Is the Comet Assay a Sensitive Procedure for Detecting Genotoxicity?

Kawaguchi, Satomi; Nakamura, Takanori; Yamamoto, Ai; Honda, Gisho; Sasaki, Yu

doi:10.4061/2010/541050

Cited by 47 publications

(29 citation statements)

References 26 publications

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“…In contrast to the current study, previous reports indicated that 2,4-DNT is genotoxic in the rat liver micronucleus assay at 200 mg/kg [28]. The discrepant results for 2,4-DNT may be due to differences in doses used (142 mg/kg-day vs. 200 mg/kg), strain differences [30], or differences in the types of damage detected [36]. The negative result for 2,4-DNT is supported by in vivo hepatocyte initiation-promotion assays in which 2,4-DNT demonstrated no initiating activity and the only carcinogenesis study conducted with pure 2,4-DNT in which 2,4-DNT did not induce hepatocarcinomas [6][7][8][9].…”

Section: Discussioncontrasting

confidence: 53%

Assessment of the in vivo genotoxicity of isomers of dinitrotoluene using the alkaline Comet and peripheral blood micronucleus assays

Lent

Crouse

Quinn

et al. 2012

Mutation Research/Genetic Toxicology and Environmental Mutagene

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a b s t r a c t Dinitrotoluene (DNT) is a nitroaromatic explosive that exists as six isomers; two major isomers (2,4-and 2,6-DNT) and four minor isomers (2,2,3,and 3,. DNT has been found in soil, surface water, and groundwater near ammunition production plants. The major isomers of DNT are classified as "likely to cause cancer in humans." In vitro studies have provided conflicting data regarding the genotoxicity of the minor isomers. Studies indicate that metabolism in the gut and liver are necessary to convert DNT to genotoxic compounds. As such, in the present study the genotoxicity of isomers of DNT was assessed using two in vivo genotoxicity assays. The Comet assay was used to detect DNA damage in liver cells from male Sprague-Dawley rats following oral exposure (14-day) to individual isomers of DNT. The micronucleus assay was conducted using flow cytometric analysis to detect chromosomal damage in peripheral blood. Treatment with 2,3-, 3,4-, 2,4-, 2,5-and 3,5-DNT did not induce DNA damage in liver cells or increase the frequency of micronucleated reticulocytes (MN-RET) in peripheral blood at the doses tested. Treatment with 2,6-DNT induced DNA damage in liver tissue at all doses tested, but did not increase the frequency of micronucleated reticulocytes (MN-RET) in peripheral blood. Thus, 2,4-DNT and the minor isomers were not genotoxic under these test conditions, while 2,6-DNT was genotoxic in the target tissue, the liver. These results support previous research which indicated that the hepatocarcinogenicity of technical grade DNT (TG-DNT) could be attributed to the 2,6-DNT isomer.Published by Elsevier B.V.

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Section: Discussioncontrasting

confidence: 53%

Assessment of the in vivo genotoxicity of isomers of dinitrotoluene using the alkaline Comet and peripheral blood micronucleus assays

Lent

Crouse

Quinn

et al. 2012

Mutation Research/Genetic Toxicology and Environmental Mutagene

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“…Although, the micronucleus assay has been conventionally used (Heddle et al, 1983;Heddle et al, 1991;Kirsch-Volders et al, 2011), other tests such as those based on DNA adduct formation (Dybing et al, 1984), in vivo chromosomal aberration (You et al, 1993), transgenic mutation (Heddle et al, 2000;Lambert et al, 2005) and comet assay (Tice et al, 2000;Kumaravel and Jha, 2006;Olive and Banáth, 2006) have also been routinely employed in the past as in vivo follow up assay when equivocal or inconclusive results are obtained in the in vitro assay. Kawaguchi et al (2010), reported an identical sensitivity of the micronucleus test and the comet assay in detecting the studied mutagens but were quick to point out that the power of the comet assay to detect a low level of genotoxic potential can be superior to that of micronucleus test by the inclusion of using DNA resynthesis inhibitors.…”

Section: Appropriate In Vivo Follow-up Assay Of Genotoxicitymentioning

confidence: 99%

Toxicity of food colours and additives: A review

Thomas¹,

Adegoke²

2015

Afr. J. Pharm. Pharmacol.

