Oxidative stress and antioxidant enzymes activities in the African catfish, Clarias gariepinus, experimentally challenged with Escherichia coli and Vibrio fischeri

Effects of 2,4-dichlorophenol on non-specific immunity, histopathological lesions, and redox balance in African Catfish, clarias gariepinus (Burchell, 1822)

The toxic effects of 2, 4-dichlorophenol (2, 4-DCP) on aquatic organisms are well-established; however, the details regarding the mechanisms underlying the toxicity, especially immunotoxicity are poorly understood. Consequently, the aim of this study was to investigate the histopathologic, oxidative stress and immunotoxic effects attributed to exposure to sublethal concentrations of 2,4-DCP in the African catfish, Clarias gariepinus. Juvenile C. gariepinus were exposed to 0.4, 0.8, or 1.6 mg/L 2, 4-DCP for 28 days after which blood and head kidney were extracted for the determination of various nonspecific innate immune parameters while the liver was excised for histopathology examination and measurement of oxidative stress biomarkers. Control fish were maintained in water spiked 10 µL/L ethanol, representing the solvent control. A significant increase was noted in the activities of lactate dehydrogenase and superoxide dismutase as well as in levels of lipid peroxidation and DNA fragmentation in a dose-dependent manner, with higher adverse effects observed at the highest concentration tested (1.6 mg/L). The total white blood cells (WBC) count was significantly elevated in fish exposed to 2,4-DCP compared to control. Myeloperoxidase content was decreased significantly in fish exposed to 2,4-DCP especially at the highest concentration (1.6 mg/L) compared to controls. The respiratory burst activity did not differ markedly amongst groups. Histopathological lesions noted included edema, leucocyte infiltration, and depletion of hemopoietic tissue in the head kidney of exposed fish. There was significant upregulation in the mRNA expression of tumor necrosis factor (TNF-α) and heat shock protein 70 (HSP 70) but downregulation of major histocompatibility complex 2 (MHC 2) in exposed fish. Data demonstrated that exposure to 2,4-DCP resulted in histopathological lesions, oxidative stress, and compromised immune system in C. gariepinus.

Tissue Accumulation, Cytotoxicity, Oxidative Stress, and Immunotoxicity in African Catfish, Clarias gariepinus Exposed to Sublethal Concentrations of Hexavalent Chromium

Hexavalent chromium (Cr6+) is one of the stable oxidation states of chromium that has been reported to elicit various toxic effects in aquatic organisms. However, the mechanisms of Cr6+ toxicity are still poorly understood. Thus, the present study investigated the tissue accumulation, cytotoxic, oxidative stress, and immunotoxic effects of Cr6+ in juvenile Clarias gariepinus. The fish were exposed to waterborne Cr6+ concentrations (0, 0.42, 0.84, and 1.68 mg/L) for 28 days, after which they were sacrificed and various organs were harvested for the determination of Cr6+ levels. Other parameters that were indicators of oxidative stress, cytotoxicity, and immunotoxicity were measured. Cr6+ accumulated more in the kidney and liver of the exposed fish, especially at the highest concentration. The levels of lipid peroxidation and DNA fragmentation increased significantly in the exposed fish. The activities of superoxide dismutase and lactate dehydrogenase increased significantly in exposed fish compared to the control. The total white blood cells, lymphocytes, and neutrophils counts were significantly higher in the exposed fish compared to the control fish. The respiratory burst activity decreased significantly in the exposed fish while the myeloperoxidase content did not differ significantly. There were upregulations of TNF-α and HSP 70 while CYP II and MHC 2 were downregulated in the exposed fish. Also, exposure to Cr6+ resulted in various histopathological alterations in the architecture of the head kidney. The results indicate concentration-dependent toxic effects of Cr6+ in C. gariepinus. The study reveals the potentials of Cr6+ to accumulate in the different tissues of fish and caused cytotoxic, oxidative stress, and immunotoxic effects in the exposed fish.

Long term integrated biomarker responses in freshwater African catfish Clarias gariepinus exposed to a new brand of herbicide fluazifop-p-butyl

The study investigated the sublethal effects of Fluazifop-p-butyl (FPB) on the haematological, biochemical and oxidative stress changes in Clarias gariepinus. Juvenile C. gariepinus were exposed to FPB concentrations of 1.80, 3.50, and 7.10 mg/l corresponding to 5, 10 and 20% of 96 h LC50 value of FPB respectively for 21 days and allowed to recover for 7 days. The blood, liver and gills were removed and analyzed. Fish exposed to different concentrations of FPB showed significant decline in the values the pack cell volume, hemoglobin and red blood cells but the white blood cell values increased. The neutrophil values increased while the lymphocyte declined but the monocytes, basophil and eosinophil values remain unchanged. The liver and gill aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase significantly increased compared to the control. There were mixed trends in the values of glucose but total protein was reduced in both tissues of the fish. There was significant decline in superoxide dismutase, catalase and glutathione peroxidase while malondialdehyde, total glutathione, and glutathione reductase increased in both liver and gill of the exposed fish. Following the 7-day withdrawal, most of the observed parameters returned to normal values. The present study revealed that FPB is toxic to C. gariepinus juveniles and prolonged exposure could result to major health risks to aquatic organisms, hence, they should be carefully used.

