Identification and analysis of icCu/Zn-SOD, Mn-SOD and ecCu/Zn-SOD in superoxide dismutase multigene family of Pseudosciaena crocea

Impact of plasticiser exposure on oyster Crassostrea (Magallana) saidii: assessing oxidative stress and biomarker responses

Plasticisers are prevalent chemical contaminants that leach from plastics into aquatic ecosystems, posing potential risks to marine life. This study investigated the effects of alternative plasticisers [epoxidised methyl oleate (EMO), di-(2-ethylhexyl) adipate (DEHA), and diisononyl phthalate (DINP)] at 100 µg/L in oysters Crassostrea (Magallana) saidii over 21 days under controlled laboratory conditions. This study focused on changes in body weight, antioxidant enzyme activities such as superoxide dismutase (SOD) and catalase (CAT), non-enzymatic antioxidant reduced glutathione (GSH), lipid peroxidation (malondialdehyde (MDA) levels) after plasticisers exposure for 7, 14 and 21 days. The results indicated a decline in body weight in DINP-exposed oysters, indicating metabolic alterations. DEHA and DINP showed a pronounced increase in SOD activity at the end of the experiment, indicating elevated oxidative stress. CAT activity increased with EMO exposure, but decreased in oysters treated with DEHA and DINP. GSH levels were inversely proportional to CAT activity. Oysters exposed to DEHA and DINP exhibited higher MDA levels, indicating oxidative lipid damage associated with these plasticisers. Multi-biomarker data were integrated using the Integrated Biomarker Response (IBR) index, which ranked the plasticisers' oxidative stress potential as DEHA > DINP > EMO. The IBR analysis also suggested distinct modes of action among the plasticisers and provided insights into their toxicity mechanisms. Notably, EMO exhibited lower toxicity compared to DEHA and DINP, supporting its potential as a more friendly alternative to conventional plasticisers, albeit not exempt from toxic effects. These insights underscore the importance of environmental risk assessments in the future development of safer chemical alternatives.

Molecular Characterization of BsCu/Zn-Superoxide Dismutases and BsMn-Superoxide Dismutases from Chinese Black Sleeper (Bostrychus sinensis)

Superoxide dismutases (SODs) are critical antioxidant enzymes that protect organisms by catalyzing the dismutation of superoxide radicals into molecular oxygen (O2) and hydrogen peroxide (H2O2). In this study, we cloned the full-length cDNA of two SODs (BsCu/Zn-SOD and BsMn-SOD) from the Chinese black sleeper. The cDNA of BsCu/Zn-SOD consists of 465 nucleotides encoding 154 amino acids, while the BsMn-SOD comprises 678 nucleotides encoding 225 amino acids. The PCR results indicated that in normal tissues, the highest expression of BsCu/Zn-SOD (1.02-fold) was primarily observed in muscle, whereas the highest expression of BsMn-SOD (6.42-fold) was noted in skin. Following treatment with Vibrio parahaemolyticus, the highest expression of BsCu/Zn-SOD (3.67-fold) was detected in the spleen, while BsMn-SOD (3.36-fold) presented the highest expression in the blood. After poly(I:C) treatment, the highest expression of BsCu/Zn-SOD (2.92-fold) was found in the blood, with BsMn-SOD (2.37-fold) showing the highest expression in the spleen. Following Cd2+ treatment, the highest expression of BsCu/Zn-SOD (3.36-fold) was recorded in the liver at the 1/2 96 h LC50 concentration, and in the spleen at both the 1/4 96 h LC50 (2.50-fold) and 1/8 96 h LC50 concentrations. In contrast, BsMn-SOD presented the highest expression (2.60-fold) in the liver across all three concentrations. These findings suggest that both BsCu/Zn-SOD and BsMn-SOD play vital roles in the innate immune response to environmental challenges, laying the foundation for further exploration of antioxidant mechanisms.

Integrated analysis of biochemical, transcriptomic, and metabolomic response mechanisms in Ussuri catfish (Pseudobagrus ussuriensis) under acute heat stress

Fish metabolism, growth, development, and physiological conditions are highly sensitive to fluctuations in water temperature. The Ussuri catfish (Pseudobagrus ussuriensis) is an important native economic species in China. However, research on heat stress in P. ussuriensis, particularly concerning gene expression and metabolites, remains limited. In this study, we conducted histological observations, biochemical measurements, transcriptomic analysis, and metabolomic analysis on liver tissue from a control group (22 ℃), an acute heat stress group (34 ℃, with samples taken at 0, 3, 6, 12, and 24 h), and a recovery group (sampled 24 h after recovery to 22 ℃). Histopathological analysis showed that liver damage worsened with the duration of heat stress. Biochemical results indicated that acute heat stress significantly impacted the activities of superoxide dismutase, catalase, and alanine aminotransferase, as well as the levels of glutathione, malondialdehyde, and total antioxidant capacity, with alterations remaining even after temperature recovery. Transcriptomic and metabolomic analyses revealed that compared to the control group, 3482, 800, 980, and 1479 differentially expressed genes (DEGs) were detected at 0, 6, and 24 h of acute heat stress and at 24 h post-recovery, respectively. Similarly, 114, 151, 365, and 326 differentially expressed metabolites (DEMs), respectively, were detected at the same time points. Furthermore, when comparing 24 h of heat stress with 24 h of recovery, 1279 DEGs and 157 DEMs were identified. Functional enrichment analysis revealed that these DEGs and DEMs were significantly enriched in key pathways, such as endoplasmic reticulum protein processing and glutathione metabolism, with significant changes continuing into the recovery phase. Additionally, substantial alterations in the expression levels of amino acids, sugars, and lipids were observed during heat stress. These findings provide valuable insights into the defense mechanisms of fish under high-temperature stress and lay a theoretical foundation for breeding heat-resistant P. ussuriensis strains, as well as improving sustainable aquaculture management.

Transduction of jellyfish superoxide dismutase mediated by TAT peptide ameliorates H2O2-induced oxidative stress in HaCaT cells

Superoxide dismutase (SOD) plays important roles in the balance of oxidation and antioxidation in body mostly by scavenging superoxide anion free radicals (O2.-). Previously, we reported a novel Cu/Zn SOD from jellyfish Cyanea capillata, named CcSOD1, which exhibited excellent SOD activity and high stability. TAT peptide is a common type of cell penetrating peptides (CPPs) that efficiently deliver extracellular biomacromolecules into cytoplasm. In this study, we constructed a recombinant expression vector that combined the coding sequences of TAT peptide and CcSOD1, and then obtained sufficient and high-purity TAT-CcSOD1 fusion protein. Compared with some reported SODs/CPP-SODs, TAT-CcSOD1 possessed stronger tolerance to heat and acid-base environment. TAT-CcSOD1 efficiently penetrated cell membrane and significantly enhanced the O2.- scavenging ability in cells, and attenuated H2O2-induced cytotoxicity and NO generation in HaCaT cells. This study serves as a critical step forward for the application of TAT-CcSOD1 as a potential protective/therapeutic agent against oxidative stress-related conditions in the future.

Biomineralized ZIF-8 Encapsulating SOD from Hydrogenobacter Thermophilus: Maintaining Activity in the Intestine and Alleviating Intestinal Oxidative Stress

Oxidative stress is a major factor leading to inflammation and disease occurrence, and superoxide dismutase (SOD) is a crucial antioxidative metalloenzyme capable of alleviating oxidative stress. In this study, a novel thermostable SOD gene is obtained from the Hydrogenobacter thermophilus strain (HtSOD), transformed and efficiently expressed in Escherichia coli with an activity of 3438 U mg-1, exhibiting excellent thermal stability suitable for scalable production. However, the activity of HtSOD is reduced to less than 10% under the acidic environment. To address the acid resistance and gastrointestinal stability issues, a biomimetic mineralization approach is employed to encapsulate HtSOD within the ZIF-8 (HtSOD@ZIF-8). Gastrointestinal simulation results show that HtSOD@ZIF-8 maintained 70% activity in simulated gastric fluid for 2 h, subsequently recovering to 97% activity in simulated intestinal fluid. Cell and in vivo experiments indicated that HtSOD@ZIF-8 exhibited no cytotoxicity and do not impair growth performance. Furthermore, HtSOD@ZIF-8 increased the relative abundance of beneficial microbiota such as Dubosiella and Alistipes, mitigated oxonic stress and intestinal injury by reducing mitochondrial and total reactive oxygen species (ROS) levels in diquat-induced. Together, HtSOD@ZIF-8 maintains and elucidates activity in the intestine and biocompatibility, providing insights into alleviating oxidative stress in hosts and paving the way for scalable production.

Enhancement of Thermal Tolerance and Growth Performances of Asian Seabass (Lates calcarifer) Fed with Grape Extract Supplemented Feed

Cold snaps during the winter present a critical challenge for Asian seabass (Lates calcarifer) in Taiwan, as sudden temperature drops significantly affect their growth and survival. This study explores the effects of dietary grape extract (GE) from Vitis vinifera on the growth performance, oxidative stress regulation, and thermal tolerance of this commercially valuable fish. Over a 60-day feeding trial, four dietary groups were tested: a control diet without GE and three diets supplemented with GE at 2% (GE20), 3% (GE30), and 4% (GE40) with commercial feed. The results demonstrated that GE supplementation positively influenced growth, with the GE20 group achieving the best weight gain and feed conversion ratio among all groups. The upregulation of the growth-related gene igf-1 in the liver of the GE20 group further supported its superior growth performance. Additionally, GE-fed groups showed increased expression of antioxidant-related genes sod1 and sod2 in the liver, while gpx1 exhibited a significant increase only in the GE20 group, indicating enhanced antioxidant defenses. Cat gene expression remained unchanged, and higher GE doses reduced the expression of gpx1, cat, and igf-1. Furthermore, GE supplementation improved cold tolerance in all treated groups compared to the control. These findings suggest that dietary GE at 20 g/kg is particularly effective in enhancing growth performance and cold tolerance in Asian seabass, offering a promising strategy for boosting fish health and adaptability in aquaculture.

