A pathophysiological role of PDE3 in allergic airway inflammation.

Phosphodiesterase 3 (PDE3) and PDE4 regulate levels of cyclic AMP, which are critical in various cell types involved in allergic airway inflammation. Although PDE4 inhibition attenuates allergic airway inflammation, reported side effects preclude its application as an antiasthma drug in humans. Case reports showed that enoximone, which is a smooth muscle relaxant that inhibits PDE3, is beneficial and lifesaving in status asthmaticus and is well tolerated. However, clinical observations also showed antiinflammatory effects of PDE3 inhibition. In this study, we investigated the role of PDE3 in a house dust mite-driven (HDM-driven) allergic airway inflammation (AAI) model that is characterized by T helper 2 cell activation, eosinophilia, and reduced mucosal barrier function. Compared with wild-type (WT) littermates, mice with a targeted deletion of the PDE3A or PDE3B gene showed significantly reduced HDM-driven AAI. Therapeutic intervention in WT mice showed that all hallmarks of HDM-driven AAI were abrogated by the PDE3 inhibitors enoximone and milrinone. Importantly, we found that enoximone also reduced the upregulation of the CD11b integrin on mouse and human eosinophils in vitro, which is crucial for their recruitment during allergic inflammation. This study provides evidence for a hitherto unknown antiinflammatory role of PDE3 inhibition in allergic airway inflammation and offers a potentially novel treatment approach.

A Bayesian network meta-analysis on the effect of inodilatory agents on mortality.

BACKGROUND: Inodilators are commonly used in critically ill patients, but their effect on survival has not been properly studied to date. The objective of this work was to conduct a network meta-analysis on the effects of inodilators on survival in adult cardiac surgery patients, and to compare and rank drugs that have not been adequately compared in head-to-head trials. METHODS: Relevant studies were independently searched in BioMedCentral, MEDLINE/PubMed, Embase, and the Cochrane Central Register of clinical trials (updated on May 1, 2014). The criteria for inclusion were: random allocation to treatment with at least one group receiving dobutamine, enoximone, levosimendan, or milrinone and at least another group receiving the above inodilators or placebo, performed in cardiac surgical patients. The endpoint was to identify differences in mortality at longest follow-up available. RESULTS: The 46 included trials were published between 1995 and 2014 and randomised 2647 patients. The Bayesian network meta-analysis found that only the use of levosimendan was associated with a decrease in mortality when compared with placebo (posterior mean of OR=0.48, 95% CrI 0.28 to 0.80). The posterior distribution of the probability for each inodilator to be the best and the worst drug showed that levosimendan is the best agent to improve survival after cardiac surgery. The sensitivity analyses performed did not produce different interpretative result. CONCLUSION: Levosimendan seems to be the most efficacious inodilator to improve survival in cardiac surgery.

Conventional hemodynamic resuscitation may fail to optimize tissue perfusion: an observational study on the effects of dobutamine, enoximone, and norepinephrine in patients with acute myocardial infarction complicated by cardiogenic shock.

AIM: To investigate the effects of inotropic agents on parameters of tissue perfusion in patients with cardiogenic shock. METHODS AND RESULTS: Thirty patients with cardiogenic shock were included. Patients received dobutamine, enoximone, or norepinephrine. We performed hemodynamic measurements at baseline and after titration of the inotropic agent until cardiac index (CI) ≥ 2.5 L.min-1.m(-2) or mixed-venous oxygen saturation (SvO2) ≥ 70% (dobutamine or enoximone), and mean arterial pressure (MAP) ≥ 70 mmHg (norepinephrine). As parameters of tissue perfusion, we measured central-peripheral temperature gradient (delta-T) and sublingual perfused capillary density (PCD). All patients reached predefined therapeutic targets. The inotropes did not significantly change delta-T. Dobutamine did not change PCD. Enoximone increased PCD (9.1 [8.9-10.2] vs. 11.4 [8.4-13.9] mm.mm(-2); p<0.05), and norepinephrine tended to decrease PCD (9.8 [8.5-11.9] vs. 8.8 [8.2-9.6] mm.mm-2, p = 0.08). Fifteen patients (50%) died within 30 days after admission. Patients who had low final PCD (≤ 10.3 mm.mm-2; 64%) were more likely to die than patients who had preserved PCD (>10.3 mm.mm(-2); mortality 72% vs. 17%, p = 0.003). CONCLUSION: This study demonstrates the effects of commonly used inotropic agents on parameters of tissue perfusion in patients with cardiogenic shock. Despite hemodynamic optimization, tissue perfusion was not sufficiently restored in most patients. In these patients, mortality was high. Interventions directed at improving microcirculation may eventually help bridging the gap between improved hemodynamics and dismal patient outcome in cardiogenic shock.

