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Myelin is a natural and dynamic multilamellar membrane structure that continues to be of significant biological and neurological interest, especially with respect to its biosynthesis and assembly during its normal formation, maintenance, and pathological breakdown. To explore the usefulness of neutron diffraction in the structural analysis of myelin, we investigated the use of in vivo labeling by metabolically incorporating non-toxic levels of deuterium (2H; D) via drinking water into a pregnant dam (D-dam) and her developing embryos. All of the mice were sacrificed when the pups (D-pups) were 55 days old. Myelinated sciatic nerves were dissected, fixed in glutaraldehyde and examined by neutron diffraction. Parallel samples that were unfixed (trigeminal nerves) were frozen for mass spectrometry (MS). The diffraction patterns of the nerves from deuterium-fed mice (D-mice) vs. the controls (H-mice) had major differences in the intensities of the Bragg peaks but no appreciable differences in myelin periodicity. Neutron scattering density profiles showed an appreciable increase in density at the center of the lipid-rich membrane bilayer. This increase was greater in D-pups than in D-dam, and its localization was consistent with deuteration of lipid hydrocarbon, which predominates over transmembrane protein in myelin. MS analysis of the lipids isolated from the trigeminal nerves demonstrated that in the pups the percentage of lipids that had one or more deuterium atoms was uniformly high across lipid species (97.6% â± â2.0%), whereas in the mother the lipids were substantially less deuterated (60.6% â± â26.4%) with levels varying among lipid species and subspecies. The mass distribution pattern of deuterium-containing isotopologues indicated the fraction (in %) of each lipid (sub-)species having one or more deuteriums incorporated: in the D-pups, the pattern was always bell-shaped, and the average number of D atoms ranged from a low of â¼4 in fatty acid to a high of â¼9 in cerebroside. By contrast, in D-dam most lipids had more complex, overlapping distributions that were weighted toward a lower average number of deuteriums, which ranged from a low of â¼3-4 in fatty acid and in one species of sulfatide to a high of 6-7 in cerebroside and sphingomyelin. The consistently high level of deuteration in D-pups can be attributed to their de novo lipogenesis during gestation and rapid, postnatal myelination. The widely varying levels of deuteration in D-dam, by contrast, likely depends on the relative metabolic stability of the particular lipid species during myelin maintenance. Our current findings demonstrate that stably-incorporated D label can be detected and localized using neutron diffraction in a complex tissue such as myelin; and moreover, that MS can be used to screen a broad range of deuterated lipid species to monitor differential rates of lipid turnover. In addition to helping to develop a comprehensive understanding of the de novo synthesis and turnover of specific lipids in normal and abnormal myelin, our results also suggest application to studies on myelin proteins (which constitute only 20-30% by dry mass of the myelin, vs. 70-80% for lipid), as well as more broadly to the molecular constituents of other biological tissues.
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In Charcot-Marie-Tooth type 1A (CMT1A), Schwann cells exhibit a preponderant transcriptional deficiency of genes involved in lipid biosynthesis. This perturbed lipid metabolism affects the peripheral nerve physiology and the structure of peripheral myelin. Nevertheless, the identification and functional characterization of the lipid species mainly responsible for CMT1A myelin impairment currently lack. This is critical in the pathogenesis of the neuropathy since lipids are many and complex molecules which play essential roles in the cell, including the structural components of cellular membranes, cell signaling, and membrane trafficking. Moreover, lipids themselves are able to modify gene transcription, thereby affecting the genotype-phenotype correlation of well-defined inherited diseases, including CMT1A. Here we report for the first time a comprehensive lipid profiling in experimental and human CMT1A, demonstrating a previously unknown specific alteration of sphingolipid (SP) and glycerophospholipid (GP) metabolism. Notably, SP, and GP changes even emerge in biological fluids of CMT1A rat and human patients, implying a systemic metabolic dysfunction for these specific lipid classes. Actually, SP and GP are not merely reduced; their expression is instead aberrant, contributing to the ultrastructural abnormalities that we detailed by X-ray diffraction in rat and human internode myelin. The modulation of SP and GP pathways in myelinating dorsal root ganglia cultures clearly sustains this issue. In fact, just selected molecules interacting with these pathways are able to modify the altered geometric parameters of CMT1A myelinated fibers. Overall, we propose to exploit the present SP and GP metabolism impairment to select effective drugs and validate a set of reliable biomarkers, which remain a challenge in CMT1A neuropathy.
