Controlled and uncontrolled studies of phosphodiesterase III inhibitors in contemporary cardiovascular medicine

Apremilast reversed carfilzomib-induced cardiotoxicity through inhibition of oxidative stress, NF-κB and MAPK signaling in rats

Carfilzomib (CFZ), is a potent, selective second generation proteasome inhibitor, used for the treatment of multiple myeloma. The aim of the present study was to investigate the possible protective effect of apremilast (AP) on the CFZ -induced cardiotoxicity. Rats were randomly divided into four groups: Group 1, served as the control group, received normal saline. Group 2, served as the toxic group, received CFZ (4 mg/kg, intraperitoneally [i.p.]). Groups 3 and 4, served as treatment groups, and received CFZ with concomitant oral administration of AP in doses of 10 and 20 mg/kg/day, respectively. In the present study, administration of CFZ resulted in a significant increase in serum aspartate transaminase (AST), lactate dehydrogenase (LDH), creatine kinase (CK) and creatine kinase-MB (CK-MB), which were reversed by treatment with AP. CFZ resulted in a significant increase in heart malondialdehyde (MDA) contents and decrease in cardiac glutathione (GSH) level and catalase (CAT) enzyme activity which were significantly reversed by treatment with AP. Induction of cardiotoxicity by CFZ significantly increased caspase-3 enzyme activity which were reversed by treatment with AP. RT-PCR analysis revealed an increased mRNA expression of NF-κB, ERK and JNK which were reversed by treatment with AP in cardiac tissues. Western blot analysis revealed an increased expression of caspase-3 and NF-κB p65 and a decrease expression of inhibitory kappa B-alpha (Iκbα) with CFZ, which were reversed by treatment with AP. In conclusion, apremilast showed protective effect against CFZ-induced cardiotoxicity.

A review of the herbal phosphodiesterase inhibitors; future perspective of new drugs

Phosphodiesterase inhibitors (PDEIs) are a class of drugs that are widely used because of their various pharmacological properties including cardiotonic, vasodilator, smooth muscle relaxant, antidepressant, antithrombotic, bronchodilator, antiinflammatory and enhancer of cognitive function. In the recent years, interest in drugs of plant origin has been progressively increased. Some pharmacologically active substances that come from plants demonstrate PDEI activity. They mainly belong to alkaloids, flavonoids, and saponins. In this review, studies on herbal PDEI were reviewed and their possible therapeutic applications were discussed. Screening plants for PDE inhibitory activity may help to develop standardized phytotherapeutic products or find new sources for new lead structures with PDEI pharmacological activity. The studies discussed in this paper are mainly in vitro and for more reasonable and conclusive results, it is required to conduct in vivo and finally human and clinical tests.

Phosphodiesterase III inhibitors for heart failure

BACKGROUND

In the treatment of chronic heart failure, vasodilating agents, ACE inhibitors and beta-blockers have shown an increase of life expectancy. Another strategy is to increase the inotropic state of the myocardium : phosphodiesterase inhibitors (PDIs) act by increasing intra-cellular cyclic AMP, thereby increasing the concentration of intracellular calcium, and lead to a positive inotropic effect.

OBJECTIVES

This overview on summarised data aims to review the data from all randomised controlled trials of PDIs III versus placebo in symptomatic patients with chronic heart failure. The primary endpoint is total mortality. Secondary endpoints are considered such as cause-specific mortality, worsening of heart failure (requiring intervention), myocardial infarction, arrhythmias and vertigos. We also examine whether the therapeutic effect is consistent in the subgroups based on the use of concomitant vasodilators, the severity of heart failure, and the type of PDI derivative and/or molecule. This overview updates our previous meta-analysis published in 1994.

SEARCH STRATEGY

Randomised trials of PDIs versus placebo in heart failure were searched using MEDLINE (1966 to 2004 January), EMBASE (1980 to 2003 December), Cochrane CENTRAL trials (The Cochrane Library Issue 1, 2004) and McMaster CVD trials registries, and through an exhaustive handsearching of international abstracting publications (abstracts published in the last 22 years in the "European Heart Journal", the "Journal of the American College of Cardiology" and "Circulation").

