title: Cholesterol efflux is LXRα isoform-dependent in human macrophages.
abstract: BACKGROUND
  The nuclear receptor liver X receptor (LXR) has two isoforms: LXRα and LXRβ. LXR activation promotes cholesterol efflux in macrophages, but the relative importance of each LXR isoform in mediating cholesterol efflux remains elusive.
  
  
  METHODS
  We evaluated the ability of different doses of LXRs agonist T0901317 to affect cholesterol efflux in human macrophages and its relationship with mRNA and protein levels of several well-characterized proteins involved in cholesterol efflux, including ABCA1, ABCG1, SR-BI, LXRβ and LXRα, using quantitative real-time PCR, Western blotting, and siRNA techniques.
  
  
  RESULTS
  Here we show that LXRα rather than LXRβ sustains baseline cholesterol efflux in human blood-derived macrophages. Treatment of human macrophages with a non-isoform-specific LXR agonist T0901317 substantially increased HDL- and apoA-I-mediated cholesterol efflux, which was associated with increased mRNA and protein expression levels of ABCA1, ABCG1, SR-BI, LXRα and LXRβ. The siRNA- mediated silencing of LXRα, but not LXRβ significantly reduced the protein levels of ABCA1,ABCG1, and SR-BI as wellas HDL- and ApoA1-mediated cholesterol in human macrophages.
  
  
  CONCLUSIONS
  These findings imply that LXRα- rather than LXRβ- specific agonists may promote reverse cholesterol transport in humans.
authors.forename: A Zhi Sha
authors.initials: AZ
authors.lastname: Ma
authors.affiliation: Department of Cardiology, Southwest Hospital, The Third Military Medical University, Chongqing, China. zysong2010@126.com.
authors.forename: Zhi Yuan
authors.initials: ZY
authors.lastname: Song
authors.forename: Qian
authors.initials: Q
authors.lastname: Zhang
mesh_terms: D001692:Biological Transport; D015153:Blotting, Western; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D006801:Humans; D006845:Hydrocarbons, Fluorinated / Q000494:pharmacology; D000071518:Liver X Receptors; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D057093:Orphan Nuclear Receptors / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D014162:Transfection; D005466:Fluorocarbons; D000096926:Benzenesulfonamides
chemical_list: D002784:Cholesterol; D006845:Hydrocarbons, Fluorinated; D000071518:Liver X Receptors; D057093:Orphan Nuclear Receptors; D020033:Protein Isoforms; D012333:RNA, Messenger; D013449:Sulfonamides; C000605213:NR1H3 protein, human; C423915:T0901317; D005466:Fluorocarbons; D000096926:Benzenesulfonamides