The cDNA cloning and mRNA expression of cytoplasmic Cu, Zn superoxide dismutase (SOD) gene in scallop Chlamys farreri

Identification and functional characterization of a superoxide dismutase (CuZnSOD) from Pinctada fucata martensii

Copper/zinc superoxide dismutase (Cu/Zn-SOD) can effectively eliminate reactive oxygen species (ROS)，avoid damage from O2 to the body, and maintain O2 balance. In this study, multi-step high-performance liquid chromatography (HPLC), combined with Mass Spectrometry (MS), was used to isolate and identify Cu/Zn-SOD from the serum of Pinctada fucata martensii (P. f. martensii) and was designated as PmECSOD. With a length of 1864 bp and an open reading frame (ORF) of 1422 bp, the cDNA encodes a 473 amino acid protein. The PmECSOD transcript was detected in multiple tissues by quantitative real-time PCR (qRT-PCR), with its highest expression level being in the gills. Additionally, the temporal expression of PmECSOD mRNA in the hemolymph was highest at 48 h after in vivo stimulation with Escherichia coli and Micrococcus luteus. The results from this study provide a valuable base for further exploration of molluscan innate immunity and immune response.

Effect of salinity on the toxicokinetics, oxidative stress, and metallothionein gene expression in Meretrix meretrix exposed to cadmium

To understand the effect of salinity on the toxicokinetics, oxidative stress, and detoxification of cadmium-exposed Meretrix meretrix, M. meretrix were acclimatized to different salinities (8, 14, 20, 26, and 32 ppt) for 14 d, exposed to 10 μg/L Cd for 7 d, followed by a 28-day depuration period. The internal Cd concentration was determined, and the activities of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), and glutathione-S-transferase (GST)), and the malondialdehyde (MDA) content were measured. The mRNA expression levels of antioxidant enzyme (Cu/Zn SOD, CAT) and detoxification-related genes metallothionein (MT) were analyzed. The mean concentrations of Cd in M. meretrix tissues were in the order gill > digestive gland > mantle > axe foot. The Cd uptake rate in the four tissues decreased with increasing salinity (range: 14-26 ppt). The Cd elimination half-lives were the highest at 8 ppt and 14 ppt salinity. Cadmium activated the four oxidative stress-related related enzymes in the gills. At the end of accumulation period, Cd exposure at 20 ppt salinity significantly increased the expression of Cu/Zn SOD. CAT expression was significantly inhibited at 20 ppt salinity, but was induced at 32 ppt. MT mRNA expression was only induced under Cd at 20 ppt salinity. At the end of depuration period, Cu/Zn SOD expression was inhibited at salinities of 8, 14, and 26 ppt. The results indicated that SOD, CAT, GST, MDA, Cu/Zn SOD, CAT, and MT were sensitive to cadmium in a water environment, and can be used as indicators of marine heavy metal pollution.

Identification and characterization of the critical genes encoding Cd-induced enhancement of SOD isozymes activities in Zhe-Maidong (Ophiopogon japonicus)

Superoxide dismutase (SOD) protects plants from abiotic stress-induced reactive oxygen species (ROS) damage. Here, the effects of cadmium (Cd) exposure on ROS accumulation and SOD isozymes, as well as the identification of significant SOD isozyme genes, were investigated under different Cd stress treatments to Zhe-Maidong (Ophiopogon japonicus). The exposure to Cd stress resulted in a notable elevation in the SOD activity in roots. Cu/ZnSODa and Cu/ZnSODb were the most critical SOD isozymes in response to Cd stress, as indicated by the detection results for SOD isozymes. A total of 22 OjSOD genes were identified and classified into three subgroups, including 10 OjCu/ZnSODs, 6 OjMnSODs, and 6 OjFeSODs, based on the analysis of conserved motif and phylogenetic tree. Cu/ZnSOD-15, Cu/ZnSOD-18, Cu/ZnSOD-20, and Cu/ZnSOD-22 were the main genes that control the increase in SOD activity under Cd stress, as revealed via quantitative PCR and transcriptome analysis. Additionally, under various heavy metal stress (Cu2+, Fe2+, Zn2+, Mn2+), Cu/ZnSOD-15, Cu/ZnSOD-18, and Cu/ZnSOD-22 gene expression were significantly upregulated, indicating that these three genes play a critical part in resisting heavy metal stress. The molecular docking experiments performed on the interaction between oxygen ion (O2•-) and OjSOD protein have revealed that the critical amino acid residues involved in the binding of Cu/ZnSOD-22 to the substrate were Pro135, Ile136, Ile140, and Arg144. Our findings provide a solid foundation for additional functional investigations on the OjSOD genes, as well as suggestions for improving genetic breeding and agricultural management strategies to increase Cd resistance in O. japonicus.

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.

Characterization of Copper/Zinc Superoxide Dismutase Activity on Phascolosoma esculenta (Sipuncula: Phascolosomatidea) and Its Protection from Oxidative Stress Induced by Cadmium

Phascolosoma esculenta, an economically important species inhabiting the high tide areas of the intertidal zone, is particularly sensitive to water pollution. Considering its potential as a bioindicator, studies on the ecotoxicology of P. esculenta are imperative. The toxic effects of cadmium (Cd) were analyzed by exposing P. esculenta to different concentrations of Cd (6, 24, 96 mg/L). In this study, the changes in the antioxidative indexes of total superoxide dismutase (T-SOD), glutathione s-transferase (GST), reduced glutathione (GSH), and microscale malondialdehyde (MDA) were recorded. Copper/zinc superoxide dismutase (Cu/Zn SOD) is one of the most important free radical scavenging members. To reveal the antioxidative function of P. esculenta, an important member of the antioxidative system, designated Pe-Cu/Zn SOD, was cloned and analyzed. Phylogenic analysis revealed that Pe-Cu/Zn SOD was located in the invertebrate evolutionary branch of intracellular Cu/Zn SOD (icCu/Zn SOD). The quantitative real-time polymerase chain reaction results showed that Pe-Cu/Zn SOD messenger ribonucleic acid was widely expressed in all tissues examined. The highest expression levels in coelomic fluid after Cd exposure indicated its function in the stress response. Using a prokaryotic expression system, we obtained a Pe-Cu/Zn SOD recombinant protein, which enhanced the heavy metal tolerance of Escherichia coli. In vivo assays also confirmed that the Pe-Cu/Zn SOD recombinant protein had an antioxidative and free radical scavenging ability. A Cd toxicity experiment, in which purified Pe-Cu/Zn SOD protein was injected into the body cavities of P. esculenta, showed that the reactive oxygen species content in the coelomic fluid of the experimental group was significantly lower compared with the control group. These results suggest that Pe-Cu/Zn SOD played a role in Cd detoxification by chelating heavy metal ions and scavenging reactive oxygen free radicals, and that P. esculenta could be used as a bioindicator to evaluate heavy metal pollution.

A Novel Disease (Water Bubble Disease) of the Giant Freshwater Prawn Macrobrachium rosenbergii Caused by Citrobacter freundii: Antibiotic Treatment and Effects on the Antioxidant Enzyme Activity and Immune Responses

The giant freshwater prawn, Macrobrachium rosenbergii, is an important and economical aquaculture species widely farmed in tropical and subtropical areas of the world. A new disease, "water bubble disease (WBD)", has emerged and resulted in a large loss of M. rosenbergii cultured in China. A water bubble with a diameter of about 7 mm under the carapace represents the main clinical sign of diseased prawns. In the present study, Citrobacter freundii was isolated and identified from the water bubble. The optimum temperature, pH, and salinity of the C. freundii were 32 °C, 6, and 1%, respectively. A challenging experiment showed that C. freundii caused the same typical signs of WBD in prawns. Median lethal dose of the C. freundii to prawn was 104.94 CFU/g. According to the antibiogram tests of C. freundii, florfenicol and ofloxacin were selected to evaluate their therapeutic effects against C. freundii in prawn. After the challenge with C. freundii, 86.67% and 72.22% survival of protective effects against C. freundii were evaluated in the oral florfenicol pellets and oral ofloxacin pellets feding prawns, respectively, whereas the mortality of prawns without fed antibiotics was 93%. After antibiotic treatment and C. freundii infection, the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), malondialdehyde (MDA), acid phosphatase (ACP), alkaline phosphatase (ALP), and lysozyme (LZM) in the hemolymph and hepatopancreas of the prawns and the immune-related gene expression levels of Cu/Zn-SOD, CAT, GPx, GST, LZM, ACP, anti-lipopolysaccharide factor, crustin, cyclophilin A, and C-type lectin in hepatopancreas were all significantly changed, indicating that innate immune responses were induced by C. freundii. These results can be beneficial for the prevention and control of C. freundii in prawns.

