Visualization of chemokine binding sites on human brain microvessels.
The chemokines monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1alpha (MIP-1alpha) aid in directing leukocytes to specific locales within the brain and spinal cord during central nervous system inflammation. However, it remains unclear how these chemokines exert their actions across a vascular barrier, raising speculation that interaction with endothelial cells might be required. Therefore, experiments were performed to determine whether binding domains for these chemokines exist along the outer surface of brain microvessels, a feature that could potentially relay chemokine signals from brain to blood. Using a biotinylated chemokine binding assay with confocal microscopy and three-dimensional image reconstruction, spatially resolved binding sites for MCP-1 and MIP-alpha around human brain microvessels were revealed for the first time. Binding of labeled MCP-1 and MIP-1alpha could be inhibited by unlabeled homologous but not heterologous chemokine, and was independent of the presence of heparan sulfate, laminin, or collagen in the subendothelial matrix. This is the first evidence of specific and separate binding domains for MCP-1 and MIP-1alpha on the parenchymal surface of microvessels, and highlights the prospect that specific interactions of chemokines with microvascular elements influence the extent and course of central nervous system inflammation.
Andjelkovic
A V
AV
Blood-Brain Barrier Laboratory, Department of Pharmacology, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.
Spencer
D D
DD
Pachter
J S
JS
D001667:Binding, Competitive; D002540:Cerebral Cortex / Q000098:blood supply*; D002560:Cerebrovascular Circulation; D018932:Chemokine CCL2 / Q000378:metabolism*; D054405:Chemokine CCL3; D054407:Chemokine CCL4; D005455:Fluorescent Antibody Technique; D006801:Humans; D007700:Kinetics; D019402:Macrophage Inflammatory Proteins / Q000378:metabolism*; D008833:Microcirculation / Q000276:immunology / Q000502:physiology*; D054390:Receptors, CCR2; D019707:Receptors, Chemokine / Q000032:analysis / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D013702:Temporal Lobe / Q000098:blood supply*
C515334:CCR2 protein, human; D018932:Chemokine CCL2; D054405:Chemokine CCL3; D054407:Chemokine CCL4; D019402:Macrophage Inflammatory Proteins; D054390:Receptors, CCR2; D019707:Receptors, Chemokine; D011994:Recombinant Proteins; C080633:macrophage inflammatory protein 1alpha receptor