Catalase eliminates reactive oxygen species and influences the intestinal microbiota of shrimp

Dietary Bacillus velezensis T23 fermented products supplementation improves growth, hepatopancreas and intestine health of Litopenaeus vannamei

This study aimed to elucidate the effects of dietary fermented products of Bacillus velezensis T23 on the growth, immune response and gut microbiota in Pacific white shrimp (Litopenaeus vannamei). Shrimp were fed with diets containing fermentation products of B. velezensis T23 at levels of (0, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 g/kg) for 4 weeks, to assess the influence on shrimp growth. The results showed that 0.3 and 0.4 g/kg T23 supplementation improved shrimp growth and feed utilization. Based on these results we selected these three diets (Control, 0.3T23 and 0.4T23) to assess the effect on immune response and gut microbiota of shrimp. Compared with the control, the 0.3T23 and 0.4T23 groups enhanced lipase and α-amylase activities in the gut significantly. Moreover, the 0.4T23 group decreased TAG and MDA levels in hepatopancreas, ALT and AST levels of serum significantly (P < 0.05). In hepatopancreas, CAT and SOD activities were improved observably and the MDA content was reduced markedly in both T23 groups. The expressions of antimicrobial related genes, Cru and peroxinectin in the 0.3T23 group, and proPO and peroxinectin in the 0.4T23 group were up-regulated remarkably (P < 0.05). Moreover, hepatopancreas of shrimp fed with a diet amended with T23 showed a significant down-regulated expression of nf-kb and tnf-α genes, while expressions of tgf-β was considerably up-regulated. Furthermore, serum LPS and LBP contents were reduced markedly in T23 groups. Intestinal SOD and CAT were noteworthy higher in T23 groups (P < 0.05). In the intestine of shrimp fed on the diet enriched with T23 the expression of nf-κb and tnf-α exhibited markedly down-regulated, whereas hif1α was up-regulated (P < 0.05). Besides, in the intestine of shrimp grouped under T23, Cru and peroxinectin genes were markedly up-regulated (P < 0.05). Dietary 0.3 g/kg T23 also upregulated the ratio of Rhodobacteraceae to Vibrionaceae in the gut of the shrimp. Taken together, the inclusion of B. velezensis T23 in the diet of shrimp enhanced the growth and feed utilization, enhanced hepatopancreas and intestine health.

Effects of environmental pollutant benzop[α]yrene on the innate immunity of Scylla paramamosain and its mechanism

Benzo[α]pyrene (BaP), a polycyclic aromatic hydrocarbon, is present in the aquatic environment and may be harmful to aquatic animals. We exposed the mud crab Scylla paramamosain to BaP for 7 days, the of superoxide dismutase (SOD), catalase (CAT), phenoloxidase (PO), lysozyme (LZM), glutathione (GSH), glutathione-S-transferase (GST), and acid phosphatase (ACP) activities in the hemolymph of mud crab were reduced. Additionally, the reactive oxygen species content was increased in mud crabs after exposed to BaP. When BaP concentration was increased, the total hemocyte count (THC), the survival rate of hemocytes and their proliferation were decreased. Histopathology analysis revealed damaged hepatopancreas cells, which indicating that BaP exposure is cytotoxic to crab hemocytes. However, the degree of DNA damage did not worsen with increasing BaP concentration. The expression levels of p53, MCM7, Caspase-3, and Myosin were changed with increasing concentration of BaP, which indicated that BaP exposure may affect apoptosis and phagocytosis in mud crabs. As BaP concentration was increased, the apoptosis rate of hemocytes was increased and the phagocytosis was decreased. These results confirmed that BaP exposure inhibited the innate immune response of mud crabs. A possible explanation for this effect is that BaP reduces the antioxidant enzyme activity and increases the reactive oxygen species content in mud crabs, thereby oxidizing and damaging hemocytes, which stimulates phagocytosis and apoptosis and negatively affects the innate immunity of S. paramamosain.

Human placental extract: a potential therapeutic in treating osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease marked by cartilage degradation and loss of function. Recently, there have been increased efforts to attenuate and reverse OA by stimulating cartilage regeneration and preventing cartilage degradation. Human placental extract (HPE) may be an option due to its anti-inflammatory, antioxidant, and growth stimulatory properties. These properties are useful in preventing cell death and senescence, which may optimize in-situ cartilage regeneration. In this review, we discuss the anatomy and physiology of the placenta, as well as explore in vivo and in vitro studies assessing its effects on tissue regeneration. Finally, we assess the potential role of HPE in cartilage regenerative medicine and OA. The Medline database was utilized for all studies that involved the use of HPE or human placenta hydrolysate. Exclusion criteria included articles not written in English, conference reviews, editorials, letters to the editor, surveys, case reports, and case series. HPE had significant anti-inflammatory and regenerative properties in vitro and in vivo. Furthermore, HPE had a role in attenuating cellular senescence and cell apoptosis via reduction of reactive oxidative species both in vitro and in vivo. One study explored the effects of HPE in OA and demonstrated reduction in cartilage catabolic gene expression, indicating HPE's effect in attenuating OA. HPE houses favorable properties that can attenuate and reverse tissue damage. This may be a beneficial therapeutic in OA as it creates a more favorable environment for in-situ cartilage regeneration. More well designed in-vitro and in-vivo studies are needed to define the role of HPE in treating OA.

Scavenger receptor B2, a type III membrane pattern recognition receptor, senses LPS and activates the IMD pathway in crustaceans

The immune deficiency (IMD) pathway is critical for elevating host immunity in both insects and crustaceans. The IMD pathway activation in insects is mediated by peptidoglycan recognition proteins, which do not exist in crustaceans, suggesting a previously unidentified mechanism involved in crustacean IMD pathway activation. In this study, we identified a Marsupenaeus japonicus B class type III scavenger receptor, SRB2, as a receptor for activation of the IMD pathway. SRB2 is up-regulated upon bacterial challenge, while its depletion exacerbates bacterial proliferation and shrimp mortality via abolishing the expression of antimicrobial peptides. The extracellular domain of SRB2 recognizes bacterial lipopolysaccharide (LPS), while its C-terminal intracellular region containing a cryptic RHIM-like motif interacts with IMD, and activates the pathway by promoting nuclear translocation of RELISH. Overexpressing shrimp SRB2 in Drosophila melanogaster S2 cells potentiates LPS-induced IMD pathway activation and diptericin expression. These results unveil a previously unrecognized SRB2-IMD axis responsible for antimicrobial peptide induction and restriction of bacterial infection in crustaceans and provide evidence of biological diversity of IMD signaling in animals. A better understanding of the innate immunity of crustaceans will permit the optimization of prevention and treatment strategies against the arising shrimp diseases.

