Synergistic interactions between selective pharmacological inhibitors of phosphodiesterase isozyme families PDE III and PDE IV to attenuate proliferation of rat vascular smooth muscle cells

A Systematic Review and Meta-Analysis of Efficacy and Safety of Cilostazol Prescription in Patients With Femoropopliteal Peripheral Artery Disease After Endovascular Therapy

PURPOSE

The purpose of this study is to assess the efficacy and safety of cilostazol prescription in patients with femoropopliteal peripheral artery disease (PAD) after endovascular therapy (EVT).

MATERIALS AND METHODS

We conducted a systematic review and meta-analysis of all studies reporting the outcomes of cilostazol after femoropopliteal EVT of PAD up to September 2022. Clinical outcomes of interest included primary patency, in-stent restenosis (ISR), vessel re-occlusion, freedom from target lesion revascularization (TLR), repeat revascularization, all-cause mortality, amputation, major adverse cardiovascular events (MACEs) and major adverse limb events (MALEs), and bleeding complication.

RESULTS

A total of 4 randomized controlled trials (RCTs) and 8 observational studies containing a total of 4898 patients met the inclusion criteria and were included in this systematic review and meta-analysis. We found that the use of cilostazol was associated with higher primary patency after femoropopliteal artery EVT (odds ratio [OR]=1.67, 95% confidence interval [CI]=1.50-1.87, p<0.001, I2=33.2%), a lower risk of ISR (OR=0.43, 95% CI=0.29-0.63, p<0.001, I2=37.6%), repeat revascularization (OR=0.43, 95% CI=0.24-0.76, p<0.005, I2=27.4%), and vessel re-occlusion (OR=0.59, 95% CI=0.38-0.93, p<0.05, I2=0%). There was an increase in freedom from TLR rate (OR=2.19, 95% CI=1.58-3.05, p<0.001, I2=0%), as well as a reduction in the occurrence of MALEs (OR=0.50, 95% CI=0.29-0.85, p<0.05, I2=0%). However, there was no significant difference in amputation, MACEs, all-cause mortality, and major bleeding complications. Subgroup analysis showed that cilostazol treatment in patients with femoropopliteal drug-eluting stents (DES) implantation remained associated with higher primary patency and a lower risk of ISR.

CONCLUSIONS

After EVT of femoropopliteal artery lesions, additional oral cilostazol enhances primary patency, reduces the occurrences of ISR and vessel re-occlusion, diminishes the risks associated with MALEs, lowers the need for repeat revascularization, and increases freedom from TLR rates. However, it does not impact amputation, MACEs, all-cause mortality, or major bleeding complications. These findings suggest cilostazol as a potentially safe and effective adjunct therapy in patients with femoropopliteal PAD after EVT.

CLINICAL IMPACT

After undergoing endovascular therapy (EVT) for femoropopliteal artery lesions, the addition of cilostazol to antiplatelet therapy can significantly improve primary patency, reducing the incidence of in-stent restenosis, repeat revascularization, vessel re-occlusion, and major adverse limb events while increasing freedom from target lesion revascularization rate. The simultaneous use of drug-eluting stents in the femoropopliteal artery lesions, combined with cilostazol, potentially results in a synergistic anti-stenotic effect. This therapeutic approach does not appear to be associated with an increased risk of major bleeding events or all-cause mortality. These findings provide additional evidence supporting the treatment of anti-stenosis in patients with femoropopliteal artery lesions after EVT.

Discovery of 2-(Methylcarbonylamino) thiazole as PDE4 inhibitors via virtual screening and biological evaluation

Phosphodiesterase-4, the primary enzyme responsible for cAMP degradation in the majority of immune and inflammatory cells, plays a critical role in the regulation of intracellular cAMP levels. Consequently, small molecular entities capable of inhibiting PDE4 have been employed in the treatment of inflammation-associated disorders, such as chronic obstructive pulmonary disease (COPD), psoriasis, atopic dermatitis (AD), inflammatory bowel diseases (IBD), rheumatic arthritis (RA). In the present investigation, a multi-faceted approach was employed to identify novel PDE4 inhibitors, utilizing the co-crystallization structure of PDE4B available in the Protein Data Bank (PDB) database, drug-like screening, false positive filtration, similarity and ADMET screen, as well as molecular docking via multiple software platforms, in conjunction with bioactivity assays. A thiazol-3-propanamides derivative, designated MR9, was discovered to inhibit PDE4B activity with IC50 values of 2.12 μM and suppress cellular inflammatory factor TNF-α release with an EC50 value of 3.587 μM. These findings suggest that the innovative active scaffold of MR9 offers a promising foundation for further structural refinement aimed at developing more potent PDE4 inhibitors.

Ending Restenosis: Inhibition of Vascular Smooth Muscle Cell Proliferation by cAMP

Increased vascular smooth muscle cell (VSMC) proliferation contributes towards restenosis after angioplasty, vein graft intimal thickening and atherogenesis. The second messenger 3′ 5′ cyclic adenosine monophosphate (cAMP) plays an important role in maintaining VSMC quiescence in healthy vessels and repressing VSMC proliferation during resolution of vascular injury. Although the anti-mitogenic properties of cAMP in VSMC have been recognised for many years, it is only recently that we gained a detailed understanding of the underlying signalling mechanisms. Stimuli that elevate cAMP in VSMC inhibit G₁-S phase cell cycle progression by inhibiting expression of cyclins and preventing S-Phase Kinase Associated Protein-2 (Skp2-mediated degradation of cyclin-dependent kinase inhibitors. Early studies implicated inhibition of MAPK signalling, although this does not fully explain the anti-mitogenic effects of cAMP. The cAMP effectors, Protein Kinase A (PKA) and Exchange Protein Activated by cAMP (EPAC) act together to inhibit VSMC proliferation by inducing Cyclic-AMP Response Element Binding protein (CREB) activity and inhibiting members of the RhoGTPases, which results in remodelling of the actin cytoskeleton. Cyclic-AMP induced actin remodelling controls proliferation by modulating the activity of Serum Response Factor (SRF) and TEA Domain Transcription Factors (TEAD), which regulate expression of genes required for proliferation. Here we review recent research characterising these mechanisms, highlighting novel drug targets that may allow the anti-mitogenic properties of cAMP to be harnessed therapeutically to limit restenosis.

