Circulatory and myocardial effects of endothelin

Acute cardiovascular effects of inhaled ambient particulate matter: Chemical composition-related oxidative stress, endothelin-1, blood pressure, and ST-segment changes in Wistar rats

Short-term increases in particulate matter (PM) are associated with heightened morbidity and mortality from cardiovascular causes. Inhalation of PM is known to increase endothelin (ET)-1 levels. Yet, less is known about particle composition-related changes at the molecular level including the endothelinergic system and relationship with cardiovascular function changes. In this work, adult Wistar male rats were exposed for 4 h by nose-only inhalation to clean air, Ottawa urban particles (EHC-93, 48 mg/m³) and water-leached (EHC-93L, 49 mg/m³) particles, to examine the effect of particle compositional changes on oxidative stress, circulating ETs, blood pressure, and heart electrophysiology. Particle deposition in the respiratory compartment was estimated at 85 μg (25 ng/cm²). Lung cell proliferation was low in both treatment groups, indicating absence of acute injury. Inhalation of EHC-93 caused statistically significant elevations (p < 0.05) of oxidative stress markers, ET-1, ET-3, blood pressure, and a decrease of ST-segment duration in the ECG at 1.5 days post-exposure. Leached particles (EHC-93L) caused rapid but transient elevation (p < 0.05) of oxidative stress, ET-1, ET-2, and ET-3 at earlier time points, with no changes in blood pressure or ST-segment. These results demonstrate that inhalation of urban particles at an internal dose inadequate to cause acute lung injury can induce oxidative stress, enhance vasoactive endothelins, leading to vasopressor response, affecting cardiac electrophysiology in Wistar rats, consistent with the cardiovascular impacts of ambient particles in human populations. Change in particle potency after removal of soluble species, notably cadmium, zinc and polar organics suggests that the toxicodynamics of cardiovascular effects can be modified by physicochemical properties of particles.

C-Terminal-Pro-Endothelin-1 Adds Incremental Prognostic Value for Risk Stratification After Ischemic Stroke

Background and Aims: Endothelins have shown to play a role in the pathophysiology of ischemic stroke. We aimed at evaluating the incremental prognostic value of C-terminal-pro-endothelin-1 (CT-pro-ET-1) in a well-described cohort of acute stroke patients. Methods: We performed serial measurements of CT-pro-ET-1 in 361 consecutively enrolled ischemic stroke patients and assessed functional outcome and mortality after 90 days. As we found peak levels of CT-pro-ET-1 and the most prominent association with mortality on day 1 after admission (n = 312), we focused on this time point for further outcome analyses. We calculated logistic regression and cox proportional hazards models to estimate the association of CT-pro-ET-1 with our outcome measures after adjusting for demographic and clinical risk factors. To evaluate the incremental value of CT-pro-ET-1, we calculated the area under the receiver operating characteristics (AUC) curve and the continuous net reclassification index (cNRI) comparing the model with and without the biomarker CT-pro-ET-1. Results: In the univariate analysis CT-pro-ET-1 with a peak on day 1 after admission was associated with unfavorable outcome with an OR of 1.32 (95% CI, 1.16-1.51, p < 0.001) and with mortality with a HR of 1.45 (95% CI, 1.29-1.63, p < 0.001). After adjusting, CT-pro-ET-1 remained an independent predictor of mortality with an adjusted HR of 1.50 (95% CI, 1.29-1.74, p < 0.001), but not for functional outcome. Adding CT-pro-ET-1 to the cox-regression model for mortality, the discriminatory accuracy improved from 0.89 (95% CI, 0.84-0.94) to 0.92 (95% CI, 0.88-0.96) p < 0.001, and the cNRI was 0.72 (95% CI, 0.17-1.13). Conclusion: CT-pro-ET-1 with a peak level on day 1 was an independent predictor of mortality adding incremental prognostic value beyond traditional risk factors.

