A soluble gradient of endogenous monocyte chemoattractant protein-1 promotes the transendothelial migration of monocytes in vitro.
Chemokines secreted by endothelium may promote diapedesis of leukocytes by a gradient-dependent chemotactic mechanism or by stimulating random motility so that leukocytes transmigrate in a gradient-independent manner. Alternatively, chemokines may bind to endothelium and extracellular matrix to stimulate haptotactic migration. We first analyzed the role of the chemokine monocyte chemoattractant protein-1 (MCP-1) in the migration of human monocytes across untreated or IL-1-stimulated HUVEC monolayers cultured on human amnion. Then we further examined whether MCP-1-dependent transmigration occurred through a chemokinetic, chemotactic, or haptotactic mechanism. A neutralizing mAb against MCP-1 inhibited passage of monocytes across untreated or IL-1-stimulated HUVEC by 74 +/- 3% and 45 +/- 4%, respectively. Addition of MCP-1 itself to the apical compartment of unstimulated HUVEC/amnion cultures also reduced the transmigration of monocytes, in this instance by 73 +/- 9%. MCP-1 suppressed diapedesis only when present above the endothelium at a concentration equal to or greater than that endogenously deposited beneath the endothelium, and its inhibitory action could be overcome by addition of more concentrated MCP-1 below the HUVEC cultures. As much as 90% of the MCP-1 secreted into the underlying basement membrane and connective tissue could be washed out of HUVEC/amnion cultures; this procedure decreased transmigration by 69 +/- 4%. These data indicate that MCP-1 promotes transmigration of monocytes, but only when present in a gradient across endothelial monolayers. They further suggest that this gradient is predominantly soluble, rather than haptotactic.
Randolph
G J
GJ
Department of Pathology, School of Medicine, State University of New York at Stony Brook 11794, USA.
Furie
M B
MB
D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism / Q000494:pharmacology*; D017077:Culture Media, Conditioned; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D009000:Monocytes / Q000166:cytology* / Q000378:metabolism
D018932:Chemokine CCL2; D017077:Culture Media, Conditioned