Effects of cilostazol in the heart

SIRT1-FOXOs signaling pathway: A potential target for attenuating cardiomyopathy

Cardiomyopathy constitutes a global health burden. It refers to myocardial injury that causes alterations in cardiac structure and function, ultimately leading to heart failure. Currently, there is no definitive treatment for cardiomyopathy. This is because existing treatments primarily focus on drug interventions to attenuate symptoms rather than addressing the underlying causes of the disease. Notably, the cardiomyocyte loss is one of the key risk factors for cardiomyopathy. This loss can occur through various mechanisms such as metabolic disturbances, cardiac stress (e.g., oxidative stress), apoptosis as well as cell death resulting from disorders in autophagic flux, etc. Sirtuins (SIRTs) are categorized as class III histone deacetylases, with their enzyme activity primarily reliant on the substrate nicotinamide adenine dinucleotide (NAD (+)). Among them, Sirtuin 1 (SIRT1) is the most intensively studied in the cardiovascular system. Forkhead O transcription factors (FOXOs) are the downstream effectors of SIRT1. Several reports have shown that SIRT1 can form a signaling pathway with FOXOs in myocardial tissue, and this pathway plays a key regulatory role in cell loss. Thus, this review describes the basic mechanism of SIRT1-FOXOs in inhibiting cardiomyocyte loss and its favorable role in cardiomyopathy. Additionally, we summarized the SIRT1-FOXOs related regulation factor and prospects the SIRT1-FOXOs potential clinical application, which provide reference for the development of cardiomyopathy treatment.

No-reflow after recanalization in ischemic stroke: From pathomechanisms to therapeutic strategies

Endovascular reperfusion therapy is the primary strategy for acute ischemic stroke. No-reflow is a common phenomenon, which is defined as the failure of microcirculatory reperfusion despite clot removal by thrombolysis or mechanical embolization. It has been reported that up to 25% of ischemic strokes suffer from no-reflow, which strongly contributes to an increased risk of poor clinical outcomes. No-reflow is associated with functional and structural alterations of cerebrovascular microcirculation, and the injury to the microcirculation seriously hinders the neural functional recovery following macrovascular reperfusion. Accumulated evidence indicates that pathology of no-reflow is linked to adhesion, aggregation, and rolling of blood components along the endothelium, capillary stagnation with neutrophils, astrocytes end-feet, and endothelial cell edema, pericyte contraction, and vasoconstriction. Prevention or treatment strategies aim to alleviate or reverse these pathological changes, including targeted therapies such as cilostazol, adhesion molecule blocking antibodies, peroxisome proliferator-activated receptors (PPARs) activator, adenosine, pericyte regulators, as well as adjunctive therapies, such as extracorporeal counterpulsation, ischemic preconditioning, and alternative or complementary therapies. Herein, we provide an overview of pathomechanisms, predictive factors, diagnosis, and intervention strategies for no-reflow, and attempt to convey a new perspective on the clinical management of no-reflow post-ischemic stroke.

Drugs targeting adenosine signaling pathways: A current view

Adenosine is an endogenous nucleoside that regulates many physiological and pathological processes. It is derived from either the intracellular or extracellular dephosphorylation of adenosine triphosphate and interacts with cell-surface G-protein-coupled receptors. Adenosine plays a substantial role in protecting against cell damage in areas of increased tissue metabolism and preventing organ dysfunction in pathological states. Targeting adenosine metabolism and receptor signaling may be an effective therapeutic approach for human diseases, including cardiovascular and central nervous system disorders, rheumatoid arthritis, asthma, renal diseases, and cancer. Several lines of evidence have shown that many drugs exert their beneficial effects by modulating adenosine signaling pathways but this knowledge urgently needs to be summarized, and most importantly, actualized. The present review collects pharmaceuticals and pharmacological or diagnostic tools that target adenosine signaling in their primary or secondary mode of action. We overviewed FDA-approved drugs as well as those currently being studied in clinical trials. Among them are already used in clinic A2A adenosine receptor modulators like istradefylline or regadenoson, but also plenty of anti-platelet, anti-inflammatory, or immunosuppressive, and anti-cancer drugs. On the other hand, we investigated dozens of specific adenosine pathway regulators that are tested in clinical trials to treat human infectious and noninfectious diseases. In conclusion, targeting purinergic signaling represents a great therapeutic challenge. The actual knowledge of the involvement of adenosinergic signaling as part of the mechanism of action of old drugs has open a path not only for drug-repurposing but also for new therapeutic strategies.

In vivo phenotypic validation of adenosine receptor-dependent activity of non-adenosine drugs

Some non-adenosinergic drugs are reported to also act through adenosine receptors (ARs). We used mouse hypothermia, which can be induced by agonism at any of the four ARs, as an in vivo screen for adenosinergic effects. An AR contribution was identified when a drug caused hypothermia in wild type mice that was diminished in mice lacking all four ARs (quadruple knockout, QKO). Alternatively, an adenosinergic effect was identified if a drug potentiated adenosine-induced hypothermia. Four drugs (dipyridamole, nimodipine, cilostazol, cyclosporin A) increased the hypothermia caused by adenosine. Dipyridamole and nimodipine probably achieved this by inhibition of adenosine clearance via ENT1. Two drugs (cannabidiol, canrenoate) did not cause hypothermia in wild type mice. Four other drugs (nifedipine, ranolazine, ketamine, ethanol) caused hypothermia, but the hypothermia was unchanged in QKO mice indicating non-adenosinergic mechanisms. Zinc chloride caused hypothermia and hypoactivity; the hypoactivity was blunted in the QKO mice. Interestingly, the antidepressant amitriptyline caused hypothermia in wild type mice that was amplified in the QKO mice. Thus, we have identified adenosine-related effects for some drugs, while other candidates do not affect adenosine signaling by this in vivo assay. The adenosine-modulating drugs could be considered for repurposing based on predicted effects on AR activation.

Long-term effectiveness and safety of cilostazol versus clopidogrel in secondary prevention of noncardioembolic ischemic stroke

PURPOSE

Cilostazol is a widely used antiplatelet drug for secondary stroke prevention in Asia, but its comparison with clopidogrel is not well understood. This study aims to investigate the effectiveness and safety of cilostazol compared to clopidogrel for the secondary prevention of noncardioembolic ischemic stroke.

