Search Results (186)

The Fukushima nuclear accident highlighted that evacuation-related psychosocial harm can outweigh direct radiation risks, underscoring the need to define the health impacts of chronic low-dose-rate (LDR) radiation and evidence-based thresholds for intervention. This study investigated the effects of continuous, postnatal LDR gamma irradiation (1.2 mGy/h, cumulative dose: 5 Gy) in male mice. While no changes in body weight, hippocampal neurogenesis, or major glial and neuronal populations were observed, persistent DNA damage (γ-H2AX foci) in dentate gyrus granule cells occurred in both irradiated male and female mice. Irradiated male mice developed anxiety-like behaviour, a phenotype not observed in a previously published study of female mice subjected to an identical irradiation protocol. Molecular profiling revealed two novel, dysregulated miRNA/mRNA axes in the hippocampus linking DNA damage to behaviour: a maladaptive miR-466i-5p/Tfcp2l1 pathway associated with genomic instability, and a potentially adaptive miR-101a-5p/BMP6 pathway promoting neuronal survival. Venn analysis further identified miR-124b-3p and novel-miR489-3p as conserved exposure biomarkers, altered in both the hippocampus and blood of irradiated animals. Our results show that a high cumulative dose of chronic LDR induces markedly less severe hippocampal pathology than has been reported for equivalent acute doses. These findings support the concept of dose-rate-dependent threshold dose and contribute to the evidence base for developing countermeasures following nuclear incidents or other radiation exposures. Full article

The rapid expansion of cardiac imaging has substantially increased patient and occupational exposure to low-dose ionizing radiation. Evidence suggests that cumulative exposures below 100 mSv may contribute to long-term risks of cancer and non-cancer diseases, including cardiovascular disease. However, establishing causality at these dose levels is challenging, as epidemiological studies are limited by heterogeneous endpoints, uncertainties in dose reconstruction, and incomplete control of confounding factors. Molecular biomarkers offer a promising strategy to bridge the gap between radiation exposure and clinically manifest disease, enabling more precise individualized risk assessment and targeted preventive strategies. This review summarizes current evidence on genetic and epigenetic biomarkers for evaluating the biological effects of radiation in cardiac imaging and interventional cardiology and examines their potential role in risk stratification and occupational surveillance. Genetic markers—including γ-H2AX foci, micronucleus assays, and telomere length alterations—alongside epigenetic modifications such as DNA methylation changes and microRNA expression profiles provide sensitive indicators of radiation-induced cellular damage. Integrating biomarker profiling with individualized dosimetry and longitudinal follow-up may improve risk prediction, enhance occupational protection, and support safer, more sustainable imaging practices in contemporary cardiovascular care. Full article

Chronic exposure to benzo[a]pyrene (BaP), a Group 1 IARC carcinogen, is a major driver of lung carcinogenesis; however, how sustained subcytotoxic exposure reprograms bronchial epithelium toward preneoplastic states remains poorly defined. Here, we subjected BEAS-2B human bronchial epithelial cells to 12 weeks of continuous BaP at environmentally relevant concentrations (0.1 and 1.0 µM) and interrogated the resulting phenotypes using an integrated multi-scale framework encompassing functional toxicology, RT-qPCR, RNA-seq, phospho-kinase/NF-κB arrays, and organotypic air–liquid interface (ALI) cultures. Cells maintained metabolic competence throughout, evidenced by sustained CYP1A1 and CYP1B1 induction at both acute (4 h) and chronic (12-week) timepoints, while accumulating genotoxic stress as demonstrated by dose-dependent nuclear γ-H2AX foci formation and ATM phosphorylation (Ser1981). RNA-seq revealed a dose-dependent transcriptional shift: 0.1 µM BaP yielded 119 differentially expressed genes (DEGs; |log2FC| ≥ 1, FDR < 0.05), whereas 1.0 µM generated 255 DEGs. Downregulated transcripts were enriched for extracellular matrix and cell-adhesion programs (COL14A1, ADAMTS2, CSMD3, CADM3), while upregulated genes encompassed inflammatory, calcium-signaling, and vesicle-trafficking modules (NFATC4, CSF2RA, SYT1, PCLO). Phospho-kinase/NF-κB arrays confirmed a p53/NF-κB signaling nexus, with concurrent activation of MAPK/ERK (Thr202/Tyr204) and PI3K/Akt (Ser473) pathways. Despite persistent genotoxic stress, cells did not acquire anchorage-independent growth and remained non-tumorigenic in vivo. Critically, ALI organotypic cultures derived from BaP-exposed cells exhibited histological dysplasia, nuclear pleomorphism, and disrupted apical-basal polarity. These findings mechanistically link chronic BaP exposure to an initiation-like preneoplastic state and establish a validated 2D/3D multi-omics platform for PAH-driven lung carcinogenesis research. Full article