Transcriptional expression analysis reveals multiple effects of nonylphenol exposure on scallop immune system

Nonylphenol (NP) is an endocrine disruptor and environmental hormone representing alkylphenol compounds. Marine mollusks are an important source of protein for people worldwide. Many researchers have begun to study the effect of NP on marine mollusks immune system in view of its toxicity; however, the underlying molecular mechanisms require in-depth analysis. In this study, we focused on the transcriptional expression change of immune-related genes and antioxidant enzymes activities variation after NP exposure in a marine bivalve mollusk, Chlamys farreri, to explore the immunomodulatory capacity of NP in marine mollusks. We identified MAVS (Mitochondrial antiviral signaling protein), a key adaptor molecule in the RLR (RIG-I like receptor) pathway, and studied the expression of multiple immune-related genes in response to different concentrations of NP. The key genes involved in RLR/TLR (Toll like receptor) innate immune pathway, apoptosis, and cellular antioxidation mechanism were investigated. Changes in the enzymatic activities of scallop antioxidant enzymes after NP exposure were also examined. The results revealed that the genes expression and the antioxidant enzymes activities show significant changes, thus proving that NP stimulation affects the scallop immune system. Our research results demonstrate the immunomodulatory capacity of NP in marine bivalve mollusks and lay the foundation for further in-depth analysis of the molecular mechanism of NP toxicity.

Toxic effects of ammonia on the intestine of the Asian clam (Corbicula fluminea)

Intestines contain a large number of microorganisms that collectively play a vital role in regulating physiological and biochemical processes, including digestion, water balance, and immune function. In this study, we explored the effects of ammonia stress on intestinal inflammation, the antioxidant system, and the microbiome of the Asian clam (Corbicula fluminea). Exposure to varying ammonia concentrations (10 and 25 mg N/L) and exposure times (7 and 14 days) resulted in damage to C. fluminea intestinal tissue, according to histological analysis. Furthermore, intestinal inflammatory responses and damage to the antioxidant system were revealed through qPCR, ELISA, and biochemical analysis experiments. Inflammatory responses were more severe in the treatment group exposed to a lower concentration of ammonia. High-throughput 16S rDNA sequencing showed that ammonia stress under different conditions altered intestinal bacterial diversity and microbial community composition, particularly impacting the dominant phylum Proteobacteria and genus Aeromonas. These results indicate that ammonia stress can activate intestinal inflammatory reactions, damage the intestinal antioxidant system, and alter intestinal microbial composition, thereby impeding intestinal physiological function and seriously threatening the health of C. fluminea.

The role of Smad1/5 in mantle immunity of the pearl oyster Pinctada fucata martensii

The Smad protein family is an important medium for transducing BMP-Smads signals, and which have been proved that their important role in regulating shell biomineralization in Pinctada fucata martensii in our previous study. The members of TGF-β superfamily were involved in innate immunity in vertebrates and invertebrates, and Smad regulatory networks construct a balanced immune system. However, little is known about the role of Smad1/5 in immunity in P. f. martensii. The present study shows that the tissue distribution and the expression profiles of Smad1/5 at developmental stages suggested its wide distribution and crucial role in development at embryonic stages other than larval stage; the increased expression of bone morphogenetic proteins 2 (BMP2), Smad4, Smad1/5 and MSX mRNAs at mantle tissue after LPS and Poly (I:C) challenged implied the potential immune role of Smad1/5 and BMP2-Smad signals to defense against bacterial and virus infections; the reduced expression of immune gene nuclear factor kappa-B (NF-κB), matrix metalloproteinase (MMP), interleukin 17 (IL-17), CuZn-superoxide dismutase (CuZn-SOD), tissue inhibitors of metalloproteinase (TIMP) and lipopolysaccharide-induced TNF-α factor (LITAF) mRNA following knockdown of Smad1/5 indicated that Smad1/5 can regulate their expression via BMP2-Smads pathway in the immunity process; the up-regulated expression of Smad1/5 and BMP2-Smad signals genes, and immune genes during wound healing indicated that Smad1/5 and BMP2-Smad signals genes may be involved in wound healing collaborated with immune genes via a different and complex Smads signaling pathway. These results indicated Smad1/5 could regulate innate immunity via BMP2-Smads signal pathway, and which provided new insights into the relationship between BMP2-Smads signal pathway and mantle immunity.

Effects of Acute Ammonia Stress on Antioxidant Responses, Histopathology and Ammonia Detoxification Metabolism in Triangle Sail Mussels (Hyriopsis cumingii)

Ammonia is one of the major pollutants in the aquatic ecosystem. Hyriopsis cumingii has great potential for the restoration of eutrophic water. However, there is no study investigating the effect of ammonia exposure in H. cumingii. The median lethal concentration (96 h LC50) of unionized ammonium was 12.86 mg/L in H. cumingii. In the study, H. cumingii were exposed to 6.43 mg L−1 unionized ammonium (1/2 96 h LC50) for 0, 6, 12, 24, 48, 72, and 96 h. High environment ammonia induced antioxidant response to protect the body from oxidative damage. After exposure to ammonia, there was a same trend of induction followed by inhibition of the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione-S-transferases (GST) in the hepatopancreas and gills of H. cumingii. However, the antioxidant response could not completely counteract the oxidation effect during the exposure period, resulting in lipid peroxidation (LPO) and tissue injury in the hepatopancreas and gills of H. cumingii eventually. Moreover, this study indicated that glutamine synthetase (GS), glutamate dehydrogenase (GDH), alanine aminotransaminase (ALT), and aspartate aminotransaminase (AST) in the hepatopancreas and gills may play an important role in ammonia detoxification of H. cumingii. Our results will be helpful to understand the mechanism of aquatic toxicology induced by ammonia in shellfish.

Basic Studies on the Oxidative Stress Markers in Two Types of Horse Breed: Semi-isolated Population of Huculs Is Different from Commercially Used Arabian Horses

Hucul and Arabian horses differ in the physiological constitution and exposition to environmental conditions. Oxidative stress plays a pathogenic role in many diseases and enables further injuries. The objective of this study was to compare the levels of enzymatic and nonenzymatic oxidative stress markers in Hucul horses living in seminatural conditions and in commercially handled Arabian horses. We tested the serum samples for total superoxide dismutase (total SOD), Cu-Zn-superoxide dismutase (CuZnSOD), and Mn-dependent superoxide dismutase (MnSOD) activity; for lipofuscin (LPS), ceruloplasmin (CER) and malondialdehyde (MDA) concentration; and for total antioxidant capacity (TAC) and total oxidant status (TOS). Total SOD (p < 0.001), MnSOD (p < 0.001), and CuZnSOD (p < 0.001) activities were significantly higher whereas LPS (p < 0.05), TAC (p < 0.001), TOS (p < 0.001), and MDA (p < 0.001) concentrations were significantly lower in the serum samples collected from Huculs vs. Arabian horses, regardless of the gender. Gender, regardless of the breed, had no significant impact on the antioxidants' activity and concentration. Total SOD and MnSOD activities were significantly higher in Hucul's mares when compared to Hucul's stallions. Concentrations of TAC and TOS were significantly lower in Arabian stallions than in Arabian mares. Commercially handled horses expressed a higher level of oxidative stress markers in comparison to breeds living in seminatural conditions. We conclude that antioxidants are important biomarkers of animal health, whether they are under maintenance care or performing physical exercise.

