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Alyson A Miller,
Kate F Maxwell,
Sophocles Chrissobolis,
Michelle L Bullen,
B Biomed,
Jacqueline M Ku,
T Michael De Silva,
Stavros Selemidis,
Elizabeth U Hooker,
Grant R Drummond,
Christopher G Sobey, Barbara K Kemp-Harper
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ABSTRACT: Nox2 oxidase activity underlies the oxidative stress and vascular dysfunction associated with several vascular-related diseases. We have reported that nitric oxide (NO.) decreases reactive oxygen species production by endothelial Nox2 oxidase. This study tested the hypothesis that nitroxyl (HNO), the redox sibling of NO., also suppresses vascular Nox2 oxidase activity. Specifically, we examined the influence of two well-characterized HNO donors, Angeli's salt and isopropylamine NONOate (IPA/NO), on Nox2 oxidase-dependent responses to angiotensin II (reactive oxygen species production and vasoconstriction) in mouse cerebral arteries. Angiotensin II (0.1μmol/L)-stimulated superoxide (measured by lucigenin-enhanced chemiluminescence) and hydrogen peroxide (Amplex Red fluorescence) levels in cerebral arteries (pooled basilar and middle cerebral [MCA]) from wild-type (WT) mice were ~60% lower (P<0.05) in the presence of either Angeli's salt (1μmol/L) or IPA/NO (1μmol/L). Similarly, phorbyl 12,13-dibutyrate (10μmol/L; Nox2 activator)-stimulated hydrogen peroxide levels were ~40% lower in the presence of IPA/NO (1μmol/L; P<0.05). The ability of IPA/NO to decrease superoxide levels was reversible and abolished by the HNO scavenger L-cysteine (3mmol/L; P<0.05), but was unaffected by hydroxocobalamin (100μmol/L; NO. scavenger), ODQ (10μmol/L; soluble guanylyl cyclase [sGC] inhibitor), or Rp-8-pCPT-cGMPs (10μmol/L; cyclic guanosine monophosphate [cGMP]-dependent protein kinase inhibitor). Angiotensin II-stimulated superoxide was substantially less in arteries from Nox2-deficient (Nox2-/y) versus WT mice (P<0.05). In contrast to WT, IPA/NO (1μmol/L) had no effect on superoxide levels in arteries from Nox2-/y mice. Finally, angiotensin II (1-1000μmol/L)-induced constriction of WT MCA was virtually abolished by IPA/NO (1μmol/L), whereas constrictor responses to either the thromboxane A2 mimetic U46619 (1-100nmol/L) or high potassium (122.7mmol/L) were unaffected. In conclusion, HNO suppresses vascular Nox2 oxidase activity via a sGC-cGMP-independent pathway. Thus, HNO donors might be useful therapeutic agents to limit and/or prevent Nox2 oxidase-dependent vascular dysfunction.
Free radical biology & medicine 02/2013; · 5.42 Impact Factor
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BMC Pharmacology 04/2012; 7:1-1.
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ABSTRACT: BACKGROUND: Although evidence now suggests cGMP is a negative regulator of cardiac hypertrophy, the direct consequences of the soluble guanylyl cyclase (sGC) activator BAY 58-2667 on cardiac remodeling, independent of changes in hemodynamic load, has not been investigated. In the present study, we tested the hypothesis that the NO(•)-independent sGC activator BAY 58-2667 inhibits cardiomyocyte hypertrophy in vitro. Concomitant impact of BAY 58-2667 on cardiac fibroblast proliferation, and insights into potential mechanisms of action, were also sought. Results were compared to the sGC stimulator BAY 41-2272. METHODS: Neonatal rat cardiomyocytes were incubated with endothelin-1 (ET(1), 60nmol/L) in the presence and absence of BAY 41-2272 and BAY 58-2667 (0.01-0.3 µmol/L). Hypertrophic responses and its triggers, as well as cGMP signaling, were determined. The impact of both sGC ligands on basal and stimulated cardiac fibroblast proliferation in vitro was also determined. RESULTS: We now demonstrate that BAY 58-2667 (0.01-0.3 µmol/L) elicited concentration-dependent antihypertrophic actions, inhibiting ET(1)-mediated increases in cardiomyocyte 2D area and de novo protein synthesis, as well as suppressing ET(1)-induced cardiomyocyte superoxide generation. This was accompanied by potent increases in cardiomyocyte cGMP accumulation and activity of its downstream signal, vasodilator-stimulated phosphoprotein (VASP), without elevating cardiomyocyte cAMP. In contrast, submicromolar concentrations of BAY 58-2667 had no effect on basal or stimulated cardiac fibroblast proliferation. Indeed, only at concentrations ≥10 µmol/L was inhibition of cardiac fibrosis seen in vitro. The effects of BAY 58-2667 in both cell types were mimicked by BAY 41-2272. CONCLUSIONS: Our results demonstrate that BAY 58-2667 elicits protective, cardiomyocyte-selective effects in vitro. These actions are associated with sGC activation and are evident in the absence of confounding hemodynamic factors, at low (submicromolar) concentrations. Thus this distinctive sGC ligand may potentially represent an alternative therapeutic approach for limiting myocardial hypertrophy.
