Inhibition of plasma-dependent monocyte chemokinesis and cytokine-triggered endothelial activation for neutrophil transmigration by administration of clopidogrel in man

P2Y12 receptor blockers are anti-inflammatory drugs inhibiting both circulating monocytes and macrophages including THP-1 cells

P₂Y₁₂ blockade improves patient outcomes after myocardial infarction. As well as antithrombotic effects, anti-inflammatory effects may contribute to this beneficial clinical outcome. Here we aimed to identify potential anti-inflammatory effects of P₂Y₁₂ receptor blockers on monocytes and macrophages. Using flow cytometry, migration assays, flow chambers and RNA microarrays, we investigated the effects of adenosine diphosphate (ADP) and P₂Y₁₂ receptor blockers on blood monocytes, THP-1 monocytes and THP-1 monocytes after differentiation to macrophages. P₂Y₁₂ -expressing platelets can form aggregates with monocytes in circulating blood. Mediated by platelets, ADP results in activation of the integrin receptor Mac-1 on blood monocytes, as detected by the conformation-specific single-chain antibody MAN-1. Via the same association with platelets, THP-1 monocyte adhesion to the endothelial intercellular adhesion molecule 1 (ICAM-1) is induced by ADP. P₂Y₁₂ receptor blockers prevent these ADP effects on monocytes. Interestingly, in contrast to THP-1 monocytes, THP-1 monocytes, after differentiation to macrophages, directly expressed the P₂Y₁₂ receptor and consequently ADP was found to be a potent chemoattractant. Again, P₂Y₁₂ receptor blockers antagonised this effect. Accordingly, stimulation of THP-1 macrophages with ADP caused a substantial change in gene expression pattern and upregulation of several genes associated with inflammation and atherogenesis. These data establish novel anti-inflammatory effects of P₂Y₁₂ receptor blockers on monocytes and macrophages, which are expected to contribute to cardiovascular risk reduction.

Comparison of differential expression of P2Y₁₂ receptor in culprit coronary plaques in patients with acute myocardial infarction versus stable angina pectoris

P2Y₁₂ receptor antagonists may have pleiotropic benefits. Little is known, however, about the expression of P2Y₁₂ receptors in coronary atherosclerotic plaques. We investigated the expression of P2Y₁₂ receptor in coronary atherectomy tissues retrieved from patients with acute myocardial infarction (AMI) or stable angina pectoris (SAP). Tissue specimens were collected from 35 patients with AMI and 19 with SAP who underwent directional coronary atherectomy. Specimens were analyzed immunohistochemically using antibodies specific to P2Y₁₂ receptor and to markers of endothelial cells, macrophages, and smooth muscle cells. The 2 groups had similar baseline clinical characteristics. Plaque types were more likely to be cellular in the AMI group. The proportion of areas immunopositive for α-smooth muscle actin was smaller but those positive for CD31 and CD68 were larger in the AMI than in the SAP group. In addition, the relative area immunopositive for P2Y₁₂ receptor was significantly larger for AMI than SAP (1.1 ± 0.9% vs 0.5 ± 0.4%, respectively, p < 0.001). P2Y₁₂ receptor positivity coincided with areas positive for CD31 and α-smooth muscle actin. In conclusion, P2Y₁₂ receptor is present in coronary atherosclerotic plaques and is increased in culprit plaques of patients with AMI. P2Y₁₂ receptor may play a role in plaque destabilization.

Clopidogrel effectively suppresses endothelial microparticle generation induced by indoxyl sulfate via inhibition of the p38 mitogen-activated protein kinase pathway

BACKGROUND/AIMS

Endothelial microparticles (EMPs) are closely associated with vascular dysfunction. We investigated the effects of several drugs on EMP generation in human umbilical vein endothelial cells (HUVECs), and the involvement of the mitogen-activated protein kinase (MAPK) in EMP generation.

METHODS

CD31+CD42-EMP counts were measured by flow cytometry in supernatants of HUVECs incubated with indoxyl sulfate. The EMP responses to losartan, lovastatin, clopidogrel, and mesoglycan were examined. We then measured the effects of MAPK inhibitors on EMPs.

