Radiation-induced oxidative stress is one of the central mechanisms pertaining to the biological effects of ionizing radiation, affecting living systems across different levels of an organism. The cascade of events begins with the radiolysis of water and generation of reactive oxygen and nitrogen species (ROS/RNS), radiation exposure cascades into widespread oxidative damage in DNA, proteins, and lipids, with notable consequences for genomic stability and cell fate. This review synthesises the insights from omics, primarily highlighting the roles of DNA repair pathways, chromatin remodeling, RNA processing, and metabolic rewiring in mediating cellular adaptation, injury, or death. An important dimension of radiation research is the evolutionary adaptation of organisms to chronic or naturally higher radiation environments and its probable implications for biomarker discovery. Insights from space-exploration setups, as well as high natural background radiation zones, may enable ascertain conserved adaptive signatures and candidate biomarkers of radiation induced oxidative stress. Integrating these data with multi-omics approaches could facilitate the translation of radiation-responsive molecular signatures into robust biomarkers. Regardless of major advances, persistent challenges remain in modelling of chronic injury, translating of large-scale omics into clinics, and protecting non-target tissues. Key focus areas are that of mechanisms of mutation and epigenetic change, systems biology integration of multi-omics stress responses, identification of cross-species conserved biomarkers, and the clinical relevance of omics-based biodosimetry and therapeutic prediction. Continued interdisciplinary research combining advanced molecular profiling, systems analysis, and translational radiobiology will be essential for reducing radiation risks and harnessing potential uses of ionizing radiation.

The transcription factor TWIST1 plays a fundamental role in the regulation of breast cancer initiation, progression, metastasis, and resistance to treatment. As a prominent driver of epithelial-mesenchymal transition (EMT), TWIST1 promotes phenotypic plasticity in cancer cells, enabling enhanced invasion, migration, and metastatic colonization. In addition, TWIST1 supports the maintenance of cancer stem cell (CSC) traits, which contribute to intratumoral heterogeneity and the likelihood of tumor relapse. Abnormal activation of TWIST1 stimulates stemness-related programs through the regulation of essential signaling pathways and stem cell markers, thereby functionally linking EMT with mechanisms of self-renewal and therapeutic resistance. The regulation of TWIST1 is highly complex and occurs at multiple levels, including epigenetic control, non-coding RNA-mediated regulation, transcriptional modulation, and post-translational modifications. Interactions with major oncogenic signaling cascades and signals originating from the tumor microenvironment further enhance its contribution to cancer progression. Increasing clinical evidence indicates that elevated TWIST1 expression is associated with poor clinical outcomes, higher metastatic burden, and reduced treatment efficacy, emphasizing its importance as a prognostic biomarker and a potential therapeutic target in breast cancer management.

This review provides an accessible and mechanistically focused overview of the structural basis of human Y-family DNA polymerases and their roles in translesion synthesis (TLS) across diverse DNA lesions. The review highlights the unique structural features of these polymerases, including Polη, Polɩ, Polκ, and Rev1, and their specific mechanisms for navigating past DNA lesions including UV-induced CPDs, platinum drug-induced DNA damage, and alkylated DNA damage. Furthermore, structural insight are discussed to understand the structural mechanisms and fidelity differences among Y-family DNA polymerases during various lesion bypasses. Summarized findings on structural insight of bypass of various DNA lesions by Y-family polymerases represent TLS mediated mechanistic view of maintaining genomic stability and cancer cell survival, particularly under conditions of replication stress and DNA damage.