Elevated level of plasma endothelin-1 in patients with atrial septal defect

Background

The study aimed to assess the level of plasma Endothelin-1 (ET-1) in patients before and after transcatheter closure of atrial septal defect (ASD) and to evaluate the usefulness of measuring ET-1 levels for the diagnosis and selection of candidates for ASD closure.

Methods

80 patients (55 F, 25 M), mean age 42,2 ± 11,5 years were enrolled for an attempt at ASD closure. A group of 19 healthy volunteers, (12 F, 7 M) mean age 39.2 ± 9.15 served as controls. All ASD patients underwent: clinical and echocardiographic study and cardiopulmonary exercise test. ET-1 levels were measured before and after closure. Whole blood was collected from femoral artery and vein and from pulmonary artery during cardiac catheterization.

Results

ET-1 levels at peripheral artery and vein in ASD patients were significantly higher than in the volunteers (p < 0.0001). The ASD subjects with highest ET-1 level presented the larger area of right ventricle and right atrium and higher pulmonary artery systolic pressure(p < 0.05). The ASD subjects with lower ET-1 level demonstrated longer time of exercise and higher peak oxygen consumption (p < 0.05). There was a decrease of ET-1 at peripheral artery (5.128 ± 8.8 vs. 2.22 ± 6.2; p < 0.001) and at peripheral vein (4.401 ± 3.33 vs. 2.05 ± 1.35; p < 0.001) within 48 hours after ASD closure, as compared to the baseline data. After 6 and 12 months farther drop in ET-1 level was observed.

Conclusions

1. The level of ET-1 in ASD patients is elevated in compare to healthy subject.

2. The significant reduction of ET-1 level is observed after percutaneous closure of ASD.

3. Elevated level of ET-1 in patients with ASD is associated with right heart enlargement.

4. Measurements of ET-1 may be a supplemental diagnostic tool and may be helpful in establishing indications for defect closure.

Role of endothelin-1 receptor blockers on hemodynamic parameters and oxidative stress

Endothelin (ET) was first isolated and described by Yanagisawa et al. and has since been described as one of the most potent known vasoconstrictor compounds. ET-1 mediates its effects via two types of receptors, ETA and ETB, which are expressed in the vascular smooth muscle cells, endothelial cells, intestines and brain. Secretion of ET-1 results in long-lasting vasoconstriction, increased blood pressure and, in turn, overproduction of free radicals. As dysregulation of the endothelin system is an important factor in the pathogenesis of several diseases including atherosclerosis, hypertension and endotoxic shock, the ETA and ETB receptors are attractive therapeutic targets for treatment of these disorders. The biosynthesis and release of ET-1 are regulated at the transcriptional level. Studies have shown that p38MAP kinase, nuclear factor kappaB (NF-kappaB), PKC/ERK and JNK/c-Jun all take part in the ROS-activated production of ET-1. Furthermore, administration of ET(A) significantly reduces the generation of free radicals. However, treatment with ETB receptor blockers does not elicit the same effect. Therefore, the effects of endothelin receptor blockers on blood pressure and the generation of free radicals remain debatable. This review summarizes recent investigations into the role of endothelin receptor blockers with respect to the modulation of hemodynamic parameters and the generation of free radicals.

Improved myocardial protection in the failing heart by selective endothelin-A receptor blockade

OBJECTIVE

Ischemia/reperfusion injury caused by cardioplegic arrest is still a major challenge in patients with reduced left ventricular function. We investigated the effect of chronic versus acute administration of the selective endothelin-A receptor antagonist (ERA) TBC-3214Na during ischemia/reperfusion in failing hearts.

METHODS

Male Sprague-Dawley rats underwent coronary ligation. Three days after myocardial infarction (MI), 19 randomly assigned animals (ERA chronic) were administered TBC-3214Na continuously with their drinking water, 29 MI rats received placebo, and 3 rats died during the observation period. Six weeks after infarction, hearts were evaluated in a blood-perfused working heart model during 60 minutes of ischemia and 30 minutes of reperfusion. In 14 MI rats, TBC-3214Na (ERA acute) was added to the cardioplegic solution during ischemia. Thirteen MI rats served as control.

