Epigenetic effects induced by silver nanoparticles in Caenorhabditis elegans after multigenerational exposure

Transgenerational reproductive toxicity induced by carboxyl and amino charged microplastics at environmental concentrations in Caenorhabditis elegans: Involvement of histone methylation

Microplastics, recognized as emerging contaminants, are commonly observed to be charged in the environment, potentially exerting toxic effects on various organisms. However, the transgenerational reproductive toxicity and underlying mechanisms of polystyrene (PS), particularly carboxyl-modified PS (PS-COOH) and amino-modified PS (PS-NH2), remain largely unexplored. In this study, the parental generation (P0) of Caenorhabditis elegans was subjected to environmental concentrations (0.1-100 μg/L) of PS, PS-COOH, and PS-NH2, with subsequent generations (F1-F4) cultured under normal conditions. Exposure to PS-NH2 at concentrations of 10-100 μg/L exhibited more pronounced reproductive toxicity compared to PS or PS-COOH, resulting in decreased brood size, egg ejection rate, number of fertilized eggs, and cell corpses per gonad. Similarly, maternal exposure to 100 μg/L of PS-NH2 induced more severe transgenerational reproductive effects in C. elegans. Significant increases in H3 on lysine 4 dimethylation (H3K4me2) and H3 on lysine 9 trimethylation (H3K9me3) levels were observed in the subsequent generation, concurrent with the transgenerational upregulation of set-30 and met-2 following parental exposure to PS, PS-COOH, and PS-NH2. Correlation analyses revealed significant associations between the expression of these genes with the reproductive ability. Molecular docking studies suggested that PS-NH2 exhibited higher affinity for SET-30 and MET-2. Further analysis demonstrated that transgenerational effects on reproduction were absent in set-30(gk315) and met-2(n4256) mutants, highlighting the pivotal role of set-30 and met-2 in mediating the transgenerational effect. This study provides novel insights into the environmental risks associated with negatively and positively charged microplastics.

Environmental behaviors and toxic mechanisms of engineered nanomaterials in soil

Engineered nanomaterials (ENMs) are inevitably released into the environment with the exponential application of nanotechnology. Parts of ENMs eventually accumulate in the soil environment leading to potential adverse effects on soil ecology, crop production, and human health. Therefore, the safety application of ENMs on soil has been widely discussed in recent years. More detailed safety information and potential soil environmental risks are urgently needed. However, most of the studies on the environmental effects of metal-based ENMs have been limited to single-species experiments, ecosystem processes, or abiotic processes. The present review formulated the source and the behaviors of the ENMs in soil, and the potential effects of single and co-exposure ENMs on soil microorganisms, soil fauna, and plants were introduced. The toxicity mechanism of ENMs to soil organisms was also reviewed including oxidative stress, the release of toxic metal ions, and physical contact. Soil properties affect the transport, transformation, and toxicity of ENMs. Toxic mechanisms of ENMs include oxidative stress, ion release, and physical contact. Joint toxic effects occur through adsorption, photodegradation, and loading. Besides, future research should focus on the toxic effects of ENMs at the food chain levels, the effects of ENMs on plant whole-lifecycle, and the co-exposure and long-term toxicity effects. A fast and accurate toxicity evaluation system and model method are urgently needed to solve the current difficulties. It is of great significance for the sustainable development of ENMs to provide the theoretical basis for the ecological risk assessment and environmental management of ENMs.

Mutuality of epigenetic and nanoparticles: two sides of a coin

Nowadays nanoparticles (NPs) due to their multidimensional applications in enormous different fields, has become an exciting research topic. In particular, they could attract a noticeable interest as drug deliver with increased bioavailability, therapeutic efficacy and drug specificity. Epigenetic can be considered as a complex network of molecular mechanism which are engaged in gene expression and have a vital role in regulation of environmental effects on ethology of different disorders like neurological disorders, cancers and cardiovascular diseases. For many of them epigenetic therapy was proposed although its application accompanied with limitations, due to drug toxicity. In this review we evaluate two aspects to epigenetic in the field of NPs: firstly, the role of epigenetic in regulation of nanotoxicity and secondly application of NPs as potential carriers for epidrugs.

