Carboxyl-modified polystyrene microplastics induces neurotoxicity by affecting dopamine, glutamate, serotonin, and GABA neurotransmission in Caenorhabditis elegans

Exploring the mechanisms of neurotoxic effects from combined exposure to polystyrene and microcystin-LR in Caenorhabditis elegans

Microplastics (MPs) are newly emerged pollutants found in water and soil, while microcystin-leucine arginine (MC-LR) is often detected in drinking water and water products, both posing serious threats to aquatic environment and food safety. MPs can serve as carriers of MC-LR. These pollutants are often found together, rather than separately. This study focused on assessing the neurotoxicity of co-exposure to MC-LR and PS in Caenorhabditis elegans (C. elegans) after combined exposure to these two pollutants. Exposure to varying concentrations of polystyrene (PS) and MC-LR individually caused a dose-dependent decrease in the locomotion behaviors of C. elegans. Exposure to either of these substances alone caused damage to the phenotypic indicators of the C. elegans. To further explore the additional damage caused by the combined exposure of PS and MC-LR, the low, medium, and high combined dose groups were selected based on the locomotion behaviors and survival results. Combined exposure increased the level of oxidative stress indicators and resulted in neuronal loss. It also reduced serotonin, glutamate, GABA, and dopamine neurotransmitters levels, without affecting cholinergic neurons. The expression of neurotransmitter-related genes also decreased. The high-dose group showed the most significant effects. This article is the first to study the combined effect of PS and MC-LR on C. elegans nervous systems, offering novel insights into the risks posed by co-occurring contaminants and their implications for aquatic ecosystems and food safety.

Size-dependent internalization of polystyrene microplastics as a key factor in macrophages and systemic toxicity

Microplastics are emerging pollutants with a wide range of ecological and biological effects, including the ability to accumulate in organisms and induce toxicity. Although numerous studies have investigated the distribution and toxicity of microplastics in murine models and cell lines, the conclusions are inconsistent owing to variations in experimental designs, particle sizes, exposure methods, and dose quantifications. To address these gaps, we systematically evaluated the size-dependent internalization and toxicity of polystyrene microplastics (PS-MPs) using in vitro and in vivo models. Fluorescently labeled PS-MPs were used to confirm the negligible toxicity of fluorophores on macrophages, demonstrating their suitability for tracking particle accumulation. In vitro experiments using RAW 264.7 cell lines and primary peritoneal macrophages revealed size-dependent phagocytosis and cytotoxicity, with smaller particles (0.5 µm) demonstrating higher internalization and causing greater mitochondrial depolarization, reactive oxygen species generation, and apoptosis compared to that with larger particles (5 µm). Acute in vivo experiments comparing oral administration and tail-vein injection revealed that the absorbed dose and toxicity were significantly influenced by particle size, with smaller PS-MPs showing higher organ retention and alterations in hematological and metabolic parameters. Additionally, a 28-day subacute oral exposure study highlighted systemic toxicity, including weight loss, disrupted food intake, elevated oxidative stress markers, and reduced antioxidant enzyme activity. By integrating multiple exposure routes, macrophage models, and fluorescence toxicity evaluations, this study provided a comprehensive and realistic assessment of microplastic toxicity, offering valuable insights for advancing toxicological evaluations and regulatory frameworks. However, this study did not address the influence of other plastic types, shapes, or environmental factors on toxicity. Future studies are thus needed to explore these variables and the long-term implications of real-world microplastic exposure.

A critical review of the ecotoxic effects of microplastics on aquatic, soil and atmospheric ecosystems and current research challenges

The extensive use of plastics has brought unparalleled convenience to human social development. However, this has also led to severe environmental and health challenges, with microplastic (MP) pollution emerging as one of the most pressing issues. As ubiquitous environmental pollutants, MPs persist in ecosystems and pose potential risks to both ecological and human health. Studies reveal that MPs impact aquatic, soil, and atmospheric ecosystems by altering their physicochemical properties and causing toxicological harm to resident organisms. Despite these findings, a comprehensive assessment and analysis of MP impacts, especially on atmospheric ecosystems, remains lacking. Similarly, the environmental biotoxicity mechanisms associated with MPs are yet to be systematically described. This review provides an in-depth discussion of the sources and characteristics of MPs, laying the background for elaborating their ecological effects. Current knowledge on MP ecotoxicity in aquatic, soil, and atmospheric ecosystems is then synthesized. Potential molecular mechanisms of biotoxicity are explored. Oxidative stress, inflammatory responses, and metabolic signaling pathway impairment are considered important pathways through which MPs induce toxic injury in environmental animals and have received widespread attention. Additionally, this review emphasizes the challenges faced in studying ecotoxic effects and mechanisms of MPs, such as the lack of reliable detection of environmental MPs and in-depth mining of relevant data, and suggests possible directions for future research. Although progress has been made, significant knowledge gaps remain. Addressing these gaps is critical if effective strategies are to be developed to reduce the environmental and health risks posed by MPs.

Studies on adsorption and synergistic biological effects induced by microplastic particles and the Platanus pollen allergenic protein 3(Pla a3)

Microplastics (MPs) are pervasive as emerging pollutants in ambient particles and may pose a potential threat to human health through respiratory exposure. Especially, impact of climate change has led to an extended blooming period for many plants, resulting in elevated pollen levels in the air, and leading to a continuous increase in the number of individuals suffering from allergenic diseases. However, the interactions between the MPs and allergenic proteins, remain largely unexplored. In this study, we investigated cellular toxicity of the MPs and Platanus pollen allergenic protein (Pla a3) based on the characterization of two typical microplastics (polystyrene, PS and polyethylene, PE). Our results indicated that UV irradiation could make surface alterations of the MPs, including breakage, particle size reduction, and an increase in surface oxygen-containing functional groups. These changes significantly enhanced the adsorption of the Pla a 3 protein. The 'protein coronas' formed by the MPs and the Pla a3 caused more damage to the A549 cells than Pla a3 alone. Reactive oxygen species (ROS) generation and elevated superoxide dismutase (SOD) levels increased significantly after the A549 cells were exposure to the protein coronas. This excessive oxidative stress led to significant inflammation and cytokine production increase, with IL-1β, IL-4, IFN-γ, and TNF-α levels rising by 1.84 ± 0.01, 2.37 ± 0.04, 1.94 ± 0.09, and 2.19 ± 0.05-fold times respectively compared to that of the Pla a 3 exposure alone. This study provided a fundamental data for further research for the allergenicity induced by the pollen proteins.

Neurobehavioral and neurochemical effects of nano-sized polypropylene accumulation in zebrafish (Danio rerio)

Plastic pollution, particularly nanoplastics (NPs), is a significant environmental contaminant that poses potential toxicological risks to organisms and ecosystems. Although extensive research has been conducted on the toxicity of NPs, our understanding remains limited, primarily because of the constraints of standardized toxicity studies using polymers of specific sizes and types. To address this gap, we conducted toxicity experiments using directly synthesized polypropylene nanoparticles (PP-NPs) in zebrafish (Danio rerio). The presence of PP-NPs in the zebrafish brain was confirmed using pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) and bio-transmission electron microscopy (bio-TEM). The accumulation of PP-NPs in the brain of D. rerio led to neurotoxicity, manifested as reduced motility and aggressiveness. Altered neurotransmitter levels and neural activity associated with behavior further supported these findings. This study suggests that environmental plastic pollutants may accumulate in the brain and cause neurotoxicity in organisms, emphasizing the need for appropriate management of these substances.

