Role of endogenous sulfur-containing nucleophiles in an in vitro model of cis-diamminedichloroplatinum(II)-induced nephrotoxicity

Quiescent LLC-PK1 cells have been shown to be a good model of cis-diamminedichloroplatinum(II) (DDP)-induced nephrotoxicity. In these nonproliferating porcine kidney epithelial cells, DDP inhibition of protein synthesis rate is the major correlate of cytotoxicity. We report here the use of this cell line to investigate the role of endogenous sulfur-containing nucleophiles in DDP-induced nephrotoxicity. Reaction of DDP with glutathione (GSH), cysteine, or methionine for up to 24 hr led to concentration- and time-dependent loss of its toxic effects, whereas dissolution of DDP alone did not alter its reduction of viability or protein synthesis rate in LLC-PK1 cells. Treatment of these cells with differing cytotoxic concentration of DDP produced an identical transient increase in intracellular GSH, whereas compounds known to bind GSH, trans-diamminedichloroplatinum(II) (t-DDP) and diethyl maleate (DEM), rapidly depleted LLC-PK1 intracellular GSH levels. Buthionine sulfoximine (BSO) treatment decreased intracellular GSH to 10% of control without altering cell viability or protein synthesis rate. However, BSO-pretreated LLC-PK1 cells exhibited enhanced DDP-induced toxicity. CdCl2 treatment produced a 30-fold induction of metallothionein-like, cadmium-binding proteins and a 10-fold increase in metallothionein isoform I (MT-I) mRNA, but this induction had no effect on DDP-induced reduction of viability or protein synthesis rate. Protracted DDP exposure did not induce MT-I mRNA levels in LLC-PK1 cells.