Vascular KCNQ Potassium Channels as Novel Targets for the Control of Mesenteric Artery Constriction by Vasopressin, Based on Studies in Single Cells, Pressurized Arteries, and in Vivo Measurements of Mesenteric Vascular Resistance

Abstract

Pressor effects of the vasoconstrictor hormone arginine vasopressin (AVP), observed when systemic AVP concentrations are less than 100 pM, are important for the physiological maintenance of blood pressure, and they are also the basis for therapeutic use of vasopressin to restore blood pressure in hypotensive patients. However, the mechanisms by which circulating AVP induces arterial constriction are unclear. We examined the novel hypothesis that KCNQ potassium channels mediate the physiological vasoconstrictor actions of AVP. Reverse transcriptase polymerase chain reaction revealed expression of KCNQ1, KCNQ4, and KCNQ5 in rat mesenteric artery smooth muscle cells (MASMCs). Whole-cell perforated patch recordings of voltage-sensitive K ϩ (K v ) currents in freshly isolated MASMCs revealed 1,3-dihydro-1-phenyl-3,3-bis(4-pyridinylmethyl)-2H-indol-2-one (linopirdine)-and 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone (XE-991)-sensitive KCNQ currents that were electrophysiologically and pharmacologically distinct from other K v currents. Suppression of KCNQ currents by AVP (100 pM) was associated with significant membrane depolarization, and it was abolished by the protein kinase C (PKC) inhibitor calphostin C (250 nM). The KCNQ channel blocker linopirdine (10 M) inhibited KCNQ currents in MASMCs, and it induced constriction of isolated rat mesenteric arteries. The vasoconstrictor responses were not additive when combined with 30 pM AVP, and they were prevented by the L-type Ca 2ϩ channel blocker verapamil. Ethyl-N-[2-amino-6-(4-fluorophenylmethylamino)pyridin-3-yl] carbamic acid (flupirtine) significantly enhanced KCNQ currents, and it reversed constrictor responses to 30 pM AVP. In vivo, i.v. administration of linopirdine induced a dose-dependent increase in mesenteric artery resistance and blood pressure, whereas flupirtine had the opposite effects. We conclude that physiological concentrations of AVP induce mesenteric artery constriction via PKCdependent suppression of KCNQ currents and L-type Ca 2ϩ channel activation in MASMCs.Membrane voltage (V m ) determines the open probability of L-type Ca 2ϩ channels in vascular smooth muscle cells (VSMCs), and K ϩ channels represent a primary effector for adjusting V m . To the extent that Kϩ channels are open in resting VSMCs, the outward flux of K ϩ through these channels (measured as K ϩ current) will tend to stabilize the resting V m at negative (hyperpolarized) voltages and prevent opening of voltage-sensitive Ca 2ϩ channels. In contrast, reduction of outward K ϩ currents in VSMCs results in a shift to more positive V m (membrane depolarization) leading to activation of L-type Ca 2ϩ channels and entry of Ca 2ϩ into the cell. Elevation of the cytosolic Ca 2ϩ concentration in this manner can trigger VSMC contraction and vasoconstriction.KCNQ channels (Kv7 family) are voltage-sensitiveThis work was supported by the National Heart Lung and Blood Institute Grant R01 HL070670 (to K.L.B.) and the American Heart Association Grant 0715618Z (to A.R.M.).The chemical st...

Use of Patch Clamp Electrophysiology to Identify Off-Target Effects of Clinically Used Drugs

“…In support of our hypothesis, celecoxib induced concentration-dependent, endothelium-independent dilation of pre-constricted mesenteric arteries. Similar effects were obtained using known L-type Ca 2+ channel blockers or activators of Kv7 channels (not shown, but see (Henderson & Byron, 2007;Mackie et al, 2008)). The maximum dilatory effect of celecoxib was achieved at a concentration of 20 µM; neither rofecoxib nor diclofenac induced significant artery dilation at the same concentration ( Figure 2B).…”

Heteromerization of chemokine (C-X-C motif) receptor 4 with α1A/B-adrenergic receptors controls α1-adrenergic receptor function

“…HeLa cells were as described (70). Rat aortic and mesenteric artery VSMC were isolated from male Lewis and Sprague-Dawley rats as described elsewhere (71)(72)(73). All procedures involving rats were in accordance with the Guide for the Care and Use of Laboratory Animals and approved by the Institutional Animal Care and Use Committee of Loyola University Chicago.…”

Facilitation of sympathetic neurotransmission by phosphatidylinositol-4,5-bisphosphate-dependent regulation of KCNQ channels in rat mesenteric arteries

“…In vascular smooth muscle cells, KCNQ1, KCNQ4 and KCNQ5 are predominantly expressed with a minimal contribution of KCNQ2 and KCNQ3. [46][47][48] In addition, Jepps et al 49 recently demonstrated that KCNQ channel activators induce arterial relaxation, and the expression of KCNQ4 is decreased in the vascular smooth muscle cells of hypertensive rodent models. The present study also suggested that perivascular sympathetic neurotransmission might also be influenced by KCNQ channels in rat mesenteric arteries.…”