Duox mediated ROS production inhibited WSSV replication in Eriocheir sinensis under short-term nitrite stress

Nitrite stress and white spot syndrome virus (WSSV) infection are major problems threatening the sustainable and healthy development of Eriocheir sinensis. Some studies have found that nitrite stress can lead to the production of reactive oxygen species (ROS), whereas synthetic ROS plays a vital role in the signaling pathway. However, whether nitrite stress influences the infection of crabs by WSSV remains unclear. NADPH oxidases, including NOX1-5 and Duox1-2, are important for ROS production. In the present study, a novel Duox gene (designated as EsDuox) was identified from E. sinensis. The studies found that nitrite stress could increase the expression of EsDuox during WSSV infection and decrease the transcription of the WSSV envelope protein VP28. Moreover, nitrite stress could increase the production of ROS, and the synthesis of ROS relied on EsDuox. These results indicated a potential "nitrite stress-Duox activation-ROS production" pathway that plays a negative role in WSSV infection in E. sinensis. Further studies found that nitrite stress and EsDuox could promote the expression of EsDorsal transcriptional factor and antimicrobial peptides (AMPs) during WSSV infection. Moreover, the synthesis of AMPs was positively regulated by EsDorsal in the process of WSSV infection under nitrite stress. Furthermore, EsDorsal played an inhibitory role in the replication of WSSV under nitrite stress. Our study reveals a new pathway for "nitrite stress-Duox activation-ROS production-Dorsal activation-AMP synthesis" that is involved in the defense against WSSV infection in E. sinensis during short-term nitrite stress.

Effects of hypoxia and reoxygenation on apoptosis, oxidative stress, immune response and gut microbiota of Chinese mitten crab, Eriocheir sinensis

Hypoxia causes irreversible damage to aquatic animals. However, few reports have explored the effect of hypoxia stress and reoxygenation on intestinal homeostatic imbalance and consequent hepatopancreas-intestine axis health in crustacean. Herein, 180 Chinese mitten crabs (Eriocheir sinensis) were equally divided into control (DO 7.0 ± 0.2 mg/L) and treatment groups. The treatment group was exposed with continuous hypoxic stress (DO 3.0 ± 0.1 mg/L) for 96 h and then reoxygenated (DO 6.9 ± 0.1 mg/L) for 96 h. The effects on intestines and hepatopancreas of Chinese mitten crab were investigated, and the role of gut microbiota in hypoxia induced damages was explored. Hypoxia impaired intestinal tissue structure, and decreased swelling and the number of goblet cells, which are features that did not significantly improve after reoxygenation. With prolonged hypoxic stress, the activities of antioxidant enzymes (LDH, SOD and CAT) and MDA content in intestine were significantly elevated. Moreover, the level of oxidative stress increased, which led to upregulated apoptosis rate and expression of apoptosis-related genes (Caspase 3, Caspase 8 and BAX). In addition, the expression of immune related genes (MyD88, ALF1, Relish and Crustin) in hepatopancreas and intestine was both significantly induced under hypoxia, which activated the immune defense mechanism of Chinese mitten crab to adapt to the hypoxic environment. Furthermore, diversity and relative abundance of gut microbiota decreased noticeably during hypoxic stress; the number of beneficial bacteria downregulated. Finally, KEGG pathway analysis revealed that nine pathways were significantly enriched in intestinal microorganisms, including autoimmune disease and environmental adaptation. Collectively, these results suggested that hypoxia negatively affected E. sinensis health by triggering oxidative stress, altering the composition of the gut microbiota and inhibiting the immune response.

Transcriptome and 16S rRNA Analyses Reveal That Hypoxic Stress Affects the Antioxidant Capacity of Largemouth Bass (Micropterus salmoides), Resulting in Intestinal Tissue Damage and Structural Changes in Microflora

Dissolved oxygen (DO) is a key factor affecting the health of aquatic organisms in an intensive aquaculture environment. In this study, largemouth bass (Micropterus salmoides) were subjected to acute hypoxic stress for 96 h (DO: 1.00 mg/L) followed by recovery under sufficient DO conditions (DO: 7.50 mg/L) for 96 h. Serum biochemical indices, intestinal histomorphology, the transcriptome, and intestinal microbiota were compared between hypoxia-treated fish and those in a control group. The results showed that hypoxia caused oxidative stress, exfoliation of the intestinal villus epithelium and villus rupture, and increased cell apoptosis. Transcriptome analyses revealed that antioxidant-, inflammation-, and apoptosis-related pathways were activated, and that the MAPK signaling pathway played an important role under hypoxic stress. In addition, 16S rRNA sequencing analyses revealed that hypoxic stress significantly decreased bacterial richness and identified the dominant phyla (Proteobacteria, Firmicutes) and genera (Mycoplasma, unclassified Enterobacterales, Cetobacterium) involved in the intestinal inflammatory response of largemouth bass. Pearson's correlation analyses showed that differentially expressed genes in the MAPK signaling pathway were significantly correlated with some microflora. The results of this study will help to develop strategies to reduce damage caused by hypoxic stress in aquacultured fish.

Hypomagnetic Field Exposure Affecting Gut Microbiota, Reactive Oxygen Species Levels, and Colonic Cell Proliferation in Mice

The gut microbiota has been considered one of the key factors in host health, which is influenced by many environmental factors. The geomagnetic field (GMF) represents one of the important environmental conditions for living organisms. Previous studies have shown that the elimination of GMF, the so-called hypomagnetic field (HMF), could affect the physiological functions and resistance to antibiotics of some microorganisms. However, whether long-term HMF exposure could alter the gut microbiota to some extent in mammals remains unclear. Here, we investigated the effects of long-term (8- and 12-week) HMF exposure on the gut microbiota in C57BL/6J mice. Our results clearly showed that 8-week HMF significantly affected the diversity and function of the mouse gut microbiota. Compared with the GMF group, the concentrations of short-chain fatty acids tended to decrease in the HMF group. Immunofluorescence analysis showed that HMF promoted colonic cell proliferation, concomitant with an increased level of reactive oxygen species (ROS). To our knowledge, this is the first in vivo finding that long-term HMF exposure could affect the mouse gut microbiota, ROS levels, and colonic cell proliferation in the colon. Moreover, the changes in gut microbiota can be restored by returning mice to the GMF environment, thus the possible harm to the microbiota caused by HMF exposure can be alleviated. © 2022 Bioelectromagnetics Society.

