Adverse effects of microplastics and oxidative stress-induced MAPK/Nrf2 pathway-mediated defense mechanisms in the marine copepod Paracyclopina nana

Toxicity of polystyrene microplastics on juvenile Oncorhynchus mykiss (rainbow trout) after individual and combined exposure with chlorpyrifos‎

Microplastic (MP) sorption and transfer of chemical contaminants has been widely reported, yet few studies have investigated combined effects of contaminant-loaded MPs on organisms. This study examined effects of pristine or chlorpyrifos (CPF)-loaded polystyrene (PS)‎ fragments on histopathological and histomorphometrical biomarkers in rainbow trout (Onchorhynchus mykiss)‎. In laboratory, O. mykiss were exposed for 96 h to pristine PS-MPs concentrations (30 or 300 µg/L), concentrations of CPF ‎alone (2 or ‎‎6 µg/L), and the same concentrations of CPF in the presence of PS-MPs in aquaria‎. Results showed the highest histopathological alterations in both CPF concentrations and when combined with PS-MPs in fish gills. Alternatively, high histopathological lesions including massive necrosis, infiltration of inflammatory cells, and shed of villi tips were observed in fish gut in high CPF concentrations combined with high PS-MP concentrations of ‎(6 μg/L CPF+300 μg/L PS-‎MPs). Individual CPF and PS-MP concentrations or combined together showed significant changes in histomorphometrical biomarkers in fish gills, gut and skin. Findings highlight that pristine PS-MPs cause toxicity and increase adverse effects of CPF in O. mykiss, especially in gill tissue. We present evidence that pristine short-term exposure to even low concentrations of PS-MPs has a significant impact on biomarker responses in O. mykiss.

Eye-glass polishing wastewater as significant microplastic source: Microplastic identification and quantification

Microplastics (MPs) and nanoplastics (NPs) seriously contaminate environments by adsorbing environmentally hazardous chemicals. NPs (<1 µm) are not removed by conventional wastewater treatment processes, and have strong sorption capacity for the environmentally hazardous chemicals because of their high surface area. This study revealed that large amounts of MPs are generated in the eye-glass lens polishing process. Qualitative analyses of MPs were performed via Fourier-transform infrared (FTIR) and Raman spectroscopy. Particle size distribution was measured through particle size analysis based on light diffraction. MPs were quantified in the wastewater by measuring the mass balance using membrane filtration with polyaluminum chloride coagulation. One liter of wastewater contained 1380-62,539 mg MPs [corrected] and 0.0136-0.0324 mg NPs. Wastewater from 140,000 eye-glass shops in South Korea is discharged into wastewater plants, and about 57 g NPs per day pass through the wastewater treatment process. The amount of NPs that accumulate daily is likely to increase dramatically. Increased heavy metal concentrations after acid digestion confirmed that MPs in the wastewater adsorbed heavy metals. Detection of various types of volatile organic compounds in the wastewater indicated that workers in eye-glass shops are exposed to the significantly hazardous environments.

Time-dependent metabolic disorders induced by short-term exposure to polystyrene microplastics in the Mediterranean mussel Mytilus galloprovincialis

In the modern society, plastic has achieved a crucial status in a myriad of applications because of its favourable properties. Despite the societal benefits, plastic has become a growing global concern due to it is persistence and bioavailability as microplastics (MPs) to aquatic biota. In order to provide mechanistic insights into the early toxicity effects of MPs on aquatic invertebrates, a short-term (up to 72 h) exposure to 3 µm red polystyrene MPs (50 particles/mL) was conducted on marine mussels Mytilus galloprovincialis, selected as model organism for their ability to ingest MPs and their commercial relevance. The use of protonic Nuclear Magnetic Resonance (¹H NMR)-based metabolomics, combined with chemometrics, enabled a comprehensive exploration at fixed exposure time-points (T24, T48, T72) of the impact of MPs accumulated in mussel digestive glands, chosen as the major site for pollutants storage and detoxification processes. In detail, ¹H NMR metabolic fingerprints of MP-treated mussels were clearly separated from control and grouped for experimental time-points by a Principal Component Analysis (PCA). Numerous metabolites, including amino acids, osmolytes, metabolites involved in energy metabolism, and antioxidants, participating in various metabolic pathways significantly changed over time in MP-exposed mussel digestive glands related to control, reflecting also the fluctuations in MPs accumulation and pointing out the occurrence of disorders in amino acid metabolism, osmotic equilibrium, antioxidant defense system and energy metabolism. Overall, the present work provides the first insights into the early mechanisms of toxicity of polystyrene MPs in marine invertebrates.

Keap1-Nrf2 pathway up-regulation via hydrogen sulfide mitigates polystyrene microplastics induced-hepatotoxic effects

Microplastics, which are new types of environmental pollutants, are recently receiving widespread attention worldwide. Hydrogen sulfide (H₂S) as the third endogenous gaseous mediator had protective effects in multiple physiological and pathological conditions. However, the protective role of H₂S in microplastics-induced hepatotoxocity remain unclear. In this study, our data showed that H₂S significantly suppressed inflammation, apoptosis and oxidative stress induced by polystyrene microplastics (mic-PS) (20 mg/kg b.w.) in the liver. Strikingly, although mic-PS exposure increased the expression of nuclear factor-E2-related factor (Nrf2), it did not influence the levels of heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQOl) in the L02 hepatocytes. Immunofluorescence assay showed that sodium hydrosulfide (NaHS) reduced micro-Ps-induced hepatic apoptosis by facilitating nuclear accumulation of Nrf2. Simultaneously, flow cytometry also showed that NaHS could prevent mic-PS-induced accumulation of reactive oxygen species (ROS) by increasing the expression of HO-1 and NQO1. Furthermore, inhibition of HO-1 could reverse the hepatic protective effects of NaHS during mic-PS exposure. Mechanistically, H₂S elevating the HO-1 and NQO1 expression by facilitating nuclear accumulation of Nrf2, and consequently reducing mic-PS-induced hepatic apoptosis and inflammation. This study unveils the hepatotoxic effects of MPs and suggest NaHS have protective effects on mic-PS-induced liver damage.

Oxidative damage and decreased aerobic energy production due to ingestion of polyethylene microplastics by Chironomus riparius (Diptera) larvae

Riverine sediments are major sinks of microplastics from inland anthropogenic activities, imposing a threat to freshwater benthic invertebrates. This study investigated the ingestion of three size-classes (SC) of irregularly shaped polyethylene microplastics (PE-MPs; SC I: 32-63 μm; II: 63-250 μm; III: 125-500 μm) after 48 h by dipteran larvae (detritivore/collector) Chironomus riparius, and the consequent effects on neurotransmission, energy allocation and oxidative stress. The tested PE-MPs concentrations (1.25; 5; 20 g kg^-1) were within the range of concentrations reported in riverbanks from highly urbanised areas (1 - 9 g kg^-1), except for 20 g kg^-1 representing the worst-case scenario. After exposure to SC I, larvae presented high amounts (up to ∼2400 particles/organism) of PE-MPs in their guts, with an average size-range of 30-60 μm. In the SC II and III, larvae presented PE-MPs of higher diameter (up to 125 μm) and a visible gut obstruction. The high number of particles in the larval gut (SC I) and/or difficulties for their egestion (SC I, II and III) induced oxidative damage and reduced aerobic energy production. In addition, larvae exposed to SC II and III revealed depletion in their total lipid reserves as a consequence of lacking nutrients, and the ones exposed to SC III presented a decrease in their detoxification capacity. These results highlight that freshwater detritivores with low selective feeding behaviour (e.g., chironomids) are more prone to ingest microplastics, with potentially adverse effects on cellular metabolism, redox status and antioxidant-detoxification defences. These harmful effects at lower levels of the biological organisation may ultimately affect organisms' physiology and fitness.

