Endothelin-1 and atherosclerosis: potential complications associated with endothelin-receptor blockade

Integrated metabolomics and network pharmacology analysis to reveal the mechanisms of naringin against atherosclerosis

OBJECTIVES

The purpose of this study was to explore the mechanism of naringin in atherosclerotic mice from the perspective of network pharmacology and non-targeted metabolomics.

METHODS

ApoE-/- mice were induced to establish an atherosclerotic model to explore the pharmacodynamics and potential mechanism of naringin in atherosclerosis (AS). Pathological section and blood lipid levels were used to evaluate the intervention effects. The core targets, metabolites, and related pathways of naringin alleviating atherosclerotic were predicted through network pharmacology and metabolomics analysis. Furthermore, the inflammatory factors and pathway-related protein expression were detected using ELISA and Western blot methods.

KEY FINDINGS

It turned out that compared with the model group, the naringin could reduce the development degree in atherosclerotic mice. The network pharmacology suggested that PI3K-AKT pathway was an important mechanism for naringin to interfere with AS. Serum metabolic data were collected and analyzed, and a total of 27 potential biomarkers were identified, involving vitamin B6 metabolism, arginine metabolism, and retinol metabolism. The experiment verified that naringin inhibited inflammation in AS through the PI3K-AKT/TLR4/NF-κB pathway.

CONCLUSIONS

This study provides a strategy combining metabolomics and network pharmacology to explore the alleviation of AS by naringin and offers a new idea for its application.

Evaluation of Metabolic and Cardiovascular Risk Measured by Laboratory Biomarkers and Cardiopulmonary Exercise Test in Children and Adolescents Recovered from Brain Tumors: The CARMEP Study

In recent decades, the improvement of treatments and the adoption of therapeutic protocols of international cooperation has led to an improvement in the survival of children affected by brain tumors. However, in parallel with the increase in survival, long-term side effects related to treatments have been observed over time, including the activation of chronic inflammatory processes and metabolic alterations, which can facilitate the onset of metabolic syndrome and increased cardiovascular risk. The aim of this study was to find possible statistically significant differences in the serum concentrations of early biomarkers of metabolic syndrome and in the results of cardiopulmonary exercise testing between survivors of childhood brain tumors and healthy controls. This is a prospective and observational study conducted on a group of 14 male patients who survived childhood brain tumors compared with the same number of healthy controls. The concentrations of early metabolic syndrome biomarkers [adiponectin, leptin, TNF-α, IL-1, IL-6, IL-10, endothelin-1, apolipoprotein B, and lipoprotein (a)] were measured and a cardiopulmonary exercise test (CPET) was performed. Results: Childhood brain tumor survivors performed worse on average than controls on the CPET. Furthermore, they showed higher endothelin-1 values than controls (p = 0.025). The CPET results showed an inverse correlation with leptin. The differences found highlight the greater cardiovascular risk of brain tumor survivors, and radiotherapy could be implicated in the genesis of this greater cardiovascular risk.

Detrimental effects of physical inactivity on peripheral and brain vasculature in humans: Insights into mechanisms, long-term health consequences and protective strategies

The growing prevalence of physical inactivity in the population highlights the urgent need for a more comprehensive understanding of how sedentary behaviour affects health, the mechanisms involved and what strategies are effective in counteracting its negative effects. Physical inactivity is an independent risk factor for different pathologies including atherosclerosis, hypertension and cardiovascular disease. It is known to progressively lead to reduced life expectancy and quality of life, and it is the fourth leading risk factor for mortality worldwide. Recent evidence indicates that uninterrupted prolonged sitting and short-term inactivity periods impair endothelial function (measured by flow-mediated dilation) and induce arterial structural alterations, predominantly in the lower body vasculature. Similar effects may occur in the cerebral vasculature, with recent evidence showing impairments in cerebral blood flow following prolonged sitting. The precise molecular and physiological mechanisms underlying inactivity-induced vascular dysfunction in humans are yet to be fully established, although evidence to date indicates that it may involve modulation of shear stress, inflammatory and vascular biomarkers. Despite the steady increase in sedentarism in our societies, only a few intervention strategies have been investigated for their efficacy in counteracting the associated vascular impairments. The current review provides a comprehensive overview of the evidence linking acute and short-term physical inactivity to detrimental effects on peripheral, central and cerebral vascular health in humans. We further examine the underlying molecular and physiological mechanisms and attempt to link these to long-term consequences for cardiovascular health. Finally, we summarize and discuss the efficacy of lifestyle interventions in offsetting the negative consequences of physical inactivity.

Big Endothelin-1 and long-term all-cause death in patients with coronary artery disease and prediabetes or diabetes after percutaneous coronary intervention

BACKGROUND AND AIMS

The present study aimed to examine the association between big endothelin-1 (big ET-1) and long-term all-cause death in patients with coronary artery disease (CAD) and different glucose metabolism status.

METHODS AND RESULTS

We consecutively enrolled 8550 patients from January 2013 to December 2013. Patients were categorized according to both status of glucose metabolism status [Diabetes Mellitus (DM), Pre-Diabetes (Pre-DM), Normoglycemia (NG)] and big ET-1 levels. Primary endpoint was all-cause death. During a median of 5.1-year follow-up periods, 301 all-cause deaths occurred. Elevated big ET-1 was significantly associated with long-term all-cause death (adjusted HR: 2.230, 95%CI 1.629-3.051; p < 0.001). Similarly, patients with DM, but not Pre-DM, had increased risk of all-cause death compared with NG group (p < 0.05). When patients were categorized by both status of glucose metabolism and big ET-1 levels, high big ET-1 were associated with significantly higher risk of all-cause death in Pre-DM (adjusted HR: 2.442, 95% CI 1.039-5.740; p = 0.041) and DM (adjusted HR: 3.162, 95% CI 1.376-7.269; p = 0.007). The Kaplan-Meier curve indicated that DM patients with the highest big ET-1 levels were associated with the greatest risk of all-cause death (p < 0.05).

CONCLUSIONS

The present data indicate that baseline big ET-1 levels were independently associated with the long-term all-cause death in DM and Pre-DM patients with CAD undergoing PCI, suggesting that big ET-1 may be a valuable marker in patients with impaired glucose metabolism.

Sex-Specific Effects of Prenatal Hypoxia on the Cardiac Endothelin System in Adult Offspring

Fetal hypoxia, a major consequence of complicated pregnancies, impairs offspring cardiac tolerance to ischemia/reperfusion (I/R) insult, however, the mechanisms remain unknown. Endothelin-1 (ET-1) signaling through the endothelin A receptors (ET_A) is associated with cardiac dysfunction. We hypothesized that prenatal hypoxia exacerbates cardiac susceptibility to I/R via increased ET-1 and ET_A levels, while ET_A inhibition ameliorates this. Pregnant Sprague-Dawley rats were exposed to normoxia (21% O₂) or hypoxia (11% O₂) on gestational days 15-21. Offspring were aged to 4 months, and hearts were aerobically perfused or subjected to ex vivo I/R, with or without pre-infusion with an ET_A antagonist (ABT-627). ET-1 levels were assessed with ELISA in aerobically perfused and post-I/R left ventricles (LV). ET_A and ET_B levels were assessed by Western blotting in non-perfused LV. As hypothesized, ABT-627 infusion tended to improve post-I/R recovery in hypoxic females (p=0.0528), however, surprisingly, ABT-627 prevented post-I/R recovery only in the hypoxic males (p<0.001). ET-1 levels were increased in post-I/R LV in both sexes regardless of the prenatal exposure (p<0.01). ET_A expression was similar among all groups, while ET_B (isoform C) levels were decreased in prenatally hypoxic females (p<0.05). In prenatally hypoxic males, ET_A signaling may be essential for tolerance to I/R, while in prenatally hypoxic females, ET_A may contribute to cardiac dysfunction. Our data illustrate that understanding the prenatal history has critical implications for treatment strategies in adult chronic diseases.