Copper-induced oxidative stress, transcriptome changes, intestinal microbiota, and histopathology of common carp (Cyprinus carpio)

Copper (Cu) is a common contaminant in aquatic environments, which could cause physiological dysfunction in aquatic organisms. However, few studies have comprehensively examined the impact of copper toxicity in freshwater fish over the past decade. In this research, the oxidative stress, liver transcriptome, intestinal microbiota, and histopathology of common carp (C. carpio) in response to Cu exposure were studied, by exposing juvenile carp to 0.2 mg/ml Cu²⁺ for 30 days. The results revealed that Cu²⁺ could induce significant changes in malondialdehyde (MDA) content and antioxidant enzyme (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx)) activity. The changes in antioxidant enzyme activities indicate that Cu can induce oxidative stress by generating reactive oxygen species (ROS) content. RNA-seq analysis of the liver identified 1069 differentially expressed genes (DEGs) after treatment with 2.0 mg/L Cu²⁺. Among the DEGs, 490 genes were upregulated and 579 genes were downregulated. GO functional enrichment analysis revealed that Cu could affect the fatty acid biosynthetic process, carnitine biosynthetic process, and activity of carboxylic acid transmembrane transporter. Meanwhile, the most significantly enriched KEGG pathway also included the lipid metabolism pathway. In addition, Cu²⁺ exposure increased bacterial richness and changed bacterial composition. At the phylum level, we found that the ratio of Bacteroidetes to Firmicutes was increased in the treatment carps, which can regulate intestinal epithelium function and reduce inflammation and immune responses. At the genus level, the abundances of 11 genera were significantly altered after exposure to Cu²⁺. The altered composition of the microbial community caused by Cu exposure may play a useful role in compensation of the intestinal lesions by Cu exposure. Furthermore, we found that Cu²⁺ exposure could cause histological alterations such as structural damage to the liver and intestines. The results of this research contribute to a better understanding of mechanisms related to Cu toxicity in fish.

Synergistic effects of exercise and catalase overexpression on gut microbiome

Exercise influences metabolic parameters in part by modulating redox stress and as recently suggested, by affecting the gut microbiome. However, whether excess endogenous antioxidant potentiates or interferes with the beneficial effects of exercise on the gut microbiome is not known. A comparison of the gut microbiome of C57Bl6 (C57/WT) mice to the 'stress-less' catalase overexpressing mice models ([Tg(CAT)± ] and Bob-Cat), that were either exercised or remained sedentary, showed differences in both alpha and beta diversity. The significant variation was explained by genotypes along with exercise, suggesting a synergistic relationship between exercise and genotypic traits. Linear discriminant analysis effect size (LEfSe) analysis also revealed differential taxa within the exercised/genotype cohorts in contrast to those within sedentary/genotype cohorts. Functional pathway predictions from PICRUSt2 showed enrichment for the metabolism of short-chain fatty acids, butanoate and propanoate pathways in exercised groups. Spearman correlations between enriched taxa and metabolic parameters showed correlations with body or fat weight in some of the cohorts. However, there were significant correlations of differential taxa among all cohorts against parameters that predict energy metabolism, such as respiratory exchange ratio and energy expenditure. Overall, our study showed that there was a synergistic beneficial influence of antioxidant overexpression and exercise on the gut microbiome.

A C-type lectin containing two carbohydrate recognition domains participates in the antibacterial response by regulating the JNK pathway and promoting phagocytosis

C-type lectins (CTLs) are important immune-related molecules in crustaceans. However, the immunologic mechanism by which CTLs eliminate invading pathogens is still unclear. In this study, we studied the antimicrobial mechanism of a CTL containing two carbohydrate recognition domains (DClec). After Aeromonas hydrophila challenge, several antimicrobial peptides (ALF1, ALF4, ALF5 and lys-i2) were upregulated. The transcript levels of ALF1, ALF4 and ALF5 were downregulated after A. hydrophila challenge in groups with DClec interference or inhibition compared with the control group. Similar results were obtained after c-Jun N-terminal kinase (JNK) interference. This finding indicates that DClec might regulate the JNK signalling pathway and subsequently adjust antimicrobial peptide (AMP) expression. Additionally, we found that DClec was secreted into the hemolymph. Recombinant protein DClec (rDClec) agglutinated gram-positive or gram-negative bacteria. Both rDClec and the native DClec in hemolymph bound to different bacteria. In this process, Ca²⁺ promoted the rDClec bacterial binding ability. After DClec interference, the phagocytosis ability of hemocytes was lower than that of the control group. Therefore, DClec can facilitate bacterial elimination by promoting AMPs expression and hemocyte phagocytosis.

Characterization of novel L-asparaginases having clinically safe profiles from bacteria inhabiting the hemolymph of the crab, Scylla serrata (Forskål, 1775)

L-asparaginase (ASNase) is the principal chemotherapeutic agent against different blood cancers. The risks associated with current clinical preparations demand screening for novel ASNases. Accordingly, the study was conducted to shortlist ASNases having clinically safer profiles from a novel niche, namely, microbes in the gut and hemolymph of apparently healthy Scylla serrata. A four-step strategic approach incorporating the essential requirements for clinically safer profiles was followed. The initial step through plate assay showed five (9.61%) potential ASNase producers. The relative prevalence of ASNase producers was higher in hemolymph (13.33%) than gut (4.5%). The positive isolates were identified as Priestia aryabhattai, Priestia megaterium, Bacillus altitudinis, Shewanella decolorationis, and Chryseomicrobium amylolyticum. Quantitative profiles revealed high ASNase production (114.29 to 287.36 U/mL) without any optimization, with an added advantage of the extracellular production. The second step for substrate specificity studies revealed the absence of L-glutaminase and urease activities in ASNases from C. amylolyticum and P. megaterium, the most desirable properties for safe clinical applications. This is the first report of glutaminase and urease-free ASNase from these two bacteria. The third step ensured type II nature of selected ASNases, the targeted form in clinical applications. The fourth step confirmed the activity and stability in human physiological conditions. Altogether, the results revealed two potential ASNases with clinically compatible profiles.

