RESUMO
BACKGROUND: Thiamine (vitamin B1) is a cofactor for enzymes of central energy metabolism and its deficiency (TD) impairs oxidative phosphorylation, increases oxidative stress, and activates inflammatory processes that can lead to neurodegeneration. Wernicke-Korsakoff syndrome (WKS) is a consequence of chronic TD, which leads to extensive neuronal death, and is associated with neuropathological disorders, including cognitive deficits and amnesia. The hippocampus is one of the brain areas most affected by WKS. B1 replacement may not be enough to prevent the irreversible cognitive deficit associated with WKS. MATERIALS AND METHODS: An organotypic hippocampal slice culture (OHC) model was developed to investigate, using immunofluorescence and confocal microscopy and transcriptome analysis, the molecular mechanisms underlying the neurodegeneration associated with TD. The effect of anti-inflammatory pharmacological intervention with resveratrol (RSV) was also assessed in B1-deprived OHCs. RESULTS: In OHCs cultured without B1, neuronal density decayed after 5 days and, on the 7th day, the epigenetic markings H3K4me3 and H3K9me3 were altered in mature neurons likely favoring gene transcription. Between the 7th and the 14th day, a pulse of neurogenesis was observed followed by a further massive neuron loss. Transcriptome analysis at day nine disclosed 89 differentially expressed genes in response to B1 deprivation. Genes involved in tryptophan metabolism and lysine degradation KEGG pathways, and those with Gene Ontology (GO) annotations related to the organization of the extracellular matrix, cell adhesion, and positive regulation of synaptic transmission were upregulated. Several genes of the TNF and FoxO signaling pathways and with GO terms related to inflammation were inhibited in response to B1 deprivation. Nsd1, whose product methylates histone H3 lysine 36, was upregulated and the epigenetic marking H3K36me3, associated with negative regulation of neurogenesis, was increased in neurons. Treating B1-deprived OHCs with RSV promoted an earlier neurogenesis pulse. CONCLUSION: Neuroregeneration occurs in B1-deficient hippocampal tissue during a time window. This phenomenon depends on reducing neuroinflammation and, likely, on metabolic changes, allowing acetyl-CoA synthesis from amino acids to ensure energy supply via oxidative phosphorylation. Thus, neuroinflammation is implicated as a major regulator of hippocampal neurogenesis in TD opening a new search space for treating WKS.
Assuntos
Doenças Neuroinflamatórias , Deficiência de Tiamina , Humanos , Lisina/metabolismo , Deficiência de Tiamina/complicações , Deficiência de Tiamina/metabolismo , Deficiência de Tiamina/patologia , Neurogênese/fisiologia , Hipocampo/metabolismo , Tiamina/metabolismo , Neurônios/metabolismoRESUMO
Thiamine deficiency is associated with cerebellar dysfunction; however, the consequences of thiamine deficiency on the electrophysiological properties of cerebellar Purkinje cells are poorly understood. Here, we evaluated these parameters in brain slices containing cerebellar vermis. Adult mice were maintained for 12-13 days on a thiamine-free diet coupled with daily injections of pyrithiamine, an inhibitor of thiamine phosphorylation. Morphological analysis revealed a 20% reduction in Purkinje cell and nuclear volume in thiamine-deficient animals compared to feeding-matched controls, with no reduction in cell count. Under whole-cell current clamp, thiamine-deficient Purkinje cells required significantly less current injection to fire an action potential. This reduction in rheobase was not due to a change in voltage threshold. Rather, thiamine-deficient neurons presented significantly higher input resistance specifically in the voltage range just below threshold, which increases their sensitivity to current at these critical membrane potentials. In addition, thiamine deficiency caused a significant decrease in the amplitude of the action potential afterhyperpolarization, broadened the action potential, and decreased the current threshold for depolarization block. When thiamine-deficient animals were allowed to recover for 1 week on a normal diet, rheobase, threshold, action potential half-width, and depolarization block threshold were no longer different from controls. We conclude that thiamine deficiency causes significant but reversible changes to the electrophysiology properties of Purkinje cells prior to pathological morphological alterations or cell loss. Thus, the data obtained in the present study indicate that increased excitability of Purkinje cells may represent a leading indicator of cerebellar dysfunction caused by lack of thiamine.
