1
|
Aroun A, Zhong JL, Tyrrell RM, Pourzand C. Iron, oxidative stress and the example of solar ultraviolet A radiation. Photochem Photobiol Sci 2012; 11:118-34. [DOI: 10.1039/c1pp05204g] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
2
|
Martin FM, Xu X, von Löhneysen K, Gilmartin TJ, Friedman JS. SOD2 deficient erythroid cells up-regulate transferrin receptor and down-regulate mitochondrial biogenesis and metabolism. PLoS One 2011; 6:e16894. [PMID: 21326867 PMCID: PMC3033911 DOI: 10.1371/journal.pone.0016894] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Accepted: 01/05/2011] [Indexed: 01/19/2023] Open
Abstract
Background Mice irradiated and reconstituted with hematopoietic cells lacking manganese superoxide dismutase (SOD2) show a persistent hemolytic anemia similar to human sideroblastic anemia (SA), including characteristic intra-mitochondrial iron deposition. SA is primarily an acquired, clonal marrow disorder occurring in individuals over 60 years of age with uncertain etiology. Methodology/Principal Findings To define early events in the pathogenesis of this murine model of SA, we compared erythroid differentiation of Sod2-/- and normal bone marrow cells using flow cytometry and gene expression profiling of erythroblasts. The predominant transcriptional differences observed include widespread down-regulation of mitochondrial metabolic pathways and mitochondrial biogenesis. Multiple nuclear encoded subunits of complexes I-IV of the electron transport chain, ATP synthase (complex V), TCA cycle and mitochondrial ribosomal proteins were coordinately down-regulated in Sod2-/- erythroblasts. Despite iron accumulation within mitochondria, we found increased expression of transferrin receptor, Tfrc, at both the transcript and protein level in SOD2 deficient cells, suggesting deregulation of iron delivery. Interestingly, there was decreased expression of ABCb7, the gene responsible for X-linked hereditary SA with ataxia, a component required for iron-sulfur cluster biogenesis. Conclusions/Significance These results indicate that in erythroblasts, mitochondrial oxidative stress reduces expression of multiple nuclear genes encoding components of the respiratory chain, TCA cycle and mitochondrial protein synthesis. An additional target of particular relevance for SA is iron:sulfur cluster biosynthesis. By decreasing transcription of components of cluster synthesis machinery, both iron utilization and regulation of iron uptake are impacted, contributing to the sideroblastic phenotype.
Collapse
Affiliation(s)
- Florent M. Martin
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California, United States of America
| | - Xiuling Xu
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California, United States of America
| | - Katharina von Löhneysen
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California, United States of America
| | - Timothy J. Gilmartin
- DNA Array Core Facility, The Scripps Research Institute, La Jolla, California, United States of America
| | - Jeffrey S. Friedman
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California, United States of America
- * E-mail:
| |
Collapse
|
3
|
Zhang Y, Mikhael M, Xu D, Li Y, Soe-Lin S, Ning B, Li W, Nie G, Zhao Y, Ponka P. Lysosomal proteolysis is the primary degradation pathway for cytosolic ferritin and cytosolic ferritin degradation is necessary for iron exit. Antioxid Redox Signal 2010; 13:999-1009. [PMID: 20406137 DOI: 10.1089/ars.2010.3129] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Cytosolic ferritins sequester and store iron, consequently protecting cells against iron-mediated free radical damage. However, the mechanisms of iron exit from the ferritin cage and reutilization are largely unknown. In a previous study, we found that mitochondrial ferritin (MtFt) expression led to a decrease in cytosolic ferritin. Here we showed that treatment with inhibitors of lysosomal proteases largely blocked cytosolic ferritin loss in both MtFt-expressing and wild-type cells. Moreover, cytosolic ferritin in cells treated with inhibitors of lysosomal proteases was found to store more iron than did cytosolic ferritins in untreated cells. The prevention of cytosolic ferritin degradation in MtFt-expressing cells significantly blocked iron mobilization from the protein cage induced by MtFt expression. These studies also showed that blockage of cytosolic ferritin loss by leupeptin resulted in decreased cytosolic ferritin synthesis and prolonged cytosolic ferritin stability, potentially resulting in diminished iron availability. Lastly, we found that proteasomes were responsible for cytosolic ferritin degradation in cells pretreated with ferric ammonium citrate. Thus, the current studies suggest that cytosolic ferritin degradation precedes the release of iron in MtFt-expressing cells; that MtFt-induced cytosolic ferritin decrease is partially preventable by lysosomal protease inhibitors; and that both lysosomal and proteasomal pathways may be involved in cytosolic ferritin degradation.
