Fate of micronuclei and micronucleated cells

DNA content, repeatome composition and origin of the Zea mays micronuclei

Micronuclei originate from DNA damage generated by clastogenic and/or by aneugenic effects. Depending on the pattern of damage, they may have distinct genomic origin and composition. Sequences of the centromere, telomere and rDNA have been identified in plant micronuclei. However, other DNA sequences may also be present in the micronuclei, as well as their DNA contents may be different. Here, we investigate the DNA content, genomic composition and origin of micronuclei induced in Zea mays by methyl methanesulfonate (MMS). DNA contents showed a wide range of distribution, suggesting their diverse genomic origins and illustrating how much of the nuclear genome can be lost due to mutagen effects. Micronuclei diversity was also evidenced by in situ probing with different DNA sequences (5S and 18S rDNAs, 180-bp knob and Grande LTR-retrotransposon) and by 6-diamidino-2 phenylindole (DAPI) fluorochrome. Perhaps these sequences are hotspots for MMS damage, especially the Grande LTR-retrotransposon, 5S and 18S rDNAs, which are rich in guanine. In addition, probe pools were constructed from individual genomic DNA of two microdissected micronuclei. These probe pools hybridized on all Z. mays chromosomes. However, the centromere, knob and secondary constriction were hybridized by only one probe pool, evidencing the distinct genomic composition of the micronuclei. We illustrate the micronuclei genomic diversity as they originated from several different chromosomes following the MMS treatment, and demonstrate the extent of the genotoxic damage to the genome. We provide some insights into micronuclei structure and diversity, and show that they can be further explored in mutagenesis research.

Propylparaben negatively impacts IN VITRO preimplantation mouse embryo development

Parabens are chemicals widely used in personal care products and food as antimicrobial preservatives. They exhibit potential estrogenic activity by binding to estrogen receptors 1 and 2, classifying them as endocrine-disrupting chemicals. Given the substantial daily exposure of women to parabens, it is crucial to investigate their effects on the female reproductive system. Previous studies in mouse models have shown that paraben exposure impacts ovarian development, resulting in an increase in cystic follicles and a decrease in corpora lutea. However, the effects of parabens on embryo development have not been extensively studied. This study aimed to determine the impact of propylparaben exposure on preimplantation embryo development in vitro. We tested the effects of 0 (0.075 % DMSO), 0.5 μg/mL, 5.0 μg/mL, 10 μg/mL, and 15 μg/mL propylparaben on rate of development of mouse zygotes to hatched blastocyst stage, quantified the number of inner cell mass (ICM) and trophectoderm (TE) cells in hatched blastocysts, and the distribution of cytoskeletal F-actin. The percentage of hatched blastocysts was significantly decreased at 0.5 μg/mL and 10 μg/mL compared to controls. Propylparaben treatment did not alter TE cell numbers. However, treatment with 0.5 or 15 μg/mL significantly decreased the number of ICM cells compared to controls. Additionally, the intensity of phalloidin fluorescence staining for F-actin was significantly reduced at 10 μg/mL and 15 μg/mL propylparaben. In summary, our findings show that propylparaben exposure disrupts ICM formation, impacts the cytoskeletal filamentous actin (F-actin) network, and alters the rate of hatched blastocyst development in preimplantation mouse embryos.

Genotoxicity testing of the anthraquinone dye Alizarin Red S

The anthraquinone dye Alizarin Red S (ARS) is used for marking live animals, specifically as a tool for monitoring the stock of the endangered European eel by marking caught fish with ARS before releasing the eels back into the wild. As ARS can be found in recaptured eels even years later, knowledge of potential health hazards of ARS is essential for assessing the food safety of eels marked with ARS. As the compound class of anthraquinones is known for their genotoxic and carcinogenic properties, concerns were raised regarding the food safety of marked eels. Up to now, no data for characterizing the hazard potential of ARS is available. In this study, we aimed at closing this data gap. We tested ARS in liver (HepG2), cervix (HeLa) and lymphoblast (TK-6) cells and identified HepG2 cells as the cell line most sensitive to ARS-induced cytotoxicity. We then investigated oxidative stress, DNA strand breaks, and micronucleus formation in these cells and did not observe effects at sub-cytotoxic concentrations.

When do the pathological signs become evident? Study of human mesenchymal stem cells in MDPL syndrome

Aging syndromes are rare genetic disorders sharing the features of accelerated senescence. Among these, Mandibular hypoplasia, Deafness and Progeroid features with concomitant Lipodystrophy (MDPL; OMIM #615381) is a rare autosomal dominant disease due to a de novo in-frame deletion in POLD1 gene, encoding the catalytic subunit of DNA polymerase delta. Here, we investigated how MSCs may contribute to the phenotypes and progression of premature aging syndromes such as MDPL. In human induced pluripotent stem cells (hiPSCs)-derived MSCs of three MDPL patients we detected several hallmarks of senescence, including (i) abnormal nuclear morphology, (ii) micronuclei presence, (iii) slow cell proliferation and cell cycle progression, (iv) reduced telomere length, and (v) increased levels of mitochondrial reactive oxygen species (ROS). We newly demonstrated that the pathological hallmarks of senescence manifest at an early stage of human development and represent a warning sign for the progression of the disease. Dissecting the mechanisms underlying stem cell dysfunction during aging can thereby contribute to the development of timely pharmacological therapies for ameliorating the pathological phenotype.

Chromosome aberrations cause tumorigenesis through chromosomal rearrangements in a hepatocarcinogenesis rat model

Chromosome aberrations (CAs), a genotoxic potential of carcinogens, are believed to contribute to tumorigenesis by chromosomal rearrangements through micronucleus formation. However, there is no direct evidence that proves the involvement of CAs in tumorigenesis in vivo. In the current study, we sought to clarify the involvement of CAs in chemical carcinogenesis using a rat model with a pure CA-inducer hepatocarcinogen, acetamide. Whole-genome analysis indicated that hepatic tumors induced by acetamide treatment for 26-30 weeks showed a broad range of copy number alterations in various chromosomes. In contrast, hepatic tumors induced by a typical mutagen (diethylnitrosamine) followed by a nonmutagen (phenobarbital) did not show such mutational patterns. Additionally, structural alterations such as translocations were observed more frequently in the acetamide-induced tumors. Moreover, most of the acetamide-induced tumors expressed c-Myc and/or MDM2 protein due to the copy number gain of each oncogene. These results suggest the occurrence of chromosomal rearrangements and subsequent oncogene amplification in the acetamide-induced tumors. Taken together, the results indicate that CAs are directly involved in tumorigenesis through chromosomal rearrangements in an acetamide-induced hepatocarcinogenesis rat model.

Biological effects in normal human fibroblasts following chronic and acute irradiation with both low- and high-LET radiation

Introduction

Radiobiological studies at low dose rates allow us to improve our knowledge of the mechanisms by which radiation exerts its effects on biological systems following chronic exposures. Moreover, these studies can complement available epidemiological data on the biological effects of low doses and dose rates of ionizing radiation. Very few studies have simultaneously compared the biological effects of low- and high-LET radiations at the same dose rate for chronic irradiation.

Methods

We compared, for the first time in the same experiment, the effects of chronic (dose rates as low as ~18 and 5 mGy/h) and acute irradiations on clonogenicity and micronucleus formation in AG1522 normal human skin fibroblasts in the confluent state exposed to doses of low- and high-LET radiation (gamma rays and alpha particles) to investigate any differences due to the different radiation quality and different dose rate (in the dose range 0.006-0.9 Gy for alpha particles and 0.4-2.3 Gy for gamma rays).

Results

As expected, alpha particles were more effective than gamma rays at inducing cytogenetic damage and reduced clonogenic cell survival. For gamma rays, the cytogenetic damage and the reduction of clonogenic cell survival were greater when the dose was delivered acutely instead of chronically. Instead, for the alpha particles, at the same dose, we found equal cytogenetic damage and reduction of clonogenic cell survival for both chronic and acute exposure (except for the highest doses of 0.4 and 0.9 Gy, where cytogenetic damage is greater at a low dose rate).

Conclusion

The results of this study may have an impact on space and terrestrial radioprotection of humans at low doses and low dose rates, on biodosimetry, and on the use of ionizing radiation in medicine. These results also provide insights into understanding damage induction and cell reaction mechanisms following chronic exposure (at dose rates as low as 18 and 5 mGy/h) to low- and high-LET radiation.

