Mutagenic Activity Research Articles

Abstract PO5-27-03: Mutational impact of APOBEC3A and APOBEC3B in a human cell line

Abstract A major source of mutation in cancer is DNA cytosine deamination by APOBEC3 enzymes resulting in C-to-T and C-to-G mutations in TCA and TCT motifs. Here, we develop a selectable system to quantify genomic mutations and compare the mutagenic activities of three leading APOBEC3 candidates - APOBEC3A, APOBEC3B, and APOBEC3H. The human cell line, HAP1, is engineered to express the thymidine kinase (TK) gene of HSV-1, which confers sensitivity to ganciclovir. Expression of APOBEC3A and APOBEC3B, but not catalytic mutant controls or APOBEC3H, triggers increased frequencies of TK mutation and nearly indistinguishable TC-biased cytosine mutation profiles in the selectable TK reporter gene. Whole genome sequences from TK mutant clones enabled an analysis of thousands of single base substitution mutations and extraction of local sequence preferences with APOBEC3A preferring YTCW motifs over 70% of the time and APOBEC3B just under 50% of the time (Y=C/T; W=A/T). Signature comparisons with breast tumor whole genome sequences indicate that most malignancies manifest intermediate percentages of APOBEC3 signature mutations in YTCW motifs, mostly between 50 and 70%, suggesting that both enzymes are contributing in a combinatorial manner to the overall mutation landscape. These studies combine to help resolve a long-standing etiologic debate on the source of APOBEC3 signature mutations in cancer and indicate that future diagnostic and therapeutic efforts should focus on both enzymes. Citation Format: Michael Carpenter, Nuri Temiz, Mahmoud Ibrahim, Matthew Jarvis, Margaret Brown, Prokopios Argyris, William Brown, Douglas Yee, Reuben Harris. Mutational impact of APOBEC3A and APOBEC3B in a human cell line [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-27-03.

Assessing the impact of two conventional wastewater treatment plants on small streams with effect-based methods

Sixty percent of discrete surface water bodies in Europe do not meet the requirements for good ecological and chemical status and in Germany, the situation is even worse with over 90% of surface water bodies failing to meet the threshold. In addition to hydromorphological degradation, intensive land use and invasive species, chemical pollution is primarily considered to be responsible for the inadequate ecological status of the water bodies. As a quantitatively important source of micropollutants, wastewater treatment plants (WWTPs) represent an important entry path for chemical stressors. It is therefore important to analyze the effectiveness of the WWTPs in eliminating micropollutants and other chemical stressors to mitigate the negative impacts of the treated wastewater (WW) in aquatic ecosystems. Accordingly, in this study, we evaluated the impacts of two conventional, medium-sized WWTPs on their small receiving water systems in the southwestern region of Hessen in Germany during two sampling campaigns (spring and fall) using effect-based methods (EBM). We hypothesized that due to the insufficient elimination of micropollutants, a broad spectrum of toxic effects would be detected in conventionally treated WW and also in the receiving surface waters downstream the WWTPs. As EBMs a battery of in vitro assays and active biomonitoring using two in vivo assays were applied. The results supported our hypothesis and showed that the untreated WW had a very high baseline toxicity and also high endocrine and mutagenic activities. Conventional WW treatment, consisting of mechanical and biological treatment with nitrification, denitrification and phosphate precipitation, reduced baseline toxicity by more than 90% and endocrine activities by more than 80% in both WWTPs. Despite these high elimination rates, the remaining baseline toxicity, the endocrine, dioxin-like and mutagenic activities of the conventionally treated WW were so high that negative effects on the two receiving waters were to be expected. This was confirmed in the active monitoring with the amphipod Gammarus fossarum and the mudsnail Potamopyrgus antipodarum, as mortality of both species increased downstream of the WWTPs and reproduction in P. antipodarum was also affected. These results indicate that advanced WW treatment is needed to more effectively eliminate chemical stressors to prevent negative impacts of treated WW particularly in small receiving waters.

