Enrichment of polystyrene microplastics induces histological damage, oxidative stress, Keap1-Nrf2 signaling pathway-related gene expression in loach juveniles (Paramisgurnus dabryanus)

Mechanisms insights into bisphenol S-induced oxidative stress, lipid metabolism disruption, and autophagy dysfunction in freshwater crayfish

Bisphenol S (BPS) is widely used in plastic products, food packaging, electronic products, and other applications. In recent years, BPS emissions have increasingly impacted aquatic ecosystems. The effects of BPS exposure on aquatic animal health have been documented; however, our understanding of its toxicology remains limited. This study aimed to explore the mechanisms of lipid metabolism disorders, oxidative stress, and autophagy dysfunction induced in freshwater crayfish (Procambarus clarkii) by exposure to different concentrations of BPS (0 µg/L, 1 µg/L, 10 µg/L, and 100 µg/L) over 14 d. The results indicated that BPS exposure led to oxidative stress by inducing elevated levels of reactive oxygen species (ROS) and inhibiting the activity of antioxidant-related enzymes. Additionally, BPS exposure led to increased lipid content in the serum and hepatopancreas, which was associated with elevated lipid-related enzyme activity and increased expression of related genes. Furthermore, BPS exposure decreased levels of phosphatidylcholine (PC) and phosphatidylinositol (PI), disrupted glycerophospholipid (GPI) metabolism, and caused lipid deposition in the hepatopancreatic. These phenomena may have occurred because BPS exposure reduced the transport of fatty acids and led to hepatopancreatic lipid deposition by inhibiting the transport and synthesis of PC and PI in the hepatopancreas, thereby inhibiting the PI3K-AMPK pathway. In conclusion, BPS exposure induced oxidative stress, promoted lipid accumulation, and led to autophagy dysfunction in the hepatopancreas of freshwater crayfish. Collectively, our findings provide the first evidence that environmentally relevant levels of BPS exposure can induce hepatopancreatic lipid deposition through multiple pathways, raising concerns about the potential population-level harm of BPS and other bisphenol analogues.

Integrated transcriptomics and proteomics analyses reveal the ameliorative effect of hepatic damage in tilapia caused by polystyrene microplastics with chlorella addition

Fish exhibit varying responses to polystyrene microplastics (MPs) depending on particle size. Previous studies suggested that microorganisms adhering to the surface of MPs can induce toxic effects. In this study, Tilapia were exposed to MPs of control (group A), 75 nm (B), 7.5 μm (C), 750 μm (D), as well as combinations of all sizes (E) and 75 nm MPs with Chlorella vulgaris addition (F) for 7, 10 and 14 days. Histopathological changes in liver of tilapia were assessed using enzyme activities, transcriptomics and proteomics. The results showed that in groups combined MPs of different particle sizes and those supplemented with chlorella, MPs were localized on the surface of goblet cells, leading to vacuoles, constricted hepatic sinuses and nuclei displacement. Exposure to 7.5 and 750 μm MPs significantly increased the contents of fatty acid synthase (FAS), adenosine triphosphate (ATP), acetyl-CoA carboxylase (ACC), lipoprotein lipase (LPL), total cholesterol (TC), total triglyceride (TG) contents at 7 and 10 days. In particular, cytochrome p450 1a1 (EROD), reactive oxygen species (ROS) and superoxide dismutase (SOD) were markedly elevated following exposure to MPs. Apoptotic markers caspase-3, and inflammatory markers, including tumor necrosis factor α (TNF-α) and interleukin-1β (IL-1β), had a similar upward trend in comparisons of group C vs A at 7 d, group D vs A at 14 d. The peroxisome proliferator activated receptor (PPAR) signaling pathway, spliceosome, was highly enriched during the 7-day exposure of medium sized MPs, while largest MPs in the comparison of group D vs A at 14 d activated pathways such as phagosome, apoptosis, salmonella infection. Transcriptomic analysis revealed that after 14 days, the kyoto encyclopedia of genes and genomes (KEGG) pathways associated with protein processing in endoplasmic reticulum and the PPAR signaling has been significantly enriched in the Chlorella-supplemented group, which was further confirmed via the proteomic analysis. Overall, the findings highlight the size-dependent effects of MPs on histopathological changes, gene and protein expression in the liver of tilapia, and C. vulgaris effectively attenuated liver damages, likely through modulation of endoplasmic reticulum protein processing and PPAR signaling pathways.

