DNA strand breaks (comet assay) in blood lymphocytes from wild bottlenose dolphins

DNA damage in cetaceans: A mini review

DNA damage has long been known to play an essential role in tumorigenesis induced by chemical carcinogen exposure. The preponderance of data generated during the past approximately 50 years of cancer research indicates that DNA damage and DNA adduct formation are necessary but not sufficient for tumor induction by chemical carcinogenesis. This is true for all of the species studied, including experimental animals, some animals in the wild, and humans. Cetaceans, which include whales, dolphins and porpoises, are a challenge to evaluate because tissues are difficult to obtain, and cancer rates, with a single exception, are low (0.7-2.0 %). However, both non-specific (chromosomal aberrations, DNA strand breaks, 8-hydroxy-2^'-deoxyguanosine, mitochondrial DNA damage), and chemical-specific (aromatic DNA adducts, and carcinogenic polycyclic aromatic hydrocarbon [PAH]-DNA adducts) DNA damage have been found in cetaceans. For some types of DNA damage, cetaceans may carry a burden similar to that seen in many other species, including humans, but linking DNA damage to cancer rates in cetaceans has been largely impossible. The one exception is a population of beluga whales in the St. Lawrence Estuary (SLE) in Quebec, Canada, where correlations have been found between long-term PAH exposure, PAH-DNA adducts in small intestinal crypt cells, and a high rate (7%) of gastrointestinal cancers. Taken together, the current literature demonstrates that cetaceans may carry a burden of many types of DNA damage and, given the example of the SLE beluga, cetaceans may sustain a potential susceptibility to pollution-induced tumorigenesis. Knowledge of DNA damage and cancer rates in whales is critically important for understanding and predicting the health of marine life, human life, and the aquatic environment of our planet.

Evaluation In Vitro of Toxicity of Hydroalcoholic Extract of Leaves and Roots from Yacon (Smallanthus sonchifolius)

Yacon is an Andean plant that has been used in folk medicine for its medicinal properties. The beneficial effects of this plant are possibly due to the high content of phenolic compounds present in its leaves and roots. This study evaluated the in vitro toxicity of the hydroalcoholic extract of leaves and roots from yacon (1, 10, 50, and 100 μg/mL) through cell viability tests, genotoxic and mutagenic activity in leukocytes culture cells; and cytotoxicity and apoptosis cell death (1, 10, 50, 100, and 500 μg/mL) in cell line originally established from the primary mouse embryonic fibroblast cells that were cultured by the designated protocol, so-called 3T3 protocol "3-day transfer, inoculum 3 × 10⁵ cells" (3T3 cell line). No mutagenic and cytotoxic activities were observed in leukocyte cultures. Cytotoxic activity was evidenced in the highest concentrations of yacon leaf extract (50 and 100 μg/mL), whereas all concentrations tested with yacon leaf extract there was induction for apoptosis in the 3T3 cells. Genotoxic potential was observed only at higher doses of leaf (50 and 100 μg/mL) and root (100 μg/mL) extract. These results suggest that yacon leaf at high concentrations may present toxic potential showing concentration-dependent behavior; however, in vivo studies should be performed to validate these results.

The comet assay in animal models: From bugs to whales - (Part 2 Vertebrates)

The 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.

Absence of genotoxic effects of the chalcone (E)-1-(2-hydroxyphenyl)-3-(4-methylphenyl)-prop-2-en-1-one) and its potential chemoprevention against DNA damage using in vitro and in vivo assays

The chalcone (E)-1-(2-hydroxyphenyl)-3-(4-methylphenyl)-prop-2-en-1-one), or 2HMC, displays antileishmanial, antimalarial, and antioxidant activities. The aim of this study was to investigate the cytotoxic, genotoxic, mutagenic, and protective effects of 2HMC using the Ames mutagenicity test, the mouse bone marrow micronucleus test, and the comet assay in mice. In the assessment using the Ames test, 2HMC did not increase the number of His⁺ revertants in Salmonella typhimurium strains, demonstrating lack of mutagenicity. 2HMC showed no significant increase in micronucleated polychromatic erythrocyte frequency (MNPCE) in the micronucleus test, or in DNA strand breaks using the comet assay, evidencing absence of genotoxicity. Regarding cytotoxicity, 2HMC exhibited moderate cytotoxicity in mouse bone marrow cells by micronucleus test. 2HMC showed antimutagenic action in co-administration with the positive controls, sodium azide (SA) and 4-nitroquinoline-1-oxide (4NQO), in the Ames test. Co-administered and mainly pre-administered with cyclophosphamide (CPA), 2HMC caused a decrease in the frequency of MNPCE using the micronucleus test and in DNA strand breaks using the comet assay. Thus, 2HMC exhibited antimutagenic and antigenotoxic effects, displaying a DNA-protective effect against CPA, SA, and 4NQO carcinogens. In conclusion, 2HMC presented antimutagenic, antigenotoxic and moderate cytotoxic effects; therefore it is a promising molecule for cancer prevention.

Evaluation of genotoxic and cytotoxic effects of hydroalcoholic extract of Euphorbia tirucalli (Euphorbiaceae) in cell cultures of human leukocytes

Euphorbia tirucalli (L.), commonly known as aveloz, has been indiscriminately used in popular medicine to treat various illnesses. However, some components can have devastating consequences. Injury to a cell's genetic material can cause mutations, cancer, and cell death. Our main goal in this work was to evaluate the genotoxic and cytotoxic effects of E. tirucalli extract on human leukocytes. For this purpose, we performed a phytochemical analysis to evaluate the plant's components. In the second step, we treated cultured human leukocytes with different concentrations of the dry extract of the plant and then evaluated the oxidative and genotoxic profiles of these leukocytes. We found that at 1% and 10% concentrations, the aveloz extract acted as a genotoxic agent that could damage DNA and increase oxidative damage. We conclude that despite its popular use, aveloz can act as a genotoxic agent, especially when it contains phorbol ester. Aveloz's indiscriminate use might actually promote tumors and therefore carry a considerable genetic risk for its users.

Effects of in vitro exposure to titanium dioxide on DNA integrity of bottlenose dolphin (Tursiops truncatus) fibroblasts and leukocytes

In the present study, the genotoxic potential of nanosized TiO2 anatase and micro-sized rutile on bottlenose dolphin (Tursiops truncatus) fibroblasts and leukocytes was investigated. Human and mouse cells were also studied in order to compare susceptibility to TiO2 in different mammalian species. Cell lines were exposed for 4, 24, and 48 h to different concentrations of TiO2 (20, 50, 100, 150 μg/ml) and DNA damage was investigated by single cell gel electrophoresis (Comet assay). Both anatase and rutile induced increased DNA damage, even though statistically significant effects were scattered according to species and cell lines. Bottlenose dolphin leukocytes and murine fibroblasts exhibited increased DNA damage after rutile exposure at some doses/times, while human fibroblasts showed a significant dose-response effect after a 4 h exposure to anatase. Human leukocytes were tolerant to both anatase and rutile. Ultrastructural investigation showed that TiO2 particles entered the cell and were compartmentalized within membrane-bound vesicles.