RESULTS

(1) Indoxyl sulfate induced EMP release in HUVECs in a dose-dependent fashion; (2) all drugs (10-50 μM) inhibited EMP generation induced by indoxyl sulfate, with clopidogrel being the most effective; (3) the p38 MAPK inhibitor suppressed EMP generation induced by indoxyl sulfate, and (4) clopidogrel significantly suppressed MAPK signaling activated by indoxyl sulfate, with the most potency on p38.

CONCLUSION

The p38 signaling involves EMP generation induced by indoxyl sulfate and is effectively suppressed by clopidogrel.

Beneficial effects of clopidogrel on glycemic indices and oxidative stress in patients with type 2 diabetes

Objective of present study is to evaluate the possible role of clopidogrel in improving glycemic indices and oxidative stress in patients with type 2 diabetes. This study was performed on 42 uncontrolled type 2 diabetic patients at the specialized center for Endocrinology and Diabetes, Al-Rasafa Directorate of Health, Baghdad. All of the patients were treated with (glibenclamide 5 mg at morning) and randomized into two groups: the first group includes 22 patients treated with clopidogrel tablets (75 mg/day) for 2 months; the second group includes 20 patients treated with a placebo formula (sodium bicarbonate 200 mg/day) for the same period. Treatment with clopidogrel produced significant improvement (P < 0.05) in fasting serum glucose (FSG), fasting serum insulin level, quantitative insulin sensitivity check index (QUICKI); and oxidative stress markers: serum malondialdehyde (MDA) and serum reduced glutathione (GSH) compared to their baseline levels. There was significant elevation (P < 0.05) in both FSG and fasting serum insulin and the MDA level with significant reduction (P < 0.05) in QUICKI of placebo group compared to their baseline levels. However, clopidogrel produced significant elevation (P < 0.05) in AST and ALT levels but placebo formula caused no significant alteration (P > 0.05) in the serum levels of these two enzymes. In conclusion the treatment with clopidogrel improved glycemic indices and reduced oxidative stress in patients with type 2 diabetes.

Role of the P2Y12 receptor in the modulation of murine dendritic cell function by ADP

The effects of ADP on the biology of dendritic cells have been studied much less than those of ATP or adenosine. In this study, we showed that adenosine-5'-O-(2-thiodiphosphate) (ADPβS) induced intracellular Ca(2+) transients in murine dendritic cells (DCs). This effect was abolished by AR-C69931MX, a dual P2Y(12) and P2Y(13) receptor antagonist. RT-PCR experiments revealed the expression of both P2Y(12) and P2Y(13) mRNA in DCs. The Ca(2+) response to ADPβS was maintained in P2Y(13)-deficient DCs, whereas it was abolished completely in P2Y(12)(-/-) DCs. ADPβS stimulated FITC-dextran and OVA capture in murine DCs through macropinocytosis, and this effect was abolished in P2Y(12)(-/-) DCs. ADPβS had a similar effect on FITC-dextran uptake by human monocyte-derived DCs. OVA loading in the presence of ADPβS increased the capacity of DCs to stimulate OVA-specific T cells, whereas ADPβS had no effect on the ability of DCs to stimulate allogeneic T cells. Moreover, after immunization against OVA, the serum level of anti-OVA IgG1 was significantly lower in P2Y(12)(-/-) mice than that in wild-type controls. In conclusion, we have shown that the P2Y(12) receptor is expressed in murine DCs and that its activation increased Ag endocytosis by DCs with subsequent enhancement of specific T cell activation.

Association between the efficacy of dual antiplatelet therapy and the development of in-stent neointimal hyperplasia in porcine coronary arteries

OBJECTIVE

We set out to compare the effectiveness of platelet aggregation therapy in association with the development of in-stent neointimal hyperplasia in porcine coronary arteries.