Environmental toxicology of microplastic particles on fish: A review

The increase in plastic debris and its environmental impact has been a major concern for scientists. Physical destruction, chemical reactions, and microbial activity can degrade plastic waste into particles smaller than 5 mm, known as microplastics (MPs). MPs may eventually enter aquatic ecosystems through surface runoff. The accumulation of MPs in aquatic environments poses a potential threat to finfish, shellfish, and the ecological balance. This study investigated the effect of MP exposure on freshwater and marine fish. MPs could cause significant harm to fish, including physical damage, death, inflammation, oxidative stress, disruption of cell signalling and cellular biochemical processes, immune system suppression, genetic damage, and reduction in fish growth and reproduction rates. The activation of the detoxification system of fish exposed to MPs may be associated with the toxicity of MPs and chemical additives to plastic polymers. Furthermore, MPs can enhance the bioavailability of other xenobiotics, allowing these harmful substances to more easily enter and accumulate in fish. Accumulation of MPs and associated chemicals in fish can have adverse effects on the fish and humans who consume them, with these toxic substances magnifying as they move up the food chain. Changes in migration and reproduction patterns and disruptions in predator-prey relationships in fish exposed to MPs can significantly affect ecological dynamics. These interconnected changes can lead to cascading effects throughout aquatic ecosystems. Thus, implementing solutions like reducing plastic production, enhancing recycling efforts, using biodegradable materials, and improving waste management is essential to minimize plastic waste and its environmental impact.

The impacts of microplastics on zebrafish behavior depend on initial personality state

Microplastic pollution is associated with inflammation, gut dysbiosis and behavioral changes in fish. Fish have distinct personality traits but the role of personality in behavioral toxicology is rarely considered. We classified zebrafish on four behavioral axes: boldness, anxiety, sociability and exploration tendency then exposed them to low- or high- concentrations of two types of polyethylene microplastics (low- and high-density) for 28 days. Behaviors, antioxidant enzymes (catalase and superoxide dismutase), and gut microbiome were then measured. There were direct effects of microplastics on boldness, anxiety and sociability. However, fish retained their initial behavioral tendencies. Exposure to all microplastic treatments reduced average swimming speed and decreased the time spent motionless. Microplastic exposure did not affect antioxidant enzymes but did cause significant changes in the composition of the gut microbiome. This study demonstrates that environmentally realistic concentrations of microplastics can alter fish behavior, but much of the variance in response can be explained by personality.

Exposure to polystyrene nanoplastics induces hepatotoxicity involving NRF2-NLRP3 signaling pathway in mice

Nanoplastic contamination has been of intense concern by virtue of the potential threat to human and ecosystem health. Animal experiments have indicated that exposure to nanoplastics (NPs) can deposit in the liver and contribute to hepatic injury. To explore the mechanisms of hepatotoxicity induced by polystyrene-NPs (PS-NPs), mice and AML-12 hepatocytes were exposed to different dosages of 20 nm PS-NPs in this study. The results illustrated that in vitro and in vivo exposure to PS-NPs triggered excessive production of reactive oxygen species and repressed nuclear factor erythroid-derived 2-like 2 (NRF2) antioxidant pathway and its downstream antioxidase expression, thus leading to hepatic oxidative stress. Moreover, PS-NPs elevated the levels of NLRP3, IL-1β and caspase-1 expression, along with an activation of NF-κB, suggesting that PS-NPs induced hepatocellular inflammatory injury. Nevertheless, the activaton of NRF2 signaling by tert-butylhydroquinone mitigated PS-NPs-caused oxidative stress and inflammation, and inbihited NLRP3 and caspase-1 expression. Conversely, the rescuing effect of NRF2 signal activation was dramatically supressed by treatment with NRF2 inhibitor brusatol. In summary, our results demonstrated that NRF2-NLRP3 pathway is involved in PS-NPs-aroused hepatotoxicity, and the activation of NRF2 signaling can protect against PS-NPs-evoked liver injury. These results provide novel insights into the hepatotoxicity elicited by NPs exposure.