PLoS ONE 01/2012; 7(11):e44481. · 4.09 Impact Factor
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ABSTRACT: New therapeutic targets for cardiac hypertrophy, an independent risk factor for heart failure and death, are essential. HNO is a novel redox sibling of NO• attracting considerable attention for the treatment of cardiovascular disorders, eliciting cGMP-dependent vasodilatation yet cGMP-independent positive inotropy. The impact of HNO on cardiac hypertrophy (which is negatively regulated by cGMP) however has not been investigated.
Neonatal rat cardiomyocytes were incubated with angiotensin II (Ang II) in the presence and absence of the HNO donor Angeli's salt (sodium trioxodinitrate) or B-type natriuretic peptide, BNP (all 1 µmol/L). Hypertrophic responses and its triggers, as well as cGMP signaling, were determined.
We now demonstrate that Angeli's salt inhibits Ang II-induced hypertrophic responses in cardiomyocytes, including increases in cardiomyocyte size, de novo protein synthesis and β-myosin heavy chain expression. Angeli's salt also suppresses Ang II induction of key triggers of the cardiomyocyte hypertrophic response, including NADPH oxidase (on both Nox2 expression and superoxide generation), as well as p38 mitogen-activated protein kinase (p38MAPK). The antihypertrophic, superoxide-suppressing and cGMP-elevating effects of Angeli's salt were mimicked by BNP. We also demonstrate that the effects of Angeli's salt are specifically mediated by HNO (with no role for NO• or nitrite), with subsequent activation of cardiomyocyte soluble guanylyl cyclase (sGC) and cGMP signaling (on both cGMP-dependent protein kinase, cGK-I and phosphorylation of vasodilator-stimulated phosphoprotein, VASP).
Our results demonstrate that HNO prevents cardiomyocyte hypertrophy, and that cGMP-dependent NADPH oxidase suppression contributes to these antihypertrophic actions. HNO donors may thus represent innovative pharmacotherapy for cardiac hypertrophy.
PLoS ONE 01/2012; 7(4):e34892. · 4.09 Impact Factor
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ABSTRACT: Nitroxyl (HNO), the one electron reduced and protonated form of nitric oxide (NO(•)), is rapidly emerging as a novel nitrogen oxide with distinct pharmacology and therapeutic advantages over its redox sibling. Whilst the cardioprotective effects of HNO in heart failure have been established, it is apparent that HNO may also confer a number of vasoprotective properties. Like NO(•), HNO induces vasodilatation, inhibits platelet aggregation, and limits vascular smooth muscle cell proliferation. In addition, HNO can be putatively generated within the vasculature, and recent evidence suggests it also serves as an endothelium-derived relaxing factor (EDRF). Significantly, HNO targets signaling pathways distinct from NO(•) with an ability to activate K(V) and K(ATP) channels in resistance arteries, cause coronary vasodilatation in part via release of calcitonin-gene related peptide (CGRP), and exhibits resistance to scavenging by superoxide and vascular tolerance development. As such, HNO synthesis and bioavailability may be preserved and/or enhanced during disease states, in particular those associated with oxidative stress. Moreover, it may compensate, in part, for a loss of NO(•) signaling. Here we explore the vasoprotective actions of HNO and discuss the therapeutic potential of HNO donors in the treatment of vascular dysfunction.
