Diminished cellular and humoral immunity in workers occupationally exposed to low levels of ionizing radiation

Assessment of some factors of cellular and humoral immunity in radiology workers

Radiation workers in medical diagnostic departments are occupationally exposed to long-term low-dose ionizing radiation, which may cause radiation-induced side effects. This study investigated subtypes of peripheral blood lymphocytes and immunoglobulin levels in workers who were occupationally exposed to X-ray radiation at the Department of Radiology. Seventeen radiology workers received low levels of ionizing radiation as the study group and 18 individuals who were not exposed to radiation were included as the control group. The percentage of lymphocyte subtypes (CD4⁺, CD8⁺ and CD4⁺/CD8⁺) and serum levels of immunoglobulins (IgA, IgG and IgM) were measured using peripheral blood samples. Considering all lymphocyte subtypes and serum levels of IgA, IgG and IgM, there was no significant difference between the study and control groups (P > 0.05). There were no significant differences in all mentioned parameters regarding gender (P > 0.05). For the length of employment period, there was a significant difference concerning CD4⁺/CD8⁺ (P < 0.05). The findings showed that exposure to low levels of ionizing radiation does not affect the immune system of workers in diagnostic radiology dose level. Because of relatively small samples of workers, it is suggested that these factors be investigated on larger samples of radiology workers.

Low dose ionizing radiation effects on the immune system

Ionizing radiation interacts with the immune system in many ways with a multiplicity that mirrors the complexity of the immune system itself: namely the need to maintain a delicate balance between different compartments, cells and soluble factors that work collectively to protect, maintain, and restore tissue function in the face of severe challenges including radiation damage. The cytotoxic effects of high dose radiation are less relevant after low dose exposure, where subtle quantitative and functional effects predominate that may go unnoticed until late after exposure or after a second challenge reveals or exacerbates the effects. For example, low doses may permanently alter immune fitness and therefore accelerate immune senescence and pave the way for a wide spectrum of possible pathophysiological events, including early-onset of age-related degenerative disorders and cancer. By contrast, the so called low dose radiation therapy displays beneficial, anti-inflammatory and pain relieving properties in chronic inflammatory and degenerative diseases. In this review, epidemiological, clinical and experimental data regarding the effects of low-dose radiation on the homeostasis and functional integrity of immune cells will be discussed, as will be the role of immune-mediated mechanisms in the systemic manifestation of localized exposures such as inflammatory reactions. The central conclusion is that ionizing radiation fundamentally and durably reshapes the immune system. Further, the importance of discovery of immunological pathways for modifying radiation resilience amongst other research directions in this field is implied.

Low-dose radiation therapy: a treatment for pneumonia resulting from COVID-19

Background:

The Coronavirus disease 2019 (COVID-19) is spreading rapidly throughout the world. Lung is the primary organ which the COVID-19 virus affects and leads to pneumonia, an acute respiratory distress syndrome. COVID-19 infects the lower respiratory system, and the lung’s response to this infection is recruiting macrophages and monocytes leading to inflammation, this response causes widespread damage to the lung’s airways.

Aim:

The purpose of this study is to review studies of using low-dose radiation as a treatment for the inflammation of the tissue and pneumonia resulting from COVID-19. These studies were compared with the risk of developing lung cancer during performed dose for the treatment of COVID-19 in radiation therapy.

Materials and methods:

Our study focused on in vitro, in vivo and clinical reports of using low-dose radiation for the treatment of inflammation, pneumonia and COVID-19. The risk of lung cancer resulting from suggested dose in these studies was also evaluated.

Conclusion:

From the review of articles, we have found that low-dose radiation can lead to improvement in inflammation in different line cells and animals; in addition, it has been effective in treating inflammation and pneumonia caused by COVID-19 in human up to 80%. Since suggested doses do not remarkably increase the lung cancer risk, low-dose radiation can be an adjuvant treatment for COVID-19 patients.

Absence of mutations in the human interferon alpha-2b gene in workers chronically exposed to ionising radiation

Individuals chronically exposed to low-level ionising radiation (IR) run the risk of harmful and long-term adverse health effects, including gene mutations and cancer development. The search for reliable biomarkers of IR exposure in human population is still of great interest, as they may have a great implementation potential for the surveillance of occupationally exposed individuals. In this context, and considering previous literature, this study aimed to identify mutations in the human interferon alpha-2b (hIFNα-2b) as a potential biomarker of occupational chronic low-dose IR exposure linking low-IR exposure to the effects on haematopoiesis and reduced immunity. The analysis was performed in the genomic DNA of 51 uranium miners and 38 controls from Kazakhstan, and in 21 medical radiology workers and 21 controls from Italy. hIFNα-2b gene mutations were analysed with the real-time polymerase chain reaction (PCR) or Sanger sequencing. However, none of the investigated workers had the hIFNα-2b mutation. This finding highlights the need for further research to identify biomarkers for early detection of health effects associated with chronic low-dose IR exposure.