Recent insights into the causes and consequences of chromosome mis-segregation

Mitotic cells face the challenging task of ensuring accurate and equal segregation of their duplicated, condensed chromosomes between the nascent daughter cells. Errors in the process result in chromosome missegregation, a significant consequence of which is the emergence of aneuploidy-characterized by an imbalance in chromosome number-and the associated phenomenon of chromosome instability (CIN). Aneuploidy and CIN are common features of cancer, which leverages them to promote genome heterogeneity and plasticity, thereby facilitating rapid tumor evolution. Recent research has provided insights into how mitotic errors shape cancer genomes by inducing both numerical and structural chromosomal changes that drive tumor initiation and progression. In this review, we survey recent findings regarding the mitotic causes and consequences of aneuploidy. We discuss new findings into the types of chromosome segregation errors that lead to aneuploidy and novel pathways that protect genome integrity during mitosis. Finally, we describe new developments in our understanding of the immediate consequences of chromosome mis-segregation on the genome stability of daughter cells.

Nuclear reassembly defects after mitosis trigger apoptotic and p53-dependent safeguard mechanisms in Drosophila

In animals, mitosis involves the breakdown of the nuclear envelope and the sorting of individualized, condensed chromosomes. During mitotic exit, emerging nuclei reassemble a nuclear envelope around a single mass of interconnecting chromosomes. The molecular mechanisms of nuclear reassembly are incompletely understood. Moreover, the cellular and physiological consequences of defects in this process are largely unexplored. Here, we have characterized a mechanism essential for nuclear reassembly in Drosophila. We show that Ankle2 promotes the PP2A-dependent recruitment of BAF and Lamin at reassembling nuclei, and that failures in this mechanism result in severe nuclear defects after mitosis. We then took advantage of perturbations in this mechanism to investigate the physiological responses to nuclear reassembly defects during tissue development in vivo. Partial depletion of Ankle2, BAF, or Lamin in imaginal wing discs results in wing development defects accompanied by apoptosis. We found that blocking apoptosis strongly enhances developmental defects. Blocking p53 does not prevent apoptosis but enhances defects due to the loss of a cell cycle checkpoint. Our results suggest that apoptotic and p53-dependent responses play a crucial role in safeguarding tissue development in response to sporadic nuclear reassembly defects.

Mobile phone specific radiation disturbs cytokinesis and causes cell death but not acute chromosomal damage in buccal cells: Results of a controlled human intervention study

Several human studies indicate that mobile phone specific electromagnetic fields may cause cancer in humans but the underlying molecular mechanisms are currently not known. Studies concerning chromosomal damage (which is causally related to cancer induction) are controversial and those addressing this issue in mobile phone users are based on the use of questionnaires to assess the exposure. We realized the first human intervention trial in which chromosomal damage and acute toxic effects were studied under controlled conditions. The participants were exposed via headsets at one randomly assigned side of the head to low and high doses of a UMTS signal (n = 20, to 0.1 W/kg and n = 21 to 1.6 W/kg Specific Absorption Rate) for 2 h on 5 consecutive days. Before and three weeks after the exposure, buccal cells were collected from both cheeks and micronuclei (MN, which are formed as a consequence of structural and numerical chromosomal aberrations) and other nuclear anomalies reflecting mitotic disturbance and acute cytotoxic effects were scored. We found no evidence for induction of MN and of nuclear buds which are caused by gene amplifications, but a significant increase of binucleated cells which are formed as a consequence of disturbed cell divisions, and of karyolitic cells, which are indicative for cell death. No such effects were seen in cells from the less exposed side. Our findings indicate that mobile phone specific high frequency electromagnetic fields do not cause acute chromosomal damage in oral mucosa cells under the present experimental conditions. However, we found clear evidence for disturbance of the cell cycle and cytotoxicity. These effects may play a causal role in the induction of adverse long term health effects in humans.

Extrachromosomal DNA in cancer

Extrachromosomal DNA (ecDNA) has recently been recognized as a major contributor to cancer pathogenesis that is identified in most cancer types and is associated with poor outcomes. When it was discovered over 60 years ago, ecDNA was considered to be rare, and its impact on tumour biology was not well understood. The application of modern imaging and computational techniques has yielded powerful new insights into the importance of ecDNA in cancer. The non-chromosomal inheritance of ecDNA during cell division results in high oncogene copy number, intra-tumoural genetic heterogeneity and rapid tumour evolution that contributes to treatment resistance and shorter patient survival. In addition, the circular architecture of ecDNA results in altered patterns of gene regulation that drive elevated oncogene expression, potentially enabling the remodelling of tumour genomes. The generation of clusters of ecDNAs, termed ecDNA hubs, results in interactions between enhancers and promoters in trans, yielding a new paradigm in oncogenic transcription. In this Review, we highlight the rapid advancements in ecDNA research, providing new insights into ecDNA biogenesis, maintenance and transcription and its role in promoting tumour heterogeneity. To conclude, we delve into a set of unanswered questions whose answers will pave the way for the development of ecDNA targeted therapeutic approaches.

In vitro and in vivo induction of ochratoxin A exposure-related micronucleus formation in rat proximal tubular epithelial cells and expression profiling of chromosomal instability-related genes

Ochratoxin A (OTA) is a renal carcinogen in rats, and repeated administration induces karyomegaly in proximal tubular epithelial cells (PTECs) of the outer stripe of the outer medulla (OSOM) before inducing proliferative lesions. To investigate whether OTA induces micronuclei (MN) in PTECs, we performed an in vitro MN assay using rat renal NRK-52E PTECs after treatment for ≤21 days, and an in vivo OSOM MN assay in rats treated with OTA, other renal carcinogens, or non-carcinogenic renal toxicants for 4 or 13 weeks. The in vitro assay revealed an increased frequency of micronucleated cells from the acceptable dose level for cell viability, even after 21 days of treatment. The in vivo assay also revealed a dose- and treatment period-dependent increase in PTECs with γ-H2AX+ MN. OTA-specific gene expression profiling by OSOM RNA sequencing after week 13 revealed the altered expression of genes related to microtubule-kinetochore binding, the kinesin superfamily, centriole assembly, DNA damage repair, and cell cycle regulation. MN formation was also observed with other renal carcinogens that induce karyomegaly similarly to OTA. These results imply that γ-H2AX+ MN formation by OTA treatment is related to the induction of chromosomal instability accompanying karyomegaly formation before proliferative lesions form, providing a new insight into the carcinogenic mechanism that may be relevant to humans.

Micronuclei and Cancer

Chromosome-containing micronuclei are a feature of human cancer. Micronuclei arise from chromosome mis-segregation and characterize tumors with elevated rates of chromosomal instability. Although their association with cancer has been long recognized, only recently have we broadened our understanding of the mechanisms that govern micronuclei formation and their role in tumor progression. In this review, we provide a brief historical account of micronuclei, depict the mechanisms underpinning their creation, and illuminate their capacity to propel tumor evolution through genetic, epigenetic, and transcriptional transformations. We also posit the prospect of leveraging micronuclei as biomarkers and therapeutic targets in chromosomally unstable cancers.

SIGNIFICANCE

Micronuclei in chromosomally unstable cancer cells serve as pivotal catalysts for cancer progression, instigating transformative genomic, epigenetic, and transcriptional alterations. This comprehensive review not only synthesizes our present comprehension but also outlines a framework for translating this knowledge into pioneering biomarkers and therapeutics, thereby illuminating novel paths for personalized cancer management.

An image analysis approach to characterize micronuclei differences in different subtypes of breast cancer

BACKGROUND

Micronuclei (MN) have been used as screening, diagnostic and prognostic markers in multiple cancer types, including breast cancer (BC). However, the question that the MN present in all subtypes of BC are similar or different remains unanswered. We thus hypothesized that MN present in different subtypes of BC may differ in their contents which may be visible as differences in their morphologic and morphometric features. This study was thus carried out with the aim to identify the differences between MN morphometry, complexity, and texture in different subtypes of BC, such as estrogen and progesterone receptor-positive (ER+/PR+; MCF-7, T-47D), human epidermal growth factor receptor-positive (Her2 +;SKBR3) and triple-negative BC (TNBC; MDA-MB-231, MDA-MB-468) cell lines (CLs) by ImageJ software.

METHODS

For analysis of MN dimensions, MN irregularity, and texture, we used morphometry and two mathematical computer-assisted algorithms, i.e., fractal dimension (FD) and grey level co-occurrence matrix (GLCM) of ImageJ software.

RESULTS

MN area and perimeter values showed differences in the size of MN in different subtypes of BC, with the largest MN in TNBC CLs. GLCM parameters (entropy, angular second moment, inverse difference moment, contrast, and correlation) showed highly heterogenous texture in case of TNBC MN as compared to the others. FD analysis also revealed more complexity and irregularity in MN found in TNBC cells.

CONCLUSION

The study for the first time showed morphometric, architectural and texture related differences amongst MN present in different subtypes of BC. The above may reflect differences in their composition and contents. Further, these differences may point towards the distinct mechanisms involved in the formation of MN in different subtypes of BC that need to be explored further.

