Cyclic AMP-dependent and cyclic AMP-independent actions of a novel cardiotonic agent, OPC-8212

Effects of phosphodiesterase (PDE) inhibitors on human ether-a-go-go related gene (hERG) channel activity

It is presumed that phosphodiesterase (PDE) inhibitors have two mechanisms for inhibition of hERG currents in the acute applications to cells: direct channel block, and downregulation of human ether-a-go-go related gene (hERG) activities by PKA-dependent pathway mediated phosphorylation through their inhibitory effects against PDE enzymes. However, it is unknown whether PDE inhibition contributes to the inhibitory effects of PDE inhibitors on hERG currents. This study examined the effects of various PDE inhibitors on hERG currents using both the whole-cell and perforated patch-clamp techniques in hERG transfected CHO-K1 cells. The study also investigated the contribution of the PKA-dependent pathway to the inhibitory effects of PDE inhibitors on hERG currents. Of the PDE inhibitors tested, vinpocetine, erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA), vesnarinone, rolipram and dipyridamole decreased hERG currents in a concentration-dependent manner. Vinpocetine and vesnarinone markedly decreased the hERG current with an IC (50)of 0.13 and 20.6 microm, respectively, at comparatively low concentrations. Furthermore, vinpocetine caused a cumulative block of hERG currents. Milrinone, amrinone and zaprinast had no effect on the hERG current up to 100 microm. Of the PDE3 inhibitors (vesnarinone, amrinone and milrinone), only vesnarinone showed an hERG inhibitory effect. The inhibitory effects of vinpocetine and vesnarinone were not significantly affected by the co-application of protein kinase inhibitors. Furthermore, the protein kinase activators had no effect on hERG currents. It is concluded that vinpocetine and vesnarinone block the hERG channel directly, and that the inhibitory effect on intracellular PDE in the PKA-dependent pathway may not be involved in the inhibition of hERG currents in hERG transfected CHO-K1 cells.

Effects of vesnarinone on peripheral circulating levels of cytokines and cytokine receptors in patients with heart failure: a report from the Vesnarinone Trial

STUDY OBJECTIVES

Proinflammatory cytokines may contribute to disease progression in heart failure by virtue of the direct toxic effects that these molecules exert on the heart and the circulation. Accordingly, there is interest in developing therapeutic agents with anticytokine properties that might be used as adjunctive therapy to modulate proinflammatory cytokine levels in patients with heart failure. Previous experimental studies suggested that vesnarinone has potent anticytokine properties in vitro. Therefore, we examined the effects of vesnarinone on circulating levels of cytokines and cytokine receptors in a large-scale, multicenter, clinical trial of patients with moderate-to-advanced heart failure: the Vesnarinone Trial (VEST).

METHODS

Circulating levels of tumor necrosis factor (TNF)-alpha, soluble TNF-receptor type 1, soluble TNF-receptor type 2, as well as interleukin (IL)-6 and soluble IL-6 receptor (sIL-6R) were measured on plasma samples by enzyme-linked immunosorbent assay at baseline and at 24 weeks in patients who were receiving placebo (n = 352), 30 mg of vesnarinone (n = 367), and 60 mg of vesnarinone (n = 327).

RESULTS

Treatment with 30 mg and 60 mg of vesnarinone had no effect on circulating levels of cytokines or cytokine receptors in patients with advanced heart failure over a 24-week period.

CONCLUSIONS

In contrast to the potent anticytokine effects observed with vesnarinone in experimental studies in vitro, the results of this clinical study suggest that vesnarinone does not have any measurable anticytokine effects in vivo in patients with moderate-to-advanced heart failure.

The role of neurohormonal antagonists in hibernating myocardium

Hibernating myocardium is characterized by chronic reduction of myocardial blood flow due to obstructive coronary artery disease, causing reversible left ventricular dysfunction and flow-metabolism mismatch. The condition is unstable and increasing demand may lead to further left ventricular dysfunction or necrosis causing death or worsening heart failure. Recognition of the condition is difficult and requires complex cardiac imaging protocols. Treatment protocols are also poorly defined. This review addresses both the diagnostic and therapeutic aspects of hibernating myocardium.