METHODS

This retrospective comparative effectiveness research analyzed 1:1 propensity scorematched data from insured individuals between 2012 and 2019, using administrative claims data in Health Insurance Review and Assessment in Korea. Patients with diagnosis codes for ischemic stroke without cardiac disease were included and divided into two groups, those receiving cilostazol and those receiving clopidogrel. The primary outcome was a recurrent ischemic stroke. Secondary outcomes included all-cause death, myocardial infarction, hemorrhagic stroke, and a composite of these outcomes. The safety outcome was major gastrointestinal bleeding.

RESULTS

The study analyzed 4,754 patients in the propensity scorematched population and found no statistically significant difference in recurrent ischemic stroke (cilostazol group vs clopidogrel group, 2.7% vs 3.2%; 95% CI, 0.62-1.21), the composite outcome of recurrent ischemic stroke, all-cause death, myocardial infarction, and hemorrhagic stroke (5.1% vs 5.5%; 0.75-1.22), and major gastrointestinal bleeding (1.3% vs 1.5%; 0.57-1.47) between patients receiving cilostazol and those receiving clopidogrel. In subgroup analysis, cilostazol was associated with a lower incidence of recurrent ischemic stroke compared to clopidogrel in hypertensive patients (2.5% vs 3.9%; interaction P = 0.041).

CONCLUSIONS

This real-world study suggests that cilostazol is effective and safe for noncardioembolic ischemic stroke and may be associated with better effectiveness in hypertensive patients compared to clopidogrel.

Pharmacological treatment of short-coupled idiopathic ventricular fibrillation: A review

Short-coupled idiopathic ventricular fibrillation (IVF) is a subtype of IVF in which episodes of polymorphic ventricular tachycardia or ventricular fibrillation are initiated by short-coupled premature ventricular contractions (PVCs). Our understanding of the pathophysiology is evolving, with evidence suggesting that these malignant PVCs originate from the Purkinje system. In most cases, the genetic underpinning has not been identified. Whereas the implantation of an implantable cardioverter-defibrillator is uncontroversial, the choice of pharmacological treatment is the subject of discussion. In this review, we summarize the available knowledge on pharmacological therapy in short-coupled IVF and provide our recommendations for management of patients with this syndrome.

J wave syndromes: What's new?

Among the inherited ion channelopathies associated with potentially life-threatening ventricular arrhythmia syndromes in nominally structurally normal hearts are the J wave syndromes, which include the Brugada (BrS) and early repolarization (ERS) syndromes. These ion channelopathies are responsible for sudden cardiac death (SCD), most often in young adults in the third and fourth decade of life. Our principal goal in this review is to briefly outline the clinical characteristics, as well as the molecular, ionic, cellular, and genetic mechanisms underlying these primary electrical diseases that have challenged the cardiology community over the past two decades. In addition, we discuss our recently developed whole-heart experimental model of BrS, providing compelling evidence in support of the repolarization hypothesis for the BrS phenotype as well as novel findings demonstrating that voltage-gated sodium and transient outward current channels can modulate each other's function via trafficking and gating mechanisms with implications for improved understanding of the genetics of both cardiac and neuronal syndromes.

Considering population variability of electrophysiological models improves the in silico assessment of drug-induced torsadogenic risk

BACKGROUND AND OBJECTIVE

In silico tools are known to aid in drug cardiotoxicity assessment. However, computational models do not usually consider electrophysiological variability, which may be crucial when predicting rare adverse events such as drug-induced Torsade de Pointes (TdP). In addition, classification tools are usually binary and are not validated using an external data set. Here we analyze the role of incorporating electrophysiological variability in the prediction of drug-induced arrhythmogenic-risk, using a ternary classification and two external validation datasets.

METHODS

The effects of the 12 training CiPA drugs were simulated at three different concentrations using a single baseline model and an electrophysiologically calibrated population of models. 9 biomarkers related with action potential (AP), calcium dynamics and net charge were measured for each simulated concentration. These biomarkers were used to build ternary classifiers based on Support Vector Machines (SVM) methodology. Classifiers were validated using two external drug sets: the 16 validation CiPA drugs and 81 drugs from CredibleMeds database.

RESULTS

Population of models allowed to obtain different AP responses under the same pharmacological intervention and improve the prediction of drug-induced TdP with respect to the baseline model. The classification tools based on population of models achieve an accuracy higher than 0.8 and a mean classification error (MCE) lower than 0.3 for both validation drug sets and for the two electrophysiological action potential models studied (Tomek et al. 2020 and a modified version of O'Hara et al. 2011). In addition, simulations with population of models allowed the identification of individuals with lower conductances of I_Kr, I_Ks, and I_NaK and higher conductances of I_CaL, I_NaL, and I_NCX, which are more prone to develop TdP.

CONCLUSIONS

The methodology presented here provides new opportunities to assess drug-induced TdP-risk, taking into account electrophysiological variability and may be helpful to improve current cardiac safety screening methods.

Update on Cilostazol: A Critical Review of Its Antithrombotic and Cardiovascular Actions and Its Clinical Applications

Cilostazol, a phosphodiesterase III inhibitor, has vasodilating and antiplatelet properties with a low rate of bleeding complications. It has been used over the past 25 years for improving intermittent claudication in patients with peripheral artery disease (PAD). Cilostazol also has demonstrated efficacy in patients undergoing percutaneous revascularization procedures for both PAD and coronary artery disease. In addition to its antithrombotic and vasodilating actions, cilostazol also inhibits vascular smooth muscle cell proliferation via phosphodiesterase III inhibition, thus mitigating restenosis. Accumulated evidence has shown that cilostazol, due to its "pleiotropic" effects, is a useful, albeit underutilized, agent for both coronary artery disease and PAD. It is also potentially useful after ischemic stroke and is an alternative in those who are allergic or intolerant to classical antithrombotic agents (eg, aspirin or clopidogrel). These issues are herein reviewed together with the pharmacology and pharmacodynamics of cilostazol. Large studies and meta-analyses are presented and evaluated. Current guidelines are also discussed, and the spectrum of cilostazol's actions and therapeutic applications are illustrated.

