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Endothelin
Terms modified by Endothelin Selected AbstractsCONTRIBUTION OF PROSTANOID TP RECEPTORS TO THE PRESSOR AND INTRARENAL HAEMODYNAMIC RESPONSE TO ENDOTHELINCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 3 2006Jan Michael Williams SUMMARY 1Previous studies have shown that endothelin (ET)-1 stimulates thromboxane (Tx)A2 production and so we hypothesized that inhibiting prostanoid TP receptors would prevent the pressor and intrarenal haemodynamic response to an acute infusion of ET-1. 2Male Sprague-Dawley rats were anaesthetized with Inactin (Sigma Chemical, St Louis, MO, USA; 50 mg/kg) and catheters were inserted into the femoral artery and vein for recording mean arterial pressure (MAP) and infusion of ET-1 and receptor antagonists, respectively. A jugular vein catheter was used for the infusion of bovine serum albumin (6.2% in saline) during surgery (1.25% bodyweight). The pressor response to a 1 h infusion of ET-1 (6 pmol/kg per min) was determined in rats that had been pretreated with vehicle (0.9% NaCl) or the TP receptor antagonist SQ29548 (2 mg/kg per h). Laser Doppler single-optic fibres were implanted in the left kidney for the measurement of medullary blood flow (MBF) and cortical blood flow (CBF). 3Prostanoid TP receptor blockade completely inhibited the acute pressor response to ET-1; the change in MAP was 14 2% versus -3 4% in vehicle and SQ29548 groups, respectively (P < 0.05). Endothelin-1 reduced CBF (-15.2 3.3%), a response that was not significantly changed by SQ29548 (-6.2 7.6%). Similarly, the ET-1-mediated response in MBF was not altered by the TP receptor antagonist (7.7 4.9 vs 6.5 5.2%). 4To determine the influence of the ETB receptor in modulating the response to ET-1 during TP receptor blockade, additional groups were pretreated with A-192621, an ETB receptor-selective antagonist (10 mg/kg, i.v.). A-192621 potentiated the increase in MAP produced by ET-1 (32 5%; P < 0.05 vs ET-1 alone). SQ29548 significantly inhibited, but did not completely block, the increase in MAP produced by ET-1 during ETB antagonist treatment (18 4%; P < 0.05). Endothelin-1-induced decreases in CBF were significantly enhanced in rats that were pretreated with A-192621, whereas ET-1 also significantly decreased MBF following A-192621 treatment. During ETB receptor blockade, TP receptor inhibition had no effect on the ET-1-mediated response of CBF and MBF. 5These results suggest that TP receptor activation is not involved in the renal haemodynamic responses to ET-1. However, TP receptor activation contributes to the acute pressor response to ET-1, but does not account for the potentiated increase in MAP during ETB receptor blockade. [source] Endothelin attenuates endothelium-dependent platelet inhibition in manACTA PHYSIOLOGICA, Issue 4 2010R. E. Malmström Abstract Aim:, The vascular endothelium produces several substances, including nitric oxide (NO) and endothelin-1 (ET-1), which participate in the regulation of vascular tone in humans. Both these substances may exert other actions of importance for cardiovascular disease, e.g. effects on vascular smooth muscle cell proliferation and inflammation, and NO inhibits platelet function. Experiments were designed to investigate the effect of ET-1 on endothelium-dependent vasodilatation and attenuation of platelet activation. Methods:, In 25 healthy male subjects (25 ± 1 years), forearm blood flow was measured by venous occlusion plethysmography, and platelet activity was assessed by whole blood flow cytometry (platelet fibrinogen binding and P-selectin expression) in unstimulated and adenosine diphosphate (ADP)-stimulated samples during administration of ET-1, the endothelium-dependent vasodilator acetylcholine and the NO synthase inhibitor l -NMMA. Results:, Acetylcholine increased forearm blood flow and significantly inhibited platelet activation in both unstimulated and ADP-stimulated samples. In samples stimulated with 0.3 ,m ADP, fibrinogen binding decreased from 41 ± 4% to 31 ± 3% (P < 0.01, n = 11) after acetylcholine administration. The vasodilator response to acetylcholine was significantly impaired during infusions of ET-1 and l -NMMA. ET-1 did not affect platelet activity per se, whereas l -NMMA increased platelet P-selectin expression. Both ET-1 and l -NMMA attenuated the acetylcholine-induced inhibition of platelet activity. Conclusions:, Our study indicates that, further to inhibiting endothelium-dependent vasodilatation, ET-1 may also attenuate endothelium-dependent inhibition of platelet activation induced by acetylcholine. An enhanced ET-1 activity, as suggested in endothelial dysfunction, may affect endothelium-dependent platelet modulation and thereby have pathophysiological implications. [source] Endothelin regulates NOS1 and NOS3 isoforms in the renal medullaACTA PHYSIOLOGICA, Issue 4 2007Erik Persson No abstract is available for this article. [source] Cardiac expression patterns of endothelin-converting enzyme (ECE): Implications for conduction system developmentDEVELOPMENTAL DYNAMICS, Issue 6 2008David Sedmera Abstract The spatiotemporal distribution of the endothelin-converting enzyme (ECE) protein in the embryonic chick heart and the association of this polypeptide with the developing cardiac conduction system is described here for the first time. Further, we show how cardiac hemodynamic load directly affects ECE level and distribution. Endothelin (ET) is a cytokine involved in the inductive recruitment of Purkinje fibers. ET is produced by proteolytic cleavage of Big-ET by ECE. We generated an antibody against chick ECE recognizing a single band at ,70 kD to correlate the cardiac expression of this protein with that reported previously for its mRNA. ECE protein expression was more widespread compared to its mRNA, being present in endothelial cells, mesenchymal cells, and myocytes, and particularly enriched in the trabeculae and nascent ventricular conduction system. The myocardial expression was significantly modified under experimentally altered hemodynamic loading. In vivo, ET receptor blockade with bosentan delayed activation sequence maturation. These data support a role for ECE in avian cardiac conduction system differentiation and maturation. Developmental Dynamics 237:1746,1753, 2008. © 2008 Wiley-Liss, Inc. [source] Equine pulmonary and systemic haemodynamic responses