Polystyrene nanoparticles trigger the activation of p38 MAPK and apoptosis via inducing oxidative stress in zebrafish and macrophage cells

Polystyrene nanoparticles (PS NPs), originated from breakdown of large plastic wastes, have already caused much concern for their environmental risks on health. This current study was aimed to reveal the toxicological mechanism of PS NPs on developing zebrafish and macrophage cells. To fulfill this purpose, 42 nm PS NPs were exposed to the early development stage of zebrafish for 5 days, the decreased heart rate and locomotor activity of zebrafish larvae were observed. The fluorescent PS NPs were used to precisely assess the accumulation of PS NPs in zebrafish larvae, and the results indicated that PS NPs not only accumulated in digestive system, but also infiltrated into the liver. More importantly, the transcriptomic analysis revealed that a total of 356 genes were differentially expressed and the KEGG class map showed significant differences in the MAPK pathway upon PS NPs treatment. Meanwhile, the induction of oxidative stress and inflammation were also observed in zebrafish larvae. Furthermore, PS NPs also induced oxidative damage and inflammatory response in RAW 264.7 cells, which activated p38 MAPK signal pathway and finally induced cell apoptosis. Our study provides a new understanding of MAPK signaling pathway involved in toxicity mechanism.

Lumbriculus variegatus (oligochaeta) exposed to polyethylene microplastics: biochemical, physiological and reproductive responses

Freshwater sediments are a repository of microplastics (MPs) resulting from inland anthropogenic activities. Benthic invertebrates, particularly endobenthic sediment-ingesting species such as the annelid Lumbriculus variegatus (blackworm), are commonly found in contaminated sediments where they likely find and ingest MPs. In the present study, L. variegatus was exposed to concentrations between 0.51 and 20 g kg^-1 dry sediment of four size-classes of irregularly-shaped polyethylene MPs (PE-MPs; size-class A: 32-63, B: 63-125, C: 125-250 and D: 250-500 μm) for 48 h to assess their sub-cellular responses to particles ingested, and for 28 days to determine chronic effects on worm's reproduction and biomass. After the short-term exposure (48 h), number of PE-MPs in blackworms' gut were related to MPs concentration in the sediment. In general, PE-MPs ingestion by blackworms induced depletion of their energy reserves (e.g., sugars in all size classes and lipids in the size-classes of PE-MPs > 125 μm), concomitant with the activation of antioxidant and detoxification mechanisms (increased level of total glutathione in all size-classes, and increased glutathione-S-transferase activity in PE-MPs > 250 μm), preventing lipid peroxidation. In addition, it was observed a reduction of aerobic energy production (decreased activity of the electron transport system) and a slight increase in neurotransmission (cholinesterase activity). After a long-term exposure (28 d), the presence and ingestion of PE-MPs did not affect reproduction and biomass of L. variegatus. The activation and efficiency of the antioxidant and detoxification mechanisms allied with the anatomy and physiology of L. variegatus, its feeding strategy and potentially dynamic ingestion/egestion capacity seem to be key features preventing MP deleterious effects under short- and chronic-exposures. Considering the MPs levels reported for freshwater sediments, and despite evidence of MPs ingestion and some sub-organismal effects, our results suggest no adverse impacts of PE-MPs contamination on L. variegatus populations fitness. This study applies an integrative approach in which data concerning the ingestion of different sized MPs and subsequent sub-cellular and apical responses are delivered, raising knowledge on endobenthic invertebrates' strategies to potentially overcome MP toxicity in field contaminated sites.

The gut retention time of microplastics in barnacle naupliar larvae from different climatic zones and marine habitats

Microplastic ingestion has been widely documented in marine zooplankton, but the retention time of microplastics in their digestive gut are still poorly studied, especially among species from different climatic zones and marine habitats. This study evaluated the ingestion and gut retention time of four sizes of fluorescent microplastic beads (1.3, 7.3, 10.6, and 19.0 μm) in stage II naupliar larvae of nine barnacle species from different habitats (epibiotic on turtles, mangroves, coral reefs, and rocky shores) and climatic zones (subtropical/tropical and temperate). Microbeads were not lethal to all species (climatic zones/habitats) tested from the four sizes of non-fluorescent virgin microbeads (1.7, 6.8, 10.4 and 19.0 μm, each at concentrations 1, 10, 100, and 1000 beads mL^-1). Gut retention time of microplastic beads in barnacle naupliar larvae significantly increased with decreasing size. Microbeads resided in digestive tracts generally 3-4 times longer in rocky shore and coral reef barnacles than in muddy shore and epibiotic ones. However, species from different climatic zone did not differ in retention time. Our results suggested nauplius larvae from rocky shore and coral reef barnacles appear to be more susceptible to the impacts of longer retained microplastics (e.g., toxic chemicals present on the surface).

Environmental fate and impacts of microplastics in aquatic ecosystems: a review

Wide usage of plastic products leads to the global occurrence of microplastics (MPs) in the aquatic environment. Due to the small size, they can be bio-ingested, which may cause certain health effects. The present review starts with summarizing the main sources of various types of MPs and their occurrences in the aquatic environment, as well as their transportation and degradation pathways. The analysis of migration of MPs in water environments shows that the ultimate fate of most MPs in water environments is cracked into small fragments and sinking into the bottom of the ocean. The advantages and disadvantages of existing methods for detection and analysis of MPs are summarized. In addition, based on recent researches, the present review discusses MPs as carriers of organic pollutants and microorganisms, and explores the specific effects of MPs on aquatic organisms in the case of single and combined pollutants. Finally, by analysing the causes and influencing factors of their trophic transfer, the impact of MPs on high-level trophic organisms is explored.

The sources, fate and impacts of microplastics in aquatic ecosystems.

Probabilistic environmental risk assessment of microplastics in marine habitats

Microplastics are ubiquitous in the environment and given the large number of published hazard and exposure studies, quantitative environmental risks assessments of microplastics become feasible. We present here the first environmental risk assessment for marine waters based only on measured concentrations. The Thevariability and uncertainty of the measured data was accounted for in the exposure assessment, while probabilistic species sensitivity distributions were used for hazard assessment, from which a probability distribution was extracted for the predicted no-effect concentration (PNEC). By dividing the exposure distribution by the PNEC-distribution, we were able to calculate probabilistic risk characterisation ratios for each water body in which measurements were performed. Results show a good coverage of the world's major water bodies by measured exposure concentrations (MECs), while the hazard assessment could be improved by aligning the type of particles tested in hazard studies (size, form, polymer) to those actually found in the oceans. Overall, the mean predicted no-effect concentration (PNEC) is 3.84·10⁶ part m^-3, with Oryzias melastigma being the most sensitive species (calculated mean NOEC of 3.90·10⁶ part m^-3). Interestingly, the only type of dose descriptor that could be extracted from the literature for particles above 10-20 μm was the highest observed no effect concentration (HONEC), which indicates a very low or null toxicity of these larger MPs towards marine organisms. The mean MEC is 1.5·10³ part m^-3, the highest concentrations being measured in the Atlantic and Pacific Ocean. Although there is a very small overlap of the probability distribution associated with the RCR (0.00002 % of the data points), the mean RCR is 4·10^-4 and therefore risks are unlikely given the available data. However, as increasing amounts of plastic reach the environment, RCRs can be expected to increase in the future.

Exposure to polystyrene microplastics impairs gonads of zebrafish (Danio rerio)

Microplastic contamination poses a great threat to the health of aquatic species, which may affect their reproduction and result in ecological consequences. There is a need to further elucidate the potential impact microplastics can impose on aquatic species. In this study, the effects of exposure to polystyrene microplastics on reproductive organs, and the underlying response mechanisms, were investigated using zebrafish Danio rerio. After 21 days of continuous waterborne exposure, no significant difference was observed at the lower concentration of 10 μg/L. At concentrations above 100 μg/L, significantly enhanced reactive oxygen species (ROS) level was found in both male and female liver and gonads. At the concentration of 1000 μg/L, significantly increased apoptosis levels were observed in male testes, triggering increased expression of p53-mediated apoptotic pathways; histological alteration in the form of a significant decrease in testis basement membrane thickness was also observed. This study demonstrated that exposure to microplastics can induce molecular responses and histological alterations in fish gonads, implying potential adverse impact on fish reproductive organs. This work provided new insights on the reproductive damage microplastics can cause in fish and have implications in fields of freshwater ecology and environmental toxicology.

