Molecular and biochemical biomarkers responses in the mussel Mytilus edulis collected from Southern Brazil coast

Biochemical response and tissue-specific accumulation of scallop Aequipecten tehuelchus from Patagonia, Argentina after exposure to inorganic arsenic

This study investigates the effects of different inorganic arsenic (As III) concentrations (0, 125, 500 and 1000 μg As/L) following two exposure times (7 and 14 days) on gills, digestive gland and muscle of scallop Aequipecten tehuelchus from Patagonia, Argentina. A biochemical approach was used to investigate oxidative stress-related parameters after different As concentrations and exposure times. Although the accumulation of As was of the same order of magnitude in all tissues, the results showed distinct tissue-specific oxidative responses to this metalloid. Furthermore, the variation in exposure time had no significant effect on As accumulation in any of the three tissues. In gills, despite no reactive oxygen and nitrogen species (RONS) were detected, there was an increase in catalase (CAT) activity and metallothionein (MT) levels. Conversely, digestive gland showed RONS production without a rise in CAT and glutathione S-transferases (GST) activities, but with an increase in MT levels. In muscle, RONS production and CAT activity kept constant or decreased, while MT levels remained unchanged. In addition, exposure time demonstrated its critical role in gills by influencing the response of CAT, GST and MT, particularly at high As concentrations, while exposure time did not affect the biochemical stress parameters in the digestive gland and muscle. Interestingly, neither concentration of As produced lipid damage, showing the effectiveness of the antioxidant mechanisms to avoid it. These results emphasize that A. tehuelchus exhibited no time-dependent effects in response to As exposure, while showing tissue-specific responses characterized by significant concentration-dependent effects of As. This study provides a comprehensive insight by considering the combined effects of time and concentration of a contaminant and distinguishing its effects on specific tissues, a dimension often overlooked in the existing literature. Subsequent studies should prioritize the analysis of additional contaminants in species with increased sensitivity.

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.

Size and site specific transcriptomic responses of blue mussel (Mytilus edulis) to acute hypoxia

The Prince Edward Island (PEI) mussel aquaculture industry is being challenged by climate change induced environmental stressors including hypoxic/anoxic episodes, that can impact mussel health and survival. Physiological responses of mussels to hypoxia/anoxia have been studied; however, less is known about how transcriptomic response leads to physiology. The present study examined the transcriptomic response of acute (4 h) hypoxia in blue mussels (Mytilus edulis) from two sites and size classes in PEI, Canada. Overall, major changes in whole-mussel transcriptomics associated with metabolism, cellular organelles/processes and environmental sensing were observed in the first hours of hypoxia exposure. Differences in differentially expressed transcripts were observed between each site and size, indicating that responses to acute hypoxia exposure are highly complex. A size related pattern was observed, with seed size mussels having differential expression of transcripts associated with development, muscle function, and byssal attachment compared to the adults. Adult mussels had higher HSP 90 expression, while HSPs were predominately under-expressed in seed mussels. Seed mussels had significant under-expression of several classes of byssal thread attachment transcripts, indicating a decline in the production of byssal thread or detachment, both which have negative consequences for mussel aquaculture.

Metabolic variation and oxidative stress response of blue mussels (Mytilus sp.) perturbed by norfloxacin exposure

Antibiotics are currently widely applied in agricultural cultivation, animal husbandry, and medical treatment, but the effects and ecological risks of antibiotics need to be further investigated. Norfloxacin is one of the most widely applied fluoroquinolone antibiotics and is commonly detected in aquatic ecosystems. In this study, the activities of catalase (CAT) and glutathione S-transferase (GST) in blue mussels (Mytilus sp.) exposed to norfloxacin (from 25 to 200 mg/L) for 2 d of acute exposure and 7 d of subacute exposure were measured. ¹H nuclear magnetic resonance (¹H-NMR)-based metabolomics was applied to identify the metabolites and to investigate the physiological metabolism of blue mussels (Mytilus sp.) under different concentrations of norfloxacin. The activity of the CAT enzyme was induced in acute exposure, while the activity of GST was inhibited in subacute exposure when the concentration of norfloxacin reached 200 mg/L. Orthogonal partial least squares discriminant analysis (OPLS-DA) revealed that the increased concentrations of norfloxacin might cause greater metabolic differences between the treatment and control groups and cause greater metabolic variation within the same treatment group. The contents of taurine in the 150 mg/L acute exposure group were 5.17 times higher than those in the control group. The pathway analysis indicated that exposure to high concentrations of norfloxacin disturbed different pathways involved in energy metabolism, amino acid metabolism, neuroregulation, and the regulation of osmotic pressure. These results may provide a molecular and metabolic view of the effects of norfloxacin and the regulatory mechanism of blue mussels when exposed to extremely high doses of antibiotics.

