Oxidative Stress In Fish Research Articles

Metals as a cause of oxidative stress in fish: a review

This review summarizes the current knowledge on the contribution of metals to the development of oxidative stress in fish. Metals are important inducers of oxidative stress in aquatic organisms, promoting formation of reactive oxygen species through two mechanisms. Redox active metals generate reactive oxygen species through redox cycling, while metals without redox potential impair antioxidant defences, especially that of thiol-containing antioxidants and enzymes. Elevated levels of reactive oxygen species lead to oxidative damage including lipid peroxidation, protein and DNA oxidation, and enzyme inactivation. Antioxidant defences include the enzyme system and low molecular weight antioxidants. Metal-binding proteins, such as ferritin, ceruloplasmin and metallothioneins, have special functions in the detoxification of toxic metals and also play a role in the metabolism and homeostasis of essential metals. Recent studies of metallothioneins as biomarkers indicate that quantitative analysis of mRNA expression of metallothionein genes can be appropriate in cases with elevated levels of metals and no evidence of oxidative damage in fish tissue. Components of the antioxidant defence are used as biochemical markers of oxidative stress. These markers may be manifested differently in the field than in results found in laboratory studies. A complex approach should be taken in field studies of metal contamination of the aquatic environment.  

Myo-inositol prevents copper-induced oxidative damage and changes in antioxidant capacity in various organs and the enterocytes of juvenile Jian carp ( Cyprinus carpio var. Jian)

Although oxidative stress has been demonstrated to be involved in copper (Cu)-induced toxicity, information regarding the effect of antioxidants on Cu toxicity is still scarce. This study assessed the possible protective effects of myo-inositol (MI) against subsequent Cu exposure in juvenile Jian carp ( Cyprinus carpio var. Jian) in vivo and in their enterocytes in vitro. First, oxidative stress was established by exposing fish to different concentrations of Cu (0–7.2 mg Cu/L water) for 4 days. Next, the protective effects of MI (administered as a dietary supplement for 60 days) against subsequent Cu exposure (0.6 mg Cu/L water for 4 days) were studied in fish. The third trial determined the effects of Cu exposure (0–6.0 mg Cu/L of medium for 24 h) on enterocytes in vitro. Finally, enterocytes were pre-incubated with graded levels of MI (0–75 mg MI/L of medium) for 72 h and exposed to 6.0 mg Cu/L of medium for 24 h. The results indicated that ≥0.6 mg Cu/L water could induce oxidative stress in fish ( P < 0.05). Cu exposure significantly induced increases in lipid peroxidation and protein oxidation in the gill, hepatopancreas and intestine in fish. However, these oxidative effects were prevented by MI pre-supplementation. MI also prevented the toxic effects of Cu on anti-superoxide anion (ASA), anti-hydroxyl radical (AHR), superoxide dismutase (SOD), catalase (CAT), glutathione- S-transferase (GST), glutathione peroxidase (GPx) and glutathione reductase (GR) activities and glutathione (GSH) content in these organs. In vitro, enterocytes exposed to Cu displayed a dose-dependent injury. Moreover, cell viability, protein retention (PR), alkaline phosphatase, total-SOD (T-SOD) and Cu/ZnSOD activities were all depressed by Cu ( P < 0.05). Interestingly, the final experiment showed that MI pre-supplementation could block the toxic effects of Cu on the antioxidant system, and thus protect enterocytes from Cu-induced oxidative damage. All of these results indicated that the induction of key antioxidant defenses by MI pre-supplementation, including SOD, CAT, GPx, GST and GSH, may play an important role in the protection of fish against oxidative stress.

Perfluorooctane sulfonic acid exposure increases cadmium toxicity in early life stage of zebrafish, Danio rerio

