ALDOA coordinates PDE3A through the ß-catenin/ID3 axis to stimulate cancer metastasis and M2 polarization in lung cancer with EGFR mutations.

Lung cancer has a high incidence rate and requires more effective treatment strategies and drug options for clinical patients. EGFR is a common genetic alteration event in lung cancer that affects patient survival and drug strategy. Our study discovered aberrant aldolase A (ALDOA) expression and dysfunction in lung cancer patients with EGFR mutations. In addition to investigating relevant metabolic processes like glucose uptake, lactate production, and ATPase activity, we examined multi-omics profiles (transcriptomics, proteomics, and pull-down assays). It was observed that phosphodiesterase 3A (PDE3A) enzyme and ALDOA exhibit correlation, and furthermore, they impact M2 macrophage polarization through ß-catenin and downstream ID3. In addition to demonstrating the aforementioned mechanism of action, our experiments discovered that the PDE3 inhibitor trequinsin has a substantial impact on lung cancer cell lines with EGFR mutants. The trequinsin medication was found to decrease the M2 macrophage polarization status and several cancer phenotypes, in addition to transduction. These findings have potential prognostic and therapeutic applications for clinical patients with EGFR mutation and lung cancer.

Discovery and SAR Study of Boronic Acid-Based Selective PDE3B Inhibitors from a Novel DNA-Encoded Library.

Human genetic evidence shows that PDE3B is associated with metabolic and dyslipidemia phenotypes. A number of PDE3 family selective inhibitors have been approved by the FDA for various indications; however, given the undesirable proarrhythmic effects in the heart, selectivity for PDE3B inhibition over closely related family members (such as PDE3A; 48% identity) is a critical consideration for development of PDE3B therapeutics. Selectivity for PDE3B over PDE3A may be achieved in a variety of ways, including properties intrinsic to the compound or tissue-selective targeting. The high (>95%) active site homology between PDE3A and B represents a massive obstacle for obtaining selectivity at the active site; however, utilization of libraries with high molecular diversity in high throughput screens may uncover selective chemical matter. Herein, we employed a DNA-encoded library screen to identify PDE3B-selective inhibitors and identified potent and selective boronic acid compounds bound at the active site.

PDE3B regulates KRT6B and increases the sensitivity of bladder cancer cells to copper ionophores.

Cuproptosis is a new Cu-dependent programmed cell death manner that has shown regulatory functions in many tumor types, however, its mechanism in bladder cancer remains unclear. Here, we reveal that Phosphodiesterase 3B (PDE3B), a cuproptosis-associated gene, could reduce the invasion and migration of bladder cancer. PDE3B is downregulated in bladder cancer tissues, which is correlated with better prognosis. Conversely, overexpression of PDE3B in bladder cancer cell could significantly resist invasion and migration, which is consistent with the TCGA database results. Future study demonstrate the anti-cancer effect of PDE3B is mediated by Keratin 6B (KRT6B) which leads to the keratinization. Therefore, PDE3B can reduce KRT6B expression and inhibit the invasion and migration of bladder cancer. Meanwhile, increased expression of PDE3B was able to enhance the sensitivity of Cuproptosis drug thiram. This study show that PDE3B/KRT6B is a potential cancer therapeutic target and PDE3B activation is able to increase the sensitivity of bladder cancer cells to copper ionophores.

Protein Kinase A Regulates Platelet Phosphodiesterase 3A through an A-Kinase Anchoring Protein Dependent Manner.

Platelet activation is critical for haemostasis, but if unregulated can lead to pathological thrombosis. Endogenous platelet inhibitory mechanisms are mediated by prostacyclin (PGI2)-stimulated cAMP signalling, which is regulated by phosphodiesterase 3A (PDE3A). However, spatiotemporal regulation of PDE3A activity in platelets is unknown. Here, we report that platelets possess multiple PDE3A isoforms with seemingly identical molecular weights (100 kDa). One isoform contained a unique N-terminal sequence that corresponded to PDE3A1 in nucleated cells but with negligible contribution to overall PDE3A activity. The predominant cytosolic PDE3A isoform did not possess the unique N-terminal sequence and accounted for >99% of basal PDE3A activity. PGI2 treatment induced a dose and time-dependent increase in PDE3A phosphorylation which was PKA-dependent and associated with an increase in phosphodiesterase enzymatic activity. The effects of PGI2 on PDE3A were modulated by A-kinase anchoring protein (AKAP) disruptor peptides, suggesting an AKAP-mediated PDE3A signalosome. We identified AKAP7, AKAP9, AKAP12, AKAP13, and moesin expressed in platelets but focussed on AKAP7 as a potential PDE3A binding partner. Using a combination of immunoprecipitation, proximity ligation techniques, and activity assays, we identified a novel PDE3A/PKA RII/AKAP7 signalosome in platelets that integrates propagation and termination of cAMP signalling through coupling of PKA and PDE3A.