Oxidative stress-induced DNA damage and DNA repair mechanisms in mangrove bacteria exposed to climatic and heavy metal stressors

Bacteria thriving in the mangrove ecosystem are major drivers of elemental cycles. Climate change and environmental stressors (heavy metals) influence the performance of these microorganisms, thereby affecting the biogeochemical cycle. The present study reports the genotoxic effect of climatic and heavy metal stressors on mangrove bacteria and their adaptation strategies. Comparative analysis between two bacterial strains, Bacillus stercoris GST-03 and Pseudomonas balearica DST-02 isolated from the Bhitarkanika mangrove ecosystem, Odisha, India, showed cellular injuries in response to various stressors as evident by declined growth, elevated levels of reactive oxygen species (ROS) and resulted DNA damage. B. stercoris GST-03 showed more tolerance towards acidic pH, whereas P. balearica DST-02 showed higher tolerance towards UV exposure and heavy metals (Lead and Cadmium). The adaptation strategies of the strains revealed a significant role of GST in ROS scavenging activity and the involvement of Nucleotide excision repair or SOS response pathways. However, irreparable DNA damage was observed at pH 9 and 200 ppm Cd in B. stercoris GST-03, and at pH 4, 1000 ppm of Pb and 200 ppm of Cd in P. balearica DST-02. The current findings provide a broad overview of bacterial response and adaptability concerning future climate and environmental changes.

Alterations in certain immunological parameters in the skin mucus of the carp, Cirrhinus mrigala, infected with the bacteria, Edwardsiella tarda

The bacterial fish pathogen Edwardsiella tarda causes heavy stock mortality, severely hampering fish production, resulting in great economic loss to the farming industry. The first biological barriers that confer immune protection against pathogen entry are the fish mucosal surfaces. The present study was undertaken to investigate the influence of E. tarda on certain enzymatic and non-enzymatic parameters in the skin mucous secretions of the fish Cirrhinus mrigala using spectrophotometry and zymography. Fish were randomly divided into three groups: control, vehicle control, and infected. A sublethal dose of E. tarda (2.2 × 106 CFU/fish) suspended in 50 μL of PBS was injected intra-peritoneally at 0 day (d). Subsequently, mucus samples were collected at 2 d, 4 d, 6 d and 8 d post-infection. The activities of lysozyme (LYZ), protease (PROT), alkaline phosphatase (ALP), acid phosphatase (ACP), catalase (CAT), peroxidase (PER), superoxide dismutase (SOD), and glutathione S-transferase (GST) decreased significantly in the skin mucus of the challenged fish, indicating the suppressed immune system and decreased antioxidant capacity of C. mrigala to E. tarda infection. Lipid peroxidation (LPO) and total nitrate-nitrite were significantly higher at several time points post-infection, suggesting that physiological functions have been impaired following pathogen challenge. The present findings could be relevant for fish aquaculture and underline the importance of skin mucus not only for assessing fish immune status but also for identifying early warning signals of disease caused by pathogens.

Cytotoxicity, redox and immune status in African catfish, Clarias gariepinus (Burchell, 1822) exposed to bisphenol A (BPA) and its analogues

The objective of the study was to determine the comparative toxicities and immune dysfunction in the African catfish, Clarias gariepinus, exposed to bisphenol A (BPA) and its two analogues: bisphenol AP (BPAP) and bisphenol P (BPP). Juveniles of C. gariepinus were exposed to sublethal concentrations (70 and 140 μg/L) of BPA, BPAP and BPP for 7, 14 or 21 days after which various endpoints which are indicative of cytotoxicity, oxidative stress and haematological and innate immune parameters were determined in the liver homogenates or blood plasma. The exposure of C. gariepinus to BPA and its analogues caused significant increased activities of lactate dehydrogenase, catalase and superoxide dismutase. The exposed fish had increased levels of DNA fragmentation, lipid peroxidation, white blood cells, nitric oxide and respiratory burst, while the red blood cell counts and the percentage packed cell volume decreased significantly in the exposed fish compared to control. The toxic effects elicited by the bisphenols were both concentration- and duration-dependent. Generally, BPA exerted the most toxic effects on the fish, followed by BPAP, while BPP exerted the least toxic effects to C. gariepinus. Summarily, the findings indicated that BPA and its two analogues studied in the research are capable of causing cytotoxicity, oxidative stress and immune dysfunction in C. gariepinus.

