Factors influencing heterogeneity of radiation-induced DNA-damage measured by the alkaline comet assay

Evaluation of Genetic Damage and Antigenotoxic Effect of Ascorbic Acid in Erythrocytes of Orochromis niloticus and Ambystoma mexicanum Using Migration Groups as a Parameter

The comet assay system is an efficient method used to assess DNA damage and repair; however, it currently provides the average result and, unfortunately, the heterogeneity of DNA damage loses relevance. To take advantage of this heterogeneity, migration groups (MGs) of cell comets can be formed. In this study, genetic damage was quantified in erythrocytes of Oreochromis niloticus and Ambystoma mexicanum exposed to ethyl methanesulfonate (ethyl methanesulfonate (EMS) 2.5, 5, and 10 mM over two hours) and ultraviolet C radiation (UV-C) for 5, 10, and 15 min using the tail length, tail moment, and migration group parameters. Additionally, blood cells were exposed to UV-C radiation for 5 min and treated post-treatment at 5, 10, and 15 mM ascorbic acid (AA) for two hours. With the MG parameter, it was possible to observe variations in the magnitude of genetic damage. Our data indicate that MGs help to detect basal and induced genetic damage or damage reduction with approximately the same efficiency of the tail length and tail moment parameters. MGs can be a complementary parameter used to assess DNA integrity in species exposed to mutagens.

Assays of genotoxic damage in peripheral blood lymphocytes of individuals occupationally exposed to different x-ray systems in hospital radiology departments

We obtained peripheral blood lymphocyte samples from individuals occupationally exposed to X-rays in hospital radiology departments that use different radiology systems: analog film (AF), computerized radiology (CR), or digital radiology (DR). The micronucleus test (MNT) and comet assay were performed on the samples. Micronucleus cell counts (means vs. controls, i.e., individuals not occupationally exposed to ionizing radiation) were as follows: AF, 1.96 ± 0.21 vs 1.2 ± 0.25; CR, 1.89 ± 0.15 vs 1.31 ± 0.36; and DR, 1.75 ± 0.11 vs 1.59 ± 0.32. For the comet assay, damage scores were as follows; AF, 0.84 ± 0.22 vs 0.47 ± 0.04; CR, 0.64 ± 0.26 vs 0.43 ± 0.04; and DR, 0.56 ± 0.19 vs 0.49 ± 0035. These findings were consistent with cytogenetic damage due to radiation exposure.

Effects of different mobile phone UMTS signals on DNA, apoptosis and oxidative stress in human lymphocytes

Different scientific reports suggested link between exposure to radiofrequency radiation (RF) from mobile communications and induction of reactive oxygen species (ROS) and DNA damage while other studies have not found such a link. However, the available studies are not directly comparable because they were performed at different parameters of exposure, including carrier frequency of RF signal, which was shown to be a critical for appearance of the RF effects. For the first time, we comparatively analyzed genotoxic effects of UMTS signals at different frequency channels used by 3G mobile phones (1923, 1947.47, and 1977 MHz). Genotoxicity was examined in human lymphocytes exposed to RF for 1 h and 3 h using complimentary endpoints such as induction of ROS by imaging flow cytometry, DNA damage by alkaline comet assay, mutations in TP53 gene by RSM assay, preleukemic fusion genes (PFG) by RT-qPCR, and apoptosis by flow cytometry. No effects of RF exposure on ROS, apoptosis, PFG, and mutations in TP53 gene were revealed regardless the UMTS frequency while inhibition of a bulk RNA expression was found. On the other hand, we found relatively small but statistically significant induction of DNA damage in dependence on UMTS frequency channel with maximal effect at 1977.0 MHz. Our data support a notion that each specific signal used in mobile communication should be tested in specially designed experiments to rule out that prolonged exposure to RF from mobile communication would induce genotoxic effects and affect the health of human population.

The Effects of Mobile Phone Radiofrequency Radiation on Cochlear Stria Marginal Cells in Sprague-Dawley Rats

To investigate the possible mechanisms for biological effects of 1,800 MHz mobile radiofrequency radiation (RFR), the radiation-specific absorption rate was applied at 2 and 4 W/kg, and the exposure mode was 5 min on and 10 min off (conversation mode). Exposure time was 24 h short-term exposure. Following exposure, to detect cell DNA damage, cell apoptosis, and reactive oxygen species (ROS) generation, the Comet assay test, flow cytometry, DAPI (4',6-diamidino-2-phenylindole dihydrochloride) staining, and a fluorescent probe were used, respectively. Our experiments revealed that mobile phone RFR did not cause DNA damage in marginal cells, and the rate of cell apoptosis did not increase (P > 0.05). However, the production of ROS in the 4 W/kg exposure group was greater than that in the control group (P < 0.05). In conclusion, these results suggest that mobile phone energy was insufficient to cause cell DNA damage and cell apoptosis following short-term exposure, but the cumulative effect of mobile phone radiation still requires further confirmation. Activation of the ROS system plays a significant role in the biological effects of RFR. Bioelectromagnetics. © 2020 The Authors. Bioelectromagnetics published by Wiley Periodicals, Inc.

