Oxidative stress, DNA damage and antioxidant enzyme gene expression in the Pacific white shrimp, Litopenaeus vannamei when exposed to acute pH stress

Occurrence, detection and ecotoxicity of microplastics in selected environments-a systematic appraisal

Microplastics (MPs) are being released into the environment in large quantities, especially in less developed parts of the world. This group of pollutants is mostly leached into the environment through heavy plastic dumpsites, pharmaceutical and personal care product containers, hospital wastes, plastic package accessories, and litter from food packaging. Consequently, these compounds are found in different compartments of the ecosystem, such as soils, sediments, biota, and, surprisingly, drinking water. The present study systematically appraised recent studies on MP pollution in the Asian and African environments. It also summarized the trends in the methods for the environmental monitoring of MPs and the removal strategies that have been employed. From the data gathered, the two key instrumentations involved are the microscopes for visualization and the Fourier transform-infra-red (FT-IR) spectrometer to classify or characterize the MPs. Based on the surveyed works of literature, China and South Africa have relatively more information on MP contamination of diverse matrices within their countries. Meanwhile, studies on the status of MP contamination should be conducted across all countries. Hence, this study becomes an eye-opener regarding the commencement of research works on the MP contamination of the environment, especially in other Asian and African countries with little or no information. Furthermore, the literature on ecotoxicity studies of MPs was investigated to ascertain the toxic nature of these compounds. This aspect of research is vital because it serves as a prerequisite for the remediation of these compounds. Microplastics have been declared lethal to biotic components, so all hands must be on deck to continuously remove them from the environment.

Integrated microbiome and metabolome analyses reveal the effects of low pH on intestinal health and homeostasis of crayfish (Procambarus clarkii)

Low pH (LpH) poses a significant challenge to the health, immune response, and growth of aquatic animals worldwide. Crayfish (Procambarus clarkii) is a globally farmed freshwater species with a remarkable adaptability to various environmental stressors. However, the effects of LpH stress on the microbiota and host metabolism in crayfish intestines remain poorly understood. In this study, integrated analyses of antioxidant enzyme activity, histopathological damage, 16S rRNA gene sequencing, and liquid chromatography-mass spectrometry (LC-MS) were performed to investigate the physiology, histopathology, microbiota, and metabolite changes in crayfish intestines exposed to LpH treatment. The results showed that LpH stress induced obvious changes in superoxide dismutase and catalase activities and histopathological alterations in crayfish intestines. Furthermore, 16S rRNA gene sequencing analysis revealed that exposure to LpH caused significant alterations in the diversity and composition of the crayfish intestinal microbiota at the phylum and genus levels. At the genus level, 14 genera including Bacilloplasma, Citrobacter, Shewanella, Vibrio, RsaHf231, Erysipelatoclostridium, Anaerorhabdus, Dysgonomonas, Flavobacterium, Tyzzerella, Brachymonas, Muribaculaceae, Propionivibrio, and Comamonas, exhibited significant differences in their relative abundances. The LC-MS analysis revealed 859 differentially expressed metabolites in crayfish intestines in response to LpH, including 363 and 496 upregulated and downregulated metabolites, respectively. These identified metabolites exhibited significant enrichment in 24 Kyoto Encyclopedia of Genes and Genomes pathways (p < 0.05), including seven and 17 upregulated and downregulated pathways, respectively. These pathways are mainly associated with energy and amino acid metabolism. Correlation analysis revealed a strong correlation between the metabolites and intestinal microbiota of crayfish during LpH treatment. These findings suggest that LpH may induce significant oxidative stress, intestinal tissue damage, disruption of intestinal microbiota homeostasis, and alterations in the metabolism in crayfish. These findings provide valuable insights into how the microbial and metabolic processes of crayfish intestines respond to LpH stress.

Combined effects of ammonia-N exposure and salinity changes on hematological and serum biochemical factors and thyroid hormones in Nile tilapia (Oreochromis niloticus)

The aim of this research was to evaluate the interaction effects of ammonia-N levels and salinity on hematological and serum biochemical parameters in Nile tilapia (Oreochromis niloticus). The fish were randomly divided into 12 treatments including the levels of salinity (0, 4, 8 and 12 ppt) and 0, 50% of LC50-96 h of ammonia-N and 30% of LC50-96 h of ammonia-N in a factorial design (4 salinity levels x 3 ammonia levels). Hemoglobin value in all treatments, except for salinity treatments, namely 2, 3, 4, showed a significant decrease than the control (0 ppt and no poisoning). Also, red blood cells in treatment ammonia-N levels were significantly less than the control. Serum protein concentration, in treatments 9 (50% of LC50-96 h of ammonia-N) and 5 and also with increasing salinity (treatments 2, 3 and 4) had a significant decrease compared to the control. There is a significant increase in serum glucose, cortisol, ammonia and urea levels in 50% and 30% of LC50-96 h of ammonia-N treatments compared to the control, meanwhile these parameters were significantly increased with increasing salinity. Serum thyroid stimulating hormone (TSH), T3 and T4 levels in acute and sub-acute ammonia-N treatments were significantly lower than the control. Moreover, with increasing salinity in 50% and 30% of LC50-96 h of ammonia-N treatments, TSH showed a decreasing pattern. According to the results, fluctuations in blood biochemical factors, increase of stress and decrease of thyroid hormones show that the salinity, ammonia, and their interaction caused adverse effects on fish health during the 96 h of testing.

Integrated physiological, transcriptome, and metabolome analyses of the hepatopancreas of Litopenaeus vannamei under cold stress

Temperature is a limiting factor in the growth of aquatic organisms and can directly affect many chemical and biological processes, including metabolic enzyme activity, aerobic respiration, and signal transduction. In this study, physiological, transcriptomic, and metabolomic analyses were performed to characterize the response of Litopenaeus vannamei to cold stress. We subjected L. vannamei to gradually decreasing temperatures (24 °C, 20 °C, 18 °C, 14 °C, and 12 °C) and studied the changes in the hepatopancreas. The results showed that extreme cold stress (12 °C) caused structural damage to the hepatopancreas of L. vannamei. However, shrimp exhibited response mechanisms to enhance cold tolerance, through regulating changes in key genes and metabolites in amino acid, lipid metabolism, and carbohydrate metabolism, including (a) increased level of methylation in cells to enhance cold tolerance; (b) increased content of critical amino acids, such as proline, alanine, glutamic acid and taurine, to ameliorate energy metabolism, protect cells from cold-induced osmotic imbalance, and promote ion transport and DNA repair; (c) accumulation of unsaturated fatty acids to improve cell membrane fluidity; and (d) regulation of the metabolic pattern shift to rely on anaerobic metabolism with a gradual decrease in aerobic metabolism and enhance glycolysis to produce enough ATP to maintain energy metabolic balance. When the temperature dropped further, cold stress impaired antioxidant and immune defense responses in shrimp. This study provides an integrated analysis of the physiology, transcriptome, and metabolome of L. vannamei in response to cold stress.