Exposure to perfluorooctane sulfonic acid (PFOS) is known to induce thyroid-related adverse effects in aquatic organisms. Because an antioxidant defense mechanism is one of the key functions of the thyroid gland, we examined whether preexposure to PFOS could disrupt thyroid function and enhance cadmium (Cd)-induced oxidative stress in fish. Zebrafish embryos were exposed to control or 0.5 mg/L PFOS for 7 d after fertilization and subsequently exposed to 0.038 mg/L of Cd(2+) or a mixture of the PFOS and Cd for an additional 3 d until 10 d postfertilization (dpf). Survival rates, body length, messenger RNA (mRNA) expressions related to thyroid function and oxidative stress, the levels of thyroid hormones, and malondialdehyde and antioxidant enzyme activities were measured. Significant down-regulation of mRNAs related to thyroid function (thyroid hormone receptor-alpha [THRα], thyroid hormone receptor-beta [THRβ], hematopoietically expressed homeobox [hhex], and paired box gene 8 [pax8]) and decrease of throxine (T4) levels were observed in the PFOS preexposure group, suggesting that PFOS preexposure would influence the performance of thyroid gland in the later stages of life. Certain genes relative to oxidative stress, such as superoxide dismutase 1 (sod1) and heat shock protein 70 (hsp70), in the PFOS preexposure group were significantly up-regulated when the larvae were subsequently exposed to Cd or to the mixture of PFOS and Cd. Glutathione S-transferase activity and malondialdehyde levels of the PFOS-preexposed group were increased significantly by Cd exposure. Significant decrease of the survival rates and body length of fish were observed at 10 dpf among the larvae that were previously exposed to PFOS. These results suggest that preexposure to PFOS could affect antioxidant defense mechanisms and potentially increase the toxicity of Cd on mRNA expression and enzyme activity level responses, as well as on survival or growth of individuals.

Mercuric chloride induced proteotoxicity and structural destabilization in marine fish (Therapon jarbua)

The reaction byproducts derived from lipid peroxidation (LPO), as well as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) enzyme activities were measured in tissues of marine fish (Therapon jarbua) exposed to mercuric chloride (HgCl) in water dispersions of 0.125 or 0.25 ppm. LPO was significantly increased in various tissues relative to control values after 96-h exposure. SOD and GPx activities significantly decreased after exposure to first two doses but significantly elevated CAT in Dose II kidney and liver tissues. The elevated levels of LPO, decreased activities of SOD and GPx, and increased CAT activities in all tissues examined in T. jarbua are an index of oxidative stress in fish. Structural analysis by scanning electron microscopy studies revealed the structural deformation in HgCl2-exposed animals. These observations suggest that HgCl acts as a mediator in free radical generation. The increase in CAT and decrease in SOD and GPx activities in these tissues may be an adaptive response.

Deltamethrin attenuates antioxidant defense system and induces the expression of heat shock protein 70 in rainbow trout

The current research aims to determine alterations in gene expression and enzymatic activity of fish antioxidant metabolism in response to pesticide administration. To this end, three different deltamethrin concentrations (0.25, 1, 2.5μg/L) were administrated to rainbow trout (Oncorhynchus mykiss) at different time intervals (6, 12, 24, 48 and 72h) in order to observe the influences of the pesticide on the activity of glutathione reductase, glucose 6-phosphate dehydrogenase, 6-ghosphogluconate dehydrogenase, and the expression of Hsp70 gene. We observed that the activities of the enzymes decreased with increasing deltamethrin concentrations and exposure time. The pesticide had more inhibitory effects on gill enzymes than those of muscle, liver and kidney. In addition, we detected that deltamethrin increased the expression of the stress-related protein Hsp70 with significant fold-chance values. The efficiency rate was 96.4% which is equal to 1.96 calculated via conversion formula used to calculate fold-chance value. We conclude that deltamethrin causes oxidative stress in fish both at protein and mRNA levels.

Molecular cloning, phylogenetic analysis and expression of a MAPEG superfamily gene from the pufferfish Takifugu obscurus

The microsomal glutathione S-transferases (MGSTs) of membrane-associated proteins in eicosanoid and glutathione metabolism (MAPEG) superfamily play an important role in xenobiotics detoxification. Compared to mammals, there is limited information on MAPEGS from fish. We cloned a full length of cDNA sequence of a MGST gene from the river pufferfish ( Takifugu obscurus), studied its phylogenetic relationship, and measured its expression in different tissues and in liver of fish exposed to cadmium. Phylogenetic analysis revealed that the identified gene encoded for MGST3. Liver showed the highest expression of MGST3 transcripts. When MSGT expression was compared with the expression of other GSTs ( GST-Alpha, GST-Mu and GST-Theta), a similar pattern of highest expression was observed in the liver. Upon Cd exposure (5 ppm) for 96 h, the highest expression of MGST was observed at 24 h. GST-Mu also showed highest expression at 24 h. These findings indicate that MGSTs may be playing a role in detoxification of xenobiotics or free radicals generated by Cd-induced oxidative stress in fish.