Ionizing radiation (IR) generates chemically heterogeneous DNA damage whose spatial organization depends on radiation quality, including linear energy transfer (LET), the amount of energy deposited per unit path length. Among these lesions, non-double-strand-break (non-DSB) clusters comprise combinations of oxidized bases, abasic (AP) sites, and strand-break intermediates that do not initially constitute a double-strand break (DSB). Their biological effects depend on lesion identity, spacing, strand orientation, and the repair-state transitions that occur during base excision repair (BER). Prompt DSBs remain major determinants of immediate chromosome disruption and acute cytotoxicity, whereas non-DSB clusters represent a distinct processing-dependent hazard through lesion persistence, replication encounter, mutagenesis, and BER-mediated formation of repair-generated DSBs. This review integrates radiation chemistry, lesion-specific BER, defined-substrate studies, irradiation-based measurements, mutational outcomes, and track-structure modeling across the causal sequence from lesion formation to mutation. A structured, non-exhaustive evidence map showed that direct pairwise evidence occupied only 12.1-19.1% of lesion-pair categories across five inclusion scenarios; in the full 18-lesion ontology, 30 of 171 categories had direct pairwise support. These values describe coverage within the review-specific classification and search record, not biological lesion-pair frequencies. Defined-substrate studies provide configuration-specific mechanistic evidence, whereas irradiation-based assays retain biological context but generally lack complete lesion and repair-history resolution, and genome-wide sequencing records survival-conditioned mutational outcomes without identifying the initiating cluster. Together, the available evidence defines which lesion attributes, BER intermediates, contextual modifiers, and validation endpoints can currently constrain lesion-resolved state-transition models and where inference and uncertainty remain unavoidable. It also delineates the present limits of attributing cancer or other tissue-level health effects to specific non-DSB clustered configurations.

Impairments in folate metabolism have long been suspected to contribute to chromosome 21 aneuploidy and Down syndrome (DS). Indeed, several studies have investigated the role of a functional polymorphism in the reduced folate carrier gene, known as either SLC19A1 or RFC-1 A80G polymorphism (rs1051266), as a maternal risk factor for having a child with DS. We searched for available case-control studies investigating this association and included 16 independent studies, for a total of 1958 DS mothers and 2750 control mothers. We performed random-effects meta-analyses to summarize the results on the association between the presence of this polymorphism and the risk of giving birth to a DS child, and reported odds ratios (ORs) with 95% confidence intervals (CIs) as measures of association. We also performed a trial sequential analysis (TSA) to clarify the robustness of the meta-analyses. Under the recessive model (GG vs AA+AG), the association was significant (OR=1.29, 95% CI: 1.03-1.61), also when including only studies with Hardy-Weinberg equilibrium (HWE) in control mothers (OR=1.38, 95% CI: 1.09-1.75). Additionally, significant associations emerged from allelic contrast (G vs A; OR=1.21, 95% CI: 1.02-1.43) and homozygote comparison (GG vs AA; OR=1.47, 95% CI: 1.04-2.07) when considering only the studies in which controls were in HWE. Results from TSA indicate that the number of studies might be sufficient to support the observed associations. The present meta-analysis suggests that the RFC-1 A80G polymorphism is associated with a slight yet significant increase in the risk of having a child with DS, especially in homozygous GG mothers.

In the bacterial reverse mutation (Ames) test, Salmonella typhimurium strains TA1537, TA97, and TA97a are generally regarded as interchangeable for detection of frameshift mutations. A uniform two‑fold increase criterion, vs. the concurrent negative control, is commonly applied when using these strains, without consideration of strain-specific background characteristics. To investigate control criteria applicability, we analyzed negative-control revertant counts for TA97, TA97a, and TA1537, using data from 20 independent experiments, conducted with and without metabolic activation. TA97 and TA97a showed higher mean negative-control counts than TA1537 but exhibited narrower variability, when assessed using historical control ranges defined as the mean ± 2 standard deviations. The upper limits of these ranges corresponded to approximately 1.12-1.45‑fold × the mean for TA97 and TA97a, whereas wider relative ranges were observed for TA1537. These findings indicate that the applicability of a two‑fold increase criterion differs among frameshift‑detecting strains and that interpretation of TA97 and TA97a data may benefit from strain‑specific historical-control data rather than relying solely on a uniform threshold.

