Endogenous Endothelin-1 Research Articles

RISK OF DEVELOPMENT CARDIOVASCULAR СOMPLICATIONS IN PATIENTS WITH ARTERIAL HYPERTENSION AND METABOLIC SYNDROME

The combination of arterial hypertension and metabolic syndrome leads to an increased risk of development cardiovascular complications. Early detection of asymptomatic target organ damage to determine additional risk is important, because pressure-dependent subclinical damage to several organs reflects progression along the cardiovascular disease continuum. The SCORE scale is based on data from a number of recent European multicenter studies and takes into account all variants of fatal cardiovascular events over a 10-year period. However, the SCORE scale does not take into account the presence of such subclinical risk factors for the development of cardiovascular complications as insulin resistance, endothelial dysfunction, microalbuminuria
 The aim was to assess the ten-years risk of development of cardiovascular complications in hypertensive's with metabolic syndrome, depending on the type of insulinemia, endothelial dysfunction, and the presence of microalbuminuria.
 Materials and methods. Were examined 96 patients (34 men, 62 women) with arterial hypertension and metabolic syndrome, average age (57±9) years. Office blood pressure measurement, the level of total cholesterol in the blood and microalbuminuria in daily urine were determined for all patients. An oral glucose tolerance test was performed with parallel determination of the level of endogenous insulin, endothelin-1, and vasculoendothelial growth factor in blood serum by the immunoenzymatic method. Patients were divided into three groups. Group 1 included 29 patients with normal basal and postprandial levels of endogenous insulin; in the 2nd group – 39 patients with reactive hyperinsulinemia, in the 3rd group – 28 patients with spontaneous hyperinsulinemia. To estimate the total cardiovascular risk, the version of the SCORE scale for countries with high cardiovascular mortality was used. Moderate risk criteria are defined – SCORE index level 1-4%, high risk – 5-9% and very high risk – ≥ 10%.
 Research results. A moderate cardiovascular risk prevailed in almost 52% of patients of group 1 with a normal level of endogenous insulin, high – in 35% of patients group 2 with reactive hyperinsulinemia, very high – in 48% of patients group 2 and 43% of patients of group 3 with spontaneous hyperinsulinemia. The highest levels of systolic and diastolic blood pressure were characteristic of high-risk patients with spontaneous hyperinsulinemia combined with impaired glucose tolerance, with increasing of total cholesterol levels in 1.7 times under obesity, increasing of endothelin levels by 7 times, vasculoendothelial growth factor in 2.7 times and the presence of microalbuminuria in 75% of cases.
 Conclusions. More than half patients with arterial hypertensive and metabolic syndrome have a high and very high cardiovascular risk according to the SCORE scale, which is associated with hyperinsulinemia and insulin resistance, hypercholesterolemia and obesity, microalbuminuria and disorders of endothelial vasoregulation. The risk of cardiovascular complications based on subclinical signs of target organs damage to increases with the severity of insulin resistance and progression of endothelial dysfunction, which creates prerequisites for the development of atherosclerosis.

Role of Brain Endothelin Receptor Type B (ETB) in the Regulation of Tyrosine Hydroxylase in the Olfactory Bulb of DOCA-Salt Hypertensive Rats.

We previously reported that endothelins (ETs) regulate tyrosine hydroxylase (TH) activity and expression in the olfactory bulb (OB) of normotensive and hypertensive animals. Applying an ET receptor type A (ETA) antagonist to the brain suggested that endogenous ETs bind to ET receptor type B (ETB) to elicit effects. The aim of the present work was to evaluate the role of central ETB stimulation on the regulation of blood pressure (BP) and the catecholaminergic system in the OB of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. DOCA-salt hypertensive rats were infused for 7 days with cerebrospinal fluid or IRL-1620 (ETB receptor agonist) through a cannula placed in the lateral brain ventricle. Systolic BP (SBP) and heart rate were recorded by plethysmography. The expression of TH and its phosphorylated forms in the OB were determined by immunoblotting, TH activity by a radioenzymatic assay, and TH mRNA by quantitative real-time polymerase chain reaction. Chronic administration of IRL-1620 decreased SBP in hypertensive rats but not in normotensive animals. Furthermore, the blockade of ETB receptors also decreased TH-mRNA in DOCA-salt rats, but it did not modify TH activity or protein expression. These findings suggest that brain ETs through the activation of ETB receptors contribute to SBP regulation in DOCA-salt hypertension. However, the catecholaminergic system in the OB does not appear to be conclusively involved although mRNA TH was reduced. Present and previous findings suggest that in this salt-sensitive animal model of hypertension, the OB contributes to chronic BP elevation.

