Liver X receptors inhibit macrophage proliferation through downregulation of cyclins D1 and B1 and cyclin-dependent kinases 2 and 4

J Immunol. 2011 Apr 15;186(8):4656-67. doi: 10.4049/jimmunol.1000585. Epub 2011 Mar 11.

Abstract

Macrophages serve essential functions as regulators of immunity and homeostasis, and their proliferation contributes to pathogenesis of certain disorders. In this report, we show that induction of macrophage proliferation by the growth factor M-CSF is negatively modulated by agonists that activate the nuclear receptor liver X receptor (LXR), both in vitro and in vivo. Both isoforms LXR α and β are involved in the antiproliferative actions of LXR ligands in macrophages. In contrast, M-CSF does not exert negative effects on LXR-mediated gene expression. Treatment with LXR agonists results in the accumulation of macrophages in the G(0)/G(1) phase of the cell cycle without affecting ERK-1/2 phosphorylation. The use of small interfering RNA or genetically modified mice revealed that, in contrast to other cellular models, functional expression of either the cyclin-dependent kinase inhibitor p27KIP1 or the cholesterol transporters ATP-binding cassette A1 or ATP-binding cassette G1 was not required for the antiproliferative effects of LXR agonists in macrophages. Western blot analysis revealed that protein expression of key molecules that regulate progression through the cell cycle, such as cyclins D1 and B1 and cyclin-dependent kinases 2 and 4, was downregulated upon LXR activation. These observations suggest a role for LXR agonists in limiting macrophage proliferative responses associated to pathogenic disorders.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Benzoates / pharmacology
  • Benzylamines / pharmacology
  • Blotting, Western
  • Cell Cycle / drug effects
  • Cell Proliferation*
  • Cells, Cultured
  • Cyclin B1 / metabolism
  • Cyclin D1 / metabolism
  • Cyclin-Dependent Kinase 2 / metabolism
  • Cyclin-Dependent Kinase 4 / metabolism
  • Cyclin-Dependent Kinases / metabolism*
  • Cyclins / metabolism*
  • Down-Regulation
  • Flow Cytometry
  • HEK293 Cells
  • Humans
  • Hydrocarbons, Fluorinated / pharmacology
  • L Cells
  • Liver X Receptors
  • Macrophage Colony-Stimulating Factor / pharmacology
  • Macrophages / cytology
  • Macrophages / drug effects
  • Macrophages / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Orphan Nuclear Receptors / agonists
  • Orphan Nuclear Receptors / genetics
  • Orphan Nuclear Receptors / metabolism*
  • Protein Isoforms / agonists
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Sulfonamides / pharmacology

Substances

  • Benzoates
  • Benzylamines
  • Cyclin B1
  • Cyclins
  • GW 3965
  • Hydrocarbons, Fluorinated
  • Liver X Receptors
  • NR1H3 protein, human
  • Nr1h3 protein, mouse
  • Orphan Nuclear Receptors
  • Protein Isoforms
  • Sulfonamides
  • T0901317
  • Cyclin D1
  • Macrophage Colony-Stimulating Factor
  • Cyclin-Dependent Kinase 2
  • Cyclin-Dependent Kinase 4
  • Cyclin-Dependent Kinases