Genoprotection and genotoxicity of green tea (<i>Camellia sinensis</i>): Are they two sides of the same redox coin?

Ho, Cyrus K.; Choi, Sung‐Woon; Siu, Parco M.; Benzie, Iris F.F.

doi:10.1179/1351000213y.0000000051

Cited by 15 publications

(11 citation statements)

References 30 publications

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“…Incubation of PBMN cells with green tea decreased DNA damage at low concentrations but increased it at the highest concentration tested (representing 71 mM catechins) [24]. Various honeys afforded slight protection of HepG2 cells against SBs produced by treatment with certain organic carcinogens [26].…”

Section: Resultsmentioning

confidence: 99%

Polyphenols and DNA Damage: A Mixed Blessing

Azqueta

Collins

2016

Nutrients

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Polyphenols are a very broad group of chemicals, widely distributed in plant foods, and endowed with antioxidant activity by virtue of their numerous phenol groups. They are widely studied as putative cancer-protective agents, potentially contributing to the cancer preventive properties of fruits and vegetables. We review recent publications relating to human trials, animal experiments and cell culture, grouping them according to whether polyphenols are investigated in whole foods and drinks, in plant extracts, or as individual compounds. A variety of assays are in use to study genetic damage endpoints. Human trials, of which there are rather few, tend to show decreases in endogenous DNA damage and protection against DNA damage induced ex vivo in blood cells. Most animal experiments have investigated the effects of polyphenols (often at high doses) in combination with known DNA-damaging agents, and generally they show protection. High concentrations can themselves induce DNA damage, as demonstrated in numerous cell culture experiments; low concentrations, on the other hand, tend to decrease DNA damage.

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Section: Resultsmentioning

confidence: 99%

Polyphenols and DNA Damage: A Mixed Blessing

Azqueta

Collins

2016

Nutrients

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“…In contrast, the functional activity of green tea has been found to be synergistic with ascorbic acid and α‐tocopherol actions, potentializing its antioxidant property . Although the bioavailability of catechins may also be lower in infusion drinks, studies show that the plasma antioxidant capacity increases within an hour of its ingestion .…”

Section: Green Tea and Oxidative Stressmentioning

confidence: 99%

Therapeutic potential of green tea on risk factors for type 2 diabetes in obese adults – a review

et al. 2016

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Green tea has been associated with positive effects in the treatment of obesity and other associated comorbidities such as type 2 diabetes. These benefits are thought to be related to the anti-inflammatory and antioxidant effects of green tea and to the reduction in body fat percentage exhibited by its bioactive compounds. The predominant active compounds in green tea are flavonoid monomers known as catechins, in particular epigallocatechin-3-gallate, which is the most abundant and most effective catechin in metabolic care, particularly among obese patients. The objective of this review was to investigate the effects of green tea on body composition, oxidative stress, inflammation and insulin resistance, risk factors for the development of type 2 diabetes in obese individuals and the mechanisms that underlie the modulatory actions of green tea compounds on these risk factors. Although green tea has therapeutic potential in the treatment of obese individuals, the findings of this review demonstrate the need for a greater number of studies to confirm the positive effects of green tea, especially regarding the modulation of obesity.

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“…ARE activation leads to upregulation of genes that produce an array of cytoprotective factors, including human oxoguanine glycosylase human oxoguanine glycosylase 1 (hOGG1), which catalyzes the first step in base excision repair (BER) of oxidation‐induced lesions in DNA, and heme oxygenase‐1 (HMOX‐1), which is regarded as a “therapeutic funnel” because of its anti‐inflammatory, immunomodulatory, and antioxidant effects . There is evidence from animal and cell culture studies that tea catechins activate the ARE and cause increased expression of HMOX‐1, indicating a pro‐oxidant shift in intracellular redox balance, but data from human studies are lacking, and in vitro study showed no acute effect of exposure to green tea on expression of several ARE‐associated genes .…”

Section: Dna Damage Assessed Using the Comet Assay In Lymphocytes Cmentioning

confidence: 99%

“…Alternatively, or in addition, there could be acute, subtle pro‐oxidant effects triggered by catechins (and perhaps other phytochemicals). Regular, small, postingestion “pro‐oxidant waves” could induce cytoprotective ARE‐triggered adaptations, such as enhanced DNA repair and increased HMOX‐1 . To date, the hypothesized effects of pro‐oxidant phytochemicals on redox tone and cellular adaptive response have not been demonstrated to occur in humans.…”

Section: Dna Damage Assessed Using the Comet Assay In Lymphocytes Cmentioning

confidence: 99%

“…anti-inflammatory, immunomodulatory, and antioxidant effects [9][10][11]. There is evidence from animal and cell culture studies that tea catechins activate the ARE and cause increased expression of HMOX-1, indicating a pro-oxidant shift in intracellular redox balance, but data from human studies are lacking, and in vitro study showed no acute effect of exposure to green tea on expression of several ARE-associated genes [12,13].…”

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confidence: 99%

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Effects of single dose and regular intake of green tea (Camellia sinensis) on DNA damage, DNA repair, and heme oxygenase-1 expression in a randomized controlled human supplementation study

Choi

Siu

et al. 2014

Mol. Nutr. Food Res.

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Regular intake of green tea (Camellia sinensis) lowers DNA damage in humans, but molecular mechanisms of genoprotection are not clear. Protection could be via direct antioxidant effects of tea catechins, but, paradoxically, catechins have pro-oxidant activity in vitro, and it is hypothesized that mechanisms relate to redox-sensitive cytoprotective adaptations. We investigated this hypothesis, focusing particularly on effects on the DNA repair enzyme human oxoguanine glycosylase 1 (hOGG1), and heme oxygenase-1, a protein that has antioxidant and anti-inflammatory effects. A randomized, placebo-controlled, human supplementation study of crossover design was performed. Subjects (n = 16) took a single dose (200 mL of 1.5%, w/v) and 7-days of (2 × 200 mL 1%, w/v per day) green tea (with water as control treatment). Lymphocytic DNA damage was ∼30% (p < 0.001) lower at 60 and 120 min after the single dose and in fasting samples collected after 7-day tea supplementation. Lymphocytic hOGG1 activity was higher (p < 0.0001) at 60 and 120 min after tea ingestion. Significant increases (p < 0.0005) were seen in hOGG1 activity and heme oxygenase-1 after 7 days. Results indicate that molecular triggering of redox-sensitive cytoprotective adaptations and posttranslational changes affecting hOGG1 occur in vivo in response to both a single dose and regular intake of green tea, and contribute to the observed genoprotective effects of green tea.

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Genoprotection and genotoxicity of green tea (Camellia sinensis): Are they two sides of the same redox coin?

Abstract: Genoprotection by low-dose green tea could be due to direct antioxidant protection by green tea polyphenols, or to H2O2-independent signalling pathways.

Cited by 15 publications

References 30 publications

Polyphenols and DNA Damage: A Mixed Blessing

Polyphenols and DNA Damage: A Mixed Blessing

Therapeutic potential of green tea on risk factors for type 2 diabetes in obese adults – a review

Effects of single dose and regular intake of green tea (Camellia sinensis) on DNA damage, DNA repair, and heme oxygenase-1 expression in a randomized controlled human supplementation study

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