Repetitive preischemic infusion of phosphodiesterase III inhibitor olprinone elicits cardioprotective effects in the failing heart after myocardial infarction

Clinical pharmacology of cardiac cyclic AMP in human heart failure: too much or too little?

INTRODUCTION

Cyclic 3', 5'-adenosine monophosphate (cAMP) is a major signaling hub in cardiac physiology. Although cAMP signaling has been extensively studied in cardiac cells and animal models of heart failure (HF), not much is known about its actual amount present inside human failing or non-failing cardiomyocytes. Since many drugs used in HF work via cAMP, it is crucial to determine the status of its intracellular levels in failing vs. normal human hearts.

AREAS COVERED

Only studies performed on explanted/excised cardiac tissues from patients were examined. Studies that contained no data from human hearts or no data on cAMP levels per se were excluded from this perspective's analysis.

EXPERT OPINION

Currently, there is no consensus on the status of cAMP levels in human failing vs. non-failing hearts. Several studies on animal models may suggest maladaptive (e.g. pro-apoptotic) effects of cAMP on HF, advocating for cAMP lowering for therapy, but human studies almost universally indicate that myocardial cAMP levels are deficient in human failing hearts. It is the expert opinion of this perspective that intracellular cAMP levels are too low in human failing hearts, contributing to the disease. Strategies to increase (restore), not decrease, these levels should be pursued in human HF.

A Double-Blind Placebo-Controlled Study of the Effects of Olprinone, a Specific Phosphodiesterase III Inhibitor, for Preventing Postoperative Atrial Fibrillation in Patients Undergoing Pulmonary Resection for Lung Cancer

BACKGROUND

We previously reported that patients with elevated preoperative B-type natriuretic peptide (BNP) levels have an increased risk for postoperative atrial fibrillation following lung cancer surgery. The present study evaluated whether the specific phosphodiesterase III inhibitor olprinone can reduce the incidence of postoperative atrial fibrillation in patients with elevated BNP levels undergoing pulmonary resection for lung cancer.

METHODS

A prospective randomized study was conducted with 40 patients who had elevated preoperative BNP levels (≥ 30 pg/mL) and underwent scheduled lung cancer surgery. All patients were in sinus rhythm at surgery. Low-dose olprinone or placebo was continuously infused for 24 h and started just before anesthesia induction. The primary end point was the incidence of postoperative atrial fibrillation. The secondary end points were perioperative hemodynamics and levels of BNP, WBC counts, and C-reactive protein.

RESULTS

The incidence of postoperative atrial fibrillation was significantly lower in the olprinone group than in the placebo group (10% vs 60%, P < .001). Patients in the olprinone group showed significantly lower BNP, WBC counts, and C-reactive protein levels after surgery.

CONCLUSIONS

Continuous infusion of olprinone during lung cancer surgery was safe and reduced the incidence of postoperative atrial fibrillation following pulmonary resection in patients with elevated preoperative BNP levels.

TRIAL REGISTRY

Japan Primary Registries Network; No.: JPRN-UMIN2404; URL: http://www.umin.ac.jp/ctr/.

Hepatoprotective effect by pretreatment with olprinone in a swine partial hepatectomy model

Excessive portal flow to a small remnant liver or small-for-size graft is a primary factor of small-for-size syndrome. We demonstrated that olprinone (OLP), a phosphodiesterase III inhibitor, had a hepatoprotective effect in a rat extended hepatectomy model and a small-for-size liver transplantation model through a modification of the portal venous pressure (PVP). To identify the appropriate dose and duration of treatment for clinical applications, we conducted experiments with a swine partial hepatectomy model. Twenty microminipigs were divided into 4 groups that received the following treatments: (A) saline (control group), (B) OLP at 0.3 μg/kg/minute (preoperative and postoperative administration), (C) OLP at 0.1 μg/kg/minute (preoperative administration), and (D) OLP at 0.3 μg/kg/minute (preoperative administration). The pigs underwent 70% partial hepatectomy. Hemodynamic changes, including changes in PVP, were examined. Liver biopsy was performed 1 and 3 hours after hepatectomy. Blood samples were collected until postoperative day 7 (POD7). In comparison with group A, PVP elevations, periportal edema, and sinusoidal hemorrhaging were attenuated after left Glisson's ligation in groups C and D. Pretreatment with OLP in groups C and D preserved the microstructure of sinusoids and improved the prothrombin activity 1 and 3 hours after hepatectomy. These animals showed better recovery of the remnant liver volume and the plasma disappearance rate of indocyanine green on POD7. In contrast, group B showed exacerbation of liver damage. Measurements of the serum OLP concentration showed that 10 ng/mL OLP was appropriate for a hepatoprotective effect. In conclusion, pretreatment with OLP shows hepatoprotective effects in a swine partial hepatectomy model. OLP may have the potential to ameliorate patients' outcomes after hepatectomy or liver transplantation.