Photoaged Polystyrene Nanoplastics Result in Transgenerational Reproductive Toxicity Associated with the Methylation of Histone H3K4 and H3K9 in Caenorhabditis elegans

Polystyrene nanoplastics (PS-NPs) are emerging environmental contaminants that are ubiquitously detected in various environments and have toxic effects on various organisms. Nevertheless, the transgenerational reproductive toxicity and underlying mechanisms of PS-NPs remain largely unknown, especially for photoaged PS-NPs under ultraviolet irradiation. In this study, only the parental generation (P0) was exposed to virgin and aged PS-NPs at environmentally relevant concentrations (0.1-100 μg/L), and subsequent generations (F1-F4) were cultured under normal conditions. Ultraviolet irradiation induced the generation of environmentally persistent free radicals and reactive oxygen species, which altered the physical and chemical characteristics of PS-NPs. The results of toxicity testing suggested that exposure to aged PS-NPs caused a more severe decrease in brood size, egg ejection rate, number of fertilized eggs, and hatchability than did the virgin PS-NPs in the P0, F1, and F2 generations. Additionally, a single maternal exposure to aged PS-NPs resulted in transgenerational effects on fertility in the F1 and F2 generations. Increased levels of H3K4 and H3K9 methylation were observed in the F1 and F2 generations, which were concomitant with the transgenerational downregulation of the expression of associated genes, such as spr-5, set-17, and met-2. On the basis of correlation analyses, the levels of histone methylation and the expression of these genes were significantly correlated to transgenerational reproductive effects. Further research showed that transgenerational effects on fertility were not observed in spr-5(by134), met-2(n4256), and set-17(n5017) mutants. Overall, maternal exposure to aged PS-NPs induced transgenerational reproductive effects via H3K4 and H3K9 methylation, and the spr-5, met-2, and set-17 genes were involved in the regulation of transgenerational toxicity. This study provides new insights into the potential risks of photoaging PS-NPs in the environment.

Long-term exposure to polystyrene nanoparticles at environmentally relevant concentration causes suppression in heme homeostasis signal associated with transgenerational toxicity induction in Caenorhabditis elegans

Heme homeostasis related signaling participates in inducing a protective response when controlling nanopolystyrene toxic effects in parental generation. However, whether the heme homeostasis signal is involved in regulation of transgenerational toxicity of nanopolystyrene toxicity is still unclear. Herein, with the model organism of Caenorhabditis elegans, 0.1-10 μg/L nanopolystyrene particles (PS-NPs) at 20-nm treatment downregulated glb-18, and the decrease was also discovered in the offspring following PS-NPs exposure. Germline glb-18 RNAi induced susceptive property to transgenerational PS-NPs toxicity, suggesting that a decreased GLB-18 level mediated induction of transgenerational toxicity. Importantly, germline GLB-18 transgenerationally activated the function of intestinal HRG-4 in controlling transgenerational PS-NPs toxicity. In transgenerational toxicity control, HRG-1/ATFS-1/HSP-6 was recognized to be the downstream pathway of HRG-4. Briefly, germline GLB-18 in P0 generation can transgenerationally activate the downstream intestinal HRG-4/HRG-1/ATFS-1/HSP-6 pathway among offspring for controlling the transgenerational toxicity of PS-NPs. Findings in the present work strengthens the possible association of heme homeostasis signal changes with transgenerational nanoplastic toxicity within the organisms.

Multigenerational Effects of Graphene Oxide Nanoparticles on Acheta domesticus DNA Stability

The use of nanoparticles like graphene oxide (GO) in nanocomposite industries is growing very fast. There is a strong concern that GO can enter the environment and become nanopollutatnt. Environmental pollutants' exposure usually relates to low concentrations but may last for a long time and impact following generations. Attention should be paid to the effects of nanoparticles, especially on the DNA stability passed on to the offspring. We investigated the multigenerational effects on two strains (wild and long-lived) of house cricket intoxicated with low GO concentrations over five generations, followed by one recovery generation. Our investigation focused on oxidative stress parameters, specifically AP sites (apurinic/apyrimidinic sites) and 8-OHdG (8-hydroxy-2'-deoxyguanosine), and examined the global DNA methylation pattern. Five intoxicated generations were able to overcome the oxidative stress, showing that relatively low doses of GO have a moderate effect on the house cricket (8-OHdG and AP sites). The last recovery generation that experienced a transition from contaminated to uncontaminated food presented greater DNA damage. The pattern of DNA methylation was comparable in every generation, suggesting that other epigenetic mechanisms might be involved.

