Biomarkers in Ruditapes decussatus: a potential bioindicator species

The clam Ruditapes decussatus is distributed worldwide and due to its ecological and economical interest has been proposed as a bioindicator in areas where mussels are not available. The accumulation of several anthropogenic compounds in their tissues suggests that they possess mechanisms that allow them to cope with the toxic effects of these contaminants. Besides pollutant uptake, the use of biomarkers is pointed out in this paper since it is a promising approach to monitor the effect of these contaminants in the marine environment. Biomarkers complement the information of the direct chemical characterization of different types of contaminants. Therefore, the aim of this paper is to review the role of several biomarkers: (metallothioneins (MT), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx) (total and selenium-dependent), lipid peroxidation (measured as MDA, one of the final products of lipid peroxidation), glutathione S-transferase (GST) and acetylcholinesterase (AChE), measured in different tissues of the clam R. decussatus, in laboratory conditions and under various environmental stresses, in two ecosystems (Ria Formosa lagoon- Portugal) and Bizerta lagoon (Tunisia) in a perspective of a multibiomarker approach to assess environmental changes. Experiment and field studies are in good agreement since MT levels, especially in the gills, the first target tissue of these contaminants, can be used as biomarker of exposure to Cd. GPx and MDA may also be determined in this respect. AChE activity is inhibited by pesticide and, to a less extent, by metal exposure in the gills and whole soft body of clams. However, the induction of GST isoforms experimentally demonstrated is not observed in the field because only global GST activity was determined. The whole set of results opens new research perspectives for the use of this species to assess the effect of mixtures of pollutants in the aquatic environment.     

Biomarkers in Ruditapes decussatus: a potential bioindicator species

The clam Ruditapes decussatus is distributed worldwide and due to its ecological and economical interest has been proposed as a bioindicator in areas where mussels are not available. The accumulation of several anthropogenic compounds in their tissues suggests that they possess mechanisms that allow them to cope with the toxic effects of these contaminants. Besides pollutant uptake, the use of biomarkers is pointed out in this paper since it is a promising approach to monitor the effect of these contaminants in the marine environment. Biomarkers complement the information of the direct chemical characterization of different types of contaminants. Therefore, the aim of this paper is to review the role of several biomarkers: (metallothioneins (MT), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx) (total and selenium-dependent), lipid peroxidation (measured as MDA, one of the final products of lipid peroxidation), glutathione S-transferase (GST) and acetylcholinesterase (AChE), measured in different tissues of the clam R. decussatus, in laboratory conditions and under various environmental stresses, in two ecosystems (Ria Formosa lagoon- Portugal) and Bizerta lagoon (Tunisia) in a perspective of a multibiomarker approach to assess environmental changes. Experiment and field studies are in good agreement since MT levels, especially in the gills, the first target tissue of these contaminants, can be used as biomarker of exposure to Cd. GPx and MDA may also be determined in this respect. AChE activity is inhibited by pesticide and, to a less extent, by metal exposure in the gills and whole soft body of clams. However, the induction of GST isoforms experimentally demonstrated is not observed in the field because only global GST activity was determined. The whole set of results opens new research perspectives for the use of this species to assess the effect of mixtures of pollutants in the aquatic environment.     

Spatial and seasonal biomarker responses in the clam Ruditapes decussatus

The clam Ruditapes decussatus is an important resource to preserve in coastal lagoon systems around the Mediterranean including the South Portugal. To assess spatial and temporal biomarker responses to contamination in the species, a multibiomarker approach was conducted using antioxidant enzymes, MFO system phase I and II; acetylcholinesterase, metallothionein (MT), δ-aminolevulinic acid dehydratase and lipid peroxidation (LPO). The condition index (CI), metals and polycyclic aromatic hydrocarbons (PAHs) were also determined. The levels of contaminants were not particularly high and the antioxidant enzymes, acetylcholinesterase (AChE), MT in the digestive gland, and δ-aminolevulinic acid dehydratase (ALAD) do not provide a suitable seasonal and spatial discrimination reversely to that regarding CYP450, glutathione-S-transferase (GST), MT in the gills, and LPO in both tissues. However, even those could vary with natural variables that may act as confounding factors. Thus, seasonal variability and natural range of biomarker responses must be carefully and accurately taken into account in ecotoxicological approaches of environmental quality assessment programmes.     

