Pharmacologic approaches to restenosis prevention

Efficacy and safety of cilostazol-based triple antiplatelet therapy compared with clopidogrel-based dual antiplatelet therapy in patients with acute ST-elevation myocardial infarction undergoing percutaneous coronary intervention: A multicenter, randomized, open-label, phase 4 trial

BACKGROUND

Previous studies reported that compared to conventional dual antiplatelet therapy (DAT; aspirin + clopidogrel), triple antiplatelet therapy (TAT), involving the addition of cilostazol to DAT, had better clinical outcomes in patients with ST-elevation myocardial infarction (STEMI). However, the optimal duration of TAT is yet to be determined.

METHODS

In total, 985 patients with STEMI who underwent primary percutaneous coronary intervention (PCI) with drug-eluting stents (DESs) were prospectively enrolled in 15 PCI centers in South Korea and China. We randomly assigned patients into 3 groups: DAT (aspirin and clopidogrel for 12 months), TAT 1M (aspirin, clopidogrel, and cilostazol for 1 month), and TAT 6M (aspirin, clopidogrel, and cilostazol for 6 months). The primary endpoint was 1-year major adverse cardiovascular events (MACEs), defined as a composite of all-cause death, recurrent myocardial infarction, stroke, or repeat revascularization.

RESULTS

The primary endpoint did not differ among the 3 groups (8.8% in DAT, 11.0% in TAT 1M, and 11.6% in TAT 6M; hazard ratio for TAT 1M vs DAT, 1.302; 95% confidence interval [CI], 0.792-2.141; P = .297; hazard ratio for TAT 6M vs DAT, 1.358; 95% CI, 0.829-2.225; P = .225). With respect to in-hospital outcomes, more bleeding events occurred in the TAT group than in the DAT group (1.3% vs 4.7% vs 2.6%, P = .029), with no significant differences in major bleeding events. Additionally, the TAT group had a higher incidence of headaches (0% vs 1.6% vs 2.6%, P = .020).

CONCLUSIONS

The addition of cilostazol to DAT did not reduce the incidence of 1-year MACEs compared with DAT alone. Instead, it may be associated with an increased risk of drug intolerance and side effects, including in-hospital bleeding and headaches.

Carotid Stent Restenosis and Thrombosis in Rabbits: The Effect of Antiplatelet Agents

BACKGROUND

The purpose of the study was the comparative assessment of ticagrelor and clopidogrel effects on carotid post-balloon injury (PBI) and on post carotid artery stenting (CAS) rate of in-stent restenosis (ISR) and in-stent thrombosis in atherosclerotic rabbits.

METHODS

Forty-eight New Zealand white rabbits on high-fat diet were randomized into 4 groups: A1: PBI and clopidogrel (30 mg/kg/d), A2: PBI and ticagrelor (21 mg/kg twice daily), B1: PBI, CAS, and clopidogrel (30 mg/kg/d), B2: PBI, CAS, and ticagrelor (21 mg/kg twice daily). All rabbits received orally aspirin (10 mg/kg/d) and interventions were performed in their right carotid arteries (RCAs). Optical coherence tomography (OCT) and carotid angiography were performed at end point, while platelet aggregation and lipid profile were measured. After euthanasia both carotids were obtained for histological examination.

RESULTS

In B1 group, 3 rabbits presented thrombotic total occlusion of the stents, while none such episode was observed in B2 group. The neointimal areas in RCAs, calculated by OCT, did not differ between A1 and A2 groups, and between B1 and B2 groups (P > .05). From the histological findings, the intima/(media + intima) percentage (%) in RCAs of balloon-injured rabbits did not present any difference between groups (P = .812). Similarly, the immunohistochemically determined accumulation of endothelial cells and macrophages on vascular walls was equivalent between groups (P > .05).

CONCLUSION

Following carotid balloon injury and stenting, clopidogrel and ticagrelor did not show any differential effects on the extent of neointimal formation and ISR in atherosclerotic rabbits receiving aspirin. Three thrombotic stent occlusions were noted in the clopidogrel treatment group, but this finding was not statistically significant.

