Chimeric 7E3 Fab (ReoPro) decreases detectable CD11b on neutrophils from patients undergoing coronary angioplasty

Current and Future Roles of Glycoprotein IIb-IIIa Inhibitors in Primary Angioplasty for ST-Segment Elevation Myocardial Infarction

Acute myocardial infarction still represents the major cause of mortality in high-income countries. Therefore, considerable efforts have been focused on the treatment of myocardial infarctions in the acute and long-term phase, with special attention being paid to reperfusion strategies and adjunctive antithrombotic therapies. In fact, despite the successful mechanical recanalization of the epicardial conduit, a substantial percentage of patients still experience poor myocardial reperfusion or acute/subacute in-stent thrombosis. Due the delayed onset of action of currently available oral antiplatelet therapies, glycoprotein (GP) IIb-IIIa inhibitors could be expected to improve clinical outcomes, especially when administrated in the early phase of the infarction, due to the larger platelet composition of fresh thrombi, the dynamic nature of early thrombi, and the larger amount of viable myocardium existing in the early, as compared to a delayed, phase. Considerable evidence has accumulated regarding the benefits from GP IIb-IIIa inhibitors on mortality, especially among high-risk patients and when administered as an upstream strategy. Therefore, based on currently available data, GP IIb-IIIa inhibitors can be considered when the drug can be administered within the first 3 h of symptom onset and among high-risk patients (e.g., those with advanced Killip class or an anterior myocardial infarction). Even though it is not universally accepted, in our opinion, this strategy should be implemented in a pre-hospital setting (in an ambulance) or as soon as possible when arriving at the hospital (at the Emergency Room or Coronary Care Unit, irrespective of whether they are in spoke or hub hospitals). A new, second-generation GP IIb-IIIa inhibitor (zalunfiban) appears to be highly suitable as a pre-hospital pharmacological facilitation strategy at the time of first medical contact due to its favourable features, including its simple subcutaneous administration, rapid onset of action (15 min), and limited time of action (with a half-life of ~1 h), which is likely to minimize the risk of bleeding. The ongoing CELEBRATE trial, including 2499 STEMI patients, may potentially provide compelling data to support the upstream treatment of STEMI patients undergoing mechanical reperfusion. In fact, although the current therapeutic target of increased rates of timely reperfusion has been achieved, the future goal in myocardial infarction treatment should be to achieve the most rapid reperfusion prior to primary percutaneous coronary intervention, thus further minimizing myocardial damage, or, in some cases, even preventing it completely, and improving survival.

Amniotic fluid CD11b levels in pregnancies complicated by preterm prelabor rupture of membranes

Objective: CD11b is an integrin molecule located on the surface of leukocytes. CD11b is involved in the processes of cell adhesion and migration. Expression of CD11b increases during inflammation. Therefore, this study was aimed at the evaluation of concentrations of CD11b in the amniotic fluid from pregnancies complicated by preterm prelabor rupture of the membranes (PPROM), with respect to the presence of microbial invasion of the amniotic cavity (MIAC), intra-amniotic inflammation (IAI), and microbial-associated IAI (the presence of both MIAC and IAI).Methods: Eighty women with singleton pregnancies complicated by PPROM were included. Amniotic fluid samples were obtained by transabdominal amniocentesis. Amniotic fluid CD11b concentrations were determined by enzyme-linked immunosorbent assay. MIAC was determined by a non-cultivation approach. IAI was defined by a bedside amniotic fluid interleukin-6 concentration ≥745 pg/mL.Result: Women with MIAC or microbial-associated IAI had higher CD11b concentrations in the amniotic fluid than women without these complications (with MIAC: median 0.31 ng/mL versus without MIAC: median 0.17 ng/mL, p = .001; with microbial associated-IAI: median 0.35 ng/mL versus without microbial-associated IAI: median 0.16 ng/mL; p =.02). The presence of IAI was not associated with elevated CD11b concentrations. A weak negative correlation was found between amniotic fluid CD11b concentrations and interleukin-6 concentrations (rho = 0.26; p = .02).Conclusions: MIAC and microbial-associated IAI are characterized by higher amniotic fluid CD11b concentrations in pregnancies complicated by PPROM.

Neutrophils disturb pulmonary microcirculation in sepsis-induced acute lung injury

The lung is highly vulnerable during sepsis, yet its functional deterioration accompanied by disturbances in the pulmonary microcirculation is poorly understood. This study aimed to investigate how the pulmonary microcirculation is distorted in sepsis-induced acute lung injury (ALI) and reveal the underlying cellular pathophysiologic mechanism.

Using a custom-made intravital lung microscopic imaging system in a murine model of sepsis-induced ALI, we achieved direct real-time visualisation of the pulmonary microcirculation and circulating cells in vivo. We derived the functional capillary ratio (FCR) as a quantitative parameter for assessing the fraction of functional microvasculature in the pulmonary microcirculation and dead space.

We identified that the FCR rapidly decreases in the early stage of sepsis-induced ALI. The intravital imaging revealed that this decrease resulted from the generation of dead space, which was induced by prolonged neutrophil entrapment within the capillaries. We further showed that the neutrophils had an extended sequestration time and an arrest-like dynamic behaviour, both of which triggered neutrophil aggregates inside the capillaries and arterioles. Finally, we found that Mac-1 (CD11b/CD18) was upregulated in the sequestered neutrophils and that a Mac-1 inhibitor restored the FCR and improved hypoxaemia.

Using the intravital lung imaging system, we observed that Mac-1-upregulated neutrophil aggregates led to the generation of dead space in the pulmonary microcirculation that was recovered by a Mac-1 inhibitor in sepsis-induced ALI.

Neutrophils induce dead space in the pulmonary microcirculation in sepsis-induced ALI, recovered by a Mac-1 inhibitorhttp://ow.ly/vUzO30nbUyU

A bumpy and winding but right path to domestic drug-eluting coronary stents

Restenosis and stent thrombosis remain major concerns after percutaneous coronary intervention for the treatment of coronary artery disease. The present review was undertaken in order to highlight the various coronary stents that have been investigated in our Heart Research Center, and how far we have come from the first heparin-coated stent first used in the late 1990s. Thereafter, from the abciximab-coated stent to the current gene-delivery stent and other newer agents, our group has applied a range of techniques in this field. However, in groups similar to ours, the restenosis rates of such stents are still high for second-generation drug-eluting stents (DESs). Moreover, our nation imports almost all of these types of stents from other countries. Thus, we need to develop domestic coronary stents. Research into newer DESs are warranted in Korea so as to achieve improved safety and efficacy outcomes.

Effect of high bolus dose tirofiban on the inflammatory response following percutaneous coronary intervention

BACKGROUND

Tirofiban at the bolus dose of 10 microg/kg does not suppress the inflammatory response following percutaneous coronary intervention (PCI). This may be due to less than optimal inhibition of platelet aggregation. High bolus dose tirofiban (25 microg/kg) allows better inhibition of platelet aggregation but its anti-inflammatory effect remains unknown.

HYPOTHESIS

High bolus dose tirofiban exhibits anti-inflammatory activity.

METHODS

A total of 100 patients referred for PCI were randomized to receive high bolus dose tirofiban followed by a 24-h infusion or a bolus and an infusion of saline. Patients with elevated troponin or with thrombus in the culprit lesion were excluded. Inflammatory markers were measured at baseline and at 24 h.

RESULTS

Levels of soluble CD40 ligand (sCD40L) were not affected by PCI while those of interleukin-6 (IL-6) and of high sensitivity C-reactive protein (hs-CRP) significantly increased. Despite inhibiting platelet's aggregation by > 90%, tirofiban did not suppress the rise of IL-6 and hs-CRP. Median (interquartile range) elevation of IL-6 was 0.6 pg/mL (-1.5-3.6) versus 0.4 pg/mL (-0.7-1.8) and that of hs-CRP was 2.1 mg/L (0.7-5.2) versus 2.4 mg/L (1-4.7) in the tirofiban and the control groups, respectively (p = ns). However, in patients with diabetes mellitus, tirofiban significantly suppressed the rise of hs-CRP by 65% (p = 0.01), but did not significantly affect the rise of IL-6.

