Vascular adhesion molecules and immunogenicity in blood vessels used as coronary artery bypass grafts

CD68 expression in aortocoronary saphenous vein bypass grafts

Atherosclerosis commonly affects the arteries harvested from patients 70 years of age or older. Saphenous vein grafts appear to maintain a higher patency rate after coronary artery bypass grafting in these subjects. The infiltration of macrophages is an early step in saphenous vein graft atherosclerosis; however, little is known regarding the underlying mechanisms of infiltration. The objective of the present report is to evaluate the presence of CD68-positive cells in the saphenous vein wall and correlate initial CD68-positive infiltration to specific clinical and biochemical parameters and the graft patency rate as estimated in patients undergoing coronary artery bypass grafting. A total of 309 patients were allocated into two groups: A1 patients, who were between 50 and 70 years of age, and A2 patients, who were 70 years or older at the time of vein harvesting. CD68 expression was evaluated by immunohistochemistry. There were no significant differences between A1 and A2 patients regarding macrophage expression within any of the analyzed vascular regions. Saphenous vein macrophages were never present in the tunica intima unless they were also expressed in the media or the adventitia. The patients with CD68-positive cells in the tunica intima had a significantly higher number of bypass stenoses when compared with the subjects who did not have CD68-positive cells in this layer. These findings suggest that the CD68-positive cells (those that have not yet developed into foam cells) present in the intima of saphenous vein grafts might serve as a very early marker of graft occlusion.

Salmon consumption by pregnant women reduces ex vivo umbilical cord endothelial cell activation

BACKGROUND

In vitro exposure of endothelial cells (ECs) to n-3 (omega-3) long-chain PUFAs (LCPUFAs) reduces cell adhesion molecule (CAM) expression. However, to our knowledge, no previous human studies have examined the influence of an altered diet on CAM expression.

OBJECTIVE

We assessed whether salmon (rich in n-3 LCPUFAs) consumption twice a week during pregnancy affected offspring umbilical vein EC CAM expression.

DESIGN

Women were randomly assigned to maintain their habitual diets or to consume 2 portions of salmon per week during pregnancy months 4-9. ECs were isolated from umbilical cord veins collected at birth and cultured. The cell surface expression of intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) was assessed by flow cytometry after the culture of ECs in the presence and absence of bacterial LPS for 24 h. Cytokine and growth factor concentrations in culture supernatant fluid were measured by using a multiplex assay.

RESULTS

LPS increased the expression of VCAM-1 and the production of several cytokines and growth factors. The level of ICAM-1 expression per cell [ie, the median fluorescence intensity (MFI)] was increased by LPS stimulation in the control group (16.9 ± 2.4 compared with 135.3 ± 20.2; P < 0.001) and to a lesser extent in the salmon group (14.1 ± 3.8 compared with 65.8 ± 22.4; P = 0.037). The ICAM-1 MFI in the salmon group after LPS stimulation was lower than in the control group (P = 0.006).

CONCLUSION

Increased dietary salmon intake in pregnancy dampens offspring EC activation, which implicates a role for n-3 LCPUFAs in the suppression of inflammatory processes in humans. This trial was registered at clinicaltrials.gov as NCT00801502.

Pathogenic mechanisms in varicose vein disease: the role of hypoxia and inflammation

AIMS

Although the aetiology of varicose veins remains unknown, recent studies have focused on endothelial cell integrity and function. Among the regulatory factors of vessel tone, synthesises, pro- and anti-inflammatory, adhesion molecules and the transcription factor hypoxia inducible factor-1 alpha (HIF-1alpha), which are responsible for recruiting leukocytes, are very important.

METHODS

Investigation in this study focused on the expression of ICAM-1, E-selectin and HIF-1alpha on endothelial cells using immunostaining and RT-PCR in varicose vein specimens compared with controls.

RESULTS

Findings of this study showed alterations of the intima, such as focal intimal discontinuity and denudation of endothelium in varicose veins. Based on data derived from immunostaining and RT-PCR, no major differences were identified between ICAM-1 and E-selectin expression in varicose vein specimens compared with controls. In contrast, immunostaining results identified HIF-1alpha expression in five (5/20) varicose vein specimens, whereas no control saphenous vein specimens expressed HIF-1alpha.

CONCLUSIONS

These findings could explain other evidence of hypoxia in varicose veins. Finally, results already obtained in this investigation suggest that the process of pathogenesis of varicose veins is not restricted to the role of adhesion molecules.

