Exogenous histidine as a co-factor which exacerbates the toxicity of hydrogen peroxide in cultured mammalian and bacterial cells

The killing of Escherichia coli cells by H2O2 is higher when exposure to the oxidant is performed in a complete culture medium, as compared to saline. Whereas MgSO4, CaCl2, thiamine or glucose, added separately or in combination with the saline, had no effect on the cytotoxic response to H2O2, the cytotoxicity appeared highly dependent upon the presence of the casamino acids in the incubation medium. One of these amino acids, histidine, was found to greatly augment the toxicity of H2O2 in E. coli. This effect of histidine was also observed in mammalian cells. In fact, both the cytoxicity and the DNA damage produced by H2O2 in Chinese hamster ovary (CHO) cells were significantly increased by this amino acid