Effects of green and black tea on hepatic xenobiotic metabolizing systems in the male F344 rat

Sohn, Ock Soon; Surace, A.; Fiala, Emerich S.; Richie, John P.; Colosimo, Steven; Zang, Edith; Weisburger, John H.

doi:10.3109/00498259409043226

Cited by 132 publications

(74 citation statements)

References 22 publications

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“…UGT microsomal activity has been enhanced by chronic treatment with green tea beverages or extracts to a variable degree in animal studies (Sohn et al, 1994;Bu-Abbas et al, 1998;Zhu et al, 1998;Embola et al, 2002). Concerning the P450 enzymes, the data are discordant.…”

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confidence: 57%

Effects of Green Tea Compounds on Irinotecan Metabolism

et al. 2006

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ABSTRACT:The effects of green tea compounds on the metabolism of irinotecan have never been investigated. We aimed to study whether catechins [ (ECG), and 44% (EGC) of the hepatocyte preparations. Phenobarbital increased the formation of SN-38G in 100% of the same hepatocyte preparations. In Hep G2 cells, no increase in SN-38G formation was observed. With the exception of ECG in one liver, catechins did not increase UGT1A1 mRNA levels. NPC production was also significantly increased in 40% of the hepatocyte preparations for each catechin. However, the production of 6␤-hydroxytestosterone remained unaffected in other hepatocyte preparations. At pharmacologically relevant concentrations, catechins are unlikely to inhibit the formation of irinotecan inactive metabolites when administered concomitantly. The induction effect of catechins on UGT1A1 seems to be modest and highly variable. Catechins do not induce CYP3A4 activity. The effect of acute and prolonged use of green tea on the pharmacokinetics of irinotecan in patients remains to be evaluated.

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confidence: 57%

Effects of Green Tea Compounds on Irinotecan Metabolism

et al. 2006

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“…Induction of these enzymes by either naturally occurring or synthetic agents represents a promising chemopreventive strategy (5)(6)(7)(8). Green tea or green tea polyphenols have been shown to modulate various xenobiotic metabolizing enzymes, including GSTs, in animal studies and in in vitro systems (9)(10)(11)(12)(13)(14). Phase II enzyme induction by green tea polyphenols is generally believed to involve the activation of the mitogenactivated protein kinase pathway via the electrophilicmediated stress response, resulting in the activation of transcription factors that bind to antioxidant/electrophile response element located on many phase II genes (15).…”

Section: Introductionmentioning

confidence: 99%

Modulation of Human Glutathione S-Transferases by Polyphenon E Intervention

Chow¹,

Hakim²,

Vining³

et al. 2007

Cancer Epidemiology, Biomarkers &Amp; Prevention

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Purpose: Green tea consumption has been associated with decreased risk of certain types of cancers in humans. Induction of detoxification enzymes has been suggested as one of the biochemical mechanisms responsible for the cancer-preventive effect of green tea. We conducted this clinical study to determine the effect of repeated green tea polyphenol administration on a major group of detoxification enzymes, glutathione S-transferases (GST). Methods: A total of 42 healthy volunteers underwent a 4-week washout period by refraining from tea or tea-related products. At the end of the washout period, a fasting blood sample was collected, and plasma and lymphocytes were isolated for assessment of GST activity and level. Following the baseline evaluation, study participants underwent 4 weeks of green tea polyphenol intervention in the form of a standardized Polyphenon E preparation at a dose that contains 800 mg epigallocatechin gallate (EGCG) once a day. Polyphenon E was taken on an empty stomach to optimize the oral bioavailability of EGCG. Upon completion of the intervention, samples were collected for postintervention GST assessment. Results: Four weeks of Polyphenon E intervention enhanced the GST activity in blood lymphocytes from 30.7 F 12.2 to 35.1 F 14.3 nmol/min/mg protein, P = 0.058. Analysis based on baseline activity showed that a statistically significant increase (80%, P = 0.004) in GST activity was observed in individuals with baseline activity in the lowest tertile, whereas a statistically significant decrease (20%, P = 0.02) in GST activity was observed in the highest tertile. In addition, Polyphenon E intervention significantly increased the GST-P level in blood lymphocytes from 2,252.9 F 734.2 to 2,634.4 F 1,138.3 ng/mg protein, P = 0.035. Analysis based on baseline level showed that this increase was only significant (P = 0.003) in individuals with baseline level in the lowest tertile, with a mean increase of 80%. Repeated Polyphenon E administration had minimal effects on lymphocyte GST-M and plasma GST-A levels. There was a small but statistically significant decrease (8%, P = 0.003) in plasma GST-A levels in the highest tertile. Conclusions: We conclude that 4 weeks of Polyphenon E administration resulted in differential effects on GST activity and level based on baseline enzyme activity/level, with GST activity and GST-P level increased significantly in individuals with low baseline enzyme activity/level. This suggests that green tea polyphenol intervention may enhance the detoxification of carcinogens in individuals with low baseline detoxification capacity. (Cancer Epidemiol Biomarkers Prev 2007;16(8):1662 -6)