CONCLUSION

In low-risk patients undergoing PCI, tirofiban did not attenuate the rise of inflammatory markers. However, the significant effect in diabetics suggests that tirofiban may have anti-inflammatory activity in higher risk patients.

Two-year clinical outcome after abciximab-coated stent implantation in patients with coronary artery disease

BACKGROUND

Despite abciximab-coated stents having an inhibitory effect on coronary artery restenosis, the medium-term clinical outcome is unknown.

METHODS AND RESULTS

This prospective, randomized study compared the effects of the abciximab-coated stent, which was implanted in 95 patients, with those of control bare metal stents (BMS) implanted in 93 patients for de novo coronary lesions. Stent implantation was performed without any complications associated with the procedure. The 6-month intravascular ultrasound analysis showed that the area of neointimal hyperplasia was significantly smaller in the abciximab-coated stent group compared with the control stent group (+2.0+/-1.6 mm(2) vs +3.4+/-1.7 mm(2), P=0.001). However, at 2-year clinical follow up, there were no statistically significant differences in the incidences of total major adverse cardiac events (16% vs 24%, P=0.19) and cardiac death (0% vs 1.1%, P=0.3), target vessel revascularization (16% vs 21%, P=0.4) or non-fatal myocardial infarction (0% vs 2.3%, P=0.16) in the abciximab-coated stent group compared with the control stent group.

CONCLUSIONS

Although abciximab-coated stents are safe and inhibit neointimal hyperplasia, they have no superiority over BMS in 2-year clinical outcome.

Developmental control of integrin expression regulates Th2 effector homing

Integrin CD18, a component of the LFA-1 complex that also includes CD11a, is essential for Th2, but not Th1, cell homing, but the explanation for this phenomenon remains obscure. In this study, we investigate the mechanism by which Th2 effector responses require the LFA-1 complex. CD11a-deficient T cells showed normal in vitro differentiation and function. However, Th2 cell-dependent allergic lung disease was markedly reduced in CD11a null mice and wild-type mice given LFA-1 inhibitors, whereas control of infection with Leishmania major, a Th1-dependent response, was enhanced. In both disease models, recruitment of IL-4-, but not IFN-gamma-secreting cells to relevant organs was impaired, as was adhesion of Th2 cells in vitro. These diverse findings were explained by the markedly reduced expression of CD29, an alternate homing integrin, on Th2, but not Th1, cells, which precludes Th2 homing in the absence of CD11a. Thus, murine Th1 and Th2 cells use distinct integrins for homing, suggesting novel opportunities for integrin-based therapeutic intervention in diverse human ailments influenced by Th2 cells.

Inhibition by soya isoflavones of human polymorphonuclear leukocyte function: possible relevance for the beneficial effects of soya intake

Lower CVD incidence is reported in Asian populations consuming soya-containing food. As polymorphonuclear leukocytes (PMN) are involved in the risk of CVD, we investigated the modulatory effect of soya isoflavones on several PMN functions and their molecular mechanisms in vitro. PMN, isolated from blood from healthy subjects, were tested upon activation with 1 microm- n-formyl-methyl-leucyl-phenylalanine (fMLP) for superoxide anion production (ferric cytochrome c reduction) and released elastase (chromogenic test). PMN homotypic aggregates stimulated by fMLP or P-selectin in dynamic conditions were detected by optical microscopy. PMN, mixed with thrombin-activated, washed platelets, formed cell aggregates, measured by flow cytometry. Phosphorylation of Pyk2, a focal adhesion kinase, was studied by immunoprecipitation and immunoblotting with specific antibodies. Genistein, daidzein and equol inhibited superoxide anion production (IC50 0.25 (sem 0.1), 21.0 (sem 4.2) and 13.0 (sem 2.8) microm, respectively); the release of elastase was prevented by genistein (IC50 63 (sem 17) microm). PMN homotypic aggregates, stimulated by fMLP, were significantly reduced (24 (sem 12) and 51 (sem 14) % of control) by 100 microm genistein and equol. P-selectin-induced aggregates were reduced to 19 (sem 6), 44 (sem 10) and 28 (sem 9) % of control by 100 microm genistein, daidzein and equol, respectively. Genistein, daidzein and equol also significantly reduced mixed platelet-PMN aggregates (IC50 4.0 (sem 0.9), 57 (sem 6) and 66 (sem 23) microm, respectively). In PMN challenged by fMLP or P-selectin, activation of Pyk2 was prevented by isoflavones. The cardioprotective effect of soya-containing food might be linked to reduction of PMN activation and PMN-platelet interaction, novel targets for the biological effects of soya isoflavones.

Impact of postprocedure minimum stent area on long-term results following abciximab-coated stent implantation: an intravascular ultrasound analysis

BACKGROUND

Smaller postprocedural minimum stent areas (MSA) measured by intravascular ultrasound (IVUS) have been associated with higher restenosis rates.

METHODS

This was a single-center, prospective, randomized trial and we assessed the predictive value of MSA for long-term patency and the incidence and extent of incomplete stent apposition (ISA) following abciximab-coated stent (n=69) compared to bare metal stent (BMS) implantation (n=69). All patients underwent IVUS follow-up at 6 months.

RESULTS

At follow-up coronary angiogram, the restenosis rate and late loss were 12%, 0.30+/-0.24 mm in abciximab-coated stent group and 29%, 0.68+/-0.36 mm in BMS group (p=0.011, 0.010, respectively). At follow-up IVUS, intrastent lumen area was significantly larger and intrastent neointimal hyperplasia area was significantly smaller in abciximab-coated stent group than those in BMS group (5.9+/-1.6 mm(2) vs. 4.5+/-1.7 mm(2), p=0.001, and 1.9+/-1.5 mm(2) vs. 3.3+/-1.9 mm(2), p<0.001, respectively). Target lesion revascularization occurred in 9%, 0%, and 0% in abciximab-coated stent group and 19%, 4%, and 1% in BMS group in lesions with a MSA <6.0 mm(2), from 6 to 7.5 mm(2), and >7.5 mm(2), respectively. Late-acquired ISA at follow-up was observed in 7 patients and there was no difference in the incidence of ISA between both groups [abciximab-coated stent: n=3 (4%) vs. BMS: n=4 (6%), p=0.698].

CONCLUSION

Abciximab-coated stent reduced restenosis and had a considerably lower optimal MSA threshold compared to BMS and showed lower incidence of late-acquired ISA.

Progress in clinical neurosciences: The 'antiplatelet' agents and the role of the endothelium

The antiplatelet drugs, commonly used in the prevention and treatment of cerebrovascular disease, possess a number of effects that are independent of direct antiplatelet actions. Beneficial and detrimental effects both occur. The endothelium is an important mediator of these non-antiplatelet effects. We performed a literature search to locate articles related to acetylsalicylic acid (aspirin), clopidogrel, ticlopidine, and dipyridamole and the interactions of these medications with the endothelium. The role of each of the above medications is explored in relation to vasodilation, inflammation, oxidation, platelet-leukocyte interactions, and thrombogenic tendency via platelet-vessel wall interactions.

Anti-inflammatory effect of abciximab-coated stent in a porcine coronary restenosis model

The aim of this study was to examine the anti-inflammatory effect of abciximab-coated stent in a porcine coronary overstretch restenosis model. Ten abciximab-coated stents, ten sirolimus-eluting stents (SES), and ten paclitaxel-eluting stents (PES) were deployed with oversizing (stent/artery ratio 1.3:1) in porcine coronary arteries, and histopathologic analysis was done at 28 days after stenting. There were no significant differences in the neointima area normalized to injury score and inflammation score among the three stent groups (1.58 +/- 0.43 mm(2), 1.57 +/-0.39 mm(2) in abciximab-coated stent group vs. 1.69 +/- 0.57 mm(2), 1.72 +/- 0.49 mm(2) in the SES group vs. 1.92 +/- 0.86 mm(2), 1.79 +/- 0.87 mm(2) in the PES group, respectively). In the neointima, most inflammatory cells were lymphohistiocytes. Significant positive correlations were found between the extent of inflammatory reaction and the neointima area (r=0.567, p<0.001) and percent area stenosis (r=0.587, p<0.001). Significant correlations were found between the injury score and neointimal area (r=0.645, p<0.001), between the injury score and the inflammation score (r=0.837, p<0.001), and between the inflammation score and neointimal area (r=0.536, p=0.001). There was no significant difference in the inflammatory cell counts normalized to injury score among the three stent groups (75.5 +/- 23.1/microL in abciximabcoated stent group vs. 78.8 +/- 33.2/microL in the SES group vs. 130.3 +/- 46.9/microL in the PES group). Abciximab-coated stent showed comparable inhibition of inflammatory cell infiltration and neointimal hyperplasia with other drug-eluting stents in a porcine coronary restenosis model.

