Repression of peroxisome proliferator-activated receptor gamma by mucosal ribotoxic insult-activated CCAAT/enhancer-binding protein homologous protein

J Immunol. 2010 Nov 1;185(9):5522-30. doi: 10.4049/jimmunol.1001315. Epub 2010 Oct 1.

Abstract

CCAAT/enhancer-binding protein homologous protein (CHOP) is a crucial stress-responsive factor in various mucosal injuries, including cellular translational stress conditions. In this study, chemical ribosome-inactivating stresses were assessed for their effects on stress-inducible CHOP expression and its association with epithelial inflammatory cytokine production. Several representative ribotoxic agents (deoxynivalenol, anisomycin, and 15-acetyldeoxynivalenol) enhanced CHOP expression and its nuclear translocation in human intestinal epithelial cells. Moreover, CHOP was a strong positive regulator of IL-8 production, but CHOP-mediated IL-8 production was inversely associated with expression of the mucosal regulatory factor peroxisome proliferator-activated receptor γ (PPARγ). Based on our recent report that PPARγ is a negative regulator of mRNA stability of IL-8, PPARγ was linked to a notable mRNA stabilizing protein, HuR, since ribotoxin-induced IL-8 mRNA is stabilized by HuR protein. Expression of exogenous PPARγ suppressed ribotoxin-triggered cytoplasmic translocation of HuR. In contrast, PPARγ-regulating CHOP was a positive modulator of HuR protein export from nuclei. Taken together, the results indicate that ribotoxin-induced CHOP protein is positively associated with production of proinflammatory cytokine IL-8, but it downregulates PPARγ action, subsequently allowing the cytosolic translocation of HuR protein and stabilization of IL-8 mRNA in gut epithelial cells. CHOP and PPARγ may represent critical mechanistic links between ribotoxic stress and proinflammatory cytokine production, and they may have a broader functional significance with regard to gastrointestinal stresses by toxic mucosal insults.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anisomycin / toxicity
  • Antigens, Surface / metabolism
  • Blotting, Western
  • Cell Line
  • ELAV Proteins
  • ELAV-Like Protein 1
  • Enzyme-Linked Immunosorbent Assay
  • Gene Expression / drug effects
  • Gene Expression Regulation / immunology*
  • Humans
  • Immunity, Mucosal / genetics
  • Immunity, Mucosal / immunology
  • Interleukin-8 / biosynthesis
  • Interleukin-8 / immunology
  • Intestinal Mucosa / immunology*
  • Intestinal Mucosa / metabolism
  • Microscopy, Confocal
  • PPAR gamma / genetics
  • PPAR gamma / immunology
  • PPAR gamma / metabolism*
  • Protein Synthesis Inhibitors / toxicity
  • RNA-Binding Proteins / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transcription Factor CHOP / biosynthesis*
  • Transcription Factor CHOP / genetics
  • Transcription Factor CHOP / immunology
  • Transfection
  • Trichothecenes / toxicity

Substances

  • Antigens, Surface
  • DDIT3 protein, human
  • ELAV Proteins
  • ELAV-Like Protein 1
  • ELAVL1 protein, human
  • Interleukin-8
  • PPAR gamma
  • Protein Synthesis Inhibitors
  • RNA-Binding Proteins
  • Trichothecenes
  • Transcription Factor CHOP
  • Anisomycin
  • 15-acetyldeoxynivalenol
  • deoxynivalenol