Renal effects of adenosine A1-receptor antagonists in congestive heart failure

Therapeutic potency of A1 adenosine receptor antagonists in the treatment of cardiovascular diseases, current status and perspectives

BACKGROUND

Cardiomyocytes form, transport, and metabolize the omnipresent metabolite adenosine. Depending upon the adenosine concentrations and the pharmacological properties of receptor subtypes, adenosine exerts (patho)physiological responses in the cardiovascular system. The objective of this review is to present different protective mechanisms of A1-adenosine receptor inhibitors in cardiovascular diseases.

METHODS AND RESULTS

Literature references were collected and sorted using relevant keywords and key phrases as search terms in scientific databases such as Web of Science, PubMed and Google Scholar. A1 adenosine receptor regulates free fatty acid metabolism, lipolysis, heart rate, blood pressure, and cardiovascular toxicity. The evidence clearly supporting the therapeutic potency of pharmacological A1 adenosine receptors agonists and antagonists in modulating cardiovascular risk factor parameters and treatment of cardiovascular diseases.

CONCLUSION

This review summarizes the protective role of pharmacological A1-adenosine receptor regulators in the pathogenesis of cardiovascular diseases for a better management of cardiovascular diseases.

Design, Synthesis and Biological Evaluation of 1,3,5-Triazine Derivatives Targeting hA1 and hA3 Adenosine Receptor

Adenosine mediates various physiological activities in the body. Adenosine receptors (ARs) are widely expressed in tumors and the tumor microenvironment (TME), and they induce tumor proliferation and suppress immune cell function. There are four types of human adenosine receptor (hARs): hA₁, hA_2A, hA_2B, and hA₃. Both hA₁ and hA₃ AR play an important role in tumor proliferation. We designed and synthesized novel 1,3,5-triazine derivatives through amination and Suzuki coupling, and evaluated them for binding affinities to each hAR subtype. Compounds 9a and 11b showed good binding affinity to both hA₁ and hA₃ AR, while 9c showed the highest binding affinity to hA₁ AR. In this study, we discovered that 9c inhibits cell viability, leading to cell death in lung cancer cell lines. Flow cytometry analysis revealed that 9c caused an increase in intracellular reactive oxygen species (ROS) and a depolarization of the mitochondrial membrane potential. The binding mode of 1,3,5-triazine derivatives to hA₁ and hA₃ AR were predicted by a molecular docking study.

In silico investigation of the selectivity mechanism of A1AR and A2AAR antagonism

Adenosine A1 receptor (A1AR) and adenosine A2A receptor (A2AAR) are AR isoforms that share high homology but play many different roles in terms of regulating arteriolar pressure and urine flow as well as relieving neurodegenerative disorders.

The New Biology of Diabetic Kidney Disease-Mechanisms and Therapeutic Implications

Diabetic kidney disease remains the most common cause of end-stage kidney disease in the world. Despite reductions in incidence rates of myocardial infarction and stroke in people with diabetes over the past 3 decades, the risk of diabetic kidney disease has remained unchanged, and may even be increasing in younger individuals afflicted with this disease. Accordingly, changes in public health policy have to be implemented to address the root causes of diabetic kidney disease, including the rise of obesity and diabetes, in addition to the use of safe and effective pharmacological agents to prevent cardiorenal complications in people with diabetes. The aim of this article is to review the mechanisms of pathogenesis and therapies that are either in clinical practice or that are emerging in clinical development programs for potential use to treat diabetic kidney disease.

New potent and selective A1 adenosine receptor antagonists as potential tools for the treatment of gastrointestinal diseases

The synthesis of 9-alkyl substituted adenine derivatives presenting aromatic groups and cycloalkyl rings in 8- and N⁶-position, respectively, is reported. The compounds were tested with radioligand binding studies showing, in some cases, a low nanomolar A₁ adenosine receptor affinity and a very good selectivity versus the other adenosine receptor subtypes. Functional assays at human adenosine receptors and at a mouse ileum tissue preparation clearly demonstrate the antagonist profile of these molecules, with inhibitory potency at nanomolar level. A molecular modeling study, consisting in docking analysis at the recently reported A₁ adenosine receptor crystal structure, was performed for the interpretation of the obtained pharmacological results. The N⁶-cyclopentyl-9-methyl-8-phenyladenine (17), resulting the most active derivative of the series (K_i = 2.8 nM and IC₅₀ = 14 nM), was also very efficacious in counteracting the effect of the agonist CCPA on mouse ileum contractility. This new compound represents a tool for the development of new agents for the treatment of intestinal diseases as constipation and postoperative ileus.

