Table 4

TNF-α Triggers Apoptosis of Epithelial HeLa Cells after Pretreatment with Wild-type Y. enterocolitica or the Proteasome Inhibitor MG-132

Pretreatment*Percent apoptotic cells‡
−TNF-α+TNF-α
None10 ± 69 ± 6
WA-C11 ± 27 ± 6
WA-31413 ± 462 ± 15
MG-13211 ± 357 ± 12
  • *  HeLa cells were either not pretreated, or pretreated for 90 min with virulence plasmid–cured yersiniae (WA-C), with wild-type yersiniae (WA-314), or with the proteasome inhibitor MG-132 (10 μM). Thereafter, half of the samples were challenged with human TNF-α (20 μg/ml).  

  •  Apoptosis was assayed 6 h after onset of stimulation with TNF-α by staining the cells with fluorescein-conjugated annexin V and propidium iodide, and counting apoptotic cells in a fluorescence microscope.