Comparison of 1-Year Outcomes of Triple (Aspirin + Clopidogrel + Cilostazol) Versus Dual Antiplatelet Therapy (Aspirin + Clopidogrel + Placebo) After Implantation of Second-Generation Drug-Eluting Stents into One or More Coronary Arteries: from the DECREASE-PCI Trial

This study sought to evaluate the impact of triple antiplatelet therapy on clinical outcomes in patients treated with second-generation drug-eluting stents (DES) for coronary artery disease. There are limited data regarding the impact of triple antiplatelet therapy in patients who underwent implantation of second-generation DES. We planned to randomly assign 2,110 patients treated with second-generation DES to triple (aspirin, clopidogrel, and cilostazol) and dual (aspirin, clopidogrel, and placebo) antiplatelet therapy groups. The primary end point was a composite of death, myocardial infarction, ischemic stroke, or target vessel revascularization (TVR) at 1 year since randomization. The study was stopped early owing to slow enrollment. In total, 404 patients (202 patients each in the triple and dual antiplatelet therapy groups) were finally enrolled. At 1 year, the primary end point had occurred in 3.6% and 9.4% of patients in the triple and dual antiplatelet therapy groups, respectively (hazard ratio [HR] of the triple group 0.396; 95% confidence interval [CI] 0.166 to 0.949; p = 0.038). There was no significant difference between the 2 groups regarding the occurrence of a composite of all-cause death, myocardial infarction, or ischemic stroke (HR 0.583; 95% CI 0.229 to 1.481; p = 0.256). However, the rates of TVR were significantly lower in the triple antiplatelet therapy group than in the dual antiplatelet therapy group (HR 0.118; 95% CI 0.015 to 0.930; p = 0.043). In conclusion, triple antiplatelet therapy with cilostazol after implantation of second-generation DES improved clinical outcomes, mainly by reducing TVR.

Effect of TGF-β1 on the Migration and Recruitment of Mesenchymal Stem Cells after Vascular Balloon Injury: Involvement of Matrix Metalloproteinase-14

Restenosis or occlusion after vascular procedures is ascribed to intimal hyperplasia. Transforming growth factor (TGF)-β1 is involved in recruitment of mesenchymal stem cells (MSCs) following arterial injury, and its release from latent TGF-binding protein by matrix metalloproteinase (MMP)-14-induced proteolysis contributes to neointima formation. However, the relationship between MMP-14 and TGF-β1 activation in restenosis is unknown. This study investigated the relationship using a rat model of balloon-induced injury. Rats were assigned to vehicle-, SB431542 (SB)-, or recombinant human (rh)TGF-β1-treated groups and examined at various time points after balloon-induced injury for expression of TGF-β1/Smad signalling pathway components, MMP-14 and MSCs markers including Nestin, CD29, and Sca1⁺CD29⁺CD11b/c⁻CD45⁻. Intimal hyperplasia was reduced in SB- and rhTGF-β1-treated rats. The expression of TGF-β1, TGF-β1RI, and Smad2/3 was decreased, but the levels of phosphorylated Smad2/3 were higher in SB-treated rats than vehicle-treated after 7 days to 14 days. rhTGF-β1 administration decreased the expression of TGF-β1/Smad pathway proteins, except for TGF-β1RI. Nestin and CD29 expression and the number of Sca1⁺CD29⁺CD11b⁻CD45⁻ cells were reduced, whereas MMP-14 expression was increased after SB431542 and rhTGF-β1 administration. These results suggest that TGF-β1/Smad signalling and MMP-14 act to recruit MSCs which differentiate to vascular smooth muscle cells and mesenchymal-like cells that participate in arterial repair/remodelling.

Plasma torch toothbrush a new insight in fear free dentisry

Dental treatment is considered painful either because of fear or anxiety. Even though fear and anxiety could be managed; the needle pricks and the heat generated with drills are both painful and destructive to the tissues of the tooth. A new technology which can reduce the pain and destruction of the dental tissues will be of huge value. Plasma torch toothbrush fits into such criteria and when developed fully, will be able to apply for many of the dental procedures for increasing the efficiency.

Targeted anti-inflammatory systemic therapy for restenosis: the Biorest Liposomal Alendronate with Stenting sTudy (BLAST)-a double blind, randomized clinical trial

BACKGROUND

Activation of systemic innate immunity is critical in the chain of events leading to restenosis. LABR-312 is a novel compound that transiently modulates circulating monocytes, reducing accumulation of these cells at vascular injury sites and around stent struts. The purpose of the study was to examine the safety and efficacy of a single intravenous bolus of LABR-312 in reducing restenosis in patients treated for coronary narrowing. Patient response was examined in light of differential inflammatory states as evidenced by baseline circulating monocyte levels, diabetes mellitus, and acute coronary syndrome.