A meta-analysis of impacts of immune response and infection on oxidative status in vertebrates

Inferring from patterns observed in biomedical research, ecoimmunological theory predicts that oxidative stress is a ubiquitous physiological cost that contributes to generating variation in immune function between individuals or species. This prediction is, however, often challenged by empirical studies testing the relationship between immune response or infection and oxidative status markers. This points out the importance of combining ecological immunology and oxidative stress ecology to further our understanding of the proximate causes and fitness consequences of individual variation in health, and adaptability to natural and anthropogenic environmental changes. I reviewed evidence and performed phylogenetic meta-analyses of changes in oxidative status markers owing to either injection of an antigen or infection in captive and free-living vertebrates (141 studies, 1262 effect sizes, 97 species). The dataset was dominated by studies on fish, birds and mammals, which provided 95.8% of effect sizes. Both antigen injection and parasite exposure were associated with changes of oxidative status. There were significant effects of taxonomic class and experimental environment (captivity vs. wild). In contrast with my predictions, age category (young vs. adult), study design (correlational vs. experimental) and proxies of pace of life (clutch size, litter size, and body mass; for birds and mammals only) were negligible in this dataset. Several methodological aspects (type of immunostimulant, laboratory assay, tissue analysed) showed significant effects on both strength and direction of effect. My results suggest that alterations of oxidative status are a widespread consequence of immune function across vertebrates. However, this work also identified heterogeneity in strength and direction of effect sizes, which suggests that immune function does not necessarily result in oxidative stress. Finally, this work identifies methodological caveats that might be relevant for the interpretation and comparability of results and for the application in conservation programs.

Effects of pre-treatment with waterborne selenium on redox homeostasis and humoral innate immune parameters in African catfish, Clarias gariepinus (Burchell, 1822), experimentally challenged with Serratia marcescens

Bacterial infections have been associated with immune dysfunction and oxidative stress in cultured fish species while essential elements could boost immunity and exhibit antioxidant properties in fish. This study was therefore aimed at determining the effects of pre-treatment with waterborne selenium on humoral immunity and redox status of Clarias gariepinus experimentally challenged with Serratia marcescens. Juveniles C. gariepinus were pre-treated with 50 µg/L selenium for 14 days after which they were challenged with 5 × 10³ CFU/mL of S. marcescens via oral gavage for 24 or 48 h. The control fish were not pre-treated with selenium and not challenged with bacteria. Thereafter, fish were sacrificed, blood collected into EDTA bottles for the determination of plasma nitric oxide levels and respiratory burst, and the liver excised for the determination of reduced glutathione, lipid peroxidation, and activities of catalase, superoxide dismutase, and glutathione peroxidase. Fish that were pre-treated with selenium prior to bacterial challenge (Sel + Bact) had decreased levels of nitric oxide and lipid peroxidation but a significant increase in the levels of reduced glutathione (at 48-h post-infection period only) compared to the fish challenged with bacteria without prior selenium pre-treatment (Bact). The respiratory burst and catalase activity decreased significantly in the Sel + Bact group especially at 48-h post-infection period while the activity of glutathione peroxidase increased significantly in the Sel + Bact group (at 24-h post-infection period only) compared to the Bact group. The results from this study showed that infection with S. marcescens is capable of disrupting the immune system and redox homeostasis in C. gariepinus, while pre-treatment with selenium has the ability to improve the physiological status of fish that were challenged with bacteria probably through its antioxidant properties. HIGHLIGHT: The pre-treatment of Clarias gariepinus to waterborne selenium for 14 days improved the redox homeostasis and innate immunity of fish that were experimentally challenged with the bacterium, Serratia marcescens.

Saxitoxin Group Toxins Accumulation Induces Antioxidant Responses in Tissues of Mytilus chilensis, Ameghinomya antiqua, and Concholepas concholepas during a Bloom of Alexandrium pacificum

Saxitoxin (STX) group toxins consist of a set of analogues which are produced by harmful algal blooms (HABs). During a HAB, filter-feeding marine organisms accumulate the dinoflagellates and concentrate the toxins in the tissues. In this study, we analyze the changes in antioxidant enzymes and oxidative damage in the bivalves Mytilus chilensis and Ameghinomya antiqua, and the gastropod Concholepas concholepas during a bloom of Alexandrium pacificum. The results show that during the exponential phase of the bloom bivalves show an increase in toxicity and activity of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, and glutathinoe reductase, p < 0.05), while in the gastropods, increased activity of antioxidant enzymes was associated with the bioaccumulation of toxins through the diet. At the end of the bloom, decreased activity of antioxidant enzymes in the visceral and non-visceral tissues was detected in the bivalves, with an increase in oxidative damage (p < 0.05), in which the latter is correlated with the detection of the most toxic analogues of the STX-group (r = 0.988). In conclusion, in areas with high incidence of blooms, shellfish show a high activity of antioxidants, however, during the stages involving the distribution and bioconversion of toxins, there is decreased activity of antioxidant enzymes resulting in oxidative damage.

