Mut-Test to detect substances suppressing spontaneous mutation due to oxidative damage

Yonezawa, Yusuke; Kawamura, Saiko; Yamato, Masayuki; Nishioka, H.

doi:10.1016/s1383-5718(00)00148-0

Cited by 7 publications

(5 citation statements)

References 29 publications

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“…52,53 In contrast, there is evidence that spontaneous mutagenesis is not suppressed by green tea polyphenols in a bacterial system. 54 Our data indicate a marginally significant increase in hprt spontaneous mutations after EGCG treatment whereas the combination of UVA and EGCG is not significantly different from EGCG treatment alone.…”

Section: Discussionmentioning

confidence: 48%

The green tea polyphenol, epigallocatechin‐3‐gallate, protects against the oxidative cellular and genotoxic damage of UVA radiation

Tobi

Gilbert

Paul

et al. 2002

Intl Journal of Cancer

100

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A number of biological activities have been ascribed to the major green tea polyphenol epigallocatechin-3-gallate (EGCG) to explain its chemopreventive properties. Its antioxidant properties emerge as a potentially important mode of action. We have examined the effect of EGCG treatment on the damaging oxidative effects of UVA radiation in a human keratinocyte line (HaCaT). Using the ROS-sensitive probes dihydrorhodamine 123 (DHR) and 2 ,7 -dichlorodihydrofluorescein diacetate (DCFH-DA), we detected a reduction in fluorescence in UVA-irradiated (100 kJ/m 2 ) cells in the case of the former but not the latter probe after a 24-hr treatment with EGCG (e.g., 14%, [p < 0.05] after 10 M EGCG). In the absence of UVA, however, both DHR and DCFH detected a pro-oxidant effect of EGCG at the highest concentration used of 50 M. Measurements of DNA damage in UVA-exposed cells using the single cell gel electrophoresis assay (comet assay) also showed the protective effects of EGCG. A concentration of 10 M EGCG decreased the level of DNA single strand breaks and alkali-labile sites to 62% of the level observed in non-EGCG, irradiated cells (p < 0.001) with a 5-fold higher concentration producing little further effect. Correspondingly, EGCG ablated the mutagenic effects of UVA (500 kJ/m 2 ) reducing an induced hypoxanthine-guanine phosphoribosyl transferase (HPRT) mutant frequency of (3.39 ؎ 0.73) ؋ 10 ؊6 to spontaneous levels (1.09 ؎ 0.19) ؋ 10 ؊6 . Despite having an antiproliferative effect in the absence of UVA, EGCG also served to protect against the cytotoxic effects of UVA radiation. Our data demonstrate the ability of EGCG to modify endpoints directly relevant to the carcinogenic process in skin. © 2002 Wiley-Liss, Inc. Key words: epigallocatechin-3-gallate; antioxidant; ultraviolet AThere has been considerable recent interest in the chemopreventive properties of the polyphenols or catechins of green tea that have been shown to inhibit tumorigenesis in a variety of organs in rodent models. 1-3 The major polyphenol component by mass, (Ϫ)-epigallocatechin-3-gallate (EGCG) is an effective protectant against the mutagenicity of a number of chemical carcinogens including benzo[a]pyrene (B[a]P), aflatoxin B1 and 3-hydroxyamino-1-methyl-5H-pyrido [4,3-b]indole. 4 -6 EGCG, together with other green tea polyphenols also exhibits growth inhibitory properties in a variety of tumour cell lines. 7-9 Several mechanisms have been proposed by which these compounds exert their anti-tumorigenic action: these include the blockade of growth factors binding to their receptors, 10 phosphorylation (activation) of mitogen-activated protein kinases (MAPKs) 11,12 possibly resulting in the observed induction of Phase II drug-metabolizing enzymes, 13,14 and the generation of oxidative stress leading to apoptosis. 7,9 In the face of an oxidative challenge, however, it is now well documented that green tea catechins act as antioxidants. For example, EGCG abrogates oxidation by hydrogen peroxide both in a cell free system 15 and in terms of DNA single-s...

