title: Singlet oxygen is the major species participating in the induction of DNA strand breakage and 8-hydroxydeoxyguanosine adduct by lead acetate.
abstract: To investigate DNA damage induced by Pb2+ and its prevention by scavengers, we determined DNA strand breakage and the formation of 8-hydroxydeoxyguanosine (8-OHdG) in DNA using plasmid relaxation assay and HPLC with electrochemical detection, respectively. Lead acetate induced DNA strand breakage in 10 mM of Hepes buffer, pH 6.8, in a time- and dose-dependent manner. Compared with lead, zinc acetate did not significantly induce DNA breakage. The singlet oxygen scavengers NaN3 and 2,2,6,6-tetramethyl-4-piperidone (TEMP) inhibited lead-induced DNA breakage more efficiently than the hydroxyl radical scavengers mannitol and DMPO. Deuterium oxide (D2O), a singlet oxygen enhancer, potentiated lead-induced DNA breakage. At low ratios to Pb2+, NADPH, glutathione, and 2-mercaptoethanol enhanced lead-induced DNA breakage, whereas high ratios of these agents protected it. Catalase and superoxide dismutase (SOD) did not protect DNA breaks induced by Pb2+. Lead-induced DNA breakage was markedly enhanced by H2O2, and this induction was inhibited by NaN3, TEMP, EDTA, catalase, BSA, and glutathione. In contrast, mannitol and SOD potentiated Pb2+/H2O2-induced DNA breaks. The results indicate that singlet oxygen, lead, and H2O2 are all involved in the reaction system, whereas hydroxyl radical and superoxide did not. Lead could cause a small amount of 8-OHdG formation in calf thymus DNA and dose-dependently induced the formation of this adduct in the presence of H2O2. Singlet oxygen scavengers were more effective than hydroxyl radical scavengers in protection from lead/H2O2-induced 8-OHdG adducts. Taken together, these results suggest that lead may induce DNA damage through a Fenton-like reaction and that singlet oxygen is the principal species involved.
authors.affiliation: Molecular Carcinogenesis Laboratory, Department of Life Sciences, National Tsing Hua University, Hsinchu, Taiwan, Republic of China. lsyjl@life.nthu.edu.tw
authors.forename: J L
authors.initials: JL
authors.lastname: Yang
authors.forename: L C
authors.initials: LC
authors.lastname: Wang
authors.forename: C Y
authors.initials: CY
authors.lastname: Chang
authors.forename: T Y
authors.initials: TY
authors.lastname: Liu
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D002374:Catalase / Q000378:metabolism / Q000494:pharmacology; D018736:DNA Adducts / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage / Q000187:drug effects* / Q000235:genetics; D004278:DNA, Superhelical / Q000235:genetics / Q000378:metabolism; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism; D017666:Deuterium Oxide / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D016166:Free Radical Scavengers / Q000378:metabolism / Q000494:pharmacology; D006207:Half-Life; D006861:Hydrogen Peroxide / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D017665:Hydroxyl Radical / Q000378:metabolism; D009942:Organometallic Compounds / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010100:Oxygen / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D019163:Reducing Agents / Q000378:metabolism / Q000494:pharmacology; D026082:Singlet Oxygen; D013482:Superoxide Dismutase / Q000378:metabolism / Q000494:pharmacology; D019345:Zinc Acetate / Q000494:pharmacology
chemical_list: D018736:DNA Adducts; D004278:DNA, Superhelical; D016166:Free Radical Scavengers; D009942:Organometallic Compounds; D017382:Reactive Oxygen Species; D019163:Reducing Agents; D026082:Singlet Oxygen; D017665:Hydroxyl Radical; D000080242:8-Hydroxy-2'-Deoxyguanosine; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase; D019345:Zinc Acetate; D003849:Deoxyguanosine; D017666:Deuterium Oxide; C008261:lead acetate; D010100:Oxygen