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Brain aging and Alzheimer's disease both demonstrate the accumulation of beta-amyloid protein containing "plaques" and tau protein containing "tangles" that contribute to accelerated memory loss and cognitive decline. In the present investigation we identified a specific plant extract and its constituents as a potential alternative natural solution for preventing and reducing both brain "plaques and tangles". PTI-00703 cat's claw (Uncaria tomentosa from a specific Peruvian source), a specific and natural plant extract from the Amazon rain forest, was identified as a potent inhibitor and reducer of both beta-amyloid fibrils (the main component of "plaques") and tau protein paired helical filaments/fibrils (the main component of "tangles"). PTI-00703 cat's claw demonstrated both the ability to prevent formation/aggregation and disaggregate preformed Aß fibrils (1-42 and 1-40) and tau protein tangles/filaments. The disaggregation/dissolution of Aß fibrils occurred nearly instantly when PTI-00703 cat's claw and Aß fibrils were mixed together as shown by a variety of methods including Thioflavin T fluorometry, Congo red staining, Thioflavin S fluorescence and electron microscopy. Sophisticated structural elucidation studies identified the major fractions and specific constituents within PTI-00703 cat's claw responsible for both the observed "plaque" and "tangle" inhibitory and reducing activity. Specific proanthocyanidins (i.e. epicatechin dimers and variants thereof) are newly identified polyphenolic components within Uncaria tomentosa that possess both "plaque and tangle" reducing and inhibitory activity. One major identified specific polyphenol within PTI-00703 cat's claw was epicatechin-4ß-8-epicatechin (i.e. an epicatechin dimer known as proanthocyanidin B2) that markedly reduced brain plaque load and improved short-term memory in younger and older APP "plaque-producing" (TASD-41) transgenic mice (bearing London and Swedish mutations). Proanthocyanidin B2 was also a potent inhibitor of brain inflammation as shown by reduction in astrocytosis and gliosis in TASD-41 transgenic mice. Blood-brain-barrier studies in Sprague-Dawley rats and CD-1 mice indicated that the major components of PTI-00703 cat's claw crossed the blood-brain-barrier and entered the brain parenchyma within 2 minutes of being in the blood. The discovery of a natural plant extract from the Amazon rain forest plant (i.e. Uncaria tomentosa or cat's claw) as both a potent "plaque and tangle" inhibitor and disaggregator is postulated to represent a potential breakthrough for the natural treatment of both normal brain aging and Alzheimer's disease.
Assuntos
Amiloide/metabolismo , Encéfalo/efeitos dos fármacos , Emaranhados Neurofibrilares/metabolismo , Extratos Vegetais/farmacologia , Placa Amiloide/tratamento farmacológico , Proantocianidinas/farmacologia , Animais , Encéfalo/patologia , Unha-de-Gato/metabolismo , Feminino , Masculino , Camundongos , Camundongos Transgênicos , Ratos , Ratos Sprague-Dawley , Proteínas tau/metabolismoRESUMO
Previous raster-scanning with a 1µm X-ray beam of individual, myelinated fibers from glutaraldehyde-fixed rat sciatic nerve revealed a spatially-dependent variation in the diffraction patterns from single fibers. Analysis indicated differences in the myelin periodicity, membrane separations, distribution of proteins, and orientation of membrane lamellae. As chemical fixation is known to produce structural artifacts, we sought to determine in the current study whether the structural heterogeneity is intrinsic to unfixed myelin. Using a 200nm-beam that was about five-fold smaller than before, we raster-scanned individual myelinated fibers from both the peripheral (PNS; mouse and rat sciatic nerves) and central (CNS; rat corpus callosum) nervous systems. As expected, the membrane stacking in the internodal region was nearly parallel to the fiber axis and in the paranodal region it was perpendicular to the axis. A myelin lattice was also frequently observed when the incident beam was injected en face to the sheath. Myelin periodicity and diffracted intensity varied with axial position along the fiber, as did the calculated membrane profiles. Raster-scanning with an X-ray beam at sub-micron resolution revealed for the first time that the individual myelin sheaths in unfixed nerve are heterogeneous in both membrane structure and packing.
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Bainha de Mielina/química , Fibras Nervosas Mielinizadas/química , Difração de Raios X/métodos , Animais , Corpo Caloso/química , Corpo Caloso/citologia , Dimetil Sulfóxido/química , Camundongos Endogâmicos C57BL , Ratos Endogâmicos F344 , Nervo Isquiático/química , Nervo Isquiático/citologia , Difração de Raios X/instrumentaçãoRESUMO
We have described a novel C-to-T mutation in the APP gene that corresponds to an alanine to valine substitution at position 673 in APP (A673V), or position 2 of the amyloid-ß (Aß) sequence. This mutation is associated with the early onset of AD-type dementia in homozygous individuals, whereas it has a protective effect in the heterozygous state. Correspondingly, we observed differences in the aggregation properties of the wild-type and mutated Aß peptides and their mixture. We have carried out neutron diffraction (ND) and x-ray diffraction (XRD) experiments on magnetically-oriented fibers of Aß1-28WT and its variant Aß1-28A2V. The orientation propensity was higher for Aß1-28A2V suggesting that it promotes the formation of fibrillar assemblies. The diffraction patterns by Aß1-28WT and Aß1-28A2V assemblies differed in shape and position of the equatorial reflections, suggesting that the two peptides adopt distinct lateral packing of the diffracting units. The diffraction patterns from a mixture of the two peptides differed from those of the single components, indicating the presence of structural interference during assembly and orientation. The lowest orientation propensity was observed for a mixture of Aß1-28WT and a short N-terminal fragment, Aß1-6A2V, which supports a role of Aß's N-terminal domain in amyloid fibril formation.
