Glutathione S-tranferases and cytochrome P450 activities in Mytilus galloprovincialis from the South coast of Portugal: effect of abiotic factors

Oxytetracycline-induced inflammatory process without oxidative stress in blue mussels Mytilus trossulus

Potentially harmful compounds including pharmaceuticals are commonly found in marine waters and sediments. Amongst those, antibiotics and their metabolites are detected worldwide in various abiotic (at concentrations as high as µg/L) and biotic matrices at ng/gram of tissue, posing a risk to non-target species exposed to them such as blue mussels. Amongst those, oxytetracycline (OTC) belongs to the most detected antibiotics in the marine environment. In this work, we concentrated on studying the potential induction of oxidative stress, activation of cellular detoxification processes (including Phase I and Phase II xenobiotic biotransformation enzymes) and multixenobiotic resistance pumps (Phase III) as well as changes in the aromatisation efficiency in Mytilus trossulus exposed to 100 μg/L OTC. Our results show that 100 µg/L OTC concentration did not provoke cellular oxidative stress and did not affect the expression of genes involved in detoxification processes in our model. Moreover, no effect of OTC on aromatisation efficiency was found. Instead, phenoloxidase activity measured in haemolymph was significantly higher in OTC exposed mussels than in those from the control (30.95 ± 3.33 U/L and 17.95 ± 2.75 U/L, respectively). OTC exposed mussels were also characterised by a tissue-dependant activation of major vault protein (MVP) gene expression (1.5 times higher in gills and 2.4 times higher in the digestive system) and a decreased expression of the nuclear factor kappa B-a (NF-κB) gene (3.4 times lower in the digestive system) when compared to those from the control. Additionally, an elevated number of regressive changes and inflammatory responses in tissues such as gills, digestive system and mantle (gonads) was observed underlining the worsening of bivalves' general health. Therefore, instead of a free-radical effect of OTC, we for the first time describe the occurrence of typical changes resulting from antibiotic therapy in non-target organisms like M. trossulus exposed to antibiotics such as OTC.

Heat stress delays detoxification of phenanthrene in the springtail Folsomia candida

Climate change has intensified the occurrence of heat waves, resulting in organisms being exposed to thermal and chemical stress at the same time. The effects of mild heat shock combined with sublethal concentrations of phenanthrene (PHE) on defense mechanisms in springtails Folsomia candida were investigated. The transcription of Heat Shock Protein 70 (HSP70) was significantly upregulated by heat shock but tended to reach the control levels after 42 h of recovery. The transcription of cytochrome P450 3A13 (CYP3A13) was upregulated 3-13 fold by PHE but suppressed by heat shock. The suppression by heat shock might contribute to the reduced detoxification of PHE during high-temperature exposure. In line with this, we found that the internal PHE concentration was approximately 70% higher in heat-shocked springtails than in animals kept at control temperature. In general, the transcription of genes encoding enzymes of detoxification phase Ⅱ (glutathione S-transferase 3) and phase Ⅲ (ABC transporter 1) and the activity of antioxidant defense enzymes (superoxide dismutase and catalase) were less influenced than genes encoding phase I detoxification mechanisms (CYP3A13). These results indicate that heat shock delays the detoxification of PHE in springtails.

Impact of Polycyclic Aromatic Hydrocarbon Accumulation on Oyster Health

In the past decade, the Deepwater Horizon oil spill triggered a spike in investigatory effort on the effects of crude oil chemicals, most notably polycyclic aromatic hydrocarbons (PAHs), on marine organisms and ecosystems. Oysters, susceptible to both waterborne and sediment-bound contaminants due to their filter-feeding and sessile nature, have become of great interest among scientists as both a bioindicator and model organism for research on environmental stressors. It has been shown in many parts of the world that PAHs readily bioaccumulate in the soft tissues of oysters. Subsequent experiments have highlighted the negative effects associated with exposure to PAHs including the upregulation of antioxidant and detoxifying gene transcripts and enzyme activities such as Superoxide dismutase, Cytochrome P450 enzymes, and Glutathione S-transferase, reduction in DNA integrity, increased infection prevalence, and reduced and abnormal larval growth. Much of these effects could be attributed to either oxidative damage, or a reallocation of energy away from critical biological processes such as reproduction and calcification toward health maintenance. Additional abiotic stressors including increased temperature, reduced salinity, and reduced pH may change how the oyster responds to environmental contaminants and may compound the negative effects of PAH exposure. The negative effects of acidification and longer-term salinity changes appear to add onto that of PAH toxicity, while shorter-term salinity changes may induce mechanisms that reduce PAH exposure. Elevated temperatures, on the other hand, cause such large physiological effects on their own that additional PAH exposure either fails to cause any significant effects or that the effects have little discernable pattern. In this review, the oyster is recognized as a model organism for the study of negative anthropogenic impacts on the environment, and the effects of various environmental stressors on the oyster model are compared, while synergistic effects of these stressors to PAH exposure are considered. Lastly, the understudied effects of PAH photo-toxicity on oysters reveals drastic increases to the toxicity of PAHs via photooxidation and the formation of quinones. The consequences of the interaction between local and global environmental stressors thus provide a glimpse into the differential response to anthropogenic impacts across regions of the world.

Monitoring of pollution in the western Black Sea coast of Turkey by striped red mullet (Mullus surmuletus)

The striped red mullet (Mullus surmuletus) is an economically important demersal fish species. In this study, our aim was to monitor the pollution in the western Black Sea coast of Turkey using striped red mullet as a bioindicator species. Fish samples were caught from four different locations in the western Black Sea coast of Turkey in 2006, 2009-2011, and 2016. Highly elevated cytochrome P4501A (CYP1A)-related 7-ethoxyresorufin O-deethylase (EROD) activities were measured in striped red mullet caught from Zonguldak Harbor in all of the sampling years. The lowest EROD activities were measured in fish samples caught from Kefken. In addition to the EROD activity measurements, glutathione S-transferase (GST), glutathione reductase, and catalase activities were also measured in the striped red mullet samples. Higher GST and catalase activities were measured in the striped red mullet samples caught from Zonguldak Harbor than from Kefken in 2016. These results indicate that the striped red mullet is responsive to CYP1A inducer pollutants. This study covers intermittent measurements of the biomonitoring data from the striped red mullet caught around the western Black Sea coast of Turkey, over a 10-year period.

The glutathione S-transferase genes in marine rotifers and copepods: Identification of GSTs and applications for ecotoxicological studies

Various xenobiotics are constantly being released and accumulated into the aquatic environments and consequently, the aquatic organisms are continuously being exposed to exogenous stressors. Among various xenobiotic detoxifying enzymes, Glutathione S-transferase (GST) is one of the major xenobiotic detoxifying enzyme which is widely distributed among living organisms and thus, understanding of the nature of GSTs is crucial. Previous studies have shown GST activity in response to various xenobiotics yet, full identification of GSTs in marine invertebrates is still limited. This review covers information on the importance of GSTs as a biomarker for emerging chemicals and their response to wide ranges of environmental pollutants as well as in-depth phylogenetic analysis of marine invertebrates, including recently identified GSTs belonging to rotifers (Brachionus spp.) and copepods (Tigriopus japonicus and Paracyclopina nana), with unique class-specific features of GSTs, as well as a new suggestion of GST evolutionary pathway.

Assessing the Effect of Contaminated and Restored Marine Sediments in Different Experimental Mesocosms Using an Integrated Approach and Mytilus galloprovincialis as a Model

The research presented here was conducted to ascertain the effectiveness of recovery technologies in remediating a compromised marine environment. The multidisciplinary approach aims to integrate traditional chemical-physical analysis and to assess the biological parameters of Mytilus galloprovincialis within different experimental mesocosms (W, G, and B). In particular, this system was designed to reproduce sediment resuspension in a marine environment, which is thought to be one cause of contaminant release. The study combined morphological and ultrastructural observations with DNA damage assessment and mRNA expression of those genes involved in cellular stress responses. The tissues of mussels maintained in the polluted mesocosm showed a higher accumulation of Pb and Hg than in those maintained in restored mesocosm. This observation correlates well with mRNA expression of MT10 and data on DNA damage. The outcome of the biological evaluation consolidates the chemical characterization and supports the concept that the remediation method should be evaluated at an early stage, both to analytically determine the reduction of toxic components and to assess its ultimate impact on the biological system.

