Objective: To study the characterization of THP-1 cell surface apoE in order to learn the further role of macrophage in development of atherosclerosis.
Methods: Using monoclonal antibodies (7C9,3H1) against apoE to analyze the effects of AcLDL, heparin, chondroitinase, and Liposyn II on the apoE of THP-1 cell surface.
Results: Cholesterol (AcLDL) loaded cell demonstrated reduced binding of 125I-7C9 to the cell surface by 19% at 4 degrees C, but if the THP-1 cell incubated at 37 degrees C for 2 hours after the removal of AcLDL there was a increase (25%) in 7C9 bound to loaded cells when compared to the 4 degrees C controls; prior loading with AcLDL also increased the secretion of apoE to the extracellular medium in a time-dependent manner; heparinase or chondroitinase ABC did not reduce the surface apoE associated with unloaded cells; the apoE on the surface of loaded macrophage was only marginally affected (9.3%) by incubation with heparinase but was efficiently reduced (50%) by incubation with chondroitinase ABC; Liposyn II dramatically increased the binding of apoA1 to the cell surface (1.5-1.8 fold), the Liposyn II mediated increased binding of apoA1 was antagonized by pre-incubation of THP-1 cells with 3H1 indicating that it was an apoE-dependent process.
Conclusions: Cell surface apoE of THP-1 macrophage relates to the process of cholesterol loading of macrophage cells and lipid mediated binding of apoA1 to the cell surface. It may affect the process of atherosclerosis development.