Effects of acute ammonia toxicity on oxidative stress, DNA damage and apoptosis in digestive gland and gill of Asian clam (Corbicula fluminea)

Ammonia is one of the major pollutants associated with the main river basins due to ammonification of uneaten food and animal excretion, which usually brings detrimental health effects to aquatic invertebrate. However, the mechanisms of ammonia toxicity in aquatic invertebrate have rarely been reported. In this study, C. fluminea was exposed to different levels of ammonia (control group, 10 mg/L, and 25 mg/L) for 24 h and 48 h, and digestive gland and gill were collected to explore toxic effects on oxidative stress, DNA damage and apoptosis under ammonia stress. The results showed that ammonia poisoning could increase the activity of oxidative stress enzyme (SOD and CAT), inducing differentially expressed genes (DRAM2, GADD45, P53, BAX, BCL2, CASP8, CASP9, CASP3, HSP70 and HSP90) and different cytokines (IL-1 beta, IL-8, IL-17 and TNF-alpha) of DNA damage and apoptosis. The difference of toxic effects induced by ammonia among digestive gland and gill were also observed by real-time PCR and TUNEL staining. Our results will be helpful to understand the mechanism of aquatic toxicology induced by ammonia in C. fluminea.

Immune signaling pathways in the endoparasitoid, Pteromalus puparum

Parasitoids serve as effective biocontrol agents for agricultural pests. However, they face constant challenges from host immune defense and numerous pathogens and must develop potent immune defense against these threats. Despite the recent advances in innate immunity, little is known about the immunological mechanisms of parasitoids. Here, we identified and characterized potential immune-related genes of the endoparasitoid, Pteromalus puparum, which act in regulating populations of some members of the Pieridae. We identified 216 immune-related genes based on interrogating the P. puparum genome and transcriptome databases. We categorized the cognate gene products into recognition molecules, signal moieties and effector proteins operating in four pathways, Toll, IMD, JAK/STAT, and JNK. Comparative analyses of immune-related genes from seven insect species indicate that recognition molecules and effector proteins are more expanded and diversified than signaling genes in these signal pathways. There are common 1:1 orthologs between the endoparasitoid P. puparum and its relative, the ectoparasitoid Nasonia vitripennis. The developmental expression profiles of immune genes randomly selected from the transcriptome analysis were verified by a quantitative polymerase chain reaction. Our work provides comprehensive analyses of P. puparum immune genes, some of which may be exploited in advancing parasitoid-based biocontrol technologies.

Roles of Carotenoids in Invertebrate Immunology

Carotenoids are biologically active pigments that are well-known to enhance the defense and immunity of the vertebrate system. However, in invertebrates, the role of carotenoids in immunity is not clear. Therefore, this study aims to review the scientific evidence for the role of carotenoids in invertebrate immunization. From the analysis of published literatures and recent studies from our laboratory, it is obvious that carotenoids are involved in invertebrate immunity in two ways. On the one hand, carotenoids can act as antioxidant enzymes to remove singlet oxygen, superoxide anion radicals, and hydroxyl radicals, thereby reducing SOD activity and reducing the cost of immunity. In some organisms, carotenoids have been shown to promote SOD activity by up-regulating the expression of the ZnCuSOD gene. Carotenoids, on the other hand, play a role in the expression and regulation of many genes involved in invertebrate immunity, including thioredoxins (TRX), peptidoglycan recognition receptor proteins (PGRPs), ferritins, prophenoloxidase (ProPO), vitellogenin (Vg), toll-like receptor (TLRs), heat shock proteins (HSPs), and CuZnSOD gene. The information in this review is very useful for updating our understanding of the progress of carotenoid research in invertebrate immunology and to help identify topics for future topics.

Effect of the Algicide Thiazolidinedione 49 on Immune Responses of Bay Scallop Argopecten Irradians

The thiazolidinedione 49 (TD₄₉) is an effective algaecide against harmful algae; however, its potential effects on the immune function of the edible bay scallop are unclear. Therefore, the present work studied the effects of TD₄₉ on the immune response in bay scallop by evaluating activities of acid phosphatase (ACP), alkaline phosphatase (ALP), and superoxide dismutase (SOD), as well as nitric oxide (NO) levels, total protein content, and expression of immune genes (CTL-6, PGRP, PrxV, MT, and Cu/Zn-SOD) at 3–48 h post-exposure (hpe) to TD₄₉. The activities of ACP and ALP significantly increased in TD₄₉-treated groups at 3–24 hpe, whereas NO levels decreased significantly in 0.58 and 0.68 μM of TD₄₉ at 6–24 hpe, after which the level was similar to that in the untreated control. Moreover, SOD activity significantly increased in all three concentration groups at 3–6 hpe, while it decreased at 12 hpe in the 0.68 μM TD₄₉ treatment group. Notably, total protein content increased with TD₄₉ treatment at each time interval. The results revealed that variable effects on the expression of immune-related genes were observed after treatment with TD₄₉. The findings demonstrate that exposure of scallops to TD₄₉ changes immune responses and expression of immune-related genes. We hypothesize that TD₄₉ may disrupt immune system in bay scallop. The current investigation highlights the potential negative effects of using TD₄₉ as an algaecide on marine economic bivalves to control harmful algal blooms in marine environments.

Effects of lactic acid on drug-metabolizing enzymes in Chinese mitten crab (Eriocheir sisnensis) after oral enrofloxacin

Enrofloxacin (ENR) is the most commonly used antibiotic in crustacean farming in China. Diet supplementation with lactic acid (LA) may, however, affect the efficacy and safety of ENR-based drugs. The aims of this study were to investigate the effects of LA on drug residues and elimination of oral ENR in Chinese mitten crab (Eriocheir sinensis) and to determine ENR and gene expression levels of drug-metabolizing enzymes in the hepatopancreas. To this end, ENR was orally administered to the crabs at a dose of 10.0 mg kg^-1 body weight on the eighth day after feeding diets supplemented with 0.3%LA. The results showed that ENR levels in the hepatopancreas were significantly different at 1 and 12 h between the ENR and ENR + 0.3% LA groups (P < 0.05). Lactic acid did not significantly affect the expression of CYP2A (phase I). However, the expressions of CYP3 (phase I) and GST (phase II) were significantly up-regulated by LA during the elimination process of ENR (6-24 h). At T_max (1 h), the expression of phosphoenolpyruvate carboxykinase (PEPCK) was induced and expression of succinate dehydrogenase (SDH) was inhibited by LA. Both of these enzymes were significantly inhibited during the elimination process of ENR. The results suggest that LA contributes to the elimination of ENR, and thus, enhances hepatopancreas biotransformation and anti-injury capacity in E. sinensis.

A superoxide dismutase (MnSOD) with identification and functional characterization from the freshwater mussel Cristaria plicata

Manganese superoxide dismutase (MnSOD) is a sort of important metalloenzyme that can catalyze ROS in the organisms. In this study, MnSOD cDNA of C. plicata, designated as CpMnSOD (accession no. MK465057), was cloned from hemocytes. The full-length cDNA of MnSOD was 1096 bp with a 672 bp open reading frame encoding 223 amino acids. The deduced amino acid sequence contained a mitochondrial-targeting sequence (MTS) of 18 amino acids in the N-terminus, and four conserved amino acids for manganese binding (H⁴⁹, H⁹⁷, D¹⁸², H¹⁸⁶). CpMnSOD showed a high level (65-73%) of sequence similarity to MnSODs from other species. The results of Real-time quantitative PCR revealed that CpMnSOD mRNA constitutively expressed in tissues. The highest expression level was in hepatopancreas, followed by muscle, mantle and gill, and the lowest expression level was in hemocytes. After microcystin challenge, the expression levels of CpMnSOD mRNA were up-regulated in hemocytes and hepatopancreas. The cDNA of CpMnSOD was cloned into the plasmid pColdI-ZZ, and the recombinant protein was expressed in Escherichia coli BL21 (DE3). The enzyme stability assay showed that the purified CpMnSOD protein maintained more than 80% enzyme activity at temperature up to 70 °C, at pH 2.0-10.0, and resistant to 8 mol/L urea or 8% SDS.

