Radiation-induced Genomic Instability Research Articles

Biological effects of radiation exposure in patients treated with X-ray guided endovascular aortic repair

Abstract Background X-ray guided cardiovascular interventions such as endovascular aortic repair (EVAR) expose patients and operators to significant amounts of repeated ionising radiation over a long period of time. The biological effect of such protracted radiation exposure is poorly understood. We have previously demonstrated a higher incidence of dicentric chromosome (DC) aberrations in high-volume endovascular interventionalists and differences in acute DNA damage in lymphocytes between individuals following in vitro irradiation. Studies suggested a higher incidence of cancer in patients who underwent EVAR compared with those who have had open aneurysm repair, but the evidence is inconclusive. Further work is required to evaluate the biological radiation risk of X-ray guided cardiovascular interventions. Purposes We aimed to examine radiation-induced genome instability from patients after complex EVAR. We also aimed to investigate the intrinsic response of each patient to radiation using biomarkers of acute DNA damage following in vitro irradiation of their blood and to correlate this response to the expression of radiation-responsive genes. Methods Lymphocytes were isolated from patients after complex (branched/fenestrated) EVAR and non-irradiated controls. DC, a type of chromosomal aberration caused by radiation exposure were enumerated. γ-H2AX, a marker of acute DNA damage/repair, was measured by immunofluorescence after in vitro irradiation at 0.2 Gy and 1 Gy, along with the expression of the radiation-responsive genes FDXR, CCNG1, P21 and PHPT1 using qPCR. Results 17 patients (82% male, median age 73[59 – 85years]) and 16 controls (56% male, median age 68[53 – 83years]) were recruited. The mean incidence of DC was 3.782 (95% CI 3.13 - 4.43) and 0.898 (95% CI 0.48 -1.32) per 1000 cells for patients and controls, respectively (P<0.0001). Patients had higher background of γ-H2AX foci than unexposed controls, (0.7056, 95% CI 0.316 - 1.10) vs (0.241 95% CI 0.077 - 0.405) per cell, P<0.05. FDXR expression was most increased following irradiation (P<0.0001), reaching a mean 13.1-fold and 11.4-fold increase at 4-hour and 24-hour time-point, respectively, but this upregulation was not significantly different between the two groups. Conclusion We have shown an increased frequency of chromosomal aberrations in patients after complex EVAR, a biological finding that may support a propensity to developing malignancies. Patients also have higher basal DNA damage/repair (γ-H2AX) activity. Expression of ferredoxin reductase, FDXR gene could be a potential radio-responsive biomarker to provide personalised biological dosimetry information for clinical monitoring. Our study further underlines the long-term radiation risk of X-ray guided cardiovascular interventions and the potential of biological assays that may guide personalised care.

"Lethal Mutations" a Misnomer or the Start of a Scientific Revolution?

The aim of this paper is to review the history surrounding the discovery of lethal mutations, later described as delayed reproductive death. Lethal mutations were suggested very early on, to be due to a generalised instability in a cell population and are considered now to be one of the first demonstrations of "radiation-induced genomic instability" which led later to the establishment of the field of "non-targeted effects." The phenomenon was first described by Seymour etal. in 1986 and was confirmed by Trott's group in Europe and by Little and colleagues in the United States before being extended by Mendonca etal. in 1989, who showed conclusively that the distinguishing feature of lethal mutation occurrence was that it happened suddenly after about 9-10 population doublings in progeny which had survived the original dose of ionizing radiation. However, many authors then suggested that in fact, lethal mutations were implicit in the original experiments by Puck and Marcus in 1956 and were described in the extensive work by Sinclair in 1964, who followed clonal progeny for up to a year after irradiation and described "small colony formation" as a persistent consequence of ionizing radiation exposure. In this paper, we examine the history from 1956 to the present using the period from 1986-1989 as an anchor point to reach into the past and to go forward through the evolution of the field of low dose radiobiology where non-targeted effects predominate.

X-ray-downregulated nucleophosmin induces abnormal polarization by anchoring to G-actin

Ionizing radiation poses significant risks to astronauts during deep space exploration. This study investigates the impact of radiation on nucleophosmin (NPM), a protein involved in DNA repair, cell cycle regulation, and proliferation. Using X-rays, a common space radiation, we found that radiation suppresses NPM expression. Knockdown of NPM increases DNA damage after irradiation, disrupts cell cycle distribution and enhances cellular radiosensitivity. Additionally, NPM interacts with globular actin (G-actin), affecting its translocation and centrosome binding during mitosis. These findings provide insights into the role of NPM in cellular processes in responding to radiation. This article enhances our comprehension of radiation-induced genomic instability and provides a foundational platform for prospective investigations within the realm of space radiation and its implications for cancer therapy.

