bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of four different methods to measure endothelium-dependent vasodilation in the human peripheral circulation
Authors: LIND Lars , HALL Jan , JOHANSSON Kristina
Published: August 2015

At present, several techniques exist that claim to evaluate endothelium-dependent vasodilation (EDV) in the human peripheral circulation. The present study aims to evaluate the relationships between four of these techniques. A group of 24 young, healthy subjects underwent measurements of EDV and endothelium-independent vasodilation (EIDV) in predominately resistance vessels in the forearm using the invasive forearm technique with local infusion of methacholine and sodium nitroprusside, evaluation of flow-mediated vasodilation (FMD) in the conduit brachial artery measured by ultrasound, with or without the addition of ischaemic hand exercise, and evaluation of the reduction in the relative height of the inflection point of the radial pulse wave following β2-adrenergic receptor stimulation. The reduction in the relative height of the inflection point following β2-adrenergic receptor stimulation was significantly related to both EDV and EIDV in the forearm (r =-0.41 and r =-0.42 respectively; both P<0.05), but not to the EDV/EIDV ratio (r =-0.10). However, FMD, with or without the addition of ischaemic hand exercise, was not significantly related to the results obtained using the other two techniques (r =-0.18 to +0.13). In conclusion, the reduction in the relative height of the inflection point of the pulse wave following β2-adrenergic receptor stimulation was related to both EDV and EIDV measured by the invasive forearm technique, indicating that the pulse wave technique does not measure EDV specifically. FMD in the brachial artery, with or without ischaemic hand exercise, was not significantly related to values obtained using the other two techniques, indicating that endothelial function differs between conduit and resistance arteries, and that both of these measurements should be evaluated in future studies.
The effect of rate of weight loss on erythrocyte glutathione concentration and synthesis in healthy obese men
Authors: FABER Peter , JOHNSTONE Alexandra M. , GIBNEY Eileen R. , ELIA Marinos , STUBBS R. James , DUTHIE Gary G. , CALDER A. Graham , LOBLEY Gerald E.
Published: August 2015

Obesity is commonly associated with a high incidence and prevalence of dyslipidaemia, cardiovascular disease and Type II diabetes. Interestingly, studies have also reported decreased antioxidant levels in obese subjects. This may constitute an independent risk factor in the pathogenesis of coronary artery disease as obese subjects would have a decreased capacity to prevent the oxidative modification of low-density lipoproteins, which is a mechanism suggested as central to the development of atherogenesis. As part of a study to investigate responses to weight loss, we have assessed the effects on GSH status of a decrease in body mass of 5%, either after 6 days of complete starvation or 11 days of a very low calorie diet (2.55MJ/day). There were significant differences between the two groups in the synthesis rate of erythrocyte GSH in response to weight loss. Both the fractional and the erythrocyte synthesis rate of GSH decreased significantly (P<0.01) in the starvation group by 22% and 16% respectively. In contrast, no change in synthesis rates was observed in the very low calorie diet group (P>0.05). Total erythrocyte concentration of GSH was unaffected by the weight loss within both groups. These results suggest that erythrocyte GSH synthesis is depressed in response to a very rapid weight loss induced by fasting. An acute reduction in GSH synthesis in response to a rapid weight loss may constitute a risk factor during periods of increased GSH demands.
Ageing is associated with impairment of nitric oxide and prostanoid dilator pathways in the human forearm
Authors: SINGH Nivedita , PRASAD Sanjay , SINGER Donald R.J. , Mac ALLISTER Raymond J.
Published: August 2015

Ageing is associated with endothelial dysfunction and increased cardiovascular risk. We assessed the activity of nitric oxide (NO) and prostaglandin pathways in older subjects. Bilateral venous occlusion plethysmography was used to measure forearm blood flow during intra-arterial infusion of the NO synthase inhibitor, NG-monomethyl-l-arginine (l-NMMA; 1, 2 and 4μmol/min), the cyclo-oxygenase inhibitor, aspirin (3, 9 and 30μmol/min), and the smooth muscle constrictor, noradrenaline (60, 120 and 240pmol/min); each dose infused for 5min. Eighteen young and 15 healthy older subjects (mean age±S.E.M., 32±1 and 65±1 years respectively) were studied. Effects of treatment were calculated from the ratio of blood flow in the infused to control arm, expressed as a percentage. Dose-response curves were compared by analysis of the area under the curve (AUC) using independent samples t test. All agents caused dose-dependent decreases in basal forearm blood flow. AUC values for noradrenaline, aspirin and l-NMMA in younger and older subjects were 162±24, 173±24 and 170±17, and 138±22, 70±22 and 89±22 respectively. Effects of aspirin and l-NMMA, but not noradrenaline, were reduced in older subjects (P = 0.004, 0.007 and 0.461 respectively). Our findings suggest a generalized abnormality of basal endothelial function in older people, with similar impairment of NO and prostanoid dilator pathways. Defects in both pathways could contribute to the development of age-related cardiovascular disease.
Pathobiology and experimental therapeutics in hepatocellular cholestasis: lessons from the hepatocyte couplet model
Authors: MILKIEWICZ Piotr , ROMA Marcelo G. , ELIAS Elwyn , COLEMAN Roger
Published: August 2015

Preparations of isolated liver cells, either freshly prepared or in culture, have been available for many years; however, because they lack the polarization of the cell in the tissue, their application to the study of processes involved in bile formation has been very limited. The hepatocyte couplet model offers a unique opportunity to study in vitro the intracellular processes involved: not only the physiology and pathophysiology of bile formation, but also the corresponding structural and molecular disturbances underlying different experimental models of cholestasis. In this review we describe the experimental data generated from this model in our laboratory over a period of years, including application of hepatocyte couplets to the study of cytoskeletal changes within the hepatocyte and mechanisms of hepatoprotection in experimentally induced, clinically relevant models of intrahepatic cholestasis.
Action of the endothelin receptor (ETA) antagonist BQ-123 on forearm blood flow in young normotensive subjects
Authors: WIMALASUNDERA R.C. , THOM S.A.McG. , REGAN L. , HUGHES A.D.
Published: August 2015

