Decreased levels of 2-amino-3-methylimidazo[4,5-f]quinoline-DNA adducts in rats treated with β-carotene, α-tocopherol and freeze-dried aloe

Nobuaki Uehara, Yoshio Iwahori, Makoto Asamoto, Hiroyasu Baba-Toriyama, Masaaki Iigo, Masako Ochiai, Minako Nagao, Masafumi Nakayama, Masakuni Degawa, Kazuyuki Matsumoto, Iwao Hirono, Hidehiko Beppu, Keisuke Fujita, Hiroyuki Tsuda

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19 Citations (Scopus)

Abstract

To assess mechanisms of chemoprevention of hepatocarcinogenesis by trans-β-carotene (β-C), DL-α-tocopherol (α-T), and freeze-dried whole leaves of Kidachi aloe (Aloe), formation of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)-DNA adducts was measured by 32P-post-labeling analysis, and CYP1A1 and CYP1A2 protein levels were analyzed by ELISA. Group 1 rats were fed diet containing 0.02% β-C, 1.5% α-T or 30% Aloe over an 8-day period, while group 2 was given basal diet alone. On day 7, all animals were subjected to two-thirds partial hepatectomy (PH). Twelve hours after PH, they received a single dose of the carcinogenic food pyrolysate IQ (100 mg/kg) intragastrically, to initiate hepatocarcinogenesis. Rats were killed 6, 12, 24 and 48 h after IQ administration. The levels of adducts, expressed as relative adduct labeling values in rats treated with β-C, α-T and Aloe, were decreased as compared with the control group at hour 24 (36 h after PH), with a significant difference in the case of the β-C group (46.4% of the control value). Similarly, all showed a tendency for decrease at hour 48. Furthermore, the levels of CYP1A2, known to be responsible for activation of IQ, showed a significant reduction at hour 24. It is concluded that β-C, and possibly also α-T and Aloe, have the potential to reduce IQ-DNA adduct formation, presumably as a result of decreased formation of active metabolites. The results may explain, at least in part, the previously observed inhibitory effects of these compounds on induction of preneoplastic hepatocellular lesions.

Original languageEnglish
Pages (from-to)342-348
Number of pages7
JournalJapanese Journal of Cancer Research
Volume87
Issue number4
DOIs
Publication statusPublished - 1996 Apr

Keywords

  • Chemoprevention
  • Hepatocarcinogenesis
  • IQ-DNA adduct
  • Initiation
  • β-carotene

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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