Administration of Liposomal-Based Pde3b Gene Therapy Protects Mice Against Collagen-Induced Rheumatoid Arthritis via Modulating Macrophage Polarization.

Background: Rheumatoid arthritis (RA) is a chronic and systemic autoimmune disease characterized by synovial inflammation and joint destruction. Despite progress in RA therapy, it remains difficult to achieve long-term remission in RA patients. Phosphodiesterase 3B (Pde3b) is a member of the phosphohydrolyase family that are involved in many signal transduction pathways. However, its role in RA is yet to be fully addressed. Methods: Studies were conducted in arthritic DBA/1 mice, a suitable mouse strain for collagen-induced rheumatoid arthritis (CIA), to dissect the role of Pde3b in RA pathogenesis. Next, RNAi-based therapy with Pde3b siRNA-loaded liposomes was assessed in a CIA model. To study the mechanism involved, we investigated the effect of Pde3b knockdown on macrophage polarization and related signaling pathway. Results: We demonstrated that mice with CIA exhibited upregulated Pde3b expression in macrophages. Notably, intravenous administration of liposomes loaded with Pde3b siRNA promoted the macrophage anti-inflammatory program and alleviated CIA in mice, as indicated by the reduced inflammatory response, synoviocyte infiltration, and bone and cartilage erosion. Mechanistic study revealed that depletion of Pde3b increased cAMP levels, by which it enhanced PKA-CREB-C/EBPß pathway to transcribe the expression of anti-inflammatory program-related genes. Conclusion: Our results support that Pde3b is involved in the pathogenesis of RA, and Pde3b siRNA-loaded liposomes might serve as a promising therapeutic approach against RA.

A PDE3A-SLFN12 Molecular Glue Exhibits Significant Antitumor Activity in TKI-Resistant Gastrointestinal Stromal Tumors.

PURPOSE: Gastrointestinal stromal tumor (GIST), the most common mesenchymal tumor with KIT or PDGFRA driver mutations, is typically treated with tyrosine kinase inhibitors (TKI). However, resistance to TKIs due to secondary mutations is a common challenge in advanced GISTs. In addition, there are currently no effective therapies for several other molecular subtypes, such as succinate dehydrogenase-deficient GISTs. Therefore, novel therapeutic strategies are needed. EXPERIMENTAL DESIGN: To address this need, we tested the efficacy of a novel non-TKI compound, OPB-171775, using patient-derived xenograft models of GISTs. In parallel, we sought to elucidate the mechanism of action of the compound. RESULTS: Our study revealed that OPB-171775 exhibited significant efficacy against GISTs regardless of their KIT mutation status by inducing complex formation between phosphodiesterase 3A (PDE3A) and Schlafen family member 12 (SLFN12), which are highly expressed in GISTs, leading to SLFN12 RNase-mediated cell death. Furthermore, we identified the activation of general control non-derepressible 2 and its downstream response as an effector pathway of SLFN12 in mediating anticancer activity and revealed potential pharmacodynamic markers. CONCLUSIONS: These findings suggest that OPB-171775, with its significant efficacy, could potentially serve as a novel and effective treatment option for advanced GISTs, particularly those resistant to TKIs.

Successful Opening of Ductus Arteriosus with Milrinone in a Newborn with Tetralogy of Fallot and Pulmonary Atresia

Tetralogy of Fallot (TOF) assumes its' most severe form when accompanied by pulmonary atresia (PA). Preserving the patent ductus arteriosus to maintain pulmonary blood flow is life-saving for patients with this congenital heart disease. Milrinone, a selective phosphodiesterase III inhibitor, is a potent vasodilator. Here, we report the successful use of milrinone for a newborn infant with TOF and PA for keeping the ductus arteriosus open and thereby maintaining pulmonary circulation. Milrinone is a useful drug because of its inotropic, lusitropic, and pulmonary vasodilating effects, in addition to its ability to keep the ductus arteriosus open and its relatively mild side-effects. Case series and comparative studies will be needed in the future to verify the effectiveness of this drug.

