Induction of oxidative stress and protection against hydrogen peroxide-mediated cytotoxicity by the superoxide dismutase-mimetic complex copper-putrescine-pyridine.

The low molecular weight Cu2Zn2-superoxide dismutase (SOD) active centre analogue copper-putrescine-pyridine (Cu-PuPy, N,N'-bis(2-pyridylmethylene)1,4-butanediamine(N,N',N",N")-Cu (II)- -diperchlorate) has been shown to dismutate superoxide with high efficiency. In the presence of glutathione it sustains the production of H2O2 via redox cycling. We investigated the influence of Cu-PuPy on the glutathione status and the clonogenic survival of Chinese hamster ovary (CHO) cells. At 0.05 mM Cu-PuPY was not toxic and exerted only a minor effect on cellular glutathione. At Cu-PuPy concentrations of 0.1-0.5 mM glutathione became increasingly oxidized and was depleted during treatment while toxicity dramatically increased. The time course of toxicity was unusual: after passing a minimum at 50 or 100 min (0.5 mM or 0.2 mM Cu-PuPy, respectively), clonogenic survival increased by two orders of magnitude in the following 50 min. On the other hand, Cu-PuPy protected cells effectively against toxic doses of hydrogen peroxide. We conclude that Cu-PuPy combines a prooxidant and an antioxidant mode of action that sequentially modify the survival response of CHO cells: initial production of hydrogen peroxide by Cu-PuPy-catalysed glutathione oxidation leads to the intracellular accumulation of potentially toxic radical intermediates that may be inactivated via superoxide dismutation upon further treatment with Cu-PuPy.