Plasma endothelin and pulmonary pressures in patients with congestive heart failure

Investigation of pulmonary artery and circulating endothelin-1 expression in dogs with pulmonary hypertension secondary to myxomatous mitral valve disease

Background and Aim

Pulmonary hypertension (PH) is a condition characterized by abnormally elevated pressure in the pulmonary vasculature. It is a common complication of myxomatous mitral valve disease (MMVD) in dogs. Several vasoactive substances, including endothelin-1 (ET-1), have been suggested to contribute to pathological changes in the pulmonary arteries of patients with PH. This study aimed to examine the local and systemic expression of ET-1 in dogs with PH secondary to MMVD.

Materials and Methods

Lung tissues were collected from 20 client-owned dogs during the first stage of the study and divided into three groups: normal dogs (n = 5), MMVD dogs (n = 8), and MMVD+PH dogs (n = 7). The expression of ET-1 and endothelin A receptor (ETAR) in the pulmonary arteries was determined using immunohistochemistry. Blood samples were collected from 61 client-owned dogs for the second stage of the study and divided into three groups: normal (n = 22), MMVD (n = 20), and MMVD+PH (n = 19). Plasma ET-1 concentration was measured using a sandwich enzyme-linked immunosorbent assay.

Results

There was no difference in ET-1 and ETAR expression in the pulmonary arteries among the three groups. Similarly, there was no difference in the plasma ET-1 concentration between the groups. In addition, no correlation was found between the immunohistochemical expression of ET-1 and ETAR and the thickness of the pulmonary arteries or between the plasma ET-1 level and echocardiographic variables.

Conclusion

The lack of difference in the expression of ET-1 and ETAR in the pulmonary arteries and in the circulating ET-1 concentration among the studied groups suggests that ET-1 may not be related to the pathological development of PH secondary to MMVD in dogs. Due to the small sample size in this study, further research is needed to confirm these findings.

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.

Neurohormonal activation in severe scorpion envenomation: correlation with hemodynamics and circulating toxin

We studied the effects of scorpion (Androctonus australis hector) venom on hemodynamics and on the release of catecholamines, neuropeptide Y (NPY), endothelin-1 (ET-1) and atrial natriuretic peptide (ANP) in dog model of severe scorpion envenomation. Nine mongrel anesthetized dogs were submitted to mechanical ventilation through intubation and were administered intravenously purified dried scorpion venom (Androctonus autstralis) 0.05 mg/kg. Measurements including pulmonary artery catheter derived parameters, serum toxin levels and humoral variables were performed at baseline (before venom injection) and 5, 15, 30 and 60 min after venom injection. Humoral variables included: serum lactate, epinephrine (EP), norepinephrine (NE), NPY, ET-1 and ANP plasma concentrations. Scorpion venom caused rapid and transient increase of mean arterial pressure (MAP) and PAOP associated with a marked and sustained decline in cardiac output (-55% at 60 min; P < 0.001). Hemodynamic changes were associated with a rapid and significant increase of all measured hormones. The highest increase was for NE (28-fold) and EP (25-fold). MAP was closely correlated with NE and less significantly correlated with toxin levels. Similarly, significant correlation was observed between PAPO and ANP plasma levels. These findings support the implication of excessive catecholamines release in hemodynamic disturbances of severe SE and suggest that NPY and ET-1 could be involved in this process. Serum toxin does not appear to consistently contribute to these effects. Through its correlation with PAOP, ANP could be a reliable and useful marker of cardiac dysfunction in SE.

Neurohormones as markers of right- and left-sided cardiac dimensions and function in patients with untreated chronic heart failure

BACKGROUND

It is now well accepted that neuroendocrine activation is of pathophysiological and prognostic importance in patients with chronic heart failure (CHF). We hypothesized that the different neuroendocrine factors reflect different aspects of the cardiac dysfunction in CHF patients and that neuroendocrine profiling could be of value. In order to study this, we investigated the relationship between hormones and cardiac dimensions and function of both the right and left ventricle.

METHODS

Twenty-three patients with newly diagnosed, untreated CHF were included. Right (RVEF) and left ventricular ejection fractions (LVEF) and volumes were measured by means of first-pass and equilibrium radionuclide ventriculography.

RESULTS

LVEF was 0.29 (range: 0.11-0.55). Two-thirds of the patients had dilated left ventricles with volumes above upper reference limit. Right ventricular ejection fraction was normal in all subjects as well as right ventricular volumes. Likewise, on average, the lung transit time (LTT) was normal. Brain natriuretic peptide (BNP) significantly correlated with LVEF, left ventricular end-diastolic volume index (LVEDVI) and left ventricular end-systolic volume index (LVESVI). Adrenaline correlated significantly with both right ventricular end-diastolic volume index and right ventricular end-systolic volume index. Lung transit time correlated with atrial natriuretic peptide (ANP) and BNP (only ANP in multivariate analysis).

CONCLUSIONS

(1) BNP reflects the LVEF as well as diastolic and systolic dimensions; (2) adrenaline reflects the right ventricular systolic and diastolic dimensions; and (3) ANP reflects the lung transit time. We conclude that "neuroendocrine profiling" may potentially be of diagnostic and therapeutic use.