SELECTION CRITERIA

All randomised controlled trials of PDIs versus placebo with a follow-up duration of more than three months.

DATA COLLECTION AND ANALYSIS

21 trials (8408 patients) were eligible for inclusion in the review. 4 specific PDI derivatives and 8 molecules of PDIs have been considered.

MAIN RESULTS

As compared with placebo, treatment with PDIs was found to be associated with a significant 17% increased mortality rate (The relative risk was 1.17 (95% confidence interval 1.06 to 1.30; p<0.001). In addition, PDIs significantly increase cardiac death, sudden death, arrhythmias and vertigos. Considering mortality from all causes, the deleterious effect of PDIs appears homogeneous whatever the concomitant use (or non-use) of vasodilating agents, the severity of heart failure, the derivative or the molecule of PDI used.

AUTHORS' CONCLUSIONS

Our results confirm that PDIs are responsible for an increase in mortality rate compared with placebo in patients suffering from chronic heart failure. Currently available results do not support the hypothesis that the increased mortality rate is due to additional vasodilator treatment. Consequently, the chronic use of PDIs should be avoided in heart failure patients.

Selective phosphodiesterase inhibitors for the treatment of bronchial asthma and chronic obstructive pulmonary disease

Theophylline is commonly used in the treatment of obstructive airway diseases. The identification and functional characterization of different phosphodiesterase (PDE) isoenzymes has led to the development of various isoenzyme-selective inhibitors as potential anti-asthma drugs. Considering the distribution of isoenzymes in target tissues, with high activity of PDE3 and PDE4 in airway smooth muscle and inflammatory cells, selective inhibitors of these isoenzymes may add to the therapy of chronic airflow obstruction. However, initial data from clinical trials with selective PDE3 and PDE4 inhibitors have been somewhat disappointing and have tempered the expectations considerably since these drugs had limited efficacy and their use was clinically limited through side effects. The improved understanding of the molecular biology of PDEs enabled the synthesis of novel drugs with an improved risk/benefit ratio. These 'second generation' selective drugs have produced more promising clinical results not only for the treatment of bronchial asthma but also for the treatment of chronic obstructive pulmonary disease.

Intratracheal administration of phosphodiesterase III inhibitor attenuates bronchoconstriction in cats: a preliminary report

The effects of intratracheal administration of MKS 492, a selective phosphodiesterase (PDE) III inhibitor, were studied in five anesthetized bronchoconstricted cats. The animals were challenged by four repeated doses of intratracheal methacholine (67 micrograms/kg), and the degree of bronchoconstriction was assessed from increases in respiratory system resistance (Rrs). All animals demonstrated good bronchoconstrictive responses (i.e., 86-99% increases in Rrs) to methacholine without tachyphylaxis. On a separate day, the cats received the same four doses of methacholine after being pretreated with either intratracheal saline or three different doses of MKS 492 (0.17, 1.7, and 17 micrograms/kg). The increases in Rrs with 1.7 micrograms/kg [52.6 +/- 8.4% (SE)] and 17 micrograms/kg of MKS 492 (44.4 +/- 10.1%) were smaller than those with saline pretreatment (88.1 +/- 16.8%) (P < 0.05). There were no treatment-associated changes in mean arterial pressure or heart rate during administration of MKS 492. We conclude that intratracheal MKS 492 effectively reduced methacholine-induced bronchoconstriction in a dose-dependent fashion without substantial systemic effects. These preliminary results suggest that inhalation of isozyme-selective PDE inhibitors may deserve consideration for clinical trials provided that more extensive preclinical investigations justify such trials.

