Polystyrene Nanoplastic Exposure Induces Developmental Toxicity by Activating the Oxidative Stress Response and Base Excision Repair Pathway in Zebrafish (Danio rerio)

Disruption of early embryonic development in mice by polymethylmethacrylate nanoplastics in an oxidative stress mechanism

Polymethylmethacrylate (PMMA) has been used in many products, such as acrylic glass, and is estimated to reach 5.7 million tons of production per year by 2028. Thus, nano-sized PMMA particles in the environment are highly likely due to the weathering process. However, information on the hazards of nanoplastics, including PMMA in mammals, especially reproductive toxicity and action mechanism, is scarce. Herein, we investigated the effect of PMMA nanoplastics on the female reproductive system of mice embryos during pre-implantation. The treated plastic particles in embryos (10, 100, and 1000 μg/mL) were endocytosed into the cytoplasm within 30 min, and the blastocyst development and indices of embryo quality were significantly decreased from at 100 μg/mL. Likewise, the transfer of nanoplastic-treated embryos at 100 μg/mL decreased the morula implantation rate on the oviduct of pseudopregnant mice by 70%, calculated by the pregnant individual, and 31.8% by the number of implanted embryos. The PMMA nanoplastics at 100 μg/mL significantly increased the cellular levels of reactive oxygen species in embryos, which was not related to the intrinsic oxidative potential of nanoplastics. This study highlights that the nanoplastics that enter systemic circulation can affect the early stage of embryos. Thus, suitable action mechanisms can be designed to address nanoplastic occurrence.

Exploring developmental toxicity of microplastics and nanoplastics (MNPS): Insights from investigations using zebrafish embryos

Microplastics and nanoplastics (MNPs) have received increasing attention due to their high detection rates in human matrices and adverse health implications. However, the toxicity of MNPs on embryo/fetal development following maternal exposure remains largely unexplored. Zebrafish, sharing genetic similarities with human, boast a shorter life cycle, rapid embryonic development, and the availability of many transgenic strains, is a suitable model for environmental toxicology studies. This review comprehensively explores the existing research on the impacts of MNPs on zebrafish embryo development. MNPs exposure induces a wide array of toxic effects, encompassing neurodevelopmental toxicity, immunotoxicity, gastrointestinal effects, microbiota dysbiosis, cardiac dysfunctions, vascular toxicity, and metabolic imbalances. Moreover, MNPs disrupt the balance between reactive oxygen species (ROS) production and antioxidant capacity, culminating in oxidative damage and apoptosis. This study also offers insight into the current omics- and multi-omics based approaches in MNPs research, which greatly expedite the discovery of biochemical or metabolic pathways, and molecular mechanisms underlying MNPs exposure. Additionally, this review proposes a preliminary adverse outcome pathway framework to predict developmental toxicity caused by MNPs. It provides a comprehensive overview of pathways, facilitating a clearer understanding of the exposure and toxicity of MNPs, from molecular effects to adverse outcomes. The compiled data in this review provide a better understanding for MNPs effects on early life development, with the goal of increasing awareness about the risks posed to pregnant women by MNPs exposure and its potential impact on the health of their future generations.

Effect of oxidative stress induced by 2,3,7,8- tetrachlorodibenzo-p-dioxin on DNA damage

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a highly toxic persistent organic pollutant (POP) that can induce DNA damage within cells. Although oxidative stress is one of the primary mechanisms causing DNA damage, its role in the process of TCDD-induced DNA damage remains unclear. In this study, the TCDD-induced production of reactive oxygen species (ROS) and the occurrence of DNA damage at the AP site were monitored simultaneously. Further investigation revealed that TCDD impaired the activities of superoxide dismutase (SOD) and catalase (CAT), compromising the cellular antioxidant defense system. Consequently, this led to an increase in the production of O2.- and NO, thus inducing DNA damage at the AP site under oxidative stress. Our findings were further substantiated by the upregulation of key genes in the base excision repair (BER) pathway and the absence of DNA AP site damage after inhibiting O2.- and NO. In addition, transcriptome sequencing revealed that TCDD induces DNA damage by upregulating genes associated with oxidative stress in the mitogen-activated protein kinase (MAPK), cyclic adenosine monophosphate (cAMP), and breast cancer pathways. This study provides important insights into the toxicity mechanisms of TCDD.