Trans-myocardial Extraction of Endothelin-1 Correlates with Increased Microcirculatory Resistance following Percutaneous Coronary Intervention.

Objective Coronary microvascular dysfunction (CMD) can complicate successful percutaneous coronary intervention (PCI). The potent endogenous vasoconstrictor peptide Endothelin-1 (ET-1) may be an important mediator. To investigate the mechanism, we sought to define the peri-procedural trans-myocardial gradient (TMG-coronary sinus minus aortic root levels) of ET-1 and its precursor peptide – Big ET-1. We then assessed correlation with pressure-wire indices of CMD: coronary flow reserve (CFR) and index of microvascular resistance (IMR). Methods Paired blood samples from the guide catheter and coronary sinus were collected before and after pressure-wire-guided PCI from patients with stable angina. Plasma was analysed using a specific enzyme-linked immunosorbent assay for quantification of ET-1 peptides and correlated with pressure-wire data. Non normally distributed continuous variables are presented as median [IQR]. Results ET-1 and Big ET-1 increased post-PCI in the aorta (ET-1: 0.98 [0.76–1.26] pg/ml to 1.20 [1.03–1.67] pg/ml, P < 0.001 and Big ET-1: 2.74 [1.78–2.50] pg/ml to 3.36 [2.33–3.97] pg/ml, P < 0.001) and coronary sinus (ET-1: 1.00 [0.81–1.28] pg/ml to 1.09 [0.91–1.30] pg/ml, P = 0.03 and Big ET-1: 2.89 [1.95–3.83] pg/ml to 3.56 [2.66–4.83] pg/ml, P = 0.01). TMG of ET-1 shifted negatively compared with baseline following PCI reflecting significantly increased extraction (0.03 [−0.12–0.17] pg/ml pre-PCI versus −0.16 [−0.36–0.07] pg/ml post-PCI, P = 0.01). Increased ET-1 trans-myocardial extraction correlated with higher IMR (Pearson's r = 0.293, P = 0.02) and increased hyperemic transit time (Pearson's r = 0.333, P < 0.01). In subgroup analysis, mean ET-1 trans-myocardial extraction was higher amongst patients with high IMR compared with low IMR (0.73 pg/ml, SD:0.78 versus 0.17 pg/ml, SD:0.42, P = 0.02). There was additionally a numerical trend towards increased ET-1 trans-myocardial extraction in subgroups of patients with low CFR and in patients with Type 4a Myocardial Infarction, albeit not reaching statistical significance. Conclusions Circulating ET-1 increases post-PCI and upregulated ET-1 trans-myocardial extraction contributes to increased microcirculatory resistance.

Endogenous Endothelin‐1 Contributes to Enhanced Basal Pulmonary Arterial Tone Following Chronic Hypoxia: Role of Mitochondria‐Derived Reactive Oxygen Species

