Size-dependent effects of plastic particles on antioxidant and immune responses of the thick-shelled mussel Mytilus coruscus

Passing the Parcels: Intercellular Nanoplastics Transfer in Mussels Perna viridis with Activated Immunomodulation

Nanoplastics (NPs) are generally considered to have a defined intracellular fate, being difficult to excrete or transport due to their stability. This study provides the first evidence of NPs intercellular transfer in the hemocytes of green mussels (Perna viridis), which subsequently activated the immunomodulation process. NPs were predominantly internalized by granulocytes, with a portion being translocated and deposited in lysosomes, whereas those retained in endosomes were subsequently transferred to new hemocytes (mainly granulocytes). The transfer direction was driven by the intracellular NP concentration gradients. Transfer kinetics was size-dependent, with smaller-sized NPs exhibiting greater potential but a lower rate, primarily due to their specific extracellular vesicle-mediated transfer pathway. Tunneling nanotubes provided the most efficient pathway for the intercellular transfer of NPs, as their continuous membrane structure allowed direct substance exchange. Crucially, NP redistribution was accompanied by a gradient-driven transfer of mitochondria to injured hemocytes. This process alleviated stress on the overburdened hemocytes and regulated reactive oxygen species production, subsequently enhancing phagocytic activity and promoting immune responses. These findings underscore that NPs exhibit far more active behavior in the immune system than previously understood and provide new insights into how immune cells maintain the health of marine organisms in the face of NP challenges.

Polystyrene microplastics reduce honeybee survival by disrupting gut microbiota and metabolism

Polystyrene microplastics (PS-MPs) pose significant risks to honeybee health. However, how microplastics (MPs) adversely influence honeybee survival through the gut pathway, especially the metabolic processes, remains poorly understood. To conduct the experiment, the honeybees (Apis mellifera L.) were exposed to PS-MPs (0.5 μm and 5 μm) at environmental concentrations of 25 mg/L and 50 mg/L for 21 days. Results revealed that PS-MPs reduced honeybee survival rates and food consumption. The accumulation of PS-MPs in honeybee guts caused structural damage to gut walls and elevated oxidative stress levels. Additionally, PS-MPs altered gut microbial communities, with a decrease in Lactobacillus and an increase in Bartonella. Gut metabolomics analysis indicated that PS-MPs disrupted metabolic pathways, upregulated amino acid and carbohydrate metabolism, and downregulated alpha-linolenic acid and lipid metabolism. Our study offers important insights into the physiological effects of accumulated MPs on honeybees, highlighting the critical need for effective strategies to manage environmental pollutants.

Effects of functionalized nanoplastics on oxidative stress in the mussel Mytilus coruscus

In the marine environment, various weathering effects on micro or nanoplastics lead to surface modifications, which in turn alter their toxic effects on aquatic organisms. This study investigated the impact of three types of nanoplastics (NPs, NPs-NH2, NPs-COOH) on the antioxidant capacity of Mytilus coruscus gills, mantle, and hemolymph over 28 days. Analyzed key antioxidant stress indicators (CAT, SOD, GSH, GSH-Px, MDA, H2O2) and conducted IBR and PCA analyses to evaluate the toxic effects of modified nanoplastics. In particular, NPs-NH2 showed the most significant inhibition of antioxidant enzymes like CAT and GSH-Px in gills and mantle, while NPs-COOH affected a wider range of oxidative stress markers. Furthermore, tissue-specific responses were observed, with gills being the most sensitive to biomarker changes. Overall, NPs-NH2 emerged as the most toxic nanoplastic, highlighting the need to assess ecological risks associated with novel nanoparticles in marine environments and offering insights into tissue-specific toxicity in mussels.

Microplastic pollution in Taihu Lake: Spatial distribution from the lake inlet to the lake centre and vertical stratification in the water column

