Glutathione-dependent resistance of the European eel Anguilla anguilla to the herbicide molinate

Assessment of biochemical biomarkers and environmental stress indicators in some freshwater fish

The mechanism by which an organism can adapt to subtle environmental changes is predicated on modifications to biochemical processes within the cellular metabolism in response to such changes. Changes in these processes have the potential to induce alterations in cellular structures and tissue organization, as well as establish a causal link between fluctuations in these parameters and stressors exposure. This investigation's main goal and innovation is to evaluate the environmental stress indicators in the aquatic ecosystem of Lake Qarun. Pesticide residues in freshwater fish should be the primary focus of evaluation of environmental stressor concentrations, since they serve as bioindicators at different times and places on a spatiotemporal scale. A thorough analysis of suggestive biochemical biomarker reactions should also be conducted. The effects of environmental stressors, specifically pesticide contamination in Qarun Lake, have been observed and investigated in relation to two fish species: Solea aejabtiaca and Oreochronis niloticus. The results of a hazard assessment conducted at six sampling sites using spatio-temporal data revealed elevated mean values for the pesticides, persistent organic pollutants (POPs), organochlorines, organophosphates, and pyrethroids that were detected. A multi biomarker approach facilitates a more comprehensive understanding of stress responses induced by exposure to pollutants. As a result, the activities of the biochemical biomarkers CYP-450, GST, GSH, and LDH in the blood and liver of fish samples were found to be notably elevated. The suitability of the identified variables for biomonitoring of aquatic pollution was validated, and the data unveiled variations in sensitivity among species, implying that Nile tilapia could potentially function as a bioindicator with high sensitivity. The findings were correlated with the concentrations of detrimental organochlorines, organophosphorus, and pyrethroids in the muscles and gills. The data indicates that pollutants linked to agricultural wastes, runoff, and municipal effluent may be discharged into the lake ecosystem. Consequently, to safeguard the environment, it is essential to enforce and implement policies, acts, and regulations that already exist. Assessing the effects of additional environmental stressors on aquatic ecosystems is another way in which biomarker screening with an integrative approach improves our comprehension of how toxicants impact various levels of biological organization and is particularly useful in realistic environmental exposure scenarios.

Toxicological, hepato-renal, endocrine disruption, oxidative stress and immunohistopathological responses of chitosan capped gold nanocomposite on Biomphalaria alexandrina snails

The present investigation aimed to synthesize chitosan‑gold nanocomposites (Ch-AuNPs) with gamma radiation, then to evaluate its toxic effect on the freshwater snails Biomphalaia alexandrina. Results showed that Ch-AuNPs is spherical shaped with average size 12 nm. It had a toxic effect against B. alexandrina snails with LC50 20.43 mg/l. Exposure of B. alexandrina snails to LC10 7.51 or LC25 13.63 mg/l of Ch-AuNPs, reduced the survival, reproductive and fecundity rates; total protein and albumin; both testosterone (T) and 17β Estradiol (E) levels; SOD and CAT activities of exposed snails while increased the activities of transaminases (AST & ALT), uric acid, creatinine, TAC and MDA levels compared to the control group. Results were supported by histopathological and immunohistopathological alterations of the digestive and hermaphrodite glands. In conclusion B. alexandrina could be used as a model to screen the negative impact of nanomaterials. Also, Ch-AuNPs could be used as a molluscicidal agent.

Changes in energy reserves and responses of some biomarkers in freshwater mussels exposed to metal-oxide nanoparticles

In this study, responses of various biomarkers in the digestive gland and foot muscle of freshwater mussels (Unio tigridis) were investigated following exposure to Al₂O₃, CuO and TiO₂ nanoparticles (NPs) for 14 days at different concentrations (0, 1, 3 and 9 mg NP/L). Mussels were fed on unicellular algae (Chlorella vulgaris) cultured in the laboratory. NP exposures caused significant increases (p < 0.05) in the levels of total glutathione (GSH), reduced-glutathione (rGSH), oxidized-glutathione (GSSG) and malondialdehyde (MDA) in the digestive gland. Oppositely, there were significant (p < 0.05) decreases in acetylcholinesterase activity in the foot muscles. Total energy reserves of the digestive gland and foot muscle significantly (p < 0.05) decreased, but only at the highest NP exposures. Nevertheless, NP exposures did not alter (p > 0.05) the algae filtering capacity of mussels. This study demonstrated that the biomarkers belonging to different metabolic systems responded to NP exposures, suggesting their usage in the monitoring studies for freshwater systems.

Mechanism of action and toxicological evaluation of engineered layered double hydroxide nanomaterials in Biomphalaria alexandrina snails

Layered double hydroxide (LDH) nanomaterials have recently become immense research area as it is used widely in industries. So, it's chance of their release into natural environment and risk assessment to nontarget aquatic invertebrate increasing. So, the present study aimed to synthesize and confirm the crystalline formation of Co-Cd-Fe LDHs and Co-Cd-Fe/PbI₂ (LDH) and then to investigate the toxic impact of the two LDH on the adult freshwater snails (Biomphalaia alexandrina). Results showed that Co-Cd-Fe/PbI₂ LDH has more toxic effect to adult Biomphalaria than Co-Cd-Fe LDHs (LC₅₀ was 56.4 and 147.7 mg/L, 72 h of exposure, respectively). The effect of LC₂₅ (117.1 mg/L) of Co-Cd-Fe LDHs exposure on the embryo showed suppression of embryonic development and induced embryo malformation. Also, it showed alterations in the tegmental architectures of the mantle-foot region of B. alexandrina snails as declared in scanning electron micrograph. Also, exposure to this sublethal concentration caused abnormalities in hemocyte shapes and upregulated IL-2 level in soft tissue. In addition, it decreased levels of nonenzymatic reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), caspase-3 activity, and total protein content in significant manner. Glutathione S-transferase (GST) activity was not affected by LDH exposure. It caused histopathological damages in both glands of snails and also caused a genotoxic effect in their cells. The results from the present study indicated that LDH has risk assessment on aquatic B. alexandrina snails and that it can be used as a biological indicator of water pollution with LDH.

Effects of Glutathione on Growth, Intestinal Antioxidant Capacity, Histology, Gene Expression, and Microbiota of Juvenile Triploid Oncorhynchus mykiss

This study aimed to demonstrate the effects of dietary glutathione (GSH) on growth, intestinal antioxidant capacity, histology, gene expression, and microbiota in juvenile triploid rainbow trout (Oncorhynchus mykiss). Different diets (G0-control, G100, G200, G400, and G800) containing graded levels of GSH (0, 100, 200, 400, and 800mgkg-1) were fed to triplicate groups of 30 fish (initial mean weight 4.12±0.04g) for 56days. G400 had significantly improved weight gain and feed conversion rate. Based on the broken-line regression analysis, the optimum dietary GSH level was 447.06mgkg-1. Catalase and superoxide dismutase activities were significantly higher in G200-G800. G200 had significantly lower malondialdehyde content. The height of the intestinal muscular layer in G400 was significantly higher than that of the control group. Intestinal PepT1 and SLC1A5 gene expression was significantly increased, and the highest was observed in G400. TNF-α, IL-1β, IL-2, and IL-8 expression were significantly decreased than that of G0. Next-generation sequencing of the 16S rDNA showed a significant difference in alpha diversity whereas no differences in beta diversity. On the genus level, LefSe analysis of indicator OTUs showed Ilumatobacter, Peptoniphilus, Limnobacter, Mizugakiibacter, Chelatococcus, Stella, Filimonas, and Streptosporangium were associated with the treatment diet, whereas Arcobacter, Ferrovibrio, Buchnera, Chitinophaga, Stenotrophobacter, Solimonadaceae, Polycyclovorans, Rhodococcus, Ramlibacter, and Azohydromonas were associated with the control diet. In summary, feeding juvenile triploid O. mykiss 200-800mgkg-1 GSH improved growth and intestinal health.

