Neuro- and hepato-toxicity of polystyrene nanoplastics and polybrominated diphenyl ethers on early life stages of zebrafish

Exacerbated interfacial impacts of nanoplastics and 6:2 chlorinated polyfluorinated ether sulfonate by natural organic matter in adult zebrafish: Evidence through histopathology, gut microbiota, and transcriptomic analysis

Nanoplastics (NPs) interact with cooccurring chemicals and natural organic matter (NOM) in the environment, forming complexes that can change their bioavailability and interfacial toxicity in aquatic organisms. This study aims to elucidate the single and combined impacts of 21-day chronic exposure to low levels of polystyrene NPs (size 80 nm) at 1 mg/L and 6:2 chlorinated polyfluorinated ether sulfonate (Cl-PFAES or F53B) at 200 μg/L in the presence and absence of NOM (humic acid-HA and bovine serum albumin-BSA at 10 mg/L) in adult zebrafish (Danio rerio). Our findings through multiple bioassays, revealed that the mixture group (M), comprising of NPs, F53B, HA, and BSA, caused a higher level of toxicity compared to the single NPs (AN), single F53B (AF), and combined NPs+F53B (ANF) groups. The mixture exposure caused the highest level of vacuolization and nuclear condensation in hepatocytes, and most of the intestinal villi were fused and highly reduced in villi length and crypt depth. Further, the T-AOC levels were significantly lower (p < 0.05), while the MDA levels in the liver and intestine were significantly higher (p < 0.05) in the M group with downregulation of nfkbiaa, while upregulation of prkcda, csf1ra, and il1b apoptosis genes in the liver. Pairwise comparison of gut microbiota showed significantly higher (p < 0.05) abundances of various genera in the M group, including Gordonia, Methylobacterium, Tundrisphaera, GKS98, Pedomicrobium, Clostridium, Candidatus and Anaerobacillus, as well as higher abundance of genera including pathogenic strains, while control group showed higher abundance of probiotic genus ZOR0006 than exposed group (p < 0.01). The transcriptomic analysis revealed highest number of DEGs in the M group (2815), followed by the AN group (506) and ANF group (206) with the activation of relaxin signaling pathway-RSP (slc9a1, slc9a2) and AMP-activated protein kinase (AMPK) pathway (plin1), and suppression of the toll-like receptor (TLR) pathway (tlr4a, tlr2, tlr1), cytokine-cytokine receptor interaction (CCRI) pathway (tnfb, il21r1, il21, ifng1), and peroxisome proliferator-activated receptors (PPAR) pathway (pfkfb3). Overall, toxicity in the M group was higher, indicating that the HA and BSA elevated the interfacial impacts of NPs and F53B in adult zebrafish after chronic environmentally relevant exposure, implying the revisitation of the critical interaction of NOM with co-occurring chemicals and associated impacts.

Interfacial effects of perfluorooctanoic acid and its alternative hexafluoropropylene oxide dimer acid with polystyrene nanoplastics on oxidative stress, histopathology and gut microbiota in Crassostrea hongkongensis oysters

The increasing interfacial impacts of polystyrene nanoplastics (PS) and per- and polyfluoroalkyl substances (PFAS) complex aquatic environments are becoming more evident, drawing attention to the potential risks to aquatic animal health and human seafood safety. This study aims to investigate the relative impacts following exposure (7 days) of Crassostrea hongkongensis oysters to the traditional PFAS congener, perfluorooctanoic acid (PFOA) at 50 μg/L, and its novel alternative, hexafluoropropylene oxide dimer acid (HFPO-DA), also known as GenX at 50 μg/L, in conjunction with fluorescent polystyrene nanoplastics (PS, 80 nm) at 1 mg/L. The research focuses on assessing the effects of combined exposure on oxidative stress responses and gut microbiota in the C. hongkongensis. Comparing the final results of PS + GenX (PG) and PS + PFOA (PF) groups, we observed bioaccumulation of PS in both groups, with the former causing more pronounced histopathological damage to the gills and intestines. Furthermore, the content of antioxidant enzymes induced by PG was higher than that of PF, including Superoxide Dismutase (SOD), Catalase (CAT), Glutathione Reductase (GR) and Glutathione Peroxidase (GSH). Additionally, in both PG and PF groups, the expression levels of several immune-related genes were significantly upregulated, including tnfα, cat, stat, tlr-4, sod, and β-gbp, with no significant difference between these two groups (p > 0.05). Combined exposure induced significant changes in the gut microbiota of C. hongkongensis at its genus level, with a significant increase in Legionella and a notable decrease in Endozoicomonas and Lactococcus caused by PG. These shifts led to beneficial bacteria declining and pathogenic microbes increasing. Consequently, the microbial community structure might be disrupted. In summary, our findings contribute to a deeper understanding of the comparative toxicities of marine bivalves under combined exposure of traditional and alternative PFAS.

