Proteomic response of mussels Mytilus galloprovincialis exposed to CuO NPs and Cu²⁺: an exploratory biomarker discovery

Integrated transcriptomic and metabolomic approaches reveal molecular response and potential biomarkers of the deep-sea mussel Gigantidas platifrons to copper exposure

Metal pollution caused by deep-sea mining activities has potential detrimental effects on deep-sea ecosystems. However, our knowledge of how deep-sea organisms respond to this pollution is limited, given the challenges of remoteness and technology. To address this, we conducted a toxicity experiment by using deep-sea mussel Gigantidas platifrons as model animals and exposing them to different copper (Cu) concentrations (50 and 500 μg/L) for 7 days. Transcriptomics and LC-MS-based metabolomics methods were employed to characterize the profiles of transcription and metabolism in deep-sea mussels exposed to Cu. Transcriptomic results suggested that Cu toxicity significantly affected the immune response, apoptosis, and signaling processes in G. platifrons. Metabolomic results demonstrated that Cu exposure disrupted its carbohydrate metabolism, anaerobic metabolism and amino acid metabolism. By integrating both sets of results, transcriptomic and metabolomic, we find that Cu exposure significantly disrupts the metabolic pathway of protein digestion and absorption in G. platifrons. Furthermore, several key genes (e.g., heat shock protein 70 and baculoviral IAP repeat-containing protein 2/3) and metabolites (e.g., alanine and succinate) were identified as potential molecular biomarkers for deep-sea mussel's responses to Cu toxicity. This study contributes novel insight for assessing the potential effects of deep-sea mining activities on deep-sea organisms.

Exposure of Mytilus galloprovincialis to Microplastics: Accumulation, Depuration and Evaluation of the Expression Levels of a Selection of Molecular Biomarkers

Microplastic contamination is a growing marine environmental issue with possible consequences for seafood safety. Filter feeders are the target species for microplastic (MPs) pollution because they filter large quantities of seawater to feed. In the present study, an experimental contamination of Mytilus galloprovincialis was conducted using a mixture of the main types of MPs usually present in the seawater column (53% filaments, 30% fragments, 3% granules) in order to test the purification process as a potential method for removing these contaminants from bivalves intended for human consumption. A set of molecular biomarkers was also evaluated in order to detect any variations in the expression levels of some genes associated with biotransformation and detoxification, DNA repair, cellular response, and the immune system. Our results demonstrate that: (a) the purification process can significantly reduce MP contamination in M. galloprovincialis; (b) a differential expression level has been observed between mussels tested and in particular most of the differences were found in the gills, thus defining it as the target organ for the use of these biomarkers. Therefore, this study further suggests the potential use of molecular biomarkers as an innovative method, encouraging their use in next-generation marine monitoring programs.

Protective effects of berberine in chronic copper-induced liver and gill injury in freshwater grouper (Acrossocheilus fasciatus)

This experiment aimed to investigate the protective effects of berberine on copper-induced liver and gill toxicities in freshwater grouper (Acrossocheilus fasciatus). Fish (initial weight 1.56 ± 0.10 g) were randomly distributed into 12 tanks (80 L, 20 fish per tank) and divided into four experimental groups: The control group, exposed to 0.02 mg/L Cu2+ (Cu group), exposed to 0.02 mg/L Cu2+ and fed 100 mg/kg berberine (BBR100 group), and exposed to 0.02 mg/L Cu2+ and fed 400 mg/kg berberine (BBR400 group). After a 30-day experiment, the results showed that berberine significantly increased the activities of catalase and glutathione peroxidase in the liver, gills, and serum inhibited by Cu2+ exposure (P < 0.05). Berberine inclusion significantly decreased the activities of lysozyme and acid phosphatase, as well as the content of immunoglobulin M compared to the Cu group (P < 0.05). Berberine significantly suppressed the expression of the proinflammatory cytokines interleukin-1β, interleukin-6 signaling transducer, and NLR family pyrin domain containing 3 in the liver and gills induced by Cu2+ exposure while downregulating the expression of the anti-inflammatory cytokine transforming growth factor β1. Additionally, berberine significantly reduced the activities of the liver injury markers alanine transaminase and aspartate transaminase, the levels of total cholesterol and triglyceride in serum, as well as alleviated the histopathological damage in the liver and gills caused by Cu2+ exposure. In summary, berberine enhanced antioxidant capacity, mitigated inflammation, and exerted significant protective effects on liver and gill damage in freshwater grouper under Cu2+ exposure.

Invertebrate C1q Domain-Containing Proteins: Molecular Structure, Functional Properties and Biomedical Potential

C1q domain-containing proteins (C1qDC proteins) unexpectedly turned out to be widespread molecules among a variety of invertebrates, despite their lack of an integral complement system. Despite the wide distribution in the genomes of various invertebrates, data on the structure and properties of the isolated and characterized C1qDC proteins, which belong to the C1q/TNF superfamily, are sporadic, although they hold great practical potential for the creation of new biotechnologies. This review not only summarizes the current data on the properties of already-isolated or bioengineered C1qDC proteins but also projects further strategies for their study and biomedical application. It has been shown that further broad study of the carbohydrate specificity of the proteins can provide great opportunities, since for many of them only interactions with pathogen-associated molecular patterns (PAMPs) was evaluated and their antimicrobial, antiviral, and fungicidal activities were studied. However, data on the properties of C1qDC proteins, which researchers originally discovered as lectins and therefore studied their fine carbohydrate specificity and antitumor activity, intriguingly show the great potential of this family of proteins for the creation of targeted drug delivery systems, vaccines, and clinical assays for the differential diagnosis of cancer. The ability of invertebrate C1qDC proteins to recognize patterns of aberrant glycosylation of human cell surfaces and interact with mammalian immunoglobulins indicates the great biomedical potential of these molecules.

Potential risks of CO2 removal project based on carbonate pump to marine ecosystem

The development of marine carbon sequestration project has an important potential for carbon neutralization in the short-term (several decades). Marine carbon sequestration technology is based on biological and carbonate pumps to increase particulate organic carbon and authigenic insoluble carbonates to the deep sea or seafloor, aiming to achieve permanent carbon sequestration. Particularly, chemical carbon sequestration technology based on carbonate pump is proposed and considered to achieve short-term marine carbon sequestration in recent years. This technology mainly includes alkaline mineral addition and combining CO₃^2- to insoluble carbonates to improve marine carbon fixation capacity. Potential marine ecosystem risks of chemical CO₂ removal method should be considered before being a feasible technology. We reviewed the potential effects of marine chemical carbon sequestration project on marine organisms. Marine chemical carbon sequestration had two main effects on marine organisms: released chemicals effect, and particle effect. Released chemicals in mineral weathering directly affected phytoplankton and bacteria community. Particles formed during carbon sequestration process mainly affected filter feeding organisms. The toxic effects of particles on aquatic organisms increased with decreasing sizes and increasing concentrations of particle. Algae and crustaceans were the most sensitive groups exposed to metal nanoparticles (nm-μm) in seawaters, thus could be used as target species to evaluate ecological risk of small particles generated in chemical carbon sequestration project. Embryos or larva of filter feeding organisms were more sensitive to large clay and metal microparticles (μm‑mm) than adults, thus could be used as sensitive groups to establish safety concentration of large particles. The relatively inert metal nanoparticles and microparticles had higher safety concentrations than active ones. These particle concentration thresholds could be as a reference to design concentrations and initial sizes of applied minerals in marine chemical carbon sequestration project. This will ensure that the ecological risk is minimized when carbon fixation efficiency is maximized.

Pulmonary Toxicity and Proteomic Analysis in Bronchoalveolar Lavage Fluids and Lungs of Rats Exposed to Copper Oxide Nanoparticles

Copper oxide nanoparticles (CuO NPs) were intratracheally instilled into lungs at concentrations of 0, 0.15, and 1.5 mg/kg bodyweight to 7-week-old Sprague-Dawley rats. The cytotoxicity, immunotoxicity, and oxidative stress were evaluated, followed by proteomic analysis of bronchoalveolar lavage fluid (BALF) and lungs of rats. The CuO NPs-exposed groups revealed dose-dependent increases in total cells, polymorphonuclear leukocytes, lactate dyhydrogenase, and total protein levels in BALF. Inflammatory cytokines, including macrophage inflammatory protein-2 and tumor necrosis factor-α, were increased in the CuO NPs-treated groups. The expression levels of catalase, glutathione peroxidase-1, and peroxiredoxin-2 were downregulated, whereas that of superoxide dismutase-2 was upregulated in the CuO NPs-exposed groups. Five heat shock proteins were downregulated in rats exposed to high concentrations of CuO NPs. In proteomic analysis, 17 proteins were upregulated or downregulated, and 6 proteins were validated via Western blot analysis. Significant upregulation of 3-hydroxy-3-methylglutaryl-CoA synthase and fidgetin-like 1 and downregulation of annexin II, HSP 47 and proteasome α1 occurred in the CuO NPs exposed groups. Taken together, this study provides additional insight into pulmonary cytotoxicity and immunotoxicity as well as oxidative stress in rats exposed to CuO NPs. Proteomic analysis revealed potential toxicological biomarkers of CuO NPs, which also reveals the toxicity mechanisms of CuO NPs.