Neuroinflammatory Triangle Presenting Novel Pharmacological Targets for Ischemic Brain Injury

Ischemic stroke is one of the leading causes of morbidity and mortality globally. Hundreds of clinical trials have proven ineffective in bringing forth a definitive and effective treatment for ischemic stroke, except a myopic class of thrombolytic drugs. That, too, has little to do with treating long-term post-stroke disabilities. These studies proposed diverse options to treat stroke, ranging from neurotropic interpolation to venting antioxidant activity, from blocking specific receptors to obstructing functional capacity of ion channels, and more recently the utilization of neuroprotective substances. However, state of the art knowledge suggests that more pragmatic focus in finding effective therapeutic remedy for stroke might be targeting intricate intracellular signaling pathways of the 'neuroinflammatory triangle': ROS burst, inflammatory cytokines, and BBB disruption. Experimental evidence reviewed here supports the notion that allowing neuroprotective mechanisms to advance, while limiting neuroinflammatory cascades, will help confine post-stroke damage and disabilities.

Elevated Plasma Big Endothelin-1 at Admission Is Associated With Poor Short-Term Outcomes in Patients With Acute Decompensated Heart Failure

Objective: We aimed to evaluate the association between plasma big endothelin-1 (ET-1) at admission and short-term outcomes in acute decompensated heart failure (ADHF) patients.

Methods: In this single-center, retrospective study, a total of 746 ADHF patients were enrolled and divided into three groups according to baseline plasma big ET-1 levels: tertile 1 (<0.43 pmol/L, n = 250), tertile 2 (between 0.43 and 0.97 pmol/L, n = 252), and tertile 3 (>0.97 pmol/L, n = 244). The primary outcomes were all-cause death, cardiac arrest, or utilization of mechanical support devices during hospitalization. Logistic regression analysis and net reclassification improvement approach were applied to assess the predictive power of big ET-1 on short-term outcomes.

Results: During hospitalization, 92 (12.3%) adverse events occurred. Etiology, arterial pH, lactic acid, total bilirubin, serum creatine, serum uric acid, presence of atrial fibrillation and N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels were positively correlated with plasma big ET-1 level, whereas systolic blood pressure, serum sodium, hemoglobin, albumin, and estimated glomerular filtration rate were negatively correlated. In multivariate logistic regression, tertile 3 compared with tertile 1 had a 3.68-fold increased risk of adverse outcomes [odds ratio (OR) = 3.681, 95% confidence interval (CI) 1.410–9.606, p = 0.008]. However, such adverse effect did not exist between tertile 2 and tertile 1 (OR = 0.953, 95% CI 0.314–2.986, p = 0.932). As a continuous variable, big ET-1 level was significantly associated with primary outcome (OR = 1.756, 95% CI 1.413–2.183, p < 0.001). The C statistic of baseline big ET-1 was 0.66 (95% CI 0.601–0.720, p < 0.001). Net reclassification index (NRI) analysis showed that big ET-1 provided additional predictive power when combining it to NT-proBNP (NRI = 0.593, p < 0.001).

Conclusion: Elevated baseline big ET-1 is an independent predictor of short-term adverse events in ADHF patients and may provide valuable information for risk stratification.

Regular aerobic exercise counteracts endothelial vasomotor dysfunction associated with insufficient sleep

Insufficient sleep is associated with endothelial vasomotor dysfunction and increased cardiovascular risk. Regular aerobic exercise is an effective lifestyle strategy for improving endothelial function and, in turn, reducing cardiovascular risk. We tested the hypotheses that regular aerobic exercise would 1) improve endothelial vasodilation and 2) decrease endothelin (ET)-1-mediated vasoconstrictor tone in middle-aged adults who chronically sleep <7 h/night. Thirty-six healthy, middle-aged adults were studied: 16 with normal sleep duration (age: 57 ± 2 yr; sleep duration: 7.4 ± 0.1 h/night) and 20 with short sleep duration (age: 56 ± 1 yr; sleep duration: 6.2 ± 0.1 h/night). The 20 short sleepers completed a 3-mo aerobic exercise training intervention. Forearm blood flow was determined (via plethysmography) in response to intra-arterial acetylcholine (ACh), BQ-123 (ET_A receptor antagonist), ACh + BQ-123, and sodium nitroprusside. Forearm blood flow responses to ACh were lower (∼20%; P < 0.05) in the short (from 4.2 ± 0.2 to 10.5 ± 0.6 mL/100 mL tissue/min) versus normal (4.2 ± 0.2 to 12.7 ± 0.6 mL/100 mL tissue/min) sleepers. In response to BQ-123, the short-sleep group had a significantly greater increase in resting forearm blood flow than the normal-sleep group (∼25% vs. ∼8%). ACh + BQ-123 resulted in a significant (∼25%) increase in the ACh-mediated vasodilation in the short-sleep group only. After exercise training, although nightly sleep duration was unchanged (6.4 ± 0.1 h/night), ACh-mediated vasodilation was significantly higher (∼20%), ET-1-mediated vasoconstriction was significantly lower (∼80%), and the vasodilator response to ACh was not increased with ET_A receptor blockade. Regular aerobic exercise, independent of changes in nightly sleep duration, can counteract insufficient sleep-related endothelial vasomotor dysfunction.NEW & NOTEWORTHY Habitual insufficient nightly sleep (<7 h/night) is associated with increased risk of cardiovascular disease and events. Endothelial dysfunction, specifically reduced endothelium-dependent vasodilation and increased endothelin (ET)-1-mediated vasoconstriction, is considered to be a major contributing mechanism underlying increased vascular risk with insufficient sleep. In contrast to insufficient sleep, regular aerobic exercise enhances endothelial vasomotor function, reducing the risk of cardiovascular disease and associated events. In the present study, we determined the effects of aerobic exercise training on endothelium-dependent vasodilation and ET-1 vasoconstriction in adults who habitually sleep <7 h/night. After exercise training, although nightly sleep duration was unchanged, endothelium-dependent vasodilation was significantly enhanced and ET-1-mediated vasoconstrictor tone was significantly reduced in adults who sleep <7 h/night. Regular aerobic exercise training can mitigate insufficient sleep-related endothelial vasomotor dysfunction and, in turn, potentially reduce the cardiovascular risk associated with habitual insufficient nightly sleep.

Endothelin-1, endothelin receptor antagonists, and vein graft occlusion in coronary artery bypass surgery: 20 years on and still no journey from bench to bedside

The saphenous vein is the most commonly used bypass graft in patients with coronary artery disease. During routine coronary artery bypass, grafting the vascular damage inflicted on the vein is likely to stimulate the release of endothelin-1, a potent endothelium-derived vasoconstrictor that also possesses cell proliferation and inflammatory properties, conditions associated with vein graft failure. In both in vitro and in vivo studies, endothelin receptor antagonists reduce neointimal thickening. The mechanisms underlying these observations are multifactorial and include an effect on cell proliferation and cell/tissue damage. Much of the data supporting the beneficial action of endothelin-1 receptor antagonism at reducing intimal thickening and occlusion in experimental vein grafts were published over 20 years ago. The theme of the recent ET-16 conference in Kobe was "Visiting Old and Learning New". This short review article provides an overview of studies showing the potential of endothelin receptor antagonists to offer an adjuvant therapeutic approach for reducing saphenous vein graft failure and poses the question why this important area of research has not been translated from bench to bedside given the potential benefit for coronary artery bypass patients.

