RESUMO
S100B, a homodimeric Ca2+-binding protein, is produced and secreted by astrocytes, and its extracellular levels have been used as a glial marker in brain damage and neurodegenerative and psychiatric diseases; however, its mechanism of secretion is elusive. We used primary astrocyte cultures and calcium measurements from real-time fluorescence microscopy to investigate the role of intracellular calcium in S100B secretion. In addition, the dimethyl sulfoxide (DMSO) effect on S100B was investigated in vitro and in vivo using Wistar rats. We found that DMSO, a widely used vehicle in biological assays, is a powerful S100B secretagogue, which caused a biphasic response of Ca2+ mobilization. Our data show that astroglial S100B secretion is triggered by the increase in intracellular Ca2+ and indicate that this increase is due to Ca2+ mobilization from the endoplasmic reticulum. Also, blocking plasma membrane Ca2+ channels involved in the Ca2+ replenishment of internal stores decreased S100B secretion. The DMSO-induced S100B secretion was confirmed in vivo and in ex vivo hippocampal slices. Our data support a nonclassic vesicular export of S100B modulated by Ca2+, and the results might contribute to understanding the mechanism underlying the astroglial release of S100B.
Assuntos
Astrócitos , Dimetil Sulfóxido , Ratos , Animais , Ratos Wistar , Dimetil Sulfóxido/farmacologia , Dimetil Sulfóxido/metabolismo , Astrócitos/metabolismo , Colforsina/farmacologia , Secretagogos/farmacologia , Cálcio/metabolismo , Fatores de Crescimento Neural/metabolismo , Subunidade beta da Proteína Ligante de Cálcio S100/metabolismo , Retículo Endoplasmático/metabolismo , Células CultivadasRESUMO
One of the changes found in the brain in Alzheimer's disease (AD) is increased calpain, derived from calcium dysregulation, oxidative stress, and/or neuroinflammation, which are all assumed to be basic pillars in neurodegenerative diseases. The role of calpain in synaptic plasticity, neuronal death, and AD has been discussed in some reviews. However, astrocytic calpain changes sometimes appear to be secondary and consequent to neuronal damage in AD. Herein, we explore the possibility of calpain-mediated astroglial reactivity in AD, both preceding and during the amyloid phase. We discuss the types of brain calpains but focus the review on calpains 1 and 2 and some important targets in astrocytes. We address the signaling involved in controlling calpain expression, mainly involving p38/mitogen-activated protein kinase and calcineurin, as well as how calpain regulates the expression of proteins involved in astroglial reactivity through calcineurin and cyclin-dependent kinase 5. Throughout the text, we have tried to provide evidence of the connection between the alterations caused by calpain and the metabolic changes associated with AD. In addition, we discuss the possibility that calpain mediates amyloid-ß clearance in astrocytes, as opposed to amyloid-ß accumulation in neurons.
Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Astrócitos/metabolismo , Encéfalo/metabolismo , Calpaína/metabolismo , Plasticidade Neuronal , Doença de Alzheimer/patologia , Animais , Astrócitos/patologia , Calcineurina/metabolismo , Quinase 5 Dependente de Ciclina/genética , Quinase 5 Dependente de Ciclina/metabolismo , Modelos Animais de Doenças , Humanos , Doenças Neuroinflamatórias/metabolismoRESUMO
Based on the concept of the tripartite synapse, we have reviewed the role of glucose-derived compounds in glycolytic pathways in astroglial cells. Glucose provides energy and substrate replenishment for brain activity, such as glutamate and lipid synthesis. In addition, glucose metabolism in the astroglial cytoplasm results in products such as lactate, methylglyoxal, and glutathione, which modulate receptors and channels in neurons. Glucose has four potential destinations in neural cells, and it is possible to propose a crossroads in "X" that can be used to describe these four destinations. Glucose-6P can be used either for glycogen synthesis or the pentose phosphate pathway on the left and right arms of the X, respectively. Fructose-6P continues through the glycolysis pathway until pyruvate is formed but can also act as the initial compound in the hexosamine pathway, representing the left and right legs of the X, respectively. We describe each glucose destination and its regulation, indicating the products of these pathways and how they can affect synaptic communication. Extracellular L-lactate, either generated from glucose or from glycogen, binds to HCAR1, a specific receptor that is abundantly localized in perivascular and post-synaptic membranes and regulates synaptic plasticity. Methylglyoxal, a product of a deviation of glycolysis, and its derivative D-lactate are also released by astrocytes and bind to GABAA receptors and HCAR1, respectively. Glutathione, in addition to its antioxidant role, also binds to ionotropic glutamate receptors in the synaptic cleft. Finally, we examined the hexosamine pathway and evaluated the effect of GlcNAc-modification on key proteins that regulate the other glucose destinations.
