An ecotoxicoproteomic approach (SELDI-TOF mass spectrometry) to biomarker discovery in crab exposed to pollutants under laboratory conditions

Transcriptomic and Histological Analysis of the Greentail Prawn (Metapenaeus bennettae) Following Light Crude Oil Exposure

Oil spills pose a significant threat to marine biodiversity. Crude oil can partition into sediments where it may be persistent, placing benthic species such as decapods at particular risk of exposure. Transcriptomic and histological tools are often used to investigate the effects of hydrocarbon exposure on marine organisms following oil spill events, allowing for the identification of metabolic pathways impacted by oil exposure. However, there is limited information available for decapod crustaceans, many of which carry significant economic value. In the present study, we assess the sublethal impacts of crude oil exposure in the commercially important Australian greentail prawn (Metapenaeus bennettae) using transcriptomic and histological analyses. Prawns exposed to light, unweathered crude oil "spiked" sediments for 90 h were transferred to clean sediments for a further 72 h to assess recovery. Chemical analyses indicated that polycyclic aromatic hydrocarbons increased by approximately 65% and 91% in prawn muscle following 24 and 90 h of exposure, respectively, and significantly decreased during 24- and 72-h recovery periods. Transcriptomic responses followed an exposure and recovery pattern with innate immunity and nutrient metabolism transcripts significantly lowered in abundance after 24 h of exposure and were higher in abundance after 72 h of recovery. In addition, transcription/translation, cellular responses, and DNA repair pathways were significantly impacted after 24 h of exposure and recovered after 72 h of recovery. However, histological alterations such as tubule atrophy indicated an increase in severity after 24 and 72 h of recovery. The present study provides new insights into the sublethal impacts of crude oil exposure in greentail prawns and identifies molecular pathways altered by exposure. We expect these findings to inform future management associated with oil extraction activity and spills. Environ Toxicol Chem 2022;41:2162-2180. © 2022 John Wiley & Sons Ltd. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Use of proteomics to detect sex-related differences in effects of toxicants: implications for using proteomics in toxicology

This review provides an overview of results obtained when using proteome analysis for detecting sex-based differences in response to toxicants. It reveals implications to be taken into account when considering the use of proteomics in toxicological studies. It appears that results may differ when studying the same chemical in the same species in different target tissues. Another result of interest is the limited dose-response behavior of differential abundance patterns observed in studies where more than one dose level is tested. It is concluded that use of proteomics to study differences in modes of action of toxic compounds is an active area of research. The examples from use of proteomics to study sex-dependent differences also reveal that further studies are needed to provide reliable insight in modes of action, novel biomarkers or even novel therapies. To eventually reach this aim for this and other toxicological endpoints, it is essential to consider background variability, consequences of timing of toxicant administration, dose-response behavior, relevant species and target organ, species and organ variability and the presence of proteoforms.

Accumulation of Polychlorinated Biphenyls in Mussels: A Proteomic Study

Polychlorinated biphenyls (PCBs) are environmental pollutants of industrial origin that can contaminate food, mainly food of animal origin. Although production of PCBs has been banned in many countries since the 1980s, they are still present in the environment and are considered dangerous pollutants for human health. In fact, they can bioaccumulate in living organisms such as marine organisms because of their chemical and physical properties. New analytical approaches are useful to monitor the presence of such contaminants in seafood products and in the environment. In this work, we evaluate changes in protein expression of Mytilus galloprovincialis (Lam.) experimentally exposed to a PCB mixture and identify chemically specific protein expression signatures by using a proteomic approach. In particular, we identify 21 proteins whose levels of expression are sensibly modified after 3 weeks of exposure. The present work shows that a proteomic approach can be a useful tool to study alterations of protein expression in mussels exposed to PCBs and represents a first step toward the development of screening protocols to be used for biomonitoring surveys of fishery products.

Applying adverse outcome pathways and species sensitivity-weighted distribution to predicted-no-effect concentration derivation and quantitative ecological risk assessment for bisphenol A and 4-nonylphenol in aquatic environments: A case study on Tianjin City, China

Adverse outcome pathways (AOPs) are a novel concept that effectively considers the toxic modes of action and guides the ecological risk assessment of chemicals. To better use toxicity data including biochemical or molecular responses and mechanistic data, we further developed a species sensitivity-weighted distribution (SSWD) method for bisphenol A and 4-nonylphenol. Their aquatic predicted-no-effect concentrations (PNECs) were derived using the log-normal statistical extrapolation method. We calculated aquatic PNECs of bisphenol A and 4-nonylphenol with values of 4.01 and 0.721 µg/L, respectively. The ecological risk of each chemical in different aquatic environments near Tianjin, China, a coastal municipality along the Bohai Sea, was characterized by hazard quotient and probabilistic risk quotient assessment techniques. Hazard quotients of 7.02 and 5.99 at 2 municipal sewage sites using all of the endpoints were observed for 4-nonylphenol, which indicated high ecological risks posed by 4-nonylphenol to aquatic organisms, especially endocrine-disrupting effects. Moreover, a high ecological risk of 4-nonylphenol was indicated based on the probabilistic risk quotient method. The present results show that combining the SSWD method and the AOP concept could better protect aquatic organisms from adverse effects such as endocrine disruption and could decrease uncertainty in ecological risk assessment. Environ Toxicol Chem 2018;37:551-562. © 2017 SETAC.

