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

Use of liquid-based cytology samples reveals genomic instability and cell death in patients undergoing orthodontic treatment

PURPOSE

To examine the use of liquid-based exfoliative cytology to determine the presence of genomic instability and cell death in the oral mucosa of patients with orthodontic appliances.

METHODS

Fifty-four oral mucosa samples were collected from 18 patients and divided into three stages: T0, before fixation of orthodontic appliances; T1, 25 days after appliance fixation; T2, 90 days after appliance fixation. All samples were Papanicolaou-stained and observed by microscopy (1,000 cells/sample) to ascertain the frequency of micronucleated cells (MN) and nuclear abnormalities (nuclear buds (NB), binucleated (BN), condensed chromatin (CC), karyorrhexis (KR), and karyolysis (KL)). Differences were analyzed statistically using the Mann-Whitney, Wilcoxon, Kruskal-Wallis and chi-squared tests.

RESULTS

After placement of orthodontic appliances, significant differences were observed for genomic instability biomarkers (MN and NB) and cell death (CC, KR and KL) (P < 0.05). Female patients and older patients exhibited a higher frequency of MN.

CONCLUSION

Liquid-based cytology has revealed that orthodontic appliances induce genomic instability and cell death in epithelial tissue of the oral mucosa, facilitating sample preservation and yielding more than one preparation per sample. Future studies should investigate whether such cell damage can be reversed through cell repair or whether cell alterations evolve and lead to disease.

Cytogenetic analysis (buccal micronucleus cytome assay) of radioactive waste management workers

The Russian Federation is implementing a program for dismantling nuclear-powered submarines and nuclear service vessels decommissioned from the Navy. Program personnel may be exposed to mutagenic and carcinogenic factors, including ionizing radiation. Improved preclinical health diagnostics are desirable, for timely identification of health effects, optimization of preventive measures, and medical interventions. We used an improved version of the buccal micronucleus cytome assay (BMCyt) to conduct cytogenetic status assessment of 59 employees of the Far Eastern Center for Radioactive Waste Management (DalRAO). We observed a statistically significant increase in the frequency of buccal epithelial cells with cytogenetic abnormalities (2.31‰ versus 1.15‰) and a small decrease in the apoptotic index (42 % versus 44 %) in the exposure group vs. controls. An accumulation index of cytogenetic disorders (the ratio of cells with nuclear abnormalities to cells in apoptosis) was determined and significant differences were found between the exposure and control groups. The proposed approach is simple, non-invasive, and highly informative for monitoring the health status of personnel exposed to complex factors in the working environment.

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.

Use of Biological Dosimetry for Monitoring Medical Workers Occupationally Exposed to Ionizing Radiation

Medical workers are the largest group exposed to man-made sources of ionizing radiation. The annual doses received by medical workers have decreased over the last several decades, however for some applications, like fluoroscopically guided procedures, the occupational doses still remain relatively high. Studies show that for some procedures the operator and staff still use insufficient protective and dosimetric equipment, which might cause an underestimation of medical exposures. Physical dosimetry methods are a staple for estimating occupational exposures, although due to the inconsistent use of protection measures, an alternative method such as biological dosimetry might complement the physical methods to achieve a more complete picture. Such methods were used to detect exposures to doses as low as 0.1 mSv/year, and could be useful for a more accurate assessment of genotoxic effects of ionizing radiation in medical workers. Biological dosimetry is usually based on the measurement of the effects present in peripheral blood lymphocytes. Although some methods, such as chromosome aberration scoring or micronucleus assay, show promising results, currently there is no one method recognized as most suitable for dosimetric application in the case of chronic, low-dose exposures. In this review we decided to evaluate different methods used for biological dosimetry in assessment of occupational exposures of medical workers.

Application of the buccal micronucleus cytome assay on child population exposed to sinus X-ray

PURPOSE

Diagnostic X-ray examinations of paranasal sinuses use a low-dose ionizing radiation to achieve medically indicated purposes. The effects of low-dose radiation are still controversial, making it a highly prioritized field of research. As there is a need to evaluate the effects of low-dose ionizing radiation and that children might be a more vulnerable population, we performed simultaneous physical dosimetry and buccal cell micronucleus cytome assay on pediatric patients before and after an X-ray examination of the sinuses.

METHODS

The study comprised 20 subjects aged 11.9 ± 3.6 years, and BMI < 25 kg/m². Physical dosimetry was performed using radiophotoluminiscent (RPL) glass dosimeters placed on four positions on the head. The buccal cell micronucleus cytome assay was performed before and 14 ± 1 days after the X-ray exam, to monitor DNA damaging, replicative, cytostatic, and cell death effects.

RESULTS

The doses in the primary beam ranged 371-1106 μGy and were several fold higher than at the other positions on the head. As for biological changes, we did not observe any DNA damaging effects. However, a significant increase in cells with condensed chromatin was observed, indicating more cells undergoing early stages of apoptosis. We also observed inter-individual differences between the subjects. A correlation between the doses detected and biological effects was not observed.

CONCLUSION

Although we did not observe significant increase in DNA damage, further studies are needed to increase the statistical power of the results and ensure patients' safety and optimal health care.