Concentration-dependent effect of abciximab on platelets and neutrophils in a model of cardiopulmonary bypass

Abciximab is a GPIIb/IIIa antagonist used in percutaneous coronary interventions to avoid platelet activation, thrombosis and inflammation. We investigated whether abciximab influenced platelet activation and platelet interaction with neutrophils and polyvinyl chloride (PVC) in a cardiopulmonary bypass (CPB) model. Isolated platelets, preincubated with and without 0.1-20 μg/mL of abciximab, were resuspended with neutrophils in plasma and recirculated by a roller pump. Platelet, but not neutrophil adhesion to PVC was inhibited by abciximab. Only high doses of abciximab reduced platelet aggregation size, but simultaneously increased platelet-neutrophil aggregation. Abciximab had no effect on platelet CD62P expression or degranulation, but platelet activation on platelet-neutrophil aggregates increased with high doses. Only low doses inhibited neutrophil degranulation. The concentration-dependent effect of abciximab on platelet-neutrophil interaction reduces its usefulness and stresses the dependency on experimental design in the evaluation of abciximab. Our study does not support the use of abciximab alone in CPB. However, incorporation of surface-coating the biomaterial with abciximab may be an interesting option.

Rationale for intracoronary administration of abciximab

The present review aims to describe the pharmacological aspects as well as the available clinical data supporting the choice of intracoronary route of administration for abciximab, an antiplatelet drug used in patients with acute coronary syndromes undergoing percutaneous coronary interventions (PCI). Abciximab is a glycoprotein (GP) IIb/IIIa receptor antagonist which determines a potent inhibition of platelet aggregation and thrombus formation. These properties seem to prevent not only thrombus formation but also to promote (at higher drug concentration) lysis of fresh thrombus. Moreover, differently from the other GP IIb/IIIa inhibitors, abciximab also binds to the vitronectin receptor on endothelial, smooth muscle, and inflammatory cells and to an activated conformation of the aMb2 receptor on leukocytes. Such cross-reactivity raises the possibility that clinical benefits derived from its use may not be exclusively due to its anti-thrombotic effect, but may also be related to the suppression of inflammatory pathways involving platelets, white blood cells, and the vascular endothelium. On such basis, the local administration of abciximab at the site of coronary thrombosis may enhance, by increasing its local concentration, the binding to both platelet and endothelium receptors. The results of several angiographic studies assessing the effect of intracoronary abciximab administration support on clinical grounds its adoption in patients with fresh coronary thrombosis. Indeed, better post-angioplasty coronary flow, greater degree of myocardial salvage and a better left ventricular function recovery have been achieved as compared to the intravenous, systemic, administration of drug's bolus. Condensed Abstract Several studies have highlighted the benefits of abciximab, a potent antiplatelet agent, in patients with acute coronary syndromes undergoing percutaneous coronary interventions. Moreover, differently from the other glycoprotein IIb/IIIa receptor antagonists, abciximab also has non-IIb/IIIa-related properties raising the possibility that clinical benefits derived from its use may not be exclusively due to its anti-thrombotic effect, but may also be related to the suppression of inflammatory pathways. Several angiographic studies in patients with fresh coronary thrombosis and recent clinical studies in patients with acute coronary syndromes undergoing mechanical revascularization support the hypothesis that local administration of abciximab at the site of the culprit coronary artery may facilitate both the de-thrombotic and the non-GP IIb/IIIa-dependent properties of the drug. On such basis, the present review aims to describe the pharmacological aspects as well as the available clinical data supporting the choice of intracoronary route of administration for abciximab.

The Clinical Results of a Platelet Glycoprotein IIb/IIIa Receptor Blocker (Abciximab: ReoPro)-Coated Stent in Acute Myocardial Infarction

OBJECTIVES

This study is a prospective randomized trial investigating clinical outcomes of patients with acute myocardial infarction (AMI) treated with abciximab (ReoPro)-coated stents.

BACKGROUND

Recently we have demonstrated that abciximab-coated stents have inhibitory effects in the prevention of coronary restenosis.

METHODS

Ninety-six patients with AMI were randomly allocated into two groups; group I received abciximab-coated stents (n = 48, 57.1 +/- 12.0 years), and group II received bare metal control stents (n = 48, 58.4 +/- 11.6 years).

RESULTS

At baseline, clinical characteristics, percent diameter stenosis, and minimal luminal diameter were no different between the two groups. One patient in group II had reinfarction and target lesion reintervention during hospital stay. Follow-up coronary angiography was obtained in 77.1% (37 of 48) in group I and 75.0% (36 of 48) in group II. Percent diameter stenosis and late loss were significantly lower in group I than group II (18.9 +/- 5.54% vs. 37.9 +/- 6.25%, p = 0.008; and 0.39 +/- 0.29 mm vs. 0.88 +/- 0.45 mm; p = 0.008, respectively). At follow-up intravascular ultrasound, intrastent lumen area and intrastent neointimal hyperplasia (NIH) area were 5.4 +/- 1.8 mm2 and 2.2 +/- 1.5 mm2, respectively, in group I and 4.3 +/- 1.6 mm2 and 3.4 +/- 1.8 mm2, respectively, in group II (p = 0.045). And, in-stent restenosis rate was lower in group I than group II (p = 0.011 and p = 0.008, respectively). During 1-year follow-up, two patients in group II (4.1%) had AMI, whereas no patient in group I suffered AMI. Target lesion revascularization and total major adverse cardiac events rates were relatively lower in group I compared with those in group II (10.4% [5 of 48] vs. 20.8% [10 of 48], p = 0.261, and 10.4% vs. 25.0%, p = 0.107, respectively).

CONCLUSIONS

Abciximab-coated stent implantation was safe and effective without stent thrombosis in AMI patients.

Platelet–monocyte aggregates predict troponin rise after percutaneous coronary intervention and are inhibited by Abciximab

BACKGROUND

Platelet-monocyte aggregates and other markers of platelet activation were investigated before and after percutaneous coronary intervention (PCI) with abciximab therapy. The study sought to assess the relationship between the level of platelet-monocyte aggregation and increases in cardiac troponin I post coronary intervention.

METHODS

Blood samples were collected from 40 patients before PCI and 10 min after abciximab administration. These were tested for platelet activation markers by flow cytometry. Cardiac troponin I levels were assayed at baseline and at 24 h post PCI.

RESULTS

Compared to healthy controls, patients with coronary artery disease had elevated markers of platelet activation including platelet-monocyte aggregates, P-selectin and PAC-1 (a marker specific for activated glycoprotein IIb/IIIa) prior to PCI. Increased levels of platelet-monocyte aggregates before PCI were associated with increased expression of P-selectin on the platelet surface. Abciximab therapy reduced platelet-monocyte aggregate levels but had no effect on P-selectin expression. The high levels of expression of activated glycoprotein IIb/IIIa (PAC-1) on platelets prior to PCI was reduced with abciximab therapy. Patients with higher levels of platelet-monocyte aggregates prior to PCI were more likely to develop an elevation of cardiac troponin I during the 24 h after PCI.

CONCLUSIONS

Increased levels of platelet-monocyte aggregates may predict patients at risk for troponin elevation following PCI and identify those most likely to benefit from abciximab.

Platelet and leukocyte adhesion and activation in unstable angina and post-PTCA

BACKGROUND

Unstable atherosclerotic plaques activate blood cells which may adhere to the coronary endothelium causing vessel occlusion. However, it is unknown if different clinical syndromes associated with plaque rupture induce similar blood cell activation and adhesion to the endothelium.

