RESUMO

The white matter is an important constituent of the central nervous system, containing axons, oligodendrocytes, and its progenitor cells, astrocytes, and microglial cells. Oligodendrocytes are central for myelin synthesis, the insulating envelope that protects axons and allows normal neural conduction. Both, oligodendrocytes and myelin, are highly vulnerable to toxic factors in many neurodevelopmental and neurodegenerative disorders associated with disturbances of myelination. Here we review the main alterations in oligodendrocytes and myelin observed in some organic acidurias/acidemias, which correspond to inherited neurometabolic disorders biochemically characterized by accumulation of potentially neurotoxic organic acids and their derivatives. The yet incompletely understood mechanisms underlying the high vulnerability of OLs and/or myelin in glutaric acidemia type I, the most prototypical cerebral organic aciduria, are particularly discussed.

Assuntos

Erros Inatos do Metabolismo dos Aminoácidos , Encefalopatias Metabólicas , Glutaril-CoA Desidrogenase , Oligodendroglia , Substância Branca , Oligodendroglia/metabolismo , Oligodendroglia/patologia , Erros Inatos do Metabolismo dos Aminoácidos/patologia , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Glutaril-CoA Desidrogenase/deficiência , Glutaril-CoA Desidrogenase/metabolismo , Humanos , Animais , Substância Branca/patologia , Substância Branca/metabolismo , Encefalopatias Metabólicas/patologia , Encefalopatias Metabólicas/metabolismo , Bainha de Mielina/metabolismo , Bainha de Mielina/patologia

RESUMO

Glutaric acidemia type I (GA-I) is an inborn error of metabolism of lysine, hydroxylysine, and tryptophan, caused by glutaryl-CoA-dehydrogenase (GCDH) deficiency, characterized by the buildup of toxic organic acids predominantly in the brain. After acute catabolic states, patients usually develop striatal degeneration, but the mechanisms behind this damage are still unknown. Quinolinic acid (QA), a metabolite of the kynurenine pathway, increases especially during infections/inflammatory processes, and could act synergically with organic acids, contributing to the neurological features of GA-I. The aim of this study was to investigate whether QA increases seizure susceptibility and modifies brain oscillation patterns in an animal model of GA-I, the Gcdh-/- mice taking high-lysine diet (Gcdh-/- -Lys). Therefore, the characteristics of QA-induced seizures and changes in brain oscillatory patterns were evaluated by video-electroencephalography (EEG) analysis recorded in Gcdh-/- -Lys, Gcdh+/+ -Lys, and Gcdh-/- -N (normal diet) animals. We found that the number of seizures per animal was similar for all groups receiving QA, Gcdh-/- -Lys-QA, Gcdh+/+ -Lys-QA, and Gcdh-/- -N-QA. However, severe seizures were observed in the majority of Gcdh-/- -Lys-QA mice (82%), and only in 25% of Gcdh+/+ -Lys-QA and 44% of Gcdh-/- -N-QA mice. All Gcdh-/- -Lys animals developed spontaneous recurrent seizures (SRS), but Gcdh-/- -Lys-QA animals had increased number of SRS, higher mortality rate, and significant predominance of lower frequency oscillations on EEG. Our results suggest that QA plays an important role in the neurological features of GA-I, as Gcdh-/- -Lys mice exhibit increased susceptibility to intrastriatal QA-induced seizures and long-term changes in brain oscillations.

Assuntos

Lisina , Ácido Quinolínico , Erros Inatos do Metabolismo dos Aminoácidos , Animais , Encéfalo/metabolismo , Encefalopatias Metabólicas , Modelos Animais de Doenças , Glutaril-CoA Desidrogenase/deficiência , Humanos , Lisina/metabolismo , Lisina/farmacologia , Camundongos , Camundongos Knockout , Ácido Quinolínico/toxicidade , Convulsões/induzido quimicamente , Convulsões/metabolismo