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Majority of consumer goods are required to be presented with good aesthetics in order to improve acceptability in terms of colours and in some instances taste. When related to food, beverages and drug products, additives are usually added to mask un-inviting colours, obscure offensive odours and increase taste. Food additives therefore include colourants, sweeteners, preservatives and anti-caking agents. Admissible daily intake limits are often recommended for these additives. Being food products, the amount consumed over time may be subject to individual preferences and thus negating the desire to regulate and control the amount consumed cumulatively. There have been several concerns about the safety of food additives and several batteries of tests, and reports are available in literature. This review attempted to give an update on reports that have surfaced in literature over recent past on the use and safety of food colours and other additives. Some safety concerns have been related to three determinations; cytotoxicity, genotoxicity and induction or potential of inducing mutagenicity. In order to accomplish these targeted evaluations, several tests have been prescribed by International conference on harmonization (ICH), organization for economic co-operation and development (OECD) and European food safety authority (EFSA). It is observed that no single test can give a full proof of safety of these food colours and additives, hence minimal tests are recommended to be carried out in order to guarantee safety of these products. Survey of literature, revealed that once some approved additives or colours become a subject of safety concerns, comprehensive evaluations are carried out by researchers and these have often led to the de-classification of some hitherto reported agents as being non-genotoxic or non-carcinogenic. The declassifications of some food colors and additives as human carcinogens are regularly done following the comprehensive evaluation of results of mutagenicity and genotoxicity tests in vitro and some in vivo tests in mammalian tissues and whole animals. However, such declassifications are often done with caution and the implication is that regular and more comprehensive tests must be carried out. In addition, the requirements of testing for chronic exposures to this and other agents must be emphasized to prevent occurrence of subtle yet terrible side effects resulting from consuming sub-toxic doses of the additives over time.

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“…b) The power of the MN test to detect a low level of genotoxic potential is superior to that of the comet assay; and c) The power of the comet assay to detect a low level of genotoxic potential can be elevated to a level higher than that of an MN test by using DNA resynthesis inhibitors, such as araC and HU [45].…”

Section: Mutagen Cometmentioning

confidence: 99%

“…However, the exposure conditions used in some of those studies differed among different assays Pfau et al [42] exposed cells for 30 min and 24 h in the comet assay and the MN test, respectively) and model mutagens with well characterized action mechanisms were not used, making it difficult to systematically compare the sensitivities of those assays including the comet assay. Kawaguchi et al [45] conducted combined experiments with TK6 cells including (standard) comet assay, acellular assay, and an MN test under identical exposure conditions. Results are summarized as follows (Table 3):…”

Section: Power Of the Comet Assay To Detect Low Level Genotoxicitymentioning

confidence: 99%

The Power of the Comet Assay to Detect Low Level Genotoxicity and DNA Repair Factors Affecting its Power

Sasaki

SatomiKawaguchi

Nakamura

2017

MOJT

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The comet assay is considered to be a rapid and sensitive procedure for quantitating DNA damage in mammalian cells. In this article, to interpret its outcomes adequately, its power to detect low level genotoxicity and factors affecting its power were reviewed. Although the development of initial lesions into alkali-labile sites and/or SSBs through repairing events is an important factor to support its detecting power, their repair reduce its power to detect SSBs as an initial DNA lesion. The acellular comet assay, in which slides with gel are prepared from untreated cells are exposed after lysis to test agents. Thus, detection of SSBs as initial lesions but not alkali-labile sites generated from DNA lesion such as alkylated bases and the power to detect low level SSBs as initial lesions is lower in the standard than in the acellular assay. The acellular comet assay would be practically used to detect SSBs as initial lesions. The inhibitors of re-synthesis andincisionsteps of the excision repair enhance and suppress comet-tail formation, respectively. Although the incision step of repairing process is necessary to support the sensitivity of the comet assay, its re-synthesis step reduces the power to detect low level genotoxicity. Although this assay can detect a wide variety of genotoxoic compounds and its power to detect genotoxicity were identical to that of the MN test, its power to detect low levels of genotoxic potential is inferior to that of the MN test. However, its power of to detect a low level of genotoxicity can be elevated to a level higher than that of the MN test by using DNA resynthesis inhibitors, such as araC and HU. In conclusion, the outcomes of comet assay should be interpretedappropriately in consideration of the action of DNA repair.

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Is the Comet Assay a Sensitive Procedure for Detecting Genotoxicity?

Cited by 47 publications

References 26 publications

Assessment of the in vivo genotoxicity of isomers of dinitrotoluene using the alkaline Comet and peripheral blood micronucleus assays

Assessment of the in vivo genotoxicity of isomers of dinitrotoluene using the alkaline Comet and peripheral blood micronucleus assays

Toxicity of food colours and additives: A review

The Power of the Comet Assay to Detect Low Level Genotoxicity and DNA Repair Factors Affecting its Power

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