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Lee NJ, Ha SK, Sati P, Absinta M, Nair G, Luciano NJ, Leibovitch EC, Yen CC, Rouault TA, Silva AC, Jacobson S, Reich DS. Potential role of iron in repair of inflammatory demyelinating lesions. J Clin Invest 2020; 129:4365-4376. [PMID: 31498148 DOI: 10.1172/jci126809] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 07/16/2019] [Indexed: 12/20/2022] Open
Abstract
Inflammatory destruction of iron-rich myelin is characteristic of multiple sclerosis (MS). Although iron is needed for oligodendrocytes to produce myelin during development, its deposition has also been linked to neurodegeneration and inflammation, including in MS. We report perivascular iron deposition in multiple sclerosis lesions that was mirrored in 72 lesions from 13 marmosets with experimental autoimmune encephalomyelitis. Iron accumulated mainly inside microglia/macrophages from 6 weeks after demyelination. Consistently, expression of transferrin receptor, the brain's main iron-influx protein, increased as lesions aged. Iron was uncorrelated with inflammation and postdated initial demyelination, suggesting that iron is not directly pathogenic. Iron homeostasis was at least partially restored in remyelinated, but not persistently demyelinated, lesions. Taken together, our results suggest that iron accumulation in the weeks after inflammatory demyelination may contribute to lesion repair rather than inflammatory demyelination per se.
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Affiliation(s)
- Nathanael J Lee
- Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.,Department of Neuroscience, Georgetown University Medical Center, Georgetown University, Washington, District of Columbia, USA
| | - Seung-Kwon Ha
- Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Pascal Sati
- Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Martina Absinta
- Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Govind Nair
- Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Nicholas J Luciano
- Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Emily C Leibovitch
- Viral Immunology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Cecil C Yen
- Cerebral Microcirculation Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Tracey A Rouault
- Section on Human Iron Metabolism, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Afonso C Silva
- Cerebral Microcirculation Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Steven Jacobson
- Viral Immunology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Daniel S Reich
- Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
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Abstract
Histochemical and MRI studies have demonstrated that MS (multiple sclerosis) patients have abnormal deposition of iron in both gray and white matter structures. Data is emerging indicating that this iron could partake in pathogenesis by various mechanisms, e.g., promoting the production of reactive oxygen species and enhancing the production of proinflammatory cytokines. Iron chelation therapy could be a viable strategy to block iron-related pathological events or it can confer cellular protection by stabilizing hypoxia inducible factor 1α, a transcription factor that normally responds to hypoxic conditions. Iron chelation has been shown to protect against disease progression and/or limit iron accumulation in some neurological disorders or their experimental models. Data from studies that administered a chelator to animals with experimental autoimmune encephalomyelitis, a model of MS, support the rationale for examining this treatment approach in MS. Preliminary clinical studies have been performed in MS patients using deferoxamine. Although some side effects were observed, the large majority of patients were able to tolerate the arduous administration regimen, i.e., 6-8 h of subcutaneous infusion, and all side effects resolved upon discontinuation of treatment. Importantly, these preliminary studies did not identify a disqualifying event for this experimental approach. More recently developed chelators, deferasirox and deferiprone, are more desirable for possible use in MS given their oral administration, and importantly, deferiprone can cross the blood-brain barrier. However, experiences from other conditions indicate that the potential for adverse events during chelation therapy necessitates close patient monitoring and a carefully considered administration regimen.
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Pirko I, Johnson AJ. Neuroimaging of demyelination and remyelination models. Curr Top Microbiol Immunol 2008; 318:241-66. [PMID: 18219821 DOI: 10.1007/978-3-540-73677-6_10] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Small-animal magnetic resonance imaging is becoming an increasingly utilized noninvasive tool in the study of animal models of MS including the most commonly used autoimmune, viral, and toxic models. Because most MS models are induced in rodents with brains and spinal cords of a smaller magnitude than humans, small-animal MRI must accomplish much higher resolution acquisition in order to generate useful data. In this review, we discuss key aspects and important differences between high field strength experimental and human MRI. We describe the role of conventional imaging sequences including T1, T2, and proton density-weighted imaging, and we discuss the studies aimed at analyzing blood-brain barrier (BBB) permeability and acute inflammation utilizing gadolinium-enhanced MRI. Advanced MRI methods, including diffusion-weighted and magnetization transfer imaging in monitoring demyelination, axonal damage, and remyelination, and studies utilizing in vivo T1 and T2 relaxometry, provide insight into the pathology of demyelinating diseases at previously unprecedented details. The technical challenges of small voxel in vivo MR spectroscopy and the biologically relevant information obtained by analysis of MR spectra in demyelinating models is also discussed. Novel cell-specific and molecular imaging techniques are becoming more readily available in the study of experimental MS models. As a growing number of tissue restorative and remyelinating strategies emerge in the coming years, noninvasive monitoring of remyelination will be an important challenge in small-animal imaging. High field strength small-animal experimental MRI will continue to evolve and interact with the development of new human MR imaging and experimental NMR techniques.
