Heat stress impairs centromere structure and segregation of meiotic chromosomes in Arabidopsis

Heat stress is a major threat to global crop production, and understanding its impact on plant fertility is crucial for developing climate-resilient crops. Despite the known negative effects of heat stress on plant reproduction, the underlying molecular mechanisms remain poorly understood. Here, we investigated the impact of elevated temperature on centromere structure and chromosome segregation during meiosis in Arabidopsis thaliana. Consistent with previous studies, heat stress leads to a decline in fertility and micronuclei formation in pollen mother cells. Our results reveal that elevated temperature causes a decrease in the amount of centromeric histone and the kinetochore protein BMF1 at meiotic centromeres with increasing temperature. Furthermore, we show that heat stress increases the duration of meiotic divisions and prolongs the activity of the spindle assembly checkpoint during meiosis I, indicating an impaired efficiency of the kinetochore attachments to spindle microtubules. Our analysis of mutants with reduced levels of centromeric histone suggests that weakened centromeres sensitize plants to elevated temperature, resulting in meiotic defects and reduced fertility even at moderate temperatures. These results indicate that the structure and functionality of meiotic centromeres in Arabidopsis are highly sensitive to heat stress, and suggest that centromeres and kinetochores may represent a critical bottleneck in plant adaptation to increasing temperatures.

The proteomic landscape of genotoxic stress-induced micronuclei

Micronuclei (MN) are induced by various genotoxic stressors and amass nuclear- and cytoplasmic-resident proteins, priming the cell for MN-driven signaling cascades. Here, we measured the proteome of micronuclear, cytoplasmic, and nuclear fractions from human cells exposed to a panel of six genotoxins, comprehensively profiling their MN protein landscape. We find that MN assemble a proteome distinct from both surrounding cytoplasm and parental nuclei, depleted of spliceosome and DNA damage repair components while enriched for a subset of the replisome. We show that the depletion of splicing machinery within transcriptionally active MN contributes to intra-MN DNA damage, a known precursor to chromothripsis. The presence of transcription machinery in MN is stress-dependent, causing a contextual induction of MN DNA damage through spliceosome deficiency. This dataset represents a unique resource detailing the global proteome of MN, guiding mechanistic studies of MN generation and MN-associated outcomes of genotoxic stress.

A comparative study on chromium-induced micronuclei assessment in the peripheral blood of Hsd:ICR mice

This study investigated the genotoxic effects of chromium (Cr) in Hsd:ICR mice, considering factors such as oxidative state, apoptosis, exposure pathway, duration, pregnancy, and transplacental exposure. Genotoxicity was assessed using the erythrocytes' micronucleus (MN) assay, while apoptosis was evaluated in nucleated blood cells. The results showed that Cr(III) (CrK(SO4 )2 and CrCl3 ) did not induce any marked genotoxic damage. However, Cr(VI) (CrO3 , K2 Cr2 O7 , Na2 Cr2 O7 , and K2 CrO4 ) produced varying degrees of genotoxicity, with CrO3 being the most potent. MN frequencies increased following 24-h exposure, with a greater effect in male mice. Administering 20 mg/kg of CrO3 via gavage did not lead to significant effects compared to intraperitoneal administration. Short-term oral treatment with a daily dose of 8.5 mg/kg for 49 days elevated MN levels only on day 14 after treatment. Pregnant female mice exposed to CrO3 on day 15 of pregnancy exhibited reduced genotoxic effects compared to nonpregnant animals. However, significant increases in MN levels were found in their fetuses starting 48 h after exposure. In summary, data indicate the potential genotoxic effects of Cr, with Cr(VI) forms inducing higher genotoxicity than Cr(III). These findings indicate that gender, exposure route, and pregnancy status might influence genotoxic responses to Cr.

End resection and telomere healing of DNA double-strand breaks during nematode programmed DNA elimination

Most DNA double-strand breaks (DSBs) are harmful to genome integrity. However, some forms of DSBs are essential to biological processes, such as meiotic recombination and V(D)J recombination. DSBs are also required for programmed DNA elimination (PDE) in ciliates and nematodes. In nematodes, the DSBs are healed with telomere addition. While telomere addition sites have been well-characterized, little is known regarding the DSBs that fragment nematode chromosomes. Here, we used embryos from the nematode Ascaris to study the timing of PDE breaks and examine the DSBs and their end processing. Using END-seq, we characterize the DSB ends and demonstrate that DNA breaks are introduced before mitosis, followed by extensive end resection. The resection profile is unique for each break site, and the resection generates 3' overhangs before the addition of telomeres. Interestingly, telomere healing occurs much more frequently on retained DSB ends than on eliminated ends. This biased repair of the DSB ends in Ascaris may be due to the sequestration of the eliminated DNA into micronuclei, preventing their ends from telomere healing. Additional DNA breaks occur within the eliminated DNA in both Ascaris and Parascaris, ensuring chromosomal breakage and providing a fail-safe mechanism for nematode PDE.

Toxoplasma gondii infection-induced host cellular DNA damage is strain-dependent and leads to the activation of the ATM-dependent homologous recombination pathway

Toxoplasma gondii is a globally occurring apicomplexan parasite that infects humans and animals. Globally, different typical and atypical haplotypes of T. gondii induce varying pathologies in hosts. As an obligate intracellular protozoon, T. gondii was shown to interfere with host cell cycle progression, leading to mitotic spindle alteration, chromosome segregation errors and cytokinesis failure which all may reflect chromosomal instability. Referring to strain-dependent virulence, we here studied the potential of different T. gondii strains (RH, Me49 and NED) to drive DNA damage in primary endothelial host cells. Utilizing microscopic analyses, comet assays and γ-H2AX quantification, we demonstrated a strain-dependent induction of binucleated host cells, DNA damage and DNA double strand breaks, respectively, in T. gondii-infected cells with the RH strain driving the most prominent effects. Interestingly, only the NED strain significantly triggered micronuclei formation in T. gondii-infected cells. Focusing on the RH strain, we furthermore demonstrated that T. gondii-infected primary host cells showed a DNA damage response by activating the ATM-dependent homologous recombination (HR) pathway. In contrast, key molecules of the nonhomologous DNA end joining (NHEJ) pathway were either not affected or downregulated in RH-infected host cells, suggesting that this pathway is not activated by infection. In conclusion, current finding suggests that T. gondii infection affects the host cell genome integrity in a strain-dependent manner by causing DNA damage and chromosomal instability.

Telomere length and micronuclei trajectories in APP/PS1 mouse model of Alzheimer's disease: Correlating with cognitive impairment and brain amyloidosis in a sexually dimorphic manner

Although studies have demonstrated that genome instability is accumulated in patients with Alzheimer's disease (AD), the specific types of genome instability linked to AD pathogenesis remain poorly understood. Here, we report the first characterization of the age- and sex-related trajectories of telomere length (TL) and micronuclei in APP/PS1 mice model and wild-type (WT) controls (C57BL/6). TL was measured in brain (prefrontal cortex, cerebellum, pituitary gland, and hippocampus), colon and skin, and MN was measured in bone marrow in 6- to 14-month-old mice. Variation in TL was attributable to tissue type, age, genotype and, to a lesser extent, sex. Compared to WT, APP/PS1 had a significantly shorter baseline TL across all examined tissues. TL was inversely associated with age in both genotypes and TL shortening was accelerated in brain of APP/PS1. Age-related increase of micronuclei was observed in both genotypes but was accelerated in APP/PS1. We integrated TL and micronuclei data with data on cognition performance and brain amyloidosis. TL and micronuclei were linearly correlated with cognition performance or Aβ40 and Aβ42 levels in both genotypes but to a greater extent in APP/PS1. These associations in APP/PS1 mice were dominantly driven by females. Together, our findings provide foundational knowledge to infer the TL and micronuclei trajectories in APP/PS1 mice during disease progression, and strongly support that TL attrition and micronucleation are tightly associated with AD pathogenesis in a female-biased manner.

Insights into embryonic chromosomal instability: mechanisms of DNA elimination during mammalian preimplantation development

Mammalian preimplantation embryos often contend with aneuploidy that arose either by the inheritance of meiotic errors from the gametes, or from mitotic mis-segregation events that occurred following fertilization. Regardless of the origin, mis-segregated chromosomes become encapsulated in micronuclei (MN) that are spatially isolated from the main nucleus. Much of our knowledge of MN formation comes from dividing somatic cells during tumorigenesis, but the error-prone cleavage-stage of early embryogenesis is fundamentally different. One unique aspect is that cellular fragmentation (CF), whereby small subcellular bodies pinch off embryonic blastomeres, is frequently observed. CF has been detected in both in vitro and in vivo-derived embryos and likely represents a response to chromosome mis-segregation since it only appears after MN formation. There are multiple fates for MN, including sequestration into CFs, but the molecular mechanism(s) by which this occurs remains unclear. Due to nuclear envelope rupture, the chromosomal material contained within MN and CFs becomes susceptible to double stranded-DNA breaks. Despite this damage, embryos may still progress to the blastocyst stage and exclude chromosome-containing CFs, as well as non-dividing aneuploid blastomeres, from participating in further development. Whether these are attempts to rectify MN formation or eliminate embryos with poor implantation potential is unknown and this review will discuss the potential implications of DNA removal by CF/blastomere exclusion. We will also extrapolate what is known about the intracellular pathways mediating MN formation and rupture in somatic cells to preimplantation embryogenesis and how nuclear budding and DNA release into the cytoplasm may impact overall development.