Short-Term Immune Responses of Gilthead Seabream (Sparus aurata) Juveniles against Photobacterium damselae subsp. piscicida

Photobacteriosis is a septicaemic bacterial disease affecting several marine species around the globe, resulting in significant economic losses. Although many studies have been performed related to the pathogen virulence and resistance factors, information regarding the host defence mechanisms activated once an infection takes place is still scarce. The present study was designed to understand innate immune responses of farmed juvenile gilthead seabream (Sparus aurata) after Photobacterium damselae subsp. piscicida (Phdp) infection. Therefore, two groups of seabream juveniles were intraperitoneally injected with 100 µL of PBS (placebo) or 100 µL of exponentially growing Phdp (1 × 10⁶ CFU/mL; infected). The blood, plasma, liver, and head kidney of six fish from each treatment were sampled immediately before infection and 3, 6, 9, 24 and 48 h after infection for the broad screening of fish immune and oxidative stress responses. Infected animals presented marked anaemia, neutrophilia and monocytosis, conditions that are correlated with an increased expression of genes related to inflammation and phagocytic activity. Similar studies with different fish species and bacteria can be useful for the definition of health biomarkers that might help fish farmers to prevent the occurrence of such diseases.

Garlic oil as a fight against histological and oxidative stress abnormalities in Wistar rats after oral inoculation of Anisakis spp. Type II (L3) (Nematoda)

ABSTRACT The consumption of inadequately thermally treated fish is a public health risk due to the possible propagation of Anisakis larvae and their antigenic proteins, the causative agent of the zoonotic disease anisakidosis. The present study demonstrated the physiological and histopathological changes that accompanied an oral inoculation of crude extracts from fresh and thermally treated Anisakis Type II (L3) in Wistar albino rats. Nematode worms were isolated from the marine fish Dicentrarchus labrax. They were examined and taxonomically identified using light and scanning electron microscopy. The study was performed in 6 rat groups: a control group (I), a garlic oil (GO) inoculated group (II), a fresh L3 inoculated group (III), a thermally treated L3 inoculated group (IV), a fresh L3 + GO inoculated group (V), and a thermally treated L3 + GO inoculated group (VI). It was observed that rats inoculated with fresh and thermally treated L3 crude extracts showed abnormal oxidative stress markers associated with the destruction of normal architecture of spleen and thymus. GO produced a protective effect in rat groups inoculated with L3 extracts + GO administration via the amelioration of oxidative stress markers, which was confirmed by the marked normal structure of the organs’ histology. Cooking of L3 infected fish induced severe physiological and histopathological alterations compared to uncooked infected fish. The administration of garlic before and after fish eating is recommended to avoid the dangerous effect of anisakids, even if they are cooked.

Diversity and succession of the microbial community and its correlation with lipid oxidation in dry-cured black carp (Mylopharyngodon piceus) during storage

This study aimed to achieve deeper insights into the microbiota composition and dynamic succession of the dry-cured black carp during storage using a high-throughput sequencing technique (HTS). The effect of lipid oxidation on microorganisms was also evaluated. Over 651 bacterial genera belonging to 37 phyla were identified. Firmicutes, Proteobacteria and Actinobacteria were the main bacterial phylum, some are highly associated with meat spoilage. Staphylococcus, Macrococcus and Acinetobacter were the most three microbial genera throughout the entire storage period (30 days). Between two different storage temperature, refrigeration at 4 °C could facilitate maintaining the microbial diversity, while 25 °C storage led to the formation of dominant microflora and the reduction of community diversity. Canonical correspondence analysis (CCA) showed that acid value (AV), malondialdehyde (MDA) and 4-hydroxy-2-hexenal (HHE) contents were three key environmental factors (oxidation products) affecting the profile of the microbiota. Staphylococcus presented a positive correlation with HHE content, while Macrococcus and Acinetobacter were negatively correlated with HHE content. These results could expand our knowledge on the effect of lipid oxidation on change of microbial distribution, it could also present an guideline to develop advanced storage methods for the vacuum packed dry-cured fish products.