Silver Nanoparticles Induced Changes in DNA Methylation and Histone H3 Methylation in a Mouse Model of Breast Cancer

The importance of epigenetic changes as a measurable endpoint in nanotoxicological studies is getting more and more appreciated. In the present work, we analyzed the epigenetic effects induced by citrate- and PEG-coated 20 nm silver nanoparticles (AgNPs) in a model consisting of 4T1 breast cancer tumors in mice. Animals were administered with AgNPs intragastrically (1 mg/kg b.w. daily-total dose 14 mg/kg b.w.) or intravenously (administration twice with 1 mg/kg b.w.-total dose 2 mg/kg b.w.). We observed a significant decrease in 5-methylcytosine (5-mC) level in tumors from mice treated with citrate-coated AgNPs regardless of the route of administration. For PEG-coated AgNPs, a significant decrease in DNA methylation was observed only after intravenous administration. Moreover, treatment of 4T1 tumor-bearing mice with AgNPs decreased histone H3 methylation in tumor tissue. This effect was the most pronounced for PEG-coated AgNPs administered intravenously. No changes in histone H3 Lys9 acetylation were observed. The decrease in methylation of DNA and histone H3 was accompanied by changes in expression of genes encoding chromatin-modifying enzymes (Setd4, Setdb1, Smyd3, Suv39h1, Suv420h1, Whsc1, Kdm1a, Kdm5b, Esco2, Hat1, Myst3, Hdac5, Dnmt1, Ube2b, and Usp22) and genes related to carcinogenesis (Akt1, Brca1, Brca2, Mlh1, Myb, Ccnd1, and Src). The significance of the observed changes and the mechanisms responsible for their development are unclear, and more research in this area is warranted. Nevertheless, the present work points to the epigenetic effects as an important level of interaction between nanomaterials and biological systems, which should always be taken into consideration during analysis of the biological activity of nanomaterials and development of nanopharmaceuticals.

Impact of progressively cumulative exposure of AgNPs on earthworms (Eisenia fetida) and implication for eco-toxicological risk assessment

Hazardous pollutants released into the real environment mostly own long-lasting cumulative characteristics and have progressively negative impacts on organisms, which are always neglected in laboratory toxicological tests. Here in this study, the different ecotoxicity of Ag nanoparticles (AgNPs) on earthworm Eisenia fetida was compared via various endpoints and transcriptional sequencing between the 28-day progressively repeated (from 60 to 80, final 100 mg/kg) and one-step (directly to 100 mg/kg) exposure. The results showed that earthworms under progressively repeated exposure showed significantly less biomass loss and reproductive inhibition, as well as lower Ag bioaccumulation (15.6 mg/kg) compared with one-step exposure (17.9 mg/kg). The increases in enzyme activities (superoxide enzyme and catalase) and gene expression (metallothionein) also implied higher antioxidant and genetic toxicity in one-step exposed earthworms compared with those from progressively repeated exposure. Furthermore, the transcriptomic analysis identified 582 and 854 differentially expressed genes in the treatments of one-step and repeated exposure respectively compared with the control group. The results of pathway annotation and classification suggested similar enrichments of damage induction but different in toxic stress responses, whereas earthworms from repeated exposure possessed more detoxification-related pathways like translation and multicellular organismal processes. This study innovatively took into account the impacts of processive exposure occurring in the real environment and elucidated distinctions of toxicity and adaptation caused by different exposure patterns, which provided the theoretical basis for real risk identification under the framework and guidance of traditional toxicology, also the implication for the improvement of eco-toxicological risk assessment.

