Size-dependent toxicological effects of polystyrene microplastics in the shrimp Litopenaeus vannamei using a histomorphology, microbiome, and metabolic approach

Toxicokinetics of microplastics in Macrobrachium nipponense and their impact on the bioavailability of loaded pollutants

Microplastics (MPs) have unique toxicokinetic (TK) processes that differ from those of soluble pollutants. This study investigated the ingestion, migration, accumulation, and clearance of environmental aging MPs in the Japanese swamp shrimp (Macrobrachium nipponense). The concentrations of plastic additives and personal care products adsorbed onto MPs in natural river water were determined, and TK models for MPs and MPs-loaded pollutants were developed. Results showed that the formation of surface biofilms and alterations in the distribution of MPs in waters caused by environmental aging affect MPs bioavailability, which is mainly related to the feeding habits of shrimp. The decrease in MPs particle size caused by biological digestion and the increase in the number of oxygen-containing functional groups caused by environmental aging affect the TK process of MPs. The TK model of MPs-loaded pollutants revealed the cleaning effect of shrimp on pollutants adsorbed onto MPs during swallowing and spitting MPs. This cleaning effect significantly increases the bioavailability of MPs-associated pollutants in aquatic environments. This study provides a new perspective for understanding the interactions between environmental MPs and their associated pollutants in aquatic ecosystems.

Colonization characteristics and surface effects of microplastic biofilms: Implications for environmental behavior of typical pollutants

This paper summarizes the colonization dynamics of biofilms on microplastics (MPs) surfaces in aquatic environments, encompassing bacterial characteristics, environmental factors affecting biofilm formation, and matrix types and characteristics. The interaction between biofilm and MPs was also discussed. Through summarizing recent literatures, it was found that MPs surfaces offer numerous benefits to microorganisms, including nutrient enrichment and enhanced resistance to environmental stress. Biofilm colonization changes the surface physical and chemical properties as well as the transport behavior of MPs. At the same time, biofilms also play an important role in the fragmentation and degradation of MPs. In addition, we also investigated the coexistence level, adsorption mechanism, enrichment, and transformation of MPs by environmental pollutants mediated by biofilms. Moreover, an interesting aspect about the colonization of biofilms was discussed. Biofilm colonization not only had a great effect on the accumulation of heavy metals by MPs, but also affects the interaction between particles and environmental pollutants, thereby changing their toxic effects and increasing the difficulty of MPs treatment. Consequently, further attention and research are warranted to delve into the internal mechanisms, environmental risks, and the control of the coexistence of MPs and biofilms.

Microplastics predominantly affect gut microbiota by altering community structure rather than richness and diversity: A meta-analysis of aquatic animals

The impacts of microplastics on the gut microbiota, a crucial component of the health of aquatic animals, remain inadequately understood. This phylogenetically controlled meta-analysis aims to identify general patterns of microplastic effects on the alpha diversity (richness and Shannon index), beta diversity, and community structure of gut microbiota in aquatic animals. Data from 63 peer-reviewed articles on the Web of Science were synthesized, encompassing 424 observations across 31 aquatic species. The analysis showed that microplastics significantly altered the community structure of gut microbiota, with between-group distances being 87.75% higher than within-group distances. This effect was significant even at environmentally relevant concentrations (≤1 mg L-1). However, their effects on richness, Shannon index, and beta diversity (community variation) were found to be insignificant. The study also indicated that the effects of microplastics were primarily dependent on their concentration and size, while the phylogeny of tested species explained limited heterogeneity. Furthermore, variations in gut microbiota alpha diversity, beta diversity, and community structure were correlated with changes in antioxidant enzyme activities from the liver and hepatopancreas. This implies that gut microbiota attributes of aquatic animals may provide insights into host antioxidant levels. In summary, this study illuminates the impacts of microplastics on the gut microbiota of aquatic animals and examines the implications of these effects for host health. It emphasizes that microplastics mainly alter the community structure of gut microbiota rather than significantly affecting richness and diversity.

Analysis of Biodistribution and in vivo Toxicity of Varying Sized Polystyrene Micro and Nanoplastics in Mice

Introduction

Studies have shown that microplastics (MPs) and nanoplastics (NPs) could accumulate in the human body and pose a potential threat to human health. The purpose of this study is to evaluate the biodistribution and toxicity of MPs/NPs with different particle sizes comprehensively and thoroughly.

