Rho protein inactivation induced apoptosis of cultured human endothelial cells

Am J Physiol Lung Cell Mol Physiol. 2002 Oct;283(4):L830-8. doi: 10.1152/ajplung.00467.2001.


Small GTP-binding Rho GTPases regulate important signaling pathways in endothelial cells, but little is known about their role in endothelial cell apoptosis. Clostridial cytotoxins specifically inactivate GTPases by glucosylation [Clostridium difficile toxin B-10463 (TcdB-10463), C. difficile toxin B-1470 (TcdB-1470)] or ADP ribosylation (C. botulinum C3 toxin). Exposure of human umbilical cord vein endothelial cells (HUVEC) to TcdB-10463, which inhibits RhoA/Rac1/Cdc42, or to C3 toxin, which inhibits RhoA, -B, -C, resulted in apoptosis, whereas inactivation of Rac1/Cdc42 with TcdB-1470 was without effect, suggesting that Rho inhibition was responsible for endothelial apoptosis. Disruption of endothelial microfilaments as well as inhibition of p160ROCK did not induce endothelial apoptosis. Exposure to TcdB-10463 resulted in activation of caspase-9 and -3 but not caspase-8 in HUVEC. Moreover, Rho inhibition reduced expression of antiapoptotic Bcl-2 and Mcl-1 and increased proapoptotic Bid but had no effect on Bax or FLIP protein levels. Caspase-3 activity and apoptosis induced by TcdB-10463 were abolished by cAMP elevation. In summary, inhibition of Rho in endothelial cells activates caspase-9- and -3-dependent apoptosis, which can be antagonized by cAMP elevation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Diphosphate Ribose / metabolism
  • Apoptosis / drug effects
  • Apoptosis / physiology*
  • BH3 Interacting Domain Death Agonist Protein
  • Bacterial Proteins*
  • Bacterial Toxins / pharmacology
  • CASP8 and FADD-Like Apoptosis Regulating Protein
  • Carrier Proteins / analysis
  • Carrier Proteins / biosynthesis
  • Caspase 3
  • Caspase 9
  • Caspases / metabolism
  • Cells, Cultured
  • Cyclic AMP / metabolism
  • Endothelium, Vascular / chemistry
  • Endothelium, Vascular / cytology*
  • Endothelium, Vascular / metabolism*
  • Humans
  • In Situ Nick-End Labeling
  • Intracellular Signaling Peptides and Proteins*
  • Myeloid Cell Leukemia Sequence 1 Protein
  • Neoplasm Proteins / analysis
  • Neoplasm Proteins / biosynthesis
  • Proto-Oncogene Proteins / analysis
  • Proto-Oncogene Proteins / biosynthesis
  • Proto-Oncogene Proteins c-bcl-2 / analysis
  • Proto-Oncogene Proteins c-bcl-2 / biosynthesis
  • Signal Transduction / physiology
  • Umbilical Veins / cytology
  • bcl-2-Associated X Protein
  • cdc42 GTP-Binding Protein / metabolism
  • rac1 GTP-Binding Protein / metabolism
  • rho GTP-Binding Proteins / metabolism*
  • rhoA GTP-Binding Protein / metabolism


  • BAX protein, human
  • BH3 Interacting Domain Death Agonist Protein
  • BID protein, human
  • Bacterial Proteins
  • Bacterial Toxins
  • CASP8 and FADD-Like Apoptosis Regulating Protein
  • CFLAR protein, human
  • Carrier Proteins
  • Intracellular Signaling Peptides and Proteins
  • Myeloid Cell Leukemia Sequence 1 Protein
  • Neoplasm Proteins
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • bcl-2-Associated X Protein
  • toxB protein, Clostridium difficile
  • Adenosine Diphosphate Ribose
  • Cyclic AMP
  • CASP3 protein, human
  • CASP9 protein, human
  • Caspase 3
  • Caspase 9
  • Caspases
  • cdc42 GTP-Binding Protein
  • rac1 GTP-Binding Protein
  • rho GTP-Binding Proteins
  • rhoA GTP-Binding Protein