RESULTS

At a similar infarct size, postischemic recovery of cardiac output (ERA chronic: 91% +/- 10%, ERA acute: 86% +/- 11% vs control: 52% +/- 15%; P < .05) and external heart work (ERA chronic: 90% +/- 10%, ERA acute: 85% +/- 13% vs control: 51% +/- 17%; P < .05) was significantly enhanced in both TBC-3214Na-treated groups whereas recovery of coronary flow was only improved in ERA acute rats (ERA acute: 121% +/- 23% vs ERA chronic: 75% +/- 13%; control: 64% +/- 15%; P < .05). Blood gas measurements showed enhanced myocardial oxygen delivery and consumption with acute TBC-3214Na therapy. Additionally, high-energy phosphates (phosphocreatine) were significantly higher and transmission electron microscopy revealed less ultrastructural damage under acute TBC-3214Na administration.

CONCLUSION

Acute endothelin-A receptor blockade is superior to chronic blockade in attenuating ischemia/reperfusion injury in failing hearts. Therefore, acute endothelin-A receptor blockade might be an interesting option for patients with heart failure undergoing cardiac surgery.

Dietary isoflavones in the prevention of cardiovascular disease--a molecular perspective

The Food and Drugs Administration has approved a health claim for soy based on clinical trials and epidemiological data indicating that high soy consumption is associated with a lower risk of coronary artery disease. Soy products contain a group of compounds called isoflavones, with genistein and daidzein being the most abundant. A number of cardioprotective benefits have been attributed to dietary isoflavones including a reduction in LDL cholesterol, an inhibition of pro-inflammatory cytokines, cell adhesion proteins and inducible nitric oxide production, potential reduction in the susceptibility of the LDL particle to oxidation, inhibition of platelet aggregation and an improvement in vascular reactivity. There is increasing interest in the use of nutrigenomic methods to understand the mechanisms by which isoflavones induce these changes, and in the use of nutrigenetics to understand why the effects vary between individuals. Nutrigenomics is a rapidly growing field making use of molecular biology methodologies, such as microarray technology and proteomics, to study how specific nutrients or diets affect gene expression and cellular protein levels. The analysis of differential gene expression and protein levels in endothelial cells, macrophages and smooth muscle cells is critical to elucidating the sequence of events leading to the formation of atherosclerotic lesions, and to understanding the potential anti-atherogenic properties of soy isoflavones. An increasing number of studies demonstrate a significant impact of genetic variation on changes in cardiovascular risk factors in response to dietary intervention. Nutrigenetic effects of this type have recently been reported for dietary isoflavones, and may help to explain some of the disparities in the current literature concerning isoflavones and cardiovascular health.

Blood pressure regulation by ETA and ETB receptors in conscious, telemetry-instrumented mice and role of ETA in hypertension produced by selective ETB blockade