Trafficking and effect of released DNA on cGAS-STING signaling pathway and cardiovascular disease

Evidence from clinical research and animal studies indicates that inflammation is an important factor in the occurrence and development of cardiovascular disease (CVD). Emerging evidence shows that nucleic acids serve as crucial pathogen-associated molecular patterns (PAMPs) or non-infectious damage-associated molecular patterns (DAMPs), are released and then recognized by pattern recognition receptors (PRRs), which activates immunological signaling pathways for host defense. Mechanistically, the released nucleic acids activate cyclic GMP-AMP synthase (cGAS) and its downstream receptor stimulator of interferon genes (STING) to promote type I interferons (IFNs) production, which play an important regulatory function during the initiation of an innate immune response to various diseases, including CVD. This pathway represents an essential defense regulatory mechanism in an organism's innate immune system. In this review, we outline the overall profile of cGAS-STING signaling, summarize the latest findings on nucleic acid release and trafficking, and discuss their potential role in CVD. This review also sheds light on potential directions for future investigations on CVD.

Genotoxicity assessment of 1,4-anhydro-4-seleno-D-talitol (SeTal) in human liver HepG2 and HepaRG cells

1,4-Anhydro-4-seleno-D-talitol (SeTal) is a highly water-soluble selenosugar with interesting antioxidant and skin-tissue-repair properties; it is highly stable in simulated gastric and gastrointestinal fluids and is a potential pharmaceutical ingredient that may be administered orally. Hepatic toxicity is often a major problem with novel drugs and can result in drug withdrawal from the market. Predicting hepatotoxicity is therefore essential to minimize late failure in the drug-discovery process. Herein, we report in vitro studies to evaluate the cytotoxic and genotoxic potential of SeTal in HepG2 and hepatocyte-like differentiated HepaRG cells. Except for extremely high concentrations (10 mM, 68 h-treatment in HepG2), SeTal did not affect the viability of each cell type. While the highest examined concentrations (0.75 and 1 mM in HepG2; 1 mM in HepaRG) were observed to induce primary DNA damage, SeTal did not exhibit clastogenic or aneugenic activity toward either HepG2 or HepaRG cells. Moreover, no significant cytostasis variations were observed in any experiment. The clearly negative results observed in the CBMN test suggest that SeTal might be used as a potential active pharmaceutical ingredient. The present study will be useful for the selection of non-toxic concentrations of SeTal in future investigations.

Polyploid cell dynamics and death before and after PEG-treatment of a NIH/3T3 derived culture: vinblastine effects on the regulation of cell subpopulations heterogeneity

BACKGROUND

Neoplastic subpopulations can include polyploid cells that can be involved in tumor evolution and recurrence. Their origin can be traced back to the tumor microenvironment or chemotherapeutic treatment, which can alter cell division or favor cell fusion, generating multinucleated cells. Their progeny, frequently genetically unstable, can result in new aggressive and more resistant to chemotherapy subpopulations. In our work, we used NIHs cells, previously derived from the NIH/3T3 line after serum deprivation, that induced a polyploidization increase with the appearance of cells with DNA content ranging from 4 to 24c. This study aimed to analyze the cellular dynamics of NIHs culture subpopulations before and after treatment with the fusogenic agent polyethylene glycol (PEG), which allowed us to obtain new giant polyploid cells. Successively, PEG-untreated and PEG-treated cultures were incubated with the antimicrotubular poison vinblastine. The dynamics of appearance, decrease and loss of cell subpopulations were evaluated by correlating cell DNA content to mono-multinuclearity resulting from cell fusion and division process alteration and to the peculiarities of cell death events.

RESULTS

DNA microfluorimetry and morphological techniques (phase contrast, fluorescence and TEM microscopies) indicated that PEG treatment induced a 4-24c cell increase and the appearance of new giant elements (64-140c DNA content). Ultrastructural analysis and autophagosomal-lysosomal compartment fluorochromization, which allowed us to correlate cytoplasmic changes to death events, indicated that cell depletion occurred through distinct mechanisms: apoptotic death involved 2c, 4c and 8c cells, while autophagic-like death involved intermediate 12-24c cells, showing nuclear (lobulation/micronucleation) and autophagic cytoplasm alterations. Death, spontaneously occurring, especially in intermediate-sized cells, was increased after vinblastine treatment. No evident cell loss by death events was detected in the 64-140c range.

CONCLUSIONS

PEG-treated NIHs cultures can represent a model of heterogeneous subpopulations originating from cell fusion and division process anomalies. Altogether, our results suggest that the different cell dynamics of NIHs subpopulations can affect the variability of responses to stimuli able to induce cell degeneration and death. Apoptptic, autophagic or hybrid forms of cell death can also depend on the DNA content and ability to progress through the cell cycle, which may influence the persistence and fate of polyploid cell descendants, also concerning chemotherapeutic agent action.

Small extrachromosomal circular DNA harboring targeted tumor suppressor gene mutations supports intratumor heterogeneity in mouse liver cancer induced by multiplexed CRISPR/Cas9

BACKGROUND

Primary liver cancer has significant intratumor genetic heterogeneity (IGH), which drives cancer evolution and prevents effective cancer treatment. CRISPR/Cas9-induced mouse liver cancer models can be used to elucidate how IGH is developed. However, as CRISPR/Cas9 could induce chromothripsis and extrachromosomal DNA in cells in addition to targeted mutations, we wondered whether this effect contributes to the development of IGH in CRISPR/Cas9-induced mouse liver cancer.

METHODS

CRISPR/Cas9-based targeted somatic multiplex-mutagenesis was used to target 34 tumor suppressor genes (TSGs) for induction of primary liver tumors in mice. Target site mutations in tumor cells were analyzed and compared between single-cell clones and their subclones, between different time points of cell proliferation, and between parental clones and single-cell clones derived from mouse subcutaneous allografts. Genomic instability and generation of extrachromosomal circular DNA (eccDNA) was explored as a potential mechanism underlying the oscillation of target site mutations in these liver tumor cells.

RESULTS

After efficiently inducing autochthonous liver tumors in mice within 30-60 days, analyses of CRISPR/Cas9-induced tumors and single-cell clones derived from tumor nodules revealed multiplexed and heterogeneous mutations at target sites. Many target sites frequently displayed more than two types of allelic variations with varying frequencies in single-cell clones, indicating increased copy number of these target sites. The types and frequencies of targeted TSG mutations continued to change at some target sites between single-cell clones and their subclones. Even the proliferation of a subclone in cell culture and in mouse subcutaneous graft altered the types and frequencies of targeted TSG mutations in the absence of continuing CRISPR/Cas9 genome editing, indicating a new source outside primary chromosomes for the development of IGH in these liver tumors. Karyotyping of tumor cells revealed genomic instability in these cells manifested by high levels of micronuclei and chromosomal aberrations including chromosomal fragments and chromosomal breaks. Sequencing analysis further demonstrated the generation of eccDNA harboring targeted TSG mutations in these tumor cells.

CONCLUSIONS

Small eccDNAs carrying TSG mutations may serve as an important source supporting intratumor heterogeneity and tumor evolution in mouse liver cancer induced by multiplexed CRISPR/Cas9.

Towards prevention of aneuploidy-associated cellular senescence and aging: more questions than answers?

The aim of this review is to discuss how aneuploidy contributes to the aging process, and to identify plausible strategies for its prevention. After an overview of mechanisms leading to aneuploidy and the major features of cellular senescence, we discuss the link between (i) aneuploidy and cellular senescence; (ii) aneuploidy and aging; and (iii) cellular senescence and aging. We also consider (i) interactions between aneuploidy, micronuclei, cellular senescence and aging, (ii) the potential of nutritional treatments to prevent aneuploidy-associated senescence and aging, and (iii) knowledge and technological gaps. Evidence for a causal link between aneuploidy, senescence and aging is emerging. In vitro, aneuploidy accompanies the entry into cellular senescence and can itself induce senescence. How aneuploidy contributes in vivo to cellular senescence is less clear. Several routes depending on aneuploidy and/or senescence converge towards chronic inflammation, the major driver of unhealthy aging. Aneuploidy can induce the pro-inflammatory Senescence Associated Secretory Phenotype (SASP), either directly or as a result of micronucleus (MN) induction leading to leakage of DNA into the cytoplasm and triggering of the cGAS-STING pathway of innate immune response. A major difficulty in understanding the impact of aneuploidy on senescence and aging in vivo, results from the heterogeneity of cellular senescence in different tissues at the cytological and molecular level. Due to this complexity, there is at the present time no biomarker or biomarker combination characteristic for all types of senescent cells. In conclusion, a deeper understanding of the critical role aneuploidy plays in cellular senescence and aging is essential to devise practical strategies to protect human populations from aneuploidy-associated pathologies. We discuss emerging evidence, based on in vitro and in vivo studies, that adequate amounts of specific micronutrients are essential for prevention of aneuploidy in humans and that precise nutritional intervention may be essential to help avoid the scourge of aneuploidy-driven diseases.

