1. Academic Validation
  2. 27-hydroxycholesterol is an endogenous ligand for liver X receptor in cholesterol-loaded cells

27-hydroxycholesterol is an endogenous ligand for liver X receptor in cholesterol-loaded cells

  • J Biol Chem. 2001 Oct 19;276(42):38378-87. doi: 10.1074/jbc.M105805200.
X Fu 1 J G Menke Y Chen G Zhou K L MacNaul S D Wright C P Sparrow E G Lund
Affiliations

Affiliation

  • 1 Department of Atherosclerosis and Endocrinology, and Metabolic Research, Merck Research Laboratories, Rahway, New Jersey 07065, USA.
Abstract

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.

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