Neurobehavioral toxicity induced by combined exposure of micro/nanoplastics and triphenyltin in marine medaka (Oryzias melastigma)

Microplastics/nanoplastics (MNPs) inevitably coexist with other pollutants in the natural environment, making it crucial to study the interactions between MNPs and other pollutants as well as their combined toxic effects. In this study, we investigated neurotoxicity in marine medaka (Oryzias melastigma) exposed to polystyrene micro/nanoplastics (PS-MNPs), triphenyltin (TPT), and PS-MNPs + TPT from physiological, behavioral, biochemical, and genetic perspectives. The results showed that marine medaka exposed to 200 ng/L TPT or 200 μg/L PS-NPs alone exhibited some degree of neurodevelopmental deficit, albeit with no significant behavioral abnormalities observed. However, in the PS-MP single exposure group, the average acceleration of short-term behavioral indices was significantly increased by 78.81%, indicating a highly stress-responsive locomotor pattern exhibited by marine medaka. After exposure to PS-MNPs + TPT, the swimming ability of marine medaka significantly decreased. In addition, PS-MNPs + TPT exposure disrupted normal neural excitability as well as activated detoxification processes in marine medaka larvae. Notably, changes in neural-related genes suggested that combined exposure to PS-MNPs and TPT significantly increased the neurotoxic effects observed with exposure to PS-MNPs or TPT alone. Furthermore, compared to the PS-MPs + TPT group, PS-NPs + TPT significantly inhibited swimming behavior and thus exacerbated the neurotoxicity. Interestingly, the neurotoxicity of PS-MPs was more pronounced than that of PS-NPs in the exposure group alone. However, the addition of TPT significantly enhanced the neurotoxicity of PS-NPs compared to PS-MPs + TPT. Overall, the study underscores the combined neurotoxic effects of MNPs and TPT, providing in-depth insights into the ecotoxicological implications of MNPs coexisting with pollutants and furnishing comprehensive data.

Effects of polystyrene nanoplastic size on zebrafish embryo development

Polystyrene nanoplastics (PS) require a comprehensive evaluation of their toxicity and potential risks to humans and the environment. The zebrafish model, a well-established animal model increasingly utilized for nanotoxicity assessments, was employed in this study. Our research aimed to explore the toxic effects of PS with sizes of 30, 100, 200, and 450 nm on zebrafish embryos. Exposure experiments were conducted on embryos at 4 h post-fertilization (hpf) using various concentrations of nanoparticles (20, 40, 60, 80, and 100 mg/L) until 96 hpf. Notably, PS ranging from 100 to 450 nm did not adversely affect zebrafish embryo development. However, PS with a size of 30 nm at a concentration of 100 mg/L resulted in embryo mortality but not embryonic malformations. Furthermore, our investigation confirmed the uptake of these nanoparticles by zebrafish larvae following the opening of their mouths, with the particles being found predominantly in the digestive system of the larvae. Additionally, 30 nm PS were found to significantly modulate the expression levels of genes associated with oxidative stress and apoptosis. These findings highlight the developmental impacts of 30 nm PS on zebrafish embryos, raising concerns about potential similar consequences in humans. Considering our findings, it is essential to encourage further research into the management and regulation of PS to mitigate their potential environmental and health impacts.

Vertebrate response to microplastics, nanoplastics and co-exposed contaminants: Assessing accumulation, toxicity, behaviour, physiology, and molecular changes

Pollution from microplastics (MPs) and nanoplastics (NPs) has gained significant public attention and has become a serious environmental problem worldwide. This review critically investigates MPs/NPs' ability to pass through biological barriers in vertebrate models and accumulate in various organs, including the brain. After accumulation, these particles can alter individuals' behaviour and exhibit toxic effects by inducing oxidative stress or eliciting an inflammatory response. One major concern is the possibility of transgenerational harm, in which toxic consequences are displayed in offspring who are not directly exposed to MPs/NPs. Due to their large and marked surface hydrophobicity, these particles can easily absorb and concentrate various environmental pollutants, which may increase their toxicity to individuals and subsequent generations. This review systematically provides an analysis of recent studies related to the toxic effects of MPs/NPs, highlighting the intricate interplay between co-contaminants in vitro and in vivo. We further delve into mechanisms of MPs/NPs-induced toxicity and provide an overview of potential therapeutic approaches to lessen the negative effects of these MPs/NPs. The review also emphasizes the urgency of future studies to examine the long-term effects of chronic exposure to MPs/NPs and their size- and type-specific hazardous dynamics, and devising approaches to safeguard the affected organisms.