Risk of Heart Failure Hospitalization Associated With Cilostazol in Diabetes: A Nationwide Case-Crossover Study

Background and Objective: It has been suggested to avoid cilostazol, the first-line therapy for peripheral arterial disease, in patients with congestive heart failure (HF). The objective of this study was to evaluate the risk of hospitalization for heart failure (HHF) associated with cilostazol use in the patients of diabetes mellitus. Methods: This case-crossover study retrieved records on diabetic patients > 20 years of age who were hospitalized for heart failure during the period of 2009-2011 from the Taiwan National Health Insurance Database. The "current" period was defined as 1-30 days prior to HHF whereas the 91-120 days prior to HHF served as the "reference" period. The exposure status just preceding the event is compared with exposure of the same person in one or more referent remote to the event. Adjusted odds ratios (OR) were used to estimate time-varying discordant exposure by the ratio of the number exposed to cilostazol only during the case period to the number exposed to cilostazol only during the control period. Results: A total of 47,506 diabetic patients were included in the analysis (average age: 72.7 ± 12.4, percentage of males: 48%). A total of 399 patients (0.84%) received cilostazol only in the current period, and 252 (0.53%) received cilostazol only in the reference period. After adjustment for other medications, a significant association was found between cilostazol and HHF (OR: 1.35, 95% CI: 1.14-1.59). After further adjustment for time-varying co-morbidities the ORs remained essentially the same. Sensitivity analyses using different definitions of control period (ranging from 31-60, 61-90, to 121-150 days before index date) yielded adjusted ORs of 1.43 (95% CI: 1.14-1.79), 1.31 (95% CI: 1.09-1.57) and 1.23 (95% CI: 1.06-1.44), respectively suggesting the robustness of our study findings. Conclusion: Use of cilostazol may be positively related to the risk of HHF. Further studies are warranted to explore the underlying mechanisms and to confirm the association.

Open-Label Phase I Clinical Study to Assess the Safety and Efficacy of Cilostazol in Patients Undergoing Internal Carotid Artery Stent Placement

BACKGROUND

One-month dual antiplatelet treatment, with aspirin and clopidogrel, following internal carotid artery stent placement is the current standard of care to prevent in-stent thrombosis. Cilostazol, an antiplatelet drug, has been demonstrated to have a safety profile comparable to aspirin and clopidogrel.

OBJECTIVE

To evaluate the safety and clinical efficacy of cilostazol and aspirin therapy following internal carotid artery stent placement up to 1 month postprocedure.

METHODS

A phase I open-label, nonrandomized two-center prospective study was conducted. All subjects received aspirin (325 mg/day) and cilostazol (200 mg/day) 3 days before extracranial stent placement. Two antiplatelet agents were continued for 1 month postprocedure followed by aspirin daily monotherapy. The primary efficacy end point was the 30-day composite occurrence of death, cerebral infarction, transient ischemic attack, and in-stent thrombosis. The primary safety end point was bleeding.

RESULTS

Twelve subjects (mean age ± SD, 66 ± 12 years; 9 males) were enrolled and underwent internal carotid artery angioplasty and stent placement. None of the subjects who successfully followed the study protocol experienced any complications at the 1- and 3-month follow-ups. One patient had a protocol deviation due to concurrent use of enoxaparin (1 mg/kg twice daily) in addition to aspirin and cilostazol, resulting in a fatal symptomatic intracerebral hemorrhage following successful stent placement on postprocedure day 1. One patient discontinued cilostazol after the first dose secondary to dizziness.

CONCLUSION

The use of cilostazol and aspirin for internal carotid artery stent placement appears to be safe, but protocol compliance needs to be emphasized.

No Association Between Single-Nucleotide Polymorphism 56 (SNP56) in Phosphodiesterase 4D (PDE4D) Gene and Susceptibility to Ischemic Stroke: A Meta-Analysis of 15 Studies

Background

Recent studies demonstrated that polymorphisms in the PDE4D gene were associated with several processes involved in the occurrence of ischemic stroke (IS). The association between specific PDE4D single-nucleotide polymorphism 56 (SNP56) and IS risk was initially identified via genome-wide association studies (GWAS), although the GWAS in different populations produced inconclusive results. Thus, we performed a meta-analysis to better explain the association between PDE4D SNP56 and IS risk.

Material/Methods

A literature search was conducted using PubMed, Embase, and Web of Science up to June 1, 2015. A fixed-effects or random-effects model was used to calculate the pooled odds ratios (ORs) based on the results from the heterogeneity tests.

Results

Finally, we performed a meta-analysis of 15 studies, involving 8731 IS patients and 10,756 controls. The results showed nonsignificant association between PDE4D SNP56 and IS risk (T vs. A: OR=1.01, 95%CI=0.88–1.15, P=0.90). Similarly, in the subgroup analysis by ethnicity, no significant association was observed in Asian (T vs. A: OR=1.08, 95%CI=0.80–1.44, P=0.62) or European (T vs. A: OR=0.96, 95%CI=0.86–1.08, P=0.54) population. Moreover, funnel plots and Egger regression testing showed no evidence of publication bias.

Conclusions

In summary, current evidence suggested that PDE4D SNP56 might not be associated with an increased susceptibility to IS. However, this conclusion needs further validation by well-designed studies with large sample sizes.

Regulation of soluble guanylyl cyclase redox state by hydrogen sulfide

Soluble guanylate cyclase (sGC) is a receptor for nitric oxide (NO). Binding of NO to ferrous (Fe(2+)) heme increases its catalytic activity, leading to the production of cGMP from GTP. Hydrogen sulfide (H2S) is a signaling molecule that exerts both direct and indirect anti-oxidant effects. In the present, study we aimed to determine whether H2S could regulate sGC redox state and affect its responsiveness to NO-releasing agents and sGC activators. Using cultured rat aortic smooth muscle cells, we observed that treatment with H2S augmented the response to the NO donor DEA/NO, while attenuating the response to the heme-independent activator BAY58-2667 that targets oxidized sGC. Similarly, overexpression of H2S-synthesizing enzyme cystathionine-γ lyase reduced the ability of BAY58-2667 to promote cGMP accumulation. In experiments with phenylephrine-constricted mouse aortic rings, treatment with rotenone (a compound that increases ROS production), caused a rightward shift of the DEA/NO concentration-response curve, an effect partially restored by H2S. When rings were pre-treated with H2S, the concentration-response curve to BAY 58-2667 shifted to the right. Using purified recombinant human sGC, we observed that treatment with H2S converted ferric to ferrous sGC enhancing NO-donor-stimulated sGC activity and reducing BAY 58-2667-triggered cGMP formation. The present study identified an additional mechanism of cross-talk between the NO and H2S pathways at the level of redox regulation of sGC. Our results provide evidence that H2S reduces sGC heme Fe, thus, facilitating NO-mediated cellular signaling events.

Clinical efficacy and safety of cilostazol: a critical review of the literature

Cilostazol is a unique antiplatelet agent that has been commercially available for over two decades. As a phosphodiesterase III inhibitor, it reversibly inhibits platelet aggregation yet also possesses vasodilatory and antiproliferative properties. It has been widely studied in a variety of disease states, including peripheral arterial disease, cerebrovascular disease, and coronary artery disease with percutaneous coronary intervention. Overall, cilostazol appears to be a promising agent in the management of these disease states with a bleeding profile comparable to placebo; even when combined with other antiplatelet agents, cilostazol does not appear to increase the rate of bleeding. Despite the possible benefit of cilostazol, its use is limited by tolerability as some patients often report drug discontinuation due to headache, diarrhea, dizziness, or increased heart rate. To date, it has been predominantly studied in the Asian population, making it difficult to extrapolate these results to a more diverse patient population. This paper discusses the evolving role of cilostazol in the treatment of vascular diseases.

Effect of Cilostazol Following Endovascular Intervention for Peripheral Artery Disease

Efficacy of endovascular therapy (EVT) with nitinol stents for femoropopliteal (FP) lesions is limited by restenosis. Oral cilostazol reduces angiographic restenosis rate; however, treatment duration remains unclear. In a retrospective analysis of a multicenter database of 3471 consecutive limbs in 2737 patients (mean age: 72 ± 9 years; 61% diabetic; and 26% on regular dialysis) undergoing EVT for FP lesions between January 2004 and December 2011, we compared Kaplan-Meier estimated primary patency after EVT followed or not by cilostazol treatment. We used Cox hazard regression analysis to assess temporal association between cilostazol treatment and post-EVT restenosis. Five-year primary patency was higher in the cilostazol group than in the noncilostazol group (57% vs 47%, P < .0001). Cilostazol treatment was inversely associated with restenosis for the first 2 years following EVT (P < .05); however, no significant association was observed thereafter. Cilostazol use therefore appears efficacious in preventing restenosis up to 2 years after EVT for FP lesions.

Levels and values of lipoprotein-associated phospholipase A2, galectin-3, RhoA/ROCK, and endothelial progenitor cells in critical limb ischemia: pharmaco-therapeutic role of cilostazol and clopidogrel combination therapy

Objective

We tested the hypothesis that clopidogrel and cilostazol combination therapy could effectively attenuate systemic inflammatory reaction, facilitate proliferation of circulating endothelial progenitor cell (EPC), and improve the clinical outcomes of critical limb ischemia (CLI) in patients unsuitable for surgical revascularization or percutaneous transluminal angioplasty (PTA).

Methods

A total 55 patients (mean age, 72 years; 56% female) were consecutively enrolled. Clopidogrel and cilostazol combination therapy was administered throughout the study period.

Results

As compared with the baseline, circulating endothelial progenitor cell level (as shown by flow cytometry) was significantly increased (p < 0.003), whereas the CLI-related ulcers and painfulness were significantly improved (all p < 0.01) by day 90 after treatment. On the other hand, after clopidogrel and cilostazol combination therapy, galectin-3 level, lipoprotein-associated phospholipase A₂ gene expression, and RhoA/ROCK-related protein expression in peripheral blood mononuclear cells were significantly suppressed (all p < 0.01). Eventually, by day 90, 5 patients (9.1%) died of other etiologies, 3 (5.5%) withdrew from the study, 6 (10.9%) required amputation, and the remaining 41 had satisfactory clinical improvement with complete wound healing in 9 (16.4%) patients.

Conclusion

The results of the present study highlight that clopidogrel and cilostazol combination therapy may be considered to be an alternative method for treating patients with CLI unsuitable for surgical revascularization or PTA.

Addition of cilostazol to conventional dual antiplatelet therapy reduces the risk of cardiac events and restenosis after drug-eluting stent implantation: a meta-analysis

This meta-analysis was performed to compare the risk of cardiac events and restenosis between triple antiplatelet therapy (TAT, addition of cilostazol to aspirin and clopidogrel) and conventional dual antiplatelet therapy (DAT, aspirin and clopidogrel) in drug-eluting stents (DES) implantation patients. We performed PUBMED, MEDLINE, EMBASE, and Cochrane CENTRAL searches for randomized clinical trials of TAT versus DAT in patients after DES implantation. Five clinical trials were involved in the study. TAT was associated with a 36% reduction in major adverse cardiac events (MACE; odds ratio (OR) = 0.64; 95% confidence interval (CI) = 0.51-0.81, P < .01), a 40% reduction (OR = 0.60, 95% CI = 0.44-0.80; P < .01) in target vessel revascularization (TVR), a 44% reduction (OR = 0.56, 95% CI = 0.34-0.91; P = .02) in target lesion revascularization (TLR) and a 47%/44% reduction in in-segment/in-stent restenosis (P < .01) and lower in-segment/in-stent late loss (P < .01). As regards to the safety assessment, there was no significant difference about the risk of stent thrombosis and bleeding between TAT and DAT group, while the risk of gastrointestinal trouble was significantly higher in TAT group (OR = 2.46, 95% CI = 1.25-4.86; P < .01). Addition of cilostazol to DAT reduced the incidence of MACE, TVR, and TLR after DES implantation. TAT also reduced the risk of restenosis and late loss in patients after DES implantation.

Efficacy and Safety of Adjunctive Cilostazol to Dual Antiplatelet Therapy After Stent Implantation

Background:

Aspirin and clopidogrel dual antiplatelet therapy (DAT) reduce ischemic events in patients with cardiovascular disease. However, recurrent ischemic event occurrence during DAT remains a major concern. This systematic review assesses the efficacy and safety of adjunctive cilostazol to DAT in combination with DAT on reducing clinical adverse events.

Methods:

We searched randomized controlled trials (RCTs) in PubMed, Embase, Cochrane library, clinicaltrial.gov, and Chinese Biomedical Database through July 2011. Pooled risk ratio (RR) with 95% confidence intervals (CIs) was calculated. Two independent reviewers evaluated the included studies. The extracted data were analyzed by Review Manager 5.1.2 (The Cochrane Collaboration, Oxford, UK) and GRADEprofiler 3.6 (GRADE Working Group).

Results:

A total of 7 RCTs (4351 patients) were included in the analysis, with a follow-up period of 6 to 12 months. Pooled analysis showed that cilostazol was associated with a significant reduction in major adverse cardiac events (MACEs; pooled RR 0.69, 95% CI 0.52-0.91; P = .008) and repeat revascularization (RR 0.74, 95% CI 0.61-0.89; P = .002); however, cilostazol was not associated with a reduction in the risk of stent thrombosis (RR 1.00, 95% CI 0.41-2.45; P = 1.00). Cilostazol seems to be safe, with no significant increase in the risk of bleeding (RR 1.06, 95% CI 0.72-1.56; P = .77). The 4 outcomes were low-quality evidence for MACE, moderate-quality evidence for repeat revascularization, and high-quality evidence for bleeding and stent thrombosis.

Conclusions:

When compared to the currently recommended DAT, triple antiplatelet therapy with cilostazol can reduce repeat revascularization with no increase in the risk of bleeding.

Combination of cilostazol and clopidogrel attenuates rat critical limb ischemia

BACKGROUND AND AIM

Procedural failure and untoward clinical outcomes after surgery remain problematic in critical limb ischemia (CLI) patients. This study tested a clopidogrel-cilostazol combination treatment compared with either treatment alone in attenuating CLI and improving CLI-region blood flow in rats.

METHODS

Male Sprague-Dawley rats (n = 40) were equally divided into five groups: control, CLI induction only, CL I + cilostazol (12.0 mg/day/kg), CLI + clopidogrel (8.0 mg/kg/day) and CLI + combined cilostazol-clopidogrel. After treatment for 21 days, Laser Doppler imaging was performed.