to endothelin-1 and a selective ETA receptor antagonistEQUINE VETERINARY JOURNAL, Issue 4 2001A. E. BENAMOU Summary Based on previous in vitro studies, we hypothesised that endothelin (ET) would induce vasoconstriction in the pulmonary circululation of the horse and that this action would be mediated via ETA receptors. Pulmonary and systemic haemodynamic responses to endothelin-1 (ET-1), a potent vasoactive endogenous peptide, were investigated in 6 conscious, nonsedated horses at rest. Bolus i.v. injections of exogenous ET-1 (0.1, 0.2 and 0.4 ,g/kg bwt) caused significant increases in pulmonary (PAP) and carotid (CAP) artery pressures, with peak increases of 79% and 51% for mean PAP and CAP, respectively. The effect of ET-1 on PAP and CAP was rapid and transient for PAP (,10 min) but prolonged for CAP (up to 60 min). ET-1 significantly decreased cardiac output by up to 35% and significantly increased systemic vascular resistance (SVR) by up to 104%. Pulmonary vascular resistance (PVR) showed a trend (P>0.05) to increase with 0.2 and 0.4 ,g/kg bwt ET-1. Infusion of a selective ETA receptor antagonist (TBC11251) completely inhibited the responses to a subsequent bolus of 0.2 ,g/kg bwt ET-1. We conclude that exogenous ET-1 exerts a potent vasoconstrictive action on the pulmonary and systemic circulations of the horse. These effects appear to be mediated largely through ETA receptors in both circulations. Endothelin may play a role in hypertensive conditions in the horse. [source] Endothelin receptor selectivity in chronic kidney disease: rationale and review of recent evidenceEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 2009W. Neuhofer Abstract Endothelin (ET) is a potent vasoconstrictory peptide with proinflammatory and profibrotic properties that exerts its biological effects through two pharmacologically distinct receptor subtypes, namely ETA and ETB. In addition to its substantial contribution to normal renal function, a large body of evidence suggests that derangement of the renal ET system is involved in the initiation and progression of chronic kidney disease (CKD) in diabetes, hypertension and glomerulonephritis. Thus, the use of ET receptor antagonists (ERAs) may offer potential novel treatment strategies in CKD. Recent literature on the role of the renal ET system in the healthy kidney was reviewed. In addition, an unbiased PubMed search was performed for studies published during the last 5 years that addressed the effects of ERAs in CKD. A particular objective was to extract information regarding whether selective or nonselective ERAs may have therapeutic potential in humans. ET-1 acts primarily as an autocrine or paracrine factor in the kidney. In normal physiology, ET-1 promotes diuresis and natriuresis by local production and action through ETB receptors in the renal medulla. In pathology, ET-1 mediates vasoconstriction, mesangial-cell proliferation, extracellular matrix production and inflammation, effects that are primarily conveyed by ETA receptors. Results obtained in animal models and in humans with the use of ERAs in CKD are encouraging; nevertheless, it is still under debate which receptor subtype should be targeted. According to most studies, selective inhibition of ETA receptors appears superior compared with nonselective ERAs because this approach does not interfere with the natriuretic, antihypertensive and ET clearance effects of ETB receptors. Although preliminary data in humans are promising, the potential role of ERAs in patients with CKD and the question of which receptor subtype should be targeted can only be clarified in randomized clinical trials. [source] Endothelin: AF-riend or AF-oe?JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2001PENELOPE A. BOYDEN Ph.D. [source] Endogenous endothelin in a rat model of acute colonic mucosal injuryJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 10 2000Masamitsu Sugimachi Abstract Background: Endothelin (ET) is involved in various biologic activities in non-vascular and vascular tissues. While ET has some significant effects on gastrointestinal functions, the possible role of endogenous ET in the host response to mucosal injury has not been well clarified. Methods: The present study describes an investigation of the effects of an endothelin A receptor antagonist, BQ-123, on lactate dehydrogenase (LDH), mucus and albumin flux into the perfusate in a rat model of acute colonic injury, induced by acetic acid perfusion. The present study also examined localization of ET in damaged rat colons by using immunohistochemistry. Results: A 4% acetic acid treatment induced mild mucosal damage of perfused rat colon and increased LDH as well as albumin and protein-bound hexose release into the perfusate. Pretreatment with BQ-123 significantly reduced LDH activity and protein-bound hexose concentration in the perfusate and delayed the reduction of albumin leakage from damaged mucosa. Vascular endothelial, neural and surface epithelial cells of the colon showed strong ET-like immunoreactivity. Mucosal damage markedly influenced ET expression by epithelial cells. Mild mucosal damage decreased the ET expression by surface epithelial cells while moderate mucosal damage induced a mosaic location of ET-positive epithelial cells in the crypt. Severe mucosal damage abolished the ET expression by epithelial cells. Conclusions: Endothelin may play a role in the host response to acute mucosal damage. Mucosal ET production is significantly affected by mucosal injury. [source] Endothelin A receptors mediate relaxation of guinea pig internal anal sphincter through cGMP pathwayNEUROGASTROENTEROLOGY & MOTILITY, Issue 9 2010S.