Methods

The purpose of this study was to investigate the biodistribution and in vivo toxicity of polystyrene (PS) MPs/NPs with different sizes (50 nm, 100 nm, and 500 nm). The BALB/c mice were given 100 μL of PS50, PS100 and PS500 at the dosage of 1 mg/kg BW or 10 mg/kg BW, respectively, by gavage once a day. After 28 consecutive days of treatment, the biodistribution of differently sized PS MPs/NPs was determined through cryosection fluorescence microscopy and fluorescent microplate reader analysis, and the subsequent effects of differently sized PS MPs/NPs on histopathology, hematology and blood biochemistry were also evaluated.

Results

The results showed that the three different sizes of PS MPs/NPs were distributed in the organs of mice, mainly in the liver, spleen, and intestine. At the same time, the smaller the particle size, the more they accumulate in the body and more easily penetrate the tissue. During the whole observation period, no abnormal behavior and weight change were observed. The results of H&E staining showed that no severe histopathological abnormalities were observed in the main organs in the low-dose exposure group, while. Exposure of three sizes of PS MPs/NPs could cause some changes in hematological parameters or biochemical parameters related to heart, liver, and kidney function; meanwhile, there were size- and dose-dependencies.

Conclusion

The biological distribution and toxicity of plastic particles in mice were more obvious with the decrease of particle size and the increase of concentration of plastic particles. Compared with MPs, NPs were easier to enter the tissues and produce changes in liver, kidney, and heart functions. Therefore, more attention should be paid to the toxicity of NPs.

Mangrove mud clam as an effective sentinel species for monitoring changes in coastal microplastic pollution

The worldwide mangrove shorelines are experiencing considerable contamination from microplastics (MPs). Finding an effective sentinel species in the mangrove ecosystem is crucial for early warning of ecological and human health risks posed by coastal microplastic pollution. This study collected 186 specimens of the widely distributed mangrove clam (Geloina expansa, Solander, 1786) from 18 stations along the Leizhou Peninsula, the largest mangrove coast in Southern China. This study discovered that mangrove mud clams accumulated a relatively high abundance of MPs (2.96 [1.61 - 6.03] items·g-1) in their soft tissue, wet weight, as compared to previously reported levels in bivalves. MPs abundance is significantly (p < 0.05 or 0.0001) influenced by coastal urban development, aquaculture, and shell size. Furthermore, the aggregated MPs exhibit a significantly high polymer risk index (Level III, H = 353.83). The estimated annual intake risk (EAI) from resident consumption, as calculated via a specific questionnaire survey, was at a moderate level (990 - 2475, items·g -1·Capita -1). However, the EAI based on suggested nutritional standards is very high, reaching 113,990 (79,298 - 148,681), items·g -1·Capita -1. We recommend utilizing the mangrove mud clam as sentinel species for the monitoring of MPs pollution changing across global coastlines.

Microplastics weaken the exoskeletal mechanical properties of Pacific whiteleg shrimp Litopenaeus vannamei

The ubiquitous presence of microplastics (MPs) in aquatic environments poses a significant threat to crustaceans. Although exoskeleton quality is critical for crustacean survival, the impact of MPs on crustacean exoskeletons remains elusive. Our study represents a pioneering effort to characterize the effects of MPs exposure on crustacean exoskeletons. In this study, the mechanical properties of whiteleg shrimp Litopenaeus vannamei exoskeletons were analyzed after exposure to environmentally realistic levels of MPs. Nanoindentation data demonstrated that MPs exposure significantly increased the hardness and modulus of both the carapace and abdominal segments of L. vannamei. Moreover, fractures and embedded MPs were detected on the exoskeleton surface using SEM-EDS analysis. Further analysis demonstrated that the degree of chitin acetylation (DA) in the shrimp exoskeleton, as indicated by FTIR peaks, was reduced by MPs exposure. In addition, exposure to MPs significantly inhibited the muscle Ca2+-ATPase activity and hemolymph calcium levels. Transcriptome and metabolome analyses revealed that the expression levels of genes encoding key enzymes and metabolites in the chitin biosynthetic pathway were significantly affected by MPs exposure. In conclusion, MPs at environmentally relevant concentrations may affect the exoskeletal mechanical properties of L. vannamei through a comprehensive mechanism involving the disruption of the crystalline structure of chitin, assimilation into the exoskeleton, and dysregulation of exoskeleton biosynthesis-related pathways.

