Characterization of antioxidant system parameters in four freshwater fish species

Effect of diets containing probiotic yeast Cystobasidium benthicum and fruit Cyrtocarpa edulis on growth and immune parameters of Nile tilapia (Oreochromisniloticus)

This study investigates Cystobasidium benthicum (Cb) probiotic yeast and Cyrtocarpa edulis (Ce) fruit dietary effects, single (0.5 %) or combined (Cb:Ce, 0.25:0.25 %), on growth performance, humoral immunity in serum and skin mucus, and intestinal morphology of Nile tilapia (Oreochromis niloticus) after 14 and 28 days. The Cb group presented the highest (P < 0.05) specific growth rate, weight gain, and absolute growth rate with respect to the control group. Immunological assays indicated that Cb, Ce and Cb:Ce groups increased serum nitric oxide concentration compared to the control group (P < 0.05). Cb and Cb:Ce groups showed the highest serum myeloperoxidase enzyme activity at day 14 and 28, respectively (P < 0.05); whereas, Cb:Ce group had the highest (P < 0.05) myeloperoxidase activity in skin mucus. The superoxide dismutase enzyme activity was unaffected. On day 28, Cb, Ce, and Cb:Ce groups showed higher and lower (P < 0.05) catalase enzyme activity in serum and skin mucus, respectively, compared with the control group. Only the Cb group had higher (P < 0.05) total protein concentration in serum (day 14) and skin mucus (day 14 and 28) with respect to the control group. The lysozyme activity in serum (day 28) and skin mucus (day 14) was higher (P < 0.05) in the Cb group compared to the control group. Only the skin mucus of Ce group showed bactericidal activity against Aeromonas dhakensis (P < 0.05). Histological studies indicated that Cb and Cb:Ce groups increased microvilli height, and Cb, Ce and Cb:Ce augmented goblet cell area at day 14 compared to the control group (P < 0.05). At day 28, microvilli height was higher in all groups and the number of intraepithelial leukocytes increased in Cb and Ce groups with respect to the control group (P < 0.05). The ex vivo assay revealed that A. dhakensis in leukocytes decreased cell viability similar to the control group (P < 0.05). A principal component analysis (PCA) confirmed the results. In conclusion, C. benthicum in the diet was the best supplement to improve the growth and immunity of Nile tilapia.

Exploration of the Synergistic Regulation Mechanism in Cerebral Ganglion and Heart of Eriocheir sinensis on Energy Metabolism and Antioxidant Homeostasis Maintenance under Alkalinity Stress

(1) The development and utilization of the vast saline-alkali land worldwide is an important way to solve the worsening food crisis. Eriocheir sinensis, due to its strong osmotic regulation capability and its characteristics of being suitable for culturing in alkaline water, has become a potential aquaculture species in saline-alkali water. The brain and heart are the key tissues for signal transduction and energy supply under environmental stress. (2) This study is the first to explore the synergistic regulatory molecular mechanism by integrated analysis on cerebral ganglion proteomics and heart metabolomics of Eriocheir sinensis under alkalinity stress. (3) The results indicate that the cerebral ganglion and heart of E. sinensis were closely related in response to acute alkalinity stress. The differential regulatory pathways mainly involved regulation of energy metabolism, amino acid metabolism, and homeostasis maintenance. Importantly, alkalinity stress induced the regulation of antioxidants and further adjusted longevity and rhythm in the cerebral ganglion and heart, reflecting that the cerebral ganglion and heart may be the key tissues for the survival of Eriocheir sinensis under an alkalinity environment. (4) This study provides a theoretical reference for research on the regulation mechanism of E. sinensis under alkalinity condition and contributes to the development of aquaculture in saline-alkali water.

A biomarker approach to study the effects of polluted Brazilian urban reservoirs in a native fish

Two of the largest water reservoirs in the Metropolitan Region of São Paulo, Brazil (MRSP), named Billings and Guarapiranga, are facing high levels of anthropic impact. This is evidenced by the presence of contaminants and pollutants, which are deteriorating their water quality. Therefore, this study evaluated antioxidant defense enzymes, lipoperoxidation and genotoxicity, in adult females of a native species, Astyanax altiparanae from the Guarapiranga and Billings reservoirs. The study also aimed to evaluate these biomarkers during two different periods of the year, the rainy (summer) and dry (winter) seasons. The oxidative stress was evaluated by the activity of enzymes such as glutathione peroxidase, glutathione S-transferases, superoxide dismutase, and catalase in the gills and liver, and the occurrence of lipoperoxidation was also evaluated in both organs. The genotoxicity was assessed by performing comet assay, micronucleus, and nuclear abnormality tests on blood samples. The results showed that fish from both reservoirs are subjected to oxidative stress and genotoxic damage, mainly during winter, but fish living in Billings showed greater alterations than fish from Guarapiranga. Likewise, the results of the principal component analysis suggested that caffeine, nitrogenous compounds, and some metals might be triggering these toxic effects in fish.