Oxidative stress biomarkers in the freshwater characid fish, Brycon cephalus, exposed to organophosphorus insecticide Folisuper 600 (methyl parathion)

Methyl parathion (MP) is an organophosphorus insecticide used worldwide in agriculture and aquaculture due to its high activity against a broad spectrum of insect pests. The effect of a single exposure to 2 mg L(- 1) of a commercial formulation of MP (MPc: Folisuper 600(R), MP 600 g L(- 1)) on catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), glutathione S-transferase (GST), reduced glutathione (GSH) and lipid peroxidation (LPO) of the liver, white muscle and gills of Brycon cephalus was evaluated after 96 h of treatment. MPc exposure resulted in a significant induction of SOD, CAT and GST activity in all tissues. However, the GPx activity decreased significantly in white muscle and gills, whereas no alterations were observed in hepatic GPx activity. MPc also induced a significant increase in LPO values in the white muscle and gills, while hepatic LPO levels did not show any significant alteration. The current data suggest that MPc has oxidative-stress-inducing potential in fish, and that gills and white muscle are the most sensitive organs of B. cephalus, with poor antioxidant potentials. The various parameters studied in this investigation can also be used as biomarkers of exposure to MPc.     

可食用文蛤中氧化性胁迫的生物标记物与甲基毒死蜱和草甘膦的生物富集

近几十年期间,在种群和个体受干扰后,对作为早期指示剂的生物标记物的研究受到越来越多的关注。我们用对水生生态系统污染敏感的生物标记物双壳类软体动物(文蛤)来评估两种有机磷杀虫剂(甲基毒死蜱、草甘膦)的影响。文蛤是水生生态系统污染的一种敏感的指示物种。在不同时间段测定文蛤中不同组织的非酶的(谷胱苷肽)和酶的(过氧化氢酶)抗氧化剂,作为文蛤中生物标记物的反应。在实验室条件下,测定了脂质过氧化作用、蛋白羰基含量、总蛋白含量、总脂质含量以及胆碱酯酶的活性。对不同的生物标记与杀虫剂的生物体内积累的相互关系进行了研究。甲基毒死蜱在文蛤组织中具有最大的诱导氧化胁迫的潜能,导致脂质过氧化反应增加并抑制抗氧化剂。而且,鳃是对该反应最敏感的器官。文蛤是一种极好的甲基毒死蜱的积聚者,因为暴露60天后,可以测定到其组织中浓度为824.0 mg/kg w.w的甲基毒死蜱。随着在草甘膦中暴露时间的增加,与背景水平相比,组织中草甘膦的浓度增加大约8×103mg/kg w.w。可以得出这样的结论:在一种生物中测定几种生物标记物是有用的。在双壳类中,蛋白质的羰基诱导可用于双壳类中化学污染物诱导的氧化胁迫的生物指示剂。抗氧化剂的防御成分是敏感的参数,是评估污染的水生生态系统的有用的生物标记物。辅以蛤组织的化学分析,生物标记参数能够提供一种有力的监测工具。     

Effects of cadmium exposure on lipid peroxidation and the antioxidant system in fourth-instar larvae of Propsilocerus akamusi (Diptera: Chironomidae) under laboratory conditions