Concerns about radiation exposure following the Fukushima Nuclear Power Plant accident continue to grow, and health risks associated with medical radiation have also become an important issue. Therefore, identifying agents that can mitigate radiation-related health effects is necessary. We focused on the antioxidant 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (tempol) and investigated its radioprotective mechanisms. HeLa and TIG-3 cells were irradiated with X-rays, γ-rays, or heavy-ion beams. The effect of tempol on reactive oxygen species (ROS) production was evaluated using fluorescence-activated cell sorting (FACS) analysis. DNA double-strand break (DSB) formation was assessed by γ-H2AX immunofluorescence staining. In mice, γ-H2AX formation in the thymus and duodenum were evaluated after acute or chronic γ-ray exposure. Inflammatory responses were analyzed through macrophage infiltration and TNF mRNA expression, while apoptosis was measured using Annexin V staining. Tempol suppressed ROS production and γ-H2AX foci formation following irradiation. It also reduced γ-H2AX induction in mouse tissues. Activated macrophage infiltration and TNF expression in the duodenum tended to decrease in tempol-treated mice, whereas apoptotic levels showed no significant differences. Notably, tempol more effectively inhibited γ-H2AX formation during chronic irradiation than acute exposure. These findings suggest that tempol mitigates radiation-induced inflammation and reduces DNA damage, supporting its potential as a radioprotective agent. Full article

The aim of the study was to define radiobiological effects of single and fractionated low doses in normal fibroblasts in 40 patients with squamous cell carcinoma of the head and neck (HNSCC) treated with induction chemotherapy combined with low-dose fractionated radiation (LDFR) and to answer the question regarding the role of low-dose hyper-radiosensitivity (HRS) in these effects. HRS status was determined using flow cytometry-based clonogenic survival assay (cells were irradiated with doses 0.1–4 Gy of 6 MV X-rays). Radiobiological effects (cell kill, kinetics of DSB recognition and repair, chemopotentiation) of LDFR 4x0.5 Gy and a single dose of 2, 0.5 and 0.2 Gy were estimated by clonogenic, pATM and γH2AX foci assays. HRS response was demonstrated for normal fibroblasts in 6 of the 40 HNSCC patients. For all assessed biological parameters, significant interindividual differences were observed. The presence of HRS had no effect on the chemopotentiating effects of LDFR 4x0.5 Gy, which were similar to that after 2 Gy. There was also no association between HRS and the maximum number of pATM and γH2AX foci induced by single (0.2, 0.5, 2 Gy) or fractionated low doses 4x0.5 Gy. Significantly higher percentages of residual pATM and γH2AX foci observed after LDFR 4x0.5 Gy than after 2 Gy were independent of HRS. HRS is a rare finding (15%) in normal fibroblasts from HNSCC patients; therefore, it is of rather little importance in healthy late-reacting connective tissues. Moreover, the fibroblast response to single and fractionated low doses (alone or in combination with carboplatin and paclitaxel) appeared more dependent on individual radiosensitivity than on HRS. Full article

Background/Objectives: DNA polymerase ε (Pol ε), encoded by POLE1, plays a pivotal role in high-fidelity DNA replication and in coordinating DNA repair. While pathogenic exonuclease-domain variants are well established in cancer, biallelic POLE1 variants remain largely unexplored in non-malignant human cells. Methods: Here, we analyzed primary fibroblasts derived from a skin biopsy of a compound-heterozygous patient carrying two POLE1 variants. Western blot analysis confirmed detectable Pol ε protein levels, indicating preserved protein expression despite the underlying variants. Results: Nevertheless, functional alterations were observed across multiple independent assays. Compared with healthy control fibroblasts, this patient-derived Pol ε fibroblast line exhibited reduced clonogenic survival following ionizing radiation. Surviving fractions were consistently lower across radiation doses from 2 to 4 Gy, with an approximately twofold reduction at 2 Gy and progressively greater differences at higher doses. The isoeffect dose corresponding to 10% survival was reduced relative to pooled control fibroblasts. In addition, chromosomal breakage was increased, supporting altered processing of radiation-induced DNA damage in this cellular model. Live-cell imaging and senescence assays revealed delayed proliferation and an increased proportion of senescent or senescence-like cells under baseline and genotoxic stress conditions, including enhanced senescence-associated β-galactosidase activity. Flow-cytometric analysis demonstrated S phase accumulation and G2/M arrest, consistent with replication stress and cell-cycle perturbation. Immunofluorescence staining revealed increased γH2AX foci, consistent with persistent DNA double strand breaks. RAD51 foci formation was not reduced; instead, increased RAD51 recruitment was observed under combined cisplatin and irradiation treatment, arguing against a primary defect in RAD51-mediated homologous recombination. POLE1-variant fibroblasts also showed impaired proliferative recovery, reduced wound closure, increased γH2AX accumulation following cisplatin exposure, suggesting heightened susceptibility to DNA crosslinking stress. Conclusions: Collectively, these findings provide the first functional characterization of a patient-derived POLE1-variant fibroblast cell line and indicate that altered Pol ε function may influence cellular responses to genotoxic stress. While based on primary fibroblasts from a single compound-heterozygous patient, validation in additional patient-derived or isogenic models will be required to determine the broader relevance of these findings. Full article