Antioxidants & Redox Signaling 05/2011; 14(9):1675-86. · 8.20 Impact Factor
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ABSTRACT: Nitroxyl (HNO) displays distinct pharmacology to its redox congener nitric oxide (NO(•)) with therapeutic potential in the treatment of heart failure. It remains unknown if HNO donors are resistant to tolerance development following chronic in vivo administration. Wistar-Kyoto rats received a 3-day subcutaneous infusion of one of the NO(•) donors, glyceryl trinitrate (GTN) or diethylamine/NONOate (DEA/NO), or the HNO donor Angeli's salt (AS). GTN infusion (10 μg/kg/min) resulted in significantly blunted depressor responses to intravenous bolus doses of GTN, demonstrating tolerance development. By contrast, infusion with AS (20 μg/kg/min) or DEA/NO (2 μg/kg/min) did not alter their subsequent depressor responses. Similarly, ex vivo vasorelaxation responses in isolated aortae revealed that GTN infusion elicited a significant 6-fold decrease in the sensitivity to GTN and reduction in the maximum response to acetylcholine (ACh). Chronic infusion of AS or DEA/NO had no effect on subsequent vasorelaxation responses to themselves or to ACh. No functional cross-tolerance between nitrovasodilators was evident, either in vivo or ex vivo, although an impaired ability of a nitrovasodilator to increase tissue cGMP content was not necessarily indicative of a reduced functional response. In conclusion, HNO donors may represent novel therapies for cardiovascular disease with therapeutic potential over clinically used organic nitrates.
Antioxidants & Redox Signaling 05/2011; 14(9):1615-24. · 8.20 Impact Factor
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ABSTRACT: Maintenance of vascular tone by the endothelium involves the production of endothelium-derived nitric oxide (NO). NO, produced from endothelial nitric oxide synthase diffuses to the underlying smooth muscle to stimulate soluble guanylate cyclase, resulting in increased cyclic GMP levels, and subsequent smooth muscle relaxation and blood vessel dilatation. Endothelial dysfunction, manifested as diminished NO bioavailability, is a common feature of a number of vascular-related diseases.. Oxidative stress can be defined as an imbalance between reactive oxygen species (ROS) production and/or impaired ROS metabolism that favours them being present in excess of physiological levels. Oxidative stress can negatively impact many cell types, including in the vasculature. There is now a wealth of evidence suggesting that oxidative stress is a major cause of endothelial dysfunction in the cerebral circulation. This review will summarize disease models in which both oxidative stress and endothelial dysfunction occur in the cerebral circulation, namely hypertension involving angiotensin II (Ang II), diabetes, subarachnoid hemorrhage, stroke and Alzheimer's disease. Molecular mechanisms by which oxidative stress occurs, (eg increased NADPH-oxidase activity) will also be discussed.
Frontiers in Bioscience 01/2011; 16:1733-45. · 3.52 Impact Factor
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ABSTRACT: Left ventricular hypertrophy (LVH), an increased left ventricular (LV) mass, is common to many cardiovascular disorders, initially developing as an adaptive response to maintain myocardial function. In the longer term, this LV remodelling becomes maladaptive, with progressive decline in LV contractility and diastolic function. Indeed LVH is recognised as an important blood-pressure independent predictor of cardiovascular morbidity and mortality. The clinical efficacy of current treatments for LVH is reduced, however, by their tendency to slow disease progression rather than induce its reversal, and thus the development of new therapies for LVH is paramount. The signalling molecule cyclic guanosine-3′,5′-monophosphate (cGMP), well-recognised for its role in regulating vascular tone, is now being increasingly identified as an important anti-hypertrophic mediator. This review is focused on the various means by which cGMP can be stimulated in the heart, such as via the natriuretic peptides, to exert anti-hypertrophic actions. In particular we address the limitations of traditional nitric oxide (NO•) donors in the face of the potential therapeutic advantages offered by novel alternatives; NO• siblings, ligands of the cGMP-generating enzymes, soluble (sGC) and particulate guanylyl cyclases (pGC), and phosphodiesterase inhibitors. Further impact of cGMP within the cardiovascular system is also discussed with a view to representing cGMP-based therapies as innovative pharmacotherapy, alone or concurrent with standard care, for the management of LVH.