Enoxaparin, effective dosage for intensive care patients: double-blinded, randomised clinical trial.

INTRODUCTION: Intensive care unit (ICU) patients are predisposed to thromboembolism. Routine prophylactic anticoagulation is widely recommended. Low-molecular-weight heparins, such as enoxaparin, are increasingly used because of predictable pharmacokinetics. This study aims to determine the subcutaneous (SC) dose of enoxaparin that would give the best anti-factor Xa levels in ICU patients. METHODS: The 72 patients admitted to a mixed ICU at Odense University Hospital (OUH) in Denmark were randomised into four groups to receive 40, 50, 60, or 70 mg SC enoxaparin for a period of 24 hours. Anti-factor Xa activity (aFXa) was measured before, and at 4, 12, and 24 hours after administration. An AFXa level between 0.1 to 0.3 IU/ml was considered evidence of effective antithrombotic activity. RESULTS: Median peak (4 hours after administration), aFXa levels increased significantly with an increase in enoxaparin dose, from 0.13 IU/ml at 40 mg, to 0.14 IU/ml at 50 mg, 0.27 IU/ml at 60 mg, and 0.29 IU/ml at 70 mg (P = 0.002). At 12 hours after administration, median aFXa levels were still within therapeutic range for those patients who received 60 mg (P = 0.02). CONCLUSIONS: Our study confirmed that a standard dose of 40 mg enoxaparin yielded subtherapeutic levels of aFXa in critically ill patients. Higher doses resulted in better peak aFXa levels, with a ceiling effect observed at 60 mg. The present study seems to suggest inadequate dosage as one of the possible mechanisms for the higher failure rate of enoxaparin in ICU patients. TRIAL REGISTRATION: ISRCTN03037804.

Apart from the other members of PDE inhibitors' family, enoximone does not enhance renal ischemic reperfusion injury: the effects of enoximone on renal ischemia reperfusion.

Many pharmacological agents were investigated for the prevention of renal ischemic reperfusion (IR) injury as well as the phosphodiesterase (PDE) inhibitors. The aim of the study was to examine the possible renoprotective effect of enoximone as a member of this family on IR injury. Thirty-six Wistar-Albino rats were allocated to six groups. Sham (S) and control groups (E1, E2) only received 0.09% NaCl, 5 mg/kg and 10 mg/kg enoximone via caudal caval vein, respectively. In ischemia (I) and treatment groups (IE1, IE2), the rats were subjected to bilateral renal artery occlusion and were given 0.09% NaCl, 5 mg/kg and 10 mg/kg enoximone in the same route, respectively. Bilateral kidneys were removed at the sixth hour of laparotomy for histopathological and biochemical analysis, such as superoxide dismutase, myeloperoxidase, malonyldialdehyde, and nitric oxide end products. Blood samples were taken in order to evaluate renal function tests. The data were analyzed by using one-way analysis of variance, and p < .05 was considered to be statistically significant. The worst results were achieved in ischemia group (p < .05). Treatments groups showed nearly similar findings with this group (p < .05). There was no significant difference between control and sham groups. In this study, we found that apart from the other members of the PDE inhibitors' family, enoximone did not contribute to the attenuation of IR injury of kidney.

Comparison between lithium dilution and pulse contour analysis techniques for cardiac output measurement in isoflurane anaesthetized ponies: influence of different inotropic drugs.

OBJECTIVE: To compare cardiac output () measurements using lithium dilution (LiDCO) and pulse contour analysis (PulseCO) techniques in isoflurane-anaesthetized ponies before and during the administration of different inotropic/vasoactive drugs. STUDY DESIGN: Prospective randomized experimental cross-over trial. ANIMALS: Six ponies aged 5.0 +/- 1.6 (4-6.5) years and weighing 286 +/- 53 (212-368) kg. METHODS: After sedation (romifidine) and induction (midazolam + ketamine), anaesthesia was maintained with isoflurane in oxygen. After 90 minutes (= T0), one of four treatments was administered: saline 0.1 mL kg(-1) (S), enoximone 0.5 mg kg(-1) IV (E), enoximone followed by dobutamine (0.5 microg kg(-1) minute(-1) for 120 minutes) (ED) or enoximone followed by a calcium chloride infusion (0.5 mg kg(-1) minute(-1) for 10 minutes) (EC). Data were recorded for 120 minutes after T0. The PulseCO (recorded from carotid artery) was calibrated before T0, no further recalibrations were performed. was determined with LiDCO ((LiDCO)) and PulseCO ((PulseCO)) simultaneously at T5, T10, T20, T40, T60, T80, T100 and T120. Systemic vascular resistances (SVR(LiDCO) and SVR(PulseCO)) were calculated. RESULTS: In the saline group, (PulseCO) was 4.9 +/- 12.3% lower than LiDCO (p < 0.01), whereas SVR(PulseCO) was 6.9 +/- 14.4% higher than SVR(LiDCO) (p < 0.01). These differences increased over time (mean +/- SEM), by 0.06 +/- 0.03% minute(-1) (p = 0.042) and SVR by 0.08 +/- 0.03% minute(-1) (p = 0.018). (PulseCO) was higher than (LiDCO) in the EC group (1.8 +/- 23.3%), but lower than (LiDCO) in groups E (-11.7 +/- 20.4%) and ED (-10.0 +/- 25.9%) (significant difference between treatments, p < 0.01). The differences in SVR in groups E (20.4 +/- 32.0%) and ED (20.7 +/- 35.3%) were significantly higher than in groups S (6.9 +/- 14.4%) and EC (3.1 +/- 22.2%) (p < 0.01). CONCLUSIONS AND CLINICAL RELEVANCE: Pulse contour analysis values deviated significantly from LiDCO measurements in isoflurane-anaesthetized ponies. This difference was influenced by inotropic/vasoactive drugs.