Chromosomal disorders in Triticum aestivum subject to prolonged radionuclide pollution of soil from the Exclusion Zone of the Chornobyl Nuclear Power Plant

Due to the large number of nuclear power plants around the globe and the growing threat of radioactive accidents, a complex assessment of the biological consequences of the Chornobyl disaster is a relevant issue. Study of mutagenic activity of prolonged and chronic action of radionuclide pollution of soil in the Chornobyl Exclusion Zone long after the accident will allow us to identify the current level of threat they pose to the human genome and can reveal specific cytogenic markers of radionuclide environmental pollution. For this purpose, we germinated seeds of wheat of soft winter varieties Smuhlianka and Bohdana in soil samples from the Chornobyl Exclusion Zone 35 years after the disaster. Specific activity of Cs-137 and Sr-90 accounted for 4.5–28.2 kBq/kg. To determine the frequency and range of chromosomal aberrations, we used the anaphase-telophase method. In aberrant cells, we studied extracellular distribution of chromosomal disorders. The frequency of aberrant cells was 3.53–7.55 times above the spontaneous level. High mutagenic activity remained in the conditions of the lowest density of radionuclide pollution of soil. The range of chromosomal disorders mostly included paired fragments and bridges and containd chromosomal acentric rings, binding of chromosomes, myocardium, and lagging and leading chromosomes. Radionuclide pollution in the Chornobyl Exclusion Zone induced multiple cellular aberrations in the rhizome meristem, the share of which was the highest in case of low specific radionuclide pollution of soil, and exhibited a tendency towards decrease against the background of the highest density of radionuclides. Pollution of the environment with radionuclides as a result of disasters at nuclear energy objects poses a threat to the human genome and is a global problem, requiring state support to solve through systematic genetic monitoring in readionuclide-polluted territories and areas adjacent to them.

Genotoxic and antiproliferative properties of Endopleura uchi bark aqueous extract

ABSTRACT The bark extract from Endopleura uchi has been widely used in traditional medicine to treat gynecological-related disorders, diabetes, and dyslipidemias albeit without scientific proof. In addition, E. uchi bark extract safety, especially regarding mutagenic activities, is not known. The aim of this study was to determine the chemical composition, antitumor, and toxicological parameters attributed to an E. uchi bark aqueous extract. The phytochemical constitution was assessed by colorimetric and chromatographic analyzes. The antiproliferative effect was determined using sulforhodamine B (SRB) assay using 4 cancer cell lines. Cytotoxic and genotoxic activities were assessed utilizing MTT and comet assays, respectively, while mutagenicity was determined through micronucleus and Salmonella/microsome assays. The chromatographic analysis detected predominantly the presence of gallic acid and isoquercitrin. The antiproliferative effect was more pronounced in human colon adenocarcinoma (HT-29) and human breast cancer (MCF-7) cell lines. In the MTT assay, the extract presented an IC50 = 39.1 µg/ml and exhibited genotoxic (comet assay) and mutagenic (micronucleus test) activities at 20 and 40 µg/ml in mouse fibroblast cell line (L929) and mutagenicity in the TA102 and TA97a strains in the absence of S9 mix. Data demonstrated that E. uchi bark possesses bioactive compounds which exert cytotoxic and genotoxic effects that might be associated with its antitumor potential. Therefore, E. uchi bark aqueous extract consumption needs to be approached with caution in therapeutic applications.

Comprehensive Ocular and Systemic Safety Evaluation of Polysialic Acid-Decorated Immune Modulating Therapeutic Nanoparticles (PolySia-NPs) to Support Entry into First-in-Human Clinical Trials.

An inflammation-resolving polysialic acid-decorated PLGA nanoparticle (PolySia-NP) has been developed to treat geographic atrophy/age-related macular degeneration and other conditions caused by macrophage and complement over-activation. While PolySia-NPs have demonstrated pre-clinical efficacy, this study evaluated its systemic and intraocular safety. PolySia-NPs were evaluated in vitro for mutagenic activity using Salmonella strains and E. coli, with and without metabolic activation; cytotoxicity was evaluated based on its interference with normal mitosis. PolySia-NPs were administered intravenously in CD-1 mice and Sprague Dawley rats and assessed for survival and toxicity. Intravitreal (IVT) administration in Dutch Belted rabbits and non-human primates was assessed for ocular or systemic toxicity. In vitro results indicate that PolySia-NPs did not induce mutagenicity or cytotoxicity. Intravenous administration did not show clastogenic activity, effects on survival, or toxicity. A single intravitreal (IVT) injection and two elevated repeat IVT doses of PolySia-NPs separated by 7 days in rabbits showed no signs of systemic or ocular toxicity. A single IVT inoculation of PolySia-NPs in non-human primates demonstrated no adverse clinical or ophthalmological effects. The demonstration of systemic and ocular safety of PolySia-NPs supports its advancement into human clinical trials as a promising therapeutic approach for systemic and retinal degenerative diseases caused by chronic immune activation.

