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1.
Glia ; 71(4): 1120-1141, 2023 04.
Artículo en Inglés | MEDLINE | ID: mdl-36583573

RESUMEN

The sphingolipids galactosylceramide (GalCer), sulfatide (ST) and sphingomyelin (SM) are essential for myelin stability and function. GalCer and ST are synthesized mostly from C22-C24 ceramides, generated by Ceramide Synthase 2 (CerS2). To clarify the requirement for C22-C24 sphingolipid synthesis in myelin biosynthesis and stability, we generated mice lacking CerS2 specifically in myelinating cells (CerS2ΔO/ΔO ). At 6 weeks of age, normal-appearing myelin had formed in CerS2ΔO/ΔO mice, however there was a reduction in myelin thickness and the percentage of myelinated axons. Pronounced loss of C22-C24 sphingolipids in myelin of CerS2ΔO/ΔO mice was compensated by greatly increased levels of C18 sphingolipids. A distinct microglial population expressing high levels of activation and phagocytic markers such as CD64, CD11c, MHC class II, and CD68 was apparent at 6 weeks of age in CerS2ΔO/ΔO mice, and had increased by 10 weeks. Increased staining for denatured myelin basic protein was also apparent in 6-week-old CerS2ΔO/ΔO mice. By 16 weeks, CerS2ΔO/ΔO mice showed pronounced myelin atrophy, motor deficits, and axon beading, a hallmark of axon stress. 90% of CerS2ΔO/ΔO mice died between 16 and 26 weeks of age. This study highlights the importance of sphingolipid acyl chain length for the structural integrity of myelin, demonstrating how a modest reduction in lipid chain length causes exposure of a denatured myelin protein epitope and expansion of phagocytic microglia, followed by axon pathology, myelin degeneration, and motor deficits. Understanding the molecular trigger for microglial activation should aid the development of therapeutics for demyelinating and neurodegenerative diseases.


Asunto(s)
Microglía , Vaina de Mielina , Ratones , Animales , Microglía/metabolismo , Vaina de Mielina/metabolismo , Ceramidas/metabolismo , Esfingolípidos/metabolismo
2.
Eur J Neurosci ; 56(12): 6099-6114, 2022 12.
Artículo en Inglés | MEDLINE | ID: mdl-36217300

RESUMEN

Oligodendrocyte production and myelination continues lifelong in the central nervous system (CNS), and all stages of this process can be adaptively regulated by neuronal activity. While artificial exogenous stimulation of neuronal circuits greatly enhances oligodendrocyte progenitor cell (OPC) production and increases myelination during development, the extent to which physiological stimuli replicates this is unclear, particularly in the adult CNS when the rate of new myelin addition slows. Here, we used environmental enrichment (EE) to physiologically stimulate neuronal activity for 6 weeks in 9-week-old C57BL/six male and female mice and found no increase in compact myelin in the corpus callosum or somatosensory cortex. Instead, we observed a global increase in callosal axon diameter with thicker myelin sheaths, elongated paranodes and shortened nodes of Ranvier. These findings indicate that EE induced the dynamic structural remodelling of myelinated axons. Additionally, we observed a global increase in the differentiation of OPCs and pre-myelinating oligodendroglia in the corpus callosum and somatosensory cortex. Our findings of structural remodelling of myelinated axons in response to physiological neural stimuli during young adulthood provide important insights in understanding experience-dependent myelin plasticity throughout the lifespan and provide a platform to investigate axon-myelin interactions in a physiologically relevant context.


Asunto(s)
Axones , Vaina de Mielina , Animales , Masculino , Femenino , Ratones , Ratones Endogámicos C57BL , Axones/fisiología , Oligodendroglía/fisiología , Encéfalo , Diferenciación Celular/fisiología
3.
J Craniofac Surg ; 33(7): 2178-2180, 2022 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-36201704

RESUMEN

BACKGROUND: The implications on the choice of donor side when using the free fibula flap for reconstruction of unilateral maxillectomy defects has not been discussed in the literature so far. METHODS: A unilateral maxillectomy reconstruction was replicated using a 3D-printed skull model and fresh cadaveric dissections of left and right osteomyocutaneous fibula flaps for comparison. Detailed photo documentation was conducted to analyze and illustrate the anatomical differences of performing a reconstruction using the ipsilateral or contralateral sides and their relative benefits and risks. RESULTS: A more favorable lie of the septum and skin paddle and flexor hallucis longus muscle is attainable depending on which donor side is used and the planned direction of the pedicle. CONCLUSION: This study demonstrates why it is preferable to use the ipsilateral fibula if anastomosis is to the ipsilateral facial or neck recipient vessels, or the contralateral fibula where the contralateral recipient vessels are preferred.