Endothelin-1 (ET-1) has been proposed to contribute to the regulation of vascular tone in humans. BQ-123, an ETA receptor antagonist, has also been reported to increase forearm blood flow (FBF) in vivo; however, the efficacy of BQ-123 as an antagonist of ET-1 has not been evaluated in the forearm. The present study investigated the effects of BQ-123 on changes in FBF in response to ET-1 and noradrenaline (NA; norepinephrine), taking into account the possible influence of vasodilator effects of BQ-123 on responses to vasoconstrictors. Six subjects (age 25-34 years) participated in a double-blind randomized study. FBF was measured by forearm occlusion plethysmography. Drugs were infused intra-arterially into the non-dominant arm (study arm) on four separate occasions; the non-infused arm was used as a control. The effects of BQ-123 (50nmol/min for 60min, or 300nmol/min for 5min followed by saline for 55min) were compared with the effects of infusion of sodium nitroprusside (SNP; 12nmol/min for 60min) or saline on vasoconstriction induced by ET-1 (10pmol/min for 7min) and NA (120pmol/min for 7min). Infusion of BQ-123 at either dose did not significantly increase FBF, whereas SNP increased FBF by 134% (P = 0.03). ET-1 significantly reduced FBF, and this effect was almost completely inhibited by both doses of BQ-123, but was unaffected by SNP. NA also reduced FBF, and this action was unaffected by BQ-123 or SNP. The data show that BQ-123 is a selective ET-1 antagonist, but do not confirm a major role for ET-1 in influencing resting forearm vascular tone in young normotensive subjects.
Myocardial abnormalities in hypertensive patients with normal and abnormal left ventricular filling: a study of ultrasound tissue characterization and strain
Authors: YUDA Satoshi , SHORT Leanne , LEANO Rodel , MARWICK Thomas H.
Published: August 2015

Abnormal left ventricular (LV) filling is common, but not universal, in hypertensive LV hypertrophy (LVH). We sought to elucidate the relative contributions of myocardial structural changes, loading and hypertrophy to LV dysfunction in 113 patients: 85 with hypertensive LVH and 28 controls without LVH and with normal filling. Patients with normal dobutamine stress echocardiography and no history of coronary artery disease were selected, in order to exclude a contribution from ischaemia or scar. Abnormal LV filling was identified in 65 LVH patients, based on Doppler measurement of transmitral filling and annular velocities. All patients underwent grey-scale and colour tissue Doppler imaging from three apical views, which were stored and analysed off line. Integrated backscatter (IB) and strain rate imaging were used to detect changes in structure and function; average cyclic variation of IB, strain rate and peak systolic strain were calculated by averaging each segment. Calibrated IB intensity, corrected for pericardial IB intensity, was measured in the septum and posterior wall from the parasternal long-axis view. Patients with LVH differed significantly from controls with respect to all backscatter and strain parameters, irrespective of the presence or absence of abnormal LV filling. LVH patients with and without abnormal LV filling differed with regard to age, LV mass and incidence of diabetes mellitus, but also showed significant differences in cyclic variation (P<0.01), calibrated IB in the posterior wall (P<0.05) and strain rate (P<0.01), although blood pressure, heart rate and LV systolic function were similar. Multivariate logistic regression analysis demonstrated that age, LV mass index and calibrated IB in the posterior wall were independent determinants of abnormal LV filling in patients with LVH. Thus structural and functional abnormalities can be detected in hypertensive patients with LVH with and without abnormal LV filling. In addition to age and LVH, structural (not functional) abnormalities are likely to contribute to abnormal LV filling, and may be an early sign of LV damage. IB is useful for the detection of myocardial abnormalities in patients with hypertensive LVH.
Genetic variation at the interleukin-1 locus is a determinant of changes in soluble endothelial factors in patients with acute coronary syndromes
Authors: RAY Kausik K. , CAMP Nicola J. , BENNETT Claire E. , FRANCIS Sheila E. , CROSSMAN David C.
Published: August 2015

Acute coronary syndromes (ACSs) are associated with both systemic inflammatory activation and endothelial cell activation, and both of these are linked to patient outcome. Genetic variation at the interleukin-1 (IL-1) locus influences the clinical patterns of inflammatory disease. We therefore examined the association between IL-1 gene polymorphisms and levels of systemic inflammatory activation markers [C-reactive protein (CRP) and IL-1 receptor antagonist (IL-1ra)] and of soluble endothelial activation markers [von Willebrand factor (vWF) and E-selectin], in a cohort of 63 patients presenting with non-ST-elevation ACS. The IL-1 locus did not significantly influence any of the markers studied at 24h after presentation. Associations of IL-1 polymorphisms with the changes (Δ) in CRP, IL-1ra, E-selectin and vWF levels between 24 and 48h were examined in later studies. ΔCRP and ΔIL-1ra showed no significant association with any of the polymorphisms studied. There was a strong association between carriage of the rare allele (allele 2) of the intron 2 variable number of tandem repeats polymorphism of IL-1RN (designated IL-1RN*2) and ΔE-selectin levels: {carriage of *2, 3.03 ng/ml [95% confidence interval (CI) 6.26 to 1.51ng/ml]; non-carriage of *2, 0.12ng/ml (95% CI 1.07 to -1.76ng/ml); P = 0.0016}, and also between carriage of IL-1RN*2 and ΔvWF levels [carriage of *2, 0.78i.u./ml (95% CI 0.96 to 0.44i.u./ml); non-carriage of *2, 0.1i.u./ml (95% CI 0.19 to -0.1i.u./ml); P = 0.0003]. A composite analysis consisting of carriage of IL-1RN*2 and the genotype at position -511 in the IL-1B gene suggests the existence of haplotypes that influence ΔvWF and ΔE-selectin in patients with ACS. Carriage of IL-1RN*2 was also associated with a 2-fold increased likelihood of a troponin-positive status compared with non-carriage (P = 0.0385). These data indicate that, in the setting of non-ST-elevation ACS, genetic variation at the IL-1 gene locus contributes to the changes in soluble markers of endothelial inflammation.
Effects of the protein kinase Cβ inhibitor LY333531 on neural and vascular function in rats with streptozotocin-induced diabetes
Authors: COTTER Mary A. , JACK Alison M. , CAMERON Norman E.
Published: August 2015