Nitric Oxide Synthase Regulates Gut Microbiota Homeostasis by ERK-NF-κB Pathway in Shrimp

The gut microbiota is a complex group of microorganisms that is not only closely related to intestinal immunity but also affects the whole immune system of the body. Antimicrobial peptides and reactive oxygen species participate in the regulation of gut microbiota homeostasis in invertebrates. However, it is unclear whether nitric oxide, as a key mediator of immunity that plays important roles in antipathogen activity and immune regulation, participates in the regulation of gut microbiota homeostasis. In this study, we identified a nitric oxide synthase responsible for NO production in the shrimp Marsupenaeus japonicus. The expression of Nos and the NO concentration in the gastrointestinal tract were increased significantly in shrimp orally infected with Vibrio anguillarum. After RNA interference of Nos or treatment with an inhibitor of NOS, L-NMMA, NO production decreased and the gut bacterial load increased significantly in shrimp. Treatment with the NO donor, sodium nitroprusside, increased the NO level and reduced the bacterial load significantly in the shrimp gastrointestinal tract. Mechanistically, V. anguillarum infection increased NO level via upregulation of NOS and induced phosphorylation of ERK. The activated ERK phosphorylated the NF-κB-like transcription factor, dorsal, and caused nuclear translocation of dorsal to increase expression of antimicrobial peptides (AMPs) responsible for bacterial clearance. In summary, as a signaling molecule, NOS-produced NO regulates intestinal microbiota homeostasis by promoting AMP expression against infected pathogens via the ERK-dorsal pathway in shrimp.

Immunotoxicity of polychlorinated biphenyls (PCBs) to the marine crustacean species, Scylla paramamosain

Polychlorinated biphenyls (PCBs) are persistent organic pollutants in environments, and they can negatively affect aquatic animal health. After 7 days of PCBs exposure, the activities of catalase, phenoloxidase, and superoxide dismutase and the total hemocyte count in the haemolymph were significantly decreased and the reactive oxygen species (ROS) content and phagocytic rate of hemocytes were significantly increased in mud crab Scylla paramamosain. Additionally, serum lysozyme, glutathione, glutathione-S-transferase, and glutathione peroxidase activities were significantly down-regulated in mud crab after PCBs exposure. The survival rate of crab hemocytes significantly declined as the PCBs concentration increased, indicating that PCBs had a cytotoxic effect on hemocytes. Exposure to increasing concentrations of PCBs also increased the degree of DNA damage in crab hemocytes. After PCBs exposure, the expression levels of P53 and caspase-3 in hemocytes were significantly up-regulated, which suggests that apoptosis was occurring. The apoptosis rate of hemocytes was up-regulated as the PCBs concentration increased, indicating that apoptosis was induced by the PCBs-activated caspase-3 pathway. These data suggest that exposure to PCBs hampered the immune response of mud crabs, most likely by (1) inducing ROS, causing DNA damage, and reducing the viability of hemocytes, (2) reducing the activities of antioxidant enzymes, and (3) inducing phagocytosis and apoptosis of hemocytes. And the final result of PCBs-induced immunotoxicity to mud crabs is the reduced bacterial disease resistance and survival rate of crabs under Vibrio alginolyticus challenge.

The antibacterial activity of erythrocytes from Clarias fuscus associated with phagocytosis and respiratory burst generation

It is widely known that red blood cells (RBCs) are responsible for respiration and the transport of gas. However, recent reports have also described the immune properties of RBCs, therefore creating new understanding for the functionality of RBCs. However, little is known about the immunological role of RBCs in bony fish. In this study, we used RBCs from Clarias fuscus as a model and demonstrate that these cells exhibited phagocytic ability with both latex beads and bacteria. Scanning electron microscopy and transmission electron microscopy provided visual confirmation of the phagocytotic process in RBCs. In addition, we used flow cytometry and fluorescence microscopy to analyse the rate of phagocytosis in RBCs. We found that RBCs exhibited stable phagocytotic ability with latex beads ranging from 0.5 to 1.0 μm in size. In response to bacterial stimulation, RBCs produced reactive oxygen species (ROS) and nitric oxide synthase (NOS), which are harmful to bacteria. RBCs also have an antioxidant system. Under conditions of oxidative stress, the expression levels of antioxidant enzymes, and particularly those of superoxide dismutase（SOD） increased significantly. Our results show that the erythrocytes of bony fish are phagocytic and also produce ROS which are toxic to bacteria. In addition, RBCs have an antioxidant system that removes excess ROS production to protect cells from oxidative damage.

Phycoerythrin from Colaconema sp. Has Immunostimulatory Effects on the Whiteleg Shrimp Litopenaeus vannamei and Increases Resistance to Vibrio parahaemolyticus and White Spot Syndrome Virus

Simple Summary

In this study, we found that phycoerythrin from Colaconema sp. can differentially stimulate the immune response of whiteleg shrimp in vitro and in vivo and could potentially be used as an immunomodulator in shrimp culture.

Abstract

We investigated whether phycoerythrin (PE), a pigment sourced from marine algae, could act as an immunomodulatory agent in whiteleg shrimp (Litopenaeus vannamei). To this end, PE was extracted and purified from a PE-rich macroalgae, Colaconema sp. Our in vitro analysis demonstrated that PE enhanced prophenoloxidase and phagocytosis activity but inhibited the production of reactive oxygen species in hemocytes. Additionally, the PE signal could be detected using an in vivo imaging system after its injection into the ventral sinus of the cephalothorax of whiteleg shrimp. The expression profiles of fourteen immune-related genes were monitored in hemocytes from whiteleg shrimp injected with 0.30 μg of PE per gram of body weight, and crustin, lysozyme, penaiedin 4, and anti-lipopolysaccharide factor showed up-regulated post-stimulation. The induction of immune genes and enhancement of innate immune parameters by PE may explain the higher survival rates for shrimp that received different doses of PE prior to being challenged with Vibrio parahaemolyticus or white spot syndrome virus compared to controls. Combined, these results show that PE from Colaconema sp. can differentially stimulate the immune response of whiteleg shrimp in vitro and in vivo and could potentially be used as an immunomodulator in shrimp culture.

