Cytogenetic analysis in lymphocytes from radiation workers exposed to low level of ionizing radiation in radiotherapy, CT-scan and angiocardiography units

Biological response to the continuous occupational exposure to antineoplastic drugs and radionuclides

PURPOSE

Antineoplastic drugs and radioiodine are recognized occupational risk factors affecting the genetic material of exposed persons. To assess cytogenetic damage and evaluate the presence of chromosomal instability during occupational exposure, a biomonitoring study was performed using a chromosomal aberration assay and a cytokinesis-block micronucleus (CBMN) test.

MATERIALS AND METHODS

Blood samples from 314 healthy donors divided into 3 groups (control, exposed to antineoplastic drugs and exposed to radioiodine) were collected and cytogenetically analyzed.

RESULTS

There was an increase in almost all analyzed parameters registered in the exposed persons. Chromatid breaks were higher in the subjects exposed to antineoplastic drugs, while dicentrics and premature centromere division (PCD) parameters were higher in nuclear medicine workers. The total number of micronuclei was higher in both groups of the exposed. The correlation analysis indicated the association of dicentrics, acentrics, chromosome and chromatid break with PCDs in both groups of the exposed, and micronuclei and nucleoplasmic bridges with PCDs in the subjects exposed to radioiodine. The discriminant analysis marked off PCD1-5 as the best predictor of exposure. Age, sex, sampling season and duration of exposure significantly influenced the analyzed parameters, while smoking habits did not show any influence.

CONCLUSION

Based on the observed results, premature centromere division can be considered a valuable parameter of genotoxic risk for individuals occupationally exposed to low doses of ionizing radiation.

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.

Genotoxic repercussion of high-intensity radiation (x-rays) on hospital radiographers

Recent technological advances in the medical field have increased the plausibility of exposing humans to high-intensity wavelength radiations like x-rays and gamma rays while diagnosing or treating specific medical maladies. These radiations induce nucleotide changes and chromosomal alterations in the exposed population, intentionally or accidentally. A radiological investigation is regularly used in identifying the disease, especially by the technicians working in intensive care units. The current study observes the genetic damages like chromosomal abnormalities (CA) in clinicians who are occupationally exposed to high-intensity radiations (x-rays) at their workplaces using universal cytogenetic tools like micronucleus assay (MN), sister chromatid exchange and comet assay. The study was conducted between 100 exposed practitioners from the abdominal scanning, chest scanning, cranial and orthopedic or bone scanning department and age-matched healthy controls. We observed a slightly higher rate of MN and CA (p < .05) in orthopedic and chest department practitioners than in other departments concerning increasing age and duration of exposure at work. Our results emphasize taking extra precautionary measures in clinical and hospital radiation laboratories to protect the practitioners.

Chromosomal damage in occupationally exposed health professionals assessed by two cytogenetic methods

The study assessed occupationally induced chromosomal damage in hospital personnel at risk of exposure to antineoplastic drugs and/or low doses of ionizing radiation by two cytogenetic methods. Cultured peripheral blood lymphocytes of eighty-five hospital workers were examined twice over 2 to 3 years by classical chromosomal aberration analysis and fluorescence in situ hybridization. The comparison of the 1^st and the 2^nd sampling of hospital workers showed a significant increase in chromatid and chromosomal aberrations (all p < .05) examined by classical chromosomal aberration analysis, and in unstable aberrations (all p < .05) detected by fluorescence in situ hybridization. Both cytogenetic methods were able to detect an increase of unstable aberrations in the 2^nd sampling. The raised frequency of unstable cytogenetic parameters suggested higher recent exposure to genotoxic agents.

DNA double-strand break repair and adaptive responses of low-dose radiation in normal and tumor lung cell lines

The adaptive response (AR), which can be induced by low-dose ionizing radiation (LD), may influence the therapeutic ratio of cancer treatment. We investigated the AR and the DNA double-strand break (DSB) repair pathway in human lung tumor cells and normal cells. We measured viability and proliferation of normal lung cells (MRC-5) and lung cancer cells (QU-DB) using the MTT and colony formation assays. Flow cytometric analysis of γ-H2AX was used to measure DNA-DSBs induction, repair, and residual damages. AR was seen in the normal cells but not in the cancer cells. Our findings suggest that LD stimulates DSB repair and that this may contribute to distinctive AR in normal vs. cancer cells.