Global DNA Adenine Methylation in Caenorhabditis elegans after Multigenerational Exposure to Silver Nanoparticles and Silver Nitrate

Multigenerational and transgenerational reproductive toxicity in a model nematode Caenorhabditis elegans has been shown previously after exposure to silver nanoparticles (Ag-NPs) and silver ions (AgNO3). However, there is a limited understanding on the transfer mechanism of the increased reproductive sensitivity to subsequent generations. This study examines changes in DNA methylation at epigenetic mark N6-methyl-2'-deoxyadenosine (6mdA) after multigenerational exposure of C. elegans to pristine and transformed-via-sulfidation Ag-NPs and AgNO3. Levels of 6mdA were measured as 6mdA/dA ratios prior to C. elegans exposure (F0) after two generations of exposure (F2) and two generations of rescue (F4) using high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS). Although both AgNO3 and Ag-NPs induced multigenerational reproductive toxicity, only AgNO3 exposure caused a significant increase in global 6mdA levels after exposures (F2). However, after two generations of rescue (F4), the 6mdA levels in AgNO3 treatment returned to F0 levels, suggesting other epigenetic modifications may be also involved. No significant changes in global DNA methylation levels were observed after exposure to pristine and sulfidized sAg-NPs. This study demonstrates the involvement of an epigenetic mark in AgNO3 reproductive toxicity and suggests that AgNO3 and Ag-NPs may have different toxicity mechanisms.

A review of transgenerational and multigenerational toxicology in the in vivo model animal Caenorhabditis elegans

A large number of pollutants existing in the environment can last for a long time, and their potential toxic effects can transfer from parents to their offspring. Thus, it is necessary to investigate the toxicity of environmental pollutants across multigenerations and the underlying mechanisms in organisms. Due to its short life cycle and sensitivity to environmental exposures, Caenorhabditis elegans is an important animal model for toxicity assessment of environmental pollutants across multigenerations. In this review, we introduced the transgenerational and multigenerational toxicity caused by various environmental pollutants in C. elegans. Moreover, we discussed the underlying mechanisms for the observed transgenerational and multigenerational toxicity of environmental contaminants in C. elegans.

Potential Environmental and Health Implications from the Scaled-Up Production and Disposal of Nanomaterials Used in Biosensors

Biosensors often combine biological recognition elements with nanomaterials of varying compositions and dimensions to facilitate or enhance the operating mechanism of the device. While incorporating nanomaterials is beneficial to developing high-performance biosensors, at the stages of scale-up and disposal, it may lead to the unmanaged release of toxic nanomaterials. Here we attempt to foster connections between the domains of biosensors development and human and environmental toxicology to encourage a holistic approach to the development and scale-up of biosensors. We begin by exploring the toxicity of nanomaterials commonly used in biosensor design. From our analysis, we introduce five factors with a role in nanotoxicity that should be considered at the biosensor development stages to better manage toxicity. Finally, we contextualize the discussion by presenting the relevant stages and routes of exposure in the biosensor life cycle. Our review found little consensus on how the factors presented govern nanomaterial toxicity, especially in composite and alloyed nanomaterials. To bridge the current gap in understanding and mitigate the risks of uncontrolled nanomaterial release, we advocate for greater collaboration through a precautionary One Health approach to future development and a movement towards a circular approach to biosensor use and disposal.

The critical role of epigenetic mechanisms involved in nanotoxicology

Over the past decades, nanomaterials (NMs) have been widely applied in the cosmetic, food, engineering, and medical fields. Along with the prevalence of NMs, the toxicological characteristics exhibited by these materials on health and the environment have gradually attracted attentions. A growing number of evidences have indicated that epigenetics holds an essential role in the onset and development of various diseases. NMs could cause epigenetic alterations such as DNA methylation, noncoding RNA (ncRNA) expression, and histone modifications. NMs might alternate either global DNA methylation or the methylation of specific genes to affect the biological function. Abnormal upregulation or downregulation of ncRNAs might also be a potential mechanism for the toxic effects caused by NMs. In parallel, the phosphorylation, acetylation, and methylation of histones also take an important part in the process of NMs-induced toxicity. As the adverse effects of NMs continue to be explored, mechanisms such as chromosomal remodeling, genomic imprinting, and m⁶ A modification are also gradually coming into the limelight. Since the epigenetic alterations often occur in the early development of diseases, thus the relevant studies not only provide insight into the pathogenesis of diseases, but also screen for the prospective biomarkers for early diagnosis and prevention. This review summarizes the epigenetic alterations elicited by NMs, hoping to provide a clue for nanotoxicity studies and security evaluation of NMs. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Review of the toxicity and potential molecular mechanisms of parental or successive exposure to environmental pollutants in the model organism Caenorhabditis elegans

