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1.
Autophagy ; 20(1): 29-44, 2024 01.
Artigo em Inglês | MEDLINE | ID: mdl-37561040

RESUMO

ABBREVIATIONS: AAV: adeno-associated virus; ATF3: activating transcription factor 3; ATG7: autophagy related 7; AVIL: advillin; cADPR: cyclic ADP ribose; CALC: calcitonin/calcitonin-related polypeptide; CMT: Charcot-Marie-Tooth disease; cKO: conditional knockout; DEG: differentially expressed gene; DRG: dorsal root ganglion; FE-SEM: field emission scanning electron microscopy; IF: immunofluorescence; NCV: nerve conduction velocity; PVALB: parvalbumin; RAG: regeneration-associated gene; ROS: reactive oxygen species; SARM1: sterile alpha and HEAT/Armadillo motif containing 1; SYN1: synapsin I.


Assuntos
Calcitonina , Doença de Charcot-Marie-Tooth , Proteínas do Domínio Armadillo/genética , Autofagia , Axônios , Proteínas do Citoesqueleto/genética , Espécies Reativas de Oxigênio , Animais , Camundongos
2.
Brain ; 146(9): 3608-3615, 2023 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-37143322

RESUMO

The duplication of the peripheral myelin protein 22 (PMP22) gene causes a demyelinating type of neuropathy, commonly known as Charcot-Marie-Tooth disease type 1A (CMT1A). Development of effective drugs for CMT1A still remains as an unmet medical need. In the present study, we assessed the role of the transforming growth factor beta 4 (TGFß4)/Nodal axis in the pathogenesis of CMT1A. First, we identified PMP22 overexpression-induced Nodal expression in Schwann cells, which might be one of the downstream effectors in CMT1A. Administration of Nodal protein at the developmental stage of peripheral nerves induced the demyelinating phenotype in vivo. Second, we further isolated TGFß4 as an antagonist that could abolish Nodal-induced demyelination. Finally, we developed a recombinant TGFß4-fragment crystallizable (Fc) fusion protein, CX201, and demonstrated that its application had promyelinating efficacy in Schwann cells. CX201 administration improved the demyelinating phenotypes of CMT1A mouse models at both pre-symptomatic and post-symptomatic stages. These results suggest that the TGFß4/Nodal axis plays a crucial role in the pathogenesis of CMT1A and might be a potential therapeutic target for CMT1A.


Assuntos
Doença de Charcot-Marie-Tooth , Animais , Camundongos , Doença de Charcot-Marie-Tooth/patologia , Proteínas da Mielina/metabolismo , Células de Schwann , Fenótipo , Fator de Crescimento Transformador beta/metabolismo
3.
Biochem Biophys Res Commun ; 597: 1-7, 2022 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-35121177

RESUMO

INTRODUCTION: Demyelinating Charcot-Marie-Tooth disease (CMT) is caused by mutations in the genes that encode myelinating proteins or their transcription factors. Our study thus sought to assess the therapeutic effects of cytokines secreted from mesenchymal stem cells (MSCs) on this disease. METHODS: The therapeutic potential of Wharton's jelly MSCs (WJ-MSCs) and cytokines secreted by WJ-MSCs was evaluated on Schwann cells (SCs) exhibiting demyelination features, as well as a mouse model of demyelinating CMT. RESULTS: Co-culture with WJ-MSC protected PMP22-overexpressing SCs from apoptotic cell death. Using a cytokine array, the secretion of growth differentiation factor-15 (GDF-15) and amphiregulin (AREG) was found to be elevated in WJ-MSCs when co-incubated with the PMP22-overexpressing SCs. Administration of both cytokines into trembler-J (Tr-J) mice, an animal model of CMT, significantly enhanced motor nerve conduction velocity compared to the control group. More importantly, this treatment alleviated the demyelinating phenotype of Tr-J mice, as demonstrated by an improvement in the mean diameter and g-ratio of the myelinated axons. CONCLUSIONS: Our findings demonstrated that WJ-MSCs alleviate the demyelinating phenotype of CMT via the secretion of several cytokines. Further elucidation of the underlying mechanisms of GDF-15 and AREG in myelination might provide a robust basis for the development of effective therapies against demyelinating CMT.