Collapse
Affiliation(s)
- Yinghui Zhang
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, National Center for Nanoscience and Technology of China, Beijing, China
| | | | | | | | | | | | | | | | | | | |
Collapse
|
4
|
Lu Z, Nie G, Li Y, Soe-Lin S, Tao Y, Cao Y, Zhang Z, Liu N, Ponka P, Zhao B. Overexpression of mitochondrial ferritin sensitizes cells to oxidative stress via an iron-mediated mechanism. Antioxid Redox Signal 2009; 11:1791-803. [PMID: 19271990 DOI: 10.1089/ars.2008.2306] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mitochondrial ferritin (MtFt) is a newly identified H-ferritin-like protein expressed only in mitochondria. Previous studies have shown that its overexpression markedly affects intracellular iron homeostasis and rescues defects caused by frataxin deficiency. To assess how MtFt exerts its function under oxidative stress conditions, MtFt overexpressing cells were treated with tert-butyl-hydroperoxide (tBHP), and the effects of MtFt expression on cell survival and iron homeostasis were examined. We found that MtFt expression was associated with decreased mitochondrial metabolic activity and reduced glutathione levels as well as a concomitant increase in reactive oxygen species levels and apoptosis. Moreover, mechanistic studies demonstrated that tBHP treatment led to a prolonged decrease in cytosolic ferritins levels in MtFt-expressing cells, while ferritin levels recovered to basal levels in control counterparts. tBHP treatment also resulted in elevated transferrin receptors, followed by more iron acquisition in MtFt expressing cells. The high molecular weight desferrioxamine, targeting to lysosomes, as well as the hydrophobic iron chelator salicylaldehyde isonicotinoyl hydrazone significantly attenuated tBHP-induced cell damage. In conclusion, the current study indicates that both the newly acquired iron from the extracellular environment and internal iron redistribution from ferritin degradation may be responsible for the increased sensitivity to oxidative stress in MtFt-expressing cells.
Collapse
Affiliation(s)
- Zhongbing Lu
- State Key Laboratory of Brain and Recognition Laboratory, Institute of Biophysics, Beijing, China
| | | | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Sheftel AD, Zhang AS, Brown C, Shirihai OS, Ponka P. Direct interorganellar transfer of iron from endosome to mitochondrion. Blood 2007; 110:125-32. [PMID: 17376890 DOI: 10.1182/blood-2007-01-068148] [Citation(s) in RCA: 197] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Iron is a transition metal whose physicochemical properties make it the focus of vital biologic processes in virtually all living organisms. Among numerous roles, iron is essential for oxygen transport, cellular respiration, and DNA synthesis. Paradoxically, the same characteristics that biochemistry exploits make iron a potentially lethal substance. In the presence of oxygen, ferrous iron (Fe(2+)) will catalyze the production of toxic hydroxyl radicals from hydrogen peroxide. In addition, Fe(3+) is virtually insoluble at physiologic pH. To protect tissues from deleterious effects of Fe, mammalian physiology has evolved specialized mechanisms for extracellular, intercellular, and intracellular iron handling. Here we show that developing erythroid cells, which are taking up vast amounts of Fe, deliver the metal directly from transferrin-containing endosomes to mitochondria (the site of heme biosynthesis), bypassing the oxygen-rich cytosol. Besides describing a new means of intracellular transport, our finding is important for developing therapies for patients with iron loading disorders.