Inflammatory response to cardiopulmonary bypass with enoximone or steroids in patients undergoing myocardial revascularization: a preliminary report study.

OBJECTIVE: Recent reports have showed an antiinflammatory effect of phosphodiesterase III inhibitors (PDEi) in patients undergoing cardiopulmonary bypass (CPB). We sought to evaluate the immunological and hemodynamic response to enoximone and methylprednisolone in patients undergoing CABG. DESIGN: Prospective, randomized, controlled study. SETTING: Cardiac surgery unit in a university hospital. PATIENTS: 40 patients undergoing CPB-CABG. INTERVENTIONS: Patients receive enoximone (20, Group A) or methylprednisolone (20, Group B). MEASUREMENTS AND MAIN RESULTS: Hemodynamic response was evaluated by Swan-Ganz catheter serial measurements and perioperative Lactate and Troponin I leakage, immunological response was analyzed by IL-2, IL-4, IL-6, TNF-alpah, IFN-gamma, IL-10 before anesthetic induction (T0), at aortic-declamping (T1), at the end of surgery (T2), ITU admission (T3), 24 hs (T4) postoperatively. Morbidity and mortality were comparable between the two groups. Group A demonstrated higher cardiac index at T2 (2.93 l/min m2 vs 2.06, p < 0.001), at T3 (3.01 vs 2.18, p < 0.001), lower indexed systemic vascular resistance at T2 (2,044 dyne s cm-5 m-2 vs 3,132, p < 0.001). Except for higher TNF-alpha in Group B at T2 (15.89 vs 22.68, p = 0.005) proinflammatory cytokines were comparable. IL-10 was higher in Group B at any postoperative time (IL-10: T1 80.74 vs 143.3, p < 0.001, T2 165.7 vs 377.4, p < 0.001, T3 203.4 vs 443.5, p < 0,001, T4 251.8 vs 437.1, p < 0.001), whereas IL-4 and IFN-gamma proved higher in Group A at all time-points (IL-4: T1 45.9 vs 31.2, p = 0.008, T2 67.2 vs 39.7, p < 0.001, T3 77.9 vs 39.2, p < 0.001, T4 102.9 vs 42.2, p < 0.001. IFN-gamma: T1 25.8 vs 15.8, p < 0.001, T2 52.2 vs 30.3, p < 0.001, T3 78.4 vs 40.8, p < 0.001, T4 159.9 vs 67.4, p < 0.001). CONCLUSIONS: Despite comparable major clinical endpoints enoximone showed a different antiinflammatory pattern compared to methylprednisolone, however, the better hemodynamic response in enoximone compared to methylprednisolone suggests enoximone as a potential antiinflammatory tool to improve the outcome in cardiac surgery.

Influence of calcium chloride on the cardio-respiratory effects of a bolus of enoximone in isoflurane anaesthetized ponies.