4.
Curr Issues Mol Biol ; 43(3): 2011-2021, 2021 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-34889893

RESUMO

Charcot-Marie-Tooth disease (CMT) is a genetically heterogeneous disease affecting the peripheral nervous system that is caused by either the demyelination of Schwann cells or degeneration of the peripheral axon. Currently, there are no treatment options to improve the degeneration of peripheral nerves in CMT patients. In this research, we assessed the potency of farnesol for improving the demyelinating phenotype using an animal model of CMT type 1A. In vitro treatment with farnesol facilitated myelin gene expression and ameliorated the myelination defect caused by PMP22 overexpression, the major causative gene in CMT. In vivo administration of farnesol enhanced the peripheral neuropathic phenotype, as shown by rotarod performance in a mouse model of CMT1A. Electrophysiologically, farnesol-administered CMT1A mice exhibited increased motor nerve conduction velocity and compound muscle action potential compared with control mice. The number and diameter of myelinated axons were also increased by farnesol treatment. The expression level of myelin protein zero (MPZ) was increased, while that of the demyelination marker, neural cell adhesion molecule (NCAM), was reduced by farnesol administration. These data imply that farnesol is efficacious in ameliorating the demyelinating phenotype of CMT, and further elucidation of the underlying mechanisms of farnesol's effect on myelination might provide a potent therapeutic strategy for the demyelinating type of CMT.


Assuntos
Doenças Desmielinizantes/metabolismo , Farneseno Álcool/farmacologia , Fenótipo , Células de Schwann/efeitos dos fármacos , Células de Schwann/metabolismo , Animais , Biomarcadores , Doença de Charcot-Marie-Tooth/tratamento farmacológico , Doença de Charcot-Marie-Tooth/etiologia , Doença de Charcot-Marie-Tooth/metabolismo , Doença de Charcot-Marie-Tooth/patologia , Doenças Desmielinizantes/tratamento farmacológico , Doenças Desmielinizantes/etiologia , Doenças Desmielinizantes/patologia , Modelos Animais de Doenças , Suscetibilidade a Doenças , Feminino , Expressão Gênica , Masculino , Camundongos , Proteínas da Mielina/genética , Proteínas da Mielina/metabolismo
5.
Cells ; 10(3)2021 03 10.
Artigo em Inglês | MEDLINE | ID: mdl-33802063

RESUMO

Mitochondrial autophagy (or mitophagy) is essential for mitochondrial quality control, which is critical for cellular and organismal health by attenuating reactive oxygen species generation and maintaining bioenergy homeostasis. Previously, we showed that mitophagy is activated in human cells through SIRT1 activation upon treatment of nicotinamide (NAM). Further, mitochondria are maintained as short fragments in the treated cells. In the current study, molecular pathways for NAM-induced mitochondrial fragmentation were sought. NAM treatment induced mitochondrial fission, at least in part by activating dynamin-1-like protein (Drp1), and this was through attenuation of the inhibitory phosphorylation at serine 637 (S637) of Drp1. This Drp1 hypo-phosphorylation was attributed to SIRT1-mediated activation of AMP-activated protein kinase (AMPK), which in turn induced a decrease in cellular levels of cyclic AMP (cAMP) and protein kinase A (PKA) activity, a kinase targeting S637 of Drp1. Furthermore, in NAM-treated cells, cytosolic Ca2+ was highly maintained; and, as a consequence, activity of calcineurin, a Drp1-dephosphorylating phosphatase, is expected to be elevated. These results suggest that NAD+-mediated SIRT1 activation facilitates mitochondrial fission through activation of Drp1 by suppressing its phosphorylation and accelerating its dephosphorylation. Additionally, it is suggested that there is a cycle of mitochondrial fragmentation and cytosolic Ca2+-mediated Drp1 dephosphorylation that may drive sustained mitochondrial fragmentation.


Assuntos
Cálcio/metabolismo , AMP Cíclico/metabolismo , Dinaminas/metabolismo , Dinâmica Mitocondrial/efeitos dos fármacos , Niacinamida/uso terapêutico , Sirtuína 1/metabolismo , Humanos , Niacinamida/farmacologia , Transfecção
6.
FASEB J ; 35(1): e21225, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33337568

RESUMO

Studies of neuroglial interaction largely depend on cell-specific gene knockout (KO) experiments using Cre recombinase. However, genes known as glial-specific genes have recently been reported to be expressed in neuroglial stem cells, leading to the possibility that a glia-specific Cre driver results in unwanted gene deletion in neurons, which may affect sound interpretation. 2',3'-Cyclic nucleotide 3'-phosphodiesterase (CNP) is generally considered to be an oligodendrocyte (OL) marker. Accordingly, Cnp promoter-controlled Cre recombinase has been used to create OL-specific gene targeting mice. However, in this study, using Rosa26-tdTomato-reporter/Cnp-Cre mice, we found that many forebrain neurons and cerebellar Purkinje neurons belong to the lineages of Cnp-expressing neuroglial stem cells. To answer whether gene targeting by Cnp-Cre can induce neuron-autonomous defects, we conditionally deleted an essential autophagy gene, Atg7, in Cnp-Cre mice. The Cnp-Cre-mediated Atg7 KO mice showed extensive p62 inclusion in neurons, including cerebellar Purkinje neurons with extensive neurodegeneration. Furthermore, neuronal areas showing p62 inclusion in Cnp-Cre-mediated Atg7 KO mice overlapped with the neuronal lineage of Cnp-expressing neuroglial stem cells. Moreover, Cnp-Cre-mediated Atg7-KO mice did not develop critical defects in myelination. Our results demonstrate that a large population of central neurons are derived from Cnp-expressing neuroglial stem cells; thus, conditional gene targeting using the Cnp promoter, which is known to be OL-specific, can induce neuron-autonomous phenotypes.


