Different activity of glyoxalase system enzymes in specimens of Sparus auratus exposed to sublethal copper concentrations

Contamination by Trace Elements and Oxidative Stress in the Skeletal Muscle of Scyliorhinus canicula from the Central Tyrrhenian Sea

Marine pollution, due to the regular discharge of contaminants by various anthropogenic sources, is a growing problem that imposes detrimental influences on natural species. Sharks, because of a diet based on smaller polluted animals, are exposed to the risk of water contamination and the subsequent bioaccumulation and biomagnification. Trace elements are very diffuse water pollutants and able to induce oxidative stress in a variety of marine organisms. However, to date, studies on sharks are rather scarce and often limited to mercury. In this context, the present study aimed to analyze the accumulation of trace elements and their putative correlation with the onset of an oxidative status in the muscle of the lesser spotted dogfish Scyliorhinus canicula, from the Central Mediterranean Sea. Ecotoxicological analysis detected the presence of Pb, As, Cd, Mn, Zn, Ni, Cu, and Fe; no significant differences were observed between sexes, while a negative correlation was found between Pb and animal length. Analysis of oxidative stress markers showed either positive or negative correlation with respect to the presence of trace elements. Lipid peroxidation (TBARS) positively correlated with Zn, Ni, and Fe; SOD enzyme activity negatively correlated with Cu and Ni; LDH was negatively correlated with Fe and positively correlated with Pb. Moreover, positive correlations between the leukocyte count and Mn and Zn, as well as with LDH activity, were also observed. The data suggested that, in sharks, trace elements accumulation may affect oxidant and antioxidant processes with important outcomes for their physiology and health.

2, 3-Dimethylsuccinic acid and fulvic acid attenuate lead-induced oxidative misbalance in brain tissues of Nile tilapia Oreochromis niloticus

Lead has long been known as neurotoxic and immunotoxic heavy metal in human and animals including fish, whereas, 2, 3-dimethylsuccinic acid (DMSA) and fulvic acid (FA) are well-known biological chelators. The present investigation was carried out to assess the potential chelating and antioxidant effects of dietary supplementation with DMSA and FA against lead acetate (Pb)-induced oxidative stress in Nile tilapia, O. niloticus. One-hundred and eighty apparently healthy O. niloticus fish (30 ± 2.5 g) were allocated into six equal groups. The first group was fed on basal diet and served as control, while the second group was fed on DMSA-supplemented basal diets at levels of 30 mg/kg diet; the third group was fed on FA-supplemented basal diet at level of 0.3 mg/kg diet; the forth, fifths, and sixth groups were exposed to 14.4 mg Pb /L water (1/10 LC50) and feed on basal diet only, basal diet supplemented with DMSA (0.3 mg/kg diet), or basal diet supplemented with FA (0.3 mg/kg diet), respectively. Antioxidant and lipid peroxidative status, activity of glucose 6-phosphate dehydrogenase (G6PD), and lactate dehydrogenase (LDH) as well as the histopathologic findings were evaluated in brain tissues, while the Pb residues were evaluated in liver, muscles, and brain tissues. The results of the present study showed that DMSA and FA decreased malondialdehyde (MDA) and Pb residue in tissues of Pb-exposed fish and improved the histologic picture and brain contents of glutathione (GSH), glutathione-s-transferase (GST), glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), G6PD, LDH, and total antioxidant capacity (TAC). It could be concluded that DMSA and FA supplementation exhibited potential neuroprotective effect against Pb-induced oxidative brain damages in O. niloticus through improvement of antioxidant status of the brain tissue.