Development of acute myocardial infarction in a young female patient with essential thrombocythemia treated with anagrelide: a case report

Essential thrombocythemia (ET) is a chronic myeloproliferative disorder with a prolonged clinical course. Since this disorder is considered to be at increased risk of thromboembolism, therapy is mainly focused on the decreased risk of thrombohemorrhagic events by use of cytotoxic agents. Anagrelide is a phosphodiesterase III inhibitor which is utilized in the treatment of ET for the reduction of platelets. However, patients treated with anagrelide might experience cardiovascular adverse effects including myocardial infarction (MI), although these events are rare. Herein, we report a case of a 30-year-old female with well controlled ET by anagrelide, who eventually developed an acute non-ST elevation myocardial infarction (MI). There has no found any cardiovascular risk factors in this ET patient, strongly suggesting that anagrelide might be the cause of MI. Therefore, cardiovascular function should be monitored in those patients prescribed with anagrelide.

Clinical Effects of Additional Cilostazol Administration After Drug-Eluting Stent Insertion

BACKGROUND AND OBJECTIVES: Cilostazol, a selective inhibitor of phosphodiesterase III (PDE III), prevents inactivation of the intracellular second messenger cyclic adenosine monophosphate (cAMP) and irreversibly inhibits platelet aggregation and vasodilation. Hence, we performed this prospective randomized study to evaluate the clinical effects of additional cilostazol administration in patients receiving dual antiplatelet therapy after drug-eluting stent (DES) insertion. SUBJECTS AND METHODS: Between December 2003 and June 2006, we enrolled a total 603 consecutive patients who underwent successful percutaneous coronary intervention (PCI) with DES insertion at Dong-A University Hospital. Study patients received dual antiplatelet therapy (aspirin and clopidogrel, n=301) for at least six months or dual antiplatelet therapy (six months) combined with cilostazol medication for one month (triple therapy, n=302) after PCI. We investigated the incidence of major adverse cardiac events (MACE) at one month and six months after the initiation of medical therapy. MACE was defined as a composite of death, myocardial infarction (MI), stent thrombosis, and target lesion revascularization (TLR). Platelet function was evaluated in 66 patients (dual therapy group, n=40; triple therapy group, n=26) using a Chrono-Log platelet aggregometer and the VerifyNow P2Y12 assay system. RESULTS: The MACE rate was 0.66% in the triple therapy group (death only, 0.67%) and 1.67% in the dual therapy group (death, 0.67%; MI, 0.67%; stent thrombosis, 0.99%; TLR, 0.99%) at one month after PCI (p=0.087). At six months, there were no differences in the MACE rate between the two groups (triple group vs. dual group=2.65% vs. 3.99%, p=0.864). In laboratory tests, platelet aggregation induced by agonists of ADP (27.92+/-13.04% vs. 40.9+/-15.78%, p=0.0008), collagen (13.73+/-6.95% vs. 27.43+/-14.87%, p=0.03), and epinephrine (10.38+/-7.82% vs. 15.5+/-10.45%, p=0.0000) were lower in the triple therapy group versus the dual therapy group. However, platelet aggregation induced by agonists of arachidonic acid (3.23+/-1.07% vs. 3.78+/-2.12%, p=0.23) and ristocetin (29.19+/-35.55% vs. 44.78+/-32.65%, p=0.07) and aspirin reaction unit (412.96+/-96.25 vs. 427.93+/-76.24, p=0.48) measured by VerifyNow were not different in the triple group versus the dual group. CONCLUSION: Additional administration of cilostazol did not decrease the MACE rate when compared to dual therapy six months after PCI in patients with DES.

The vasorelaxatory effect of the milrinone on the preconstricted rat aorta / 대한마취과학회지

BACKGROUND: Milrinone, phosphodiesterase III inhibitor, has been used effectively in patients with right heart failure, especially resulted from pulmonary hypertension. However, milrinone is often used with alpha- and beta-adrenergic receptor agonist to prevent severe systemic vasodilation and unfavorable hypotension. Furthermore, structural and functional vasacular changes are associated with aging and are greatest in the aorta. We evaluated the vasodilatory effects of milrinone and sodium nitroprusside (SNP) on young and old rat aortic rings preconstricted with various catecholamines. METHODS: Aortic rings of young and old rat were placed in 25 ml organ chamber and preconstricted with epinephrine (EPI, 10(-6) M), norepinephrine (NE, 10(-7) M) , phenylephrine 10(-7) M) , and U46619 (10(-8) M). Cummulative dose-responses to milrinone (10(-9)-10(-5) M) and SNP (10(-9)-10(-5) M) were obtained to characterize vasodilatory effects. RESULTS: Relaxation response to milrinone was markedly enhanced in both young and old aortic rings preconstricted with U46619 compared with other vasoconstrictors. The maximal response of the young rat aortic rings preconstricted with NE is significantly reduced, compared with that of EPI. The maximal vasorelaxant response of SNP in young and old aortic rings are nearly identical. CONCLUSIONS: We conclude that combined use of milrinone and epinephrine may be more useful in prevention and treatment of systemic hypotension.