Pharmacology & Therapeutics. 08/2009; 124(3):279-300.
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ABSTRACT: Background and purpose: Nitroxyl (HNO) is emerging as an important regulator of vascular tone as it is potentially produced endogenously and dilates conduit and resistance arteries. This study investigates the contribution of endogenous HNO to endothelium-dependent relaxation and hyperpolarization in resistance arteries.Experimental approach: Rat and mouse mesenteric arteries were mounted in small vessel myographs for isometric force and smooth muscle membrane potential recording.Key results: Vasorelaxation to the HNO donor, Angeli's salt, was attenuated in both species by the soluble guanylate cyclase inhibitor (ODQ, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one), the voltage-dependent K+ channel inhibitor, 4-aminopyridine (4-AP) and the HNO scavenger, l-cysteine. In mouse mesenteric arteries, nitric oxide (NO) synthase inhibition (with l-NAME, Nω-Nitro-L-arginine methyl ester) markedly attenuated acetylcholine (ACh)-mediated relaxation. Scavenging the uncharged form of NO (NO•) with hydroxocobalamin (HXC) or HNO with l-cysteine, or 4-AP decreased the sensitivity to ACh, and a combination of HXC and l-cysteine reduced ACh-mediated relaxation, as did l-NAME alone. ACh-induced hyperpolarizations were significantly attenuated by 4-AP alone and in combination with l-NAME. In rat mesenteric arteries, blocking the effects of endothelium-derived hyperpolarizing factor (EDHF) (charybdotoxin and apamin) decreased ACh-mediated relaxation 10-fold and unmasked a NO-dependent component, mediated equally by HNO and NO•, as HXC and l-cysteine in combination now abolished vasorelaxation to ACh. Furthermore, ACh-evoked hyperpolarizations, resistant to EDHF inhibition, were virtually abolished by 4-AP.Conclusions and implications: The factors contributing to vasorelaxation in mouse and rat mesenteric arteries are NO• = HNO > EDHF and EDHF > HNO = NO• respectively. This study identified HNO as an endothelium-derived relaxing and hyperpolarizing factor in resistance vessels.British Journal of Pharmacology (2009) 157, 540–550; doi:10.1111/j.1476-5381.2009.00150.x; published online 26 March 2009This article is commented on by Martin, pp. 537–539 of this issue and is part of a themed section on Endothelium in Pharmacology. For a list of all articles in this section see the end of this paper, or visit: http://www3.interscience.wiley.com/journal/121548564/issueyear?year=2009
British Journal of Pharmacology 03/2009; 157(4):540 - 550. · 4.41 Impact Factor
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ABSTRACT: The free radical form of nitric oxide (NO(.)) is a well-known mediator of vascular tone. What is not so well recognized is that NO(.) exists in several different redox forms. There is considerable evidence that NO(.) and its one-electron reduction product, nitroxyl (HNO), have pharmacologically distinct actions that extend into the regulation of the vasculature. The aim of this study was to compare the vasorelaxation mechanisms of HNO and NO(.), including an examination of the ability of these redox variants to hyperpolarize and repolarize vascular smooth muscle cells from rat mesenteric arteries. The HNO donor Angeli's salt (0.1 nM-10 microM) caused a concentration-dependent hyperpolarization of vessels at resting tone and a simultaneous, concentration-dependent vasorelaxation and repolarization of vessels precontracted and depolarized with methoxamine. Both vasorelaxation and repolarization responses to Angeli's salt were significantly attenuated by both the HNO scavenger l-cysteine (3 mM) and the voltage-dependent K(+) (K(v)) channel inhibitor 4-aminopyridine (4-AP; 1 mM) and virtually abolished by the soluble guanylate cyclase (sGC) inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 10 microM) or 30 mM K(+). In contrast, NO(.) (0.01-1 microM) repolarized arteries to a lesser extent than HNO, and these responses were resistant to inhibition by ODQ (10 microM) and 4-AP (1 mM). Blockade of K(v) channels (1 mM 4-AP) also significantly inhibited the repolarization response to YC-1 (0.1-10 microM), confirming a role for sGC/cGMP in the activation of K(v) channels in this preparation. We conclude that HNO causes vasorelaxation via a cGMP-dependent activation of K(v) channels and that there are different profiles of vasorelaxant activity for the redox siblings HNO and NO(.).