Effect of 3,4-dihydro-6-[4-(3,4-dimethoxybenzoyl)-1-piperazinyl]-2(1H)- quinolinone (vesnarinone) on the growth of gastric cancer cell lines

Vesnarinone (OPC-8212; 3,4-dihydro-6-[4-(3,4-dimethoxybenzoyl)-1-piperazinyl]-2(1H)-quinolinone ) is a synthetic oral cardiotonic agent that has been used for the treatment of patients with congestive heart failure. Six days of treatment with 30 microg/ml of vesnarinone induced 20-80% growth inhibitions in five out of six gastric carcinoma cell lines examined. Cell cycle analysis revealed that the vesnarinone-sensitive TMK-1 gastric cancer cell line exhibited a significant G0-G1 arrest without evidence of apoptotic cell death induction after 48 h of treatment. Interestingly, this phenomenon was preceded by a marked reduction in the expression of cyclin A, D1 and E as well as cyclin-dependent kinase 2 (CDK2). On the other hand, no significant change was observed in the expression of p21(Waf1/Cip1), p27Kip1 nor various growth factors and their receptor genes. Overall these results indicate that vesnarinone inhibits the growth of gastric cancer cells by down-regulating G1 cyclins and CDK2 to induce G0-G1 arrest through a pathway different from that of cyclin inactivation by p21(Waf1/Cip1) or p27Kip1.

The effect of vesnarinone on TNF alpha production in human peripheral blood mononuclear cells and microglia: a preclinical study for the treatment of multiple sclerosis

Vesnarinone (OPC-8212) is a synthetic quinolinone derivative with inotropic and immunomodulatory effects. Vesnarinone has been shown to inhibit tumor necrosis factor-alpha (TNF alpha) produced by mitogen stimulated macrophages, and to inhibit phosphodiesterase (PDE) type III in cardiac muscle. TNF alpha and interferon-gamma (IFNgamma) have been implicated in the pathogenesis of autoimmune diseases, and both cytokines are targets for therapeutic intervention. IFNgamma can enhance autoimmune disease through direct effects, and indirectly by priming macrophages to produce TNF alpha. In this study, we demonstrate that while vesnarinone enhances basal TNF alpha levels, it inhibits TNF alpha production in peripheral blood mononuclear cells from multiple sclerosis (MS) patients and healthy donors stimulated with lipopolysaccharide (LPS) or primed with IFNgamma and stimulated with suboptimal doses of LPS. In addition, vesnarinone inhibited TNF alpha production in primary adult human microglial cultures. However, in contrast to rolipram, another TNF alpha inhibiting agent, vesnarinone failed to inhibit TNF alpha production by myelin basic protein specific T-cell lines. As oral TNF inhibitors are currently being considered in the USA for clinical application in MS, the implications of our findings on the development of vesnarinone for treatment of MS are discussed.

Effect of vesnarinone on cardiac function in patients with severe congestive heart failure

BACKGROUND

Vesnarinone has yielded controversial results on morbidity in patients with congestive heart failure. We tested the hypothesis that vesnarinone may have a beneficial effect on cardiac remodeling and function.

METHODS

Thirty-four patients with left ventricular ejection fraction (LVEF) <30% (17 treated with vesnarinone) underwent an echocardiography at baseline and at 12+/-5 months. Left ventricular end-diastolic and end-systolic volume, mitral regurgitation, diastolic filling, and right ventricular area change were quantified and compared.

RESULTS

When the vesnarinone group was considered as a whole, there was no significant effect of vesnarinone on cardiac systolic and diastolic function or remodeling. However, an increase in LVEF >7% was observed in six of the vesnarinone patients and none of the control group. Vesnarinone improved right and left ventricular systolic function significantly in patients with initial LVEF <25%.

CONCLUSIONS

In severe congestive heart failure, vesnarinone induces variable responses but improves biventricular performance in patients with the most impaired initial function.

Action-potential duration and contractility in canine cardiac tissues: action of inotropic drugs

1. Inotropic and electrophysiologic effects of veratrine, vesnarinone, d-sotalol and tetraethylammonium (TEA) were compared. Action-potential duration (APD) and contractility were measured in isolated canine Purkinje fiber and ventricular trabecular muscle preparations by using standard microelectrode techniques. Each drug significantly increased APD and force development in either tissue. 2. Drug-induced increases in force development were normalized to increases in APD. The order of efficacy was found to be vesnarinone>veratrine>TEA in ventricular myocardium, whereas it was veratrine>>vesnarinone=d-sotalol=TEA in Purkinje fibers. 3. The force-APD relation was linear for all drugs in the concentrations used. 4. Simultaneous measurements of APD, force development and intracellular sodium ion activity (a(i)Na) in the presence of either veratrine or lidocaine indicated a linear relation between force development and changes in a(i)Na. 5. The relation between APD and force development was different in ventricular and Purkinje fiber preparations. Differences in the veratrine sensitivity of the force-APD relation observed between Purkinje and ventricular preparations suggest that a(i)Na-dependent changes in Na+/Ca2+ exchange may play a more important role in regulation of force generation in Purkinje fibers than in ventricular myocardium.