Meta-analysis of the hazards of microplastics in freshwaters using species sensitivity distributions

The environmental hazards of microplastics have raised concerns about their potential ecological risks. However, our understanding of the true risks may be limited because most laboratory studies used pristine microplastics. Here, we analyzed the available literature about ecotoxicological effects of microplastics, including weathered microplastics in particular, on freshwater biota and performed probabilistic species sensitivity distributions. The predicted no-effect concentrations for pristine microplastics were lower than those for weathered microplastics, both in mass concentration (6.1 and 4.8 × 102 μg/L) and number concentration (2.6 × 104 and 2.0 × 106 part/m3). In addition, the toxicological studies on microplastics contains often inconsistent and inconclusive information due to the complexity of the microplastics and the employed exposure conditions. The available data for Daphnia magna and Danio rerio was analyzed in detail to understand the effects of microplastic size, shape and polymer type on their ecotoxicity. Microplastic size was the biggest driving factor, followed by shape and polymer type. There was a tendency for increasing toxicity with smaller size, however, a high variability of effect data was observed for small microplastics. This study provided further insights into the effect thresholds for ecological risk assessment of microplastics and the effects of microplastic characteristics on toxicity.

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.

Microplastic pollution in typical seasonal rivers in northern China: temporal variation and risk assessment

Rivers are important channels for the transport of microplastics (MPs) from land to sea. In this work, the temporal variation and risk assessment of MP pollution in the surface water of the Wei River, a typical seasonal river in northern China, were quantified. The number abundance of MPs in the dry season was significantly higher than that in the wet season (p < 0.05). Fiber was the most abundant type of MP in both dry and wet seasons. Infrared spectrometer and Raman spectroscopy identification showed that polypropylene (PP) and polyethylene (PE) were the major polymers found in both dry and wet seasons, and the mixture of different MP polymers was more diverse in the dry season. The risk assessment showed that the average pollution load index (PLI) and risk quotient (RQ) were 2.10 and 1.19 in the dry season, which significantly decreased to 1.25 and 0.74, respectively, in the wet season (p < 0.05). In total, the results from this study highlight the characteristics of seasonal rivers that influence the temporal distribution and risk assessment of microplastics, providing scientific reference for policymakers and river managers to effectively deal with MP pollution.

Involvement of Microplastics in the Conflict Between Host Immunity Defense and Viral Virulence: Promoting the Susceptibility of Shrimp to WSSV Infection

As the concentration of microplastics/microspheres (MPs) in coastal and estuarine regions increases, the likelihood of disease outbreaks and epidemics also rises. Our study investigated the impact of polyvinyl chloride MPs (PVC-MPs) on white spot syndrome virus (WSSV) infection in shrimp. The results revealed that PVC-MPs obviously increased WSSV replication in vivo, leading to a high mortality rate among the larvae and facilitating the horizontal transmission of WSSV. Furthermore, the data of WSSV loads detected together with qPCR, agarose gel electrophoresis, and flow cytometry approaches indicated that PVC-MPs could interact with the virus to prolong survival and maintain the virulence of WSSV at different temperatures and pH values. In terms of host resistance, metabolomics and transcriptomics analysis demonstrated that exposure to PVC-MPs upregulated metabolic concentrations and gene expressions associated with phospholipid metabolism that were associated with innate immunity responses. Particularly, PVC-MPs stimulated the synthesis of phosphatidylcholine (PC) and induced lipid peroxidation. The inhibition of PC on Stimulator of Interferon Genes (STING) translocation from the endoplasmic reticulum to the Golgi apparatus reduces expression of the innate immunity genes (IFN-like genes Vago4 and Vago5) regulated by STING signaling pathways, resulting in a significant decrease in the shrimp's resistance to WSSV infection. Notably, a recovery operation in which the exposed larvae were transferred to a MPs-free aquatic environment led to decreased WSSV infectivity over time, indicating the restoration of antiviral properties in shrimp. Overall, these findings highlight that MPs promote shrimp susceptibility to WSSV in two aspects: host immune defense and viral virulence.

