DNA Strand Breaks Research Articles

Transcription Factor Inhibition as a Potential Additional Mechanism of Action of Pyrrolobenzodiazepine (PBD) Dimers

Background: The pyrrolobenzodiazepine (PBD) dimer SJG-136 reached Phase II clinical trials in ovarian cancer and leukaemia in the UK and USA in the 2000s. Several structural analogues of SJG-136 are currently in clinical development as payloads for Antibody-Drug Conjugates (ADCs). There is growing evidence that PBDs exert their pharmacological effects through inhibition of transcription factors (TFs) in addition to arrest at the replication fork, DNA strand breakage, and inhibition of enzymes including endonucleases and RNA polymerases. Hence, PBDs can be used to target specific DNA sequences to inhibit TFs as a novel anticancer therapy. Objective: To explore the ability of SJG-136 to bind to the cognate sequences of transcription factors using a previously described HPLC/MS method, to obtain preliminary mechanistic evidence of its ability to inhibit transcription factors (TF), and to determine its effect on TF-dependent gene expression. Methods: An HPLC/MS method was used to assess the kinetics and thermodynamics of adduct formation between the PBD dimer SJG-136 and the cognate recognition sequence of the TFs NF-κB, EGR-1, AP-1, and STAT3. CD spectroscopy, molecular dynamics simulations, and gene expression analyses were used to rationalize the findings of the HPLC/MS study. Results: Notable differences in the rate and extent of adduct formation were observed with different DNA sequences, which might explain the variations in cytotoxicity of SJG-136 observed across different tumour cell lines. The differences in adduct formation result in variable downregulation of several STAT3-dependent genes in the human colon carcinoma cell line HT-29 and the human breast cancer cell line MDA-MB-231. Conclusions: SJG-136 can disrupt transcription factor-mediated gene expression, which contributes to its exceptional cytotoxicity in addition to the DNA-strand cleavage initiated by its ability to crosslink DNA.

Valemetostat and trastuzumab deruxtecan (T-DXd) in previously treated advanced or metastatic human epidermal growth factor receptor 2 (HER2)-positive gastric cancer or gastro-esophageal junction (GEJ) adenocarcinoma.

TPS508 Background: Valemetostat tosylate (valemetostat), a novel and selective dual inhibitor of enhancer of zeste homolog (EZH)2 and EZH1, has demonstrated clinical efficacy and tolerability in multiple hematologic cancers (200 mg orally [PO] once daily [QD]). EZH2 inhibition by valemetostat is expected to upregulate DNA/RNA helicase Schlafen 11 expression and sensitize tumor cells to DNA damaging agents such as topoisomerase I inhibitor antibody–drug conjugates (ADCs). Topoisomerase inhibitors cause DNA strand breaks, which may synergize with valemetostat. HER2 gene amplification or protein expression has been associated with gastric cancer (GC) and GEJ adenocarcinoma. Patients with HER2+ locally advanced or metastatic gastric adenocarcinoma who progress after first line treatment have poor prognosis and limited therapeutic options. T-DXd is approved globally for HER2+ locally advanced or metastatic GC previously treated with a trastuzumab-based regimen. This study evaluates the clinical activity and safety of valemetostat in combination with T-DXd in patients with GC or GEJ adenocarcinoma as part of a Master Protocol trial evaluating valemetostat in combination with ADCs in solid tumors. Methods: This global, phase 1b, multicenter, open-label Master Protocol study (NCT06244485) will enroll ~ 70 patients per sub-protocol in multiple regions, including the US and Japan. The gastric cohort enrolls patients with previously treated advanced or metastatic HER2+ GC or GEJ adenocarcinoma. The dose-escalation (Part 1) will determine the recommended dose for expansion (RDE), combining valemetostat 50–200 mg PO QD with T-DXd 5.4 or 6.4 mg/kg intravenously every 3 weeks. The dose-expansion (Part 2) will assess the efficacy of valemetostat + T-DXd at the RDE. Primary endpoints include safety and tolerability in Part 1 and the objective response rate in Part 2. Secondary endpoints include response duration, progression-free and overall survival, pharmacokinetics, and HER2 expression by immunohistochemistry and in situ hybridization with clinical response. An interim futility analysis will be performed when 20 patients are enrolled with ≥ 6 months of follow-up. Clinical trial information: NCT06244485 .