Developmental toxicity and mechanism of polychlorinated biphenyls 126 and nano-polystyrene combined exposure to zebrafish larvae

3,3',4,4',5-Pentachlorobiphenyl (PCB126) is the most toxic congener of dioxin-like polychlorinated biphenyls (DL PCBs), while nanoplastics (NPs) have recently emerged as significant marine pollutants, both posing threats to aquatic organisms and human health. They coexist in the environment, but their comprehensive toxicological effects remain unclear. In this study, zebrafish embryos were simultaneously exposed to PCB126 and 80-nanometer nanoplastyrene (NPS). Researchers utilized fluorescence microscopy, qPCR, histopathological examination, and transcriptomic sequencing to investigate the developmental toxicity of different concentrations of PCB126 and NPS individually or in combination on zebrafish embryos and larvae. Results indicate that the chorion significantly impedes the accumulation of NPS (p < 0.05). It is noteworthy that this barrier effect diminishes upon simultaneous exposure to PCB126. In this experiment, the semi-lethal concentration of PCB126 for larvae was determined to be 6.33 μg/L. Exposure to PCB126 induces various deformities, primarily mediated through the aryl hydrocarbon receptor (AHR). Similarly, exposure to NPS also activates AHR, leading to developmental impairments. Furthermore, transcriptomic sequencing revealed similar effects of PCB126 and NPS on the gene expression trends in zebrafish larvae, but combined exposure to both exacerbates the risk of cancer and induces more severe cardiac toxicity. At this level, co-exposure to PCB126 and NPS adversely affects the development of zebrafish larvae. This study contributes to a deeper understanding of the in vivo accumulation of DL polychlorinated biphenyls and microplastics in actual aquatic environments and their impact on fish development.

Environmental and Sublethal Concentrations of Polystyrene Nanoplastics Induced Antioxidant System, Transcriptomic Responses, and Disturbed Gut Microbiota in Oyster Magallana Hongkongensis

Nanoplastics (NPs) are emerging contaminants having persistent nature, diverse ecological impacts, and potential food safety risks. Here, we examined the ecotoxicity of 80 nm polystyrene nanoplastics (PS-NPs) at environmentally relevant concentrations (ERCs, 10 and 100 μg/L), and sublethal concentrations (SLCs, 500 and 2500 μg/L) in Magallana hongkongensis. Results showed that SLCs significantly (p < 0.05) increased superoxide dismutase (SOD), catalase (CAT), and alkaline phosphatase (AKP) activities and altered tnfα, cat, gst, sod, and se-gpx genetic expressions. Further, PS-NP exposure at both levels reduced beneficial bacteria and increased potentially pathogenic bacteria in the gut. In transcriptomic analysis, 5118 and 4180 differentially expressed genes (DEGs) were identified at ERCs, while 5665 and 4817 DEGs were found at SLCs, respectively. Upregulated DEGs enriched lysosomes, ABC transporters, and apoptosis pathways, while downregulated DEGs enriched ribosomal pathways. Overall, ERCs significantly altered gut microbiota and transcriptomic responses, while SLCs, in addition, also impacted the antioxidant and immune systems.