Ecotoxicological effects of the UV-filter 4-MBC on sperms and adults of the mussel Mytilus galloprovincialis

Present in an increasing number of products, UV-filters are continuously discharged into aquatic environments. Despite potential risks for inhabiting organisms are recognized, the effects of UV-filter 4-methylbenzylidenecamphor (4-MBC) on marine invertebrates are poorly investigated. By combining in vitro/in vivo exposures through a multi-biomarker approach on sperms and adults, the present study evaluated how 4-MBC affect the mussel species Mytilus galloprovincialis, providing ecologically relevant information on organisms' responses. From the obtained results, considering mortality as endpoint, sperms revealed a greater sensitivity (EC₅₀:347 μg/L) than adults (EC₅₀: not calculable). From an ecotoxicological perspective, this resulted in a derived threshold concentration (LOEC) of 100 μg/L and 72 μg/L, respectively. Effects at the cell/molecular level were provided by general redox-status imbalance and oxidative stress. Sperms showed functional and structural impairments, hyperactivation and DNA damage, while adults showed physiological, metabolic/energetic dysfunctions, DNA damage and activation of oxidative and biotransformation enzymes. High 4-MBC bioaccumulation was also observed in exposed mussels (BCFs:14.0-32.0 L/kg). These findings suggest that 4-MBC may impair fitness and survival of the broadcast spawning mussel M. galloprovincialis, affecting reproduction success and population growth.

Microcystin-LR induces apoptosis in Juvenile Eriocheir sinensis via the mitochondrial pathway

Microcystin-LR (MC-LR), the toxic substance of cyanobacteria secondary metabolism, widely exists in water environments and poses great risks to living organisms. Some toxicological assessments of MC-LR have performed at physiological and biochemical levels. However, plenty of blanks about the potential mechanism in aquatic crustacean remains. In this study, we firstly assessed the exposure toxicity of MC-LR to juvenile E. sinensis and clarified that the 96 h LD50 of MC-LR was 73.23 μg/kg. Then, hepatopancreas transcriptome profiles of MC-LR stressed crabs were constructed at 6 h post-injection and 37 differential expressed genes (DEGs) were identified. These DEGs were enriched in cytoskeleton, peroxisome and apoptosis pathways. To further reveal the toxicity of MC-LR, oxidative stress parameters (SOD, CAT, GSH-px and MDA), apoptosis genes (caspase 3, bcl-2 and bax) and apoptotic cells were detected. Significant accumulated MDA and rise-fall enzyme activities verified the oxidative stress caused by MC-LR. It is noteworthy that quantitative real-time PCR and TUNEL assay indicated that MC-LR stress-induced apoptosis via the mitochondrial pathway. Interestingly, activator protein-1 may play a crucial role in mediating the hepatotoxicity of MC-LR by regulating apoptosis and oxidative stress. Taken together, our study investigated the toxic effects and the potential molecular mechanisms of MC-LR on juvenile E. sinensis. It provided useful data for exploring the toxicity of MC-LR to aquatic crustaceans at molecular levels.

Immune responses, DNA damage and ultrastructural alterations of gills in the marine mussel Lithophaga lithophaga exposed to CuO nanoparticles

Nanoparticle (NP) pollution is a worldwide problem. Copper oxide nanoparticles (CuO NPs) are one of the most used NPs in a variety of applications, which results in their increased release into the marine environment. In the present work, the marine mussel Lithophaga lithophaga was used as a model organism to evaluate the toxic effects of CuO NPs following 28 days of exposure to sub-lethal concentrations (5 and 20 μg/L). The time points were 1 day of exposure to assess the cell viability, phagocytosis in mussel haemocytes and genotoxicity (DNA damage in gills), 1, 14 and 28 days of exposure to evaluate copper concentrations in water and gills, as well as metallothionein concentration in gills, while gill histology and SEM examination were done after 28 days of exposure. The results indicated that the accumulation of CuO NPs in gills increased with concentration and time. Mussel exposure to CuO NPs increased neutral red uptake. However, the phagocytic abilities decreased in haemocytes with increased concentration. CuO NPs caused DNA damage in the gills even at low concentrations (5 µg/L). CuO NPs caused histopathological alterations in gills, such as brown cell accumulation, necrosis, dwarfism of filaments and ciliary erosion. In conclusion, exposure of the mussel L. lithophaga to CuO NPs led to concentration- and time-dependent responses for all the examined biomarkers. Thus, L. lithophaga may be used as a bioindicator organism in the assessment of CuO NP toxicity.

Immunotoxic effects of metal-based nanoparticles in fish and bivalves

There is a global research interest in metal nanoparticles (MNPs) due to their diverse applications, rapidly increasing use, and increased presence in the aquatic environment. Currently, most MNPs in the environment are at levels unlikely to cause overt toxicity. Sub-lethal effects that MNPs may induce, notable immunotoxicity, could however have significant health implications. Thus, deciphering the immunological interactions of MNPs with aquatic organisms constitutes a much-needed area of research. In this article, we critically assess the evidence for immunotoxic effects of MNPs in bivalves and fish, as key wildlife sentinels with widely differing ecological niches that are used as models in ecotoxicology. The first part of this review details the properties, fate, and fundamental physicochemical behavior of MNPs in the aquatic ecosystem. We then consider the toxicokinetics of MNP uptake, accumulation, and deposition in fish and bivalves. The main body of the review then focuses on immune reactions in response to MNPs exposure in bivalves and fish illustrating their immunotoxic potential. Finally, we identify major knowledge gaps in our current understanding of the implications of MNPs exposure for immunological functions and the associated health consequences for bivalves and fish, as well as the general lessons learned on the immunotoxic properties of the emerging class of nanoparticulate contaminants in fish and bivalves.

Exacerbation of copper pollution toxicity from ocean acidification: A comparative analysis of two bivalve species with distinct sensitivities

In estuarine ecosystems, bivalves experience large pH fluctuations caused by the anthropogenic elevation of atmospheric CO₂ and Cu pollution. This study investigates whether Cu toxicity increases indiscriminately in two bivalve species from different estuarine habitats as a result of elevated Cu bioaccumulation in acidified seawater. This was carried out by evaluating the effects of Cu exposure on two bivalve species (clams and scallops) for 28 d, at a series of gradient pH levels (pH 8.1, 7.8, and 7.6). The results demonstrated an increase in the Cu content in the soft tissues of clams and scallops in acidified seawater. Cu toxicity increased under acidified seawater by affecting the molecular pathways, physiological function, biochemical responses, and health status of clams and scallops. An iTRAQ-based quantitative proteomic analysis showed increased protein turnover, disturbed cytoskeleton and signal transduction pathways, apoptosis, and suppressed energy metabolism pathways in the clams and scallops under joint exposure to ocean acidification and Cu. The integrated biomarker response results suggested that scallops were more sensitive to Cu toxicity and/or ocean acidification than clams. The proteomic results suggested that the increased energy metabolism and suppressed protein turnover rates may contribute to a higher resistivity to ocean acidification in clams than scallops. Overall, this study provides molecular insights into the distinct sensitivities between two bivalve species from different habitats under exposure to ocean acidification and/or Cu. The findings emphasize the aggravating impact of ocean acidification on Cu toxicity in clams and scallops. The results show that ocean acidification and copper pollution may reduce the long-term viability of clams and scallops, and lead to the degradation of estuarine ecosystems.