Enzymatic antioxidants such as selenium-dependent glutathione peroxidase (GPx), glutathione transferase (GST), glutathione reductase (GR), and superoxide dismutases (SOD), as well as the concentration of hydrogen peroxide (H2O2) and malondialdehyde (MDA, an indicator of lipid peroxidation) were determined to identify which antioxidant enzymes participate in the efficient scavenging of ROS generated upon exposure to high doses of Cd2+ in fourth-instar Propsilocerus akamusi (Tokuna) (Diptera: Chironomidae) larvae after 72-h exposure. A significant increase in MDA levels and a change in GR and GPx activities in the Cd(2+)-treated P. akamusi were observed. The MDA in 25.0 and 50.0 mmol/liter treatments was significantly higher than that of the control dose after 72 h exposure. GPx activity was significantly induced by Cd2+ exposure only in the 50.0-mmol/liter treatment with a 0.59-fold increase in the control. All doses of Cd2+ significantly suppressed GR activity compared with the findings for the control dose, with an inhibited rate up to 0.55-fold in the 25.0 mmol/liter Cd2+ treatment. SOD and GST activities were not altered. The results indicate that Cd2+ can induce oxidative stress as indicated by the changes in lipid peroxidation and antioxidant status. For P. akamusi, an increase in the dose that the threshold needed for defense (namely, MDA level and GPx activity) activation was achieved. From this, organisms can be hypothesized to enable cells to avoid oxidant stress up to a certain extent where damage is again measurable (higher Cd2+ concentration).     

The effects of selenium on oxidative stress biomarkers in the freshwater characid fish matrinxã, Brycon cephalus (Günther, 1869) exposed to organophosphate insecticide Folisuper 600 BR (methyl parathion)

Methyl parathion (MP), an organophosphate widely applied in agriculture and aquaculture, induces oxidative stress due to free radical generation and changes in the antioxidant defense system. The antioxidant roles of selenium (Se) were evaluated in Brycon cephalus exposed to 2 mg L(-1) of Folisuper 600 BR (MP commercial formulation - MPc, 600 g L(-1)) for 96 h. Catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), glutathione S-transferase (GST), reduced glutathione (GSH) and lipid peroxidation (LPO) levels in the gills, white muscle and liver were evaluated in fish fed on diets containing 0 or 1.5 mg Se kg(-1) for 8 weeks. In fish treated with a Se-free diet, the MPc exposure increased SOD and CAT activities in all tissues. However, the GPx activity decreased in white muscle and gills whereas no alterations were observed in the liver. MPc also increased GST activity in all tissues with a concurrent decrease in GSH levels. LPO values increased in white muscle and gills and did not change in liver after MPc exposure. A Se-supplemented diet reversed these findings, preventing increases in LPO levels and concurrent decreases in GPx activity in gills and white muscle. Similarly, GSH levels were maintained in all tissue after MPc exposure. These results suggest that dietary Se supplementation protects cells against MPc-induced oxidative stress.     

Antioxidant response and oxidative stress levels in Macrobrachium borellii (Crustacea: Palaemonidae) exposed to the water-soluble fraction of petroleum

The aim of the present work was to evaluate the effect of the water soluble fraction of hydrocarbons (WSF) on the antioxidant status of the freshwater prawn Macrobrachium borellii. First, seasonal variations were studied in a non-polluted area. Hepatopancreas and gills showed season-related fluctuations in catalase (CAT), glutathione-S-transferase (GST) activities and in lipid peroxidation levels (LPO), but not in superoxide dismutase (SOD). Then, adults were exposed semi-statically to sublethal doses for 7days. CAT, SOD, GST, and glutathione peroxidase (GPx) activities and LPO, reduced glutathione (GSH) and protein oxidation (PO) levels were determined. Exposed individuals showed significant increases in CAT, SOD, and GST activities in hepatopancreas and CAT activity in gills. GPx activity did not vary in either tissues. While LPO levels increased, GSH levels decreased significantly in hepatopancreas of exposed animals, but PO levels showed no variation. Induction of SOD was also assessed by Real-time PCR mRNA expression in hepatopancreas. The non-enzymatic antioxidant activity was also tested; ABTS 2,2'-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid) was higher in hemolymph of treated-prawns compared to controls, but ferric reducing activity of plasma assay (FRAP) values did not change. Taken together, the present results indicated that the antioxidant defenses of M. borellii, mainly in hepatopancreas, were significantly affected by aquatic hydrocarbon contamination, regardless of the season.     