The evolutionary adaptation of shrimp hemocyanin subtypes and the consequences on their structure and functions

Hemocyanin is the main respiratory protein of arthropods and is formed by hexameric and/or oligomeric subunits. Due to changes in the living environment and gene rearrangement, various hemocyanin subtypes and subunits evolved in crustaceans. This paper reviews the various hemocyanin subtypes and isoforms in shrimp and analyses published genomic data of sixteen hemocyanin family genes from Litopenaeus vannamei to explore the evolution of hemocyanin genes, subunits, and protein structure. Analysis of hemocyanin subtypes distribution and structure in various tissues was also performed and related to multiple and tissue-specific functions, i.e., immunological activity, immune signaling, phenoloxidase activity, modulation of microbiota homeostasis, and energy metabolism. The functional diversity of shrimp hemocyanin due to molecular polymorphism, transcriptional regulation, alternative splicing, degradation into functional peptides, interaction with other proteins or genes, and structural differences will also be highlighted for future research. Inferences would be drawn from other crustaceans to explain how evolution has changed the structure-function of hemocyanin and its implication for evolutionary research into the multifunctionality of hemocyanin and other related proteins in shrimp.

Transcriptome sequencing and metabolite analysis reveal the single and combined effects of microplastics and di-(2-ethylhexyl) phthalate on Peneaus vannamei

Due to the rising usage of plastics, plastic debris are present throughout marine ecosystems and detrimentally affects marine biota. Additionally, plastics likely result in elusive toxicity effects due to addition of plasticizers. The aim of the present study was to reveal the potential effects and mechanism of microplastics (MPs), di-(2-ethylhexyl) phthalate (DEHP) and copollution of MPs and DEHP (MPs-DEHP) on Peneaus vannamei (P. vannamei) juveniles regarding oxidative stress, transcriptomics and metabolomics. MPs, DEHP and MPs-DEHP significantly induced the activities of superoxide dismutase (SOD) and catalase (CAT); MPs and DEHP have an antagonistic effect for malondialdehyde (MDA); suggesting that disorders of the antioxidant defence systems. 13, 133 and 58 differentially expressed genes and 21, 82 and 39 differentially expressed metabolites were responsible for the distinction of MPs, DEHP and MPs-DEHP groups, respectively. The combination of transcriptomic and metabolomic analyses showed that MPs, DEHP and MPs-DEHP exposure disturbed amino acid and lipid metabolism, and further induced inflammatory responses and dysfunction of purine metabolism. Furthermore, the presence of MPs might alleviate the biotoxicity of DEHP in P. vannamei. These findings provide new insights into the single and combined toxicological effects of MPs and additives for marine biota.

Effects of Sulfamethoxazole and Florfenicol on Growth, Antioxidant Capacity, Immune Responses and Intestinal Microbiota in Pacific White Shrimp Litopenaeus vannamei at Low Salinity

Antibiotic residue may pose a serious risk to aquaculture, and the culture of Litopenaeus vannamei in a low-salinity environment is a growing trend over the world. Here, we aimed to understand the combined effect of low salinity and sulfamethoxazole (SMZ) and florfenicol (FLO) antibiotics on L. vannamei. The growth performance, immune functions, antioxidant capacity and intestinal microbiota were investigated. Compared with the control group, the weight gain and survival rate significantly decreased (p < 0.05) in shrimp after they were exposed to low-salinity (salinity 3) water and the mixture of antibiotics and low-salt conditions for 28 days. The antioxidant activities of SOD and T-AOC, shown at low salinity and in the higher concentration of the SMZ treatment group (SMZH), were significantly decreased, while the GST activity was significantly increased in each treatment group in comparison with the control group. The expression of immune-related genes, including TOLL, LvIMD, PPO and HSP, in the low concentration of the SMZ treatment group (SMZL) was higher than that in the other groups. The diversity of intestine microbiota was disturbed with a lower Shannon index in the low-salinity and SMZH groups, and a higher Simpson index in the SMZH group. Proteobacteria, Actinobacteria and Bacteroidetes were the dominant phyla in the gut of L. vannamei. At the genus level, Microbacterium, Shewanella, Aeromonas, Acinetobacter, Gemmobacter, Paracoccus and Lysobacter were significantly decreased in the low-salinity group. However, the abundance of opportunistic pathogens belonging to the genus Aeromonas in the FLO group was increased. The predicted microbe-mediated functions showed that the pathway for “amino acid metabolism” and “replication and repair” was significantly inhibited in both the low-salinity and antibiotic-exposed groups. All the findings in this study indicate that the combined effect of antibiotics and low salinity on L. vannamei negatively impacted the physiological and intestinal microbiota functions.

Microplastic-Contaminated Feed Interferes with Antioxidant Enzyme and Lysozyme Gene Expression of Pacific White Shrimp (Litopenaeus vannamei) Leading to Hepatopancreas Damage and Increased Mortality

Microplastic pollution can interfere with aquatic animal health and nonspecific immunity, increasing the potential for pathogen infection in crustaceans. However, the long-term effects of microplastics on crustacean immunity are less understood, especially regarding their toxicity in Pacific white shrimp (Litopenaeus vannamei). Effects of high-density polyethylene microplastics (HDPE-MPs) in feed on the mortality rate, hepatopancreas, and nonspecific immune system gene expression of Pacific white shrimp are presented. The LC₅₀ at day 28 of HDPE-MP exposure was determined as 3.074% HDPE-MP in feed. A significant upregulation of the superoxide dismutase (SOD) and glutathione peroxidase (GPx) genes was observed in shrimp that were fed with 0.1 and 0.5% of HDPE-MP; then, they were downregulated significantly, except for the SOD gene expression of shrimp fed with 0.1% of HDPE-MP. The lysozyme (LYZ) gene was upregulated significantly in shrimp that were fed with 0.5, 1, and 3% HDPE-MP for 7 days and downregulated significantly in HDPE-receiving groups for at least 14 days. Significant histopathological changes in the hepatopancreas were observed in the treatment groups. The histopathological score of each lesion was correlated with the increase in HDPE-MP concentration. This study shows that the ingestion of HDPE microplastics can alter the expression of nonspecific immune system genes and damage the hepatopancreas in Pacific white shrimp.