RESULTS

On day 21, the untreated CLI group had the lowest ratio of ischemic/normal blood flow (p < 0.001). Inflammation measured by VCAM-1 protein expression; oxidative stress; PAI-1, MMP-9 and TNF-α mRNA expressions; and immunofluorescence staining (IF) of CD68+ cells was lower with combined treatment than with the other treatments, and lower in the two single-treatment groups than the untreated CLI group (all p < 0.01). Anti-inflammatory mRNA expression of interleukin-10, and eNOS showed a reverse pattern among these groups. Apoptosis measured by Bax, caspase-3 and PARP; and muscle damage measured by cytosolic cytochrome-C, and serum and muscle micro-RNA-206 were all lowest with combination treatment, and the two single-treatment groups showed lower values than the untreated group (all p < 0.001). Angiogenesis measured by eNOS, IF staining of CD31+ and vWF + cells; and number of vessels in CLI region were highest with combination treatment and higher in the single-treatment groups than the untreated group (all p < 0.001).

CONCLUSION

Combined cilostazol-clopidogrel therapy is superior to either agent alone in improving ischemia in rodent CLI.

Use of Cilostazol in Percutaneous Coronary Interventions

OBJECTIVE:

To evaluate the addition of cilostazol to standard dual antiplatelet therapy (DAT) with aspirin and clopidogrel in patients receiving coronary stenting.

DATA SOURCES:

Relevant information was identified through a search of MEDLINE (1966-November 2011), International Pharmaceutical Abstracts (1960-2011), and Cochrane Databases (publications archived until November 2011) using the terms cilostazol, percutaneous coronary intervention, triple therapy, and antiplatelet agents.

STUDY SELECTION AND DATA EXTRACTION:

English-language prospective and retrospective studies, including registry data in adults, were eligible for inclusion if triple therapy with cilostazol was compared with DAT with aspirin and clopidogrel in patients undergoing percutaneous coronary intervention (PCI) with stenting. Article bibliographies were also reviewed.

DATA SYNTHESIS:

Cilostazol uniquely possesses antiproliferative properties in addition to its antiplatelet effects. Several prospective and retrospective clinical trials evaluated it as a third agent in standard antiplatelet regimens after PCI with both bare metal and drug-eluting stents. Both angiographic and clinical outcomes, including major adverse cardiac events (MACEs), have been improved with the addition of cilostazol to DAT in most trials, without increasing bleeding risk. Higher-risk patients, such as elderly individuals and patients with diabetes, long lesions, or small vessels, seem to benefit the most from triple therapy. Patients who are poor responders to clopidogrel also appear to benefit from the addition of cilostazol by improving platelet reactivity with standard DAT.

CONCLUSIONS:

Triple therapy with cilostazol has been shown to reduce MACEs by providing increased inhibition of platelet aggregation and reducing the rates of in-stent thrombosis compared to DAT without increasing the risk of bleeding complications. Further studies are needed to identify proper patient selection based on risk factors for the addition of cilostazol. Additionally, studies comparing cilostazol with newer antiplatelet therapies, such as prasugrel and ticagrelor, are needed.

The effectiveness and safety of triple-antiplatelet treatment based on cilostazol for patients receiving percutaneous coronary intervention: a meta-analysis

The combination of cilostazol, aspirin, and clopidogrel (triple therapy) after percutaneous coronary intervention has been considered as an alternative therapy. We performed a meta-analysis based on 8 randomized controlled trials with a total of 3332 patients to compare the effectiveness and safety of this triple therapy with traditional dual therapy (aspirin and clopidogrel). Our findings suggested that the triple therapy is more effective than dual therapy in preventing restenosis (odds ratio [OR]: 0.52, 95% confidence interval [CI]: 0.40-0.66, P < 0.00001), maintaining minimal lumen diameter (OR: 0.15, 95% CI: 0.10-0.20, P < 0.00001), and avoiding target-vessel revascularization (OR: 0.62, 95% CI: 0.47-0.82, P = 0.001). There is also no significant difference in major adverse cardiac and cerebrovascular events between the 2 therapies, except the smaller occurrence rate of target-lesion revascularization in the triple-therapy group (OR: 0.42, 95% CI: 0.26-0.69, P = 0.0005). However, the triple therapy is associated with a higher level of adverse drug events, including rash (OR: 2.45, 95% CI: 1.41-4.23, P = 0.001), gastrointestinal disorders (OR: 2.59, 95% CI: 1.26-5.30, P = 0.009), and drug discontinuation (OR: 3.80, 95% CI: 1.59-9.10, P = 0.003), but it has no difference in bleeding compared with the dual therapy (OR: 1.05, 95% CI: 0.71-1.55, P = 0.80).

Thrombospondin-1 inhibition of vascular smooth muscle cell responses occurs via modulation of both cAMP and cGMP

Nitric oxide (NO) drives pro-survival responses in vascular cells and limits platelet adhesion, enhancing blood flow and minimizing thrombosis. The matricellular protein thrombospondin-1 (TSP1), through interaction with its receptor CD47, inhibits soluble guanylyl cyclase (sGC) activation by NO in vascular cells. In vascular smooth muscle cells (VSMCs) both intracellular cGMP and cAMP regulate adhesion, contractility, proliferation, and migration. cGMP can regulate cAMP through feedback control of hydrolysis. Inhibition of the cAMP phosphodiesterase-4 selectively interfered with the ability of exogenous TSP1 to block NO-driven VSMC adhesion but not cGMP accumulation, suggesting that cAMP also contributes to VSMC regulation by TSP1. Inhibition of phosphodiesterase-4 was sufficient to elevate cAMP levels, and inhibiting guanylyl cyclase or phosphodiesterase-3, or adding exogenous TSP1 reversed this increase in cAMP. Thus, TSP1 regulates VSMC cAMP levels in part via cGMP-dependent inhibition of phosphodiesterase-3. Additionally basal cAMP levels were consistently elevated in both VSMCs and skeletal muscle from TSP1 null mice, and treating null cells with exogenous TSP1 suppressed cAMP levels to those of wild type cells. TSP1 inhibited both forskolin and isoproterenol stimulated increases in cAMP in VSMCs. TSP1 also abrogated forskolin and isoproterenol stimulated vasodilation. Consistent with its ability to directly limit adenylyl cyclase-activated vasodilation, TSP1 also limited cAMP-induced dephosphorylation of myosin light chain-2. These findings demonstrate that TSP1 limits both cGMP and cAMP signaling pathways and functional responses in VSMCs and arteries, by both phosphodiesterase-dependent cross talk between these second messengers and by inhibition of adenylyl cyclase activation.

Triple antiplatelet therapy vs. dual antiplatelet therapy in patients undergoing percutaneous coronary intervention: an evidence-based approach to answering a clinical query

AIMS

Outcomes of patients undergoing percutaneous coronary intervention (PCI) with drug-eluting stents (DES) and bare metal stents (BMS) have not been evaluated separately for specific dual and triple antiplatelet agent use. The purpose of this meta-analysis was to determine whether triple antiplatelet therapy (combination of clopidogrel, aspirin and cilostazol) has any advantage in efficacy compared with standard dual antiplatelet therapy (aspirin and clopidogrel) in patients undergoing PCI.

