Oxidative and modulatory effects of trace metals on metabolism of polycyclic aromatic hydrocarbons in the Antarctic fish Trematomus bernacchii

Combined effect of dietary cadmium and benzo(a)pyrene on metallothionein induction and apoptosis in the liver and kidneys of bank voles

Bank voles free living in a contaminated environment have been shown to be more sensitive to cadmium (Cd) toxicity than the rodents exposed to Cd under laboratory conditions. The objective of this study was to find out whether benzo(a)pyrene (BaP), a common environmental co-contaminant, increases Cd toxicity through inhibition of metallothionein (MT) synthesis-a low molecular weight protein that is considered to be primary intracellular component of the protective mechanism. For 6 weeks, the female bank voles were provided with diet containing Cd [less than 0.1 μg/g (control) and 60 μg/g dry wt.] and BaP (0, 5, and 10 μg/g dry wt.) alone or in combination. At the end of exposure period, apoptosis and analyses of MT, Cd, and zinc (Zn) in the liver and kidneys were carried out. Dietary BaP 5 μg/g did not affect but BaP 10 μg/g potentiated rather than inhibited induction of hepatic and renal MT by Cd, and diminished Cd-induced apoptosis in both organs. The hepatic and renal Zn followed a pattern similar to that of MT, attaining the highest level in the Cd + BaP 10-μg/g group. These data indicate that dietary BaP attenuates rather than exacerbates Cd toxicity in bank voles, probably by potentiating MT synthesis and increasing Zn concentration in the liver and kidneys.

A multibiomarker approach in juvenile turbot, Scophthalmus maximus, exposed to contaminated sediments

Juvenile turbot were exposed in laboratory conditions to a mixture of chemical contaminants associated with harbour and estuarine sediments for seven and 21 days. Several molecular biomarkers of exposure were then measured in fish liver: two biotransformation parameters [ethoxyresorufin-O-deethylase (EROD) and phase II glutathione S-transferase (GST) activities] and an antioxidant enzyme activity [catalase (CAT)]. Modifications at the histological level were analysed by the measurement of the number and size of melanomacrophage centres (MMCs) and disturbances to the immune function by the measurement of cytokine transforming growth factor-beta (TGF-β) and development of the thymus. The responses of these molecular and immunological biomarkers were correlated with metal and PAH concentrations measured in sediments and with the physiological performance of turbot analysed in a previous study on the same fish (growth rates, condition factor K, RNA:DNA ratio and lipid index). While no difference was found in thymus analysis, some molecular and immunological responses were observed in fish exposed to contaminated sediments. Weak relationships between molecular biomarkers' responses and PAH concentrations were recorded, while their responses were significantly correlated with some metals. MMC and aggregates were weakly related to chemical contaminants whereas some significant correlations were found between TGF-b1 responses and some metal concentrations. However, molecular and immunological biomarkers were weakly related to fish physiological damages since low responses were observed in the condition which led to the lowest growth and condition indices. These data suggest the complexity of cause-effect relationships between exposure to pollutants, metabolisms and health damages. Precautions should be considered in the use of molecular and immunological biomarkers alone in biomonitoring programs. Their complementary use with physiological biomarkers, such as fish growth and condition indices, could improve their utilisation.

Comparative study on metal homeostasis and detoxification in two Antarctic teleosts

The main characteristic of Antarctic seawater is its low constant temperature and its high concentration of O(2), which can increase the formation rate of reactive oxygen species (ROS), together with a natural occurrence of elevated cadmium and copper levels. In the present paper, we studied the presence of cadmium, copper and zinc, metallothioneins (MTs) and glutathione (GSH), and antioxidant enzyme activities in the Antarctic teleosts Trematomus bernacchii and Trematomus newnesi, in order to determine the influence of the peculiar physico-chemical features of the Antarctic marine environment on these physiological defence systems in two species of teleosts. In both of them, cadmium and copper accumulation occurs mostly in the liver. T. bernacchii accumulates zinc mostly in the hepatic tissue, whereas T. newnesi does not show a preferential accumulation site. In addition to the intra-specific analysis, we decided to compare the two species of the Trematomus genus in order to verify if the different feeding habits and motility of these fish affects metal accumulation. Our results show that the liver of T. bernacchii accumulates cadmium and zinc at a higher extent with respect to T. newnesi. Glutathione (GSH) and metallothioneins (MTs) are present in great quantity in the liver of both species. Moreover liver is the tissue which generally showed the highest antioxidant enzyme levels. The results provide further insights in the physiological mechanisms evolved by animals living in this extreme environment.