Blood biomarkers as diagnostic tools: An overview of climate-driven stress responses in fish

Global climate change due to anthropogenic activities affects the dynamics of aquatic communities by altering the adaptive capacities of their inhabitants. Analysis of blood provides valuable insights in the form of a comprehensive representation of the physiological and functional status of fish under various environmental and treatment conditions. This review synthesizes currently available information about blood biomarkers used in climate change induced stress responses in fish. Alterations in informative blood-based indicators are used to monitor the physiological fitness of individual fishes or entire populations. Specific characteristics of fish blood, such as serum and plasma metabolites, cell composition, cellular abnormalities, cellular and antioxidant enzymes necessitate adapted protocols, as well as careful attention to experimental designs and meticulous interpretation of patterns of data. Moreover, the sampling technique, transportation, type of culture system, acclimation procedure, and water quality must all be considered for valid interpretation of hemato-biochemical parameters. Besides, blood collection, handling, and storage time of blood samples can all have significant impacts on the results of a hematological analysis, so it is optimal to perform hemato-biochemical evaluations immediately after blood collection because long-term storage can alter the results of the analyses, at least in part as a result of storage-related degenerative changes that may occur. However, the scarcity of high-throughput sophisticated approaches makes fish blood examination studies promising for climate-driven stress responses in fish.

Acute Nitrite Exposure Induces Dysfunction and Oxidative Damage in Grass Carp Isolated Hemocytes

To evaluate the effects of nitrite on the oxidative damage of blood cells of Grass Carp Ctenopharyngodon idella, the isolated hemocytes were exposed to nitrite (0, 1, 10, or 100 mg/L) for up to 24 h. Hemoglobin (Hb) and methemoglobin (MetHb) concentrations, reactive oxygen species (ROS) and malondialdehyde (MDA) levels, mitochondrial membrane potential (∆Ψm), and antioxidant enzyme activity were assayed to assess hematological parameters and the antioxidant defense mechanism. Results showed a remarkable decrease in Hb concentration with increasing nitrite concentration after a 24-h exposure, while the MetHb concentration increased significantly in nitrite exposure groups. The levels of ROS, ∆Ψm, and MDA increased to varying degrees with increases in nitrite exposure concentration and time. The total antioxidant capacity, catalase (CAT) activity, glutathione peroxidase (GPx) activity, and glutathione content showed a trend of rising initially and then decreasing with prolonged exposure time. Superoxide dismutase (SOD) activity was higher in the 1-mg/L nitrite exposure group and lower in the 100-mg/L group than in the control. The relative messenger RNA expression ratios of cat, sod1, and gpx were up-regulated significantly in the 1- and 10-mg/L groups and then declined in the 100-mg/L group. Therefore, it can be concluded that nitrite exposure activates the antioxidant defense mechanism of Grass Carp hemocytes and that the balance of oxidant-antioxidant homeostasis will be undermined by higher nitrite doses or longer exposure periods.

Transcriptome Analysis to Study the Molecular Response in the Gill and Hepatopancreas Tissues of Macrobrachium nipponense to Salinity Acclimation

Macrobrachium nipponense is an economically important prawn species and common in Chinese inland capture fisheries. During aquaculture, M. nipponense can survive under freshwater and low salinity conditions. The molecular mechanism underlying the response to salinity acclimation remains unclear in this species; thus, in this study, we used the Illumina RNA sequencing platform for transcriptome analyses of the gill and hepatopancreas tissues of M. nipponense exposed to salinity stress [0.4‰ (S0, control group), 6‰ (S6, low salinity group), and 12‰ (S12, high salinity group)]. Differentially expressed genes were identified, and several important salinity adaptation-related terms and signaling pathways were found to be enriched, such as “ion transport,” “oxidative phosphorylation,” and “glycometabolism.” Quantitative real-time PCR demonstrated the participation of 12 key genes in osmotic pressure regulation in M. nipponense under acute salinity stress. Further, the role of carbonic anhydrase in response to salinity acclimation was investigated by subjecting the gill tissues of M. nipponense to in situ hybridization. Collectively, the results reported herein enhance our understanding of the mechanisms via which M. nipponense adapts to changes in salinity.

Physiological mechanisms of stress-induced evolution

Organisms mount the cellular stress response whenever environmental parameters exceed the range that is conducive to maintaining homeostasis. This response is critical for survival in emergency situations because it protects macromolecular integrity and, therefore, cell/organismal function. From an evolutionary perspective, the cellular stress response counteracts severe stress by accelerating adaptation via a process called stress-induced evolution. In this Review, we summarize five key physiological mechanisms of stress-induced evolution. Namely, these are stress-induced changes in: (1) mutation rates, (2) histone post-translational modifications, (3) DNA methylation, (4) chromoanagenesis and (5) transposable element activity. Through each of these mechanisms, organisms rapidly generate heritable phenotypes that may be adaptive, maladaptive or neutral in specific contexts. Regardless of their consequences to individual fitness, these mechanisms produce phenotypic variation at the population level. Because variation fuels natural selection, the physiological mechanisms of stress-induced evolution increase the likelihood that populations can avoid extirpation and instead adapt under the stress of new environmental conditions.

iTRAQ-based quantitative proteomic analysis of Pelteobagrus vachelli liver in response to hypoxia

Dissolved oxygen is one of the determinants in the healthy farming of Pelteobagrus vachelli. This study, we conducted quantitative proteomics on the juvenile P. vachelli livers using iTRAQ. P. vachelli were treated by 3.75 ± 0.25 mg O₂/L (hypoxia group) and 7.25 ± 0.25 mg O₂/L (control group) for 90 days. The results revealed that under hypoxic conditions, P. vachelli grew slower than control group. Proteomic profiling enabled us to identify 2618 proteins, of which 176 were significantly differentially abundant proteins (DAPs). Verification of protein regulation based on qRT-PCR indicated that the proteomics data were reliable. The top 20 significantly DAPs (10 up-regulated, 10 down-regulated) were primarily involved in energy metabolism, apoptosis inhibition, and heavy metal detoxification. KEGG pathway enrichment analysis revealed significant enrichment of 'protein digestion and absorption', 'glycolysis/gluconeogenesis', and 'phagosome'. Combining the proteomics results of short-term hypoxia (treated with 0.70 ± 0.10 mg O₂ /L for 4 h), we screened 36 common DAPs. The analysis of the 36 common DAPs indicated that P. vachelli responded to the hypoxia by regulating energy supply, inhibiting apoptosis, and disturbing defensive system. Our results lay a theoretical foundation for the cultivation of hypoxia-tolerant species and eco-breeding of P. vachelli. SIGNIFICANCE OF THE STUDY: The hypoxia tolerance of Pelteobagrus vachelli is poor, which will seriously lead to its death in high-density culture. This study analysed the liver proteome of P. vachelli under long-term hypoxia stress (treated for 90 days at 3.75 ± 0.25 mg O₂/L), and then combined the proteome results of short-term hypoxia stress (treated for 4 h at 0.70 ± 0.10 mg O₂/L). The results showed P. vachelli responded to the hypoxia by regulating energy supply, inhibiting apoptosis and disturbing defensive system. The study contributes to the breeding of new hypoxia-tolerant species of P. vachelli and lays the theoretical foundation for eco-breeding.

