Effect of cilostazol in preventing restenosis after percutaneous transluminal coronary angioplasty

Cilostazol-imprinted polymer film-coated electrode as an electrochemical chemosensor for selective determination of cilostazol and its active primary metabolite

An electrochemical chemosensor for cilostazol (CIL) determination was devised, engineered, and tested. For that, a unique conducting film of the functionalized thiophene-appended carbazole-based polymer, molecularly imprinted with cilostazol (MIP-CIL), was potentiodynamically deposited on a Pt disk electrode by oxidative electropolymerization. Thanks to electro-oxidation potentials lower than that of CIL, the carbazole monomers outperformed pyrrole, thiophene, and phenol monomers, in this electropolymerization. The pre-polymerization complexes quantum-mechanical and molecular dynamics analysis allowed selecting the most appropriate monomer from the three thiophene-appended carbazoles examined. The electrode was then used as a selective CIL chemosensor in the linear dynamic concentration range of 50 to 924 nM with a high apparent imprinting factor, IF = 10.6. The MIP-CIL responded similarly to CIL and CIL's pharmacologically active primary metabolite, 3,4-dehydrocilostazol (dhCIL), thus proving suitable for their determination together. Simulated models of the MIP cavities binding of the CIL, dhCIL, and interferences' molecules allowed predicting chemosensor selectivity. The MIP film sorption of CIL and dhCIL was examined using DPV by peak current data fitting with the Langmuir (L), Freundlich (F), and Langmuir-Freundlich (LF) isotherms. The LF isotherm best described this sorption with the sorption equilibrium constant (K_LF) for CIL and dhCIL of 12.75 × 10^-6 and 0.23 × 10^-6 M, respectively. Moreover, the chemosensor cross-reactivity to common interferences study resulted in the selectivity to cholesterol and dehydroaripiprazole of 1.52 and 8.0, respectively. The chemosensor proved helpful in determining CIL and dhCIL in spiked human plasma with appreciable recovery (99.3-134.1%) and limit of detection (15 nM).

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.

Microbe-Derived Butyrate and Its Receptor, Free Fatty Acid Receptor 3, But Not Free Fatty Acid Receptor 2, Mitigate Neointimal Hyperplasia Susceptibility After Arterial Injury

Background

Arterial restenosis after vascular surgery is a common cause of midterm restenosis and treatment failure. Herein, we aim to investigate the role of microbe‐derived butyrate, FFAR2 (free fatty acid receptor 2), and FFAR3 (free fatty acid receptor 3) in mitigating neointimal hyperplasia development in remodeling murine arteries after injury.

Methods and Results

C57BL/6 mice treated with oral vancomycin before unilateral femoral wire injury to deplete gut microbiota had significantly diminished serum and stool butyrate and more neointimal hyperplasia development after arterial injury, which was reversed by concomitant butyrate supplementation. Deficiency of FFAR3 but not FFAR2, both receptors for butyrate, exacerbated neointimal hyperplasia development after injury. FFAR3 deficiency was also associated with delayed recovery of the endothelial layer in vivo. FFAR3 gene expression was observed in multiple peripheral arteries, and expression was increased after arterial injury. Treatment of endothelial but not vascular smooth muscle cells with the pharmacologic FFAR3 agonist 1‐methylcyclopropane carboxylate stimulated cellular migration and proliferation in scratch assays.

Conclusions

Our results support a protective role for butyrate and FFAR3 in the development of neointimal hyperplasia after arterial injury and delineate activation of the butyrate‐FFAR3 pathway as a valuable strategy for the prevention and treatment of neointimal hyperplasia.

The efficacy and safety of cilostazol as an alternative to aspirin in Chinese patients with aspirin intolerance after coronary stent implantation: a combined clinical study and computational system pharmacology analysis

Dual antiplatelet therapy (DAT) with aspirin and clopidogrel is the standard regimen to achieve rapid platelet inhibition and prevent thrombotic events. Currently, little information is available regarding alternative antiplatelet therapy in patients with an allergy or intolerance to aspirin. Although cilostazol is already a common alternative to aspirin in clinical practice in China, its efficacy and safety remain to be determined. We retrospectively analyzed 613 Chinese patients who had undergone primary percutaneous coronary intervention (PCI). Among them, 405 patients received standard DAT (aspirin plus clopidogrel) and 205 patients were identified with intolerance to aspirin and received alternative DAT (cilostazol plus clopidogrel). There were no significant differences between the two groups in their baseline clinical characteristics. The main outcomes of the study included major adverse cardiac events (MACEs) and bleeding events during 12 months of follow-up. The MACEs endpoint was reached in 10 of 205 patients treated with cilostazol (4.9%) and in 34 of 408 patients treated with aspirin (8.3%). No statistically significant difference was observed in MACEs between the two groups. However, patients in the cilostazol group had less restenosis than did patients in the aspirin group (1.5% vs 4.9%, P=0.035). The occurrence of bleeding events tended to be lower in the cilostazol group (0.49% vs 2.7%, P=0.063). These clinical observations were further analyzed using network system pharmacology analysis, and the outcomes were consistent with clinical observations and preclinical data reports. We conclude that in Chinese patients with aspirin intolerance undergoing coronary stent implantation, the combination of clopidogrel with cilostazol may be an efficacious and safe alternative to the standard DAT regimen.

Bilirubin coating attenuates the inflammatory response to everolimus-coated stents

The aim of this study was to evaluate the effects of bilirubin- and/or everolimus (EVL)-coated stents to prevent arterial neointimal hyperplasia and inflammation in vitro and in vivo. The stents were prepared by spray coating bare metal stents (BMS) with bilirubin and/or EVL. Study groups were divided into (1) BMS, (2) bilirubin-coated stents (BES), (3) commercialized stents (Synergy™; EES), and (4) bilirubin/EVL-coated stents (B-EES). The coating thickness and drug release rates were comparable to previous reports (i.e., <4 µm thickness and 50% drug release in 7 days). Smooth muscle cell migration was inhibited in both EVL-containing groups (20.5 ± 3.80% in EES and 18.4 ± 2.55% in B-EES) compared to the non-EVL-containing groups (78.0 ± 6.41% in BMS and 76.1 ± 4.88% in BES) (n = 10, p < 0.05). Stents were randomly implanted to 40 coronary arteries in 20 pigs and subjected to various analyses after 4 weeks of implantation. As results, the inflammation score was dramatically increased in the EES group (2.1 ± 0.42) compared to that of the other groups (1.5 ± 0.55, 1.3 ± 0.23, and 1.5 ± 0.27 for BMS, BES, and B-EES, respectively, n = 10, p < 0.05). Immunofluorescence analysis revealed that inflammation was prevented in the bilirubin-containing groups (BES and B-EES). However, the percent area of restenosis was decreased in the EVL-containing groups (20.5 ± 4.11% for EES and 18.4 ± 3.61% for B-EES) compared to the non-EVL-containing groups (32.3 ± 6.41% for BMS and 29.6 ± 5.95% for BES, n = 10, p < 0.05). The percent areas of restenosis determined by histopathology, optical coherence tomography, and micro-computed tomography were consistent. In addition, the stent was barely covered in the EES and B-EES groups at 4 weeks postimplantation. These dual drug-coated stents may be especially beneficial to patients who have an increased risk of inflammation. These stents have great potential for use in cardiovascular applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1486-1495, 2018.

