Anguilla anguilla L. oxidative stress biomarkers responses to copper exposure with or without beta-naphthoflavone pre-exposure

Tissue Accumulation, Cytotoxicity, Oxidative Stress, and Immunotoxicity in African Catfish, Clarias gariepinus Exposed to Sublethal Concentrations of Hexavalent Chromium

Hexavalent chromium (Cr6+) is one of the stable oxidation states of chromium that has been reported to elicit various toxic effects in aquatic organisms. However, the mechanisms of Cr6+ toxicity are still poorly understood. Thus, the present study investigated the tissue accumulation, cytotoxic, oxidative stress, and immunotoxic effects of Cr6+ in juvenile Clarias gariepinus. The fish were exposed to waterborne Cr6+ concentrations (0, 0.42, 0.84, and 1.68 mg/L) for 28 days, after which they were sacrificed and various organs were harvested for the determination of Cr6+ levels. Other parameters that were indicators of oxidative stress, cytotoxicity, and immunotoxicity were measured. Cr6+ accumulated more in the kidney and liver of the exposed fish, especially at the highest concentration. The levels of lipid peroxidation and DNA fragmentation increased significantly in the exposed fish. The activities of superoxide dismutase and lactate dehydrogenase increased significantly in exposed fish compared to the control. The total white blood cells, lymphocytes, and neutrophils counts were significantly higher in the exposed fish compared to the control fish. The respiratory burst activity decreased significantly in the exposed fish while the myeloperoxidase content did not differ significantly. There were upregulations of TNF-α and HSP 70 while CYP II and MHC 2 were downregulated in the exposed fish. Also, exposure to Cr6+ resulted in various histopathological alterations in the architecture of the head kidney. The results indicate concentration-dependent toxic effects of Cr6+ in C. gariepinus. The study reveals the potentials of Cr6+ to accumulate in the different tissues of fish and caused cytotoxic, oxidative stress, and immunotoxic effects in the exposed fish.

Copper and nanocopper toxicity using integrated biomarker response in Pangasianodon hypophthalmus

The current study focused on assessing the toxicological effects of copper (Cu) and copper nanoparticles (Cu-NPs) in acute condition on Pangasianodon hypophthalmus. The median lethal concentration (LC50 ) for Cu and Cu-NPs were determined as 8.04 and 3.85 mg L-1 , respectively. For the subsequent definitive test, varying concentrations were selected: 7.0, 7.5, 8.0, 8.5, and 9.0 mg L-1 for Cu, and 3.0, 3.3, 3.6, 3.9, and 4.2 mg L-1 for Cu-NPs. To encompass these concentration levels and assess their toxic effects, biomarkers associated with toxicological studies like oxidative stress, neurotransmission, and cellular metabolism were measured in the liver, kidney, and gill tissues. Notably, during the acute test, the activities of catalase, superoxide dismutase, glutathione-s-transferase, glutathione peroxidase, and lipid peroxide in the liver, gill, and kidney tissues were significantly increased due to exposure to Cu and Cu-NPs. Similarly, acetylcholinesterase activity in the brain was notably inhibited in the presence of Cu and Cu-NPs when compared to the control group. Cellular metabolic stress was greatly influenced by the exposure to Cu and Cu-NPs, evident from the considerable elevation of cortisol, HSP 70, and blood glucose levels in the treated groups. Furthermore, integrated biomarker response, genotoxicity, DNA damage in gill tissue, karyotyping in kidney tissue, and histopathology in gill and liver were investigated, revealing tissue damage attributed to exposure to Cu and Cu-NPs. In conclusion, this study determined that elevated concentrations of essential trace elements, namely Cu and Cu-NPs, induce toxicity and disrupt cellular metabolic activities in fish.

Impacts of aqueous extracts of wildfire ashes on aquatic life-stages of Xenopus laevis: Influence of plant coverage

Wildfires have emerged as a global ecological concern due to their wide-ranging off-site effects. One particular consequence is the adverse impact on aquatic environments, as wildfires are acknowledged as a significant source of aquatic contamination through ash runoffs containing toxic compounds. Yet, amphibian response to this source of contamination remains largely undocumented. This study assessed how ash runoffs from Eucalyptus sp. and Pinus sp. affect early aquatic life-stages of Xenopus laevis. Embryos and tadpoles were exposed, respectively, for 96 h and 14 days to serial concentrations (26.9% - 100%) of aqueous extracts of ashes (AEAs; 10 gL-1) composed of eucalypt (ELS) and pine (PLS) ashes. Mortality and development were monitored, and biometric data (snout-to-vent, tail and total length, and weight) measured. Sub-individual endpoints regarding oxidative stress (catalase-CAT; total glutathione-TG; lipid peroxidation-TBARS), neurotoxicity (acetylcholinesterase-AChE), transformation metabolism (glutathione-S-transferase-GST) and energetic metabolism (carbohydrate, lipid and protein content and O2 consumption), were also measured. The two AEAs induced no significant lethal effects on embryos or tadpoles. However, in general, AEAs caused a developmental delay in both life stages. Effects of AEAs on biometric endpoint were only reported for tadpoles, which showed a decreased body length (snout-to-vent, tail and total) and weight (embryos were not weighed), with PLS exerting higher effect than ELS. As for the sub-individual endpoints, embryos showed mostly no alterations on the activity of the monitored parameters, except for PLS, which reduced embryos' carbohydrate content (at ≥59.2%) and increased O2 consumption (at ≥35.0%). Regarding tadpoles, AEA exposure decreased the activity of CAT and GST (at ≥26.0%) and decreased carbohydrate (at ≥26.0%) and lipid (at ≥45.5%), whereas oxygen consumption increased (at ≥26.0%) only on PLS. Overall, the tested AEAs differentially affected amphibians across life-stages, indicating that plant coverage might affect ash toxicity.

Responses of oxidative stress biomarkers of freshwater fish (Oreochromis niloticus) exposed to Cr6+, Hg2+, Ni2+ and Zn2+ in differing calcium levels

Freshwaters from different geographical locations show different hardness, affecting metal uptake and toxicity in fish. The most important ion that determines water hardness is calcium. In this study, acute and chronic effects of metals on the oxidative stress biomarkers in the liver of freshwater fish (Oreochromis niloticus) were investigated in differing Ca²⁺ (30, 60 and 120 mg Ca²⁺/L) levels. Fish were exposed to Cr⁶⁺, Ni²⁺ and Zn²⁺ (30 μM) and Hg²⁺ (0.3 μM) for 3 days in acute experiments, while they were exposed to Cr⁶⁺, Ni²⁺ and Zn⁺² (10 μM) and Hg²⁺ 0.03 μM) for 30 days in chronic experiments. Data showed that the oxidative stress biomarkers significantly (p < 0.05) altered after metal exposures at all calcium levels, though there was no significant change (p > 0.05) among calcium controls. In both acute and chronic exposures, catalase CAT) and superoxide dismutase (SOD) activities increased significantly, while glutathione peroxidase (GPX), glutathione reductase (GR) and glutathione S-transferase (GST) activities decreased. There were significant decreases in total glutathione (GSH) levels in acute exposures, though GSH levels increased in chronic exposures. Malondialdehyde (MDA) levels significantly increased in both durations. The highest significant alterations in the biomarkers occurred at the lowest Ca²⁺ levels. GPX and GST were found to be the most sensitive enzymes in all exposures and the least alterations in biomarker response occurred in fish exposed to Ni²⁺. This study demonstrated that calcium levels (hardness) were important factors in the evaluation of metal toxicity for freshwater fish.