Is blue mussel caging an efficient method for monitoring environmental microplastics pollution?

The effectiveness of mussel caging for active microplastics (MPs) biomonitoring was investigated for the first time by comparing abundance and characteristics (shape, size, color and type of polymers) of MPs ingested by caged depurated blue mussels with those ingested by native mussels collected at the same sites and with those found in their surrounding environment (surface water and sediments). Mussels were exposed along a pollution gradient originating from a wastewater treatment plant discharge and near an abandoned coastal landfill. After 6 weeks of deployment, the majority (93%) of clean transplanted mussels had ingested MPs with a mean number of items ranging from 0.61 to 1.67 items/g. The occurrence, abundance and properties of MPs ingested by caged mussels were similar to those found in native mussels. Among the debris items detected in caged and native mussels, fragments were the most predominant type, consistent with the MPs found in their surrounding environment. MPs sizes were very similar whether in the water, sediments and both caged and native mussels, with a dominance of items <150 μm. Although some polymers were under-represented or totally absent in the caged mussels compared to overlying seawater or surrounding sediment, there was a good overlap in polymer types proportion being found between caged mussels and sediments (Morisita's index of similarity = 0.93) or seawater (0.86). Polystyrene dominated all samples in all the different matrices. Our study suggests that blue mussels caging may be a promising tool for MPs biomonitoring making monitoring more reliable with an accurate assessment of the biological effects of MPs over a predetermined exposure period. However, further methodological improvements should be considered to define a uniform protocol for blue mussels caging to allow spatial and temporal microplastics active biomonitoring.

Mesocosm System to Evaluate BF-MBR Efficacy in Mitigating Oily Wastewater Discharges: an Integrated Study on Mytilus galloprovincialis

This work presents the results of recovery efficacy of the system "BioFilm Membrane BioReactor" (BF-MBR), in the treatment of oily contaminated seawaters. To this aim, we proposed a multidisciplinary approach that integrates traditional chemical-physical measures together with the assessment on biological sentinel Mytilus galloprovincialis, maintained in a medium-scale artificial system named mesocosm. The setup included: (1) a mesocosm consisting of uncontaminated seawater; (2) a mesocosm composed of an untreated oily wastewater discharge; and (3) a mesocosm receiving the same oily wastewater previously treated by a BF-MBR pilot scale plant. The multidisciplinary approach that included traditional chemical measures on mesocosms together with the evaluation of morphological organization, mRNA expression of those genes involved in cellular stress response, immunohistochemistry and metabolomic analysis on mussel tissues, was able to provide a robust and holistic evidence of how the proposed treatment is able to reduce the overall impact of oily wastewater discharges on the marine ecosystem.

Seasonal and spatial variations in biomarker baseline levels within Arctic populations of mussels (Mytilus spp.)

Climate change and pollution resulting from human activities in the Arctic require reliable monitoring systems in sentinel species. Mytilus spp. are used as sentinel species all around the world. The use of Mytilus spp. in environmental monitoring requires knowledge about natural variations in pollution biomarkers. Seasonal variations in baseline levels of biomarkers were studied over a year in the mussels from both upper and lower littoral zones in Rakkfjorden, Norway, as they underwent their annual reproductive cycle. Spatial variations of these biomarker baseline levels were measured in five mussel populations within a 60-km radius from Rakkfjorden to investigate universality of the results from the specific population of Rakkfjorden at a regional scale. Seasonal variations in biomarker baseline levels were revealed and seemed to be related to the reproductive state of the mussels and the tidal zone. The mussels appeared to be more sensitive to oxidative stress during gametogenesis in autumn and winter, when having lower lysosome membrane stability and lower baseline levels of antioxidant biomarkers. An increase in baseline levels of these biomarkers was reported during spawning in spring, however, it was not possible to reveal whether these changes were due to spawning, or to a higher metabolic activity in mussels in response to elevated water temperature and food abundance. The differences between the tidal zones were reflected in reduced size of the mussels from the upper littoral zone, their late spawning in the season and increased baseline levels of antioxidant biomarkers during the coldest month, indicating a more challenging environment in the upper littoral zone. The spatial study indicated that the biomarker baseline levels measured in Rakkfjorden were no different from the levels measured in the mussels from five other sites and thus, are representative for mussels on a regional scale.

Effects of a common pharmaceutical, atorvastatin, on energy metabolism and detoxification mechanisms of a marine bivalve Mytilus edulis

Biologically active compounds from pharmaceuticals cause concern due to their common occurrence in water and sediments of urbanized coasts and potential threat to marine organisms. Atorvastatin (ATO), a globally prescribed drug, is environmentally stable and bioavailable to marine organisms; however, the physiological and toxic effects of this drug on ecologically important coastal species are yet to be elucidated. We studied the effect of ATO (˜1.2 μg L^-1) on bioenergetics (including whole-organism and mitochondrial respiration, as well as tissue energy reserves and mRNA expression of genes involved in mitochondrial biogenesis and fatty acid metabolism in the gills and the digestive gland) of a keystone bivalve Mytulis edulis (the blue mussel) from the Baltic Sea. Xenobiotic detoxification systems including activity and mRNA expression of P-glycoprotein, and Phase I and II biotransformation enzymes (cytochrome P450 monooxygenase CYP1A and glutathione transferase, GST) were also assessed in the gill and digestive gland of the mussels. Exposure to ATO caused rapid uptake and biotransformation of the drug by the mussels. Standard metabolic rate of ATO-exposed mussels increased by 56% indicating higher maintenance costs, yet no changes were detected in the respiratory capacity of isolated mitochondria. ATO exposure led to ˜60% decrease in the lysosomal membrane stability of hemocytes and ˜3-fold decrease in the whole-organism P-glycoprotein-driven and diffusional efflux of xenobiotics indicating altered membrane properties. The digestive gland was a major target of ATO toxicity in the mussels. Exposure of mussels to ATO led to depletion of lipid, carbohydrate and protein pools, and suppressed transcription of key enzymes involved in mitochondrial biogenesis (peroxisome proliferator-activated receptor gamma coactivator 1-alpha PGC-1α) and fatty acid metabolism (acetyl-CoA carboxylase and CYP4Y1) in the digestive gland. No bioenergetic disturbances were observed in the gills of ATO-exposed mussels, and elevated GST activity indicated enhanced ATO detoxification in this tissue. These data demonstrate that ATO can act as a metabolic disruptor and chemosensitizer in keystone marine bivalves and warrant further investigations of statins as emerging pollutants of concern in coastal marine ecosystems.