Collapse
Affiliation(s)
- Alex D Sheftel
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital and Department of Physiology, McGill University, Montréal, QC, Canada
| | | | | | | | | |
Collapse
|
6
|
Martin FM, Bydlon G, Friedman JS. SOD2-deficiency sideroblastic anemia and red blood cell oxidative stress. Antioxid Redox Signal 2006; 8:1217-25. [PMID: 16910769 DOI: 10.1089/ars.2006.8.1217] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Iron overload is a feature of an array of human disorders such as sideroblastic anemias, a heterogeneous group of erythropoietic disorders without identified cause in most cases. However, sideroblastic anemias appear to result from a disturbance at the interface between mitochondrial function and iron metabolism. A defining feature is excessive iron deposition within mitochondria of developing red cells, the consequences of which are an increase in cellular free radicals production, increased damage to proteins, and reduced cell survival. Because of its mitochondrial location, superoxide dismutase (SOD2) is the principal defense against the toxicity of superoxide anions generated by the oxidative phosphorylation. We have used hematopoietic stem cell transplantation to study blood cells lacking SOD2. We became interested in the role SOD2 plays in the metabolism of superoxide anions during erythroid development, as anemia is the major phenotype in transplanted animals. Our exploration of this model suggests that oxidative stress-and in particular, mitochondrial- derived oxidants-plays an important role in the pathogenesis of the human disorder, sideroblastic anemia. Here we review the relation between mitochondrial dysfunction and sideroblastic anemia, describe several methods for assessing oxidative damage to mature or developing red cells, present data on, and discuss the potential of antioxidant therapy for this disorder.
Collapse
Affiliation(s)
- Florent M Martin
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | | | | |
Collapse
|
7
|
Nie G, Chen G, Sheftel AD, Pantopoulos K, Ponka P. In vivo tumor growth is inhibited by cytosolic iron deprivation caused by the expression of mitochondrial ferritin. Blood 2006; 108:2428-34. [PMID: 16757684 DOI: 10.1182/blood-2006-04-018341] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Mitochondrial ferritin (MtFt) is a mitochondrial iron-storage protein whose function and regulation is largely unknown. Our previous results have shown that MtFt overexpression markedly affects intracellular iron homeostasis in mammalian cells. Using tumor xenografts, we examined the effects of MtFt overexpression on tumor iron metabolism and growth. The expression of MtFt dramatically reduced implanted tumor growth in nude mice. Mitochondrial iron deposition in MtFt-expressing tumors was directly observed by transmission electron microscopy. A cytosolic iron starvation phenotype in MtFt-expressing tumors was revealed by increased RNA-binding activity of iron regulatory proteins, and concomitantly both an increase in transferrin receptor levels and a decrease in cytosolic ferritin. MtFt overexpression also led to decreases in total cellular heme content and heme oxygenase-1 levels. In addition, elevated MtFt in tumors was also associated with a decrease in total aconitase activity and lower frataxin protein level. In conclusion, our study shows that high MtFt levels can significantly affect tumor iron homeostasis by shunting iron into mitochondria; iron scarcity resulted in partially deficient heme and iron-sulfur cluster synthesis. It is likely that deprivation of iron in the cytosol is the cause for the significant inhibition of xenograft tumor growth.
