title: Iron ion induces mitochondrial DNA damage in HTC rat hepatoma cell culture--role of antioxidants in mitochondrial DNA protection from oxidative stresses.
abstract: The mitochondrial DNA (mtDNA) is exposed to the reactive oxygen species generated in the mitochondrial electron transfer system. While mitochondrial superoxide dismutase (Mn-SOD) scavenges superoxide anions to prevent damage of mtDNA, excess amount of reactive oxygen generated by quinone compounds impairs the mtDNA, in which involvement of iron ion-catalyzed reactions is suggested. In this communication, we report that the mtDNA in HTC rat hepatoma cells was markedly damaged in the presence of either ferrous (Fe2+) or ferric (Fe3+) iron in the culture medium. The mtDNA of HTC cells was damaged in the presence of 100 microM of iron ions in the culture medium within 3 h. There was no significant difference in the potency of Fe2+ and Fe3+. Deferoxamine, a Fe(3+)-specific chelating reagent, blocked the iron ion-induced mtDNA damage completely. The mtDNA in rat hepatocyte primary culture was, on the other hand, not damaged by either Fe2+ or Fe3+. To understand the difference between iron ion-induced damage of mtDNA in HTC cells and in the primary hepatocytes, the Mn-SOD activity and lipid-soluble antioxidant contents were compared. The Mn-SOD activity in HTC cells was markedly lower (< 0.02 U/mg cell protein) than that in rat hepatocyte primary cell cultures (1.5 U/mg cell protein). Immunoreactive Mn-SOD content in HTC cells was also lower (21 ng/mg cell protein) than in the primary cultures (99 ng/mg cell protein). HTC cells contain much smaller amounts (3-11% of that of normal rat hepatocytes) of alpha-tocopherol and coenzyme Q homologs (CoQn). These results suggest that reactive oxygen species produced by iron ion impaired mtDNA of HTC cells, in which antioxidant activity was markedly decreased.
authors.affiliation: Department of Internal Medicine, Hiroshima University School of Medicine, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Itoh
authors.forename: T
authors.initials: T
authors.lastname: Shioda
authors.forename: T
authors.initials: T
authors.lastname: Matsura
authors.forename: S
authors.initials: S
authors.lastname: Koyama
authors.forename: T
authors.initials: T
authors.lastname: Nakanishi
authors.forename: G
authors.initials: G
authors.lastname: Kajiyama
authors.forename: T
authors.initials: T
authors.lastname: Kawasaki
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000737:chemistry; D002460:Cell Line; D002478:Cells, Cultured; D004249:DNA Damage; D004272:DNA, Mitochondrial / Q000737:chemistry*; D003676:Deferoxamine / Q000737:chemistry; D066298:In Vitro Techniques; D007501:Iron / Q000633:toxicity*; D008099:Liver / Q000737:chemistry; D008114:Liver Neoplasms, Experimental / Q000737:chemistry; D010084:Oxidation-Reduction; D051381:Rats; D014451:Ubiquinone / Q000737:chemistry; D014810:Vitamin E / Q000737:chemistry
chemical_list: D000975:Antioxidants; D004272:DNA, Mitochondrial; D014451:Ubiquinone; D014810:Vitamin E; D007501:Iron; D003676:Deferoxamine