Tezosentan in the Treatment of Acute Heart Failure

Nutraceuticals in the Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe disease characterized by the loss and obstructive remodeling of the pulmonary arterial wall, causing a rise in pulmonary arterial pressure and pulmonary vascular resistance, which is responsible for right heart failure, functional decline, and death. Although many drugs are available for the treatment of this condition, it continues to be life-threatening, and its long-term treatment is expensive. On the other hand, many natural compounds present in food have beneficial effects on several cardiovascular conditions. Several studies have explored many of the potential beneficial effects of natural plant products on PAH. However, the mechanisms by which natural products, such as nutraceuticals, exert protective and therapeutic effects on PAH are not fully understood. In this review, we analyze the current knowledge on nutraceuticals and their potential use in the protection and treatment of PAH, as well as whether nutraceuticals could enhance the effects of drugs used in PAH through similar mechanisms.

Pharmacological Potential of Endothelin Receptors Agonists and Antagonists

Endothelins are potent predominantly vasoconstricting agents that act as local autocrine and paracrine mediators. Endothelin-1 is the most potent and sustained vasoconstrictor and pressor substance yet identified. Abnormalities of the endothelin system occur in a range of diseases associated with vasoconstriction, vasospasm, and vascular hypertrophy. ET receptor antagonists were until recently regarded as drugs of great promise in patients with congestive heart failure, pulmonary hypertension and others. The aim of this article is a survey of compounds that affect the endothelin receptors and clinical trials with these agents.

Cardiopulmonary bypass is associated with altered vascular reactivity of isolated pulmonary artery in a porcine model: therapeutic potential of inhaled tezosentan

OBJECTIVE

Whereas it is established that endothelin-1 elicits sustained deleterious effects on the cardiovascular system during cardiopulmonary bypass (CPB), presently it remains unknown whether the inhaled administration of the dual ETA and ETB antagonist tezosentan prevents the development of pulmonary endothelial dysfunction.

DESIGN

A prospective, randomized laboratory investigation.

SETTING

University research laboratory.

PARTICIPANTS

Landrace swine.

INTERVENTIONS

Three groups of animals underwent a 90-minute period of full bypass followed by a 60-minute period of reperfusion. Among treated groups, one received tezosentan through inhalation prior to CPB, whereas the other one received it intravenously at weaning from CPB; the third group remained untreated. Pulmonary vascular reactivity studies, realized on a total of 285 rings, were performed in all groups, including 1 sham.

MEASUREMENTS AND MAIN RESULTS

The contractility of pulmonary arteries to prostaglandin F2α and to the thromboxane A2 mimetic U46619 was preserved in animals submitted to CPB. By contrast, there were significant increases both in the maximal contraction to endothelin-1 and in the plasma levels of the peptide 60 minutes after reperfusion. Tezosentan administered by inhalation or intravenously did not prevent the development of pulmonary CPB-associated endothelial dysfunction. However, while hemodynamic disturbances were improved with both routes, the inhaled administration had a beneficial effect on oxygen parameters over intravenous administration.

CONCLUSIONS

Despite the blockade of the endothelin-1 pathway with tezosentan, the development of the pulmonary endothelial dysfunction associated with CPB still occurred. However, only the inhalation route had a significant impact on gas exchange during CPB.

Effect of intra-abdominal pressure on hepatic microcirculation: implications of the endothelin-1 receptor

OBJECTIVE

To investigate the effect of endothelin receptor A (ET(A)) and endothelin receptor B (ET(B)) blockade on liver microcirculation and oxygenation during intra-abdominal pressure (IAP) increase.

METHODS

Fifteen anesthetized pigs were randomized to receive either nonselective endothelin-1 (ET-1) blocker tezosentan (TG, n = 7) or saline (CG, n = 8). Helium was insufflated to increase IAP from 0 to 25 mmHg. Stroke volume variability was maintained ≤ 12% with colloid infusion. Total liver blood flow (TLBF), hepatic microcirculatory blood flow (MBF), hepatic tissue oxygenation (HpO(2)), hyaluronic acid and plasma disappearance rate (PDR) of indocyanine green (ICG) were recorded.

RESULTS

TLBF remained mostly unaltered in both groups at low IAP and decreased only in CG at the IAP of 25 mmHg. As IAP increased, a significant decline in MBF was observed without correlation with cardiac output or TLBF. In CG, HpO(2) decreased as early as IAP of 10 mmHg to high levels of pressure. However, in TG the decrease was significant only at the IAP of 25 mmHg. PDR of ICG decreased in both groups at IAP of 25 mmHg (P = 0.046 and P = 0.009 in TG and CG, respectively). These changes correlated with MBF (r = 0.793).