Collapse
Affiliation(s)
- Guangjun Nie
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital and Department of Physiology, McGill University, 3755 Cote Ste-Catherine Rd, Montreal, QC H3T 1E2, Canada
| | | | | | | | | |
Collapse
|
8
|
Sung JS, Kim KH, Han DG, Kim MJ, Cho YK, Chung HY, Baek HJ, Ma JS, Kook H, Hwang TJ. Pyridoxine responsive sideroblastic anemia in a boy with mitral valve prolapse. KOREAN JOURNAL OF PEDIATRICS 2006. [DOI: 10.3345/kjp.2006.49.11.1223] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- June Seung Sung
- Department of Pediatrics, Hwasun Chonnam National University Hospital Chonnam National University Medical School, Gwangju, Korea
| | - Ki Hwan Kim
- Department of Pediatrics, Hwasun Chonnam National University Hospital Chonnam National University Medical School, Gwangju, Korea
| | - Dong Gyun Han
- Department of Pediatrics, Hwasun Chonnam National University Hospital Chonnam National University Medical School, Gwangju, Korea
| | - Mi Jeong Kim
- Department of Pediatrics, Hwasun Chonnam National University Hospital Chonnam National University Medical School, Gwangju, Korea
| | - Young Kook Cho
- Department of Pediatrics, Hwasun Chonnam National University Hospital Chonnam National University Medical School, Gwangju, Korea
| | - Hae Yul Chung
- Department of Pediatrics, Hwasun Chonnam National University Hospital Chonnam National University Medical School, Gwangju, Korea
| | - Hee Jo Baek
- Department of Pediatrics, Hwasun Chonnam National University Hospital Chonnam National University Medical School, Gwangju, Korea
| | - Jae Sook Ma
- Department of Pediatrics, Hwasun Chonnam National University Hospital Chonnam National University Medical School, Gwangju, Korea
| | - Hoon Kook
- Department of Pediatrics, Hwasun Chonnam National University Hospital Chonnam National University Medical School, Gwangju, Korea
| | - Tai Ju Hwang
- Department of Pediatrics, Hwasun Chonnam National University Hospital Chonnam National University Medical School, Gwangju, Korea
| |
Collapse
|
9
|
Zeharia A, Fischel-Ghodsian N, Casas K, Bykhocskaya Y, Tamari H, Lev D, Mimouni M, Lerman-Sagie T. Mitochondrial myopathy, sideroblastic anemia, and lactic acidosis: an autosomal recessive syndrome in Persian Jews caused by a mutation in the PUS1 gene. J Child Neurol 2005; 20:449-52. [PMID: 15971356 DOI: 10.1177/08830738050200051301] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We report the seventh case of autosomal recessive inherited mitochondrial myopathy, lactic acidosis, and sideroblastic anemia The patient, a product of consanguineous Persian Jews, had the association of mental retardation, dysmorphic features, lactic acidosis, myopathy, and sideroblastic anemia. Muscle biopsy demonstrated low activity of complexes 1 and 4 of the respiratory chain. Electron microscopy revealed paracrystalline inclusions in most mitochondria. Southern blot of the mitochondrial DNA did not show any large-scale rearrangements. The patient was found to be homozygous for the 656C-->T mutation in the pseudouridine synthase 1 gene (PUS1). Mitochondrial myopathy, lactic acidosis, and sideroblastic anemia is an oxidative phosphorylation disorder causing sideroblastic anemia, myopathy, and, in some cases, mental retardation that is due to mutations in the nuclear-encoded PUS1 gene. This finding provides additional evidence that mitochondrial ribonucleic acid modification impacts the phenotypic expression of oxidative phosphorylation disorders.
Collapse
Affiliation(s)
- Avraham Zeharia
- Department of Pediatircs, Schneider Children's Medical of Israel, Petah-Tiqva
| | | | | | | | | | | | | | | |
Collapse
|
10
|
Nie G, Sheftel AD, Kim SF, Ponka P. Overexpression of mitochondrial ferritin causes cytosolic iron depletion and changes cellular iron homeostasis. Blood 2004; 105:2161-7. [PMID: 15522954 DOI: 10.1182/blood-2004-07-2722] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cytosolic ferritin sequesters and stores iron and, consequently, protects cells against iron-mediated free radical damage. However, the function of the newly discovered mitochondrial ferritin (MtFt) is unknown. To examine the role of MtFt in cellular iron metabolism, we established a cell line that stably overexpresses mouse MtFt under the control of a tetracycline-responsive promoter. The overexpression of MtFt caused a dose-dependent iron deficiency in the cytosol that was revealed by increased RNA-binding activity of iron regulatory proteins (IRPs) along with an increase in transferrin receptor levels and decrease in cytosolic ferritin. Consequently, the induction of MtFt resulted in a dramatic increase in cellular iron uptake from transferrin, most of which was incorporated into MtFt. The induction of MtFt caused a shift of iron from cytosolic ferritin to MtFt. In addition, iron inserted into MtFt was less available for chelation than that in cytosolic ferritin and the expression of MtFt was associated with decreased mitochondrial and cytosolic aconitase activities, the latter being consistent with the increase in IRP-binding activity. In conclusion, our results indicate that overexpression of MtFt causes a dramatic change in intracellular iron homeostasis and that shunting iron to MtFt likely limits its availability for active iron proteins.
