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Rac mediates TNF-induced cytokine production via modulation of NF-kappaB

Lynn M Williams1, Ferdinand Lali, Kate Willetts

  • 1Kennedy Institute of Rheumatology Division, Imperial College London, Hammersmith, London W6 8LH, United Kingdom. lynn.williams@imperial.ac.uk

Molecular Immunology
|February 9, 2008
PubMed

Insights

Tumor necrosis factor (TNF) triggers inflammatory cytokine production via the Rho GTPase Rac. Rac activation is upstream of NF-kappaB, inhibiting cytokine synthesis in inflammatory diseases.

Area of Science:

  • Molecular Biology
  • Immunology
  • Cell Signaling

Background:

  • Tumor necrosis factor (TNF) is a critical mediator in various inflammatory diseases.
  • Pro-inflammatory cytokine synthesis, including Interleukin-6 (IL-6) and Interleukin-8 (IL-8), is a hallmark of these conditions.

Purpose of the Study:

  • To elucidate the role of Rho GTPase Rac in TNF-induced pro-inflammatory cytokine synthesis.
  • To investigate the signaling pathways, including Mitogen-Activated Protein Kinase (MAPK) and Nuclear Factor-kappaB (NF-kappaB), involved in TNF-mediated inflammation.

Main Methods:

  • Utilized dominant-negative Rac expression to inhibit Rac activity.
  • Employed luciferase-reporter assays and Electrophoretic Mobility Shift Assays (EMSA) to assess NF-kappaB activity.
  • Analyzed MAPK kinase activation (p42/44, p54, p38, JNK) and p65 phosphorylation.

Main Results:

  • Dominant-negative Rac significantly inhibited TNF-induced p42/44 MAPK activation but not JNK or p38 MAPK.
  • Rac inhibition completely abrogated TNF-induced NF-kappaB activity.
  • Inhibition of the Extracellular signal-Regulated Kinase (ERK) pathway reduced NF-kappaB activity and p65 phosphorylation.

Conclusions:

  • TNF-induced pro-inflammatory cytokine production (IL-6, IL-8) is mediated by the Rho GTPase Rac.
  • Rac activation is upstream of NF-kappaB activation, playing a crucial role in the inflammatory signaling cascade.
  • Targeting the Rac-NF-kappaB pathway offers a potential therapeutic strategy for inflammatory diseases.

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