RESUMO
The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces motor and nonmotor dysfunctions resembling Parkinson's disease (PD); however, studies investigating the effects of 1-methyl-4-phenylpyridinium (MPP+), an active oxidative product of MPTP, are scarce. This study investigated the behavioral and striatal neurochemical changes (related to oxidative damage, glial markers, and neurotrophic factors) 24 h after intracerebroventricular administration of MPP+ (1.8-18 µg/mouse) in C57BL6 mice. MPP+ administration at high dose (18 µg/mouse) altered motor parameters, since it increased the latency to leave the first quadrant and reduced crossing, rearing, and grooming responses in the open-field test and decreased rotarod latency time. MPP+ administration at low dose (1.8 µg/mouse) caused specific nonmotor dysfunctions as it produced a depressive-like effect in the forced swim test and tail suspension test, loss of motivational and self-care behavior in the splash test, anxiety-like effect in the elevated plus maze test, and short-term memory deficit in the step-down inhibitory avoidance task, without altering ambulation. MPP+ at doses of 1.8-18 µg/mouse increased tyrosine hydroxylase (TH) immunocontent and at 18 µg/mouse increased α-synuclein and decreased parkin immunocontent. The astrocytic calcium-binding protein S100B and glial fibrillary acidic protein (GFAP)/S100B ratio was decreased following MPP+ administration (18 µg/mouse). At this highest dose, MPP+ increased the ionized calcium-binding adapter molecule 1 (Iba-1) immunocontent, suggesting microglial activation. Also, MPP+ at a dose of 18 µg/mouse increased thiobarbituric acid reactive substances (TBARS) and glutathione (GSH) levels and increased glutathione peroxidase (GPx) and hemeoxygenase-1 (HO-1) immunocontent, suggesting a significant role for oxidative stress in the MPP+-induced striatal damage. MPP+ (18 µg/mouse) also increased striatal fibroblast growth factor 2 (FGF-2) and brain-derived neurotrophic factor (BDNF) levels. Moreover, MPP+ decreased tropomyosin receptor kinase B (TrkB) immunocontent. Finally, MPP+ (1.8-18 µg/mouse) increased serum corticosterone levels and did not alter acetylcholinesterase (AChE) activity in the striatum but increased it in cerebral cortex and hippocampus. Collectively, these results indicate that MPP+ administration at low doses may be used as a model of emotional and memory/learning behavioral deficit related to PD and that MPP+ administration at high dose could be useful for analysis of striatal dysfunctions associated with motor deficits in PD.