This study investigated the potential of the lizard Phyllopezus pollicaris as a bioindicator of genotoxic damage caused by exposure to ionizing radiation in uranium-rich areas of Rio Grande do Norte State, Brazil. The hypothesis tested was that P. pollicaris is sensitive to ionizing radiation due to its wide distribution and generalist ecological behavior and may exhibit cytogenetic effects in areas with high natural background radiation. Blood samples were collected from specimens in three localities with medium to high natural background radiation levels in the Seridó Caatinga and were compared with samples from a low-radiation area, the Mata Estrela Reserve in the Atlantic Forest. Cytogenetic analyses were conducted by assessing the frequency of micronuclei and other nuclear abnormalities in erythrocytes using the micronucleus test. The results indicated a significant increase in the frequency of micronuclei and other nuclear abnormalities in specimens from areas with high natural background radiation compared to the absence of micronuclei (MN) in individuals from the Mata Estrela reference (non-exposed) area. Thus, this study suggests a link between ionizing radiation and genotoxic damage, highlighting the potential of P. pollicaris as a bioindicator of environmental quality in areas with high natural background radiation, such as the Seridó region of Rio Grande do Norte, Brazil.

Histones, essential building blocks of the nucleosome, undergo dynamic changes during the cell cycle. Phosphorylation of histone protein H2AX occurs at sites of DNA double-strand breaks (DSBs) and is a sensitive marker of DNA damage. Detection of phosphorylated H2AX, the γ-H2AX assay, has been widely used in experimental models, including human tissues and cell lines. The assay has been used in research on DNA repair, drug development, genotoxicity assessment, radiation biology, diagnostic radiology, and radiotherapy protocol optimization. Among these applications, the γ-H2AX assay has gained particular attention in radiation biodosimetry due to its rapid turnaround time. Despite its potential for radiation triage, the assay's utility in cases of delayed sample collection/processing remains limited, because quantitation is constrained by rapid dephosphorylation, catalyzed by phosphatases such as Protein Phosphatase 2 A (PP2A). Potential stabilizing agents, such as fostriecin, okadaic acid, calyculin A, and LiCl, have been suggested to preserve γ-H2AX by modulating phosphatase activity. We evaluated the possible stabilising effects of calyculin A and LiCl on γ-H2AX foci in irradiated human blood lymphocytes. Pre-treatment with either calyculin A (10 nM) or LiCl (20 mM) yielded higher levels of γ-H2AX foci, 0.5 h post-X-irradiation; however, the stability of the γ-H2AX foci declined, 24 h post-irradiation.

The in vivo erythrocyte micronucleus (MN) test is a standard assay for detecting chromosomal damage; however, conventional manual scoring is labor-intensive and subject to inter-scorer variability. Although automated image-based scoring offers a practical alternative, its application to bone marrow analysis requires effective enrichment of erythrocytes, to reduce interference from non-target nucleated cells. We have established and validated an automated bone marrow MN scoring workflow, using the Metafer slide-scanning system and associated software platform. We have compared a conventional cellulose column-based enrichment method with a syringe-filter-based method. The filter method reduced residual non-erythroid cellular components more effectively than the column method, although both methods yielded preparations suitable for automated analysis. Automated scoring showed no significant differences from manual microscopy in MN frequency or polychromatic erythrocyte ratio, in either negative- or positive-control groups. Repeated analysis of the same slide demonstrated high repeatability. Automated and manual MN frequencies showed positive linear correlations in both column- and filter-enriched preparations, and Bland-Altman analysis showed overall agreement between the two scoring methods. Automated historical control data (HCD) generated from male and female rats and mice were comparable to manually established laboratory HCD. These findings demonstrate that automated image-based scoring combined with appropriate erythrocyte enrichment is a reliable and practical alternative to conventional manual scoring in the in vivo bone marrow MN assay and may improve analytical efficiency, objectivity, and reproducibility in genotoxicity testing.