Therapeutic Potential of Phosphodiesterase Inhibitors for Endothelial Dysfunction- Related Diseases

Cardiovascular diseases (CVD) are considered a major health problem worldwide, being the main cause of mortality in developing and developed countries. Endothelial dysfunction, characterized by a decline in nitric oxide production and/or bioavailability, increased oxidative stress, decreased prostacyclin levels, and a reduction of endothelium-derived hyperpolarizing factor is considered an important prognostic indicator of various CVD. Changes in cyclic nucleotides production and/ or signalling, such as guanosine 3', 5'-monophosphate (cGMP) and adenosine 3', 5'-monophosphate (cAMP), also accompany many vascular disorders that course with altered endothelial function. Phosphodiesterases (PDE) are metallophosphohydrolases that catalyse cAMP and cGMP hydrolysis, thereby terminating the cyclic nucleotide-dependent signalling. The development of drugs that selectively block the activity of specific PDE families remains of great interest to the research, clinical and pharmaceutical industries. In the present review, we will discuss the effects of PDE inhibitors on CVD related to altered endothelial function, such as atherosclerosis, diabetes mellitus, arterial hypertension, stroke, aging and cirrhosis. Multiple evidences suggest that PDEs inhibition represents an attractive medical approach for the treatment of endothelial dysfunction-related diseases. Selective PDE inhibitors, especially PDE3 and PDE5 inhibitors are proposed to increase vascular NO levels by increasing antioxidant status or endothelial nitric oxide synthase expression and activation and to improve the morphological architecture of the endothelial surface. Thereby, selective PDE inhibitors can improve the endothelial function in various CVD, increasing the evidence that these drugs are potential treatment strategies for vascular dysfunction and reinforcing their potential role as an adjuvant in the pharmacotherapy of CVD.

In Silico Classifiers for the Assessment of Drug Proarrhythmicity

Drug-induced torsade de pointes (TdP) is a life-threatening ventricular arrhythmia responsible for the withdrawal of many drugs from the market. Although currently used TdP risk-assessment methods are effective, they are expensive and prone to produce false positives. In recent years, in silico cardiac simulations have proven to be a valuable tool for the prediction of drug effects. The objective of this work is to evaluate different biomarkers of drug-induced proarrhythmic risk and to develop an in silico risk classifier. Cellular simulations were performed using a modified version of the O'Hara et al. ventricular action potential model and existing pharmacological data (IC₅₀ and effective free therapeutic plasma concentration, EFTPC) for 109 drugs of known torsadogenic risk (51 positive). For each compound, four biomarkers were tested: T_x (drug concentration leading to a 10% prolongation of the action potential over the EFTPC), T_qNet (net charge carried by ionic currents when exposed to 10 times the EFTPC with respect to the net charge in control), T_triang (triangulation for a drug concentration of 10 times the EFTPC over triangulation in control), and T_EAD (drug concentration originating early afterdepolarizations over EFTPC). Receiver operating characteristic (ROC) curves were built for each biomarker to evaluate their individual predictive quality. At the optimal cutoff point, accuracies for T_x, T_qNet, T_triang, and T_EAD were 89.9, 91.7, 90.8, and 78.9% respectively. The resulting accuracy of the hERG IC₅₀ test (current biomarker) was 78.9%. When combining T_x, T_qNet and T_triang into a classifier based on decision trees, the prediction improves, achieving an accuracy of 94.5%. The sensitivity analysis revealed that most of the effects on the action potential are mainly due to changes in I_Kr, I_CaL, I_NaL and I_Ks. In fact, considering that drugs affect only these four currents, TdP risk classification can be as accurate as when considering effects on the seven main currents proposed by the CiPA initiative. Finally, we built a ready-to-use tool (based on more than 450 000 simulations), which can be used to quickly assess the proarrhythmic risk of a compound. In conclusion, our in silico tool can be useful for the preclinical assessment of TdP-risk and to reduce costs related with new drug development. The TdP risk-assessment tool and the software used in this work are available at https://riunet.upv.es/handle/10251/136919.

Cilostazol restores autophagy flux in bafilomycin A1-treated, cultured cortical astrocytes through lysosomal reacidification: roles of PKA, zinc and metallothionein 3

Cilostazol, a phosphodiesterase 3 inhibitor, reduces the amyloid-beta (Aβ) burden in mouse models of Alzheimer disease by as yet unidentified mechanisms. In the present study, we examined the possibility that cilostazol ameliorates lysosomal dysfunction. Astrocytes treated with bafilomycin A1 (BafA1) exhibited markedly reduced DND-189 and acridine orange (AO) fluorescence, indicating reduced lysosomal acidity. In both cases, BafA1-induced alkalization was reversed by addition of cilostazol, dibutyryl cAMP or forskolin. All three agents significantly increased free zinc levels in lysosomes, and addition of the zinc chelator TPEN abrogated lysosomal reacidification. These treatments did not raise free zinc levels or reverse BafA1-mediated lysosomal alkalization in metallothionein 3 (Mt3)-null astrocytes, indicating that the increases in zinc in astrocytes were derived mainly from Mt3. Lastly, in FITC-Aβ-treated astrocytes, cilostazol reversed lysosomal alkalization, increased cathepsin D activity, and reduced Aβ accumulation in astrocytes. Cilostazol also reduced mHtt aggregate formation in GFP-mHttQ74–expressing astrocytes. Collectively, our results present the novel finding that cAMP/PKA can overcome the v-ATPase blocking effect of BafA1 in a zinc- and Mt3-dependent manner.

Suppression of experimental atrial fibrillation in a canine model of rapid atrial pacing by the phosphodiesterase 3 inhibitor cilostazol

OBJECTIVE

Atrial fibrillation (AF) represents the most common arrhythmia encountered in cardiology department. The purpose of this study was designed to investigate whether cilostazol, an oral phosphodiesterase 3 inhibitor (PDE3) could have protective effects on atrial remodeling in a canine model of AF and explore the potential molecular mechanisms.

METHODS

Dogs were randomly assigned to Sham, Paced, Paced + cilostazol group, 7 dogs in each group. In Sham group, pacemaker was instrumented but without pacing. Rapid atrial pacing (RAP) at 600 or 500 bpm/min was maintained in Paced group and Paced + cilo group for 2 h or 2 weeks in acute or chronic experiment, respectively. The Paced + cilo group of dogs were pretreated with cilostazol orally (10 mg·kg^-1·d^-1, cilo) for 1 h or 2 days prior RAP induction and served as treatment group. Atrial effective refractory periods (AERP) at different basic cycle lengths (BCLs), inducibility, and duration time of AF were measured after pacing for 2 h. The blood sample, echocardiography, histopathology, inflammation and oxidative stress makers, protein and mRNA expression levels of matrix metalloproteinase-2 (MMP-2) and MMP-9 were detected after 2 weeks pacing in each group.