Ecotoxicological evaluation of water from the Sorocaba River using an integrated analysis of biochemical and morphological biomarkers in bullfrog tadpoles, Lithobates catesbeianus ()

Lithobates catesbeianus tadpoles were exposed for 96 h to water from two sites of the Sorocaba River (summer and winter), Ibiúna (PI) and Itupararanga reservoir (PIR) that contained metals. In the liver, in PI, the glutathione peroxidase (GPx) decreased, and the glutathione S-transferase (GST) and carbonyl proteins (PCO) increased. In PIR, the glutathione reduced (GSH) increased, while there was a decrease in catalase (CAT), GPx, GST, PCO, and superoxide dismutase (SOD). In winter, GPx and GST increased in both points. Regarding the kidneys, lipoperoxidation (LPO) levels and GST decreased, while GSH increased in the summer. In the winter, LPO increased in PI. In the muscle, in the summer, there was an increase in GSH and GST and change in PCO. In the winter, the levels of PCO increased and CAT decreased in PIR. The area and volume of the hepatocyte and nucleus area increased in the summer and decreased in the winter. Hepatic melanin decreased in the summer after exposure to PIR water. There were the systemic effects of Sorocaba River water exposure at different times of the year with alterations in biomarkers at different levels, in which kidney shows highest Integrated Response of Biomarkers (IBR) value followed by liver and muscle. Biochemical biomarkers were more sensitive than morphological ones. The more sensitive biochemical markers were MT, PCO, GST and LPO. These effects confirm the hypothesis of metabolic alteration in bullfrog tadpoles by the Sorocaba River water.

Metabolite profiling, histological and oxidative stress responses in the grey mullet, Mugil cephalus exposed to the environmentally relevant concentrations of the heavy metal, Pb (NO3)2

In this study, a metabolomics approach was applied to investigate the metabolic responses of grey mullet, Mugil cephalus to toxicity induced by heavy metal, Pb (NO3)₂. In addition, the study was followed by assessing the peroxidation index and histology of liver as supplementary data. Pb (NO3)₂ exposure affected the plasma metabolome, especially four group metabolites including amino acids, methylated metabolites, energetic metabolites and citric acid intermediates. Pb (NO3)₂ in medium and high concentrations (15 and 25 μg/l) increased the levels of plasma amino acids compared to control (P < 0.01). In contrast, Pb (NO3)₂ decreased the plasma levels of methylated metabolites (P < 0.01). The ketogenic metabolites and glycerol levels significantly elevated in fish exposed to 25 μg/l Pb (NO3)₂ (P < 0.01). The plasma glucose levels increased in treatment, 5 μg/l Pb (NO3)₂ and after a decline in treatment 15 μg/l Pb (NO3)₂ elevated again in treatment 25 μg/l Pb (NO3)₂ (P < 0.01).The plasma levels of lactate significantly increased in fish exposed to 5 and 15 μg/l Pb (NO3)₂ and then declined to initial levels in treatment, 25 μg/l Pb (NO3)₂ (P < 0.01). The plasma levels of TCA cycle intermediates significantly elevated in treatments 15 and 25 μg/l Pb (NO3)₂ (P < 0.01). As a biomarker of oxidative stress, the plasma levels of malondialdehyde (MDA) showed significant increases in Pb (NO3)₂ exposed fish (P < 0.01). During exposure period, wide ranges of liver tissue damages were also observed in Pb (NO3)₂ exposed fish. In conclusion, exposure to Pb (NO3)₂ affected the metabolome content of blood in grey mullet, mainly through inducing the biochemical pathways related to the metabolism of the amino acids, energetic metabolites and methylated metabolites. Our results may help to understand the effects of heavy metals on fish hematology from a molecular point of view.

Biochemical and Histological Biomarkers in Crassostrea sp. (Bivalvia, Ostreidae) for Environmental Monitoring of a Neotropical Estuarine Area (São José Bay, Northeastern Brazil)

This study aimed to compare biochemical and histological biomarkers in oysters to identify impacted areas in a Brazilian port region. Oysters belonging to the Crassostrea genus were collected in two points in São José Bay (Brazil): (A1) Curupu Island (control area) and (A2) Braga Port (impacted area). Digestive glands from oysters were used to analyze the enzymatic activity of glutathione S-transferase and Catalase. The gills were used for standard histology analyses. Water samples were collected for metal analyses. Our results indicated that there was a change in the activity of oyster GST and CAT enzymes, especially in A2. Histological gill analysis indicated more frequent changes in A2. The analyzed metals presented higher values in A2. The results of this study suggest that enzymatic alterations, histological changes and higher metal values are indicative of initial stress caused by contaminants in São José Bay, especially in the port region.

Use of biochemical markers to quantify the toxicological effects of metals on the fish Sciades herzbergii: potential use to assess the environmental status of Amazon estuaries

Enzymatic biomarkers, especially oxidative-stress enzymes, are useful for assessing the status of aquatic environments. The present study used biochemical markers determined in nervous, gill, and liver tissues of Sciades herzbergii, concomitantly with analyses of trace metals in the tissues and bottom sediment, to evaluate environmental quality in Amazon estuaries. The study was conducted from March 2014 to February 2016 in two areas: Caeté estuary in Bragança, state of Pará, which is relatively unimpacted; and São Marcos Bay, next to a harbor in São Luís, state of Maranhão. In the laboratory, the fish were weighed (g) and measured (cm). Fragments of the gills, the brain, and the liver were biochemically analyzed, and the metal contents in the brain, the liver, and the muscle tissues were determined. Turbidity was significantly higher (p < 0.05) in São Marcos than in Bragança. Specimens of S. herzbergii were smaller in São Marcos, and aluminum, iron, nickel, copper, cadmium, and mercury levels were higher in bottom sediment (p < 0.05) collected at this location. Fish from São Marcos contained significantly higher (p < 0.05) concentrations of aluminum, iron, and cadmium in the muscle tissue than fish from Bragança. In addition, fish from São Marcos had significantly higher concentrations of nickel in both the nervous and hepatic tissues. Only fish from São Marcos contained measurable concentrations of mercury in the liver and muscle. Fish from Bragança had copper concentrations in the liver significantly different from those captured at São Marcos (p < 0.05). The activities of gill glutathione S-transferases (GSTs) (F = 6.62; df = 1, 16; p < 0.05) and liver CAT (F = 10.22; df = 1, 16; p < 0.05) were higher in fish from São Marcos. However, ChE in brain tissues and lipid peroxidation (LPO) in the gills and liver did not differ significantly between fish from both areas. The physico-chemical conditions of the water and the concentrations of metals found in sediment and biological tissues, together with the biochemical responses of S. herzbergii in the study areas, indicate that this species is still tolerant to adverse environmental conditions, but the presence of metals is a risk to the health of fish, mainly to fish from São Marcos, especially if chronically exposed.

Residual quantification and oxidative stress induced by malachite green after subacute and sublethal exposure in red tilapia

Background and Aim:

Malachite green (MG) is an effective antiparasitic and antifungal chemical for treatment of fish. However, MG is reported to be a potential carcinogen. Yet, it is widely used in aquaculture despite its prohibition for use in food-producing animals by the EU and USFDA. The present study quantified MG residues and evaluated the oxidative stress in red tilapia when exposed to subacute and sublethal concentrations of MG.

Materials and Methods:

Red tilapia exposed to subacute (0.105 mg/L for 20 days) and sublethal (0.053 mg/L for 60 days) concentrations were evaluated for total plasma protein, total immunoglobulin, nitroblue tetrazolium activity, malondialdehyde, reduced glutathione (GSH), and catalase (CAT) activity levels. The residues of MG and leuco-MG (LMG) were also quantified in the fish muscles using liquid chromatography–tandem mass spectrometry.

Results:

Fish exposed to subacute concentration showed higher CAT on day 10 in the liver and days 5 and 15 in the spleen, whereas in fish exposed to the sublethal concentration, higher levels of GSH were observed on day 1 in the kidney and day 50 in the spleen. Fish muscle was able to accumulate the sum of MG and LMG of 108.04 µg/kg for subacute (day 20) and 82.68 µg/kg for sublethal (day 60).

Conclusion:

This study showed that red tilapia was able to adapt to the stress caused by exposure to MG at sublethal concentration.

