Characterization of the effects of reactive oxygen species on GABAAa1b2 receptors

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

San Luis

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Biofísica; 2019

Sociedad Argentina de Biofísica

Endogenous reactive oxygen species (ROS) were involved in neuronal signaling 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 found earlier that H2O2 modulates GABAAα1β2 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. Now, we further characterized H2O2 effects on GABAAα1β2 responses. H2O2 induced dose-dependent, reversible and voltage insensitive potentiating effects, which were 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 GABA Aα1β2 responses decreased as GABA concentration increased. Additional experiments are being performed to elucidate the mechanisms of action underlying the effects of H2O2 on GABAAα1β2 receptors.