Dose-Response Effects of Low-Dose Ionizing Radiation on Blood Parameters in Industrial Irradiation Workers

While previous studies have focused on the health effects of occupational exposure of radiations on medical radiation workers, few have analyzed the dose-response relationship between low radiation doses and changes in blood parameters. Even fewer studies have been conducted on industrial worker populations. Using a prospective cohort study design, this study collected health examination reports and personal dose monitoring data from 705 industrial irradiation workers who underwent regular physical examinations at Dongguan Sixth People’s Hospital. The dose-response effects of low-dose ionizing radiation on blood parameters were assessed using a generalized linear model and restricted cubic spline model. Red blood cell counts decreased then increased, before decreasing again with increasing ionizing radiation. This was in contrast to the curve of the total platelet count after irradiation. Additionally, a radiation dose of 2.904 mSv was the turning point for the nonlinear curve of hemoglobin count changes. In conclusion, long-term, low-dose ionizing radiation affects blood cell levels in industrial irradiation workers. There is a nonlinear dose-response relationship between red blood cell, platelet, and hemoglobin counts and the cumulative radiation dose. These findings should alert radiation workers to seek preventive medical treatment before the occurrence of any serious hematopoietic disease.

Dose-Effects Models for Space Radiobiology: An Overview on Dose-Effect Relationships

Space radiobiology is an interdisciplinary science that examines the biological effects of ionizing radiation on humans involved in aerospace missions. The dose-effect models are one of the relevant topics of space radiobiology. Their knowledge is crucial for optimizing radioprotection strategies (e.g., spaceship and lunar space station-shielding and lunar/Mars village design), the risk assessment of the health hazard related to human space exploration, and reducing damages induced to astronauts from galactic cosmic radiation. Dose-effect relationships describe the observed damages to normal tissues or cancer induction during and after space flights. They are developed for the various dose ranges and radiation qualities characterizing the actual and the forecast space missions [International Space Station (ISS) and solar system exploration]. Based on a Pubmed search including 53 papers reporting the collected dose-effect relationships after space missions or in ground simulations, 7 significant dose-effect relationships (e.g., eye flashes, cataract, central nervous systems, cardiovascular disease, cancer, chromosomal aberrations, and biomarkers) have been identified. For each considered effect, the absorbed dose thresholds and the uncertainties/limitations of the developed relationships are summarized and discussed. The current knowledge on this topic can benefit from further in vitro and in vivo radiobiological studies, an accurate characterization of the quality of space radiation, and the numerous experimental dose-effects data derived from the experience in the clinical use of ionizing radiation for diagnostic or treatments with doses similar to those foreseen for the future space missions. The growing number of pooled studies could improve the prediction ability of dose-effect relationships for space exposure and reduce their uncertainty level. Novel research in the field is of paramount importance to reduce damages to astronauts from cosmic radiation before Beyond Low Earth Orbit exploration in the next future. The study aims at providing an overview of the published dose-effect relationships and illustrates novel perspectives to inspire future research.

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.

Cytogenetic monitoring of peripheral blood lymphocytes from medical radiation professionals occupationally exposed to low-dose ionizing radiation

In order to assess the health risk of low-dose radiation to radiation professionals, monitoring is performed through chromosomal aberration analysis and micronuclei (MN) analysis. MN formation has drawbacks for monitoring in the low-dose range. Nucleoplasmic bridge (NPB) analysis, with a lower background level, has good dose-response relationships at both high and relatively low dose ranges. Dicentric and ring chromosomes were analyzed in 199 medical radiation professionals, and NPB/MN yields were analyzed in 205 radiation professionals. The effects of sex, age of donor, types of work, and length of service on these cytogenetic endpoints were also analyzed. The yields of the three cytogenetic endpoints were significantly higher in radiation professionals versus controls. Frequencies of dicentric plus ring chromosomes were affected by length of service. NPB frequencies were influenced by type of work and length of service. MN yields were affected not only by types of work and length of service but also by donor sex and age. In conclusion, dicentric plus ring chromosomes, NPB, and MN can be induced by low-dose radiation in radiation professionals. NPB is a potential biomarker to assess the health risk of occupational low-dose radiation exposure.