A better effect of cilostazol for reducing in-stent restenosis after femoropopliteal artery stent placement in comparison with ticlopidine

Purpose

The purpose of this study was to assess the preventive effect of cilostazol on in-stent restenosis in patients after superficial femoral artery (SFA) stent placement.

Materials and methods

Of 28 patients with peripheral arterial disease, who had successfully undergone stent implantation, 15 received cilostazol and 13 received ticlopidine. Primary patency rates were retrospectively analyzed by means of Kaplan–Meier survival curves, with differences between the two medication groups compared by log-rank test. A multivariate Cox proportional hazards model was applied to assess the effect of cilostazol versus ticlopidine on primary patency.

Results

The cilostazol group had significantly better primary patency rates than the ticlopidine group. Cumulative primary patency rates at 12 and 24 months after stent placement were, respectively, 100% and 75% in the cilostazol group versus 39% and 30% in the ticlopidine group (P = 0.0073, log-rank test). In a multivariate Cox proportional hazards model with adjustment for potentially confounding factors, including history of diabetes, cumulative stent length, and poor runoff, patients receiving cilostazol had significantly reduced risk of restenosis (hazard ratio 5.4; P = 0.042).

Conclusion

This retrospective study showed that cilostazol significantly reduces in-stent stenosis after SFA stent placement compared with ticlopidine.

Cilostazol reduces restenosis after carotid artery stenting

BACKGROUND

Although carotid artery stenting (CAS) has been proposed as an alternative to carotid endarterectomy in cerebral revascularization, restenosis remains an unsolved issue. Cilostazol is a unique antiplatelet drug that has vasodilatory effects and inhibits smooth muscle cell proliferation. We investigated whether cilostazol reduces restenosis after CAS.

METHODS

A database of 113 consecutive CAS procedures between April 2002 and December 2007 was assessed retrospectively. All patients received aspirin (100 mg/d) and another antiplatelet drug such as cilostazol (200 mg/d), ticlopidine (200 mg/d), or clopidogrel (75 mg/d) at least 3 days before CAS. Two antiplatelet drugs were continued for 2 to 3 months after CAS and reduced to one thereafter. Patients were evaluated at 3 and 6 months and at 6-month intervals thereafter with duplex ultrasound (DUS) imaging. Angiography was used for confirmation when stenosis was suspected as >50% with DUS imaging.

RESULTS

We were able to monitor 97 patients for a 12-month period. The overall combined rate of stroke, myocardial infarction, and death was 3.1% at 30 days and 4.1% at 1 year. In-stent recurrent stenosis was documented in 11 patients (11%); in 10 patients (9.7%), this occurred <or=12 months of CAS. In-stent restenosis was significantly reduced in the cilostazol (+) group (0% vs 15.7% [11 of 70], P = .03). Patient characteristics were similar between the cilostazol (+) and cilostazol (-) groups.

CONCLUSIONS

Although this study was retrospective and nonrandomized, the results suggest that cilostazol administration improves long-term patency after CAS due to its inhibitory effect on smooth muscle cell growth.

Efficacy of cilostazol in reducing restenosis in patients undergoing contemporary stent based PCI: a meta-analysis of randomised controlled trials

AIMS

Cilostazol has been associated with reduction in restenosis in patients undergoing coronary and peripheral arterial angioplasty. Our objective was to evaluate the impact of cilostazol on restenosis in patients undergoing contemporary PCI with bare metal (BMS) or drug eluting stents (DES) and treated with aspirin and thienopyridine.

METHODS AND RESULTS

Ten randomised trials (n=2,809 patients) comparing triple antiplatelet therapy (aspirin, thienopyridine and cilostazol) with standard dual antiplatelet therapy were included. Summary risk ratios for restenosis, late loss, target lesion revascularisation (TLR) and target vessel revascularisation (TVR) were calculated using fixed-effects models. Cilostazol was associated with a significant reduction in late loss in BMS (mean difference 0.24 mm, 95% CI 0.15-0.33, p<0.001) and DES groups (mean difference 0.12 mm, 95% CI 0.07-0.18, p<0.001). Cilostazol therapy was associated with a significant reduction in angiographic restenosis (Odds ratio [OR] 0.52, 95% CI 0.41- 0.66, p<0.001) with consistent benefits in patients treated with BMS (OR 0.49, 95% CI 0.35-0.70, p<0.001) or DES (OR 0.54, 95% CI 0.38-0.76, p=0.001). Addition of cilostazol to dual antiplatelet therapy was associated with a significant reduction in TLR (OR 0.38, 95% CI 0.25-0.58, p<0.001), with no difference in subacute stent thrombosis (OR 1.91, 95% CI 0.33-11.08, p=0.47), or major bleeding (OR 0.87, 95% CI 0.44-1.74, P=0.69) but with an increased risk of skin rash (OR 3.67, 95% CI 1.86-7.24, p<0.001).

CONCLUSIONS

Cilostazol in addition to dual antiplatelet therapy is associated with a reduction in angiographic restenosis in patients undergoing stent based PCI. This inexpensive drug may be particularly beneficial in patients who are at high risk of restenosis and it should undergo further evaluation in large, definitive randomised controlled trials.

Systematic review and meta-analysis of randomized clinical trials appraising the impact of cilostazol after percutaneous coronary intervention

BACKGROUND

Drug-eluting stents reduce the risk of restenosis after percutaneous coronary intervention (PCI) but may pose a risk of thrombosis. Cilostazol, an oral antiplatelet agent with pleiotropic effects including inhibition of neointimal hyperplasia, could hold the promise of preventing both restenosis and thrombosis. We systematically reviewed randomized clinical trials (RCTs) on the angiographic and clinical impact of cilostazol after PCI.

METHODS

We searched RCT in BioMedCentral, CENTRAL, clinicaltrials.gov, EMBASE, and PubMed (November 2007). Coprimary end points were binary angiographic restenosis and repeat revascularization, abstracted and pooled by means of random-effect relative risks (RRs). Small study/publication bias was appraised with multiple methods.