METHODS

Thirty-two pigs underwent coronary stenting with bare-metal stents under general anaesthesia. One hundred milligrams of aspirin and loading doses of either 300 mg clopidogrel (group C, n=13) or 2 x 500 mg ticlopidine (group T, n=19) were administered before intervention. During the follow-up, the animals received a daily dose of 100 mg aspirin and 75 mg clopidogrel or 2 x 250 mg ticlopidine, respectively. After 4 weeks, the histopathological and histomorphometric parameters of the explanted stented coronaries were assessed. Levels of circulating cytokines and platelet activation factors were measured. ADP-induced and collagen-induced aggregation was measured immediately before stenting and then every 3rd day. The aggregation profiles were calculated and correlated with the histological parameters.

RESULTS

The fibrin deposition scores and inflammation scores were higher in group T than in group C, with similar injury scores. Endothelialization was complete in both groups. A significantly lower neointimal area (1.08+/-0.36 vs. 1.58+/-0.5, group C vs. T, P=0.026) and percentage of area stenosis (29.8+/-12.1 vs. 44.3+/-16.3, group C vs. T, P=0.032) were observed in group C. The loading dose of clopidogrel significantly reduced the platelet activation parameters before the first angiography as compared with ticlopidone. Clopidogrel treatment resulted in a significantly better aggregation profile relative to ticlopidine (mean ADP-induced aggregation: 28.4+/-9.1 vs. 52.5+/-12.0%, P<0.001). Significant (P<0.05) positive linear correlations were observed between the ADP-induced aggregation profile and the neointimal area (r=0.584), percentage of area stenosis (r=0.666), inflammation (r=0.476) and fibrin deposition (r=0.496).

CONCLUSION

The effectiveness of dual antiplatelet therapy plays an important role in the inhibition of in-stent neointimal hyperplasia.

Clinical evidence for anti-inflammatory effects of antiplatelet therapy in patients with atherothrombotic disease

Recent advances in our understanding of cardiovascular disease have revealed that atherothrombotic events, such as myocardial infarction and ischemic stroke, are the end result of a complex inflammatory response to multifaceted vascular pathology. As well as initiating thrombus formation at the site of a ruptured atherosclerotic plaque, platelets play a key role in vascular inflammation, through release of their own pro-inflammatory mediators and interactions with other relevant cell types (endothelial cells, leukocytes, and smooth muscle cells). An increasing body of literature shows that inflammatory biomarkers can be used to predict atherothrombotic risk and that antiplatelet therapy may reduce the levels of these markers. Acetylsalicylic acid (ASA) has been attributed with reducing levels of the transcription factor nuclear factor kappaB (NF-kappaB), C-reactive protein, and soluble CD40 ligand, although the evidence relating to the latter two markers is conflicting. There is also substantial evidence that therapy with clopidogrel, a specific antagonist of the platelet P2Y12 ADP-receptor, also leads to reductions in serum levels of CD40 ligand, C-reactive protein, P-selectin, and platelet-leukocyte aggregate formation. Beneficial effects of clopidogrel on inflammatory markers have been demonstrated across the spectrum of atherothrombotic disease (acute coronary syndrome patients, patients undergoing percutaneous coronary intervention (PCI), acute ischemic stroke patients, and those with peripheral arterial disease). Oral glycoprotein (GP) IIb/IIIa receptor antagonists, at doses that achieve moderate levels of receptor blockade, may paradoxically be associated with platelet-mediated pro-inflammatory effects. A similar phenomenon has been observed with intravenous GP IIb/IIIa antagonists in vitro, but most often at low doses, and data from clinical studies suggest that these agents may actually attenuate release of inflammatory mediators when administered at doses producing more complete receptor blockade.

Clopidogrel increases expression of chemokines in peripheral blood mononuclear cells in patients with coronary artery disease: results of a double-blind placebo-controlled study

BACKGROUND

Chemokines and platelet activation are both important in atherogenesis. Platelet inhibitors are widely used in coronary artery disease (CAD), and we hypothesized that the platelet inhibitor clopidogrel could modify chemokines in CAD patients.

OBJECTIVES

We sought to investigate the effect of clopidogrel on the expression of chemokines and chemokine receptors in peripheral blood mononuclear cells (PBMC) in CAD patients.