GIP as a Potential Therapeutic Target for Atherosclerotic Cardiovascular Disease-A Systematic Review

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are gut hormones that are secreted from enteroendocrine L cells and K cells in response to digested nutrients, respectively. They are also referred to incretin for their ability to stimulate insulin secretion from pancreatic beta cells in a glucose-dependent manner. Furthermore, GLP-1 exerts anorexic effects via its actions in the central nervous system. Since native incretin is rapidly inactivated by dipeptidyl peptidase-4 (DPP-4), DPP-resistant GLP-1 receptor agonists (GLP-1RAs), and DPP-4 inhibitors are currently used for the treatment of type 2 diabetes as incretin-based therapy. These new-class agents have superiority to classical oral hypoglycemic agents such as sulfonylureas because of their low risks for hypoglycemia and body weight gain. In addition, a number of preclinical studies have shown the cardioprotective properties of incretin-based therapy, whose findings are further supported by several randomized clinical trials. Indeed, GLP-1RA has been significantly shown to reduce the risk of cardiovascular and renal events in patients with type 2 diabetes. However, the role of GIP in cardiovascular disease remains to be elucidated. Recently, pharmacological doses of GIP receptor agonists (GIPRAs) have been found to exert anti-obesity effects in animal models. These observations suggest that combination therapy of GLP-1R and GIPR may induce superior metabolic and anti-diabetic effects compared with each agonist individually. Clinical trials with GLP-1R/GIPR dual agonists are ongoing in diabetic patients. Therefore, in this review, we summarize the cardiovascular effects of GIP and GIPRAs in cell culture systems, animal models, and humans.

Impact of Exercise on Inflammatory Mediators of Metabolic and Vascular Insulin Resistance in Type 2 Diabetes

The development of obesity is cornerstone in the etiology of metabolic and vascular insulin resistance and consequently exacerbates glycemic control. Exercise is an efficacious first-line therapy for type 2 diabetes that improves insulin action through, in part, reducing hormone mediated inflammation. Together, improving the coordination of skeletal muscle metabolism with vascular delivery of glucose will be required for optimizing type 2 diabetes and cardiovascular disease treatment.

Big endothelin-1 level is a useful marker for predicting the presence of isolated coronary artery ectasia

CONTEXT

Endothelin-1(ET-1) has been implicated in coronary artery disease (CAD) and may be associated with coronary artery ectasia (CAE).

OBJECTIVE

To clarify the relationship between big ET-1 and isolated CAE.

METHODS

We measured big ET-1 with ELISA in 216 patients (CAE, n = 72; CAD, n = 72; normal, n = 72) and evaluated the link with isolated CAE.

RESULTS

The level of plasma big ET-1 was significantly higher in patients with isolated CAE (p < 0.001). Big ET-1 was strongly and independently associated with CAE by multivariate analysis (OR 95%CI: 1.026 (1.018-1.034), p = 0.000).

CONCLUSIONS

Big ET-1 may be a useful predictor for the presence of isolated CAE.

Combined markers of initial stages of coronary atherosclerosis

Abnormalities in energy metabolism and endothelial dysfunction contribute to signaling processes associated with atherogenesis. The goal of our study was to develop diagnostic tests based on endothelial functional markers and adiponectin to differentiate early stages of coronary lesions during atherogenesis. The cohort included male and female patients from 25 to 86 years of age. All subjects underwent coronary angiography and severity of coronary lesions was quantified by the Gensini score that assigns points depending on location and extent of the lesions. We have estimated associations between the Gensini score and some known primary and secondary diagnostic parameters and have found that the ratio of serum levels of adiponectin to endothelin strongly correlates with severity of coronary lesions and can be used for differentiation of male patients lacking coronary atherosclerosis (despite symptoms of ischemic heart disease) from patients that have severe coronary lesions. Predictive power of adiponectin to endothelin ratio did not depend on drug therapy.

Chronic Nebivolol Treatment Suppresses Endothelin-1-Mediated Vasoconstrictor Tone in Adults With Elevated Blood Pressure

Endothelin-1 (ET-1) plays a major role in the pathophysiology of hypertension and its associated cardiovascular risk. We tested the hypothesis that chronic nebivolol treatment reduces ET-1-mediated vasoconstrictor tone in adult humans with elevated blood pressure (BP). Furthermore, reducing ET-1 vasoconstrictor activity contributes to the improvement in endothelial vasodilator function associated with nebivolol treatment. Forty-two middle-aged adults with elevated BP (systolic BP ≥130 mm Hg or diastolic BP ≥85 mm Hg) completed a 3-month, double-blind, randomized, placebo controlled trial: 14 received nebivolol (8 men/6 women; 5 mg per day); 14 received metoprolol succinate (9 men/5 women; 100 mg per day); and 14 received placebo (9 men/5 women). Forearm blood flow (plethysmography) responses to selective (BQ-123: 100 nmol/min; 60 minutes) and nonselective (BQ-123+BQ-788 [50 nmol/min]; 60 minutes) ET-1 receptor blockade, as well as acetylcholine (4.0, 8.0, and 16.0 μg per 100 mL of tissue per minute) in the absence and presence of nonselective ET-1 receptor blockade were determined before and after each treatment intervention. Forearm blood flow responses to BQ-123 and BQ-123+BQ-788 were similarly and significantly elevated (≈30% and 60%, respectively) from baseline in all 3 groups. Nebivolol, but not metoprolol or placebo, therapy resulted in a marked (≈25% and 45%; P<0.05) reduction in forearm blood flow response to BQ-123 and BQ-123+BQ-788. Moreover, after nebivolol therapy only, vasodilator response to acetylcholine was not significantly increased by ET-1 receptor blockade. These results demonstrate that nebivolol, but not metoprolol, treatment reduces ET-1-mediated vasoconstrictor tone in adult humans with elevated BP. In addition, nebivolol-induced reduction in ET-1-mediated vasoconstrictor tone underlies the favorable effects of this β-blocker on endothelial vasodilation.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01395329.

Circulating microRNA profile in patients with membranous obstruction of the inferior vena cava

Membranous obstruction of the inferior vena cava (MOVC) is a common type of Budd-Chiari syndrome. However, the pathogenesis of MOVC has not been fully elucidated. Recent studies demonstrated that microRNAs (miRNAs or miRs) are involved in multiple diseases. To the best of our knowledge, specific changes in the expression of miRNAs in MOVC patients have not been previously assessed. The present study used a microarray analysis, followed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) validation, with the aim to access the miRNA expression levels in the plasma of 34 MOVC patients, compared with those in healthy controls. The results revealed a total of 16 differentially expressed miRNAs in MOVC patients. Subsequently, RT-qPCR analysis verified the statistically consistent expression of 5 selected miRNAs (miR-125a-5p, miR-133b, miR-423-5p, miR-1228-5p and miR-1266), in line with the results of the microarray analysis. These 5 miRNAs, which were described as crucial regulators in numerous biological processes and vascular diseases, may play an important role in the pathogenesis of MOVC. Bioinformatics analysis of target genes of the differentially expressed miRNAs revealed that these predicted targets were significantly enriched and involved in several key signaling pathways important for MOVC, including the ErbB, Wnt, MAPK and VEGF signaling pathway. In conclusion, miRNAs may involve in multiple signaling pathways contributing to the pathological processes of MOVC. The present study offers an intriguing new perspective on the involvement of miRNAs in MOVC; however, the precise underlying mechanisms require further validation.

Metabolic syndrome and endothelin-1 mediated vasoconstrictor tone in overweight/obese adults

OBJECTIVE

To determine whether endothelin (ET)-1 vasoconstrictor tone is greater in overweight and obese adults with the metabolic syndrome (MetS).

MATERIALS/METHODS

Forty overweight/obese middle-aged and older adults (age: 43-71 years; BMI: 25.1-36.9 kg/m²) were studied: 20 without MetS (13 M/7 F) and 20 with MetS (13 M/7 F). MetS was established according to NCEP ATP III guidelines. Forearm blood flow (FBF; plethysmography) responses to intra-arterial infusion of selective ET(A) receptor blockade (BQ-123; 100 nmol/min; for 60 min) and non-selective ET(A/B) receptor blockade (BQ-123 + BQ-788 [50 nmol/min for 60 min]) were determined.

