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Winter M, Funk J, Körner A, Alberati D, Christen F, Schmitt G, Altmann B, Pospischil A, Singer T. Effects of GlyT1 inhibition on erythropoiesis and iron homeostasis in rats. Exp Hematol 2016; 44:964-974.e4. [PMID: 27403535 DOI: 10.1016/j.exphem.2016.07.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 06/28/2016] [Accepted: 06/29/2016] [Indexed: 01/19/2023]
Abstract
Glycine is a key rate-limiting component of heme biosynthesis in erythropoietic cells, where the high intracellular glycine demand is primarily supplied by the glycine transporter 1 (GlyT1). The impact of intracellular glycine restriction after GlyT1 inhibition on hematopoiesis and iron regulation is not well established. We investigated the effects of a potent and selective inhibitor of GlyT1, bitopertin, on erythropoiesis and iron homeostasis in rats. GlyT1 inhibition significantly affected erythroid heme biosynthesis, manifesting as microcytic hypochromic regenerative anemia with a 20% steady-state reduction in hemoglobin. Reduced erythropoietic iron utilization was characterized by down-regulation of the transferrin receptor 1 (TfR1) on reticulocytes and modest increased iron storage in the spleen. Hepatic hepcidin expression was not affected. However, under the condition of reduced heme biosynthesis with reduced iron reutilization and increased storage iron, hepcidin at the lower and higher range of normal showed a striking role in tissue distribution of iron. Rapid formation of iron-positive inclusion bodies (IBs) was observed in circulating reticulocytes, with an ultrastructure of iron-containing polymorphic mitochondrial remnants. IB or mitochondrial iron accumulation was absent in bone marrow erythroblasts. In conclusion, GlyT1 inhibition in rats induced a steady-state microcytic hypochromic regenerative anemia and a species-specific accumulation of uncommitted mitochondrial iron in reticulocytes. Importantly, this glycine-restricted anemia provides no feedback signal for increased systemic iron acquisition and the effects reported are pathogenetically distinct from systemic iron-overload anemias and erythropoietic disorders such as acquired sideroblastic anemia.
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Affiliation(s)
- Michael Winter
- Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland.
| | - Jürgen Funk
- Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland
| | - Annette Körner
- Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland
| | - Daniela Alberati
- Pharmaceutical Research and Early Development, Neuroscience Discovery, Roche Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland
| | - Francois Christen
- Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland
| | - Georg Schmitt
- Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland
| | - Bernd Altmann
- Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland
| | - Andreas Pospischil
- Institute of Veterinary Pathology, Vetsuisse-Faculty, University Zurich, Switzerland
| | - Thomas Singer
- Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland
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Holmes-Hampton GP, Tong WH, Rouault TA. Biochemical and biophysical methods for studying mitochondrial iron metabolism. Methods Enzymol 2014; 547:275-307. [PMID: 25416363 DOI: 10.1016/b978-0-12-801415-8.00015-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Iron is a heavily utilized element in organisms and numerous mechanisms accordingly regulate the trafficking, metabolism, and storage of iron. Despite the high regulation of iron homeostasis, several diseases and mutations can lead to the misregulation and often accumulation of iron in the cytosol or mitochondria of tissues. To understand the genesis of iron overload, it is necessary to employ various techniques to quantify iron in organisms and mitochondria. This chapter discusses techniques for determining the total iron content of tissue samples, ranging from colorimetric determination of iron concentrations, atomic absorption spectroscopy, inductively coupled plasma-optical emission spectroscopy, and inductively coupled plasma-mass spectrometry. In addition, we discuss in situ techniques for analyzing iron including electron microscopic nonheme iron histochemistry, electron energy loss spectroscopy, synchrotron X-ray fluorescence imaging, and confocal Raman microscopy. Finally, we discuss biophysical methods for studying iron in isolated mitochondria, including ultraviolet-visible, electron paramagnetic resonance, X-ray absorbance, and Mössbauer spectroscopies. This chapter should aid researchers to select and interpret mitochondrial iron quantifications.
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Affiliation(s)
- Gregory P Holmes-Hampton
- Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, USA
| | - Wing-Hang Tong
- Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, USA
| | - Tracey A Rouault
- Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, USA.
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Fujioka H, Tandler B, Haldar SM, Jain MK, Hoppel CL. String mitochondria in mouse soleus muscle. Microsc Res Tech 2012; 76:237-41. [PMID: 23174930 DOI: 10.1002/jemt.22158] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Accepted: 11/02/2012] [Indexed: 11/06/2022]
Abstract
Red myofibers in mouse soleus muscle have two spatially distinct populations of mitochondria: one where these organelles are disposed in large clusters just inside the sarcolemma and the other situated between the myofibrils. In most cases, the interfibrillar mitochondria (IFM), which are much smaller than the subsarcolemmal ones (SSM), are arranged as pairs, with each member on opposite sides of the Z-line. In some myofibers, the IFM have fused end-to-end to form greatly elongated organelles, which we call "string mitochondria." Although narrow, these can be many sarcomeres in length. The SSM do not form string mitochondria. Most of the string mitochondria exhibit many instances of "pinching," a process involved in mitochondrial division. Elements of sarcoplasmic reticulum are intimately involved with each mitochondrial membrane invagination. It appears as if the fusion:fission balance of IFM in the soleus muscle is slightly out of kilter, with end-to-end fusion predominating over fission.