Highly efficient expression of human extracellular superoxide dismutase (rhEcSOD) with ultraviolet-B-induced damage-resistance activity in transgenic silkworm cocoons

Extracellular superoxide dismutase (EcSOD) protects tissues from oxidative stress, and thus is considered as a therapeutic agent for many diseases such as atherosclerosis, hypertension, and cancer. However, cost-effective production of bioactive recombinant human EcSOD (rhEcSOD) remains a challenge. Herein, we developed an efficient strategy for producing active rhEcSOD by transgenic silkworms. rhEcSOD was successfully synthesized as homodimers and homotetramers in the middle silk gland and spun into the cocoons with a concentration of 9.48 ± 0.21 mg/g. Purification of rhEcSOD from the cocoons could be conveniently achieved with a purity of 99.50% and a yield of 3.5 ± 0.5 mg/g. Additionally, N-glycosylation at the only site of N89 in rhEcSOD with 10 types were identified. The purified rhEcSOD gained the potent enzymatic activity of 4 162 ± 293 U/mg after Cu/Zn ions incorporation. More importantly, rhEcSOD was capable of penetrating and accumulating in the nuclei of cells to maintain cell morphology and attenuate ultraviolet B-induced cell apoptosis by eliminating reactive oxygen species and inhibiting the C-Jun N-terminal kinase signaling pathway. These results demonstrated that the transgenic silkworm could successfully produce rhEcSOD with enzymatic and biological activities for biomedical applications.

Transcriptome Analysis of Different Aquaculture Substrates on the Immune Response of Babylonia areolata

To assess the impact of different substrates in a recirculating water system on the immune response and antioxidant capacity of Babylonia areolata, we conducted a comparative analysis of the transcriptomes and antioxidant performance of the digestive glands in three substrate environments (sand-S group, ceramic granules-C group, and PVC breeding nest-P group). Transcriptome results revealed that the S group and P group exhibited the highest number of differentially expressed genes (DEGs), with a total of 2218 DEGs, including 928 upregulated and 1290 downregulated DEGs. The C group and P group had 1055 DEGs in common, with 316 upregulated and 739 downregulated DEGs. The C group and S group had the fewest DEGs, with 521 in total, including 303 upregulated and 218 downregulated DEGs. GO enrichment analysis showed that in the S vs P group, terms such as catalytic activity, membrane part, and cellular process were enriched with 287, 262, and 180 DEGs, respectively. In the C vs P group, binding, cellular process, and cell part were enriched with 146, 135, and 127 DEGs, respectively. In the C vs S group, catalytic activity, membrane part, and metabolic process were enriched with 90, 83, and 59 DEGs, respectively. Kegg enrichment analysis revealed significant changes in immune-related pathways in the S vs P group, including lysosome, phagosome, and leukocyte transendothelial migration, with 30, 13, and 10 enriched DEGs, respectively. In the C vs P group, phagosome, drug metabolism-other enzymes, and N-Glycan biosynthesis showed significant changes in immune-related pathways, with 9, 6, and 4 enriched DEGs, respectively. In the C vs S group, lysosome, PPAR signaling pathway, and fatty acid degradation exhibited significant changes in immune-related pathways, with 8, 4, and 3 enriched DEGs, respectively. Regarding antioxidant capacity, the S group showed significantly higher total T-AOC than the other experimental groups, while CAT, SOD, POD, and AKP were lower than in the C and P groups. The ACP level in the Sand group was not significantly different from the P group but significantly lower than the C group. In conclusion, substrate environments significantly influence the immune-related genes and key antioxidant enzyme activities in B. areolata.

Transcriptome Analysis of Brain and Skin Reveals Immune Responses to Acute Hypoxia and Reoxygenation in Pseudobagrus ussuriensis

Pseudobagrus ussuriensis is an unscaled fish that is more susceptible to skin damage than scaled fish. To investigate the impacts of hypoxia and reoxygenation on skin and brain immunity, juvenile P. ussuriensis were subjected to hypoxia conditions (DO: 0.8 ± 0.05 mg/L) for durations of 0, 3, 6, and 12 h, followed by 12 h of reoxygenation (DO > 6 mg/L). Histological analysis showed a significant increase in the number of skin mucosal cells after 12 h of hypoxia and a significant decrease after 12 h of reoxygenation when compared to the control group. As the duration of hypoxia increased, an increase in antioxidant (SOD, CAT, GSH, MDA) and immune (cortisol, LZM) physiological parameters of the skin and brain appeared. The results of transcriptomic studies showed that the number of differential genes was greater in skin than in brain. Most of the immune pathways in both tissues under hypoxia conditions were all nonspecific immunity (TNF, IL-17, chemokines), while both tissues maintained their homeostasis through active energy supply and cell cycle regulation. Meanwhile, both physiological parameters and RNA transcriptome results showed that 12 h of reoxygenation could not completely eliminate the negative effects of 12 h of hypoxia. This study offers new insights into the immune responses of P. ussuriensis skin and brain during acute hypoxia and reoxygenation.

Antioxidant Defence in Labeo rohita to Biotic and Abiotic Stress: Insight from mRNA Expression, Molecular Characterization and Recombinant Protein-Based ELISA of Catalase, Glutathione Peroxidase, CuZn Superoxide Dismutase, and Glutathione S-Transferase

Fish possess numerous enzymatic antioxidant systems as part of their innate immunity. These systems have been poorly studied in Labeo rohita (rohu). The present study characterized and investigated the role of antioxidant genes in the defence mechanisms against two types of stressors, including infection and ammonia stress. Four key genes associated with antioxidant activity-catalase, glutathione peroxidase, glutathione S-transferase, and CuZn superoxide dismutase were successfully cloned and sequenced. These genes were found to be expressed in different tissues and developmental stages of rohu. The expression levels of these antioxidant genes in the liver and anterior kidney tissues of rohu juveniles were modulated in response to bacterial infection (Aeromonas hydrophila), parasite infection (Argulus siamensis), poly I:C stimulation and ammonia stress. Additionally, the recombinant proteins derived from these genes exhibited significant antioxidant and antibacterial activities. These proteins also demonstrated a protective effect against A. hydrophila infection in rohu and had an immunomodulatory role. Furthermore, indirect ELISA assay systems were developed to measure these protein levels in healthy as well as A. hydrophila and ammonia-induced rohu serum. Overall, this study characterized and emphasised the importance of the antioxidant mechanism in rohu's defence against oxidative damage and microbial diseases.

Genomic organization and transcription of superoxide dismutase genes (sod1, sod2, and sod3b) and response to diazinon toxicity in platyfish (Xiphophorus maculatus) by using SOD enzyme activity

The aim of this study is to determine the effects of 50% of 96 h LC50 (5.25 ppm) diazinon on the expression of superoxide dismutase (SOD) enzyme genes (sod1, sod2, and sod3b) and SOD enzyme activity at the end of 24, 48, 72, and 96 h in platyfish liver and gill tissues. To this end, we determined the tissue-specific distribution of sod1, sod2, and sod3b genes and performed in silico analyses in platyfish (Xiphophorus maculatus). It was determined that malondialdehyde (MDA) level and SOD enzyme activity were increased in the liver [(43.90 EU mg protein-1 (control), 62.45 EU mg protein-1 (24 h), 73.17 EU mg protein-1 (48 h), 82.18 EU mg protein-1 (72 h), 92.93 EU mg protein-1 (96 h)] and gill [(16.44 EU mg protein-1 (control), 33.47 EU mg protein-1 (24 h), 50.38 EU mg protein-1 (48 h), 64.62 EU mg protein-1 (72 h), 74.04 EU mg protein-1 (96 h)] tissues of platyfish exposed to diazinon, while the expression of the sod genes was down-regulated. The tissue-specific distribution of the sod genes varied, with the tissues and the sod genes expression were being predominant in the liver (628.32 in sod1, 637.59 in sod2, 888.5 in sod3b). Thus, the liver was considered a suitable tissue for further gene expression studies. Based on the phylogenetic analyses, platyfish sod genes can be reported to be orthologs of sod/SOD genes from other vertebrates. Identity/similarity analyses supported this determination. Conserved gene synteny proved that there are conserved sod genes in platyfish, zebrafish, and humans.

The superoxide dismutase (SOD) genes family mediates the response of Nilaparvata lugens to jinggangmycin and sugar

Introduction: Brown planthopper (BPH), Nilaparvata lugens Stål (Hemiptera: Delphacidae), is a major rice pest causing significant damage to rice throughout the world. Intensive pesticide usage often causes resistance in these seasonal pests, mainly through the modulation of antioxidant machinery. The superoxide dismutase (SOD) gene family is known for regulating BPH response to pesticides. Methods: In the present study, we identified eight NlSOD genes from the NCBI using the BLASTP program. The bioinformatics analysis includes a phylogenetic tree, conserved domain, motifs, gene ontology (GO) analysis, Kyoto encyclopedia of genes and genomes (KEGG) pathways, and protein-protein interaction, highlighting the distinctive functional elements of NlSOD genes. Results and discussion: Additionally, the NlSOD genes showed expression in all developmental stages of BPH. Under three sugars (glucose, sucrose, and trehalose) treatment, the respective upregulation of NlSOD8, NlSOD6, and NlSOD2 was noted. The NlSOD1 induced significantly under jinggamycin (JGM) deduced its potential as a key regulator of BPH response to the pesticide. Our study has provided detailed knowledge of the NlSOD gene family in-silico analysis and the defensive response to insecticide and high sugar of BPH. We hope the results of this research will help to shed light on the resistance of BPH towards insecticide toxicity and high sugar and help to control it more efficiently.