PATIENTS/METHODS

Thirty-seven patients with stable angina were randomized to clopidogrel (n = 18) or placebo (n = 19). PBMC, blood platelets and plasma were collected at baseline and after 7-10 days in the patients, and in 10 healthy controls. mRNA levels of chemokines and chemokine receptors in PBMC were analyzed by ribonuclease protection assays and real-time reverse transcriptase polymerase chain reaction. Platelet activation was studied by flow cytometry.

RESULTS

(i) At baseline, the gene expression of the regulated on activation normally T-cell expressed and secreted (RANTES) chemokines and macrophage inflammatory peptide (MIP)-1beta in PBMC, the expression of CD62P and CD63 on platelets and the levels of platelet-derived microparticles (PMP) were elevated in angina patients comparing healthy controls; (ii) markers of platelet activation were either reduced (CD63) or unchanged (CD62P, PMP, beta-thromboglobulin) during clopidogrel therapy; (iii) in contrast, clopidogrel significantly up-regulated the gene expression of RANTES and MIP-1beta in PBMC, while no changes were found in the placebo group; (iv) a stable adenosine 5'-diphosphate metabolite attenuated the release of MIP-1beta, but not of RANTES, from activated PBMC in vitro.

CONCLUSIONS

Even if we do not argue against a beneficial role for clopidogrel in CAD, our findings may suggest potential inflammatory effects of clopidogrel in CAD.

Randomized comparison of the effects of ASA plus clopidogrel versus ASA alone on early platelet activation in acute coronary syndromes with elevated high-sensitivity C-reactive protein and soluble CD40 ligand levels

BACKGROUND

High-sensitivity C-reactive protein (hsCRP) and soluble cluster of differentiation 40 ligand (sCD40L) have been established as effective markers of inflammation in predicting the risk for adverse outcomes in patients with acute coronary syndromes (ACSs). Activated platelets secrete certain inflammatory mediators such as P-selectin and sCD40L, which play a role in the pathogenesis of ACSs. Although acetylsalicylic acid (ASA) has been found to be an effective treatment of ACSs, the addition of clopidogrel bisulfate has been found tofurther improve clinical outcomes as a result of additional antiplatelet and anti-inflammatory action. Few data exist concerning the effects of dual antiplatelet therapy on these markers in patients with ACSs.

OBJECTIVE

The aim of this study was to assess the effectiveness and clinical significance of clopidogrel administration in patients with ACSs without ST segment elevation treated with ASA.

METHODS

This randomized, single-blind, controlled trial was conducted at the First Department of Cardiology, Hippokration Hospital, Athens, Greece. Inpatients aged>or=21 years with ACSs without ST segment elevation were randomly assigned to 1 of 2 groups: ASA 325 mg/d for 1 week, followed by ASA (100 mg/d) plus clopidogrel (300-mg loading dose followed by 100 mg/d) for 36 weeks (ASA+Clop group) or ASA alone (325 mg/d for 1 week, followed by 75 mg/d for 36 weeks) (ASA group). Levels of serum sCD40L, hsCRP, and P-selectin were determined on admission and at 8 hours, 48 hours, and 6 days of treatment. By means of clinical follow-up, Kaplan-Meier free-of-major adverse cardiovascular events (MACES) plots were used to assess the prevalence of MACES, including cardiovascular-related death, in patients with and without high levels of hsCRP (>or=3 mg/L) and sCD40L (>or=5 microg/L) for 52 weeks.

RESULTS

A total of 86 patients were enrolled (71 men, 15 women; mean [SD] age, 68 [3] years; mean [SD] weight, 86 [18] kg; white race, 86 [100%]; 43 patients per group). Both groups had similar initial clinical characteristics and P-selectin levels. Baseline hsCRP and sCD40L levels were correlated with baseline P-selectin levels (hsCRP, r2=0.099

CONCLUSIONS

The results of this small study suggest that early activation of platelets, as measured using P-selectin levels, was effectively inhibited by the addition of clopidogrel to a regimen of ASA in the subgroup of patients with ACSs and intense activation of platelets (defined as high hsCRP and sCD40L levels). In patients without high hsCRP and sCD40L levels, the addition of clopidogrel did not have a significant effect on P-selectin levels.