RESULTS

A total of 23 RCTs were included (5428 patients), with median follow-up of 6 months. Pooled analysis showed that cilostazol was associated with statistically significant reductions in binary angiographic restenosis (RR = 0.60 [0.49-0.73], P < .001) and repeat revascularization (RR = 0.69 [0.55-0.86], P = .001). Cilostazol appeared also safe, with no significant increase in the risk of stent thrombosis (RR = 1.35 [0.71-2.57], P = .36) or bleeding (RR = 0.71 [0.43-1.16], P = .17). However, small study bias was evident for both binary restenosis (P < .001) and repeat revascularization (P < .001), suggesting that at least part of the apparent benefits of cilostazol could be due to this type of confounding effect.

CONCLUSIONS

Cilostazol appears effective and safe in reducing the risk of restenosis and repeat revascularization after PCI, but available evidence is limited by small study effects. Awaiting larger RCTs, this inexpensive treatment can be envisaged in selected patients in which drug-eluting stents are contraindicated or when there is a need for neointimal hyperplasia inhibition.

The vascular effects of cilostazol

Cilostazol is a phosphodiesterase III inhibitor with pharmacological effects that include vasodilation, inhibition of platelet activation and aggregation, inhibition of thrombosis, increased blood flow to the limbs, improvement in serum lipids with lowering of triglycerides and elevation of high density lipoprotein cholesterol, and inhibition of vascular smooth muscle cell growth. Cilostazol has been shown in multiple randomized clinical trials to result in decreased claudication and improved ability to walk in patients with peripheral arterial disease. In addition, cilostazol has been shown in multiple randomized clinical trials to decrease restenosis in the setting of coronary stent implantation. The purpose of the present paper was to review the vascular effects of cilostazol and to present results of the major clinical trials of the use of cilostazol in peripheral arterial disease and percutaneous coronary intervention with stent implantation.

Dose-dependent coronary artery intimal thickening after local delivery of the anti-oxidant tetradecylthioacetic acid from stents

OBJECTIVE

To examine the in vitro uptake and elution of the anti-oxidant tetradecylthioacetic acid (TTA) from phosphorylcholine (PC)-coated stents, and the in vivo uptake, retention, inflammatory response and histomorphometric changes after overstretch injury of the porcine coronary artery.

METHODS

PC-coated stents were loaded in one of three different concentrations of TTA (87, 174 and 347 mmol/L, i.e. 25, 50 and 100 mg/mL) and randomized versus PC-coated stents to the right coronary or left circumflex artery (18 pigs). Uptake of TTA into the coronary wall from the 347 mmol/L concentration was measured after 3 h and 24 h, 7 days, 14 days and 28 days (two pigs at each time point).

RESULTS

In vitro, TTA was successfully loaded onto the stents and elution was nearly complete after 48 h. In vivo, TTA could be demonstrated in the vessel wall for up to 4 weeks. Percent area stenosis was significantly higher in the TTA group, 35.2+/-20.9% versus 27.5+/-17.0% (p=0.03). Dose-related comparison showed increased intimal thickness, 0.66+/-0.53 mm versus 0.29+/-0.26 mm (p=0.008) and intimal area, 2.83+/-1.61 mm2 versus 1.58+/-0.91 mm2 (p=0.004) for the 347 mmol/L TTA versus controls. There was a significantly positive relationship between the TTA-loading dose and both intimal area (B=0.69, p=0.01) and maximal intimal thickness (B=0.17, p=0.02). The pro-inflammatory precursor arachidonic acid increased four-fold in the arterial wall of the TTA group, while the anti-inflammatory fatty acid index, calculated as (docosapentaenoic acid+docosahexaenoic acid+dihomo-linolenic acid)/arachidonic acid, was suppressed to 0.65+/-0.27 compared to 1.13+/-0.23 in control vessels (p<0.001).

CONCLUSION

TTA caused a dose-dependent intimal thickening and reduced anti-inflammatory fatty acid index. Contrary to expectations, TTA seems unsuitable as stent coating.

Comparison of the protective effects of type III phosphodiesterase (PDE3) inhibitor (cilostazol) and acetylsalicylic acid on intestinal microcirculation after ischemia reperfusion injury in mice

Antiplatelet therapy has been proposed as the treatment of choice for ischemia/reperfusion injury. The aim of this study is to elucidate the difference in effect between cilostazol (CZ) and acetylsalicylic acid (ASA) on microcirculatory disturbance in ischemia/reperfusion injury. Either 10 mg/kg of CZ (n = 14) or 100 mg/kg of ASA (n = 14) was administered orally to mice. Thereafter, 20 min of intestinal ischemia, followed by 60-min reperfusion, was applied; then, the status of submucosal microcirculation was observed under intravital microscopy. The blood cell counts and organ damage markers were examined in the portal blood. Next, 5 mm of the ileum was excised and was then histologically examined. Platelet-leukocyte aggregates were often observed in the postcapillary venules, and this formation was significantly reduced by both CZ and ASA. The number of adherent leukocytes was significantly lesser in the CZ-treated mice than in the ASA-treated mice (P < 0.01). The leukocyte number, lactate dehydrogenase, and lactate levels were best maintained in the CZ-treated mice (P < 0.05). The villus height was best preserved in the CZ-treated mice. Cilostazol inhibited not only the platelet aggregation but also the leukocyte adhesion to the endothelium, thereby inducing organ protection.

Reevaluating the role of phosphodiesterase inhibitors in the treatment of cardiovascular disease

First developed for clinical use in the late 1980s, the phosphodiesterase inhibitors were found to increase the levels of the ubiquitous second messenger cyclic adenosine monophosphate and could effect changes in vascular tone, cardiac function, and other cellular events. After several early studies using high doses of phosphodiesterase inhibitors in patients with severe heart failure suggested adverse consequences, they fell out of favor. However, recent investigations of phosphodiesterase inhibitors in patients with intermittent claudication have demonstrated profound benefits. Furthermore, these agents have proven useful in prevention of cerebral infarction and coronary restenosis, and their use in the treatment of heart failure is being reevaluated. The reemergence of phosphodiesterase inhibitors can be attributed to a better understanding of dosing and drug-specific pharmacology, the use of concomitant medications, and a recognition of unique ancillary properties; however, their use still requires caution.