Nrf2 pathway in vegetable oil-induced inflammation of large yellow croaker (Larimichthys crocea)

This study was conducted to investigate the effects and regulation of dietary vegetable oil (VO, enriched with α-linolenic acid [ALA] and linoleic acid [LNA]) on the nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-κB (NF-κB) pathways in large yellow croaker. In vivo study showed that the VO diet significantly decreased the activity of antioxidant enzymes and antioxidant enzyme-related mRNA expression in the liver tissue, in comparison with the fish oil (FO) diet (P < 0.05). The suppression of antioxidant capacity might be due to the decrease of nuclear Nrf2 protein translocation, Nrf2 binding to antioxidant response element (ARE) sequences, and subsequently, antioxidant genes transcription as electrophoretic mobility shift assay (EMSA) and luciferase assay showed. VO-derivated ALA and LNA exerted a lower antioxidant capacity than FO-derivated DHA and EPA, characterized by significantly lower nucleus Nfr2 protein expression but significantly higher ROS production values in primary hepatocytes (P < 0.05). The pro-inflammatory genes (tumor necrosis factor α [TNFα] and interleukin 1β [IL1β]) expression was significantly higher in the liver tissue of fish fed the VO diet which might be due to the activation of the NF-κB pathway (P < 0.05). Knockdown of the Nrf2 gene negatively affected the anti-inflammatory effect of fatty acids by increasing the expression of TNFα and the IL1β gene and nuclear p65 protein (P < 0.05). In general, the results indicated that dietary vegetable oil decreased antioxidant capacity but induced inflammatory responses through the Nrf2/NF-κB pathway.

Genome-wide identification of seven superoxide dismutase genes in the marine rotifer Brachionus rotundiformis and modulated expression and enzymatic activity in response to microplastics and nutritional status

Microplastics (MPs) pollution has attracted worldwide attention. Superoxide dismutase (SOD) is a sensitive indicator for assessing the toxic effects of MPs in aquatic organisms. However, few studies have been performed to identify all genes encoding SOD in aquatic invertebrates. Especially, effects of MPs on SOD activity and expression in aquatic organisms under starvation or a subsequent refeeding status are unclear. In the present study, all full-length genes encoding SOD were cloned and characterized from the marine rotifer Brachionus rotundiformis, including CuZnSOD1, CuZnSOD2, CuZnSOD3, CuZnSOD4, CuZnSOD5, MnSOD1, and MnSOD2. The CuZnSOD1, CuZnSOD2 and MnSOD2 are homologous to SODs from vertebrates and the other SOD proteins are rotifer-specific according to the results from the phylogenetic tree. The conserved signature sequences and binding sites of Cu²⁺, Zn²⁺and Mn²⁺ were also identified in the seven SOD proteins. Compared with feeding, starvation down-regulated SOD activity and mRNA expression of CuZnSOD2, CuZnSOD4, CuZnSOD5, MnSOD1 and MnSOD2 while refeeding maintained SOD activity comparable to the feeding level and up-regulated CuZnSOD5 and MnSOD2. Intake of MPs by B. rotundiformis was observed by examining fluorescence signals from the fluorescently-labeled microplastics under different nutritional status. Exposure to MPs reduced rotifer density and increased malondialdehyde (MDA) content and SOD activity in the rotifers under the refeeding condition, but did not affect these indicators under the feeding and starvation conditions. However, mRNA expression of some tested genes was responsive to MPs in the fed, starved and refed rotifers. The present study for the first time demonstrated a nutritional status-dependent effect of MPs on oxidative stress response, and provided more sensitive molecular biomarkers for assessing the toxicity of MPs using B. rotundiformis as a model animal.

Cu/Zn Superoxide Dismutase and Catalase of Yangtze Sturgeon, Acipenser dabryanus: Molecular Cloning, Tissue Distribution and Response to Fasting and Refeeding

Superoxide dismutase and catalase are two major antioxidant enzymes in the fish antioxidant defense system, which can remove excess reactive oxygen species and protect fish from stress-induced oxidative damage. The present study aimed to clone the sequences of Yangtze sturgeon, Acipenser dabryanus, Cu/Zn superoxide dismutase (AdCu/Zn-SOD) and catalase (AdCAT), and to explore changes of gene expression in the liver and intestine during fasting and refeeding. A total of 120 fish were exposed to four fasting and refeeding protocols (fasting for 0, 3, 7, or 14 d and then refeeding for 14 d). The coding sequences of AdCu/Zn-SOD and AdCAT encoded 155 and 526 amino acid proteins, respectively, both of which were expressed mainly in the liver. During fasting, when compared to the control group, liver AdCu/Zn-SOD expression was significantly higher in the 3- and 14-d groups, whereas its intestinal expression increased significantly only in the 7-d group. Liver AdCAT expression increased significantly in the 3-, 7-, and 14-d groups. During refeeding, liver AdCu/Zn-SOD expression increased significantly in the 3-, 7-, and 14-d groups compared with those in the control group. Similarly, intestinal AdCu/Zn-SOD expression increased significantly in the 3- and 7-d groups. Moreover, intestinal AdCAT expression was significantly higher in the 3-d group than in the control group, but decreased significantly in the 14-d group. Our findings indicated that AdCu/Zn-SOD and AdCAT play important roles in protecting fish against starvation-induced oxidative stress. Yangtze sturgeon exhibited the potential to adapt to a starvation and refeeding regime.

Molecular characterization of superoxide dismutase and catalase genes, and the induction of antioxidant genes under the zinc oxide nanoparticle-induced oxidative stress in air-breathing magur catfish (Clarias magur)

The deduced amino acid sequences from the complete cDNA coding sequences of three antioxidant enzyme genes (sod1, sod2, and cat) demonstrated that phylogenetically the magur catfish (Clarias magur) is very much close to other bony fishes with complete conservation of active site residues among piscine, amphibian, and mammalian species. The three-dimensional structures of three antioxidant enzyme proteins are very much similar to mammalian counterparts, thereby suggesting the functional similarities of these enzymes. Exposure to ZnO NPs resulted in an oxidative stress as evidenced by an initial sharp rise of intracellular concentrations of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) but decreased gradually at later stages. The level of glutathione (GSH) also increased gradually in all the tissues examined after an initial decrease. Biochemical and gene expression analyses indicated that the magur catfish has the ability to defend the ZnO NP-induced oxidative stress by inducing the SOD/CAT enzyme system and also the GSH-related enzymes that are mediated through the activation of various antioxidant-related genes both at the transcriptional and translational levels in various tissues. Furthermore, it appeared that the stimulation of NO, as a consequence of induction nos2 gene, under NP-induced oxidative stress serves as a modulator to induce the SOD/CAT system in various tissues of magur catfish as an antioxidant strategy. Thus, it can be contemplated that the magur catfish possesses a very efficient antioxidant defensive mechanisms to defend against the oxidative stress and also from related cellular damages during exposure to ZnO NPs into their natural environment.

Cloning of Mn-SOD gene and its mRNA expression difference and antioxidant enzyme activities under hypoxia stress of cobia Rachycentron canadum

BACKGROUND

Environmental hypoxia affects the survival and development of organisms. It is also an important environmental factor that leads to oxidative damage. Hypoxia is a condition in which tissues are deprived of oxygen; reoxygenation is the phenomenon in which hypoxic tissues are exposed to oxygen. Hypoxia-reoxygenation is vital in pathogenesis, where the production of reactive oxygen species and antioxidant disparity significantly contribute to disease progression, and it is one of the most common physiological stressors in the aquaculture industry.

METHODS AND RESULTS

In this study, the full length of complementary DNA (cDNA) of the manganese superoxide dismutase (Mn-SOD) gene of healthy cobia Rachycentron canadum was analysed using rapid amplification of cDNA ends. The real-time quantitative Polymerase Chain Reaction was used to measure the expression levels of Mn-SOD mRNAs in various tissues (heart, muscle, brain, liver, kidney, gill, intestine, and spleen). The 2^-ΔΔCT method was used to performed the expression analysis. The experimental data were analysed using SPSS ver. 19.0 ( https://spss.software.informer.com/19.0/ ). P < 0.05 and P < 0.01 were set as significant differences. The values were articulated as mean ± standard deviation. The Mn-SOD gene cDNA sequence was 1209 bp long, including a 684 bp open reading frame, 42 bp 5'UTR and 483 bp 3'UTR, encoding 227 amino acids. Under hypoxia-reoxygen stress, the expression of Mn-SOD in brain tissue was significantly lower than in the control group after 8 h of reoxygenation and higher than the control group after 24 h. Hypoxia and subsequent reoxygenation triggered a disturbance in antioxidant homeostasis, displayed in the modification of GPx expression/activity in the liver: GPx was improved.

CONCLUSIONS

These results provide valuable information on the role of Mn-SOD regulation in oxidative stress caused by hypoxia.

Superoxide Dismutase Multigene Family from a Primitive Chondrostean Sturgeon, Acipenser baerii: Molecular Characterization, Evolution, and Antioxidant Defense during Development and Pathogen Infection

Three distinct superoxide dismutases (SODs)-copper/zinc-SOD (SOD1), manganese-SOD (SOD2), and extracellular copper/zinc-SOD (SOD3)-were identified from a primitive chondrostean fish, Acipenser baerii, enabling the comparison of their transcriptional regulation patterns during development, prelarval ontogeny, and immune stimulation. Each A. baerii SOD isoform (AbSOD) shared conserved structural features with its vertebrate orthologs; however, phylogenetic analyses hypothesized a different evolutionary history for AbSOD3 relative to AbSOD1 and AbSOD2 in the vertebrate lineage. The AbSOD isoforms showed different tissue distribution patterns; AbSOD1 was predominantly expressed in most tissues. The expression of the AbSOD isoforms showed isoform-dependent dynamic modulation according to embryonic development and prelarval ontogenic behaviors. Prelarval microinjections revealed that lipopolysaccharide only induced AbSOD3 expression, while Aeromonas hydrophila induced the expression of AbSOD2 and AbSOD3. In fingerlings, the transcriptional response of each AbSOD isoform to bacterial infection was highly tissue-specific, and the three isoforms exhibited different response patterns within a given tissue type; AbSOD3 was induced the most sensitively, and its induction was the most pronounced in the kidneys and skin. Collectively, these findings suggest isoform-dependent roles for the multigene SOD family in antioxidant defenses against the oxidative stress associated with development and immune responses in these endangered sturgeon fish.