Transcriptional, biochemical and histological alterations in adult zebrafish (Danio rerio) exposed to benzotriazole ultraviolet stabilizer-328

The occurrence of Benzotriazole Ultraviolet Stabilizer-328 (BUV-328) in different environmental and biological matrices is of immediate environmental concern. In the present study, we evaluated the toxicity of BUV-328 in zebrafish liver tissues to understand the role of oxidative damage in hepatotoxicity. Adult zebrafish were exposed to 0.01, 0.1 and 1 mg/L of BUV-328. At the end of 14, 28 and 42 days, liver tissues were examined for the responses of antioxidant enzymes, gene expression and histopathological alterations. The results indicated that superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities were elevated at concentrations of 0.1 and 1 mg/L on 14th and 28th day. Glutathione S-transferase (GST) activity and malondialdehyde (MDA) levels were elevated in all the treated groups. The transcriptional levels of genes encoding sod, cat, gpx and gst enzymes were increased at 14th day and then declined (except sod on 28th day). Moreover, transcription of cyp1a and hsp70 were up-regulated throughout the study period. Histopathological lesions such as hypertrophy, cellular and nuclear enlargement, cytoplasmic and nuclear degeneration, necrosis with pyknotic nuclei, lipid and cytoplasmic vacuolization and nuclear displacement to the periphery were found to be increased with the dose and exposure duration. In brief, our findings indicate that even a low dose of BUV-328 is toxic to induce oxidative stress and liver damage in zebrafish over a long period of exposure.

Hypoosmotic stress induced tissue-specific immune responses of yellowfin seabream (Acanthopagrus latus) revealed by transcriptomic analysis

Salinity is a limiting factor for many marine organisms, including fishes. The shift in the ambient salinity can cause osmotic stress and arouse immune responses in fish. In this study, yellowfin seabream (Acanthopagrus latus), a euryhaline marine teleost, was used to investigate immune responses of different tissues (gill, liver, and muscle) under hypoosmotic stress. Comparative transcriptomic and physiological analyses of three tissues were conducted after fish exposed to the fresh water (FW, salinity = 0 ppt), low-saline water (LW, salinity = 3 ppt), and brackish water (BW, salinity = 6 ppt) for 8 days. The results showed that hypoosmotic stress dramatically altered the gene expression of three tissues in yellowfin seabream; The investigation of differentially expressed genes (DEGs) related to osmoregulation and immune response indicated that T cell-mediate immunity pathways were essential to tackle such stress. In terms of tissues, gill was found to be the most sensitive tissue under hypoosmotic stress by enhancing of Na⁺K⁺-ATPase activity and preventing the loss of Na⁺ and K⁺; Liver, on the other hand, was under the most sever oxidative stress indicated by the fluctuation of SOD, CAT activities and the MDA content; In contrast, muscle had the least osmoregulation and immune related response. We also identified several potential candidate genes, which may serve as gene indicators to identify the stressor. Overall, this study provides preliminary mechanistic insights into hypoosmotic stress adaption of aquatic organism.

Dietary Supplementation of Probiotic Bacillus subtilis Affects Antioxidant Defenses and Immune Response in Grass Carp Under Aeromonas hydrophila Challenge

This study investigated whether Bacillus subtilis can provide protection for grass carp against oxidative stress damage induced by Aeromonas hydrophila. A total of 240 healthy grass carp (Ctenopharyngodon idellus) (average weight of 71.42 ± 4.36g) were randomly divided into four groups with three replicates: control group, A. hydrophila group, B. subtilis + A. hydrophila group, and A. hydrophila + B. subtilis group. After challenge with A. hydrophila, the lipid oxidative damage, antioxidant defenses, and the gene expression of inflammatory cytokines of the grass carp were investigated. Our results showed that A. hydrophila caused lipid oxidative damage, led to significant decreases in antioxidant defenses, and induced inflammatory responses of grass carp. However, the grass carp group fed the probiotic B. subtilis diet for 42 days before the challenge and the group fed the probiotic B. subtilis diet immediately after the challenge both showed (i) a reduced level of oxidative stress with a decrease in the level of MDA; (ii) an increase in antioxidant defenses, including an increase in total antioxidant capacity (T-AOC), increased activities of SOD and CAT, increased levels of GSH, and upregulated gene expression of antioxidant enzymes (SOD, CAT, and Gpx); and (iii) an improved immune response with the level of antiinflammatory cytokines IL-10 messenger RNA (mRNA) upregulated and the levels of pro-inflammatory cytokines TNF-α, IL-1β, and IL-8 mRNA downregulated. Based on this study, B. subtilis can provide effective protection of fish against oxidative stress damage induced by A. hydrophila infection.

