Palmitate and minimally-modified low-density lipoprotein cooperatively promote inflammatory responses in macrophages

Increased consumption of Western-type diets and environmental insults lead to wide-spread increases in the plasma levels of saturated fatty acids and lipoprotein oxidation. The aim of this study is to examine whether palmitate and minimally modified low-density lipoprotein (mmLDL) exert an additive effect on macrophage activation. We found that CXCL2 and TNF-α secretion as well as ERK and p38 phosphorylation were additively increased by co-treatment of J774 macrophages with palmitate and mmLDL in the presence of lipopolysaccharide (LPS). Furthermore, the analysis of differentially expressed genes using the KEGG database revealed that several pathways, including cytokine-cytokine receptor interaction, and genes were significantly altered. These results were validated with real-time PCR, showing upregulation of Il-6, Csf3, Il-1β, and Clec4d. The present study demonstrated that palmitate and mmLDL additively potentiate the LPS-induced activation of macrophages. These results suggest the existence of synergistic mechanisms by which saturated fatty acids and oxidized lipoproteins activate immune cells.