Multi-biomarker approach in Mytilus galloprovincialis and Ruditapes decussatus as a predictor of pelago-benthic responses after exposure to Benzo[a]Pyrene

This study evaluated the biomarker responses indicative of exposure to Benzo[a] Pyrene (B[a]P) in Mytilus galloprovincialis and Ruditapes decussatus. A significant increase of the total oxyradical scavenging capacity (TOSC) was observed after seven days of exposure to two concentrations of B[a]P (100 and 300 μg.L^-1), in the digestive gland with the lowest concentration tested. The TOSC in the gills increased notably only after the exposure to 300 μg.L^-1 of B[a]P. Interestingly, the superoxide dismutase (SOD) and catalase (CAT) activities in gills and digestive gland on one hand and glutathione S-transferase (GST) in gills in the other, were positively correlated with the concentration of B[a]P with a significant induction noticed at the highest concentration. In contrast, a significant increase of the GST activity was observed in the digestive gland following the exposure of bivalves to 100 μg.L^-1. In pelagic (M. galloprovincialis) or benthic (R. decussatus) bivalves, the AChE activity decreased discernibly in digestive glands and gills with the increase of B[a]P concentrations as evidence of neurotoxic effects. In clams, the exposure to B[a]P was followed by a significant increase of Malondialdehyde level (MDA) in gills and digestive gland, this does not occur in gills of Mytilus galloprovincialis at the concentration of 100 μg.L^-1. Overall, the results found seems to indicate that the mussel was more suitable as a predictor tool of toxicity of B[a]P.

Functional, biochemical and molecular impact of sediment plumes from deep-sea mining on Mytilus galloprovincialis under hyperbaric conditions

The deep-sea is the biggest ecosystem in the world and despite the extreme conditions that characterize it, is highly biodiverse and complex. Deep-sea mining has been foreseen as a potential and concerning new stressor, and among the deep-sea mining associated stressors, sediment plumes, likely to be released into the water column as a side effect of mining, can reach habitats within a radius of more than a hundred kilometers. The present study examined the effects of suspended sediments of different grain sizes (63-125 μm, 125-250 μm and 250-500 μm) in the model species Mytilus galloprovincialis, at 4 bar, as a proxy to address the potential effects of sediment plumes, in the water column, with different grain sizes under high pressure conditions. Functional (filtration rate - FR), biochemical (catalase - CAT, glutathione s-transferase - GST, lipid peroxidation - LPO) and molecular (gene expression of [actin (ACTN), glutathione S-transferase alpha (GSTA), superoxide dismutase 2 (SOD2), catalase (CAT), heat shock protein 60 (HSP60), cytochrome c oxidase (COI) and DNA mismatch repair protein (MSH6)]) endpoints were studied in juvenile organisms. The FR decreased significantly for all tested grain size ranges, with a more severe effect for the particles with a diameter between 63 and 125 μm. In addition to the FR, significant changes were also observed for all tested biomarkers. Gene expression was significantly downregulated for CAT and ACTN. Overall, this study demonstrated that the smaller sized particles are the ones leading to more severe effects. Given their high dispersion potential and longer suspension periods under mining operation scenarios, particular attention should be given to the release of sediment plumes that may affect deep-sea environments and the water column. It is, therefore, vital to create standards and guidelines for sustainable mining practices.

Stress responses to warming in the mussel Brachidontes rodriguezii (d'Orbigny, 1842) from different environmental scenarios

The intertidal mussel B. rodriguezii is a representative species from hard bottom substrates where both anthropogenic and natural stressors are present. Pre-exposure to these different stressors can modify the tolerance to additional stressors such as warming. Moreover, this tolerance can vary depending on intraspecific variables such as the organism's sex. The effects of warming and its intraspecific variability in representative coastal species are crucial to understanding the tolerance to future environmental scenarios. The mussels were collected in different environmental scenarios, including low (Control), chemical (Harbour) and natural stressed (Estuary) sites, and then exposed to different water temperatures (10-30 °C) for 14 days. Lethal and sublethal responses were evaluated in different mussel populations. Thus, cumulative death rate, air survival time, heat shock proteins (HSC70/HSP70), total ubiquitin, catalase (CAT), glutathione-s-transferase (GST) and lipid peroxidation (TBARS) were assessed in mussels from different areas and different sexes. The results revealed diminished air survival time and high cumulative mortality rate in mussels collected at the harbour and those exposed to higher temperatures, respectively. The sublethal responses of the field animals showed different patterns according to the different areas investigated. Besides, the results revealed that these differences were also observed between sexes. Regarding the sublethal responses in mussels exposed to warming, the interactive effects of temperature and sites showed a strong influence on all biochemical parameters analyzed (p < 0.001). Therefore, harbour mussels showed a distinct pattern compared to other locations and reflecting the most damaging effects of warming. The influence of sex and its interactions with warming were also crucial in most of the sublethal responses (p < 0.05). Multivariate analysis was performed with all sublethal responses, and the different warming scenarios showed different groups according to the sites. In the predicted warming scenarios, males showed no differences between sites. In contrast to males, females showed differences between sites in the predicted and the worse-case warming scenarios. Our results highlight the importance of compensatory mechanisms in the mussel warming tolerance like HSP70. The influence of sex is also crucial in understanding warming tolerance in mussels chronically exposed to pollutants in their natural environment. Also, lethal endpoints are essential for understanding the non-reversibility signature of the observed biochemical responses.