Toxicological effects of tris(2-chloropropyl) phosphate in human hepatic cells

Organophosphate flame retardants (OPFRs) are widely used as flame retardants which are ubiquitous in various environment media. As many of OPFRs are toxic and persistent, concerns have been raised in regards to their environmental impact. In this study, the toxicological effects of tris(2-chloropropyl) phosphate (TCPP) in human L02 cells was investigated by cell proliferation and apoptosis, oxidative stress, metabolomic and proteomic responses as well as gene expressions related to apoptosis. Results showed that TCPP did not significantly affect the L02 cell apoptosis, however, a significant increase of ROS production was observed in L02 cells with TCPP treatment compared with that in control group (p < 0.05). The expression levels of Bcl-2 family-encoding genes (Bax, Hrk and Bax/Bcl-2) were up-regulated significantly in 10^-4 M group (p < 0.05). Metabolomic and proteomic responses indicated that TCPP mainly caused disturbance in cell growth/division and gene expression, energy and material metabolism, signal transduction, defense and cytoskeleton, which was further confirmed by the western blot analysis.

Proteomic response of Macrobrachium rosenbergii hepatopancreas exposed to chlordecone: Identification of endocrine disruption biomarkers?

The present work is the first study investigating the impacts of chlordecone, an organochlorine insecticide, on the proteome of the decapod crustacean Macrobrachium rosenbergii, by gel-free proteomic analysis. The hepatopancreas protein expression variations were analysed in organisms exposed to three environmental relevant concentrations of chlordecone (i.e. 0.2, 2 and 20µg/L). Results revealed that 62 proteins were significantly up- or down-regulated in exposed prawns compared to controls. Most of these proteins are involved in important physiological processes such as ion transport, defense mechanisms and immune system, cytoskeleton dynamics, or protein synthesis and degradation. Moreover, it appears that 6% of the deregulated protein are involved in the endocrine system and in the hormonal control of reproduction or development processes of M. rosenbergii (e.g. vitellogenin, farnesoic acid o-methyltransferase). These results indicate that chlordecone is potentially an endocrine disruptor compound for decapods, as already observed in vertebrates. These protein modifications could lead to disruptions of M. rosenbergii growth and reproduction, and therefore of the fitness population on the long-term. Besides, these disrupted proteins could be suggested as biomarkers of exposure for endocrine disruptions in invertebrates. However, further investigations are needed to complete understanding of action mechanisms of chlordecone on proteome and endocrine system of crustaceans.

Investigating the emerging role of comparative proteomics in the search for new biomarkers of metal contamination under varying abiotic conditions

This study aims at investigating the potential use of comparative proteomics as a multi-marker approach of metal contamination, taking into account the potential confounding effect of water temperature. The major objective was to identify combinations of proteins specifically responding to a given metal, even if included in a metal mixture. The diagnostic approach was performed via the comparative analysis of protein expression on spot mapping provided by adult males of Gammarus pulex (Amphipoda, Crustacea) respectively exposed to arsenate (As), cadmium (Cd) or a binary mixture of these metals (AsCd) at three realistic temperatures (5, 10 and 15°C). Proteomic expression analysis was performed by Differential in-Gel Electrophoresis (2D-DiGE), and completed by an adapted inferential statistical approach. Combinations of under/over-expressed protein spots discriminated the metal identity. However, none of these spots discriminated both the individual metal effect (As or Cd) and its effect in metal mixture (AsCd) whatever the tested temperature. Some limits of the two-dimensional analysis of protein spot maps in G. pulex have been highlighted: (i) the presence of contaminating peptides and/or abundant "déja-vu" proteins which can mask the responses of other proteins of interest or (ii) the presence of post-translational modifications. An optimization of the experimental design (especially during the sample preparation) has been described for future investigations. This study has also highlighted (i) the importance of precisely identifying the protein spots of interest to avoid erroneous interpretations in terms of action mechanisms of chemicals and (ii) the importance of working under controlled laboratory conditions with a temperature close to 10°C. In such conditions, we have demonstrated a higher impact of As than Cd on the energetic metabolism of Gammarus. This As impact is reduced in AsCd mixture confirming the antagonistic interaction of this binary mixture previously observed on G. pulex mortality at 10°C.

Toxicological effects of benzo(a)pyrene, DDT and their mixture on the green mussel Perna viridis revealed by proteomic and metabolomic approaches

Benzo(a)pyrene (BaP) and dichlorodiphenyltrichloroethane (DDT) are persistent organic pollutants and environmental estrogens (EEs) with known toxicity towards the green mussel, Perna viridis. In this study, the toxic effects of BaP (10 µg/L) and DDT (10 µg/L) and their mixture were assessed in green mussel gills with proteomic and metabolomic approaches. Metabolic responses indicated that BaP mainly caused disturbance in osmotic regulation by significantly decrease in branched chain amino acids, dimethylamine and dimethylglycine in gills of male green mussels after exposure for 7 days. DDT mainly caused disturbance in osmotic regulation and energy metabolism by differential alteration of betaine, dimethylamine, dimethylglycine, amino acids, and succinate in gills of male green mussels. However, the mixture of BaP and DDT didn't show obvious metabolite changes. Proteomic analysis showed different protein expression profiles between different treatment groups, which demonstrated that BaP, DDT and their mixture may have different modes of action. Proteomic responses revealed that BaP induced cell apoptosis, disturbance in protein digestion and energy metabolism in gills of green mussels, whereas DDT exposure altered proteins that were associated with oxidative stress, cytoskeleton and cell structure, protein digestion and energy metabolism. However, the mixture of BaP and DDT affected proteins related to the oxidative stress, cytoskeleton and cell structure, protein biosynthesis and modification, energy metabolism, growth and apoptosis.