Proteome Response of Meretrix Bivalves Hepatopancreas Exposed to Paralytic Shellfish Toxins Producing Dinoflagellate Gymnodinium catenatum

Paralytic shellfish toxins (PSTs) contamination of seafood has become a growing global problem. However, the molecular response of bivalves, some of the most popular seafoods, to PSP toxins has seldom been reported and the underlying molecular mechanisms of the interactions between Meretrix meretrix bivalves and PSTs-producing dinoflagellates are scarcely known. This study compared the protein expression profiles between PSP toxin-contaminated and non-PSP toxin contaminated M. meretrix, determined proteome responses and identified potential biomarkers based on feeding experiments. Results showed that the content of total PSP toxins in contaminated bivalves was 40.63 ± 4.08 μg saxitoxin (STX) equivalents per gram, with 95.3% in hepatopancreas, followed by gill (1.82%) and foot (1.79%). According to two-dimensional gel electrophoresis (2-DE), 15 differentially expressed proteins (at least 2-fold difference) between the hepatopancreas of bivalves with and without PSP toxins were detected. Eight of them were successfully identified by MALDI-TOF MS. These were catalase, protein ultraspiracle homolog, G2 and S phase-expression protein, paramyosin, Mn-superoxide dismutase, response regulator receiver domain-containing protein, sarcoplasmic calcium-binding protein and major facilitator superfamily transporters. The differences in the expression levels of the last three proteins involving in cell signaling, structure and membrane transport were 4.2, 5.3 and 4.9-fold, respectively. These proteins could be further developed as potential biomarkers. The other two up-regulated proteins, Mn-superoxide dismutase and catalase, were involved in cell defence mechanisms against oxidative stress, suggesting PSP toxin acts as xenobiotics and poses oxidative stress in bivalves. This study gives insights into the response of bivalves to PSP toxin-producing dinoflagellate at the proteomic level and the potential of using 2-DE to develop specific protein markers in bivalves.

Comparative transcriptome analysis of the gills and hepatopancreas from Macrobrachium rosenbergii exposed to the heavy metal Cadmium (Cd2+)

Heavy metal Cadmium (Cd²⁺) pollution has become a severe environmental problem for aquatic organisms. In crustaceans, gills (Gi) and hepatopancreas (Hp) play a vital role in the toxicology. However, in Macrobrachium rosenbergill, there are few researches about gill and hepatopancreases responding to Cd²⁺ stress at a molecular level. In this study, transcriptomic analysis was applied to characterize gene expression profiles of gills and hepatopancreas of M. rosenbergill after Cd²⁺ exposure for 0 h, 3 h and 3 d. Six cDNA libraries (Gi 0 h, Gi 3 h, Gi 3 d, Hp 0 h, Hp 3 h, and Hp 3 d) were constructed and a total of 66,676 transcripts and 48,991 unigenes were annotated. Furthermore, differentially expressed genes (DEGs) were isolated by comparing the Cd²⁺ treated time-point libraries (3 h and 3 d group) with the control library (0 h group). The results showed that most of the DEGs were down-regulated after Cd²⁺ exposure and the number of DEGs among gill groups were significantly higher than those among hepatopancreas groups. GO functional and KEGG pathway analysis suggested many key DEGs in response to the Cd²⁺ stress, such as metallothionein and Hemocyanin. Additionally, a total of six DEGs were randomly selected to further identify their expressional profile by qPCR. The results indicated that these DEGs were involved in the response to Cd²⁺. This comparative transcriptome provides valuable molecular information on the mechanisms of responding to Cd²⁺ stress in M. rosenbergii, which lays the foundation for further understanding of heavy metal stress.

Changes of Gene Expression Patterns from Aquatic Organisms Exposed to Metal Nanoparticles

Metal nanoparticles are used in various branches of industry due to their physicochemical properties. However, with intensive use, most of the waste and by-products from industries and household items, and from weathering of products containing nanoparticles, end up in the waters. These pollutants pose a risk to aquatic organisms, one of which is a change in the expression of various genes. Most of the data that focus on metal nanoparticles and their effects on aquatic organisms are about copper and silver nanoparticles, which is due to their popularity in general industry, but information about other nanoparticulate metals can also be found. This review aims to evaluate gene expression patterns in aquatic organisms by metal nanoparticles, specifying details about the transcription changes of singular genes and, if possible, comparing the changes in the expression of the same genes in different organisms. To achieve this goal, available publications tackling this problem are studied and summarized. Nanometals were found to have a modulatory effect on gene expression in different aquatic organisms. Data show both up-regulation and down-regulation of genes. Nano silver, nano copper, and nano zinc show a regulatory effect on genes involved in inflammation and apoptosis, cell cycle regulation and ROS defense as well as in general stress response and have a negative effect on the expression of genes involved in development. Nano gold, nano titanium, nano zinc, and nano iron tend to elevate the transcripts of genes involved in response to ROS, but also pro-apoptotic genes and down-regulate DNA repair-involved genes and anti-apoptotic-involved genes. Nano selenium showed a rare effect that is protective against harmful effects of other nanoparticles, but also induced up-regulation of stress response genes. This review focuses only on the effects of metal nanoparticles on the expression of various genes of aquatic organisms from different taxonomic groups.

Involvement of glucosinolates in the resistance to zinc oxide nanoparticle-induced toxicity and growth inhibition in Arabidopsis

Zinc oxide nanoparticles (ZnO NPs) are widely used to manufacture textile fibers, synthetic rubber, and paint. However, crop yields and quality are threatened by the increased use of metallic NPs in industry, which has resulted in their accumulation in agricultural land. Many studies have shown that plants defend against biotic and abiotic stresses through the activities of metabolites and hormones. However, whether glucosinolates (GSs) are involved in plant responses to ZnO NP-related stress remains unknown. In this study, wild-type (WT) and GS mutant (myb28/29 and cyp79B2/B3) Arabidopsis plants were subjected to ZnO NP stress to address this question. Our results showed that exposure to ZnO NPs promoted GS accumulation and induced the relative messenger RNA (mRNA) expression levels of GS biosynthesis-related genes. Moreover, ZnO NP treatment adversely affected root length, the number of lateral roots, chlorophyll contents, and plant biomass. Importantly, our results showed that root growth, chlorophyll contents, and plant biomass were all decreased in the GS mutants compared with those in WT plants. Overall, our results showed that WT plants tolerated ZnO NP-induced stress more efficiently than the GS mutants, suggesting that GSs are involved in plant resistance to ZnO NP-induced toxicity.

Molecular response of a sub-antarctic population of the blue mussel (Mytilus edulis platensis) to a moderate thermal stress

The Kerguelen Islands (49°26'S, 69°50'E) represent a unique environment due to their geographical isolation, which protects them from anthropogenic pollution. The ability of the endemic mussel, part of the Mytilus complex, to cope with moderate heat stress was explored using omic tools. Transcripts involved in six major metabolic functions were selected and the qRT-PCR data indicated mainly changes in aerobic and anaerobic energy metabolism and stress response. Proteomic comparisons revealed a typical stress response pattern with cytoskeleton modifications and elements suggesting increased energy metabolism. Results also suggest conservation of protein homeostasis by the long-lasting presence of HSP while a general decrease in transcription is observed. The overall findings are consistent with an adaptive response to moderate stresses in mussels in good physiological condition, i.e. living in a low-impact site, and with the literature concerning this model species. Therefore, local blue mussels could be advantageously integrated into biomonitoring strategies, especially in the context of Global Change.

Comparative transcriptome analyses of the liver between Xenocypris microlepis and Xenocypris davidi under low copper exposure

Copper is one of the most ubiquitous environmental pollutants worldwide. Previous studies have focused on the toxicology of high copper exposure, while there has been comparatively less research on the biological effects of low copper exposure. Low concentrations of copper often exist in freshwater ecosystems, and its impact on the fish is unclear. Both Xenocypris microlepis and Xenocypris davidi are bottom-feeding fishes widely distributed in freshwater ecosystems of China, and they are more likely to be contaminated by low concentrations of copper. Low copper exposure may have effects on molecular regulation at the level of gene expression in the two Xenocypris species. To investigate gene expression differences involved in the response to low copper concentrations between X. microlepis and X. davidi, we established the responses to low copper exposure of 0.01 mg/L for 14 days at the transcriptional level, and RNA-Seq was used to perform a comparative transcriptomic analysis of the liver. A total of 74,135 and 60,894 unigenes from X. microlepis and X. davidi were assembled by transcriptome profiling, respectively. Among these, 84 genes of X. microlepis and 165 genes of X. davidi were identified as differentially expressed genes (DEGs). There were 60 and 135 up-regulated, 24 and 30 down-regulated genes in the two species, respectively. Comparative transcriptome analyses identified five differentially co-expressed genes (DCGs) related to low copper exposure from the DEGs of the two Xenocypris species. The five DCGs were related to the fishes' growth, antioxidant system, immune system and heavy metal tolerance. The results could help us to understand the molecular mechanisms of the response to low copper exposure, and the data should provide a valuable transcriptomic resource for the genus Xenocypris.