Proton therapy offers superior dose localization, yet the biological effects of low-energy protons relevant to superficial tissues remain underexplored. We report the design and validation of a proton irradiation setup developed at the Tandem Accelerator of NCSR “Demokritos” for controlled radiobiological experiments. Monte Carlo simulations using Geant4 and Monte Carlo Damage Simulation (MCDS—Monte Carlo Damage Simulation) were used to determine proton energy spectra, linear energy transfer (LET), and predicted DNA damage yields. A single layer (15–20 μm in thickness) of human keratinocytes (HaCaT) was irradiated at doses from 0.65 to 3.65 Gy, and γ-H2AX foci were quantified as markers of tracks including one or more DNA double-strand breaks. The system achieved a uniform dose rate of 0.37 Gy/min, as calculated with Geant4, with a mean proton energy of 4.1 MeV (LET ≈ 8 keV/μm). A strong correlation (R² = 0.93) was observed between proton dose and γH2AX foci per nucleus (~10 foci/Gy), reflecting damage-inducing proton tracks rather than individual DNA double-strand breaks. At higher doses, an increased fraction of cells exhibited pan-nuclear γH2AX staining, characterized by a diffuse γH2AX signal throughout the nucleus and commonly associated with extensive or clustered DNA damage and global chromatin phosphorylation. These responses are consistent with the well-established dense ionization patterns produced by low-energy protons, as indicated by the LET spectrum and supported by MCDS-predicted clustered damage yields. While the γH2AX assay does not directly resolve simple versus complex DNA lesions, the agreement between Monte Carlo modeling and the observed cellular stress responses indicates that the irradiation platform reliably reproduces the expected biological signatures of low-energy proton exposure. Consequently, the developed system provides a robust experimental tool for systematic investigations of cellular radiosensitivity and radiotoxicity, with potential applications in skin dosimetry and radioprotection. Full article

Quantifying DNA repair capacity (DRC) is pivotal for stratifying patients in oncology and autoimmune disorders, yet methodological heterogeneity compromises data reproducibility. While basic research relies on genetically encoded reporters, translational settings demand robust assays compatible with biobanked material, particularly Peripheral Blood Mononuclear Cells (PBMCs). This review benchmarks functional DNA repair assays—ranging from alkaline/neutral comet variants and high-content foci imaging (γH2AX/53BP1) to emerging Next-generation sequencing (NGS)-based break mapping—against the rigors of clinical application. We critically evaluate sensitivity, specificity, and throughput, identifying artifacts introduced by cryopreservation, steroid therapy, and oxidative stress. Furthermore, we propose a “Minimum Reporting Standard” checklist to harmonize DRC quantification. By distinguishing established validation tools from experimental artifacts, this framework aligns assay selection with specific biological endpoints and clinical feasibility. Full article

The biological effects of radiofrequency electromagnetic fields (RF-EMFs) remain an unresolved scientific issue with important societal relevance, particularly in the context of the global deployment of fifth-generation (5G) wireless technologies. The skin is continuously exposed to both RF-EMFs and ultraviolet (UV) radiation, a well-established inducer of oxidative stress and DNA damage, making it a relevant model for assessing combined environmental exposures. In this study, we investigated whether post-exposure to 5G RF-EMFs (3.5 and 28 GHz) modulates ultraviolet A (UVA)-induced genotoxic stress in human keratinocytes (HaCaT) and murine melanoma (B16) cells. Post-UV RF-EMF exposure significantly reduced DNA damage markers, including phosphorylated histone H2AX (γH2AX) foci formation (by approximately 30–50%) and comet tail moments (by 60–80%), and suppressed intracellular reactive oxygen species (ROS) accumulation (by 56–93%). These effects were accompanied by selective attenuation of p38 mitogen-activated protein kinase (MAPK) phosphorylation (reduced by 55–85%). The magnitude of molecular protection was comparable to that observed with N-acetylcysteine treatment or pharmacological inhibition of p38 MAPK. In contrast, RF-EMF exposure did not reverse UV-induced reductions in cell viability or alterations in cell cycle distribution, indicating that its protective effects are confined to early molecular stress-response pathways rather than downstream survival outcomes. Together, these findings demonstrate that 5G RF-EMFs can facilitate recovery from UVA-induced molecular damage via redox-sensitive and p38-dependent mechanisms, providing mechanistic insight into the interaction between modern telecommunication frequencies and UV-induced skin stress. Full article