Phosphodiesterase 4D Gene and Risk of Noncardiogenic Ischemic Stroke in a Korean Population

Recently published studies from different populations provide apparently conflicting evidence on the association between the phosphodiesterase 4D (PDE4D) gene and ischemic stroke. The relationship between a representative PDE4D genotype and ischemic stroke was explored in a case-control study of 205 consecutive Korean patients with noncardiogenic ischemic stroke and 103 healthy controls who were neurologically and radiologically proven to be stroke-free. We selected and genotyped a PDE4D single nucleotide polymorphism (SNP 41, rs152312) as a candidate marker for susceptibility to ischemic stroke because SNP 41 has shown the most significant association with stroke in both a meta-analysis and the original Icelandic study of the PDE4D gene. No significant difference was observed between the cases and controls in the distribution of the PDE4D SNP 41 genotypes. The results from the adjusted conditional logistic regression analysis (adjusted for age, hypertension, diabetes and smoking status) showed no significant association between PDE4D SNP 41 genotypes and an increased risk of noncardiogenic ischemic stroke. The PDE4D gene is not a major risk factor for noncardiogenic ischemic stroke in a Korean population, which supports the recent evidence suggesting that the causative genetic variants of ischemic stroke may differ across populations.

Cilostazol Reduces PAC-1 Expression on Platelets in Ischemic Stroke

BACKGROUND AND PURPOSE: Cilostazol, a phosphodiesterase III inhibitor, is known to be a useful antiplatelet agent that inhibits the progression of atherosclerosis in ischemic stroke. This study investigated the effects of combining cilostazol with aspirin on the expressions of P-selectin and PAC-1 on activated platelets in acute ischemic stroke. METHODS: We analyzed 70 patients with acute ischemic stroke (<72 hrs of an ischemic event). The daily intake was 100 mg of aspirin in 37 patients and 100 mg of aspirin plus 200 mg of cilostazol in 33 patients. The expressions of P-selectin and PAC-1 on activated platelets were measured on the day of admission and 5 days later. We also evaluated the clinical progression using the National Institutes of Health Stroke Scale (NIHSS) at the same times. RESULTS: After 5 days the extent of PAC-1 expression on activated platelets was significantly lower for combined aspirin and cilostazol treatment (61.0+/-19.3%, p=0.008; mean+/-standard deviation) than the baseline level (70.9+/-12.9%), but did not differ between aspirin alone (66.0 +/-19.0%) and baseline (70.1+/-15.7%). The expression of P-selectin did not differ between combined aspirin and cilostazol treatment and baseline. The clinical progression did not differ between the two groups, as indicated by the absence of significant changes on the NIHSS in the acute period. CONCLUSIONS:This study found that the combined regimen of aspirin and cilostazol exerts the beneficial effect of reducing PAC-1 activity on activated platelets in acute ischemic stroke. However, the clinical outcome of this regimen was no better than that of the aspirin-only regimen. Therefore, further detailed studies of the possible clinical benefits of cilostazol in acute ischemic stroke are needed.

The Clinical Effects of Cilostazol on Atherosclerotic Vascular Disease

Cilostazol inhibits phosphodiesterase III (PDE III), which is predominantly distributed to and regulates physiologic responses in platelets, cardiac muscle cells, vascular smooth muscle cells, and adipose cells. Clinically, it is well known as an antiplatelet agent that inhibits the platelet aggregation normally induced by collagen, 5'-adenosine diphosphase (ADP), epinephrine, and arachidonic acid. It also has pleotropic effects, including the prevention of restenosis after angioplasty and the promotion of peripheral vascular flow in patients with peripheral vascular diseases. In the drug-eluting stent era, it has emerged as an effective post-intervention anti-atherothrombotic agent and a useful agent for therapy in diabetic patients. The aim of this study was to review the mechanisms of action and clinical trial results associated with cilostazol in cardiovascular disease patients.