METHODS

We studied changes in adhesion molecule expression of platelets (GPIIb/IIIa), neutrophils--CD18, CD11b and L-selectin--and monocytes (CD14) after interaction with active lesions of patients with stable angina subjected to PTCA and patients with unstable angina (UA). Generation of superoxide (SO) radicals from PMNs and PMN sequestration in the coronary circulation were also assessed. Blood samples were collected from the aorta (Ao) and coronary sinus (CS) before and 15 min after PTCA (n=13) and within the first 48 h of UA (n=12).

RESULTS

PTCA induced a marked up-regulation of CD18, CD11b, CD14 and GPIIb/IIIa with L-selectin shedding and reduced SO formation, whereas only minor L-selectin down-regulation and decreased SO production indicated activation in UA. However, a significant decrease in neutrophil count in the CS compared to the Ao was only observed in UA.

CONCLUSIONS

The magnitude of cellular activation depends on the underlying clinical setting and just partially contributes to cell adhesion to the endothelium which might be modulated by different extent of vascular occlusion and shear forces.

Effects of tirofiban and statins on high-sensitivity C-reactive protein, interleukin-6, and soluble CD40 ligand following percutaneous coronary interventions in patients with stable coronary artery disease

This study assessed the effects of tirofiban and statins on high-sensitivity C-reactive protein, interleukin-6, and soluble CD40 ligand after percutaneous coronary intervention in patients who had stable coronary artery disease. Tirofiban insignificantly limited the increase of soluble CD40 ligand after revascularization, especially in patients who had high levels of this marker at baseline (p = 0.06), whereas statins significantly inhibited increases in interleukin-6 and, to a lesser extent, high-sensitivity C-reactive protein without affecting the soluble CD40 ligand.

Biomaterial-associated thrombosis: roles of coagulation factors, complement, platelets and leukocytes

Our failure to produce truly non-thrombogenic materials may reflect a failure to fully understand the mechanisms of biomaterial-associated thrombosis. The community has focused on minimizing coagulation or minimizing platelet adhesion and activation. We have infrequently considered the interactions between the two although we are generally familiar with these interactions. However, we have rarely considered in the context of biomaterial-associated thrombosis the other major players in blood: complement and leukocytes. Biomaterials are known agonists of complement and leukocyte activation, but this is frequently studied only in the context of inflammation. For us, thrombosis is a special case of inflammation. Here we summarize current perspectives on all four of these components in thrombosis and with biomaterials and cardiovascular devices. We also briefly highlight a few features of biomaterial-associated thrombosis that are not often considered in the biomaterials literature: The importance of tissue factor and the extrinsic coagulation system. Complement activation as a prelude to platelet activation and its role in thrombosis. The role of leukocytes in thrombin formation. The differing time scales of these contributions.

The long-term clinical results of a platelet glycoprotein IIb/IIIa receptor blocker (Abciximab: Reopro) coated stent in patients with coronary artery disease

BACKGROUND

Previously, the inhibition of coronary restenosis with Abciximab (ReoPro)-coated stent in a porcine model was reported. ReoPro inhibits platelet aggregation, the proliferation of vascular smooth muscle cells and the inflammatory reaction.

METHODS

A prospective randomized trial was performed to compare two types of stent for revascularization in the native coronary artery. The primary effective end points were major adverse coronary events (MACE): cardiac death, acute myocardial infarction, target vessel revascularization (TVR) and restenosis at the 6-month clinical and angiographic follow-ups.

RESULTS

One hundred and fifty-five patients were enrolled between August 2001 and June 2003. The mean ages (56.0 +/- 10.0 vs. 56.9 +/- 10.8 years), baseline diameter of stenosis and minimal luminal diameter were no different between the two groups. There was one myocardial infarction and revascularization during the hospital stay in control stent group. During the clinical follow-up there were two myocardial infarctions in control group. Follow-up coronary angiograms were performed in 62.3% (48/77) and 65.4% (51/78) of the coated and control groups, respectively. The diameter of stenosis and late loss were significantly less in the ReoPro-coated stent group compared with the controls (16.4 +/- 5.8% vs. 34.3 +/- 6.1%, p = 0.009; and 0.33 +/- 0.28 mm vs. 0.88 +/- 0.41 mm; p = 0.002). The restenosis and TVR rates of the ReoPro-coated stent were relatively lower compared with the control stent [14.6% (7/48) vs. 29.4% (15/51), p = 0.062; and 9.2% (7/76) vs. 14.7% (11/75); p = 0.327].

CONCLUSION

A ReoPro-coated stent is safe, and may be effective in the prevention of coronary restenosis.

Effect of abciximab-coated stent on in-stent intimal hyperplasia in human coronary arteries

The investigators tested whether abciximab-coated stents prevent neointimal hyperplasia (NIH) formation in coronary de novo lesions. Abciximab-coated stents were compared with control stents. All patients underwent follow-up coronary angiography and intravascular ultrasound (IVUS). All stents were successfully deployed, and patients were discharged home without clinical events. At follow-up coronary angiography, the restenosis rate and late loss were 14% and 0.33 +/- 0.28 mm in the abciximab-coated stent group and 28.6% and 0.64 +/- 0.32 mm in the control stent group (p = 0.099 and p = 0.014, respectively). At follow-up IVUS, the intrastent luminal area and intrastent NIH area were 5.7 +/- 1.6 and 2.0 +/- 1.6 mm(2), respectively, in the abciximab-coated stent group and 4.2 +/- 0.8 and 3.4 +/- 1.7 mm(2), respectively, in the control stent group (p = 0.001 and p = 0.001, respectively). Abciximab-coated stents are feasible and significantly inhibit NIH, with potential therapeutic benefit in preventing stent restenosis.

Rhodostomin, a disintegrin, inhibits adhesion of neutrophils to fibrinogen and attenuates superoxide production

Disintegrins are a group of Arg (or Lys)-Gly-Asp-containing snake venom proteins which inhibit platelet aggregation via the blockade of alpha(IIb)beta(3) integrin. Here, we studied the effect of rhodostomin, a disintegrin purified from the venom of Calloselasma rhodostoma, on the functions of neutrophils. By flow cytometric analysis of whole blood, we found that rhodostomin interacted with leukocytes of the myeloid and monocytic lineage as well as with platelets. The binding of rhodostomin to neutrophils could reach saturation in a dose-dependent manner, and its binding was increased in neutrophils stimulated with phorbol 12-myristate 13-acetate (PMA) and N-formyl-Met-Leu-Phe. EDTA did not inhibit the binding of rhodostomin. In addition, bound rhodostomin was not internalized. Soluble fibrinogen, a natural ligand of Mac-1 (CD11b/CD18, alpha(M)beta(2)), and the peptide, GRGDS, inhibited the binding of rhodostomin to PMA-activated neutrophils, while 7E3, a monoclonal antibody (mAb) raised against beta(3) integrin, or mAbs raised against alpha(M) and beta(2) integrin did not. Rhodostomin blocked the Mac-1-dependent adhesion of neutrophils to immobilized fibrinogen, in parallel with decreasing the production of superoxide from adherent neutrophils. Taken together, our results indicate that rhodostomin binds to activated neutrophils in an RGD-dependent manner, blocks the adhesion of activated neutrophils to fibrinogen and attenuates superoxide production, suggesting that rhodostomin may have anti-inflammatory properties.

Automated quantitation of peripheral blood neutrophil activation in patients with myocardial ischaemia

BACKGROUND

Coronary ischaemic syndromes are associated with neutrophil activation. The Bayer automated haematology analysers can detect increased light scatter of neutrophil populations, which correlates with neutrophil activation. We aimed to assess the role of an automated analyser in detecting systemic neutrophil activation in peripheral blood samples of patients with coronary ischaemia.

METHODS

A prospective cross-sectional study was undertaken in 18 patients with chronic stable angina, 9 with unstable angina and 26 normal control subjects. Whole blood samples were taken to assess neutrophil count and light scatter, and serum samples were taken from some patients for assessment of Troponin T, C-reactive protein (CRP) and myeloperoxidase (MPO). In addition, whole blood was stimulated in vitro with interleukin (IL)-8 and N-formyl-methionyl-leucyl-phenylalanine (fMLP) to assess changes in neutrophil light scatter detected by the analyser.