Relationship between calcineurin inhibition and plasma endothelin concentrations in cyclosporine-A-treated kidney transplant patients

OBJECTIVE

The inter-individual variability of cyclosporine (CsA) pharmacokinetics is well known. However, there is obviously also an inter-individual pharmacodynamic variability, which might be explored by the measurement of biomarkers of CsA effects.

METHODS

In 11 renal transplant patients, blood CsA concentrations, calcineurin inhibition in peripheral blood mononuclear cells and endothelin plasma concentrations were measured over a 4-h period after CsA intake.

RESULTS

Mean plasma endothelin concentrations were higher than those of healthy subjects (3.66+/-0.46 pg ml(-1) versus 3.15+/-0.40 pg ml(-1), P<0.01) but were not related to CsA dose or blood concentrations. There was a linear relationship between calcineurin inhibition at t (0) and mean endothelin concentrations (r (2)=0.51, P<0.05). Patients with gingival hypertrophy had higher mean endothelin concentrations than patients without this complication (4.0 pg ml(-1) versus 3.4 pg ml(-1), P<0.01), although CsA doses and concentrations were not different between these two groups.

CONCLUSION

We observed a correlation between calcineurin inhibition and endothelin concentrations. Endothelin plasma concentrations is a biomarker of CsA effect, which may provide more information than CsA blood concentrations.

Endothelin upregulates the expression of vasopressin V2 mRNA in the inner medullary collecting duct of the rat

Recent studies in our laboratory have demonstrated that bosentan, a mixed endothelin ET(A)/ET(B) receptor antagonist, prevented the upregulation of the arginine vasopressin (AVP) V(2) receptor in the inner medullary collecting duct (IMCD) of cardiomyopathic hamsters. These results suggested that endothelin-1 (ET-1) is involved in the upregulation of AVP V(2) receptors. Studies were performed to detect the effect of ET-1 on the expression of AVP V(2) receptors and the ET receptor mediating these effects within the IMCD of the rat. Rat IMCD tissue was isolated and incubated with the following: ET-1, or ET-1 in combination with ET(A) and ET(B) receptor antagonists BQ-123 and BQ-788, respectively, and sarafotoxin c (S6c), an ET(B) receptor-specific agonist. Tissue samples were then analyzed using quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) and Western blotting. ET-1 treatment resulted in increased V(2) mRNA from a control level of 186.8 +/- 15.0 amol/microg total RNA to 430.7 +/- 49.0 amol/microg total RNA (P <.003). ET-1/ET(A) treatment resulted in no significant decrease in V(2) mRNA expression 335.0 +/- 38.0 amol/microg total RNA. Whereas ET-1/ET(B), and ET-1/ET(B)/ET(A) treatment resulted in V(2) mRNA approaching control 256.0 +/- 15.0 amol/microg total RNA, and 215.6 +/- 42.3 amol/microg total RNA. However, ET-3 treatment produced no significant changes in V(2) receptor mRNA expression. Sarafotoxin treatment corroborated both the ET-1 and ET receptor antagonist data, demonstrating striking significant increases in V(2) receptor mRNA and protein expression. S6c treatment increased V(2) mRNA expression from a control level of 199 +/- 17.3 amol/microg total RNA to 284.3 +/- 42.1 amol/microg total RNA (P < 05). Western blotting revealed that changes in V(2) mRNA expression in the various treatment conditions were similar to changes in protein expression. Overall, these data indicate that in the IMCD ET-1 increases AVP V(2) receptor expression and these changes are mediated by the ET(B) receptor.

Right and left ventricular cardiac function in a developed world population with human immunodeficiency virus studied with radionuclide ventriculography

BACKGROUND

Cardiac dysfunction has been reported in a substantial part of patients infected with the human immunodeficiency virus (HIV). However, most studies are from a time before the introduction of highly active antiretroviral treatment (HAART), which has significantly reduced HIV-associated morbidity and mortality rates. Accordingly, the prevalence of HIV-associated cardiac dysfunction may also have changed. The aim of the study was to establish the prevalence of right- and left-sided cardiac dysfunction in a Danish HIV population, most of whom were undergoing HAART, with radionuclide ventriculography.

METHODS

Ninety-five consecutive patients with HIV infection were included. Mean HIV duration was 104 months, and 84% of the patients received HAART. All patients underwent radionuclide ventriculography, and plasma levels of atrial natriuetic peptide (ANP), brain natriuetic peptide (BNP), and endothelin-1 (ET-1) were measured. Thirty age- and sex-matched healthy volunteer subjects were included to establish reference values of radionuclide measurements of left and right ventricular ejection fraction and of left ventricular volume.

RESULTS

Of 95 patients with HIV, 1 (1%) had a reduced left ventricular ejection fraction and 6 (7%) had a reduced right ventricle ejection fraction (0.35-0.42) compared with reference values from the age- and sex-matched reference population. Patients with HIV and reduced cardiac function did not differ in the duration of HIV, CD4 count, CD4 nadir, or HIV RNA load. No correlations were found between reduced cardiac function and levels of the 3 peptides measured.

CONCLUSIONS

No major dysfunction of the left ventricle is present in a developed world HIV population. However, a small but significant part of this population has modestly reduced right-sided systolic function.

