Polystyrene Microplastics Exposure: An Insight into Multiple Organ Histological Alterations, Oxidative Stress and Neurotoxicity in Javanese Medaka Fish (Oryzias javanicus Bleeker, 1854)

Ecotoxicological evaluation of chitosan biopolymer films particles in adult zebrafish (Danio rerio): A comparative study with polystyrene microplastics

To mitigate the environmental impact of microplastics (MPs), the scientific community has innovated sustainable and biodegradable polymers as viable alternatives to traditional plastics. Chitosan, the deacetylated form of chitin, stands as one of the most thoroughly investigated biopolymers and has garnered significant interest due to its versatile applications in both medical and cosmetic fields. Nevertheless, there is still a knowledge gap regarding the impact that chitosan biopolymer films (CBPF) may generate in aquatic organisms. In light of the foregoing, this study aimed to assess and compare the potential effects of CBPF on the gastrointestinal tract, gills, brain, and liver of Danio rerio against those induced by MPs. The findings revealed that both CBPF and MPs induced changes in the levels of oxidative stress biomarkers across all organs. However, it is essential to note that our star plots illustrate a tendency for CBPF to activate antioxidant enzymes and for MPs to produce oxidative damage. Regarding gene expression, our findings indicate that MPs led to an up-regulation in the expression of genes associated with apoptotic response (p53, casp3, cas9, bax, and bcl2) in all fish organs. Meanwhile, CBPF produced the same effect in genes related to antioxidant response (nrf1 and nrf2). Overall, our histological observations substantiated these effects, revealing the presence of plastic particles and tissue alterations in the gills and gastrointestinal tract of fish subjected to MPs. From these results, it can be concluded that CBPF does not represent a risk to fish after long exposure.

Health effects of microplastics and nanoplastics: review of published case reports

Microplastics and nanoplastics (MNPs) represent a pervasive environmental pollutant, raising significant concerns about potential health effects on humans. These tiny plastic particles have been detected across various environmental matrices, including air, water, soil, and food sources. While the adverse impacts of MNPs on wildlife and ecosystems are well-documented, understanding their effects on human health is still in its infancy. This study aims to comprehensively review existing case reports documenting adverse health outcomes associated with MNPs exposure. Through an extensive literature search, relevant articles were identified and analyzed. MNPs exposure primarily occurs through ingestion and inhalation routes. Health effects on the digestive system include oxidative stress, inflammation, dysbiosis, and metabolic disorders, with cases linking MNPs exposure to gastrointestinal injury and liver dysfunction. Respiratory system impacts include asthma exacerbation and hypersensitivity pneumonitis, particularly in industries involving plastic production. MNPs exposure has also been associated with nervous system conditions, reproductive toxicity, skeletal system interference, excretory system disruption, and cardiovascular morbidity and mortality. Despite limited case reports, the widespread presence of MNPs warrants further investigation into their potential health risks. This study underscores the urgency of understanding and mitigating the adverse health effects posed by MNPs exposure. Further research is imperative in order to comprehensively assess and address the dangers associated with MNPs contamination in the environment.

Photoaged polystyrene microplastics result in neurotoxicity associated with neurotransmission and neurodevelopment in zebrafish larvae (Danio rerio)

Microplastics (MPs) are emerging pollutants widely distributed in the environment, inducing toxic effects in various organisms. However, the neurotoxicity and underlying mechanisms of simulated sunlight-aged MPs have rarely been investigated. In this study, zebrafish (Danio rerio) were exposed to environmentally relevant concentrations (0, 0.1, 1, 10, and 100 μg/L) of virgin polystyrene (V-PS) and aged polystyrene (A-PS) for 120 hpf to evaluate the neurotoxicity. The results demonstrated that simulated sunlight irradiation altered the physicochemical properties (morphology, functional groups, and chemical composition) of V-PS. Exposure to A-PS causes greater toxicity on locomotor ability in larval zebrafish than V-PS. Motor neuron development was disrupted by transgenic (hb9-GFP) zebrafish larvae exposed to A-PS, with significant alterations in neurotransmitter levels (ACh, DA, 5-HT, and GABA) and enzyme activity (AChE, ChAT, and ChE). Further investigation found that exposure to A-PS had a significantly impact on the expression of neurotransmission and neurodevelopment-related genes in zebrafish. These findings suggest that A-PS induces neurotoxicity by its effects on neurotransmission and neurodevelopment. This study highlights the neurotoxic effects and mechanisms of simulated sunlight irradiation of MPs, providing new insights for assessing the ecological risks of photoaged MPs in the environment.

