27-hydroxycholesterol is an endogenous ligand for liver X receptor in cholesterol-loaded cells.
The nuclear receptors liver X receptor alpha (LXRalpha) (NR1H3) and LXRbeta (NR1H2) are important regulators of genes involved in lipid metabolism, including ABCA1, ABCG1, and sterol regulatory element-binding protein-1c (SREBP-1c). Although it has been demonstrated that oxysterols are LXR ligands, little is known about the identity of the physiological activators of these receptors. Here we confirm earlier studies demonstrating a dose-dependent induction of ABCA1 and ABCG1 in human monocyte-derived macrophages by cholesterol loading. In addition, we show that formation of 27-hydroxycholesterol and cholestenoic acid, products of CYP27 action on cholesterol, is dependent on the dose of cholesterol used to load the cells. Other proposed LXR ligands, including 20(S)-hydroxycholesterol, 22(R)-hydroxycholesterol, and 24(S),25-epoxycholesterol, could not be detected under these conditions. A role for CYP27 in regulation of cholesterol-induced genes was demonstrated by the following findings. 1) Introduction of CYP27 into HEK-293 cells conferred an induction of ABCG1 and SREBP-1c; 2) upon cholesterol loading, CYP27-expressing cells induce these genes to a greater extent than in control cells; 3) in CYP27-deficient human skin fibroblasts, the induction of ABCA1 in response to cholesterol loading was ablated; and 4) in a coactivator association assay, 27-hydroxycholesterol functionally activated LXR. We conclude that 27-hydroxylation of cholesterol is an important pathway for LXR activation in response to cholesterol overload.
Fu
X
X
Department of Atherosclerosis and Endocrinology, and Metabolic Research, Merck Research Laboratories, Rahway, New Jersey 07065, USA.
Menke
J G
JG
Chen
Y
Y
Zhou
G
G
MacNaul
K L
KL
Wright
S D
SD
Sparrow
C P
CP
Lund
E G
EG
D064286:ATP Binding Cassette Transporter 1; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D002478:Cells, Cultured; D002783:Cholestenones / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D008078:Cholesterol, LDL / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D006888:Hydroxycholesterols / Q000378:metabolism*; D008024:Ligands; D000071518:Liver X Receptors; D008264:Macrophages / Q000378:metabolism; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012867:Skin / Q000378:metabolism; D051780:Sterol Regulatory Element Binding Protein 1; D013997:Time Factors; D014157:Transcription Factors; D014162:Transfection; D019294:Xanthomatosis, Cerebrotendinous / Q000378:metabolism
C577836:ABCA1 protein, human; C419353:ABCG1 protein, human; D064286:ATP Binding Cassette Transporter 1; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters; D022762:CCAAT-Enhancer-Binding Proteins; D002783:Cholestenones; D008078:Cholesterol, LDL; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D006888:Hydroxycholesterols; D008024:Ligands; D000071518:Liver X Receptors; C000605210:NR1H2 protein, human; C000605213:NR1H3 protein, human; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; C497387:SREBF1 protein, human; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; C076996:27-hydroxycholesterol; D002784:Cholesterol