Effects of Aeration on the Formation of Arbuscular Mycorrhiza under a Flooded State and Copper Oxide Nanoparticle Removal in Vertical Flow Constructed Wetlands

In this study, six vertical flow constructed wetlands (VFCWs) planted with Phragmites australis were operated at different aeration times (4 h day^-1 and 8 h day^-1), aeration modes (continuous and intermittent), and arbuscular mycorrhizal fungi (AMF) inoculation treatments (inoculation with Rhizophagus intraradices and no inoculation) to explore the effects of different aeration strategies on the formation of arbuscular mycorrhiza under a flooded state in VFCWs. In addition, these VFCWs were further used to treat copper oxide nanoparticle (CuO-NP) wastewater to evaluate the correlations among aeration, colonization, growth, and CuO-NP removal. The highest AMF 28S copy number (1.99×10⁵) and colonization in reed roots, with values of 67%, 21%, and 1% for frequency (F%), intensity (M%), and arbuscule abundance (A%), were observed in the treatment with intermittent aeration for 4 h day^-1. Aeration significantly increased the dissolved oxygen (DO) concentration and AMF colonization in VFCWs, thereby promoting plant growth and the purification of the CuO-NPs. However, excessive and continuous aeration had little positive effect on AMF colonization. This study provides a theoretical basis for the application of AMF for improving pollutant removal performance in constructed wetlands.

Differential Proteomics Analysis of Penaeus vannamei Muscles with Quality Characteristics by TMT Quantitative Proteomics during Low-Temperature Storage

A tandem mass tag technology, based on the quantitative proteomics strategy, was applied to investigate the relationships between proteome changes of Penaeus vannamei (PNVN) muscles and quality characteristics during low-temperature storage. 506 proteins were found as differentially expressed proteins (DEPs) after 10 days of storage under treatments of refrigerated storage (5 °C), ice temperature storage (0 °C), and particle freezing storage (-3 °C) compared with a fresh group (0 day). In addition, Uniprot Knowledgebase (UniprotKB), Gene Ontology enrichment, and Kyoto Encyclopedia of Genes and Genomes were reported. Correlation analysis indicated that nine DEPs were significantly related to quality characteristics-pH, color, and texture. Bioinformatics analysis showed that most of DEPs were involved in binding proteins, metabolic enzyme, and protein turnover. Besides, several DEPs could be good candidate biomarkers of muscle decline. These results could help to further comprehend the proteome changes and mechanisms of the quality decline of PNVN muscles during low-temperature storage.

iTRAQ and PRM-based comparative proteomic profiling in gills of white shrimp Litopenaeus vannamei under copper stress

Crustaceans are particularly sensitive to heavy metal pollution. Copper (Cu) is one of typical heavy metal pollutants in aquatic ecosystems. However, limited attention has been paid on the proteomic responses of shrimp under Cu stress. White shrimp Litopenaeus vannamei held in 5‰ seawater were exposed to 5 mg L^-1 Cu for 3 h, and the regulatory mechanism in the gills was elucidated using iTRAQ-based quantitative proteomics. The results showed that a total of 5034 proteins were identified, 385 differentially expressed proteins (DEPs), including 147 differentially up-regulated proteins (DUPs) and 238 differentially down-regulated proteins (DDPs) were found. Bioinformatics analysis indicated the DEPs responding to Cu stress mainly involved in cytoskeleton, immune response, stress response, protein synthesis, detoxification, ion homeostasis and apoptosis. Furthermore, we still performed PRM analysis on sarcoplasmic calcium binding protein (SCP), serine proteinase inhibitor B3 (SPIB3), C-type lectin 4 (CTL4), cathepsin L (CATHL), JHE-like carboxylesterase 1 (CXE1) and paramyosin (PMY), and biochemical analysis on Cu/Zn-superoxide dismutase (Cu/Zn-SOD) to validate the iTRAQ results, respectively. The present proteome analysis revealed that Cu stress disrupted the ion homeostasis and protein synthesis, and L.vannamei mainly regulates a series of molecular pathways which contained many key proteins involved in the immune process to protect the organism from Cu stress. Our data provides more insight about the underlying mechanisms that related to the stress response of Cu exposure in crustacean.

Can Proteomics Be Considered as a Valuable Tool to Assess the Toxicity of Nanoparticles in Marine Bivalves?

Exposure to nanoparticles (NPs) has been identified as a major concern for marine ecosystems. Because of their peculiar physico-chemical features, NPs are accumulated in marine organisms, which suffer a variety of adverse effects. In particular, bivalve mollusks represent a unique target for NPs, mainly because they are suspension-feeders with highly developed processes for cellular internalization of nano- and micrometric particles. Several studies have demonstrated that the uptake and the accumulation of NPs can induce sub-lethal effects towards marine bivalves. However, to understand the real risk of NP exposures the application of the so-called “omics” techniques (e.g., proteomics, genomics, metabolomics, lipidomics) has been suggested. In particular, proteomics has been used to study the effects of NPs and their mechanism(s) of action in marine bivalves, but to date its application is still limited. The present review aims at summarizing the state of the art concerning the application of proteomics as a tool to investigate the effects of nanoparticles on the proteome of marine bivalves, and to critically discuss the advantages and limitations of proteomics in this field of research. Relying on results obtained by studies that applied proteomics on bivalve tissues, proteomics application needs to be considered cautiously as a promising and valuable tool to shed light on toxicity and mechanism(s) of action of NPs. Although on one hand, the analysis of the current literature demonstrated undeniable strengths, potentiality and reliability of proteomics, on the other hand a number of limitations suggest that some gaps of knowledge need to be bridged, and methodological and technical improvements are necessary before proteomics can be readily and routinely applied to nanotoxicology studies.

Can proteomics contribute to biomonitoring of aquatic pollution? A critical review

Aquatic pollution is one of the greatest environmental problems, and therefore its control represents one of the major challenges in this century. In recent years, proteomics has emerged as a powerful tool for searching protein biomarkers in the field of pollution biomonitoring. For biomonitoring marine contamination, there is a consensus that bivalves are preferred organisms to assess organic and inorganic pollutants. Thus, the bivalve proteome was intensively studied, particularly the mussel. It is well documented that heavy metal pollution and organic chemicals altered the structural proteins causing degradation of tissues of molluscs. Also, it is well known that proteins involved in stress oxidative such as glutathione and enzymes as catalase, superoxide dismutase or peroxisomes are overexpressed in response to contaminants. Additionally, using bivalves, other groups of proteins proposed as pollution biomarkers are the metabolic proteins. Even though other marine species are used to monitor the pollution, the presence of proteomic tools in these studies is scarce. Concerning freshwater pollution field, a great variety of animal species (fish and crustaceans) are used as biomonitors in proteomics studies compared to plants that are scarcely analysed. In fish species, proteins involved in stress oxidative such as heat shock family or proteins from lipid and carbohydrate metabolism were proposed as candidate biomarkers. On the contrary, for crustaceans there is a lack of proteomic studies individually assessing the contaminants. Novel scenarios, including emerging contaminants and new threats, will require proteomic technology for a systematic search of protein biomarkers and a greater knowledge at molecular level of those cellular pathways induced by contamination.

Effects of copper oxide nanoparticle on gill filtration rate, respiration rate, hemocyte associated immune parameters and oxidative status of an Indian freshwater mussel

Waterbodies of India support a wide range of molluscs including Lamellidens marginalis, a pearl forming edible mussel of ecological significance. Report of copper oxide nanoparticle toxicity in Indian molluscs is limited in scientific literature. L. marginalis is a gill respiring filter feeder, which is toxicologically vulnerable to exposure of copper oxide nanoparticles liberated from electrical, textile and polymer industries. Experimental exposure of copper oxide nanoparticles for 7 days yielded a decrease in gill filtration rate, respiration rate, total count and phagocytic response of hemocytes, the chief immunoeffector cells of L. marginalis. Nanoparticle exposure resulted in decrease of phagocytic response of mussel hemocytes. Decrease in nitric oxide generation and phenoloxidase activity were recorded in L. marginalis exposed to 0.5, 1 and 5 mg copper oxide nanoparticles per litre of water for 7 and 14 days. Superoxide anion generation in hemocytes was increased under the exposure of copper oxide nanoparticles. Increase in superoxide anion and decrease in the activities of superoxide dismutase and catalase were indicative to oxidative stress in mussels. Copper oxide nanoparticle induced shift in filtration and respiration rate along with the hemocyte associated immune parameters were suggestive to an acute immunophysiological stress in L. marginalis. We estimated the functional performance of gill and physiological status of aquatic respiration in L. marginalis exposed to copper oxide nanoparticles. A parallel set of estimation of each parameter was carried out in L. marginalis exposed to identical copper sulphate concentrations to record and compare the ionic toxicity of copper in the same specimen.

Oxidative Damage of Mussels Living in Seawater Enriched with Trace Metals, from the Viewpoint of Proteins Expression and Modification

The impact of metals bioaccumulation in marine organisms is a subject of intense investigation. This study was designed to determine the association between oxidative stress induced by seawater enriched with trace metals and protein synthesis using as a model the mussels Mytilus galloprovincialis. Mussels were exposed to 40 μg/L Cu, 30 μg/L Hg, or 100 μg/L Cd for 5 and 15 days, and the pollution effect was evaluated by measuring established oxidative biomarkers. The results showed damage on the protein synthesis machine integrity and specifically on translation factors and ribosomal proteins expression and modifications. The exposure of mussels to all metals caused oxidative damage that was milder in the cases of Cu and Hg and more pronounced for Cd. However, after prolonged exposure of mussels to Cd (15 days), the effects receded. These changes that perturb protein biosynthesis can serve as a great tool for elucidating the mechanisms of toxicity and could be integrated in biomonitoring programs.

