Prolonged, but not acute, glutathione depletion promotes Fas‐mediated mitochondrial permeability transition and apoptosis in mice

Glutathione depletion either decreased or increased death‐receptor–mediated apoptosis in previous studies. Comparison of the durations of glutathione depletion before death‐receptor stimulation in these studies might suggest a different effect of prolonged versus acute thiol depletion. We compared the effects of the prolonged glutathione depletion caused by a sulfur amino acid–deficient (SAA − ) diet and the acute depletion caused by a single dose of phorone on hepatic apoptosis triggered by the administration of an agonistic anti‐Fas antibody. The chronic SAA − diet did not affect hepatic Fas or Bcl‐XL, but increased p53 and Bax, and exacerbated Fas‐mediated mitochondrial membrane depolarization, electron‐microscopy–proven outer mitochondrial membrane rupture, cytochrome c translocation to the cytosol, and caspase 3 activation. These effects were prevented by cyclosporin A, an inhibitor of mitochondrial permeability transition. The SAA − diet increased internucleosomal DNA fragmentation, the percentage of apoptotic hepatocytes, serum alanine transaminase (ALT) activity, and mortality after Fas stimulation. Despite a similar decrease in hepatic glutathione, administration of a single dose of phorone 1 hour before the anti‐Fas antibody did not change p53 or Bax, and did not enhance Fas‐induced mitochondrial permeability transition and toxicity. However, 4 repeated doses of phorone (causing more prolonged glutathione depletion) increased Bax and Fas‐mediated toxicity. In conclusion, a chronic SAA − diet, but not acute phorone administration, increases p53 and Bax, and enhances Fas‐induced mitochondrial permeability transition and apoptosis. Thiol depletion could cause oxidative stress that requires several hours to increase p53; the latter induces Bax, which translocates to mitochondria after Fas stimulation.