Epigenetic dysregulation from chromosomal transit in micronuclei

Chromosomal instability (CIN) and epigenetic alterations are characteristics of advanced and metastatic cancers1-4, but whether they are mechanistically linked is unknown. Here we show that missegregation of mitotic chromosomes, their sequestration in micronuclei5,6 and subsequent rupture of the micronuclear envelope7 profoundly disrupt normal histone post-translational modifications (PTMs), a phenomenon conserved across humans and mice, as well as in cancer and non-transformed cells. Some of the changes in histone PTMs occur because of the rupture of the micronuclear envelope, whereas others are inherited from mitotic abnormalities before the micronucleus is formed. Using orthogonal approaches, we demonstrate that micronuclei exhibit extensive differences in chromatin accessibility, with a strong positional bias between promoters and distal or intergenic regions, in line with observed redistributions of histone PTMs. Inducing CIN causes widespread epigenetic dysregulation, and chromosomes that transit in micronuclei experience heritable abnormalities in their accessibility long after they have been reincorporated into the primary nucleus. Thus, as well as altering genomic copy number, CIN promotes epigenetic reprogramming and heterogeneity in cancer.

Long-term exposure of zebrafish juveniles to carbon nanofibers at predicted environmentally relevant concentrations: Outspreading warns about ecotoxicological risks to freshwater fish

Although carbon-based nanomaterials (CNMs) toxicity has already been demonstrated in some animal models, little is known about the impact of carbon nanofibers (CNFs) on aquatic vertebrates. Thus, we aimed to evaluate the possible effects of long-term exposure of zebrafish (Danio rerio) juveniles (90 days) to CNFs in predicted environmentally relevant concentrations (10 ng/L and 10 μg/L). Our data revealed that exposure to CNFs did not affect the growth and development of the animals, in addition to not having induced locomotor alterations or anxiety-like behavior. On the other hand, we observed that zebrafish exposed to CNFs showed a response deficit to the vibratory stimulus test, alteration in the density of neuromasts recorded in the final ventral region, as well as an increase in thiobarbituric acid reactive substances levels and a reduction in total antioxidant activity, nitric oxide, and acetylcholinesterase activity in the brain. Such data were directly associated with a higher concentration of total organic carbon in the brain, which suggests the bioaccumulation of CNFs. Furthermore, exposure to CNFs induced a picture suggestive of genomic instability, inferred by the increased frequency of nuclear abnormalities and DNA damage in circulating erythrocytes. Although the individual analyses of the biomarkers did not point to a concentration-dependent effect, the principal component analysis (PCA) and the Integrated Biomarker Response Index (IBRv2) indicate a more prominent effect induced by the higher CNFs concentration (10 μg/L). Therefore, our study confirms the impact of CNFs in the studied model (D. rerio) and sheds light on the ecotoxicological risks of these nanomaterials to freshwater fish. Based on the ecotoxicological screening provided by our study, new horizons are opened for investigations into the mechanisms of action of CNFs, which will help understand the magnitude of the impact of these materials on aquatic biota.

The relationship of the efficiency of energy conversion into growth as an indicator for the determination of the optimal dose for mutation breeding with the appearance of chromosomal abnormalities and incomplete mitosis after gamma irradiation of kernels of Triticum turgidum ssp. durum L

The study aim was to determine the optimal gamma irradiation dose for mutation breeding in Triticum turgidum ssp. durum L. Root, shoot and seedling growth, as well as the efficiency of energy conversion into growth were determined to examine the growth retardation effects of gamma irradiation that are the result of DNA damage (bridges, ring chromosomes, micronuclei, incomplete mitosis) in Triticum turgidum ssp. durum L. The kernels were irradiated with doses of 50, 150, 250 and 350 Gy using a ⁶⁰Cobalt gamma-ray source. The kernels were placed in germination paper at 25 °C to grow for a 132 h period for the determination of shoot and root growth and the efficiency of energy conversion into growth. Root tips were collected and fixated over a 47.5 h growth period for the determination of the chromosomal abnormalities and incomplete mitosis. The control differed highly significantly (p < 0.01) from irradiated samples at all doses in root growth and from 250 to 350 Gy samples in shoot growth and the efficiency of energy conversion into growth. There was a highly significant (p < 0.01) increase in the number of bridges and micronuclei between 50 Gy samples and samples irradiated with the higher irradiation doses while 50 Gy samples differed only from 250 and 350 Gy samples regarding ring chromosomes and interphase cells with incomplete mitosis. Root and seedling growth on the one hand and the efficiency of energy conversion into growth on the other were found to be measuring different effects of gamma irradiation on plant growth. The latter was used for the determination of the optimal dose for mutation breeding as 155.52 Gy.

Immunomodulatory effects of targeted radionuclide therapy

It is now clear that conventional radiation therapy can reinstate cell death immunogenicity. Recent preclinical data indicate that targeted radionuclide therapy that irradiate tumors at continuous low dose rate also can elicit immunostimulatory effects and represents a promising strategy to circumvent immune checkpoint inhibitor resistance. In this perspective, we discuss the accumulating preclinical and clinical data suggesting that activation of the immune system through the cGAS-STING axis and the release of extracellular vesicles by irradiated cells, participate to this antitumor immunity. This should need to be considered for adapting clinical practices to state of the art of the radiobiology and to increase targeted radionuclide therapy effectiveness.

APE1 promotes non-homologous end joining by initiating DNA double-strand break formation and decreasing ubiquitination of artemis following oxidative genotoxic stress

BACKGROUND

Apurinic/apyrimidinic endonuclease 1 (APE1) imparts radio-resistance by repairing isolated lesions via the base excision repair (BER) pathway, but whether and how it is involved in the formation and/or repair of DSBs remains mostly unknown.

METHODS

Immunoblotting, fluorescent immunostaining, and the Comet assay were used to investigate the effect of APE1 on temporal DSB formation. Chromatin extraction, 53BP1 foci and co-immunoprecipitation, and rescue assays were used to evaluate non-homologous end joining (NHEJ) repair and APE1 effects. Colony formation, micronuclei measurements, flow cytometry, and xenograft models were used to examine the effect of APE1 expression on survival and synergistic lethality. Immunohistochemistry was used to detect APE1 and Artemis expression in cervical tumor tissues.

RESULTS

APE1 is upregulated in cervical tumor tissue compared to paired peri-tumor, and elevated APE1 expression is associated with radio-resistance. APE1 mediates resistance to oxidative genotoxic stress by activating NHEJ repair. APE1, via its endonuclease activity, initiates clustered lesion conversion to DSBs (within 1 h), promoting the activation of the DNA-dependent protein kinase catalytic subunit (DNA-PK_cs), a key kinase in the DNA damage response (DDR) and NHEJ pathway. APE1 then participates in NHEJ repair directly by interacting with DNA- PK_cs. Additionally, APE1 promotes NHEJ activity by decreasing the ubiquitination and degradation of Artemis, a nuclease with a critical role in the NHEJ pathway. Overall, APE1 deficiency leads to DSB accumulation at a late phase following oxidative stress (after 24 h), which also triggers activation of Ataxia-telangiectasia mutated (ATM), another key kinase of the DDR. Inhibition of ATM activity significantly promotes synergistic lethality with oxidative stress in APE1-deficient cells and tumors.

CONCLUSION

APE1 promotes NHEJ repair by temporally regulating DBS formation and repair following oxidative stress. This knowledge provides new insights into the design of combinatorial therapies and indicates the timing of administration and maintenance of DDR inhibitors for overcoming radio-resistance.

Empirical relationship between chromosomal damage and airborne particulate matter: A systematic review and meta-analysis of studies in exposed populations

Ambient particulate matter (PM) has gained significant attention as an environmental risk factor for human health. Although the association between ambient PM and micronucleus (MN) induction has been investigated, the quantitative association of PM and genomic instability is inconclusive. We conducted a systematic review and meta-analysis to study the association between PM exposure and MN endpoint. Four databases were systematically searched for studies published up to November 2022, to find papers investigating the relationship between ambient PM and MN induction. Random effect models were conducted to estimate the overall effect based on the Ratio of Means (RoM) with 95% confidence intervals (95% CIs). Subgroup analysis, funnel plot, and Egger and Begg tests, were also performed. Twenty-three studies across nine countries, including 4450 participants, were included. A meta-RoM of 2.13 for MN (95% CI 1.63-2.79) was observed for individuals exposed to ambient PM compared to non-exposed. A significant difference in the subgroup test was found for buccal cells (3.16, 95% CI 2.20-4.52) and low economy level (3.61, 95% CI 1.44-9.01). Our meta-analysis suggests the presence of an association between PM exposure and the frequency of MN and identified the kind of cells and economic status as possible effect modifiers. The use of effective methods, such as the MN assay, enables identification of early genetic damage in humans, which in turn may anticipate the risk of developing respiratory diseases, including lung cancer.

