Ionizing radiation (IR) as a stress inducer has a significant impact on various normal stem cells differentiation through activation of various signaling pathways. Low levels of oxidative stress of IR may preserve or even enhance cell differentiation. In response to IR, reactive oxygen species (ROS) can activate various signaling pathways that promote cell differentiation, notably through the involvement of nuclear factor erythroid 2–related factor 2 (NRF2). NRF2 interacts with multiple pathways, including Wnt/β-catenin (osteogenesis), PPARγ (adipogenesis), and BDNF/TrkB (neurogenesis). This response is dose-dependent: low doses of IR activate NRF2 and support differentiation, while high doses can overwhelm the antioxidant system, resulting in cell death. However, the quality of various types of IR, such as proton and carbon ion radiation, may have a varied impact on stem cells (SCs) differentiation compared to X-rays. Hence, activation of the NRF2 signaling pathway in SCs and cell differentiation depends on the level of stress and the quality and quantity of IR. This review is an update to explore how IR modulates SCs fate toward osteogenic, adipogenic, and neurogenic lineages through the NRF2 signaling pathway. We highlight mechanistic insights, dose-dependent effects, and therapeutic implications, bridging gaps between experimental models and clinical translation.

Nuclear factor erythroid 2-related factor 2 (NRF2) is a key transcription factor that controls the antioxidant response to oxidative stress, especially after exposure to ionizing radiation (IR). This review examines NRF2’s emerging role as a complementary biomarker in radiobiological dosimetry for assessing radiation exposure and its potential health effects. When cells encounter IR, the resulting reactive oxygen species (ROS) interfere with the NRF2 repressor KEAP1, leading to NRF2 activation and the expression of cytoprotective genes such as HO-1, NQO1, and GCLC. Evidence suggests that NRF2 levels increase in a dose- and time-dependent manner, primarily at low to moderate radiation doses, highlighting its potential for early detection of radiation exposure. However, at high doses (>8 Gy), NRF2 activation may be suppressed due to apoptosis or irreversible damage, which limits its reliability in those situations. The review also compares NRF2 with other biomarkers used in biodosimetry, discussing its advantages, such as sensitivity and early response, along with its limitations, including variability in activation at high doses and expression influenced by other oxidative factors. The authors introduce a comprehensive radiobiological model that illustrates how low-dose IR exposure affects NRF2 expression patterns, thereby improving the understanding of dose-dependent oxidative stress mechanisms. Additionally, the role of NRF2 in inflammation and general health risk assessment is emphasized, suggesting broader applications beyond biodosimetry. Overall, NRF2 holds significant promise for use in evaluating radiation exposure, developing radioprotection strategies, and informing future radiobiological research frameworks.

The ozone layer in the Earth’s atmosphere filters solar radiation and limits the unwanted effects on humans. A depletion of this ozone shield would permit hazardous levels of UV solar radiation, especially in the UVB range, to bombard Earth’s surface, resulting in potentially significant effects on human health. The concern for these adverse effects intensifies if we consider that the UVB solar radiation is combined with secondary cosmic radiation (SCR) components, such as protons and muons, as well as terrestrial gamma rays. This research aims to delve into the intricate interplay between cosmic and solar radiation on earth at the cellular level, focusing on their synergistic effects on human cell biology. Through a multidisciplinary approach integrating radiobiology and physics, we aim to explore key aspects of biological responses, including cell viability, DNA damage, stress gene expression, and finally, genomic instability. To assess the impact of the combined exposure, normal i.e., non-malignant human cells (skin fibroblasts, keratinocytes, monocytes, and lymphocytes) were exposed to high-energy protons or gamma rays in combination with UVB. Cellular molecular and cytogenetic biomarkers of radiation exposure, such as DNA damage (γH2AΧ histone protein and dicentric chromosomes), as well as the expression pattern of various stress genes, were analyzed. In parallel, the MTS reduction and lactate dehydrogenase assays were used as indicators of cell viability, proliferation, and cytotoxicity. Results reveal remaining DNA damage for the co-exposed samples compared to samples exposed to only one type of radiation in all types of cells, accompanied by increased genomic instability and distinct stress gene expression patterns detected at 24–48 h post-exposure. Understanding the impact of combined radiation exposures is crucial for assessing the health risks posed to humans if the ozone layer is partially depleted, with structural and functional damages inflicted by combined cosmic and UVB exposure.