Morphological markers of chromosomal instability as predictors of malignancy in pleural effusion

BACKGROUND

Malignancy in pleural effusion is an indication of poor prognosis. The distinction between malignant cells and reactive mesothelial cells in effusion cytology is sometimes difficult and requires ancillary techniques. Evaluation of morphological indicators of chromosomal instability (CI) like micronuclei (MN), chromatin bridging (CB), nuclear budding (NB), and multipolar mitosis (MM) on routine cytology smears is a promising tool to distinguish malignant from benign ascitic fluids. However, it has been scarcely evaluated in pleural effusions. The present study was conducted to evaluate the diagnostic value of these markers in differentiating between malignant and benign pleural fluids.

METHODS

It is a cross sectional study in which a total of 72 pleural fluid samples over a period of 2 years received in the cytology department of the hospital were evaluated. The cytological analysis was done by two independent cytopathologists and interpreted as either malignant or benign. Four morphological markers of CI were counted in the May-Grünwald Giemsa (MGG) stained smears of all the cases and the score was compared with the conventional cyto-morphological diagnosis.

RESULTS

Out of 72 cases, there were 42 malignant and 30 benign effusions on cytological examination. The mean score of micronuclei count, nuclear budding, chromatin bridging and multipolar mitosis in malignant effusions were 7.26 ± 2.74, 9.55 ± 5.53, 1.83 ± 1.17, and 2.21 ± 1.62 respectively that was significantly higher than the benign effusions (1 ± 0.71, 1.1 ± 0.86, 0.38 ± 0.50, and 0.15 ± 0.37 respectively) (p < .05). On Receiver operating characteristic (ROC) curve analysis, a cut-off of 5 for the MN count had a sensitivity of 88% and specificity of 100% in detecting malignant pleural effusion [Area under curve (AUC) 95.8%, p < .001].

CONCLUSION

Evaluation of morphological indicators of CI on routine MGG stained smears is a simple and cost-effective method to differentiate between benign and malignant pleural fluids.

Genoprotective role of pembrolizumab liposome in isolated lymphocytes from head and neck squamous cell carcinoma patients compared to those from healthy individuals in vitro

Pembrolizumab has shown significant anticancer effects against various human cancers. The present study investigated the effects of pembrolizumab liposome and nano (naked) forms in treated lymphocytes from head and neck squamous cell carcinoma (HNSCC) patients compared to healthy individuals. The level of oxidative DNA damage induced by hydrogen peroxide (H2O2) was also investigated. A concentration of 10 µg/ml of pembrolizumab liposome was used to treat the lymphocytes in the Comet and micronucleus assays based on the preliminary dosage optimization tests. To determine the cellular pathways involved in the protective role of pembrolizumab against H2O2, several proteins involved in apoptosis (P53, P21 and Bcl-2) were assessed. Pembrolizumab significantly reduced DNA damage and decreased the number of micronuclei in lymphocytes from HNSCC patients (p < 0.01) compared with healthy individuals. The 10 µg/ml of pembrolizumab liposome significantly reduced the oxidative stress induced by H2O2 and was effective in healthy and HNSCC groups using the Comet and micronucleus assays (p < 0.001). To our knowledge, this is the first report of pembrolizumab in liposome and naked forms exhibiting a protective effect on DNA damage in the treatment of HNSCC patients.

Assessment of genotoxic instability markers in peripheral blood lymphocytes of breast cancer patients: a case control study

Changes in genetic constitution of an individual leads to uncontrollable cell growth and tumour formation. The acquisition of genomic instability predisposes cells to accumulate stable genome mutations causing carcinogenesis. The cytokinesis-block micronucleus cytome assay (CBMN), a well-established marker assay for chromosomal mutagen sensitivity, was applied in this study enrolling breast cancer patients and age and sex-matched controls. This work aimed to assess the predictive value of the frequency of genotoxic markers in peripheral blood lymphocytes for the risk/susceptibility of breast cancer. Samples from a hundred untreated breast cancer patients and age and sex matched controls were enrolled in the study from Government Medical College, Alappuzha. The genomic instability was assessed using cytokinesis block micronucleus assay where cytome events were marked. The results showed a significant increase in the frequency of micronucleus, nucleoplasmic bridge, and buds in the binucleated cells of breast cancer patients compared to the control samples. The variability was assessed by CBMN Cyt assay. The frequency of Micronuclei and Nucleoplasmic buds was significantly higher in the patient groups than in the controls (p < 0.0001). In Breast cancer patients, the median (IQR) range of MNi was 12(6), the Nucleoplasmic bridge 3(3) and the Nuclear buds were 2(1) and, in the controls, it was 6(5), 1(2) and 1(1) respectively. A larger difference in the frequency of genetic markers in cancer patients over control cases support a significant role of these markers in the population screening of individuals at high risk of cancer.Communicated by Ramaswamy H. Sarma.

Boveri and beyond: Chromothripsis and genomic instability from mitotic errors

Mitotic cell division is tightly monitored by checkpoints that safeguard the genome from instability. Failures in accurate chromosome segregation during mitosis can cause numerical aneuploidy, which was hypothesized by Theodor Boveri over a century ago to promote tumorigenesis. Recent interrogation of pan-cancer genomes has identified unexpected classes of chromosomal abnormalities, including complex rearrangements arising through chromothripsis. This process is driven by mitotic errors that generate abnormal nuclear structures that provoke extensive yet localized shattering of mis-segregated chromosomes. Here, we discuss emerging mechanisms underlying chromothripsis from micronuclei and chromatin bridges, as well as highlight how this mutational cascade converges on the DNA damage response. A fundamental understanding of these catastrophic processes will provide insight into how initial errors in mitosis can precipitate rapid cancer genome evolution.

In vitro anticancer and antifungal properties of the essential oil from the leaves of Lippia origanoides kunth

The essential oil from Lippia origanoides (EOLO) is employed in traditional medicine as it has both antimicrobial and anti-inflammatory properties. The current investigation first evaluated the EOLO's cytotoxic activity in tumour (SiHa and HT-29) and non-tumour (human lymphocyte) cells by MTT. The effect on ROS production was further evaluated in cancer cells by fluorimetry. The oil's mutagenic and antifungal activities were also evaluated using, respectively, the in vitro micronucleus test and the broth microdilution method. The EOLO displayed significant cytotoxicity in both cancer cell lines, with IC50 values of 20.2 μg/mL and 24.3 μg/mL for HT-29 and for SiHa cell lines, respectively. EOLO increased ROS production, was unable to raise the micronucleus frequencies and significantly reduced the cytokinesis block proliferation indices, revealing its anti-proliferative action. The results demonstrate that EOLO is devoid of mutagenic activity but possesses significant activity against tumour and non-tumour human cells, reinforcing its biological potential.

Exploratory Study on Micronuclei and Metanuclear Abnormalities in Exfoliated Buccal Cells of COVID-19 Suspected Patients

Context

SARS-CoV-2 virus causes COVID-19 by infecting nasal and oral cavities primarily by attaching its spike proteins to ACE 2 receptors expressed in epithelial cells.

Aim

This study was done to evaluate the micronucleated cell count, metanuclear abnormalities, and genotoxic factor in exfoliated buccal mucosal cell among the COVID-19 suspected patients.

Settings and Design

This cross-sectional study was conducted at AIIMS, Mangalagiri, between August and October 2022.

Methods

One hundred COVID-19 suspected patients were recruited for this study after obtaining informed and written consent; buccal smear was obtained and stained for papanicolaou test (PAP). The PAP-stained slides were analyzed for micronuclei (MN), pyknotic, karyolytic, and karyorrhexic cell count, respectively. Based on their reverse transcription-polymerase chain reaction (RT-PCR) report, the patients were grouped into COVID-19 positive and negative groups.

Statistical Analysis

The genotoxicity factor was calculated using the micronucleated cell count from both the groups using mean and standard deviation.

Results

The MN, micronucleated cell, pyknotic, karyolitic, and karyorrhexic cell count in COVID-19 positive patients were 24.12, 15.24, 3.08, 2.88 and 4.40, respectively, than COVID-19 negative patients 5.69, 8.17, 1.08, 1.00 and 2.43, respectively. The genotoxicity factor for SARS-CoV-2 was 2.68 which is a positive genotoxic effect on buccal mucosal cells.