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Affiliation(s)
- Hisashi Fujioka
- Electron Microscopy Facility, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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Olins DE, Olins AL. Nuclear envelope-limited chromatin sheets (ELCS) and heterochromatin higher order structure. Chromosoma 2009; 118:537-48. [PMID: 19521714 DOI: 10.1007/s00412-009-0219-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Revised: 05/07/2009] [Accepted: 05/19/2009] [Indexed: 12/28/2022]
Abstract
The interphase nucleus and nuclear envelope can acquire a myriad of shapes in normal or pathological cell states. There exist a wide variety of indentations and invaginations, of protrusions and evaginations. It has been difficult to classify and name all of these nuclear shapes and, consequently, a barrier to understanding the biochemical and biophysical causes. This review focuses upon one type of nuclear envelope shape change, named "nuclear envelope-limited chromatin sheets" (ELCS), which appears to involve exaggerated nuclear envelope growth, carrying with it one or more layers of approximately 30 nm diameter heterochromatin. A hypothesis on the formation of ELCS is proposed, relating higher order heterochromatin structure in an interphase nucleus, nuclear envelope growth, and nuclear envelope-heterochromatin interactions.
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Affiliation(s)
- Donald E Olins
- Department of Biology, Bowdoin College, Brunswick, ME 04011, USA.
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Abstract
Originally conceived as an uncommon disorder, with the advent of MRI, CNS superficial siderosis has been observed more frequently. We present histologic, histochemical, immunohistochemical, immunofluorescent and ultrastructural evaluation of a 56-year-old woman with superficial siderosis. Iron was concentrated in macrophages, superficial astrocytes and gray matter oligodendroglia deep within the cord. While spatially associated with dystrophic glial and neuronal spheroids, iron did not colocalize with mitochondria. Neurotoxic effects were observed despite selective iron localization only within a variety of non-neuronal cell types.
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Affiliation(s)
- Harry Kellermier
- Neuropathology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA.
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Rouault TA, Tong WH. Iron-sulfur cluster biogenesis and human disease. Trends Genet 2008; 24:398-407. [PMID: 18606475 PMCID: PMC2574672 DOI: 10.1016/j.tig.2008.05.008] [Citation(s) in RCA: 285] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Revised: 05/19/2008] [Accepted: 05/20/2008] [Indexed: 10/21/2022]
Abstract
Iron-sulfur (Fe-S) clusters are essential for numerous biological processes, including mitochondrial respiratory chain activity and various other enzymatic and regulatory functions. Human Fe-S cluster assembly proteins are frequently encoded by single genes, and inherited defects in some of these genes cause disease. Recently, the spectrum of diseases attributable to abnormal Fe-S cluster biogenesis has extended beyond Friedreich ataxia to include a sideroblastic anemia with deficiency of glutaredoxin 5 and a myopathy associated with a deficiency of a Fe-S cluster assembly scaffold protein, ISCU. Mutations within other mammalian Fe-S cluster assembly genes could be causative for human diseases that manifest distinctive combinations of tissue-specific impairments. Thus, defects in the iron-sulfur cluster biogenesis pathway could underlie many human diseases.
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Affiliation(s)
- Tracey A Rouault
- Molecular Medicine Program, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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Michael S, Petrocine SV, Qian J, Lamarche JB, Knutson MD, Garrick MD, Koeppen AH. Iron and iron-responsive proteins in the cardiomyopathy of Friedreich's ataxia. THE CEREBELLUM 2007; 5:257-67. [PMID: 17134988 DOI: 10.1080/14734220600913246] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Hypertrophic cardiomyopathy is a common complication of Friedreich's ataxia (FRDA). Histological sections reveal abnormal cardiomyocytes, muscle fiber necrosis, reactive inflammation, and increased endomysial connective tissue. Scattered muscle fibers display perinuclear collections of minute iron-positive granules that lie in rows between myofibrils. Frataxin deficiency in FRDA causes mitochondrial iron dysmetabolism. We studied total iron and the iron-related proteins ferritin, mitochondrial ferritin, divalent metal transporter 1 (DMT1), and ferroportin in FRDA hearts by biochemical and histological techniques. Total iron in the left ventricular wall of FRDA patients (30.7+/-19.3 mg/100 g dry weight) was not significantly higher than normal (31.3+/-24.1 mg/100 g dry weight). Similarly, cytosolic holoferritin levels in FRDA hearts (230+/-172 microg/g wet weight) were not significantly elevated above normal (148+/-86 microg/g wet weight). The iron-positive granules exhibited immunoreactivity for cytosolic ferritin, mitochondrial ferritin, and ferroportin. Electron microscopy showed enhanced electron density of mitochondrial deposits after treatment with bismuth subnitrate supporting ferritin accumulation. The inflammatory cells in the endomysium were reactive for CD68, cytosolic ferritin, and the DMT1 isoform(s) translated from messenger ribonucleic acids containing iron-responsive elements (DMT1+). Progressive cardiomyopathy in FRDA is the likely result of iron-catalyzed mitochondrial damage followed by muscle fiber necrosis and a chronic reactive myocarditis.
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Affiliation(s)
- Susan Michael
- Research Service, Veterans Affairs Medical Center, Albany, New York, USA
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Rouault TA, Tong WH. Iron–sulphur cluster biogenesis and mitochondrial iron homeostasis. Nat Rev Mol Cell Biol 2005; 6:345-51. [PMID: 15803140 DOI: 10.1038/nrm1620] [Citation(s) in RCA: 317] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Iron-sulphur clusters are important cofactors for proteins that are involved in many cellular processes, including electron transport, enzymatic catalysis and regulation. The enzymes that catalyse the formation of iron-sulphur clusters are widely conserved from bacteria to humans. Recent studies in model systems and humans reveal that iron-sulphur proteins have important roles in mitochondrial iron homeostasis and in the pathogenesis of the human disease Friedreich ataxia.
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Affiliation(s)
- Tracey A Rouault
- National Institute of Child Health and Human Development, Cell Biology and Metabolism Branch, Bethesda, Maryland 20892, USA.
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