The effects of 100 nm pure boron nanoparticles on the primary antioxidant system of Nile tilapia (Oreochromisniloticus)

In this study, the effects of 100 nm boron nanoparticles (B-NPs) on the primary antioxidant status of Nile tilapia were researched via analysis of enzyme activities and related gene expressions. This is a new study which focuses on the relationship between B-NPs and oxidative stress that contribute to the literature in terms of its scope. Fish (n = 15) for each group were exposed to three different concentrations as 5, 25 (n2) and 125 (n3) mg/L during 96 h to see the response of the primary antioxidant system. According to the results, SOD expressions differed in all treatment groups compared to the control group (P < 0.05). CAT expressions were different in 5 and 125 mg/L groups compared to control and 25 mg/L groups (P < 0.05). GPX expressions were only different in 125 mg/L group (P < 0.05). The changes in enzyme activities of SOD and CAT were significantly different in 25 mg/L groups. GPX enzyme activities were not significant (P > 0.05). TBARS concentrations in 25 mg/L group were significantly different from those in the control and 125 mg/L groups (P < 0.05).

Mannan oligosaccharides alleviate oxidative injury in the head kidney and spleen in grass carp (Ctenopharyngodon idella) via the Nrf2 signaling pathway after Aeromonas hydrophila infection

BACKGROUND

Mannan oligosaccharides (MOS) are recommended as aquaculture additives owing to their excellent antioxidant properties. In the present study, we examined the effects of dietary MOS on the head kidney and spleen of grass carp (Ctenopharyngodon idella) with Aeromonas hydrophila infection.

METHODS

A total of 540 grass carp were used for the study. They were administered six gradient dosages of the MOS diet (0, 200, 400, 600, 800, and 1,000 mg/kg) for 60 d. Subsequently, we performed a 14-day Aeromonas hydrophila challenge experiment. The antioxidant capacity of the head kidney and spleen were examined using spectrophotometry, DNA fragmentation, qRT-PCR, and Western blotting.

RESULTS

After infection with Aeromonas hydrophila, 400-600 mg/kg MOS supplementation decreased the levels of reactive oxygen species, protein carbonyl, and malonaldehyde and increased the levels of anti-superoxide anion, anti-hydroxyl radical, and glutathione in the head kidney and spleen of grass carp. The activities of copper-zinc superoxide dismutase, manganese superoxide dismutase, catalase, glutathione S-transferase, glutathione reductase, and glutathione peroxidase were also enhanced by supplementation with 400-600 mg/kg MOS. Furthermore, the expression of most antioxidant enzymes and their corresponding genes increased significantly with supplementation of 200-800 mg/kg MOS. mRNA and protein levels of nuclear factor erythroid 2-related factor 2 also increased following supplementation with 400-600 mg/kg MOS. In addition, supplementation with 400-600 mg/kg MOS reduced excessive apoptosis by inhibiting the death receptor pathway and mitochondrial pathway processes.

CONCLUSIONS

Based on the quadratic regression analysis of the above biomarkers (reactive oxygen species, malondialdehyde, and protein carbonyl) of oxidative damage in the head kidney and spleen of on-growing grass carp, the recommended MOS supplementation is 575.21, 557.58, 531.86, 597.35, 570.16, and 553.80 mg/kg, respectively. Collectively, MOS supplementation could alleviate oxidative injury in the head kidney and spleen of grass carp infected with Aeromonas hydrophila.

