Endothelium-derived dopamine modulates EFS-induced contractions of human umbilical vessels

Epithelium-derived 6-nitrodopamine modulates noradrenaline-induced contractions in human seminal vesicles

AIMS

To evaluate the basal release of 6-nitrodopamine (6-ND) from human isolated seminal vesicles (HISV) and to characterize its action and origin.

MAIN METHODS

Left HISV obtained from patients undergoing prostatectomy surgery was suspended in a 3-mL organ bath containing warmed (37 °C) and gassed (95%O2:5%CO2) Krebs-Henseleit's solution (KHS) with ascorbic acid. An aliquot of 2 mL of the supernatant was used to quantify catecholamines by LC-MS/MS. For functional studies, concentration-responses curves to catecholamines were obtained, and pEC50 and Emax values were calculated. Detection of tyrosine hydroxylase and S100 protein were also carried out by both immunohistochemistry and fluorescence in-situ hybridization assays (FISH).

KEY FINDINGS

Basal release of 6-ND was higher than the other catecholamines (14.76 ± 14.54, 4.99 ± 6.92, 3.72 ± 4.35 and 5.13 ± 5.76 nM for 6-ND, noradrenaline, adrenaline, and dopamine, respectively). In contrast to the other catecholamines, the basal release of 6-ND was not affected by the sodium current (Nav) channel inhibitor tetrodotoxin (1 μM; 10.4 ± 8.9 and 10.4 ± 7.9 nM, before and after tetrodotoxin, respectively). All the catecholamines produced concentration-dependent HISV contractions (pEC50 4.1 ± 0.2, 4.9 ± 0.3, 5.0 ± 0.3, and 3.9 ± 0.8 for 6-ND, noradrenaline, adrenaline, and dopamine, respectively), but 6-ND was 10-times less potent than noradrenaline and adrenaline. However, preincubation with very low concentration of 6-ND (10-8 M, 30 min) produced significant leftward shifts of the concentration-response curves to noradrenaline. Immunohistochemical and FISH assays identified tyrosine hydroxylase in tissue epithelium of HISV strips.

SIGNIFICANCE

Epithelium-derived 6-ND is the major catecholamine released from human isolated seminal vesicles and that modulates smooth muscle contractility by potentiating noradrenaline-induced contractions.

GKT137831 and hydrogen peroxide increase the release of 6-nitrodopamine from the human umbilical artery, rat-isolated right atrium, and rat-isolated vas deferens

Introduction: The human umbilical artery (HUA), rat-isolated right atrium, and rat-isolated vas deferens present a basal release of 6-nitrodopamine (6-ND). The basal release of 6-ND from these tissues was significantly decreased (but not abolished) when the tissues were pre-incubated with Nω-nitro-L-arginine methyl ester (L-NAME). Methods: In this study, the effect of the pharmacological modulation of the redox environment on the basal release of 6-ND was investigated. The basal release of 6-ND was measured using Liquid chromatography with tandem mass spectrometry (LC-MS/MS). Results and Discussion: Pre-incubation (30 min) of the tissues with GKT137831 (1 μM) caused a significant increase in the basal release of 6-ND from all tissues. In the HUA, pre-incubation with diphenyleneiodonium (DPI) (100 μM) also caused significant increases in the basal release of 6-ND. Preincubation of the HUA with hydrogen peroxide (H2O2) (100 μM) increased 6-ND basal release, whereas pre-incubation with catalase (1,000 U/mL) significantly decreased it. Pre-incubation of the HUA with superoxide dismutase (SOD) (250 U/mL; 30 min) also significantly increased the basal release of 6-ND. Preincubation of the HUA with either allopurinol (100 μM) or uric acid (1 mM) had no effect on the basal release of 6-ND. Pre-treatment of the HUA with L-NAME (100 μM) prevented the increase in the basal release of 6-ND induced by GKT137831, diphenyleneiodonium, and H2O2. The results obtained indicate a major role of endogenous H2O2 and peroxidases as modulators of 6- ND biosynthesis/release and a lack of peroxynitrite contribution.