Differential responses of a pi-class glutathione S-transferase (CnGSTp) expression and antioxidant status between golden and brown noble scallops under pathogenic stress

Glutathione S-transferases (GSTs) play important roles in immunity by protecting organisms against the damage of reactive oxygen species (ROS). In this study, a pi-class GST cDNA sequence was first cloned from noble scallop Chlamys nobilis (named CnGSTp). The full length cDNA of CnGSTp was 922 bp, encoding a cytosolic protein of 202 amino acids residues, with predicted molecular masses of 23.1 kDa. Then an acute Vibrio Parahaemolyticus challenge experiment was conducted by using the Golden and Brown noble scallops with different total carotenoids content (TCC), and CnGSTp expression level, TCC and ROS level was separately determined. The results showed that ROS and CnGSTp expression levels were significantly up-regulate under Vibrio Parahaemolyticus challenge than the control group (P < 0.05). The Golden scallops showed significantly higher CnGSTp expression level and lower ROS level in hemocytes than the Brown ones (P < 0.05). Moreover, there is a significantly positive correlation between TCC and ROS in the Golden scallops. The present results revealed that CnGSTp plays important roles in immune response and carotenoids play assistant roles in antioxidant defense system under pathogenic stress in the noble scallop.

Uso de biomarcadores en la evaluación ambiental de ecosistemas marinos en América

The use of biomarkers in the assessment of the marine environmental status offers an integrated approach to the effects caused by diverse pollutants. This article compiles and analyzes the original research on the study of possible biomarkers in wild coastal-marine organisms from America. One of the outcomes of this review research is the need for a continuous evaluation of organisms in conjunction with the assessment of environmental vari-ables and the levels of pollutants that may be found in any ecosystem. It is well stated that the use of biomarkers is a practical tool for the environmental management; however, some limitations apply and there are several questions in regards to specificity, sensibility, usability, replicability, and interpretation to be solved, yet. Along the American continent, multiple biomarkers have been used to evaluate specific pollutants or highly impacted zones at marine-coastal environments. The most commonly used organisms are fishes and bivalves and they have been also extensively used in marine turtles. In regards of the type of biomarkers, plenty of authors integrate biomarkers from different groups, sorted in this review as biometric biomarkers (morphologic and corporal in-dexes), histological biomarkers (for tissues), molecular biomarkers (genetic) and biochemical and physiological biomarkers (both at the cellular and molecular levels). Following this classification, the most used biomarkers were biochemical and physiological biomarkers, due to the great advantages and information that they provide. It is of utmost importance to set guidelines and referenced threshold values for each biomarker to allow the early environmental diagnosis and integrated evaluation of harmful pollutants effects. Keywords: Biomarkers, environmental assessment, America.

Baseline bio-accumulation concentrations and resulting oxidative stress in Synodontis zambezensis after an acute laboratory exposure to 4,4'-DDT

The use of 1,1'-(2,2,2-Trichloro-1,1-ethanediyl)bis(4-chlorobenzene) (DDT) as a pesticide for the control of insects vectors responsible for the spread of many life threatening diseases was officially banned in 1972 by the United States Environmental Protection Agency (USEPA). It was banned throughout the world, in most developed countries, because of the toxic effects it causes in wildlife, including birds and fish. However, DDT is still used in approximately 43 African countries, including South Africa, to control the spread of malaria. The lipophilic nature of DDT and therefore its persistence in the environment makes it extremely important for laboratory based studies to be conducted in an effort to evaluate the accumulation potential and possible physiological effects of DDT in aquatic organisms under controlled conditions. The aim of this study was to establish baseline bioaccumulation concentrations within Synodontis zambezensis following an acute exposure to 4,4'-DDT. The three metabolites analysed were 4,4'-DDE, 4,4'-DDD and 4,4'-DDT. None of the 2,4'-isomers were analysed in this study since the acute exposure used a solution of 98.7% pure 4,4'-DDT (Sigma-Aldrich PESTANAL®, Analytical Standard, CAS-No 50-29-3, Batch number SZBE057XV) and not a mixture of 4,4'-DDT and 2,4'-DDT as found in technical grade DDT. Soxhlet extraction of tissue samples and liquid/liquid extraction of water samples followed by analysis through Gas-chromatography mass-spectrophotometry was completed. Mean 4,4'-DDE, 4,4'-DDD and 4,4'-DDT concentrations ranged from 15.34 ng/g to 45.34 ng/g, 28.16 ng/g to 63.25 ng/g and 28.64 ng/g to 96.21 ng/g respectively. All of the accumulated concentrations fell within environmentally relevant concentrations with no input through the food web. The accumulated concentrations of 4,4'-DDT and its three metabolites resulted in oxidative stress responses within the gills and the liver tissue of S. zambezensis. Significant differences (p ≤ .05) were observed between malondialdehyde (MDA) and reduced glutathione (GSH) within the liver and in superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH) in the gills.