Heavy metal toxicity in Buriganga river alters the immunology of Nile tilapia (Oreochromis niloticus L)

The objective of the current study was to evaluate the biochemical and immunological responses of tilapia, Oreochromis niloticus due to heavy metals pollution. Histomorphological alterations in the liver and kidney suggested tissue damages due to this polluted water exposure. The brain acetylcholinesterase (AChE) as an indicator of neurotoxicity was significantly (P < 0.01) decreased after 10 days exposure of fish to heavy metal contained river water, while plasma glutamate oxalacetate transaminase and plasma glutamate pyruvate transaminase were significantly increased (P < 0.01). Moreover, superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase enzyme activities, as well as reduced glutathione and malondialdehyde levels were significantly increased in heavy metals contained river water treated fish compared to the control. Additionally, glucose level and blood serum Ca2+ concentrations were significantly (P < 0.01) decreased in fish exposed to heavy metal contained river water compared to the control. Hematological indices such as Hemoglobin, RBC, WBC, MCV etc. of polluted river water treated fish were significantly (P < 0.01) different in comparison to that of control fish. The cytokines i.e. IL-1β, IL-6, and TNF-α level were significantly (P < 0.01) increased in the fish exposed to heavy metals contained river water in comparison to that of control fish. The present findings explored the detrimental effects of heavy metal contained river water on fish at biochemical and immunological levels.

How metals directly affect the antioxidant status in the liver and kidney of Oreochromis niloticus? An in vitro study

BACKGROUND

Metals can disturb the integrity of physiological and biochemical mechanisms in fish. Thus components of defense as an antioxidant system are significant biomarkers due to their vital role in coping with metal stress. The aim of the current study is to investigate the direct effects of Cd, Cu, and Zn sublethal exposures (in vitro) on the antioxidant system parameters in the liver and kidney of Nile tilapia.

METHODS

The antioxidant enzyme activities and GSH levels were analyzed after in vitro sublethal metal (200 and 400 μg/L Cd, Cu, and Zn) treatments of Oreochromis niloticus liver and kidney supernatants.

RESULTS

Metals even at lower levels caused significant changes in the levels of antioxidant system parameters due to concentration, metal, and tissue type. GSH metabolism parameters were more responsive to the metal effect. TBARS levels and GPX activity were mostly increased while CAT, SOD, rGSH, and GSH/GSSG levels decreased. The kidney was more affected than the liver in vitro conditions. Cu was more effective in the liver whereas it was Zn for the kidney. Cd caused negative correlations among the antioxidant enzymes. Significant correlations were found between enzymes and GSH levels upon Zn and Cu exposures.

CONCLUSIONS

Direct metal effects may trigger different response trends due to their nature and tissue differences. The current data provide a knowledge about which antioxidant biomarkers can define better the oxidative stress caused by direct metal effect for further studies including in vivo experiments.

Targeting redox metabolism: the perfect storm induced by acrylamide poisoning in the brain

Exposure to acrylamide may lead to different neurotoxic effects in humans and in experimental animals. To gain insights into this poorly understood type of neurotoxicological damage, we used a multi-omic approach to characterize the molecular changes occurring in the zebrafish brain exposed to acrylamide at metabolite, transcript and protein levels. We detected the formation of acrylamide adducts with thiol groups from both metabolites and protein residues, leading to a quasi-complete depletion of glutathione and to the inactivation of different components of the thioredoxin system. We propose that the combined loss-of-function of both redox metabolism-related systems configure a perfect storm that explains many acrylamide neurotoxic effects, like the dysregulation of genes related to microtubules, presynaptic vesicle alteration, and behavioral alterations. We consider that our mechanistical approach may help developing new treatments against the neurotoxic effects of acrylamide and of other neurotoxicants that may share its toxic mode of action.

The effects of titanium nanoparticles on enzymatic and non-enzymatic biomarkers in female Wistar rats

Titanium dioxide (TiO₂) nanoparticles (NPs) are widely used in industry, pharmacy, medicine, and food sectors. Therefore, this study deals with the effects of TiO₂ NPs in female rats following oral administration in differing doses for 14 days (0, 0.5, 5, and 50 mg/kg b.w./d). The response of enzymatic biomarkers (Na,K-ATPase, Mg-ATPase, and AChE) was measured in the brain, kidney, and small intestine, while non-enzymatic biomarker levels, such as different forms of glutathione (GSH) and thiobarbituric acid reactive substances (TBARSs) were measured in the liver. The images of the tissues were obtained using a transmission electron microscope (TEM) to demonstrate TiO₂ NP accumulation. Data showed that brain AChE activity decreased at all TiO₂ NP doses, though brain ATPase activities increased. However, ATPase activities in the intestine and kidney did not change significantly. Levels of GSH forms did not change significantly, though there was a significant decrease in TBARS level at the highest NP dose. TEM images demonstrated that TiO₂ NPs accumulated in a dose-dependent manner in the tissues. Data emphasized that the brain was the most sensitive organ against the effects of TiO₂ NPs. This study suggests the need for further studies to evaluate better the toxic effects of TiO₂ NPs.

Responses of biomarkers belonging to different metabolic systems of rats following oral administration of aluminium nanoparticle

Nanoparticle (NP) forms of aluminium oxide (Al₂O₃) are used in various fields such as engineering, pharmacy, medicine etc. Compounds containing aluminium oxide NPs may present toxic effects after certain thresholds. Thus, the present study was carried out to determine the effects of Al₂O₃ nanoparticles (Al-NPs) in rats. For this aim, different doses (0, 0.5, 5, 50 mg/kg b.w./day) of Al NP (˜40 nm) were orally administered to female rats (Rattus norvegicus var. albinus) for 14 days and the response of several biomarkers such as activities of ATPases (total ATPase, Na,K-ATPase, Mg-ATPase) and acetylcholinesterase (AChE), levels of different glutathione forms and thiobarbituric acid reactive substances (TBARS) were measured in different tissues. Additionally, tissue accumulation of Al-NPs was demonstrated by a transmission electron microscope (TEM). The images showed the presence of Al-NP aggregates in all the tissues at all doses. The sizes of NP aggregates were dependent on NP doses and it was a bit more loose in the brain than in the liver and kidney. AChE activity in the brain decreased significantly at all NP doses, whereas TBARS levels in the liver did not alter significantly at any NP dose. Although there was no significant change in ATPase activities in the intestine at any NP dose, there were significant decreases in the kidney and brain. There were some variations in the levels of total glutathione (tGSH), oxidized glutathione (GSSG) and reduced glutathione (rGSH), though these variations were not significant (P > 0.05). Likewise, the ratio of rGSH/GSSG also did not differ significantly among NP doses and control. The brain seems most affected organ following Al-NP administration. This study demonstrated that most biomarkers in the tissues of rats were affected by Al-NP, showing the signal of toxic effects and suggests further studies to understand better the effects of Al NPs, especially in their use for pharmacology.

Metabolomic responses of mussel Mytilus galloprovincialis to fluoranthene exposure under different nutritive conditions

Biomarkers are useful tools to assess biological effects of pollutants that are extensively used in monitoring programs to assess ecosystem health. However, they are strongly affected by mussel physiological state, especially nutritive status, which has led to the search of new biological indicators of chemical pollutants exposition. Environmental metabolomics is an approach for examining the metabolic responses (measurement of low molecular weight endogenous metabolites) of an organism to both natural and anthropogenic stressors that can occur in its environment. The aim of the present work was to assess the effect of the polycyclic aromatic hydrocarbon fluoranthene (FLU) exposure on the metabolomic profiles of mussel digestive glands under different nutritive conditions. To achieve this objective, mussels were reared, for a period of 56 days, under three different food rations in order to obtain a gradient of nutritive status (negative, zero and positive energy balance), and after that, they were exposed, during 3 weeks, to a nominal concentration of 3 μg FLU L^-1. A total of 43 metabolites, including aminoacids (Ala, Val, Leu, Ile, etc.), energy metabolism related metabolites (ATP, AMP, etc.), organic osmolytes (taurine, etc.), redox metabolism (GSH, NADP+) and nucleotides, were identified and quantified in the digestive glands of the mussels. Principal Component Analysis (PCA) defined two principal components (PC1 and PC2) that explained 55.6% of the total variance, although the first component explains more than 80% of this variance, this being related to the mussel nutritive condition. The effect of the toxicant, explained by the PC2, is similar to that produced under conditions of food restriction, which masks the effect of the toxicant under these conditions. As the feeding conditions are more favorable, the toxic effect becomes more apparent. Therefore, the great influence of nutritive condition on mussel metabolome implies a handicap for the use of metabolomic biomarkers, as previously demonstrated for biochemical and other molecular biomarkers, in large-scale monitoring programs in which several food conditions coexist with pollution levels.

