RESUMO
The GATs are the membrane proteins responsible for the uptake of GABA in the central nervous system. Alterations in GAT activity are implicated in several neurological diseases, including retinopathies. The present study describes an alternative method to determine GAT activity in tissue preparations of the central nervous system, using high performance liquid chromatography (HPLC) with fluorescence detection. The GABA concentration in the medium was determined using the o-phthaldehyde (OPA)-derivation protocol validated by the Brazilian Health Regulatory Agency (ANVISA) and the United States Food and Drug Administration (US-FDA). The GAT activity in the retinal preparations was determined through the evaluation of the GABA uptake, which was measured by assessing the difference between the initial and final concentrations of GABA in the incubation medium. The evaluation of the GAT kinetics returned values of Km = 382.5 ± 32.2 µM and Vmax = 34 nmol/mg of protein. The data also demonstrated that the GABA uptake was predominantly Na+- and temperature-dependent, and was also inhibited by incubation with nipecotic acid, a substrate of GABA transporters. Taken together, these findings confirm that our approach provided a specific measure of GAT activity in retinal tissue. The data presented here thus validate, for the first time, an alternative, simple and sensitive method for the evaluation of GAT activity using high performance chromatography on preparations of the central nervous system.
Assuntos
Retina , Ácido gama-Aminobutírico , Sistema Nervoso Central/metabolismo , Cromatografia Líquida de Alta Pressão , Proteínas da Membrana Plasmática de Transporte de GABA/metabolismo , Retina/metabolismo , Ácido gama-Aminobutírico/metabolismoRESUMO
Anxiety disorder is a well-recognized condition observed in subjects submitted to acute stress. Although the brain mechanisms underlying this disorder remain unclear, the available evidence indicates that oxidative stress and GABAergic dysfunction mediate the generation of stress-induced anxiety. Cannabinoids are known to be efficient modulators of behavior, given that the activation of the cannabinoid receptors type-1 (CB1 receptors) induces anxiolytic-like effects in animal models. In the present study, we aimed to describe the effects of the stimulation of the CB1 receptors on anxiety-like behavior, oxidative stress, and the GABA content of the brains of zebrafish submitted to acute restraint stress (ARS). The animals submitted to the ARS protocol presented evident anxiety-like behavior with increased lipid peroxidation in the brain tissue. The evaluation of the levels of GABA in the zebrafish telencephalon presented decreased levels of GABA in the ARS group in comparison with the control. Treatment with ACEA, a specific CB1 receptor agonist, prevented ARS-induced anxiety-like behavior and oxidative stress in the zebrafish brain. ACEA treatment also prevented a decrease in GABA in the telencephalon of the animals submitted to the ARS protocol. Overall, these preclinical data strongly suggest that the CB1 receptors represent a potential target for the development of the treatment of anxiety disorders elicited by acute stress.
RESUMO
Glutamate release in response to a hypertonic stimulus is a well described phenomenon in the hypothalamus. Evidence suggests that hypothalamic glial cells release glutamate into the extracellular environment in hypertonic conditions. In the current study, we described autocrine regulation of adenosine on glutamate release induced by Na+hypertonicity in hypothalamic glial cell cultures. We showed that glial cells cultured from the cerebral cortex did not release glutamate or adenosine under hypertonic conditions. The findings suggest that the hypothalamus has specialized glial cells, which are responsive to osmotic variations. Stimulation or inhibition of adenosine A1 receptors modulates extracellular glutamate levels in hypothalamic glial cell cultures under hypertonic stimulation. Our results extend previous observations regarding the role of glial cells in the control of hypothalamic physiology. They further demonstrate for the first time that hypothalamic glial cells regulate Na+-hypertonicity-induced glutamate release by activation of adenosine A1 receptors via adenosine release.