Collapse
Affiliation(s)
- Guangjun Nie
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital and Department of Physiology, McGill University, 3755 Cote Ste-Catherine Rd, Montreal, QC H3T 1E2, Canada
| | | | | | | |
Collapse
|
11
|
Zhang AS, Sheftel AD, Ponka P. Intracellular kinetics of iron in reticulocytes: evidence for endosome involvement in iron targeting to mitochondria. Blood 2004; 105:368-75. [PMID: 15331447 DOI: 10.1182/blood-2004-06-2226] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In erythroid cells the vast majority of iron (Fe) released from endosomes must cross both the outer and the inner mitochondrial membranes to reach ferrochelatase that inserts Fe into protoporphyrin IX. In the present study, we developed a method whereby a cohort of 59Fe-transferrin (Tf)-laden endosomal vesicles were generated, from which we could evaluate the transfer of 59Fe into mitochondria. Iron chelators, dipyridyl or salicylaldehyde isonicotinoyl hydrazone (SIH), were able to bind the 59Fe when they were present during a 37 degrees C incubation; however, addition of these agents only during lysis at 4 degrees C chelated virtually no 59Fe. Bafilomycin A1 (which prevents endosome acidification) and succinylacetone (an inhibitor of 5-aminolevulinate dehydratase) prevented endosomal 59Fe incorporation into heme. Importantly, both the myosin light chain kinase inhibitor wortmannin and the calmodulin antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide (W-7), caused significant inhibition of 59Fe incorporation from 59Fe-Tf-labeled endosomes into heme, suggesting that myosin is required for Tf-vesicle movement. Our results reaffirm the astonishing efficiency of Tf-derived Fe utilization in hemoglobin (Hb)-producing cells and demonstrate that very little of this Fe is present in a chelatable pool. Collectively, these results are congruent with our hypothesis that a transient endosome-mitochondrion interaction mediates iron transfer between these organelles.
Collapse
Affiliation(s)
- An-Sheng Zhang
- Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, QC, Canada
| | | | | |
Collapse
|
12
|
|
13
|
Affiliation(s)
- Thierry Alcindor
- Division of Haematology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | | |
Collapse
|
14
|
Maguire A, Hellier K, Hammans S, May A. X-linked cerebellar ataxia and sideroblastic anaemia associated with a missense mutation in the ABC7 gene predicting V411L. Br J Haematol 2001; 115:910-7. [PMID: 11843825 DOI: 10.1046/j.1365-2141.2001.03015.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Two brothers with X-linked ataxia (XLA) were found to have hypochromic red cells and increased erythrocyte protoporphyrin despite normal iron stores. The mother was unaffected by ataxia and had normal iron stores but showed evidence of some red cell hypochromia with heavy basophilic stippling that stained positive for iron. Bone marrow biopsy confirmed the presence of ring sideroblasts in one of the brothers. The absence of mutations in the ALAS2 gene and the predominance of zinc over free protoporphyrin led to a search using a combination of DNA and cDNA analysis for the presence of mutations in the ABC7 gene. ABC7 encodes a mitochondrial half-type ATP Binding Cassette transporter involved in iron homeostasis. The published cDNA sequence was used to search databases for the genomic sequence of which 12 exons spanning 23.4 kb were mapped leaving the most 5' nucleotides unaccounted for. The identified exons and their exon-intron boundaries were amplified from DNA while the most 5' sequence including the initiation codon was amplified from cDNA of peripheral blood cells. Direct sequencing revealed hemizygosity in the brothers and heterozygosity in the mother for a G-->C transversion at position 1299 of the published cDNA. This predicts a V411L substitution at the beginning of the last of six putative transmembrane regions of the protein. Restriction enzyme digestion confirmed the presence of this mutation in the three family members but could not detect it in 200 normal alleles. An uncle affected by ataxia also carried this mutation. This study supports the recently hypothesized involvement of the ABC7 gene in XLSA/A and highlights a protein structure region of importance to this syndrome.
