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

Differential effects of ocean warming and BDE-47 on mussels with various personalities

Marine warming and polybrominated diphenyl ethers (PBDEs) pollution are two of the most concerning environmental problems in recent years. However, the impact of their co-occurrence on marine bivalves and the tolerance of bivalves with different traits remain unknown. In this study, thick shell mussels Mytilus coruscus were divided into two personalities according to individual feeding and byssus growth. The reliability of the classification was validated by respiration, self-organization, and post-stress behavior. Then, the survival rate, hemolymph immunity, and digestive glands oxidase activity of classified mussels were evaluated after 21 days of compound exposure to warming and BDE-47. The results showed that mussels could be divided into proactive and reactive types consistently. Compared to reactive mussels, proactive mussels exhibited some traits, such as faster food recovery, more byssus growth, higher metabolic rate, and more efficient clustering. Both single or combined warming and BDE-47 exposure impacted the individual survival, hemolymph, and antioxidase of mussels. Notably, the negative impacts of BDE-47 were exacerbated by warming. Moreover, proactive mussels displayed better adaptability with higher survival rates along with less damage to hemolymph immunity and antioxidant ability compared to reactive ones when facing environmental challenges. This study highlights potential risks associated with the coexistence of marine warming and PBDEs pollution while demonstrating differential fitness among individuals with distinct personalities.

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.

Vitamin C regulates the production of reactive oxygen species through Wnt10b signaling in the gill of zebrafish

In this study, the mechanism that vitamin C (VC) regulates the production of reactive oxygen species (ROS) through Wnt10b signaling was investigated in the gill of zebrafish (Danio rerio). The results showed that 0.5 and 1.0 g/kg VC diets induced the gene expression of Wnt10b, β-catenin, SOD, CAT, and GSH-PX in gill. In addition, VC decreased the levels of H₂O₂, O₂^·- and ·OH, whereas the activities of SOD, CAT, and GSH-PX were increased by VC in the gill of zebrafish. To evaluate the role of Wnt10b in regulating oxidative stress, Wnt10b RNA was further interfered and the gene expression and activities of antioxidant enzymes were detected in gill. The result of Wnt10b RNA interference showed that Wnt10b signaling played a key role in regulating the gene expression of SOD, CAT, and GSH-PX. In all, VC may regulate the production of ROS through Wnt10b signaling in the gill of zebrafish (Danio rerio).

Using meiobenthic taxa, nematofauna biological traits, and bacterial abundance to assess the effects of the polybrominated diphenyl ethers compound: Case study of tetrabromo diphenyl ether BDE-47

Trophic web structuring in aquatic sediments is dependent on the biological interactions between metazoans and microbial communities. The presence of pollutants in these biotas can therefore impact the meiofauna structure via the modification of the microbial communities. The current study examined in a laboratory bioassay the response of meiobenthic communities, particularly marine nematode taxa from the Bizerte Lagoon to the effect of the most detected polybrominated diphenyl ether in this aquatic environment, BDE-47. Four doses [D1 (2.5 ppb Dry weight (DW)), D2 (25 ppb DW), D3 (50 ppb DW), and D4 (100 ppb DW)] were gradually applied and sediment microcosms were incubated for 30 days in the presence or absence of meiofauna. Our results show that BDE-47-enriched sediments decreased the meiofaunal taxa and bacterial abundance. A lower taxonomic diversity of the nematodes' general structure was observed with all doses used. The numerical analysis of the two dimensional (2D) non-metric multidimensional scaling (nMDS) plots and the evolution of the relative abundances of each functional group of nematode genus assemblages revealed that the abundance of all biological traits was modified. Nevertheless, only three of the functional traits, adult length, feeding group, and amphid shape, showed a clear difference between the control and the treated microcosms. The similarity percentage analysis (SIMPER) revealed that the average dissimilarity between nematode genera communities and biological traits increased with BDE-47-enriched sediments. The nMDS second-stage ordination of inter-matrix rank correlations for matrices including genera and biological traits showed that the amphid shape was the functional trait closest to the generic distribution. Finally, the Principal Component Analysis (PCA) for the nematode biological traits and bacteria indicated a positive correlation of these microbes with the functional groups [1A, Cr, and ef], and a negative correlation only with the "cla"-type tail shape.

