Cytogenetic analysis of peripheral blood lymphocytes, many years after exposure of workers to low-dose ionizing radiation

Physiological Effects of Co-exposure to Ionizing Radiation and Noise within Occupational Exposure Limits

ABSTRACT

Workers are frequently exposed to the occupational hazards of ionizing radiation and noise. Co-exposure to these hazards is not well understood in terms of their physiological effects. The aim of this study was to investigate the physiological effects of co-exposure to ionizing radiation and noise within the occupational limit. This study extracted the physical examination parameters of workers who met the screening criteria from the occupational health surveillance database. The workers were divided into three groups: the co-exposure (COE) group, the ionizing radiation exposure (ION) group, and the non-exposure (NON) group. The age and sex of the three groups were matched with a sample size ratio of 1:3:3. The physical examination parameters of the three groups of workers were compared. The results showed that there was no significant difference in blood pressure and blood biochemical parameters among the three groups. The COE group had higher levels of free triiodothyronine than the ION group, but there was no difference with the NON group. Moreover, the COE group had lower levels of free tetraiodothyronine than the ION group and the NON group. There was no significant difference in thyroid stimulating hormone, total triiodothyronine, and total tetraiodothyronine among the three groups. Additionally, the number of white blood cells of the COE group was lower than that of ION group and NON group. This study suggests that co-exposure to low-dose ionizing radiation and noise can cause alterations in thyroid hormone and peripheral white blood cells. These alterations are different from those observed after single exposure to low-dose ionizing radiation and require further research.

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.

A comprehensive and universal approach for embryo testing in patients with different genetic disorders

BACKGROUND

In vitro fertilization (IVF) with preimplantation genetic testing (PGT) has markedly improved clinical pregnancy outcomes for carriers of gene mutations or chromosomal structural rearrangements by the selection of embryos free of disease-causing genes and chromosome abnormalities. However, for detecting whole or segmental chromosome aneuploidies, gene variants or balanced chromosome rearrangements in the same embryo require separate procedures, and none of the existing detection platforms is universal for all patients with different genetic disorders.

METHODS

Here, we report a cost-effective, family-based haplotype phasing approach that can simultaneously evaluate multiple genetic variants, including monogenic disorders, aneuploidy, and balanced chromosome rearrangements in the same embryo with a single test. A total of 12 monogenic diseases carrier couples and either of them carried chromosomal rearrangements were enrolled simultaneously in this present study. Genome-wide genotyping was performed with single-nucleotide polymorphism (SNP)-array, and aneuploidies were analyzed through SNP allele frequency and Log R ratio. Parental haplotypes were phased by an available genotype from a close relative, and the embryonic genome-wide haplotypes were determined through family haplotype linkage analysis (FHLA). Disease-causing genes and chromosomal rearrangements were detected by haplotypes located within the 2 Mb region covering the targeted genes or breakpoint regions.

RESULTS

Twelve blastocysts were thawed, and then transferred into the uterus of female patients. Nine pregnancies had reached the second trimester and five healthy babies have been born. Fetus validation results, performed with the amniotic fluid or umbilical cord blood samples, were consistent with those at the blastocyst stage diagnosed by PGT.

CONCLUSIONS

We demonstrate that SNP-based FHLA enables the accurate genetic detection of a wide spectrum of monogenic diseases and chromosome abnormalities in embryos, preventing the transfer of parental genetic abnormalities to the fetus. This method can be implemented as a universal platform for embryo testing in patients with different genetic disorders.

Challenges in the quantification approach to a radiation relevant adverse outcome pathway for lung cancer

PURPOSE

Adverse outcome pathways (AOPs) provide a modular framework for describing sequences of biological key events (KEs) and key event relationships (KERs) across levels of biological organization. Empirical evidence across KERs can support construction of quantified AOPs (qAOPs). Using an example AOP of energy deposition from ionizing radiation onto DNA leading to lung cancer incidence, we investigate the feasibility of quantifying data from KERs supported by all types of stressors. The merits and challenges of this process in the context of AOP construction are discussed.