A SELDI-TOF approach to ecotoxicology: comparative profiling of low molecular weight proteins from a marine diatom exposed to CdSe/ZnS quantum dots

Quantum dots (QDs), namely semiconductor nanocrystals, due to their particular optical and electronic properties, have growing applications in device technology, biotechnology and biomedical fields. Nevertheless, the possible threat to human health and the environment have attracted increasing attention as the production and applications of QDs increases rapidly while standard evaluation of safety lags. In the present study we performed proteomic analyses, by means of 2D gel electrophoresis and Surface Enhanced Laser Desorption Ionization-Time of Flight-Mass Spectrometry (SELDI-TOF-MS). We aimed to identify potential biomarkers of exposure to CdSe/ZnS quantum dots. The marine diatom Phaeodactylum tricornutum exposed to 2.5nM QDs was used as a model system. Both 2DE and SELDI showed the presence of differentially expressed proteins. By Principal Component Analysis (PCA) we were able to show that the differentially expressed proteins can discriminate between exposed and not exposed cells. Furthermore, a protein profile specific for exposed cells was obtained by SELDI analysis. To our knowledge, this is the first example of the application of SELDI technology to the analysis of microorganisms used as biological sentinel model of marine environmental pollution.

Determination of biomarkers for polycyclic aromatic hydrocarbons (PAHs) toxicity to earthworm (Eisenia fetida)

Polycyclic aromatic hydrocarbon (PAH) compounds are persistent, carcinogenic, and mutagenic. When PAHs enter agricultural soils through sewage sludge, they pose an environmental risk to soil organisms, including earthworms. Therefore, we aimed to determine the toxic effects of PAHs on earthworms. Five PAHs were used: fluorene, anthracene, phenanthrene, fluoranthene, and pyrene. Only fluorene and phenanthrene exhibited toxicity (LC50 values 394.09 and 114.02 g L(-1), respectively) against the earthworm Eisenia fetida. None of the other PAHs tested in this study enhanced the mortality of adult earthworm until the concentrations reached to 1000 g L(-1). After exposure to PAHs, acetylcholinesterase (AChE) activity in E. fetida decreased in a concentration-dependent manner, and phenanthrene exhibited the strongest inhibitory effect on AChE, followed by fluorene. Activity of a representative detoxifying enzyme, carboxylesterase, was dramatically reduced in E. fetida exposed to all tested PAHs in comparison with that observed in the control test. The remaining glutathione S-transferase activity significantly decreased in E. fetida after exposure to PAHs. To profile small proteins <20 kDa, SELDI-TOF MS with Q10 ProteinChips was used, and 54 proteins were identified as being significantly different from the control (p = 0.05). Among them, the expressions of three proteins at 4501.8, 4712.4, and 4747.9 m/z were only enhanced in E. fetida exposed to anthracene and pyrene. One protein with 16,174 m/z was selectively expressed in E. fetida exposed to fluorene, phenanthrene, and fluoranthene. These proteins may be potential biomarkers for the five PAHs tested in E. fetida.

Proteomic analysis in caged Mediterranean crab (Carcinus maenas) and chemical contaminant exposure in Téboulba Harbour, Tunisia

This study uses proteomics approach to assess the toxic effects of contaminants in the Mediterranean crab (Carcinus maenas) after transplantation into Téboulba fishing harbour. High levels of aliphatic and aromatic hydrocarbons were detected in sediments. Although their effects on vertebrates are well described, little is known about their early biological effects in marine invertebrates under realistic conditions. Protein expression profiles of crabs caged for 15, 30 and 60 days were compared to unexposed animals. Nineteen proteins with significant expression differences were identified by capLC-µESI-IT MS/MS and homology search on databases. Differentially expressed proteins were assigned to five different categories of biological function including: (1) chitin catabolism, (2) proteolysis, (3) exoskeleton biosynthesis, (4) protein folding and stress response, and (5) transport. The proteins showing major expression changes in C. maenas after different caging times may be considered as novel molecular biomarkers for effectively biomonitoring aquatic environment contamination.

The added value of proteomics for toxicological studies

Proteomics has the potential to elucidate complex patterns of toxic action attributed to its unique holistic a posteriori approach. In the case of toxic compounds for which the mechanism of action is not completely understood, a proteomic approach may provide valuable mechanistic insight. This review provides an overview of currently available proteomic techniques, including examples of their application in toxicological in vivo and in vitro studies. Future perspectives for a wider application of state-of-the-art proteomic techniques in the field of toxicology are discussed. The examples concern experiments with dioxins, polychlorinated biphenyls, and polybrominated diphenyl ethers as model compounds, as they exhibit a plethora of sublethal effects, of which some mechanisms were revealed via successful proteomic studies. Generally, this review shows the added value of including proteomics in a modern tool box for toxicological studies.

