Micronuclei as a marker for medical screening of subjects continuously occupationally exposed to low doses of ionizing radiation

Evaluation of micronuclei and antioxidant status in hospital radiation workers occupationally exposed to low-dose ionizing radiation

PURPOSE

There is scientific evidence that ionizing radiation (IR) can be responsible for various health hazards that are one of the concerns in occupational exposure. This study was performed to evaluate DNA damage and antioxidant status in hospital workers who are occupationally exposed to low doses of IR.

MATERIALS AND METHODS

In this study, twenty occupationally exposed to low doses of IR (CT and angiography) comprising with control groups which matched them. In order to investigate the effects of chronic irradiation of radiation workers, Micronuclei (MN) frequency and the antioxidant activity of Superoxide Dismutase (SOD), Catalase (CAT) and Total Antioxidant Capacity (TAC) were measured. Then, to check adaptation against high challenge dose, the samples (in all groups) were irradiated in vitro and MN frequency was compared. Finally, to investigated the effect of the high dose after the acute and chronic low dose of ionizing radiation, MN frequency was compared in two groups (the control group that was to in-vitro irradiated (acute low dose + high dose) and radiation workers (chronic low dose + high dose)).

RESULTS

MN frequency in the occupationally exposed group (n = 30) increased significantly when compared to the control group (p-value < 0.0001). However, chronic irradiation of radiation workers could not lead to an adaptive Sresponse, while acute low-doses could produce this effect (p-value ˂ 0.05). In addition, the activity levels of antioxidant enzymes SOD, CAT, and TAC were not statistically different between the radiation workers and the control group (p-value > 0.05).

CONCLUSIONS

We observed that exposure to low doses of IR leads to increased cytogenetic damage, could not cause an adaptive-response, and improve antioxidant capacity in radiation workers. Controlling healthcare workers' exposure is the first step to improving the health of hospital workers and the quality of patient care, thus decreasing human and economic costs.

Re-evaluation of CBMN test reference values of persons continuously occupationally exposed to low doses of ionizing radiation in Serbia

When established, cytokinesis-block micronucleus (CBMN) test reference values should be periodically evaluated according to the recommendations of reference documents. The biodosimetry cytogenetic laboratory of the Serbian Institute of Occupational Health established the CBMN test reference range for people occupationally exposed to ionizing radiation in 2016. Since then, new occupationally exposed persons have been subjected to micronucleus testing, resulting in the need for re-evaluation of existing CBMN test values. The examined population comprised 608 occupationally exposed subjects - 201 from the previous laboratory database and 407 newly examined. Comparison of groups based on gender, age and cigarette consumption did not show significant differences, although certain CBMN values differed significantly between the old and new groups. Duration of occupational exposure, gender, age and smoking habit influenced micronuclei frequency in all three analyzed groups, while no relation was found between type of work and micronucleus test parameters. Since the mean values of all tested parameters in the new group of examinees are within previously established reference ranges, existing values can be used in further research.

Medical personnel occupationally exposed to low-dose ionising radiation in Federation of Bosnia and Herzegovina: A cytogenetic study

Medical radiation exposures have been reduced significantly with modern equipment and protection measures. Biomonitoring of medical personnel can provide information concerning possible effects of radiation exposure. However, chromosome aberration (CA) analysis is now recommended only when the estimated effective dose is 200 mSv or higher. In this retrospective study in Bosnia and Herzegovina, we have measured the cytogenetic status of medical workers and healthy volunteers (controls). Peripheral blood samples from 66 medical workers exposed to low-dose ionising radiation and 89 non-exposed volunteers were collected for chromosome aberrations (CA) analysis and the cytokinesis-block micronucleus (CBMN) assay. Higher rates of chromatid and chromosome breaks, acentric fragments, double minutes, micronuclei, and micronucleated binuclear cells were observed in the control group, while the rate of nucleoplasmic bridges was higher in the medical workers group.

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.

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.

Evaluation of Genetic Damage in Persons Occupationally Exposed to Antineoplastic Drugs in Serbian Hospitals

INTRODUCTION

Although useful in the treatment of malignant cells, antineoplastic drugs (ANPDs) as chemical genotoxic agents, can interfere with normal cell physiology causing genetic damage and unfavourable health effects, especially in occupationally exposed persons. The Cytokinesis-block Micronucleus (CBMN) Cytome assay has been widely used in human biomonitoring studies as a reliable biomarker of chemical genotoxic exposure.

OBJECTIVES

Our comprehensive research was conducted in order to evaluate micronuclei as a marker for preventive medical screening purposes for persons occupationally exposed to ANPDs.

METHODS

Using the CBMN Cytome test, peripheral blood lymphocytes of 201 control and 222 exposed subjects were screened for genetic damage.

RESULTS

Age and gender influenced micronucleus (MN) frequency, but smoking habit did not. The mean micronuclei frequencies and other parameters of the CBMN Cytome test [numbers of binuclear lymphocytes with one (MN1) or two (MN2) micronuclei] were significantly higher in the group of exposed persons. Positive correlation between duration of occupational exposure and MN frequency was revealed.

CONCLUSIONS

The results of our study performed on a large sample confirmed the capacity of the CBMN Cytome assay to serve as a reliable biomarker of long-term ANPD exposure.

Ionizing radiation-induced genotoxic and oxidative damage in peripheral lymphocytes and plasma of healthy donors

Biological dosimetry of ionizing radiation (IR) exposure relies on validated cytogenetic tests measuring the frequencies of micronuclei (MN) and dicentric chromosomes (DC). IR also causes oxidative damage of biomolecules, including DNA. We evaluated IR-induced genotoxic and oxidative damage in a carefully defined cohort of healthy donors, reducing confounding factors as much as possible. Frequencies of MN and DC (peripheral blood lymphocyte cultures) and oxidative stress parameters (plasma) were quantified. We observed dose dependence of both cytogenetic and biochemical endpoints, independent of age, sex, and smoking habits. Oxidative stress parameters, especially oxidative stress index, malondialdehyde, advanced oxidation protein products, and catalase, may be used confidently to assess IR-induced damage, if cytogenetic results are unavailable.

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.

Cytogenetic surveillance of persons occupationally exposed to genotoxic chemicals

Human genotoxic exposures can occur environmentally, occupationally, or medicinally. The aim of this study was to assess cytogenetic damage (chromosomal aberrations and micronuclei) in persons exposed to chemical agents in medical, agricultural, and industrial occupations. The results showed influences of age, gender, occurrence, and duration of exposure on the extent of cytogenetic damage, but no influence of smoking. Persons exposed to pesticides were allocated significantly higher values of most examined parameters. Among all tested parameters, logistic regression analysis marked tMN, CB, and iCB as the best predictors with high discrimination accuracy of separation between exposed and unexposed persons. The obtained data encourage us to consider certain cytogenetic parameters as valuable markers for preventive medical screening as the extent of cytogenetic damage reflects cumulative exposure events and possible health consequences related to chronic occupational genotoxic exposure.