Polystyrene microplastics promote intestinal colonization of Aeromonas veronii through inducing intestinal microbiota dysbiosis

The premise that pathogen colonized microplastics (MPs) can promote the spread of pathogens has been widely recognized, however, their role in the colonization of pathogens in a host intestine has not been fully elucidated. Here, we investigated the effect of polystyrene MPs (PS-MPs) on the colonization levels of Aeromonas veronii, a typical aquatic pathogen, in the loach (Misgurnus anguillicaudatus) intestine. Multiple types of MPs were observed to promote the intestinal colonization of A. veronii, among which PS-MPs exhibited the most significant stimulating effect (67.18% increase in A. veronii colonization). PS-MPs inflicted serious damage to the intestinal tracts of loaches and induced intestinal microbiota dysbiosis. The abundance of certain intestinal bacteria with resistance against A. veronii colonization decreased, with Lactococcus sp. showing the strongest colonization resistance (73.64% decline in A. veronii colonization). Fecal microbiota transplantation was performed, which revealed that PS-MPs induced intestinal microbiota dysbiosis was responsible for the increased colonization of A. veronii in the intestine. It was determined that PS-MPs reshaped the intestinal microbiota community to attenuate the colonization resistance against A. veronii colonization, resulting in an elevated intestinal colonization levels of A. veronii.

Liver Injury Induced by Exposure to Polystyrene Microplastics Alone or in Combination with Cadmium in Mice Is Mediated by Oxidative Stress and Apoptosis

Microplastics (MPs) have been considered an emerging environmental pollutant which, when combined with toxic metals, enter the circulatory system of mammals and eventually cause damage. Therefore, it is important to study the toxicity of the mixture of MPs and heavy metals for evaluating risk assessment of mammals. In the present study, the toxicological effects of different concentrations of polystyrene (PS)-MPs alone or in combination with cadmium chloride (CdCl2) during chronic exposure (8 weeks) were evaluated using intragastric administration in mice. Using comparative analysis, it was revealed that PS-MPs alone or in combination with Cd could destroy the normal structural morphology of liver tissue and increase the levels of two biochemical indicators of liver damage, thereby inducing changes in antioxidant and hyperoxide capacities. In addition, PS-MPs and/or Cd activated the antioxidant signaling pathway Nrf2-Keap1 and affected the endogenous apoptosis signaling pathway p53-Bcl-2/Bax, thus promoting apoptosis. These findings suggested that exposure to MPs alone or in combination with Cd led to adverse effects on the liver. Furthermore, it was revealed that co-exposure to MPs and Cd reduced Cd toxicity, thereby highlighting the possibility MPs may act as carriers of other toxic substances and coordinate with them. Therefore, evaluating the synergistic or anti-agonistic effects of MPs on the toxicity and bioavailability of xenobiotics is in the future critical in environmental toxicological studies.