Developmental toxicity and biological responses of zebrafish (Danio rerio) exposed to anti-inflammatory drug ketoprofen

Ketoprofen a nonsteroidal anti-inflammatory drug (NSAID) is widely used in over-the-counter to treat pain, swelling and inflammation. Due to extensive application these drugs has been detected in surface waters which may create a risk to aquatic organisms. The aim of the present study is to assess the ecotoxicity of ketoprofen at different concentrations (1, 10 and 100 μg/ml) on embryos and adult zebrafish (1, 10 and 100 μg L^-1) under laboratory conditions. In embryos, concentration dependent developmental changes such as edema, spinal curvature, slow heartbeat, delayed hatching, and mortality rate were observed. In adult zebrafish, biochemical enzymes such as AST, ALT and LDH activities were significantly (P < 0.05) increased whereas a decrease in Na⁺/K⁺-ATPase activity was noticed in all the tested concentrations of the drug ketoprofen. Similarly, exposure of ketoprofen caused a significant decrease in antioxidant levels in liver tissue (SOD, CAT, GSH, GPx, and GST). However, lipid peroxidation (LPO) level in liver tissue was found to be increased. The histopathological studies further evidenced the impact of ketoprofen in the liver tissue of zebrafish. The present result concludes that ketoprofen could have an impact on the development and biological endpoints of the zebra fish at above concentrations. The malformation in the development of the embryo and changes in the biological end points may provide integrated evaluation of the toxic effect of ketoprofen on zebrafish in a new perspective.

Short communication: Alteration in blood parameters by enrofloxacin in juvenile lesser spotted dogfish (Scyliorhinus canicula, Linnaeus, 1758) after intramuscular injection

Enrofloxacin (EF) is a veterinary drug for respiratory, gastrointestinal and urinary tract infections. Parenteral administration at doses higher than the manufacturer recommended dosage has induced cartilage lesions in juvenile mammals and poultry. In elasmobranchs EF is commonly used for the treatment of infectious diseases, however only one study has been performed previously to evaluate pharmacokinetics and the potential chondrotoxicity of a fluoroquinolone in adult skates. In present study juvenile lesser spotted dogfish (Scyliorhinus canicula, Linnaeus, 1758) were treated with low (LD, 5mg/kg) and high dose (HD, 10mg/kg) of EF daily via intramuscular injection for 15 consecutive days, as indicated in a recognized treatment. Hematological parameters, oxidative stress and histology of vertebral cartilage were evaluated. No cartilage damage was observed. Hematological parameters evaluation underlined a significant (p=0.035), dose-dependent reduction in red blood cell count and in hematocrit (40% and 6%, respectively). Anyway, the biological significance of this reduction is doubtful, due to limited decrease observed. The evaluation of oxidative stress parameters underlined that glutathione levels, as well as glutathione S-transferase and catalase activities, were significantly increased in HD group animals, with respect to untreated and solvent control groups. Obtained data do not support a toxic effect of EF on dogfish cartilage, while concern arises from hematological and oxidative stress data.

Neurotoxic effects, molecular responses and oxidative stress biomarkers in Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) exposed to verapamil

Pharmaceutical drugs and their metabolites are detected in aquatic ecosystems and have been reported to cause ecotoxicological consequences to resident aquatic organisms. The study investigated the effects of acute and long-term exposure to verapamil on activities of acetylcholinesterase and antioxidant enzymes as well as mRNA expression of stress-related genes in brain and muscle tissues of Nile tilapia, Oreochromis niloticus. The 96h LC₅₀ of verapamil to O. niloticus was 2.29mgL^-1. Exposure to sub-lethal concentrations of verapamil (0.14, 0.29 and 0.57mgL^-1) for period of 15, 30, 45 and 60days, led to inhibition of acetylcholinesterase activities in the brain and muscle of the fish. The activities of the oxidative enzymes such as the catalase, superoxide dismutase and glutathione peroxidase were also inhibited in both the tissues while there was an increase in the activities of glutathione-S-transferase and reduced glutathione in the muscle after 15 days at 0.29mgL^-1. Lipid peroxidation and carbonyl protein showed elevated level, indicating a positive correlation with both time and concentration. The activities of energy-related biomarker (Na⁺-K⁺-ATPase) in both the tissues were significantly inhibited (p<0.05) compared with the control. Transcription of catalase (cat), superoxide dismutase (sod) and heat shock proteins 70 (hsp70) were up-regulated in both the tissues after the study period. Prolonged exposure to sub-lethal verapamil can result in oxidative stress, up-regulation of stress-related genes and neurotoxicity in O. niloticus.

Vicissitudes of oxidative stress biomarkers in the estuarine crab Scylla serrata with reference to dry and wet weather conditions in Ennore estuary, Tamil Nadu, India

The primary objective of this study was to understand the impact of monsoon and summer seasons on the Polychlorinated Biphenyls (PCB's) and petroleum hydrocarbon compounds (PHC's) load in Ennore estuary and how the physiological response of estuarine Scylla serrata inhabiting in this estuary changed with reference to antioxidant defense. Seasonal levels of PCB's and PHC's were assessed in the water along with their bioaccumulation in gills, hemolymph, hepatopancreas and ovary of S. serrata. Concentration of PCB's and PHC's in water and their bioaccumulation was found to be higher in summer season when compared to monsoon season. Enzymic antioxidant assays [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), glutathione-S-transferase (GST)]; non-enzymic antioxidant assays [glutathione (GSH), vitamin C, vitamin E] and macromolecular alterations [membrane lipid peroxidation (LPO), and DNA Damage (strand breaks)] were assessed in the gills, hemolymph and hepatopancreas of S. serrata. There was a significant (p<0.05) upregulation in lipid peroxidation activity and DNA damage activity collected during the summer season when compared to the pre- and post-monsoon seasons. On the contrary, the enzymic and non-enzymic antioxidants exhibited significant (p<0.05) down regulation in the gills, hemolymph, hepatopancreas and ovary of S. serrata. Oxidative stress biomarkers represented a significant (p<0.05) maximum in gills when compared to hemolymph and hepatopancreas of S. serrata. Present study provided scientific evidences of how the antioxidant defense status of S. serrata responded to PCB's and PAH's stress with reference to seasonal vicissitudes, which indirectly represented the environmental health conditions of the estuary.

Response of the antioxidant enzymes of the erythrocyte and alterations in the serum biomarkers in rats following oral administration of nanoparticles

In this study, Al₂O₃, CuO and TiO₂ nanoparticles (NPs) were administered to mature female rats (Rattus norvegicus var. albinos) via oral gavage (0, 0.5, 5, 50mg/kg b.w./day) for 14days to investigate their effects on 14 serum biomarkers and 4 antioxidant enzyme (catalase, superoxide dismutase, glutathione peroxidase, glutathione S-transferase) activities in the erythrocyte. Data showed that Al₂O₃ did not cause any significant (P>0.05) change in the parameters, except few cases, while CuO and TiO₂ caused significant alterations in antioxidant system parameters of the erythrocytes. Activities of catalase and superoxide dismutase significantly decreased in CuO and TiO₂ administered rats. Oppositely, glutathione peroxidase activity increased in CuO and TiO₂ administered rats. There were no significant alterations in the activity of glutathione S-transferase in the erythrocytes. Levels of glucose, cholesterol, bilirubin, triglyceride, triiodothyronine (T3), estradiol, prolactin and immunoglobulin M (IgM) in the serum altered after some of NP administrations, whereas cortisol, protein, creatinine, blood urea nitrogen (BUN), thyroxine (T4) and immunoglobulin G (IgG) levels in the serum did not change significantly after any of NP administration. There were outstanding increases in the levels of bilirubin and prolactin and decreases in the levels of triglyceride and estradiol. The present study demonstrated that the antioxidant enzymes in the erythrocyte were generally affected from copper and titanium NPs, while aluminium and copper NPs caused more significant alterations in serum biomarkers.