Assuntos
1-Metil-4-fenilpiridínio/toxicidade , Corpo Estriado/efeitos dos fármacos , Emoções/efeitos dos fármacos , Aprendizagem/efeitos dos fármacos , Memória/efeitos dos fármacos , Atividade Motora/efeitos dos fármacos , Acetilcolinesterase/metabolismo , Animais , Corpo Estriado/metabolismo , Proteína Glial Fibrilar Ácida/metabolismo , Glutationa/metabolismo , Camundongos , Subunidade beta da Proteína Ligante de Cálcio S100/metabolismo , Substâncias Reativas com Ácido Tiobarbitúrico/metabolismoRESUMO
The developing brain is vulnerable to the effects of ethanol. Glutamate is the main mediator of excitatory signals in the brain and is probably involved in most aspects of normal brain function during development. The aim of this study was to investigate vulnerability to and the impact of ethanol toxicity on glutamate uptake signaling in adolescent rats after moderate pre and postnatal ethanol exposure. Pregnant female rats were divided into three groups and treated only with water (control), non-alcoholic beer (vehicle) or 10% (v/v) beer solution (moderate prenatal alcohol exposure-MPAE). Thirty days after birth, adolescent male offspring were submitted to hippocampal acute slice procedure. We assayed glutamate uptake and measured glutathione content and also quantified glial glutamate transporters (EAAT 1 and EAAT 2). The glutamate system vulnerability was tested with different acute ethanol doses in naïve rats and compared with the MPAE group. We also performed a (lipopolysaccharide-challenge (LPS-challenge) with all groups to test the glutamate uptake response after an insult. The MPAE group presented a decrease in glutamate uptake corroborating a decrease in glutathione (GSH) content. The reduction in GSH content suggests oxidative damage after acute ethanol exposure. The glial glutamate transporters were also altered after prenatal ethanol treatment, suggesting a disturbance in glutamate signaling. This study indicates that impairment of glutamate uptake can be dose-dependent and the glutamate system has a higher vulnerability to ethanol toxicity after moderate ethanol exposure In utero. The effects of pre- and postnatal ethanol exposure can have long-lasting impacts on the glutamate system in adolescence and potentially into adulthood.
Assuntos
Etanol/efeitos adversos , Ácido Glutâmico/metabolismo , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Efeitos Tardios da Exposição Pré-Natal/induzido quimicamente , Efeitos Tardios da Exposição Pré-Natal/metabolismo , Animais , Feminino , Glutationa/metabolismo , Masculino , Gravidez , RatosRESUMO
In this study we investigated the anti-inflammatory effects of chronic ethanol (EtOH) treatment on lipopolysaccharide (LPS)-stimulated C6 glioma cells. The cells were chronically treated with 200mM EtOH; coincubation with LPS and EtOH was obtained upon addition of 2µg/ml LPS to the incubation medium in the last 24h of EtOH exposure. We found that EtOH prevented the LPS-induced production of tumor necrosis factor α (TNFα) without decreasing cell viability. Either LPS treated or EtOH plus LPS treated cells presented upregulated glial fibrillary acidic protein (GFAP) and downregulated vimentin levels characterizing a program of reactive astrogliosis. Also, EtOH plus LPS stimulation greatly increased the oxidative stress generation evaluated by DCF-DA measurement, while either EtOH alone or LPS alone was unable to induce oxidative stress. Western blot analysis indicated that either EtOH, LPS or EtOH plus LPS treatments are unable to affect Akt/GSK3ß signaling pathway. However, LPS alone and EtOH plus LPS co-treatment inhibited Erk phosphorylation. A dramatic loss of stress fibers was found in EtOH exposed cells, evaluated by cytochemistry using phalloidin-fluorescein. However, LPS alone was not able to disrupt actin organization. Furthermore, cells co-incubated with LPS and EtOH presented reversion of the disrupted stress fibers provoked by EtOH. Supporting this action, RhoA and vinculin immunocontent were upregulated in response to EtOH plus LPS. Interestingly, EtOH suppresses the inflammatory cascade (TNFα production) in response to LPS. Concomitantly it sustains Erk inhibition, increases oxidative stress generation and induces reactive astrogliosis in the presence of LPS, conditions associated with neurotoxicity. The effects observed were not supported by actin reorganization. Altogether, these findings suggest that Erk signaling inhibition could play a role in both suppressing TNFα production and inducing oxidative stress generation and astrogliosis, therefore modulating a dual action of EtOH plus LPS in glial cells.