The influence of short-term experimental fasting on biomarker responsiveness in oil WAF exposed mussels

Mussels are widely used in toxicological experimentation; however, experimental setups are not standardized yet. Although there is evidence of changes in biomarker values during food digestion and depending on the mussel nutritive status, the mode of feeding differs among toxicological experiments. Typically, mussels are fed with different diets in different long-term experiments, while fasting is the most common approach for short-term studies. Consequently, comparisons among experiments and reliable interpretations of biomarker results are often unfeasible. The present investigation aimed at determining the influence of fasting (against feeding with Isochrysis galbana) on biomarkers and their responsiveness in mussels exposed for 96 h to the water accommodated fraction (WAF) of a heavy fuel oil (0%, 6.25%, 12.5% and 25% WAF in sea water). PAH tissue levels in digestive gland and a battery of biomarkers were compared. WAF exposure led to decrease of cytochrome-C-oxidase activity, modulated glutathione-S-transferase activity, augmented lipid peroxidation, inhibited acetyl cholinesterase (AChE) activity, and led to lysosomal enlargement (Vv_LYS and S/V_LYS) and membrane destabilisation, lipofuscin accumulation, and histopathological alterations (Vv_BAS, MLR/MET and CTD ratio) in the digestive gland epithelium; and were integrated as IBR/n (biological response index). Overall, no significant changes were recorded in AChE activity, S/V_LYS and CTD ratio in any experimental treatment, while all the other biomarkers showed significant changes depending on the fasting/feeding condition, the exposure to WAF and/or their interaction. As a result, the integrated biomarker index IBR/n was higher at increasing WAF exposure levels both in fasted and fed mussels albeit the response was more marked in the latter. The response profiles were qualitatively similar between fasted and fed mussels but quantitatively more pronounced in fed mussels, especially upon exposure to the highest concentration (25% WAF). Therefore, it is highly recommended that mussels are also supplied with food during short-term, like during long-term toxicological experiments. This practice would avoid the interference of fasting with biological responses elicited by the tested chemicals and allow for reliable comparison with data obtained in long-term experiments and monitoring programmes.

Performance of biomarkers metallothionein and ethoxyresorufin O-deethylase in aquatic environments: A meta-analytic approach

The preservation of natural environments guarantees the conservation of biodiversity and ecosystem processes. Biomonitoring programs in preserved sites can be carried out using molecular biomarkers, which reflect possible stresses that exist in the monitored location. The metallothionein (MT) proteins and isoenzyme Cytochrome P4501A (CYP4501A) are among the most used biomarkers and reflect the detoxification of metal and organic xenobiotics, respectively. This study aimed to assess the performance of these biomarkers in natural aquatic environments using a meta-analytic approach. The data search was conducted in ISI Web of Science™, considering papers published until August 2016. Studies included in this research needed to compare reference or control sites and sites under stress and be conducted in situ. In general, both biomarkers were useful when comparing control sites with sites under stress. Moreover, when the data were categorized into groups of organisms, mainly bivalves and fishes, there were differences between the groups and between the monitored environments, marine or freshwater. The use of these biomarkers in fish is suitable for freshwater environments, and bivalves are suitable for marine environments. We concluded that the concomitant use of vertebrate and invertebrate bioindicators is useful to develop an effective biomonitoring program and to avoid biases due the physiology of the selected bioindicator.

Bioaccumulation of Polycyclic Aromatic Hydrocarbons (PAHs) by the Marine Clam, Mactra veneriformis, Chronically Exposed to Oil-Suspended Particulate Matter Aggregates

Dispersion and biodegradation of petroleum hydrocarbons are significantly enhanced by formation of oil-suspended particulate matter aggregates (OSAs), but little is known about their adverse effects on benthic invertebrates or microbes. In this study, we investigated: (1) bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) by the marine bivalve, Mactra veneriformis and (2) changes in composition and relative abundances of microbes, during 50-d of an OSAs feeding experiment. Total concentrations of PAHs increased more rapidly during the first week of exposure, peaked at Day 30, then gradually declined to the end of experiment. While bioaccumulation of PAHs by clams varied among the 20 target compounds, two major groups of PAHs were identified by cluster analysis. One group including 3-methylphenanthrene, 1,6-dimethylphenanthrene, 1,2,6,9-tetramethylphenanthrene, and benzo[ a]anthracene showed a fairly constant rate of accumulation, while the second group including 2-methyldibenzothiophene, 2,4-dimethyldibenzothiophene, 2,4,7-trimethyldibenzothiophene, 3-methylchrysene, 6-ethylchrysene, and 1,3,6-trimethylchrysene exhibited a bell-shaped pattern. Bioaccumulation of PAHs by clams was dependent on changes in abundance of Gammaproteobacteria, indicating active degradations of hydrocarbons by selected species. Six key species included: Porticoccus litoralis, Porticoccus hydrocarbonoclasticus, Cycloclasticus spirillensus, Alcanivorax borkumensis, Alcanivorax dieselolei, and Alkalimarinus sediminis. These results are the first to demonstrate interactions of OSAs and macrofauna/microbe in oil cleanup operations.

Effects of Camellia sinensis crude saponin on survival and biochemical markers of oxidative stress and multixenobiotic resistance of the Mediterranean mussel, Mytilus galloprovincialis

The Ebro Delta (NE Spain), formed by two bays, northern and southern hemidelta, is an area mainly devoted to rice farming. As a result shellfish species inhabiting or cultured in nearby bays may become increasingly threatened by exposure to pollutants associated to agriculture. The latest product applied in the rice fields is a plant based molluscicide called saponin, used to control populations of the giant apple snail (GAS). Saponins are known to also affect other organisms, hence research of its toxicity towards non target species is needed. In this study, mussels (Mytilus galloprovincialis) were exposed to three concentrations of suspended solid pellets containing saponin extracts from the plant species Camellia sinensis. Effects across a large set of biochemical markers were investigated in the digestive gland and gill tissue of exposed mussels to saponin for 1 and 7days. In addition, crude saponin was extracted from solid pellets to confirm its correct concentration. Results obtained from this study, showed that the concentration of crude saponin in dry pellets was of 5.5%. Lethal levels of saponin were 3.2 fold higher than the maximal predicted field concentration, and activated respiratory metabolism and expression of transmembrane protein transporters. Mussels, exposed to sub lethal concentrations of saponin showed increase of antioxidant defenses.

Experimental exposure of blue mussels (Mytilus galloprovincialis) to high levels of benzo[a]pyrene and possible implications for human health

Polycyclic aromatic hydrocarbons (PAHs) are lipophilic compounds able to accumulate in the food chain. Mussels showed to bioaccumulate contaminants, such as PAHs, so that recurrent consumption of such contaminated food represents a risk for human health. This study was aimed to elucidate if acute exposure of Mediterranean blue mussel (Mytilus galloprovincialis), a bivalve of great economic importance in several countries, to a PAH, benzo[a]pyrene (B[a]P), at doses able to induce cytochrome P450 1A (CYP1A) and pathological changes in mussel gills, can produce accumulation in soft tissue. We explored the cytotoxic effects (cell viability, DNA laddering, and glutathione levels) of in vitro exposure of human peripheral blood mononuclear cells (PBMCs) to organic extracts obtained from blue mussels previously exposed for 12 and 72h via water to B[a]P (0.5-1mg/L). In our experimental conditions, B[a]P induced CYP1A induction and morphological changes in mussel gills and a significant B[a]P accumulation in soft tissue. Conversely, exposing PBMCs to organic extracts obtained from contaminated mussels, resulted in a significant reduction of cell viability and cell glutathione content, and in an increase in DNA laddering. This confirms that consumption of mussels from B[a]P polluted waters might affect human health. Our data lead us to suggest that CYP1A activity in mussel gills may be useful (more than the amount of detected PAHs in the mussel edible tissue) as a marker in assessment of risk for health of consumers exposed to PAHs through ingestion of shellfish.

Biomarkers of physiological responses of Octopus vulgaris to different coastal environments in the western Mediterranean Sea

The increase of pollutants in coastal seawater could produce several harmful biological effects on marine organisms related to the production of reactive oxygen species (ROS) causing cellular and tissue damages through oxidative stress mechanisms. Common octopuses (Octopus vulgaris) inhabiting coastal areas under high anthropogenic activity of Mallorca (W-Mediterranean Sea) have the ability to control oxidative damage by triggering antioxidant enzyme responses. Analyzing the digestive glands, octopuses from human-altered coastal areas showed higher activity of superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) compared to octopuses from non-influenced coastal waters (i.e. marine reserve area). Higher metallothionein (MT) concentrations and lack of malondialdehyde (MDA) variations also reflect adaptations of O. vulgaris to polluted areas. This is the first study assessing the levels of the oxidative stress biomarkers on O. vulgaris in the Mediterranean Sea, revealing their usefulness to assess diverse environmental pollution effects on this relevant ecological and commercial species.