Microplastics in the Food Chain: Food Safety and Environmental Aspects

Plastic has been an incredibly useful and indispensable material in all aspects of human life. Without it many advances in medicine, technology or industry would not have been possible. However, its easy accessibility and low cost have led to global misuse. Basically, the production of the plastics from different chemical agents is very easy but unfortunately difficult to reuse or recycle, and it is thrown away as litter, incinerated or disposed of in landfill. Plastic once in the environment begins to degrade to very small sizes. Thus, many animals mistake them for food, so plastic enters a marine, terrestrial or freshwater food web. These microplastics although chemically inert have been shown to act as tiny "bio-sponges" for harmful chemicals found in the environment changing the nature of a plastic particle from chemically harmless to potentially toxic. It was believed that microparticles would simply pass through the gastrointestinal tract of animals and humans with no biological effect. However, studies have shown that they are sometimes taken up and distributed throughout the circulatory and lymphatic system and may be stored in the fatty tissues of different organisms. The result of the uptake of them showed potential carcinogenic effects, liver dysfunction and endocrine disruption. This review focuses on micro- and nanoplastics and their way entering marine and freshwater food webs, with particular attention to microplastic trophic transfer, their toxic side effects and influence to the human consumer in health and safety in the future.

Molecular and cellular responses to short exposure to bisphenols A, F, and S and eluates of microplastics in C. elegans

Bisphenol F (BPF) and bisphenol S (BPS) have been developed as an alternative to bisphenol A (BPA), a well-known endocrine disruptor, leading to their detection in the aquatic environment. In this work, we used the animal model Caenorhabditis elegans to improve our understanding of their potential effects on the biota and the environment. Our findings demonstrated that, after 24 h exposure, all the bisphenols examined increased the number of apoptotic corpses and the expression of the detoxifying enzymes SOD-3 and GST-4, without affecting the ROS levels, while BPA and BPS significantly enhanced DNA fragmentation. Furthermore, similarly to BPA, BPF and BPS did not alter the lifespan through the activation of SEK-1 and SKN-1 pathways. Thus, this study raises the attention of the risks associated with exposure to BPA alternatives. We also examined the effects of microplastic (MP) eluates on C. elegans. Aqueous extracts of weathered microplastic samples, both at high and low degradation state and pellets, have been evaluated for their effects on lifespan, DNA fragmentation, germline apoptosis, and oxidative stress response. Overall, our findings showed that eluates of low degraded plastics exert a greater toxic effect on the nematode C. elegans compared with the aqueous sample of high degraded plastic fragments and pellets.

Polystyrene microplastics cause granulosa cells apoptosis and fibrosis in ovary through oxidative stress in rats

Microplastics (MPs) are receiving increased attention as a harmful environmental pollutant. Studies have investigated that MPs have reproductive toxicity, but the mechanism is little known. Here, we aimed to investigate the effects of polystyrene microplastics (PS-MPs) on ovary in rats and the underlying molecular mechanisms. in vivo, thirty-two female Wistar rats were exposed to 0.5 μm PS-MPs at different concentrations (0, 0.015, 0.15 and 1.5 mg/d) for 90 days. And then, all animals were sacrificed, ovaries and blood were collected for testing. in vitro, granulosa cells (GCs) were separated from rat ovary and treated with 0、1、5、25 μg/mL PS-MPs and reactive oxygen species (ROS) inhibitor N-Acetyl-l-cysteine (NAC) respectively. Our results showed that PS-MPs could enter into GCs and result in the reducing of growing follicles number. And the Enzyme-linked immunosorbent assay (ELISA) manifested that PS-MPs could obviously decrease the level of anti-Müllerian hormone (AMH). In addition, PS-MPs induced oxidative stress, apoptosis of GCs and ovary fibrosis evidenced by assay kits, flow cytometry, immunohistochemistry, Masson's trichrome and Sirius red staining. Moreover, the western blot assay manifested that PS-MPs exposure significantly increased the expression levels of Wnt/β-Catenin signaling pathways-related proteins (Wnt, β-catenin, p-β-catenin) and the main fibrosis markers (transforming growth factor-β (TGF-β), fibronectin, α-smooth muscle actin (α-SMA). Additionally, the expression levels of Wnt and p-β-catenin, apoptosis of GCs decreased after NAC treatment. In summary, polystyrene microplastics cause fibrosis via Wnt/β-Catenin signaling pathway activation and granulosa cells apoptosis of ovary through oxidative stress in rats, both of which ultimately resulted in decrease of ovarian reserve capacity.

Toxicity and biomarkers of micro-plastic in aquatic environment: a review

Microplastics (MPs; <5 mm) are found in all aquatic environments. Due to harmful impacts, MPs pose a great threat to the aquatic ecology. Therefore, this review aims to provide an overview of the risk, bioavailability, and toxicity of MPs in aquatic organisms. Various factors affecting MPs bioavailability and level of risks at cellular and molecular level on aquatic organisms are comprehensively discussed. More specifically biomarkers for antioxidant response (superoxide dismutase, catalase, glutathione peroxidase, reductase, and glutathione S-transferase), neurotoxic impairment (acetylcholinesterase), lysosomal activity alteration, and genotoxicity have been discussed in detail. Biomarkers are powerful tool in the monitoring programme, but the collection of literature on biomarkers for MPs is limited. Thus, here we demonstrate how to evaluate MPs impact, in monitoring programme, on organisms using biomarkers in aquatic environment. This review would broaden the existing knowledge on the toxic effect and biomarkers of MPs and offer research priorities for future studies.

An emerging class of air pollutants: Potential effects of microplastics to respiratory human health?

It is increasingly recognized that the ubiquity of convenient single-use plastic has resulted in a global plastic pollution challenge, with substantial environmental and health consequences. Physical, chemical, and biological processes result in plastic weathering, with eventual formation of debris in the micro to nano size range. There is an increasing awareness that plastic fragments are dispersed in the air and can be inhaled by humans, which may cause adverse effects on the respiratory system and on other systems. Urban environments are often characterized by high concentrations of fine airborne dust from various sources. To date, however, there is limited information on the distribution, shape, and size of microplastics in the air in urban and other environments. In this article, we review and discuss our current understanding of the exposure characteristics of airborne plastic debris in urbanized areas, focusing on concentration, size, morphology, presence of additives and distributions of different polymers. The natural and extend data are compiled and compared to laboratory-based analyses to further our understanding of the potential adverse effects of inhaled plastic particles on human health.

Currently monitored microplastics pose negligible ecological risk to the global ocean

Given the rise in plastic production, microplastics (MP) dominate marine debris, and their impact on marine ecosystems will likely increase. However a global quantitative assessment of this risk is still lacking. We conducted an ecological risk assessment of MP in the global ocean by comparing the thresholds of biological effects with the probability of exposure to those concentrations, according to plastic density data adjusted to a log-normal distribution. Levels of MP from 100 to 5000 µm span from < 0.0001 to 1.89 mg/L, whereas the most conservative safe concentration is 13.8 mg/L, and probability of exposure is p = 0.00004. Therefore large MP pose negligible global risk. However, MP bioavailability, translocation and toxicity increase as size decreases, and particles < 10 µm are not identified by current monitoring methods. Future research should target the lowest size fractions of MP and nanoplastics, and use in toxicity testing environmental plastic particles rather than engineered materials.

Microplastics mixture exposure at environmentally relevant conditions induce oxidative stress and neurotoxicity in the wedge clam Donax trunculus

Contamination by micro and nano plastics is actually considered as a global environmental preoccupation. The quantification of microplastics in natural habitats and the characterization of their potential effects in marine wild organisms is currently of high importance. The main objective of this work was to investigate the fate and the effects of a microplastic mixture (ratio of 1: polyethylene (PE), 1: polypropylene (PP)) in the wedge clam Donax trunculus. The assimilation kinetics of microplastics particles was assessed in different organs (gills, digestive gland and flesh) using three different protocols (direct observation, H₂O_2, and HNO₃/HCl digestion) in order to compare method's efficacity. The main biological endpoints studied were Aceylcholinesterase (AChE) inhibition as a neurotoxicity biomarker, the Catalase (CAT) enzymatic activity and the Gluthation-S-Transfereases (GSTs) activities as oxidative stress and phase II detoxification phase markers, respectively. Results showed that the H₂O₂ digestion method was more efficient to assess particles assimilation than the direct observation and acid digestion. In all cases no particles were detected in clam's flesh and gills were the first target organ for micro-plastics accumulation. The exposure of Donax truculus to PP/PE mixture (0.06 g/Kg of sand) induce a significant inhibition of AChE activity in both gills and digestive gland and oxidative stress in all organs studied. This study brings new results on the potential accumulation of PP and PE associated to neurotoxicity and oxidative stress of the wedge clam Donax trunculus.

