Plasma endothelin in congestive heart failure: a predictor of cardiac death?

Endothelin 1 Is Associated with Heart Failure Hospitalization and Long-Term Mortality in Patients with Heart Failure with Preserved Ejection Fraction and Pulmonary Hypertension

BACKGROUND

The prevalence of pulmonary hypertension (PH) in heart failure with preserved ejection fraction (HFpEF) is increasing. We aim to study the role of big endothelin 1 (Big ET1), endothelin 1 (ET1), and neprilysin (NE) in HFpEF with PH.

METHOD

This was a single center prospective cohort study including 90 HFpEF patients; 30 with no PH, 30 with postcapillary PH, and 30 with combined post- and precapillary PH. After enrollment, pulmonary venous and pulmonary arterial samples of Big ET1, ET1, and NE were collected during right heart catheterization. Subjects were then followed long term for adverse outcomes which included echocardiographic evidence of right ventricular dysfunction, heart failure hospitalization, and all-cause mortality.

RESULTS

Patients with HFpEF-PH were found to have increased ET1 in pulmonary veins (endothelin from the wedge; ET1W) compared to controls (2.3 ± 1.4 and 1.6 ± 0.9 pg/mL, respectively). ET1W levels were associated with both PH (OR 2.7, 95% CI 1.5-4.7, p = 0.01) and pulmonary vascular resistance (OR 1.6, 95% CI 1.04-2.3, p = 0.03). No evidence of right ventricular dysfunction was observed after 1 year of follow-up. ET1W (OR 1.8, 95% CI 1.2-2.6, p = 0.01) and ET1 gradient (ET1G; OR 1.4, 95% CI 1.04-2, p = 0.03) were predictive of 1-year hospitalization. ET1G ≥0.2 pg/mL was associated with long-term mortality (log-rank 4.8, p = 0.03).

CONCLUSION

In HFpEF patients, ET1W and ET1G are predictive of 1-year heart failure hospitalization, while elevated ET1G levels were found to be associated with long-term mortality in HFpEF. This study highlights the role of ET1 in developing PH in HFpEF patients and also explores the potential of ET1 as a prognostic biomarker.

Renal function, N-terminal Pro-B-Type natriuretic peptide, propeptide big-endothelin and patients with heart failure and preserved ejection fraction

Renal dysfunction may limit the clinical application of NT-proBNP in the diagnosis of heart failure. In general practice, where echocardiography is not readily available, a biomarker for the diagnosis of a heart failure with preserved ejection fraction (HFpEF) would be useful. Since cardiac diseases frequently coincide with renal disease, there is a high need of valid risk stratification methods in patients affected with both. We therefore examined NT-proBNP and another biomarker, Big-Endothelin-1, as a marker of HFpEF in patients with CKD. NT-proBNP and Big-ET-1 were determined in 439 patients with HFpEF in the Ludwigshafen Risk and Cardiovascular Health (LURIC) study. NT-proBNP plasma level has shown an exponential increase with declining GFR, while Big-ET-1 plasma level increased only in a moderate and linear fashion. In patients without CKD, a NT-proBNP cut-off point at 250 pg/mL was suitable for the discrimination between HFpEF and patients without HF. When the GFR was less than 60 mL/min/1.73m², the NT-proBNP cut-off point should be raised to 750 pg/mL. At a cutoff point at 0.85 fmol/L, Big-ET-1 allowed to distinguish patients with HFpEF from persons without HF, independently of GFR. In general, NT-proBNP is a good indicator of suspected heart failure. While for NT-proBNP different cut-off points have to be considered in the diagnosis of HFpEF, a single cut-off point of Big-ET-1 was appropriate in the diagnosis of HFpEF, regardless of the presence or absence of CKD. An additional measurement of Big-ET-1 improves the diagnosis of HFpEF in patients with chronic kidney disease.

Cardiovascular and inflammatory mechanisms in healthy humans exposed to air pollution in the vicinity of a steel mill

Background

There is a paucity of mechanistic information that is central to the understanding of the adverse health effects of source emission exposures. To identify source emission-related effects, blood and saliva samples from healthy volunteers who spent five days near a steel plant (Bayview site, with and without a mask that filtered many criteria pollutants) and at a well-removed College site were tested for oxidative stress, inflammation and endothelial dysfunction markers.

Methods

Biomarker analyses were done using multiplexed protein-array, HPLC-Fluorescence, EIA and ELISA methods. Mixed effects models were used to test for associations between exposure, biological markers and physiological outcomes. Heat map with hierarchical clustering and Ingenuity Pathway Analysis (IPA) were used for mechanistic analyses.

Results

Mean CO, SO₂ and ultrafine particles (UFP) levels on the day of biological sampling were higher at the Bayview site compared to College site. Bayview site exposures “without” mask were associated with increased (p < 0.05) pro-inflammatory cytokines (e.g IL-4, IL-6) and endothelins (ETs) compared to College site. Plasma IL-1β, IL-2 were increased (p < 0.05) after Bayview site “without” compared to “with” mask exposures. Interquartile range (IQR) increases in CO, UFP and SO₂ were associated with increased (p < 0.05) plasma pro-inflammatory cytokines (e.g. IL-6, IL-8) and ET-1_(1–21) levels. Plasma/saliva BET-1 levels were positively associated (p < 0.05) with increased systolic BP. C-reactive protein (CRP) was positively associated (p < 0.05) with increased heart rate. Protein network analyses exhibited activation of distinct inflammatory mechanisms after “with” and “without” mask exposures at the Bayview site relative to College site exposures.