Effects of lithium and selenium in the tail muscle of American bullfrog tadpoles (Lithobates catesbeianus) during premetamorphosis

The amphibian populations have faced a drastic decline over the past decades. This decline has been associated with the presence of contaminants in the environment, among other environmental stressors. The present study tested the responses following the exposure to lithium (2.5 mg L^-1) and selenium (10μg L^-1), both isolated and as a mixture, on the metabolic status of the tail muscle of premetamorphic American bullfrog (Lithobates catesbeianus) through the assessment of the total protein content, mobilization of glucose and triglycerides, and the activity of lactate dehydrogenase (LDH). The exposure followed a 21-day assay with two sampling periods (on the 7th and 21st day after the onset of exposure) to evaluate the effects over time. The group exposed to the mixture presented a statistically decreased LDH activity (P < 0.05) in both sampling periods. The presence of selenium elicited a statistically significant increase (P < 0.05) in the glucose mobilization after 7 days of exposure. After 21 days, the animals exposed to selenium presented levels of glucose mobilization comparable to the control group. The mobilization of glucose and triglycerides remained similar to the control group for the animals exposed to lithium and to the mixture in both periods of sampling (P > 0.05). The total protein content did not show any statistical difference in the treated groups throughout the experiment (P > 0.05). The presented results highlight the importance of the assessment of mixtures that can occur in the environment, since the combination of contaminants may elicit distinct toxicity compared with the effects triggered by the chemicals isolated.

Combining elevated temperature with waterborne copper: Impacts on the energy metabolism of the killifish Poecilia vivipara

We have previously demonstrated in a companion work that acclimation to 28 °C potentiated waterborne copper (Cu) toxic effects in Poecilia vivipara through oxidative stress-related processes. In the present study, we hypothesized that these results were related to kinetic metabolic adjustments in enzymes from aerobic and anaerobic pathways. To test this, P. vivipara was acclimated to two temperatures (22 °C or 28 °C) for three weeks and then exposed to Cu (control, 9 or 20 μg/L) for 96 h. The activity of enzymes from glycolysis (pyruvate kinase [PK] and lactate dehydrogenase [LDH]), Krebs cycle (citrate synthase [CS]) and the electron transport chain system (ETS) were assessed in gills, liver and muscle. Interactive effects were only seen for hepatic LDH activity, as both metal exposure and heat stress, combined or not, inhibited this enzyme, showing a suppression in anaerobic pathways. Conversely, a Cu main effect was present in the liver, expressed as an elevation in ETS activity, showing an enhancement in hepatic aerobic metabolism likely related with the very energy-demanding process of metal detoxification. Moreover, this study shows that P. vivipara has a remarkable ability to compensate heat stress in terms of energy metabolism, as we could not observe acclimation temperature effects for most of the cases. Nonetheless, a tissue-dependent effect of elevated temperature was observed, as we could observe an inhibition in muscular CS activity. Finally, it is concluded that kinetic adjustments in terms of the energy metabolism are not related with the temperature-dependent elevation of Cu toxicity in P. vivipara as we previously hypothesized.

Metabolic responses in bullfrog, Lithobates catesbeianus after exposure to zinc, copper and cadmium

This study investigated the activity of lactated dehydrogenase (LDH), malate dehydrogenase (MDH) enzymes and the levels of glucose, protein and triglyceride in bullfrog tadpoles after exposure to 1 μg L^-1 of zinc (Zn), copper (Cu) and cadmium (Cd) isolated and combined for 2 and 16 days. Zn, Cu + Cd and Zn + Cu + Cd increased the activity of the LDH (2 and 16 days) and MDH (2 days) enzymes in the liver; and MDH increased in the kidney after 16 days in all co-exposed groups compared to the control. Glucose increased in the liver in the Zn and Cu groups at 2 and 16 days of exposure and decreased in the kidney (groups Cd, Zn + Cd and Cu + Cd) and muscle (Cd) at 2 days of exposure. After 2 days of exposure, the protein increased in the liver (Zn), in the kidney in all groups exposed to metals except in the groups exposed to Cd and Zn + Cu + Cd, which did not change and decreased in muscle in all the groups exposed to isolated metals. Regarding triglycerides, the kidney and muscle were the most affected, leading to a decrease in the Zn, Cu and Cd groups and in the Zn + Cu (16 days) and Zn + Cu + Cd groups (2 days). The anaerobiosis and aerobiosis were activated in the liver and kidney after short-term exposure (2 days) and in the kidney, the aerobic metabolism was activated after chronic exposure (16 days). The metals caused toxicity and were higher in co-exposure to metals with a potential to cause metabolism damage in L. catesbeianus.