Asunto(s)
Colgajos Tisulares Libres , Procedimientos de Cirugía Plástica , Peroné/trasplante , Colgajos Tisulares Libres/cirugía , Humanos , Maxilar/cirugía
4.
Glia ; 68(12): 2725-2743, 2020 12.
Artículo en Inglés | MEDLINE | ID: mdl-32658363

RESUMEN

Diabetic neuropathy has an incidence as high as 50% of diabetic patients and is characterized by damage to neurons, Schwann cells and blood vessels within the peripheral nervous system. The low-affinity neurotrophin receptor p75 (p75NTR ), particularly expressed by the Schwann cells in the peripheral nerve, has previously been reported to play a role in developmental myelination and cell survival/death. Increased levels of p75NTR , in the endoneurium and plasma from diabetic patients and rodent models of disease, have been observed, proposing that this receptor might be involved in the pathogenesis of diabetic neuropathy. Therefore, in this study, we addressed this hypothesis by utilizing a mouse model of selective nerve growth factor receptor (Ngfr) deletion in Schwann cells (SC-p75NTR -KO). Electron microscopy of sciatic nerves from mice with high fat diet induced obesity demonstrated how loss of Schwann cell-p75NTR aggravated axonal atrophy and loss of C-fibers. RNA sequencing disclosed several pre-clinical signaling alterations in the diabetic peripheral nerves, dependent on Schwann cell p75NTR signaling, specially related with lysosome, phagosome, and immune pathways. Morphological and biochemical analyses identified abundant lysosomes and autophagosomes in the C-fiber axoplasm of the diabetic SC-p75NTR -KO nerves, which together with increased Cathepsin B protein levels corroborates gene upregulation from the phagolysosomal pathways. Altogether, this study demonstrates that Schwann cell p75NTR deficiency amplifies diabetic neuropathy disease by triggering overactivation of immune-related pathways and increased lysosomal stress.


Asunto(s)
Neuropatías Diabéticas , Células de Schwann , Animales , Axones , Humanos , Ratones , Receptor de Factor de Crecimiento Nervioso , Receptores de Factor de Crecimiento Nervioso/genética , Nervio Ciático
5.
J Neurosci Res ; 98(10): 1987-1998, 2020 10.
Artículo en Inglés | MEDLINE | ID: mdl-32585763

RESUMEN

The p75 neurotrophin receptor (p75NTR ) is required for maintaining peripheral sensory neuron survival and function; however, the underlying cellular mechanism remains unclear. The general view is that expression of p75NTR by the neuron itself is required for maintaining sensory neuron survival and myelination in the peripheral nervous system (PNS). Adopting a neuronal-specific conditional knockout strategy, we demonstrate the partial depletion of p75NTR in neurons exerts little influence upon maintaining sensory neuron survival and peripheral nerve myelination in health and after demyelinating neuropathy. Our data show that the density and total number of dorsal root ganglion (DRG) neurons in 2-month-old mice is not affected following the deletion of p75NTR in large-diameter myelinating neurons, as assessed by stereology. Adopting experimental autoimmune neuritis induced in adult male mice, an animal model of demyelinating peripheral neuropathy, we identify that deleting p75NTR in myelinating neurons exerts no influence upon the disease progression, the total number of DRG neurons, and the extent of myelin damage in the sciatic nerve, indicating that the expression of neuronal p75NTR is not essential for maintaining peripheral neuron survival and myelination after a demyelinating insult in vivo. Together, results of this study suggest that the survival and myelination of peripheral sensory neurons is independent of p75NTR expressed by a subtype of neurons in vivo. Thus, our findings provide new insights into the mechanism underpinning p75NTR -mediated neuronal survival in the PNS.


Asunto(s)
Ganglios Espinales/metabolismo , Receptores de Factor de Crecimiento Nervioso/deficiencia , Receptores de Factor de Crecimiento Nervioso/genética , Células Receptoras Sensoriales/metabolismo , Animales , Supervivencia Celular/fisiología , Femenino , Eliminación de Gen , Masculino , Ratones , Ratones Noqueados , Ratones Transgénicos
6.
J Neurosci ; 38(32): 7088-7099, 2018 08 08.
Artículo en Inglés | MEDLINE | ID: mdl-29976621

RESUMEN

Methods to promote myelin regeneration in response to central myelin loss are essential to prevent the progression of clinical disability in demyelinating diseases. The neurotrophin brain-derived neurotrophic factor (BDNF) is known to promote myelination during development via oligodendrocyte expressed TrkB receptors. Here, we use a structural mimetic of BDNF to promote myelin regeneration in a preclinical mouse model of central demyelination. In female mice, we show that selective targeting of TrkB with the BDNF-mimetic enhances remyelination, increasing oligodendrocyte differentiation, the frequency of myelinated axons, and myelin sheath thickness after a demyelinating insult. Treatment with exogenous BDNF exerted an attenuated effect, increasing myelin sheath thickness only. Further, following conditional deletion of TrkB from premyelinating oligodendrocytes, we show the effects of the BDNF-mimetic on oligodendrocyte differentiation and remyelination are lost, indicating these are dependent on oligodendrocyte expression of TrkB. Overall, these studies demonstrate that targeting oligodendrocyte TrkB promotes in vivo remyelination in the brain.SIGNIFICANCE STATEMENT Novel strategies to promote myelin regeneration are required to prevent progressive neurodegeneration and clinical disability in patients with central demyelinating disease. Here, we test whether selectively targeting the TrkB receptor on the myelin-producing oligodendrocytes, can promote remyelination in the brain. Using a structural mimetic of its native ligand, BDNF, we show that stimulation of TrkB enhances remyelination, increasing oligodendrocyte differentiation, the frequency of myelinated axons and thickness of the myelin sheath following a demyelinating insult. Further, we show that these effects are dependent on the phosphorylation of oligodendrocyte expressed TrkB receptors in vivo Overall, we demonstrate that selective targeting of TrkB has therapeutic potential to promote remyelination in the brain.