METHODS

BLAST is a Phase II prospective, randomized, multicenter, double-blind, placebo-controlled trial that assessed the safety and efficacy of LABR-312. Patients were randomized to receive LABR-312 at 2 dose levels or placebo as an intravenous infusion during percutaneous coronary intervention and bare metal stent implantation. The primary end point was mean angiographic in-stent late loss at 6 months.

RESULTS

Patients (N = 225) were enrolled at 12 centers. There were no safety concerns associated with the study drug. For the overall cohort, there were no differences between the groups in the primary efficacy end point (in-stent late loss of 0.86 ± 0.60 mm, 0.83 ± 0.57 mm, and 0.81 ± 0.68 mm for the placebo, low-dose, and high-dose group, respectively; P = not significant for all comparisons). In the prespecified subgroups of patients with a baseline proinflammatory state, patients with diabetes mellitus, and patients with high baseline monocyte count, there was a significant treatment effect.

CONCLUSIONS

Intravenous administration of LABR-312 to patients undergoing percutaneous coronary intervention is safe and effectively modulates monocyte behavior. The average late loss did not differ between the treatment and placebo groups. However, in the inflammatory patient group with baseline monocyte count higher than the median value, there was a significant reduction in late loss with LABR-312.

Mast cells and vascular diseases

Mast cells are increasingly being recognized as effector cells in many cardiovascular conditions. Many mast-cell-derived products such as tryptase and chymase can, through their enzymic action, have detrimental effects on blood vessel structure while mast cell-derived mediators such as cytokines and chemokines can perpetuate vascular inflammation. Mice lacking mast cells have been developed and these are providing an insight into how mast cells are involved in cardiovascular diseases and, as knowledge increase, mast cells may become a viable therapeutic target to slow progression of cardiovascular disease.

Targeting cannabinoid receptor CB(2) in cardiovascular disorders: promises and controversies

Cardiovascular disease is the leading cause of death and disability worldwide, which can be largely attributed to atherosclerosis, a chronic inflammation of the arteries characterized by lesions containing immune and smooth muscle cells, lipids and extracellular matrix. In recent years, the lipid endocannabinoid system has emerged as a new therapeutic target in variety of disorders associated with inflammation and tissue injury, including those of the cardiovascular system. The discovery that Δ-9-tetrahydrocannabinol (Δ9-THC), the main active constituent of marijuana, inhibited atherosclerotic plaque progression via a cannabinoid 2 (CB(2) ) receptor-dependent anti-inflammatory mechanism, and that certain natural and synthetic cannabinoid ligands could modulate the myocardial or cerebral ischaemia-reperfusion-induced tissue damage, have stimulated impetus for a growing number of studies investigating the implication of CB(2) receptors in atherosclerosis, restenosis, stroke, myocardial infarction and heart failure. The aim of this review is to update on recent findings and controversies on the role of CB(2) receptors in cardiovascular disease. Particular emphasis will be placed on novel insights in the potential cellular targets of CB(2) stimulation in cardiovascular system (e.g. endothelial and vascular smooth muscle cells, cardiomyocytes, infiltrating and/or resident monocytes/macrophages and leukocytes, etc.), their interplay and intracellular signalling mechanisms identified, as well as on experimental and clinical studies.

Antibody-targeted drug delivery to injured arteries using layered double hydroxide nanoparticles

Targeted local delivery of a nanoparticle-based, antibody-targeted, and low molecular weight heparin (LMWH) delivery system successfully reduces restenosis and thrombus formation in an animal model. An antibody recognizing cross-linked fibrin (XLF) D-dimer is successfully conjugated to layered double hydroxide nanoparticles. Use of the anti-XLF-conjugated LMWH-carrying layered double hydroxide nanoparticles shows successful targeting of the nanoparticles (red) to the injured artery wall (green), resulting in decreased neointimal thickening and thrombus formation.