Proteomic and metabolomic analysis reveal gender-specific responses of mussel Mytilus galloprovincialis to 2,2',4,4'-tetrabromodiphenyl ether (BDE 47)

Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame-retardants (BFRs) that are widely used in industrial products and have posed potential risk on the coastal environment of the Laizhou Bay in China. They are of great concern due to their toxicities, such as hepatotoxicity, carcinogenecity, neurotoxicity, immunotoxicity and endocrine disrupting effects in animals. In this work, we focused on the gender-specific responses of BDE 47 in mussel Mytilus galloprovincialis using a combined proteomic and metabolomic approach. Metabolic responses indicated that BDE 47 mainly caused disturbance in energy metabolism in male mussel gills. For female mussel samples, disruption in both osmotic regulation and energy metabolism was found in terms of differential metabolic profiles. Proteomic responses revealed that BDE 47 induced cell apoptosis and reduced reactive oxygen species (ROS) production in both male and female mussels, disturbance in protein homeostasis in male mussels as well as disturbance in female mussel proteolysis based on the differential proteomic biomarkers. Overall, these results confirmed the gender-specific responses in mussels to BDE 47 exposures. This work demonstrated that an integrated metabolomic and proteomic approach could provide an important insight into the toxicological effects of environmental pollutant to organisms.

Effect of crude oil petroleum hydrocarbons on protein expression of the prawn Macrobrachium borellii

Hydrocarbon pollution is a major environmental threat to ecosystems in marine and freshwater environments, but its toxicological effect on aquatic organisms remains little studied. A proteomic approach was used to analyze the effect of a freshwater oil spill on the prawn Macrobrachium borellii. To this aim, proteins were extracted from midgut gland (hepatopancreas) of male and female prawns exposed 7 days to a sublethal concentration (0.6 ppm) of water-soluble fraction of crude oil (WSF). Exposure to WSF induced responses at the protein expression level. Two-dimensional gel electrophoresis (2-DE) revealed 10 protein spots that were differentially expressed by WSF exposure. Seven proteins were identified using MS/MS and de novo sequencing. Nm23 oncoprotein, arginine methyltransferase, fatty aldehyde dehydrogenase and glutathione S-transferase were down-regulated, whereas two glyceraldehyde-3-phosphate dehydrogenase isoforms and a lipocalin-like crustacyanin (CTC) were up-regulated after WSF exposure. CTC mRNA levels were further analyzed by quantitative real-time PCR showing an increased expression after WSF exposure. The proteins identified are involved in carbohydrate and amino acid metabolism, detoxification, transport of hydrophobic molecules and cellular homeostasis among others. These results provide evidence for better understanding the toxic mechanisms of hydrocarbons. Moreover, some of these differentially expressed proteins would be employed as potential novel biomarkers.

Marine proteomics: a critical assessment of an emerging technology

The application of proteomics to marine sciences has increased in recent years because the proteome represents the interface between genotypic and phenotypic variability and, thus, corresponds to the broadest possible biomarker for eco-physiological responses and adaptations. Likewise, proteomics can provide important functional information regarding biosynthetic pathways, as well as insights into mechanism of action, of novel marine natural products. The goal of this review is to (1) explore the application of proteomics methodologies to marine systems, (2) assess the technical approaches that have been used, and (3) evaluate the pros and cons of this proteomic research, with the intent of providing a critical analysis of its future roles in marine sciences. To date, proteomics techniques have been utilized to investigate marine microbe, plant, invertebrate, and vertebrate physiology, developmental biology, seafood safety, susceptibility to disease, and responses to environmental change. However, marine proteomics studies often suffer from poor experimental design, sample processing/optimization difficulties, and data analysis/interpretation issues. Moreover, a major limitation is the lack of available annotated genomes and proteomes for most marine organisms, including several "model species". Even with these challenges in mind, there is no doubt that marine proteomics is a rapidly expanding and powerful integrative molecular research tool from which our knowledge of the marine environment, and the natural products from this resource, will be significantly expanded.

Toxic effects of two brominated flame retardants BDE-47 and BDE-183 on the survival and protein expression of the tubificid Monopylephorus limosus

The toxic effects of two brominated diphenyl ethers (BDE), BDE-47, and BDE-183, on a benthic oligochaete tubificid, Monopylephorus limosus were studied under laboratory conditions. Investigated responses included survival, growth, and protein expression profiles, at BDE concentrations of 1, 10, 100, and 700 ng/g on a dry soil weight basis, with isooctane as the carrier solvent. Body weight losses among treatments were insignificant after 8 weeks of exposure. The 8-wk LC(50) of BDE-47 and -183 were 2311 and 169 ng/g, respectively. By applying multivariate analysis techniques, protein expression patterns were compared and correlated with stressful sources of long-term culture, carrier solvent, BDE-47 and -183. The treatment of 8-wk 100 ng/g BDE-47 was most closely clustered to the 10 ng/g BDE-183 treatment, based on the 40 examined protein spots. This indicated that BDE-183 was more potent to M. limosus, than was BDE-47. The 2-wk and 8-wk controls clustered into different groups indicating the occurrence of physiological changes due to long-term laboratory culture. Additionally, solvent effect was shown by grouping the isooctane carrier to different clusters. With further characterization by principle component analysis, it was found that the separation was mainly contributed by the 2nd principal-component. And, the primarily inhibitory variation was at spots 2 (UMP-CMP kinase) and 40 (plasma retinol-binding protein precursor) in the 8-wk groups. On the contrary, protein spots 16 (cell division control protein 2 homolog) and 24 (mitochondrial DNA mismatch repair protein) showed stimulatory variation. In all, the observed proteomic responses suggest that BDEs disrupted metabolic function in M. limosus and multivariate analysis tool offers significant potential for the assessment of various stress sources at biochemical level.