Conclusion

SARS-CoV-2 increases the expression of micronucleated cells, pyknotic cells, karyolytic cells, and karyorhexic cells and concludes SARS-CoV-2 is having cytogenotoxic effect on the buccal mucosal cells. This can be used as a reliable marker in identifying the early carcinogenic effects of virus causing COVID-19.

X-ray and DNA Damage: Limitations of the Dose as a Parameter for In Vitro Studies

A century of studies has demonstrated that the magnitude of a radiation dose determines the extent of its biological effect. However, different types of radiation show different levels of effectiveness. Although all types of X-rays are usually considered to be equivalent, several authors have demonstrated an inverse relationship between photon energy and the biological effectiveness of the X-ray. Nonetheless, the differences among 50-100 keV X-rays are usually considered absent. However, comparing different types of X-rays with different energies is not easy since they are often used with different dose rates, and the latter can be a confounding factor. We compared the biological effectiveness of X-rays with different photon energies but with the same dose rate. Moreover, we also studied X-ray with different dose rates but the same photon energy. Biological effectiveness was assessed measuring DNA damage and cell survival. We confirmed that both the dose rate and photon energy influence the effectiveness of an X-ray. Moreover, we observed that differences in the 50-100 keV range are detectable after controlling for dose-rate variations. Our results, confirming those of previous studies in a more consistent way (and accompanied by hypotheses on the importance of the number of incident photons), underline the limitations of using the dose as the sole parameter for in vitro studies.

Protective Effects of Micronutrient Supplements, Phytochemicals and Phytochemical-Rich Beverages and Foods Against DNA Damage in Humans: A Systematic Review of Randomized Controlled Trials and Prospective Studies

Accumulation of deoxyribonucleic acid (DNA) damage diminishes cellular health, increases risk of developmental and degenerative diseases, and accelerates aging. Optimizing nutrient intake can minimize accrual of DNA damage. The objectives of this review are to: 1) assemble and systematically analyze high-level evidence for the effect of supplementation with micronutrients and phytochemicals on baseline levels of DNA damage in humans, and 2) use this knowledge to identify which of these essential micronutrients or nonessential phytochemicals promote DNA integrity in vivo in humans. We conducted systematic literature searches of the PubMed database to identify interventional, prospective, cross-sectional, or in vitro studies that explored the association between nutrients and established biomarkers of DNA damage associated with developmental and degenerative disease risk. Biomarkers included lymphocyte chromosome aberrations, lymphocyte and buccal cell micronuclei, DNA methylation, lymphocyte/leukocyte DNA strand breaks, DNA oxidation, telomere length, telomerase activity, and mitochondrial DNA mutations. Only randomized, controlled interventions and uncontrolled longitudinal intervention studies conducted in humans were selected for evaluation and data extraction. These studies were ranked for the quality of their study design. In all, 96 of the 124 articles identified reported studies that achieved a quality assessment score ≥ 5 (from a maximum score of 7) and were included in the final review. Based on these studies, nutrients associated with protective effects included vitamin A and its precursor β-carotene, vitamins C, E, B1, B12, folate, minerals selenium and zinc, and phytochemicals such as curcumin (with piperine), lycopene, and proanthocyanidins. These findings highlight the importance of nutrients involved in (i) DNA metabolism and repair (folate, vitamin B12, and zinc) and (ii) prevention of oxidative stress and inflammation (vitamins A, C, E, lycopene, curcumin, proanthocyanidins, selenium, and zinc). Supplementation with certain micronutrients and their combinations may reduce DNA damage and promote cellular health by improving the maintenance of genome integrity.

ATR promotes clearance of damaged DNA and damaged cells by rupturing micronuclei

The human ataxia telangiectasia mutated and Rad3-related (ATR) kinase functions in the nucleus to protect genomic integrity. Micronuclei (MN) arise from genomic and chromosomal instability and cause aneuploidy and chromothripsis, but how MN are removed is poorly understood. Here, we show that ATR is active in MN and promotes their rupture in S phase by phosphorylating Lamin A/C at Ser395, which primes Ser392 for CDK1 phosphorylation and destabilizes the MN envelope. In cells harboring MN, ATR or CDK1 inhibition reduces MN rupture. Consequently, ATR inhibitor (ATRi) diminishes activation of the cytoplasmic DNA sensor cGAS and compromises cGAS-dependent autophagosome accumulation in MN and clearance of micronuclear DNA. Furthermore, ATRi reduces cGAS-mediated senescence and killing of MN-bearing cancer cells by natural killer cells. Thus, in addition to the canonical ATR signaling pathway, an ATR-CDK1-Lamin A/C axis promotes MN rupture to clear damaged DNA and cells, protecting the genome in cell populations through unexpected cell-autonomous and cell-non-autonomous mechanisms.

Lymnaea stagnalis and Ophryotrocha diadema as Model Organisms for Studying Genotoxicological and Physiological Effects of Benzophenone-3

Benzophenone-3 (BP-3) is a lipophilic organic compound that occurs naturally in flower pigments. Since it adsorbs ultraviolet (UV) radiation in the UVA and UVB regions, it is one of the most common UV filters found in sunscreen and cosmetic products. We explored by in vivo micronuclei (MNi) assay the genotoxic effects of BP-3 on hemocytes from the freshwater gastropod Lymnaea stagnalis. We also studied its possible toxic effects on life-history traits: body growth in L. stagnalis and egg production of both L. stagnalis and the marine polychaete worm Ophryotrocha diadema. Adult individuals were exposed to increasing concentrations of BP-3 (0.025, 0.050, 0.100, and 0.200 mg/L) once a week for 4 weeks. In L. stagnalis, exposure to BP-3 at concentrations of both 0.2 and 0.1 mg/L produced genotoxic effects on the micronuclei frequencies, but only concentrations of 0.2 mg/L affected the NBUDs frequencies. Similarly, negative effects on body growth were observed at the concentrations of 0.2 and 0.1 mg/L and a significant reduction of egg production at 0.2 mg/L. In O. diadema, a negative correlation between egg production and increasing BP-3 concentrations was observed. Our findings suggest the need for more stringent measures to reduce the presence of BP-3 in the environment.

Genomic Instability and Cytotoxicity Evaluation of Two Communities Exposed to Pesticides in the Mexicali Valley by the L-CBMN Assay

The continuous biomonitoring of a population directly or indirectly exposed to pesticides could be an additional tool for decision makers to improve their health conditions. In this work, we performed biomonitoring on two groups of people from the Mexicali Valley who were continuously exposed to pesticides using the cytokinesis-block micronucleus cytome assay (L-CBMN) to evaluate cytotoxic and genotoxic damage in human peripheral blood lymphocytes. The study groups comprised 14 indigenous Cucapah with non-vegetarian habits (NV group) from Ejido el Mayor (32.12594°, -115.27265°) and 21 lacto-ovo vegetarian (LOV) persons from the Seventh-day Adventist Church of Ejido Vicente Guerrero (32.3961°, -115.14023°). The L-CBMN assay determines the nuclear division index (NDI), apoptosis, necrosis, micronuclei (MNs), nuclear buds (NBUDs), and nucleoplasmic bridges (NPBs). Our results show that, regardless of diet or daily habits, both the studied groups presented with cytogenotoxic damage compared with non-exposed pesticide individuals, without modifications to the nuclear division index. In the rest of the evaluated biomarkers, the NV group exhibited greater cytotoxic and genotoxic damage than the LOV group. Nevertheless, individuals practicing a lacto-ovo vegetarian diet (LOV) showed lower damage than those with non-vegetarian habits (NV), suggesting a better antioxidant response that helps decrease the genotoxic damage due to the enhanced intake of folates and antioxidants from a plant-based diet.

Chronic exposure of industrial grade calcium carbide and ethylene glycol exert genotoxic effect in Wistar albino rats

OBJECTIVES

Calcium carbide (CaC2) and ethylene glycol (EG) are the two commonly used fruit ripening agents. The toxic effects of these chemicals on internal organs were reported in experimental animals. Even though the adverse effects of these compounds have been investigated for many years, there are no sufficient data available with regard to genotoxic effects. The present study evaluates the genotoxic effect of chronic exposures of CaC2 and EG in Wistar albino rats.

METHODS

CaC2 and EG were administered to the rats orally for 180 days. Chromosomal aberrations and micronuclei formation were analysed in bone marrow and peripheral blood cells. Comet assay was performed to analyse the DNA strand break. The toxic effects of the chemicals were analysed by MTT assay with normal human intestinal epithelial (IEC-6) cells.

RESULTS

Upon chronic exposure, CaC2 and EG caused chromosomal aberrations, micronuclei formation and  DNA strand breaks extensively in bone marrow and peripheral blood cells. In MTT assay, the chemicals were found to be toxic to IEC-6 cells with IC50 values at 160 and 200 μg/mL for CaC2 and EG, respectively.

