Atrial natriuretic peptide and its potential role in pharmacotherapy

A Mechanistic Basis for the Beneficial Effects of Caloric Restriction On Longevity and Disease: Consequences for the Interpretation of Rodent Toxicity Studies

Caloric restriction in rodents has been repeatedly shown to increase life span while reducing the severity and retarding the onset of both spontaneous and chemically induced neoplasms. These effects of caloric restriction are associated with a spectrum of biochemical and physiological changes that characterize the organism's adaptation to reduced caloric intake and provide the mechanistic basis for caloric restriction's effect on longevity. Here, we review evidence suggesting that the primary adaptation appears to be a rhythmic hypercorticism in the absence of elevated adrenocorticotropin (ACTH) levels. This characteristic hypercorticism evokes a spectrum of responses, including reduced body temperature and increased metabolic efficiency, decreased mitogenic response coupled with increased rates of apoptosis, reduced inflammatory response, reduced oxidative damage to proteins and DNA, reduced reproductive capacity, and altered drug-metabolizing enzyme expression. The net effect of these changes is to (1) decrease growth and metabolism in peripheral tissues to spare energy for central functions, and (2) increase the organism's capacity to withstand stress and chemical toxicity. Thus, caloric restriction research has uncovered an evolutionary mechanism that provides rodents with an adaptive advantage in conditions of fluctuating food supply. During periods of abundance, body growth and fecundity are favored over endurance and longevity. Conversely, during periods of famine, reproductive performance and growth are sacrificed to ensure survival of individuals to breed in better times. This phenomena can be observed in rodent populations that are used in toxicity testing. Improvements over the last 30 years in animal husbandry and nutrition, coupled with selective breeding for growth and fecundity, have resulted in several strains now exhibiting larger animals with reduced survival and increased incidence of background lesions. The mechanistic data from caloric restriction studies suggest that these large animals will also be more susceptible to chemically induced toxicity. This creates a problem in comparing tests performed on animals of different weights and comparing data generated today with the historical database. The rational use of caloric restriction to control body weight to within preset guidelines is a possible way of alleviating this problem.

Nesiritide: a novel approach for acute heart failure

OBJECTIVE

To review preclinical and clinical information related to nesiritide, a recombinant form of B-type natriuretic peptide approved for treatment of acutely decompensated heart failure.

DATA SOURCES

Primary and review articles were identified by MEDLINE search (1966-May 2002) using the key words natriuretic peptide and heart failure, and through secondary sources. Natrecor's document submitted for the Food and Drug Administration (FDA) New Drug Application were obtained from the FDA Web site.

STUDY SELECTION/DATA EXTRACTION

Peer-reviewed articles and abstracts of randomized clinical trials in humans were included in this review.

DATA SYNTHESIS

Nesiritide has beneficial actions for treatment of heart failure, including arterial and venous dilatation, enhanced sodium and urinary excretion, and suppression of the renin-angiotensin-aldosterone and sympathetic nervous systems. It has been shown to improve hemodynamic parameters, primarily pulmonary capillary wedge pressure, as well as clinical symptoms in patients with acutely decompensated heart failure. Nesiritide produced more rapid hemodynamic improvement and caused significantly fewer adverse effects than intravenous nitroglycerin. The incidence of hypotension, the most common adverse effect, was comparable between nesiritide and nitroglycerin. Additionally, nesiritide is associated with a lower incidence of arrhythmias than dobutamine and has a neutral effect on mortality.

CONCLUSIONS

Nesiritide offers an alternative for management of acutely decompensated heart failure. It is considered an option for patients who do not respond to other vasodilators, inotropes, or diuretics and for those at high risk of arrhythmias. Further pharmacoeconomic investigations for nesiritide are warranted.

Effects of omapatrilat on pharmacodynamic biomarkers of neutral endopeptidase and Angiotensin-converting enzyme activity in humans

Vasopeptidase inhibition is a new concept in blood pressure management. A single molecule simultaneously inhibits two enzymes that regulate cardiovascular function: neutral endopeptidase (NEP) and angiotensin-converting enzyme (ACE)[1]. Development of vasopeptidase inhibitors stemmed from the need for new and more efficacious antihypertensive agents that not only reduce blood pressure but also treat hypertension as part of a larger syndrome involving endothelial dysfunction [2]. By inhibiting NEP and ACE, vasopeptidase inhibitors enhance the natriuretic peptide and kallikrein-kinin systems and inhibit the renin-angiotensin-aldosterone system. This article outlines the pharmacodynamic effects of the vasopeptidase inhibitor omapatrilat on biomarkers of NEP and ACE activity in humans.

Nesiritide (hBNP): a new class of therapeutic peptide for the treatment of decompensated congestive heart failure

Natriuretic peptides are a family of endogenous peptide hormones with vasodilating, natriuretic, diuretic, and lusitropic properties. Administration of pharmacologic doses of exogenous natriuretic peptides may provide therapeutic benefit in patients with chronic heart failure. In controlled clinical trials, short-term administration of nesiritide (human brain natriuretic peptide) to patients with heart failure is associated with improved resting hemodynamics, modest increases in sodium excretion, evidence of suppression of neurohormonal activation, and improvements in symptoms of heart failure. Additional trials to determine the clinical efficacy and safety of nesiritide are warranted. (c)2001 by CHF, Inc.

The discovery of non-basic atrial natriuretic peptide clearance receptor antagonists. Part 1

The cyclic peptide ANP 4-23 and the linear peptide analogue AP-811 have been shown to be selective ANP-CR antagonists. Via alanine scanning and truncation studies we sought to determine which residues in these molecules were important in their binding to the clearance receptor and the relationship between these two molecules. These studies show that several modifications to these compounds are possible which improve physical properties of these molecules while retaining high affinity for the ANP-CR.