Proteomic discovery of biomarkers of metal contamination in Sydney Rock oysters (Saccostrea glomerata)

In the current study we examined the effects of metal contamination on the protein complement of Sydney Rock oysters. Saccostrea glomerata were exposed for 4 days to three environmentally relevant concentrations (100 μg/l, 50 μg/l and 5 μg/l) of cadmium, copper, lead and zinc. Protein abundances in oyster haemolymph from metal-exposed oysters were compared to those from non-exposed controls using two-dimensional electrophoresis to display differentially expressed proteins. Differentially expressed proteins were subsequently identified using tandem mass spectrometry (LC-MS/MS), to assign their putative biological functions. Unique sets of differentially expressed proteins were affected by each metal, in addition to proteins that were affected by more than one metal. The proteins identified included some that are commonly associated with environmental monitoring, such as HSP 70, and other novel proteins not previously considered as candidates for molecular biomonitoring. The most common biological functions of proteins were associated with stress response, cytoskeletal activity and protein synthesis.

An estrogen-responsive plasma protein expression signature in Atlantic cod (Gadus morhua) revealed by SELDI-TOF MS

Compound-specific protein expression signatures (PESs) can be revealed by proteomic techniques. The SELDI-TOF MS approach is advantageous due to its simplicity and high-throughput capacity, however, there are concerns regarding the reproducibility of this method. The aim of this study was to define an estrogen-responsive PES in plasma of Atlantic cod (Gadus morhua) using the SELDI-TOF MS technique. Protein expression analysis of male cod exposed to 17β-estradiol (E₂) showed that 27 plasma peaks were differentially expressed following exposure. The reproducibility of this result was evaluated by reanalyzing the samples six months later, and a significant change in expression was confirmed for 13 of the 27 peaks detected in the first analysis. The performance of the reproducible E₂-responsive PES, constituting these 13 peaks, was then tested on samples from juvenile cod exposed to 4-nonylphenol, North Sea oil, or North Sea oil spiked with alkylphenols. Principal component analysis revealed that nonylphenol-exposed cod could be separated from unexposed cod based on the E₂-responsive PES, indicating that the PES can be used to assess estrogenic exposure of both juvenile and adult specimens of cod. A targeted antibody-assisted SELDI-TOF MS approach was carried out in an attempt to identify the E₂-responsive peaks. Results indicated that 2 peaks were fragments of the well-known biomarkers VTG and/or ZRP. In this study, the SELDI-TOF MS technology has shown its potential for defining compound-specific PESs in fish. Nevertheless, thorough validation of reproducibility, specificity and sensitivity of a PES is required before it can be applied in environmental monitoring.

SELDI-TOF MS analysis of alkylphenol exposed Atlantic cod with phenotypic variation in gonadosomatic index

Proteomics is a new and promising approach to evaluate potential effects of pollution. In order to investigate if there is a direct link between the protein expression profiles obtained by the SELDI-TOF MS technology and effects observed at the organism level in fish, plasma samples from unexposed and 20 ppb alkylphenol exposed female Atlantic cod (Gadus morhua) with high phenotypic variation in gonadosomatic index (GSI) were analyzed by SELDI-TOF MS. Principle component analysis (PCA) showed that the major proteomic variation present in the dataset (i.e. 23.6%) could be significantly correlated to the individual variation in GSI, which indicates that SELDI-TOF MS data can reflect effects observed at higher levels of organization in fish. Further exploration of the other principal components revealed an additional proteomic pattern specific for the alkylphenol exposed females. Hence, this study supports the usefulness of SELDI-TOF MS as a proteomic tool in ecotoxicological research.

Proteomic analysis of zebrafish brain tissue following exposure to the pesticide prochloraz

The hypothalamus-pituitary-gonadal (HPG) axis plays a central role in the maintenance of homeostasis and disruptions in its function can have important implications for reproduction and other critical biological processes. A number of compounds found in aquatic environments are known to affect the HPG axis. In the present study, we used two-dimensional electrophoresis to investigate the proteome of female and male zebrafish brain after 96 h exposure to the fungicide prochloraz. Prochloraz has known effects on a number of key HPG molecules, including antagonism of Cyp17 and Cyp19 (aromatase). Twenty-eight proteins were shown to be differentially expressed in the brains of females and 22 in males. Proteins were identified using LC-MS/MS and identities were examined relative to brain function in the context of changing steroid hormone levels. There was little overlap between sexes in proteins exhibiting differential expression. Proteins with known roles in metabolism, learning, neuroprotection, and calcium regulation were determined to be differentially regulated. Relationships between identified proteins were also examined using Ingenuity Pathway Analysis, and females were shown to exhibit enrichment of several metabolic pathways. We used differentially expressed proteins to establish a putative classifier consisting of three proteins that was able to discriminate prochloraz-exposed from control females. Putatively impacted brain functions and specific protein changes that were observed have the potential to be generalized to other that similarly impact steroid hormone levels.