Conclusions

These findings suggest that air pollutants in the proximity of steel mill site can influence inflammatory and vascular mechanisms. Use of mask and multiple biomarker data can be valuable in gaining insight into source emission-related health impacts.

Electronic supplementary material

The online version of this article (10.1186/s12989-018-0270-4) contains supplementary material, which is available to authorized users.

Plasma endothelin-1-related peptides as the prognostic biomarkers for heart failure: A PRISMA-compliant meta-analysis

BACKGROUND

Most studies reported that high plasma endothelin-1 (ET-1), big ET-1, and C-terminal proET-1 (CT-proET-1) were correlated with poor prognosis of heart failure (HF). However, available evidence remains controversial. To help solve the debate, we collected all the available studies and performed a meta-analysis.

METHODS

We searched the databases covering Embase, PubMed, Ovid, and Web of Science on June 28, 2017. The hazard ratio (HR) or risk ratio (RR) and its 95% confidence intervals (CIs) were collected and calculated by use of a random-effect model. Heterogeneity was assessed by Cochran's Q test, and publication bias was assessed by funnel plots with Egger's and Begg's linear regression test.

RESULTS

Thirty-two studies with 18,497 patients were included in the analysis. Results showed that circulating ET-1, big ET-1, and CT-proET-1 were positively correlated with high risk of adverse outcomes, with pooled RRs (95% CIs) of 2.22 (1.82-2.71, P < .001), 2.47 (1.93-3.17, P < .001), and 2.27 (1.57-3.29, P < .001), respectively. In the subgroup of death as primary outcome, the pooled RRs (95% CIs) were 2.13 (1.68-2.70, P < .001), 2.55 (1.82-3.57, P < .001), and 2.02 (1.39-2.92, P < .001) for ET-1, big ET-1, and CT-proET-1, respectively. No significant publication bias was observed in this study.

CONCLUSION

Our meta-analysis provided evidence that increased plasma levels of ET-1, big ET-1, and CT-proET-1 were associated with poor prognosis or mortality for HF populations.

Nitrative stress, oxidative stress and plasma endothelin levels after inhalation of particulate matter and ozone

BACKGROUND

While exposure to ambient air contaminants is clearly associated with adverse health outcomes, disentangling mechanisms of pollutant interactions remains a challenge.

OBJECTIVES

We aimed at characterizing free radical pathways and the endothelinergic system in rats after inhalation of urban particulate matter, ozone, and a combination of particles plus ozone to gain insight into pollutant-specific toxicity mechanisms and any effect modification due to air pollutant mixtures.

METHODS

Fischer 344 rats were exposed for 4 h to a 3 × 3 concentration matrix of ozone (0, 0.4, 0.8 ppm) and EHC-93 particles (0, 5, 50 mg/m(3)). Bronchoalveolar lavage fluid (BALF), BAL cells, blood and plasma were analysed for biomarkers of effects immediately and 24 h post-exposure.

RESULTS

Inhalation of ozone increased (p < 0.05) lipid oxidation products in BAL cells immediately post-exposure, and increased (p < 0.05) total protein, neutrophils and mature macrophages in the BALF 24 h post-exposure. Ozone increased (p < 0.05) the formation of reactive oxygen species (ROS), assessed by m-, p-, o-tyrosines in BALF (Ozone main effects, p < 0.05), while formation of reactive nitrogen species (RNS), indicated by 3-nitrotyrosine, correlated with dose of urban particles (EHC-93 main effects or EHC-93 × Ozone interactions, p < 0.05). Carboxyhemoglobin levels in blood exhibited particle exposure-related increase (p < 0.05) 24 h post recovery. Plasma 3-nitrotyrosine and o-tyrosine were increased (p < 0.05) after inhalation of particles; the effect on 3-nitrotyrosine was abrogated after exposure to ozone plus particles (EHC-93 × Ozone, p < 0.05). Big endothelin-1 (BET-1) and ET-1 were increased in plasma after inhalation of particles or ozone alone, but the effects appeared to be attenuated by co-exposure to contaminants (EHC-93 × Ozone, p < 0.05). Plasma ET levels were positively correlated (p < 0.05) with BALF m- and o-tyrosine levels.

CONCLUSIONS

Pollutant-specific changes can be amplified or abrogated following multi-pollutant exposures. Oxidative and nitrative stress in the lung compartment may contribute to secondary extra-pulmonary ROS/RNS formation. Nitrative stress and endothelinergic imbalance emerge as potential key pathways of air pollutant health effects, notably of ambient particulate matter.

Nitrative stress, oxidative stress and plasma endothelin levels after inhalation of particulate matter and ozone

Background

While exposure to ambient air contaminants is clearly associated with adverse health outcomes, disentangling mechanisms of pollutant interactions remains a challenge.

Objectives

We aimed at characterizing free radical pathways and the endothelinergic system in rats after inhalation of urban particulate matter, ozone, and a combination of particles plus ozone to gain insight into pollutant-specific toxicity mechanisms and any effect modification due to air pollutant mixtures.

