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Steven Petratos,
Ezgi Ozturk, Michael F Azari,
Rachel Kenny,
Jae Young Lee,
Kylie A Magee,
Alan R Harvey,
Courtney McDonald,
Kasra Taghian,
Leon Moussa,
Pei Mun Aui,
Christopher Siatskas,
Sara Litwak,
Michael G Fehlings,
Stephen M Strittmatter,
Claude C A Bernard
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ABSTRACT: Multiple sclerosis involves demyelination and axonal degeneration of the central nervous system. The molecular mechanisms of axonal degeneration are relatively unexplored in both multiple sclerosis and its mouse model, experimental autoimmune encephalomyelitis. We previously reported that targeting the axonal growth inhibitor, Nogo-A, may protect against neurodegeneration in experimental autoimmune encephalomyelitis; however, the mechanism by which this occurs is unclear. We now show that the collapsin response mediator protein 2 (CRMP-2), an important tubulin-associated protein that regulates axonal growth, is phosphorylated and hence inhibited during the progression of experimental autoimmune encephalomyelitis in degenerating axons. The phosphorylated form of CRMP-2 (pThr555CRMP-2) is localized to spinal cord neurons and axons in chronic-active multiple sclerosis lesions. Specifically, pThr555CRMP-2 is implicated to be Nogo-66 receptor 1 (NgR1)-dependent, since myelin oligodendrocyte glycoprotein (MOG)(35-55)-induced NgR1 knock-out (ngr1(-)(/)(-)) mice display a reduced experimental autoimmune encephalomyelitis disease progression, without a deregulation of ngr1(-)(/)(-) MOG(35-55)-reactive lymphocytes and monocytes. The limitation of axonal degeneration/loss in experimental autoimmune encephalomyelitis-induced ngr1(-)(/)(-) mice is associated with lower levels of pThr555CRMP-2 in the spinal cord and optic nerve during experimental autoimmune encephalomyelitis. Furthermore, transduction of retinal ganglion cells with an adeno-associated viral vector encoding a site-specific mutant T555ACRMP-2 construct, limits optic nerve axonal degeneration occurring at peak stage of experimental autoimmune encephalomyelitis. Therapeutic administration of the anti-Nogo(623-640) antibody during the course of experimental autoimmune encephalomyelitis, associated with an improved clinical outcome, is demonstrated to abrogate the protein levels of pThr555CRMP-2 in the spinal cord and improve pathological outcome. We conclude that phosphorylation of CRMP-2 may be downstream of NgR1 activation and play a role in axonal degeneration in experimental autoimmune encephalomyelitis and multiple sclerosis. Blockade of Nogo-A/NgR1 interaction may serve as a viable therapeutic target in multiple sclerosis.
Brain 04/2012; 135(Pt 6):1794-818. · 9.46 Impact Factor
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ABSTRACT: Brain and spinal cord injuries present significant therapeutic challenges. The treatments available for these conditions are largely ineffective, partly due to limitations in directly targeting the therapeutic agents to sites of pathology within the central nervous system (CNS). The use of stem cells to treat these conditions presents a novel therapeutic strategy. A variety of stem cell treatments have been examined in animal models of CNS trauma. Many of these studies have used stem cells as a cell-replacement strategy. These investigations have also highlighted the significant limitations of this approach. Another potential strategy for stem cell therapy utilises stem cells as a delivery mechanism for therapeutic molecules. This review surveys the literature relevant to the potential of mesenchymal stem cells for delivery of therapeutic agents in CNS trauma in humans.
DNA research: an international journal for rapid publication of reports on genes and genomes 12/2010; 8(4):316-23. · 1.73 Impact Factor
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ABSTRACT: Multiple sclerosis (MS) is a devastating neurological condition that mainly affects young adults and is associated with long-standing morbidity. The pathophysiology of MS is believed to involve immune-mediated multifocal lesions in the CNS that are characterized by inflammation, demyelination, and axonal injury. Most research efforts to date have concentrated on the mechanisms of immune-mediated demyelination, whereas mechanisms of axonal injury, the major determinant of neurological deficits in MS patients, have been elusive beyond observational analyses. This review discusses current understanding of the pathology and novel clinical investigations of axonal injury in MS and the commonly used MS animal model, experimental autoimmune encephalomyelitis. The review focuses on the etiology and the induction of axonal degeneration through molecular signaling cascades downstream of myelin-associated inhibitory factors. Defining and eventually elucidating the signaling pathways elicited during the onset and progression of MS may provide novel therapeutic strategies to limit axonal degeneration in the acute phase of the disease. Furthermore, blocking or potentiating specific signaling pathways, particularly those that mediate axon retraction and promote disassembly of the tubulin network, may promote regrowth of damaged axons in CNS regions affected by many acute and chronic disease processes.