Protective role of vitamin E on the microcystin‐induced oxidative stress in tilapia fish (Oreochromis niloticus)

Microcystins (MCs) are potent hepatotoxins produced by cyanobacteria in water systems that induce oxidative stress in fish. The present study investigated the effect of vitamin E pretreatment on MC-induced oxidative damage in the liver, kidneys, and gills of tilapia fish (Oreochromis niloticus). Groups of fish were fed vitamin E supplements (200 or 700 mg per kilogram of diet) for 7 d or received only commercial fish food and then were exposed to a single oral dose of cyanobacterial cells (120 microg of MC-LR [2:Leu, 4:Arg] per fish), and were sacrificed in 24 h. The potential benefits of vitamin E were evaluated based on lipid peroxidation (LPO), protein oxidation, catalase (CAT, Enzyme Commission [EC] 1.11.1.6), superoxide dismutase (EC 1.15.1.1), glutathione peroxidase (EC 1.11.1.9), glutathione reductase (EC 1.8.1.7), and the ratio of reduced glutathione to oxidized glutathione (GSH/GSSG). Microcystins induced a 1.6-fold increase in LPO values in liver, whereas vitamin E-pretreated fish showed no alteration on this biomarker. Enzyme activities levels were also ameliorated by the chemoprotectant, whereas protein oxidation and GSH/GSSG did not show any significant change. The higher vitamin E dose used proved to have the greater protective effects, particularly on the biomarkers LPO and CAT. The results show that vitamin E could have a potential use as a preventive or therapeutic measure in MC-exposed fish.

The use of palm oil in aquaculture feeds for salmonid species

AbstractIn this overview, our current knowledge and research being conducted on the use of palm oil in the commercial feeds for cold‐water salmonid species such as Atlantic salmon and rainbow trout will be highlighted. Salmonid diets have a high lipid content to provide a source of easily available energy and also n‐3 polyunsaturated fatty acids (PUFA) which is used to maintain membrane fluidity in a cold‐water environment. The culture of salmonid fishes has traditionally depended on marine fish oils for this purpose, but with limited supplies and the rapid increase in salmon production, alternatives to fish oils must be investigated. Research has shown that crude palm oil can be used to replace 100% of added fish oils in salmonid diets without compromising growth performance and feed utilization efficiency, despite reductions in lipid and fatty acid digestibilities that occur during low water temperatures over the winter rearing period. Fatty acid desaturation and elongation activities increased with increasing dietary palm oil and, to a certain extent, decreasing water temperatures. The effects of palm oil on fish health requires further research, but the use of this more saturated vegetable oil may reduce oxidative stress in fish, thereby reducing pathological conditions associated with this physiological state. It is generally known that the fish fillet fatty acid composition directly reflects that of the dietary oil used. Extrapolating from work done with other vegetable oils, the supply of beneficial n‐3 PUFA in salmon fillets to the human consumer can be maintained by using a finishing diet strategy just prior to harvesting, despite significant reductions in these fatty acids when high levels of dietary palm oil are used in grower feeds. Compared to vegetable oils such as soybean or rapeseed oil, palm oil has several advantages in terms of high oil productivity, lower cost, less deposition of undesirable fatty acids such as 18:2(n‐6), superior energy source in the form of saturated and monounsaturated fatty acids, and a high content of natural antioxidants (carotenes and vitamin E). Fillet texture and color were not affected by feeding salmon palm oil‐based diets.

THYROID HORMONES REGULATE MITOCHONDRIAL RESPIRATION AS WELL AS ANTIOXIDANT DEFENSE IN TELEOSTS TOO

Our studies describe the effect of T 3 on the regulation of mitochondrial metabolism, lipid peroxidation and antioxidant enzyme homeostasis in a fresh water teleost, Anabas testudineus . These experiments suggest the possibility that certain of the clinical and biochemical manifestations of T 3 can be attributed to a direct effect of T 3 on mitochondria. Thyroid hormone enhances mitochondrial ATP production rate in the highly oxidative tissue such as liver. These in vitro and in vivo studies substantiate and confirm the earlier reported T 3 -induced oxidative metabolism in lower vertebrates. These induced oxidative metabolisms create oxidative stress in tissues. This confirms that T 3 has an immediate response in in vivo and in vitro system on energy adjustment in the fish, A. testudineus. Tri-iodothyronine is also capable of combating the oxidative stress by activating the antioxidant system to remove the ROS. Tri-iodothyronine appears to have a dual role, as a stimulator of oxidative process and as a regulator of antioxidant enzyme activity. This establishes another example for the multi-functional role of T 3 in lower vertebrates also. However, the precise mechanism of action remains to be understood. The protein expression study revealed that T 3 administration in fish creates hypermetaolic state. This hypermetabolic state creates oxidative stress in fish. To maintain the homeostasis of the fish, physiology the main antioxidant CuZn SOD is directly altered. Due to augmented SOD utilization, expression of CuZn SOD is diminished in fish liver and brain. These findings conclude that thyroid hormone effectively maintains physiological status of fresh water fish. It is obvious that thyroid hormones have an over all effect on metabolism in responsive tissue and that their effect is a direct one. Theses studies establish multi-functional role of T 3 in lower vertebrates.