Green synthesis, characterization and biological activity of silver nanoparticles of Hypnum cupressiforme Hedw extract

Mosses are one of the oldest land plants that constitute the second largest group of the plant kingdom, are found in almost every region, have known therapeutic effects, are rich in secondary metabolites, can withstand harsh climatic conditions and thirst for a long time. Volatile extracts of Hypnum cupressiforme Hedw. were analyzed by gas chromatography-mass spectrometry in this study, and the presence of 18 different phytocompounds was determined as secondary metabolites. Using these extracts, silver nanoparticles (AgNPs) were synthesized using a green synthesis method. The AgNPs that were created were characterized. The extracts and AgNPs were tested for antibacterial, antibiofilm, antioxidant, mutagenic, and DNA-cleavage activity. The tests revealed no evidence of mutagenicity. Antibiofilm and antibacterial activity of AgNPs against P. vulgaris, P. aeruginosa, and E. faecalis were demonstrated. Both oxidatively and hydrolytically, H. cupressiforme the extract was found to have higher antioxidant properties and high DNA cleavage activity.

Narcissus cv. Hawera Leaves' Extract Cleaves DNA in Chlamydomonas reinhardtii by Inducing DSBs

The aim of this study is to go inside the mode of action of Narcissus cv. Hawera leaves' extract on Chlamydomonas reinhardtii by analyzing its chemical composition, genotoxic, mutagenic, and DNA damaging effects.
 GC/MS analysis of the methanol extract shows that alkaloids comprise about 23.93% of the total ion current (TIC). Considering the alkaloid pattern, lycorine is the major alkaloid (8.53% of TIC), followed by 6-epi-mesembrenol (4.59% of TIC), galanthamine (2.63% of TIC), and mesembrenone (2.01% of TIC). Other compounds in the extract are mono- and di-saccharides, organic acids, and fatty acids.
 Based on our experiments, both well-expressed genotoxic and DNA damaging potential of Narcissus cv. Hawera total leaves' extract was revealed for the first time. The most pronounced effect is obtained after the treatment with concentrations equal to or higher than 500 μg/ml. Cell survival decrease in a dose-dependent manner correlates with increased levels of induced DNA double-strand breaks (DSBs) but does not correspond with statistically confirmed mutagenic action. A good correlation is obtained between the levels of DSBs induced and cell survival rate.
 Here, for the first time, experimental evidence that Narcissus cv. Hawera leaves' extract can cleave DNA of Chlamydomonas reinhardtii inducing DSBs was reported by us. Our finding could be considered a good reason for further investigation of its biocidal capacity on other test systems for the purposes of “green” practice.

Efficient and sensitive determination of storage time-temperature marker 5-hydroxy methyl furfural in bee honey based on Fluorescence quenching of human serum albumin

5-hydroxymethyl furfural (HMF) exhibits mutagenic and DNA strand-breaking activity. It is a useful tool to evaluate the effect of heat and time on foodstuffs processing. The fluorescence interaction of HMF with HSA has not been explored to date. Therefore, this work reports the interaction mechanism of HMF with HSA via fluorescence spectroscopy analysis in a simulated physiological environment. The experimental tries showed that HMF intensely quenched the native fluorescence of HSA via the dynamic quenching. According to fluorescence quenching calculations, the binding constants Kb are 1.26x10-4, 2.71x10-4 and 3.19x10-4 M-1 at 298, 303 and 308 K respectively, and the number of binding sites n is almost 1. Thermodynamic parameters values expose that both electrostatic and hydrophobic interactions are accountable for the interaction of HSA and HMF. The presented quenching method for the assay of HMF exhibited a good linearity in the range of 0.1 to 6.66 µg/mL with a detecting limit of 0.0184 µg/mL. These values made the developed method appropriate to be used in the estimation of HMF in samples of bee honey after its extraction using SupelcleanTM ENVI™ -18 SPE Tube. Five bee honey samples show a positive response of HMF after exposing these samples for inappropriate storage or extreme heating.