Elevated protein kinase C activity has been linked to the vascular and neural complications of diabetes. The aim of the present study was to examine the involvement of the β-isoform of protein kinase C in abnormalities of neuronal function, neural tissue perfusion and endothelium-dependent vasodilation in diabetes, by treatment with the selective inhibitor LY333531 (10mg·kg-1·day-1). Diabetes was induced in rats by streptozotocin; the duration of diabetes was 8 weeks. Nerve conduction velocity was monitored, and responses to noxious mechanical and thermal stimuli were estimated by the Randall–Sellito and Hargreaves tests respectively. Sciatic nerve and superior cervical ganglion blood flow were measured by microelectrode polarography and hydrogen clearance. Vascular responses were examined using the in vitro mesenteric bed preparation. An 8-week period of diabetes caused deficits in sciatic motor (20%) and saphenous nerve sensory (16%) conduction velocity, which were reversed by LY333531. Diabetic rats had mechanical and thermal hyperalgesia. LY333531 treatment did not affect mechanical thresholds, but corrected thermal hyperalgesia. Sciatic nerve and superior cervical ganglion blood flow were both reduced by 50% by diabetes; this was almost completely corrected by 2 weeks of LY333531 treatment. Diabetes caused a 32% reduction in vasodilation of the mesenteric vascular bed in response to acetylcholine, mediated by nitric oxide and endothelium-derived hyperpolarizing factor. When the former was abolished during nitric oxide synthase inhibition, an 80% diabetic deficit in the remaining relaxation was noted. LY333531 treatment attenuated the development of these defects by 64% and 53% respectively. Thus protein kinase Cβ contributes to the neural and vascular complications of experimental diabetes; LY333531 is a candidate for further study in clinical trials of diabetic neuropathy and vasculopathy.
Human internal mammary artery organ culture model of coronary stenting: a novel investigation of smooth muscle cell response to drug-eluting stents
Authors: SWANSON Neil , JAVED Qamar , HOGREFE Kai , GERSHLICK Anthony
Published: August 2015

Local drug delivery by coronary stents is of current research interest. Organ culture of human vascular tissue is a model of intimal hyperplasia. We report an ex vivo organ culture model of stented vessels. This allows stent–artery interactions to be studied in living tissue. The recognized anti-restenosis agent paclitaxel was chosen to test the organ culture model. Mammary artery specimens were cultured ‘closed’ (i.e. without opening them flat) for 72h. Phosphocholine-coated stents, half of them loaded with the anti-restenosis drug paclitaxel, were implanted. The absorption and elution characteristics of paclitaxel were established. Artery tissue remained viable at 72h when cultured closed, despite stent implantation. Specimens developed smooth muscle cell proliferation. The stents absorbed up to 127±29μg of paclitaxel, with a biphasic elution curve. A mean of 13% of the absorbed paclitaxel remained after a 24h perfusion. In mammary artery, these paclitaxel stents reduced or abolished smooth muscle cell proliferation compared with controls. This model allows the effects of stenting on human arterial tissue to be studied for at least 72h, long enough to demonstrate effects on smooth muscle cell proliferation. Phosphocholine-coated stents absorb adequate doses of paclitaxel, which is eluted gradually, inhibiting muscle cell proliferation. Such an organ culture model of stented mammary artery will provide useful data in addition to that from animal or cell culture models of drug-eluting stents.
Role of macrophage CD44 in the disposal of inflammatory cell corpses
Authors: VIVERS Sharon , DRANSFIELD Ian , HART Simon P.
Published: August 2015

Understanding the cellular and molecular mechanisms that determine whether inflammation resolves or progresses to scarring and tissue destruction should lead to the development of effective therapeutic strategies for inflammatory diseases. Apoptosis of neutrophil granulocytes is an important determinant of the resolution of inflammation, providing a mechanism for down-regulation of function and triggering clearance by macrophages without inducing a pro-inflammatory response. However, if the rate of cell death by apoptosis is such that the macrophage clearance capacity is exceeded, apoptotic cells may progress to secondary necrosis, resulting in the release of harmful cellular contents and in damage to the surrounding tissue. There are many possible ways in which the rate and capacity of the macrophage-mediated clearance of apoptotic cells may be enhanced or suppressed. Ligation of human macrophage surface CD44 by bivalent monoclonal antibodies rapidly and profoundly augments the capacity of macrophages to phagocytose apoptotic neutrophils in vitro. The molecular mechanism behind this effect and its potential significance in vivo is a current focus of research.
Comparison of the effects of atherosclerosis and nitrate therapy on responses to nitric oxide and endothelin-1 in human arteries in vitro
Authors: WILEY Katherine E. , DAVENPORT Anthony P.
Published: August 2015