Journal of Neuropathology and Experimental Neurology 04/2010; 69(4):323-34. · 4.26 Impact Factor
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David H Small,
Danuta Maksel,
Megan L Kerr,
Judy Ng,
Xu Hou,
Cindy Chu,
Hossein Mehrani,
Sharon Unabia, Michael F Azari,
Richard Loiacono,
Marie-Isabel Aguilar,
Mary Chebib
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ABSTRACT: Accumulation of the amyloid protein (Abeta) in the brain is an important step in the pathogenesis of Alzheimer's disease. However, the mechanism by which Abeta exerts its neurotoxic effect is largely unknown. It has been suggested that the peptide can bind to the alpha7 nicotinic acetylcholine receptor (alpha7nAChR). In this study, we examined the binding of Abeta1-42 to endogenous and recombinantly expressed alpha7nAChRs. Abeta1-42 did neither inhibit the specific binding of alpha7nAChR ligands to rat brain homogenate or slice preparations, nor did it influence the activity of alpha7nAChRs expressed in Xenopus oocytes. Similarly, Abeta1-42 did not compete for alpha-bungarotoxin-binding sites on SH-SY5Y cells stably expressing alpha7nAChRs. The effect of the Abeta1-42 on tau phosphorylation was also examined. Although Abeta1-42 altered tau phosphorylation in alpha7nAChR-transfected SH-SY5Y cells, the effect of the peptide was unrelated to alpha7nAChR expression or activity. Binding studies using surface plasmon resonance indicated that the majority of the Abeta bound to membrane lipid, rather than to a protein component. Fluorescence anisotropy experiments indicated that Abeta may disrupt membrane lipid structure or fluidity. We conclude that the effects of Abeta are unlikely to be mediated by direct binding to the alpha7nAChR. Instead, we speculate that Abeta may exert its effects by altering the packing of lipids within the plasma membrane, which could, in turn, influence the function of a variety of receptors and channels on the cell surface.
Journal of Neurochemistry 07/2007; 101(6):1527-38. · 4.06 Impact Factor
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David H. Small,
Danuta Maksel,
Megan L. Kerr,
Judy Ng,
Xu Hou,
Cindy Chu,
Hossein Mehrani,
Sharon Unabia, Michael F. Azari,
Richard Loiacono,
Marie-Isabel Aguilar,
Mary Chebib
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ABSTRACT: Accumulation of the amyloid protein (Aβ) in the brain is an important step in the pathogenesis of Alzheimer’s disease. However, the mechanism by which Aβ exerts its neurotoxic effect is largely unknown. It has been suggested that the peptide can bind to the 7 nicotinic acetylcholine receptor (7nAChR). In this study, we examined the binding of Aβ1-42 to endogenous and recombinantly expressed 7nAChRs. Aβ1-42 did neither inhibit the specific binding of 7nAChR ligands to rat brain homogenate or slice preparations, nor did it influence the activity of 7nAChRs expressed in Xenopus oocytes. Similarly, Aβ1-42 did not compete for -bungarotoxin-binding sites on SH-SY5Y cells stably expressing 7nAChRs. The effect of the Aβ1-42 on tau phosphorylation was also examined. Although Aβ1-42 altered tau phosphorylation in 7nAChR-transfected SH-SY5Y cells, the effect of the peptide was unrelated to 7nAChR expression or activity. Binding studies using surface plasmon resonance indicated that the majority of the Aβ bound to membrane lipid, rather than to a protein component. Fluorescence anisotropy experiments indicated that Aβ may disrupt membrane lipid structure or fluidity. We conclude that the effects of Aβ are unlikely to be mediated by direct binding to the 7nAChR. Instead, we speculate that Aβ may exert its effects by altering the packing of lipids within the plasma membrane, which could, in turn, influence the function of a variety of receptors and channels on the cell surface.
