Selective activation of cannabinoid receptor 2 in leukocytes suppresses their engagement of the brain endothelium and protects the blood-brain barrier.
Cannabinoid receptor 2 (CB2) is highly expressed in immune cells and stimulation decreases inflammatory responses. We tested the idea that selective CB2 activation in human monocytes suppresses their ability to engage the brain endothelium and migrate across the blood-brain barrier (BBB), preventing consequent injury. Intravital videomicroscopy was used to quantify adhesion of leukocytes to cortical vessels in lipopolysaccharide-induced neuroinflammation, after injection of ex vivo CB2-activated leukocytes into mice; CB2 agonists markedly decreased adhesion of ex vivo labeled cells in vivo. In an in vitro BBB model, CB2 activation in monocytes largely attenuated adhesion to and migration across monolayers of primary human brain microvascular endothelial cells and diminished BBB damage. CB2 stimulation in monocytes down-regulated active forms of integrins, lymphocyte function-associated antigen 1 (LFA-1), and very late antigen 4 (VLA-4). Cells treated with CB2 agonists exhibited increased phosphorylation levels of inhibitory sites of the actin-binding proteins cofilin and VASP, which are upstream regulators of conformational integrin changes. Up-regulated by relevant stimuli, Rac1 and RhoA were suppressed by CB2 agonists in monocytes. CB2 stimulation decreased formation of lamellipodia, which play a key role in monocyte migration. These results indicate that selective CB2 activation in leukocytes decreases key steps in monocyte-BBB engagement, thus suppressing inflammatory leukocyte responses and preventing neuroinflammation.
Department of Pathology and Laboratory Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania. Electronic address: srom@temple.edu.
Slava
S
Rom
Department of Pathology and Laboratory Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania.
Viviana
V
Zuluaga-Ramirez
Department of Pathology and Laboratory Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania.
Holly
H
Dykstra
Department of Pathology and Laboratory Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania.
Nancy L
NL
Reichenbach
Section on Oxidative Stress and Tissue Injury, Laboratory of Physiological Studies, National Institutes of Health/Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland.
Pal
P
Pacher
Department of Pathology and Laboratory Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania. Electronic address: yuri.persidsky@tuhs.temple.edu.
Yuri
Y
Persidsky
D051339:Actin Depolymerizing Factors / Q000378:metabolism; D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism* / Q000473:pathology*; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002460:Cell Line; D002540:Cerebral Cortex / Q000098:blood supply / Q000473:pathology; D004660:Encephalitis / Q000378:metabolism / Q000473:pathology; D042783:Endothelial Cells / Q000378:metabolism / Q000473:pathology; D004727:Endothelium / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D039041:Integrin alpha4beta1 / Q000737:chemistry / Q000378:metabolism; D019012:Integrin beta1 / Q000378:metabolism; D007962:Leukocytes / Q000378:metabolism*; D008070:Lipopolysaccharides; D016169:Lymphocyte Function-Associated Antigen-1 / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism; D055806:Microvessels / Q000473:pathology; D009000:Monocytes / Q000378:metabolism / Q000473:pathology; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011554:Pseudopodia / Q000378:metabolism; D043885:Receptor, Cannabinoid, CB2 / Q000819:agonists / Q000378:metabolism*; D057705:Transendothelial and Transepithelial Migration; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020742:rhoA GTP-Binding Protein; D000098662:Vasodilator-Stimulated Phosphoprotein
D051339:Actin Depolymerizing Factors; D015815:Cell Adhesion Molecules; D039041:Integrin alpha4beta1; D019012:Integrin beta1; D008070:Lipopolysaccharides; D016169:Lymphocyte Function-Associated Antigen-1; D008840:Microfilament Proteins; D010750:Phosphoproteins; D043885:Receptor, Cannabinoid, CB2; D000098662:Vasodilator-Stimulated Phosphoprotein; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein