Chromosomal aberrations and oxidative DNA adduct 8-hydroxy-2-deoxyguanosine as biomarkers of radiotoxicity in radiation workers

Analyses of oxidative DNA damage among coal vendors via single cell gel electrophoresis and quantification of 8-hydroxy-2'-deoxyguanosine

Looking at the development status of Nigeria and other developing nations, most low-income and rural households often use coal as a source of energy which necessitates its trade very close to the communities. Moreover, the effects of exposure to coal mining activities are rarely explored or yet to be studied, not to mention the numerous street coal vendors in Nigeria. This study investigated the oxidative stress levels in serum and urine through the biomarker 8-OHdG and DNA damage via single cell gel electrophoresis (alkaline comet assay). Blood and urine levels of 8-OHdG from 130 coal vendors and 130 population-based controls were determined by ELISA. Alkaline comet assay was also performed on white blood cells for DNA damage. The average values of 8-OHdG in serum and urine of coal vendors were 22.82 and 16.03 ng/ml respectively, which were significantly greater than those detected in controls (p < 0.001; 15.46 and 10.40 ng/ml of 8-OHdG in serum and urine respectively). The average tail length, % DNA in tail and olive tail moment were 25.06 μm, 18.71% and 4.42 respectively for coal vendors. However, for controls, the average values were 4.72 μm, 3.63% and 1.50 for tail length, % DNA in tail and olive tail moment respectively which were much lower than coal vendors (p < 0.001). Therefore, prolonged exposure to coal dusts could lead to higher serum and urinary 8-OHdG and significant DNA damage in coal vendors observed in tail length, % DNA in tail, and olive tail moment by single cell gel electrophoresis. It is therefore established that coal vendors exhibit a huge risk from oxidative stress and assessment of 8-OHdG with single cell gel electrophoresis has proven to be a feasible tool as biomarkers of DNA damage.

Telomere fragility in radiology workers occupationally exposed to low doses of ionising radiation

Ionising radiation damages DNA directly and indirectly through increased production of reactive oxygen species. Although telomeres have been reported as indicators of radiosensitivity, their maintenance in response to occupational exposure to low radiation doses is still a matter of debate. In this work we aimed to investigate telomere length and structure in hospital workers occupationally exposed to X-rays and to relate these findings to oxidation of biomolecules and chromosome aberrations. Blood samples of exposed participants and matching controls were taken during periodical check-ups. Chromosome aberrations and telomere length and structure were analysed in peripheral blood lymphocytes using Q-FISH, whereas oxidative stress parameters [pro/antioxidant balance (PAB), lipid peroxidation, and 8-oxo-dG] were measured in plasma samples. Based on the CA findings we divided the exposed group into two subgroups, of which one had chromosome aberrations in the first division metaphases and the other did not. There was no significant difference in telomere length between any of the groups. However, both subgroups showed significantly higher rate of fragile telomeres and higher lipid peroxidation product and 8-oxo-dG levels than controls. The rate of fragile telomeres significantly correlated with plasma levels of 8-oxo-dG, which suggests that continuous exposure to low radiation doses induces oxidative base damage of guanine resulting in telomere fragility.

Biomarkers of Genotoxicity in Medical Workers Exposed to Low-Dose Ionizing Radiation: Systematic Review and Meta-Analyses

Medical staff represent the largest group of workers occupationally exposed to ionizing radiation (IR). Chronic exposure to low-dose IR may result in DNA damage and genotoxicity associated with increased risk of cancer. This review aims to identify the genotoxicity biomarkers that are the most elevated in IR-exposed vs. unexposed health workers. A systematic review of the literature was performed to retrieve relevant studies with various biomarkers of genotoxicity. Subsequent meta-analyses produced a pooled effect size for several endpoints. The search procedure yielded 65 studies. Chromosome aberrations (CA) and micronuclei (MN) frequencies were significantly different between IR-exposed and unexposed workers (θ_pooled = 3.19, 95% CI 1.46–4.93; and θ_pooled = 1.41, 95% CI 0.97–1.86, for total aberrant cells and MN frequencies, respectively), which was not the case for ring chromosomes and nucleoplasmic bridges. Although less frequently used, stable translocations, sister chromatid exchanges (SCE) and comet assay endpoints were also statistically different between IR-exposed and unexposed workers. This review confirms the relevance of CA and MN as genotoxicity biomarkers that are consistently elevated in IR-exposed vs. unexposed workers. Other endpoints are strong candidates but require further studies to validate their usefulness. The integration of the identified biomarkers in future prospective epidemiological studies is encouraged.

Antioxidant activity of curcumin protects against the radiation-induced micronuclei formation in cultured human peripheral blood lymphocytes exposed to various doses of γ-Radiation

PURPOSE

Ionizing radiations trigger the formation of free radicals that damage DNA and cause cell death. DNA damage may be simply evaluated by micronucleus assay and the pharmacophores that impede free radicals could effectively reduce the DNA damage initiated by irradiation. Therefore, it was desired to determine the capacity of curcumin to alleviate micronuclei formation in human peripheral blood lymphocytes (HPBLs) exposed to 0-4 Gy of γ-radiation.

MATERIALS AND METHODS

HPBLs were exposed to 3 Gy after 30 minutes of 0.125, 0.25, 0.5, 1, 2, 5, 10, 20 or 50 µg/mL curcumin treatment or with 0.5 μg/mL curcumin 30 minutes early to 0, 0.5, 1, 2, 3 or 4 Gy 60Co γ-irradiation. Cytokinesis of HPBLs was blocked by cytochalasin B and micronuclei scored. The ability of curcumin to suppress free radical induction in vitro was determined by standard methods.

RESULTS

HPBLs treated with different concentrations of curcumin before 3 Gy irradiation alleviated the micronuclei formation depending on curcumin concentration and the lowest micronuclei were detected at 0.5 µg/mL curcumin when compared to 3 Gy irradiation alone. Increasing curcumin concentration caused a gradual rise in micronuclei, and the significant increases were detected at 10-50 µg/mL curcumin than 3 Gy irradiation alone. Irradiation of HPBLs to different doses of γ-rays caused a significant rise in micronuclei depending on radiation dose, whereas HPBLs treated with 0.5 µg/mL curcumin 30 minutes before irradiation to different doses of γ-rays significantly reduced frequencies of HPBLs with one, two, or more micronuclei. Curcumin treatment inhibited the formation of hydroxyl (OH), 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 2,2'-diphenyl-1-picrylhydrazyl (DPPH), and (nitric oxide) NO free radicals in a concentration-related way.

CONCLUSIONS

Curcumin when treated at a dose of 0.5 μg/mL attenuated micronuclei formation after γ-irradiation by inhibiting the formation of radiation-induced free radicals.

(E)4-[4-N,N-dimethylaminophenyl]but-3-en-2-one mitigates radiation-induced chromosome damage in BALB/c mouse bone marrow

We examined the effects of administration of (E) 4-[4-N,N-dimethylaminophenyl]but-3-en-2-one (DMAP) on radiation-induced chromosome damage in mice. Mice were whole-body exposed to γ-rays, 0-4 Gy, and then immediately administered DMAP, 20 mg/kg. After 24 h, mice were sacrificed, femora were removed, marrow was extracted, and chromosome aberrations were scored in the bone marrow cells. With vehicle-only (saline or oil) treatment, radiation dose-dependent damage was seen in aberrant cells, chromosome breaks, chromatid breaks, centric rings, di-, tri-, and tetracentrics, acentric fragments, total aberrations, polyploidy, and pulverization. Post-administration of DMAP was protective as it reduced chromosome damage. DMAP treatment may be a useful protective agent following radiation accidents or radiotherapy.

Amelioration of Radiation-Induced Damages in Mice by Curcuminoids: The Role of Bioavailability

PURPOSE

The present study investigated the role of free curcuminoids bioavailability on the relative radioprotective efficacy of natural unformulated curcuminoids.