Journal of Neurochemistry 05/2007; 101(6):1527 - 1538. · 4.06 Impact Factor
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ABSTRACT: As a consequence of secondary pathophysiological mechanisms elicited after spinal cord injury (SCI), oligodendrocytes die by waves of apoptosis. This ultimately results in demyelination of intact axons leading to a loss of their conducting properties. Preservation of as few as 5% to 10% of myelinated axons in individual tracts can confer locomotor recovery. Thus, strategies aimed at rescuing mature oligodendrocytes ensheathing viable axons are likely to be of therapeutic significance. We report that leukemia inhibitory factor (LIF) can prevent oligodendrocyte apoptosis, notably contralateral to the spinal cord lesion, through the induction of the JAK/STAT and Akt signaling pathways as well as by potentiating the expression of the antiapoptotic molecule, cIAP2. Reduced oligodendrocyte apoptosis after SCI with LIF administration resulted in a substantial decrease in demyelination shown by the preservation of lamellated myelin surrounding viable axons and deposition of the degraded myelin basic protein. The data suggest that LIF signals survival in oligodendrocytes after SCI, prevents the secondary wave of demyelination, and thereby reduces inhibitory myelin deposits.
Journal of Neuropathology and Experimental Neurology 10/2006; 65(9):914-29. · 4.26 Impact Factor
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ABSTRACT: Administration of tumour necrosis factor alpha (TNFalpha) to axotomised mouse neonatal sciatic nerves increased Schwann cell apoptosis in the distal nerve segments, 5-fold greater than axotomy alone. TNFalpha upregulated the low affinity neurotrophin receptor, p75NTR, indicative of phenotype reversion in Schwann cells. Furthermore, re-expression of p75NTR and downregulation of the pro-myelinating transcription factor, Oct 6, in Schwann cells occurred by treatment with TNFalpha, even after the maturation of these cells with brain derived neurotrophic factor (BDNF). TNFalpha treatment of Schwann cells produced only a transient activation of NFkappaB. More importantly, in NFkappaB (p65) mutant mice, axotomy increased Schwann cell apoptosis further than that seen in mice expressing NFkappaB (p65), implicating a survival role for NFkappaB. Collectively, these data suggest that TNFalpha can potentiate Schwann cell death through the modulation of their phenotype. Immature Schwann cells express a high level of p75NTR and as a consequence are susceptible to extracellular death stimuli because of the lack of sustained NFkappaB translocation.
Neurobiology of Disease 12/2005; 20(2):412-27. · 5.40 Impact Factor
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ABSTRACT: The mechanisms determining the fate of Schwann cells during disease and injury of the adult mammalian peripheral nervous system (PNS) are becoming defined by current advances in molecular neurobiology. It is now apparent that the molecular pathways which regulate the production of the mature myelinating Schwann cell during development may also apply to degenerative and regenerative mechanisms following PNS disease. This review outlines neurobiological responses of Schwann cells during development, injury and disease in order to define the molecular pathways which regulate these crucial events. These mechanisms have implications for our attempts to intervene pharmacologically during pathologies of the PNS.
Neurotoxicity Research 02/2005; 7(1-2):151-67. · 3.51 Impact Factor
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Steven Petratos,
Michael F Gonzales, Michael F Azari,
Mark Marriott,
Rebecca A Minichiello,
Kylie A Shipham,
Christos Profyris,
Antonis Nicolaou,
Kristy Boyle,
Surindar S Cheema,
Trevor J Kilpatrick
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ABSTRACT: Precursor cells have the capacity to repopulate the demyelinated brain, but the molecular mechanisms that facilitate their recruitment are largely unknown. The low-affinity neurotrophin receptor, p75(NTR), may be one of these regulators; however, its expression profile by oligodendroglia within the multiple sclerosis (MS) brain remains uncertain. We therefore assessed the expression profile of this receptor within 8 MS and 4 control brains. We found no evidence of expression of p75(NTR) by mature oligodendrocytes. Instead, we demonstrated the presence of p75(NTR) on a subgroup of NG2-positive oligodendroglial progenitors in a periventricular plaque in one MS sample. Notably, p75(NTR)-expressing cells were also detected within the subventricular zone (SVZ) of this brain, adjacent to the periventricular plaque. In animals with experimental demyelination we observed similar patterns of p75(NTR) expression, initially confined to precursor cells within the SVZ, followed at later stages in the disease course by its expression amongst a subset of oligodendroglial progenitors within the corpus callosum. These data suggest that a population of precursor cells within the SVZ can be induced to express p75(NTR) and to subsequently assume an oligodendroglial progenitor phenotype in response to demyelination in the adjacent white matter.
