Induction and mechanism of DNA single- and double-strand breaks by tetracycline/Cu(II) in the absence of light

In the absence of light, tetracycline (TC) induced single- and double-strand breaks in PM2 DNA at micromolar concentrations in combination with CuCl2, whereas TC or CuCl2 alone had no effect. Strand break formation was completely suppressed by catalase and the specific Cu(I) scavenger neocuproine. The extent of strand break formation depended on the ratio of Cu(II):TC. At a ratio of > or = 2 most DNA damage was observed. The influence of the kind of Cu(II)/TC complexation on DNA strand break formation is discussed. The DNA damage in PM2 DNA provoked by TC/CuCl2 was indirectly detected also in human fibroblasts by the induction of DNA repair. The results are discussed with regard to human risk from TC/Cu(II).