Induction of protective response to polystyrene nanoparticles associated with dysregulation of intestinal long non-coding RNAs in Caenorhabditis elegans

A systematic review on the impact of micro-nanoplastics on human health: Potential modulation of epigenetic mechanisms and identification of biomarkers

Epigenetic-mediated modifications, induced by adverse environmental conditions, significantly alter an organism's physiological mechanisms. Even after elimination of the stimulus, these epigenetic modifications can be inherited through mitosis, thereby triggering transgenerational epigenetics. Plastics, with their versatile properties, are indispensable in various aspects of daily life. However, due to mismanagement, plastics have become so ubiquitous in the environment that no ecosystem on Earth is free from micro-nanoplastics (MNPs). This situation has raised profound concerns regarding their potential impact on human health. Recently, both in vivo animal and in vitro human cellular models have shown the potential to identify the harmful effects of MNPs at the genome level. The emerging epigenetic impact of MNP exposure is characterized by short-term alterations in chromatin remodelling and miRNA modulation. However, to understand long-term epigenetic changes and potential transgenerational effects, substantial and more environmentally realistic exposure studies are needed. In the current review, the intricate epigenetic responses, including the NHL-2-EKL-1, NDK-1-KSR1/2, and WRT-3-ASP-2 cascades, wnt-signalling, and TGF- β signalling, established in model organisms such as C. elegans, mice, and human cell lines upon exposure to MNPs, were systematically examined. This comprehensive analysis aimed to predict human pathways by identifying human homologs using databases and algorithms. We are confident that various parallel miRNA pathways, specifically the KSR-ERK-MAPK pathway, FOXO-Insulin cascade, and GPX3-HIF-α in humans, may be influenced by MNP exposure. This influence may lead to disruptions in key metabolic and immune pathways, including glucose balance, apoptosis, cell proliferation, and angiogenesis. Therefore, we believe that these genes and pathways could serve as potential biomarkers for future studies. Additionally, this review emphasizes the origin, dispersion, and distribution of plastics, providing valuable insights into the complex relationship between plastics and human health while elaborating on the epigenetic impacts.

Molecular effects of polystyrene nanoplastics toxicity in zebrafish embryos (Daniorerio)

Plastics pose a health hazard to living beings and the environment. Plastic degradation produces nano-sized plastic particles (NPs) that end up in terrestrial and aquatic ecosystems, including oceans, rivers, and lakes. Their presence in air, drinking water, sediments, food, and personal care products leads to a variety of exposure routes for living beings, including humans. The toxicity mechanisms of these nanomaterials (NMs) in living organisms and ecosystems are currently unknown, making it a priority to understand their effects at the molecular and cellular levels. The zebrafish (Zf) (Danio rerio) is a model organism which has a high homology with humans and has been widely used to assess the hazard of different xenobiotics. In this study, the expression changes of different genes in 120 hpf Zf embryos (Zfe) after exposure to polystyrene (PS) NPs (30 nm) at concentrations of 0.1, 0.5 and 3 ppm were investigated. The results showed that the gene encoding heat shock protein (hsp70) was down-regulated in a dose-dependent manner. The genes encoding superoxide dismutase (SOD 1 and SOD 2), apoptotic genes (cas 1 and cas 8) and interleukin 1-β (il1β) were activated at the concentration of 3 ppm PS NP, while the anti-apoptotic gene Bcl2α was inhibited at 0.5 and 3 ppm. In addition, the neurotransmitter-related gene Acetyl-Cholinesterase (ache) was significantly inhibited and the DNA repair genes (gadd45α and rad51) were also down-regulated. In contrast, the mitochondrial metabolism-related gene cox1 did not alter its expression in any of the treatments. Most of the changes in gene expression occurred at the highest concentration of NPs. Overall, the results indicated that NPs generated cellular stress that caused certain alterations in normal gene expression (oxidative stress, apoptotic and inflammatory processes, neurotoxicity and anti-apoptotic proteins), but did not cause any mortality after 120 hpf exposure at the three concentrations assayed. These results highlight the need for further studies investigating the effects, at the molecular level, of these materials in humans and other living organisms.