Recognizing hospitalized heart failure as an entity and developing new therapies to improve outcomes: academics', clinicians', industry's, regulators', and payers' perspectives

Hospitalized heart failure (HHF) is associated with unacceptably high postdischarge mortality and rehospitalization rates. This heterogeneous group of patients, however, is still treated with standard, homogenous therapies that are not preventing their rapid deterioration. The costs associated with HHF have added demands from society, government, and payers to improve outcomes. With coordinated and committed efforts in the development of new therapies, improvements may be seen in outcomes for patients with HHF. This article summarizes concepts in developing therapies for HHF discussed during a multidisciplinary panel at the Heart Failure Society of America's Annual Scientific Meeting, September 2012.

Homodimerization of adenosine A₁ receptors in brain cortex explains the biphasic effects of caffeine

Using bioluminescence resonance energy transfer and proximity ligation assays, we obtained the first direct evidence that adenosine A₁ receptors (A₁Rs) form homomers not only in cell cultures but also in brain cortex. By radioligand binding experiments in the absence or in the presence of the A₁Rs allosteric modulator, adenosine deaminase, and by using the two-state dimer receptor model to fit binding data, we demonstrated that the protomer-protomer interactions in the A₁R homomers account for some of the pharmacological characteristics of agonist and antagonist binding to A₁Rs. These pharmacological properties include the appearance of cooperativity in agonist binding, the change from a biphasic saturation curve to a monophasic curve in self-competition experiments and the molecular cross-talk detected when two different specific molecules bind to the receptor. In this last case, we discovered that caffeine binding to one protomer increases the agonist affinity for the other protomer in the A₁R homomer, a pharmacological characteristic that correlates with the low caffeine concentrations-induced activation of agonist-promoted A₁R signaling. This pharmacological property can explain the biphasic effects reported at low and high concentration of caffeine on locomotor activity.

Update in diuretic therapy: clinical pharmacology

All diuretics except spironolactone exert their effects from the lumen of the nephron. Thus, to exert an effect, they must reach the urine. Pharmacokinetics (PK) describes this access. Different edematous disorders can affect access to this site of action and therein affect response to a diuretic. In addition, once a diuretic reaches the site of action, a response ensues. The characteristics of this response that can be affected by a patient's clinical condition are described by the pharmacodynamics (PD) of a diuretic. To understand the mechanisms of abnormal response to a diuretic one must dissect its PK and PD in different edematous disorders. For example, in patients with renal insufficiency, the mechanism of poor diuretic response is PK. In contrast, in patients with cirrhosis or in those with congestive heart failure, it is PD. In patients with nephrotic syndrome, both PK and PD are operative. These different mechanisms mandate differences in therapeutic strategy, as explained in this article.

The challenge of treating congestion in advanced heart failure

Volume overload is a common manifestation of heart failure decompensation. Interaction between impaired renal and heart function constitutes an important pathophysiologic mechanism that leads to congestion. In addition to improving symptoms and volume status, reduction of rehospitalization rates, maintenance of renal function and improvement of survival are all important goals of every therapeutic strategy. Currently, the use of diuretics, vasodilators, inotropes and ultrafiltration, together with investigational agents such as oral vasopressin antagonists and adenosine A1-receptor antagonists, constitute the main therapeutic options for the congested heart failure patient.

Metabolic and toxicological considerations for diuretic therapy in patients with acute heart failure

INTRODUCTION

Diuretics are widely recommended in patients with acute heart failure (AHF). However, loop diuretics predispose patients to electrolyte imbalance and hypovolemia, which in turn leads to neurohormonal activation and worsening renal function (WRF). Unfortunately, despite their widespread use, limited data from randomized clinical trials are available to guide clinicians with the appropriate management of this diuretic therapy.

AREAS COVERED

This review focuses on the current management of diuretic therapy and discusses data supporting the efficacy and safety of loop diuretics in patients with AHF. The authors consider the challenges in performing clinical trials of diuretics in AHF, and describe ongoing clinical trials designed to rigorously evaluate optimal diuretic use in this syndrome. The authors review the current evidence for diuretics and suggest hypothetical bases for their efficacy relying on the complex relationship among diuretics, neurohormonal activation, renal function, fluid and sodium management, and heart failure syndrome.