MATERIALS AND METHODS

Empirical evidence across studies of dose-response from four KERs of the AOP were compiled independently for quantification. Three upstream KERs comprised of evidence from various radiation types in line with AOP guidelines. For these three KERs, a focused analysis of data from alpha-particle studies was undertaken to better characterize the process to the adverse outcome (AO) for a radon gas stressor. Numerical information was extracted from tables and graphs to plot and tabulate the response of KEs. To complement areas of the AOP quantification process, Monte Carlo (MC) simulations in TOPAS-nBio were performed to model exposure conditions relevant to the AO for an example bronchial compartment of the lung with secretory cell nuclei targets.

RESULTS

Quantification of AOP KERs highlighted the relevance of radiation types under the stressor-agnostic intent of AOP design, motivating a focus on specific types. For a given type, significant differences of KE response indicate meaningful data to derive linkages from the MIE to the AO is lacking and that better response-response focused studies are required. The MC study estimates the linear energy transfer (LET) of alpha-particles emitted by radon-222 and its progeny in the secretory cell nuclei of the example lung compartment to range from 94 - 5 + 5 to 192 - 18 + 15 keV/µm.

CONCLUSION

Quantifying AOP components provides a means to assemble empirical evidence across different studies. This highlights challenges in the context of studies examining similar endpoints using different radiation types. Data linking KERs to a MIE of 'deposition of energy' is shown to be non-compatible with the stressor-agnostic principles of AOP design. Limiting data to that describing response-response relationships between adjacent KERs may better delineate studies relevant to the damage that drives a pathway to the next KE and still support an 'all hazards' approach. Such data remains limited and future investigations in the radiation field may consider this approach when designing experiments and reporting their results and outcomes.

Complex preimplantation genetic tests for Robertsonian translocation, HLA, and X-linked hyper IgM syndrome caused by a novel mutation of CD40LG gene

PURPOSE

To perform complex preimplantation genetic tests (PGT) for aneuploidy screening, Robertsonian translocation, HLA-matching, and X-linked hyper IgM syndrome (XHIGM) caused by a novel mutation c.156 G>T of CD40LG gene.

METHODS

Reverse transcription PCR (RT-PCR) and Sanger sequencing were carried out to confirm the causative variant of CD40LG gene in the proband and parents. Day 5 and D6 blastocysts, obtained by in vitro fertilization (IVF) with intracytoplasmic sperm injection, underwent trophectoderm (TE) biopsy and whole genomic amplification (WGA) and next generation sequencing (NGS)-based PGT to detect the presence of a maternal CD40LG mutation, aneuploidy, Robertsonian translocation carrier, and human leukocyte antigen (HLA) haplotype.

RESULTS

Sanger sequencing data of the genomic DNA showed that the proband has a hemizygous variant of c. 156 G>T in the CD40LG gene, while his mother has a heterozygous variant at the same position. Complementary DNA (cDNA) of CD40LG amplification and sequencing displayed that no cDNA of CD40LG was found in proband, while only wild-type cDNA of CD40LG was amplified in the mother. PGT results showed that only one of the six tested embryos is free of the variant c.156 G>T and aneuploidy and having the consistent HLA type as the proband. Meanwhile, the embryo is a Robertsonian translocation carrier. The embryo was transplanted into the mother's uterus. Amniotic fluid testing results are consistent with that of PGT. A healthy baby girl was delivered, and the peripheral blood testing data was also consistent with the testing results of transplanted embryo.

CONCLUSIONS

The novel mutation of c. 156 G>T in CD40LG gene probably leads to XHIGM by nonsense-meditated mRNA decay (NMD), and complex PGT of preimplantation genetic testing for monogenic disease (PGT-M), aneuploidy (PGT-A), structural rearrangement (PGT-SR), and HLA-matching (PGT-HLA) can be performed in pedigree with both X-linked hyper IgM syndrome and Robertsonian translocation.