Chromosomal Instability in Various Generations of Human Mesenchymal Stem Cells Following the Therapeutic Radiation.

Radiotherapy is a crucial treatment for most malignancies. However, it can cause several side effects, including the development of secondary malignancies due to radiation-induced genomic instability (RIGI). The aim of this study was to evaluate genomic instability in human mesenchymal stem cells (hMSCs) at different X-ray radiation doses. Additionally, the study aimed to examine the relative expression of certain genes involved in DNA repair, proto-oncogenes, and tumor suppressor genes. After extracting, characterizing, and expanding hMSCs, they were exposed to X-ray beams at doses of 0, 0.5, 2, and 6 Gy. Nuclear alterations were evaluated through the cytokinesis-block micronucleus (CBMN) assay at 2, 10, and 15 days postirradiation. The expressions of BRCA1, BRCA2, TP53, Bax, Bcl2, and KRAS genes were analyzed 48 hr after irradiation to evaluate genomic responses to different radiation doses. The mean incidence of micronuclei, nucleoplasmic bridges, and nuclear buds was 4.8 ± 1.6, 47.6 ± 6, and 18 ± 2.6, respectively, in the nonirradiated group 48 hr after the fourth passage, per 1,000 binucleated cells. The incidence of micronuclei in groups exposed to 0.5, 2, and 6 Gy of radiation was 14.3 ± 4.9, 32.3 ± 6.5, and 55 ± 9.1, respectively, 48 hr after irradiation. The expression levels of the BRCA2, Bax, TP53, and KRAS genes significantly increased after exposure to 6 Gy radiation compared to the control groups. However, there was no significant increase in BRCA1 and Bcl2 gene expression in our study. This study demonstrated significant nuclear alterations in the 10 days postirradiation due to the RIGIs that they inherited from their irradiated ancestral cells. While chromosomal instability is a prevalent event in malignant cells, so it seems necessary to optimize radiotherapy treatment protocols for tissues that contain stem cells, especially with IMRT, which delivers a low dose to a larger volume of tissues.

Pollution of ionising radiation diagnostic dose and its targeted and non-targeted effects on human primary fibroblast cells

One of the key issues of current radiation research is the biological effect of low doses of X-ray, which can instigate to chromosomal damage in direct irradiated and bystander cells. Additionally, the direct irradiated and bystander cells demonstrate delayed damage responses within their progeny, underlying radiation-induced genomic instability (GI). In this study we tried to mimic the effects of diagnostic procedure doses of X-ray (0.5 rad) on human fibroblast cells, which are considered as a one of the environmental polluter. Human fibroblast cells were irradiated with 0.5 rad X-ray, which were considered the direct irradiated cells; whilst radiation-induced bystander effects (BE) were induced by media transfer. Both cell populations were propagated until 24 generations for delayed responses. The direct, bystander and their progeny cells were subjected to chromosomal analysis and comet assay to measure chromosomal and total DNA damage in these cells. Early response of chromosome damage was observed in the direct irradiated cells; however it was statistically insignificant. Bystander cells showed higher chromosomal damage than the irradiated cells; but it was insignificant compare to the corresponding control groups. Conversely, comet data demonstrated a significant DNA damage in both direct irradiated and bystander cells as initial responses. Interestingly, progeny of direct irradiated and bystander cells showed a significant chromosomal instability and DNA damage after 24 population doublings following irradiation. The findings suggested that the diagnostic procedure doses of X-ray could cause a profound chromosomal instability within human primary fibroblast cells; which are considered as a hallmark of carcinogenesis.