Molecular characterization, expression and functional analysis of TGFβ1-b in crucian carp (Carassius carassius)

Transforming growth factor β1 (TGFβ1) is a polyfunctional cytokine with important roles in growth, differentiation and immune function in various animals. In this study, PCR, bioinformatics, real-time quantitative PCR, prokaryotic expression, protein purification and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-TOF-MS) were applied to investigate the structural features and function of TGFβ1-b in crucian carp. The complete coding sequence (CDS) of TGFβ1-b was 1134 bp in length and was submitted to GenBank (ID: MH473141). TGFβ1-b encoded a putative protein of 377 amino acids and included a signal peptide consisting of 22 amino acids. TGFβ1-b was relatively conservative in fish and distant from mammals in terms of evolutionary relationship. TGFβ1-b was found to be expressed in various tissues, with the highest expression in the kidney. The expressions of TGFβ1-b in muscle, heart and liver were increased with the addition of Rhodopseudomonas palustris, Bacillus subtilis and Enterococcus faecium at 30 days (p < 0.01). While, the expressions of SMAD2, SMAD3 and SMAD7 were also up-regulated with the addition of R. palustris at 20 days (p < 0.01). The expression of TGFβ1-b could be affected by time and group factors (p < 0.05). Moreover, the expression vector TGFβ1-b-pDE2 was successfully constructed. Prokaryotic expression indicated that a 43 kDa target protein was obtained after induction with 1.5 mM isopropyl-beta-D-thiogalactopyranoside (IPTG) for 3.5 h at 37 °C for 200 r/h. The activities of alkaline phosphatase and lysozyme in injection TGFβ1-b protein group (ITg) and feeding broken bacterial liquid group (BTg) were significantly increased at 24 h (p < 0.01). And the activities of superoxide dismutase in ITg were significantly increased at 36 h (p < 0.01). Besides, the expressions of heat shock protein 30 and heat shock protein 47 in ITg and BTg were significantly increased (p < 0.01). Whereas, the expression of interleukin-11 was significantly reduced (p < 0.01). These results indicated that TGFβ1-b protein might play a role in immunity of crucian carp.

Epigenetic, transcriptional and phenotypic responses in Daphnia magna exposed to low-level ionizing radiation

Ionizing radiation is known to induce oxidative stress and DNA damage as well as epigenetic effects in aquatic organisms. Epigenetic changes can be part of the adaptive responses to protect organisms from radiation-induced damage, or act as drivers of toxicity pathways leading to adverse effects. To investigate the potential roles of epigenetic mechanisms in low-dose ionizing radiation-induced stress responses, an ecologically relevant crustacean, adult Daphnia magna were chronically exposed to low and medium level external ⁶⁰Co gamma radiation ranging from 0.4, 1, 4, 10, and 40 mGy/h for seven days. Biological effects at the molecular (global DNA methylation, histone modification, gene expression), cellular (reactive oxygen species formation), tissue/organ (ovary, gut and epidermal histology) and organismal (fecundity) levels were investigated using a suite of effect assessment tools. The results showed an increase in global DNA methylation associated with loci-specific alterations of histone H3K9 methylation and acetylation, and downregulation of genes involved in DNA methylation, one-carbon metabolism, antioxidant defense, DNA repair, apoptosis, calcium signaling and endocrine regulation of development and reproduction. Temporal changes of reactive oxygen species (ROS) formation were also observed with an apparent transition from ROS suppression to induction from 2 to 7 days after gamma exposure. The cumulative fecundity, however, was not significantly changed by the gamma exposure. On the basis of the new experimental evidence and existing knowledge, a hypothetical model was proposed to provide in-depth mechanistic understanding of the roles of epigenetic mechanisms in low dose ionizing radiation induced stress responses in D. magna.

Comparative Transcriptome Analysis Reveals the Mechanism Related to Fluazinam Stress of Panonychus citri (Acarina: Tetranychidae)

Simple Summary

The citrus red mite, Panonychus citri, is an important pest that causes serious citrus production losses in China. The insecticide fluazinam has a good control effect on the pest mites; however, its mechanism of action on mites remains unclear. In this study, we analyzed the transcriptomic sequencing and differential expression genes in P. citri treated with fluazinam, and identified some of the genes potential involved in detoxification metabolism related with the fluazinam exposure. Evaluating the efficacy of fluazinam, and analyzing the transcriptome data of P. citri under fluazinam stress, potentially provide a new agent for prevention and control of P. citri, and also preliminary research results for exploring the mechanism of action of fluazinam on P. citri. Given the up-regulated expression levels of genes for Mn-superoxide dismutase and catalase, we speculate that they play an important role in fluazinam-stress action on P. citri.

Abstract

The use of a large number of chemical acaricides to control these pest mites has led to an increasing problem of pesticide resistance, which has always been the difficulty in integrated pest management (IPM). Fluazinam has a good control effect on Panonychus citri, the serious pest on citrus; however, we only know the mechanism of action of fluazinam as a fungicide and its mechanism of action on mites remains unclear. Through analysis using Illumina high-throughput transcriptomic sequencing and differential expression genes in P. citri treated with fluazinam, 59 cytochrome P450 genes, 23 glutathione s-transferase genes, five carboxylate esterase genes, 11 superoxide dismutase genes and 15 catalase genes were identified. The Gene Ontology enrichment and the enrichment of KEGG results showed that the treatment were enrichment for redox enzyme pathways. Evaluating the efficacy of fluazinam, and analyzing the transcriptome data of P. citri under fluazinam stress, potentially provide a new agent for prevention and control of P. citri, and also preliminary research results for exploring the mechanism of action of fluazinam on P. citri. Given the up-regulated expression levels of genes for Mn-superoxide dismutase and catalase, we speculate that they play an important role in fluazinam-stress action on P. citri.

Genome-wide analysis of the superoxide dismutase (SOD) gene family in Zostera marina and expression profile analysis under temperature stress

Superoxide dismutases (SODs) serve as the first line of defense in the plant antioxidant enzyme system, and play a primary role in the removal of reactive oxygen species (ROS). However, our understanding of the functions of the SOD family in Zostera marina is limited. In this study, a systematic analysis was conducted on the characteristics of the SOD genes in Z. marina at the whole-genome level. Five SOD genes were identified, consisting of two Cu/ZnSODs, two FeSODs, and one MnSOD. Phylogenetic analysis showed that ZmSOD proteins could be divided into two major categories (Cu/ZnSODs and Fe-MnSODs). Sequence motifs, gene structure, and the 3D-modeled protein structures further supported the phylogenetic analysis, with each subgroup having similar motifs, exon-intron structures, and protein structures. Additionally, several cis-elements were identified that may respond to biotic and abiotic stresses. Transcriptome analysis revealed expression diversity of ZmSODs in various tissues. Moreover, qRT-PCR analysis showed that the expression level of most ZmSOD genes trended to decreased expression with the increase of temperature, indicating that heat stress inhibits expression of ZmSODs and may result in reduced ability of ZmSODs to scavenge ROS. Our results provide a basis for further functional research on the SOD gene family in Z. marina, which will help to determine the molecular mechanism of ZmSOD genes in response to environmental stress.

Characterizations of intracellular copper/zinc superoxide dismutase from yellow drum (Nibea albiflora, Richardson 1846) and its gene expressions under the ammonia/nitrite stress

Intracellular copper/zinc superoxide dismutase (icCuZnSOD) is a member of superoxide dismutase family that is capable of catalyzing the superoxide radicals into either hydrogen peroxide (H₂O₂) or ordinary molecular oxygen (O₂). Unlike mammals, the study of icCuZnSOD in aquatic animals is still in the infancy stage. Here, we identified the cDNA of na-iccuznsod from yellow drum (Nibea albiflora, Richardson 1846) and obtained its fusion protein for the first time. The mRNA expressions of na-iccuznsod were investigated in different tissues, and the dominant distribution was found in head-kidney, followed by brain, liver, heart, and gill. The effects of ammonia-N/nitrite-N on the mRNA expressions of na-iccuznsod were investigated. Na-iccuznsod transcription levels showed a general tendency of an initial up-regulation followed by a down-regulation in liver, gill, and head-kidney when yellow drum were exposed to ammonia-N/nitrite-N at the lethal concentration 50 at 96 h post-treatment, suggesting the important role of Na-icCuZnSOD in eliminating reactive oxygen species (ROS) induced by ammonia-N/nitrite-N. In addition, the characteristics of Na-icCuZnSOD protein and its comparative analysis with Na-ecCuZnSOD were investigated. Na-icCuZnSOD protein showed high enzyme stabilities over a wide range of temperature (10 to 60 °C) and pH (4.9 to 11.0), indicating its broad in vitro applications in many industries. Furthermore, the comparative analysis of Na-icCuZnSOD and Na-ecCuZnSOD gives a new perspective for the study of their structure-function relationship. Collectively, the present study will advance our understanding of the toxicity of ammonia-N/nitrite-N on yellow drum through testing the mRNA expression of iccuznsod gene, and broaden our knowledge of the protein characteristics of icCuZnSOD from fish.

miR-489-3p Regulates the Oxidative Stress Response in the Liver and Gill Tissues of Hybrid Yellow Catfish (Pelteobagrus fulvidraco♀ × P. vachelli♂) Under Cu2+ Exposure by Targeting Cu/Zn-SOD

Copper/zinc superoxide dismutase (Cu/Zn-SOD) plays critical roles in protecting cells and tissues against oxidative damage. Excessive copper ions (Cu2+) in water can damage the cells of aquatic organisms, leading to impaired growth and development and reduced antioxidant defenses. Many regulatory factors control the response to excess Cu2+. Among them, microRNAs (miRNAs) are important small RNAs that regulate the expression of their target genes and participate in the oxidative stress response. In the present study, we used bioinformatics and dual luciferase reporter gene analyses to demonstrate that the miR-489-3p of hybrid yellow catfish (Pelteobagrus fulvidraco♀ × P. vachelli♂) binds to the 3'-untranslated region (UTR) of its target gene, which encodes a Cu/Zn-SOD. The regulatory relationship between this miRNA and its target gene Cu/Zn-SOD was analyzed using qRT-PCR and luciferase activity assays. We also investigated the effect of the loss of miR-489-3p expression on the oxidative stress response of hybrid yellow catfish exposed to Cu2+. The Cu/Zn-SOD 3'UTR region was found to be fully complementary to positions 2-9 of the 5'-end seed region of miR-489-3p. The miR-489-3p expression levels were negatively related to Cu/Zn-SOD expression. Silencing of miR-489-3p up-regulated Cu/Zn-SOD expression in the liver and gill tissues, increased activities of SOD and catalase, and reduced the malondialdehyde content. This study is the first to demonstrate that miR-489-3p targets Cu/Zn-SOD to mediate the oxidative response to metal stress. These findings provide a theoretical basis for further studies on the response to oxidative stress caused by metals in cultured fish, and provide an experimental basis for the management of the culture environment.