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Substituição de Aminoácidos , Peptídeos beta-Amiloides/química , Precursor de Proteína beta-Amiloide/genética , Humanos , Difração de Nêutrons , Domínios Proteicos , Difração de Raios XRESUMO
Cerebral ischemia/reperfusion (I/R) triggers a cascade of uncontrolled cellular processes that perturb cell homeostasis. The arctic ground squirrel (AGS), a seasonal hibernator resists brain damage following cerebral I/R caused by cardiac arrest and resuscitation. However, it remains unclear if tolerance to I/R injury in AGS depends on the hibernation season. Moreover, it is also not clear if events such as depletion of ATP, acidosis, and glutamate efflux that are associated with anoxic depolarization are attenuated in AGS. Here, we employ a novel microperfusion technique to test the hypothesis that tolerance to I/R injury modeled in an acute hippocampal slice preparation in AGS is independent of the hibernation season and persists even after glutamate efflux. Acute hippocampal slices were harvested from summer euthermic AGS, hibernating AGS, and interbout euthermic AGS. Slices were subjected to oxygen glucose deprivation (OGD), an in vitro model of I/R injury to determine cell death marked by lactate dehydrogenase (LDH) release. ATP was assayed using ENLITEN ATP assay. Glutamate and aspartate efflux was measured using capillary electrophoresis. For acidosis, slices were subjected to pH 6.4 or ischemic shift solution (ISS). Acute hippocampal slices from rats were used as a positive control, susceptible to I/R injury. Our results indicate that when tissue temperature is maintained at 36°C, hibernation season has no influence on OGD-induced cell death in AGS hippocampal slices. Our data also show that tolerance to OGD in AGS hippocampal slices occurs despite loss of ATP and glutamate release, and persists during conditions that mimic acidosis and ionic shifts, characteristic of cerebral I/R. Read the Editorial Comment for this article on page 10.
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Acidose/metabolismo , Trifosfato de Adenosina/metabolismo , Glucose/deficiência , Ácido Glutâmico/metabolismo , Hibernação/fisiologia , Hipocampo/fisiologia , Hipocampo/fisiopatologia , Hipóxia Encefálica/fisiopatologia , Sciuridae/fisiologia , Animais , Ácido Aspártico/metabolismo , Morte Celular , Técnicas In Vitro , L-Lactato Desidrogenase/metabolismo , Ratos , Ratos Sprague-Dawley , Estações do Ano , TemperaturaRESUMO
Ischemic reperfusion (I/R) injury is associated with a complex and multifactorial cascade of events involving excitotoxicity, acidotoxicity, and ionic imbalance. While it is known that acidosis occurs concomitantly with glutamate-mediated excitotoxicity during brain ischemia, it remains elusive how acidosis-mediated acidotoxicity interacts with glutamate-mediated excitotoxicity. Here, we investigated the effect of acidosis on glutamate-mediated excitotoxicity in acute hippocampal slices. We tested the hypothesis that mild acidosis protects against I/R injury via modulation of NMDAR, but produces injury via activation of acid sensing ion channels (ASIC1a). Using a novel microperfusion approach, we monitored time course of injury in acutely prepared, adult hippocampal slices. We varied the duration of insult to delay the return to preinsult conditions to determine if injury was caused by the primary insult or by the modeled reperfusion phase. We also manipulated pH in presence and absence of oxygen glucose deprivation (OGD). The role of ASIC1a and NMDAR was deciphered by treating the slices with and without an ASIC or NMDAR antagonist. Our results show that injury due to OGD or low pH occurs during the insult rather than the modeled reperfusion phase. Injury mediated by low pH or low pH OGD requires ASIC1a and is independent of NMDAR activation. These findings point to ASIC1a as a mediator of ischemic cell death caused by stroke and cardiac arrest.