Hazards of microplastics exposure to liver function in fishes: A systematic review and meta-analysis

Microplastics (5 mm - 1 μm) have become one of the major pollutants in the environment. Numerous studies have shown that microplastics can have negative impacts on aquatic organisms, affecting their liver function levels. However, the extent of these effects and their potential toxicological mechanisms are largely unknown. In this study, a meta-analysis and systematic review were conducted to assess the effects of microplastics on fish liver function and summarize the potential toxicological mechanisms of microplastic-induced liver toxicity. The meta-analysis results indicate that compared to the control group, exposure to microplastics significantly affects fish liver indicators: aspartate aminotransferase (AST) (p < 0.001), alanine aminotransferase (ALT) (p < 0.001), alkaline phosphatase (ALP) (p < 0.001), total protein (TP) (p < 0.001), and lactate dehydrogenase (LDH) (p < 0.001), including oxidative stress indicators: superoxide dismutase (SOD) (p < 0.001), glutathione S-transferase (GST) (p < 0.001), glutathione (GSH) (p < 0.001), and malondialdehyde (MDA) (p < 0.001) in fish liver. For fish living in different environments, the potential toxicological mechanisms of microplastics exposure on fish liver may exhibit some differences. For freshwater fish, the mechanism may be that microplastics exposure causes overproduction of reactive oxygen species (ROS) in fish hepatocyte mitochondria. ROS promotes the expression of toll-like receptor 2 (TLR2) and activates downstream molecules myeloid differentiation factor 88 (MyD88) and tumor necrosis factor receptor-associated factor 6 (TRAF6) of the TLR2 signaling pathway, leading to phosphorylation of NF-κB p65. This leads to the release of inflammatory factors and oxidative stress and inflammation in fish liver. In addition, for seawater fish, the mechanism may be that microplastics exposure can cause damage or death of fish hepatocytes, leading to continuous pathological changes, inflammation, lipid and energy metabolism disorders, thereby causing significant changes in liver function indexes.

Microplastic-induced NAFLD: Hepatoprotective effects of nanosized selenium

Polystyrene microplastics (MPs) are persistent environmental pollutants commonly encountered in daily human life. Numerous studies have demonstrated their ability to induce liver damage, including oxidative stress, inflammation, and lipid accumulation. However, limited information exists regarding preventive measures against this issue. In our study, we investigated the potential preventive role of selenium nanoparticles (YC-3-SeNPs) derived from Yak-derived Bacillus cereus, a novel nanobiomaterial known for its antioxidant properties and lipid metabolism regulation. Using transcriptomic and metabolomic analyses, we identified key genes and metabolites associated with oxidative stress and lipid metabolism imbalance induced by MPs. Upregulated genes (Scd1, Fasn, Irs2, and Lpin) and elevated levels of arachidonic and palmitic acid accumulation were observed in MP-exposed mice, but not in those exposed to SeNPs. Further experiments confirmed that SeNPs significantly attenuated liver lipid accumulation and degeneration caused by MPs. Histological results and pathway screening validated our findings, revealing that MPs suppressed the Pparα pathway and Nrf2 pathway, whereas SeNPs activated both pathways. These findings suggest that MPs may contribute to the development of nonalcoholic fatty liver disease (NAFLD), while SeNPs hold promise as a future nanobio-product for its prevention.

Salvia miltiorrhiza Bunge extract and Przewalskin ameliorate Bleomycin-induced pulmonary fibrosis by inhibition of apoptosis, oxidative stress and collagen deposition via the TGF-β1 pathway

BACKGROUND

Salvia miltiorrhiza Bunge (Labiatae) (DS) is a key part of the traditional Chinese medicine, whose roots are used to remove blood stasis, relieve pain, eliminate carbuncle and calm the nerves. Our research team found that the DS extract could significantly reverse LPS-induced lung injury, and five new diterpenoid quinones in DS extract with excellent lung protective activity for the first time. However, the material basis and mechanism of DS on pulmonary fibrosis (PF) needs to be explored in depth.

OBJECTIVE

Bleomycin (BLM) was employed to establish the PF model, and Transcriptome and Surface plasmon resonance (SPR) ligand fishing technology were used to explore the material basis and mechanism of DS on PF, and provided theoretical research for clinical treatment of PF.

