Roles of oxygen radical production and lipid peroxidation in the cytotoxicity of cephaloridine on cultured renal epithelial cells (LLC-PK1)

To clarify the mechanism of cephalosporin nephrotoxicity, the cytotoxic effects of cephaloridine(CER), a nephrotoxic cephalosporin antibiotic, on the pig kidney proximal tubular epithelial cell line(LLC−PK1)were studied in culture.CER increased the content of hydrogen peroxide and decreased the activity of catalase in the treated cells, followed by an increase in the content of lipid peroxide and decreases in both glutathione peroxidase activity and in the non−protein sulfhydryl content.The levels of NADPH−dependent hydrogen peroxide and superoxide anion production by microsomes prepared from LLC−PK1 cells, and by NADPH−cytochrome P−450 reductase purified from the rat renal cortex were significantly increased by paraquat.The production of these molecules was antagonized by ρ−chloromercuribenzoate, an inhibitor of NADPH−cytochrome P−450 reductase.On the other hand, CER did not significantly affect the production of hydrogen peroxide or superoxide anions.These results suggested that the cytotoxic effect of CER on cultured LLC−PK1 cells was due to the increases in hydrogen peroxide and lipid peroxide levels and not microsomal oxygen radical production, and that the mechanism of this cytotoxicity is very different from that of paraquat which induces microsomal oxygen radical production.