Background: In nuclear medicine, numerous cancer types are treated via internal irradiation with radiopharmaceuticals, including low-LET (linear energy transfer) beta-emitting radionuclides like Lu-177. In most cases, such treatments lead to low-dose exposure of organ systems with β-irradiation, which induces only few isolated DSBs (double-strand breaks) in the nuclei of hit cells, the most threatening DNA damage type. That damaging effect contrasts with the clustering of DNA damage and DSBs in nuclei traversed by high-LET particles (α particles, ions, etc.). Methods: After in-solution β-irradiation for 1 h with Lu-177 leading to an absorbed dose of about 100 mGy, we investigated the spatial nano-organization of chromatin at DSB damage sites, of repair proteins and of heterochromatin marks via single-molecule localization microscopy (SMLM) in PBMCs. For evaluation, mathematical approaches were used (Ripley distance frequency statistics, DBScan clustering, persistent homology and similarity measurements). Results: We analyzed, at the nanoscale, the distribution of the DNA damage response (DDR) proteins γH2AX, 53BP1, MRE11 and pATM in the chromatin regions surrounding a DSB. Furthermore, local changes in spatial H3K9me3 heterochromatin organization were analyzed relative to γH2AX distribution. SMLM measurements of the different fluorescent molecule tags revealed characteristic clustering of the DDR markers around one or two damage foci per PBMC cell nucleus. Ripley distance histograms suggested the concentration of MRE11 molecules inside γH2AX-clusters, while 53BP1 was present throughout the entire γH2AX clusters. Persistent homology comparisons for 53BP1, MRE11 and γH2AX by Jaccard index calculation revealed significant topological similarities for each of these markers. Since the heterochromatin organization of cell nuclei determines the identity of cell nuclei and correlates to genome activity, it also influences DNA repair. Therefore, the histone H3 tri methyl mark H3K9me3 was analyzed for its topology. In contrast to typical results obtained through photon irradiation, where γH2AX and H3K9me3 markers were well separated, the results obtained here also showed a close spatial proximity (“co-localization”) in many cases (minimum distance of markers = marker size), even with the strictest co-localization distance threshold (20 nm) for γH2AX and H3K9me3. The data support the results from the literature where only one DSB induced by low-dose low LET irradiation (<100 mGy) can remain without heterochromatin relaxation for subsequent repair. Full article

Thyroid hormones (THs) regulate metabolism, proliferation, and genomic stability. Clinical studies have linked levothyroxine therapy with higher Oncotype DX Recurrence Scores in breast cancer (BC), suggesting a potential effect of thyroid hormone signaling on genomic risk. Here, we investigated the impact of triiodothyronine (T3) on DNA damage and repair pathways in estrogen receptor-positive T47D breast cancer and non-tumorigenic MCF10A cells. RNA sequencing revealed significant upregulation of RAD51 and enrichment of DNA repair pathways following 24 h T3 exposure. Consistently, T3 increased γH2AX and 53BP1 nuclear foci, indicating transient activation of the DNA damage response (DDR). These effects were transient, returning to baseline after 48 h, suggesting cellular adaptation. T3 also enhanced proliferation at 10 μM but inhibited growth at higher concentrations. Our findings indicate that acute exposure to T3 induces transient genomic stress, providing a potential mechanistic basis for the observed association between thyroid hormone therapy and increased BC recurrence risk. Full article

Ionizing radiation remains the primary approach for treating brain cancer and is frequently used in combination with chemotherapy. However, when it comes to gliomas, the effective delivery of therapeutic agents is hindered by the limited permeability of the blood–brain barrier (BBB). Consequently, selecting the most suitable and least harmful type of ionizing radiation is essential, given its potential side effects on healthy cells within the tumor microenvironment. In this study, we explored the impact of X-ray exposure on two in vitro BBB endothelial cell models—murine and human. Post-irradiation, we evaluated cell viability, clonogenic capacity, cell cycle progression, reactive oxygen species (ROS) levels, formation of micronuclei and γ-H2AX foci, as well as alterations in cytoskeletal organization, cell migration, and intracellular calcium dynamics. The results demonstrate notable differences between the two endothelial cell lines, suggesting the human cell line is more sensitive to X-rays. In conclusion, our study provides valuable insights into the brain microvascular endothelial cells’ response to radiation, laying the groundwork for strategies to protect healthy brain tissue. Full article