The Effects of Different UVA Photoperiods on the Growth Performance, Immune Responses, Antioxidant Status and Apoptosis-Related Gene Expression of the Pacific White Shrimp (Penaeus vannamei)

UVA is the most common type of solar UV radiation in aquatic environments; however, the effects it causes in shrimp farming in recirculating water systems (RAS) is unclear. Thus, the growth performance, immune responses, antioxidant status and apoptosis-related gene expression in Pacific white shrimp, Penaeus vannamei (body weight 9.56 ± 0.10 g), reared with 12L: 12D full spectrum light as background light under five UVA (peak at 400 nm) photoperiods (0L: 24D, 2L: 22D, 4L: 20D, 8L: 16D and 12L: 12D) at a light intensity of 1 W/m2 were investigated. The results showed that the 2L: 22D and 4L: 20D UVA photoperiods enhanced the growth performance and reduced the feed conversion ratio and the shrimp mortality. Shrimp exposed to UVA (2L: 22D and 4L: 20D) also displayed higher levels of hepatopancreas catalase (CAT), superoxide dismutase (SOD), acid phosphatase (ACP), phenol oxidase (PO) and lysozyme (LZM) compared to the 8L: 16D and 12L: 12D groups. The malondialdehyde (MDA) levels increased in line with the extension of the UVA irradiation time. The mRNA expression of apoptosis-related genes in all the UVA treatments were significantly higher than with the control treatment, except for the 2L: 22D group. The results of the 2L: 22D and 4L: 20D treatments were significantly higher than those of the control group, except for LGBP. In conclusion, 2L: 22D and 4L: 20D UVA photoperiods increased growth performance and decreased FCR, improved the innate immunity and antioxidant response and reduced the mortality rate in adult shrimp.

Multifunctional carbonized nanogels to treat lethal acute hepatopancreatic necrosis disease

Background

Shrimp aquaculture has suffered huge economic losses over the past decade due to the outbreak of acute hepatopancreatic necrosis disease (AHPND), which is mainly caused by the bacteria Vibrio parahaemolyticus (V. parahaemolyticus) with the virulence pVA1 plasmid, which encodes a secretory photorhabdus insect-related (Pir) toxin composed of PirA and PirB proteins. The Pir toxin mainly attacks the hepatopancreas, a major metabolic organ in shrimp, thereby causing necrosis and loss of function. The pandemic of antibiotic-resistant strains makes the impact worse.

Methods

Mild pyrolysis of a mixture of polysaccharide dextran 70 and the crosslinker 1,8-diaminooctane at 180 ℃ for 3 h to form carbonized nanogels (DAO/DEX-CNGs) through controlled cross-linking and carbonization. The multifunctional therapeutic CNGs inherit nanogel-like structures and functional groups from their precursor molecules.

Results

DAO/DEX-CNGs manifest broad-spectrum antibacterial activity against Vibrio parahaemolyticus responsible for AHPND and even multiple drug-resistant strains. The polymer-like structures and functional groups on graphitic-carbon within the CNGs exhibit multiple treatment effects, including disruption of bacterial membranes, elevating bacterial oxidative stress, and neutralization of PirAB toxins. The inhibition of Vibrio in the midgut of infected shrimp, protection of hepatopancreas tissue from Pir toxin, and suppressing overstimulation of the immune system in severe V. parahaemolyticus infection, revealing that CNGs can effectively guard shrimp from Vibrio invasion. Moreover, shrimps fed with DAO/DEX-CNGs were carefully examined, such as the expression of the immune-related genes, hepatopancreas biopsy, and intestinal microbiota. Few adverse effects on shrimps were observed.

Conclusion

Our work proposes brand-new applications of multifunctional carbon-based nanomaterials as efficient anti-Vibrio agents in the aquatic industry that hold great potential as feed additives to reduce antibiotic overuse in aquaculture.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01194-8.

Determining the function of LvSmad3 on Litopenaeus vannamei in response to acute low temperature stress

Smad3 is a key mediator of the canonical TGF-β signaling pathway and plays an important role in TGF-β1-mediated transcriptional regulation. However, the function of Smad3 in crustaceans such as shrimp, is still poorly understood and needs to be further explored. We characterized Litopenaeus vannamei Smad3 (LvSmad3) and its biological functions were investigated in response low temperature stress. Full-length LvSmad3 cDNA was 2341bp and contained an open reading frame (ORF) of 1326 bp that encoded a 441 amino acid long protein, with a predicted molecular mass of 48.35 kDa. Phylogenetic analysis revealed that LvSmad3 has a high degree of similarity with other known species. LvSmad3 mRNA was detected in all the tested tissues and highest transcription occurred mostly in gills. Further research showed that suppressing the expression of Smad3 could reduce ROS production, DNA damage and the apoptosis rate in shrimp hemocyte under low temperature compared with the dsGFP group. Thus, we speculated that Smad3 could promote the apoptosis of hemocytes. We confirmed that Smad3 could inhibit apoptosis in the hepatopancreas by suppressing the expression of pro-apoptotic genes. Taken together, the silencing of Smad3 can reduce ROS production induced by low temperature stress, weaken the damage to hemocytes and the hepatopancreas by inhibit the apoptosis.