Ecotoxicity of polybrominated diphenyl ether (BDE-47) on a meiobenthic community with special emphasis on nematodes: Taxonomic and trophic diversity assessment

The response taxonomic and trophic of meiobenthic organisms, especially marine nematodes to polybrominated diphenyl ether (BDE-47) was studied using a community from Bizerte lagoon (Nord-East Tunisia). Four concentrations of BDE-47 [D1 (2.5 μg/kg dw), D2 (25 μg/kg dw), D3 (50 μg/kg dw), and D4 (100 μg/kg dw)] were applied, and responses were determined 30 days after exposure. Species abundance and all univariate indices were significantly affected in all treated microcosms compared to the control. The non-parametric cluster based on species abundance separated the nematode population into two groups: control + all treated microcosms. After grouping nematode species according to their trophic diversity, their abundance showed differential responses. The non-metric multi-dimensional scaling analysis and cumulative k-dominance based on the abundance of trophic groups abundances reflected significant separation between the control microcosm and each treatment condition. The correspondence analysis 2D plot generated from nematode species and trophic groups abundance showed the control microcosm was dominated by microvores, represented by two species of Terschellingia. However, when treated with the highest concentration of BDE-47, the community was occupied by the resistant trophic groups of facultative predators and epigrowth feeders represented by Metoncholaimus pristiurus and Paracomesoma dubium, respectively.

Nutritional manipulation to combat heat stress in poultry - A comprehensive review

Global warming and climate change adversely affect livestock and poultry production sectors under tropical and subtropical conditions. Heat stress is amongst the most significant stressors influencing poultry productivity in hot climate regions, causing substantial economic losses in poultry industry. These economic losses are speculated to increase in the coming years with the rise of global temperature. Moreover, modern poultry strains are more susceptible to high ambient temperature. Heat stress has negative effects on physiological response, growth performance and laying performance, which appeared in the form of reducing feed consumption, body weight gain, egg production, feed efficiency, meat quality, egg quality and immune response. Numerous practical procedures were used to ameliorate the negative impacts of increased temperature; among them the dietary manipulation, which gains a great concern in different regions around the world. These nutritional manipulations are feed additives (natural antioxidants, minerals, electrolytes, phytobiotics, probiotics, fat, and protein), feed restriction, feed form, drinking cold water and others. However, in the large scale of poultry industry, only a few of these strategies are commonly used. The current review article deliberates the different practical applications of useful nutritional manipulations to mitigate the heat load in poultry. The documented information will be useful to poultry producers to improve the general health status and productivity of heat-stressed birds via enhancing stress tolerance, oxidative status and immune response, and thereby provide recommendations to minimize production losses due to heat stress in particular under the growing global warming crisis.

Bioaccumulation of decabromodiphenyl ether affects the antioxidant system in the clam Mactra veneriformis

Antioxidant enzymes play vital roles against oxidative stress induced by decabromodiphenyl ether (BDE-209), being widespread in marine environment. However, the effect of BDE-209 on antioxidant enzymes remains poorly understood in marine bivalves. In this study, the clams Mactra veneriformis were exposed to 0.1, 1, and 10 μg/L BDE-209 for 7 days and then maintained in clean seawater for 3 days as the depuration. The bioaccumulation of BDE-209 and the effects on superoxide dismutase, catalase, and glutathione peroxidase were investigated. BDE-209 accumulation was concentration-dependent and decreased by 36%-52% after recovery. Malondialdehyde contents increased in a time- and dose-dependent manner. mRNA expression and activity of antioxidant enzymes changed with different patterns and recovered after depuration. These results suggested that antioxidant systems were triggered to protect the clams from oxidative damage caused by BDE-209. Thus, this research is helpful in elucidating the effect of BDE-209 on antioxidant system in marine bivalves.

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.

Responses of antioxidant defenses in the clam Mactra veneriformis to 2,2',4,4'‑tetrabromodiphenyl ether exposure

Antioxidant enzymes play essential roles against oxidative stress caused by 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), which is ubiquitous in marine environment and organisms. However, research on antioxidant responses to BDE-47 in marine bivalves is scarce. In this study, we identified the full-length cDNA of catalase (CAT), and glutathione peroxidase (GPx) in the clam Mactra veneriformis. Subsequently, the responses of CAT, GPx, and copper, zinc-superoxide dismutase (Cu, Zn-SOD) were investigated in the clams exposed to 0.1, 1, and 10 μg/L BDE-47 for 7 days, and then depurated in natural seawater for 3 days. MvCAT and MvGPx contained conserved sequences. The deduced amino acid sequences shared high similarity with CATs and GPxs in other mollusks. M. veneriformis accumulated BDE-47 in a dose-dependent manner and eliminated BDE-47 poorly. BDE-47 induced a time- and dose-dependent increase of malondialdehyde content. Both the dose and the duration had significant effect on mRNA expressions and activities of the three antioxidants. Cu, Zn-SOD responded to BDE-47 earlier than CAT and GPx. The antioxidant responses could recover after depuration. These results suggested that M. veneriformis could accumulate BDE-47 efficiently. Antioxidant enzymes were triggered to counter the oxidative stress generated by BDE-47. Cu, Zn-SOD acted as the first defense against oxidative stress, while CAT and GPx intervened later. This study is therefore helpful in understanding the antioxidant responses to PBDEs in marine bivalves.

