Cephaloridine-Induced Inhibition of Cytochrome c Oxidase Activity in the Mitochondria of Cultured Renal Epithelial Cells (LLC-PK1) as a Possible Mechanism of Its Nephrotoxicity

Abstract

To clarify the mechanism of cephalosporin nephrotoxicity, the effects of cephaloridine (CLD), a nephrotoxic cephalosporin antibiotic, on the mitochondria of the pig kidney proximal tubular epithelial cell line LLC-PK1 were studied in culture. The activity of cytochrome c oxidase in the mitochondria of LLC-PK1 cells was significantly decreased from 9 h after addition of 1.0 mM CLD to the cultured cells. These effects were dose-dependent and accompanied with a significant decrease in the ATP content in the cells, followed by marked morphological changes in the mitochondria. These alterations were observed in the treated cells before the increase in lipid peroxidation. The activities of NADH–cytochrome c reductase and succinate dehydrogenase in the mitochondria and NADPH–cytochrome P450 reductase, NADH-cytochrome b5 reductase, and 7-ethoxycoumarin O-deethylase in the microsomes of the treated cells were not affected. Superoxide anion production by the mitochondria prepared from LLC-PK1 cells or NADH–cytochrome c reductase was not affected by addition of CLD (1–10 mM), but adriamycin (0.1 mM) or paraquat (0.1 mM) significantly increased the superoxide anion production. These results suggested that the primary action of CLD is inhibition of cytochrome c oxidase activity in the mitochondrial electron transport chain, which decreases intracellular ATP content in renal tubular epithelial cells and that these effects of CLD are followed by increased lipid peroxidation and cellular injury.