Mortality of embryos, developmental disorders and changes in biochemical parameters in marsh frog (Rana ridibunda) tadpoles exposed to the water-soluble fraction of Kazakhstan crude oil and O-Xylene

The effects of different concentrations of water-soluble fraction of crude oil (WSFO) from the Zhanazhol oil field (Aktobe region, Kazakhstan) and compared to o-xylene, prevalent in this oil, on growth and development of marsh frog (Rana ridibunda) were assessed. In subchronic experiments (7 d), a dose-related increase in mortality and incidence of deformities in embryos were observed. In chronic experiments (60 d; starting from the Gosner stage 26), a dose-dependent decrease in body weight, size and developmental delay by 3-4 stages were also detected. In addition, the content of lipid hyperoxide (LHO) and malondialdehyde (MDA), as well as activities of superoxide dismutase (SOD) and catalase (CAT) enzymes in liver of the tadpoles were determined at the end of chronic experiment. Exposure to 0.5 mg/L or 1.5 mg/L WSFO elevated the content of LHO by 76% and 86%, and MDA by 47% and 58% but decreased SOD activity by 26% and 49%, and CAT by 35% and 46%, respectively. A less pronounced adverse effect was found after chronic exposure to the same concentrations of o-xylene. In tadpole liver exposed to o-xylene levels of LHO was increased by 40% and 51%, MDA by 11% and 29%, while the activity of SOD was lowered by 18% and 41%, and CAT - by 13% and 37% in the 0.5 mg/L and 1.5 mg/L treatment groups, respectively. Data demonstrated the embryotoxic and teratogenic effects attributed to WSFO and o-xylene exposure which may involve oxidative stress mechanisms.

Selenium deficiency impaired structural integrity of the head kidney, spleen and skin in young grass carp (Ctenopharyngodon idella)

This study focused on the effects of dietary selenium deficiency on structural integrity of the head kidney, spleen and skin in young grass carp (Ctenopharyngodon idella). A total of 540 healthy grass carp (mean weight 226.48 ± 0.68 g) were randomly divided into six groups and fed six separate diets with graded dietary levels of selenium (0.025-1.049 mg/kg diet) for 80 days. Results showed that selenium deficiency (1) caused oxidative damage in part by reducing the activities of antioxidant enzymes (such as SOD, CAT, GPx, GST and GR) and glutathione (GSH) content, down-regulating the transcript abundances of antioxidant enzymes (except GSTp1) partly related to Kelch-like-ECH-associated protein 1a (Keap1a)/NF-E2-related factor 2 (Nrf2) signalling; (2) aggravated apoptosis in part by up-regulating the mRNA levels of caspase-2, -3, -7, -8 and -9, which were partially related to p38MAPK/FasL/caspase-8 signalling and JNK/(BAX, Bcl-2, Mcl-1b, IAP)/(Apaf1, caspase-9) signalling; (3) damaged the tight junctions in part by down-regulating the mRNA levels of ZO-1 (except spleen), ZO-2 (except spleen), claudin-c, -f, -7, -11 and claudin-15, and up-regulating the mRNA levels of claudin-12, which were partially related to myosin light chain kinase (MLCK) signalling. Interesting, selenium deficiency failed to affect the expression of GSTp1, Keap1a, occludin, claudin-b, claudin-3c, ZO-1 (spleen only) and ZO-2 (spleen only) in the head kidney, spleen and skin of grass carp. Finally, based on the activities of glutathione peroxidase (GPx) and reactive oxygen species (ROS) content in the head kidney, spleen and skin, the dietary selenium requirements for young grass carp were estimated to be 0.558-0.588 mg/kg diet.

Differential effects of exposure to parasites and bacteria on stress response in turbot Scophthalmus maximus simultaneously stressed by low water depth

The stress response of turbot Scophthalmus maximus was evaluated in fish maintained 8 days under different water depths, normal (NWD, 30 cm depth, total water volume 40 l) or low (LWD, 5 cm depth, total water volume 10 l), in the additional presence of infection-infestation of two pathogens of this species. This was caused by intraperitoneal injection of sublethal doses of the bacterium Aeromonas salmonicida subsp. salmonicida or the parasite Philasterides dicentrarchi (Ciliophora:Scuticociliatida). The LWD conditions were stressful for fish, causing increased levels of cortisol in plasma, decreased levels of glycogen in liver and nicotinamide adenine dinucleotide phosphate (NADP) and increased activities of G6Pase and GSase. The presence of bacteria or parasites in fish under NWD resulted in increased cortisol levels in plasma whereas in liver, changes were of minor importance including decreased levels of lactate and GSase activity. The simultaneous presence of bacteria and parasites in fish under NWD resulted a sharp increase in the levels of cortisol in plasma and decreased levels of glucose. Decreased levels of glycogen and lactate and activities of GSase and glutathione reductase (GR), as well as increased activities of glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH) and levels of nicotinamide adenine dinucleotide phosphate (NADPH) occurred in the same fish in liver. Finally, the presence of pathogens in S. maximus under stressful conditions elicited by LWD resulted in synergistic actions of both type of stressors in cortisol levels. In liver, the presence of bacteria or parasites induced a synergistic action on several variables such as decreased activities of G6Pase and GSase as well as increased levels of NADP and NADPH and increased activities of GPase, G6PDH and 6PGDH.

