Purpose This pilot study investigated promoter DNA methylation in key DNA damage response (DDR) genes in individuals chronically exposed to low-dose ionizing radiation (LDIR) in Kerala, India. Materials and methods 26 healthy male residents of Kerala’s high level natural radiation areas (HLNRA) were selected and stratified based on lifetime cumulative radiation dose (<100 mSv, n = 10; >100 mSv, n = 16). Promoter methylation of 16 DDR-related genes was assessed using Methylation Sensitive High resolution Melting (MS-HRM), with LINE-1 as a surrogate for global methylation. Gene expression of selected targets was measured by RT-qPCR. Results Global DNA methylation showed no significant difference across exposure groups. In contrast, promoters of RAD23B, DNMT3A, MRE11A, and BRCA1 were significantly hypermethylated in individuals with cumulative dose >100 mSv, with RAD23B showing the strongest correlation. Gene expression displayed high inter-individual variation with no dose-dependent changes or correlation with promoter methylation. Conclusions Chronic LDIR exposure induces significant hypermethylation in specific DDR genes like RAD23B, DNMT3A, MRE11A, and BRCA1, suggesting a possible selective modulation of DNA repair pathways. but direct functional impact on gene expression was not observed in this study. The observed promoter methylation and gene expression alterations provide preliminary evidence of epigenetic modifications in response to chronic LDIR.

Purpose Artificial Intelligence (AI) and Machine Learning (ML) are being explored to improve systematic evidence gathering and to identify patterns across datasets. Their integration into the development of radiation Adverse Outcome Pathways (AOPs) offers an opportunity to accelerate data consolidation in radiation protection. AOPs provide a structured, transparent framework that links molecular-level perturbations to adverse outcomes relevant to risk assessment. Despite their value, AOP development is hindered by manual evidence mapping, the complexity of multi-level biological responses, and fragmented data across platforms, experimental models, and epidemiological studies. Herein, we explore the role of AI/ML in overcoming these challenges by enabling extraction, annotation, and integration of heterogeneous data sources. AI assist in identifying Key Events (KEs), inferring Key Event Relationships (KERs), and suggesting putative AOP structures by mining scientific literature and experimental datasets. We propose an AI-driven AOP development plan that includes: (1) establishing curated, open-access training datasets annotated with AOP-relevant biological and exposure entities; (2) applying domain-specific natural language processing techniques to extract mechanistic insights from unstructured literature; (3) deploying supervised and unsupervised ML methods to identify and prioritize KEs; (4) constructing transparent causal models using knowledge graphs and probabilistic inference to capture mechanistic directionality; (5) enabling automated narrative generation and evidence scoring; and (6) integrating iterative expert feedback and new data for continuous model refinement. This phased approach bridges data readiness, computational modeling, and domain expertise to advance the integration of AI/ML into AOP development. Challenges such as model interpretability, data sparsity for low-dose radiation effects, ethical considerations, hallucination in large language models and validation of AI-inferred pathways are discussed. Conclusions While fully AI-assisted radiation AOPs remain conceptual, the review provides a methodological foundation for their future development. AI/ML offers a means to accelerate radiation AOP development, facilitating systematic organization, integration, and prioritization of biological and experimental data.

Purpose: Ecological observations in the Chernobyl Exclusion Zone (CEZ) show that populations of large mammals, such as wolves, boars, and elks, have recovered and remain stable despite chronic exposure to radiation. This study applies the Whack-A-Mole (WAM) model—a dynamic, dose-rate-dependent mathematical model—to the CEZ environment to explain the observed ecological stability under persistent low-dose-rate exposure that conventional Linear Non-Threshold (LNT) models fail to predict. Materials and Methods: The WAM model explicitly incorporates removal processes of radiation-induced mutated cells, allowing evaluation of mutation frequency at steady state under chronic exposure. Using standardized parameters calibrated across species and reported dose rates from wolf tracking studies (external 10–35 mGy/y; internal + external up to 87 mGy/y), we calculated the time evolution and equilibrium values of mutation frequency in mammalian cells. Results: The equilibrium value of the mutation frequency increased as the radiation dose increased. This increase, however, remained below 1% of the natural baseline even under the upper-end CEZ exposure (87 mGy/y). At mean (18.4 mGy/y) and maximum (35.9 mGy/y) external dose rates, increases were only +0.18% and +0.35%, respectively. The boundary between LNT-like linear behavior and WAM saturation occurred around 330 hours regardless of dose rate. In contrast, the LNT model predicts mutation accumulation at levels incompatible with the continued growth of wolf populations, contradicting ecological observations in the CEZ. Conclusions: The WAM model characterizes the dynamics of mutation frequency under chronic exposure and provides a mechanistic interpretation compatible with the absence of population-level health effects observed in the CEZ. Observed molecular responses, including endogenous retrovirus (ERV) activation and immune alterations, represent functioning repair and removal mechanisms rather than pathological damage.