Highlights:

Empirical evidence about late outcomes of contemporary radiotherapy in paediatrics is needed.

HARMONIC-RT registers patients under 22 years of age treated since 2000 with first external beam radiotherapy in the participating European centres.

HARMONIC-RT is conducting sub-studies and collecting biological samples for detailed investigation of endocrine disorders, neuro- and cardio-vascular damages, second primary cancers and quality of life.

Radiotherapy (RT), a common cancer treatment, unintentionally harms surrounding tissues, including the skin, and hinders wound healing years after treatment. This study aims to understand the mechanisms behind these late-onset adverse effects. We compare skin biopsies from previously irradiated (RT+) and non-irradiated (RT−) sites in breast cancer survivors who underwent RT years ago. Here we show that the RT+ skin has compromised healing capacity and fibroblast functions. Using ATAC-seq, we discover altered chromatin landscapes in RT+ fibroblasts, with THBS1 identified as a crucial epigenetically primed wound repair-related gene. This is further confirmed by single-cell RNA-sequencing and spatial transcriptomic analysis of human wounds. Notably, fibroblasts in both murine and human post-radiation wound models show heightened and sustained THBS1 expression, impairing fibroblast motility and contractility. Treatment with anti-THBS1 antibodies promotes ex vivo wound closure in RT+ skin from breast cancer survivors. Our findings suggest that fibroblasts retain a long-term radiation memory in the form of epigenetic changes. Targeting this maladaptive epigenetic memory could mitigate RT’s late-onset adverse effects, improving the quality of life for cancer survivors.

Some cancers have a poor prognosis and often lead to local recurrence because they are resistant to available treatments, e.g., glioblastoma. Attempts have been made to increase the sensitivity of resistant tumors by targeting pathways involved in the resistance and combining it, for example, with radiotherapy (RT). We have previously reported that treating glioblastoma stem cells with an Nrf2 inhibitor increases their radiosensitivity. Unfortunately, the application of drugs can also affect normal cells. In the present study, we aim to investigate the role of the Nrf2 pathway in the survival and differentiation of normal human adipose-derived stem cells (ADSCs) exposed to radiation. We treated ADSCs with an Nrf2 inhibitor and then exposed them to X-rays, protons or carbon ions. All three radiation qualities are used to treat cancer. The survival and differentiation abilities of the surviving ADSCs were studied. We found that the enhancing effect of Nrf2 inhibition on cell survival levels was radiation-quality-dependent (X-rays > proton > carbon ions). Furthermore, our results indicate that Nrf2 inhibition reduces stem cell differentiation by 35% and 28% for adipogenesis and osteogenesis, respectively, using all applied radiation qualities. Interestingly, the results show that the cells that survive proton and carbon ion irradiations have an increased ability, compared with X-rays, to differentiate into osteogenesis and adipogenesis lineages. Therefore, we can conclude that the use of carbon ions or protons can affect the stemness of irradiated ADSCs at lower levels than X-rays and is thus more beneficial for long-time cancer survivors, such as pediatric patients.

The Health Effects of Cardiac Fluoroscopy and Modern Radiotherapy (photon and proton) in Pediatrics (HARMONIC) is a five-year project funded by the European Commission that aimed to improve the understanding of the long-term ionizing radiation (IR) risks for pediatric patients. In this paper, we provide a detailed overview of the rationale, design, and methods for the biological aspect of the project with objectives to provide a mechanistic understanding of the molecular pathways involved in the IR response and to identify potential predictive biomarkers of individual response involved in long-term health risks. Biological samples will be collected at three time points: before the first exposure, at the end of the exposure, and one year after the exposure. The average whole-body dose, the dose to the target organ, and the dose to some important out-of-field organs will be estimated. State-of-the-art analytical methods will be used to assess the levels of a set of known biomarkers and also explore high-resolution approaches of proteomics and miRNA transcriptomes to provide an integrated assessment. By using bioinformatics and systems biology, biological pathways and novel pathways involved in the response to IR exposure will be deciphered.