The net contribution of endothelin type A (ET(A)) and type B (ET(B)) receptors in blood pressure regulation in humans and experimental animals, including the conscious mouse, remains undefined. Thus we assessed the role of ET(A) and ET(B) receptors in the control of basal blood pressure and also the role of ET(A) receptors in maintaining the hypertensive effects of systemic ET(B) blockade in telemetry-instrumented mice. Mean arterial pressure (MAP) and heart rate were recorded continuously from the carotid artery and daily (24 h) values determined. At baseline, MAP ranged from 99 +/- 1 to 101 +/- 1 mmHg and heart rate ranged between 547 +/- 15 and 567 +/- 19 beats/min (n = 6). Daily oral administration of the ET(B) selective antagonist A-192621 [10 mg/kg twice daily] increased MAP to 108 +/- 1 and 112 +/- 2 mmHg on days 1 and 5, respectively. Subsequent coadministration of the ET(A) selective antagonist atrasentan (5 mg/kg twice daily) in conjunction with A-192621 (10 mg/kg twice daily) decreased MAP to baseline values on day 6 (99 +/- 2 mmHg) and to below baseline on day 8 (89 +/- 3 mmHg). In a separate group of mice (n = 6) in which the treatment was reversed, systemic blockade of ET(B) receptors produced no hypertension in animals pretreated with atrasentan, underscoring the importance of ET(A) receptors to maintain the hypertension produced by ET(B) blockade. In a third group of mice (n = 10), ET(A) blockade alone (atrasentan; 5 mg/kg twice daily) produced an immediate and sustained decrease in MAP to values below baseline (baseline values = 101 +/- 2 to 103 +/- 2 mmHg; atrasentan decreased pressure to 95 +/- 2 mmHg). Thus these data suggest that ET(A) and ET(B) receptors play a physiologically relevant role in the regulation of basal blood pressure in normal, conscious mice. Furthermore, systemic ET(B) receptor blockade produces sustained hypertension in conscious telemetry-instrumented mice that is absent in mice pretreated with an ET(A) antagonist, suggesting that ET(A) receptors maintain the hypertension produced by ET(B) blockade.

Selective endothelin a (ETA) receptor antagonist (BQ-123) reduces both myocardial infarct size and oxidant injury

OBJECTIVE

Endothelins (ET) can be considered stress-responsive regulators working in paracrine and autocrine fashion. It has been suggested that elevated levels of ET may be responsible for the low coronary re-flow phenomena. Ischemia-reperfusion (I/R) was shown to stimulate ET release in rat heart; however, the mechanism(s) of this effect has not been clarified. Therefore, this study was focused to investigate the effect of BQ-123, selective ETA receptor antagonist, on three aspects of myocardial ischemia-reperfusion (MI/R) injury: hemodynamic parameters, infarct size and oxidant-antioxidant status in the absence and presence of ET-1 in an vivo rat model.

METHODS AND RESULTS

To produce MI/R, a branch of the descending left coronary artery was occluded for 30 min followed by 2h reperfusion. ECG changes, blood pressure (BP), and heart rate (HR) were measured before occlusion and continued both occlusion and reperfusion. Forty rats were randomly assigned to five groups equally: (1) sham-operated rats without coronary ligation, (2) I/R group, (3) I/R+BQ-123-treated group (10 microg/kg/min i.v.), (4) I/R+ET-treated group (25 ng/kg/min i.v.), (5) I/R+ET+BQ-123-treated group. The results are expressed as mean+/-S.E.M. In the ET-1 plus I/R group, the ratio between the infarcted area and area at risk 56+/-1% was significantly higher than I/R group (49+/-1%). In the BQ-123 group with or without exogenous ET-1 treatment in I/R group, this ratio was significantly lower at 40+/-2 and 37+/-1%, respectively. As compared to sham group, I/R increased lipid peroxidation whereas decreased nitric oxide (NO), glutathione (GSH), catalase (CAT) and superoxide dismutase (SOD) contents. This decreased antioxidant enzymatic defense could result in aggravated oxidative damage in I/R group rat hearts. ET-1 administration group showed severe oxidative damage. BQ-123 administrations to I/R group with or without ET-1 caused significantly decrease in lipid peroxidation and increased in SOD, CAT activities and NO generation and GSH content when compared with I/R group alone.

CONCLUSIONS

The most important finding of the present study is that the ET blockade reduced I/R-induced myocardial injury. The mechanism of this reduction was speculated to be a resistance to ischemic injury in the subcellular levels of the myocardium conferred by a reduction of vascular constriction and improvement of imbalance in the antioxidant status.

Genistein affects the expression of genes involved in blood pressure regulation and angiogenesis in primary human endothelial cells

BACKGROUND

Several lines of evidence suggest that the dietary isoflavone genistein (Gen) has beneficial effects with regard to cardiovascular disease and in particular on aspects related to blood pressure and angiogenesis. The biological action of Gen may be, at least in part, attributed to its ability to affect cell signalling and response. However, so far, most of the molecular mechanisms underlying the activity of Gen in the endothelium are unknown.