EXPERT OPINION

Data from several large registries that evaluated diuretic therapy in hospitalized patients with AHF suggest that its efficacy is far from being universal. Further studies are warranted to determine whether high-dose diuretics are responsible for WRF and a higher rate of coexisting renal disease are instead markers of more severe heart failure. The authors believe that monitoring congestion during diuretic therapy in AHF would refine the current approach to AHF treatment. This would allow clinicians to identify high-risk patients and possibly reduce the incidence of complications secondary to fluid management strategies.

Caffeine-induced natriuresis and diuresis via blockade of hepatic adenosine-mediated sensory nerves and a hepatorenal reflex

The hepatorenal reflex, activated by intrahepatic adenosine, is involved in the regulation of urine production in healthy rats and renal pathogenesis secondary to liver injury. Hepatic adenosine A1 receptors regulate the hepatorenal reflex. The aim of the present study was to evaluate whether caffeine mediates renal natriuresis and diuresis in healthy and diseased liver through this mechanism. Rats were anesthetized and instrumented to monitor systemic, hepatic, and renal circulation and urine production. Intrahepatic (intraportal but not intravenous) caffeine (5 mg·kg-1) increased urine flow (~82%) in healthy rats. This effect was abolished by liver denervation. Intraportal infusion of adenosine decreased urine production, and this response was abolished by intraportal but not intravenous caffeine. Liver injury was induced by intraperitoneal injection of thioacetamide (500 mg·kg-1), and functional assessment was performed 24 h later. Liver injury was associated with lower (~30%) glomerular filtration rate, lower (~18%) renal arterial blood flow, and lower urine production. Intraportal but not intravenous caffeine improved basal urine production and renal ability to increase urine production in response to saline overload. The liver-dependent diuretic effect of caffeine is consistent with the hypothesis for the adenosine-mediated mechanism of hepatorenal syndrome.

Rolofylline, an adenosine A1-receptor antagonist, in acute heart failure

BACKGROUND

Worsening renal function, which is associated with adverse outcomes, often develops in patients with acute heart failure. Experimental and clinical studies suggest that counterregulatory responses mediated by adenosine may be involved. We tested the hypothesis that the use of rolofylline, an adenosine A1-receptor antagonist, would improve dyspnea, reduce the risk of worsening renal function, and lead to a more favorable clinical course in patients with acute heart failure.

METHODS

We conducted a multicenter, double-blind, placebo-controlled trial involving patients hospitalized for acute heart failure with impaired renal function. Within 24 hours after presentation, 2033 patients were randomly assigned, in a 2:1 ratio, to receive daily intravenous rolofylline (30 mg) or placebo for up to 3 days. The primary end point was treatment success, treatment failure, or no change in the patient's clinical condition; this end point was defined according to survival, heart-failure status, and changes in renal function. Secondary end points were the post-treatment development of persistent renal impairment and the 60-day rate of death or readmission for cardiovascular or renal causes.

RESULTS

Rolofylline, as compared with placebo, did not provide a benefit with respect to the primary end point (odds ratio, 0.92; 95% confidence interval, 0.78 to 1.09; P=0.35). Persistent renal impairment developed in 15.0% of patients in the rolofylline group and in 13.7% of patients in the placebo group (P=0.44). By 60 days, death or readmission for cardiovascular or renal causes had occurred in similar proportions of patients assigned to rolofylline and placebo (30.7% and 31.9%, respectively; P=0.86). Adverse-event rates were similar overall; however, only patients in the rolofylline group had seizures, a known potential adverse effect of A1-receptor antagonists.

CONCLUSIONS

Rolofylline did not have a favorable effect with respect to the primary clinical composite end point, nor did it improve renal function or 60-day outcomes. It does not show promise in the treatment of acute heart failure with renal dysfunction. (Funded by NovaCardia, a subsidiary of Merck; ClinicalTrials.gov numbers, NCT00328692 and NCT00354458.).

Design and rationale of the PROTECT study: a placebo-controlled randomized study of the selective A1 adenosine receptor antagonist rolofylline for patients hospitalized with acute decompensated heart failure and volume overload to assess treatment effect on congestion and renal function

BACKGROUND

Current treatment for acute decompensated heart failure (ADHF) is associated with incomplete resolution of symptoms and signs, recurrent symptoms of heart failure in-hospital and after discharge and high mortality. Studies have consistently demonstrated an association between worsening renal function in ADHF and adverse outcomes. Adenosine A(1) receptor antagonists, such as rolofylline, appear in preliminary studies to produce potentially beneficial effects on natriuresis, diuresis, renal blood flow, and glomerular filtration rate. In a previous dose-finding study, rolofylline 30 mg intravenously daily for 3 days was associated with symptom improvement, less worsening of renal function, and trends toward lower 60-day rates of death or readmission for cardiovascular or renal causes.

