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doi:10.1016/j.taap.2004.06.014 
Copyright © 2004 Elsevier Inc. All rights reserved.
Cytochrome P450 expression and activities in human tongue cells and their modulation by green tea extract
Received 17 May 2004;
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Abstract
The expression, inducibility, and activities of several cytochrome P450 (CYP) enzymes were investigated in a human tongue carcinoma cell model, CAL 27, and compared with the human liver model HepG2 cells. The modulation effects of green tea on various CYP isoforms in both cell lines were also examined. RT-PCR analysis of CAL 27 cells demonstrated constitutive expression of mRNA for CYPs 1A1, 1A2, 2C, 2E1, 2D6, and 4F3. The results were negative for CYP2A6, 2B6/7, 3A3/4, and 3A7. Both cell lines displayed identical expression and induction profiles for all of the isoforms examined in this study except 3A7 and 2B6/7, which were produced constitutively in HepG2 but not Cal-27 cells. CYP1A1 and 1A2 were both induced by treatment with β-napthoflavone as indicated by RT-PCR and Western blotting, while CYP2C mRNA was upregulated by all-trans retinoic acid and farnesol. RT-PCR and Western blot analysis showed that the expressions of CYP1A1 and 1A2 were induced by green tea extract (GTE), which also caused an increase in mRNA for CYP2E1, CYP2D6, and CYP2C isoforms. The four tea catechins, EGC, EC, EGCG and ECG, applied to either HepG2 or Cal-27 cells at the concentration found in GTE failed to induce CYP1A1 or CYP1A2, as determined by RT-PCR. Of the isoforms that were apparently induced by GTE, only 7-ethoxycoumarin deethylase (ECOD) activity could be detected in CAL 27 or HepG2 cells. Interestingly, mRNA and protein for CYP1A1 and CYP1A2 were detected in both cell lines, and although protein and mRNA levels of CYP1A1 and CYP1A2 were increased by GTE, the observed ECOD activity in both cell lines was decreased.
Keywords: Cytochrome P450; Tongue; Oral; Green tea; RT-PCR
Article Outline
- Introduction
- Materials and methods
- Cell culture
- Chemical inducer and green tea extract treatment
- HPLC analysis of catechins in GTE
- Total RNA isolation and RT-PCR analysis
- Preparation of S9 and microsomal fraction
- Western blot analysis
- Metabolism of various CYP substrates
- Statistical analysis of data
- Results
- Constitutive expression of P450 isoforms in CAL 27 and HepG2 cells
- Induction of CYP1A1 and 1A2 isoforms by β-napthoflavone and CYP2C by all-trans retinoic acid and farnesol
- Western blot analysis of CYP1A induction by β-napthoflavone
- The effects of green tea extract on the expression of various P450 isoforms in CAL 27 and HepG2 cells
- P450-dependent metabolism in CAL 27 and HepG2 cells
- Western blot analysis of CYP1A and CYP2E1 by green tea extract
- Discussion
- Acknowledgements
- References