Comparison of caged and native blue mussels (Mytilus edulis spp.) for environmental monitoring of PAH, PCB and trace metals

Contaminant bioaccumulation was studied in blue mussels (Mytilus edulis spp.) using the harbor waters of Kristiansand (Norway) as a case study. A suite of chemical contaminants (trace metals, PAHs and PCBs) was analyzed in caged and native mussels as well as in passive samplers (Diffusive Gradients in Thin films (DGT)-devices and silicone rubbers) placed alongside the mussels for estimation of contaminant concentrations in water and uptake rates and bioaccumulation factors (BAFs) in mussels during a six-months deployment period. Estimated logBAFs were in the ranges 2.3-5.5, 3.8-5.2 and 3.2-4.4 for metals, PCBs and PAHs, respectively. Contaminant levels in caged mussels increased rapidly to stable levels for trace metals, whereas for hydrophobic organic contaminants the increase was steady but slow and for many compounds did not reach the levels observed in native mussels. Some key issues related to mussel caging design, such as mussel deployment time and confounding influence from seasonal fluctuations, are discussed herein.

Free fatty acid profiling of marine sentinels by nanoLC-EI-MS for the assessment of environmental pollution effects

The present work aims to elucidate the free fatty acid (FFA) profile of the mussel Mytilus galloprovincialis caged in an anthropogenically impacted area and in a reference site through an innovative and validated analytical approach for the assessment of biological alterations induced by marine pollution. The FFA pattern is involved in the regulation of different cellular pathways and differs with respect to metabolic stimuli. To this purpose, the lipid fraction of mussels coming from both sampling areas was extracted and the FFA fractions were isolated and purified by a solid phase extraction; then, nano-scale liquid chromatography coupled to electron ionization mass spectrometry (nanoLC-EI-MS) was employed for the characterization of the two samples. A total of 19 and 17 FFAs were reliably identified in the mussels coming from the reference and polluted site, respectively. Significant qualitative and quantitative differences found in saturated, monounsaturated and polyunsaturated species may be exploited as typical pollution biomarkers (e.g. alteration of the fatty acid biosynthetic system and lipotoxicity) and explain adverse and compromising effects (e.g. oxidative stress and inflammatory processes) related to environmental pollution.

Biochemical and lysosomal biomarkers in the mussel Mytilus galloprovincialis from the Mar Piccolo of Taranto (Ionian Sea, Southern Italy)

Biomarkers are internationally recognized as useful tools in marine coastal biomonitoring, in particular, as early-warning signals at the level of individual organisms to assess biological effects of pollutants and other stressors. In the present study, Mytilus galloprovincialis has been employed as a sentinel organism to assess biological pollution effects in the Mar Piccolo of Taranto (Southern Italy), a coastal lagoon divided into two small inlets, connected to the open sea through one natural and one artificial narrow openings. Mussels were collected in June 2013 at three sites located within each of the two inlets of the Mar Piccolo. Biological effects were investigated through a suite of biomarkers suitable to reflect effects and/or exposure to contaminants at biochemical and cellular levels. Biochemical biomarkers included glutathione-S-transferase (GST) and acetylcholinesterase (AChE) enzyme activities; as histochemical biomarkers, lysosomal membrane stability, lipofuscin and neutral lipid accumulation, and lysosomal structural changes were considered. As a whole, results highlighted differences among the three study sites, particularly for GST, AChE, and lipofuscins, which are consistent with the variations of the chemical pollutants in sediments. The applied biomarkers showed that a stress syndrome likely to be ascribed to environmental pollutants is occurring in mussels living in the Mar Piccolo of Taranto, in particular, the ones inhabiting the first inlet.

General stress, detoxification pathways, neurotoxicity and genotoxicity evaluated in Ruditapes philippinarum exposed to human pharmaceuticals

A battery of biomarkers was evaluated on Ruditapes philippinarum exposed during 14 days to caffeine, ibuprofen, carbamazepine and novobiocin (0.1, 1, 5, 10, 15, and 50µgL(-1)). The battery included general stress (lysosomal membrane stability - LMS) analysed in the hemolymph, and biochemical biomarkers analysed in digestive gland tissues including: biomarkers of phase I (etoxyresorufin O-deethylase - EROD, dibenzylfluorescein dealkylase - DBF), phase II (gluthathione-S-transferase - GST), oxidative stress (gluthathione reductase - GR, gluthathione peroxidase - GPX, lipid peroxidation - LPO), neurotoxicity (acetylcholinesterase activity - AChE), and genotoxicity (DNA damage). Pharmaceuticals tested induced the sublethal responses (even at the environmental range 0.1µgL(-1)). At this low concentration; caffeine, ibuprofen and carbamazepine decreased the LMS significantly compared with controls (p<0.05). The four compounds induced significantly the detoxification metabolism and oxidative stress (p<0.05). Neurotoxicity was noticed in clams exposed to caffeine and carbamazepine (p<0.05). Ibuprofen, carbamazepine and novobiocin produced genotoxic effects (p<0.05). Results from this research validate the use of biomarkers when assessing the effects of pharmaceuticals within a marine environmental risk assessment framework, using as a laboratory bioassay model the species R. philippinarum.

Molecular cloning and characterization of a sigma-class glutathione S-transferase from the freshwater mussel Hyriopsis cumingii

A full-length cDNA of a sigma-like glutathione S-transferase (GST) was identified from Hyriopsis cumingii (HcGSTS). The deduced amino acid sequence of HcGSTS was found to comprise 203 amino acid residues and to contain the distinct highly conserved glutathione binding site of N-terminal and the relatively diverse substrate binding site of C-terminal. Alignment analysis and phylogenetic relationship suggested that the HcGSTS is a sigma-class GST. The mRNA of HcGSTS was constitutively expressed in all tested tissues, the strongest expression being in the hepatopancreas. The mRNA expression of HcGSTS was significantly up-regulated (P < 0.05) in all assessed tissues after stimulation of the mussels with peptidoglycan (PGN) and LPS, the only exception being when the gills were challenged with PGN. The expression of HcGSTS mRNA in kidney and foot was also significantly up-regulated (P < 0.05) by microcystin-LR. Recombinant HcGSTS exhibited high activity towards the substrate 1-chloro-2,4-dinitrobenzene. The optimal pH was 8.0 and temperature 35 °C.

Biochemical biomarker responses to pollution in selected sentinel organisms across the Eastern Mediterranean and the Black Sea

Pollution effects were assessed by means of biochemical biomarkers (catalase, glutathione S-transferase and acetylcholinesterase activities, and metallothioneins content) in five species at selected coastal sites across the Eastern Mediterranean and the Black Sea. The mussel Mytilus galloprovincialis, a well-established sentinel species, was investigated in the Adriatic Sea, Aegean Sea, and Black Sea. The mussel Brachidontes pharaonis and the striped red mullet Mullus surmuletus were used in the Levantine Sea where M. galloprovincialis is not present. The white seabream Diplodus sargus sargus and the gastropod Rapana venosa were additionally sampled in the Adriatic and the Black Sea, respectively. Mussels showed catalase, glutathione S-transferase, and acetylcholinesterase responses to pollution in most geographical areas while the response of metallothioneins was restricted to a few sites. R. venosa showed marked responses of catalase and metallothioneins whereas both fish species did not generally exhibit variations in biomarker values among sites. The approach based on the reference deviation concept using the "Integrated Biological Responses version 2" index was useful for the interpretation of overall biomarker responses.

Is the step-wise tiered approach for ERA of pharmaceuticals useful for the assessment of cancer therapeutic drugs present in marine environment?