A multidisciplinary weight of evidence approach for classifying polluted sediments: Integrating sediment chemistry, bioavailability, biomarkers responses and bioassays

Evaluation of chemical bioavailability and onset of biological alterations is fundamental to assess the hazard of environmental pollutants, particularly when associated to sediments which need to be removed. In the present work, five sediment samples were collected from the Venice Lagoon and data from sediment chemistry were integrated with those of bioaccumulation of chemicals in European eel (Anguilla anguilla) exposed under laboratory conditions, responses of a wide battery of biomarkers, and standardized ecotoxicological bioassays. The overall results were elaborated within a recently developed, software-assisted weight of evidence (WOE) model which provides synthetic indices for each of considered line of evidence (LOE), before a general evaluation of sediment hazard. Levels of chemicals in sediments were not particularly elevated when compared to sediment quality guidelines of Venice Protocol. On the other hand, bioavailability was evident in some samples for Cd, Cu, Zn and, especially, polycyclic aromatic hydrocarbons. The ecotoxicological approach provided further evidence on the biological and potentially harmful effects due to released contaminants, and oxidative-mediated responses appeared of primary importance in modulating sublethal responses and the onset of cellular alterations. Biomarkers variations were sensitive, and more evident variations included significant changes of cytochrome P450 biotransformation pathway, antioxidant responses, onset of oxidative damages, lysosomal membrane stability and genotoxic effects. The results obtained from the battery of bioassays indicated that responses measured at organism level were in general accordance but less marked compared to the onset of sublethal changes measured through biomarkers. Overall this study revealed differences when comparing evaluations obtained from different LOEs, confirming the importance of considering synergistic effects between chemicals in complex mixtures. Compared to a qualitative pass-fail approach toward normative values, the proposed WOE model allowed a quantitative characterization of sediment hazard and a better discrimination of on the basis of various types of chemical and biological data.

Molecular and biochemical biomarkers in environmental monitoring: a comparison of biotransformation and antioxidant defense systems in multiple tissues

The cytochrome P450 pathway and antioxidant responses are known for their responsiveness to environmental pollutants and are frequently used as biomarkers at the transcriptional, translational and catalytic levels. Although molecular responses are often assumed to reflect similar changes in enzyme function, several factors can influence intracellular effects, including mRNA stability and protein turnover, signal sensing and transduction, post-translational modifications of proteins, and multiple mode of action of chemicals in complex mixtures. The aim of this study was to use experimental data for a general discussion on the importance of mechanisms modulating transcriptional and catalytic responses of these pathways, and the resulting implications for environmental monitoring. The European eel Anguilla anguilla was selected as fish model to compare the effects of polluted sediments on gene expression and functional levels of cytochrome P450, glutathione S-transferases, UDP-glucoronosyl transferases, catalase, glutathione peroxidases, superoxide dismutase, glutathione, glutathione reductase, glucose 6-phosphate dehydrogenase and γ-glutamylcysteine ligase in the liver and gills. The overall results confirmed significant changes in gene transcription related to biotransformation and oxyradical metabolism, but also supported the evidence of a frequent dissociation between mRNA expression and protein activity. More similar trends of variations and exposure-dependent relationships was observed in the liver for transcriptional and catalytic responses of those pathways closely regulated by specific interactions between substrate, transcription factors, gene and metabolizing protein (i.e. phase I and phase II). On the other hand, the lower metabolism and the cellular machinery of gill cells may prevent elevated transcriptional responsiveness to be translated to an adequate functional response of a protein. Relationships between transcriptional and catalytic effects were often inconsistent for antioxidant responses confirming the complexity of interactions between exposure to chemical pollutants and regulation of oxidative stress responses. Oxidative stress responses may not necessarily be associated with transcriptional variations of genes, but rather with post-translational modifications of proteins. These mechanisms are just beginning to be revealed in marine organisms, but their characterization will be fundamental for better understanding of the implications of variations in gene expressions according to system, tissue, intensity and duration of exposure.

