Size-Dependent Uptake and Depuration of Nanoplastics in Tilapia (Oreochromis niloticus) and Distinct Intestinal Impacts

Contrasting the distribution kinetics of microplastics and nanoplastics in medaka following exposure and depuration

Direct ingestion of micro/nanoplastics (MNPs) results in significant accumulation in gastrointestinal (GI) tract of fish. The breathing process of fish makes MNPs easily retained in their gills. However, the uptake of MNPs in other fish organs remains largely unknown, let alone their kinetic processes. Herein, microplastics (MPs) and nanoplastics (NPs) in vivo imaging and precise quantification in various tissues (GI tract, gill, liver, brain, eye, and skin) of seawater (SW)- and freshwater (FW)- acclimated medaka Oryzias melastigma were achieved at an environmentally relevant concentration. Subsequently, the distribution kinetics of MNPs was investigated over a 96-h uptake and 48-h depuration period. MNPs were quickly and mostly captured in GI tract and gill of O. melastigma, and then transferred to liver and brain likely via blood circulation. Such transport was more efficient for NPs as compared to MPs, as evidenced by the consistently higher bioconcentration factors in both SW and FW conditions. The detection of MNPs in eye and skin of O. melastigma was more of an adsorption process, although the specific mechanisms of adsorption and absorption process can hardly be clearly differentiated. This study presented distribution kinetics of MNPs in O. melastigma and highlighted their possible transportation among tissues.

Polystyrene nanoplastics alter intestinal toxicity of 2,4-DTBP in a sex-dependent manner in zebrafish (Danio rerio)

Nanoplastics (NPs) and 2,4-di-tert-butylphenol (2,4-DTBP) are ubiquitous emerging environmental contaminants detected in aquatic environment. While the intestinal toxicity of 2,4-DTBP alone has been studied, its combined effects with NPs remain unclear. Herein, adult zebrafish were exposed to 80 nm polystyrene nanoplastics (PS-NPs) or/ and 2,4-DTBP for 28 days. With co-exposure of PS-NPs, impact of 2,4-DTBP on feeding capacity and intestinal histopathology was enhanced in males while attenuated in females. Addition of PS-NPs significantly decreased the uptake of 2,4-DTBP in females, while the intestinal concentrations of 2,4-DTBP were not different between the sexes in co-exposure groups. Furthermore, lower intestinal pH and higher contents of digestive enzymes were detected in male fish, while bile acid was significantly increased in co-exposed females. In addition, co-exposure of PS-NPs stimulated female fish to remodel microbial composition to potentially enhance xenobiotics degradation, while negative Aeromonas aggravated inflammation in males. These results indicated that in the presence of PS-NPs, the gut microenvironment in females can facilitate the detoxification of 2,4-DTBP, while exaggerating toxiciy in males. Overall, this study demonstrates that toxicological outcomes of NPs-chemical mixtures may be modified by sex-specific physiology and microbiota composition, furthering understanding for environmental risk assessment and management of aquatic environments.

Visible Combined Near-Infrared in Situ Imaging Revealed Dynamic Effects of Microplastic Fibers and Beads in Zebrafish

Microplastics (MPs) as emerging contaminants are widely present in the environment and are ubiquitously ingested and accumulated by aquatic organisms. MPs may be quickly eliminated after a brief retention in aquatic animals (such as the digestive tract); thus, understanding the damage caused by MPs during this process and whether the damage can be recovered is important. Here, we proposed the use of visible light imaging to track MPs combined with near-infrared (NIR) imaging to reveal the in situ impacts of MPs. The combination of these two techniques allows for the simultaneous investigation of the localization and functionality of MPs in vivo. We investigated the effects of two types of MPs on zebrafish, microplastic fibers (MFs) and microplastic beads (MBs). The results showed that MPs larger than 10 μm primarily accumulated in the intestines of zebrafish. Both MFs and MBs disrupted the redox balance of the intestine, and the location of the damage was consistent with the heterogeneous accumulation of MPs. MFs caused greater and more difficult-to-recover damage compared to MBs, which was closely related to the slower elimination rate of MFs. Our study highlights the importance of capturing the dynamic toxicological effects of MPs on organisms. Fibrous MPs and spherical MPs clearly had distinct effects on their toxicokinetics and toxicodynamics in fish.

The size-dependent effects of nanoplastics in mouse primary hepatocytes from cells to molecules

Nanoplastics (NPs) are easily ingested by organisms and their major accumulation organ was determined to be liver. To date, the size-dependent cytotoxicity of NPs on mammalian hepatocytes remains unclear. This study utilized mouse primary hepatocytes and catalase (CAT) as specific receptors to investigate the toxicity of NPs from cells to molecules, focusing on size-dependent effects. Results showed that the larger the particle size of NP at low doses (≤50 mg/L), the most pronounced inhibitory effect on hepatocyte viability. 20 nm NPs significantly inhibit cell viability only at high doses (100 mg/L). Larger NP particles (500 nm and 1000 nm) resulted in a massive release of lactate dehydrogenase (LDH) from the cell (cell membrane damage). Reactive oxygen species (ROS), superoxide dismutase (SOD) and CAT tests suggest that NPs disturbed the cellular antioxidant system. 20 nm NPs show great strength in oxidizing lipids and disrupting mitochondrial function compared to NPs of other particle sizes. The degree of inhibition of CAT activity by different sized NPs was coherent at the cellular and molecular levels, and NP-500 had the most impact. This suggests that the structure and microenvironment of the polypeptide chain in the vicinity of the CAT active site is more susceptible to proximity and alteration by NP-500. In addition, the smaller NPs are capable of inducing relaxation of CAT backbone, disruption of H-bonding and reduction of α-helix content, whereas the larger NPs cause contraction of CAT backbone and increase in α-helix content. All NPs induce CAT fluorescence sensitization and make the chromophore microenvironment hydrophobic. This study provides new insights for NP risk assessment and applications.