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.

Impact of Low-Dose Occupational Exposure to Ionizing Radiation on T-Cell Populations and Subpopulations and Humoral Factors Included in the Immune Response

The aim of the present study is to assess the effects of low-dose occupational exposure on T helper response. One Hundred five employees working in Nuclear Power Plant, Kozloduy, Bulgaria and control group of 32 persons are included in this investigation. Flow cytometry measurements of T-cell populations and subpopulations and natural killer T cells are performed and levels of G, A, and M immunoglobulins and interleukin 2 (IL-2), IL-4, and interferon γ were determined. The data interpreted with regard to cumulative doses, length of service, and age. The results of the present study are not enough to outline a clear impact of occupational radiation exposure on T helper populations. Nevertheless, the observed even slight trends in some lymphocyte’s populations and in cytokines profile give us the reason to assume a possibility of a gradual polarization of T helper 1 to T helper 2 immune response at dose range 100 to 200 mSv. The results of the present study indicate the need to perform a more detailed epidemiological survey including potential confounding and misclassifying factors and possible selection bias that could influence the results.

Effects of low-dose irradiation on mice with Escherichia coli-induced sepsis

Although favorable immune responses to low-dose irradiation (LDI) have been observed in normal mice, i.e., a hormesis effect, little is known about the effects of LDI in infectious diseases. In this study, we examined the effects of LDI on mice with sepsis, a severe and often lethal hyperinflammatory response to bacteria. Female C57BL/6 mice were whole-body irradiated with 10cGy 48h before Escherichia coli infection, and survival, bacterial clearance, cytokines, and antioxidants were quantified. LDI pretreatment significantly increased survival from 46.7% in control mice to 75% in mice with sepsis. The bacterial burden was significantly lower in the blood, spleen, and kidney of LDI-treated mice than in those of control septic mice. The levels of pro-inflammatory cytokines, e.g., IL-1β and IL-6, as well as anti-inflammatory IL-10 were markedly reduced in pre-LDI septic mice. Nitric oxide production by peritoneal macrophages was also reduced in pre-LDI septic mice. Immune cells in the spleen increased and Nrf2 and HO-1 were induced in pre-LDI septic mice. LDI stimulates the immune response and minimizes lethality in septic mice via enhanced bacterial clearance and reduced initial proinflammatory responses.

Correlation between infectious disease and soil radiation in Japan: an exploratory study using national sentinel surveillance data

We investigated the relationship between epidemics and soil radiation through an exploratory study using sentinel surveillance data (individuals aged <20 years) during the last three epidemic seasons of influenza and norovirus in Japan. We used a spatial analysis method of a geographical information system (GIS). We mapped the epidemic spreading patterns from sentinel incidence rates. We calculated the average soil radiation [dm (μGy/h)] for each sentinel site using data on uranium, thorium, and potassium oxide in the soil and examined the incidence rate in units of 0·01 μGy/h. The correlations between the incidence rate and the average soil radiation were assessed. Epidemic clusters of influenza and norovirus infections were observed in areas with relatively high radiation exposure. A positive correlation was detected between the average incidence rate and radiation dose, at r = 0·61-0·84 (P < 0·01) for influenza infections and r = 0·61-0·72 (P < 0·01) for norovirus infections. An increase in the incidence rate was found between areas with radiation exposure of 0 < dm < 0·01 and 0·15 ⩽ dm < 0·16, at 1·80 [95% confidence interval (CI) 1·47-2·12] times higher for influenza infection and 2·07 (95% CI 1·53-2·61) times higher for norovirus infection. Our results suggest a potential association between decreased immunity and irradiation because of soil radiation. Further studies on immunity in these epidemic-prone areas are desirable.

