Thiram-induced cytotoxicity is accompanied by a rapid and drastic oxidation of reduced glutathione with consecutive lipid peroxidation and cell death

The toxic effect of thiram, a widely used dithiocarbamate fungicide. was in vestigated in cultured human skin fibroblasts. Cell survival assays demonst rated that thiram induced a dose-dependent decrease in the viable cell reco very. Thiram exposure resulted in a rapid depletion of intracellular reduce d glutathione (GSH) content with a concomitant increase in oxidized glutath ione (GSSG) concentration. Alteration of glutathione levels was accompanied by a dose-dependent decrease in the activity of glutathione reductase (GR) , a key enzyme for the regeneration of GSH from GSSG. Thiram-exposed cells exhibited increased lipid peroxidation reflected by enhanced thiobarbituric acid reactive substances (TBARS) production. suggesting that GSH depletion and the lower GR activity gave rise to increased oxidative processes. To i nvestigate the rule of decreased GSH content in the toxicity of thiram, GSH levels were modulated prior to exposure. Pretreatment of fibroblasts with N-acetyl-L-cysteine (NAC), a GSH biosynthesis precursor. prevented both lip id peroxidation and cell death induced by thiram exposure. Tn contrast. thi ram cytotoxicity was exacerbated by the previous depletion of cellular GSH by L-buthionine-(S,R)-sulfoximine (BSO). Taken together. these results stro ngly suggest that thiram induces GSH depletion. leading to oxidative stress and finally cell death. (C) 2001 Elsevier Science ireland Ltd. All rights reserved.