Pharmacological treatment for prevention of restenosis

Coronary artery disease (CAD) is the leading cause of mortality and morbidity among adults in the Western world. Coronary artery bypass grafting and percutaneous coronary interventions (PCI) have gained widespread acceptance for the treatment of symptomatic CAD. There has been an explosive growth worldwide in the utilisation of PCI, such as balloon angioplasty and stenting, which now accounts for over 50% of coronary revascularisation. Despite the popularity of PCI, the problem of recurrent narrowing of the dilated artery (restenosis) continues to vex investigators. In recent years, significant advances have occurred in the understanding of restenosis. Two processes seem to contribute to restenosis: remodelling (vessel size changes) and intimal hyperplasia (vascular smooth muscle cell [VSMC] proliferation and extracellular matrix [ECM] deposition). Despite considerable efforts, pharmacological approaches to decrease restenosis have been largely unsuccessful and the only currently applied modality to reduce the restenosis rate is stenting. However, stenting only prevents remodelling and does not inhibit intimal hyperplasia. Several potential targets for inhibiting restenosis are currently under investigation including platelet activation, the coagulation cascade, VSMC proliferation and migration, and ECM synthesis. In addition, new approaches for local drug therapy, such as drug eluting stents, are currently being evaluated in preclinical and clinical studies. In this article, we critically review the current status of drugs that are being evaluated for restenosis at various stages of development (in vitro, preclinical animal models and human trials).

Cilostazol inhibits vascular smooth muscle cell growth by downregulation of the transcription factor E2F

Neointimal formation, the leading cause of restenosis, is caused by proliferation of vascular smooth muscle cells (VSMCs). Patients with diabetes mellitus have higher restenosis rates after coronary angioplasty than nondiabetic patients. Cilostazol, a selective type 3 phosphodiesterase inhibitor, is currently used to treat patients with diabetic vascular complications. Cilostazol is a potent antiplatelet agent that inhibits VSMC proliferation. In the present study, we examine whether the antiproliferative effect of cilostazol on VSMCs is mediated by inhibition of an important cell cycle transcription factor, E2F. Cilostazol inhibited the proliferation of human VSMCs in response to high glucose in vitro and virtually abolished neointimal formation in rats subjected to carotid artery injury in vivo. Moreover, the compound suppressed high-glucose-induced E2F-DNA binding activity, and the expression of E2F1, E2F2, cyclin A, and PCNA proteins. These data suggest that the beneficial effects of cilostazol on high-glucose-stimulated proliferation of VSMCs are mediated by the downregulation of E2F activity and expression of its downstream target genes, including E2F1, E2F2, cyclin A, and PCNA.

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.

Initial accumulation of platelets during arterial thrombus formation in vivo is inhibited by elevation of basal cAMP levels

Platelet accumulation at sites of vascular injury is the primary event in arterial thrombosis. Initial platelet accrual into thrombi is mediated by interactions of platelet adhesion receptors with ligands on the injured endothelium or in the sub-endothelial matrix. The role of intracellular signals in initial platelet accumulation at sites of endothelial injury, however, is the subject of debate. We have used a newly discovered inhibitor of phosphodiesterase 3A (PDE3A) and the well-characterized PDE3A inhibitor, cilostazol, to modulate 3',5'-cyclic adenosine monophosphate (cAMP) levels in an in vivo model that enables the kinetic analysis of platelet accumulation. These studies demonstrate that elevation of basal cAMP levels results in an overall decline in platelet accumulation at the site of vascular injury. In particular, the initial rate of accumulation of platelets is inhibited by elevation of cAMP. Analysis of the kinetics of individual platelets at injury sites using intravital microscopy demonstrates that cAMP directs the rate at which platelets attach to and detach from thrombi. These studies demonstrate that cAMP in circulating platelets controls attachment to and detachment from sites of arteriolar injury. Thus, the status of the intracellular signaling machinery prior to engagement of platelet receptors influences the rate of platelet accumulation during thrombus formation.

Randomized comparison of cilostazol versus ticlopidine hydrochloride for antiplatelet therapy after coronary stent implantation for prevention of late restenosis

BACKGROUND

Cilostazol is a newly developed antiplatelet drug that has been widely applied for clinical use. Its antiplatelet action appears to be mainly related to inhibition of intracellular phosphodiesterase activity. Recently, cilostazol has been used for antiplatelet therapy after coronary stent implantation. However, its evaluation has not been established yet.

METHODS

This prospective randomized trial was designed to investigate the efficacy of cilostazol for the prevention of late restenosis and acute or subacute stent thrombosis in comparison with ticlopidine hydrochloride. One hundred thirty consecutive patients, scheduled for elective coronary stenting, were randomly assigned to receive oral aspirin (81 mg/day) plus ticlopidine hydrochloride therapy (200 mg/day; group I) or aspirin plus cilostazol therapy (200 mg/day; group II). These medications were started at least 2 days before coronary intervention and continued until follow-up coronary angiography was performed 6 months later.

RESULTS

Subacute stent thrombosis was observed in 2 patients of group I but in no patients of group II. Major cardiac events were similarly present in both groups. Elevated transaminase levels were observed more frequently in group I than in group II (P <.05). Each of the quantitative coronary angiography variables before and immediately after coronary stenting were similar in both groups. At follow-up angiography, however, late lumen loss (0.69 +/- 0.79 mm vs 0.28 +/- 0.40 mm; P <.01) and loss index (0.42 +/- 0.56 vs 0.16 +/- 0.27; P <.01) were smaller in group II than in group I. Restenosis rate (13% vs 31%; P <.05) and target lesion revascularization rate (7% vs 21%; P <.05) were both lower in group II than in group I.

CONCLUSION

Aspirin plus cilostazol therapy may be an effective regimen for prevention of not only stent thrombosis but also restenosis.

Potential emerging therapeutic strategies to prevent restenosis in the peripheral vasculature

Despite the availability of antiplatelet and antithrombotic therapies, recent advances in catheter and stent technology and improved operator skill, restenosis remains the most frequent problem associated with percutaneous and surgical revascularization interventions for both coronary and peripheral arterial disease. Prevention of restenosis in the coronary vasculature has been demonstrated with cilostazol, trapidil, probucol, tranilast, nitric oxide donors, and clopidogrel. Given the similarities in revascularization procedures and in the pathophysiology of restenosis, it is possible that these results may be extrapolated to the setting of restenosis in the peripheral vasculature, making trials with these agents imperative. Several new agents have shown promising preliminary results for the prevention of restenosis in the peripheral vasculature, including cilostazol, low-molecular-weight heparins, and elastase. Several nonpharmacologic treatment modalities are also under study to prevent peripheral and coronary restenosis and have shown favorable initial results. These include endovascular radiation brachytherapy, arterial gene therapy, photoangioplasty, and several novel treatment delivery systems.