Mild inflammatory activation of mammary arteries in patients with acute coronary syndromes

Acute coronary syndromes (ACS) are characterized by multiple unstable coronary plaques and elevated circulating levels of inflammatory biomarkers. The endothelium of internal mammary arteries (IMA), which are atherosclerosis resistant, is exposed to proinflammatory stimuli as vessels that develop atherosclerosis. Our study investigated the IMA endothelial expression of inflammatory molecules in patients with ACS or chronic stable angina (CSA). IMA demonstrated normal morphology, intact endothelial lining, and strong immunoreactivity for glucose transporter 1. E-selectin expression was observed more frequently in IMA of ACS patiention than CSA patients (ACS 61% vs. CSA 14%, P = 0.01). High fluorescence for major histocompatibility complex (MHC) was significantly more frequent on the luminal endothelium (ACS 66.7% vs. CSA 17.6%, P = 0.001 for class I; and ACS 66.7% vs. CSA 6.2%, P = 0.0003 for class II-DR) and on the vasa vasorum (ACS 92.9% vs. CSA 33.3% and 7.7%, P = 0.0007 and P < 0.0001 for class I and class II-DR, respectively) of ACS patients than CSA patients. ICAM-1, VCAM-1, Toll-like receptor 4, tissue factor, IL-6, inducible nitric oxide synthase, and TNF-alpha expression were not significantly different in ACS and CSA. Circulating C-reactive protein [ACS 4.8 (2.6-7.3) mg/l vs. CSA 1.8 (0.6-3.5) mg/l, P = 0.01] and IL-6 [ACS 4.0 (2.6-5.5) pg/ml vs. CSA 1.7 (1.4-4.0) pg/ml, P = 0.02] were higher in ACS than CSA, without a correlation with IMA inflammation. The higher E-selectin, MHC class I and MHC class II-DR on the endothelium and vasa vasorum of IMA from ACS patients suggests a mild, endothelial inflammatory activation in ACS, which can be unrelated to the presence of atherosclerotic coronary lesions. These findings indicated IMA as active vessels in coronary syndromes.

Neutrophil adherence to activated saphenous vein and mammary endothelium after graft preparation

BACKGROUND

Interaction of circulating leukocytes and vascular endothelium plays an important role in vasoconstriction, endothelial dysfunction, and vascular injury. Dilation procedures of grafts before coronary artery bypass graft surgery might lead to vascular injury and subsequent bypass graft disease.

METHODS

We analyzed in vitro the adherence of fluorescence-labeled polymorphonuclear neutrophils (PMNs) to endothelium of human saphenous vein grafts or internal mammary artery grafts after stimulation with thrombin (0.5 to 2 U/mL) or dilating procedures. Furthermore, we investigated endothelial function of prepared grafts.

RESULTS

Thrombin stimulation resulted in a dose-dependent increase of PMN adherence to the endothelium of saphenous vein and internal mammary artery, which was attenuated by the selectin-blocking carbohydrate fucoidin or anti-P-selectin monoclonal antibody. Mechanical dilation of saphenous vein or internal mammary artery led to a marked increase in PMN adherence (65 +/- 5 versus 5 +/- 3 PMN/mm2; p < 0.01), which was significantly attenuated by fucoidin or anti-P-selectin monoclonal antibodies. Treatment of internal mammary artery with the vasodilator papaverine led to a marked increase of PMN adherence (59 +/- 8 versus 12 +/- 4 PMN/mm2; p < 0.01) when papaverine was administered directly into the vessel. However, external treatment with papaverine did not affect PMN adhesion. Endothelial dysfunction was observed in dilated venous grafts and in arterial grafts internally treated with papaverine; in contrast, external treatment did not affect endothelial function.

CONCLUSIONS

This study showed that mechanical or pharmacologic dilation of venous or arterial coronary grafts, usually performed before anastomosis of aortocoronary bypass grafts, led to increased selectin-mediated PMN adhesion on vascular endothelium and subsequent endothelial dysfunction.

Evaluation of serum levels of solubilized adhesion molecules in patients with aortocoronary saphenous vein grafts

OBJECTIVE

To assess the diagnostic importance of serum-solubilized adhesion molecules, vascular cell adhesion molecule-1, intercellular adhesion molecule-1, sE-selectin and sP-selectin in aortocoronary saphenous vein graft disease.

METHODS

The study population was composed of two groups consisting of 41 patients with saphenous vein graft stenosis (stenosis group) and 43 patients without saphenous vein graft stenosis (no-stenosis group) based on the results of coronary angiography. All patients underwent coronary artery bypass graft operation involving the use of at least one saphenous vein graft for bypass. At the time of cardiac catheterization, it had been more than 1 year since the operation.

RESULTS

Serum level of sP-selectin was significantly higher in the stenosis group than in the no-stenosis group (72.9+/-21.7 versus 48.7+/-18.6 ng/ml, P<0.001). No differences were found between the two groups with respect to serum levels of sE-selectin, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. Multivariate analysis revealed that only serum levels of sP-selectin, high-density lipoprotein cholesterol and low-density lipoprotein cholesterol were independently correlated with the stenosis of saphenous vein grafts. A cutoff value of serum sP-selectin >57.5 ng/ml yields a specificity of 79.5%, a sensitivity of 73.3% and a positive predictive value of 80.5% for saphenous vein graft stenosis.