Genotoxic risk in health-care professionals occupationally exposed to low doses of ionizing radiation

The purpose of this study was to evaluate the potential influence of occupational ionizing radiation (IR) exposure on health professionals, assessing DNA damage using the comet and micronucleus (MN) assays and analyzing relative risks, correlations, and associated factors between outcomes and socioeconomic and lifestyle factors. Blood and buccal samples were collected from 36 workers, who actively participated in an imaging sector of a hospital, who were either exposed to IR directly or indirectly (9 internal control and 27 exposed), and 27 individuals living in the same city but with no occupational exposure (external control, unexposed/healthy). All radiation dosages performed on the 36 workers were less than 20 mSv/y, not exceeding the effective dose limit for occupational exposure. A questionnaire identified socioeconomic and lifestyle factors associated with the outcomes. The results of the MN assay showed a significant difference between both internal control and the exposed group when compared to the external control. For the comet assay, there were significant differences between the percent of tail DNA of the exposed group and external controls, but no difference was found between the exposed group and internal controls. Relative risk associations were found in time of exposure, hours worked per week, and perceived stress. Correlations were found between the outcomes and age, consumption of alcohol, and frequencies of X-rays during life. Variables that showed to be significant in the adjusted analysis were skin color and recent exposure to radiation. Albeit limited, the findings of this study suggest genotoxicity in both blood and buccal mucosa cells of workers exposed directly or indirectly to IR and that lifestyle and socioeconomic factors are associated and correlated with the risk of developing these outcomes.

Genotoxic risk in health-care professionals occupationally exposed to low doses of ionizing radiation

The purpose of this study was to evaluate the potential influence of occupational ionizing radiation (IR) exposure on health professionals, assessing DNA damage using the comet and micronucleus (MN) assays and analyzing relative risks, correlations, and associated factors between outcomes and socioeconomic and lifestyle factors. Blood and buccal samples were collected from 36 workers, who actively participated in an imaging sector of a hospital, who were either exposed to IR directly or indirectly (9 internal control and 27 exposed), and 27 individuals living in the same city but with no occupational exposure (external control, unexposed/healthy). All radiation dosages performed on the 36 workers were less than 20 mSv/y, not exceeding the effective dose limit for occupational exposure. A questionnaire identified socioeconomic and lifestyle factors associated with the outcomes. The results of the MN assay showed a significant difference between both internal control and the exposed group when compared to the external control. For the comet assay, there were significant differences between the percent of tail DNA of the exposed group and external controls, but no difference was found between the exposed group and internal controls. Relative risk associations were found in time of exposure, hours worked per week, and perceived stress. Correlations were found between the outcomes and age, consumption of alcohol, and frequencies of X-rays during life. Variables that showed to be significant in the adjusted analysis were skin color and recent exposure to radiation. Albeit limited, the findings of this study suggest genotoxicity in both blood and buccal mucosa cells of workers exposed directly or indirectly to IR and that lifestyle and socioeconomic factors are associated and correlated with the risk of developing these outcomes.

Micronucleus Assay: The State of Art, and Future Directions

During almost 40 years of use, the micronucleus assay (MN) has become one of the most popular methods to assess genotoxicity of different chemical and physical factors, including ionizing radiation-induced DNA damage. In this minireview, we focus on the position of MN among the other genotoxicity tests, its usefulness in different applications and visibility by international organizations, such as International Atomic Energy Agency, Organization for Economic Co-operation and Development and International Organization for Standardization. In addition, the mechanism of micronuclei formation is discussed. Finally, foreseen directions of the MN development are pointed, such as automation, buccal cells MN and chromothripsis phenomenon.

Automodified Poly(ADP-Ribose) Polymerase Analysisto Monitor DNA Damagein Peripheral Lymphocytes of Floriculturists Occupationally Exposed to Pesticides

Increased DNA damage and the propension to cancer development, depend on the modulation of the mechanisms to control and maintain genomic integrity. Poly(ADP-Ribose)Polymerase activation and automodification are early responses to genotoxic stress. Upon binding to DNA strand breaks, the enzyme, a molecular DNA nick sensor, is hyperactivated: this is the first step in a series of events leading to either DNA repair or apoptosis. Enzyme hyperactivation and automodification can be easily measured and are widely used to look at DNA damage extent in the cell. We investigated whether these two markers (increased catalytic activity and auto modification), could help to monitor DNA damage in lymphocytes of flower growers from Southern Italy, occupationally exposed to pesticides. Peripheral lymphocyte lysates were analyzed for Poly(ADP-Ribose)Polymerase activity, and by SDS-PAGE and anti-Poly(ADP-Ribose)Polymerase 1-antibodyto measure automodified Poly(ADP-Ribose)Polymerase levels bydensitometry. Poly(ADP-Ribose)Polymerase activity and PARP automodification followed the same trend. Growers daily exposed to pesticides, showed both biomarkers very high, either in the presence or in the absence of pathologies. PARP activity and auto-modification in peripheral blood lymphocytes are possible, non-invasive, androutinartools to monitor the healthy conditions of floricoltorists.