RESULTS

Significant changes in electrophysiological parameters were observed in the acute RAP canine model, the AERPs shortened with increased inducibility and duration of AF, which was attenuated by cilostazol (P < 0.05). The serum inflammation makers as interleukin-8 (IL-8) and toll like receptor 4 (TLR 4) levels and oxidative stress indicators like xanthine oxidative (XO) and reactive oxygen species (ROS) in the Paced group was significantly higher than that in Sham group (P < 0.01), and was significantly reduced by cilostazol treatment (P < 0.01). The level of mean platelet volume (MPV) which is one of the platelet indices was significantly elevated in Paced group (P < 0.01). While after cilostazol treated for 2 weeks, the level of MPV was obviously decreased than Paced group (P < 0.01). Pathology and echocardiography studies showed that cilostazol can also prevent RAP induced cardiac fibrosis and structural remodeling. The MPV level has close correlations with IL-8, TLR4, XO and ROS (all P < 0.01). MMP-2 and MMP-9 expression were significantly increased in Paced group (all P < 0.01), which can be attenuated by cilostazol.

CONCLUSIONS

Cilostazol may have protective effects on RAP-induced atrial remodeling by anti-inflammatory, anti-oxidative stress action and regulate the extracellular collagen matrix in a canine model. Moreover, MPV level is associated with inflammation and oxidative stress response of RAP, which might be an important predictors of new-onset and recurrent AF.

microRNA-142-mediated repression of phosphodiesterase 3B critically regulates peripheral immune tolerance

Tregs play a fundamental role in immune tolerance via control of self-reactive effector T cells (Teffs). This function is dependent on maintenance of a high intracellular cAMP concentration. A number of microRNAs are implicated in the maintenance of Tregs. In this study, we demonstrate that peripheral immune tolerance is critically dependent on posttranscriptional repression of the cAMP-hydrolyzing enzyme phosphodiesterase-3b (Pde3b) by microRNA-142-5p (miR-142-5p). In this manner, miR-142-5p acts as an immunometabolic regulator of intracellular cAMP, controlling Treg suppressive function. Mir142 was associated with a super enhancer bound by the Treg lineage–determining transcription factor forkhead box P3 (FOXP3), and Treg-specific deletion of miR-142 in mice (Treg^Δ142) resulted in spontaneous, lethal, multisystem autoimmunity, despite preserved numbers of phenotypically normal Tregs. Pharmacological inhibition and genetic ablation of PDE3B prevented autoimmune disease and reversed the impaired suppressive function of Tregs in Treg^Δ142 animals. These findings reveal a critical molecular switch, specifying Treg function through the modulation of a highly conserved, cell-intrinsic metabolic pathway. Modulation of this pathway has direct relevance to the pathogenesis and treatment of autoimmunity and cancer.

J wave syndromes as a cause of malignant cardiac arrhythmias

The J wave syndromes, including the Brugada (BrS) and early repolarization (ERS) syndromes, are characterized by the manifestation of prominent J waves in the electrocardiogram appearing as an ST segment elevation and the development of life-threatening cardiac arrhythmias. BrS and ERS differ with respect to the magnitude and lead location of abnormal J waves and are thought to represent a continuous spectrum of phenotypic expression termed J wave syndromes. Despite over 25 years of intensive research, risk stratification and the approach to therapy of these two inherited cardiac arrhythmia syndromes are still rapidly evolving. Our objective in this review is to provide an integrated synopsis of the clinical characteristics, risk stratifiers, as well as the molecular, ionic, cellular, and genetic mechanisms underlying these two syndromes that have captured the interest and attention of the cardiology community over the past two decades.

In Silico QT and APD Prolongation Assay for Early Screening of Drug-Induced Proarrhythmic Risk

Drug-induced proarrhythmicity is a major concern for regulators and pharmaceutical companies. For novel drug candidates, the standard assessment involves the evaluation of the potassium hERG channels block and the in vivo prolongation of the QT interval. However, this method is known to be too restrictive and to stop the development of potentially valuable therapeutic drugs. The aim of this work is to create an in silico tool for early detection of drug-induced proarrhythmic risk. The system is based on simulations of how different compounds affect the action potential duration (APD) of isolated endocardial, midmyocardial, and epicardial cells as well as the QT prolongation in a virtual tissue. Multiple channel-drug interactions and state-of-the-art human ventricular action potential models ( O'Hara , T. , PLos Comput. Biol. 2011 , 7 , e1002061 ) were used in our simulations. Specifically, 206.766 cellular and 7072 tissue simulations were performed by blocking the slow and the fast components of the delayed rectifier current ( I_Ks and I_Kr, respectively) and the L-type calcium current ( I_CaL) at different levels. The performance of our system was validated by classifying the proarrhythmic risk of 84 compounds, 40 of which present torsadogenic properties. On the basis of these results, we propose the use of a new index (Tx) for discriminating torsadogenic compounds, defined as the ratio of the drug concentrations producing 10% prolongation of the cellular endocardial, midmyocardial, and epicardial APDs and the QT interval, over the maximum effective free therapeutic plasma concentration (EFTPC). Our results show that the Tx index outperforms standard methods for early identification of torsadogenic compounds. Indeed, for the analyzed compounds, the Tx tests accuracy was in the range of 87-88% compared with a 73% accuracy of the hERG IC₅₀ based test.

Phosphodiesterase 3A expression and activity in the murine vasculature is influenced by NO-sensitive guanylyl cyclase

Phosphodiesterase 3 (PDE3) exists in two isoforms (PDE3A and PDE3B) and is known to act as cGMP-inhibited cAMP-degrading PDE. Therefore, PDE3 may likely be involved in the interaction between the two second messenger pathways. NO-sensitive guanylyl cyclase (NO-GC) is the most important cytosolic generator of cGMP. Here, we investigated the effect of NO-GC deletion on PDE3A-mediated signaling in animals lacking NO-GC either globally (GCKO) or specifically in smooth muscle cells (SMC-GCKO). PDE3A expression is detected in murine aortic smooth muscle, platelets, and heart tissue. Expression and activity of PDE3A in aortae from GCKO and SMC-GCKO mice was reduced by approx. 50% compared to that in control animals. PDE3A downregulation can be linked to the reduction in NO-GC and is not an effect of the increased blood pressure levels resulting from NO-GC deletion. Despite the different PDE3A expression levels, smooth muscle relaxation induced by forskolin to stimulate cAMP signaling was similar in all genotypes. Basal and forskolin-stimulated cAMP levels in aortic tissue were not different between KO and control strains. However, the potency of milrinone, a selective inhibitor of PDE3A, to induce relaxation was higher in aortae from GCKO and SMC-GCKO than that in aorta from control animals. These data were corroborated by the effect of milrinone in vivo, which led to an increase in systolic blood pressure in both KO strains but not in control mice. We conclude that NO-GC modulates PDE3A expression and activity in SMC in vivo conceivably to preserve functional cAMP signaling.