CONCLUSION

In this study, sP-selectin level was found to be significantly higher in the group that had late aortocoronary saphenous vein bypass graft disease. This result suggests that platelet activation may play a causal role in late graft disease.

Pressure distension stimulates the expression of endothelial adhesion molecules in the human saphenous vein graft

BACKGROUND

Mechanical trauma occurring during saphenous vein graft harvesting plays a major role in graft failure after coronary bypass surgery. There is increasing evidence that neutrophil-endothelial interaction is involved in the pathogenesis of early graft occlusion. This study evaluates the effect of pressure distension on the expression of endothelial adhesion molecules in human saphenous vein.

METHODS

Segments of saphenous vein graft (SVG) were collected from 20 patients undergoing coronary bypass surgery. We evaluated the expression of intercellular adhesion molecule (ICAM-1), vascular cell adhesion molecule (VCAM-1), and P-selectin on SVG endothelium under basal conditions and after pressure distension at 300 mm Hg. In the same experimental setting we also evaluated adhesion of both unstimulated and activated neutrophils to the endothelium of SVG.

RESULTS

Control endothelial cells exhibited only a weak staining for intercellular adhesion molecule (ICAM-1), vascular cell adhesion molecule (VCAM-1), and P-selectin, whereas the levels of adhesion molecules increased significantly in the distended veins. Similarly, significantly greater adhesion of both unstimulated and activated neutrophils was observed in distended veins compared with control veins.

CONCLUSIONS

Pressure distension of SVG before coronary bypass surgery induces upregulation of endothelial adhesion molecules, with subsequent increase in neutrophil adhesion to the endothelium. Neutrophil adhesion to endothelial cells may contribute to early failure of SVG.

Antagonizing leukotriene B4 receptors delays cardiac allograft rejection in mice

BACKGROUND

Allograft rejection is a cellular immunological/inflammatory response that is, in part, directed by potent proinflammatory mediators. This study was designed to test the hypothesis that leukotriene B4 (LTB4) may have a role in graft rejection and that LTB4 receptor antagonists may be clinically useful in the treatment of allograft rejection.

METHODS

We evaluated the potent and selective LTB4 receptor antagonist CP-105696 in a murine heterotopic cardiac allograft model with oral dosing daily for 28 days or in an induction protocol (day -1 to day 3).

RESULTS

At a dose of 50 mg/kg/day (28 days), B10.BR (H2k) allografts transplanted into C57Bl/6 (H2b) recipients were significantly protected, as reflected by the mean survival time versus control grafts (27+/-20 days [n=10] vs. 12+/-6 days [n=14]; P=0.0146). Using an induction protocol (day -1 to day 3), CP-105696 at 100 mg/kg/day significantly prolonged allograft survival (33+/-23 days [n=9]; P=0.0026), but CP-105696 at 10 mg/kg/day did not (18+/-16 days [n=8]; P=0.1433). Syngeneic grafts survived indefinitely (n=11). Immunohistological evaluation of allografts at rejection revealed a mononuclear cell infiltrate composed primarily of CD3+ and CD11b+ (Mac-1+) cells, which were infrequent in syngeneic grafts. Allografts from mice treated with CP-105696 at 50 or 100 mg/kg/day demonstrated a selective reduction in beta2-integrin (Mac-1) expression on monocytes/macrophages, as demonstrated by CD11b staining density compared with allograft controls.

CONCLUSIONS

The results suggest that LTB4 or other potential ligands for LTB4 receptors may be important mediators of allograft rejection and support the clinical evaluation of LTB4 receptor antagonists in human organ transplantation.

Expression of vascular adhesion molecules in saphenous vein coronary bypass grafts

BACKGROUND

Adhesion of blood elements to the endothelium is an important step in the development of vein graft disease. This study examines the expression of vascular adhesion molecules on explanted saphenous vein bypass grafts.

METHODS

Immunocytochemical staining was performed using explanted saphenous vein grafts from 28 patients. Antibodies against the endothelial markers CD31, von Willebrand factor, intercellular adhesion molecule-1, vascular adhesion molecule-1, and E-selectin were used.

RESULTS

Staining for CD31 and von Willebrand factor demonstrated the presence of endothelial cells in the lumen and the vasa vasorum. Expression of intercellular adhesion molecule-1 was variable between grafts, whereas vascular adhesion molecule-1 and E-selectin were almost always absent on the luminal endothelium. In contrast, the endothelium of the vasa vasorum stained positively for intercellular adhesion molecule-1 and vascular adhesion molecule-1, and was also seen on nonendothelial cells within the vessel wall. Expression of these adhesion molecules did not vary with the severity of vein graft disease.

CONCLUSIONS

This study highlights the blood vessels in the adventitia as possible sites for the adhesion and migration of cells into the vessel wall.