Effect of antioxidants on radical intensity and cytotoxicity of hydroquinone

Hydroquinone (HQ) dose-dependently reduced the viable cell number of oral t umor cell lines (HSC-2 MSG). He induced internucleosomal DNA fragmentation in human promyelocytic leukemic HL-60 cells, but not in HSC-2 nor HSG cells . Cytotoxic activity of HQ was slightly reduced by catalase, bill was enhan ced by superoxide dismutase, suggesting the possible involvement of hydroge n peroxide in HQ-induced cytotoxicity. This was supported by slight increas e ol decrease of cytotoxicity of He in the presence of Cu2+ and Fe3+, respe ctively. Lower concentrations of sodium ascorbate, ascorbic acid and ascorb ic acid 6-palmitate reduced both the radical intensity and cytotoxic activi ty of He, mole efficiently than ascorbic acid 2,6-dipalmitate, in contrast to the cytotoxic action of these ascorbates at. higher (millimolar;) concen trations. Popular antioxidants such as N-acetyl-L-cysteine and cysteine als o reduced the radical intensity and cytotoxic activity of HQ The present st udy suggests that cytotoxic activity of He is generated by radical-mediated oxidation mechanism.