METHODS

Electronic and printed sources were searched till May 2008 for randomized controlled clinical trials (RCTs) of cilostazol in combination with aspirin and clopidogrel. Pooled weighted mean difference (WMD) and pooled odds ratio (OR) with 95% confidence intervals (CIs) were calculated.

RESULTS

A total of four RCTs including 1457 patients with a median follow-up period of 6-9 months were included in the analysis. The rates of major adverse cardiac and/or cerebrovascular events (MACE/MACCE), stent thrombosis and bleeding were not significantly different between triple and dual antiplatelet therapy groups. Pooled analysis showed that cilostazol was associated with significantly decreased incidence of in segment restenosis (ISR) (OR 0.51, 95% CI 0.38, 0.68; P < 0.00001), increased minimum luminal diameter (MLD) (WMD 0.16, 95% CI 0.10, 0.22; P < 0.00001) for both DES and BMS and also individually. However, the rates of target vessel revascularization (OR 0.45, 95% CI 0.25, 0.83; P = 0.01 and late lumen loss (pooled WMD 0.14, 95% CI 0.2, 0.07; P = 0.001) were decreased significantly only in the DES group receiving triple therapy.

CONCLUSIONS

Cilostazol appears to be effective in reducing the rates of ISR without any significant benefit for MACE/MACCE.

Addition of cilostazol to aspirin and a thienopyridine for prevention of restenosis after coronary artery stenting: a meta-analysis

The purpose of this study is to evaluate the effect of adding cilostazol to dual antiplatelet therapy (aspirin and thienopyridine) on rates of restenosis after coronary artery stenting. A meta-analysis is conducted of randomized, controlled trials comparing 3 drug regimens (cilostazol, thienopyridine, aspirin [triple therapy]) with dual antiplatelet therapy to reduce restenosis after coronary stenting. A total of 5 studies are included for analysis. The analysis reveals that triple therapy is used in 796 patients, whereas dual therapy is used in 801 patients. Approximately 56% of patients receive a drug-eluting stent. The 6-month restenosis rates are significantly lower with triple versus dual antiplatelet therapy (12.7% vs 21.9%; odds ratio 0.5; 95% confidence interval, 0.38-0.66; P < .001). This benefit is seen regardless of whether a bare-metal or drug-eluting stent is used. Rates of major adverse cardiac events and bleeding are reported for 3 of the 5 studies (n = 1426); analysis of these outcomes shows no difference between treatment groups (P = .21 and .48, respectively). The addition of cilostazol to standard dual antiplatelet therapy reduces angiographic restenosis and increases MLD at 6 months without significantly affecting rates of major adverse cardiac events or bleeding.

Early combined treatment with cilostazol and bone marrow-derived endothelial progenitor cells markedly attenuates pulmonary arterial hypertension in rats

We investigated whether early combined cilostazol and bone marrow-derived endothelial progenitor cell (BMDEPC) treatment offers synergistic benefit in ameliorating monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) in rats. Male Sprague-Dawley rats (n = 10/group) were randomized to receive saline injection only (group 1), MCT (70 mg/kg) (group 2), and MCT plus cilostazol (20 mg/kg/day) (group 3), MCT plus BMDEPCs (2.0 x 10(6) cells) (group 4), and MCT plus combined cilostazol/BMDEPCs (group 5). Intravenous BMDEPCs and oral cilostazol were given on day 3 after MCT administration. By day 42, connexin43 protein expression in right ventricle (RV) was reduced in group 2 compared with other groups and also was decreased in groups 3 and 4 compared with groups 1 and 5 (all p < 0.05). In addition, mRNA expressions of matrix metalloproteinase-9, tumor necrosis factor-alpha, and caspase-3 were higher, whereas Bcl-2 and endothelial nitric-oxide synthase were lower in lung and RV in group 2 compared with the other groups (all p < 0.05). The number of alveolar sacs and lung arterioles was lower in group 2 than in other groups and lower in groups 3 and 4 than in group 5 (all p < 0.05). RV systolic pressure (RVSP) and weight were increased in group 2 compared with the other groups (all p < 0.0001). Moreover, RVSP and RV-to-left ventricle plus septum weight ratio were higher in groups 3 and 4 than in groups 1 and 5 (p < 0.001) but showed no difference between groups 1 and 5. In conclusion, early combined autologous BMDEPC/cilostazol treatment is superior to BMDEPC or cilostazol only for preventing MCT-induced PAH.

Expression, activity, and function of phosphodiesterases in the mature and immature ductus arteriosus

A patent ductus arteriosus is due in large part to increased sensitivity of the premature ductus to PGE2. After PGE2 stimulation, cAMP concentrations are higher in the immature than in the mature ductus. cAMP concentrations depend on the rates of adenyl cyclase production and phosphodiesterase (PDE)-mediated degradation. We used ductus from immature (n = 25) and mature (n = 21) fetal sheep to investigate whether a developmental increase in PDE activity could explain the diminished cAMP accumulation that follows PGE2 stimulation in the mature ductus. With advancing gestation, mRNA expression of the smooth muscle PDE isoforms (PDE1A, 1B, 1C, 3A, 3B, 4D, and 5A) increased in the ductus as did their hydrolytic activities. Selective inhibitors of PDE1, PDE3, and PDE4 relaxed the mature and immature ductus in the presence of inhibitors of prostaglandin and nitric oxide production. The mature ductus required higher concentrations of each of the PDE inhibitors to inhibit its tension to the same extent as in the immature ductus. There were no developmental changes in PDE expression in the fetal aorta. In conclusion, we observed a developmental increase in cAMP and cGMP PDE activity that contributes to the decreased sensitivity of the late-gestation ductus arteriosus to vasodilators like PGE2.

Cilostazol therapy attenuates monocrotaline-induced pulmonary arterial hypertension in rat model

BACKGROUND

Pulmonary arterial hypertension (PAH) is characterized by a progressive increase in pulmonary vascular resistance caused by a proliferation of vascular endothelial and smooth muscle cells, resulting in occlusion of the lumen of small pulmonary arteries. Cilostazol, with its antiproliferative effects on vascular endothelial and smooth muscle cells, may ameliorate monocrotaline (MCT)-induced PAH in rats.

METHODS AND RESULTS

Male Sprague - Dawley rats (n=10/each group) were randomized to receive MCT (75 mg/kg) only (group 1), MCT plus cilostazol (20 mg .kg(-1 ). day(-1)) (group 2) and saline injection only (group 3). Hemodynamic measurement on day 28 following MCT treatment indicated the development of significant PAH on MCT-treated groups (p<0.0001). Cilostazol was given to group 2 orally on days 28-90. By day 90 following MCT treatment, the right ventricular (RV) systolic blood pressure and RV hypertrophy were significantly higher in group 1 than in groups 2 and 3 (all values of p<0.01). Additionally, connexin43 and endothelial nitric oxide synthase gene expressions of lung and RV, and Bcl-2 protein expression of RV, were significantly lower in group 1 than in groups 2 and 3 (all values of p<0.01). Furthermore, the number of alveolar sac and small arterioles of the lung were significantly lower in group 1 than in groups 2 and 3 (all values of p<0.01).