Roxithromycin exposure induces motoneuron malformation and behavioral deficits of zebrafish by interfering with the differentiation of motor neuron progenitor cells

Roxithromycin (ROX), a commonly used macrolide antibiotic, is extensively employed in human medicine and livestock industries. Due to its structural stability and resistance to biological degradation, ROX persists as a resilient environmental contaminant, detectable in aquatic ecosystems and food products. However, our understanding of the potential health risks to humans from continuous ROX exposure remains limited. In this study, we used the zebrafish as a vertebrate model to explore the potential developmental toxicity of early ROX exposure, particularly focusing on its effects on locomotor functionality and CaP motoneuron development. Early exposure to ROX induces marked developmental toxicity in zebrafish embryos, significantly reducing hatching rates (n=100), body lengths (n=100), and increased malformation rates (n=100). The zebrafish embryos treated with a corresponding volume of DMSO (0.1%, v/v) served as vehicle controls (veh). Moreover, ROX exposure adversely affected the locomotive capacity of zebrafish embryos, and observations in transgenic zebrafish Tg(hb9:eGFP) revealed axonal loss in motor neurons, evident through reduced or irregular axonal lengths (n=80). Concurrently, abnormal apoptosis in ROX-exposed zebrafish embryos intensified alongside the upregulation of apoptosis-related genes (bax, bcl2, caspase-3a). Single-cell sequencing further disclosed substantial effects of ROX on genes involved in the differentiation of motor neuron progenitor cells (ngn1, olig2), axon development (cd82a, mbpa, plp1b, sema5a), and neuroimmunity (aplnrb, aplnra) in zebrafish larvae (n=30). Furthermore, the CaP motor neuron defects and behavioral deficits induced by ROX can be rescued by administering ngn1 agonist (n=80). In summary, ROX exposure leads to early-life abnormalities in zebrafish motor neurons and locomotor behavior by hindering the differentiation of motor neuron progenitor cells and inducing abnormal apoptosis.

Nanoplastic Exposure Mediates Neurodevelopmental Toxicity by Activating the Oxidative Stress Response in Zebrafish (Danio rerio)

The global accumulation and adverse effects of nanoplastics (NPs) are a growing concern for the environment and human health. In recent years, more and more studies have begun to focus on the toxicity of plastic particles for early animal development. Different particle sizes of plastic particles have different toxicities to biological development. Nevertheless, the potential toxicological effects of 20 nm NPs, especially on neurodevelopment, have not been well investigated. In this paper, we used fluorescence microscopy to determine neurotoxicity in zebrafish at different concentrations of NPs. Moreover, the behavioral analysis demonstrated that NPs induced abnormal behavior of zebrafish. The results revealed developmental defects in zebrafish embryos after exposure to different concentrations (0, 0.3, 3, and 9 mg/L) of NPs. The morphological deformities, including abnormal body length and the rates of heart, survival, and hatching, were induced after NP exposure in zebrafish embryos. In addition, the development of primary motor neurons was observed the inhibitory effects of NPs on the length, occurrence, and development of primary motor neurons in Tg(hb9:GFP). Quantitative polymerase chain reaction analysis suggested that exposure to NPs significantly affects the expression of the genes involved in the occurrence and differentiation of primary motor neurons in zebrafish. Furthermore, the indicators associated with oxidative stress and apoptosis were found to be modified in zebrafish embryos at 24 and 48 h following exposure to NPs. Our findings demonstrated that NPs could cause toxicity in primary motor neurons by activating the oxidative stress response and inducing apoptosis, consequently impairing motor performance.

Are bioplastics safe? Hazardous effects of polylactic acid (PLA) nanoplastics in Drosophila

The expanded uses of bioplastics require understanding the potential health risks associated with their exposure. To address this issue, Drosophila melanogaster as a versatile terrestrial in vivo model was employed, and polylactic acid nanoplastics (PLA-NPLs), as a proxy for bioplastics, were tested as a material model. Effects were determined in larvae exposed for 4 days to different concentrations (25, 100, and 400 μg/mL) of 463.9 ± 129.4 nm PLA-NPLs. Transmission electron microscopy (TEM) and scanning electron microscope (SEM) approaches permitted the detection of PLA-NPLs in the midgut lumen of Drosophila larvae, interacting with symbiotic bacteria. Enzymatic vacuoles were observed as carriers, collecting PLA-NPLs and enabling the crossing of the peritrophic membrane, finally internalizing into enterocytes. Although no toxic effects were observed in egg-to-adult survival, cell uptake of PLA-NPLs causes cytological disturbances and the formation of large vacuoles. The translocation across the intestinal barrier was demonstrated by their presence in the hemolymph. PLA-NPL exposure triggered intestinal damage, oxidative stress, DNA damage, and inflammation responses, as evaluated via a wide set of marker genes. Collectively, these structural and molecular interferences caused by PLA-NPLs generated high levels of oxidative stress and DNA damage in the hemocytes of Drosophila larvae. The observed effects point out the need for further studies aiming to deepen the health risks of bioplastics before adopting their uses as a safe plastic alternative.