Effect of copper exposure and recovery period in reared Diplodus sargus

The aquaculture growth can be followed by the occurrence of more and new pathogenic agents, since the production leads to higher fish densities in confined areas more appropriate to the appearance and propagation of pathologies. Copper sulfate has been widely used in preventing and controlling fish parasites. The objective of this study is to investigate the effects of copper treatments in the fish tissues (bioaccumulation and histological changes in different organs), mortality and evaluate what happens during the recovery period. White sea bream (Diplodus sargus) were exposed to copper sulfate (0.25 and 0.5 mg L^-1) during 60 days followed with a 75-day recovery period. The results showed that the concentration of copper in fish liver was significantly higher in the 0.5 mg L^-1 treatment than in the 0.25 mg L^-1 treatment. Conversely, copper load in the muscle did not differ significantly between treatments and control. Copper levels in muscle, and especially in liver, increased during copper exposure (up to 60 days). In summary, at higher concentrations copper sulfate treatment (0.5 mg L^-1) might be toxic to fish, which showed histological alterations and copper accumulation in their tissues, mainly in the liver. Nevertheless, individuals returned to their original state after a 75-day recovery period and the tested copper concentrations does not represents risk for food safety.

Silver nanoparticles cause osmoregulatory impairment and oxidative stress in Caspian kutum (Rutilus kutum, Kamensky 1901)

Silver nanoparticles (AgNPs) are increasingly used in several industrial and household products because of their antibacterial and antifungal properties. Hence, there is an inevitable risk that these chemicals may end up in aquatic biotopes and have adverse effects on the fauna. In order to assess potential health effects on aquatic organisms, this study evaluated the effects of waterborne AgNP exposure for 7 days on a set of critical stress parameters in juvenile Caspian kutum (Rutilus kutum), an economically important fish in the Caspian Sea. The applied level 11 μg/l of AgNP is high compared to reported water concentrations and corresponds to 40% of the 96 h LC₅₀ value, initially determined to be 28 μg/l. Gill heat shock protein 70 (hsp70) mRNA expression, Na⁺/K⁺-ATPase activity and enzymatic activities of liver superoxide dismutase (SOD), glutathione peroxidase (Gpx), lactate dehyrogenase (LDH) and alkaline phosphatase (ALP), and whole-body cortisol and thyroid hormones (T3 and T4) were measured as endpoints. Gill hsp70 mRNA expression increased and gill Na⁺/K⁺-ATPase activity decreased in AgNP-exposed fish compared to controls. The specific activities of all liver enzymes decreased significantly compared to controls. Whole-body cortisol and thyroid hormones decreased compared to controls. In conclusion, the study demonstrates that AgNPs cause oxidative stress and gill osmoregulatory disruption in Caspian kutum juveniles.

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

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

Blue sharks (Prionace glauca) as bioindicators of pollution and health in the Atlantic Ocean: Contamination levels and biochemical stress responses

Marine ecosystems are constantly being threatened by contaminants produced by human activities. There is an urge to better understand their impacts on marine organisms and develop reliable tools for biomonitoring studies, while also assessing their potential impacts on human health. Given their position on top of food webs, sharks are particularly susceptible to bioaccumulation, making them potential sentinel species of marine contamination. The main objective of this study was to find suitable biomarkers for future marine pollution biomonitoring studies by correlating biochemical responses with tissue contaminant body burden in blue sharks (Prionace glauca), a species heavily caught and consumed by humans, while also addressing their general health. The chemical contaminants analysed comprised different persistent organic pollutants (POPs) families from polychlorinated compounds to brominated flame retardants (BFRs) and perfluorinated compounds (PFCs) and different trace and heavy metals. Concentrations of some contaminants in sharks' tissues were found to be above the legally allowed limits for human consumption. A canonical correspondence analysis (CCA) was performed and some strong associations were found between biochemical responses and contaminants' accumulation levels. DNA damage and lipid peroxidation levels, as well as the inhibition of the antioxidant enzyme glutathione peroxidase, were the main effects and consequences of contamination. The impact of contamination on these vital macromolecules underlines the suboptimal conditions of the sampled P. glauca, which can ultimately lead to the degradation of core ecological aspects, such as swimming, feeding, and reproduction. It can be concluded that P. glauca demonstrates great potential to be used as environmental sentinel and suitable biomarker candidates were identified in this work. Moreover, this study also highlights the risks that the consumption of blue shark derived products can pose to human health, which is of upmost interest as the sampled organisms were still juveniles and already presented values above regulatory limits.

