Metallothionein suppresses the formation of 8-hydroxy-2′-deoxyguanosine in DNA induced by ferric nitrilotriacetate in vitro

Metallothionein (NIT) is endowed with strong antioxidant and nucleophilic properties and is found not only in the cytosol but also in the nucleus. To investigate whether MT can directly protect against oxidative DNA damage in the nucleus, the effect of NIT on 8-hydroxy-2'-deoxyguanosine (8-OHdG) formation induced by ferric nitrilotriacetate (Fe-NTA) was studied using purified MT or the primary cultures of MT-enriched hepatocytes. The level of 8-OHdG was increased in a dose-dependent fashion by incubation of salmon sperm DNA with Fe-NTA in the presence of hydrogen peroxide. Addition of purified NIT at 12.5 mu M to its incubation mixture resulted in a decrease of the 8-OHdG content in DNA by approximately 50%. In the primary cultures of control hepatocytes, treatment of Fe-NTA at 200 mu M resulted in significant decreases in cell survival and an increased in the concentration of 8-OHdG following depletion of glutathione. However, these toxic effects of Fe-NTA were modulated in MT-enriched cells. These results suggest that NIT may protect DNA against radical attack as a cellular radical scavenger.