Methods

Fischer 344 rats were exposed for 4 h to a 3 × 3 concentration matrix of ozone (0, 0.4, 0.8 ppm) and EHC-93 particles (0, 5, 50 mg/m³). Bronchoalveolar lavage fluid (BALF), BAL cells, blood and plasma were analysed for biomarkers of effects immediately and 24 h post-exposure.

Results

Inhalation of ozone increased (p < 0.05) lipid oxidation products in BAL cells immediately post-exposure, and increased (p < 0.05) total protein, neutrophils and mature macrophages in the BALF 24 h post-exposure. Ozone increased (p < 0.05) the formation of reactive oxygen species (ROS), assessed by m-, p-, o-tyrosines in BALF (Ozone main effects, p < 0.05), while formation of reactive nitrogen species (RNS), indicated by 3-nitrotyrosine, correlated with dose of urban particles (EHC-93 main effects or EHC-93 × Ozone interactions, p < 0.05). Carboxyhemoglobin levels in blood exhibited particle exposure-related increase (p < 0.05) 24 h post recovery. Plasma 3-nitrotyrosine and o-tyrosine were increased (p < 0.05) after inhalation of particles; the effect on 3-nitrotyrosine was abrogated after exposure to ozone plus particles (EHC-93 × Ozone, p < 0.05). Big endothelin-1 (BET-1) and ET-1 were increased in plasma after inhalation of particles or ozone alone, but the effects appeared to be attenuated by co-exposure to contaminants (EHC-93 × Ozone, p < 0.05). Plasma ET levels were positively correlated (p < 0.05) with BALF m- and o-tyrosine levels.

Conclusions

Pollutant-specific changes can be amplified or abrogated following multi-pollutant exposures. Oxidative and nitrative stress in the lung compartment may contribute to secondary extra-pulmonary ROS/RNS formation. Nitrative stress and endothelinergic imbalance emerge as potential key pathways of air pollutant health effects, notably of ambient particulate matter.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-015-0103-7) contains supplementary material, which is available to authorized users.

Correlation between Saliva and Plasma Levels of Endothelin Isoforms ET-1, ET-2, and ET-3

Although saliva endothelins are emerging as valuable noninvasive cardiovascular biomarkers, reports on the relationship between isoforms in saliva and plasma remain scarce. We measured endothelins in concurrent saliva and plasma samples (n = 30 males; age 18–63) by HPLC-fluorescence. Results revealed statistically significant positive correlations among all isoforms between saliva and plasma: big endothelin-1 (BET-1, 0.55 ± 0.27 versus 3.35 ± 1.28 pmol/mL; r = 0.38, p = 0.041), endothelin-1 (ET-1, 0.52 ± 0.21 versus 3.45 ± 1.28 pmol/mL; r = 0.53, p = 0.003), endothelin-2 (ET-2, 0.21 ± 0.07 versus 1.63 ± 0.66 pmol/mL; r = 0.51, p = 0.004), and endothelin-3 (ET-3, 0.39 ± 0.19 versus 2.32 ± 1.44 pmol/mL; r = 0.75, p < 0.001). Correlations of BET-1, ET-1, and ET-3 within each compartment were positive in both plasma (p < 0.05) and saliva (p ≤ 0.1), whereas ET-2 was not significantly correlated with other isoforms in either plasma or saliva. For all isoforms, concentrations varied on average fivefold between individuals (90th/10th percentiles); individuals with high plasma endothelin levels generally had high saliva endothelin levels. Our results reveal that salivary ET isoform profiles portray the plasmatic profiles and support the view of coordinated regulation of ET-1 and ET-3, but distinct regulatory pathways for ET-2.

Toxicogenomic analysis of susceptibility to inhaled urban particulate matter in mice with chronic lung inflammation

Background

Individuals with chronic lung disease are at increased risk of adverse health effects from airborne particulate matter. Characterization of underlying pollutant-phenotype interactions may require comprehensive strategies. Here, a toxicogenomic approach was used to investigate how inflammation modifies the pulmonary response to urban particulate matter.

Results

Transgenic mice with constitutive pulmonary overexpression of tumour necrosis factor (TNF)-α under the control of the surfactant protein C promoter and wildtype littermates (C57BL/6 background) were exposed by inhalation for 4 h to particulate matter (0 or 42 mg/m³ EHC-6802) and euthanized 0 or 24 h post-exposure. The low alveolar dose of particles (16 μg) did not provoke an inflammatory response in the lungs of wildtype mice, nor exacerbate the chronic inflammation in TNF animals. Real-time PCR confirmed particle-dependent increases of CYP1A1 (30–100%), endothelin-1 (20–40%), and metallothionein-II (20–40%) mRNA in wildtype and TNF mice (p < 0.05), validating delivery of a biologically-effective dose. Despite detection of striking genotype-related differences, including activation of immune and inflammatory pathways consistent with the TNF-induced pathology, and time-related effects attributable to stress from nose-only exposure, microarray analysis failed to identify effects of the inhaled particles. Remarkably, the presence of chronic inflammation did not measurably amplify the transcriptional response to particulate matter.

Conclusion

Our data support the hypothesis that health effects of acute exposure to urban particles are dominated by activation of specific physiological response cascades rather than widespread changes in gene expression.