CONCLUSION

Cilostazol therapy effectively attenuates of MCT-induced PAH.

Effect of cilostazol on in-stent neointimal hyperplasia after coronary artery stenting: a quantative coronary angiography and volumetric intravascular ultrasound study

BACKGROUND

This study was designed to investigate the efficacy of cilostazol on the prevention of in-stent neointimal hyperplasia as measured by both quantitative coronary angiography (CAG) and volumetric intravascular ultrasound (IVUS).

METHODS AND RESULTS

Fifty-nine patients (39 men, age 62 years) undergoing elective coronary stenting were randomly assigned to receive aspirin plus clopidogrel or ticlopidine (Group I, n=28, 30 lesions) or aspirin plus clopidogrel or ticlopidine plus cilostazol (Group II, n=31, 35 lesions). CAG and IVUS were performed and repeated at 6 months to assess the primary endpoints of minimal luminal diameter (MLD) and in-stent neointimal hyperplasia volume. Follow-up CAG was performed on all patients and follow-up IVUS study was available for 50 lesions in 48 patients (24 lesions in Group I, 26 in Group II). There were no significant differences in the baseline angiographic data between the 2 groups. At 6 months follow-up, in-stent MLD was 1.90+/-0.76 mm in Group I and 2.41+/-0.85 mm in Group II (p=0.006). Volumetric IVUS at 6 months demonstrated that in-stent intimal hyperplasia volume per stent length was 2.2+/-1.4 mm3/mm in Group I and 1.0+/-0.5 mm3/mm in Group II (p=0.001).

CONCLUSIONS

Triple antiplatelet therapy including cilostazol seems to be more effective at preventing in-stent neointimal hyperplasia than a dual antiplatelet regimen.

Comparison of triple versus dual antiplatelet therapy after drug-eluting stent implantation (from the DECLARE-Long trial)

To evaluate the impact of cilostazol on neointimal hyperplasia after drug-eluting stent (DES) implantation for long coronary lesions, we performed a randomized multicenter prospective study comparing triple antiplatelet therapy (aspirin, clopidogrel, and cilostazol; triple group, n = 250) and dual antiplatelet therapy (aspirin and clopidogrel; standard group, n = 250) for 6 months in patients with long lesions (> or =25 mm) requiring a long DES (> or =32 mm). The primary end point was in-stent late loss at 6-month angiography. The 2 groups had similar baseline clinical and angiographic characteristics. In-stent late loss (0.22 +/- 0.48 mm vs 0.32 +/- 0.51 mm, p = 0.031) and in-segment late loss (0.34 +/- 0.49 mm vs 0.51 +/- 0.49 mm, p = 0.001) at 6-month follow-up angiography were significantly lower in the triple group versus the standard group. There was a trend toward lower rates of in-segment restenosis in the triple group versus the standard group (6.7% vs 11.2%, p = 0.104). Target lesion revascularization (TLR; 2.8% vs 6.8%, p = 0.036) and major adverse cardiac events (2.8% vs 7.6%, p = 0.016), including death, myocardial infarction, and TLR at 9 months were significantly lower in the triple group than in the standard group. At 9 months, the 2 groups had similar rates of stent thrombosis (0.4% vs 0.4%, p = 0.999), death (0% vs 0.8%, p = 0.499), and myocardial infarction (0.4% vs 0.4%, p = 0.999). In conclusion, cilostazol significantly reduced late loss at 6 months after DES implantation and the occurrence of TLR and major adverse cardiac events in patients with long coronary lesions.

Hypoxia-induced remodelling of PDE4 isoform expression and cAMP handling in human pulmonary artery smooth muscle cells

Human pulmonary artery smooth muscle cells (hPASM cells) express PDE4A10, PDE4A11, PDE4B2, PDE4C and PDE4D5 isoforms. Hypoxia causes a transient up-regulation of PDE4B2 that reaches a maximum after 7 days and sustained up-regulation of PDE4A10/11 and PDE4D5 over 14 days in hypoxia. Seven days in hypoxia increases both intracellular cAMP levels, protein kinase A (PKA) activity and activated, phosphorylated extracellular signal regulated kinase (pERK) but does not alter either PKA isoform expression or total cAMP phosphodiesterase-4 (PDE4) activity or cAMP phosphodiesterase-3 (PDE3) activity. Both the cyclooxygenase inhibitor, indomethacin and the ERK inhibitors, UO126 and PD980589 reverse the hypoxia-induced increase in intracellular cAMP levels back to those seen in normoxic hPASM cells. Challenge of normoxic hPASM cells with prostaglandin E(2) (PGE(2)) elevates cAMP to levels comparable to those seen in hypoxic cells but fails to increase intracellular cAMP levels in hypoxic hPASM cells. The adenylyl cyclase activator, forskolin increases cAMP levels in both normoxic and hypoxic hPASM cells to comparable elevated levels. Challenge of hypoxic hPASM cells with indomethacin attenuates total PDE4 activity whilst challenge with UO126 increases total PDE4 activity. We propose that the hypoxia-induced activation of ERK initiates a phospholipase A(2)/COX-driven autocrine effect whereupon PGE(2) is generated, causing the activation of adenylyl cyclase and increase in intracellular cAMP. Despite the hypoxia-induced increases in the expression of PDE4A10/11, PDE4B2 and PDE4D5 and activation of certain of these long PDE4 isoforms through PKA phosphorylation, we suggest that the failure to see any overall increase in PDE4 activity is due to ERK-mediated phosphorylation and inhibition of particular PDE4 long isoforms. Such hypoxia-induced increase in expression of PDE4 isoforms known to interact with certain signalling scaffold proteins may result in alterations in compartmentalised cAMP signalling. The hypoxia-induced increase in cAMP may represent a compensatory protective mechanism against hypoxia-induced mitogens such as endothelin-1 and serotonin.

Subcellular localization and regulation of type-1C and type-5 phosphodiesterases

We investigated the subcellular localization of PDE5 in in vitro human myometrial cells. We demonstrated for the first time that PDE5 is localized in discrete cytoplasmic foci and vesicular compartments corresponding to centrosomes. We also found that PDE5 intracellular localization is not cell- or species-specific, as it is conserved in different animal and human cells. PDE5 protein levels are strongly regulated by the mitotic activity of the smooth muscle cells (SMCs), as they were increased in quiescent, contractile myometrial cultures, and conditions in which proliferation was inhibited. In contrast, PDE1C levels decreased in all conditions that inhibited proliferation. This mirrored the enzymatic activity of both PDE5 and PDE1C. Increasing cGMP intracellular levels by dbcGMP or sildenafil treatments did not block proliferation, while dbcAMP inhibited myometrial cell proliferation. Together, these results suggest that PDE5 regulation of cGMP intracellular levels is not involved in the control of SMC cycle progression, but may represent one of the markers of the contractile phenotype.