The effect of previous nitrate therapy on vascular responses to endothelin-1 (ET-1) and NO was investigated in human internal mammary artery (IMA) in vitro. Cumulative concentration–response curves to ET-1 were constructed in rings of IMA and the data grouped into IMA from patients given nitrates prior to the bypass graft operation (nitrate group) and IMA from patients who were not prescribed nitrates (control group). No significant differences were observed between the two groups, either in EC50 value [P>0.05; 3.5nM (2.4–5.3nM; 95% confidence interval) and 4.8 (2.2–10nM), nitrate and control groups respectively] or Emax (P>0.05; 78±7.5% and 85±9.5%, nitrate and control group respectively). No significant differences in concentration–response curves to the NO-donor diethylamine NONOate (DEA/NO) in rings of IMA pre-constricted with 10nM ET-1 were observed between control and nitrate groups [P>0.05; EC50 values 0.59 (0.21–1.7) µM and 0.17 (0.03–0.87) µM; Emax 110±5.7% and 112±4.5%, nitrate and control groups respectively]. Concentration–response curves to DEA/NO constructed in normal coronary artery were not significantly different from those in coronary artery obtained from patients with ischaemic heart disease (IHD) [P>0.05; Emax 124±11% and 138±20%; EC50 0.08 (0.02–0.30) µM and 0.23 (0.02–24) µM, normal and IHD respectively]. These data indicate that nitrate therapy does not induce long-term changes in the ET signalling pathway. Furthermore, the tolerance to nitrate therapy is likely to be because of impaired bio-transformation of the drug rather than reduced sensitivity of the media to NO. The similar responses to DEA/NO in normal and atherosclerotic coronary artery suggests that the reduced vasodilator responses in IHD is because of a dysfunctional endothelium and is not mediated by changes in the NO signalling pathway of the smooth muscle.
Expression of endothelin-1 and vasoactive intestinal contractor genes in mouse organs during the perinatal period
Authors: UCHIDE Tsuyoshi , FUJIMORI Yuki , SASAKI Takushi , TEMMA Kyosuke , ADUR Javier , MASUO Yoshinori , KOZAKAI Takaharu , LEE Yun-Sik , SAIDA Kaname
Published: August 2015

In an attempt to understand the significance of endothelin-1 (ET-1) and vasoactive intestinal contractor (VIC)/ET-2 peptides in organs during perinatal development, we performed quantitative analysis of ET-1 and VIC gene expression in mouse organs obtained from embryos at days 14 and 17 (E-14 and E-17) of pregnancy, neonates at days 0, 1, 3 and 7 after birth (N-0, -1, -3 and -7), and adult mice (10 weeks old). In intestine, VIC gene expression progressively increased between E-14 and N-1 (approximately 10-fold) and then remained constant into adulthood. ET-1 gene expression exhibited a one-step increase between E-17 and N-0, subsequently remaining constant. In lung, a sharp increase in ET-1 mRNA level (approximately 10-fold) was noticed between E-14 and N-0. The gene expression pattern of VIC, with a peak at N-0, was similar to that of ET-1 although the expression level of VIC was two to three orders of magnitudes lower than that of ET-1. Gene expression patterns of ET-1 and VIC remained nearly constant in brain, heart, liver and kidney throughout the period examined. Considering that the intestinal and pulmonary gene expression levels of both genes reached almost the same level as observed in adult soon after birth, we suggest that these peptides may be involved in the emergence and maintenance of intestinal and pulmonary functions vital after birth.
Differential vasoactive response to endothelin receptor antagonists and prostacyclin in patients with severe pulmonary hypertension
Authors: APOSTOLOPOULOU Sotiria C. , KOURGIANNIDIS Georgios , MANGINAS Athanassios , KYRIAKIDES Zenon S. , WEBB David , RAMMOS Spyridon , KREMASTINOS Dimitrios T. , COKKINOS Dennis V.
Published: August 2015

Pulmonary hypertension (PH) is a rare disease of the pulmonary vasculature with diverse pathogenetic mechanisms. Vasoactive substances such as endothelin A receptor (ETA) antagonists and prostanoids have been used to improve haemodynamics and clinical outcome. We compared the hemodynamic response to BQ-123 (an ETA receptor antagonist) and prostacyclin or its analogue iloprost in ten patients (four men) with a mean age of 35.9±15.6 years. Seven patients had primary PH and three had PH owing to connective tissue disease. Patients underwent haemodynamic evaluation before and after administration of intra-atrial BQ-123 (200mmol/min for 60min), intravenous prostacyclin (3ng·kg-1·min-1 for 4h) or iloprost as an aerosol (100µg over 24h). Response to vasodilator administration was defined as >15% decrease in pulmonary vascular resistance index (PVRI). Of the ten patients, five showed a response to BQ-123 and eight responded to prostanoids. Four patients were responders and one patient was a non-responder to both agents. PVRI decreased by 16.6±13.4% with BQ-123, and 24.4±15.7% with prostanoids (not statistically significant). The aetiology of PH did not affect the response to either drug. In conclusion, response to ETA antagonist or prostanoid administration can be achieved in a large group of patients with severe PH, however few patients respond identically to both agents. These findings are consistent with a multifactorial mechanism involved in this disease.
Endothelin-1 acts as a survival factor in ovarian carcinoma cells
Authors: DEL BUFALO Donatella , DI CASTRO Valeriana , BIROCCIO Annamaria , SALANI Debora , ROSANÒ Laura , SPINELLA Francesca , BAGNATO Anna
Published: August 2015