Inflammatory mediator-induced bystander effects and genomic instability: role of tissue-specificity

Much evidence showed that radiation-induced inflammation can cause cellular damage in direct irradiated and bystander cells, which are in vicinity of irradiated cells underlying radiation-induced bystander effects (BE). As well as radiation-induced genomic instability (GI) is observed within the progeny of irradiated and bystander cells as a delayed damage responses. This study tried to mimic the effects of radiation-induced GI and BE by exploring the inflammatory effect of lipopolysaccharide (LPS) on human primary fibroblast (HF 19) and umbilical vein endothelial (HUVEC) cells. To prove the principles of LPS can cause DNA damage in HF 19; cells were treated with 1 μg/ml LPS, and BE was induced by media transfer. Comet assay was used to estimate DNA damage in the direct treated and bystander cells. The early DNA damage result was significantly observed in the direct treated and bystander HF 19 cells. However, these cells did not show a significant delayed DNA damage within their progeny. Comet data showed that LPS frequently induced only initial DNA damage in HF 19 cells. The experiment was repeated utilising HF 19 and HUVEC cells, in order to investigate whether LPS could be involved in the induction of GI in a tissue-specificity manner. Both HF 19 and HUVEC cells were treated with 1 μg/ml LPS. BE was also induced by media transfer. Chromosomal analysis was used for early and late chromosomal damage estimation. Data showed that LPS treatment could significantly cause early chromosomal aberrations in the direct treated and bystander HF 19 and HUVEC cells. However, delayed chromosomal instability was observed only in the direct treated HUVEC cells. Our finding suggested that LPS frequently induced BE in HF 19 and HUVEC cells, which could be mediated by pro-inflammatory cytokines that stimulated by LPS treatment. Moreover, LPS could be involved in the GI induction in a tissue-specificity manner.Keywords:

Relationship of radiation-induced genomic instability and antioxidant production in the chamomile plant

Purpose To verify the hypothesis about the preservation of signs of radiation-induced genomic instability at the flowering stage of the chamomile plant after pre-sowing seed irradiation, the interaction of dose-dependent changes in the level of DNA damage and stimulation of antioxidant production. Materials and methods The study was carried out on two genotypes of chamomile, Perlyna Lisostepu variety and its mutant, using pre-sowing seed radiation exposure at dose levels 5–15 Gy. Studies of the rearrangement of the primary DNA structure of under different doses were studied on plant tissues at the flowering stage using – ISSR and RAPD DNA markers. Dose-dependent changes relative to the control of the amplicons’ spectra were analyzed using the Jacquard similarity index. Antioxidants such as flavonoids and phenols were isolated from pharmaceutical raw materials (inflorescences) using traditional methods. Results Preservation of multiple DNA damages at the stage of plant flowering under pre-sowing seed irradiation at low doses was confirmed. It was found that the largest rearrangements of the primary DNA structure of both genotypes, manifested in reduced similarity with the control spectra of amplicons, were observed under irradiation dose levels 5–10 Gy. There was a tendency to approach this indicator to the control under 15 Gy dose, which means increasing efficiency of the reparative processes. The relationship between the polymorphism of the primary structure of DNA by ISSR-RAPD-markers in different genotypes and the nature of its rearrangement under radiation exposure was shown. Dose dependences of changes in the specific content of antioxidants were non-monotonic with a maximum at 5–10 Gy. Conclusions Comparison of dose dependences of changes in the coefficient of similarity of the spectrum of amplicons between irradiated and control variants with nonmonotonic dose curves in the specific content of antioxidants allowed to suggest that there was the antioxidant protection stimulation under the doses corresponding to low efficiency of repair processes. The decrease in the specific content of antioxidants followed the restoration of the genetic material normal state. The interpretation of the identified phenomenon has been based on both known connection between the effects of genomic instability and the increasing yield of the reactive oxygen species and general principles of antioxidant protection.

Exosome-like vesicles released from ob/ob mouse adipose tissue enhance cell survival of cells with radiation-induced genomic instability.

Multiple epidemiological studies have shown that obesity is a serious risk factor for cancer development. While the underlying mechanisms between obesity and cancer are still unknown, obesity disrupts the role of adipocytes in energy homeostasis, and the alteration of adipokine, insulin and sex steroid signaling. Recently, it has been identified that adipose tissue-derived exosome-like vesicles (ELVs) regulate metabolic homeostasis. In this study, we collected ELVs from adipose tissue of an obese mouse (ob/ob) strain and control mouse (C57BL/6) strain, and checked whether adipose ELVs influence radiation-induced cell death on mouse fibroblast cells (m5S). Furthermore, we analyzed the micronucleus (MN) frequency in survived cells after radiation exposure to investigate the effect of ELVs on radiation-induced genomic instability. We first observed that ELVs from control and obese mice showed enhanced colony forming ability in un-irradiated m5S cells. However, enhanced survival was observed only in 3Gy-irradiated m5S cells with obese ELV treatment. Despite no ELV effect on colony size, interestingly, the frequency of MN in survived m5S cells after 3Gy irradiation was elevated when treated obese ELVs compared to control ELVs. These results suggested that obese mouse adipose ELVs could enhance the survival of irradiated cells harboring increased radiation-induced genomic instability.