Nanoplastics: Focus on the role of microRNAs and long non-coding RNAs

When plastic objects in our surroundings are degraded, they may produce particles ranging in size from 1 to 100 nm therefore called nanoplastics. The environmental chemicals including nanoplastics may be able to affect biological processes in the nuclear level like altering DNA methylation and regulating microRNAs (miRNAs) as well as long non-coding RNAs (lncRNAs) expression and therefore are implicated in chronic human diseases like neoplasms. The regulatory role of miRNAs and lncRNAs in gene expression is appreciated. In vitro as well as in vivo experiments have shown that environmental elements including nanoplastics are able to dysregulate miRNAs and lncRNAs expression with possible genetic consequences that increase the risk of cancer development. In the current article, we review the biological effects of miRNAs and lncRNAs alterations following nanoplastics exposure.

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.

Multi-walled carbon nanotubes induce transgenerational toxicity associated with activation of germline long non-coding RNA linc-7 in C.elegans

With the increase in application, multi-walled carbon nanotubes (MWCNTs) are potentially bioavailable to environmental organisms. However, the potential transgenerational effect of MWCNTs and underlying mechanisms remains still unclear. Here, we examined transgenerational MWCNT toxicity and the underlying mechanism mediated by germline long non-coding RNAs (lncRNAs) in Caenorhabditis elegans. Exposure to 0.1-10 μg/L MWCNT caused transgenerational toxicity reflected by endpoints of brood size and locomotion behavior. Meanwhile, among germline lncRNAs, expression of 5 lncRNAs were dysregulated by MWCNT exposure. Among these 5 dysregulated lncRNAs, only germline RNAi of linc-7 affected MWCNT toxicity. Increase in germline linc-7 expression was observed transgenerationally, and transgenerational MWCNT toxicity was prevented in linc-7(RNAi) nematodes. Moreover, germline linc-7 controlled transgenerational MWCNT toxicity by activating downstream DAF-12, a transcriptional factor. Therefore, our data indicated the association between induction of transgenerational MWCNT toxicity and increase in germline linc-7 expression in organisms.

Opportunities and challenges of using high-sensitivity nanobiosensors to detect long noncoding RNAs: A preliminary review

The two types ofncRNAs, including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), are responsible for several biological processes within cells, such as the immune responses, cell growth and invasion, and regulation of the cell cycle. Rapidly expanding class of ncRNAs, lncRNAsinteract with other molecules to form chromatin-remodeling complexes. These potential hallmarks of diseases contribute to transcriptional and post-transcriptional regulation of several genes, possibly via cross-talk with other RNAs. Aberrant expression of lncRNAshas drawn increasing attention to the pathophysiology of different diseases, includingcancer and cardiovasculardiseases. Unfortunately, circulating lncRNAs are presented in the bloodstream at very low levels, making sensitive detection difficult. Currently, there are few methods for detecting these ncRNAs from which quantitative real-time-polymerase chain reaction (qRT-PCR) is the most routinely used technique. These techniqueslack sensitivity for intracellular detection of lncRNAs. Moreover, they are tedious and require a large sample size. Currently, nanotechnology has taken over the diagnostic field because of the tunable properties and modification opportunities. Furthermore, these conventional techniques can be merged with nanotechnology to improve detection sensitivity.This review highlights some of the most recent findings on nanotechnology-based methods and possible obstacles intheir application for moreaccurate sensing of lncRNAs.

