Plasma mediated neutrophil stimulation during coronary angioplasty: autocrine effect of platelet activating factor

Transcardiac release of soluble adhesion molecules during coronary artery bypass grafting: effects of crystalloid and blood cardioplegia

BACKGROUND

Dysfunction of myocardium as a result of ischemia/reperfusion during coronary artery bypass grafting (CABG) is currently one of the biggest problems in cardiovascular surgery. In previous studies, it has been well established that activated leukocytes and coronary vascular endothelial cells play an important role in the development of cardiac tissue damage during ischemia followed by reperfusion. Interactions between both of these cell types require the expression of adhesion molecules on their surface. In certain conditions, on cell activation, the adhesion proteins may be released from activated cells in soluble form into circulation. The purpose of our study was to establish whether the use of blood cardioplegia modifies plasma levels of soluble intracellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble E-selectin (sE-selectin), and soluble L-selectin (sL-selectin) in comparison with crystalloid cardioplegia in patients undergoing CABG.

METHODS

Patients undergoing CABG were classified into two groups to receive cold crystalloid cardioplegia (St. Thomas' Hospital) or cold blood cardioplegia (method of Buckberg), followed by a "warm-shot" of the solution. Coronary sinus and arterial blood samples were obtained from 50 patients (42 men and 8 women; age range, 34 to 73 years) before aortic cross-clamping, at the beginning of reperfusion, and after 30 min of reperfusion. Plasma levels of soluble adhesion molecules were measured using sensitive enzyme-linked immunosorbent assays.

RESULTS

The transcardiac release of sICAM-1 and sVCAM-1 following myocardial ischemia/reperfusion during CABG was evident in both groups of patients. However, the increase of soluble forms of both of these adhesion proteins was more significant in the group of patients receiving crystalloid cardioplegia. Crystalloid cardioplegia resulted in decreased plasma level of sE-selectin in the coronary sinus blood sample after 30 min of reperfusion. No significant changes in plasma levels of sL-selectin in either group were observed.

CONCLUSION

Cardioplegia may affect the release of soluble forms of adhesion molecules from ischemic myocardium and modify endothelium activation in patients undergoing CABG.

[Endothelial adhesion molecules ICAM-1, VCAM-1 and E-selectin in patients with acute coronary syndrome]

INTRODUCTION AND OBJECTIVES

The acute inflammatory response is an important phenomenon in the pathogenesis of myocardial damage during acute coronary syndrome. Endothelial dysfunction has been found in unstable angina and acute myocardial infarction, although the results are controversial. The purpose of this study was to determine the levels of the soluble endothelial adhesion molecules ICAM-1, VCAM-1 and E-selectin, in patients with unstable angina and acute myocardial infarction, compare the results in both groups, and analyze their relation with the degree of myocardial injury.

METHODS

Serum concentrations of ICAM-1, VCAM-1, and E-selectin were measured in 37 control subjects and 43 patients (32 with acute myocardial infarction and 11 with unstable angina). Measurements were made at the time of admission and ten days later using commercial enzyme-linked immunoabsorbent assay (ELISA) kits (R&D Systems, UK).

RESULTS

There was a significant increase in E-selectin (p < 0.05) in patients with unstable angina at admission and ten days later. In contrast, patients with acute myocardial infarction showed no significant differences in E-selectin compared with the control group at admission or ten days later. A significant increase in VCAM-1 levels was demonstrated in both groups of patients and ICAM-1 levels in acute myocardial infarction, but the concentrations of VCAM-1 and ICAM-1 in both groups of patients at admission and ten days later did not differ significantly. There was no relation between soluble endothelial adhesion molecule levels and the severity of myocardial damage estimated by cardiac enzymes or electrocardiographic changes.

CONCLUSION

This study indicates that serum levels of E-selectin, measured at time of admission and ten days later, could be a marker for unstable angina and might be useful in the differential diagnosis with myocardial infarction.

Platelet and leukocyte deactivation after intracoronary stent placement in patients receiving combined antiplatelet therapy

Activated platelets and leukocytes have been demonstrated to play a role in the development of stent thrombosis, and coronary angioplasty has been shown to result in activation of platelets, leukocytes, and endothelial cells. We aimed to evaluate the effects of intracoronary stent placement and aspirin plus ticlopidine treatment on platelets, leukocytes, and endothelial cells via observing the serial changes in the circulating soluble forms of adhesion molecules in 54 patients with coronary artery disease, who had elective coronary angioplasty and stent implantation for a single lesion of the left anterior descending artery. After stent placement, intravenous heparin infusion was administered only for 24 hours, and aspirin plus ticlopidine treatment was applied for 1 month. Venous blood samples were drawn before stent placement, and repeated 24 and 48 hours after the procedure. Patients were excluded if they had had recent cardiovascular events or any illness that might influence platelet, leukocyte, and endothelial cell function. The plasma level of sL-selectin was significantly decreased 48 hours after coronary stenting (636+/-110 ng/mL vs 567+/-93 ng/mL; P = 0.001, respectively). Likewise, the plasma level of sP-selectin was also decreased significantly 48 hours after the procedure (260+/-61 ng/mL vs 233+/-83 ng/mL, P = 0.01). The sE-selectin level was found to be significantly increased 24 hours (31+/-9 ng/mL vs 39+/-12 ng/mL, P = 0.0001) and 48hours(31+/-9 ng/mL vs 42+/-15 ng/mL, P = 0.001) after coronary stenting. The results of our study suggest that significant platelet and leukocyte deactivation take place in patients treated with combined antiplatelet therapy after stenting; endothelial cell activation also occurs during this treatment.

Role of platelet-activating factor in cardiovascular pathophysiology

Platelet-activating factor (PAF) is a phospholipid mediator that belongs to a family of biologically active, structurally related alkyl phosphoglycerides. PAF acts via a specific receptor that is coupled with a G protein, which activates a phosphatidylinositol-specific phospholipase C. In this review we focus on the aspects that are more relevant for the cell biology of the cardiovascular system. The in vitro studies provided evidence for a role of PAF both as intercellular and intracellular messenger involved in cell-to-cell communication. In the cardiovascular system, PAF may have a role in embryogenesis because it stimulates endothelial cell migration and angiogenesis and may affect cardiac function because it exhibits mechanical and electrophysiological actions on cardiomyocytes. Moreover, PAF may contribute to modulation of blood pressure mainly by affecting the renal vascular circulation. In pathological conditions, PAF has been involved in the hypotension and cardiac dysfunctions occurring in various cardiovascular stress situations such as cardiac anaphylaxis and hemorrhagic, traumatic, and septic shock syndromes. In addition, experimental studies indicate that PAF has a critical role in the development of myocardial ischemia-reperfusion injury. Indeed, PAF cooperates in the recruitment of leukocytes in inflamed tissue by promoting adhesion to the endothelium and extravascular transmigration of leukocytes. The finding that human heart can produce PAF, expresses PAF receptor, and is sensitive to the negative inotropic action of PAF suggests that this mediator may have a role also in human cardiovascular pathophysiology.

Stimulation of neutrophil integrin expression during coronary artery bypass grafting: comparison of crystalloid and blood cardioplegic solutions

OBJECTIVES

This study was designed (1) to evaluate the influence of plasma obtained from patients undergoing coronary artery bypass grafting on L-selectin, CD11b, and CD18 expression on human neutrophils and (2) to determine the influence of the use of crystalloid or blood cardioplegia during bypass grafting on plasma-mediated expression of adhesion molecules on polymorphonuclear neutrophils.

PATIENTS AND METHODS

Patients undergoing coronary artery bypass grafting were divided into 2 groups to receive crystalloid or blood cardioplegic solutions. Peripheral vein, radial artery, and coronary sinus blood samples were drawn at aortic crossclamping, aortic crossclamp release, and 30 minutes after reperfusion. Human neutrophils were incubated with patients' plasma, and the expression of CD11b, CD18, and L-selectin was determined with flow cytometry.

RESULTS

In patients receiving crystalloid cardioplegic solutions, plasma samples collected from the coronary sinus at aortic clamp release and 30 minutes thereafter induced significantly higher expression of neutrophil CD11b and CD18 than plasma samples obtained from a peripheral vein or artery at the same time points. The expression of L-selectin on polymorphonuclear neutrophils was significantly reduced with plasma obtained 30 minutes after reperfusion as compared with samples collected at aortic crossclamp release. In the group receiving blood cardioplegia, no significant differences in CD11b, CD18, or L-selectin expression were found.