Association between mRNA level of Pde4d and Alox5ap and hypertensive stroke as well as hypertension in rats / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To evaluate whether mRNA levels of Pde4d and Alox5ap were associated with hypertensive stroke and hypertension in stroke-prone renovascular hypertensive rats (RHRSP) which could simulate human being's hypertensive cerebral stroke.</p><p><b>METHODS</b>Five groups were established: normotensive group, gradient hypertensive groups I, II and III(with contractive pressure of 140-159 mmHg, 160-179 mmHg and 180-199 mmHg respectively) and spontaneous stroke group. RNA from leukocytes in peripheral blood of each rat underwent real time PCR after reversed.</p><p><b>RESULTS</b>The mRNA levels of Pde4d and Alox5ap of spontaneous stroke group were statistically higher than that of the other groups. Expression of Pde4d of hypertensive group I was a bit higher than that of normotensive group and hypertensive groups II and III; as for Alox5ap, there was no statistical difference between normotensive group and all gradient hypertensive groups.</p><p><b>CONCLUSION</b>Animal experiments come to conclusions that over-expression of Pde4d and Alox5ap are associated with hypertensive stroke but not with hypertension. Therefore, the two genes confer the risk of hypertensive stroke independent of traditional risk factors. It is speculated that over-expression of Pde4d and Alox5ap can motivate onset of hypertensive cerebral stroke by participating in inflammation of arterial walls.</p>

New Inotropic Agent-Levosimendan / 대한마취과학회지

Several clinical studies suggest substantial limitations of currently available positive inotropic substances, including beta1-adrenoceptor agonists and phosphodiesterase III inhibitors. Levosimendan, a myofilament calcium sensitizer with inotropic effects, increases myocardial performance without substantial changes in oxygen consumption and with neutral effects on heart rhythm. In addition, levosimendan has vasodilatory effects that are achieved by stimulation of adenosine triphosphate-dependent potassium channels. This review article briefly discusses the pharmacology of levosimendan and evaluates current available evidence to assess the safety and efficacy of levosimendan.

Expression of human phosphodiesterase 3A gene using baculovirus expression system in insect cell / 药学学报

<p><b>AIM</b>To investigate the expression of recombinant human phosphodiesterase 3A (HPDE3A) using baculovirus expression system in Tn cell line.</p><p><b>METHODS</b>The HPDE3A cDNA was recombined with baculovirus, and then the recombinant was transfected into Tn cell line. The expression of HPDE3A in Tn cell line was detected and identified by the RT-PCR, SDS-PAGE and Western blotting.</p><p><b>RESULTS</b>The recombinant HPDE3A protein was stably expressed in Tn cell line and detected by the distinct morphological changes of Tn cell, RT-PCR, SDS-PAGE and Western blotting using polyclonal antibody. The M(w) of the recombinant protein was about 120 kD.</p><p><b>CONCLUSION</b>Recombinant HPDE3A can be expressed in Tn cell line using the baculovirus expression system, and thus provided the basic material for studying its bioactivity and application in screening for HPDE3A inhibitor.</p>

The Combined Effect of Desflurane and Milrinone on the Function of the Isolated Rat Heart / 대한마취과학회지

BACKGROUND: Desflurane depresses the contractile function of the myocardium. It also causes direct coronary vasodilation. Milrinone, a phosphodiesterase III inhibitor, usually increases myocardial contractility and also has vasodilatory activity. Some inhalation anesthetic agents, such as isoflurane, are safely combined with phosphodiesterase III inhibitors clinically, but milrinone sometimes causes significant hypotension by reducing systemic vascular resistance. The purpose of this study was to evaluate the effect of the combined use of desflurane and milrinone on the function of the isolated rat heart. METHOD: Thirty isolated rat hearts were divided into two groups. [Group 1 (n = 15): desflurane, Group 2 (n = 15): desflurane and milrinone] They were perfused continuously with modified Krebs' solution in a Langendorff retrograde perfusion apparatus. After measuring the control values of the hemodynamic and oxygenation parameters in each group, we administered 6.6 vol% of desflurane to both groups and added sequential perfusion of modified Krebs' solution containing 0.5, 1.0, and 1.5mug/ml of milrinone in Group 2 and then measured the parameters and analyzed them statistically. RESULTS: Baseline measurements in both groups were not statistically different. In Group 1, desflurane significantly decreased LVP (55+/-5 mmHg), dp/dt (557+/-65 mmHg/sec) and MVO2 (71.2+/-16.3 ml/g/min) after 15 minutes. CF (13.9+/-3.1 ml/g/min) and DO2 (176.7+/-43.4 ml/g/min) were increased after 15 minutes. There was no further change after this. In Group 2, desflurane decreased LVP (53+/-18 mmHg), dp/dt (558 90 mmHg/sec) and MVO2 (72.0+/-11.0 ml/g/min) and increased CF (14.2+/-1.9 ml/g/min) and DO2 (175.3+/-29.1 ml/g/min). But, there was no significant difference in the effects of desflurane between the two groups. Milrinone restored LVP, dp/dt and MVO2 to the baseline level, but not with dose-dependency. Desflurane-induced elevated CF and DO2 did not show further changes. CONCLUSIONS: These findings suggest that milrinone increased myocardial contractility and restored the desflurane-induced myocardial depression of the isolated rat heart without further increase of oxygen consumption from the baseline control value. In addition, no additive effects was observed on coronary blood flow when these two agents were used in combination.