The aim of this study was to analyse the distribution characteristics of microplastics in lakes, assess their potential impacts on ecosystems, and explore effective management and control strategies. Despite a wealth of research focused on lake water, the variations in microplastics with offshore distance and their vertical distribution within the water column are not well understood. Here, we investigated the freshwater continuum from the inlet of Taihu Lake to the centre, and vertically from the surface to the bottom water. The results revealed that the distribution of microplastics (<5 mm in size) exhibited a clear spatial gradient. The microplastic abundance at the lake entrance was 2.12 times greater than that at the centre, and on the lake surface, the microplastic abundance was 1.36-1.69 times higher than that estimated from the water column. Notably, the proportion of small-sized microplastics (<0.1 mm) in the bottom water was 1.72 times higher than that in the surface water. The main types of polymers identified were polyamide (PA) and polyvinyl chloride (PVC), and their main sources may be from clothes washing and industrial activities. The Monte Carlo simulation results indicated that the overall risk of microplastics in surface water was higher than that in the water column, and the contributions of PVC and polyurethane (PU) to the ecological risk were 90.10% and 9.57%, respectively. Therefore, PVC and PU should be the priority of microplastic pollution control. This study provides the first comprehensive evaluation of the spatial ecological risk of microplastics in Taihu Lake, which improves our understanding of the distribution and environmental risks of microplastics in lake systems.

Assessing the physiological effects of microplastics on cultured mussels in the Mediterranean Sea

Microplastics (MPs) pollution has gained attention due to its ecological threats and potential economic impacts. Yet significant knowledge gaps remain in understanding MPs effects on marine organisms' physiology. This study quantifies the physiological impacts of MPs on farmed mussels (Mytilus galloprovincialis) across various locations in the Mediterranean Sea by combining a laboratory experiment with a Dynamic Energy Budget (DEB) model. Mussels' clearance rates (CR) were measured under different conditions of microplastics and suspended sediment. The DEB model, driven by satellite data and an MPs distribution model, was validated with literature growth and CR data, supporting further the data extracted from the conducted experiment. Results indicate that while the physiological impacts are minimal in most areas, important reductions in CR (8-25%) were estimated in regions like the Gulf of Napoli, leading to reduced growth (6-16%) and reduced reproductive output (7-19%). In addition to microplastic concentrations, seasonal and spatial variations of food availability and suspended inorganic matter importantly control the impacts, with mussels in oligotrophic environments (such as the Gulf of Napoli) showing higher vulnerability to MPs compared to those in more eutrophic locations. This study underscores the utility of bioenergetics models, such as DEB, in evaluating the ecological risks of microplastics and suggests their broader application in MPs research.

Combined ecotoxicity of polystyrene microplastics and Di-(2-ethylhexyl) phthalate increase exposure risks to Mytilus coruscus based on the bioaccumulation, oxidative stress, metabolic profiles, and nutritional interferences

Di-(2-ethylhexyl) phthalate (DEHP) and microplastics (MPs) are emerging contaminants frequently detected in the marine environment. However, the influence of MPs on DEHP bioaccumulation and their combined effects on eco-environmental risks remain underexplored. Mytilus coruscus (M. coruscus) were exposed to DEHP (200.0 µg/L), polystyrene (PS) (0.050, 0.50, and 5.0 mg/L), and their combination at environmentally relevant concentrations for 15-day, followed by a 7-day depuration period. The amount of DEHP accumulation followed the order of digestive gland > gills > muscles > gonad, with PS dose-dependently amplifying DEHP bioaccumulation in digestive gland. The changes in antioxidant enzyme activity indicated disruptions in oxidative defense. Furthermore, metabolomic analysis revealed that PS and DEHP considerably altered the lipid, energy, and citric acid cycles in digestive gland and gonad. Post-depuration analysis showed combined exposure resulted in persistent effects. Compared with single exposures, combined exposure had a greater adverse effect on the metabolism of essential amino acids, fatty acids, and volatile compounds, potentially influencing edibility and nutritional value of M. coruscus. This study underscores cumulative eco-environmental toxicity of PS and DEHP toward M. coruscus and highlights the potential increased risks of co-pollution.

Microplastic contamination in the agri-food chain: The case of honeybees and beehive products

Microplastics, MPs, plastic fragments with a dimension lower than 5 mm, and microfibers, MFs, synthetic and natural/artificial fibrous fragments with a diameter lower than 50 μm, are ubiquitous pollutants identified in different environmental compartments. In this work the occurrence of MPs and MFs on honeybees, Apis mellifera, and beehive products was evaluated, using Fourier transform infrared microspectroscopy, confirming that MPs and MFs are widely present as air contaminants in all the apiary's areas (high and low urbanized areas) in Southern Italy. Results indicated that independently from the site, both honeybees and honey samples, are contaminated by MFs with non-natural color. The majority of MFs were of natural origin followed by artificial MFs and synthetic MFs. Moreover, the chemical composition of MFs isolated from honeybees reflect that used in synthetic fabrics, leading to the hypothesis that they are released from textile to air where are captured by bees. Results highlight that MFs represent a class of ubiquitous airborne anthropogenic pollutants. The identification of polytetrafluoroethylene, PTFE, MPs in honeybees confirm the recent findings that PTFE MPs are diffuse soil and air contaminants while the identification of polyethylene, PE, based MPs in honey samples, from low density urban sites, could be correlated to the large use of PE in agriculture. In the honey samples, also polycaprolactone, PCL, MPs were identified, mainly in high density urban sites, confirming that biodegradable materials could be further pollutants in the environments. The results indicate that honeybees are contaminated by MPs and MFs during their flights or picking up from the hive components, flowers, from other nest mates, from the clothes of the beekeeper, among others and some of them could be transferred to honey samples that could be also affected by soil contamination.