From metabolism to lifespan trade-offs: polyethylene microplastics induce circadian disruption and sex-specific aging in Drosophila melanogaster

Microplastics (MPs), particularly polyethylene microplastics (PE-MPs), are increasingly recognized as contaminants in both aquatic and terrestrial environments. However, the ecological impacts of PE-MPs on terrestrial organisms remain underexplored. This study investigates the physiological and behavioral effects of PE-MPs exposure in the terrestrial model organism Drosophila melanogaster, shedding light on the potential risks posed by PE-MPs in land-based ecosystems. After exposing the fruit flies to different concentrations of PE-MPs for 20 days, we assessed several physiological biomarkers, including spontaneous behavioral activity, starvation resistance, metabolic biomarkers, and lifespan. Our findings indicate that PE-MPs exposure significantly affects fruit fly physiology, with increased spontaneous activity, decreased starvation resistance, and reduced triglyceride (TG) and protein levels (in males), reflecting disruption of metabolic processes. While PE-MPs did not affect female reproductive capacity, they did result in sex-specific impacts on lifespan, with male fruit flies showing a significant reduction in both mean and median lifespan at higher PE-MPs concentrations. These results highlight the need to consider the sex-dependent nature of PE-MPs toxicity when assessing their ecological risks. This study contributes new insights into the potential for PE-MPs to disrupt terrestrial ecosystems and underscores the importance of investigating the effects of microplastics on terrestrial invertebrates, providing a foundation for future ecotoxicological research.

High-performance amino-crosslinked phosphorylated microcrystalline cellulose/MoS2 hybrid aerogel for polystyrene nanoplastics removal from aqueous environments

Currently, the development of high-performance adsorbents for the removal of nanoplastics in complex aquatic environments is challenging. In this study, a functionalized polyethyleneimine-phosphorylated microcrystalline cellulose/MoS2 (PEI-PMCC/MoS2) hybrid aerogel was prepared and applied to remove carboxyl-modified polystyrene (PS-COOH) nanoplastics from the aqueous solution. Benefiting from the introduced functional groups and the expanded lamellar structure in MoS2 nanosheets as well as the highly porous 3D structure of the aerogel, PEI-PMCC/MoS2 demonstrated high efficiency in PS-COOH nanoplastics removal, achieving a 402.4 ± 7.5 mg/g maximum adsorption capacity at the optimal adsorption pH of 7.0 (C0 = 300 mg/L). The adsorption isotherm and kinetics data fitted well with the Langmuir and pseudo-second-order models, respectively, suggesting that the removal of PS-COOH nanoplastics was dominated by the monolayer chemisorption process, and the thermodynamic studies revealed the exothermic nature of the spontaneous adsorption process. Furthermore, the adsorption performance of PEI-PMCC/MoS2 in different complex aqueous environments, as well as its reusability, was evaluated, and the interactions between PEI-PMCC/MoS2 and PS-COOH nanoplastics were analyzed to elaborate the adsorption mechanism. These results confirmed the high nanoplastics removal efficiency and favorable reusability in PEI-PMCC/MoS2, laying a solid foundation for developing high-performance adsorbents for nanoplastics removal.

Behavioral and molecular neurotoxicity of thermally degraded polystyrene in Caenorhabditis elegans

Microplastics are pervasive environmental contaminants found across diverse ecosystems, inducing toxic effects in a wide range of organisms. However, the neurotoxic effects of thermally degraded polystyrene (T-PS) and its underlying mechanisms remain poorly unexplored. In this study, Caenorhabditis elegans was exposed to environmentally relevant concentrations of T-PS (0.1-100 μg/L), and endpoints including locomotion behaviors, neuronal development, neurotransmitter levels, and gene expression were assessed. Significant alterations in morphology, crystallinity, elemental composition, and functional groups were observed in T-PS compared to virgin polystyrene (V-PS), indicating that thermal degradation modifies the physicochemical properties of V-PS. Exposure to 10-100 μg/L T-PS resulted in a more pronounced decrease in head thrashes, body bends, forward turns, and backward turns compared to V-PS. In transgenic nematodes, T-PS exposure significantly impacted fluorescence intensity and the percentage of worms exhibiting neurodegeneration in serotonergic, cholinergic, dopaminergic, and γ-aminobutyric acid (GABA) neurons. Correspondingly, marked reductions were observed in the levels of dopamine, serotonin, GABA, and choline neurotransmitters, alongside significant declines in neurotransmitter-related gene expression (e.g., dat-1, tph-1, unc-30, and cha-1). Pearson's correlation analysis revealed a significant positive association between these genes and locomotion behaviors. Furthermore, the absence of locomotion behavior impairment in dat-1 (ok157), tph-1 (mg280), unc-30 (e191), and cha-1 (e1152) mutants highlights the pivotal roles of these genes in mediating T-PS-induced neurotoxicity in C. elegans. This study enhances our understanding of the neurotoxic mechanisms of T-PS at environmental concentrations, providing valuable insights into its potential environmental health risks.

Toxicity enhancement of microplastics released from food containers through thermal aging: Absorbing more serum proteins thus activating the innate immune response via actin polymerization

This study examined the effects of hot high-fat simulants on the physicochemical properties of microplastics (MPs) from polypropylene (PP)-, low-density polyethylene (LDPE)-, and polylactic acid (PLA)-based single-use food container (SUFC) leachates and those of aging on their immunomodulatory effectors. Scenario studies have demonstrated that MPs were released from these three types of SUFCs. LDPE- and PLA-based SUFCs also released cellulose. Among the SUFCs, only the PP leachates particles exhibited a new absorption peak at 1725 cm-1, which aging phenomenon may be attributed to the presence of unstable tertiary carbon atoms. Subsequently, we investigated the immunomodulatory effects of removing additive both PP and thermal-aged PP with polystyrene (PS) and carboxyl-modified PS (PS-COOH) polymer backbones as reference materials. The findings indicated that thermal-aged PP and PS-COOH induced comparable innate immune responses, with PS-COOH particles exhibiting a similar size to SUFC percolates. Consequently, PS and PS-COOH were selected as original and thermal-aged MPs, respectively, to evaluate the effects of aging on innate immunity. The results revealed thata protein corona formed on both particle types, with more protein adsorption observed on PS-COOH particles. The complex enhanced the phagocytosis of RAW264.7 macrophages and increased the expression of pro-inflammatory genes NOS2 and TNF-α through an actin polymerization cross-linking mechanism. In this study, we investigated how thermal-aged MPs affect innate immune responses using PS-COOH as a model system, emphasizing the importance of a comprehensive safety evaluations of MPs.

Microplastics/nanoplastics and neurological health: An overview of neurological defects and mechanisms

The widespread use of plastic products worldwide has brought about serious environmental issues. In natural environments, it's difficult for plastic products to degrade completely, and so they exist in the form of micro/nanoplastics (M/NPs), which have become a new type of pollutant. Prolonged exposure to M/NPs can lead to a series of health problems in humans, particularly toxicity to the nervous system, with consequences including neurodevelopmental abnormalities, neuronal death, neurological inflammation, and neurodegenerative diseases. Although direct evidence from humans is still limited, model organisms and organoids serve as powerful tools to provide important insights. This article summarizes the effects of M/NPs on the nervous system, focusing on cognitive function, neural development, and neuronal death. Mechanisms such as neurotransmitter synthesis and release, inflammatory responses, oxidative stress, the gut-brain axis, and the liver-brain axis are covered. The neurotoxicity induced by M/NPs may exacerbate or directly trigger neurodegenerative diseases and neurodevelopmental disorders. We particularly emphasize potential therapeutic agents that may counteract the neurotoxic effects induced by M/NPs, highlighting a novel future research direction. In summary, this paper cites evidence and provides mechanistic perspectives on the effects of M/NPs on neurological health, providing clues for eliminating M/NP hazards to human health in the future.

The Effects of Nanoplastics on the Dopamine System of Cerebrocortical Neurons

Nanoplastics (NPx) can enter living organisms, including humans, through ecosystems, inhalation, and dermal contact and can be found from the intestine to the brain. However, it is unclear whether NPx accumulates and affects the dopamine system. In this study, we investigated the effects of NPx on the dopamine system in cultured murine cerebral cortex neurons. Cultured cerebrocortical neurons were treated with 100 nm NPx at the following concentrations for 24 h: 1.896 × 105, 3.791 × 106, 7.583 × 107, 1.571 × 109, 3.033 × 1010, and 3.033 × 1011 particles/mL. Dopamine-associated proteins were analyzed using immunofluorescence staining. NPx treatment induced its accumulation in neurons in a dose-dependent manner and increased the levels of dopamine receptors D1 and D2 and their co-expression. However, NPx treatment did not affect the levels of other dopamine receptors, dopamine transporters, tyrosine hydroxylase, and microtubule-associated protein 2, or synaptophysin in neuronal structures. This study demonstrated that NPx is a potential modulator of the dopamine system via its receptors rather than its synthesis and reuptake in neurons and may be associated with dopamine-based psychiatric disorders.

