A Cytofluorometric Study of Membrane Rafts in Human Monocyte Subsets in Atherosclerosis

The peripheral blood monocytes of atherosclerotic patients are pre-activated and have some of the features of tissue macrophages. Their adhesion to the endothelium is 1.5 times higher than that of monocytes from healthy subjects, and they express a number of receptors and antigens typical of tissue macrophages. Additionally, earlier we showed that the biosynthesis of gangliosides, whose main function is the formation of membrane rafts, is significantly activated in blood monocytes from atherosclerotic patients, as well as during the in vitro differentiation of normal monocytes into macrophages. In this study, we investigated the expression of membrane rafts on various monocyte subsets from healthy subjects and atherosclerotic patients. Based on flow cytometry results, the monocytes in the examined atherosclerotic patients were found to differ from those in healthy subjects by a twofold increase in the proportion of the intermediate subset (CD14(++)/CD16(+)) and by enhancement in the expression of the fractalkine receptor CX3CR1 on the intermediate and non-classical subsets (CD14(++)/CD16(+) and CD14(+)/CD16(++)) (2.3 and 1.8 times, respectively). This suggests a pre-activated state of monocytes in atherosclerotic patients. At the same time, the expression of the membrane raft marker on the monocyte subsets was similar in both studied groups. However, a study of the in vitro differentiation of monocytes into macrophages showed that the membrane raft expression increased 2 times as early as on the 1st day of culturing and 3 times on the 7th day compared to that in freshly isolated monocytes. Therefore, it is suggested that monocytes in atherosclerosis accumulate gangliosides that are used to form membrane rafts during the macrophage differentiation after the migration of monocytes into the arterial intima.