Effects of copper, hypoxia and acute temperature shifts on mitochondrial oxidation in rainbow trout (Oncorhynchus mykiss) acclimated to warm temperature

Temperature fluctuations, hypoxia and metals pollution frequently occur simultaneously or sequentially in aquatic systems and their interactions may confound interpretation of their biological impacts. With a focus on energy homeostasis, the present study examined how warm acclimation influences the responses and interactions of acute temperature shift, hypoxia and copper (Cu) exposure in fish. Rainbow trout (Oncorhynchus mykiss) were acclimated to cold (11°C; control) and warm (20°C) temperature for 3 weeks followed by exposure to environmentally realistic levels of Cu and hypoxia for 24h. Subsequently, mitochondrial electron transport system (ETS) respiratory activity supported by complexes I-IV (CI-IV), plasma metabolites and condition indices were measured. Warm acclimation reduced fish condition, induced aerobic metabolism and altered the responses of fish to acute temperature shift, hypoxia and Cu. Whereas warm acclimation decelerated the ETS and increased the sensitivity of maximal oxidation rates of the proximal (CI and II) complexes to acute temperature shift, it reduced the thermal sensitivity of state 4 (proton leak). Effects of Cu with and without hypoxia were variable depending on the acclimation status and functional index. Notably, Cu stimulated respiratory activity in the proximal ETS segments, while hypoxia was mostly inhibitory and minimized the stimulatory effect of Cu. The effects of Cu and hypoxia were modified by temperature and showed reciprocal antagonistic interaction on the ETS and plasma metabolites, with modest additive actions limited to CII and IV state 4. Overall, our results indicate that warm acclimation came at a cost of reduced ETS efficiency and increased sensitivity to added stressors.

Oxidative stress and metabolic responses to copper in freshwater- and seawater-acclimated killifish, Fundulus heteroclitus

In freshwater (FW), many of the main mechanisms of copper (Cu) toxicity have been characterized; however, toxicity mechanisms in seawater (SW) are less well understood. We investigated the effects of salinity on Cu-induced oxidative stress and metabolic responses in adult killifish, Fundulus heteroclitus. We exposed FW and SW-acclimated killifish to either low Cu (LC, 50 μg/L) or high Cu (HC, 200 μg/L) for 96 h and compared them to controls (CTRL) under the same salinities without added Cu. Cu exerted minimal influence on tissue ion levels in either FW or SW. Salinity generally protected against Cu bioaccumulation in the gills and liver, but not in the carcass. Hematocrit (Hct) and hemoglobin (Hb) levels were increased by LC and HC in both FW and SW, and blood lactate was reduced in FW-killifish exposed to LC and HC. Rates of oxygen consumption were similar across treatments. Salinity reduced Cu load in gill, liver and intestine at LC but only in the gills at HC. In general, Cu increased gill, liver, and intestine catalase (CAT) activity, while superoxide dismutase (SOD) either decreased or remained unchanged depending on tissue-type. These changes did not directly correlate with levels of protein carbonyls, used as an index of oxidative stress. Cu-induced changes in carbohydrate metabolic enzymes were low across tissues and the effect of salinity was variable. Thus, while salinity clearly protects against Cu bioaccumulation in some tissues, it is unclear whether salinity protects against Cu-induced oxidative stress and metabolic responses.