Previous studies from our laboratory demonstrate the importance of mitochondria-derived reactive oxygen species (mitoROS) in the development of pulmonary hypertension after chronic hypoxia (CH) exposure. Furthermore, we have identified a major role for the endothelium to augment mitoROS-dependent pulmonary vascular tone following CH. However, the mechanism of this response remains unclear. We hypothesized that the endogenous vasoconstrictor peptide, endothelin-1 (ET-1), facilitates mitoROS-dependent increases in basal tone after CH exposure. To test our hypothesis, we measured basal tone by videomicroscopy in isolated, pressurized, small pulmonary arteries [~150 μm inner diameter (i.d.)] from normoxic and CH (4 wk, 0.5 atm) rats with and without the ETA receptor and ETB receptor inhibitors, BQ123 and BQ788 (10 μM each), respectively. Parallel protocols were conducted in the presence of the mitochondria-targeted antioxidant, MitoQ (1 μM). All experiments were performed in the presence of the nitric oxide (NO) synthase inhibitor, Nω-nitro-L-arginine (300 μM), to limit the influence of endogenous NO. Pulmonary arterial tone was calculated as the percent difference in i.d. between Ca2+-free and Ca2+-containing conditions. To evaluate the contribution of mitoROS to ET-1-mediated vasoconstriction, we further assessed vasoconstrictor responses (percentage of baseline i.d.) to serial concentrations of exogenous ET-1 (10-11 to 10-7 M) in the presence or absence of MitoQ in endothelium-disrupted pulmonary arteries from each group. Additional experiments employed confocal microscopy to measure ET-1 (1 nM)-induced mitoROS production in primary cultures of pulmonary arterial smooth muscle cells (PASMCs) from control and CH rats using the fluorescent mitochondrial superoxide indicator MitoSOX (10 μM). Antimycin A (10 µM) treatment, which stimulates mitoROS production from complex III of electron transport chain, was used as a positive control. Both MitoQ and the combined administration of ETA and ETB receptor blockers abolished the effect of CH to increase basal tone (P<0.05). Arteries from CH rats also exhibited greater constriction to exogenous ET-1 (at 1 nM) compared to vessels from normoxic controls, which was prevented by MitoQ (P<0.05). Consistent with these findings, application of ET-1 significantly increased mitoROS production in PASMCs from CH rats (P<0.05), but not control animals. Application of antimycin A led to mitoROS generation in both control and CH groups (P<0.05). We conclude that endogenous ET-1 promotes pulmonary arterial constriction through mitoROS signaling in PASMCs following CH. These findings advance our understanding of the mechanistic basis for the vasoconstrictor component of CH-induced pulmonary hypertension.

Endogenous ET-1 promotes ANP secretion through activation of COX2-L–PGDS–PPARγ signaling in hypoxic beating rat atria

Endothelin-1 (ET-1) is a potent stimulus for the secretion of atrial natriuretic peptide (ANP) and hypoxia stimulates the release of ET-1, which is involved in the regulation of atrial ANP secretion. However, the precise mechanism of endogenous ET-1 in the regulation of hypoxia-induced ANP secretion is unclear. Therefore, this study aimed to investigate the mechanism of hypoxia-induced endogenous ET-1 regulation of ANP secretion in isolated perfused hypoxic beating rat atria. The results of this study showed that acute hypoxia significantly stimulated ET-1 release and upregulated the expression of its type A as well as type B receptors (ETA and ETB receptors). Endogenous ET-1 induced by hypoxia markedly upregulated the expression of cyclooxygenase 2 (COX2) through activation of its two receptors, leading to an increase in lipocalin-type prostaglandin D synthase (L-PGDS) expression and prostaglandin D2 (PGD2) production. L-PGDS-derived PGD2 activated peroxisome proliferator-activated receptor γ (PPARγ), ultimately promoting hypoxia-induced ANP secretion. Conversely, L-PGDS-derived PGD2 may in turn regulate L-PGDS expression by a nuclear factor erythroid-2-related factor 2 (NRF2)-mediated feedback mechanism. These results indicate that endogenous ET-1 induced by hypoxia promotes hypoxia-induced ANP secretion by activation of COX2–L-PGDS–PPARγ signaling in beating rat atria. In addition, the positive feedback loop between L-PGDS-derived PGD2 and L-PGDS expression induced by hypoxia is part of the mechanism of hypoxia-induced ANP secretion by endogenous ET-1.

Lipopolysaccharide-induced necroptosis of brain microvascular endothelial cells can be prevented by inhibition of endothelin receptors.

Over activation of the endothelin-1 (ET-1) system in disease states contributes to endothelial dysfunction. On the other hand, ET-1 promotes proliferation and survival of endothelial cells. Regulation of programmed cell death (PCD) pathways is critical for cell survival. Recently discovered necroptosis (regulated necrosis) is a pathological PCD mechanism mediated by the activation of toll like receptor 4 (TLR4), which also happens to stimulate ET-1 production in dendritic cells. To establish the effect of ET-1 on PCD and survival of human brain microvascular endothelial cells (BMVECs) under control and inflammatory conditions, BMVECs were treated with ET-1 (10 nM, 100 nM and 1 microM) or lipopolysaccharide (LPS, 100 ng/ml). ET receptors were blocked with bosentan (10 microM). Under normal growth conditions, exogenous ET-1 reduced BMVEC viability and migration at a relatively high concentration (1 microM). This was accompanied with activation of necroptosis and apoptosis marker genes. LPS decreased endogenous ET-1 secretion, increased ET(B) receptor expression and activated necroptosis. Even though ET-1 levels were low (less than 10 nM levels used under normal growth conditions), blocking of ET receptors with bosentan inhibited the necroptosis pathway and improved the cell migration ability of BMVECs, suggesting that under inflammatory conditions, ET-1 activates PCD pathways in BMVECs even at physiological levels.