Collapse
Affiliation(s)
- A Maguire
- Department of Haematology, University of Wales College of Medicine, Heath Park, Cardiff, Wales, UK
| | | | | | | |
Collapse
|
15
|
Ayas M, Al-Jefri A, Mustafa MM, Al-Mahr M, Shalaby L, Solh H. Congenital sideroblastic anaemia successfully treated using allogeneic stem cell transplantation. Br J Haematol 2001; 113:938-9. [PMID: 11442487 DOI: 10.1046/j.1365-2141.2001.02855.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Therapy for patients with congenital sideroblastic anaemia has been limited to blood transfusions and chelation. Three children with congenital sideroblastic anaemia (SA) who were blood transfusion dependent underwent stem cell transplantation (SCT) from matched sibling donors. Conditioning consisted of cyclophosphamide 50 mg/kg/d for 4 d, busulphan 4 mg/kg/d for 4 d and anti-thymocyte globulin (ATG) 30 mg/kg for four doses pretransplant. Graft-versus-host disease (GVHD) prophylaxis was with cyclosporin A and methotrexate. All patients engrafted, and are alive and transfusion independent. SCT can be curative for patients with SA.
Collapse
Affiliation(s)
- M Ayas
- Department of Oncology, King Faisal Specialist Hospital and Research Centre (KFSH & RC), Riyadh, Saudi Arabia.
| | | | | | | | | | | |
Collapse
|
16
|
Abstract
Anemia, usually mild, is one of the more common problems of the aged, especially in men. Although the anemia is often multifactorial, the specific entities can be grouped into three broad categories: (a) anemias due to causes more common in the elderly; (b) anemias without special predilection for the elderly; (c) anemias of unknown cause. The major biological questions concern the third category, which accounts for 14-17% of the anemias, and whether senescence itself contributes to anemia. Current opinion favors a diminished erythropoietic reserve with aging, but the data are inconsistent and the mechanism has not been established. It may be that cytokine modulation of erythropoiesis is abnormal. Some findings in unexplained anemia bear partial resemblance to the changes of anemia of chronic disease, suggesting the possibility that subtle unidentified inflammatory responses of unknown origin may be operative in many elderly people. Of the anemias of known cause that are especially common in the elderly, anemia of chronic disease is an important entity but is sometimes obscured or overlooked and its diagnosis rests on crude tests. Cobalamin deficiency is very common also, although most cases are mild and not accompanied by anemia. Because the basic diagnostic approach to anemia is neither complex nor very invasive and anemia may be a marker of poor prognosis, attribution of anemia to senescence is not advisable until other causes have been ruled out.
Collapse
Affiliation(s)
- R Carmel
- Department of Medicine, New York Methodist Hospital, Brooklyn, New York 11215-9008, USA
| |
Collapse
|
17
|
Gattermann N. From sideroblastic anemia to the role of mitochondrial DNA mutations in myelodysplastic syndromes. Leuk Res 2000; 24:141-51. [PMID: 10654450 DOI: 10.1016/s0145-2126(99)00160-5] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A primary mitochondrial defect may be pivotal in the pathogenesis of acquired idiopathic sideroblastic anemia (AISA). The mitochondrial respiratory chain is involved in mitochondrial iron uptake and supply of ferrous iron (Fe2+) for heme synthesis. Mitochondrial DNA (mtDNA) comes into play because several subunits of the respiratory chain are encoded by the mitochondrial genome. We have identified heteroplasmic mutations of mtDNA, which may not only impair mitochondrial iron metabolism and heme synthesis, but through impairment of mitochondrial energy production may have much broader implications for MDS pathogenesis. For example, increased apoptosis and genetic instability may be phenomena linked to mitochondrial dysfunction.
