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Signaling pathways involved in TRAIL-induced rheumatoid arthritis synovial fibroblast proliferation

  • J Morel
  • R Audo
  • B Combe
Poster presentation
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Keywords

Rheumatoid Arthritis Synovial Fibroblast Inhibitor PD98059 Induce Cell Proliferation Rheumatoid Arthritis Synovial Fibroblast 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Tumor necrosis factor alpha-related apoptosis inducing ligand (TRAIL) is a pro-apoptotic factor that can also induce cell proliferation. The role of TRAIL in rheumatoid arthritis (RA) is still unclear. Previously, we reported that TRAIL induces RA fibroblast-like synoviocyte (FLS) proliferation. We now investigate the intracellular mechanisms involved in TRAIL-induced cell proliferation. Therefore, we tested the effect of TRAIL on signaling pathways including MAP kinases (p38 and ERK1/2) and PI3 kinase/Akt, known to control cell proliferation. For all these experiments, the concentration of TRAIL used to stimulate cell was 0.5 nM. TRAIL induced p38 MAP kinase but with a lower intensity in comparison with tumor necrosis factor alpha (TNF-α) (n = 3). TRAIL also induced ERK1/2 and Akt phosphorylation in RA FLS in a time-dependent manner, showing maximum activation between 5 and 10 min by western blot (n = 3). This kinetic and intensity of ERK and Akt activation were similar to positive control TNF-α (n = 3). The transcription factor NF-κB plays a major role in cell survival and is activated by MAP kinases and Akt. When NF-κB is activated, it translocates from the cytoplasm to the nucleus. We examined NF-κB translocation into the nucleus of RA FLS following TRAIL stimulation using immunofluorescence. RA FLS treated with TRAIL did not induce a nuclear uptake of NF-κB (n = 3). The percentages of RA FLS-positive NF-κB translocation was increased from 4.3 ± 0.9% to 8.9 ± 2.3% when stimulated with TRAIL. For the positive control IL-1β, this percentage increased to 97.9 ± 1.1%. This result was confirmed by western blot. To determine the implication of MAP kinases, and PI3 kinase/Akt in TRAIL-induced proliferation, we therefore tested different specific signaling inhibitors including PI3 kinase inhibitor LY294002, ERK1/2 inhibitor PD98059, and p38 inhibitor SB203580. RA FLS were pretreated with the specific inhibitors at different concentrations or Me2SO vehicle control for 1 hour and were then stimulated with TRAIL. Proliferation was assessed according to the level of incorporated tritiated thymidine. ERK 1/2 inhibitor PD98059 and p38 inhibitor SB203580 significantly downregulated TRAIL-induced proliferation in a dose-dependent manner (n = 3). PI3 kinase inhibitor LY294002 almost completely blocked proliferation promoted by TRAIL. These results highlight the main role of Akt in TRAIL-mediated proliferation.

Copyright information

© BioMed Central Ltd 2005

Authors and Affiliations

  • J Morel
    • 1
    • 2
  • R Audo
    • 2
  • B Combe
    • 1
    • 2
  1. 1.CHU LapeyronieMontpellierFrance
  2. 2.INSERM U454MontpellierFrance

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