Effects of different light spectra on embryo development and the performance of newly hatched turbot (Scophthalmus maximus) larvae

Light is a key environmental factor that synchronizes various life stages from embryo development to sexual maturation in fish. For turbot, light spectra have the most influence at the larval and juvenile stages. In the current study, differences in the development of embryos and the performance of newly hatched turbot larvae exposed to five different spectra: full spectrum (LDF), blue (LDB, peak at 450 nm), green (LDG, peak at 533 nm), orange (LDO, peak at 595 nm) and red (LDR, peak at 629 nm), were examined. At 62.8 h post fertilization, a higher number of embryos exposed to short-wavelengths (LDG and LDB) had developed a heartbeat in comparison with embryos exposed to other wavelengths. Larvae exposed to the green spectrum had higher malformation rates than larvae exposed to the other spectra, indicating that larvae exposed to green light may have significantly reduced survival rates. The results of non-specific immunity parameters showed that the mRNA expression levels of cathepsin D (CTSD), cathepsin F (CTSF), catalase (CAT) and metallothionein (MT) in larvae exposed to LDB were significantly higher than those exposed to other spectra, but CAT activity in larvae exposed to LDB was significantly lower than larvae exposed to the other spectra. There was no significant difference in MT activity in larvae exposed to the five different spectra. The mRNA expression level of lysozyme (LZM) in larvae exposed to LDR was significantly higher than other spectra, while there was no significant difference in LZM activity observed in larvae exposed to LDR, LDG, LDB and LDF. The difference of the enzyme activity of total superoxide dismutase (T-SOD) was not significant among larvae exposed to the five spectra. mRNA expression of the heat shock protein 70 (HSP70) was significantly higher in newly hatched larvae exposed to LDB, LDR and LDG, indicating that larvae exposed to LDB, LDG and LDR exhibited a stress response. The mRNA expression level of the insulin-like growth factor-1 (IGF-1) and growth parameters in the newly hatched larvae exposed to the different spectra were not significantly different. The results of the present study indicate that LDO and LDF should be used for embryo incubation and newly hatched larvae when rearing turbot. This study provides a theoretical basis for optimizing the incubation light environment for fertilized turbot eggs, promoting immunity and reducing stress responses in newly hatched larvae.

Molecular characterization of manganese superoxide dismutase (MnSOD) from sterlet Acipenser ruthenus and its responses to Aeromonas hydrophila challenge and hypoxia stress

A novel gene encoding the mitochondrial manganese superoxide dismutase from sterlet Acipenser ruthenus (Ar-MnSOD) was cloned. The full-length cDNA of MnSOD was of 1040 bp with a 672 bp open reading frame encoding 224 amino acids and the deduced amino acid sequence was located in mitochondria. Sequence comparison analysis showed that Ar-MnSOD was highly similar to MnSODs of invertebrates and vertebrates, especially those of freshwater Cyprinidae fishes and mammals. Phylogenetic analysis revealed that Ar-MnSOD was distant from MnSODs of other fishes and belonged to the family of mitochondrial MnSODs (mMnSOD). Consistently, Ar-MnSOD was located in mitochondria. The 3D structure of Ar-MnSOD was predicted and the overall structure was similar to that of MnSODs of humans and the bay scallop Argopecten irradians. In addition, mRNA of Ar-MnSOD was detected to extensively express in all tissues, with the highest level in brain and liver. Spleen and head kidney inoculation of Aeromonas hydrophila led to a significant up-regulation of Ar-MnSOD transcript levels. Also, hypoxia induced a transient increase in transcription of Ar-MnSOD in the gills, but not in the heart and brain, suggesting metabolic depression in these vital organs. The results also implied the anti-hypoxia properties of Ar-MnSOD in the related tissues and proved that Ar-MnSOD was involved in the stress response and (anti) oxidative processes triggered by hypoxia. The results indicated that Ar-MnSOD is induced upon A. hydrophila infection and hypoxia, consistent with its role in host immune and stress-induced anti-oxidative responses.

Environmental Salinity Affects Growth and Metabolism in Fingerling Meagre (Argyrosomus Regius)

The meagre (Argyrosomus regius), a farmed fish in Mediterranean countries, seasonally migrates from offshore areas to estuaries for reproduction. During the first two years of life, the meagre evidences a certain grade of euryhalinity by staying in brackish waters close to the shore. The aim of the present study was to establish if fingerling growth in brackish water is improved compared to seawater, where current culture procedures are conducted. Three-month-old fingerlings were maintained for 45 days under two different salinity regimens (12 and 39 ppt). Several growth parameters as well as osmoregulatory and metabolic variables were assessed. Specific growth rate and hepatosomatic index values revealed that fingerlings performed better in brackish waters (12 ppt) compared to 39 ppt. This study contributes to optimizing meagre rearing conditions, thereby supporting the role of A. regius in aquaculture diversification.

Two metalloenzymes from rockfish (Sebastes schligellii): Deciphering their potential involvement in redox homeostasis against oxidative stress

Disturbance in the balance between pro-oxidants and anti-oxidants result oxidative stress in aerobic organisms. However, oxidative stress can be inhibited by enzymatic and non-enzymatic defense mechanisms. Superoxide dismutases (SODs) are well-known scavengers of superoxide radicals, and they protect cells by detoxifying hazardous reactive oxygen species. Here, we have identified and characterized two different SODs, CuZnSOD and MnSOD, from black rockfish (RfCuZnSOD and RfMnSOD, respectively). In silico analysis revealed the well-conserved molecular structures comprising all essential properties of CuZnSOD and MnSOD. Phylogenetic analysis revealed that both RfCuZnSOD and RfMnSOD cladded with their fish counterparts. The recombinant RfSOD proteins demonstrated their potential superoxide scavenging abilities through a xanthine oxidase assay. The optimum temperature and pH conditions for both rRfSODs were 25 °C and pH 8, respectively. Moreover, the potential peroxidation function of rRfCuZnSOD was observed in the presence of HCO₃^-. The highest peroxidation activity was observed at 100 μg/mL of rRfCuZnSOD using the MTT cell viability assay and flow cytometry. The analogous tissue-specific expression profile indicated ubiquitous expression of both RfCuZnSOD and RfMnSOD in selected tissues of healthy juvenile rockfish. An immune challenge experiment illustrated the altered expression profiles of both RfCuZnSOD and RfMnSOD against lipopolysaccharide, Streptococcus iniae, and polyinosinic-polycytidylic acid (poly I:C). Collectively, these results strengthen the general understanding of the structural and functional characteristics of SODs within the host defense system.

Molecular characterization and functional analysis of two phospholipid hydroperoxide isoforms from Larimichthys crocea under Vibrio parahaemolyticus challenge

Glutathione peroxidases family is a key role in the antioxidant system in oxybiotic organisms for cell redox homeostasis. One of their members, phospholipid hydroperoxide glutathione peroxidase (GPx4) have unique monomeric structure and can directly react with complex lipid and membrane-bound peroxides under the presence of glutathione(GSH). In this paper, two complete GPx4 cDNAs (designated as LcGPx4a and LcGPx4b) from Larimichthys crocea are identified by rapid amplification of cDNA ends. The cDNA of LcGPx4a was consisted of a 5'-untranslated region (UTR) of 258 bp, a 3'-UTR of 330 bp, and an open reading frame (ORF) of 561 bp encoding 186 amino acid (aa) polypeptides. And the full-length sequence of LcGPx4b was 1164 bp with a 5'-UTR of 34 bp, a 3'-UTR of 551 bp and an ORF of 576 bp encoding a polypeptide of 191 aa residues with a predicted signal peptide of 15 aa. The characteristic selenocysteine insertion (SECIS) sequence was detected in the 3'UTR of the two sequences with 78 bp in length. The conserved active site of selenocysteine (Sec) encoded by TGA was also identified and formed a tetrad functional structure with glutamine, tryptophan, and asparagine in LcGPx4a and LcGPx4b. Two signature site motifs ("LRILAFPSNQFGNQEPG" and "LRILGFPCNQFGGQEPG") were both conserved in the deduced amino acid of LcGPx4a and LcGPx4b. The genomic structure analysis revealed that the two sequences both had 7 exons and 6 introns, and the Sec opal codon and SECIS element were located at the third and seventh exons, respectively. LcGPx4a and LcGPx4b both have a wide distribution in 9 tissues with various relative expression levels and a highest expression pattern in the liver. Under Vibrio parahaemolyticus challenge, their relative expression levels were altered in the liver, spleen, kidney, and head kidney but with different magnitudes and response time. LcGPx4a and LcGPx4b showed a significantly up-regulated trend in the spleen during experimental period. Above results suggested that LcGPx4a and LcGPx4b were two conserved immune molecules and might play a role in the immune response of fish with a tissue-depemdent manners.

