scholarly journals Effect of nitric oxide on expression of transferrin receptor and ferritin and on cellular iron metabolism in K562 human erythroleukemia cells

Blood ◽  
1995 ◽  
Vol 85 (10) ◽  
pp. 2962-2966 ◽  
Author(s):  
R Oria ◽  
L Sanchez ◽  
T Houston ◽  
MW Hentze ◽  
FY Liew ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Iron Metabolism ◽  
Transferrin Receptor ◽  
Regulatory Protein ◽  
Inhibitory Effect ◽  
Receptor Expression ◽  
Mrna Levels ◽  
Intracellular Iron ◽  
Cellular Iron ◽  
Erythroleukemia Cells

Nitric oxide (NO) is known to increase the affinity of the intracellular iron-regulatory protein (IRP) for iron-response elements (IREs) in transferrin receptor and ferritin mRNAs, suggesting that it may act as a regulator of cellular iron metabolism. In this study, exogenous NO produced by adding the NO-generator S-nitroso-N-acetyl penicillamine gave a dose-dependent upregulation of transferrin receptor expression by K562 erythroleukemia cells and increased levels of transferrin receptor mRNA. NO did not affect the affinity of transferrin binding by the transferrin receptor. NO alone did not alter intracellular ferritin levels, but it did abrogate the inhibitory effect of the iron chelator desferrioxamine and potentiated the stimulatory effect of additional iron. NO also caused some increase in ferritin mRNA levels, which might mask any IRP-/IRE-mediated inhibitory effect of NO on ferritin translation. Although NO did not affect net iron uptake, it increased release of iron from K562 cells pulsed previously with 59Fe, and subcellular fractionation showed that it also increased the proportion of intracellular iron bound to ferritin. These findings provide direct evidence that NO can affect cellular iron metabolism and suggest that NO produced in vivo by activated bone marrow macrophages might affect erythropoiesis.

scholarly journals Regulation of Cellular Iron Metabolism by Erythropoietin: Activation of Iron-Regulatory Protein and Upregulation of Transferrin Receptor Expression in Erythroid Cells

Blood ◽  
1997 ◽  
Vol 89 (2) ◽  
pp. 680-687 ◽  
Author(s):  
Günter Weiss ◽  
Tracey Houston ◽  
Stefan Kastner ◽  
Karin Jöhrer ◽  
Kurt Grünewald ◽  
...  
Keyword(s):  
Progenitor Cells ◽  
Iron Metabolism ◽  
Transferrin Receptor ◽  
Regulatory Protein ◽  
Receptor Expression ◽  
General Mechanism ◽  
Iron Regulatory Protein ◽  
Erythroid Progenitor ◽  
Cellular Iron ◽  
Erythroid Progenitor Cells

Abstract Erythropoietin (Epo) is the central regulator of red blood cell production and acts primarily by inducing proliferation and differentiation of erythroid progenitor cells. Because a sufficient supply of iron is a prerequisite for erythroid proliferation and hemoglobin synthesis, we have investigated whether Epo can regulate cellular iron metabolism. We present here a novel biologic function of Epo, namely as a potential modulator of cellular iron homeostasis. We show that, in human (K562) and murine erythroleukemic cells (MEL), Epo enhances the binding affinity of iron-regulatory protein (IRP)-1, the central regulator of cellular iron metabolism, to specific RNA stem-loop structures, known as iron-responsive elements (IREs). Activation of IRP-1 by Epo is associated with a marked increase in transferrin receptor (trf-rec) mRNA levels in K562 and MEL, enhanced cell surface expression of trf-recs, and increased uptake of iron into cells. These findings are in agreement with the well-established mechanism whereby high-affinity binding of IRPs to IREs stabilizes trf-rec mRNA by protecting it from degradation by a specific RNase. The effects of Epo on IRE-binding of IRPs were not observed in human myelomonocytic cells (THP-1), which indicates that this response to Epo is not a general mechanism observed in all cells but is likely to be erythroid-specific. Our results provide evidence for a direct functional connection between Epo biology and iron metabolism by which Epo increases iron uptake into erythroid progenitor cells via posttranscriptional induction of trf-rec expression. Our data suggest that sequential administration of Epo and iron might improve the response to Epo therapy in some anemias.

scholarly journals Iron regulates nitric oxide synthase activity by controlling nuclear transcription.