CONCLUSIONS

The results show that these chemicals have a potential to cause genomic level of toxicity which may lead to carcinogenic event at a chronic level exposure. The study warns to reinforce the administrative measures against the use of CaC2 and EG for fruit ripening process.

Cytogenetic Studies on Genoprotective Effect of Rosa damascena Mill. Hydrosol in Plant and Lymphocyte Test Systems

Bulgarian Rosa damascena Mill. is has been known since ancient times for its high-quality oil, hydrosol, and other aromatic products. Rose hydrosol has various biological activities, but no research on its anticytotoxic/antigenotoxic effects exists. This study aimed to assess its defense potential against the genotoxin N-methyl-N'-nitro-N-nitrosoguanidine and to test its cytotoxic/genotoxic activity in plant and human lymphocyte test systems. Endpoints for cytotoxicity (mitotic index and nuclear division index) and genotoxicity (chromosome aberration and micronuclei) were used. Hydrosol was applied as a single treatment in concentrations ranging from 3% to 20% (4 h) to assess its cytotoxic and genotoxic effects. Its protective potential against MNNG was tested by applying an experimental scheme involving (i) conditioning treatment with non-toxic or slightly toxic concentrations of hydrosol, followed by genotoxin challenge (50 μg/mL) with a 4 h intertreatment time and (ii) treatment with hydrosol and mutagen with no time between the treatments. Hydrosol induces low cytotoxicity and clastogenicity, demonstrating cytoprotective/genoprotective effects against the mutagen in both applied test systems. The hydrosol defense potential was expressed by a more than twofold reduction in both chromosomal aberrations and micronuclei and by enhancing the mitotic activity compared with that of the mutagen, regardless of the experimental conditions. The results are promising for further hydrosol applications in pharmaceutical and medical practice.

Regular Sport Activity Is Able to Reduce the Level of Genomic Damage

Regular physical activity is considered one of the most valid tools capable of reducing the risk of onset of many diseases in humans. However, it is known that intense physical activity can induce high levels of genomic damage, while moderate exercise can elicit a favorable adaptive response by the organism. We evaluated, by the buccal micronuclei assay, the frequencies of micronuclei, nuclear buds and binucleated cells in a sample of amateur athletes practicing different disciplines, comparing the obtained data with those of subjects who practiced sports just occasionally and subjects that did not practice sport at all. The aim was to evaluate whether physical activity affects background levels of genomic damage and whether the different sports disciplines, as well as some gene polymorphisms, differentially affect these levels. A total of 206 subjects, 125 athletes and 81 controls, were recruited. Athletes showed significantly lower values of micronuclei, nuclear buds and binucleated cells with respect to controls. Sprinters and Martial Artists displayed significantly higher frequencies of micronuclei than other categories of athletes. Finally, neither sex nor gene polymorphisms seemed to influence the levels of genomic damage, confirming that the observed genomic damage is probably due to the nature of the sport activity.

Biological response to the continuous occupational exposure to antineoplastic drugs and radionuclides

PURPOSE

Antineoplastic drugs and radioiodine are recognized occupational risk factors affecting the genetic material of exposed persons. To assess cytogenetic damage and evaluate the presence of chromosomal instability during occupational exposure, a biomonitoring study was performed using a chromosomal aberration assay and a cytokinesis-block micronucleus (CBMN) test.

MATERIALS AND METHODS

Blood samples from 314 healthy donors divided into 3 groups (control, exposed to antineoplastic drugs and exposed to radioiodine) were collected and cytogenetically analyzed.

RESULTS

There was an increase in almost all analyzed parameters registered in the exposed persons. Chromatid breaks were higher in the subjects exposed to antineoplastic drugs, while dicentrics and premature centromere division (PCD) parameters were higher in nuclear medicine workers. The total number of micronuclei was higher in both groups of the exposed. The correlation analysis indicated the association of dicentrics, acentrics, chromosome and chromatid break with PCDs in both groups of the exposed, and micronuclei and nucleoplasmic bridges with PCDs in the subjects exposed to radioiodine. The discriminant analysis marked off PCD1-5 as the best predictor of exposure. Age, sex, sampling season and duration of exposure significantly influenced the analyzed parameters, while smoking habits did not show any influence.

CONCLUSION

Based on the observed results, premature centromere division can be considered a valuable parameter of genotoxic risk for individuals occupationally exposed to low doses of ionizing radiation.

Twenty years of merotelic kinetochore attachments: a historical perspective

Micronuclei, small DNA-containing structures separate from the main nucleus, were used for decades as an indicator of genotoxic damage. Micronuclei containing whole chromosomes were considered a biomarker of aneuploidy and were believed to form, upon mitotic exit, from chromosomes that lagged behind in anaphase as all other chromosomes segregated to the poles of the mitotic spindle. However, the mechanism responsible for inducing anaphase lagging chromosomes remained unknown until just over twenty years ago. Here, I summarize what preceded and what followed this discovery, highlighting some of the open questions and opportunities for future investigation.

Evaluation of Cytogenetic Alterations in Patients of Chronic Kidney Disease

Introduction

In recent years, there has been a rise in chronic kidney disease (CKD), and it has been estimated that by 2040, CKD will be the fifth most common cause of death globally. In addition to diabetes, hypertension, obesity, hyperlipidemia, and nonalcoholic fatty liver disease commonly associated with CKD, exposure to various toxins as a result of pollution or industrial disasters is also discussed as a cause for multi-organ pathology including kidneys. Although few cytogenetic studies were undertaken to assess the genetic damage in survivors of the disaster, no studies are available on the cytogenetic damage of toxic-gas exposed population having CKD. Therefore, the present multi-group cross-sectional study was undertaken to assess the independent role of CKD as well as toxic gas exposure on cytogenetics.

Methods

The cytogenetic alterations were evaluated through chromosomal aberration analysis and micronuclei assay. The study included 608 study participants divided into four groups on the basis of history of exposure to the leaked gas and presence or absence of CKD.

Results

The results of the study showed no statistically significant difference in cytogenetic damage between gas-exposed and non-exposed patients of CKD, whereas significantly higher cytogenetic damage was observed among gas-exposed participants having CKD compared to gas-exposed participants free from CKD, suggesting that cytogenetic changes could be due to CKD itself.

Conclusions

Thus, to conclude, the cytogenetic alterations observed in the study can be partly attributed to the disease itself.

Teratogen Potential Evaluation of the Aqueous and Hydroalcoholic Leaf Extracts of Crataegus oxyacantha in Pregnancy Rats

Crataegus oxyacantha is used in the treatment of cardiovascular diseases. The aim of this study was to evaluate the transplacental genotoxicity effect of aqueous (AE) and hydroalcoholic extract (HE) of leaves C. oxyacantha in a rat model and the quantification of malondialdehyde (MDA) in the liver. Three different doses of the AE and HE of the C. oxyacantha leaf were administered orally (500, 1000 and 2000 mg/kg) to Wistar rats during 5 days through the pregnancy term (16-21 days), and sampling in rats occurred every 24 h during the last 6 days of gestation, while only one sample was taken in neonates at birth. A sample of the mother's and the neonate's liver was taken for the determination of MDA. The results show that, at the hepatic level, the evaluated doses of extracts C. oxyacantha in pregnant rats and their pups did not show cytotoxicity. However, the AE and HE generated cytotoxic and genotoxic damage in the short term. On the other hand, only the AE showed a teratogenic effect. Based on these results, the AE and HE of the C. oxyacantha leaf should not be administered during pregnancy.

Metastatic Adrenocortical Carcinoma With Chromothripsis: A Case Report and Literature Review

Metastatic adrenocortical carcinoma (ACC) often has a poor outcome, with a five-year survival of less than 25%. We report a rare case of metastatic ACC with a myxoid variant with chromothripsis. We review the histologic variants of ACC, including myxoid type, molecular drivers, and current and investigational therapies for adrenocortical carcinoma. We also discuss the mechanism of chromothripsis, chromothripsis in ACC tumorigenesis, and propose potential therapies targeting chromothripsis.

Chromosomal Instability in Genome Evolution: From Cancer to Macroevolution

The integrity of the genome is crucial for the survival of all living organisms. However, genomes need to adapt to survive certain pressures, and for this purpose use several mechanisms to diversify. Chromosomal instability (CIN) is one of the main mechanisms leading to the creation of genomic heterogeneity by altering the number of chromosomes and changing their structures. In this review, we will discuss the different chromosomal patterns and changes observed in speciation, in evolutional biology as well as during tumor progression. By nature, the human genome shows an induction of diversity during gametogenesis but as well during tumorigenesis that can conclude in drastic changes such as the whole genome doubling to more discrete changes as the complex chromosomal rearrangement chromothripsis. More importantly, changes observed during speciation are strikingly similar to the genomic evolution observed during tumor progression and resistance to therapy. The different origins of CIN will be treated as the importance of double-strand breaks (DSBs) or the consequences of micronuclei. We will also explain the mechanisms behind the controlled DSBs, and recombination of homologous chromosomes observed during meiosis, to explain how errors lead to similar patterns observed during tumorigenesis. Then, we will also list several diseases associated with CIN, resulting in fertility issues, miscarriage, rare genetic diseases, and cancer. Understanding better chromosomal instability as a whole is primordial for the understanding of mechanisms leading to tumor progression.