RESULTS

Neutrophil light scatter was increased in patients with chronic stable and unstable angina compared to normal control subjects (normal subjects 74.1 (73.3, 75.0) (mean arbitrary units (95% confidence intervals, (CI)) vs. 78.6 (76.9, 80.3) in the chronic stable angina group P<0.001 and 77.1 (75.3, 79.0) in the unstable angina group P<0.007). In vitro stimulation of whole blood produced comparable increases in neutrophil light scatter when morphological changes in neutrophils were demonstrable under electron microscopy.

CONCLUSIONS

Automated measurement of neutrophil activation by light scatter is possible using the Advia 120 analyser and is superior to a neutrophil count in discriminating groups with angina. This technique may be useful in monitoring disease activity and progression in coronary artery disease and in guiding the use of anti-inflammatory therapies.

Adjunctive Pharmacotherapy before Percutaneous Coronary Intervention in Non-ST-Elevation Acute Coronary Syndromes: The Role of Modulating Inflammation

Vascular inflammation is central to the pathogenesis of acute coronary syndromes (ACS) and the response to vascular injury after percutaneous coronary intervention (PCI). For both ACS and PCI, the magnitude of vascular inflammation is linked to adverse late clinical outcomes (e.g., death, recurrent myocardial infarction [MI] or ischemia, and restenosis). Many pharmacologic therapies with demonstrated efficacy for the treatment of ACS have anti-inflammatory properties, which are distinct from their perceived primary mechanism of action. The anti-inflammatory effects of aspirin, clopidogrel, low-molecular-weight heparin (LMWH), platelet glycoprotein (GP) IIb/IIIa receptor inhibitors, statins, and angiotensin converting enzyme (ACE) inhibitors are reviewed, and the hypothesis is generated that modulation of vascular inflammation at least in part contributes a common basis for the long-term clinical benefit ascribed to these medications. A therapeutic algorithm based on clinical risk stratification and coronary revascularization strategy is proposed for incorporating the current American College of Cardiology (ACC)/American Heart Association (AHA) guideline recommendations for treatment of patients who present with non-ST-elevation ACS.

Inflammation as a therapeutic target: a unique role for abciximab

Vascular inflammation is a central pathogenic mechanism for both acute coronary syndromes and the vascular response to injury after percutaneous coronary intervention. The magnitude of vascular inflammation has been correlated with adverse late clinical outcomes (death, myocardial infarction, recurrent ischemia, restenosis). Vascular inflammation is also increased in patients with diabetes mellitus. Many adjunctive pharmacotherapies used in the treatment of acute coronary syndromes or during percutaneous coronary intervention have anti-inflammatory effects, which are distinct from their perceived primary mechanism of action. Data in support of the anti-inflammatory effects of abciximab are presented and the role that these effects may play in modulating atherosclerotic plaque stability and late clinical outcomes is discussed. Vascular inflammation represents the "final common pathway" for many disease processes and thus represents the "ultimate therapeutic target" for pharmacologic intervention.

Abciximab: an updated review of its therapeutic use in patients with ischaemic heart disease undergoing percutaneous coronary revascularisation

Abciximab (Reopro) is an antibody fragment that dose-dependently inhibits platelet aggregation and leucocyte adhesion by binding to the glycoprotein (GP) IIb/IIIa, vitronectin and Mac-1 receptors. Abciximab (0.25 mg/kg bolus plus infusion of 0.125 micro g/kg/min for 12 hours) showed greater efficacy than tirofiban in reducing the 30-day composite endpoint of death, nonfatal myocardial infarction (MI) or urgent target-vessel revascularisation in the randomised, double-blind TARGET study in patients scheduled for stent placement. In addition, the beneficial effects of treatment with abciximab previously observed in the randomised, multicentre, placebo-controlled EPILOG and EPISTENT studies have been maintained to 1 year, with a significantly reduced incidence of ischaemic complications relative to placebo consistently observed across a range of subgroups including age, sex, bodyweight and indication for revascularisation. The incidence of the composite endpoint was reduced in patients presenting with acute MI of <48 hours' duration in comparison with either fibrinolytic therapy or stenting alone in the randomised STOPAMI and ADMIRAL trials, primarily because of a reduced requirement for urgent repeat revascularisation and reduced incidence of mortality. In the randomised, nonblind, multicentre CADILLAC trial in patients with acute myocardial infarction (MI), stenting alone was superior to percutaneous transluminal coronary angioplasty (PTCA) and stenting alone was not inferior to PTCA plus abciximab. Recent large randomised, multicentre studies (ASSENT-3 and GUSTO-V) have shown higher efficacy (on various ischaemic endpoints) of abciximab in combination with either a reduced dose of tenecteplase or reteplase compared with the fibrinolytic drug alone. TIMI grade 3 flow rates at 60 and 90 minutes in the TIMI-14 and SPEED trials were higher in patients who received abciximab in combination with either alteplase or reteplase than abciximab alone and were similar to that seen with the full-dose fibrinolytic alone. In the randomised, multicentre GUSTO IV-ACS study, no significant differences in any of the ischaemic endpoints at either 7 or 30 days in patients with acute coronary syndromes who were not scheduled to undergo early revascularisation (within 12 hours of end of infusion) were apparent between those who received abciximab (bolus and either 24- or 48-hour infusion) and those who received placebo in addition to aspirin and heparin. The most common adverse events associated with the use of abciximab are bleeding complications and thrombocytopenia, although the risk of major bleeding can be limited through adhering to current administration protocols. Treatment costs are generally higher in both stent plus abciximab and angioplasty plus abciximab groups than stent plus placebo, primarily because of the acquisition cost of abciximab. Abciximab appeared most cost beneficial in high-risk patients undergoing elective percutaneous coronary revascularisation; among lower risk patients, abciximab therapy has been associated with higher total in-hospital and 6-month medical costs than eptifibatide.

CONCLUSION

The GP IIb/IIIa receptor antagonist abciximab, when used with aspirin and heparin, has demonstrated efficacy in reducing the short- and long-term risk of ischaemic complications in patients with ischaemic heart disease undergoing percutaneous coronary intervention, when used with aspirin and heparin. High-risk patients (including those with diabetes mellitus) derive particular benefits from abciximab treatment. Abciximab remains an important therapeutic option for the prevention of complications in patients with ischaemic heart disease.

Glycoprotein IIb/IIIa inhibition attenuates platelet-activating factor-induced platelet activation by reducing protein kinase C activity

Glycoprotein (GP)IIb/IIIa inhibition may abolish activated leukocyte-induced platelet activation, in which leukocyte-released platelet-activating factor (PAF) is a major mediator. The present study thus investigated if and how GPIIb/IIIa inhibitors interfere with PAF-induced platelet activation. Platelet and leukocyte activation were monitored by flow cytometry and immunoblotting. GPIIb/IIIa inhibitors (c7E3, non-peptide SR121566, and MAb RFGP56) attenuated PAF-induced, but not adenosine diphosphate (ADP)- or thrombin receptor activating peptide (TRAP)-induced platelet P-selectin expression in whole blood. GPIIb/IIIa blockade enhanced ADP- or TRAP-induced leukocyte CD11b expression, but not the response to PAF. GPIIb/IIIa blockade attenuated PAF-induced, but enhanced ADP- or TRAP-induced platelet-leukocyte aggregation. Under the present experimental conditions, thromboxane A2 receptor antagonism did not significantly influence PAF-induced platelet activation, and GPIIb/IIIa inhibition did not interfere with calcium mobilization/influx in platelets. Protein kinase C (PKC) blockade inhibited PAF-induced platelet P-selectin expression, and PAF-induced PKC activity was reduced by GPIIb/IIIa inhibition. PAF (=1 micro m) did not induce MEK 1/2 or ERK 1/2 phosphorylation, whilst thrombin induced marked responses, which were enhanced by GPIIb/IIIa blockade. Thus, GPIIb/IIIa inhibition attenuates PAF-induced platelet activation via inhibiting PKC activity. GPIIb/IIIa blockade enhances thrombin-induced platelet MEK 1/2 and ERK 1/2 activation, and augments ADP- and TRAP-induced leukocyte activation by enhancing platelet-leukocyte aggregation.