Cyclic nucleotide phosphodiesterase 3A1 protects the heart against ischemia-reperfusion injury

Phosphodiesterase 3A (PDE3A) is a major regulator of cAMP in cardiomyocytes. PDE3 inhibitors are used for acute treatment of congestive heart failure, but are associated with increased incidence of arrhythmias and sudden death with long-term use. We previously reported that chronic PDE3A downregulation or inhibition induced myocyte apoptosis in vitro. However, the cardiac protective effect of PDE3A has not been demonstrated in vivo in disease models. In this study, we examined the role of PDE3A in regulating myocardial function and survival in vivo using genetically engineered transgenic mice with myocardial overexpression of the PDE3A1 isozyme (TG). TG mice have reduced cardiac function characterized by reduced heart rate and ejection fraction (52.5±7.8% vs. 83.9±4.7%) as well as compensatory expansion of left ventricular diameter (4.19±0.19mm vs. 3.10±0.18mm). However, there was no maladaptive increase of fibrosis and apoptosis in TG hearts compared to wild type (WT) hearts, and the survival rates also remained the same. The diminution of cardiac contractile function is very likely attributed to a decrease in beta-adrenergic receptor (β-AR) response in TG mice. Importantly, the myocardial infarct size (4.0±1.8% vs. 24.6±3.8%) and apoptotic cell number (1.3±1.0% vs. 5.6±1.5%) induced by ischemia/reperfusion (I/R) injury were significantly attenuated in TG mice. This was associated with decreased expression of inducible cAMP early repressor (ICER) and increased expression of anti-apoptotic protein BCL-2. To further verify the anti-apoptotic effects of PDE3A1, we performed in vitro apoptosis study in isolated adult TG and WT cardiomyocytes. We found that the apoptotic rates stimulated by hypoxia/reoxygenation or H2O2 were indeed significantly reduced in TG myocytes, and the differences between TG and WT myocytes were completely reversed in the presence of the PDE3 inhibitor milrinone. These together indicate that PDE3A1 negatively regulates β-AR signaling and protects against I/R injury by inhibiting cardiomyocyte apoptosis.

Activation ofβ2-adrenergic receptor plays a pivotal role in generating the protective effect of ischemic preconditioning in rat hearts

BACKGROUND

Ischemic preconditioning (IPC) protects hearts against ischemia by reducing infarct size. However, IPC does not preserve cardiac function, such as left ventricular peak developed pressure (LVPDP). Moreover, IPC fails to protect the post-myocardial infarct (MI) heart.

DESIGN

Rat hearts were transfected with beta2-adrenergic receptor (B2AR) cDNA by the hemagglutinating virus of Japan-liposome method. After the gene transfer, the hearts were perfused in a Langendorff mode and preconditioned with two cycles of 5 min of ischemia and reperfusion. After 20 min of global ischemia, the hearts were reperfused under aerobic conditions for 90 min. LVPDP was measured as an indicator of the cardiac function.

RESULTS

LVPDP of ischemic hearts was well preserved by the combination treatment of IPC and gene transfer of B2AR, but not IPC or gene transfer of B2AR alone. Moreover, the treatment was beneficial to even the post-MI heart. On the contrary, gene transfer of beta-adrenergic receptor kinase 1 (BARK1) reduced the protective effect of IPC. We also found that the mRNA ratio of B2AR and BARK1 was well correlated with the preservation of the LVPDP.

CONCLUSIONS

The combination treatment of IPC and gene transfer of B2AR protects cardiac function against ischemia and it shows the beneficial effect also in post-MI hearts.