A tubule-sheet continuum model for the mechanism of nuclear envelope assembly

Nuclear envelope (NE) assembly defects cause chromosome fragmentation, cancer, and aging. However, major questions about the mechanism of NE assembly and its relationship to nuclear pathology are unresolved. In particular, how cells efficiently assemble the NE starting from vastly different, cell type-specific endoplasmic reticulum (ER) morphologies is unclear. Here, we identify a NE assembly mechanism, "membrane infiltration," that defines one end of a continuum with another NE assembly mechanism, "lateral sheet expansion," in human cells. Membrane infiltration involves the recruitment of ER tubules or small sheets to the chromatin surface by mitotic actin filaments. Lateral sheet expansion involves actin-independent envelopment of peripheral chromatin by large ER sheets that then extend over chromatin within the spindle. We propose a "tubule-sheet continuum" model that explains the efficient NE assembly from any starting ER morphology, the cell type-specific patterns of nuclear pore complex (NPC) assembly, and the obligatory NPC assembly defect of micronuclei.

Evaluation of oxidative stress-mediated cytotoxicity and genotoxicity of copper and flubendiamide: amelioration by antioxidants in vivo and in vitro

Present study was designed to evaluate toxic effects of copper (Cu) (@ 33 mg/kg b.wt.) and flubendimide (Flb) (@ 200 mg/kg b.wt.) alone and/or in combination on blood-biochemical indices, oxidative stress, and drug metabolizing enzymes (DMEs) in vivo in male Wistar rats following oral exposure continuously for 90 days and their immunotoxic (cyto-genotoxic and apoptotic) potential in vitro on thymocytes. In in vivo study, ameliorative potential of α-tocopherol was assessed, whereas α-tocopherol, curcumin, resveratrol, and catechin were evaluated for protective effect in vitro. Significantly (P < 0.05) increased AST activity and increment in total bilirubin, uric acid, creatinine, and BUN levels; however, reduction in total protein, GSH content, reduced activities of SOD and GST, and increased lipid peroxidation and GPx activity with severe degenerative changes in histopathological examination of liver and kidney in group of Cu and Flb were observed. Treatment with α-tocopherol improved biochemical variables, redox status, and histoarchitecture of liver and kidney tissues. Reduced hepatic CYP450, CYPb5, APH, UGT, and GST activities observed in both Cu and α-tocopherol alone and their combination groups, whereas significant increment in Flb alone, while α-tocopherol in combination with xenobiotics improved the activities of hepatic DMEs. Primary cell culture of thymocytes (106 cells/ml) exposed to Cu and Flb each @ 40 μM increased TUNEL+ve cells, micronuclei induction, DNA shearing, and comet formation establishes their apoptotic and genotoxic potential, whereas treatment with antioxidants showed concentration-dependent significant reduction and their order of potency on equimolar concentration (10 μM) basis is: curcumin > resveratrol > catechin = α-tocopherol.

Human myeloid progenitor glucocorticoid receptor activation causes genomic instability, type 1 IFN- response pathway activation and senescence in differentiated microglia; an early life stress model

One form of early life stress, prenatal exposure to glucocorticoids (GCs), confers a higher risk of psychiatric and neurodevelopmental disorders in later life. Increasingly, the importance of microglia in these disorders is recognized. Studies on GCs exposure during microglial development have been limited, and there are few, if any, human studies. We established an in vitro model of ELS by continuous pre-exposure of human iPS-microglia to GCs during primitive hematopoiesis (the critical stage of iPS-microglial differentiation) and then examined how this exposure affected the microglial phenotype as they differentiated and matured to microglia, using RNA-seq analyses and functional assays. The iPS-microglia predominantly expressed glucocorticoid receptors over mineralocorticoid receptors, and in particular, the GR-α splice variant. Chronic GCs exposure during primitive hematopoiesis was able to recapitulate in vivo ELS effects. Thus, pre-exposure to prolonged GCs resulted in increased type I interferon signaling, the presence of Cyclic GMP-AMP synthase-positive (cGAS) micronuclei, cellular senescence and reduced proliferation in the matured iPS-microglia. The findings from this in vitro ELS model have ramifications for the responses of microglia in the pathogenesis of GC- mediated ELS-associated disorders such as schizophrenia, attention-deficit hyperactivity disorder and autism spectrum disorder.

Aurora kinases: Generators of spatial control during mitosis

Cell division events require regulatory systems to ensure that events happen in a distinct order. The classic view of temporal control of the cell cycle posits that cells order events by linking them to changes in Cyclin Dependent Kinase (CDK) activities. However, a new paradigm is emerging from studies of anaphase where chromatids separate at the central metaphase plate and then move to opposite poles of the cell. These studies suggest that distinct events are ordered depending upon the location of each chromosome along its journey from the central metaphase plate to the elongated spindle poles. This system is dependent upon a gradient of Aurora B kinase activity that emerges during anaphase and acts as a spatial beacon to control numerous anaphase/telophase events and cytokinesis. Recent studies also suggest that Aurora A kinase activity specifies proximity of chromosomes or proteins to spindle poles during prometaphase. Together these studies argue that a key role for Aurora kinases is to provide spatial information that controls events depending upon the location of chromosomes or proteins along the mitotic spindle.

Gallic acid a flavonoid isolated from Euphorbia hirta antagonizes gamma radiation induced radiotoxicity in lymphocytes in vitro

OBJECTIVES

The current study was executed to isolate and evaluate gallic acid from Euphorbia hirta for in vitro radioprotective potentials against gamma irradiation caused radiotoxicity in human lymphocytes.

METHODS

The defatted E. hirta plant material was treated to methanol extraction using the soxhlet device. Bioflavonoids were isolated from the E. hirta methanol extract using column chromatography. In human cells exhibited to gamma radiation, separated flavonoid gallic acid was examined for in vitro radioprotective potentials using the micronucleus test, DNA fragmentation assay, superoxide free radical scavenging method, and apoptic assay.

RESULTS

The frequency of micronuclei was considerably declined when cells were preprocessed with gallic acid (25 g/mL) before being exhibited to 2 Gy gamma radiation, as determined by the cytokinesis blocked micronucleus test. Similarly, pre-gamma radiation treatment of human cells with gallic acid led in markedly less DNA injury, as assessed by comet metrics like olive tail moment and percent tail DNA. Gallic acid (25 g/mL) given to lymphocytes prior to gamma irradiation considerably decreased the percentage of apoptotic bodies. Gallic acid also considerably lowered the reactive oxygen species concentrations elicited by gamma radiation.

CONCLUSIONS

Our findings showed that gallic acid protects lymphocytes isolated from human blood from gamma radiation-induced DNA destruction and anti-apoptotic activity, which could be because of inhibition of free radicals formed by gamma radiation as well as the decline of gamma radiation-induced oxidative stress.

Lack of hydroxyurea-associated mutagenesis in pediatric sickle cell disease patients

Hydroxyurea is approved for treating children and adults with sickle cell anemia (SCA). Despite its proven efficacy, concerns remain about its mutagenic and carcinogenic potential that hamper its widespread use. Cell culture- and animal-based investigations indicate that hydroxyurea's genotoxic effects are due to indirect clastogenicity in select cell types when high dose and time thresholds are exceeded (reviewed by Ware & Dertinger, 2021). The current study extends these preclinical observations to pediatric patients receiving hydroxyurea for treatment of SCA. First, proof-of-principle experiments with testicular cancer patients exposed to a cisplatin-based regimen validated the ability of flow cytometric blood-based micronucleated reticulocyte (MN-RET) and PIG-A mutant reticulocyte (MUT RET) assays to detect clastogenicity and gene mutations, respectively. Second, these biomarkers were measured in a cross-sectional study with 26 SCA patients receiving hydroxyurea and 13 SCA patients without exposure. Finally, a prospective study was conducted with 10 SCA patients using pretreatment blood samples and after 6 or 12 months of therapy. Cancer patients exposed to cisplatin exhibited increased MN-RET within days of exposure, while the MUT RET endpoint required more time to reach maximal levels. In SCA patients, hydroxyurea induced MN-RET in both the cross-sectional and prospective studies. However, no evidence of PIG-A gene mutation was found in hydroxyurea-treated children, despite the fact that the two assays use the same rapidly-dividing, highly-exposed cell type. Collectively, these results reinforce the complementary nature of MN-RET and MUT RET biomarkers, and indicate that hydroxyurea can be clastogenic but was not mutagenic in young patients with SCA.

