Increased plasma GlyCAM-1, a mouse L-selectin ligand, in response to an inflammatory stimulus

GlyCAM-1 (glycosylation-dependent cell adhesion molecule-1) is one of the sialomucin-like ligands for L-selectin, which is a member of the selectin family and mediates initial adhesion of leukocytes to specialized high endothelial venules in lymph nodes and venules at sites of inflammation. GlyCAM-1, lacking a transmembrane domain, is supposed to be secreted into the blood. To understand the functional role of secreted GlyCAM-1, we performed sandwich enzyme-linked immunosorbent assay to measure GlyCAM-1 plasma levels after inflammatory stimulus. BALB/c mice were injected with complete Freund's adjuvant (CFA) in the hind footpads; serum levels of GlyCAM-1 and L-selectin bound to GlyCAM-1 and several inflammatory cytokines, including interleukin-6 (IL-6), were measured at various intervals. IL-6 showed a significant increase 3 h after CFA stimulation. GlyCAM-1 was increased at 3 h, reached peak levels at 12 h, and gradually decreased thereafter. Levels of L-selectin bound to the plasma GlyCAM-1 changed over a similar time course, reached peak at 12 h after, and then began to decrease. The binding of L-selectin to plasma GlyCAM-1 was completely eliminated with the presence of ethyleneglycol-bis (β-aminoethylether)-N,N'-tetraacetic acid, showing the calcium dependency of this binding. These findings show that GlyCAM-1 release is enhanced by inflammatory stimulation and also suggest that released plasma GlyCAM-1 may trap, at least in part, soluble L-selectin shed from stimulated leukocytes to neutralize each other.