Phagocyte activation in coronary artery disease

The influence of tobacco smoking on adhesion molecule profiles

Sequential interactions between several adhesion molecules and their ligands regulate lymphocyte circulation and leukocyte recruitment to inflammatory foci. Adhesion molecules are, therefore, central and critical components of the immune and inflammatory system. We review the evidence that tobacco smoking dysregulates specific components of the adhesion cascade, which may be a common factor in several smoking-induced diseases. Smoking causes inappropriate leukocyte activation, leukocyte-endothelial adhesion, and neutrophil entrapment in the microvasculature, which may help initiate local tissue destruction. Appropriate inflammatory reactions may thus be compromised. In addition to smoke-induced alterations to membrane bound endothelial and leukocyte adhesion molecule expression, which may help explain the above phenomena, smoking has a profound influence on circulating adhesion molecule profiles, most notably sICAM-1 and specific sCD44 variants. Elevated concentrations of soluble adhesion molecules may simply reflect ongoing inflammatory processes. However, increasing evidence suggests that specific soluble adhesion molecules are immunomodulatory, and that alterations to soluble adhesion molecule profiles may represent a significant risk factor for several diverse diseases. This evidence is discussed herein.

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.

Inhibition of leukocyte 5-lipoxygenase by phenolics from virgin olive oil

Interest in the health-promoting effects of virgin olive oil, an important part of the 'Mediterranean diet', prompted us to determine the anti-eicosanoid and antioxidant effects in leukocytes of the principal phenolic compounds from the 'polar fraction': oleuropein, tyrosol, hydroxytyrosol, and caffeic acid. In intact rat peritoneal leukocytes stimulated with calcium ionophore, all four phenolics inhibited leukotriene B4 generation at the 5-lipoxygenase level with effectiveness hydroxytyrosol > oleuropein > caffeic acid > tyrosol (approximate EC50 values: 15, 80, 200, and 500 microM, respectively). In contrast, none of these compounds caused substantial inhibition of thromboxane generation via the cyclo-oxygenase pathway. Hydroxytyrosol, caffeic acid, oleuropein, and tyrosol (decreasing order of effectiveness) also quenched the chemiluminescence signal due to reactive oxygen species generated by phorbol myristate acetate-stimulated rat leukocytes. None of these compounds were toxic to leukocytes at the concentrations tested. We conclude that the phenolics found in virgin olive oil possess an array of potentially beneficial lipoxygenase-inhibitory, prostaglandin-sparing, and antioxidant properties.

Neutrophil adhesion and activation during systemic thrombolysis in acute myocardial infarction

In a pilot study, alterations of polymorphonuclear neutrophil function during systemic thrombolysis in acute myocardial infarction have been investigated in humans. The following parameters of neutrophil function were measured before and at 15 and 45 minutes after initiation of systemic thrombolysis with a recombinant tissue-type plasminogen activator in 20 patients with acute myocardial infarction: (1) neutrophil adhesion and (2) neutrophil activation. During systemic thrombolysis a significant decrease was observed in neutrophil adhesion (5.5+/-6.4 to 3.2+/-3.3; p<0.05), in phagocyting neutrophil activation (39+/-18 to 25+/-14%; p<0.05), and in resting neutrophil activation (9+/-7 to 3+/-4%; p<0.05). Successful reperfusion coincided with a significantly higher reduction of phagocyting neutrophil activation (40+/-14 to 20+/-12% vs. 39+/-24 to 26+/-19% in unsuccessful reperfusion; p<0.05), and of neutrophil adhesion (6.2+/-5.7 to 2.7+/-3.0 vs. 4.1+/-3.8 to 3.5+/-4.0 in unsuccessful reperfusion; p<0.05) during thrombolysis. Systemic thrombolysis in acute myocardial infarction is accompanied by a reduction in neutrophil adhesion and activation dependent on thrombolytic success.

Priming of neutrophils after elective percutaneous transluminal coronary angioplasty is unrelated to accompanying brief myocardial ischemia

OBJECTIVE

The purpose of this study was to investigate the effect of brief myocardial ischemia and vascular trauma induced by elective percutaneous transluminal coronary angioplasty on in vivo 'priming' and activation of neutrophils.

PATIENTS AND METHODS

We studied 16 patients undergoing elective coronary angioplasty for symptomatic coronary artery disease and a control group of seven patients undergoing diagnostic cardiac catheterization. Free radical production from purified neutrophils (Ficoll-Hypaque density gradient method) was measured indirectly by the chemiluminescence method. Myocardial ischemia during balloon inflation was assessed by serial lactate determinations from coronary sinus and arterial blood. The degree of transient angioplasty-related myocardial ischemia was related to the oxidative response of activated neutrophils.