Chloroacetonitrile reduces rat prenatal bone length and induces oxidative stress, apoptosis, and DNA damage in rat fetal liver

One of the disinfection byproducts of chlorinating drinking water is chloroacetonitrile (CAN). Thirty-six female rats were used and distributed equally into four groups. The low dose treated group received CAN at a dose of 5.5 mg/kg body weight/day (1/40 LD₅₀ ) orally from the 6th to 12th day of gestation. The high dose treated group received 11 mg/kg body weight/day (1/20 LD₅₀ ) of CAN orally for the same period, the vehicle control group received 1 mL of corn oil, and the water control group received 1 mL of distilled water orally for the same period. High dose exposure to CAN significantly reduced gravid uterine weight, fetal body weights, and length, and caused obvious skeletal deformities, weak mineralization. Fetal tibial growth plates displayed histopathologic changes. Induced oxidative stress and redox imbalance in fetal liver tissues was evidenced by significantly decreased in catalase and superoxide dismutase activity, and elevated malondialdehyde levels. Histopathological, glycogen content changes, and DNA damage were observed in the fetal liver of high dose treated group. Additionally, administration of high dose of CAN induced apoptosis, evidenced by increased caspase-3 concentration in fetal liver. Thus, extensive exposure to CAN induces poor pregnancy outcomes. CAN levels in water should be monitored regularly.

Accumulation and Elimination of Cadmium by the Nile Tilapia (Oreochromis niloticus) in differing Temperatures and Responses of Oxidative Stress Biomarkers

The aims of this study were to investigate the accumulation (15 days) and elimination (15 and 30 days) of cadmium (Cd) in the liver, gill, kidney and muscle of Oreochromis niloticus following exposures to different concentrations (1 and 2 mg/L) of Cd at different water temperatures (20, 25, 30 ^oC). Additionally, responses of oxidative stress biomarkers (superoxide dismutase, SOD; catalase CAT; glutathione peroxidase, GPx and malondialdehyde, MDA) of the liver were determined following Cd exposures. In accumulation period, Cd levels increased significantly in all the tissues at all temperatures and tissue accumulation order was kidney > liver > gill. All tissues, except the muscle, accumulated Cd in relation to exposure concentrations and water temperatures. There was no measurable level of Cd accumulation in the muscle, except in fish exposed to 2 mg Cd/L at 30 ^oC. Likewise, elimination of Cd from the tissues also increased in depends on periods and water temperatures. The order of Cd elimination from the tissues was gill > liver > kidney. The oxidative stress biomarkers also responded to both Cd exposure and temperature increases. The activities of antioxidant enzymes such as SOD, CAT, GPx and MDA levels in the liver increased in relation to increases in Cd concentrations and water temperatures.

Distinct vulnerability to oxidative stress determines the ammonia sensitivity of crayfish (Procambarus clarkii) at different developmental stages

Red swamp crayfish (Procambarus clarkii) has increasingly become a high-value freshwater product in China. During the intensive cultivation, excessive ammonia exposure is an important lethal factor of crayfish. We investigated the toxic effects and mechanisms of ammonia on crayfish at two different developmental stages. A preliminary ammonia stress test showed a 96-h LC₅₀ of 135.10 mg/L and 299.61 mg/L for Stage_1 crayfish (8.47 ± 1.68 g) and Stage_2 crayfish (18.33 ± 2.41 g), respectively. During a prolonged ammonia exposure (up to 96 h), serum acid phosphatase and alkaline phosphatase showed a time-dependent decrease. Histological assessment indicated the degree of hepatopancreatic injury, which was mainly characterized as tubule lumen dilatation, degenerated tubule, vacuolization and dissolved hepatic epithelial cell, increased with exposure time. Enhanced malondialdehyde level and reduced antioxidant capacity of hepatopancreas were also observed. The mRNA expression and activity of catalase and superoxide dismutase showed an initial up-regulation within 24 h, and then gradually down-regulated with the exposure time. In the post-treatment recovery period, the Stage_2 crayfish exerted a stronger antioxidant and detoxification capacity than that of the Stage_1 crayfish, and thus quickly recovered from the ammonia exposure. Our findings provide a further understanding of the adverse effects of ammonia stress and suggest guidelines for water quality management during crayfish farming.