Cilostazol (pletal): a dual inhibitor of cyclic nucleotide phosphodiesterase type 3 and adenosine uptake

Cilostazol (Pletal), a quinolinone derivative, has been approved in the U.S. for the treatment of symptoms of intermittent claudication (IC) since 1999 and for related indications since 1988 in Japan and other Asian countries. The vasodilatory and antiplatelet actions of cilostazol are due mainly to the inhibition of phosphodiesterase 3 (PDE3) and subsequent elevation of intracellular cAMP levels. Recent preclinical studies have demonstrated that cilostazol also possesses the ability to inhibit adenosine uptake, a property that may distinguish it from other PDE3 inhibitors, such as milrinone. Elevation of interstitial and circulating adenosine levels by cilostazol has been found to potentiate the cAMP-elevating effect of PDE3 inhibition in platelets and smooth muscle, thereby augmenting antiplatelet and vasodilatory effects of the drug. In contrast, elevation of interstitial adenosine by cilostazol in the heart has been shown to reduce increases in cAMP caused by the PDE3-inhibitory action of cilostazol, thus attenuating the cardiotonic effects. Cilostazol has also been reported to inhibit smooth muscle cell proliferation in vitro and has been demonstrated in a clinical study to favorably alter plasma lipids: to decrease triglyceride and to increase HDL-cholesterol levels. One, or a combination of several of these effects may contribute to the clinical benefits and safety of this drug in IC and other disease conditions secondary to atherosclerosis. In eight double-blind randomized placebo-controlled trials, cilostazol significantly increased maximal walking distance, or absolute claudication distance on a treadmill. In addition, cilostazol improved quality of life indices as assessed by patient questionnaire. One large randomized, double-blinded, placebo-controlled, multicenter competitor trial demonstrated the superiority of cilostazol over pentoxifylline, the only other drug approved for IC. Cilostazol has been generally well-tolerated, with the most common adverse events being headache, diarrhea, abnormal stools and dizziness. Studies involving off-label use of cilostazol for prevention of coronary thrombosis/restenosis and stroke recurrence have also recently been reported.

Cilostazol represses vascular cell adhesion molecule-1 gene transcription via inhibiting NF-kappaB binding to its recognition sequence

Cilostazol is a specific inhibitor of cAMP phosphodiesterase, which is used for treatment of ischemic symptoms of peripheral vascular disease. Although cilostazol has antiplatelet and vasodilator properties, its effect on the expression of adhesion molecules in vascular endothelium is not known. In the present investigation, we examined the effect of cilostazol on the expression of vascular cell adhesion molecule-1 (VCAM-1) in cultured vascular endothelial cells. Cilostazol strongly inhibited tumor necrosis factor (TNF)-alpha-induced expression of VCAM-1 protein and its mRNA. In addition, cilostazol reduced TNF-alpha-induced U937 cell adhesion to the vascular endothelial cells. In transient transfection studies, cilostazol inhibited TNF-alpha-induced transcriptional activation of VCAM-1 promoter. Electrophoretic mobility shift assays revealed that cilostazol repressed TNF-alpha-induced increase in binding of the transcription nuclear factor-kappaB (NF-kappaB) to its recognition site of VCAM-1 promoter. Cilostazol, however, failed to prevent nuclear translocation of the NF-kappaB p65 protein. These data indicate that cilostazol repressed VCAM-1 gene transcription in cultured vascular endothelial cells, via inhibiting NF-kappaB binding to its recognition sequence. Since the expression of the adhesion molecule is one of the earliest events occurred in atherogenic process, cilostazol might have the potential to prevent atherosclerosis at least via inhibition of the expression of the adhesion molecule.

Effect of cilostazol on restenosis after coronary angioplasty and stenting in comparison to conventional coronary artery stenting with ticlopidine

BACKGROUND

The role of antiplatelet therapy with ticlopidine plus aspirin in the prevention of subacute thrombosis after coronary artery stenting has been established. However, restenosis remains a major limitation in coronary artery stenting.

METHODS

To compare the effect of cilostazol on restenosis after coronary angioplasty and stenting with that of ticlopidine after coronary artery stenting, 213 patients with 230 lesions who underwent successful coronary interventions were evaluated. Optimal results (residual stenosis less than 30%) were obtained by balloon angioplasty in 112 lesions, 64 lesions were treated with aspirin 81 mg/day (balloon-aspirin group) and 48 lesions with cilostazol 200 mg/day and aspirin 81 mg/day (balloon-cilostazol group). Stent implantation was performed in the remaining 118 lesions; 55 lesions were treated with ticlopidine 200 mg/day and aspirin 243 mg/day (stent-ticlopidine group) and 63 lesions with cilostazol 200 mg/day and aspirin 81 mg/day (stent-cilostazol group). Concomitant medications were continued for 4 to 6 months of follow-up.

RESULTS

No adverse events including acute occlusion and subacute thrombosis occurred in any groups. Although immediate gain and minimal lumen diameter immediately after angioplasty were significantly larger in stent groups than those in balloon groups, net gain at follow-up was significantly larger in cilostazol groups (1.54+/-0.83 mm in balloon-cilostazol group and 1.65+/-0.78 mm in stent-cilostazol group) than other groups (1.02+/-0.81 mm in balloon-aspirin group and 1.21+/-0.70 in stent-ticlopidine group) as a result of significantly lower late loss and loss index in cilostazol groups. The restenosis rate was significantly lower in cilostazol groups (12.5% in balloon-cilostazol group and 14.3% in stent-cilostazol group) than other groups (43.8% in balloon-aspirin group and 32.7% in stent-ticlopidine group). The rate of recurrent angina was significantly lower in cilostazol groups (4.3% in balloon-cilostazol group and 1.9% in stent-cilostazol group) than in other groups (17.5% in balloon-aspirin group and 14.0% in stent-ticlopidine groups).

CONCLUSIONS

Both optimal balloon angioplasty with cilostazol and coronary artery stenting with cilostazol have a potential to reduce restenosis compared with optimal balloon angioplasty with aspirin or conventional coronary artery stenting with ticlopidine plus aspirin.

Cilostazol: treatment of intermittent claudication

OBJECTIVE

To review the pharmacology and clinical utility of cilostazol, an antiplatelet and vasodilator agent approved for the management of intermittent claudication.

DATA SOURCES

Primary literature on cilostazol was identified from a comprehensive MEDLINE literature search (1980-February 2000). Selected meeting abstracts and manufacturer literature were also used as source material. Indexing terms included cilostazol, intermittent claudication, platelet inhibitors, and restenosis.

STUDY SELECTION

Human clinical, pharmacokinetic and randomized comparative trials performed in the US and Asia were reviewed. Selected in vitro, ex vivo, and animal studies were evaluated when human data were not available.

