Detection of drug-induced, superoxide-mediated cell damage and its prevention by antioxidants

The mode of the cytotoxic activity of three benzo(c)fluorene derivatives wa s characterized. The observed morphological changes of lysosomes or variati ons of mitochondrial activity are assumed to be the consequence of cell pro tection against oxidative damage and/or the part of the damage process. To establish the relationship between the quantity of superoxide (O-2(.-)) gen erated and the degree of damage resulting from O-2(.-), a simple system bas ed on measurement of 3-(4-iodophenyl)-2-(4-nitrophenyl)-5-phenyltetrazolium chloride (INT) reductase activity in the presence of superoxide dismutase (SOD) was used. The functionality of the chosen battery of in vitro tests w as proved using several known superoxide inducers: cyclosporin A (CsA) and benzo(a)pyrene (BP), as well as noninducers: citrinin (CT) and cycloheximid e (CH). From the results followed that the cell growth tests are much bette r indices of toxicity than the other tests. The model system for the evalua tion of the protective capacity of antioxidants against superoxide-induced cytotoxicity included simultaneous exposure of HeLa cells to cytotoxic drug s and to quercetin (Qe), an antioxidant of plant origin. The complete aboli shment of the inhibition of cell proliferation and clonogenic survival was concluded to be due to the protective effect of the antioxidant. These obse rvations correlated with the decrease of superoxide content as estimated by the INT-reductase assay in the presence of SOD using the same model system , as well as with the increase of intracellular SOD content and its activit y. (C) 2001 Elsevier Science Inc.