Benchmark dose and the adverse effects of exposure to pendimethalin at low dose in female rats

Pendimethalin (PND) is a dinitroaniline herbicide widely used to control broadleaf and annual grasses. Although the acute oral toxicity of PND is >5 g/kg b.wt. in humans (LD₅₀ for rats >5000 g/kg b.wt.), it has been classified as a possible human carcinogen. It is still used in agriculture so, agricultural workers and their families, as well as consumers, can be exposed to this herbicide. The present study is the first report investigating the dose-response effect using the benchmark dose (BMD) and the adverse effects of exposure to PND at low dose via apoptosis responses linked to the expression of tumor necrosis factor-α (TNF-α), FAS, and BAX proteins; oxidative stress; and DNA and liver damage in female rats. The rats were exposed to PND via drinking water at doses equivalent to no-observed-adverse-effect level (NOAEL = 100 mg/kg b.wt.), 200, and 400 mg/kg b.wt. for 28 days. PND caused the overexpression of Tnf-α, Fas, and Bax; increased the levels of serum liver biomarkers; and increased oxidative stress in the liver and erythrocytes. Furthermore, it induced DNA and liver damage in a dose-dependent manner. The BMD showed that serum alkaline phosphatase (ALP) and total antioxidant capacity (78.4 and 30.1 mg/kg b.wt./day, respectively), lipid peroxidation in liver tissue (30.9 mg/kg b.wt./day), catalase in erythrocytes (14.0 mg/kg b.wt./day), and FAS expression in liver tissue (6.89 mg/kg b.wt./day) were highly sensitive biomarkers of PND toxicity. Our findings suggest the generation of reactive oxygen species as a possible mechanism of PND-induced gene overexpression of tumor necrosis factor-α (TNF-α), FAS, and BAX proteins, oxidative stress, and DNA and liver damage in female rats.

Dietary supplementation of curcumin-loaded chitosan nanoparticles stimulates immune response in the white leg shrimp Litopenaeus vannamei challenged with Vibrio harveyi

Pathogen infections in shrimps trigger the release of reactive oxygen species (ROS) as a part of immune response. The excessive accumulation of ROS causes the production of oxidative stress, which leads to oxidative damage of the biomolecules in the host cells. The inclusion of dietary antioxidants is known to mitigate oxidative stress and stimulate immunity. Curcumin, a potential antioxidant was encapsulated in chitosan nanoparticles to surge its bioavailability and was administered orally to Vibrio harveyi challenged and non-challenged Litopenaeus vannamei. The non-challenged shrimps fed with curcumin-loaded chitosan nanoparticles (Cur-CSNPs) showed a significant increase (p ≤ 0.05) in the specific growth rate, daily growth coefficient and survival rate. A significant increase (p ≤ 0.05) in the phenoloxidase activity, total hemocyte count and superoxide dismutase activity was observed in both the challenged and non-challenged shrimps fed with Cur-CSNPs. Additionally, a significant increase (p ≤ 0.05) in the relative mRNA expression of lysozyme, cMnSOD and lectin was observed in the Cur-CSNPs fed shrimps. The findings of this research suggest that Cur-CSNPs reinforce the immune system of L. vannamei against V. harveyi infection. Moreover, the non-challenged shrimps showed improvement in the growth parameters in addition to immunostimulation. Thereby a routine inclusion of dietary Cur-CSNPs could mitigate the oxidative damage caused by the incidence of environmental or pathogen-mediated oxidative stress.

Hypoxia-induced oxidative stress and transcriptome changes in the mud crab (Scylla paramamosain)

Mud crab (Scylla paramamosain) is an economically important cultured species in China. Hypoxia is a major environmental stressor during mud crab culture. In the present study, we investigated the oxidative stress and transcriptome changes in the gills of mud crab after intermediate hypoxia stress with dissolved oxygen (DO) 3.0 ± 0.2 mg/L (named as "DO3") and acute hypoxia stress with DO 1.0 ± 0.2 mg/L (named as "DO1") for 0, 3, 6, 12 and 24 h. The superoxide dismutase (SOD) activity of DO1 increased significantly at 3, 6 and 24 h after hypoxia stress, while SOD activity of DO3 increased significantly at 6 and 24 h. The total antioxidant capacity (T-AOC) increased significantly at 6, 12 and 24 h after hypoxia stress. The malondialdehyde (MDA) concentration of DO1 increased significantly at 6, 12 and 24 h after hypoxia stress, while MDA concentration of DO3 only increased significantly at 6 h. The lactate dehydrogenase (LDH) activity of DO1 increased significantly at 3, 6, 12 and 24 h after hypoxia stress, while LDH activity of DO3 increased significantly at 12 and 24 h. Transcriptomic analysis was conducted at 24 h of gill tissues after hypoxia stress. A total of 1052 differentially expressed genes (DEGs) were obtained, including 394 DEGs between DO1 and DO3, 481 DEGs between DO1 and control group, 177 DEGs between DO3 and control group. DEGs were enriched in the pathways related to metabolism, immune functions, ion transport, and signal transduction. Transcriptional analysis showed that glycolysis and tricarboxylic acid cycle genes were the key factors in regulating the adaptation of mud crab to hypoxia stress.

miR-151 Affects Low-Temperature Tolerance of Penaeus vannamei by Modulating Autophagy Under Low-Temperature Stress

MicroRNAs (miRNAs) play key roles in many physiologic and pathologic processes, including autophagy. Autophagy is cellular in an emergency response mechanism of environment stress, but their complex molecular regulatory mechanism under low-temperature stress is largely unknown in shrimp, especially miRNA-mediated regulation of autophagy in low-temperature tolerance. In this article, a shrimp PvTOR and miRNA pva-miR-151 cooperation in response to low-temperature stress has been reported. Pva-miR-151 showed expression patterns opposite to target PvTOR under low-temperature stress. The pva-miR-151 targets the 3'-UTR region of PvTOR, regulate the formation of autophagosome, which contribute to the degradation and recycling of damaged organelles. In addition, the low-temperature tolerance was correlated positively with autophagy in shrimp. Silenced pva-miR-151 increased sensitivity to low-temperature stress, whereas overexpression pva-miR-151 decreased the expression of PvTOR and p-TOR and increased tolerance to low-temperature stress by improving the formation of autophagosome and total hemocyte count. In addition, the TOR activator 3BDO can partially rescue autophagy induced by overexpression of pva-miR-151; these results indicate that miR-151 was necessary for the low-temperature tolerance in shrimp. Taken together, we provide a novel strategy and mechanism for shrimp breeding to improve shrimp low-temperature tolerance.