Macrobrachium rosenbergii Cu/Zn superoxide dismutase (Cu/Zn SOD) expressed in Saccharomyces cerevisiae and evaluation of the immune function to Vibrio parahaemolyticus

Superoxide dismutases (SODs) are important antioxidant enzymes that occur in virtually all oxygen-respiring organisms, and copper/zinc SOD (Cu/ZnSOD) is one of the most important SODs. In the present study, Macrobrachium rosenbergii Cu/Zn-SOD was expressed in a yeast eukaryotic system. The open reading frame (ORF) of MrCu/ZnSOD was cloned into the plasmid vector pHAC181, and the recombinant plasmid was integrated into the downstream region of the GAL1 promoter in Saccharomyces cerevisiae strain GAL1-ScRCH1 via homologous recombination. The resulting recombinant MrCu/ZnSOD consisted of a 3 × HA-tag at its C-terminal. Via western blot, the molecular weight of the recombinant MrCu/ZnSOD was estimated at about 30 kDa. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of this recombinant MrCu/ZnSOD ranged from 0.556 to 0.840 μM, and from 0.967 to 2.015 μM, respectively. The recombinant MrCu/ZnSOD protein was able to agglutinate four Gram-negative bacterial strains, as well as two of three Gram-positive strains (except Staphylococcus aureus). This demonstrated that the recombinant protein possessed some antimicrobial activity against certain Gram-positive and Gram-negative bacteria. M. rosenbergii were fed with the recombinant yeast strain MrCu/ZnSOD for 4 weeks and then challenged with the most common crustacean pathogen, Vibrio parahaemolyticus. This group of prawns presented lower mortality, higher enzymatic activity, and higher expression of the mRNA of immune-related genes than that in the control groups. Taken together, these results suggest that MrCu/ZnSOD is an antioxidant enzyme and antimicrobial peptide involved in the crustacean innate immune system and offers protection to the host against pathogenic bacteria.

The distribution, expression of the Cu/Zn superoxide dismutase in Apostichopus japonicus and its function for sea cucumber immunity

Cu/Zn superoxide dismutases (SODs) are antioxidative metalloenzymes that exist ubiquitously in different species and are distributed widely in various tissues and cell types. In this study, the distribution and biological function of the Cu/Zn superoxide dismutase in Apostichopus japonicus (AjSOD1) is first characterized. The AjSOD1 cDNA is 1219 bp in length and contains an open reading frame (ORF) of 459 bp that encodes a protein of 152 amino acids with a deduced molecular weight of 15.47 kDa and a predicted isoelectric point of 5.65. The Cu²⁺/Zn²⁺ binding domain and conserved residues were found in the AjSOD1 amino acid sequence. A quantitative reverse transcriptase real-time PCR (qRT-PCR) assay was developed to assess the expression of AjSOD1 in different tissues. Spatial distribution analysis showed that AjSOD1 was constitutively expressed in all tested tissues, with strong expression in the intestine and weak expression in the respiratory tree. mRNA Expression of AjSOD1 was significantly upregulated when challenged with the pathogen Vibrio splendidus. Functional investigation revealed that recombinant AjSOD1 displayed good antioxidant activity. More importantly, the addition of AjSOD1 resulted in a significant decrease in coelomocyte apoptosis by LPS/H₂O₂ challenge in vitro. The results indicate that sea cucumber SOD1 may play critical roles not only in the defense against oxidative stress but also in the innate immune defense against bacterial infections.

CuZnSOD and MnSOD from freshwater planarian Dugesia japonica: cDNA cloning, mRNA expression and enzyme activity in response to environmental pollutants

As an important antioxidant enzyme, the superoxide dismutase (SOD) can protect aerobic organisms from oxidative damage through catalyzing the dismutation of superoxide into hydrogen peroxide and oxygen. The SODs have been cloned in some species and their dynamic expression or enzymatic activity in response to environmental stressors were investigated. In the current study, the full-length cDNA of two SODs from freshwater planarian Dugesia japonica were firstly cloned (named as DjCuZnSOD and DjMnSOD, respectively). The complete cDNA of DjCuZnSOD consists of 661 nucleotides encoding 186 amino acids while the 765 bp DjMnSOD encodes a polypeptide of 226 residues. Sequence analysis and multiple alignment showed that DjCuZnSOD possesses two CuZnSOD family signature motifs and an N-terminal signal peptide suggesting it is an extracellular secretory protein. DjMnSOD possesses the MnSOD family signature sequence and is predicted to be located in mitochondrion with a mitochondrial targeting sequence. Phylogenetic analysis based on CuZnSOD and MnSOD orthologs from representative species further verified that DjCuZnSOD is an extracellular CuZnSOD while DjMnSOD is a mitochondrial MnSOD. For the purpose of studying their potential role against environmental pollutants, D. japonica were exposed to glyphosate or 1-decyl-3-methylimidazolium bromide ([C₁₀mim]Br), and the mRNA expression levels of DjCuZnSOD and DjMnSOD along with total SOD activity were measured. The results showed that DjCuZnSOD exhibited more sensitive expression profiles in response to environmental pollutants in contrast with DjMnSOD, and the total SOD activity in response to both pollutants was more related to the expression level of DjCuZnSOD than to DjMnSOD, indicating that the mRNA expression of CuZnSOD would be a more sensitive biomarker than MnSOD in monitoring the pollution of aquatic environment and CuZnSOD might play more important role than MnSOD in eliminating superoxide anions caused by pollutants in D. japonica.

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.

A mitochondrial manganese superoxide dismutase involved in innate immunity is essential for the survival of Chlamys farreri

Superoxide dismutase (SOD) ubiquitously found in both prokaryotes and eukaryotes functions as the first and essential enzyme in the antioxidant system. In the present study, a manganese SOD (designated as CfmtMnSOD) was cloned from Zhikong scallop Chlamys farreri. The complete cDNA sequence of CfmtMnSOD contained a 681 bp open reading frame (ORF), encoding a peptide of 226 amino acids. A SOD_Fe_N domain and a SOD_Fe_C domain were found in the deduced amino acid sequence of CfmtMnSOD. The mRNA transcripts of CfmtMnSOD were constitutively expressed in all the tested tissues, including gill, gonad, hepatopancreas, hemocytes, mantle and muscle, with the highest expression level in hemocytes. After the stimulation of Vibrio splendidus, Staphylococcus aureus and Yarrowia lipolytica, the mRNA transcripts of CfmtMnSOD in hemocytes all significantly increased. The purified rCfmtMnSOD protein exhibited Mn²⁺ dependent specific and low stable enzymatic activities. After Vibrio challenge, the cumulative mortality of CfmtMnSOD-suppressed scallops was significantly higher than those of control groups and the semi-lethal time for CfmtMnSOD-suppressed scallops was rather shorter than those of control groups either. Moreover, the final mortality rate of CfmtMnSOD-suppressed group was significant higher than those of control groups, even without Vibrio challenge. All these results indicated that CfmtMnSOD was efficient antioxidant enzyme involved in the innate immunity, and also essential for the survival of C. farreri.

Effects of tannery wastewater exposure on adult Drosophila melanogaster

Our aim was to evaluate the effects of exposure to tannery wastewater on mortality and/or antioxidant enzyme system in adult wild-type Canton-S Drosophila melanogaster. Exposure to tannery wastewater induced a concentration-dependent lethality in adult Canton-S flies. Tannery wastewater was able to alter antioxidant enzyme activities, specifically glutathione peroxidase-like and glutathione S-transferase, in adult Canton-S D. melanogaster. We conclude that D. melanogaster is a reliable model to evaluate the toxicity induced by tannery wastewater.

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.