Cardiac catheterization procedures in children with congenital heart disease: Increased chromosomal aberrations in peripheral lymphocytes

Cardiac catheterization procedures are performed on about 20,000 children with congenital heart disease (CHD) annually in China. The procedure, which involves exposure to ionizing radiation, causes DNA damage and may lead to increased cancer risk. We have studied chromosomal aberrations (CA) in peripheral lymphocytes of CHD children. CA frequencies were assessed in an interventional group of 70 children who underwent cardiac catheterization and a control group of 51 children receiving open-heart surgery. Total CA and all chromosome-type aberrations were higher in the exposed children than in the control group. With respect to the type of septal defect, the translocation frequency was higher in patients with ventricular rather than atrial defects. Cardiac catheterization procedures increase CA frequencies and may also increase the risk of cancer.

Buccal epithelial cell micronuclei: Sensitive, non-invasive biomarkers of occupational exposure to low doses of ionizing radiation

We have evaluated buccal epithelial cell micronucleus formation as a biomarker of genotoxic damage following occupational exposure to low doses of ionizing radiation. Buccal epithelial cells were collected from 42 occupationally exposed medical personnel and 39 non-exposed individuals (reference group). Each individual in the exposed group was routinely monitored with a personal radiation badge. The frequency of micronucleated cells (MNC) was significantly higher in the exposed group (5.26 vs. 1.33 MNC/2000 cells) and correlated strongly with accumulated radiation dose (Annual Deep Dose, mSv). Occupational exposure to low doses of ionizing radiation was associated with an 80% relative increase in the frequency of MNC (MRR = 1.8; 95% CI: 1.1-2.8), suggesting that such exposures cause DNA damage. This non-invasive biomonitoring method should be generally applicable to studies of workers who are exposed occupationally to low doses of IR.

Cytogenetic monitoring of hospital staff exposed to ionizing radiation: optimize protocol considering DNA repair genes variability

PURPOSE

Chronic occupational exposure to ionizing radiation (IR) induces a wide spectrum of DNA damages. The aim of this study was to assess the frequencies of micronucleus (MN), sister chromatid exchanges (SCE) and to evaluate their association with XRCC1 399 Arg/Gln and XRCC3 241 Thr/Met polymorphisms in Hospital staff occupationally exposed to IR.

MATERIALS AND METHODS

A questionnaire followed by a cytogenetic analysis was concluded for each subject in our study. The exposed subjects were classified into two groups based on duration of employment (Group I < 15 years; Group II ≥15years). The genotypes of all individuals (subjects and controls) were determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

DNA damage frequencies were significantly greater in IR workers compared with controls (p < .05). However, no association arised between XRCC1 399 Arg/Gln and XRCC3 241 Thr/Met polymorphisms, on one hand, and the severity of DNA damages in the studied cohort of Tunisian population, on the other hand.

CONCLUSION

Our data provide evidence for an obvious genotoxic effect associated with IR exposure and reinforce the high sensitivity of cytogenetic assays for biomonitoring of occupationally exposed populations. These results indicate that workers exposed to IR should have periodic monitoring, along their exposure. The variants, rs25487 and rs861539, of XRCC1 and XRCC3 genes have obvious functional effects. Paradoxically, these variants are not associated with the severity of damages, according to used assays, in the studied cohort of Tunisian population, unlike other studies.

Single Low-Dose Ionizing Radiation Induces Genotoxicity in Adult Zebrafish and its Non-Irradiated Progeny

This study investigated to what extent a single exposure to low doses of ionizing radiation can induce genotoxic damage in irradiated adult zebrafish (Danio rerio) and its non-irradiated F1 progeny. Four groups of adult zebrafish were irradiated with a single dose of X-rays at 0 (control), 100, 500 and 1000 mGy, respectively, and couples of each group were allowed to reproduce following irradiation. Blood of parental fish and whole-body offspring were analysed by the comet assay for detection of DNA damage. The level of DNA damage in irradiated parental fish increased in a radiation dose-dependent manner at day 1 post-irradiation, but returned to the control level thereafter. The level of DNA damage in the progeny was directly correlated with the parental irradiation dose. Results highlight the genotoxic risk of a single exposure to low-dose ionizing radiation in irradiated individuals and also in its non-irradiated progeny.