Co-exposure to polystyrene nanoplastics and triclosan induces synergistic cytotoxicity in human KGN granulosa cells by promoting reactive oxygen species accumulation

In recent years, nanoplastics (NPs) and triclosan (TCS, a pharmaceutical and personal care product) have emerged as environmental pollution issues, and their combined presence has raised widespread concern regarding potential risks to organisms. However, the combined toxicity and mechanisms of NPs and TCS remain unclear. In this study, we investigated the toxic effects of polystyrene NPs and TCS and their mechanisms on KGN cells, a human ovarian granulosa cell line. We exposed KGN cells to NPs (150 μg/mL) and TCS (15 μM) alone or together for 24 hours. Co-exposure significantly reduced cell viability. Compared with exposure to NPs or TCS alone, co-exposure increased reactive oxygen species (ROS) production. Interestingly, co-exposure to NPs and TCS produced synergistic effects. We examined the activity of superoxide dismutase (SOD) and catalase (CAT), two antioxidant enzymes; it was significantly decreased after co-exposure. We also noted an increase in the lipid oxidation product malondialdehyde (MDA) after co-exposure. Furthermore, co-exposure to NPs and TCS had a more detrimental effect on mitochondrial function than the individual treatments. Co-exposure activated the NRF2-KEAP1-HO-1 antioxidant stress pathway. Surprisingly, the expression of SESTRIN2, an antioxidant protein, was inhibited by co-exposure treatments. Co-exposure to NPs and TCS significantly increased the autophagy-related proteins LC3B-II and LC3B-Ⅰ and decreased P62. Moreover, co-exposure enhanced CASPASE-3 expression and inhibited the BCL-2/BAX ratio. In summary, our study revealed the synergistic toxic effects of NPs and TCS in vitro exposure. Our findings provide insight into the toxic mechanisms associated with co-exposure to NPs and TCS to KGN cells by inducing oxidative stress, activations of the NRF2-KEAP1-HO-1 pathway, autophagy, and apoptosis.

Continuous generation and release of microplastics and nanoplastics from polystyrene by plastic-degrading marine bacteria

Plastic waste released into the environments breaks down into microplastics due to weathering, ultraviolet (UV) radiation, mechanical abrasion, and animal grazing. However, little is known about the plastic fragmentation mediated by microbial degradation. Marine plastic-degrading bacteria may have a double-edged effect in removing plastics. In this study, two ubiquitous marine bacteria, Alcanivorax xenomutans and Halomonas titanicae, were confirmed to degrade polystyrene (PS) and lead to microplastic and nanoplastic generation. Biodegradation occurred during bacterial growth with PS as the sole energy source, and the formation of carboxyl and carboxylic acid groups, decreased heat resistance, generation of PS metabolic intermediates in cultures, and plastic weight loss were observed. The generation of microplastics was dynamic alongside PS biodegradation. The size of the released microplastics gradually changed from microsized plastics on the first day (1344 nm and 1480 nm, respectively) to nanoplastics on the 30th day (614 nm and 496 nm, respectively) by the two tested strains. The peak release from PS films reached 6.29 × 106 particles/L and 7.64 × 106 particles/L from degradation by A. xenomutans (Day 10) and H. titanicae (Day 5), respectively. Quantification revealed that 1.3% and 1.9% of PS was retained in the form of micro- and nanoplastics, while 4.5% and 1.9% were mineralized by A. xenomutans and H. titanicae at the end of incubation, respectively. This highlights the negative effects of microbial degradation, which results in the continuous release of numerous microplastics, especially nanoplastics, as a notable secondary pollution into marine ecosystems. Their fates in the vast aquatic system and their impact on marine lives are noted for further study.

Polystyrene nanoplastics exposure alters muscle amino acid composition and nutritional quality of Pacific whiteleg shrimp (Litopenaeus vannamei)

Litopenaeus vannamei were exposed to 80-nm polystyrene nanoplastics (NPs) at different concentrations (0, 0.1, 1, 5, and 10 mg/L) for 28 days to study the effects on muscle nutritional quality. Our results showed that with increasing NPs concentrations, the survival rate, specific gain rate, and protein efficiency ratio decreased but the feed conversion ratio increased. There was no significant difference in moisture, ash, and crude lipid content in the muscle, and a general decrease in crude protein content was observed. However, the total amino acid and semi-essential amino acid contents decreased. The spacing between muscle fibers and the melting morphology of muscle increased. The hardness of muscle flesh texture increased, but springiness, cohesiveness, and chewiness decreased. Regarding antioxidant enzyme activity, the activity of catalase decreased, but the total antioxidant capacity, superoxide dismutase activity, and reduced glutathione first increased and then decreased. The expression level of the growth-related genes retinoid X receptor (RXR), chitin synthase (CHS), and calmodulin A (CaM) first increased then decreased, but calcium/calmodulin-dependent protein kinase I (CaMKI), ecdysteroid receptor (EcR), chitinase 5 (CHT5), cell division cycle 2 (Cdc2), and cyclin-dependent kinase 2 (CDK2) decreased. Our results suggest that exposure to NPs can inhibit growth by inducing oxidative stress, which leads to muscle tissue damage and changes in amino acid composition. These results will provide a theoretical reference for the risk assessment of NPs and the ecological health aquaculture of shrimp.