Effects of ectoine on behavioral, physiological and biochemical parameters of Daphnia magna exposed to dimethyl sulfoxide

DMSO is a very common solvent for hydrophobic chemicals that may pose a threat to aquatic organisms. Ectoine (ECT) is a protective amino acid produced by various strains of halophilic bacteria with high potential to alleviate detrimental effects induced by environmental stressors. This amino acid is used in many cosmetics and pharmaceuticals may enter aquatic ecosystems interacting with ions and macromolecules. Little is known on the effects of DMSO and its interaction with ECT on behavioral, physiological and biochemical endpoints of aquatic invertebrates. Therefore, the purpose of the present study was to determine protective effects of DMSO alone and in the combination with ECT on hopping frequency, swimming speed, heart rate, thoracic limb activity, catalase activity and NOx level in an animal model, Daphnia magna subjected to 0.1% and 1% DMSO alone and during combinatorial exposure to ECT (0-25 mg/L) and DMSO for 24 h and 48 h. The results showed that swimming speed, heart rate and thoracic limb activity were inhibited by both 0.1% and 1% DMSO alone however alleviating effects were observed in the combination DMSO + ECT. Thoracic limb activity was higher in the animals exposed to both solutions of DMSO alone, however the parameter was more stimulated at DMSO + ECT. The results suggest that DMSO alone may alter Daphnia behavior and physiological parameters, therefore use of the control group of non-treated animals with DMSO alone would be recommended to avoid data misinterpretation.

Genome-wide identification and expression of the entire 52 glutathione S-transferase (GST) subfamily genes in the Cu2+-exposed marine copepods Tigriopus japonicus and Paracyclopina nana

In this study, the entire glutathione S-transferases (GSTs), the major phase II detoxification enzyme, were identified in two marine copepod species Tigriopus japonicus and Paracyclopina nana. The genome-wide identification of GSTs in T. japonicus and P. nana resulted in 32 and 20 GSTs in total, respectively. Among the identified GSTs, two specific classes of GSTs, specifically sigma and delta/epsilon GSTs were the dominant form of cytosolic GSTs in T. japonicus, while delta/epsilon and mu classes were dominant cytosolic GSTs in P. nana. In addition, Membrane-Associated Proteins in Eicosanoid and Glutathione metabolism (MAPEG) family were found in relatively higher proportion compared to other classes. Moreover, sigma, delta/epsilon, and microsomal GSTs have shown to expand through tandem duplication. To validate the detoxification function of the identified GSTs, both copepods were exposed to copper (Cu²⁺) and the reactive oxygen species (ROS) level and GST activity were measured. With integration of phylogenetic analysis and xenobiotic-mediated GST mRNA expression patterns along with previous enzymatic activities, the functional divergence among species-specific GST genes was clearly observed. This study covers full identification of GST classes in two marine copepod species and their important role in marine environmental ecotoxicology.

Protective effects of compatible solute ectoine against ethanol-induced toxic alterations in Daphnia magna

Ectoine (ECT) is a compatible solute synthesized mostly by halophilic microorganisms subjected to various stressful factors. Its protective properties in bacteria and some populations of isolated cells subjected to different stressors are reported; however, little is known on its effects against a commonly used compound, ethanol (ETH). The purpose of our study was to determine the effects of ETH alone (at 20 and 60 g/L) and in the combination with various concentrations of ECT (5, 10, and 25 mg/L) at various times of exposure on behavioural, physiological, and biochemical parameters of a model invertebrate Daphnia magna. In the present study, we determined the following parameters: immobilisation, heart rate, thoracic limb movement, catalase (CAT) activity, and nitric oxide species (NOx) level. Our study revealed that both concentrations of ETH alone induced immobilisation and decrease of swimming velocity, heart rate, and thoracic limb activity; however, catalase activity and NOx levels were increased. On the other hand, the animals exposed to the combinations of ETH + ECT showed a reduced immobilisation and alleviated inhibition of heart rate and thoracic limb activity, lower increase of CAT activity, and NOx level when compared to the crustaceans subjected to ETH alone. The most distinct alleviation of toxic effects was noted in the combinations in which the highest concentration of ECT were used. The results suggest that ETH may induce oxidative stress in daphnids and attenuating effects of ECT probably result from its antioxidative properties.

Evaluating toxicity of copper(II) oxide nanoparticles (CuO-NPs) through waterborne exposure to tilapia (Oreochromis mossambicus) by tissue accumulation, oxidative stress, histopathology, and genotoxicity

Metal oxide nanoparticles are widely used in industries, and peak level can be confirmed in their surroundings. In the present study, the sub-lethal effects of CuO-NPs from low to high concentration as 0.5 to 1.5 mg/L were observed in tilapia (Oreochromis mossambicus). Accumulation of copper from CuO-NPs was increased with the increase in doses, and maximum accumulation was found in the gill than liver and muscles. The increased lipid peroxidation level was observed in the gill as compared to liver, and the similar results were obtained in catalase and glutathione while superoxide dismutase level was higher in the liver than gills. In histological alterations, gill edema, curved tips, fusion of gill lamellae, and thickening of primary and secondary gill lamellae were observed. Necrosis and apoptosis with condensed nuclear bodies and pyknotic nuclei were observed in the liver at the highest dose concentration. In a genotoxic study, the highest value of % tail DNA and olive tail movement was observed with increasing concentrations. Copper oxide nanoparticles has greater potential to accumulate in the soft tissues, which may cause respiratory distress such as oxidative stress, induction of antioxidant defense by raising glutathione, organ pathology, and genotoxicity.

Metabolomic and oxidative effects of quantum dots-indolicidin on three generations of Daphnia magna

This study evaluated the effect of QDs functionalized with the antimicrobial peptide indolicidin on oxidative stress and metabolomics profiles of Daphnia magna across three generations (F0, F1, and F2). Exposing D. magna to sub-lethal concentrations of the complex QDs-indolicidin, a normal survival of daphnids was observed from F0 to F2, but a delay of first brood, fewer broods per female, a decrease of length of about 50% compared to control. In addition, QDs-indolicidin induced a significantly higher production of reactive oxygen species (ROS) gradually in each generation and an impairment of enzymes response to oxidative stress such as superoxide dismutase (SOD), catalase (CAT) and glutathione transferase (GST). Effects were confirmed by metabolomics profiles that pointed out a gradual decrease of metabolomics content over the three generations and a toxic effect of QDs-indolicidin likely related to the higher accumulation of ROS and decreased antioxidant capacity in F1 and F2 generations. Results highlighted the capability of metabolomics to reveal an early metabolic response to stress induced by environmental QDs-indolicidin complex.

Preventive and reparative effects of isoleucine against copper-induced oxidative damage in primary fish enterocytes

The present study aimed to assess the possible preventive and reparative effects of isoleucine (Ile) against copper (Cu)-induced oxidative stress in fish enterocytes in vitro. In experiment 1, enterocytes were preincubated with increasing concentrations of Ile (0, 50, 120, 190, 260, and 330 mg L^-1) for 72 h followed by exposure to 6 mg L^-1 Cu for 24 h. In experiment 2, the enterocytes were pretreated with 6 mg L^-1 Cu for 24 h and then treated with 0-330 mg L^-1 Ile for 72 h to investigate its potential reparative role. The results of experiment 1 showed that Cu exposure increased lactate dehydrogenase (LDH) activity and malondialdehyde and protein carbonyl (PC) content; these changes were completely suppressed by pretreatment with Ile at optimum concentrations (P < 0.05). Moreover, Ile pretreatment prevented the decrease in superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in the enterocytes exposed to Cu (P < 0.05). Additionally, cells exposed to Cu exhibited adaptive increases in glutathione-S-transferase (GST) activity. In experiment 2, the LDH activity and protein oxidation induced by Cu were completely reversed by Ile posttreatment. Meanwhile, the Cu-induced decrease in SOD, GPx, and GST activity was completely reversed by subsequent Ile treatment, but the reduced glutathione content was not restored. Collectively, these results indicate that Ile suppresses Cu-induced oxidative damage via preventive and reparative pathways in primary enterocytes and thus protects the structural integrity of enterocytes in fish.

