstract
Dexras1 is a 30 kDa G protein in the Ras subfamily whose discovery was based on its pronounced inducibility by the glucocorticoid dexamethasone. It binds to neuronal nitric oxide synthase (nNOS) via the adaptor protein CAPON, eliciting S-nitrosylation and activation of Dexras1. We report that Dexras1 binds to the peripheral benzodiazepine receptor-associated protein (PAP7), a protein of unknown function that binds to cyclic AMP-dependent protein kinase and the peripheral benzodiazepine receptor. PAP7 in turn binds to the divalent metal transporter (DMT1), an iron import channel. We have identified a signaling cascade in neurons whereby stimulation of NMDA receptors activates nNOS, leading to S-nitrosylation and activation of Dexras1, which, via PAP7 and DMT1, physiologically induces iron uptake. As selective iron chelation prevents NMDA neurotoxicity in cortical cultures, the NMDA-NO-Dexras1-PAP7-DMT1-iron uptake signaling cascade also appears to mediate NMDA neurotoxicity.
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Affiliation(s)
- Jaime H Cheah
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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32
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Arnaud N, Murgia I, Boucherez J, Briat JF, Cellier F, Gaymard F. An iron-induced nitric oxide burst precedes ubiquitin-dependent protein degradation for Arabidopsis AtFer1 ferritin gene expression. J Biol Chem 2006; 281:23579-88. [PMID: 16782706 DOI: 10.1074/jbc.m602135200] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Ferritins play an essential role in iron homeostasis by sequestering iron in a bioavailable and non-toxic form. In plants, ferritin mRNAs are highly and quickly accumulated in response to iron overload. Such accumulation leads to a subsequent ferritin protein synthesis and iron storage, thus avoiding oxidative stress to take place. By combining pharmacological and imaging approaches in an Arabidopsis cell culture system, we have identified several elements in the signal transduction pathway leading to the increase of AtFer1 transcript level after iron treatment. Nitric oxide quickly accumulates in the plastids after iron treatment. This compound acts downstream of iron and upstream of a PP2A-type phosphatase to promote an increase of AtFer1 mRNA level. The AtFer1 gene transcription has been previously shown to be repressed under low iron conditions with the involvement of the cis-acting element iron-dependent regulatory sequence identified within the AtFer1 promoter sequence. We show here that the repressor is unlikely a transcription factor directly bound to the iron-dependent regulatory sequence; such a repressor is ubiquitinated upon iron treatment and subsequently degraded through a 26 S proteasome-dependent pathway.
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Affiliation(s)
- Nicolas Arnaud
- Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, UMR 5004 Agro-M/CNRS/INRA/UMII, Bat 7, 2 place Viala, 34060 Montpellier Cedex 1, France
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33
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Wang J, Fillebeen C, Chen G, Andriopoulos B, Pantopoulos K. Sodium nitroprusside promotes IRP2 degradation via an increase in intracellular iron and in the absence of S nitrosylation at C178. Mol Cell Biol 2006; 26:1948-54. [PMID: 16479012 PMCID: PMC1430246 DOI: 10.1128/mcb.26.5.1948-1954.2006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In iron-replete cells the posttranscriptional regulator IRP2 undergoes ubiquitination and proteasomal degradation. A similar response occurs in cells exposed to sodium nitroprusside (SNP), an NO-releasing drug. It has been proposed that nitroprusside ([Fe(CN)5NO]2-) fails to donate iron into cells and that it promotes IRP2 degradation via S nitrosylation at C178. This residue is located within a stretch of 73 amino acids, earlier proposed to define an iron-dependent degradation domain. Surprisingly, we show that IRP2 bearing a C178S mutation or a Delta73 deletion is sensitive to degradation not only by ferric ammonium citrate (FAC) but also by SNP. Moreover, FAC and SNP attenuate the RNA-binding activities of IRP2 and its homologue IRP1 with similar kinetics. Actinomycin D, cycloheximide, succinylacetone, and dimethyl-oxalylglycine antagonize IRP2 degradation in response to both FAC and SNP, suggesting a common mechanistic basis. IRP2 is not only sensitive to fresh, but also to photodegraded SNP and remains unaffected by S-nitrosoglutathione (GSNO), an established nitrosation agent. Importantly, both fresh and photodegraded SNP, but not GSNO, promote a >4-fold increase in the calcein-accessible labile iron pool. Collectively, these results suggest that IRP2 degradation by SNP does not require S nitrosylation but rather represents a response to iron loading.