Hepatoprotective effect of the radiation countermeasure flagellin in the long term after irradiation of mice

PURPOSE

Purpose is to study the hepatoprotective effect of a new promising radiation countermeasure flagellin, in the long term after irradiation. The results of the study can be useful for mitigating the consequences of man-made radiation accidents, protecting professional contingents, reducing the toxic effect of radiation therapy, and expanding the range of drug use.

MATERIALS AND METHODS

Effect of flagellin was investigated 10 months after its administration of irradiated male of mice F1 (CBAхC57Bl/6). Flagellin (0.2 mg/kg) was administrated once intraperitoneally before exposure of mice to low-intensive (10 mGy/min) γ-radiation at a dose of 12.65 Gy. The effect was evaluated in three groups: control, irradiated mice without of flagellin and with the administration flagellin 30 minutes before irradiation. Cytogenetic and cytotoxic effect in bone marrow was studied with micronucleus assay (OECD 474), in liver - with the original technique for cytome analysis of hepatocytes after fixation of liver pieces with 10% formalin, dissociation of cells with 50% KOH, staining with aceto-orcein and light green. The proportion of cells 2n, 2n + 2n, 4n, 4n + 4n, ≥8n and ≥8n + 8n was determined. Cytogenetic disorders were counted as cells with micronuclei, nuclear buds, and internuclear bridges. The ploidy index and nuclearity index were defined.

RESULTS

In all studied groups of mice, the frequency of polychromatic bone marrow erythrocytes with micronuclei and hepatocytes with cytogenetic disorders did not exceed the background level. A decrease in the ploidy index of hepatocytes by 4.3 times was established 10 months after exposure to low-power ionizing radiation. In mice treated with flagellin before irradiation, the ploidy index was normalized to control.

CONCLUSIONS

A decrease in the ploidy of hepatocytes was revealed 10 months after exposure to a high dose of low-power ionizing radiation, which may indicate the initiation of carcinogenesis. For the first time, a new aspect of the anti-radiation effect of promising radiation countermeasure flagellin was established and its hepatoprotective properties were determined in the long term after exposure to ionizing radiation.

Rapid communication: insights into the role of extracellular vesicles during Auger radioimmunotherapy

PURPOSE

Non-targeted effects, including bystander and systemic effects, play a crucial role during Auger targeted radionuclide therapy. Here, we investigated whether small extracellular vesicles (sEVs) produced by irradiated cells could contribute to the bystander cytotoxic effects in vitro and also to therapeutic efficacy in vivo, after their injection in tumor xenografts.

MATERIALS AND METHODS

B16F10 melanoma donor cells were exposed to radiolabeled antibodies (Auger radioimmunotherapy, RIT) for 48 h or to X-rays (donor cells). Then, donor cells were incubated with fresh medium for 2 h to prepare conditioned medium (CM) that was transferred onto recipient cells for bystander effect assessment, or used for sEVs enrichment. Resulting sEVs were incubated in vitro with recipient cells for determining bystander cytotoxicity, or injected in B16F10 melanoma tumors harbored by athymic and C57BL/6 mice.

RESULTS

In vitro analysis of bystander cytotoxic effects showed that CM killed about 30-40% of melanoma cells. SEVs isolated from CM contributed to this effect. Moreover, the double-stranded DNA (dsDNA) content was increased in sEVs isolated from CM of exposed cells compared to control (not exposed), but the difference was significant only for the X-ray condition. These results were supported by immunodetection of cytosolic dsDNA in donor cells, a phenomenon that should precede dsDNA enrichment in sEVs. However, sEVs cytotoxicity could not be detected in vivo. Indeed, in athymic and in immunocompetent mice that received four intratumoral injections of sEVs (1/day), tumor growth was not delayed compared with untreated controls. Tumor growth was slightly (not significantly) delayed in immunocompetent mice treated with sEVs from X-ray-exposed cells, and significantly with sEVs purified from CM collected after 48 h of incubation. These results highlight the need to determine the optimal conditions, including radiation absorbed dose and sEVs collection time, to obtain the strongest cytotoxic effects.

CONCLUSIONS

This study demonstrates that sEVs could play a role during Auger RIT through bystander effects in vitro. No systemic effects were observed in vivo, under our experimental conditions. However, X-rays experiments showed that sEVs collection time might be influencing the nature of sEVs, a parameter that should also be investigated during Auger RIT.

Impact of mono(2-ethylhexyl) phthalate (MEHP) on the development of mouse embryo in vitro

Mono(2-ethylhexyl) phthalate (MEHP) is the most studied metabolite of di(2-ethylhexyl) phthalate (DEHP), a phthalate found in cosmetics, flooring, paints, and plastics products, including toys and medical tubing. Humans are frequently exposed to this compound due to its ubiquitous presence in our environment. DEHP and MEHP are known to be endocrine-disrupting chemicals and exposure levels have been associated to decreased reproductive success. However, few studies have focused on the direct effects of MEHP on embryos. The present study investigated effects of MEHP (0.1, 1, 10, 100 and 1000 µM) on mice preimplantation embryonic development, evaluating percentage of blastocyst formation, hatching from zona pellucida, methylation-related genes, cell lineage commitment, micronucleation, and adherens junction marker at different stages of development during in vitro culture for 6 days. We show MEHP negatively impacts embryo competence by reducing blastocyst formation and hatching at 100 and 1000 µM. In addition, 100 µM MEHP increases the expression of Tet3 gene in blastocysts, which is related to a reduction of DNA methylation, an important mechanism regulating gene expression. Exposed embryos that completed the hatching process in groups 0.1, 1 and 10 µM MEHP had similar number of inner cell mass and trophectoderm cells compared to the control, while micronucleation occurrence and E-cadherin expression was not affected in exposed morulae by MEHP at 10 or 100 µM. Our results showed that high concentrations of MEHP can negatively impact embryo development. New studies unveiling the mechanism of toxicity involved and encompassing further developmental stages are warranted for further understanding.

Ecogenotoxicity of environmentally relevant atrazine concentrations: A threat to aquatic bioindicators

Atrazine (ATZ) is a herbicide that is frequently present in surface waters and may result in damage to the health of various organisms, including humans. However, most scientific literature reports injuries caused by ATZ at high concentrations, which are not found in the environment. Therefore, the scope of this study was to investigate the impacts of realistic concentrations of ATZ found in surface waters (1, 2, 5, 10, 15 and 20 μg/L) using the bioindicators Allium cepa, Daphnia magna and zebrafish (Danio rerio). ATZ elicited a genotoxic effect in A. cepa, manifested by the induction of chromosomal aberrations, and a mutagenic effect with increased incidence of micronuclei formation, promotion of cell death and reduction in nuclear size revealed by flow cytometry analysis. D. magna exposed to 10, 15 and 20 μg/L of ATZ showed significant reduction in body size after 21 days, delayed first-brood release, decreased egg production and total offspring, as well as swimming behavioral changes. ATZ exposure promoted physiological and developmental alterations in zebrafish embryos, including an increased spontaneous movement rate, which led to premature hatching at all concentrations investigated. Increase in total body length, decrease of the yolk sac area, pericardial edema and higher heart rate were also detected in ATZ-treated zebrafish. In summary, environmentally relevant concentrations of ATZ can induce substantial alterations in the three bioindicators investigated. This study evidences the deleterious effects of ATZ on three aquatic bioindicators employing established and current techniques, and may contribute to elucidate the risks caused by this widely used herbicide even at low concentrations and short-to-medium-term exposure.

Nucleophagy contributes to genome stability through degradation of type II topoisomerases A and B and nucleolar components

The nuclear architecture of mammalian cells can be altered as a consequence of anomalous accumulation of nuclear proteins or genomic alterations. Most of the knowledge about nuclear dynamics comes from studies on cancerous cells. How normal healthy cells maintain genome stability, avoiding accumulation of nuclear damaged material, is less understood. Here, we describe that primary mouse embryonic fibroblasts develop a basal level of nuclear buds and micronuclei, which increase after etoposide-induced DNA double-stranded breaks. Both basal and induced nuclear buds and micronuclei colocalize with the autophagic proteins BECN1 and LC3B (also known as MAP1LC3B) and with acidic vesicles, suggesting their clearance by nucleophagy. Some of the nuclear alterations also contain autophagic proteins and type II DNA topoisomerases (TOP2A and TOP2B), or the nucleolar protein fibrillarin, implying they are also targets of nucleophagy. We propose that basal nucleophagy contributes to genome and nuclear stability, as well as in response to DNA damage.

