Inflammation is pivotal to atherosclerosis. The monocyte-macrophage, a crucial cell in atherogenesis, is present during all stages of atherosclerosis. However, there is a paucity of data comparing circulating monocytes to cholesterol-laden macrophages (foam cells), with regard to their atherogenic properties, especially in subjects with established risk factors such as hyperlipidemia.
To determine whether the circulating blood monocyte is representative of the cholesterol-loaded macrophage with regard to its proatherogenicity in healthy controls and hyperlipidemic patients.
Fasting blood was drawn from 32 subjects (n = 16 controls and n = 16 hyperlipidemic patients), and peripheral blood monocytes were obtained. Also, macrophages were cultured and loaded with acetyl low-density lipoprotein on day 10. Day 1 peripheral blood monocytes and day 11 cholesterol-loaded macrophages were assessed for release of superoxide anion and cytokines (interleukin 1, interleukin 6, tumor necrosis factor alpha); surface expression of CD11b, VLA-4, and CD40; and adhesion to human endothelium.
Monocyte and cholesterol-loaded macrophage superoxide anion release, cytokines, and adhesion of monocytes to human endothelium were significantly increased in hyperlipidemic patients compared with controls. Furthermore, following cholesterol loading, there were no significant differences in monocyte versus cholesterol-loaded macrophage activity (P = .71). Also, CD14 and CD11b surface expression on monocytes was significantly increased in hyperlipidemic patients as compared with controls. The magnitude of change in the monocytes versus cholesterol-loaded macrophages was similar.
From these studies, we can conclude that the monocyte, which is readily accessible, is an appropriate cell to study for modulation of proatherogenic activity, especially with regard to genomic and proteomic analyses/ microarrays.