Research Progress and Forensic Application on the Pathogenesis of Coronary Artery Spasm

Coronary artery spasm （CAS） is a hyper-contraction of segmental coronary artery in response to multiple stimuli. At present, it's still in lack of specific diagnostic indicators of sudden cardiac death caused by CAS. This review summarizes current researches on the mechanisms of CAS and describes the roles of vascular endothelial dysfunction and vascular smooth muscle hypersensitivity in the course of CAS. Furthermore, the molecular mechanisms of the endogenous NO and endothelin-1 cause vascular endothelial dysfunction, and the phosphorylation of MLC2, Rho kinase and endoplasmic reticulum stress related to vascular smooth muscle hypersensitivity are discussed. Meanwhile, the possibility of forensic application for the related molecules on the diagnosis of sudden cardiac death caused by CAS are also explored.

Target-Mediated Drug Disposition Pharmacokinetic–Pharmacodynamic Model of Bosentan and Endothelin-1

Bosentan is a competitive antagonist on endothelin receptor A and B (ETA and ETB), displacing the endogenous binding partner endothelin-1 (ET-1) from its binding sites. After administration of escalating single doses of 10-750mg as an intravenous (i.v.) infusion, bosentan showed dose-dependent pharmacokinetics (PK). The aim of this analysis was to develop a PK model of bosentan after i.v. administration including competitive antagonism with ET-1 and to analyze its influence on blood pressure and heart rate with a combined pharmacokinetic/pharmacodynamic (PK/PD) model. PK/PD data from 70 young male Caucasian subjects were analyzed after single i.v. administration of 10, 50, 250, 500, and 750mg of bosentan. Population analyses, simulations, and evaluation were performed using a non-linear mixed-effects modeling approach. The PK of bosentan was best described by a two-compartment, target-mediated drug disposition (TMDD) model. ET-1 plasma and urine profiles were successfully integrated into the bosentan two-compartment, TMDD model encompassing competition for the same receptor. A multiple-peak phenomenon of bosentan plasma concentrations after i.v. administration was best described by a diurnal expression or reappearance of ET receptors on the cell surface. Blood pressure was best described by an E max model; heart rate was modeled as a compensatory effect of changes in blood pressure. The developed competitive PK/PD model of bosentan and ET-1 after i.v. administration provides a first step towards understanding the complex PK properties of bosentan and offers a valuable tool for future PK/PD research.

Hippocampal Endothelin-1 decreases excitability of pyramidal neurons and produces anxiolytic effects

Anxiety disorders contribute to the pathophysiology of psychiatric diseases, including major depression, substance abuse, and schizophrenia. The hippocampus is important for anxiety modulation. However, the mechanisms that control the neuronal activity of the hippocampus in anxiety are still not clear. We found that Endothelin-1 (ET1) mRNA in the hippocampus was down-regulated in high-anxiety mice. Neutralizing endogenous ET1 in the hippocampal CA1 enhanced anxiety-like behaviors. We next revealed that most expression of ET1 and its receptors in the CA1 takes place in pyramidal neurons, and the ET1 signaling pathway directly regulated the excitability of CA1 pyramidal neurons and glutamatergic synaptic neurotransmission. Finally, we proved that neutralizing endogenous CA1 ET1 produces anxiogenic effects on low-anxiety mice, whereas infusing exogenous ET1 into the CA1 alleviates the anxiety susceptibility of high-anxiety mice. Together, these results indicate that ET1 signaling is critical in maintaining the excitability of glutamatergic neurons in the hippocampus and, thus, in modulating anxiety-like behaviors. Because ET1 is a risk factor for ischemic stroke, our findings might also help to explain the potential mechanism of emotional abnormality in stroke.

Endothelin contributes to the blood pressure rise triggered by hypoxia in severe obstructive sleep apnea.