The size-dependence and reversibility of polystyrene nanoplastics-induced hepatic pyroptosis in mice through TXNIP/NLRP3/GSDMD pathway

As emerging environmental contaminants, nanoplastics (NPs) are progressively accumulating in terrestrial and aquatic ecosystems worldwide, posing a potential threat to human health. The liver is considered as one of the primary organs targeted by NPs accumulation in living organisms. However, there remains a large knowledge gap concerning NPs-induced hepatotoxicity. In this study, we examined the impact of chronic exposure to environmentally relevant doses of polystyrene (PS) NPs on hepatic pyroptosis in mice. The results demonstrated that both particle sizes of PS-NPs (100 nm and 500 nm) significantly triggered pyroptosis in the mouse liver, as evidenced by the upregulation of GSDMD-N protein levels; moreover, this pyroptotic effect induced by 100 nm PS-NPs was more pronounced compared to that of 500 nm PS-NPs. Mechanistically, exposure to 100 nm and 500 nm PS-NPs resulted in an upregulation of TXNIP protein expression, thereby activating NLRP3 inflammasome and subsequently inducing inflammatory responses and pyroptosis. Notably, following the termination of PS-NPs exposure and a subsequent recovery period of 50 days, PS-NPs-mediated inflammation and pyroptosis via TXNIP/NLRP3 pathway were effectively ameliorated, even returning to levels close to the baseline. Collectively, our findings provide novel evidence for the size-dependence and reversibility of NPs-induced hepatic pyroptosis through TXNIP/NLRP3/GSDMD pathway in vivo.

Untargeted lipidomics uncover hepatic lipid signatures induced by long-term exposure to polystyrene microplastics in Vivo

OBJECTIVE

This study evaluated the effects of long-term polystyrene microplastics (PS-MPs) exposure on hepatic lipid metabolism in vivo by lipidomics.

RESULTS

H&E staining showed long-term PS-MPs exposure could trigger the hepatic inflammatory cell infiltration and hepatic steatosis in SD rats, indicating long-term PS-MPs exposure caused hepatoxicity. Lipidomics revealed that the concentrations of 8 lipid metabolites in the liver were altered after exposure to PS-MPs for both 6 and 12 months, namely LdMePE (16:0), LPC (18:1), LPC (18:2), LPC (20:4), PC (17:0_20:4), PC (18:2_22:6), PC (22:6_13:0) and SM (d18:1_24:0), which were all statistically different from the control groups detected at both time points after PS-MPs exposure, suggesting the mainly metabolic pathway was glycerolipid metabolism.

CONCLUSION

This study showed chronic exposure to PS-MPs could cause hepatotoxicity and induce hepatic lipidomics alterations in vivo, which could provide an essential clue for the safety assessment of PS-MPs.

Surface functionalization, particle size and pharmaceutical co-contaminant dependent impact of nanoplastics on marine crustacean - Artemia salina

Despite a significant amount of research on micronanoplastics (MNPs), there is still a gap in our understanding of their function as transporters of other environmental pollutants (known as the Trojan horse effect) and the combined effects of ingestion, bioaccumulation, and toxicity to organisms. This study examined the individual effects of polystyrene nanoplastics (PSNPs) with various surface functionalizations (plain (PS), carboxylated (PS-COOH), and aminated (PS-NH2)), particle sizes (100 nm and 500 nm), and a pharmaceutical co-contaminant (metformin hydrochloride (MH), an anti-diabetic drug) on the marine crustacean - Artemia salina. The study specifically aimed to determine if MH alters the detrimental effects of PSNPs on A. salina. The potential toxicity of these emerging pollutants was assessed by examining mortality, hatching rate, morphological changes, and biochemical changes. Smaller nanoparticles had a more significant impact than larger ones, and PS-NH2 was more harmful than PS and PS-COOH. Exposure to the nanoparticle complex with MH resulted in a decrease in hatching rate, an increase in mortality, developmental abnormalities, an increase in reactive oxygen species, catalase, and lipid peroxidase, and a decrease in total protein and superoxide dismutase, indicating a synergistic effect. There were no significant differences between the complex and the individual nanoparticles. However, accumulating these particles in organisms could contaminate the food chain. These results highlight the potential environmental risks associated with the simultaneous exposure of aquatic species to plastics, particularly smaller PS, aminated PS, and pharmaceutical complex PS.