Environmental pollutants such as heavy metals, nano/microparticles, and organic compounds have been detected in a wide range of environmental media, causing long-term exposure in various organisms and even humans through breathing, contacting, ingestion, and other routes. Long-term exposure to environmental pollutants in organisms or humans promotes exposure of offspring to parental and environmental pollutants, and subsequently results in multiple biological defects in the offspring. This review dialectically summarizes and discusses the existing studies using Caenorhabditis elegans (C. elegans) as a model organism to explore the multi/transgenerational toxicity and potential underlying molecular mechanisms induced by environmental pollutants following parental or successive exposure patterns. Parental and successive exposure to environmental pollutants induces various biological defects in C. elegans across multiple generations, including multi/transgenerational developmental toxicity, neurotoxicity, reproductive toxicity, and metabolic disturbances, which may be transmitted to progeny through reactive oxygen species-induced damage, epigenetic mechanisms, insulin/insulin-like growth factor-1 signaling pathway. This review aims to arouse researchers' interest in the multi/transgenerational toxicity of pollutants and hopes to explore the possible long-term effects of environmental pollutants on organisms and even humans, as well as to provide constructive suggestions for the safety and management of emerging alternatives.

Alteration in Wnt signaling mediates induction of transgenerational toxicity of polystyrene nanoplastics in C. elegans

Polystyrene nanoparticles (PS-NPs) have a potential toxicity on offspring after the exposure. However, the molecular basis for PS-NP in inducing transgenerational toxicity remains largely unknown. In this study, the role and the underlying mechanism of germline Wnt signaling in regulating transgenerational toxicity of PS-NPs were determined using an in vivo animal model of Caenorhabditis elegans. Exposure to PS-NP (1-100 μg/L) increased expression of Wnt ligand LIN-44 and decreased expression of Wnt receptor MIG-1. After the exposure, the transgenerational PS-NP toxicity on locomotion behavior and brood size were inhibited in lin-44(RNAi) nematodes, while enhanced in mig-1(RNAi) nematodes. The resistance to transgenerational PS-NP toxicity induced by RNAi of lin-44 in P0 generation (P0-G) was inhibited by RNAi of mig-1 in F1-G. In addition, after PS-NP exposure, germline RNAi of lin-44 at P0-G could increase the mig-1 expression in F1-G. Exposure to PS-NP (1-100 μg/L) further decreased expressions of Dishevelled proteins of DSH-1/2, increased APC complex component APR-1, and decreased expression of BAR-1/β-catenin. Meanwhile, transgenerational PS-NP toxicity was enhanced by RNAi of dsh-1, dsh-2, or bar-1 and inhibited by RNAi of apr-1, suggesting that the DSH-1/2-APR-1-BAR-1 signaling cascade acted downstream of Wnt receptor MIG-1 to control transgenerational PS-NP toxicity. Moreover, BAR-1 acted upstream of DVE-1 to activate mitochondrial unfolded protein response (mt UPR) against the transgenerational PS-NP toxicity. Our data highlights the potential link between alteration in germline Wnt signaling and induction of transgenerational nanoplastic toxicity in organisms.