DATA SYNTHESIS

Intermittent claudication, defined as reproducible discomfort of a muscle group induced by exercise and relieved by rest, is the most common clinical manifestation of peripheral arterial disease (PAD). Cilostazol, a specific inhibitor of cyclic adenosine monophosphate phosphodiesterase in platelets and vascular smooth-muscle cells, is a potent antiplatelet agent and vasodilator that reduces vascular proliferation and has lipid-lowering effects in vivo. Recent multicenter, randomized, placebo-controlled trials have led to approval of cilostazol by the Food and Drug Administration for relief of intermittent claudication in patients with stable PAD. Cilostazol doubled walking distances and improved quality of life compared with placebo in these studies. One trial found that cilostazol was more effective than pentoxifylline, the only alternative pharmacologic therapy for claudication. Although frequent (approximately 50%) minor adverse effects, including headache, diarrhea, and palpitations, may occur in clinical practice, cilostazol has not been associated with major adverse events or increased mortality. Small, nonblind studies suggest that cilostazol may prove useful in preventing thrombosis and restenosis following percutaneous coronary interventions, although these remain unlabeled uses.

CONCLUSIONS

The unique combination of antiplatelet, vasodilatory, and antiproliferative effects of cilostazol appear to make it an attractive agent for use in patients with PAD. Clinical trials demonstrating a significant improvement in walking distances with cilostazol therapy suggest that it will be an important tool in improving symptoms and quality of life in patients with intermittent claudication.

Effects of cilostazol on late lumen loss and repeat revascularization after Palmaz-Schatz coronary stent implantation

BACKGROUND

Cilostazol is an antiplatelet agent that increases the intracellular concentration of cyclic adenosine monophosphate by inhibiting phosphodiesterase III; it has been shown to reduce neointimal hyperplasia in animal balloon injury models.

METHODS

One hundred thirty patients who underwent elective stenting (Palmaz-Schatz stent) were randomly assigned to cilostazol treatment 200 mg/d (n = 65) or to ticlopidine treatment 200 mg/d (n = 65). Angiographic follow-up was performed at 6 months, and clinical follow-up was continued up to 1 year.

RESULTS

One sudden death and one myocardial infarction resulting from subacute occlusion were observed in the ticlopidine group. Drug adverse effects were observed in 3 patients in the cilostazol group, as opposed to 6 patients in the ticlopidine group. In the intention-to-treat analysis, 56 patients (61 lesions) in the cilostazol group and 58 patients (58 lesions) in the ticlopidine group were assessed with quantitative coronary angiography. Late loss in the cilostazol group was smaller (0.58+/-0.52 mm vs. 1.09+/-0.65 mm, P<.0001) than in the ticlopidine group. The restenosis rate was lower in the cilostazol group than in the ticlopidine group (16% vs. 33%, P = .044). The target vessel revascularization rate at 1 year was 23% in the cilostazol group and 42% in the ticlopidine group (P =.03).

CONCLUSIONS

The results of this study suggest that cilostazol may be a safe medication that is effective in preventing restenosis after stent implantation.

Comparison of ticlopidine and cilostazol for the prevention of restenosis after percutaneous transluminal coronary angioplasty

Prevention of restenosis after percutaneous transluminal coronary angioplasty (PTCA) continues to be a significant problem. Recent controlled studies have demonstrated that cilostazol suppresses restenosis after PTCA. The effects of ticlopidine, another antiplatelet agent, were compared in terms of outcomes of patients randomized for treatment with the two drugs after PTCA. A total of 35 patients (47 lesions) were assigned prospectively and randomly to ticlopidine (17 patients, 24 lesions) and cilostazol (18 patients, 23 lesions) groups. Minimal luminal diameter (MLD) and percentage of stenosis to reference diameter were estimated before PTCA, just after the procedure and after 4 months follow-up. All patients underwent 4 months angiographic follow-up, at the end of which MLD was 2.03+/-0.71 mm in the ticlopidine group and 2.05+/-0.68 mm in the cilostazol group (p = 0.95), and the percentage of stenosis to reference diameter was 31.4+/-16.7% and 30.0+/-17.0%, respectively (p = 0.78). The restenosis rate was 12.5% in the ticlopidine group and 17.4% in the cilostazol group (p = 0.69), relatively low as compared to the 20% to 30% reported in previous studies. Adverse drug reactions during the follow-up period were observed in two of the ticlopidine group and none of the cilostazol group. We conclude that both ticlopidine and cilostazol are effective for the prevention of restenosis after PTCA, however the former may be associated with slight side effects.

Nitric oxide and postangioplasty restenosis: pathological correlates and therapeutic potential

Balloon angioplasty revolutionized interventional cardiology as a nonsurgical procedure to clear a diseased artery of atherosclerotic blockage. Despite its procedural reliability, angioplasty's long-term outcome can be compromised by restenosis, the recurrence of arterial blockage in response to balloon-induced vascular trauma. Restenosis constitutes an important unmet medical need whose pathogenesis has yet to be understood fully and remains to be solved therapeutically. The radical biomediator, nitric oxide (NO), is a natural modulator of several processes contributing to postangioplasty restenosis. An arterial NO deficiency has been implicated in the establishment and progression of restenosis. Efforts to address the restenosis problem have included trials evaluating a wide range of NO-based interventions for their potential to inhibit balloon-induced arterial occlusion. All types of NO-based interventions yet investigated benefit at least one aspect of balloon injury to a naive vessel in a laboratory animal without inducing significant side effects. The extent to which this positive, albeit largely descriptive, body of experimental data can be translated into the clinic remains to be determined. Further insight into the pathogenesis of restenosis and the molecular mechanisms by which NO regulates vascular homeostasis would help bridge this gap. At present, NO supplementation represents a unique and potentially powerful approach to help control restenosis, either alone or as a pharmaceutical adjunct to a vascular device.

Effects of cilostazol on angiographic restenosis after coronary stent placement

This study evaluates the impact of cilostazol on post-stenting restenosis. Cilostazol is a potent antiplatelet agent with antiproliferative properties. Few data are available about the effect of cilostazol on poststenting restenosis. Four hundred nine patients (494 lesions) who were scheduled for elective stenting were randomized to receive aspirin plus ticlopidine (group I, n = 201, 240 lesions) or aspirin plus cilostazol (group II, n = 208, 254 lesions), starting 2 days before stenting. Ticlopidine was given for 1 month and cilostazol for 6 months. Follow-up angiography was performed at 6 months, and clinical evaluation at regular intervals. Baseline characteristics were similar between the 2 groups. The procedural success rate was 99.6% in group I and 100% in group II. There were no cases of stent thrombosis after stenting. Angiographic follow-up was performed in 380 of the 494 eligible lesions and the angiographic restenosis rate was 27% in group I and 22.9% in group II (p = NS). However, diffuse type in-stent restenosis was more common in group I than in group II (54.2% vs 26.8%, respectively, p <0.05). In diabetic patients, the angiographic restenosis rate was 50% in group I and 21.7% in group II (p <0.05). Clinical events during follow-up did not differ between the 2 groups. In conclusion, aspirin plus cilostazol seems to be an effective antithrombotic regimen with comparable results to aspirin plus ticlopidine, but it does not reduce the overall angiographic restenosis rate after elective coronary stenting.