Unraveling toxicity of nanoparticles from different subway materials in lung epithelial cells and macrophages.

Nanoparticles (ultrafine particles) are prevalent in various environments and raise concerns due to their potential health effects. In this study, we aimed to enhance the understanding of the toxicity associated with nanoparticles generated within subway systems. Specifically, we investigated nanoparticles produced using spark discharge from electrodes made of the same material as the third rail (which provides electric power), rail, and wheel components in the Stockholm subway system. Characterization revealed that the generated nanoparticles typically had a primary size of 6-10 nm and exhibited high agglomeration. They consisted mainly of iron, along with varying amounts of manganese and silicon. Despite having low oxidative potential, they showed some cytotoxicity and clearly induced DNA strand breaks in both dTHP-1 cells (monocyte-derived macrophages) and A549 cells (lung epithelial cells). In addition, gene expression analysis showed an upregulation of the cytokine IL-8 in dTHP-1 cells. No increased release of IL-1β, IL-8, IL-6, and TNF-a was noted. Consistent differences in toxicity between the nanoparticles from different materials were not observed. In conclusion, the results show that subway-related nanoparticles can cause DNA damage in cultured lung cells, but the inflammatory potential in terms of cytokine release was limited.

Bioassays to Assess the Safety of Potassium and Sodium Nitrates and Nitrites

(1) Background: Advances in food processing practices and health care are some of the most significant advances in modern daily life. The goal of this study is to evaluate the safety of potassium and sodium nitrates and nitrites when they are used as fertilizers in agriculture and food additives, as well as the known conversion of nitrate to nitrite in humans. (2) Methods: Various bioassays were conducted to investigate the effects of nitrates and nitrites in the Drosophila melanogaster genetic tester system. These assays focused on the modulation of degenerative processes at the molecular, cellular, individual, and population levels. Additionally, we assessed the chemopreventive potential and the ability to induce DNA strand breaks in HL-60 tumour cells. (3) Results: All nitrate and nitrite concentrations tested were shown to not be toxic or genotoxic in Drosophila since none of the compounds reached the LD50 and significant genetic mutation. A positive or null protective capacity against a toxic agent was found for nitrates, not for nitrites, showing that sodium nitrite has a synergistic effect when combined with the oxidant toxin hydrogen peroxide; and a nutraceutical potential in the lifespan only for sodium nitrate to improve the quality of life in 5 days at ADI concentration. The in vitro results in human leukemia cells showed a chemopreventive potential only for potassium nitrate and sodium nitrite due to reducing the viability of HL-60 cells growth to 18% and 29%, respectively, compared to the controls at ADI (acceptable daily intake) concentrations. However, neither of these showed DNA damage or methylation modifications. (4) Conclusions: The tested compounds were shown to be safe to use during in vivo and in vitro tests when used at the extrapolated ADI concentrations.

Etoposide as a Key Therapeutic Agent in Lung Cancer: Mechanisms, Efficacy, and Emerging Strategies.

Topoisomerase II inhibitors, particularly etoposide, have long been integral to the treatment of lung cancer, especially small cell lung cancer. This review comprehensively examines the mechanisms of action of etoposide, its clinical efficacy, and its role in current lung cancer treatment regimens. Etoposide exerts its anticancer effects by inducing DNA strand breaks through the inhibition of topoisomerase II, leading to cancer cell apoptosis. Despite their widespread use, challenges such as drug resistance, toxicity, and limited efficacy in non-small cell lung cancer have spurred ongoing research on combination therapies and novel drug formulations. Emerging therapeutic strategies include the integration of etoposide with immunotherapy, targeted therapies, and novel drug delivery systems aimed at enhancing the therapeutic window and overcoming drug resistance. This article aims to inform the development of more effective treatment strategies by providing a critical overview of the clinical applications of etoposide and exploring future directions for lung cancer therapy.

The potential synergistic effect of combining doxorubicin with vorinostat in urothelial carcinoma therapy.