METHODS

DS extract (24.58 or 49.16 mg/kg, i.g.) was administered daily from Day 8 to Day 28, followed by intratracheal BLM drip (5 mg/kg) to induce PF. Data about the influences of DS on PF were collected by transcriptome sequencing technology. Pulmonary ultrasound, airway responsiveness, lung damage, collagen deposition, and the levels of TNF-α, IL-1β, apoptosis, oxidative stress (OS), immune cells, TGF-β1, α-SMA, E-Cadherin and Collage Ⅰ were examined. The affinity component (Przewalskin) in DS extract targeted by TGF-β1 was fished by SPR ligand fishing technology. Furthermore, an in vivo PF mouse model and an in vitro TGF-β1 induced BEAS-2B cell model were established, to explore the mechanism of Przewalskin on PF from the apoptosis, OS and epithelial mesenchymal transformation pathway.

RESULTS

DS extract improved pulmonary ultrasound, reduced lung damage and collagen deposition, downregulated TNF-α, IL-1β, apoptosis, OS, TGF-β1, α-SMA, E-Cadherin and Collage Ⅰ, transformed immune cells following Bleomycin challenge. Furthermore, affinity component (Przewalskin) also improved pulmonary ultrasound and airway responsiveness, reduced lung damage and collagen deposition, downregulated TNF-α, IL-1β, apoptosis, OS in vivo and in vitro.

CONCLUSION

Analysis using a mouse model revealed that DS extract and Przewalskin can relieve clinical symptoms of PF, reduce lung injury and improve lung function. Meanwhile, DS extract and Przewalskin can improve BLM-induced PF by inhibition of, OS, apoptosis and collagen deposition might via the TGF-β1 pathway. This study provides references to identification of novel therapeutic targets, thereby facilitating drug development for PF.

Synergistic effect of PS-MPs and Cd on male reproductive toxicity: Ferroptosis via Keap1-Nrf2 pathway

It has been wildly reported that microplastics (MPs) can adsorb heavy metals and act as carriers for their transport into organisms. However, the combined toxicity of MPs and heavy metals remains poorly studied. In this study, we established single or co-exposure (i.e. complex/combined exposure) mice models to investigate the combined toxicity of MPs and cadmium (Cd) on male reproduction. The complexation of MPs and Cd enhanced the bioavailability of Cd, while the combination of MPs and Cd exerted synergistic effect. Ultimately, the co-exposure was reported to enhance the reproduction toxicity by single exposure, which reflected in testicular structure, spermatogenesis and sex hormone synthesis. More in-depth mechanistic investigation suggested that MPs and Cd synergistically inhibited the Keap1-Nrf2 pathway and its downstream genes, induced lipid peroxidation and ferroptosis, ultimately caused damage to reproductive structures and functions. Our results highlighted the synergistic effect of MPs and Cd on the reproductive toxicity in male mammals for the first time, which also provided valuable insights into the combined toxicity mechanisms of MPs and other pollutants.

Microplastics in aquaculture systems: Occurrence, ecological threats and control strategies

With the intensification of microplastic pollution globally, aquaculture environments also face risks of microplastic contamination through various pathways such as plastic fishing gear. Compared to wild aquatic products, cultured aquatic products are more susceptible to microplastic exposure through fishing tackle, thus assessing the impacts of microplastics on farmed species and human health. However, current research on microplastic pollution and its ecological effects in aquaculture environments still remains insufficient. This article comprehensively summarizes the pollution characteristics and interrelationships of microplastics in aquaculture environments. We analyzed the influence of microplastics on the sustainable development of the aquaculture industry. Then, the potential hazards of microplastics on pond ecosystems and consumer health were elucidated. The strategies for removing microplastics in aquaculture environments are also discussed. Finally, an outlook on the current challenge and the promising opportunities in this area was proposed. This review aims to evaluate the value of assessing microplastic pollution in aquaculture environments and provide guidance for the sustainable development of the aquaculture industry.