The repeated-dose liver micronucleus (RDLMN) assay is being developed toward an International Workshop on Genotoxicity Testing (IWGT)-recommended protocol, for potential adoption as an Organisation for Economic Co-operation and Development (OECD) guideline. During this development, the possible effect of animal age has been identified as a key issue, since, in general rodent toxicity studies, agent administration is typically initiated at 6-8 weeks of age (OECD Test Guideline 407, "Repeated-Dose 28-Day Oral Toxicity Study in Rodents"). To address this issue, we have conducted an RDLMN assay in rats treated with 2-acetamidofluorene (2-AAF), with dosing initiated at either 6 or 8 weeks of age. 2-AAF was selected as a representative compound known to produce weak positive responses in genotoxicity studies. The results demonstrated comparable increases in micronucleus frequency between the two age groups, indicating no clear impact of age. These findings, obtained with a weakly positive compound, provide further supporting evidence that the RDLMN assay can be reliably applied to animals when dosing is initiated at either 6 or 8 weeks of age, thereby supporting its integration into repeated-dose toxicity studies. Using PCNA- and Ki-67-positive cell counts as indicators of cell proliferative activity, we examined the suppressive effect of 2-AAF on cell proliferation; such suppression may affect the sensitivity of the assay. Our findings support the use of both PCNA and Ki-67 as indicators of cell proliferative activity in the RDLMN assay.

Nuclear factor-kappa B (NF-κB), a proinflammatory transcription factor, plays a pivotal role in chemotherapeutic resistance and chemotherapy-induced organ injury. Consequently, combining conventional chemotherapy with an NF-κB inhibitor may optimize therapeutic outcomes by enhancing tumor cell cytotoxicity while mitigating systemic toxicity. In this study, we synthesized a novel thiazolidinedione-based small molecule, O-prenylated benzylidene-thiazolidinedione (PBT), and evaluated its efficacy in combination with cisplatin (CDDP). Ehrlich ascites carcinoma (EAC)-bearing Swiss albino mice received oral PBT (4 mg/kg b.w.,) either alone or in combination with a single intraperitoneal dose of cisplatin (CDDP; 5 mg/kg b.w.,). PBT effectively suppressed NF-κB expression in both tumor cells and renal tissue. PBT effectively inhibited tumor cell proliferation, leading to significant suppression of in vivo tumor growth and prolonged host survival. Mechanistic analysis confirmed that PBT triggered tumor cell apoptosis by upregulating Bax, cytochrome-c, and caspases, while downregulating the anti-apoptotic protein Bcl-2. Furthermore, PBT treatment significantly reduced vascular endothelial growth factor (VEGF) expression and matrix metalloproteinase-9 (MMP-9) levels, underscoring its tumor sensitization potential. Concurrently, PBT attenuated CDDP-induced nephrotoxicity and genotoxicity by modulating inflammatory mediators and antioxidant enzymes. While CDDP monotherapy induced a significant increase (p < 0.05) in chromosomal aberrations and DNA damage in bone marrow cells, PBT co-treatment significantly (p < 0.05) mitigated these genotoxic effects. These findings demonstrate that NF-κB inhibition by PBT represents a promising strategy to improve the efficacy and safety profile of conventional cancer chemotherapy.

OECD TG 489 recognizes that some modifications of the in vivo comet assay (e.g., longer electrophoresis times) can detect DNA crosslink inductions expressed as DNA migration decreases. But the application of these methods in regulated safety testing has been limited because identifying an in vivo crosslinking positive control for every tissue that can be evaluated with the comet assay can be very challenging. Most crosslinking agents induce crosslinks in just one tissue (e.g., site of contact) with the agent's toxicity limiting exposure and effects induced in other tissues. This complication can require different positive control compounds with additional animals for each compound to adequately evaluate crosslinks in the multiple tissues typically evaluated with the comet assay. Our objective was to develop a method for generating concurrent in vivo crosslinking positive control comet data for any tissue without using additional animals. We accomplished this by preparing for each tissue evaluated extra comet slides from the conventional positive control (EMS) dosed animals and ex vivo crosslinking the heavily damaged cells on these slides with 10% neutral buffered formalin (NBF) immediately before lysis. These ex vivo crosslinked slides were then electrophoresed with the rest of the study slides with the same standard conditions and electrophoresis time. The conventional comet study slides prepared from the liver, duodenum, glandular stomach, and lung tissues collected from the EMS dosed animals and lysed without ex vivo crosslinking expressed a statistically significant DNA migration increase when compared to the concurrent vehicle control dose group. The ex vivo crosslinked slides from the EMS dose group tissue samples expressed a statistically significant decrease in DNA migration when compared to the concurrent vehicle control group. Although no statistical analysis was conducted, it is clear by the data that the ex vivo crosslinked slides from the EMS dose group tissue samples also expressed a significant decrease compared to the same samples from the EMS dose group without the ex vivo NBF treatment. This data demonstrate that the method can be easily incorporated into any existing comet study design to evaluate crosslink induction in any comet assay tissue with minimal effort or cost and without the use of any additional animals.

