Threshold dose of liver tumor promoting effect of β-naphthoflavone in rats.
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.
Laboratory of Veterinary Pathology, Tokyo University of Agriculture and Technology, Tokyo Japan.
Hitomi
H
Hayashi
Eriko
E
Taniai
Reiko
R
Morita
Atsunori
A
Yafune
Kazuhiko
K
Suzuki
Makoto
M
Shibutani
Kunitoshi
K
Mitsumori
D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000378:metabolism; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2; D065633:Cytochrome P-450 CYP1B1; D003580:Cytochromes / Q000235:genetics / Q000378:metabolism; D004052:Diethylnitrosamine / Q000633:toxicity; D004305:Dose-Response Relationship, Drug; D014453:Glucuronosyltransferase / Q000235:genetics / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000235:genetics / Q000378:metabolism; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006498:Hepatectomy / Q000379:methods; D007150:Immunohistochemistry; D015227:Lipid Peroxidation / Q000187:drug effects; D008099:Liver / Q000187:drug effects* / Q000473:pathology; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced / Q000473:pathology*; D008297:Male; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D017382:Reactive Oxygen Species / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D015854:Up-Regulation; D019324:beta-Naphthoflavone / Q000633:toxicity*
D001189:Aryl Hydrocarbon Hydroxylases; D018932:Chemokine CCL2; D051546:Cyclooxygenase 2; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D065633:Cytochrome P-450 CYP1B1; D003580:Cytochromes; D004052:Diethylnitrosamine; D014453:Glucuronosyltransferase; D005979:Glutathione Peroxidase; D005982:Glutathione Transferase; D016660:NAD(P)H Dehydrogenase (Quinone); D017395:Plasminogen Activator Inhibitor 1; D017382:Reactive Oxygen Species; D017392:Thiobarbituric Acid Reactive Substances; D019324:beta-Naphthoflavone; C491766:Ccl2 protein, rat; C547314:Serpine1 protein, rat; C525844:glutathione peroxidase 2, rat; C017170:Cyp1a2 protein, rat; C585499:Cyp1b1 protein, rat; C489691:Ptgs2 protein, rat; C507703:NQO1 protein, rat; C107611:UDP-glucuronosyltransferase, UGT1A7