Combined effect of alcohol and cigarette smoke on lipid peroxidation and antioxidant status in rats

The effect of long-term administration of alcohol and cigarette smoke independently and both in combination on lipid peroxidation and antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione-S-transferase (GST) was studied in liver, kidney, heart and lungs of albino rats. The levels of peroxidation products viz., malondialdehyde, hydroperoxides and conjugated dienes were increased in all the tissues of alcohol administered and smoke-exposed rats. Activities of SOD and CAT were decreased in alcohol-treated and alcohol and smoke combination groups, but increased in smoke-exposed group. Activities of GPx and GST have shown an increase, while concentration of reduced glutathione was found decreased in all the three groups.     

Tissue lipid peroxidation and glutathione‐dependent enzyme status in patients with oral squamous cell carcinoma

We examined the extent of lipid peroxidation and the status of reduced glutathione (GSH) and the GSH‐dependent enzymes—glutathione peroxidase (GPx) and glutathione‐S‐transferase (GST)—in oral tumour tissues from 33 adult oral cancer patients and an equal number of age‐ and sex‐matched normal subjects. Diminished lipid peroxidation in the oral tumour tissue was accompanied by a significant decrease in phospholipids and an increase in the cholesterol/phospholipid (C/P) ratio. The concentration of glutathione and the activities of GPx and GST were elevated in oral tumour tissues. These findings suggest that GSH‐ and GSH‐dependent enzymes play a crucial role in tobacco‐related tumourigenesis and may be considered as markers of carcinogen exposure. Copyright © 1999 John Wiley & Sons, Ltd.     

Effect of cadmium on antioxidant enzyme activities and lipid peroxidation in the gills of the clam Ruditapes decussatus

Metals are known to influence the oxidative status of marine organisms, and antioxidant enzymes have been often proposed as biomarkers of effect. The clam Ruditapes decussatus is a well-known metal bioindicator. In this species cadmium (Cd) induces metallothionein (MT) synthesis only after 7 days of exposure. Before MT synthesis is induced, the other mechanisms capable of handling the excess of Cd are unknown. In order to identify some of these mechanisms, variations in antioxidant systems (superoxide dismutase, catalase, selenium-dependent glutathione peroxidase and non-selenium-dependent glutathione peroxidase), malondialdehyde (MDA) and MT were studied in the gills of R. decussatus exposed to different Cd concentrations (4, 40 and 100 gl^-1) for 28 days. These parameters, together with total proteins and Cd concentrations, were measured in the gills of the clams over different periods of exposure. Results indicate that Cd accumulation increased linearly in the gills of R. decussatus with the increase in Cd concentration. This increase induces an imbalance in the oxygen metabolism during the first days of Cd exposure. An increase in cytosolic superoxide dismutase (SOD) activity and a decrease in mitochondrial SOD activity was observed at the same time as or after a decrease in cytosolic and mitochondrial catalase activity and of selenium-dependent and non-selenium-dependent glutathione peroxidase activity. After 14 days of exposure, Cd no longer affect these enzymes but there was elevation of other cellular activities, such as MDA and MT production. MT bound excess Cd present in the cell. These variations in these parameters suggest their potential use as biomarkers of effects such as oxidative stress resulting from Cd contamination in molluscs.     

Effect of cadmium on antioxidant enzyme activities and lipid peroxidation in the gills of the clam Ruditapes decussatus