Microplastic pollution as a grand challenge in marine research: A closer look at their adverse impacts on the immune and reproductive systems

Microplastic (MP) pollution of the marine environment is now a growing global concern posing a threat to a variety of species through the ingestion and transfer within food webs. This is considered a potential toxicological threat to marine species due to the chemical additives used to make many plastic products, or the persistent organic pollutants that may accumulate on them while residing in the environment. While the presence of MPs in the marine environment is widely documented, there are no other review articles providing a summary of published effect studies of MPs on the immune and reproductive systems of marine species. This manuscript reviews reproductive and immune-system changes in response to MPs in 7 and 9 species, respectively. Some species such as Mytilus galloprovincialis and oyster Crassostrea gigas were investigated in multiple papers. Most studies have been conducted on invertebrates, and only 3 studies have been performed on vertebrates, with exposure times ranging between 30 min and 60 days. A review of the literature revealed that the most common MPs types studied in relation to adverse impacts on immune system and reproductive success in marine species were polystyrene (PS) and polyethylene (PE). The immune system's responses to MPs exposure varied depending on the species, with altered organismal defense mechanisms and neutrophil function observed in fish and changes in lysosomal membrane stability and apoptotic-like nuclear alterations in phagocytes reported in invertebrate species. Reproductive responses to MPs exposure, varied depending on species, but included significant reduction in gamete and oocyte quality, fecundity, sperm swimming speed, and quality of offspring. The lack of published data means that developing a clear understanding of the impact across taxonomic groups with different feeding and behavioral traits is often difficult. Further work is required to better understand the risk MPs pose to the immune and reproductive systems of marine species in order to fully evaluate the impact these ubiquitous pollutants are having on marine ecosystems and the associated goods and services they provide.

Micro- and nano-plastics activation of oxidative and inflammatory adverse outcome pathways

Microplastics (MPs) and nanoplastics (NPs) have attracted considerable attention in the recent years as potential threats to the ecosystem and public health. This review summarizes current knowledge of pathological events triggered by micro- and nano-plastics (MP/NPs) with focus on oxidative damages at different levels of biological complexity (molecular, cellular, tissue, organ, individual and population). Based on published information, we matched the apical toxicity endpoints induced by MP/NPs with key event (KE) or adverse outcomes (AO) and categorized them according to the Adverse Outcome Pathway (AOP) online knowledgebase. We used existing AOPs and applied them to highlight formal mechanistic links between identified KEs and AOs in two possible scenarios: first from ecological, and second from public health perspective. Ecological perspective AOP based literature analysis revealed that MP/NPs share formation of reactive oxygen species as their molecular initiating event, leading to adverse outcomes such as growth inhibition and behavior alteration through oxidative stress cascades and inflammatory responses. Application of AOP on literature data related to public health perspective of MP/NPs showed that oxidative stress and its responding pathways, including inflammatory responses, could play the role of key events. However insufficient information prevented precise definitions of AOPs at this level. To overcome this knowledge gap, further mammalian model and epidemiological studies are necessary to support development and construction of detailed AOPs with public health focus.

Ingestion and effects of polystyrene nanoparticles in the silkworm Bombyx mori

Information on the occurrence and effects of nanoplastics in ecosystems worldwide currently represent one of the main challenges from the ecotoxicological point of view. This is particularly true for terrestrial environments, in which nanoplastics are released directly by human activities or derive from the fragmentation of larger plastic items incorrectly disposed. Since insects can represent a target for these emerging contaminants in land-based community, the aim of this study was the evaluation of ingestion of 0.5 μm polystyrene nanoplastics and their effects in silkworm (Bombyx mori) larvae, a useful and well-studied insect model. The ingestion of nanoplastics, the possible infiltration in the tissues and organ accumulation were checked by confocal microscopy, while we evaluated the effects due to the administered nanoplastics through a multi-tier approach based on insect development and behaviour assessment, as endpoints at organism level, and the measurements of some biochemical responses associated with the imbalance of the redox status (superoxide dismutase, catalase, glutathione s-transferase, reactive oxygen species evaluation, lipid peroxidation) to investigate the cellular and molecular effects. We observed the presence of microplastics in the intestinal lumen, but also inside the larvae, specifically into the midgut epithelium, the Malpighian tubules and in the haemocytes. The behavioural observations revealed a significant (p < 0.05) increase of erratic movements and chemotaxis defects, potentially reflecting negative indirect effects on B. mori survival and fitness, while neither effect on insect development nor redox status imbalance were measured, with the exception of the significant (p < 0.05) inhibition of superoxide dismutase activity.

Synthetic microfibers: Pollution toxicity and remediation

The ever-increasing use of domestic washing machine by urban population is playing a major role in synthetic microfibers (SMFs) pollution via entering the ecosystem. Although many of the sources of fragmented plastic pollution in oceanic environments have been well known, urban areas are playing a major contributor due to huge populations. Thousands of scientific investigations are now reporting the adverse effect of these micro pollutants on aquatic and terrestrial environment, food chain and human health. Microfiber particles along with washing machine grey waters are emitted into urban drainage adjoining the lakes and river which ultimately mix in ocean water and after emission these tiny particles dispersed though out the ocean water by currents due to their low density. Environmental pollution cause by domestic laundering processes of synthetic clothes has been reported as the major cause of primary microplastics in the marine system. While community awareness and improved education will be successful in making public conscious of this problem, there needs to be more research on global scale to mitigate the ecological consequences of microfiber pollution by urban habitats through environmental friendly approach. This paper focuses to improve the understanding of urban population influence on microfiber pollution, their ecological toxicity to aquatic organism and humans, detection and characterization techniques with an emphasis on future research for prevention and control of microfiber pollution.

Ingestion of microplastics and occurrence of parasite association in Mediterranean anchovy and sardine

We quantified the incidence of microplastics in the gut contents of the European sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) in the Northwestern Mediterranean Sea and tested which variables influence this abundance, including the prevalence of parasites (i.e., trematoda larvae and nematodes). We detected a 58% occurrence of microplastics ingestion in sardines and a 60% in anchovies. With respect to sardines, the individuals with lower body conditions were found to have the highest microplastics ingestion probabilities, whereas in anchovies such probabilities were observed in individuals with higher gonadosomatic indices and smaller size. The areas with the highest microplastics ingestion probabilities were the Gulf of Alicante for sardines and the Gulf of Lion - Ebro Delta for anchovies. Both species showed a positive relationship between parasites and microplastics ingestion. These results highlight that both parasitism and ingestion of microplastics are concerns for the health of marine stocks and human consumers.

How sea urchins face microplastics: Uptake, tissue distribution and immune system response

Plastic pollution represents one of the major threats to the marine environment. A wide range of marine organisms has been shown to ingest microplastics due to their small dimensions (less than 1 mm). This negatively affects some biological processes, such as feeding, energy reserves and reproduction. Very few studies have been performed on the effect of microplastics on sea urchin development and virtually none on adults. The aim of this work was to evaluate the uptake and distribution of fluorescent labelled polystyrene microbeads (micro-PS) in the Mediterranean sea urchin Paracentrotus lividus and the potential impact on circulating immune cells. Differential uptake was observed in the digestive and water vascular systems as well as in the gonads based on microbeads size (10 and 45 μm in diameter). Treatment of sea urchins with particles of both sizes induced an increase of the total number of immune cells already after 24 h. No significant differences were observed among immune cell types. However, the ratio between red and white amoebocytes, indicative of sea urchin healthy status, increased with both particles. This effect was detectable already at 24 h upon exposure to smaller micro-PS (10 μm). An increase of intracellular levels of reactive oxygen and nitrogen species was observed at 24 h upon both micro-PS exposure, whereas at later time these levels became comparable to those of controls. A significant increase of total antioxidant capacity was observed after treatment with 10 μm micro-PS. Overall data provide the first evidence on polystyrene microbeads uptake and tissue distribution in sea urchins, indicating a stress-related impact on circulating immune cells.