Gasoline effects on biotransformation and antioxidant defenses of the freshwater fish Prochilodus lineatus

Biochemical biomarkers in the Neotropical freshwater fish Prochilodus lineatus were evaluated following acute exposures to the water-soluble fraction of gasoline (WSFG). Fish were exposed to the WSFG diluted to 5% in water (WSFG group) or only to water (Control group) for 6, 24 and 96 h and the gills and liver were removed for the biochemical analyses. Fish exposed to WSFG for 24 and 96 h showed significant increase in the activity of 7-ethoxyresorufin-O-deethylase (EROD) and glutathione-S-transferase (GST) both in liver and gills, pointing toward phase I and phase II biotransformation of the compounds present in the WSFG. The results also indicated the activation of antioxidant defenses in both the liver and gills after fish exposure to WSFG. The liver showed activation of catalase (CAT) and glutathione peroxidase (GPx) after 96 h exposure. An increase in hepatic content of reduced glutathione (GSH) together with decreased glutathione reductase (GR) activity was observed after 24 and 96 h of exposure to WSFG. In the gills, only catalase (CAT) activity augmented after 6 and 24 h of exposure and GSH content increased after 24 h of WSFG exposure. However, in both the organs, activation of the antioxidant defenses was not enough to prevent oxidative damage since they showed lipid peroxidation (LPO) at one of the experimental times: the liver after 6 h and the gills only after 96 h of exposure to WSFG. This may indicate better adaptation of the liver to longer exposures, starting from 24 h. As the gills are the first organ to be exposed to xenobiotics, the antioxidant defenses were triggered immediately upon exposure to WSFG and were able to prevent the occurrence of LPO during the initial times.

Effects of soil polycyclic musk and cadmium on pollutant uptake and biochemical responses of wheat (Triticum aestivum)

The single and joint toxicological effects of AHTN and cadmium (Cd) on early developmental stages of wheat, including AHTN and Cd uptake, chlorophyll (CHL), malondialdehyde (MDA), superoxide dismutase (SOD), and peroxidase (POD) contents in the seedlings, were investigated. Uptake of AHTN or Cd by seedlings increased with an increase in the concentrations of AHTN and Cd in soil. The presence of Cd inhibited the uptake of AHTN in wheat seedlings, while the low concentration of AHTN could induce the uptake of Cd. The biosynthesis of CHL was significantly inhibited by single AHTN and joint stress with AHTN and Cd. The MDA contents in wheat leaves and roots were significantly affected by single and joint stress with AHTN and Cd. SOD and POD activities in leaves was significantly induced by AHTN and Cd. However, the effect of AHTN and Cd on SOD and POD activities in roots was insignificant. This might indicate that wheat leaves were more sensitive to the binary mixture than wheat roots.

Seasonal baseline levels of physiological and biochemical parameters in polar cod (Boreogadus saida): Implications for environmental monitoring

Seasonality of biomarker baseline levels were studied in polar cod (Boreogadus saida), caught in Kongsfjorden, Svalbard, in April, July, September and December, 2006-2007. Physiological parameters (condition factor, gonado- and hepato-somatic indexes, energy reserves, potential metabolic activity and antifreeze activity) in polar cod were used to interpret the seasonality of potential biomarkers. The highest levels of ethoxyresorufin-O-deethylase (EROD) activity occurred concomitantly with the highest potential metabolic activity in July due to e.g. intense feeding. During pre-spawning, EROD showed significant inhibition and gender differences. Hence, its potential use in environmental monitoring should imply gender differentiation at least during this period. Glutathione S-transferase and catalase activities were stable from April to September, but changed in December suggesting a link to low biological activity. Knowledge of the biomarker baseline levels and their seasonal trends in polar cod is essential for a trustworthy interpretation of forthcoming toxicity data and environmental monitoring in the Arctic.

Identification of five partial ABC genes in the liver of the Antarctic fish Trematomus bernacchii and sensitivity of ABCB1 and ABCC2 to Cd exposure

Several ABC transporters have been characterized from many aquatic organisms, but no information is yet available for Antarctic fish. The aim of this work was to identify the expression of genes for ABC proteins in Trematomus bernacchii, a bioindicator species of the Southern Ocean. Partial cDNA sequences of ABCB1, ABCC1, ABCC2, ABCC4 and ABCC9 were cloned from liver. Using RACE technology, 3.5 and 2.2 kb contigs were obtained for ABCB1 and ABCC2. Considering the elevated natural bioavailability of cadmium at Terra Nova Bay, responsiveness of ABCB1 and ABCC2 to this element was investigated under laboratory conditions. ABCB1 and ABCC2 mRNA levels were approximately four-fold higher in Cd-exposed fish compared to the controls. Induction of ABCB1 protein was also found by western blot. This study provides the first identification of five ABC genes in the liver of an Antarctic key species, some of which may be involved in cellular detoxification.