METHODS AND RESULTS

This manuscript describes the rationale underlying the design of the phase 3 PROTECT (Placebo-controlled Randomized study of the selective A(1) adenosine receptor antagonist rolofylline for patients hospitalized with acute heart failure and volume Overload to assess Treatment Effect on Congestion and renal funcTion) trial.

CONCLUSION

Rolofylline 30 mg or matching placebo was given intravenously as a 4-hour continuous infusion on 3 consecutive days and the hospital course was assessed by measurements dyspnea, clinical status, renal function, and subsequent morbidity and mortality in a large population of patients with ADHF with renal impairment.

Overview of emerging pharmacologic agents for acute heart failure syndromes

BACKGROUND

Several therapies commonly used for the treatment of acute heart failure syndromes (AHFS) present some well-known limitations and have been associated with an early increase in the risk of death. There is, therefore, an unmet need for new pharmacologic agents for the early management of AHFS that may improve both short- and long-term outcomes.

AIM

To review the recent evidence on emerging pharmacologic therapies in AHFS.

METHODS

A systematic search of peer-reviewed publications was performed on MEDLINE, EMBASE and Clinical Trials.gov from January 1990 to August 2007. The results of unpublished or ongoing trials were obtained from presentations at national and international meetings and pharmaceutical industry releases. Bibliographies from these references were also reviewed, as were additional articles identified by content experts.

RESULTS

Cumulative data from large studies and randomised trials suggest that therapies with innovative mechanisms of action may safely and effectively reduce pulmonary congestion or improve cardiac performance in AHFS patients.

CONCLUSION

Some investigational agents for the management of AHFS are able to improve haemodynamics and/or clinical status. In spite of these promising findings, no new agent has demonstrated a clear benefit in terms of long-term clinical outcomes compared to placebo or conventional therapies.

Search for new antagonist ligands for adenosine receptors from QSAR point of view. How close are we?

In view of the large libraries of nucleoside analogues that are now being handled in organic synthesis, the identification of drug biological activity is advisable prior to synthesis and this can be achieved by employing predictive biological property methods. In this sense, Quantitative Structure-Activity Relationships (QSAR) or docking approaches have emerged as promising tools. Although a large number of in silico approaches have been described in the literature for the prediction of different biological activities, the use of QSAR applications to develop adenosine receptor (AR) antagonists is not common as for the case of the antibiotics and anticancer compounds for instance. The intention of this review is to summarize the present knowledge concerning computational predictions of new molecules as adenosine receptor antagonists.

Review of current and investigational pharmacologic agents for acute heart failure syndromes

Acute heart failure syndromes (AHFS) are a major public health problem and present a therapeutic challenge to clinicians. Commonly used agents in the treatment of AHFS include diuretics, vasodilators (eg, nitroglycerin, nitroprusside, nesiritide), and inotropes (eg, dobutamine, dopamine, milrinone). Patients admitted to hospital with AHFS and low cardiac output state (AHFS/LO) represent a subgroup with very high inhospital and postdischarge mortality rates. Most of these patients require intravenous inotropic therapy. However, the use of current intravenous inotropes has been associated with risk for hypotension, atrial and ventricular arrhythmias, and possibly increased postdischarge mortality, particularly in those with coronary artery disease. Consequently, there is an unmet need for new agents to safely improve cardiac performance (contractility and/or active relaxation) in this patient population. This article reviews a selection of current and investigational agents for the treatment of AHFS, with a main focus on the high-risk patient population with AHFS/LO.

Emerging therapies for the management of decompensated heart failure: from bench to bedside

While pharmaceutical innovation has been highly successful in reducing mortality in chronic heart failure, this has not been matched by similar success in decompensated heart failure syndromes. Despite outstanding issues over definitions and end points, we argue in this paper that an unprecedented wealth of pharmacologic innovation may soon transform the management of these challenging patients. Agents that target contractility, such as cardiac myosin activators and novel adenosine triphosphate-dependent transmembrane sodium-potassium pump inhibitors, provide inotropic support without arrhythmogenic increases in cytosolic calcium or side effects of more traditional agents. Adenosine receptor blockade may improve glomerular filtration and diuresis by exerting a direct beneficial effect on glomerular blood flow while vasopressin antagonists promote free water excretion without compromising renal function and may simultaneously inhibit myocardial remodeling. Urodilatin, the renally synthesized isoform of atrial natriuretic peptide, may improve pulmonary congestion via vasodilation and enhanced diuresis. Finally, metabolic modulators such as perhexiline may optimize myocardial energy utilization by shifting adenosine triphosphate production from free fatty acids to glucose, a unique and conceptually appealing approach to the management of heart failure. These advances allow optimism not only for the advancement of our understanding and management of decompensated heart failure syndromes but for the translational research effort in heart failure biology in general.