Impacts of microplastics on three different juvenile shrimps: Investigating the organism response distinction

The effects of microplastics (MPs) on aquaculture animals have raised increasing concern, but studies on MPs contamination in cultured shrimp are still limited. Therefore, the responses of three widely farmed shrimp species to MPs, including Penaeus monodon (P. monodon), Marsupenaeus japonicas (M. japonicus) and Litopenaeus vannamei (L. vannamei), were investigated in this study. The results showed that the mortality of P. monodon, M. japonicus and L. vannamei were 47%, 53% and 20% respectively after 48 h of 300 mg/L MPs exposure. After 48 h of 100 mg/L MPs exposure, for P. monodon, the MPs content in water and excreta were significantly different from that in M. japonicus and L. vannamei. For genes expressions, the expression of catalase (Cat) was significantly increased and the expression of apoptosis protein (IAP) was inhibited in these three shrimps, but only the expression of Lysozyme (Lys) was increased in L. vannamei after MPs exposure. After 48 h of depuration, the Cat and IAP expression of P. monodon and M. japonicus was significant decreased while the IAP and Lys expression of L. vannamei still maintained at a high level. The results suggested that the metabolic rate of MPs in P. monodon was significantly higher than that in M. japonicus and L. vannamei. The tolerance of L. vannamei to MPs was higher than that of P. monodon and M. japonicas and their different responses in anti-microbial gene might be one of the reasons for the difference of their mortality. This study provides the first report comparing the organism response distinction in cultured shrimp and enriching to the understanding of the impact of MPs on ecosystem.

Experimental Infection of the Biomphalaria glabrata Vector Snail by Schistosoma mansoni Parasites Drives Snail Microbiota Dysbiosis

Host-parasite interaction can result in a strong alteration of the host-associated microbiota. This dysbiosis can affect the fitness of the host; can modify pathogen interaction and the outcome of diseases. Biomphalaria glabrata is the snail intermediate host of the trematode Schistosoma mansoni, the agent of human schistosomiasis, causing hundreds of thousands of deaths every year. Here, we present the first study of the snail bacterial microbiota in response to Schistosoma infection. We examined the interplay between B. glabrata, S. mansoni and host microbiota. Snails were infected and the microbiota composition was analysed by 16S rDNA amplicon sequencing approach. We demonstrated that the microbial composition of water did not affect the microbiota composition. Then, we characterised the Biomphalaria bacterial microbiota at the individual scale in both naive and infected snails. Sympatric and allopatric strains of parasites were used for infections and re-infections to analyse the modification or dysbiosis of snail microbiota in different host-parasite co-evolutionary contexts. Concomitantly, using RNAseq, we investigated the link between bacterial microbiota dysbiosis and snail anti-microbial peptide immune response. This work paves the way for a better understanding of snail/schistosome interaction and should have critical consequences in terms of snail control strategies for fighting schistosomiasis disease in the field.

Effects of dietary synbiotics supplementation methods on growth, intestinal health, non-specific immunity and disease resistance of Pacific white shrimp, Litopenaeus vannamei

The present study aims to investigate the effects of dietary synbiotics supplementation methods on growth, feed utilization, hepatopancreas and intestinal histology, non-specific immunity and microbiota community of Pacific white shrimp (Litopenaeus vannamei). A control diet was designed to contain 18% fish meal (CON), and then 3 g kg^-1 synbiotics (Bioture, consisting of Bacillus subtilis, Saccharomyces cerevisiae, β-glucan and mannan oligosaccharide, etc) was supplemented to the control diet with three methods, directly adding in diets for pelleting (DAP), spraying diets after pelleting at once (SDA), spraying diets before feeding every day (SDE). Shrimp with initial body weight of 1.5 ± 0.12 g were fed one of the four diets for 56 days. The results showed that dietary synbiotics significantly increased the weight gain (WG), apparent digestibility coefficient (ADC) of crude protein (CP) and dry matter (DM), hepatopancreatic protease activity and decreased feed conversion ratio (FCR) (P < 0.05). Among the three synbiotics-added diets, SDE group showed the best growth with significantly higher WG than DAP group (P < 0.05). Serum activities of total superoxide dismutase, catalase, acid phosphatase, lysozyme and alkaline phosphatase of synbiotics-added groups were significantly higher, and serum malondialdehyde level was significantly lower than those of the control (P < 0.05). The intestinal villus width and villus number were also increased by the supplementation of synbiotics. The cumulative mortality was reduced in the three synbiotics-added groups after challenging with Vibrio parahaemolyticus (P < 0.05), and SDE group showed a significantly lower mortality than the control and DAP groups (P < 0.05). In intestinal microbiota composition, the abundance of Lactococcus tended to increase and Vibro tended to decreased in SDA and SDE groups. In conclusion, dietary synbiotics improved the growth, feed utilization, intestine health and non-specific immunity of Pacific white shrimp, and spraying synbiotics on diet presented better performance than adding synbiotics in diet for pelleting.

Proteomic Analysis of the Hemolymph After Metschnikowia bicuspidata Infection in the Chinese Mitten Crab Eriocheir sinensis

The “milky disease” of the Chinese mitten crab, Eriocheir sinensis, is a highly lethal fungal disease caused by Metschnikowia bicuspidata infection. To elucidate the immune responses of the hemolymph of E. sinensis to M. bicuspidata infection, a comparative analysis of the hemolymph of E. sinensis infected with M. bicuspidata and that treated with phosphate buffered saline was performed using label-free quantitative proteomics. A total of 429 proteins were identified. Using a 1.5-fold change in expression as a physiologically significant benchmark, 62 differentially expressed proteins were identified, of which 38 were significantly upregulated and 24 were significantly downregulated. The upregulated proteins mainly included cytoskeleton-related proteins (myosin regulatory light chain 2, myosin light chain alkali, tubulin α-2 chain, and tubulin β-1 chain), serine protease and serine protease inhibitor (clip domain-containing serine protease, leukocyte elastase inhibitor, serine protein inhibitor 42Dd), catalase, transferrin, and heat shock protein 70. Upregulation of these proteins indicated that phenoloxidase system, phagocytosis and the ROS systems were induced by M. bicuspidata. The downregulated proteins were mainly organ and tissue regeneration proteins (PDGF/VEGF-related factor protein, integrin-linked protein kinase homing pat-4 gene) and hemagglutination-associated proteins (hemolymph clottable protein, hemocyte protein-glutamine gamma-glutamyltransferase). Downregulation of these proteins indicated that M. bicuspidata inhibited hemocyte regeneration and hemolymph agglutination. Fifteen differentially expressed proteins related to immunity were verified using a parallel reaction monitoring method. The expression trend of these proteins was similar to that of the proteome. To the best of our knowledge, this is the first report on the proteome of E. sinensis in response to M. bicuspidata infection. These results not only provide new and important information on the immune response of crustaceans to yeast infection but also provide a basis for further understanding the molecular mechanism of complex host pathogen interactions between crustaceans and fungi.