Asunto(s)
Factor Neurotrófico Derivado del Encéfalo/uso terapéutico , Encéfalo/efectos de los fármacos , Enfermedades Desmielinizantes/tratamiento farmacológico , Glicoproteínas de Membrana/agonistas , Terapia Molecular Dirigida , Vaina de Mielina/metabolismo , Oligodendroglía/efectos de los fármacos , Remielinización/efectos de los fármacos , Animales , Encéfalo/metabolismo , Encéfalo/patología , Factor Neurotrófico Derivado del Encéfalo/farmacología , División Celular/efectos de los fármacos , Cuerpo Calloso/metabolismo , Cuerpo Calloso/patología , Cuprizona/toxicidad , Enfermedades Desmielinizantes/inducido químicamente , Enfermedades Desmielinizantes/patología , Femenino , Bombas de Infusión Implantables , Infusiones Intraventriculares , Masculino , Glicoproteínas de Membrana/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteína Básica de Mielina/biosíntesis , Células-Madre Neurales/efectos de los fármacos , Péptidos Cíclicos/farmacología , Péptidos Cíclicos/uso terapéutico , Fosforilación , Procesamiento Proteico-Postraduccional/efectos de los fármacos , Proteínas Tirosina Quinasas/metabolismo , Organismos Libres de Patógenos Específicos
7.
Mol Cell Neurosci ; 90: 12-21, 2018 May 18.
Artículo en Inglés | MEDLINE | ID: mdl-29782918

RESUMEN

Brain-Derived Neurotrophic Factor (BDNF) plays important roles in promoting myelination in the developing central nervous system (CNS), however the influence it exerts on oligodendrocyte development in vivo remains unclear. As BDNF knockout mice die in the perinatal period, we undertook a systematic developmental analysis of oligodendroglial lineage cells within multiple CNS regions of BDNF heterozygous (HET) mice. Our data identify that BDNF heterozygosity results in transient reductions in oligodendroglial lineage cell density and progression that are largely restricted to the optic nerve, whereas the corpus callosum, cerebral cortex, basal forebrain and spinal cord white matter tracts are unaffected. In the first two postnatal weeks, BDNF HET mice exhibit reductions in the density of oligodendroglial lineage cells, oligodendrocyte precursor cells (OPCs) and postmitotic oligodendrocytes selectively in the optic nerve, but not in the brain or spinal cord white matter tracts. However, this normalizes later in development. The overall proportion of OPCs and mature oligodendrocytes remains unchanged from P9 to P30 in all CNS regions. This study identifies that BDNF exerts transient effects on oligodendroglial lineage cells selectively in the optic nerve during postnatal development. Taken together, this provides compelling evidence that BDNF haploinsufficiency exerts modest effects upon oligodendroglial cell density and lineage progression in vivo, suggesting its major role is restricted to promoting oligodendrocyte myelination.

8.
Int J Mol Sci ; 19(12)2018 Dec 19.
Artículo en Inglés | MEDLINE | ID: mdl-30572673

RESUMEN

Brain-derived neurotrophic factor (BDNF) plays vitally important roles in neural development and plasticity in both health and disease. Recent studies using mutant mice to selectively manipulate BDNF signalling in desired cell types, in combination with animal models of demyelinating disease, have demonstrated that BDNF not only potentiates normal central nervous system myelination in development but enhances recovery after myelin injury. However, the precise mechanisms by which BDNF enhances myelination in development and repair are unclear. Here, we review some of the recent progress made in understanding the influence BDNF exerts upon the myelinating process during development and after injury, and discuss the cellular and molecular mechanisms underlying its effects. In doing so, we raise new questions for future research.


Asunto(s)
Factor Neurotrófico Derivado del Encéfalo/metabolismo , Sistema Nervioso Central/metabolismo , Vaina de Mielina/metabolismo , Regeneración Nerviosa , Plasticidad Neuronal , Animales , Humanos , Receptor trkB/metabolismo
9.
Glia ; 64(2): 255-69, 2016 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-26449489

RESUMEN

Fyn, a member of the Src family of nonreceptor tyrosine kinases, promotes central nervous system myelination during development; however the mechanisms mediating this effect remain unknown. Here we show that Fyn phosphorylation is modulated by BDNF in vivo. Concordant with this, we find that BDNF stimulates Fyn phosphorylation in myelinating cocultures, an effect dependent on oligodendroglial expression of TrkB. Importantly, PP2, a pharmacological inhibitor of Src family kinases, not only abrogated the promyelinating influence of BDNF in vitro, but also attenuated BDNF-induced phosphorylation of Erk1/2 in oligodendrocytes. Over-expression of Fyn in oligodendrocytes significantly promotes phosphorylation of Erk1/2, and promotes myelination to the extent that exogenous BDNF exerts no additive effect in vitro. In contrast, expression of a kinase-dead mutant of Fyn in oligodendrocytes significantly inhibited BDNF-induced activation of Erk1/2 and abrogated the promyelinating effect of BDNF. Analysis of white matter tracts in vivo revealed that phosphorylated Fyn primarily colocalized with mature oligodendrocytes, and was rarely observed in oligodendrocyte progenitor cells, a profile that closely parallels the detection of phosphorylated Erk1/2 in the developing central nervous system. Taken together, these data identify that Fyn kinase exerts a key role in mediating the promyelinating influence of BDNF. Here we identify a pathway in which BDNF activation of oligodendroglial TrkB receptors stimulates the phosphorylation of Fyn, a necessary step required to potentiate the phosphorylation of Erk1/2, which in turn regulates oligodendrocyte myelination.


