Hydrogen peroxide-induced reduction of delayed rectifier potassium current in hippocampal neurons involves oxidation of sulfhydryl groups

Abstract This study examined the effect of H 2 O 2 on the delayed rectifier potassium current (IK DR ) in isolated hippocampal neurons. Whole-cell voltage-clamp experiments were performed on freshly dissociated hippocampal CA1 neurons of SD rats before and after treatment with H 2 O 2 . To reveal the mechanism behind H 2 O 2 -induced changes in IK DR , cells were treated with different oxidizing and reducing agents. External application of membrane permeable H 2 O 2 reduced the amplitude and voltage-dependence of IK DR in a concentration dependent manner. Desferoxamine (DFO), an iron-chelator that prevents hydroxyl radical ( OH) generation, prevented H 2 O 2 -induced reduction in IK DR . Application of the sulfhydryl-oxidizing agent 5,5 dithio-bis-nitrobenzoic acid (DTNB) mimicked the effect of H 2 O 2 . Sulfhydryl-reducing agents dithiothreitol (DTT) and glutathione (GSH) alone did not affect IK DR ; however, DTT and GSH reversed and prevented the H 2 O 2 -induced inhibition of IK DR, respectively. Membrane impermeable agents GSH and DTNB showed effects only when added intracellularly identifying intracellular sulfhydryl groups as potential targets for hydroxyl-mediated oxidation. However, the inhibitory effects of DTNB and H 2 O 2 at the positive test potentials were completely and partially abolished by DTT, respectively, suggesting an additional mechanism of action for H 2 O 2 , that is not shared by DTNB. In summary, this study provides evidence for the redox modulation of IK DR , identifies hydroxyl radical as an intermediate oxidant responsible for the H 2 O 2 -induced decrease in current amplitude and identifies intracellular sulfhydryl groups as an oxidative target.