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.

Contaminant-induced oxidative stress in fish: a mechanistic approach

The presence of reactive oxygen species (ROS) in living organisms was described more than 60 years ago and virtually immediately it was suggested that ROS were involved in various pathological processes and aging. The state when ROS generation exceeds elimination leading to an increased steady-state ROS level has been called "oxidative stress." Although ROS association with many pathological states in animals is well established, the question of ROS responsibility for the development of these states is still open. Fish represent the largest group of vertebrates and they inhabit a broad range of ecosystems where they are subjected to many different aquatic contaminants. In many cases, the deleterious effects of contaminants have been connected to induction of oxidative stress. Therefore, deciphering of molecular mechanisms leading to such contaminant effects and organisms' response may let prevent or minimize deleterious impacts of oxidative stress. This review describes general aspects of ROS homeostasis, in particular highlighting its basic aspects, modification of cellular constituents, operation of defense systems and ROS-based signaling with an emphasis on fish systems. A brief introduction to oxidative stress theory is accompanied by the description of a recently developed classification system for oxidative stress based on its intensity and time course. Specific information on contaminant-induced oxidative stress in fish is covered in sections devoted to such pollutants as metal ions (particularly iron, copper, chromium, mercury, arsenic, nickel, etc.), pesticides (insecticides, herbicides, and fungicides) and oil with accompanying pollutants. In the last section, certain problems and perspectives in studies of oxidative stress in fish are described.

Azinphos-methyl and chlorpyrifos, alone or in a binary mixture, produce oxidative stress and lipid peroxidation in the freshwater gastropod Planorbarius corneus

Azinphos-methyl (AZM) and chlorpyrifos (CPF) are broad-spectrum organophosphate insecticides used for pest control on a number of food crops in many parts of the world that have been shown to inhibit cholinesterase activity in the non-target freshwater gastropod Planorbarius corneus. The present study was undertaken to determine: (a) whether AZM and CPF induce oxidative stress in P. corneus, and (b) whether a mixture of both organophosphates that causes a higher neurotoxicity than single pesticides also causes an enhanced oxidative stress. To this end, non-enzymatic and enzymatic parameters were measured in the soft tissues of snails acutely exposed to the insecticides in single-chemical (2.5 mg AZM L(-1) and 7.5 μg CPF L(-1)) and a binary-mixture (1.25 mg AZM L(-1) plus 3.75 μg CPF L(-1)) studies. At 24 h, all pesticide-exposed groups showed significantly decreased glutathione (GSH) and glutathione disulfide (GSSG) levels when compared to control animals. At 48 h, all exposed groups showed an alteration of the redox status (GSH/GSSG ratio) and a significant increase in malondialdehyde levels. The exposure for 48 h to AZM and CPF, alone or in the binary mixture, also resulted in a significant decrease of the antioxidant superoxide dismutase activity. The greatest decrease was observed with CPF exposure (59% of decrease relative to the control group). A significant increase in catalase and glutathione S-transferase activities was observed in CPF group and in CPF and AZM+CPF groups, respectively. The activities of glutathione reductase and glucose 6-phosphate dehydrogenase did not show significant changes with respect to controls in any treatment group. In conclusion, the data shown in the present study provide evidence that AZM, CPF and a mixture of both organophosphates are able to induce oxidative stress and oxidative damage in P. corneus tissues. However, no similarities between the degree of neurotoxicity and the degree of alterations of the measured oxidative stress parameters were found.

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.

Betanin attenuates carbon tetrachloride (CCl4)-induced liver injury in common carp (Cyprinus carpio L.)

This study investigates the protective effect of betanin against liver injury induced by carbon tetrachloride (CCl4) in common carp (Cyprinus carpio L.). The fish were treated with 1, 2, and 4 % betanin in fodder throughout the experiment. After 20 days of treatment, the fish were intraperitoneally injected with 20 % (v/v in peanut oil) CCl4 at a volume of 0.5 mL/kg body weight. The fish were killed 3 days after CCl4 intoxication, and then, histological and biochemical assays were performed. Results showed that CCl4-induced liver CYP2E1 activity, oxidative stress, and injury, as indicated by the depleted glycogen storage, increased serum aspartate aminotransferase (AST)/alanine aminotransferase (ALT) activities and liver histological damage. Compared with the CCl4 control group, the betanin-treated groups exhibited reduced CYP2E1 activity, decreased malondialdehyde level, increased liver antioxidative capacity (increased glutathione level and superoxide dismutase and catalase activities), increased liver glycogen storage, and reduced serum AST/ALT activities, with significant differences in the 2 and 4 % groups (p < 0.05). Histological assay further confirmed the protective effect of betanin. In conclusion, betanin attenuates CCl4-induced liver damage in common carp. Moreover, the inhibition of CYP2E1 activity and oxidative stress may have significant roles in the protective effect of betanin.

Tissue-specific induction of oxidative stress in goldfish by 2,4-dichlorophenoxyacetic acid: mild in brain and moderate in liver and kidney

This study investigated the effects of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on free radical-related processes in tissues of goldfish given 96 h exposures to 1, 10 or 100 mg/L of 2,4-D as well as 96 h recovery from the 100 mg/L treatment. In liver, 2,4-D exposure increased levels of protein carbonyls and lipid peroxides by 36-53% and 24-43%, respectively, but both parameters reverted during recovery, whereas in brain glutathione status improved in response to 2,4-D. Lipid peroxide content in kidney was enhanced by 40-43% after exposure to 2,4-D with a decrease during recovery. Exposure to 2,4-D also reduced liver acetylcholinesterase activity by 31-41%. The treatment increased catalase activity in brain, but returned it to initial levels after recovery. In kidney, exposure to 100 mg/L of 2,4-D caused a 33% decrease of superoxide dismutase activity. Thus, goldfish exposure to 2,4-D induced moderate oxidative stress in liver and kidney and mild oxidative stress in brain.

Organic insecticide spinosad causes in vivo oxidative effects in the brain of Oreochromis niloticus

Spinosad is an organic insecticide derived from a naturally occurring soil bacterium and is used in organic farming worldwide. The aim of this study was to evaluate in vivo toxic effects of spinosad in the brain of Oreochromis niloticus as a model organism. The fish were exposed to sublethal spinosad concentrations (25, 50, 75 mg L(-1) ) for 24-48-72 h to determine tGSH, GSH, GSSG, and TBARS contents, GSH/GSSG ratio, and GPx, GR, GST enzymes activities using spectrophotometrical methods, and Hsp70 content by an ELISA technique. Spinosad caused elevations in the contents of tGSH, GSH, GSSG, Hsp70, and reductions in the ratio of GSH/GSSG and GPx activity and an induction in the GR activity. The results indicated that spinosad had oxidative effects in the brain tissue by altering the parameters in GSH-related antioxidant system and Hsp70. It was also suggested that spinosad-induced free-radicals were eliminated by GSH-related antioxidant system in the brain of Oreochromis niloticus.