Sublethal effects in Perinereis gualpensis (Polychaeta: Nereididae) exposed to mercury-pyrene sediment mixture observed in a multipolluted estuary

Sediment-living organisms can be subjected to a multi-pollution condition due to an increase in the diversity of contaminants. Sediment mixtures of Mercury (Hg) and some polycyclic aromatics hydrocarbons like Pyrene (Pyr) are common in heavily industrialized coastal zones. In the present study, greater than (>) and less than (<) probable effect concentration levels (PELs) of Hg and Pyr were assessed using spiked sediments in order to determine combined (Hg + Pyr) effects in uptake, metabolization and oxidative balance in the polychaete Perinereis gualpensis at short and medium-term exposure. Hg + Pyr significantly influenced the uptake/kinetics of Hg and Pyr metabolite 1-OH-pyrene in polychaete tissues during the exposure time compared with separate treatments of each analyte (p < 0.05). Both the Hg-only and Pyr-only exposures significantly influenced both enzymatic and non-enzymatic responses respect to control groups (p < 0.05). The Hg-only treatment showed the worst scenario related to the activation and subsequent inhibition of glutathione S- transferase (GST) and peroxidase (GPx) activities, high levels of Thiol-groups (SH-groups), low antioxidant capacity (ACAP) and enhanced lipid peroxidation (TBARS) in the last days of exposure (p < 0.05). In contrast, ragworms exposed to Hg + Pyr showed a significant increase in both enzymatic and non-enzymatic activity during the first days of exposure and the absence of lipid peroxidation during the whole experiment. Our results suggest different oxidative stress scenarios in P. gualpensis when exposed to >PEL Hg concentration with <PEL Pyr in sediments. Results also reveal the importance of the exposure time, endpoints involved as well as of the contaminant monitoring during the whole experiments in assessing the interactive effects of the contaminant mixture.

Oxidative stress and related biomarkers in cupric and cuprous chloride-treated rainbow trout

We examined the time-course stress responses in the liver of rainbow trout exposed to cuprous chloride (CuCl) and cupric chloride (CuCl₂). The treatment groups received a single intraperitoneal injection of CuCl or CuCl₂ (both at a dose of 0.01 and 0.05 mg/kg); the control group received only the physiologic solution vehicle. Liver tissue samples were analyzed for total copper, superoxide dismutase, catalase, glutathione peroxidases, glutathione reductase, glutathione S-transferase, glyoxalases, and lactate dehydrogenase at 3, 6, and 9 days post-injection. Total glutathione, metallothionein, and malondialdehyde levels were also measured. The time course of metal accumulation differed between the groups; no dose-response relationship for metal load was found. Both copper species elicited significant changes in oxidative stress markers and in metal trapping. Copper underwent adaptive shifts in glutathione and metallothionein concentrations. The defense strategy primarily versus CuCl₂ first involved glutathione, with a peak in metallothionein levels at day 6 for CuCl₂ (at both doses) and for CuCl (0.05 mg/kg). Early stimulation of lipid peroxidation was noted after treatment with the higher copper dose and at day 9 after treatment with the lower dose of both CuCl and CuCl₂. Antioxidant enzyme activity was impaired due to a more or a less severe oxidative stress condition in relation to the copper species and exposure time. Copper dynamics, in terms of metal accumulation and homeostatic regulation, is noticeably complex. The present findings may advance our understanding of the effects of both copper species on the antioxidant response of rainbow trout.

Oxidative stress biomarkers, cholinesterase activity and biotransformation enzymes in the liver of dice snake (Natrix tessellata Laurenti) during pre-hibernation and post-hibernation: A possible correlation with heavy metals in the environment

We investigated in the liver of dice snakes during pre- and post-hibernation changes in the following antioxidant parameters: total, manganese and copper zinc containing superoxide dismutases (Tot SOD, MnSOD, CuZn SOD, respectively), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and the concentrations of total glutathione (GSH) and sulfhydryl groups (-SH). In addition, we examined the expression of phase I biotransformation enzyme cytochrome P₄₅₀1A (CYP1A) and the activity of phase II biotransformation enzyme glutathioneS-transferase (GST), the level of lipid peroxidation (by measuring the thiobarbituric acid-reactive substances (TBARS)), cholinesterase activity (ChE) and metallothionein expression (MT). We also measured the concentrations of heavy metals, including Al, Cd, As, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb and Zn in the water and snake liver during both periods. During the post-hibernation period, the activities of Tot SOD, CuZn SOD and GST and the concentration of GSH were significantly decreased, while GSH-Px and GR activities, the concentrations of -SH groups and TBARS were significantly increased. The activities of Mn SOD, CAT and ChE, and the relative amounts of CYP1A and MT did not significantly change during the investigated periods. The observed differences in the examined parameters probably represent adaptive physiological responses to sudden changes in tissue oxygenation during arousal from hibernation. Our findings also indicate that the accumulated metals modulated the responses of the examined parameters during the investigated periods.

Off-site impacts of wildfires on aquatic systems - Biomarker responses of the mosquitofish Gambusia holbrooki

The number of wildfires has markedly increased in Mediterranean Europe, including in Portugal. Wildfires are environmentally concerning, not only due to the loss of biodiversity and forest area, but also as a consequence of environmental contamination by specific compounds including metals and polycyclic aromatic compounds (PAHs). These contaminants, mostly bound to ashes, can reach downstream water bodies, namely through surface runoff, being ultimately dispersed by vast areas and contacting with aquatic biota. Being toxicologically noteworthy, the potential toxic outcomes of the input of such chemicals across the aquatic compartment must be characterized. In this context, the present study used a biomarker-based approach to find early-warning signals of toxicity triggered by the exposure of the mosquitofish, Gambusia holbrooki, to affected aqueous runoff and stream water samples collected from a forest burnt area. The chemical analysis revealed concerning levels of metals and polycyclic aromatic hydrocarbons in both runoff and stream water samples. Biological responses elicited by the collected samples showed the occurrence of pro-oxidative modifications, specifically driven by enzymatic forms involved in the metabolism of glutathione. Despite these effects, no further signs of involvement of metals and PAHs were elicited in terms of neurotoxicity. The overall set of data implicates chemicals resulting from wildfires in clear deleterious effects in exposed fish.

Effects of sub-chronic exposure to lead (Pb) and ascorbic acid in juvenile rockfish: Antioxidant responses, MT gene expression, and neurotransmitters

Juvenile rockfish Sebastes schlegelii were exposed to varying levels of dietary lead (Pb²⁺) at 0, 120 and 240 mg/L, and ascorbic acid (AsA) at 100, 200 and 400 mg/L for four weeks. Antioxidant responses such as superoxide dismutase (SOD), glutathione S-transferase (GST), and glutathione (GSH) were analyzed to assess oxidative stress. SOD and GST activity in the liver and gills were considerably elevated by dietary Pb. In contrast, GSH levels in the liver and gills were significantly reduced following Pb exposure. High levels of AsA supplementation attenuated the increase in SOD and GST activity and reduction in GSH levels. The metallothionein gene (MT) in the liver was notably stimulated by Pb exposure, and AsA supplementation attenuated this increase. With respect to neurotoxicity, acetylcholinesterase (AChE) activity was substantially inhibited in the brain and muscle following Pb exposure. AsA supplementation also attenuated AChE inhibition following Pb exposure. The results of this study presented Pb exposure affected rockfish as toxicity, and AsA was effective to alleviate toxic effects of Pb.