-c. Huang Abstract Background, Endothelin (ET) modulates motility of the internal anal sphincter through unclear receptor subtypes. Methods, We measured relaxation of guinea pig internal anal sphincter strips caused by ET-related peptides and binding of 125I-ET-1 to cell membranes prepared from the internal anal sphincter muscle. Visualization of 125I-ET-1 binding sites in tissue was performed by autoradiography. Key Results , In the guinea pig internal anal sphincter, ET-1 caused a marked relaxation insensitive to tetrodotoxin, atropine, or ,-conotoxin GVIA. ET-2 was as potent as ET-1. ET-3 caused a mild relaxation. The relative potencies for ETs to cause relaxation were ET-1 = ET-2 > ET-3. The ET-1-induced relaxation was inhibited by BQ-123, an ETA antagonist, but not by BQ-788, an ETB antagonist. These indicate that ETA receptors mediate the relaxation. The relaxant response of ET-1 was attenuated by LY 83583, KT 5823, Rp-8CPT-cGMPS, tetraethyl ammonium, 4-aminopyridine and N(omega)-nitro-l-arginine, but not significantly affected by NG -nitro-l-arginine methyl ester, NG -methyl-l-arginine, charybdotoxin, apamin, KT 5720, and Rp-cAMPS. These suggest the involvement of cyclic guanosine 3,,5,-cyclic monophosphate (cGMP), and potassium channels. Autoradiography localized 125I-ET-1 binding to the internal anal sphincter. Binding of 125I-ET-1 to the cell membranes prepared from the internal anal sphincter revealed the presence of two subtypes of ET receptors, ETA and ETB receptors. Conclusions & Inferences, Taken together, these results demonstrate that ETA receptors mediate relaxation of guinea pig internal anal sphincter through the cGMP pathway. [source] Endothelin-A-receptor antagonist LU 302146 inhibits electrostimulation-induced bladder contractions in vivoNEUROUROLOGY AND URODYNAMICS, Issue 5 2006J.R. Scheepe Abstract Objectives Endothelin (ET) is a strong constrictor of smooth muscle structures. The relevance of Endothelin-A receptors in the bladder was demonstrated in several in vitro studies. The aim of this functional study was to evaluate the acute effect of the selective ET-A-antagonist LU 302146 (LU) on neurostimulation-induced bladder contractions in vivo. Methods Eight male mini pigs were anesthesized. The bladder was exposed and a double lumen catheter was inserted to perform intravesical pressure (pves) measurements. Laminectomy was performed for sacral anterior root stimulation (SARS) of S2. Four animals received the selective ET-A-antagonist LU, three atropine and one animal was treated with vehicle. Pves was recorded before and after drug administration as well as before and during neurostimulation. At the end of each LU trial, a supplementary application of 4 mg atropine was administered followed by a final SARS. Results In all experiments reproducible pves values were elicited during electrostimulation before administration of the test substance. The selective ET-A-antagonist reduced stimulation-induced bladder contraction by a mean of 57%. Additional administration of atropine inhibited the detrusor contraction almost completely during SARS. The vehicle had no effect on bladder contraction. Conclusions In the presented animal model, ET-1 inhibition with the selective ET receptor-A-antagonist LU 302146 decreases stimulation-induced bladder contraction in vivo. The results suggest that the selective ET-A antagonist LU acts on the atropine-resistant component of efferent detrusor activation since additional administration of atropine almost completely abolish detrusor contraction. This observation in addition to the involvement of ET-1 in bladder smooth muscle proliferation, raises the possibility that ET-receptor antagonists might be beneficial in patients with neurogenic bladder dysfunction or in patients with functional or anatomical BOO. Neurourol. Urodynam. © 2006 Wiley-Liss, Inc. [source] Corresponding distributions of increased endothelin-B receptor expression and increased endothelin-1 expression in the aorta of apolipoprotein E-deficient mice with advanced atherosclerosisPATHOLOGY INTERNATIONAL, Issue 12 2000Tsutomu Kobayashi Endothelin (ET)-1 causes proliferation of vascular smooth muscle cells (VSMC). Although it has been reported that stimulation of ETB receptors as well as ETA receptors promote proliferation of VSMC, the precise distribution of each receptor subtype in atherosclerotic vessels is unknown. Previous studies demonstrated that apolipoprotein E (apoE)-deficient mice have hypercholesterolaemia and develop severe atherosclerosis. To investigate the pathophysiological roles of vascular ET system in atherosclerosis, we examined preproET-1 messenger ribonucleic acid expression in the aorta of apoE-deficient mice, and performed immunohistochemical staining for ET-1 and each ET receptor subtype (ETA and ETB receptors) in the atherosclerotic lesions of these mice. The level of preproET-1 mRNA in the aorta was significantly higher in the apoE-deficient mice than in the control mice. Strong ET-1 staining was observed in the macrophage-foam cells, intimal and medial VSMC in the atherosclerotic lesions of the apoE-deficient mice. In addition, in the atherosclerotic lesions, strong ETB receptor staining was observed in the macrophage-foam cells, intimal and medial VSMC, which distribution corresponded closely to that of ET-1. ETA receptor staining was observed in the medial VSMC of both groups, but not in the macrophage-foam cells of the apoE-deficient mice. ETA receptor staining in the medial VSMC was stronger in the apoE-deficient mice than in the control mice. These results suggest that the vascular ET system, including ET-1 and ET receptors, is activated in the atherosclerotic lesions of apoE-deficient mice. Since the distribution of strong ETB receptor staining corresponded closely to that of ET-1, it is suggested that the ET system, mediated by ETB receptors, has an important role in the pathophysiology of the atherosclerotic lesions of apoE-deficient mice. [source] Randomized, prospective, placebo-controlled trial of bosentan in interstitial lung disease secondary to systemic sclerosis,ARTHRITIS & RHEUMATISM, Issue 7 2010J. R. Seibold Objective Endothelin is implicated as a participatory pathway in systemic sclerosis (SSc). We tested this hypothesis in a 12-month trial of bosentan, a nonselective endothelin receptor antagonist, as a therapy for SSc-related interstitial lung disease (ILD). Method Patients with SSc and significant ILD were recruited to this prospective, double-blind, randomized, placebo-controlled, parallel group study. The inclusion criteria were designed to select a cohort enriched for patients with active and progressive disease. Exclusion factors included significant pulmonary hypertension. Patients with a diffusing capacity for carbon monoxide of <80% predicted and a 6-minute walk distance of 150,500 meters or a 6-minute walk distance of ,500 meters with a decrease in oxygen saturation received bosentan or placebo. The primary efficacy end point was a change in the 6-minute walk distance from baseline up to month 12. Secondary end points included time to death or worsening results