Effect of CYP3A inhibition on vesnarinone metabolism in humans

OBJECTIVE

To identify the cytochrome P450 (CYP) enzymes involved in the conversion of vesnarinone to it main primary metabolite OPC-18692 and to investigate the effect of CYP3A inhibition on the pharmacokinetics of vesnarinone in vivo.

METHODS

Formation of the primary vesnarinone metabolite OPC-18692 was measured in microsomes from AHH-1 TK +/- cells heterologously expressing CYP1A1, CYP1A2, CYP2A6, CYP2C9, CYP2D6, CYP2E1, or CYP3A4. The pharmacokinetics of vesnarinone and OPC-18692 were defined for 12 health white men after oral administration of 60 mg vesnarinone before and after CYP3A inhibition, which was produced by pretreatment with erythromycin. CYP3A inhibition was verified with erythromycin breath test.

RESULTS

In vitro, expressed CYP2E1 and CYP3A4 produced significant amounts of OPC-18692 with the higher formation rate observed by CYP3A4 (12.3 pmol/pmol VYP3A4 per 2 hours versus 1 pmol/pmol CYP2E1 per 2 hours). In vivo, the area under the concentration-time curve extrapolated to infinity (AUC[infinity]) of vesnarinone after pretreatment with erythromycin increased from 133 +/- 26 micrograms.hr/ml to 202 +/- 47 micrograms.hr/ml (p < 0.001), and the half-life increased from 36.5 +/- 9.6 hours to 46.2 +/- 9.2 hours (p < 0.01). Clearance decreased from 372 +/- 68 ml/min to 256 +/- 49 ml/min (p < 0.001). These changes in the disposition of vesnarinone were accompanied by a decrease in plasma concentration of the metabolite OPC-18692 so that the AUC(0-48) was reduced from 1311 +/- 513 micrograms.hr/ml to 850 +/- 148 micrograms.hr/ml (p < 0.001). The total amount of vesnarinone excreted in the urine up to 168 hours after administration increased after erythromycin pretreatment (p < 0.001). Although renal clearance did not change, OPC-18692 was not detectable in the urine. The erythromycin breath test showed significant inhibition after pretreatment with erythromycin (p < 0.001).

CONCLUSIONS

CYP2E1 and CYP3A4 are involved in the phase I metabolism of vesnarinone. Inhibition of CYP3A activity in vivo increases the plasma concentration of vesnarinone and delays its elimination in humans so that monitoring of its plasma levels may be helpful in preventing concentration-related toxicity when CYP3A activity is impaired. Whether CYP3A induction and altered CYP2E1 activity may also change the in vivo disposition of vesnarinone remains to be determined.

Dose dependence of chronic positive inotropic effect of vesnarinone in patients with congestive heart failure due to idiopathic or ischemic cardiomyopathy

Vesnarinone is a novel oral agent that improves survival and symptoms of patients with dilated cardiomyopathy. Although it is thought to have positive inotropic effects, clinical data supporting this mechanism in patients with severe heart failure remain scant. The present study tested whether 3 months of oral vesnarinone therapy increases the inotropic state and whether this response is dose dependent. Twenty-one patients with dilated cardiomyopathy (New York Heart Association class III to IV) were randomized to 30 mg/day (n = 11) or to 60 mg/day (n = 10) of vesnarinone. Cardiac function was assessed before and after therapy by radionuclide ventriculography to measure left ventricular volume and flow and by noninvasive measurement of the central aortic pressure wave. The inotropic effect of vesnarinone was assessed by a recently validated index equal to the ratio of left ventricular maximal ventricular power divided by the square of end-diastolic volume (PWRmax/ EDV2). This ratio is sensitive to inotropic change but is minimally altered by chamber loading. After 3 months of 60 mg/day therapy, PWRmax/EDV2 increased by 28 +/- 32%. Ejection fraction and cardiac output also increased by 21 +/- 14% and 14 +/- 14%, respectively, and arterial load decreased by 10.5 +/- 12.4% (all p < 0.005). End-systolic volume also declined by 7 +/- 10%, suggesting reverse remodeling. These changes were smaller and none achieved statistical significance at the 30 mg/day dose (e.g., 14.2 +/- 35.4% for PWRmax/ EDV2). Heart rate was unchanged with either dose. Thus, chronic vesnarinone treatment dose modestly raises the inotropic state and lowers afterload in patients with dilated cardiomyopathy in a dose-dependent fashion.