Evaluation of interactive effects of phosphorus-32 and copper on marine and freshwater bivalve mollusks

PURPOSE

Contaminants seldom occur in isolation in the aquatic environment. While pollution of coastal and inland water bodies has received considerable attention to date, there is limited information on potential interactive effects between radionuclides and metals. Whether by accidental or controlled release, such contaminants co-exist in aquatic ecosystems and can pose an enhanced threat to biota. Using a range of biological responses, the study aimed to evaluate relative interactive effects on representative freshwater and marine bivalve species.

METHODS

An integrated, multi-biomarker approach was adopted to investigate response to copper (Cu, 18 μg L^-1), a known environmentally relevant genotoxic metal and differing concentrations of phosphorus-32 (³²P; 0.1 and 1 mGy d^-1), alone and in combination in marine (Mytilus galloprovincialis) and freshwater (Dreissena polymorpha) mussels. Genetic and molecular biomarkers were determined post-exposure and included DNA damage (as measured by the comet assay), micronuclei (MN) formation, γ-H2AX foci induction and the expression of key stress-related genes (i.e. hsp70/90, sod, cat, gst).

RESULTS

Overall, using a tissue-specific (i.e. gill and digestive gland) approach, genotoxic response was reflective of exposures where Cu had a slight additive effect on ³²P-induced damage across the species (but not all), cell types and dose rates. Multivariate analysis found significant correlations between comet and γ-H2AX assays, across both the tissues. Transcriptional expression of selected genes were generally unaltered in response to contaminant exposures, independent of species or tissues.

CONCLUSIONS

Our study is the first to explore the interactive effects of ionizing radiation (IR) and Cu on two bivalve species representing two ecological habitats. The complexity of IR-metal interactions demonstrate that extrapolation of findings obtained from single stressor studies into field conditions could be misrepresentative of real-world environments. In turn, environmental protective strategies deemed suitable in protecting biota from a single, isolated stressor may not be wholly adequate.

Toxicity assessment and comparison of the land snail's Cornu aspersum responses against CuO nanoparticles and ZnO nanoparticles

The goal of the present study was to examine the effects of ZnO NPs and CuO NPs on Cornu aspersum land snail, enlightening their cytotoxic profile. ZnO NPs and CuO NPs were synthesized and thoroughly characterized. Α series of concentrations of either ZnO NPs or CuO NPs were administered in the feed of snails for 20 days. Thereafter, neutral red retention assay was conducted, in order to estimate NRRT50 values. Subsequently, snails were fed with NPs concentrations slightly lower than the concentrations that were corresponding to the NRRT50 values, i.e. 3 mg·L^-1 ZnO NPs and 6 mg·L^-1 CuO NPs, for 1, 5, 10 and 20 days. Both NPs agglomerates were detected in hemocytes by Transmission Electron Microscopy. Moreover, both effectors resulted to toxicity in the snails' hemocytes. The latter was shown by changes in the NRRT50 values, increased reactive oxygen species (ROS) production, lipid peroxidation, DNA integrity loss, protein carbonyl content, ubiquitin conjugates and cleaved caspases conjugates levels compared to the untreated animals. Although ZnO NPs exhibited higher toxicity, as indicated by the NRRT50 values, both NPs affected similarly a wide range of the cellular parameters mentioned above. The latter parameters could constitute sensitive biomarkers in biomonitoring studies of terrestrial environment against nanoparticles.

New Insights into Cellular Impacts of Metals in Aquatic Animals

Toxic metals remain a current important threat to aquatic ecosystems, despite regulatory efforts to reduce their release. Several toxic metals already appear in the list of priority substances polluting surface waters, while concerns arise from the increasing use of technology-critical metals such as metallic nanoparticles, rare-earth, and platinum group metals. In aquatic environments, various chemical, biological and physical processes determine the impact of metals on the biota. This review provides insights into responses to toxic metals recently reported in freshwater and marine animals. The specific emphasis is on: (i) common cellular and molecular responses; (ii) stress proteins; (iii) redox homeostasis; (iv) cytoskeleton rearrangement; (v) metabolism reshuffle; (vi) free cellular energy and mitochondrial metabolism; and (vi) immunity. These endpoints are promising, notably in multi-biomarker approaches to identify precise cellular toxicity pathways and anticipate the impact of environmental metal pollution.

Effects of gold nanoparticles in gilthead seabream-A proteomic approach

Despite the widespread use of nanoparticles (NPs), there are still major gaps of knowledge regarding the impact of nanomaterials in the environment and aquatic animals. The present work aimed to study the effects of 7 and 40 nm gold nanoparticles (AuNPs) - citrate and polyvinylpyrrolidone (PVP) coated - on the liver proteome of the estuarine/marine fish gilthead seabream (Sparus aurata). After 96 h, exposure to AuNP elicited alterations on the abundance of 26 proteins, when compared to the control group. AuNPs differentially affected several metabolic pathways in S. aurata liver cells. Among the affected proteins were those related to cytoskeleton and cell structure, gluconeogenesis, amino acids metabolism and several processes related to protein activity (protein synthesis, catabolism, folding and transport). The increased abundance of proteins associated with energy metabolism (ATP synthase subunit beta), stress response (94 kDa glucose-regulated protein) and cytoskeleton structure (actins and tubulins) may represent the first signs of cellular oxidative stress induced by AuNPs. Although higher gold accumulation was found in the liver of S. aurata exposed to 7 nm PVP-AuNPs, the 7 nm cAuNPs were more bioactive, inducing more effects in liver proteome. Gold accumulated more in the spleen than in the other assessed tissues of S. aurata exposed to AuNPs, highlighting its potential role on the elimination of these NPs.

Magnetite nanoparticles effects on adverse responses of aquatic and terrestrial animal models

Among pollutants, nanoparticles (NPs) consist a potential environmental hazard, as they could possibly harm the aquatic and terrestrial ecosystems while having unpredictable repercussions on human health. Since monitoring the impact of NPs on aquatic and terrestrial life is challenging, due to the differential sensitivities of organisms to a given nanomaterial, the present study examines magnetite nanoparticles' mediated toxicity in different animal models, representing distinctive environments (terrestrial and aquatic). Oxidative, proteolytic and genotoxic effects were evaluated on the hemocytes of the snail Cornu aspersum; in addition to those, apoptotic effects were measured in gills and liver of the zebrafish Danio rerio, and the prussian carp Carassius gibelio. All biochemical parameters studied increased significantly in animals after 8 days exposure to NPs. Inter-species and inter-tissues differences in responses were evident. Our results suggest a common toxicity response mechanism functioning in the tissues of the three animals studied that is triggered by magnetite NPs. The simultaneous use of these parameters could be established after further investigation as a reliable multi-parameter approach for biomonitoring of terrestrial and aquatic ecosystems against magnetite nanoparticles. Additionally, the results of our study could contribute to the design of studies for the production and rational utilization of nanoparticles.

Interaction of Copper-Based Nanoparticles to Soil, Terrestrial, and Aquatic Systems: Critical Review of the State of the Science and Future Perspectives

In the past two decades, increased production and usage of metallic nanoparticles (NPs) have inevitably increased their discharge into the different compartments of the environment, which ultimately paved the way for their uptake and accumulation in various trophic levels of the food chain. Due to these issues, several questions have been raised on the usage of NPs in everyday life and have become a matter of public health concern. Among the metallic NPs, Cu-based NPs have gained popularity due to their cost-effectiveness and multifarious promising uses. Several studies in the past represented the phytotoxicity of Cu-based NPs on plants. However, comprehensive knowledge is still lacking. Additionally, the impact of Cu-based NPs on soil organisms such as agriculturally important microbes, fungi, mycorrhiza, nematode, and earthworms is poorly studied. This review article critically analyses the literature data to achieve a more comprehensive knowledge on the toxicological profile of Cu-based NPs and increase our understanding of the effects of Cu-based NPs on aquatic and terrestrial plants as well as on soil microbial communities. The underlying mechanism of biotransformation of Cu-based NPs and the process of their penetration into plants have also been discussed herein. Overall, this review could provide valuable information to design rules and regulations for the safe disposal of Cu-based NPs into a sustainable environment.