of pulmonary function tests (PFTs). The safety and tolerability of bosentan were also assessed. Results Among the 163 patients, 77 were randomized to receive bosentan, and 86 were randomized to receive placebo. No significant difference between treatment groups was observed for change in the 6-minute walk distance up to month 12. No deaths occurred in this study group. Forced vital capacity and diffusing capacity for carbon monoxide remained stable in the majority of patients in both groups. Significant worsening of PFT results occurred in 25.6% of patients receiving placebo and 22.5% of those receiving bosentan (P not significant). Conclusion No improvement in exercise capacity was observed in the bosentan-treated group compared with the placebo group, and no significant treatment effect was observed for the other end points. Although many outcome variables were stable, bosentan did not reduce the frequency of clinically important worsening. These data do not support the use of endothelin receptor antagonists as therapy for ILD secondary to SSc. [source] Endothelin 1 contributes to the effect of transforming growth factor ,1 on wound repair and skin fibrosisARTHRITIS & RHEUMATISM, Issue 3 2010David Lagares Objective To characterize the pathways induced by transforming growth factor ,1 (TGF,1) that lead to the expression of endothelin 1 (ET-1) in human dermal fibroblasts, and to study the effects of TGF,1 and ET-1 on the acquisition of a profibrotic phenotype and assess the contribution of the TGF,1/ET-1 axis to skin wound healing and fibrosis in vivo. Methods The mechanism of induction of ET-1 expression by TGF,1 and its effect on the expression of ,-smooth muscle actin and type I collagen were studied in human dermal fibroblasts, in experiments involving the TGF, receptor inhibitor GW788388 and the ET receptor antagonist bosentan, by real-time reverse transcription,polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay, immunofluorescence, Western blotting, and promoter/reporter transient transfection analyses. Experiments assessing dermal wound healing in mice were performed with adenovirus-driven overexpression of active TGF,1 and ET-1, with or without treatment with bosentan. The contributions of TGF,1 and ET-1 to the fibrotic response were also assessed in a mouse model of bleomycin-induced skin fibrosis, by histologic, immunohistochemical, RT-PCR, and protein analyses. Results TGF,1 induced ET-1 expression in human dermal fibroblasts through Smad- and activator protein 1/JNK,dependent signaling. The ability of TGF,1 to induce the expression of profibrotic genes was dependent on ET-1. Adenovirus-mediated overexpression of TGF,1 and ET-1 in mouse skin was associated with accelerated wound closure, increased fibrogenesis, and excessive scarring. Treatment with bosentan prevented the effects of TGF,1. In the bleomycin-induced fibrosis model, treatment with GW788388 and bosentan prevented the fibrotic response. Conclusion Our results strongly support the notion that the TGF,1/ET-1 axis has a role in wound repair and skin fibrosis. ET-1 receptor antagonists, such as bosentan, may represent a useful therapeutic tool in the treatment of excessive scarring and fibrosis-related diseases. [source] EndothelinA (ETA) and ETB receptor-mediated regulation of nitric oxide synthase 1 (NOS1) and NOS3 isoforms in the renal inner medullaACTA PHYSIOLOGICA, Issue 4 2007J. C. Sullivan Abstract Aim:, Our laboratory and others have shown that endothelin (ET)-1 directly stimulates nitric oxide (NO) production in inner medullary collecting duct (IMCD) cells. The goal of this study was to determine which NO synthase (NOS) isoforms in IMCD are sensitive to ET-1, and the role of ETA and ETB receptor activation in vivo and in vitro. Methods:, NOS enzymatic activity and NOS isoform protein expression were examined in cultured IMCD-3 cells and isolated renal inner medulla. ETB receptor-deficient homozygous rats (sl/sl) have elevated levels of circulating ET-1 and lack a functional ETB signalling pathway in kidneys, and furthermore provides a unique model to study ETA receptor signalling in the renal inner medulla in vivo. Results:, Incubation of IMCD-3 cells with exogenous ET-1 (50 nm) resulted in ETA -dependent increased NOS1 protein expression in IMCD-3 cells with no effect on NOS2 or NOS3 expression. ETB receptor antagonism has no effect on NOS expression in IMCD-3 cells. Consistent with in vitro results, cytosolic NOS1 protein expression was significantly greater in the renal inner medulla of sl/sl rats compared with heterozygous (sl/+) controls, with no alteration in NOS3 expression. In contrast to protein expression data, NOS1- and NOS3-specific enzymatic activities decreased in the cytosolic fraction from the renal inner medulla of sl/sl compared with sl/+. Conclusion:, These results provide evidence that both ETA and ETB receptors regulate NOS isoform activity in the renal inner medulla and specifically support the hypothesis that ETA receptor activation increases NOS1 expression. [source] Leptin and endothelin-1 mediated increased extracellular matrix protein production and cardiomyocyte hypertrophy in diabetic heart diseaseDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 5 2009Pijush Majumdar Abstract Background We investigated the role of leptin and its interaction with endothelin 1 (ET-1) in fibronectin (FN) synthesis and cardiomyocyte hypertrophy, two characteristic features of diabetic cardiomyopathy. Methods Endothelial cells [human umbilical vein endothelial cells (HUVECs)] were examined for FN production and neonatal rat cardiomyocytes for hypertrophy, following incubation with glucose, ET-1, leptin and specific blockers. FN, ET-1, leptin and leptin receptors mRNA expression and FN protein were measured. Myocytes were also morphometrically examined. Furthermore, hearts from streptozotocin-diabetic rats were analysed. Results Glucose caused increased FN mRNA and protein expression in HUVECs and cardiomyocytes hypertrophy along with upregulation of ET-1 mRNA, leptin mRNA and protein. Glucosemimetic effects were seen with leptin and ET-1. Leptin receptor antagonist (leptin quadruple mutant) and dual endothelin A endothelin B (ETA/ETB) receptor blocker bosentan normalized such abnormalities. Hearts from the diabetic animals showed hypertrophy and similar mRNA changes. Conclusion These data indicate that in