Integrated toxicity evaluation of metals in sediments of Jiaozhou Bay (China): Based on biomarkers responses in clam Ruditapes philippinarum exposed to sediment extracts

To evaluate the integrated toxicity of metals in sediments of Jiaozhou Bay, we exposed clam (Ruditapes philippinarum) to sediments extracts obtained using of sediment extraction with deionised water adjusted to pH 4 which simulated the weak acidity in the digestive juice of clams and tested the selected biomarkers responses in clams for exposure over 15 days. At the same time, the contents of metals in sediments were assessed with method of the mean sediment quality guideline quotient (SQG-Q). The integrated biomarker response version 2 (IBR_v2) was used to assess the integrated toxicity induced by metals in sediment extracts based on biomarkers response in clams: the results demonstrated that site S7 located in the mouth of Nanxin'an River show higher IBR_v2 values compared to the other sites. The IBR_v2 values exhibited the good consistency with SQG-Q values.

Interactive effects of nutrition, reproductive state and pollution on molecular stress responses of mussels, Mytilus galloprovincialis Lamarck, 1819

Marine bivalves including mussels Mytilus galloprovincialis are commonly used as sentinels for pollution monitoring and ecosystem health assessment in the coastal zones. Use of biomarkers to assess the pollution effects assumes that the effects of pollutants on the biomarkers exceed the natural background variability; yet this assumption has rarely been tested. We exposed mussels at different reproductive stages and nutritive states to two concentrations of a polycyclic aromatic hydrocarbon (fluoranthene, 3 and 60 μg L^-1) for three weeks. Expression levels of the molecular biomarkers related to the detoxification and general stress response [cytochrome P450 oxidase (CYP450), glutathione S-transferases (GST-α; GST-S1; GST-S2), the multixenobiotic resistance protein P-glycoprotein (PgP), metallothioneins (MT10 and MT20), heat shock proteins (HSP22, HSP70-2; HSP70-3; HSP70-4), as well as mRNA expression of two reproduction-related genes, vitellogenin (Vitel) and vitelline coat lysin M7 (VCLM7)] were measured. The mussels' nutrition and reproductive state affected the baseline mRNA levels of molecular biomarkers and modulated the transcriptional responses of biomarker genes to the pollutant exposure. Thus, mussel physiological state could act as a confounding factor in the evaluation of the response of pollution through molecular biomarkers. The biomarker baseline levels must be determined across a range of physiological states to enable the use of biomarkers in monitoring programs.

Functional and molecular responses of the blue mussel Mytilus edulis' hemocytes exposed to cadmium - An in vitro model and transcriptomic approach

The bivalve mollusk, Mytilus edulis, is used as a sentinel species in several monitoring programs due to its ability to bio-accumulate contaminants. Its immune system consists of hemocytes and humoral components, which constitute the main part of the hemolymph. The present study is aimed at understanding the effects of Cd on the differentially expressed genes involved in the phagocytosis of M. edulis' hemocytes. Our approach focuses on an in vitro model by exposing hemocytes to different concentrations of Cd ranging from 10^-9 M to 10^-3 M. Phagocytosis and cell viability as functional markers were measured using flow cytometry. The molecular mechanisms regulated by Cd were investigated using RNA-seq and DGE analysis. Results showed that viability and phagocytosis of hemocytes exposed to 10^-3 M of Cd were significantly decreased after 21 h of exposure. RNA sequencing data showed that 1112 transcripts (out of 352,976 contigs) were differentially regulated by the highest concentration of Cd. Among these identified transcripts, 1028 and 84 were up and down-regulated respectively. The induction of super oxide dismutase (SOD), glutathion-s-transferase (GST), cytochrome P450 2C8 (CYP2C8), multidrug resistance protein (MRP1) and heat shock protein 70 (HSP70) suggests that Cd can regulate key molecular mechanisms. In addition, several toll-like receptors (TLR) as well as genes involved in phagocytosis (actin and CDC42) and apoptosis (caspase 8 and XIAP/IAP) were induced by Cd. Thus, our model highlights the effect of Cd on the phagocytic function of M. edulis' hemocytes along with the regulation of gene expression involved in innate immunity, detoxification and apoptosis. Further investigations need to be pursued to unravel the effects of Cd on the molecular mechanisms identified in this study.