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Canais Iônicos Sensíveis a Ácido/metabolismo , Acidose/metabolismo , Hipóxia-Isquemia Encefálica/metabolismo , Traumatismo por Reperfusão/metabolismo , Acidose/patologia , Acidose/fisiopatologia , Animais , Morte Celular/fisiologia , Glucose , Hipocampo/metabolismo , Hipocampo/patologia , Hipóxia-Isquemia Encefálica/patologia , Hipóxia-Isquemia Encefálica/fisiopatologia , Masculino , Técnicas de Cultura de Órgãos , Oxigênio , Ratos , Ratos Sprague-Dawley , Traumatismo por Reperfusão/patologia , Traumatismo por Reperfusão/fisiopatologiaRESUMO
Aspartoacylase (AspA) gene mutations cause the pediatric lethal neurodegenerative Canavan disease (CD). There is emerging promise of successful gene therapy for CD using recombinant adeno-associated viruses (rAAVs). Here, we report an intracerebroventricularly delivered AspA gene therapy regime using three serotypes of rAAVs at a 20-fold reduced dose than previously described in AspA(-/-) mice, a bona-fide mouse model of CD. Interestingly, central nervous system (CNS)-restricted therapy prolonged survival over systemic therapy in CD mice but failed to sustain motor functions seen in systemically treated mice. Importantly, we reveal through histological and functional examination of untreated CD mice that AspA deficiency in peripheral tissues causes morphological and functional abnormalities in this heretofore CNS-defined disorder. We demonstrate for the first time that AspA deficiency, possibly through excessive N-acetyl aspartic acid accumulation, elicits both a peripheral and CNS immune response in CD mice. Our data establish a role for peripheral tissues in CD pathology and serve to aid the development of more efficacious and sustained gene therapy for this disease.
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Amidoidrolases/genética , Doença de Canavan/terapia , Sistema Nervoso Central/patologia , Terapia Genética/métodos , Animais , Doença de Canavan/genética , Doença de Canavan/patologia , Sistema Nervoso Central/metabolismo , Dependovirus/genética , Modelos Animais de Doenças , Vetores Genéticos/administração & dosagem , Humanos , Camundongos , Especificidade de Órgãos , Análise de Sobrevida , Resultado do TratamentoRESUMO
Myelin sheaths, as the specialized tissue wrapping the nerve fibers in the central and peripheral nervous systems (CNS and PNS), are responsible for rapid conduction of electrical signals in these fibers. We compare the nerve myelin sheaths of different phylogenetic origins-including mammal, rodent, bird, reptile, amphibian, lungfish, teleost, and elasmobranch-with respect to periodicities and inter-membrane separations at their cytoplasmic and extracellular appositions, and correlate these structural parameters with biochemical composition. P0 glycoprotein and P0-like proteins are present in PNS of terrestrial species or land vertebrates (Tetrapod) and in CNS and PNS of aquatic species. Proteolipid protein (PLP) is a major component only in the CNS myelin of terrestrial species and is involved in compaction of the extracellular apposition. The myelin structures of aquatic garfish and lungfish, which contain P0-like protein both in CNS and PNS, are similar to those of terrestrial species, indicating that they may be transitional organisms between water and land species. This article is part of a Special Issue entitled SI: Myelin Evolution.
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Evolução Biológica , Proteínas da Mielina/metabolismo , Bainha de Mielina/metabolismo , Bainha de Mielina/ultraestrutura , Animais , Humanos , Proteínas da Mielina/genética , Bainha de Mielina/genéticaRESUMO
The radial component is a network of interlamellar tight junctions (TJs) unique to central nervous system myelin. Ablation of claudin-11, a TJ protein, results in the absence of the radial component and compromises the passive electrical properties of myelin. Although TJs are known to regulate paracellular diffusion, this barrier function has not been directly demonstrated for the radial component, and some evidence suggests that the radial component may also mediate adhesion between myelin membranes. To investigate the physical properties of claudin-11 TJs, we compared fresh, unfixed Claudin 11-null and control nerves using x-ray and neutron diffraction. In Claudin 11-null tissue, we detected no changes in myelin structure, stability, or membrane interactions, which argues against the notion that myelin TJs exhibit significant adhesive properties. Moreover, our osmotic stressing and D2O-H2O exchange experiments demonstrate that myelin lacking claudin-11 is more permeable to water and small osmolytes. Thus, our data indicate that the radial component serves primarily as a diffusion barrier and elucidate the mechanism by which TJs govern myelin function.
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Claudinas/metabolismo , Bainha de Mielina/metabolismo , Junções Íntimas/metabolismo , Animais , Fenômenos Biomecânicos , Membrana Celular/metabolismo , Claudinas/genética , Difusão , Camundongos Knockout , Difração de Nêutrons , Nervo Óptico/citologia , Nervo Óptico/metabolismo , Nervo Isquiático/citologia , Nervo Isquiático/metabolismo , Medula Espinal/citologia , Medula Espinal/metabolismo , Água/metabolismo , Difração de Raios XRESUMO
Reactive oxygen species (ROS) are implicated in a range of degenerative conditions, including aging, neurodegenerative diseases, and neurological disorders. Myelin is a lipid-rich multilamellar sheath that facilitates rapid nerve conduction in vertebrates. Given the high energetic demands and low antioxidant capacity of the cells that elaborate the sheaths, myelin is considered intrinsically vulnerable to oxidative damage, raising the question whether additional mechanisms prevent structural damage. We characterized the structural and biochemical basis of ROS-mediated myelin damage in murine tissues from both central nervous system (CNS) and peripheral nervous system (PNS). To determine whether ROS can cause structural damage to the internodal myelin, whole sciatic and optic nerves were incubated ex vivo with a hydroxyl radical-generating system consisting of copper (Cu), hydrogen peroxide (HP), and ortho-phenanthroline (OP). Quantitative assessment of unfixed tissue by X-ray diffraction revealed irreversible compaction of myelin membrane stacking in both sciatic and optic nerves. Incubation in the presence of the hydroxyl radical scavenger sodium formate prevented this damage, implicating hydroxyl radical species. Myelin membranes are particularly enriched in plasmalogens, a class of ether-linked phospholipids proposed to have antioxidant properties. Myelin in sciatic nerve from plasmalogen-deficient (Pex7 knockout) mice was significantly more vulnerable to Cu/OP/HP-mediated ROS-induced compaction than myelin from WT mice. Our results directly support the role of plasmalogens as endogenous antioxidants providing a defense that protects ROS-vulnerable myelin.