AJP Heart and Circulatory Physiology 03/2009; 296(5):H1274-80. · 3.71 Impact Factor
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ABSTRACT: Until recently, most of the biological effects of nitric oxide (NO) have been attributed to its uncharged state (NO*), yet NO can also exist in the reduced state as nitroxyl (HNO or NO(-)). Putatively generated from both NO synthase (NOS)-dependent and -independent sources, HNO is rapidly emerging as a novel entity with distinct pharmacology and therapeutic advantages over its redox sibling, NO*. Thus, unlike NO*, HNO can target cardiac sarcoplasmic ryanodine receptors to increase myocardial contractility, can interact directly with thiols and is resistant to both scavenging by superoxide (*O2-) and tolerance development. HNO donors are protective in the setting of heart failure in which NO donors have minimal impact. Here, we discuss the unique pharmacology of HNO versus NO* and highlight the therapeutic potential of HNO donors in the treatment of cardiovascular disease.
Trends in Pharmacological Sciences 11/2008; 29(12):601-8. · 10.93 Impact Factor
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ABSTRACT: We determined whether nitric oxide (NO) counters the development of hypertension at the onset of diabetes in mice, whether this is dependent on endothelial NO synthase (eNOS), and whether non-NO endothelium-dependent vasodilator mechanisms are altered in diabetes in mice. Male mice were instrumented for chronic measurement of mean arterial pressure (MAP). In wild-type mice, MAP was greater after 5 wk of N(omega)-nitro-L-arginine methyl ester (L-NAME; 100 mg x kg(-1) x day(-1) in drinking water; 97 +/- 3 mmHg) than after vehicle treatment (88 +/- 3 mmHg). MAP was also elevated in eNOS null mice (113 +/- 4 mmHg). Seven days after streptozotocin treatment (200 mg/kg iv) MAP was further increased in L-NAME-treated mice (108 +/- 5 mmHg) but not in vehicle-treated mice (88 +/- 3 mmHg) nor eNOS null mice (104 +/- 3 mmHg). In wild-type mice, maximal vasorelaxation of mesenteric arteries to acetylcholine was not altered by chronic L-NAME or induction of diabetes but was reduced by 42 +/- 6% in L-NAME-treated diabetic mice. Furthermore, the relative roles of NO and endothelium-derived hyperpolarizing factor (EDHF) in acetylcholine-induced vasorelaxation were altered; the EDHF component was enhanced by L-NAME and blunted by diabetes. These data suggest that NO protects against the development of hypertension during early-stage diabetes in mice, even in the absence of eNOS. Furthermore, in mesenteric arteries, diabetes is associated with reduced EDHF function, with an apparent compensatory increase in NO function. Thus, prior inhibition of NOS results in endothelial dysfunction in early diabetes, since the diabetes-induced reduction in EDHF function cannot be compensated by increases in NO production.
AJP Regulatory Integrative and Comparative Physiology 09/2007; 293(2):R707-13. · 3.34 Impact Factor
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ABSTRACT: Endothelial NADPH oxidase is a major source of superoxide in blood vessels and is implicated in the oxidative stress accompanying vascular diseases, including atherosclerosis. Here we investigate the regulation of NADPH oxidase activity by nitric oxide (NO).
Human cultured microvascular endothelial cells (HMEC-1) were treated with the NO donors, diethylenetriamine (DETA)-NONOate, S-nitroso-N-acetylpenicillamine (SNAP) or sodium nitroprusside (SNP) for 0.5-24 h. Superoxide production was measured by lucigenin chemiluminescence and dihydroethidium fluorescence, while NADPH oxidase subunit expression was measured via Western blotting. S-nitrosylation was assessed using the 2,3-diaminonapthalene (DAN) assay, and via immunoblotting with an anti-nitrosocysteine antibody.