The aim of this study was to evaluate the role of endothelin-1 (ET-1) in the sensitivity of ovarian carcinoma to paclitaxel, one of the most common drugs used for the management of this tumour histotype. ET-1 is a powerful mitogenic peptide produced by ovarian carcinomas and it acts as an autocrine growth factor, selectively through ETA receptor (ETAR), which is predominantly expressed in this tumour. OVCA 433 and HEY, two ovarian carcinoma cell lines, which produce elevated amounts of ET-1 and express abundantly high-affinity ETARs, were used. As demonstrated by sub-G1 peak in DNA content histograms and terminal transferase deoxytidyl uridine end labelling assay, we found that paclitaxel induces cytotoxic effect through the activation of apoptosis in both cell lines. When the treatment with paclitaxel was performed in association with ET-1, paclitaxel-induced apoptosis was inhibited. In order to evaluate which ET-1 receptor mediated the effect of ET-1 on protection from paclitaxel-induced apoptosis, we performed experiments using two selective antagonists for ETAR (BQ-123) and for ETBR (BQ-788). We showed that ETAR blockade inhibits the ET-1-induced survival activity against paclitaxel-mediated apoptosis. However, no effect was observed on blocking ETBR with BQ-788. Our results establish a novel role for ET-1 in determining survival of ovarian carcinoma cells and suggest that pharmacological ETAR blockade using a specific ETAR antagonist may provide a novel approach to the treatment of ovarian carcinoma in combination therapy.
Effects of endothelin receptor antagonists on endothelin-1 and inducible nitric oxide synthase genes in a rat endotoxic shock model
Authors: HIRATA Yukio , ISHIMARU Shinya
Published: August 2015

Levels of the endothelium-derived vasoconstrictor endothelin (ET)-1 and the vasodilator nitric oxide (NO) are markedly increased in endotoxic shock, although the pathophysiological role of ET-1 and its relation to NO under septic conditions remains obscure. To delineate the roles of ET-1 and the ET receptors, and the NO/inducible NO synthase (iNOS) system in endotoxic shock, we examined the gene expression of ET-1, ET receptors A and B (ETA and ETB) and iNOS in the heart and the liver of a rat endotoxic shock model, and we studied the effects of ET receptor antagonists on haemodynamics, survival rate and expression of ET-1, ET receptors and iNOS. Administration of bacterial lipopolysaccharide (LPS) into rats caused a profound hypotension with resultant death. However, these effects were blocked by a non-selective ETA/ETB receptor antagonist (TAK044), but not by an ETA-selective antagonist (BQ123). Injection of LPS caused a marked elevation in the plasma levels of both ET-1 and NO, which were not affected by treatment with either ET receptor antagonist. Administration of LPS caused increases in levels of ET-1, ETB and iNOS mRNA in the heart and the liver, whereas ETA mRNA expression was markedly downregulated in these organs. These results suggest that ET receptor subtype genes are differentially regulated in major organs from endotoxic shock rats, and that non-selective ET receptor antagonists ameliorate endotoxin-induced hypotension and death irrespective of iNOS-derived NO.
Elevated systemic levels of endothelin-1 and blood pressure correlate with blunted constrictor responses and downregulation of endothelinA, but not endothelinB, receptors in an animal model of hypertension
Authors: TÉLÉMAQUE-POTTS Sabine , KUC Rhoda E. , MAGUIRE Janet J. , OHLSTEIN Eliot , YANAGISAWA Masashi , DAVENPORT Anthony P.
Published: August 2015

Hypertension is a major risk factor in the development of cardiovascular disease. Adenovirus gene transfer of endothelin-1 (Ad.CMV.ET-1) in rats produced significant (5-fold) increases in plasma ET-1 and systemic blood pressure (46%) 4 days after viral administration, compared with β-galactosidase (Ad.CMV.β-gal) injected as control. The density (Bmax) of the ET receptor ETA measured in aortas was reduced significantly by more than 50% to 17±2fmol·mg-1 of protein for the Ad.CMV.ET-1 group compared with 39±6fmol·mg-1 of protein for the control. There was no change in the density of the smaller population of the ETB sub-type. In agreement, the ratio of ETA mRNA to cyclophilin mRNA (a housekeeping gene) measured by Northern analysis was reduced in Ad.CMV.ET-1 rats compared with controls. The ratio of mRNA encoding the ETB sub-type did not change. ET-1 vasoconstriction was significantly reduced (P<0.05) in aortas from Ad.CMV.ET-1-treated rats [pD2 = 8.67±0.14 (where pD2 is -log10EC50); n = 11] versus the control (pD2 = 9.11±0.06; n = 14) but there was no significant difference in the potency of two other vasoconstrictors tested (noradrenaline and Arg-vasopressin), indicating this was a specific effect on ET receptors. There was no change in the affinity of ET-1 binding to either receptor sub-type in the experimental group compared with the control, demonstrating that the attenuation in the constrictor response is the result of the reduced density of receptors rather than a change in affinity. The results show that ETA (but not ETB) receptors are modulated in this experimental model of hypertension and provide further evidence for selective blockade of the ETA receptor as a therapeutic strategy.
Effects of a selective ETA-receptor antagonist, atrasentan (ABT-627), in murine models of allergic asthma: demonstration of mouse strain specificity
Authors: GOSSELIN Mélanie , GOULET Stéphanie , WU-WONG Jinshyun R. , WESSALE Jerry L. , OPGENORTH Terry J. , BOULET Louis-Philippe , BATTISTINI Bruno
Published: August 2015