Endothelium-Derived Dopamine and 6-Nitrodopamine in the Cardiovascular System

The review deals with the release of endothelium-derived dopamine and 6-nitrodopamine (6-ND) and its effects on isolated vascular tissues and isolated hearts. Basal release of both dopamine and 6-ND is present in human isolated umbilical cord vessels, human popliteal vessels, nonhuman primate vessels, and reptilia aortas. The 6-ND basal release was significantly reduced when the tissues were treated with Nω-nitro-l-arginine methyl ester and virtually abolished when the endothelium was mechanically removed. 6-Nitrodopamine is a potent vasodilator, and the mechanism of action responsible for this effect is the antagonism of dopamine D2-like receptors. As a vasodilator, 6-ND constitutes a novel mechanism by which nitric oxide modulates vascular tone. The basal release of 6-ND was substantially decreased in endothelial nitric oxide synthase knockout (eNOS-/-) mice and not altered in neuronal nitric oxide synthase knockout (nNOS-/-) mice, indicating a nonneurogenic source for 6-ND in the heart. Indeed, in rat isolated right atrium, the release of 6-ND was not affected when the atria were treated with tetrodotoxin. In the rat isolated right atrium, 6-ND is the most potent endogenous positive chronotropic agent, and in Langendorff's heart preparation, it is the most potent endogenous positive inotropic agent. The positive chronotropic and inotropic effects of 6-ND are antagonized by β1-adrenoceptor antagonists at concentrations that do not affect the effects induced by noradrenaline, adrenaline, and dopamine, indicating that blockade of the 6-ND receptor is the major modulator of heart chronotropism and inotropism. The review proposes that endothelium-derived catecholamines may constitute a major mechanism for control of vascular tone and heart functions, in contrast to the overrated role attributed to the autonomic nervous system.

6-Nitrodopamine is an endogenous mediator of the rabbit corpus cavernosum relaxation

BACKGROUND

6-Nitrodopamine (6-ND) is a novel endogenous catecholamine that has a potent relaxant action on vascular smooth muscle in vitro.

OBJECTIVES

To evaluate the basal release of 6-ND and noradrenaline from rabbit-isolated corpus cavernosum (RbCC) and its relaxing action on this tissue.

METHODS

Rabbit corpus cavernosa were dissected and suspended in a 5-mL organ bath containing oxygenated Krebs-Henseleit's solution. 6-ND and noradrenaline release was quantified by liquid chromatography coupled to tandem mass spectrometry. The relaxant activity of 6-ND was assessed in RbCC strips pre-contracted with endothelin-1 (10 nM).

RESULTS

Rabbit corpus cavernosum presented basal release of both 6-ND (2.9 ± 0.8 ng/mL, n = 12) and noradrenaline (1.7 ± 1.3 ng/mL, n = 12). The 6-ND release was reduced by pre-treatment with Nω -nitro-l-arginine methyl ester (l-NAME) (100 µM), whereas that of noradrenaline was unaffected. Tetrodotoxin (TTX, 1 µM) abolished the noradrenaline release but had no effect on 6-ND release, indicating a non-neurogenic origin for 6-ND. 6-ND and the selective dopamine D2 -agonist L-741,626 caused concentration-dependent RbCC relaxations (pEC50 of 11 ± 0.15 and 11.15 ± 0.28, respectively). Pre-treatment with either l-NAME or the soluble guanylate cyclase inhibitor 1H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1-on (ODQ) (100 µM) caused a rightward shift of the concentration-response curve to 6-ND, without affecting the L-741,626 responses. In TTX (100 nM)-pre-treated preparations, neither l-NAME nor ODQ shifted the 6-ND concentration-response curve. Dopamine, noradrenaline, and adrenaline caused concentration-dependent RbCC contractions. Pre-incubation with 6-ND concentration-dependently inhibited the dopamine-induced contractions, without affecting those induced by either noradrenaline or adrenaline.

