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 CD18null mice with wild-type, junctional adhesion molecule-A−/−, ICAM-1null, ICAM-2−/− , or ICAM-1null/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.

Role of liver ICAM-1 in metastasis

“…The contraction of endothelial cells through actin cytoskeletal reorganization is essential for the infiltration of invading cells (78,79). The remodeling of the cytoskeleton is also observed after the binding of endothelial ICAM-1 to leukocyte LFA-1 during transmigration of immune cells, including leukocytes, lymphocytes and neutrophils (44,80,81). In this scenario, ICAM-1 expression has also been reported to be correlated with efficient transmigration across the endothelial cell layer and the subsequent extravasation of tumor cells, which in turn, facilitates the colonization of the organ (29,82,83).…”

Astrocytic TYMP and VEGFA drive blood–brain barrier opening in inflammatory central nervous system lesions

“…Blood-brain barrier opening results in oedema, disruption of metabolic function, excitotoxicity, and parenchymal entry of autoantibodies and plasma proteins that potentiate inflammation and limit repair (Schluesener et al, 1987;Adams et al, 2007;Germano et al, 2007;Schachtrup et al, 2007). Bloodbrain barrier disruption also facilitates ingress into the CNS parenchyma of T and B lymphocytes, monocytederived macrophages, and polymorphonuclear leucocytes (Graesser et al, 2002;Gorina et al, 2014). In conditions such as multiple sclerosis, therapies for clinical exacerbation are limited.…”

Annexin A2 Limits Neutrophil Transendothelial Migration by Organizing the Spatial Distribution of ICAM-1

“…Thus, annexin A2 negatively regulates ICAM-1 mobility at the EC surface. Downregulation of endothelial annexin A2 increases neutrophil adhesion to TNF-a-stimulated ECs ICAM-1 at the EC surface has been described to support the rolling, arrest, crawling, and transmigration of neutrophils (1)(2)(3)(4)(5)(6). To investigate how altered ICAM-1 membrane distribution and dynamics in annexin A2-deficient ECs affect neutrophil TEM under physiological flow conditions, we simultaneously measured neutrophil TEM through control and annexin A2-deficient ECs in a parallel flow setup (Fig.…”

“…In conclusion, our data show that annexin A2 limits neutrophil transendothelial migration by organizing the spatial distribution of ICAM-1. The Journal of Immunology, 2016Immunology, , 196: 2767Immunology, -2778 I ntracellular adhesion molecule-1 (ICAM-1) at the endothelial cell (EC) surface functions as an adhesive ligand for neutrophil b2-integrins, supporting the rolling, arrest, crawling, and transmigration of neutrophils in vivo (1)(2)(3)(4)(5)(6). However, to what extent ICAM-1 is specifically involved and how ICAM-1 functionally facilitates each distinct step during neutrophil transmigration has been controversial.…”

“…This work established the importance of the intracellular domain of ICAM-1 as signaling molecule in orchestrating leukocyte transmigration, but also showed the importance of the extracellular domain of ICAM-1 in leukocyte adhesion. Studies that used LFA-1-(a L b2,CD11a/ CD18) and MAC-1 (a M b2,CD11b/CD18)-deficient mice showed that neutrophil arrest depends mainly on LFA-1-ICAM-1 interactions, whereas neutrophil crawling requires MAC-1-ICAM-1 interactions (2,3). Moreover, the binding site of ICAM-1 for MAC-1, but not LFA-1, is regulated by glycosylation, which may provide a mechanistic explanation for sequential roles in ICAM-1-mediated arrest and crawling (10,11).…”