Abstract 3289: APOBEC3A drives tumor evolution through activation of ERVs in non small cell lung cancer

Abstract Acquired drug resistance to even the most effective anti-cancer targeted therapies remains an unsolved clinical problem. Although many drivers of acquired drug resistance have been identified, the underlying molecular mechanisms shaping tumor evolution during treatment are incompletely understood. We recently demonstrated that lung cancer targeted therapies commonly used in the clinic induce the expression of cytidine deaminase APOBEC3A (A3A), leading to sustained mutagenesis in drug-tolerant cancer cells persisting during therapy. Preventing therapy-induced A3A mutagenesis by gene deletion decreased the chromosomal aberration events and delayed the emergence of drug resistance. Thus, inhibition of A3A may represent a potential therapeutic strategy to prevent acquired resistance. Understanding the regulatory mechanisms of A3A may provide alternative approaches to inhibit A3A mutagenesis. Using a panel drug screen, we found that DNA methyltransferase (DNMT) inhibitor remarkably induces A3A in non-small cell lung cancer cells. RNA-seq profiling revealed that targeted therapy as well as DNMT inhibitor treatment activate expression of distinct classes non-coding repetitive RNA elements, including endogenous retrovirus (ERVs), in drug-tolerant persister cells. Activation of intracellular viral sensing pathways by introduction of exogenous nucleic acids mimicking viral elements induced A3A expression. While the transcription factor NFkB was acutely activated by targeted therapy, TBK1-IRF3 signaling was activated at later time points. These findings suggest that reactivation of ERVs may underlie A3A mutagenic activity and tumor evolution during targeted therapy. Citation Format: Hideko Isozaki, Ramin Sakhtemani, Naveed Nikpour, Susanna Monroe, Michael Lawrence, Aaron Hata. APOBEC3A drives tumor evolution through activation of ERVs in non small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3289.

Conditions and Mechanism of Formation of the Maillard Reaction Pigment, Furpenthiazinate, in a Model System and in Some Acid Hydrolyzates of Foods and its Biological Properties.

Furpenthiazinate is a yellow pigment formed by the Maillard reaction between cysteine and furfural under strongly acidic conditions. Here, we describe the conditions and mechanism of pigment formation in a model system and in an acid hydrolyzate of food and analyze its biological properties. A reaction solution containing 32 mM cysteine and 128 mM furfural or 64 mM cysteine and 256 mM furfural in the presence of 2-6 M hydrochloric acid that was heated to 110 °C for 1-2 h yielded approximately 3 mM furpenthiazinate. Nuclear magnetic resonance analysis of furpenthiazinate prepared using 1-13C or 5-13C d-ribose suggests that it was formed through the condensation of cysteine and two C5 chains derived from pentose with the dehydration and elimination of formic acid. Furpenthiazinate was detected in mieki, a seasoning, and some acid hydrolyzates of food, and it did not show antibacterial or mutagenic activity.

Abstract A052: ROS in ovulatory follicular fluid exert de novo mutagenic activities through activation-induced cytidine deaminase acting on the TP53 gene in the fallopian tube epithelial cell

Abstract Objective: Ovulation is a major risk factor of epithelial ovarian cancer (EOC), presumably acts from the cancer initiation stage. High-grade serous carcinoma (HGSC) is the most prevalent and fatal EOC, mainly arising from fallopian tube fimbrial epithelium (FTE). TP53 missense mutations are considered the earliest event of carcinogenesis since they form “p53 signatures” in FTE and were found in virtually all HGSC. Previously, we discovered that a subset of ovulatory follicular fluids (FF) harbored high levels of ROS, which were both mutagenic and oncogenic, causing DNA double-strand breaks (DSB) and tumorigenesis. However, DSB is unlikely the cause of TP53 mutations which are mostly CG: TA base substitutions involving deamination. We hypothesized that during ovulation FF exposes the fallopian tube fimbria and causes TP53 mutations by activating the activation-induced cytidine deaminase (AID). Materials and Methods: By conducting an HPRT gene mutation assay, we determined the mutagenic activity of FF on FTE cells with or without AID-knockdown. AID gene activation and protein nuclear translocation were analyzed in human FTE tissues and cells with different degrees of transformation, as well as in the oviducts of mice under controlled ovulation. The binding of AID to the TP53 gene and the subsequent deamination were determined by ChIP-PCR and uracil-qPCR, respectively. Results: After FF exposure, the mutation frequency of HPRT in FTE cells increased by 4.1 folds, at levels 40% higher than the ethyl methane sulfonate control and could be diminished by antioxidants or knockdown of the AID gene. AID activation, including mRNA and protein inductions and nuclear translocation, was evident in FTE cells and tissue after FF exposure and in mouse oviducts after ovulation. Two waves of AID activations were noted, peaking at 45 minutes (early activity) and 8.5 hours (late activity) after ovulation or FF exposure. TNF-α and ROS were found to be responsible for the activities in FF. Mechanistically, the early activity worked through the MAPK, while the late activity worked through the NF-κB pathway. The induced AID in both activities physically binds to and biochemically deaminates the TP53 gene irrelative to the known mutational hotspots of HGSC. However, it did not act on PTEN, the other prevalent tumor suppressor gene in HGSC. Meanwhile, ovulatory FF also activates the putative tumor-initiating and stemness gene LGR6 in FTE at locations where AID was also activated. Conclusion: The serial studies characterized the mutagenic activities of ovulatory FF, which acts on the LGR6-expressing cells in the fallopian tube fimbria and targets the TP53 gene. The study also identified ROS as the mutagen and pointed to strategies of ovulation inhibition and antioxidation for the prevention of EOC. Citation Format: Tang-Yuan Chu, Sanchana Subramani, Hsuan-Shun Huang. ROS in ovulatory follicular fluid exert de novo mutagenic activities through activation-induced cytidine deaminase acting on the TP53 gene in the fallopian tube epithelial cell [abstract]. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_2):Abstract nr A052.

