title: Black tea polyphenols, theaflavins, prevent cellular DNA damage by inhibiting oxidative stress and suppressing cytochrome P450 1A1 in cell cultures.
abstract: Tea polyphenols have been demonstrated as chemopreventive agents in a number of experimental models. However, less is known about the mechanism of chemoprevention by black tea compared with that of green tea. Some beneficial properties of theaflavins, the black tea polyphenols, were investigated in the present study. Theaflavins showed inhibitory effects on H(2)O(2)- and tert-butyl hydroperoxide (tBuOOH)-induced cytotoxicity (evaluated by tetrazolium bromide reduction), cellular oxidative stress (detected by oxidation of 2', 7'-dichlorofluorescin), and DNA damage (measured by amount of 8-OHdG and comet assay) in rat normal liver epithelium cell RL-34 cell lines. In addition, theaflavins also exhibited suppression of cytochrome P450 1A1 induced by omeprazole in the human hepatoma HepG2 cell line. Furthermore, when HepG2 cells were pretreated with omeprazole to induce CYP1A1, then exposed to benzo[a]pyrene (B[a]P), DNA damage was observed using the comet assay. However, theaflavins could inhibit this DNA damage. These results indicated that theaflavins could prevent cellular DNA damage by inhibiting oxidative stress and suppressing cytochrome P450 1A1 in cell cultures.
authors.affiliation: Laboratory of Food and Biodynamics, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464 8601, Japan.
authors.forename: Qing
authors.initials: Q
authors.lastname: Feng
authors.forename: Yasuyoshi
authors.initials: Y
authors.lastname: Torii
authors.forename: Koji
authors.initials: K
authors.lastname: Uchida
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Yokihiko
authors.initials: Y
authors.lastname: Hara
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Osawa
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D044946:Biflavonoids; D002392:Catechin; D002460:Cell Line; D019363:Cytochrome P-450 CYP1A1 / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D004249:DNA Damage / Q000187:drug effects*; D005419:Flavonoids; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D010636:Phenols / Q000494:pharmacology*; D011108:Polymers / Q000494:pharmacology*; D059808:Polyphenols; D051381:Rats; D013662:Tea / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D044946:Biflavonoids; D005419:Flavonoids; D010636:Phenols; D011108:Polymers; D059808:Polyphenols; D013662:Tea; C056068:theaflavin; D002392:Catechin; D019363:Cytochrome P-450 CYP1A1