Radio-adaptive response in peripheral blood lymphocytes of individuals residing in high-level natural radiation areas of Kerala in the southwest coast of India

The present study investigates whether the chronic low-dose radiation exposure induces an in vivo radio-adaptive response in individuals from high-level natural radiation areas (HLNRA) of the Kerala coast. Peripheral blood samples from 54 adult male individuals aged between 26 and 65 years were collected for the study with written informed consent. Each of the whole blood sample was divided into three, one was sham irradiated, second and third was exposed to challenging doses of 1.0 and 2.0 Gy gamma radiation, respectively. Cytokinesis-block micronucleus (CBMN) assay was employed to study the radio-adaptive response. Seventeen individuals were from normal-level natural radiation area (NLNRA ≤1.5 mGy/year) and 37 from HLNRA (> 1.5 mGy/year). Based on the annual dose received, individuals from HLNRA were further classified into low-dose group (LDG, 1.51-5.0 mGy/year, N = 19) and high-dose group (HDG >5.0 mGy/year, N = 18). Basal frequency of micronucleus (MN) was comparable across the three dose groups (NLNRA, LDG and HDG, P = 0.64). Age of the individuals showed a significant effect on the frequency of MN after challenging dose exposures. The mean frequency of MN was significantly lower in elder (>40 years) individuals from HDG of HLNRA as compared to the young (≤40 years) individuals after 1.0 Gy (P < 0.001) and 2.0 Gy (P = 0.002) of challenging doses. However, young and elder individuals within NLNRA and LDG of HLNRA showed similar frequency of MN after the challenging dose exposures. Thus, increased level of chronic low-dose radiation (>5.0 mGy/year) seems to act as a priming dose resulting in the induction of an in vivo radio-adaptive response in elder individuals of the Kerala coast.

Buccal mucosa micronuclei counts in relation to exposure to low dose-rate radiation from the Chornobyl nuclear accident and other medical and occupational radiation exposures

BACKGROUND

Ionizing radiation is a well-known carcinogen. Chromosome aberrations, and in particular micronuclei represent an early biological predictor of cancer risk. There are well-documented associations of micronuclei with ionizing radiation dose in some radiation-exposed groups, although not all. That associations are not seen in all radiation-exposed groups may be because cells with micronuclei will not generally pass through mitosis, so that radiation-induced micronuclei decay, generally within a few years after exposure.

METHODS

Buccal samples from a group of 111 male workers in Ukraine exposed to ionizing radiation during the cleanup activities at the Chornobyl nuclear power plant were studied. Samples were taken between 12 and 18 years after their last radiation exposure from the Chornobyl cleanup. The frequency of binucleated micronuclei was analyzed in relation to estimated bone marrow dose from the cleanup activities along with a number of environmental/occupational risk factors using Poisson regression adjusted for overdispersion.

RESULTS

Among the 105 persons without a previous cancer diagnosis, the mean Chornobyl-related dose was 59.5 mSv (range 0-748.4 mSv). There was a borderline significant increase in micronuclei frequency among those reporting work as an industrial radiographer compared with all others, with a relative risk of 6.19 (95% CI 0.90, 31.08, 2-sided p = 0.0729), although this was based on a single person. There was a borderline significant positive radiation dose response for micronuclei frequency with increase in micronuclei per 1000 scored cells per Gy of 3.03 (95% CI -0.78, 7.65, 2-sided p = 0.1170), and a borderline significant reduction of excess relative MN prevalence with increasing time since last exposure (p = 0.0949). There was a significant (p = 0.0388) reduction in MN prevalence associated with bone X-ray exposure, but no significant trend (p = 0.3845) of MN prevalence with numbers of bone X-ray procedures.

CONCLUSIONS

There are indications of increasing trends of micronuclei prevalence with Chornobyl-cleanup-associated dose, and indications of reduction in radiation-associated excess prevalence of micronuclei with time after exposure. There are also indications of substantially increased micronuclei associated with work as an industrial radiographer. This analysis adds to the understanding of the long-term effects of low-dose radiation exposures on relevant cellular structures and methods appropriate for long-term radiation biodosimetry.

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.

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.