Transcriptomic responses of Antarctic clam Laternula elliptica to nanoparticles, at single and combined exposures reveal ecologically relevant biomarkers

In recent years micro- and nanoplastics and metal-oxide nanomaterials have been found in several environmental compartments. The Antarctic soft clam Laternula elliptica is an endemic Antarctic species having a wide distribution in the Southern Ocean. Being a filter-feeder, it could act as suitable bioindicator of pollution from nanoparticles also considering its sensitivity to various sources of stress. The present study aims to assess the impact of polystyrene nanoparticles (PS-NP) and the nanometal titanium-dioxide (n-TiO2) on genome-wide transcript expression of L. elliptica either alone and in combination and at two toxicological relevant concentrations (5 and 50 µg/L) during 96 h exposure. Transcript-target qRT-PCR was performed with the aim to identify suitable biomarkers of exposure and effects. As expected, at the highest concentration tested, the clustering was clearer between control and exposed clams. A total of 221 genes resulted differentially expressed in exposed clams and control ones, and 21 of them had functional annotation such as ribosomal proteins, antioxidant, ion transport (osmoregulation), acid-base balance, immunity, lipid metabolism, cell adhesion, cytoskeleton, apoptosis, chromatin condensation and cell signaling. At functional level, relevant transcripts were shared among some treatments and could be considered as general stress due to nanoparticle exposure. After applying transcript-target approach duplicating the number of clam samples, four ecologically relevant transcripts were revealed as biomarkers for PS-NP, n-TiO2 and their combination at 50 µg/L, that could be used for monitoring clams' health status in different Antarctic localities.

In Vitro Toxicity and Modeling Reveal Nanoplastic Effects on Marine Bivalves

Nanoplastics (NPs) represent a growing concern for global environmental health, particularly in marine ecosystems where they predominantly accumulate. The impact of NPs on marine benthic organisms, such as bivalves, raises critical questions regarding ecological integrity and food safety. Traditional methods for assessing NP toxicity are often limited by their time-intensive nature and ethical considerations. Herein, we explore the toxicological effects of NPs on the marine bivalve Ruditapes philippinarum, employing a combination of in vitro cellular assays and advanced modeling techniques. Results indicate a range of adverse effects at the organismal level, including growth inhibition (69.5-108%), oxidative stress, lipid peroxidation, and DNA damage in bivalves, following exposure to NPs at concentrations in the range of 1.6 × 109-1.6 × 1011 particles/mL (p/mL). Interestingly, the growth inhibition predicted by models (54.7-104%), based on in vitro cellular proliferation assays, shows strong agreement with the in vivo outcomes of NP exposure. Furthermore, we establish a clear correlation between cytotoxicity observed in vitro and the toxicological responses at the organismal level. Taken together, this work suggests that the integration of computational modeling with in vitro toxicity assays can predict the detrimental effects of NPs on bivalves, offering insightful references for assessing the environmental risk assessment of NPs in marine benthic ecosystems.

Understanding the links between micro/nanoplastics-induced gut microbes dysbiosis and potential diseases in fish: A review

At present, the quantity of micro/nano plastics in the environment is steadily rising, and their pollution has emerged as a global environmental issue. The tendency of their bioaccumulation in aquatic organisms (especially fish) has intensified people's attention to their persistent ecotoxicology. This review critically studies the accumulation of fish in the intestines of fish through active or passive intake of micro/nano plastics, resulting in their accumulation in intestinal organs and subsequent disturbance of intestinal microflora. The key lies in the complex toxic effect on the host after the disturbance of fish intestinal microflora. In addition, this review pointed out the characteristics of micro/nano plastics and the effects of their combined toxicity with adsorbed pollutants on fish intestinal microorganisms, in order to fully understand the characteristics of micro/nano plastics and emphasize the complex interaction between MNPs and other pollutants. We have an in-depth understanding of MNPs-induced intestinal flora disorders and intestinal dysfunction, affecting the host's systemic system, including immune system, nervous system, and reproductive system. The review also underscores the imperative for future research to investigate the toxic effects of prolonged exposure to MNPs, which are crucial for evaluating the ecological risks posed by MNPs and devising strategies to safeguard aquatic organisms.

Toxicological review of micro- and nano-plastics in aquatic environments: Risks to ecosystems, food web dynamics and human health

The increase of micro- and nano-plastics (MNPs) in aquatic environments has become a significant concern due to their potential toxicological effects on ecosystems, food web dynamics, and human health. These plastic particles emerge from a range of sources, such as the breakdown of larger plastic waste, consumer products, and industrial outputs. This review provides a detailed report of the transmission and dangers of MNPs in aquatic ecosystems, environmental behavior, and interactions within aquatic food webs, emphasizing their toxic impact on marine life. It explores the relationship between particle size and toxicity, their distribution in different tissues, and the process of trophic transfer through the food web. MNPs, once consumed, can be found in various organs, including the digestive system, gills, and liver. Their consumption by lower trophic level organisms facilitates their progression up the food chain, potentially leading to bioaccumulation and biomagnification, thereby posing substantial risks to the health, reproduction, and behavior of aquatic species. This work also explores how MNPs, through their persistence and bioaccumulation, pose risks to aquatic biodiversity and disrupt trophic relationships. The review also addresses the implications of MNPs for human health, particularly through the consumption of contaminated seafood, highlighting the direct and indirect pathways through which humans are exposed to these pollutants. Furthermore, the review highlights the recommendations for future research directions, emphasizing the integration of ecological, toxicological, and human health studies to inform risk assessments and develop mitigation strategies to address the global challenge of plastic pollution in aquatic environments.