Assuntos
Células de Purkinje/patologia , Deficiência de Tiamina/patologia , Deficiência de Tiamina/fisiopatologia , Potenciais de Ação/fisiologia , Animais , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Técnicas de Cultura de Órgãos , Técnicas de Patch-ClampRESUMO
Thiamine deficiency (TD) produces severe neurodegenerative lesions. Studies have suggested that primary neurodegenerative events are associated with both oxidative stress and inflammation. Very little is known about the downstream effects on intracellular signaling pathways involved in neuronal death. The primary aim of this work was to evaluate the modulation of p38MAPK and the expression of heme oxygenase 1 (HO-1) in the central nervous system (CNS). Behavioral, metabolic, and morphological parameters were assessed. Mice were separated into six groups: control (Cont), TD with pyrithiamine (Ptd), TD with pyrithiamine and Trolox (Ptd + Tr), TD with pyrithiamine and dimethyl sulfoxide (Ptd + Dmso), Trolox (Tr) and DMSO (Dmso) control groups and treated for 9 days. Control groups received standard feed (AIN-93M), while TD groups received thiamine deficient feed (AIN-93DT). All the groups were subjected to behavioral tests, and CNS samples were collected for cell viability, histopathology and western blot analyses. The Ptd group showed a reduction in weight gain and feed intake, as well as a reduction in locomotor, grooming, and motor coordination activities. Also, Ptd group showed a robust increase in p38MAPK phosphorylation and mild HO-1 expression in the cerebral cortex and thalamus. The Ptd group showed a decreased cell viability, hemorrhage, spongiosis, and astrocytic swelling in the thalamus. Groups treated with Trolox and DMSO displayed diminished p38MAPK phosphorylation in both the structures, as well as attenuated thalamic lesions and behavioral activities. These data suggest that p38MAPK and HO-1 are involved in the TD-induced neurodegeneration in vivo, possibly modulated by oxidative stress and neuroinflammation.
Assuntos
Encéfalo/metabolismo , Heme Oxigenase-1/metabolismo , Proteínas de Membrana/metabolismo , Deficiência de Tiamina/fisiopatologia , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Animais , Comportamento Animal/fisiologia , Peso Corporal/fisiologia , Encéfalo/patologia , Sobrevivência Celular/fisiologia , Cromanos/farmacologia , Dimetil Sulfóxido/farmacologia , Ingestão de Alimentos/fisiologia , Inflamação/etiologia , Inflamação/fisiopatologia , Masculino , Camundongos , Fármacos Neuroprotetores/farmacologia , Estresse Oxidativo/fisiologia , Piritiamina , Deficiência de Tiamina/induzido quimicamente , Deficiência de Tiamina/complicações , Deficiência de Tiamina/patologiaRESUMO
A 19-month-old, white, Pennsylvanian boy, with an unremarkable medical history, presented to our hospital with a 3-week history of nonbloody, nonbilious emesis up to 5 times a day and nonbloody diarrhea. Ten days before admission, his gait became progressively unsteady, until he finally refused to walk. A day before admission, he found it difficult to move his eyes. The patient was hypoactive. History, physical and neurologic examination, blood and cerebrospinal (CSF) fluid studies, and neuroimaging studies ruled out the most frequent causes of acute ataxia. The etiology of bilateral, complete ophthalmoplegia was also taken into consideration. Magnetic resonance imaging (MRI) findings of bilateral thalami and mammillary bodies provided diagnostic clues. Additional history and specific tests established the final diagnosis and treatment plan. The patient improved to a normal neurologic state. This case provides important practical information about an unusual malnutrition cause of acute ataxia, particularly in young children of developing countries.
