Browsing by Author "Collins, Andrew"
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- DNA damage in circulating leukocytes measured with the comet assay may predict the risk of deathPublication . Bonassi, Stefano; Ceppi, Marcello; Møller, Peter; Azqueta, Amaya; Milić, Mirta; Neri, Monica; Brunborg, Gunnar; Godschalk, Roger; Koppen, Gudrun; Langie, Sabine A.S.; Teixeira, João Paulo; Bruzzone, Marco; Da Silva, Juliana; Benedetti, Danieli; Cavallo, Delia; Ursini, Cinzia Lucia; Giovannelli, Lisa; Moretti, Silvia; Riso, Patrizia; Del Bo’, Cristian; Russo, Patrizia; Dobrzyńska, Malgorzata; Goroshinskaya, Irina A.; Surikova, Ekaterina I.; Staruchova, Marta; Barančokova, Magdalena; Volkovova, Katarina; Kažimirova, Alena; Smolkova, Bozena; Laffon, Blanca; Valdiglesias, Vanessa; Pastor, Susana; Marcos, Ricard; Hernández, Alba; Gajski, Goran; Spremo-Potparević, Biljana; Živković, Lada; Boutet-Robinet, Elisa; Perdry, Hervé; Lebailly, Pierre; Perez, Carlos L.; Basaran, Nursen; Nemeth, Zsuzsanna; Safar, Anna; Dusinska, Maria; Collins, Andrew; Anderson, Diana; Andrade, Vanessa; Pereira, Cristiana Costa; Costa, Solange; Gutzkow, Kristine B.; Ladeira, Carina; Moretti, Massimo; Costa, Carla; Orlow, Irene; Rojas, Emilio; Pourrut, Bertrand; Kruszewski, Marcin; Knasmueller, Siegfried; Shaposhnikov, Sergey; Žegura, Bojana; Stopper, HelgaThe comet assay or single cell gel electrophoresis, is the most common method used to measure strand breaks and a variety of other DNA lesions in human populations. To estimate the risk of overall mortality, mortality by cause, and cancer incidence associated to DNA damage, a cohort of 2,403 healthy individuals (25,978 person-years) screened in 16 laboratories using the comet assay between 1996 and 2016 was followed-up. Kaplan-Meier analysis indicated a worse overall survival in the medium and high tertile of DNA damage (p < 0.001). The effect of DNA damage on survival was modelled according to Cox proportional hazard regression model. The adjusted hazard ratio (HR) was 1.42 (1.06-1.90) for overall mortality, and 1.94 (1.04-3.59) for diseases of the circulatory system in subjects with the highest tertile of DNA damage. The findings of this study provide epidemiological evidence encouraging the implementation of the comet assay in preventive strategies for non-communicable diseases.
- DNA strand break levels in cryopreserved mononuclear blood cell lines measured by the alkaline comet assay: results from the hCOMET ring trialPublication . Møller, Peter; Azqueta, Amaya; Rodriguez-Garraus, Adriana; Bakuradze, Tamara; Richling, Elke; Bankoglu, Ezgi Eyluel; Stopper, Helga; Claudino Bastos, Victoria; Langie, Sabine A.S.; Jensen, Annie; Ristori, Sara; Scavone, Francesca; Giovannelli, Lisa; Wojewódzka, Maria; Kruszewski, Marcin; Valdiglesias, Vanessa; Laffon, Blanca; Costa, Carla; Costa, Solange; Paulo Teixeira, João; Marino, Mirko; Del Bo, Cristian; Riso, Patrizia; Zheng, Congying; Shaposhnikov, Sergey; Collins, AndrewThe comet assay is widely used in biomonitoring studies for the analysis of DNA damage in leukocytes and peripheral blood mononuclear cells. Rather than processing blood samples directly, it can be desirable to cryopreserve whole blood or isolated cells for later analysis by the comet assay. However, this creates concern about artificial accumulation of DNA damage during cryopreservation. In this study, 10 laboratories used standardized cryopreservation and thawing procedures of monocytic (THP-1) or lymphocytic (TK6) cells. Samples were cryopreserved in small aliquots in 50% foetal bovine serum, 40% cell culture medium, and 10% dimethyl sulphoxide. Subsequently, cryopreserved samples were analysed by the standard comet assay on three occasions over a 3-year period. Levels of DNA strand breaks in THP-1 cells were increased (four laboratories), unaltered (four laboratories), or decreased (two laboratories) by long-term storage. Pooled analysis indicates only a modest positive association between storage time and levels of DNA strand breaks in THP-1 cells (0.37% Tail DNA per year, 95% confidence interval: -0.05, 0.78). In contrast, DNA strand break levels were not increased by cryopreservation in TK6 cells. There was inter-laboratory variation in levels of DNA strand breaks in THP-1 cells (SD = 3.7% Tail DNA) and TK6 reference sample cells (SD = 9.4% Tail DNA), whereas the intra-laboratory residual variation was substantially smaller (i.e. SD = 0.4%-2.2% Tail DNA in laboratories with the smallest and largest variation). In conclusion, the study shows that accumulation of DNA strand breaks in cryopreserved mononuclear blood cell lines is not a matter of concern.