Revealing Metabolic Dysregulation Induced by Polypropylene Nano- and Microplastics in Nile Tilapia via Noninvasive Probing Epidermal Mucus

A noninvasive sampling technology was conceived, employing a disposable acupuncture needle in conjunction with high-resolution mass spectrometry (termed as noninvasive direct sampling extractive electrospray ionization mass spectrometry, NIDS-EESI-MS) to scrutinize the epidermal mucus of Nile tilapia for insights into the metabolic dysregulation induced by polypropylene nano- and microplastics. This analytical method initiates with the dispensing of an extraction solvent onto the needles coated with the mucus sample, almost simultaneously applying a high voltage to generate analyte ions. This innovative strategy obliterates the necessitation for laborious sample preparation, thereby simplifying the sampling process. Employing this technique facilitated the delineation of a plethora of metabolites, encompassing, but not confined to, amino acids, peptides, carbohydrates, ketones, fatty acids, and their derivatives. Follow-up pathway enrichment analysis exposed notable alterations within key metabolic pathways, including the biosynthesis of phenylalanine, tyrosine, and tryptophan, lysine degradation, as well as the biosynthesis and metabolism of valine, leucine, and isoleucine pathways in Nile tilapia, consequent to increased concentrations of polypropylene nanoplastics. These metabolic alterations portend potential implications such as immune suppression, among other deleterious outcomes. This trailblazing application of this methodology not only spares aquatic life from sacrifice but also inaugurates an ethical paradigm for conducting longitudinal studies on the same organisms, facilitating detailed investigations into the long-term effects of environmental pollutants. This technique enhances the ability to observe and understand the subtle yet significant impacts of such contaminants over time.

Nematode Uptake Preference toward Different Nanoplastics through Avoidance Behavior Regulation

Expounding bioaccumulation pathways of nanoplastics in organisms is a prerequisite for assessing their ecological risks in the context of global plastic pollution. Invertebrate uptake preference toward nanoplastics is a key initial step of nanoplastic food chain transport that controls their global biosafety, while the biological regulatory mechanism remains unclear. Here, we reveal a preferential uptake mechanism involving active avoidance of nanoplastics by Caenorhabditis elegans and demonstrate the relationship between the uptake preference and nanoplastic characteristics. Nanoplastics with 100 nm in size or positive surface charges induce stronger avoidance due to higher toxicity, causing lower accumulation in nematodes, compared to the 500 nm-sized or negatively charged nanoplastics, respectively. Further evidence showed that nematodes did not actively ingest any types of nanoplastics, while different nanoplastics induced defense responses in a toxicity-dependent manner and distinctly stimulated the avoidance behavior of nematodes (ranged from 15.8 to 68.7%). Transcriptomics and validations using mutants confirmed that the insulin/IGF signaling (IIS) pathway is essential for the selective avoidance of nanoplastics. Specifically, the activation of DAF-16 promoted the IIS pathway-mediated defense against nanoplastics and stimulated the avoidance behavior, increasing the survival chances of nematodes. Considering the genetical universality of this defense response among invertebrates, such an uptake preference toward certain nanoplastics could lead to cascaded risks in the ecosystem.

Decreased transport of nano- and micro-plastics in the presence of low-molecular-weight organic acids in saturated quartz sand

Low-molecular-weight organic acids (LMWOAs) and nano- and micro-plastics (NPs and MPs) are both widely distributed in terrestrial systems. To better understand the influence of LMWOAs on the transport of NPs and MPs, the effects of 0.5 mM citric- (CA), malic- (MA), and tartaric- (TA) acid on the transport of nano- (0.51 μm, PS NPs) and micro- (1.1 μm, PS MPs) polystyrene particles (2 mg L-1) in saturated quartz sand were investigated. All three LMWOAs decreased the transport of PS NPs and MPs, regardless of ionic composition or strength (0.1-10 mM NaCl and 0.1-1 mM CaCl2). Further investigation revealed that the interfacial interactions between PS-quartz sand surfaces and PS-PS were altered by LMWOAs. LMWOAs adsorbed to quartz sand surfaces could serve as new deposition sites, as evidenced by the decreased transport of PS NPs and MPs in quartz sand that was subjected to pre-equilibration with selected MA, the low inhibition of PS transport with low concentrations of LMWOAs (0.1 mM), and also the adsorption of LMWOAs onto quartz sand surfaces by batch experiments. Meanwhile, the adsorption of LMWOAs on PS, hydrodynamic measurement and visual TEM observation together clarified the slight aggregation of PS NPs and MPs in suspensions, inducing the subsequent decrease in transport. Among them, the adsorption of LMWOAs onto quartz sand surfaces was found to be the main factor dominating the decreased transport of both PS NPs and MPs in saturated quartz sand.

Single-Cell RNA Sequencing Profiling Cellular Heterogeneity and Specific Responses of Fish Gills to Microplastics and Nanoplastics

Fish gills are highly sensitive organs for microplastic (MP) and nanoplastic (NP) invasions, but the cellular heterogeneity of fish gills to MPs and NPs remains largely unknown. We employed single-cell RNA sequencing to investigate the responses of individual cell populations in tilapia Oreochromis niloticus gills to MP and NP exposure at an environmentally relevant concentration. Based on the detected differentially expressed gene (DEG) numbers, the most affected immune cells by MP exposure were macrophages, while the stimulus of NPs primarily targeted T cells. In response to MPs and NPs, H+-ATPase-rich cells exhibited distinct changes as compared with Na+/K+-ATPase-rich cells and pavement cells. Fibroblasts were identified as a potential sensitive cell-type biomarker for MP interaction with O. niloticus gills, as evidenced by the largely reduced cell counts and the mostly detected DEGs among the 12 identified cell populations. The most MP-sensitive fibroblast subpopulation in O. niloticus gills was lipofibroblasts. Cell-cell communications between fibroblasts and H+-ATPase-rich cells, neurons, macrophages, neuroepithelial cells, and Na+/K+-ATPase-rich cells in O. niloticus gills were significantly inhibited by MP exposure. Collectively, our study demonstrated the cellular heterogeneity of O. niloticus gills to MPs and NPs and provided sensitive markers for their toxicological mechanisms at single-cell resolution.