Metals are known to influence the oxidative status of marine organisms, and antioxidant enzymes have been often proposed as biomarkers of effect. The clam Ruditapes decussatus is a well-known metal bioindicator. In this species cadmium (Cd) induces metallothionein (MT) synthesis only after 7 days of exposure. Before MT synthesis is induced, the other mechanisms capable of handling the excess of Cd are unknown. In order to identify some of these mechanisms, variations in antioxidant systems (superoxide dismutase, catalase, selenium-dependent glutathione peroxidase and non-selenium-dependent glutathione peroxidase), malondialdehyde (MDA) and MT were studied in the gills of R. decussatus exposed to different Cd concentrations (4, 40 and 100 gl^-1) for 28 days. These parameters, together with total proteins and Cd concentrations, were measured in the gills of the clams over different periods of exposure. Results indicate that Cd accumulation increased linearly in the gills of R. decussatus with the increase in Cd concentration. This increase induces an imbalance in the oxygen metabolism during the first days of Cd exposure. An increase in cytosolic superoxide dismutase (SOD) activity and a decrease in mitochondrial SOD activity was observed at the same time as or after a decrease in cytosolic and mitochondrial catalase activity and of selenium-dependent and non-selenium-dependent glutathione peroxidase activity. After 14 days of exposure, Cd no longer affect these enzymes but there was elevation of other cellular activities, such as MDA and MT production. MT bound excess Cd present in the cell. These variations in these parameters suggest their potential use as biomarkers of effects such as oxidative stress resulting from Cd contamination in molluscs.     

Seasonal changes in antioxidant defence system of liver and gills of Salmo trutta caspius, Salmo trutta labrax and Salmo trutta macrostigma

Seasonal changes in antioxidant enzyme activities (superoxide dismutase, SOD, EC 1.15.1.1; catalase, CAT, EC 1.11.1.16; glutathione peroxidase, GPx, EC 1.11.1.9; glutathione reductase, GR, EC 1.6.4.2; glucose-6-phosphate dehydrogenase, G6PD, EC 1.1.1.49 and glutathione S -transferase, GST, EC 1.5.1.18) and lipid peroxidation (LPO) levels of livers and gills of female Caspian trout Salmo trutta caspius , Black Sea trout Salmo trutta labrax and mountain trout Salmo trutta macrostigma were investigated. SOD, CAT, GPx, G6PD and GST activities were higher in liver compared to gills of all sub-species; concomitantly, the GR activity was also higher in the livers of S. t. caspius and S. t. labrax , but the reverse was seen in S. t. macrostigma . LPO levels were higher in the gills compared to the liver of all sub-species. There was no general trend in the seasonal changes in the gill antioxidant enzyme (AE) activities or LPO levels. Higher AE activities, however, were found in the liver of each sub-species during autumn, and this coincided with an increase in the gonado-somatic index.     

Oxidative stress in digestive gland and gill of the brown mussel (Perna perna) exposed to air and re-submersed

Mussels Perna perna were exposed to air for 24 h showing a clear increase in the levels of lipid peroxidation and oxidative DNA damage, measured as 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo). The levels of lipid peroxidation increased both in the digestive gland and gills, while oxidative DNA damage increased only in the gills. After the 24 h of air exposure, mussels were re-submersed for a period of 3 h, leading values to return to a pre-aerial exposure levels. Control animals were kept immersed during the whole period. Several antioxidant and complementary enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH), glutathione S-transferase (GST) and the levels of total glutathione (Total GSH) were assayed in a second set of experiments where one group of mussels were exposed to air for 18 h and other to 1 h re-submersion after 18 h aerial exposure. Only a 52% increase in the glutathione S-transferase activity was observed in the digestive gland, which remained elevated to about 40% after 1 h re-submersion, showing that defense systems can be modulated even during oxygen deprivation in P. perna. The DNA and lipid oxidative damage observed after aerial exposure indicates that mussels face an oxidative challenge, and are able to counteract such an “insult” as values of lipid peroxidation and DNA damage returned to control values after 3 h re-submersion.     