- Inter-laboratory variation in measurement of DNA damage by the alkaline comet assay in the hCOMET ring trialPublication . Møller, Peter; Azqueta, Amaya; Collia, Miguel; Bakuradze, Tamara; Richling, Elke; Bankoglu, Ezgi Eyluel; Stopper, Helga; Bastos, Victoria Claudino; Langie, Sabine A.S.; Jensen, Annie; Ristori, Sara; Scavone, Francesca; Giovannelli, Lisa; Wojewódzka, Maria; Kruszewski, Marcin; Valdiglesias, Vanessa; Laffon, Blanca; Costa, Carla; Costa, Solange; Teixeira, João Paulo; Marino, Mirko; Del Bo, Cristian; Riso, Patrizia; Zheng, Congying; Shaposhnikov, Sergey; Collins, AndrewThe comet assay is a simple and versatile method for measurement of DNA damage in eukaryotic cells. More specifically, the assay detects DNA migration from agarose gel-embedded nucleoids, which depends on assay conditions and the level of DNA damage. Certain steps in the comet assay procedure have substantial impact on the magnitude of DNA migration (e.g. electric potential and time of electrophoresis). Inter-laboratory variation in DNA migration levels occurs because there is no agreement on optimal assay conditions or suitable assay controls. The purpose of the hCOMET ring trial was to test potassium bromate (KBrO3) as a positive control for the formamidopyrimidine DNA glycosylase (Fpg)-modified comet assay. To this end, participating laboratories used semi-standardized protocols for cell culture (i.e. cell culture, KBrO3 exposure, and cryopreservation of cells) and comet assay procedures, whereas the data acquisition was not standardized (i.e. staining of comets and image analysis). Segregation of the total variation into partial standard deviation (SD) in % Tail DNA units indicates the importance of cell culture procedures (SD = 10.9), comet assay procedures (SD = 12.3), staining (SD = 7.9) and image analysis (SD = 0.5) on the overall inter-laboratory variation of DNA migration (SD = 18.2). Future studies should assess sources of variation in each of these steps. On the positive side, the hCOMET ring trial demonstrates that KBrO3 is a robust positive control for the Fpg-modified comet assay. In conclusion, the hCOMET ring trial has demonstrated a high reproducibility of detecting genotoxic effects by the comet assay, but inter-laboratory variation of DNA migration levels is a concern.
- Introduction to hCOMET special issue, ‘Comet assay in vitro’Publication . Dusinska, Maria; Costa, Solange; Collins, AndrewThis special issue is produced as a valuable outcome of the COST Action hCOMET. A major aim of this project is to encourage the adoption of standard procedures for the comet assay, in order to improve reliability. Comet assay procedures tend to vary from one laboratory to another, and so comparing results between laboratories can be problematic. Much work has been done to establish how different parameters, such as agarose concentration, lysis time, or electrophoresis voltage gradient can affect results, and an aspiration of hCOMET is to devise standard procedures. In addition to papers on practical issues relating to the use of the comet assay, there are several descriptions of novel model cell systems. Finally, there are accounts of various applications of the assay to in vitro genotoxicity testing (mainly on human cell lines), as well as investigations of antigenotoxicity. (...)