Biomarkers responses in muscle of Senegal sole (Solea senegalensis) from a heavy metals and PAHs polluted estuary

The biochemical responses in muscle, such as the enzymatic activities of acetylcholinesterase, lactate dehydrogenase and isocitrate dehydrogenase, were studied in sole (Solea senegalensis) collected in Huelva estuary (SW Spain), in the vicinity of a petrochemical and mining industry. The sampling sites showed different type and degree of pollution. The results demonstrated significant differences in muscle activities of AChE and IDH in Odiel and Tinto Rivers compared to control fish. LDH activity did not show any difference between sampling sites. Significant correlations were established between some biomarkers and heavy metals: AChE was correlated with Pb, Cd and Cu concentrations in water; IDH activity was correlated with Cd and Cu concentrations in water and As, Pb and Cd concentrations in sediments; LDH activity was correlated with As and Zn concentration in water and Cd concentration in sediment. Only one correlation was established between the biomarkers analysed and the concentrations of PAHs: benzo(b)fluoranthene concentration in sediment and IDH.

Protective effects of calcium on copper toxicity in Pelteobagrus fulvidraco: copper accumulation, enzymatic activities, histology

The present study was conducted to determine interactive effects of waterborne co-exposure of copper (Cu) and calcium (Ca) on Cu accumulation, enzymatic activities and histology in yellow catfish Pelteobagrus fulvidraco and test the prediction that Ca could protect against Cu--induced toxicity in the fish species. Yellow catfish were exposed to 0, 1.0, 2.0 mg Cu/l, in combination with 0 and 50 mg Ca/l. Waterborne Cu and Ca co-exposure influenced the majority of tested enzymatic activities (succinate dehydrogenase, malic dehydrogenase, lactate dehydrogenase, lipoprotein lipase and hepatic lipase), and changed Cu contents in several organs (gill, liver, kidney, gastrointestine and muscle). For histological observations, at the same Ca level, waterborne Cu exposure induced injuries in gills and liver. However, Ca addition seemed to mitigate the severity of Cu--induced injuries. Thus, our study demonstrated that Ca had the capacity to reduce Cu toxicity in P. fulvidraco.

Effect of waterborne copper exposure on growth, hepatic enzymatic activities and histology in Synechogobius hasta

The present study was conducted to determine growth, hepatic enzymatic activities and histology in Synechogobius hasta exposed to waterborne copper concentrations of 0 (control), 0.15 and 0.3 mg Cu/l, respectively, for 15 days, and explore whether waterborne copper exposure could induce the fatty liver syndrome for the fish species. Growth (WG and SGR) declined, but HSI increased in S. hasta with increasing waterborne copper levels (P<0.05). Waterborne copper exposure also significantly increased lipid content and reduced protein content in both whole body and liver, and increased copper accumulation in whole body and vertebrae. Copper exposure changed hepatic enzymatic activities (SOD, CAT, SDH, PK, LDH, LPL and HL) and increased hepatic lipid peroxidation level, impaired the histological structure of the gill and liver in S. hasta. Thus, our study demonstrated for the first time that waterborne Cu exposure could induce fatty liver syndrome in fish.

Acute effects of copper and mercury on the estuarine fish Pomatoschistus microps: linking biomarkers to behaviour