Neurotoxic, biotransformation, oxidative stress and genotoxic effects in Astyanax altiparanae (Teleostei, Characiformes) males exposed to environmentally relevant concentrations of diclofenac and/or caffeine

The present study evaluated neurotoxic, biotransformation, genotoxic and antioxidant responses to relevant environmental concentrations of diclofenac (0.4 μg L^-1) and caffeine (27.5 μg L^-1), separate and combined, in adult males of the freshwater fish Astyanax altiparanae after a subchronic exposure (14 days). Fish exposed to diclofenac and caffeine, both separate and combined, revealed a neurotoxic effect through the inhibition of acetylcholinesterase activity in the muscle, while diclofenac alone and in combination caused cyclooxygenase inhibition. Caffeine alone produces genotoxicity on this species but, when combined with diclofenac, it potentiates hepatic lipoperoxidation and the inhibition of oxidative stress enzymes, while diclofenac alone or in combination produces a general inhibition of important enzymes. This study suggests that aquatic contamination produced by these pharmaceuticals has the potential to affect homeostasis and locomotion in A. altiparanae and compromise their immune system and general health.

Emerging investigator series: metal nanoparticles in freshwater: transformation, bioavailability and effects on invertebrates

MNPs may undergo different environmental transformations in aquatic systems, consequently changing their mobility, bioavailability and toxicity to freshwater invertebrates.

Effects of tris (2-chloroethyl) phosphate (TCEP) on survival, growth, histological changes and gene expressions in juvenile yellow catfish Pelteobagrus fulvidraco

Tris (2-chloroethyl) phosphate (TCEP) is an emerging aquatic environmental pollutant. In the present study, juvenile yellow catfish (Pelteobagrus fulvidraco) were exposed to environmentally relevant concentrations of TCEP for 30 days. The results showed that TCEP exposure decreased the survival rate (100 μg/L), body weight (10 and 100 μg/L) and specific growth rate (10 and 100 μg/L) of juvenile yellow catfish. Exposure to TCEP resulted in pronounced damages of gill structures. Gene transcription analysis showed that the antioxidant capacity of the liver and gills was affected; CYP1A1 might contribute to phase I metabolism of TCEP in the liver rather than CYP1B1; TCEP stress might increase the demand of ion transport in fish gill; TCEP could stimulate the immune response and might induce apoptosis via a p53-Bax pathway and caspase-dependent pathway in gills. Collectively, these findings provide new insights into the toxic effects of TCEP on fish.

Antioxidant system biomarkers of freshwater mussel (Unio tigridis) respond to nanoparticle (Al2O3, CuO, TiO2) exposures

PURPOSE

Mussels are known as the natural filters of the aquatic systems and are accepted as one of the best bioindicator organism. There is no data on the response of Unio tigridis to metal-oxide nanoparticle (NP) exposures. This study aimed to investigate the response of the antioxidant enzymes of U. tigridis following exposure to NPs.

MATERIALS AND METHODS

The mussels were exposed to different concentrations (0, 1, 3, 9 mg NP/L) of Al₂O₃, CuO and TiO₂ NPs for 14 days and subsequently, the activities of CAT (catalase), SOD (superoxide dismutase), GPx (glutathione peroxidase), GST (glutathione S-transferase) and GR (glutathione reductase) were measured in the gill and digestive gland. Mussels were fed with cultured unicellular algae (Chlorella vulgaris) during experiments.

RESULTS

Data showed that algae consumptions of mussels were not significantly (p>0.05) altered by NPs. However, all enzyme activities in the digestive gland and gill altered significantly (p<0.05) after NP exposures. The activities of CAT and SOD decreased, while the activities of enzymes belonging to glutathione metabolism (GPx and GST) increased in both tissues.

CONCLUSION

This study representing the first record on the antioxidant system response of U. tigridis toward NP exposures suggests that NP toxicity should be investigated thoroughly in organisms and some regulations must be done on their usages.

Diclofenac and caffeine inhibit hepatic antioxidant enzymes in the freshwater fish Astyanax altiparanae (Teleostei: Characiformes)