CONCLUSION

Blocking ET(A) and ET(B) receptors partially protects sinusoidal circulation and tissue oxygenation against stress induced by high IAP.

Right ventricular failure complicating heart failure: pathophysiology, significance, and management strategies

Right heart failure most commonly results from the complication of left heart failure (systolic or nonsystolic dysfunction) or pulmonary hypertension. Over the past decade, greater attention has been paid to the role of right ventricular failure in the morbidity and mortality associated with cardiomyopathy and pulmonary hypertension. The right ventricle is distinct from the left ventricle not only in its spatial localization, but also in its response to increased afterload and signaling mechanisms. This article discusses the role of right ventricular failure in the setting of heart failure as well as the clinical diagnosis and management of right ventricular failure.

Comparison of the pharmacokinetics, pharmacodynamics and tolerability of tezosentan between caucasian and Japanese subjects

AIM

To investigate the pharmacokinetics, pharmacodynamics and tolerability of the dual endothelin receptor antagonist tezosentan in caucasian and Japanese subjects.

METHODS

Twelve subjects of each ethnic origin were treated in a double-blind, randomized design with sequential 3-h infusions of 2.5, 5.0, 12.5 and 25 mg h(-1), or placebo. Vital signs, ECG and adverse events were recorded and blood samples collected for determination of plasma concentrations of tezosentan and endothelin-1 (ET-1).

RESULTS

Tezosentan was well tolerated in both ethnic groups with no clinically significant differences in laboratory measurements, ECG parameters and vital signs. The plasma concentration-time profiles of tezosentan were described by a three-compartment model with half-lives of approximately 5 min, 41 min and 3.6 h. Mean clearance and volume of distribution were approximately 35 l h(-1) and 20 l, respectively. Differences in the means (95% confidence intervals) between ethnic groups in these two parameters were 6.0 l h(-1) (-1.3, 13.3) and 4.3 l (-1.3, 9.9), respectively. Baseline ET-1 concentrations were similar but increases in response to tezosentan were greater in caucasian than in Japanese subjects. An indirect response model described the relationship between tezosentan and ET-1 plasma concentrations. The mean concentrations inhibiting 50% of ET-1 clearance (IC(50)) in caucasian and Japanese subjects were 243 and 227 ng ml(-1), respectively, with a difference in the means of 28.6 ng ml(-1) (-52.7, 110).

CONCLUSIONS

The data in healthy subjects suggest that caucasian and Japanese patients can be treated with a similar dosing regimen of tezosentan.

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.

Optimizing outcomes in the patient with acute decompensated heart failure

Heart failure (HF) and episodes of acute decompensated HF (ADHF) continue to pose a substantial clinical challenge in the United States and represent a significant source of morbidity, mortality, and health care resource use. Recent therapeutic advances have shifted ADHF treatment paradigms from diuretic management with or without inotrope use to therapy where intravenous vasodilators are the central component, above a background of diuretics. This shift in treatment has resulted in more rapid symptomatic improvements as well as in decreases in overall morbidity and mortality. Elevated left ventricular filling pressure has become an important clinical target for resolution during ADHF, as this parameter most closely correlates with degree of symptoms, extent of ischemic complications, and the deleterious neurohormonal activation in response to ADHF. Therapies that lead to rapid improvements in left ventricular filling pressure, including the use of nesiritide, a recombinant analog of B-type natriuretic peptide, have been shown to provide rapid symptomatic relief, but effects on long-term morbidity and mortality are as yet unclear. In addition to new treatments, new technologies--including assays based on cardiac biomarkers and techniques such as impedance cardiography for noninvasive monitoring of hemodynamic parameters--are contributing to improvements in care that will ultimately reduce the sizeable clinical and economic burden that HF represents.

Tezosentan in the Management of Decompensated Heart Failure

Decompensated heart failure continues to significantly impact the economics of our healthcare system. In recent years, the focus on management of decompensated heart failure has changed from solely improving hemodynamics to modifying neurohormones. Endothelin (ET) is one of the important mediators in heart failure. This article reviews the clinical pharmacology, clinical efficacy, and tolerability of tezosentan, a dual-action ET-1 receptor antagonist. Using the search term tezosentan, a literature review was conducted to identify peer-reviewed articles and abstracts in MEDLINE (1966 to April 2004) and Current Content (1966 to April 2004) databases. Citations from available articles were also reviewed for additional references. When given as an intravenous infusion, tezosentan achieves steady-state concentration within the first 6 hours. Tezosentan is excreted almost entirely through the bile (>95%) and has a terminal elimination half-life of 3 hours. The side effects of tezosentan include headache, nausea, and hypotension. Clinical studies demonstrated mixed results for tezosentan regarding its efficacy and tolerability in the management of decompensated heart failure. The role or tezosentan in treating heart failure is yet to be defined.