Cytokines and myocardial dysfunction: state of the art

BACKGROUND

Myocardial dysfunction has been associated with inflammation and cytokine modulation.

OBJECTIVES

The study objective was to understand the role of cytokines in the pathophysiology and management of myocardial dysfunction.

METHODS

Heart failure has been revisited with revision of the pertinent published articles in the Medline, Scopus, Cochrane Database of Systematic Reviews, and EBSCO Host research.

RESULTS

For the proinflammatory cytokines, illumination of this important point requires further diagnostic and therapeutic investigations. Data on chronic heart failure are not so reassuring; therefore, patients with advanced heart failure should not be treated with anticytokines at this time.

CONCLUSION

Further studies are warranted to pave the way for introducing cytokine and immunomodulation therapy at the optimal and appropriate time.

Endothelin receptor antagonists

Endothelin receptor antagonists (ERAs) have been developed to block the effects of endothelin-1 (ET-1) in a variety of cardiovascular conditions. ET-1 is a powerful vasoconstrictor with mitogenic or co-mitogenic properties, which acts through the stimulation of 2 subtypes of receptors [endothelin receptor subtype A (ETA) and endothelin receptor subtype B (ETB) receptors]. Endogenous ET-1 is involved in a variety of conditions including systemic and pulmonary hypertension (PH), congestive heart failure (CHF), vascular remodeling (restenosis, atherosclerosis), renal failure, cancer, and cerebrovascular disease. The first dual ETA/ETB receptor blocker, bosentan, has already been approved by the Food and Drug Administration for the treatment of pulmonary arterial hypertension (PAH). Trials of endothelin receptor antagonists in heart failure have been completed with mixed results so far. Studies are ongoing on the effects of selective ETA antagonists or dual ETA/ETB antagonists in lung fibrosis, cancer, and subarachnoid hemorrhage. While non-peptidic ET-1 receptor antagonists suitable for oral intake with excellent bioavailability have become available, proven efficacy is limited to pulmonary hypertension, but it is possible that these agents might find a place in the treatment of several cardiovascular and non-cardiovascular diseases in the coming future.

Differential regulation of the lung endothelin system by urban particulate matter and ozone

Periodic elevation of ambient particulate matter and ozone levels is linked to acute cardiac morbidity and mortality. Increased plasma levels of the potent vasoconstrictor endothelin (ET)-1, a prognostic indicator of cardiac mortality, have been detected in both animal models and humans after exposure to air pollutants. The lungs are the primary source of circulating ET-1, but the direct effects of individual air pollutants and their interaction in modulating the pulmonary endothelin system are unknown. Fischer-344 rats were exposed to particles (0, 5, 50 mg/m3 EHC-93), ozone (0, 0.4, 0.8 ppm), or combinations of particles and ozone for 4 h. Changes in gene expression were measured using real-time reverse transcription polymerase chain reaction immediately after exposure and following 24 h recovery in clean air. Both pollutants individually increased preproET-1, endothelin converting enzyme-1, and endothelial nitric oxide synthase mRNA levels in the lungs shortly after exposure, consistent with the concomitant increase in plasma of the 21 amino acid ET-1[1-21] peptide measured by HPLC-fluorescence. PreproET-1 mRNA remained elevated 24 h after exposure to particles but not after ozone, in line with previously documented changes of the peptide in plasma. Both pollutants transiently increased endothelin-B receptor mRNA expression, while ozone decreased endothelin-A receptor mRNA levels. Coexposure to particles plus ozone increased lung preproET-1 mRNA but not plasma ET-1[1-21], suggesting alternative processing or degradation of endothelins. This coincided with an increase in the lungs of matrix metalloproteinase-2 (MMP-2), an enzyme that cleaves bigET-1 to ET-1[1-32]. Taken together, our data indicate that ozone and particulate matter independently regulate the expression of lung endothelin system genes, but show complex toxicological interaction with respect to plasma ET-1.

Potential role of ultrafine particles in associations between airborne particle mass and cardiovascular health

Numerous epidemiologic time-series studies have shown generally consistent associations of cardiovascular hospital admissions and mortality with outdoor air pollution, particularly mass concentrations of particulate matter (PM) < or = 2.5 or < or = 10 microm in diameter (PM2.5, PM10). Panel studies with repeated measures have supported the time-series results showing associations between PM and risk of cardiac ischemia and arrhythmias, increased blood pressure, decreased heart rate variability, and increased circulating markers of inflammation and thrombosis. The causal components driving the PM associations remain to be identified. Epidemiologic data using pollutant gases and particle characteristics such as particle number concentration and elemental carbon have provided indirect evidence that products of fossil fuel combustion are important. Ultrafine particles < 0.1 microm (UFPs) dominate particle number concentrations and surface area and are therefore capable of carrying large concentrations of adsorbed or condensed toxic air pollutants. It is likely that redox-active components in UFPs from fossil fuel combustion reach cardiovascular target sites. High UFP exposures may lead to systemic inflammation through oxidative stress responses to reactive oxygen species and thereby promote the progression of atherosclerosis and precipitate acute cardiovascular responses ranging from increased blood pressure to myocardial infarction. The next steps in epidemiologic research are to identify more clearly the putative PM casual components and size fractions linked to their sources. To advance this, we discuss in a companion article (Sioutas C, Delfino RJ, Singh M. 2005. Environ Health Perspect 113:947-955) the need for and methods of UFP exposure assessment.