Glutathione-S-transferase, Superoxide Dismutase (GST, SOD) Levels, Protein Content and Lipid Peroxidation in <I>Schizothorax plagiostomus </I>under the Infection of <I>Pomphorhynchus </I>in Nallah Sukhnag of Kashmir Valley

BACKGROUND AND OBJECTIVE

Presence of parasites in fishes has been reported to severely damage the status of antioxidants in them. Among helminth parasites, Pomphorhyncus an acanthocephalan parasite is commonly found in Schizothorax fish of Kashmir and is causing a considerable damage to fish health. The aim of this study was to investigate the antioxidant status in muscle, intestine and liver tissues of Schizothorax plagiostomus parasitized by Pomphorhyncus.

MATERIALS AND METHODS

For this, 9 fish specimens collected from Nallah Sukhnag (Budgam) were found to be infected only with Pomphorhyncus, an acanthocephalan parasite. Fishes having the infection of Pomphorhynchus and the same number of uninfected ones were then analyzed for enzymatic antioxidants. Lipid peroxidation and protein content was also assayed for both infected and uninfected fishes. Statistically the whole data were represented as mean and standard deviation.

RESULTS

RESULTS showed the reduction of glutathione-s-transferase (GST), superoxide dismutase (SOD), protein content while increase in lipid peroxidation in infected muscle, intestine and liver tissues as compared to respective organs of the uninfected fishes.

CONCLUSION

This study concluded that parasitic infections induce oxidative stress.

Short-Term Effects of Albendazole on the Oxidative Stress Markers and Hematological Parameters in Tissues of African Catfish Clarias gariepinus

Albendazole (ABZ) is a typical broad-spectrum benzimidazole drug used for the treatment of parasitic worm infestations in humans and animals. The present study investigated the oxidative stress biomarkers and hematological parameters in juvenile African Catfish (also known as Sharptooth Catfish) Clarias gariepinus exposed to ABZ for 96 h. Fish were exposed to 0 (control) 20, 40, and 60 mg/L ABZ. The liver and gill tissues were sampled at regular intervals of 24 h, and the results showed significant concentration- and time-dependent increases in the values of lipid peroxidation but reductions in glutathione peroxidase, catalase, superoxide dismutase, and glutathione reductase in both tissues. Erythrocytes were sampled to evaluate hematological parameters. The results showed significant concentration- and time-dependent increases in white blood cells but no significant differences in mean cellular hemoglobin. Hemoglobin values, red blood cell counts, packed cell volume, mean cell volume, and mean cellular hemoglobin concentration decreased significantly over the experimental period. The activities of lymphocytes and neutrophils increased significantly, whereas there were no significant differences in basophils, eosinophils, and monocytes among the treatment groups. Albendazole should be used with caution, as sublethal concentrations induced oxidative stress in the liver and gill tissues along with hematological changes that were more evident in liver cells. Received November 20, 2015; accepted May 4, 2015.

Effect of N-acetyl cysteine and glycine supplementation on growth performance, glutathione synthesis, anti-oxidative and immune ability of Nile tilapia, Oreochromis niloticus

An 8-week feeding trial was conducted to evaluate the effect of N-acetyl cysteine (NAC) and glycine supplementation on growth performance, glutathione (GSH) synthesis, anti-oxidative and immune ability of Nile tilapia, Oreochromis niloticus. Four practical diets were formulated, control, control +0.2% NAC, control +0.5% glycine, control +0.2% NAC +0.5% glycine. Each diet was randomly assigned to quadruplicate groups of 30 fish (approximately 9.5 g). The weight gain and specific growth rate were significantly increased with the supplementation of NAC and glycine. While they had no effect on feed efficiency feed intake and survival. Glutathion peroxidase (GPx) was increased by NAC and γ-glutamine cysteine synthase (γ-GCS) in plasma were increased by glycine. After the feeding trail, fish were challenged by Streptococcus iniae, fish fed the diet supplemented with NAC obtained significantly higher survival rate after 72 h challenge test. NAC also decreased malonaldehyde (MDA) in liver, increased glutathione S-transferase (GST) activity in plasma, up-regulated mRNA expression of Superoxide dismutase (SOD) and GPx in liver and headkidney. Dietary supplementation of glycine increased the anti-oxidative ability of tilapia through increase anti-oxidative enzyme activity (SOD, glutathione reductase, myeloperoxidase) and up-regulate anti-oxidative gene expression (SOD). Immune ability only enhanced by the supplementation of NAC through increased interleukin-1β (IL-1β) mRNA expression. These results clearly indicated that the supplementation of NAC and glycine can significantly improve the growth performance of tilapia, and NAC also enhance the anti-oxidative and immune capacity of tilapia, glycine could only enhance the anti-oxidative ability.