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.

Polystyrene nanoplastic and engine oil synergistically intensify toxicity in Nile tilapia, Oreochromis niloticus : Polystyrene nanoplastic and engine oil toxicity in Nile tilapia

Polystyrene nanoplastic (PS-NPs) and Engine oil (EO) pose multiple ecotoxic effects with increasing threat to fish ecosystems. The current study investigated the toxicity of 15 days exposure to PS-NPs and / or EO to explore their combined synergistic effects on Nile tilapia, Oreochromis niloticus (O. niloticus). Hematobiochemical parameters, proinflammatory cytokines, and oxidative stress biomarkers as well as histological alterations were evaluated. The experimental design contained 120 acclimated Nile tilapia distributed into four groups, control, PS-NPs (5 mg/L), EO (1%) and their combination (PS-NPs + EO). After 15-days of exposure, blood and tissue samples were collected from all fish experimental groups. Results indicated that Nile tilapia exposed to PS-NPs and / or EO revealed a significant decrease in almost all the measured hematological parameters in comparison to the control, whereas WBCs and lymphocyte counts were significantly increased in the combined group only. Results clarified that the combined PS-NPs + EO group showed the maximum decrease in RBCs, Hb, MCH and MCHC, and showed the maximum significant rise in interleukin-1β (IL-1β), and interleukin-6 (IL-6) in comparison to all other exposed groups. Meanwhile, total antioxidant capacity (TAC) showed a significant (p < 0.05) decline only in the combination group, whereas reduced glutathione (GSH) showed a significant decline in all exposed groups in comparison to the control. Both malondialdehyde (MDA) and aspartate aminotransferase (AST) showed a significant elevation only in the combination group. Uric acid showed the maximum elevation in the combination group than all other groups, whereas creatinine showed significant elevation in the EO and combination group when compared to the control. Furthermore, the present experiment proved that exposure to these toxicants either individually or in combination is accompanied by pronounced histomorpholgical damage characterized by severe necrosis and hemorrhage of the vital organs of Nile tilapia, additionally extensively inflammatory conditions with leucocytes infiltration. We concluded that combination exposure to both PS-NPs and EO caused severe anemia, extreme inflammatory response, oxidative stress, and lipid peroxidation effects, thus they can synergize with each other to intensify toxicity in fish.

Pharmacotherapeutic potential of ginkgetin against polystyrene microplastics-instigated testicular toxicity in rats: A biochemical, spermatological, and histopathological assessment

Polystyrene microplastics (PSMPs) have emerged as a ubiquitous environmental toxicant that affects different organs including testes. Ginkgetin (GNG) is a biflavonoid that shows antioxidant properties. The current research was undertaken to evaluate the ameliorative potential of GNG against PSMPs-instigated testicular damages. Forty-eight albino rats (male) were randomly divided into 4 equal groups: control, PSMPs-treated group (0.01 mgkg-1), GNG + PSMPs-exposed group (25 mgkg-1 + 0.01 mgkg-1), and only GNG-supplemented group (25 mgkg-1). After 56 days of treatment, it was revealed that PSMPs significantly reduced the activity of glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), and glutathione reductase (GSR), while concurrently augmented the levels of lipid peroxidation marker, i.e., malondialdehyde (MDA) along with reactive oxygen species (ROS). Rats administered with PSMPs showed a significant reduction in the spermatogenic indices (sperm count, viability, and motility), HOS coiled tail sperm along with increased sperm structural deformities, i.e., tail, head, and mid-piece. Additionally, PSMPs exposure decreased the levels of testosterone, luteinizing (LH), and follicle-stimulating hormones (FSH). Besides, administration of PSMPs reduced the steroidogenic enzymes (13β-HSD, StAR, and 17β-HSD) and Bcl-2 expression, while augmented the caspase-3 and Bax expression. PSMPs also elevated the levels of inflammatory markers (IL-6, IL-1β, TNF-α, and NF-κB) and activity of COX-2 in the testes. Furthermore, PSMPs treatment induced various histopathological damages in the testes of rats. Therefore, findings of the current study suggested that GNG effectively mitigated the PSMPs-induced testicular toxicity owing to its chemoprotective potential possibly through its anti-inflammatory, antioxidant, anti-apoptotic, and androgenic properties.