RESUMO

We investigated redox homeostasis in cerebral and peripheral tissues of wild type (WT) and glutaryl-CoA dehydrogenase knockout mice (Gcdh-/-) submitted to inflammation induced by lipopolysaccharide (LPS) since patients with glutaric aciduria type I (GA I) manifest acute encephalopathy during catabolic events triggered by inflammation. WT and Gcdh-/- mice fed a low (0.9%) or high (4.7%) Lys chow were euthanized 4 h after LPS intraperitoneal injection. Cerebral cortex of Lys-restricted Gcdh-/- animals presented no alterations of redox homeostasis, whereas those fed a high Lys chow showed increased malondialdehyde (MDA) levels and superoxide dismutase (SOD) activity, compared to WT mice. Furthermore, Gcdh-/- mice receiving low Lys and injected with LPS presented elevated MDA levels and decreased reduced glutathione (GSH) concentrations, glutathione peroxidase (GPx), and glutathione reductase (GR) activities in cerebral cortex. LPS administration also decreased GSH values, as well as GPx and GR activities in cerebral cortex of Gcdh-/- mice receiving Lys overload. Further experiments performed in WT and Gcdh-/- mice injected with LPS and receiving either a low or high Lys chow revealed increased MDA levels and decreased GSH concentrations in cerebral cortex and striatum, but not in hippocampus, liver and heart of Gcdh-/- mice, suggesting a selective vulnerability of these cerebral structures to oxidative stress during an inflammatory process. LPS administration also increased S100B and NF-κF protein levels in brain of Gcdh-/- mice receiving high Lys. These data support the hypothesis that low Lys diet is beneficial in GA I by preventing redox imbalance, whereas a high Lys diet or systemic inflammation per se or combined induce oxidative stress in striatum and cerebral cortex that are mainly damaged in this disorder.

Assuntos

Córtex Cerebral/metabolismo , Corpo Estriado/metabolismo , Glutaril-CoA Desidrogenase/deficiência , Mediadores da Inflamação/metabolismo , Lipopolissacarídeos/toxicidade , Estresse Oxidativo/fisiologia , Animais , Córtex Cerebral/efeitos dos fármacos , Corpo Estriado/efeitos dos fármacos , Relação Dose-Resposta a Droga , Feminino , Masculino , Camundongos , Camundongos da Linhagem 129 , Camundongos Knockout , Estresse Oxidativo/efeitos dos fármacos

RESUMO

The endocannabinoid system (ECS) regulates several physiological processes in the Central Nervous System, including the modulation of neuronal excitability via activation of cannabinoid receptors (CBr). Both glutaric acid (GA) and quinolinic acid (QUIN) are endogenous metabolites that, under pathological conditions, recruit common toxic mechanisms. A synergistic effect between them has already been demonstrated, supporting potential implications for glutaric acidemia type I (GA I). Here we investigated the possible involvement of a cannabinoid component in the toxic model exerted by QUIN + GA in rat cortical slices and primary neuronal cell cultures. The effects of the CB1 receptor agonist anandamide (AEA), and the fatty acid amide hydrolase inhibitor URB597, were tested on cell viability in cortical brain slices and primary neuronal cultures exposed to QUIN, GA, or QUIN + GA. As a pre-treatment to the QUIN + GA condition, AEA prevented the loss of cell viability in both preparations. URB597 only protected in a moderate manner the cultured neuronal cells against the QUIN + GA-induced damage. The use of the CB1 receptor reverse agonist AM251 in both biological preparations prevented partially the protective effects exerted by AEA, thus suggesting a partial role of CB1 receptors in this toxic model. AEA also prevented the cell damage and apoptotic death induced by the synergic model in cell cultures. Altogether, these findings demonstrate a modulatory role of the ECS on the synergic toxic actions exerted by QUIN + GA, thus providing key information for the understanding of the pathophysiological events occurring in GA I.

Assuntos

Ácidos Araquidônicos/farmacologia , Córtex Cerebral/efeitos dos fármacos , Endocanabinoides/farmacologia , Glutaratos/toxicidade , Neurônios/efeitos dos fármacos , Alcamidas Poli-Insaturadas/farmacologia , Ácido Quinolínico/toxicidade , Animais , Benzamidas/farmacologia , Agonistas de Receptores de Canabinoides/farmacologia , Carbamatos/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Sinergismo Farmacológico , Endocanabinoides/metabolismo , Feminino , Masculino , Neurônios/metabolismo , Piperidinas/farmacologia , Gravidez , Pirazóis/farmacologia , Ratos , Ratos Endogâmicos WF , Receptores de Canabinoides/metabolismo