Interaction analysis between genetic polymorphisms and pharmacodynamic effect in patients treated with adjunctive cilostazol to dual antiplatelet therapy: results of the ACCEL-TRIPLE (Accelerated Platelet Inhibition by Triple Antiplatelet Therapy According to Gene Polymorphism) study

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Compared with standard dual antiplatelet therapy, adjunctive cilostazol to dual antiplatelet therapy ('triple antiplatelet therapy') has a potential to reduce ischemic event occurrence after percutaneous coronary intervention. The pharmacokinetic and pharmacodynamic effects of clopidogrel have been significantly influenced by the enzyme activity of the ABCB1 C3435T and the CYP2C19 system. • For the pharmacokinetics of cilostazol, genetic polymorphisms of the CYP3A5 and CYP2C19 have been associated with the substantial interindividual variability in healthy volunteers.

WHAT THIS STUDY ADDS

Loss-of-function polymorphism of the CYP2C19 gene, but not the ABCB1 C3435T and CYP3A5*3 genes, affects the antiplatelet effect of triple antiplatelet therapy. Most of extensive and intermediate East Asian metabolizers (0 or 1 CYP2C19 loss-of-function allele) show adequate platelet inhibition when treated with triple antiplatelet therapy after percutaneous coronary intervention. However, carriage of 2 CYP2C19 loss-of-function alleles is still associated with the risk of high platelet reactivity (defined by by 5 µM ADP-induced maximal platelet aggregation >46%), which clinical impact needs to be validated in future clinical trials. AIMS Although adjunctive cilostazol to dual antiplatelet therapy can reduce the risks of clinical events after percutaneous coronary intervention (PCI), whether genetic polymorphism can influence the pharmacodynamics of this regimen has not been evaluated.

METHODS

One hundred and twenty-seven patients treated with PCI and taking triple antiplatelet therapy (≥1 month) were enrolled. Platelet reactivity was assessed by conventional aggregometry and the VerifyNow P2Y12 assay. High on-treatment platelet reactivity (HPR) was defined as 5 µm ADP-induced maximal platelet reactivity (Agg(max) ) >46%. CYP3A5*3, CYP2C19*2/*3 and ABCB1 3435C > T were genotyped.

RESULTS

CYP3A5*3 and ABCB1 3435C > T variants did not affect the antiplatelet effect of triple antiplatelet therapy. For non-carriers, one and two carriers of the CYP2C19 loss-of-function (LOF) allele, Agg(max) consecutively increased after the addition of 5 µm[mean (95% confidence intervals): 24.6% (20.8 to 28.5%) vs. 28.7% (25.4 to 32.0%) vs. 32.3% (25.8 to 38.7%), P = 0.062, respectively] and 20 µm ADP [34.2% (29.3 to 39.0%) vs. 41.7% (37.8 to 45.6%) vs. 44.9% (37.9 to 51.9%), P = 0.007, respectively]. Likewise, late platelet reactivity and P2Y12 reaction units proportionally changed according to the number of CYP2C19 LOF alleles. HPRs were observed in 9.2% of subjects: 6.3%, 7.4% and 20.0% with 0, 1 and 2 carriers of CYP2C19 LOF allele(s) (P = 0.099). In multivariate analysis, carriage of two CYP2C19 LOF alleles was a significant predictor for the prevalence of HPR (odds ratio 5.78, 95% CI 1.21, 27.78, P = 0.028).

CONCLUSION

Among PCI-treated patients, the effect of triple antiplatelet therapy is influenced by the CYP2C19 LOF allele. Its clinical benefit needs to be validated according to the CYP2C19 metabolic phenotype in future clinical trials. [Adjunctive Cilostazol Versus High Maintenance dose ClopidogrEL in Acute Myocardial Infarction Patients According to CYP2C19 Polymorphism (ACCEL-AMI-2C19), NCT00915733 and Adjunctive Cilostazol Versus High Maintenance-dose Clopidogrel According to Cytochrome 2C19 Polymorphism (ACCEL-2C19), NCT01012193].

