title: Lipid peroxides as endogenous oxidants forming 8-oxo-guanosine and lipid-soluble antioxidants as suppressing agents.
abstract: The oxidation of guanosine to 8-oxo-2'-deoxyguanosine (8-oxo-dG) in DNA is closely associated with induction of various diseases, but the endogenous oxidant species involved remains unclear. Hydrogen peroxides (H2O2) have been considered to be the oxidant, while lipid peroxides are another possible oxidant because generated easily in bio-membranes surrounding DNA. The oxidant potency was compared between lipid peroxides and H2O2. Linoleic acid hydroperoxides (LOOH) formed 8-oxo-dG at a higher level than H2O2 in guanosine or double-stranded DNA. In the presence of a physiological concentration of Fe(2+) to produce hydroxyl radicals, LOOH was also a stronger oxidant. In a lipid micelle, LOOH markedly produced 8-oxo-dG at a concentration one-tenth of that of H2O2. Upon adding to rat hepatic mitochondria, phosphatidylcholine hydroperoxides produced 8-oxo-dG abundantly. Employing HepG2 cells after pretreated with glutathione peroxidase inhibitor, LOOH formed 8-oxo-dG more abundantly than H2O2. Then, antioxidants to suppress the 8-oxo-dG formation were examined, when the nuclei of pre-incubated HepG2 with antioxidants were exposed to LOOH. Water-soluble ascorbic acid, trolox, and N-acetyl cysteine showed no or weak antioxidant potency, while lipid-soluble 2,6-dipalmitoyl ascorbic acid, α-tocopherol, and lipid-soluble phytochemicals exhibited stronger potency. The present study shows preferential formation of 8-oxo-dG upon LOOH and the inhibition by lipid-soluble antioxidants.
authors: School of Agricultural Regional Vitalization, Kibi International University, Sareo 370-1, Sichi, Minami Awaji 656-0484, Japan.
authors: Kazuki
authors: K
authors: Kanazawa
authors: Laboratory of Food and Nutritional Chemistry, Graduate School of Agricultural Science, Kobe University, Rokkodai, Nada-ku, Kobe 657-8501, Japan.
authors: Miku
authors: M
authors: Sakamoto
authors: School of Agricultural Regional Vitalization, Kibi International University, Sareo 370-1, Sichi, Minami Awaji 656-0484, Japan.
authors: Ko
authors: K
authors: Kanazawa
authors: Laboratory of Food and Nutritional Chemistry, Graduate School of Agricultural Science, Kobe University, Rokkodai, Nada-ku, Kobe 657-8501, Japan.
authors: Yoriko
authors: Y
authors: Ishigaki
authors: Laboratory of Food and Nutritional Chemistry, Graduate School of Agricultural Science, Kobe University, Rokkodai, Nada-ku, Kobe 657-8501, Japan.
authors: Yoshiko
authors: Y
authors: Aihara
authors: Laboratory of Food and Nutritional Chemistry, Graduate School of Agricultural Science, Kobe University, Rokkodai, Nada-ku, Kobe 657-8501, Japan.
authors: Takashi
authors: T
authors: Hashimoto
authors: Laboratory of Food and Nutritional Chemistry, Graduate School of Agricultural Science, Kobe University, Rokkodai, Nada-ku, Kobe 657-8501, Japan.
authors: Masashi
authors: M
authors: Mizuno
keywords: 8-OHdG; hydrogen peroxide; lipid peroxides; lipid-soluble antioxidants; oxidation of guanosine