RESULTS

In response to the selective ET(A) antagonism, there was a significant increase in forearm blood flow from baseline in both groups. However, the increase in forearm blood flow was significantly higher (P=0.03; ~45%) in the overweight/obese group with MetS than the group without MetS. In contrast, there were no significant group differences in FBF responses to non-selective ET(A/B) receptor blockade. Peak vasodilator responses to nonselective ET(A/B) blockade were ~50% higher than baseline blood flow in the overweight/obese groups without and with MetS.

CONCLUSION

MetS is associated with higher ET-1 vasoconstrictor tone in overweight/obese adults. The enhanced ET-1 vasoconstrictor activity with MetS is mediated by the ET(A) receptor subtype.

The up-regulation of endothelin-1 and down-regulation of miRNA-125a-5p, -155, and -199a/b-3p in human atherosclerotic coronary artery

BACKGROUND

Previous studies have reported important roles of endothelin-1 (ET-1) and angiotensin II (Ang II) in the pathogenesis of atherosclerosis. However, the expression of these two proteins and the underlying mechanisms in human atherosclerotic coronary arteries are largely unknown.

METHODS

We examined the expression of ET-1 and Ang II in pericardial fluid and coronary arteries from 25 individuals (n = 25) using enzyme-linked immuno sorbent assay (ELISA) and immunohistochemistry. Twelve patients died from acute coronary syndrome were classified as atherosclerotic plaque group (AP group) (n = 12), while 13 patients died from other causes were classified as non-AP group (n = 13). Meanwhile, we performed reverse transcription-polymerase chain reaction (RT-PCR) to measure the expression of six microRNAs targeting ET-1 in formalin-fixed, paraffin-embedded coronary arteries.

RESULTS

Our data showed that ET-1 was significantly higher in both pericardial fluid and coronary arteries from AP group. However, Ang II showed no significant difference in pericardial fluid between the two groups, while it was even significantly lower in coronary arteries from AP group. Besides, miR-125a-5p, miR-155, and miR-199a/b-3p, which suppressed the expression of ET-1, were down-regulated in the coronary arteries from AP group.

CONCLUSION

The up-regulation of ET-1, regulated by miR-125a-5p, miR-155, and miR-199a/b-3p, indicated that ET-1 played an important role in human coronary atherosclerosis.

SUMMARY

We focused on the human coronary arteries with atherosclerotic plaques. The expression of ET-1, as well as its upstream miRNAs, was determined. Unlike any of previous study regarding miRNAs expression, we could exclude the discrepancy of artery-bed-specific miRNA expression. Besides, our data indicated, to some degree, that ET-1 might play a more vital role than Ang II in coronary atherosclerosis.

Relationship between Endothelial Nitric Oxide Synthase, Insulin Resistance and Macrovascular Disease in Patients with Acute Myocardial Infarction

OBJECTIVE: To explore the relationship between endothelial nitric oxide synthase (eNOS) activity, insulin resistance and macrovascular disease in patients with acute myocardial infarction (AMI). METHODS: AMI patients were grouped according to the presence (group A, n = 49) or absence (group B, n = 48) of macrovascular disease. A healthy control group was also recruited (group C, n = 43). eNOS activity and nitric oxide (NO), endothelin-1 (ET-1), fasting plasma glucose and fasting insulin levels were compared across groups. The homeostasis model assessment of insulin resistance (HOMA—IR) was calculated in each participant and correlations between biochemical parameters were determined. RESULTS: eNOS and NO levels were significantly lower in group A compared with the other groups. Conversely, ET-1 levels and the HOMA-IR were significantly higher in group A. eNOS activity and NO levels were significantly lower, and ET-1 levels and HOMA-IR were significantly higher, in group B compared with controls. Across the groups there were inverse correlations in AMI patients between eNOS and HOMA-IR, NO and HOMA-IR, eNOS and ET-1, and NO and ET-1, and positive correlations between eNOS and NO, regardless of whether macrovascular disease was present. CONCLUSION: There is a close relationship between eNOS activity and the development of insulin resistance and macrovascular disease in AMI patients.

Beneficial effects of combinatorial micronutrition on body fat and atherosclerosis in mice

AIMS

More than two billion people worldwide are deficient in key micronutrients. Single micronutrients have been used at high doses to prevent and treat dietary insufficiencies. Yet the impact of combinations of micronutrients in small doses aiming to improve lipid disorders and the corresponding metabolic pathways remains incompletely understood. Thus, we investigated whether a combination of micronutrients would reduce fat accumulation and atherosclerosis in mice.

METHODS AND RESULTS

Lipoprotein receptor-null mice fed with an original combination of micronutrients incorporated into the daily chow showed reduced weight gain, body fat, plasma triglycerides, and increased oxygen consumption. These effects were achieved through enhanced lipid utilization and reduced lipid accumulation in metabolic organs and were mediated, in part, by the nuclear receptor PPARα. Moreover, the micronutrients partially prevented atherogenesis when administered early in life to apolipoprotein E-null mice. When the micronutrient treatment was started before conception, the anti-atherosclerotic effect was stronger in the progeny. This finding correlated with decreased post-prandial triglyceridaemia and vascular inflammation, two major atherogenic factors.

CONCLUSION

Our data indicate beneficial effects of a combination of micronutritients on body weight gain, hypertriglyceridaemia, liver steatosis, and atherosclerosis in mice, and thus our findings suggest a novel cost-effective combinatorial micronutrient-based strategy worthy of being tested in humans.

Endothelin-1 in peripheral arterial disease: a potential role in muscle damage

The evidence for the role of endothelin-1 (ET-1) in endothelial dysfunction and atherosclerosis has been growing since its discovery. However most studies have focussed on cardiac disease and its role in peripheral arterial disease (PAD) is less clear. In addition to its role in the development and progression of atherosclerotic lesions in lower limb arteries, there is evidence that ET-1 adversely affects microvessels within the muscle and the viability of the ischemic muscle itself. This review summarises some of these findings which underscore the potential use of ET antagonists as an adjunct in the treatment of PAD.

The interaction between endothelin-1 and nitric oxide in the vasculature: new perspectives

Nitric oxide (NO) and endothelin-1 (ET-1) are natural counterparts in vascular function, and it is becoming increasingly clear that an imbalance between these two mediators is a characteristic of endothelial dysfunction and is important in the progression of vascular disease. Here, we review classical and more recent data that suggest that ET-1 should be regarded as an essential component of NO signaling. In particular, we review evidence of the role of ET-1 in models of acute and chronic NO synthase blockade. Furthermore, we discuss the possible mechanisms by which NO modulates ET-1 activity. On the basis of these studies, we suggest that NO tonically inhibits ET-1 function, and in conditions of diminished NO bioavailability, the deleterious effects of unmitigated ET-1 actions result in vasoconstriction and eventually lead to vascular remodeling and dysfunction.