Micro(nano)plastics in marine medaka: Entry pathways and cardiotoxicity with triphenyltin

The simultaneous presence of micro(nano)plastics (MNPs) and pollutants represents a prevalent environmental challenge that necessitates understanding their combined impact on toxicity. This study examined the distribution of 5 μm (PS-MP5) and 50 nm (PS-NP50) polystyrene plastic particles during the early developmental stages of marine medaka (Oryzias melastigma) and assessed their combined toxicity with triphenyltin (TPT). Results showed that 2 mg/L PS-MP5 and PS-NP50 could adhere to the embryo surface. PS-NP50 can passively enter the larvae and accumulate predominantly in the intestine and head, while PS-MP5 cannot. Nonetheless, both types can be actively ingested by the larvae and distributed in the intestine. 2 mg/L PS-MNPs enhance the acute toxicity of TPT. Interestingly, high concentrations of PS-NP50 (20 mg/L) diminish the acute toxicity of TPT due to their sedimentation properties and interactions with TPT. 200 μg/L PS-MNPs and 200 ng/L TPT affect complement and coagulation cascade pathways and cardiac development of medaka larvae. PS-MNPs exacerbate TPT-induced cardiotoxicity, with PS-NP50 exhibiting stronger effects than PS-MP5, which may be related to the higher adsorption capacity of NPs to TPT and their ability to enter the embryos before hatching. This study elucidates the distribution of MNPs during the early developmental stages of marine medaka and their effects on TPT toxicity, offering a theoretical foundation for the ecological risk assessment of MNPs.

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.

The organism fate of inland freshwater system under micro-/nano-plastic pollution: A review of past decade

Micro- and nano-plastics (MPs/NPs) are characterized by their small size and extensive surface area, making them global environmental pollutants with adverse effects on organisms at various levels, including organs, cells, and molecules. Freshwater organisms, such as microalgae, emerging plants, zooplankton, benthic species, and fish, experience varying impacts from MPs/NPs, which are prevalent in both terrestrial and aquatic inland environments. MPs/NPs significantly impact plant physiological processes, including photosynthesis, antioxidant response, energy metabolism, and nitrogen removal. Extended exposure and ingestion to MPs/NPs might cause metabolic and behavioral deviations in zooplankton, posing an extinction risk. Upon exposure to MPs/NPs, both benthic organisms and fish display behavioral and metabolic disturbances, due to oxidative stress, neural toxicity, intestinal damage, and metabolic changes. Results from laboratory and field investigations have confirmed that MPs/NPs can be transported across multiple trophic levels. Moreover, MPs/NPs-induced alterations in zooplankton populations can impede energy transfer, leading to food scarcity for filter-feeding fish, larvae of benthic organism and fish, thus jeopardizing aquatic ecosystems. Furthermore, MPs/NPs can harm the nervous systems of aquatic organisms, influencing their feeding patterns, circadian rhythms, and mobility. Such behavioral alterations might also introduce unforeseen ecological risks. This comprehensive review aims to explore the consequences of MPs/NPs on freshwater organisms and their interconnected food webs. The investigation encompasses various aspects, including behavioral changes, alterations in physiology, impacts on metabolism, transgenerational effects, and the disruption of energy transfer within the ecosystem. This review elucidated the physiological and biochemical toxicity of MPs/NPs on freshwater organisms, and the ensuing risks to inland aquatic ecosystems.

Dimethenamid promotes oxidative stress and apoptosis leading to cardiovascular, hepatic, and pancreatic toxicities in zebrafish embryo

Dimethenamid, one of the acetamide herbicides, is widely used on soybeans and corns to inhibit weed growth. Although other acetamide herbicides have been reported to have several toxicities in non-target organisms including developmental toxicity, the toxicity of dimethenamid has not yet been studied. In this research, we utilized the zebrafish animal model to verify the developmental toxicity of dimethenamid. It not only led to morphological abnormalities in zebrafish larvae but also reduced their viability. ROS production and inflammation responses were promoted in zebrafish larvae. Also, uncontrolled apoptosis occurred when the gene expression level related to the cell cycle and apoptosis was altered by dimethenamid. These changes resulted in toxicities in the cardiovascular system, liver, and pancreas are observed in transgenic zebrafish models including fli1a:EGFP and L-fabp:dsRed;elastase:GFP. Dimethenamid triggered morphological defects in the heart and vasculature by altering the mRNA levels related to cardiovascular development. The liver and pancreas were also damaged through not only the changes of their morphology but also through the dysregulation in their function related to metabolic activity. This study shows the developmental defects induced by dimethenamid in zebrafish larvae and the possibility of toxicity in other non-target organisms.