- Long-term cryopreservation of potassium bromate positive assay controls for measurement of oxidatively damaged DNA by the Fpg-modified comet assay: results from the hCOMET ring trialPublication . Møller, Peter; Azqueta, Amaya; Rodriguez-Garraus, Adriana; Bakuradze, Tamara; Richling, Elke; Bankoglu, Ezgi Eyluel; Stopper, Helga; Claudino Bastos, Victoria; Langie, Sabine A.S.; Jensen, Annie; Ristori, Sara; Scavone, Francesca; Giovannelli, Lisa; Wojewódzka, Maria; Kruszewski, Marcin; Valdiglesias, Vanessa; Laffon, Blanca; Costa, Carla; Costa, Solange; Paulo Teixeira, João; Marino, Mirko; Del Bo’, Cristian; Riso, Patrizia; Zheng, Congying; Shaposhnikov, Sergey; Collins, AndrewThe formamidopyrimidine DNA glycosylase (Fpg)-modified comet assay is widely used for the measurement of oxidatively generated damage to DNA. However, there has not been a recommended long-term positive control for this version of the comet assay. We have investigated potassium bromate as a positive control for the Fpg-modified comet assay because it generates many Fpg-sensitive sites with a little concurrent generation of DNA strand breaks. Eight laboratories used the same procedure for the treatment of monocytic THP-1 cells with potassium bromate (0, 0.5, 1.5, and 4.5 mM) and subsequent cryopreservation in a freezing medium consisting of 50% foetal bovine serum, 40% RPMI-1640 medium, and 10% dimethyl sulphoxide. The samples were analysed by the Fpg-modified comet assay three times over a 3-year period. All laboratories obtained a positive concentration-response relationship in cryopreserved samples (linear regression coefficients ranging from 0.79 to 0.99). However, there was a wide difference in the levels of Fpg-sensitive sites between the laboratory with the lowest (4.2% Tail DNA) and highest (74% Tail DNA) values in THP-1 cells after exposure to 4.5 mM KBrO3. In an attempt to assess sources of inter-laboratory variation in Fpg-sensitive sites, comet images from one experiment in each laboratory were forwarded to a central laboratory for visual scoring. There was high consistency between measurements of %Tail DNA values in each laboratory and the visual score of the same comets done in the central laboratory (r = 0.98, P < 0.001, linear regression). In conclusion, the results show that potassium bromate is a suitable positive comet assay control.
- Measuring DNA modifications with the comet assay: a compendium of protocolsPublication . Collins, Andrew; Møller, Peter; Gajski, Goran; Vodenková, Soňa; Abdulwahed, Abdulhadi; Anderson, Diana; Bankoglu, Ezgi Eyluel; Bonassi, Stefano; Boutet-Robinet, Elisa; Brunborg, Gunnar; Chao, Christy; Cooke, Marcus S.; Costa, Carla; Costa, Solange; Dhawan, Alok; de Lapuente, Joaquin; Bo’, Cristian Del; Dubus, Julien; Dusinska, Maria; Duthie, Susan J.; Yamani, Naouale El; Engelward, Bevin; Gaivão, Isabel; Giovannelli, Lisa; Godschalk, Roger; Guilherme, Sofia; Gutzkow, Kristine B.; Habas, Khaled; Hernández, Alba; Herrero, Oscar; Isidori, Marina; Jha, Awadhesh N.; Knasmüller, Siegfried; Kooter, Ingeborg M.; Koppen, Gudrun; Kruszewski, Marcin; Ladeira, Carina; Laffon, Blanca; Larramendy, Marcelo; Hégarat, Ludovic Le; Lewies, Angélique; Lewinska, Anna; Liwszyc, Guillermo E.; de Cerain, Adela López; Manjanatha, Mugimane; Marcos, Ricard; Milić, Mirta; de Andrade, Vanessa Moraes; Moretti, Massimo; Muruzabal, Damian; Novak, Matjaž; Oliveira, Rui; Olsen, Ann-Karin; Owiti, Norah; Pacheco, Mário; Pandey, Alok K.; Pfuhler, Stefan; Pourrut, Bertrand; Reisinger, Kerstin; Rojas, Emilio; Rundén-Pran, Elise; Sanz-Serrano, Julen; Shaposhnikov, Sergey; Sipinen, Ville; Smeets, Karen; Stopper, Helga; Teixeira, João Paulo; Valdiglesias, Vanessa; Valverde, Mahara; van Acker, Frederique; van Schooten, Frederik-Jan; Vasquez, Marie; Wentzel, Johannes F.; Wnuk, Maciej; Wouters, Annelies; Žegura, Bojana; Zikmund, Tomas; Langie, Sabine A.S.; Azqueta, AmayaThe comet assay is a versatile method to detect nuclear DNA damage in individual eukaryotic cells, from yeast to human. The types of damage detected encompass DNA strand breaks and alkali-labile sites (e.g., apurinic/apyrimidinic sites), alkylated and oxidized nucleobases, DNA-DNA crosslinks, UV-induced cyclobutane pyrimidine dimers and some chemically induced DNA adducts. Depending on the specimen type, there are important modifications to the comet assay protocol to avoid the formation of additional DNA damage during the processing of samples and to ensure sufficient sensitivity to detect differences in damage levels between sample groups. Various applications of the comet assay have been validated by research groups in academia, industry and regulatory agencies, and its strengths are highlighted by the adoption of the comet assay as an in vivo test for genotoxicity in animal organs by the Organisation for Economic Co-operation and Development. The present document includes a series of consensus protocols that describe the application of the comet assay to a wide variety of cell types, species and types of DNA damage, thereby demonstrating its versatility.