Improved detection of colibactin-induced mutations by genotoxic E. coli in organoids and colorectal cancer

Co-culture of intestinal organoids with a colibactin-producing pks+E.coli strain (EcC) revealed mutational signatures also found in colorectal cancer (CRC). E.coli Nissle 1917 (EcN) remains a commonly used probiotic, despite harboring the pks operon and inducing double strand DNA breaks. We determine the mutagenicity of EcN and three CRC-derived pks+E.coli strains with an analytical framework based on sequence characteristic of colibactin-induced mutations. All strains, including EcN, display varying levels of mutagenic activity. Furthermore, a machine learning approach attributing individual mutations to colibactin reveals that patients with colibactin-induced mutations are diagnosed at a younger age and that colibactin can induce a specific APC mutation. These approaches allow the sensitive detection of colibactin-induced mutations in ∼12% of CRC genomes and even in whole exome sequencing data, representing a crucial step toward pinpointing the mutagenic activity of distinct pks+E.coli strains.

Fecal Carriage of Colibactin-Encoding Escherichia coli Associated With Colorectal Cancer Among a Student Populace.

Fecal carriage of the colibactin (clb) gene in Escherichia coli is described as a source that could promote carcinogenesis, progressing to colorectal cancer. The present study investigated the demographic, dietary, and antibiotic consumption variables as correlates for fecal carriage of clb+/E coli among the student populace. In a randomized cross-sectional survey, E coli (N = 136) from the fecal samples of eligible students were characterized and evaluated for antibiotic resistance, β-lactamase (blm), biofilm, virulence factor production, and strain tryptophan reverse mutagenic activity. The encoded clb+/E coli were analyzed for correlates with principal component analysis. Of all the E coli strains, a low rate of 2 clb+/E coli (1.5%) and higher rates of biofilm (13.2%) and blm producers (11.8%) were recorded among the mutant strains as compared with the nonmutant types. All the clb+/E coli showed complete resistance to amoxicillin, Augmentin (amoxicillin and clavulanate), gentamicin, and trimethoprim/sulfamethoxazole. The fecal clb-encoded E coli (1.5%) were not associated with demographic status, fiber-based food (odds ratio [OR], 1.03; 95% CI, 56.74-138.7; P = .213), alcohol (OR, 1.27; 95% CI, 61.74-147.1; P = .221), antibiotic consumptions (OR, 1.11; 95% CI, 61.29-145.3; P = .222), and handwashing (OR, 1.17; 95% CI, 60.19-145.5; P = .216). The hierarchical cluster of blm+/E coli revealed high-level resistance with a multiantibiotic resistance index ≥0.2 (P < .05). Only 12% of all strains were tryptophan mutant/blm+, and 1.5% of clb+/ECblm+ were observed in fecal samples with a 452-base pair size. Trimethoprim/sulfamethoxazole and biofilm production positively regressed with clb expression (P > .05). Principal component analysis score plot indicated an association of clb+/ECblm+ with dietary pattern, alcohol, blm, and hemolysin production. The combined activity of blm and biofilm production in the gut microbiota could promote clb+/E coli colonization, facilitating genotoxin production and possible colorectal cancer induction.

