Byrnes R W, Antholine W E, Petering D H
Department of Chemistry, University of Wisconsin-Milwaukee 53201.
Free Radic Biol Med. 1992;12(6):457-69. doi: 10.1016/0891-5849(92)90099-3.
Mechanistic details of the interaction of 1,10-phenanthroline and its copper complex with Ehrlich ascites tumor cells were examined, using inhibition of cell proliferation, DNA breakage, and increased membrane permeability as indices of cellular damage. The metal chelating agent, 1,10-phenanthroline (OP), the 1:0.5 complex of 1,10-phenanthroline and CuCl2 [(OP)2Cu], and CuCl2 inhibited growth of Ehrlich ascites tumor cell monolayers during 48-h treatments by 50% at about 3.5, 2, and 70 nmol/10(5) cells/mL, respectively. (OP)2Cu at 10 nmol/10(5) cells also enhanced uptake of trypan blue dye during 6 h of treatment, while dye uptake in OP- and CuCl2-treated cells remained similar to controls. DNA breakage, measured by DNA alkaline elution, was produced during 1-h treatments with (OP)2Cu at drug/cell ratios similar to those producing growth inhibition. Copper uptake was similar for both (OP)2Cu and CuCl2. Electron spin resonance (ESR) spectroscopy suggested that cellular ligands bind copper added as (OP)2Cu or CuCl2 and then undergo time-dependent reductions of Cu(II) to Cu(I) for both forms. Inhibition of (OP)2Cu-induced single-strand scission and trypan blue uptake by scavengers of activated oxygen is consistent with participation of superoxide and H2O2 in both processes. In contrast, superoxide dismutase (SOD) did not reduce the magnitude of the fraction of cellular DNA appearing in lysis fractions prior to alkaline elution of (OP)2Cu-treated cells. Dimethyl sulfoxide (DMSO) inhibited uptake of trypan blue dye but did not inhibit DNA strand scission produced by (OP)2Cu. Thus, multiple mechanisms for generation of oxidative damage occur in (OP)2Cu-treated cells. Growth inhibition produced by OP or (OP)2Cu, as well as the low levels of strand scission produced by OP, was not reversed by scavengers.