Comparative evaluation of genotoxicity and cytotoxicity of flowable, bulk-fill flowable, and nanohybrid composites in human gingival cells using cytome assay: An in vivo study

Context

Biocompatibility is one of the major prerequisites for safe clinical application of materials. Resin composites release their components into oral environment following restoration which cause adverse reactions.

Aims

To evaluate and compare the genotoxicity and cytotoxicity of flowable, bulk-fill flowable, and nanohybrid composites with glass ionomer cement in human gingival cells using epithelial-based cytome assay.

Methodology

Sixty healthy patients with noncarious cervical lesions were selected and randomly assigned to four groups (n = 15): Group A, glass ionomer cement; Group B, flowable composite; Group C, bulk-fill flowable composite; and Group D, nanohybrid composite. Class V restorations were done in each group with the respective restorative materials. Samples of epithelial cells were collected from gingiva before (control) (T1) and after 10 and 30 days (T2 and T3) postrestoration and examined for the presence of micronuclei and other nuclear anomalies.

Statistical Analysis Used

The results were subjected to statistical analysis using Friedman's test and Kruskal-Wallis test.

Results

The highest level of cytotoxicity was noted at T2 time point with a significant decline at T3 time point. Least cytotoxic damage was exhibited by Group A followed by Group D. Highest cytotoxic effect was shown by Group B followed by Group C. There was no significant level of genotoxicity induced by any of the materials tested at different time points.

Conclusion

There is significant cytotoxicity induced by the tested composite materials which had no long-term effects and no genotoxicity was induced by any of the restorative materials tested.

Cadmium exposure and DNA damage (genotoxicity): a systematic review and meta-analysis

Existing literature suggests an association between chronic cadmium (Cd) exposure and the induction of DNA damage and genotoxicity. However, observations from individual studies are inconsistent and conflicting. Therefore current systematic review aimed to pool evidence from existing literature to synthesize quantitative and qualitative corroboration on the association between markers of genotoxicity and occupational Cd exposed population. Studies that evaluated markers of DNA damage among occupationally Cd-exposed and unexposed workers were selected after a systematic literature search. The DNA damage markers included were chromosomal aberrations (chromosomal, chromatid, sister chromatid exchange), Micronucleus (MN) frequency in mono and binucleated cells (MN with condensed chromatin, lobed nucleus, nuclear buds, mitotic index, nucleoplasmatic bridges, pyknosis, and karyorrhexis), comet assay (tail intensity, tail length, tail moment, and olive tail moment), and oxidative DNA damage (8-hydroxy-deoxyguanosine). Mean differences or standardized mean differences were pooled using a random-effects model. The Cochran-Q test and I² statistic were used to monitor heterogeneity among included studies. Twenty-nine studies with 3080 occupationally Cd-exposed and 1807 unexposed workers were included in the review. Cd among the exposed group was higher in blood [4.77 μg/L (-4.94-14.48)] and urine samples [standardized mean difference 0.47 (0.10-0.85)] than in the exposed group. The Cd exposure is positively associated with higher levels of DNA damage characterized by increased frequency of MN [7.35 (-0.32-15.02)], sister chromatid exchange [20.30 (4.34-36.26)], chromosomal aberrations, and oxidative DNA damage (comet assay and 8OHdG [0.41 (0.20-0.63)]) compared to the unexposed. However, with considerable between-study heterogeneity. Chronic Cd exposure is associated with augmented DNA damage. However, more extensive longitudinal studies with adequate sample sizes are necessary to assist the current observations and promote comprehension of the Cd's role in inducing DNA damage.Prospero Registration ID: CRD42022348874.

NuMA deficiency causes micronuclei via checkpoint-insensitive k-fiber minus-end detachment from mitotic spindle poles

Micronuclei resulting from improper chromosome segregation foster chromosome rearrangements.^1,2 To prevent micronuclei formation in mitosis, the dynamic plus ends of bundled kinetochore microtubules (k-fibers) must establish bipolar attachment with all sister kinetochores on chromosomes,³ whereas k-fiber minus ends must be clustered at the two opposing spindle poles, which are normally connected with centrosomes.⁴ The establishment of chromosome biorientation via k-fiber plus ends is carefully monitored by the spindle assembly checkpoint (SAC).⁵ However, how k-fiber minus-end clustering near centrosomes is maintained and monitored remains poorly understood. Here, we show that degradation of NuMA by auxin-inducible degron technologies results in micronuclei formation through k-fiber minus-end detachment from spindle poles during metaphase in HCT116 colon cancer cells. Importantly, k-fiber minus-end detachment from one pole creates misaligned chromosomes that maintain chromosome biorientation and satisfy the SAC, resulting in abnormal chromosome segregation. NuMA depletion also causes minus-end clustering defects in non-transformed Rpe1 cells, but it additionally induces centrosome detachment from partially focused poles, resulting in highly disorganized anaphase. Moreover, we find that NuMA depletion causes centrosome clustering defects in tetraploid-like cells, leading to an increased frequency of multipolar divisions. Together, our data indicate that NuMA is required for faithful chromosome segregation in human mitotic cells, generally by maintaining k-fiber minus-end clustering but also by promoting spindle pole-centrosome or centrosome-centrosome connection in specific cell types or contexts. Similar to erroneous merotelic kinetochore attachments,⁶ detachment of k-fiber minus ends from spindle poles evades spindle checkpoint surveillance and may therefore be a source of genomic instability in dividing cells.

Effect of Selenium and Lycopene on Radiation Sensitivity in Prostate Cancer Patients Relative to Controls

Almost half of prostate cancer (PC) patients receive radiation therapy as primary curative treatment. In spite of advances in our understanding of both nutrition and the genomics of prostate cancer, studies on the effects of nutrients on the radiation sensitivity of PC patients are lacking. We tested the hypothesis that low plasma levels of selenium and lycopene have detrimental effects on ionising radiation-induced DNA damage in prostate cancer patients relative to healthy individuals. The present study was performed in 106 PC patients and 132 age-matched controls. We found that the radiation-induced micronucleus (MN) and nuclear buds (NBuds) frequencies were significantly higher in PC patients with low selenium (p = 0.008 and p = 0.0006 respectively) or low lycopene (p = 0.007 and p = 0.0006 respectively) levels compared to the controls. The frequency of NBuds was significantly higher (p < 0.0001) in PC patients who had low levels of both selenium and lycopene compared to (i) controls with low levels of both selenium and lycopene and (ii) PC patients with high levels of both selenium and lycopene (p = 0.0001). Our results support the hypothesis that low selenium and lycopene levels increase the sensitivity to radiation-induced DNA damage and suggest that nutrition-based treatment strategies are important to minimise the DNA-damaging effects in PC patients receiving radiotherapy.

Quality and Purity of L929 Cell Cultures: Isoenzyme Profiles As a Sensitive Marker of Cross-Contamination

Objective: Inappropriate handling of cells can generate modifications in the genomic DNA. The additional risk is cross-contamination. Isoenzyme analysis with gel agarose electrophoresis is a known, fast, and cheap technique for detection of species-specific isoforms of intracellular enzymes. The aim of the experimental work was to check if variations in the cell growth conditions can affect morphology and/or nuclear anomalies including micronuclei (MN) in the L929 cells; and to define how sensitive and selective is the classic gel agarose electrophoresis for analysis of isoforms of the selected enzymes to detect cross-contamination of L929 cultures with HeLa cells or with the related species, such as CHO-K1 cells, in the case of unavailability of the commercial kits. Methods: The experiments were done with use of the National Collection of Type Cultures clone 929 (L929)-mouse fibroblasts from subcutaneous connective tissue; HeLa-human cervix adenocarcinoma; and CHO-K1-epithelial-like hamster ovary cells. Cell morphology was evaluated with a light/fluorescence microscope. MN were determined with the cytokinesis-block micronucleus assay, and the isoenzyme analysis was performed using gel agarose electrophoresis. Results: As shown, the overgrown cultures result in a significant increase of the MN in the L929 cells. The band patterns for lactate dehydrogenate, glucose-6-phosphate dehydrogenase, or malate dehydrogenase allow identification of the single L929, HeLa, or CHO-K1 cell line and to detect the cross-contamination, even up to 0.4%. Conclusions: There can be no exceptions from the recommended cell culture conditions in the passage scheme. The sensitivity of the gel agarose separation depends on the cells and on the type of enzyme tested and seems to be sufficient in a quick screening of the CHO-K1, L929, or HeLa cell cultures through the possible mutual contamination.