Bladder cancer ranks as the 9th most common type of cancer worldwide. Approximately 70% of bladder cancers are diagnosed as non-muscle invasive, and they are treated with transurethral resection followed by intravesical therapy. Doxorubicin is one of the effective cytotoxic drugs used in intravesical and systemic therapy, but its cardiotoxicity and nephrotoxicity limit therapeutic dosages. Vorinostat is an anticancer drug used to treat cutaneous T-cell lymphoma, and it demonstrates potent combination effects in various anticancer treatments. We aim to investigate the combined effects and mechanisms of doxorubicin and vorinostat in human bladder cancer cells. Human bladder cancer cells (5637 and BFTC 905) were used in this study. Cell viability of 5637 and BFTC 905cells decreases in a time- and dose-dependent manner when treated with doxorubicin or vorinostat. Compared to the single drug treatment, the combination of doxorubicin and vorinostat synergistically induces cell death in 5637 and BFTC 905cells. Combination drug treatment improves the expression of apoptosis-related proteins, including cleaved PARP, cleaved caspase 8, cleaved caspase 9, cleaved caspase-3, and γ-H2AX in both cell lines. Cell viability of combined treatment in both cell lines is partially restored by pre-treating with Z-VAD-FMK, a pan-caspase inhibitor. Z-VAD-FMK also completely reduced the protein expression of cleaved caspase 3 and γ-H2AX, suggesting that combining doxorubicin and vorinostat leads to DNA strand breaks and apoptosis. Pre-treatment with Z-IETD-FMK, a specific caspase 8 inhibitor, shows a slight recovery of cell viability in 5637 and BFTC 905cells following combined treatment. Cleaved caspase 8, and γ-H2AX proteins in both cell lines are totally inhibited, and cleaved PARP is partially inhibited. Pre-treatment with Ac-LEHD-CMK, a specific caspase 9 inhibitor, no cell viability recovery in both cell lines. These results indicate that the combination of doxorubicin and vorinostat activates the caspase 8 and caspase 9 apoptosis pathways, and induces DNA strand breaks mainly via the caspase 8 pathway. The combination of doxorubicin and vorinostat also significantly inhibits the growth of BFTC 905 tumorspheres and BFTC 905 xenograft tumors in mice. In conclusion, our findings demonstrate that the combination of doxorubicin with vorinostat could potentially serve as a new treatment regimen for urothelial bladder cancer, for avoiding the high-dose side effect of doxorubicin.

Assessing the impact of sub-chronic polyethylene terephthalate nanoplastic exposure on male reproductive health in mice.

The widespread use of polyethylene terephthalate (PET) in food and beverage packaging raises concerns about its potential health effects, particularly when PET-derived nanoplastics (PET-NPs) are released into the environment. This study investigates the reproductive toxicity of PET-NPs in male mice. Mice were exposed to PET-NPs at doses of 0.1mg/day and 0.5mg/day for 28days, and the testes index, sperm count, sperm morphology, Reactive Oxygen Species (ROS) production, DNA integrity, histopathology, and spermatogenesis were evaluated. PET-NP exposure resulted in a significant decrease in sperm concentration and an increase in abnormal spermatozoa-particularly blunt-headed sperm and sperm with neck and tail anomalies- and elevated ROS levels in testicular tissue in a dose-dependent manner (p<0.05). Additionally, PET-NPs induced DNA strand breaks, as demonstrated by the COMET assay (p<0.05). Histopathological analysis revealed disorganization of the germinal epithelium, vacuolization, reduced sperm density, and increased interstitial spaces, accompanied by a significant decline in spermatogenic activity, as assessed by Johnsen scoring. These findings strongly suggest that the observed adverse effects on male reproductive health, including sperm abnormalities, DNA damage, and impaired spermatogenesis, are primarily driven by ROS-induced oxidative stress. The observed changes provide clear evidence of the adverse effects of subchronic exposure to PET nanoplastics on male reproductive health, highlighting the inherent risks associated with nanoplastic exposure and offering crucial insights for public health awareness and regulatory considerations.

Simulation of cell cycle effects on DNA strand break induction due to α-particles.

Understanding cell cycle variations in radiosensitivity is important for α-particle therapies. Differences are due to both repair response mechanisms and the quantity of initial radiation-induced DNA strand breaks. Genome compaction within the nucleus has been shown to impact the yield of strand breaks. Compaction changes during the cell cycle are therefore likely to contribute to radiosensitivity differences. Simulation allows the strand break yield to be calculated independently of repair mechanisms which would be challenging experimentally. Using Geant4 the impact of genome compaction changes on strand break induction due to α-particles was simulated. Genome compaction is considered to be described by three metrics: global base pair density, chromatin fibre packing fraction and chromosome condensation. Nuclei in the G1, S, G2 and M phases from two cancer cell lines and one normal cell line are simulated. Repair mechanisms are not considered to study only the impact of genome compaction changes. The three compaction metrics have differing effects on the strand break yield. For all cell lines the strand break yield is greatest in G2 cells and least in G1 cells. More strand breaks are induced in the two cancer cell lines than in the normal cell line. Compaction of the genome affects the initial yield of strand breaks. Some radiosensitivity differences between cell lines can be attributed to genome compaction changes between the phases of the cell cycle. This study provides a basis for further analysis of how repair deficiencies impact radiation-induced lethality in normal and malignant cells.