Optimal Timing for the Initiation of Pre-Treatment With 300 mg Clopidogrel Before Percutaneous Coronary Intervention

OBJECTIVES

This study sought to determine the optimal timing of a 300-mg clopidogrel loading dose before percutaneous coronary intervention (PCI) in patients enrolled in the Clopidogrel for the Reduction of Events During Observation (CREDO) trial.

BACKGROUND

A loading dose of clopidogrel before a PCI has become relatively commonplace, although the data supporting this practice are limited and sometimes conflicting.

METHODS

Patients were randomized to receive either 300 mg clopidogrel or a matching placebo administered a minimum of 3 h and a maximum of 24 h before PCI. The primary 28-day combined end point was death, myocardial infarction, or urgent target vessel revascularization. Linear splines were used to summarize the effect of the time of pre-treatment as a continuous variable.

RESULTS

A total of 1,762 patients were evaluated. For patients randomized to placebo, there was no relationship between the duration of pre-treatment and the occurrence of the primary end point, whereas longer durations of pre-treatment in patients randomized to clopidogrel were associated with improved outcomes. The event rates diverged maximally at 24 h. The difference in outcomes between placebo and clopidogrel pre-treated patients was not significant until > or =15 h pre-treatment, with a 58.8% (p = 0.028) reduction in the primary end point in patients pre-treated with clopidogrel > or =15 h compared with placebo.

CONCLUSIONS

When a 300-mg loading dose of clopidogrel is used, little benefit is obtained compared with just 75 mg at the time of the PCI when the treatment duration is <12 h. In patients pre-treated for longer durations, the optimal duration seems to approach 24 h.

Clopidogrel induced suppression of bovine platelet activation in vitro and a preliminary study of its effect on the development of Mannheimia haemolytica induced pneumonia

We report here on the influence of the platelet antagonist clopidogrel (Plavix) on bovine platelet function. We first evaluated the capacity of clopidogrel to inhibit adenosine diphosphate (ADP)-stimulated platelet function in the bovine species, using an ex vivo approach with blood from treated animals. Platelets isolated from treated calves displayed rapid and consistent reduction in function (aggregation, thromboxane production) upon ADP, but not platelet activating factor (PAF), stimulation. We then examined the possibility that clopidogrel could influence Mannheimia haemolytica pneumonia pathobiology using an experimental challenge model. We were unable to detect significant differences between clopidogrel treated and untreated animals when challenged with intra-tracheal inoculation of M. haemolytica. There was a trend towards inhibition of platelet degranulation in the affected regions of lungs from clopidogrel treated calves, and pre-treated challenged animals had similar amounts of fibrin deposition and enhanced fibrous tissue formation in their lungs when compared with control counterparts.

The role of inflammation in atherothrombosis: implications for clinical practice

Inflammation plays a key role in atherothrombosis: in the development of plaques, plaque rupture and thrombus formation. Various biochemical substances have been shown to be involved in the inflammatory process, some with pro-inflammatory activity and others with anti-inflammatory activity. Increased expression of many inflammatory mediators (e.g. C-reactive protein, CD40 ligand, P-selectin and IL-6) has been shown to correlate with increased risk of atherothrombotic events. One possible strategy for primary and secondary prevention is likely to focus on minimizing the inflammatory response and tipping the balance in favour of anti-inflammatory mediators and, therefore, plaque stability.

Protective effects of clopidogrel on oxidant damage in a rat model of acute ischemia

Reperfusion injury is a consequence of inadequate energy supply and acidosis in ischemic tissues and a chain of events triggered by oxygen-derived free radicals released in response to exposure of oxygen. In this study, we aimed to assess the effects of clopidogrel, an antithrombotic agent, on experimental ischemia-reperfusion model in rats. The ischemia was performed by blockade of the circulation of right lower extremity at trochanter major level for 6 hours. Then, the extremity was reperfused for 4 hours. Another group of rats pretreated with clopidogrel (0.2 mg/kg/day) for 10 days prior to ischemia-reperfusion. After the reperfusion period, all rats were anesthetized with ketamine. Blood and tissue samples from the gastrocnemius muscle, liver and lungs were taken for the measurement of malondialdehyde (MDA), glutathione (GSH) levels and superoxide dismutase (SOD) activity. The results revealed that clopidogrel prevented the increase in MDA level and the decrease in GSH level and SOD activity caused by ischemia-reperfusion both in tissue samples and plasma. These findings suggest that clopidogrel is beneficial in prevention of ischemia-reperfusion injury probably via its effects on inflammatory cells, platelets, and endothelial cells.

