Validation of Comet assay in Oregon-R and Wild type strains of Drosophila melanogaster exposed to a natural radioactive environment in Brazilian semiarid region

Accessing the Health Risk of Ingestion of Surface Water from Lucrécia and Parelhas Dams in Northeast Brazil Using the Sentinel Organism Drosophila melanogaster

This study investigated the genotoxic risk of chronic exposure of hemolymph's cells of Drosophila melanogaster (Insecta, Diptera) to water samples from Boqueirão de Parelhas Dam and from Lucrécia Dam in the semiarid region of Brazil. The dams are located over the Pegmatite Province of Borborema, with rocks rich in uranium and thorium. Water samples hydrated a culture medium composed of mashed potatoes, where larvae of D. melanogaster fed for 24 h, before be underwent to the Comet assay. The same water was evaluated for the presence of dissolved Radon gas (222Rn) and concentrations of 11 toxic metals (Ag, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn). The results indicated a genotoxic effect resulting from exposure to the waters of the Parelhas dam, in the samples of August 2018; and in Lucrécia dam, in January 2019. D. melanogaster stood out for its high sensitivity to monitor the genotoxic effects of compounds dissolved in public dams. And unlike to other essentially aquatic sentinel organisms, this species stood out as a model to concomitant studies of air and water possible contaminated, in a scenario of natural environmental radioactivity present in semiarid of Brazil.

Genotoxic Effects of Anthropogenic Environments in the Leaf Litter-dwelling Scorpion Tityus pusillus Pocock, 1893 (Scorpiones; Buthidae)

Invertebrates are harmed by pollution of their habitats. Litter-dwelling sedentary scorpions, such as Tityus pusillus, studied here, may be good models for examining the genotoxic effects of xenobiotics in soil. Thirty specimens were collected from five sites in Northeast Brazil with different levels of human disturbance, as well as a laboratory group. The comet assay was performed on hemolymph cell samples. Damage Index (DI) and Damage Frequency (DF%) were measured. Much higher genotoxicity was observed in animals collected in an area with human interference and solid waste, compared to those obtained in more pristine areas or the laboratory. T. pusillus may be a useful model for environmental genotoxicity assays.

First transcriptome profiling of D. melanogaster after development in a deep underground low radiation background laboratory

Natural background radiation is a permanent multicomponent factor. It has an influence on biological organisms, but effects of its deprivation still remain unclear. The aim of our work was to study for the first time responses of D. melanogaster to conditions of the Deep Underground Low-Background Laboratory DULB-4900 (BNO, INR, RAS, Russia) at the transcriptome level by RNA-seq profiling. Overall 77 transcripts demonstrated differential abundance between flies exposed to low and natural background radiation. Enriched biological process functional categories were established for all genes with differential expression. The results showed down-regulation of primary metabolic processes and up-regulation of both the immune system process and the response to stimuli. The comparative analysis of our data and publicly available transcriptome data on D. melanogaster exposed to low and high doses of ionizing radiation did not reveal common DEGs in them. We hypothesize that the observed changes in gene expression can be explained by the influence of the underground conditions in DULB-4900, in particular, by the lack of stimuli. Thus, our study challenges the validity of the LNT model for the region of background radiation doses below a certain level (~16.4 nGy h-1) and the presence of a dose threshold for D. melanogaster.

Cytogenetic analysis of nuclear abnormalities in the erythrocytes of gecko lizards (Phyllopezus periosus) collected in a semi-arid region of northeast Brazil: Possible effects of natural background radioactivity

High natural-background radioactivity levels occur in the semi-arid region of the State of Rio Grande do Norte, northeastern Brazil. We have studied the lizard Phyllopezus periosus, an endemic species of the Brazilian caatinga with saxicolous habitat, as a bioindicator of environmental quality. Specimens were collected in three areas, an environmental protection area and two areas recognized as having high natural background radiation, one of these being a mining area. Level of metals and gamma radiation emitters present in the water sources potentially used by the lizards were measured. The biological endpoints assessed were micronuclei and nuclear abnormalities in blood samples. Significant differences in background radioactivity levels were found among the assessed areas. Statistically significant differences in micronuclei and nuclear abnormality frequencies were seen, among the study areas and a relationship between radioactivity level and genetic damage was observed.

Residential exposure to radon and levels of histone γH2AX and DNA damage in peripheral blood lymphocytes of residents of Kowary city regions (Poland)

INTRODUCTION

Radon-induced biological effects have been studied mainly through epidemiological investigations, and well-controlled in vitro and in vivo experiments. To provide data explaining radon exposure-induced harmful effects in natural environment, exposure assessment under these conditions is needed. The objective of the study was to examine the level of genetic damage assessed with biomarkers of DNA single- and double-strand breaks (SSBs and DSBs) in peripheral blood mononuclear cells obtained from individuals continuously exposed to Rn in homes. Naturally elevated Rn concentrations in homes can be found in the South of Poland, in Kowary city.

METHODS

Measurements of expression of phosphorylated histone γH2AX was used as a marker of DNA double strand breaks. To detect DNA single and double-strand breaks and alkali labile sites, the alkaline comet assay was used. Oxidative damage of DNA was evaluated by formamidopyrimidyne (FPG)-modified comet assay. The blood was collected from 94 volunteers living in Kowary. Subjects were grouped according to their status of living in radon concentration ≥100 Bq/m³ (n = 67), and <100 Bq/m³ (n = 27).

RESULTS

The statistically significant differences in levels of DNA damage in peripheral lymphocytes assessed with comet assay were found to be associated with levels of radon exposure in indoor air (p = 0.034). DNA damage in the comet assay was significantly correlated with DNA damage assessed with γH2AX staining.