METHODS AND RESULTS

To examine the transcriptional response to 2.5 microM Gen on primary human endothelial cells (HUVEC), we applied cDNA array technology both under baseline condition and after treatment with the pro-atherogenic stimulus, copper-oxidized LDL. The alteration of the expression patterns of individual transcripts was substantiated using either RT-PCR or Northern blotting. Gen significantly affected the expression of genes encoding for proteins centrally involved in the vascular tone such as endothelin-converting enzyme-1, endothelin-2, estrogen related receptor alpha and atrial natriuretic peptide receptor A precursor. Furthermore, Gen countered the effect of oxLDL on mRNA levels encoding for vascular endothelial growth factor receptor 165, types 1 and 2.

CONCLUSIONS

Our data indicate that physiologically achievable levels of Gen change the expression of mRNA encoding for proteins involved in the control of blood pressure under baseline conditions and reduce the angiogenic response to oxLDL in the endothelium.

Myocardial function and effect of serum in isolated heart from hypertriglyceridemic and hypertensive rats

We evaluated the myocardial function of rats with sugar-induced hypertriglyceridemia (HTG) and hypertension, and the effect of serum on myocardial performance in the isolated heart preparation. Also, the response to reperfusion after 30 minutes of global ischemia was investigated. Hearts from HTG rats developed lower ventricular pressure (VP) and the conduction rate was higher than in hearts from control rats (CR). The recovery of VP after ischemia was significantly lower in HTG than in CR hearts (p < 0.05). The HTG sera produced a higher increase in the VP and in the perfusion pressure. During reperfusion, the incidence of premature beats, ventricular fibrillation and tachycardia in HTG hearts was increased so hypertriglyceridemia caused alterations in the mechanical and electrical conduction of the myocardium and exacerbated the injury produced by ischemia-reperfusion. Also a circulating factor in the HTG serum induced a vasoactive response of the heart which was reflected in its mechanical performance.

Endothelin: what does the radiologist need to know?

Endothelin (ET) is a potent endogenous vasoconstrictor peptide. It has been implicated in various pathological states since its discovery in 1988. The cardiovascular system and the kidneys are important sites for the action of this peptide. Two types of ET receptor, ETA and ETB, govern the biological effects of ET. Drugs that can prevent the endogenous synthesis of ET or block its binding to receptors may offer important therapeutic impact to patients with congestive heart failure, pulmonary hypertension and acute renal failure. Areas of particular interest to the radiologist include the role of ET in mediating some of the side effects of contrast media, particularly contrast medium nephropathy, and the involvement of ET in the pathogenesis of restenosis following angioplasty. This review outlines the basic biology of this important mediator and its role in health and disease.

Nonerythropoietic roles of erythropoietin in the fetus and neonate

Epo was once regarded as a cytokine with only hematopoietic effects. It is now clear that the distributions of Epo and Epo-R are more widespread in the developing human. Epo-R is widely distributed during early fetal development, leading to speculation that Epo acts in concert with other growth factors to optimize growth and development. Areas in which Epo has important recognized effects are on endothelial cells, and in the developing heart, gastrointestinal tract, and brain. It may also be important in the regulation of vascular growth during the menstrual cycle, and in the stimulation of testosterone production in men. Epo and Epo-R are prominent in the brain during fetal development, leading to speculation that they play an important role in neurodevelopment. There are also promising data regarding rEpo as a possible neuroprotective agent in such conditions as hypoxia, because it decreases programmed cell death induced during such adverse conditions. It is unlikely, however, that rEpo crosses the blood-brain barrier in normal premature infants, and it is not clear whether the CNS effects of rEpo, should it cross the blood-brain barrier, are harmful or beneficial in the setting of a developing brain.

Dilated and failing cardiomyopathy in bradykinin B(2) receptor knockout mice

BACKGROUND

The activation of B(2) receptors by kinins could exert cardioprotective effects in myocardial ischemia and heart failure.