RESULTS

Mean (+/-S.E.M.) oxidative response, i.e. the lucigenin- and luminol-enhanced-chemiluminescence (counts per minute) of neutrophils sampled from the coronary sinus increased significantly after percutaneous transluminal coronary angioplasty (Lucigenin-chemiluminescence: pre-angioplasty 3.69+/-0.64x10(5) vs. post-angioplasty 7.08+/-1.2x10(5), P<0.01; Luminol-chemiluminescence: pre-angioplasty 2.81+/-0.67x10(6) vs. post-angioplasty 5.2+/-0.92x10(6), P<0.01). Twelve of 16 patients developed transient cardiac lactate production (mean coronary sinus lactate excess: +0.12 mmol/l) and three disclosed a lactate extraction ratio <10%, both suggestive of myocardial ischemia. However, there was no correlation between the cardiac lactate production and the increased oxidative response after coronary angioplasty (r2 (Lucigenin-chemiluminescence)=0.02, n.s.; r2 (Luminol-chemiluminescence)=0.06, n.s.).

CONCLUSION

'Priming' of neutrophils, as reflected by increased oxidative response, is likely to occur after coronary angioplasty, but not after the angiographic procedure itself. However, 'priming' seems to be unrelated to the transient brief period of myocardial ischemia and rather depends on an alternative mechanism.

Complement activates neutrophils during PTCA procedure in patients with unstable angina pectoris

We estimated adherence, aggregation and chemiluminescence of neutrophils as well as concentrations of C3c, C4 and C5 complement components and complement haemolytic activity (CH50) in 27 patients with unstable angina pectoris subjected to percutaneous transluminal coronary angioplasty (PTCA). The control group consisted of 12 patients with unstable angina pectoris, in whom coronary angiography was performed but PTCA was decided against for various reasons. Blood samples for examination were taken from coronary sinus and peripheral vein just before, 1 min and 20 min after PTCA or coronary angiography. We observed enhancement of neutrophil adherence, aggregation and chemiluminescence, and decrease in concentrations of C3c, C5 and complement haemolytic activity (CH50) after PTCA procedure. In conclusion we think that ischemia resulting from PTCA causes complement activation in an alternative pathway which seems to be connected with neutrophil activation.

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

BACKGROUND

Polymorphonuclear neutrophils are involved in the development of myocardial injury during ischaemia and reperfusion. Coronary angioplasty has been shown to result in neutrophil activation. This may be a result of contact with ligands expressed by endothelial cells or response to soluble stimuli released from ischaemic tissue into the plasma or both.

OBJECTIVE

To investigate plasma mediated neutrophil activation during angioplasty.

METHODS AND RESULTS

Plasma samples were collected from the coronary sinus, femoral artery, and femoral vein of 14 patients undergoing angioplasty, before and after the first balloon inflation and at the end of the procedure. Plasma samples were incubated with washed neutrophils isolated from healthy donors. Expression of the adhesion molecules CD18 integrin and L-selectin (Leu-8) was measured by flow cytometry, and superoxide anion production was measured by chemiluminescence. Plasma samples from the coronary sinus and femoral artery but not from the peripheral vein induced increased expression of neutrophil CD18 after balloon deflation. Modification of the expression of L-selectin was not noted. Production of superoxide anion by neutrophils was stimulated by plasma samples from the coronary sinus, but not by those from the femoral artery or vein. This plasma mediated neutrophil stimulation was prevented when the neutrophils were pretreated with platelet activating factor receptor antagonists BN52021 or BN50739. The platelet activating factor concentration detected in the coronary sinus was not higher than in control plasma.

CONCLUSION

Brief ischaemia during coronary angioplasty leads to the release of soluble stimuli capable of inducing neutrophil integrin expression and free oxygen radical production. Platelet activating factor may act as an autocrine neutrophil stimulus under these conditions.

The effect of short-term myocardial ischemia on the expression of adhesion molecules and the oxidative burst of coronary sinus blood neutrophils

We examined the influence of transient myocardial ischemia on the number and function of neutrophils in patients with effort angina (EA). We tested fluorometrically the expression of neutrophil membrane molecules (CD11b, CD11c, CD18) and neutrophil oxidative burst using a chemiluminescence (CL) generation system. The estimations were conducted before, 1 min after and 20 min after percutaneous transluminal coronary angioplasty (PTCA) in 15 patients qualified for the treatment because of single-vessel disease. Eight EA patients subjected to coronary arteriography (CA) comprised a control group. We did not observe any marked changes in leucocytosis or lymphocyte number in peripheral blood (PB) or in coronary sinus blood (CSB) after the procedure. The percentage of granulocytes in coronary blood decreased significantly 20 min after reperfusion. No significant changes in white blood cell count were noted in peripheral blood of PTCA patients or in control CA subjects. Oxidative burst of nonstimulated and fMLP, PMA and zymosan stimulated sinus blood neutrophils was significantly depressed 1 min after inflation, and enhanced 20 min after reperfusion. We found a significant increase in the percentage of the CD11c+ neutrophils from 56.7 +/- 7.4% to 64 +/- 6.5% 20 min after inflation and postischemic decrease in the CD11c molecule expression on CSB neutrophils. Significant positive linear correlation (Rval = 0.71) between inflation time and the CD11c molecule expression on CSB immediately after reperfusion was also noted. The results may reflect local activation of neutrophils in ischemic myocardium as a response to ischemia induced increase of activating stimuli.