Growth, Metabolite, Antioxidative Capacity, Transcriptome, and the Metabolome Response to Dietary Choline Chloride in Pacific White Shrimp Litopenaeus vannamei

Simple Summary

Choline is a vitamin-like nutrient and has many metabolic and physiological functions in aquatic animals. Unfortunately, the information on the optimal requirement of dietary choline in Litopenaeus vannamei is limited, and the molecular and metabolic mechanisms of choline on L. vannamei are unclear. Hence, in this study, the growth performance, whole-body composition, serum characteristics, hepatopancreatic antioxidant indexes, serum metabolome and hepatopancreas transcriptome were performed. In this study, the growth of L. vannamei was not affected by dietary choline. Dietary choline played an important role in arachidonic acid and glycerophospholipid metabolism and decreased the oxidant damage of L. vannamei, while excessive choline can inhibit the digestion of protein and reduce the whole-body crude protein in shrimp. Based on the results of weight gain and lipid peroxidation reduction, 1082 mg/kg dietary choline could meet the growth requirement of L. vannamei, but 2822 mg/kg dietary choline was needed to reduce peroxidation damage. The present study would provide valuable information on the requirement of choline in L. vannamei, and help to understand the molecular and metabolic mechanisms of choline in shrimp.

Abstract

To determine the response of Pacific white shrimp Litopenaeus vannamei to different levels of dietary choline, juvenile white shrimp (1.75 ± 0.09 g) were fed six semi-purified diets supplemented with 0 (control), 2000, 4000, 6000, 8000, and 12,000 mg/kg choline chloride for eight weeks. Growth performance, whole-body composition, serum characteristics and hepatopancreatic antioxidant indexes were evaluated. Meanwhile, serum metabolome and hepatopancreas transcriptome were performed to examine the overall difference in metabolite and gene expression. The weight gain, survival, specific growth rate, condition factor and hepatosomatic index were not affected by dietary choline levels. The shrimp fed 6000 mg/kg dietary choline chloride gained the maximal whole-body crude protein, which was significantly higher than that of shrimp fed with 12,000 mg/kg dietary choline. Serum total cholesterol of shrimp fed 6000 mg/kg dietary choline was higher than that in shrimp fed 4000 mg/kg choline. Dietary choline significantly decreased malondialdehyde content, superoxide dismutase, and glutathione peroxidase activities in shrimp hepatopancreas. Compared with the shrimp fed 6000 mg/kg dietary choline chloride, the glycerophospholipid metabolism pathway was significantly enriched in the shrimp fed 0 mg/kg dietary choline chloride, and the choline content and bile salt-activated lipase-like expression were upregulated. The expression of trypsin-1-like in protein digestion and absorption pathway was significantly downregulated in the shrimp fed 12,000 mg/kg dietary choline chloride. Apolipoprotein D might be a potential biomarker in shrimp, and dietary choline played an important role in lipid metabolism, especially in the reduction of oxidative damage in L. vannamei. Based on the results of weight gain and degree of oxidative damage, 1082 mg/kg dietary choline could meet the growth requirement of L. vannamei, but 2822 mg/kg dietary choline was needed to reduce peroxidation damage.

Total replacement of fishmeal with poultry by-product meal affected the growth, muscle quality, histological structure, antioxidant capacity and immune response of juvenile barramundi, Lates calcarifer

The present study investigates if the total replacement of dietary fishmeal (FM) with poultry by-product meal (PBM), supplemented with methionine influences the muscle fatty acids composition, normal gut morphology, histological traits of the liver, muscle, and gill, liver enzymes, immune and antioxidant response, and stress-related gene in juvenile barramundi, Lates calcarifer in relation to growth and feed utilization. Barramundi (3.58±0.01g) were randomly distributed into six 300 L seawater recirculating tanks (25 fish/tank) and fed two formulated isonitrogenous and isolipidic diets for 6 weeks. The control diet had FM as the sole animal protein source, whereas other test diet had only PBM as an animal protein source. Dietary PBM affected the fish performance and feed utilization. Regarding muscle fatty acid profile, total saturated fatty acids and monounsaturated fatty acids elevated while total PUFA particularly n-3 LC-PUFA and EPA decreased in PBM fed fish than control diet fed fish. Liver, muscle, gill, and intestinal histology showed no obvious alteration in control diet fed fish, however, more lipid droplets and hepatic vacuolization in the liver, necrotic myotome in muscle, hyperplasia in secondary lamellae in gill and short and broken folds in the intestine were observed in PBM fed fish. Similar to light microscopy observation of intestinal morphology, the transmission electron microscopy (TEM) analysis revealed shorter and smaller microvilli in fish fed PBM. Histopathological alterations in the liver of PBM fed fish were further associated with the elevated levels of aspartate aminotransferase (AST) and glutamate dehydrogenase (GLDH) and the significant upregulation of stress-related genes, HSP70 and HSP90. Also, a negative influence on lysozyme activity, and antioxidant enzymatic activities were recorded in fish fed PBM. Overall, it can be concluded that a total substitution of FM protein by methionine supplemented PBM negatively influenced the growth performance, liver health, histological traits of different organs, immune and antioxidant response, and expression of stress-related genes in juvenile barramundi.

Mitochondrial manganese superoxide dismutase knock-down increases oxidative stress and caspase-3 activity in the white shrimp Litopenaeus vannamei exposed to high temperature, hypoxia, and reoxygenation

Shrimp are increasingly exposed to warmer temperatures and lower oxygen concentrations in their habitat due to climate change. These conditions may lead to oxidative stress and apoptosis. We studied the effects of high temperature, hypoxia, reoxygenation, and the combination of these factors on lipid peroxidation, protein carbonylation, and caspase-3 activity in gills of white shrimp Litopenaeus vannamei. Silencing of mitochondrial manganese superoxide dismutase (mMnSOD) was used to determine the role of this enzyme in response to the abiotic stressors described above, to avoid oxidative damage and apoptosis. In addition, mMnSOD gene expression and mitochondrial SOD activity were evaluated to determine the efficiency of silencing this enzyme. The results showed that there was no effect of the abiotic stress conditions on the thiobarbituric acid reactive substances (TBARS), but protein carbonylation increased in all the oxidative stress treatments and caspase-3 activity decreased in hypoxia at 28 °C. On the other hand, mMnSOD-silenced shrimp experienced higher oxidative stress, since TBARS, carbonylated proteins and caspase-3 activity increased in some silenced treatments. Unexpectedly, mitochondrial SOD activity increased in some of the silenced treatments as well. Altogether, these results suggest that mMnSOD has a key role in shrimp for the prevention of oxidative damage development and induction of apoptosis in response to hypoxia, reoxygenation, high temperature, and their interactions, as conditions derived from climate change.