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Affiliation(s)
- Jian Wang
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, 3755 Cote-Ste-Catherine Rd., Montreal, Quebec H3T 1E2, Canada
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34
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Paradkar PN, Roth JA. Nitric oxide transcriptionally down-regulates specific isoforms of divalent metal transporter (DMT1) via NF-?B. J Neurochem 2006; 96:1768-77. [PMID: 16539692 DOI: 10.1111/j.1471-4159.2006.03702.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Studies were performed to examine the affect of nitric oxide (NO) on expression of the divalent metal transporter (DMT1) in undifferentiated P19 embryonic carcinoma cells. DMT1 has four known isoforms which differ in both the N- and C-terminals. Results demonstrate that exposure of P19 cells to the NO precursor, sodium nitro-prusside (SNP), resulted in a decrease in expression of both positive (+) and negative (-) IRE isoforms of DMT1 with no change in the 1A species. Regulation was not as a result of decreased stability of message but was caused by reduction in transcription of the DMT1 1B isoforms. Similar results were observed in other cell lines, including PC12 and SH-SY5Y cells and rat primary sympathetic neurons. Nuclear NF-kappaB was decreased after SNP treatment, suggesting that NF-kappaB may mediate this response. Luciferase reporter assays with normal and NF-kappaB mutated constructs of the 1B promoter confirm that the NF-kappaB site between -23 to -19 upstream from the transcription start site was responsible for regulating expression. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assays further demonstrate that the p65 subunit of NF-kappaB and not p50 binding is specifically decreased by NO treatment. Results of these studies provide a general mechanism responsible for regulating DMT1 expression induced by stress-related signaling processes in vivo.
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Affiliation(s)
- Prasad N Paradkar
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA
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35
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Ray JCJ, Kirschner DE. Requirement for multiple activation signals by anti-inflammatory feedback in macrophages. J Theor Biol 2006; 241:276-94. [PMID: 16460764 DOI: 10.1016/j.jtbi.2005.11.037] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Revised: 10/25/2005] [Accepted: 11/26/2005] [Indexed: 12/19/2022]
Abstract
Pathogen killing is one of the primary roles of macrophages, utilizing potent effectors such as nitric oxide (NO) and involving other cellular machinery including iron regulatory apparatus. Macrophages become strongly activated upon receipt of appropriate signaling with cytokines and pathogen-derived endotoxins. However, they must resist activation in the absence of decisive signaling due to the energetic demands of activation coupled with the toxic nature of effector molecules to surrounding tissues. We have developed a mathematical model of the modular biochemical network of macrophages involved with activation, pathogen killing and iron regulation. This model requires synergistic interaction of multiple activation signals to overcome the quiescent state. To achieve a trade-off between macrophage quiescence and activation, strong activation signals are modulated via negative regulation by NO. In this way a single activation signal is insufficient for complete activation. In addition, our results suggest that iron regulation is usually controlled by activation signals. However, under conditions of partial macrophage activation, exogenous iron levels play a key role in regulating NO production. This model will be useful for evaluating macrophage control of intracellular pathogens in addition to the biochemical mechanisms examined here.