- Minimum Information for Reporting on the Comet Assay (MIRCA): recommendations for describing comet assay procedures and resultsPublication . Møller, Peter; Azqueta, Amaya; Boutet-Robinet, Elisa; Koppen, Gudrun; Bonassi, Stefano; Milić, Mirta; Gajski, Goran; Costa, Solange; Teixeira, João Paulo; Costa Pereira, Cristiana; Dusinska, Maria; Godschalk, Roger; Brunborg, Gunnar; Gutzkow, Kristine B.; Giovannelli, Lisa; Cooke, Marcus S.; Richling, Elke; Laffon, Blanca; Valdiglesias, Vanessa; Basaran, Nursen; Del Bo’, Cristian; Zegura, Bojana; Novak, Matjaz; Stopper, Helga; Vodicka, Pavel; Vodenkova, Sona; de Andrade, Vanessa Moraes; Sramkova, Monika; Gabelova, Alena; Collins, Andrew; Langie, Sabine A.S.The comet assay is a widely used test for the detection of DNA damage and repair activity. However, there are interlaboratory differences in reported levels of baseline and induced damage in the same experimental systems. These differences may be attributed to protocol differences, although it is difficult to identify the relevant conditions because detailed comet assay procedures are not always published. Here, we present a Consensus Statement for the Minimum Information for Reporting Comet Assay (MIRCA) providing recommendations for describing comet assay conditions and results. These recommendations differentiate between 'desirable' and 'essential' information: 'essential' information refers to the precise details that are necessary to assess the quality of the experimental work, whereas 'desirable' information relates to technical issues that might be encountered when repeating the experiments. Adherence to MIRCA recommendations should ensure that comet assay results can be easily interpreted and independently verified by other researchers.
- Potassium bromate as positive assay control for the Fpg-modified comet assayPublication . Møller, Peter; Muruzabal, Damian; Bakuradze, Tamara; Richling, Elke; Bankoglu, Ezgi Eyluel; Stopper, Helga; Langie, Sabine A.S.; Azqueta, Amaya; Jensen, Annie; Scavone, Francesca; Giovannelli, Lisa; Wojewódzka, Maria; Kruszewski, Marcin; Valdiglesias, Vanessa; Laffon, Blanca; Costa, Carla; Costa, Solange; Teixeira, João Paulo; Marino, Mirko; Del Bo’, Cristian; Riso, Patrizia; Shaposhnikov, Sergey; Collins, AndrewThe comet assay is a popular assay in biomonitoring studies. DNA strand breaks (or unspecific DNA lesions) are measured using the standard comet assay. Oxidative stress-generated DNA lesions can be measured by employing DNA repair enzymes to recognise oxidatively damaged DNA. Unfortunately, there has been a tendency to fail to report results from assay controls (or maybe even not to employ assay controls). We believe this might have been due to uncertainty as to what really constitutes a positive control. It should go without saying that a biomonitoring study cannot have a positive control group as it is unethical to expose healthy humans to DNA damaging (and thus potentially carcinogenic) agents. However, it is possible to include assay controls in the analysis (here meant as a cryopreserved sample of cells i.e. included in each experiment as a reference sample). In the present report we tested potassium bromate (KBrO3) as a positive comet assay control for the formamidopyrimidine DNA glycosylase (Fpg)-modified comet assay. Ten laboratories used the same procedure for treatment of monocytic THP-1 cells with KBrO3 (0.5, 1.5 and 4.5 mM for 1 h at 37°C) and subsequent cryopreservation. Results from one laboratory were excluded in the statistical analysis because of technical issues in the Fpg-modified comet assay. All other laboratories found a concentration-response relationship in cryopreserved samples (regression coefficients from 0.80 to 0.98), although with different slopes ranging from 1.25 to 11.9 Fpg-sensitive sites (%DNA in tail) per 1 mM KBrO3. Our results demonstrate that KBrO3 is a suitable positive comet assay control.