Assuntos
2',3'-Nucleotídeo Cíclico 3'-Fosfodiesterase/deficiência , Doenças Neurodegenerativas/enzimologia , Neuroglia/enzimologia , Células de Purkinje/enzimologia , Células-Tronco/enzimologia , 2',3'-Nucleotídeo Cíclico 3'-Fosfodiesterase/metabolismo , Animais , Proteína 7 Relacionada à Autofagia/genética , Integrases/genética , Integrases/metabolismo , Camundongos , Camundongos Knockout , Doenças Neurodegenerativas/genética , Doenças Neurodegenerativas/patologia , Neuroglia/patologia , Células de Purkinje/patologia , Células-Tronco/patologia
7.
Sci Rep ; 9(1): 16535, 2019 11 11.
Artigo em Inglês | MEDLINE | ID: mdl-31712675

RESUMO

Immune damages on the peripheral myelin sheath under pro-inflammatory milieu result in primary demyelination in inflammatory demyelinating neuropathy. Inflammatory cytokines implicating in the pathogenesis of inflammatory demyelinating neuropathy have been used for the development of potential biomarkers for the diagnosis of the diseases. In this study, we have found that macrophages, which induce demyelination, expressed a B-cell-recruiting factor CXC chemokine ligand 13 (CXCL13) in mouse and human inflammatory demyelinating nerves. The serum levels of CXCL13 were also higher in inflammatory demyelinating neuropathic patients but not in acute motor axonal neuropathy or a hereditary demyelinating neuropathy, Charcot-Marie-Tooth disease type 1a. In addition, CXCL13-expressing macrophages were not observed in the sciatic nerves after axonal injury, which causes the activation of innate immunity and Wallerian demyelination. Our findings indicate that the detection of serum CXCL13 will be useful to specifically recognize inflammatory demyelinating neuropathies in human.


Assuntos
Linfócitos B/imunologia , Linfócitos B/metabolismo , Quimiocina CXCL13/sangue , Doenças Desmielinizantes/sangue , Doenças Desmielinizantes/imunologia , Doenças do Sistema Nervoso Periférico/sangue , Doenças do Sistema Nervoso Periférico/imunologia , Animais , Biomarcadores , Citocinas/sangue , Citocinas/metabolismo , Doenças Desmielinizantes/patologia , Modelos Animais de Doenças , Suscetibilidade a Doenças , Humanos , Mediadores da Inflamação/sangue , Mediadores da Inflamação/metabolismo , Macrófagos/imunologia , Macrófagos/metabolismo , Camundongos , Camundongos Knockout , Doenças do Sistema Nervoso Periférico/patologia
8.
Dalton Trans ; 47(4): 1140-1150, 2018 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-29271458

RESUMO

Indium sulfide nanoparticle (NP)-embedded microporous carbons co-doped with S- and N-dopants are easily prepared by a direct carbonization of the as-prepared In(iii)-based metal-organic framework (In-MOF), [Et2NH2][In(tdc)2]·DEF, containing ditopic S-containing 2,5-thiophenedicarboxylate (tdc2-) bridging linkers as a potential source of S-dopant. The charge on the anionic framework of [In(tdc)2]- is balanced by Et2NH2+, which is also a potential N-dopant. Simultaneous embedding of In-based NPs, S-, and N-co-doping is achieved in a simple single step carbonization of In-MOF. Three porous carbon materials (PCMs), PCM-700, PCM-800, and PCM-900, are obtained from the carbonization of In-MOF at 700, 800, and 900 °C, respectively. The gas sorption analysis indicates them as good CO2 sorbents. The photocatalytic degradation of methyl orange by PCMs under visible light irradiation is also effectively operable owing to the photocatalytically active semiconducting indium sulfide NP with a small bandgap. The main component of indium sulfide NPs is revealed as In6S7 based on the powder X-ray diffraction pattern. Small amounts of metallic In and In2S3 are also observed. The specific capacitances of PCMs are also estimated from the galvanostatic charge/discharge curves. PCM-900 exhibits the highest gravimetric specific capacitance of 99.0 F g-1 at a current density of 0.05 A g-1.

