Protective effect of metallothionein to ras DNA damage induced by hydrogen peroxide and ferric ion-nitrilotriacetic acid

• Published in: Chemico-biological interactions Vol. 122; no. 3; pp. 137 - 152
• Main Authors: Min, Kyong-Son, Nishida, Kayo, Onosaka, Satomi
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 01.11.1999
• Subjects: Animals; Cadmium - pharmacology; Deoxyribose - metabolism; DNA Damage - drug effects; DNA strand scission; DNA, Single-Stranded - drug effects; Edetic Acid - pharmacology; Ethylmaleimide - pharmacology; Ferric Compounds - antagonists & inhibitors; Ferric Compounds - toxicity; Genes, ras - genetics; Glutathione - pharmacology; Humans; Hydrogen Peroxide - antagonists & inhibitors; Hydrogen Peroxide - toxicity; Hydroxyl radical; Male; Metallothionein; Metallothionein - pharmacology; Mice; Nitrilotriacetic Acid - analogs & derivatives; Nitrilotriacetic Acid - antagonists & inhibitors; Nitrilotriacetic Acid - toxicity; Protective effect; Zinc - pharmacology; NTA, nitrilotriacetic acid; GSH, glutathione; Protective effect; O 2 −, superoxide anion; EDTA, ethylenediamine- N, N, N′, N′-tetraacetic acid; OH, hydroxyl radical; DTPA, diethylenetriaminepentaacetic acid; MT, metallothionein; CA, citric acid; DNA strand scission; CDTA, trans-1,2-diaminocyclohexane- N, N, N′, N′-tetraacetic acid; Metallothionein; Hydroxyl radical
• ISSN: 0009-2797; 1872-7786
• DOI: 10.1016/S0009-2797(99)00113-1

Metallothionein (MT) is a strong antioxidant, due to a large number of thiol groups in the MT molecule and MT has been found in the nucleus. To investigate whether MT can directly protect DNA from damage induced by hydroxyl radical, the effects of MTs on DNA strand scission due to incubation with ferric ion-nitrilotriacetic acid and H 2O 2 (Fe 3+-NTA/H 2O 2) were studied. The Fe 3+-NTA/H 2O 2 resulted in a higher rate of deoxyribose degradation, compared to incubation of Fe 3+/H 2O 2, presumably mediated by the formation of hydroxyl radicals ( OH). This degradation was inhibited by either Zn-MT or Cd-MT, but not by Zn 2+ or Cd 2+ at similar concentrations. The Fe 3+-NTA/H 2O 2 resulted in a concentration dependent of increase in DNA strand scission. Damage to the sugar-phosphodiester chain was predominant over chemical modifications of the base moieties. Incubation with either Zn-MT or Cd-MT inhibited DNA damage by ∼50%. Preincubation of MT with EDTA and N-ethylmaleimide, to alkylate sulfhydryl groups of MT, resulted in MT that was no longer able to inhibit DNA damage. These results indicates that MT can protect DNA from hydroxyl radical attack and that the cysteine thiol groups of MT may be involved in its nuclear antioxidant properties.