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Sequestradores de Radicais Livres/farmacologia , Bainha de Mielina/metabolismo , Plasmalogênios/farmacologia , Animais , Quelantes/farmacologia , Avaliação Pré-Clínica de Medicamentos , Ácido Edético/farmacologia , Formiatos/farmacologia , Camundongos Knockout , Bainha de Mielina/efeitos dos fármacos , Nervo Óptico/metabolismo , Nervo Óptico/patologia , Oxirredução , Estresse Oxidativo , Receptor 2 de Sinal de Orientação para Peroxissomos , Carbonilação Proteica , Espécies Reativas de Oxigênio/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , Nervo Isquiático/metabolismo , Nervo Isquiático/patologiaRESUMO
GM1-gangliosidosis is a glycosphingolipid lysosomal storage disease involving accumulation of GM1 and its asialo form (GA1) primarily in the brain. Thin-layer chromatography and X-ray diffraction were used to analyze the lipid content/composition and the myelin structure of the optic and sciatic nerves from 7- and 10-month old ß-galactosidase (ß-gal) +/? and ß-gal -/- mice, a model of GM1gangliosidosis. Optic nerve weight was lower in the ß-gal -/- mice than in unaffected ß-gal +/? mice, but no difference was seen in sciatic nerve weight. The levels of GM1 and GA1 were significantly increased in both the optic nerve and sciatic nerve of the ß-gal -/- mice. The content of myelin-enriched cerebrosides, sulfatides, and plasmalogen ethanolamines was significantly lower in optic nerve of ß-gal -/- mice than in ß-gal +/? mice; however, cholesteryl esters were enriched in the ß-gal -/- mice. No major abnormalities in these lipids were detected in the sciatic nerve of the ß-gal -/- mice. The abnormalities in GM1 and myelin lipids in optic nerve of ß-gal -/- mice correlated with a reduction in the relative amount of myelin and periodicity in fresh nerve. By contrast, the relative amount of myelin and periodicity in the sciatic nerves from control and ß-gal -/- mice were indistinguishable, suggesting minimal pathological involvement in sciatic nerve. Our results indicate that the greater neurochemical pathology observed in the optic nerve than in the sciatic nerve of ß-gal -/- mice is likely due to the greater glycolipid storage in optic nerve.
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Gangliosidose GM1/genética , Gangliosidose GM1/patologia , Bainha de Mielina/patologia , Nervo Óptico/citologia , Nervo Óptico/patologia , Nervo Isquiático/patologia , beta-Galactosidase/deficiência , Animais , Cromatografia em Camada Fina , Densitometria , Genótipo , Metabolismo dos Lipídeos/genética , Camundongos , Camundongos Transgênicos , Bainha de Mielina/metabolismo , Difração de Raios X , beta-Galactosidase/genéticaRESUMO
Rapid nerve conduction in the central and peripheral nervous systems (CNS and PNS, respectively) of higher vertebrates is brought about by the ensheathment of axons with myelin, a lipid-rich, multilamellar assembly of membranes. The ability of myelin to electrically insulate depends on the regular stacking of these plasma membranes and on the presence of a number of specialized membrane-protein assemblies in the sheath, including the radial component, Schmidt-Lanterman incisures and the axo-glial junctions of the paranodal loops. The disruption of this fine-structure is the basis for many demyelinating neuropathies in the CNS and PNS. Understanding the processes that govern myelin biogenesis, maintenance and destabilization requires knowledge of myelin structure; however, the tight packing of internodal myelin and the complexity of its junctional specializations make myelin a challenging target for comprehensive structural analysis. This paper describes an examination of myelin from the CNS and PNS using neutron diffraction. This investigation revealed the dimensions of the bilayers and aqueous spaces of myelin, asymmetry between the cytoplasmic and extracellular leaflets of the membrane, and the distribution of water and exchangeable hydrogen in internodal multilamellar myelin. It also uncovered differences between CNS and PNS myelin in their water-exchange kinetics.