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Affiliation(s)
- J Christian J Ray
- Department of Microbiology and Immunology, The University of Michigan Medical School, Ann Arbor, MI 48109-0620, USA
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36
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Salazar J, Mena N, Núñez MT. Iron dyshomeostasis in Parkinson's disease. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 2006:205-13. [PMID: 17447431 DOI: 10.1007/978-3-211-33328-0_22] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Owing to its ability to undergo one-electron reactions, iron transforms the mild oxidant hydrogen peroxide into hydroxyl radical, one of the most reactive species in nature. Deleterious effects of iron accumulation are dramatically evidenced in several neurodegenerative diseases. The work of Youdim and collaborators has been fundamental in describing the accumulation of iron confined to the substantia nigra (SN) in Parkinson's disease (PD) and to clarify iron toxicity pathways and oxidative damage in dopaminergic neurons. Nevertheless, how the mechanisms involved in normal neuronal iron homeostasis are surpassed, remain largely undetermined. How nigral neurons survive or succumb to iron-induced oxidative stress are relevant questions both to know about the etiology of the disease and to design neuroprotective strategies. In this work, we review the components of neural iron homeostasis and we summarize evidence from recent studies aimed to unravel the molecular basis of iron accumulation and dyshomeostasis in PD.
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Affiliation(s)
- J Salazar
- Department of Biology, and Cell Dynamic and Biotechnology Research Center, Faculty of Sciences, University of Chile, Santiago, Chile
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37
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Reis K, Hälldin J, Fernaeus S, Pettersson C, Land T. NADPH oxidase inhibitor diphenyliodonium abolishes lipopolysaccharide-induced down-regulation of transferrin receptor expression in N2a and BV-2 cells. J Neurosci Res 2006; 84:1047-52. [PMID: 16881050 DOI: 10.1002/jnr.21005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The activation of cellular inflammatory response is tightly linked to induced production of reactive oxygen species (ROS) and nitric oxide (NO), which in turn have been identified as important regulators of cellular iron metabolism. In the present study, we have used the microglia cell line BV-2 and the neuroblastoma cell line N2a to study the regulatory effects of the microbial agent lipopolysaccharide (LPS) on the expression of the transferrin receptor (TfR) and ferritin in cell lines with different characteristics. The receptor mainly responsible for LPS recognition is the Toll-like receptor 4 (TLR4) that triggers a variety of intracellular signalling cascades leading to the induction of transcription of target genes involved in the innate immune response. Among the pathways to be activated is the MAPK cascade leading to the activation of nuclear factor-kappaB that induces transcription of a variety of genes, e.g., inducible nitric oxide synthase (iNOS). The TLR4-mediated LPS response also induces the production of ROS through a mechanism(s) suggested to involve the activation of NADPH oxidase(s). This study shows that exposure of BV-2 and N2a cells to LPS results in decreased TfR protein levels and increased H-ferritin mRNA levels. The LPS down-regulatory effect on TfR protein expression is abolished by the NADPH oxidase inhibitor diphenyliodonium (DPI) but is not affected by the free radical scavenger N-acetyl-L-cysteine (NAC) or the iNOS inhibitor aminoguanidine (AG). The increased H-ferritin mRNA levels in response to LPS are not affected by DPI, NAC, or AG.
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Affiliation(s)
- Katarina Reis
- Department of Neurochemistry, Stockholm University, Stockholm, Sweden.
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38
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Kallianpur AR, Hall LD, Yadav M, Byrne DW, Speroff T, Dittus RS, Haines JL, Christman BW, Summar ML. The hemochromatosis C282Y allele: a risk factor for hepatic veno-occlusive disease after hematopoietic stem cell transplantation. Bone Marrow Transplant 2005; 35:1155-64. [PMID: 15834437 DOI: 10.1038/sj.bmt.1704943] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Hepatic veno-occlusive disease (HVOD) is a serious complication of hematopoietic stem cell transplantation (HSCT). Since the liver is a major site of iron deposition in HFE-associated hemochromatosis, and iron has oxidative toxicity, we hypothesized that HFE genotype might influence the risk of HVOD after myeloablative HSCT. We determined HFE genotypes in 166 HSCT recipients who were evaluated prospectively for HVOD. We also tested whether a common variant of the rate-limiting urea cycle enzyme, carbamyl-phosphate synthetase (CPS), previously observed to protect against HVOD in this cohort, modified the effect of HFE genotype. Risk of HVOD was significantly higher in carriers of at least one C282Y allele (RR=3.7, 95% CI 1.2-12.1) and increased progressively with C282Y allelic dose (RR=1.7, 95% CI 0.4-6.8 in heterozygotes; RR=8.6, 95% CI 1.5-48.5 in homozygotes). The CPS A allele, which encodes a more efficient urea cycle enzyme, reduced the risk of HVOD associated with HFE C282Y. We conclude that HFE C282Y is a risk factor for HVOD and that CPS polymorphisms may counteract its adverse effects. Knowledge of these genotypes and monitoring of iron stores may facilitate risk-stratification and testing of strategies to prevent HVOD, such as iron chelation and pharmacologic support of the urea cycle.