Pharmacological Therapy in Brugada Syndrome

Brugada syndrome (BrS) is a cardiac disease caused by an inherited ion channelopathy associated with a propensity to develop ventricular fibrillation. Implantable cardioverter defibrillator implantation is recommended in BrS, based on the clinical presentation in the presence of diagnostic ECG criteria. Implantable cardioverter defibrillator implantation is not always indicated or sufficient in BrS, and is associated with a high device complication rate. Pharmacological therapy aimed at rebalancing the membrane action potential can prevent arrhythmogenesis in BrS. Quinidine, a class 1A antiarrhythmic drug with significant Ito blocking properties, is the most extensively used drug for the prevention of arrhythmias in BrS. The present review provides contemporary data gathered on all drugs effective in the therapy of BrS, and on ineffective or contraindicated antiarrhythmic drugs.

Discovery of an Orally Bioavailable, Brain-Penetrating, in Vivo Active Phosphodiesterase 2A Inhibitor Lead Series for the Treatment of Cognitive Disorders

Herein, we describe the discovery of a potent, selective, brain-penetrating, in vivo active phosphodiesterase (PDE) 2A inhibitor lead series. To identify high-quality leads suitable for optimization and enable validation of the physiological function of PDE2A in vivo, structural modifications of the high-throughput screening hit 18 were performed. Our lead generation efforts revealed three key potency-enhancing functionalities with minimal increases in molecular weight (MW) and no change in topological polar surface area (TPSA). Combining these structural elements led to the identification of 6-methyl-N-((1R)-1-(4-(trifluoromethoxy)phenyl)propyl)pyrazolo[1,5-a]pyrimidine-3-carboxamide (38a), a molecule with the desired balance of preclinical properties. Further characterization by cocrystal structure analysis of 38a bound to PDE2A uncovered a unique binding mode and provided insights into its observed potency and PDE selectivity. Compound 38a significantly elevated 3',5'-cyclic guanosine monophosphate (cGMP) levels in mouse brain following oral administration, thus validating this compound as a useful pharmacological tool and an attractive lead for future optimization.

A genome-wide association analysis identifies PDE1A|DNAJC10 locus on chromosome 2 associated with idiopathic pulmonary arterial hypertension in a Japanese population

Pulmonary arterial hypertension (PAH) is a lethal disease that often affects the young. Although Bone Morphogenetic Protein Receptor Type 2 gene (BMPR2) mutations are related with idiopathic and heritable PAH, the low penetrance and variable expressivity in PAH suggest the existence of other genetic and/or environmental factors. In this study, we aimed to identify novel genetic factors associated with PAH, irrespective of BMPR2 mutation.

We performed genome-wide association study (GWAS) in a Japanese population comprising 44 individuals with idiopathic and heritable PAH, and 2,993 controls.

Seven loci identified in the genome-wide study were submitted to the validation study, and a novel susceptibility locus, PDE1A|DNAJC10, was identified that maps to 2q32.1 (rs71427857, P = 7.9 × 10^-9, odds ratio in the validation study = 5.18; 95% CI 1.86 – 14.42). We also found the augmentation of PDE1A protein in distal remodeled pulmonary artery walls in idiopathic PAH patients.

Given that phosphodiesterase 5 inhibitors are effective for the treatment of idiopathic and heritable PAH, our findings suggest that PDE1A could be a novel therapeutic target of PAH.

Cilostazol Prevents Atrial Structural Remodeling through the MEK/ERK Pathway in a Canine Model of Atrial Tachycardia

OBJECTIVES

Atrial fibrillation (AF) is the most common sustained arrhythmia in clinical practice. Atrial structural remodeling (ASR), particularly atrial fibrosis, is an important contributor to the AF substrate. This study aimed to investigate the preventive effects of the phosphodiesterase 3 inhibitor cilostazol on ASR and its potential molecular mechanisms in a canine model of rapid atrial pacing (RAP).

METHODS

Thirty dogs were assigned to sham (Sham), paced/ no treatment (Paced) and paced + cilostazol 5 mg/kg/day (Paced + cilo) groups, with 10 dogs in each group. RAP at 500 beats/min was maintained for 2 weeks, while the Sham group was instrumented without pacing. Cilostazol was provided orally during pacing. Western blotting, RT-PCR and pathology were used to assess ASR.

RESULTS

Cilostazol attenuated atrial interstitial fibrosis and structural remodeling in canines with RAP. MEK/ERK transduction pathway gene expression was upregulated in the Paced group compared with the Sham group. Cilostazol markedly alleviated these changes in the MEK/ERK pathway. Transforming growth factor-β1 protein expression in the Paced group was significantly higher than in the Sham group (p < 0.01), and was significantly reduced by cilostazol (p < 0.01).

CONCLUSIONS

Our findings suggest that cilostazol is beneficial for prevention and treatment in atrial tachycardia-induced ASR in a canine model of RAP.

Safety of Intravenous Methamphetamine Administration During Ibudilast Treatment

BACKGROUND

Methamphetamine dependence is a significant public health concern without any approved medications for treatment. We evaluated ibudilast, a nonselective phosphodiesterase inhibitor, to assess the safety and tolerability during intravenous methamphetamine administration. We conducted a randomized, double-blind, placebo-controlled, within-subjects crossover clinical trial.

METHODS

Participants received ibudilast (20 mg twice daily followed by 50 mg twice daily) and placebo, with order determined by randomization, and then underwent intravenous methamphetamine challenges (15 and 30 mg). We monitored cardiovascular effects, methamphetamine pharmacokinetics, and reported adverse events.

RESULTS

Ibudilast treatment had similar rates of adverse events compared with placebo, and there was no significant augmentation of cardiovascular effects of methamphetamine. Pharmacokinetic analysis revealed no clinically significant change in maximum concentration or half-life of methamphetamine with ibudilast.

CONCLUSIONS

Methamphetamine administration during ibudilast treatment was well tolerated without additive cardiovascular effects or serious adverse events, providing initial safety data to pursue ibudilast's effectiveness for the treatment of methamphetamine dependence.