Contemporary Issues in the Pharmacologic Management of Acute Heart Failure

Acute heart failure is an evolving syndrome that continues to be defined by ongoing studies and registries. It is associated with significant morbidity and mortality and places a huge economic burden on health care systems. Improved understanding of the underlying pathophysiologic processes has prompted interest into understanding the implications of current and future pharmacologic management strategies beyond hemodynamics. Diuretics, vasodilators, and inotropes remain the mainstays of therapy with several new classes of agents on the horizon. Clinicians should understand the rationale for use and limitations of each therapy to maximize benefit and cost-effectiveness, while minimizing the potential for adverse outcomes.

Novel pharmacological treatments for heart failure

Pharmacological therapies remain the primary strategy for treating patients with acute and chronic heart failure. Several novel neurohormonal antagonists, inotropic agents, immune modulators, and metabolic and replacement therapies are currently in development to meet the demands of an increasing number of patients with heart failure. The success in drug development in this field will require a better understanding of the effects of heart failure on drug dosing, better integration of novel and existing drug therapies, the development of more reliable surrogate markers to effectively tailor medical therapy to individual needs and the ability to detect and treat patients at risk before the onset of heart failure.

Cellular mechanisms for the treatment of chronic heart failure: the nitric oxide- and adenosine-dependent pathways

Accumulated evidence suggests that several drugs proven to improve survival in patients with chronic heart failure (CHF) enhance endogenous nitric oxide (NO)- and/or adenosine-dependent pathways. Indeed, we and others have demonstrated that: i) antagonists of either renin-angiotensin-aldosterone or beta-adrenergic systems enhance NO-dependent pathways; ii) although carvedilol and amlodipine belong to different drug classes, both of them can increase cardiac adenosine levels; iii) increased adenosine levels by dipyridamole are associated with the improvement of CHF. Interestingly, both NO and adenosine have multifactorial beneficial actions in cardiovascular systems. First of all, both of them induce vasodilation and decrease myocardial hypercontractility, which may contribute to a reduction in the severity of myocardial ischaemia. Both adenosine and NO are also involved in cardioprotection attributable to acute and late phases of ischaemic preconditioning, respectively. Secondly, they can modulate the neurohormonal systems that contribute to the progression of CHF. Thus, we propose that enhancement of endogenous NO and/or adenosine as potential therapeutic targets in a new strategy for the treatment for CHF.

Comparison of three different A1 adenosine receptor antagonists on infarct size and multiple cycle ischemic preconditioning in anesthetized dogs

A(1) adenosine receptor (AR) antagonists are effective diuretic agents that may be useful for treating fluid retention disorders including congestive heart failure. However, antagonism of A(1)ARs is potentially a concern when using these agents in patients with ischemic heart disease. To address this concern, the present study was designed to compare the actions of the A(1)AR antagonists CPX (1,3-dipropyl-8-cyclopentylxanthine), BG 9719 (1,3-dipropyl-8-[2-(5,6-epoxynorbornyl)]xanthine), and BG 9928 (1,3-dipropyl-8-[1-(4-propionate)-bicyclo-[2,2,2]octyl]xanthine) on acute myocardial ischemia/reperfusion injury and ischemic preconditioning (IPC) in an in vivo dog model of infarction. Barbital-anesthetized dogs were subjected to 60 min of left anterior descending coronary artery occlusion followed by 3 h of reperfusion, after which infarct size was assessed by staining with triphenyltetrazolium chloride. IPC was elicited by four 5-min occlusion/5-min reperfusion cycles produced 10 min before the 60-min occlusion. Multiple-cycle IPC produced a robust reduction ( approximately 65%) in infarct size; this effect of IPC on infarct size was not abrogated in dogs pretreated with any of the three AR antagonists. Surprisingly, in the absence of IPC, pretreatment with CPX or BG 9928 before occlusion or immediately before reperfusion resulted in significant reductions ( approximately 40-50%) in myocardial infarct size. However, treatment with an equivalent dose of BG 9719 had no similar effect. We conclude that the A(1)AR antagonists BG 9719, BG 9928, and CPX do not exacerbate cardiac injury and do not interfere with IPC induced by multiple ischemia/reperfusion cycles. We discuss the possibility that the cardioprotective actions of CPX and BG 9928 may be related to antagonism of A(2B)ARs.