Asunto(s)
Factor Neurotrófico Derivado del Encéfalo/metabolismo , Vaina de Mielina/fisiología , Proteínas Proto-Oncogénicas c-fyn/metabolismo , Animales , Encéfalo/crecimiento & desarrollo , Encéfalo/fisiología , Factor Neurotrófico Derivado del Encéfalo/genética , Células Cultivadas , Técnicas de Cocultivo , Ganglios Espinales/fisiología , Sistema de Señalización de MAP Quinasas/fisiología , Ratones Endogámicos C57BL , Ratones Transgénicos , Neuronas/fisiología , Fosforilación , Ratas Sprague-Dawley , Receptor trkB/metabolismo
10.
Mol Cell Neurosci ; 63: 132-40, 2014 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-25461619

RESUMEN

Brain-derived neurotrophic factor (BDNF) plays critical roles in the development and maintenance of the central (CNS) and peripheral nervous systems (PNS). BDNF exerts its biological effects via tropomyosin-related kinase B (TrkB) and the p75 neurotrophin receptor (p75NTR). We have recently identified that BDNF promotes CNS myelination via oligodendroglial TrkB receptors. In order to selectively target TrkB to promote CNS myelination, we have used a putative TrkB agonist, a small multicyclic peptide (tricyclic dimeric peptide 6, TDP6) previously described by us that structurally mimics a region of BDNF that binds TrkB. We confirmed that TDP6 acts as a TrkB agonist as it provoked autophosphorylation of TrkB and its downstream signalling effector extracellular related-kinase 1 and 2 (Erk1/2) in primary oligodendrocytes. Using an in vitro myelination assay, we show that TDP6 significantly promotes myelination by oligodendrocytes in vitro, as evidenced by enhanced myelin protein expression and an increased number of myelinated axonal segments. In contrast, a second, structurally distinct BDNF mimetic (cyclo-dPAKKR) that targets p75NTR had no effect upon oligodendrocyte myelination in vitro, despite the fact that cyclo-dPAKKR is a very effective promoter of peripheral (Schwann cell) myelination. The selectivity of TDP6 was further verified by using TrkB-deficient oligodendrocytes, in which TDP6 failed to promote myelination, indicating that the pro-myelinating effect of TDP6 is oligodendroglial TrkB-dependent. Together, our results demonstrate that TDP6 is a novel BDNF mimetic that promotes oligodendrocyte myelination in vitro via targeting TrkB.


Asunto(s)
Vaina de Mielina/metabolismo , Oligodendroglía/efectos de los fármacos , Peptidomiméticos/farmacología , Receptor trkB/agonistas , Animales , Axones/efectos de los fármacos , Axones/metabolismo , Factor Neurotrófico Derivado del Encéfalo/química , Células Cultivadas , Ratones , Ratones Endogámicos C57BL , Vaina de Mielina/genética , Oligodendroglía/metabolismo , Fosforilación , Ratas , Ratas Sprague-Dawley , Receptor trkB/metabolismo
11.
J Neurosci ; 33(11): 4947-57, 2013 Mar 13.
Artículo en Inglés | MEDLINE | ID: mdl-23486965

RESUMEN

The neurotrophin brain-derived neurotrophic factor (BDNF) has been implicated in regulating CNS myelination. BDNF mutant mice exhibit a hypomyelinating phenotype, and BDNF exerts distinct effects upon oligodendroglial proliferation, differentiation, and myelination in vitro. To investigate the precise influence that BDNF exerts in regulating CNS myelination in vivo, we have generated conditional knock-out mice in which TrkB has been deleted specifically in oligodendrocytes. Deletion of TrkB disrupted normal oligodendrocyte myelination, resulting in a significant reduction in myelin protein expression and myelination of CNS white matter tracts during development. Importantly, conditional knock-out mice exhibited normal numbers of mature oligodendrocytes and normal numbers of myelinated axons; however, myelin thickness was significantly reduced during development. These data indicate that while TrkB expression in oligodendrocytes plays no role in the initial contact with axons, it exerts an important influence in subsequent stages to promote myelin ensheathment. The conditional knock-out mice also exhibited an increased density of oligodendrocyte progenitor cells (OPCs) in CNS white matter tracts. Concordant with these results, in vitro analyses using OPCs subjected to TrkB knockdown also revealed increased OPC proliferation. Our data suggested this effect was dependent upon TrkC and p75 expression. Thus, our data demonstrate that TrkB expression in oligodendroglia exerts a direct effect on oligodendrocytes to promote myelination and an indirect effect upon the OPC population, modifying their proliferative potential.


