Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/22516
Title: Genoprotection and genotoxicity of green tea (Camellia sinensis) : are they two sides of the same redox coin?
Authors: Ho, CK
Choi, SW
Siu, PM 
Benzie, IF 
Keywords: ARE
DNA damage
Genoprotection
Green tea
HO-1
Hydrogen peroxide
Oxidative stress
Pro-oxidant
Redox tone
Issue Date: 2013
Source: Redox report, 2013, v. 18, no. 4, p. 150-154 How to cite?
Journal: Redox Report 
Abstract: Objectives: Regular intake of green tea associates with lower DNA damage and increased resistance of DNA to oxidant challenge. However, in vitro pro-oxidant effects of green tea have been reported. Both effects could be mediated by hydrogen peroxide (H2O2) which is generated by autoxidation of tea catechins. In large amounts, H2O2 is genotoxic, but low concentrations could activate the redox-sensitive antioxidant response element (ARE) via the Keap-1/Nrf2 redox switch, inducing genoprotective adaptations. Our objective was to test this hypothesis. Methods: Peripheral lymphocytes from healthy volunteers were incubated for 30 minutes at 37°C in freshly prepared tea solutions (0.005, 0.01, 0.05%w/v (7, 14, 71 μmol/l total catechins) in phosphate buffered saline (PBS), with PBS as control) in the presence and absence of catalase (CAT). H2O2 in tea was measured colorimetrically. Oxidation-induced DNA lesions were measured by the Fpg-assisted comet assay. Results: H2O2 concentrations in 0.005, 0.01, and 0.05% green tea after 30 minutes at 37°C were, respectively, ~3, ~7, and ~52 μmol/l. Cells incubated in 0.005 and 0.01% tea showed less (P < 0.001) DNA damage compared to control cells. Cells treated with 0.05% green tea showed ~50% (P < 0.001) more DNA damage. The presence of CAT prevented this damage, but did not remove the genoprotective effects of low-dose tea. No significant changes in expression of ARE-associated genes (HMOX1, NRF2, KEAP1, BACH1, and hOGG1) were seen in cells treated with tea or tea + CAT. Conclusion: Genoprotection by low-dose green tea could be due to direct antioxidant protection by green tea polyphenols, or to H2O2-independent signalling pathways.
URI: http://hdl.handle.net/10397/22516
ISSN: 1351-0002
DOI: 10.1179/1351000213Y.0000000051
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