Sodium nitroprusside alleviates nanoplastics-induced developmental toxicity by suppressing apoptosis, ferroptosis and inflammation

The health damage caused by nanoplastics (NPs) pollution has become one of the global scientific problems to be solved urgently. However, the toxicological mechanism of NPs is complex, and the research progress of anti-toxicity is limited. Thus, it has potential application value to explore or develop drugs that can effectively alleviate or remove NPs with biological toxicity. In this research, 8 μM sodium nitroprusside (SNP) solution was used to treat zebrafish larvae with 20 mg/L NPs for up to 12 days, and the results showed that SNP treatments were effective in alleviating NPs-caused developmental toxicity in zebrafish larvae. Further examination of its signaling pathway revealed that NPs-induced oxidative stress was mitigated by activating the NO-sGC-cGMP signaling pathway and reduced most of the reactive oxygen species (ROS). Subsequently, we detected the key substances and the key enzymes involved in apoptosis and ferroptosis, and found that oxidative stress-induced mitochondria-dependent apoptosis and lipid peroxidation-caused ferroptosis were alleviated. Finally, observed the accumulation of NPs and ROS in the liver of zebrafish larvae, which is the target organ of immunotoxicity, and we found that SNP could alleviate NPs-caused inflammation by analyzing the fluorescence intensity of neutrophils and macrophages in transgenic zebrafish and detecting the expression of key immune genes. In conclusion, this research has shown for the first time that SNP treatment can significantly inhibit NPs-induced developmental toxicity, resulting from oxidative stress-induced apoptosis, ferroptosis and inflammation in zebrafish larvae.

Uptake of Nanoplastic particles by zebrafish embryos triggers the macrophage response at early developmental stage

Plastic pollution continues to erupt as a global ecological concern. As plastic debris is degraded into nanoscale and microscale particles via biodegradation, UV-irradiation, and mechanical processes, nanoplastic pollution arises as a threat to virtually every biological and ecological system on the planet. In this study, zebrafish (Danio rerio) embryos were exposed to fluorescently labeled plastic particles at nanoscales (30 nm and 100 nm). The uptake of both the nanoplastic particles (NPs) was found to exponentially increase with incubation time. Penetration of NPs through the natural barrier of the zebrafish embryos, the chorion, was observed prior to the hatching of the embryo. As a result, the NPs were found to accumulate on the body surface as well as inside the body of the zebrafish. The invasion of NPs into zebrafish embryos induced the upregulation of several stress and immune response genes including interleukins (il6 and il1b), cytochrome P450 (cyp1a and cyp51), and reactive oxygen species (ROS) removal protein-encoding genes (sod and cat). This suggested the initiation of ROS generation and removal as well as the activation of the immune response of zebrafish embryos. Colocalization of macrophages and NPs in zebrafish embryos indicated the involvement of macrophage response to the NP invasion at the early developmental stage of zebrafish.

Screening for microplastics in drinking water and its toxicity profiling in zebrafish

Microplastics (MPs) have emerged as a major environmental problem in freshwater and marine environments. The effects of these polymers on aquatic life are well studied; however, there is limited knowledge of MP-associated health hazards in humans. We estimated the presence of MPs in different brands of bottled water available in India using the Nile red (NR) staining method. The FTIR examination revealed the presence of polystyrene (PS), polyethylene (PE), and polyamide (PA) in the bottled water samples with PE being the most prevalent one. Zebrafish embryos exposed to different concentrations of fluorescent-tagged polyethylene microplastics (PE-MPs) (10-150 μm) showed accumulation patterns at different time points in various organs. The exposure to PE MPs induced a concentration-dependent ROS activity. The expression of first-line antioxidative defense marker genes were significantly downregulated in embryos exposed to varying concentrations of PE-MPs, suggesting concentration and time-dependent effects on zebrafish. The results of this study suggest that the potential negative consequences on human health could be due to the oxidative stress and time-dependent toxicity of MPs.