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.

miR-122 promotes hepatic antioxidant defense of genetically improved farmed tilapia (GIFT, Oreochromis niloticus) exposed to cadmium by directly targeting a metallothionein gene

MicroRNAs (miRNAs) are small, non-coding RNAs that regulate target gene expression by binding to the 3'untranslated region (3'UTR) of the target mRNA. MiRNAs regulate a large variety of genes, including those involved in liver homeostasis and energy metabolism. Down-regulated levels of hepatic miR-122 were found in genetically improved farmed tilapia (GIFT, Oreochromis niloticus) exposed to cadmium (Cd) stress. Here, we report for the first time that reduction of miR-122 post-transcriptionally increased metallothionein (MT) mRNA levels by binding to its 3'UTR, as shown by a 3' UTR luciferase reporter assay. The expression levels of miR-122 were negatively related to MT levels in GIFT under Cd stress. We performed in vivo functional analysis of miR-122 by injecting the fish with a miR-122 antagomir. Inhibition of miR-122 levels in GIFT liver caused a significant increase in MT expression, affected white blood cell and red blood cell counts, and serum alanine and aspartate aminotransferase activities, and glucose levels, all of which may help to relieve Cd stress-related liver stress. miR-122 silencing modulated oxidative stress and stimulated the activity of antioxidant enzymes. Our findings indicate that miR-122 regulated MT levels by binding to the 3'UTR of MT mRNA, and this interaction affected Cd stress induction and the resistance response in GIFT. We concluded that miR-122 plays an important role in regulating the stress response in GIFT liver. Our findings may contribute to understanding the mechanisms of miRNA-mediated gene regulation in tilapia in response to environmental stresses.

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.

Effects of dietary oxidized konjac glucomannan sulfates (OKGMS) and acidolysis-oxidized konjac glucomannan (A-OKGM) on the immunity and expression of immune-related genes of Schizothorax prenanti

In the present study, konjac glucomannan (KGM) was degraded by H2O2, and then used trisulfonated sodium amine and HCl, individually, to obtain two kinds of derivatives: oxidized konjac glucomannan sulfates (OKGMS) and acidolysis-oxidized konjac glucomannan (A-OKGM). The effects of two OKGM modified products on the immune parameters and expressions of toll-like receptor 22 (TLR22), myeloid differentiation factor 88 (MyD88) and interferon regulatory factors 7 (IRF7) genes in Schizothorax prenanti were determined. The alternative haemolytic complement (ACH50) activity was found to be significantly increased by the OKGMS diets. The immunoglobulin M (IgM) level was significantly enhanced by the OKGMS diets. The lysozyme activity was significantly increased by both OKGMS and A-OKGM diets. The superoxide dismutase (T-SOD) activity in fish fed with all doses of OKGMS diets was significantly higher than that in fish fed with basal diet. The glutathione peroxidase (GSH-PX) activity in fish fed with 0.8% and 1.6% A-OKGM diets was significantly higher than control group. The malondialdehyde (MDA) level was significantly decreased by both OKGMS and A-OKGM diets. The 0.8% A-OKGM diet significantly up-regulated TLR22 gene expression in the head kidney and spleen. TLR22 gene expression was significantly promoted by all OKGMS diets in the mesonephros and liver. The MyD88 mRNA level in 1.6% A-OKGM group significantly increased in the head kidney. The low dose of OKGMS significantly induced the MyD88 gene expression in the mesonephros, gut and liver, while 0.8% A-OKGM group also showed a significantly enhanced MyD88 mRNA expression in the gut. High dose of OKGMS significantly increased the IRF7 mRNA expression in the mesonephros and spleen. Fish fed with low dose of A-OKGM showed significantly higher expression of IRF7 in the gut and liver. Present study suggested that OKGMS and A-OKGM can act as immunostimulant to improve the immune indexes and up-regulate the immune-related gene expressions.

Differential expression of CuZnSOD gene under low temperature stress in noble scallop Chlamys nobilis with different carotenoid content

The noble scallop Chlamys nobilis belongs to a warm-water mollusk and has been cultured in the sea of southern China since 1980s'. However, accidents of massive mortality have often occurred during the winter, and one of the reasons could be accumulation of harmful reactive oxygen species caused by lower temperature. Carotenoids are well known for their anti-oxidant function. To investigate whether carotenoids do play a role in mollusks' antioxidant defense system under lower temperature stress, an acute lower temperature experiment was conducted by using two types of scallops: the orange with higher carotenoids content and the brown with lower carotenoids content. Their CuZnSOD gene was cloned, mRNA expression levels were determined, and SOD activity and carotenoids content were measured. The complete CuZnSOD cDNA consists of 1078 nucleotides with an open reading frame encoding 154 amino acid residues, which has high identity with that of its sister species Chlamys farreri. The mRNA expression levels in both the mantle and gill from the orange scallops were significantly higher (P < 0.05) than that of the brown ones, but the result was the opposite in the blood. SOD activity in the mantle and gill from the orange scallops was significantly higher than (P < 0.05) that from the brown ones. Further, significantly positive correlations were found among CuZnSOD gene transcript levels, SOD activity and total carotenoids content in the orange scallops. The present results suggested that carotenoids could play roles in antioxidant defense system by upregulating gene expression under lower temperature stress in the noble scallop.

Effects of norfloxacin on hepatic genes expression of P450 isoforms (CYP1A and CYP3A), GST and P-glycoprotein (P-gp) in Swordtail fish (Xiphophorus Helleri)

The presence of antibiotics including norfloxacin in the aquatic environment may cause adverse effects in non-target organisms. But the toxic mechanisms of fluoroquinolone to fish species are still not completely elucidated. Thus, it is essential to investigate the response of fish to the exposure of fluoroquinolone at molecular or cellular level for better and earlier prediction of these environmental pollutants toxicity. The sub-chronic toxic effects of norfloxacin (NOR) on swordtail fish (Xiphophoru s helleri) were investigated by measuring mRNA expression of cytochrome P450 1A (CYP1A), cytochrome P450 3A (CYP3A), glutathione S-transferase (GST) and P-glycoprotein (P-gp) and their corresponding enzyme activities (including ethoxyresorufin O-deethylase, erythromycin N-demethylase and GST. Results showed that NOR significantly affected the expression of CYP1A, CYP3A, GST and P-gp genes in swordtails. The gene expressions were more responsive to NOR exposure than their corresponding enzyme activities. Moreover, sexual differences were found in gene expression and enzyme activities of swordtails exposed to NOR. Females displayed more dramatic changes than males. The study further demonstrated that the combined biochemical and molecular parameters were considered as useful biomarkers to improve our understanding of potential ecotoxicological risks of NOR exposure to aquatic organisms.

The immune system and its modulation mechanism in scallop

Scallops are a cosmopolitan family of bivalves, and some of them are highly prized as dominant aquaculture species. In the past decades, there have been increasing studies on the basic biology and immunology of scallops, and this review summarizes the research progresses of immune system and its modulation mechanism in scallop. As invertebrate, scallops lack adaptive immunity and they have evolved an array of sophisticated strategies to recognize and eliminate various invaders by employing a set of molecules and cells. It is evident that basic immune reactions such as immune recognition, signal transduction, and effector synthesis involved in immune response are accomplished in a variety of ways. They rely upon an extensive repertoire of phagocytosis, apoptosis and encapsulation of the circulating hemocytes for eliminating invasive pathogens, as well as the production of immune effectors that are active against a large range of pathogens or sensitive for the environmental stress. Furthermore, the molecular constitutions, metabolic pathways and immunomodulation mechanisms of the primitive catecholaminergic, cholinergic, enkephalinergic system and NO system in scallop are also discussed, which can be taken as an entrance to better understand the origin and evolution of the neuroendocrine-immune regulatory network in lower invertebrates.