Cannabinoid receptor CB2 protects against balloon-induced neointima formation

Cannabinoid receptor CB(2) activation inhibits inflammatory proliferation and migration of vascular smooth muscle cells in vitro. The potential in vivo relevance of these findings is unclear. We performed carotid balloon distension injury in hypercholesterolemic apolipoprotein E knockout (ApoE(-/-)) mice receiving daily intraperitoneal injection of the CB(2) agonist JWH133 (5 mg/kg) or vehicle, with the first injection given 30 min before injury. Alternatively, we subjected CB(2)(-/-) and wild-type (WT) mice to balloon injury. We determined CB(2) mRNA and protein expression in dilated arteries of ApoE(-/-) mice. Neointima formation was assessed histologically. We used bone marrow-derived murine CB(2)(-/-) and WT macrophages to study adhesion to plastic, fibronectin, or collagen, and migration was assayed by modified Boyden chamber. Aortic smooth muscle cells were isolated to determine in vitro proliferation rates. We found increased vascular CB(2) expression in ApoE(-/-) mice in response to balloon injury. Seven to twenty-one days after dilatation, injured vessels of JWH133-treated mice had less intimal nuclei numbers as well as intimal and medial areas, associated with less staining for proliferating cells, smooth muscle cells, and macrophages. Complete endothelial repair was observed after 14 days in both JWH133- and vehicle-treated mice. CB(2) deficiency resulted in increased intima formation compared with WT, whereas JWH133 did not affect intimal formation in CB(2)(-/-) mice. Apoptosis rates assessed by in situ terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling staining 1 h postballooning were significantly higher in the CB(2) knockouts. In vitro, bone marrow-derived CB(2)(-/-) macrophages showed enhanced adherence and migration compared with WT cells and elevated mRNA levels of adhesion molecules, chemokine receptors CCR1 and 5, and chemokine CCL2. Proliferation rates were significantly increased in CB(2)(-/-) smooth muscle cells compared with WT. In conclusion, pharmacological activation or genetic deletion of CB(2) receptors modulate neointima formation via protective effects in macrophages and smooth muscle cells.

Influence of topography of an endovascular stent material on smooth muscle cell response

The phenotypic shift of smooth muscle cells (SMCs) from contractile to synthetic phenotype after endovascular stenting has been deemed to be the predominant cause of restenosis. Although substrate topography has been shown to affect SMC response for a variety of polymers, effect of topography on phenotype of SMCs has not been well studied for endovascular stent materials. Thus, the objective of the present study was to evaluate SMC phenotype, manifested in morphology, proliferation, and contractile marker smooth muscle α-actin expression, as a function of 316L stainless steel topography. Results of this study showed that the cells grown on micro-grooved surface (groove depth: 13 μm) were significantly more elongated than those on the electropolished surface. Ascertained by repeated proliferation studies, cells grown on micro-grooved surface demonstrated a significantly lower proliferation rate relative to the electropolished surface. An enhanced expression of smooth muscle α-actin grown on micro-grooved surface was also found near confluence. Furthermore, cells on electropolished surface demonstrated a substantial loss of smooth muscle α-actin between days 1 and 4. Therefore, given the favorable SMC response reported in this study, our findings suggest that a micro-grooved topography might prove beneficial for endovascular stent applications.

Protease-activated receptor-2 modulates protease-activated receptor-1-driven neointimal hyperplasia

OBJECTIVE

Emerging evidence suggests that protease-activated receptors-1 and -2 (PAR1 and PAR2) can signal together in response to proteases found in the rapidly changing microenvironment of damaged blood vessels. However, it is unknown whether PAR1 and PAR2 promote or mitigate the hyperplastic response to arterial injury. Using cell-penetrating PAR1 pepducins and mice deficient in PAR1 or PAR2, we set out to determine the respective contributions of the receptors to hyperplasia and phenotypic modulation of smooth muscle cells (SMCs) in response to arterial injury.

METHODS AND RESULTS

SMCs were strongly activated by PAR1 stimulation, as evidenced by increased mitogenesis, mitochondrial activity, and calcium mobilization. The effects of chronic PAR1 stimulation following vascular injury were studied by performing carotid artery ligations in mice treated with the PAR1 agonist pepducin, P1pal-13. Histological analysis revealed that PAR1 stimulation caused striking hyperplasia, which was ablated in PAR1(-/-) and, surprisingly, PAR2(-/-) mice. P1pal-13 treatment yielded an expression pattern consistent with a dedifferentiated phenotype in carotid artery SMCs. Detection of PAR1-PAR2 complexes provided an explanation for the hyperplastic effects of the PAR1 agonist requiring the presence of both receptors.

CONCLUSIONS

We conclude that PAR2 regulates the PAR1 hyperplastic response to arterial injury leading to stenosis.