Gas stunning with CO2 affected meat color, lipid peroxidation, oxidative stress, and gene expression of mitogen-activated protein kinases, glutathione S-transferases, and Cu/Zn-superoxide dismutase in the skeletal muscles of broilers

BACKGROUND

Meat color and lipid peroxidation are important traits related to meat quality. CO2 concentration is a critical factor that can affect meat quality in the commercial use of gas stunning (GS). However, the effect and mechanism of CO2 stunning on meat color and lipid peroxidation during long-term storage remain poorly studied. We aimed to study the effects of GS methods, especially CO2 concentration, on meat color and meat lipid peroxidation in broilers during long-term storage at 4 °C and to explore the potential mechanism of meat color change via lipid peroxidation and the inner lipid peroxide scavenging system.

METHODS

Eighteen broilers were sacrificed after exposure to one of the following gas mixtures for 90 s: 40% CO2 + 21% O2 + 39% N2 (G40%), 79% CO2 + 21% O2 (G79%), or no stunning (0% CO2, control). Meat color, serum variables, enzyme activities, and the gene expression of mitogen-activated protein kinase (MAPK), nuclear factor-erythroid 2-related factor 2 (Nrf2), glutathione S-transferase (GST) and superoxide dismutase (SOD) were determined.

RESULTS

The concentrations of serum triiodothyronine (T3, P = 0.03) and the ratio of serum free triiodothyronine/free thyroxine (FT3/FT4, P <  0.01) were decreased, whereas levels of serum cortisol (P <  0.01) were increased in the 40% CO2 group compared with the control group. Additionally, the thiobarbituric acid-reactive substances (TBARS) 3 d (P <  0.01) and TBARS 6 d (P = 0.01) in breast meat and the TBARS 3 d in thigh meat (P <  0.01) were increased in the 40% CO2 group compared with the control group. Serum T3 was negatively correlated with TBARS6 d both in the breast and thigh meat (r = - 0.63, P <  0.01 and r = - 0.47, P = 0.05 respectively). T3/T4 was negatively correlated with TBARS6 d in the breast meat and in the thigh meat (r = - 0.57, P = 0.01; and r = - 0.53, P = 0.03 respectively). Compared with the control group, Lightness (L*) 1 d (P = 0.03) and L*9 d (P < 0.01) were increased, whereas total chromatic aberration (E*) 1 d (P = 0.05) and E*3 d (P < 0.01) were decreased in the breast meat of both the G40% and G79% groups. The values of yellowness (b*) 3 d (P = 0.01), b*6 d (P < 0.01) and E*6 d (P < 0.01) in the thigh meat were lower in both the G40% and G79% groups than in the control group. In the breast muscle, the mRNA levels of c-Jun N-terminal kinase 2 (JNK2, P = 0.03), GSTT1 (P = 0.04), and SOD1 (P = 0.05) were decreased, and the mRNA levels of JNK1 (P = 0.07), Nrf2 (P = 0.09), and GSTA3 (P = 0.06) were slightly lower in both the G40% and G79% groups compared with the control group. However, among these genes, only the mRNA level of JNK1 was decreased in the G40% group compared with the control group and the G79% group (P = 0.03) in the thigh muscle.

CONCLUSIONS

Compared with the control group, meat color quality in the breast meat was decreased, and the expression of genes in the MAPK/Nrf2/ARE (antioxidant responsive element) antioxidant pathway in breast muscle was partly suppressed by GS of both 40% and 79% CO2. However, oxidative stress and meat lipid peroxidation during storage were aggravated by GS with 40% CO2 compared to GS with 79% CO2 and no GS.

Relationship between metabolic enzyme activities and bioaccumulation kinetics of PAHs in zebrafish (Danio rerio)

Many studies have investigated bioaccumulation and metabolism of polycyclic aromatic hydrocarbons (PAHs) in aquatic organisms. However, lack of studies investigated both processes simultaneously, and the interaction between these two processes is less understood so far. This study investigated the bioaccumulation kinetics of PAHs and metabolic enzyme activities, including total cytochrome P450 (CYPs) and total superoxide dismutase (T-SOD), in zebrafish. Mature zebrafish were exposed to the mixture of phenanthrene and anthracene under constant concentration maintained by passive dosing systems for 16days. The results showed that PAH concentrations in zebrafish experienced a peak value after exposure for 1.5days, and then decreased gradually. The bioaccumulation equilibrium was achieved after exposure for 12days. Both of the uptake rate constants (k_u) and the elimination rate constants (k_e) decreased after the peak value. The variation of PAH concentrations and metabolic enzyme activities in zebrafish had an interactive relationship. The activities of CYPs and T-SOD increased initially with the increase of PAH concentrations, but decreased to the lowest state when PAH concentrations reached the peak value. When the bioaccumulation equilibrium of PAHs was achieved, CYPs and T-SOD activities also reached the steady state. In general, CYPs and T-SOD activities were activated after exposure to PAHs. The decrease of PAH concentrations in zebrafish after the peak value may be attributed to the great drop of k_u and the variation of CYPs activities. This study suggests that an interactive relationship exists between bioaccumulation kinetics of PAHs and metabolic enzyme activities in aquatic organisms.

Antioxidant effect of peony seed oil on aging mice

d-galactose was injected into mice of ages 4-5 months, and peony seed oil was administered using an oral gavage to assess its possible anti-aging functions. The content of malondialdehyde (MDA) and the activities of monoamine oxidase (MAO), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) in the brain and liver of these mice were determined using biochemical kits. The significance of the differences in the content of the components associated with aging and anti-aging among each group was analyzed statistically. The MDA content and activities of MAO in the brain and liver of mice in the peony seed oil group were significantly lower than those in the aging group. The activities of GSH-Px, Cu/Zn-SOD, and Mn-SOD in the brain and liver of mice in the peony seed oil group were very significantly higher than those in the aging group. Peony seed oil was determined to have an obvious anti-aging function.

Identification and characterization of two selenium-dependent glutathione peroxidase 1 isoforms from Larimichthys crocea

Glutathione peroxidases, a vital family of antioxidant enzymes in oxybiotic organisms, are involved in anti-pathogen immune response. In this study, two complete selenium-dependent glutathione peroxidase 1 cDNAs (designated as LcGPx1a and LcGPx1b) were obtained from the large yellow croaker Larimichthys crocea by rapid amplification of cDNA ends. The full-length sequence of LcGPx1a was 917 bp with a 5'-untranslated region (UTR) of 52 bp, a 3'-UTR of 289 bp, and an open reading frame of 576 bp encoding 191 amino acid (aa) polypeptides. The cDNA of LcGPx1b was composed of 884 bp with a 5'-UTR of 59 bp, a 3'-UTR of 258 bp, and an open reading frame of 567 bp encoding 188 aa polypeptides. The conserved selenocysteine insertion sequence was detected in the 3'-UTR of both isoforms, which can classify types I and II. Protein sequence analysis revealed that both isoforms included a selenocysteine encoded by an opal codon (TGA) and formed the functioning tetrad site with glutamine, tryptophan, and asparagine. Three conservative motifs, including one active site motif ("GKVVLIENVASLUGTT") and two signature site motifs ("LVILGVPCNQFGHQENC" and "V(A/S)WNFEKFLI"), were conserved both in sequence and location. Multiple alignments revealed that they exhibited a high level of identities with GPx1 from other organisms, especially in the abovementioned conserved amino acid sequence motifs. Tissue expression analysis indicated that LcGPx1a and LcGPx1b had a wide distribution in nine tissues with various abundances. The transcript level of LcGPx1a was not significantly different among the nine tissues, whereas that of LcGPx1b was higher in the kidney and head kidney than in the other tissues. After Vibrio parahaemolyticus stimulation, the expression levels of LcGPx1a and LcGPx1b were unanimously altered in the liver, spleen, kidney, and head kidney but with different magnitudes and response time. LcGPx1a and LcGPx1b showed distinct expression trends in the liver, where LcGPx1b was induced and LcGPx1a was depressed in response to pathogen infection. These results indicate that LcGPx1a and LcGPx1b display functional diversities and play crucial roles in mediating the immune response of fish.

The expression of superoxide dismutase in Mytilus coruscus under various stressors

Superoxide dismutases (SODs), a by-product of antioxidative defence system, protects organisms for eliminating excess reactive oxygen species (ROS) and maintaining the redox balance of immune system. The complete open reading frames (ORFs) of Cu/Zn-SOD and Mn-SOD were identified from Mytilus coruscus (designated as McSOD and MnSOD) by homologous cloning. The sequence lengths were 474bp and 687bp, encoding 157 and 228 amino acids respectively. The deduced amino acid sequences of McSOD and MnSOD shared high identities with Cu/Zn-SOD and Mn-SOD from other mollusca. The distributions of McSOD and MnSOD were detected in six tissues including adductor, hemocyte, gill, gonad, mantle and hepatopancreas, and the highest expressions were both in gills. The temporal expression of McSOD and MnSOD were up-regulated in gills under a variety of stress factors, including Vibrio parahemolyticus, Aeromonas hydrophila, Cu²⁺ and Pb²⁺. After being challenged with V. Parahemolyticus, the expressions of McSOD and MnSOD were increased rapidly at the initial hours, reaching the peaks of 4.9-fold and 15.3-fold respectively, and got to the highest levels of 43.5-fold and 7.1-fold after being challenged with A. hydrophila. The highest point of McSOD mRNA appeared at 15 d after being exposed to copper (7-fold at 0.5 mg/L and 13.2-fold at 1.5 mg/L), except for 0.1 mg/L group of Cu²⁺ maintaining to the normal level, but plumbum at 1 d (2.4-fold at 1.0 mg/L and 4.4-fold at 3.0 mg/L) and at 15 d (2.1-fold at 0.2 mg/L). The temporal expression peaks of MnSOD appeared differently after exposing to copper of various concentrations (0.1 mg/L at 10 d with 4.7-fold, 0.5 mg/L at 1 d with 17.9-fold and 1.5 mg/L at 3 d with 13.2-fold). Whereas in plumbum exposing treatments, the 3.0 mg/L group jumped to the peak at 1 d (18.2-fold), the 0.2 mg/L and 1.0 mg/L groups had little change and maintained at the normal level throughout the experiment. The results provided several new evidences for further understanding of the regulatory mechanism of SOD on the innate immune system in bivalve.

