Effect of iron and ascorbate on cyclosporine-induced oxidative damage of kidney mitochondria and microsomes

The stimulatory effect of iron and ascorbate on the damaging action of cycl osporine in kidney mitochondria, microsomes and epithelial cells was examin ed. Cyclosporine induced malondialdehyde formation and hydrogen peroxide pr oduction in mitochondria and attenuated the activity of MnSOD and glutathio ne peroxidase. The damaging effect of cyclosporine (50 muM) plus Fe2+ (20 m uM) on mitochondrial and microsomal lipids and proteins as well as mitochon drial thiols was greater than the summation of the oxidizing action of cycl osporine alone and Fe2+ alone. As for tissue components, iron enhanced cycl osporine-induced viability loss in kidney epithelial cells. Fe2+, EDTA and H2O2-induced 2-alpha deoxyribose degradation was attenuated by 10 mM DMSO a nd 200 muM DTPA but not affected by 200 muM cyclosporine. The addition of F e2+ caused a change in the absorbance spectrum of cyclosporine in the wavel ength range 230-350 nm. The simultaneous addition of cyclosporine (50 muM) and ascorbate (100 muM) showed the enhanced peroxidative effect on mitochon drial and microsomal lipids, which was inhibited by DTPA and EDTA(1 mM). Si milar to iron, ascorbate enhanced cyclosporine-induced cell viability loss. The results show that iron and ascorbate promote the damaging action of cy closporine in kidney cortex mitochondria and microsomes and in kidney epith elial cells, which may contribute to the enhancement of cyclosporine-induce d nephrotoxicity. (C) 2001 Academic Press.