Effect of functional groups of polystyrene nanoplastics on the neurodevelopmental toxicity of acrylamide in the early life stage of zebrafish

Polystyrene nanoplastics (PS NPs) and acrylamide (ACR), both emerging contaminants, have been found to be related to neurotoxicity. However, the effects of PS NPs on ACR-induced neurodevelopmental toxicity remain unclear. In this study, anionic carboxyl polystyrene nanoplastics (PS NPs-COOH), cationic amino polystyrene nanoplastics (PS NPs-NH2) and unmodified PS NPs were selected to investigate their interaction with ACR. A serious of the neurotoxicity biomarkers from individual to molecular level were evaluated to explore the specific mechanisms. The results indicated that the unmodified PS NPs had the most significant impact on embryonic development at low concentrations in combination with ACR. The toxicity of the other two functionalized PS NPs increased with concentration, exhibiting a clear dose-response relationship. Meanwhile, all three kinds of PS NPs significantly enhanced the impacts of ACR on the locomotion behavior of zebrafish larvae. Analysis of zebrafish nervous system development showed that PS NPs-COOH exhibit greater toxicity to the central nervous system. In contrast, PS NPs-NH2 had a more significant impact on the motor nervous system. Gene expression analysis revealed that ACR and PS NPs significantly affected the expression levels of neurodevelopmental related genes, including Neurog1, Elavl3, Gfap, Gap43, Mbpa, Shha. PS NPs modified with functional groups could induce corresponding neurotoxicity by affecting genes expression related to neuronal differentiation, motor neuron, and axonal development. Based on the comprehensive biomarker response index, the order of the impacts of NPs on the neurotoxicity of ACR was PS NPs-COOH > PS NPs-NH2 > PS NPs. In conclusion, this study provides new insights into the interactive biological effects of NPs and ACR on zebrafish embryo, contributing to a better understanding of their environmental risk to aquatic ecosystem.

Cross-Generational Exposure to Low-Density Polyethylene Microplastics Induced Hyperactive Responses in Eisenia fetida Offsprings

The extensive application of plastic products in daily human life has led to the accumulation of microplastics (MPs) in agricultural soil. However, little is known about the cross-generational toxicity of MPs on terrestrial invertebrates. In this study, two-generational Eisenia fetida was exposed to low-density polyethylene (LDPE, 0-5%, w/w) for 98 days to reveal the cross-generational toxicity and the underlying mechanisms. Results showed that LDPE-MPs not only perpetrated deleterious effects on the development, hatchability, and fecundity of the F0 generation but also stimulated the antioxidant defense activity, inhibited lipid peroxidation, and disordered neurotransmission in F1 generation individuals. The susceptibility of the epidermal-intestinal barrier to LDPE-MPs was dose-dependent. According to the transcriptomic analysis, the cross-generational earthworms confirmed significant perturbances in the cell cycle, neural activity-related pathways, and amino acid metabolism pathways (p < 0.05). Nevertheless, the metabolomic profile of F1 generation individuals exhibited significant hyperactive responses in glutathione metabolism and alanine, aspartate, and glutamate metabolism (p < 0.05). This study provides a comprehensive knowledge of LDPE-MPs toxicity on cross-generational earthworms and highlights the hyperactive responses in the antioxidant defense performance of the offsprings. Our findings also underscore the necessity for long-term investigations in assessing the adverse impacts of emerging pollutants.

Association between blood microplastic levels and severity of extracranial artery stenosis

Microplastics (MPs) contamination raises concerns about their impact on human health, particularly cardiovascular diseases. This study investigated the blood MPs levels in patients with extracranial artery stenosis (ECAS) and their possible link to disease severity. 20 ECAS and 10 control patients were recruited. Blood samples, collected before the digital subtract angiography (DSA) procedure, were analyzed by pyrolysis-gas chromatography mass spectrometry (Py-GC/MS), laser direct infrared (LDIR) spectroscopy, and scanning electron microscopy (SEM). Demographic and clinical information was also examined. Strict quality controls were implemented to prevent contamination. MPs were detected by Py-GC/MS in all blood samples, with concentrations significantly higher in ECAS group compared to control (174.89 ± 24.95 vs 79.82 ± 31.73 μg/g, p < 0.001), and polyvinyl chloride (PVC) and polyamide 66 (PA66) were the most abundant among the detected polymers. Further analyses suggested that higher concentrations of MPs may be associated with more severe artery stenosis (p < 0.001). Compared with the normal group, ECAS group had a higher level of D-dimer (0.61 ± 0.6 μg/L vs 0.28 ± 0.09 μg/L, p < 0.05) and longer Thrombin Time (sec) (18.30 ± 3.43 μg/L vs 16.25 ± 1.74 μg/L, p < 0.05). Additionally, LDIR and SEM detected the shape and physical properties of the MPs. In this study, we revealed significant higher blood MPs levels in ECAS patients, with a notable correlation between MPs concentrations and arterial stenosis severity.

Nematodes exposed to furfural acetone exhibit a species-specific vacuolar H+-ATPase response

Furfural acetone (FAc) is widely used as an additive by the food industry, as well as an intermediate in several fine chemical industries. Its nematicidal activity against the free-living model organism Caenorhabditis elegans and the parasitic nematode Meloidogyne incognita are well known, but its molecular mechanism of action remains unclear. To deep this subject, we performed 48-h lethal tests on eight nematode species, encompassing free-living, plant-parasitic, and animal-parasitic nematodes. Our results revealed that FAc possesses broad-spectrum nematicidal activity, with potent effects against parasitic nematodes such as Strongyloides stercoralis and M. incognita. In contrast, it exhibited weak activity against the free-living nematode C. elegans, suggesting its potential as a selective nematicide. Our investigation unveiled that FAc binds to the vacuolar H+-ATPase subunits VHA-12 and VHA-13, accelerating intestinal cell necrosis and leading to the death of C. elegans. It is the first discovery that VHA-12 and VHA-13 can serve as target proteins for triggering nematode cell necrosis. The interaction results indicated that FAc targets proteins VHA-12 and VHA-13 of different nematodes and confers broad-spectrum nematicidal activity. And the Spearman analysis results illustrated that the differential nematicidal activity of FAc against various nematodes is attributed to variations in the sequence and structure of the receptor proteins VHA-12 and VHA-13 among different nematode species. Our results illuminate the molecular mechanism underlying the differential toxicity of FAc to different nematodes, and provide valuable data for the comprehensive risk assessment of FAc release into the environment.

Neurotoxicity induced by aged microplastics from plastic bowls: Abnormal neurotransmission in Caenorhabditis elegans

The use of plastic bowls (PB) has garnered increasing scrutiny due to the inevitable generation of microplastics (MPs) throughout their lifecycle. Despite this concern, there exists a limited understanding of the behaviors, toxicological effects, and mechanisms associated with aged PB (A-PB). This research investigated the photoaging properties of A-PB following ultraviolet irradiation and evaluated the neurotoxic impact of exposure to A-PB at environmentally relevant concentrations (0.001-1 mg/L) on Caenorhabditis elegans. Significant alterations in the crystallinity, elemental composition, and functional groups of A-PB were observed compared to virgin PB (V-PB), along with the emergence of environmentally persistent free radicals and reactive oxygen species. Toxicity assessments revealed that exposure to 0.1-1 mg/L A-PB induced greater neurotoxicity on locomotion behaviors compared to V-PB, as evidenced by marked reductions in head thrashes, body bends, wavelength, and mean amplitude. Exposure to A-PB also altered the fluorescence intensities and neurodegeneration percentage of dopaminergic, serotonergic, and GABAergic neurons, suggesting neuronal damage in the nematodes. Correspondingly, decreases in the levels of dopamine, serotonin, and GABA were noted together with significant drops in the expression of neurotransmitter-related genes (e.g., dat-1, tph-1, and unc-47). Correlation analyses established a significant positive relationship between these genes and locomotion behaviors. Further exploration showed the absence of locomotion behaviors in dat-1 (ok157), tph-1 (mg280), and unc-47 (e307) mutants, underscoring the pivotal roles of the dat-1, tph-1, and unc-47 genes in mediating neurotoxicity in C. elegans. This study sheds light on the photoaging characteristics and heightened toxicity of A-PB, elucidating the mechanisms driving A-PB-induced neurotoxicity.