The role of platelet receptors and adhesion molecules in coronary artery disease

Platelets play a significant role in coronary artery disease through interactions with each other and with other cell types. These interactions are mediated by certain receptors on the surface of platelets and other cells which can lead to intra-coronary thrombus formation and occlusion that may result in acute coronary syndromes. The important roles of the currently available anti-platelet therapies have been well established in many clinical outcome trials in cardiovascular patients. An understanding of these different interactions provides the clinician with a background that supports the clinical importance of currently available anti-platelet therapies. Moreover, knowledge of the mechanisms of cellular crosstalk will lead to important advances in the development of better antithrombotic therapies.

Material-induced tissue factor expression but not CD11b upregulation depends on the presence of platelets

Biomaterials activate leukocytes as well as platelets when exposed to blood. One feature of leukocyte activation at least at times beyond a few hours is tissue factor expression, contributing to a procoagulant state. We show here that platelet activation and specifically platelet-monocyte aggregate formation appears to be a precondition for tissue factor expression. Material-induced Tissue Factor (TF) expression by isolated leukocytes (6 x 10(6) cells/mL) resuspended in increasing concentrations of platelets in plasma was elevated when the platelet concentration was 50 x 10(6) platelets/mL or more; at lower platelet concentrations (1-25 x 10(6). cells/mL) the TF expression remained at background levels. On the other hand, significant CD11b upregulation was observed on leukocytes, in bulk and adherent to beads, at all platelet concentrations. This platelet effect on material-induced TF expression appeared to be mediated by the formation of platelet-monocyte aggregates. Anti-P-selectin, which blocked the association between platelets and leukocytes, reduced monocyte adhesion and material-induced TF expression for bulk monocytes. Anti-GPIIb/IIIa, a GPIIb/IIIa platelet antagonist, also reduced monocyte adhesion and material-induced TF expression in the bulk, most likely due to its inhibiting effect on the formation of platelet-monocyte aggregates, secondary to platelet activation. However, the antibody-associated reductions for bulk leukocytes (mainly neutrophils) were small and incomplete. Similar levels of TF expression, in the bulk, were observed with both polystyrene (PS), a strong platelet activator, and polyethylene glycol-modified PEG (PS-PEG), a mild platelet activator. The role of platelets in material-induced TF expression appears to be mediated in part via the formation of platelet-monocyte aggregates, although other mechanisms are likely also involved.

Nitric oxide, atherosclerosis and the clinical relevance of endothelial dysfunction

The endothelium plays a key role in vascular homeostasis through the release of a variety of autocrine and paracrine substances, the best characterized being nitric oxide. A healthy endothelium acts to prevent atherosclerosis development and its complications through a complex and favorable effect on vasomotion, platelet and leukocyte adhesion and plaque stabilization. The assessment of endothelial function in humans has generally involved the description of vasomotor responses, but more widely includes physiological, biochemical and genetic markers that characterize the interaction of the endothelium with platelets, leukocytes and the coagulation system. Stable markers of inflammation such as high sensitivity C-reactive protein are indirect and potentially useful measures of endothelial function for example. Attenuation of the effect of nitric oxide accounts for the majority of what is described as endothelial dysfunction. This occurs in response to atherosclerosis or its risk factors. Much remains to be learned about the molecular and genetic pathophysiological mechanisms of endothelial cell abnormalities. However, pharmacological intervention with a growing list of medications can favorably modify endothelial function, paralleling beneficial effects on cardiovascular morbidity and mortality. In addition, several small studies have provided tantalizing evidence that measures of endothelial health might provide prognostic information about an individual patient's risk of subsequent events. As such, the sum of this evidence makes the clinical assessment of endothelial function an attractive surrogate marker of atherosclerosis disease activity. The review will focus on the role of nitric oxide in atherosclerosis and the clinical relevance of these findings.

Oxidative stress and neutrophil activation—the two keystones of ischemia/reperfusion injury

The widespread introduction of fibrinolytics and recently also PTCA in the treatment of myocardial infarction has changed the picture of modern cardiology. But this therapy also raises new problems and challenges. One of them is the occurrence of extensive tissue injury caused by reperfusion. Reinstitution of oxygen to the ischemic tissues initiates various processes leading to generation of reactive oxygen species (ROSs). Acting on the plasma membrane ROS damage its organization and release various proinflammatory agents. Different proteins, including receptors, ionic channels, transporters or components of transduction pathways are substrates of oxidation by ROSs. Their changed structure results in altered functioning and disruption of vital cellular processes. Another key factor of reperfusion injury is activation and infiltration of infarcted area by polymorphonuclear leukocytes (PMNs). Multiple studies identified consecutive stages of PMN activation and substances being involved in it. Main interest lies in cellular adhesion molecules, particularly selectins and beta2 integrins, as their antagonists were repeatedly found to diminish neutrophil activation and infarct size. Nevertheless new publications strike at the foundations of the established order and confront the relation between neutrophil infiltration and infarct size. PMNs are linked by close ties to other cells involved in inflammatory response. Seemingly also in cardiac ischemia-reperfusion injury, the activity of neutrophils is modulated by lymphocytes and macrophages. The article describes mutual interactions between different factors involved in the reperfusion injury that may enable preparing new treatments, hopefully as effective and successful as reperfusion therapy.

Multi-year follow-up of abciximab therapy in three randomized, placebo-controlled trials of percutaneous coronary revascularization

There is considerable evidence supporting the use of platelet glycoprotein IIb/IIIa inhibitors to reduce ischemic complications of percutaneous coronary revascularization. However, long-term follow-up has been limited. In three large-scale randomized trials that tested abciximab at a uniform bolus dose and 12-hour infusion against placebo, in a double-blind fashion, a total of 5799 patients had their long-term follow-up vital status determined at a minimum of 7 years (EPIC), 4.5 years (EPILOG), or 3 years (EPISTENT) after randomization (median, 4.8 years). The prespecified primary endpoint was all-cause mortality by intention-to-treat analysis at 3 years in patients randomly assigned to a common intervention. Follow-up for 5603 of the 5799 patients was 96.6% complete at 3 years; 320 deaths had occurred by that time. After 3 years of follow-up, mortality was 6.4% in the placebo groups and 5.0% in the abciximab groups (hazard ratio [HR] = 0.78; 95% confidence interval [CI]: 0.63 to 0.98; P = 0.03). A similar reduction in mortality was observed on an intention-to-treat basis when all follow-up information was utilized after a median of 4.8 years of follow-up (n = 652 deaths): 12.6% in the placebo groups and 10.2% in the abciximab groups (HR = 0.82; 95% CI: 0.70 to 0.96; P = 0.01).Abciximab treatment reduced all-cause mortality by about 20% during long-term follow-up after percutaneous coronary intervention. The findings were similar in magnitude and consistent in direction for each of the three trials, and the absolute survival benefit appeared to increase over time. Brief intervention with this monoclonal antibody during percutaneous coronary revascularization is associated with significant improvement of long-term survival.

Abciximab attenuates coronary microvascular endothelial dysfunction after coronary stenting

BACKGROUND

Platelet glycoprotein IIb/IIIa receptor blockade with abciximab decreases ischemic events after percutaneous coronary intervention (PCI); however, the mechanism of this benefit has not been fully elucidated. The present study was designed to assess endothelium-dependent vasomotion after coronary stenting and to determine if abciximab alters this response.

METHODS AND RESULTS

The study group consisted of 48 patients (59+/-10 years of age) with discrete coronary stenoses who underwent stenting alone (n=28) or stenting plus abciximab (n=20). A control group consisted of 31 additional patients who had vasomotor testing on a non-PCI vessel. Coronary blood flow (CBF) was measured (0.014-inch Doppler wire) 30 minutes after uncomplicated PCI and in response to the intracoronary infusion of acetylcholine (Ach) (10(-7), 10(-6) mol/L Ach) and adenosine (24 microg). Ach-mediated increase in CBF was impaired after stent insertion when compared with the control group (41+/-52% versus 70+/-48%; P<0.05). The stenting plus abciximab group demonstrated a superior CBF response to Ach compared with the stenting alone group (83+/-93% versus 41+/-52%; P<0.05), with no difference between groups in the peak flow or percent change in flow to adenosine. By multivariate analysis, concomitant administration of abciximab was strongly predictive of the change in CBF to Ach (P<0.005).