Brugada Syndrome: Clinical, Genetic, Molecular, Cellular, and Ionic Aspects

Brugada syndrome (BrS) is an inherited cardiac arrhythmia syndrome first described as a new clinical entity in 1992. Electrocardiographically characterized by distinct coved type ST segment elevation in the right-precordial leads, the syndrome is associated with a high risk for sudden cardiac death in young adults, and less frequently in infants and children. The electrocardiographic manifestations of BrS are often concealed and may be unmasked or aggravated by sodium channel blockers, a febrile state, vagotonic agents, as well as by tricyclic and tetracyclic antidepressants. An implantable cardioverter defibrillator is the most widely accepted approach to therapy. Pharmacologic therapy is designed to produce an inward shift in the balance of currents active during the early phases of the right ventricular action potential (AP) and can be used to abort electrical storms or as an adjunct or alternative to device therapy when use of an implantable cardioverter defibrillator is not possible. Isoproterenol, cilostazol, and milrinone boost calcium channel current and drugs like quinidine, bepridil, and the Chinese herb extract Wenxin Keli inhibit the transient outward current, acting to diminish the AP notch and thus to suppress the substrate and trigger for ventricular tachycardia or fibrillation. Radiofrequency ablation of the right ventricular outflow tract epicardium of patients with BrS has recently been shown to reduce arrhythmia vulnerability and the electrocardiographic manifestation of the disease, presumably by destroying the cells with more prominent AP notch. This review provides an overview of the clinical, genetic, molecular, and cellular aspects of BrS as well as the approach to therapy.

Comparing the effectiveness and safety between triple antiplatelet therapy and dual antiplatelet therapy in type 2 diabetes mellitus patients after coronary stents implantation: a systematic review and meta-analysis of randomized controlled trials

Background

Since antiplatelet therapy in type 2 diabetes mellitus (T2DM) patients is very important after intracoronary stenting, and because the most commonly used therapies have been the dual antiplatelet therapy (DAPT) consisting of aspirin and clopidogrel and the triple antiplatelet therapy (TAPT) consisting of aspirin, clopidogrel and cilostazol, we aim to compare the effectiveness and safety between triple antiplatelet therapy and dual antiplatelet therapy in T2DM patients.

Methods

Systematic literature search was done from the databases of PubMed, Cochrane, Embase, China National Knowledge Infrastructure (CNKI) and WanFang. Randomized controlled trials (RCTs) comparing the effectiveness and safety between triple therapy and dual therapy in T2DM patients after coronary stents placement were included. Endpoints included major adverse cardiac effects (MACEs), target lesion revascularization (TLR), target vessel revascularization (TVR), death, stent thrombosis, bleeding and adverse drug reactions during a 9–12 months period, as well as platelet activities.

Results

Four studies including 1005 patients reporting the adverse clinical outcomes and six studies including 519 patients reporting the platelet activities, with a total of 1524 patients have been analyzed in this meta-analysis. The pooling analysis shows that TAPT has significantly decreased the occurrence of MACEs (RR: 0.55; 95 % CI: 0.36–0.86, P = 0.009), TLR (RR 0.41; 95 % CI: 0.21–0.80, P = 0.008), TVR (RR 0.55; 95 % CI: 0.34–0.88, P = 0.01) and the overall incidence of Death/ Myocardial Infarction (MI)/TVR (RR 0.54; 95 % CI: 0.31–0.94, P = 0.03) during this 9 to 12 months follow up period after stents implantation. Stent thrombosis was almost similar in both groups. Bleeding seemed to favor DAPT but the result was not statistically significant. Platelet aggregation, platelet reactivity index (PRI) and platelet reactivity unit (PRU) were also reduced with Weight Mean Difference (WMD) of (−13.80; 95 % CI: −17.03 to −10.56, P < 0.00001), (−22.87; 95 % CI: −23.66 to −22.07, P < 0.00001) and (−44.17; 95 % CI: −58.56 to −29.77, P < 0.00001) respectively.

Conclusion

Since MACEs have been significantly decreased in the triple group, TAPT appears to be more effective than DAPT in T2DM patients after intracoronary stenting. No significant difference in stent thrombosis and bleeding risks between these 2 groups shows TAPT to be almost as safe as DAPT in these diabetic patients.

J-wave syndromes: Brugada and early repolarization syndromes

A prominent J wave is encountered in a number of life-threatening cardiac arrhythmia syndromes, including the Brugada syndrome and early repolarization syndromes. Brugada syndrome and early repolarization syndromes differ with respect to the magnitude and lead location of abnormal J waves and are thought to represent a continuous spectrum of phenotypic expression termed J-wave syndromes. Despite two decades of intensive research, risk stratification and the approach to therapy of these 2 inherited cardiac arrhythmia syndromes are still undergoing rapid evolution. Our objective in this review is to provide an integrated synopsis of the clinical characteristics, risk stratifiers, and molecular, ionic, cellular, and genetic mechanisms underlying these 2 fascinating syndromes that have captured the interest and attention of the cardiology community in recent years.

Efficacy of cilostazol for the treatment of Raynaud's phenomenon in systemic sclerosis patients

Cilostazol is a selective inhibitor of phosphodiesterase-III with antiplatelet, antithrombotic and vasodilating properties. The aim of our study was to evaluate the effect of the drug on vasculopathy and Raynaud's phenomenon (RP), in a series of patients with systemic sclerosis (SSc), before and after cilostazol treatment. Twenty-one consecutive SSc patients with moderate or severe RP were enrolled in an open-label study. Cilostazol was administered at the dose of 100 mg twice a day, for 12 months. Evaluations included: daily RP attack diary documenting the frequency and duration of RP episodes, Health Assessment Questionnaire-Disability Index, scleroderma visual analogue scales (VAS), flow-mediated dilation and immunological status, including endothelin 1 and interleukin 6 plasma levels. Thirteen patients completed the study. RP duration and daily number episodes recorded over a 3-week period significantly decreased after cilostazol treatment (p = 0.0049 and p = 0.0067, respectively). VAS score indicated a significant amelioration of the patients' perception of RP (p = 0.0117), and both baseline and post-ischemic brachial artery diameters were significantly increased after cilostazol treatment, as compared with basal values (p = 0.0119 and p = 0.0076, respectively). None of the patients developed digital ulcers during the study. A significant clinical improvement of RP was recorded in SSc patients undergoing cilostazol treatment. Study results indicate a potential role of cilostazol as oral maintenance therapy in SSc patients with RP.

Use of whole exome sequencing for the identification of Ito-based arrhythmia mechanism and therapy

BACKGROUND

Identified genetic variants are insufficient to explain all cases of inherited arrhythmia. We tested whether the integration of whole exome sequencing with well-established clinical, translational, and basic science platforms could provide rapid and novel insight into human arrhythmia pathophysiology and disease treatment.