OBJECTIVE: To investigate the influence of calcium chloride (CaCl(2)) on the cardio-respiratory effects of enoximone in isoflurane anaesthetized ponies. STUDY DESIGN: Prospective consecutive experimental trial. Animals Six healthy ponies, weighing 287 +/- 55 kg were included in this study. METHODS: After sedation (romifidine, 80 microg kg(-1)), anaesthesia was induced with midazolam (0.06 mg kg(-1)) and ketamine (2.2 mg kg(-1)) and maintained with isoflurane in oxygen. The ponies' lungs were ventilated to maintain normocapnia. After 90 minutes, a bolus of enoximone (0.5 mg kg(-1)) was administered, followed by a CaCl(2) infusion (0.5 mg kg(-1) minute(-1) over 10 minutes) (treatment EC). Sodium, potassium, ionized and total calcium concentrations, cardiovascular variables and blood-gases were measured in the 120 minutes after treatment. Using a mixed model anova, the results were compared to those of a previous report [Vet Anaesth Analg, 34 (2007) 416], evaluating the effects of 0.5 mg kg(-1) enoximone in the same ponies and under identical circumstances (treatment E). Both an overall comparison and comparisons at specific time points after treatment were performed (alpha = 0.05). RESULTS: Although ionized and total calcium concentrations were higher during treatment EC, the cardio-respiratory effects of enoximone were comparable for both treatments. A small but significant difference in packed cell volume was detected. CONCLUSIONS AND CLINICAL RELEVANCE: Calcium chloride did not enhance the effects of enoximone in normocalcaemic anaesthetized ponies.

Cardiorespiratory effects of enoximone in anaesthetised colic horses.

REASONS FOR PERFORMING STUDY: No studies have been reported on the effects of enoximone in anaesthetised colic horses. OBJECTIVE: To examine whether enoximone improves cardiovascular function and reduces dobutamine requirement in anaesthetised colic horses. METHODS: Forty-eight mature colic horses were enrolled in this prospective, randomised clinical trial. After sedation (xylazine 0.7 mg/kg bwt) and induction (midazolam 0.06 mg/kg bwt, ketamine 2.2 mg/kg bwt), anaesthesia was maintained with isoflurane in oxygen and a lidocaine constant rate infusion (15 mg/kg bwt, 2 mg/kg/h). Horses were ventilated (PaCO2 < 8.00 kPa). If hypotension occurred, dobutamine and/or colloids were administered. Ten minutes after skin incision, horses randomly received an i.v. bolus of enoximone (0.5 mg/kg bwt) or saline. Monitoring included respiratory and arterial blood gases, heart rate (HR), arterial pressure and cardiac index (CI). Systemic vascular resistance (SVR), stroke index (SI) and oxygen delivery index (DO2I) were calculated. For each variable, changes between baseline and T10 within each treatment group and/or colic type (small intestines, large intestines or mixed) were analysed and compared between treatments in a fixed effects model. Differences between treatments until T30 were investigated using a mixed model (a = 0.05). RESULTS: Ten minutes after enoximone treatment, CI (P = 0.0010), HR (P = 0.0033) and DO2I (P = 0.0007) were higher and SVR lower (P = 0.0043) than at baseline. The changes in CI, HR and SVR were significantly different from those after saline treatment. During the first 30 min after enoximone treatment, DO2I (P = 0.0224) and HR (P = 0.0003) were higher than after saline administration. Because the difference in HR between treatments was much clearer in large intestine colic cases, an interaction was detected between treatment and colic type in both analyses (P = 0.0076 and 0.0038, respectively). CONCLUSIONS: Enoximone produced significant, but short lasting, cardiovascular effects in colic horses. POTENTIAL RELEVANCE: Enoximone's cardiovascular effects in colic horses were of shorter duration than in healthy ponies.

Effects of dobutamine on cardiovascular function and respiratory gas exchange after enoximone in isoflurane-anaesthetized ponies.

OBJECTIVE: To evaluate the combined effects of enoximone and dobutamine on the cardiovascular system and respiratory gas exchange in isoflurane-anaesthetized ponies. STUDY DESIGN: Prospective, randomized, experimental study. ANIMALS: Six ponies (286 +/- 52 kg), aged 5.0 +/- 1.6 years. METHODS: After sedation (romifidine 80 microg kg(-1)), anaesthesia was induced with midazolam (0.06 mg kg(-1)) and ketamine (2.2 mg kg(-1)) and maintained with isoflurane in oxygen. The ponies were ventilated to maintain eucapnia. After 90 minutes (=T0), enoximone alone (0.5 mg kg(-1)) (E) or enoximone, followed by a constant rate infusion of dobutamine (0.5 microg kg(-1) minute(-1)) (ED) for 120 minutes, was administered. Each pony received both treatments in a crossover trial, with at least 2 weeks between treatments. Heart rate (HR), cardiac output (CO), stroke volume (SV), right atrial (RAP), systolic (SAP), diastolic (DAP) and mean arterial pressure (MAP), blood gases, systemic vascular resistance (SVR), oxygen delivery (DO(2)) and several respiratory gas exchange variables were measured before treatment and until T120. Statistical analysis was based on a mixed model with treatment, time and their interaction as fixed categorical effects, pony as random effect, comparing treatments globally (alpha = 0.05) and at specific timepoints (Bonferroni-adjusted alpha = 0.00625). RESULTS: Compared to enoximone alone, ED treatment produced an increase in HR, CO, SV, RAP, SAP, DAP, MAP, packed cell volume (PCV) and DO(2). The difference was significant from T60 to T120 (except at T80) for HR, throughout the observational period for CO, SAP, MAP, PCV and DO(2), from T40 to T120 for DAP, at T10,T60,T80 and T120 for SV and at T10 and T20 for RAP. Overall decreases occurred in SVR and dead space ventilation (V(D)/V(T)). V(D)/V(T) was lower at T20 and from T80 to T120. Venous oxygen saturation was increased from T60 onwards. CONCLUSIONS AND CLINICAL RELEVANCE: The results suggest that enoximone and dobutamine have additive cardiovascular effects and reduce V(D)/V(T) in isoflurane-anaesthetized ponies.

