INCREASED ADHESION OF ERYTHROCYTES TO COMPONENTS OF THE EXTRACELLULAR-MATRIX - ISOLATION AND CHARACTERIZATION OF A RED-BLOOD-CELL LIPID THAT BINDS THROMBOSPONDIN AND LAMININ

Red blood cell (RBC) adhesion to the vascular endothelium is increased in several pathologic conditions, including sickle cell disease and m alaria. However, RBC interactions with components of the subendothelia l matrix are not well-characterized. Under in vitro flow conditions of 1 dyne/cm(2), washed RBCs bound to the purified adhesive molecules th rombospondin (TSP) and laminin. Sickle RBCs had the greatest adhesion of all tested RBCs. The adhesion of sickle RBCs to immobilized TSP was inhibited by the anionic polysaccharides high molecular weight (MW) d extran sulfate and chondroitin sulfate A, but not other anionic polysa ccharides of similar structure and/or charge density. These data were consistent with the RBC adhesive molecule being a sulfated glycolipid. Therefore. TSP-binding lipids from normal and sickle RBCs were isolat ed and characterized. The TSP-binding lipid was purified by alkaline m ethanolysis, anion exchange chromatography and preparative thin layer chromatography (TLC). A homogeneous band on TLC was identified using a specific overlay TSP-binding assay. TSP binding to the purified lipid was stable to base and neuraminidase treatment, labile to acid treatm ent, and was inhibited by high MW dextran sulfate, similar to that see n with intact RBCs binding to immobilized TSP under conditions of flow . In addition, soluble laminin bound to the purified RBC lipid. This a cidic TSP- and laminin-binding lipid(s) isolated from both sickle and normal RBC membranes may contribute to erythrocyte interactions with t he subendothelial matrix, thereby participating in the pathogenesis of vaso-occlusive diseases. (C) 1996 by The American Society of Hematolo gy.