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Rho protein inhibition blocks cyclooxygenase-2 expression by proinflammatory mediators in endothelial cells

Bernd Schmeck1, Marco Brunsch, Joachim Seybold

  • 1Charité, Department of Internal Medicine, Humboldt-University, Berlin, Germany.

Inflammation
|June 12, 2003
PubMed

Insights

Rho proteins regulate inflammatory gene expression. Inhibiting RhoA, Rac1, and Cdc42 prevented lipopolysaccharide-induced cyclooxygenase-2 (COX-2) expression in endothelial cells by blocking nuclear factor-kappaB activation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Immunology

Background:

  • Rho proteins are key regulators of inflammatory gene expression in endothelial cells.
  • Cyclooxygenase-2 (COX-2) plays a critical role in inflammatory processes.
  • Understanding the upstream regulators of COX-2 is crucial for developing anti-inflammatory strategies.

Purpose of the Study:

  • To investigate the role of RhoA, Rac1, and Cdc42 in the regulation of cyclooxygenase-2 (COX-2) expression in endothelial cells.
  • To determine the impact of Rho protein inhibition on lipopolysaccharide (LPS)- and tumor necrosis factor-alpha (TNFα)-induced COX-2 expression.
  • To elucidate the signaling pathways, specifically nuclear factor-kappaB (NF-κB), involved in Rho-mediated COX-2 regulation.

Main Methods:

  • Endothelial cells (EC) were treated with Clostridium difficile toxin B-10643 (TcdB-10643) to inhibit RhoA, Rac1, and Cdc42.
  • COX-2 and COX-1 protein levels were assessed following stimulation with LPS or TNFα.
  • NF-κB activation was measured to evaluate its dependence on Rho proteins.
  • The release of 6-ketoprostaglandin F1α (6k-PGF1α), a product of COX-2 activity, was quantified under various experimental conditions.

Main Results:

  • TcdB-10643 pretreatment prevented LPS- or TNFα-induced COX-2 expression but did not affect COX-1 levels.
  • Inhibition of Rho proteins suppressed LPS-dependent NF-κB activation.
  • Rho inactivation blocked the release of 6k-PGF1α induced by arachidonic acid, thrombin, and E. coli hemolysin (HlyA) when performed before LPS stimulation.
  • Rho inhibition did not affect COX-2-dependent 6k-PGF1α release when TcdB-10643 was added after LPS or TNFα stimulation.

Conclusions:

  • RhoA, Rac1, and Cdc42 are essential for NF-κB-dependent induction of COX-2 (encoded by PGHS-2) in endothelial cells stimulated by LPS and TNFα.
  • Rho proteins do not influence the enzymatic activity of expressed COX-1 or COX-2.
  • These findings highlight Rho proteins as critical upstream regulators of inflammatory mediator production in endothelial cells.

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