diabetes increased FN production and cardiomyocyte hypertrophy may be mediated through leptin with its interaction with ET-1. Copyright © 2009 John Wiley & Sons, Ltd. [source] Mechanistic studies of blood pressure in rats treated with a series of cholesteryl ester transfer protein inhibitors,DRUG DEVELOPMENT RESEARCH, Issue 1 2009Michael DePasquale Abstract ILLUMINATE, the Phase 3 clinical trial of morbidity and mortality (M&M) with the cholesteryl ester transfer protein inhibitor (CETPi), torcetrapib (CP-529,414), was terminated in December 2006 due to an imbalance in all cause mortality. The underlying cause of the M&M remains undetermined. While torcetrapib produced dose-related increases in blood pressure in clinical trials, the mechanism of the increase in blood pressure is also undetermined. The pressor effects of torcetrapib and structurally related compounds were studied in several pathways involved in blood pressure control. Studies were conducted in rats treated with a series of structurally related molecules (CP-529,414, CP-532,623, PF-868,348, CP-746,281, CP-792,485, PF-868,343, and CE-308,958). CP-529,414, CP-532,623, CP-868,343, and CP-792,485 are potent CETP inhibitors; PF-868,348 is weakly potent and CP-746,281 and CE-308,958 are CETP-inactive. Changes in blood pressure were determined in conscious animals in conjunction with pharmacologic blockade of numerous pressor agents/pathways. Torcetrapib and CP-532,623 increased blood pressure following both chronic PO and acute IV administration. The CETP-inactive enantiomer of CP-532,623, CP-746,281 failed to raise blood pressure. PF-868,348, a structural analogue with ,50-fold lower CETPi activity also displayed pressor activity. Blockade of adrenergic, cholinergic, angiotensin, endothelin, NOS, Rho kinase, and thromboxane pathways failed to attenuate the pressor response. These data demonstrate that the blood pressure activity seen with torcetrapib can be dissociated from CETP inhibitor pharmacology and numerous pharmacology pathways can be discounted in the attempt to understand the molecular basis of the pressor pharmacology. Drug Dev Res 70:2009 © 2009 Wiley-Liss, Inc. [source] Spasmogenic action of endothelin-1 on isolated equine pulmonary artery and bronchusEQUINE VETERINARY JOURNAL, Issue 2 2003A. E. M. BENAMOU Summary Reasons for performing study: There is currently little published information about the effects of endothelin-1 (ET-1), a potent endogenous spasmogen of vascular and airway smooth muscle, on pulmonary vasculature and airways or which ET receptor subtypes mediate ET-1-induced vasoconstrictive and bronchoconstrictive action in the horse. Objectives: To investigate the effect of endothelin-1 (ET-1) on smooth muscle from isolated equine pulmonary artery and bronchus. In addition, the roles of ETA and ETB receptors in ET-1 mediated contraction in these tissues were assessed. Methods: The force generation of ring segments from pulmonary arteries or third-generation airways (obtained from horses subjected to euthanasia fororthopaedic reasons) were studied in an organ bath at 37°C in response to exogenous endothelin and selective endothelin A (BQ123) or B receptor (BQ788) antagonists. Results: ET-1 produced concentration-dependent contractions of the equine pulmonary artery and bronchus. The threshold for contraction was 10,10 and 10,9 mol/l ET-1 for pulmonary artery and bronchus, respectively. The maximal contraction induced by the highest ET-1 concentration (10,7 mol/l) was 173 and 194% of the contraction obtained with 100 mmol/l KCl in pulmonary artery and bronchus, respectively. ET-1 potency was 25 times greater in equine pulmonary artery than in equine bronchus (concentration of ET-1 producing 50% of maximal contraction [EC50] = 5.6 10,9 mol/l and 2.2 10,8 mol/l, respectively). In pulmonary artery, ET-1 induced contractions were significantly inhibited by the ETA receptor antagonist BQ123 (1 ,mol/l; dose-response curve to ET-1 was shifted to the right by 5.4-fold), but not by the ETB antagonist BQ788. In bronchus, dose-responses curves to ET-1 were shifted to the right by BQ123 (1 ,mol/l; 2.5-fold), but not by BQ788 (1 ,mol/l). In the presence of both antagonists, the dose-response curve to ET-1 was shifted to the right by 4.5-fold. Conclusions: These functional studies demonstrate that ET-1 is a potent spasmogen of equine third generation pulmonary artery and bronchus, and that contractions are mediated via ETA receptors in the former and both ETA and ETB receptors in the latter. Potential clinical relevance: Endothelin receptor antagonists may have potential for treating equine pulmonary hypertension or bronchoconstriction. [source] Equine pulmonary and systemic haemodynamic responses to endothelin-1 and a selective ETA receptor antagonistEQUINE VETERINARY JOURNAL, Issue 4 2001A. E. BENAMOU Summary Based on previous in vitro studies, we hypothesised that endothelin (ET) would induce vasoconstriction in the pulmonary circululation of the horse and that this action would be mediated via ETA receptors. Pulmonary and systemic haemodynamic responses to endothelin-1 (ET-1), a potent vasoactive endogenous peptide, were investigated in 6 conscious, nonsedated horses at rest. Bolus i.v. injections of exogenous ET-1 (0.1, 0.2 and 0.4 ,g/kg bwt) caused significant increases in pulmonary (PAP) and carotid (CAP) artery pressures, with peak increases of 79% and 51% for mean PAP and CAP, respectively. The effect of ET-1 on PAP and CAP was rapid and transient for PAP (,10 min) but prolonged for CAP (up to 60 min). ET-1 significantly decreased cardiac output by up to 35% and significantly increased systemic vascular resistance (SVR) by up to 104%. Pulmonary vascular resistance (PVR) showed a trend (P>0.05) to increase with 0.2 and 0.4 ,g/kg bwt ET-1. Infusion of a selective ETA receptor antagonist (TBC11251) completely inhibited the responses to a subsequent bolus of 0.2 ,g/kg bwt ET-1. We conclude that exogenous ET-1 exerts a potent vasoconstrictive action on the pulmonary and systemic circulations of the horse. These effects appear to be mediated largely through ETA receptors in both circulations. Endothelin may play a role in hypertensive conditions in the horse. [source] The science of endothelin-1 and endothelin receptor antagonists in the management of pulmonary arterial hypertension: current understanding and future studiesEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 2009N. J. Davie Abstract Pathological vascular remodelling is a key contributor to the symptomatology of pulmonary arterial hypertension (PAH), and reversing this process may offer the best hope for improving this debilitating condition. The vascular remodelling process is believed to be due to endothelial cell dysfunction and to involve altered production of endothelial cell-derived vasoactive mediators. The observation that circulating plasma levels of the vasoactive peptide endothelin (ET)-1 are raised in patients with PAH, and that ET-1 production is increased in the pulmonary tissue of affected individuals, makes it a particularly interesting target for a therapeutic intervention in PAH. Clinical trials with ET receptor antagonists (ETRAs) show that they provide symptomatic benefit in patients with PAH, thereby proving the clinical relevance of the ET system as a therapeutic target. In this paper, we review the role of ET-1 together with the available data on the roles of the specific ET receptors and ETRAs in PAH. In particular, we discuss the possible role of ET receptor selectivity in the vascular remodelling process in PAH and whether selective ETA or nonselective ETA/ETB blockade offers the greatest potential to improve symptoms and alter the clinical course of the disease. [source] Dual ETA/ETB vs. selective ETA endothelin receptor antagonism in patients with pulmonary hypertensionEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 2006C. F. Opitz Abstract Since the identification of endothelin as a key mediator in the pathogenesis of several diseases, including pulmonary arterial hypertension (PAH), the pharmacologic control of the activated endothelin system with endothelin receptor antagonists (ETRA) has been a major therapeutic achievement for the treatment of patients with PAH. To date, dual ETA/ETB and selective ETA receptor antagonists have clinically been evaluated. To answer the question of whether selective or dual ETRA is preferable in patients with PAH, experimental and clinical data with relevance to the pulmonary circulation are reviewed in this article. Whereas experimental and clinical data provide unambiguous evidence that ETA receptors mediate the detrimental effects of ET-1, such as vasoconstriction and cell proliferation, the elucidation of the role of ETB receptors has been more complex. It has been shown that there is a subpopulation of ETB receptors on smooth muscle cells and fibroblasts mediating vasoconstriction and proliferation. On the contrary, there is clear evidence that endothelial ETB receptors continue to mediate vasodilation, vasoprotection and ET-1 clearance despite the pathology associated with pulmonary hypertension. More difficult to assess is the net effect of these mechanisms in patients to be treated with ETRA. When considering the available data from controlled clinical trials, nonselectivity does not appear to carry a relevant clinical benefit for the treatment of patients with PAH when compared with selective ETA receptor antagonism. [source] Mechanisms of renal hyporesponsiveness to ANP in heart failureEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 9 2003A. Charloux Abstract The atrial natriuretic peptide (ANP) plays an important role in chronic heart failure (CHF), delaying the progression of the disease. However, despite high ANP levels, natriuresis falls when CHF progresses from a compensated to a decompensated state, suggesting emergence of renal resistance to ANP. Several mechanisms have been proposed to explain renal hyporesponsiveness, including decreased renal ANP availability, down-regulation of natriuretic peptide receptors and altered ANP intracellular transduction signal. It has been demonstrated that the activity of neutral endopeptidase (NEP) is increased in CHF, and that its inhibition enhances renal cGMP production and renal sodium excretion. In vitro as well as in vivo studies have provided strong evidence of an increased degradation of intracellular cGMP by phosphodiesterase in CHF. In experimental models, ANP-dependent natriuresis is improved by phosphodiesterase inhibitors, which may arise as new therapeutic agents in CHF. Sodium-retaining systems likely contribute to renal hyporesponsiveness to ANP through different mechanisms. Among these systems, the renin-angiotensin-aldosterone system has received particular attention, as angiotensin II and ANP have renal actions at the same sites and inhibition of angiotensin-converting enzyme and angiotensin-receptor blockade improve ANP hyporesponsiveness. Less is known about the interactions between the sympathetic nervous system, endothelin or vasopressin and ANP, which may also blunt ANP-induced natriuresis. To summarize, renal hyporesponsiveness to ANP is probably multifactorial. New treatments designed to restore renal ANP efficiency should limit sodium retention in CHF patients and thus delay the progression to overt heart failure. [source] Role of gap junctional coupling in astrocytic networks in the determination of global ischaemia-induced oxidative stress and hippocampal damageEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2006Jose L. Perez Velazquez Abstract While there is evidence that gap junctions play important roles in the determination of cell injuries, there is not much known about mechanisms by which gap junctional communication may exert these functions. Using a global model of transient ischaemia in rats, we found that pretreatment with the gap junctional blockers carbenoxolone, 18,-glycyrrhetinic acid and endothelin, applied via cannulae implanted into the hippocampus in one hemisphere, resulted in decreased numbers of TUNEL-positive neurons, as compared with the contralateral hippocampus that received saline injection. Post-treatment with carbenoxolone for up to 30 min after the stroke injury still resulted in decreased cell death, but post-treatment at 90 min after the ischaemic insult did not result in differences in cell death. However, quinine, an inhibitor of Cx36-mediated gap junctional coupling, did not result in appreciable neuroprotection. Searching for a possible mechanism for the observed protective effects, possible actions of the gap junctional blockers in the electrical activity of the hippocampus during the ischaemic insult were assessed using intracerebral recordings, with no differences observed between