Premium
A Metabolomic Investigation of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) Metabolism in the Mouse
Author(s) -
Chen Chi,
Ma Xiaochao,
Malfatti Michael A,
Krausz Kristopher W,
Kimura Shioko,
Felton James S,
Idle Jeffery R,
Gonzalez Frank J
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a813
Subject(s) - cyp1a2 , chemistry , metabolite , carcinogen , biochemistry , sulfotransferase , microsome , glucuronide , metabolism , cytochrome p450 , dna adduct , enzyme
PhIP is a potent rodent carcinogen and a potential human carcinogen because of its existence in the normal human diet. Several major PhIP metabolites were identified, including N2‐OH‐PhIP, 4′‐OH‐PhIP, 5‐OH‐PhIP and their corresponding glucuronide and sulfate conjugates. Among these, N2‐OH‐PhIP is the precursor metabolite that can further be transformed into a genotoxic species by O‐acetylation or O‐sulfation. In vitro data support the view that CYP1A2 is the major enzyme responsible for formation of N2‐OH‐PhIP. However, disruption of the mouse Cyp1a2 gene failed to inhibit the PhIP‐induced carcinogenesis. To investigate the mechanism underlying this observation, the metabolism of PhIP in wild‐type, Cyp1a2‐null and CYP1A2‐humanized mice was examined using LC‐MS‐based metabolomics, and the relative abundance of major PhIP metabolites was further quantified by a radio‐HPLC assay. Furthermore, genotoxicity of PhIP in three mouse lines was evaluated by measuring DNA adduct levels in liver, lung, colon and mammary gland. From the metabolomic analysis, 17 urinary PhIP metabolites, including 8 novel metabolites, were identified and structurally elucidated. The profiles of PhIP metabolism in three CYP1A2 animal models confirmed the importance of CYP1A2 and the human‐mouse interspecies difference on the catalytic activity of CYP1A2. In addition, the results also showed that Cyp1a2‐null mice still possess significant N2‐hydroxylation and DNA adduction activities, which are partially attributed to mouse CYP2C enzymes as revealed by in vitro microsome and recombinant CYP incubations, and antibody inhibition experiments.