Hydroxyl radical production and human DNA damage induced by ferric nitrilotriacetate and hydrogen peroxide

Reactivities of Fe3+ chelates of aminopolycarboxylic acids with DNA were investigated by the DNA-sequencing technique using 32P 5'-end-labeled DNA fragments obtained from the human c-Ha-ras-1 protooncogene, and the reaction mechanism was studied by electron spin resonance spectroscopy. Ferric nitrilotriacetate (Fe3+-NTA) plus hydrogen peroxide caused strong DNA cleavage in the presence of albumin. No or little DNA cleavage was observed with ferric chloride or Fe3+ chelates of other aminopolycarboxylic acids tested in the presence of hydrogen peroxide. The DNA cleavage by Fe3+-NTA plus hydrogen peroxide without piperidine treatment occurred at positions of every nucleotide although a specific cleavage was observed, whereas cleavages at the positions of guanine and thymine increased predominantly with piperidine treatment. Electron spin resonance studies using free radical traps demonstrated that of Fe3+ chelates of aminopolycarboxylic acids, Fe3+-NTA was the most effective catalyst in hydrogen peroxide-derived production of hydroxyl radicals under our conditions. The results suggest that Fe3+-NTA catalyzes the decomposition of hydrogen peroxide to produce hydroxyl radicals, which subsequently cause the strong base alterations of guanine and thymine, and deoxyribose-phosphate backbone breakages. The possibility that the Fe3+-NTA-induced DNA damage is the initiation and/or promotion of carcinogenesis by Fe3+-NTA is discussed.