The role of phosphodiesterase inhibitors in heart failure

Myocardial contractility is dependent on available intracellular calcium and this can be enhanced by increasing intracellular cyclic adenosine monophosphate. One way of achieving this is by inhibiting the phosphodiesterase III enzyme. Over the last 15 years, a number of new drugs with this mechanism of action have been studied in man and have been found not only to have a positive inotropic action on the heart but also a vasodilating action on peripheral blood vessels. This combination of effects produces favourable haemodynamic improvement in patients with chronic heart failure. While some smaller studies showed that this did translate into an improvement in symptoms and functional capacity, a large well-designed and controlled clinical trial showed that survival was decreased when milrinone was used in target daily doses of 40 mg. For this reason, chronic long-term oral therapy with phosphodiesterase III inhibitors is not currently being actively pursued. They may still have a role as acute short-term therapy in severely ill patients who do not respond adequately to optimal standard drug therapy. Milrinone has been one of the most widely studied drugs in this regard. Even during short-term administration, its use should be closely monitored for any evidence of an increase in ventricular arrhythmias or decrease in ventricular function.

Effectiveness of imazodan for treatment of chronic congestive heart failure. The Imazodan Research Group

A 12-week, multicenter, double-blind, randomized, placebo-controlled trial of imazodan, a type III phosphodiesterase inhibitor, was conducted in 147 patients with congestive heart failure to determine clinical efficacy and safety. Patients were randomized to placebo or 2, 5 or 10 mg of imazodan administered twice daily. Patients were maintained on their standard therapy including diuretics, digoxin and an angiotensin-converting enzyme inhibitor. The mean ejection fraction was 23 +/- 10%. Exercise time increased from baseline in all 4 groups. There was no significant difference observed between the placebo group and any of the treated groups with regard to exercise time, ejection fraction, frequency of ventricular premature complexes or ventricular tachycardia. When analyzed by intent to treat, the placebo mortality was 7% (3 of 44) and the imazodan mortality was 8% (8 of 103) (p = not significant). This study failed to demonstrate that imazodan provided any benefit in exercise performance when compared with placebo.

Risks and benefits of the treatment of heart failure. Current status

Congestive heart failure is an increasingly common patient problem. It is a multisystem disease that involves not only the heart but also the kidneys and neurohormonal systems. Any treatment for heart failure should address depressed contractility and exercise intolerance, as well as control compensatory mechanisms. There are many different approaches to the treatment of congestive heart failure: among the drugs used are diuretics, digitalis compounds, nitrates, calcium channel blockers, beta-blockers, beta-agonists, vasodilators, angiotensin-converting enzyme (ACE) inhibitors and the new phosphodiesterase inhibitors. The therapy usually involves a multiple drug treatment plan to achieve the maximum effect for the patient with the lowest incidence of side effects. Heart failure involves a large spectrum of patients with left ventricular dysfunction, and success at achieving treatment goals with these patients will vary with the severity of that symptom. A major concern is that increasing contractility may further damage the myocardium and shorten the survival of these patients, although there is as yet no evidence of such shortening. The new phosphodiesterase inhibitor drugs are an exciting development in the treatment of heart failure, because they add a dimension to the treatment for patients who are not sufficiently improved by a regimen of digoxin, diuretics and ACE inhibitors. Any new heart failure medication should be able to improve rest and exercise haemodynamics, maintain its benefits when given orally and result in an improved exercise capacity and quality of life, and prolonged survival.

Overview of cardiovascular physiologic and pharmacologic aspects of selective phosphodiesterase peak III inhibitors

In recent years several agents have been developed as selective inhibitors of the low Michaelis constant cyclic adenosine monophosphate (cAMP) phosphodiesterase (peak III), a fraction of the cyclic nucleotide phosphodiesterases that is specific for the metabolic breakdown of cAMP. These agents are often referred to as PDE III inhibitors and share similar pharmacologic profiles. The principal interest in these agents--the therapy of congestive heart failure--is based on the cardiovascular effects that result from sequential elevation of intracellular cAMP, cAMP-dependent protein kinase activation, phosphorylation of cellular proteins and change in cellular function. The selective PDE III inhibitors have a triad of cardiovascular activities that provide hemodynamic benefit to patients with congestive heart failure. As a representative drug from this class of compounds, milrinone increases myocardial contractility, increases the rate of ventricular relaxation, and unloads the heart by way of a peripheral vasodilator action. The selective PDE III inhibitors offer a new modality for oral therapy of congestive heart failure.