Asunto(s)
Proliferación Celular , Vaina de Mielina/fisiología , Oligodendroglía/metabolismo , Receptor trkB/metabolismo , Células Madre/fisiología , Factores de Edad , Análisis de Varianza , Animales , Animales Recién Nacidos , Proteínas Relacionadas con la Autofagia , Diferenciación Celular/genética , Células Cultivadas , Sistema Nervioso Central/crecimiento & desarrollo , Sistema Nervioso Central/metabolismo , Técnicas de Cocultivo , Femenino , Ganglios Espinales/citología , Ganglios Espinales/metabolismo , Regulación de la Expresión Génica/genética , Proteínas Fluorescentes Verdes/genética , Humanos , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Microscopía Electrónica de Transmisión , Proteína Básica de Mielina/genética , Proteína Básica de Mielina/metabolismo , Vaina de Mielina/ultraestructura , Oligodendroglía/ultraestructura , ARN Mensajero/metabolismo , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Ratas , Ratas Sprague-Dawley , Receptor de Factor de Crecimiento Nervioso/metabolismo , Receptor alfa de Factor de Crecimiento Derivado de Plaquetas/metabolismo , Receptor trkB/genética , Receptor trkC/metabolismo , Proteína Serina-Treonina Quinasas de Interacción con Receptores/genética , Proteína Serina-Treonina Quinasas de Interacción con Receptores/metabolismo , Células Madre/ultraestructura , Transfección
12.
J Neurochem ; 129(4): 614-27, 2014 May.
Artículo en Inglés | MEDLINE | ID: mdl-24484474

RESUMEN

Suppressor of cytokine signaling-2 (SOCS2) is a regulator of intracellular responses to growth factors and cytokines. Cultured dorsal root ganglia neurons from neonatal mice with increased or decreased SOCS2 expression were examined for altered responsiveness to nerve growth factor (NGF). In the presence of NGF, SOCS2 over-expression increased neurite length and complexity, whereas loss of SOCS2 reduced neurite outgrowth. Neither loss nor gain of SOCS2 expression altered the relative survival of these cells, suggesting that SOCS2 can discriminate between the differentiation and survival responses to NGF. Interaction studies in 293T cells revealed that SOCS2 immunoprecipitates with TrkA and a juxtamembrane motif of TrkA was required for this interaction. SOCS2 also immunoprecipitated with endogenous TrkA in PC12 Tet-On cells. Over-expression of SOCS2 in PC12 Tet-On cells increased total and surface TrkA expression. In contrast, dorsal root ganglion neurons which over-expressed SOCS2 did not exhibit significant changes in total levels but an increase in surface TrkA was noted. SOCS2-induced neurite outgrowth in PC12 Tet-On cells correlated with increased and prolonged activation of pAKT and pErk1/2 and required an intact SOCS2 SH2 domain and SOCS box domain. This study highlights a novel role for SOCS2 in the regulation of TrkA signaling and biology.


Asunto(s)
Receptor trkA/biosíntesis , Proteínas Supresoras de la Señalización de Citocinas/fisiología , Animales , Membrana Celular/metabolismo , Células Cultivadas , Ganglios Espinales/citología , Ratones , Ratones Endogámicos C57BL , Factor de Crecimiento Nervioso/fisiología , Neuritas/ultraestructura , Neurogénesis/fisiología , Neuronas/metabolismo , Células PC12 , Ratas , Receptor trkA/química , Receptor trkA/genética , Transducción de Señal/fisiología , Proteínas Supresoras de la Señalización de Citocinas/química
13.
Metallomics ; 16(1)2024 01 05.
Artículo en Inglés | MEDLINE | ID: mdl-38178638

RESUMEN

Demyelination within the central nervous system (CNS) is a significant feature of debilitating neurological diseases such as multiple sclerosis and administering the copper-selective chelatorcuprizone to mice is widely used to model demyelination in vivo. Conspicuous demyelination within the corpus callosum is generally attributed to cuprizone's ability to restrict copper availability in this vulnerable brain region. However, the small number of studies that have assessed copper in brain tissue from cuprizone-treated mice have produced seemingly conflicting outcomes, leaving the role of CNS copper availability in demyelination unresolved. Herein we describe our assessment of copper concentrations in brain samples from mice treated with cuprizone for 40 d. Importantly, we applied an inductively coupled plasma mass spectrometry methodology that enabled assessment of copper partitioned into soluble and insoluble fractions within distinct brain regions, including the corpus callosum. Our results show that cuprizone-induced demyelination in the corpus callosum was associated with decreased soluble copper in this brain region. Insoluble copper in the corpus callosum was unaffected, as were pools of soluble and insoluble copper in other brain regions. Treatment with the blood-brain barrier permeant copper compound CuII(atsm) increased brain copper levels and this was most pronounced in the soluble fraction of the corpus callosum. This effect was associated with significant mitigation of cuprizone-induced demyelination. These results provide support for the involvement of decreased CNS copper availability in demyelination in the cuprizone model. Relevance to human demyelinating disease is discussed.