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Affiliation(s)
- A R Kallianpur
- Division of General Internal Medicine and Public Health, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37212, USA.
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39
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Abstract
Iron and copper are essential nutrients, excesses or deficiencies of which cause impaired cellular functions and eventually cell death. The metabolic fates of copper and iron are intimately related. Systemic copper deficiency generates cellular iron deficiency, which in humans results in diminished work capacity, reduced intellectual capacity, diminished growth, alterations in bone mineralization, and diminished immune response. Copper is required for the function of over 30 proteins, including superoxide dismutase, ceruloplasmin, lysyl oxidase, cytochrome c oxidase, tyrosinase and dopamine-beta-hydroxylase. Iron is similarly required in numerous essential proteins, such as the heme-containing proteins, electron transport chain and microsomal electron transport proteins, and iron-sulfur proteins and enzymes such as ribonucleotide reductase, prolyl hydroxylase phenylalanine hydroxylase, tyrosine hydroxylase and aconitase. The essentiality of iron and copper resides in their capacity to participate in one-electron exchange reactions. However, the same property that makes them essential also generates free radicals that can be seriously deleterious to cells. Thus, these seemingly paradoxical properties of iron and copper demand a concerted regulation of cellular copper and iron levels. Here we review the most salient characteristics of their homeostasis.
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Affiliation(s)
- Miguel Arredondo
- Nutrition and Food Technology Institute, University of Chile, Casilla 13811, Santiago, Chile
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40
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Turpaev K, Bouton C, Diet A, Glatigny A, Drapier JC. Analysis of differentially expressed genes in nitric oxide-exposed human monocytic cells. Free Radic Biol Med 2005; 38:1392-400. [PMID: 15855057 DOI: 10.1016/j.freeradbiomed.2005.02.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2004] [Revised: 12/08/2004] [Accepted: 02/02/2005] [Indexed: 11/25/2022]
Abstract
In this study we examined the gene expression pattern of *NO-dependent genes in U937 and Mono Mac 6 monocytes exposed to the synthetic NO-donor DPTA-NO using microarray technology. cDNA microarray data were validated by Northern blot analysis and quantitative real-time PCR. This approach allowed the identification of 17 *NO-sensitive genes that showed at least a twofold difference in expression, in both U937 cells and Mono Mac 6 cells exposed to 500 microM DPTA-NO for 4 h. NO-stimulated genes belong to various functional groups, including transcription factors, signaling molecules, and cytokines. Among the selected genes, 11 (ATF-4, c-maf, SGK-1, PBEF, ATPase 8, NADH dehydrogenase 4, STK6, TRAF4-associated factor 1, molybdopterin synthase, CKS1, and CIDE-B) have not been previously reported to be sensitive to *NO. Because several *NO-stimulated genes are transcription factors, we analyzed the mRNA expression profile in U937 cells exposed to DPTA-NO for 14 h. We found that long-term *NO treatment influenced transcription rates of a rather limited set of genes, including CIDE-B, BNIP3, p21/Cip1, molybdopterin synthase, and TRAF4-associated factor 1. To accelerate formation of nitrosating species, U937 cells were exposed to DPTA-NO along with suboptimal concentrations of 2-phenyl-4,4,5,5-tetramethylimidazole-1-oxyl 3-oxide (PTIO). PTIO-mediated increase in nitrosating species remarkably enhanced *NO-dependent induction of IL-8, p21/Cip1, and MKP-1 and built a specific gene expression profile.