Selective ATM inhibition augments radiation-induced inflammatory signaling and cancer cell death

Over half of all cancer patients undergo radiation therapy but there is an unmet need for more efficacious combination strategies with molecular targeted drugs. DNA damage response has emerged as an important intervention point for improving anti-tumor effects of radiation and several inhibitors are currently in development. Ataxia telangiectasia mutated (ATM) kinase is a key regulator of cellular response to DNA double strand breaks and a potential target for radiosensitization. We recently reported two new potent and selective ATM inhibitors, M3541 and M4076, that effectively sensitize cancer cells to radiation and regress human xenografts in clinically relevant animal models. Here, we dive deeper into the cellular events in irradiated cancer cells exposed to ATM inhibitors. Suppression of ATM activity inhibited radiation-induced ATM signaling and abrogated G1 checkpoint activation resulting in enhanced cell death. Our data indicated that entry into mitosis with gross structural abnormalities in multiple chromosomes is the main mechanism behind the increased cell killing. Misalignment and mis-segregation led to formation of multiple micronuclei and robust activation of the interferon response and inflammatory signaling via the cGAS/STING/TBK1 pathway. Cancer cells exposed to radiation in the presence of M3541 were more susceptible to killing in co-culture with NK cells from healthy donors. In addition, strong upregulation of PD-L1 expression was observed in the surviving irradiated cancer cells exposed to M3541. Simultaneous activation of the STING pathway and PD-L1 suggested that combination of radiation, ATM inhibitors and PD-L1 targeted therapy may offer a novel approach to radio-immunotherapy of locally advanced tumors.

Impact of Extended and Combined Exposure of Bisphenol Compounds on Their Chromosome-Damaging Effect─Increased Potency and Shifted Mode of Action

Bisphenol (BP) compounds are important environmental pollutants and endocrine disruptors. BPs are capable of inducing DNA/chromosome breaks (clastogenesis, involved in carcinogenesis), which requires activation by human CYP1A1. We hypothesized that combined BPs and extended (from the standard two-cell cycle) exposure may enhance their genotoxicity via modulating CYP enzymes. In this study, individual and combined BPA/BPF/BPS/BPAF and a human hepatoma (HepG2) cell line were used for testing several genotoxicity end points. Exposing for a two-cell cycle period (48 h), each BP alone (0.625-10 μM) was negative in the micronucleus test, while micronucleus was formed under three- (72 h) and four-cell cycle (96 h) exposure; BP combinations further elevated the potency (with nanomolar thresholds). Immunofluorescence analysis of the centromere with formed micronucleus indicated that 48 h exposure produced centromere-negative micronucleus and phosphorylated histone H2AX (γ-H2AX) (evidencing clastogenesis), while extended (72 and 96 h) exposure formed centromere-positive micronucleus and phosphorylated histone H3 (p-H3) (indicating chromosome loss, i.e., aneugenesis); moreover, 1-aminotriabenzotriazole (CYP inhibitor) selectively blocked the formation of centromere-negative micronucleus and γ-H2AX, without affecting that of centromere-positive micronucleus and p-H3. This study suggests that the genotoxicity of BPs is potentiated by combined and extended exposure, the latter being specific for aneuploidy formation, a CYP activity-independent effect.

Cytomorphometric Analysis of Oral Buccal Mucosa of Dental Colleges' Students in Sulaimani City

This study evaluates the cytomorphometric measures of cells obtained from the buccal mucosa of dental students to assess the fluctuation of the cellular characteristics among relatively normal subjects, with any potential correlations with demographic information, different habits, and hormonal disturbance. This prospective study included 100 dental students with no detectable oral alterations submitted to brush cytology. The smears were fixed with 95% ethyl alcohol and stained with hematoxylin and eosin stain. The stained section was observed under an image analyzer for cytomorphometric analysis. Cytopathological observations were recorded, including inflammation, microbial colonies, micronuclei, keratinization, overlapping, and hemorrhage. Chi-square tests were applied for non-parametric variables. One-way analysis of variance (ANOVA) was used to compare the cytometric parameters to habits and hormonal disturbances. A p-value < 0.05 was considered statistically significant. The results showed close proximity among subjects in the matter of cytomorphometric measures; no significant influence of sex, smoking, alcohol drinking habits, and menstruation was found on cytomorphometric diameters or cytopathological observation, and vice versa, while polycystic ovary syndrome impacted nuclear and nuclear-cytoplasmic ratio (p = 0.003, p = 0.02), respectively. Oral exfoliative cytology combined with cytomorphometric analysis for the studied normal individuals can be helpful in various investigations of oral and systemic diseases.

The effect of arsenic, cadmium, mercury, and lead on the genotoxic activity of Boletaceae family mushrooms present in Serbia

The aim of this study was to determine accumulation of heavy metals and metalloids which are widely distributed in the environment and in food chain using wild edible mushrooms belonging to the Boletaceae family mushrooms. In addition, methanol extracts of mushrooms were tested for in vitro protective effect by the cytochalasin-B blocked micronucleus (CBMN) assay using chromosome aberrations in human peripheral lymphocytes as a model. The genotoxic activity of methanol extracts prepared at 4 different concentrations (1, 2, 3 or 6 µg/ml) was examined using amifostine and mitomycin C as positive controls. Extracts of species B. regius and B. edulis exhibited the greatest reduction in the frequency of micronuclei (MN). Extract of B. regius at concentrations of 2 µg/ml showed the highest decrease in number of MN. In comparison, extract of mushroom B. edulis at a concentration of 3 µg/ml displayed less reduction. However, as heavy metals and metalloids are found in mushrooms, another aim was to examine whether these agents affected genotoxicity. Principal component analysis (PCA) identified clustering differences between control and heavy metals and metalloids groups and might explain the influence of heavy element content and genotoxic activity in mushrooms.

Novel assay to measure chromosome instability identifies Punica granatum extract that elevates CIN and has a potential for tumor- suppressing therapies

Human artificial chromosomes (HACs) have provided a useful tool to study kinetochore structure and function, gene delivery, and gene expression. The HAC propagates and segregates properly in the cells. Recently, we have developed an experimental high-throughput imaging (HTI) HAC-based assay that allows the identification of genes whose depletion leads to chromosome instability (CIN). The HAC carries a GFP transgene that facilitates quantitative measurement of CIN. The loss of HAC/GFP may be measured by flow cytometry or fluorescence scanning microscope. Therefore, CIN rate can be measured by counting the proportion of fluorescent cells. Here, the HAC/GFP-based assay has been adapted to screen anticancer compounds for possible induction or elevation of CIN. We analyzed 24 cytotoxic plant extracts. Punica granatum leaf extract (PLE) indeed sharply increases CIN rate in HT1080 fibrosarcoma cells. PLE treatment leads to cell cycle arrest, reduction of mitotic index, and the increased numbers of micronuclei (MNi) and nucleoplasmic bridges (NPBs). PLE-mediated increased CIN correlates with the induction of double-stranded breaks (DSBs). We infer that the PLE extract contains a component(s) that elevate CIN, making it a candidate for further study as a potential cancer treatment. The data also provide a proof of principle for the utility of the HAC/GFP-based system in screening for natural products and other compounds that elevate CIN in cancer cells.

A cross-sectional clinical study in women to investigate possible genotoxicity and hematological abnormalities related to the use of black cohosh botanical dietary supplements

Black cohosh (BC; Actaea racemosa L.), a top-selling botanical dietary supplement, is marketed to women primarily to ameliorate a variety of gynecological symptoms. Due to widespread usage, limited safety information, and sporadic reports of hepatotoxicity, the Division of the National Toxicology Program (DNTP) initially evaluated BC extract in female rats and mice. Following administration of up to 1000 mg/kg/day BC extract by gavage for 90 days, dose-related increases in micronucleated peripheral blood erythrocytes were observed, along with a nonregenerative macrocytic anemia resembling megaloblastic anemia in humans. Because both micronuclei and megaloblastic anemia may signal disruption of folate metabolism, and inadequate folate levels in early pregnancy can adversely affect neurodevelopment, the DNTP conducted a pilot cross-sectional study comparing erythrocyte micronucleus frequencies, folate and B12 levels, and a variety of hematological and clinical chemistry parameters between women who used BC and BC-naïve women. Twenty-three women were enrolled in the BC-exposed group and 28 in the BC-naïve group. Use of any brand of BC-only supplement for at least 3 months was required for inclusion in the BC-exposed group. Supplements were analyzed for chemical composition to allow cross-product comparisons. All participants were healthy, with no known exposures (e.g., x-rays, certain medications) that could influence study endpoints. Findings revealed no increased micronucleus frequencies and no hematological abnormalities in women who used BC supplements. Although reassuring, a larger, prospective study with fewer confounders (e.g., BC product diversity and duration of use) providing greater power to detect subtle effects would increase confidence in these findings.