Innovative mechanisms of micro- and nanoplastic-induced brain injury: Emphasis on the microbiota-gut-brain axis

Micro- and nanoplastics (MNPs), emerging environmental pollutants, infiltrate marine, terrestrial, and freshwater systems via diverse pathways, culminating in their accumulation in the human body through food chain transmission, posing potential health risks. Researches have demonstrated that MNPs disrupt gut microbiota equilibrium and compromise intestinal barrier integrity, as well as traverse the blood-brain barrier, leading to brain damage. Moreover, the complex interaction between the gut and the nervous system, facilitated by the "gut-brain axis," indicates an additional pathway for MNPs-induced brain damage. This has intensified scientific interest in the intercommunication between MNPs and the gut-brain axis. While existing studies have documented microbial imbalances and metabolic disruptions subsequent to MNPs exposure, the precise mechanisms by which the microbiota-gut-brain axis contributes to MNPs-induced central nervous system damage remain unclear. This review synthesizes current knowledge on the microbiota-gut-brain axis, elucidating the pathogenesis of MNPs-induced gut microbiota dysbiosis and its consequent brain injury. It emphasizes the complex interrelation between MNPs and the microbiota-gut-brain axis, advocating for the gut microbiota as a novel therapeutic target to alleviate MNP-induced brain harm.

Microplastic and the Enteric Nervous System: Effect of PET Microparticles on Selected Neurotransmitters and Cytokines in the Porcine Ileum

Microplastic is an environmental hazard to which both animals and humans are exposed. Current reports show that it can cause inflammation, including in the gastrointestinal tract. To examine the impact on the ileum, 15 eight-week-old gilts (five individuals/group) were exposed to PET microplastics (7.6 µm-416.9 µm) at a dose of 0.1 g/day or 1 g/day for 28 days. The collected ileum fragments were investigated for the cytokine concentrations (IL-1β, IL-6, IL-8, IL-10, and TNF-α; ELISA test), neuron populations (cocaine and amphetamine-regulated transcript, galanin, neuronal nitric oxide synthase, substance P, vesicular acetylcholine transporter, and vasoactive intestinal peptide; immunofluorescence staining), and morphometric parameters (histological analysis). Under the influence of MP-PET, there was a reduction in the populations of CART- and GAL-positive neurons in the submucosal plexuses and of nNOS-, VAChT-, and VIP-positive neurons in all the plexuses. In contrast, there was an increase in GAL-positive neurons in the myenteric plexus and SP-positive neurons in all the plexuses. The concentrations of IL-1β, IL-6, IL-8, IL-10, and TNF-α did not undergo statistically significant changes under the influence of the low or high dose of MP-PET. The changes in the histological structure exclusively concerned the thinning of the mucosa and the muscularis externa. The results support the thesis that MP-PET is not neutral to the ileal cells.

The role of gut microbiota in MP/NP-induced toxicity

Microplastics (MPs) and nanoplastics (NPs) are globally recognized as emerging environmental pollutants in various environmental media, posing potential threats to ecosystems and human health. MPs/NPs are unavoidably ingested by humans, mainly through contaminated food and drinks, impairing the gastrointestinal ecology and seriously impacting the human body. The specific role of gut microbiota in the gastrointestinal tract upon MP/NP exposure remains unknown. Given the importance of gut microbiota in metabolism, immunity, and homeostasis, this review aims to enhance our current understanding of the role of gut microbiota in MP/NP-induced toxicity. First, it discusses human exposure to MPs/NPs through the diet and MP/NP-induced adverse effects on the respiratory, digestive, neural, urinary, reproductive, and immune systems. Second, it elucidates the complex interactions between the gut microbiota and MPs/NPs. MPs/NPs can disrupt gut microbiota homeostasis, while the gut microbiota can degrade MPs/NPs. Third, it reveals the role of the gut microbiota in MP/NP-mediated systematic toxicity. MPs/NPs cause direct intestinal toxicity and indirect toxicity in other organs via regulating the gut-brain, gut-liver, and gut-lung axes. Finally, novel approaches such as dietary interventions, prebiotics, probiotics, polyphenols, engineered bacteria, microalgae, and micro/nanorobots are recommended to reduce MP/NP toxicity in humans. Overall, this review provides a theoretical basis for targeting the gut microbiota to study MP/NP toxicity and develop novel strategies for its mitigation.

Critical review on unveiling the toxic and recalcitrant effects of microplastics in aquatic ecosystems and their degradation by microbes

Production of synthetic plastic obtained from fossil fuels are considered as a constantly growing problem and lack in the management of plastic waste has led to severe microplastic pollution in the aquatic ecosystem. Plastic particles less than 5mm are termed as microplastics (MPs), these are pervasive in water and soil, it can also withstand longer period of time with high durability. It can be broken down into smaller particles and can be adsorbed by various life-forms. Most marine organisms tend to consume plastic debris that can be accumulated easily into the vertebrates, invertebrates and planktonic entities. Often these plastic particles surpass the food chain, resulting in the damage of various organs and inhibiting the uptake of food due to the accumulation of microplastics. In this review, the physical and chemical properties of microplastics, as well as their effects on the environment and toxicity of their chemical constituents are discussed. In addition, the paper also sheds light on the potential of microorganisms such as bacteria, fungi, and algae which play a pivotal role in the process of microplastics degradation. The mechanism of microbial degradation, the factors that affect degradation, and the current advancements in genetic and metabolic engineering of microbes to promote degradation are also summarized. The paper also provides information on the bacterial, algal and fungal degradation mechanism including the possible enzymes involved in microplastic degradation. It also investigates the difficulties, limitations, and potential developments that may occur in the field of microbial microplastic degradation.

A Potential Neurotoxic Mechanism: Bisphenol S-Induced Inhibition of Glucose Transporter 1 Leads to ATP Excitotoxicity in the Zebrafish Brain

Many environmental pollutants have neurotoxic effects, but the initial molecular events involved in these effects are unclear. Here, zebrafish were exposed to the neurotoxicant bisphenol S (BPS, 1, 10, or 100 μg/L) from the embryonic stage to the larval stage to explore the ability of BPS to interfere with energy metabolism in the brain. BPS, which is similar to a glucose transporter 1 (GLUT1) inhibitor, inhibited GLUT1 function but increased mitochondrial activity in the brains of larval zebrafish. Interestingly, GLUT1 inhibitor treatment and BPS exposure did not reduce energy production in the brain; instead, they increased ATP production by inducing the preferential use of ketone bodies. Moreover, BPS promoted the protein expression of the purinergic 2X receptor but inhibited the purinergic 2Y-mediated phosphatidylinositol signaling pathway, indicating that excess ATP acts as a neurotransmitter to activate the purinergic 2X receptor under the BPS-induced restriction of GLUT1 function. BPS-induced inhibition of GLUT1 increased the number of neurons but promoted apoptosis by activating ATP-purinergic 2X receptors in the brain, causing ATP excitatory neurotoxicity. Our data reveal a potential neurotoxic mechanism induced by BPS that may represent a new adverse outcome pathway.