1994 ◽  
Vol 180 (3) ◽  
pp. 969-976 ◽  
Author(s):  
G Weiss ◽  
G Werner-Felmayer ◽  
E R Werner ◽  
K Grünewald ◽  
H Wachter ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Iron Metabolism ◽  
Regulatory Protein ◽  
Antigen Expression ◽  
Iron Chelator ◽  
Mrna Levels ◽  
Intracellular Iron ◽  
Ifn Gamma ◽  
Inducible Nos

Recently, it was reported that nitric oxide (NO) directly controls intracellular iron metabolism by activating iron regulatory protein (IRP), a cytoplasmic protein that regulates ferritin translation. To determine whether intracellular iron levels themselves affect NO synthase (NOS), we studied the effect of iron on cytokine-inducible NOS activity and mRNA expression in the murine macrophage cell line J774A.1. We show here that NOS activity is decreased by about 50% in homogenates obtained from cells treated with interferon gamma plus lipopolysaccharide (IFN-gamma/LPS) in the presence of 50 microM ferric iron [Fe(3+)] as compared with extracts from cells treated with IFN-gamma/LPS alone. Conversely, addition of the iron chelator desferrioxamine (100 microM) at the time of stimulation with IFN-gamma/LPS increases NOS activity up to 2.5-fold in J774 cells. These effects of changing the cellular iron state cannot be attributed to a general alteration of the IFN-gamma/LPS signal, since IFN-gamma/LPS-mediated major histocompatibility complex class II antigen expression is unaffected. Furthermore, neither was the intracellular availability of the NOS cofactor tetrahydrobiopterin altered by treatment with Fe(3+) or desferrioxamine, nor do these compounds interfere with the activity of the hemoprotein NOS in vitro. We demonstrate that the mRNA levels for NOS are profoundly increased by treatment with desferrioxamine and reduced by Fe(3+). The half-life of NOS mRNA appeared not to be significantly altered by administration of ferric ion, and NOS mRNA stability was only slightly prolonged by desferrioxamine treatment. Nuclear run-off experiments demonstrate that nuclear transcription of cytokine-inducible NOS mRNA is strongly increased by desferrioxamine whereas it is decreased by Fe(3+). Thus, this transcriptional response appears to account quantitatively for the changes in enzyme activity. Our results suggest the existence of a regulatory loop between iron metabolism and the NO/NOS pathway.

HFE Downregulates Iron Uptake From Transferrin and Induces Iron-Regulatory Protein Activity in Stably Transfected Cells

Blood ◽  
1999 ◽  
Vol 94 (11) ◽  
pp. 3915-3921 ◽  
Author(s):  
H.D. Riedel ◽  
M.U. Muckenthaler ◽  
S.G. Gehrke ◽  
I. Mohr ◽  
K. Brennan ◽  
...  
Keyword(s):  
Transferrin Receptor ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Hereditary Hemochromatosis ◽  
Regulatory Protein ◽  
Intracellular Iron ◽  
Iron Storage ◽  
Iron Regulatory Proteins ◽  
Cellular Iron

Hereditary hemochromatosis (HH) is a common autosomal-recessive disorder of iron metabolism. More than 80% of HH patients are homozygous for a point mutation in a major histocompatibility complex (MHC) class I type protein (HFE), which results in a lack of HFE expression on the cell surface. A previously identified interaction of HFE and the transferrin receptor suggests a possible regulatory role of HFE in cellular iron absorption. Using an HeLa cell line stably transfected with HFE under the control of a tetracycline-sensitive promoter, we investigated the effect of HFE expression on cellular iron uptake. We demonstrate that the overproduction of HFE results in decreased iron uptake from diferric transferrin. Moreover, HFE expression activates the key regulators of intracellular iron homeostasis, the iron-regulatory proteins (IRPs), implying that HFE can affect the intracellular “labile iron pool.” The increase in IRP activity is accompanied by the downregulation of the iron-storage protein, ferritin, and an upregulation of transferrin receptor levels. These findings are discussed in the context of the pathophysiology of HH and a possible role of iron-responsive element (IRE)-containing mRNAs.

scholarly journals Crucial function of vertebrate glutaredoxin 3 (PICOT) in iron homeostasis and hemoglobin maturation