Protons are conventionally regarded as a low-linear energy transfer (low-LET) radiation modality with a relative biological effectiveness (RBE) of 1.1, suggesting direct mechanistic similarity to X-rays in the underpinning biological effects. However, exposure to spread-out Bragg peak (SOBP) protons reveals instructive deviations from this assumption. Indeed, proton beams have a maximum LET of ~5 keV/µm but display reduced reliance on classical non-homologous end joining (c-NHEJ) as well as an increased dependence on homologous recombination (HR) and alternative end joining (alt-EJ). These features are well described in cells exposed to high-LET radiation and typically manifest between 100 and 150 keV/µm. We hypothesized that this apparent discrepancy reflects biological consequences of proton-beam properties that remain uncharacterized. In the present study, we outline exploratory experiments aiming at uncovering such mechanisms. We begin by investigating for both entrance and SOBP protons the dose-dependent engagement of HR we recently showed for X-rays. Consistent with our previous findings with X-rays, HR engagement after exposure to both types of proton beams declined with dose, from ~80% at 0.2 Gy to less than 20% at higher doses. RAD51/γH2AX foci ratios, reflecting HR engagement, were modestly higher following proton irradiation, in line with increased HR utilization. G₂-checkpoint activation, previously linked to HR, was also stronger after exposure to protons, as was DNA end resection. Moreover, the formation of structural chromosomal abnormalities (SCAs) was higher for SOBP than entrance protons and X-rays. Collectively, our results suggest quasi-high-LET characteristics for proton beams and raise the question as to the physical proton properties that underpin them. We discuss that the commonly employed definition of LET may be insufficient for this purpose. Full article

The SNF2-related chromatin remodeler Srcap is the principal ATPase responsible for the deposition of the histone variant H2A.Z at promoters and regulatory chromatin regions. Although this activity is known to modulate transcription, its contribution to DNA replication remains unexplored. Here we show that Srcap is required for efficient replication fork progression and origin firing in mammalian cells. Using RNA interference in human PC3 cells, we found that Srcap depletion leads to a ~25% reduction in fork elongation rate, decreased replication fork density, accumulation of the replication-stress marker γH2AX, and reduced chromatin-bound H2A.Z. High-resolution expansion microscopy further revealed diminished intensity and increased spacing of replication foci, consistent with reduced origin activation. Transcriptomic analysis of published data identified broad downregulation of replication-associated genes. These data uncover a dual mechanism by which Srcap sustains replication efficiency—through both H2A.Z-dependent chromatin organization and transcriptional maintenance of the replication machinery. Our findings establish Srcap as an important coordinator of replication dynamics, with implications for genome stability. Full article

High-grade serous ovarian cancer (HGSOC) is the most commonly diagnosed ovarian cancer subtype. Approximately half of all patients diagnosed with HGSOC are deficient in homologous recombination (HR), harbor BRCA1/2 mutations, and are treated with poly (ADP-ribose) polymerase (PARP) inhibitors (PARPis). FDA-approved PARPis Olaparib, Niraparib, and Rucaparib all contribute to adverse effects in patients due to their poly-pharmacological properties. This feature necessitates investigation of global protein responses to PARPi treatment beyond DNA repair in the context of BRCA mutational status and HR deficiency. We sought to determine the landscape of differential PARPi-induced proteomes in HGSOC cells exhibiting different BRCA1/2 mutational statuses. Here, we applied immunofluorescence microscopy to detect γH2AX, Rad51, and geminin foci as markers of DNA damage and repair upon treatment of HGSOC cells with IC₅₀ doses of PARPis. Global proteome perturbations upon PARPi treatment were measured using quantitative mass spectrometry-based proteomics. The proteomic data highlighted cell line effects, masking high-dose PARPi treatment response. Interrogation of PARPi response within biological pathways identified through gene set enrichment analysis (GSEA) revealed significant changes to proteins involved in Epithelial–Mesenchymal Transition (EMT), E2F targets, and cholesterol homeostasis. Our study establishes proteomic evidence supporting the poly-pharmacological characteristics of Niraparib, Olaparib, and Rucaparib in HGSOC cells. Full article