Effects of enoximone on peripheral and central chemoreflex responses in humans.

cAMP plays an important role in peripheral chemoreflex function in animals. We tested the hypothesis that the phosphodiesterase inhibitor and inotropic medication enoximone increases peripheral chemoreflex function in humans. In a single-blind, randomized, placebo-controlled crossover study of 15 men, we measured ventilatory, muscle sympathetic nerve activity, and hemodynamic responses to 5 min of isocapnic hypoxia, 5 min of hyperoxic hypercapnia, and 3 min of isometric handgrip exercise, separated by 1 wk, with enoximone and placebo administration. Enoximone increased cardiac output by 120 +/- 3.7% from baseline (P < 0.001); it also increased the ventilatory response to acute hypoxia [13.6 +/- 1 vs. 11.2 +/- 0.7 l/min at 5 min of hypoxia, P = 0.03 vs. placebo (by ANOVA)]. Despite a larger minute ventilation and a smaller decrease in O(2) desaturation (83 +/- 1 vs. 79 +/- 2%, P = 0.003), the muscle sympathetic nerve response to hypoxia was similar between enoximone and placebo (123 +/- 6 and 117 +/- 6%, respectively, P = 0.28). In multivariate regression analyses, enoximone enhanced the ventilatory (P < 0.001) and sympathetic responses to isocapnic hypoxia. Hyperoxic hypercapnia and isometric handgrip responses were not different between enoximone and placebo (P = 0.13). Enoximone increases modestly the chemoreflex responses to isocapnic hypoxia. Moreover, this effect is specific for the peripheral chemoreflex, inasmuch as central chemoreflex and isometric handgrip responses were not altered by enoximone.

Cardiovascular effects of enoximone in isoflurane anaesthetized ponies.

OBJECTIVE: Enoximone is a phosphodiesterase III inhibitor frequently used to improve cardiac output (CO) in man. As the use of enoximone has not been reported in horses, the effects of this inodilator were examined in isoflurane anaesthetized ponies. STUDY DESIGN: Prospective, randomised, experimental study. ANIMALS: Six healthy ponies, weighing 286 (212-367) +/- 52 kg, aged 5.0 +/- 1.6 years (4-6.5). METHODS: After sedation with romifidine [80 microg kg(-1) intravenously (IV)], general anaesthesia was induced with midazolam (0.06 mg kg(-1) IV) and ketamine (2.2 mg kg(-1) IV) and maintained with isoflurane in oxygen (Et Iso 1.7%). The ponies were ventilated to maintain eucapnia (PaCO(2) 4.66-6.00 kPa). Each pony was anaesthetized twice with an interval of 3 weeks; receiving enoximone 0.5 mg kg(-1) IV (E) or saline (S) 90 minutes post-induction. Heart rate (HR), arterial (AP) and right atrial pressure (RAP) were measured before treatment, every 5 minutes between T0 (treatment) and T30 and then every 10 minutes until T120. Cardiac output measurements (lithium dilution technique) and blood gas analysis (arterial and central venous samples) were performed before T0 and at T5, T10, T20, T40, T60, T80, T100 and T120. Stroke volume (SV), systemic vascular resistance (SVR), venous admixture (Qs/Qt) and oxygen delivery (DO(2)) were calculated. RESULTS: Enoximone induced significant increases in HR, CO, SV, Qs/Qt and DO(2) and a significant decrease in RAP. No significant differences were detected for AP, SVR and blood gases. No cardiac arrhythmias or other side effects were observed. CONCLUSIONS AND CLINICAL RELEVANCE: The present results suggest that in isoflurane anaesthetized ponies, enoximone has beneficial effects on CO and SV without producing significant changes in blood pressure. Despite an increase in Qs/Qt, DO(2) to the tissues was improved.