Vesnarinone is a selective inhibitor of macrophage TNF(alpha) release

Vesnarinone is an experimental drug that has been used successfully in the treatment of congestive heart failure patients. In this report we investigate the effect of vesnarinone on the cytokine secretory products of mononuclear phagocytes. In a concentration-dependent manner, the drug inhibits the endotoxin(LPS)-stimulated release of tumor necrosis factor (TNF) alpha and suppresses interleukin(IL)-6 release, but does not affect the release of IL-1 alpha, IL-10 and leukemia inhibitory factor (LIF) by mouse peritoneal macrophages. Using competitive polymerase chain reaction (PCR) analyses, we find that vesnarinone significantly reduces TNF(alpha), but not IL-10 mRNA. In addition to LPS, the drug inhibits TNF(alpha) release induced by several other stimuli. The inhibitory effect of the drug on the TNF(alpha) biosynthesis can be observed in differentiated human monocytes, in macrophage cell lines, and in synovial adherent cells from rheumatoid arthritis patients. Although the precise mode of action of vesnarinone in the signal transduction pathway leading to the selective inhibition of TNF(alpha) is not known, the drug might be useful in the treatment of diseases involving that cytokine.

Comparison of the Electromechanical Effects of Vesnarinone and Amrinone in Isolated Dog Purkinje Strands and Ventricular Trabeculae

BACKGROUND: Conventional microelectrode techniques were used to compare the concentration-dependent effects of vesnarinone (0.1-100 µM) and amrinone (1 µM-1 mM) on action potential duration (APD) and developed force in both isolated dog ventricular trabeculae and Purkinje strands. METHODS AND RESULTS: Both drugs increased contractility of trabecular muscle preparations, while, in Purkinje strands, vesnarinone failed to increase developed force during continuous pacing at 2 Hz. Vesnarinone lengthened APD in both preparations; although this effect was more marked in Purkinje strands. Ventricular muscle APD was not affected by amrinone (1 µM to 1 mM), while, in Purkinje strands, amrinone produced a biphasic effect on APD. Low concentrations (1-100 µM) of amrinone shortened Purkinje fiber APD, while only the highest concentration (1 mM) used lengthened APD. In addition, in Purkinje strand preparations the effects of vesnarinone (10 µM) on APD and developed force were proportional to pacing cycle length at frequencies slower than 2 Hz; however, at frequencies faster than 2 Hz vesnarinone decreased developed force while APD was lengthened. In ventricular trabecular muscle preparations, the effects of vesnarinone were not affected by frequency. CONCLUSIONS: These results indicate clear differences between the effects of vesnarinone and amrinone in isolated cardiac preparations. These differences in experimental effects in isolated cardiac preparations may help provide an explanation for the disappointing clinical response of patients in heart failure to amrinone, while vesnarinone has appeared to be beneficial.

Mechanism of action of OPC-8490 in human ventricular myocardium

BACKGROUND

The quinolinone compounds OPC-8212 (vesnarinone), OPC-18790, and OPC-8490 are members of a family of unique positive inotropic compounds that have no positive chronotropic effects. In subjects with heart failure, the prototypic compound OPC-8212 may reduce morbidity and mortality at low doses but increase mortality at high doses.

METHODS AND RESULTS

To further characterize the inotropic mechanism(s) of action of these compounds, we investigated the effects of OPC-8490, a water-soluble quinolinone, on the inotropic response, inhibition of phosphodiesterase (PDE), and action potential in human ventricular myocardial preparations. In isolated right ventricular trabeculae and membranes prepared from left ventricular myocardium, OPC-8490 produced dose-related positive inotropic effects, inhibited type III PDE activity, and prolonged action potential. Comparative experiments with other PDE inhibitors, sodium channel agonists, and potassium channel antagonists indicated that the positive inotropic effects are due to PDE inhibition, whereas the action potential effects of OPC-8490 are due to effects on ion channels.

CONCLUSIONS

We conclude that OPC-8490 produces selective positive inotropic effects because of type III PDE inhibition combined with ion channel effects, with the latter property inhibiting the positive chronotropic response usually associated with agents that increase intracellular cAMP concentrations.

Effects of a novel cardiotonic agent, Org 9731, on force and aequorin light transients in intact ventricular myocardium of the dog: involvement of a cyclic AMP-mediated mechanism and myofibrillar responsiveness to Ca2+ ions