Exposure to polystyrene microplastics and perfluorooctane sulfonate disrupt the homeostasis of intact planarians and the growth of regenerating planarians

Microplastics (MPs) and perfluorinated compounds (PFAS) are widespread in the global ecosystem. MPs have the ability to adsorb organic contaminants such as perfluorooctane sulfonate (PFOS), leading to combined effects. The current work aims to explore the individual and combined toxicological effects of polystyrene (PS) and PFOS on the growth and nerves of the freshwater planarian (Dugesia japonica). The results showed that PS particles could adsorb PFOS. PS and PFOS impeded the regeneration of decapitated planarians eyespots, whereas the combined treatment increased the locomotor speed of intact planarians. PS and PFOS caused significant DNA damage, while co-treatment with different PS concentrations aggravated and attenuated DNA damage, respectively. Further studies at the molecular level have shown that PS and PFOS affect the proliferation and differentiation of neoblasts in both intact and regenerating planarians, alter the expression levels of neuronal genes, and impede the development of the nervous system. PS and PFOS not only disrupted the homeostasis of intact planarians, but also inhibited the regeneration of decapitated planarians. This study is the first to assess the multiple toxicity of PS and PFOS to planarians after combined exposure. It provides a basis for the environmental and human health risks of MPs and PFAS.

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

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

Combined neurotoxicity of aged microplastics and thiamethoxam in the early developmental stages of zebrafish (Daniorerio)

Microplastics (MPs) pollution, together with its consequential effect on aquatic biota, represent a burgeoning environmental concern that has garnered significant scholarly attention. Thiamethoxam (TMX), a prevalently utilized neonicotinoid insecticide, is renowned for its neurotoxic impact and selective action against targeted pests. The aquatic environment serves as a receptacle for numerous pollutants, such as MPs and neonicotinoid insecticides. However, there is currently a lack of comprehensive understanding regarding the toxic effects of co-exposure to aged MPs and neonicotinoid insecticides in aquatic organisms. Therefore, we endeavor to elucidate the deleterious impacts of aged polystyrene (PS) and TMX on zebrafish (Danio rerio) larvae when present at environmentally relevant concentrations, and to reveal the underlying molecular mechanisms driving these effects. Our study showed that exposure to aged PS, TMX, or their combination notably inhibited the heart rate and locomotion of zebrafish larvae, with a pronounced effect observed under combined exposure. Aged PS and TMX were found to diminish the activity of antioxidative enzymes (SOD, CAT, and GST), elevate MDA levels, and disrupt neurotransmitter homeostasis (5-HT, GABA and ACh). Notably, the mixtures exhibited synergistic effects. Moreover, gene expression related to oxidative stress (e.g., gstr1, gpx1a, sod1, cat1, p38a, ho-1, and nrf2b) and neurotransmission (e.g., ache, ChAT, gat1, gabra1, 5ht1b, and 5ht1aa) was significantly altered upon co-exposure to aged PS and TMX in larval zebrafish. In summary, our findings support the harmful effects of aged MPs and the neonicotinoid insecticides they carry on aquatic organisms. Results from this study enhance our understanding of the biological risks of MPs and insecticides, as well as help fill existing knowledge gaps on neonicotinoid insecticides and MPs coexistence toxicity in aquatic environment.

Impact of microplastics and nanoplastics on liver health: Current understanding and future research directions

With continuous population and economic growth in the 21st century, plastic pollution is a major global issue. However, the health concern of microplastics/ nanoplastics (MPs/NPs) decomposed from plastic wastes has drawn public attention only in the recent decade. This article summarizes recent works dedicated to understanding the impact of MPs/NPs on the liver-the largest digestive organ, which is one of the primary routes that MPs/NPs enter human bodies. The interrelated mechanisms including oxidative stress, hepatocyte energy re-distribution, cell death and autophagy, as well as immune responses and inflammation, were also featured. In addition, the disturbance of microbiome and gut-liver axis, and the association with clinical diseases such as metabolic dysfunction-associated fatty liver disease, steatohepatitis, liver fibrosis, and cirrhosis were briefly discussed. Finally, we discussed potential directions in regard to this trending topic, highlighted current challenges in research, and proposed possible solutions.