Tissue-specific oxidative stress responses in fish exposed to 2,4-D and azinphosmethyl

Species- and tissue-specific defenses against the possibility of oxidative stress and lipid peroxidation were compared in adult fish, Oreochromis niloticus and Cyprinus carpio, exposed to 2,4-dichlorophenoxyacetic acid (2,4-D), azinphosmethyl and their combination for 96 h. Superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase activities were monitored in kidney, brain and gill. In all exposure groups there was a marked increase in SOD activity in gill tissues in both fish species, while it was at the control level in other tissues. The highest elevation of SOD activity by combined treatment was observed in C. carpio. Individual and combined treatments caused an elevation in catalase and GPx activities in kidney of C. carpio. Catalase activity was unaffected in brain of O. niloticus, while GPx activity was decreased after all treatments. Glutathione S-transferase (GST) activity was higher than the control levels in kidney of both fish exposed to pesticides. No significant changes were observed in malondialdehyde level in kidney and brain of C. carpio. Our results indicate that the toxicities of azinphosmethyl and 2,4-D may be related to oxidative stress. Also, the results show that SOD activity in gill and GST activity in kidney may be used as biomarkers for pollution monitoring and indicate that the activities of certain biomarkers in C. carpio are more sensitive to pesticides than those in O. niloticus.     

In vitro and in vivo studies of potential biomarkers of lead and uranium contamination: lipid peroxidation, acetylcholinesterase, catalase and glutathione peroxidase activities in three non-mammalian species

The aim of this work was to assess the relationships between lead (Pb) and uranium (U) exposure, lipid peroxidation and some enzyme activities in a mollusc (Cohicula sp.), an earthworm (Eisenia fetida) and a fish (Brachydanio redo). A comparative shrdy was perfotmed both in vibo and in vivo on whole organism postmitochondrial fractions and four potential biomarken were analyted: a marker of neurotoxicity (acetylcholinesterase activity, AChE, EC 3.1.1.7), a marker of oxidative sbss (malondialdehyde (MDA) level), and two markers of hydroperoxide detoxication: catalase (EC 1.11.1.6) and glutathione pemxidase (GPx, EC 1.11.1.9) activities. Our results have shown that the MDA contents were not signilicantty changed by exposures to lead either in vitro or in vivo. During uranium exposure, the MDA content was increased in vitro (particularly in fish samples) whereas this metal failed to sthnulate Spid peroxidation in vivo. With some exceptions, in vitro and in vivo exposures to lead and uranium showed that the AChE, catalase and GPx acbirites were decreased in the three species. These exceptions indicated that different mechanisms occurred in the different species. In conclusion, it was shown that S9 fractions of whole organisms could be useful for environmental contamination biomonitoring. Moreover, it was shown that AChE activities wen modulated by metals in viva and cannot be considered as specific bomarken of organophosphorus or carbaw pedcide exposure. Acetylcholinesterase and catalase activieies cwld be used to survey lead and uranium contamination.     

Assessment of environmental pollution at Balearic Islands applying oxidative stress biomarkers in the mussel Mytilus galloprovincialis

The antioxidant enzyme response of the mussel Mytilus galloprovincialis to different degree of pollution was investigated. Antioxidant enzyme activities - catalase (CAT), glutathione peroxidase (GSH-PX), glutathione reductase (GR), superoxide dismutase (SOD) - and malondialdehyde (MDA) concentration were measured in gills and digestive glands of mussels. Mussels from the same origin were transplanted along the Balearic coastal waters in eight stations characterized by a different degree of contamination and human impacts. Antioxidant enzyme activities showed an adaptive response to increase the activities in the more polluted areas. CAT, GR and SOD in gills and CAT and GR in digestive gland presented significant differences between polluted and non-polluted stations. No significant differences were observed in MDA concentration indicating that the antioxidant response is capable to avoid the lipid peroxidation. The use of biomarkers such as CAT and GR in gills and digestive glands of the mussel M. galloprovincialis is a good tool to categorize differences between polluted and non-polluted areas.     