CONCLUSIONS

(1) Ischemia/reperfusion after coronary artery bypass grafting is associated with the release of factors capable of neutrophil activation from myocardium into the circulating blood. (2) The release of soluble stimuli for neutrophils during bypass grafting may be modified by the cardioplegic solution.

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.

Soluble L-selectin and neutrophil derived oxidative stress after pacing induced myocardial ischemia in chronic stable coronary artery disease

We studied the effect of atrial pacing induced myocardial ischemia on levels of soluble L-selectin (sL-selectin) and generation of neutrophil derived reactive oxygen species (ROS) in 10 patients with coronary artery disease (CAD) and stable angina and in six individuals without CAD. Myocardial ischemia was measured metabolically by lactate sampling from the coronary sinus (CS) and arterial blood at each pacing step. Before each pacing step, at peak pacing and shortly after cessation, plasma concentrations of sL-selectin and generation of ROS using the chemiluminescence method were measured in CS and femoral artery blood. Baseline sL-selectin levels in CS samples were significantly lower in the CAD compared to the control group (547 +/- 80 vs 836 +/- 82 ng/mL, P = 0.03). At peak pacing, nine of ten patients with CAD developed myocardial ischemia (lactate extraction ratio at rest 28% +/- 7%, at peak pacing -16% +/- 6%). In these patients, luminol-enhanced chemiluminescence (CL, 0.88 +/- 0.45 vs 1.9 +/- 0.9 cpm x 10(5), P = 0.09) and levels of sL-selectin (547 +/- 80 vs 764 +/- 86 ng/mL, P = 0.03) from naive neutrophils increased significantly in CS blood suggesting a potent in vivo activation of neutrophils. In control patients, incremental pacing caused neither myocardial ischemia nor a significant change of chemiluminescence or of sL-selectin levels. In conclusion, myocardial ischemia induced by pacing tachycardia is able to activate neutrophils in patients with chronic stable coronary artery disease leading to increased generation of ROS and shedding of L-selectin into the coronary circulation.

Cardioprotective effects of the calcineurin inhibitor FK506 and the PAF receptor antagonist and free radical scavenger, EGb 761, in isolated ischemic/reperfused rat hearts

Effects of the calcineurin inhibitor FK506, the platelet-activating factor (PAF) antagonist, and free radical scavenger Ginkgo biloba extract, EGb 761, and their combination on reperfusion-induced ventricular fibrillation (VF), ventricular tachycardia (VT), and recovery of cardiac function were studied after 30 min of global ischemia followed by 2 h of reperfusion in isolated rat hearts. In the first series of studies, rats received a daily (oral) dose of 0, 1, 5, 10, 20, or 40 mg/kg/day FK506 for 10 days. FK506 dose-dependently reduced the incidence of reperfusion-induced total (irreversible plus reversible) VF from a value of 92% for untreated animals to 92% (NS), 83% (NS), 67% (NS), 33% (p<0.05), and 25% (p<0.05), for doses of 1-40 mg/kg/day, respectively, with effects on incidence of VT showing the same pattern. FK506, between 20 and 40 mg/kg/day, also resulted in significant recovery of postischemic cardiac function. In the second series of studies, rats were treated with EGb 761 alone or in combination with FK506. Whereas no significant reduction in arrhythmias or improvement in cardiac function resulted from a single intervention of EGb 761 at 25 mg/kg/day, combined treatment of rats with 25 mg/kg/day of EGb 761 and 1 or 5 mg/kg/day of FK506 resulted in a reduction in total and irreversible VF of 92% and 92% to 42% (p<0.05) and 33% (p<0.05), 25% (p<0.05) and 8% (p<0.05), respectively, versus untreated control animals, paralleled by similar effects on the incidence of VT and accompanied by significant improvements in postischemic cardiac function. Our results demonstrate a novel cardioprotective characteristic of FK506 and suggest that combination therapy by using FK506 plus EGb 761 synergistically improves postischemic cardiac function, while reducing the incidence of reperfusion-induced VF and VT, which may expand the clinical utility of FK506 and allow therapy with FK506 at lower doses than are currently useful.

