Hydroxyl radical generation and oxidative stress in Carassius auratus liver as affected by 2,4,6-trichlorophenol

With Carassius auratus, one of the main economic fish species in Eastern China as test material, this paper studied the hydroxyl radical generation and oxidative stress in its liver under the effect of 2,4,6-trichlorophenol (2,4,6-TCP). Different doses of 2,4,6-TCP were injected intraperitoneally into the fishes, and the Electron paramagnetic resonance (EPR) spectra of hepatic free radicals, activities of superoxide dismutase (SOD), catalase (CAT) and glutathione-s-transferase (GST), levels of reduced glutathione (GSH) and oxidized glutathione (GSSG), and malondialdehyde (MDA) contents were determined 24h after injection. The results showed that under the effects of 2,4,6-TCP, the generation of free radical that was considered to be hydroxyl radical increased significantly, the activities of antioxidant enzymes decreased, with CAT most strongly affected and followed by SOD and GST, the GSH level decreased significantly while GSSG level had little difference, resulting in a decreased GSH/GSSG ratio, and the MDA content increased significantly. All the test parameters showed that C. auratus was subjected to oxidative stress and damage when exposed to 2,4,6-TCP.     

Effects of malathion and chlorpyrifos on acetylcholinesterase and antioxidant defense system in Oxya chinensis (Thunberg) (Orthoptera: Acrididae)

The study was undertaken to evaluate the effects of malathion and chlorpyrifos on acetylcholinesterase (AChE), esterase (EST) activity and antioxidant system after topical application with different concentration to Oxya chinensis. The results showed that malathion and chlorpyrifos inhibited EST, AChE activity and increased malondialdehyde (MDA) contents. A change in superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione peroxidase (GPx), and glutathione reductase (GR) activity combined with reduced glutathione (GSH) and total glutathione (tGSH) contents was found in O. chinensis after malathion and chlorpyrifos treatments. Malathion and chlorpyrifos increased SOD and CAT activity compared with the control. With the concentrations increasing, SOD and CAT activity showed the similar tendency, namely, SOD and CAT activity increased at the lower concentrations and decreased at the higher concentrations. The results showed that malathion and chlorpyrifos decreased significantly GR activity. GST and GPx activity at the studied concentrations of chlorpyrifos was lower than that of the control. However, no significance was observed. GPx and GST activity in malathion treated grasshoppers showed a biphasic response with an initial increase followed by a decline in its activity. Malathion and chlorpyrifos decreased GSH contents and the ratio of GSH/GSSG. The present findings indicated that the toxicity of malathion and chlorpyrifos might be associated with oxidative stress.     

Effects of long-term alachlor exposure on hepatic antioxidant defense and detoxifying enzyme activities in crucian carp (Carassius auratus)

Alachlor has been widely used in agriculture all over the world. It is suggested that it may be a carcinogen and also an environmental estrogen. In this paper, the physiological and biochemical perturbations of crucian carp (Carassius auratus) exposed to alachlor at different concentrations over 60 days were investigated. The gonadosomatic index (GSI) and hepatosomatic index (HSI) were measured. The activity of hepatic antioxidant defense and detoxifying enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) and the content of glutathione (GSH) were determined and compared with the control group. The result showed that GSI and HSI decreased significantly (P<0.05) in almost all treatments. The activities of SOD, CAT and GST were induced continuously (P<0.05), while the content of reduced glutathione (GSH) was inhibited on the whole. These changes reflect that the antioxidant systems of the tested fishes were affected. The possible defense mechanistic implications about the changes were thus discussed. Furthermore, hepatic SOD and GST were sensitive to alachlor at low concentration, indicating that they might be potential biomarkers in early detection of alachlor contamination in aquatic ecosystems.     