Long-term exposure to polystyrene nanoparticles causes transgenerational toxicity by affecting the function and expression of MEV-1 and DAF-2 signals in Caenorhabditis elegans

In this study, we determined the roles of oxidative stress and related signals in mediating transgenerational toxicity of 30 nm polystyrene nanoparticles (PS-NPs) in Caenorhabditis elegans. Using brood size and locomotion behavior as endpoints, exposure to 1-100 μg/L PS-NPs caused transgenerational toxicity. Meanwhile, the activation of reactive oxygen species (ROS) was also observed transgenerationally after exposure to 1-100 μg/L PS-NPs. After exposure to 1 μg/L PS-NPs, the transgenerational toxicity was monitored until F2 generation (F2-G) and recovered at F3-G. At the F1-G of 1 μg/L PS-NPs-exposed nematodes, RNAi knockdown of daf-2 with function to inhibit oxidative stress suppressed the transgenerational toxicity and increased the mitochondrial SOD-3 expression. In contrast, at F3-G of 1 μg/L PS-NPs-exposed nematodes, RNAi knockdown of mev-1 with function to induce oxidative stress promoted locomotion and brood size, and suppressed the SOD-3 expression. Moreover, we observed the dynamic expressions of mev-1, daf-2, and sod-2 transgenerationally after exposure to 1 μg/L PS-NPs at P0-G, which further suggested the involvement of MEV-1, DAF-2, and SOD-3 in affecting induction of transgenerational PS-NP toxicity. Therefore, we provided the evidence to suggest the roles of oxidative stress activation and related molecular signals in mediating induction of transgenerational PS-NP toxicity. Our data highlights the crucial function of oxidative stress-related signals during induction of transgenerational PS-NP toxicity.

Microplastics and Their Impact on Reproduction—Can we Learn From the C. elegans Model?

Biologically active environmental pollutants have significant impact on ecosystems, wildlife, and human health. Microplastic (MP) and nanoplastic (NP) particles are pollutants that are present in the terrestrial and aquatic ecosystems at virtually every level of the food chain. Moreover, recently, airborne microplastic particles have been shown to reach and potentially damage respiratory systems. Microplastics and nanoplastics have been shown to cause increased oxidative stress, inflammation, altered metabolism leading to cellular damage, which ultimately affects tissue and organismal homeostasis in numerous animal species and human cells. However, the full impact of these plastic particles on living organisms is not completely understood. The ability of MPs/NPs to carry contaminants, toxic chemicals, pesticides, and bioactive compounds, such as endocrine disrupting chemicals, present an additional risk to animal and human health. This review will discusses the current knowledge on pathways by which microplastic and nanoplastic particles impact reproduction and reproductive behaviors from the level of the whole organism down to plastics-induced cellular defects, while also identifying gaps in current knowledge regarding mechanisms of action. Furthermore, we suggest that the nematode Caenorhabditis elegans provides an advantageous high-throughput model system for determining the effect of plastic particles on animal reproduction, using reproductive behavioral end points and cellular readouts.

Materials, surfaces, and interfacial phenomena in nanoplastics toxicology research

In response to the growing worldwide plastic pollution problem, the field of nanoplastics research is attempting to determine the risk of exposure to nanoparticles amidst their ever-increasing presence in the environment. Since little is known about the attributes of environmental nanoplastics (concentration, composition, morphology, and size) due to fundamental limitations in detection and quantification of smaller plastic particles, researchers often improvise by engineering nanoplastic particles with various surface modifications as models for laboratory toxicological testing. Polystyrene and other commercially available or easily synthesized polymer materials functionalized with surfactants or fluorophores are typically used for these studies. How surfactants, additives, fluorophores, the addition of surface functional groups for conjugation, or other changes to surface attributes alter toxicological profiles remains unclear. Additionally, the limited polymers used in laboratory models do not mimic the vast range of polymer types comprising environmental pollutants. Nanomaterials are tricky materials to investigate due to their high surface area, high surface energies, and their propensity to interact with molecules, proteins, and biological probes. These unique properties can often invalidate common laboratory assays. Extreme care must be taken to ensure that results are not artefactual. We have gathered zeta potential values for various polystyrene nanoparticles with different functionalization, in different solvents, from the reported literature. We also discuss the effects of surface engineering and solvent properties on interparticle interactions, agglomeration, particle-protein interactions, corona formation, nano-bio interfaces, and contemplate how these parameters might confound results. Various toxicological exemplars are critically reviewed, and the relevance and shortfalls of the most popular models used in nanoplastics toxicity studies published in the current literature are considered.