First insight of the intergenerational effects of tri-n-butyl phosphate and polystyrene microplastics to Daphnia magna

As an emerging organic pollutant, tributyl phosphate (TnBP) can be easily adsorbed by microplastics, resulting in compound toxic effects. In the present work, the effects of polystyrene microplastics (PS-MPs) and TnBP on the survival, growth, reproduction and oxidative stress of Daphnia magna (D. magna) have been evaluated through multigenerational test. Compared with the alone exposure groups, the somatic growth rate and the expression values of growth related genes rpa1, mre11, rnha, and rfc3_5 in the F1 generation of the combined exposure groups were significantly lower (p < 0.05), indicating synergistic effect of PS-MPs and TnBP on the growth toxicity and transgenerational effects. In addition, compared with the PS-MPs groups, significantly lower average number of offspring and expression values of reproduction related genes ccnb, mcm2, sgrap, and ptch1 were observed in the combined exposure group and TnBP group (p < 0.05), indicating TnBP might be the major factor causing reproductive toxicity to D. magna. Although PS-MPs and TnBP alone or in combination also had toxic impacts on the growth, survival and reproduction of D. magna in generations F0 and F2, the effects were less than F1 generation. Regarding oxidative stress, the activity of SOD, CAT and GSH-Px and MDA content in the generations F0 and F1 of combined exposure groups were higher than the TnBP group but lower than the PS-MPs groups, suggesting that PS-MPs might be the dominant cause of the oxidative damage in D. magna and the presence of TnBP would alleviate oxidative stress by reducing the bioaccumulation of PS-MPs. The present work will provide a theoretical basis for further understanding of the toxic effects and ecological risks of combined TnBP and microplastic pollution on aquatic organisms.

Toxic effect of mussel Mytilus galloprovincialis exposed to Ag-TiO2 and ZnTi2O4-TiO2 bicomponent nanoparticles

Nanoparticles (NPs) are widely used in various fields, including antifouling paints for ships and industrial structures submerged in water. The potential impact of NPs on aquatic organisms, particularly their potential toxicity, is a significant concern, as their negative impact has been relatively poorly studied. In this study, we evaluated the effect of different concentrations of bimetallic Ag-TiO₂ and ZnTi₂O₄-TiO₂ NPs, which could potentially be used in antifouling coatings, on the hemocytes of the Mediterranean mussel Mytilus galloprovincialis. Hemocytes were exposed to NPs at concentrations of 0.1-1 mg/L for 1 and 2 h, and the production of reactive oxygen species (ROS), levels of DNA damage, and number of dead cells were measured. Exposure to Ag-TiO₂ NPs at 1 mg/L concentration for 1 h suppressed ROS production in hemocytes and reduced the relative number of agranulocytes in cell suspensions, without inducing DNA damage or cell death. Exposure to ZnTi2O4-TiO2 NPs did not cause changes in the ratio of granulocytes to agranulocytes in suspensions, nor did it affect other functional parameters of hemocytes. However, after a 2 h exposure period, ZnTi2O4-TiO2 NPs (1 mg/L) significantly reduced the production of ROS by hemocytes. These findings suggest that Ag-TiO2 and ZnTi2O4-TiO2 NPs have low acute toxicity for marine bivalves.