Purpose Radiation-induced meningiomas (RIMs) are an uncommon late complication of cranial irradiation that frequently display aggressive behavior. Although recent genomic and epigenomic studies have redefined sporadic meningiomas into four molecular groups with distinct biological and clinical characteristics, the same analysis has not yet been conducted on RIMs. This study sought to contextualize RIMs within the current methylation-based meningioma classification. Methods DNA methylation data from RIMs (n = 20) were integrated with a reference cohort of sporadic (n = 121) meningiomas previously used to define molecular subgroups. Molecular group membership was assigned using a supervised machine-learning approach. Copy-number alterations and pathway enrichment analyses were derived from methylation data, and clinical features were compared between RIMs and sporadic meningiomas. Results Supervised molecular classification assigned 70% RIMs to the hypermetabolic subtype. The RIM cohort demonstrated broad DNA hypomethylation enriched for metabolic and biosynthetic pathways. Copy-number profiling revealed widespread chromosomal instability, including recurrent 22q loss involving NF2 and SMARCB1 as well as PTEN, MYB, and C19MC, consistent with the copy number alterations observed in hypermetabolic meningiomas. Conclusions RIMs predominantly align with the hypermetabolic molecular group, characterized by metabolic pathway activation and genomic instability. This distribution indicates a distinct molecular profile compared with sporadic meningiomas.

Purpose Radiation-induced skin injury is a common complication that seriously affects the follow-up treatment and life quality of tumor patients. Nocardia rubra cell‐wall skeleton (N-CWS) has been reported to have pro-angiogenesis effects, and its role on RISI remains unclear. The aim of this study was to investigate its effect on repair of radiation induced skin injury. Materials and Methods After exposure to 45 Gy X-rays, the irradiated areas of SD rats were treated by N-CWS every 3 days. The radioprotective effects of N-CWS were evaluated by body weight changes, skin scores, H&E staining and TUNEL staining. Microvascular monitoring system and immunofluorescence staining of CD31 were performed to assess angiogenic capacity in vivo. In vitro, the activity and apoptosis of HUVECs were measured by CCK8 and flow cytometry. The angiogenic capacity of HUVECs was evaluated by tubule formation assay and Transwell assay. Western blot was performed to verify the possible mechanisms of the protective effect of N-CWS against radiation-induced skin damage. Results N-CWS was demonstrated to have low toxicity and radioprotective effects, maintained cell activity and attenuated radiation-induced apoptosis. In addition, N-CWS attenuated radiation-induced vascular injury in vivo and in vitro. Furthermore, P38 MAPK was shown to be associated with the radiation protection capability of N-CWS in HUVECs. Conclusions N-CWS promoted the repair of radiation-induced skin injury by enhancing angiogenesis, and the mechanism was related to the activation of P38 MAPK.

Purpose The transgenerational effects of preconception parental radiation exposure in humans remain unclear. We assessed genomic integrity in adult children of British nuclear test (NT) veterans—a community that has expressed long-standing concerns about adverse health effects, including in their offspring—to investigate for any constitutional chromosomal abnormalities and/or cytogenetic indicators of genomic instability that might be associated with paternal participation at NT sites. Materials and Methods Peripheral blood samples were obtained from 86 adult children (45 from nuclear test (NT) and 41 control), all born to veterans from the British Army, Royal Air Force, or Royal Navy. Results G-banded karyotyping revealed no constitutional chromosomal abnormalities in any NT sample, including those from families reporting adverse health outcomes. We next assessed for unstable aberrations using conventional Giemsa staining and found some evidence of instability. Specifically, a small subset of NT children (N = 4) showed elevated chromatid aberration frequencies (7.81 ± 4.01 per 100 cells) compared with controls (4.36 ± 0.62; N = 26). To investigate further, we analyzed matched veteran father–child pairs observing a weak association between fathers’ unstable aberration burden and chromatid aberrations in their children, suggesting a potential transgenerational effect. This positive trend was most pronounced in the small group of families (N = 8; 2 control and 6 NT) previously identified as being enriched for mutation signature SBS16 in the germline. Conclusions Although based on a small sample size, this observation warrants further investigation to understand the significance of SBS16, if any, including whether it may serve as a potential transgenerational mutational signature of radiation exposure. Overall, and in the context of health concerns raised by NT families, none of the self-reported health-related variables showed any association with unstable aberration burden in either the veteran fathers or their adult children.

