Monocyte adhesion to activated aortic endothelium: role of L-selectin and heparan sulfate proteoglycans.
This study examines the role of L-selectin in monocyte adhesion to arterial endothelium, a key pathogenic event of atherosclerosis. Using a nonstatic (rotation) adhesion assay, we observed that monocyte binding to bovine aortic endothelium at 4 degrees C increased four to nine times upon endothelium activation with tumor necrosis factor (TNF)-alpha. mAb-blocking experiments demonstrated that L-selectin mediates a major part (64 +/- 18%) of monocyte attachment. Videomicroscopy experiments performed under flow indicated that monocytes abruptly halted on 8-h TNF-alpha-activated aortic endothelium, approximately 80% of monocyte attachment being mediated by L-selectin. Flow cytometric studies with a L-selectin/IgM heavy chain chimeric protein showed calcium-dependent L-selectin binding to cytokine-activated and, unexpectedly, unactivated aortic cells. Soluble L-selectin binding was completely inhibited by anti-L-selectin mAb or by aortic cell exposure to trypsin. Experiments with cycloheximide, chlorate, or neuraminidase showed that protein synthesis and sulfate groups, but not sialic acid residues, were essential for L-selectin counterreceptor function. Moreover, heparin lyases partially inhibited soluble L-selectin binding to cytokine-activated aortic cells, whereas a stronger inhibition was seen with unstimulated endothelial cells, suggesting that cytokine activation could induce the expression of additional ligand(s) for L-selectin, distinct from heparan sulfate proteoglycans. Under flow, endothelial cell treatment with heparinase inhibited by approximately 80% monocyte attachment to TNF-alpha-activated aortic endothelium, indicating a major role for heparan sulfate proteoglycans in monocyte-endothelial interactions. Thus, L-selectin mediates monocyte attachment to activated aortic endothelium, and heparan sulfate proteoglycans serve as arterial ligands for monocyte L-selectin.
Giuffrè
L
L
Division of Hematology, Hematology Central Laboratory of the University of Lausanne, Switzerland.
Cordey
A S
AS
Monai
N
N
Tardy
Y
Y
Schapira
M
M
Spertini
O
O
D000818:Animals; D001011:Aorta; D002417:Cattle; D002448:Cell Adhesion / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D019041:L-Selectin / Q000096:biosynthesis / Q000502:physiology*; D008024:Ligands; D009000:Monocytes / Q000187:drug effects / Q000502:physiology*; D011509:Proteoglycans / Q000502:physiology*
D016207:Cytokines; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate; D019041:L-Selectin; D008024:Ligands; D011509:Proteoglycans