Hydrogen Peroxide Increases K V Currents by Altering Intracellular Glutathione Redox Status in Rat Mesenteric Arterial Smooth Muscle Cell

Abstract

Hydrogen peroxide (H2O2) was reported as an endothelium-derived hyperpolarizing factor in mammalian arteries. However, the effect of H2O2 on voltage-gated K+ (KV) currents, which are reportedly the primary regulator of resting membrane potential in many arterial smooth muscles including rat mesenteric artery, is unclear. In this study, using whole-cell patch-clamp technique, we examined the effect of H2O2 on the Kv currents of rat mesenteric arterial smooth muscle cells (MASMCs). H2O2 increased the Kv currents in major portion of MASMCs, whereas a slight decreasing effect of H2O2 on the Kv currents was evident in minor portion of MASMCs. As a reason for this heterogeneity, we hypothesized that heterogeneity exists in the basal intracellular redox status of MASMCs and that the effects of H2O2 on the Kv currents are intracellular redox-dependent. Pipette application of either H2O2 or oxidized glutathione (GSSG) resulted in the increased Kv currents compared with control. Under that condition, subsequent bath application of H2O2 decreased the Kv currents. Pipette application of glutathione reductase and NADPH for blocking conversion of GSH to GSSG prevented the increasing effect of H2O2 on the Kv currents. In organ chamber mechanics experiment, bath application of H2O2 relaxed arterial rings precontracted with norepinephrine. Pretreatment of dithiothreitol, a thiol-specific reducing agent prevented the relaxation by H2O2. Present results indicate that H2O2 activates KV channels under reduced, physiologic conditions whereas it inhibits the channels under oxidized conditions in MASMCs. The glutathione redox system seems to primarily mediate the H2O2-regulation of the Kv channels. Key words: Hydrogen peroxide; Mesenteric arterial smooth muscle cell; Kv channels; Redox; Glutathione.