Dietary supplementation of the citrus antioxidant auraptene inhibits N,N-diethylnitrosamine-induced rat hepatocarcinogenesis.
OBJECTIVE
We have previously reported that an antioxidant, auraptene (AUR), isolated from citrus fruit effectively inhibits chemically induced carcinogenesis in digestive tracts, such as the oral cavity, esophagus and large bowel. In this study, we investigated the modifying effects of dietary supplementation with AUR on N,N-diethylnitrosamine (DEN)-initiated hepatocarcinogenesis in male F344 rats in two different experiments to determine whether the compound exerts a cancer-chemopreventive action in other organs.


METHODS
In the first experiment, animals were fed diets containing AUR at dose levels of 100 and 500 ppm for 7 weeks 1 week before, during, and 1 week after the start of liver carcinogenesis induced by DEN (40 ppm in drinking water for 5 weeks) to predict the modulatory effect on hepatocarcinogenesis. After 7 weeks, the numbers of hepatocellular enzyme-altered foci (EAF; cm(2)) which stained positive for the placental form of glutathione S-transferase (GST-P) and transforming growth factor (TGF)-alpha were determined on immunohistochemically stained sections. In the second experiment conducted to confirm the findings, animals subjected to DEN treatment were fed AUR-containing diets (100 and 500 ppm) during either the initiation stage ('initiation' feeding for 7 weeks) or post-initiation phase ('post-initiation' feeding for 25 weeks) of DEN-induced hepatocarcinogenesis.


RESULTS
In the first experiment, feeding with AUR at both doses during DEN exposure decreased the mean numbers of GST-P-positive and TGF-alpha-positive EAF/cm(2), and the reduction in the number of TGF-alpha-positive EAF by feeding 500 ppm AUR was statistically significant (p < 0.005). In the second experiment, the 'initiation' feeding with 500 ppm AUR significantly inhibited the incidence (33 vs. 83%, p = 0.000511) and multiplicity (0.67 +/- 1.09 vs. 1.96 +/- 1.85, p < 0.005) of liver cell carcinoma. Also, the 'post-initiation' feeding with AUR at both doses significantly reduced the development of hepatocellular carcinoma (100 ppm: incidence, 15%, p = 0.000006; multiplicity: 0.25 +/- 0.64, p < 0.001; 500 ppm: incidence, 11%, p = 0.000002; multiplicity, 0.26 +/- 0.81, p < 0.001). In addition, AUR feeding reduced cell proliferation and the apoptotic index in liver cell neoplasms.


CONCLUSIONS
The results suggest that the citrus antioxidant AUR is a potential chemopreventive agent against DEN-induced hepatocarcinogenesis in rats.
Sakata
Keiko
K
Department of Pathology, Gifu University School of Medicine, Gifu, Japan. f2101002@guedu.cc.gifu-u.ac.jp
Hara
Akira
A
Hirose
Yoshinobu
Y
Yamada
Yasuhiro
Y
Kuno
Toshiya
T
Katayama
Masaki
M
Yoshida
Koujiro
K
Zheng
Qiao
Q
Murakami
Akira
A
Ohigashi
Hajime
H
Ikemoto
Kohei
K
Koshimizu
Koichi
K
Tanaka
Takuji
T
Mori
Hideki
H
D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis; D001835:Body Weight; D002273:Carcinogens; D002957:Citrus; D003374:Coumarins / Q000494:pharmacology*; D019587:Dietary Supplements; D004052:Diethylnitrosamine; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control*; D008297:Male; D009929:Organ Size; D051381:Rats; D011916:Rats, Inbred F344
D016588:Anticarcinogenic Agents; D000975:Antioxidants; D002273:Carcinogens; D003374:Coumarins; D004052:Diethylnitrosamine; C105832:aurapten