Comparison of the protective effects of antioxidant compounds in the liver and kidney of Cd- and Cr-exposed common carp

The aim of this study was to see whether the taurine (TAU), alpha-lipoic acid (LA), curcumin (CUR), and N-acetylcysteine (NAC) protection against oxidative stress caused by heavy metals is owed to the metal-decreasing or antioxidative effect. In this context, liver and kidney tissues of common carp (Cyprinus carpio carpio L.) were exposed in vivo to model toxicants cadmium (Cd) and chromium (Cr). The tissues were dissected 96 h after intraperitoneal injection of the metals and antioxidant substances. Cd and Cr levels were determined in the liver using the ICP-OES, but we could not obtain enough kidney tissue to make the same measurements in the kidney. The enzymatic activities of SOD, CAT, and GPx, and the GSH redox status and lipid peroxidation levels were analyzed using spectrophotometric methods. Of all investigated antioxidants, only NAC decreased metal levels in the liver. Cd had little effect on oxidative stress parameters, while Cr showed a weak prooxidative effect. Cotreatment with TAU/LA/CUR/NAC and Cr significantly increased liver SOD activity. Chromium induced kidney SOD and CAT, but all antioxidants lowered CAT activity. Cadmium reduced liver and increased kidney GSSG. NAC increased liver GSH, but the increase did not correlate with decrease in Cd. Curcumin given with Cd increased kidney and decreased liver lipid peroxidation, whereas TAU with Cr increased lipid peroxidation in both tissues. N-Acetylcysteine was the most effective antioxidative agent, owing to its metal-decreasing function as well as to its effects on the GSH redox status. We believe that the investigated antioxidant substances which may have been involved in the reduction of Cr caused an increase in SOD activity and a decrease in CAT activity. Changes in the GSSG levels in both tissues might be an adaptive response to the prooxidative potential of Cd. Because of their respective tissue- and metal-dependent prooxidative effects, CUR and TAU deserve particular attention in regard to their use against metal toxicity, Cr in particular.

Oxidative stress and apoptosis was induced by bio-insecticide spinosad in the liver of Oreochromis niloticus

This study was conducted to investigate acute toxic effects of spinosad on Glutathione-related oxidative stress markers, lipid peroxidation, heat shock proteins, apoptosis in the liver of Oreochromis niloticus selected as a model organism. The fish were exposed to sublethal spinosad concentrations (25, 50, 75 mg/L) for 24-48-72 h. tGSH, GSH, GSSG, and TBARS contents, GSH/GSSG ratio, and GPx, GR, GST and caspase enzyme activities were measured using spectrophotometrical methods, and Hsp70 content was measured by ELISA technique. The results demonstrated that spinosad exposure caused significant alterations in the GSH-related oxidative stress markers, and also caused increases in lipid peroxidation and stress proteins with inducing ROS generation in the liver. Apoptosis initiated with the induction of caspase-3 and Hsp70 could not protect the liver cells. Our results indicated that GSH-related antioxidant system tried to protect the liver cells from spinosad-induced hepatotoxicity however, the oxidative stress resulting from induction of ROS generation induced apoptosis in the liver of O. niloticus.

Detrimental effects of metronidazole on the liver of freshwater common carp (Cyprinus carpio L.)

The widely used antibiotic metronidazole (MTZ) was investigated for its toxic effects on the liver of the common carp (Cyprinus carpio L.). The fish were exposed to 0.1, 0.5, and 2.5 mg/L MTZ in water for 30 days, and parameters that are indicative of liver damage and oxidative stress were measured. MTZ increased liver ethoxyresorufin-O-deethylase, malondialdehyde, and glutathione levels, and elevated the activities of superoxide dismutase, catalase, aspartate aminotransferase, and alanine aminotransferase. These parameters usually showed significant differences in the 0.5 and 2.5 mg/L MTZ groups compared to the control group (p < 0.05). These findings indicated that MTZ induced oxidative stress and caused liver damage in common carp, suggesting that measures should be taken to avoid contamination of surface waters with MTZ.

Oxidative DNA damage induced by iron chloride in the larvae of the lace coral Pocillopora damicornis

Biochemical and molecular biomarkers tools are utilized as early warning signatures of contaminant exposure to target and non-target organisms. The objective of this study was to investigate the sublethal effects of iron chloride to the larvae of the lace coral Pocillopora damicornis by measuring a suit of oxidative-stress biomarkers. The larvae were exposed to a range of sublethal concentrations of iron chloride (0.01, 0.1, 1, 10, and 100 ppm) for seven days. With reference to oxidative stress biomarkers, the no-observed effect concentration (NOEC) and the lowest observed effect concentration (LOEC) of iron chloride were observed to be 0.01 and 100 ppm respectively. At the end of the seventh day the antioxidant status of the larvae was evaluated by the levels of glutathione (GSH), glutathione peroxidase (GPX), glutathione reductase (GR), and glutathione-S-transferase (GST), in both experimental and control groups. For the quantification of cellular oxidative damage, lipid peroxidation (LPO) activity was determined in the same and the extent of DNA damage was assessed by the expression of DNA apurinic/apyrimidinic (AP) sites. Iron chloride exhibited a concentration-dependent inhibition of GSH and GPX and induction of GR, GST, LPO, and DNA-AP sites in the P. damicornis larvae when compared to the control group. The oxidative stress biomarkers of the larvae exposed to 0.1, 1, and 10 ppm of iron chloride did not show any significant overall differences when compared to the control group. However the activities of LPO, GSH, GPX, GR, GST and DNA-AP in the larval group exposed to 100 ppm of iron chloride exhibited statistically significant (P=0.002, 0.003, 0.002, 0.002, 0.005 and 0.007) differences when compared to the control group. The research results indicated that iron chloride in concentrations at the 100 ppm level caused oxidative stress in the P. damicornis larvae.

Development and maturation in the nereidid polychaetes Platynereis dumerilii and Nereis succinea exposed to xenoestrogens

Few studies link biochemical, cellular and whole animal effects of toxic compounds with growth and reproductive output on invertebrate model organisms. Thus, we explore the effects of xenoestrogens on nereid worms. Larvae of Platynereis dumerilii exposed to estradiol (E(2)) ethynylestradiol (EE(2)) and nonyplhenol (NP) observing the effects on growth, primordial germ cell (PGC) proliferation and maturation. In addition, a single exposure study was performed with a 50 days latency period on adult worms of Nereis succinea. Since reduced glutathione (GSH) is required in detoxification of NP and is the precursor of the spawning pheromone nereithione (CSSG) in N. succinea, we analysed how the estrogenic chemical NP affects GSH concentrations. PGC were not affected by exposure to E(2) and EE(2) from 24hpf to 6 days. Chronic exposure of P. dumerilii with NP over the full life cycle did not influence segment proliferation. Mature females that developed, even at high concentrations, were able to spawn and successful fertilization occurred. However, at high NP levels no P. dumerilii males matured. A significant decline of GSH can be seen in N. succinea males upon treatment with NP, but not in females, indicating that females stabilize GSH levels even in stress situations. This study shows some results that link the foundation to causally integrate toxic exposure to xenoestrogens with development, growth and reproductive outputs in nereidid polychaetes.