RESUMO

Glutaric acidemia type I (GA-I) is a neurometabolic disease caused by deficient activity of glutaryl-CoA dehydrogenase (GCDH) that results in accumulation of metabolites derived from lysine (Lys), hydroxylysine, and tryptophan catabolism. GA-I patients typically develop encephalopatic crises with striatal degeneration and progressive white matter defects. However, late onset patients as well as Gcdh-/- mice only suffer diffuse myelinopathy, suggesting that neuronal death and white matter defects are different pathophysiological events. To test this hypothesis, striatal myelin was studied in Gcdh-/- mice fed from 30 days of age during up to 60 days with a diet containing normal or moderately increased amounts of Lys (2.8%), which ensure sustained elevated levels of GA-I metabolites. Gcdh-/- mice fed with 2.8% Lys diet showed a significant decrease in striatal-myelinated areas and progressive vacuolation of white matter tracts, as compared with animals fed with normal diet. Myelin pathology increased with the time of exposure to high Lys diet and was also detected in 90-day old Gcdh-/- mice fed with normal diet, suggesting that dietary Lys accelerated the undergoing white matter damage. Gcdh-/- mice fed with 2.8% Lys diet also showed increased GRP78/BiP immunoreactivity in oligodendrocytes and neurons, denoting ER stress. However, the striatal and cortical neuronal density was unchanged with respect to normal diet. Thus, myelin damage seen in Gcdh-/- mice fed with 2.8% Lys seems to be mediated by a long-term increased levels of GA-I metabolites having deleterious effects in myelinating oligodendrocytes over neurons.

Assuntos

Dieta , Glutaril-CoA Desidrogenase/deficiência , Lisina/efeitos adversos , Substância Branca/enzimologia , Substância Branca/lesões , Animais , Contagem de Células , Morte Celular/efeitos dos fármacos , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/metabolismo , Corpo Estriado/patologia , Chaperona BiP do Retículo Endoplasmático , Glutaril-CoA Desidrogenase/metabolismo , Camundongos , Bainha de Mielina/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Oligodendroglia/efeitos dos fármacos , Oligodendroglia/metabolismo , Substância Branca/patologia

RESUMO

Glutaric acidemia type I (GA I) is an inherited neurometabolic disorder caused by a severe deficiency of the mitochondrial glutaryl-CoA dehydrogenase (GCDH) activity. Patients usually present progressive cortical leukodystrophy and commonly develop acute bilateral striatal degeneration mainly during infections that markedly worse their prognosis. A role for quinolinic acid (QA), a key metabolite of the kynurenine pathway, which is activated during inflammatory processes, on the pathogenesis of the acute striatum degeneration occurring in GA I was proposed but so far has not yet been evaluated. Therefore, we investigated whether an acute intrastriatal administration of quinolinic acid (QA) could induce histopathological alterations in the striatum of 30-day-old wild-type (WT) and GCDH knockout (Gcdh-/-) mice. Striatum morphology was evaluated by hematoxylin and eosin, T lymphocyte presence (CD3), and glial activation (GFAP and S100ß) by immunohistochemistry and 3-nitrotyrosine (YNO2) by immunofluorescence. QA provoked extensive vacuolation, edema, and especially lymphocyte infiltration in the striatum of Gcdh-/-. QA also enhanced CD3 staining and the number of YNO2 positive cells in Gcdh-/- mice, relatively to WT, indicating T lymphocyte infiltration and nitrosative stress, respectively. QA-treated WT mice also showed an increase of GFAP and S100ß staining, which is indicative of reactive astrogliosis, whereas the levels of these astrocytic proteins were not changed in Gcdh-/- QA-injected mice. The present data indicate that QA significantly contributes to the histopathological changes observed in the striatum of Gcdh-/- mice.

Assuntos

Erros Inatos do Metabolismo dos Aminoácidos/patologia , Encefalopatias Metabólicas/patologia , Corpo Estriado/efeitos dos fármacos , Regulação da Expressão Gênica/efeitos dos fármacos , Glutaril-CoA Desidrogenase/deficiência , Inflamação/induzido quimicamente , Inflamação/genética , Ácido Quinolínico/toxicidade , Erros Inatos do Metabolismo dos Aminoácidos/dietoterapia , Erros Inatos do Metabolismo dos Aminoácidos/genética , Animais , Encefalopatias Metabólicas/dietoterapia , Encefalopatias Metabólicas/genética , Complexo CD3/metabolismo , Corpo Estriado/metabolismo , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Regulação da Expressão Gênica/genética , Proteína Glial Fibrilar Ácida/metabolismo , Glutaril-CoA Desidrogenase/genética , Lisina/administração & dosagem , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Oxirredução/efeitos dos fármacos , Subunidade beta da Proteína Ligante de Cálcio S100/metabolismo , Estatísticas não Paramétricas , Fatores de Tempo , Tirosina/análogos & derivados , Tirosina/metabolismo