Polystyrene nanoplastics induced size-dependent developmental and neurobehavioral toxicities in embryonic and juvenile zebrafish

Because of widespread environmental contamination, there is growing concern that nanoplastics may pose a risk to humans and the environment. Due to their small particle size, nanoplastics may cross the blood-nerve barrier and distribute within the nervous system. The present study systematically investigated the uptake/distribution and developmental/neurobehavioral toxicities of different sizes (80, 200, and 500 nm) of polystyrene nanoplastics (PS) in embryonic and juvenile zebrafish. The results indicate that all three sizes of PS could cross the chorion, adsorb by the yolk, and distribute into the intestinal tract, eye, brain, and dorsal trunk of zebrafish, but with different patterns. The organ distribution and observed developmental and neurobehavioral effects varied as a function of PS size. Although all PS exposures induced cell death and inflammation at the cellular level, only exposures to the larger PS resulted in oxidative stress. Meanwhile, exposure to the 80 nm PS increased the expression of neural and optical-specific mRNAs. Collectively, these studies indicate that early life-stage exposures to PS adversely affect zebrafish neurodevelopment and that the observed toxicities are influenced by particle size.

Impacts of high-dose riboflavin on cytotoxicity, antioxidant, growth, reproductive gene expressions, and genotoxicity in the rainbow trout gonadal cells

Riboflavin (vitamin B2 found in food) is a precursor of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which study as coenzymes for a variety of cellular processes including biosynthesis, homocysteine metabolism, detoxification, and various oxidation and reduction reactions. Although studies on the symptoms resulting from riboflavin deficiency are intense, studies on the effects of high doses of riboflavin are almost absent. This report aimed to examine the actions of riboflavin on cell viability, the transcriptional expressions of antioxidant enzyme (gsr and gpx1a), growth (gh1, igf1, and igf2), the reproductive (bol) genes and DNA damage in the rainbow trout gonad cells (RTG-2) for 48 h. All concentrations of riboflavin (3.125, 6.25, 12.5, 25, 50, and 100 μM) significantly reduced the RTG-2 cell viability. Riboflavin (LD50: 12.5 μM) significantly downregulated the transcriptional expressions of gpx1a, igf1, and bol genes, while it non-significantly upregulated or downregulated the transcriptional expression of gsr, igf2, and gh1 genes in the RTG-2 cells in comparison to the control group for 48 h. The comet assay demonstrated that riboflavin significantly raised tail DNA% >10% DMSO (positive control). Based on the outcomes, high doses of riboflavin exhibit the potential to have a role in cellular mechanisms, including especially reproduction, DNA damage, and cell death.

20 years of polybrominated diphenyl ethers on toxicity assessments

Polybrominated diphenyl ethers (PBDEs) serve as brominated flame retardants which continue to receive considerable attention because of their persistence, bioaccumulation, and potential toxicity. Although PBDEs have been restricted and phased out, large amounts of commercial products containing PBDEs are still in use and discarded annually. Consequently, PBDEs added to products can be released into our surrounding environments, particularly in aquatic systems, thus posing great risks to human health. Many studies and reviews have described the possible toxic effects of PBDEs, while few studies have comprehensively summarized and analyzed the global trends of their toxicity assessment. Therefore, this study utilizes bibliometrics to evaluate the worldwide scientific output of PBDE toxicity and analyze the hotspots and future trends of this field. Firstly, the basic information including the most contributing countries/institutions, journals, co-citations, influential authors, and keywords involved in PBDE toxicity assessment will be visualized. Subsequently, the potential toxicity of PBDE exposure to diverse systems, such as endocrine, reproductive, neural, and gastrointestinal tract systems, and related toxic mechanisms will be discussed. Finally, we conclude this review by outlining the current challenges and future perspectives in environmentally relevant PBDE exposure, potential carriers for PBDE transport, the fate of PBDEs in the environment and human bodies, advanced stem cell-derived organoid models for toxicity assessment, and promising omics technologies for obtaining toxic mechanisms. This review is expected to offer systematical insights into PBDE toxicity assessments and facilitate the development of PBDE-based research.

BDE-47-mediated cytotoxicity via autophagy blockade in 3D HepaRG spheroids cultured in alginate microcapsules