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Bainha de Mielina/química , Água/química , Animais , Sistema Nervoso Central/química , Medição da Troca de Deutério , Cinética , Camundongos Endogâmicos C57BL , Difração de Nêutrons , Sistema Nervoso Periférico/química , Ratos , Ratos Endogâmicos F344 , Difração de Raios XRESUMO
X-ray diffraction has provided extensive information about the arrangement of lipids and proteins in multilamellar myelin. This information has been limited to the abundant inter-nodal regions of the sheath because these regions dominate the scattering when x-ray beams of 100 µm diameter or more are used. Here, we used a 1 µm beam, raster-scanned across a single nerve fiber, to obtain detailed information about the molecular architecture in the nodal, paranodal, and juxtaparanodal regions. Orientation of the lamellar membrane stacks and membrane periodicity varied spatially. In the juxtaparanode-internode, 198-202 Å-period membrane arrays oriented normal to the nerve fiber axis predominated, whereas in the paranode-node, 205-208 Å-period arrays oriented along the fiber direction predominated. In parts of the sheath distal to the node, multiple sets of lamellar reflections were observed at angles to one another, suggesting that the myelin multilayers are deformed at the Schmidt-Lanterman incisures. The calculated electron density of myelin in the different regions exhibited membrane bilayer profiles with varied electron densities at the polar head groups, likely due to different amounts of major myelin proteins (P0 glycoprotein and myelin basic protein). Scattering from the center of the nerve fibers, where the x-rays are incident en face (perpendicular) to the membrane planes, provided information about the lateral distribution of protein. By underscoring the heterogeneity of membrane packing, microdiffraction analysis suggests a powerful new strategy for understanding the underlying molecular foundation of a broad spectrum of myelinopathies dependent on local specializations of myelin structure in both the PNS and CNS.
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Membrana Celular/química , Proteína Básica da Mielina/química , Proteína P0 da Mielina/química , Bainha de Mielina/química , Difração de Raios X , Animais , Membrana Celular/metabolismo , Camundongos , Proteína Básica da Mielina/metabolismo , Proteína P0 da Mielina/metabolismo , Bainha de Mielina/metabolismoRESUMO
Rhizomelic chondrodysplasia punctata (RCDP) is a developmental disorder characterized by hypotonia, cataracts, abnormal ossification, impaired motor development, and intellectual disability. The underlying etiology of RCDP is a deficiency in the biosynthesis of ether phospholipids, of which plasmalogens are the most abundant form in nervous tissue and myelin; however, the role of plasmalogens in the peripheral nervous system is poorly defined. Here, we used mouse models of RCDP and analyzed the consequence of plasmalogen deficiency in peripheral nerves. We determined that plasmalogens are crucial for Schwann cell development and differentiation and that plasmalogen defects impaired radial sorting, myelination, and myelin structure. Plasmalogen insufficiency resulted in defective protein kinase B (AKT) phosphorylation and subsequent signaling, causing overt activation of glycogen synthase kinase 3ß (GSK3ß) in nerves of mutant mice. Treatment with GSK3ß inhibitors, lithium, or 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8) restored Schwann cell defects, effectively bypassing plasmalogen deficiency. Our results demonstrate the requirement of plasmalogens for the correct and timely differentiation of Schwann cells and for the process of myelination. In addition, these studies identify a mechanism by which the lack of a membrane phospholipid causes neuropathology, implicating plasmalogens as regulators of membrane and cell signaling.
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Sistema Nervoso Periférico/citologia , Sistema Nervoso Periférico/fisiologia , Plasmalogênios/fisiologia , Células de Schwann/citologia , Células de Schwann/fisiologia , Animais , Diferenciação Celular/fisiologia , Condrodisplasia Punctata Rizomélica/etiologia , Condrodisplasia Punctata Rizomélica/patologia , Condrodisplasia Punctata Rizomélica/fisiopatologia , Feminino , Quinase 3 da Glicogênio Sintase/antagonistas & inibidores , Quinase 3 da Glicogênio Sintase/metabolismo , Glicogênio Sintase Quinase 3 beta , Humanos , Masculino , Camundongos , Camundongos Knockout , Camundongos Mutantes Neurológicos , Modelos Neurológicos , Proteína Básica da Mielina/metabolismo , Bainha de Mielina/fisiologia , Regeneração Nervosa , Receptor 2 de Sinal de Orientação para Peroxissomos , Proteínas Proto-Oncogênicas c-akt/metabolismo , Receptores Citoplasmáticos e Nucleares/deficiência , Receptores Citoplasmáticos e Nucleares/genética , Transdução de SinaisRESUMO
Misfolded protein aggregates, characterized by a canonical amyloid fold, play a central role in the pathobiology of neurodegenerative diseases. Agents that bind and sequester neurotoxic intermediates of amyloid assembly, inhibit the assembly or promote the destabilization of such protein aggregates are in clinical testing. Here, we show that the gene 3 protein (g3p) of filamentous bacteriophage mediates potent generic binding to the amyloid fold. We have characterized the amyloid binding and conformational remodeling activities using an array of techniques, including X-ray fiber diffraction and NMR. The mechanism for g3p binding with amyloid appears to reflect its physiological role during infection of Escherichia coli, which is dependent on temperature-sensitive interdomain unfolding and cis-trans prolyl isomerization of g3p. In addition, a natural receptor for g3p, TolA-C, competitively interferes with Aß binding to g3p. NMR studies show that g3p binding to Aß fibers is predominantly through middle and C-terminal residues of the Aß subunit, indicating ß strand-g3p interactions. A recombinant bivalent g3p molecule, an immunoglobulin Fc (Ig) fusion of the two N-terminal g3p domains, (1) potently binds Aß fibers (fAß) (KD=9.4nM); (2); blocks fAß assembly (IC50~50nM) and (3) dissociates fAß (EC50=40-100nM). The binding of g3p to misfolded protein assemblies is generic, and amyloid-targeted activities can be demonstrated using other misfolded protein systems. Taken together, our studies show that g3p(N1N2) acts as a general amyloid interaction motif.