NORMAL TISSUE REACTIONS TO CHRONIC RADIATION EXPOSURE IN MAN

This paper presents an overview of radiobiological dependences governing the occurrence of tissue (organ) reactions that determine the outcomes of chronic exposure to low-LET ionizing radiation (IR) in humans. The mechanisms involved in the development of tissue reactions (TRs) to long-term exposures to IR and radioadaptation are considered. The overview describes the reactions of the haematopoietic, immune, nervous, reproductive and endocrine systems, lungs, skin and crystalline lens to chronic radiation exposure, which are of fundamental importance in view of radiation protection. It is shown that the individual's physiological tissue (organ) reserve, and also that induced by radiation exposure at low-dose rates are of great significance in the context of TR development.

Contrasting roles for C/EBPα and Notch in irradiation-induced multipotent hematopoietic progenitor cell defects

Ionizing radiation (IR) is associated with reduced hematopoietic function and increased risk of hematopoietic malignancies, although the mechanisms behind these relationships remain poorly understood. Both effects of IR have been commonly attributed to the direct induction of DNA mutations, but evidence supporting these hypotheses is largely lacking. Here we demonstrate that IR causes long-term, somatically heritable, cell-intrinsic reductions in hematopoietic stem cell (HSC) and multipotent hematopoietic progenitor cell (mHPC) self-renewal that are mediated by C/EBPα and reversed by Notch. mHPC from previously irradiated (>9 weeks prior), homeostatically restored mice exhibit gene expression profiles consistent with their precocious differentiation phenotype, including decreased expression of HSC-specific genes and increased expression of myeloid program genes (including C/EBPα). These gene expression changes are reversed by ligand-mediated activation of Notch. Loss of C/EBPα expression is selected for within previously irradiated HSC and mHPC pools and is associated with reversal of IR-dependent precocious differentiation and restoration of self-renewal. Remarkably, restoration of mHPC self-renewal by ligand-mediated activation of Notch prevents selection for C/EBPα loss of function in previously irradiated mHPC pools. We propose that environmental insults prompt HSC to initiate a program limiting their self-renewal, leading to loss of the damaged HSC from the pool while allowing this HSC to temporarily contribute to differentiated cell pools. This "programmed mediocrity" is advantageous for the sporadic genotoxic insults animals have evolved to deal with but becomes tumor promoting when the entire HSC compartment is damaged, such as during total body irradiation, by increasing selective pressure for adaptive oncogenic mutations.

Assessment of Some Immune Parameters in Occupationally Exposed Nuclear Power Plants Workers: Flowcytometry Measurements of T, B, NK and NKT Cells

The purpose of this article is to analyze the results of a 10-year survey of the radiation effects of some immune parameters of occupationally exposed personnel from the Nuclear Power Plant “Kozloduy”, Bulgaria. 438 persons working in NPP with cumulative doses between 0.06 mSv and 766.36mSv and a control group with 65 persons were studied. Flow cytometry measurements of T, B, natural killer (NK) and natural killer T (NKT) cell lymphocyte populations were performed. Data were interpreted with regard to cumulative doses, length of service and age. The average values of the studied parameters of cellular immunity were in the reference range relative to age and for most of the workers were not significantly different from the control values. Low doses of ionizing radiation showed some trends of change in the number of CD3+CD4+ helper-inducer lymphocytes, CD3+ CD8+ and NKT cell counts. The observed changes in some of the studied parameters could be interpreted in terms of adaptation processes at low doses. At doses above 100–200 mSv, compensatory mechanisms might be involved to balance deviations in lymphocyte subsets. The observed variations in some cases could not be attributed only to the radiation exposure because of the impact of a number of other exogenous and endogenous factors on the immune system.

Assessment of Some Immune Parameters in Occupationally Exposed Nuclear Power Plant Workers: Flow Cytometry Measurements of T Lymphocyte Subpopulations and Immunoglobulin Determination

A 10-year survey of immune status of nuclear power plant (NPP) workers was assessed by cellular and humoral immune parameters. The cumulative doses of NPP workers were in the range of 0.06 to 766.36 mSv. The results did not show significant deviations in the studied parameters of cellular and humoral immunity, but a tendency of elevated values in CD3+4+ helper inducers cells, especially its CD4+62L+ subpopulation, regulatory CD4+25+ cells, CD8+28+ cytotoxic subpopulation, and immunoglobulin M, was established. The observed trend of the above-mentioned parameters could be interpreted by assumption that while the adaptation processes are dominated with low prevalence of T-helper (Th) 1 immune response to cumulative doses less than 100 mSv, a switch to Th-2 response occurred at doses above 100 mSv. The impact of a number of other confounding factors on the immune system does not allow definitive conclusions about the direct radiation-induced changes in immune parameters.

