Signaling via beta(2) integrins triggers neutrophil-dependent alteration in endothelial barrier function.
Activation of polymorphonuclear leukocytes (PMNs) and adhesion to the endothelial lining is a major cause of edema formation. Although known to be dependent on the function of beta(2) integrins (CD11/CD18), the precise mechanisms by which adherent PMNs may impair endothelial barrier capacity remain unclear. Here, the role of transmembrane signaling by beta(2) integrins in PMN-induced alterations in tight junctional permeability of cultured endothelial cell (EC) monolayers was investigated. PMN activation, in the absence of proinflammatory stimuli, was accomplished through antibody cross-linking of CD11b/CD18, mimicking adhesion-dependent receptor engagement. CD18 cross-linking in PMNs added to the EC monolayer provoked a prompt increase in EC permeability that coincided with a rise in EC cytosolic free Ca(2+) and rearrangement of actin filaments, events similar to those evoked by chemoattractant PMN activation. Cell-free supernatant obtained after CD18 cross-linking in suspended PMNs triggered an EC response indistinguishable from that induced by direct PMN activation, and caused clear-cut venular plasma leakage when added to the hamster cheek pouch in vivo preparation. The PMN-evoked EC response was specific to beta(2) integrin engagement inasmuch as antibody cross-linking of l-selectin or CD44 was without effect on EC function. Our data demonstrate a causal link between outside-in signaling by beta(2) integrins and the capacity of PMNs to induce alterations in vascular permeability, and suggest a paracrine mechanism that involves PMN-derived cationic protein(s) in the cellular crosstalk between PMNs and ECs.
Gautam
N
N
Department of Physiology and Pharmacology, Karolinska Institutet, S-171 77 Stockholm, Sweden.
Herwald
H
H
Hedqvist
P
P
Lindbom
L
L
D000199:Actins / Q000378:metabolism; D000818:Animals; D018845:CD11 Antigens / Q000378:metabolism; D018821:CD18 Antigens / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002448:Cell Adhesion / Q000502:physiology; D002463:Cell Membrane Permeability / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D006224:Cricetinae; D003432:Cross-Linking Reagents; D003600:Cytosol / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D006801:Humans; D016177:Macrophage-1 Antigen / Q000378:metabolism*; D051379:Mice; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*
D000199:Actins; D018845:CD11 Antigens; D018821:CD18 Antigens; D003432:Cross-Linking Reagents; D016177:Macrophage-1 Antigen; D002118:Calcium