Characterization and response of antioxidant systems in the tissues of the freshwater pond snail (Lymnaea stagnalis) during acute copper exposure

The response of enzymatic (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX and glutathione reductase, GR) and non-enzymatic responses (glutathione, GSH, oxidized glutathione, GSSG and GSH/GSSG) against acute Cu toxicity (2-90μg/mL for 48h) in different tissues of Lymnaea stagnalis were measured. Incubation conditions for enzymatic activity measurements were optimized for L. stagnalis tissues. Three examined tissues, the hepatopancreas, the foot muscle and the mantle, exhibited variable responses in antioxidant parameters as a function of Cu concentrations. The most responsive antioxidant enzymes were GPX and CAT while GR appeared less sensitive. In general antioxidant enzymes at higher Cu concentrations though GSH levels at lower Cu concentrations exhibited the greatest changes in hepatopancreas and foot muscle, respectively. All antioxidant enzymes except GR increased after exposure to the highest Cu concentration in mantle. Total and reduced GSH increased in hepatopancreas but decreased with GSH/GSSG ratios at all Cu concentrations in foot muscle. The present results show that antioxidants respond to acute Cu exposure at concentrations as low as 2μg Cu/L in adult L. stagnalis with variable responses in different tissues. Antioxidants both including enzymatic and non-enzymatic parameters may account, in part, for the high tolerance to acute metal exposure observed in adult L. stagnalis and could form suited biomarkers to evaluate the metal exposure and toxicity in aquatic environment even at relatively low level short term exposure.

Multivariate analysis of potential biomarkers of oxidative stress in Notopterus notopterus tissues from Mahanadi River as a function of concentration of heavy metals

In this study, investigation were done on the Mahanadi River water and health of dwelling Indian Knife fish Notopterus notopterus from three sites along the course of the river in an around Cuttack city (Odisha). Oxidative stress biomarker assays such as thiobarbituric acid reactive substances, protein carbonyls, protein and non-protein thionyls, reduced glutathione, metallothionein, superoxide dismutase, catalase, glutathione peroxidase/reductase couple, glutathione-S-transferase, and tissue metal (Fe, Cu, Ni, Cd, Pb and Zn) levels along with water quality assessments were assayed to measure the impacts on fish health. Results indicate that except Fe all other metals studied were within approved limits for fish liver and gill as approved by FAO/WHO. However, the muscle tissue do not have any metal beyond the permissible limit. A site and tissue specific response of the above mentioned oxidative biomarkers as well as metal accumulation in the fish tissues were noticed. Lipid peroxidation and protein carbonylation were increased gradually in the fish tissues collected from experimental sites along the course of the River in comparison to upstream reference site. Glutathione-S-transferase, glutathione peroxidase/reductase couple, reduced glutathione and non-protein thiol content were significantly decreased in fish tissues from experimental sites. An increase in metallothionein content was observed while superoxide dismutase and catalase showed tissue specific responses. Multivariate (Discriminant Function) analysis revealed that lipid peroxidation, protein carbonylation and superoxide dismutase have highest association as predictors of impact in the muscle and liver while that for gill is protein carbonylation, superoxide dismutase and glutathione reductase.

Ectoine alleviates behavioural, physiological and biochemical changes in Daphnia magna subjected to formaldehyde

Ectoine (ECT) is produced by halophilic microorganisms in response to various stressful factors. Its protective properties in bacteria and some populations of isolated cells are known; however, no data are available on its protective influence on aquatic invertebrates subjected to a common pollutant, formaldehyde (FA). The purpose of this study was to determine the effects of FA alone (at 20 and 60 mg/L) and in the combination with various concentrations of ECT (5, 10 and 25 mg/L) at various times of exposure on behavioural, physiological and biochemical parameters of Daphnia magna. Specifically, mortality, heart rate, thoracic limb movement, reduced glutathione (GSH)/oxidised glutathione (GSSG) ratio, catalase (CAT) activity and nitric oxide (NOx) levels were determined. The results showed that both concentrations of FA when administered alone induced significant alterations of the determined parameters. On the other hand, animals treated with the combinations of FA + ECT showed decreased mortalities, attenuated inhibition of heart rates and thoracic limb activities, less decreased GSH/GSSG ratios, lower stimulation of CAT activities and NOx levels when compared to the crustaceans subjected to FA alone. The most distinct attenuation of toxic effects was observed in the combinations in which the highest concentrations of ECT were used. The results suggest that oxidative stress induced by FA in daphnids is likely to be alleviated by the antioxidative action of ECT.

A multibiomarker evaluation of urban, industrial, and agricultural exposure of small characins in a large freshwater basin in southern Brazil

Iguaçu River is the second most polluted river of Brazil. It receives agrochemicals and contaminants of urban and industrial sources along its course. A multibiomarker approach was employed here to evaluate the health of a small characin (Astyanax spp.) at two sites along the river, sampled during a dry (autumn) and a rainy (spring) season. Biomarkers were condition factor and somatic indices (gonads and liver); genetic damage (comet assay and micronucleus test); enzyme activities such as hepatic catalase (CAT) and glutathione S-transferase (GST), lipoperoxidation (LPO), branchial and renal carbonic anhydrase (CA), acetylcholinesterase (AChE) in the muscle and the brain, histopathology of the liver and gills, and concentrations of polycyclic aromatic hydrocarbons (PAHs) in bile. There were no consistent differences in biomarker responses between the two study sites. Some biomarkers revealed greater potential impact in the rainy season, when increased amounts of contaminants are washed into the river (combined CAT inhibition and LPO increase, CA upregulation). Other biomarkers, however, revealed potential greater impact in the dry season, when contaminants potentially concentrate (GST induction, AChE inhibition, and liver histopathological alterations). Although of a complex nature, field experiments such as this provide rich data for monitoring protocols and assessment of general risk of exposure to pollutants of river systems.

Effects of the essential metals copper and zinc in two freshwater detritivores species: Biochemical approach

The input of metals into freshwater ecosystems from natural and anthropogenic sources impairs water quality and can lead to biological alterations in organisms and plants, compromising the structure and the function of these ecosystems. Biochemical biomarkers may provide early detection of exposure to contaminants and indicate potential effects at higher levels of biological organisation. The effects of 48h exposures to copper and zinc on Atyaephyra desmarestii and Echinogammarus meridionalis were evaluated with a battery of biomarkers of oxidative stress and the determination of ingestion rates. The results showed different responses of biomarkers between species and each metal. Copper inhibited the enzymatic defence system of both species without signs of oxidative damage. Zinc induced the defence system in E. meriodionalis with no evidence of oxidative damage. However, in A. desmarestii exposed to zinc was observed oxidative damage. In addition, only zinc had significantly reduced the ingestion rate and just for E. meridionalis. The value of the integrated biomarkers response increased with concentration of both metals, which indicates that might be a valuable tool to interpretation of data as a whole, as different parameters have different weight according to type of exposure.

Effects of Waterborne Lead Exposure in Mozambique Tilapia: Oxidative Stress, Osmoregulatory Responses, and Tissue Accumulation

We studied the oxidative stress and osmoregulatory damage as well as the accumulation of lead in Mozambique Tilapia Oreochromis mossambicus exposed to different sublethal concentrations-low, medium, and high (0.5, 2.5, and 5.0 mg/L)-of waterborne lead for 14 d in a semistatic condition. The accumulated levels of Na⁺, K⁺-ATPase, glutathione (GSH), and thiobarbituric acid reactive substances (TBARS) were determined from samples of gill, liver, intestine, brain, kidney, and muscle tissues. At the end of the experiment, the GSH levels of most tissues were higher in the treated group than in the control group (especially in the liver and kidney) but lower in the intestine. The levels of TBARS in the gill and brain tissues of the fish exposed to high lead doses were significantly higher than those of fish in the control group. Na⁺, K⁺-ATPase activity seemed to be significantly inhibited in the gill, intestine, and brain tissues across all treatment groups. At the end of the study, the total amount of lead that had accumulated within the various tissues ranked as follows: intestines > kidney > brain > gill > liver > muscle. Our findings suggest that sublethal concentrations of lead can disrupt the health of Mozambique Tilapia and cause oxidative stress and osmoregulatory damage.