Asunto(s)
Cuprizona , Enfermedades Desmielinizantes , Humanos , Animales , Ratones , Cuprizona/efectos adversos , Cuerpo Calloso , Enfermedades Desmielinizantes/inducido químicamente , Enfermedades Desmielinizantes/tratamiento farmacológico , Cobre/farmacología , Oligodendroglía , Ratones Endogámicos C57BL , Modelos Animales de Enfermedad , Vaina de Mielina
14.
Neurotherapeutics ; 21(5): e00432, 2024 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-39164165

RESUMEN

Multiple sclerosis (MS) is a debilitating affliction of the central nervous system (CNS) that involves demyelination of neuronal axons and neurodegeneration resulting in disability that becomes more pronounced in progressive forms of the disease. The involvement of neurodegeneration in MS underscores the need for effective neuroprotective approaches necessitating identification of new therapeutic targets. Herein, we applied an integrated elemental analysis workflow to human MS-affected spinal cord tissue utilising multiple inductively coupled plasma-mass spectrometry methodologies. These analyses revealed shifts in atomic copper as a notable aspect of disease. Complementary gene expression and biochemical analyses demonstrated that changes in copper levels coincided with altered expression of copper handling genes and downstream functionality of cuproenzymes. Copper-related problems observed in the human MS spinal cord were largely reproduced in the experimental autoimmune encephalomyelitis (EAE) mouse model during the acute phase of disease characterised by axonal demyelination, lesion formation, and motor neuron loss. Treatment of EAE mice with the CNS-permeant copper modulating compound CuII(atsm) resulted in recovery of cuproenzyme function, improved myelination and lesion volume, and neuroprotection. These findings support targeting copper perturbations as a therapeutic strategy for MS with CuII(atsm) showing initial promise.


Asunto(s)
Cobre , Encefalomielitis Autoinmune Experimental , Esclerosis Múltiple , Médula Espinal , Cobre/metabolismo , Animales , Encefalomielitis Autoinmune Experimental/metabolismo , Encefalomielitis Autoinmune Experimental/tratamiento farmacológico , Esclerosis Múltiple/metabolismo , Esclerosis Múltiple/tratamiento farmacológico , Ratones , Humanos , Femenino , Médula Espinal/metabolismo , Médula Espinal/efectos de los fármacos , Médula Espinal/patología , Ratones Endogámicos C57BL , Compuestos Organometálicos , Complejos de Coordinación , Tiosemicarbazonas
15.
J Neurochem ; 125(3): 386-98, 2013 May.
Artículo en Inglés | MEDLINE | ID: mdl-23350698

RESUMEN

The expression of the neurotrophins and their receptors is essential for peripheral nervous system development and myelination. We have previously demonstrated that brain-derived neurotrophic factor (BDNF) exerts contrasting influences upon Schwann cell myelination in vitro - promoting myelination via neuronally expressed p75NTR, but inhibiting myelination via neuronally expressed TrkB. We have generated a small peptide called cyclo-dPAKKR that structurally mimics the region of BDNF that binds p75NTR. Here, we have investigated whether utilizing cyclo-dPAKKR to selectively target p75NTR is an approach that could exert a unified promyelinating response. Like BDNF, cyclo-dPAKKR promoted myelination of nerve growth factor-dependent neurons in vitro, an effect dependent on the neuronal expression of p75NTR. Importantly, cyclo-dPAKKR also significantly promoted the myelination of tropomyosin-related kinase receptor B-expressing neurons in vitro, whereas BDNF exerted a significant inhibitory effect. This indicated that while BDNF exerted a contrasting influence upon the myelination of distinct subsets of dorsal root ganglion (DRG) neurons in vitro, cyclo-dPAKKR uniformly promoted their myelination. Local injection of cyclo-dPAKKR adjacent to the developing sciatic nerve in vivo significantly enhanced myelin protein expression and significantly increased the number of myelinated axons. These results demonstrate that cyclo-dPAKKR promotes peripheral myelination in vitro and in vivo, suggesting it is a strategy worthy of further investigation for the treatment of peripheral demyelinating diseases.


Asunto(s)
Factor Neurotrófico Derivado del Encéfalo/química , Factor Neurotrófico Derivado del Encéfalo/farmacología , Vaina de Mielina/metabolismo , Péptidos/farmacología , Nervio Ciático/metabolismo , Animales , Animales Recién Nacidos , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Técnicas de Cocultivo , Relación Dosis-Respuesta a Droga , Ganglios Espinales/citología , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Regulación del Desarrollo de la Expresión Génica/genética , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Vaina de Mielina/efectos de los fármacos , Neurregulinas , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Ratas , Ratas Sprague-Dawley , Receptores de Factor de Crecimiento Nervioso/deficiencia , Células de Schwann , Nervio Ciático/efectos de los fármacos
16.
J Neurochem ; 122(6): 1167-80, 2012 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-22784206

RESUMEN

Multiple extracellular factors have been implicated in orchestrating myelination of the CNS; however, less is known about the intracellular signaling cascades that regulate this process. We have previously shown that brain-derived neurotrophic factor (BDNF) promotes oligodendrocyte myelination. Here, we screened for the activation of candidate signaling pathways in in vitro myelination assays and found that extracellular signal-regulated kinase (Erk) signaling positively correlated with basal levels of oligodendrocyte myelination as well as BDNF-induced myelination in vitro. By selectively manipulating Erk1/2 activation in oligodendrocytes in vitro, we found that constitutive activation of Erk1/2 significantly increased myelination, mimicking the promyelinating effect of BDNF, and also caused myelination to occur earlier. Conversely, selective inhibition of Erk1/2 in oligodendrocytes significantly reduced the basal level of myelination and blocked the promyelinating effect of BDNF. Analysis of myelinating spinal cord and corpus callosum white matter tracts revealed that the majority of mature oligodendrocytes are co-labeled with phospho-Erk1/2, whereas phospho-Erk1/2 was rarely observed in oligodendrocyte progenitor cells. Finally, the total level of phospho-Erk1/2 correlated with myelin formation during the early postnatal period. Collectively, these data identify that Erk1/2 signaling within oligodendrocytes exerts an important and direct effect to promote myelination.