Tooth bleaching is one of the most frequently performed esthetic procedures in dentistry. Although peroxide-based bleaching agents effectively promote color change, their decomposition generates reactive oxygen species that may induce oxidative stress, cytotoxicity, genotoxicity, inflammation, and oral tissue alterations. This scoping review mapped and synthesized the available evidence regarding genotoxicity and oral tissue damage associated with tooth bleaching procedures, identified the biological models and analytical methods used to investigate these outcomes, and explored differences among bleaching protocols. The review followed the Joanna Briggs Institute methodology and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews guidelines. Searches were conducted in major electronic databases and supplementary searches. Ninety-four studies were included, comprising laboratory, animal, and human investigations. The most commonly used analytical methods included micronucleus assays, comet assays, oxidative stress biomarkers, molecular analyses, and histopathological evaluations. Peroxide-based bleaching agents were frequently associated with oxidative stress, cytotoxicity, genotoxicity, inflammatory responses, apoptosis, and tissue alterations, which appeared to occur in a concentration-dependent and time-dependent manner. Laboratory studies generally reported more pronounced biological effects, whereas animal and clinical investigations demonstrated the influence of physiological defense and repair mechanisms. Clinical studies frequently reported transient biological alterations. Oxidative stress emerged as the central mechanism linking peroxide exposure to cellular and tissue damage. Overall, peroxide concentration, exposure duration, and protocol design emerged as relevant factors modulating biological responses, whereas catalysts, antioxidants, and photobiomodulation therapies represented promising strategies to mitigate bleaching-induced damage. Further standardized and long-term clinical studies are required to clarify the biological significance and clinical relevance of these effects.

Epigenetic regulatory activity through chromatin remodelling is essential for maintaining gene expression integrity, and alterations in chromatin-associated proteins can cause pathological consequences. The conserved PWWP domain in PWWP2A and PWWP2B, which are Royal family of chromatin readers, can recognize methylated histones and regulate transcriptional mechanisms. Beyond their biological significance, the structural effects of missense mutations in the PWWP2A and PWWP2B domains remain unknown. No previous study has been done on the effect of missense mutations in PWWP2A and PWWP2B that affect their stability, folding, chromatin-interacting functions. To predict pathogenicity and structural disruption, in silico characterization of missense mutations was conducted in both genes using SIFT, PolyPhen-2, GERP, Mutation Assessor, MutPred, I-Mutant 2.0, Project HOPE. As a result, 354 and 352 missense variants were obtained from 1712 and 1301 SNPs in PWWP2A and PWWP2B, respectively. Of which, fifteen missense variants were recognized as highly pathogenic: 11 in PWWP2A (R195W, G650D, V655A, D657H/G, A661D, L674V, R680W, W695R, F716V, Y728C) and 4 in PWWP2B (P505L, A506V, Y563C, R564W). These mutations changed the protein's hydrophobic and electrostatic properties and reduced stability. They occur on conserved residues of the PWWP domain, indicating possible link to disease mechanisms. Furthermore, AlphaFold2-based 3D modelling and Ramachandran plot analysis indicated potential misfolding and domain perturbations. To conclude, this study proposes a predictive structural framework to understand the impact of missense mutations in the PWWP2A and PWWP2B domains on transcriptional regulation and chromatin binding; further experimental validation will be required to confirm the effects predicted in this study. The integrative computational approach of this study provides a foundation for experimental validation and therapeutic investigation of PWWP2-associated disorders.