The main objective of the present study was to investigate possible links between biomarkers and swimming performance in the estuarine fish Pomatoschistus microps acutely exposed to metals (copper and mercury). In independent bioassays, P. microps juveniles were individually exposed for 96 h to sub-lethal concentrations of copper or mercury. At the end of the assays, swimming performance of fish was measured using a device specially developed for epibenthic fish (SPEDE). Furthermore, the following biomarkers were measured: lipid peroxidation (LPO) and the activity of the enzymes acetylcholinesterase (AChE), lactate dehydrogenase (LDH), glutathione S-transferases (GST), 7-ethoxyresorufin-O-deethylase (EROD), superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GPx). LC(50)s of copper and mercury (dissolved throughout metal concentrations) at 96h were 568 microg L(-1), and 62 microg L(-1), respectively. Significant and concentration-dependent effects of both metals on swimming resistance and covered distance against water flow were found at concentrations equal or higher than 50 microg L(-1) for copper and 3 microg L(-1) for mercury (dissolved throughout metal concentrations). These results indicate that SPEDE was efficacious to quantify behavioural alterations in the epibenthic fish P. microps at ecologically relevant concentrations. Significant alterations by both metals on biomarkers were found including: inhibition of AChE and EROD activities, induction of LDH, GST and anti-oxidant enzymes, and increased LPO levels, with LOEC values ranging from 25 to 200 microg L(-1), for copper and from 3 to 25 microg L(-1) for mercury (dissolved throughout metal concentrations). Furthermore, significant and positive correlations were found between some biomarkers (AChE and EROD) and behavioural parameters, while negative correlations were found for others (LPO, anti-oxidant enzymes and LDH) suggesting that disruption of cholinergic function through AChE inhibition, decreased detoxification capability due to EROD inhibition, additional energetic demands to face chemical stress, and oxidative stress and damage may contribute to decrease the swimming performance of fish. Since a reduced swimming capability of fish may reduce their ability to capture preys, avoid predators, and interfere with social and reproductive behaviour, the exposure of P. microps to copper and/or mercury concentrations similar to those tested here may decrease the fitness of wild populations of this species.

Effect of copper on liver key enzymes of anaerobic glucose metabolism from freshwater tropical fish Prochilodus lineatus

We investigated the effect of copper on liver key enzymes of the anaerobic glucose metabolism (hexokinase, HK; phosphofructokinase, PFK; pyruvate kinase, PK; lactate dehydrogenase, LDH) as well as of the pentose pathway (glycose-6-phosphate dehydrogenase, G6PDH) from the fish Prochilodus lineatus. The fish were acclimated at either 20 degrees C or 30 degrees C at pH 7.0, transferred to water at pH 4.5 or 8.0, and exposed to 96 h-CL(50) copper concentrations. Copper accumulation in liver was higher in fish acclimated at 20 degrees C and maintained in water pH 8.0. Three-way analysis of variance revealed a significant effect of temperature on all enzymes, a significant effect of pH on all enzymes except for PK, and a significant effect of copper on only PFK, and LDH in pH 4.5 at 20 degrees C and, at 30 degrees C, on PFK and PK at pH 4.5 and 8.0, HK at pH 4.5 and G6PDH at pH 8.0. There were significant interactions between treatments for many enzymes. These changes suggest that the activity of enzymes in question is modified by a change in ambient water. At least at 30 degrees C, the overall reduction in the glycolytic enzyme activities of copper-exposed fish seems to reduce energy availability via glucose metabolism, thereby contributing to enhance copper toxic effects.

Proline and glycinebetaine enhance antioxidant defense and methylglyoxal detoxification systems and reduce NaCl-induced damage in cultured tobacco cells

Salt stress impairs reactive oxygen species (ROS) and methylglyoxal (MG) detoxification systems, and causes oxidative damage to plants. Up-regulation of the antioxidant and glyoxalase systems provides protection against NaCl-induced oxidative damage in plants. Thiol-disulfide contents, glutathione content and its associated enzyme activities involved in the antioxidant defense and glyoxalase systems, and protein carbonylation in tobacco Bright Yellow-2 cells grown in suspension culture were investigated to assess the protection offered by proline and glycinebetaine against salt stress. Salt stress increased protein carbonylation, contents of thiol, disulfide, reduced (GSH) and oxidized (GSSG) forms of glutathione, and the activity of glutathione-S-transferase and glyoxalase II enzymes, but decreased redox state of both thiol-disulfide and glutathione, and the activity of glutathione peroxidase and glyoxalase I enzymes involved in the ROS and MG detoxification systems. Exogenous application of proline or glycinebetaine resulted in a reduction of protein carbonylation, and in an increase in glutathione redox state and activity of glutathione peroxidase, glutathione-S-transferase and glyoxalase I under salt stress. Neither proline nor glycinebetaine, however, had any direct protective effect on NaCl-induced GSH-associated enzyme activities. The present study, therefore, suggests that both proline and glycinebetaine provide a protective action against NaCl-induced oxidative damage by reducing protein carbonylation, and enhancing antioxidant defense and MG detoxification systems.