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Affiliation(s)
- Kyril Turpaev
- Institut de Chimie des Substances Naturelles, Centre National de la Recherche Scientifique, 91198 Gif-sur-Yvette Cedex, France
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41
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Abstract
Mathematical models are emerging as important tools in the study of microbiology. As an illustrative example, we present results from several models each generated to study the interaction of Mycobacterium tuberculosis and the immune system. Different mathematical models were formulated on the basis of assumptions regarding system-component interactions, enabling us to explore specific aspects at diverse biological scales (e.g. intracellular, cell-cell interactions, and cell population dynamics). In addition, we were able to examine both temporal and spatial aspects. At each scale, there were consistent themes that emerged as determinative in infection outcome. Factors we identified include both host and microbial characteristics. The use of the models lies in generating hypotheses that can then be tested experimentally. Here, we outline the primary host and bacterial factors that we have identified as key mechanisms that contribute to the success of M. tuberculosis as a human pathogen. Our goal is to stimulate experimentation and foster collaborations between theoretical and experimental scientists.
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Affiliation(s)
- Denise Kirschner
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109-0260, USA.
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42
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Abstract
Iron-regulatory protein 2 (IRP2), a posttranscriptional regulator of iron metabolism, undergoes proteasomal degradation in iron-replete cells, while it is stabilized in iron deficiency or hypoxia. IRP2 also responds to nitric oxide (NO), as shown in various cell types exposed to pharmacological NO donors and in gamma interferon/lipopolysaccharide-stimulated macrophages. However, the diverse experimental systems have yielded conflicting results on whether NO activates or inhibits IRP2. We show here that a treatment of mouse B6 fibroblasts or human H1299 lung cancer cells with the NO-releasing drug S-nitroso-N-acetyl-penicillamine (SNAP) activates IRP2 expression. Moreover, the exposure of H1299 cells to SNAP leads to stabilization of hemagglutinin (HA)-tagged IRP2, with kinetics analogous to those elicited by the iron chelator desferrioxamine. Similar results were obtained with IRP2(Delta)(73), a mutant lacking a conserved, IRP2-specific proline- and cysteine-rich domain. Importantly, SNAP fails to stabilize HA-tagged p53, suggesting that under the above experimental conditions, NO does not impair the capacity of the proteasome for protein degradation. Finally, by employing a coculture system of B6 and H1299 cells expressing NO synthase II or IRP2-HA cDNAs, respectively, we demonstrate that NO generated in B6 cells stabilizes IRP2-HA in target H1299 cells by passive diffusion. Thus, biologically synthesized NO promotes IRP2 stabilization without compromising the overall proteasomal activity. These results are consistent with the idea that NO may negatively affect the labile iron pool and thereby trigger responses to iron deficiency.
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Affiliation(s)
- Jian Wang
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, 3755 Cote-Ste-Catherine Rd., Montreal, Quebec H3T 1E2, Canada
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43
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Abstract
Iron regulatory proteins (IRP1 and 2) function as translational regulators that coordinate the cellular iron metabolism of eukaryotes by binding to the mRNA of target genes such as the transferrin receptor or ferritin. In addition to IRP2, IRP1 serves as sensor of reactive oxygen species (ROS). As iron and oxygen are essential but potentially toxic constituents of most organisms, ROS-mediated modulation of IRP1 activity may be an important regulatory element in dissecting iron homeostasis and oxidative stress. The responses of IRP1 towards reactive oxygen species are compartment-specific and rather complex: H2O2 activates IRP1 via a signaling cascade that leads to upregulation of the transferrin receptor and cellular iron accumulation. Contrary, superoxide inactivates IRP1 by a direct chemical attack being limited to the intracellular compartment. In particular, activation of IRP1 by H2O2 has established a new regulatory link between inflammation and iron metabolism with new clinical implications. This mechanism seems to contribute to the anemia of chronic disease and inflammation-mediated iron accumulation in tissues. In addition, the cytotoxic side effects of redox-cycling anticancer drugs such as doxorubicin may involve H2O2-mediated IRP1 activation. These molecular insights open up new therapeutic strategies for the clinical management of chronic inflammation and drug-mediated cardiotoxicity.