The use of ionising radiation (IR) for medical diagnosis and treatment procedures has had a major impact on the survival of paediatric patients. Although the benefits of these techniques lead to efficient health care, evaluation of potential associated long-term health effects is required. HARMONIC aims to better understand the increased risk of cancer and non-cancer effects after exposure to medical IR in children with cancer treated with modern external beam radiotherapy (EBRT) – radiation energy in MeV range – and in children with cardiac defects diagnosed and treated with cardiac fluoroscopy procedures (CFP) – radiation energy in keV range. The project investigates, among survivors of paediatric cancer, potential endocrine dysfunction, cardiovascular and neurovascular damage, health-related quality of life and second (and subsequent) primary cancer (SPC). The cardiac component builds a pooled cohort of approximately 90 000 paediatric patients who underwent CFP during childhood and adolescence to investigate cancer risk following exposure to IR and explore the potential effects of conditions predisposing to cancer. HARMONIC develops software tools to allow dose reconstruction in both EBRT and CFP to enable epidemiological investigations and future optimisation of treatments. With the creation of a biobank of blood and saliva samples, HARMONIC aims to provide a mechanistic understanding of radiation-induced adverse health effects and identify potential biomarkers that can predict these effects.

Background: Exposure to low dose rate (LDR) radiation may accelerate aging processes. Previously, we identified numerous LDR-induced pathways involved in oxidative stress (OS) and antioxidant systems, suggesting that these pathways protect against premature senescence (PS). This study aimed to investigate if there are differences between young replicative senescent (RS) and PS cells considering DNA repair kinetics, OS, and DNA damage localized in the telomeres. Methods: We established PS cells by culturing and passaging young primary fibroblasts exposed to LDR. Then, RS cells were established by culturing and passaging young fibroblasts until they stopped proliferating. Senescence was characterized by analyzing telomere length and senescence-associated β-galactosidase (SA-β-gal) staining. DNA damage and repair were evaluated with γH2AX foci formation; telomere identification was carried out using the fluorescence in situ hybridization (FISH) probe; and oxidative stress was assessed by measuring 8-oxo-dG in the medium. Results: The data indicate the following: young cells have a better ability to cope with LDR-induced oxidative stress; RS and PS have higher steady-state levels of DNA damage; RS have slower DNA repair kinetics; and PS/RS have elevated levels of telomeric DNA damage. Conclusion: Our main conclusion is that PS and RS differ regarding DNA repair kinetics and SA-β-gal levels.

The coordinating role of nuclear factor erythroid-2-related factor 2 (Nrf2) in cellular function is undeniable. Evidence indicates that this transcription factor exerts massive regulatory functions in multiple signaling pathways concerning redox homeostasis and xenobiotics, macromolecules, and iron metabolism. Being the master regulator of antioxidant system, Nrf2 controls cellular fate, influencing cell proliferation, differentiation, apoptosis, resistance to therapy, and senescence processes, as well as infection disease success. Because Nrf2 is the key coordinator of cell defence mechanisms, dysregulation of its signaling has been associated with carcinogenic phenomena and infectious and age-related diseases. Deregulation of this cytoprotective system may also interfere with immune response. Oxidative burst, one of the main microbicidal mechanisms, could be impaired during the initial phagocytosis of pathogens, which could lead to the successful establishment of infection and promote susceptibility to infectious diseases. There is still a knowledge gap to fill regarding the molecular mechanisms by which Nrf2 orchestrates such complex networks involving multiple pathways. This review describes the role of Nrf2 in non-pathogenic and pathogenic cells.