Lactoperoxidase and thiocyanate protect cultured mammalian cells against hydrogen peroxide toxicity

The toxicity of various combinations of lactoperoxidase-thiocyanate-hydrogen peroxide was tested on a cell line of human epidermoid carcinoma of the cervix (HeLa), a Chinese hamster ovary cell line (CHO), and human gingival fibroblasts. The capacity of the cells to proliferate, to exclude trypan blue and to produce acids from glucose was evaluated. There was no significant difference between the three cell types in their reactions to the various test combinations. A 1 h exposure of the cells to 10 microM hydrogen peroxide reduced their capacity to proliferate. After a 1 h exposure to 100 microM hydrogen peroxide the cells were damaged to such an extent that none survived. In the presence of lactoperoxidase and thiocyanate the cells were protected from the toxic effects of hydrogen peroxide as disclosed by their capacity to proliferate and exclude trypan blue. The rate of acid production of the cells in the presence of glucose was inhibited, however, by the combination lactoperoxidase-thiocyanate-hydrogen peroxide.