Treatment with quercetin mitigates polystyrene nanoparticle-induced reduction in neuron capacity by inhibiting dopaminergic neurodegeneration and facilitating dopamine metabolism in Caenorhabditis elegans

In organisms, long-term nanopolystyrenes (PS-NPs) exposure can cause toxicity, including neurotoxicity. Quercetin, the flavonol with extensive distribution within plants, possesses diverse biological activities. Nevertheless, the possible effect of quercetin to suppress PS-NPs-induced neurotoxicity and its associated mechanism remains unknown. Thus, in the present work, Caenorhabditis elegans was utilized as the model animal to investigate quercetin's pharmacological effect on suppressing PS-NPs-induced neurotoxicity and the underlying mechanism. PS-NPs exposure at 1-100 μg/L remarkably reduced locomotion behavior, while only PS-NPs exposure at 100 μg/L significantly decrease sensory perception behavior. Meanwhile, the increase in the number of worms with dopaminergic neurodegeneration was detected in nematodes exposed to 100 μg/L PS-NPs and the decreased dopamine content was observed within nematodes exposed to 10-100 μg/L PS-NPs, demonstrating the function of dopaminergic neurodegeneration and disruption of dopamine metabolism in inducing PS-NPs toxicity on neuron capacity. After 100 μg/L PS-NPs exposure, the 25-100 μM quercetin treatment effectively increased the locomotion behavior and the sensory perception behavior. Developmentally, quercetin treatment (100 μM) remarkably enhanced fluorescence intensity while decreasing worm number with neurodegeneration within BZ555 transgenic strains exposed to 100 μg/L PS-NPs. Physiologically, quercetin treatment (100 μM) significantly enhanced dopamine content within nematodes exposed to 100 μg/L PS-NPs. Molecularly, quercetin treatment (100 μM) notably decreased the expressions of genes governing neurodegeneration (mec-4, deg-3, unc-68, itr-1, clp-1, and asp-3) while significantly increasing the expression of genes governing dopamine metabolism (cat-2, cat-1, dop-1, dop-2, dop-3). As revealed by molecular docking results, quercetin might bind to excitotoxic-like ion channels receptors (MEC-4 and DEG-3) and dopamine secreted protein (CAT-2). Consequently, findings in this work demonstrated that long-term PS-NPs exposure within the μg/L range (1-100 μg/L) was toxic to neuron capacity, which was associated with the enhancement in dopaminergic neurodegeneration and disruption of dopamine metabolism. Notably, PS-NPs-mediated neurotoxicity to nematodes is probably suppressed through subsequent quercetin treatment.

A systematic review of microplastics emissions in kitchens: Understanding the links with diseases in daily life

The intensification of microplastics (MPs) pollution has emerged as a formidable environmental challenge, with profound global implications. The pervasive presence of MPs across a multitude of environmental mediums, such as the atmosphere, soil, and oceans, extends to commonplace items, culminating in widespread human ingestion and accumulation via channels like food, water, and air. In the domestic realm, kitchens have become significant epicenters for MPs pollution. A plethora of kitchen utensils, encompassing coated non-stick pans, plastic cutting boards, and disposable utensils, are known to release substantial quantities of MPs particles in everyday use, which can then be ingested alongside food. This paper conducts a thorough examination of contemporary research addressing the release of MPs from kitchen utensils during usage and focuses on the health risks associated with MPs ingestion, as well as the myriad factors influencing the release of MPs in kitchen utensils. Leveraging the insights derived from this analysis, this paper proposes a series of strategic recommendations and measures targeted at mitigating the production of MPs in kitchen settings. These initiatives are designed not solely to diminish the release of MPs but also to enhance public awareness regarding this pressing environmental concern. By adopting more informed practices in kitchens, we can significantly contribute to the reduction of the environmental burden of MPs pollution, thus safeguarding both human health and the ecological system.

Photoaged Nanopolystyrene Affects Neurotransmission to Induce Transgenerational Neurotoxicity in Caenorhabditis elegans

Nanopolystyrene (NPS), a frequently employed nanoplastic, is an emerging environmental contaminant known to cause neurotoxicity in various organisms. However, the potential for transgenerational neurotoxic effects, especially from photoaged NPS (P-NPS), remains underexplored. This study investigated the aging of virgin NPS (V-NPS) under a xenon lamp to simulate natural sunlight exposure, which altered the physicochemical characteristics of the NPS. The parental generation (P0) of Caenorhabditis elegans was exposed to environmental concentrations (0.1-100 μg/L) of V-NPS and P-NPS, with subsequent offspring (F1-F4 generations) cultured under NPS-free conditions. Exposure to 100 μg/L P-NPS resulted in more pronounced deterioration in locomotion behavior in the P0 generation compared to V-NPS; this deterioration persisted into the F1-F2 generations but returned to normal in the F3-F4 generations. Additionally, maternal exposure to P-NPS damaged dopaminergic, glutamatergic, and serotonergic neurons in subsequent generations. Correspondingly, there was a significant decrease in the levels of dopamine, glutamate, and serotonin, associated with reduced expression of neurotransmission-related genes dat-1, eat-4, and tph-1 in the P0 and F1-F2 generations. Further analysis showed that the effects of P-NPS on locomotion behavior were absent in subsequent generations of eat-4(ad572), tph-1(mg280), and dat-1(ok157) mutants, highlighting the pivotal roles of these genes in mediating P-NPS-induced transgenerational neurotoxicity. These findings emphasize the crucial role of neurotransmission in the transgenerational effects of P-NPS on locomotion behavior, providing new insights into the environmental risks associated with exposure to photoaged nanoplastics.

The Caenorhabditis elegans neuroendocrine system and their modulators: An overview

In this review we seek to systematically bring what has been published in the literature about the nervous system, endocrine system, neuroendocrine relationships, neuroendocrine modulations and endocrine disruptors in the alternative model Caenorhabditis elegans. The serotonergic, dopaminergic, GABAergic and glutamatergic neurotransmitters are related to the modulation of the neuroendocrine axis, leading to the activation or inhibition of several processes that occur in the worm through distinct and interconnected pathways. Furthermore, this review addresses the gut-neuronal axis as it has been revealed in recent years that gut microbiota impacts on neuronal functions. This review also approaches xenobiotics that can positively or negatively impact the neuroendocrine system in C. elegans as in mammals, which allows the application of this nematode to screen new drugs and to identify toxicants that are endocrine disruptors.

Nanoplastics and Neurodegeneration in ALS

Plastic production, which exceeds one million tons per year, is of global concern. The constituent low-density polymers enable spread over large distances and micro/nano particles (MNPLs) induce organ toxicity via digestion, inhalation, and skin contact. Particles have been documented in all human tissues including breast milk. MNPLs, especially weathered particles, can breach the blood-brain barrier, inducing neurotoxicity. This has been documented in non-human species, and in human-induced pluripotent stem cell lines. Within the brain, MNPLs initiate an inflammatory response with pro-inflammatory cytokine production, oxidative stress with generation of reactive oxygen species, and mitochondrial dysfunction. Glutamate and GABA neurotransmitter dysfunction also ensues with alteration of excitatory/inhibitory balance in favor of reduced inhibition and resultant neuro-excitation. Inflammation and cortical hyperexcitability are key abnormalities involved in the pathogenic cascade of amyotrophic lateral sclerosis (ALS) and are intricately related to the mislocalization and aggregation of TDP-43, a hallmark of ALS. Water and many foods contain MNPLs and in humans, ingestion is the main form of exposure. Digestion of plastics within the gut can alter their properties, rendering them more toxic, and they cause gut microbiome dysbiosis and a dysfunctional gut-brain axis. This is recognized as a trigger and/or aggravating factor for ALS. ALS is associated with a long (years or decades) preclinical period and neonates and infants are exposed to MNPLs through breast milk, milk substitutes, and toys. This endangers a time of intense neurogenesis and establishment of neuronal circuitry, setting the stage for development of neurodegeneration in later life. MNPL neurotoxicity should be considered as a yet unrecognized risk factor for ALS and related diseases.