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Affiliation(s)
- Sebastian Mueller
- Department of Internal Medicine, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.
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44
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Graziano M, Lamattina L. Nitric oxide and iron in plants: an emerging and converging story. TRENDS IN PLANT SCIENCE 2005; 10:4-8. [PMID: 15642517 DOI: 10.1016/j.tplants.2004.12.004] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Although iron is plentiful, it exists primarily in its insoluble form and is therefore not freely available to plants. Thus, complex strategies involving chelators, production of reductive agents, reductase activities, proton-mediated processes, specialized storage proteins, and others, act in concert to mobilize iron from the environment into the plant and within the plant. Because of its fundamental role in plant productivity and ultimately in human nutrition, several unsolved and central questions concerning sensing, trafficking, homeostasis and delivery of iron in plants are currently a matter of intense debate. Here, we discuss some recent studies focusing on iron nutrition in plants as well as evidence from iron homeostasis in animals and propose a new scenario involving the formation of nitric oxide and iron-nitrosyl complexes as part of the dynamic network that governs plant iron homeostasis.
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Affiliation(s)
- Magdalena Graziano
- Instituto de Investigaciones Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, CC 1245, 7600 Mar del Plata, Argentina
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45
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Li JY, Ram G, Gast K, Chen X, Barasch K, Mori K, Schmidt-Ott K, Wang J, Kuo HC, Savage-Dunn C, Garrick MD, Barasch J. Detection of intracellular iron by its regulatory effect. Am J Physiol Cell Physiol 2004; 287:C1547-59. [PMID: 15282194 DOI: 10.1152/ajpcell.00260.2004] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Intracellular iron regulates gene expression by inhibiting the interaction of iron regulatory proteins (IRPs) with RNA motifs called iron-responsive elements (IREs). To assay this interaction in living cells we have developed two fluorescent IRE-based reporters that rapidly, reversibly, and specifically respond to changes in cellular iron status as well as signaling that modifies IRP activity. The reporters were also sufficiently sensitive to distinguish apo- from holotransferrin in the medium, to detect the effect of modifiers of the transferrin pathway such as HFE, and to detect the donation or chelation of iron by siderophores bound to the lipocalin neutrophil gelatinase-associated lipocalin (Ngal). In addition, alternative configurations of the IRE motif either enhanced or repressed fluorescence, permitting a ratio analysis of the iron-dependent response. These characteristics make it possible to visualize iron-IRP-IRE interactions in vivo.
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Affiliation(s)
- Jau-Yi Li
- College of Physicians and Surgeons, Columbia Univ., 630 W 168th St., New York, NY 10032, USA
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46
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Abstract
Cellular iron homeostasis is accomplished by the coordinated regulated expression of the transferrin receptor and ferritin, which mediate iron uptake and storage, respectively. The mechanism is posttranscriptional and involves two cytoplasmic iron regulatory proteins, IRP1 and IRP2. Under conditions of iron starvation, IRPs stabilize the transferrin receptor and inhibit the translation of ferritin mRNAs by binding to "iron responsive elements" (IREs) within their untranslated regions. The IRE/IRP system also controls the expression of additional IRE-containing mRNAs, encoding proteins of iron and energy metabolism. The activities of IRP1 and IRP2 are regulated by distinct posttranslational mechanisms in response to cellular iron levels. Thus, in iron-replete cells, IRP1 assembles a cubane iron-sulfur cluster, which prevents IRE binding, while IRP2 undergoes proteasomal degradation. IRP1 and IRP2 also respond, albeit differentially, to iron-independent signals, such as hydrogen peroxide, hypoxia, or nitric oxide. Basic principles of the IRE/IRP system and recent advances in understanding the regulation and the function of IRP1 and IRP2 are discussed.
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Affiliation(s)
- Kostas Pantopoulos
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, and Department of Medicine, McGill University, Montreal, Quebec, Canada.