Differentially proteomic analysis of the hemocytes against Aeromonas hydrophila infection in oriental river prawn Macrobrachium nipponense by iTRAQ approach

As the direct executors of biological function, the expression level of proteins in host will reveal the molecular mechanisms regulating bacteria infection more directly. In the present study, the differential proteomes of Macrobrachium nipponense hemocytes response to Aeromonas hydrophila infection were identified with isobaric tags for relative and absolute quantitation (iTRAQ) labeling followed by liquid chromatography electrospray ionization tandem mass spectrometry. The hemocyte proteins from the unchallenged and A. hydrophila challenged prawn, M. nipponense, at 12, 24 and 36 h post infection were compared. From this, a total of 3372 proteins were identified and 1014 proteins were considered differentially expressed, of which 117 common differentially expressed proteins were indicated between the time points. Hierarchical clustering, Gene Ontology, Kyoto Encyclopedia of Genes and Genomes enrichment and protein-protein interaction network analyses were performed for the general characterization of overall enriched proteins. Cytoskeletal proteins including myosin heavy chain, myosin regulatory light chain, actin, tubulin alpha/beta chain, troponin I and troponin T as well as antioxidant enzymes such as catalase and cytosolic MnSOD were found significantly up-regulated in hemocytes, indicating that the phagocytosis process and ROS system were induced after challenge with A. hydrophila. And other proteins such as integrin β, innexin inx2-like and heat shock protein 60 also participate in prawn immune response against bacteria. Parallel reaction monitoring analyses were carried out for validation of the expression levels of differentially expressed proteins, which indicated high reliability of the proteomic results. This is the first report on proteome of M. nipponense hemocytes against A. hydrophila infection, which contributes to better understanding on the molecular mechanisms of prawns.

Molecular cloning, mRNA expression and functional characterization of a catalase from Chinese black sleeper (Bostrychus sinensis)

In this study, the catalase gene of Chinese black sleeper Bostrychus sinensis (termed as BsCat) was sequenced and characterized. The BsCat, which encodes 525 amino acids, contains a catalase proximal active site signature domain (⁶⁴FDRERIPERVVHAKGAG⁸⁰) and a catalase proximal heme-ligand signature domain (³⁵⁴RLFAYPDTH³⁶²). The BsCat exhibits high sequence similarity with Cat of other species. Phylogenetic tree reconstruction revealed a close evolutionary relationship of BsCat to catalase genes of other fishes. The results of Real-time PCR showed that the BsCat gene was constitutively expressed in most organs of B. sinensis, with predominant expression detected in liver, followed by peripheral blood and spleen. Moreover, the BsCat gene was significantly changed after either poly (I:C) stimulation or Vibrio parahemolyticus infection in peripheral blood, head kidney, liver and spleen. The enzymatic activity of purified recombinant BsCat (rBsCat) was 2261 ± 96 U/mg. The rBsCat exhibits optimum enzymatic activity at 15 °C and pH 7.0. Our results suggested that the BsCat is involved in the antioxidant defense and host immune response of Chinese black sleeper during pathogen invasion.

Source of hemolymph microbiota and their roles in the immune system of mud crab

Special innate immune mechanisms against pathogens are developed in marine invertebrates such as mud crab, which is also an economically important aquaculture species in many coastal countries. Hemolymph is a critical site in host immune response, but its source of microorganisms is less known. In this study, we provided a detailed investigation of the microorganisms inhabiting various body sites of healthy mud crabs, including hemolymph, midgut, gill, subcuticular epidermis and hepatopancreas. By using fluorescence microscopy and high-throughput sequencing of the bacterial 16S rRNA genes, various abundances and kinds of microorganisms were observed in the healthy mud crabs, of which some are potential pathogens to mud crab and human. The SourceTracker analysis and oral injection experiment confirm the hypothesis that hemolymph microorganisms are derived from the digestive systems of invertebrates with open circulatory systems, indicating that these microorganisms play vital roles in crab immune response. Moreover, physiological differences (gut length), behavioral characteristics (foraging behavior), diet preferences (herbivory), and/or sex hormones (testosterone) possibly determine the unique features of the crab-associated microbiota for both sexes. These findings also contribute to the development of appropriate microbial immunoenhancers, which has potential applications for improving quality and yield during crab aquaculture.

Effects of dietary mixed probiotics on growth, non-specific immunity, intestinal morphology and microbiota of juvenile pacific white shrimp, Litopenaeus vannamei

