Introduction Cardiovascular disease, especially atherosclerosis and related pathologies, is one of the leading causes of death globally. It is well established that macrophages play a crucial role in the formation and progression of atherosclerotic plaques. Macrophages are very plastic and can alter their phenotypes and functions according to their environment. Distinct macrophage phenotypes within atherosclerotic plaques have been described. Different macrophage phenotypes can have different functional characteristics and their contributions towards lesion development are not well understood. Hence, a better understanding of the functional characteristics of macrophage phenotypes could potentially lead to novel treatment methods. The aim of our study was to characterise five different macrophage phenotypes, namely M^IFNγ-LPS, M^IL4, M^IL10, M^oxPAPC and M^CXCL4 for their ability to metabolise lipids and propensity to form foam cells.

Methods Macrophages were differentiated from blood monocytes with 100 ng/ml macrophage colony-stimulating factor in RPMI media containing fetal bovine serum for 7 days before they were polarised to selected phenotypes by treating with 20ng/ml rhIFNg + 100ng/ml LPS, 20ng/ml rhIL-4, 20 ng/ml rhIL-10, 25 μg/ml oxPAPC or 1 μM rhCXCL4 for 24 h. Unpolarised macrophages were used as control. Lipid uptake was tested by FACS using 488-labelled AcLDL. Foam cell formation was induced with 25 μg/ml AcLDL and stained with Oil-red-O. Enumeration of foam cells were performed by microscopy. Cholesterol efflux was measured by TopFluor labelled cholesterol based assay. The cell surface expression of ABCA1 and ABCG1 was measured by FACS.

Results Our data summarised in the following table.

Conclusion Distinct polarised macrophage phenotypes exhibit significant differences in uptake and handling of AcLDL, suggesting their differential contribution to disease development and progression. The identification of these phenotypes in human atherosclerotic plaques is currently under investigation.