ROLE OF RADIOPROTECTORS IN MINIMIZATION OF STOCHASTIC EFFECTS OF RADIATION INCIDENTS.

Thereal threat of emergency situations in Ukraine dictates theneed to take into account theexperience of previous radiation accidents, during which a significant part of thepopulation was exposed to low-dose radiation. In such a case clinical manifestations of irradiation were mostly absent, while thedanger of stochastic (carcinogenic) effects remained. Therefore, at present, thestrategy of radiation protection of thepopulation should be aimed at revising and choosing effective and low-toxic anti-radiation means. Themain criterion for thedevelopment of stochastic consequences of exposure is radiation-induced genome instability, which is a promoter of carcinogenesis. Theuse of radiomitigators, which are able to weaken theharmful effect of ionizing radiation on critical highly radiosensitive systems of thehuman body, is promising. Our research showed theradiomitigative effect of inosine in cultured human T-lymphocytes on thegenetic level with thesignificant decrease in thefrequency of gamma-induced chromosome aberrations. Theresults experimentally justified an expediency of use of radiomitigators in theconditions of an emergency situation to minimize theoccurrence and development of stochastic effects in population.

More efficient induction of genotoxicity by high-LET Fe-particle radiation than low-LET X-ray radiation at low doses

ObjectiveTo understand differential effects on induction of genotoxicity and genomic instability (GI) by high-LET particle radiation and low-LET photon radiation, based on ground-based experiments using total body irradiation (TBI) of mice with Fe-particle radiation and X-ray radiation. MethodsTBI was delivered to C57BL/6J Jms strain female mice of 8 weeks old at a dose ranging from 0.1 to 3.0 Gy of Fe-particle radiation or at a dose ranging from 0.1 to 5.0 Gy of X-ray radiation. Induction of genotoxicity and GI by TBI was determined respectively at 1 and 2 months after exposure using frequency of micronuclei in bone marrow erythrocytes as the endpoint. Inhibition of bone marrow cell proliferation by TBI was measured as reduced erythropoiesis. Physiological conditions were also investigated. ResultsTBI, regardless of the type of radiation, caused statistically significant increase in genotoxicity at 1 month after exposure, but did not induce GI at 2 months after exposure even at higher doses (>1.0 Gy). The dose-response curve for the frequency of micronucleated polychromatic erythrocytes induced by Fe-particle radiation and X-ray radiation was y ​= ​0.7798 ​+ ​1.7889x– 0.5978x2 (R2 = 0.8109) and y ​= ​0.7421 ​+ ​1.3792x – 0.2588 x2 (R2 = 0.8081), respectively. The dose-response curve for the frequency of micronucleated normochromatic erythrocytes induced by Fe-particle radiation and X-ray radiation was y ​= ​0.7191 ​+ ​1.4545x – 0.4978x2 (R2 = 0.7047) and y ​= ​0.658 ​+ ​1.344x – 0.2531x2 (R2 = 0.7853), respectively. In general, high-LET Fe-particle radiation was more efficient in inducing genotoxicity than low-LET X-ray radiation at lower doses (<0.5 Gy). ConclusionsThese results further confirm that exposure to TBI, even at higher doses and regardless the type of radiation, does not induce GI in C57BL/6J strain mice measured as increased micronuclei in bone marrow erythrocytes. These findings indicate that radiation-induced GI is mouse strain dependent and suggest that more comprehensive studies should be done to explore the late health consequences from exposure to high-LET radiation at low doses.