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Abstract
Iron is essential for oxidation-reduction catalysis and bioenergetics; however, unless appropriately shielded, this metal plays a crucial role in the formation of toxic oxygen radicals that can attack all biological molecules. Organisms are equipped with specific proteins designed for iron acquisition, export and transport, and storage, as well as with sophisticated mechanisms that maintain the intracellular labile iron pool at an appropriate level. Despite these homeostatic mechanisms, organisms often face the threat of either iron deficiency or iron overload. This review describes several hereditary iron-overloading conditions that are confined to the brain. Recently, a mutation in the L-subunit of ferritin has been described that causes the formation of aberrant L-ferritin with an altered C-terminus. Individuals with this mutation in one allele of L-ferritin have abnormal aggregates of ferritin and iron in the brain, primarily in the globus pallidus. Patients with this dominantly inherited late-onset disease present with symptoms of extrapyramidal dysfunction. Mice with a targeted disruption of a gene for iron regulatory protein 2 (IRP2), a translational repressor of ferritin, misregulate iron metabolism in the intestinal mucosa and the central nervous system. Significant amounts of ferritin and iron accumulate in white matter tracts and nuclei, and adult IRP2-deficient mice develop a movement disorder consisting of ataxia, bradykinesia, and tremor. Mutations in the frataxin gene are responsible for Friedreich's ataxia, the most common of the inherited ataxias. Frataxin appears to regulate mitochondrial iron-sulfur cluster formation, and the neurologic and cardiac manifestations of Friedreich's ataxia are due to iron-mediated mitochondrial toxicity. Patients with Hallervorden-Spatz syndrome, an autosomal recessive, progressive neurodegenerative disorder, have mutations in a novel pantothenate kinase gene (PANK2). The cardinal feature of this extrapyramidal disease is pathologic iron accumulation in the globus pallidus. The defect in PANK2 is predicted to cause the accumulation of cysteine, which binds iron and causes oxidative stress in the iron-rich globus pallidus. Finally, aceruloplasminemia is an autosomal recessive disorder of iron metabolism caused by loss-of-function mutations in ceruloplasmin gene that leads to misregulation of both systemic and central nervous system iron trafficking. Affected individuals suffer from extrapyramidal signs, cerebellar ataxia, progressive neurodegeneration of retina, and diabetes mellitus. Excessive iron depositions are found in the brain, liver, pancreas, and other parenchymal cells, but plasma iron concentrations are decreased. These conditions are not common, but awareness about them is important for differential diagnosis of various neurodegenerative disorders.
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Affiliation(s)
- Prem Ponka
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, Department of Physiology and Medicine, McGill University, Montreal, Quebec, Canada.
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Wang J, Chen G, Muckenthaler M, Galy B, Hentze MW, Pantopoulos K. Iron-mediated degradation of IRP2, an unexpected pathway involving a 2-oxoglutarate-dependent oxygenase activity. Mol Cell Biol 2004; 24:954-65. [PMID: 14729944 PMCID: PMC321427 DOI: 10.1128/mcb.24.3.954-965.2004] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Iron regulatory protein 2 (IRP2), a central posttranscriptional regulator of cellular and systemic iron metabolism, undergoes proteasomal degradation in iron-replete cells. The prevailing model postulates that the mechanism involves site-specific oxidation of 3 cysteine residues (C168, C174, and C178) within a 73-amino-acid (73-aa) degradation domain. By expressing wild-type and mutated versions of IRP2 in H1299 cells, we find that a C168S C174S C178S triple mutant, or a deletion mutant lacking the entire "73-aa domain," is sensitive to iron-mediated degradation, like wild-type IRP2. The antioxidants N-acetylcysteine, ascorbate, and alpha-tocopherol not only fail to stabilize IRP2 but, furthermore, promote its proteasomal degradation. The pathway for IRP2 degradation is saturable, which may explain earlier data supporting the "cysteine oxidation model," and shows remarkable similarities with the degradation of the hypoxia-inducible factor 1 alpha (HIF-1 alpha): dimethyl-oxalylglycine, a specific inhibitor of 2-oxoglutarate-dependent oxygenases, stabilizes IRP2 following the administration of iron to iron-deficient cells. Our results challenge the current model for IRP2 regulation and provide direct pharmacological evidence for the involvement of 2-oxoglutarate-dependent oxygenases in a pathway for IRP2 degradation.