Effects of Elevated pCO2 on the Survival and Growth of Portunus trituberculatus

Identifying the response of Portunus trituberculatus to ocean acidification (OA) is critical to understanding the future development of this commercially important Chinese crab species. Recent studies have reported negative effects of OA on crustaceans. Here, we subjected swimming crabs to projected oceanic CO₂ levels (current: 380 μatm; 2100: 750 μatm; 2200: 1500 μatm) for 4 weeks and analyzed the effects on survival, growth, digestion, antioxidant capacity, immune function, tissue metabolites, and gut bacteria of the crabs and on seawater bacteria. We integrated these findings to construct a structural equation model to evaluate the contribution of these variables to the survival and growth of swimming crabs. Reduced crab growth shown under OA is significantly correlated with changes in gut, muscle, and hepatopancreas metabolites whereas enhanced crab survival is significantly associated with changes in the carbonate system, seawater and gut bacteria, and activities of antioxidative and digestive enzymes. In addition, seawater bacteria appear to play a central role in the digestion, stress response, immune response, and metabolism of swimming crabs and their gut bacteria. We predict that if anthropogenic CO₂ emissions continue to rise, future OA could lead to severe alterations in antioxidative, immune, and metabolic functions and gut bacterial community composition in the swimming crabs through direct oxidative stress and/or indirect seawater bacterial roles. These effects appear to mediate improved survival, but at the cost of growth of the swimming crabs.

Multigenerational Mitigating Effects of Ocean Acidification on In Vivo Endpoints, Antioxidant Defense, DNA Damage Response, and Epigenetic Modification in an Asexual Monogonont Rotifer

Ocean acidification (OA) is caused by changes in ocean carbon chemistry due to increased atmospheric pCO₂ and is predicted to have deleterious effects on marine ecosystems. While the potential impacts of OA on many marine species have been studied, the multigenerational effects on asexual organisms remain unknown. We found that low seawater pH induced oxidative stress and DNA damage, decreasing growth rates, fecundity, and lifespans in the parental generation, whereas deleterious effects on in vivo endpoints in F1 and F2 offspring were less evident. The findings suggest that multigenerational adaptive effects play a role in antioxidant abilities and other defense mechanisms. OA-induced DNA damage, including double-strand breaks (DSBs), was fully repaired in F1 offspring of parents exposed to OA for 7 days, indicating that an adaptation mechanism may be the major driving force behind multigenerational adaptive effects. Analysis of epigenetic modification in response to OA involved examination of histone modification of DNA repair genes and a chromatin immunoprecipitation assay, as Bombus koreanus has no methylation pattern for CpG in its genome. We conclude that DSBs, DNA repair, and histone modification play important roles in multigenerational plasticity in response to OA in an asexual monogonont rotifer.

Exploring the multilevel hazards of thiamethoxam using Drosophila melanogaster

Thiamethoxam (THIA) is a widely used pesticide. However, its effects on the growth and development of insects remain unclear. Herein, the lethal concentration 50 (LC50) of THIA (3.13 μg/mL for adults, 20.25 μg/mL for third-instar larvae) were identified. THIA (1/3 LC50) prolonged the time required for growth and development, and decreased the fecundity, the rates of pupation and eclosion, and lifespan of Drosophila. The uniform architecture of the compound eyes was disturbed. It also triggered DNA damage, and reduced the viability of fat body cells and hemocytes. Moreover, RNA-sequencing showed that differentially expressed genes in response to THIA were mainly related to stratum corneum development, immune function. Genes involved in stratum corneum proteins (Lcp65Ag3, Cpr65Ax1), hemocyte proliferation (RyR), and immune responses (IM4) were significantly induced. Genes associated with lipid metabolism (sxe2), lifespan (Atg7 and NalZ), pupa development (IIp8, Blimp-1), female fertility (Ddc), male mating behavior (ple), neural retina development (Nnad), was significantly downregulated. These findings provide a basis for further research to fully assess the hazards of exposure to neonicotinoid pesticides.

Effects of pH and nitrites on the toxicity of a cypermetrin-based pesticide to shrimps

The Pantanal (Brazil) is a wetland region characterized by seasonal flooding. Hydrological cycles influence the water physicochemical parameters, causing seasonal variations in pH and nitrites. Thus, the objective of this study was to evaluate the effects of varying pH and nitrite concentrations on the toxicity of the cypermethrin-based pesticide Barrage®, considering both lethal (mortality) and sublethal endpoints (growth and development). Larvae of the endemic shrimp Macrobrachium pantanalense and of the estuarine Amazonian congener Macrobrachium amazonicum were exposed to cypermethrin (through Barrage®) under several pH levels (6.5, 7.5 and 8.5) or nitrite concentrations (0.1, 0.2 and 0.4 mg/L). The pH had direct effects on all the tested endpoints for both species. For M. pantanalense, the lethal effects of the cypermethrin formulation were more pronounced at low pH (96-h LC₅₀ = 0.004 μg/L at pH 6.5, and 0.146 μg/L at pH 8.5). For M. amazonicum, an opposite response was observed, with increased toxicity of the formulation at high pH (96-h LC₅₀ = 0.110 μg/L at pH 6.5 and 0.044 μg/L at pH 8.5). Variations in pH also seemed to modify the sublethal effects of the formulation on larval growth and development of M. pantanalense. Nitrite concentrations affected larval growth of both species, modifying also the effects of the cypermethrin formulation on the larval development of M. amazonicum. This work shows the importance of considering abiotic factors for risk assessment either due to possible direct effects on the physiology of organisms and/or due to interactions with other stressors, particularly in fragile biomes such as Pantanal.

Comparative transcriptome analysis of the gills of Procambarus clarkii provides novel insights into the immune-related mechanism of copper stress tolerance

The red-swamp crayfish (Procambarus clarkii) is the most important economic shrimp species in China, and is an important model crustacean organism in many fields of research. In crustaceans, gills interface directly with the ambient environment and thus play a vital role in the toxicology. In the context of increasing environmental heavy metal pollution, the relationship between copper (Cu²⁺) stress and the immune response of P. clarkii has recently received considerable attention. However, impact of Cu²⁺ on the crayfish immune system is still not fully understood. In this study, we used Illumina sequencing technology to perform a transcriptome analysis of the gills of P. clarkii after 24 h of Cu²⁺ treatment. A total of 37,226,812 unigenes were assembled, and 1943 unigenes were significantly differentially expressed between the control and Cu²⁺ treatment groups. Functional categorization of differentially expressed genes (DEGs) revealed that genes related to antioxidant activity, detoxication, metabolic processes, biosynthetic processes, and immune system processes were differentially regulated during Cu²⁺ stress. In addition, DEGs in the immune system were classified as being related to the MAPK signaling pathway, purine metabolism, Toll and Imd signaling pathway, PI3K-Akt signaling pathway and Hippo signaling pathway. Five genes (CuZnSOD, CAT, IDH1, PHYH and DECR2) were significantly up-regulated in the peroxisome pathway, which plays an important role in reacting to oxidative stress. Importantly, qRT-PCR validation of the results for seven genes chosen at random (NDK, ATP6L, ATP5C1, RPS14, RPL22e, CTSF and HSP90A) confirmed the Illumina sequencing results. This study provides a valuable starting point for further studies to elucidate the molecular basis of the immune system's response to Cu²⁺ stress in crayfish.