METHODS AND RESULTS

To test whether the absence of bradykinin B(2) receptors may affect cardiac structure and function, we examined the developmental changes in blood pressure (BP), heart rate, and heart morphology of bradykinin B(2) receptor gene knockout (B(2)(-/-)), heterozygous (B(2)(+/-)), and wild-type (B(2)(+/+)) mice. The BP of B(2)(-/-) mice, which was still normal at 50 days of age, gradually increased, reaching a plateau at 6 months (136+/-3 versus 109+/-1 mm Hg in B(2)(+/+), P<0.01). In B(2)(+/-) mice, BP elevation was delayed. At 40 days, the heart rate was higher (P<0.01) in B(2)(-/-) and B(2)(+/-) than in B(2)(+/+) mice, whereas the left ventricular (LV) weight and chamber volume were similar among groups. Thereafter, the LV growth rate of B(2)(-/-) and B(2)(+/-) mice was accelerated, leading at 360 days to a LV weight-to-body weight ratio that was 9% and 17% higher, respectively, than that of B(2)(+/+) mice. In B(2)(-/-) mice, hypertrophy was associated with a marked chamber dilatation (42% larger than that of B(2)(+/+) mice), an elevation in LV end-diastolic pressure (25+/-3 versus 5+/-1 mm Hg in B(2)(+/+) mice, P<0.01), and reparative fibrosis.

CONCLUSIONS

The disruption of the bradykinin B(2) receptor leads to hypertension, LV remodeling, and functional impairment, implying that kinins are essential for the functional and structural preservation of the heart.

Contribution of the endothelin system to the renal hypoperfusion associated with experimental congestive heart failure

The objective of this study was to define further the local activation of endothelin-1 (ET-1) and the ETA receptor as well as the functional consequences of activated ET-1 for renal hypoperfusion associated with experimental congestive heart failure (CHF). We studied eight rabbits permanently instrumented with Doppler flow probes around the renal arteries before and after the induction of epinephrine-induced CHF. CHF was characterized by left-ventricular dysfunction (fractional shortening 34+/-2% vs. 46+/-3%; p < or = 0.05) and dilatation (LVEDd 13.6+/-0.3 vs. 11.5+/-0.4 mm; p < or = 0.05), decreased mean arterial pressure (59.4+/-2.9 vs. 74.6+/-3.7 mm Hg; p < or = 0.05), increased heart rate (236+/-11 vs. 216+/-8 beats/min; p < or = 0.05) and renal vasoconstriction (vascular resistance 49.65 +/-8.55 vs. 24.61+/-5.85 U; p < 0.05; blood flow velocity, 1.58+/-0.21 vs. 3.63+/-0.31 kHz; p < 0.05). ET-1 concentrations were significantly increased not only in plasma (7.67+/-0.47 vs. 4.56 +/-0.69 pg/ml; p < 0.05) but also in renal tissue (4.8+/-0.5 vs. 3.5 +/-0.64 pg/mg; p < 0.05). Northern analysis revealed an unchanged expression of ETA receptor messenger RNA (0.79+/-0.05 vs. 0.77+/-0.04 arbitrary units; NS) in renal tissue, whereas expression of prepro-ET-1 was below the range of detection. In CHF, selective ETA-receptor antagonism with BQ-123 (1 mg/ kg bolus, i.v.) significantly increased renal blood flow velocity (3.07+/-0.38 vs. 1.33+/-0.19 kHz; p < 0.05) and reduced renal vascular resistance (29.63+/-6.22 vs. 58.17+/-8.75 U; p < 0.05) without significant effects on mean arterial pressure or heart rate. These studies demonstrate activation of the renal ET system, unaltered gene expression, and functional integrity of the renal ETA receptor in CHF. They indicate a principal functional role for the ETA receptor in renal vasoconstriction and suggest blockade of the renal ETA receptor as an important strategy to attenuate renal hypoperfusion in CHF.