The toxicity of polystyrene micro- and nano-plastics on rare minnow (Gobiocypris rarus) varies with the particle size and concentration

How the particle size and concentration of microplastics impact their toxicity is largely unknown. Herein, the effects of polystyrene microplastics (1 μm, MPs) and nanoplastics (100 nm, NPs) exposed at 1 mg/L (L) and 10 mg/L (H), respectively, on the growth, histopathology, oxidative stress, gut microbiome, and metabolism of rare minnow (Gobiocypris rarus) were investigated by chemical analysis and multi-omics. MPs and NPs inhibited the growth, induced histopathological injury and aggravated oxidative stress markedly with contrasting significance of particle size and concentration. The composition of core gut microbiota changed dramatically especially for the MPs-H. Similarly, gut bacterial communities were reshaped by the MPs and NPs but only NPs-H decreased both richness and Shannon indexes significantly. Co-occurrence network analysis revealed that the potential keystone genera underwent great changes in exposed groups compared to the control. MPs-H increased the network complexity and the frequency of positive interactions which was opposite to other exposed groups. Moreover, the metabolomic profiles associated with amino acid, lipid, unsaturated fatty acid and hormone metabolism were disturbed significantly especially for MPs-H and NPs-H. In conclusion, the toxicity of MPs depends on both the particle size and concentration, and varies with the specific indicators as well.

Implications of exposure route for the bioaccumulation potential of nanopolystyrene particles

Microplastics and nanoplastics are found in marine biota across a wide range of trophic levels and environments. While a large portion of the information about plastic exposure comes from gastrointestinal (GI) data, the relevance of particle accumulation from an oral exposure compared with other types of exposure (e.g. dermal, respiratory) is unknown. To address this gap in knowledge, larval zebrafish (7 days post fertilization) were exposed to two different sizes of nanoplastics through either oral gavage or a waterborne exposure. Larvae were tracked for 48 h post exposure (hpe) to assess the migration and elimination of plastics. Larvae eliminated orally gavaged nanoplastics within 48 hpe. Oral gavage showed limited particle movement from the GI tract into other tissues. In contrast, waterborne nanoplastic-exposed larvae displayed notable fluorescence in tissues outside of the GI tract. The 50 nm waterborne-exposed larvae retained the particles past 48 hpe, and showed accumulation with neuromasts. For both sizes of plastic particles, the nanoplastics were eliminated from non-GI tract tissues by 24 hpe. Our results suggest that waterborne exposure leads to greater accumulation of plastic in comparison to oral exposure, suggesting that plastic accumulation in certain tissues is greater via routes of exposure other than oral consumption.

Size-dependent toxicity of polystyrene microplastics on the gastrointestinal tract: Oxidative stress related-DNA damage and potential carcinogenicity

Microplastics (MPs) and nanoplastics (NPs) have been generally regarded as emerging pollutants and received worldwide attention in recent years. Water and food consumption are the primary pathways for human exposure to MPs/NPs, thus gastrointestinal tracts may be susceptible to their toxicity. Although the recent report has indicated the presence of MPs/NPs in multiple human organs, little is known about their gastric effects. Therefore, this study focused on the adverse effects of polystyrene microplastics (PS-MPs) on gastric epithelium in vivo and in vitro. Surface-enhanced Raman spectroscopy (SERS) revealed the distribution of PS-MPs was associated with their particle sizes, and predominantly concentrated in gastric tissues. Gastric barrier injury and mitochondrial damage were observed in rats after exposure to PS-MPs. Compared with the larger ones, polystyrene nanoplastics (PS-NPs) more significantly reduced the activity of antioxidant enzymes while enhancing the level of MDA, 8-OhdG and γ-H2AX. Meanwhile, PS-MPs caused upregulation of β-catenin/YAP through redox-dependent regulation of nucleoredoxin (NXN) and dishevelled (Dvl). These findings supported the size-dependent effects of PS-MPs on oxidative stress and DNA damage. Moreover, the redox-dependent activation of the β-catenin/YAP cascade suggested a novel toxic mechanism for PS-MPs and implied the potential carcinogenic effects.

A Latest Review on Micro- and Nanoplastics in the Aquatic Environment: The Comparative Impact of Size on Environmental Behavior and Toxic Effect

Micro and nanoplastics (MNPs) have attracted growing global research attention due to their distinct environmental impacts, addressing escalating concerns. The diverse materials, sizes, and shapes of MNPs result in a range of environmental impacts. Size, a crucial characteristic of MNPs, influences their environmental behavior, affecting processes like migration, sedimentation, aggregation, and adsorption. Moreover, size modulates the biodistribution and toxicity of MNPs in aquatic organisms. This review delves into the comprehensive impacts of plastic size, with a primary focus on environmental behavior and toxic effects. Ultimately, this review emphasizes the ecological implications of MNP size, laying a foundation for future research in this field.