the saline-injected and the contralateral drug-injected hippocampus. However, a significant reduction in lipid peroxides, a measure of free radical formation, in the hippocampus treated with carbenoxolone, revealed that the actions of gap junctional coupling during injuries may be causally related to oxidative stress. These observations suggest that coupling in glial networks may be functionally important in determining neuronal vulnerability to oxidative injuries. [source] Ouabain stimulates endothelin release and expression in human endothelial cells without inhibiting the sodium pumpFEBS JOURNAL, Issue 5 2004Robert Saunders Ouabain, a sodium pump (Na+/,K+ -ATPase) inhibitor, has been shown to act as a hormone and is possibly involved in the pathogenesis of hypertension. The mechanism by which ouabain may act was investigated using primary cultures of human umbilical artery endothelial cells (HUAECs), which are known to express and release the vasoconstrictive hormone endothelin (ET-1). Five minutes after application, low concentrations of ouabain induced Ca2+ oscillations and stimulated ET-1 release from endothelial cells into the medium. To investigate whether the observed effects were due to inhibition of the sodium pump, the effects of ouabain on the uptake of 86Rb+ by HUAECs were examined. Unexpectedly, ouabain concentrations below 10 nm stimulated 86Rb+ uptake by 15,20%, and in some experiments by 50%, results that are consistent with a stimulation of the pump. Within the concentration range 1,10 nm, ouabain induced a 2.5-fold stimulation (phosphorylation) of mitogen-activated protein kinase (MAP kinase). After incubation of HUAECs with ouabain for 12 h, the glycoside stimulated cell growth by 49 ± 4%, as measured by cell number, with a maximum response at 5 nm. At similar concentrations, ouabain also increased ET-1 mRNA abundance by 19.5 ± 3.1%. The results indicate that, by influencing ET-1 expression and release, ouabain may contribute to the regulation of vascular tone. The data also confirm that it is not a global inhibition of the sodium pump that is involved in the mechanism of action of this cardiac glycoside. [source] Gq/11-induced intracellular calcium mobilization mediates Per2 acute induction in Rat-1 fibroblastsGENES TO CELLS, Issue 9 2006Naoyuki Takashima Phase resetting is one of the essential properties of circadian clocks that is required for the adjustment to a particular environment and the induction of Per1 and Per2 clock genes is believed to be a primary molecular event during this process. Although the intracellular signal transduction pathway underlying Per1 gene activation has been well characterized, the mechanisms that control Per2 up-regulation have not yet been elucidated. In our present study, we demonstrate that Gq/11 coupled receptors mediate serum-induced immediate rat Per2 (rPer2) transactivation in Rat-1 fibroblasts via intracellular Ca2+ mobilization. Stimulation of these cells with a high concentration of serum was found to rapidly increase the intracellular Ca2+ levels and strongly up-regulated rPer2 gene. rPer2 induction by serum stimulation was abrogated by intracellular Ca2+ chelation and depletion of intracellular Ca2+ store, which suggests that the calcium mobilization is necessary for the up-regulation of rPer2 gene. In addition, suppression of Gq/11 function was observed to inhibit both Ca2+ mobilization and rPer2 induction. Further, we demonstrated that endothelin-induced acute rPer2 transactivation via Gq/11-coupled endothelin receptors is also suppressed by a Gq/11 specific inhibitor. These findings together suggest that serum and endothelin utilize a common Gq/11-PLC mediated pathway for the transactivation of rPer2, which involves the mobilization of calcium from the intracellular calcium store. [source] Morpholino phenocopies of endothelin 1 (sucker) and other anterior arch class mutationsGENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 3 2001Craig T. Miller No abstract is available for this article. [source] Role of the astrocytic ETB receptor in the regulation of extracellular endothelin-1 during hypoxiaGLIA, Issue 1 2001Martin Hasselblatt Abstract Astrocytes are known to possess an effective endothelin (ET) eliminatory system which involves astrocytic ETA and ETB receptors and may become particularly relevant under pathophysiological conditions. The present study has therefore been designed to explore the effect of standardized hypoxia on extracellular concentrations of endothelin-1 (ET-1) and on endothelin-converting enzyme (ECE) activity in primary rat astrocytes genetically (sl/sl) or experimentally (dexamethasone) deficient in ETB receptors. The results revealed (1) a hypoxia-mediated decrease of extracellular ET-1 in wildtype astrocytes (+/+) that was not observed in ETB -deficient (sl/sl) cultures; (2) an ET receptor antagonist-induced increase in ET-1 in the media of both genotypes with further elevation upon hypoxia in +/+ cultures only; (3) augmentation of the dexamethasone-induced increase in extracellular ET-1 by hypoxia in +/+, but not in sl/sl cultures; (4) synergistic reduction of ETB gene transcription by hypoxia and dexamethasone; and (5) significant increases in endothelin-converting enzyme activity in the presence of hypoxia. To conclude, hypoxia stimulates astrocytic release of mature ET-1. This stimulation is (over)compensated for by increased ET-1 binding to functional ETB receptors. ETB deficiency, whether genetic or experimentally induced, impairs elimination of extracellular ET-1. GLIA 34:18,26, 2001. © 2001 Wiley-Liss, Inc. [source] Role of endothelin in endotoxin-induced hepatic microvascular dysfunction in rats fed chronically with ethanolJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 8 2001Yoshinori Horie Abstract Background: We examined the role of endothelin in endotoxin-induced hepatic microcirculatory disturbance in pair-fed rats given a liquid diet containing ethanol or isocaloric control. Methods and Results: One lobe of the liver was observed with the use of an intravital microscope. Erythrocytes (RBCs) labeled with fluorescein isothiocyanate (FITC) were injected, and the flow velocity of the FITC-RBCs in the sinusoids was measured with an off-line velocimeter. The flow velocity decreased 30 min after 1 mg/kg of lipopolysaccharide (LPS) was administered to the controls, and portal pressure (PP) was