Assuntos
Peptídeos beta-Amiloides/química , Peptídeos beta-Amiloides/metabolismo , Bacteriófago M13/metabolismo , Proteínas do Capsídeo/química , Proteínas do Capsídeo/metabolismo , Proteínas da Membrana Bacteriana Externa/química , Proteínas da Membrana Bacteriana Externa/metabolismo , Bacteriófago M13/genética , Proteínas do Capsídeo/genética , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , Humanos , Cinética , Proteínas de Membrana Transportadoras/química , Proteínas de Membrana Transportadoras/metabolismo , Modelos Moleculares , Doenças Neurodegenerativas/etiologia , Doenças Neurodegenerativas/metabolismo , Ligação Proteica , Conformação Proteica , Dobramento de Proteína , Domínios e Motivos de Interação entre Proteínas , Multimerização Proteica , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , alfa-Sinucleína/química , alfa-Sinucleína/metabolismo , Proteínas tau/química , Proteínas tau/metabolismoRESUMO
Determination of the charged state distributions of partially- and fully-substituted sulfoalkylated cyclodextrins was achieved using hydrophilic interaction liquid chromatography (HILIC). HILIC analysis of a spiked sample of the partially sulfopropylated cyclodextrins was achieved using a gradient to baseline resolve the charged states from -1 to -14. The fully-substituted CDs yielded a major peak with some trace impurities and the partially-substituted sulfopropylated cyclodextrins showed a wide range of charge states present in the mixture. Small changes in the structure of the cyclodextrins have a significant impact on the retention times of the various types of cyclodextrins investigated.
Assuntos
Cromatografia Líquida/métodos , Ciclodextrinas/isolamento & purificação , Ciclodextrinas/análise , Ciclodextrinas/química , Interações Hidrofóbicas e Hidrofílicas , Modelos Moleculares , Peso MolecularRESUMO
Canavan's disease (CD) is a fatal pediatric leukodystrophy caused by mutations in aspartoacylase (AspA) gene. Currently, there is no effective treatment for CD; however, gene therapy is an attractive approach to ameliorate the disease. Here, we studied progressive neuropathology and gene therapy in short-lived (≤ 1 month) AspA(-/-) mice, a bona-fide animal model for the severest form of CD. Single intravenous (IV) injections of several primate-derived recombinant adeno-associated viruses (rAAVs) as late as postnatal day 20 (P20) completely rescued their early lethality and alleviated the major disease symptoms, extending survival in P0-injected rAAV9 and rAAVrh8 groups to as long as 2 years thus far. We successfully used microRNA (miRNA)-mediated post-transcriptional detargeting for the first time to restrict therapeutic rAAV expression in the central nervous system (CNS) and minimize potentially deleterious effects of transgene overexpression in peripheral tissues. rAAV treatment globally improved CNS myelination, although some abnormalities persisted in the content and distribution of myelin-specific and -enriched lipids. We demonstrate that systemically delivered and CNS-restricted rAAVs can serve as efficacious and sustained gene therapeutics in a model of a severe neurodegenerative disorder even when administered as late as P20.