Assuntos
Ácido Glutâmico/metabolismo , Hipotálamo/metabolismo , Neuroglia/metabolismo , Receptor A1 de Adenosina/fisiologia , Cloreto de Sódio/farmacologia , Adenosina/farmacologia , Agonistas do Receptor A1 de Adenosina/farmacologia , Animais , Animais Recém-Nascidos , Células Cultivadas , Relação Dose-Resposta a Droga , Líquido Extracelular/efeitos dos fármacos , Líquido Extracelular/metabolismo , Hipotálamo/efeitos dos fármacos , Neuroglia/efeitos dos fármacos , Ratos , Ratos WistarRESUMO
INTRODUCTION: The present study investigated the association of the rs2794521 polymorphism in the CRP gene in individuals with chronic hepatitis B and C, correlating it with markers of hepatic inflammation, fibrosis scores, viral load, and plasma protein levels. METHODS: The study analyzed 185 blood samples obtained from patients with hepatitis B (n=74) and hepatitis C (n=111) and 300 samples from healthy donors. Genotyping was performed by real-time polymerase chain reaction, and protein levels were quantified using the automated immunoturbidimetric method. RESULTS: The TT genotype was the most frequent in all studied groups and was associated with higher plasma levels of the protein but not with the progression of liver disease. Low levels of C-reactive protein were associated with increased viremia and scores indicative of severe fibrosis and cirrhosis. CONCLUSIONS: The present results demonstrated a close relationship between the ability of the virus to replicate and cause liver damage and low serum concentrations of C-reactive protein. Future research may determine if these results can be interpreted as a possible form of escape for the virus by decreasing its action as an opsonin and decreasing phagocytosis, which are functions of C-reactive protein in the immune response.
Assuntos
Proteína C-Reativa/análise , Hepatite B Crônica/sangue , Hepatite C Crônica/sangue , Cirrose Hepática/virologia , Biomarcadores/sangue , Proteína C-Reativa/genética , Estudos de Casos e Controles , Estudos Transversais , Feminino , Genótipo , Hepatite B Crônica/genética , Hepatite C Crônica/genética , Humanos , Cirrose Hepática/sangue , Masculino , Índice de Gravidade de Doença , Carga ViralRESUMO
Abstract INTRODUCTION: The present study investigated the association of the rs2794521 polymorphism in the CRP gene in individuals with chronic hepatitis B and C, correlating it with markers of hepatic inflammation, fibrosis scores, viral load, and plasma protein levels. METHODS: The study analyzed 185 blood samples obtained from patients with hepatitis B (n=74) and hepatitis C (n=111) and 300 samples from healthy donors. Genotyping was performed by real-time polymerase chain reaction, and protein levels were quantified using the automated immunoturbidimetric method. RESULTS: The TT genotype was the most frequent in all studied groups and was associated with higher plasma levels of the protein but not with the progression of liver disease. Low levels of C-reactive protein were associated with increased viremia and scores indicative of severe fibrosis and cirrhosis. CONCLUSIONS: The present results demonstrated a close relationship between the ability of the virus to replicate and cause liver damage and low serum concentrations of C-reactive protein. Future research may determine if these results can be interpreted as a possible form of escape for the virus by decreasing its action as an opsonin and decreasing phagocytosis, which are functions of C-reactive protein in the immune response.
Assuntos
Humanos , Masculino , Feminino , Proteína C-Reativa/análise , Hepatite B Crônica/sangue , Hepatite C Crônica/sangue , Cirrose Hepática/virologia , Índice de Gravidade de Doença , Proteína C-Reativa/genética , Biomarcadores/sangue , Estudos de Casos e Controles , Estudos Transversais , Carga Viral , Hepatite B Crônica/genética , Hepatite C Crônica/genética , Genótipo , Cirrose Hepática/sangueRESUMO
Hyperammonemia is a common finding in children with methylmalonic acidemia. However, its contribution to methylmalonate-induced excitotoxicty is poorly understood. The aim of this study was to evaluate the mechanisms by which ammonia influences in the neurotoxicity induced by methylmalonate (MMA) in mice. The effects of ammonium chloride (NH4Cl 3, 6, and 12 mmol/kg; s.c.) on electroencephalographic (EEG) and behavioral convulsions induced by MMA (0.3, 0.66, and 1 µmol/2 µL, i.c.v.) were observed in mice. After, ammonia, TNF-α, IL1ß, IL-6, nitrite/nitrate (NOx) levels, mitochondrial potential (ΔΨ), reactive oxygen species (ROS) generation, Methyl-Tetrazolium (MTT) reduction, succinate dehydrogenase (SDH), and Na(+), K(+)-ATPase activity levels were measured in the cerebral cortex. The binding of [(3)H]flunitrazepam, release of glutamate-GABA; glutamate decarboxylase (GAD) and glutamine synthetase (GS) activity and neuronal damage [opening of blood brain barrier (BBB) permeability and cellular death volume] were also measured. EEG recordings showed that an intermediate dose of NH4Cl (6 mmol/kg) increased the duration of convulsive episodes induced by MMA (0.66 µmol/2 µL i.c.v). NH4Cl (6 mmol/kg) administration also induced neuronal ammonia and NOx increase, as well as mitochondrial ROS generation throughout oxidation of 2,7-dichlorofluorescein diacetate (DCFH-DA) to DCF-RS, followed by GS and GAD inhibition. The NH4Cl plus MMA administration did not alter cytokine levels, plasma fluorescein extravasation, or neuronal damage. However, it potentiated DCF-RS levels, decreased the ΔΨ potential, reduced MTT, inhibited SDH activity, and increased Na(+), K(+)-ATPase activity. NH4Cl also altered the GABA cycle characterized by GS and GAD activity inhibition, [(3)H]flunitrazepam binding, and GABA release after MMA injection. On the basis of our findings, the changes in ROS and reactive nitrogen species (RNS) levels elicited by ammonia alter the glycine/glutamate (GABA) cycle and contribute to MMA-induced excitability.
