CISPLATIN-INDUCED NEPHROTOXICITY IN PORCINE PROXIMAL TUBULAR CELLS - MITOCHONDRIAL DYSFUNCTION BY INHIBITION OF COMPLEX-I TO COMPLEX-IV OF THE RESPIRATORY-CHAIN

Cisplatin-induced nephrotoxicity was studied in porcine proximal tubul ar cells, focusing on the relationship between mitochondrial damage, r eactive oxygen species (ROS) and cell death. Cisplatin specifically af fected mitochondrial functions: complexes I to IV of the respiratory c hain were inhibited 15 to 55% after 20 min of incubation with 50 to 50 0 mu M, respectively. As a result, intracellular ATP was decreased to 70%. The mitochondrial glutathione (reduced form) (GSH)-regenerating e nzyme GSH-reductase (GSH-Rd) activity was reduced by 20%, which contri buted to a 70% reduction of GSH levels and ROS formation. The residual electron flow through the mitochondrial respiratory chain was the sou rce of ROS because additional inhibition of the complexes I to IV redu ced ROS formation. Because cisplatin affects both GSH-Rd and complexes I to IV, cells were incubated with N,N'-bis(2-chloroethyl)-N-nitrosou rea (inhibitor of GSH-Rd) and inhibitors of the different complexes. O nly N,N'-bis(2-chloroethyl)-N-nitrosourea with rotenone (complex I inh ibitor) induced ROS formation, which indicates that inhibition of comp lex I and inhibition of the GSH-Rd is probably the cause of ROS format ion. However, the resulting ROS is not the cause of cell death because diphenyl-p-phenylene-diamine and deferoxamine, which completely preve nted ROS, could not prevent cell death. Similarly, the antioxidants di d not completely prevent the decrease in activity of complexes I to IV , ATP or GSH levels. In conclusion, ROS formation does occur during ci splatin-induced toxicity, but it is not the direct cause of cell death .