The effects of cell displacement on DNA damages in targeted radiation therapy using Geant4-DNA

Charged particle radiation can, directly and indirectly, affect cells by breaking DNA strands. This effect includes DNA single-strand breaks (SSB) and DNA double-strand breaks (DSB), which may cause cell death and mitotic failure. Thus, using short-range charged particles such as Auger electrons (AEs) not only leads to the destruction of the target cell but also prevents the nearby healthy cells from exposing to ionizing radiation. In this study, two spherical cells (C and C2) and their cell nucleus, both made of liquid water, were modeled. An atomic DNA model constructed in the Geant4-DNA Monte Carlo (MC) simulation toolkit was placed inside the nucleus of the C and C2 cells. The number of direct and indirect SSB, DSB, and hybrid DSB (HDSB), caused by some of the most widely-used Auger electron-emitting (AEE) radionuclides, including 99mTc, 111In, 123I, 125I, and 201Tl, distributed within different compartments of the C cell, was calculated in the C and C2 cells, considering the distance between the surface of the two cells ranges from 0 to 5 μm. The present work aimed to investigate the biological effects of AEE radionuclides and their potential for cancer treatment through targeted radiation therapy. The results indicate the impact of 201Tl > 125I > 123I > 111In > 99mTc on DNA damage when the target is C (first spherical cell). On the other hand, for C2 at distances of 0 to 5 μm, the impact of 99mTc > 123I > 111In > 201Tl > 125I on DNA damage is observed.

New advanced models (NAMs) for risk assessment of bisphenol A alternatives.

The safety of bisphenol A (BPA) due to its adverse effects on the immune system has led to an increasing concern and a significant regulatory shift. The European Food Safety Authority (EFSA) proposed a reduction in the tolerable daily intake (TDI) of BPA in food in their 2023 scientific opinion, highlighting the need for stricter regulations compared to their previous assessment in 2015. This regulatory action has spurred the production of BPA alternatives, raising concerns about their safety due to insufficient toxicological data. Addressing this gap is crucial for ensuring human and environmental health. In this project, multiple genotoxicity endpoints were applied for testing of two regulatory relevant BPA alternatives, bisphenol E (BPE) and bisphenol P (BPP), in different human models: 2D HepG2 liver cells, 3D liver spheroids and primary human peripheral blood lymphocytes. DNA strand breaks and oxidised base lesions were evaluated by the enzyme-modified version of the comet assay, while clastogenicity and aneugenicity were analysed by the invitro micronucleus assay (OECD TG 487, 2016), together with cytotoxicity. Development of new advanced models (NAMs), as 3D spheroids, are essential for next-generation risk assessment (NGRA) in line with the 3R's to replace, reduce or refine animal experiments. In this aspect, validation and standardisation of NAMs are needed to reach regulatory readiness level and development of OECD Test Guidelines. Therefore, a standardisation and pre-validation of the advanced 3D liver spheroid model was performed by using multiple genotoxicity endpoints and by comparing the obtained results with standard genotoxicity models.

Genotoxicity testing of the anthraquinone dye Alizarin Red S.

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

AuNPs-based lateral flow strip genotoxicity biosensor by sensitive quantification of 8-oxodGuo