Sediment Mutagenicity and Liver Oxidative Stress in Fish Under Tannery Influence

The mutagenicity of interstitial water and organic extracts from the sediments in the Cadeia and Feitoria Rivers, RS, Brazil, were evaluated by Salmonella microsuspension bioassay using TA97a, TA98, TA100 and TA102 strains, in the absence and presence of S9 mix. At the contaminated site, the mutagenic responses for interstitial water, suggested the presence of frameshift and base pair substitution mutagens, including substances that generate oxidative stress. Organic extracts presented direct or indicative mutagenesis to the TA97a, TA98 and TA100 strains. In general, an exogenous metabolic systems decreased the mutagenicity of the samples. The livers of Gymnogeophagus gymnogenys, family Cichlidae, collected in this impacted area, compared to a non-polluted site, were analyzed for oxidative stress parameters. Compared to the controls, there was a significant increase in the activity of superoxide dismutase (SOD), levels of substances reactive to thiobarbituric acid (TBARS), and in the chemiluminescence of hepatic cells in fish collected at the polluted area. The concentration of cytochromes P450 and b5 decreased drastically in the fish at the polluted site, while the catalase activity did not change. It was possible to correlate the biological changes in the fish with the presence of mutagenic compounds in interstitial water in this area.

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

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

Induction of oxidative stress by arsenic in Clarias batrachus: Involvement of peroxisomes

Indian catfish, Clarias batrachus, were exposed to two nonlethal doses of arsenic for 10 days, which induced tissue lipid peroxidation, increased the ratio of oxidized to reduced glutathione and produced excess H 2O 2 within 1–2 days of exposure. Furthermore, arsenic treatment increased the activity of antioxidant enzymes such as glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase but decreased glutathione reductase (GR) activity within a day of exposure, indicating the generation of oxidative stress in fish at an early stage. Reversibility of these arsenic-induced responses by pretreatment with N-acetylcysteine indicates that the oxidative stress was due to excess H 2O 2 production, which was found to be partially contributed by altered H 2O 2 metabolism in the peroxisomes. It is therefore concluded that peroxisomal H 2O 2 metabolizing enzymes are potential targets of arsenic toxicity in C. batrachus.

Sediment Mutagenicity and Liver Oxidative Stress in Fish Under Tannery Influence

The mutagenicity of interstitial water and organic extracts from the sediments in the Cadeia and Feitoria Rivers, RS, Brazil, were evaluated by Salmonella microsuspension bioassay using TA97a, TA98, TA100 and TA102 strains, in the absence and presence of S9 mix. At the contaminated site, the mutagenic responses for interstitial water, suggested the presence of frameshift and base pair substitution mutagens, including substances that generate oxidative stress. Organic extracts presented direct or indicative mutagenesis to the TA97a, TA98 and TA100 strains. In general, an exogenous metabolic systems decreased the mutagenicity of the samples. The livers of Gymnogeophagus gymnogenys, family Cichlidae, collected in this impacted area, compared to a non-polluted site, were analyzed for oxidative stress parameters. Compared to the controls, there was a significant increase in the activity of superoxide dismutase (SOD), levels of substances reactive to thiobarbituric acid (TBARS), and in the chemiluminescence of hepatic cells in fish collected at the polluted area. The concentration of cytochromes P450 and b5 decreased drastically in the fish at the polluted site, while the catalase activity did not change. It was possible to correlate the biological changes in the fish with the presence of mutagenic compounds in interstitial water in this area.