9.
Glia ; 65(11): 1848-1862, 2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28795433

RESUMO

Schwann cells (SCs), which form the peripheral myelin sheath, have the unique ability to dedifferentiate and to destroy the myelin sheath under various demyelination conditions. During SC dedifferentiation-associated demyelination (SAD) in Wallerian degeneration (WD) after axonal injury, SCs exhibit myelin and junctional instability, down-regulation of myelin gene expression and autophagic myelin breakdown. However, in inflammatory demyelinating neuropathy (IDN), it is still unclear how SCs react and contribute to segmental demyelination before myelin scavengers, macrophages, are activated for phagocytotic myelin digestion. Here, we compared the initial SC demyelination mechanism of IDN to that of WD using microarray and histochemical analyses and found that SCs in IDN exhibited several typical characteristics of SAD, including actin-associated E-cadherin destruction, without obvious axonal degeneration. However, autophagolysosome activation in SAD did not appear to be involved in direct myelin lipid digestion by SCs but was required for the separation of SC body from destabilized myelin sheath in IDN. Thus, lysosome inhibition in SCs suppressed segmental demyelination by preventing the exocytotic myelin clearance of SCs. In addition, we found that myelin rejection, which might also require the separation of SC cytoplasm from destabilized myelin sheath, was delayed in SC-specific Atg7 knockout mice in WD, suggesting that autophagolysosome-dependent exocytotic myelin clearance by SCs in IDN and WD is a shared mechanism. Finally, autophagolysosome activation in SAD was mechanistically dissociated with the junctional destruction in both IDN and WD. Thus, our findings indicate that SAD could be a common myelin clearance mechanism of SCs in various demyelinating conditions.


Assuntos
Desdiferenciação Celular/fisiologia , Neurite Autoimune Experimental/patologia , Neurite Autoimune Experimental/fisiopatologia , Células de Schwann/patologia , Neuropatia Ciática/patologia , Neuropatia Ciática/fisiopatologia , Animais , Proteína 7 Relacionada à Autofagia/genética , Proteína 7 Relacionada à Autofagia/metabolismo , Axotomia/efeitos adversos , Cloroquina/uso terapêutico , Doenças Desmielinizantes/tratamento farmacológico , Doenças Desmielinizantes/etiologia , Modelos Animais de Doenças , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/genética , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteínas da Mielina/genética , Proteínas da Mielina/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Neurite Autoimune Experimental/tratamento farmacológico , Ratos , Ratos Endogâmicos Lew , Receptores de Ativador de Plasminogênio Tipo Uroquinase/genética , Receptores de Ativador de Plasminogênio Tipo Uroquinase/metabolismo , Células de Schwann/metabolismo , Células de Schwann/ultraestrutura , Neuropatia Ciática/tratamento farmacológico
10.
Exp Neurobiol ; 26(3): 141-150, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28680299

RESUMO

The vertebrate neuromuscular junction (NMJ) is considered as a "tripartite synapse" consisting of a motor axon terminal, a muscle endplate, and terminal Schwann cells that envelope the motor axon terminal. The neuregulin 1 (NRG1)-ErbB2 signaling pathway plays an important role in the development of the NMJ. We previously showed that Grb2-associated binder 1 (Gab1), a scaffolding mediator of receptor tyrosine kinase signaling, is required for NRG1-induced peripheral nerve myelination. Here, we determined the role of Gab1 in the development of the NMJ using muscle-specific conditional Gab1 knockout mice. The mutant mice showed delayed postnatal maturation of the NMJ. Furthermore, the selective loss of the gab1 gene in terminal Schwann cells produced delayed synaptic elimination with abnormal morphology of the motor endplate, suggesting that Gab1 in both muscles and terminal Schwann cells is required for proper NMJ development. Gab1 in terminal Schwann cells appeared to regulate the number and process elongation of terminal Schwann cells during synaptic elimination. However, Gab2 knockout mice did not show any defects in the development of the NMJ. Considering the role of Gab1 in postnatal peripheral nerve myelination, our findings suggest that Gab1 is a pleiotropic and important component of NRG1 signals during postnatal development of the peripheral neuromuscular system.