Obstructive sleep apnea (OSA) is strongly correlated with an increased risk of systemic hypertension. However, the link between systemic hypertension and nocturnal apneas remains incompletely understood. Animal studies suggest an implication of the endothelin system. The aim of the present study is to determine if endogenous endothelin plays a role in the increase in blood pressure observed during hypoxic episodes in OSA patients, in addition to peripheral chemoreflex and neural sympathetic activation. We assessed the effects of the nonspecific endothelin antagonist bosentan (500 mg; Tracleer; Actelion; Basel, Switzerland) on ventilation, hemodynamics, and muscle sympathetic nerve activity (MSNA) during normoxia and isocapnic hypoxia using a randomized, crossover, double-blinded, placebo-controlled study design, and in 13 severely untreated sleep apneic patients (age 50 ± 9 years, apnea-hypopnea index 35 ± 21/h). Hypoxia increased blood pressure, MSNA, and minute ventilation as oxygen saturation decreased. Bosentan suppressed completely the increase in SBP during a 5-min hypoxic challenge (143 ± 5 mmHg during hypoxia vs. 133 ± 5 mmHg during normoxia with placebo and 127 ± 3 mmHg during hypoxia vs. 125 ± 3 mmHg during normoxia under bosentan, P = 0.023). DBP as well as the rise in MSNA and ventilation during isocapnic hypoxia did not differ between bosentan and placebo. Endothelin contributes to the rise in SBP in response to acute hypoxia in patients with severely untreated OSA. This was not due to lower chemoreflex activation with bosentan.

Activation mechanism of endothelin ETB receptor by endothelin-1.

Endothelin, a 21-amino-acid peptide, participates in various physiological processes, such as regulation of vascular tone, humoral homeostasis, neural crest cell development and neurotransmission. Endothelin and its G-protein-coupled receptor are involved in the development of various diseases, such as pulmonary arterial hypertension, and thus are important therapeutic targets. Here we report crystal structures of human endothelin type B receptor in the ligand-free form and in complex with the endogenous agonist endothelin-1. The structures and mutation analysis reveal the mechanism for the isopeptide selectivity between endothelin-1 and -3. Transmembrane helices 1, 2, 6 and 7 move and envelop the entire endothelin peptide, in a virtually irreversible manner. The agonist-induced conformational changes are propagated to the receptor core and the cytoplasmic G-protein coupling interface, and probably induce conformational flexibility in TM6. A comparison with the M2 muscarinic receptor suggests a shared mechanism for signal transduction in class A G-protein-coupled receptors.

Endogenous endothelin-1 and femoral artery shear rate: impact of age and implications for atherosclerosis.

Both altered shear rate and endothelin-1 (ET-1) are associated with the age-related development of atherosclerosis. However, the role of ET-1, a potent endogenous vasoconstrictor, in altering shear rate in humans, especially in the atherosclerotic-prone vasculature of the leg, is unknown. Therefore, this study examined the contribution of ET-1 to the age-related alterations in common femoral artery (CFA) shear rate. BQ-123, a specific endothelin type A (ET(A)) receptor antagonist, was infused into the CFA, and diameter and blood velocity were measured by Doppler ultrasound in young (n = 8, 24 ± 2 years) and old (n = 9, 70 ± 2 years) study participants. The old had greater intima-media thickening in the CFA, indicative of a preatherogenic phenotype. Prior to infusion, the old study participants exhibited reduced mean shear rate (27 ± 3/s) compared with the young study participants (62 ± 9/s). This difference was likely driven by attenuated antegrade shear rate in the old as retrograde shear rate was similar in the young and old. Inhibition of ETA receptors, by BQ-123, increased leg blood flow in the old, but not in the young, abolishing age-related differences. Older study participants had a larger CFA (young: 0.82 ± 0.03 cm, old: 0.99 ± 0.03 cm) in which BQ-123 induced significant vasodilation (5.1 ± 1.0%), but had no such effect in the young (-0.8 ± 0.8%). Interestingly, despite the age-specific, BQ-123-induced increase in leg blood flow and CFA diameter, shear rate patterns remained largely unchanged. Therefore, ET-1, acting through the ETA receptors, exerts a powerful age-specific vasoconstriction. However, removal of this vasoconstrictor stimulus does not augment mean shear rate in the old.