Methotrexate (MTX) and tamoxifen (TMX) cancer therapeutic drugs have been detected within the aquatic environment. Nevertheless, MTX and TMX research is essentially bio-medically orientated, with few studies addressing the question of its toxicity in fresh water organisms, and none to its' effect in the marine environment. To the authors' knowledge, Environmental Risk Assessments (ERA) for pharmaceuticals has mainly been designed for freshwater and terrestrial environments (European Medicines Agency-EMEA guideline, 2006). Therefore, the purpose of this research was (1) to assess effect of MTX and TMX in marine organism using the EMEA guideline, (2) to develop an ERA methodology for marine environment, and (3) to evaluate the suitability of including a biomarker approach in Phase III. To reach these aims, a risk assessment of MTX and TMX was performed following EMEA guideline, including a 2-tier approach during Phase III, applying lysosomal membrane stability (LMS) as a screening biomarker in tier-1 and a battery of biochemical biomarkers in tier-2. Results from Phase II indicated that MTX was not toxic for bacteria, microalgae and sea urchin at the concentrations tested, thus no further assessment was required, while TMX indicated a possible risk. Therefore, Phase III was performed for only TMX. Ruditapes philippinarum were exposed during 14 days to TMX (0.1, 1, 10, 50 μg L(-1)). At the end of the experiment, clams exposed to environmental concentration indicated significant changes in LMS compared to the control (p<0.01); thus a second tier was applied. A significant induction of biomarkers (activity of Ethoxyresorufin O-deethylase [EROD], glutathione S-transferase [GST], glutathione peroxidase [GPX], and lipid peroxidation [LPO] levels) was observed in digestive gland tissues of clams compared with control (p<0.01). Finally, this study indicated that MTX was not toxic at an environmental concentration, whilst TMX was potentially toxic for marine biota. This study has shown the necessity to create specific guidelines in order to evaluate effects of pharmaceuticals in marine environment which includes sensitive endpoints. The inadequacy of current EMEA guideline to predict chemotherapy agents toxicity in Phase II was displayed whilst the usefulness of other tests were demonstrated. The 2-tier approach, applied in Phase III, appears to be suitable for an ERA of cancer therapeutic drugs in the marine environment.

Biomarkers of environmental stress in gills of Pinna nobilis (Linnaeus 1758) from Balearic Island

In aquatic environments, bivalve molluscs are used as sentinel species for environmental biomonitoring. In this study Pinna nobilis specimens, the biggest Mediterranean bivalve, were collected in the Magaluf bay (Mallorca), a touristic location and in a pristine area of the Cabrera National Park as the control location. Histological and histochemical analysis in gills of specimens sampled from Magaluf exhibited evident tissue alterations with high presence of haemocytes. Lower acetylcholinesterase (AChE) activity and protein expression were also found in the gills of specimens collected from Magaluf compared with the control area. The determination of antioxidant enzyme activities, such as superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase, showed a higher activities of these antioxidant enzymes and total glutathione content in samples from Magaluf bay than in Cabrera. In conclusion, the present study demonstrated that human activities result in morphological tissue alterations and a reduced AChE activity in gills of P. nobilis. Moreover, these stressful environmental conditions induced an adaptive response in P. nobilis as evidenced by increased antioxidant defences and a decreased AChE activity.

CAPSULE

The human activities induce oxidative stress in P. nobilis as evidenced by increased antioxidant defences and a decreased acetylcholinesterase activity.

Yes, caffeine, ibuprofen, carbamazepine, novobiocin and tamoxifen have an effect on Corbicula fluminea (Müller, 1774)

Reports indicating the presence of pharmaceutical in fresh water environment in the ngL(-1) to µgL(-1) range are occurring with increasing frequency. It is also a fact that pharmaceuticals may produce adverse effects on aquatic organisms. Nevertheless, there is still a lack of knowledge regarding how these emergent contaminants may affect aquatic biota. The goal of this research was to evaluate the sublethal responses in Corbicula fluminea such as, general stress (lysosomal membrane stability [LMS]), biomarkers of phase I and II (etoxyresorufin O-deethylase [EROD], dibenzylfluorescein dealkylase [DBF], gluthathione-S-transferase [GST]), oxidative stress (gluthathione reductase [GR], gluthathione peroxidase [GPX], lipid peroxidation [LPO]), and biomarkers of effect (DNA damage) after 21 days of exposure to caffeine, ibuprofen, carbamazepine, novobiocin and tamoxifen at 0.1, 1, 5, 10, 15, 50µgL(-1). Environmental concentrations tested in this study caused general stress and produced changes on biomarkers tested. LMS, responses from phase I and II enzymatic activity, oxidative stress, and biomarker of effect represent important ecotoxicological information, and will provide a useful reference for the assessment of selected drugs and the effects which these compounds may have on aquatic invertebrates, using C. fluminea as a bioindicator species.

Proteomic profiling of gill GSTs in Mytilus galloprovincialis from the North of Portugal and Galicia evidences variations at protein isoform level with a possible relation with water quality

Glutathione transferases (GSTs) are key for xenobiotic detoxification at the molecular level across phyla. These enzymes are therefore likely to be part of the defence mechanisms used by marine organisms, such as mussels, that thrive in highly polluted environments. Taking this hypothesis into account, we used proteomics to characterize the profile of GSTs from the gills of marine mussel Mytilus galloprovincialis in order to discriminate natural mussel populations exposed to different levels of pollution. Samples were collected between Cabo Home (Spain) and Matosinhos (Portugal) covering a north-south transect of approximately 122 Km of the Atlantic Ocean along the Western Coast of the Iberian Peninsula. GSTs from mussel gills were extracted and purified by affinity chromatography with glutathione as the binding substrate to the solid medium. We studied the abundance of GST isoforms by two-dimensional gel electrophoresis and matrix assisted laser desorption/ionization-time of flight mass spectrometry and assessed total activity. Eleven putative individual GSTs from classes Mu, Pi and Sigma were identified by proteomics. Few variations were observed in total GST activity of post-mitochondrial samples between sampling sites, with animals from Matosinhos (polluted site) showing highest GST activity and Cabo Home (clean site) showing lowest. This contrasts with the increased number of differences in the individual GST isoforms. Each mussel population showed unique GST proteomic profiles. Based on the results we conclude that proteomics surpasses the conventional GST enzymatic activity method to discriminate natural mussel populations and has potential application in environmental monitoring. It is reasonable to suggest that the GST proteomic profiles observed may reflect differences in contamination levels.

Biochemical and physiological responses of Carcinus maenas to temperature and the fungicide azoxystrobin

Research on the effects of thermal stress is currently pertinent as climate change is expected to cause more severe climate-driven events. Carcinus maenas, a recognised estuarine model organism, was selected to test temperature-dependence of azoxystrobin toxicity, a widely applied fungicide. Crabs' responses were assessed after a 10-d acclimation at different temperatures (5°C, 22°C, and 27°C) of which the last 72h were of exposure to an environmental concentration of azoxystrobin. SOD and GST activities, mitochondrial oxygen consumption rates and protein content, as well as the Coupling Index were determined. The hypothesis proposed that extreme temperatures (5°C and 27°C) and azoxystrobin would affect crabs' responses. Results showed statistically significant different effects of SOD and all oxygen rates measured promoted by temperature, and that neither 30.3μgL(-1) of azoxystrobin nor the combined effect were crab-responsive. Protein content at 5°C was statistically higher when compared with the control temperature (22°C). The Coupling Index revealed both a slight and a drastic decrease of this index promoted by 5°C and 27°C, respectively. Regarding azoxystrobin effects, at 22°C, this index only decreased slightly. However, at extreme temperatures it fell 47% at 5°C and slightly increased at 27°C. Results provided evidence that crabs' responses to cope with low temperatures were more effective than their responses to cope with high temperatures, which are expected in future climate projections. Moreover, crabs are capable of handling environmental concentrations of azoxystrobin. However, the Coupling Index showed that combined stress factors unbalance crabs' natural capability to handle a single stressor.