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.

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

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

Polystyrene Microplastics Induce Oxidative Stress in Mouse Hepatocytes in Relation to Their Size

Microplastics have become a new type of environmental pollutant that can accumulate in various tissues and organs of the body and cause chronic damage. In this study, two different size polystyrene microplastics (PS-MPs, 5 μm and 0.5 μm) exposure models were established in mice to investigate the effects of PS-MPs with different particle sizes on oxidative stress in the liver. The results showed that PS-MPs exposure caused a decrease in body weight and liver-to-body weight. The hematoxylin and eosin staining and transmission electron microscopy results showed that exposure to PS-MPs led to the disorganized cellular structure of liver tissue, nuclear crinkling, and mitochondrial vacuolation. The extent of damage in the 5 μm PS-MP exposure group was more extensive when compared with the other group. The evaluation of oxidative-stress-related indicators showed that PS-MPs exposure exacerbated oxidative stress in hepatocytes, especially in the 5 μm PS-MPs group. The expression of oxidative-stress-related proteins sirtuin 3(SIRT3) and superoxide dismutase (SOD2) was significantly reduced, and the reduction was more pronounced in the 5 μm PS-MPs group. In conclusion, PS-MPs exposure led to oxidative stress in mouse hepatocytes and caused more severe damage in the 5 μm PS-MPs group when compared with the 0.5 μm PS-MPs group.

Chronic nanoplastic exposure induced oxidative and immune stress in medaka gonad

Nanoplastic (NP) pollution is a global issue because of its widespread occurrence and potential toxicity. Many studies have investigated the impacts of the short-term toxicity of NPs on organisms. Until now, only a few studies have assessed the toxicological effects of prolonged exposure to NPs at low concentrations in fish. In this study, the effects of NPs (nano-polystyrene microspheres, diameter: 100 nm) on immune and oxidative stress response, histopathology, and survival in medaka were evaluated. The effects of different concentrations (0, 10, 10⁴, and 10⁶ particles/L) of nanoplastics were studied in medaka Oryzias latipes after 3 months of exposure. Lysozyme enzyme activity, oxidative stress-related biomarkers (i.e., superoxide dismutase, catalase, and glutathione peroxidase), and malondialdehyde levels were decreased under NP exposure. The gonadal histology showed that high NP exposure (10⁶ particles/L) inhibited the process of spermatogenesis and oogenesis processes, implying delayed maturation of the gonad. Furthermore, the IBR and PCA analysis revealed the potential biotoxicity of NPs and the total survival rate of medaka was significantly reduced due to the long-term exposure to NPs. Overall, prolonged exposure to low concentrations of NPs is harmful to the health of medaka gonads. In the long run, this may threaten the fish reproduction and population, suggesting the need for long-term toxicological studies to predict the aquatic animal health in nature.

Microplastics inhibit biofloc formation and alter microbial community composition and nitrogen transformation function in aquaculture