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.

Short-term exposure to polystyrene microplastics hampers the cellular function of gills in the Mediterranean mussel Mytilus galloprovincialis

Plastic is undoubtedly the most useful and versatile polymeric material that man has developed in the last two centuries Despite the societal benefits, plastic is now a serious global issue because it is persistent and may bioaccumulate into aquatic biota as microplastics (MPs). This study was designed to evaluate the daily uptake and cellular effects due to a short-term (up to 72 h) exposure to 3 μm red polystyrene MPs (50 beads/mL) in the gills of the Mediterranean mussel Mytilus galloprovincialis, chosen as model species for its ecological and commercial relevance. After measuring the daily uptake of MPs and detecting their presence within the branchial epithelium at all the exposure time-points (T24, T48, T72), some cleaning mechanisms were observed by neutral and acid mucous secretions at mussel gills. The protonic Nuclear Magnetic Resonance (1H NMR)-based metabolomics, combined with chemometrics, allowed to comprehensively explore the time-dependent metabolic disorders triggered by MPs in mussel gills over the short-term trial. Specifically, the clear clustering between MP-treated mussel gills and those from control, together with the grouping for experimental time-points as depicted by the Principal Component Analysis (PCA), were due to changes in the amino acids and energy metabolism, disturbances in the osmoregulatory processes, as well as in the cholinergic neurotransmission. Moreover, as evidenced by enzymatic assays, even the oxidative defense systems and lipid metabolism were hampered by MP exposure. Overall, these findings provides the first insights into the early time-dependent mechanisms of toxicity of polystyrene MPs in marine mussels, and underline the potential environment and human health risk posed by MPs contamination.

Microplastic polyamide toxicity: Neurotoxicity, stress indicators and immune responses in crucian carp, Carassius carassius

This study aimed to determine the toxicity standard and potential risks and effects of polyamide (PA) exposure on neurotoxicity, stress indicators, and immune responses in juvenile crucian carp Carassius carassius. Numerous microplastics (MPs) exists within aquatic environments, leading to diverse detrimental impacts on aquatic organisms. The C. carassius (mean weight, 23.7 ± 1.6 g; mean length, 13.9 ± 1.4 cm) were exposed to PA concentrations of 0, 4, 8, 16, 32 and 64 mg/L for 2 weeks. Among the neurotransmitters, the acetylcholinesterase (AChE) activity in the liver, gill, and intestine of C. carassius was significantly inhibited by PA exposure. Stress indicators such as cortisol and heat shock protein 70 (HSP70) in the liver, gill, and intestine of C. carassius were significantly increased, while immune responses to lysozyme and immunoglobulin M (IgM) were significantly decreased. Our study demonstrates the toxic effects of MP exposure on crucian carp's neurotoxicity, stress indicators, and immune responses.

Photoaged microplastics induce neurotoxicity via oxidative stress and abnormal neurotransmission in zebrafish larvae (Danio rerio)

Microplastics (MPs) are ubiquitous environmental contaminants and cause neurotoxicity in various organisms. However, previous studies that analyzed the effects of MPs mainly focused on virgin polystyrene (V-PS) as representative models of MPs, and the mechanism underlying the neurotoxicity of photoaged polystyrene (P-PS) remains largely unknown. In this study, zebrafish (Danio rerio) were exposed to environmentally relevant concentrations (0.1-100 μg/L) of V-PS and P-PS(10 μm). The results indicated that UV radiation accelerated the aging process and changed physical and chemical properties of PS. Whereas exposure to both V-PS and P-PS at low concentrations (100 μg/L) significantly reduced the locomotor behavior of zebrafish larvae, P-PS caused more severe neurotoxicity compared to V-PS. The activity of antioxidant enzymes (SOD, CAT, and GST) and MDA content were significantly altered in zebrafish exposed to 10-100 μg/L of P-PS. Similarly, exposure to P-PS significantly increased neurotransmitter (5-HT, GABA, DA, and ACh) levels and activity of AChE, ChAT, and ChE. Star plots based on integrated biomarker response (IBR) values showed more incline toward neurotransmitter biomarkers in response to increasing P-PS concentration, and the behavioral parameters negatively correlated with the neurotransmitter biomarkers. Further investigations revealed that the expression of neurotransmission- (e.g., ache, drd3, 5th2c, and gat1) and oxidative stress- (e.g., cat1, sod1, gpx1a, and gstrl) related genes was significantly affected by PS in larval zebrafish. Thus, this study provides new insights on the potential risks of MPs into the environment.