Quercetin 3 Rutinoside Alleviates Chromosomes Instability Induced by Lethal Dose of Gamma Radiation

Radiation-induced genomic instability always remains a major concern for the medical society, following radiation exposure. Hence, development of a safe and effective radioprotector is of considerable interest in case of radiotherapy and radiation emergencies. Quercetin-3-Rutinoside (Q-3-R), a naturally occurring bioflavonoid, has shown promising potential against radiation injuries. The present study reports anti-genotoxic potential of Q-3-R against lethal (9Gy) dose of ionizing radiation. The mice were injected intramuscularly with Q-3-R (10mg/kg b.wt.), 1hr prior to lethal dose of radiation and dissected at 24hrs post treatment. Different kinds of chromosomal aberrations, micronuclei as well as pulverized metaphase and polyploidy were scored in bone marrow cells. Irradiated mice showed significantly (p&lt;0.001) increased number of double minutes, fragments, dicentrics, rings, gaps and end to end association. Pulverized metaphases and polyploidy were also found to be elevated in irradiated group. Pretreatment of Q-3-R significantly countered these radiation-induced genetic variations in lethally exposed mice. Data from the present study support the anti-genotoxic potential of Q-3-R even at lethal dose of radiation. Q-3-R, possessing various pharmacological activities and being a safe supplement for treatment of other ailments, can be further explored for its radioprotective potential.

ПЕРЕДАЧА РАДИАЦИОННО-ИНДУЦИРОВАННОЙ ГЕНОМНОЙ НЕСТАБИЛЬНОСТИ ОТ ОБЛУЧЕННЫХ РОДИТЕЛЕЙ ПОТОМКАМ

Numerous studies allow to suppose a transmission of radiation-induced genome instability from irradiated parents to their offspring on cell, chromosome and molecular genetic level. This review focuses on transmission of radiation-induced genome instability from irradiated parents to their offspring. Data of genome instability in animal experiments and in offspring of occupationally exposed human or human exposed in a radiation accident, and in offspring of parents exposed to radiotherapy are reviewed. The possible mechanisms of lineage transmission of genome instability are discussed. High dose irradiation can lead to DNA damage, changes in methylation patterns and miRNAs expression in parents and their offspring and result in mutations, chromosome aberration and destabilization of genome. Non-coding RNAs (miRNA, piRNA, nsRNA) are supposed to contribute to transgenerational effects, since they can target genes, change chromatin structure and disregulate gene expression.

188Rhenium Treatment Induces DACT2 Expression in Hepatocellular Carcinoma Cells.

ObjectivesEpigenetic alterations, including any change in DNA methylation pattern, could be the missing link of understanding radiation-induced genomic instability. Dapper, Dishevelled-associated antagonist of β-catenin homolog 2 (DACT2) is a tumor suppressor gene regulating Wnt/β-catenin. In hepatocellular carcinoma (HCC), DACT2 is hypermethylated, while methylation status of its promoter regulates the corresponding expression. Radionuclides have been used to reduce proliferation and induce apoptosis in cancerous cells. Epigenetic impact of radionuclides as therapeutic agents for treatment of HCC is still unknown. The aim of this study was to evaluate epigenetic impact of 188Rhenium perrhenate (188ReO4) on HCC cells.Material and MethodsIn this in vitro experimental study, HepG2 and Huh7 cells were treated with 188ReO4, receiving 55 and 73 Mega Becquerel (MBq) exposures, respectively. For cell viability measurement, live/dead staining was carried out 18, 24, and 48 hours post-exposure. mRNA expression level of β-Catenin, Wnt1, DNMT1, DACT2 and WIF-1 genes were quantified by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Then, possible regulatory impact of DACT2 upregulation was investigated through evaluating methylation-specific PCR (MS-PCR).Results Results showed that viability of both cells was reduced after treatment with 188ReO4 at three time points post- exposure compared to the control groups. The qRT-PCR results showed that DACT2 mRNA level was significantly increased at 24, and 48 hours post-exposure in HepG2 cells compared to the control group, while, no significant change was observed in Huh7 cells. Methylation pattern of DACT2 promoter remained unchanged in HepG2 and Huh7 cells. ConclusionTreatment with 188ReO4 reduced viability of HepG2 and Huh7 cells. Although DACT2 expression was increased after 188ReO4 exposure in HepG2 cells, methylation pattern of its promoter remained unchanged. This study assessed impacts of the 188ReO4 β-irradiation on expression and induction of DACT2 epigenetic aberrations as well as the correlation of this agent with viability of cells.