Protective effects of ectoine on behavioral, physiological and biochemical parameters of Daphnia magna subjected to hydrogen peroxide

Ectoine (ECT) is an osmoprotectant produced by halophilic microorganisms inducing protective effects against various stressful factors. However, little is known about its influence on aquatic invertebrates subjected to hydrogen peroxide (H2O2)-a commonly used oxidative disinfectant. Therefore, the aim of our study was to determine the effects of H2O2 alone (at 5 and 10 mg/L) and in the combination with various concentrations of ECT (5, 10 and 25 mg/L) on behavioral, physiological and biochemical parameters of Daphnia magna. The following endpoints were determined: mortality, heart rate, thoracic limb movement, total glutathione (GSH)/oxidized glutathione (GSSG) ratio, catalase (CAT) activity and nitric oxide (NOx) level. The study showed that daphnids exposed to the combination of H2O2+ECT showed decreased mortality, attenuated inhibition of heart rate and thoracic limb activity, less decreased GSH/GSSG ratio, lower stimulation of CAT activity and NOx level when compared to the crustaceans exposed to H2O2 alone. The most pronounced alleviation of toxic effects was observed in the combination of 5 mg/L H2O2+25 mg/L ECT. The results suggest that protective effects of ECT in D. magna subjected to H2O2 may be related to antioxidative properties of the osmoprotectant.

Perturbations in ROS-related processes of the fish Gambusia holbrooki after acute and chronic exposures to the metals copper and cadmium

Metallic contamination is a widespread phenomena, particularly in areas impacted by human activities, and has become a relevant environmental concern. However, the toxicity of metals on fish requires full characterization in terms of short- and long-term effects. Thus, the purpose of this study was to determine the acute and chronic oxidative stress response in liver and gills of Gambusia holbrooki exposed to copper and cadmium. To assess the effects of these two metals, we adopted a strategy of analyzing the pollution effects caused by salts of the two metallic elements, and we quantified the oxidative stress biomarkers catalase, glutathione reductase, glutathione-S-transferases, and lipid peroxidation after exposure (4 and 28 days) to ecologically relevant concentrations, thus simulating actual conditions of exposure in the wild. Our results showed that copper elicited strong effects in all tested biomarkers for both acute and chronic challenges. Cadmium caused a similar response and was shown to cause significant changes particularly in catalase and glutathione-S-transferases activities. These findings evidence that ecologically relevant concentrations of common anthropogenic contaminants are causative agents of serious imbalances (namely oxidative stress) that are likely to trigger life-threatening events.

Effects of heavy metals (Cd, Cu, Cr, Pb, Zn) on fish glutathione metabolism

The glutathione metabolism contains crucial antioxidant molecules to defend the organisms against oxidants. Thus, the aim of this study was to investigate the response of the glutathione metabolism in the liver of freshwater fish Oreochromis niloticus exposed to metals (Cu, Cd, Cr, Pb, Zn) in different periods. Fish were exposed to metals (as 1 μg/mL) individually for 1, 7, and 14 days and subsequently antioxidant enzymes (glutathione peroxidase, GPX; glutathione reductase, GR and glutathione S-transferase, GST) and glutathione levels (total glutathione, tGSH; reduced glutathione, rGSH; oxidized glutathione, GSSG and GSH/GSSG ratios) in the liver were measured. There was no fish mortality during the experiments, except Cu exposure. The antioxidant enzymes responded differently to metal exposures depending on metal types and exposure durations. GPX activity increased only after Cd exposure, while GST activity increased following 7 days of all metal exposures. However, GR activity did not alter in most cases. Total GSH and GSH/GSSG levels generally decreased, especially after 7 days. Data showed that metal exposures significantly altered the response of antioxidant system parameters, particularly at day 7 and some recovery occurred after 14 days. This study suggests that the response of antioxidant system could help to predict metal toxicity in the aquatic environments and be useful as an "early warning tool" in natural monitoring studies.

Ecotoxicological assessment of tannery effluent using guppy fish (Poecilia reticulata) as an experimental model: a biomarker study

Tannery wastewater in the East Calcutta Wetlands (a Ramsar site of West Bengal; number 1208) exerts adverse effects on commercial fish production and subsequently affects humans. The present study was conducted to investigate acute and chronic toxicity of tannery effluent on a fish biosystem by examining oxidative stress enzyme expression in different organs including liver, gills, and muscle following exposure. Phosphatases, both alkaline phosphatase and acid phosphatase, and antioxidant superoxide dismutase and catalase enzyme activities were determined in guppy fish (Poecilia reticulata) exposed to sublethal concentrations of composite tannery effluent. Data demonstrated that tannery effluent was capable of interfering with metabolic processes of fish by altering stress enzyme activities in fish organs, resulting in cellular injury. Data suggest that elevated activities of stress enzymes in fish upon exposure to environmental pollutants may serve as important biomarkers for oxidative stress.

EROD activity and antioxidant defenses of sea bass (Dicentrarchus labrax) after an in vivo chronic hydrocarbon pollution followed by a post-exposure period

Chronic concentrations of polycyclic aromatic hydrocarbons (PAHs) have been commonly detected in international estuaries ecosystems. Reliable indicators still need to be found in order to properly assess the impact of PAHs in fish. After an in vivo chronic exposure to hydrocarbons, the enzymatic activity of 7-ethoxyresorufin O-deethylase (EROD) and the antioxidant defense system were assessed in sea bass, Dicentrarchus labrax. A total of 45 fish were exposed to the water-soluble fraction of Arabian crude oil, similar to a complex pollution by hydrocarbons chronically observed in situ, while 45 other control fish sustained the same experimental conditions in clean seawater. Fish samples were made after a 21-day exposure period and after a 15-day recovery period in clean fresh water. Throughout the experiment, liver EROD activity was significantly higher in contaminated fish than in control fish. In addition, nonenzymatic (total glutathione) and enzymatic (GPx, SOD, and CAT) antioxidant defense parameters measured in liver were not significantly different in fish. Furthermore, in gills, glutathione content had significantly increased while SOD activity had significantly decreased in contaminated fish compared to controls. On the other hand, CAT and GPx activities were not affected. Chronic exposure to PAHs disturbing the first step (SOD) and inhibiting the second step (GPx and CAT) could induce oxidative stress in tissues by the formation of oxygen radicals. After the postexposure period, there was no significant difference between control and contaminated fish in any of the antioxidant defense parameters measured in gills, attesting to the reversibility of the effects.

Metal-PAH mixtures in the aquatic environment: a review of co-toxic mechanisms leading to more-than-additive outcomes

Mixtures of metals and polycyclic aromatic hydrocarbons (PAHs) occur ubiquitously in aquatic environments, yet relatively little is known regarding their combined toxicities. Emerging reports investigating the additive mortality in metal-PAH mixtures have indicated that more-than-additive effects are equally as common as strictly-additive effects, raising concern for ecological risk assessment typically based on the summation of individual toxicities. Moreover, the current separation of focus between in vivo and in vitro studies, and fine- and coarse-scale endpoints, creates uncertainty regarding the mechanisms of co-toxicity involved in more-than-additive effects on whole organisms. Drawing from literature on metal and PAH toxicity in bacteria, protozoa, invertebrates, fish, and mammalian models, this review outlines several key mechanistic interactions likely to promote more-than-additive toxicity in metal-PAH mixtures. Namely, the deleterious effects of PAHs on membrane integrity and permeability to metals, the potential for metal-PAH complexation, the inhibitory nature of metals to the detoxification of PAHs via the cytochrome P450 pathway, the inhibitory nature of PAHs towards the detoxification of metals via metallothionein, and the potentiated production of reactive oxygenated species (ROS) in certain metal (e.g. Cu) and PAH (e.g., phenanthrenequinone) mixtures. Moreover, the mutual inhibition of detoxification suggests the possibility of positive feedback among these mechanisms. The individual toxicities and interactive aspects of contaminant transport, detoxification, and the production of ROS are herein discussed.