Nanopolystyrene beads affect motility and reproductive success of oyster spermatozoa (Crassostrea gigas)

Oysters are keystone species that use external fertilization as a sexual mode. The gametes are planktonic and face a wide range of stressors, including plastic litter. Nanoplastics are of increasing concern because their size allows pronounced interactions with biological membranes, making them a potential hazard to marine life. In the present study, oyster spermatozoa were exposed for 1 h to various doses (from 0.1 to 25 µg mL^-1) of 50-nm polystyrene beads with amine (50-NH₂ beads) or carboxyl (50-COOH beads) functions. Microscopy revealed adhesion of particles to the spermatozoa membranes, but no translocation of either particle type into cells. Nevertheless, the 50-NH₂ beads at 10 µg mL^-1 induced a high spermiotoxicity, characterized by a decrease in the percentage of motile spermatozoa (-79%) and in the velocity (-62%) compared to control spermatozoa, with an overall drop in embryogenesis success (-59%). This major reproduction failure could be linked to a homeostasis disruption in exposed spermatozoa. The 50-COOH beads hampered spermatozoa motility only when administered at 25 µg mL^-1 and caused a decrease in the percentage of motile spermatozoa (-66%) and in the velocity (-38%), but did not affect embryogenesis success. Microscopy analyses indicated these effects were probably due to physical blockages by microscale aggregates formed by the 50-COOH beads in seawater. This toxicological study emphasizes that oyster spermatozoa are a useful and sensitive model for (i) deciphering the fine interactions underpinning nanoplastic toxicity and (ii) evaluating adverse effects of plastic nanoparticles on marine biota while waiting for their concentration to be known in the environment.

Effects of MP Polyethylene Microparticles on Microbiome and Inflammatory Response of Larval Zebrafish

Plastic polymers have quickly become one of the most abundant materials on Earth due to their low production cost and high versatility. Unfortunately, some of the discarded plastic can make its way into the environment and become fragmented into smaller microscopic particles, termed secondary microplastics (MP). In addition, primary MP, purposely manufactured microscopic plastic particles, can also make their way into our environment via various routes. Owing to their size and resilience, these MP can then be easily ingested by living organisms. The effect of MP particles on living organisms is suspected to have negative implications, especially during early development. In this study, we examined the effects of polyethylene MP ingestion for four and ten days of exposure starting at 5 days post-fertilization (dpf). In particular, we examined the effects of polyethylene MP exposure on resting metabolic rate, on gene expression of several inflammatory and oxidative stress linked genes, and on microbiome composition between treatments. Overall, we found no evidence of broad metabolic disturbances or inflammatory markers in MP-exposed fish for either period of time. However, there was a significant increase in the oxidative stress mediator L-FABP that occurred at 15 dpf. Furthermore, the microbiome was disrupted by MP exposure, with evidence of an increased abundance of Bacteroidetes in MP fish, a combination frequently found in intestinal pathologies. Thus, it appears that acute polyethylene MP exposure can increase oxidative stress and dysbiosis, which may render the animal more susceptible to diseases.

Interspecific biotransformation and detoxification of arsenic compounds in marine rotifer and copepod

The toxicity of arsenic (As) has been reported to be different depending on their chemical forms. However, its toxicity mechanisms largely remain unknown. In this study, to investigate toxicity mechanism of As in marine zooplanktons, namely, the rotifer Brachionus plicatilis and the copepod Paracyclopina nana, metabolites of As were analyzed by using a high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry with in vivo toxicity and antioxidant responses in response to inorganic As, including arsenate (As^V) and arsenite (As^III). While As^III was more toxic than As^V in both organisms, the rotifer B. plicatilis exhibited stronger tolerance, compared to the copepod P. nana. The As speciation analysis revealed differences in biotransformation processes in two species with B. plicatilis having a more simplified process than P. nana, contributing to a better tolerance against As in the rotifer B. plicatilis compared to P. nana. Moreover, the levels of GSH content and the regulation of omega class glutathione S-transferases were different in response to oxidative stress between B. plicatilis and P. nana. These results suggest that the rotifer B. plicatilis has a unique survival strategy with more efficient biotransformation and antioxidant responses, compared to P. nana, conferring higher tolerance to As.

Effects of temperature changes on life parameters, oxidative stress, and antioxidant defense system in the monogonont marine rotifer Brachionus plicatilis

Global warming is a big concern for all organisms and many efforts have been made to reveal the potential effects of temperature elevation on aquatic organisms. However, limited studies on molecular mechanistic approaches on physiological effects due to temperature changes are available. Here, we investigated the effects of temperature changes on life parameters (e.g., population growth [total number of rotifers], and lifespan), oxidative stress levels and antioxidant activities (e.g., glutathione S-transferase [GST], catalase [CAT], superoxide dismutase [SOD]) with expression levels in the monogonont marine rotifer Brachionus plicatilis. The changes in temperatures led to significant reduction (P < 0.05) in lifespan, possibly due to significant decrease (P < 0.05) in antioxidant activities, reducing the potential to cope with significant elevation in the temperature-induced oxidative stress in B. plicatilis. To further assess the actual induction and clearance of reactive oxygen species (ROS), N-acetyl-L-cysteine was used to examine whether the temperature-induced oxidative stress could be successfully scavenged. Furthermore, expression patterns of the antioxidant-related genes (GSTs, SODs, and CATs) were down- or upregulated (P < 0.05) in response to different temperatures in B. plicatilis. Overall, these findings indicate that ROS-mediated oxidative stress led to cellular damage and antioxidant defense system, resulting in deleterious effects on life parameters in rotifer.

Effects of different routes of exposure to metals on bioaccumulation and population growth of the cyclopoid copepod Paracyclopina nana

We examined effects of the three metals cadmium (Cd), copper (Cu), and nickel (Ni) on two subpopulations of the cyclopoid copepod Paracyclopina nana. We sought to investigate the effects of metal exposure on population growth and structure of P. nana and to understand the parameters affecting the metal bioaccumulation in copepods. A first experiment tested the hypothesis of competition between these metals in a mixture using a P. nana mass culture in 10 L beakers with the sublethal concentrations (1/3 of LC50) as determined for E. affinis. A second experiment pursued the same with a P. nana population which was adapted to a higher Cu concentration for several generations (226.9 ± 15.9 μg g^-1 dw Cu in copepods) and using the proper sublethal concentrations for P. nana. After 96 h of exposure, results from the first experiment showed a decreasing population growth and instead of an increasing metal accumulation in copepods. Cd also appeared to be more accumulated when it was alone, confirming the hypothesis of metal competition in mixture. Results from the second experiment revealed less marked effects. When metal concentrations increased in the treatment it decreased in copepods, indicating depuration activity in the population already adapted to metal exposure. This paper is the first one investigating the parameters affecting the bioaccumulation capacity of P. nana in response to metals. It offers a better understanding of copepod responses to metal contamination in a complex aquatic environment.

Effects of polystyrene microplastics on larval development, settlement, and metamorphosis of the intertidal barnacle Amphibalanus amphitrite

The effects of microplastic on mortality and sublethal responses on larval development of meroplankton are still largely unknown. Present study investigated the effects of four sizes of virgin spherical polystyrene microplastics (diameter 1.7, 6.8, 10.4, 19.0 μm) on naupliar (stage II-VI) and cypris larvae of barnacle Amphibalanus amphitrite at environmentally relevant concentrations (1, 10, 100, 1000 beads mL^-1). Essential life-history traits, including mortality, development time and rates of growth, settling, and metamorphosis were measured throughout the entire larval development. Feeding experiments were conducted to evaluate if microplastics decreased naupliar feeding due to physical impacts or selective feeding of nauplii. The results showed that A. amphitrite stage II nauplii were able to ingest and efficiently egest all sizes of microplastics. All the life-history endpoints measured were not significantly affected by all sizes of microplastics at any concentration tested. Presence of all sizes of microplastics did not cause physical interference on naupliar feeding and all stages of nauplius larvae (stage III-VI) did not selectively feed on microplastics. However, the feeding ability of stage III nauplius appeared to be affected by 1.7 μm at 1000 beads mL^-1 which was possibly due to individual variations rather than microplastics' impacts. Overall, the full larval development of barnacle A. amphitrite was not affected by microplastics at environmentally relevant concentrations under laboratory condition.