Cellular DNA effects of radiation and cancer risk assessment in cells with mitochondrial defects

Mitochondria play a key role in mediating non-targeted effects (NTE) post-radiation exposure. Mitochondrial DNA (mtDNA), due to its less efficient repair as compared to nuclear DNA, is more severely affected by radiation exposure and mutations in essential mtDNA genes can further exacerbate oxidative stress. Our objective was to evaluate the impact of mitochondrial defects on radiation-induced DDR and genomic instability, biomarkers that can foreshadow cancer development. To better understand this relationship, we used commercially available lymphoblastoid cell lines containing characterized mitochondrial mutations and studied the kinetics of DNA damage and relative telomere length (RTL) changes over time post 0.5 Gy X-ray exposure. Our work suggests that cells containing different mitochondrial mutations exhibit unique DNA damage and telomere length effects following radiation exposure. For example, a cell line containing a mitochondrial mutation in the ND4 subunit of complex 1 showed decreased growth rate, higher levels of persistent DNA damage, and telomere instability as compared to wild type. In contrast, a cell line with a mutation in the ATPase 6 mitochondrial protein showed more subtle negative alterations. These findings suggest mitochondrial integrity may play an important role in cellular changes that promote cancer. In total results indicate mitochondrial mutations can influence DNA damage kinetics and genomic instability and have long-term consequences in the ability to regain homeostasis following radiation exposure. These results may help explain, at least in part, the rationale for the persistent genomic instability often observed following a low dose of radiation and how it may promote cancer.

Kinetics of DNA Repair Under Chronic Irradiation at Low and Medium Dose Rates in Repair Proficient and Repair Compromised Normal Fibroblasts.

We present time and dose dependencies for the formation of 53BP1 and γH2AX DNA damage repair foci after chronic radiation exposure at dose rates of 140, 250 and 450 mGy/day from 3 to 96 h, in human and mouse repair proficient and ATM or DNA-PK deficient repair compromised cell models. We describe the time/dose-response curves using a mathematical equation which contains a linear component for the induction of DNA damage repair foci after irradiation, and an exponential component for their resolution. We show that under conditions of chronic irradiation at low and medium dose rates, the processes of DNA double-strand breaks (DSBs) induction and repair establish an equilibrium, which in repair proficient cells manifests as a plateau-shaped dose-response where the plateau is reached within the first 24 h postirradiation, and its height is proportionate to the radiation dose rate. In contrast, in repair compromised cells, where the rate of repair may be exceeded by the DSB induction rate, DNA damage accumulates with time of exposure and total absorbed dose. In addition, we discuss the biological meaning of the observed dependencies by presenting the frequency of micronuclei formation under the same irradiation conditions as a marker of radiation-induced genomic instability. We believe that the data and analysis presented here shed light on the kinetics of DNA repair under chronic radiation and are useful for future studies in the low-to-medium dose rate range.

Quercetin 3 Rutinoside Facilitates Protection Against Radiation Induced Genotoxic and Oxidative Damage A Study in C57bl 6 Mice

Radiation-induced oxidative stress and haematopoietic genomic instability is the major concern during planned or unplanned exposure. Use of the natural phytochemicals is an emerging strategy to prevent from the harmful effects of radiation. In the current investigation, Quercetin 3-Rutinoside (Q-3-R), a polyphenolic bioflavonoid, has been evaluated against gamma radiation (2Gy) induced genotoxic damage and oxidative imbalance in mice. Mice were administered with Q-3-R (10mg/kg body weight) 1hr prior to irradiation and evaluated for its antioxidant potential. Anti-genotoxic potential was assessed in terms of chromosomal aberrations in bone marrow cells. Findings revealed that Q-3-R had very high reducing potential, effectively scavenged 1,1-Diphenyl-2-picryl hydrazyl (DPPH) and hydrogen peroxide radicals, chelated metal ions and inhibited lipid peroxidation in a dose dependant manner. The glutathione (GSH) levels were found elevated (p&lt;0.05), while reduced malondialdehyde (MDA) levels were seen in blood and liver tissues of Q-3-R pretreated mice. Significant (p&lt;0.01) reduction in Reactive Oxygen Species (ROS) levels and radiation induced aberrations (dicentrics, rings, fragments, end to end association, robertsonian translocation) following Q-3-R pretreatment was found in bone marrow cells. The present findings demonstrate that Q-3-R can effectively minimise radiation-induced genotoxic and oxidative damages and can be explored further to be used as a potent radioprotector in humans.

Replication stress and FOXM1 drive radiation induced genomic instability and cell transformation.

