Peroxisome proliferator-activated receptor α controls cellular cholesterol trafficking in macrophages

The mobilization of cholesterol from intracellular pools to the plasma membrane is a determinant that governs its availability for efflux to extracellular acceptors. NPC1 and NPC2 are proteins localized in the late endosome and control cholesterol transport from the lysosome to the plasma membrane. Here, we report that NPC1 and NPC2 gene expression is induced by oxidized LDL ( OxLDL) in human macrophages. Because OxLDLs contain natural activators of peroxisome proliferator-activated receptor alpha (PPAR alpha),a fatty acid-activated nuclear receptor, the regulation of NPC1 and NPC2 by PPAR alpha and the consequences on cholesterol trafficking were further studied. NPC1 and NPC2 expression is induced by synthetic PPAR alpha ligands in human macrophages. Furthermore, PPAR alpha activation leads to an enrichment of cholesterol in the plasma membrane. By contrast, incubation with progesterone, which blocks postlysosomal cholesterol trafficking, as well as NPC1 and NPC2 mRNA depletion using small interfering RNA, abolished ABCA1-dependent cholesterol efflux induced by PPAR alpha activators. These observations identify a novel regulatory role for PPAR alpha in the control of cholesterol availability for efflux that, associated with its ability to inhibit cholesterol esterification and to stimulate ABCA1 and scavenger receptor class B type I expression, may contribute to the stimulation of reverse cholesterol transport.