Low-current & high-frequency electrical stunning increased oxidative stress, lipid peroxidation, and gene transcription of the mitogen-activated protein kinase/nuclear factor-erythroid 2-related factor 2/antioxidant responsive element (MAPK/Nrf2/ARE) signaling pathway in breast muscle of broilers

Mechanism of electrical stunning (ES) methods on lipid peroxidation and antioxidant protection were studied by determining meat color, serum variables, antioxidant-related enzyme activities, gene expressions of mitogen-activated protein kinases (MAPKs), nuclear factor-erythroid 2-related factor 2 (Nrf2), glutathione S-transferases (GSTs), and superoxide dismutases (SODs). Broilers were sacrificed without stunning, or after ES with 65V, 86mA, 1000Hz (E65V) or 150V, 130mA, 60Hz (E150V). Serum cortisol and uric acid, muscular malondialdehyde and mRNA levels of MAPKs, Nrf2, GSTA3, GSTT1 and SOD2 were increased, whereas, serum free triiodothyronine, free thyroxine, muscular GST_1d activity were decreased in E65V compared with E150V. Overall, the serum uric acid and transcription of the MAPK/Nrf2/ARE (antioxidant responsive element) signaling pathway were elevated, but didn't overcome the oxidative stress stimulated by low-current & high-frequency ES, leading to aggravated lipid peroxidation at 1d and 9d postmortem in breast muscle compared with high-current & low-frequency ES.

Dynamic responses of antioxidant enzymes in pearl oyster Pinctada martensii exposed to di(2-ethylhexyl) phthalate (DEHP)

Di(2-ethylhexyl) phthalate (DEHP) is recognized as one of the most ubiquitous contaminants in marine environments and causes adverse effects on the health of marine organisms. The purpose of this study was to investigate the toxic effects of DEHP on the pearl oyster Pinctada martensii. The Pinctada martensii was exposed to 0.0, 0.5, 2, 8, or 32mgL^-1 DEHP for 7 and 10days using parameters of antioxidant. Antioxidant indicators included levels of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), peroxidase (POD), and total antioxidant capacity (T-AOC) in the gills and hepatopancreas of Pinctada martensii for 7 and 10days. Besides, we used the lowest observed effect concentration (LOEC) of five enzyme activities in different tissues of Pinctada martensii for 7 and 10days to compare sensitivity. The results showed that the gills were more sensitive than the hepatopancreas of Pinctada martensii and that GSH activity in the gills and CAT activity in the hepatopancreas might be suitable biomarkers after 7days of DEHP exposure. After 10days of DEHP exposure, the GSH activity and CAT activity in the gills and SOD activity in the hepatopancreas could be regarded as biomarkers. Compared to the LOEC, GSH activity in the gills and CAT activity in the hepatopancreas after 7days of DEHP exposure were more sensitive than any other biomarkers. In addition, after 10days of DEHP exposure, GSH activity in the gills and hepatopancreas were much more sensitive than other activities. In conclusion, GSH activity demonstrated its potential to be used as a biomarker for the monitoring of DEHP pollution in the marine environment.

The molecular characterizations of Cu/ZnSOD and MnSOD and its responses of mRNA expression and enzyme activity to Aeromonas hydrophila or lipopolysaccharide challenge in Qihe crucian carp Carassius auratus

Superoxide dismutases (SODs), as the prime antioxidant enzymes, present the first line of defense against oxidative stress caused by excessive reactive oxygen species (ROS) in organism. In the study, two distinct members of SOD family were cloned and analyzed in Qihe crucian carp Carassius auratus (designated as CaCu/ZnSOD and CaMnSOD, respectively). The full-length cDNA of CaCu/ZnSOD is 759 bp, containing a 5' -untranslated region (UTR) of 39 bp, a ORF (including stop codon, TAG) of 465 bp and a 3'-UTR of 255 bp. The ORF of CaCu/ZnSOD encodes a protein of 154 amino acids (aa), in which, two Cu/ZnSOD signature (⁴⁵GFHVHAFGDNT⁵⁵ and ¹³⁹GNAGGRLACGVI¹⁵⁰) and four conserved amino acids for Cu/Zn²⁺-binding sites (H64, H72, H81 and D84) were observed. The full-length CaMnSOD cDNA (960 bp) consists of a 5'-UTR of 114 bp, a ORF of 675 bp and a 3'-UTR of 231 bp, the ORF of CaMnSOD encodes a 224 aa protein with a 26 aa mitochondrial-targeting sequence (MTS) in the N-terminus, and four conserved amino acids for manganese binding (H52, H100, D185 and H189) were observed. Multiple alignment and the structural analysis revealed two Cu/ZnSOD signature motifs and a MnSOD signature motif as well as the invariant binding sites for Cu²⁺/Zn²⁺ in CaCu/ZnSOD and Mn²⁺ in CaMnSOD. The phylogenetic analysis indicated that CaCu/ZnSOD was homologous to cytosolic Cu/ZnSODs, and CaMnSOD was high similarity with mitochondrial MnSODs from other fish. The tissue distribution analysis demonstrated that CaCu/ZnSOD and CaMnSOD were highly expressed in liver, heart and muscle. The dynamic expressions of CaCu/ZnSOD and CaMnSOD were observed after the challenges with Aeromonas hydrophila or LPS, which generally increased in liver, gill, kidney and spleen, while, the mRNA expressions were down-regulated at some time points in head kidney. The enzyme activities increased after A. hydrophila or LPS challenge, compared to the control. In this study, the molecular structures and functional motifs of CaCu/ZnSOD and CaMnSOD were determined, and it is crucial for us to understand the biological functions of SODs. The highest level in liver showed that the function of liver to remove ROS is much more important. The obvious responses of mRNA expression levels and enzyme activities to pathogens indicate the important roles of CaCu/ZnSOD and CaMnSOD in antioxidant defense in C. auratus.

α-lipoic acid ameliorates n-3 highly-unsaturated fatty acids induced lipid peroxidation via regulating antioxidant defenses in grass carp (Ctenopharyngodon idellus)

This study evaluated the protective effect of α-lipoic acid (LA) on n-3 highly unsaturated fatty acids (HUFAs)-induced lipid peroxidation in grass carp. The result indicated that diets with n-3 HUFAs increased the production of malondialdehyde (MDA) (P < 0.05), thereby inducing lipid peroxidation in liver and muscle of grass carp. Meanwhile, compared with control group, the hepatosomatic index (HSI) and kidney index (KI) of grass carp were markedly increased in n-3 HUFAs-only group. However, diets with LA remarkably inhibited the n-3 HUFAs-induced increase of HSI, KI, and MDA level in serum, liver and muscle (P < 0.05). Interestingly, LA also significantly elevated the ratio of total n-3 HUFAs in fatty acid composition of muscle and liver (P < 0.05). Furthermore, LA significantly promoted the activity of antioxidant enzymes in serum, muscle and liver of grass carp (P < 0.05), including superoxide dismutase (SOD), catalase (CAT), and glutathione s-transferase (GST). The further results showed that LA significantly elevated mRNA expression of antioxidant enzymes with promoting the mRNA expression of NF-E2-related nuclear factor 2 (Nrf2) and decreasing Kelch-like-ECH-associated protein 1 (Keap1) mRNA level. From the above, these results suggested that LA could attenuate n-3 HUFAs-induced lipid peroxidation, remit the toxicity of the lipid peroxidant, and protect n-3 HUFAs against lipid peroxidation to promote its deposition in fish, likely strengthening the activity of antioxidant enzymes through regulating mRNA expressions of antioxidant enzyme genes via mediating Nrf2-Keap1 signaling pathways.

Debaryomyces hansenii up regulates superoxide dismutase gene expression and enhances the immune response and survival in Pacific red snapper (Lutjanus peru) leukocytes after Vibrio parahaemolyticus infection

Application of yeast is increasing to improve welfare and promotes growth in aquaculture. The halotolerant yeast Debaryomyces hansenii is normally a non-pathogenic yeast with probiotic properties and potential source of antioxidant enzymes as superoxide dismutase. Here, first, we characterized the sequence features of MnSOD and icCu/ZnSOD from Pacific red snapper, and second, we evaluated the potential antioxidant immune responses of the marine yeast Debaryomyces hansenii strain CBS004 in leukocytes which were then subjected to Vibrio parahaemolyticus infection. In silico analysis revealed that LpMnSOD consisted of 1186 bp, with an ORF of 678 bp encoding a 225 amino acid protein and LpicCu/ZnSOD consisted of 1090 bp in length with an ORF of 465 bp encoding a 154 amino acid protein. Multiple alignment analyzes revealed many conserved regions and active sites among its orthologs. In vitro assays using head-kidney and spleen leukocytes immunostimulated with D. hansenii and zymosan in response to V. parahaemolyticus infection reveled that D. hansenii strain CBS004 significantly increased transcriptions of MnSOD and icCu/ZnSOD genes. Flow cytometry assay showed that D. hansenii was able to inhibit apoptosis caused by V. parahaemolyticus in the Pacific red snapper leukocytes and enhanced the phagocytic capacity in head-kidney leukocytes. Immunological assays reveled an increased in superoxide dismutase and peroxidase activities, as well as, in nitric oxide production and reactive oxygen species production (respiratory burst) in fish stimulated with D. hansenii. Finally, our results. These results strongly support the idea that marine yeast Debaryomyces hansenii strain CBS004 can stimulate the antioxidant immune mechanism in head-kidney and spleen leukocytes.