Effects of hexachlorobenzene on antioxidant status of liver and brain of common carp (Cyprinus carpio)

Hexachlorobenzene (HCB)-induced oxidative damages have been published in rats while the effects have not yet been reported in fishes. Juvenile common carps (Cyprinus carpio) were exposed to waterborne HCB from 2 to 200 microg l-1 for 5, 10 or 20 days. Liver and brain were analyzed for various parameters of oxidative stress. There were no significant changes of glutathione (GSH) content and superoxide dismutase (SOD) activity in liver after 5 or 10 days exposure, whereas obvious drops were observed at higher concentrations after 20 days exposure. Significant decreases of GSH content and SOD activity in brain were found during all the exposure days. In brain, HCB also significantly elevated the contents of reactive oxygen species (ROS), thiobarbituric acid- reactive substances (TBARS, as an indicator of lipid peroxidation products), glutathione disulfide (GSSG), and activities of nitric oxide synthase (NOS), glutathione peroxidase (GPx), and glutathione reductase (GR), and inhibited activities of acetylcholinesterase (AchE) and glutathione S-transferase (GST). The results clearly demonstrated that environmentally possible level of HCB could result in oxidative stress in fish and brain was a sensitive target organ of HCB toxicity.     

Atrazine promotes biochemical changes and DNA damage in a Neotropical fish species

The effects of Atrazine, an herbicide used worldwide and considered as a potential contaminant in aquatic environments, were assessed on the Neotropical fish Prochilodus lineatus acutely (24 and 48 h) exposed to 2 or 10 μg L⁻¹ of atrazine by using a set of biochemical and genetic biomarkers. The following parameters were measured in the liver: activity of the biotransformation enzymes ethoxyresorufin-O-deethylase (EROD) and glutathione S transferase (GST), antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), content of reduced glutathione (GSH), generation of reactive oxygen species (ROS) and occurrence of lipid peroxidation (LPO); in brain and muscle the activity of acetylcholinesterase (AChE) and DNA damage (comet assay) on erythrocytes, gills and liver cells. A general decreasing trend on the biotransformation and antioxidant enzymes was observed in the liver of P. lineatus exposed to atrazine; except for GR, all the other antioxidant enzymes (SOD, CAT and GPx) and biotransformation enzymes (EROD and GST) showed inhibited activity. Changes in muscle or brain AChE were not detected. DNA damage was observed in the different cell types of fish exposed to the herbicide, and it was probably not from oxidative origin, since no increase in ROS generation and LPO was detected in the liver. These results show that atrazine behaves as enzyme inhibitor, impairing hepatic metabolism, and produces genotoxic damage to different cell types of P. lineatus.     

Effects of cadmium on glutathione synthesis in hepatopancreas of freshwater crab, Sinopotamon yangtsekiense

Cadmium (Cd) is one of the most deleterious heavy metals in aquatic systems that could promote oxidative damage. To explore the effects of Cd exposure of a freshwater crab (Sinopotamon yangtsekiense) on hepatopancreatic glutathione (GSH) synthesis, crabs were exposed to the reagent with a dose range of 7.25-116.00 mg L(-1) for 48 h. The concentrations of GSH, oxidized glutathione (GSSG), NADPH and NADP(+), as well as the activities of enzymes involved in GSH synthesis, i.e. glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PD), gamma-glutamylcysteine synthetase (gamma-GCS) were determined. Progressive depletion of cellular GSH content was observed with the increasing of Cd concentrations, while the level of GSSG remained constant. In response to Cd exposure, crabs showed significant induction of G6PD and NADPH, however, only up to moderate exposures. GR activity remained at a steady level at all exposure concentrations. The activity of gamma-GCS was significantly positively correlated with the Cd concentration. These results suggested that GSH synthesis could be activated against reactive oxygen species induced by lower Cd exposure; under the higher Cd exposure conditions, an inhibition of NADPH-dependant redox cycling and de novo GSH synthesis led to significant decrease in GSH content.     

Establishing the redox potential of Tibouchina pulchra (Cham.) Cogn., a native tree species from the Atlantic Rain Forest,in the vicinity of an oil refinery in SE Brazil

The present study aimed to establish the seasonal variations in the redox potential ranges of young Tibouchina pulchra plants growing in the Cubatão region (SE Brazil) under varying levels of oxidative stress caused by air pollutants. The plants were exposed to filtered air (FA) and non-filtered air (NFA) in open-top chambers installed next to an oil refinery in Cubatão during six exposure periods of 90 days each, which included the winter and summer seasons. After exposure, several analyses were performed, including the foliar concentrations of ascorbic acid and glutathione in its reduced (AsA and GSH), total (totAA and totG) and oxidized forms (DHA and GSSG); their ratios (AsA/totAA and GSH/totG); the enzymatic activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR); and the content of malondialdehyde (MDA). The range of antioxidant responses in T. pulchra plants varied seasonally and was stimulated by high or low air pollutant concentrations and/or air temperatures. Glutathione and APX were primarily responsible for increasing plant tolerance to oxidative stress originating from air pollution in the region. The high or low air temperatures mainly affected enzymatic activity. The content of MDA increased in response to increasing ozone concentration, thus indicating that the pro-oxidant/antioxidant balance may not have been reached.     