In contrast to the vast majority of research that has focused on the immediate effects of ionizing radiation, this work concentrates on the molecular mechanism driving delayed effects that emerge in the progeny of the exposed cells. We employed functional protein arrays to identify molecular changes induced in a human bronchial epithelial cell line (HBEC3-KT) and osteosarcoma cell line (U2OS) and evaluated their impact on outcomes associated with radiation induced genomic instability (RIGI) at day 5 and 7 post-exposure to a 2Gy X-ray dose, which revealed replication stress in the context of increased FOXM1b expression. Irradiated cells had reduced DNA replication rate detected by the DNA fiber assay and increased DNA resection detected by RPA foci and phosphorylation. Irradiated cells increased utilization of homologous recombination-dependent repair detected by a gene conversion assay and DNA damage at mitosis reflected by RPA positive chromosomal bridges, micronuclei formation and 53BP1 positive bodies in G1, all known outcomes of replication stress. Interference with the function of FOXM1, a transcription factor widely expressed in cancer, employing an aptamer, decreased radiation-induced micronuclei formation and cell transformation while plasmid-driven overexpression of FOXM1b was sufficient to induce replication stress, micronuclei formation and cell transformation.

Environmental radiation on large Japanese field mice in Fukushima reduced colony forming potential in hematopoietic progenitor cells without inducing genomic instability

Purpose To study the environmental radiation effects of wild animals after the Fukushima Dai-ichi nuclear power plant accident, we assessed effects on hematopoietic progenitor cells (HPCs) in large Japanese field mice (Apodemus speciosus). Materials and methods A. speciosus were collected from three contaminated sites and control area. The air dose-rates at the control and contaminated areas were 0.96 ± 0.05 μGy/d (Hirosaki), 14.4 ± 2.4 μGy/d (Tanashio), 208.8 ± 31.2 μGy/d (Ide), 470.4 ± 93.6 μGy/d (Omaru), respectively. We investigated possible DNA damage and pro-inflammatory markers in the bone marrow (BM) cells. The colony-forming potential of BM cells was estimated by the number of HPC colony-forming cells. Radiation-induced genomic instability (RIGI) in HPCs was also analyzed by quantifying delayed DNA damage in CFU-GM clones. Results Although no significant differences in DNA damage and inflammation markers in BM cells from control and contaminated areas, the number of HPC colonies exhibited an inverse correlation with air dose-rate. With regard to RIGI, no significant differences in DNA damage of CFU-GM clones between the mice from the control and the three contaminated areas. Conclusions Our study suggests that low dose-rate radiation of more than 200 Gy/d reduced HPCs, possibly eliminating genomically unstable HPCs.

Individual features of radiation-induced genomic instability in patients with glioblastoma

Individual features of radiation-induced genomic instability in patients with glioblastoma

The Role of Telomerase in Radiation-Induced Genomic Instability.

Findings from previous studies have suggested that the telomerase system is involved in radiation-induced genomic instability. In this study, we investigated the involvement of telomerase in the development and processing of chromosomal damage at different cell cycle stages after irradiation of human fibroblasts. Several response criteria were investigated, including cell survival, chromosomal damage (using the micronucleus assay), G2-induced chromatid aberrations (using the conventional G2 assay as well as a chemically-induced premature chromosome condensation assay) and DNA double-strand breaks (DSBs; using γ-H2AX, 53BP1 and Rad51) in an isogenic pair of cell lines: BJ human foreskin fibroblasts and BJ1-hTERT, a telomerase-immortalized BJ cell line. To distinguish among G1, S and G2 phase, cells were co-immunostained for CENP-F and cyclin A, which are tightly regulated proteins in the cell cycle. After X-ray irradiation at doses in the range of 0.1-6 Gy, the results showed that for cell survival and micronuclei induction, where the overall effect is dominated by the cells in G1 and S phase, no difference was observed between the two cell types; in contrast, when radiation sensitivity at the G2 stage of the cell cycle was analyzed, a significantly higher number of chromatid-type aberrations (breaks and exchanges), and higher levels of γ-H2AX and of Rad51 foci were observed for the BJ cells compared to the BJ1-hTERT cells. Therefore, it can be concluded that telomerase appears to be involved in DNA DSB repair processes, mainly in the G2 phase. These data, taken overall, reinforce the notion that hTERT or other elements of the telomere/telomerase system may defend chromosome integrity in human fibroblasts by promoting repair in G2 phase of the cell cycle.