increased at 60 min. In ethanol-fed rats, however, both the flow velocity and PP increased in the early phase (at 10 min), and in the late phase, flow velocity decreased and PP increased more than in the controls. The LPS-induced decrease in flow velocity was blunted, when BQ-123, an antagonist of endothelin receptor subtype A, was infused into ethanol-fed rats, and BQ-123 also attenuated the change in PP. The plasma endothelin levels in both systemic and portal blood of the ethanol-fed rats were higher than in the controls. Conclusions: These results suggest that endothelin plays a role in the LPS-induced hepatic microcirculatory disturbance, especially in alcohol-fed animals. [source] Endogenous endothelin in a rat model of acute colonic mucosal injuryJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 10 2000Masamitsu Sugimachi Abstract Background: Endothelin (ET) is involved in various biologic activities in non-vascular and vascular tissues. While ET has some significant effects on gastrointestinal functions, the possible role of endogenous ET in the host response to mucosal injury has not been well clarified. Methods: The present study describes an investigation of the effects of an endothelin A receptor antagonist, BQ-123, on lactate dehydrogenase (LDH), mucus and albumin flux into the perfusate in a rat model of acute colonic injury, induced by acetic acid perfusion. The present study also examined localization of ET in damaged rat colons by using immunohistochemistry. Results: A 4% acetic acid treatment induced mild mucosal damage of perfused rat colon and increased LDH as well as albumin and protein-bound hexose release into the perfusate. Pretreatment with BQ-123 significantly reduced LDH activity and protein-bound hexose concentration in the perfusate and delayed the reduction of albumin leakage from damaged mucosa. Vascular endothelial, neural and surface epithelial cells of the colon showed strong ET-like immunoreactivity. Mucosal damage markedly influenced ET expression by epithelial cells. Mild mucosal damage decreased the ET expression by surface epithelial cells while moderate mucosal damage induced a mosaic location of ET-positive epithelial cells in the crypt. Severe mucosal damage abolished the ET expression by epithelial cells. Conclusions: Endothelin may play a role in the host response to acute mucosal damage. Mucosal ET production is significantly affected by mucosal injury. [source] Raloxifene, conjugated oestrogen and endothelial function in postmenopausal womenJOURNAL OF INTERNAL MEDICINE, Issue 1 2003E. J. J. Duschek Abstract., Duschek EJJ, Stehouwer CDA, de Valk-de Roo GW, Schalkwijk CG, Lambert J, Netelenbos C (VU University Medical Center, Amsterdam; Sophia Hospital, Zwolle; The Netherlands). Raloxifene, conjugated oestrogen and endothelial function in postmenopausal women. J Intern Med 2003; 254: 85,94. Objectives., To study the long-term effects of raloxifene, a potential designer oestrogen, and oestrogen monotherapy on endothelial function in healthy postmenopausal women. Design., A 2-year double-blind, randomized and placebo-controlled study in an Academic Medical Center. Fifty-six hysterectomized but otherwise healthy postmenopausal women randomly received raloxifene hydrochloride 60 mg day,1 (n = 15) or 150 mg day,1 (n = 13), conjugated equine oestrogen (CEE) 0.625 mg day,1 (n = 15), or placebo (n = 13). Main outcome measures., Endothelial function as estimated from brachial artery flow-mediated, endothelium-dependent vasodilation and nitroglycerine-induced endothelium-independent vasodilation, and plasma levels of the endothelium-derived regulatory proteins, von Willebrand factor (vWF) and endothelin (ET). Results., Raloxifene 60 mg did not significantly affect endothelial function. As compared with placebo, at 6 months of therapy, raloxifene 150 mg and CEE were associated with a mean increase in vWF of 25.5% point (95% CI 3.6,47.3) and 26.6% point (95% CI 6.9,46.3), respectively. At 24 months of therapy, raloxifene 150 mg was associated with a mean decrease in ET of 0.96 pg mL,1 (95% CI ,1.57 to ,0.36). Raloxifene nor CEE significantly affected endothelium-dependent and/or -independent vasodilation. Conclusions., Our results suggest that long-term therapy with raloxifene or oral CEE does not affect endothelium-dependent vasodilation in healthy postmenopausal women. Raloxifene 150 mg day,1 might have both positive and negative effects on endothelium. The clinical significance of these findings remains to be investigated. [source] Characterizing closely spaced, complex disulfide bond patterns in peptides and proteins by liquid chromatography/electrospray ionization tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2002Ten-Yang Yen Abstract Identifying the Cys residues involved in disulfide linkages of peptides and proteins that contain complex disulfide bond patterns is a significant analytical challenge. This is especially true when the Cys residues involved in the disulfide bonds are closely spaced in the primary sequence. Peptides and proteins that contain free Cys residues located near disulfide bonds present the additional problem of disulfide shuffling via the thiol,disulfide exchange reaction. In this paper, we report a convenient method to identify complex disulfide patterns in peptides and proteins using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) in combination with partial reduction by tris(2-carboxyethyl)phosphine (TCEP). The method was validated using well-characterized peptides and proteins including endothelin, insulin, ,-conotoxin SI and immunoglobulin G (IgG2a, mouse). Peptide or protein digests were treated with TCEP in the presence of an alkylation reagent, maleimide-biotin (M-biotin) or N -ethylmaleimide (NEM), followed by complete reduction with dithiothreitol and alkylation by iodoacetamide (IAM). Subsequently, peptides that contained alkylated Cys were analyzed by capillary LC/ESI-MS/MS to determine which Cys residues were modified with M-biotin/NEM or IAM. The presence of the alkylating reagent (M-biotin or NEM) during TCEP reduction was found to minimize the occurrence of the thiol,disulfide exchange reaction. A critical feature of the method is the stepwise reduction of the disulfide bonds and the orderly, sequential use of specific alkylating reagents. Copyright © 2001 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||||||||