The effect of
reduced glutathione (GSH) depletion by
acetaminophen (
APAP),
diethylmaleate (DEM), or
phorone on the mode of cell death and susceptibility to
tumor necrosis factor (TNF)-induced cell death was studied in cultured mouse hepatocytes. Dose-dependent
necrosis was the exclusive mode of cell death with
APAP alone, but the addition of
TNF-alpha induced a switch to about half apoptosis without changing total loss of viability. This effect was seen at 1 and 5 mmol/L but was inhibited
at 10 and 20 mmol/L
APAP. The switch to apoptosis was associated with increased
caspase activities, release of
cytochrome c, and
DNA laddering and was inhibited by
caspase inhibitors. DEM and
phorone also induced dose-dependent
necrosis. Treatment with
TNF-alpha under these conditions lead to incremental cell death in the form of apoptosis at 0.25 and 0.5 mmol/L DEM and 0.1 and 0.2 mmol/L
phorone. At 1.0 and 2.0 mmol/L DEM and 0.5 mmol/L
phorone, 90% to 100%
necrosis was observed with resistance to
TNF-alpha effects. The apoptosis with
TNF-alpha plus DEM was confirmed by
DNA laddering and inhibition by
caspase inhibitors. However, in the presence of
caspase inhibitors, the increment in cell death induced by
TNF-alpha persisted as an increase in
necrosis. A combination of
antioxidants,
vitamin E, and
butylated hydroxytoluene (
BHT) markedly inhibited
necrosis induced by
APAP or DEM alone, but the sensitization to
TNF-alpha-induced apoptosis was unaffected. GSH monoethylester (GSH-EE) protected against
necrosis and apoptosis. In conclusion, depletion of GSH by
APAP, DEM, or
phorone causes oxidative stress-induced
necrosis and sensitizes to an oxidative stress independent
TNF-alpha-induced apoptosis.