title: β2 integrin-mediated crawling on endothelial ICAM-1 and ICAM-2 is a prerequisite for transcellular neutrophil diapedesis across the inflamed blood-brain barrier.
abstract: In acute neuroinflammatory states such as meningitis, neutrophils cross the blood-brain barrier (BBB) and contribute to pathological alterations of cerebral function. The mechanisms that govern neutrophil migration across the BBB are ill defined. Using live-cell imaging, we show that LPS-stimulated BBB endothelium supports neutrophil arrest, crawling, and diapedesis under physiological flow in vitro. Investigating the interactions of neutrophils from wild-type, CD11a(-/-), CD11b(-/-), and CD18(null) mice with wild-type, junctional adhesion molecule-A(-/-), ICAM-1(null), ICAM-2(-/-), or ICAM-1(null)/ICAM-2(-/-) primary mouse brain microvascular endothelial cells, we demonstrate that neutrophil arrest, polarization, and crawling required G-protein-coupled receptor-dependent activation of β2 integrins and binding to endothelial ICAM-1. LFA-1 was the prevailing ligand for endothelial ICAM-1 in mediating neutrophil shear resistant arrest, whereas Mac-1 was dominant over LFA-1 in mediating neutrophil polarization on the BBB in vitro. Neutrophil crawling was mediated by endothelial ICAM-1 and ICAM-2 and neutrophil LFA-1 and Mac-1. In the absence of crawling, few neutrophils maintained adhesive interactions with the BBB endothelium by remaining either stationary on endothelial junctions or displaying transient adhesive interactions characterized by a fast displacement on the endothelium along the direction of flow. Diapedesis of stationary neutrophils was unchanged by the lack of endothelial ICAM-1 and ICAM-2 and occurred exclusively via the paracellular pathway. Crawling neutrophils, although preferentially crossing the BBB through the endothelial junctions, could additionally breach the BBB via the transcellular route. Thus, β2 integrin-mediated neutrophil crawling on endothelial ICAM-1 and ICAM-2 is a prerequisite for transcellular neutrophil diapedesis across the inflamed BBB.
authors.affiliation: Theodor Kocher Institute, University of Bern, Bern CH-3012, Switzerland.
authors.forename: Roser
authors.initials: R
authors.lastname: Gorina
authors.forename: Ruth
authors.initials: R
authors.lastname: Lyck
authors.forename: Dietmar
authors.initials: D
authors.lastname: Vestweber
authors.forename: Britta
authors.initials: B
authors.lastname: Engelhardt
mesh_terms: D000818:Animals; D015703:Antigens, CD; D001812:Blood-Brain Barrier / Q000276:immunology* / Q000378:metabolism* / Q000473:pathology; D018821:CD18 Antigens / Q000378:metabolism*; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism; D004730:Endothelium, Vascular / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D007249:Inflammation / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000276:immunology; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism; D016177:Macrophage-1 Antigen / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009504:Neutrophils / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D015398:Signal Transduction; D057688:Transcellular Cell Migration / Q000502:physiology*
chemical_list: D015703:Antigens, CD; D018821:CD18 Antigens; D015815:Cell Adhesion Molecules; C480027:ICAM-2 protein, mouse; D008070:Lipopolysaccharides; D016169:Lymphocyte Function-Associated Antigen-1; D016177:Macrophage-1 Antigen; D043562:Receptors, G-Protein-Coupled; D018799:Intercellular Adhesion Molecule-1