Zymosan phagocytosis by mouse peritoneal macrophages is increased by apoHDL- and not by intact HDL-covered particles

The uptake of lipids and lipoprotein particles by macrophages undergoes pha gocytic activation and the formation of foam cells are key events in athero sclerosis. In this study we determined how intact high density lipoproteins (HDL) and apolipoproteins-HDL (removal of the lipid component from HDL, i. e., apoHDL) influence the phagocytosis of zymosan by mouse peritoneal macro phages. Zymosan particles preincubated together with lipoproteins or alone (control) were incubated with the macrophages. Phagocytosis activity was re ported as the percent of macrophages that internalized three or more zymosa n particles. HDL co-incubated with zymosan did not influence the overall up take of zymosan particles compared to apoHDL, which greatly enhanced the ab ility of the particle to be phagocytized (P<0.001). Part of this effect mig ht be related to a greater binding of apoHDL to the particles compared to t hat of HDL (P<0.05). We conclude that this can be a useful method to study the ability of lipoproteins, including modified lipoproteins obtained from subjects with genetic forms of hyperlipidemia, to opsonize particles such a s red blood cells and thus to investigate the processes that control the fo rmation of foam cells and the mechanisms of atherogenesis.