Endothelin-1 vasoconstriction and the age-related decline in endothelium-dependent vasodilatation in men

ET (endothelin)-1, a potent vasoconstrictor peptide released by the endothelium, plays an important role in vasomotor regulation and has been linked to diminished endothelial vasodilator capacity in several pathologies associated with human aging, including hypertension, Type 2 diabetes and coronary artery disease. However, it is currently unknown whether the decline in endothelial vasodilatation with advancing age is due to elevated ET-1 vasconstrictor activity. Accordingly, we tested the hypothesis that the age-related impairment in ACh (acetylcholine)-mediated endothelium-dependent vasodilatation is due, at least in part, to increased ET-1-mediated vasoconstrictor tone. FBF (forearm blood flow) responses to ACh, SNP (sodium nitroprusside) and BQ-123 (ETA receptor blocker) were determined in 14 young (age, 25±1 years) and 14 older (age, 61±2 years) healthy non-obese men. Additionally, FBF responses to ACh were determined in the presence of ETA blockade. Vasodilatation to ACh was lower (approx. 25%; P<0.05) in the older men (from 4.9±0.2 to 13.9±0.9 ml·100 ml−1 of tissue·min−1) compared with the young men (4.6±0.3 to 17.2±1.0 ml·100 ml−1 of tissue·min−1). There were no differences in FBF responses to SNP between the young (4.8±0.3 to 18.5±0.3 ml·100 ml−1 of tissue·min−1) and older (5.1±0.3 to 17.3±0.8 ml·100 ml−1 of tissue·min−1) men. In the young men, resting FBF was not significantly altered by BQ-123, whereas, in the older men, FBF increased approx. 25% in response to BQ-123 infusion (P<0.05). Co-infusion of ACh with BQ-123 resulted in an approx. 20% increase in the ACh-induced vasodilatation in older men compared with saline. In contrast, FBF responses to ACh were not significantly altered by ETA blockade in the young men. In conclusion, these results demonstrate that ET-1 vasoconstrictor activity contributes, at least in part, to diminished endothelium-dependent vasodilatation in older men.

Short sleep duration is associated with enhanced endothelin-1 vasoconstrictor tone

Short sleep duration is associated with increased cardiovascular disease (CVD) morbidity. Endothelial vasomotor dysfunction represents a potential mechanism contributing to the increased CVD risk associated with habitual short sleep duration. Endothelin (ET)-1 is a potent vasoconstrictor peptide that is associated with endothelial vasomotor dysfunction and increased CVD risk. Currently, there is no information regarding the influence of short sleep duration on ET-1 vasoconstrictor activity in adults. We tested the hypothesis that ET-1-mediated vasoconstrictor activity is greater in adults who sleep less than 7 h/night (short sleep duration) compared with those who sleep 7-9 h/night (normal sleep duration). Forearm blood flow (FBF) responses to intra-arterial infusion of BQ-123 (100 nmol/min for 60 min), a selective ETA receptor antagonist, were determined in 80 adults: 50 with normal sleep duration (32 males and 18 females; age: 56.6 +/- 1.2 years; sleep: 7.6 +/- 0.1 h/night) and 30 with short sleep duration (17 males and 13 females; age: 56.5 +/- 1.2 years; sleep: 6.1 +/- 0.1 h/night). In response to BQ-123, adults reporting short sleep duration had a greater increase in resting FBF compared with adults reporting normal sleep duration (approximately 20% vs. approximately 8%; P < 0.05). There was an inverse relation between mean nightly sleep duration and the FBF response to BQ-123 at 60 min (r = -0.29, P < 0.05). These findings indicate that habitual short sleep duration is associated with greater ET-1-mediated vasoconstrictor tone. Increased ET-1 vasoconstrictor activity may contribute to the elevated CVD risk associated with chronic reductions in sleep duration.

MicroRNA-125a/b-5p inhibits endothelin-1 expression in vascular endothelial cells

BACKGROUND

Endothelin-1 (ET-1) is considered to be one of the most potent and long-lasting vasoconstrictive peptides, but the mechanisms on the regulation of ET-1 expression are not fully understood.

METHOD AND RESULTS

In this study, we found that microRNA (miR)-125a-5p and miR-125b-5p are highly expressed in vascular endothelial cells (VECs), which can be regulated by oxidized low-density lipoprotein (oxLDL). To explore the function of miR-125a/b-5p in VECs, we examined the roles of potential targets of miR-125a/b-5p that could influence endothelium function. We found that both miR-125a/b-5p can suppress oxLDL-induced ET-1 expression by directly targeting 3' untranslated region of prepro-endothelin-1 (preproET-1) mRNA determined by luciferase reporter assay, western blot, and enzyme immunometric assay. Consistently, inhibitors of miR-125a/b-5p can directly enhance preproET-1 expression. The decreased expressions of miR-125a-5p and miR-125b-5p are negatively associated with upregulation of preproET-1 expression in aorta of stroke-prone spontaneously hypertensive rats (SHR-SPs).

CONCLUSION

Our finding demonstrated that endothelial miR-125a/b-5p inhibits ET-1 expression in VECs, which revealed a novel miRNA-mediated mechanism in vasomotor homeostasis.

Working under pressure: coronary arteries and the endothelin system

Endogenous endothelin-1-dependent (ET-1) tone in coronary arteries depends on the balance between ET(A) and ET(B) receptor-mediated effects and on parameters such as receptor distribution and endothelial integrity. Numerous studies highlight the striking functional interactions that exist between nitric oxide (NO) and ET-1 in the regulation of vascular tone. Many of the cardiovascular complications associated with cardiovascular risk factors and aging are initially attributable, at least in part, to endothelial dysfunction characterized by a dysregulation between NO and ET-1. The contribution of the imbalance between smooth muscle ET(A/B) and endothelial ET(B) receptors to this process is poorly understood. An increased contribution of ET-1 that is associated with a proportional decrease in that of NO accompanies the development of coronary endothelial dysfunction, coronary vasospasm, and atherosclerosis. These data form the basis for the rationale of testing therapeutic approaches counteracting ET-1-induced cardiovascular dysfunction. It remains to be determined whether the beneficial role of endothelial ET(B) receptors declines with age and risk factors for cardiovascular diseases, revealing smooth muscle ET(B) receptors with proconstricting and proinflammatory activities.

The cardiovascular physiology and pharmacology of endothelin-1

One year after the discovery in 1980 that the endothelium was obligatory for acetylcholine to relax isolated arteries, it was clearly shown that the endothelium could also promote contraction. In 1988, Dr Yanagisawa's group identified endothelin-1 (ET-1) as the first endothelium-derived contracting factor. The circulating levels of this short (21 amino acids) peptide were quickly determined in humans and it was reported that in most cardiovascular diseases, circulating levels of ET-1 were increased and ET-1 was then recognized as a likely mediator of pathological vasoconstriction in human. The discovery of two receptor subtypes in 1990, ET(A) and ET(B), permitted optimization of bosentan, which entered clinical development in 1993, and was offered to patients with pulmonary arterial hypertension in 2001. In this report, we discuss the physiological and pathophysiological role of endothelium-derived ET-1, the pharmacology of its two receptors, focusing on the regulation of the vascular tone and as much as possible in humans. The coronary bed will be used as a running example, but references to the pulmonary, cerebral, and renal circulation will also be made. Many of the cardiovascular complications associated with aging and cardiovascular risk factors are initially attributable, at least in part, to endothelial dysfunction, particularly dysregulation of the vascular function associated with an imbalance in the close interdependence of NO and ET-1, in which the implication of the ET(B) receptor may be central.

Endothelium-derived endothelin-1

One year after the revelation by Dr. Furchgott in 1980 that the endothelium was obligatory for acetylcholine to relax isolated arteries, it was clearly shown that the endothelium could also promote contraction. In 1988, Dr. Yanagisawa's group identified endothelin-1 (ET-1) as the first endothelium-derived contracting factor. The circulating levels of this short (21-amino acid) peptide were quickly determined in humans, and it was reported that, in most cardiovascular diseases, circulating levels of ET-1 were increased, and ET-1 was then tagged as "a bad guy." The discovery of two receptor subtypes in 1990, ET(A) and ET(B), permitted optimization of the first dual ET-1 receptor antagonist in 1993 by Dr. Clozel's team, who entered clinical development with bosentan, which was offered to patients with pulmonary arterial hypertension in 2001. The revelation of Dr. Furchgott opened a Pandora's box with ET-1 as one of the actors. In this brief review, we will discuss the physiological and pathophysiological role of endothelium-derived ET-1 focusing on the regulation of the vascular tone, and as much as possible in humans. The coronary bed will be used as a running example in this review because it is the most susceptible to endothelial dysfunction, but references to the cerebral and renal circulation will also be made. Many of the cardiovascular complications associated with aging and cardiovascular risk factors are initially attributable, at least in part, to endothelial dysfunction, particularly dysregulation of the vascular function associated with an imbalance in the close interdependence of nitric oxide and ET-1.