RESUMO

It has been shown that synergistic toxic effects of quinolinic acid (QUIN) and glutaric acid (GA), both in isolated nerve endings and in vivo conditions, suggest the contribution of these metabolites to neurodegeneration. However, this synergism still requires a detailed characterization of the mechanisms involved in cell damage during its occurrence. In this study, the effects of subtoxic concentrations of QUIN and/or GA were tested in neuronal cultures, co-cultures (neuronal cells + astrocytes), and mixed cultures (neuronal cells + astrocytes + microglia) from rat cortex and striatum. The exposure of different cortical and striatal cell cultures to QUIN + GA resulted in cell death and stimulated different markers of oxidative stress, including reactive oxygen species (ROS) formation; changes in the activity of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione peroxidase; and depletion of endogenous antioxidants such as -SH groups and glutathione. The co-incubation of neuronal cultures with QUIN + GA plus the N-methyl-D-aspartate antagonist MK-801 prevented cell death but not ROS formation, whereas the antioxidant melatonin reduced both parameters. Our results demonstrated that QUIN and GA can create synergistic scenarios, inducing toxic effects on some parameters of cell viability via the stimulation of oxidative damage. Therefore, it is likely that oxidative stress may play a major causative role in the synergistic actions exerted by QUIN + GA in a variety of cell culture conditions involving the interaction of different neural types.

Assuntos

Glutaratos/toxicidade , Modelos Biológicos , Neurônios/metabolismo , Estresse Oxidativo , Ácido Quinolínico/toxicidade , Animais , Antioxidantes/metabolismo , Catalase/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Córtex Cerebral/patologia , Técnicas de Cocultura , Maleato de Dizocilpina/farmacologia , Feminino , Gliose/metabolismo , Gliose/patologia , Glutaratos/administração & dosagem , Glutationa/metabolismo , Melatonina/farmacologia , Neostriado/patologia , Neuritos/efeitos dos fármacos , Neuritos/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/patologia , Estresse Oxidativo/efeitos dos fármacos , Ácido Quinolínico/administração & dosagem , Ratos Wistar , Espécies Reativas de Oxigênio/metabolismo , Superóxido Dismutase/metabolismo

RESUMO

Bioenergetics dysfunction has been postulated as an important pathomechanism of brain damage in glutaric aciduria type I, but this is still under debate. We investigated activities of citric acid cycle (CAC) enzymes, lactate release, respiration and membrane potential (ΔΨm) in mitochondrial preparations from cerebral cortex and striatum of 30-day-old glutaryl-CoA dehydrogenase deficient (Gcdh-/-) and wild type mice fed a baseline or a high lysine (Lys, 4.7%) chow for 60 or 96h. Brain histological analyses were performed in these animals, as well as in 90-day-old animals fed a baseline or a high Lys chow during 30 days starting at 60-day-old. A moderate reduction of citrate synthase and isocitrate dehydrogenase activities was observed only in the striatum from 30-day-old Gcdh-/- animals submitted to a high Lys chow. In contrast, the other CAC enzyme activities, lactate release, the respiratory parameters state 3, state 4, the respiratory control ratio and CCCP-stimulated (uncoupled) state, as well as ΔΨm were not altered in the striatum. Similarly, none of the evaluated parameters were changed in the cerebral cortex from these animals under baseline or Lys overload. On the other hand, histological analyses revealed the presence of intense vacuolation in the cerebral cortex of 60 and 90-day-old Gcdh-/- mice fed a baseline chow and in the striatum of 90-day-old Gcdh-/- mice submitted to Lys overload for 30 days. Taken together, the present data demonstrate mild impairment of bioenergetics homeostasis and marked histological alterations in striatum from Gcdh-/- mice under a high Lys chow, suggesting that disruption of energy metabolism is not mainly involved in the brain injury of these animals.