Non-negligible vector effect of micro(nano)plastics on tris(1,3-dichloro-2-propyl) phosphate in zebrafish quantified by toxicokinetic model

Micro(nano)plastics (MNPs) inevitably interact with coexisting contaminants and can act as vectors to affect their fate in organisms. However, the quantitative contribution of MNPs in the in vivo bioaccumulation and distribution of their coexisting contaminants remains unclear. Here, by selecting tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) as the typical coexisting contaminant, we quantified the contribution of MNPs to bioaccumulation and distribution of TDCIPP with toxicokinetic models. Results indicated that MNPs differentially facilitated TDCIPP bioaccumulation and distribution, and NPs slowed down TDCIPP depuration more significantly than MPs. Model analysis further revealed increasing contributions of MNPs to whole-fish TDCIPP bioaccumulation over time, with NPs (33-42%) contributing more than MPs (12-32%) at 48 h exposure. NPs contributed more than MPs to TDCIPP distribution in the liver (13-19% for MPs; 36-52% for NPs) and carcass (24-45% for MPs; 57-71% for NPs). The size-dependent vector effect might be attributed to the fact that MNPs promote contaminant transfer by damaging biofilm structure and increasing tissue membrane permeability, with NPs exerting stronger effects. This work demonstrated the effectiveness of using modeling tools to understand the relative importance of MNPs as contaminant vectors in the TK process and highlighted the higher contaminant transfer potential of NPs under combined exposure scenarios.

Histopathological, physiological, and multi-omics insights into the hepatotoxicity mechanism of nanopolystyrene and/or diclofenac in Mylopharyngodon piceus

Nanopolystyrene (NP) and diclofenac (DCF) are common environmental contaminants in the aquatic ecosystem; therefore, the present study aimed to investigate the hepatotoxicity of NP and/or DCF exposure on aquatic organisms and the underlying mechanisms. Juvenile Mylopharyngodon piceus were used as a model organism to study the effects of NP and/or DCF exposure at environmentally relevant concentrations for 21 days. Subchronic exposure to NP and/or DCF resulted in liver histological damage. In the NP group, the presence of large lipid droplets was observed, whereas the DCF group exhibited marked hepatic sinusoidal dilatation accompanied by inflammation. Additionally, this exposure induced liver oxidative stress, as evidenced by the changes in several physiological parameters, including catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), total antioxidant capacity (T-AOC), reactive oxygen species (ROS), and malondialdehyde (MDA). Integrated transcriptomic and metabolomic analysis was performed to further investigate the molecular mechanism underlying hepatotoxicity. Multi-omics analysis demonstrated, for the first time to our knowledge, that NP induced hepatic steatosis mainly through activating the glycerol-3-phosphate pathway and inhibiting VLDL assembly by targeting several key enzyme genes including GPAT, DGAT, ACSL, APOB, and MTTP. Furthermore, NP exposure disrupted arachidonic acid metabolism, which induced the release of inflammatory factors and inhibited the release of anti-inflammatory factors, ultimately causing liver inflammation in M. piceus. In contrast, DCF induced interleukin production and downregulated KLF2, causing hepatic sinusoidal dilatation with inflammation in juvenile M. piceus, which is consistent with the finding of JAK-STAT signaling pathway activation. In addition, the upregulated AMPK signaling pathway in the DCF group suggested perturbation of energy metabolism. Collectively, these findings provide novel insights into the molecular mechanism of the multiple hepatotoxicity endpoints of NP and/or DCF exposure in aquatic organisms.

Emergence of nanoplastics in the aquatic environment and possible impacts on aquatic organisms

Plastic production on a global scale is instrumental in advancing modern society. However, plastic can be broken down by mechanical and chemical forces of humans and nature, and knowledge of the fate and effects of plastic, especially nanoplastics, in the aquatic environment remains poor. We provide an overview of current knowledge on the environmental occurrence and toxicity of nanoplastics, and suggestions for future research. There are nanoplastics present in seas, rivers, and nature reserves from Asia, Europe, Antarctica, and the Arctic Ocean at levels of 0.3-488 microgram per liter. Once in the aquatic environment, nanoplastics accumulate in plankton, nekton, benthos through ingestion and adherence, with multiple toxic results including inhibited growth, reproductive abnormalities, oxidative stress, and immune system dysfunction. Further investigations should focus on chemical analysis methods for nanoplastics, effect and mechanism of nanoplastics at environmental relevant concentrations in aquatic organisms, as well as the mechanism of the Trojan horse effect of nanoplastics.

Limited effects of different real groundwaters from three coastal cities in China on the transport of low-concentration nanoplastics in quartz sand

Nanoplastics (NPs) have been widely detected in soil-groundwater systems. However, to date, the effect of real groundwater on the fate and transport of NPs has been poorly understood. In this study, the transport and retention behaviors of both polystyrene and poly(lactic-co-glycolic acid) NPs (PS NPs and PLGA NPs) in different real groundwaters from three coastal cities in China were explored using column experiments. PS (0.51 and 1.1 μm) and PLGA (1 μm) NPs with a low concentration of 2 mg L-1 were employed. Close observation showed that the transport of PS NPs was much higher than PLGA NPs in different groundwaters, with an average breakthrough curve plateau (C/Co) of ∼0.81 for PS NPs and ∼0.19 for PLGA NPs, respectively. As observed for PLGA, the plastic shape- and size-induced straining may be the reason for the minimal transport. Interestingly, we found that although the physicochemical characteristics of different real groundwaters varied significantly, the transport of certain NPs in real groundwater was similar with negligible differences. Closer inspection indicated that similar pHs of different groundwaters may be the reason contributing to these findings. Further investigation revealed that the transport behaviors of PS and PLGA NPs in real groundwater did not follow the classical DLVO theory. These findings suggest that the fate and transport of NPs in real soil-groundwater systems are much more comprehensive than the prediction based on DLVO theory and need intensive investigation.