Sex differences in endothelin-1-mediated vasoconstrictor tone in middle-aged and older adults

The prevalence of cardiovascular disease is lower in middle-aged and older women than men. Increased endothelin-1-mediated vasoconstriction has been linked to the etiology of a number of cardiovascular diseases, including atherosclerosis, heart failure, and hypertension. It is unknown whether a sex difference in endothelin-1-mediated vasoconstrictor tone exists in middle-aged and older adults. Therefore, we tested the hypothesis that middle-aged and older men would demonstrate greater ET-1-mediated vasoconstrictor tone than age-matched women. Forearm blood flow in response to intra-arterial infusions of endothelin (ET)-1, BQ-123 (a selective ET(A) receptor antagonist), and BQ-788 (a selective ET(B) receptor antagonist) was assessed by venous occlusion plethysmography in 21 women (age: 58 + or - 1 yr; body mass index: 26.0 + or - 1.0 kg/m(2)) and 25 men (age: 57 + or - 2 yr; body mass index: 26.8 + or - 0.7 kg/m(2)). In response to BQ-123, the increase in forearm blood flow from baseline was significantly higher in the men than the women (24 + or - 5% vs. 9 + or - 5%; P < 0.05). In contrast, the increase in forearm blood flow in response to BQ-123 coinfused with BQ-788 was greater in the women than the men, such that the maximum vasodilation to dual endothelin receptor blockade was similar between men and women (approximately 25%). There was no difference in the vasoconstrictor response to ET-1 between the sexes. These results indicate that middle-aged and older men are under greater ET(A) receptor-mediated vasoconstrictor tone than age-matched women. Since the ET(A) receptor is the predominant receptor subtype in the coronary vasculature, this sex difference in vasoconstrictor tone may be a mechanism contributing to the sex difference in the prevalence of coronary heart disease in middle-aged and older adults.

Endothelin-1, aging and hypertension

PURPOSE OF REVIEW

Endothelin-1 system activation plays an important role in the etiology of atherosclerotic vascular disease. Aging and hypertension are two independent cardiovascular risk factors that have been shown to exhibit increased endothelin-1 system activation. This review focuses on the cardiovascular effects of the endothelin system, its relation to aging and hypertension, as well as potential treatment options.

RECENT FINDINGS

Many of the cardiovascular complications associated with both aging and hypertension are attributable, in part, to endothelial dysfunction, particularly vasomotor dysregulation. To date most studies have focused on the effects of aging and hypertension on endothelium-dependent nitric oxide-mediated vasodilation. However, endothelin-1-mediated vasoconstrictor tone increases with age and contributes to the pathogenesis of hypertension. Pharmacologic approaches to reduce endothelin-1 system activation have produced limited results and are largely disease-specific. In contrast, regular aerobic exercise has been shown to be extremely effective at reducing endothelin-1 system activity.

SUMMARY

Both aging and hypertension represent important cardiovascular disease risk factors that are characterized by increased endothelin-1-mediated vasoconstrictor tone. Future studies are needed to elucidate pharmacologic options for reducing endothelin-1 system activity especially in older hypertensive adults, though regular aerobic exercise must continue to be a point of emphasis for maintaining/improving vascular health.

Transcriptional and post-transcriptional regulation of preproendothelin-1 by plaque-prone hemodynamics

OBJECTIVE

Plaque-prone areas are exposed to a particular hemodynamic environment characterized by a low mean shear stress value and a cyclic reversal flow. This mechanical environment, also termed oscillatory shear stress (OSS), induces the expression of several pro-atherogenic genes in the endothelial cells including the preproendothelin-1 (ppET-1) gene. The present paper investigates the molecular mechanisms of this induction.

METHODS AND RESULTS

Several deletional mutants of ppET-1 gene promoter were cloned upstream of a luciferase gene and transiently transfected in bovine arterial endothelial cells that were further exposed to plaque-prone hemodynamics. After 24h of flow exposure, analysis of the transfected cells showed that a proximal promoter of 156 base pairs length retained OSS responsiveness. Mutation of an activator protein-1 (AP-1) binding site present in this minimal promoter completely abolished its activation by OSS. Consistently, electrophoresis mobility shift assay revealed a sustained activation of AP-1 transcription factor in endothelial cells exposed to OSS. In addition to the transcriptional activation, we demonstrated that OSS also induces a stabilization of ppET-1mRNA through the 3'-untranslated region (3'-UTR) of this gene. Fluvastatin, a drug known to improve endothelial function, was shown to prevent OSS up-regulation of the ppET-1 gene expression. Under this flow condition, fluvastatin affects ppET-1 gene expression via inhibition of its promoter activity without affecting ppET-1mRNA stability.

CONCLUSIONS

The present study demonstrate that plaque-prone hemodynamic induces ppET-1 gene expression by both transcriptional and post-transcriptional mechanisms via an activation of AP-1 transcriptional factor and stabilization of mRNA. The transcriptional up-regulation of ppET-1 was shown to be fluvastatin sensitive.

Overweight and obese humans demonstrate increased vascular endothelial NAD(P)H oxidase-p47(phox) expression and evidence of endothelial oxidative stress

BACKGROUND

Obesity may alter vascular endothelial cell protein expression (VECPE) of molecules that influence susceptibility to atherosclerosis.

METHODS AND RESULTS

Quantitative immunofluorescence was performed on vascular endothelial cells collected from 108 men and women free of clinical disease who varied widely in adiposity (body mass index 18.4 to 36.7 kg/m2; total body fat 5.8 to 55.0 kg; waist circumference: 63.0 to 122.9 cm). All 3 expressions of adiposity were positively associated with VECPE of the oxidant enzyme subunit NAD(P)H oxidase-p47(phox) (part correlation coefficient [r(part)] 0.22 to 0.24, all P < 0.05) and the antioxidant enzyme catalase (r(part) = 0.71 to 0.75, all P < 0.001). Total body fat was positively associated with VECPE of nitrotyrosine (r(part) = 0.36, P = 0.003), a marker of protein oxidation, and, in men, with Ser1177-phosphorylated endothelial nitric oxide synthase (r(part) = 0.46, P = 0.02), an activated form of endothelial nitric oxide synthase. Overweight/obese subjects (body mass index > or = 25 kg/m2) had 35% to 130% higher VECPE of NAD(P)H oxidase-p47(phox), nitrotyrosine, catalase, and the cytosolic antioxidant CuZn superoxide dismutase (all P < 0.05), as well as a 56% greater VECPE of the potent local vasoconstrictor endothelin-1 (P = 0.05) than normal-weight subjects (body mass index < 25 kg/m2). Nuclear factor-kappaB protein expression was approximately 60% to 100% greater in the most obese adults than in the leanest adults (P < or = 0.01). These relations were independent of sex but were selectively reduced after accounting for the influence of plasma C-reactive protein, fasting glucose-insulin metabolism, or serum triglycerides.

CONCLUSIONS

Compared with their normal-weight peers, overweight and obese adults demonstrate increased vascular endothelial expression of NAD(P)H oxidase-p47(phox) and evidence of endothelial oxidative stress, with selective compensatory upregulation of antioxidant enzymes and Ser1177-phosphorylated endothelial nitric oxide synthase. Endothelin-1 and nuclear factor-kappaB protein expression also appear to be elevated in obese compared with lean adults. These findings may provide novel insight into the molecular mechanisms linking obesity to increased risk of clinical atherosclerotic diseases in humans.

