AimTo use the antioxidant compounds (sodium selenite, selenomethionine, D-pantethine) for modulation of cytotoxic effect of doxorubicin and cisplatin toward wild type and drug-resistant mutants of several human tumor cells. Similar treatments were applied in vivo toward adult male Wistar rats.MethodsHuman tumor cells of different lines (HCT-116, Jurkat and HL-60) with various mechanisms of drug-resistance were treated with doxorubicin or cisplatin, alone or in combination with sodium selenite, selenomethionine, or D-pantethine. Cell viability, induction of apoptosis, and production of O2- radicals were measured. Activity of redox potential modulating enzymes was measured in the liver and blood plasma of adult male Wistar rats subjected to similar treatments.ResultsAll antioxidants used in physiologically harmless concentration inhibited cytotoxic action of doxorubicin toward tumor cells sensitive to chemotherapy treatment by 15%-30%, and slightly enhanced cytotoxic effect of this medicine toward drug-resistant malignant cells. At the same time, there was no significant effect of these antioxidants on cisplatin action. Such effects were accompanied by a complete inhibition of production of superoxide radicals induced by doxorubicin. The results of in vivo study in adult male Wistar rats were in agreement with the results of in vitro study of human tumor cells.ConclusionProtective effect of specific antioxidant agents during cytotoxic action of doxorubicin was demonstrated in vitro in drug-sensitive human tumor cells and in adult male Wistar rats, while there was no protective effect in drug-resistant sub-lines of these tumor cells during action of doxorubicin and cisplatin.

AimTo investigate the potential tissue-protective effects of antioxidants selenomethionine and D-pantethine applied together with doxorubicin (Dx) on NK/Ly lymphoma-bearing mice. The impact of this chemotherapy scheme on animal survival, blood cell profile, hepatotoxicity, glutathione level, and activity of glutathione-converting enzymes in the liver was compared with the action of Dx applied alone.MethodsThe hematological profile of animals was studied by the analysis of blood smears under light microscopy. Hepatotoxicity of studied drugs was evaluated measuring the activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) enzymes, De Ritis ratio, and coenzyme A fractions by McDougal assay. Glutathione level in animal tissues was measured with Ellman reagent, and the activity of glutathione reductase, transferase, and peroxidase was measured using standard biochemical assays.ResultsD-pantethine (500 mg/kg) and, to a lower extent, selenomethionine (600 µg/kg) partially reduced the negative side effects (leukocytopenia and erythropenia) of Dx (5 mg/kg) in NK/Ly lymphoma bearing animals on the 14th day of their treatment. This increased animal survival time from 47-48 to 60+ days and improved the quality of their life. This ability of D-pantethine and selenomethionine was realized via hepatoprotective and immunomodulating activities. D-pantethine also restored the levels of acid-soluble and free CoA in the liver of tumor-bearing animals, while selenomethionine caused the recovery of glutathione peroxidase levels in the liver, which was significantly diminished under Dx treatment. Both compounds decreased glutathione level in the liver, which was considerably induced by Dx.ConclusionsAntioxidants selenomethionine and D-pantethine partially reversed the negative side effects of Dx in NK/Ly lymphoma-bearing mice and significantly increased the therapeutic efficiency of this drug in tumor treatment.

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We investigated if IRFI 042, an analog of vitamin E, protects the brain against oxidative stress induced by intraperitoneal administration of Kainic acid (KA) (10 mg/kg); sham brain injury rats were used as controls. Animals received either IRFI 042 (20 mg/kg) or its vehicle 30 min before KA injection and after 6 h were sacrificed to measure malonildyaldheide (MDA) and glutathione levels (GSH) in the diencephalon. Behavioral changes were also monitored. Intraperitoneal administration of IRFI decreased MDA (micromol/g wet tissue: KA + vehicle ¼ 22.5 ± 4.2; KA + IRFI ¼ 17.1 ± 1; P < 0.005) and prevented GSH loss (nmol/g wet tissue: KA + vehicle ¼ 0.41 ± 0.1; KA + IRFI ¼ 1.86 ± 0.2; P < 0.005) in the diencephalon. The latency of occurrence of behavioral signs increased from 39 ± 1 to 62 ± 6 min in IRFI 042 group. The data suggest that IRFI 042 might protect against KA-induced oxidative stress. PS6-02Reactive oxygen species production in synaptosomes is independent of DW m I. Sipos, L. Tretter and V. Adam-Vizi Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary, sipos@puskin.sote.hu This study addressed whether dissipation of DW m had any influence on ROS generation of in situ neuronal mitochondria. The ROS formation was measured as a release of H 2 O 2 by Amplex Red assay. Complete blockage of Complex I by rotenone or Complex III by antimycin caused enhanced H 2 O 2 release. Dissipation of DW m by FCCP or DNP had no effect on the H 2 O 2 production induced by rotenone or antimycin. Antimycin substantially diminishes the DW m , but part of the membrane potential still maintained by the reverse function of mitochondrial ATP synthase. When antimycin was applied together with oligomycin, DW m was totally dissipated, but the ROS production decreased only by 15%. Rotenone inhibited the antimycin-induced H 2 O 2 release by 55%, but not eliminated completely. These experiments suggest that in in situ mitochondria of synaptosomes (i) ROS generation because of inhibition of Complex I or III is not dependent on DW m and (ii) when Complex I is completely inhibited electrons entering the respiratory chain distal from rotenone site could fuel the ROS formation. PS6-03Free radical production in synaptosomes: the effect of respiratory substrates L. Tretter, I. Sipos, M. Miklos and V. Adam-Vizi Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary, tretter@puskin.sote.huWe investigated whether reactive oxygen species (ROS) production is different when the metabolism is driven by alternative respiratory substrates (RES) in synaptosomes. ROS production was monitored with the Amplex Red assay and parallel with that aconitase activity was measured, as this enzyme is sensitive to inhibition by ROS. Inactivation of aconitase and ROS production in synaptosomes run parallel when ROS production is induced by inhibition of respiratory complexes. In the presence of either isocitrate, alphaketoglutarate (a-KG), succinate or pyruvate but not citrate ROS production was enhanced as indicated by the ...