2013 ◽  
Vol 24 (12) ◽  
pp. 1895-1903 ◽  
Author(s):  
Petra Haunhorst ◽  
Eva-Maria Hanschmann ◽  
Lars Bräutigam ◽  
Oliver Stehling ◽  
Bastian Hoffmann ◽  
...  
Keyword(s):  
Iron Metabolism ◽  
Iron Homeostasis ◽  
Regulatory Protein ◽  
Iron Regulation ◽  
Iron Starvation ◽  
Intracellular Iron ◽  
Cellular Iron ◽  
Cellular Iron Uptake ◽  
S Proteins

The mechanisms by which eukaryotic cells handle and distribute the essential micronutrient iron within the cytosol and other cellular compartments are only beginning to emerge. The yeast monothiol multidomain glutaredoxins (Grx) 3 and 4 are essential for both transcriptional iron regulation and intracellular iron distribution. Despite the fact that the mechanisms of iron metabolism differ drastically in fungi and higher eukaryotes, the glutaredoxins are conserved, yet their precise function in vertebrates has remained elusive. Here we demonstrate a crucial role of the vertebrate-specific monothiol multidomain Grx3 (PICOT) in cellular iron homeostasis. During zebrafish embryonic development, depletion of Grx3 severely impairs the maturation of hemoglobin, the major iron-consuming process. Silencing of human Grx3 expression in HeLa cells decreases the activities of several cytosolic Fe/S proteins, for example, iron-regulatory protein 1, a major component of posttranscriptional iron regulation. As a consequence, Grx3-depleted cells show decreased levels of ferritin and increased levels of transferrin receptor, features characteristic of cellular iron starvation. Apparently, Grx3-deficient cells are unable to efficiently use iron, despite unimpaired cellular iron uptake. These data suggest an evolutionarily conserved role of cytosolic monothiol multidomain glutaredoxins in cellular iron metabolism pathways, including the biogenesis of Fe/S proteins and hemoglobin maturation.

HFE Downregulates Iron Uptake From Transferrin and Induces Iron-Regulatory Protein Activity in Stably Transfected Cells

Blood ◽  
1999 ◽  
Vol 94 (11) ◽  
pp. 3915-3921 ◽  
Author(s):  
H.D. Riedel ◽  
M.U. Muckenthaler ◽  
S.G. Gehrke ◽  
I. Mohr ◽  
K. Brennan ◽  
...  
Keyword(s):  
Transferrin Receptor ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Hereditary Hemochromatosis ◽  
Regulatory Protein ◽  
Intracellular Iron ◽  
Iron Storage ◽  
Iron Regulatory Proteins ◽  
Cellular Iron

Abstract Hereditary hemochromatosis (HH) is a common autosomal-recessive disorder of iron metabolism. More than 80% of HH patients are homozygous for a point mutation in a major histocompatibility complex (MHC) class I type protein (HFE), which results in a lack of HFE expression on the cell surface. A previously identified interaction of HFE and the transferrin receptor suggests a possible regulatory role of HFE in cellular iron absorption. Using an HeLa cell line stably transfected with HFE under the control of a tetracycline-sensitive promoter, we investigated the effect of HFE expression on cellular iron uptake. We demonstrate that the overproduction of HFE results in decreased iron uptake from diferric transferrin. Moreover, HFE expression activates the key regulators of intracellular iron homeostasis, the iron-regulatory proteins (IRPs), implying that HFE can affect the intracellular “labile iron pool.” The increase in IRP activity is accompanied by the downregulation of the iron-storage protein, ferritin, and an upregulation of transferrin receptor levels. These findings are discussed in the context of the pathophysiology of HH and a possible role of iron-responsive element (IRE)-containing mRNAs.

scholarly journals Effects of sham air and cigarette smoke on A549 lung cells: implications for iron-mediated oxidative damage

2004 ◽  
Vol 286 (4) ◽  
pp. L866-L876 ◽  
Author(s):  
Jonathan J. Mayo ◽  
Pete Kohlhepp ◽  
Dianzheng Zhang ◽  
Joy J. Winzerling
Keyword(s):  
Oxidative Stress ◽  
Cigarette Smoke ◽  
Iron Metabolism ◽  
Iron Uptake ◽  
Regulatory Protein ◽  
A549 Cells ◽  
Lung Cells ◽  
Mrna Levels ◽  
Iron Regulatory Protein ◽  
Intracellular Iron