Analysis of SIKVAV’s receptor affinity, pharmacokinetics, and pharmacological characteristics: a matrikine with potent biological function

Matrikines are biologically active peptides generated from fragments fragmentation of extracellular matrix components (ECM) that are functionally distinct from the original full-length molecule. The active matricryptic sites can be unmasked by ECM components enzymatic degradation or multimerization, heterotypic binding, adsorption to other molecules, cell-mediated mechanical forces, exposure to reactive oxygen species, ECM denaturation, and others. Laminin α1-derived peptide (SIKVAV) is a bioactive peptide derived from laminin-111 that participates in tumor development, cell proliferation, angiogenesis in various cell types. SIKVAV has also a potential pharmaceutical activity that may be used for tissue regeneration and bioengineering in Alzheimer’s disease and muscular dystrophies. In this work, we made computational analyzes of SIKVAV regarding the ADMET panel, that stands for Administration, Distribution, Metabolism, Excretion, and Toxicity. Docking analyzes using the α3β1 and α6β1 integrin receptors were performed to fill in the gaps in the SIKVAV’s signaling pathway and coupling tests showed that SIKVAV can interact with both receptors. Moreover, there is no indication of cytotoxicity, mutagenic or carcinogenic activity, skin or oral sensitivity. Our analysis suggests that SIKVAV has a high probability of interacting with peroxisome proliferator-activated receptor-gamma (NR-PPAR-γ), which has anti-inflammatory activity. The results of bioinformatics can help understand the participation of SIKVAV in homeostasis and influence the understanding of how this peptide can act as a biological asset in the control of dystrophies, neurodegenerative diseases, and tissue engineering. Communicated by Ramaswamy H. Sarma

Genotoxicity and mutagenicity assessment of electronic cigarette liquids.

Electronic cigarettes (e-cigarettes) are often advertised as a safer alternative to traditional smoking. However, recent data suggest they may not be as safe as previously believed. This study aims to evaluate the genotoxicity and mutagenicity of e-cigarette liquids. We randomly selected eight varieties of e-cigarette liquids from the local market in Jeddah, Saudi Arabia. We evaluated their genotoxicity using the Genotoxicity SOS-Chromo Test™ Kit. In this investigation, a rat liver S9 fraction was utilized to emulate liver metabolic function to measure any chemical substance's mutagenic potential. The SOS-Chromo Test was performed by recording the β-galactosidase and alkaline phosphatase activity with and without the metabolic activation enzyme (S-9). All samples, except for the first two dilutions of sample 2, were nongenotoxic in the absence of the S9 activation enzyme, according to the genotoxicity analysis. However, when tested in the presence of the S9 enzyme, samples 2, 4, and 7 exhibited mutagenic activity at varying concentrations. Contrary to common belief, e-cigarettes are not safe. The present investigation confirms the presence of both toxicants and carcinogens in some e-cigarette liquids. This exposure could increase users' risk of various health complications.

Legacy and Emerging Plasticizers and Stabilizers in PVC Floorings and Implications for Recycling.

Hazardous chemicals in building and construction plastics can lead to health risks due to indoor exposure and may contaminate recycled materials. We systematically sampled new polyvinyl chloride floorings on the Swiss market (n = 151). We performed elemental analysis by X-ray fluorescence, targeted and suspect gas chromatography-mass spectrometry analysis of ortho-phthalates and alternative plasticizers, and bioassay tests for cytotoxicity and oxidative stress, and endocrine, mutagenic, and genotoxic activities (for selected samples). Surprisingly, 16% of the samples contained regulated chemicals above 0.1 wt %, mainly lead and bis(2-ethylhexyl) phthalate (DEHP). Their presence is likely related to the use of recycled PVC in new flooring, highlighting that uncontrolled recycling can delay the phase-out of hazardous chemicals. Besides DEHP, 29% of the samples contained other ortho-phthalates (mainly diisononyl and diisodecyl phthalates, DiNP and DiDP) above 0.1 wt %, and 17% of the samples indicated a potential to cause biological effects. Considering some overlap between these groups, they together make up an additional 35% of the samples of potential concern. Moreover, both suspect screening and bioassay results indicate the presence of additional potentially hazardous substances. Overall, our study highlights the urgent need to accelerate the phase-out of hazardous substances, increase the transparency of chemical compositions in plastics to protect human and ecosystem health, and enable the transition to a safe and sustainable circular economy.