Acute toxicity study of the interaction between titanium dioxide nanoparticles and lead acetate in mice

Titanium dioxide (TiO(2)) is one kind of widely used nanoparticle, which was used as a solid-phase extraction to preconcentrated and measured of lead (Pb) in river water and seawater. However the interaction of nanoparticle TiO(2) and Pb was unknown. The aim of this study is to investigate the potential acute toxicity of the interaction between nanoparticle TiO(2) (50 and 120nm) and lead acetate (PbAC) in adult mice. The animals were randomly divided into six groups: a control group and five treatment groups (TiO(2)-50, TiO(2)-120, PbAC, TiO(2)-50+PbAC and TiO(2)-120+PbAC groups). Suspensions of TiO(2) (5g/kg body weight), PbAC (500mg/kg body weigh) and TiO(2) (5g/kg body weight)+PbAC (500mg/kg body weigh) were administrated to mice via oral gavage, respectively. Seven days later, the animals were sacrificed after being anesthetized by ether. There were no significant changes of the body weight coefficients of liver, kidney and brain. However, the results of liver function and nephrotoxicity examination revealed that there were serious damages to liver and kidney between the group treated with the mix suspension and the one with TiO(2). After the mix suspension treatment, ROS levels were significantly increased in liver but not in kidney, cortex and hippocampus. There were no increase of MDA levels in these tissues, and no activity reductions of SOD and GSH-Px in liver and kidney but in the cortex and hippocampus. Therefore, though our results have not suggested that TiO(2) particle and PbAC have a synergistic acute toxicity in mice after oral administration, PbAC may increase the acute toxicity of TiO(2) nanoparticle in some degree. The potential toxic mechanism maybe related with oxidative damages.

Biomarker responses in the bivalve (Chlamys farreri) to exposure of the environmentally relevant concentrations of lead, mercury, copper

Water samples collected from Bohai Bay were determined to describe the distributions of lead, mercury, and copper in this area, indicating that mean values of the three metals were 1.63μg/L, 4.85×10(-2)μg/L, and 2.68μg/L, respectively. Only lead exceeded the first class limit of seawater quality standard in China. Then, antioxidant enzymes, lipid peroxidation, and metabolic enzymes were investigated in bivalves (Chlamys farreri), exposed to three metals at the environmental concentration levels obtained from our investigation. Significantly reduced SOD, CAT and GPx activities, in lead-exposed group were observed and resulted in obvious lipid peroxidation. In contrast, mercury and copper did not show such clear oxidative stresses. In consistent with the oxidative stress variations, exposed only to lead caused a great inhibition on EROD activity. Multi-biomarker responses in bivalve when exposed to lead at the environmentally relevant concentration in Bohai Bay suggested that lead may possess a potential risk in this area.

Concentrations of cadmium and zinc in seawater of Bohai Bay and their effects on biomarker responses in the bivalve Chlamys farreri

Both in-field chemical investigation and in the laboratory toxic tests were carried out to systematically understand the pollution status of cadmium (Cd) and zinc (Zn) in Bohai Bay. Samples collected from surface seawater were determined to describe the distributions of Cd and Zn in Bohai Bay. The average values in our study of Cd and Zn were 0.15 microg/L and 19.68 microg/L, respectively. Both of them were lower than the first class limit of seawater quality standard in China. In the laboratory, antioxidant enzymes [SOD (Cu/Zn-SOD, Mn-SOD), CAT], lipid peroxidation (MDA), phase I and phase II enzymes (CYP4501A and GST) were investigated in the bivalves Chlamys farreri exposed to Cd and Zn at the concentration levels of Bohai Bay seawater, which were obtained from our in-field investigation. The reduced SOD, CAT, and EROD (7-ethoxyresorufin-O-deethylase) activities (with the inhibitory rate of 16.8%, 31.5%, and 51.6%, respectively) in Cd treatment were observed and resulted in obvious lipid peroxidation damage. However, treatment of Zn showed elevations in SOD and GST by 13.3% and 29.9%, respectively, and with no influence on lipid peroxidation. In summary, seawater quality in Bohai Bay seawater was ranked as good in general, but it seemed that Cd might possess a potential environmental risk by effecting pro-oxidant/antioxidant balance and phase I detoxification in C. farreri.

