title: beta-Naphthoflavone enhances oxidative stress responses and the induction of preneoplastic lesions in a diethylnitrosamine-initiated hepatocarcinogenesis model in partially hepatectomized rats.
abstract: The tumour-promoting effects of beta-naphthoflavone (BNF), a novel aryl hydrocarbon receptor (AhR) agonist, were investigated using a medium-term hepatocarcinogenesis model in rats. Six-week-old male F344 rats received an intraperitoneal injection of N-diethylnitrosamine (DEN) at a dose of 200mg/kg body weight and were fed a diet containing 0% (basal diet), 0.5% or 1% BNF for 6 weeks from 2 weeks after DEN treatment. All animals were subjected to two-thirds partial hepatectomy 1 week after the BNF treatment. The number and area of glutathione S-transferase placental form (GST-P) positive foci significantly increased in the livers of rats treated with BNF with concomitantly increased cell proliferation compared to those in the livers of the DEN alone group. Global gene expression analysis and subsequent quantitative real-time reverse transcription-polymerase chain reaction revealed that BNF induced not only the 'AhR gene battery'Cyp1a1, Cyp1a2, Cyp1b1, Nqo1, Aldh3a1 and Ugt1a6 but also the transcription factor NF-E2-related factor 2 (Nrf2)-regulated genes such as Gstm1, Gpx2, Akr7a3 and Yc2 (and also Nqo1), presumably due to the adaptive response against BNF-triggered oxidative stress responses. Reactive oxygen species production increased in microsomes isolated from the livers of BNF-treated rats, and this enhancement was suppressed by the P450 inhibitor SKF-525A. Furthermore, BNF enhanced oxidative DNA damage and lipid peroxidation, estimated by the levels of 8-hydroxydeoxyguanosine (8-OHdG) and thiobarbituric acid-reactive substances. These results suggest that the administration of BNF at a high dose and over a long-term enhance oxidative stress responses which may contribute to its hepatocarcinogenic potential in rats.
authors.affiliation: Laboratory of Veterinary Pathology, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan. dewa@cc.tuat.ac.jp
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Dewa
authors.forename: Jihei
authors.initials: J
authors.lastname: Nishimura
authors.forename: Masako
authors.initials: M
authors.lastname: Muguruma
authors.forename: Meilan
authors.initials: M
authors.lastname: Jin
authors.forename: Yukie
authors.initials: Y
authors.lastname: Saegusa
authors.forename: Toshiya
authors.initials: T
authors.lastname: Okamura
authors.forename: Masako
authors.initials: M
authors.lastname: Tasaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Umemura
authors.forename: Kunitoshi
authors.initials: K
authors.lastname: Mitsumori
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D004052:Diethylnitrosamine / Q000633:toxicity*; D004791:Enzyme Inhibitors / Q000633:toxicity*; D005982:Glutathione Transferase / Q000378:metabolism; D006498:Hepatectomy; D007150:Immunohistochemistry; D008099:Liver / Q000201:enzymology / Q000473:pathology; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced* / Q000473:pathology*; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress / Q000187:drug effects*; D011230:Precancerous Conditions / Q000139:chemically induced* / Q000473:pathology; D051381:Rats; D011916:Rats, Inbred F344; D017382:Reactive Oxygen Species / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000187:drug effects / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D019324:beta-Naphthoflavone / Q000633:toxicity*
chemical_list: D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; D018336:Receptors, Aryl Hydrocarbon; D017392:Thiobarbituric Acid Reactive Substances; D004052:Diethylnitrosamine; D019324:beta-Naphthoflavone; D000080242:8-Hydroxy-2'-Deoxyguanosine; D005982:Glutathione Transferase; D003849:Deoxyguanosine