The action of a novel cardiotonic agent, Org 9731 (4-fluoro-N-hydroxy-5, 6-dimethoxy-benzo[b]thiophene-2-carboximidamide methanesulphonate), on intracellular aequorin light transients and isometric contractions was investigated in ventricular trabeculae isolated from dogs. The positive inotropic effect of Org 9731 at 3 microM and higher (up to 0.1 mM) was associated with an increase in the amplitude of the intracellular Ca2+ transient, but the effect of the compound at 0.3 and 1 mM was accompanied by a decrease of the transient. The maximum inotropic response to Org 9731 was approximately 70% of the maximum response to isoproterenol, while the maximum increase in the amplitude of Ca2+ transients produced by Org 9731 was about 30% of the maximum increase induced by isoproterenol. The duration of isometric contractions was prolonged by Org 9731 at 0.3 and 1 mM, with accompanying prolongation of the duration of light transients. The concentration-response curve for the positive inotropic effect of Org 9731 was markedly shifted by carbachol (3 microM), being moved to the right and downward, and the maximum response to Org 9731 was about 10% of that to isoproterenol in the presence of carbachol. Carbachol abolished the increase in the light transient and the accumulation of adenosine 3',5'-cyclic monophosphate (cyclic AMP) induced by Org 9731. These results indicate that Org 9731 increases cardiac contractility, mainly through the accumulation of cyclic AMP up to a concentration of 0.1 mM and also by increasing the responsiveness of myofibrils to Ca2+ ions at 0.3 mM and higher in association with the attenuation of Ca2+ transients. The structure-activity relationship implies that the introduction of a fluorine atom at position 4 of the benzothiophene ring of Org 30,029 attenuated its Ca(2+)-sensitizing action but markedly increased the activity of mechanisms dependent on cyclic AMP.

The effects of various drugs on the myocardial inotropic response

1. The signal transduction process mediated by cyclic AMP that leads to the characteristic positive inotropic effect (PIE) in association with a positive lusitropic effect (acceleration of rate of twitch relaxation) has been well established. Relationships between accumulation of cyclic AMP, changes in intracellular Ca2+ transients and the PIE differ, however, depending on the mechanism of particular drugs that affect different steps in the metabolism of cyclic AMP. Selective partial agonists of beta 1-adrenoceptors and inhibitors of phosphodiesterase (PDE) III cause the accumulation of less cyclic AMP for a given PIE than does isoproterenol. In addition, in aequorin-microinjected canine ventricular muscle, selective inhibitors of PDE III, OPC 18790 and Org 9731, produced smaller decreases in the responsiveness of myofilaments to Ca2+ ions than isoproterenol, while a partial agonist of beta 1-adrenoceptors, denopamine, elicits a decrease in Ca2+ responsiveness of the same extent as does isoproterenol. 2. Activation of myocardial alpha 1-adrenoceptors, as well as stimulation of receptors for endothelin and angiotensin II, which accelerates hydrolysis of phosphoinositide (PI) to result in production of inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG) are associated with very similar inotropic regulation: (1) the dependence on the species of animals of induction of the PIE; (2) an excellent correlation between the extent of acceleration of hydrolysis of PI and the PIE; (3) isometric contraction curves associated with a negative lusitropic effect; (4) the PIE associated with increases in myofibrillar responsiveness to Ca2+ ions; and (5) the selective inhibition of the PIE by an activator of protein kinase C (PKC), phorbol 12,13-dibutyrate (PDBu), with little effect on the PIE of isoproterenol and Bay k 8644. 3. A novel class of cardiotonic agents, namely, Ca2+ sensitizers such as EMD 53998 and Org 30029, act on the Ca(2+)-binding site of troponin C, increasing the affinity of these sites for Ca2+ ions, or at the actin-myosin interface to facilitate the cycling of cross-bridges. These agents produce a PIE with little change or decrease in Ca2+ transients and may bring about a significant breakthrough in the development of drugs for reversal of myocardial failure in the treatment of congestive heart failure.

The inotropic mechanism of the phosphodiesterase inhibitor OPC 3911 alone and in combination with rolipram, studied in papillary muscles of ferret and guinea-pig and isolated myocytes of guinea-pig ventricular muscle

