Characterization of reactive oxygen species effects on GABAA receptors

LÓPEZ PAZOS MI; DEL VAS M; BELTRÁN GONZÁLEZ AN; CALVO DJ

Congreso; Reunión Anual de las Sociedades de Biociencias SAIC SAI SAFIS 2020; 2020

SAIC SAI SAFIS

Endogenous reactive oxygen species (ROS) were involved in neuronal signalling and plasticity, in normal physiology, aging and neurodegenerative disorders. Besides, GABAergic neurotransmission was shown to be sensitive to redox agents. We previously demonstrated that tonic responses mediated by homomeric GABAAρ1 receptors can be modulated by hydrogen peroxide (H2O2), ascorbic acid, glutathione and nitric oxide, through thiol modification of cysteines. We also identified endogenous redox agents that modulate GABAA receptors involved in fast inhibitory neurotransmission in the retina and hippocampus, but the molecular mechanisms of action remain elusive. We analysed the effect of H2O2 on different heteropentameric GABAA receptors by using heterologous expression of these GABA-gated Cl- channels in Xenopus laevis oocytes, followed by two-electrode voltage-clamp recordings of the GABA-evoked ionic currents. H2O2 induced dose-dependent, reversible and voltage-insensitive potentiating effects on GABAAα1β2 and GABAAα5β3 receptors. In contrast, GABAAα1β2γ2 and GABAAα5β3γ2 receptors activity were not altered during exposure to H2O2, suggesting that the γ2 subunit conferred a relative insensitivity to these endogenous redox agents. H2O2 effect on GABAAα1β2 was partially prevented by irreversible alkylation of sulphydryl groups with NEM. Concentration-response curves in the presence of H2O2, compared to control values, showed a leftward shift and an increase in the maximal response (EC50 GABA= 2.7(2.4 to 3.0) µM, nH=1.46±0.12; EC50 GABA+H2O2=1.9 (1.5 to 2.4) µM, nH=1.85±0.38). As observed for many redox agents acting on GABAAρ1 receptors, the degree of potentiation exerted by H2O2 on GABAAα1β2 responses decreased as GABA concentration increased. Additional experiments are being performed to elucidate the mechanisms of action underlying the effects of H2O2 on GABAA receptors.