Does Milrinone Improve Hemodynamic Variables in Patients with Pulmonary Hypertension Due to Valvular Heart Disease? / 대한마취과학회지

BACKGROUND: Milrinone is a bipyridine phosphodiesterase III inhibitor that exerts both positive inotropic and direct vasodilatory effects. The efficacy and safety of intravenous milrinone in heart failure has been evaluated in a number of clinical studies. In addition, performance of the right ventricle is improved primarily in reduced right ventricular afterload, and pulmonary vascular resistence as milrinone produces minimal inotropic effects on the right ventricle. Most clinical studies have been performed in left ventricular failure patients. Therefore, we investigated whether intravenous milrinone improves the hemodynamics in patients with pulmonary hypertension due to valvular heart disease. METHODS: This study included 33 patients undergoing a valvular replacement with pulmonary hypertension (mean pulmonary artery pressure > or = 30 mmHg after induction). Patients were randomly divided into two groups, normal saline group (N) and milrinone group (M). In group N, normal saline was infused. In group M, a single intravenous bolus of milrinone (50mug/kg body weight) was injected over 10 min. Hemodynamic data were measured at preinjection, 5, 10, and 20 min after injection. RESULTS: There was no significant difference in systemic mean arterial pressure and central venous pressure between both groups. In group M, systemic vascular resistance was reduced at 5 min after injection and cardiac index was improved at 10 min after injection. There was no significant difference in pulmonary mean arterial pressure and vascular resistance between both groups. CONCLUSIONS: Milrinone had no effect on pulmonary artery pressure and pulmonary vascular resistance in patients with pulmonary hypertension due to valvular heart disease. However, it increased cardiac index and decreased systemic vascular resistance.

Effect of Amrinone, a Selective Inhibitor of Phosphodiesterase III, on PMNs-induced Cardiac Dysfunction in Ischemia/reperfusion

Ischemia followed by reperfusion in the presence of polymorphonuclear leukocytes (PMNs) results in a marked cardiac contractile dysfunction. Amrinone, a specific inhibitor of phosphodiesterase 3, has an antioxidant activity against PMNs. Therefore, we hypothesized that amrinone could attenuate PMNs-induced cardiac dysfunction by suppression of reactive oxygen species (ROS) produced fby PMNs. In the present study, we examined the effects of amrinone on isolated ischemic (20 min) and reperfused (45 min) rat hearts perfused with PMNs. Amrinone at 25microM, given to hearts during the first 5 min of reperfusion, significantly improved coronary flow, left ventricular developed pressure (P< 0.001), and the maximal rate of development of left ventricular developed pressure (P< 0.001), compared with ischemic/reperfused hearts perfused with PMNs in the absence of amrinone. In addition, amrinone significantly reduced myeloperoxidase activity by 50.8%, indicating decreased PMNs infiltration (p< 0.001). Superoxide radical and hydrogen peroxide production were also significantly reduced in fMLP- and PMA-stimulated PMNs pretreated with amrinone. Hydroxyl radical was scavenged by amrinone. fMLP-induced elevation of [Ca2+]i was also inhibited by amrinone. These results provide evidence that amrinone can significantly attenuate PMN-induced cardiac contractile dysfunction in the ischemic/ reperfused rat heart via attenuation of PMNs infiltration into the myocardium and suppression of ROS release by PMNs.