The gut-brain axis involved in polystyrene nanoplastics-induced neurotoxicity via reprogramming the circadian rhythm-related pathways

The production of plastic is still increasing globally, which has led to an increasing number of plastic particles in the environment. Nanoplastics (NPs) can penetrate the blood-brain barrier and induce neurotoxicity, but in-depth mechanism and effective protection strategies are lacking. Here, C57BL/6 J mice were treated with 60 μg polystyrene NPs (PS-NPs, 80 nm) by intragastric administration for 42 days to establish NPs exposure model. We found that 80 nm PS-NPs could reach and cause neuronal damage in the hippocampus, and alter the expression of neuroplasticity-related molecules (5-HT, AChE, GABA, BDNF and CREB), and even affect the learning and memory ability of mice. Mechanistically, combined with the results of hippocampus transcriptome, gut microbiota 16 s ribosomal RNA and plasma metabolomics, we found that the gut-brain axis mediated circadian rhythm related pathways were involved in the neurotoxicity of NPs, especially Camk2g, Adcyap1 and Per1 may be the key genes. Both melatonin and probiotic can significantly reduce intestinal injury and restore the expression of circadian rhythm-related genes and neuroplasticity molecules, and the intervention effect of melatonin is more effective. Collectively, the results strongly suggest the gut-brain axis mediated hippocampal circadian rhythm changes involved in the neurotoxicity of PS-NPs. Melatonin or probiotics supplementation may have the application value in the prevention of neurotoxicity of PS-NPs.

Effects of microplastics, pesticides and nano-materials on fish health, oxidative stress and antioxidant defense mechanism

Microplastics and pesticides are emerging contaminants in the marine biota, which cause many harmful effects on aquatic organisms, especially on fish. Fish is a staple and affordable food source, rich in animal protein, along with various vitamins, essential amino acids, and minerals. Exposure of fish to microplastics, pesticides, and various nanoparticles generates ROS and induces oxidative stress, inflammation, immunotoxicity, genotoxicity, and DNA damage and alters gut microbiota, thus reducing the growth and quality of fish. Changes in fish behavioral patterns, swimming, and feeding habits were also observed under exposures to the above contaminants. These contaminants also affect the Nrf-2, JNK, ERK, NF-κB, and MAPK signaling pathways. And Nrf2-KEAP1 signalling modulates redox status marinating enzymes in fish. Effects of pesticides, microplastics, and nanoparticles found to modulate many antioxidant enzymes, including superoxide dismutase, catalase, and glutathione system. So, to protect fish health from stress, the contribution of nano-technology or nano-formulations was researched. A decrease in fish nutritional quality and population significantly impacts on the human diet, influencing traditions and economics worldwide. On the other hand, traces of microplastics and pesticides in the habitat water can enter humans by consuming contaminated fish which may result in serious health hazards. This review summarizes the oxidative stress caused due to microplastics, pesticides and nano-particle contamination or exposure in fish habitat water and their impact on human health. As a rescue mechanism, the use of nano-technology in the management of fish health and disease was discussed.

The detrimental effects of micro-and nano-plastics on digestive system: An overview of oxidative stress-related adverse outcome pathway

With the massive manufacture and use of plastics, plastic pollution-related environmental impacts have raised great concern in recent years. As byproducts of plastic fragmentation and degradation, microplastics (MPs) and nanoplastics (NPs) have been identified as novel pollutants that posed a threat to the ecosystem and humans. Since MPs/NPs could be transported via the food chain and retained in the water, the digestive system should be one of the major targets of MPs/NPs-related toxicity. Although considerable evidence has supported the digestive toxicity of MPs/NPs, the proposed mechanisms remained ambiguous due to the variety of study types, models, and endpoints. This review provided a mechanism-based perspective on MPs/NPs-induced digestive effects by adopting the adverse outcome pathway framework as a promising tool. The overproduction of reactive oxygen species was identified as the molecular initiating event in MPs/NPs-mediated injury to the digestive system. A series of detrimental effects including oxidative stress, apoptosis, inflammation, dysbiosis, and metabolic disorders were summarized as key events. Finally, the occurrence of these effects eventually led to an adverse outcome, suggesting a possible increase in the incidence of digestive morbidity and mortality.