A randomized trial of ecadotril versus placebo in patients with mild to moderate heart failure: the U.S. ecadotril pilot safety study

OBJECTIVE

To determine the short-term safety and tolerability of the addition of ecadotril to conventional therapy in patients with mild to moderate heart failure.

METHODS

Fifty ambulatory patients, 18 to 75 years of age, with mild to moderate heart failure, left ventricular ejection fraction </=35%, taking stable doses of angiotensin-converting enzyme inhibitor, diuretics, and optionally digoxin were enrolled in a randomized, double-blind, placebo-controlled dose-escalation study of ecadotril 50 to 400 mg twice daily versus conventional therapy alone.

RESULTS

No increases in deaths, serious adverse events, or dropouts from adverse events were observed for the ecadotril group compared with placebo. The serum measures of neurohormonal activation were highly variable. Changes in signs and symptoms of heart failure, New York Heart Association class, and patient self-assessment of symptoms were not observed with ecadotril therapy; however, the study was not designed to detect differences in these parameters.

CONCLUSION

In this small pilot study, ecadotril in doses of 50 to 400 mg twice daily was generally well-tolerated and without severe short-term adverse effects in patients with mild to moderate heart failure. Evaluation of the clinical efficacy and long-term safety of ecadotril and other neutral endopeptidase inhibitors in patients with heart failure requires further study.

New classes of antihypertensive drugs: therapeutic potentials

A number of new classes of antihypertensive drugs have become available in the recent years which appear to hold therapeutic potential for better management of hypertension. Losartan, an angiotensin II receptor antagonist, does not produce cough which is classically seen with ACE inhibitors. Fenoldopam, a dopamine D1-receptor agonist, has a rapid and short duration of action and is ideally suited by intravenous infusion for quick control of BP in hypertensive emergencies. Kentaserin, a serotonin (5-HT2A) receptor antagonist, has a long duration of action and can be given once daily. It has the added benefit of having antiplatelet effect. Monatepil, a dual alpha-receptor and calcium channel blocker, has potent antihypertensive effect, lowers serum cholesterol and also has antiatherosclerotic effect. Dual ACE and endopeptidase inhibitor, such as alatriopril, has a "broad spectrum" antihypertensive effect and may be effective in majority of hypertensive patients. Many other classes of antihypertensive drugs are still in the investigative stage, and their therapeutic potentials and safety need to be ascertained in long-term controlled clinical trials.

Cardiovascular effects of ozone exposure in human volunteers

We hypothesized that ozone (O3) exposure acutely affects cardiovascular hemodynamics in humans and, in particular, in subjects with essential hypertension. We studied 10 nonmedicated hypertensive and six healthy male adults. Each subject, after catheterization of the right heart and a radial artery, was exposed in an environmentally controlled chamber to filtered air (FA) on one day and to 0.3 ppm O3 on the following day for 3 h with intermittent exercise. Relative to FA exposure, O3 exposure induced no statistically significant changes in cardiac index, ventricular performance, pulmonary artery pressure, pulmonary and systemic vascular resistances, ECG, serum cardiac enzymes, plasma catecholamines and atrial natriuretic factor, and SaO2. The overall results did not indicate major acute cardiovascular effects of O3 in either the hypertensive or the control subjects. However, mean preexposure to postexposure changes were significantly (p < 0.02) larger with O3 than with FA for rate-pressure product (1,353 beats/min/mm Hg) and for heart rate (8 beats/min); these responses were not significantly different between the hypertensive and the control subjects. Significant O3 effects were also observed for mean FEV1 (-6%), and AaPO2 (> 10 mm Hg increase), which were not significantly different between the two groups. These results suggest that O3 exposure can increase myocardial work and impair pulmonary gas exchange to a degree that might be clinically important in persons with significant preexisting cardiovascular impairment, with or without concomitant lung disease.

Hemodynamic and renal excretory effects of human brain natriuretic peptide infusion in patients with congestive heart failure. A double-blind, placebo-controlled, randomized crossover trial

BACKGROUND

The pharmacological effects of infusion of human brain natriuretic peptide (hBNP) in patients with severe congestive heart failure have not been characterized previously.

METHODS AND RESULTS

Twenty patients with severe congestive heart failure were randomized in a double-blind, placebo-controlled, crossover trial to receive incremental 90-minute infusions of hBNP (0.003, 0.01, 0.03, and 0.1 microgram/kg per minute) or placebo on 2 consecutive days. At the highest completed dose of the hBNP, mean pulmonary artery pressure decreased from 38.3 +/- 1.6 to 25.9 +/- 1.7 mm Hg; mean pulmonary capillary wedge pressure decreased from 25.1 +/- 1.1 to 13.2 +/- 1.3 mm Hg; mean right atrial pressure decreased from 10.9 +/- 1 to 4.8 +/- 1.0 mm Hg; mean arterial pressure decreased from 85.2 +/- 2.0 to 74.9 +/- 1.7 mm Hg; and cardiac index increased from 2.0 +/- 0.1 to 2.5 +/- 0.1 L/min per square meter (all P < .01 versus placebo). Urine volume and urine sodium excretion increased significantly during hBNP infusion when compared with placebo infusion (90 +/- 38 versus 67 +/- 27 mL/h and 2.6 +/- 2.4 versus 1.4 +/- 1.2 mEq/h, respectively, both P < .05 versus placebo), whereas creatinine clearance and urinary potassium excretion did not change.

CONCLUSIONS

Infusion of incremental doses of hBNP is associated with favorable hemodynamic and natriuretic effects in patients with severe congestive heart failure.