Assuntos
Anti-Inflamatórios/farmacologia , Etanol/farmacologia , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Neuroglia/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Animais , Western Blotting , Linhagem Celular Tumoral , Sobrevivência Celular , Eletroforese em Gel de Poliacrilamida , Gliose/induzido quimicamente , Gliose/metabolismo , Gliose/patologia , Imuno-Histoquímica , Inflamação/induzido quimicamente , Inflamação/metabolismo , Lipopolissacarídeos/toxicidade , Neuroglia/metabolismo , Neuroglia/patologia , Ratos , Fibras de Estresse/efeitos dos fármacos , Fibras de Estresse/metabolismo , Fator de Necrose Tumoral alfa/metabolismoRESUMO
BACKGROUND: Inflammatory responses in brain are primarily mediated by microglia, but growing evidence suggests a crucial importance of astrocytes. S100B, a calcium-binding protein secreted by astrocytes, has properties of a neurotrophic or an inflammatory cytokine. However, it is not known whether primary signals occurring during induction of an inflammatory response (e.g. lipopolysaccharide, LPS) directly modulate S100B. METHODS: In this work, we evaluated whether S100B levels in cerebrospinal fluid (CSF) and serum of Wistar rats are affected by LPS administered by intraperitoneal (IP) or intracerebroventricular (ICV) injection, as well as whether primary astrocyte cultures respond directly to lipopolysaccharide. RESULTS: Our data suggest that S100B secretion in brain tissue is stimulated rapidly and persistently (for at least 24 h) by ICV LPS administration. This increase in CSF S100B was transient when LPS was IP administered. In contrast to these S100B results, we observed an increase in in TNFα levels in serum, but not in CSF, after IP administration of LPS. In isolated astrocytes and in acute hippocampal slices, we observed a direct stimulation of S100B secretion by LPS at a concentration of 10 µg/mL. An involvement of TLR4 was confirmed by use of specific inhibitors. However, lower levels of LPS in astrocyte cultures were able to induce a decrease in S100B secretion after 24 h, without significant change in intracellular content of S100B. In addition, after 24 h exposure to LPS, we observed a decrease in astrocytic glutathione and an increase in astrocytic glial fibrillary acidic protein. CONCLUSIONS: Together, these data contribute to the understanding of the effects of LPS on astrocytes, particularly on S100B secretion, and help us to interpret cerebrospinal fluid and serum changes for this protein in neuroinflammatory diseases. Moreover, non-brain S100B-expressing tissues may be differentially regulated, since LPS administration did not lead to increased serum levels of S100B.
Assuntos
Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Lipopolissacarídeos/farmacologia , Fatores de Crescimento Neural/líquido cefalorraquidiano , Fatores de Crescimento Neural/metabolismo , Proteínas S100/líquido cefalorraquidiano , Proteínas S100/metabolismo , Animais , Astrócitos/citologia , Células Cultivadas , Córtex Cerebral/citologia , Glutationa/metabolismo , Infusões Intraventriculares , Lipopolissacarídeos/administração & dosagem , Ratos , Ratos Wistar , Subunidade beta da Proteína Ligante de Cálcio S100 , Fator de Necrose Tumoral alfa/sangue , Fator de Necrose Tumoral alfa/líquido cefalorraquidianoRESUMO
The intracerebroventricular infusion of streptozotocin (icv-STZ) has been largely used in research to mimic the main characteristics of Alzheimer's disease (AD), including cognitive decline, impairment of cholinergic transmission, oxidative stress and astrogliosis. Moderate physical exercise has a number of beneficial effects on the central nervous system, as demonstrated both in animals and in human studies. This study aimed to evaluate the effect of 5-week treadmill training, in the icv-SZT model of sporadic AD, on cognitive function, oxidative stress (particularly mediated by NO) and on the astrocyte marker proteins, glial fibrillary acidic protein (GFAP) and S100B. Results confirm the spatial cognitive deficit and oxidative stress in this model, as well as astroglial alterations, particularly a decrease in CSF S100B. Physical exercise prevented these alterations, as well as increasing the hippocampal content of glutathione and GFAP per se in the CA1 region. These findings reinforce the potential neuroprotective role of moderate physical exercise. Astroglial changes observed in this dementia model contribute to understanding AD and other diseases that are accompanied by cognitive deficit.