Asunto(s)
Sistema de Señalización de MAP Quinasas/fisiología , Vaina de Mielina/fisiología , Oligodendroglía/citología , Oligodendroglía/enzimología , Animales , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Factor Neurotrófico Derivado del Encéfalo/fisiología , Comunicación Celular/fisiología , Células Cultivadas , Técnicas de Cocultivo , Femenino , Ratones , Ratones Endogámicos C57BL , Proteína Quinasa 3 Activada por Mitógenos/fisiología , Oligodendroglía/fisiología , Ratas , Ratas Sprague-Dawley
17.
Hippocampus ; 21(4): 434-45, 2011 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-20087884

RESUMEN

Several studies have suggested a close interaction between serotonin (5-HT) and BDNF; however, little is known of the specific relationship between BDNF and the 5-HT(2C) receptor. Therefore, in this study we investigated BDNF expression in 5-HT(2C) receptor knockout mice (5-HT(2C) KO). We also assessed functional consequences of any changes in BDNF using a behavioral test battery. Western blot analysis demonstrated a significant 2.2-fold increase in the expression of the mature form of BDNF in 5-HT(2C) KO mice when compared with wild-type controls (WT) in the hippocampus (P = 0.008), but not frontal cortex or striatum. No differences in the expression of the pro-BDNF isoform were found, and the ratio of mature/pro BDNF was significantly increased in 5-HT(2C) KO (P = 0.003). BDNF mRNA expression in the hippocampus was not different between the genotypes. Hence, increased mature BDNF levels in 5-HT(2C) KO hippocampus are most likely due to increased extracellular cleavage rates of pro-BDNF to its mature form. Protein expression of the BDNF receptor, tropomycin-related receptor B (TrkB), was also unchanged in the hippocampus, frontal cortex and striatum. With repeated training in a 10-day win-shift radial arm maze task, 5-HT(2C) KO and WT showed similar decreases of the number of working memory and reference memory errors. In addition, no genotype specific differences were observed for passive or active avoidance learning. 5-HT(2C) KO showed modest locomotor hyperactivity but no differences in tests for anxiety, sensorimotor gating, or depressive-like behaviors; however, in the tail suspension test 5-HT(2C) KO showed significantly reduced climbing (P < 0.05). In conclusion, loss of 5-HT(2C) receptor expression leads to a marked and selective increase in levels of the mature form of BDNF in the hippocampus. Despite this marked increase, 5-HT(2C) KO show only subtle behavioral changes.


Asunto(s)
Factor Neurotrófico Derivado del Encéfalo , Hipocampo/metabolismo , Precursores de Proteínas , Receptor de Serotonina 5-HT2C/metabolismo , Animales , Conducta Animal/fisiología , Factor Neurotrófico Derivado del Encéfalo/genética , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Cuerpo Estriado/metabolismo , Depresión/metabolismo , Lóbulo Frontal/metabolismo , Memoria , Ratones , Ratones Noqueados , Precursores de Proteínas/genética , Precursores de Proteínas/metabolismo , Receptor trkB/metabolismo , Serotonina/metabolismo
18.
Exp Neurol ; 339: 113652, 2021 05.
Artículo en Inglés | MEDLINE | ID: mdl-33609501

RESUMEN

Young children have a high risk of sustaining a traumatic brain injury (TBI), which can have debilitating life-long consequences. Importantly, the young brain shows particular vulnerability to injury, likely attributed to ongoing maturation of the myelinating nervous system at the time of insult. Here, we examined the effect of acute treatment with the partial tropomyosin receptor kinase B (TrkB) agonist, LM22A-4, on pathological and neurobehavioral outcomes after pediatric TBI, with the hypothesis that targeting TrkB would minimize tissue damage and support functional recovery. We focused on myelinated tracts-the corpus callosum and external capsules-based on recent evidence that TrkB activation potentiates oligodendrocyte remyelination. Male mice at postnatal day 21 received an experimental TBI or sham surgery. Acutely post-injury, extensive cell death, a robust glial response and disruption of compact myelin were evident in the injured brain. TBI or sham mice then received intranasal saline vehicle or LM22A-4 for 14 days. Behavior testing was performed from 4 weeks post-injury, and brains were collected at 5 weeks for histology. TBI mice showed hyperactivity, reduced anxiety-like behavior, and social memory impairments. LM22A-4 ameliorated the abnormal anxiolytic phenotype but had no effect on social memory deficits. Use of spectral confocal reflectance microscopy detected persistent myelin fragmentation in the external capsule of TBI mice at 5 weeks post-injury, which was accompanied by regionally distinct deficits in oligodendrocyte progenitor cells and post-mitotic oligodendrocytes, as well as chronic reactive gliosis and atrophy of the corpus callosum and injured external capsule. LM22A-4 treatment ameliorated myelin deficits in the perilesional external capsule, as well as tissue volume loss and the extent of reactive gliosis. However, there was no effect of this TrkB agonist on oligodendroglial populations detected at 5 weeks post-injury. Collectively, our results demonstrate that targeting TrkB immediately after TBI during early life confers neuroprotection and preserves myelin integrity, and this was associated with some improved neurobehavioral outcomes as the pediatric injured brain matures.


