NO ⁻ Activates Soluble Guanylate Cyclase and K _v Channels to Vasodilate Resistance Arteries

Abstract

Abstract-Nitric oxide (NO) plays an important role in the control of vascular tone. Traditionally, its vasorelaxant activity has been attributed to the free radical form of NO (NO ⅷ ), yet the reduced form of NO (NO Ϫ ) is also produced endogenously and is a potent vasodilator of large conduit arteries. The effects of NO Ϫ in the resistance vasculature remain unknown. This study examines the activity of NO Ϫ in rat small isolated mesenteric resistance-like arteries and characterizes its mechanism(s) of action. With the use of standard myographic techniques, the vasorelaxant properties of NO ⅷ (NO gas solution), NO Ϫ (Angeli's salt), and the NO donor sodium nitroprusside were compared. Relaxation responses to Angeli's salt (pEC 50 ϭ7.51Ϯ0.13, R max ϭ95.5Ϯ1.5%) were unchanged in the presence of carboxy-PTIO (NO ⅷ scavenger) but those to NO ⅷ and sodium nitroprusside were inhibited. L-Cysteine (NO Ϫ scavenger) decreased the sensitivity to Angeli's salt (PϽ0.01) and sodium nitroprusside (PϽ0.01) but not to NO ⅷ . The soluble guanylate cyclase inhibitor ODQ (3 and 10 mol/L) concentration-dependently inhibited relaxation responses to Angeli's salt (41.0Ϯ6.0% versus control 93.4Ϯ1.9% at 10 mol/L). The voltage-dependent K ϩ channel inhibitor 4-aminopyridine (1 mmol/L) caused a 9-fold (PϽ0.01) decrease in sensitivity to Angeli's salt, whereas glibenclamide, iberiotoxin, charybdotoxin, and apamin were without effect. In combination, ODQ and 4-aminopyridine abolished the response to Angeli's salt. In conclusion, NO Ϫ functions as a potent vasodilator of resistance arteries, mediating its response independently of NO , which mediates vascular smooth muscle relaxation predominantly through the activation of soluble guanylate cyclase and subsequent accumulation of cGMP. 1 NO, however, can also exist in the oxidized state as the nitrosonium cation (NO ϩ ) and in the reduced state as the nitroxyl anion (NO Ϫ ). Little attention has been afforded to the biological activity of these alternative redox forms of NO, yet recent findings that the nitroxyl anion is produced endogenously 2,3 and displays relaxant activity within the vasculature 4,5 highlights a possible physiological role for this nitrogen oxide species. NO Ϫ can be generated directly from the enzymatic activity of NO synthase (NOS) 2,3 such that NOS-catalyzed oxidation of L-arginine results in the production of NO Ϫ , which is further oxidized to NO ⅷ by superoxide dismutase. In addition, NO Ϫ can also be formed during oxidation of the decoupled NOS product N-hydroxy-L-arginine, 6,7 from NOS in the absence of tetrahydrobiopterin, 8 after the decomposition of S-nitrosothiols 9,10 and peroxynitrite 11 and from the reduction of NO ⅷ by mitochondrial cytochrome c. 12 The biological activity of NO Ϫ can be studied by using NO Ϫ donors such as Angeli's salt. Of particular interest is the identification of NO Ϫ as a potent vasodilator, mediating relaxation of large isolated conduit arteries, 4,5,13 exerting dilator activity in the intact pulmonary vascular bed, 14 and decreas...

Involvement of Guanylate Cyclase and K+ Channels in Relaxation Evoked by Ferulate Nitrate in Rat Aorta Artery

“…It suggests that neither K ATP nor K V channels are involved in the pathway by which FLNT produces a relaxation of the rat aorta artery. These findings are in agreement with the previous report that 4-AP and GLM did not antagonize the vasorelaxant effects induced by NO donors in rat aorta artery (3), but not in agreement with other reports that NO or NO donor has been found to activate K ATP channels or K V channels in rabbit mesenteric arteries (38), human umbilical artery (39), or rat small mesenteric arteries (19); these discrepancies may be due to the variations in the K + channel distribution or receptor sensitivity in smooth muscle cells among the different species or tissues (40 -42). In addition, comparative studies show that relaxation responses to nicorandil are inhibited significantly by the K ATP blocker GLM, but not by the other K + -channel blocker.…”

“…To determine whether the effect of FLNT and nicorandil on K + channels is sGC/cGMP pathway-dependent or -independent, we studied the effect of BaCl 2 (1 μM), CHT or GLM and ODQ (10 μM) in combination on the rat aorta rings, as described previously (19).…”

Generation of nitroxyl by heme protein-mediated peroxidation of hydroxylamine but not N-hydroxy-L-arginine

“…Certainly, HNO donors have been shown to be effective pharmacology agents both in vitro and in vivo for a variety of conditions ranging from treatment of congestive heart failure to alcoholism (e.g. [1][2][3][4][5][6][7][8][9][58][59][60][61][62][63][64][65]), despite high levels of cytoplasmic GSH.…”

“…While HNO can induce early preconditioning-like effects that protect heart tissue against ischemia-reperfusion injury [3], the outcome is dependent upon the timing of administration [4]. In addition, HNO regulates calcium channels, both in the cardiovascular and nervous systems [5][6][7][8][9][10]. These responses to HNO are often discrete from those of its redox cousin nitric oxide (NO) [11,12].…”

A near-infrared fluorescent probe for the selective detection of HNO in living cells and in vivo

“…1 HNO may possess some unique and favorable properties, which are relevant in the treatment of cardiovascular disorders such as angina, acute hypertensive crises and atherosclerosis. 1 Some reports confirm that Angeli's salt (an HNO donor) is a potent vasodilator both in vitro and in vivo, which can elicit vasorelaxation in an isolated large conduits, [2][3][4][5] small resistance arteries 6 and intact coronary vessels. 7 In addition, HNO demonstrates distinct actions on myocardial contractile function that differ from NO.…”