Iron requirement for cellular DNA damage and growth inhibition by hydrogen peroxide and bleomycin

Abstract

Studies with Euglena gracilis and HL-60 cells have assessed the need for intracellular iron in the mechanisms of inhibition of cell growth and DNA damage by H2O2 and bleomycin. Cell culture media were directly depleted of iron in order to deprive cells of nutrient iron. Major pools of cellular iron were reduced in both cell types. Nevertheless, iron bound in e.s.r.-observable haem protein and ribonucleotide diphosphate reductase in HL-60 cells was not decreased. In both control cell populations, there was a concentration-dependent reduction in proliferation and cell survival caused by H2O2. In comparison, the proliferation rates of both iron-deficient cell types were significantly less sensitive to H2O2. H2O2 caused concentration-dependent single-strand breakage in DNA in control HL-60 and Euglena gracilis cells. Iron deficiency reduced the amount of strand breaks in HL-60 cells at each concentration of H2O2 used. Single-strand breakage caused by H2O2 in Euglena gracilis was a direct function of the concentration of iron in which the cells had been grown. Growth inhibition and both single- and double-strand DNA damage caused by bleomycin were substantially reduced or eliminated in iron-deficient cells. Copper bleomycin behaved like metal-free bleomycin when assayed for the capacity to cause DNA damage in iron-normal and iron-deficient HL-60 cells. In contrast, iron bleomycin was equally active under the two conditions in these cells.

Spectroscopic Studies of the Interaction of Ferrous Bleomycin with DNA

“…Although BLM is isolated from Streptomyces verticillus as a Cu complex, it is administered clinically in a metal-free form. The active species in vivo is believed to be Fe II BLM …”

Nucleic Acid Recognition by Metal Complexes of Bleomycin

“…Notably, the bleomycins are isolated as Cu(II) complexes, although clinically administered in the apo-form. Thus, while evidence pointing toward Fe as the relevant cofactor exists, 47 the identity of the metal ion responsible for DNA degradation in vivo remains a subject of debate. As with other DNA binding and cleaving metal complexes, 48 the bleomycin ligand appears to employ the redox capabilities of a metal ion to promote nucleic acid scission and also to impart a defined structure to the metallodrug to effect nucleic acid recognition.…”

Definition of the intermediates and mechanism of the anticancer drug bleomycin using nuclear resonance vibrational spectroscopy and related methods

“…Its cytotoxicity is due to its ability to effect singleand double-strand cleavage of DNA with a number of reduced metal ions and dioxygen (3)(4)(5); Fe II displays the highest in vivo activity (6). BLM provides five nitrogen-based ligands ( Fig.…”