Variations of biomarkers response in mussels Mytilus galloprovincialis to low, moderate and high concentrations of organic chemicals and metals

The changes of acetylcholinesterase activity (AChE), metallothioneins content (MTs), catalase activity (CAT) and lipid peroxidation (LPO) were assessed after 4 days exposure of mussels Mytilus galloprovincialis to a wide range of sublethal concentrations of chlorpyrifos (CHP, 0.03-100 μg/L), benzo(a)pyrene (B(a)P, 0.01-100 μg/L), cadmium (Cd, 0.2-200 μg/L) and copper (Cu, 0.2-100 μg/L). The activity of AChE in the gills decreased after exposure to CHP and Cu, whereas no change of activity was detected after exposure to B(a)P and Cd. Both induction and decrease of MTs content in digestive gland occurred after exposure to CHP and B(a)P, while a marked increase was evident at highest exposure concentrations of Cd. The content of MTs progressively decreased of MTs with increasing concentration of Cu. CAT activity and LPO in the gills did not change after exposure to any of the chemicals. The results demonstrate different response profile in relation to the type of chemical compound, and highlight the potential implications for evaluation of biological effect of contaminants in marine environment. Furthermore, the AChE activity in the gills and MTs content in the digestive gland could be modulated by CHP and Cu at environmentally relevant concentrations indicating the potential risks of short-term transient mussels exposure that may occur due to run-off from land or accidental releases.

Molecular cloning and functional characterization of theta class glutathione S-transferase from Apostichopus japonicus

Glutathione S-transferases (GSTs) are the superfamily of multifunctional detoxification isoenzymes and play crucial roles in innate immunity. In the present study, a theta class GST homology was identified from A. japonicus (designated as AjGST-θ) by RACE approaches. The full-length cDNA of AjGST-θ was of 1013 bp encoded a cytosolic protein of 231 amino acids residues. Structural analysis revealed that AjGST-θ processed the characteristic N-terminal GSH-binding site (G-site) and the C-terminal hydrophobic substrate binding site (H-site). Multiple sequence alignment and phylogenetic analysis together supported that AjGST-θ belonged to a new member of theta class GST protein subfamily. Spatial expression analysis revealed that AjGST-θ was ubiquitously expressed in all examined tissues with the larger magnitude in intestine. The Vibrio splendidus challenge in vivo and LPS stimulation in vitro could both significantly up-regulate the mRNA expression of AjGST-θ when compared with control group. The recombinant protein was expressed in Escherichia coli and the purified AjGST-θ showed high activity with GST substrate. Meantime, disc diffusion assay showed that recombinant AjGST-θ protein could markedly improve bacterial growth under Cumene hydroperoxide exposure. More importantly, the recombinant AjGST-θ could effectively prevent primary coelomocytes apoptosis after LPS exposure. Our present findings suggested that AjGST-θ might play significantly roles in the modulation of immune response and protect cells from pathogens infection in A. japonicus.

Baseline levels of oxidative stress biomarkers in species from a subtropical estuarine system (Paranaguá Bay, southern Brazil)

Offshore petroleum exploration has increased the risks of oil spills in coastal tropical and subtropical habitats. Monitoring tools are needed to assess and protect environmental health. We determined baseline values of antioxidant biomarkers (CAT, SOD, GPx, GST, MDA) for five ecologically relevant species in a subtropical system in southern Brazil. Regional baseline levels are compared with literature data as a basis to eventually test their efficacy as post-spill monitoring tools. Differences in the antioxidant response among species, contamination, and seasons were tested using univariate and multivariate analyses. The bivalves Anomalocardia flexuosa and Crassostrea rhizophorae and the catfish Genidens genidens emerge as suitable sentinel species. Seasonality is the main factor accounting for biomarkers variability, and not background contamination level. However, interactions between season and contamination level are also significant, indicating that biomarkers respond to complex environmental settings, a fact that needs to be fully understood for designing proper monitoring programs.