Neurotoxicities induced by micro/nanoplastics: A review focusing on the risks of neurological diseases

Pollution of micro/nano-plastics (MPs/NPs) is ubiquitously prevalent in the environment, leading to an unavoidable exposure of the human body. Despite the protection of the blood-brain barrier, MPs/NPs can be transferred and accumulated in the brain, which subsequently exert negative effects on the brain. Nevertheless, the potential neurodevelopmental and/or neurodegenerative risks of MPs/NPs remain largely unexplored. In this review, we provide a systematic overview of recent studies related to the neurotoxicity of MPs/NPs. It covers the environmental hazards and human exposure pathways, translocation and distribution into the brain, the neurotoxic effects, and the possible mechanisms of environmental MPs/NPs. MPs/NPs are widely found in different environment matrices, including air, water, soil, and human food. Ambient MPs/NPs can enter the human body by ingestion, inhalation and dermal contact, then be transferred into the brain via the blood circulation and nerve pathways. When MPs/NPs are present in the brain, they can initiate a series of molecular or cellular reactions that may harm the blood-brain barrier, cause oxidative stress, trigger inflammatory responses, affect acetylcholinesterase activity, lead to mitochondrial dysfunction, and impair autophagy. This can result in abnormal protein folding, loss of neurons, disruptions in neurotransmitters, and unusual behaviours, ultimately contributing to the initiation and progression of neurodegenerative changes and neurodevelopmental abnormalities. Key challenges and further research directions are also proposed in this review as more studies are needed to focus on the potential neurotoxicity of MPs/NPs under realistic conditions.

Long-term exposure to 6-PPD quinone at environmentally relevant concentrations causes neurotoxicity by affecting dopaminergic, serotonergic, glutamatergic, and GABAergic neuronal systems in Caenorhabditis elegans

6-PPD quinone (6-PPDQ), an emerging environmental pollutant, is converted based on 6-PPD via ozonation. However, a systematic evaluation on possible neurotoxicity of long-term and low-dose 6-PPDQ exposure and the underlying mechanism remain unknown. In the present work, 0.1-10 μg/L 6-PPDQ was added to treat Caenorhabditis elegans for 4.5 days, with locomotion behavior, neuronal development, sensory perception behavior, neurotransmitter content, and levels of neurotransmission-related genes being the endpoints. 6-PPDQ exposure at 0.1-10 μg/L significantly reduced locomotion behavior, and that at 1-10 μg/L decreased sensory perception behavior in nematodes. Moreover, 6-PPDQ exposure at 10 μg/L notably induced damage to the development of dopaminergic, glutamatergic, serotonergic, and GABAergic neurons. Importantly, nematodes with chronic 6-PPDQ exposure at 10 μg/L were confirmed to suffer obviously decreased dopamine, serotonin, glutamate, dopamine, and GABA contents and altered neurotransmission-related gene expression. Meanwhile, the potential binding sites of 6-PPDQ and neurotransmitter synthesis-related proteins were further shown by molecular docking method. Lastly, Pearson's correlation analysis showed that locomotion behavior and sensory perception behavior were positively correlated with the dopaminergic, serotonergic, glutamatergic, and GABAergic neurotransmission. Consequently, 6-PPDQ exposure disturbed neurotransmitter transmission, while such changed molecular foundation for neurotransmitter transmission was related to 6-PPDQ toxicity induction. The present work sheds new lights on the mechanisms of 6-PPDQ and its possible neurotoxicity to organisms at environmentally relevant concentrations.

Generation of environmentally persistent free radicals on photoaged tire wear particles and their neurotoxic effects on neurotransmission in Caenorhabditis elegans

Tire wear particles (TWP) are a prevalent form of microplastics (MPs) extensively distributed in the environment, raising concerns about their environmental behaviors and risks. However, knowledge regarding the properties and toxicity of these particles at environmentally relevant concentrations, specifically regarding the role of environmentally persistent free radicals (EPFRs) generated during TWP photoaging, remains limited. In this study, the evolution of EPFRs on TWP under different photoaging times and their adverse effects on Caenorhabditis elegans were systematically investigated. The photoaging process primarily resulted in the formation of EPFRs and reactive oxygen species (O2•-, ⋅OH, and 1O2), altering the physicochemical properties of TWP. The exposure of nematodes to 100 μg/L of TWP-50 (TWP with a photoaging time of 50 d) led to a significant decrease in locomotory behaviors (e.g., head thrashes, body bends, and wavelength) and neurotransmitter contents (e.g., dopamine, glutamate, and serotonin). Similarly, the expression of neurotransmission-related genes was reduced in nematodes exposed to TWP-50. Furthermore, the addition of free-radical inhibitors significantly suppressed TWP-induced neurotoxicity. Notably, correlation analysis revealed a significantly negative correlation between EPFRs levels and the locomotory behaviors and neurotransmitter contents of nematodes. Thus, it was concluded that EPFRs on photoaged TWP induce neurotoxicity by affecting neurotransmission. These findings elucidate the toxicity effects and mechanisms of EPFRs, emphasizing the importance of considering their contributions when evaluating the environmental risks associated with TWP.

Low-frequency noise impairs righting reflex behavior by disrupting central nervous system in the sea slug Onchidium reevesii

Anthropogenic noise has significantly increased due to human activities, posing a threat to the health and survival of marine organisms. However, current studies have often emphasized its effects on the physiological aspects of marine organisms, while ignored the relationship between the neuroendocrine system and behavior. This study aimed to evaluate the righting behavior and relevant physiological functions of the central nervous system (CNS) in sea slug (Onchidium reevesii) exposed to low-frequency noise and subsequent noise removal. The duration of the sea slugs' righting reflex increased with longer noise exposure time. The degree of neuronal cell damage and apoptosis were significantly increased and relevant gene expressions were affected (Glu, AChE, FMRFamide and CaMKII) (P < 0.05). After the removal of noise, the righting reflex speed gradually recovered, and the degree of neuronal cell damage, apoptosis and the expression levels of genes continued to decrease. Pearson correlation analysis showed that the righting time was positively correlated with CNS tissue and DNA damage, apoptosis rate, and negatively correlated with the expression levels of genes. Therefore, low-frequency noise exposure causes damage to the CNS of sea slugs, subsequently impairing their normal behavior. Sea slugs exhibited partial recovery within 384 h after removing noise. These findings provide valuable insights into the effects of low-frequency noise on the CNS and behavior of marine invertebrates.

Uptake and effect of carboxyl-modified polystyrene microplastics on cotton plants

Microplastics (MPs) have emerged as a significant global environmental concern, particularly within agricultural soil systems. The extensive use of plastic film mulching in cotton cultivation has led to the alarming presence of MP pollution in cotton fields. However, the uptake and effects of MPs on the growth of cotton plants are poorly understood. In this study, we conducted a comprehensive analysis of hydroponically cultured cotton seedlings at the phenotypic, transcriptional, and metabolic levels after exposure to carboxyl-modified polystyrene microplastics (PS-COOH). Treatment with three concentrations of PS-COOH (100, 300, and 500 mg/L) resulted in notable growth inhibition of treated plants and exhibited a dose-dependent effect. And, PS-COOH can invade cotton roots and be absorbed through the intercellular spaces via apoplastic uptake, with accumulation commensurate with treatment duration. Transcriptomic analysis showed significant up-regulation of genes associated with antioxidant activity in response to 300 mg/L PS-COOH treatment, suggesting the induction of oxidative stress. In addition, the PS-COOH treatment activated the phenylpropanoid biosynthesis pathway, leading to lignin and flavonoid accumulation, and altered sucrose catabolism. These findings illustrate the absorption and effects of MPs on cotton seedlings and offer valuable insights into the potential toxicity of MPs to plants in soil mulched with plastic film.