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Affiliation(s)
- Jian Wang
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, Montreal, Quebec, Canada
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49
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Meyron-Holtz EG, Ghosh MC, Iwai K, LaVaute T, Brazzolotto X, Berger UV, Land W, Ollivierre-Wilson H, Grinberg A, Love P, Rouault TA. Genetic ablations of iron regulatory proteins 1 and 2 reveal why iron regulatory protein 2 dominates iron homeostasis. EMBO J 2004; 23:386-95. [PMID: 14726953 PMCID: PMC1271751 DOI: 10.1038/sj.emboj.7600041] [Citation(s) in RCA: 328] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2003] [Accepted: 11/25/2003] [Indexed: 01/04/2023] Open
Abstract
The two iron regulatory proteins IRP1 and IRP2 bind to transcripts of ferritin, transferrin receptor and other target genes to control the expression of iron metabolism proteins at the post-transcriptional level. Here we compare the effects of genetic ablation of IRP1 to IRP2 in mice. IRP1-/- mice misregulate iron metabolism only in the kidney and brown fat, two tissues in which the endogenous expression level of IRP1 greatly exceeds that of IRP2, whereas IRP2-/- mice misregulate the expression of target proteins in all tissues. Surprisingly, the RNA-binding activity of IRP1 does not increase in animals on a low-iron diet that is sufficient to activate IRP2. In animal tissues, most of the bifunctional IRP1 is in the form of cytosolic aconitase rather than an RNA-binding protein. Our findings indicate that the small RNA-binding fraction of IRP1, which is insensitive to cellular iron status, contributes to basal mammalian iron homeostasis, whereas IRP2 is sensitive to iron status and can compensate for the loss of IRP1 by increasing its binding activity. Thus, IRP2 dominates post-transcriptional regulation of iron metabolism in mammals.
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Affiliation(s)
| | - Manik C Ghosh
- Cell Biology and Metabolism Branch, Bethesda, MD, USA
| | - Kazuhiro Iwai
- Cell Biology and Metabolism Branch, Bethesda, MD, USA
| | | | | | | | - William Land
- Cell Biology and Metabolism Branch, Bethesda, MD, USA
| | | | - Alex Grinberg
- Laboratory of Mammalian Gene Regulation and Development, National Institute of Child Health and Human Development, Bethesda, MD, USA
| | - Paul Love
- Laboratory of Mammalian Gene Regulation and Development, National Institute of Child Health and Human Development, Bethesda, MD, USA
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Kim S, Wing SS, Ponka P. S-nitrosylation of IRP2 regulates its stability via the ubiquitin-proteasome pathway. Mol Cell Biol 2004; 24:330-7. [PMID: 14673166 PMCID: PMC303342 DOI: 10.1128/mcb.24.1.330-337.2004] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nitric oxide (NO) is an important signaling molecule that interacts with different targets depending on its redox state. NO can interact with thiol groups resulting in S-nitrosylation of proteins, but the functional implications of this modification are not yet fully understood. We have reported that treatment of RAW 264.7 cells with NO caused a decrease in levels of iron regulatory protein 2 (IRP2), which binds to iron-responsive elements present in untranslated regions of mRNAs for several proteins involved in iron metabolism. In this study, we show that NO causes S-nitrosylation of IRP2, both in vitro and in vivo, and this modification leads to IRP2 ubiquitination followed by its degradation in the proteasome. Moreover, mutation of one cysteine (C178S) prevents NO-mediated degradation of IRP2. Hence, S-nitrosylation is a novel signal for IRP2 degradation via the ubiquitin-proteasome pathway.
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Affiliation(s)
- Sangwon Kim
- Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec H3T 1E2, Canada
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