Evaluation of tissue morphology and gene expression as biomarkers of pollution in mussel Mytilus galloprovincialis caging experiment

The ecosystem is being anthropogenically disturbed, which has serious consequences for the environment and human health, having strong social and economic impacts on the community. One of the most common methods to evaluate the effects of toxic contaminants is based on biomonitoring, e.g., placing Mytilus galloprovincialis in the polluted areas investigated. In this study, we have combined two different methods, transcriptomic and morphological analysis, with the purpose of determining whether cell morphology and the ultrastructural organization of our animal model are related to gene expression in outdoor experiments. The most pronounced changes were observed in mussel gills and digestive gland for mRNA involved in protein machinery (18S, 28S and EF1), while HSP70, MT10, CYP4Y1, SOD1, and CAT mRNAs showed scattered modifications not related to the studied area. In agreement with 18S, 28S, and EF1 mRNA evaluation, optical and electron microscopy demonstrated an initial inflammatory response of the cells that can lead to apoptosis in the caged mussels in all the polluted areas. In conclusion, the application of a multi-disciplinary approach proved to be effective for assessing the biological effects of contaminations on the health of aquatic organisms, and thus suitable to be applied in eco-toxicological studies. Although affected by several uncontrolled environmental variables, the assessment of mRNA can represent a useful endpoint for an integrated estimation of the overall threats to the sea environment within a field research approach.

Exposure to phenanthrene and depuration: Changes on gene transcription, enzymatic activity and lipid peroxidation in gill of scallops Nodipecten nodosus

Understanding the mechanism of phenanthrene (PHE) biotransformation and related cellular responses in bivalves can be an important tool to elucidate the risks of polycyclic aromatic hydrocarbons (PAHs) to aquatic organisms. In the present study it was analyzed the transcriptional levels of 13 biotransformation genes related to cytochrome P450 (CYP), glutathione S-transferase (GST), sulfotransferase (SULT), flavin-containing monooxygenase and fatty acid-binding proteins by qPCR in gill of scallops Nodipecten nodosus exposed for 24 or 96h to 50 or 200μgL(-1) PHE (equivalent to 0.28 and 1.12μM, respectively), followed by depuration in clean water for 96h (DEP). Likewise, it was quantified the activity of catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), glutathione reductase (GR), glucose 6-phosphate dehydrogenase (G6PDH), GST and levels of lipid peroxidation. Increased transcriptional levels of CYP2UI-like, CYP2D20-like, CYP3A11-like, GSTomega-like, SULT1B1-like genes were detected in organisms exposed to PHE for 24 or 96h. In parallel, GR and GPX activities increased after 96h exposure to 200μgL(-1) PHE and G6PDH activity increased after 24h exposure to 50μgL(-1) PHE. This enhancement of antioxidant and phase I and II biotransformation systems may be related to the 2.7 and 12.5 fold increases in PHE bioaccumulation after 96h exposure to 50 and 200μgL(-1) PHE, respectively. Interestingly, DEP caused reestablishment of GPX and GR activity, as well as to the transcript levels of all upregulated biotransformation genes (except for SULT1B1-like). Bioaccumulated PHE levels decreased 2.5-2.9 fold after depuration, although some biochemical and molecular modifications were still present. Lipid peroxidation levels remained lower in animals exposed to 200μgL(-1) PHE for 24h and DEP. These data indicate that N. nodosus is able to induce an antioxidant and biotransformation-related response to PHE exposure, counteracting its toxicity, and DEP can be an effective protocol for bivalve depuration after PHE exposure.

Responses of cytochrome P450, GST, and MXR in the mollusk Corbicula fluminea to the exposure to hospital wastewater effluents

Pharmaceutical products are a major group of chemical compounds that are continuously released into the environment. The primary pathway of pharmaceuticals to the aquatic environment is the discharge of wastewater effluents. The Psychiatric hospital of Montpon (Dordogne, France) operates with its wastewater treatment plant. We first evaluated the presence and concentrations of 27 pharmaceuticals compounds in these effluents. All of the 27 compounds were detected in these wastewater effluents at concentrations ranging between 37,500 ng L(-1) (paracetamol) and 150 ng L(-1) (citalopram). The aim of the study was then to evaluate the exposure effects of the effluents on cytochrome P450, GST, and MXR responses in Corbicula fluminea gills and digestive glands. Experiments on clams exposed during 1, 3, 7 14, and 21 days revealed a strong and continuous overexpression of mdr1 (multidrug resistant 1) gene expression in gills and transitory variations in pi-gst expression and GST activity. EROD activity increased also transitory after 1 day in the digestive gland of exposed clams. These results indicated that in the effluent, some molecules have undergone metabolism of phase 1 and/or phase 2.

