Receptor A2A de adenosina modula o transporte de glutamato independente de sodio em cultura primaria de celulas da retina

Abstract

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