Increased platelet aggregability in response to shear stress in acute myocardial infarction and its inhibition by combined therapy with aspirin and cilostazol after coronary intervention

Although antiplatelet therapy with a specific inhibitor of phosphodiesterase-3 cilostazol improves stent patency compared with use of aspirin (ASA) alone, the specific role of cilostazol on platelet aggregation in patients with acute myocardial infarction (AMI) is less well understood. Thirty-six patients with AMI who were successfully treated with primary angioplasty were randomized to 3 antiplatelet regimens: ASA alone (n = 12), ASA + ticlopidine (n = 12), and ASA + cilostazol (n = 12). We measured shear stress-induced platelet aggregation (SIPA) using a modified cone-plate viscometer on admission and on day 7, and evaluated the inhibitory effects of combination therapy with ASA + cilostazol on SIPA. Compared with cases of stable coronary artery disease, significant increases in SIPA and plasma von Willebrand factor activity were observed in patients with AMI before they received antiplatelet therapy. On day 7 after primary angioplasty, ASA did not inhibit SIPA (65 +/- 15% vs 57 +/- 11%, p = 0.086), whereas both combination therapies of ASA + ticlopidine and ASA + cilostazol significantly inhibited SIPA in patients with AMI (ASA + ticlopidine: 61 +/- 15% vs 45 +/- 13%, p <0. 0001; ASA + cilostazol: 64 +/- 14% vs 43 +/- 9%, p <0.005). There was a significant correlation of SIPA with adenosine diphosphate (ADP)-induced platelet aggregation (r = 0.412, p = 0.003) and with plasma von Willebrand factor activity (r = 0.461, p = 0.0008). These data suggest that patients with AMI have increased platelet aggregability in response to high shear stress. Combined antiplatelet therapy with ASA + cilostazol appears to be as effective as therapy with ASA + ticlopidine for reducing SIPA in patients with AMI who are undergoing primary angioplasty.

Platelets and restenosis

Restenosis is currently the major limitation of percutaneous transluminal coronary angioplasty (PTCA). Factors such as elastic recoil, migration of vascular smooth muscle cells from media to intima, neointimal proliferation and vascular remodeling underly the restenotic process. Presently there is no effective therapy available for restenosis. The role of platelets in the development of thrombosis and abrupt closure after PTCA is well recognized. However, the effects of platelets in PTCA extend well beyond the early phase. Although antiplatelet agents such as glycoprotein IIb/IIIa antagonists have been reported to reduce target vessel revascularization, major unresolved controversies still exist. This report reviews the potential role of platelets in restenosis. Various drugs, successfully tested in experimental studies and in a small number of human studies, that inhibit the effect of platelets on the restenotic process are also reviewed.

Cyclic AMP inhibited proliferation of human aortic vascular smooth muscle cells, accompanied by induction of p53 and p21

Although cAMP is an important second messenger that plays a pivotal role in the regulation of platelet aggregation and dilatation of blood vessels, little is known about the action of cAMP on the growth of vascular smooth muscle cells (VSMCs). Thus, we initially studied the effects of cAMP accumulation by using various cAMP stimulants, including a phosphodiesterase type 3 inhibitor (cilostazol) on human aortic VSMC growth. Accumulation of cAMP inhibited the platelet-derived growth factor (PDGF)-stimulated VSMC growth in a dose-dependent manner (P<0.01), whereas PDGF significantly stimulated the growth of human VSMCs. Thus, we focused on the role of cell cycle regulatory genes, especially on a negative regulator, an anti-oncogene, p53. The protein of p53 was potentiated by cilostazol as well as forskolin and 8-bromo-cAMP, whereas PDGF decreased p53 expression. Upregulation of p53 protein by cAMP was further confirmed by the observation that the decrease in p21, a p53-inducible protein, by PDGF was significantly attenuated by cilostazol in a dose-dependent manner (P<0.01). These results revealed that accumulation of cAMP inhibited VSMC proliferation, which was at least in part due to an increase in p53-p21 expression. Because p53 and p21 have been reported to induce apoptosis, we examined apoptotic cells for cAMP accumulation. Incubation of VSMCs with cilostazol resulted in a significant increase in apoptotic cells in a dose-dependent manner compared with vehicle treatment as assessed by nuclear chromatic morphology (P<0.01); forskolin also stimulated apoptotic cells. Consistent with nuclear staining, DNA fragmentation in VSMCs treated with forskolin as well as 8-bromo-cAMP and cilostazol was significantly increased compared with DNA fragmentation in VSMCs treated with vehicle, whereas PDGF significantly decreased the rate of DNA fragmentation (P<0.01). Overall, these results demonstrated that cAMP inhibited the proliferation of human aortic VSMCs, accompanied by p53-p21-mediated apoptosis. Analogues of cAMP that have direct inhibitory effects on VSMC proliferation can be considered as potential antiproliferative drugs against VSMC growth.

Phosphodiesterase 4 conformers: preparation of recombinant enzymes and assay for inhibitors

Cyclic nucleotides are key regulators of many cellular processes. Their immediate action is terminated through the activity of phosphodiesterases, a diverse family of enzymes. This diversity has given rise to drug discovery opportunities, and assay technology is therefore of key importance. Inhibitors of the cyclic-AMP-specific phosphodiesterases (the PDE4 family) are drug candidates for a variety of inflammatory disorders. However, PDE4 inhibitors, besides their immunomodulatory effects, also cause side effects including nausea and emesis. Recently, it has been suggested that PDE4 exists in two different conformations with respect to inhibition by the prototypical compound rolipram. Inhibition of the low-affinity conformer is thought to give rise to anti-inflammatory effects, and inhibition of the high-affinity conformer to side effects. Therefore, a selective inhibitor of the low-affinity conformer may have clinical utility. Methods are described to prepare recombinant forms of PDE4B that allow screening for compounds that could preferentially inhibit the low-affinity conformer. Furthermore, conditions for an efficient, scintillation proximity, microtiter plate-based assay are described, providing a considerable advance over previous assays in terms of throughput and automatability.