Endothelin-1 is involved in plasma mediated stimulation of neutrophil adherence during coronary artery bypass grafting

OBJECTIVE

Myocardial ischaemia followed by reperfusion during coronary artery bypass grafting (CABG) is known to result in the activation of polymorphonuclear neutrophils (PMN). The activation of PMN during ischaemia/reperfusion may be a result of their direct contact with activated endothelial cells and/or an effect of stimuli released from ischaemic myocardium. Increased expression of adhesion molecules on the PMN surface, after activation, leads to coronary capillary plugging with a subsequent decrease in blood flow. The purpose of the study was to evaluate plasma-mediated stimulation of PMN adhesion during CABG and to verify if endothelin-1 (ET-1), known to be a potent stimulus for PMN, is involved in stimulation of neutrophils adhesion mediated by integrins.

METHODS

Coronary sinus, peripheral artery and peripheral venous plasma samples were taken from 11 patients undergoing coronary surgery before aortal cross-clamping, at the beginning of reperfusion and 30 min thereafter. PMN isolated from five healthy volunteers were incubated with the plasma (20 samples per patient) in the presence of saline or a specific ET-1 receptor blocker, and PMN adherence to a microtiter plate covered with a monoclonal antibody against CD 18 antigen (beta-subunit of the integrin family of adhesion molecules) was evaluated.

RESULTS

We have observed a significant increase in adhesion of PMN incubated in the presence of saline with the plasma taken from coronary sinus at the beginning of reperfusion (7.79+/-1.64% of adhering cells) as compared with plasma obtained before aortal cross-clamping from the same place (6.78+/-1.3%, P = 0.04) and from peripheral artery at the beginning of reperfusion (6.64+/-1.1%, P = 0.04, means +/- SEM). ET-1 receptor blocker, significantly decreased stimulation of PMN adhesion by coronary sinus plasma obtained at the beginning of reperfusion (6.7+/-1.51%, P = 0.02). Plasma levels of ET-1 (ELISA) in the samples taken from coronary sinus at the beginning of reperfusion, were higher than in samples obtained before myocardial ischaemia or 30 min after reperfusion.

CONCLUSIONS

We conclude, that soluble stimuli capable of stimulation of PMN adhesion are released following myocardial ischaemia during CABG and ET-1 may be involved in PMN stimulation.

The release of soluble adhesion molecules ICAM-1 and E-selectin after acute myocardial infarction and following coronary angioplasty

Endothelial cells express surface adhesion molecules for leukocytes in response to myocardial ischaemia. These molecules may be released into plasma by activated cells and be detectable in soluble form. Samples were collected from the peripheral vein of 14 consecutive patients with acute myocardial infarction (AMI) at the time of admission, 6 h, and 1 and 5 days post-admission. Additionally, samples were drawn from the coronary sinus ostium and peripheral artery of seven patients undergoing coronary angioplasty (PTCA) before and after the first balloon inflation. We measured the plasma levels of soluble intercellular adhesion molecule-1 (sICAM-1) and soluble E-selectin (sELAM-1). In patients with AMI plasma levels of sICAM-1 exceeded those observed in age and sex-matched healthy subjects, (mean+/-SEM; 220.6+/-18 ng/ml) at all the time intervals assessed (358.9+/-24.5; 330.9+/-24.4; 379.4+/-39.7 and 366.8+/-47.5 ng/ml, respectively, p<0.01). sELAM-1 levels, however, were normal on admission, increased at 6 h to 52.7+/-3.8 ng/ml, p<0.05, and at day 1 (56.0+/-4.6 ng/ml) before decreasing to normal levels on the fifth day. After brief myocardial ischaemia occurring during PTCA, an increased level of sICAM-1 was observed following balloon deflation in the coronary sinus (329.2+/-20 ng/ml; p<0.05) as compared to the subjects undergoing coronary angiography, but not in the peripheral artery. sELAM-1 levels remained unchanged during angioplasty. Thus, soluble adhesion molecules expressed by activated endothelial cells are released into peripheral blood during both AMI and brief myocardial ischaemia and measurement of such molecules may prove useful for monitoring vascular endothelium activation following myocardial ischaemia/necrosis.