Genes contributing to risk for common forms of stroke

The quest for disease genes that confer risk for stroke is now being undertaken using three complementary approaches. Positional cloning using rare Mendelian phenocopies of stroke has found genes that contribute to rare forms of stroke but, so far, not to the common forms of stroke. Candidate-gene case-control association studies using the common forms of stroke have found suggestive associations of modest effect. However, positional cloning using hundreds of Icelandic families affected by the common forms of stroke has recently found two genes conferring substantial risk for ischemic stroke that have apparently been confirmed in the USA and other European populations. Both genes encode enzymes, phosphodiesterase 4D (PDE4D) and arachidonate 5-lipoxygenase-activating protein (FLAP), which suggest novel treatment strategies for stroke prevention.

The role of cyclic nucleotide phosphodiesterases in the regulation of adipocyte lipolysis

This study assessed the effects of selective inhibitors of 3',5'-cyclic nucleotide phosphodiesterases (PDEs) on adipocyte lipolysis. IC224, a selective inhibitor of type 1 phosphodiesterase (PDE1), suppressed lipolysis in murine 3T3-L1 adipocytes (69.6 +/- 5.4% of vehicle control) but had no effect in human adipocytes. IC933, a selective inhibitor of PDE2, had no effect on lipolysis in either cultured murine 3T3-L1 adipocytes or human adipocytes. Inhibition of PDE3 with cilostamide moderately stimulated lipolysis in murine 3T3-L1 and rat adipocytes (397 +/- 25% and 235 +/- 26% of control, respectively) and markedly stimulated lipolysis in human adipocytes (932 +/- 7.6% of control). Inhibition of PDE4 with rolipram moderately stimulated lipolysis in murine 3T3-L1 adipocytes (291 +/- 13% of control) and weakly stimulated lipolysis in rat adipocytes (149 +/- 7.0% of control) but had no effect on lipolysis in human adipocytes. Cultured adipocytes also responded differently to a combination of PDE3 and PDE4 inhibitors. Simultaneous exposure to cilostamide and rolipram had a synergistic effect on lipolysis in murine 3T3-L1 and rat adipocytes but not in human adipocytes. Hence, the relative importance of PDE3 and PDE4 in regulating lipolysis differed in cultured murine, rat, and human adipocytes.

Cilostazol inhibits leukocyte integrin Mac-1, leading to a potential reduction in restenosis after coronary stent implantation

OBJECTIVES

The aim of this study was to confirm clinically a hypothesis that cilostazol inhibits leukocyte Mac-1, leading to prevention of post-stent restenosis.

BACKGROUND

The platelet phosphodiesterase III inhibitor called cilostazol also inhibits alpha-granule release of P-selectin in platelets. The P-selectin-mediated platelet-leukocyte interaction promotes activation and upregulation of leukocyte Mac-1 after coronary stenting, which plays a key role on the mechanism of restenosis. Thus, cilostazol's potential inhibition of this process may lead to prevention of restenosis.

METHODS

Using flow cytometric analysis of whole blood obtained from the coronary sinus, the expression of platelet membrane glycoproteins and neutrophil adhesion molecules was observed in 70 consecutive patients undergoing coronary stenting. The patients were randomly assigned to either a cilostazol or ticlopidine group before stent placement.

RESULTS

The restenosis rate was lower (15% vs. 31%, p < 0.05) in the cilostazol group (n = 34) than in the ticlopidine group (n = 32). A stent-induced increase in platelet P-selectin (CD62P) expression and an increase in neutrophil Mac-1 (CD11b) expression were suppressed in the cilostazol group compared with the ticlopidine group. Angiographic late lumen loss was correlated with the relative changes in platelet P-selectin and neutrophil Mac-1 at 48 h after coronary stenting.

CONCLUSIONS

Cilostazol may have effects on suppression of P-selectin-mediated platelet activation, platelet-leukocyte interaction, and subsequent Mac-1-mediated leukocyte activation, which might lead to a reduced restenosis rate after coronary stent implantation.

Balloon angioplasty plus cilostazol administration versus primary stenting of small coronary artery disease: Final results of COMPASS

Efficacy of primary stenting in small coronary artery disease is still controversial. Cilostazol has been reported to control restenosis after balloon angioplasty (BA). The aim was to compare primary stenting with BA plus cilostazol administration in small coronary artery disease. Of 106 lesions located in small coronary artery (reference < 3.0 mm), 50 lesions were randomly assigned to the stenting and 56 lesions to the BA-cilostazol group. Multilink stent was implanted in the stenting group. In the BA-cilostazol group, cilostazol (200 mg/day) without aspirin was administered for 6 months after BA. Ticlopidine was given for 1 month when bailout stent was implanted. Serial quantitative angiography was performed at the procedure and 6 months. The primary endpoint was 6-month angiographic restenosis. Clinical event rates at 1 year were also assessed. Baseline characteristics were similar. All procedures were successful. Bailout stenting was performed in three lesions in the BA-cilostazol group. No side effects of cilostazol were observed. Postprocedural lumen diameter was significantly larger (2.69 vs. 2.03 mm; P < 0.0001) in the stenting group. However, the follow-up lumen diameter was not different (1.76 vs. 1.85 mm, stenting vs. BA-cilostazol). Although the difference was not statistically significant, restenosis rate was lower in the BA-cilostazol group (13.2% vs. 24.5%; P = 0.11). Subacute thrombosis occurred in one patient and target revascularization rate was higher in the stenting group (22.0% vs. 10.7%; P = 0.10). BA plus cilostazol administration seems to be a favorable strategy for small coronary artery disease.

The gene encoding phosphodiesterase 4D confers risk of ischemic stroke

We previously mapped susceptibility to stroke to chromosome 5q12. Here we finely mapped this locus and tested it for association with stroke. We found the strongest association in the gene encoding phosphodiesterase 4D (PDE4D), especially for carotid and cardiogenic stroke, the forms of stroke related to atherosclerosis. Notably, we found that haplotypes can be classified into three distinct groups: wild-type, at-risk and protective. We also observed a substantial disregulation of multiple PDE4D isoforms in affected individuals. We propose that PDE4D is involved in the pathogenesis of stroke, possibly through atherosclerosis, which is the primary pathological process underlying ischemic stroke.

Cyclic nucleotide phosphodiesterase activity, expression, and targeting in cells of the cardiovascular system

Cyclic AMP (cAMP) and cGMP regulate a myriad of cellular functions, such as metabolism, contractility, motility, and transcription in virtually all cell types, including those of the cardiovascular system. Considerable effort over the last 20 years has allowed identification of the cellular components involved in the synthesis of cyclic nucleotides, as well as effectors of cyclic nucleotide-mediated signaling. More recently, a central role for cyclic nucleotide phosphodiesterase (PDE) has also been elaborated in many cell types, including those involved in regulating the activities of the cardiovascular system. In this review, we introduce the PDE families whose members are expressed in cells of the cardiovascular system including cardiomyocytes, vascular smooth muscle cells, and vascular endothelial cells. Because cell behavior is a dynamic process influenced by numerous factors, we will attempt to emphasize how changes in the activity, expression, and targeting of PDE influence cyclic nucleotide-mediated regulation of the behavior of these cells.