Fish biomarker responses reflect landscape anthropic disturbance in savanna streams

Disturbance in the landscape surrounding streams can interfere with water quality and cause harm to aquatic organisms. In this study, we evaluate the influence of land use on the genetic and biochemical biomarkers of fish in streams of Brazilian savanna (Cerrado). We also evaluated whether biomarker responses are seasonally consistent. For this purpose, individuals of the Neotropical tetra fish Astyanax lacustris were exposed in cages for 96 h, in 13 streams draining agroecosystems with different degrees of disturbance during the dry and wet seasons. After exposure, blood, liver, and gills were collected for multibiomarker analyses (micronuclei, erythrocytic nuclear abnormalities, lipid peroxidation, antioxidant enzymes, and biotransformation enzyme). The results showed that the gradient of anthropic disturbance was positively associated with genotoxic damage (erythrocytic nuclear abnormalities) and negatively associated with antioxidant and biotransformation enzymes of the liver in both seasons. No association of the gradient of anthropic disturbance with the frequency of micronuclei and for most gill enzymes was found for both seasons. Landscape disturbance was also negatively associated with water quality in the wet season. These results indicate that changes in land use interfere with the genetic and biochemical processes of organisms. Thus, the multibiomarker approach may represent an effective strategy for assessing and monitoring terrestrial landscape disturbance.

Genotoxic Effect of Cadmium and Zinc in the Peripheral Erythrocytes of Prussian Carp (Carassius Gibelio B.)

Introduction

Cadmium and zinc are often found in aquatic environment and may accumulate in living organisms. The aim of this study was to evaluate the genotoxic effect of Cd, Zn, and their binary mixture on the peripheral blood erythrocytes of Prussian carp (Carassius gibelio B.).

Material and Methods

The fish were exposed to 4.0 mg/L Cd, 4.0 mg/L Zn or a mixture of 4.0 mg/L Cd and 4.0 mg/L Zn for a period of 14, 21 or 28 days. Genotoxic effects were investigated in peripheral blood cells using the comet assay and the erythrocyte micronucleus assay.

Results

The results demonstrated that the frequencies of micronuclei (MN) and both nuclear and cellular abnormalities in erythrocytes were significantly higher in all exposure groups as compared to the control group. The fish exposed to the mixture of Cd and Zn presented the highest frequency of MN. Furthermore, there was a decrease in the frequency of MN and an increase in the occurrence of DNA integrity defects (DNA damage) with longer time of exposure to the metals studied.

Conclusion

Erythrocyte micronucleus and comet assays confirmed the genotoxicity of Cd and Zn. The results of the tests applied (which showed considerable variability) suggest the involvement of various toxicity mechanisms. Therefore, an integrative and comprehensive approach, using a set of assays for toxicity profile determination, should be adopted during ecotoxicological studies and environmental risk assessment pertaining to these elements.

Ambient PM2.5 exposure causes cellular senescence via DNA damage, micronuclei formation, and cGAS activation

Ambient PM2.5 is one of the environmental risk factors and was correlated with senescence-related diseases based on the epidemiologic investigation. However, little is known about senescence induced by PM2.5 as well as the underlying mechanisms. In this study, we demonstrated that PM2.5 exposure aggravated cellular senescence in vivo and in vitro, and disrupted micronuclei (MN) played a vital role in this process. Our results suggested that the nuclear envelope (NE) of PM2.5-induced MN was ruptured. Subsequently, cGAS was found to localize to approximately 80% of the disrupted MN but few for intact MN. Upon examination of cGAMP and SA-β-Gal, the cGAS-STING pathway was found activated and related to cellular senescence induced by PM2.5. Taken together, we reported a novel finding that PM2.5 exposure causes cellular senescence via DNA damage, MN formation, and cGAS activation. These results revealed the potential toxicity of PM2.5 and its related mechanisms in cellular senescence.

JAK2-CHK2 signaling safeguards the integrity of the mitotic spindle assembly checkpoint and genome stability

Checkpoint kinase 2 (CHK2) plays an important role in safeguarding the mitotic progression, specifically the spindle assembly, though the mechanism of regulation remains poorly understood. Here, we identified a novel mitotic phosphorylation site on CHK2 Tyr156, and its responsible kinase JAK2. Expression of a phospho-deficient mutant CHK2 Y156F or treatment with JAK2 inhibitor IV compromised mitotic spindle assembly, leading to genome instability. In contrast, a phospho-mimicking mutant CHK2 Y156E restored mitotic normalcy in JAK2-inhibited cells. Mechanistically, we show that this phosphorylation is required for CHK2 interaction with and phosphorylation of the spindle assembly checkpoint (SAC) kinase Mps1, and failure of which results in impaired Mps1 kinetochore localization and defective SAC. Concordantly, analysis of clinical cancer datasets revealed that deletion of JAK2 is associated with increased genome alteration; and alteration in CHEK2 and JAK2 is linked to preferential deletion or amplification of cancer-related genes. Thus, our findings not only reveal a novel JAK2-CHK2 signaling axis that maintains genome integrity through SAC but also highlight the potential impact on genomic stability with clinical JAK2 inhibition.

Interplay of cGAS with micronuclei: Regulation and diseases

In higher eukaryotes, sophisticate regulation of genome function requires all chromosomes to be packed into a single nucleus. Micronucleus (MN), the dissociative nucleus-like structure frequently observed in aging and multiple disease settings, has critical, yet under-recognized, pathophysiological functions. Micronuclei (MNi) have recently emerged as major sources of cytosolic DNA that can activate the cGAS-STING axis in a cell-intrinsic manner. However, MNi induced from different genotoxic stressors display great heterogeneity in binding or activating cGAS and the signaling responses downstream of the MN-induced cGAS-STING axis have divergent outcomes including autoimmunity, autoinflammation, metastasis, or cell death. Thus, full characterization of molecular network underpinning the interplay of cGAS and MN is important to elucidate the pathophysiological roles of immunogenic MN and design improved drugs that selectively target cancer via boosting the MN-derived cGAS-STING axis. Here, we summarize our current understanding of the mechanisms for self-DNA discrimination by cGAS. We focus on discussing how MN immunogencity is dictated by multiple mechanisms including integrity of micronuclear envelope, state of nucleosome and DNA, competitive factors, damaged mitochondrial DNA and micronucleophagy. We also describe emerging links between immunogenic MN and human diseases including cancer, neurodegenerative diseases and COVID-19. Particularly, we explore the exciting concept of inducing immunogenic MN as a therapeutic approach in treating cancer. We propose a new theoretical framework to describe immunogenic MN as a biological sensor to modulate cellular processes in response to genotoxic stress and provide perspectives on developing novel experimental approaches to unravel the complexity of MN immunogenicity regulation and immunogenic MN pathophysiology.

Modulatory effect of myricitrin against chromosome instability and cytostasis induced by bleomycin and oxaliplatin in CHO-K1 cells

Myricitrin (MYR), a flavonol consumed in the leaves and fruits of plants of the Myrtaceae family, presents anti-proliferative, anti-inflammatory, anti-diabetic, and antioxidant properties in humans. However, there are few studies regarding the cyto-genotoxicity and the chemopreventive potential of MYR. Using the in vitro Micronucleus test, the cytostasis, mutagenicity, and modulatory effect of MYR in CHO-K1 cells were assessed. The concentrations of 39 and 78 µg/mL (p < 0.001.) of MYR decrease the cytokinesis-block proliferation index (CBPI) in the short exposure treatment (4 h), while in the extended treatment (24 h), concentrations of 4.8, 9.7, 19.5, 39 and 78 µg/mL (p < 0.001.) decreased the CBPI. MYR associated with oxaliplatin decreased CBPI at all tested concentrations in the pre-(p < 0.001) and post-treatments (p < 0.001), but there was no decrease when associated with bleomycin. As for chromosome instability, MYR did not increase the frequency of micronuclei (MNi), nucleoplasmic bridges (NPBs), or nuclear buds (NBUDs) in the 4 h exposure time, however, in the 24 h treatment, MYR increased the frequency of MNi and NPBs at concentration 19.5 µg/mL (p < 0.001). As for the modulatory effect, MYR associated with bleomycin decreased the frequency of MNi, NPBs, and NBUDs at all concentrations in the pretreatment (MNi and NPBs p < 0.001, NBUDs p < 0.05) and simultaneously (MNi, NPBs and NBUDs p < 0.001). When associated with oxaliplatin, the simultaneous treatment decreased the frequency of MNi (p < 0.001) and NBUDs (p < 0.01) at all concentrations, however, in the post-treatment, MYR increased MNi (p < 0.001) and NPBs p < 0.05) in CHO-K1 cells, when compared to oxaliplatin alone. The results demonstrated that MYR could modulate the mutagenic and cytostatic actions of bleomycin and oxaliplatin, demonstrating distinct behaviors, depending on the mechanism of action of the chemotherapeutic agent.