Beta Human Papillomavirus 8 E6 Induces Micronucleus Formation and Promotes Chromothripsis

Cutaneous beta genus human papillomaviruses (β-HPVs) are suspected to promote the development of nonmelanoma skin cancer (NMSC) by destabilizing the host genome. Multiple studies have established the genome destabilizing capacities of β-HPV proteins E6 and E7 as a cofactor with UV. However, the E6 protein from β-HPV8 (HPV8 E6) induces tumors in mice without UV exposure. Here, we examined a UV-independent mechanism of HPV8 E6-induced genome destabilization. We showed that HPV8 E6 reduced the abundance of anaphase bridge resolving helicase, Bloom syndrome protein (BLM). The diminished BLM was associated with increased segregation errors and micronuclei. These HPV8 E6-induced micronuclei had disordered micronuclear envelopes but retained replication and transcription competence. HPV8 E6 decreased antiproliferative responses to micronuclei and time-lapse imaging revealed HPV8 E6 promoted cells with micronuclei to complete mitosis. Finally, whole-genome sequencing revealed that HPV8 E6 induced chromothripsis in nine chromosomes. These data provide insight into mechanisms by which HPV8 E6 induces genome instability independent of UV exposure. IMPORTANCE Some beta genus human papillomaviruses (β-HPVs) may promote skin carcinogenesis by inducing mutations in the host genome. Supporting this, the E6 protein from β-HPV8 (8 E6) promotes skin cancer in mice with or without UV exposure. Many mechanisms by which 8 E6 increases mutations caused by UV have been elucidated, but less is known about how 8 E6 induces mutations without UV. We address that knowledge gap by showing that 8 E6 causes mutations stemming from mitotic errors. Specifically, 8 E6 reduces the abundance of BLM, a helicase that resolves and prevents anaphase bridges. This hinders anaphase bridge resolution and increases their frequency. 8 E6 makes the micronuclei that can result from anaphase bridges more common. These micronuclei often have disrupted envelopes yet retain localization of nuclear-trafficked proteins. 8 E6 promotes the growth of cells with micronuclei and causes chromothripsis, a mutagenic process where hundreds to thousands of mutations occur in a chromosome.

Micronuclei from misaligned chromosomes that satisfy the spindle assembly checkpoint in cancer cells

Chromosome alignment to the spindle equator is a hallmark of mitosis thought to promote chromosome segregation fidelity in metazoans. Yet chromosome alignment is only indirectly supervised by the spindle assembly checkpoint (SAC) as a byproduct of chromosome bi-orientation, and the consequences of defective chromosome alignment remain unclear. Here, we investigated how human cells respond to chromosome alignment defects of distinct molecular nature by following the fate of live HeLa cells after RNAi-mediated depletion of 125 proteins previously implicated in chromosome alignment. We confirmed chromosome alignment defects upon depletion of 108/125 proteins. Surprisingly, in all confirmed cases, depleted cells frequently entered anaphase after a delay with misaligned chromosomes. Using depletion of prototype proteins resulting in defective chromosome alignment, we show that misaligned chromosomes often satisfy the SAC and directly missegregate without lagging behind in anaphase. In-depth analysis of specific molecular perturbations that prevent proper kinetochore-microtubule attachments revealed that misaligned chromosomes that missegregate frequently result in micronuclei. Higher-resolution live-cell imaging indicated that, contrary to most anaphase lagging chromosomes that correct and reintegrate the main nuclei, misaligned chromosomes are a strong predictor of micronuclei formation in a cancer cell model of chromosomal instability, but not in non-transformed near-diploid cells. We provide evidence supporting that intrinsic differences in kinetochore-microtubule attachment stability on misaligned chromosomes account for this distinct outcome. Thus, misaligned chromosomes that satisfy the SAC may represent a previously overlooked mechanism driving chromosomal/genomic instability during cancer cell division, and we unveil genetic conditions predisposing for these events.

Cytotoxic and genotoxic effects of cigarette and waterpipe tobacco smoking on buccal mucosa: A systematic review and meta-analysis

Background

Waterpipe tobacco smoking (WTS) is an issue all over the world, although it is particularly prevalent in the Middle East, and Southeast Asia. The genotoxic effects of smoking were reported to be associated with nucleus abnormalities such as micronuclei (MN), karyorrhexis (KR), karyolysis, pyknosis, binucleates, broken eggs, condensed chromatin in exfoliated buccal mucosal cells, and was believed to be associated with apoptosis of cells and was not correlated to the exposure time.

Aim

The aim of this study was to evaluate and compare the cytotoxic and genotoxic effects of cigarette and WTS on buccal mucosa.

Materials and Methods

The pertinent search was done through the computerized literature on MEDLINE, EMBASE, and PUBMED databases, which included case-control, clinical and observational studies regarding the mutagenic effects of cigarettes and WTS in oral tissues. The retraction of data in this study was undertaken from May 2010 to May 2022. A total of 60 articles from the search data were retrieved. This investigation was registered with the research center of Riyadh Elm University for institution review board approval (IRB) and obtained the IRB number "FRP/2021/448/733/707 and the systematic review registration number with respect to PROSPERO is 345417.

Results

After the removal of duplicates, 32 were evaluated for the inclusion and exclusion criteria. Out of 32 articles, twenty studies were evaluated for cytogenetic abnormalities in buccal mucosal cells of waterpipe tobacco smokers (WTS) and cigarette smokers, and 12 were excluded. The mean MN levels in the oral tissues of WTS were more (1.94 ± 0.39) than in non-smokers (1.68 ± 0.35).

Conclusion

Therefore, we conclude that the MN count can be employed as a biomarker and preliminary signal for the identification of changes in oral mucosa among smokers, which develop towards cancer formation.

Determination of the effects of environmental pollution on the Balkan terrapin, Mauremys rivulata (Valenciennes, 1833)

The effects of environmental pollution on three populations of the Balkan terrapin [Mauremys rivulata (Valenciennes, 1833)] from the Bozcaada, Gökçeada and Dardanos regions were evaluated. The morphological parameters of Balkan terrapins collected on each site were measured and blood samples were taken for haematological analysis and micronucleus detection. The physicochemical, microbiological and microelement analyses of the water samples from each region were conducted by standard methods. The highest red blood cell, white blood cell and mean corpuscular haemoglobin concentration values were seen in the samples from Gökçeada. The highest haemoglobin value was found in the samples originating from Bozcaada, whereas the highest haematocrit and mean corpuscular volume values were found in the animals from Dardanos. Based on the microbiological analysis of the water samples, the most polluted site was Gökçeada. The microelement contents of the water and blood samples were different at the three sites, the lowest being in the Gökçeada area. It was revealed that the percentage of red blood cell micronuclei and other nucleus abnormalities in the M. rivulata blood samples was the lowest also in the animals living in the region of Gökçeada.

CRISPRthripsis: The Risk of CRISPR/Cas9-induced Chromothripsis in Gene Therapy

The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 nuclease system has allowed the generation of disease models and the development of therapeutic approaches for many genetic and non-genetic disorders. However, the generation of large genomic rearrangements has raised safety concerns for the clinical application of CRISPR/Cas9 nuclease approaches. Among these events, the formation of micronuclei and chromosome bridges due to chromosomal truncations can lead to massive genomic rearrangements localized to one or few chromosomes. This phenomenon, known as chromothripsis, was originally described in cancer cells, where it is believed to be caused by defective chromosome segregation during mitosis or DNA double-strand breaks. Here, we will discuss the factors influencing CRISPR/Cas9-induced chromothripsis, hereafter termed CRISPRthripsis, and its outcomes, the tools to characterize these events and strategies to minimize them.

HBM4EU Chromates Study-Genotoxicity and Oxidative Stress Biomarkers in Workers Exposed to Hexavalent Chromium

A study was conducted within the European Human Biomonitoring Initiative (HBM4EU) to characterize occupational exposure to Cr(VI). Herein we present the results of biomarkers of genotoxicity and oxidative stress, including micronucleus analysis in lymphocytes and reticulocytes, the comet assay in whole blood, and malondialdehyde and 8-oxo-2′-deoxyguanosine in urine. Workers from several Cr(VI)-related industrial activities and controls from industrial (within company) and non-industrial (outwith company) environments were included. The significantly increased genotoxicity (p = 0.03 for MN in lymphocytes and reticulocytes; p < 0.001 for comet assay data) and oxidative stress levels (p = 0.007 and p < 0.001 for MDA and 8-OHdG levels in pre-shift urine samples, respectively) that were detected in the exposed workers over the outwith company controls suggest that Cr(VI) exposure might still represent a health risk, particularly, for chrome painters and electrolytic bath platers, despite the low Cr exposure. The within-company controls displayed DNA and chromosomal damage levels that were comparable to those of the exposed group, highlighting the relevance of considering all industry workers as potentially exposed. The use of effect biomarkers proved their capacity to detect the early biological effects from low Cr(VI) exposure, and to contribute to identifying subgroups that are at higher risk. Overall, this study reinforces the need for further re-evaluation of the occupational exposure limit and better application of protection measures. However, it also raised some additional questions and unexplained inconsistencies that need follow-up studies to be clarified.