- The comet assay in animal models: From bugs to whales – (Part 1 Invertebrates)Publication . Gajski, Goran; Žegura, Bojana; Ladeira, Carina; Pourrut, Bertrand; Del Bo’, Cristian; Novak, Matjaž; Sramkova, Monika; Milić, Mirta; Gutzkow, Kristine Bjerve; Costa, Solange; Dusinska, Maria; Brunborg, Gunnar; Collins, AndrewThe comet assay, also called single cell gel electrophoresis, is a sensitive, rapid and low-cost technique for quantifying and analysing DNA damage and repair at the level of individual cells. The assay itself can be applied on virtually any cell type derived from different organs and tissues of eukaryotic organisms. Although it is mainly used on human cells, the assay has applications also in the evaluation of DNA damage in yeast, plant and animal cells. Therefore, the purpose of this review is to give an extensive overview on the usage of the comet assay in animal models from invertebrates to vertebrates, covering both terrestrial and water biota. The comet assay is used in a variety of invertebrate species since they are regarded as interesting subjects in ecotoxicological research due to their significance in ecosystems. Hence, the first part of the review (Part 1) will discuss the application of the comet assay in invertebrates covering protozoans, platyhelminthes, planarians, cnidarians, molluscs, annelids, arthropods and echinoderms. Besides a large number of animal species, the assay is also performed on a variety of cells, which includes haemolymph, gills, digestive gland, sperm and embryo cells. The mentioned cells have been used for the evaluation of a broad spectrum of genotoxic agents both in vitro and in vivo. Moreover, the use of invertebrate models and their role from an ecotoxicological point of view will also be discussed as well as the comparison of the use of the comet assay in invertebrate and human models. Since the comet assay is still developing, its increasing potential in assessing DNA damage in animal models is crucial especially in the field of ecotoxicology and biomonitoring at the level of different species, not only humans.
- The comet assay in animal models: From bugs to whales – (Part 2 Vertebrates)Publication . Gajski, Goran; Žegura, Bojana; Ladeira, Carina; Novak, Matjaž; Sramkova, Monika; Pourrut, Bertrand; Del Bo’, Cristian; Milić, Mirta; Gutzkow, Kristine Bjerve; Costa, Solange; Dusinska, Maria; Brunborg, Gunnar; Collins, AndrewThe comet assay has become one of the methods of choice for the evaluation and measurement of DNA damage. It is sensitive, quick to perform and relatively affordable for the evaluation of DNA damage and repair at the level of individual cells. The comet assay can be applied to virtually any cell type derived from different organs and tissues. Even though the comet assay is predominantly used on human cells, the application of the assay for the evaluation of DNA damage in yeast, plant and animal cells is also quite high, especially in terms of biomonitoring. The present extensive overview on the usage of the comet assay in animal models will cover both terrestrial and water environments. The first part of the review was focused on studies describing the comet assay applied in invertebrates. The second part of the review, (Part 2) will discuss the application of the comet assay in vertebrates covering cyclostomata, fishes, amphibians, reptiles, birds and mammals, in addition to chordates that are regarded as a transitional form towards vertebrates. Besides numerous vertebrate species, the assay is also performed on a range of cells, which includes blood, liver, kidney, brain, gill, bone marrow and sperm cells. These cells are readily used for the evaluation of a wide spectrum of genotoxic agents both in vitro and in vivo. Moreover, the use of vertebrate models and their role in environmental biomonitoring will also be discussed as well as the comparison of the use of the comet assay in vertebrate and human models in line with ethical principles. Although the comet assay in vertebrates is most commonly used in laboratory animals such as mice, rats and lately zebrafish, this paper will only briefly review its use regarding laboratory animal models and rather give special emphasis to the increasing usage of the assay in domestic and wildlife animals as well as in various ecotoxicological studies.