Air pollutants increase gene expression of the vasoconstrictor endothelin-1 in the lungs

Inhalation of urban pollutants elevates the circulating levels of the vasoactive peptides endothelin (ET)-1 and ET-3 in rats. This effect could explain the association between episodic variations of urban pollutants and acute cardiopulmonary morbidity and mortality documented in epidemiological studies. Because the lungs are the primary source of circulating ET-1 and the main site of clearance from circulation, we investigated the response of endothelin system genes in the lungs of Fischer-344 rats after 4-h nose-only inhalation of 0.8 ppm ozone plus 49 mg/m(3) EHC-93 (Ottawa particles). The mRNA levels for preproET-1, preproET-3, endothelin-converting enzyme (ECE)-1, and ET receptor subtypes A and B were determined at 2 h, and 1, 2, 3, 7, and 14 days after exposure. The pollutants induced preproET-1 and ECE-1 (P<0.05) after 2 h, consistent with the notion of increased synthesis and conversion of the peptide ET-1 in lung endothelial cells. PreproET-3 mRNA was down-regulated at 2 h post-exposure (P<0.05), and returned to control levels by 24 h, indicating that induction of ET-3 in the lungs is not responsible for the sustained elevation of ET-3 in plasma reported after inhalation of pollutants. Our results indicate that lung endothelin system genes respond rapidly and transiently to inhalation of urban pollutants, consistent with the dynamics of urban pollutant health effects in the human population.

Drug therapy in chronic heart failure

Chronic heart failure is widely recognised as a common and escalating problem that causes major disability and often shortens life. Diuretics and digoxin have formed the mainstay of treatment for many years. Clinical trials have demonstrated that angiotensin converting enzymes and beta-blockers, in selected patients, improve symptoms and reduce mortality. Angiotensin-II antagonists and spironolactone may also have a role in certain individuals. Newer pharmacological approaches to the management of this complex disease are being developed, but await full evaluation.

Endothelin A Receptor Antagonism in Experimental Congestive Heart Failure Results in Augmentation of the Renin-Angiotensin System and Sustained Sodium Retention

Background— While both the endothelin-1 (ET-1) and renin-angiotensin systems (RAS) are activated in congestive heart failure (CHF), the temporal sequence of this activation remains unclear. Understanding this pattern of neurohumoral activation may aid in understanding the significance of ET-1 in CHF and provide strategies for ET-1 antagonism. Although acute endothelin (ET) receptor antagonism improves systemic hemodynamics in CHF, clinical trials with chronic ET receptor antagonism report worsening CHF symptoms.

Methods and Results— In a canine model of progressive left ventricular dysfunction, we demonstrated activation of myocardial and plasma ET-1 without activation of the RAS during transition to overt CHF, suggesting that ET-1 contributes to this transition. We next evaluated the effects of chronic oral ET-A receptor antagonism on neurohumoral function, renal hemodynamics, and sodium excretion in pacing-induced CHF. After 7 days of treatment (n=7) with ET-A receptor antagonism (with LU135252), sodium excretion did not improve in treated versus untreated CHF (n=6). Furthermore, both plasma renin activity and plasma ET-1 increased with ET-A receptor blockade.

Conclusions— Activation of the myocardial and plasma ET-1 systems precedes activation of the myocardial and plasma RAS in CHF. ET-A receptor antagonism in experimental CHF further activates the RAS without improving sodium excretion. These findings suggest an important role for ET-1 in the progression of CHF and a potential mechanism for the exacerbation of CHF symptoms observed in clinical trials with chronic ET receptor antagonism. Further studies with combined modulation of the ET and other neurohumoral systems in CHF are required.

Comparative Sequences of Canine and Feline Endothelin-1

BACKGROUND

Endothelin-1 (ET-1, "mature ET-1") is a potent vasoconstrictor peptide that is made along with "big ET-1" from its precursor, preproET-1. Increased plasma concentrations of ET-1 and big ET-1 occur with various forms of cardiovascular disease in humans. Our laboratory is investigating plasma endothelins as diagnostic tests of cardiovascular disease in dogs and cats; however, commercial immunoassays designed specifically for use in dogs and cats are limited.

OBJECTIVE

Amino acid sequences of feline and canine big ET-1 were obtained and used to predict antibody cross-reactivity with immunoassay test kits from other species.

METHODS

Genomic DNA was extracted from peripheral blood and total RNA was extracted from canine and feline left ventricles for reverse transcription polymerase chain reaction (PCR) and PCR amplification of segments of the canine and feline preprohormone containing the big ET-1 sequences. The derived amino acid sequences were compared with known big ET-1 and ET-1 sequences of several other species, including human, mouse, and rat.

RESULTS

Feline and canine big ET-1 had 87-97% and 89-100% homology, respectively, with that of other mammalian species. Canine ET-1 was identical to human, mouse, and rat ET-1. In contrast, the amino acid sequence of feline ET-1 was unique owing to a leucine for methionine substitution at position 7.