Inhalation of airborne pollution particles that contain iron can result in a variety of detrimental changes to lung cells and tissues. The lung iron burden can be substantially increased by exposure to cigarette smoke, and cigarette smoke contains iron particulates, as well as several environmental toxins, that could influence intracellular iron status. We are interested in the effects of environmental contaminants on intracellular iron metabolism. We initiated our studies using lung A549 type II epithelial cells as a model, and we evaluated the effects of iron dose and smoke treatment on several parameters of intracellular iron metabolism. We show that iron at a physiological dose stimulates ferritin synthesis without altering the transferrin receptor (TfR) mRNA levels of these cells. This is mediated primarily by a reduction of iron regulatory protein 2. Higher doses of iron reduce iron regulatory protein-1 binding activity and are accompanied by a reduction in TfR mRNA. Thus, for A549 cells, different mechanisms influencing IRP-IRE interaction allow ferritin translation in the presence of TfR mRNA to provide for iron needs and yet prevent excessive iron uptake. More importantly, we report that smoke treatment diminishes ferritin levels and increases TfR mRNA of A549 cells. Ferritin serves as a cytoprotective agent against oxidative stress. These data suggest that exposure of lung cells to low levels of smoke as are present in environmental pollutants could result in reduced cytoprotection by ferritin at a time when iron uptake is sustained, thus enhancing the possibility of lung damage by iron-mediated oxidative stress.

scholarly journals Divergent effects of α1-antitrypsin on the regulation of iron metabolism in human erythroleukaemic (K562) and myelomonocytic (THP-1) cells

1996 ◽  
Vol 319 (3) ◽  
pp. 897-902 ◽  
Author(s):  
Günter WEISS ◽  
Ivo GRAZIADEI ◽  
Martina URBANEK ◽  
Kurt GRÜNEWALD ◽  
Wolfgang VOGEL
Keyword(s):  
Cell Surface ◽  
Iron Metabolism ◽  
Iron Homeostasis ◽  
Regulatory Protein ◽  
Cell Surface Receptor ◽  
Cell Surface Expression ◽  
Concomitant Treatment ◽  
Mrna Levels ◽  
Uptake System ◽  
Cellular Iron

The acute-phase protein α1-antitrypsin (α1-AT) has been shown to inhibit the binding of transferrin to its cell-surface receptor. Here we demonstrate that in human erythroleukaemic cells (K562) α1-AT enhances the binding affinity of iron-regulatory protein (IRP), the central regulator of cellular iron metabolism, to iron-responsive elements. Activation of IRP by α1-AT is associated with a marked increase in transferrin receptor (trf-rec) mRNA levels in K562 and enhanced cell-surface expression of transferrin-binding sites, whereas ferritin production is decreased, although ferritin mRNA levels remain unchanged. In agreement with the well-established mechanism of cellular iron regulation, α1-AT seems to modulate trf-rec and ferritin expression primarily post-transcriptionally/translationally by influencing IRP activity. In contrast, α1-AT produces only minor changes in IRP activity, and subsequently in trf-rec expression and ferritin synthesis in THP-1 cells. Moreover the effects of α1-AT on iron homeostasis in K562 cannot be overcome by the addition of iron salts, whereas concomitant treatment of THP-1 with iron and α1-AT results in the same metabolic changes as the addition of iron alone. Because α1-AT blocks transferrin binding on K562 as well as on THP-1 cells, it is suggested, on the basis of the results presented here, (1) that erythroid and monocytic cells might differ in their dependence on transferrin-mediated iron supply and (2) that THP-1 might be able to acquire iron by a transferrin-independent iron uptake system. α1-AT might therefore be involved in the diversion of iron traffic between various cellular compartments under inflammatory conditions.