A sub-individual multilevel approach for an integrative assessment of CuO nanoparticle effects on Corbicula fluminea

Because they are widely used, copper oxide nanoparticles (CuO NPs) are likely to enter the aquatic environment and then reach the sediment. We have examined the effect of CuO NPs in the freshwater endobenthic bivalve Corbicula fluminea. Some previous studies have investigated effects at biochemical and physiological levels, but molecular endpoints are still poorly studied despite they are sensitive in early detection of NPs effect. In the present study, we have investigated short-term effects (96 h) of CuO NP (12, 30 nm; 0, 20 and 100 μg/L) using molecular endpoints as well as more conventional biochemical and physiological markers. The expression of antioxidant (CuZnSOD, MnSOD, Cat, Se-GPx, Trxr) and antitoxic (GST-Pi, HSP70, MT, Pgp, MRP1) related genes was measured at the mRNA level while antioxidant (SOD, TAC) and antitoxic (GST, ACP) defenses, energetic reserves and metabolism (ETS, Tri, LDH), and cellular damages (LPO) were assessed using a biochemical approach. The filtration rate measured at 96 h provided information at the physiological scale. Gene expression and filtration rate were responsive to CuO NPs but the effects differed according to the NP size. The results suggest that defense mechanisms may have been set up following 30 nm-NP exposure. The response to 12 nm-NP was lower but still showed that exposure to 12 nm-NP led to activation of cellular elimination mechanisms. The lowering of the filtration rate may have protected the organisms from the contamination. However, this raised the question of further repercussions on organism biology. Together, the results (i) indicate that CuO NP may exert effects at different levels even after a short-term exposure and (ii) point out the precocity of molecular response.

Season influences the transcriptomic effects of dietary exposure to PVP/PEI coated Ag nanoparticles on mussels Mytilus galloprovincialis

Toxicity of AgNPs has been widely studied in waterborne exposed aquatic organisms. However, toxic effects caused by AgNPs ingested through the diet and depending on the season are still unexplored. The first cell response after exposure to xenobiotics occurs at gene transcription level. Thus, the aim of this study was to assess transcription level effects in the digestive gland of female mussels after dietary exposure to AgNPs both in autumn and in spring. Mussels were fed daily for 21 days with Isochrysis galbana microalgae previously exposed for 24 h to a dose close to environmentally relevant concentrations of 1 μg Ag/L PVP/PEI coated 5 nm AgNPs (in spring) and to a higher dose of 10 μg Ag/L of the same AgNPs both in autumn and in spring. After 1 and 21 days, mussels RNA was hybridized in a custom microarray containing 7806 annotated genes. Mussels were more responsive to the high dose compared to the low dose of AgNPs and a higher number of probes were altered in autumn than in spring. In both seasons, significantly regulated genes were involved in the cytoskeleton and lipid transport and metabolism COG categories, among others, while genes involved in carbohydrate transport and metabolism were specifically altered in autumn. Overall, transcription patterns were differently altered depending on the exposure time and season, indicating that season should be considered in ecotoxicological studies of metal nanoparticles in mussels.

Changes in protein expression in mussels Mytilus galloprovincialis dietarily exposed to PVP/PEI coated silver nanoparticles at different seasons

Potential toxic effects of Ag NPs ingested through the food web and depending on the season have not been addressed in marine bivalves. This work aimed to assess differences in protein expression in the digestive gland of female mussels after dietary exposure to Ag NPs in autumn and spring. Mussels were fed daily with microalgae previously exposed for 24 h to 10 μg/L of PVP/PEI coated 5 nm Ag NPs. After 21 days, mussels significantly accumulated Ag in both seasons and Ag NPs were found within digestive gland cells and gills. Two-dimensional electrophoresis distinguished 104 differentially expressed protein spots in autumn and 142 in spring. Among them, chitinase like protein-3, partial and glyceraldehyde-3-phosphate dehydrogenase, that are involved in amino sugar and nucleotide sugar metabolism, carbon metabolism, glycolysis/gluconeogenesis and the biosynthesis of amino acids KEGG pathways, were overexpressed in autumn but underexpressed in spring. In autumn, pyruvate metabolism, citrate cycle, cysteine and methionine metabolism and glyoxylate and dicarboxylate metabolism were altered, while in spring, proteins related to the formation of phagosomes and hydrogen peroxide metabolism were differentially expressed. Overall, protein expression signatures depended on season and Ag NPs exposure, suggesting that season significantly influences responses of mussels to NP exposure.

Effects of nanoplastics on Mytilus galloprovincialis after individual and combined exposure with carbamazepine

Plastic pollution is a worldwide problem, highlighted by the fact that plastic materials degrade into nano-size particles (<100 nm), potentially becoming more bioavailable as well as a source of entry of other contaminants into organisms. The present study aimed to assess the effects of polystyrene nanoplastics (PS), individually or combined with carbamazepine (Cbz), on the Mediterranean mussel, Mytilus galloprovincialis. For this purpose, mussels were exposed for 96 h to a concentration range of PS (from 0.05 up to 50 mg L^-1), to Cbz (6.3 μg L^-1) alone and to the mixture of PS + Cbz (0.05 mg L^-1+ 6.3 μg L^-1). Molecular and biochemical biomarkers were assessed in the digestive glands, gills and haemolymph. The abundance of mRNA in the digestive glands and gills revealed significant alterations in the expression of genes associated with biotransformation, DNA repair, cell stress-response and innate immunity. Combined exposure of PS + Cbz induced significant downregulation in gene expression (e.g., hsp70) when compared to individual exposure. Total oxidant status increased in digestive glands after exposure to 0.5 mg L^-1 PS. Moreover, increased total antioxidant capacity and esterase activity were observed for PS 50 mg L^-1, in digestive glands and gills, respectively. The PS induced effects on neurotransmission, measured as inhibition of cholinesterase activity in haemolymph. Genotoxicity was found in haemocytes after exposure to PS, Cbz and their mixture. Moreover, lipid peroxidation was observed for 0.05 mg L^-1 PS exposure, showing that nanoplastics can induce oxidative damage. The present study demonstrated that PS, even at low concentrations, led to alterations on the assessed mussels' endpoints.

Highly polluted life history and acute heat stress, a hazardous mix for blue mussels

Intertidal sessile organisms constitute through their life history unintended stress recorders. This study focuses on the impact of pollution on Mytilus edulis ability to cope with an additional stress. For this purpose, two acclimation stages to different temperatures were conducted before an acute stress exposure in mussels collected from a heavily polluted site. Gill proteomes were analyzed by 2DE and regulated proteins identified. Massive mortality was observed for organisms acclimated to colder temperatures. Despite this major difference, both groups shared a common response with a strong representation of proteoforms corresponding to "folding, sorting and degradation" processes. Nevertheless, surviving mussels exhibit a marked increase in protein degradation consistent with the observed decrease of cell defense proteins. Mussels acclimated to warmer temperature response is essentially characterized by an improved heat shock response. These results show the differential ability of mussels to face both pollution and acute heat stress, particularly for low-acclimated organisms.

Cytotoxicity and cellular mechanisms of toxicity of CuO NPs in mussel cells in vitro and comparative sensitivity with human cells

There is a need to assess human and ecosystem health effects of copper oxide nanoparticles (CuO NPs), extensively used in many industrial products. Here, we aimed to determine the cytotoxicity and cellular mechanisms involved in the toxicity of CuO NPs in mussel cells (hemocytes and gill cells) in parallel with exposures to ionic Cu and bulk CuO, and to compare the sensitivity of mussel primary cells with a well-established human cell line (pulmonary TT1 cells). At similar doses, CuO NPs promoted dose-dependent cytotoxicity and increased reactive oxygen species (ROS) production in mussel and human cells. In mussel cells, ionic Cu was more toxic than CuO NPs and the latter more than bulk CuO. Ionic Cu and CuO NPs increased catalase and acid phosphatase activities in both mussel cells and decreased gill cells Na-K-ATPase activity. All Cu forms produced DNA damage in hemocytes, whereas in gill cells only ionic Cu and CuO NPs were genotoxic. Induction of the MXR transport activity was found in gill cells exposed to all forms of Cu and in hemocytes exposed to ionic Cu and CuO NPs. Phagocytosis increased only in hemocytes exposed to CuO NPs, indicating a nanoparticle-specific immunostimulatory effect. In conclusion, toxicity of CuO NPs is driven by ROS in human and mussel cells. Mussel cells respond to CuO NP exposure by triggering an array of defensive mechanisms.

