Characterization of the effects of reactive oxygen species on GABAAα1β2 receptors.

LÓPEZ PAZOS, MANUEL I.; DEL VAS, MARIANA; BELTRÁN GONZÁLEZ, ANDREA N.; CALVO, DANIEL J.

San Luis

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

Soc Arg Biofísica

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 homomericGABAAρ1 receptors can be modulated by hydrogen peroxide (H2O2), ascorbic acid, glutathione and nitric oxide, through thiol modification of cysteines. Wealso identified endogenous redox agents that modulate GABAAreceptors involved in fast inhibitory neurotransmission in the retina and hippocampus, but the molecular mechanismsof actionremain elusive. We found earlier that H2O2modulates GABAAα1β2 receptors byusing heterologous expressionof these GABA-gated Cl-channels in Xenopuslaevis oocytes,followed by two-electrode voltage-clamp recordings of the GABA-evokedionic currents.Now, we further characterizedH2O2 effectsonGABAAα1β2responses.H2O2 induceddose-dependent, reversible and voltage-insensitivepotentiating effects, whichwere 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)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 beingperformedto elucidate the mechanisms of action underlying the effects of H2O2 on GABAAα1β2 receptors.Supported by ANPCyT and CONICET