Effects of cadmium and 17β-estradiol on Mytilus galloprovincialis redox status. Prooxidant-antioxidant balance (PAB) as a novel approach in biomonitoring of marine environments

Cadmium and 17β-estradiol are rapidly accumulated in mussel tissues, making mussels excellent pollution sentinel organisms. The aim of the present study was to compare the oxidative responses of the mussels after 1, 3 and 7 days of exposure to cadmium with those to 17β-estradiol and subsequently, to suggest a multi-parametric approach for biomonitoring studies. Our results showed that environmentally relevant concentrations of either cadmium or 17β-estradiol for 1, 3 and 7 days induced oxidative stress in hemocytes of exposed mussels. The latter was determined by significantly increased ROS levels and apoptosis, by suppression of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and glutathione-S-transferase (GST) expression levels and subsequent increased prooxidant levels, as measured by prooxidant-antioxidant balance (PAB) assay. To our knowledge this is the first time that prooxidant-antioxidant balance is evaluated in invertebrates as an index of oxidative stress. The simultaneous use of the parameters of prooxidant-antioxidant balance and antioxidant enzymes expression patterns, in combination with ROS production levels and apoptosis, in mussel hemocytes is suggested as an approach that may help to better evaluate the impact of environmental pollution on marine organisms and thereupon ecosystems.

A selection of reference genes and early-warning mRNA biomarkers for environmental monitoring using Mytilus spp. as sentinel species

mRNA biomarkers are promising tools for environmental health assessment and reference genes are needed to perform relevant qPCR analyses in tissue samples of sentinel species. In the present study, potential reference genes and mRNA biomarkers were tested in the gills and digestive glands of native and caged mussels (Mytilus spp.) exposed to harbor pollution. Results highlighted the difficulty to find stable reference genes in wild, non-model species and suggested the use of normalization indices instead of single genes as they exhibit a higher stability. Several target genes were found differentially expressed between mussel groups, especially in gills where cyp32, π-gst and CuZn-sod mRNA levels could be biomarker candidates. Multivariate analyses confirmed the ability of mRNA levels to highlight site-effects and suggested the use of several combined markers instead of individual ones. These findings support the use of qPCR technology and mRNA levels as early-warning biomarkers in marine monitoring programs.

Induction of brown cells in Venerupis philippinarum exposed to benzo(a)pyrene

Benzo(a)pyrene is an important polycyclic aromatic hydrocarbon (PAH) commonly present in the marine environment and responsible for carcinogenic, teratogenic and mutagenic effects in various animal species. In the present study, we investigated by both histochemical and immunohistochemical approaches the effect of an acute exposure to different concentrations of B(a)P in the Manila clam Venerupis philippinarum. The general morphology of the different clam tissues, which was investigated histologically, evidenced a significant increase in the number of intestinal brown cells after B(a)P exposure. An increasing trend response to B(a)P was detected. The histochemical analysis for lipofuscin revealed the presence of lipofuscin-like substances inside the cytoplasm of intestinal brown cells. The same cells exhibited a PAS positivity and a reactivity to Schmorl's solution for melanin pigment. Moreover, intestinal brown cells exhibited an immunopositivity to HSP70 antibody confirming the increasing trend response to B(a)P detected by the histochemical analysis. Our results suggest that histological tissue changes resulting from exposure to B(a)P can be an useful marker in biomonitoring studies.

Biomarkers of environmental stress in gills of ribbed mussel Aulacomya atra atra (Nuevo Gulf, Northern Patagonia)

In this study, we assessed in gills of native ribbed mussels Aulacomya atra atra from three sites within Nuevo Gulf (Northern Patagonia) several biomarkers such as reactive oxygen species (ROS), lipid radicals (LR), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and metallothionein (MT). Furthermore, concentrations of main trace metals (Fe, Al, Zn, Cu, Cd and Pb) were quantified in mussel tissue. Results showed significant induction of SOD, GST, MT and MDA, as well as, higher concentration of Fe, Al and Cd in winter than in summer. The high MDA content measured in mussels from Folías Wreck seemed to be caused by the very high levels of Fe that would come from the corrosion of the vessel. Mussels from the control site Punta Cuevas presented the lowest levels of Cd and the highest of Al in winter. Despite positive correlations were found between Al and GST and MT, no spatial differentiation was detected in those biomarkers. On the other hand, MT was only related to Al been most likely influenced by environmental variables than by the trace metals. It has to be highlighted that the relationship detected among water temperature, nutrients and antioxidant responses in gills is probably related to the fact that this tissue is in direct contact with water and it is sensitive to its fluctuations. Taking into account that mussel gill is a tissue actively proliferating and the first target of contaminants present in water, so that changes in its antioxidant system can provide an earlier warning signal than in other tissues.

