Antagonism of selectin-dependent adhesion of human eosinophils and neutrophils by glycomimetics and oligosaccharide compounds

Early in inflammation, adhesion occurs between leukocytes and endothelium when selectins bind to sialyl Lewis X (sLe^x) and related oligosaccharides. We tested novel compounds that mimic sLe^x for their ability to inhibit selectin-mediated adhesion of human eosinophils and neutrophils in vitro. Neutrophils and eosinophils were isolated by density gradient centrifugation, and eosinophils were further purified by immunomagnetic negative selection. Adhesion to unstimulated or interleukin-1β-stimulated (5 ng/ml, 4-6 h) umbilical vein endothelial monolayers was tested under static or rotating conditions, where adhesion is primarily E-or L-selectin dependent, respectively. P-selectin-dependent adhesion was tested on immobilized platelets treated with or without phorbol myristate acetate (10 ⁷ M, 10 min). Stimulus-induced adhesion was always at least 4-fold higher than without stimulus, and selectin dependence was confirmed with specific blocking monoclonal antibodies. E-selectin-dependent adhesion of eosinophils and neutrophils was inhibited by compound GM2296 (the concentration producing 50% inhibition of adhesion [IC₅₀] ≈ 0.5-1 mM). E-selectin-dependent adhesion of neutrophils, but not eosinophils, was also inhibited by another compound, sLe^x with a lipid tail (30 ± 6% inhibition at 3 mM), whereas compound GM1292 slightly inhibited adhesion of both (23 ± 5 and 20 ± 6% inhibition, respectively, at 1 mM). L-selectin-dependent adhesion was more effectively inhibited by GM2296 (IC₅₀ ≈ 0.2-0.5 mM), although P-selectin-dependent adhesion was also inhibited (IC₅₀ ≈ 1 mM). Inhibition was reversible without affecting viability, and no effect was seen with these compounds in assays testing neutrophil adhesion to immobilized intercellular adhesion molecule-1. Thus, compound GM2296, a carbon-fucosylated derivative of glycyrrhetinic acid, inhibits E-, L-, and P-selectin-dependent eosinophil and neutrophil adhesion. The ability of these and perhaps other related glycomimetic compounds to interfere with the function of more than one type of selectin makes them desirable candidates as anti-inflammatory agents.