Asthma is a chronic respiratory disease that is characterized by airway inflammation, bronchoconstriction and the influx of pro-inflammatory cells, mostly eosinophils in the lung tissue and bronchoalveolar space. Amongst the many physiopathological roles attributed to endothelins (ETs), one is to modulate pulmonary functions. It is established that Balb/c mice develop allergen-induced Th2-cytokine gene expression, airway inflammation and hyper-responsiveness whereas C57Bl/6 mice are much less reactive. In the present study, we investigated the roles of ETs in these two murine models of allergic asthma (AA). Mice were sensitized and challenged with either saline (S) and/or ovalbumin (O) over 6 weeks (groups S/S and O/O) and treated chronically with ABT-627 or its vehicle. Twenty-four hours after the last sensitization, challenged mice developed a marked airway inflammatory response characterized by the accumulation of total inflammatory cells (a 21-fold increase) in the bronchoalveolar space, similar in both mouse strains. The increase in eosinophils was marked in both groups, representing 98% of total cell count in O/O versus <1% in S/S. Macrophages were also increased 3-fold in both strains. ABT-627 did reduce the accumulation of macrophages in both stains (36 to 53%) whereas it blocked by 76% the influx of eosinophils in Balb/c but not in C57Bl/6 mice. These results show that ETA-receptor antagonism is more effective against O/O-induced AA in Balb/c mice, even though both strains were associated with the same increase in key pro-inflammatory cells in the bronchoalveolar space. It is unclear whether this is due to a lack or a disproportionate expression of ETA receptors in these two murine strains, or in post-receptor transduction modulation, or different regulation of ET receptors in various pulmonary cells, after sensitization and challenge.
Endothelin in human cerebrovascular nerves
Authors: LOESCH Andrzej , BURNSTOCK Geoffrey
Published: August 2015

Novel data is presented from this electron-immunocytochemical study that demonstrates endothelin-containing cerebrovascular nerves in the human middle cerebral artery.
The effect of diabetes on endothelin, interleukin-8 and vascular endothelial growth factor-mediated angiogenesis in rats
Authors: BEK Eugene L. , MCMILLEN Marvin A. , SCOTT Paul , ANGUS L. D. George , SHAFTAN Gerald W.
Published: August 2015

In diabetes mellitus, there is a problem of both premature atherosclerosis as well as impaired collateralization. Studies were performed using the rat corneal angiogenesis model as a surrogate for collateralization to determine the effect of diabetes mellitus on endothelin (ET)-1, ET-3, vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8)-mediated angiogenesis. In an initial group of experiments, streptozotocin-induced diabetes resulted in impairment of ET-1-mediated angiogenesis from 69% to 32%, but was only impaired from 74% to 59% for ET-3. When rats were fluid-resuscitated, mortality fell, and the incidence of inhibition of angiogenesis decreased for ET-1, but was still at 47%. Inhibition of ET-3-mediated angiogenesis in fluid-resuscitated rats was essentially unaffected from 74% to 75%. Studies of VEGF and IL-8 in fluid-resuscitated rats demonstrated that VEGF-mediated angiogenesis was only inhibited from 49% to 45%, but there was inhibition of IL-8-mediated angiogenesis from 62% to 31%. We concluded that there may be two mechanisms by which ET-1-mediated corneal angiogenesis is inhibited: a decrease in intravascular volume and dynamic forces affecting angiogenesis, and a direct effect of diabetes on some aspect of cell growth or angiogenic process. Diabetes also appeared to inhibit IL-8-mediated angiogenesis, but had very little or no effect on ET-3- or VEGF-mediated angiogenesis.
Reduction of endothelin-1 binding and inhibition of endothelin-1-mediated detrusor contraction by naftidrofuryl
Authors: CALVERT Robert C. , MUMTAZ Faiz H. , DASHWOOD Mick R. , KHAN Masood A. , MORGAN Robert J. , MIKHAILIDIS Dimitri P. , THOMPSON Cecil S.
Published: August 2015

Endothelin-1 (ET-1) causes urinary bladder smooth muscle contraction and the endothelin receptors A and B (ETA and ETB) are both known to be present in the rabbit urinary bladder. Alterations in ET-1 signalling have been implicated in the pathophysiology of urinary tract disorders secondary to bladder outlet obstruction and also in diabetic cystopathy. Naftidrofuryl (Naf) (marketed under the trade name Praxilene) improves walking distance in patients with peripheral vascular disease, an effect which may be partially attributed to ET-1 antagonism. The purpose of this study is to assess whether Naf will reduce ET-1 binding in the rabbit detrusor muscle and to assess whether there is inhibition of ET-1-mediated detrusor contraction. Detrusor smooth muscle strips were mounted in organ baths and cumulative response curves were measured for ET-1-mediated contractions in the presence and absence of 10-6M Naf (therapeutic concentration). In addition, ET-1 was added to the detrusor strips in the presence of the ETA antagonist, BQ123, and the ETB antagonist, BQ788, to identify the receptor subtype functionally involved. Overall inhibition of [125I]ET-1 binding by Naf was assessed using autoradiography. Identification of receptor-subtype binding reduction was assessed using the radioligands [125I]PD151242 and [125I]BQ3020. Naf inhibited ET-1-mediated detrusor contractions significantly (P<0.04), e.g. at 10-10M ET-1, contraction was completely abolished by Naf. Autoradiography indicated that Naf competitively inhibited [125I]ET-1 binding in a dose-dependent manner (IC50 = 3×10-7M). All radioligand binding was reduced indicating binding of Naf to both ETA and ETB receptors. Naf reduces binding of ET-1 to rabbit detrusor ETA and ETB receptors and inhibits ET-1-induced detrusor contractions mediated by ETA receptors. Naf may have therapeutic potential in the treatment of bladder disorders secondary to bladder outlet obstruction and diabetes mellitus.
Increased plasma urotensin II levels in patients with diabetes mellitus
Authors: TOTSUNE Kazuhito , TAKAHASHI Kazuhiro , ARIHARA Zenei , SONE Masahiko , ITO Sadayoshi , MURAKAMI Osamu
Published: August 2015