Mutational signatures of ionizing radiation in second malignancies

Ionizing radiation is a potent carcinogen, inducing cancer through DNA damage. The signatures of mutations arising in human tissues following in vivo exposure to ionizing radiation have not been documented. Here, we searched for signatures of ionizing radiation in 12 radiation-associated second malignancies of different tumour types. Two signatures of somatic mutation characterize ionizing radiation exposure irrespective of tumour type. Compared with 319 radiation-naive tumours, radiation-associated tumours carry a median extra 201 deletions genome-wide, sized 1-100 base pairs often with microhomology at the junction. Unlike deletions of radiation-naive tumours, these show no variation in density across the genome or correlation with sequence context, replication timing or chromatin structure. Furthermore, we observe a significant increase in balanced inversions in radiation-associated tumours. Both small deletions and inversions generate driver mutations. Thus, ionizing radiation generates distinctive mutational signatures that explain its carcinogenic potential.

Effects of ionising radiation on micronucleus formation and chromosomal aberrations in Chinese radiation workers

This study is aimed to investigate the effects of ionising radiation (IR) on micronuclei (MN) formation and chromosome aberrations (CAs) in Chinese radiation workers. The study was conducted using peripheral blood lymphocytes from 1392 radiation workers from Public Hospitals of the city of Tangshan (the exposed group), and 143 healthy individuals as the control group. Fluorescence in situ hybridisation (FISH) was used to detect the unstable and stable nuclear CAs on metaphase. The MN assay was performed using the cytochalasin B method for cytokinesis-block. The MN and CA frequencies were significantly higher in the exposed group than in healthy controls (both p < 0.001). Examination of the incidence rates of MN and CA showed an increasing trend among workers in some occupations compared with the others (all p < 0.05). There were also significant differences in MN and CA rates among workers with different exposure times (all p < 0.05). Stable CA rates demonstrated an increased trend among workers with different exposure times (all p < 0.05), while no significance of unstable CA rates was found among workers with different exposure times (all p < 0.05). Importantly, the frequencies of CA and MN increased among different cumulative radiation dose groups (all p < 0.05). Correlation analysis showed that the frequencies of MN and CA were positively associated with the cumulative radiation dose. Long-term exposure to IR may have harmful effects on the health of radiation workers. The data obtained here show an increased risk of genetic instability that correlated with occupation, exposure time and equivalent dose among Chinese radiation workers.

A cytogenetic study of hospital workers occupationally exposed to radionuclides in Serbia: premature centromere division as novel biomarker of exposure?

PURPOSE

The health risk of chronic exposure to radionuclides includes changes in the genome (e.g., chromosomal aberrations and micronuclei) that increase chromosomal instability. There are also other phenomena, which seem to appear more frequently in metaphases of exposed persons (such as premature centromere division). The aim of this study was to discover whether or not there is correlation between incidence of named cytogenetic changes in persons occupationally exposed to radionuclides in comparison with unexposed control group, and if significant correlation is determined, can premature centromere division be consider as a biomarker of radiation exposure?

METHODS

The exposed group comprised 50 individuals occupationally exposed to radionuclides. The reference control group consisted of 40 unexposed individuals. Chromosomal aberrations, micronuclei and premature centromere division were analyzed according to a standard International Atomic Energy Agency protocol. Statistical analyses were performed using SPSS 17.0 statistics.

RESULTS

The means for analyzed cytogenetic changes were significantly higher in the exposed group. Positive correlation between them was found in exposed group. Premature centromere division parameter PCD5-10 was selected as particularly suitable for separating groups (exposed/unexposed).

CONCLUSIONS

Identification of other phenomena related to radionuclide exposure, beside well known, may clarify recent problems in radiobiology concerning the biological response to low doses of ionizing radiation and its consequences.