Histopathological changes and antioxidant response in brain and kidney of common carp exposed to atrazine and chlorpyrifos

We investigated oxidative stress response and histopathological changes in the brain and kidney of the common carp after a 40-d exposure to CPF and ATR, alone or in combination, and a 20-d recovery. Superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities and malondialdehyde (MDA) content were measured using standard assays. Our results indicated that exposure to ATR, CPF or a combination of the two for 40 d induced significant changes in antioxidant enzyme (SOD, CAT and GSH-Px) activities and MDA content in the brain and kidney of the common carp. Pathological changes included tissue damage that was more severe with increased of exposure dose. To our knowledge, this is the first report to study oxidative stress and histopathological effects caused by subchronic exposure to ATR, CPF and ATR/CPF combination on common carp. The information presented in this study may be helpful to understanding the mechanisms of ATR-, CPF- and ATR/CPF combination-induced oxidative stress in fish.     

Acrylamide-induced disturbance of the redox balance in the chick embryonic brain

This study was undertaken to determine the redox balance in the developing brain after exposure to acrylamide (ACR), a potent neurotoxin. The studies were performed using an in ovo chick embryo model. The antioxidant enzymes SOD, GPx, CAT, and reduced glutathione (GSH) were used as indicators of the redox balance. Eggs were injected with ACR doses of 40 mg kg^?1 egg mass (2.4 mg egg^?1) on embryonic day 17 (E17). The activity of the antioxidant enzymes and the concentration of GSH were measured at E17, E18, and E19 in the medulla oblongata, cerebrum, cerebellum, and optic lobe. The results indicated a significant decrease in the GSH concentrations in the optic lobe (E19, E20) and cerebrum (E20) of embryos exposed to ACR. The activities of SOD and GPx were significantly increased in the majority of the examined structures after injection of ACR. CAT activity was completely inhibited in the brains of the embryos exposed to ACR compared to that in the brains of the control embryos. Thus, we concluded that ACR exerts a significant influence on the redox balance in the developing brain by impacting the activity of antioxidant enzymes and the levels of GSH.     

Lead detoxification by coontail (Ceratophyllum demersum L.) involves induction of phytochelatins and antioxidant system in response to its accumulation

Coontail (Ceratophyllum demersum L.) plants when exposed to various concentrations of Pb (1-100microM) for 1-7days, exhibited both phytotoxic and tolerance responses. The specific responses were function of concentration and duration. Plants accumulated 1748mugPbg(-1) dw after 7d which reflected its metal accumulation ability, however most of the metal (1222microgg(-1) dw, 70%) was accumulated after 1d exposure only. The toxic effect and oxidative stress caused by Pb were evident by the reduction in biomass and photosynthetic pigments and increase in malondialddehyde (MDA) content and electrical conductivity with increase in metal concentration and exposure duration. Morphological symptoms of senescence phenomena such as chlorosis and fragmentation of leaves were observed after 7d. The metal tolerance and detoxification strategy adopted by the plant was investigated with reference to antioxidant system and synthesis of phytochelatins. Protein and antioxidant enzymes viz., superoxide dismutase (SOD, EC 1.15.1.1), guaiacol peroxidase (GPX, EC 1.11.1.7) ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6) and glutathione reductase (GR, EC 1.6.4.2) showed induction at lower concentration and duration followed by decline. All enzymes except GPX showed maximum activity after 1d. An increase in cysteine, non-protein thiols (NP-SH) and glutathione (GSH) content was observed at moderate exposure conditions followed by decline. Phytochelatins (PC(2) and PC(3)) were synthesized to significant levels at 10 and 50microM Pb with concomitant decrease in GSH levels. Thus production of PCs seems important for the detoxification of metal, however it may lead to depletion of GSH and consequently oxidative stress. Results suggest that plants responded positively to moderate Pb concentrations and accumulated high amount of metal. Due to metal accumulation coupled with detoxification potential, the plant appears to have potential for its use as phytoremediator species in aquatic environments having moderate pollution of Pb.     

