Abstract 12930: M1, but Not M2 Macrophages, Characteristically Respond to Oxidized Low-Density Lipoprotein: Transcriptional Analysis in Human Polarized Macrophages
Aim: It has become evident that macrophages have heterogeneous sub-populations, such as the classically activated macrophages (M1) and the alternatively activated macrophages (M2). Both subsets of macrophages are already known to be present in human atherosclerotic plaques, however, their contributions to atherogenesis are not entirely clear. To clarify the involvement of these subsets of macrophages in foam cell formation, we investigated the transcriptional alterations in M1 and M2 macrophages during oxidized low-density lipoprotein (oxLDL) uptake.
Methods: Human monocytes were differentiated into macrophages in the presence of macrophage-colony stimulating factor (M0), followed by polarization toward M1 with interferon-γ and lipopolysaccharide, or toward M2 with interleukin-4. Then, all subsets of macrophages were incubated with or without oxLDL, and the total RNA was extracted and analyzed by cDNA microarray.
Results: In M1 and M2, we identified 1822 and 1882 genes as the significantly up-regulated genes, and 436 and 359 genes as the significantly down-regulated genes, respectively. We further investigated the biological functions and molecular networks using Ingenuity Pathway Analysis. In molecular network analysis, elucidating the strength of relationship among up-regulated molecules, nearly all the molecules in the most strongly relevant molecular network altered by oxLDL were associated to transforming growth factor (TGF)-β in M1 macrophages. In hierarchical cluster analysis, which allows visual comprehension of differential patterns over microarray data, the cluster of genes that were specifically up-regulated in M1 macrophages included molecules related to NF-κB signaling pathway. Conversely, pathway analysis, which is able to show the relationship of molecules by schemes of signal pathways, revealed up-regulation of inhibitor of I-κB in M0 and M2 macrophages.
Conclusions: The data suggested that oxLDL uptake may affect TGF-β- and NF-κB -mediated functions of M1 macrophages, but not of M0 or M2 macrophages. It is likely that M1 macrophages, but not M2 macrophages, characteristically respond to oxLDL.
- © 2011 by American Heart Association, Inc.