Mesenchymal stem cell seeding promotes reendothelialization of the endovascular stent

This study is designed to make a novel cell seeding stent and to evaluate reendothelialization and anti-restenosis after the stent implantation. In comparison with cell seeding stents utilized in previous studies, Mesenchymal stem cells (MSCs) have advantages on promoting of issue repair. Thus it was employed to improve the reendothelialization effects of endovascular stent in present work. MSCs were isolated by density gradient centrifugation and determined as CD29(+) CD44(+) CD34(-) cells by immunofluorescence and immunocytochemistry; gluten and polylysine coated stents were prepared by ultrasonic atomization spray, and MSCs seeded stents were made through rotation culture according to the optimized conditions that were determined in previous studies. The results from animal experiments, in which male New Zealand white rabbits were used, show that the reendothelialization of MSCs coated stents can be completed within one month; in comparison with 316L stainless steel stents (316L SS stents) and gluten and polylysine coated stents, the intimal hyperplasia and in-stent restenosis are significantly inhibited by MSCs coated stents. Endovascular stent seeded with MSCs promotes reendothelialization and inhibits the intimal hyperplasia and in-stent restenosis compared with the 316L SS stents and the gluten and polylysine coated stents.

Impact of the tissue factor pathway inhibitor gene on apoptosis in human vascular smooth muscle cells

Tissue factor pathway inhibitor (TFPI) plays a vitally important role in the blood coagulation pathway. Recent studies indicated that TFPI induces apoptosis in vascular smooth-muscle cells (VSMCs) in animals. The present study investigated whether the TFPI gene could also induce apoptosis in human vascular smooth-muscle cells (hVSMCs). Such cells were isolated from human umbilical arteries and subsequently transfected with pIRES-TFPI plasmid (2 μg/mL). MTT assaying and cell counting were applied to measure cell viability and proliferation, RT-PCR was utilized to analyze TFPI gene expression in the cells. Apoptosis was analyzed by fluorescence activated cell sorting (FACS). Several key proteins involved in apoptosis were examined through Western blotting. It was shown that TFPI gene transfer led to its increased cellular expression, with a subsequent reduction in hVSMC proliferation. Further investigation demonstrated that TFPI gene expression resulted in lesser amounts of procaspase-3, procaspase-8 and procascase-9, and an increased release of mitochondrial cytochrome c (cyt-c) into cytoplasm, thereby implying the involvement of both extrinsic and intrinsic pathways in TFPI gene-induced apoptosis in hVSMCs.

Impact of adjunctive cilostazol therapy on platelet function profiles in patients with and without diabetes mellitus on aspirin and clopidogrel therapy

Cilostazol is a platelet inhibitor which when added to aspirin and clopidogrel has shown to reduce the risk of recurrent ischaemic events without an increase in bleeding. These clinical benefits have shown to be more pronounced in patients with diabetes mellitus (DM). However, it remains unknown whether cilostazol exerts different pharmacodynamic effects in patients with and without DM. This was a randomised, double-blind, placebo-controlled, cross-over pharmacodynamic study comparing platelet function in patients with and without DM on aspirin and clopidogrel therapy. Patients (n=111) were randomly assigned to either cilostazol 100 mg or placebo twice daily for 14 days and afterwards crossed-over treatment for another 14 days. Platelet function was performed at baseline, 14 days post-randomisation, and 14 days post-cross-over. Functional testing to assess P2Y12 signalling included flow cytometric analysis of phosphorylation status of vasodilator-stimulated phosphoprotein measured by P2Y12 reactivity index (PRI), light transmittance aggregometry and VerifyNow. Thrombin generation processes were also studied using thrombelastography. Significantly lower PRI values were observed following treatment with cilostazol compared with placebo both in DM and non-DM groups (p < 0.0001). The absolute between-treatment differences of PRI between groups was a 35.1% lower in patients with DM (p=0.039). Similar results were obtained using all other functional measures assessing P2Y12 signalling. Thrombin generation was not affected by cilostazol. Cilostazol reduces platelet reactivity both in patients with and without DM, although these pharmacodynamic effects are enhanced in patients with DM. Despite the marked platelet inhibition, cilostazol does not alter thrombin-mediated haemostatic processes, which may explain its ischaemic benefit without the increased risk of bleeding.

