Cilostazol for prevention of thrombosis and restenosis after intracoronary stenting

Use of Alternative Antiplatelet Agents for Clopidogrel Hypersensitivity

Clopidogrel is a widely used agent for secondary prevention of vascular events and is a cornerstone of dual antiplatelet therapy in patients with acute coronary syndrome (ACS) post coronary stent implantation. Hypersensitivity reactions to clopidogrel are well documented and may range from localized to systemic in presentation. This can lead to discontinuation of therapy, thus increasing the risk of vascular events. The authors have developed recommendations for potential alternative agents for the management of clopidogrel hypersensitivity reactions. Proposed strategies include treatment with an alternative P2Y12 inhibitor, cilostazol or warfarin.

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.

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.

Neuroprotective effect of cilostazol against retinal ischemic damage via inhibition of leukocyte-endothelial cell interactions

BACKGROUND

Cilostazol, a selective platelet phosphodiesterase inhibitor, has been shown to reduce neuronal injury after transient cerebral ischemia. Its neuroprotective effect is thought to result from an antiplatelet function. This study was designed to evaluate the inhibitory effects of cilostazol against retinal ischemic damage focusing on leukocyte-endothelial cell interactions.

METHODS

Retinal ischemia was induced for 60 min in male Sprague-Dawley rats (n = 144) by temporary ligation of the optic sheath. Cilostazol was administered just before ischemia induction. Leukocyte behavior in the retinal microcirculation was evaluated in vivo with scanning laser ophthalmoscopy and ex vivo with fluorescence microscopy. Retinal expression of P-selectin, intracellular adhesion molecule-1 (ICAM-1), and vascular endothelial growth factor were evaluated by real-time quantitative reverse transcriptase-polymerase chain reaction. Ischemia-induced retinal damage was evaluated histologically.

RESULTS

Treatment with cilostazol significantly suppressed leukocyte-endothelial cell interactions; the maximal numbers of rolling leukocytes were reduced by 77.6% (P < 0.01) 12 h after ischemia. Twenty-four hours after ischemia, adherent and accumulated leukocytes were also suppressed by treatment with cilostazol (36.1% and 20.4% respectively, P < 0.01). The expressions of P-selectin and ICAM-1 mRNA were suppressed significantly in cilostazol-treated retinas (P < 0.05). The retinal histological examination demonstrated a significant protective effect of cilostazol against ischemia-induced retinal damage (P < 0.01).

CONCLUSIONS

The present study demonstrates that cilostazol attenuates retinal injury after transient ischemia via inhibition of leukocyte-endothelial cell interactions. This inhibitory effect on postischemic leukocyte-endothelial cell interactions might partially contribute to its neuroprotective effects.

Identification of interaction sites of cyclic nucleotide phosphodiesterase type 3A with milrinone and cilostazol using molecular modeling and site-directed mutagenesis

To identify amino acid residues involved in PDE3-selective inhibitor binding, we selected eight presumed interacting residues in the substrate-binding pocket of PDE3A using a model created on basis of homology to the PDE4B crystal structure. We changed the residues to alanine using site-directed mutagenesis technique, expressed the mutants in a baculovirus/Sf9 cell system, and analyzed the kinetic characteristics of inhibition of the mutant enzymes by milrinone and cilostazol, specific inhibitors of PDE3. The mutants displayed differential sensitivity to the inhibitors. Mutants Y751A, D950A, and F1004A had reduced sensitivity to milrinone (K(i) changed from 0.66 microM for the recombinant PDE3A to 7.5 to 156 microM for the mutants), and diminished sensitivity to cilostazol (K(i) of the mutants were 18- to 371-fold higher than that of the recombinant PDE3A). In contrast, the mutants T844A, F972A and Q975A showed increased K(i) for cilostazol but no difference for milrinone from the recombinant PDE3A. Molecular models show that the PDE3 inhibitors cilostazol and milrinone share some of common residues but interact with distinct residues at the active site, suggesting that selective inhibitors can be designed with flexible size against PDE3 active site. Our study implies that highly conserved residuals Y751, D950 and F1004 in the PDE families are key residues for binding of both substrate and inhibitors, and nonconserved T844 may be responsible for the cilostazol selectivity of PDE3A. Detailed knowledge of the structure of inhibitory sites should contribute to development of more potent and specific inhibitory drugs.

Reduced phosphodiesterase 3 activity and phosphodiesterase 3A level in synthetic vascular smooth muscle cells: implications for use of phosphodiesterase 3 inhibitors in cardiovascular tissues

Vascular smooth muscle cells (VSMC) in situ function to control contraction and are said to express a contractile phenotype. However, during development or in response to vascular damage, VSMC proliferate and express a more synthetic phenotype. A survey of literature values for contractile and synthetic VSMC phosphodiesterase (PDE) 3 and PDE4 activities identified a marked difference in the PDE3 and PDE4 activities of these cells. In this study, a comparison of PDE3 and PDE4 activities in contractile and synthetic VSMC demonstrates that a reduced PDE3/PDE4 activity ratio in synthetic VSMC correlates with a reduced PDE3 activity and is associated with marked reductions in PDE3A mRNA and protein levels. Because we show that similar reductions in PDE3 activity and PDE3A levels occur upon culture of human aortic VSMC and that this phenomenon associates with the phenotypic switch that occurs to VSMC in response to vascular damage, our findings are presented in the context that PDE3 inhibition might be expected to selectively alter functions of contractile VSMC.