Histopathology and stress biomarkers in the clam Venerupis philippinarum from the Venice Lagoon (Italy)

The aim of this study was to evaluate the histomorphology and the stress response in the bivalve Venerupis philippinarum sampled in four differently polluted sites of the Venice Lagoon (Palude del Monte, Marghera, Ca' Roman and Val di Brenta). This species is often used as bioindicator of environmental pollution since it can bioaccumulate a large variety of pollutants because of its filter feeding. Chemical analyses for heavy metals (Cd, Cu, Hg and Pb) and polycyclic aromatic hydrocarbons (PAHs) were performed on whole soft tissues of V. philippinarum. The histological evaluation of clams revealed the presence of Perkinsus sp. infection in animals from all sites, although a very high prevalence of parasites was evidenced in clams from Ca' Roman. Perkinsus sp. were systemically distributed in the mantle, in the intestine and digestive gland, in gonads and gills. The trophozoites of Perkinsus sp. were found isolated or in cluster surrounded by a heavy hemocitical response. Haemocytes always exhibited an immunopositivity to cytochrome P4501A (CYP1A), heat shock protein 70 (HSP70), 4-hydroxy-2-nonenal (HNE) and nitrotyrosine (NT) antibodies. The digestive gland of animals from Palude del Monte showed the highest malondialdehyde (MDA) concentration, whereas clams from Ca' Roman exhibited the highest quantity of metallothioneins.

A multibiomarker approach to the assessment of pollution impacts in two Baltic Sea coastal areas in Sweden using caged mussels (Mytilus trossulus)

Blue mussels (Mytilus trossulus) were transplanted in cages for three months in two Swedish coastal areas in the Bothnian Sea (northern Baltic Sea) to investigate the interactions between analysed environmental chemicals and biological responses. A wide array of biological parameters (biomarkers) including antioxidant and biotransformation activity, geno-, cyto- and neurotoxic effects, phagocytosis, bioenergetic status and heart rate were measured to detect the possible effects of contaminants. Integrated Biomarker Response index and Principal Component Analysis performed on the individual biological response data were able to discriminate between the two study areas as well as the contaminated sites from their respective local reference sites. The two contaminated sites outside the cities of Sundsvall (station S1) and Gävle (station G1) were characterised by different biomarker response patterns. Mussels at station S1 showed a low condition index, increased heart rate recovery time and phagocytosis activity coinciding with the highest tissue concentrations of some trace metals, polycyclic aromatic hydrocarbons and organotins. At station G1 the highest organochlorine pesticide concentration was recorded as well as elevations in glutathione S-transferase activity, thiamine content and low lysosomal membrane stability. Significant variability in the geno- and cytotoxic responses and bioenergetic status was also observed at the different caging stations. The results obtained suggest that different chemical mixtures present in the study areas cause variable biological response patterns in organisms.

Oxidative stress parameters induced by exposure to either cadmium or 17β-estradiol on Mytilus galloprovincialis hemocytes. The role of signaling molecules

The aim of the present study was to determine and compare the possible effects of exposure to an estrogen, 17β-estradiol and to a metal, cadmium on oxidative parameters of Mytilus galloprovincialis hemocytes and to elucidate the signaling pathways that probably mediate the studied effects exerted by these two chemicals. In addition, it was of interest to investigate if the studied parameters could constitute biomarkers for aquatic pollution monitoring. Our results suggest that micromolar concentrations of either cadmium or 17β-estradiol affected the redox status of mussels by modulating oxidative parameters and antioxidant enzymes gene expression in mussel M. galloprovincialis hemocytes. In particular, our results showed that treatment of hemocytes with either 5 μM of cadmium chloride or with 25 nM of 17β-estradiol for 30 min caused significant increased ROS production; this led to oxidative damage exemplified by significant increased DNA damage, protein carbonylation and lipid peroxidation, as well as increased mRNA levels of the antioxidant enzymes catalase (CAT), superoxide dismoutase (SOD) and glutathione S-transferase (GST). Furthermore, our results suggest that either cadmium or 17β-estradiol signal is mediated either through one of the already known pathways initiated by photatidyl-inositol 3-kinase (PI3K) and reaching Na(+)/H(+) exchanger (NHE) probably through protein kinase C (PKC) or a kinase-mediated signaling pathway that involves in most of the cases NHE, PKC, Ca(2+)-dependent PKC isoforms, PI3-K, NADPH oxidase, nitric oxide (NO) synthase, c-Jun N-terminal kinase (JNK) and cyclic adenosine-3'-5'-monophosphate (cAMP). Our results also attribute a protective role to cAMP, since pre-elevated intracellular cAMP levels inhibited the signal induced by each exposure. Finally, since aquatic invertebrates have been the most widely used monitoring organisms for pollution impact evaluation in marine environments and taking under consideration the positive correlation obtained between the studied parameters, we can suggest the simultaneous use of these oxidative stress parameters offering an effective early warning system in biomonitoring of aquatic environments.