Effects of preemptive enoximone on left ventricular diastolic function after valve replacement for aortic stenosis.

OBJECTIVE: Left ventricular (LV) hypertrophy is associated with increased diastolic chamber stiffness early after aortic valve replacement for valve stenosis. Enoximone, a phosphodiesterase III inhibitor, has been shown to improve myocardial contractility and relaxation when administered as a single dose after cardiac surgery. The present study investigated, by analysis of transmitral flow velocity patterns and end-diastolic pressure-area relations, whether enoximone administered before aortic valve surgery has an effect on LV diastolic properties. DESIGN: Prospective, randomized study. SETTING: Referral center for cardiothoracic surgery at a university hospital. PARTICIPANTS: Thirty-four patients undergoing aortic valve replacement for aortic stenosis. INTERVENTIONS: Patients in the enoximone group (n = 17) received a bolus dose of 0.35 mg/kg (0.15 mg/kg before aortic cross-clamping and 0.2 mg/kg added to the cardioplegic solution). Individual pressure-area relations (pulmonary capillary wedge pressure v left ventricular end-diastolic area) were obtained by using volume loading by leg elevation before and after surgery with closed chest. MEASUREMENTS AND MAIN RESULTS: The pressure-area relation on the pressure-area plot was shifted to the left after surgery, indicating decreased LV diastolic distensibility in the enoximone and control groups and providing evidence of decreased LV diastolic function. Indices of LV diastolic chamber stiffness, LV operating stiffness (K(LV)) derived from the deceleration time of early ventricular filling, and the constant of chamber stiffness (beta) derived from pressure-area relations were not different after enoximone treatment. Systolic LV function was unaltered after cardiac surgery in both groups. Analysis of changes in transmitral flow patterns identified an increased atrial filling fraction in enoximone-treated patients, suggesting increased atrial systolic function. The unaltered systolic pulmonary venous flow velocity compared with the decrease in the control group after volume loading further supports preservation of left atrial reservoir function with enoximone in the absence of evidence for decreased LV stiffness. CONCLUSION: Preemptive enoximone did not change LV diastolic function based on diastolic filling patterns or LV stiffness indices (K(LV) and beta) derived from Doppler early filling deceleration time and pressure-area relations. Doppler data suggested improvement of left atrial systolic function and preservation of left atrial reservoir function with enoximone.

A comparison of three phosphodiesterase type III inhibitors on mechanical and metabolic function in guinea pig isolated hearts.

Little is known about of the comparative cardiac lusitropic and coronary vasoactive effects of type III phosphodiesterase inhibitors independent of their systemic circulatory effects. We hypothesized that phosphodiesterase inhibitors have dissimilar concentration-dependent effects on cardiac function and metabolism and that their coronary vasodilatory effects are solely dependent on flow autoregulation secondary to positive inotropic effects. Our aim was to compare the dose-response electrophysiologic, mechanical, vasodilatory, and metabolic properties of three clinically available phosphodiesterase inhibitors in isolated Langendorff perfused guinea pig hearts. We found that, over a range from 10(-7) to 10(-4) M, amrinone, enoximone, and milrinone each produced maximal concentration-dependent positive chronotropic (12%, 18%, 26%), inotropic (16%, 26%, 26%), and lusitropic (14%, 21%, 19%) effects. At clinical concentrations, all phosphodiesterase inhibitors increased heart rate, but only milrinone significantly enhanced contractility and relaxation (11%). Each phosphodiesterase inhibitor similarly increased contractility at its highest concentration; this was accompanied by an increase in oxygen consumption, which was matched by comparable increases in coronary flow and oxygen delivery. Coronary flow reserve was preserved at the highest concentration of each drug, indicating that an increased metabolic rate was responsible for the increase in coronary flow by each drug at each concentration. Over the concentrations examined, we conclude that each of the phosphodiesterase inhibitors does not directly promote coronary vasodilation and that milrinone has the most prominent effects on contractility and relaxation at clinically relevant concentrations.

Two inotropes with different mechanisms of action: contractile, PDE-inhibitory and direct myofibrillar effects of levosimendan and enoximone.

