Effects of glutathione depletion and induction of metallothioneins on the cytotoxicity of an organic hydroperoxide in cultured mammalian cells.

The effects of glutathione depletion and induction of metallothioneins (MTs) on the cytotoxicity of t-butyl hydroperoxide (t-BHP) were investigated in cultured Chinese hamster V79 cells. The cytotoxicity of t-BHP was enhanced with increasing duration of the pretreatment with L-buthionine-SR-sulfoximine (BSO), a selective inhibitor of gamma-glutamylcysteine synthetase, and was correlated with the decrease of cell glutathione, indicating that glutathione constitutes a cellular defense against toxicity by t-BHP. Desferrioxamine, a specific iron chelator, suppressed partly inhibition of cell growth induced by t-BHP and suppressed completely the increase of the cytotoxicity caused by glutathione depletion. Butylated hydroxytoluene, a diffusible radical scavenger, showed almost the same suppressive effect as desferrioxamine. These results suggest that the cytotoxicity of t-BHP enhanced by the depletion of glutathione is attributable to an action of iron-mediated reactive radical species. Pretreatment with zinc (10(-4) M) suppressed the cytotoxicity of t-BHP that was enhanced by depletion of glutathione and the extent of suppression was paralleled with increasing duration of zinc pretreatment that correlated with increased synthesis of metallothioneins (MTs). Maximum induction of MTs also suppressed the t-BHP-induced inhibition of cell growth at 4 degrees C in glutathione-depleted cells. These results suggest that MTs act as a scavenger for the reactive radical species which are formed in an iron-mediated manner.