The neurodevelopmental toxicity induced by combined exposure of nanoplastics and penicillin in embryonic zebrafish: The role of aging processes

As ubiquitous contaminants, nanoplastics and antibiotics are frequently co-presence and widely detected in the freshwater environment and biota, posing a high co-exposure risk to aquatic organisms and even humans. More importantly, how the aging process of nanoplastics affects the joint toxic potential of nanoplastics and antibiotics has not been explored. Here, we generated two aged polystyrene nanoplastics (PS) by UV radiation (UV-PS) and ozonation (O3-PS). Non-teratogenic concentrations of pristine PS (80 nm) and antibiotics penicillin (PNC) co-exposure synergistically suppressed the embryo heart beating and behaviors of spontaneous movement, touch response, and larval swimming behavioral response. Pristine PS and aged UV-PS, but not aged O3-PS, showed similar effects on zebrafish embryo/larval neurodevelopment. However, when co-exposure with PNC, both aged PS, but not pristine PS, showed antagonistic effects. In late-stage juvenile social behavior testing, we found that PS decreased the exploration in light/dark preference assay. The synergistic effect of aged PS with PNC was further explored, including cellular apoptosis, ROS formation, and neurotransmitter metabolite regulation. Mechanistically, aged UV-PS but not O3-PS significantly increased the adsorption rate of PNC compared to pristine PS, which may account for the toxicity difference between the two aged PS. In conclusion, our results confirmed that PS served as a carrier for PNC, and the environmental aging process changed their neurobehavioral toxicity pattern in vivo.

Bisphenol A decreases the developmental toxicity and histopathological alterations caused by polystyrene nanoplastics in developing marine medaka Oryzias melastigma

Nanoplastics (NPs) are emerging pollutants posing risks to marine biota and human health due to their small size and high bioavailability. However, there are still knowledge gaps regarding effects of co-existing pollutants on NPs toxicity to marine organisms at their respective environmentally relevant concentrations. Herein we investigated developmental toxicity and histopathological alterations caused by co-exposure of polystyrene nanoplastics (PS-NPs) and bisphenol A (BPA) to marine medaka, Oryzias melastigma. Embryos at 6 h post-fertilization were exposed to 50-nm PS-NPs (55 μg/L) or BPA (100 μg/L) or co-exposed to a combination of both. Results showed that PS-NPs exhibited decreased embryonic heart rate, larval body length, and embryonic survival as well as larval deformities such as hemorrhaging and craniofacial abnormality. When co-exposed, BPA mitigated all the adverse developmental effects caused by PS-NPs. PS-NPs also led to an increase in histopathological condition index of liver with early inflammatory responses, while co-exposure of BPA with PS-NPs did not. Our data suggest that the toxicity reduction of PS-NPs in the presence of BPA might result from the decreased bioaccumulation of PS-NPs caused by the interaction between BPA and PS-NPs. This study unveiled the impact of BPA on the toxicity of nanoplastics in marine fish during early developmental stages and highlight the need of more research on the long-term effects of complex mixtures in the marine environment by applying omics approaches to better understand the toxicity mechanism.

Reproductive toxicity of micro- and nanoplastics

Large-scale plastic pollution occurs in terrestrial and marine environments and degrades into microparticles (MP) and nanoparticles (NP) of plastic. Micro/nanoplastics (MP/NPs) are found throughout the environment and different kinds of marine organisms and can enter the human body through inhalation or ingestion, particularly through the food chain. MPs/NPs can enter different organisms, and affect different body systems, including the reproductive, digestive, and nervous systems via the induction of different stresses such as oxidative stress and endoplasmic reticulum stress. This paper summarizes the effects of MPs/NPs of different sizes on the reproduction of different organisms including terrestrial and marine invertebrates and vertebrates, the amplification of toxic effects between them through the food chain, the serious threat to biodiversity, and, more importantly, the imminent challenge to human reproductive health. There is a need to strengthen international communication and cooperation on the remediation of plastic pollution and the protection of biodiversity to build a sustainable association between humans and other organisms.

Elevated temperature decreases cardiovascular toxicity of nanoplastics but adds to their lethality: A case study during zebrafish (Danio rerio) development

To highlight the key role of global warming on the toxicity of contaminants, the cardiovascular toxicity of nanoparticles (NPs) was estimated in developing zebrafish (Danio rerio) at different exposure temperatures, and the toxicity mechanisms were explored via multi-omic analyses. Polystyrene NPs (50 nm) at 0.1 mg·L^-1 entered zebrafish embryos at 24 h post-fertilization and caused cardiovascular toxicity in the developing zebrafish at 27 ℃. This was explained by the down-regulation of the branched-chain amino acid and insulin signaling pathways owing to induced oxidative stress. Elevated exposure temperatures promoted the accumulation of NPs in developing zebrafish, increased the levels of oxidative stress and enhanced the oxidative phosphorylation rate in mitochondria, thus resulting in an additive effect on the mortality of zebrafish larvae. Notably, elevated exposure temperatures reduced the cardiovascular toxicity of NPs, as the effective concentration of NPs for inhibiting embryonic heartbeat rate increased from 0.1 mg·L^-1 at 27 ℃ to 1.0 mg·L^-1 at 30 ℃. Experiments of transgenic zebrafish Tg(myl7:GFP) and multi-omic analyses revealed that elevated temperatures enhanced the myocardial contractility of larvae, thus reducing the cardiovascular toxicity of NPs. However, the health risks of enhanced myocardial contraction caused by NP exposure at elevated temperatures requires further consideration.