Copper and zinc induction of lipid peroxidation and effects on antioxidant enzyme activities in the microalga Pavlova viridis (Prymnesiophyceae)

The metal-induced lipid peroxidation and response of antioxidative enzymes have been investigated in the marine microalga Pavlova viridis to understand the mechanisms of metal resistance in algal cells. We have analyzed superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) activities and glutathione (GSH) contents in microalgal cells grown at different concentrations of copper and zinc. In response to each metal, lipid peroxidation was enhanced with the increase of concentrations, as an indication of the oxidative damage caused by metal concentration assayed in the microalgae cells. Exposure of P. viridis to the two metals caused changes in enzyme activities in a different manner, depending on the metal assayed: after copper treatments, total SOD activity was enhanced, while it was reduced after zinc exposure. Copper and zinc stimulated the activities of CAT and GSH whereas GPX showed a remarkable increase in activity in response to copper treatments and decrease after zinc treatments. These results suggest that an activation of some antioxidant enzymes was enhanced to counteract the oxidative stress induced by the two metals.     

Toxicity assessment of municipal sewage treatment plant effluent by an integrated biomarker response in the liver of crucian carp (Carassius auratus)

In this study, crucian carp (Carassius auratus) was exposed to the increasing concentrations of municipal sewage treatment plant effluent (MSTPE) for 15 days, and the activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and acetylcholinesterase (AChE), together with the contents of malondialdehyde (MDA) and glutathione (GSH) in the liver of C. auratus were investigated. Moreover, the integrated biomarker response (IBR) approach was applied to assess the adverse effects of MSTPE in freshwater. The aim of the study was to provide an effective biological indicator for evaluating the toxicity effects and ecological risks of MSTPE in the freshwater environment quantitatively. Results showed that MSTPE could cause oxidative damage to the liver of C. auratus, which reflected through the increasing MDA content over the exposure period. MSTPE also led to the biochemical responses of antioxidant defense in C. auratus liver, such as the enhancement of SOD, CAT, and GPx activities, as well as the inhibition of AChE activity and GSH content. It was found that MDA, SOD, GPx, and GSH could be used as the biomarkers for reflecting the adverse effects of MSTPE in the receiving freshwater on the 12th day of exposure. A significant increase of IBR values was observed as the increasing concentration of MSTPE, and the IBR values presented a significant positive correlation (r?=?0.891, P?<?0.05) with the increasing concentrations of MSTPE, indicating that IBR approach is a promising tool for assessing the toxicity effects of MSTPE in environmental freshwater.

     

Anguilla anguilla L. oxidative stress biomarkers: an in situ study of freshwater wetland ecosystem (Pateira de Fermentelos, Portugal)

Pateira de Fermentelos (PF) is a natural freshwater wetland in the central region of Portugal. In the last decade, the introduction of agricultural chemicals, heavy metals, domestic wastes, as well as eutrophication and incorrect utility of resources resulted in an increased water pollution. The present research work was carried out to check the various oxidative stress biomarker responses in European eel (Anguilla anguilla L.) gill, kidney and liver due to this complex water pollution. Eels were caged and plunged at five different PF sites (A-E) for 48h. A reference site (R) was also selected at the river spring where no industrial contamination should be detected. Lipid peroxidation (LPO), catalase (CAT), glutathione peroxidase (GPX), glutathione S-transferase (GST) and reduced glutathione (GSH) were the oxidative stress biomarkers studied. In gill, site A exposure induced a significant GST activity increase and site B exposure induced CAT activity increase when compared to R. Site C exposure showed a significant CAT and GPX activity increase. Data concerning site D exposure were not determined due to cage disappearance. Site E exposure displayed a significant CAT and GST activity increase. In kidney, site A exposure induced a significant CAT and GPX decrease as well as a GST increase. Site B exposure showed a significant decrease in GPX activity and GSH content. However, site C exposure demonstrated a significant increase in CAT and a decrease in GPX. Site E exposure showed a significant decrease in GPX and increase in GST. In liver, site A exposure showed a significant GST activity decrease as well as GSH content increase. Site B exposure showed a significant CAT, GST and LPO decrease. Site C exposure showed only GST activity decrease, while site E exposure induced a significant increase in GPX. These investigation findings provide a rational use of oxidative stress biomarkers in freshwater ecosystem pollution biomonitoring using caged fish, and the first attempt reported in Portugal as a study of this particular watercourse under the previous conditions. The presence of pollutants in the PF water was denunciated even without a clear relation to the main pollution source distance. The organ specificity was evident for each parameter but without a clear pattern.     