Impacts of Nile Tilapia (Oreochromis niloticus) exposed to microplastics in bioflocs system

Microplastics (MPs) are abundant in aquaculture water, including in bioflocs aquaculture systems. Compared with other aquaculture systems, biofloc technology systems have the richest microbes and are beneficial to cultivated organisms. Therefore, this study provides a comprehensive assessment of the potential effects of MPs on aquaculture organisms in bioflocs systems. Here, Nile Tilapia (Oreochromis niloticus) were exposed to MPs (polystyrene; 32-40 μm diameter) with 0, 80 items/L (30 μg/L), and 800 items/L (300 μg/L) for 28 days in a bioflocs aquaculture system. The results showed that the MPs generally had no apparent effect on water quality, tilapia growth, or digestive enzyme activity. However, MPs accumulated the most in the liver (5.65 ± 0.74 μg/mg) and significantly increased the hepato-somatic index of tilapia and reduced the crude protein and lipid of tilapia muscle (p < 0.05). The levels of the antioxidant enzymes catalase and glutathione S-transferase increased significantly in response to MPs (p < 0.05). In contrast, MPs did not affect the content of glutathione, glutathione peroxidase, oxidized glutathione, and malondialdehyde, or the enzyme activity of Na+/K+-ATPase. Moreover, using an improved integrated biomarker response index, growth performance was found to be less responsive to MPs than to oxidative stress and digestive activity. Exposure to MPs did not significantly influence the microbial communities of the bioflocs and tilapia guts (p < 0.05). These results suggest that MPs barely affected tilapia in the bioflocs system. This study contributes to the evaluation of the ecological risk of MPs in aquaculture systems and a better understanding of the integrated response of cultivated vertebrates to MPs in biofloc technology systems.

Impacts of exposure to nanopolystyrene and/or chrysene at ambient concentrations on neurotoxicity in Siniperca chuatsi

Health risks caused by widespread environmental pollutants such as nanopolystyrene (NP) and chrysene (CHR) in aquatic ecosystems have aroused considerable concern. The present study established juvenile Mandarin fish (Siniperca chuatsi) models of NP and/or CHR exposure at ambient concentrations for 21 days to systematically investigate the underlying neurotoxicity mechanisms. The results showed that single and combined exposure to NP and CHR not only reduced the density of small neuronal cells in the grey matter layer of the optic tectum, but also induced brain oxidative stress according to physiological parameters including CAT, GSH-Px, SOD, T-AOC, and MDA. The co-exposure alleviated the histopathological damage, compared to NP and CHR single exposure group. These results indicate that NP and/or CHR causes neurotoxicity in S. chuatsi, in accordance with decreased acetylcholinesterase activity and altered expression of several marker genes of nervous system functions and development including c-fos, shha, elavl3, and mbpa. Transcriptomics analysis was performed to further investigate the potential molecular mechanisms of neurotoxicity. We propose that single NP and co-exposure induced oxidative stress activates MMP, which degrades tight junction proteins according to decreased expression of claudin, JAM, caveolin and TJP, ultimately damaging the integrity of the blood-brain barrier in S. chuatsi. Remarkably, the co-exposure exacerbated the blood-brain barrier disruption. More importantly, single NP and co-exposure induced neuronal apoptosis mainly activates the expression of apoptosis-related genes through the death receptor apoptosis pathway, while CHR acted through both death receptor apoptosis and endoplasmic reticulum apoptosis pathways. Additionally, subchronic CHR exposure caused neuroinflammation, supported by activation of TNF/NF-κB and JAK-STAT signaling pathways via targeting-related genes, while the co-exposure greatly alleviated the neuroinflammation. Collectively, our findings illuminate the underlying neurotoxicity molecular mechanisms of NP and/or CHR exposure on aquatic organisms.

Near-Infrared-II In Vivo Visualization and Quantitative Tracking of Micro/Nanoplastics in Fish

As emerging contaminants, micro/nanoplastics (MNPs) are widely present in aquatic environments and are often ingested by aquatic organisms. However, the in vivo trafficking and fate of MNPs remain largely unknown. Here, we developed near-infrared (NIR) aggregated-induced emission (AIE) fluorophore-labeled microplastics (2 μm) and nanoplastics (100 nm) as models of MNPs. This model was based on the NIR-AIE technique with strong emission at the second near-infrared (NIR-IIII) window, which overcomes the interference of autofluorescence and observation artifacts in the detection of commercial fluorescent-labeled particles. Due to its deep tissue penetration and noninvasiveness, the dynamic process of accumulation and transport of MNPs in individuals can be tracked with NIR imaging. We then directly visualized and quantified the uptake and depuration processes of MPs and NPs in zebrafish. The results showed that the MPs and NPs were mainly accumulated in the fish gut, and the distribution was heterogeneous. MPs tended to accumulate more in the fore and mid areas of the gut compared with NPs. Besides, both MPs and NPs could accumulate in large quantities locally in the gut and might cause intestinal obstruction. MNPs accumulated slowly during the initial exposure followed by rapid and sustained accumulation in gut. Based on these kinetic accumulation and depuration, we developed a refined toxicokinetic (TK) model to describe the dynamic changes in the uptake and depuration of MNPs. Overall, this study proposed a MNP model based on the NIR-AIE technique, which provided a reliable tracer technology for the visualization, tracking and quantification of MNPs in vivo.