Urotensin II (UII) is the most potent vasoconstrictor peptide, whereas it acts as a vasodilator on some arteries. We studied plasma levels of UII in diabetic patients with normal serum creatinine levels (<90µmol/l) and the expression of UII and its receptor in cultured human vascular endothelial cells. Plasma UII levels were significantly elevated by 1.8-fold in diabetic patients without proteinuria (7.8±0.6fmol/ml; P<0.0001) and 1.7-fold in those with overt proteinuria (7.3±0.9fmol/ml; P = 0.0018) when compared with healthy subjects (4.4±0.2fmol/ml). No significant correlation was obtained between plasma UII levels and fasting blood sugar (P = 0.631 and P = 0.853 in non-proteinuric and proteinuric diabetic patients respectively), glycated haemoglobin levels (P = 0.376 and P = 0.888 respectively) or serum creatinine levels (P = 0.301 and P = 0.568 respectively). Reverse transcriptase-PCR analysis showed the expression of mRNAs encoding UII precursor and UII-receptor precursors in cultured human coronary artery endothelial cells and umbilical vein endothelial cells, suggesting that vascular endothelial cells are one of the sources of UII in blood. These findings suggest that elevation of plasma UII levels may be an important background factor in diabetic cardiovascular and organ complications in diabetic subjects without renal failure.
Vasoactive properties of lignocaine administered by iontophoresis in human skin
Authors: NEWTON David J. , AMYES Alexandra K.B. , KHAN Faisel , MCLEOD Graeme A. , BANNISTER Jonathan , BELCH Jill J.F.
Published: August 2015

The vasoactivity of lignocaine has an important influence on its clinical efficacy and systemic vascular absorption. The aim of this study was to evaluate its vasoactive properties when administered by the non-invasive technique of iontophoresis. We used laser Doppler imaging to measure the forearm skin blood flow responses of seven healthy young males to iontophoretic delivery of two preparations of 20g/l of lignocaine hydrochloride, one containing the preservatives methylparaben and propylparaben and one without. The subjects were blind to the order of drug administration, and we assessed analgesia at the sites using a pinprick test. Delivery of both preparations of (positively charged) lignocaine under the anode caused demonstrable analgesia, but no change in skin blood flow. An increase in perfusion was measured, however, when the preservative-containing preparation was administered under the cathode. There was little or no response to the solution without preservatives, although the difference in response between the two preparations was not statistically significant (P = 0.063). Although there were no vasoactive effects of lignocaine at the relatively low dose used in the present study, our results suggest that the preservatives methylparaben and propylparaben are the most likely cause of the vasodilatation that we observed under the cathode, and may therefore have a significant influence on the vasoactivity of this preparation when administered by injection. Both are negatively charged in solution and have been reported to possess vasodilator properties. It might be worth considering the use of alternative, non-vasoactive preservatives in local anaesthetic preparations, or avoiding the use of additives altogether, when this is feasible.
ETA receptors mediate vasoconstriction, whereas ETB receptors clear endothelin-1 in the splanchnic and renal circulation of healthy men
Authors: BÖHM Felix , PERNOW John , LINDSTRÖM Jonas , AHLBORG Gunvor
Published: August 2015

The contribution of the endothelin (ET) receptors ETA and ETB to basal vascular tone and ET-1-induced vasoconstriction in the renal and splanchnic vasculature was investigated in six healthy humans. ET-1 was infused alone and in combination with the selective ETA receptor antagonist BQ123 or the selective ETB receptor antagonist BQ788 on three different occasions. BQ123 did not affect basal arterial blood pressure, splanchnic vascular resistance (SplVR) or renal vascular resistance (RVR), but inhibited the increase in vascular resistance induced by ET-1 [64±18 versus -1±7% in SplVR (P<0.05); 36±6 versus 12±3% in RVR (P<0.0001)]. BQ788 increased basal SplVR and RVR [38±16% (P = 0.01) and 21±5% (P<0.0001) respectively], and potentiated the ET-1-induced vasoconstriction. Plasma ET-1 increased more after ETB blockade than under control conditions or after ETA blockade. These findings suggest that the ETA receptor mediates the splanchnic and renal vasoconstriction induced by ET-1 in healthy humans. The ETB receptor seems to function as a clearance receptor and may modulate vascular tone by altering the plasma concentration of ET-1.
Orthostatic challenge reveals impaired vascular resistance control, but normal venous pooling and capillary filtration in familial dysautonomia
Authors: BROWN Clive M. , STEMPER Brigitte , WELSCH Götz , BRYS Miroslaw , AXELROD Felicia B. , HILZ Max J.
Published: August 2015

Patients with familial dysautonomia (FD) frequently have profound orthostatic hypotension without compensatory tachycardia. Although the aetiology is presumed to be sympathetic impairment, peripheral vascular responses to orthostasis have not been assessed. The aim of this study was to evaluate the control of vascular responses to postural stress in FD patients. Measurements of heart rate, blood pressure, cardiac stroke volume and cardiac output (CO), by impedance cardiography, and calf-volume changes, by impedance plethysmography, were taken from nine FD patients and 11 control subjects while supine and during head-up tilt. During leg lowering, we also assessed the venoarteriolar reflex by measuring skin red-cell flux. Head-up tilting for 10min induced sustained decreases in mean arterial pressure in the FD patients, but not in the controls. Total peripheral resistance (TPR, i.e. mean arterial pressure/CO) increased significantly in the controls (39.8±6.8%), but not in the FD patients. Calf-volume changes during tilting, when normalized for the initial calf volume, did not differ significantly between the patients (4.62±1.99ml·100ml-1) and the controls (3.18±0.74ml·100ml-1). The vasoconstrictor response to limb lowering was present in the patients (47.7±9.0% decrease in skin red-cell flux), but was impaired as compared with the controls (80.7±3.4%) (P<0.05). The impaired vasoconstriction during limb lowering and absent increase of TPR during tilting confirm that orthostatic hypotension in FD is due primarily to a lack of sympathetically mediated vasoconstriction without evidence of abnormally large shifts in blood volume towards the legs during orthostasis. This may be due, in part, to a preserved myogenic response to increased vascular pressure in the dependent vascular beds.
Effects of breathing air containing 3% carbon dioxide, 35% oxygen or a mixture of 3% carbon dioxide/35% oxygen on cerebral and peripheral oxygenation at 150 m and 3459 m
Authors: IMRAY C.H.E. , WALSH S. , CLARKE T. , TIIVAS C. , HOAR H. , HARVEY T.C. , CHAN C.W.M. , FORSTER P.J.G. , BRADWELL A.R. , WRIGHT A.D.
Published: August 2015