Hepatic antioxidant enzymes and total glutathione of Cyprinus carpio exposed to three disinfectants, chlorine dioxide, sodium hypochlorite and peracetic acid, for superficial water potabilization

This study was carried out in order to assess the effects of disinfectant-treatment on antioxidant response of Cyprinus carpio L. Therefore, enzymatic activities of glutathione S-transferases, glyoxalase I, glyoxalase II, glutathione peroxidases, glutathione reductase, catalase and total glutathione content of carp liver, exposed to surface water treated with three disinfectants for potabilization, sodium hypochlorite, chlorine dioxide and peracetic acid were investigated. Specimens of carp were exposed in four experimental tanks supplied with a continuous water flow from Lake Trasimeno (Italy), three of them treated with constant concentration of sodium hypochlorite, chlorine dioxide and peracetic acid, for 10 and 20 days, while the control tank was supplied with untreated lake water. Differences in biochemical parameters were observed in specimens following exposure to these disinfectants and mainly, chlorine compounds induced marked biochemical variations of carp liver, compared to those induced by peracetic acid treatment. Our results showed that antioxidant parameters of Cyprinus carpio could be used as biomarkers of oxidative stress when this species is exposed to disinfectants for water potabilization.

Characterization of the glyoxalases of the malarial parasite Plasmodium falciparum and comparison with their human counterparts

The glyoxalase system consisting of glyoxalase I (GloI) and glyoxalase II (GloII) constitutes a glutathione-dependent intracellular pathway converting toxic 2-oxoaldehydes, such as methylglyoxal, to the corresponding 2-hydroxyacids. Here we describe a complete glyoxalase system in the malarial parasitePlasmodium falciparum. The biochemical, kinetic and structural properties of cytosolic GloI (cGloI) and two GloIIs (cytosolic GloII named cGloII, and tGloII preceded by a targeting sequence) were directly compared with the respective isofunctional host enzymes. cGloI and cGloII exhibit lowerKmvalues and higher catalytic efficiencies (kcat/Km) than the human counterparts, pointing to the importance of the system in malarial parasites. A Tyr185Phe mutant of cGloII shows a 2.5-fold increase inKm, proving the contribution of Tyr185 to substrate binding. Molecular models suggest very similar active sites/metal binding sites of parasite and host cell enzymes. However, a fourth protein, which has highest similarities to GloI, was found to be unique for malarial parasites; it is likely to act in the apicoplast, and has as yet undefined substrate specificity. Various S-(N-hydroxy-N-arylcarbamoyl)glutathiones tested asP. falciparumGlo inhibitors were active in the lower nanomolar range. The Glo system ofPlasmodiumwill be further evaluated as a target for the development of antimalarial drugs.

Increased acetylcholinesterase activities in specimens of Sparus auratus exposed to sublethal copper concentrations

The present study looks at possible changes in the activity of acetylcholinesterase (AChE) in tissues (brain and white muscle) of the Mediterranean bony fish Sparus auratus after a 20 days exposure to sublethal concentrations (0.1 or 0.5 ppm) of copper in the marine water and on control untreated animals. The trials also included measurements of Cu concentration in the tissues to evaluate possible metal accumulation. Moreover, sedimentation analysis as well as V(max) and K(m) determination were carried out in tissue extracts of Cu-exposed or control animals. V(max) and K(m) were also determined with or without addition of Cu(2+) in the assay. No Cu accumulation occurred in brain and muscle after Cu exposure. AChE showed in both tissues a molecular polymorphism with putative globular (G) and asymmetric (A) forms. Cu exposition led to an increased specific activity and improved catalytic efficiency of AChE in brain and muscle, seemingly regarding G forms. The increase in catalytic efficiency also resulted from the in vitro assay with tissue extracts and Cu(2+) addition. The higher AChE activity and catalytic efficiency in both tissues after Cu exposition and without metal accumulation, suggests an increase of free Cu aliquot into the cells, likely due to mechanisms of metal homeostasis.