The antioxidant status during maturation of reticulocytes to erythrocytes in type 2 diabetics

Free radical-induced lipid peroxidation has been associated with numerous disease processes including diabetes mellitus. The extent of lipid peroxidation (LPO) and antioxidant defense system [i.e., levels of glutathione (GSH), glucose-6-phosphate dehydrogenase (G6PDH), glutathione reductase (GR), glutathione peroxidase (GPx), glutathione-S-transferase (GST), and catalase (CAT)] were evaluated in reticulocytes and erythrocytes of type 2 diabetic males and age-matched controls. Type 2 diabetics have shown increased lipid peroxidation and decreased levels of GSH, GR, GPx, G6PDH, and GST both in reticulocytes and erythrocytes compared to controls, indicating the presence of oxidative stress and defective antioxidant systems in these patients. CAT activity is found to be enhanced in both the reticulocytes and erythrocytes of diabetics, with a greater percentage enhancement in reticulocytes. The extent of increase in lipid peroxidation is greater in erythrocytes compared to reticulocytes in these patients. Furthermore, the maturation of reticulocytes to erythrocytes resulted in decreased GSH and decreased activities of all antioxidant enzymes (except CAT) both in normals and type 2 diabetes individuals, indicating decreased scavenging capacity as reticulocytes mature to erythrocytes. These maturational alterations are further intensified in type 2 diabetics. The present study reveals that the alterations in lipid peroxidation and antioxidant system lean toward early senescence of erythrocytes in type 2 diabetic patients.     

Proteasome and antioxidant responses in Cottus gobio during a combined exposure to heat stress and cadmium

Temperature and trace metals are common environmental stressors, and their importance is increasing due to global climate change and anthropogenic pollution. Oxidative damage and antioxidant properties have been studied in liver and gills of the European bullhead (Cottus gobio) subjected to cadmium (CdCl(2) at nominal concentrations of 0.01 and 1mg/L) for 4 days at either 15°C or 21°C. First, exposure to 1mg Cd/L induced a high mortality rate (67%) in fish held at 21°C. Regarding the antioxidant enzymes, exposure to 0.01 mg Cd/L significantly increased the activity of superoxide dismutase (SOD) and decreased the activity of glutathione reductase (GR) in liver, independently of heat stress. In gills, exposure to 21°C resulted in a significantly increased activity of glutathione peroxidase (GPx), whereas the activity of glutathione S-transferase (GST) was significantly reduced as compared to fish exposed to 15°C. Furthermore, regardless of Cd stress, exposure to elevated temperature resulted in a significant decrease of lipid peroxidation (LPO) level in liver and in a significant increase in the activity of chymotrypsin-like 20S proteasome in both studied tissues of C. gobio. Overall, the present results indicated that elevated temperature and cadmium exposure independently influenced the antioxidant defense system in bullhead with clear tissue-specific and stress-specific antioxidant responses. Further, elevated temperature affected the hepatic lipid peroxidation and the activity of 20S proteasome in both tissues.     

Metallothionein, antioxidant enzymes and DNA strand breaks as biomarkers of Cd exposure in a marine crab, Charybdis japonica

Cadmium (Cd) is one of the most toxic heavy metals that are widespread in inshore sediments of China, and can induce the production of toxic hydroxyl radicals that cause cell damage. The present study investigated the effect of two Cd concentrations (the final Cd concentration of 0.025 and 0.05 mg/L, prepared with CdCl2 x 2.5H2O) on metallothioneins (MT), antioxidant enzyme activities (superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)) and DNA integrity (DNA strand breaks) for up to 15 days in the gills and hepatopancreas of the portunid crab Charybdis japonica. The result indicated that MT was significantly induced after 3 days, with a dose-response relation between MT contents and Cd concentrations in two tissues and has a time-response relation in hepatopancreas during the experimental period; SOD, CAT and GPx activities could be stimulated after 0.5 day, all attained peak value and then reduced during the experimental period, but were not inhibited at day 15, except SOD and CAT in gills. Gill was more sensitive to Cd than hepatopancreas, and the hepatopancreas was the main detoxification tissue to deal with oxyradicals. DNA strand breaks were induced after 0.5 day, and there was a positive dose-response relation between DNA damage levels and Cd concentrations in gills, rather than hepatopancreas due to higher DNA repair activities. These results suggest the mechanisms of Cd toxicity and detoxification strategies in both tissues of C. japonica; in addition, the use of the biomarkers as indices for biomonitoring potential toxic effect of Cd in situ is discussed.