The interaction of human apoB-containing lipoproteins with mouse peritoneal macrophages: a comparison of Lp(a) with LDL.

Abstract

Cholesteryl ester accumulation in macrophages and foam cell formation is believed to play an important role in atherogenesis. The effect of Lp(a) on the incorporation of [14C]oleate into cholesteryl esters was studied in mouse peritoneal macrophages. In view of the physico-chemical similarities between Lp(a) and LDL, the results were compared with those obtained with LDL. Native Lp(a) and LDL did not stimulate cholesteryl ester formation. Incubation of macrophages with Lp(a)- or LDL-dextran sulfate complexes caused a significant increase in cholesteryl ester formation. A similar effect was observed when Lp(a) or LDL were incubated with macrophages in the presence of antibodies directed against the specific Lp(a) apoprotein or against LpB. Treatment of Lp(a) with acetic anhydride or malondialdehyde (MDA) was followed by precipitation of most of the lipoprotein. Therefore, these modifications were not suitable to study the uptake of modified Lp(a) by macrophages. Studies with acetyl-LDL or MDA-treated LDL caused the well-known stimulation of [14C]oleate incorporation into cholesteryl esters. Thus, the modification of Lp(a) by sulfated polysaccharides or by treatment with antibodies yields similar cholesteryl ester deposition in mouse peritoneal macrophages as observed with modified LDL. This might be one mechanism by which Lp(a) exerts its atherogenicity.