Effects of Virgin Micro- and Nanoplastics on Fish: Trends, Meta-Analysis, and Perspectives

Environmental plastic pollution is a major ecological and societal concern today. Over the past decade, a broad range of laboratory and experimental studies have complemented field observations in the hope of achieving a better understanding of the fate and impact of micro- and/or nanoplastics (MP/NP) on diverse organisms (e.g., birds, fish, and mammals). However, plastic pollution remains challenging to monitor in the environment and to control under laboratory conditions, and plastic particles are often naturally or experimentally co-contaminated with diverse chemical pollutants. Therefore, our understanding of the effects of virgin MP/NP in freshwater and marine fish is still limited. Here, we performed a systematic review of the most up-to-date literature on the effects of virgin MP/NP on fish under laboratory conditions. A total of 782 biological endpoints investigated in 46 studies were extracted. Among these endpoints, 32% were significantly affected by exposure to virgin MP/NP. More effects were observed for smaller plastic particles (i.e., size ≤20 μm), affecting fish behavioral and neurological functions, intestinal permeability, metabolism, and intestinal microbiome diversity. In addition, we propose suggestions for new research directions to lead toward innovative, robust, and scientifically sound experiments in this field. This review of experimental studies reveals that the toxicity of virgin MP/NP on fish should be more systematically evaluated using rigorous laboratory-based methods and aims toward a better understanding of the underlying mechanisms of this toxicity to fish.

Microplastic exposure represses the growth of endosymbiotic dinoflagellate Cladocopium goreaui in culture through affecting its apoptosis and metabolism

Microplastics are widespread emerging marine pollutants that have been found in the coral reef ecosystem. In the present study, using Cladocopium goreaui as a symbiont representative, we investigated cytological, physiological, and molecular responses of a Symbiodiniaceae species to weeklong microplastic exposure (Polystyrene, diameter 1.0 μm, 9.0 × 10⁹ particles L^-1). The density and size of algal cells decreased significantly at 7 d and 6-7 d of microplastic exposure, respectively. Chlorophyll a content increased significantly at 7 d of exposure, whereas Fv/Fm did not change significantly during the entire exposure period. We observed significant increases in superoxide dismutase activity and caspase3 activation level, significant decrease in glutathione S-transferase activity, but no change in catalase activity during the whole exposure period. Transcriptomic analysis revealed 191 significantly upregulated and 71 significantly downregulated genes at 7 d after microplastic exposure. Fifteen GO terms were overrepresented for these significantly upregulated genes, which were grouped into four categories including transmembrane ion transport, substrate-specific transmembrane transporter activity, calcium ion binding, and calcium-dependent cysteine-type endopeptidase activity. Thirteen of the significantly upregulated genes encode metal ion transporter and ammonium transporter, and five light-harvesting protein genes were among the significantly downregulated genes. These results demonstrate that microplastics can act as an exogenous stressor, suppress detoxification activity, nutrient uptake, and photosynthesis, elevate oxidative stress, and raise the apoptosis level through upregulating ion transport and apoptotic enzymes to repress the growth of C. goreaui. These effects have implications in negative impacts of microplastics on coral-Symbiodiniaceae symbiosis that involves C. goreaui.

What is known and unknown about the effects of plastic pollution: A meta-analysis and systematic review

As a consequence of the global ubiquity of plastic pollution, scientists, decision-makers, and the public often ask whether macroplastics (>5 mm) and microplastics (<5 mm) have a realized ecological threat. In 2016, we conducted a systematic review of the literature and made a call for further research testing hypotheses about ecological effects. In the subsequent years, the amount of relevant research has risen tremendously. Here, we reassess the literature to determine the current weight of evidence about the effects of plastic pollution across all levels of biological organization. Our data spans marine, freshwater, and terrestrial environments. We extracted data from 139 lab and field studies testing 577 independent effects across a variety of taxa and with various types, sizes, and shapes of plastic. Overall, 59% of the tested effects were detected. Of these, 58% were due to microplastics and 42% were due to macroplastics. Of the effects that were not detected, 94% were from microplastics and 6% were from macroplastics. We found evidence that whether or not an effect is detected, as well as the severity and direction of the effect, is driven by dose, particle shape, polymer type, and particle size. Based on our analyses, there is no doubt that macroplastics are causing ecological effects, however, the effects of microplastics are much more complex. We also assessed the environmental relevancy of experimental studies by comparing the doses used in each exposure to the concentrations and sizes of microplastics found in the environment. We determined that only 17% of the concentrations used in experimental studies have been found in nature, and that 80% of particle sizes used in experiments fall below the size range of the majority of environmental sampling. Based on our systematic review and meta-analysis, we make a call for future work that recognizes the complexity of microplastics and designs tests to better understand how different types, sizes, shapes, doses, and exposure durations affect wildlife. We also call for more ecologically and environmentally relevant studies, particularly in freshwater and terrestrial environments.

Exposure to polystyrene microplastics causes reproductive toxicity through oxidative stress and activation of the p38 MAPK signaling pathway

Microplastics (MP) are receiving increased attention as a harmful environmental pollutant, however information on the reproduction toxicity of MP in terrestrial animals, especially mammals, is limited. In this experiment, we investigated the impact of polystyrene microplastics (micro-PS) on the reproductive system of male mice. Healthy Balb/c mice were exposed to saline or to different doses of micro-PS for 6 weeks. The results showed that micro-PS exposure resulted in a significant decrease in the number and motility of sperm, and a significant increase in sperm deformity rate. We also detected a decrease in the activity of the sperm metabolism-related enzymes, succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH), and a decrease in the serum testosterone content in the micro-PS exposure group. We found that micro-PS exposure caused oxidative stress and activated JNK and p38 MAPK. In addition, we found that when N-acetylcysteine (NAC) scavenges ROS, and when the p38 MAPK-specific inhibitor SB203580 inhibits p38MAPK, the micro-PS-induced sperm damage is alleviated and testosterone secretion improves. In conclusion, our findings suggest that micro-PS induces reproductive toxicity in mice through oxidative stress and activation of the p38 MAPK signaling pathways.

Polystyrene nanoplastic induces ROS production and affects the MAPK-HIF-1/NFkB-mediated antioxidant system in Daphnia pulex

Recently, research on the biological effects of nanoplastics has grown exponentially. However, studies on the effects of nanoplastics on freshwater organisms and the mechanisms of the biological effects of nanoplastics are limited. In this study, the content of reactive oxygen species (ROS), gene and protein expression in the MAPK-HIF-1/NFkB pathway, and antioxidant gene expressions and enzyme activities were measured in Daphnia pulex exposed to polystyrene nanoplastic. In addition, the full-length extracellular signal-regulated kinases (ERK) gene, which plays an important role in the MAPK pathway, was cloned in D. pulex, and the amino acid sequence, function domain, and phylogenetic tree were analyzed. The results show that nanoplastic caused the overproduction of ROS along with other dose-dependent effects. Low nanoplastic concentrations (0.1 and/or 0.5 mg/L) significantly increased the expressions of genes of the MAPK pathway (ERK; p38 mitogen-activated protein kinases, p38; c-Jun amino-terminal kinases, JNK; and protein kinase B, AKT), HIF-1 pathway (prolyl hydroxylasedomain, PHD; vascular endothelial growth factor, VEGF; glucose transporter, GLUT; pyruvate kinase M, PKM; hypoxia-inducible factor 1, HIF1), and CuZn superoxide dismutase (SOD) along with the activity of glutathione-S-transferase. As the nanoplastic concentration increased, these indicators were significantly suppressed. The protein expression ratio of ERK, JNK, AKT, HIF1α, and NFkBp65 (nuclear transcription factor-kB p65) as well as the phosphorylation of ERK and NFkBp65 were increased in a dose-dependent manner. The activities of other antioxidant enzymes (catalase, total SOD, and CuZn SOD) were significantly decreased upon exposure to nanoplastic. Combined with our previous work, these results suggest that polystyrene nanoplastic causes the overproduction of ROS and activates the downstream pathway, resulting in inhibited growth, development, and reproduction. The present study fosters a better understanding of the biological effects of nanoplastics on zooplankton.