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Affiliation(s)
- I Pirko
- Department of Neurology, Waddell Center for Multiple Sclerosis, University of Cincinnati, 260 Stetson St, Suite 2300, Cincinnati, OH 45267-0525, USA.
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Abstract
Optic neuropathy related to toxins is a complex, multifactorial disease potentially affecting individuals of all ages. We report a case of presumed toxic optic neuropathy secondary to H2O2 exposure. This has not been previously reported, and the temporal relationship of the exposure to the optic neuropathy is compelling, although not definite, evidence of a causal relationship.
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Affiliation(s)
- Füsun M Domaç
- Haydarpapa Numune Teaching Hospital, Neurology Department, Istanbul, Turkey
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Abstract
This review summarises the role that reactive oxygen and nitrogen species play in demyelination, such as that occurring in the inflammatory demyelinating disorders multiple sclerosis and Guillain-Barré syndrome. The concentrations of reactive oxygen and nitrogen species (e.g. superoxide, nitric oxide and peroxynitrite) can increase dramatically under conditions such as inflammation, and this can overwhelm the inherent antioxidant defences within lesions. Such oxidative and/or nitrative stress can damage the lipids, proteins and nucleic acids of cells and mitochondria, potentially causing cell death. Oligodendrocytes are more sensitive to oxidative and nitrative stress in vitro than are astrocytes and microglia, seemingly due to a diminished capacity for antioxidant defence, and the presence of raised risk factors, including a high iron content. Oxidative and nitrative stress might therefore result in vivo in selective oligodendrocyte death, and thereby demyelination. The reactive species may also damage the myelin sheath, promoting its attack by macrophages. Damage can occur directly by lipid peroxidation, and indirectly by the activation of proteases and phospholipase A2. Evidence for the existence of oxidative and nitrative stress within inflammatory demyelinating lesions includes the presence of both lipid and protein peroxides, and nitrotyrosine (a marker for peroxynitrite formation). The neurological deficit resulting from experimental autoimmune demyelinating disease has generally been reduced by trial therapies intended to diminish the concentration of reactive oxygen species. However, therapies aimed at diminishing reactive nitrogen species have had a more variable outcome, sometimes exacerbating disease.
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Affiliation(s)
- K J Smith
- Department of Clinical Neurological Sciences, Guy's, King's and St. Thomas' School of Medicine, London.
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Scott GS, Hooper DC. The role of uric acid in protection against peroxynitrite-mediated pathology. Med Hypotheses 2001; 56:95-100. [PMID: 11133262 DOI: 10.1054/mehy.2000.1118] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Peroxynitrite, the product of the free radicals nitric oxide and superoxide, has been implicated in the pathogenesis of inflammatory CNS disorders. Uric acid, an effective scavenger of peroxynitrite, is a purine metabolite present at high levels in the serum of hominoids relative to lower-order animals due to the functional deletion of urate oxidase. Raising the normally low levels of uric acid in mice is therapeutic for experimental allergic encephalomyelitis, an animal model of multiple sclerosis. This therapeutic activity of uric acid is associated with the inhibition of peroxynitrite-induced tissue damage, blood-CNS barrier permeability changes, and CNS inflammation. Based on these findings we have concluded that peroxynitrite has an important role in promoting enhanced vascular permeability and inflammatory cell extravasation. We hypothesize that higher uric acid levels in hominoids evolved to protect against this process.
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Affiliation(s)
- G S Scott
- Department of Microbiology and Immunology and Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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Abstract
Experimental models of human diseases have affected the design and direction of both basic and clinical research into understanding the pathogenesis and treatments of demyelinating disease, stroke, and hereditary disorders of the central nervous system. However, in spite of major advances in molecular research that have linked Leber Hereditary Optic Neuropathy to mutations in mitochondrial DNA, there has been relatively little focus in applying basic scientific methodologies to optic neuropathies other than glaucoma. The relative absence of detailed scientific knowledge about the basic mechanisms involved in the pathogenesis of optic nerve injury has contributed to the use of empiric therapies for neuro-ophthalmic optic neuropathies. Over the past decade major clinical trials, such as the Optic Neuritis Treatment Trial and Ischemic Optic Neuropathy Decompression Trial, have proven that currently available treatment options for demyelinating and ischemic optic neuropathies are ineffective and can even be harmful. Although the pathogenesis of visual failure in demyelinating, ischemic, and hereditary optic neuropathies appears diverse, a final common pathway for irreparable optic nerve injury may exist. This article reviews several models of experimental optic neuropathies that may aid in the development of novel treatments for neuro-ophthalmic disorders of the optic nerve during the 21st century.