Endogenous Endothelin-1 Regulates Hypoxia-Induced Atrial Natriuretic Peptide Secretion by Activating the MAPK/ERK and PI3K/Akt Signaling Pathways in Isolated Beating Rabbit Atria

The present study investigated a possible mechanism for endogenous endothelin-1 (ET-1) regulation of atrial natriuretic peptide (ANP) secretion in isolated perfused acute hypoxic rabbit atria. Acute hypoxia significantly enhanced the release of ET-1 and the expression of the ET receptor (ETR) type A and B (ETRA and ETRB) in atrial tissues, with a concomitant increase in ANP secretion. The ETRA or ETRB antagonist, BQ123 (0.3 μmol/L) or BQ788 (0.3 μmol/L), respectively attenuated hypoxia-induced ANP secretion. Both antagonists significantly attenuated the levels of hypoxiainduced atrial phosphorylated (p)-extracellular signal-regulated kinase (ERK) and p-protein kinase B (Akt). The ERK and Akt inhibitors, PD098059 (30 μmol/L) and LY294002 (30 μmol/L), respectively mimicked the effect of the ETR antagonists. These results demonstrated that acute hypoxia- mediated atrial ET-1 regulated ANP secretion through ETR and the subsequent mitogenactivated protein kinase (MAPK)/ERK and ETR-phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathways. These pathways may mediate atrial endocrine functions under hypoxic conditions.

Endothelin contributes to blunted renal autoregulation observed with a high-salt diet.

Autoregulation of renal blood flow (RBF) is an essential function of the renal microcirculation that has been previously shown to be blunted by excessive dietary salt. Endogenous endothelin 1 (ET-1) is increased following a high-salt (HS) diet and contributes to the control of RBF but the differential effects of ET-1 on renal microvessel autoregulation in response to HS remain to be established. We hypothesized that a HS diet increases endothelin receptor activation in normal Sprague-Dawley rats and blunts autoregulation of RBF. The role of ET-1 in the blunted autoregulation produced by a HS diet was assessed in vitro and in vivo using the blood-perfused juxtamedullary nephron preparation and anesthetized rats, respectively. Using highly selective antagonists, we observed that blockade of either ETA or ETB receptors was sufficient to restore normal autoregulatory behavior in afferent arterioles from HS-fed rats. Additionally, normal autoregulatory behavior was restored in vivo in HS-fed rats by simultaneous ETA and ETB receptor blockade, whereas blockade of ETB receptors alone showed significant improvement of normal autoregulation of RBF. Consistent with this observation, autoregulation of RBF in ETB receptor-deficient rats fed HS was similar to both ETB-deficient rats and transgenic control rats on normal-salt diets. These data support the hypothesis that endogenous ET-1, working through ETB and possibly ETA receptors, contributes to the blunted renal autoregulatory behavior in rats fed a HS diet.

Targeted Overexpression of Astrocytic Endothelin-1 Attenuates Neuropathic Pain by Upregulating Spinal Excitatory Amino Acid Transporter-2

We previously demonstrated that endogenous endothelin-1 (ET-1) inhibits pathological pain in a transgenic mouse model with astrocyte-specific ET-1 overexpression (GET-1 mice); however, the underlying mechanism is unclear. ET-1 regulates excitatory amino acid transporter-2 (EAAT-2), a predominant subtype of glutamate transporters that plays critical role in pain modulation in spinal astrocytes. We hypothesized that astrocytic ET-1 overexpression alleviates neuropathic pain through modulating EAAT-2. GET-1 or nontransgenic (NTg) mice either received sham operation or sciatic nerve ligation (SNL) with or without ceftriaxone (CEF, an EAAT-2 inducer, for 4days before termination). In GET-1 mice, mRNA and protein expressions of EAAT-2, but not EAAT-1, were upregulated associated with reduced SNL-induced neuropathic pain. Despite that SNL induced a significant reduction of EAAT-2 mRNA expression in both genotypes of mice, post-SNL EAAT-2 mRNA expression was higher in GET-1 mice than that in NTg mice. EAAT-2 induction by CEF reduced SNL-induced neuropathic pain in both NTg and GET-1 mice. In cultured rat astrocytic cell line, overexpression of ET-1 mRNA expression also elevated EAAT-2 mRNA expression, which was reversed by ET receptor antagonists. In conclusion, overexpressed astrocytic ET-1 suppressed neuropathic pain by upregulating spinal EAAT-2 expression via ET receptors.