Biological dose assessment after low-dose overexposures in nuclear medicine

This paper focuses on the application of dicentric chromosome assay biodosimetry in cases of low-dose overexposures to professionals working in nuclear medicine and discusses how to present the results and associated uncertainties, to make possible a better understanding of biodosimetric reports. Five examples are presented of low or possibly zero exposure dose that are illustrative of typical problems that arise in occupational settings, in this instance in nuclear medicine departments. This is a scenario of minor concern in terms of health consequences but it is relevant in legal terms. They pose dilemmas for investigators but biological dosimetry can make a valuable contribution to resolving the cases.

Cytogenetic endpoints and Xenobiotic gene polymorphism in lymphocytes of hospital workers chronically exposed to ionizing radiation in Cardiology, Radiology and Orthopedic Laboratories

Ionizing radiation (IR) is known as a classical mutagen capable of inducing various kinds of stable and unstable chromosomal aberrations (CA) including the possibility of increasing the incidence of DNA damage. This study aims to assess occupationally induced CA in workers chronically exposed to low doses of IR in Radiology (RL), Cardiology (CL) and Orthopedic (OL) Laboratories in hospitals of Tamil Nadu. We performed the analysis of CA by trypsin G-banding, micronucleus (MN) assay, Comet assay and Xenobiotic-metabolizing gene polymorphisms (GSTM1, GSTT1 and GSTP1) in 56 exposed and 56 control subjects who were matched for gender and age (± 2 years). Higher degree of CA and MN frequencies were observed in exposed groups, especially in CL subjects compared to other exposed groups and controls (p<0.05). Higher frequency of DNA tail length and tail moment was observed in the CL exposed subjects compared to the RL and OL subjects. The frequencies of GSTM1 and GSTT1 null genotypes were 39.3 percent and 14.3 percent, respectively. No significant difference in allele frequencies between exposed subjects and controls were observed (p=0.0128). Using multiple linear regression analysis, statistical significance was determined for work duration and age for the CL, RL and OL workers and the examination of the possible impact by confounding factors showed few significant influences on the radiation exposure, as a specific biomarker. However, the findings from the present study suggest that, awareness should be created among the personnel exposed to radiations in hospital laboratories, highlighting the necessity of applying radiation protection principles against medical radiation exposure.

Exposure to ionizing radiation during liver transplantation evaluation, waitlist time, and in the postoperative period: a cause for concern

Substantial evidence has linked ionizing radiation exposure (RE) to oncogenesis. Patients evaluated for transplantation undergo extensive diagnostic imaging and have increased baseline cancer risk factors. The objective was to examine exposure in a cohort of patients undergoing evaluation and liver transplantation. Radiation exposure from all diagnostic examinations and procedures were retrospectively recorded. Radiation exposure is reported in mSv, a standardized measure of the detrimental biologic effect of radiation which allows for population-level comparisons. Seventy-four patients (69% male, mean 57 years) were evaluated, of which 13 of 35 subsequently listed patients were transplanted; an additional 18 previously evaluated patients were also transplanted during 2010. The most common indications were hepatitis C (55%) and hepatocellular carcinoma (HCC) (30%). The median observation period was 14 months. In all, 1,826 imaging examinations were performed, of which 408 (22%) involved considerable ionizing radiation and were the focus of investigation. Median annualized effective RE was 51 mSv (interquartile range [IQR]: 19,126), with 10% exposed to almost twice the amount of radiation recommended for a 5-year period. Patients with HCC received significantly (P < 0.00001) higher median annualized effective RE than patients without HCC, 137 mSv (IQR: 87,259) versus 32 mSv (IQR: 13,57), respectively. Computed tomography (CT) abdomen (23%) and chest (16%) accounted for the most common exposures, with CT abdomen accounting for 46% of overall cohort RE.

CONCLUSION

Patients undergoing evaluation and liver transplantation at our center are exposed to very high levels of ionizing radiation. Although long-term effects in these patients are yet to be defined, the theoretical increased risk of malignancy must be given its due consideration. Routine use of nonradiation imaging and reconsideration of indications may be preferred and justified in this population.