METHODS AND RESULTS

We report a proband with recurrent ventricular fibrillation, resistant to standard therapeutic interventions. Using whole-exome sequencing, we identified a variant in a previously unidentified exon of the dipeptidyl aminopeptidase-like protein-6 (DPP6) gene. This variant is the first identified coding mutation in DPP6 and augments cardiac repolarizing current (Ito) causing pathological changes in Ito and action potential morphology. We designed a therapeutic regimen incorporating dalfampridine to target Ito. Dalfampridine, approved for multiple sclerosis, normalized the ECG and reduced arrhythmia burden in the proband by >90-fold. This was combined with cilostazol to accelerate the heart rate to minimize the reverse-rate dependence of augmented Ito.

CONCLUSIONS

We describe a novel arrhythmia mechanism and therapeutic approach to ameliorate the disease. Specifically, we identify the first coding variant of DPP6 in human ventricular fibrillation. These findings illustrate the power of genetic approaches for the elucidation and treatment of disease when carefully integrated with clinical and basic/translational research teams.

Novel Therapeutic Strategies for the Management of Ventricular Arrhythmias Associated with the Brugada Syndrome

INTRODUCTION

Brugada syndrome (BrS) is an inherited cardiac arrhythmia syndrome characterized by prominent J waves appearing as distinct coved type ST segment elevation in the right precordial leads of the ECG. It is associated with a high risk for sudden cardiac death.

AREAS COVERED

We discuss 1) ECG manifestations of BrS which can be unmasked or aggravated by sodium channel blockers, febrile states, vagotonic agents, as well as tricyclic and tetracyclic antidepressants; 2) Genetic basis of BrS; 3) Ionic and cellular mechanisms underlying BrS; 4) Therapy involving devices including an implantable cardioverter defibrillator (ICD); 5) Therapy involving radiofrequency ablation; and 6) Therapy involving pharmacological therapy which is aimed at producing an inward shift in the balance of the currents active during phase 1 of the right ventricular action potential either by boosting calcium channel current (isoproterenol, cilostazol and milrinone) or by inhibition of transient outward current Ito (quinidine, bepridil and the Chinese herb extract Wenxin Keli).

EXPERT OPINION

This review provides an overview of the clinical and molecular aspects of BrS with a focus on approaches to therapy. Available data suggest that agents capable of inhibiting the transient outward current Ito can exert an ameliorative effect regardless of the underlying cause.

Cilostazol ameliorates atrial ionic remodeling in long-term rapid atrial pacing dogs

Objective:

Ionic remodeling has a close correlation with the occurrence of atrial fibrillation (AF). Atrial tachypacing remodeling is associated with characteristic ionic remodeling. The purpose of this study was to assess the efficacy of cilostazol, an oral phosphodiesterase 3 inhibitor, for preventing atrial ionic remodeling in long-term rapid atrial pacing (RAP) dogs.

Methods:

We use the methods of patch-clamp and molecular biology to investigate the effect of cilostazol on ion channel and channel gene expression in long-term RAP dogs. Twenty-one dogs were randomly assigned to sham, control paced, and paced+cilostazol (5 mg/kg/d, cilo) groups, with 7 dogs in each group. The sham group was instrumented with a pacemaker but without pacing. RAP at 500 beats/min was maintained for 2 weeks in the paced and cilo groups. During the pacing, cilostazol was given orally in the cilo group. Whole-cell patch-clamp technique was used to record atrial L-type Ca²+ (I_CaL) and fast sodium channel (I_Na) ionic currents. Western blot and RT-PCR were applied to estimate the gene expression of the I_CaLa) 1C (Cav1.2) and I_Nav1.5a) Nav1.5a) subunits. Statistical analysis was performed using SPSS 13.0.

Results:

The density of I_CaL and I_Na currents (pA/pF) was significantly reduced in the paced group (I_CaL: -6.55±1.42 vs. -4.46±0.59 pA/pF; I_Na: -48.24±10.54 vs. -30.48±5.20 pA/pF, p<0.01). The paced+cilo group could not increase the density of I_CaL currents (I_CaL: -4.37±1.25 pA/pF, p>0.05], while the I_Na currents were recovered (-44.54±12.65 pA/pF, p<0.01) compared with the paced group. The mRNA and protein expression levels of Cav1.2 and Nav1.5a were apparently down-regulated in the paced group (p<0.01), but after cilostazol treatment, both of these subunits were up-regulated significantly (p<0.01).

Conclusion:

Cilostazol may have protective effects on RAP-induced atrial ionic remodeling.

Phosphodiesterase-3 inhibitor (cilostazol) attenuates oxidative stress-induced mitochondrial dysfunction in the heart

Background

Cilostazol is a type 3 phosphodiesterase inhibitor which has been previously demonstrated to prevent the occurrence of tachyarrhythmia and improve defibrillation efficacy. However, the mechanism for this beneficial effect is still unclear. Since cardiac mitochondria have been shown to play a crucial role in fatal cardiac arrhythmias and that oxidative stress is one of the main contributors to arrhythmia generation, we tested the effects of cilostazol on cardiac mitochondria under severe oxidative stress.

Methods

Mitochondria were isolated from rat hearts and treated with H₂O₂ to induce oxidative stress. Cilostazol, at various concentrations, was used to study its protective effects. Pharmacological interventions, including a mitochondrial permeability transition pore (mPTP) blocker, cyclosporine A (CsA), and an inner membrane anion channel (IMAC) blocker, 4′-chlorodiazepam (CDP), were used to investigate the mechanistic role of cilostazol on cardiac mitochondria. Cardiac mitochondrial reactive oxygen species (ROS) production, mitochondrial membrane potential change and mitochondrial swelling were determined as indicators of cardiac mitochondrial function.

Results

Cilostazol preserved cardiac mitochondrial function when exposed to oxidative stress by preventing mitochondrial depolarization, mitochondrial swelling, and decreasing ROS production.

Conclusions

Our findings suggest that cardioprotective effects of cilostazol reported previously could be due to its prevention of cardiac mitochondrial dysfunction caused by severe oxidative stress.

Advances in targeting cyclic nucleotide phosphodiesterases

Cyclic nucleotide phosphodiesterases (PDEs) catalyse the hydrolysis of cyclic AMP and cyclic GMP, thereby regulating the intracellular concentrations of these cyclic nucleotides, their signalling pathways and, consequently, myriad biological responses in health and disease. Currently, a small number of PDE inhibitors are used clinically for treating the pathophysiological dysregulation of cyclic nucleotide signalling in several disorders, including erectile dysfunction, pulmonary hypertension, acute refractory cardiac failure, intermittent claudication and chronic obstructive pulmonary disease. However, pharmaceutical interest in PDEs has been reignited by the increasing understanding of the roles of individual PDEs in regulating the subcellular compartmentalization of specific cyclic nucleotide signalling pathways, by the structure-based design of novel specific inhibitors and by the development of more sophisticated strategies to target individual PDE variants.