Mechanisms of disease: paracine effects of adipose tissue, progenitor cell function, and epigenetics of diabetic vascular disease.

![Graphic][1] Adipose tissue has been recognized as a source of cytokines that contributes to chronic inflammation in patients with metabolic syndrome and diabetes.1,2 Furthermore, perivascular epicardial adipose tissue has been related to cardiovascular risk factors and coronary artery calcification,3 as well as to the severity of coronary artery disease.4 Endothelial dysfunction is an early stage of atherosclerosis,5 and hence it is of interest to see how perivascular adipose tissue interferes with the control of vascular tone. The first paper in this issue, entitled ‘Tumour necrosis factor-alpha participates on the endothelin-1/nitric oxide imbalance in small arteries from obese patients: role of perivascular adipose tissue’ 6 by Agostino Virdis from the University of Pisa in Italy assessed the impact of the cytokine tumour necrosis factor-alpha (TNF-α) produced by vascular and perivascular tissue on the endothelin-1 (ET-1)7 and nitric oxide (NO) system,8 which are both altered in many disease states. To that end, small arteries from 16 obese subjects and 14 controls were mounted in a pressurized myograph, and endogenous ET-1 activity was assessed by adding the ETA blocker BQ-123. The contributions of TNF-α and NO were tested using the anti-TNF-α antibody infliximab and the inhibitor of the l-arginine pathway l-NAME ( N ω-nitro-l-arginine methylester). Obese subjects showed a blunted l-NAME-induced vasoconstriction (reflecting a reduced basal NO release), which was augmented by infliximab, while the relaxation to BQ-123 (reflecting basal ET-1 production) was attenuated by infliximab but unaffected by l-NAME. Interestingly, removal of perivascular adipose tissue reversed these effects. Obese subjects also produced more superoxide, which was decreased by the NADPH oxidase inhibitor apocynin, l-NAME, and BQ-123, and abolished by infliximab. An increased vascular expression of ET-1, ETA, and ETB receptors, and higher vascular and … [1]: /embed/inline-graphic-1.gif

Bile Synthesis Peculiarities following Changes in the Functional State of the Endothelin Receptors

Endothelin-1(ET-1) regulates a variety of biochemical processes in liver. However, there is no clear view concerning endothelin receptors participation in the regulation of qualitative and quantitative characteristics of liver secretory function. The purpose of this study is to evaluate the choleretic effect of ET-1 and to determine the role of ЕТА receptors functional state in mediating the effect of ET-1 on bile and its organic components secretion. Endothelin-1 and BQ-123 (cyclo-Asppro-Val-Leu-Trp) were intraportally injected. Bile flow, bile acid concentration and content, hydroxylation and conjugation coefficients were estimated. The results of this study showed that the secreted bile volume was decreased under the effect of endothelin-1and BQ-123, although this decrease was more prolonged and profound in BQ-123 treated animals. Concentration of taurocholates, glycocholic acid and free bile acids was increased in the endothelin treated rats. When BQ123 was administered, an increase in glycochenodeoxycholic acid+glycodeoxycholic acid (GCDCA+GDCA) and the taurin-conjugated bile acids concentration was found, whereas the free bile acids concentration altered reversely. Coefficient of hydroxylation was diminished when entholelin receptors were blocked. Activation of endothelin receptors by exogenous endothelin-1 intensified bile acids biosynthesis via “neutral pathway,”involving microsomal oxidation enzymes. The present study concludes that the endothelin receptors blockade eliminated the regulatory function of endogenous endothelin and caused a shift in bile acids synthesis to mitochondrial enzymes through “acidic pathway”.

Dans la sclérodermie systémique, le contrôle de la maladie ulcéreuse digitale sous bosentan est associé à une amélioration du handicap de la main