Assuntos
Ataxia/fisiopatologia , Transtornos da Consciência/fisiopatologia , Oftalmoplegia/fisiopatologia , Deficiência de Tiamina/diagnóstico , Deficiência de Tiamina/fisiopatologia , Ataxia/diagnóstico , Ataxia/patologia , Transtornos da Consciência/diagnóstico , Transtornos da Consciência/patologia , Diagnóstico Diferencial , Humanos , Lactente , Imageamento por Ressonância Magnética , Masculino , Oftalmoplegia/diagnóstico , Oftalmoplegia/patologia , Tiamina/administração & dosagem , Deficiência de Tiamina/patologia , Deficiência de Tiamina/terapia , Estados UnidosRESUMO
BACKGROUND AND AIMS: Thiamine deficiency is a condition that is known to cause damage to the nervous and cardiovascular systems because it interferes with cellular metabolism. It is well known that the control of vascular function is highly dependent on the production of nitric oxide (NO) by NO synthases. Studies exploring the physiological relevance of NO signaling under conditions of thiamine deficiency are scarce. The present study sought to investigate whether chronic metabolic changes would cause alterations in vascular responsiveness. METHODS AND RESULTS: By removing thiamine from the diet, we observed a reduced acetylcholine-mediated relaxation and an increased phenylephrine-mediated vasoconstriction in the aortas containing functional endothelium. Removal of the endothelium or the pre-treatment of vessels with l-NAME restored the contractile responses to the level of controls. Conversely, indomethacin did not modify phenylephrine-mediated contractions. We also used carbon microsensors to continually measure NO production in situ while simultaneously measuring the vascular tone. The results revealed a significant decrease in NO production. Western blot analysis showed a decreased expression of the total eNOS in the thiamine-deficient aorta compared to the control. Concentration-response curves for phenylephrine indicated no difference between the control and deficient groups in the presence and absence of SOD or Tyron. The NO donor DEA-NONOate produced a concentration-dependent relaxation response in the endothelium-denuded vessels that did not differ between the control and thiamine-deficient rats. CONCLUSION: Thiamine deficiency modulates eNOS-dependent NO production, leading to a decreased vasorelaxation and an increased contractile response in the rat aorta.
Assuntos
Óxido Nítrico/metabolismo , Deficiência de Tiamina/patologia , Doenças Vasculares/patologia , Acetilcolina/farmacologia , Animais , Aorta/efeitos dos fármacos , Aorta/metabolismo , Hidrazinas/farmacologia , Indometacina/farmacologia , Masculino , Contração Muscular/efeitos dos fármacos , NG-Nitroarginina Metil Éster/metabolismo , Óxido Nítrico Sintase/metabolismo , Óxido Nítrico Sintase Tipo III/genética , Óxido Nítrico Sintase Tipo III/metabolismo , Fenilefrina/farmacologia , Ratos , Ratos Wistar , Deficiência de Tiamina/complicações , Doenças Vasculares/etiologia , Vasoconstrição/efeitos dos fármacos , Vasodilatação/efeitos dos fármacosRESUMO
AIMS: Thiamine is an important cofactor present in many biochemical reactions, and its deprivation can lead to heart dysfunction. Little is known about the influence of thiamine deprivation on the electrophysiological behavior of the isolated heart cells and information about thiamine deficiency in heart morphology is controversial. Thus, we decided to investigate the major repolarizing conductances and their influence in the action potential (AP) waveform as well as the changes in the heart structure in a set of thiamine deficiency in rats. MAIN METHODS: Using the patch-clamp technique, we investigated inward (I(K1)) and outward K(+) currents (I(to)), T-type and L-type Ca(2+) currents and APs. To evaluate heart morphology we used hematoxylin and eosin in transversal heart sections. KEY FINDINGS: Thiamine deficiency caused a marked decrease in left ventricle thickness, cardiomyocyte number, cell length and width, and membrane capacitance. When evaluating I(to) we did not find difference in current amplitude; however an acceleration of I(to) inactivation was observed. I(K1) showed a reduction in the amplitude and slope conductance, which implicated a less negative resting membrane potential in cardiac myocytes isolated from thiamine-deficient rats. We did not find any difference in L-type Ca(2+) current density. T-type Ca(2+) current was not observed. In addition, we did not observe significant changes in AP repolarization. SIGNIFICANCE: Based on our study we can conclude that thiamine deficiency causes heart hypotrophy and not heart hypertrophy. Moreover, we provided evidence that there is no major electrical remodeling during thiamine deficiency, a feature of heart failure models.