Development of rapid and sensitive methods for screening of large number of chemical pollutants with potential genotoxicity is in urgent demands. In this work, we reported a chemical genotoxicity sensor based on the lateral flow strip (LFS) quantification of the 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo). The proposed sensing strategy introduced human 8-oxoguanine DNA glycosylase (hOGG 1) and human apyrimidinic endonuclease (APE 1) to convert 8-oxodGuo to strand break. Then, the DNA conjugated gold nanoparticles (AuNPs) complexes could not be captured on test line (T-line), showing visible red color fading. Additionally, the mean grey value of the optical density in the T-line zone was analyzed by using a mobile phone camera and Image J software to quantify 8-oxodGuo. Under the optimized experimental conditions, the LFS DNA biosensor could detect the lowest concentration of 8-oxodGuo down to 0.2 pmol. To demonstrate its universal applications, in vitro generation of 8-oxodGuo by Rose Bengal under irradiation and Fe2+-mediated Fenton reagent were successfully measured. The detection limit of oxidative DNA damage induced by Rose Bengal or Fenton reagent could be down to 0.01 μM or 1 nM Fe2+/4 nM H2O2, respectively. The 10-fold higher sensitivity for Fenton reagent was attributed to much more severe damage than Rose Bengal, producing both DNA strand break and nucleobases conversion. The results demonstrated that the LFS DNA biosensor could detect oxidative DNA damage for the first time, showing its potential application for assessment of the genotoxicity of abundant chemical pollutants.

Mechanistic Insight Into the Conformational Changes of Cas8 Upon Binding to Different PAM Sequences in the Transposon-Encoded Type I-F CRISPR-Cas System.

The INTEGRATE system is a gene-editing approach that offers advantages over the widely used CRISPR-Cas9 system. It does not introduce double strand breaks in the target DNA but rather integrates the desired DNA sequence directly into it. The first step in the integration process is PAM recognition, which is critical to understanding and optimizing the system. Experimental testing revealed varying integration efficiencies of different PAM mutants, and computational simulations were carried out to gain mechanistic insight into the conformational changes of Cas8 during PAM recognition. Our results showed that the interaction between Arg246 and guanine at position (-1) of the target strand is critical for PAM recognition. We found that unfavorable interactions in the 5'-AC-3' PAM mutant disrupted this interaction and may be responsible for its 0% integration efficiency. Additionally, we discovered that PAM sequences not only initiate the integration process but also regulate it through an allosteric mechanism that connects the N-terminal domain and the helical bundle of Cas8. This allosteric regulation was present in all PAMs tested, even those with lower integration efficiencies, such as 5'-TC-3' and 5'-AC-3'. We identified the Cas8 residues that are involved in this regulation. Our findings provide valuable insights into PAM recognition mechanisms in the INTEGRATE system and can help improve the gene-editing technology.

RSF1 orchestrates p53 transcriptional activity by coordinating p300 acetyltransferase and FACT complex.

The transcriptional regulation of p53-dependent genes in response to DNA damage is critical for effective DNA repair and cell survival. We previously established that RSF1 (remodeling and spacing factor 1) is necessary for p53-dependent gene transcription in response to DNA strand breaks. Here, we further elucidate that the role of RSF1 in p53 regulation by demonstrating that its depletion results in a reduction in the acetylated-Lys(K)382 level of p53, which governs its transcriptional activity. RSF1 was co-precipitated with p300 acetyltransferase upon etoposide treatment. Chromatin immunoprecipitation assays on the upstream region of CDKN1A gene revealed reduced p300 and TBP accumulation, which were accompanied with low H3H27ac and H3K4me1 levels in RSF1 knockout cells. Moreover, RSF1 depletion led to a reduced accumulation of SSRP1 and SPT16, subunits of FACT complex at the promoter of CDKN1A gene. These findings suggest that RSF1 promotes p53-dependent p21 gene transcription by facilitating the accumulation of p300 acetyltransferase at the enhancer and FACT at the promoter region of CDKN1A gene, respectively.

Methodological steps forward in toxicological in vitro screening of mineral wools in primary rat alveolar macrophages and normal rat mesothelial NRM2 cells.

Man-made vitreous fibers (MMVF) comprise diverse materials for thermal and acoustic insulation, including stone wool. Depending on dimension, durability, and dose, MMVF might induce adverse health effects. Therefore, early predictive in vitro (geno)toxicity screening of new MMVF is highly desired to ensure safety for exposed workers and consumers. Here, we investigated, as a starting point, critical in vitro screening determinants and pitfalls using primary rat alveolar macrophages (AM) and normal rat mesothelial cells (NRM2). A stone wool fiber (RIF56008) served as an exemplary MMVF (fibrous vs. ground to estimate impact of fiber shape) and long amosite (asbestos) as insoluble fiber reference. Materials were comprehensively characterized, and in vivo-relevant in vitro concentrations defined, based on different approaches (low to supposed overload: 0.5, 5 and 50µg/cm2). After 4-48h of incubation, certain readouts were analyzed and material uptake was investigated by light and fluorescence-coupled darkfield microscopy. DNA-strand break induction was not morphology-dependent and nearly absent in both cell types. However, NRM2 demonstrated material-, morphology- and concentration-dependent membrane damage, CINC-1 release, reduction in cell count, and induction of binucleated cells (asbestos > RIF56008 > RIF56008 ground). In contrast to NRM2, asbestos was nearly inactive in AM, with CINC-1 release solely induced by RIF56008. In conclusion, to define an MMVF-adapted, predictive in vitro (geno)toxicity screening tool, references, endpoints, and concentrations should be carefully chosen, based on in vivo relevance, and sensitivity and specificity of the chosen cell model. Next, further endpoints should be evaluated, ideally with validation by in vivo data regarding their predictivity.