Analysis of immune cell populations and cytokine profiles in murine splenocytes exposed to whole-body low-dose irradiation

PURPOSE

In contrast to high-dose therapeutic irradiation, definitive research detailing the physiological effects of low-dose irradiation is limited. Notably, the immunological response elicited after low-dose irradiation remains controversial.

MATERIALS AND METHODS

Female C57BL/6 mice were whole- body-irradiated with a single or three daily fractions up to a total dose of 0.1, 1, or 10 cGy. Blood and spleen were harvested 2, 7 and 14 days after irradiation.

RESULTS

The splenic CD4(+) T cell subpopulations were temporarily increased at 2 days after single or fractionated irradiation, whereas the percentage of dendritic cells (DC) and macrophages was decreased. Whereas CD8(+) T cell populations were decreased in single-dose irradiated mice at day 7, early and sustained reduction of CD8(+) T cell numbers was observed in fractionated- dose-irradiated mice from day 2 until day 14. In addition, single-dose irradiation resulted in a Th1 cytokine expression profile, whereas fractionated-dose irradiation drove a Th2 shift. Additionally, increased expression of immune-related factors was observed at early time-points with single-dose irradiation, in contrast to the dose-independent induction following fractionated-dose irradiation.

CONCLUSIONS

Our results demonstrate that low-dose irradiation modulates the immune response in mice, where the sensitivity and kinetics of the induced response vary according to the dosing method.

Mutations of the human interferon alpha-2b (hIFNα-2b) gene in low-dose natural terrestrial ionizing radiation exposed dwellers

Natural terrestrial ionizing radiations emerge from uranium deposits and can impact human tissues by affecting DNA bases which constitute genes. Human interferon alpha-2b (hIFNα-2b) gene synthesizes a protein which exhibits anticancerous, immunomodulatory, anti-proliferative and antiviral properties. This research aimed to find out hIFNα-2b gene mutations for those residents who were chronically exposed to low-dose natural terrestrial ionizing radiations. The gene amplifications was done through PCR technique and gene mutations were identified by bioinformatics in order to conclude as to how mutations identified in hIFNα-2b gene sequences will lead to alterations in the hIFNα-2b protein in radiation exposed residents. The range of radiation dose exposure was 0.4383-4.55832 (mSv/y) for the selected radiation exposed locations which were having uranium mineralization. Mutations (24%) in hIFNα-2b gene shows that some of the radiation exposed inhabitants were having a modulated immune response. The CBC (Complete Blood Count) parameters: WBC (White Blood Cells), MCH (Mean Corpuscular Hemoglobin), MCHC (MCH Concentration) and PLT (Platelets) on average were below the normal range in 24% radiation exposed subjects who were having hIFNα-2b gene mutations. Immunomodulation is observed by the mixed trend of either lymphocytosis or lymphopenia and neutropenia or neutrophilia in the exposed population. Thus, a radioactive exposure from uranium can affect the immune system and can induce mutations.

Alteration of cytokine profiles in uranium miners exposed to long-term low dose ionizing radiation

Objective. The aim of the study is to estimate the immune function through cytokine profiles in sera of uranium mines. Methods. Antibody arrays were used to detect 50 cytokines in sera of uranium miners. Miners who had continuously worked underground for <5 years were treated as control group and those who worked for ⩾5 years as experimental group. Results. Of 28 measurable cytokines, the release of IL-1α, IL-1RI, IL-15, IL-3, and IP-10 were significantly upregulated in the experimental group, and no cytokine was found significantly downregulated. Other proinflammatory cytokines such as IFN-γ, IL-10, IL-6, and TNFα levels were slightly upregulated in the experimental group. With adjustment to age, BMI, and cigarette smoking, IL-1α and IL-3 levels increased significantly with underground time. Conclusion. Alteration of cytokine profiles in this study may indicate persistent inflammatory responses in uranium miners exposed to long-term low doses radiation.

Gene expression as a biomarker for human radiation exposure

Accidental exposure to ionizing radiation can be unforeseen, rapid, and devastating. The detonation of a radiological device leading to such an exposure can be detrimental to the exposed population. The radiation-induced damage may manifest as acute effects that can be detected clinically or may be more subtle effects that can lead to long-term radiation-induced abnormalities. Accurate identification of the individuals exposed to radiation is challenging. The availability of a rapid and effective screening test that could be used as a biomarker of radiation exposure detection is mandatory. We tested the suitability of alterations in gene expression to serve as a biomarker of human radiation exposure. To develop a useful gene expression biomonitor, however, gene expression changes occurring in response to irradiation in vivo must be measured directly. Patients undergoing radiation therapy provide a suitable test population for this purpose. We examined the expression of CC3, MADH7, and SEC PRO in blood samples of these patients before and after radiotherapy to measure the in vivo response. The gene expression after ionizing radiation treatment varied among different patients, suggesting the complexity of the response. The expression of the SEC PRO gene was repressed in most of the patients. The MADH7 gene was found to be upregulated in most of the subjects and could serve as a molecular marker of radiation exposure.