CONCLUSIONS

It is highly likely that anti-human and anti-rodent ET-1 antibodies will cross-react with mature canine ET-1. In contrast, antibodies to mature ET-1 intended for use with feline tissues and antibodies to big ET-1 in either dogs or cats may have partial or no cross-reactivity depending on the peptide sequences used to produce the antibodies.

Role of endothelins in congestive heart failure

Despite major advances in conventional medical therapy, patients with heart failure continue to experience significant morbidity and mortality. Endothelin-1 (ET-1) is a potent vasocontrictor and mitogenic peptide that is activated in heart failure. There is increasing experimental and clinical evidence in support of an important role of ET-1 in the pathophysiology of heart failure. Manipulation of the activity of ET-1, especially using endothelin receptor blockers, has allowed for the further elucidation of the role of this neurohormonal system and development of novel therapeutic strategies in heart failure. Published clinical studies of these agents to date have involved relatively small numbers of patients with severe heart failure, followed for a relatively short period of time, and have mainly examined surrogate endpoints. Large-scale trials that address to hard clinical outcomes are ongoing and their results forthcoming. A key question that remains concerns whether selective ETA or dual ETA-ETB receptor blockade will be more effective.

Associations between ambient air pollution and daily mortality among persons with congestive heart failure

We conducted a mortality time series study to investigate the association between daily mortality for congestive heart failure (CHF), and daily concentrations of particles and gaseous pollutants in the ambient air of Montreal, Quebec, during the period 1984-1993. In addition, using data from the universal Quebec Health Insurance Plan, we identified individuals >/=65 years of age who, one year before death, had a diagnosis of CHF. Fixed-site air pollution monitors in Montreal provided daily mean levels of pollutants. We regressed the logarithm of daily counts of mortality on the daily mean levels of each pollutant, after accounting for seasonal and subseasonal fluctuations in the mortality time series, non-Poisson dispersion, weather variables, and other gaseous and particle pollutants. Using cause of death information, we did not find any associations between daily mortality for CHF and any air pollutants. The analyses of CHF defined from the medical record showed positive associations with coefficient of haze, the extinction coefficient, SO(2), and NO(2). For example, the mean percent increase in daily mortality for an increase in the coefficient of haze across the interquartile range was 4.32% (95% CI: 0.95-7.80%) and for NO(2) it was 4.08% (95% CI: 0.59-7.68%). These effects were generally higher in the warm season.

Diagnostic and therapeutic potential of the endothelin system in patients with chronic heart failure

There is now considerable evidence to support a role for the endothelin (ET) system in the pathogenesis and progression of chronic heart failure (CHF). As such, the potential exists for this system to be useful in both diagnosis (by measurement of peptide levels in plasma and other body fluids) and treatment (by pharmacological blockade) of this condition. Plasma levels of endothelin-1 (ET-1) are elevated in CHF and the magnitude of elevation correlates with disease severity. ET-1 levels in plasma predict subsequent mortality in patients with CHF. ET-1 may also contribute to symptoms associated with CHF, such as exercise intolerance. In the diagnosis of CHF, plasma levels of ET-1 appear to be a less powerful discriminator between patients with mild disease and control subjects with normal ventricular function on multivariate analyses, compared to brain natriuretic peptide (BNP), or its N-terminal fragment. ET-1 concentrations are also elevated in the saliva of patients with CHF and may represent an alternative approach to assessment of the status of the ET system in these patients. Specific ET receptor antagonists (both mixed and ET(A)-selective) have been developed. Studies with these agents in animal models of CHF have demonstrated beneficial effects via both haemodynamic and non-haemodynamic pathways. A number of short-term clinical studies have been performed demonstrating improvements in haemodynamic parameters without neurohormonal activation. Long-term clinical studies with ET receptor antagonists are currently underway to definitively test the impact of blockade of this system on mortality and major cardiovascular endpoints. Endothelin converting enzyme (ECE) inhibitors represent an alternative strategy of ET blockade, and early data from animal models suggest these agents may be of clinical utility, either alone or, more likely, in combination with other zinc metallopeptidases.

Basic and therapeutic relevance of endothelin-mediated regulation

Three endothelin family peptides (endothelin-1, -2 and -3) exert an extremely potent and long-lasting vasoconstrictor action as well as other various actions through stimulating two subtypes of receptor (ETA and ETB). Vascular endothelial cells produce only endothelin-1. Although the pharmacological actions of exogenous endothelin-1 have been extensively analyzed, the physiological roles of endogenous endothelin-1 have long been obscure. Using potent and selective receptor antagonists, endothelin-1 has been demonstrated to contribute slightly to the maintenance of regional vascular tone. In gene-targeted mice, endothelin family peptides and their receptors have been shown to play an important role in the embryonic development of neural crest-derived tissues. In addition to its potent vasoconstrictor action, endothelin-1 has direct mitogenic actions on cardiovascular tissues, as well as co-mitogenic actions with a wide variety of growth factors and vasoactive substances. Endothelin-1 also promotes the synthesis and secretion of various substances including extracellular constituents. These effects of endogenous endothelin-1 would appear to be naturally concerned with the development and/or aggravation of chronic cardiovascular diseases, e.g. hypertension, pulmonary hypertension, vascular remodeling (restenosis, atherosclerosis), renal failure, and heart failure. A great many non-peptide and orally active endothelin receptor antagonists have been developed, and shown to exert excellent therapeutic effects in animal models as well as human patients with these diseases.