DISCUSSION AND CONCLUSION

6-Nitrodopamine is the most potent endogenous relaxant agent in RbCC ever described and represents a novel mechanism by which NO causes corpus cavernosum smooth muscle relaxation. The finding that 6-ND acts as a truly selective dopamine D2 -receptor antagonist indicates that the balance of dopamine and 6-ND release/synthesis may be the main mechanism that modulates corpus cavernosum smooth muscle tonus in vivo.

6-Nitrodopamine Is the Most Potent Endogenous Positive Inotropic Agent in the Isolated Rat Heart

BACKGROUND

6-nitrodopamine released from rat isolated atria exerts positive chronotropic action, being more potent than noradrenaline, adrenaline, and dopamine. Here, we determined whether 6-nitrodopamine is released from rat isolated ventricles (RIV) and modulates heart inotropism.

METHODS

Catecholamines released from RIV were quantified by LC-MS/MS and their effects on heart inotropism were evaluated by measuring left ventricular developed pressure (LVDP) in Langendorff's preparation.

RESULTS

6-nitrodopamine was the major released catecholamine from RIV. Incubation with L-NAME (100 µM), but not with tetrodotoxin (1 µM), caused a significant reduction in 6-nitrodopamine basal release. 6-nitrodopamine release was significantly reduced in ventricles obtained from L-NAME chronically treated animals. 6-nitrodopamine (0.01 pmol) caused significant increases in LVDP and dP/dtmax, whereas dopamine and noradrenaline required 10 pmol, and adrenaline required 100 pmol, to induce similar increases in LVDP and dP/dtmax. The infusion of atenolol (10 nM) reduced basal LVDP and blocked the increases in LVDP induced by 6-ND (0.01 pmol), without affecting the increases in LVDP induced by 10 nmol of dopamine and noradrenaline and that induced by adrenaline (100 nmol).

CONCLUSIONS

6-nitrodopamine is the major catecholamine released from rat isolated ventricles. It is 1000 times more potent than dopamine and noradrenaline and is selectively blocked by atenolol, indicating that 6-ND is a main regulator of heart inotropism.

Release of 6-nitrodopamine from human popliteal artery and vein

6-Nitrodopamine (6-ND) is a novel catecholamine that is released from human umbilical cord vessels, and it causes vascular relaxation by acting as a dopamine D₂-receptor antagonist. Here it was investigated whether human peripheral vessels obtained from patients who have undergone surgery for leg amputation release 6-ND, and its action in these tissues. Popliteal artery and vein strips present basal release of 6-ND, as measure by liquid chromatography coupled to tandem mass spectrometry. The release was significantly reduced when the tissues were pre-treated with the nitric oxide synthase inhibitor L-NAME (100 μM), or when the endothelium was mechanically removed. In U-46619 (3 nM) pre-contracted rings, 6-ND induced concentration-dependent relaxations (pEC50 8.18 ± 0.05 and 8.40 ± 0.08, in artery and vein rings, respectively). The concentration-dependent relaxations induced by 6-ND were unaffected in tissues pre-treated with L-NAME, but significantly reduced in tissues where the endothelium has been mechanically removed. In U-46619 (3 nM) pre-contracted rings, the selective dopamine D₂ receptor antagonist L-741,626 also caused concentration-dependent relaxations (pEC₅₀ 8.92 ± 0.22 and 8.79 ± 0.19, in artery and vein rings, respectively). The concentration-dependent relaxations induced by L-741,626 were unaffected in tissues pre-treated with L-NAME, but significantly reduced in tissues where the endothelium has been mechanically removed. This is the first demonstration that 6-nitrodopamine is released from human peripheral artery and vein rings. The results also indicate that endothelium-derived dopamine is a major contractile agent in the popliteal artery and vein, and that selective dopamine D₂-receptor antagonists such as 6-ND, may have therapeutic potential in the treatment of human peripheral vascular diseases.