Effects of ionizing radiation on the immune system with special emphasis on the interaction of dendritic and T cells

Dendritic cells (DCs), as professional antigen-presenting cells, are members of the innate immune system and function as key players during the induction phase of adaptive immune responses. Uptake, processing, and presentation of antigens direct the outcome toward either tolerance or immunity. The cells of the immune system are among the most highly radiosensitive cells in the body. For high doses of ionizing radiation (HD-IR) both immune-suppressive effects after whole body irradiation and possible immune activation during tumor therapy were observed. On the other hand, the effects of low doses of ionizing radiation (LD-IR) on the immune system are controversial and seem to show high variability among different individuals and species. There are reports revealing that protracted LD-IR can result in radioresistance. But immune-suppressive effects of chronic LD-IR are also reported, including the killing or sensitizing of certain cell types. This article shall review the current knowledge of radiation-induced effects on the immune system, paying special attention to the interaction of DCs and T cells.

ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context

This report provides a review of early and late effects of radiation in normal tissues and organs with respect to radiation protection. It was instigated following a recommendation in Publication 103 (ICRP, 2007), and it provides updated estimates of 'practical' threshold doses for tissue injury defined at the level of 1% incidence. Estimates are given for morbidity and mortality endpoints in all organ systems following acute, fractionated, or chronic exposure. The organ systems comprise the haematopoietic, immune, reproductive, circulatory, respiratory, musculoskeletal, endocrine, and nervous systems; the digestive and urinary tracts; the skin; and the eye. Particular attention is paid to circulatory disease and cataracts because of recent evidence of higher incidences of injury than expected after lower doses; hence, threshold doses appear to be lower than previously considered. This is largely because of the increasing incidences with increasing times after exposure. In the context of protection, it is the threshold doses for very long follow-up times that are the most relevant for workers and the public; for example, the atomic bomb survivors with 40-50years of follow-up. Radiotherapy data generally apply for shorter follow-up times because of competing causes of death in cancer patients, and hence the risks of radiation-induced circulatory disease at those earlier times are lower. A variety of biological response modifiers have been used to help reduce late reactions in many tissues. These include antioxidants, radical scavengers, inhibitors of apoptosis, anti-inflammatory drugs, angiotensin-converting enzyme inhibitors, growth factors, and cytokines. In many cases, these give dose modification factors of 1.1-1.2, and in a few cases 1.5-2, indicating the potential for increasing threshold doses in known exposure cases. In contrast, there are agents that enhance radiation responses, notably other cytotoxic agents such as antimetabolites, alkylating agents, anti-angiogenic drugs, and antibiotics, as well as genetic and comorbidity factors. Most tissues show a sparing effect of dose fractionation, so that total doses for a given endpoint are higher if the dose is fractionated rather than when given as a single dose. However, for reactions manifesting very late after low total doses, particularly for cataracts and circulatory disease, it appears that the rate of dose delivery does not modify the low incidence. This implies that the injury in these cases and at these low dose levels is caused by single-hit irreparable-type events. For these two tissues, a threshold dose of 0.5Gy is proposed herein for practical purposes, irrespective of the rate of dose delivery, and future studies may elucidate this judgement further.

Effect of cesium radioisotope on humoral immune status in Ukrainian children with clinical symptoms of irritable bowel syndrome related to Chernobyl disaster

The aim of this study is to determine humoral immune status in Ukrainian children with clinical symptoms of irritable bowel syndrome 23 years after the Chernobyl disaster.

METHOD AND MATERIAL

The test population consisted of 95 participants: 75 rural patients aged 4-18, who lived in a contaminated area exposed to natural environmental radiation (falling under three groups) and 20 healthy urban participants from Kiev aged 5-15 as a control group. Internal radiation activity has been measured by gamma-ray spectrometry. B-lymphocytes population was analyzed with monoclonal antibody against antigen CD22(+). Serum immunoglobulins were evaluated by enzyme-linked immunosorbent assay (ELISA) method. p < 0.05 was considered significant.