Polybrominated Diphenyl Ethers (PBDEs) are a major class of brominated flame retardants, and their widespread use has led them to be considered contaminants with emerging concern. PBDEs have been detected in the indoor air, house dust, food, and all environmental compartments. The congener BDE-47 (2,2',4,4'-tetrabromodiphenyl ether) is the most prevalent, and hepatotoxicity, neurotoxicity, immunological changes, endocrine disruption, and genotoxic potential have been related to its exposure. Although the BDE-47 molecular toxicity pathway is directly related to intrinsic apoptotic cell death, the role of autophagy in BDE-47 toxicity remains unclear. In this context, three-dimensional cell culture has emerged as a good strategy for the replacement of animals in toxicological testing. Here, we used HepaRG spheroids cultured in alginate microcapsules to investigate the role of autophagy in BDE-47-mediated hepatotoxicity. We developed mature and functional HepaRG spheroids by culturing them in alginate microcapsules. Histological analysis revealed that HepaRG spheroids formed an extracellular matrix and stored glycogen. No apoptotic and/or necrotic cores were observed. BDE-47 showed concentration- and time-dependent cytotoxicity in HepaRG spheroids. In the early exposure period, BDE-47 initially disrupted mitochondrial activity and increased the formation of acid compartments that promoted the increase in autophagic activity; however, this autophagy was blocked, and long-term exposure to BDE-47 promoted efficient apoptotic cell death through autophagy blockade, as evidenced by an increased number of fragmented/condensed nuclei. Therefore, for the first time, we demonstrated BDE-47 toxicity and its cell pathway induces cell death using a three-dimensional liver cell culture, the HepaRG cell line.

Bioaccumulation of polystyrene nanoplastics and BDE-209 induced oxidative stress, photosynthesis and growth impairments in floating fern Salvinia natans

Aquatic ecosystems are facing increasing exposure to pollutants, posing potential threats to the stability and wellness of aquatic species. This study focused on evaluating the impacts of single and combined exposure to 80 nm polystyrene nanoplastics (PS-NPs, 0.1, 1, 10, 20 mg/L) and decabromodiphenyl ether (BDE-209, 300 ng/L) for 14 days on the bioaccumulation, growth, photosynthesis and oxidative stress in the free-floating fern Salvinia natans. PS-NPs primarily accumulated in the epidermis and trichomes of S. natans. Meanwhile, the levels of superoxide dismutase (SOD) and malondialdehyde (MDA) were significantly increased, while those for peroxidase (POD), catalase (CAT), total antioxidant capacity (T-AOC), and relative growth rate (RGR) decreased. Furthermore, the chlorophyll contents in submerged leaves were decreased, while those in floating leaves were increased at PS-NPs concentrations of 0.1 and 1 mg/L. However, the chlorophyll contents in both submerged and floating leaves displayed a decreasing trend with increasing concentrations of PS-NPs. Under the co-exposure of PS-NPs and BDE-209, the contents of MDA were significantly elevated, whereas CAT, POD, SOD, T-AOC and RGR were significantly decreased (p < 0.05). Our results revealed that, compared to single exposure, more pronounced ecotoxic effects are observed in S. natans under co-exposure to PS-NPs and BDE-209. These findings offer valuable perspectives into the possible environmental risks of BDE-209 and PS-NPs in freshwater ecosystems, contributing to the development of effective management strategies for protecting aquatic organisms and ecosystems. This research highlights the urgent need to understand the toxic effects of emerging contaminants on different aquatic organisms, emphasizing the importance of protecting and preserving aquatic ecosystems.

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.

PLASTAMINATION: Outcomes on the Central Nervous System and Reproduction

BACKGROUND

Environmental exposures to non-biodegradable and biodegradable plastics are unavoidable. Microplastics (MPs) and nanoplastics (NPs) from the manufacturing of plastics (primary sources) and the degradation of plastic waste (secondary sources) can enter the food chain directly or indirectly and, passing biological barriers, could target both the brain and the gonads. Hence, the worldwide diffusion of environmental plastic contamination (PLASTAMINATION) in daily life may represent a possible and potentially serious risk to human health.

OBJECTIVE

This review provides an overview of the effects of non-biodegradable and the more recently introduced biodegradable MPs and NPs on the brain and brain-dependent reproductive functions, summarizing the molecular mechanisms and outcomes on nervous and reproductive organs. Data from in vitro, ex vivo, non-mammalian and mammalian animal models and epidemiological studies have been reviewed and discussed.

RESULTS

MPs and NPs from non-biodegradable plastics affect organs, tissues and cells from sensitive systems such as the brain and reproductive organs. Both MPs and NPs induce oxidative stress, chronic inflammation, energy metabolism disorders, mitochondrial dysfunction and cytotoxicity, which in turn are responsible for neuroinflammation, dysregulation of synaptic functions, metabolic dysbiosis, poor gamete quality, and neuronal and reproductive toxicity. In spite of this mechanistic knowledge gained from studies of non-biodegradable plastics, relatively little is known about the adverse effects or molecular mechanisms of MPs and NPs from biodegradable plastics.