Nano titanium dioxide alleviates the toxic effects of tris (2-chloropropyl) phosphate on the digestive gland and hemolymph of thick-shell mussel Mytilus coruscus

In the marine environment, nanoparticles play a role in adsorbing and catalytically degrading organic pollutants, thereby mitigating their toxic effects on aquatic organisms. This study aimed to investigate the impact of nano titanium dioxide (nTiO2) and tris (2-chloropropyl) phosphate (TCPP) on the hemolymph and digestive function of the thick-shell mussel Mytilus coruscus. Mussels were divided into a control group, a group exposed to TCPP alone, a group exposed to a combination of TCPP and 0.5 mg/L nTiO2, and a group exposed to a combination of TCPP and 1 mg/L nTiO2. After 14 days of exposure, oxidative stress responses, including superoxide dismutase (SOD) activity and malondialdehyde (MDA) content, immune defense responses, including acid phosphatase (ACP) and alkaline phosphatase (AKP) activities, and gene expression, including HSP70 expression, were measured in the hemolymph and digestive glands of the mussels. Compared to the control group, mussels solely exposed to 100 μg/L TCPP exhibited a significant reduction in SOD activity in the hemolymph. When TCPP was co-exposed with 0.5 mg/L nTiO2, there were significant increases in MDA content and AKP activity in both the digestive gland and hemolymph compared to the control group. Upon co-exposure of TCPP with 1 mg/L nTiO2, MDA content and AKP activity in the digestive gland significantly decreased, while SOD, ACP, and AKP activity in the hemolymph significantly increased and MDA content significantly decreased, returning to the control group levels. Furthermore, in the combined exposure, HSP70 gene expression significantly decreased as the nTiO2 concentration increased from 0.5 mg/L to 1 mg/L. In summary, TCPP impacted the hemolymph and digestive function of mussels, whereas a concentration of 1 mg/L nTiO2 effectively alleviated the toxic effects of TCPP. This study is crucial for assessing the ecological risks of nanoparticles and emerging organic pollutants in marine environments, and provides new insights into the interaction between nTiO2 and TCPP, as well as the influence of nTiO2 concentration on mitigating TCPP toxicity.

In Vitro Toxicity and Modeling Reveal Nanoplastic Effects on Marine Bivalves

Nanoplastics (NPs) represent a growing concern for global environmental health, particularly in marine ecosystems where they predominantly accumulate. The impact of NPs on marine benthic organisms, such as bivalves, raises critical questions regarding ecological integrity and food safety. Traditional methods for assessing NP toxicity are often limited by their time-intensive nature and ethical considerations. Herein, we explore the toxicological effects of NPs on the marine bivalve Ruditapes philippinarum, employing a combination of in vitro cellular assays and advanced modeling techniques. Results indicate a range of adverse effects at the organismal level, including growth inhibition (69.5-108%), oxidative stress, lipid peroxidation, and DNA damage in bivalves, following exposure to NPs at concentrations in the range of 1.6 × 109-1.6 × 1011 particles/mL (p/mL). Interestingly, the growth inhibition predicted by models (54.7-104%), based on in vitro cellular proliferation assays, shows strong agreement with the in vivo outcomes of NP exposure. Furthermore, we establish a clear correlation between cytotoxicity observed in vitro and the toxicological responses at the organismal level. Taken together, this work suggests that the integration of computational modeling with in vitro toxicity assays can predict the detrimental effects of NPs on bivalves, offering insightful references for assessing the environmental risk assessment of NPs in marine benthic ecosystems.

Toxicological Research on Nano and Microplastics in Environmental Pollution: Current Advances and Future Directions

This review explains the sources of nanoplastics (NPs) and microplastics (MPs), their release, fate, and associated health risks in the aquatic environment. In the 21st century, scientists are grappling with a major challenge posed by MPs and NPs. The global production of plastic has skyrocketed from 1.5 million tons in the 1950s to an astonishing 390.7 million tons in 2021. This pervasive presence of these materials in our environment has spurred scientific inquiry into their potentially harmful effects on living organisms. Studies have revealed that while MPs, with their larger surface area, are capable of absorbing contaminants and pathogens from the surroundings, NPs can easily be transferred through the food chain. As a result, living organisms may ingest them and accumulate them within their bodies. Due to their minuscule size, NPs are particularly difficult to isolate and quantify. Furthermore, exposure to both NPs and MPs has been linked to various adverse health effects in aquatic species, including neurological impairments, disruption of lipid and energy metabolism, and increased susceptibility to cytotoxicity, oxidative stress, inflammation, and reactive oxygen species (ROS) production. It is alarming to note that MPs have even been detected in commercial fish, highlighting the severity of this issue. There are also challenges associated with elucidating the toxicological effects of NPs and MPs, which are discussed in detail in this review. In conclusion, plastic pollution is a pressing issue that governments should tackle by ensuring proper implementation of rules and regulations at national and provincial levels to reduce its health risks.