From the environment into the biomass: microplastic uptake in a protected lamprey species

The relationship between the ubiquitous presence of microplastics in the environment and exposure of biota needs to be better understood, particularly for vulnerable species and their habitats. In this study, we address the presence of microplastics in the riverine habitat of a threatened lamprey species (Lampetra sp.), both in habitats with protective interventions in place (designated as Special Areas of Conservation), and those without these protective interventions. By sampling both riverbed sediments and larval lamprey, we provide a direct comparison of the microplastic loadings in both, and insights into how knowledge of sediment loadings might predict biological uptake. Microplastic particles, analysed using micro-Fourier transform infrared (μFTIR) spectroscopy, were detected in all samples of lamprey larvae and paired sediment, ranging in abundance from 1.00 to 27.47 particles g^-1 in dry lamprey gastrointestinal tract (GIT) tissue, and 0.40 to 105.41 particles g^-1 in dry sediment. The most urbanised catchment exhibited the highest average microplastic particle count in both lamprey and sediment. Across sites, the microplastic abundance in lamprey GIT tissue was not correlated with that of the surrounding sediment, suggesting that either specific polymer types are retained or other factors such as larvae residence time within sediment patches may influence biological uptake. The most encountered polymer types in lamprey from their immediate habitat were polyurethane, polyamide, and cellulose acetate. To the best of our knowledge, this is the first study to document microplastic contamination of larval lamprey in-situ, contributing another potential stressor to the population status of a vulnerable species. This highlights where further research on the impacts of plastic contamination of freshwater environments is needed to aid conservation management of this ecologically important species.

Effects of microfiber exposure on medaka (Oryzias latipes): Oxidative stress, cell damage, and mortality

Fiber-type microplastics are major anthropogenic contaminants of marine environments. They are released mainly during cloth washing and are discharged from wastewater treatment plants into aquatic environments. This study aimed to evaluate whether microfiber exposure causes oxidative stress and cell damage in medaka (Oryzias latipes Temminck and Schlegel 1846). Fish were exposed to one of two different concentrations (500 and 1000 fibers/L) of a polyester-based microfiber (MF) for 21 days, and the degree of cell damage and changes in expression of antioxidant enzymes were investigated. Fish survival decreased with increasing concentrations of MF. The expression levels of superoxide dismutase (SOD) and catalase (CAT) increased in MF-exposed groups compared to those in the control. SOD activity increased compared to the control group, and MF exposure induced a significant increase in both SOD activity and mRNA expression over time. CAT mRNA expression increased from day 10 onwards following exposure. Plasma malondialdehyde content increased significantly on day 7 of exposure in the 1000 fiber/L group and on day 10 in the 500 fiber/L group. Caspase-3 mRNA expression significantly increased until day 10 of exposure. A terminal transferase dUTP nick end labeling assay confirmed increased apoptosis, and a comet assay demonstrated that higher DNA damage occurred in response to increased MF concentration and exposure time. In conclusion, we confirmed that MF exposure affects antioxidant reactions in fish, thus inducing oxidative stress, apoptosis, and DNA damage. In addition, a comprehensive understanding of MF pollution in aquatic systems is urgently required.

Subchronic Exposure to Polystyrene Microplastic Differently Affects Redox Balance in the Anterior and Posterior Intestine of Sparus aurata

Microplastics (MPs) are pollutants widely distributed in aquatic ecosystems. MPs are introduced mainly by ingestion acting locally or in organs far from the gastroenteric tract. MPs-induced health consequences for fish species still need to be fully understood. We aimed to investigate the effects of the subchronic oral exposure to polystyrene microplastics (PS-MPs) (1-20 μm) in the gilthead seabreams (Sparus aurata) used as the experimental model. We studied the detrimental impact of PS-MPs (25 and 250 mg/kg b.w./day) on the redox balance and antioxidant status in the intestine using histological analysis and molecular techniques. The research goal was to examine the anterior (AI) and posterior intestine (PI) tracts, characterized by morphological and functional differences. PS-MPs caused an increase of reactive oxygen species and nitrosylated proteins in both tracts, as well as augmented malondialdehyde production in the PI. PS-MPs also differently affected gene expression of antioxidant enzymes (i.e., superoxide dismutase, catalase, glutathione reductase). Moreover, an increased up-regulation of protective heat shock proteins (HSPs) (i.e., hsp70 and hsp90) was observed in PI. Our findings demonstrate that PS-MPs are responsible for oxidative/nitrosative stress and alterations of detoxifying defense system responses with differences in AI and PI of gilthead seabreams.