CONCLUSION

The neurological and reproductive health risks of MPs/NPs exposure warrant serious consideration, and further studies on biodegradable plastics are recommended.

2,2',4,4'-tetrabromodiphenyl ether causes depigmentation in zebrafish larvae via a light-mediated pathway

Polybrominated diphenyl ethers (PBDEs) are organic pollutants widely detected in various environmental media due to their high persistence and bioaccumulation. PBDE-induced visual impairment and neurotoxicity were previously demonstrated using zebrafish (Danio rerio) models, and recent research reported the phenotypic depigmentation effect of PBDEs at high concentrations on zebrafish, but whether those effects are still present at environment-relevant levels is still unclear. Herein, we performed both phenotypic examination and mechanism investigation in zebrafish embryos (48 hpf) and larvae (5 dpf) about their pigmentation status when exposing to PBDE congener BDE-47 (2,2',4,4'-tetrabrominated diphenyl ether) at levels from 0.25 to 25 μg/L. Results showed that low-level BDE-47 can restrain the relative melanin abundance of zebrafish larvae to 70.47% (p < 0.05) and 61.54% (p < 0.01) respectively under 2.5 and 25 μg/L BDE-47 compared with control, and the thickness of retinal pigment epithelium (RPE) remarkably reduced from 571.4 nm to 350.3 nm (p < 0.001) under 25 μg/L BDE-47 exposure. We also observed disrupted expressions of melanin synthesis genes and disorganized mitfa differentiation patterns based on Tg(mifta:EGFP), as well as visual impairment resulting from thinner RPE. Considering both processes of visual development and melanin synthesis are highly sensitive to ambient light conditions, we prolonged the light regime of maintaining zebrafish larvae from 14 hours light versus 10 hours dark (14L:10D) to 18 hours light versus 6 hours dark (18L:6D). Lengthening photoperiod successfully rescued the fluorescent level of mitfa in zebrafish epidermis and most gene expressions associated with melanin synthesis under 25 μg/L BDE-47 exposure to the normal level. In conclusion, our work reported the effects of low-level PBDEs on melanin production using zebrafish embryos and larvae, and identified the potential role of a light-mediated pathway in the neurotoxic mechanism of PBDEs.

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.

The Other Side of Plastics: Bioplastic-Based Nanoparticles for Drug Delivery Systems in the Brain

Plastics have changed human lives, finding a broad range of applications from packaging to medical devices. However, plastics can degrade into microscopic forms known as micro- and nanoplastics, which have raised concerns about their accumulation in the environment but mainly about the potential risk to human health. Recently, biodegradable plastic materials have been introduced on the market. These polymers are biodegradable but also bioresorbable and, indeed, are fundamental tools for drug formulations, thanks to their transient ability to pass through biological barriers and concentrate in specific tissues. However, this "other side" of bioplastics raises concerns about their toxic potential, in the form of micro- and nanoparticles, due to easier and faster tissue accumulation, with unknown long-term biological effects. This review aims to provide an update on bioplastic-based particles by analyzing the advantages and drawbacks of their potential use as components of innovative formulations for brain diseases. However, a critical analysis of the literature indicates the need for further studies to assess the safety of bioplastic micro- and nanoparticles despite they appear as promising tools for several nanomedicine applications.

The emerging role of microplastics in systemic toxicity: Involvement of reactive oxygen species (ROS)