Assuntos
Amônia/farmacologia , Córtex Cerebral , Ácido Glutâmico/farmacologia , Glicina/farmacologia , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Ácido Metilmalônico/toxicidade , Amônia/metabolismo , Animais , Córtex Cerebral/metabolismo , Córtex Cerebral/fisiopatologia , Citocinas/metabolismo , Eletroencefalografia , Ácido Glutâmico/metabolismo , Glicina/metabolismo , Homeostase/efeitos dos fármacos , Hiperamonemia/induzido quimicamente , Hiperamonemia/metabolismo , Hiperamonemia/fisiopatologia , Camundongos , Oxirredução/efeitos dos fármacos , Convulsões/induzido quimicamente , Convulsões/metabolismo , Convulsões/fisiopatologiaRESUMO
The present study describes a simple and efficient method utilizing high performance liquid chromatography (HPLC) coupled to fluorescence detection for the determination of kinetic parameters of glutamate uptake in nervous tissue. Retinal tissue obtained from 7-day-old chicks was incubated with known concentrations of glutamate (50-2000 µM) for 10 min, and the levels of the o-phtaldehyde (OPA)-derivatized neurotransmitter in the incubation medium were measured. By assessing the difference between initial and final concentrations of glutamate in the medium, a saturable uptake mechanism was characterized (K(m)=8.2 and V(max)=9.8 nmol/mg protein/min). This measure was largely sodium- and temperature-dependent, strongly supporting that the mechanism for concentration decrements is indeed uptake by high-affinity transporters. Added to this, our results also demonstrated that zinc chloride (an inhibitor of glutamate/aspartate transporters) evoked a concentration-dependent decrease in glutamate uptake, demonstrating the specificity of our methodology. Overall, the present work characterizes an alternative methodology to evaluate glutamate uptake in nervous tissue using HPLC. This approach could be an important tool for studies associated to the characterization of minute alterations in glutamate transport related with central nervous system injury.
Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Ácido Glutâmico/análise , Ácido Glutâmico/farmacocinética , Retina/química , Retina/metabolismo , Análise de Variância , Animais , Galinhas , Cloretos/química , Homosserina/análise , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Espectrometria de Fluorescência , Temperatura , Compostos de Zinco/químicaRESUMO
Adult zebrafish were treated acutely with methylmercury (1.0 or 5.0 µg g(-1), i.p.) and, 24h after treatment, were tested in two behavioral models of anxiety, the novel tank and the light/dark preference tests. At the smaller dose, methylmercury produced a marked anxiogenic profile in both tests, while the greater dose produced hyperlocomotion in the novel tank test. These effects were accompanied by a decrease in extracellular levels of serotonin, and an increase in extracellular levels of tryptamine-4,5-dione, a partially oxidized metabolite of serotonin. A marked increase in the formation of malondialdehyde, a marker of oxidative stress, accompanied these parameters. It is suggested that methylmercury-induced oxidative stress produced mitochondrial dysfunction and originated tryptamine-4,5-dione, which could have further inhibited tryptophan hydroxylase. These results underscore the importance of assessing acute, low-level neurobehavioral effects of methylmercury.