Abstract
To determine the threshold dose of β-Naphthoflavone (BNF) that induces hepatocellular tumor promoting effects, reactive oxygen species (ROS) generation and thiobarbituric acid-reactive substance (TBARS) formation, and drug-metabolizing enzymes that protect against ROS generation, two-stage liver carcinogenesis model was used. Partial hepatectomized rats (n = 11 to 12) were fed diets containing 0, 0.03, 0.06, 0.125 or 0.25% BNF for 6 weeks after an intraperitoneal injection of N-diethylnitrosamine (DEN) to initiate hepatocarcinogenesis. Histopathologically, glutathione S-transferase placental form (GST-P)-positive foci significantly increased in rats given 0.25% BNF. No marked changes in ROS production and TBARS contents were observed between the BNF treated and DEN alone groups. Real-time RT-PCR showed that the expression of Cyp1a1, Cyp1a2, Cyp1b1 and Nqo1 significantly increased in the groups given 0.03% BNF or more, but Ugt1a6, Akr7a3 and Gstm1 significantly increased in the groups given 0.125% BNF or more. Gpx2 and Yc2 significantly increased in the groups given 0.06% BNF or more and 0.25% BNF, respectively. Inflammation-related genes such as Ccl2, Mmp12, Serpine1 and Cox-2 significantly increased in the 0.25% BNF group. In immunohistochemistry, the number of cyclooxygenase-2 (COX-2)-positive cells increased in rats given 0.25% BNF. These results suggest that 0.25% BNF is the threshold dose for liver tumor promotion, and the fact that inflammation-related genes and COX-2 protein increased in the 0.25% BNF group strongly suggests that inflammation is involved in the liver tumor promoting effect of BNF in rats.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Aryl Hydrocarbon Hydroxylases / genetics
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Aryl Hydrocarbon Hydroxylases / metabolism
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Chemokine CCL2 / genetics
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Chemokine CCL2 / metabolism
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Cyclooxygenase 2 / genetics
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Cyclooxygenase 2 / metabolism
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Cytochrome P-450 CYP1A1 / genetics
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Cytochrome P-450 CYP1A1 / metabolism
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Cytochrome P-450 CYP1A2
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Cytochrome P-450 CYP1B1
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Cytochromes / genetics
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Cytochromes / metabolism
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Diethylnitrosamine / toxicity
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Dose-Response Relationship, Drug
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Glucuronosyltransferase / genetics
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Glucuronosyltransferase / metabolism
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Glutathione Peroxidase / genetics
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Glutathione Peroxidase / metabolism
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Glutathione Transferase / genetics
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Glutathione Transferase / metabolism
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Hepatectomy / methods
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Immunohistochemistry
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Lipid Peroxidation / drug effects
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Liver / drug effects*
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Liver / pathology
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Liver Neoplasms, Experimental / chemically induced
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Liver Neoplasms, Experimental / pathology*
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Male
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NAD(P)H Dehydrogenase (Quinone) / genetics
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NAD(P)H Dehydrogenase (Quinone) / metabolism
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Oxidative Stress / drug effects
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Plasminogen Activator Inhibitor 1 / genetics
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Plasminogen Activator Inhibitor 1 / metabolism
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Rats
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Rats, Inbred F344
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Reactive Oxygen Species / metabolism
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Real-Time Polymerase Chain Reaction
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Thiobarbituric Acid Reactive Substances / metabolism
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Up-Regulation
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beta-Naphthoflavone / toxicity*
Substances
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Ccl2 protein, rat
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Chemokine CCL2
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Cytochromes
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Plasminogen Activator Inhibitor 1
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Reactive Oxygen Species
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Serpine1 protein, rat
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Thiobarbituric Acid Reactive Substances
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Diethylnitrosamine
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beta-Naphthoflavone
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Glutathione Peroxidase
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glutathione peroxidase 2, rat
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Aryl Hydrocarbon Hydroxylases
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Cyp1a2 protein, rat
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Cyp1b1 protein, rat
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Cytochrome P-450 CYP1A1
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Cytochrome P-450 CYP1A2
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Cytochrome P-450 CYP1B1
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Cyclooxygenase 2
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Ptgs2 protein, rat
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NAD(P)H Dehydrogenase (Quinone)
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NQO1 protein, rat
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Glucuronosyltransferase
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UDP-glucuronosyltransferase, UGT1A7
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Glutathione Transferase
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glutathione S-transferase M1