Effect of Endothelin on Sodium/Hydrogen Exchanger Activity of Human Monocytes and Atherosclerosis-Related Functions

The objective of this article is to investigate the influence of endothelin-1 (ET-1) on human monocyte Na(+)/H(+) exchanger (NHE) activity and on the atherosclerosis-related monocyte functions. ET-1 caused an increase in pHi and in (22)Na influx of monocytes. A reversal of ET-1 effect on pHi was observed in the presence of the NHE1 inhibitor, cariporide. In addition, the activation of NHE1 by ET-1 was mediated via protein kinase C (PKC), mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K), and NADPH oxidase. Also, a link between ET-1 and nitric oxide (NO) was observed. Furthermore, after ET-1 treatment, an increase of the adhesive capacity, the migration ability on laminin and CD36 expression of monocytes, was observed; using cariporide this increase was abolished. Our results showed that ET-1 induces a signaling pathway with the involvement of PKC, MAPK, PI3K, and NADPH oxidase where NHE1 plays a key role. ET-1 also plays a significant role in atherosclerosis-related functions of human monocytes, via NHE1 activation.

Enhanced endothelium-dependent vasodilatation by dual endothelin receptor blockade in individuals with insulin resistance

Insulin resistance is associated with endothelial dysfunction and increased production of the pro-inflammatory vasoconstrictor peptide endothelin-1 (ET-1). The aim of this study was to test the hypothesis that blockade of ET receptors results in enhanced endothelium-dependent vasodilatation (EDV) in individuals with insulin resistance. Twelve individuals with insulin resistance without any history of diabetes or cardiovascular disease and 8 age-matched controls with high insulin sensitivity, as determined by hyperinsulinemic-euglycemic clamp, were investigated on 2 separate occasions using forearm venous occlusion plethysmography. Endothelium-dependent and endothelium-independent vasodilatation was determined before and after selective ET(A) and dual ET(A)/ET(B) receptor blockade. A 60 minute intraarterial infusion of the ET(A) receptor antagonist BQ123 (10 nmol/min) combined with the ET(B) receptor antagonist BQ788 (5 nmol/min) evoked a significant increase in acetylcholine-mediated EDV (P < 0.01) in individuals with insulin resistance. The endothelium-independent vasodilator response to nitroprusside was not changed by dual ET(A)/ET(B) receptor blockade. Dual ET(A)/ET(B) receptor blockade did not affect the response to acetylcholine or nitroprusside in the insulin-sensitive group. Selective ET(A) receptor blockade did not evoke any changes in endothelium-dependent or endothelium-independent vasodilatation in either group. This study demonstrates that dual ET(A)/ET(B) receptor blockade, but not selective ET(A) blockade, enhances EDV in subjects with insulin resistance, suggesting that ET-1 is involved in the regulation of endothelial function in individuals with insulin resistance.

Cryptotanshinone inhibits endothelin-1 expression and stimulates nitric oxide production in human vascular endothelial cells

The Chinese herb Salvia miltiorrhiza (SM) has been found to have beneficial effects on the circulatory system. In the present study, we investigated the effects of cryptotanshinone (derived from SM) on endothelin-1 (ET-1) expression in human umbilical vein endothelial cells (HUVECs). The effect of cryptotanshinone on nitric oxide (NO) in HUVECs was also examined. We found that cryptotanshinone inhibited basal and tumor necrosis factor-alpha (TNF-alpha) stimulated ET-1 secretion in a concentration-dependent manner. Cryptotanshinone also induced a concentration-dependent decrease in ET-1 mRNA expression. Cryptotanshinone increased basal and TNF-alpha-attenuated NO production in a dose-dependent fashion. Cryptotanshinone induced a concentration-dependent increase in endothelial nitric oxide synthase (eNOS) expression without significantly changing neuronal nitric oxide synthase (nNOS) expression in HUVECs in the presence or absence of TNF-alpha. NOS activities in the HUVECs were also induced by cryptotanshinone. Furthermore, decreased ET-1 expression in response to cryptotanshinone was not antagonized by the NOS inhibitor l-NAME. A gel shift assay further showed that TNF-alpha-induced Nuclear Factor-kappaB (NF-kappaB) activity was significantly reduced by cryptotanshinone. These data suggest that cryptotanshinone inhibits ET-1 production, at least in part, through a mechanism that involves NF-kappaB but not NO production.

Mechanisms of endothelial dysfunction in obesity

Obesity is a chronic disease, whose incidence is alarmingly growing, affecting not only adults but also children and adolescents. It is associated with severe metabolic abnormalities and increased cardiovascular morbidity and mortality. Adipose tissue secretes a great number of hormones and cytokines that not only regulate substrate metabolism but may deeply and negatively influence endothelial physiology, a condition which may lead to the formation of the atherosclerotic plaque. In this review, the physiology of the endothelium is summarised and the mechanisms by which obesity, through the secretory products of adipose tissue, influences endothelial function are explained. A short description of methodological approaches to diagnose endothelial dysfunction is presented. The possible pathogenetic links between obesity and cardiovascular disease, mediated by oxidative stress, inflammation and endothelial dysfunction are described as well.

Usefulness of serum endothelin levels in predicting death and myocardial infarction but not coronary progression in postmenopausal women with coronary disease (from the Women's Angiographic Vitamin and Estrogen [WAVE] study)

We performed a cohort study of 392 postmenopausal women who had coronary disease to assess whether baseline serum endothelin-1 level predicts angiographic disease progression, nonfatal myocardial infarction, or death. Angiographic progression was defined as the annualized change in minimal lumen diameter of all qualifying lesions for each patient. Twenty-nine patients died or had a myocardial infarction during follow-up. Each picogram per milliliter increase in endothelin-1 was associated with a 1.8-fold increased risk of death or myocardial infarction. After adjustment for potential confounders, endothelin-1 remained a predictor of clinical events but was not correlated with angiographic progression.

Endothelin receptor blockade improves endothelial function in atherosclerotic patients on angiotensin converting enzyme inhibition

OBJECTIVES

Endothelin-1 (ET-1) and angiotensin II may contribute to endothelial dysfunction, which is associated with increased risk of events in patients with coronary artery disease. The objective was to test whether dual ETA/ETB receptor antagonism improves endothelium-dependent vasodilatation (EDV) in atherosclerotic patients, also on treatment with angiotensin converting enzyme (ACE) inhibitor.

DESIGN AND SETTING

EDV and endothelium-independent vasodilatation were determined in 37 patients with atherosclerosis during measurement of forearm blood flow (FBF) with venous occlusion plethysmography. The patients were then randomized to treatment with ramipril 10 mg o.d. (n=21) or placebo (n=16) for 3 months in a double-blind fashion.

RESULTS

Intra-arterial infusion of the ETA receptor antagonist BQ123 and the ETB receptor antagonist BQ788 (both 10 nmol min(-1)) increased basal FBF by 42 +/- 4% (P <0.001) and enhanced EDV (P <0.001). Following 3 months ramipril treatment, ET receptor blockade still enhanced EDV. Acetylcholine 10 and 30 mg min(-1) increased FBF by 68 +/- 12 and 64 +/- 12 mL min(-1)/1000 mL before vs. 101 +/- 17 and 101 +/- 16 mL min(-1)/1000 mL following ET receptor blockade in the ramipril group (P <0.001).

CONCLUSIONS

Dual ETA/ETB receptor blockade improves endothelial function and exerts direct vasodilator effects in patients with atherosclerosis, also on treatment with ramipril suggesting that ET receptor blockade may have important therapeutic effects when added to ACE inhibition in these patients.

Crosstalk Between Mesangial and Endothelial Cells: Angiotensin II Down-Regulates Endothelin-Converting Enzyme 1

OBJECTIVE

Since mesangial and endothelial cells interact in the kidney, the present experiments were designed to analyze the ability of human mesangial cells (HMC) to modulate endothelin-1 (ET-1) synthesis by human umbilical vein endothelial cells (HuVEC).

