Selective glutathione depletion of mitochondria by ethanol sensitizes hepatocytes to tumor necrosis factor.
OBJECTIVE
Tumor necrosis factor (TNF)-alpha induces cell injury by generating oxidative stress from mitochondria. The purpose of this study was to determine the effect of ethanol on the sensitization of hepatocytes to TNF-alpha.


METHODS
Cultured hepatocytes from ethanol-fed (ethanol hepatocytes) or pair-fed (control hepatocytes) rats were exposed to TNF-alpha, and the extent of oxidative stress, gene expression, and viability were evaluated.


RESULTS
Ethanol hepatocytes, which develop a selective deficiency of mitochondrial glutathione (mGSH), showed marked susceptibility to TNF-alpha. The susceptibility to TNF-alpha, manifested as necrosis rather than apoptosis, was accompanied by a progressive increase in hydrogen peroxide that correlated inversely with cell survival. Nuclear factor kappaB activation by TNF-alpha was significantly greater in ethanol hepatocytes than in control hepatocytes, an effect paralleled by the expression of cytokine-induced neutrophil chemoattractant. Similar sensitization of normal hepatocytes to TNF-alpha was obtained by depleting the mitochondrial pool of GSH with 3-hydroxyl-4-pentenoate. Restoration of mGSH by S-adenosyl-L-methionine or by GSH-ethyl ester prevented the increased susceptibility of ethanol hepatocytes to TNF-alpha.


CONCLUSIONS
These results indicate that mGSH controls the fate of hepatocytes in response to TNF-alpha. Its depletion caused by alcohol consumption amplifies the power of TNF-alpha to generate reactive oxygen species, compromising mitochondrial and cellular functions that culminate in cell death.
Colell
A
A
Liver Unit, Department of Medicine, Hospital Clinic i Provincial and Instituto Investigaciones Biomédicas, Consejo Superior Investigaciones Cientificas, Barcelona, Spain.
García-Ruiz
C
C
Miranda
M
M
Ardite
E
E
Marí
M
M
Morales
A
A
Corrales
F
F
Kaplowitz
N
N
Fernández-Checa
J C
JC
D000818:Animals; D000431:Ethanol / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D008099:Liver / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012436:S-Adenosylmethionine / Q000494:pharmacology; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
D014409:Tumor Necrosis Factor-alpha; D000431:Ethanol; D012436:S-Adenosylmethionine; D005978:Glutathione