Structural Variation in Cancer: Role, Prevalence, and Mechanisms

Somatic rearrangements resulting in genomic structural variation drive malignant phenotypes by altering the expression or function of cancer genes. Pan-cancer studies have revealed that structural variants (SVs) are the predominant class of driver mutation in most cancer types, but because they are difficult to discover, they remain understudied when compared with point mutations. This review provides an overview of the current knowledge of somatic SVs, discussing their primary roles, prevalence in different contexts, and mutational mechanisms. SVs arise throughout the life history of cancer, and 55% of driver mutations uncovered by the Pan-Cancer Analysis of Whole Genomes project represent SVs. Leveraging the convergence of cell biology and genomics, we propose a mechanistic classification of somatic SVs, from simple to highly complex DNA rearrangement classes. The actions of DNA repair and DNA replication processes together with mitotic errors result in a rich spectrum of SV formation processes, with cascading effects mediating extensive structural diversity after an initiating DNA lesion has formed. Thanks to new sequencing technologies, including the sequencing of single-cell genomes, open questions about the molecular triggers and the biomolecules involved in SV formation as well as their mutational rates can now be addressed.

Expected final online publication date for the Annual Review of Genomics and Human Genetics, Volume 23 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Comparative investigation of toxicity induced by UV-A and UV-C radiation using Allium test

Organisms are increasingly exposed to ultraviolet (UV) rays of sunlight, due to the thinning of the ozone layer and its widespread use in sterilization processes, especially against the SARS-CoV-2 virus. The present study was conducted with the purpose of evaluating the damages of UV-A and UV-C radiations in Allium cepa L. roots. The effects of two different types of UV on some physiological, biochemical, cytogenotoxic, and anatomical parameters were investigated in a multifaceted study. Three groups were formed from Allium bulbs, one of which was the control group. One of the other groups was exposed to 254 nm (UV-C) and the other to 365 nm (UV-A) UV. Growth retardation effect of UV was investigated with respect to germination percentage, total weight gain, and root elongation, while cytogenotoxicity arisen from UV exposure was analyzed using mitotic index (MI) and chromosomal aberration (CA) and micronucleus (MN) frequency. Oxidative stress due to UV application was investigated based on the accumulation of malondialdehyde (MDA) and the total activities of superoxide dismutase (SOD) and catalase (CAT) enzymes. Also, anatomical changes induced by UV-A and UV-C were analyzed in root meristematic cells. UV treatments caused significant reductions in growth-related parameters. Both UV treatments caused a significant increase in MDA levels and induction of SOD and CAT enzymes in root meristematic cells. A decrease in MI and an increase in the frequency of MN and CAs were observed in root tip cells, indicating the cytogenotoxic effect of UV application. Anatomical damages such as epidermis cell damage, cortex cell damage, necrotic zones, giant cell nucleus, and indistinct transmission tissue occurred in cells exposed to UV. All of the physiological, biochemical, cytogenetic, and anatomical damages observed in this study were more severe in cells treated with UV-C compared to UV-A. This study suggested that UV exposure triggered growth inhibition, cytogenotoxicity, oxidative stress, and meristematic cell damages in A. cepa roots depending on the wavelength.

Detection of Nuclear Biomarkers for Chromosomal Instability

Chromosomal instability (CIN) is a hallmark of cancer, which is characterized by the gain or loss of chromosomes as well as the rearrangement of the genetic material during cell division. Detection of mitotic errors such as misaligned chromosomes or chromosomal bridges (also known as lagging chromosomes) is challenging as it requires the analysis and manual discrimination of chromosomal aberrations in mitotic cells by molecular techniques. In interphase cells, more frequent in the cell population than mitotic cells, two distinct nuclear phenotypes are associated with CIN: the micronucleus and the toroidal nucleus. Several methods are available for the detection of micronuclei, but none for toroidal nuclei. Here, we provide a method to quantify the presence of both nuclear biomarkers for the evaluation of CIN status in non-mitotic cells particularly suited for genotoxicity screens.

DNA Damage and Activation of cGAS/STING Pathway Induce Tumor Microenvironment Remodeling

DNA damage occurs throughout tumorigenesis and development. The immunogenicity of DNA makes it an immune stimulatory molecule that initiates strong inflammatory responses. The cGAS/STING pathway has been investigated as a critical receptor in both exogenous and endogenous DNA sensing to activate the innate immune response. Growing lines of evidence have indicated that activation of the cGAS/STING pathway is critical in antitumor immunity. Recent studies have demonstrated the outstanding advancement of this pathway in tumor-combined immunotherapy; accordingly, increased studies focus on exploration of STING pathway agonists and analogues. However, current studies propose the potential use of the cGAS/STING pathway in tumor initiation and metastasis. Here, we review the molecular mechanisms and activation of the cGAS/STING pathway, and the relationship between DNA damage and this pathway, particularly highlighting the remodeling of immune contexture in tumor environment (TME) triggered by cascade inflammatory signals. A detailed understanding of TME reprogramming initiated by this pathway may pave the way for the development of new therapeutic strategies and rational clinical application.

Effect of gamma irradiation on nucleolar activity in root tip cells of tetraploid Triticum turgidum ssp. durum L

Ionizing irradiation induces positive or negative changes in plant growth (M1) depending on the amount of irradiation applied to seeds or plant parts. The effect of 50-350 Gy gamma irradiation of kernels on nucleolar activity, as an indicator of metabolic activity, in root tip cells of tetraploid wheat Triticum turgidum ssp. durum L. cv. Orania (AABB) was investigated. The number of nucleoli present in nuclei and micronuclei as well as the mitotic index in the different irradiation dosages was used as an indicator of the cells entering mitosis, the chromosomes with nucleolar organizer regions that are active as well as chromosome doubling in the event of unsuccessful mitotic division. Nucleolar activity was investigated from 17.5 to 47.5 h after the onset of imbibition to study the first mitotic division and its consequences on the cells that were in G₂ and G₁ phases at the time of gamma irradiation. Untreated material produced a maximum of four nucleoli formed by the nucleolar organizing regions (NORs) on chromosomes 1B and 6B. In irradiated material, additional nucleoli were noted that are due to the activation of the NORs on chromosome 1A in micronuclei. The onset of mitosis was highly significantly retarded in comparison to the control due to checkpoints in the G₂ phase for the repairing of damaged DNA. This study is the first to report on the appearance of nucleoli in micronuclei as well as activation of NORs in the micronuclei that are inactive in the nucleus and the effect of chromosome doubling on nucleolar activity in the event of unsuccessful mitotic division.

The evaluation of the efficacy and potential genotoxic hazard of combined SAHA and 5-FU treatment in the chemoresistant colorectal cancer cell lines

5-Fluorouracil (5-FU) is an essential chemotherapeutic drug for colorectal cancer (CRC) treatment. However, the frequent development of drug resistance has dramatically affected its clinical use. Therefore, novel treatment strategies are critical to improving patient outcomes. Herein, we investigated the ability of the epigenetic drug SAHA to increase the sensitivity of chemoresistant CRC cells to 5-FU. In addition, we evaluated the potential genotoxic risk of SAHA+5-FU combination treatment. As a model system, we used three CRC cell lines, HT-29, SW480, and HT-29/EGFP/FUR, differing in their resistance to 5-FU. CRC cell lines were exposed to sub-toxic SAHA concentrations for 24 h, followed by a 48 h treatment with 5-FU. The cytotoxicity of SAHA, 5-FU, and SAHA+5-FU was measured by the MTT test, the genotoxicity by the comet assay, and the micronucleus test. The apoptotic/necrotic activity was assessed using morphological criteria. We found a synergic decrease in the viability of HT-29 and SW480 cells, but not the most resistant HT-29/EGFP/FUR cells after combined SAHA+5-FU exposure compared to 5-FU. Remarkably, SAHA most efficiently induced apoptosis in HT-29/EGFP/FUR cells compared to HT-29 and SW480 cells. Combined SAHA+5-FU treatment resulted in a synergistic increase in apoptotic/necrotic cells in HT-29 cell line, while rather additive/sub-additive effect was determined in the SW480 and HT-29/EGFP/FUR cells. At the same time, however, a synergistic rise in micronuclei was found in CRC cell lines (at least at some concentrations). We have shown that SAHA can sensitize CRC cells to 5-FU; therefore, epigenetic and convential drug combinations could be beneficial for the patients. However, the increase in micronucleus formation after combined SAHA+5-FU treatment indicates a potential health hazard. The clastogenic activity could contribute to cancer heterogeneity, favoring progeny of such aberrant cells to clonal expansion. Therefore, developing new specific epigenetic drugs or nanocarriers for targeted drug delivery might reduce the potential genotoxic risk.

