Suppression of inducible nitric oxide synthase and cyclooxygenase-2 gene expression by 22(R)-hydroxycholesterol requires de novo protein synthesis in activated macrophages

J Steroid Biochem Mol Biol. 2005 Dec;97(4):376-83. doi: 10.1016/j.jsbmb.2005.06.030. Epub 2005 Sep 16.

Abstract

Liver X receptors (LXRs) play an important role in lipid metabolism. Recently, a role for these proteins was identified in suppressing the inflammatory response. However, it is not known whether the natural ligands of LXRs, e.g. 22(R)-hydroxycholesterol (22R-HC), can suppress the inflammatory response after the onset of inflammation. We demonstrate here that treatment of Lipopolysaccharide (LPS)-activated RAW264.7 macrophages with 22R-HC markedly suppressed nitric oxide (NO) production and inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) mRNA expression. Additionally, 22R-HC did not affect the DNA binding activity of NF-kappaB, AP-1 and C/EBP(s), important transcriptional factors for iNOS and COX-2 genes expression. Furthermore iNOS and COX-2 mRNA suppression by 22R-HC was diminished by cellular treatment with cycloheximide. These results suggest that 22R-HC suppresses the expression of iNOS and COX-2 genes through de novo protein synthesis of an unidentified protein in LPS-activated macrophages.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CCAAT-Enhancer-Binding Proteins / metabolism
  • Cell Line
  • Cells, Cultured
  • Cyclooxygenase 2 / metabolism*
  • Cyclooxygenase Inhibitors / pharmacology*
  • DNA / chemistry
  • DNA-Binding Proteins / metabolism
  • Gene Expression Regulation, Enzymologic*
  • Glucocorticoids / metabolism
  • Hydroxycholesterols / pharmacology*
  • Inflammation
  • Ligands
  • Lipopolysaccharides / chemistry
  • Lipopolysaccharides / metabolism
  • Liver X Receptors
  • Macrophage Activation
  • Macrophages / metabolism*
  • Mice
  • Models, Statistical
  • NF-kappa B / metabolism
  • Nitric Oxide / metabolism
  • Nitric Oxide Synthase Type II / antagonists & inhibitors*
  • Nitrites / metabolism
  • Orphan Nuclear Receptors
  • Protein Binding
  • Proteins / metabolism*
  • RNA / chemistry
  • RNA / metabolism
  • RNA, Messenger / metabolism
  • Receptors, Cytoplasmic and Nuclear / metabolism
  • Time Factors
  • Transcription Factor AP-1 / metabolism
  • Transcription, Genetic

Substances

  • CCAAT-Enhancer-Binding Proteins
  • Cyclooxygenase Inhibitors
  • DNA-Binding Proteins
  • Glucocorticoids
  • Hydroxycholesterols
  • Ligands
  • Lipopolysaccharides
  • Liver X Receptors
  • NF-kappa B
  • Nitrites
  • Orphan Nuclear Receptors
  • Proteins
  • RNA, Messenger
  • Receptors, Cytoplasmic and Nuclear
  • Transcription Factor AP-1
  • 22-hydroxycholesterol
  • Nitric Oxide
  • RNA
  • DNA
  • Nitric Oxide Synthase Type II
  • Cyclooxygenase 2