Endothelin receptor antagonists and cardiovascular diseases of aging

Our understanding of the role of the endothelin system in human cardiovascular physiology and pathophysiology has evolved very rapidly since the initial description of its constituent parts in 1988. Endothelin-1 (ET-1) is the predominant endothelin isoform in the human cardiovascular system and has potent vasoconstrictor, mitogenic and antinatriuretic properties which have implicated it in the pathophysiology of a number of cardiovascular diseases. The effects of ET-1 have been shown to be mediated by 2 principal endothelin receptor subtypes: ET(A) and ET(B). The development of a range of peptidic and nonpeptidic endothelin receptor antagonists represents an exciting breakthrough in human cardiovascular therapeutics. Two main classes of endothelin receptor antagonist have been developed for possible human therapeutic use: ET(A)-selective and nonselective antagonists. Extensive laboratory and clinical research with these agents has highlighted their promise in various cardiovascular diseases. Randomised, placebo-controlled clinical trials have yielded very encouraging results in patients with hypertension and chronic heart failure with more preliminary data suggesting a possible role in the treatment and prevention of atherosclerosis and stroke. Much more research is needed, however, before endothelin receptor antagonists can be considered for clinical use.

The kidney in congestive heart failure: renal adverse event rate of treatment

In this paper we review the effect of medical treatment on renal function in patients with congestive heart failure. We have examined data from the large-scale heart failure studies with angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, calcium channel blockers, beta-receptor blockers, an aldosterone antagonist, and a vasopeptidase inhibitor. Renal outcome was reported in almost all of the studies with angiotensin-converting enzyme inhibitors. Despite concern about renal adverse events with drugs in this class, they seem to be safe in patients with congestive heart failure. In contrast, we did not find any report about renal function in patients treated with beta-receptor blockers for congestive heart failure.

Plasma endothelin levels and outcome in patients undergoing repair of ruptured infrarenal abdominal aortic aneurysm

BACKGROUND

Endothelin-1 (ET-1) is the most potent known vasoconstrictor. Elevated plasma levels have been demonstrated in patients with myocardial infarction, cardiogenic and septic shock, and respiratory, heart, and kidney failure, as well as in those undergoing elective abdominal aortic aneurysm (AAA) repair. However, endothelin levels have not previously been examined in patients undergoing repair of ruptured AAA. We hypothesized that hemorrhagic shock, lower torso ischemia, and reperfusion associated with ruptured AAA repair lead to increased synthesis and secretion of ET-1, which, in turn, predispose to organ failure, one of the principal causes of death in this condition.

METHODS

Fourteen patients were studied. Plasma levels of big ET-1 and ET-1 were measured immediately before operation and immediately before, 5 minutes, and 6 hours after aortic clamp release.

RESULTS

All patients survived for at least 24 hours after operation. Big ET-1 levels were above the normal range at one or more sample points in all patients, and the ET-1 levels were above the normal range in all survivors and four of five nonsurvivors. Five patients who died of organ failure had significantly lower big ET-1 levels at all sample points and significantly lower ET-1 levels after 5 minutes of reperfusion when compared with survivors. Preoperative ET-1 levels were significantly lower in eight patients who subsequently developed kidney failure than in six patients who did not.

CONCLUSION

Contrary to our original hypothesis, these novel data demonstrate that patients with ruptured AAA in whom fatal postoperative organ failure develops have significantly lower perioperative endothelin levels than survivors.

Direct comparison between endothelin-1, N-terminal proatrial natriuretic factor, and brain natriuretic peptide as prognostic markers of survival in congestive heart failure

BACKGROUND

Endothelin-1 (ET-1) and cardiac natriuretic peptide plasma concentrations have prognostic significance in congestive heart failure (CHF). However, their respective prognostic values in this setting have never been directly compared.

METHODS AND RESULTS

We studied the prognostic performances of ET-1, N-terminal proatrial natriuretic factor (N-proANF), and brain natriuretic peptide (BNP) to predict the long-term cardiac mortality in fully treated patients with CHF. Peripheral plasma concentrations of the 3 peptides were measured in 109 patients (left ventricular ejection fraction [LVEF] < 35%) in New York Heart Association (NYHA) functional classes II (n = 65) or III to IV (n = 44). The outcome of the patients was evaluated 3 years after the beginning of the study, and a Cox regression model was used to identify predictors of death. Plasma concentrations of the 3 peptides increased with the severity of heart failure. By univariate analysis, 6 parameters were significantly associated with death during follow-up: ET-1 level, NYHA classes III to IV, N-proANF level, BNP level, LVEF, and age (all P < .01). By multivariate analysis, only ET-1 level and, to a lesser extent, N-proANF level contributed significantly and independently to risk stratification (chi2 = 53.4 and 12.8; P < .0001 and P < .001, respectively).

CONCLUSION

In a group of patients in whom the vast majority were administered angiotensin-converting enzyme inhibitor therapy, plasma ET-1 and N-proANF concentrations identify better than several clinical markers a very high-risk group, fairly amenable to heart transplantation or new therapies.