Exposure of the cyanobacterium Nostoc muscorum from Portuguese rice fields to Molinate (Ordram(®)): Effects on the antioxidant system and fatty acid profile

Herbicide contamination of aquatic ecosystems is a serious global environmental concern. Several herbicides enhance the intracellular formation of reactive oxygen species, and can lead to the damage of macromolecules and to a decrease of oxidant defenses in a wide range of non-target microorganisms including cyanobacteria. The effects of molinate (a thiocarbamate herbicide used for controlling grassy weeds in rice fields) on the activities of antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and glutathione S-transferase were evaluated in Nostoc muscorum, a freshwater cyanobacterium with a significant spread in Portuguese rice fields. These were determined in N. muscorum cultures acutely (72h) exposed to concentrations ranging from 0.75 to 2mM of molinate. This study also analyzed the effects of molinate on: (1) the nonenzymatic antioxidant contents (reduced and oxidized glutathione, carotenoids, and proline), (2) the oxidative cell damage measured in terms of lipid peroxidation (MDA level) and electrolyte leakage (intactness of plasma membrane), and (3) the total fatty acid profile. The results showed that the activities of all antioxidant enzymes decreased dramatically with the rising concentration of molinate after 72h. Time-dependent and concentration-dependent increase in MDA and enhanced cell membrane leakage were indicative of lipid peroxidation, formation of free radicals and oxidative damage. Compared to control, 72-h herbicide exposure increased lipid peroxidation by 5.4%, 19% and 28% with 0.75, 1.5 and 2mM of molinate, respectively. Similarly, herbicide stress induced an increase in electrolyte leakage (5.8%, 29.5% and 30.2% above control, with 0.75, 1.5 and 2mM of molinate, respectively). The increased production of proline at higher molinate concentrations (the values rose above control by 45%, 95% and 156% with 0.75, 1.5 and 2mM, respectively) indicated the involvement of this osmoprotectant in a free radical scavenging mechanism. Moreover, a radical decline in both glutathione pool, carotenoids and saturated fatty acids were also observed. The results of the present study lead us to conclude that: (1) both enzymatic and nonenzymatic antioxidative defense system of N. muscorum are dramatically affected by molinate, (2) the herbicide induces peroxidation, (3) it contributes to an increase of the unsaturation level of cell membrane fatty acids. These evidences should be taken in account when using N. muscorum as an environmental indicator species in studies of herbicide biotransformation and biomarker response as well as in environmental monitoring programmes.

Environmentally induced oxidative stress in aquatic animals

Reactive oxygen species (ROS) are an unenviable part of aerobic life. Their steady-state concentration is a balance between production and elimination providing certain steady-state ROS level. The dynamic equilibrium can be disturbed leading to enhanced ROS level and damage to cellular constituents which is called "oxidative stress". This review describes the general processes responsible for ROS generation in aquatic animals and critically analyses used markers for identification of oxidative stress. Changes in temperature, oxygen levels and salinity can cause the stress in natural and artificial conditions via induction of disbalance between ROS production and elimination. Human borne pollutants can also enhance ROS level in hydrobionts. The role of transition metal ions, such as copper, chromium, mercury and arsenic, and pesticides, namely insecticides, herbicides, and fungicides along with oil products in induction of oxidative stress is highlighted. Last years the research in biology of free radicals was refocused from only descriptive works to molecular mechanisms with particular interest to ones enhancing tolerance. The function of some transcription regulators (Keap1-Nrf2 and HIF-1α) in coordination of organisms' response to oxidative stress is discussed. The future directions in the field are related with more accurate description of oxidative stress, the identification of its general characteristics and mechanisms responsible for adaptation to the stress have been also discussed. The last part marks some perspectives in the study of oxidative stress in hydrobionts, which, in addition to classic use, became more and more popular to address general biological questions such as development, aging and pathologies.

Teratogenicity and embryotoxicity in aquatic organisms after pesticide exposure and the role of oxidative stress

Many pesticides have been documented to induce embryotoxicity and teratogenicity in non-target aquatic biota such a fish, amphibians and invertebrates. Our review of the existing literature shows that a broad range of pesticides, representing several different chemical classes, induce variable toxic effects in aquatic species. The effects observed include diverse morphological malformations as well as physiological and behavioral effects. When development malformations occur, the myoskeletal system is among the most highly sensitive of targets. Myoskeletal effects that have been documented to result from pesticides were also known to interfere with the development of organ systems including the eyes or the heart and are also known to often cause lethal or sublethal edema in exposed organisms. The Physiological, behavioral, and population endpoints affected by pesticides include low or delayed hatching, growth suppression, as well as embryonal or larval mortality. The risks associated with pesticide exposure increase particularly during the spring. This is the period of time in which major pepticide applications take place, and this period unfortunately also coincides with many sensitive reproductive events such as spawning, egg laying, and early development of many aquatic organisms. Only few experimental studies with pesticides have directly linked developmental toxicity with key oxidative stress endpoints, such as lipid peroxidation, oxidative DNA damage, or modulation of antioxidant mechanisms. On the other hand, it has been documented in many reports that pesticide-related oxidative damage occurs in exposed adult fish, amphibians, and invertebrates. Moreover, the contribution of oxidative stress to the toxicity of pesticides has been emphasized in several recent review papers that have treated this topic. In conclusion, the available experimental data, augmented by several indirect lines of evidence, provide support to the concept that oxidative stress is a highly important mechanism in pesticide-induce reproductive or developmental toxicity. Other stressors may also act by oxidative mechanisms. This notwithstanding, there is much yet to learn about the details of this phenomenon and further research is needed to more fully elucidate the effects that pesticides have and the environmental risks they pose in the early development of aquatic organisms.

Linking behavioural alterations with biomarkers responses in the European seabass Dicentrarchus labrax L. exposed to the organophosphate pesticide fenitrothion

The acute effects of the organophosphate insecticide fenitrothion on Dicentrarchus labrax juveniles were investigated through a bioassay using biomarkers and swimming behaviour as effect criteria. After 96 h of exposure to sub-lethal concentrations of fenitrothion, the swimming velocity and several biomarkers were individually determined, namely: brain acetylcholinesterase (AChE) activity; muscle cholinesterases (ChE), lactate dehydrogenase and isocitrate dehydrogenase activities; liver ethoxyresorufin-O-deethylase (EROD), glutathione S-transferases, glutathione peroxidase, glutathione reductase, catalase and superoxide dismutase (SOD) activities and lipid peroxidation levels (LPO). A significant decrease of the swimming velocity (LOEC = 2 mg l(-1)), an inhibition of both AChE (LOEC = 0.06 mg l(-1)) and ChE activities (LOEC = 0.03 mg l(-1)), and a positive and significant correlation between the swimming velocity and AChE were found in exposed fish, suggesting an influence of the inhibition of these enzymes in the swimming velocity decrease. An increase of EROD activity (LOEC = 1 mg l(-1)), indicating the involvement of this enzyme in fenitrothion biotransformation, and a negative and significant correlation between EROD activity and swimming velocity were also found, suggesting that the two findings may somehow be related. Furthermore, results show a significant induction of SOD (LOEC = 0.13 mg l(-1)) without LPO increase, suggesting that the enzyme is preventing oxidative stress damage. No significant alterations were found in any of the other parameters tested. Thus, exposure of seabass to fenitrothion in the wild at concentrations similar to those tested here may have adverse consequences at population level as neurotransmission and swimming ability are essential for fish performance and survival.

Comparative study about the effects of pollution on glass and yellow eels (Anguilla anguilla) from the estuaries of Minho, Lima and Douro Rivers (NW Portugal)

The health status of eels (Anguilla anguilla) developing in three estuaries of the NW Portuguese coast with different types and levels of pollution was compared in relation to morphometric parameters, Fulton condition index (F index) and several biomarkers. Relatively to the reference population, glass eels from the Lima estuary had lower weight and length, cholinesterase (ChE) and lactate dehydrogenase (LDH) inhibition, and lower levels of some anti-oxidant parameters, while yellow eels also showed a decreased F index, and increased Na(+)/K(+)-ATPase and lipid peroxidation (LPO) levels. Relatively to the reference population, glass eels from the Douro estuary had increased Na(+)/K(+)-ATPase and glutathione-S-transferase activities and LDH inhibition, while yellow eels also had ChE inhibition and increased LPO. Overall, these results indicate that eels from polluted estuaries showed a poor health status than those from a reference estuary, and that adverse effects become more pronounced after spending several years in polluted estuaries.