11.
Glia ; 65(11): 1794-1808, 2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28722233

RESUMO

The sequential reactive changes in Schwann cell phenotypes in transected peripheral nerves, including dedifferentiation, proliferation and migration, are essential for nerve repair. Even though the injury-induced migratory and proliferative behaviors of Schwann cells resemble epithelial and mesenchymal transition (EMT) in tumors, the molecular mechanisms underlying this phenotypic change of Schwann cells are still unclear. Here we show that the reactive Schwann cells exhibit migratory features dependent on the expression of a scaffolding oncoprotein Grb2-associated binder-2 (Gab2), which was transcriptionally induced by neuregulin 1-ErbB2 signaling following nerve injury. Injury-induced Gab2 expression was dependent on c-Jun, a transcription factor critical to a Schwann cell reprograming into a repair-type cell. Interestingly, the injury-induced activation (tyrosine phosphorylation) of Gab2 in Schwann cells was regulated by an EMT signal, the hepatocyte growth factor-c-Met signaling, but not by neuregulin 1. Gab2 knockout mice exhibited a deficit in nerve repair after nerve transection due to limited Schwann cell migration. Furthermore, Gab2 was required for the proliferation of Schwann cells following nerve injury and in vitro, and was over-expressed in human Schwann cell-derived tumors. In contrast, the tyrosine phosphorylation of Gab1 after nerve injury was principally regulated by the neuregulin 1-ErbB2 signaling and was indispensable for remyelination after crush injury, but not for the proliferation and migration of Schwann cells. Our findings indicate that Gab1 and Gab2 in Schwann cells are nonredundant and play a crucial role in peripheral nerve repair.


Assuntos
Movimento Celular/fisiologia , Proliferação de Células/fisiologia , Proteína Adaptadora GRB2/metabolismo , Regulação da Expressão Gênica/genética , Fator de Crescimento de Hepatócito/metabolismo , Células de Schwann/fisiologia , Neuropatia Ciática/patologia , Potenciais de Ação/genética , Potenciais de Ação/fisiologia , Proteínas Adaptadoras de Transdução de Sinal , Animais , Animais Geneticamente Modificados , Movimento Celular/genética , Proliferação de Células/genética , Células Cultivadas , Modelos Animais de Doenças , Proteína Adaptadora GRB2/genética , Camundongos , Microscopia Eletrônica de Transmissão , Neuregulina-1/genética , Neuregulina-1/metabolismo , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Receptores de Fator de Crescimento Neural/metabolismo , Células de Schwann/metabolismo , Células de Schwann/patologia , Nervo Isquiático/metabolismo , Nervo Isquiático/patologia , Nervo Isquiático/fisiopatologia , Nervo Isquiático/ultraestrutura , Transdução de Sinais/genética , Transfecção
12.
Mol Cells ; 40(7): 503-514, 2017 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-28736426

RESUMO

Nicotinamide (NAM) plays essential roles in physiology through facilitating NAD+ redox homeostasis. Importantly, at high doses, it protects cells under oxidative stresses, and has shown therapeutic effectiveness in a variety of disease conditions. In our previous studies, NAM lowered reactive oxygen species (ROS) levels and extended cellular life span in primary human cells. In the treated cells, levels of NAD+/NADH and SIRT1 activity increased, while mitochondrial content decreased through autophagy activation. The remaining mitochondria were marked with low superoxide levels and high membrane potentials (Δψm); we posited that the treatment of NAM induced an activation of mitophagy that is selective for depolarized mitochondria, which produce high levels of ROS. However, evidence for the selective mitophagy that is mediated by SIRT1 has never been provided. This study sought to explain the mechanisms by which NAM lowers ROS levels and increases Δψm. Our results showed that NAM and SIRT1 activation exert quite different effects on mitochondrial physiology. Furthermore, the changes in ROS and Δψm were not found to be mediated through autophagy or SIRT activation. Rather, NAM suppressed superoxide generation via a direct reduction of electron transport, and increased Δψm via suppression of mitochondrial permeability transition pore formation. Our results dissected the effects of cellular NAD+ redox modulation, and emphasized the importance of the NAD+/NADH ratio in the mitochondria as well as the cytosol in maintaining mitochondrial quality.


Assuntos
Potencial da Membrana Mitocondrial/efeitos dos fármacos , Mitofagia/efeitos dos fármacos , Niacinamida/farmacologia , Espécies Reativas de Oxigênio/metabolismo , Sirtuína 1/metabolismo , Acetilação/efeitos dos fármacos , Peptidil-Prolil Isomerase F , Ciclofilinas/farmacologia , Citosol/efeitos dos fármacos , Citosol/metabolismo , Transporte de Elétrons/efeitos dos fármacos , Compostos Heterocíclicos de 4 ou mais Anéis/farmacologia , Humanos , Recém-Nascido , Masculino , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Poro de Transição de Permeabilidade Mitocondrial , Proteínas Mitocondriais/metabolismo , Modelos Biológicos , Proteínas Quinases/metabolismo , Ubiquitina-Proteína Ligases/metabolismo
13.
Glia ; 64(5): 730-42, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26712109