Comparative toxicity of micro and nanopolystyrene particles in Mya arenaria clams

The contamination of coastal marine environments by plastics of sizes ranging from mm down to the nanoscale (nm) could pose a threat to aquatic organisms. The purpose of this study was to examine the toxicity of polystyrene nanoparticles (PsNP) of various sizes (50, 100 and 1000 nm) to the marine clams Mya arenaria. Clams were exposed to concentrations of PsPP for 7 days at 15 °C and analyzed for uptake/transformation, changes in energy metabolism, oxidative stress, genotoxicity and circadian neural activity. The results revealed that PsNP accumulated in the digestive gland was 50 nm > 100 nm > 1000 nm. All sized increased oxidative stress as follows: 50 nm (peroxidase, antioxidant potential and LPO), 100 nm (LPO and antioxidant potential) and 1000 nm (LPO). Tissue damage was also size dependent by increasing genotoxicity. The 100 nm PsPP altered the levels of the circadian metabolite melatonin. We conclude that the toxicity of plastics is size dependent in clams.

Comparative study of the impact of dietary supplementation with different types of CpG oligodeoxynucleotides (CpG ODNs) on enhancing intestinal microbiota diversity, antioxidant capacity, and immune-related gene expression profiles in Pacific white shrimp (Litopenaeus vannamei)

The CpG oligodeoxynucleotides (CpG ODNs) reportedly possess the capacity to strengthen immunity in mammals. This experiment was conducted to evaluate the impact of dietary supplementation with 17 types of CpG ODNs on intestinal microbiota diversity, antioxidant capacity, and immune-related gene expression profiles of the shrimp Litopenaeus vannamei. Diets including 50 mg kg^-1 CpG ODNs wrapped in egg whites were prepared and divided into 17 different groups, with 2 control groups (normal feed and feed with egg whites). These CpG ODNs supplemented diets and the control diets were fed to L. vannamei (5.15 ± 0.54 g) three times daily at 5%-8% shrimp body weight for three weeks. The results of consecutive detection of intestinal microbiota by 16S rDNA sequencing indicated that 11 of the 17 types of CpG ODNs significantly enhanced intestinal microbiota diversity, increased the populations of several probiotic bacteria, and activated possible mechanisms relevant to diseases. The immune-related genes expression and antioxidant capacity in hepatopancreas further demonstrated that the 11 types of CpG ODNs effectively improved the innate immunity of shrimp. Additionally, histology results showed that the CpG ODNs in the experiment did not damage the tissue structure of hepatopancreas. The results suggest that CpG ODNs could be used as a trace supplement to improve the intestinal health and immunity of shrimp.

Transcriptome, intestinal microbiome and histomorphology profiling of differences in the response of Chinese sea bass (Lateolabrax maculatus) to Aeromonas hydrophila infection

The Chinese sea bass (Lateolabrax maculatus) is an important aquaculture fish, but diseases caused by Aeromonas hydrophila have led to severe economic losses to the aquaculture industry in recent years. To date, only a few studies have focused on the relationship between the intestinal immune response and changes in intestinal microbes by A. hydrophila infection. Here, we report the transcriptome and intestinal changes in infected sea bass. Histopathological results showed that severe steatosis and vacuolation occurred in the liver and that the intestinal villi and mesentery were seriously affected after infection. By extracting total RNA from intestinal tissue and studying the transcriptome profile, 1,678 genes (1,013 upregulated and 665 downregulated) were identified as significantly differentially expressed genes (DEGs). These genes are involved in many immune-related signalling pathways, such as the NOD-like receptor, C-type lectin receptor, and Toll-like receptor signalling pathways. Moreover, the intestinal microbes of sea bass changed significantly after infection. Interestingly, at the genus level, there was an increase in Serratia, Candida arthromitus and Faecalibacterium as well as a decrease in Akkermansia and Parabacteroides after infection. The results also indicated that some of the DEGs involved in the immune response were related to the genus level of intestinal microbiota. Finally, there was a relationship between gene expression patterns and the bacterial structure in the host intestine. Our study provides a reference for the study of the immune response and particular functions of intestinal microbes of sea bass after pathogen infection.