Hydrogen sulfide dilates rat mesenteric arteries by activating endothelial large-conductance Ca²⁺-activated K⁺ channels and smooth muscle Ca²⁺ sparks

Abstract

Jackson-Weaver O, Osmond JM, Riddle MA, Naik JS, Gonzalez Bosc LV, Walker BR, Kanagy NL. Hydrogen sulfide dilates rat mesenteric arteries by activating endothelial large-conductance Ca 2ϩ -activated K ϩ channels and smooth muscle Ca 2ϩ sparks. Am J Physiol Heart Circ Physiol 304: H1446 -H1454, 2013. First published March 22, 2013 doi:10.1152/ajpheart.00506.2012We have previously shown that hydrogen sulfide (H2S) reduces myogenic tone and causes relaxation of phenylephrine (PE)-constricted mesenteric arteries. This effect of H2S to cause vasodilation and vascular smooth muscle cell (VSMC) hyperpolarization was mediated by large-conductance Ca 2ϩ -activated potassium channels (BKCa). Ca 2ϩ sparks are ryanodine receptor (RyR)-mediated Ca 2ϩ -release events that activate BKCa channels in VSMCs to cause membrane hyperpolarization and vasodilation. We hypothesized that H2S activates Ca 2ϩ sparks in small mesenteric arteries. Ca 2ϩ sparks were measured using confocal microscopy in rat mesenteric arteries loaded with the Ca 2ϩ indicator fluo-4. VSMC membrane potential (Em) was measured in isolated arteries using sharp microelectrodes. In PE-constricted arteries, the H2S donor NaHS caused vasodilation that was inhibited by ryanodine (RyR blocker), abluminal or luminal iberiotoxin (IbTx, BKCa blocker), endothelial cell (EC) disruption, and sulfaphenazole [cytochrome P-450 2C (Cyp2C) inhibitor]. The H2S donor NaHS (10 mol/l) increased Ca 2ϩ sparks but only in the presence of intact EC and this was blocked by sulfaphenazole or luminal IbTx. Inhibiting cystathionine ␥-lyase (CSE)-derived H2S with ␤-cyano-L-alanine (BCA) also reduced VSMC Ca 2ϩ spark frequency in mesenteric arteries, as did EC disruption. However, excess CSE substrate homocysteine did not affect spark activity. NaHS hyperpolarized VSMC E m in PE-depolarized mesenteric arteries with intact EC and also hyperpolarized EC Em in arteries cut open to expose the lumen. This hyperpolarization was prevented by ryanodine, sulfaphenazole, and abluminal or luminal IbTx. BCA reduced IbTx-sensitive K ϩ currents in freshly dispersed mesenteric ECs. These results suggest that H2S increases Ca 2ϩ spark activity in mesenteric artery VSMC through activation of endothelial BKCa channels and Cyp2C, a novel vasodilatory pathway for this emerging signaling molecule.cytochrome P-450 epoxygenase; sodium hydrosulfide; membrane potential HYDROGEN SULFIDE (H 2 S) is a recently described vasodilator produced in the vasculature by the enzymes cystathionine ␥-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3MST). H 2 S has been proposed to cause vasodilation through a variety of mechanisms (1,3,26,33) and genetic knockout of the CSE gene causes hypertension (32). We previously reported that inhibiting CSE or disrupting the endothelium enhances myogenic tone in small mesenteric arteries from rats and that exogenous H 2 S hyperpolarizes vascular smooth muscle cell (VSMC) membrane potential (E m ) and dilates arteries through activation of large-conductance Ca 2ϩ -activated K (4) and ...

Involvement of Potassium Channels and Calcium-Independent Mechanisms in Hydrogen Sulfide-Induced Relaxation of Rat Mesenteric Small Arteries

“…Opening of K channels leads to reduced [Ca 21 ] i and vasodilation. NaHS and Na 2 S were found to activate calcium sparks and reduce global [Ca 21 ] i (Liang et al, 2012;Jackson-Weaver et al, 2013). In the present study, simultaneous measurements of [Ca 21 ] i in NE-contracted preparations revealed that NaHS lowered [Ca 21 ] i and induced relaxation and, as expected based on the calcium measurements, phosphorylation of MLC decreased compared with controls.…”

“…K ATP channels (Zhao and Wang, 2002;Tang et al, 2005;Webb et al, 2008), K V 7 channels (Schleifenbaum et al, 2010;Martelli et al, 2013;Hedegaard et al, 2014), and BK Ca (Liang et al, 2012;Jackson-Weaver et al, 2013) have been suggested to be involved in H 2 S vasodilatation. Glibenclamide, 4-aminopyridine (a blocker of voltage-gated K channels), and iberiotoxin (a blocker of BK Ca channels) failed to affect NaHS relaxation in our study.…”

“…Other potassium channels (K channels) have also been reported to play a role in H 2 S relaxation such as voltage-gated K channels (Cheang et al, 2010), K V 7 channels (Schleifenbaum et al, 2010;Martelli et al, 2013;Hedegaard et al, 2014), and large conductance calcium-activated potassium channels (BK Ca ) (Jackson-Weaver et al, 2011Li et al, 2012). It has been shown that the H 2 S donors NaHS and Na 2 S activate calcium sparks (Liang et al, 2012;Jackson-Weaver et al, 2013) and also that they reduce global [Ca 21 ] in cerebral arterioles (Liang et al, 2012). However, so far there have been no attempts to directly correlate vascular smooth muscle cell calcium to changes in vascular tone by simultaneous measurements of [Ca 21 ] i and relaxation.…”

Hydrogen Sulfide Attenuates sFlt1-Induced Hypertension and Renal Damage by Upregulating Vascular Endothelial Growth Factor

“…22,23 However, K ATP channel blockers do not completely abolish H 2 S-induced relaxation, and H 2 S stimulates vasorelaxation in an endothelial cell-dependent manner at lower doses. [24][25][26][27] This suggests that H 2 S likely stimulates vasorelaxation through additional pathways that have not yet been elucidated.…”

Ryanodine receptor 2 contributes to hemorrhagic shock-induced bi-phasic vascular reactivity in rats

“…In VSMCs, freeCaM binding with Ca 2+ could accelerate the formation of the CaM-CaM related kinase II (CaMK II) complex, a ubiquitous multifunctional serine/threonine kinase expressed in VSMCs as multimers of γ-and/or δ-sun units [29] , and increase MLCK activity and MLC20 phosphorylation, which contribute to vascular contraction [30] . However, Ca 2+ release located next to cytomembranes, also known as Ca 2+ spark, triggers the formation of STOCs [31] and activates the large conductance calcium activated potassium channel (BK Ca ), which at least partially contributes to the vascular hyporeactivity observed after hemorrhagic shock [32] . However, more research is required to determine whether the over-activation of RyR2-mediated Ca 2+ release during the early stage after hemorrhagic shock is coupled with the activation of CaM-CaMK II signal cascade and vascular hyperreactivity or whether the over-activation of RyR2-mediated Ca 2+ release during the late stage after hemorrhagic shock is linked to the BK Ca -dependent signaling pathway and the occurrence of vascular hyporeactivity.…”