Analysis of copy number variations induced by ultrashort electron beam radiation in human leukocytes in vitro

BACKGROUND

Environmental risk factors have been shown to alter DNA copy number variations (CNVs). Recently, CNVs have been described to arise after low-dose ionizing radiation in vitro and in vivo. Development of cost- and size-effective laser-driven electron accelerators (LDEAs), capable to deliver high energy beams in pico- or femtosecond durations requires examination of their biological effects. Here we studied in vitro impact of LDEAs radiation on known CNV hotspots in human peripheral blood lymphocytes on single cell level.

RESULTS

Here CNVs in chromosomal regions 1p31.1, 7q11.22, 9q21.3, 10q21.1 and 16q23.1 earlier reported to be sensitive to ionizing radiation were analyzed using molecular cytogenetics. Irradiation of cells with 0.5, 1.5 and 3.0 Gy significantly increased signal intensities in all analyzed chromosomal regions compared to controls. The latter is suggested to be due to radiation-induced duplication or amplification of CNV stretches. As significantly lower gains in mean fluorescence intensities were observed only for chromosomal locus 1p31.1 (after irradiation with 3.0 Gy variant sensitivites of different loci to LDEA is suggested. Negative correlation was found between fluorescence intensities and chromosome size (r = - 0.783, p < 0.001) in cells exposed to 3.0 Gy irradiation and between fluorescence intensities and gene density (r = - 0.475, p < 0.05) in cells exposed to 0.5 Gy irradiation.

CONCLUSIONS

In this study we demonstrated that irradiation with laser-driven electron bunches can induce molecular-cytogenetically visible CNVs in human blood leukocytes in vitro. These CNVs occur most likely due to duplications or amplification and tend to inversely correlate with chromosome size and gene density. CNVs can last in cell population as stable chromosomal changes for several days after radiation exposure; therefore this endpoint can be used for characterization of genetic effects of accelerated electrons. These findings should be complemented with other studies and implementation of more sophisticated approaches for CNVs analysis.

Assessment of DNA Damage After Ionizing Radiation Exposure in Patients Undergoing Cardiac Resynchronization Therapy Device Implantation or Atrial Fibrillation Ablation (The RADAR Study)

Background

There is limited data regarding effect of prolonged radiation exposure during electrophysiological (EP) procedures on direct DNA damage. Comet test has shown to assess DNA damage following radiation exposure.

Methods

We performed a single-center prospective observational study assessing direct DNA damage using the quantitative comet assay in patients undergoing cardiac resynchronization (CRT) and atrial fibrillation (AF) catheter ablation procedures. Venous comet assay was performed pre, immediately post procedure and at 3-month duration in twenty-two (N=22) patients who underwent catheter ablation for symptomatic AF and fourteen (N=14) patients who underwent CRT implantation.

Results

The median [interquartile range (IQR)] fluoroscopy time, radiation dose and dose area product (DAP) were 34.3 (27.97 - 45.48) minutes, 853.07 (611.36 - 1334.76) mGy and 16,994.10 (9,023.65 - 58,845.00) UGym2 in the ablation group and 30.05 (18.75 - 37.33) minutes, 345.00 (165.09 - 924.79) mGy and 11,837.20 [7182.67 - 35567.75] UGym2 in the CRT group. When compared with pre-procedure, there was a statistically significant increase in median (IQR) DNA migration on comet assay in the ablation group immediately post procedure [+6.55 µm (0.78, 10.25, p=0.02)] that subsequently decreased at 3 months [-1.00 µm (-2.20, 0.78), p=0.03] but not in the CRT group.

Conclusion

There was a significant increase in DNA damage as detected by comet assay immediately post procedure that normalized at 3 months in patients undergoing AF ablation. Further large prospective studies are warranted to evaluate the impact of this prolonged radiation exposure and DNA damage on long-term follow up.

