CYCLOSPORINE-A-INDUCED HYDROGEN-PEROXIDE SYNTHESIS BY CULTURED HUMAN MESANGIAL CELLS IS BLOCKED BY EXOGENOUS ANTIOXIDANTS

Cyclosporin A (CsA) is the immunosupressor most widely used in transpl anted patients for preventing organ rejection, but it has some toxic s ide effects in vascular beds and kidney. The purpose of this work was to study if H2O2 a reactive oxygen species, is involved in the CsA-ind uced toxic effects on kidney in vitro. Human mesangial cells (HMC) in culture were incubated in presence of CsA (10(-5)-10(-8)M) and H2O2 wa s measured by flow cytometry. The specificity of the probe used in thi s method was demonstrated as fluorescence was not detected when supero xide anion generated through a Xanthine-Xanthine oxidase system was pr esent, but fluorescence was noted when H2O2 was present in the incubat ion medium, both directly and after addition of superoxide dismutase t o the medium thus promoting H2O2 synthesis. CsA induced a significant dose and time-response increased H2O2 synthesis by cultured HMC. This increase appeared 5 min after CsA addition, being maximal between 15-4 5 min at CsA concentration of 10(-7)M. When HMC were preincubated with antioxidants as vitamin E or selenium, the CsA-induced H2O2 productio n was partially blocked. In addition, selenium also induced an increas ed activity of glutathion peroxidase in HMC after 24 hours of incubati on, suggesting that it exerted its H2O2 sacavenging action through the modulation of the activity of this enzyme.