Basal and exercise-induced neuroendocrine activation in patients with heart failure and in normal subjects

BACKGROUND

Neuroendocrine activation is a pathophysiological response and an important prognostic marker in patients with chronic heart failure (CHF). Although chronic activation is well described, data on the responsiveness of the hormone systems are more limited. Most previous studies have looked at activation during maximal exercise, whereas we believe that activation at a submaximal level might be more pathophysiologically relevant.

AIM

To compare exercise-induced neurohormonal activation between CHF patients and normal subjects using the same relative and submaximal workload.

SUBJECTS

Twenty-three newly-diagnosed CHF patients and 18 age- and gender-matched healthy subjects were exercised at two workloads, which were calculated to correspond to 50 and 75% of each individual's heart rate response.

RESULTS

In CHF patients, baseline levels of ANP, BNP, AVP, PRA and ET-1 were elevated compared to healthy subjects. Exercise induced an increase in ANP, A and NA in both CHF patients and in normal subjects, however BNP was only increased in CHF patients and not in normal subjects.

CONCLUSION

When CHF patients exercise at the same relative and submaximal level as age-matched healthy subjects, the relative increases in ANP, A and NA were similar, however, BNP levels only increased in the CHF group.

The endothelin system in pulmonary hypertension

Pulmonary hypertension (PH) may result from numerous clinical entities affecting the pulmonary circulation primarily or secondarily. It is recognized that vascular endothelial dysfunction contributes to the development and perpetuation of PH by creating an imbalance between vasodilating and antiproliferative forces and between vasoconstrictive and proliferative forces. In that context, endothelin-1 (ET-1) overproduction was rapidly targeted as a plausible contributor to the pathogenesis of PH. The lung is recognized as the major site for ET production and clearance. In all animal models of PH studied, circulating plasma ET-1 levels are elevated, accompanied by an increase in lung tissue expression of the peptide. The use of selective ETA and dual ETA-ETB receptor antagonists in these models both in prevention and in therapeutic studies have confirmed the contribution of ET-1 to the rise in pulmonary vascular tone, pulmonary medial hypertrophy, and right ventricular hypertrophy. This is found consistently in models affecting the pulmonary circulation primarily or producing PH secondarily. Recent clinical trials in patients with pulmonary arterial hypertension have confirmed the therapeutic effectiveness of ET-receptor antagonists in humans. We offer a systematic review of the pathogenic role of the ET system in the development of PH as well as the rationale behind the preclinical and ongoing clinical trials with this new class of agents.

Increased endothelin in infants of pre-eclamptic mothers

OBJECTIVE

Endothelin (ET), a vasoactive mediator, like others which originate from the endothelium or circulating cells, may participate in myocardial injury. In full-term neonates of mild pre-eclamptic mothers (NMPM), it identifies minor myocardial damage missed by other biochemical markers. The present study was designed to determine the diagnostic value of ET concentrations in NMPM.

METHODS

Seventeen NMPM were studied (10 boys and seven girls), and 17 healthy full-term (nine boys and eight girls) were selected for a control group. Birthweights in NMPM and control group were 2950 g (2.300-3.850) and 3.350 g (2.650-4.000), respectively. The ET measured by the radioimmunoassay method, Troponin T (TnT) were measured by enzyme-linked immunosorbent assay method and creatine kinase (CK-MB) determined in chemical 1 analysis.

RESULTS

Serum ET and TnT concentrations in NMPM (3.32 pg/mL vs 0.74 ng/mL) were significantly higher than the control group (0.82 pg/mL vs 0.10 ng/mL) (P < 0.01 and < 0.001).

CONCLUSION

Our study demonstrated high levels of ET, cardiac TnT in NMPM, presumably associated with myocardial damage in NMPM.

Heart failure and neuroendocrine activation: diagnostic, prognostic and therapeutic perspectives

The important neuroendocrine systems involved in heart failure are reviewed with special emphasis on their possible role in pathophysiology and their relation to prognostic and diagnostic information. Plasma levels of noradrenaline (NA), renin, vasopressin, endothelin-1, atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and tumour necrosis factor-alpha (TNF-alpha) are all elevated in heart failure. Activity of the sympathetic nervous system as reflected by NA is correlated to mortality and seems to possess independent prognostic information. Several studies have now documented the beneficial effect of beta-blockade in chronic heart failure (CHF). Renin seems to be a poor prognostic marker in CHF possibly because of the interference with diuretic treatment, angiotensin converting enzyme (ACE)-inhibitors and angiotensin II antagonist, and probably also because of the significance of tissue renin-angiotensin system (RAS), poorly reflected by plasma renin. On the other hand, several large-scale trials with ACE-inhibitors and angiotensin II antagonists have demonstrated reduced mortality and morbidity in CHF. Plasma vasopressin does not seem to possess prognostic information but testing of non-peptide antagonists is ongoing. Endothelin-1 seems to have independent prognostic information and endothelin receptor antagonists may represent a therapeutic possibility. The natriuretic peptides ANP and BNP are correlated to prognosis and possess independent information. Brain natriuretic peptide and N-terminal ANP seem to increase early, i.e. in asymptomatic heart failure. Plasma BNP being more stable than ANP is therefore a promising measure of left ventricular dysfunction. Increase in ANP and BNP, potentially beneficial, may be achieved by administration of neutral endopeptidase inhibitors, at present an unsettled therapeutic possibility. Several cytokines are increased in heart failure and especially TNF-alpha has drawn attention. Experimental studies suggest that TNF-alpha is important in the pathophysiology of heart failure and preliminary studies indicate that inhibition of TNF-alpha seems to be a possible therapeutic approach. Thus, neuroendocrine markers seem to (i) have a role in diagnosis and classification of heart failure, (ii) be useful in providing a 'neuroendocrine profile' which enlightens different aspects of heart failure, and therefore (iii) in the future probably will be valuable in the choice of medical treatment of the individual patient. In addition to beta-blockers, ACE-inhibitors and angiotensin II antagonists several new drugs based on neuroendocrine modification are on their way and might become important in the future.