OPC 3911 is a potent inhibitor and PDE III is a specific inhibitor in cardiac muscle. The effects of the drug alone and in combination with the non-inotropic PDE IV inhibitor rolipram were analysed using hearts from guinea-pigs and ferrets. OPC 3911 had an EC50 value of 0.1 microM. At 0.1 microM peak force was increased by 50.7 +/- 7.6% (n = 6, P < 0.001), time to peak tension (TPT) reduced by 18.7 +/- 5.6% (n = 6, P < 0.05). Time to half relaxation (THR) was prolonged by 19 +/- 4.2% (n = 6, P < 0.001). After addition of rolipram (30 microM), there was a potentiation of peak force at all concentrations of OPC 3911. At 0.1 microM OPC rolipram increased peak force by 82.8 +/- 8.9% (n = 6, P < 0.001), reduced TPT by 73 +/- 6% (n = 6, P < 0.005) and increased THR by 27 +/- 5% (P < 0.01). OPC 3911 shortened action potential duration (APD) at 50% repolarization by 5.3 +/- 2.5% (n = 6, P < 0.05). Addition of rolipram prolonged APD by 3.7 +/- 2.5% (n = 6, P < 0.05). Second inward current (Isi) was increased at 3 microM OPC 3911 by 46 +/- 6% (n = 6, P < 0.05). The combination of OPC 3911 and rolipram intensified the Isi to 101 +/- 5% (n = 3). Rolipram slowed the rate of restitution and the onset of restitution was prolonged. Relative maximum post-extrasystolic potentiation was reduced in the presence of OPC 3911 from 67 +/- 5% to 45 +/- 6%. Adding rolipram caused potentiation of 55 +/- 6%. OPC 3911 increased the recirculation fraction of activator calcium from 0.36 to 0.42 (n = 10, P < 0.05). After addition of rolipram the recirculation fraction was 0.41 +/- 0.04 (n = 10, P < 0.05). The results suggest that rolipram exerts its potentiating effect on OPC 3911 via an increased Isi.

Inhibition of cytokine production by a new inotropic agent, vesnarinone, in human lymphocytes, T cell line, and monocytic cell line

Vesnarinone, a recently synthesized quinolinone derivative with positive inotropic properties, has been reported to improve survival of patients with congestive heart failure. However, the mechanisms that contribute to the increased survival are unknown. In this study, we showed vesnarinone had inhibitory effects on the production of tumor necrosis factor-alpha, interferon-gamma, interleukin-1 beta and interleukin-2 by stimulated human peripheral blood mononuclear cells, human Jurkat T cell line and THP-1 monocytic cell line. Vesnarinone may exert its beneficial effect on patients with congestive heart failure, in part, by its immunomodulating activity.

Cardiotonic actions of selective phosphodiesterase inhibitors in rat isolated ventricular cardiomyocytes

1. The contractile effects of the novel cardiotonic agent HN-10200 (2-[3-methoxy-5-methylsulphinyl-2-thienyl]-1H-imidazo-[4,5-c]-p yri dine hydrochloride), were examined and comparisons made with the responses obtained to a structurally similar compound, sulmazole, and to a number of other compounds which are known to inhibit phosphodiesterase (PDE) isoenzymes with differing selectivities; namely, enoximone (PDE III inhibitor), Ro 20-1724 (PDE IV inhibitor) and 3-isobutyl-1-methylxanthine (non-selective PDE inhibitor). 2. Contractile function, as measured by mechanical shortening, and biochemical systems involving cyclic AMP were investigated in ventricular cardiomyocytes isolated from adult Sprague-Dawley rats (200-250 g). 3. HN-10200 exerted a concentration-dependent (10(-8) M-10(-4) M) positive contractile effect, which was independent of alpha- or beta-adrenoceptor, or histamine receptor stimulation. 4. The efficacies of the contractile responses to the PDE inhibitors were of the order: HN-10200 > IBMX > sulmazole > enoximone and maximum stimulations, which were obtained at concentrations of 10(-4) M, were 54 +/- 4%, 41 +/- 7%, 38 +/- 7% and 26 +/- 5% (mean +/- s.e.) greater than basal levels, respectively (n = 6); the basal value of contractile amplitude (dL), in the absence of PDE inhibitors was 7.39 +/- 0.18% (mean +/- s.e.). Ro 20-1724 did not have any effect on contractile activity. 5. Due to low basal levels of cyclic nucleotides in isolated cells, accumulation of cyclic AMP due to the presence of the PDE inhibitors was detected only when the levels of cyclic nucleotide were enhanced with forskolin (10 microM). 6. The PDE inhibitors increased levels of cyclic AMP only at concentrations> 10-4 M. HN-10200 and sulmazole had similar concentration-dependent profiles for the accumulation of cyclic AMP; their potencies were lower than that of IBMX (concentrations of forskolin required to increase cyclic AMP by 4 pmol mg-1 protein, in the presence of maximum concentrations of the PDE inhibitors, were 13 +/- 311M, 14 +/- 3 JAM and 3 +/- 0.6 JAM [mean +/- s.e.], respectively).7. These results indicate that a similar mechanism, probably through a weak inhibition of the cyclic AMP-specific PDE isoenzymes, is responsible for the increase in levels of cyclic AMP by HN-10200 and sulmazole. However, cyclic AMP is only partially responsible for the positive contractile effect of HN-10200 and, similarly, sulmazole and IBMX. The lack of apparent increase in levels of cyclic AMP by enoximone, highlights its degree of selectivity for the PDE III isoenzyme, such that the PDE IV isoform is still present in sufficient quantity to degrade cyclic AMP within the cell. On the other hand,the potent action of Ro 20-1724 on accumulation of cyclic AMP, in addition to the lack of effect on contractile function, is in agreement with the selectivity of this compound for the PDE IV isoenzyme and compartmentalization of cyclic AMP in rat isolated ventricular cardiomyocytes.