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Affiliation(s)
- J Guy
- University of Florida College of Medicine, Box 100284 Gainesville 32610-0284, Florida, USA.
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Kean RB, Spitsin SV, Mikheeva T, Scott GS, Hooper DC. The peroxynitrite scavenger uric acid prevents inflammatory cell invasion into the central nervous system in experimental allergic encephalomyelitis through maintenance of blood-central nervous system barrier integrity. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:6511-8. [PMID: 11086092 DOI: 10.4049/jimmunol.165.11.6511] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Uric acid (UA), a product of purine metabolism, is a known scavenger of peroxynitrite (ONOO(-)), which has been implicated in the pathogenesis of multiple sclerosis and experimental allergic encephalomyelitis (EAE). To determine whether the known therapeutic action of UA in EAE is mediated through its capacity to inactivate ONOO(-) or some other immunoregulatory phenomenon, the effects of UA on Ag presentation, T cell reactivity, Ab production, and evidence of CNS inflammation were assessed. The inclusion of physiological levels of UA in culture effectively inhibited ONOO(-)-mediated oxidation as well as tyrosine nitration, which has been associated with damage in EAE and multiple sclerosis, but had no inhibitory effect on the T cell-proliferative response to myelin basic protein (MBP) or on APC function. In addition, UA treatment was found to have no notable effect on the development of the immune response to MBP in vivo, as measured by the production of MBP-specific Ab and the induction of MBP-specific T cells. The appearance of cells expressing mRNA for inducible NO synthase in the circulation of MBP-immunized mice was also unaffected by UA treatment. However, in UA-treated animals, the blood-CNS barrier breakdown normally associated with EAE did not occur, and inducible NO synthase-positive cells most often failed to reach CNS tissue. These findings are consistent with the notion that UA is therapeutic in EAE by inactivating ONOO(-), or a related molecule, which is produced by activated monocytes and contributes to both enhanced blood-CNS barrier permeability as well as CNS tissue pathology.
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MESH Headings
- Animals
- Blood-Brain Barrier/drug effects
- Blood-Brain Barrier/immunology
- Capillary Permeability/drug effects
- Capillary Permeability/immunology
- Cell Movement/drug effects
- Cell Movement/immunology
- Central Nervous System/immunology
- Central Nervous System/pathology
- Encephalomyelitis, Autoimmune, Experimental/immunology
- Encephalomyelitis, Autoimmune, Experimental/metabolism
- Encephalomyelitis, Autoimmune, Experimental/pathology
- Encephalomyelitis, Autoimmune, Experimental/physiopathology
- Female
- Free Radical Scavengers/administration & dosage
- Free Radical Scavengers/metabolism
- Free Radical Scavengers/pharmacology
- Injections, Intraperitoneal
- Injections, Subcutaneous
- Macrophages, Peritoneal/drug effects
- Macrophages, Peritoneal/immunology
- Macrophages, Peritoneal/metabolism
- Mice
- Mice, Inbred Strains
- Myelin Basic Protein/administration & dosage
- Myelin Basic Protein/immunology
- Nitrates/antagonists & inhibitors
- Nitrates/metabolism
- Oxidation-Reduction
- Uric Acid/administration & dosage
- Uric Acid/metabolism
- Uric Acid/pharmacology
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Affiliation(s)
- R B Kean
- Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA 19107, USA
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Hooper DC, Scott GS, Zborek A, Mikheeva T, Kean RB, Koprowski H, Spitsin SV. Uric acid, a peroxynitrite scavenger, inhibits CNS inflammation, blood-CNS barrier permeability changes, and tissue damage in a mouse model of multiple sclerosis. FASEB J 2000; 14:691-8. [PMID: 10744626 DOI: 10.1096/fasebj.14.5.691] [Citation(s) in RCA: 278] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Peroxynitrite (ONOO(-)), a toxic product of the free radicals nitric oxide and superoxide, has been implicated in the pathogenesis of CNS inflammatory diseases, including multiple sclerosis and its animal correlate experimental autoimmune encephalomyelitis (EAE). In this study we have assessed the mode of action of uric acid (UA), a purine metabolite and ONOO(-) scavenger, in the treatment of EAE. We show that if administered to mice before the onset of clinical EAE, UA interferes with the invasion of inflammatory cells into the CNS and prevents development of the disease. In mice with active EAE, exogenously administered UA penetrates the already compromised blood-CNS barrier, blocks ONOO(-)-mediated tyrosine nitration and apoptotic cell death in areas of inflammation in spinal cord tissues and promotes recovery of the animals. Moreover, UA treatment suppresses the enhanced blood-CNS barrier permeability characteristic of EAE. We postulate that UA acts at two levels in EAE: 1) by protecting the integrity of the blood-CNS barrier from ONOO(-)-induced permeability changes such that cell invasion and the resulting pathology is minimized; and 2) through a compromised blood-CNS barrier, by scavenging the ONOO(-) directly responsible for CNS tissue damage and death.