Relaxation of thoracic aorta and pulmonary artery rings of marmosets (Callithrix spp.) by endothelium-derived 6-nitrodopamine

6-Nitrodopamine is a novel catecholamine released by vascular tissues, heart, and vas deferens. The aim of this study was to investigate whether 6-nitrodopamine is released from the thoracic aorta and pulmonary artery rings of marmosets (Callithrix spp.) and to evaluate the relaxing and anti-contractile actions of this catecholamine. Release of 6-nitrodopamine, dopamine, noradrenaline, and adrenaline was assessed by liquid chromatography with tandem mass spectrometry (LC-MS/MS). The relaxations induced by 6-nitrodopamine and by the selective dopamine D2 receptor antagonist L-741,626 were evaluated on U-46619 (3 nM)-pre-contracted vessels. The effects of 6-nitrodopamine and L-741,626 on the contractions induced by electric-field stimulation (EFS), dopamine, noradrenaline, and adrenaline were also investigated. Both aorta and pulmonary artery rings exhibited endothelium-dependent release of 6-nitrodopamine, which was significantly reduced by the NO synthesis inhibitor L-NAME. Addition of 6-nitrodopamine or L-741,626 caused concentration-dependent relaxations of both vascular tissues, which were almost abolished by endothelium removal, whereas L-NAME and the soluble guanylate cyclase inhibitor ODQ had no effect on 6-nitrodopamine-induced relaxations. Additionally, pre-incubation with 6-nitrodopamine antagonized the dopamine-induced contractions, without affecting the noradrenaline- and adrenaline-induced contractions. Pre-incubation with L-741,626 antagonized the contractions induced by all catecholamines. The EFS-induced contractions were significantly increased by L-NAME, but unaffected by ODQ. Immunohistochemical assays showed no immunostaining of the neural tissue markers S-100 and calretinin in either vascular tissue. The results indicated that 6-nitrodopamine is the major catecholamine released by marmoset vascular tissues, and it acts as a potent and selective antagonist of dopamine D2-like receptors. 6-nitrodopamine release may be the major mechanism by which NO causes vasodilatation.

Myography of isolated blood vessels: Considerations for experimental design and combination with supplementary techniques

The study of the mechanisms of regulation of vascular tone is an urgent task of modern science, since diseases of the cardiovascular system remain the main cause of reduction in the quality of life and mortality of the population. Myography (isometric and isobaric) of isolated blood vessels is one of the most physiologically relevant approaches to study the function of cells in the vessel wall. On the one hand, cell-cell interactions as well as mechanical stretch of the vessel wall remain preserved in myography studies, in contrast to studies on isolated cells, e.g., cell culture. On the other hand, in vitro studies in isolated vessels allow control of numerous parameters that are difficult to control in vivo. The aim of this review was to 1) discuss the specifics of experimental design and interpretation of data obtained by myography and 2) highlight the importance of the combined use of myography with various complementary techniques necessary for a deep understanding of vascular physiology.

Release of 6-nitrodopamine modulates vascular reactivity of Pantherophis guttatus aortic rings

6-Nitrodopamine (6-ND) is a novel catecholamine that is released from human umbilical cord vessels and Chelonoidis carbonaria aortic rings. The synthesis/release of 6-ND is inhibited by either pre-incubation of the vessels with the nitric oxide (NO) synthase inhibitor L-NAME or by mechanical removal of the endothelium. 6-ND causes powerful vasorelaxation, acting as a potent and selective dopamine D₂-like receptor antagonist. Basal release of 6-ND from Panterophis guttatus endothelium intact and denuded aortic rings was quantified by LC-MS/MS. In order to evaluate the interaction of 6-ND with other catecholamines, aortic rings were suspended vertically between two metal hooks in 10-mL organ baths containing Krebs-Henseleit's solution and attached to isometric transducers. Endothelium intact aortic rings presented basal release of 6-ND, which was significantly reduced by previous incubation with L-NAME (100 μM). In endothelin-1 (3 nM) pre-contracted endothelium intact aortic rings, 6-ND (10pM-1 μM) and the dopamine D₂-receptor antagonist L-761,626 (10 pM-1 μM) induced concentration-dependent relaxations, which were not affected by incubation with L-NAME but greatly reduced in endothelium-removed aortic rings. 6-ND (0.1-1 μM) produced significant rightward shifts of the concentration-response curves to dopamine in L-NAME pre-treated endothelium-intact (pA₂ 7.01) rings. Contractions induced by noradrenaline and adrenaline were not affected by pre-incubation with 6-ND (1 μM). The EFS-induced contractions of L-NAME pre-treated endothelium-intact aortic rings were significantly inhibited by incubation with 6-ND (1 μM). The results indicate that 6-ND released from Pantherophis guttatus aortic rings is coupled to NO release and represents a new mechanism by which NO can modulate vascular reactivity independently of cGMP production.