Veratric Acid as a Potential Antidiabetic Agent: Molecular Docking and In vivo Enzyme Inhibition Studies with Insights from STz-NA Induced Diabetic Rat Model

Streptozotocin-nicotinamide (STz-NA) has proven to be an effective agent in inducing type 2 diabetes (T2DM) in experimental models due to its genotoxic impact on pancreatic β-cells. STz reduces nicotinamide adenine dinucleotide (NAD+) through the glucose transporter GLUT2, leading to cellular damage, DNA strand breaks, and cell death. Nicotinamide (NA), a biochemical precursor of NAD+ and poly-ADP-ribose-polymerase-1 (PARP-1) inhibitor, plays a crucial protective role by modulating NAD+ levels, which are essential in ATP production and other metabolic processes. Excessive DNA damage, however, triggers PARP-1 over-activation, depleting cellular reserves and resulting in cell necrosis. This study further investigates the antidiabetic and hepatoprotective effects of Veratric Acid (VA) by comparing it to Glibenclamide. Utilizing Computer-Aided Drug Design (CADD), VA was identified as a structurally similar compound with potential antidiabetic properties. Molecular docking studies targeting proteins, such as GLUT-1 (PDB ID: 4PYP) and 1BSI, along with in vivo assays in STz-NA-induced diabetic Wistar rats, were conducted. VA demonstrated significant binding affinity and molecular interactions comparable to standard antidiabetic agents, showing inhibitory effects on liver enzymes SGOT and SGPT, and supporting its potential role in diabetes management. Docking and histopathology results revealed that VA effectively reduced blood glucose, improved insulin levels, and enhanced liver function in diabetic rats. Additionally, VA promoted insulin secretion from pancreatic β-cells and upregulated insulin-related markers, with minimal hepatotoxicity compared to Glibenclamide. VA treatment significantly improved enzymatic and non-enzymatic antioxidant levels, lowered lipid peroxidation, and improved lipid profiles, which were confirmed by histopathological liver observations. Veratric Acid at low doses effectively modulates blood glucose and diabetes-related biochemical parameters, highlighting its promise as a safer, natural therapeutic alternative for diabetes treatment.

Hypnea musciformis Seaweed Extract Protected Human Mesenchymal Stem Cells From Oxidative Stress Through NRF2 Activation.

Previous studies have shown that Hypnea musciformis seaweed extracts (HMEs) possess antioxidant properties, but the molecular mechanisms accounting for this activity are not known. Thus, the present study investigated the molecular mechanisms through which HME exerted its antioxidant activity in human mesenchymal stem cells (WJ-MSCs). After the isolation of HME, its chemical composition was analyzed with gas chromatography mass spectrometry, indicating that it contained amino acids, organic acids, organic amides, sugar alcohols, saturated fatty acids, hydrogenated diterpene alcohols, and other organic compounds. Afterward, HME was shown invitro to scavenge DPPH·, ABTS·+, ·OH, and O2 ·- radicals, possess reducing activity, and protect from ROO·-induced DNA strand breakage. Finally, the results showed that HME treatment of WJ-MSCs prevented H2O2-induced oxidative stress by decreasing lipid peroxidation, protein oxidation, reactive oxygen species levels, and DNA damage and by increasing glutathione levels. Moreover, our findings showed for the first time that HME's antioxidant activity in WJ-MSCs was mediated through the activation of NRF2, which upregulated the expression of the antioxidant proteins GCLC, GSR, HMOX1, SOD1, TXN, and GPX1. These results provide new insights into H. musciformis' antioxidant properties, which could help substantially its use as a food supplement or for developing biofunctional foods.