Mussel digestive gland as a model tissue for assessing xenobiotics: An overview

Control strategies and routine biomonitoring programs are commonly performed worldwide using sentinel marine invertebrates, such as mussels of the genus Mytilus, for assessing the "health status" of the aquatic environment. Those species can accumulate and tolerate xenobiotics at levels higher than those being present into the aquatic environment, thus providing accurate and reliable biological endpoints (e.g. physiological, behavioral, cellular, biochemical and molecular indices) that can be measured in their tissues. Taking under consideration the significance of bivalves for assessing the environmental hazard of xenobiotics being present into the water medium, as well as the key role of digestive gland as a target-tissue for the compounds ingested in the organism, the present study aimed to summarize available data on the effects of different categories of xenobiotic compounds, previously characterized as a potential threat for the marine ecosystems. In this context, different types of pharmaceuticals and personal care products (PPCPs), biocides, microplastics (MPs) and nanoparticles (NPs), currently investigated in mussels' digestive gland, using a battery of experimental approaches and analytical methods, as well as stress indices evaluation, are briefly described and further discussed in order to elucidate not only the presence and the toxic mode of action of xenobiotics, but also the important role of the digestive gland as a reliable target-tissue for investigating the effects of xenobiotics at cellular, biochemical, and molecular levels.

Proteomic response of gill microsomes of Crassostrea brasiliana exposed to diesel fuel water-accommodated fraction

Diesel fuel water-accommodated fraction (diesel-WAF) is a complex mixture of organic compounds that may cause harmful effects to marine invertebrates. Expression of microsomal proteins can be changed by oil exposure, causing functional alterations in endoplasmic reticulum (ER). The aim of this study was to investigate changes in protein expression signatures in microsomes of oysterl Crassostrea brasiliana (=C.gasar) gill after exposure to 10% diesel-WAF for 24 and 72 h. Protein expression signatures of gills of oysters exposed to diesel-WAF were compared to those of unexposed oysters using two-dimensional electrophoresis (2-DE) to identify differentially expressed proteins. A total of 458 protein spots with molecular weights between 30-75 kDa were detected by 2-DE in six replicates of exposed oyster proteomes compared to unexposed ones. Fourteen differentially expressed proteins (six up-regulated and eight down-regulated) were identified. They are: proteins related to xenobiotic biotransformation (cytochrome P450 6 A, NADPH-cytochrome P450 reductase); cytoskeleton (α-tubulin, β-tubulin, gelsolin); processing and degradation of proteins pathways (thioredoxin domain-containing protein E3 ubiquitin-protein ligase MIB2); involved in the biosynthesis of glycolipids and glycoproteins (beta-1,3-galactosyltransferase 1); associated with stress responses (glutamate receptor 4 and 14-3-3 protein zeta, corticotropin-releasing factor-binding protein); plasmalogen biosynthesis (fatty acyl-CoA reductase 1), and sodium-and chloride-dependent glycine transporter 2 and glyoxylate reductase/hydroxypyruvate reductase. Different patterns of protein responses were observed between 24 and 72 h-exposed groups. Expression pattern of microsomal proteins provided a first insight on the potential diesel-WAF effects at protein level in microsomal fraction of oyster gills and indicated new potential biomarkers of exposure and effect. The present work can be a basis for future ecotoxicological studies in oysters aiming to elucidate the molecular mechanisms behind diesel-WAF toxicity and for environmental monitoring programs.

Synthesis methods influence characteristics, behaviour and toxicity of bare CuO NPs compared to bulk CuO and ionic Cu after in vitro exposure of Ruditapes philippinarum hemocytes

Copper oxide (CuO) nanoparticles (NPs) are increasingly investigated, developed and produced for a wide range of industrial and consumer products. Notwithstanding their promising novel applications, concern has been raised that their increased use and disposal could consequently increase their release into marine systems and potentially affect species within. To date the understanding of factors and mechanisms of CuO (nano-) toxicity to marine invertebrates is still limited. Hence, we studied the characteristics and behaviour of two commercially available CuO NPs of similar size, but produced employing distinct synthesis methods, under various environmentally and experimentally relevant conditions. In addition, cell viability and DNA damage, as well as gene expression of detoxification, oxidative stress, inflammatory response, DNA damage repair and cell death mediator markers were studied in primary cultures of hemocytes from the marine clam Ruditapes philippinarum and, where applicable, compared to bulk CuO and ionic Cu (as CuSO₄) behaviour and effects. We found that the synthesis method can influence particle characteristics and behaviour, as well as the toxicity of CuO NPs to Ruditapes philippinarum hemocytes. Our results further indicate that under the tested conditions aggregating behaviour influences the toxicity of CuO NPs by influencing their rate of extra- and intracellular dissolution. In addition, gene expression analysis identified similar transcriptional de-regulation for all tested copper treatments for the here measured suite of genes. Finally, our work highlights various differences in the aggregation and dissolution kinetics of CuO particles under environmental (marine) and cell culture exposure conditions that need consideration when extrapolating in vitro findings.

Alterations in haemolymph proteome of Mytilus galloprovincialis mussel after an induced injury

A proteomic and biochemical approach was performed to assess the effects of an induced muscle injury on the haemolymph of bivalve molluscs. For this purpose, Mytilus galloprovincialis were exposed to puncture of adductor muscle for three consecutive days, and their haemolymph proteome was then compared to healthy animals using 2-dimensional electrophoresis (2-DE) to identify proteins that differed significantly in abundance. Those proteins were then subjected to tandem mass spectrometry and 6 proteins, namely myosin, tropomyosin, CuZn superoxide dismutase (SOD), triosephosphate isomerase, EP protein and small heat shock protein were identified. SOD and tropomyosin changes were verified by spectrophotometric measurements and western blotting, respectively. As some of the proteins identified are related to muscular damage and oxidative stress, other biomarkers associated with these processes that can be evaluated by automatic biochemical assays were measured including troponin, creatine kinase (CK), and aspartate aminotransferase (AST) for muscle damage, and SOD, trolox equivalent antioxidant capacity (TEAC) and esterase activity (EA) for oxidative stress. Significantly higher concentrations of troponin, CK, AST, and TEAC were observed in mussels after puncture, being also possible biomarkers of non-specific induced damage.

Early ecotoxic effects of ZnO nanoparticle chronic exposure in Mytilus galloprovincialis revealed by transcription of apoptosis and antioxidant-related genes

Recently, China became one of the largest nanomaterial markets in the world. The wide use of ZnO nanoparticles in a number of products implies an increasing release in marine environment and consequently the evaluation of the potential effects upon marine organisms largely cultured in China for commercial purposes, such as invertebrate bivalves is a current need. To this aim, survival, bioaccumulation, and transcription pattern of key genes, p53, PDRP, SOD, CAT, and GST, involved in DNA damage/repair and antioxidation, in Mytilus galloprovincialis digestive gland, exposed to ZnO NPs (<100 nm) and ZnO bulk (150-200 nm) for 4 weeks, were evaluated. ZnSO₄ was also assessed to appraise the role of zinc ions. Starting from 72 h, increasing mortality values along the exposure time were observed for all ZnO compounds. The highest difference was evident after 28 d when NPs resulted three times more toxic than bulk, (LC₅₀) = 0.78 mg Zn/L (confidence limits: 0.64, 1.00) and 2.62 mg Zn/L (confidence limits: 1.00, 4.00), respectively. For ZnSO₄ the (LC₅₀) was always the lowest reaching the minimum value at 28 d 0.25 mg Zn/L (confidence limits: 0.10-0.40). Digestive gland showed higher uptake rate of ionic Zn respect to ZnO NPs and bulk during the first three days of exposure. In particular at the end of the exposure time (28 d) at 1 mg Zn/L the rank of Zn uptake rate was Zinc ion > ZnO NPs > ZnO bulk. The relative expression of investigated genes evidenced that distinct actions of apoptosis and antioxidation occurred in M. galloprovincialis exposed to ZnO NPs with a peculiar pattern dependent on exposure time and concentration. Application of the qRT-PCR technique revealed evidence of sensitivity to the nanomaterial since the first time of exposure.

Insights into the toxicity of iron oxides nanoparticles in land snails

The use of manufactured nanoparticles (NPs) is spreading rapidly across technology and medicine fields, posing concerns about their consequence on ecosystems and human health. The present study aims to assess the biological responses triggered by iron oxide NPs (IONPs) and iron oxide NPs incorporated into zeolite (IONPZ) in relation to oxidative stress on the land snail Helix aspersa in order to investigate its use as a biomarker for terrestrial environments. Morphology and structure of both NPs were characterized. Snail food was supplemented with a range of concentrations of IONPs and IONPZ and values of the hemocyte lysosomal membranes' destabilization by 50% were estimated by the neutral red retention (NRRT50) assay. Subsequently, snails were fed with NPs concentrations equal to half of the NRRT50 values, 0.05 mg L^-1 for IONPs and 1 mg L^-1 for IONPZ, for 1, 5, 10 and 20 days. Both effectors induced oxidative stress in snails' hemocytes compared to untreated animals. The latter was detected by NRRT changes, reactive oxygen species (ROS) production, lipid peroxidation estimation, DNA integrity loss, measurement of protein carbonyl content by an enzyme-linked immunoabsorbent assay (ELISA), determination of ubiquitin conjugates and cleaved caspases conjugates levels. The results showed that the simultaneous use of the parameters tested could constitute possible reliable biomarkers for the evaluation of NPs toxicity. However, more research is required in order to enlighten the disposal and toxic impact of iron oxide NPs on the environment to ensure their safe use in the future.

