Inhibition of MLC kinase or Rho kinase attenuated TNF-alpha-induced stress fiber formation and apoptosis, but not barrier dysfunction, indicating a central role for the cytoskeleton in apoptosis.
In pulmonary endothelial cells, TNF-alpha-mediated apoptosis depends on the cytoskeleton and contractile tension, whereas barrier dysfunction occurs independently of these mechanisms.
Tumor necrosis factor (TNF)-alpha is released in acute inflammatory lung syndromes linked to the extensive vascular dysfunction associated with increased permeability and endothelial cell apoptosis. TNF-alpha induced significant decreases in transcellular electrical resistance across pulmonary endothelial cell monolayers, reflecting vascular barrier dysfunction (beginning at 4 h and persisting for 48 h). TNF-alpha also triggered endothelial cell apoptosis beginning at 4 h, which was attenuated by the caspase inhibitor Z-Val-Ala-Asp-fluoromethylketone. Exploring the involvement of the actomyosin cytoskeleton in these important endothelial cell responses, we determined that TNF-alpha significantly increased myosin light chain (MLC) phosphorylation, with prominent stress fiber and paracellular gap formation, which paralleled the onset of decreases in transcellular electrical resistance and enhanced apoptosis. Reductions in MLC phosphorylation by the inhibition of either MLC kinase (ML-7, cholera toxin) or Rho kinase (Y-27632) dramatically attenuated TNF-alpha-induced stress fiber formation, indexes of apoptosis, and caspase-8 activity but not TNF-alpha-induced barrier dysfunction. These studies indicate a central role for the endothelial cell cytoskeleton in TNF-alpha-mediated apoptosis, whereas TNF-alpha-induced vascular permeability appears to evolve independently of contractile tension generation.
Petrache et al. (Fri,) conducted a other in Acute inflammatory lung syndromes / Endothelial cell apoptosis. Inhibition of MLC kinase (ML-7, cholera toxin) or Rho kinase (Y-27632) was evaluated on TNF-alpha-induced apoptosis and barrier dysfunction. Inhibition of MLC kinase or Rho kinase attenuated TNF-alpha-induced stress fiber formation and apoptosis, but not barrier dysfunction, indicating a central role for the cytoskeleton in apoptosis.