The effects of gas mixtures comprising supplementary 3% carbon dioxide, 35% oxygen or a combination of 3% CO2 plus 35% O2 in ambient air have been compared on arterial blood gases, peripheral and cerebral oxygenation and middle cerebral artery velocity (MCAV) at 150m and on acute exposure to 3459m in 12 healthy subjects. Breathing 3% CO2 or 35% O2 increased arterial blood oxygen at both altitudes, and the CO2/O2 combination resulted in the most marked rise. MCAV increased on ascent to 3459m, increasing further with 3% CO2 and decreasing with 35% O2 at both altitudes. The CO2/O2 combination resulted in an increase in MCAV at 150m, but not at 3549m. Cerebral regional oxygenation fell on ascent to 3459m. Breathing 3% CO2 or 35% O2 increased cerebral oxygenation at both altitudes, and the CO2/O2 combination resulted in the greatest rise at both altitudes. The combination also resulted in significant rises in cutaneous and muscle oxygenation at 3459m. The key role of carbon dioxide in oxygenation at altitude is confirmed, and the importance of this gas for tissue oxygenation is demonstrated.
5-Hydroxytryptamine 5-HT2A receptor and 5-hydroxytryptamine transporter polymorphisms in acute myocardial infarction
Authors: COTO Eliecer , REGUERO Julián R. , ALVAREZ Victoria , MORALES Blanca , BATALLA Alberto , GONZÁLEZ Pelayo , MARTÍN María , GARCÍA-CASTRO Mónica , IGLESIAS-CUBERO Gustavo , CORTINA Arturo
Published: August 2015

This study was designed to analyse possible associations between DNA polymorphisms in the 5-hydroxytryptamine (5-HT; serotonin) 5-HT2A receptor and the 5-HT transporter (5-HTT) genes, and myocardial infarction (MI). 5-HT has been shown to be involved in cardiovascular pathophysiology. In addition to platelet aggregation and vascular contraction, 5-HT induces hyperplasia of artery smooth muscle cells. Recently, a 5-HT transporter gene polymorphism has been associated with MI. To determine the influence of genetic variation at the 5-HT2A receptor (T102C polymorphism) and the 5-HTT (insertion/deletion polymorphism) on the risk of developing early MI, we genotyped 210 MI patients of <55 years old and 238 healthy control subjects for DNA polymorphisms in these genes. In addition, we genotyped 95 patients with late-onset MI (>60 years old) to analyse the effects of these polymorphisms on the age at which the first MI episode occurred. The 5-HT2A receptor polymorphism was not associated with MI in our population. In addition, since the 5-HT2A receptor gene and genotype frequencies did not differ between patients with early and late onset of MI, this polymorphism does not appear to have an effect on age at the first MI episode. Gene and genotype frequencies for the 5-HTT promoter did not differ between patients <55 years old and healthy controls (independent of smoking status). However, homozygotes for the deletion (the ss genotype, where s denotes the short allele) were present at a significantly higher frequency in patients >60 years old compared with patients <55 years old (P = 0.009; P = 0.004 when only smokers were compared). According to our data, the ss genotype would seem to have a protective role against MI, delaying the age of onset of the first episode, especially among smokers. This could be a consequence of the lower 5-HTT levels linked to the s allele, so that individuals homozygous for the ss genotype may have lower 5-HT re-uptake by platelets.
Detection of glucagon receptor mRNA in the rat proximal tubule: potential role for glucagon in the control of renal glucose transport
Authors: MARKS J. , DEBNAM E.S. , DASHWOOD M.R. , SRAI S.K. , UNWIN R.J.
Published: August 2015

Glucagon is known to affect glomerular filtration rate and renal tubular solute and fluid transport, although it is only thought to act directly on the thick ascending limb (TAL) and collecting duct (CD). Indeed, previous studies have detected glucagon-sensitive adenylate cyclase exclusively in these nephron segments, suggesting the presence of glucagon receptors. In the present study, we have demonstrated for the first time that glucagon receptor mRNA is expressed in the rat proximal tubule, as well as in the TAL and CD. By autoradiography, we have also shown that specific binding of glucagon occurs in both the renal cortex and medulla. In addition, using proximal tubule brush-border membrane (BBM) vesicles for studies of glucose transport, we have established that glucagon stimulates glucose uptake via a facilitative GLUT-mediated transport process (by 58%; P<0.005), whereas cAMP stimulates only the sodium glucose-linked transporter (‘SGLT’)-mediated glucose uptake (by 53%; P<0.05). Taken together, these findings suggest that glucagon could have a role in controlling proximal tubular transport function, including glucose reabsorption, but unlike in the TAL and CD, the proximal tubule glucagon receptor might not be coupled primarily to adenylate cyclase.