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.

Enrasentan improves survival, limits left ventricular remodeling, and preserves myocardial performance in hypertensive cardiac hypertrophy and dysfunction

Evidence suggests that endothelin receptor antagonists may have therapeutic potential for the chronic treatment of heart failure. In the current study, the effects of an orally active mixed endothelin-A/endothelin-B (ETA /ETB ) receptor antagonist (enrasentan) were assessed in a model of cardiac hypertrophy and dysfunction (spontaneously hypertensive stroke prone rats) maintained on a high-salt/high-fat diet. Echocardiography was used to quantify cardiac performance and left ventricular dimensions. Enrasentan (1,200 and 2,400 parts per million in the high-salt/high-fat diet) had no significant effects on body weight and systolic blood pressure. However, increases in heart rate were not observed in the enrasentan-treated groups at 12 weeks (p < 0.05). Enrasentan-treated groups exhibited significantly improved survival (90-95% vs. 30% [control rats] at 18 weeks; p < 0.001). Enrasentan treatments also increased stroke volume (at 8, 12, and 16 weeks) and cardiac index (at 8 and 16 weeks) 33-50% and 45-63%, respectively. Enrasentan treatments reduced the relative wall thickness (14-27% at 8 and 12 weeks), ratio of left ventricular mass to body weight (20% at 12 weeks), and ratio of terminal heart weight to body weight (16-23%, p < 0.05). Finally, circulating aldosterone concentration (54-57%) and proANF fragment (33%) were reduced in enrasentan-treated groups (54-57% and 33%, respectively). Mixed ETA /ETB receptor antagonism improves cardiac performance and attenuates ventricular remodeling and premature mortality in an aggressive hypertension model.

The role of endothelins and their receptors in heart failure

Endothelin (ET) is a peptide composed of 21 amino acids, derived from a larger precursor, the big-endothelin, by action of the endothelin-converting enzyme (ECE) family; three isoforms of endothelin, named ET-1, ET-2 and ET-3, have been identified. Endothelin-1 is generated mainly by vascular endothelial cells and exerts various important biological actions, mediated by two receptor subtypes, ET-A and ET-B, belonging to the G protein-coupled family that have been identified in various human tissues such as the cardiac tissue. Endothelin-1 is a potent vasoconstrictive agent, has inotropic and mitogenic actions, modulates salt and water homeostasis and plays an important role in the maintenance of vascular tone and blood pressure in healthy subjects. Endothelin-1, as well as ET-A and ECE-1, also has an important role in cardiovascular development, as observed by the variety of abnormalities related to neural crest-derived tissues in mouse embryos deficient of a member of the ET-1/ECE-1/ET-A pathway. Various evidence indicates that endogenous endothelin-1 may contribute to the pathophysiology of conditions associated with sustained vasoconstriction, such as heart failure. In heart failure, elevated circulating levels of both endothelin-1 and big-endothelin-1 are observed; in failing hearts an activation of the endothelin system is found: tissue level of ET-1 is increased with respect to non-failing hearts as well as receptor density, due mainly to an upregulation of the ET-A subtype, the prevalent receptor subclass in cardiac tissue. Finally, studies in both humans and animal models of cardiovascular disease show that inhibition of the endothelin function (anti-endothelin strategy) is associated with an improvement of haemodynamic conditions; these observations indicate that endothelin receptor antagonists or endothelin-converting enzyme inhibitors may constitute a novel and potentially important class of agents for the treatment of this disease.

Temporal endothelin dynamics of the myocardial interstitium and systemic circulation in cardiopulmonary bypass

OBJECTIVE

Increased systemic levels of the bioactive peptide endothelin 1 during and after cardioplegic arrest and cardiopulmonary bypass have been well documented. However, endothelin 1 is synthesized locally, and therefore myocardial endothelin 1 production during and after cardiopulmonary bypass remains unknown.

METHODS

Pigs (n = 11) were instrumented for cardiopulmonary bypass, and cardioplegic arrest was initiated. Myocardial interstitial and systemic arterial levels of endothelin 1 were measured before cardiopulmonary bypass, throughout bypass and cardioplegic arrest (90 minutes), and up to 90 minutes after separation from bypass. Myocardial interstitial endothelin 1 was determined by microdialysis and radioimmunoassay.

RESULTS

Baseline myocardial endothelin 1 levels were higher than systemic endothelin 1 levels (25.6 +/- 6.7 vs 8.3 +/- 1.1 fmol/mL, P <.05). With the onset of bypass, myocardial endothelin 1 increased by 327% +/- 92% from baseline (P <.05), which preceded the increase in systemic endothelin 1 levels.