RESUMO

As lysosomal hydrolysis has long been suggested to be responsible for myelin clearance after peripheral nerve injury, in this study, we investigated the possible role of autophagolysosome formation in myelin phagocytosis by Schwann cells and its final contribution to nerve regeneration. We found that the canonical formation of autophagolysosomes was induced in demyelinating Schwann cells after injury, and the inhibition of autophagy via Schwann cell-specific knockout of the atg7 gene or pharmacological intervention of lysosomal function caused a significant delay in myelin clearance. However, Schwann cell dedifferentiation, as demonstrated by extracellular signal-regulated kinase activation and c-Jun induction, and redifferentiation were not significantly affected, and thus the entire repair program progressed normally in atg7 knockout mice. Finally, autophagic Schwann cells were also found during segmental demyelination in a mouse model of inflammatory peripheral neuropathy. Together, our findings suggest that autophagy is the self-myelin destruction mechanism of Schwann cells, but mechanistically, it is a process distinct from Schwann cell plasticity for nerve repair.


Assuntos
Proteína 7 Relacionada à Autofagia/metabolismo , Autofagia/fisiologia , Doenças Desmielinizantes/etiologia , Bainha de Mielina/patologia , Degeneração Walleriana/complicações , Degeneração Walleriana/patologia , Animais , Autofagia/genética , Proteína 7 Relacionada à Autofagia/genética , Modelos Animais de Doenças , Inibidores Enzimáticos/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/genética , Técnicas In Vitro , Lisossomos/patologia , Macrolídeos/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos NOD , Camundongos Transgênicos , Bainha de Mielina/ultraestrutura , Técnicas de Cultura de Órgãos , Células de Schwann/ultraestrutura , Ciática/genética , Ciática/patologia , Fatores de Tempo , Degeneração Walleriana/genética
14.
Mol Cells ; 38(10): 918-24, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26442863

RESUMO

During T cell activation, mitochondrial content increases to meet the high energy demand of rapid cell proliferation. With this increase, the level of reactive oxygen species (ROS) also increases and causes the rapid apoptotic death of activated cells, thereby facilitating T cell homeostasis. Nicotinamide (NAM) has previously been shown to enhance mitochondria quality and extend the replicative life span of human fibroblasts. In this study, we examined the effect of NAM on CD8(+) T cell activation. NAM treatment attenuated the increase of mitochondrial content and ROS in T cells activated by CD3/CD28 antibodies. This was accompanied by an accelerated and higher-level clonal expansion resulting from attenuated apoptotic death but not increased division of the activated cells. Attenuation of ROS-triggered pro-apoptotic events and upregulation of Bcl-2 expression appeared to be involved. Although cells activated in the presence of NAM exhibited compromised cytokine gene expression, our results suggest a means to augment the size of T cell expansion during activation without consuming their limited replicative potential.


Assuntos
Linfócitos T CD8-Positivos/efeitos dos fármacos , Ativação Linfocitária/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Niacinamida/farmacologia , Espécies Reativas de Oxigênio/antagonistas & inibidores , Adulto , Apoptose/efeitos dos fármacos , Linfócitos T CD8-Positivos/imunologia , Divisão Celular/efeitos dos fármacos , Citocinas/genética , Relação Dose-Resposta a Droga , Feminino , Expressão Gênica/efeitos dos fármacos , Humanos , Masculino , Pessoa de Meia-Idade , Mitocôndrias/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Espécies Reativas de Oxigênio/metabolismo
15.
PLoS One ; 10(1): e0116624, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25581066

RESUMO

Peripheral nerve myelination involves dynamic changes in Schwann cell morphology and membrane structure. Recent studies have demonstrated that autophagy regulates organelle biogenesis and plasma membrane dynamics. In the present study, we investigated the role of autophagy in the development and differentiation of myelinating Schwann cells during sciatic nerve myelination. Electron microscopy and biochemical assays have shown that Schwann cells remove excess cytoplasmic organelles during myelination through macroautophagy. Inhibition of autophagy via Schwann cell-specific removal of ATG7, an essential molecule for macroautophagy, using a conditional knockout strategy, resulted in abnormally enlarged abaxonal cytoplasm in myelinating Schwann cells that contained a large number of ribosomes and an atypically expanded endoplasmic reticulum. Small fiber hypermyelination and minor anomalous peripheral nerve functions are observed in this mutant. Rapamycin-induced suppression of mTOR activity during the early postnatal period enhanced not only autophagy but also developmental reduction of myelinating Schwann cells cytoplasm in vivo. Together, our findings suggest that autophagy is a regulatory mechanism of Schwann cells structural plasticity during myelination.