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Affiliation(s)
- D C Hooper
- Department of Microbiology and Immunology, Kimmel Cancer Institute, and the Biotechnology Foundation Laboratories, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
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Abstract
Uveitis is a major cause of blindness, with the visual loss that occurs being due primarily to retinal tissue damage. The tissue damage is mediated mainly by phagocytic inflammatory cells, such as macrophages, by the release of various proteolytic enzymes, arachidonic acid metabolites, cytokines and free radicals. The latter are found to be potent cytotoxic agents that readily cause tissue damage by peroxidation of lipid cell membranes. Recent studies of experimental uveitis indicate that other potent oxidants are generated in uveitis by macrophages. One of these is ONOO-, which is formed from *NO and O(-)2. The macrophages generate *NO preferentially in the outer retina following iNOS expression. In these phagocytes, outer retinal proteins, especially arrestin, are found to be potent iNOS inducers. Current studies of RPE show that these cells protect the retina from ONOO- mediated damage in uveitis by releasing a novel protein called retinal pigment epithelial protective protein. This protein is found to suppress O(-)2 and *NO generation by the phagocytes, in both in vitro and in vivo uveitis models. The protective protein expression is restricted to RPE, its suppressive effect is a result of the inhibition of the phosphorylation of cytosolic proteins, p47-phox, required for the assembly of NADPH and activation of NFkappaB, which are required for generation of 0(-)2 and expression of iNOS respectively. Either pharmacologically or chemically, up-regulation of RPP generation could help in preventing retinal degeneration in uveitis or other degenerative dis
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Affiliation(s)
- N A Rao
- Doheny Eye Institute and Department of Ophthalmology and Pathology, University of Southern California, Los Angeles 90033-1088, USA.
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Pedchenko TV, LeVine SM. Desferrioxamine suppresses experimental allergic encephalomyelitis induced by MBP in SJL mice. J Neuroimmunol 1998; 84:188-97. [PMID: 9628462 DOI: 10.1016/s0165-5728(97)00256-7] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Data from several studies indicate that free radicals have a pathogenic role in experimental allergic encephalomyelitis (EAE). Iron can contribute to free radical damage by catalyzing the formation of hydroxyl radical, inducing secondary initiation of lipid peroxidation and by promoting the oxidation of proteins. The iron chelator, desferrioxamine, can limit these oxidative reactions and it can scavenge peroxynitrite independent of iron chelation. Two previous studies have examined the therapeutic value of desferrioxamine in EAE. One study observed an effect when disease was induced by spinal cord homogenates (J. Exp. Med. 160, p. 1532, 1984), but a second study found no therapeutic value of desferrioxamine for myelin basic protein (MBP)-induced EAE (J. Neuroimmunol. 17, p. 127, 1988). In the second study, the drug was only administered during the preclinical stages of disease. Since desferrioxamine scavenges free radicals and prevents their formation, we hypothesized that the drug should be given during the active stage of disease to have therapeutic value. We first demonstrated that the drug enters the CNS around inflammatory cells in EAE animals. In animals treated during the active stage of MBP-induced EAE, the clinical signs were significantly reduced compared to vehicle-treated animals. The iron-bound form of this drug, ferrioxamine, was without therapeutic value. A derivative of desferrioxamine, hydroxylethyl starch (HES)-desferrioxamine, has a greater plasma half-life than desferrioxamine and it was also tested. Although there was a suggestion of improvement in these animals, the effects were less than that observed for desferrioxamine which may be related to the greater molecular size of HES-desferrioxamine. In summary, these data suggest that chelation of iron is an effective therapeutic target for EAE.
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Affiliation(s)
- T V Pedchenko
- Department of Molecular and Integrative Physiology and the Smith Mental Retardation and Human Development Center, University of Kansas Medical Center, Kansas City 66160, USA
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