Effects of fish size on the response of antioxidant systems of Oreochromis niloticus following metal exposures

The size of a fish is an important factor in its physiology, and metal uptake is affected by animal physiology. In this study, small and large tilapias (Oreochromis niloticus) differing approximately twofold in length and fivefold in weight were compared for their antioxidant response. Both groups were exposed to Cu or Cr (1.0 μg/mL) in a freshwater (-80 mg CaCO3/L, conductivity 1.77 mS/cm) using 2 exposure protocols (20 μM for 48 h and 10 μM for 6 days). Following the exposures, the antioxidant enzyme activities (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX; glutathione reductase, GR and glutathione S-transferase, GST) and glutathione (GSH) levels were measured in the liver of fish. Results showed that small fish was affected from exposure conditions much more than large ones as their antioxidant parameters significantly decreased even in controls. Metal exposures of small fish caused significant increases in SOD and CAT activity in acute Cu or Cr exposures. Subchronic Cr exposure of small fish also caused significant increases in CAT, GPx and GST activities, while there was no significant change in Cu-exposed ones. Large fish, however, showed different antioxidant responses as their levels mostly decreased. This study demonstrated that the response of antioxidant system in the liver of tilapia varied in relation to fish sizes and emphasized using different size groups in environmental monitoring and also in evaluation of fish biomarkers.

Effects of chronic exposure to lead, copper, zinc, and cadmium on biomarkers of the European eel, Anguilla anguilla

Exposure to specific metallic compounds can cause severe deleterious modifications in organisms. Fishes are particularly prone to toxic effects from exposure to metallic compounds via their environment. Species that inhabit estuaries or freshwater environments can be chronically affected by persistent exposure to a large number of metallic compounds, particularly those released by industrial activities. In this study, we exposed yellow eels (European eel, Anguilla anguilla) for 28 days to environmentally relevant concentrations of four specific metals; lead (300, 600, and 1,200 μg/l), copper (40, 120, and 360 μg/l), zinc (30, 60, and 120 μg/l) and cadmium (50, 150, and 450 μg/l). The selected endpoints to assess the toxicological effects were neurotransmission (cholinesterasic activity in nervous tissue), antioxidant defense, and phase II metabolism (glutathione-S-transferase [GST] activity, in both gills and liver tissues), and peroxidative damage. The results showed an overall lack of effects on acetylcholinesterase for all tested metals. Lead, copper, and cadmium exposure caused a significant, dose-dependent, increase in GST activity in gill tissue. However, liver GST only significantly increased following zinc exposure. No statistically significant effects were observed for the thiobarbituric acid reactive substances assay, indicating the absence of peroxidative damage. These findings suggest that, despite the occurrence of an oxidative-based response after exposure to lead, copper, and cadmium, this had no consequence in terms of peroxidative membrane damage; furthermore, cholinergic neurotoxicity caused by lead, copper, and cadmium did not occur. The implications of these results are further discussed.

Tissue-specific copper accumulation, zinc levels, induction, and purification of metallothionein in freshwater crab Sinopotamon henanense exposed to subacute waterborne copper

Copper (Cu) is one of the most important essential metals for crustaceans, buttoxic in excess. Metallothioneins (MT) are a family of low molecular weight, cysteine-rich, metal-binding proteins, which play important roles in metal homeostasis, detoxification, and cytoprotection. In the present study, Sinopotamon henanense were exposed to 0 (controls), 2.86, and 14.3 mg L(-1) waterborne Cu, Cu accumulation, zinc (Zn) levels and MT induction in gills and hepatopancreas were determined with Cd/Hemoglobin saturation assay and atomic absorption spectrophotometry method. Results showed that Cu accumulation and MT levels were both tissue-specific and revealed some time-dependent and dose-dependent, respectively. The highest Cu accumulations of 82.10 ± 16.38 μg g(-1) w wt were observed in the gill after 15 days of 14.3 mg L(-1) Cu exposure, the peak MT induction of 136.16 ± 19.39 μg g(-1) w wt were observed in the hepatopancreas after 3 day of 14.3 mg L(-1) Cu exposure.In addition, the essential metal homeostasis of Zn was disturbed in some ways by subacute Cu exposure. The calculated ratios of actual Cu to theoretical maximum metal bound by MT indicating that the hepatopancreas had much greater Cu-binding potentials than the gills. Positive correlation were shown between MT induction and Cu accumulation both in hepatopancreas and gills, indicating that MT induction in S. henanense can be considered as a biomarker for subacute waterborne Cu pollution. Furthermore, the Cu induced MT (CuMT) from S. henanense was purified using acetone precipitation (50-80%), followed by gel filtration chromatography and anion exchange chromatography. SDS-PAGE and time-of-flight mass spectrometry analysis showed that S. henanense CuMT possess two isoforms and both mainly existed as monomer and dimmer forms. These present studies will be helpful to increase the database information of heavy metal-induced MT in terms of crustaceans.

Catalasic activity in fish liver: improvement of the UV to visible analytic method

Antioxidative defenses and more especially catalasic activity (CAT) are studied in a large range of scientific research thematics. In environmental sciences, the problematic of oxidative stress is of great interest as pollutants can induce perturbations of redox homeostasis. Consequently, changes in antioxidative defenses levels in fish tissues and particularly in liver are used as potential biomarkers of pollution. In most studies, the CAT was assayed by following during 5 min the consumption of H2O2 in cytosolic buffered extracts at 240 nm (UV-method). This study proposed a development of this method in the visible, using permanganate and a 525-nm detection, which was more accurate, sensitive, and rapid. Moreover, the hepatic CAT of six different fish species [a cyclidae (Nimbochromis linni), 3 cyprinidae (Brachydanio rerio, Rutilus rutilus, Cyprinus carpio), an anguillidae (Anguilla anguilla), and a percidae (Perca fluviatilus)] was evaluated with the two protocols (UV- and KMnO4-method). The results but also the thermal optimum of the reaction and the interest of CAT as biomarker in ecotoxicology were discussed.

Glutathione and its dependent enzymes' modulatory responses to toxic metals and metalloids in fish--a review

Toxic metals and metalloid are being rapidly added from multiple pathways to aquatic ecosystem and causing severe threats to inhabiting fauna including fish. Being common in all the type of aquatic ecosystems such as freshwater, marine and brackish water fish are the first to get prone to toxic metals and metalloids. In addition to a number of physiological/biochemical alterations, toxic metals and metalloids cause enhanced generation of varied reactive oxygen species (ROS) ultimately leading to a situation called oxidative stress. However, as an important component of antioxidant defence system in fish, the tripeptide glutathione (GSH) directly or indirectly regulates the scavenging of ROS and their reaction products. Additionally, several other GSH-associated enzymes such as GSH reductase (GR, EC 1.6.4.2), GSH peroxidase (EC 1.11.1.9), and GSH sulfotransferase (glutathione-S-transferase (GST), EC 2.5.1.18) cumulatively protect fish against ROS and their reaction products accrued anomalies under toxic metals and metalloids stress conditions. The current review highlights recent research findings on the modulation of GSH, its redox couple (reduced glutathione/oxidised glutathione), and other GSH-related enzymes (GR, glutathione peroxidase, GST) involved in the detoxification of harmful ROS and their reaction products in toxic metals and metalloids-exposed fish.

The effects of increased freshwater salinity in the biodisponibility of metals (Cr, Pb) and effects on antioxidant systems of Oreochromis niloticus

Anthropogenic activities can increase the salinity of freshwaters and this may cause stress for fish and affect metal bioavailability. Oxidative stress biomarkers are of great interest due to their responses to environmental stressors which provide valuable data for biological monitoring of aquatic pollution. Thus, the individual and combined effects of salinity and metals (Cr, Pb) were investigated in the liver of freshwater fish Oreochromis niloticus in the present study. Fish were exposed to salinity (2 and 8 ppt) alone and salinity+metal (1 μg/mL Pb and Cr) combination exposures for 0, 1, 7 and 14 days and subsequently antioxidant enzymes (superoxide dismutase, SOD; glutathione peroxidase, GPX; glutathione reductase, GR and glutathione S-transferase, GST) activities and glutathione (GSH) levels in the liver were measured. Data showed that all the parameters varied in relation to metal species, exposure durations and salinity levels. Profound alterations on the measured parameters were detected at the lower salinity compared to the higher one. Salinity increase effectively stimulated the antioxidant parameters. The effects of salinity and metals on the measured parameters increased as the exposure duration prolonged. SOD was the most affected antioxidant parameter from both salinity and metals. Because metal and salinity stresses affect fish antioxidant system, this work suggests that the chemistry of freshwaters should be taken into account in natural monitoring for metal contamination in the field.