Joint effects of parasitism and pollution on oxidative stress biomarkers in yellow perch Perca flavescens

Yellow perch Perca flavescens were collected from a contaminated site and a reference site in the St. Lawrence River, Quebec, Canada. Fish were assessed for oxidative stress (lipid peroxidation and reduced glutathione levels) and parasitism by the nematode Raphidascaris acus and metacercariae of the digenean Apophallus brevis. Lipid peroxidation is not only considered a measure of oxidative stress, but of stress in general, and thus serves as an indicator of fish health. Fish from the contaminated site exhibited higher levels of lipid peroxidation than those from the reference site, independent of parasitic infections. However, fish infected with R. acus at the contaminated site tended to have higher levels of lipid peroxidation than uninfected fish at the same site, whereas no difference was observed between infected and uninfected fish at the reference site. Yellow perch infected with > 10 metacercariae of A. brevis expressed higher levels of lipid peroxidation than those infected with < 10 metacercariae at both the contaminated and the reference sites. No differences were found in levels of reduced glutathione in liver or muscle in relation to site or either parasite species. Results support the use of lipid peroxidation as a biomarker of water contamination. They further suggest that lipid peroxidation may be used as a biomarker of pathological effects caused by parasitism. Most importantly, results demonstrate that contaminants and parasites occurring together exacerbate oxidative stress in fish, suggesting that parasitized fish in polluted environments are in a poorer state of health than uninfected fish.

Oxidative stress damage in the liver of fish and rats receiving an intraperitoneal injection of hexavalent chromium as evaluated by chemiluminescence

The livers fractions of Oreochromis niloticus (Tilapia) and Wistar rats taken from treated animals to single intraperitoneal doses of hexavalent chromium (K 2Cr 2O 7), were analyzed for tert butyl hydroperoxide-initiated chemiluminescence (CL), lipid peroxidation using thiobarbituric acid reactive substances (TBARS), enzymes superoxide dismutase (SOD) and catalase activities, and the quantification of cytochromes P450 and b5. The CL time course curve was significantly higher in O. niloticus treated with Cr(VI) at all times studied. The maximum CL was observed after 24 h of exposure. The CL mean ratio treated/control was 4.6 and the initial velocity ( V 0) increased 7.4 times at 24 h of intoxication. The TBARS levels however increased only 24 h after intoxication. The CL time course curve was significantly higher in rats treated with Cr(VI) as early as 3 h after intoxication. The maximum CL occurred 24 h after exposure. The CL mean ratio treated/control was 2.1 and the V 0 increased 3.8 times at 24 h of intoxication. On the contrary, was not observed any increase in TBARS in this study. Compared to the controls, in fish, SOD activity increased significantly only 24 h after of exposure. In rats, there was a significant increase in SOD activity after 3 and 24 h of intoxication. There was no catalase activity, nor cytochrome P450 and cytochrome b5 variation in both species studied. Through CL approach, it was possible to detect oxidative stress as early as 15 min in fish and 3 h in rats. Also a marked oxidative stress was revealed by the increased CL parameters that at 24 h of intoxication was accompanied by arose SOD activity in liver of O. niloticus and Wistar rats and increased TBARS in O. niloticus. In addition, it was possible to show higher levels of oxidative stress in fish compared to the rat in spite of the dose to be four times smaller. Furthermore, CL provide a sensitive method for possible use to detect earlier biological impact in contaminated environments.

Mutagenicity of sediment and biomarkers of oxidative stress in fish from aquatic environments under the influence of tanneries

The mutagenicity of interstitial water and organic extracts from the sediments in the Cadeia and Feitoria Rivers, RS, Brazil, were evaluated by Salmonella microsuspension bioassay using TA97a, TA98, TA100 and TA102 strains, in the absence and presence of S9 mix. At the contaminated site, the mutagenic responses for interstitial water, suggested the presence of frameshift and base pair substitution mutagens, including oxidative substances. Organic extracts presented direct or indicative mutagenesis to the TA97a, TA98 and TA100 strains. In general, an exogenous metabolic systems decreased the mutagenicity of the samples. High concentrations of total chromium found in the sediment and interstitial water as well as total mercury in the sediment of the contaminated site, when compared to the control area, may help explain the mutagenic results. The livers of Gymnogeophagus gymnogenys collected in this impacted area, compared to a non-polluted site, were analyzed for oxidative stress parameters. Compared to the controls, there was a significant increase in the activity of superoxide dismutase (SOD) at levels of substances reactive to thiobarbituric acid (TBARS), and in the chemiluminescence of hepatic cells in fish in the polluted area. The concentration of cytochromes P450 and b5 decreased drastically in the fish at the polluted site, while the catalase activity did not change. It was possible to correlate the biological changes in the fish with the presence of mutagenic compounds in sediment and interstitial water in this area.