The cooperative expression of Heat Shock Protein 70 KD and 90 KD gene in juvenile Larimichthys crocea under Vibrio alginolyticus stress

Heat shock proteins (HSPs) play significant roles in the immune response of fish in defending against diverse environmental threats or stresses. In this study, two complete HSP70 and HSP90 genes of Larimichthys crocea (designated as LycHSP70 and LycHSP90) were identified and characterized (GenBank accession no. KT456551 and KT456552). The complete open reading frame (ORF) fragments of LycHSP70 and LycHSP90 were 1917 bp and 2151 bp, encoding 638 and 716 amino acids residues respectively. Many significant functional domains and motifs were found, such as Hsp70 family signatures, Hsp90 family signatures, ATP-GTP binding site and EEVD motif regions, and they were associated with relative functions. Phylogenetic relationship and BLASTp analysis interpreted that they were unambiguously assigned to HSP70 and HSP90 family. The total length DNA of LycHSP70 was 7889bp, LycHSP90 was 5618 bp, and the gene location mapping were analyzed based on the whole-genomic DNA sequence of L. crocea. LycHSP70 and LycHSP90 were constantly expressed in eight tested tissues, with their expression peaks appearing in liver. Spleen, brain and head kidney also witnessed higher expression level. LycHSP70 and LycHSP90 were significantly induced by pathogenic bacteria V. alginolyticus, and they were both up-regulated in liver and spleen from 0 to 72 h post-injection. All the findings would contribute to better understanding the biologic function of HSPs in defending against pathogenic bacteria challenge and further exploring the innate immune response in fish.

Identification and functional analysis of interferon regulatory factor 3 in Lateolabrax maculatus

The interferon (IFN) regulatory factor 3 (IRF3) is a member of the IFN regulatory transcription factor family, which binds to the IFN-stimulated response element (ISRE) within the promoter of IFN genes and IFN-stimulated genes. In this study, the IRF3 cDNA of sea perch Lateolabrax maculatus (SpIRF3) was identified, which contained 1781 bp with an open reading frame of 1398 bp that coded a 465 amino acid protein. The SpIRF3 protein shared conserved characterizations with its homologues and displayed the conserved DNA-binding domain, IRF association domain, serine-rich C-terminal domain, and tryptophan residue cluster. Phylogenetic analysis illustrated that SpIRF3 belonged to the IRF3 subfamily. Subcellular localization analysis showed that SpIRF3 mainly resided in the cytoplasm without stimuli but translocated into nuclei in the presence of poly I:C. Real-time PCR data indicated that SpIRF3 was transcriptionally up-regulated by poly I:C stimulation in various organs. Moreover, reporter assay revealed that SpIRF3 functioned as a modulator in triggering the IFN response by inducing the activity of IFN and ISRE-containing promoter. These data revealed that SpIRF3 was a potential molecule in the IFN immune defense system against viral infection.

Copper-zinc-superoxide dismutase (CuZnSOD), an antioxidant gene from seahorse (Hippocampus abdominalis); molecular cloning, sequence characterization, antioxidant activity and potential peroxidation function of its recombinant protein

Copper-zinc-superoxide dismutase (CuZnSOD) from Hippocampus abdominalis (HaCuZnSOD) is a metalloenzyme which belongs to the ubiquitous family of SODs. Here, we determined the characteristic structural features of HaCuZnSOD, analyzed its evolutionary relationships, and identified its potential immune responses and biological functions in relation to antioxidant defense mechanisms in the seahorse. The gene had a 5' untranslated region (UTR) of 67 bp, a coding sequence of 465 bp and a 3' UTR of 313 bp. The putative peptide consists of 154 amino acids. HaCuZnSOD had a predicted molecular mass of 15.94 kDa and a theoretical pI value of 5.73, which is favorable for copper binding activity. In silico analysis revealed that HaCuZnSOD had a prominent Cu-Zn_superoxide_dismutase domain, two Cu/Zn signature sequences, a putative N-glycosylation site, and several active sites including Cu(2+) and Zn(2+) binding sites. The three dimensional structure indicated a β-sheet barrel with 8 β-sheets and two short α-helical regions. Multiple alignment analyses revealed many conserved regions and active sites among its orthologs. The highest amino acid identity to HaCuZnSOD was found in Siniperca chuatsi (87.4%), while Maylandia zebra shared a close relationship in the phylogenetic analysis. Functional assays were performed to assess the antioxidant, biophysical and biochemical properties of overexpressed recombinant (r) HaCuZnSOD. A xanthine/XOD assay gave optimum results at pH 9 and 25 °C indicating these may be the best conditions for its antioxidant action in the seahorse. An MTT assay and flow cytometry confirmed that rHaCuZnSOD showed peroxidase activity in the presence of HCO3(-). In all the functional assays, the level of antioxidant activity of rHaCuZnSOD was concentration dependent; metal ion supplementation also increased its activity. The highest mRNA expressional level of HaCuZnSOD was found in blood. Temporal assessment under pathological stress showed a delay response by HaCuZnSOD. Our findings demonstrated that HaCuZnSOD is an important antioxidant, which might be involved in the host antioxidant defense mechanism against oxidative stress.

Identification of differentially expressed genes in the spleens of polyriboinosinic polyribocytidylic acid (poly I:C)-stimulated yellow catfish Pelteobagrus fulvidraco

The yellow catfish, Pelteobagrus fulvidraco (Siluriformes: Bagridae) is an economically important fish in China. However, genomic research and resources on this species are largely unavailable and still in infancy. In the present study, we constructed a cDNA library following poly I:C injection to screen for immune response genes in the spleens of P. fulvidraco using suppression subtractive hybridization (SSH). A total of 420 putative expressed sequence tag (EST) clones were identified at 24 h post-injection, which contain 103 genes consisting of 25 immune response genes, 12 cytoskeleton genes, 7 cell cycle and apoptosis genes, 7 respiration and energy metabolism genes, 7 transport genes, 26 metabolism genes, 10 stress response genes, 9 translational regulation genes, and 71 unknown genes. Real-time quantitative reverse transcription-PCR (qRT-PCR) results revealed that a set of randomly selected immune response genes were identified to be up-regulated after 24 h of poly I:C stimulation compared to controls. Our study provides an annotation of immune genes in detail and insight into fish immunity.

Characterization of immune-related genes in the yellow catfish Pelteobagrus fulvidraco in response to LPS challenge

Fish are considered an excellent model for studies in comparative immunology as they are a representative population of lower vertebrates linked to invertebrate evolution. To gain a better understanding of the immune response in fish, we constructed a subtractive cDNA library from the head kidney of lipopolysaccharide-stimulated yellow catfish (Pelteobagrus fulvidraco) using suppression subtractive hybridization (SSH). A total of 300 putative EST clones were identified which contained 95 genes, including 27 immune-related genes, 7 cytoskeleton-related genes, 3 genes involved in the cell cycle and apoptosis, 9 respiration and energy metabolism-related genes, 7 genes related to transport, 24 metabolism-related genes, 10 genes involved in stress responses, seven genes involved in regulation of transcription and translation and 59 unknown genes. Using real-time quantitative reverse transcription PCR, a subset of randomly selected genes involved in the immune response to lipopolysaccharide challenge were investigated to verify the reliability of the SSH data which identified 16 up-regulated genes. The genes identified in this study provide novel insight into the immune response in fish.

Effects of salinity change on two superoxide dismutases (SODs) in juvenile marbled eel Anguilla marmorata

Salinity is one of the most important factors that affect the fish growth and survival. Superoxide dismutases (SODs), as the primary antioxidant enzymes, play a first role in the process of preventing oxidative stress caused by excessive superoxide anion (O\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${}_{2}^{-}$\end{document}2−) in living organisms. In the present study, we investigated the effects of salinity on the gene expressions as well as enzymatic activities of MnSOD and Cu/ZnSOD in gill, intestine, kidney, liver and muscle tissues of the marbled eel Anguilla marmorata. We found that the liver might possess stronger redox capacity compared with other tissues. Furthermore, the gene expressions and enzymatic activities of SODs in juvenile marbled eels could be effectively enhanced by low salinity but inhibited when the salinity was higher than the body tolerance. Our findings indicated that MnSOD and Cu/ZnSOD played vital roles in the adaptation of marbled eels to salinity variation, which contributed to the elucidation of physiological adaptation and regulatory mechanism of SODs in eels.

Modulated expression and enzymatic activities of Darkbarbel catfish, Pelteobagrus vachelli for oxidative stress induced by acute hypoxia and reoxygenation

Large changes in oxygen availability in aquatic environments, ranging from anoxia through to hyperoxia, can lead to corresponding wide variation in the production of reactive oxygen species (ROS) by fish with aquatic respiration. In order to evaluate the effects of hypoxia and reoxygenation on oxidative stress in fish, the mRNA and protein expression of SODs (Cu/Zn-SOD and Mn-SOD) as well as indices (CP, LPO and MDA) and enzymatic activities (SOD, CAT, GPx, GR and GST) were analyzed in liver and brain tissues of Pelteobagrus vachelli. Predominant expression of PvSOD2 was detected in heart, brain, and liver. In contrast, PvSOD1 was highly expressed in liver. Based on the expression patterns of above parameters, we inferred that brain tissue of P. vachelli under 0.7 mg/L degree of acute hypoxia condition could experience hypometabolic states or no suffering stress, but brain tissue has effective mechanisms to minimize or prevent oxidative stress during the transition from hypoxia to reoxygenation. Our results also demonstrated an increased expression of SODs and enzymatic activities for oxidative stress in liver under hypoxic conditions, which supports the hypothesis that anticipatory preparation takes place in order to deal with the encountered oxidative stress during the recovery from hypoxia as proposed by M. Hermes-Lima. Therefore, this study will provide a clue to better understand the action mode of antioxidant genes and enzymes under oxidative stress in fish.