Neuronal Gα subunits required for the control of response to polystyrene nanoparticles in the range of μg/L in C. elegans

The aim of this study was to identify Gα proteins mediating function of neuronal G protein-coupled receptors (GPCRs) in controlling the response to polystyrene nanoparticles (PS-NPs). Caenorhabditis elegans was used as an animal model, and both gene expression and functional analysis were performed to identify the Gα proteins in controlling PS-NPs toxicity. In nematodes, exposure to PS-NPs (1-100 μg/L) significantly altered transcriptional expressions of some neuronal Gα genes, including gpa-5, gpa-10, gpa-11, gpa-15 gsa-1, egl-30, and goa-1. Among these 7 Gα genes, only neuronal RNAi knockdown of gsa-1, gpa-10, and goa-1 affected toxicity of PS-NPs in inducing ROS production and in decreasing locomotion behavior. Some neuronal GPCRs (such as GTR-1, DCAR-1, DOP-2, NPR-8, NPR-12, NPR-9, and DAF-37) functioned upstream of GOA-1, some neuronal GPCRs (such as DCAR-1, DOP-2, NPR-9, NPR-8, and DAF-37) functioned upstream of GSA-1, and some neuronal GPCRs (such as DOP-2, NPR-8, DAF-37, and DCAR-1) functioned upstream of GPA-10 to regulate the toxicity of PS-NPs. Moreover, GOA-1 acted upstream of MPK-1/ERK MAPK, JNK-1/JNK MAPK, DBL-1/TGF-β, and DAF-7/ TGF-β, GSA-1 functioned upstream of MPK-1/ERK MAPK, JNK-1/JNK MAPK, and DBL-1/TGF-β, and GPA-10 functioned upstream of GLB-1/Globin and DBL-1/TGF-β to control the PS-NPs toxicity. Therefore, neuronal Gα proteins of GOA-1, GSA-1, and GPA-10 functioned to transduce signals of multiple GPCRs to different downstream signaling pathways during the control of PS-NPs toxicity in nematodes. Our results provide clues for understanding the important function of GPCRs-Gα signaling cascade in the neurons in controlling response to nanoplastics in organisms.

Size-dependent transgenerational toxicity induced by nanoplastics in nematode Caenorhabditis elegans

Nanoplastic exposure can potentially cause the severe transgenerational toxicity in organisms. However, the transgenerational nanoplastic toxicity and the underlying mechanisms are still largely unclear. Using Caenorhabditis elegans as an animal model, we here compared the transgenerational toxicity of two sizes of polystyrene nanoparticles (PS-NPs, 20 and 100 nm). The nematodes were exposed to PS-NPs at the P0 generation, and from the F1 generation the nematodes were grown under the normal condition. Exposure to 20 nm PS-NPs resulted in more severe transgenerational toxicity than exposure to 100 nm PS-NPs. At the concentration of 100 μg/L, the toxicity of 20 nm PS-NPs on locomotion and reproduction was detected at the F1-F6 generations, whereas the toxicity of 100 nm PS-NPs could only be observed at the F1-F3 generations. The difference in transgeneration toxicity between PS-NPs (20 nm) and PS-NPs (100 nm) was associated with the difference in transgenerational activation of oxidative stress. Based on observations on SOD-3::GFP, HSP-6::GFP, and HSP-4::GFP expressions, PS-NPs (20 nm) and PS-NPs (100 nm) further induced different transgenerational responses of anti-oxidation, mt UPR, and ER UPR. Our data suggested that the induction of transgenerational toxicity of PS-NPs was size dependent in nematodes. The results are helpful for our understanding the cellular mechanisms for the induction of transgenerational nanoplastic toxicity in organisms.