Molecular cloning, characterization, expression and enzyme activity of catalase from planarian Dugesia japonica in response to environmental pollutants

Catalase (CAT) is an important antioxidant enzyme that protects aerobic organisms against oxidative damage by degrading hydrogen peroxide to oxygen and water. CAT mRNAs have been cloned from many species and employed as useful biomarkers of oxidative stress. In the present study, we cloned the cDNA sequence of CAT gene from freshwater planarian Dugesia japonica (designated as DjCAT) by means of RACE method. Sequence analysis and multiple alignment jointly showed that the full-length cDNA sequence consists of 1734 nucleotides, encoding 506 amino acids. Three catalytic amino acid residues of His71, Asn144 and Tyr354, two CAT family signature sequences of a proximal active site signature (60FDRERIPERVVHAKGGGA77) and a heme-ligand signature motif (350RLFSYRDTQ358) are highly conserved, suggesting that the DjCAT belongs to the NADPH and heme-binding CAT family and has similar functions. In addition, the transcriptional level of CAT gene and activity of CAT enzyme upon acute exposure of environmental pollutants glyphosate and 1-decyl-3-methylimidazolium bromide ([C10mim]Br) were investigated systematically. The variation of CAT mRNA expression in D. japonica was quantified by real-time PCR and the results indicated that it was up-regulated after exposure to glyphosate or [C10mim]Br with a dose-dependent manner but not linearly. Even though the variation trend of CAT activity upon glyphosate stress was not monotonously increased and inconsistent with that after [C10mim]Br exposure on day 1 and 3 sampling time, with the duration prolonged to day 5 they both presented a dose-dependent increase and the differences achieved extreme significance in all treated groups compared to the control. These findings suggested that DjCAT plays an important role in antioxidant defense in D. japonica, and the mRNA expression of CAT would also be used as an effective biomarker to monitor the pollution in aquatic environment just like its corresponding enzyme.

A novel biomarker for marine environmental pollution of CAT from Mytilus coruscus

Bivalves use anti-oxidative enzyme systems to defend themselves against excessive reactive oxygen species, which are often catalyzed by environmental pollution. As a key member of anti-oxidative enzyme family, catalase plays a crucial role in scavenging the high level of reactive oxygen species to protect organisms against various oxidative stresses. In this study, a catalase homologue was identified from Mytilus coruscus (named McCAT, KX957929). The open reading frame of McCAT was 1844bp with a 5' untranslated region of 341bp and a 3' untranslated region of 927bp. The deduced amino acid sequence was 512 residues in length with theoretical pI/MW 8.02/57.91kDa. BLASTn and phylogenetic analyses strongly suggested that it was a member of catalase, also known as CAT family for its conserved catalytic site motif and proximal heme-ligand signature motif. Real-time fluorescence quantitative PCR showed that constitutive expression of McCAT was occurred, with increasing order in mantle, adductor, gill, hemocyte, gonad and hepatopancreas. It was observed that bacterial infection and heavy metals stimulation up-regulated McCAT mRNA expression in hepatopancreas with time-dependent manners. The maximum expression appeared at 8h after pathogenic bacteria injecting, with 15-fold in Vibrio parahemolyticus and 60-fold in Aeromonas hydrophila than that of 0h. The highest point of McCAT mRNA appeared at different times for exposure to heavy metals with copper at day 5 (0.1mg/L 30-fold, 0.5mg/L 15-fold, 1.5mg/L 6-fold) and plumbum at day 3 (3.0mg/L 20-fold). The enzymatic activity analysis found that McCAT activity in the gill of M. coruscus was affected by heavy metals concentration. The results suggested that McCAT plays a significant role in antioxidation and the expression of McCAT can be used as a biomarker for detection of marine environmental pollution.