Linking protein oxidation to environmental pollutants: redox proteomic approaches

Environmental pollutants, such as compounds used in agriculture or deriving from vehicles, industries and human activities, can represent major concern for human health since they are considered to contribute significantly to many diseased states with major public health significance. Besides considerable epidemiological evidence linking environmental pollutants with adverse health effects, little information is provided on the effects of these compounds at the cellular and molecular level. Though oxidative stress is generally acknowledged as one of the most important mechanisms of action for pollutant-induced toxicity, redox proteomics, the elective tool to identify post-translationally oxidized proteins, is still in its very infancy in this field of investigation. This review will provide the readers with an outline of the use of redox proteomics in evaluating pollutant-induced oxidative damage to proteins in various biological systems. Future potential applications of redox proteomic approaches from an environmental point of view will be discussed as well.

A proteomic analysis of the effects of metal contamination on Sydney Rock Oyster (Saccostrea glomerata) haemolymph

The current study uses proteomics to assess the effects of metal contamination on Sydney Rock oyster haemolymph. Saccostrea glomerata were exposed in aquaria for four days to three environmentally relevant metals (copper, lead or zinc). Oyster haemolymph proteins from metal-exposed oysters were then compared to haemolymph from non-exposed controls using 2-dimensional electrophoresis to identify proteins that differed significantly in intensity. These proteins were then subjected to tandem mass spectrometry so that putative protein identities could be assigned. The data suggest that there are unique protein expression profiles for each metal. Exposure to 100 μg/l of copper, lead or zinc yielded a total of 25 differentially expressed proteins. However, only one of these protein spots exhibited altered intensities in response to all three metals. Eighteen of the 25 spots were significantly affected by just one of the three metals. Differentially expressed proteins were assigned to five different categories of biological function. Proteins affecting shell properties were the most common functional group accounting for 34% of the identified proteins. Cytoskeletal activities and metabolism/stress responses each accounted for a further 25% of the proteins.

Review of recent proteomic applications in aquatic toxicology

Over the last decade, the environmental sciences have witnessed an incredible movement towards the utilization of high-throughput molecular tools that are capable of detecting simultaneous changes of hundreds, and even thousands, of molecules and molecular components after exposure of organisms to different environmental stressors. These techniques have received a great deal of attention because they not only offer the potential to unravel novel mechanisms of physiological and toxic action but are also amenable to the discovery of biomarkers of exposure and effects. In this article, we review the state of knowledge of one of these tools in ecotoxicological research: proteomics. We summarize the state of proteomics research in fish, and follow with studies conducted with aquatic invertebrates. A brief discussion on proteomic methods is also presented. We conclude with some ideas for future proteomic studies with fish and aquatic invertebrates.

Liquid chromatography and mass spectrometry in food allergen detection

Food allergy is an important issue in the field of food safety because of the hazards for affected persons and the hygiene requirements and legal regulations imposed on the food industry. Consumer protection and law enforcement require suitable analytical techniques for the detection of allergens in foods. Immunological methods are currently preferred; however, confirmatory alternatives are needed. The determination of allergenic proteins by liquid chromatography and mass spectrometry has greatly advanced in recent years, and gel-free allergenomics is becoming a routinely used approach for the identification and quantitation of food allergens. The present review provides a brief overview of the principles of proteomic procedures, various chromatographic set ups, and mass spectrometry instrumentation used in allergenomics. A compendium of published liquid chromatography methods, proteomic analyses, typical marker peptides, and quantitative assays for 14 main allergy-causing foods is also included.

Application of mass spectrometry in the analysis of polybrominated diphenyl ethers

This review summarized the applications of mass spectrometric techniques for the analysis of the important flame retardants polybrominated diphenyl ethers (PBDEs) to understand the environmental sources, fate and toxicity of PBDEs that were briefly discussed to give a general idea for the need of analytical methodologies. Specific performance of various mass spectrometers hyphenated with, for example, gas chromatograph, liquid chromatograph, and inductively coupled plasma (GC/MS, LC/MS, and ICP/MS, respectively) for the analysis of PBDEs was compared with an objective to present the information on the evolution of MS techniques for determining PBDEs in environmental and human samples. GC/electron capture negative ionization quadrupole MS (GC/NCI qMS), GC/high resolution MS (GC/HRMS) and GC ion trap MS (GC/ITMS) are most commonly used MS techniques for the determination of PBDEs. New analytical technologies such as fast tandem GC/MS and LC/MS become available to improve analyses of higher PBDEs. The development and application of the tandem MS techniques have helped to understand environmental fate and transformations of PBDEs of which abiotic and biotic degradation of decaBDE is thought to be one major source of Br(1-9)BDEs present in the environment in addition to direct loading from commercial mixtures. MS-based proteomics will offer an insight into the molecular mechanisms of toxicity and potential developmental and neurotoxicity of PBDEs.

Proteins in ecotoxicology - how, why and why not?