Asunto(s)
Benzamidas/administración & dosificación , Lesiones Traumáticas del Encéfalo/prevención & control , Glicoproteínas de Membrana/agonistas , Vaina de Mielina/efectos de los fármacos , Neuroprotección/efectos de los fármacos , Remielinización/efectos de los fármacos , Animales , Lesiones Traumáticas del Encéfalo/metabolismo , Lesiones Traumáticas del Encéfalo/patología , Modelos Animales de Enfermedad , Esquema de Medicación , Masculino , Ratones , Ratones Endogámicos C57BL , Vaina de Mielina/metabolismo , Vaina de Mielina/patología , Neuroprotección/fisiología , Proteínas Tirosina Quinasas , Remielinización/fisiología , Resultado del Tratamiento
19.
J Neurosci ; 29(13): 4016-22, 2009 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-19339597

RESUMEN

Although brain-derived neurotrophic factor (BDNF) has been shown to promote peripheral myelination during development and remyelination after injury, the precise mechanisms mediating this effect remain unknown. Here, we determine that BDNF promotes myelination of nerve growth factor-dependent neurons, an effect dependent on neuronal expression of the p75 neurotrophin receptor, whereas BDNF inhibits myelination of BDNF-dependent neurons via the full-length TrkB receptor. Thus, BDNF exerts contrasting effects on Schwann cell myelination, depending on the complement of BDNF receptors that are expressed by different subpopulations of dorsal root ganglion neurons. These results demonstrate that BDNF exerts contrasting modulatory roles in peripheral nervous system myelination, and that its mechanism of action is acutely regulated and specifically targeted to neurons.


Asunto(s)
Factor Neurotrófico Derivado del Encéfalo/fisiología , Ganglios Espinales/citología , Proteínas de la Mielina/metabolismo , Factor de Crecimiento Nervioso/fisiología , Neuronas/fisiología , Animales , Animales Modificados Genéticamente , Animales Recién Nacidos , Factor Neurotrófico Derivado del Encéfalo/farmacología , Carbazoles/farmacología , Células Cultivadas , Técnicas de Cocultivo/métodos , Inhibidores Enzimáticos/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Alcaloides Indólicos/farmacología , Ratones , Proteína Básica de Mielina/metabolismo , Proteína P0 de la Mielina/metabolismo , Glicoproteína Asociada a Mielina/metabolismo , Factor de Crecimiento Nervioso/farmacología , Proteínas del Tejido Nervioso/genética , Neuronas/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Receptores de Factores de Crecimiento/genética , Receptores de Factor de Crecimiento Nervioso/genética , Células de Schwann/efectos de los fármacos , Técnicas de Cultivo de Tejidos , Transfección
20.
Neurosignals ; 18(3): 186-202, 2010.
Artículo en Inglés | MEDLINE | ID: mdl-21242670

RESUMEN

The extracellular factors that are responsible for inducing myelination in the central nervous system (CNS) remain elusive. We investigated whether brain-derived neurotrophic factor (BDNF) is implicated, by first confirming that BDNF heterozygous mice exhibit delayed CNS myelination during early postnatal development. We next established that the influence of BDNF upon myelination was direct, by acting on oligodendrocytes, using co-cultures of dorsal root ganglia neurons and oligodendrocyte precursor cells. Importantly, we found that BDNF retains its capacity to enhance myelination of neurons or by oligodendrocytes derived from p75NTR knockout mice, indicating the expression of p75NTR is not necessary for BDNF-induced myelination. Conversely, we observed that phosphorylation of TrkB correlated with myelination, and that inhibiting TrkB signalling also inhibited the promyelinating effect of BDNF, suggesting that BDNF enhances CNS myelination via activating oligodendroglial TrkB-FL receptors. Together, our data reveal a previously unknown role for BDNF in potentiating the normal development of CNS myelination, via signalling within oligodendrocytes.


Asunto(s)
Factor Neurotrófico Derivado del Encéfalo/genética , Sistema Nervioso Central/crecimiento & desarrollo , Sistema Nervioso Central/metabolismo , Fibras Nerviosas Mielínicas/metabolismo , Oligodendroglía/metabolismo , Animales , Factor Neurotrófico Derivado del Encéfalo/deficiencia , Factor Neurotrófico Derivado del Encéfalo/fisiología , Células Cultivadas , Sistema Nervioso Central/citología , Técnicas de Cocultivo , Ratones , Ratones Noqueados , Vaina de Mielina/genética , Vaina de Mielina/fisiología , Fibras Nerviosas Mielínicas/fisiología , Fibras Nerviosas Mielínicas/ultraestructura , Oligodendroglía/citología , Oligodendroglía/fisiología , Ratas , Ratas Sprague-Dawley
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