THE IRON CHELATOR PYRIDOXAL ISONICOTINOYL HYDRAZONE (PIH) PROTECTS PLASMID PUC-18 DNA AGAINST (OH)-O-CENTER-DOT-MEDIATED STRAND BREAKS

Pyridoxal isonicotinoyl hydrazone (PIH) has previously been studied fo r use in iron chelation therapy in iron-overload diseases. It is an ef ficient in vitro antioxidant due to its Fe(III) complexing activity (S chulman, H. M., et al. Redox Report 1:373-378; 1995). Pathologies asso ciated with iron-overload include hepatic and other cancers. Since oxi dative alterations of DNA can be linked to the development of cancer, we decided to study whether PIH protects DNA against in vitro oxidativ e stress. We report here that pUC-18 plasmid DNA is damaged by (OH)-O- . radicals generated from Fe(II) plus H2O2 or from Fe(II) plus hypoxan thine/xanthine oxidase. The DNA damage was quantified by determining t he diminution of supercoiled DNA forms after oxidative attack using ag ar gel electrophoresis. Micromolar amounts of PIH (20-30 mu M) were ab le to half-protect DNA from iron (1-7.5 mu M)-mediated (OH)-O-. format ion. The antioxidant capacity of PIH was significantly higher than tha t of some of its analogs and desferrioxamine. PIH and some of its anal ogues could also inhibit the oxidative degradation of 2-deoxyribose ca used by Fenton reagents. Since we observed that PIH enhances the Fe(II ) autoxidation rate, measured by the ferrozine technique, PIH may limi t (OH)-O-. formation and consequently DNA damage by decreasing the amo unt of Fe(II) available to catalyze Fenton reactions. (C) 1998 Elsevie r Science Inc.