This study was conducted to elucidate the effects of dietary mixed probiotics on growth, non-specific immunity, intestinal morphology and microbiota of juvenile pacific white shrimp, Litopenaeus vannamei. Juvenile shrimp (initial body weight 1.21 ± 0.01 g) were fed diets containing graded probiotics (F1: 0 mg/kg probiotics; F2: 1000 mg/kg probiotics; F3: 2000 mg/kg probiotics; F4: 4000 mg/kg compound probiotics; F5: 6000 mg/kg probiotics; F6: 8000 mg/kg probiotics) for 8 weeks. The result of this trial showed that the growth performance (SGR, WG, FBW) of shrimp fed diets containing probiotics (F2∼F6) were significantly higher than that of shrimp fed diet without supplemental probiotics (F1) (P < 0.05), and the highest values of the growth performance (SGR, WG, FBW) and lowest FCR were found in shrimp fed the diet containing 2000 mg/kg probiotics. Total antioxidant capacity of shrimp fed diet F2 and F3 were significantly higher than that of shrimp fed the basal diets (P < 0.05). Superoxide dismutase in F4 treatment was significantly higher than that of basal treatment (P < 0.05). Catalase of shrimp in all probiotics supplemented (F2∼F6) treatments were significantly higher than that of the control one (F1) (P < 0.05). Malondialdehyde in F5 groups was significantly lower than that of F1 groups (P < 0.05). Alkline phosphatase and acid phosphatase in F3 treatments were significantly higher than those of the basal one (P < 0.05). Lysozyme of shrimp fed F2∼F6 were significantly higher than that of shrimp fed F1 diet (P < 0.05). The lipase and amylase activities in 2000 mg/kg probiotics groups showed the highest activities and were significantly higher than that of control one (P < 0.05). Intestinal villi height in F3∼F6 treatments were significantly higher than that of control one (P < 0.05). Alpha diversity indices including observed species, chao1, ACE and shannon indices showed that F2 and F3 groups had higher microbial diversity in their intestines, both richness and evenness. PCA plot showed that there was a clear shift of F2 and F3 groups from the control groups in microbial community structure. The dominant phyla in pacific white shrimp are proteobacteria, bacteroidetes and actinobacteria, the dominant genus were algoriphagus and vibrio. As the probiotics increased, the gemmatimonadetes, acidobacteria, deltaproteobacteria and xanthomonadales firstly increased and then decreased, with the highest content in F2 group, which was no significant difference to F3 group (P > 0.05) while significantly higher than other groups (P < 0.05). In conclusion, the supplement of mixed species probiotics can promote growth performance, enhance the non-specific immunity, influence the microbiota of the pacific white shrimps and the recommended optimum dosage in diet of Litopenaeus vannamei was 2000 mg/kg.

Molecular cloning, characterization, and expression level analysis of a marine teleost homolog of catalase from big belly seahorse (Hippocampus abdominalis)

Organisms possess a cellular antioxidant defense system inclusive of ROS scavengers to maintain the homeostasis of antioxidant levels. Catalase is a major ROS scavenger enzyme that plays a significant role in the antioxidant defense mechanism of organisms by reducing toxic hydrogen peroxide molecules into a nontoxic form of oxygen and water with a high turnover rate. In the present study, we performed molecular and functional characterization of the catalase homolog from Hippocampus abdominalis (HaCat). The HaCat cDNA sequence was identified as a 1578 bp ORF (open reading frame) that encodes a polypeptide of 526 amino acids with 59.33 kDa molecular weight. Its estimated pI value is 7.7, and it does not have any signal sequences. HaCat shared a conserved domain arrangement including the catalase proximal active site signature and heme ligand signature domain with the previously identified catalase counterparts. Phylogenetic analysis displayed close evolutionary relationships between HaCat and catalases from other teleost fish. According to our qPCR results, ubiquitous expression of HaCat transcripts were observed in all the tested tissues with high expression in the kidney followed by liver. Significant modulations of HaCat transcription were observed in blood, liver, and kidney tissues post-challenge with Streptococcus iniae, Edwardsiella tarda, poly I:C, and LPS. Peroxidase activity of recombinant HaCat (rHaCat) was evaluated using an ABTS assay and the ROS removal effect was further confirmed by oxidative DNA damage protection and cell viability assays. The rHaCat showed more than 97% activity over a temperature and pH range of 10 °C-40 °C and 5 to 6, respectively. The above results suggest that HaCat plays an indispensable role in the oxidative homeostasis of the seahorse during pathogenic attack.

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.

Effects of environmental stress on shrimp innate immunity and white spot syndrome virus infection

The shrimp aquaculture industry is plagued by disease. Due to the lack of deep understanding of the relationship between innate immune mechanism and environmental adaptation mechanism, it is difficult to prevent and control the diseases of shrimp. The shrimp innate immune system has received much recent attention, and the functions of the humoral immune response and the cellular immune response have been preliminarily characterized. The role of environmental stress in shrimp disease has also been investigated recently, attempting to clarify the interactions among the innate immune response, the environmental stress response, and disease. Both the innate immune response and the environmental stress response have a complex relationship with shrimp diseases. Although these systems are important safeguards, allowing shrimp to adapt to adverse environments and resist infection, some pathogens, such as white spot syndrome virus, hijack these host systems. As shrimp lack an adaptive immune system, immunization therapy cannot be used to prevent and control shrimp disease. However, shrimp diseases can be controlled using ecological techniques. These techniques, which are based on the innate immune response and the environmental stress response, significantly reduce the impact of shrimp diseases. The object of this review is to summarize the recent research on shrimp environmental adaptation mechanisms, innate immune response mechanisms, and the relationship between these systems. We also suggest some directions for future research.

Enteric nervous system analyses: New biomarkers for environmental quality assessment

The gastrointestinal tract (GIT) of fish is a target of contaminants since it can absorb these substances. We evaluated the morphophysiological alterations in the GIT of Sphoeroides testudineus collected in two estuaries presenting differences in their environmental quality (NIA and IA). The intestine was analyzed for histological and neuronal changes; liver and gills for biochemical markers; muscle tissues for neurotoxicity and peripheral blood for genotoxic damage. The results showed alterations in the GIT of the animals collected in the IA, such as muscle tunica and goblet cell density reduction, increased intraepithelial lymphocytes density and changes in neuronal density. Furthermore, changes were observed in MTs and LPO in the gills. Thus, we suggest that TGI is functioning as a barrier that responds to ingested contaminants, in order to reduce their absorption and translocation. Thus, alterations in morphophysiological and enteric neurons in S. testudineus can be used as biomarkers of environmental contamination.

An immune-related gene expression atlas of the shrimp digestive system in response to two major pathogens brings insights into the involvement of hemocytes in gut immunity

Much of our current knowledge on shrimp immune system is restricted to the defense reactions mediated by the hemocytes and little is known about gut immunity. Here, we have investigated the transcriptional profile of immune-related genes in different organs of the digestive system of the shrimp Litopenaeus vannamei. First, the tissue distribution of 52 well-known immune-related genes has been assessed by semiquantitative analysis in the gastrointestinal tract (foregut, midgut and hindgut) and in the hepatopancreas and circulating hemocytes of shrimp stimulated or not with heat-killed bacteria. Then, the expression levels of 18 genes from key immune functional categories were quantified by fluorescence-based quantitative PCR in the midgut of animals experimentally infected with the Gram-negative Vibrio harveyi or the White spot syndrome virus (WSSV). Whereas the expression of some genes was induced at 48 h after the bacterial infection, any of the analyzed genes showed to be modulated in response to the virus. Whole-mount immunofluorescence assays confirmed the presence of infiltrating hemocytes in the intestines, indicating that the expression of some immune-related genes in gut is probably due to the migratory behavior of these circulating cells. This evidence suggests the participation of hemocytes in the delivery of antimicrobial molecules into different portions of the digestive system. Taken all together, our results revealed that gut is an important immune organ in L. vannamei with intimate association with hemocytes.