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Section: Discussionmentioning

confidence: 48%

The green tea polyphenol, epigallocatechin‐3‐gallate, protects against the oxidative cellular and genotoxic damage of UVA radiation

Tobi

Gilbert

Paul

et al. 2002

Intl Journal of Cancer

100

View full text Add to dashboard Cite

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“…Pre-incubation (30′/37°C) or co-incubation with D-mannitol (10 mM) had little effect on cell killing (Fig. 2) even though at this concentration D-mannitol was previously shown to essentially eliminate oxidative DNA damage [30]. Pre-incubation (30′/37°C) with 200 mM thiourea led to a small reduction in killing (Fig.…”

Section: Resultsmentioning

confidence: 89%

“…Because of recently hypothesized role of hydroxyl radicals in cell killing by aminoglycosides [7, 28, 29], and because hydroxyurea could conceivably attenuate streptomycin killing by acting as a weak hydroxyl radical scavenger, we also tested the effects of the much more efficient hydroxyl radical scavengers D-mannitol [30, 31] and thiourea [7, 30], as well as the iron chelator 2,2′-dipyridyl [7] on cell killing by streptomycin. In addition, because polA1 cells (defective for DNA polymerase I, the “repair polymerase”) are known to be exquisitely sensitive to killing by hydroxyl radical-mediated DNA damage [32], we also examined the effect of streptomycin exposure in polA1 (Am) cells.…”

Section: Resultsmentioning

confidence: 99%

Potential roles for DNA replication and repair functions in cell killing by streptomycin

Humayun

Ayyappan

2013

Mutation Research/Fundamental and Molecular Mechanisms of Mutag

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The aminoglycoside streptomycin binds to ribosomes to promote mistranslation and eventual inhibition of translation. Streptomycin kills bacteria, whereas many other non-aminoglycoside inhibitors of translation do not. Because mistranslation is now known to affect DNA replication, we asked if hydroxyurea, a specific inhibitor of DNA synthesis, affects killing, and find that hydroxyurea significantly attenuates killing by streptomycin. We find that the hydroxyl radical scavengers D-mannitol and thiourea have either no effect or only a modest protective effect. The iron chelator 2,2′-dipyridyl eliminated killing by streptomycin, but further investigation revealed that it blocks streptomycin uptake. Prior treatment of cells with low-levels of methyl methanesulfonate to induce the adaptive response to alkylation leads to a significant attenuation of killing, which, together with the hydroxyurea effect, suggests roles for DNA replication and repair functions in cell killing by streptomycin.

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“…The fluctuation test has been put to a variety of uses besides the most common of determining the resistance rate to an antibacterial agent per generation. The test has been used to compare the propensity for developing resistance (mutator phenotype) between strains of a given species (Werngren and Hoffner, 2003), and to detect substances suppressing spontaneous mutation due to oxidative damage (Yonezawa et al, 2001). Both the fluctuation test and a frequency of resistance experiment can be used to compare new and older agents in a given antibacterial class to determine their propensity to select resistant bacteria (Ince and Hooper, 2000;Griggs et al, 2003).…”

Section: Commentary Background Informationmentioning

confidence: 99%

In Vitro Antibacterial Resistance Selection and Quantitation

Young

2006

CP Pharmacology

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The study of resistance is vital to the discovery and development of new antibacterial agents. Consider the case where the resistance frequency (the proportion of cells within a population that exhibit a resistance phenotype to the agent under study) of an agent is such that, in an average infection, a mutant resistant to the agent is likely to already exist. This compound will not be useful in the clinic as a single agent, since this mutant can survive its administration, leading to potential clinical failure. This unit provides protocols for determining the frequency and rate of resistance to antibacterial agents, as well as generating resistant mutants for mechanism of action determinations or for use in antibacterial discovery or development programs.

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Mut-Test to detect substances suppressing spontaneous mutation due to oxidative damage

Cited by 7 publications

References 29 publications

The green tea polyphenol, epigallocatechin‐3‐gallate, protects against the oxidative cellular and genotoxic damage of UVA radiation

The green tea polyphenol, epigallocatechin‐3‐gallate, protects against the oxidative cellular and genotoxic damage of UVA radiation

Potential roles for DNA replication and repair functions in cell killing by streptomycin

In Vitro Antibacterial Resistance Selection and Quantitation

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