Assuntos

Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Encefalopatias Metabólicas/metabolismo , Encefalopatias/metabolismo , Córtex Cerebral/metabolismo , Corpo Estriado/metabolismo , Metabolismo Energético , Glutaril-CoA Desidrogenase/deficiência , Lisina/administração & dosagem , Animais , Encefalopatias/patologia , Córtex Cerebral/patologia , Corpo Estriado/patologia , Dieta , Modelos Animais de Doenças , Glutaril-CoA Desidrogenase/genética , Glutaril-CoA Desidrogenase/metabolismo , Isocitrato Desidrogenase/metabolismo , Ácido Láctico/metabolismo , Potencial da Membrana Mitocondrial/fisiologia , Camundongos da Linhagem 129 , Camundongos Knockout , Consumo de Oxigênio/fisiologia

RESUMO

The role of excitotoxicity on the neuropathology of glutaric acidemia type I (GA I) is still under debate. Therefore, in the present work, we evaluated glutamate uptake by brain slices and glutamate binding to synaptic membranes, as well as glutamine synthetase activity in cerebral cortex and striatum from glutaryl-CoA dehydrogenase deficient (Gcdh(-/-)) mice along development (7, 15, 30 and 60 days of life) in the hopes of clarifying this matter. We also tested the influence of glutaric acid (GA) added exogenously on these parameters. [(3)H]Glutamate uptake was not significantly altered in cerebral cortex and striatum from Gcdh(-/-) mice, as compared to WT mice. However, GA provoked a significant decrease of [(3)H]glutamate uptake in striatum from both WT and Gcdh(-/-) mice older than 7 days. This inhibitory effect was more pronounced in Gcdh(-/-), as compared to WT mice. The use of a competitive inhibitor of glutamate astrocytic transporters indicated that the decrease of [(3)H]glutamate uptake caused by GA was due to the competition between this organic acid and glutamate for the same astrocytic transporter site. We also found that Na(+)-dependent [(3)H]glutamate binding (binding to transporters) was increased in the striatum from Gcdh(-/-) mice and that GA significantly diminished this binding both in striatum and cerebral cortex from Gcdh(-/-), but not from WT mice. Finally, we observed that glutamine synthetase activity was not changed in brain cortex and striatum from Gcdh(-/-) and WT mice and that GA was not able to alter this activity. It is therefore presumed that a disturbance of the glutamatergic neurotransmission system caused by GA may potentially be involved in the neuropathology of GA I, particularly in the striatum.

Assuntos

Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Encefalopatias Metabólicas/metabolismo , Córtex Cerebral/metabolismo , Corpo Estriado/metabolismo , Glutaratos/farmacologia , Glutaril-CoA Desidrogenase/deficiência , Glutaril-CoA Desidrogenase/genética , Erros Inatos do Metabolismo dos Aminoácidos/patologia , Animais , Encefalopatias Metabólicas/patologia , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/patologia , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/patologia , Modelos Animais de Doenças , Glutamato-Amônia Ligase/metabolismo , Glutaril-CoA Desidrogenase/metabolismo , Camundongos , Camundongos Knockout

RESUMO

BACKGROUND: Glutaric acid (GA) is a dicarboxylic acid that accumulates in millimolar concentrations in glutaric acidemia I (GA-I), an inherited neurometabolic childhood disease characterized by extensive neurodegeneration. Vascular dysfunction is a common and early pathological feature in GA-I, although the underlying mechanisms remain unknown. In the present study, we have used a previously-validated rat model of GA-I to determine the effect of GA on the blood- brain barrier (BBB) and the neurovascular unit. METHODS: Newborn rat pups received a single injection of GA (1 µmol/g) or vehicle into the cisterna magna. BBB permeability was analyzed at 14 and 30 days post injection (DPI) by assessing Evans blue (EB) and immunoglobulin G (IgG) extravasation. Blood vessels and microglia were labeled with tomato lectin. Characterization of EB positive cells was made by double labeling with antibodies to astrocyte and neuronal markers. Immunohistochemistry against aquaporin 4 (AQP4), ß receptor of the platelet derived growth factor (PDGFRß) and laminin was used to recognize astrocyte endfeet, pericytes and basal lamina. Zonula occludens 1 (ZO-1) and occludin striatal expression was assessed by Western blotting. RESULTS: Perinatal intracisternal GA administration caused an increased extravasation of free EB, but not of IgG, into the striatal parenchyma at 14 and 30 DPI. EB extravasated through the BBB was internalized exclusively into neurons. GA-injected animals did not show significant changes in the area of small blood vessels in the striatum, but at 30 DPI there was a significant decrease in AQP4, PDGFRß and laminin positive areas associated with small blood vessels. Occludin and ZO-1 expression in the striatal tissue was unchanged in all conditions analyzed. CONCLUSIONS: The present study shows a previously-unknown effect of a perinatal administration of a single intracisternal GA injection on BBB permeability and on key components of the neurovascular unit. The results suggest BBB leakage is a pathogenic mechanism and a potential therapeutic target for patients with GA-I.