Fly ash leachate induces oxidative stress in freshwater fish Channa punctata (Bloch)

Oxidative stress inducing potential of fly ash leachate (FAL) was studied in a freshwater fish, Channa punctata (Bloch). Fish were exposed to fly ash leachate for 24 h and lipid peroxidation (LPO) was studied as a marker of oxidative stress. Catalase (CAT), glutathione S-transferase (GST) activities and levels of reduced glutathione (GSH) were also estimated in the exposed fish. FAL (1 ml/l) induced LPO in all the organs and most prominent response was in the gill. It also caused induction of enzymes and glutathione. Liver showed highest level of induction of enzyme activities. The results of this study demonstrate that fly ash constituents have potential to induce oxidative stress in fish and gills are the most vulnerable organs. It is also suggested that in case of exposure to FAL, along with LPO antioxidant defense is also activated to counteract the reactive oxygen species (ROS) at least partly in the initial stages of exposure.

Effect of food deprivation on oxidative stress biomarkers in fish ( Sparus aurata)

Oxidative stress in fish ( Sparus aurata) as a consequence of food restriction and fasting, has been studied. Four groups of fish were maintained for 46 days under different conditions of food supplementation: a control group with no food restriction (ratio of food/fish of 2% w/w), two groups of animals with restricted food supplement (1 and 0.5%) and a fasting group (no meal addition). Finally, all the fish were provided with food at the same ratio as the control group for the last 7 days. Sampling and weighing of fish were carried out every week and their livers were used for the analysis of known biomarkers of oxidative stress. Malondialdehyde and oxidized glutathione levels increased at the third week in fish with partial or total food deprivation, but these levels returned to normal values when the fish readapted to the control conditions. Antioxidant enzymes were also analyzed and significant increases in superoxide dismutase (SOD), glutathione reductase and glutathione peroxidase activities were found in parallel with food restriction; however catalase activity decreased in fasting fish. New SOD isoforms were detected by isoelectrofocusing in fish under food restriction at the second week, which disappeared when starved fish returned to the control conditions. These new SOD isoforms were detected before the appearance of other usual oxidative stress biomarkers.

Effects of a fermented vegetable product on hemolysis and lipid peroxidation of Japanese flounder erythrocytes

: We investigated the protective effects of a fermented vegetable product (FVP) against the hemolysis and lipid peroxidation of Japanese flounder (Paralichthys olivaceus) erythrocytes in vitro. 2,2′-Azobis (2-aminopropane) dihydrochloride (AAPH) and tert-butyl hydroperoxide were used as model compounds that cause oxidative stress through the generation of free radicals and induction of lipid peroxidation, respectively, in erythrocytes. The hemolysis and lipid peroxidation of erythrocytes induced with 125 mM AAPH and 25 mM tert-butyl hydroperoxide, respectively, were suppressed by the administration of 1–2 mg/mL FVP (P < 0.01). These results suggested that the FVP reduces oxidative stress in fish and may be useful for the rearing of cultured fish.

Effects of redox cycling compounds on glutathione content and activity of glutathione-related enzymes in rainbow trout liver

In fish, as in other aerobic organisms, glutathione and glutathione-related enzymes are important components in the defences against oxidative stress. To study if hepatic glutathione levels and/or activities of glutathione-related enzymes can act as indicators of oxidative stress in fish, we injected rainbow trout ( Oncorhynchus mykiss) intraperitoneally with paraquat (PQ), menadione (MD), naphthazarin (DHNQ), or β-naphthoflavone (β-NF), all known to cause a rise in reactive oxygen species (ROS). After 2 and 5 days of exposure, we measured the activities of hepatic glutathione peroxidase (GPox), glutathione S-transferase (GST), γ-glutamylcysteine synthetase (GCS), and glutathione reductase (GR). We also measured total glutathione (tGSH) and oxidised glutathione (GSSG) in the liver of fish treated with PQ and MD. All chemicals caused an increase in GR activity after 5 days, which ranged from 160% in fish treated with β-NF to 1500% in fish treated with PQ. All chemicals except β-NF caused moderate elevation in GST activity; GPox activity was lower in fish treated with DHNQ and MD, while GCS activity increased twofold in the fish treated with DHNQ, without being affected by β-NF, PQ or MD. After 5 days of treatment with PQ or MD, tGSH content was elevated. Our findings demonstrated that of the parameters included in the study, GR activity was the most responsive to treatment with redox cycling compounds, indicating that GR activity is a promising biomarker of such compounds and possibly indicating oxidative stress in rainbow trout.