CONCLUSIONS

Abciximab preserves the CBF response to Ach after coronary stenting. The preservation of microvascular endothelial function may help explain the beneficial clinical effect of this agent in patients undergoing PCI.

Suppression of cyclic coronary flow variation and reduction of restenosis with abciximab for morphologically high-risk lesions undergoing percutaneous coronary intervention

Cyclic coronary flow variation (CCFV), a phenomenon related to repetitive accumulation of platelet aggregates at sites with endothelial injury, was reported to predict the acute ischemic complication after percutaneous coronary intervention. Platelet activation also stimulates neointimal proliferation, which is essential in the late restenosis process. Abciximab, a nonspecific antagonist to the platelet membrane glycoprotein IIb/IIIa as well as other integrins, may eliminate CCFV. A randomized study was conducted to evaluate the effect of abciximab on CCFV and restenosis in morphologically high-risk lesions. Forty-six coronary arteries with objective ischemia on the corresponding vascular territories were successfully treated. The use of abciximab successfully suppressed the occurrence of CCFV (p < or = 0.001) after balloon dilatation. In the follow-up study 3 months later, the use of abciximab predicted a lower loss index and less clinical recurrence (p = 0.008 and 0.03, respectively). The occurrence of CCFV, however, did not affect the angiographic or clinical outcome. The reduction of restenosis and clinical recurrence by the use of abciximab may thus be related to its nonglycoprotein IIb/IIIa effects, in addition to platelet inhibition.

Glycoprotein IIb/IIIa antagonist, murine 7E3 F(ab') 2, and tissue plasminogen activator in focal ischemia: evaluation of efficacy and risk of hemorrhage with combination therapy

Tissue hypoperfusion during cerebral ischemia results from occlusion of large and small vessels. Combination treatment strategies using fibrinolytics to thrombolyse an embolic clot and antiplatelet agents to prevent reocclusion and the formation of new platelet thrombi in the microcirculation may offer advantages over single-agent therapy. The authors report on the effects of tissue plasminogen activator (rt-PA), a glycoprotein (GP) IIb/IIIa receptor antagonist, 7E3 F(ab') 2, or a combination of the two agents in a focal embolic model of cerebral ischemia in Wistar rats. Focal ischemia was produced by introducing an autologous thrombus into the right side middle cerebral artery. Forty-six male Wistar rats were randomly divided into 6 groups: control (n = 8), 7E3 F(ab') 2 (n = 9, 6 mg/kg), rt-PA (n = 9, 10 mg/kg), rt-PA (n = 6, 20 mg/kg), and 7E3 F(ab') 2 with either 10 mg/kg (n = 10) (low-dose combination) or 20 mg/kg (n = 6) (high-dose combination) rt-PA. Evaluation of neurobehavioral scores, cerebral angiography, bleeding time, and measurement of brain infarction volume were used to determine efficacy. All actively treated groups showed a significant reduction in the infarct volume. Animals treated with 7E3 F(ab') 2 showed reduced infarction volumes (24.0 +/- 5.1%) compared with controls (42.43 +/- 5.6%, P < 0.02). Treatment with rt-PA significantly reduced infarction volume (20.7 +/- 3.3, = 0.01) at 10 mg/kg and at 20 mg/kg (19.5 +/- 8.2%, P < 0.05). Compared with vehicle-treated animals, the low-dose combination (16.4 +/- 5.5, P < 0.003) and high-dose combination (23.7 +/- 6.2%, P < 0.05) showed significant reduction in infarction volume. Cerebral angiography revealed significantly better recanalization in the combination group (5/6 animals in the high dose and 4/6 in low dose) compared with animals treated with 7E3 F(ab') 2 (3/10) or rt-PA alone (2/6). Bleeding time significantly increased from 11.25 +/- 1.9 minutes in the control group to 17 +/- 3.1 minutes in the rt-PA group, 24.5 +/- 2.6 minutes in the 7E3 F(ab') 2 group, 25.7 +/- 3.1 minutes in the low-dose combination group, and 32.5 +/- 4.7 minutes in the high-dose combination group. The incidence of intercerebral hemorrhage was highest in the high-dose combination group (6 of 6 animals) and lowest in the single treatment with 7E3 F(ab') 2 alone (1 of 10 animals) ( P < 0.05). Our data show that murine 7E3 F(ab') 2 alone has therapeutic effects when used after cerebral ischemia. Although this study suggests that higher doses of thrombolytic combined with anti-GPIIb/IIIa therapy may increases the risk of intracranial hemorrhage, the data also support the notion that anti-GPIIb/IIIa agents can safely be combined with low doses of thrombolytic agent to produce significant attenuation of neuronal damage with no increase in the incidence of cerebral hemorrhage.

Double-blind, randomized trial of an anti-CD18 antibody in conjunction with recombinant tissue plasminogen activator for acute myocardial infarction: limitation of myocardial infarction following thrombolysis in acute myocardial infarction (LIMIT AMI) study

BACKGROUND

Inhibition of leukocyte adhesion can reduce myocardial infarct size in animals. This study was designed to define the safety and efficacy of a recombinant, humanized, monoclonal antibody to the CD18 subunit of the beta2 integrin adhesion receptors (rhuMAb CD18), in reducing infarct size in patients treated with a thrombolytic agent.

METHODS AND RESULTS

The Limitation of Myocardial Infarction following Thrombolysis in Acute Myocardial Infarction Study (LIMIT AMI) was a randomized, double-blind, placebo-controlled, multicenter study conducted in 60 centers in the United States and Canada. A total of 394 subjects who presented within 12 hours of symptom onset with ECG findings (ST-segment elevation) consistent with AMI were treated with recombinant tissue plasminogen activator and were also given an intravenous bolus of 0.5 or 2.0 mg/kg rhuMAb CD18 or placebo. Coronary angiography was performed at 90 minutes, 12-lead ECGs were obtained at baseline, 90, and 180 minutes, and resting sestamibi scans were performed at >/=120 hours. Adjunctive angioplasty and use of glycoprotein IIb/IIIa antiplatelet agents at the time of angiography were discretionary. There were no treatment effects on coronary blood flow, infarct size, or the rate of ECG ST-segment elevation resolution, despite the expected induction of peripheral leukocytosis. A slight trend toward an increase in bacterial infections was observed with rhuMAb CD18 (P=0.33).

CONCLUSIONS

RhuMAb CD18 was well tolerated but not effective in modifying cardiac end points.

The potential of monoclonal antibodies to reduce reperfusion injury in myocardial infarction

Reperfusion injury is mediated, in part, by the accumulation of platelets and leucocytes in the microvasculature after reflow. These components of the blood pool form aggregates that can obstruct flow in small vessels. In addition, mediators released from leucocytes and platelets further damage the reperfused myocardium. A strategy to limit reperfusion injury exploits the important role of membrane-bound adhesion molecules that attach platelets and leucocytes to themselves and to the vascular endothelium. Monoclonal antibodies against specific adhesion receptors effectively eliminate the function of the receptor. The most widely investigated receptors are P-selectin, present on platelets and the endothelium, CD11/CD18, present on leucocytes, and the fibrinogen receptor on platelets. Numerous animal studies have strongly supported the use of these monoclonal antibodies to block adhesion receptors as adjunctive reperfusion therapy. However, recent human trials have yielded disappointing results.

ReoPro rules: results from the 'Do Tirofiban and ReoPro Give Similar Efficacy Trial' (TARGET)

In the treatment of atherosclerotic disease, stenting in the presence of a glycoprotein (GP) IIb/IIIa antagonist is becoming an increasingly common procedure. The 'Do Tirofiban and ReoPro Give Similar Efficacy Trial' (TARGET) was designed to determine whether the cheaper tirofiban was as effective and safe as abciximab in the prevention of ischaemic events with stenting. Unexpectedly, abciximab was shown to be superior to tirofiban. Tirofiban is a selective GP IIb/IIIa antagonist whereas abciximab has additional anti-inflammatory actions, which may contribute to its superiority.

Comparison of two platelet glycoprotein IIb/IIIa inhibitors, tirofiban and abciximab, for the prevention of ischemic events with percutaneous coronary revascularization

BACKGROUND

In the setting of percutaneous coronary revascularization, agents in the class known as platelet glycoprotein IIb/IIIa inhibitors have significantly reduced the incidence of death or nonfatal myocardial infarction at 30 days. We assessed whether there are differences in safety or efficacy between two such inhibitors, tirofiban and abciximab.