We characterized the Ca2+-sensitizing and phosphodiesterase (PDE)-inhibitory potentials of levosimendan and enoximone to assess their contributions to the positive inotropic effects of these drugs. In guinea pig hearts perfused in the working-heart mode, the maximal increase in cardiac output (55%, P<0.05) was attained at 50 nM levosimendan. The corresponding value for enoximone (36%) was significantly smaller (P<0.05) and was observed at a higher concentration (500 nM). In permeabilized myocyte-sized preparations levosimendan evoked a maximal increase of 55.8+/-8% (mean+/-SEM) in isometric force production via Ca2+ sensitization (pCa 6.2, EC50 8.4 nM). Enoximone up to a concentration of 10 microM failed to influence the isometric force. The PDE-inhibitory effects were probed on the PDE III and PDE IV isoforms. Levosimendan proved to be a 1300-fold more potent and a 90-fold more selective PDE III inhibitor (IC50 for PDE III 1.4 nM, and IC50 for PDE IV 11 microM, selectivity factor approximately 8000) than enoximone (IC50 for PDE III 1.8 microM, and IC50 for PDE IV 160 microM, selectivity factor approximately 90). Hence, our data support the hypothesis that levosimendan exerts positive inotropy via a Ca2+-sensitizing mechanism, whereas enoximone does so via PDE inhibition with a limited PDE III versus PDE IV selectivity.

Pharmacological effects of ATI22-107 [2-(2-{2-[2-chloro-4-(6-oxo-1,4,5,6-tetrahydro-pyridazin-3-yl)-phenoxy]-acetylamino}-ethoxymethyl)-4-(2-chloro-phenyl)-6-methyl-1,4-dihydro-pyridine-3,5-dicarboxylic acid dimethyl ester)], a novel dual pharmacophore, on myocyte calcium cycling and contractility.

Historically, inhibitors of type III phosphodiesterases (PDE-III) have been effective inotropes in mammalian myocardium, but their clinical utility has been limited by adverse events, including arrhythmias that are considered to be due to Ca(2+) overload. ATI22-107 [2-(2-{2-[2-chloro-4-(6-oxo-1,4,5,6-tetrahydro-pyridazin-3-yl)-phenoxy]-acetylamino}-ethoxymethyl)-4-(2-chlorophenyl)-6-methyl-1,4-dihydro-pyridine-3,5-dicarboxylic acid dimethyl ester)], a novel, dual pharmacophore compound, was designed to simultaneously inhibit the cardiac phosphodiesterase (PDE-III) and produce inotropic effects, whereas inhibiting the L-type calcium channel (LTCC) was designed to minimize increases in diastolic Ca(2+). We compared the effects of ATI22-107 and enoximone, a pure PDE-III inhibitor, on the Fluo-3 calcium transient in normal feline ventricular myocytes and trabeculae. Enoximone-induced dose-dependent increases in peak [Ca(2+)](i), diastolic [Ca(2+)](i), T50, and T75. ATI22-107 demonstrated similar dose-dependent increases in peak [Ca(2+)](i) at 300 nM and 1.0 microM doses, with no further increases at higher doses. Throughout the dosing range, ATI22-107 induced much smaller, if any, increases in diastolic [Ca(2+)](i), T(25), and T(75). Current measurement of LTCC via patch-clamp techniques revealed dose-dependent decreases in LTCC current with an increasing dose of ATI22-107, thereby validating the dual functionality of the drug that has been proposed in this study. Studies in isolated trabeculae demonstrated that enoximone-induced a dose-dependent augmentation of the entire force-frequency relation in normal myocardium, whereas augmentation of contractility was only observed at lower stimulation frequencies with ATI22-107. These results demonstrate the effects of the LTCC-antagonizing moiety of ATI22-107 and suggest that the novel simultaneous combination of PDE-III and LTCC inhibition by one molecule may produce a favorable profile of limited inotropy without detrimental effects of increased diastolic [Ca(2+)](i).

Effect of activators and the phosphodiesterase inhibitors pentoxifylline and enoximone on the deformability of neutrophils in neonates and adults.

BACKGROUND: Stimulated polymorphonuclear leukocytes (PMN) are extremely rigid compared to resting PMN. They may obstruct narrow vessels and contribute to ischaemic organ injury. Deformability is a prerequisite for both active and passive movement in the microcirculation. AIM: The investigation was designed to study whether stimulators and inhibitors of stimulation show different effects on deformability of neonatal and adult PMN. METHODS: Deformability of PMN was assessed by complete aspiration of a PMN into a micropipette with an internal diameter of 5 microm. Blood samples from 20 neonates and 20 adults were studied before and after stimulation with N-formyl-methionyl-leucyl-phenylalanine (fMLP), interleukin-8 (IL-8) or tumour necrosis factor-alpha (TNF-alpha). Moreover, effects of the phosphodiesterase inhibitors Pentoxifylline (PTX) and Enoximone on the deformability of stimulated PMN were investigated. RESULTS: fMLP, IL-8 and TNF-alpha significantly delayed aspiration times of PMN in relation to the concentrations of the stimulators. The addition of PTX or Enoximone to stimulated PMN increased the deformability up to 60% depending on the concentration of the inhibitors. No significant differences in the aspiration times were found between neonatal and adult PMN at any of the experimental conditions after activation with the three stimulators and treatment with the two inhibitors. CONCLUSION: Neonatal and adult PMN show similar reduction of passive deformability when stimulated with either fMLP, IL-8 or TNF-alpha compared to resting PMN and a similar improvement of deformability in response to PTX or Enoximone.

