Volume 14 Supplement 1

Proceedings of the 8th Global Arthritis Research Network (GARN) Meeting and 1st Bio-Rheumatology International Congress (BRIC)

Open Access

Egr-1 mediates the suppressive effect of IL-1 on PPARg expression in human OA chondrocytes

  • Sarah S Nebbaki1,
  • Fatima Ezzahra El Mansouri1,
  • Mohamed Benderdour1,
  • Johanne Martel-Pelletier1,
  • Jean-Pierre Pelletier1 and
  • Hassan Fahmi1
Arthritis Research & Therapy201214(Suppl 1):P12

DOI: 10.1186/ar3613

Published: 29 February 2012

Background

Peroxisome proliferator-activated receptor gamma (PPARg) is a ligand activated transcription factor and member the nuclear hormone receptor superfamily. Several lines of evidence indicate that PPARg have protective effects in osteoarthritis (OA). Indeed, PPARg has been shown to down-regulate several inflammatory and catabolic responses in articular joint cells and to be protective in animal models of OA. We have previously shown that IL-1 down-regulated PPARg expression in OA chondrocytes. In the present study we will investigate the mechanisms underlying this effect of IL-1.

Materials and methods

Chondrocytes were stimulated with IL-1, and the level of PPARg and Egr-1 protein and mRNA were evaluated using Western blotting and real-time reverse-transcription polymerase chain reaction, respectively. The PPARg promoter activity was analyzed in transient transfection experiments. Egr-1 recruitment to the PPARg promoter was evaluated using chromatin immunoprecipitation (ChIP) assays.

Results

We demonstrated that the suppressive effect of IL-1 on PPARg expression requires de novo protein synthesis and was concomitant with the induction of the transcription factor Egr-1. ChIP analyses revealed that IL-1 induced Egr-1 recruitment at the PPARg promoter. IL-1 inhibited the activity of PPARg promoter and overexpression of Egr-1 potentiated the inhibitory effect of IL-1, suggesting that Egr-1 may mediate the suppressive effect of IL-1.

Conclusions

These results indicate that Egr-1 contributes to IL-1-mediated down-regulation of PPARg expression in OA chondrocytes and suggest that this pathway could be a potential target for pharmacologic intervention in the treatment of OA and possibly other arthritic diseases.

Authors’ Affiliations

(1)
Osteoarthritis Research Unit

Copyright

© Nebbaki et al.; licensee BioMed Central Ltd. 2012

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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