Assuntos
Amidoidrolases/genética , Doença de Canavan/terapia , Sistema Nervoso Central/patologia , Dependovirus/genética , Amidoidrolases/deficiência , Amidoidrolases/metabolismo , Animais , Animais Recém-Nascidos , Doença de Canavan/patologia , Sistema Nervoso Central/metabolismo , Modelos Animais de Doenças , Técnicas de Inativação de Genes , Terapia Genética , Vetores Genéticos , Humanos , Injeções Intravenosas , Camundongos , MicroRNAs/genética , Especificidade de Órgãos , Difração de Raios XRESUMO
Charcot-Marie-Tooth disease type 1B is caused by mutations in myelin protein zero. R98C mice, an authentic model of early onset Charcot-Marie-Tooth disease type 1B, develop neuropathy in part because the misfolded mutant myelin protein zero is retained in the endoplasmic reticulum where it activates the unfolded protein response. Because oral curcumin, a component of the spice turmeric, has been shown to relieve endoplasmic reticulum stress and decrease the activation of the unfolded protein response, we treated R98C mutant mice with daily gastric lavage of curcumin or curcumin derivatives starting at 4 days of age and analysed them for clinical disability, electrophysiological parameters and peripheral nerve morphology. Heterozygous R98C mice treated with curcumin dissolved in sesame oil or phosphatidylcholine curcumin performed as well as wild-type littermates on a rotarod test and had increased numbers of large-diameter axons in their sciatic nerves. Treatment with the latter two compounds also increased compound muscle action potential amplitudes and the innervation of neuromuscular junctions in both heterozygous and homozygous R98C animals, but it did not improve nerve conduction velocity, myelin thickness, G-ratios or myelin period. The expression of c-Jun and suppressed cAMP-inducible POU (SCIP)-transcription factors that inhibit myelination when overexpressed-was also decreased by treatment. Consistent with its role in reducing endoplasmic reticulum stress, treatment with curcumin dissolved in sesame oil or phosphatidylcholine curcumin was associated with decreased X-box binding protein (XBP1) splicing. Taken together, these data demonstrate that treatment with curcumin dissolved in sesame oil or phosphatidylcholine curcumin improves the peripheral neuropathy of R98C mice by alleviating endoplasmic reticulum stress, by reducing the activation of unfolded protein response and by promoting Schwann cell differentiation.
Assuntos
Anti-Inflamatórios não Esteroides/uso terapêutico , Diferenciação Celular/efeitos dos fármacos , Doença de Charcot-Marie-Tooth , Curcumina/uso terapêutico , Proteína P0 da Mielina/genética , Células de Schwann/efeitos dos fármacos , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/genética , Fatores Etários , Análise de Variância , Animais , Animais Recém-Nascidos , Arginina/genética , Células COS/efeitos dos fármacos , Células Cultivadas , Doença de Charcot-Marie-Tooth/tratamento farmacológico , Doença de Charcot-Marie-Tooth/genética , Doença de Charcot-Marie-Tooth/patologia , Chlorocebus aethiops , Cisteína/genética , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Modelos Animais de Doenças , Proteína 2 de Resposta de Crescimento Precoce/metabolismo , Estimulação Elétrica/métodos , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/genética , Proteínas de Fluorescência Verde/genética , Humanos , Camundongos , Camundongos Transgênicos , Atividade Motora/efeitos dos fármacos , Atividade Motora/genética , Força Muscular/efeitos dos fármacos , Força Muscular/genética , Mutação/genética , Proteína P0 da Mielina/metabolismo , Junção Neuromuscular/efeitos dos fármacos , Junção Neuromuscular/genética , Fator 6 de Transcrição de Octâmero/metabolismo , Dobramento de Proteína/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-jun/metabolismo , Fatores de Transcrição de Fator Regulador X , Teste de Desempenho do Rota-Rod , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transfecção , Proteína 1 de Ligação a X-BoxRESUMO
PURPOSE: Alterations in mRNA for myelin proteins are reported in animal models of chemotherapy-induced peripheral neuropathies (CIPN); however, ultrastructural changes in aldehyde-fixed and plastic-embedded myelin are not evident by electron microscopy. Therefore, we used X-ray diffraction (XRD) to investigate more subtle changes in myelin sheath structure from unfixed nerves. EXPERIMENTAL DESIGN: We used in vivo chronic animal models of CIPN in female Wistar rats, administering cisplatin (CDDP 2mg/kg, i.p. twice/week), paclitaxel (PT 10mg/kg, i.v. once/week) or bortezomib (0.20mg/kg, i.v. three times/week) over a total period of 4weeks. Animal weights were monitored, and tail nerve conduction velocity (NCV) was determined at the end of the treatments to assess the occurrence of peripheral neuropathy. Sciatic nerves were collected and the myelin structure was analyzed using electron microscopy (EM) and XRD. RESULTS: All the rats treated with the chemotherapy agents developed peripheral neuropathy, as indicated by a decrease in NCV values; however, light and electron microscopy indicated no severe pathological alterations of the myelin morphology. XRD also did not demonstrate significant differences between sciatic nerves in treated vs. control rats with respect to myelin period, relative amount of myelin, membrane structure, and regularity of membrane packing. CONCLUSIONS: These results indicate that experimental peripheral neuropathy caused by CDDP, PT, and bortezomib-which are among the most widely used chemotherapy agents-does not significantly affect the structure of internodal myelin in peripheral nerve.