Clopidogrel for the secondary prevention of stroke

Patients suffering a transient ischaemic attack (TIA) or ischaemic stroke (IS) have a high risk of recurrence. The inhibition of platelet function is effective in the reduction of secondary vascular events in patients with TIA or stroke. This is true for acetylsalicylic acid (ASA), clopidogrel, ticlopidine and the combination of ASA plus slow-release dipyridamole. This overview analyses the results of recent trials and presents ongoing or future trials with clopidogrel as well as the combination of clopidogrel plus ASA. Clopidogrel is superior to ASA in the prevention of vascular events in patients with IS, myocardial infarction (MI) or peripheral arterial disease (PAD). The difference is highest for high-risk patients such as diabetics, patients who underwent coronary bypass surgery and patients with a remote prior history of ischaemic events. A prediction model is presented which allows the identification of patients in whom clopidogrel is superior to ASA for the secondary prevention of stroke. The combination of clopidogrel and ASA is better than ASA alone in patients undergoing coronary stent implantations and patients with unstable angina or non-Q-wave MI. In high-risk patients with TIA or stroke, the addition of ASA to clopidogrel is not superior to ASA monotherapy but results in a higher rate of bleeding complications. The long-term combination therapy is currently investigated in several large trials in > 30,000 patients, with a large number of stroke patients.

Effects of ADP-receptor antagonism beyond traditional inhibition of platelet aggregation

Atherothrombosis, or thrombus formation, at the site of a disrupted atherosclerotic plaque is the common pathophysiology related to myocardial infarction, ischaemic stroke and peripheral arterial disease. A growing body of evidence demonstrates an important role for vascular inflammation in the pathophysiology of atherosclerosis/atherothrombosis and the importance of the platelet as a mediator of inflammation. Clopidogrel is an ADP receptor antagonist that is superior to acetylsalicylic acid (ASA) for the prevention of ischaemic stroke, myocardial infarction and vascular death in patients with symptomatic atherosclerosis. The use of clopidogrel as well as ASA provides sustained, incremental benefit in patients with coronary manifestations of atherothrombosis. Recent evidence indicates that clopidogrel reduces markers of vascular inflammation across the cerebrovascular, coronary and peripheral circulations. These effects are not observed after treatment with ASA alone. Further studies have revealed that clopidogrel may have potential anticoagulant effects and may inhibit arterial vasoconstriction. These broader effects may contribute to the protective benefits of clopidogrel and should be considered when evaluating antiplatelet agents and optimising antiplatelet regimens.

Acute coronary disease Athero-Inflammation: Therapeutic approach

Antithrombotic therapy is the cornerstone of the treatment of acute coronary syndromes, but there is now evidence which indicates that by blocking inflammation, thrombosis and thus, acute coronary events, could be lowered. The concept of athero-inflammation emerges as the meeting point of different morbidities; dyslipemia, diabetes, hypertension, obesity, immunity, infection, hyperhomocyteinemia, smoking, etc. usual named as risk factors. Thus, beside specific drugs, earliest treatment, in the stage of inflammation, using anti-inflammatory drugs, should be considered since in patients with increased risk of acute coronary process are likely to have many point of origen throughout the coronary arteries. There are a body of evidences for supporting the potential of anti-inflammatory therapy to the prevention of inflammation and atherosclerosis. COX-2 inhibition may decrease endothelial inflammation reducing monocytes infiltration improving vascular cells function, plaque stability and probably resulting in a decrease of coronary atherothrombotic events.Trials including large numbers of patients in prospective double-blind randomized studies worthwhile to confirm the efficacy of NSAID, mainly, COX-2 inhibitors, together with aspirin in the prevention of coronary events in patients with acute coronary disease.