Nanoparticles in the environment: where do we come from, where do we go to?

Nanoparticles serve various industrial and domestic purposes which is reflected in their steadily increasing production volume. This economic success comes along with their presence in the environment and the risk of potentially adverse effects in natural systems. Over the last decade, substantial progress regarding the understanding of sources, fate, and effects of nanoparticles has been made. Predictions of environmental concentrations based on modelling approaches could recently be confirmed by measured concentrations in the field. Nonetheless, analytical techniques are, as covered elsewhere, still under development to more efficiently and reliably characterize and quantify nanoparticles, as well as to detect them in complex environmental matrixes. Simultaneously, the effects of nanoparticles on aquatic and terrestrial systems have received increasing attention. While the debate on the relevance of nanoparticle-released metal ions for their toxicity is still ongoing, it is a re-occurring phenomenon that inert nanoparticles are able to interact with biota through physical pathways such as biological surface coating. This among others interferes with the growth and behaviour of exposed organisms. Moreover, co-occurring contaminants interact with nanoparticles. There is multiple evidence suggesting nanoparticles as a sink for organic and inorganic co-contaminants. On the other hand, in the presence of nanoparticles, repeatedly an elevated effect on the test species induced by the co-contaminants has been reported. In this paper, we highlight recent achievements in the field of nano-ecotoxicology in both aquatic and terrestrial systems but also refer to substantial gaps that require further attention in the future.

Transcriptomic approach: A promising tool for rapid screening nanomaterial-mediated toxicity in the marine bivalve Mytilus edulis-Application to copper oxide nanoparticles

The extensive development of nanotechnologies will inevitably lead to the release of nanomaterials (NMs) in the environment. As the aquatic environments represent the ultimate sink for various contaminants, it is highly probable that they also constitute a reservoir for NMs and hence aquatic animals represent potential targets. In a regulatory perspective, it is necessary to develop tools to rapidly screen the impact of NMs on model organisms, given that the number of NMs on the market will be increasing. In this context High Throughput Screening approaches represent relevant tools for the investigation of NM-mediated toxicity. The objective of this work was to study the effects of copper oxide nanoparticles (CuONPs) in the marine bivalve Mytilus edulis, using a transcriptomic approach. Mussels were exposed in vivo to CuONPs (10 μg·L^-1CuO NPs) for 24 h and analysis of mRNA expression levels of genes implicated in immune response, antioxidant activities, cell metabolism, cell transport and cytoskeleton was investigated by qPCR on hemocytes and gills. Results showed common effects of CuONPs and its ionic counterpart. However, greater effects of CuONPs on GST, SOD, MT, Actin, ATP synthase gene expressions were observed compared to ionic form indicating that toxicity of CuONPs is not solely due to the release of Cu²⁺. Even though M. edulis genome is not fully characterized, this study provides additional knowledge on the signaling pathways implicated in CuONP-mediated toxicity and demonstrates the reliability of using a qPCR approach to go further in the cellular aspects implicated in response to NPs in marine bivalves.

Effects of metal contamination on the gene expression profile of two benthic species: Cerastoderma edule and Ruditapes philippinarum

This study aimed to identify new biomarkers for metal exposure in two bivalve species. Suppressive Subtractive Hybridization (SSH) was employed to evaluate the transcriptomic response of Cerastoderma edule and Ruditapes philippinarum to metal pollution. Protein synthesis and catalytic activity were the most affected metabolic processes in C. edule and R. philippinarum, respectively. Also, different genes responded to the effect of contamination in each species. The different response observed in both species reinforces the importance of including more than one bioindicator species in risk assessment studies. These results provide the basis for new studies, which are necessary for further validation of the use of the identified genes as molecular biomarkers for metal exposure.

Blue mussels (Mytilus edulis spp.) as sentinel organisms in coastal pollution monitoring: A review

The blue mussel (Mytilus spp.) is widely used as a bioindicator for monitoring of coastal water pollution (mussel watch programs). Herein we provide a review of this study field with emphasis on: the suitability of Mytilus spp. as environmental sentinels; uptake and bioaccumulation patterns of key pollutant classes; the use of Mytilus spp. in mussel watch programs; recent trends in Norwegian mussel monitoring; environmental quality standards and background concentrations of key contaminants; pollutant effect biomarkers; confounding factors; particulate contaminants (microplastics, engineered nanomaterials); climate change; harmonization of monitoring procedures; and the use of deployed mussels (transplant caging) in pollution monitoring. Lastly, the overall state of the art of blue mussel pollution monitoring is discussed and some important issues for future research and development are highlighted.

Consequences of acclimation on the resistance to acute thermal stress: Proteomic focus on mussels from pristine site

Climate change constitutes an additional threat for intertidal species that already have to cope with a challenging environment. The present study focuses on the blue mussel Mytilus edulis and aims at investigating the importance of thermal acclimation in heat stress response. Microcosm exposures were performed with mussels submitted to an identical acute thermal stress following two thermal summer acclimations standing for present or future temperature conditions. Gill proteomes were analyzed by 2DE and 96 differentially expressed proteoforms were identified. Our results show that cell integrity appears to be maintained by the rise in molecular protective systems (i.e. Heat Shock Proteins), and by the reallocation of energy production via a switch to anaerobic metabolism and the setting up of alternative energy pathways. Finally, our results indicate that the response of mussels to acute thermal stress is conditioned by the acclimation temperature with an improved response in organisms acclimated to higher temperatures.

Tralopyril bioconcentration and effects on the gill proteome of the Mediterranean mussel Mytilus galloprovincialis

Antifouling (AF) systems are used worldwide as one of the most cost-effective ways of protecting submerged structures against heavy biofouling. The emergence of environmentally friendly AF biocides requires knowledge on their environmental fate and toxicity. In this study we measured the bioconcentration of the emerging AF biocide tralopyril (TP) in the Mediterranean mussel Mytilus galloprovincialis and investigated the effects of TP on the mussel gill proteome following acute (2days) and chronic (30days) exposure, as well as after a 10-day depuration period. The experiments were carried out with 1μg/L TP; blank and solvent (5×10(-5)% DMSO) controls were also included. Proteomics analysis was performed by mass spectrometry-based multidimensional protein identification technology (MudPIT). Differentially expressed proteins were identified using a label-free approach based on spectral counts and G-test. Our results show that TP is rapidly accumulated by mussels at concentrations up to 362ng/g dw (whole tissues), reaching steady-state condition within 13days. Ten days of depuration resulted in 80% elimination of accumulated TP from the organism, suggesting that a complete elimination could be reached with longer depuration times. In total, 46 proteins were found to be regulated in the different exposure scenarios. Interestingly, not only TP but also DMSO alone significantly modulated the protein expression in mussel gills following acute and chronic exposure. Both compounds regulated proteins involved in bioenergetics, immune system, active efflux and oxidative stress, often in the opposite way. Alterations of several proteins, notably several cytoskeletal ones, were still observed after the depuration period. These may reflect either the continuing chemical effect due to incomplete elimination or an onset of recovery processes in the mussel gills. Our study shows that exposure of adult mussels to sublethal TP concentration results in the bioconcentration of this biocide in the tissues and modulates the expression of several proteins that may intervene in important metabolic pathways.

Proteomic and metabolomic analysis on the toxicological effects of As (III) and As (V) in juvenile mussel Mytilus galloprovincialis

Inorganic arsenic (As) is a known pollutant including two chemical forms (arsenite (As III) and arsenate (As V)), in marine and coastal environment. Marine mussel Mytilus galloprovincialis is an important environmental monitoring species around the world. In this study, we focused on valence-specific responses of As in juvenile mussel M. galloprovincialis using a combined proteomic and metabolomic approach. Metabolic responses indicated that As (III) mainly caused disturbance in osmotic regulation in juvenile mussels. As (V) caused disturbances in both osmotic regulation and energy metabolism marked by different metabolic responses, including betaine, taurine, glucose and glycogen. Proteomic responses exhibited that As (III) had a significant negative effect on cytoskeleton and cell structure (actin and collagen alpha-6(VI) chain). As (V) affected some key enzymes involved in energy metabolism (cytosolic malate dehydrogenase, cMDH) and cell development (ornithine aminotransferase and astacin). Overall, all these results confirmed the valence-specific responses in juvenile mussels to As exposures. These findings demonstrate that a combined metabolomic and proteomic approach could provide an important insight into the toxicological effects of environmental pollutants in organisms.