Navegando por Assunto "Adenosina"

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Acesso aberto (Open Access)
Adenosina modula os níveis extracelulares de glutamato induzido por hiperosmolaridade em cultura de astrócitos hipotalâmicos
(Universidade Federal do Pará, 2016-04-29) BRAGA, Danielle Valente; DINIZ, Domingos Luiz Wanderley Picanço; http://lattes.cnpq.br/9601463988942971; SILVA, Anderson Manoel Herculano Oliveira da; http://lattes.cnpq.br/8407177208423247
Recent studies have shown that glutamate release by hypothalamic glial cells is an important physiological response to hyperosmolarity. Furthermore, previous studies point out an accentuated increase of the adenosine levels in renal interstitial fluid after the intake sodium increases. This study aims to evaluate the possible relationship between the adenosine and glutamate releases in primary cultures of astrocytes exposed to hyperosmolarity conditions. Hypothalamic astrocytes cultures of Wistar rats at the first two days after birth were exposed to hypertonic sodium solution (340mOsm/L) in different times (3, 5, 10 e 15 min). After this stimulus, the incubation medium was harvested and the extracellular levels of glutamate and adenosine were determined by High Performance Liquid Chromatography. In order to evaluate the relationship between these compounds in hyperosmotic conditions, we have used treatment of the cultures with adenosine, with R-PIA (an agonist of the A1 receptor), as well as with glutamate (an agonist of the NMDA receptor). Our results showed a significant increase of the extracellular levels of glutamate after the hyperosmotic stimulus with a peak at 5 min. Similarly, we have seen an increase of the adenosine levels in the incubation medium after 10 and 15 min. The treatment with glutamate induced an increase in extracellular levels of adenosine after 15 and 20 minutes in isosmotic medium. The exposure to the NMDA receptor did not induce the release of adenosine in none of the concentrations utilized. The pretreatment with adenosine and R-PIA A1 agonist blocked the release of glutamate induced by hyperosmolarity. Our results also showed that the effect of the stimulus on the release of glutamate and adenosine is sodium-dependent and presents a specific response for hypothalamic astrocytes, which can be modulated by the adenosine A1 receptor activation.
Acesso aberto (Open Access)
Glutationa modula a liberação de adenosina em cultura primária de astrócitos corticais de camundongo
(Universidade Federal do Pará, 2022-09-06) SILVA, Mateus dos Santos; OLIVEIRA, Karen Renata Herculano Matos; http://lattes.cnpq.br/3032008039259369; SILVA, Anderson Manoel Herculano Oliveira da; http://lattes.cnpq.br/8407177208423247
Glutathione (GSH) is one of the main antioxidants in the Central Nervous System (CNS) and a potential gliotransmitter, inducing calcium waves in the cytosol of glial cells. Adenosine (Adn) is a neuromodulator widely expressed in the CNS and its extracellular levels are a critical factor in determining its effect on nervous tissue. It is known that Ca2+- dependent pathways regulate Adn release. Since GSH has the ability to induce Ca2+ waves in the cytosol of glial cells, the present work aims to investigate whether this molecule can regulate extracellular DNA levels. To assess this, we used primary cultures of cortical astrocytes maintained in DMEM+10% SBF in a CO2 oven (37oC, 95% O2/5% CO2) for 12-15 days, when they reached confluence. The cells were incubated with Hank buffer for different time intervals, after which this solution was collected and the neurotransmitters present there were quantified by High Performance Liquid Chromatography. Our data show that GSH induces an 80% increase in extracellular Adn levels at two analyzed times: 5 and 20 minutes. Removal of GSH from the incubation medium returns the Adn concentration to baseline levels. Removal of Na+ or Ca2+ from the medium did not affect the effect of GSH. Blockade of nucleoside equilibrative transporters by dipyridamole (10 µM) significantly decreased the levels of Adn in the medium, but did not interfere with the action of GSH. In order to assess whether the effect of GSH derives from an indirect modulation on the release of glutamate or GABA (two agents described as regulators of Adn release), the quantification of these transmitters was performed. Both were significantly increased in the presence of GSH. However, unlike what was observed with Adn, the removal of Na+ from the incubation medium mitigated the effect of GSH on glutamate release. The incubation of astrocytes with GABA (50 and 100 µM) did not influence the extracellular Adn concentration in our experimental model, ruling out a GABAergic modulation behind the effect of GSH. The evaluation of redox agents showed that thiol compounds reproduce the effect of GSH, while the non thiol antioxidant alpha-tocopherol did not regulate extracellular Adn levels. Thus, the present work concludes that astrocytes express a GSH-sensitive component that can be modulated by its sulfhydryl group.