Integrated approach to assess ecosystem health in harbor areas

Harbors are critical environments with strategic economic importance but with potential environmental impact: health assessment criteria are a key issue. An ecosystem health status approach was carried out in Portimão harbor as a case-study. Priority and specific chemical levels in sediments along with their bioavailability in mussels, bioassays and a wide array of biomarkers were integrated in a biomarker index (IBR index) and the overall data in a weight of evidence (WOE) model. Metals, PAHs, PCBs and HCB were not particularly high compared with sediment guidelines and standards for dredging. Bioavailability was evident for Cd, Cu and Zn. Biomarkers proved more sensitive namely changes of antioxidant responses, metallothioneins and vittellogenin-like proteins. IBR index indicated that site 4 was the most impacted area. Assessment of the health status by WOE approach highlighted the importance of integrating sediment chemistry, bioaccumulation, biomarkers and bioassays and revealed that despite some disturbance in the harbor area, there was also an impact of urban effluents from upstream.

CAPSULE ABSTRACT

Environmental quality assessment in harbors.

Transcriptional responses of glutathione transferase genes in Ruditapes philippinarum exposed to microcystin-LR

Glutathione Transferases (GSTs) are phase II detoxification enzymes known to be involved in the molecular response against microcystins (MCs) induced toxicity. However, the individual role of the several GST isoforms in the MC detoxification process is still unknown. In this study, the time-dependent changes on gene expression of several GST isoforms (pi, mu, sigma 1, sigma 2) in parallel with enzymatic activity of total GST were investigated in gills and hepatopancreas of the bivalve Ruditapes philippinarum exposed to pure MC-LR (10 and 100 µg/L). No significant changes in GST enzyme activities were found on both organs. In contrast, MC-LR affected the transcriptional activities of these detoxification enzymes both in gills and hepatopancreas. GST transcriptional changes in gills promoted by MC-LR were characterized by an early (12 h) induction of mu and sigma 1 transcripts. On the other hand, the GST transcriptional changes in hepatopancreas were characterized by a later induction (48 h) of mu transcript, but also by an early inhibition (6 h) of the four transcripts. The different transcription patterns obtained for the tested GST isoforms in this study highlight the potential divergent physiological roles played by these isoenzymes during the detoxification of MC-LR.

Expression and immunohistochemical localization of the cytochrome P450 isoform 356A1 (CYP356A1) in oyster Crassostrea gigas

Cytochrome P450 family (CYP) is a group of proteins virtually found in all living organisms. The main role of most CYPs is to metabolize endo and xenobiotics. Most of the studies on CYP have been carried out in mammals and other vertebrates, however recently a growing interest has been devoted to the identification of CYP isoforms in invertebrates. A gene belonging to the CYP sub-family, CYP356A1, was identified in sanitary sewage-exposed Pacific oysters, Crassostrea gigas. Through heterologous expression, we produced CYP356A1 purified protein and raised a mouse polyclonal antibody. Dot blot tests showed that oysters exposed in situ for 14 days to untreated urban effluent discharges had significantly higher levels of CYP356A1 in digestive gland. Using immunohistochemical techniques we observed that the lining epithelial cells of mantle, stomach and intestine showed a strong CYP356A1 staining, but the mucus and secretory cells were negative. Digestive diverticulum parenchyma and gills lining cells showed strong CYP356A1 reaction, while the filamentary rod (connective tissue) was negative. Free cells, as hemocytes and brown cells also showed CYP356A1 immunoreactions indicating the presence of biotransformation activity in these cells. Male germ cells at early stages expressed CYP356A1 but not sperm mature cells, suggesting that this protein could be involved in the male gonadal development. This study shows the use of a specific antibody to a mollusk CYP isoform and that this protein is inducible in oysters environmentally exposed to urban sewage effluents.

Seasonal variations of gene expression biomarkers in Mytilus galloprovincialis cultured populations: temperature, oxidative stress and reproductive cycle as major modulators

The blue mussel Mytilus galloprovincialis has been used as monitoring organism in many biomonitoring programs because of its broad distribution in South European sea waters and its physiological characteristics. Different pollution-stress biomarkers, including gene expression biomarkers, have been developed to determine its physiological response to the presence of different pollutants. However, the existing information about basal expression profiles is very limited, as very few biomarker-based studies were designed to reflect the natural seasonal variations. In the present study, we analyzed the natural expression patterns of several genes commonly used in biomonitoring, namely ferritin, metallothionein, cytochrome P450, glutathione S-transferase, heat shock protein and the kinase responsive to stress KRS, during an annual life cycle. Analysis of mantle-gonad samples of cultured populations of M. galloprovincialis from the Delta del Ebro (North East Spain) showed natural seasonal variability of these biomarkers, pointing to temperature and oxidative stress as major abiotic modulators. In turn, the reproductive cycle, a process that can be tracked by VCLM7 expression, and known to be influenced by temperature, seems to be the major biotic factor involved in seasonality. Our results illustrate the influence of environmental factors in the physiology of mussels through their annual cycle, a crucial information for the correct interpretation of responses under stress conditions.

Integrated biomarker responses in zebrafish exposed to sulfonamides

Dispersed pharmaceuticals such as sulfonamides pose a threat to aquatic ecosystems. We evaluated potential biomarkers of sulfonamide exposure using an extended zebrafish (Danio rerio) toxicity test. The tested sulfonamides induced obvious effects on spontaneous swimming activity and heartbeat rate in zebrafish. Glutathione S-transferase (GST) and malondialdehyde (MDA) were examined to reflect the biomarker response of zebrafish exposed to three sulfonamides (sulfamethoxazole, sulfadiazine (SDZ) and sulfadimidine). Both GST and MDA showed time-dependent responses to sulfonamide exposure. GST activity was significantly increased after exposure to sulfonamides for 3 days, while MDA concentration reached a maximum during the first day and then declined. These results suggest that MDA may be a more sensitive biomarker of sulfonamide toxicity than GST. These investigations demonstrated that SDZ was a typical inducer of metabolic enzymes, suggesting that it poses a potential ecotoxicological risk to aquatic ecosystems.

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.

Temperature enhanced effects of chlorine exposure on the health status of the sentinel organism Mytilus galloprovincialis

It now is widely recognised that the global temperature is rising, a phenomenon which could alter the effects of pollution on wildlife. In order to assess the role of temperature and exposure to chlorine due to cooling water discharges, a battery of metabolic, oxidative stress and histological parameters were evaluated in Mytilus galloprovincialis after 15 and 30 days at 15 °C and at two increased temperatures (+5 and +10 °C). Diverse gill pathologies such as haemolymphatic sinus dilatation, an increased number of mucocytes and granulocytes as well as a lower number of cilia were observed after 30 days exposure at higher temperatures. Protein, amino acid, triglyceride and fatty acid levels decreased when the temperature increased, as a consequence of higher energetic demand. Similarly, acetylcholinesterase, catalase and glutathione S-transferase activities showed an inhibition at higher temperatures, although gill lipid peroxidation levels remained unaffected. Our results suggest that increased temperatures induce deterioration in the health status of the mussels and in their defensive capacity against a polluted environment.