Assuntos
Autofagia/fisiologia , Citoplasma/fisiologia , Bainha de Mielina/metabolismo , Nervos Periféricos/fisiologia , Células de Schwann/fisiologia , Animais , Proteína 7 Relacionada à Autofagia , Diferenciação Celular/fisiologia , Membrana Celular/metabolismo , Membrana Celular/fisiologia , Citoplasma/metabolismo , Retículo Endoplasmático/metabolismo , Retículo Endoplasmático/fisiologia , Camundongos , Proteínas Associadas aos Microtúbulos/metabolismo , Nervos Periféricos/metabolismo , Ribossomos/metabolismo , Ribossomos/fisiologia , Células de Schwann/metabolismo
16.
J Neurosci ; 34(22): 7657-62, 2014 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-24872569

RESUMO

Grb2-associated binders (Gabs) are scaffolding proteins implicated in cell signaling via receptor tyrosine kinases including neuregulin-1(NRG1)-ErbB receptor signaling, which is essential for peripheral nerve myelination. Here, we show that the conditional removal of Gab1 from Schwann cells resulted in hypomyelination and abnormal development of Remak bundles. In contrast, hypomyelination was not observed in conventional Gab2 knock-out mice. Tyrosine phosphorylation of Gab1, but not Gab2, in sciatic nerves was upregulated during the myelination period and was found to be suppressed in NRG1-type III(+/-) mice, which display a hypomyelinated phenotype similar to that observed in Gab1 knock-out mice. Gab1 knock-out and NRG1-type III(+/-) mice both exhibited reduced extracellular signal-regulated kinase activity in myelinating nerves. In addition, Krox20, a transcription factor that is critical for myelination, has been identified as a target of the NRG1-Gab1 pathway during the myelination process. Our findings suggest that Gab1 is an essential component of NRG1-type III signaling during peripheral nerve development.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Bainha de Mielina/metabolismo , Neuregulina-1/metabolismo , Nervos Periféricos/metabolismo , Animais , Células Cultivadas , Feminino , Sistema de Sinalização das MAP Quinases/fisiologia , Masculino , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Bainha de Mielina/ultraestrutura , Nervos Periféricos/efeitos dos fármacos , Nervos Periféricos/ultraestrutura , Ratos Sprague-Dawley
17.
Glia ; 61(6): 892-904, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23505039

RESUMO

Schwann cells respond to nerve injury by dedifferentiating into immature states and producing neurotrophic factors, two actions that facilitate successful regeneration of axons. Previous reports have implicated the Raf-ERK cascade and the expression of c-jun in these Schwann cell responses. Here we used cultured primary Schwann cells to demonstrate that active Rac1 GTPase (Rac) functions as a negative regulator of Schwann cell differentiation by upregulating c-jun and downregulating Krox20 through the MKK7-JNK pathway, but not through the Raf-ERK pathway. The activation of MKK7 and induction of c-jun in sciatic nerves after axotomy was blocked by Rac inhibition. Microarray experiments revealed that the expression of regeneration-associated genes, such as glial cell line-derived neurotrophic factor and p75 neurotrophin receptor, after nerve injury was dependent on Rac but not on ERK. Finally, the inhibition of ErbB2 signaling prevented MKK7 activation, c-jun induction, and Rac-dependent gene expression in sciatic nerve explant cultures. Taken together, our results indicate that the neuregulin-Rac-MKK7-JNK/c-jun pathway regulates Schwann cell dedifferentiation following nerve injury.


Assuntos
Desdiferenciação Celular/fisiologia , Proteína 2 de Resposta de Crescimento Precoce/metabolismo , MAP Quinase Quinase 7/metabolismo , Neuregulina-1/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Proteínas Proto-Oncogênicas c-jun/metabolismo , Células de Schwann/metabolismo , Aminoquinolinas/farmacologia , Animais , Desdiferenciação Celular/efeitos dos fármacos , Camundongos , Fosforilação/efeitos dos fármacos , Pirimidinas/farmacologia , Células de Schwann/citologia , Células de Schwann/efeitos dos fármacos , Nervo Isquiático/citologia , Nervo Isquiático/efeitos dos fármacos , Nervo Isquiático/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologia
18.
Neural Regen Res ; 8(36): 3401-9, 2013 Dec 25.
Artigo em Inglês | MEDLINE | ID: mdl-25206662

RESUMO

Even though many studies have identified roles of proteasomes in axonal degeneration, the molecular mechanisms by which axonal injury regulates proteasome activity are still unclear. In the present study, we found evidence indicating that extracellular calcium influx is an upstream regulator of proteasome activity during axonal degeneration in injured peripheral nerves. In degenerating axons, the increase in proteasome activity and the degradation of ubiquitinated proteins were significantly suppressed by extracellular calcium chelation. In addition, electron microscopic findings revealed selective inhibition of neurofilament degradation, but not microtubule depolymerization or mitochondrial swelling, by the inhibition of calpain and proteasomes. Taken together, our findings suggest that calcium increase and subsequent proteasome activation are an essential initiator of neurofilament degradation in Wallerian degeneration.