A molluscan TNF receptor-associated factor 2 (TRAF2) was involved in host defense against immune challenges

Tumor necrosis factor (TNF) receptor-associated factor 2 (TRAF2) is a member of the TRAF superfamily that acted as a key signal transduction protein and has been implicated in inflammatory and apoptosis processes in mammals. However, identification of TRAF2s in invertebrates is very limited and its function, in particular that under immune challenges, is still unknown. In this report, a molluscan TRAF2 gene (referred to as AwTRAF2) was cloned and characterized from the freshwater bivalve, Anodonta woodiana. The open reading frame (ORF) of AwTRAF2 was 1683 bp in length, which encoded a putative 560 amino acid-protein. The deduced AwTRAF2 sequence shared similar structural characteristics and close evolutionary relationship with mollusk TRAF2s. The tissue-specific expression analysis revealed that AwTRAF2 mRNA was broadly expressed in all tested tissues, with high expression in gill and hepatopancreas. In addition, in vivo injection experiments directly showed that AwTRAF2 mRNA levels in hepatopancreas were significantly up-regulated in response to bacterial pathogen (Vibrio alginolyticus and Staphylococcus aureus) and PAMPs (Lipopolysaccharides and Peptidoglycan) challenges. Moreover, fluorescence microscopy observations revealed that AwTRAF2 was mainly located in cytoplasm of HEK293T cells and its overexpression significantly increased the transcriptional activities of the NF-κB-Luc reporter gene in HEK293T cells. Taken together, this study provided the experimental evidence of the presence of a functional TRAF2 in freshwater bivalves, which revealed its involvement in host response to immune challenges in A. woodiana.

Tumor necrosis factor receptor-associated factor 3 from Anodonta woodiana is an important factor in bivalve immune response to pathogen infection

Tumor necrosis factor receptor-associated factor 3 (TRAF3) is a multifunctional adaptor protein in innate and acquired immune system that plays a key role in the regulation of the RIG-I-like receptor (RLR) and Toll-like receptor (TLR) signaling pathway in mammals. However, the immune function of TRAF3 homologs in freshwater mollusks is not well understood. In this study, we identified a bivalve TRAF3 gene (AwTRAF3) from Anodonta woodiana and investigated its potential roles during immune challenges. The present AwTRAF3 encoded a polypeptide of 562 amino acids with predicted molecular mass of 64.5 kDa and PI of 7.9. Similar to other reported TRAF3s, AwTRAF3 contained a RING finger domain, two TRAF domains with zinc finger domains, a coiled coli region and a conserved C-terminal meprin and TRAF homology (MATH) domain. Quantitative real-time PCR (qRT-PCR) analysis revealed that AwTRAF3 mRNA was broadly expressed in all of the examined tissues, with high expression in hepatopancreas, gill and heart. In addition, immune challenge experiments directly showed that transcript levels of AwTRAF3 in hepatopancreas were significantly regulated upon bacterial (Vibrio alginolyticus and Staphylococcus aureus) and viral (poly (I:C)) challenges, respectively. Moreover, GFP-tagged AwTRAF3 fusion protein was found to be located primarily in the cytoplasm in HEK293T cells. Altogether, these data provided the first experimental demonstration that freshwater mollusks possess a functional TRAF3 that was involved in the innate defense against bacterial and viral infection.

Response a chronic effects of PBDE-47: Up-regulations of HSP60 and HSP70 expression in freshwater bivalve Anodonta woodiana

Heat shock proteins (HSPs) play an important role in adaption of environmental stress by protein folding, membrane translocation, degradation of misfolded proteins and other regulatory processes. Our previous study showed oxidative stress generated from polybrominated diphenyl ether-47 (PBDE-47) could cause an acute toxicity on freshwater bivalve Anodonta Woodiana, but the effect of chronic toxicity need to be elucidated. In order to further investigate the chronic effect of PBDE-47, clams A. Woodiana were randomly divided into the PBDE-47 treated group administrated with PBDE-47 at a concentration 3.36 μg/L and control group treated with a similar volume dimethyl sulfoxide. Two complete HSP sequences were isolated from A. Woodianaa and respectively named AwHSP60 and AwHSP70. They were widely distributed in foot, gill, hepatopancreas, adductor muscle, heart, hemocytes and mantle. Administration of PBDE-47 could result in a significant up-regulation of AwHSP60 and AwHSP70 expressions in the hepatopancreas, gill and hemocytes. In the hepatopancreas, compared with that of control group, mRNA level of AwHSP60 increased more than 89.9% (P < 0.05) from day 1-15, AwHSP70 increased more 2.79 times (P < 0.01). In the gill, during experiment observed, expression of AwHSP60 increased more 2.09 times (P < 0.01) in contrasted with that of control group. Significant up-regulation of AwHSP70 expression showed a reversed U shape. In the hemocytes, AwHSP60 and AwHSP70 expressions of PBDE-47 treated group respectively increased more 2.09 times (P < 0.05) and 1.81 times (P < 0.05) compared with that of control group. These results indicated that up-regulations of AwHSP60 and AwHSP70 expression are contribute to enhancing adaption of bivalve A. Woodiana exposed to PBDE-47 treatment.

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.