Alterações astrogliais em ratos wistar submetidos à estimulação transcraniana por corrente contínua

A estimulação transcraniana por corrente contínua (ETCC) consiste na aplicação de corrente elétrica sobre o córtex cerebral, sendo atribuída para diversas patologias, incluindo a dor, inflamação, epilepsia e depressão. É uma técnica de neuromodulação central, de baixo custo, não invasivo e indolor; compreende a aplicação de uma corrente elétrica 0,5 – 2 mA, contínua fraca, aplicada através de pequenos eletrodos (cátodo e ânodo) durante 15-20 minutos, sobre o córtex motor primário (M1) posicionados no escalpo íntegro em modelos animais. A corrente anodal despolariza a membrana celular, enquanto a catodal a hiperpolariza. ETCC é considerada um tratamento adjuvante e muitas vezes podendo substituir como por exemplo, fármacos antidepressivos, anticonvulsionantes e opioides, por se tratar de uma terapia não farmacológica de fácil execução, baixo custo e sem efeitos adversos de grandes proporções. Seus mecanismos de ação não estão totalmente elucidados, o que limita o seu potencial terapêutico em diversas áreas da saúde, bem como, a base celular e molecular de mecanismo de ação de ETCC ainda foi pouco esclarecida. Desta forma, o presente trabalho teve como objetivo geral demonstrar que uma única sessão de ETCC bimodal (20 min, 0,5 mA), aumentaria o limiar de dor induzida por estímulos mecânicos e térmicos, avaliados pelos testes de von Frey e placa quente, respectivamente. O trabalho foi executado em duas etapas: (1) Avaliação do efeito temporal da ETCC sobre parâmetros inflamatórios e gliais no córtex cerebral (resultados já publicados, capítulo 1) e (2) Avaliação das mudanças astrogliais – celulares e funcionais no hipocampo induzidas pela ETCC (manuscrito em preparação, capítulo 2). Assim, foi testada a hipótese que o tratamento com ETCC bimodal provocaria alterações de curto prazo em astrócitos no córtex cerebral e hipocampais nos ratos após trinta minutos da estimulação elétrica. Avaliando, os marcadores astrogliais no córtex cerebral total, apresentou diminuição da proteína ligante de cálcio (S100B) e em relação a proteína ácida fibrilar glial (GFAP) não ocorreu diferença significativa em animais submetidos à eletroestimulação. O mesmo, ocorreu no hipocampo, sendo analisado também, a captação de glutamato, glutamina sintetase (GS), que sofreu aumento e conteúdo de glutationa (GSH) onde ocorreu diminuição em animais eletroestimulados. O líquido cerebroespinal (LCR) também foi coletado, e apresentou alteração na proteína S100B em animais estimulados eletricamente com a ETCC. Estes dados poderão dar suporte a eficácia para aplicação da ETCC em ratos, para diversas situações como dor inflamatória e neuropática e posterior aplicação em seres humanos.Transcranial direct current stimulation (tDCS) consists of the application of electrical current on the cerebral cortex, being attributed to several pathologies, including pain, inflammation, epilepsy and depression. It is a low cost, non-invasive and painless central neuromodulation technique; comprises the application of a weak continuous 0.5 - 2 mA electric current, applied through small electrodes (cathode and anode) for 15-20 minutes, on the primary motor cortex (M1) positioned on the intact scalp in animal models. Anodal current depolarizes the cell membrane, while cathodal current hyperpolarizes it. tDCS is considered an adjuvant treatment and can often replace, for example, antidepressant drugs, anticonvulsants and opioids, as it is a non-pharmacological therapy that is easy to perform, low cost and without major adverse effects. Its mechanisms of action are not fully elucidated, which limits its therapeutic potential in several areas of health, as well as the cellular and molecular basis of the tDCS mechanism of action is still unclear. Thus, the present work had the general objective of demonstrating that a single session of bimodal tDCS (20 min, 0.5 mA) would increase the pain threshold induced by mechanical and thermal stimuli, assessed by von Frey and hot plate tests, respectively. The work was carried out in two stages: (1) Evaluation of the temporal effect of tDCS on inflammatory and glial parameters in the cerebral cortex (results already published, chapter 1) and (2) Evaluation of astroglial – cellular and functional changes in the hippocampus induced by tDCS (manuscript in preparation, chapter 2). Thus, the hypothesis was tested that treatment with bimodal tDCS would cause short-term changes in astrocytes in the cerebral cortex and hippocampus in rats after thirty minutes of electrical stimulation. Evaluating the astroglial markers in the total cerebral cortex, there was a decrease in calcium binding protein (S100B) and in relation to glial fibrillary acidic protein (GFAP) there was no significant difference in animals submitted to electrostimulation