Glia 11/2004; 48(1):64-75. · 4.82 Impact Factor
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ABSTRACT: Spinal cord injury (SCI) is a major cause of disability, and at present, there is no universally accepted treatment. The functional decline following SCI is contributed to both direct mechanical injury and secondary pathophysiological mechanisms that are induced by the initial trauma. These mechanisms initially involve widespread haemorrhage at the site of injury and necrosis of central nervous system (CNS) cellular components. At later stages of injury, the cord is observed to display reactive gliosis. The actions of astrocytes as well as numerous other cells in this response create an environment that is highly nonpermissive to axonal regrowth. Also manifesting important effects is the immune system. The early recruitment of neutrophils and at later stages, macrophages to the site of insult cause exacerbation of injury. However, at more chronic stages, macrophages and recruited T helper cells may potentially be helpful by providing trophic support for neuronal and non-neuronal components of the injured CNS. Within this sea of injurious mechanisms, the oligodendrocytes appear to be highly vulnerable. At chronic stages of SCI, a large number of oligodendrocytes undergo apoptosis at sites that are distant to the vicinity of primary injury. This leads to denudement of axons and deterioration of their conductive abilities, which adds significantly to functional decline. By indulging into the molecular mechanisms that cause oligodendrocyte apoptosis and identifying potential targets for therapeutic intervention, the prevention of this apoptotic wave will be of tremendous value to individuals living with SCI.
Neurobiology of Disease 05/2004; 15(3):415-36. · 5.40 Impact Factor
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ABSTRACT: We investigated the anatomical and behavioural effects of daily intraperitoneal injection of 25 microg/kg of LIF in the SOD1(G93A G1H) mouse model of familial ALS. We found some subtle beneficial behavioural changes in LIF treated mice. These included later onset of clinical disease in females as determined by clinical scoring; better grip strength in males; and delayed development of motor impairment in males as determined by the rotarod test. However, we found no significant rescue of motoneurons or prolongation of survival as a result of this systemic dose of LIF in these mice.
Brain Research 09/2003; 982(1):92-7. · 2.73 Impact Factor
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ABSTRACT: Administration of tumour necrosis factor α (TNFα) to axotomised mouse neonatal sciatic nerves increased Schwann cell apoptosis in the distal nerve segments, 5-fold greater than axotomy alone. TNFα upregulated the low affinity neurotrophin receptor, p75NTR, indicative of phenotype reversion in Schwann cells. Furthermore, re-expression of p75NTR and downregulation of the pro-myelinating transcription factor, Oct 6, in Schwann cells occurred by treatment with TNFα, even after the maturation of these cells with brain derived neurotrophic factor (BDNF). TNFα treatment of Schwann cells produced only a transient activation of NFκB. More importantly, in NFκB (p65) mutant mice, axotomy increased Schwann cell apoptosis further than that seen in mice expressing NFκB (p65), implicating a survival role for NFκB. Collectively, these data suggest that TNFα can potentiate Schwann cell death through the modulation of their phenotype. Immature Schwann cells express a high level of p75NTR and as a consequence are susceptible to extracellular death stimuli because of the lack of sustained NFκB translocation.
Neurobiology of Disease 20(2):412-427. · 5.40 Impact Factor
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ABSTRACT: Leukemia inhibitory factor (LIF) is a survival factor for motoneurons. In this study we investigated whether intense systemic LIF therapy prevents the loss of lumbar motoneurons in the transgenic SOD1 G93A mouse model of familial amyotrophic lateral sclerosis. Treatment involved daily 25 μg/kg intraperitoneal injection for a period of 6 weeks starting at 70 days of age. Using the unbiased optical dissector technique, significant rescue of motoneurons in the LIF-treated group (3809±455) was found compared to the vehicle group (1085±140).
Brain Research.