Insights into pathogenesis and treatment of cytokines in cardiomyopathy

Our understanding of the pathophysiology of chronic heart failure is rapidly expanding. recent investigations suggest a role for various proinflammatory and vasoconstrictive cytokines in the development and progression of the disease. In particular, tumor necrosis factor-alpha, interlukin-6, and endothelin have all been implicated in heart failure desease progression. These cytokines appear to be activated in response to a remodeling, induction of programmed cell death, neurohormonal activation, and hemodynamics, these agents cause a variety of deleterious effects in the setting of ventricular dysfunction. Investigational inhibitors and antagonists of these substances show promise for the future treatment of heart failure.

Minoxidil and male-pattern alopecia: a potential role for a local regulator of sebum secretion with vasoconstrictive effects?

Regulation of the hair cycle takes place at the pilo-sebaceous unit with the sebaceous gland as a sex hormone-dependent part. Although minoxidil stimulates proliferation of follicular cells and activation of prostaglandin endoperoxide synthase-1, it was suggested that other mechanisms, such as an increase in the local blood flow, might mediate the drug effect on hair growth. If that is the case, it is possible that minoxidil counteracts some vasoconstrictive mediator of male-pattern alopecia. This hypothetical vasoconstrictive mediator X would have to meet some criteria: (I) vasoconstriction both in the general circulation and in the hair-growing skin; (II) local vasoconstrictive activity in the hair growing skin should be related to the circulating testosterone level; (III) only an increase in the local mediator X activity causes male-pattern alopecia, since hypertensive patients are not balder than expected. The sebaceous gland is a possible place of the mediator X secretion since it is a sex-hormone-dependent part of the pilo-sebaceous unit. ET-1 might be a suitable candidate for the mediator X, since male hormones raise ET-1 plasma levels and female hormones lower them. The speculation presented here is that ET-1, beside vasoconstriction in the general circulation, might also regulate the sebum secretion, by triggering contractions of the myoepithelial cells. This hypothetical mechanism would normally remain confined to the sebaceous gland. During puberty, sex hormones stimulate growth of sebaceous glands in both sexes. In women hypertrophied sebaceous glands under estrogen control would not increase its ET-1 content, while in men, testosterone would increase ET-1 secretion that might affect the neighboring arterioles. Induced vasoconstriction might reduce the hair growth and promote hair loss. If ET-1 plays the described role, then an ET-1 antagonist, i.e. bosentane, should also have some hair-growing properties.

Endothelin in heart failure

Congestive heart failure is a complex disease that results from pumping failure of the cardiac muscle and adaptational processes of the cardiovascular system to correct for the reduced blood supply to the organism. It is associated with increased vasoconstriction and impaired vasodilation in response to physical activity. The elevated vasoconstrictor tone is caused by the activation of compensatory mechanisms including the sympathetic nervous system and stimulation of the release of neurohormones like angiotensin II, catecholamines, and vasopressin. Furthermore, the vascular endothelium is importantly involved in the regulation of vascular tone as it releases a variety of vasoactive substances that act locally and systemically. In congestive heart failure, there is a marked imbalance between the diminished release or the increased inactivation of vasodilators on the one hand, ie, nitric oxide, and the elevated production, release, or reduced inactivation of vasoconstrictors such as endothelin-1 on the other hand. In addition to its very potent vasoconstrictor effects, endothelin-1 possesses antinatriuretic and mitogenic properties that are a common feature of substances that are involved in development of the deleterious consequences that render congestive heart failure a lethal disease. The spectrum of action of the endothelin system and the advent of specific antagonists for its receptors have made this system a very interesting target for clinical research and possibly for future therapeutic approaches.

Chronic oral endothelin type A receptor antagonism in experimental heart failure

Endothelin-1 (ET-1) is a cardiovascular peptide that binds to two distinct receptors, ET(A) and ET(B), resulting in systemic and regional vasoconstriction, alteration in sodium excretion, mitogenesis, and release of other vasoactive peptides such as atrial natriuretic peptide (ANP). A role for ET-1 has been proposed in congestive heart failure (CHF) based on the increase in circulating ET-1 in this cardiovascular disease state. The present study determined the cardiorenal and endocrine responses to chronic selective oral ETA antagonism in experimental CHF. Two groups of conscious dogs underwent 21 days of pacing-induced CHF. These groups included a control untreated group (n = 6) and a group that received an orally active ET(A) receptor antagonist (A-127722, Abbott Pharmaceuticals, 5 mg/kg PO bid, n = 6). Each group was studied at baseline before the onset of CHF and after 14 and 21 days of CHF. Compared with the CHF control group, the ET(A) receptor antagonism group at 14 days of CHF showed lower mean arterial pressure and systemic vascular resistance. Similarly, ET(A) receptor antagonism markedly attenuated the increase in circulating ANP despite similar atrial pressures. At 21 days of CHF, ET(A) receptor antagonism lowered pulmonary artery pressure, pulmonary vascular resistance, and systemic vascular resistance in association with a higher cardiac output. Plasma ANP remained suppressed. Despite the lower mean arterial pressure and circulating ANP in the ET(A) receptor antagonist group, the absolute decrease in sodium excretion from baseline was less compared with the untreated CHF control group. The present investigation supports the conclusion that endogenous ET-1 participates in the systemic and pulmonary vasoconstriction, the elevation of ANP, and the sodium retention that characterize this model of experimental CHF, suggesting a potential therapeutic role for ET(A) receptor antagonism in CHF.