Comparison of reproductive toxicity between pristine and aged polylactic acid microplastics in Caenorhabditis elegans

Caenorhabditis elegans was employed as model to compare reproductive toxicity between pristine and aged polylactic acid microplastics (PLA-MPs). Aged PLA-MPs induced by UV irradiation showed degradation reflected by decrease in size and alteration in morphological surface. Aged PLA-MPs also exhibited some certain changes of chemical properties compared to pristine PLA-MP. Compared with pristine PLA-MPs, more severe toxicity on reproductive capacity and gonad development was detected in 1-100 μg/L aged PLA-MPs. Meanwhile, aged PLA-MPs caused more severe enhancement in germline apoptosis and alterations in expressions of ced-9, ced-4, ced-3, and egl-1 governing cell apoptosis. In addition, aged PLA-MPs resulted in more severe increase in expression of DNA damage related genes (cep-1, mrt-2, hus-1, and clk-2) compared to pristine PLA-MPs, and the alterations in expression of ced-9, ced-4, ced-3, and egl-1 in pristine and aged PLA-MPs could be reversed by RNAi of cep-1, mrt-2, hus-1, and clk-2. Besides this, enhanced germline apoptosis in pristine and aged PLA-MPs exposed animals was also suppressed by RNAi of cep-1, mrt-2, hus-1, and clk-2. Therefore, our results suggested the more severe exposure risk of aged PLA-MPs than pristine PLA-MPs in causing reproductive toxicity, which was associated with the changed physicochemical properties and DNA damage induced germline apoptosis.

Potential nervous threat of nanoplastics to Monopterus albus: Implications from a metabolomics study

Nanoplastics, as a new class of environmental pollutants, have been frequently detected in environmental media and organisms. Monopterus albus (M. albus) is an important economic aquatic product with a high dietary consumption. However, the potential biological effects of nanoplastics on M. albus remain unknown. In this study, the effects of polystyrene nanoplastics (PS-NPs) at different concentrations (0, 0.5, 1, 5 and 10 mg/L) on M. albus were investigated using an untargeted metabolomics approach. The results showed that 59, 44, 24, and 31 individual differential metabolites and 16, 9, 6, and 2 significant differential metabolic pathways were significantly changed in 0.5, 1, 5, and 10 mg/L respectively, indicating the greater effect of PS-NPs at the relatively low concentrations. After further analysis, there are four same significant differential metabolic pathways for the 0.5 and 1 mg/L groups, i.e., ABC transporters, cAMP signaling pathway, Neuroactive ligand-receptor interaction, and Synaptic vesicle cycle. In addition, there was one mutual differential metabolic pathway (Neuroactive ligand-receptor interaction) among the four groups, indicative of the probably universal nervous influence of nanoplastics on M. albus. In a word, the current work suggests that PS-NPs might affect the nervous systems of M. albus through disturbing their liver metabolism, and nanoplastics at relatively low concentrations may possess a greater effect, which provides significant information for assessing the toxic effect and exposure risk of nanoplastics to organisms in aquatic environment.

Environmentally persistent free radicals on photoaged nanopolystyrene induce neurotoxicity by affecting dopamine, glutamate, serotonin and GABA in Caenorhabditis elegans

Microplastics are widely detected in the environment and induce toxic effects in various organisms. However, the properties and toxicity associated with environmentally persistent free radicals (EPFRs) in photoaged nanopolystyrene (NPS) remain largely unknown. We investigated the generation of EPFRs on photoaged NPS and their neurotoxicity and underlying mechanism in Caenorhabditis elegans. The results suggested that photoaging induces the generation of EPFRs and reactive oxygen species (O2•-, •OH, and 1O2), which altered the physicochemical properties (morphology, crystallinity, and functional groups) of NPS. Acute exposure to 1 μg/L of NPS-60 (NPS with light irradiation time of 60 d) significantly decreased locomotion behaviors and neurotransmitter contents (e.g., glutamate, serotonin, dopamine, and γ-aminobutyric acid). Treatment with N-acetyl-L-cysteine (NAC) by radical quenching test significantly reduced EPFRs levels on the aged NPS, and the toxicity of NAC-quenching NPS was decreased in nematodes compared to those in photoaged NPS. EPFRs also caused dysfunction of neurotransmission-related gene expression in C. elegans. Thus, EPFRs generated on photoaged NPS contributed to neurotoxicity by affecting dopamine, glutamate, serotonin, and γ-aminobutyric acid neurotransmission. The study highlights the potential risks of photoaged NPS and the contributions of EPFRs to toxicity.

Direct Quantification of Nanoplastics Neurotoxicity by Single-Vesicle Electrochemistry

Nanoplastics are recently recognized as neurotoxic factors for the nervous systems. However, whether and how they affect vesicle chemistry (i.e., vesicular catecholamine content and exocytosis) remains unclear. This study offers the first direct evidence for the nanoplastics-induced neurotoxicity by single-vesicle electrochemistry. We observe the cellular uptake of polystyrene (PS) nanoplastics into model neuronal cells and mouse primary neurons, leading to cell viability loss depending on nanoplastics exposure time and concentration. By using single-vesicle electrochemistry, we find the reductions in the vesicular catecholamine content, the frequency of stimulated exocytotic spikes, the neurotransmitter release amount of single exocytotic event, and the membrane-vesicle fusion pore opening-closing speed. Mechanistic investigations suggest that PS nanoplastics can cause disruption of filamentous actin (F-actin) assemblies at cytomembrane zones and change the kinetic patterns of vesicle exocytosis. Our finding shapes the first quantitative picture of neurotoxicity induced by high-concentration nanoplastics exposure at a single-cell level.

Polystyrene size-dependent impacts on microbial decomposers and nutrient cycling in streams

The particle size of plastic is one of the most important factors influencing its ecotoxicity, but we are unclear about the effect of polystyrene (PS) particle size on microbial decomposers and consequent nutrient cycling in streams. Here, using microcosm experiments, we assessed how three PS sizes (50 nm, 1 μm, and 20 μm) influenced the process and consequences of leaf litter decomposition. Under acute exposure to 1 μm and 20 μm PS, fungal biomass significantly decreased, but microbial biomass significantly increased, indicating compensations may work between fungi and other microbial decomposers. After chronic exposure to 50 nm and 1 μm PS, the leaf decomposition rate decreased by 19.27 % and 15.22 %, respectively, due to the reduced microbial enzyme activity, fungal diversity, and dominance of Anguillospora. As a result, the regeneration of nutrients, especially phosphorus, was significantly depressed, which might influence the primary productivity of streams. Therefore, our results suggest that nanoscale PS has a greater impact on microbial activity, thus affecting their functioning in leaf litter decomposition and consequent nutrient cycling. The findings provide a data support for the risk assessment of plastic pollution in freshwater systems.

Deciphering the interplay between LPS/TLR4 pathways, neurotransmitter, and deltamethrin-induced depressive-like behavior: Perspectives from the gut-brain axis

The improper use of deltamethrin (DM) can result in its accumulation in soil, water, food, and even the human body, which is associated with an elevated risk of neurotoxicity and behavioral abnormalities; however, the underlying mechanisms remain insufficiently investigated. Emerging evidence underscores the significance of the gut-brain axis in central nervous system (CNS) dysfunctions. Accordingly, this study investigates the role of the gut-brain axis in DM-induced behavioral anomalies in mice. The results showed that DM exposure induced depressive-like behavior, and the hippocampus, the region that is responsible for the modulation of emotional behavior, showed structural integrity disrupted (neuronal nuclear shrinkage and decreased tight junction protein expression). In addition, DM exposure led to compromised gut barrier integrity (disruptions on crypt surfaces and decreased tight junction protein expression), which might contribute to the gut bacterial-derived lipopolysaccharide (LPS) leakage into the bloodstream and reaching the brain, triggering LPS/toll-like receptor (TLR) 4 -mediated increases in brain pro-inflammatory cytokines. Subsequently, we observed a disturbance in neurotransmitter metabolic pathways following DM exposure, which inhibited the production of 5-hydroxytryptamine (5-HT). Additionally, DM exposure resulted in gut microbiota dysbiosis. Characteristic bacteria, such as Alistipes, Bifidobacterium, Gram-negative bacterium cTPY-13, and Odoribacter exhibited significant correlations with behavior, tight junction proteins, inflammatory response, and neurotransmitters. Further fecal microbiota transplantation (FMT) experiments suggested that DM-induced gut microbiota dysbiosis might contribute to depressive-like behavior. These results provide a new perspective on the toxicity mechanism of DM, indicating that its neurotoxicity may be partially regulated by the microbiota-gut-brain axis.