Cilostazol decreases total atrial conduction time in patients with peripheral artery disease

Objective:

Total atrial conduction time (TACT) is the most important parameter in predicting the development of new-onset atrial fibrillation. We investigated the effect of cilostazol therapy on TACT in patients with peripheral artery disease.

Methods:

Thirty patients with peripheral artery disease were treated with cilostazol (200 mg/day) for 6 months. The baseline echocardiographic total atrial conduction time parameter was compared with the 6-month follow-up.

Results:

The TACT duration was decreased in all patients compared with the baseline after therapy (121.8 ± 19.3 vs. 109.1 ± 15.9 milliseconds, p<0.001). However, left atrial (LA) diameter was not changed with the therapy. The reduction of TACT duration was correlated with the increase in mitral E wave velocity/mitral A wave velocity ratio (r=-0.48, p<0.003).

Conclusion:

Our results showed that 200 mg cilostazol treatment decreased TACT duration in patients with peripheral artery disease, which may also prevent the development and/or recurrence of atrial fibrillation (AF).

Efficacy of cilostazol on uncontrolled coronary vasospastic angina: a pilot study

BACKGROUND

Although an angina attack by vasospastic angina (VSA) can usually be relieved or controlled with nitrates and calcium channel blockers (CCBs), there are some patients who cannot be controlled even by higher doses and combinations of these drugs. Cilostazol is a selective inhibitor of phosphodiesterase 3 that increases intracellular cyclic adenosine monophosphate (cAMP) contents. A stimulation of cAMP signal transduction increases coronary nitric oxide production. We examined whether cilostazol improved angina symptoms in patients with VSA uncontrolled by conventional treatment.

METHODS

This study was conducted in a prospective, multicenter, nonrandomized manner. The subject consisted of 21 patients (13 men, 57 ± 9 year-old) who were diagnosed with VSA and had at least two angina attacks during the past 1 week despite of conventional medications such as CCBs and/or nitrates. They took cilostazol 100 mg twice daily for 2 weeks in addition to the conventional medications. The patients recorded the frequency of angina attack and wrote down the numeric rating scale of a "severity of angina attack" while taking conventional medications and cilostazol for 2 weeks, and also recorded an averaged scale or total number of event during the last week at the time of the assessment. Using the Wilcoxon rank-sum test, we compared the changes in the scores of frequency and severity of angina attack before and after adding cilostazol to the conventional medications.

RESULTS

After adding cilostazol to the conventional medications, there were 78.9% relative reduction of the score of angina intensity and 73.5% of angina frequency (P < 0.001). There were four patients (19%) who were forced to stop cilostazol due to headache as an adverse event.

CONCLUSIONS

Cilostazol appears to be an effective therapy in VSA uncontrolled with conventional medical treatment. A further prospective, randomized, placebo-controlled study will be needed to validate this result.

Cellular mechanisms underlying the effects of milrinone and cilostazol to suppress arrhythmogenesis associated with Brugada syndrome

BACKGROUND

Brugada syndrome is an inherited disease associated with vulnerability to ventricular tachycardia and sudden cardiac death in young adults. Milrinone and cilostazol, oral phosphodiesterase (PDE) type III inhibitors, have been shown to increase L-type calcium channel current (ICa) and modestly increase heart rate by elevating the level of intracellular cyclic adenosine monophosphate.

OBJECTIVE

To examine the effectiveness of these PDE inhibitors to suppress arrhythmogenesis in an experimental model of Brugada syndrome.

METHODS

Action potential (AP) and electrocardiographic recordings were obtained from epicardial and endocardial sites of coronary-perfused canine right ventricular wedge preparations. The Ito agonist NS5806 (5 μM) and Ca(2+) channel blocker verapamil (2 μM) were used to pharmacologically mimic Brugada phenotype.

RESULTS

The combination induced all-or-none repolarization at some epicardial sites but not others, leading to ST-segment elevation as well as an increase in both epicardial and transmural dispersion of repolarization. Under these conditions, phase 2 reentry developed as the epicardial AP dome propagated from sites where it was maintained to sites at which it was lost, generating closely coupled extrasystoles and ventricular tachycardia. The addition of the PDE inhibitor milrinone (2.5 μM) or cilostazol (5-10 μM) to the coronary perfusate restored the epicardial AP dome, reduced dispersion, and abolished phase 2 reentry-induced extrasystoles and ventricular tachycardia.

CONCLUSIONS

Our study identifies milrinone as a more potent alternative to cilostazol for reversing the repolarization defects responsible for the electrocardiographic and arrhythmic manifestations of Brugada syndrome. Both drugs normalize ST-segment elevation and suppress arrhythmogenesis in experimental models of Brugada syndrome.

Cilostazol promotes mitochondrial biogenesis in human umbilical vein endothelial cells through activating the expression of PGC-1α

Mitochondrial dysfunction is frequently observed in vascular diseases. Cilostazol is a drug approved by the US Food and Drug Administration for the treatment of intermittent claudication. Cilostazol increases intracellular cyclic adenosine monophosphate (cAMP) levels through inhibition of type III phosphodiesterase. The effects of cilostazol in mitochondrial biogenesis in human umbilical vein endothelial cells (HUVECs) were investigated in this study. Cilostazol treated HUVECs displayed increased levels of ATP, mitochondrial DNA/nuclear DNA ratio, expressions of cytochrome B, and mitochondrial mass, suggesting an enhanced mitochondrial biogenesis induced by cilostazol. The promoted mitochondrial biogenesis could be abolished by Protein kinase A (PKA) specific inhibitor H-89, implying that PKA pathway played a critical role in increased mitochondrial biogenesis after cilostazol treatment. Indeed, expression levels of peroxisome proliferator activator receptor gamma-coactivator 1α (PGC-1α), NRF 1 and mitochondrial transcription factor A (TFAM) were significantly increased in HUVECs after incubation with cilostazol at both mRNA levels and protein levels. Importantly, knockdown of PGC-1α could abolish cilostazol-induced mitochondrial biogenesis. Enhanced expression of p-CREB and PGC-1α induced by cilostazol could be inhibited by H-89. Moreover, the increased expression of PGC-1α induced by cilostazol could be inhibited by downregulation of CREB using CREB siRNA at both mRNA and protein levels. All the results indicated that cilostazol promoted mitochondrial biogenesis through activating the expression of PGC-1α in HUVECs, which was mediated by PKA/CREB pathway.