Oxidized low-density lipoprotein inhibits the binding of monoclonal antibody to platelet glycoprotein IIb-IIIa

Previous studies have shown that oxidized low-density lipoprotein (LDL) ind uces platelet activation more effectively than native LDL. To achieve a bet ter understanding of the mechanism underlying the activation of human plate lets by oxidized LDL, the present study relates the effect of oxidized LDL to changes of binding characteristics for glycoprotein (GP) IIb-IIIa. Washe d human platelets were treated by monoclonal antibody against GP IIb-IIIa, and the ligand-receptor complexes were revealed by immunocytochemical techn iques on the ultrastructural level. The localization of the antiglycoprotei n IIb-IIIa was time-dependent. After binding to the platelet surface membra ne and open canalicular system, the surface-membrane labeling decreased dur ing longer incubation periods. Preincubation with oxidized LDL inhibited th e binding of antiglycoprotein IIb-IIIa. Our findings suggest that GP IIb-II Ia acts as a receptor for oxidized LDL. The binding of oxidized LDL to the GP IIb-IIIa might be the first step in platelet activation by plasma lipopr oteins. (C) 1999 Elsevier Science Ltd. All rights reserved.