METHODS

Using a double-blind, double-dummy design at 149 hospitals in 18 countries, we randomly assigned patients to receive either tirofiban or abciximab before undergoing percutaneous coronary revascularization with the intent to perform stenting. The primary end point was a composite of death, nonfatal myocardial infarction, or urgent target-vessel revascularization at 30 days. The trial was designed and statistically powered to demonstrate the noninferiority of tirofiban as compared with abciximab.

RESULTS

The primary end point occurred more frequently among the 2398 patients in the tirofiban group than among the 2411 patients in the abciximab group (7.6 percent vs. 6.0 percent; hazard ratio, 1.26; one-sided 95 percent confidence interval of 1.51, demonstrating lack of equivalence, and two-sided 95 percent confidence interval of 1.01 to 1.57, demonstrating the superiority of abciximab over tirofiban; P=0.038). The magnitude and the direction of the effect were similar for each component of the composite end point (hazard ratio for death, 1.21; hazard ratio for myocardial infarction, 1.27; and hazard ratio for urgent target-vessel revascularization, 1.26), and the difference in the incidence of myocardial infarction between the tirofiban group and the abciximab group was significant (6.9 percent and 5.4 percent, respectively; P=0.04). The relative benefit of abciximab was consistent regardless of age, sex, the presence or absence of diabetes, or the presence or absence of pretreatment with clopidogrel. There were no significant differences in the rates of major bleeding complications or transfusions, but tirofiban was associated with a lower rate of minor bleeding episodes and thrombocytopenia.

CONCLUSIONS

Although the trial was intended to assess the noninferiority of tirofiban as compared with abciximab, the findings demonstrated that tirofiban offered less protection from major ischemic events than did abciximab.

c7E3Fab reduces postischemic leukocyte-thrombocyte interaction mediated by fibrinogen. Implications for myocardial reperfusion injury

Reperfusion injury after coronary occlusion is in part mediated by leukocyte activation and adhesion. Platelets may interact with polymorphonuclear granulocytes (PMNs), causing aggravated reperfusion injury. We studied whether c7E3Fab, a chimeric Fab fragment blocking platelet glycoprotein (GP) IIb/IIIa, decreases PMN-platelet-dependent myocardial dysfunction after ischemia. Isolated guinea pig hearts (n=5 per group) perfused at a constant flow of 5 mL/min were subjected to ischemia (15 minutes, 37 degrees C) and reperfusion. Human PMNs (10x10(6) cells, 3 mL), platelets (400x10(6), 3 mL), and fibrinogen (1 mg/mL) were infused for 3 minutes after 2 minutes of reperfusion, with or without c7E3Fab. Flow cytometry detected GPIIb/IIIa (platelets) and MAC-1 (aMbeta2, PMNs) as well as coaggregates of both in the effluent, whereas double-fluorescence microscopy visualized intracoronary PMN-platelet coaggregates. Postischemic recovery of pressure-volume work (12-cm H(2)O preload and 60-mm Hg afterload) was defined as the ratio of postischemic to preischemic external heart work (mean+/-SEM). c7E3Fab reduced platelet GPIIb/IIIa detection to 10% of controls, blocked a transcoronary MAC-1 increase (+25% without versus -23% with c7E3Fab), and inhibited PMN-platelet coaggregation in the effluent (49+/-12% without versus 17+/-2% with c7E3Fab) as well as in the hearts themselves (5.0+/-0.7/cm(2) without versus 1.2+/-0.3/cm(2) surface area with c7E3Fab). Postischemic recovery of external heart work (83+/-5% in cell-free hearts) declined to 46+/-4% after postischemic PMN-platelet infusion, but not in the presence of c7E3Fab (74+/-11%) or LPM19c (71+/-6%). We conclude that c7E3Fab inhibits formation of PMN-platelet aggregates during myocardial reperfusion, an effect that protects against PMN-platelet-dependent stunning.

Reperfusion injury after focal myocardial ischaemia: polymorphonuclear leukocyte activation and its clinical implications

The only way to rescue ischaemic tissue is to re-instate the oxygen supply to the tissue. However reperfusion of the ischaemic area not only oxygenates the tissue but also initiates a cascade of processes, which may in some cases result in temporary dysfunction of the myocardium. In order to devise protective measures, it is essential to understand the mechanisms and the triggers of this reperfusion phenomenon. In this review we will mainly focus on the inflammatory response caused by reperfusion. We will cover the different steps of polymorphonuclear leukocyte activation and will briefly discuss the molecular biology of the receptors involved. The currently used pharmacological medications in acute cardiology will be reviewed and in particular their actions on polymorphonuclear leukocyte activation, adhesion and degranulation. This review is a compilation of the current knowledge in the field and the therapeutic progress in the prevention of reperfusion injury made today.

The benefit of abciximab in percutaneous coronary revascularization is not device-specific

Abciximab has been shown to decrease adverse outcomes after percutaneous coronary interventions, but it is unclear whether this beneficial effect is more or less pronounced with specific devices. This study sought to determine the relative magnitude of the benefit of abciximab among different interventional devices. Data from the 5 placebo-controlled trials of abciximab during coronary intervention were pooled. Patients were divided into groups based on whether they received balloon angioplasty alone, elective stenting, bailout stenting, or directional coronary atherectomy. In the patients undergoing balloon angioplasty, the 30-day hazard ratio for death or myocardial infarction (MI) in the group randomized to abciximab versus the placebo-treated group was 0.52 (p <0.001), for elective stenting the hazard ratio was 0.51 (p <0.001), for bailout stenting the hazard ratio was 0.38 (p <0.001), and for directional coronary atherectomy the hazard ratio was 0.38 (p = 0.007). A Cox proportional-hazards model revealed that overall, the use of abciximab decreased the composite end point of 30-day death or MI rates (hazard ratio 0.55, 95% confidence interval 0.43 to 0.69, p <0. 001). However, bailout stenting and directional coronary atherectomy were associated with increased rates of death or MI compared with balloon angioplasty, as was elective stenting in women compared with men. There was no significant increase in major bleeding episodes associated with abciximab in any of the device categories. These findings from all the controlled coronary revascularization trials using abciximab demonstrate that a decrease in death and MI is achieved with abciximab regardless of the type of device used, without an increase in significant bleeding complications.

IIb's are not IIb's

Platelet glycoprotein (GP) IIb/IIIa receptor blockade improves clinical outcomes after percutaneous coronary intervention (PCI) and for patients who present with non-ST-segment elevation acute coronary syndromes. Although this class of therapeutic agents has been defined by a common affinity for the platelet GP IIb/IIIa receptor, the 3 currently available agents differ markedly in pharmacodynamic and pharmacokinetic profile as well as receptor affinity. Differential (separate) binding sites on the GP IIb/IIIa receptor explain the observation that abciximab binding to platelets is not influenced by either tirofiban or eptifibatide. Abciximab (ReoPro, chimeric 7E3 Fab) is a low K(d) (high affinity) agent with a very short plasma t(1/2) and a prolonged duration of action at the platelet target receptor. Eptifibatide and tirofiban are high K(d) (low affinity) agents with a relatively long plasma t(1/2) and short duration of action at the platelet target receptor. These pharmacodynamic differences underlie the phenomena of gradual redistribution in abciximab binding and smooth tapering of abciximab antiplatelet effect after discontinuation of therapy. Furthermore, abciximab demonstrates affinity for both the CD11b/18 (alpha(m)beta(2) or MAC 1) and alpha(V)beta(3) (vitronectin) receptors. Although a survival advantage in favor of abciximab has been observed after PCI in both randomized controlled trials and high-volume clinical practice, no survival benefit has been observed to date after eptifibatide or tirofiban therapy for PCI. The mechanism of survival advantage after abciximab therapy has not been defined but may be distinct from the degree of platelet GP IIb/IIIa receptor inhibition during the duration of intravenous treatment. Although this important new "class" of therapeutic agent was simplistically defined by a common affinity for the GP IIb/IIIa receptor, this solitary unifying attribute may not define agent-specific benefit.