Specific siRNA reduced Nox2 and Nox4 protein expression and markedly decreased superoxide production in HMEC-1. DETA-NONOate (10-300 micromol/L) suppressed superoxide production in HMEC-1 in a concentration- and time-dependent manner, which was not entirely attributable to stoichiometric reaction with NO, for the effect was observed more than 6 h after removing DETA-NONOate from solution. Similarly, sustained attenuation of superoxide production was achieved with SNP (10-100 micromol/L) and SNAP (10-100 micromol/L). The suppressive effect of NO was not dependent on (1) the sGC/cGMP/PKG pathway, (2) peroxynitrite-formation, (3) reduced protein expression of NADPH oxidase subunits or (4) dissociation of NADPH oxidase subunits. Treatment with NO caused S-nitrosylation of the crucial organizer subunit p47phox, and de-nitrosylation with UV light restored superoxide production.
NO causes sustained suppression of NADPH oxidase-dependent superoxide production in human endothelial cells by S-nitrosylation of p47phox. These findings highlight a novel approach by which vascular oxidative stress might be suppressed by NO donors.
Cardiovascular Research 08/2007; 75(2):349-58. · 6.06 Impact Factor
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ABSTRACT: The nitroxyl anion (HNO) is emerging as a novel regulator of cardiovascular function with therapeutic potential in the treatment of diseases such as heart failure. It remains unknown whether tolerance develops to HNO donors, a limitation of currently used nitrovasodilators. The susceptibility of the HNO donor, Angeli's salt (AS), to the development of vascular tolerance was compared with the NO donors, glyceryl trinitrate (GTN) and diethylamine/NONOate (DEA/NO) in rat isolated aortae. Vasorelaxation to AS was attenuated (P<0.01) by the HNO scavenger l-cysteine, whereas the sensitivity to GTN and DEA/NO was decreased (P<0.01) by the NO. scavenger carboxy-[2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidozoline-1-oxy-3-oxide]. The soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one impaired responses to GTN>or=AS>DEA/NO. Pretreatment with 10, 30, and 100 micromol/L of GTN for 60 minutes induced a 4- (P<0.05), 13- (P<0.01), and 48-fold (P<0.01) decrease in sensitivity to GTN, demonstrating tolerance development. In contrast, pretreatment with AS or DEA/NO (10, 30, and 100 micromol/L) did not alter their subsequent vasorelaxation. All of the nitrovasodilators (30 micromol/L) displayed a similar time course of vasorelaxation and cGMP accumulation over a 60-minute period. Unlike vasorelaxation, the magnitude of peak cGMP accumulation differed substantially: DEA/NO>AS>GTN. GTN did not induce cross-tolerance to either AS or DEA/NO. In contrast, pre-exposure to DEA/NO, but not AS, caused a concentration-dependent attenuation (P<0.01) of GTN-mediated relaxation, which was negated by the protein kinase G inhibitor guanosine 3',5'-cyclic monophosphorothioate, 8-(4-chlorophenylthio)-,Rp-isomer, triethylammonium salt. In conclusion, vascular tolerance does not develop to HNO, nor does cross-tolerance between HNO and GTN occur. Thus, HNO donors may have therapeutic advantages over traditional nitrovasodilators.
Hypertension 04/2007; 49(4):885-92. · 6.21 Impact Factor
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ABSTRACT: The nitroxyl anion (HNO) is the one-electron reduction product of NO(). This redox variant has been shown to be endogenously produced and to have effects that are pharmacologically distinct from NO(). This study investigates the vasodilator and chronotropic effects of HNO in the rat isolated coronary vasculature.
Sprague-Dawley rat hearts were retrogradely perfused with Krebs' solution (8 ml/min) using the Langendorff technique. Perfusion pressure was raised using a combination of infusion of phenylephrine and bolus additions of the thromboxane mimetic U46619 to attain a baseline perfusion pressure of 100-120 mm Hg. The vasodilator effects of a nitroxyl anion donor, Angeli's salt, were examined in the absence and presence of HNO and NO* scavengers, K+ channel inhibition, and soluble guanylate cyclase (sGC) inhibition. In addition, the inotropic and chronotropic effects of Angeli's salt were examined in hearts at resting perfusion pressure (50-60 mm Hg) and compared to responses evoked by acetylcholine and isoprenaline.