Cytotoxic effect of fenitrothion and lambda-cyhalothrin mixture on lipid peroxidation and antioxidant defense system in rat kidney

A mixture of pyrethroids plus organophosphates was assessed for their potential effects on lipid peroxidation, the antioxidant defense system and lactate dehydrogenase (LDH) in rat kidney in vitro. Various insecticide concentrations were incubated with kidney homogenate at 37°C for different incubation times. Treatment with fenitothion (FNT) plus lambda-cyhalothrin (LC) caused a significant induction (P < 0.05) in thiobarbituric acid reactive substances (TBARS), which might be associated to decreased levels of reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) activities and protein content in rat kidney. However, a significant induction of lactate dehydrogenase (LDH) activity was observed. The effect was concentration and time dependent. It can be concluded that depletion of GSH might indicate that reactive oxygen species (ROS) could be involved in the toxic effects of FNT plus LC which lead to marked perturbations in antioxidant defense system.     

Oxidative stress and biochemical perturbations induced by insecticides mixture in rat testes

The joint action of pyrethroids, lambda-cyhalothrin (LC) in combination with organophosphates, fenitrothione (FNT) on antioxidant defense system and lipid peroxidation biomarkers in rat testes was studied. The results suggest that incubation of testes homogenate with different concentrations of insecticide mixture for different time intervals significantly decreased the activity of antioxidant enzymes, like glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT), and the level of reduced glutathione (GSH). In addition, a significant inhibition in transaminases (AST, ALT), phosphatases (AcP, AlP) activity and protein content were observed. On the other hand, FNT plus LC increased the cellular lipid peroxidation (LPO) level and the activity of lactate dehydrogenase (LDH). In conclusion, the use of insecticides mixture might cause marked oxidative damage in a concentration and time-dependent manner.     

The redox state and activity of superoxide dismutase classes in Arabidopsis thaliana under cadmium or copper stress

The redox state of glutathione and ascorbate as well as the activity of superoxide dismutase classes were determined in leaves of Arabidopsis thaliana grown for seven days in the nutrient solution containing 0, 5 and 50 microM Cd or Cu excess. A decrease in GSH/GSSG ratio was found in plants under Cd and Cu stress. In the plants exposed to Cu stress the activity of all SOD classes increased. However, in the plants treated with Cd the activity of FeSOD and MnSOD was elevated, but CuZnSOD activity was diminished in comparison with control. In these plants the activity of SOD classes was dependent on both the GSH/GSSG and AA/DHA ratios, while in those exposed to Cu excess - on the GSH/GSSG ratio. Differences were shown in the changes both in redox state and activity of SOD classes caused by the metals differing in physiochemical properties. Moreover, relationships between changes in SOD class activities and ROS levels were discussed.     

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.     

Cytotoxic effect of fenitrothion and lambda-cyhalothrin mixture on lipid peroxidation and antioxidant defense system in rat kidney

A mixture of pyrethroids plus organophosphates was assessed for their potential effects on lipid peroxidation, the antioxidant defense system and lactate dehydrogenase (LDH) in rat kidney in vitro. Various insecticide concentrations were incubated with kidney homogenate at 37°C for different incubation times. Treatment with fenitothion (FNT) plus lambda-cyhalothrin (LC) caused a significant induction (P < 0.05) in thiobarbituric acid reactive substances (TBARS), which might be associated to decreased levels of reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) activities and protein content in rat kidney. However, a significant induction of lactate dehydrogenase (LDH) activity was observed. The effect was concentration and time dependent. It can be concluded that depletion of GSH might indicate that reactive oxygen species (ROS) could be involved in the toxic effects of FNT plus LC which lead to marked perturbations in antioxidant defense system.     