Nano polystyrene induced changes in anxiety and learning behaviour are mediated through oxidative stress and gene disturbance in mouse brain regions

It is widely reported now that nanoplastic particles have potential neurotoxic effects and may disturb central nervous system (CNS) function. However, the mechanism behind these toxic effects still needs to be elucidated. In the current study, we investigated the effects of polystyrene nanoplastics (PS-NPs) on changes in learning, memory, and anxiety-related behavior in mice based on some selected biochemical, molecular, and histopathological changes in three important brain regions (Cortex, Hypothalamus, and Hippocampus). Male mice were orally administered daily with two doses of 50 nm PS-NPs (0.2 mg/ml and 1 mg/ml) for 8 weeks. We observed decreased expression of neurotransmitter-related genes (VAChT, GAD, and SYP) in the cortex, hypothalamus, and hippocampus areas of the mouse brain. Other biochemical variables including, antioxidant enzymes, biomarkers for oxidative stress, and acetylcholinesterase activity showed significant alterations in all three brain regions. Molecular and neurochemical data thus suggest significant neurobehavioral changes following sub-chronic exposure to PS-NPs which may lead to enhanced anxiety-related and spatial learning and memory-related impairments by affecting limbic areas of the brain.

Photoaged microplastics induce neurotoxicity associated with damage to serotonergic, glutamatergic, dopaminergic, and GABAergic neuronal systems in Caenorhabditis elegans

Microplastics (MPs) are ubiquitous environmental contaminants that cause neurotoxicity in various organisms. MPs are typically affected by light irradiation and undergo photoaging. However, the neurotoxic effects of photoaged polystyrene (P-PS) and its underlying mechanisms remain unclear. In this study, locomotion behaviors, neuronal development, neurotransmitter levels, and the expression of neurotransmission-related genes were investigated in Caenorhabditis elegans exposed to P-PS at environment-relevant concentrations (0.1-100 μg/L). The characterization results showed that photoaging accelerated the aging process and changed the physicochemical properties of the MPs. The toxicity results suggested that exposure to 1-100 μg/L P-PS caused more severe neurotoxicity than virgin polystyrene (V-PS) with endpoints of head thrashes, body bends, wavelength, and mean amplitude. Exposure to P-PS also altered the fluorescence intensity and neurodegeneration percentage of serotonergic, glutamatergic, dopaminergic, and aminobutyric acid (GABA) in transgenic nematodes. Similarly, significant reductions in the levels of these neurotransmitters were also observed. Based on Pearson's correlation, locomotion behaviors were negatively correlated with the neurotransmission of serotonin, glutamate, dopamine, and GABA. Further investigation suggested that the expression of neurotransmitter-related genes (e.g., tph-1, eat-4, and unc-46) was significantly altered in the nematodes. Collectively, the neurotoxic effects of P-PS were attributed to abnormal neurotransmission. This study highlights the potential toxicity of MPs photoaged under environmentally relevant conditions.

Combined Effects of Micro- and Nanoplastics at the Predicted Environmental Concentration on Functional State of Intestinal Barrier in Caenorhabditis elegans

The possible toxicity caused by nanoplastics or microplastics on organisms has been extensively studied. However, the unavoidably combined effects of nanoplastics and microplastics on organisms, particularly intestinal toxicity, are rarely clear. Here, we employed Caenorhabditis elegans to investigate the combined effects of PS-50 (50 nm nanopolystyrene) and PS-500 (500 nm micropolystyrene) at environmentally relevant concentrations on the functional state of the intestinal barrier. Environmentally, after long-term treatment (4.5 days), coexposure to PS-50 (10 and 15 μg/L) and PS-500 (1 μg/L) resulted in more severe formation of toxicity in decreasing locomotion behavior, in inhibiting brood size, in inducing intestinal ROS production, and in inducting intestinal autofluorescence production, compared with single-exposure to PS-50 (10 and 15 μg/L) or PS-500 (1 μg/L). Additionally, coexposure to PS-50 (15 μg/L) and PS-500 (1 μg/L) remarkably caused an enhancement in intestinal permeability, but no detectable abnormality of intestinal morphology was observed in wild-type nematodes. Lastly, the downregulation of acs-22 or erm-1 expression and the upregulation expressions of genes required for controlling oxidative stress (sod-2, sod-3, isp-1, clk-1, gas-1, and ctl-3) served as a molecular basis to strongly explain the formation of intestinal toxicity caused by coexposure to PS-50 (15 μg/L) and PS-500 (1 μg/L). Our results suggested that combined exposure to microplastics and nanoplastics at the predicted environmental concentration causes intestinal toxicity by affecting the functional state of the intestinal barrier in organisms.

Exposure to polystyrene nanoparticles at predicted environmental concentrations enhances toxic effects of Acinetobacter johnsonii AC15 infection on Caenorhabditis elegans

Nanoplastics and microbial pathogens are both widely distributed in the environment; however, their combined toxicity remains largely unclear. Using Caenorhabditis elegans as an animal model, we examined the possible effect of exposure to polystyrene nanoparticle (PS-NP) in Acinetobacter johnsonii AC15 (a bacterial pathogen) infected animals. Exposure to PS-NP at the concentrations of 0.1-10 μg/L significantly enhanced the toxicity of Acinetobacter johnsonii AC15 infection on lifespan and locomotion behaviors. In addition, after exposure to 0.1-10 μg/L PS-NP, the accumulation of Acinetobacter johnsonii AC15 in body of nematodes was also increased. Meanwhile, the innate immune response indicated by the increase of antimicrobial gene expressions in Acinetobacter johnsonii AC15 infected nematodes was suppressed by exposure to 0.1-10 μg/L PS-NP. Moreover, expressions of egl-1, dbl-1, bar-1, daf-16, pmk-1, and elt-2 governing the bacterial infection and immunity in Acinetobacter johnsonii AC15 infected nematodes were further inhibited by exposure to 0.1-10 μg/L PS-NP. Therefore, our data suggested the possible exposure risk of nanoplastic at predicted environmental concentrations in enhancing the toxic effects of bacterial pathogens on environmental organisms.

The generation of environmentally persistent free radicals on photoaged microbeads from cosmetics enhances the toxicity via oxidative stress

Microbeads used in personal care products have been one of the important sources of microplastics (MPs), and little has been reported on their environmental behaviors and health risks. The characteristics of environmentally persistent free radicals (EPFRs) and the toxicity assessment of MPs (environmentally relevant concentrations) from cosmetics during photoaging remains largely unknown. In this study, the formation of EPFRs on polyethylene (PE) microbeads from facial scrubs under light irradiation and their toxicity were investigated using C. elegans as a model organism. The results suggested that light irradiation induced the generation of EPFRs, which accelerates the aging process and alters the physicochemical properties of PE microbeads. Acute exposure to PE (1 mg/L) at photoaged times of 45-60 d significantly decreased the physiological indicators (e.g., head thrashes, body bends, and brood size). The oxidative stress response and stress-related gene expression were also enhanced in nematodes. The addition of N-acetyl-l-cysteine induced significant inhibition of toxicity and oxidative stress in nematodes exposed to 45-60 d of photoaged PE. The Pearson correlation results showed that the concentration of EPFRs was significantly correlated with physiological indicators, oxidative stress, and related-genes expression in nematodes. The data confirmed that the generation of EPFRs combined with heavy metals and organics contributed to toxicity induced by photoaged PE, and oxidative stress might be involved in regulating adverse effects in C. elegans. The study provides new insight into the potential risks of microbeads released into the environment during photoaging. The findings also highlight the necessity for considering the role of EPFRs formation in evaluating the impacts of microbeads.