Plastic pollution is one of the most pressing environmental threats the world is facing currently. The degradation of macroplastics into smaller forms viz. microplastics (MPs) or Nanoplastics (NPs) is a potential threat to both terrestrial and marine ecosystems and also to human health by directly affecting the organs and activating a plethora of intracellular signaling, that may lead to cell death. There is accumulating evidence that supports the serious toxicity caused by MP/NPs at all levels of biological complexities (biomolecules, organelles, cells, tissues, organs, and organ systems) and the involvement of the reactive oxygen species (ROS) in this process. Studies indicate that MPs or NPs can accumulate in mitochondria and further disrupt the mitochondrial electron transport chain, cause mitochondrial membrane damage, and perturb the mitochondrial membrane potential or depolarization of the mitochondria. These events eventually lead to the generation of different types of reactive free radicals, which can induce DNA damage, protein oxidation, lipid peroxidation, and compromization of the antioxidant defense pool. Furthermore, MP-induced ROS was found to trigger a plethora of signaling cascades, such as the p53 signaling pathway, Mitogen-activated protein kinases (MAPKs) signaling pathway including the c-Jun N-terminal kinases (JNK), p38 kinase, and extracellular signal related kinases (ERK1/2) signaling cascades, Nuclear factor erythroid 2-related factor 2 (Nrf2)-pathway, Phosphatidylinositol-3-kinases (PI3Ks)/Akt signaling pathway, and Transforming growth factor-beta (TGF-β) pathways, to name a few. As a consequence of oxidative stress caused by the MPs/NPs, different types of organ damage are observed in living species, including humans, such as pulmonary toxicity, cardiotoxicity, neurotoxicity, nephrotoxicity, immunotoxicity, reproductive toxicity, hepatotoxicity, etc. Although presently, a good amount of research is going on to access the detrimental effects of MPs/NPs on human health, there is a lack of proper model systems, multi-omics approaches, interdisciplinary research, and mitigation strategies.

Impact and mitigation of lead, cadmium and micro/nano plastics in fragrant rice

Heavy metals (HMs) and micro(nano)plastics (MNPs), represent a significant risk to global food supply as well as a potential risk to humankind. Over 50% of the worldwide population eat rice every day, and rice aroma is a significant qualitative trait that is highly valued by consumers and fetches premium prices in the global market. Despite the huge commercial importance of fragrant rice, limited studies were directed to investigate the influence of HMs and MNPs on yield related traits and 2-Acetyl-1-pyrroline (2-AP) compound, mainly responsible for aroma production in fragrant rice. In this review, we found that the interaction of HMs and MNPs in fragrant rice is complex and accumulation of HMs and MNPs was higher in root as compared to the grains. Nutrients and phytohormones mediated mitigation of HMs and MNPs were most effective sustainable strategies. In addition, monitoring the checkpoints of 2-AP biosynthesis and its interaction with HMs and MNPs is challenging. Finally, we explained the potential challenges that fragrant rice faces considering the continuous rise in environmental pollutants and discussed the future avenues of research to improve fragrant rice's yield and qualitative traits.

Toxic Effects and Mechanisms of Polybrominated Diphenyl Ethers

Polybrominated diphenyl ethers (PBDEs) are a group of flame retardants used in plastics, textiles, polyurethane foam, and other materials. They contain two halogenated aromatic rings bonded by an ester bond and are classified according to the number and position of bromine atoms. Due to their widespread use, PBDEs have been detected in soil, air, water, dust, and animal tissues. Besides, PBDEs have been found in various tissues, including liver, kidney, adipose, brain, breast milk and plasma. The continued accumulation of PBDEs has raised concerns about their potential toxicity, including hepatotoxicity, kidney toxicity, gut toxicity, thyroid toxicity, embryotoxicity, reproductive toxicity, neurotoxicity, and immunotoxicity. Previous studies have suggested that there may be various mechanisms contributing to PBDEs toxicity. The present study aimed to outline PBDEs' toxic effects and mechanisms on different organ systems. Given PBDEs' bioaccumulation and adverse impacts on human health and other living organisms, we summarize PBDEs' effects and potential toxicity mechanisms and tend to broaden the horizons to facilitate the design of new prevention strategies for PBDEs-induced toxicity.

Developmental toxicity of the emerging contaminant cyclophosphamide and the integrated biomarker response (IBRv2) in zebrafish