6-Nitrodopamine is an endogenous mediator of rat isolated epididymal vas deferens contractions induced by electric-field stimulation

6-nitrodopamine (6-ND) is released from human umbilical cord vessels and modulates vascular reactivity by acting as a dopamine antagonist. Here we investigate whether 6-ND is released by the rat isolated vas deferens and its effect on this tissue. Dopamine, noradrenaline, adrenaline and 6-ND levels were quantified in rat isolated vas deferens by LC-MS-MS. Electric-field stimulation (EFS) and concentration-response curves to 6-ND, noradrenaline, dopamine and adrenaline were performed in the absence and in the presence (30 min) of L-NAME, SCH-23390, haloperidol, PG-01037, sonepiprazole, desipramine, clomipramine, amitriptyline, cyclobenzaprine, carbamazepine, maprotiline, paroxetine, oxcarbazepine and ketanserin in the rat isolated epididymal vas deferens (RIEVD). Basal releases of 6-ND and noradrenaline were detected from the rat isolated vas deferens. 6-ND release was reduced by tissue incubation with L-NAME and from the vas deferens obtained from L-NAME-treated rats. SCH-23390 caused leftward shifts on concentration-response curves to 6-ND without affecting dopamine- or EFS-induced RIEVD contractions. Haloperidol, PG-01037 and sonepiprazole caused significant rightward shifts on concentration-response curves to dopamine but had no effect on either the 6-ND or EFS-induced RIEVD contractions. The tricyclic compounds desipramine, clomipramine, amitriptyline, cyclobenzaprine and carbamazepine induced rightward shifts on 6-ND concentration-response curve but did not reduce the noradrenaline, dopamine and adrenaline contractile responses. They also reduced the EFS-induced RIEVD contractions in control but not in tissues obtained from L-NAME-treated animals. Maprotiline, oxcarbazepine, paroxetine and ketanserin had no effect in either 6-ND or EFS-induced RIEVD contractions. Thus, 6-ND modulates RIEVD contractility, and desipramine, clomipramine, amitriptyline, cyclobenzaprine and carbamazepine act as selective 6-ND receptor antagonists.

6-Nitrodopamine is released by human umbilical cord vessels and modulates vascular reactivity

AIMS

Human umbilical cord vessels (HUCV) release dopamine and nitric oxide (NO). This study aims to verify whether HUCV release nitrocatecholamines such as 6-nitrodopamine (6-ND).

MAIN METHODS

Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used to identify 6-ND release from HUCV rings incubated in Krebs-Henseileit's solution. Vascular reactivity of HUCV rings was tested (with and without endothelium integrity) by suspension of the rings in an organ bath under isometric tension and application of 6-ND and other known mediators.

KEY FINDINGS

LC-MS/MS revealed a basal release of 6-ND from endothelium intact from both human umbilical artery (HUA) and vein (HUV). The endothelium intact release was inhibited by the pre-treatment with NO synthesis inhibitor L-NAME (100 μM). In contrast to dopamine, noradrenaline and adrenaline, 6-ND did not contract HUCV, even in presence of L-NAME or ODQ. 6-ND (10 μM) produced a rightward shift of the concentration-response curves to dopamine (pA2: 5.96 in HUA and 5.72 in HUV). Contractions induced by noradrenaline and adrenaline were not affected by pre-incubation with 6-ND (10 μM). In U-46619 (10 nM) pre-contracted endothelium intact tissues, 6-ND and the dopamine D₂-receptor antagonist haloperidol induced concentration-dependent relaxations of HUA and HUV. Incubation with the dopamine D₁-receptor antagonist SCH-23390 (10 nM) abolished relaxation induced by fenoldopam but did not affect those induced by 6-ND.