An orally active adenosine A1 receptor antagonist, FK838, increases renal excretion and maintains glomerular filtration rate in furosemide-resistant rats

1. Loop and thiazide diuretics are common therapeutic agents for the treatment of sodium retention and oedema. However, resistance to diuretics and decreases in renal function can develop during diuretic therapy. Adenosine causes renal vasoconstriction, sodium reabsorption, and participates in the tubuloglomerular feedback mechanism for the regulation of glomerular filtration rate. 2. We tested the hypothesis that the selective adenosine A(1) receptor antagonist FK838 is orally active and causes diuresis and natriuresis, but maintains glomerular filtration rate in normal rats or in rats with furosemide resistance. 3. In normal male Sprague - Dawley rats, FK838 dose-dependently increased urine flow and sodium and chloride excretion while sparing potassium. In combination with furosemide, FK838 enhanced the diuretic and natriuretic actions of furosemide to the same extent as hydrochlorothiazide and did not increase the potassium loss in normal rats. In furosemide-resistant rats, FK838 increased urine flow and electrolyte excretion to a greater extent than hydrochlorothiazide. In addition, hydrochlorothiazide significantly decreased glomerular filtration rate, whereas FK838 maintained glomerular filtration rate in furosemide-resistant rats. 4. This study shows that the adenosine A(1) receptor antagonist FK838 is orally active and causes potent diuresis and natriuresis and maintains glomerular filtration rate in normal or furosemide-resistant rats. Adenosine A(1) receptor antagonists may be novel therapeutics for the treatment of oedema in normal or otherwise diuretic-resistant patients.

The rational use of diuretics in heart failure

Congestive heart failure is a progressive hemodynamic disorder associated with significant morbidity and mortality. Concomitant renal dysfunction is frequently seen in patients with heart failure, and can compromise fluid regulation, leading to acute decompensation, and increased morbidity and mortality. Diuretic therapy has been the mainstay for treatment of congestive symptoms, despite documented mortality benefits. Misuse or overuse of diuretics can have negative consequences in heart failure, and optimizing diuretic efficiency may improve outcomes. In addition, new agents targeting elevated neuropeptides may prove to be beneficial in regulating fluid status and optimizing renal function.

Revisiting salt and water retention: new diuretics, aquaretics, and natriuretics

Diuretics continue to be a mainstay in patients with CHF. Conventional diuretic therapy is associated, however, with potentially deleterious neurohumoral activation and renal impairment. It is not known to what extent these neurohumoral effects are offset by concurrent therapy with ACE-I, beta-blockers, and other agents. In the past, there was no alternative to conventional diuretic therapy, so their potential for adverse outcome in the long term could not be assessed. Enhancement of the natriuretic peptide system could provide us with a better strategy to treat sodium and water retention. In a unique way, the natriuretic peptides combine several of the beneficial actions of the other diuretics, but without the associated cost. Natriuretic peptides, like conventional diuretics, are natriuretic and diuretic. There are important differences, however. First, unlike conventional diuretics, NPs do not activate RAAS. Activation of this system is associated with progression of CHF. Second, NPs inhibit the sympathetic nervous system, the activation of which is associated with heart failure progression, myocyte necrosis and apoptosis, and arrhythmias. Third, unlike conventional diuretics that lead to a decrease in GFR by reflex mechanisms. NPs maintain or even improve GFR. We now appreciate that some "old" drugs may be beneficial to CHF patients in a new way, as is the case with spironolactone. The survival benefit of this aldosterone antagonist is clear: its usefulness, however, may be more a result of both its antifibrotic actions in addition to its tradional role as a potassium-sparing and natriuretic agent. It is hoped that the SARAs will provide the same survival benefit, but with fewer of the sex-steroid side effects. In addition, AVP-receptor antagonists may become useful tools in the treatment of patients with hyponatremia. Likewise, the A1 AR antagonists may find a role in the CHF armamentarium by providing good diuresis and natriuresis while at the same time maintaining GFR through inhibition of TGF. Many questions remain unanswered, and studies are needed to demonstrate that the positive results seen in basic research translate into improved morbidity and mortality.