The enkephalinergic nervous system and its immunomodulation on the developing immune system during the ontogenesis of oyster Crassostrea gigas

Enkephalinergic neuroendocrine-immune regulatory system is one of the most important neuroendocrine-immune systems in both vertebrates and invertebrates for its significant role in the immune regulation. In the present study, the early onset of enkephalinergic nervous system and its immunomodulation on the developing immune system during the ontogenesis of oyster Crassostrea gigas were investigated to illustrate the function of neural regulation on the innate immune system in oyster larvae. [Met(5)]-enkephalin (Met-ENK) was firstly observed on the marginal of the dorsal half of D-hinged larvae. Six immune-related molecules, including four PRRs (CgCTL-1, CgCTL-2, CgCTL-4, CgNatterin-3) and two immune effectors (CgTNF-1 and CgEcSOD) were detected in the early developmental stages of trochophore, D-hinged and umbo larvae of oyster. After incubated with [Met(5)]-enkephalin, the mRNA expression level of all the PRRs changed significantly (p < 0.05). In trochophore larvae, the expression level of CgNatterin-3 decreased dramatically (p < 0.05) at 6 h, and the expression level of CgCTL-4 was significantly down-regulated at 3 h and 6 h (p < 0.05), respectively. In D-hinged and umbo larvae, only CgCTL-1 was significantly down-regulated and the differences were significant at 3 h and 6 h (p < 0.05), while the expression level of CgCTL-2 and CgCTL-4 increased significantly at 3 h after treatment (p < 0.05). Moreover, the expression levels of immune effectors were up-regulated significantly at 3 h and 6 h in trochophore larvae (p < 0.05). The expression level of CgTNF-1 in both blank and experiment groups was up-regulated but there was no significant difference in D-hinged larvae stage. On the contrary, the expression level of CgEcSOD in D-hinged larvae decreased dramatically at 3 h and 6 h after [Met(5)]-enkephalin incubation (p < 0.05). In umbo larvae, the expression level of CgTNF-1 and CgEcSOD in the experiment group increased significantly at 6 h after [Met(5)]-enkephalin treatment (p < 0.05), while no significant difference was found in the blank group. In addition, the anti-bacterial activities of the total protein extract from trochophore, D-hinged and umbo larvae increased significantly (p < 0.05) at both 3 h and 6 h after [Met(5)]-enkephalin incubation compared to that in the blank group, and PO activities of both D-hinged and umbo larvae total protein extract increased significantly (p < 0.05) while no significant difference was observed in trochophore larvae. The PO activities of the total protein extract in all the experiment groups decreased after the treatment with [Met(5)]-enkephalin for 6 h, but no significant difference was observed when compared to the blank group. Furthermore, after incubation for 6 h, the concentration of both CgTNF-1 and CgIL17-5 increased dramatically compared to that in the blank group (p < 0.05). These results together indicated that the enkephalinergic nervous system of oyster was firstly appeared in D-hinged larvae, while the primitive immune defense system existed in the region of prototroch in trochophore larvae and developed maturely after D-hinged larvae. The developing immune system could be regulated by the neurotransmitter [Met(5)]-enkephalin released by the neuroendocrine system in oyster C. gigas.

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

Superoxide dismutases (SODs) belong to a significant and ubiquitous family of metalloenzymes for eliminating excess reactive oxygen species (ROS). In this paper, the complete open reading frames (ORFs) of intracellular Cu/Zn-SOD (icCu/Zn-SOD), Mn-SOD and extracellular Cu/Zn-SOD (ecCu/Zn-SOD) were identified from the large yellow croaker (Pseudosciaena crocea, designated as LycSOD1, LycSOD2 and LycSOD3). The sequences were 465 bp, 678 bp and 645 bp (GenBank accession no. KJ908287, KJ908285 and KJ908286), encoding 154, 225 and 215 amino acid (aa) residues respectively. The deduced aa sequences of LycSOD1, LycSOD2 and LycSOD3 shared high identity to the known icCu/Zn-SODs, Mn-SODs and ecCu/Zn-SODs with BLASTp and Phylogenetic analysis. Two conserved Cu-/Zn-binding sites (H-44, H-47, H-64, H-121 for Cu binding and H-64, H-72, H-81, D-84 for Zn binding in LycSOD1, H-98, H-100, H-115, H-164 for Cu binding and H-115, H-163, H-166, D-169 for Zn binding in LycSOD3) and one conserved manganese coordinating sites (H-57, H-101, D-186, H-190 in LycSOD2) were identified. The total length of DNA sequences of LycSOD1, LycSOD2 and LycSOD3 were 3447 bp, 3387 bp and 3886 bp respectively, and there were 4 introns and 5 exons in Cu/Zn-SODs (LycSOD1 and LycSOD3), but only 3 exons and 2 introns in LycSOD3. Spatial expression analysis indicated the highest mRNA expression of three SODs all appeared in liver among eight detected tissues, the highest expression level was LycSOD1, then LycSOD2 and the lowest was LycSOD3 for almost each tissue. The expression of LycSOD1, LycSOD2 and LycSOD3 mRNA were all up-regulated in liver after Vibrio alginolyticus stimulation. The temporal expression peak of LycSOD1 and LycSOD2 were around 9-fold and 8-fold compared to control respectively, whereas, LycSOD3 got the highest level at 48 h post-injection (about 4.2-fold). All the results gave several new and useful evidences for further understanding the regulatory mechanism of superoxide dismutases in the innate immune system of sciaenidae fish.

Cloning of a putative extracellular Cu/Zn superoxide dismutase and functional differences of superoxide dismutases in invasive and indigenous whiteflies

Superoxide dismutases (SODs) are a group of important antioxidant defense enzymes. In this study, a putative extracellular Cu/Zn superoxide dismutase (ecCuZnSOD) complementary DNA was cloned and characterized from the whitefly, Bemisia tabaci. Quantitative polymerase chain reaction analysis showed that the expression level of BtecCuZnSOD was more than 10-fold higher in the invasive Middle East Asia Minor 1 (MEAM1) than in the native Asia II 3 species of the B. tabaci species complex. After exposure to low temperature (4 °C), the expression of Bt-ecCuZnSOD gene was significantly up-regulated in MEAM1 but not in Asia II 3. Furthermore, the expression level of B. tabaci intracellular CuZnSOD (Bt-icCuZnSOD), Bt-ecCuZnSOD and mitochondrial MnSOD (Bt-mMnSOD) was compared after transferring MEAM1 and Asia II 3 whiteflies from favorable (cotton) to unfavorable host plants (tobacco). On cotton, both CuZnSOD genes were expressed at a higher level in MEAM1 compared with Asia II 3. Interestingly, after transferring onto tobacco, the expression of Bt-ecCuZnSOD was significantly induced in Asia II 3 but not in MEAM1. On the other hand, while Bt-mMnSOD was expressed equally in both species on cotton, Bt-mMnSOD messenger RNA was up-regulated in MEAM1 on tobacco. Consistently, enzymatic activity assays of CuZnSOD and MnSOD demonstrated that CuZnSOD might play an important protective role against oxidative stress in Asia II 3, whereas MnSOD activation was critical for MEAM1 whiteflies during host adaptation. Taken together, our results suggest that the successful invasion of MEAM1 is correlated with its constitutive high activity of CuZnSOD and inducible expression of MnSOD under stress conditions.

The role of Cu/Zn-SOD and Mn-SOD in the immune response to oxidative stress and pathogen challenge in the clam Meretrix meretrix

The copper/zinc superoxide dismutase (Cu/Zn-SOD) and manganese superoxide dismutase (Mn-SOD) could effectively eliminate reactive oxygen species (ROS) and maintain the redox balance of immune system. In the present study, the potential synergy of Cu/Zn-SOD and Mn-SOD in immune system was investigated in the clam Meretrix meretrix. The expression of Cu/Zn-SOD mainly distributed in hepatopancreas and that of Mn-SOD was higher in gill of M. meretrix, and their mRNA and protein activity paralleled with each other. In response to H2O2 challenge, Cu/Zn-SOD mRNA showed significantly higher level at 24 h post-challenge and Mn-SOD mRNA was significantly higher at 12 and 24 h post-challenge in the experimental clams than in the control clams (P<0.05). After injection with Vibrio-parahaemolyticus-related bacterium (MM21), the Cu/Zn-SOD mRNA was significantly up-regulated at 24 h and 48 h post-injection and Mn-SOD mRNA was significantly higher at 24 h post-injection in MM21-injected clams than in control clams (P<0.05), suggesting that both of them might involve in the immune defense to Vibrio challenge. The mRNA expression of Cu/Zn-SOD and Mn-SOD was examined in a Vibrio-resistant population and a control population after MM21 immersion challenge. The increased transcription of Cu/Zn-SOD and Mn-SOD in the resistant population suggested both of them could benefit the immune system to defend against pathogen infection. As expression of Mn-SOD mRNA depended on stimuli and was more easily inducible, its response to H2O2 and Vibrio challenge was earlier than Cu/Zn-SOD. Our study suggested the redox balance might play an important role in M. meretrix to resist pathogen infection.