Microplastics induce neurotoxicity in aquatic animals at environmentally realistic concentrations: A meta-analysis

Microplastics (MPs) draw international attention owing to their widespread distribution in water ecosystems, but whether MPs cause neurotoxic effects in aquatic animals at environmentally realistic concentrations is still controversial. This meta-analysis recompiled 35 studies to determine whether MPs could change the levels of brain (in vivo) neurotransmitters in aquatic animals at environmentally realistic concentrations (≤1 mg/L, median = 0.100 mg/L). Then, a group comparison was conducted to compare the effects of different factors on the effect size and to explore the significant factors affecting the neurotoxicity of MPs. The results demonstrated that MP exposure could considerably decrease the levels of acetylcholinesterase (AchE) in the brain of aquatic animals by 16.2%. However, the effects of MPs on cholinesterase (CHE), acetylcholine (ACh), dopamine (DA) and γ-aminobutyric acid (GABA) were not statistically significant due to the small number of studies and samples. The neurotoxicity of MPs was closely linked with particle size and exposure time but independent of animal species, MP compositions, MP morphology and MP concentrations. Further literatures review indicated that MP-induced neurotoxicity and behavioral changes are related with multiple biological processes, including nerve damage, oxidative stress, intestinal flora disturbance and metabolic disorder. Furthermore, some factors influencing MP neurotoxicity in the real environment (e.g. the aging of MPs, the release of MP additives, and the co-exposure of MPs and pollutants) were discussed. Overall, this study preliminarily explored whether MPs induced changes in neurotoxicity-related indicators in aquatic animals through meta-analysis and provided scientific evidence for evaluating the health risks and neurotoxicity of MPs at the environmental level.

Comparison of metabolome profiles in zebrafish (Danio rerio) intestine induced by polystyrene microplastics with different sizes

Microplastics (MPs) are widespread in aquatic environments. They could induce intestinal toxicity in the fish. However, research on the metabolic toxicity of polystyrene microplastics (PS-MPs) with different particle sizes to the zebrafish intestine is still limited. Here, metabolomics using ultra-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was applied to characterize the metabolic disorders in zebrafish intestine after exposure to 500 μg/L PS-MPs with different sizes (100 nm, 5 μm, and 200 μm) for 21 days. Results showed that the 100 nm PS-MPs group increased glutathione content. A total of 35, 165, and 87 metabolites were significantly altered in zebrafish intestines of 100 nm, 5 μm, and 200 μm groups under positive ion mode, respectively. In comparison, 31, 115, and 45 metabolites were changed in the 100 nm, 5 μm, and 200 μm groups under negative ion mode, respectively. Metabolic pathway analysis indicated that carbohydrate metabolism, amino acid metabolism, and nucleotide metabolism were changed in all three groups. The greatest changes were found in the 5 μm group. Moreover, treatment with micro-sized PS-MP groups specifically changed lipid metabolism, which might be related to pathogenic bacteria (Streptococcus and Moraxella). In the 100 nm PS-MP group, S-adenosyl-L-methionine (SAM) was found to be markedly related to the intestinal microbiota. SAM level was significantly increased, which might account for the elevated glutathione content. To sum up, the mechanisms of nano-sized MPs (oxidative stress) and micro-sized MPs (lipid metabolism disorder) were distinct. This study provides novel insight into the toxicity mechanism of MPs in the zebrafish intestine.

Are microplastics contributing to pollution-induced neurotoxicity? A pilot study with wild fish in a real scenario

Pollution-induced neurotoxicity is of high concern. This pilot study investigated the potential relationship between the presence of microplastics (MPs) in the brain of 180 wild fish (Dicentrarchus labrax, Platichthys flesus, Mugil cephalus) from a contaminated estuary and the activity of the acetylcholinesterase (AChE) enzyme. MPs were found in 9 samples (5% of the total), all of them from D. labrax collected in the summer, which represents 45% of the samples of this species collected in that season (20). Seventeen MPs were recovered from brain samples, with sizes ranging from 8 to 96 μm. Polyacrylamide, polyacrylic acid and one biopolymer (zein) were identified by Micro-Raman spectroscopy. Fish with MPs showed lower (p ≤ 0.05) AChE activity than those where MPs were not found. These findings point to the contribution of MPs to the neurotoxicity induced by long-term exposure to pollution, stressing the need of further studies on the topic to increase 'One Health' protection.