CONCLUSION

Myocardial compartmentalization of endothelin 1 exists in vivo. Cardiopulmonary bypass and cardioplegic arrest induce temporal differences in endothelin 1 levels within the myocardial interstitium and systemic circulation, which, in turn, may influence left ventricular function in the postbypass period.

Endothelin-1, endothelin receptors and ecNOS gene transcription in vital organs during traumatic shock in rats

Endothelin-1 (ET-1) is a vasoconstrictor peptide that may play an important role in the pathophysiology of severe trauma. We examined ET-1 gene expression in vital organs (i.e., heart, lungs, kidneys, liver and small intestine) during murine traumatic shock using ribonuclease protection assays. Our data show that ET-1 mRNA was significantly increased in the lungs two hours after trauma when compared with control anesthetized rats. There was also a significant increase in ET-1 transcripts occurring in the kidneys, heart and liver. During these experimental conditions, we also observed statistically significant increased endothelin type B (ET(B)) receptor mRNA expression in the lung, heart, liver, kidney and small intestine. Expression of endothelial constitutive nitric oxide synthase (ecNOS) gene, which is functionally coupled to ET(B) receptor, also was increased in vital organs during traumatic shock. Endothelin type A (ET(A)) receptor gene expression was slightly decreased in the lung, liver and small intestine. These results suggest that ET-1 and ET(B) mRNA expression are mainly increased in the lung and other vital organs and may play a functional role in the pathophysiology of murine traumatic shock.

Effect of cryopreservation on endothelin-1 productions of human mammary artery

The aim of this study was to determine the ability of human mammary artery cells to maintain a metabolic activity by measuring the artery concentration of two vasoactive substances, endothelin-1 (ET-1) and cyclic guanosyl monophosphate (cGMP), and a neurohumoral substance-neuropeptide Y (NPY)-prior to and following cryostorage. Ten distal segments of internal mammary arteries were obtained at the time of surgery in patients who had undergone coronary artery bypass grafting. One ring of each vessel served as a fresh control for the other ring that was used in cryopreservation experiments. The arteries were frozen with liquid nitrogen at a controlled rate down to -130 degrees C with an automatic freezing machine and were then stored in a liquid nitrogen vapor at -150 degrees C. After mammary artery extraction, ET-1, cGMP, and NPY concentrations were studied before and after cryopreservation. Cryopreserved, compared to fresh arteries, exhibited an increase in ET-1 (11.11+/-1.61 vs. 3. 09+/-0.06 pg/mg; p=0.004) and a decrease in cGMP (9.88+/-2.04 vs. 8. 55+/-2.07 p moles/mg; p<0.02), whereas there was no significant NPY variation. An increase in ET-1 and decrease in cGMP was found in 10 out of 10 and 6 out of 10 of cryopreserved artery specimen, respectively. There was no significant correlation between ET-1 and cGMP production in fresh or in cryopreserved arteries. The present method of cryostorage is effective in preserving "hormonal" mammary artery activity. However, the particularly high ET-1 concentration without associated cGMP concentration may be deleterious by increasing smooth-muscle cell proliferation and vascular tone of cryopreserved arteries.

Dilated cardiomyopathy: changing pathophysiological concepts and mechanisms of dysfunction

Experimental observations made over the past two decades have led to a profound shift in the conceptual paradigms about the syndrome of heart failure and dilated cardiomyopathy. As a consequence, heart failure is currently considered a complex disease and is not merely characterized by hemodynamic disturbances. It is now believed that the syndrome is governed and impelled by neurohormonal imbalances and intracardiac paracrine processes. The latter processes are mediated by activated cardiac endothelial cells and cytokines, creating a state of cardiac maladaption and leading to disease progression. Therapeutic interventions such as operative left ventricular volume reduction or mitral valve reconstruction should therefore no longer be solely interpreted in terms of hemodynamics (i.e., symptomatic improvements). Effects on neurohormonal, endothelial, and cytokine activities should be taken equally into account.

Reduced pulmonary metabolism of endothelin-1 in canine tachycardia-induced heart failure

OBJECTIVES

Plasma endothelin-1 (ET-1) increases in congestive heart failure (CHF). The pulmonary vascular bed could contribute to this increase through a reduced clearance. We evaluated the effect of tachycardia-induced CHF on pulmonary ET-1 kinetics. To discern between changes due to variations in pulmonary hemodynamics from true alterations of endothelial cell functions, we quantified ET-1 kinetics in isolated rat lungs under variable pressure and flow-rate conditions.

METHODS AND RESULTS

Indicator-dilution studies were performed in anesthetized dogs (n = 14) before and 3 weeks after rapid ventricular pacing and in isolated lungs from healthy rats (n = 4). In isolated lungs, graded increases in perfusion rate from 5-25 ml/min caused gradual reductions in ET-1 extraction from 60 +/- 1.5% to 17 +/- 4.9% (mean +/- S.D.). The capacity to clear ET-1 from the circulation, as computed from the permeability-surface area product (PS), however did not vary over this range of flows. CHF increased plasma ET-1 (11.2 +/- 11.4 vs. 5.2 +/- 1.6 fmol/ml, p < 0.01), did not affect pulmonary ET-1 extraction (29.4 +/- 12.5% vs. 29.9 +/- 12.9%), but decreased the PS (8.3 +/- 5.4 cm3/s vs. 14.4 +/- 9.9 cm3/s, p = 0.038). Contrary to the invariability of the PS in normal isolated rat lungs, CHF was associated with a positive relationship between the PS and pulmonary plasma flow (r = 0.65, p < 0.01). ET-1 binding studies in lung tissues showed no significant variations in ETA and ETB receptors densities but revealed a threefold decrease in binding affinity (p < 0.01) that may explain the reduced clearance.