CRISPR/Cas9 as a Mutagenic Factor.

The discovery of the CRISPR/Cas9 microbial adaptive immune system has revolutionized the field of genetics, by greatly enhancing the capacity for genome editing. CRISPR/Cas9-based editing starts with DNA breaks (or other lesions) predominantly at target sites and, unfortunately, at off-target genome sites. DNA repair systems differing in accuracy participate in establishing desired genetic changes but also introduce unwanted mutations, that may lead to hereditary, oncological, and other diseases. New approaches to alleviate the risks associated with genome editing include attenuating the off-target activity of editing complex through the use of modified forms of Cas9 nuclease and single guide RNA (sgRNA), improving delivery methods for sgRNA/Cas9 complex, and directing DNA lesions caused by the sgRNA/Cas9 to non-mutagenic repair pathways. Here, we have described CRISPR/Cas9 as a new powerful mutagenic factor, discussed its mutagenic properties, and reviewed factors influencing the mutagenic activity of CRISPR/Cas9.

Assessment of the genotoxic potential of soil-associated DDTs and its metabolites using the Salmonella/microsome assay

The study aimed to assess the genotoxicity of different DDT contaminated soils (with different amendment types) in benzene extracts. A Salmonella/microsome assay without metabolic activation (-S9) was performed to evaluate the efficiency to initiate the mutations of remediated and non-remediated soils. The number of revertants mutations in his+ in TA100 and TA98 strains were obtained, and compared to soils without DDT, and remediated DDT containing soils. The interpretation of the data suggests that, mutagenic activity was high for the non-remediated soils samples Kyzylkairat and Beskainar, and revealed in the scale as a weak mutagen. Soil samples treated with DARCO, ORBO, Sarg&lt;150μm, and Sarg&gt;150μm in Kyzylkairat and Beskainar exhibited a decreasing level of mutagenic activity, which is in line with the decreased environmental availability in these soil. Overall, the study indicates that strains TA100 and TA98 are valuable tools for rapidly assessing the potential mutagenicity of soil contaminated with OCPs.

Mutagenic activity of water samples from Kaskelen River (Kazakhstan) on plant test systems

Rivers are pivotal in the life processes of all living organisms, including humans. The engagement of rivers in daily human economic endeavours has precipitated and continues to precipitate disturbances in the ecological equilibrium, long-established by the forces of evolution. Consequently, providing clean, high-quality water is paramount for sustaining all life forms. This investigation aimed to examine the mutagenic potential of water samples from the Kaskelen River, which is subjected to anthropogenic influences, employing plant-based test subjects. The water’s mutagenic properties were assessed through an assay for chromosomal aberrations (utilizing the metaphase approach) on Hordeum vulgare L. The results demonstrated a statistically significant decline in the mitotic index under all experimental conditions compared to the negative control (p&lt;0.05), indicating the cytotoxic effects of the water samples under study. Further analysis of the water’s mutagenic activity elucidated its capacity to induce structural mutations within the root meristem cells of barley, manifesting a significant uptick in the frequency of chromosomal aberrations relative to the negative control (p&lt;0.05). The extensive array of observed chromosomal rearrangements underscores the existence of mutagenic agents in the river’s water, possessing a broad spectrum of effects.

AID in non-Hodgkin B-cell lymphomas: The consequences of on- and off-target activity.

Activation induced cytidine deaminase (AID) is a key element of the adaptive immune system, required for immunoglobulin isotype switching and affinity maturation of B-cells as they undergo the germinal center (GC) reaction in peripheral lymphoid tissue. The inherent DNA damaging activity of this enzyme can also have off-target effects in B-cells, producing lymphomagenic chromosomal translocations that are characteristic features of various classes of non-Hodgkin B-cell lymphoma (B-NHL), and generating oncogenic mutations, so-called aberrant somatic hypermutation (aSHM). Additionally, AID has been found to affect gene expression through demethylation as well as altered interactions between gene regulatory elements. These changes have been most thoroughly studied in B-NHL arising from GC B-cells. Here, we describe the most common classes of GC-derived B-NHL and explore the consequences of on- and off-target AID activity in B and plasma cell neoplasms. The relationships between AID expression, including effects of infection and other exposures/agents, mutagenic activity and lymphoma biology are also discussed.