Identification and involvement of ferritin in the response to pathogen challenge in the abalone, Haliotis diversicolor

Accumulating data has demonstrated that ferritin plays an important role in host defense responses against infection by pathogens in many organisms. In this study, ultracentrifugation was used to isolate ferritin from abalone, Haliotis diversicolor, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that this ferritin consisted of two subunits (designated as HdFer1 and HdFer2). There are no disulfide bonds between the HdFer1 and HdFer2 subunits; however, these subunits co-assemble to form heteropolymers. A novel ferritin subunit (HdFer2) was cloned from H. diversicolor by 5' and 3' RACE (rapid amplification of cDNA ends) approach. The full-length HdFer2 cDNA sequence consists of 878 bp with an open reading frame of 513 bp that encodes a protein that is 170 amino acids in length. Quantitative real-time PCR analysis revealed that HdFer1 and HdFer2 were transcribed in various tissues, such as the mantle, gill and hepatopancreas, with the highest levels of expression in the hepatopancreas. Following a challenge with the pathogen, Vibrio harveyi, the expression of HdFer1 and HdFer2 were markedly induced at different times. This study has identified a novel ferritin subunit in H. diversicolor which will contribute to further exploration of the role of ferritin in mollusk innate immune defense against invading pathogens.

Feeding rates affect stress and non-specific immune responses of juvenile blunt snout bream Megalobrama amblycephala subjected to hypoxia

This study aimed to investigate the effects of feeding rates on stress response, innate immunity and hypoxia resistance of juvenile blunt snout bream Megalobrama amblycephala. Fish were randomly assigned to one of six feeding rates (2, 3, 4, 5, 6 and 7% of body weight/day) for 60 days. Then, fish were subjected to hypoxic conditions and haemato-immunological parameters were analyzed pre- and post-challenge. Low feed ration resulted in decreased liver superoxide dismutase and catalase activities and reduced glutathione contents. Inadequate feeding also adversely affected the immune functions of fish, as was characterized by the relatively low haemato-immunological parameters (including alternative complement (ACH50), myeloperoxidase (MPO), plasma protein profiles and transferring) and high hypoxia-induced mortality. High feed ration did not lead to the improvement in antioxidant capability, immune responses and survival. In addition, plasma cortisol, glucose and transferrin levels as well as lysozyme activities all increased significantly after hypoxia challenge, whereas the opposite was true for plasma ACH50 and MPO activities as well as protein profiles in terms of hypoxia challenge. An interaction between feeding rate and hypoxia was also observed in plasma cortisol, glucose and protein profiles. In conclusion, a feeding rate of 4-5% of body weight/day is optimal to boost the innate immunity of juvenile blunt snout bream. Low ration resulted in decreased antioxidant capability, compromised immune functions and reduced hypoxia resistance, while over feeding did not benefit the health status.

Oxidative stress and biochemical responses in the tissues of African catfish Clarias gariepinus juvenile following exposure to primextra herbicide

Primextra is a commercial herbicide formulation generally used in agriculture for weed control. The present study was designed to investigate the oxidative stress biomarkers and biochemical responses in the tissues of Clarias gariepinus juvenile exposed to primextra. Fish were exposed to 0.24 and 0.47 mgL(-1) corresponding to 1/20 and 1/10th of 96 h LC50 of the herbicide. The liver and muscle tissues were sampled on day 1, 5, 10 and 15 and results showed concentration and time dependent significant increase (p < 0.05) in the values of lipid peroxidation, glutathione peroxidase, catalase and alkaline phosphatase in both tissues. A marked significant increase (p < 0.05) was observed in the values of aspartate aminotransferase, alanine aminotransferase and glucose in the liver while a mixed trend in their values were observed in the muscle. The values of superoxide dismutase and protein in both tissues were comparable to the control except on day 15 in the liver where the values significantly declined. The condition factor was not directly affected but values of hepatosomatic index were significantly reduced. The present findings revealed that primextra induced toxic stress even at sublethal concentrations resulting in alterations of the studied parameters which were more evident in the fish liver than in the muscle tissue.