Biological interactions of polystyrene nanoplastics: Their cytotoxic and immunotoxic effects on the hepatic and enteric systems

As emerging pollutants in the environment, nanoplastics (NPs) can cross biological barriers and be enriched in organisms, posing a greatest threat to the health of livestock and humans. However, the size-dependent toxic effects of NPs in higher mammals remain largely unknown. To determine the size-dependent potential toxicities of NPs, we exposed mouse (AML-12) and human (L02) liver cell lines in vitro, and 6-week-old C57BL/6 mice (well-known preclinical model) in vivo to five different sizes of polystyrene NPs (PS-NPs) (20, 50, 100, 200 and 500 nm). We found that ultra-small NPs (20 nm) induced the highest cytotoxicity in mouse and human liver cell lines, causing oxidative stress and mitochondrial membrane potential loss on AML-12 cells. Unexpectedly in vivo, after long-term oral exposure to PS-NPs (75 mg/kg), medium NPs (200 nm) and large NPs (500 nm) induced significant hepatotoxicity, evidenced by increased oxidative stress, liver dysfunction, and lipid metabolism disorders. Most importantly, medium or large NPs generated local immunotoxic effects via recruiting and activating more numbers of neutrophils and monocytes in the liver or intestine, which potentially resulted in increased proinflammatory cytokine secretion and the tissue damage. The discrepancy in in vitro-in vivo toxic results might be attributed to the different properties of biodistribution and tissue accumulation of different sized NPs in vivo. Our study provides new insights regarding the hepatotoxicity and immunotoxicity of NPs on human and livestock health, warranting us to take immense measures to prevent these NPs-associated health damage.

Nanoplastic Exposure at Environmental Concentrations Disrupts Hepatic Lipid Metabolism through Oxidative Stress Induction and Endoplasmic Reticulum Homeostasis Perturbation

In this study, we investigated the mechanism underlying the perturbation of hepatic lipid metabolism in response to micro/nanoplastic (MP/NP) exposure at environmentally relevant concentrations. Polystyrene (PS) MPs/NPs with different sizes (0.1, 0.5, and 5.0 μm) were studied for their effects on the homeostasis and function of Nile tilapia (Oreochromis niloticus) liver. Results showed that PS MPs/NPs were readily internalized and accumulated in various internal organs/tissues, especially in fish liver and muscle. Smaller-sized NPs caused more severe toxicity than larger MPs, including hepatic steatosis, inflammatory response, and disturbed liver function. Mechanistically, PS NPs with a particle size of 100 nm perturbed protein homeostasis in the endoplasmic reticulum (ER) by inhibiting the expression of chaperone proteins and genes involved in ER-associated degradation. This led to the activation of the PERK-eIF2α pathway, which caused dysfunction of hepatic lipid metabolism. Induction of oxidative stress and activation of the Nrf2/Keap1 pathway were also involved in the PS NP-induced hepatic lipid accumulation. These findings highlight the potential adverse effects of environmental MPs/NPs on aquatic organisms, raising concerns about their ecotoxicity and food safety.

Plastics and Micro/Nano-Plastics (MNPs) in the Environment: Occurrence, Impact, and Toxicity

Plastics, due to their varied properties, find use in different sectors such as agriculture, packaging, pharmaceuticals, textiles, and construction, to mention a few. Excessive use of plastics results in a lot of plastic waste buildup. Poorly managed plastic waste (as shown by heaps of plastic waste on dumpsites, in free spaces, along roads, and in marine systems) and the plastic in landfills, are just a fraction of the plastic waste in the environment. A complete picture should include the micro and nano-plastics (MNPs) in the hydrosphere, biosphere, lithosphere, and atmosphere, as the current extreme weather conditions (which are effects of climate change), wear and tear, and other factors promote MNP formation. MNPs pose a threat to the environment more than their pristine counterparts. This review highlights the entry and occurrence of primary and secondary MNPs in the soil, water and air, together with their aging. Furthermore, the uptake and internalization, by plants, animals, and humans are discussed, together with their toxicity effects. Finally, the future perspective and conclusion are given. The material utilized in this work was acquired from published articles and the internet using keywords such as plastic waste, degradation, microplastic, aging, internalization, and toxicity.

Nanoplastics exposure disrupts circadian rhythm associated with dysfunction of the endolysosomal pathway and autophagy in Caenorhabditis elegans

Nanoplastics (NPs), an emerging pollutant, have raised great safety concerns due to their widespread applications and continuous release into the environment, which lead to potential human and environmental risks. Recently, polystyrene NPs (100 nm; 100 mg/L) exposure has been reported to disrupt circadian rhythms under five days temperature entrainment and be associated with stress resistance decline in Caenorhabditis elegans. This study explored the possible relationship between circadian rhythm disruption and endocytosis and autophagy under polystyrene NPs exposure in C. elegans. We show that the disrupted circadian rhythm induced by NPs exposure reduced stress resistance via endocytosis and autophagy impairment. Furthermore, we found that most NPs taken up by intestinal cells were localized to early endosomes, late endosomes, and lysosomes and delivered to autophagosomes. In addition, the disruption of circadian rhythm inhibited NPs localization to these organelles. These findings indicate that NPs exposure disrupts circadian rhythm and alters its subcellular trafficking, leading to enhanced toxicity in C. elegans. Our results shed light on the prominent role of NPs exposure in circadian rhythm disruption associated with endocytosis and autophagy impairments, which may be conserved in higher animals such as humans.