Assuntos
Potenciais de Ação/fisiologia , Modelos Animais de Doenças , Cardiopatias/patologia , Cardiopatias/fisiopatologia , Deficiência de Tiamina/patologia , Deficiência de Tiamina/fisiopatologia , Animais , Cardiopatias/etiologia , Hipertrofia Ventricular Esquerda/patologia , Hipertrofia Ventricular Esquerda/fisiopatologia , Masculino , Potenciais da Membrana/fisiologia , Miócitos Cardíacos/patologia , Miócitos Cardíacos/fisiologia , Ratos , Ratos WistarRESUMO
Extensive work has been done regarding the impact of thiamine deprivation on the nervous system. In cardiac tissue, chronic thiamine deficiency is described to cause changes in the myocardium that can be associated with arrhythmias. However, compared with the brain, very little is known about the effects of thiamine deficiency on the heart. Thus this study was undertaken to explore whether thiamine deprivation has a role in cardiac arrhythmogenesis. We examined hearts isolated from thiamine-deprived and control rats. We measured heart rate, diastolic and systolic tension, and contraction and relaxation rates. Whole cell voltage clamp was performed in rat isolated cardiac myocytes to measure L-type Ca(2+) current. In addition, we investigated the global intracellular calcium transients by using confocal microscopy in the line-scan mode. The hearts from thiamine-deficient rats did not degenerate into ventricular fibrillation during 30 min of reperfusion after 15 min of coronary occlusion. The antiarrhythmogenic effects were characterized by the arrhythmia severity index. Our results suggest that hearts from thiamine-deficient rats did not experience irreversible arrhythmias. There was no change in L-type Ca(2+) current density. Inactivation kinetics of this current in Ca(2+)-buffered cells was retarded in thiamine-deficient cardiac myocytes. The global Ca(2+) release was significantly reduced in thiamine-deficient cardiac myocytes. The amplitude of caffeine-releasable Ca(2+) was lower in thiamine-deficient myocytes. In summary, we have found that thiamine deprivation attenuates the incidence and severity of postischemic arrhythmias, possibly through a mechanism involving a decrease in global Ca(2+) release.
Assuntos
Arritmias Cardíacas/fisiopatologia , Traumatismo por Reperfusão Miocárdica/fisiopatologia , Deficiência de Tiamina/fisiopatologia , Tiamina/sangue , Animais , Arritmias Cardíacas/complicações , Arritmias Cardíacas/patologia , Traumatismo por Reperfusão Miocárdica/complicações , Traumatismo por Reperfusão Miocárdica/patologia , Ratos , Ratos Wistar , Deficiência de Tiamina/complicações , Deficiência de Tiamina/patologiaRESUMO
The effect of acute thiamin deficiency on the jejunum epithelial cell was investigated in rats. The following results were obtained: The animals in the thiamin deficiency group (ATD) started to show a significant body weight loss from the 17th day in relation to pair fed controls (PFC). The length of the villus, depth and the cell population of the crypt from ATD animals were significantly decreased as compared to PFC. Crypt cell production rate (CCPR) was similar in both groups. However, even with epithelial hypoplasia, CCPR was maintained in thiamin-deficient animal, probably due to the presence of immature villus cells, which may reduced chalone and thus cause crypt to be more proliferative.