Cocktail effects of emerging contaminants on zebrafish: Nanoplastics and the pharmaceutical diphenhydramine

Nanoplastics (NPLs) became ubiquitous in the environment, from the air we breathe to the food we eat. One of the main concerns about the NPLs risks is their role as carrier of other environmental contaminants, potentially increasing their uptake, bioaccumulation and toxicity to the organisms. Therefore, the main aim of this study was to understand how the presence of polystyrene NPLs (∅ 44 nm) will influence the toxicity (synergism, additivity or antagonism) of the antihistamine diphenhydramine (DPH), towards zebrafish (Danio rerio) embryos, when in dual mixtures. After 96 hours (h) exposure, at the organismal level, NPLs (0.015 or 1.5 mg/L) + DPH (10 mg/L) induced embryo mortality (90%) and malformations (100%) and decreased hatching (80%) and heartbeat rates (60%). After 120 h exposure, NPLs (0.015 or 1.5 mg/L) + DPH (0.01 mg/L) decreased larvae swimming distance (30-40%). At the biochemical level, increased glutathione S-transferases (55-122%) and cholinesterase (182-343%) activities were found after 96 h exposure to NPLs (0.015 or 1.5 mg/L) + DPH (0.01 mg/L). However, catalase (CAT) activity remained similar to the control group in the mixtures, inhibiting the effects detected after the exposure to 1.5 mg/L NPLs alone (increased 230% of CAT activity). In general, the effects of dual combination - NPLs + DPH (even at concentrations as low as 10 μg/L of DPH) - were more harmful than the correspondent individual exposures, showing the synergistic interactions of the dual mixture and answering to the main question of this work. The obtained results, namely the altered toxicity patterns of NPLs + DPH compared with the individual exposures, show the importance of an environmental risk assessment considering NPLs as a co-contaminant due to the potential NPLs role as vector for other contaminants.

Co-exposure to nanoplastics and acetaminophen causes skeletal dysplasia and behavioral abnormalities in zebrafish

Nanoplastics (NPs) and acetaminophen (APAP) are thought to be common contaminants and are invariably detected in the environment. Despite the increasing awareness of their toxicity to humans and animals, the embryonic toxicity, skeletal development toxicity, and mechanism of action of their combined exposure have not been clarified. This study was performed to investigate whether combined exposure to NPs and APAP induces abnormal embryonic and skeletal development in zebrafish and to explore the potential toxicological mechanisms. All zebrafish juveniles in the high-concentration compound exposure group showed some abnormal phenomena such as pericardial edema, spinal curvature, cartilage developmental abnormality and melanin inhibition together with a significant downward trend in body length. Behavioral data also implicated that the exposure of APAP alone, as well as the co-exposure of NPs and APAP, caused a depression in the total distance, swimming speed and the maximum acceleration. Furthermore, real-time polymerase chain reaction analysis showed that compared with exposure alone, the expression level of genes related to osteogenesis, runx2a, runx2b, Sp7, bmp2b and shh was significantly reduced with compound exposure. These results suggest that the compound exposure of NPs and APAP has adverse impacts on zebrafish embryonic development and skeletal growth.

Polystyrene nanoplastics enhance the toxicological effects of DDE in zebrafish (Danio rerio) larvae

Anthropogenic releases of plastics, persistent organic pollutants (POPs), and heavy metals can impact the environment, including aquatic ecosystems. Nanoplastics (NPs) have recently emerged as pervasive environmental pollutants that have the ability to adsorb POPs and can cause stress in organisms. Among POPs, DDT and its metabolites are ubiquitous environmental pollutants due to their long persistence. Despite the discontinued use of DDT in Europe, DDT and its metabolites (primarily p,p'-DDE) are still found at detectable levels in fish feed used in salmon aquaculture. Our study aimed to look at the individual and combined toxicity of NPs (50 mg/L polystyrene) and DDE (100 μg/L) using zebrafish larvae as a model. We found no significant morphological, cardiac, respiratory, or behavioural changes in zebrafish larvae exposed to NPs alone. Conversely, morphological, cardiac and respiratory alterations were observed in zebrafish larvae exposed to DDE and NPs + DDE. Interestingly, behavioural changes were only observed in zebrafish larvae exposed to NPs + DDE. These findings were supported by RNA-seq results, which showed that some cardiac, vascular, and immunogenic pathways were downregulated only in zebrafish larvae exposed to NPs + DDE. In summary, we found an enhanced toxicological impact of DDE when combined with NPs.