Collapse
Affiliation(s)
- N Gattermann
- Department of Hematology, Oncology, and Clinical Immunology, Heinrich-Heine-University, Düsseldorf, Germany.
| |
Collapse
|
18
|
Abstract
Heme is a complex of iron with protoporphyrin IX that is essential for the function of all aerobic cells. Heme serves as the prosthetic group of numerous hemoproteins (eg, hemoglobin, myoglobin, cytochromes, guanylate cyclase, and nitric oxide synthase) and plays an important role in controlling protein synthesis and cell differentiation. Cellular heme levels are tightly controlled; this is achieved by a fine balance between heme biosynthesis and catabolism by the enzyme heme oxygenase. On a per-cell basis, the rate of heme synthesis in the developing erythroid cells is at least 1 order of magnitude higher than in the liver, which is in turn the second most active heme producer in the organism. Differences in iron metabolism and in genes for 5-aminolevulinic acid synthase (ALA-S, the first enzyme in heme biosynthesis) are responsible for the differences in regulation and rates of heme synthesis in erythroid and nonerythroid cells. There are 2 different genes for ALA-S, one of which is expressed ubiquitously (ALA-S1), whereas the expression of the other (ALA-S2) is specific to erythroid cells. Because the 5'-untranslated region of the erythroid-specific ALA-S2 mRNA contains the iron-responsive element, a cis-acting sequence responsible for translational induction of erythroid ALA-S2 by iron, the availability of iron controls protoporphyrin IX levels in hemoglobin-synthesizing cells. In nonerythroid cells, the rate-limiting step of heme production is catalyzed by ALA-S1, whose synthesis is feedback-inhibited by heme. On the other hand, in erythroid cells, heme does not inhibit either the activity or the synthesis of ALA-S but does inhibit cellular iron acquisition from transferrin without affecting its utilization for heme synthesis. This negative feedback is likely to explain the mechanism by which the availability of transferrin iron limits heme synthesis rate. Moreover, in erythroid cells heme seems to enhance globin gene transcription, is essential for globin translation, and supplies the prosthetic group for hemoglobin assembly. Heme may also be involved in the expression of other erythroid-specific proteins. Furthermore, heme seems to play a role in regulating either transcription, translation, processing, assembly, or stability of hemoproteins in nonerythroid cells. Heme oxygenase, which catalyzes heme degradation, seems to be an important enzymatic antioxidant system, probably by providing biliverdin, which is an antioxidant agent.
Collapse
Affiliation(s)
- P Ponka
- Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada.
| |
Collapse
|
19
|
|
20
|
Edgar AJ, Wickramasinghe SN. Hereditary sideroblastic anaemia due to a mutation in exon 10 of the erythroid 5-aminolaevulinate synthase gene. Br J Haematol 1998; 100:389-92. [PMID: 9488633 DOI: 10.1046/j.1365-2141.1998.00569.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
DNA sequencing of the coding region of the erythroid 5-aminolaevulinate synthase (ALAS2) cDNA from a male with pyridoxine-responsive sideroblastic anaemia revealed a missense mutation C1622G and a closely linked polymorphism C1612A in exon 10 of the gene. Sequence analysis of the genomic DNA from other family members revealed that the proband's mother and daughter were heterozygous carriers of the mutation, consistent with the X-linked inheritance. The C1622G mutation results in a histidine to aspartic acid substitution at amino acid residue 524. The histidine residue is conserved in both the erythroid and housekeeping ALAS proteins in vertebrates, all other known ALAS proteins and other oxamine synthases that have pyridoxal 5'-phosphate as a co-factor. This histidine is located in a predicted loop, preceding a long alpha-helix region near the carboxy-terminus.
Collapse
Affiliation(s)
- A J Edgar
- Department of Haematology, Imperial College School of Medicine, St Mary's Hospital, London
| | | |
Collapse
|
21
|
Affiliation(s)
- K R Bridges
- Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
| |
Collapse
|