Monitoring pollution of coastal lagoon using Liza aurata kidney oxidative stress and genetic endpoints: an integrated biomarker approach

Despite the importance of fish kidney in several functions (immune, metabolism and excretion of xenobiotics) its use in coastal water biomonitoring focusing on protection and damage is scarce. Five critical sites in Ria de Aveiro (Portugal; Barra--BAR, Gafanha--GAF, Rio Novo do Principe--RIO; Laranjo--LAR and Vagos--VAG) were assessed in comparison to a reference site (Torreira--TOR), focusing on Liza aurata kidney antioxidant defences versus damage responses. Non protein thiols were higher at RIO (near a former bleached kraft pulp mill effluent) and total glutathione at RIO, LAR (mercury contaminated) and VAG (polycyclic aromatic hydrocarbons contaminated). Catalase and glutathione S-transferase activities were higher at RIO and LAR whereas no differences were found in glutathione peroxidase activity. However, glutathione reductase was higher at BAR (subject to naval traffic), GAF (harbour water area), RIO and LAR. No peroxidative damage was observed despite the decreased DNA integrity at RIO and VAG. The integrated biomarker response index ranked impacted sites as: LAR>RIO>BAR>GAF>VAG>TOR.

Inorganic mercury exposure: toxicological effects, oxidative stress biomarkers and bioaccumulation in the tropical freshwater fish matrinxã, Brycon amazonicus (Spix and Agassiz, 1829)

Alterations in the antioxidant cellular system have often been proposed as biomarkers of pollutant-mediated toxicity. This study evaluated the effects of mercury on oxidative stress biomarkers and bioaccumulation in the liver, gills, white muscle and heart of the freshwater fish matrinxã, Brycon amazonicus, exposed to a nominal and sub-lethal concentration (~20% of 96 h-LC(50)) of 0.15 mg L(-1) of mercury chloride (HgCl(2)) for 96 h in a static system. Increases in superoxide dismutase, catalase, glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione reductase (GR) were observed in all tissues after HgCl(2) exposure, except for white muscle GR activity and hepatic GPx. In the liver and gills, the exposure to HgCl(2) also induced significant increases in reduced glutathione (GSH). Conversely, exposure to HgCl(2) caused a significant decrease in the GSH levels and an increase in the oxidized glutathione (GSSG) content in the white muscle, while both GSH and GSSG levels increased significantly in the heart muscle. Metallothionein concentrations were significantly high after HgCl(2) exposure in the liver, gills and heart, but remained at control values in the white muscle. HgCl(2) exposure induced oxidative damage, increasing the lipid peroxidation and protein carbonyl content in all tissues. Mercury accumulated significantly in all the fish tissue. The pattern of accumulation follows the order gills > liver >> heart > white muscle. In conclusion, these data suggest that oxidative stress in response to inorganic mercury exposure could be the main pathway of toxicity induced by this metal in fish.

Wild juvenile Dicentrarchus labrax L. liver antioxidant and damage responses at Aveiro Lagoon, Portugal

The Aveiro Lagoon, at the north-western coast of Portugal, has been under considerable anthropogenic pressure for the last 5 decades. In order to perform an adequate survey of the effects induced by the contaminants in presence, wild juveniles Dicentrarchus labrax (sea bass) were selected. Thus, sea bass was captured at five sites: Torreira (TOR, as reference site), Gafanha (GAF), Rio Novo Príncipe (RIO), Laranjo (LAR) and Vagos (VAG) in autumn 2005. Liver defence responses such as catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), total glutathione (GSHt), total non-protein thiols (NP-SH) and metallothioneins (MT) were measured. Liver damage was determined as lipid peroxidation (LPO) and DNA integrity loss. RIO, LAR and VAG presented lower CAT, GR, GST activities and NP-SH and GSHt depletion in comparison to TOR. VAG and LAR showed higher GPx activity when compared to TOR. The highest MT level was found at GAF and VAG. The NP-SH and DNA integrity decreased at GAF compared to TOR. This field study demonstrated that not only antioxidant induction but also inhibitory responses must be considered as a signal of contamination.

Sub-lethal effects of profenofos on tissue-specific antioxidative responses in a Euryhyaline fish, Oreochromis mossambicus

The euryhaline fish, Oreochromis mossambicus was exposed to sub-lethal concentration (30 microg/L) of profenofos (PF) for 28 days and allowed to recover for 7 days. Responses were evaluated through antioxidant enzyme activities in various tissues of fish. Glutathione-S-transferase (GST) and superoxide dismutase (SOD) activities showed transient increases in gill, viscera and muscle, but decreased in brain. However, catalase (CAT) and glutathione reductase (GR) were inhibited in gill and viscera. Reduced glutathione (GSH) levels were depleted in all the tissues and a significant induction in lipid peroxidation (LPO) was observed. Significant recovery in all the studied parameters was noticed at the end of recuperation period. The enhanced LPO in the present study suggests that reactive oxygen species (ROS)-induced oxidative damage could be one of the main toxic effect of PF. The increased LPO and alterations in the antioxidant defense system can be used as biomarkers in the pesticide-contaminated aquatic streams.

N-Acetylcysteine provides dose-dependent protection against fenthion toxicity in the brain of Cyprinus carpio L

N-Acetyl-L-cysteine, a low-molecular weight thiol compound, with two different doses was used to prevent fenthion, an organophosphorus insecticide and acaricide, related oxidative stress in the brain of a model organism, Cyprinus carpio. Fish were exposed to sub-lethal and nominal concentration of fenthion after intraperitoneal injection of 0.5 or 400 mg/kg NAC. Brain tissues were then dissected and homogenized to analyse GSH, GSSG, TBARS, and protein contents. Enzymes that constitute the first line antioxidant defence, namely SOD and CAT, GSH-related enzymes, GR and GST, together with AChE activities were also determined spectrophotometrically. Fenthion did not cause any alteration in SOD and CAT activities while increasing GSH content, GSH/GSSG ratio and GST specific enzyme activity and decreasing GSSG, TBARS, and protein contents. Although, the highest induction in SOD and GST enzymes activities and the highest increase in GSH content were observed in the 0.5 mg/kg NAC-injected fish, their protein contents showed a decrease. 400 mg/kg NAC impeded the activation of the GST enzyme and a higher decrease in lipid peroxidation was observed. Fish were also protected against protein depletion by the higher dose NAC application. AChE activity was not influenced by fenthion exposure. Xenobiotic and GSH transporters may cause mild oxidative stress conditions in brain. Cellular redox status could trigger a series of reactions that result in an increase in SOD activity and a decrease in protein content. Based on the present results, it was suggested that the usefulness of NAC against fenthion depends on applied dose and tissue characteristics. Species-specifity and concentration selection should be taken into consideration in studies dealing with anticholinesterases.

Yellow eel (Anguilla anguilla) development in NW Portuguese estuaries with different contamination levels

The aims of the present study were to compare the health status of yellow eels (Anguilla anguilla) developing in three estuaries of the NW Portuguese coast with different levels of pollution and their physiological responses to combined effects of environmental variation and pollution. For this, a field study was performed using a multi-parameter approach, including eels condition indexes and biomarkers, water quality variables and other environmental factors. Sixteen biological parameters were assessed, namely: hepatosomatic index (LSI), Fulton's condition index (K), lipid peroxidation (LPO), total glutathione (TG), reduced glutathione (GSH), oxidised glutathione (GSSG), GSH/GSSG, and the activity of the enzymes acetylcholinesterase (AChE), lactate dehydrogenase (LDH), sodium-potassium ATPase (Na(+)/K(+)-ATPase), ethoxyresorufin O-deethylase (EROD), glutathione S-transferases (GST), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR). Ten environmental factors were also measured in water: temperature, salinity, pH, phosphates, nitrates, nitrites, ammonium, silica, phenol and hardness. Globally, the biomarkers indicate exposure and toxic effects of pollutants on eels living in contaminated estuaries. The relationships between biological and environmental variables were assessed through redundancy analysis. K and LSI indexes, AChE and Na(+)/K(+)-ATPase, total glutathione levels and the antioxidant enzymes CAT, GR, and SOD where the factors most discriminating reference (Minho River estuary) from contaminated estuaries (Lima and Douro Rivers estuaries). Moreover, the most striking outcomes of pollutants exposure on biological responses were observed during winter, probably due to a joint effect of cold weather and pollution stress. Altogether, the results indicate that the development of eels in the polluted estuaries of Lima and Douro rivers is interfering with physiological functions determinant for their survival and performance. This may increase the mortality rates during the continental life-phase of the species and decrease the percentage of animals able to successfully complete their oceanic migration and, thus, reduce the contribution of each generation to the next one.

