Differential oxidative stress induced by two different types of skin tumor promoters, benzoyl peroxide and 12-O-tetradecanoylphorbol-13-acetate

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Abstract
The oxidative stress induced in vivo by benzoyl peroxide (BzPo) or 12-O-tetradecanoylphorbol-13-acetate (TPA) was evaluated in terms of ehemiluminescence (CL) emitted by SENCAR mouse skin, a non-invasive method that allows an estimation of overall oxidative stress. The ability of a biomimetic superoxide dismutase, copper(ll)(3,5-diisopro-pylsalicylate)2 (CuDIPS), to inhibit that response was also evaluated. A single application of BzPo to mouse skin resulted in a dose-dependent increase in CL up to 0.083 µmol. Sequential treatment with BzPo in a dose used for tumor promotion resulted in a fall in CL induced by the second topical application. There were no differences between initiated and non-initiated mice in their responses to BzPo-induced CL. CuDIPS, an inhibitor of tumor promotion, was an effective inhibitor of CL in all the protocols evaluated. Conversely, ZnDIPS and DIPS did not inhibit CL. Phenolic antloxidants induced partial inhibition of CL. Unlike BzPo treatment, a single application of TPA up to 105 nmol did not induce an increase in CL, but the second topical application with TPA in a dose used for tumor promotion resulted in a small but significant increase in CL. However, these values of CL were much smaller than the CL induced by BzPo. Our results show a differential response of the skin in terms of the oxidative stress induced by BzPo or TPA.

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