Although concentrations of pharmaceutical compounds in aquatic ecosystems are low, they can cause toxic effects on organisms. The aim of this study was to evaluate the effects of diclofenac (DCF), a non-steroidal anti-inflammatory drug, and caffeine (CAF), a central nervous system stimulant, both alone or combined, in Astyanax altiparanae males under acute exposure (96 h), measuring neurotoxicity biomarkers, antioxidant response and damage at biochemical and cellular levels. DCF concentration in water, separated and combined, was 3.08 mg L^-1 and that of CAF was 9.59 mg L^-1. To assess neurotoxicity, brain and muscle acetylcholinesterase (AChE) activities were measured. To evaluate oxidative stress, the enzymatic activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione S-transferase (GST), as well as lipoperoxidation (LPO), were analyzed in liver and gills. Activity of hepatic cyclooxygenase (COX) was also evaluated. Genotoxicity was assessed in blood using comet assay and micronucleus test, as well as nuclear abnormalities. DCF and CAF, alone or combined, had neither effect on AChE activity, nor in the activity of SOD, CAT, GPx and GST in gills. In liver, DCF inhibited SOD and GPx activity, CAF inhibited CAT activity, the mixture inhibited SOD and GST activity; although only fish exposed to CAF showed increased hepatic LPO. Under these experimental conditions, no effect on COX activity was observed, nor cytotoxic and genotoxic damage. The most pronounced effects were caused by the drugs separately, since both compounds altered the enzymes, but only CAF triggered LPO, showing more harmful effects.

Ecological impacts of pesticides on Astyanax jacuhiensis (Characiformes: Characidae) from the Uruguay river, Brazil

Brazilian freshwater ecosystems are continuously exposed to pesticides and domestic sewage. The Uruguay River was chosen for this study because of its international importance, as it flows through Brazil, Argentina, and Uruguay. It receives contaminants such as pesticides and domestic residues. Thus, the aim of this study to assess the accumulation of pesticides in muscle of the fish Astyanax jacuhiensis, its biochemical responses, and the presence of pesticides in water. In total, seven pesticides were registered in water from both river sites. Eight pesticides were detected in fish muscle. The biochemical responses showed that brain lipid peroxidation (LPO) and protein carbonyl (PC) in A. jacuhiensis were higher in the summer. Muscle showed the highest LPO levels in the spring and the highest PC in the summer. Liver LPO and PC levels were higher in the spring and summer. In the gills, the PC was higher in the spring and the LPO in the spring and winter. In the brain and in the gills, glutathione-S-transferase activity was high in the summer and autumn. Catalase activity was lower during the winter and spring. Non-protein thiol (NPSH) levels were lower in the brain in the winter and spring. Muscle tissue showed lower NPSH in the winter (site 1). Liver NPSH showed increased levels in liver in the spring and winter (site 2). The biochemical results clearly is related to pesticides and/or to the presence of other contaminants in the water such as metals or domestic sewage. The accumulation of pesticides in fish muscle added evidence that pesticides have been used in the area surrounding the Uruguay River. In conclusion, the biomarkers assayed in the present study could be used in future investigations considering other sampling sites along Uruguay River.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Antioxidant system status in threatened native fish Barbus meridionalis from the Osor River (Iberian Peninsula): I. Characterization and II. In vitro Zn assays

The evaluation of antioxidant system capacity is important in aquatic toxicology. It was aimed to characterize the liver antioxidant enzymes (SOD, CAT, GPX, GR, and GST) and to test the in vitro Zn effect (200 and 400 ZnSO₄ μg/L) in native fish Barbus meridionalis obtained from the Osor River (NE, Spain) influenced by Zn contamination. The maximal enzyme activities were at pH 7.0-7.5 and 100 mM phosphate buffer. Barbel showed high catalytic activity (high Vmax and low Km) indicating the efficient antioxidant detoxification ability. Direct Zn effect caused an antioxidant system imbalance. Mostly upon lower Zn concentration, GPX activity decreased (95-100 %) though CAT, GR, and GST increased (36-1543 %). GSH values either stimulated (290 %) or inhibited (85-93 %) due to tissue differences. The first record of barbel antioxidant enzyme characterization and in vitro data presenting an unbalanced antioxidant pattern could be significant to evaluate the metal pollution in the Osor River for further in vivo studies.

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

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

Response of the antioxidant enzymes of rats following oral administration of metal-oxide nanoparticles (Al2O3, CuO, TiO2)