Nanoplastics cause transgenerational toxicity through inhibiting germline microRNA mir-38 in C. elegans

Nanoplastic exposure potentially caused the induction of transgenerational toxicity. Nevertheless, the molecular basis for nanoplastic exposure-induced transgenerational toxicity remains largely unclear. Using Caenorhabditis elegans as an animal model, we examined the role of germline microRNA (miRNA) mir-38 in regulating the transgenerational toxicity of polystyrene nanoparticles (PS-NPs). After the exposure, 1-100 μg/L PS-NP decreased expression of germline mir-38. Meanwhile, germline mir-38 overexpression conferred a resistance to transgenerational PS-NP toxicity, which suggested that the decrease in germline mir-38 mediated the induction of transgenerational PS-NP toxicity. In the germline, mir-38 regulated transgenerational PS-NP toxicity by inhibiting activity of downstream targets (NDK-1, NHL-2, and WRT-3). Among these three downstream targets, germline NDK-1 further controlled transgenerational PS-NP toxicity by suppressing the function of KSR-1/2, two kinase suppressors of Ras. Therefore, in the germline, the decrease in mir-38 mediated induction of transgenerational PS-NP toxicity by at least inhibiting signaling cascade of NDK-1-KSR-1/2 in nematodes. The findings in this study are helpful for providing relevantly molecular endpoints to assess potential transgenerational toxicity of nanoplastics.

A critical review of advances in reproductive toxicity of common nanomaterials to Caenorhabditis elegans and influencing factors

In recent decades, nanotechnology has rapidly developed. Therefore, there is growing concern about the potential environmental risks of nanoparticles (NPs). Caenorhabditis elegans (C. elegans) has been used as a powerful tool for studying the potential ecotoxicological impacts of nanomaterials from the whole animal level to single cell level, especially in the area of reproduction. In this review, we discuss the reproductive toxicity of common nanomaterials in C. elegans, such as metal-based nanomaterial (silver nanoparticles (NPs), gold NPs, zinc oxide NPs, copper oxide NPs), carbon-based nanomaterial (graphene oxide, multi-walled carbon nanotubes, fullerene nanoparticles), polymeric NPs, silica NPs, quantum dots, and the potential mechanisms involved. This insights into the toxic effects of existing nanomaterials on the human reproductive system. In addition, we summarize how the physicochemical properties (e.g., size, charge, surface modification, shape) of nanomaterials influence their reproductive toxicity. Overall, using C. elegans as a platform to develop rapid detection techniques and prediction methods for nanomaterial reproductive toxicity is expected to reduce the gap between biosafety evaluation of nanomaterials and their application.

Nanosafety: An Evolving Concept to Bring the Safest Possible Nanomaterials to Society and Environment

The use of nanomaterials has been increasing in recent times, and they are widely used in industries such as cosmetics, drugs, food, water treatment, and agriculture. The rapid development of new nanomaterials demands a set of approaches to evaluate the potential toxicity and risks related to them. In this regard, nanosafety has been using and adapting already existing methods (toxicological approach), but the unique characteristics of nanomaterials demand new approaches (nanotoxicology) to fully understand the potential toxicity, immunotoxicity, and (epi)genotoxicity. In addition, new technologies, such as organs-on-chips and sophisticated sensors, are under development and/or adaptation. All the information generated is used to develop new in silico approaches trying to predict the potential effects of newly developed materials. The overall evaluation of nanomaterials from their production to their final disposal chain is completed using the life cycle assessment (LCA), which is becoming an important element of nanosafety considering sustainability and environmental impact. In this review, we give an overview of all these elements of nanosafety.

Evidence for the metal resistance of earthworm Eisenia fetida across generations (F1 and F2) under laboratory metal exposure

Environmental stressors are persistent but most toxicological studies always evaluate the risk via short-term acute toxicity, while continuous toxicity and biological resistance across generations are relatively unknown. Here, earthworm Eisenia fetida was laboratory-reared and exposed to historically contaminated soils with an increasing metal gradient (CK, LM and HM), to investigate cross-generation toxicity and resistance of F1 and F2 worms. The results elucidated that biomass and juvenile hatching rate of F2 E. fetida showed maximum decreases of 20.8% and 38.5% than those of F1, which indicated severer toxicity of earthworm offspring. However, metal bioaccumulation in F2 E. fetida showed maximum increases of 150%, 49.2%, 19.7% and 25.5% than F1 for Cd, Cu, Zn and Pb, respectively. F2 E. fetida suffered less oxidative stress because the activities of superoxide dismutase (SOD), peroxidase (POD), glutathione (GSH), and malondialdehyde (MDA) contents were basically lower than that of F1. Meanwhile, the detoxification genes of metallothionein and heat shock protein 70 in F2 E. fetida showed maximum of 296% and 78.9% up-regulations, respectively, which suggested greater metal resistance of F2 E. fetida. This study confirmed the cross-generation toxicity and resistance of earthworms, which provides novel insights to reveal specific contaminant risks from longer lifecycles. CAPSULE: Earthworms under cross-generation exposure can develop metal resistance despite suffering worse toxicity effects.