The effects of acyl-coenzyme a: lysolecithin acyltransferase (LAT) inhibitor thimerosal (20, 30 and 40mgkg−1), anti-ischaemic and free radical scavenging drug trimetazidine (10mgkg−1) and endothelin ETA–ETBreceptor blocker bosentan [30mgkg−1) were investigated in an anaesthetized rat model of coronary artery ligation (7min) and release (7min) induced myocardial ischaemia-reperfusion arrhythmias. Neither of the drugs produced significant effects on blood pressure except thimerosal which induced a transient fall lasting 5–8min. The total number of ectopic beats during occlusion (controls 141.8±73.5,n=12) and reperfusion (controls 1151.1±199.1,n=10) was not modified by either trimetazidine (occlusion 452.5±128.6,n=10; reperfusion 1002.0±198.4,n=6) or bosentan (occlusion 431.2±112.8,n=10; reperfusion 1530.7±296.8,n=9) while thimerosal attenuated them (occlusion 50.2±14.9,n=10,P<0.01vscontrols; reperfusion 345.1±83.8,n=8,P<0.01vscontrols). The durations (in seconds) of ventricular tachycardia (occlusion 33.9±6.1,n=12; reperfusion 94.2±18.1,n=10) were also shortened by thimerosal (occlusion 2.6±1.0,n=10,P<0.01; reperfusion 28.5±7.8,n=8,P<0.01) while trimetazidine or bosentan did not significantly modify them. The incidences of ventricular fibrillation or mortality were not significantly modified by either of the drugs. Besides the lack of any effect of trimetazidine, we conclude that endogenous endothelin has no pathophysiological significance in this experimental model while LAT inhibition does.

Catalpol provides protective effects against cerebral ischaemia/reperfusion injury in gerbils

To investigate the protective effect of catalpol on cerebral ischaemia/reperfusion (CI/R) injury in gerbils and further explore the underlying mechanism. A gerbil model of CI/R was prepared by bilateral common carotid occlusion for 10 min followed by 6 h reperfusion. Catalpol (5, 10 or 20 mg/kg per day) was injected intraperitoneally for 3 days before the carotid occlusion. Stroke index was measured during the reperfusion. The contents of endogenous neuropeptides, endothelin-1 (ET-1) and calcitonin gene-related peptide in plasma were evaluated by radioimmunoassay. Superoxide dismutase (SOD) and malondialdehyde (MDA) in brain tissue homogenate were also examined. The results showed that catalpol significantly improved the stroke index compared with CI/R control group (P < 0.05 or P < 0.01). Catalpol significantly increased the activity of SOD at the doses of 10 and 20 mg/kg (P ≤ 0.05), decreased the brain MDA content and the plasma level of ET-1 at the doses of 10 and 20 mg/kg (P ≤ 0.01). These data suggested that the efficacy of catalpol pretreatment on CI/R injury may be attributed to reduction of free radicals and inhibition of lipid peroxidation and ET-1 production.

Over-expression of astrocytic ET-1 attenuates neuropathic pain by inhibition of ERK1/2 and Akt(s) via activation of ETA receptor

A differential role of endothelin-1 (ET-1) in pain processing has recently been suggested. However, the function of central ET-1 in neuropathic pain (NP) has not been fully elucidated to date. We report here the action of endogenous central ET-1 in sciatic nerve ligation-induced NP (SNL-NP) in a transgenic animal model that over-expresses ET-1 in the astrocytes (GET-1 mice). We hypothesized that the over-expression of astrocytic ET-1 would exert anti-allodynic and anti-hyperalgesic effects in NP, as demonstrated by mechanical threshold and plantar withdrawal latency using the von Frey filament and heat stimuli. In our animal model, GET-1 mice showed an increase in the withdrawal threshold and latency in response to the mechanical and thermal stimuli, respectively, in pain behavior tests after SNL. ET-1 and endothelin type A receptor (ETA-R) levels were increased significantly in L4-L6 segments of the spinal cord (ipsilateral to SNL) of GET-1 mice at 7 and 21days after surgery. Moreover, intrathecal administration of a specific ETA-R antagonist, BQ-123, attenuated the anti-allodynic and anti-hyperalgesic phenotype in GET-1 mice. The effects of BQ-123 on the mRNA expression of extracellular signal-regulated protein kinase 1/2 (ERK1/2) and protein kinase B/serine protein kinase (Akt(s)) were assessed in the ipsilateral L4-L6 segments harvested 30min after BQ-123 administration on day 7 after surgery. Phosphorylation of ERK1/2 and Akt(s) in the ipsilateral spinal cord of GET-1 mice was reduced following SNL, whereas no reduction was observed after intrathecal injection of BQ-123. In conclusion, our results showed that the xover-expression of astrocytic ET-1 reduced SNL-induced allodynia and hyperalgesia by inhibiting the activation of ERK1/2 and Akt(s) via the ETA-R-mediated pathway.