Metal-oxide nanoparticles (NPs), as a new emerging technological compound, promise a wide range of usage areas and consequently have the potential to cause environmental toxicology. In the present work, aluminum (Al₂O₃), copper (CuO), and titanium (TiO₂) nanoparticles (NPs) were administered via oral gavage to mature female rats (Rattus norvegicus var. albinos) for 14 days with a dose series of 0 (control), 0.5, 5, and 50 (mg/kg b.w./day). Enzyme activities of the antioxidant system such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S-transferase (GST), and glutathione reductase (GR) in the liver were measured. Transmission electron microscope (TEM) images of the liver were taken to demonstrate NP accumulation and distribution in liver tissue. Data showed that all NPs caused some significant (P > 0.05) alterations in the activities of antioxidant enzymes. CAT activity increased after CuO and TiO₂ administrations, while SOD activity decreased after Al₂O₃ administration. The activities of enzymes associated with glutathione (GR, GPx, GST) metabolisms were also significantly altered by NPs. GPx activity increased in rats received Al₂O₃, CuO NPs, while GR activity increased only by Al₂O₃. However, there were increases (TiO₂) and decreases (CuO) in GST activity in the liver of rats. TEM images of the liver demonstrated that all NPs accumulated in the liver, even at the lowest dose. This study indicated that the antioxidant enzymes in the liver of rats were affected by all NPs, suggesting the antioxidant system of rats suffered after NP administration.

Response of selenium-dependent glutathione peroxidase in the freshwater bivalve Anodonta woodiana exposed to 2,4-dichlorophenol,2,4,6-trichlorophenol and pentachlorophenol

2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP) pose a health risk to aquatic organism and humans, and are recognized as persistent priority pollutants. Selenium dependent glutathione peroxidase (Se-GPx) belongs to the family of selenoprotein, which acts mainly as an antioxidant role in the cellular defense system. In the current study, a Se-GPx full length cDNA was cloned from Anodonta woodiana and named as AwSeGPx. It had a characteristic codon at 165TGA167 that corresponds to selenocysteine(Sec) amino acid as U44. The full length cDNA consists of 870 bp, an open reading frame (ORF) of 585 bp encoded a polypeptide of 195 amino in which conserved domain (68LGFPCNQF75) and a glutathione peroxide-1 GPx active site (32GKVILVENVASLUGTT47) were observed. Additionally, the eukaryotic selenocysteine insertion sequence (SECIS) was conserved in the 3'UTR. The AwSeGPx amino acid sequence exhibited a high similarity with that of other Se-GPx. Real-time PCR analysis revealed that AwSeGPx mRNA had a widely distribution, but the highest level was observed in hepatopancreas. AwSeGPx mRNA expression was significantly up-regulated in hepatopancreas, gill and hemocytes after 2,4-DCP, 2,4,6-TCP and PCP exposure. Under similar environment, clams A. woodiana showed a more sensitive to PCP than that of 2,4-DCP and 2,4,6-TCP. These results indicate that AwSeGPx plays a protective role in eliminating oxidative stress derived from 2,4-DCP, 2,4,6-TCP and PCP treatment.

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

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

Molecular cloning, characterization, and the response of Cu/Zn superoxide dismutase and catalase to PBDE-47 and -209 from the freshwater bivalve Anodonta woodiana

Polybrominated diphenyl ethers-47 (PBDE-47) and -209 are significant components of total PBDEs in water and can catalyze the production of reactive oxygen species (ROS) in the organisms. Anti-oxidant enzymes play an important role in scavenging the high level of ROS. In the current study, two full-length cDNAs of Cu/Zn superoxide dismutase (CuZnSODs) and catalase (CAT) were isolated from freshwater bivalve Anodonta woodiana by rapid amplification of cDNA ends approach and respectively named as AwSOD and AwCAT. The nucleotide sequence of AwSOD cDNA had an open reading frame (ORF) of 465 bp encoding a polypeptide of 155 amino acids in which signature 1 GKHGFHVHEFGDNT and signature 2 GNAGARSACGVI of SODs were observed. Deduced amino acid sequence of AwSOD showed a significant similarity with that of CuZnSODs. AwCAT had an ORF 1536 bp encoding a polypeptide of 512 amino acids which contains a conserved catalytic site motif, and a proximal heme-ligand signature motif of CATs. The time-course expressions of AwSOD and AwCAT in hepatopancreas were measured by quantitative real-time PCR. Expressions of AwSOD and AwCAT showed a significant up-regulation in groups at a low concentration treatment of PBDE-47, a biphasic pattern in groups with a high concentration treatment. Administration of PBDE-209 could result in an up-regulation of AwSOD and AwCAT expressions with time- and dose-dependent matter. These results indicate that up-regulations of AwSOD and AwCAT expression of hepatopancreas of freshwater bivalve A. woodiana contribute to eliminate oxidative stress derived from PBDE-47 and -209 treated.