Pretreatment with black tea polyphenols modulates xenobiotic-metabolizing enzymes in an experimental oral carcinogenesis model.
The objective of this study was to evaluate the chemopreventive potential of the black tea polyphenols Polyphenon-B and BTF-35 during the preinitiation phase of 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. Hamsters were divided into six groups. Animals in groups 2 and 3 received diet containing Polyphenon-B and BTF-35, respectively, 4 weeks before carcinogen administration when they were 6 weeks of age and continued until the final exposure to carcinogen. At 10 weeks of age, animals in groups 1, 2, and 3 were painted with 0.5% DMBA three times a week for 14 weeks. Animals in groups 4 and 5 were given Polyphenon-B and BTF-35 alone, respectively, as in groups 2 and 3. Animals in group 6 served as control. All the animals were sacrificed after an experimental period of 18 weeks. Phase I and phase II xenobiotic-metabolizing enzymes and 8-hydroxy-deoxyguanosine (8-OH-dG) in the buccal pouch and liver were used as biomarkers of chemoprevention. Hamsters painted with DMBA showed increased expression of 8-OH-dG and enhanced activities of phase I (CYP450; total as well as CYP1A1, 1A2, and 2B isoforms and cytochrome b5) and phase II (GST and quinone reductase) xenobiotic-metabolizing enzymes with increased immunohistochemical expression of CYP1A1, and CYP1B1 isoforms in the buccal pouch. This was accompanied by increased phase I and decreased phase II enzyme activities in the liver. Administration of Polyphenon-B and BTF-35 significantly decreased tumor incidence, oxidative DNA damage, phase I enzyme activities as well as expression of CYP1A1 and CYP1B1 isoforms, while enhancing phase II enzyme activities in the buccal pouch and liver. Our results provide a mechanistic basis for the chemopreventive potential of black tea polyphenols. Furthermore, the greater efficacy of BTF-35 in chemoprevention of HBP carcinomas via inhibition of oxidative DNA damage and modulation of xenobiotic-metabolizing enzymes may have a major impact in human oral cancer prevention.
Vidjaya Letchoumy
P
P
Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Annamalainagar-608 002, Tamil Nadu, India.
Chandra Mohan
K V P
KV
Stegeman
J J
JJ
Gelboin
H V
HV
Hara
Y
Y
Nagini
S
S
D000080242:8-Hydroxy-2'-Deoxyguanosine; D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D002273:Carcinogens; D006224:Cricetinae; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D004195:Disease Models, Animal; D005419:Flavonoids / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D007124:Immunoenzyme Techniques; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D008297:Male; D008647:Mesocricetus; D009061:Mouth Mucosa / Q000378:metabolism; D009062:Mouth Neoplasms / Q000139:chemically induced / Q000517:prevention & control*; D010636:Phenols / Q000494:pharmacology*; D013662:Tea; D015262:Xenobiotics / Q000378:metabolism*
D002273:Carcinogens; D005419:Flavonoids; D010636:Phenols; D013662:Tea; D015262:Xenobiotics; C506663:polyphenon B; D015127:9,10-Dimethyl-1,2-benzanthracene; D000080242:8-Hydroxy-2'-Deoxyguanosine; D003577:Cytochrome P-450 Enzyme System; D003849:Deoxyguanosine