The development of positive inotropic agents for chronic heart failure: how have we gone astray?

Because cardiac contractility is impaired in chronic heart failure, many pharmacologic agents have been developed to increase the contractile state of the failing heart. These drugs produce impressive hemodynamic effects, but long-term therapy has failed to produce clinical benefits and has increased mortality in treated patients. This experience has led many physicians to suggest that positive inotropic therapy be abandoned as a therapeutic approach for heart failure. However, recent studies suggest that the efficacy and safety of many (if not all) positive inotropic drugs can be greatly enhanced by reducing the dose of these drugs. The importance of dose is dramatically illustrated by the results of trials with vesnarinone, which decreases mortality when used in low doses but increases mortality when administered in doses only twice as large. Although low doses of positive inotropic drugs may be clinically superior to high doses, it is not clear that these low doses exert significant inotropic effects. All positive inotropic drugs exert actions on the circulation in addition to stimulating the heart, and these ancillary properties may be particularly important at low doses of these drugs. Low doses of milrinone and pimobendan may act primarily to dilate peripheral blood vessels; low doses of digitalis may exert only neurohormonal effects, and low doses of vesnarinone may act as an antiarrhythmic agent. If the noninotropic actions of low doses account for the therapeutic benefits of these drugs, then the positive inotropic effects seen at high doses may be primarily responsible for their adverse effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Ionic basis for OPC-8212-induced increase in action potential duration in isolated rabbit, guinea pig and human ventricular myocytes

Changes in transmembrane ionic currents induced by OPC-8212 (3,4-dihydro-6-[4-(3,4-dimethoxybenzoyl)-1-piperazinyl]-2(1H)-quinoline) , a recently introduced positive inotropic agent which lengthens cardiac action potential duration, were examined using whole-cell voltage-clamp techniques in single rabbit, guinea pig and human ventricular myocytes. In rabbit, OPC-8212 (12 mumol/l) significantly increased membrane action potential duration measured at 90% of repolarization by an average of 88 ms (from 462 +/- 25 to 550 +/- 35 ms, n = 4; P < 0.05). In rabbit this increase in duration was not associated with significant changes in either the inward rectifier or transient outward K+ currents. The magnitude of the secondary inward current evoked from a holding potential of -50 mV was significantly increased by 97 +/- 8% (n = 6; P < 0.01) while a demonstrable delayed rectifier outward current could not be identified in the rabbit myocytes examined at room temperature. In guinea pig ventricular myocytes, where the delayed rectifier was large, 12 mumol/l OPC-8212 significantly depressed the current by 58 +/- 10% (n = 6; P < 0.01). The effects of OPC-8212 in human ventricular myocytes obtained from the explanted heart of a single patient having an idiopathic cardiomyopathy most closely resembled those observed in isolated rabbit ventricular myocytes. Thus, in rabbit and a few human ventricular myocytes examined at room temperature, OPC-8212 appeared to lengthen cardiac membrane action potential duration primarily by increasing the amplitude of the secondary inward current believed to primarily represent current through L-type Ca2+ channels. In guinea pig preparations, OPC-8212 also decreased the delayed rectifier outward K+ current which also would account for an increase in action potential duration. OPC-8212 could not be demonstrated to affect Na+ current inactivation in a manner similar to that produced by 1 mg/l veratrine, a recognized Na+ channel agonist, which dramatically slowed this process.

Effects of vesnarinone on morbidity and mortality in patients with heart failure. Vesnarinone Study Group

BACKGROUND

Inotropic therapy, other than with digitalis glycosides, has had limited success in patients with chronic congestive heart failure. We investigated whether vesnarinone, a new positive inotropic agent, reduces morbidity and mortality and improves the quality of life of patients with symptomatic heart failure.

METHODS

Patients receiving concomitant therapy with digoxin (87 percent) and an angiotensin-converting-enzyme inhibitor (90 percent) who had ejection fractions of 30 percent or less were randomly assigned to receive double-blinded therapy with 60 mg of vesnarinone per day, 120 mg of vesnarinone per day, or placebo. Afer 253 patients had been enrolled, randomization to the 120-mg vesnarinone group had to be stopped because of a significant increase in early mortality in this group. Thereafter, patients were randomly assigned only to 60 mg of vesnarinone per day (a total of 239 patients) or placebo (a total of 238 patients).