Introduction The vertebrate retina is a laminated tissue with a relatively simple structure compared with the brain, and its accessibility makes it an excellent model for studying damage and repair in the central nervous system. This study investigated the regenerative process of the photoreceptor layer in medaka (Oryzias latipes) larvae following embryonic exposure to sub-lethal gamma irradiation and examined whether transient damage influences visual function using the optomotor response (OMR) assay. Methods Medaka embryos at 3 days post fertilization (dpf) were irradiated with 7–10 Gy to determine the lethal threshold, from which 8 Gy was determined to be a sub-lethal dose. In 8 Gy–irradiated embryos, eye size was assessed by stereomicroscopy and photoreceptor regeneration was histologically evaluated by Zpr1 immunohistochemistry at 8, 14, and 21 dpf. Visual function was evaluated by optomotor response under standard and reduced-contrast conditions. Results Irradiation at 10 Gy induced severe cone loss, resulting in mortality from 15 dpf. In contrast, larvae exposed to 8 Gy showed no significant alterations in central or dorsal cones compared with controls, whereas ventral cones were significantly shorter and fewer in number. These abnormalities, as well as eye size, gradually recovered to control levels by 21 dpf. Although transient reductions in eye size and ventral cones were observed, OMR testing revealed no impairment of visual performance at 8, 14, or 21 dpf, even under stringent low-contrast conditions. Discussion Sub-lethal gamma irradiation transiently induced localized damage especially in the ventral retina and reduction in eye size, both of which were fully repaired within 21 dpf. Behavioral analysis demonstrated that such transient, repairable damage does not impair visual function in irradiated medaka larvae.

Purpose Chironomus ramosus, an Indian tropical midge, exhibits remarkable tolerance to radiation and desiccation stress, making it an ideal model for studying cellular adaptive responses. The salivary gland (SG) cells of fourth instar larvae, known for their high metabolic activity, serve as a valuable system for investigating molecular mechanisms underlying stress response. This study aimed to investigate the significance of tropomyosin and actin in cellular recovery post gamma radiation exposure from salivary gland cells of Chironomus ramosus larvae in mediating the radiation-induced stress response. Materials and methods The SG cells were isolated from control and gamma-irradiated fourth instar larvae and subjected to metabolic labeling ([35S] methionine) to assess protein synthesis dynamics. Western blotting and immunofluorescence staining confirmed the radiation-induced expression of tropomyosin and actin following 2200 Gy gamma radiation exposure. Semi-quantitative RT-PCR was employed to confirm transcriptional upregulation of the target genes. Results Gamma radiation exposure triggered two to three-fold elevation in tropomyosin and actin protein levels in SG cells of Chironomus ramosus, with sustained upregulated expression through 24–48 h of post-irradiation recovery. The corresponding mRNA expression profiles paralleled these protein-level changes, reinforcing the notion of radiation-induced transcriptional regulation of cytoskeletal proteins in SG cells of C. ramosus. Conclusion This study provides compelling evidence that tropomyosin and actin stress fibers are overexpressed in C. ramosus larvae following gamma radiation exposure, suggesting a crucial role for cytoskeletal remodeling in radiation-induced adaptive responses.

Purpose This review summarizes the discoveries of 8-bromopurine nucleosides (8-Br-Pu), particularly 8-bromo-2′-deoxyadenosine (8-Br-dA) and 8-bromo-2′-deoxyguanosine (8-Br-dG), in chemistry and biology over the past two decades. It compiles available data on the reactions of hydrated electrons (eaq –) with various 8-bromopurines, as determined by pulse radiolysis and supported by theoretical studies. Three distinct mechanistic pathways are identified: dissociative electron attachment, sequential electron transfer-proton transfer, and concerted electron-proton transfer. This review also highlights the use of 8-Br-dA and 8-Br-dG in the synthesis of a library of 5′,8-cyclopurine nucleosides (cPu) for quantifying them in genetic material and incorporating them into oligonucleotides (ODNs) for DNA repair research. Additionally, the summary covers the use of 8-Br-dA and 8-Br-dG embedded in various ODNs to study excess electron transfer (EET), their potential as radiosensitizers, and their formation in vivo via hypobromous acid. Conclusion Based on radiation chemistry, our understanding of the one-electron reduction of 8-Br-dA and 8-Br-dG has been enhanced substantially. This mechanistic background is crucial for a better understanding of and addressing their significant roles in the biological environment, such as DNA radiosensitizers for cancer radiation therapy or as biomarkers for early inflammation.

Purpose Understanding the energy-dependent variation in relative biological effectiveness (RBE) is crucial for both neutron radioprotection and therapeutic applications. This study aims to evaluate the biological impact of neutron irradiation on A375 human melanoma cells using neutron beams of different energy ranges, with the goal of contributing to the optimization of radioprotection standards and the advancement of neutron-based cancer therapies, such as Boron Neutron Capture Therapy (BNCT). Material and methods A375 human melanoma cells were irradiated using two distinct neutron beams: one in the keV range at the CNA facility in Sevilla, and another in the MeV range at the CIEMAT facility in Madrid. Clonogenic assays were performed to evaluate cellular response and determine RBE values. The biological effects were assessed and compared with previously obtained data from thermal-equivalent neutron energies and reference photon irradiation. Results The MeV-range neutron beam induced slightly stronger biological effects than the keV-range beam, but the observed RBE difference was notably smaller than the ∼50% gap predicted by ICRP models. Instead, the experimental trend closely aligned with previous theoretical RBE estimations based on secondary particle contributions. These results underscore the need to reevaluate current radioprotection weighting factors and support the refinement of neutron-based therapeutic protocols.