EVIDENCE THAT THE LIPID MOIETY OF OXIDIZED LOW-DENSITY-LIPOPROTEIN PLAYS A ROLE IN ITS INTERACTION WITH MACROPHAGE RECEPTORS

The binding of oxidatively damaged red blood cells (OxRBCs) to residen t mouse peritoneal macrophages correlates with an increase in phosphat idylserine on the external leaflet of the plasma membrane. Liposomes r ich in phosphatidylserine can inhibit this binding and also the bindin g of certain apoptotic cells, We have shown previously that oxidized l ow density lipoproteins (OxLDL) also can inhibit the binding of OxRBCs to resident mouse peritoneal macrophages. The present studies show th at microemulsions prepared from the lipids extracted from OxLDL are ve ry effective in inhibiting the binding of OxRBCs and also, to a lesser extent, of apoptotic thymocytes to macrophages. OxRBC binding was als o inhibited by cholesterol phospholipid liposomes containing oxidized 1-stearoyl-2-linoleoyl-phosphatidylcholine. The binding and uptake of I-125-labeled OxLDL were also strongly inhibited by microemulsions of the lipids extracted from OxLDL and by cholesterol phospholipid liposo mes containing oxidized 1-palmitoyl-2-arachidonoyl-phosphatidylcholine . Earlier studies have shown that the delipidated protein moiety of Ox LDL can competitively inhibit macrophage binding of intact OxLDL, impl icating the protein moiety as an effective receptor-binding domain of OxLDL with respect to some macrophage scavenger receptors, The present studies suggest that the lipid moiety of OxLDL may also play a role.