Acesso aberto (Open Access)
Possible involvement of A1 receptors in the inhibition of gonadotropin secretion induced by adenosine in rat hemipituitaries in vitro
(1999-09) DINIZ, Domingos Luiz Wanderley Picanço; VALENÇA, Marcelo Moraes; FAVARETTO, Ana Lucia Vianna; MCCANN, S.M.; RODRIGUES, José Antunes
We investigated the participation of A1 or A2 receptors in the gonadotrope and their role in the regulation of LH and FSH secretion in adult rat hemipituitary preparations, using adenosine analogues. A dose-dependent inhibition of LH and FSH secretion was observed after the administration of graded doses of the R-isomer of phenylisopropyladenosine (R-PIA; 1 nM, 10 nM, 100 nM, 1 µM and 10 µM). The effect of R-PIA (10 nM) was blocked by the addition of 8-cyclopentyltheophylline (CPT), a selective A1 adenosine receptor antagonist, at the dose of 1 µM. The addition of an A2 receptor-specific agonist, 5-N-methylcarboxamidoadenosine (MECA), at the doses of 1 nM to 1 µM had no significant effect on LH or FSH secretion, suggesting the absence of this receptor subtype in the gonadotrope. However, a sharp inhibition of the basal secretion of these gonadotropins was observed after the administration of 10 µM MECA. This effect mimicked the inhibition induced by R-PIA, supporting the hypothesis of the presence of A1 receptors in the gonadotrope. R-PIA (1 nM to 1 µM) also inhibited the secretion of LH and FSH induced by phospholipase C (0.5 IU/ml) in a dose-dependent manner. These results suggest the presence of A1 receptors and the absence of A2 receptors in the gonadotrope. It is possible that the inhibition of LH and FSH secretion resulting from the activation of A1 receptors may have occurred independently of the increase in membrane phosphoinositide synthesis.
Acesso aberto (Open Access)
Receptor A2A de adenosina modula o transporte de glutamato independente de sodio em cultura primaria de celulas da retina
(Universidade Federal do Pará, 2024-11) LIMA, Caroline Araujo Costa de; OLIVEIRA, Karen Renata Herculano Matos; http://lattes.cnpq.br/3032008039259369
Dysregulation of extracellular glutamate levels is directly associated with several CNS pathologies, highlighting the importance of glutamate transporters in maintaining tissue homeostasis and developing new therapeutic approaches. The retina is particularly vulnerable toexcitotoxic events due to its high levels of glutamate extracelular and the frequente exposure to oxidative stimuli, reinforcing the need for regulatory mecanisms to preserve retinal physiology. In this context, adenosine emerges as an essential neuromodulator, exhibiting regulatory effects that are concentration- and receptor-dependent. Therefore, the objetive of this study was to characterize the effect of adenosine on sodium-independent glutamate transport in retinal cell culture. As such, mixed primary cell cultures from White leghorn chick embryos (E7-E8) were maintained for 7 days in DMEM+10% FBS at 37°C and 5% CO₂. The cells were submitted to apre-incubation with an A2A receptor blocker and incubated with different adenosine concentrations for glutamate release and uptake assays. Glutamate levels were quantified by HPLC, and protein levels were measured by the Bradford method, with equimolar substitution of NaCl by LiCl. Furthermore, immunofluorescence with an anti-xCT antibody and the nuclear marker DAPI was used to identify the sodium-independent glutamate transporter, with image analysis performed using ImageJ e Photoshop CS6. Statistical analysis was conducted using Student’s test T and ANOVA one-way with Tukey post-hoc test via GraphPad 9.0, with data expressed as percentage of control±S.D. with p<0,05. The results confirmed the expression of the xCT subunit, indicating that the system xCG-is the sodium-independent glutamate transporter in retinal cells. Additionally, adenosine at a concentration of 50μM increased glutamate release by approximately 800%, while glutamate sodium-independent uptake was completely inhibited.These effects were fully by A2A receptor blockade. Therefore, we demonstrated that activation of the A2A receptor modulates glutamate sodium independent transport, whose