POLD3 as Controller of Replicative DNA Repair.

Multiple modes of DNA repair need DNA synthesis by DNA polymerase enzymes. The eukaryotic B-family DNA polymerase complexes delta (Polδ) and zeta (Polζ) help to repair DNA strand breaks when primed by homologous recombination or single-strand DNA annealing. DNA synthesis by Polδ and Polζ is mutagenic, but is needed for the survival of cells in the presence of DNA strand breaks. The POLD3 subunit of Polδ and Polζ is at the heart of DNA repair by recombination, by modulating polymerase functions and interacting with other DNA repair proteins. We provide the background to POLD3 discovery, investigate its structure, as well as function in cells. We highlight unexplored structural aspects of POLD3 and new biochemical data that will help to understand the pivotal role of POLD3 in DNA repair and mutagenesis in eukaryotes, and its impact on human health.

Dynamics of metal/metalloid bioaccumulation and sensitivity in post-larvae shrimp (Macrobrachium rosenbergii) exposed to settleable atmospheric particulate matter from an industrial source

The metallurgy industry is a potent global source of particulate matter (PM) atmospheric emissions. A portion of this PM may settle in aquatic (SePM) carrying metal/metalloid particles and metallic nanoparticles. Surprisingly, this form of contamination has not received due attention from most environmental monitoring agencies. We analyzed the effect of exposure to SePM on shrimp post-larvae, a critical stage for the viability of shrimp populations and for the trophic chain. After acclimation, shrimp were exposed to contaminants using a randomized experimental design—a 4 × 4 factorial arrangement with 2 factors: exposure time (24, 48, 72, and 96 h) and SePM concentration (0.00, 0.01, 0.10, and 1.00 g L−1). The bioaccumulation of metals, contamination rates, mortality, and ROS-related biomarkers (lipid peroxidation – LPO; DNA strand breakage DNA SB and metallothionein content – MTs;) were evaluated. After contamination, the water contained 27 different metals/metalloids. Post-larvae accumulated metals, such as Cd, Pb, Al, As, Se, Sr, Zr, Ba, La, Ce, W, and Hg. However, the rise in SePM did not result in a proportional bioaccumulation rise, indicating that effective biological barriers may work for some metals. Although the different levels of SePM changed mortality dynamics, they resulted in a similar final lethality (60–80 %). SePM caused significant damage to lipids (increased LPO), genetic material (DNA SB), and increased Mts. Such effects may reflect a particularly deleterious ecological problem as it is present at such an early stage of life. These results identified a clear environmental risk since the lower level of exposure used was 102 times lower than that measured in the habitats affected by local industry. Consequently, our results emphasize the need for clear protocols for monitoring the effects of SePM in aquatic environments.

Effects of Co-Exposure to Benzene, Toluene, and Xylene, Polymorphisms of microRNA Genes, and Their Interactions on Genetic Damage in Chinese Petrochemical Workers.

Benzene, toluene, and xylene (BTX) co-exist in human environments, yet their individual and combined effects on genetic damage at low exposure levels are not fully understood. Additionally, single nucleotide polymorphisms in microRNAs (mirSNPs) might be involved in cancer etiology by affecting the related early health damage. To investigate the influence of BTX exposure, mirSNPs, and their interactions on genetic damage, we conducted a cross-sectional study in 1083 Chinese petrochemical workers, quantifying the BTX cumulative exposure levels and multiple genetic damage biomarkers. Additionally, we genotyped multiple common mirSNPs. Benzene and a BTX mixture were positive associated with the olive tail moment (OTM) and tail DNA% (p < 0.05). Higher levels of toluene and xylene enhanced the association of benzene with genetic damage levels. Genotypes and/or mutant allele counts of miR-4482-related rs11191980, miR-4433-related rs136547, miR-27a-related rs2594716, miR-3130-related rs725980, and miR-3928-related rs878718 might significantly influence genetic damage levels. Stronger effect estimates of benzene/BTX exposure were found in carriers of miR-196a-2-related rs11614913 heterozygotes and of wild homozygotes of miR-1269b-related rs12451747, miR-612-related rs12803915, and miR-4804-related rs266437. Our findings provide further support of the involvement of BTX co-exposure, mirSNPs, and their gene-environment interactions in determining the severity of DNA strand break in a complex manner.