Plant Cytogenetics in the Micronuclei Investigation-The Past, Current Status, and Perspectives

Cytogenetic approaches play an essential role as a quick evaluation of the first genetic effects after mutagenic treatment. Although labor-intensive and time-consuming, they are essential for the analyses of cytotoxic and genotoxic effects in mutagenesis and environmental monitoring. Over the years, conventional cytogenetic analyses were a part of routine laboratory testing in plant genotoxicity. Among the methods that are used to study genotoxicity in plants, the micronucleus test particularly represents a significant force. Currently, cytogenetic techniques go beyond the simple detection of chromosome aberrations. The intensive development of molecular biology and the significantly improved microscopic visualization and evaluation methods constituted significant support to traditional cytogenetics. Over the past years, distinct approaches have allowed an understanding the mechanisms of formation, structure, and genetic activity of the micronuclei. Although there are many studies on this topic in humans and animals, knowledge in plants is significantly limited. This article provides a comprehensive overview of the current knowledge on micronuclei characteristics in plants. We pay particular attention to how the recent contemporary achievements have influenced the understanding of micronuclei in plant cells. Together with the current progress, we present the latest applications of the micronucleus test in mutagenesis and assess the state of the environment.

Blue light induces DNA damage in normal human skin keratinocytes

BACKGROUND

The generation of DNA damage by ultra-violet radiations (UV) is well established, and both the nature of the DNA lesions and their respective DNA repair pathways have largely been described. Besides UV rays, visible light constitutes a very important part of the sun spectrum where blue light is considered a significant contributor to premature aging. However, blue light-induced DNA damage has not been deeply explored yet.

METHODS

In the present study, we assessed in human skin keratinocytes the DNA and chromosome damaging activities of blue light rays (415 nm) as well as their associated DNA repair mechanisms.

RESULTS

Our results demonstrated that blue light induced dose-dependent DNA damage in human keratinocytes. Both oxidative and cyclobutane-pyrimidine-dimer (CPD) DNA lesions were generated. They were repaired through base excision repair (BER) and nucleotide excision repair (NER) pathways, respectively. Moreover, by using the micronucleus assay we demonstrated, for the first time, that a blue wavelength exerted a clastogenic/aneugenic effect in human keratinocytes, leading to chromosome aberration.

CONCLUSION

We concluded that, in normal human keratinocytes, blue light creates genotoxic lesions which might accelerate or at least contribute to premature skin aging.

Targeting DNA Repair Response Promotes Immunotherapy in Ovarian Cancer: Rationale and Clinical Application

Immune checkpoint inhibitors (ICI) have emerged as a powerful oncologic treatment modality for patients with different solid tumors. Unfortunately, the efficacy of ICI monotherapy in ovarian cancer is limited, and combination therapy provides a new opportunity for immunotherapy in ovarian cancer. DNA damage repair (DDR) pathways play central roles in the maintenance of genomic integrity and promote the progression of cancer. A deficiency in DDR genes can cause different degrees of DNA damage that enhance local antigen release, resulting in systemic antitumor immune responses. Thus, the combination of DDR inhibitors with ICI represents an attractive therapeutic strategy with the potential to improve the clinical outcomes of patients with ovarian cancer. In this review, we provide an overview of the interconnectivity between DDR pathway deficiency and immune response, summarize available clinical trials on the combination therapy in ovarian cancer, and discuss the potential predictive biomarkers that can be utilized to guide the use of combination therapy.

Extenuating role of lycopene against 254-nm UV-C radiation-mediated damages in Allium cepa L. roots

UV-C exposure has become a crucial risk for living organisms due to its widespread use in sterilization. In this study, the mitigating potential of lycopene was investigated against UV-C-mediated toxicity in Allium cepa L. roots. Allium bulbs were separated into six groups which treated with tap water, 215 mg/L lycopene, 430 mg/L lycopene, 254-nm UV radiation, 215 mg/L lycopene + 254-nm UV radiation, and 430 mg/L lycopene + 254-nm UV radiation. Germination percentage, root length, weight gain, mitotic index, micronucleus frequency, and other chromosomal aberrations as well as meristematic cell damages were investigated in all groups. Malondialdehyde level and the activities of superoxide dismutase and catalase enzymes were also analyzed to understand the severity of oxidative stress. UV-C radiation was revealed to negatively affect all parameters investigated, while the mitigating activities of lycopene against UV-C-mediated toxicity were dose-dependent. Therefore, the study evidently demonstrated the promising potential of lycopene in the protection against the detrimental effects of UV-C exposure in A. cepa.

A new 3D model for genotoxicity assessment: EpiSkin™ Micronucleus Assay

The European Regulation on Cosmetics (no. 1223/2009) has prohibited the use of animals in safety testing since March 2009 for ingredients used in cosmetics. Irreversible events at the chromosome level (clastogenesis and aneugenesis) are commonly evaluated by scoring either micronuclei or chromosome aberrations using cell-based genotoxicity assays. Like most in vitro genotoxicity assays, the 2D in vitro micronucleus assay exhibits a poor specificity and does not mimic the dermal route. To address these limitations, the current project aims to develop and validate a 3D micronucleus assay using the EpiSkin™ model. This project is scientifically supported by the Cosmetics Europe Genotoxicity Task Force. In a first step, two key criteria for the development of micronucleus assay, namely, the sufficient yield of cells from the EpiSkin™ model and an acceptable proliferation rate of the basal layer, were assessed and demonstrated. Subsequently, six chemicals (vinblastine, n-ethylnitrosourea, β-butyrolactone, 2-acetylaminofluorene, 2,4-dichlorophenoland d-limonene) were evaluated in the EpiSkin™ Micronucleus Assay. At least two independent experiments using 48- and 72-h incubations were performed for each chemical. Results showed good inter-experimental reproducibility, as well as the correct identification of all six tested chemicals. The metabolism of 2-acetylaminofluorene on the EpiSkin™ model was also investigated and confirmed by the formation of an intermediate metabolite (2-aminofluorene). These preliminary results from the EpiSkin™ Micronucleus Assay indicate that it is a promising in vitro assay for assessing genotoxicity. The availability and suitability of this test method contribute significantly to the development of non-animal testing methods in China and its impact on the worldwide field.

Progressive use of multispectral imaging flow cytometry in various research areas

Multi-spectral imaging flow cytometry (MIFC) has become one of the most powerful technologies for investigating general analytics, molecular and cell biology, biotechnology, medicine, and related fields. It combines the capabilities of the morphometric and photometric analysis of single cells and micrometer-sized particles in flux with regard to thousands of events. It has become the tool of choice for a wide range of research and clinical applications. By combining the features of flow cytometry and fluorescence microscopy, it offers researchers the ability to couple the spatial resolution of multicolour images of cells and organelles with the simultaneous analysis of a large number of events in a single system. This provides the opportunity to visually confirm findings and collect novel data that would otherwise be more difficult to obtain. This has led many researchers to design innovative assays to gain new insight into important research questions. To date, it has been successfully used to study cell morphology, surface and nuclear protein co-localization, protein-protein interactions, cell signaling, cell cycle, cell death, and cytotoxicity, intracellular calcium, drug uptake, pathogen internalization, and other applications. Herein we describe some of the recent advances in the field of multiparametric imaging flow cytometry methods in various research areas.

Characterization of acute toxicity, genotoxicity, and oxidative stress of dimethoate in Rhinella arenarum larvae

There is a great concern worldwide about the global decline of amphibians, particularly by agrochemical pollution. The aim of this study was to assess oxidative stress and genotoxicity of a commercial formulation of the insecticide dimethoate in Rhinella arenarum larvae, using sublethal biomarkers. The 24- and 96-h LC50 values of dimethoate to R. arenarum were 48.81 and 38.86 mg L^-1, while the 96-h no observed effect concentration (NOEC) value was 20 mg L^-1. For sublethal biomarker assays, R. arenarum larvae were exposed to 1.25, 2.5, and 5% of the 96-h NOEC (0.25, 0.5, and 1 mg L^-1 dimethoate, respectively). After 96 h of exposure, inhibition of catalase (CAT) and glutathione S-transferase (GST) activities were registered. Also, an increased superoxide dismutase (SOD) activity was observed in larvae exposed to the highest concentration (1 mg L^-1). Lipid peroxidation by increased thiobarbituric acid reactive substance levels in larvae exposed to 0.5 and 1 mg L^-1 was detected. No differences in micronuclei frequency between treatments and negative control were observed. These results demonstrate the oxidative toxicity of dimethoate at sublethal concentrations in Rhinella arenarum larvae. The disruption of defense mechanisms may contribute to a deleterious impact on amphibian populations from habitats exposed to this organophosphorus insecticide.