Acesso aberto (Open Access)
A sinalização adenosinérgica na regulação da gravidade da sepse e da liberação de armadilhas extracelulares de neutrófilos (NETs)
(Universidade Federal do Pará, 2024-09) PAMPOLHA, Ana Flavia Oliveira; CUNHA, Fernando de Queiroz; http://lattes.cnpq.br/2869737621338203; HTTPS://ORCID.ORG/0000-0003-4755-1670; MONTEIRO, Marta Chagas; http://lattes.cnpq.br/6710783324317390; https://orcid.org/0000-0002-3328-5650
Neutrophils express different purinergic receptors, including four adenosine-ligand P1 receptors, which regulate their primary functions, such as migration and production of inflammatory mediators, including neutrophil extracellular traps (NETs). In sepsis, NETs exhibit a dual role: microbicidal properties but also contribute to organ damage, leading to multiple organ failure and worsening the clinical condition. In this study, we investigated the role of adenosine in NETs release and the progression of experimental sepsis induced by the Cecum Ligation and Puncture (CLP) or endotoxemia models. We observed that treatment of mice subjected to both models with adenosine deaminase (ADA), which metabolizes adenosine to inosine, aggravates organ damage and reduces the survival rate of septic animals. Supporting these findings, we demonstrated that NET production in vitro by neutrophils stimulated with PMA was enhanced by ADA treatment and reduced by NECA, a molecule that mimics adenosine's actions. The modulation of NET production by adenosine was attributed to the activation of A2AAR receptors. In conclusion, our results suggest that during sepsis, adenosine is released and decrease NET production via A2AAR activation.
Acesso aberto (Open Access)
Stimulatory effects of adenosine on prolactin secretion in the pituitary gland of the rat
(2002-07) DINIZ, Domingos Luiz Wanderley Picanço; VALENÇA, Marcelo Moraes; FAVARETTO, Ana Lucia Vianna; RODRIGUES, José Antunes
We investigated the effects of adenosine on prolactin (PRL) secretion from rat anterior pituitaries incubated in vitro. The administration of 5-N- methylcarboxamidoadenosine (MECA), an analog agonist that preferentially activates A2 receptors, induced a dose-dependent (1 nM to 1 µM) increase in the levels of PRL released, an effect abolished by 1,3-dipropyl-7-methylxanthine, an antagonist of A2 adenosine receptors. In addition, the basal levels of PRL secretion were decreased by the blockade of cyclooxygenase or lipoxygenase pathways, with indomethacin and nordihydroguaiaretic acid (NDGA), respectively. The stimulatory effects of MECA on PRL secretion persisted even after the addition of indomethacin, but not of NDGA, to the medium. MECA was unable to stimulate PRL secretion in the presence of dopamine, the strongest inhibitor of PRL release that works by inducing a decrease in adenylyl cyclase activity. Furthermore, the addition of adenosine (10 nM) mimicked the effects of MECA on PRL secretion, an effect that persisted regardless of the presence of LiCl (5 mM). The basal secretion of PRL was significatively reduced by LiCl, and restored by the concomitant addition of both LiCl and myo-inositol. These results indicate that PRL secretion is under a multifactorial regulatory mechanism, with the participation of different enzymes, including adenylyl cyclase, inositol-1-phosphatase, cyclooxygenase, and lipoxygenase. However, the increase in PRL secretion observed in the lactotroph in response to A2 adenosine receptor activation probably was mediated by mechanisms involving regulation of adenylyl cyclase, independent of membrane phosphoinositide synthesis or cyclooxygenase activity and partially dependent on lipoxygenase arachidonic acid-derived substances.