The comet assay in marine animals

Benchmark Dose Approach to DNA and Liver Damage by Chlorpyrifos and Imidacloprid in Male Rats: The Protective Effect of a Clove-Oil-Based Nanoemulsion Loaded with Pomegranate Peel Extract

Pesticides are widely used around the world to increase crop production. They also have negative impacts on animals, humans, and the ecosystem. This is the first report evaluating a novel pomegranate-extract-loaded clove-oil-based nanoemulsion (PELCN) and its potential for reducing oxidative stress and DNA damage, as well as its hepatoprotective effects against imidacloprid (IM) and chlorpyrifos (CPF) toxicity in male rats. The benchmark dose (BMD) approach was also used to study the dose-response toxicity of IM and CPF. IM and CPF were administered daily for 28 days at doses of 14, 28, and 54 mg/kg body weight (bw) of IM and 1, 2, and 4 mg/kg bw of CPF via drinking water. The PELCN was administered orally at a dose of 50 mg/kg bw/day of pomegranate extract, 500 mg/kg bw of the clove oil nanoemulsion, and IM or CPF at high doses in the drinking water. In male rats, IM and CPF caused a reduction in body weight gain and hepatotoxic effects as evidenced by increases in the liver enzymes AST, ALT, and ALP. They caused oxidative damage in the liver of male rats as indicated by the decreased liver activity of the GST, GPX, SOD, and CAT enzymes and decreased serum TAC. IM and CPF produced a significant dose-dependent increase in DNA damage in hepatocyte cells, resulting in moderate to severe liver damage with cells that are more inflammatory and have enlarged sinusoids and compacted nuclei. IM had a higher BMD than CPF for both body and liver weight, suggesting that CPF was more dose-dependently toxic than IM. Albumin was a highly sensitive liver biomarker for IM, while total protein was a biomarker for the CPF-treated rats. GPx was an extremely sensitive biomarker of oxidative stress in the IM treatment, while CAT and GPx were highly sensitive parameters in the CPF-treated rats. Therefore, at comparable doses, CPF has a higher potential to cause liver damage and oxidative stress than IM. The hepatotoxicity of IM and CPF can be mitigated by administering a nanoemulsion containing clove oil and pomegranate extract. The nanoemulsion acts as a protector against the oxidative stress caused by these insecticides, especially at high doses. The nanoemulsion based on clove oil increases the bioavailability and stability of the pomegranate extract, which has antioxidant properties.

The impact of several hydraulic fracking chemicals on Nile tilapia and evaluation of the protective effects of Spirulina platensis

Hydraulic fracturing (fracking) chemicals are used to maximize the extraction of hard-to-reach underground energy resources. Large amounts of fracking fluid could escape to the surrounding environments, including underground and surface water resources, during the chemical mixing stage of the hydraulic fracturing water cycle due to equipment failure or human error. However, the impact of pollution resulting from operational discharges is difficult to assess in aquatic ecosystems. In this study, pathological investigations, chromosomal aberrations, DNA damage, and biochemical and hematological parameters were used to evaluate the effects of such chemicals on Nile tilapia. Chromosomal aberrations are considered very sensitive genetic markers of exposure to genotoxic chemicals and are used as indicators of DNA damage. The appearance of different types of chromosomal aberrations (gaps and breaks) due to chemical exposure was significantly reduced by treatment with spirulina. Various deleterious findings in Nile tilapia, in the current study, could attributed to the presence of fracking chemicals in the aquatic environment. However, the presence of spirulina in the diet reduced the hazards of such chemicals. In addition, cytogenetic studies in the current work revealed the importance of spirulina in ameliorating the genotoxic effects of a mixture of some chemicals used in fracking.

Comet assay in ecogenotoxicology: Applications in Mytilus sp

The comet assay is a sensitive technique to detect DNA damage caused by exposure to genotoxic chemical and physical agents and is widely used in ecotoxicology. The assay has been applied in aquatic species, mainly fish and bivalves, in field biomonitoring programs and in experimental studies. The aim of the present study was to retrieve and review the published evidence to define the role of the comet assay in the assessment of genotoxic pollutants. The study focused on the application of the test in Mytilus sp, used as a sentinel organism. Twenty-one biomonitoring studies, carried out in wild and in transplanted mussels, were evaluated. An increase of the comet parameters in animals from polluted areas with respect to the controls was observed in the majority of the studies with a large variability (frequency ratio:1.2-14.5) associated with types and extent of exposure to pollutants. Three studies out of 21 reported a lack of response. Heavy metals, polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB) and pesticides were the main types of chemicals detected in sediments and/or mussel tissues from polluted areas. Twenty-nine laboratory studies were retrieved showing the sensitivity of the comet assay in detecting DNA damage in mussels exposed to the most relevant pollutants and mixtures of relevant contaminants, such as pharmaceuticals, anti-fouling agents or crude oil. The comet test also appeared to be a suitable approach to detect the genotoxic effects of nanoparticles. In some studies problems in the interpretation of data or discrepancies between the results from different laboratories were noted. Critical steps in experimental protocol and characterization of pollution, environmental variables such as temperature, salinity, food availability, physiological and pathological status of the animals are important factors which should be controlled and considered in the analysis of the 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.