The safety of cyclophosphamide (CP) in the early developmental stages is not studied yet; it is important to study the responses at these stages because they might have relevance to CP-administered humans. We studied the developmental toxicity of CP by analysing physiological, morphological, and oxidative stress, neurotransmission enzymes, gene expression and histological endpoints in zebrafish embryos/larvae. The study lasted for 120 hpf at environmentally relevant concentrations of CP. No visible alterations were noticed in the control group. Delayed hatching, slow heart rate, yolk sac oedema, pericardial oedema, morphological deformities, the incompetence of oxidative stress biomarkers, excessive generation of ROS, apoptosis, inhibition of neurotransmitters and histopathological anomalies were observed in CP-treated groups. These alterations were found to be concentration- and duration-dependent effects for physiological and morphological endpoints, whereas concentration-dependent effects were antioxidants, ROS, apoptosis and histological endpoints. Biomarkers and gene expression were standardised using the integrated biomarker response-IBRv2 index. The IBRv2 index showed a concentration-dependent behaviour. A non-lethal developmental and teratogenic effect was observed in CP-treated zebrafish embryos/larvae at the studied concentrations. The studied biomarkers are sensitive, and the responses are interrelated; thus, their responses are useful to assess veiled and unseen hazards of pharmaceuticals.

BDE-47 Induces Mitochondrial Dysfunction and Endoplasmic Reticulum Stress to Inhibit Early Porcine Embryonic Development

Widely used as a flame retardant, 2,2'4,4'-tetrabromodiphenyl ether (BDE-47) is a persistent environmental pollutant with toxicological effects, including hepatotoxicity, neurotoxicity, reproductive toxicity, and endocrine disruption. To investigate the toxicological effects of BDE-47 on early porcine embryogenesis in vitro, cultured porcine embryos were exposed to BDE-47 during early development. Exposure to 100 μM BDE-47 decreased the blastocyst rate and mRNA level of pluripotency genes but increased the level of LC3 and the expression of autophagy-related genes. After BDE-47 exposure, porcine embryos' antioxidant capability decreased; ROS levels increased, while glutathione (GSH) levels and the expression of antioxidant-related genes decreased. In addition, BDE-47 exposure reduced mitochondrial abundance and mitochondrial membrane potential levels, downregulated mitochondrial biogenesis-associated genes, decreased endoplasmic reticulum (ER) abundance, increased the levels of GRP78, a marker of ER stress (ERS), and upregulated the expression of ERS-related genes. However, ER damage and low embryo quality induced by BDE-47 exposure were reversed with the ERS inhibitor, the 4-phenylbutyric acid. In conclusion, BDE-47 inhibits the development of early porcine embryos in vitro by inducing mitochondrial dysfunction and ERS. This study sheds light on the mechanisms of BDE-47-induced embryonic toxicity.

Interactive effects of polystyrene nanoplastics and 6:2 chlorinated polyfluorinated ether sulfonates on the histomorphology, oxidative stress and gut microbiota in Hainan Medaka (Oryzias curvinotus)

Nanoplastics adsorb surrounding organic contaminants in the environment, which alters the physicochemical properties of contaminants and affects associated ecotoxicological effects on aquatic life. The current work aims to explore the individual and combined toxicological implications of polystyrene nanoplastics (80 nm) and 6:2 chlorinated polyfluorinated ether sulfonate (Cl-PFAES, trade name: F-53B) in an emerging freshwater fish model Hainan Medaka (Oryzias curvinotus). Therefore, O. curvinotus were exposed to 200 μg/L of PS-NPs or 500 μg/L of F-53B in the single or mixture exposure for 7 days to investigate the effects on fluorescence accumulation, tissue damage, antioxidant capacity and intestinal flora. The PS-NPs fluorescence intensity was significantly higher in the single exposure treatment than it in combined exposure treatment (p < 0.01). Histopathological results showed that exposure to PS-NPs or F-53B inflicted varying degree of damages to the gill, liver, and intestine, and these damage were also present in the corresponding tissues of the combined treatment group, illustrating a stronger extent of destruction of these tissues by the combined treatment. Compared to the control group, combined exposure group elevated the malondialdehyde (MDA) content, superoxide dismutase (SOD) and catalase (CAT) activities except in the gill. In addition, the adverse contribution of PS-NPs and F-53B on the enteric flora in the single and combined exposure groups was mainly characterised in the form of reductions in the number of probiotic bacteria (Firmicutes) and this reduction was aggravated by the combined exposure group. Collectively, our results indicated that the toxicological effects of PS-NPs and F-53B on pathology, antioxidant capacity and microbiomics of medaka may be modulated by the interaction of two contaminants with mutually interactive effects. And our work offers fresh information on the combined toxicity of PS-NPs and F-53B to aquatic creatures along with a molecular foundation for the environmental toxicological mechanism.