Biomarker responses in polar cod (Boreogadus saida) exposed to the water soluble fraction of crude oil

In order to mimic the biological effects of an oil spill in Arctic waters, we examined several types of biomarkers (genes, enzymes, metabolites, and DNA damage) in polar cod Boreogadus saida experimentally exposed to the water soluble fractions of crude oil. During 4 weeks of exposure, induction of the studied biomarkers exceeded baseline levels. The mRNA expression of the cytochrome P4501A1 (cyp1a1) gene was the most promising biomarker, with glutathione S-transferase (gst) as a suitable complement. The delayed ethoxyresorufin O-deethylase (EROD) and GST activities and their persistence following 2 weeks of depuration may allow detection of previous exposures in field samples. The composition of PAH metabolites in the bile indicated the bioavailability of different PAH size-classes. Although mRNA expressions of antioxidant defense genes were induced at start of the exposure, with the strongest responses from catalase and cytosolic superoxide dismutase, they were poor for oil monitoring purposes due to their very short response times. Significant DNA damage demonstrated genotoxicity even at low PAH concentrations (<15microgL(-1)) and was correlated with benzo(a)pyrene and pyrene metabolites in the bile.

Mixture toxicity assessment of cadmium and benzo[a]pyrene in the sea worm Hediste diversicolor

In the present study, Hediste diversicolor biotransformation and anti-oxidant responses to acute exposure to cadmium (Cd) and to the polycyclic aromatic hydrocarbons benzo[a]pyrene (B[a]P) were investigated. Worms were submitted to 0.2, 0.4 and 1 microM of each contaminant and to their mixture during a period of test of 48h. Following biological responses were measured: (1) NADPH cytochrome c reductase (NADPH cyt c) activity, as phase I biotransformation parameter; (2) gluthathione-S-transferase (GST) activity as a phase II conjugation enzyme, (3) catalase activity as anti-oxidant response and (4) malondialdehyde accumulation (MDA) as lipid peroxydation marker. The cholinergic system was evaluated using the acetylcholinesterase activity (AChE). Exposure to the mixture resulted in low dose level additive effects on the investigated biomarkers. However, worms exposed to 1 microM of the single compounds and to their mixture exhibited the highest MDA accumulation and the lowest enzymatic biomarkers activities suggesting severe toxicological effects. These data should be carefully considered in view of the biological effects of mixture pollutants and particularly in marine sediment ecosystems.

Biological effects of diethylene glycol (DEG) and produced waters (PWs) released from offshore activities: a multi-biomarker approach with the sea bass Dicentrarchus labrax

Diethylene glycol (DEG) is largely used during oil and gas exploitation by offshore platforms. The aim of this work was to investigate if this compound induces direct molecular/cellular effects in marine organisms, or indirectly modulate those of produced waters (PWs). Sea bass (Dicentrarchus labrax) were exposed to DEG dosed alone or in combination with PWs from an Adriatic platform. A wide array of analysed biomarkers included cytochrome P450-dependent enzymatic activity, bile metabolites, glutathione S-transferases, acetylcholinesterase, peroxisomal proliferation, antioxidant defences (catalase, glutathione reductase, glutathione peroxidases, glutathione), total oxyradical scavenging capacity, malondialdehyde and DNA integrity (single strand breaks and frequency of micronuclei). Results did not reveal marked effects of DEG, while PWs influenced the biotransformation system, the oxidative status and the onset of genotoxic damages. Co-exposures caused only limited differences of biomarker responses at some experimental conditions, overall suggesting a limited biological impact of DEG at levels normally deriving from offshore activities.

Contaminant effects in shore crabs (Carcinus maenas) from Ria Formosa Lagoon

Defence and damage biomarkers signals were studied in female and male shore crabs Carcinus maenas transplanted between two sites at Ria Formosa Lagoon (South of Portugal). The cross transplantation occurred during 6 days at a hypothetical reference site (Ramalhete), and a contaminated site (Olhão). DNA unwinding technique was used for DNA integrity measurement. General enzymatic antioxidant responses in gills and hepatopancreas (catalase and gills glutathione peroxidase activities increase) showed that cross transplanted crabs (female and male) are suffering from pro-oxidant challenges at the Olhão site. Gills and hepatopancreas glutathione-S-transferase were reduced in both gender crabs transplanted from Ramalhete to Olhão. Metallothioneins induction occurred in crabs transplanted from Ramalhete to Olhão (contaminated by metals and polycyclic aromatic hydrocarbons (PAHs)). However metallothionein differences were also observed towards gender and organ specificities. High gills lipid peroxidation exist in male crabs transplanted from Ramalhete to Olhão, while in females it was the opposite. In both gender crabs from the Olhão site, gills DNA integrity decreased compared to the Ramalhete feral crabs. Moreover, hepatopancreas DNA integrity decreased in male crabs transplanted from Olhão to Ramalhete site which may be related to the environmental conditions (lower contamination levels) revealing the difficulty of selection of reference sites in field studies. Data demonstrated that female and male C. maenas antioxidant defences and damage biomarkers were sensitive to the mixture of contaminants present in these sites as well as good indicators of general stress.