Antimicrobial peptides in marine invertebrate health and disease

Aquaculture contributes more than one-third of the animal protein from marine sources worldwide. A significant proportion of aquaculture products are derived from marine protostomes that are commonly referred to as 'marine invertebrates'. Among them, penaeid shrimp (Ecdysozosoa, Arthropoda) and bivalve molluscs (Lophotrochozoa, Mollusca) are economically important. Mass rearing of arthropods and molluscs causes problems with pathogens in aquatic ecosystems that are exploited by humans. Remarkably, species of corals (Cnidaria) living in non-exploited ecosystems also suffer from devastating infectious diseases that display intriguing similarities with those affecting farmed animals. Infectious diseases affecting wild and farmed animals that are present in marine environments are predicted to increase in the future. This paper summarizes the role of the main pathogens and their interaction with host immunity, with a specific focus on antimicrobial peptides (AMPs) and pathogen resistance against AMPs. We provide a detailed review of penaeid shrimp AMPs and their role at the interface between the host and its resident/pathogenic microbiota. We also briefly describe the relevance of marine invertebrate AMPs in an applied context.This article is part of the themed issue 'Evolutionary ecology of arthropod antimicrobial peptides'.

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

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

Leucine-rich repeats containing protein functions in the antibacterial immune reaction in stomach of kuruma shrimp Marsupenaeus japonicus

Leucine rich repeat (LRR) motif exists in many immune receptors of animals and plants. Most LRR containing (LRRC) proteins are involved in protein-ligand and protein-protein interaction, but the exact functions of most LRRC proteins were not well-studied. In this study, an LRRC protein was identified from kuruma shrimp Marsupenaeus japonicus, and named as MjLRRC1. MjLRRC1 was consistently expressed in different tissues of normal shrimp with higher expression in gills and stomach. At the transcriptional level, there were no significant changes of MjLRRC1 after injection of Vibrio anguillarum or Staphylococcus aureus in gills and hepatopancreas. While in V. anguillarum oral infection, MjLRRC1 was upregulated in stomach but not in intestine. The recombinant MjLRRC1 protein could bind to Gram-positive and Gram-negative bacteria, bacterial cell wall components including peptidoglycan, lipoteichoic acid, and lipopolysaccharide. MjLRRC1 regulated the expression of some antimicrobial peptide (AMP) genes and participated in bacteria clearance of stomach. All these results suggested that MjLRRC1 might play important roles in antibacterial immune response of kuruma shrimp.

Assessment of arsenic trioxide in the heart of Gallus gallus: alterations of oxidative damage parameters, inflammatory cytokines, and cardiac enzymes

The aim of this study was to assess the effects of arsenic trioxide (As₂O₃) in the chicken heart, and 72 1-day-old male Hy-line chickens were fed either a commercial diet (C group) or an arsenic supplement diet containing 7.5 mg/kg (L group), 15 mg/kg (M group), or 30 mg/kg (H group) As₂O₃ for 90 days. The results showed that exposure to As₂O₃ merely lowered (P < 0.05) the activities of catalase (CAT) and glutathione peroxidase (GSH-Px) in M and H groups at 90 days, significantly downregulated the inhibition ability of hydroxyl radicals (OH·), and upregulated (P < 0.05) the contents of malondialdehyde (MDA) in As₂O₃ exposure groups at 30, 60, and 90 days. Meanwhile, the messenger RNA levels of inflammatory cytokines (tumor necrosis factor-α (TNF-α), nuclear factor-kappa B (NF-κB), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and prostaglandin E synthase (PTGEs)) significantly increased (P < 0.05) in As₂O₃ exposure groups at 30, 60, and 90 days, and histological and ultrastructural damage was observed in As₂O₃ exposure groups. Additionally, As₂O₃-induced cardiac enzyme (aspartate transaminase (AST), creatine kinase (CK), creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), and α-hydroxybutyrate dehydrogenase (α-HBDH)) levels increased (P < 0.05) at 90 days. These findings suggested that As₂O₃ exposure led to oxidative stress, inflammatory response, and histological and ultrastructural damage and altered the levels of cardiac enzymes in chicken heart tissues. This result may be helpful for further studies on the toxicological mechanisms of As₂O₃ in the chicken heart.

Dual oxidases participate in the regulation of intestinal microbiotic homeostasis in the kuruma shrimp Marsupenaeus japonicus

The metazoan gut lumen harbors numerous microbial communities. Tolerance for high bacterial counts and maintenance of microbiota homeostasis remain insufficiently studied. In this study, we identified a novel dual oxidase (MjDUOX2) involved in reactive oxygen species (ROS) production in the kuruma shrimp Marsupenaeus japonicus. MjDUOX2 is a transmembrane protein with an N-signal peptide region (19 aa) and a peroxidase homology domain (PHD, 554 aa) in the extracellular region; seven transmembrane regions; and three EF (calcium-binding region) domains (110 aa), a FAD-binding domain (104 aa), and a NAD-binding domain (156 aa) in the intracellular region. The novel MjDUOX2 exhibits a relatively low similarity (26.84% identity) to a previously reported DUOX in the shrimp (designated as MjDUOX1). The mRNA of MjDUOXs was widely distributed in the hemocytes, heart, hepatopancreas, gills, stomach, and intestine. Oral infection of the shrimp with pathogenic bacteria upregulated the mRNA expression of MjDUOXs and increased the ROS level in the intestine. However, High ROS level could inhibit the expression of MjDUOXs in shrimp after Vibrio anguillarum infection. Knockdown of MjDUOXs by RNA interference (RNAi) decreased the ROS level, increased the bacterial count in the intestine, and decreased the survival rate of the MjDUOX-RNAi shrimp infected with V. anguillarum. These results suggest that MjDUOXs play an important role for microbiota homeostasis in intestine of shrimp.