Comparison of cilostazol versus ticlopidine therapy after stent implantation

The aim of this study was to evaluate the efficacy of cilostazol for prevention of stent thrombosis compared with ticlopidine. Cilostazol is a potent antiplatelet agent with less serious side effects. However, few data are available about the effect of cilostazol in preventing stent thrombosis after coronary stent implantation. Four hundred ninety patients selected for elective stent placement were randomized to receive aspirin plus ticlopidine (n = 243) or aspirin plus cilostazol (n = 247) for 1 month. Clinical and laboratory evaluations were performed at regular interval. There were no differences in baseline characteristics between the 2 groups. During the first 30 days after stent implantation, major cardiac events or adverse drug effects were similar between the 2 groups: ticlopidine (2.9%) vs cilostazol (1.6%) group, p = NS; stent thrombosis (0.4% vs 0.8%, p = NS, respectively), myocardial infarction (0.4% vs 0.8%, p = NS), severe leukopenia (1.2% vs 0%, p = NS), severe thrombocytopenia (0.4% vs 0%, p = NS), and cerebral hemorrhage (0.4% vs 0%, p = NS). Adverse effects led to drug withdrawal in 7 patients in the ticlopidine group (2.9%) and in 5 in the cilostazol group (2.0%). There was no death during the follow-up period. Thus, aspirin plus cilostazol may be an effective antithrombotic regimen with comparable results to aspirin plus ticlopidine after elective coronary stenting.

Cilostazol

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Effects of a single local administration of cilostazol on neointimal formation in balloon-injured rat carotid artery

To elucidate if locally administered cilostazol, an inhibitor of cyclic AMP phosphodiesterase III, suppresses neointimal formation in balloon-injured carotid artery of the rat, 20 mg of cilostazol was topically applied using pluronic gel at the time of balloon injury. Rats were sacrificed 14 days after balloon injury to measure the extent of neointimal formation. Plasma and tissue concentrations of cilostazol were also measured at 1, 3, 7 and 14 days after topical application. The 5-bromo-2'-deoxyuridine (BrdU, a thymidine analogue) was given intraperitoneally to detect proliferation of smooth muscle cells in the injured media at 3 days after balloon injury. At 1 day after injury, plasma and tissue concentrations were 0.147+/-0.043 microg/ml and 1380 microg/g tissue. Although the plasma concentration of cilostazol was undetectable ( < 0.02 microg/ml), a significant amount of cilostazol (46 microg/g tissue) was still detected in the tissue at the site of application even after 2 weeks. The intimal area of the injured carotid after 2 weeks was significantly smaller in the cilostazol-treated group than in the gel-treated control group (0.06+/-0.01 vs 0.15+/-0.02 mm2, P<0.001). BrdU-positive smooth muscle cells in the injured media after 3 days were also significantly fewer in the cilostazol-treated group than in the gel-treated control group (4.3+/-0.5 vs 9.1+/-0.9% of total cells, P < 0.001). These results suggest that local administration of cilostazol using pluronic gel maintains a high concentration of the drug at the application site, has an anti-proliferative effect on smooth muscle cells, and may have potential for clinical therapeutic use for the prevention of restenosis following arterial intervention.

Cyclic-3',5'-nucleotide phosphodiesterase isozymes in cell biology and pathophysiology of the kidney

Investigations of recent years revealed that isozymes of cyclic-3', 5'-nucleotide phosphodiesterase (PDE) are a critically important component of the cyclic-3',5'-adenosine monophosphate (cAMP) protein kinase A (PKA) signaling pathway. The superfamily of cyclic-3', 5'-phosphodiesterase (PDE) isozymes consists of at least nine gene families (types): PDE1 to PDE9. Some PDE families are very diverse and consist of several subtypes and numerous PDE isoform-splice variants. PDE isozymes differ in molecular structure, catalytic properties, intracellular regulation and location, and sensitivity to selective inhibitors, as well as differential expression in various cell types. A number of type-specific "second-generation" PDE inhibitors have been developed. Current evidence indicates that PDE isozymes play a role in several pathobiologic processes in kidney cells. In rat mesangial cells, PDE3 and PDE4 compartmentalize cAMP signaling to the PDE3-linked cAMP-PKA pathway that modulates mitogenesis and PDE4-linked cAMP-PKA pathway that modulates generation of reactive oxygen species. Administration of selective PDE isozyme inhibitors in vivo suppresses proteinuria and pathologic changes in experimental anti-Thy-1.1 mesangial proliferative glomerulonephritis in rats. Increased activity of PDE5 (and perhaps also PDE9) in glomeruli and in cells of collecting ducts in sodium-retaining states, such as nephrotic syndrome, accounts for renal resistance to atriopeptin; diminished ability to excrete sodium can be corrected by administration of the selective PDE5 inhibitor zaprinast. Anomalously high PDE4 activity in collecting ducts is a basis of unresponsiveness to vasopressin in mice with hereditary nephrogenic diabetes insipidus. Apparently, PDE isozymes apparently also play an important role in the pathogenesis of acute renal failure of different origins. Administration of PDE isozyme-selective inhibitors suppresses some components of immune responses to allograft transplant and improves preservation and survival of transplanted organ. PDE isozymes are a target for action of numerous novel selective PDE inhibitors, which are key components in the design of novel "signal transduction" pharmacotherapies of kidney diseases.

Effects of probucol and cilostazol alone and in combination on frequency of poststenting restenosis

The present study was conducted to assess the preventive effect of combined treatment with probucol, an antioxidant, and cilostazol, a phosphodiesterase inhibitor, against poststenting restenosis. Study patients were randomized to 4 modality groups 1 week before stenting: control, probucol (500 mg/day), cilostazol (200 mg/day), and probucol plus cilostazol. Treatment on these modalities was conducted from 5 prestent days until the poststenting follow-up evaluation (6 poststenting months). All patients received aspirin (81 mg/day). The efficacy of each modality against restenosis was evaluated in a total 126 patients with 165 coronary arterial lesions, using a quantitative method. The decrease in luminal diameter at the poststenting follow-up was 1.04 +/- 0.57 mm for controls, 0.88 +/- 0.82 mm for those taking probucol, 0.61 +/- 0.59 mm for those taking cilostazol (p <0.05 vs control), and 0.40 +/- 0.52 mm (p <0.01 vs control) for the combined treatment group. Restenosis rate per segment was 31.7% for controls, 16.7% for the probucol group, 12.5% for the cilostazol group (p <0.05 vs control), and 9.5% for the combined treatment group (p <0.05 vs the control). Neither mortality, myocardial infarction, stent thrombosis, or coronary bypass surgery, nor any serious complications were observed in the combined treatment group. Combined treatment with probucol and cilostazol has thus proved safe and effective in preventing acute poststenting complications and suppressing chronic restenosis.