| Summary: | 碩士 === 國立陽明大學 === 口腔生物研究所 === 96 === In 2007, Department of Health in Taiwan has documented that oral cancer is the sixth leading causes of cancer death, and the fourth for man. The mortality of oral cancer is gradually increased every year, so oral cancer is an important health problem in Taiwan. Safrole is a nature plant constituent of a number of spices, such as nutmeg, anise, cinnamon and black pepper, and also in drinks. Piper betle inflorescence which contains high concentration of safrole, about 15 mg/g wet weight, is a unique ingredient of betel quid（BQ）in Taiwan. Chewing such prepared betel quid could result in safrole concentration as high as 420 μM in saliva. Safrole is an animal hempatocarcinogen. Safrole has various toxicities including genotoxicity, cytotocixity, mutagenicity and tumorigenicity, indicating a possible correlation between safrole and oral cancer. The metabolic bioactivation of safrole are mediated through cytochrome P450, and then produce a number of proximate carcinogens which can give rise to DNA adducts and cause carcinogenesis. Drug metabolizing-enzymes play an important role in bioactivation and detoxification of carcinogens, so regulation of these enzymes could affect carcinogenesis and pharmacology. This study aims to know the effects of safrole on drug metabolizing-enzymes including NADPH-cytochrome P450 reductase, 7-ethoxyresorufin O-deethylation (EROD), glutathione S-transferase (GST) and NAD(P)H-quinone oxidoreductase 1 (NQO1). In oxidative stress analysis of reactive oxygen species and lipid hydroperoxides, OECM-1 are treated by 420 µM safrole for 6 hours can increase 80% lipid hydroxyperoxides production, but doesn’t significant increase reactive oxygen species production. In time-course and dose-dependent of effects of safrole on drug metabolizing-enzymes activities, at a concentration of 420 µM safrole for thirty hours result in 3.6-fold and 0.2-fold increases of EROD and NQO1, respectively. But activities of NADPH-cytochrome P450 reductase and GST are no effects. Immunoblot analysis and RT-PCR reveal that safrole increases both protein and mRNA expressions of CYP1A and NQO1, but no effect in GSTP1 protein expression. Immunoblot analysis of cytosolic proteins and nuclear extracts showed that safrole-exposure caused 20% and 60% decreases in the level of cytosolic AhR and Nrf2, respectively. Safrole-exposure caused 27% and 270% increases in the level of nuclear AhR and Nrf2, respectively. These results suggest that safrole can activate cytosolic AhR and Nrf2, and make them translocate to nucleus and further induce CYP1A and NQO1 expression. These results demonstrated that safrole induced CYP1A and NQO1 through AhR and Nrf2. However, many carcinogens and pollutants are bioactived through CYP1A, so safrole maybe a possible factor to enhance other toxic compounds like tobacco smoke to cause oral cancer.
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