Pivotal effects of phosphodiesterase inhibitors on myocyte contractility and viability in normal and ischemic hearts

Phosphodiesterases (PDEs) are enzymes that degrade cellular cAMP and cGMP and are thus essential for regulating the cyclic nucleotides. At least 11 families of PDEs have been identified, each with a distinctive structure, activity, expression, and tissue distribution. The PDE type-3, -4, and -5 (PDE3, PDE4, PDE5) are localized to specific regions of the cardiomyocyte, such as the sarcoplasmic reticulum and Z-disc, where they are likely to influence cAMP/cGMP signaling to the end effectors of contractility. Several PDE inhibitors exhibit remarkable hemodynamic and inotropic properties that may be valuable to clinical practice. In particular, PDE3 inhibitors have potent cardiotonic effects that can be used for short-term inotropic support, especially in situations where adrenergic stimulation is insufficient. Most relevant to this review, PDE inhibitors have also been found to have cytoprotective effects in the heart. For example, PDE3 inhibitors have been shown to be cardioprotective when given before ischemic attack, whereas PDE5 inhibitors, which include three widely used erectile dysfunction drugs (sildenafil, vardenafil and tadalafil), can induce remarkable cardioprotection when administered either prior to ischemia or upon reperfusion. This article provides an overview of the current laboratory and clinical evidence, as well as the cellular mechanisms by which the inhibitors of PDE3, PDE4 and PDE5 exert their beneficial effects on normal and ischemic hearts. It seems that PDE inhibitors hold great promise as clinically applicable agents that can improve cardiac performance and cell survival under critical situations, such as ischemic heart attack, cardiopulmonary bypass surgery, and heart failure.

Cardioprotection induced by olprinone, a phosphodiesterase III inhibitor, involves phosphatidylinositol-3-OH kinase-Akt and a mitochondrial permeability transition pore during early reperfusion

PURPOSE

Ischemic preconditioning is mediated by the activation of phosphatidylinositol-3-OH kinase-Akt (PI3K-Akt) and by the inhibition of the opening of a mitochondrial permeability transition pore (mPTP) during early reperfusion. Preischemic administration of the phosphodiesterase type III inhibitor olprinone protects the myocardium against infarction, but its mechanism has not been fully clarified. We hypothesized that this olprinone-induced cardioprotective effect was mediated by the activation of PI3K-Akt and by the inhibition of mPTP during early reperfusion.

METHODS

Pentobarbital-anesthetized rats (n = 42) subjected to 30-min coronary occlusion followed by 2-h reperfusion, received olprinone (20 microg.kg(-1)) or saline (control) in the preischemic phase in the presence or absence of the PI3K-Akt inhibitor wortmannin (0.6 mg.kg(-1)) or the mPTP opener atractyloside (5 mg.kg(-1)) before 5 min of reperfusion. The myocardial infarct size was expressed as a percentage of the area at risk. All values were expressed as means +/- SD. Statistical comparisons within groups were made using repeated-measures analysis of variance (ANOVA), followed by a paired t-test, and comparisons among groups were analyzed using a two-way ANOVA, followed by the Tukey-Kramer test.

RESULTS

Mean arterial pressure and heart rate showed no significant differences within or among groups. The preischemic administration of olprinone significantly reduced the infarct size (12 +/- 4%) as compared with that in the control group (43 +/- 4%). Wortmannin or atractyloside abolished the protective effect of olprinone (42 +/- 11% or 41 +/- 10%).

CONCLUSION

The olprinone-induced cardioprotective effect could be exerted via the activation of PI3K-Akt and the inhibition of mPTP during early reperfusion.

Milrinone administered before ischemia or just after reperfusion, attenuates myocardial stunning in anesthetized swine

PURPOSE

We assessed the dose or timing effect of milrinone administered against myocardial stunning in 37 anesthetized open-chest swine.

METHODS

All swine were subjected to 12-min ischemia followed by reperfusion to produce myocardial stunning. Group A (n = 12) received saline in place of milrinone both before and after ischemia. Group B (n = 9) and C (n = 9) received intravenous milrinone at a rate of 5 microg/kg/min for 10 min followed by 0.5 microg/kg/min for 10 min and 10 microg/kg/min for 10 min followed by 1 microg/kg/min for 10 min, respectively, until 30 min before coronary occlusion. Group D (n = 7) received the same dose of milrinone as group B starting 1 min after reperfusion. Myocardial contractility was assessed by percentage segment shortening (%SS).