Na(+)-channel modulation, a new principle of inotropic intervention: effects on hemodynamic and myocardial energetics in the immature rabbit heart.

Na+-channel modulators exert their positive inotropic action without affecting the adenylate-cyclase pathway by an increase in the open probability of the sarcolemmal Na+ channels. Although inotropic effects in neonatal hearts are less pronounced compared with adult hearts, the Na+-channel modulator BDF 9148 increases contractility and relaxation velocity in immature myocardium. Effects on hemodynamics and myocardial energetics are not known. Therefore, we studied the Na+-channel modulator BDF 9148 in isolated antegrade perfused rabbit hearts of different ages (2-28 d) and compared the effects with isoproterenol, enoximone, and ouabain. ANOVA showed significant effects in the concentration response curves for heart rate, stroke volume, cardiac output, and oxygen consumption but not for myocardial efficiency (p = 0.06). Age-dependent differences were observed for heart rate and stroke volume. Administration of BDF 9148 resulted in a maximal increase in stroke volume and cardiac output up to 25% in neonatal and 40% to 60% in adult preparations. Heart rate decreased by 15% in adult hearts only. Myocardial oxygen consumption was increased in a concentration-dependent manner between 25% in neonatal and 50% in adult hearts. Myocardial efficiency was increased by 35% in adult and by 10% in neonatal preparations. Although positive hemodynamic and energetic effects were less pronounced in immature compared with adult hearts, neonatal hearts also profited from the administration of the Na+-channel modulator BDF 9148. Further studies are necessary to clarify the risk of arrhythmia during application of Na+-channel modulators such as BDF 9148.

Enoximone very low-dose dobutamine stress echocardiography: a new test for detecting viability in severe myocardial dysfunction after acute myocardial infarction.

Relying on the synergistic action on contractility of enoximone and dobutamine when concomitantly infused, 25 patients with their first acute Q-wave anterior myocardial infarctions underwent conventional low-dose dobutamine echocardiography (LDE) and enoximone very-LDE to assess myocardial viability in severely dysfunctioning areas. Images were recorded at peak of pharmacodynamic effect of drugs and 4 months after revascularization. At peak-dose stage of LDE and enoximone very-LDE the regional infarct zone wall-motion score significantly decreased from the basal value of 25.6 +/- 2.9 to 16 +/- 6.0 (P <.001) and to 14.5 +/- 5.2 (P <.001), respectively. A high correlation was found by comparing the wall-motion score of each patient calculated at peak effect of combined drug administration with follow-up values (r(s) = 0.9). Enoximone very-LDE has proven to be a new test useful to evaluate viability in asynergic segments especially when the results of conventional tests are questionable.

In vitro and in vivo effects of the phosphodiesterase-III inhibitor enoximone on malignant hyperthermia-susceptible swine.

BACKGROUND: In human skeletal muscles, the phosphodiesterase-III inhibitor enoximone induces in vitro contracture development, and it has been suggested that enoximone could trigger malignant hyperthermia (MH). In this study, the in vitro and in vivo effects of enoximone in MH-normal (MHN) and MH-susceptible (MHS) swine were investigated. METHODS: Malignant hyperthermia trigger-free general anesthesia was performed in MHS and MHN swine. Skeletal muscle specimens were excised for an in vitro contracture test with 0.6 mm enoximone. Thereafter, MHS and MHN swine were exposed to cumulative administration of 0.5, 1, 2, 4, 8, 16, and 32 mg/kg enoximone intravenously. Clinical occurrence of MH was defined by a Pco(2) greater than 70 mmHg, a pH less than 7.20, and an increase in body temperature of more than 2.0 degrees C. RESULTS: Enoximone induced marked contractures in all MHS muscle specimens in vitro. In contrast, only small or no contracture development was observed in MHN muscle specimens, without an overlap in contractures between MHS and MHN muscles. However, in vivo, no clinical differences were found between MHS and MHN swine following cumulative enoximone doses. According to the defined criteria, none of the swine developed MH during the experiment. Furthermore, high enoximone doses induced progressive circulatory insufficiency, and after receiving 32 mg/kg enoximone, all animals died of cardiovascular failure. CONCLUSIONS: The cumulative enoximone doses used in this study were 30- to 50-fold higher than therapeutic doses in humans. Enoximone does not trigger MH in genetically determined swine. However, enoximone might be useful for in vitro diagnosis of MH.