title: Oxidative stress induced by a dihydropyrazine derivative.
abstract: The Maillard reaction contributes to the complications of diabetes and normal aging. Dihydropyrazines (DHPs), which are produced during the Maillard reaction, generate radicals and possess DNA strand-cleaving activities in vitro. In the present study, we evaluated the genotoxic and cytotoxic potentials of a DHP derivative, cyclohexyl-DHP, which is obtained as a mixture of two isomers, 2,3,5,6,7,8-hexahydroquinoxaline (endo-type) and 1,2,3,5,6,7-hexahydroquinoxaline (exo-type), fused with a cyclohexyl ring. Cyclohexyl-DHP caused DNA strand breaks in plasmid pUC18, especially in the presence of Cu(2+). By using Escherichia coli mutant strains, we observed that cyclohexyl-DHP exposure strongly reduced the survival rate of a cytosolic sodium dodecyl sulfate (SOD)-deficient strain (sodA sodB), significantly reduced the survival rates of DNA repair-deficient strains (recA and uvrB) and mildly reduced the survival rate of a catalase-deficient strain (katE katG) compared with the survival rate of the wild-type strain. Addition of Cu(2+) enhanced the cell killing ability of cyclohexyl-DHP. The frequency of mutations induced by cyclohexyl-DHP increased dose-dependently in the sodA sodB strain. Assays with the highly water-soluble tetrazolium salt WST-1 revealed that cyclohexyl-DHP strongly generated superoxide anions. Moreover, cyclohexyl-DHP elevated the protein carbonyl levels in E. coli. These findings indicate that cyclohexyl-DHP could potentially generate superoxide anions, and cause not only breakage of chromosomal DNA leading to mutagenic lesions but also induce damage to cellular proteins.
authors.affiliation: Faculty of Pharmaceutical Sciences, Sojo University, Kumamoto, Japan. stakechi@ph.sojo-u.ac.jp
authors.forename: Shinji
authors.initials: S
authors.lastname: Takechi
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Nakahara
authors.forename: Masaru
authors.initials: M
authors.lastname: Adachi
authors.forename: Tadatoshi
authors.initials: T
authors.lastname: Yamaguchi
mesh_terms: D019457:Chromosome Breakage / Q000187:drug effects; D004249:DNA Damage; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D016296:Mutagenesis; D018384:Oxidative Stress / Q000187:drug effects*; D010957:Plasmids; D050050:Protein Carbonylation / Q000187:drug effects; D011810:Quinoxalines / Q000138:chemical synthesis / Q000494:pharmacology*; D013482:Superoxide Dismutase / Q000187:drug effects / Q000235:genetics; D013481:Superoxides / Q000378:metabolism; D013778:Tetrazolium Salts / Q000378:metabolism
chemical_list: C539014:1,2,3,5,6,7-hexahydroquinoxaline; C539013:2,3,5,6,7,8-hexahydroquinoxaline; C110656:2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium; D011810:Quinoxalines; D013778:Tetrazolium Salts; D013481:Superoxides; D013482:Superoxide Dismutase