Figure 6. Schematic representation of vitamin D regulation of nascent HDL formation and macrophage polarization via promoting cholesterol efflux in hepatocytes and macrophage-derived foam cells.

In hepatocytes (Left), the 1,25(OH)₂D₃ increases CYP27A1 expression as well as the production of the endogenous LXR ligand, 27-hydroxycholesterol(27HOC), which stimulated ABCA1-mediated cholesterol efflux and nascent HDL formation. In macrophages-derived foam cells (Right), 1,25(OH)₂D₃ markedly induced CYP27A1 expression and increased 27HOC levels, which induced LXRα, ABCA1 and ABCG1 expression, stimulated intercellular cholesterol efflux, reduced the cholesterol accumulation and attenuated LPS induced M1-polarization via a VDR-dependent JNK/SAPK signal manner.