PPARγ-independent thiazolidinedione-mediated inhibition of NUR77 expression in vascular endothelial cells

J Endocrinol. 2011 Jan;208(1):R1-7. doi: 10.1677/JOE-10-0393. Epub 2010 Oct 26.

Abstract

The thiazolidinediones (TZDs) have been reported to reduce atherogenesis in preclinical models and atherosclerosis in clinical trials in pre-diabetic and diabetic patients. Although peroxisome proliferator-activated receptor γ (PPARγ)-mediated effects on gene expression have been thought responsible for this effect, a complete understanding of the molecular mechanisms responsible remains to be fully elucidated. We have previously reported PPARγ-independent modulation of NUR77 (also known as Nr4a1), an orphan nuclear receptor deemed important in the atherogenic process, in association with TZD-mediated inhibition of tumour necrosis factor α (TNFα) induction of plasminogen activator inhibitor type 1 expression. Here, we report NUR77 mRNA expression is increased in human vascular endothelial cells (HUVEC) stimulated by TNFα and that this effect is inhibited by a TZD in a PPARγ-independent manner. TZD treatment of HUVEC also inhibited the stimulatory effects of TNFα on NUR77 promoter activity, again in a PPARγ-independent manner, confirming the transcriptional nature of this effect. TZD treatment also attenuated the binding of nuclear proteins to the nuclear factor kappa B (NF-κB)-binding site of the NUR77 promoter in HUVEC in a PPARγ-independent manner. In addition, TZD treatment also inhibited TNFα-mediated induction of NF-κB1 mRNA expression. Our results suggest a potential PPARγ-independent molecular mechanism for the anti-atherogenic effects of TZDs involving NF-κB-mediated transcriptional inhibition of cytokine-mediated induction of the orphan nuclear receptor NUR77 in HUVEC.

MeSH terms

  • Analysis of Variance
  • Cells, Cultured
  • Electrophoretic Mobility Shift Assay
  • Endothelial Cells / drug effects
  • Endothelial Cells / metabolism*
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / drug effects
  • Endothelium, Vascular / metabolism*
  • Humans
  • Nuclear Receptor Subfamily 4, Group A, Member 1 / genetics
  • Nuclear Receptor Subfamily 4, Group A, Member 1 / metabolism*
  • PPAR gamma / genetics
  • PPAR gamma / metabolism*
  • Promoter Regions, Genetic / drug effects
  • Reverse Transcriptase Polymerase Chain Reaction
  • Thiazolidinediones / pharmacology*
  • Transfection
  • Tumor Necrosis Factor-alpha / pharmacology

Substances

  • Nuclear Receptor Subfamily 4, Group A, Member 1
  • PPAR gamma
  • Thiazolidinediones
  • Tumor Necrosis Factor-alpha