SIGNIFICANCE

6-ND is released by HUCV and acts as a selective dopamine D₂-receptor antagonist in this tissue. This represents a novel mechanism by which NO may modulate vascular reactivity independently of cGMP production.

Quantification of 6-nitrodopamine in Krebs-Henseleit's solution by LC-MS/MS for the assessment of its basal release from Chelonoidis carbonaria aortae in vitro

In this study, the development and validation of a method for quantification of 6-nitrodopamine in Krebs-Henseleit's solution by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) with positive ion electrospray ionization is described. Aortic rings taken from tortoise were either denuded or left with endothelium intact (15 mm, N = 6) and were incubated for 30 min in 5 mL Krebs-Henseleit's solution in an organ bath. Solid phase extraction (SPE) was performed for aliquots of 1 mL of the supernatant. The separation of 6-nitrodopamine was obtained on a 150 mm × 3 mm Shim-pack GIST-HP C18 column, using 75% of mobile phase A consisted of deionized water with 0.1% formic acid (v/v) and 25% of mobile phase B consisted of acetonitrile/deionized water (50/50, v/v) + 0.1% formic acid at a flow rate of 350 μL/min in an isocratic mode. The method was linear over the concentration range of 0.1-20 ng/mL. The method was sensitive, precise and accurate for the assessment of the basal release of 6-nitrodopamine from Chelonoidis carbonaria aortae in vitro. The mean ± SEM concentrations of 6-nitrodopamine released from endothelium-intact and endothelium-denuded aortae were 0.44 ± 0.06 ng/mL and 0.18 ± 0.05 ng/mL, respectively. These results indicate that tortoise's aortae display a basal endothelium-derived 6-nitrodopamine release.

The basal release of endothelium-derived catecholamines regulates the contractions of Chelonoidis carbonaria aorta caused by electrical-field stimulation

The contractions of Chelonoidis carbonaria aortic rings induced by electrical field stimulation (EFS) are not inhibited by blockade of the voltage-gated sodium channels by tetrodotoxin but almost abolished by the α1/α2-adrenoceptor antagonist phentolamine. The objective of this study was to identify the mediator(s) responsible for the EFS-induced contractions of Chelonoidis carbonaria aortic rings. Each ring was suspended between two wire hooks and mounted in isolated 10 ml organ chambers filled with oxygenated and heated Krebs-Henseleit's solution. Dopamine, noradrenaline and adrenaline concentrations were analysed by liquid chromatography coupled to tandem mass spectrometry. The contractions caused by dopamine and EFS were done in absence and presence of the nitric oxide (NO) synthesis inhibitor L-NAME, the NO-sensitive guanylyl cyclase inhibitor ODQ, the D1-like receptor antagonist SCH-23390, the D2-like receptor antagonists risperidone, quetiapine, haloperidol, and the tyrosine hydroxylase inhibitors salsolinol and 3-iodo-L-tyrosine. Basal concentrations of dopamine, noradrenaline and adrenaline were detected in Krebs-Henseleit solution containing the aortic rings. The catecholamine concentrations were significantly reduced in endothelium-denuded aortic rings. L-NAME and ODQ significantly potentiated the dopamine-induced contractions. The D2-like receptor antagonists inhibited the EFS-induced contractions of the aortic rings treated with L-NAME, whereas SCH 23390 had no effect. Similar results were observed in the contractions induced by dopamine in L-NAME treated aortic rings. These results indicate that catecholamines released by endothelium regulate the EFS-induced contractions. This may constitute a suitable mechanism by which reptilia modulate specific organ blood flow distribution.

This paper has an associated First Person interview with the first author of the article.

Summary:Chelonoidis carbonaria aortic rings release endothelium-derived catecholamines that modulate vascular smooth muscle reactivity.