Radioprotective effect of lactoferrin in mice exposed to sublethal X-ray irradiation

The radioprotective effect of lactoferrin (LF) was studied in mice subjected to sublethal X-ray irradiation. The mice were randomly divided into the Control (non-irradiated mice fed a standard diet without LF), IR (irradiated mice fed a standard diet) and IR+LF (irradiated mice fed LF) groups. The mice were fed daily for 7 days prior to irradiation and for 30 continuous days following irradiation. The survival ratio of the mice in the IR+LF group was significantly increased compared with the IR group between days 15 and 30 after irradiation. The body weight of the mice in the IR+LF group was increased compared with the IR group, and the difference was statistically significant. Blood was collected from the mice via the tail vein on days 2, 7, 14, 21 and 30 following irradiation. The laboratory indicators, including leukocyte, erythrocyte and platelet counts recovered more rapidly following irradiation in the IR+LF group compared with the IR group. Treatment of the irradiated mice with LF significantly reduced the DNA damage. In the hepatic tissue the level of superoxide dismutase in the IR+LF group was significantly increased, while malondialdehyde was significantly decreased compared with the IR group. These findings indicate that LF may prevent radiation damage and may have potential as a treatment for patients with cancer who receive radiotherapy.

Sensitivity of spiral ganglion neurons to damage caused by mobile phone electromagnetic radiation will increase in lipopolysaccharide-induced inflammation in vitro model

Background

With the increasing popularity of mobile phones, the potential hazards of radiofrequency electromagnetic radiation (RF-EMR) on the auditory system remain unclear. Apart from RF-EMR, humans are also exposed to various physical and chemical factors. We established a lipopolysaccharide (LPS)-induced inflammation in vitro model to investigate whether the possible sensitivity of spiral ganglion neurons to damage caused by mobile phone electromagnetic radiation (at specific absorption rates: 2, 4 W/kg) will increase.

Methods

Spiral ganglion neurons (SGN) were obtained from neonatal (1- to 3-day-old) Sprague Dawley® (SD) rats. After the SGN were treated with different concentrations (0, 20, 40, 50, 100, 200, and 400 μg/ml) of LPS, the Cell Counting Kit-8 (CCK-8) and alkaline comet assay were used to quantify cellular activity and DNA damage, respectively. The SGN were treated with the moderate LPS concentrations before RF-EMR exposure. After 24 h intermittent exposure at an absorption rate of 2 and 4 W/kg, DNA damage was examined by alkaline comet assay, ultrastructure changes were detected by transmission electron microscopy, and expression of the autophagy markers LC3-II and Beclin1 were examined by immunofluorescence and confocal laser scanning microscopy. Reactive oxygen species (ROS) production was quantified by the dichlorofluorescin-diacetate assay.

Results

LPS (100 μg/ml) induced DNA damage and suppressed cellular activity (P < 0.05). LPS (40 μg/ml) did not exhibit cellular activity changes or DNA damage (P > 0.05); therefore, 40 μg/ml was used to pretreat the concentration before exposure to RF-EMR. RF-EMR could not directly induce DNA damage. However, the 4 W/kg combined with LPS (40 μg/ml) group showed mitochondria vacuoles, karyopyknosis, presence of lysosomes and autophagosome, and increasing expression of LC3-II and Beclin1. The ROS values significantly increased in the 4 W/kg exposure, 4 W/kg combined with LPS (40 μg/ml) exposure, and H₂O₂ groups (P < 0.05, 0.01).

Conclusions

Short-term exposure to radiofrequency electromagnetic radiation could not directly induce DNA damage in normal spiral ganglion neurons, but it could cause the changes of cellular ultrastructure at special SAR 4.0 W/kg when cells are in fragile or micro-damaged condition. It seems that the sensitivity of SGN to damage caused by mobile phone electromagnetic radiation will increase in a lipopolysaccharide-induced inflammation in vitro model.

Evaluation of the comet assay for assessing the dose-response relationship of DNA damage induced by ionizing radiation

Dose- and time-response curves were combined to assess the potential of the comet assay in radiation biodosimetry. The neutral comet assay was used to detect DNA double-strand breaks in lymphocytes caused by γ-ray irradiation. A clear dose-response relationship with DNA double-strand breaks using the comet assay was found at different times after irradiation (p < 0.001). A time-response relationship was also found within 72 h after irradiation (p < 0.001). The curves for DNA double-strand breaks and DNA repair in vitro of human lymphocytes presented a nice model, and a smooth, three-dimensional plane model was obtained when the two curves were combined.