Endothelial cell E- and P-selectin and vascular cell adhesion molecule-1 function as signaling receptors.
Previous studies have shown that polymorphonuclear leukocyte (PMN) adherence to endothelial cells (EC) induces transient increases in EC cytosolic free calcium concentration ([Ca2+]i) that are required for PMN transit across the EC barrier (Huang, A.J., J.E. Manning, T. M. Bandak, M.C. Ratau, K.R. Hanser, and S.C. Silverstein. 1993. J. Cell Biol. 120:1371-1380). To determine whether stimulation of [Ca2+]i changes in EC by leukocytes was induced by the same molecules that mediate leukocyte adherence to EC, [Ca2+]i was measured in Fura2-loaded human EC monolayers. Expression of adhesion molecules by EC was induced by a pretreatment of the cells with histamine or with Escherichia coli lipopolysaccharide (LPS), and [Ca2+]i was measured in single EC after the addition of mAbs directed against the EC adhesion proteins P-selectin, E-selectin, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), or platelet/endothelial cell adhesion molecule-1 (PECAM-1). Both anti-P- and anti-E-selectin mAb, as well as anti-VCAM-1 mAb, induced transient increases in EC [Ca2+]i that were comparable to those induced by 200 microM histamine. In contrast, no effect was obtained by mAbs directed against the endothelial ICAM-1 or PECAM-1. PMN adherence directly stimulated increases in [Ca2+]i in histamine- or LPS-treated EC. mAbs directed against leukocyte CD18 or PECAM-1, the leukocyte counter-receptors for endothelial ICAM-1 and PECAM-1, respectively, did not inhibit PMN-induced EC activation. In contrast, mAb directed against sialyl Lewis x (sLex), a PMN ligand for endothelial P- and E-selectin, completely inhibited EC stimulation by adherent PMN. Changes in EC [Ca2+]i were also observed after adherence of peripheral blood monocytes to EC treated with LPS for 5 or 24 h. In these experiments, the combined addition of mAbs to sLex and VLA-4, the leukocyte counter-receptor for endothelial VCAM-1, inhibited [Ca2+]i changes in the 5 h-treated EC, whereas the anti-VLA-4 mAb alone was sufficient to inhibit [Ca2+]i changes in the 24 h-treated EC. Again, no inhibitory effect was observed with an anti-CD18 or anti-PECAM-1 mAb. Of note, the conditions that induced changes in EC [Ca2+]i, i.e. , mAbs directed against endothelial selectins or VCAM-1, and PMN or monocyte adhesion to EC via selectins or VCAM-1, but not via ICAM-1 or PECAM-1, also induced a rearrangement of EC cytoskeletal microfilaments from a circumferential ring to stress fibers. We conclude that, in addition to their role as adhesion receptors, endothelial selectins and VCAM-1 mediate endothelial stimulation by adhering leukocytes.
Lorenzon
P
P
Department of Physiology and Pathology, University of Trieste, Trieste, Italy.
Vecile
E
E
Nardon
E
E
Ferrero
E
E
Harlan
J M
JM
Tedesco
F
F
Dobrina
A
A
D000199:Actins / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000276:immunology / Q000502:physiology*; D002478:Cells, Cultured; D019040:E-Selectin / Q000276:immunology / Q000502:physiology*; D004730:Endothelium, Vascular / Q000502:physiology*; D016257:Fura-2 / Q000378:metabolism; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D039041:Integrin alpha4beta1; D016023:Integrins / Q000276:immunology; D007962:Leukocytes; D008070:Lipopolysaccharides / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D009844:Oligosaccharides / Q000276:immunology; D019007:P-Selectin / Q000276:immunology / Q000502:physiology*; D016201:Receptors, Lymphocyte Homing / Q000276:immunology; D000080506:Sialyl Lewis X Antigen; D019010:Vascular Cell Adhesion Molecule-1 / Q000276:immunology / Q000502:physiology
D000199:Actins; D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules; D019040:E-Selectin; D039041:Integrin alpha4beta1; D016023:Integrins; D008070:Lipopolysaccharides; D009844:Oligosaccharides; D019007:P-Selectin; D016201:Receptors, Lymphocyte Homing; D000080506:Sialyl Lewis X Antigen; D019010:Vascular Cell Adhesion Molecule-1; D006632:Histamine; D002118:Calcium; D016257:Fura-2