Sublethal toxicity of graphene oxide in Caenorhabditis elegans under multi-generational exposure

Nanomaterials have received increasing attentions owing to their potential hazards to the environment and human health; however, the multi-generational toxicity of graphene oxide under consecutive multi-generational exposure scenario still remains unclear. In the present study, Caenorhabditis elegans as an in vivo model organism was employed to explore the multi-generational toxicity effects of graphene oxide and the underlying mechanisms. Endpoints including development and lifespan, locomotion behaviors, defecation cycle, brood sizes, and oxidative response were evaluated in the parental generation and subsequent five filial generations. After continuous exposure for several generations, worms grew smaller and lived shorter. The locomotion behaviors were reduced across the filial generations and these reduced trends were following the impairments of locomotion-related neurons. In addition, the extended defecation cycles from the third filial generation were in consistency with the relative size reduction of the defecation related neuron. Simultaneously, the fertility function of the nematode was impaired under consecutive exposure as reduced brood sizes and oocytes numbers, increased apoptosis of germline, and aberrant expression of reproductive related genes ced-3, ced-4, ced-9, egl-1 and ced-13 were detected in exposed worms. Furthermore, the antioxidant enzyme, SOD-3 was significantly increased in the parent and filial generations. Thus, continuous multi-generational exposure to graphene oxide caused damage to the neuron development and the reproductive system in nematodes. These toxic effects could be reflected by indicators such as growth inhibition, shortened lifespan, and locomotion behavior impairment and induced oxidative response.

Ecotoxicological epigenetics in invertebrates: Emerging tool for the evaluation of present and past pollution burden

The effect of environmental pollution on epigenetic changes and their heredity in affected organisms is of major concern as such changes can play a significant role in adaptation to changing environmental conditions. Changes of epigenetic marks including DNA methylation, histone modifications, and non-coding RNA's can induce changes in gene transcription leading to physiological long-term changes or even transgenerational inheritance. Such mechanisms have until recently been scarcely studied in invertebrate organisms, mainly focusing on model species including Caenorhabditis elegans and Daphnia magna. However, more data are becoming available, particularly focused on DNA methylation changes caused by anthropogenic pollutants in a wide range of invertebrates. This review examines the literature from field and laboratory studies utilising invertebrate species exposed to environmental pollutants and their effect on DNA methylation. Possible mechanisms of epigenetic modifications and their role on physiology and adaptation as well as the incidence of intergenerational and transgenerational inheritance are discussed. Furthermore, critical research challenges are defined and the way forward is proposed. Future studies should focus on the use of next generation sequencing tools to define invertebrate methylomes under environmental stress in higher resolution, those data should further be linked to gene expression patterns and phenotypes and detailed studies focusing on transgenerational effects are encouraged. Moreover, studies of other epigenetic mechanisms in various invertebrate species, apart from DNA methylation would provide better understanding of interconnected cross-talk between epigenetic marks. Taken together incorporating epigenetic studies in ecotoxicology context presents a promising tool for development of sensitive biomarkers for environmental stress assessment.

Multigenerational graphene oxide intoxication results in reproduction disorders at the molecular level of vitellogenin protein expression in Acheta domesticus

The anthropogenic activities may lead to accumulation of graphene oxide (GO) pollution in the environment. Organisms exposed to chronic or multigenerational GO intoxication can present reproduction depletion. Vitellogenin (Vg) has been used as a parameter for evaluating female fertility due to its importance in embryo nutrition. In this study, we used a promising model organism, Acheta domesticus, which was intoxicated with GO in food for three generations. The aim of the study was to investigate the process of Vg synthesis in crickets depending on the exposure time, GO concentration, and age of the females. The results revealed that chronic GO intoxication had adverse effects on the Vg expression pattern. The 1st generation of insects showing low Vg expression was most affected. The 2nd generation of A. domesticus presented a high Vg expression. The last investigated generation seemed to cope with stress caused by GO, and the Vg expression was balanced. We suggest that the epigenetic mechanisms may play a role in the information transfer to the next generations on how to react to the risk factor and keep reproduction at a high rate. We suspect that chronic GO intoxication can disturb the regular formation of the Vg quaternary structure, resulting in consequences for developing an embryo.