METHODS AND RESULTS

The supernatants of HuVEC/HMC contained significantly lower amounts of ET-1 than those of HuVEC alone. This effect was not due to a decreased prepro-ET-1 mRNA expression and was only partially the consequence of HMC-dependent ET-1 degradation. Therefore, we tested the influence of the coculture on endothelin-converting enzyme-1 (ECE-1), and found a significant reduction of its mRNA and protein levels as well as a decreased activity in HuVEC/HMC as compared to HuVEC alone. Using a pharmacological blockade approach (sulotrobam, BN52021, losartan or catalase), losartan was shown to completely abolish down-regulation of ECE-1 observed in HuVEC/HMC. Angiotensin II (AII) induced a dose and time-dependent inhibition of ECE-1 expression in HuVEC.

CONCLUSIONS

These results support the importance of cross-talk among different cell types in the regulation of vascular or renal function. ET-1, and particularly ECE-1, might constitute a target in this regulation. In addition, locally synthesized AII could be one of the mediators involved in the down-regulation of ECE-1.

Proatherosclerotic mechanisms involving protein kinase C in diabetes and insulin resistance

In diabetes and insulin resistance, activation of protein kinase C (PKC) in vascular cells may be a key link between elevated plasma and tissue concentrations of glucose and nonesterified fatty acids and abnormal vascular cell signaling. Initial studies of PKC activation in diabetes focused on microvascular complications, but increasing evidence supports that PKC plays a role in several mechanisms promoting atherosclerosis. This review explains how PKC is thought to be activated in diabetes and insulin resistance through de novo synthesis of diacylglycerol. Furthermore, the review summarizes studies that implicate PKC in promoting proatherogenic mechanisms or inhibiting antiatherogenic mechanisms, including studies of endothelial dysfunction; gene induction and activation of vascular NAD(P)H oxidase; endothelial nitric oxide synthase expression and function; endothelin-1 expression; growth, migration, and apoptosis of vascular smooth muscle cells; induction of adhesion molecules; and oxidized low-density lipoprotein uptake by monocyte-derived macrophages.

Insulin resistance and the endothelium

There is increasing evidence of a parallel progression between insulin resistance and endothelial dysfunction, suggesting a close association between insulin action and the endothelium. Numerous studies have demonstrated that endothelial dysfunction occurs early in the insulin-resistant state and is predictive of future cardiovascular events. Similarly, insulin resistance has been associated with the metabolic syndrome, which also increases the risk of adverse cardiovascular outcomes. Approaches that improve endothelial dysfunction, such as treatment with statins, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, or peroxisome proliferator-activated receptor gamma ligands, have been shown to prevent both diabetes and cardiovascular disease. This article reviews the relation between endothelial dysfunction and cardiovascular disease, assesses the endothelium in the spectrum of insulin resistance, and examines the effect of the thiazolidinediones on endothelial function.

The endothelin 1a receptor antagonist BSF 302146 is a potent inhibitor of neointimal and medial thickening in porcine saphenous vein–carotid artery interposition grafts

OBJECTIVE

Late saphenous vein graft failure after coronary artery bypass graft surgery is initiated by medial thickening and neointima formation, both of which are mediated by the proliferation of vascular smooth muscle cells. Because porcine vein grafts contain high levels of endothelin 1 receptor subtypes and endothelin 1 promotes the proliferation of vascular smooth muscle cells, the effect of administration of the endothelin 1(A) receptor antagonist BSF 302146 ([+]-[S]-2-[4,6-dimethyl-pyrimidin-2-yloxy]-3,3-diphenyl-butanoic acid) on porcine vein graft thickening was investigated.

METHODS

Saphenous vein-carotid artery interposition grafting was performed in 4 groups of large white pigs (30-35 kg, n = 10 for each group). BSF 302146 was administered orally (3, 10, and 30 mg x kg(-1) x d(-1)) for 4 weeks to one group of pigs, and placebo was administered to the other group (control animals). Pigs were then anesthetized, and the grafts were removed and fixed at 100 mm Hg with 4% paraformaldehyde. Histologic sections were prepared, and graft morphometry was carried out by using computer-aided planimetry.

RESULTS

In vein grafts from animals treated with BSF 302146 compared with grafts from control animals (untreated), there were significant dose-dependent reductions in the increase in medial thickness and neointimal thickness, an increase in luminal area, and a decrease in proliferating cell nuclear antigen-positive cells in the medial-intimal area.

CONCLUSIONS

The administration of BSF 302146 reduces graft thickening and promotes positive remodeling through an endothelin 1(A)-mediated effect on vascular smooth muscle cell replication. The administration of this endothelin 1(A) receptor antagonist might therefore be therapeutically effective in preventing late vein graft failure in patients undergoing coronary artery bypass grafting.

Mechanisms of 17beta-estradiol on the production of ET-1 in ovariectomized rats

In order to clarify the mechanism underlying the possible preventive effect of estrogen on atherogenesis, we investigated the role of 17beta-estradiol (E2) in the regulation of endothelin-1 (ET-1) production in ovariectomized rats, which may contribute to atherogenesis. Female Spragure-Dawly rats were randomly divided into three groups: sham-operated group (sham), ovariectomized group (OVX) and 17beta-estradiol replacement group (OVX + E2, 20 microg(-1).kg.d(-1),s.c.). 4 weeks after operation, the plasma concentration of ET-1, clearance of ET-1, functional ECE activity and preproET-1 mRNA expression in aorta were measured. Concentration of plasma ET-1 change from 107.8 +/- 18.3 pg/ml (sham) and 135.5 +/- 27.6 pg/ml (OVX + E2) to 190.7 +/- 25.5 pg/ml (OVX ) (n = 8, p < 0.05). There was no significant difference in the clearance of 125IET-1 among three groups (p > 0.05). Functional ECE activity was increased in OVX group in comparison to that in sham group (p < 0.05). The OVX increased the preproET-1 mRNA expression in sham, whereas treatment with estrogen reversed these changes (p < 0.05). The present study have shown that estrogen down-regulates plasma ET-1 levels by inhibiting the preproET-1 mRNA expression and functional ECE activity. Clearance of ET-1 was not affected. Inhibition of ET-1 production mediated by modulating ECE activity may be one of the novel mechanisms of the protective of estrogens on the cardiovascular system.

Evidence for the involvement of endothelin-1 but not urotensin-II in chronic lower limb ischaemia in man

BACKGROUND

endogenous vasoconstrictor peptides may play a role in the pathophysiology of critical limb ischaemia (CLI). This study investigated endothelin-1 (ET-1) and urotensin-II (U-II) mRNA expression, peptide distribution and ET receptor subtype binding in chronically ischaemic muscle.

METHODS

open muscle biopsies were taken from patients undergoing amputations for CLI and from patients undergoing coronary artery bypass surgery (controls). ET-1 and U-II mRNA expression in muscle biopsies was studied using real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). ET-1 and U-II immunohistochemistry was performed on muscle sections and ET receptor binding studied using in vitro autoradiography.

RESULTS

ET-1 mRNA expression was significantly increased in CLI compared to controls (p<0.05) whilst no significant change in U-II expression occurred. ET-1 immunoreactivity was also increased in CLI with no difference in U-II immunostaining observed. ET(B) receptor binding was significantly increased in CLI (median 4, range 1-8 vs 2, range 1-3, dpm x 10(3)/mm(2), p=0.01, Mann-Whitney test) whilst ET(A) receptor binding was not significantly raised. Binding was associated with microvessels and macrophages.

CONCLUSIONS

in CLI, the ET-1 pathway is upregulated but U-II is unaffected. ET-1 may vasoconstrict microvessels and mediate inflammation in chronically ischaemic muscle. ET-1 binding to ET(B) receptors in particular may play an important role in the pathophysiology of CLI underscoring the therapeutic potential of ET(B) receptor antagonists in the management of CLI.