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“…Qin et al 46) have reported that the pretreatment of rats with 0.5% green tea in their drinking water for 2 or 4 weeks did not produce a significant increase in cytochrome P450 content but enhanced microsome-mediated formation of non-toxic hydroxylated metabolites of AFB 1 by 2-3 fold. It has also been reported by Sohn et al 47) and Bu-Abbas et al 48) that rats administered GTE for 4 or 6 weeks displayed no significant increase in total cytochrome P450 content in the liver but did display a significant increase in O-dealkylase activity of ethoxyresorufin (CYP1A1), methoxyresorufin (CYP1A2) and pentoxyresorufin (CYP2B1). Table 2 indicates the suppressive effect of individual GTP on AFB 1 -induced CA.…”

Section: Discussionmentioning

confidence: 82%

Suppressive Effect of (-)-Epigallocatechin Gallate on Aflatoxin B1-induced Chromosome Aberrations in Rat Bone Marrow Cells.

Ito¹,

Itô²

2001

JOURNAL OF HEALTH SCIENCE

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The suppressive effect of (-)-epigallocatechin gallate (EGCG), the major polyphenolic constituent present in green tea, on aflatoxin B 1 (AFB 1 )-induced chromosome aberrations (CA) in rat bone marrow cells was studied. The administration of EGCG 24 hr before the AFB 1 injection significantly suppressed AFB 1 -induced CA. The suppression was observed 18 hr, 24 hr and 48 hr after the AFB 1 treatment but no suppressive effect was observed at the early period (6 hr and 12 hr) after the AFB 1 treatment. Furthermore, the suppression was observed in all doses of AFB 1 (1, 5, 10 and 20 mg/kg) investigated. Rats given EGCG 2 hr before the AFB 1 injection displayed no suppressive effect. The suppressive effect of EGCG paralleled the dose of EGCG when given in a dose range of 10-60 mg/kg body weight. The administration of (-)-epicatechin gallate 24 hr before the AFB 1 injection significantly suppressed AFB 1 -induced CA as well as EGCG. On the other hand, in rats given green tea polyphenols (GTP) 2 hr before the AFB 1 injection, (-)-epigallocatechin and gallic acid significantly suppressed AFB 1 -induced CA. The pretreatment with EGCG or gallic acid did not induce the drug-metabolizing enzymes in rat liver, such as cytochrome P450 and glutathione S-transeferase. Rats given 2% green tea infusion as the sole source of drinking water for four days before sacrifice displayed significantly suppressed AFB 1 -induced CA. However, rats given various kinds of canned tea for four days showed no suppressive effect. The amount of GTP in canned tea determined by high performance liquid chromatography (HPLC) analysis was much less than that in 2% green tea infusion.

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Effects of green and black tea on hepatic xenobiotic metabolizing systems in the male F344 rat

Cited by 132 publications

References 22 publications

Effects of Green Tea Compounds on Irinotecan Metabolism

Effects of Green Tea Compounds on Irinotecan Metabolism

Modulation of Human Glutathione S-Transferases by Polyphenon E Intervention

Suppressive Effect of (-)-Epigallocatechin Gallate on Aflatoxin B1-induced Chromosome Aberrations in Rat Bone Marrow Cells.

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