Biofloc technology, extensively used in intensive aquaculture systems, can prompt the formation of microbial aggregates. Microplastics (MPs) are detected abundantly in aquaculture waters. This study explored the effects of MPs on biofloc formation, microbial community composition and nitrogen transformation function in simulated biofloc aquaculture production systems. The formation process and settling performance of bioflocs were examined. High-throughput sequencing of 16S and 18S rRNA genes was used to investigate the microbial community compositions of bioflocs. Nitrogen dynamics were monitored and further explained from functional genes and microorganisms related to nitrogen transformation by metagenome sequencing. We found that the aggregates consisting of bioflocs and MPs were formed and the systems with MPs had relatively weak settling performance. No significant differences in bacterial diversity (p > 0.05) but significant differences in eukaryotic diversity (p < 0.05) were found between systems without and with MPs. Significant separations in the microbial communities of prokaryotes (p = 0.01) and eukaryotes (p = 0.01) between systems without and with MPs were observed. The peak concentration of nitrite nitrogen (NO₂^--N) in systems with MPs was lower than that in systems without MPs (p_{Control/MPs Low} = 0.02 and p_{Control/MPs High} = 0.03), probably due to the low abundance of hao and affiliated Alphaproteobacteria_bacterium_HGW-Alphaproteobacteria-1 and Alphaproteobacteria_bacterium, but the high abundance of nxrA and affiliated Alphaproteobacteria_bacterium_SYSU_XM001 and Hydrogenophaga_pseudoflava that related to nitrification. The low concentration of NO₂^--N in systems with MPs suggested that the presence of MPs might inhibit ammonia oxidation but promote nitrite oxidation by altering the microbial community structure and function. These results indicated that aggregates consisting of bioflocs and MPs could be formed in aquaculture water, and thus, inhibiting their settlement and altering nitrogen transformation function by affecting the microbial community composition.

A review of microplastic pollution in aquaculture: Sources, effects, removal strategies and prospects

As microplastic pollution has become an emerging environmental issue of global concern, microplastics in aquaculture have become a research hotspot. For environmental safety, economic efficiency and food safety considerations, a comprehensive understanding of microplastic pollution in aquaculture is necessary. This review outlines an overview of sources and effects of microplastics in aquaculture. External environmental inputs and aquaculture processes are sources of microplastics in aquaculture. Microplastics may release harmful additives and adsorb pollutants in aquaculture environment, cause deterioration of aquaculture environment, as well as cause toxicological effects, affect the behavior, growth and reproduction of aquaculture products, ultimately reducing the economic benefits of aquaculture. Microplastics entering the human body through aquaculture products also pose potential health risks at multiple levels. Microplastic pollution removal strategies used in aquaculture in various countries are also reviewed. Ecological interception and purification are considered to be effective methods. In addition, strengthening aquaculture management and improving fishing gear and packaging are also currently feasible solutions. As proactive measures, new portable microplastic monitoring system and remote sensing technology are considered to have broad application prospects. And it was encouraged to comprehensively strengthen the supervision of microplastic pollution in aquaculture through talent exchange and strengthening the construction of laws and regulations.

Polystyrene microplastics induced inflammation with activating the TLR2 signal by excessive accumulation of ROS in hepatopancreas of carp (Cyprinus carpio)

Polystyrene microplastics (PS-MPs) affect the immune defense function on carp (Cyprinus carpio). The PS-MPs model of carp was established by feeding with PS-MPs particle size of 8 µm and concentration of 1000 ng/L water. Hepatopancreas function test revealed the activities of AKP, ALT, AST and LDH abnormal increase. PS-MPs induced tissue damage and lead to abnormal hepatopancreas function. The PS-MPs also induced a oxidative stress with the antioxidant enzymes SOD, CAT, GSH-PX, and T-AOC activities decreasing and reactive oxygen species (ROS) excessive accumulation. PS-MPs activated the Toll like receptor-2 (TLR2) signaling pathway. The mRNA and protein expressions of TLR2, Myeloid differentiation primary response 88 (MyD88), tumor necrosis factor receptor-associated factor 6 (TRAF6), NF-κB p65, Tumor necrosis factor (TNF-α), Interleukin-1β (IL-1β), Inducible Nitric Oxide Synthase (iNOS), and cycooxygenase 2(COX2) was revealed increased in both hepatopancreas and hepatocytes with the qPCR and Western blotting analysis mode. ELISA showed the expressions of TNF-α, IL-1β, iNOS, and COX2 inflammatory molecule were increased in both hepatopancreas and hepatocytes. The results showed that PS-MPs caused a serious injure in the hepatopancreas and brought serious effects on the inflammatory response of carp. The present study displayed the harm caused by PS-MPs in freshwater fish, and provided some suggestions and references for toxicological studies of microplastics in freshwater environment.