RESULTS

Significantly fewer patients in the group receiving 60 mg of vesnarinone than in the group receiving placebo (26 vs. 50 patients; P = 0.003) died or had worsening heart failure during the six-month study period. The reduction in risk was 50 percent (95 percent confidence interval, 20 to 69 percent). Similarly, there was a 62 percent reduction (95 percent confidence interval, 28 to 80 percent) in the risk of dying from any cause among the patients receiving vesnarinone. Furthermore, quality of life improved to a greater extent in the vesnarinone group than in the placebo group over 12 weeks (P = 0.008). The principal side effect associated with vesnarinone was reversible neutropenia, which occurred in 2.5 percent of the patients.

CONCLUSIONS

Six months of therapy with 60 mg of vesnarinone per day resulted in lower morbidity and mortality and improved the quality of life of patients with congestive heart failure. However, a higher dose of vesnarinone (120 mg per day) increased mortality, suggesting that this drug has a narrow therapeutic range; the long-term effects of vesnarinone are unknown.

The cytosolic acidification in rat parotid cells is associated with an increase in cytosolic Ca2+ concentration

A transient decrease in cytosolic pH ([pH]i) in rat parotid cells was evoked by the addition of carbachol (CCh), phenylephrine, or substance P, whereas isoproterenol and dibutyryl cyclic AMP had little or no effect on [pH]i. The decrease in [pH]i induced by the Ca(2+)-mobilizing agonists was also observed in Ca(2+)-free medium, but not when the intracellular Ca2+ stores were previously depleted. Ionomycin and thapsigargin elicited a decrease in [pH]i with an increase in cytosolic Ca2+ concentration ([Ca2+]i). The protein kinase C activator and inhibitor had no effect on the agonist-induced decrease in [pH]i. These results suggest that the cytosolic acidification is associated with an increase in [Ca2+]i.

Usefulness of OPC-8212, a quinolinone derivative, for chronic congestive heart failure in patients with ischemic heart disease or idiopathic dilated cardiomyopathy

To evaluate the safety and efficacy of the inotropic agent OPC-8212 in patients with chronic congestive heart failure, 76 patients with impaired cardiac function and diminished exercise tolerance were studied. They were randomized to 12 weeks of double-blind therapy with either 60 mg/day of OPC-8212 or placebo. The study drug was added to their baseline medical regimen. The primary study outcome was the combined outcome of the time to either mortality (of all cause) or substantial worsening of heart failure (major morbidity), whichever occurred first. Treatment with OPC-8212 significantly (p less than 0.01) decreased the combination of major morbidity/mortality over 12 weeks of therapy. Quality of life, assessed by the Sickness Impact Profile questionnaire, was significantly improved in patients receiving OPC-8212 (p less than 0.01). Furthermore, ventricular premature contractions as assessed by 24-hour Holter monitoring were not increased with OPC-8212 treatment. Although patients treated with OPC-8212 were able to reach a significantly higher peak oxygen uptake and exercise longer during symptom-limited exercise, when data were analyzed as percent change from baseline, the absolute increases were small. These results suggest that OPC-8212 is beneficial in treating patients with congestive heart failure and that further evaluation of this new inotropic agent is warranted.

Effects of a new 1,3-thiazole derivative ZSY-39 on force of contraction and cyclic AMP content in canine ventricular muscle

A newly synthesized 1,3-thiazole derivative ZSY-39 increased the force of contraction in a concentration-dependent manner in association with elevation of tissue cyclic AMP levels in the isolated canine ventricular trabeculae electrically driven at 0.5 Hz at 37 degrees C. ZSY-39 shortened the duration of isometric contractions mainly by abbreviation of the relaxation time. The maximal response to and EC50 of ZSY-39 were 0.7 (isoproterenol = 1.0) and 4.6 x 10(-5) M. Bupranolol (3 x 10(-7) M) did not affect the positive inotropic effect of ZSY-39. The time course of increases in the force of contraction induced by ZSY-39 (10(-4) M) coincided with that of cyclic AMP accumulation. The concentration-response curve for the increase in the force of contraction produced by ZSY-39 was superimposable on that of the elevation of cyclic AMP levels. Carbachol (3 x 10(-6) M) shifted the concentration-response curve for the increase in force by ZSY-39 to the right and downward, and decreased the accumulation of cyclic AMP induced by ZSY-39 (10(-4) M). ZSY-39 (10(-5) M) enhanced significantly the positive inotropic effect of isoproterenol. The relationship between the force of contraction and cyclic AMP levels after the administration of ZSY-39 was not modified by the addition of carbachol or isoproterenol. These findings indicate that cyclic AMP plays an important role in the positive inotropic effect of ZSY-39 on canine ventricular muscle.