Modulation of sialyl Lewis X dependent binding to E-Selectin by glycoformsof alpha-1-acid glycoprotein expressed in rheumatoid arthritis

Alpha-1-acid glycoprotein (AGP) is an extensively glycosylated acute phase protein of imprecisely defined physiological function. Nonetheless it is kn own that the oligosaccharide component comprising 42% of the 41 kDa molecul ar weight is critical to the previously described multifarious immunomodula tory functions of AGP in vitro. Complex oligosaccharides were enzymically r eleased from AGP purified from the blood of rheumatoid arthritis sufferers by our oligosaccharide protective method. Oligosaccharide profiling was by means of high pH anion-exchange chromatography with pulsed amperometric det ection (HPAEC-PAD), Monosaccharide composition analysis revealed increased fucosylation of inflammatory AGP oligosaccharide chains, suggesting the pot ential for expression of the tetrasaccharide antigen and E-Selectin ligand, sialyl Lewis X (sLeX), The hypothesis that AGP may function to inhibit blo od cell binding to activated endothelium at E-Selectin was tested in a micr otitre cell-protein binding assay. In this system we have shown that the ol igosaccharide moiety of AGP, as expressed in inflammatory disease, can inhi bit the sLeX/E-Selectin interaction. Thus we have identified a correlation between the abnormal glycosylation of AGP in rheumatoid arthritis and suppr ession of sLeX dependent cell adhesion through inhibition of E-selectin bin ding which could be the basis of a novel, site specific, anti-inflammatory agent. (C) 1998 John Wiley & Sons, Ltd.