Polystyrene microplastics mitigate the embryotoxic damage of metformin and guanylurea in Danio rerio

Microplastics (MPs) alone may endanger the health and fitness of aquatic species through different mechanisms. However, the harmful effects of these when mixed with other emerging contaminants require additional research. Herein, we aimed to determine whether a mixture of MPs with metformin (MET) or guanylurea (GUA) might induce embryotoxicity and oxidative stress in Danio rerio. Upon exposure to mixtures, our results showed MPs reduced the mortality rate of MET and GUA in embryos. Moreover, the severity and the rate of malformations were also decreased in all mixtures with MPs. Concerning oxidative stress, our findings indicated MET, GUA, MPs, and the mixtures increased the levels of lipoperoxidation, hydroperoxide content, and protein carbonyl content in D. rerio larvae. However, the oxidative damage induced in all mixtures was lower than that produced by both drugs alone. Thus, it is likely that the accumulation of MPs avoided the entrance of MET and GUA into the embryos. Once the embryo hatched, MPs did only remain accumulated in the yolk sac of larvae and did not translocate to other organs. Our risk assessment analysis confirmed that MPs shrunk the damage produced by MET and GUA. In a nutshell, MPs mitigate the embryotoxic damage of metformin and guanylurea in D. rerio by blocking their entrance.

Effects of polystyrene microplastics acute exposure in the liver of swordtail fish (Xiphophorus helleri) revealed by LC-MS metabolomics

As global pollution, microplastics pollution has aroused growing concerns. In our experiment, the effect of microplastics acute exposure on the liver of swordtail fish was investigated by using LC-MS metabolomics. Fishes treated with high concentration polystyrene microspheres (1 μm) for 72 h were divided into three concentration groups: (A) no microplastics, (B): 1 × 10⁶ microspheres L^-1, (C): 1 × 10⁷ microspheres L^-1. Metabolomic analysis indicated that exposure to microplastics caused alterations of metabolic profiles in swordtail fish, including 37 differential metabolites were identified in B vs. A, screened out ten significant metabolites, which involved 14 metabolic pathways. One hundred three differential metabolites were identified in C vs. A, screened out 16 significant metabolites, which involved 30 metabolic pathways. Six significant metabolites were overlapping in group B vs. A and C vs. A; they are 3-hydroxyanthranilic acid, l-histidine, citrulline, linoleic acid, pantothenate, and xanthine. In addition, four metabolic pathways are overlapping in group B vs. A and C vs. A; they are beta-alanine metabolism, biosynthesis of amino acids, linoleic acid metabolism, and aminoacyl-tRNA biosynthesis. These differential metabolites were involved in oxidative stress, immune function, energy metabolism, sugar metabolism, lipid metabolism, molecule transport, and weakened feed utilization, growth performance, nutrient metabolism, and animal growth. Furthermore, we found that the number of interfered amino acids and microplastics showed a dose-effect. In summary, great attention should be paid to the potential impact of microplastics on aquatic organisms.

Nanoplastics and Microplastics May Be Damaging Our Livers

Plastics in the environment can be degraded and even broken into pieces under the action of natural factors, and the degraded products with a particle size of less than 5 mm are called microplastics (MPs). MPs exist in a variety of environmental media that come into contact with the human body. It can enter the body through environmental media and food chains. At present, there are many studies investigating the damage of MPs to marine organisms and mammals. The liver is the largest metabolizing organ and plays an important role in the metabolism of MPs in the body. However, there is no available systematic review on the toxic effects of MPs on the liver. This paper summarizes the adverse effects and mechanisms of MPs on the liver, by searching the literature and highlighting the studies that have been published to date, and provides a scenario for the liver toxicity caused by MPs.