RESULT

The percentage of CD22(+) in study groups is increased significantly in comparison to control group at p < 0.05. Reduced serum immunoglobulins levels have developed in the majority of the participants.

CONCLUSION

Humoral immune status of study groups with clinical symptom of irritable bowel syndrome residing in a contaminated area has changed.

Ionizing radiation and hematopoietic malignancies: altering the adaptive landscape

Somatic evolution, which underlies tumor progression, is driven by two essential components: (1) diversification of phenotypes through heritable mutations and epigenetic changes and (2) selection for mutant clones which possess higher fitness. Exposure to ionizing radiation (IR ) is highly associated with increased risk of carcinogenesis. This link is traditionally attributed to causation of oncogenic mutations through the mutagenic effects of irradiation. On the other hand, potential effects of irradiation on altering fitness and increasing selection for mutant clones are frequently ignored. Recent studies bring the effects of irradiation on fitness and selection into focus, demonstrating that IR exposure results in stable reductions in the fitness of hematopoietic stem and progenitor cell populations. These reductions of fitness are associated with alteration of the adaptive landscape, increasing the selective advantages conferred by certain oncogenic mutations. Therefore, the link between irradiation and carcinogenesis might be more complex than traditionally appreciated: while mutagenic effects of irradiation should increase the probability of occurrence of oncogenic mutations, IR can also work as a tumor promoter, increasing the selective expansion of clones bearing mutations which become advantageous in the irradiation-altered environment, such as activated mutations in Notch1 or disrupting mutations in p53.

Biological effects of low-dose ionizing radiation exposure on interventional cardiologists

BACKGROUND

Interventional cardiologists (ICs) are likely to receive high radiation exposure as a result of procedures they undertake.

AIMS

To assess the effects of low-dose X-ray radiation exposure on chromosomal damage and on selected indices of cellular and humoral immunity in ICs.

METHODS

The study population consisted of 37 ICs and 37 clinical physicians as the control group with similar age, sex and duration of employment, without any work-related exposure to ionizing radiation. Cytogenetic studies were performed by chromosome aberration analysis and immunological studies by flow cytometry, enzyme-linked immunosorbent assay and immunodiffusion techniques.

RESULTS

The frequencies of aberrant cells, chromosome breaks and dicentrics plus centric rings were significantly higher in the exposed group compared to the control group (P < 0.05; P < 0.01; P < 0.001, respectively), without positive correlation between the frequency of dicentric and centric ring aberrations and the cumulative doses of the ICs (r = 0.24, not significant). A significant increase was observed in the expression of activation marker CD69 on TCD4(+) stimulated cells in serum immunoglobulin G and interleukin (IL)-2 (P < 0.05) and a significant decrease in serum IL-10 (P < 0.05) in the ICs compared with that of the control group. There was no statistical difference between the two groups in terms of number of white blood cells and lymphocytes, CD3(+), CD4(+) and CD8(+) T cells, CD19(+) and CD16(+) 56(+) cells and concentrations of interferon (IFN)-gamma, IL-4, IL-6 and IL-8 cytokines.

CONCLUSIONS

While cytogenetic results show higher chromosomal damage, some immune responses are stimulated or modulated immunologically in ICs.

Analysis of gene expression in normal and cancer cells exposed to gamma-radiation

The expression of many genes is modulated after exposure to ionizing radiation. Identification of specific genes may allow the determination of pathways important in radiation responses. We previously identified modulation of the expression of several genes in response to ionizing radiation treatment. In the present study, we monitored the expression of RGS1, CC3, THBS1, vWF, MADH7, and a novel gene encoding a secreted protein in irradiated Jurkat, TK6, HeLa, and HFL1 cells. The RGS1 is involved in G-protein signaling pathway, CC3 belongs to the complement system, THBS1 is a component of the extracellular matrix, vWF takes part in blood coagulation, and MADH7 is a member of the TGF-β signal transduction pathway. Our objective was to find similarities and differences in the expression of these genes in ionizing radiation-exposed diverse cell types. RGS1 was downregulated in Jurkat cells but was upregulated in TK6 and HFL1 cells. The expression of CC3 was repressed in Jurkat and HFL1 cells but was induced in TK6 and HeLa cells. THBS1 was downregulated in irradiated TK6 and HFL1 cells. vWF was induced in radiation-exposed HeLa cells, but its expression was downregulated in Jurkat cells. The expression of MADH7 was induced in all the cell types examined. These results indicate cell specific modulation of gene expression and suggest the involvement of different pathways in cellular response to radiation treatment in different cells.