Identification and expression of antioxidant and immune defense genes in the surf clam Mesodesma donacium challenged with Vibrio anguillarum

The immune system in marine invertebrates is mediated through cellular and humoral components, which act together to address the action of potential pathogenic microorganisms. In bivalve mollusks biomolecules implicated in oxidative stress and recognition of pathogens have been involved in the innate immune response. To better understand the molecular basis of the immune response of surf clam Mesodesma donacium, qPCR approaches were used to identify genes related to its immune response against Vibrio anguillarum infection. Genes related to oxidative stress response and recognition of pathogens like superoxide dismutase (MdSOD), catalase (MdCAT), ferritin (MdFER) and filamin (MdFLMN) were identified from 454-pyrosequencing cDNA library of M. donacium and were evaluated in mantle, adductor muscle and gills. The results for transcripts expression indicated that MdSOD, MdFLMN and MdFER were primarily expressed in the muscle, while MdCAT was more expressed in gills. Challenge experiments with the pathogen V. anguillarum had showed that levels of transcript expression for MdSOD, MdCAT, MdFER, and MdFLMN were positively regulated by pathogen, following a time-dependent expression pattern with significant statistical differences between control and challenge group responses (p<0.05). These results suggest that superoxide dismutase, catalase, ferritin and filamin, could be contributing to the innate immune response of M. donacium against the pathogen V. anguillarum.

Identification and analysis of an intracellular Cu/Zn superoxide dismutase from Sepiella maindroni under stress of Vibrio harveyi and Cd2+

Superoxide dismutases (SODs) are ubiquitous family of metalloenzymes involved in protecting organisms from excess reactive oxygen species damage. In this paper, a novel intracellular Cu/ZnSOD from Sepiella maindroni (designated as SmSOD) was identified and characterized. The full-length cDNA sequence of SmSOD (GenBank accession No. KF908850) was 709 bp containing an open reading frame (ORF) of 459 bp, encoding 153 amino acid residues peptide with predicted pI/MW (6.02/15.75 kDa), a 131 bp-5'- and 116 bp-3'- untranslated region (UTR). BLASTn analysis and phylogenetic relationship strongly suggested that the sequence shared high similarity with known Cu/Zn SODs. Several highly conserved motifs, including two typical Cu/Zn SOD family domains, two conserved Cu-/Zn-binding sites (H-47, H-49, H-64, H-120 for Cu binding, and H-64, H-72, H-81, D-84 for Zn binding) and intracellular disulfide bond (C-58 and C-146), were also identified in SmSOD. Time-dependent mRNA expression of SmSOD in hepatopancreas was recorded by quantitative real-time RT-PCR after Vibrio harveyi injection and Cd(2+) exposure. The results indicated that SmSOD was an acute-phase protein involved in the immune responses against pathogens and biological indicator for metal contaminants in aquatic environment.

Acetylcholine modulates the immune response in Zhikong scallop Chlamys farreri

Acetylcholine (ACh) is an indispensable neurotransmitter and neuromodulator in the cholinergic nervous system and it is implicated in the dynamic modulation of immune response in vertebrates. Although ACh has also been identified in most invertebrates, the knowledge about its immunomodulation is still limited. In the present study, the immunoreactivities of ACh and acetylcholinesterase (AChE) were observed in all the tested tissues of scallop Chlamys farreri, including adductor muscle, mantle, gill, hepatopancreas, kidney and gonad. The ACh concentration in the supernate of scallop hemolymph increased from 11.59 ± 0.27 to 14.36 ± 0.17 μM L(-1) at 6 h after LPS (0.5 mg ml(-1)) stimulation, and increased to 15.51 ± 1.20 μM L(-1) at 3 h after the stimulation of tumor necrosis factor alpha (TNF-α) (50 ng ml(-1)). After LPS stimulation, the mRNA expression levels of superoxide dismutase (CfSOD), catalase (CfCAT) and lysozyme (CfLYZ) in hemocytes increased significantly at 3 h (P < 0.05), 6 h (P < 0.05) and 12 h (P < 0.05), respectively. Compared with the LPS treatment, the induction of CfSOD, CfCAT and CfLYZ expression in hemocytes was repressed effectively (P < 0.05) by the co-stimulation of LPS and ACh (5 × 10(-7) M) at 3 h (P < 0.05), 6 h (P < 0.05) and 12 h (P < 0.05), respectively. Furthermore, the expression level of CfCAT in hemocytes increased significantly after 12 h by the co-stimulation with LPS and ACh (P < 0.05). These results indicated collectively that the scallop cholinergic nervous system could be activated by immune stimulations, and it might play an essential role in immunomodulation of scallops.

Maternal transfer of immunity in scallop Chlamys farreri and its trans-generational immune protection to offspring against bacterial challenge

Maternal immunity plays a crucial role in protecting the offspring at early stages of life and contributes a trans-generational effect on the offspring's phenotype. In the present study, maternal transfer of immunity and its trans-generational effect on offspring in scallop Chlamys farreri were investigated. The proteins including CfLGBP, CfLBP/BPI, CfLYZ and CfCu/Zn-SOD existed in the scallop eggs with high level while CfLec-3 was not detected. In contrast, the mRNA levels of these proteins were extremely low except that of CfCu/Zn-SOD. The protein extracts of scallop eggs exhibited remarkable agglutination activity and bactericidal effect against gram-negative bacteria Escherichia coli and Vibro anguillarum, and fungi Pichia pastoris. When the maternal scallops were stimulated with heat-killed V. anguillarum, the mRNA levels of CfLBP/BPI and CfLYZ in their offspring were expressed significant higher in D-shaped larvae. Furthermore, the protein levels of CfLBP/BPI and CfCu/Zn-SOD in the offspring of maternal immune stimulation group were higher than that of control at almost all the developmental stages, while the level of CfLec-3 and CfLYZ was higher than that of control just in eggs or trochophore, respectively. A significant enhancement of Cu/Zn-SOD and antibacterial activities was also observed in eggs, 4-cell embryos and trochophore of offspring from immune stimulated mother scallops. Moreover, the mortality of offspring from the immune stimulated mother scallops was significantly lower than that of control after bacterial challenge, especially in trochophore. The results indicated that scallop eggs or embryos received maternal derived immune competence to defense against the invading pathogens, and the maternal scallops received an immune stimulation endowed their offspring with a trans-generational immune capability to protect them against infections effectively.

Differential effects of metal contamination on the transcript expression of immune- and stress-response genes in the Sydney Rock oyster, Saccostrea glomerata

Environmental contamination by metals is a serious threat to the biological sustainability of coastal ecosystems. Our current understanding of the potential biological effects of metals in these ecosystems is limited. This study tested the transcriptional expression of immune- and stress-response genes in Sydney Rock oysters (Saccostrea glomerata). Oysters were exposed to four metals (cadmium, copper, lead and zinc) commonly associated with anthropogenic pollution in coastal waterways. Seven target genes (superoxide dismutase, ferritin, ficolin, defensin, HSP70, HSP90 and metallothionein) were selected. Quantitative (real-time) PCR analyses of the transcript expression of these genes showed that each of the different metals elicited unique transcriptional profiles. Significant changes in transcription were found for 18 of the 28 combinations tested (4 metals × 7 genes). Of these, 16 reflected down-regulation of gene transcription. HSP90 was the only gene significantly up-regulated by metal contamination (cadmium and zinc only), while defensin expression was significantly down-regulated by exposure to all four metals. This inhibition could have a significant negative effect on the oyster immune system, promoting susceptibility to opportunistic infections and disease.