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

The redox cycling of heavy metals as well as their interactions with organic pollutants is a major contributor to the oxidative stress resulting from aquatic pollution. Therefore, in order to evaluate beta-naphthoflavone (BNF), Cu and BNF/Cu-induced oxidative stress with single and subsequent exposures, research was carried out in European eel (Anguilla anguilla L.). Eel gill and kidney oxidative stress biomarker responses such as lipid peroxidation (LPO), glutathione peroxidase (GPX), catalase (CAT), glutathione S-transferase (GST) and total reduced glutathione (GSH) to a single 24 h exposure to two copper concentrations (Cu-1 microM, 2.5 microM) and BNF (2.7 microM) with or without 24 h BNF (2.7 microM) pre-exposure were investigated. Cu exposure alone showed a significant gill GST increase at the lowest concentration and GSH content decrease for the highest concentration. Double BNF exposure in gill demonstrated a significant increase in LPO, CAT, GPX and GST, as well as a decrease in GSH content. However, in sequential BNF/Cu exposures, only the highest Cu concentration exhibited a significant increase in LPO and GSH as well as a decrease in GPX (vs. BNF + CW). In kidney, Cu exposure alone showed a significant CAT and GSH contents decrease for both concentrations, and at highest concentration in GPX; as well as GST increase at the lowest concentration. Double BNF exposure showed a significant increase in LPO and GST. Nevertheless, in sequential BNF/Cu exposures, both concentrations exhibited a significant increase in LPO and decrease in GSH contents. Moreover, LPO was also increased significantly in comparison to BNF+CW and the equivalent Cu exposures without BNF pre-exposure. Concerning GPX, a significant increase was observed at highest Cu concentration. In GST, a significant decrease at the lowest Cu concentration and increase at the highest Cu concentration was observed. Summarizing, a simple copper or BNF exposures have no ability to induce LPO in both gill and kidney. However, double BNF exposure induced LPO in both organs and sequential BNF/Cu exposures potentiated the risk of peroxidative damage occurrence in both organs. BNF/Cu interference on antioxidant responses differs between the studied organs. In gill, antagonistic effects were denoted with probable reflex in terms of peroxidative damage increase. In kidney, BNF pre-exposure prevented CAT and GPX inhibition by copper; though, no advantage of this effect was perceptible as defence against LPO generation. Considering BNF as a surrogate for a PAH and the detected interactions with copper, as well as the likelihood that these effects would be observed in polluted ecosystems, current results demonstrate their relevance to actual ecological exposures contributing to a better knowledge on oxidative stress mechanisms in fish.     

Effects of chitosan on oxidative stress and metallothioneins in aquatic worm Tubifex tubifex (Oligochaeta, Tubificidae)

Chitosan is a natural polymer which has the property to elicit the natural defenses mechanism in plant and which can be an interesting biopesticides. It is then necessary to investigate the potential toxicity of chitosan for aquatic animal health. Metallothioneins (MTs) are low molecular weight proteins, mainly implicated in metal ion detoxification. Increase in MTs contents had been considered as a specific biomarker of metal exposure. However recently it has been demonstrated that MTs participate in several cellular functions such as regulation of growth and anti-oxidative defenses. Therefore, the induction of MTs has been investigated in the aquatic worms Tubifex tubifex exposed to chitosan. MTs levels in exposed worm increased significantly (p > 0.05) after 2, 4, and 7 days of exposure to different concentrations of chitosan (maximum + 158.19 +/- 10.2% after 2 days of exposure to 125 mgl(-1) of chitosan). Several antioxidant parameters including glutathione (GSH), glutathione-S-transferase (GST), glutathione reductase (GR), and catalase (CAT) were quantified in T. tubifex after 2, 4, and 7 days of exposure to chitosan. Exposure to chitosan had a negative effect on T. tubifex growth (maximum effect -6.11 +/- 1.6% after 7 days with 125 mgl(-1)) demonstrating the toxic effect of the pesticide. This growth rate decrease was accompanied by a reduction in protein contents. The activity of catalase (CAT), glutathione-S-transferase (GST), and glutathione reductase (GR) increased in response to the chitosan demonstrating an oxidative stress in the worms.