The growing interest in the application of proteomic technologies to solve toxicology issues and its relevance in ecotoxicology research has resulted in the emergence of "ecotoxicoproteomics". There is a general consensus that ecotoxicoproteomics is a powerful tool to spot early molecular events involved in toxicant responses, which are responsible for the adverse effects observed at higher levels of biological organization, thus contributing to elucidate the mode of action of stressors and to identify specific biomarkers. Ultimately, early-warning indicators can then be developed and deployed in "in situ" bioassays and in environmental risk assessment. The number of field experiments or laboratory trials using ecologically relevant test-species and involving proteomics has been, until recently, insufficient to allow a critical analysis of the real benefits of the application of this approach to ecotoxicology. This article intends to present an overview on the applications of proteomics in the context of ecotoxicology, focusing mainly on the prospective research to be done in invertebrates. Although these represent around 95% of all animal species and in spite of the key structural and functional roles they play in ecosystems, proteomic research in invertebrates is still in an incipient stage. We will review applications of ecotoxicoproteomics by evaluating the technical methods employed, the organisms and the contexts studied, the advances achieved until now and lastly the limitations yet to overcome will be discussed.

Development of ecotoxicoproteomics on the freshwater amphipod Gammarus pulex: identification of PCB biomarkers in glycolysis and glutamate pathways

PCBs are persistent organic pollutants largely distributed in the biosphere. Although their effects on vertebrates are well described, little is known about their action on freshwater invertebrate's metabolism. Gammarus pulex (Linné) was selected as an indicator model to develop a proteomic approach in order to characterize the effects of PCBs on the protein profile of this freshwater crustacean. Sublethal coplanar PCBs exposition and related 2D gel were performed. More than 560 spots were detected and a total of 21 proteins exhibiting significant expression differences in PCB exposed to G. pulex were identified by mass spectrometry. Database searches were conducted to relate the results to well-known metabolic pathways (pentose phosphate, cytoskeleton, energy, etc.). In particular, glyceraldehyde 3-phosphate dehydrogenase and arginine kinase were found to be sensitive to the PCB exposition of G. pulex. The aim of the present study was to assess the biochemical responses and the metabolic changes in G. pulex following intoxication to coplanar PCB congeners CB77 and CB169 by a proteomic approach. This approach allowed us, by the identification of key proteins, to highlight important biochemical mechanisms disturbed by the presence of these contaminants in G. pulex.

Effects of zinc on molting and body weight of the estuarine crab Neohelice granulata (Brachyura: Varunidae)

The semiterrestrial burrowing crab Neohelice granulata is one of the main inhabitants of the supratidal and intertidal zones of brackish salt marshes, estuaries and coastal lagoons from South America's Atlantic littoral. A large population of this species spreads out Mar Chiquita coastal lagoon (in Argentina) and its corresponding wetlands, and is considered as a key species within this system. Since high values of dissolved heavy metals (including Zn) have been recently reported within Mar Chiquita coastal lagoon, with levels unusually higher than those from other coastal systems within Argentina, it has been explored that the existence of a risk of environmental conditions endanger these populations. So, juveniles of this estuarine crab were experimentally exposed to increasing concentrations of dissolved Zn (i.e., 0, 0.5 and 1 mg Zn(2+)L(-1)) during six months, the time involved between two successive molts; in addition, both the size and weight reached after each molt were also studied in this assay. It can be concluded that zinc can be toxic to crabs only at high concentrations. Considering that levels up to 1 mg ZnL(-1) were recently reported in Mar Chiquita coastal lagoon waters, the potential occurrence of mean chronic effects on the crab population within the coastal lagoon is discussed.

Proteomic studies in zebrafish liver cells exposed to the brominated flame retardants HBCD and TBBPA

Proteomic effect screening in zebrafish liver cells was performed to generate hypotheses regarding single and mixed exposure to the BFRs HBCD and TBBPA. Responses at sublethal exposure were analysed by two-dimensional gel electrophoresis followed by MALDI-TOF and FT-ICR protein identification. Mixing of HBCD and TBBPA at sublethal doses of individual substances seemed to increase toxicity. Proteomic analyses revealed distinct exposure-specific and overlapping responses suggesting novel mechanisms with regard to HBCD and TBBPA exposure. While distinct HBCD responses were related to decreased protein metabolism, TBBPA revealed effects related to protein folding and NADPH production. Overlapping responses suggest increased gluconeogenesis (GAPDH and aldolase) while distinct mixture effects suggest a pronounced NADPH production and changes in proteins related to cell cycle control (prohibitin and crk-like oncogene). We conclude that mixtures containing HBCD and TBBPA may result in unexpected effects highlighting proteomics as a sensitive tool for detecting and hypothesis generation of mixture effects.

Toxicity and physiological effects of brominated flame retardant PBDE-47 on two life stages of grass shrimp, Palaemonetes pugio

This study examined the effects of a polybrominated diphenyl ether (PBDE) compound, PBDE-47, on adult and larval stages of the estuarine grass shrimp (Palaemonetes pugio). The 96-h LC50 test resulted in an estimate of 23.60 microg/L (95% confidence interval=14.51-38.37 microg/L) for larval shrimp. Adult shrimp had a higher 96-h LC50 of 78.07 microg/L (95% CI=65.1-93.63 microg/L). Four physiological biomarkers glutathione (GSH), lipid peroxidation (LPx), cholesterol (CHL) and acetylcholinesterase (AChE) were then assessed to study the sublethal effects of PBDE-47 exposure. GSH, LPx and AChE levels in both adults and larvae were not affected by PBDE-47 at concentrations up to 50 microg/L for 96 h. CHL levels were elevated in adults and larvae at the lowest exposure concentrations tested, but significant differences were found only in adult exposures. Effects associated with PBDE-47 aqueous exposures were observed at levels well above those reported in the environment.