Biomarker responses as indication of contaminant effects in Oreochromis niloticus

The current study investigated oxidative stress parameters (enzymes activities, metallothionein content and lipid peroxidation) in freshwater fish, Oreochromis niloticus, tilapia exposure to Monjolinho River (in 4 months of year: January, April, July and November). One critical site in Monjolinho River (site B) was assessed in comparison to a reference site (site A). Water pH and oxygen concentration was lower than that recommended by CONAMA (Brazilian National Environmental Committee), resolution 357/2005 for protection of aquatic communities, and ammonium and the metals Cu, Zn, Mn and Fe (on all months) concentrations were higher than the maximum concentration recommended. Glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities were significantly decreased in liver and muscle in tilapia from Monjolinho River, throughout the year, in relation to reference except in gills that SOD activity increased. Glutathione S-transferase (GST) activity was significantly increased in liver of the tilapia from Monjolinho River in all sites, in relation to reference except in gills that GST activity increased in July and decreased in November, suggesting that GST activity could be induced to neutralize the pollutants toxicity. On the other hand, GST activity was significantly decreased in white muscle indicating a toxic effect of pollutants, resulting in a decreased ability of tilapia to perform defense reactions associated to GSTs. The decrease of catalase (CAT) activity in gills of the O. niloticus together with the increase of SOD activity, could explain the increased lipid peroxidation (LPO) level in this organ. Metallothionein levels in liver and gills were significantly high in all sites. Results indicate that the exposure to metals caused severe damage to tissues; despite the consensually assumed antioxidant induction as a sign of exposure to contaminants the effects seem in part to be mediated by suppression of antioxidant system with SOD, CAT and GPx as potential candidates for tissues toxicity biomarkers of pollutants.

Indicators of environmental stress: cellular biomarkers and reproductive responses in the Sydney rock oyster (Saccostrea glomerata)

We measured a suite of common biomarker responses for the first time in the Sydney rock oyster Saccostrea glomerata to evaluate their utility as biological effects measures for pollution monitoring. To examine the relationship between biomarker responses and population level effects, fertilisation and embryo development assays were also conducted. Adult oysters were deployed in two contaminated estuaries and a reference estuary in Sydney, Australia. The concentrations of various contaminants (metals and polycyclic aromatic hydrocarbon, PAHs) were quantified in oyster's tissue from each site and both metals and total PAHs were significantly elevated in contaminated estuaries relative to the reference estuary. Lysosomal membrane destabilisation, lipid peroxidation levels and glutathione (GSH) concentrations were measured in the digestive gland of oysters. Of all biomarkers measured, lysosomal membrane destabilisation proved to be the most useful indicator of oysters facing anthropogenic stress and we suggest this may be an especially useful biomarker for incorporation into local environmental monitoring programs. Moreover, lysosomal membrane destabilisation showed good correlations with fertilisation, normal embryo development and estuary status. GSH and lipid peroxidation were not as valuable for distinguishing between estuaries exposed to differing levels of anthropogenic stress, but did provide additional valuable information regarding overall health status of the oysters.

Multi-biomarker approach in wild European bullhead, Cottus sp., exposed to agricultural and urban environmental pressures: practical recommendations for experimental design

In freshwater ecosystems, a large number of chemical substances are able to disturb homeostasis of fish by modulating one or more physiological functions including the immune system. The aim of this study was to assess multi-biomarker responses including immunotoxicity induced by urban and agricultural pressure in European bullheads living in a small French river basin. For this purpose, a set of biochemical, immunological, physiological and histological parameters was measured in wild bullheads from five locations characterized by various environmental pressures. Moreover, to address effects of physiological status and contamination level variation on biomarker responses, fish were sampled during three periods (April, July and October). Results revealed a clear impact of environmental pressure on fish health and particularly on immunological status. An increase of EROD activity was recorded between upstream and downstream sites. Upstream sites were also characterized by neurotoxicological effects. Fish exhibited upstream/downstream variations of immunological status but strong differences were observed according to sampling season. Conversely, regarding biochemical and immunological effects, no significant response of physiological indexes was recorded related to environmental pressures. According to these results, the European bullhead appears as a valuable model fish species to assess adverse effects in wildlife due to urban and agricultural pressures.

Construction and characterization of a normalized cDNA library from the river snail Bellamya aeruginosa after exposure to copper

The construction of a normalized cDNA library is a popular tool for identifying novel biomarkers for monitoring environmental pollution. In the present study, a normalized cDNA library was constructed from the river snail Bellamya aeruginosa after exposure to Cu(2+) by using the SMART technique. The titer of the cDNA library was 1.78 × 10(6) pfu/ml, with a recombinant efficiency of 95.8%. In addition, from 6,000 randomly selected and sequenced clones, 5,473 high-quality ESTs were identified. After processing the sequences, 3,961 unigenes representing 897 contigs and 3,064 singlets were obtained with 27.6% redundancy. Analysis of expressed sequenced tags using COG and GO annotation and KEGG pathway data showed that a large group of genes related to growth and development, signal transduction, and defense mechanisms were present in the cDNA library. Based on our findings, this normalized cDNA library will provide a valuable resource for further research on functional genes and ecotoxicology in B. aeruginosa.

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.

Effect of starving and feeding on some haematological and physiological responses of the Nile catfish, Clarias gariepinus exposed to copper at extreme seasons

The lethal concentration for 50% of fish for 96h (96h LC(50)) of copper (Cu(2+)) was estimated for the Nile catfish (Clarias gariepinus) in extreme seasons, winter and summer, 4.31 and 4.79 mg/l, respectively. The Nile catfish was exposed to 96h LC(50) of copper for 7 days in extreme winter and summer. The body indices, haematological parameters as well as some plasma and liver enzyme activities and metabolite level were significantly differed in fish exposed to copper over than those of the control fish. Most of the tested parameters were not significantly different between the control fish of winter and summer (winter, water temperature 18 ± 2°C and summer, 27 ± 2°C). The effect of two ration sizes on copper toxicity in two different seasons on C. gariepinus was justified. It was found that the haematological parameters and the tested plasma activities of enzymes were significantly valid due to season differences. The blood parameters as well as plasma activities of enzymes were significantly differed in fishes fed elevated ration (3%) and exposed to copper challenge. On the other hand, the exploit of low feeding ration (0.5%) along with copper exposure during the examined seasons induced non-significant differences of the tested parameters, from those of the corresponding control. Therefore, the low feeding ration provides some tolerance against the possible water-borne copper exposure.

Effect of Yerbimat herbicide on lipid peroxidation, catalase activity, and histological damage in gills and liver of the freshwater fish Goodea atripinnis

The use of herbicides for agricultural and aquatic weed control has increased worldwide. These substances are potentially toxic pollutants because they induce the production of reactive oxygen species for biological systems and exert oxidative stress in nontarget organisms living in the treated aquatic systems. Recent evidence suggests differences in the toxicity of glyphosate in the form of an active ingredient compared to the toxicity of glyphosate in combination with surfactants, such as those found in commercial formulations. In Mexico, one of the most widely used glyphosate-based herbicides is Yerbimat, which has agricultural as well as aquatic weed control applications. However, there are no aquatic toxicity data, particularly regarding native fish. Therefore, we determined the acute toxicity of commercial-formulation Yerbimat in a static bioassay at 96 h (LC(50)). We also determined its toxicity at 96 h in sublethal concentrations to assess the lipid peroxidation levels (LPX), catalase activity, hepatic glycogen content, and histological damage in the liver and gills of the fish Goodea atripinnis associated with chronic exposure (75 days). The LC(50) was 38.95 ± 0.33 mg/L. The results of the short-term exposure study indicate that Yerbimat can potentially induce oxidative stress in G. atripinnis, because LPX was increased in the gills and liver. Catalase activity was reduced in the gills but increased in the liver, whereas hepatic glycogen was depleted. Chronic exposure was associated with histopathological damage in the gills and liver, some of which was irreversible. Yerbimat represents a potential risk for aquatic biota; therefore, we recommend that its application be carefully considered.