Hydrogen peroxide induces vasorelaxation by enhancing 4-aminopyridine-sensitive Kv currents through <i>S</i> -glutathionylation

다국어 초록 (Multilingual Abstract)

<P>Hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>) is an endothelium-derived hyperpolarizing factor. Since opposing vasoactive effects have been reported for H<SUB>2</SUB>O<SUB>2</SUB> depending on the vascular bed and experimental conditions, this study was performed to assess whether H<SUB>2</SUB>O<SUB>2</SUB> acts as a vasodilator in the rat mesenteric artery and, if so, to determine the underlying mechanisms. H<SUB>2</SUB>O<SUB>2</SUB> elicited concentration-dependent relaxation in mesenteric arteries precontracted with norepinephrine. The vasodilatory effect of H<SUB>2</SUB>O<SUB>2</SUB> was reversed by treatment with dithiothreitol. H<SUB>2</SUB>O<SUB>2</SUB>-elicited vasodilation was significantly reduced by blocking 4-aminopyridine (4-AP)-sensitive Kv channels, but it was resistant to blockers of big-conductance Ca<SUP>2+</SUP>-activated K<SUP>+</SUP> channels and inward rectifier K<SUP>+</SUP> channels. A patch-clamp study in mesenteric arterial smooth muscle cells (MASMCs) showed that H<SUB>2</SUB>O<SUB>2</SUB> increased Kv currents in a concentration-dependent manner. H<SUB>2</SUB>O<SUB>2</SUB> speeded up Kv channel activation and shifted steady state activation to hyperpolarizing potentials. Similar channel activation was seen with oxidized glutathione (GSSG). The H<SUB>2</SUB>O<SUB>2</SUB>-mediated channel activation was prevented by glutathione reductase. Consistent with <I>S</I>-glutathionylation, streptavidin pull-down assays with biotinylated glutathione ethyl ester showed incorporation of glutathione (GSH) in the Kv channel proteins in the presence of H<SUB>2</SUB>O<SUB>2</SUB>. Interestingly, conditions of increased oxidative stress within MASMCs impaired the capacity of H<SUB>2</SUB>O<SUB>2</SUB> to stimulate Kv channels. Not only was the H<SUB>2</SUB>O<SUB>2</SUB> stimulatory effect much weaker, but the inhibitory effect of H<SUB>2</SUB>O<SUB>2</SUB> was unmasked. These data suggest that H<SUB>2</SUB>O<SUB>2</SUB> activates 4-AP-sensitive Kv channels, possibly through <I>S</I>-glutathionylation, which elicits smooth muscle relaxation in rat mesenteric arteries. Furthermore, our results support the idea that the basal redox status of MASMCs determines the response of Kv currents to H<SUB>2</SUB>O<SUB>2</SUB>.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1007/s00424-014-1513-3) contains supplementary material, which is available to authorized users.</P>