MATERIALS AND METHODS

A food-grade bioavailable formulation of curcuminoids as curcumagalactomannosides (CGM) and unformulated curcuminoids (UC) were employed for the study. Swiss albino mice were randomized into Normal control, Radiation control, Radiation + UC, and Radiation + CGM groups and irradiated with γ-radiation of 6, 8, 10 and 12 Gy. Survival rate, hematological and biochemical parameters, bone marrow cellularity, chromosomal aberrations and histopathology of intestine were followed as a measure of the relative efficacy.Results and Discussion: Oral administration with both UC and CGM at 100 mg/kg. b.wt. produced significant radioprotective effect over the untreated control group of animals. However, CGM treatment was found to provide better clastogenic and genotoxic potential as compared to UC. Further, the histopathology analysis of intestine confirmed the better protective effect of CGM over UC-treated animals.

CONCLUSION

The present study demonstrated the positive role of the bioavailability of curcuminoids in the amelioration of radiation-induced damages in mice since CGM treatment exerted better survival rate and radioprotective effect as compared with UC, despite the relatively low concentrations of curcuminoids in CGM (39% w/w).

Serum 8-Hydroxy-2'-Deoxyguanosine Level as a Potential Biomarker of Oxidative DNA Damage Induced by Ionizing Radiation in Human Peripheral Blood

In this study, the effect of ionizing radiation on 8-hydroxy-2'-deoxyguanosine (8-OHdG) in human peripheral blood was investigated. Blood samples were collected from 230 radiation workers and 8 patients who underwent radiotherapy for population study. Blood samples from 2 healthy individuals were irradiated with different X-ray doses for in vitro experiment, and levels of 8-OHdG in serum and cell culture supernatants were assessed by enzyme-linked immunosorbent assay. Observations demonstrated the positive relationships between serum 8-OHdG level and radiation dose and working period were observed, and serum 8-OHdG levels were higher among interventional radiation workers than among other hospital radiation workers. In addition, 8-OHdG yields in supernatants increased, peaked at 3 Gy of radiation dose, and then decreased with further increases in radiation; the dose-response curve obtained fitted a polynomial function. By contrast, a similar trend was not found in radiotherapy patients. The present study suggests that 8-OHdG may be a useful biomarker reflecting oxidative damage among workers occupationally exposed to low-dose radiation.

Healthcare Workers Occupationally Exposed to Ionizing Radiation Exhibit Altered Levels of Inflammatory Cytokines and Redox Parameters

Studies have shown an increased risk for a variety of cancers, specifically brain cancer, in healthcare workers occupationally exposed to ionizing radiation. Although the mechanisms mediating these phenomena are not fully understood, ionizing radiation-mediated elevated levels of reactive oxygen species (ROS), oxidative DNA damage, and immune modulation are likely involved. A group of 20 radiation exposed workers and 40 sex- and age-matched non-exposed control subjects were recruited for the study. We measured superoxide (O₂•⁻) levels in whole blood of healthcare workers and all other measurements of cytokines, oxidative DNA damage, extracellular superoxide dismutase (EcSOD) activity and reduced/oxidized glutathione ratio (GSH/GSSG) in plasma. Levels of O₂•⁻ were significantly higher in radiation exposed workers compared to control. Similarly, a significant increase in the levels of interleukin (IL)-6, IL-1α and macrophage inflammatory protein (MIP)-1α in radiation exposed workers compared to control was observed, while there was no significance difference in the other 27 screened cytokines. A significant positive correlation was found between MIP-1α and O₂•⁻ levels with no correlation in either IL-6 or IL-1α. Further, a dose-dependent relationship with significant O₂•⁻ production and immune alterations in radiation exposed workers was demonstrated. There was no statistical difference between the groups in terms of oxidative DNA damage, GSH/GSSG levels, or EcSOD activity. Although the biologic significance of cytokines alterations in radiation exposed workers is unclear, further studies are needed for determining the underlying mechanism of their elevation.