Protease-activated receptor-1 antagonist F 16618 reduces arterial restenosis by down-regulation of tumor necrosis factor α and matrix metalloproteinase 7 expression, migration, and proliferation of vascular smooth muscle cells

Wound healing after angioplasty or stenting is associated with increased production of thrombin and the activation of protease-activated receptor 1 (PAR1). The aim of the present study was to examine the effects of a new selective PAR1 antagonist, 2-[5-oxo-5-(4-pyridin-2-ylpiperazin-1-yl)-penta-1,3-dienyl]-benzonitrile (F 16618), in restenosis and vascular smooth muscle cell (SMC) proliferation and migration using both in vivo and in vitro approaches. Daily oral administration of F 16618 inhibited the restenosis induced by balloon angioplasty on rat carotid artery in a dose-dependent manner. Furthermore, single intravenous administration of F 16618 during the angioplasty procedure was sufficient to protect the carotid artery against restenosis. In vitro, F 16618 inhibited the growth of human aortic SMCs in a concentration-dependent manner with maximal effects at 10 μM. At that concentration, F 16618 also prevented thrombin-mediated SMC migration. In vivo, oral and intravenous F 16618 treatments reduced by 30 and 50% the expression of the inflammatory cytokine tumor necrosis factor α (TNFα) 24 h after angioplasty. However, only acute intravenous administration prevented the induction of matrix metalloproteinase 7 expression. In contrast, F 16618 treatments had no effect on early SMC de-differentiation and transcription of monocyte chemoattractant protein-1 and interleukin-6 and late re-endothelialization of injured arteries. Furthermore, F 16618 compensated for the carotid endothelium loss by inhibiting PAR1-mediated contraction. Altogether, these data demonstrate that PAR1 antagonists such as F 16618 are a highly effective treatment of restenosis after vascular injury, by inhibition of TNFα, matrix metalloproteinase 7, and SMC migration and proliferation in addition to an antithrombotic effect.

Haemoglobin-induced oxidative stress is associated with both endogenous peroxidase activity and H2O2 generation from polyunsaturated fatty acids

Patients with increased haemolytic haemoglobin (Hb) have 10-20-times greater incidence of cardiovascular mortality. The objective of this study was to evaluate the role of Hb peroxidase activity in LDL oxidation. The role of Hb in lipid peroxidation, H(2)O(2) generation and intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) was assessed using NaN(3), a peroxidase inhibitor, catalase, a H(2)O(2) decomposing enzyme and human umbilical vein endothelial cells (HUVECs), respectively. Hb induced H(2)O(2) production by reacting with LDL, linoleate and cell membrane lipid extracts. Hb-induced LDL oxidation was inhibited by NaN(3) and catalase. Furthermore, Hb stimulated ICAM-1 and VCAM-1 expression, which was inhibited by the antioxidant, probucol. Thus, the present study suggests that the peroxidase activity of Hb produces atherogenic, oxidized LDL and oxidized polyunsaturated fatty acids (PUFAs) in the cell membrane and reactive oxygen species (ROS) formation mediated Hb-induced ICAM-1 and VCAM-1 expression.

Development of transgenic endothelial progenitor cell-seeded stents

Endothelial progenitor cell (EPC)-seeded intravascular stents may reduce or prevent in-stent restenosis. A20 can play an important role for preventing vascular restenosis. Therefore, it is very important how to enhance the seeding efficiency of A20-modified EPCs on the stent for preventing in-stent restenosis. To approach this problem, we developed a novel transgenic EPC-seeded stent and evaluated its feasibility and efficiency. EPCs were isolated and purified from umbilical blood using immunomagnetic beads and then transfected with the A20 gene. One stent type (type 1) was coated with EDC cross-linked collagen, and another stent type (type 2) was coated with EDC cross-linked collagen and bound to the CD34 antibody using the bifunctional coupling agent N-succinmidyl3-(2-pyridyldithio) propionate (SPDP). Then, the stents were seeded with EPCs transfected with the A20 gene. The stents were implanted in biological artificial vessels, and cell adhesion was determined in a flow chamber. Cell growth was also measured. EPCs were transfected successfully with the A20 gene. The cells covered both types of stents with favorable biological function. After placement in a flow chamber, the number of cells attached to type 1 stents significantly dropped and their distribution was scattered. Type 2 stents were basically covered with cells and there were more cells on type 2 stents than on type 1 stents (p < 0.01). Collagen-coupled antibody effectively improves the seeding of transgenic EPCs, offering a new choice of stents to prevent restenosis caused by vascular disease after interventional treatment.