The methylglyoxal/RAGE/NOX-2 pathway is persistently activated in the hippocampus of rats with STZ-induced sporadic Alzheimer’s Disease

Alzheimer’s disease (AD) is the leading cause of dementia in humans, with a high social and economic cost. AD is predominantly a sporadic disease, and the intracerebroventricular (ICV) administration of streptozotocin (STZ) has been widely used as an AD-like model of dementia. While the etiology of AD remains unknown, changes such as glucose metabolism and activation of receptors for advanced glycation end products (RAGE) seem to underlie its pathogenesis. We hypothesized that methylglyoxal, an endogenous toxin derived from the glycolytic pathway, could be the precursor of advanced glycated end products that activates RAGE and that, consequently, may activate membrane NADPH oxidase (NOX), contributing to the inflammatory status of the model and the disease. We administered ICV-STZ to Wistar rats and evaluated several neurochemical parameters in the hippocampus, particularly glyoxalase 1 (GLO-1) activity, which serves as an index of high levels of methylglyoxal, and the contents of RAGE and NOX-2, the most abundant brain NOX isoform. At the times evaluated (4 and 24 weeks after STZ), we observed cognitive deficit, increased beta-amyloid content, and increased tau phosphorylation. A persistent increase in GLO-1 activity was found, as well as increases in RAGE and NOX-2 contents, suggesting astroglial and microglial commitment. The increase in NOX-2 may reflect elevated microglial activity (confirmed by IBA-1 marker), which may contribute to the synaptic dysfunction and pruning described in the literature, both in this model and AD patients. Furthermore, reinforcing this possibility, we found a reduction in cholinergic communication in the hippocampus (as shown by decreased choline acetyltransferase), a reduction in BDNF, and an increase in TGF-β, the combination of which may result in synaptic deterioration

Evaluation of the immediate effects of a single transcranial direct current stimulation session on astrocyte activation, inflammatory response, and pain threshold in naïve rats

Transcranial direct current stimulation (tDCS) has demonstrated clinical benefits such as analgesia, anti- inflammatory, and neuroprotective effects. However, the mechanisms of action of a single tDCS session are poorly characterized. The present study aimed to evaluate the effects of a single tDCS session on pain sensitivity, inflammatory parameters, and astrocyte activity in naive rats. In the first experiment, sixty-day-old male Wistar rats (n = 95) were tested for mechanical pain threshold (von Frey test). Afterward, animals were submitted to a single bimodal tDCS (0.5 mA, 20 min) or sham-tDCS session. According to the group, animals were re-tested at different time intervals (30, 60, 120 min, or 24 h) after the intervention, euthanized, and the cerebral cortex collected for biochemical analysis. A second experiment (n = 16) was performed using a similar protocol to test the hypotheses that S100B levels in the cerebrospinal fluid (CSF) are altered by tDCS. Elisa assay quantified the levels of tumor necrosis factor–alfa (TNF-α), interleukin-10 (IL10), S100 calcium-binding protein B (S100B), and Glial fibrillary acidic protein (GFAP). Data were analyzed using ANOVA and independent t-test (P < 0.05). Results showed that tDCS decreased pain sensitivity (30 and 60 min), cerebral TNF-α and S100B levels (30 min). CSF S100B levels increased 30 min after intervention. There were no differences in IL10 and GFAP levels. TCDS showed analgesic, anti-inflammatory, and neuroprotective effects in naive animals. Therefore, this non-invasive and inexpensive therapy may potentially be a preemptive alternative to reduce pain, inflammation, and neu- rodegeneration in situations where patients will undergo medical procedures (e.g., surgery)