Effect of Tacrolimus on the Production of Oxygen Free Radicals in Hepatic Mitochondria

Abstract

Objectives Cyclosporine (CsA) causes side effects that occur mainly in the kidney but also in the liver. Several reports have strongly suggested that the production of oxygen free radicals (OFRs) is a common mechanism of CsA toxicity. However, tacrolimus is believed to suppress the production of OFRs. Methods We obtained the mitochondrial fraction with 96% purity from rat liver using a sucrose density gradient solution. Zero to 100 μmol/L tacrolimus was incubated with the mitochondrial fraction for 6 hours at 37°C. OFRs were evaluated by measuring the fluorescent product from the oxidation of an oxidant-sensitive 2,7-dichlorefluorescein using a VICTOR3 multilabel counter. Results The fluorescence units for OFR production were increased as the time of exposure to tacrolimus passed from 1 to 6 hours. The fluorescence units in 0.1 μmol/L tacrolimus were 6.0 × 10 5 at 1 hour, 7.8 × 10 5 at 2 hours, 9.0 × 10 5 at 3 hours, 10.0 × 10 5 at 4 hours, 11.1 × 10 5 at 5 hours, and 11.4 × 10 5 at 6 hours. However, the fluorescence units were similar although the tacrolimus concentration increases from 0.1 to 100 μmol/L. Conclusions The results in this experiment suggested that tacrolimus induced the production of OFRs depending on the exposure time.