ZnCl2 and vitamin C, known as antioxidants, differently potentiate the cytotoxicity of H2O2 in rat thymocytes : Cytometric analysis using forward and side scatters

The ‘antioxidant hypothesis’ proposes that antioxidant nutrients afford protection against chronic diseases by
decreasing oxidative damages. The ability of zinc to retard oxidative processes has been recognized for many
years. However, the application of ZnCl2 potentiates the cytotoxicity of H2O2. Thus, some antioxidants may
be cytotoxic under certain oxidative conditions. Therefore, in this study, the effect of vitamin C, one of
antioxidant nutrients, on the cells treated with H2O2 has been examined to see if vitamin C potentiates the
cytotoxicity of H2O2. Experiments were carried out with flow cytometer and rat thymocytes. Vitamin C also
potentiated the cytotoxicity of H2O2. The increase in cell lethality induced by the combination of H2O2 and
ZnCl2 was associated with the increase in population of shrunken cells with increased intensity of side scatter.
However, it was not the case for the combination of H2O2 and vitamin C. The profile of cytotoxicity induced
by H2O2 and vitamin C was different from that by H2O2 and ZnCl2. It may be suggested that the effects of zinc
and vitamin C varies from cytoprotective to cytotoxic, being dependent on the type of oxidative stress.