CONCLUSION

CHF causes a reduction of pulmonary ET-1 clearance that likely contributes to the increased circulating ET-1 levels and reflects pulmonary metabolic dysfunction associated with this condition.

Humoral response in patients with chronic heart failure

AIM

Correlation of five humoral markers with laboratory, echocardiographic and right heart catheterization parameters in patients with chronic heart failure.

STUDY POPULATION

29 patients, heart failure NYHA II and III, ejection fraction below 40% with coronary artery disease or dilated cardiomyopathy.

METHODS

evaluation of thromboxane, prostaglandin F (PGF), tumor necrosis factor (TNF) alpha, endothelin-1 and big endothelin rest levels and their correlation with: (1) laboratory parameters: Sodium, urea, creatinine, fibrinogen, (2) chest X-ray: cardiothoracic index (CTI), pulmonary congestion, (3) right heart catheterization parameters at rest, hand-grip and bicycle ergometry: mean pulmonary artery pressure (AP), wedge pressure (WP), systemic and pulmonary vascular resistance (SVR, PVR) and cardiac index (CI), (4) echocardiographic parameters at rest, hand-grip and bicycle ergometry: end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), mitral flow E/A, filling period of left ventricle and time of duration of mitral regurgitation.

RESULTS

No correlation was found between thromboxane, prostaglandin F and tumor necrosis factor alpha with the above mentioned parameters. Endothelin-1 level correlated with E/A, PVR and MPA at rest and at hand-grip. Big endothelin level correlated with EDV and ESV, AP, WP and SVR at rest and at both types of exercise. The highest correlation was between big endothelin and rest AP (r=0.79), rest WP (r=0.78) and CTI (r=0.58), all P<0.01.

CONCLUSIONS

Big endothelin and partly endothelin-1 levels showed a close correlation with some parameters used for the evaluation of chronic heart failure severity.

Pulmonary and systemic responses to exogenous endothelin-1 in patients with left ventricular dysfunction

Plasma levels of immunoreactive endothelin-1 (ET-1) are elevated in chronic heart failure (CHF) and have been reported to correlate closely with pulmonary hemodynamic measurements. We investigated the effects of exogenous ET-1 on the pulmonary vasculature in patients with left ventricular systolic dysfunction (LVD), with or without overt heart failure. ET-1 was infused at 1, 5, and 15 pmol/min into a distal pulmonary artery of 10 patients with LVD. Hemodynamics were measured by a thermodilution catheter and arterial line. Intravascular Doppler and local pulmonary angiography were used to assess local pulmonary blood flow in the first four patients. Systemic hemodynamic changes occurred with ET-1 infusion in a dose-dependent fashion. Mean arterial pressure (100 +/- 8-107 +/- 11 mm Hg; p < 0.01) and systemic vascular resistance (1,699 +/- 375-2,033 +/- 427 dynes/s/cm-5; p < 0.001) rose, whereas the cardiac index fell from 2.43 +/- 0.53 to 2.20 +/- 0.491/min/m2 (p < 0.002). However, mean pulmonary artery pressure (21 +/- 7 mm Hg) and pulmonary vascular resistance (151 +/- 43-147 +/- 43 dynes/s/cm-5) did not change. Exogenous ET-1, when infused into patients with LVD, causes systemic but not pulmonary vasoconstriction.

Cellular localization of endothelin-1 and increased production in liver injury in the rat: potential for autocrine and paracrine effects on stellate cells

Endothelin (ET) peptides have been implicated in the pathogenesis of several biological processes within the liver. ET levels are elevated in the circulation of patients with cirrhosis, and recent data suggest that ET may be overproduced in the liver itself in this condition. The aims of the current study were to elucidate the cellular source and expression of endothelin-1 (ET-1) in normal and injured liver, and to investigate its biological effects on stellate cells, the primary target of ETs in the liver. In normal hepatic cells, preproET-1 messenger RNA (mRNA) was detected in only nonparenchymal cells, predominantly in sinusoidal endothelial cells. After biliary fibrosis and early cirrhosis induced by bile duct ligation, preproET-1 mRNA and immunoreactive ET levels increased with progressive injury in whole liver extracts, as well as in isolated stellate and endothelial cell fractions. Eight days after bile duct ligation, the relative increase in preproET-1 mRNA was 1.6- and 7.6-fold above normal in sinusoidal endothelial and stellate cells, respectively. Additionally, immunoreactive ET peptide levels increased by 60% +/- 27% over basal values in sinusoidal endothelial cells and 98% +/- 40% in stellate cells. Cultured stellate cells responded dramatically to exogenous ET-1 by the spreading and up-regulation of smooth muscle alpha actin expression. Furthermore, in early culture before cellular activation, ET-1 (10 nmol/L) caused over a twofold increase in [3H]thymidine incorporation, while activated cells (i.e., those cultured for >1 week) exposed to ET-1 exhibited up to a fivefold decrease in [3H]thymidine incorporation. The data indicate that not only is ET-1 overproduced by both sinusoidal endothelial and stellate cells during liver injury, but that it also has potent effects on features of stellate cell activation. We conclude that autocrine and paracrine production of ET-1 is prominent and is likely to be important in the pathogenesis of hepatic diseases.