Molecular characterization of a manganese superoxide dismutase and copper/zinc superoxide dismutase from the mussel Mytilus galloprovincialis

The full-length cDNA sequences coding respectively for a manganese superoxide dismutase (Mg-MnSOD) and copper/zinc superoxide dismutase (Mg-CuZnSOD) were cloned from Mytilus galloprovincialis. Mg-MnSOD and Mg-CuZnSOD cDNAs encoded a polypeptide of 228 and 211 amino acids, respectively. Sequence analysis indicated Mg-MnSOD was a mitochondrial MnSOD and Mg-CuZnSOD was an intracellular CuZnSOD. Multiple alignment analysis showed that both Mg-MnSOD and Mg-CuZnSOD sequences had the common features conserved in MnSODs and CuZnSODs, respectively. Phylogenetic analysis revealed that Mg-MnSOD clustered together with MnSODs from other mollusks, whereas Mg-CuZnSOD clustered with other mollusk intracellular CuZnSODs with a wider phylogenetic distance. By quantitative real-time RT-PCR (qPCR) analysis, both Mg-MnSOD and Mg-CuZnSOD transcripts were detected in all tissues examined with the highest expression level in hepatopancreas. Following bacterial challenge, the expression level of Mg-MnSOD and Mg-CuZnSOD increased first and subsequently decreased to the original level in hemocytes. In hepatopancreas, Mg-CuZnSOD mRNA was up-regulated significantly at 72 h and 96 h post challenge, while the level of Mg-MnSOD transcript had no significant change. Therefore, Mg-MnSOD and Mg-CuZnSOD expressions were inducible and they were probably involved in the immune response against bacterial challenge. These results suggest that these SODs may play important roles in the immune defense system of M. galloprovincialis and perhaps contribute to the protective effects against oxidative stress in this mussel.

The expression of immune-related genes during the ontogenesis of scallop Chlamys farreri and their response to bacterial challenge

In the present study, the expression of some immune-related genes was examined as indicator to understand the development of immune defense system during the ontogenesis of scallop Chlamys farreri. The mRNA transcripts of pattern-recognition receptors (PRRs) including CfPGRP-S1, CfLGBP, CfLec-1 and CfLec-3 were observed at a low level or even undetected at early developmental stages from eggs to blastula, and then began to increase overwhelmingly in trochophore. For the genes of immune effector including CfLYZ, CfLBP/BPI, CfSOD and CfCAT, their mRNA transcripts were higher expressed in embryos, and increased significantly in D-hinged or early veliger larvae. The whole-mount immunofluorescence assay revealed two immunoreactive spots of CfPGRP-S1 were first observed in the mid-ventral region of prototroch in trochophore, and the immunopositive fluorescence of CfLGBP, CfLec-1 and CfLec-3 appeared at the same spots in early D-hinged larvae. Most of the PRRs were located in velum, mouth, esophagus and stomach region in early and mid-veliger larvae, and especially the strong immunopositive fluorescence of CfLec-3 was observed in velum. The immunoreactive areas of CfLYZ, CfLBP/BPI, CfSOD and CfCAT were observed in trochophore and early D-hinged larvae. After D-hinged larvae, they distributed in different tissues from the edge of velum, mouth, esophagus to the region around digestive gland. After bacterial challenge, the mRNA expression of CfLGBP, CfLec-1 and CfLec-3 did not change significantly in trochophore, while a down-regulation of CfPGRP-S1 was observed at 6 h (P < 0.05). The expression of CfPGRP-S1 and CfLGBP decreased or increased inversely in D-hinged and late veliger larvae respectively, whereas CfLec-1 and CfLec-3 increased significantly during 6-24 h after bacterial challenge in the two stages (P < 0.05). In contrast, the expressions of immune effectors in trochophore and late veliger larvae were significant up-regulated at 6 h, 12 h or 24 h after bacterial challenge (P < 0.05). However, in late D-hinged larvae, CfLYZ and CfSOD expressions were significantly down-regulated at 6 h, while CfLBP/BPI expression was up-regulated at 6 h and 24 h post challenge (P < 0.05). These results indicated that the immune defense system of scallop might appear firstly in the mid-ventral region of prototroch in trochophore, and developed maturely after late D-hinged larvae. The developing immune system in the D-hinged and late veliger larvae could respond to the immune stimulation in different manner.

Research progress on the mollusc immunity in China

The economical and phylogenic importance of mollusc has led an increasing number of investigations giving emphasis to immune defense mechanism. This review discusses the advances in immunological study of mollusc in China, with special reference to dominant aquaculture species over the past decades. As an invertebrate group, molluscs lack adaptive immunity and consequently they have evolved sophisticated strategies of innate immunity for defense against pathogens. This review aims to present the various immunologically significant pattern recognition receptors (PRRs), such as Toll-like receptors (TLRs), lectins, lipopolysaccharide and β-1, 3-glucan binding protein (LGBP), scavenger receptors (SRs) employed by mollucans. This work also highlights immune proteolytic cascade, TLR signaling pathway and an extensive repertoire of immune effectors including antimicrobial peptide, lysozyme, antioxidant enzyme and heat shock protein. Further, the review presents the preliminary progress made on the catecholaminergic neuroendocrine system in scallop and its immunomodulation function to throw light into neuroendocrine-immune regulatory network in lower invertebrates.

Transcriptional response of lysozyme, metallothionein, and superoxide dismutase to combined exposure to heavy metals and bacteria in Mactra veneriformis

The response of the defense components lysozyme (LYZ), metallothionein (MT), and superoxide dismutase (SOD) to combined exposure to heavy metals and bacteria was assessed at transcriptional level in the surf clam Mactra veneriformis. First, the full-length LYZ cDNA containing 808 nucleotides and encoding 194 deduced amino acids was identified from the clam. Multiple alignments revealed that MvLYZ had a high identity with invertebrate-type LYZs from other mollusks. Next, clams were exposed to Vibrio parahaemolyticus and a mixture of cadmium and mercury, alone or in combination, for 7 days. Cumulative mortality of clams and mRNA expressions of the three defense components were analyzed. The highest cumulative mortality took place in the combined treatment on day 7. The expression of the three genes was up-regulated in response to treatments compared to the control with different response times and transcriptional levels; the response to combined exposure occurred earlier than to single exposure. Among the experimental groups, MvLYZ expression and MvSOD expression peaked in the combined treatment on day 3, whereas MvMT expression peaked in heavy metals treatment on day 5. Furthermore, interactive effects of heavy metals and Vibrio on transcriptional response changed over the exposure time. Therefore, transcriptional regulation of the three genes under combined exposure was more complex than under single exposure.

Assessment of toxic effects of triclosan on the swordtail fish (Xiphophorus helleri) by a multi-biomarker approach

The toxic effects of triclosan (TCS) on the swordtail fish (Xiphophorus helleri) were assessed based on various biomarkers including enzymatic activities of ethoxyresorufin O-deethylase (EROD), erythromycin N-demethylase (ERND) and glutathione-s-transferase (GST) and mRNA expression levels of CYP1A, CYP3A, glutathione S-transferase (GST) and P-glycoprotein (P-gp). The acute toxicity test showed the LC(50) value of 1.47 mg L(-1) for TCS. The mRNA expressions of CYP1A, CYP3A, GST and P-gp showed dose-effect relationships in female swordtail fish when exposed to TCS, These mRNA expression levels were found more sensitive to TCS exposure than the enzymatic activities of EROD, ERND and GST do. In addition, the male fish displayed higher gene expression levels and more dramatic changes in enzyme activities than the females did. Our data further demonstrated that TCS was a typical inducer to Phase I and Phase II metabolism enzymes and genes, suggesting it is a potential ecotoxicological risk to aquatic ecosystems.