CONCLUSIONS

Results of the present study indicate the suitability of alkaline comet assay for the detection of DNA damage in peripheral blood lymphocytes of people environmentally exposed to radon.

Genotoxic Assessment of the Dry Decoction of Myracrodruon urundeuva Allemão (Anacardiaceae) Leaves in Somatic Cells of Drosophila melanogaster by the Comet and SMART Assays

Medicinal plants are worldwide used as an efficient treatment of many diseases. Myracrodruon urundeuva Allemão (Anacardiaceae) is widely used Brazilian folk medicine to treat inflammations and infections of the female genital tract, conditions of the stomach and throat, and to heal wounds on the skin and mucous membranes. Several pharmacological properties of extracts and compounds isolated from M. urundeuva are found in the literature, corroborating its uses as antiulcer and gastroprotective, anti-inflammatory and analgesic, as well as antimicrobial. Despite these many uses in traditional herbal medicine, there are few reports of its toxic-genetic effect. This work aimed to investigate the genotoxic and mutagenic potential in vivo of the dry decoction of M. urundeuva leaves on somatic cells of Drosophila melanogaster, through the Comet assay and somatic mutation and recombination test (SMART). Six concentrations (0.5, 1.0, 2.0, 4.0, 8.0, and 16.0 mg/mL) were studied after feeding individuals for 24 hr in culture medium hydrated with extracts of M. urundeuva. In the Comet assay, all concentrations showed a genotoxic effect significantly higher than the negative control group, treated with distilled water. The two highest concentrations were also superior to the positive control group, treated with cyclophosphamide (1 mg/mL). In the SMART, there was a mutagenic effect at all concentrations tested, with a clear dose-dependent relationship. Both recombination and mutation account for these mutagenic effects. The set of results indicate that the dry decoction of M. urundeuva leaves is genotoxic and mutagenic for D. melanogaster under the experimental conditions of this study. Environ. Mol. Mutagen. 61:329-337, 2020. © 2019 Wiley Periodicals, Inc.

The cytotoxic and genotoxic effects of daidzein on MIA PaCa-2 human pancreatic carcinoma cells and HT-29 human colon cancer cells

Daidzein (DZ) has anti-inflammatory and antioxidant effects, as well as the dose-dependent inhibition effect on cancer cells. In this study, the cytotoxic and genotoxic effects of DZ on HT-29 (human colorectal adenocarcinoma cells) and MIA PaCa-2 (human pancreatic cancer cells) cell lines were determined using the XTT method and Comet assay, respectively. IC₅₀ concentrations of DZ were found to be 200 µM in both MIA PaCa-2 and HT-29 cells treated with DZ for 48 hours (h). When the cells were treated with 200 μM of DZ for 48 h, DNA damage was observed in both cell lines. DNA tail length (TL), tail moment (TM), and tail intensity (TI) increased more in MIA PaCa-2 cells treated with 200 μM of DZ than those in the control cell (untreated MIA PaCa-2 cell) group (p < 0.01). However, only DNA-TI and DNA-TM exhibited higher increases in HT-29 cells treated with 200 μM of DZ than those in the control cell (untreated HT-29 cell) group (p < 0.01). This shows that DZ has cytotoxic and genotoxic effects on both cell lines. The observed genotoxic effects of DZ still need to be confirmed in additional future studies.

Drosophila melanogaster as model organism for monitoring and analyzing genotoxicity associated with city air pollution

This study evaluated the genotoxic potential of atmospheric pollution associated with urbanization using the model organism Drosophila melanogaster and the Comet assay with hemolymph cells. Larvae were exposed to atmospheric compounds in an urban and a rural area in the municipality of Vitória de Santo Antão, Pernambuco, Brazil, for 6 days (from the embryo stage to the third larval stage) in April 2015 and April 2017. The results were compared to a negative environmental control group exposed to a preserved area (Catimbau National Park) and to a negative control exposed to the laboratory room conditions. The Comet assay demonstrated significant genetic damage in the organisms exposed to the urban area compared with those exposed to the rural area and negative control groups. The evidences were supported by particulate matter analysis showing higher photopeaks of chemical elements such as aluminum, silicon, sulfur, potassium, calcium, titanium, and iron, associated to road dust fraction in urban environment. Once again, the results confirm D. melanogaster an ideal bioindicator organism to monitor genotoxic hazard associated with atmospheric pollution.

Epithelial cell shape change of Drosophila as a biomonitoring model for the dose assessment of environmental radiation

Inevitable exposure to ionizing radiation from natural and human-made sources has been increasing over time. After nuclear disasters, such as the Fukushima accident, the public concerns on health risk of radiation exposure because of radioactive contamination of the environment have increased. However, it is very difficult to assess the biological effects of exposure caused by environmental radiation. A reliable and rapid bioassay to monitor the physiological effects of radiation exposure is therefore needed. Here, we quantitatively analyzed the changes in cell shape in Drosophila epidermis after irradiation as a model for biomonitoring of radiation. Interestingly, the number of irregularly shaped epithelial cells was increased by irradiation in a dose-dependent manner. A dose-response curve constructed with the obtained data suggests that the measurement of the number of irregular shaped cell in the epidermis is useful for the assessment of radiation dose. In addition, a comparison of the variation in the different samples and the data scored by different observers showed that our evaluation for cellular morphology was highly reliable and accurate and would, therefore, have immense practical application. Overall, our study suggests that detection of morphological changes in the epithelial cells is one of the efficient ways to quantify the levels of exposure to radioactive radiation from the environment.