Effects of propanil on the European eel Anguilla anguilla and post-exposure recovery using selected biomarkers as effect criteria

The aim of this study was to assess the physiological response of Anguilla anguilla to propanil and the degree of recovery after being moved to clean water. Preliminary acute toxicity test was carried out in the laboratory and the median lethal concentration (LC50) at 96 h was calculated as 31.33 mg/L (29.60-33.59 mg/L). NOEC and LOEC values (at 96 h) were also calculated as 20 and 25mg/L, respectively. The fish were exposed to 0.63 and 3.16 mg/L of propanil for 72 h and allowed to recover for 144 h. Total proteins (TPs), gamma-glutamil transpeptidase (gamma-GT), alanin aminotransferase (AlAT), alkaline phosphatase (AP), lactate dehydrogenase (LDH) and water content (WC) were assayed in muscle and liver tissues, liver somatic index (LSI) was also determined. Liver TPs and gamma-GT activity decreased after propanil exposure while AlAT and LDH increased. Muscular AP, AlAT and proteins decreased in intoxicated eels while LDH and gamma-GT activities increased. WC increased in both tissues after herbicide exposure as well as LSI. These results revealed that propanil affects the intermediary metabolism of A. anguilla and that the assayed enzymes can be used as good biomarkers of herbicide contamination. However a longer recovery period should be necessary to re-establish eel physiology. The parameters measured in the present study can be used as herbicide toxicity indicators and are recommended for environmental monitoring assessments.

Effects of four carbamate compounds on antioxidant parameters

The effect of four carbamates, aldicarb and its metabolites (aldicarb sulfone and aldicarb sulfoxide) and propoxur on glutathione content and the activity of the enzymes involved in the sulfur-redox cycle in the mammalian cellular model CHO-K1 cells after 24-h exposure were determined. Carbamate exposure resulted in a depletion of intracellular reduced glutathione (GSH) content, no change was observed in oxidized glutathione (GSSG) and a decrease in GSH/GSSG ratio was detected. After carbamates exposition a GSH/GSSG decreases in ranged from 12.44% to 21.35% of control was observed. Depletion of GSH levels was accompanied by the induction of glutathione reductase (GR) after 24h exposure with each of the four carbamates to CHO-K1 cells. After aldicarb sulfone, aldicarb sulfoxide, and propoxur exposure, glutathione peroxidase (GPx) activity increased in CHO-K1 cells by 198%, 32%, and 228% of control, respectively. After aldicarb sulfone and propoxur exposure, glutathione transferase (GST) activities increased by 49% and 230% of control, respectively. Due to the role played by GSH in preventing cytotoxicity via free-radical scavenging, results obtained suggest that high concentrations of aldicarb sulfone and propoxur closely resembling oxidative stress in CHO-K1 cells.

Contamination assessment of a coastal lagoon (Ria de Aveiro, Portugal) using defence and damage biochemical indicators in gill of Liza aurata--an integrated biomarker approach

Fish gill importance in toxicants uptake, bioconcentration and excretion allied to meagre knowledge on branchial damage/protection responses substantiate this study. Five critical sites in Ria de Aveiro (Portugal) were assessed in comparison with a reference site (Torreira), focusing on Liza aurata gill antioxidant defences versus damage (oxidative and genetic). Only in Barra fish displayed damage (lipid peroxidation) though no differences were found in antioxidants. In all other sites, except Rio, antioxidant alterations were found. Thus, fish from Gafanha, Laranjo and Vagos showed higher total glutathione, glutathione peroxidase and catalase. Higher glutathione reductase and glutathione S-transferase activity was also found in the first and the last sites, respectively. In Laranjo, metallothionein levels were higher though lower in Gafanha and Vagos. In general, damage was not accompanied by defences weakening confirming that predicting damage based on antioxidants depletion is not straightforward. The integrated biomarker response index ranked sites as: Gafanha>Barra>Laranjo>Vagos>Rio>Torreira.

Effects of molinate on survival and development of Bombina orientalis (Boulenger) embryos

Molinate, a thiocarbamate chemical is a slightly to moderately toxic herbicide in EPA (Environmental Protection Agency) toxicity class III, and is a registered as a General Use Pesticide (GUP). Bombina orientalis is one of the most common amphibians in the world and comprise a large proportion of their total number in Korea. B. orientalis spawns in the rice fields at spring when the massive application of agricultural chemicals occurs. In the present study, we examined the effects of molinate on embryonic survival and developmental abnormality in B. orientalis embryos. The difference in survival rate between vehicle control and molinate treated embryos was not observed until the blastula stage. The first statistically significant decrease in embryonic survival was observed at mouth open stage following exposure to 100 microM molinate (46.8% vs. 81.1% in control). When the embryos develop to tadpole stage survival was significantly decreased at 50 microM molinate (35.9% vs. 68.9% in control), suggesting that the lowest observed effective dose (LOED) for systemic toxicity in B. orientalis embryos is 50 microM. In survived embryos molinate exposure produced several types of severe developmental abnormalities in order of frequency with bent trunk, neurula with yolk plug, bent tail, tail dysplasia, ventral blister, eye dysplasia, thick-set body and cephalic dysplasia. This suggests that molinate targets multiple events in embryonic and larval development in this frog species. Together this suggested that molinate was detrimental for survival and development following zygotic transcription after midblastula transition in B. orientalis embryos.

Interactions of 2,4,6-trinitrotoluene (TNT) with xenobiotic biotransformation system in European eel Anguilla anguilla (Linnaeus, 1758)

The aim of the present study was to investigate the interaction of 2,4,6-trinitrotoluene (TNT) with liver biotransformation enzymes in European eel Anguilla anguilla (Linnaeus, 1758). Eels were exposed to 0.5, 1 and 2.5mg/l nominal concentrations of TNT for 6 and 24h. Modulation of CYP1A1, UDPGT and GST genes was investigated by real-time PCR. Total CYP450 content, NADPH cytochrome c reductase activity, CYP1A and CYP2B-like activities, such as EROD, MROD and BROD, as well as GST and UDPGT activities, were measured by biochemical assays. An in vitro study was performed on EROD in order to evaluate catalytic modulation by TNT. No modulation of the CYP1A1 gene or protein was observed in TNT-exposed eels. On the other hand, a significant decline of EROD and MROD activities was observed in vivo. An increase in NADPH cyt c reductase, and phase II enzymes (UDPGT and GST) were observed at both gene expression and activity levels. The overall results indicated that TNT is a potential competitive inhibitor of CYP1A activities. A TNT metabolic pathway involving NADPH cyt c reductase and phase II enzymes is also suggested.

Responses of metallothionein and reduced glutathione in a freshwater fish Oreochromis niloticus following metal exposures

In this study, levels of reduced glutathione (GSH) and metallothionein (MT) which are known to be biomarker of metal exposures were measured in a freshwater fish Oreochromis niloticus following exposure to 0, 5, 10 and 20μM concentrations of Cu, Zn, Cd and Pb for 14 days. Metals and GSH were measured in the liver, gill, intestine, muscle and blood, and MT in the liver. Copper accumulation occurred only in the gill, while Zn accumulation occurred only in the muscle. Lead accumulated in the liver and gill, whereas Cd accumulated in all the tissues. Metal exposures did not alter GSH levels in the blood, muscle and gill, but its levels increased in the liver following Cd, Zn and Cu exposures. MT levels in the liver increased only in Cd-exposed fish. The results showed that there was no significant change in tissue GSH levels following metal exposures, except in the liver. The levels of liver GSH increased significantly by all the metals, except lead. Data indicated that only the liver may be suitable indicator tissue to determine the response of GSH and MTs to metal exposure in environmental monitoring studies.