Microplastic (1 and 5 μm) exposure disturbs lifespan and intestine function in the nematode Caenorhabditis elegans

As an emerging environmental pollutant, microplastics (MPs) are increasingly viewed as a serious health concern to terrestrial and aquatic ecosystems. However, previous toxicological studies examining MPs on freshwater and terrestrial organisms provide contradictory results, possibly due to few investigations at environmentally relevant concentrations. Here, the nematode Caenorhabditis elegans (C. elegans), a model organisms with both aquatic and terrestrial free-living forms, was employed to investigate the effects of 1 and 5 μm MPs (10⁷-10¹⁰ particles/m²) on the intake, lifespan, defecation rhythm, defecation-related neurons and transcriptional expression of related genes (skn-1, mkk-4, pmk-1, cpr-1 and itr-1). We demonstrated that the percentage of MP-contaminated nematodes increased with increasing exposure concentrations and duration. The lifespan of nematodes in the lower concentration exposure groups (2.4 × 10⁷ and 2.4 × 10⁸ particles/m²) decreased more prominently than that of higher concentration groups (2.4 × 10⁹ and 2.4 × 10¹⁰ particles/m²) after a 72-h exposure period. Concomitantly, expression of the skn-1 gene, involved in detoxification and lifespan regulation, was significantly altered at lower MP concentrations. Physiologically, the defecation rhythm after a 72-h exposure period was most strongly affected by 1 μm MPs at 2.4 × 10⁸ particles/m². The significant up-regulation of related genes by 1 μm MPs appears responsible for the shortened defecation interval. Results of this study identified a potential toxicity threat to C. elegans from exposure to MPs at environmentally relevant concentrations and provide novel evidence for MP risks to freshwater and terrestrial organisms. Capsule. After exposure to 1 and 5 μm MPs (10⁷-10¹⁰ particles/m²), the lifespan of C. elegans decreased more rapidly at lower concentrations.

18α-Glycyrrhetinic acid (GA) ameliorates fructose-induced nephropathy in mice by suppressing oxidative stress, dyslipidemia and inflammation

Excessive fructose (FRU) intake can result in insulin resistance and metabolic disorder, which are related to renal injury.18α-Glycyrrhetinic acid (GA) is a bioactive component mainly extracted from Glycyrrhiza radix, and has anti-oxidant and anti-inflammatory activities. However, its effects on FRU-induced renal injury still remain unclear. In this study, we found that 18α-GA treatments could significantly ameliorate the cell viability in FRU-treated tubule epithelial cells, accompanied with improved mitochondrial membrane potential. Furthermore, reactive oxygen species (ROS) accumulation in FRU-stimulated cells was markedly reduced by 18α-GA, which were associated with the activation of nuclear factor (erythroid-derived-2)-like 2 (Nrf-2) and the blockage of MAPKs signaling. Additionally, dyslipidemia detected in FRU-treated cells was greatly inhibited by 18α-GA. We also found that 18α-GA significantly ameliorated FRU-induced inflammation in cells through reducing the expression of pro-inflammatory cytokines and chemokine. The anti-inflammatory effects regulated by 18α-GA were mainly related to the repression of nuclear factor-κB(NF-κB) signaling. Furthermore, the protective effects of 18α-GA against ROS production, lipid accumulation and inflammation were verified in renal tissues from FRU-challenged mice, consequently improving metabolic disorder and kidney injury. Taken together, these findings demonstrated that 18α-GA exerted renal protective effects through reducing oxidative stress, lipid deposition and inflammatory response, and thus could be considered as a promising therapeutic strategy for metabolic stress-induced kidney injury.

Enchytraeus crypticus Avoid Soil Spiked with Microplastic

Microplastics (MPs) of varying sizes are widespread pollutants in our environment. The general opinion is that the smaller the size, the more dangerous the MPs are due to enhanced uptake possibilities. It would be of considerably ecological significance to understand the response of biota to microplastic contamination both physically and physiologically. Here, we report on an area choice experiment (avoidance test) using Enchytraeus crypticus, in which we mixed different amounts of high-density polyethylene microplastic particles into the soil. In all experimental scenarios, more Enchytraeids moved to the unspiked sections or chose a lower MP-concentration. Worms in contact with MP exhibited an enhanced oxidative stress status, measured as the induced activity of the antioxidative enzymes catalase and glutathione S-transferase. As plastic polymers per se are nontoxic, the exposure time employed was too short for chemicals to leach from the microplastic, and as the microplastic particles used in these experiments were too large (4 mm) to be consumed by the Enchytraeids, the likely cause for the avoidance and oxidative stress could be linked to altered soil properties.

Surface-Related Toxicity of Polystyrene Beads to Nematodes and the Role of Food Availability

Microplastics released into freshwaters from anthropogenic sources settle in the sediments, where they may pose an environmental threat to benthic organisms. However, few studies have considered the ecotoxicological hazard of microplastic particles for nematodes, one of the most abundant taxa of the benthic meiofauna. This study investigated the toxic effects of polystyrene (PS) beads (0.1-10.0 μm) and the underlying mechanisms thereof on the reproduction of the nematode Caenorhabditis elegans. The observed effect of the PS beads on the nematodes correlated well with the total surface area of the beads per volume, with a 50% inhibition of reproduction at 55.4 ± 12.9 cm²/mL, independent of the bead size. The adverse effects were not explained by styrene monomers leaching from the beads because chemical activities of styrene in PS suspensions were well below the toxic levels. However, the observed effects could be related to the bead material because the same-sized silica (SiO₂) beads had considerably less impact, probably due to their higher specific density. PS and SiO₂ beads affected the food availability of C. elegans, with greater effects by the PS beads. Our results demonstrate the importance of including indirect food web effects in studies of the ecological risks posed by microplastics.

Ecological and toxicological manifestations of microplastics: current scenario, research gaps, and possible alleviation measures

Microplastics (MPs) and associated contaminants have become a major environmental concern. From available literature, their ubiquitous presence is now well established. However, the kind and level of toxicological impacts these MPs accomplish on various life forms are not well understood. Nevertheless, the environmental toxicity of MP is now being revealed gradually with supporting studies involving groups of lower organisms. Additionally, the presence of microplastics also disturbs the functions of ecosystem through affecting the vulnerable life forms, thus ecological manifestations of MPs also need to be analyzed. The present review encompasses an overview of toxicological effects mediated by various types of MPs present in the environment; it covers the types of toxicity they may cause and other effects on humans and other species. In this review, aquatic systems are used as primary models to describe various eco-toxicological effects of MPs. Various research gaps as well as methods to alleviate the level of MPs, and future strategies are also comprehensively highlighted in the review.

Evaluation of microplastic toxicity in accordance with different sizes and exposure times in the marine copepod Tigriopus japonicus

The indiscriminate use of plastic has greatly increased microplastic contamination risk in the marine environment. Microplastics can affect all marine life via the food web, from primary producers (e.g., microalgae) to final consumers (e.g., carnivorous fish). Thus, several studies have attempted to evaluate microplastic toxicity, but information about the underlying mechanisms of their effect is limited. Therefore, in this study, we examined multiple factors that could contribute to microplastic-induced toxicity. We investigated the potential molecular effects of microplastic size and exposure time. We exposed the marine copepod Tigriopus japonicus to 50 nm and 10 μm polystyrene microbeads. We found that both size and exposure time increased intracellular levels of reactive oxygen species. In addition, antioxidant-related gene expression was modulated and antioxidant enzyme activities were changed significantly. The results of this study provide important insights into the molecular mechanisms of microplastic-induced toxicity in a marine organism.

Dietary administration of PVC and PE microplastics produces histological damage, oxidative stress and immunoregulation in European sea bass (Dicentrarchus labrax L.)

Worldwide, plastic waste is increasingly being discharged into the oceans, where it breaks down into smaller particles. Of these particles, the ingestion of microplastics (MPs; particles smaller than 5 mm) have been documented in some aquatic animals, including fish, whose health and welfare suffer as a consequence. However, their precise effects are not completely understood. To shed light on this issue, European sea bass (Dicentrarchus labrax L.) specimens were fed diets containing 0 (control), 100 or 500 mg polyvinylchloride (PVC) or polyethylene (PE) MPs kg^-1 diet for three weeks, after which samples of liver, intestine, skin mucus and head kidney (HK) were obtained. A histological study of the liver and intestine revealed important alterations in the fish fed the MP diets, compared with control fish. At a functional level, PE-MPs, but not PVC-MPs, decreased the activity of antioxidant enzymes, suggesting a certain level of oxidative stress. As regards immunity, the intake of PVC-MPs increased the phagocytic and respiratory burst activities of HK leucocytes whilst the intake of PE-MPs increased skin mucus immunoglobulin M levels and the respiratory burst activity of leucocytes. The results suggest that the short-medium term intake of PVC- or PE-MPs by fish slightly depresses their immunity and produces oxidative stress. However, based on the histological alterations found, it seems that longer exposure times might lead to irreversible damage that could compromise fish health and welfare.