Trophic effect of human pericardial fluid on adult cardiac myocytes. Differential role of fibroblast growth factor-2 and factors related to ventricular hypertrophy

Pericardial fluid (PF) may contain myocardial growth factors that exert paracrine actions on cardiac myocytes. The aims of this study were (1) to investigate the effects of human PF and serum, collected from patients undergoing cardiac surgery, on the growth of cultured adult rat cardiac myocytes and (2) to relate the growth activity of both fluids to the adaptive changes in overloaded human hearts. Both PF and serum increased the rate of protein synthesis, measured by [14C]phenylalanine incorporation in adult rat cardiomyocytes (PF, +71.9 +/- 8.2% [n = 17]; serum, +14.9 +/- 6.5% [n = 13]; both P < .01 versus control medium). The effects of both PF and serum on cardiomyocyte growth correlated positively with the respective left ventricular (LV) mass. However, the magnitude of change with PF was 3-fold greater than with serum (P < .01). These trophic effects of PF were mimicked by exogenous basic fibroblast growth factor (FGF2) and inhibited by anti-FGF2 antibodies and transforming growth factor-beta (TGF-beta), suggesting a relationship to FGF2. In addition, FGF2 concentration in PF was 20 times greater than in serum. On the other hand, the LV mass-dependent trophic effect, present in both fluids, was independent of FGF2 concentration or other factors, such as angiotensin II, atrial natriuretic factor, and TGF-beta. These data suggest that FGF2 in human PF is a major determining factor in normal myocyte growth, whereas unidentified LV mass-dependent factor(s), present in both PF and serum, participates in the development of ventricular hypertrophy.

Hypoxia stimulates human preproendothelin-1 promoter activity in transgenic mice

Significant elevations in endothelin (ET)-1 levels accompany many diseases, but the underlying regulatory mechanisms are unclear. To investigate the in vivo regulation of human preproendothelin-1 (PPET-1), we examined the activity of the PPET-1 promoter in transgenic mice exposed to hypoxia. Mice expressing one of three PPET-1 promoter-luciferase (PPET-1/LUC) reporter transgenes (approximately 2.5 kb, 138 bp, or none of the 5'-flanking sequences of the PPET-1 gene) were generated. LUC expression was reduced in mice with a truncated 138-bp PPET-1 promoter. Exposure of mice bearing the 2.5-kb PPET-1/LUC transgene to hypoxia (10% O2 for 24 h) increased LUC expression sixfold in pulmonary tissue but only twofold in other tissues. In situ hybridization revealed the strongest transgene expression in the pulmonary vasculature and bronchiolar epithelium. These data are consistent with the hypothesis that hypoxic induction of the PPET-1 gene leads to increased pulmonary production of ET-1 in diseases associated with low O2 tension.

Endothelin-1 in heart and pulmonary tissue in experimental heart failure

We studied the effect of congestive heart failure (CHF) on the tissue levels of endothelin 1 (ET-1) and of the mRNA of prepro-ET-1 in the rat. Congestive heart failure was produced by ligation of the left coronary artery. The rats were killed 3 weeks after the ligation. Congestive heart failure was determined by elevated plasma atrial natriuretic peptide and by a myocardial infarction scar covering more than 30% of the left ventricular circumference. Both ET-1 and prepro-ET-1 mRNA were measured in cardiac ventricles and lungs by radioimmunoassay and quantitative polymerase chain reaction. The rats with CHF had an increased heart weight/body weight ratio and elevated plasma atrial natriuretic peptide levels. In rats with CHF, as compared to controls, the concentration of ET-1 was elevated 3.6-fold in pulmonary tissue and 1.4-fold in the right ventricle, respectively, but not in the left ventricle. The concentration of mRNA showed a similar pattern, but due to methodological limitations this was assumed to represent a rough estimate only. The enhanced production of ET-1 in the right ventricle and in the pulmonary tissue may be of pathophysiological importance for the development of high pulmonary vascular resistance in CHF.

Molecular pharmacology and pathophysiological significance of endothelin

Since the discovery of the most potent vasoconstrictor peptide, endothelin, in 1988, explosive investigations have rapidly clarified much of the basic pharmacological, biochemical and molecular biological features of endothelin, including the presence and structure of isopeptides and their genes (endothelin-1, -2 and -3), regulation of gene expression, intracellular processing, specific endothelin converting enzyme (ECE), receptor subtypes (ETA and ETB), intracellular signal transduction following receptor activation, etc. ECE was recently cloned, and its structure was shown to be a single transmembrane protein with a short intracellular N-terminal and a long extracellular C-terminal that contains the catalytic domain and numerous N-glycosylation sites. In addition to acute contractile or secretory actions, endothelin has been shown to exert long-term proliferative actions on many cell types. In this case, intracellular signal transduction appears to converge to activation of mitogen-activated protein kinase. As a recent dramatic advance, a number of non-peptide and orally active receptor antagonists have been developed. They, as well as current peptide antagonists, markedly accelerated the pace of investigations into the true pathophysiological roles of endogenous endothelin-1 in mature animals; e.g., hypertension, pulmonary hypertension, acute renal failure, cerebral vasospasm, vascular thickening, cardiac hypertrophy, chronic heart failure, etc. Thus, the interference with the endothelin pathway by either ECE-inhibition or receptor blockade may provide an exciting prospect for the development of novel therapeutic drugs.