Research Advances on the Adverse Effects of Nanomaterials in a Model Organism, Caenorhabditis elegans

Along with the rapid development of nanotechnology, the biosafety assessment of nanotechnology products, including nanomaterials (NMs), has become more and more important. The nematode Caenorhabditis elegans is a valuable model organism that has been widely used in the field of biology because of its excellent advantages, including low cost, small size, short life span, and highly conservative genomes with vertebral animals. In recent years, the number of nanotoxicological researchers using C. elegans has been growing. According to these available studies, the present review classified the adverse effects of NMs in C. elegans into systematic, cellular, and molecular toxicity, and focused on summarizing and analyzing the underlying mechanisms of metal, metal oxide, and nonmetallic NMs causing toxic effects in C. elegans. Our findings provide insights into what further studies are needed to assess the biosafety of NMs in the ecosystem using C. elegans. Environ Toxicol Chem 2021;40:2406-2424. © 2021 SETAC.

How can exposure to engineered nanomaterials influence our epigenetic code? A review of the mechanisms and molecular targets

Evidence suggests that engineered nanomaterials (ENM) can induce epigenetic modifications. In this review, we provide an overview of the epigenetic modulation of gene expression induced by ENM used in a variety of applications: titanium dioxide (TiO₂), silver (Ag), gold (Au), silica (SiO₂) nanoparticles and carbon-based nanomaterials (CNM). Exposure to these ENM can trigger alterations in cell patterns of DNA methylation, post-transcriptional histone modifications and expression of non-coding RNA. Such effects are dependent on ENM dose and physicochemical properties including size, shape and surface chemistry, as well as on the cell/organism sensitivity. The genes affected are mostly involved in the regulation of the epigenetic machinery itself, as well as in apoptosis, cell cycle, DNA repair and inflammation related pathways, whose long-term alterations might lead to the onset or progression of certain pathologies. In addition, some DNA methylation patterns may be retained as a form of epigenetic memory. Prenatal exposure to ENM may impair the normal development of the offspring by transplacental effects and/or putative transmission of epimutations in imprinting genes. Thus, understanding the impact of ENM on the epigenome is of paramount importance and epigenetic evaluation must be considered when assessing the risk of ENM to human health.

Parental CuO nanoparticles exposure results in transgenerational toxicity in Caenorhabditis elegans associated with possible epigenetic regulation

Environmental nanomaterials contamination is a great concern for organisms including human. Copper oxide nanoparticles (CuO NPs) are widely used in a huge range of applications which might pose potential risk to organisms. This study investigated the in vivo transgenerational toxicity on development and reproduction with parental CuO NPs exposure in the nematode Caenorhabditis elegans. The results showed that CuO NPs (150 mg/L) significantly reduced the body length of parental C. elegans (P0). Only about 1 mg/L Cu²⁺ (~0.73%) were detected from 150 mg/L CuO NPs in 0.5X K-medium after 48 h. In transgenerational assays, CuO NPs (150 mg/L) parental exposure significantly induced developmental and reproductive toxicity in non-exposed C. elegans progeny (CuO NPs free) on body length (F1) and brood size (F1 and F2), respectively. In contrast, parental exposure to Cu²⁺ (1 mg/L) did not cause transgenerational toxicity on growth and reproduction. This suggests that the transgenerational toxicity was mostly attributed to the particulate form of CuO NPs. Moreover, qRT-PCR results showed that the mRNA levels of met-2 and spr-5 genes were significantly decreased at P0 and F1 upon only maternal exposure to CuO NPs (150 mg/L), suggesting the observed transgenerational toxicity was associated with possible epigenetic regulation in C. elegans.