19.
Glia ; 60(10): 1619-28, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22777957

RESUMO

The elevation of serum levels of serum amyloid A (SAA) has been regarded as an acute reactive response following inflammation and various types of injuries. SAA from the liver and extrahepatic tissues plays an immunomodulatory role in a variety of pathophysiological conditions. Inflammatory cytokines in the peripheral nerves have been implicated in the Wallerian degeneration of peripheral nerves after injury and in certain types of inflammatory neuropathies. In the present study, we found that a sciatic nerve axotomy could induce an increase of SAA1 and SAA3 mRNA expression in sciatic nerves. Immunohistochemical staining showed that Schwann cells are the primary sources of SAA production after nerve injury. In addition, interleukin-6-null mice, but not tumor necrosis factor-α-null mice showed a defect in the production of SAA1 in sciatic nerve following injury. Dexamethasone treatment enhanced the expression and secretion of SAA1 and SAA3 in sciatic nerve explants cultures, suggesting that interleukin-6 and corticosteroids might be major regulators for SAA production in Schwann cells following injury. Moreover, the stimulation of Schwann cells with SAA1 elicited the production of the macrophage chemoattractants, Ccl2 and Ccl3, in part through a G-protein coupled receptor. Our findings suggest that locally produced SAA might play an important role in Wallerian degeneration after peripheral nerve injury.


Assuntos
Fatores Quimiotáticos/metabolismo , Células de Schwann/metabolismo , Nervo Isquiático/patologia , Proteína Amiloide A Sérica/metabolismo , Degeneração Walleriana/patologia , Animais , Anti-Inflamatórios/farmacologia , Axotomia , Quimiocina CCL2/metabolismo , Quimiocina CCL3/metabolismo , Dexametasona/farmacologia , Modelos Animais de Doenças , Ensaio de Imunoadsorção Enzimática/métodos , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/genética , Interleucina-6/deficiência , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Técnicas de Cultura de Órgãos , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de Formil Peptídeo/genética , Receptores de Formil Peptídeo/metabolismo , Células de Schwann/efeitos dos fármacos , Células de Schwann/patologia , Nervo Isquiático/metabolismo , Neuropatia Ciática/complicações , Neuropatia Ciática/etiologia , Neuropatia Ciática/patologia , Proteína Amiloide A Sérica/genética , Fator de Necrose Tumoral alfa/deficiência , Degeneração Walleriana/tratamento farmacológico , Degeneração Walleriana/etiologia
20.
Asian Pac J Cancer Prev ; 13(3): 1003-10, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22631628

RESUMO

BACKGROUND: This study examined the influence of body mass index (BMI), subjective body perception (SBP), and the differences between BMI and SBP influence on smoking among women. METHODS: This study used the Korea National Health and Nutrition Examination Survey IV-2, 3 2008-2009. A urinary cotinine test was administered to 5485 women at least 19 years of age. Individuals whose cotinine level was at least 50 ng/mL were categorized as smokers. A multiple logistic regression analysis was performed to estimate the extent to which body-related variables affect female smoking. RESULTS: Women with a lower BMI who perceived themselves to be normal or very fat were 2.09 times (1.14-3.83) more likely to smoke than women with a normal BMI and SBP. Women who were never married with a low BMI and thin SBP were 3.11 times (1.47-6.55) more likely to smoke than women with a normal BMI and SBP. Married women with a high BMI who considered themselves very fat were 0.63 times (0.43-0.94) less likely to smoke than women with a normal BMI and SBP. In contrast, divorced and widowed women with a low or normal BMI who considered themselves very fat were 26.1 times (1.35-507.3) more likely to smoke. CONCLUSIONS: Discrepancies between the objective physical condition (BMI) and the subjective body image (SBP) influence the female smoking rate. To reduce the number of female smokers, public education on the association between smoking behavior and weight issues is needed, especially among women with low BMI and distorted weight perception.


Assuntos
Imagem Corporal , Índice de Massa Corporal , Cotinina/urina , Fumar/epidemiologia , Adulto , Idoso , Peso Corporal , Feminino , Humanos , Pessoa de Meia-Idade , Inquéritos Nutricionais , Obesidade , República da Coreia/epidemiologia , Adulto Jovem
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