Impact of environmental pollution on caged mussels Mytilus galloprovincialis using NMR-based metabolomics

Metabolic responses to environmental pollution, mainly related to Hg and PAHs, were investigated in mussels. Specimens of Mytilus galloprovincialis, sedentary filter-feeders, were caged in anthropogenic-impacted and reference sites along the Augusta coastline (Sicily, Italy). The gills, mainly involved in nutrient uptake, digestion and gas exchange, were selected as target organ being the first organ to be affected by pollutants. Severe alterations in gill tissue were observed in mussels from the industrial area compared with control, while gill metabolic profiles, obtained by (1)H NMR spectroscopy and analyzed by multivariate statistics, exhibited significant changes in amino acids, energy metabolites, osmolytes and neurotransmitters. Overall, the morphological changes and metabolic disturbance detected in gill tissues may suggest that the mussels transplanted to the contaminated field site were suffering from adverse environmental condition. The concurrent morphological and metabolomic investigations as applied here result effective in assessing the environmental influences on health status of aquatic organisms.

Early responses measured in the brachyuran crab Carcinus maenas exposed to carbamazepine and novobiocin: application of a 2-tier approach

One of the main consequences of the constant input of pharmaceuticals to the aquatic environment is that biota might develop unknown chronic effects, thus affecting their health even at low concentrations. The aim of this study is to evaluate the health status of Carcinus maenas employing a 2-tier approach, after 28 days of exposure to carbamazepine (CBZ) and novobiocin (NOV) at 0.1, 1, 10 and 50µgL(-1). Lysosomal membrane stability (LMS) is employed in tier 1. In tier 2 was applied a battery of biomarkers of exposure and effect (ethoxyresorufin O-deethylase (EROD), dibenzyl flourescein dealkylase (DBF), glutathione S-transferase (GST), glutathione peroxidase (GPx), lipid peroxidation (LPO) and DNA adducts) measured in gill, hepatopancreas, muscle and gonad tissues. Results show a dose-dependent effect. LMS in crabs exposed to environmental concentrations of pharmaceuticals was significantly lower compared to controls (p<0.05), indicating their stressed status. EROD activity was induced significantly (p<0.05) in all tissues by NOV (10-50µgL(-1)). DBF activity was induced significantly (p<0.05) in gill and hepatopancreas tissues by CBZ (10-50µgL(-1)). GST activity was activated in all tissues of crabs exposed to the highest concentrations tested (p<0.05). All tissues showed induction of GPX activity after exposure to selected drugs (p<0.05). LPO was activated in gill and hepatopancreas tissues by the pharmaceuticals at 50µgL(-1) (p<0.05). Crabs exposed to NOV (50µgL(-1)) presented DNA damage in gill and hepatopancreas tissues (p<0.05). Environmental concentrations of these pharmaceuticals have a measurable effect on the biomarkers studied. The 2-tier approach applied might be a suitable tool for the assessment of sublethal responses in crabs exposed to pharmaceuticals in the marine environment.

Effects of environmental pollution in caged mussels (Mytilus galloprovincialis)

Biological effects of environmental pollution, mainly related to presence of PAHs, were assessed in mussels Mytilus galloprovincialis caged in Priolo, an anthropogenically-impacted area, and Vendicari, a reference site, both located along the eastern coastline of Sicily (Italy). PAHs concentration and histopathological changes were measured in digestive gland tissues. Expression of cytochrome P4504Y1 (CYP4Y1) and glutathione S-transferase (GST), indicative of xenobiotic detoxification, and activity of catalase (CAT) as oxidative stress index, were evaluated. The results show a direct correlation between the high concentrations of PAHs in digestive glands of mussels from Priolo and the significantly altered activity of phase I (P < 0.001) and phase II (P < 0.0001) biotransformation enzymes, along with increased levels of CAT activity (P < 0.05). These findings show the enhancement of the detoxification and antioxidant defense systems. The mussel caging approach and selected biomarkers demonstrated to be reliable for the assessment of environmental pollution effects on aquatic organisms.

Seasonal variations of biomarker responses in the marine blue mussel (Mytilus spp.)

Biomarkers, which can detect changes at the biochemical level, have been used for many years as early warning tools in environmental monitoring. In order to distinguish between natural variability and the potential effects of anthropogenic pollution, it is essential to identify background levels and establish the potential influence of abiotic (season, temperature and salinity) and biotic (gametogenesis) factors. In this study, we examined various biomarkers of stress (glutathione S-transferase (GST)), reproduction (vitellin-like proteins) and damage (lipid peroxidation (LPO) and DNA damage (DNA)) in marine mussels (Mytilus spp.) from a known pristine hybrid zone. Levels of all biomarker expression varied between seasons and appeared to be linked to the reproductive cycle. Oxidative stress in winter, with low GST expression and a higher expression of LPO and DNA damage displayed could be explained by low food availability. These data provide vital baseline information for future ecotoxicological and environmental monitoring studies.

Practical procedures for selected biomarkers in mussels, Mytilus galloprovincialis--implications for marine pollution monitoring

Biomarkers are required to assess the biological effects of pollutants on marine organisms in order to monitor ecosystem status, but their use is often limited by their strong variability due to environmental and/or intrinsic biological factors. Accordingly, the main aim of this work was to set up practical procedures for a battery of widely used biomarkers in mussels (Mytilus galloprovincialis). Antioxidant enzymes (catalase [CAT] and glutathione peroxidase [GPx]), a phase II detoxification enzyme (glutathione S-transferase [GST]) and a neurotransmitter catabolism enzyme (acetylcholinesterase [AChE]), were considered. Several relevant aspects were studied in order to obtain a more realistic interpretation of biomarker responses, including the calculation of the minimum sample size required to estimate the population mean with a fixed error margin, the selection of the specific organ or tissue where the enzymatic activity is higher for each biomarker, and the influence of tidal height and temperature on the basal enzymatic activity. GST and CAT activities needed a minimum sample size of 12, whereas for GPx and AChE activities a minimum sample size of 14 was required. The gills were the organ with higher GST, GPx and AChE enzymatic activities, whereas the digestive gland showed the highest CAT activity. Also, the low inter-tidal was the recommended tide level whilst no significant effect of temperature was observed on GST, GPx and CAT, and no clear pattern could be identified for AChE. The implications for environmental monitoring are discussed.

Cloning and identification of four Mu-type glutathione S-transferases from the giant freshwater prawn Macrobrachium rosenbergii

Glutathione S-transferases (GSTs) are essential components of the cellular detoxification system because of their capability to protect organisms against the toxicity of reactive oxygen species (ROSs). Four different GSTs (MrMuGST1-MrMuGST4) showing similarities with Mu-type GSTs were cloned from the hepatopancreas of Macrobrachium rosenbergii. These four GSTs have 219, 216, 218 and 219 amino acids in length, respectively. MrMuGST1-MrMuGST4 proteins all have a G-site in the N-terminus and an H-site in the C-terminus. Phylogenetic analysis reveals that four Mu-type GSTs are classified into two different clades (MrMuGST2 one clade; MrMuGST1, MrMuGST3 and MrMuGST4 other clades). Nonetheless, no site under positive selection was detected but rapid evolution was found in the few of MuGST genes. Reverse transcription-polymerase chain reaction (RT-PCR) results showed that MrMuGST1 and MrMuGST2 transcripts were expressed in all detected tissues, however, MrMuGST3 and MrMuGST4 were just mainly expressed in hepatopancreas and intestines. Quantitative RT-PCR analysis showed that MrMuGST1 and MrMuGST2 were down-regulated upon Vibrio anguillarum challenge, whereas MrMuGST3 and MrMuGST4 were quickly up-regulated 2 h after the Vibrio challenge. Our results imply that different Mu-type GSTs may respond to Vibrio challenge with different manners.