Proteomic applications in ecotoxicology

Within the growing body of proteomics studies, issues addressing problems of ecotoxicology are on the rise. Generally speaking, ecotoxicology uses quantitative expression changes of distinct proteins known to be involved in toxicological responses as biomarkers. Unlike these directed approaches, proteomics examines how multiple expression changes are associated with a contamination that is suspected to be detrimental. Consequently, proteins involved in toxicological responses that have not been described previously may be revealed. Following identification of key proteins indicating exposure or effect, proteomics can potentially be employed in environmental risk assessment. To this end, bioinformatics may unveil protein patterns specific to an environmental stress that would constitute a classifier able to distinguish an exposure from a control state. The combined use of sets of marker proteins associated with a given pollution impact may prove to be more reliable, as they are based not only on a few unique markers which are measured independently, but reflect the complexity of a toxicological response. Such a proteomic pattern might also integrate some of the already established biomarkers of environmental toxicity. Proteomics applications in ecotoxicology may also comprise functional examination of known classes of proteins, such as glutathione transferases or metallothioneins, to elucidate their toxicological responses.

Mass spectral profiling: an effective tool for quality control of herbal medicines

Quality control of herbal medicines (HMs) is a big big headache because of the high complexity and unknown mechanism on disease treatment. In this work, mass spectral profiling, a new tool for data processing is proposed to help a lot in solving this problem as gas chromatography-mass spectroscopy (GC-MS) is used to detect both the active and non-active ingredients buried in HMs. The main idea of mass spectral profiling is employment of target m/z points of GC-MS data on the extraction of chromatographic profiles of pure and/or mixed compositions concerned. Further, the absolute or relative abundance at these m/z points can be utilized for results interpretation. With the help of this tool, the qualitative and quantitative information of chemical components within complicated HMs will be mined out effectively. It can then be recommended as reference indices to assess the importance of target compositions in HMs, such as efficacy evaluation on disease treatment of the active constituents. Mass spectral profiling with less data points significantly improves the possibility to get the rich information with no strong requirements of data preprocessing procedures, like alignment of shift of retention times among different chromatographic profiles. It is powerful for quality control of HMs coupled with pattern recognition techniques on high-throughput data sets. In this study, a commonly used herbal medicine, Houttuynia cordata Thunb and its finished injection products, were used to deliver the strategies. Absolutely, the working principles can be extended to the investigation of metabonomics with gas chromatography-time-of-flight-mass spectrometry (GC-MS-TOF). The good performance of mass spectral profiling shows that it can be a promising tool in the future studies of complex mixture systems.

The potential of proteomics for providing new insights into environmental impacts on human health

The effects of environmental chemicals have traditionally been detected by monitoring biomarkers of exposure or biomarkers of effect. Proteomics, the study of the complete profile of proteins in a given cell, tissue or biological system, is a new approach using a set of high-throughput methodologies with a wide dynamic range that makes possible the discovery of novel biomarkers. This article reviews the application of two-dimensional electrophoresis and mass-spectrometry methods to environmental toxicology. Emphasis is placed on the protein-expression signature approach and on identifying redox-based post-translational protein modifications. The methodological links between studies in sentinel organisms and humans are explored. Significant limitations and challenges are placed on this approach by the shortage of genome sequence data necessary for protein identification and the growing requirement for more stringent study design. Proteomics will continue to be an important toolkit to help address the growing environmental threat posed by nanoparticles and endocrine disrupting agents.

Data processing and classification analysis of proteomic changes: a case study of oil pollution in the mussel, Mytilus edulis

BACKGROUND

Proteomics may help to detect subtle pollution-related changes, such as responses to mixture pollution at low concentrations, where clear signs of toxicity are absent. The challenges associated with the analysis of large-scale multivariate proteomic datasets have been widely discussed in medical research and biomarker discovery. This concept has been introduced to ecotoxicology only recently, so data processing and classification analysis need to be refined before they can be readily applied in biomarker discovery and monitoring studies.

RESULTS

Data sets obtained from a case study of oil pollution in the Blue mussel were investigated for differential protein expression by retentate chromatography-mass spectrometry and decision tree classification. Different tissues and different settings were used to evaluate classifiers towards their discriminatory power. It was found that, due the intrinsic variability of the data sets, reliable classification of unknown samples could only be achieved on a broad statistical basis (n > 60) with the observed expression changes comprising high statistical significance and sufficient amplitude. The application of stringent criteria to guard against overfitting of the models eventually allowed satisfactory classification for only one of the investigated data sets and settings.

CONCLUSION

Machine learning techniques provide a promising approach to process and extract informative expression signatures from high-dimensional mass-spectrometry data. Even though characterisation of the proteins forming the expression signatures would be ideal, knowledge of the specific proteins is not mandatory for effective class discrimination. This may constitute a new biomarker approach in ecotoxicology, where working with organisms, which do not have sequenced genomes render protein identification by database searching problematic. However, data processing has to be critically evaluated and statistical constraints have to be considered before supervised classification algorithms are employed.