Angeli's salt causes a potent and reproducible vasodilatation in isolated perfused rat hearts. This response is unaffected by the NO* scavenger hydroxocobalamin (0.1 mM) but is significantly inhibited by the HNO scavenger N-acetyl-L-cysteine (4 mM), suggesting that HNO is the mediator of the observed responses. Vasodilatation responses to Angeli's salt were virtually abolished in the presence of the sGC inhibitor ODQ (10 microM). The magnitude of the vasodilatation response to Angeli's salt was significantly reduced in the presence of 30 mM K+, 10 microM glibenclamide and in the presence of the calcitonin gene-related peptide (CGRP) antagonist CGRP((8-37)) (0.1 microM). Angeli's salt had little effect on heart rate or force of contraction, whilst isoprenaline and acetylcholine elicited significant positive and negative cardiotropic effects, respectively.
The HNO donor Angeli's salt elicits a potent and reproducible vasodilatation response. The results suggest that the response is elicited by HNO through sGC-mediated CGRP release and K(ATP) channel activation.
Cardiovascular Research 03/2007; 73(3):587-96. · 6.06 Impact Factor
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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*), yet the reduced form of NO (NO-) is also produced endogenously and is a potent vasodilator of large conduit arteries. The effects of NO- in the resistance vasculature remain unknown. This study examines the activity of NO- 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* (NO gas solution), NO- (Angeli's salt), and the NO donor sodium nitroprusside were compared. Relaxation responses to Angeli's salt (pEC50=7.51+/-0.13, Rmax=95.5+/-1.5%) were unchanged in the presence of carboxy-PTIO (NO* scavenger) but those to NO* and sodium nitroprusside were inhibited. l-Cysteine (NO- scavenger) decreased the sensitivity to Angeli's salt (P<0.01) and sodium nitroprusside (P<0.01) but not to NO*. The soluble guanylate cyclase inhibitor ODQ (3 and 10 micromol/L) concentration-dependently inhibited relaxation responses to Angeli's salt (41.0+/-6.0% versus control 93.4+/-1.9% at 10 micromol/L). The voltage-dependent K+ channel inhibitor 4-aminopyridine (1 mmol/L) caused a 9-fold (P<0.01) 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- functions as a potent vasodilator of resistance arteries, mediating its response independently of NO* and through the activation of soluble guanylate cyclase and voltage-dependent K+ channels. NO- donors may represent a novel class of nitrovasodilator relevant for the treatment of cardiovascular disorders such as angina.
Hypertension 06/2003; 41(6):1301-7. · 6.21 Impact Factor
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ABSTRACT: 1. Under normal conditions, the endothelium plays a major role in the maintenance of vasodilatory tone via the production of endothelium-derived vasodilator agents, such as prostacyclin, nitric oxide and endothelium-derived hyperpolarizing factor (EDHF). Inhibition of endothelium-dependent relaxation features prominently in a range of cardiovascular diseases, including hypertension, coronary artery disease and diabetes. 2. Endothelium-derived hyperpolarizing factor is a prominent vasodilator, particularly in smaller arteries and arterioles. There is now emerging evidence to suggest that EDHF may play a role in the endothelial dysfunction in diabetes. 3. Since the first description of endothelium-dependent hyperpolarization some 20 years ago, it has emerged that EDHF is heterogeneous in nature, consisting of diffusible factors and contact-mediated mechanisms. The specific identity of EDHF in any particular vascular bed may influence the impact of diabetes on vascular function. 4. There is accumulating evidence in diabetic rat models and humans showing impaired EDHF activity in small resistance vessels. In contrast, studies in mice suggest that EDHF activity is actually enhanced under diabetic conditions. 5. It is clear that alterations in EDHF activity may have an important contribution in diabetes, more specifically in contributing to microvascular complications observed under diabetic conditions.
Clinical and Experimental Pharmacology and Physiology 32(5-6):482-7. · 1.85 Impact Factor