Accumulation of different shapes of microplastics initiates intestinal injury and gut microbiota dysbiosis in the gut of zebrafish

Different shapes of microplastics are widely detected in the environment and organisms and most of them remain in the gut. However, the influences of shapes on the bioaccumulation and toxicity of microplastics in the gut are largely unknown. Three shapes (bead, fragment, and fiber) of microplastics of comparable size in one dimension were prepared to exposure to zebrafish. The accumulation and toxicities of microplastics in the gut were detected. Shape-dependent accumulation in the gut was observed with the order of fibers (8.0 μg/mg) > fragments (1.7 μg/mg) > beads (0.5 μg/mg). The accumulation of microplastics caused multiple toxic effects in fish intestine, including mucosal damage, and increased permeability, inflammation and metabolism disruption. Based on these toxic effects, microplastic fibers resulted in more severe intestinal toxicity than microplastic fragments and beads did. Furthermore, microplastics also induced gut microbiota dysbiosis and specific bacteria alterations, which will provide novel insights into the potential mechanism of microplastics causing intestinal toxicities in fish. Our results also suggested that shape-depended effects should not be ignored in the health risk assessment of microplastics.

Evaluation of the infiltration of polystyrene nanobeads in zebrafish embryo tissues after short-term exposure and the related biochemical and behavioural effects

One of the current main challenges faced by the scientific community is concerning the fate and toxicity of plastics, due to both the well-known threats made by larger plastic items spreading in ecosystems and their fragmentation into micro- and nanoparticles. Since the chemical and physical characteristics of these smaller plastic fragments are markedly different with respect to their bulk product, the potential toxicological effects in the environment need to be deeply investigated. To partially fill this gap of knowledge, the aim of this study was to evaluate the polystyrene nanobead intake in the tissues of zebrafish (Danio rerio) embryos and their related toxicity. Embryos at 72 h post fertilization (hpf) were exposed for 48 h to 0.5 μm fluorescent polystyrene nanobeads at a concentration of 1 mg L^-1. Confocal microscopy was employed to investigate nanoplastic ingestion and tissue infiltration, while potential sub-lethal effects were evaluated by measuring several endpoints, which covered the adverse effects at the molecular (protein carbonylation), cellular (P-glycoprotein, activity of several antioxidant/detoxifying enzymes) and organism levels by evaluating of possible changes in the embryos' swimming behaviour. Imaging observations clearly highlighted the nanoplastics' uptake, showing nanobeads not only in the digestive tract, but also migrating to other tissues through the gut epithelium. Biomarker analyses revealed a significant decrease in cyclooxygenase activity and an induction of superoxide dismutase. The behavioural test highlighted a significant (p < 0.05) variation in the turn angle between the control and exposed embryos. This study points out the capability of nanoplastics to infiltrate zebrafish embryo tissues, even after a short exposure, thus suggesting the need for deeper investigations following longer exposure times, and highlighting the potential of nanoplastics to cause toxicological effects on freshwater organisms, at the organism level.

How to get rid of ingested microplastic fibers? A straightforward approach of the Atlantic ditch shrimp Palaemon varians

Microplastic fibers represent a significant share of the global marine micrcroplastic pollution, particularly in coastal areas. In controlled laboratory experiments, we offered fluorescent microplastic fibers (40-4400 μm lengths, median 150 μm) and spherical microplastic beads (9.9 μm Ø) together with commercial fish food to the Atlantic ditch shrimp Palaemonetes varians. The shrimps ingested fibers and beads along with the food. Upon ingestion, the beads and the shortest fibers (up to 100 μm) passed from the stomach into the gut and were egested within the fecal strings. The longer fibers first remained in the stomach but were regurgitated, i.e. extruded through the esophagus, within 12-14 h. Regurgitation is an evolutionary adaptation of particular crustacean species and other invertebrates to remove large and indigestible food particles from the stomach. Accordingly, the process of regurgitation attained a new task nowadays, i.e. the elimination of anthropogenic filamentous microplastic debris from the stomach to avoid harm. This behavioral feature may represent a selective advantage in view of the continuously increasing environmental plastic pollution.

Effects of micro-sized polyethylene spheres on the marine microalga Dunaliella salina: Focusing on the algal cell to plastic particle size ratio

There is increasing concern about how microplastics (MPs) are impacting marine ecosystems. In particular, studies on how MPs impact microalgae are required because of the abundance of MPs and importance of green microalgae as primary producers. This study investigated how MPs that are larger (200 μm) than algal cells impact them, using the marine microalga Dunaliella salina as the test species. The microalga was exposed to polyethylene MPs for 6 days. Of interest, the growth and photosynthetic activity of D. salina was enhanced with exposure to MPs, while cell morphology (size and granularity) was not impacted. This phenomenon might be explained by trace concentrations of additive chemicals (endocrine disruptors, phthalates, stabilizers) that possibly leached from MPs promoting the growth and photosynthetic activity of D. salina. We also confirmed that MP size contributes towards determining how plastics affect microalgae. Specifically, as MP size shrinks compared to algal cell size, MPs have increasingly adverse effects. MPs of very small size (like nanoplastics) induce particularly adverse effects on algae. Further studies are required to establish the relationship between algal cell size and MP size.

Molecular toxicity of nanoplastics involving in oxidative stress and desoxyribonucleic acid damage

Microplastic pollution attracted extensive attention because of its global presence and adverse effects on ecosystem. However, it is insufficient to clear the effects of nanoplastics on organisms at the molecular level. Herein, a nanopolystyrene (50 nm) was used to examine molecular responses of superoxide dismutase (SOD) and desoxyribonucleic acid (DNA) using spectroscopy (UV-vis, circular dichroism spectra, and fluorescence measurements) and single cell gel electrophoresis methods. Results showed that nanopolystyrene induced oxidative stress, involving in the increase of SOD activity and malondialdehide (MDA) content, and DNA damage because of the significant increase of olive tail moment, head optical density, and tail DNA percentage in the groups at exposure concentrations above 5 × 10^-6  mol/L. The second structural and microenvironment of aromatic amino acids of SOD were changed with nanopolystyrene exposure. The fluorescence of SOD was quenched by nanopolystyrene at exposure concentration above 1 × 10^-5  mol/L, and the quenching mode could be ascribed to the static type. The results and the combined methods are favorable to explore the molecular toxicity of other nanoplastics and the interaction mechanism.

Aquatic behavior and toxicity of polystyrene nanoplastic particles with different functional groups: Complex roles of pH, dissolved organic carbon and divalent cations

Herein we systematically examined the roles of water chemistry (pH, dissolved organic carbon (DOC), and divalent cations) and particle surface functionality that control the aqueous stability, aggregation, and toxicity of engineered nanoplastic particles in simulated natural environmental conditions. Model polystyrene latex nanoparticles (PLNPs) with three different functional groups, namely unmodified (uPLNPs), amine-modified (aPLNPs), and carboxyl-modified (cPLNPs), were investigated. Results indicate that the presence of only DOC increased the surface charge and exhibited negligible effects on the size distribution of the PLNPs in aqueous suspensions. The presence of the divalent cations (Ca²⁺ and Mg²⁺) was observed to decrease the surface charge and increase the size of the PLNPs. The coexistence of DOC and the divalent cations enhanced the extent of aggregation of the PLNPs in the water columns. The surface modification and pH were sensitive factors influencing the stability of PLNPs during long-term suspension when DOC and the divalent cations coexisted. Direct visual further testified the conclusions on the combined effects of solution and surface chemistry parameters. Furthermore, in situ transmission electron microscope observations revealed that the enhancement of PLNP aggregation in the presence of DOC and the divalent cation was caused by bridge formation. Toxicity test indicated the PLNPs exhibited acute toxicity and physical damage to Daphnia magna. The more complex the solution conditions, the more toxicity the aPLNPs and cPLNPs. Analysis of mode of toxic action implied that the PLNPs mainly caused the accumulation of oxidative damage to the gut of D. magna.