RESULTS

Five swine in group A and two swine in groups B and C each had ventricular fibrillation or tachycardia after reperfusion, and were thus excluded from further analysis. The percentage changes of %SS from the baseline 90 min after reperfusion in groups B, C, and D were 78 +/- 9%, 82 +/- 13%, and 79 +/- 7%, respectively, which were significantly higher than those in group A (43 +/- 13%).

CONCLUSION

We conclude that milrinone administered before ischemia or just after reperfusion attenuates myocardial stunning.

The role of β‐Adrenergic Receptor Signaling in Cardioprotection

This study examines the role of the beta2-adrenergic receptor (beta2-AR) in cardioprotection. The beta2-AR couples to Gs and Gi proteins. Gs activates PKA, which phosphorylates the receptor and switches beta2-AR coupling from Gs to Gi. Prior to 20 min of global ischemia, mouse hearts were either perfused for 30 min without treatment (control), treated with 10 nmol/L of isoproterenol (ISO) for 5 min followed by 5 min washout, or preconditioned with 4 cycles of 5 min ischemia and 5 min reflow (PC). Recovery of left ventricular developed pressure (LVDP) and infarct size were measured. Intermittent ISO treatment improved post-ischemic recovery of LVDP (58.5+/-4.8% vs. 22.0+/-6.3% in control) and reduced infarct size (31.0+/-2.4% vs. 53.0+/-4.6% in control). The Gi inhibitor pertussis toxin blocked the ISO-induced improvement in postischemic LVDP and infarct size. To test the role of beta2-AR in PC, we studied mice lacking beta2-AR (beta2-AR-/-) and found that PC had no effect on postischemic LVDP or infarct size in beta2-AR-/-. To test whether PKA is required for the PC and ISO-induced protection, hearts were treated with the PKA inhibitors PKI and H-89. We found that PKI and H-89 blocked the PC- and ISO-induced improvement in postischemic LVDP and infarct size. These data show an important role for beta2-AR in cardioprotection and support the novel hypothesis that preconditioning involves switching of beta2-AR coupling from Gs to Gi.

Protein kinase A as another mediator of ischemic preconditioning independent of protein kinase C

BACKGROUND

We and others have reported that transient accumulation of cyclic AMP (cAMP) in the myocardium during ischemic preconditioning (IP) limits infarct size independent of protein kinase C (PKC). Accumulation of cAMP activates protein kinase A (PKA), which has been demonstrated to cause reversible inhibition of RhoA and Rho-kinase. We investigated the involvement of PKA and Rho-kinase in the infarct limitation by IP.

METHODS AND RESULTS

Dogs were subjected to 90-minute ischemia and 6-hour reperfusion. We examined the effect on Rho-kinase activity during sustained ischemia and infarct size of (1) preischemic transient coronary occlusion (IP), (2) preischemic activation of PKA/PKC, (3) inhibition of PKA/PKC during IP, and (4) inhibition of Rho-kinase or actin cytoskeletal deactivation during myocardial ischemia. Either IP or dibutyryl-cAMP treatment activated PKA, which was dose-dependently inhibited by 2 PKA inhibitors (H89 and Rp-cAMP). IP and preischemic PKA activation substantially reduced infarct size, which was blunted by preischemic PKA inhibition. IP and preischemic PKA activation, but not PKC activation, caused a substantial decrease of Rho-kinase activation during sustained ischemia. These changes were cancelled by preischemic inhibition of PKA but not PKC. Furthermore, either Rho-kinase inhibition (hydroxyfasudil or Y27632) or actin cytoskeletal deactivation (cytochalasin-D) during sustained ischemia achieved the same infarct limitation as preischemic PKA activation without affecting systemic hemodynamic parameters, the area at risk, or collateral blood flow.

CONCLUSIONS

Transient preischemic activation of PKA reduces infarct size through Rho-kinase inhibition and actin cytoskeletal deactivation during sustained ischemia, implicating a novel mechanism for cardioprotection by ischemic preconditioning independent of PKC and a potential new therapeutic target.