Polystyrene Microplastics Postpone APAP-Induced Liver Injury through Impeding Macrophage Polarization

Polystyrene microplastics (PS MPs) are micrometer-scale items degraded from plastics and have been detected in various organisms. PS MPs have been identified as causing cognitive, cardiac, intestinal, and hepatic damage. However, their role in liver regeneration under drug-induced liver injury remains unknown. Thus, the current study aims to evaluate the impact of PS MPs on liver repair during APAP hepatotoxicity. PS MPs pretreatment exacerbates mice mortality and hepatocyte apoptosis, suppresses hepatic cell proliferation, and disturbs the inflammatory response in the APAP-induced damage model. Further mechanism exploration uncovers that prior PS MPs administration is sufficient to recruit neutrophils and macrophages, which are necessary for tissue recovery in the acute liver injury model. However, the polarization capacity of macrophages to anti-inflammatory sub-type is significantly delayed in PS MPs plus APAP group compared to the single APAP group, which is the leading cause of tissue repair suppression. Overall, the current study supports a new insight to realize the toxicity of PS MPs in acute liver injury, which should be considered in health risk assessment.

Vitamin E performs antioxidant effect via PAP retrograde signaling pathway in Nile tilapia (Oreochromis niloticus)

PAP (3'-phosphoadenosine 5'-phosphate) is a ubiquitous phosphoric acid and a natural inhibitor of the XRN (5'-3'exoribonuclease) family. It was proved to enter the nucleus through the retrograde signaling pathway and inhibit XRN2 to prevent the degradation of miRNA precursors, thus promoting the anti-oxidation miRNA level in Arabidopsis thaliana. Vitamin E (tocopherol) was proved to promote the accumulation of PAP in the plant, which facilitates PAP into the nucleus to accomplish its antioxidant function. However, the relationship between VE and PAP in animals is unclear. To identify the relationship between VE and PAP and to uncover the function of PAP in fish, we investigated the performance of VE and PAP in Nile tilapia by comparing the antioxidant indicators (SOD, GSH-Px, and CAT), the Keap1-Nrf2 signaling pathway, and the miRNA expression profiles. Results showed that the antioxidant effect of VE and PAP showed similar character either in tilapia liver or in serum: the activities of GSH-Px and CAT of both groups were significantly increased (P < 0.05); the SOD activity of the VE group was significantly increased (P < 0.05), and although the result of the PAP group was not so significant (P > 0.05), PAP improved the SOD level, too. The two groups also showed similar character in the tilapia liver; both did not significantly increase the liver δ-VE content (P > 0.05). However, VE significantly increased the content of α-VE and γ-VE (P < 0.05), while the PAP group was insignificant (P > 0.05). Feed with VE and intraperitoneal injection of PAPs reagent both increased the PAP content in the liver of tilapia, and the effect of the VE group was more significant (P < 0.05) than that of the PAP group (P > 0.05). Both groups reduced the expression of Keap1 and Cullin3 genes and improved the level of HO-1 gene expression, with the improved miRNA level of Nrf2. As a logical result, they decreased the expression of XRN1 and XRN2. By profile sequencing, we further identified some antioxidant closely related miRNAs shared in the VE and PAP groups, including miR-30, miR-24, miR-19b, and miR-100. By comparing the regulating mechanism of VE and PAP of feed supply and intraperitoneal injection, we proved that VE and PAP were closely related in fish; VE promoted the gathering of PAP. The latter retrograded into the nucleus of the fish liver to inhibit the expression of XRN genes and to up-regulate antioxidant miRNA levels as it does in plants. Only the PAP can accomplish the antioxidant activities, while VE promotes the process. Our study laid the foundation for the application of PAP as a new antioxidant agent in fish farming and benefit a further understanding of the VE antioxidant function in fish.