Inhibition of endothelin ETB receptor system aggravates neointimal hyperplasia after balloon injury of rat carotid artery

Endothelin-1 (ET)/ET(A) receptor system has been known to play an important role in the pathogenesis of neointimal hyperplasia after endothelial injury. However, the pathological role of endothelin ET(B) receptors on neointimal hyperplasia remains to be elucidated. In the present study, we investigated the pathological role of ET(B) receptors on neointimal hyperplasia in balloon-injured rat carotid arteries by pharmacological blockade with use of 2R-(4-propoxyphenyl)-4S-(1,3-benzodioxol-5-yl)-1-(N-(2,6-diethylphenyl)aminocarbonyl-methyl)-pyrrolidine-3R-carboxylic acid (A-192621), a selective ET(B) receptor antagonist, 2R-(4-methoxyphenyl)-4S-(1,3-benzodioxol-5-yl)-1-(N,N-di(n-butyl)aminocarbonyl-methyl)-pyrrolidine-3R-carboxylic acid (ABT-627), a selective ET(A) receptor antagonist, and (+)-(5S,6R,7R)-2-butyl-7-[2-((2S)-2-carboxypropyl)-4-methoxyphenyl]-5-(3,4-methylenedioxyphenyl)cyclopenteno[1,2-b]pyridine-6-carboxylic acid (J-104132), an ET(A)/ET(B) dual receptor antagonist. Moreover, the spotting-lethal rats, which carry a naturally occurring deletion in the endothelin ET(B) receptor gene, were used to examine the effects of genetic deficiency for this receptor subtype. Two weeks after balloon injury, the ratio of the neointimal to the medial area (neointima/media ratio) was determined. Treatment with A-192621 (30 mg/kg/day) for 2 weeks after injury significantly increased the neointima/media ratio in the injured artery. In contrast, ABT-627 (10 mg/kg/day) and J-104132 (10 mg/kg/day) markedly decreased the neointima/media ratio to the same extent. Furthermore, the neointima/media ratio in the injured artery of the ET(B)-deficient rat was significantly increased compared with that of the wild-type rat, and this increase was abolished by treatment with J-104132. These findings suggest that the inhibition of the ET(B) receptor system leads to an aggravation of neointimal hyperplasia after balloon injury, and the augmentation of ET(A)-mediated actions are responsible for the neointimal hyperplasia aggravated by the pharmacological blockade of ET(B) receptor or by its genetic deficiency. The antagonism of the ET(A) receptor system is essential for preventing restenosis after angioplasty.

Avoiding restenosis: is there a role for glucocorticoids in the drug-eluting stent era?

Restenosis is an important limitation of percutaneous coronary interventions (PCI). In-stent restenosis is mainly due to neointimal hyperplasia, a proliferative process modulated by inflammatory mechanisms. Numerous technical and pharmacological means have been tested to reduce restenosis rates, with frequently disappointing clinical results. Drug-eluting stents (DES) have demonstrated a high efficacy in reducing restenosis, but there are some associated problems that limit its generalized utilization. Glucocorticoids (GC), as potent anti-inflammatory agents, may exert beneficial effects on neointimal proliferation. Clinical studies with oral and intracoronary GC therapy have demonstrated reduction in restenosis rates in selected patients. Although further investigations are warranted, GC might have a potential role for restenosis prevention in selected cases.

The pathophysiology and burden of restenosis

The introduction of percutaneous transluminal coronary angioplasty (PTCA) revolutionized the surgical treatment of coronary artery disease. However, despite increased surgical experience and technical breakthroughs, restenosis occurs in 30%-50% of patients undergoing simple balloon angioplasty and in 10%-30% of patients who receive an intravascular stent. Animal and human data indicate that restenosis is a response to injury incurred during PTCA. The need for reintervention in a high percentage of patients due to restenosis remains an important limitation to the long-term success of PTCA. Stenting reduces initial elastic recoil and limits negative arterial remodeling; however, bare-metal stents may promote intimal hyperplasia by eliciting an immune and proliferative response. Consistent with these data, clinical studies suggest that drug-eluting stents, coated with anti-inflammatory or antiproliferative agents, reduce the risk for restenosis. Stenting represents a considerable cost burden. Treatment strategy should focus on selective use of expensive drug-eluting stents in populations where they have been found to be more clinically effective than bare-metal stents--patients who are at high risk for restenosis or who develop restenosis with bare-metal stents. Recent studies suggest that the pharmacologic management of restenosis is now feasible. Together, the judicious use of stents and oral pharmacotherapy promise to reduce the risk for restenosis, even among high-risk patients.