Identification of biomarkers responsive to chronic exposure to pharmaceuticals in target tissues of Carcinus maenas

A 28-day bioassay was performed with Carcinus maenas to evaluate chronic effects caused by exposure to caffeine and ibuprofen (0.1-50 μg L(-1)) in sea water. Lysosomal membrane stability (LMS) was evaluated in hemolymph applying the neutral red retention assay (NRRA); several biomarkers including ethoxyresorufin O-deethylase (EROD), dibenzylfluorescein dealkylase (DBF), glutathione S-transferase (GST), glutathione peroxidase (GPX), lipid peroxidation (LPO) and DNA damage were studied in gill, hepatopancreas, muscle and gonad tissues. In crabs exposed to environmental concentrations of the drugs, retention time was reduced by 50%. EROD and DBFOD activities were induced by caffeine in muscle and hepatopancreas tissues (p < 0.05); GST activity was activated by ibuprofen in gill, hepatopancreas and muscle at the highest concentrations tested (p < 0.05). All tissues showed GPX activity and LPO induction (p < 0.05). Crabs exposed to caffeine and ibuprofen showed evidence of DNA damage mainly in hepatopancreas tissues (p < 0.05). Environmental concentrations of pharmaceuticals induce LMS and the biochemical responses studied in this crab. This methodology is a suitable technique for assessing pharmaceutical toxicity in the marine environment.

Identification and expression of multiple CYP1-like and CYP3-like genes in the bivalve mollusk Mytilus edulis

Various sequencing projects over the last several years have aided the discovery of previously uncharacterized invertebrate sequences, including new cytochrome P450 genes (CYPs). Here we present data on the identification and characterization of two CYP1-like and three CYP3-like genes from the bivalve mollusk Mytilus edulis, and assess their potential as biomarkers based on their responses to several known vertebrate aryl hydrocarbon receptor (AHR) agonists. Quantitative real-time PCR was used to measure CYP transcript levels in digestive gland, labial palps, adductor muscle, gill, foot, and different regions of the mantle. Levels of both CYP1-like genes were highest in digestive gland, whereas labial palps had the highest expression levels of the three CYP3-like genes followed by digestive gland and outer margin of the mantle. Mussels were exposed by injection to the AHR agonists, β-naphthoflavone (BNF; 25 μg g(-1)), 3,3',4,4',5-polychlorinated biphenyl (PCB126; 2 μg g(-1)), or 6-formylindolo[3,2-b]carbazole (FICZ; 0.1 μg g(-1)), or to Aroclor 1254 (a mixture of PCBs; 50 μg g(-1)) for 24 h, followed by CYP expression analysis. There was no statistically significant change in expression of either of the CYP1-like genes after exposure to the various AHR agonists. The CYP3-like-1 gene was significantly up-regulated by BNF in gill tissues and the CYP3-like-2 gene was up-regulated in digestive gland by PCB126 and in gill tissue by BNF. These results suggest that distinct mechanisms of CYP gene activation could be present in M. edulis, although the importance of the CYP1-like and CYP3-like genes for xenobiotic and endogenous lipids biotransformation requires additional investigation.

Fuzzy logic and adaptive neuro-fuzzy inference system for characterization of contaminant exposure through selected biomarkers in African catfish

This study represents a first attempt at applying a fuzzy inference system (FIS) and an adaptive neuro-fuzzy inference system (ANFIS) to the field of aquatic biomonitoring for classification of the dosage and time of benzo[a]pyrene (BaP) injection through selected biomarkers in African catfish (Clarias gariepinus). Fish were injected either intramuscularly (i.m.) or intraperitoneally (i.p.) with BaP. Hepatic glutathione S-transferase (GST) activities, relative visceral fat weights (LSI), and four biliary fluorescent aromatic compounds (FACs) concentrations were used as the inputs in the modeling study. Contradictory rules in FIS and ANFIS models appeared after conversion of bioassay results into human language (rule-based system). A "data trimming" approach was proposed to eliminate the conflicts prior to fuzzification. However, the model produced was relevant only to relatively low exposures to BaP, especially through the i.m. route of exposure. Furthermore, sensitivity analysis was unable to raise the classification rate to an acceptable level. In conclusion, FIS and ANFIS models have limited applications in the field of fish biomarker studies.

Comparative study of biochemical and immunological biomarkers in three marine bivalves exposed at a polluted site

A battery of biochemical and immunological biomarkers used for pollution assessment were measured for first time in the clams Venus verrucosa and Callista chione and were compared with those of the mussel Mytilus galloprovincialis, a well-established indicator organism utilized in numerous environmental monitoring programs. Clams and mussel were transplanted at a polluted and a reference site or maintained at the laboratory. Among biochemical biomarkers, acetylcholinesterase did not differ at the polluted site in all species, but there was a significant difference between the mussel and the clams, glutathione S-transferase showed a clear inhibition at the polluted site in all species and a significant difference between the two clams was also indicated, while catalase activities were increased only in V. verrucosa at the polluted site and not in mussel or the other clam. Immunological biomarkers responses were also pronounced at the polluted site. Lysozyme activity was species-dependent whereas respiratory burst activity measured as luminol-dependent chemiluminescence (CL) was site and stimulus dependent, and it was evident in M. galloprovincialis and V. verrucosa and not in C. chione. Further investigation focused on biochemical and immunological biomarkers related with the oxidative mechanisms in clams will strengthen and expand their use as bioindicators for pollution assessment.

Assessment of toxic effects of triclosan on the swordtail fish (Xiphophorus helleri) by a multi-biomarker approach

The toxic effects of triclosan (TCS) on the swordtail fish (Xiphophorus helleri) were assessed based on various biomarkers including enzymatic activities of ethoxyresorufin O-deethylase (EROD), erythromycin N-demethylase (ERND) and glutathione-s-transferase (GST) and mRNA expression levels of CYP1A, CYP3A, glutathione S-transferase (GST) and P-glycoprotein (P-gp). The acute toxicity test showed the LC(50) value of 1.47 mg L(-1) for TCS. The mRNA expressions of CYP1A, CYP3A, GST and P-gp showed dose-effect relationships in female swordtail fish when exposed to TCS, These mRNA expression levels were found more sensitive to TCS exposure than the enzymatic activities of EROD, ERND and GST do. In addition, the male fish displayed higher gene expression levels and more dramatic changes in enzyme activities than the females did. Our data further demonstrated that TCS was a typical inducer to Phase I and Phase II metabolism enzymes and genes, suggesting it is a potential ecotoxicological risk to aquatic ecosystems.

Oxidative stress responses and biological indices in the giant clam Tridacna maxima and the reef fish Epinephelus merra from the French Polynesian Moorea Island

Responses of biological indices and oxidative stress biomarkers were studied in the giant clam Tridacna maxima and in the fish Epinephelus merra collected from two sites differing by their level of contamination in the French Polynesian Moorea island. Higher levels of catalase (CAT), glutathione-S-transferases (GST) and thiobarbituric acid reactive substances (TBARs) were observed in the hepatopancreas of T. maxima and in the liver of E. merra compared to muscle. CAT and TBARs levels were significantly higher in the hepatopancreas of clams collected from the impacted site (Vaiare) compared to the reference site (bay of Cook). The same pattern was observed for TBARs levels in the liver of E. merra. These results indicate that both organisms from the impacted site were exposed to contaminants leading to an oxidative stress and demonstrate, for the first time, the usefulness of T. maxima and E. merra as sentinel species for biomonitoring reef environments.

The effect of shore location on biomarker expression in wild Mytilus spp. and its comparison with long line cultivated mussels

Biomarkers are a common tool in the assessment of potential effects of contaminants in aquatic organisms. In order to identify the effects of anthropogenic pollution it is essential to identify background levels and to know the range of natural variability in the biomarker response. In this study, we examined various biomarkers of stress (glutathione S-transferase and metallothionein), damage (lipid peroxidation (LPO) and DNA damage (DNA)) and reproduction (vitellin-like proteins) in marine mussels (Mytilus spp.) from four locations along a vertical transect from high to low shore and compared them with cultivated long line mussels. High shore and cultivated mussels showed significantly higher LPO and DNA damage expression than the low shore mussels indicating a level of oxidative stress resulting from mussel location. Significant effects in physiological endpoints were also found. This study highlights the need to consider the diversity of natural environmental stress factors when using biomarkers in environmental assessment.