Assuntos
Transtornos Cognitivos/reabilitação , Hipocampo/fisiologia , Atividade Motora/fisiologia , Estresse Oxidativo/fisiologia , Doença de Alzheimer/reabilitação , Animais , Transtornos Cognitivos/induzido quimicamente , Modelos Animais de Doenças , Proteína Glial Fibrilar Ácida/metabolismo , Glutationa/metabolismo , Hipocampo/efeitos dos fármacos , Imuno-Histoquímica , Injeções Intraventriculares , Masculino , Aprendizagem em Labirinto/fisiologia , Neurotoxinas/administração & dosagem , Neurotoxinas/toxicidade , Ratos , Ratos Wistar , Estreptozocina/administração & dosagem , Estreptozocina/toxicidadeRESUMO
We have previously demonstrated that early environment influences the metabolic response, affecting abdominal fat deposition in adult female rats exposed to a long-term highly caloric diet. In the present study, our goal was to verify the effects of the chronic exposure, in adulthood, to a highly palatable diet (chocolate) on cerebral Na+,K+-ATPase activity and S100B protein concentrations, and the response to its withdrawal in neonatally handled and non-handled rats. We measured the consumption of foods (standard lab chow and chocolate), body weight gain, S100B protein concentrations, as well as cerebral Na(+),K(+)-ATPase activity during chronic exposure and after chocolate withdrawal in adult female rats that had been exposed or not to neonatal handling (10 min/day, 10 first days of life). Non-handled rats chronically exposed to chocolate exhibited increased plasma S100B levels, but there was no difference in abdominal fat S100B concentration between groups. Chronic chocolate consumption decreased Na+,K+-ATPase activity in both amygdala and hippocampus in non-handled, but not in handled rats, and this effect disappeared after chocolate withdrawal. Non-handled animals also demonstrated increased frequency of head shaking in the open field after 24h of chocolate withdrawal in comparison to handled ones. These findings suggest that neonatal handling modifies the vulnerability to metabolic and brain alterations induced by chronic exposure to a highly palatable diet in adulthood.
Assuntos
Envelhecimento/metabolismo , Encéfalo/enzimologia , Carboidratos da Dieta/metabolismo , Privação de Alimentos/fisiologia , Fatores de Crescimento Neural/metabolismo , Proteínas S100/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Animais , Animais Recém-Nascidos , Feminino , Ratos , Ratos Wistar , Subunidade beta da Proteína Ligante de Cálcio S100RESUMO
Although the exact cause of Alzheimer's disease remains elusive, many possible risk factors and pathological alterations have been used in the elaboration of in vitro and in vivo models of this disease in rodents, including intracerebral infusion of streptozotocin (STZ). Using this model, we evaluated spatial cognitive deficit and neurochemical hippocampal alterations, particularly astroglial protein markers such as glial fibrillary acidic protein (GFAP) and S100B, glutathione content, nitric oxide production, and cerebrospinal fluid (CSF) S100B. In addition, prevention of these alterations by aminoguanidine administration was evaluated. Results confirm a spatial cognitive deficit and nitrative stress in this dementia model as well as specific astroglial alterations, particularly S100B accumulation in the hippocampus and decreased CSF S100B. The hippocampal astroglial activation occurred independently of the significant alteration in GFAP content. Moreover, all these alterations were completely prevented by aminoguanidine administration, confirming the neuroprotective potential of this compound, but suggesting that nitrative stress and/or glycation may be underlying these alterations. These findings contribute to the understanding of diseases accompanied by cognitive deficits and the STZ-model of dementia.