Pulmonary hypertension caused by congestive heart failure is ameliorated by long-term application of an endothelin receptor antagonist. Increased expression of endothelin-1 messenger ribonucleic acid and endothelin-1-like immunoreactivity in the lung in congestive heart failure in rats

OBJECTIVES

The purpose of this study was to investigate whether 1) endothelin-1, a potent vasoconstrictor peptide, is involved in progression of pulmonary hypertension caused by congestive heart failure (CHF); and 2) whether long-term treatment with BQ-123, an endothelin receptor antagonist, ameliorates pulmonary hypertension caused by CHF.

BACKGROUND

Congestive heart failure accompanies pulmonary hypertension, and the severity of pulmonary hypertension is an important determinant of prognosis. Although we reported that production of endothelin-1 is increased in the failing heart in rats with CHF, it is not known whether production of endothelin-1 in the lung is altered by CHF.

METHODS

Congestive heart failure was induced by coronary artery ligation in rats. Expression of preproendothelin-1 messenger ribonucleic acid (mRNA) in the lung and kidney was determined. Endothelin-1 staining (immunoreactivity) in the lung was studied by immunohistochemical analysis. Effects of long-term BQ-123 treatment on the rats were studied.

RESULTS

Two weeks postoperatively, CHF accompanied by pulmonary hypertension developed in the rats (CHF rats). Expression of preproendothelin-1 mRNA in the lung was markedly higher in the CHF rats than in the sham-operated rats, whereas that in the kidney did not differ between the two groups. Endothelin-1 staining on the pulmonary vascular endothelial cells was more intense in the CHF rats. BQ-123 treatment over a 2-week period in the CHF rats greatly reduced right ventricular systolic pressure and central venous pressure, but it did not affect blood pressure or left ventricular contractility (peak positive first derivative of left ventricular pressure) in these rats.

CONCLUSIONS

Long-term BQ-123 treatment greatly ameliorated pulmonary hypertension in the CHF rats. The present study suggests that endothelin-1 plays an important role in the progression of pulmonary hypertension caused by CHF and that an endothelin receptor antagonist may be a new therapeutic agent for CHF-induced pulmonary hypertension.

Vasodilator effects of endothelin-converting enzyme inhibition and endothelin ETA receptor blockade in chronic heart failure patients treated with ACE inhibitors

BACKGROUND

The importance of endothelin-1 in chronic heart failure (CHF) is unclear. We therefore investigated the effects of endothelin-converting enzyme (ECE) inhibition and endothelin ETA receptor blockade in CHF patients treated with ACE inhibitors. We also compared the function of ETA and ETB receptors in healthy subjects and patients with CHF.

METHODS AND RESULTS

Locally active doses of study drugs were infused into the nondominant brachial artery while forearm blood flow (FBF was measured by venous occlusion plethysmography. In CHF patients (n = 10), phosphoramidon (a combined ECE and neutral endopeptidase inhibitor) and BQ-123 (an ETA receptor antagonist) increased FBF by 52 +/- 10% (P = .0006) and 31 +/- 6% (P = .002), respectively, and thiorphan (a selective neutral endopeptidase inhibitor) reduced FBF by 15 +/- 5% (P = .0007). Forearm vasoconstriction to endothelin-1 (an ETA and ETB receptor agonist) was significantly blunted in CHF patients compared with control subjects (both n = 10; CHF versus control subjects, P < .001), whereas vasoconstriction to sarafotoxin S6c (an ETB receptor agonist) was significantly enhanced in CHF patients compared with control subjects (both n = 10; CHF versus control subjects. P < .05).

CONCLUSIONS

ECE inhibitors and ETA receptor antagonists may be useful as vasodilator agents in CHF patients already receiving treatment with an ACE inhibitor. Both ETA and ETB receptors can mediate agonist-induced vasoconstriction in healthy subjects and patients with CHF, but further studies are required to clarify the contribution of each receptor subtype in mediating the effects of endogenous endothelin-1.

Endothelin in congestive heart failure

The endothelin (ET) family of peptides have potent vascular, cardiac and renal actions which may be of pathophysiological importance in congestive heart failure (CHF). In vivo studies with selective and non-selective ET receptor antagonists are required to clarify the role of ET in the pathophysiology of CHF and determine whether anti-ET drugs may be therapeutically useful in CHF. The impact of angiotensin converting enzyme (ACE) inhibitors on the management of CHF has been such that for any new treatment to be of value it will probably have to offer hemodynamic benefit over and above that already obtained with an ACE inhibitor; anti-ET agents seem to have this potential. The recent formal cloning and characterization of endothelin converting enzyme (ECE) should hasten the development of specific and selective ECE inhibitors and thus provide an alternative investigative, and perhaps therapeutic, tool. Morbidity and mortality from CHF remain unacceptably high even in patients receiving maximal medical therapy, including an ACE inhibitor. Blockade of either the generation (through ECE inhibition) or actions (through receptor blockade) of ET warrant further investigation as potential new therapeutic strategies.