Biosafety assessment of Acinetobacter strains isolated from the Three Gorges Reservoir region in nematode Caenorhabditis elegans

Acinetobacter has been frequently detected in backwater areas of the Three Gorges Reservoir (TGR) region. We here employed Caenorhabditis elegans to perform biosafety assessment of Acinetobacter strains isolated from backwater area in the TGR region. Among 21 isolates and 5 reference strains of Acinetobacter, exposure to Acinetobacter strains of AC1, AC15, AC18, AC21, A. baumannii ATCC 19606T, A. junii NH88-14, and A. lwoffii DSM 2403T resulted in significant decrease in locomotion behavior and reduction in lifespan of Caenorhabditis elegans. In nematodes, exposure to Acinetobacter strains of AC1, AC15, AC18, AC21, A. baumannii, A. junii and A. lwoffii also resulted in significant reactive oxygen species (ROS) production. Moreover, exposure to Acinetobacter isolates of AC1, AC15, AC18, and AC21 led to significant increase in expressions of both SOD-3::GFP and some antimicrobial genes (lys-1, spp-12, lys-7, dod-6, spp-1, dod-22, lys-8, and/or F55G11.4) in nematodes. The Acinetobacter isolates of AC1, AC15, AC18, and AC21 had different morphological, biochemical, phylogenetical, and virulence gene properties. Our results suggested that exposure risk of some Acinetobacter strains isolated from the TGR region exists for environmental organisms and human health. In addition, C. elegans is useful to assess biosafety of Acinetobacter isolates from the environment.

Induction of Protective Response Associated with Expressional Alterations in Neuronal G Protein-Coupled Receptors in Polystyrene Nanoparticle Exposed Caenorhabditis elegans

In this study, the association of expressional alterations in neuronal G protein-coupled receptors (GPCRs) with induction of protective response to polystyrene nanoparticles (PS-NPs) was investigated in Caenorhabditis elegans. On the basis of both phenotypic analysis and expression levels, the alterations in expressions of NPR-1, NPR-4, NPR-8, NPR-9, NPR-12, DCAR-1, GTR-1, DOP-2, SER-4, and DAF-37 in neuronal cells mediated the protective response to PS-NPs exposure. In neuronal cells, NPR-9, NPR-12, DCAR-1, and GTR-1 controlled the PS-NPs toxicity by activating or inhibiting JNK-1/JNK MAPK signaling. Neuronal NPR-8, NPR-9, DCAR-1, DOP-2, and DAF-37 controlled the PS-NPs toxicity by activating or inhibiting MPK-1/ERK MAPK signaling. Neuronal NPR-4, NPR-8, NPR-9, NPR-12, GTR-1, DOP-2, and DAF-37 controlled the PS-NPs toxicity by activating or inhibiting DBL-1/TGF-β signaling. Neuronal NPR-1, NPR-4, NPR-12, and GTR-1 controlled the PS-NPs toxicity by activating or inhibiting DAF-7/TGF-β signaling. Our data provides an important neuronal basis for induction of protective response to PS-NPs in C. elegans.

Impact of Microplastics and Nanoplastics on Human Health

Plastics have enormous impacts to every aspect of daily life including technology, medicine and treatments, and domestic appliances. Most of the used plastics are thrown away by consumers after a single use, which has become a huge environmental problem as they will end up in landfill, oceans and other waterways. These plastics are discarded in vast numbers each day, and the breaking down of the plastics from micro- to nano-sizes has led to worries about how toxic these plastics are to the environment and humans. While, there are several earlier studies reported the effects of micro- and nano-plastics have on the environment, there is scant research into their impact on the human body at subcellular or molecular levels. In particular, the potential of how nano-plastics move through the gut, lungs and skin epithelia in causing systemic exposure has not been examined thoroughly. This review explores thoroughly on how nanoplastics are created, how they behave/breakdown within the environment, levels of toxicity and pollution of these nanoplastics, and the possible health impacts on humans, as well as suggestions for additional research. This paper aims to inspire future studies into core elements of micro- and nano-plastics, the biological reactions caused by their specific and unusual qualities.