Effect of cilostazol on impaired vasodilatory response of the brachial artery to ischemia in smokers

The vascular endothelial function of smokers is known to be impaired. This study investigated whether cilostazol could improve the vasodilatory response of the brachial artery to ischemia, an indicator of endothelial function, in ten male smokers. Endothelium-dependent vasodilatation and endothelium-independent vasodilatation of the brachial artery were measured in 11 male non-smokers and 20 male smokers with matching age and weight. The results showed that the vasodilatory response to reactive hyperemia was significantly smaller in the smokers (4.8 +/- 1.6%) when compared to that in the non-smokers (7.6 +/- 2.5%) (p = 0.0013). However, no significant difference in the vasodilatory response to isosorbide dinitrate was observed between the two groups. In addition, there were no significant differences in serum lipid, Lp (a), or blood homocysteine between the smokers and non-smokers. When 150 mg/day of cilostazol was administered for two weeks, the vasodilatory response to reactive hyperemia significantly improved (4.2 +/- 1.2% to 7.8 +/- 3.5%, p = 0.0032). The increased vasodilatory response to reactive hyperemia by cilostazol was reduced after cessation of the drug (4.5 +/- 1.5%). These findings suggest that cilostazol improves vascular endothelial dysfunction in smokers.

Effect of cilostazol on vasomotor reactivity in patients with vasospastic angina pectoris

We examined the effects of cilostazol on impaired coronary arterial responses in patients with vasospastic angina (VSA). Thirty patients who were diagnosed with VSA based on an acetylcholine provocation test and 10 subjects with normal coronary arteries were enrolled. The patients were divided into the following 3 groups: no antiplatelet agent treatment group, aspirin treatment, or cilostazol treatment groups. Coronary flow reserve (CFR), coronary flow volume at maximum hyperemia, and epicardial coronary artery diameter after administration of N(G)-monomethyl-L-arginine (L-NMMA) were examined using a Doppler flow wire before and 6 months after the start of this study. CFR, coronary flow volume at maximum hyperemia, and diameter changes by L-NMMA were significantly increased in the cilostazol treatment group compared with the other 2 groups. In conclusion, cilostazol increased CFR and flow-dependent coronary dilation; these changes were attributable to nitric oxide. Cilostazol may improve coronary vascular endothelial dysfunction and coronary hemodynamics in patients with VSA.

Phosphodiesterase 4 in osteoblastic osteosarcoma cells as a potential target for growth inhibition

Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that HOSM-1 cells, an osteosarcoma cell line established from human mandible, expressed mRNA for osteoblastic markers, such as alkaline phosphatase, osteonectin, osteocalcin and parathyroid hormone receptor, thus exhibiting an osteoblastic phenotype. We have investigated a possible role of cyclic nucleotide phosphodiesterases (PDEs) in osteosarcoma cells. RT-PCR analysis revealed that HOSM-1 cells expressed mRNA for PDE4A, 4B and 4C. In addition, rolipram, a specific inhibitor of PDE4, inhibited HOSM-1 cell proliferation. The finding that PDE4 is involved in proliferation of osteosarcoma cells suggests the possibility that PDE4 may be a new target for antitumor therapy.

Debulking and stenting versus debulking only of coronary artery disease in patients treated with cilostazol (final results of ESPRIT)

Stenting inhibits vascular constrictive remodeling after directional coronary atherectomy (DCA). Cilostazol has been reported to control neointimal proliferation after stenting. This study's aim was to examine the effect of debulking and stenting with antirestenotic medication on restenosis. After optimal DCA, 117 lesions were randomly assigned to either the DCA with stent (DCA-stent) (58 lesions) group or the DCA only (59 lesions) group. Multilink stents were implanted in the DCA-stent group. Cilostazol (200 mg/day) without aspirin was administered to both groups for 6 months. Ticlopidine (200 mg/day) was given to the DCA-stent group for 1 month. Serial quantitative angiography and intravascular ultrasound (IVUS) were performed at the time of the procedure and at 6-month follow-up. The primary end point was 6-month angiographic restenosis. Clinical event rates at 1 year were also assessed. Baseline characteristics were similar. All procedures were successful. No adverse effects to cilostazol were observed. Postprocedural lumen diameter was significantly larger (3.27 vs 2.92 mm; p <0.0001) in the DCA-stent group. However, the follow-up lumen diameter was not significantly different (2.53 vs 2.41 mm, DCA-stent vs DCA). IVUS revealed that intimal proliferation was significantly larger in the DCA-stent group (4.2 vs 1.5 mm(2); p <0.0001), which accounted for the similar follow-up lumen area (6.5 vs 7.1 mm(2)). The restenosis rate was low in both groups (5.4% vs 8.9%), and the difference was not significant. Clinical event rates at 1 year were also not significantly different. These results suggest that optimal lesion debulking by DCA does not always need adjunctive stenting if cilostazol is administered.

Expression and role of phosphodiesterase 3 in human squamous cell carcinoma KB cells

Phosphodiesterase (PDE) 3s have been characterized in human squamous cell carcinoma KB cells. PDE3 activity was detected in homogenates of KB cells. PDE3A and 3B mRNAs were detected by RT-PCR in RNA from KB cells; the nucleotide sequences of the fragments were identical to those of human PDE3A and 3B. Immunoblotting with anti-PDE3 antibodies detected both PDE3A- and 3B-immunoreactive proteins in KB cells. The PDE3-specific inhibitor, cilostamide, inhibited the proliferation of KB cells. Our results indicate that PDE3s may be important regulators of the growth of KB cells. Therefore, PDE3 inhibitors may be potential new drugs for antiproliferative therapies in squamous cell carcinoma in the head and neck.

Expression of phosphodiesterase 3 in rat submandibular gland cell lines

A recent preliminary (unpublished) study showed that phosphodiesterase (PDE) 3A and 3B are expressed in rat submandibular glands. Here, PDE3 activity was detected in homogenates of rat submandibular gland acinar epithelial (SMIE) cells, but not rat A5 (epithelial duct) cells. Most of the PDE3 activity in SMIE cells was recovered in the particulate fraction. Only PDE3B mRNA was detected by reverse transcription-polymerase chain reaction in RNA from SMIE cells. The nucleotide sequence of the fragment was identical to the sequence of rat PDE3B. The PDE3 specific inhibitor, OPC3689 (10 and 50 microM), inhibited the growth of SMIE cells (19 and 63%), but not A5 cells. As the submandibular gland contains many types of cells, these results indicate that PDE3B may regulate a cAMP pool that is important in submandibular gland acinar epithelial cell function.