Fluoride enhances polystyrene nanoparticles cytotoxicity in colonocytes in vitro model

Human gastrointestinal cells can be exposed to different xenobiotics present in food or drinking water. In this work, we assessed the cytotoxicity of polystyrene nanoparticles (PS-NPs) and how it is impacted by fluoride (F^-) presence. We decided to examine PS-NPs and F^- which can be easily found in drinking water and food. Commercially available amine-modified 100 nm PS-NPs were used in the study. Scanning Electron Microscopy with Electron Dispersive Spectroscopy (SEM-EDS) and Dynamic Light Scattering (DLS) were used to characterize PS-NPs. The colon cell lines (HT-29, Caco-2, CCD 841 CoN) were used. Cytotoxicity of PS-NPs and F^- alone or in co-exposition were assessed with MTT assay in a time- and concentration-dependent manner. Flow cytometry was used to measure reactive oxygen species (ROS) production, cell cycle distribution, and apoptosis analysis. Transmission electron microscopy (TEM) was used to determine whether PS-NPs and/or F^- can cause ultrastructure changes in the cells. We have shown that PS-NPs are cytotoxic to human colon cells in a time- and concentration-dependent manner. PS-NPs did not impact neither intracellular ROS production nor the cells cell cycle distribution. However, if HT-29 cells were co-exposed to PS-NPs and F^-, an increased number of cells in G0/G1 phase and decreased number of cells in G2/M were observed. PS-NPs can cause apoptosis in HT-29 cells, this effect was enhanced if cells were co-exposed to PS-NP and F^-. PS-NPs were internalised by the cells and caused ultrastructure changes. Fluoride itself (1 mM) was not cytotoxic to the cells and did not cause any changes in the ultrastructure of the cells. We have proven that polystyrene nanoparticles can be cytotoxic to human gastrointestinal cells and this effect is enhanced by fluoride.

The Burden of Microplastics Pollution and Contending Policies and Regulations

The relationship between humans and plastics has become intricate due to their versatile nature and low production cost. Plastics generation has surpassed that of other manufactured products, which, coupled with the prevailing poor waste management systems, makes it a serious problem for the terrestrial and aquatic environments as its final destination. Their extensive presence has continued to pose a significant threat, not only to the aquatic ecosystem but also to the approximately 3 billion people relying on it for their livelihood. Even more disturbing were the recent findings of these plastics in food and drinking water and the evidence of human exposure, the long-term health effects of which are largely unknown. This ubiquitous phenomenon has over time put plastics under critical observation, leading to the development of many local and international policies, resolutions, and directives aimed at addressing and reversing the menace. This review provided the first snapshot of the global and local governance strategies currently aimed at mitigating plastic pollution, their limitations, and future directions. The findings of the review revealed several aspects of microplastics (MPs) pollution to be overlooked in policy formulation, a laxity in policy implementation, and an apparent lack of indices to ascertain the impact of the regulations. Furthermore, there is currently no regulation on MPs contamination of food and drinking water and an apparent lack of funding for research into the health effects of plastics and their alternatives. This, therefore, necessitates the need for a well-coordinated approach at international and national levels to scale up these policies in all countries and translate them from paper to measurable, holistic, and realizable actions that will address all forms of plastic pollution.

Paeonol increases the antioxidant and anti-inflammatory capacity of gibel carp (Carassius auratus gibelio) challenged with Aeromonas hydrophila

Paeonol, a naturally occurring polyphenol isolated from medical plant, has been known to exhibit anti-oxidative and anti-inflammatory effects. In order to evaluate the effect of paeonol on Carassius auratus gibelio infected by pathogenic bacteria Aeromonas hydriphila. 750 fish were randomly divided into 5 groups, which separately treated with 0.85% sterile saline (blank), A. hydriphila (negative control), A. hydriphila with paeonol (4 mg/kg, 64 mg/kg), and A. hydriphila with enrofloxacin (12 mg/kg, positive control). Fish were anaesthetized with MS-222 (100 mg/L), and samples were collected at 6 and 72 h after A. hydriphila challenge. The results showed that compared with the negative group, the survival in paeonol groups marked increased by 14.75% and 18.94%. The plasma immunoglobulin M (IgM) was notably increased, and low density lipoprotein (LDL) was significantly decreased in paeonol groups at 6 h (P < 0.05). The antioxidative enzymes catalase (CAT), total antioxidant capacity (T-AOC) and glutathione peroxidase (GSH-Px) were significantly increased in paeonol groups at 6 h, while malondialdehyde (MDA) and myeloperoxidase (MPO) contents were lower (P < 0.05). The inflammatory related genes MyD88 and TLR-5 were significantly downregulated, and the TLR-3 was significantly increased in paeonol groups at 72 h (P < 0.05). In addition, histopathological analyses showed that the lesion in liver, spleen and caudal kidney were considerably attenuated in paeonol groups. In conclusion, paeonol could increase the survival rate, mitigate oxidative damage, inflammation, tissue lesions, and improve the immunity of gibel carp challenged with A. hydrophila.