Effect of iron deficiency on placental transfer of iron and expression of iron transport proteins in vivo and in vitro

2001 ◽  
Vol 356 (3) ◽  
pp. 883-889 ◽  
Author(s):  
Lorraine GAMBLING ◽  
Ruth DANZEISEN ◽  
Susan GAIR ◽  
Richard G. LEA ◽  
Zehane CHARANIA ◽  
...  
Keyword(s):  
Iron Deficiency ◽  
Transferrin Receptor ◽  
Iron Transport ◽  
Receptor Expression ◽  
Mrna Levels ◽  
Iron Transfer ◽  
Metal Transporter ◽  
Protein Levels ◽  
Copper Oxidase ◽  
Maternal Iron

Maternal iron deficiency during pregnancy induces anaemia in the developing fetus; however, the severity tends to be less than in the mother. The mechanism underlying this resistance has not been determined. We have measured placental expression of proteins involved in iron transfer in pregnant rats given diets with decreasing levels of iron and examined the effect of iron deficiency on iron transfer across BeWo cell layers, a model for placental iron transfer. Transferrin receptor expression was increased at both mRNA and protein levels. Similarly, expression of the iron-responsive element (IRE)-regulated form of the divalent metal transporter 1 (DMT1) was also increased. In contrast, the non-IRE regulated isoform showed no change in mRNA levels. Protein levels of DMT1 increased significantly. Iron efflux is thought to be mediated by the metal transporter protein, IREG1/ferroportin1/MTP1, and oxidation of Fe(II) to Fe(III) prior to incorporation into fetal transferrin is carried out by the placental copper oxidase. Expression of IREG1 was not altered by iron deficiency, whereas copper oxidase activity was increased. In BeWo cells made iron deficient by treatment with desferrioxamine (‘deferioxamine’), iron accumulation from iron-transferrin increased, in parallel with increased expression of the transferrin receptor. At the same time, iron efflux also increased, showing a higher flux of iron from the apical to the basolateral side. The data show that expression of placental proteins of iron transport are up-regulated in maternal iron deficiency, resulting in an increased efficiency of iron flux and a consequent minimization of the severity of fetal anaemia.

scholarly journals Glia maturation factor-γ regulates murine macrophage iron metabolism and M2 polarization through mitochondrial ROS

2019 ◽  
Vol 3 (8) ◽  
pp. 1211-1225 ◽  
Author(s):  
Wulin Aerbajinai ◽  
Manik C. Ghosh ◽  
Jie Liu ◽  
Chutima Kumkhaek ◽  
Jianqing Zhu ◽  
...  
Keyword(s):  
Iron Metabolism ◽  
Mitochondrial Function ◽  
Regulatory Protein ◽  
M2 Macrophage ◽  
Macrophage Phenotype ◽  
Glia Maturation Factor ◽  
Altered Expression ◽  
Murine Macrophages ◽  
Cellular Iron ◽  
Maturation Factor

Abstract In macrophages, cellular iron metabolism status is tightly integrated with macrophage phenotype and associated with mitochondrial function. However, how molecular events regulate mitochondrial activity to integrate regulation of iron metabolism and macrophage phenotype remains unclear. Here, we explored the important role of the actin-regulatory protein glia maturation factor-γ (GMFG) in the regulation of cellular iron metabolism and macrophage phenotype. We found that GMFG was downregulated in murine macrophages by exposure to iron and hydrogen peroxide. GMFG knockdown altered the expression of iron metabolism proteins and increased iron levels in murine macrophages and concomitantly promoted their polarization toward an anti-inflammatory M2 phenotype. GMFG-knockdown macrophages exhibited moderately increased levels of mitochondrial reactive oxygen species (mtROS), which were accompanied by decreased expression of some mitochondrial respiration chain components, including the iron-sulfur cluster assembly scaffold protein ISCU as well as the antioxidant enzymes SOD1 and SOD2. Importantly, treatment of GMFG-knockdown macrophages with the antioxidant N-acetylcysteine reversed the altered expression of iron metabolism proteins and significantly inhibited the enhanced gene expression of M2 macrophage markers, suggesting that mtROS is mechanistically linked to cellular iron metabolism and macrophage phenotype. Finally, GMFG interacted with the mitochondrial membrane ATPase ATAD3A, suggesting that GMFG knockdown–induced mtROS production might be attributed to alteration of mitochondrial function in macrophages. Our findings suggest that GMFG is an important regulator in cellular iron metabolism and macrophage phenotype and could be a novel therapeutic target for modulating macrophage function in immune and metabolic disorders.

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