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Singlet oxygen is the major species participating in the induction of DNA strand breakage and 8‐hydroxydeoxyguanosine adduct by lead acetate
Author(s) -
Yang JiaLing,
Wang LihChiann,
Chang ChunYao,
Liu TsungYun
Publication year - 1999
Publication title -
environmental and molecular mutagenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1
H-Index - 87
eISSN - 1098-2280
pISSN - 0893-6692
DOI - 10.1002/(sici)1098-2280(1999)33:3<194::aid-em3>3.0.co;2-o
Subject(s) - chemistry , singlet oxygen , dna damage , catalase , superoxide dismutase , dna , hydroxyl radical , reactive oxygen species , adduct , superoxide , hydrogen peroxide , radical , biochemistry , photochemistry , antioxidant , oxygen , enzyme , organic chemistry
To investigate DNA damage induced by Pb 2+ 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 NaN 3 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 (D 2 O), a singlet oxygen enhancer, potentiated lead‐induced DNA breakage. At low ratios to Pb 2+ , 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 Pb 2+ . Lead‐induced DNA breakage was markedly enhanced by H 2 O 2 , and this induction was inhibited by NaN 3 , TEMP, EDTA, catalase, BSA, and glutathione. In contrast, mannitol and SOD potentiated Pb 2+ /H 2 O 2 ‐induced DNA breaks. The results indicate that singlet oxygen, lead, and H 2 O 2 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 H 2 O 2 . Singlet oxygen scavengers were more effective than hydroxyl radical scavengers in protection from lead/H 2 O 2 ‐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. Environ. Mol. Mutagen. 33:194–201, 1999 © 1999 Wiley‐Liss, Inc.