Effect of ammonia stress on immune variables of Pacific white shrimp Penaeus vannamei under varying levels of pH and susceptibility to white spot syndrome virus

Of late, Pacific white shrimp Penaeus vannamei culture has intensified globally and is a major contributor to the cultured shrimp produced worldwide. Intensification of its culture has led to elevated ammonia concentration during grow-out. Ammonia toxicity is a function of water pH, temperature, salinity and beyond the optimum range, creates stress to cultured aquatic species which can reduce growth, increase susceptibility to diseases and eventually mortality. The present study was aimed at quantifying the toxic effect of total ammonia nitrogen (TAN) (1, 3, 6 & 9 mg/l) and pH levels (6, 8 & 10) individually and in combination on median survival (50% lethal time) of shrimp (8 g) after exposure for 14 days followed by post-stress challenge with white spot syndrome virus (WSSV) for 9 days. Mortality risk factor and the toxicity effect on the immune variables were evaluated. Individual stressors showed a risk factor of 1-13 times, whereas combined treatments considerably increased the risk of dying compared to control. Low survival (15%) was observed in pH6TAN9 and pH10TAN3 treatments and was substantiated by prominent histological obliteration in gills of shrimp. The cumulative mortality in post-stress WSSV challenged trials was 1-5 times and 1-35 times in individual and combination treatments, respectively compared to control. The study revealed that variations in ammonia and pH beyond the optimal range significantly influence the non-specific immune mechanisms in P.vannamei and increases the susceptibility to WSSV especially in combination treatments.

The role of delta-1-pyrroline-5-carboxylate dehydrogenase (P5CDh) in the Pacific white shrimp (Litopenaeus vannamei) during biotic and abiotic stress

Proline (Pro) metabolism is intimately associated with stress adaptation. The catabolism of Pro includes two dehydrogenation reactions catalyzed by proline dehydrogenase (ProDH) and Δ¹-pyrroline-5-carboxylate dehydrogenase (P5CDh). P5CDh is a mitochondrial matrix NAD⁺-dependent dehydrogenase that is critical in preventing P5C-Pro intensive cycling and avoiding ROS production from electron run-off. Little is known about the roles of P5CDh in invertebrates, however. We cloned the P5CDh sequence in the Pacific white shrimp, Litopenaeus vannamei, and found that LvP5CDh is expressed predominantly in pleopod, hepatopancreas and gill. Subcellular localization analysis revealed that LvP5CDh protein was mainly found in the cytoplasm. In addition, overexpressing LvP5CDh in cells reduced ROS formation and inhibited apoptosis induced by LC₅₀ Cd²⁺. Shrimp were exposed to various stress factors including infection with Vibrio alginolyticus, (½ LC₅₀ and LC₅₀) Cd²⁺, acid (pH 5.6) and alkali stress (pH 9.3). Both biotic and abiotic stress resulted in increased LvP5CDh expression and Pro accumulation; V. alginolyticus infection, pH 9.3 and LC₅₀ Cd²⁺ stress apparently stimulated the Glu pathway of Pro synthesis, while pH 5.6 and ½ LC₅₀ Cd²⁺ stress promoted the Orn pathway of Pro synthesis. Silencing of Lvp53 in shrimp attenuated LvP5CDh expression during Cd²⁺ stress, but had no effect on LvP5CDh mRNA levels if no Cd²⁺ stress was imposed. Our study contributes to the functional characterization of LvP5CDh in biotic and abiotic stress and reveals it to protect against ROS generation, damage to the cell, including the mitochondria, and apoptosis. Thus, LvP5CDh plays a critical role in immune defense and antioxidant responses.

Effects of Bacillus aryabhattai TBRC8450 on vibriosis resistance and immune enhancement in Pacific white shrimp, Litopenaeus vannamei

The use of probiotics in aquaculture is a practical alternative to promote animal health and disease prevention. Meanwhile, this practice can also reduce the use of prophylactic antibiotics. The purpose of this study was to identify candidate probiotics that could control pathogen populations in host's gastrointestinal (GI) tract and stimulate host immunity in shrimp aquaculture. Bacillus aryabhattai TBRC8450, a bacterial strain isolated from the environment in a shrimp farm, has an antimicrobial activity against many pathogenic strains of Vibrio harveyi and V. parahaemolyticus. Supplementation of B. aryabhattai to Pacific white shrimp (Litopenaeus vannamei) not only decreased the abundance of Vibrio populations, but also shifted the bacterial community in the shrimp GI tract. We found that supplementation of B. aryabhattai triggered shrimp innate immunity and antioxidant activities. mRNA expression of genes encoding microbial peptides and antioxidant enzymes, including C-type lectin, penaeidin-3, heat shock protein 60, thioredoxin, and ferritin, was significantly upregulated in the hepatopancreas of shrimp fed B. aryabhattai. Furthermore, phenoloxidase activity in the hemocytes and the total antioxidant activity in the plasma were increased, indicating enhanced immune and antioxidant responses at the systemic level. In contrast, supplementation of B. aryabhattai had no effect on the total hemocyte count and superoxide dismutase activity in the plasma and hepatopancreas. Importantly, a pathogen challenge test using V. harveyi 1562 showed a significant increase in survival rates of shrimp fed B. aryabhattai compared to the control group. Our findings suggest that B. aryabhattai TBRC8450 can likely be used as a probiotic to reduce the population of V. harveyi in the shrimp GI tract and to enhance shrimp innate immunity and antioxidant capacity for vibriosis resistance in shrimp aquaculture.

Effect of magnesium on reducing the UV-induced oxidative damage in marrow mesenchymal stem cells

Oxidative stress could cause damage to lipids, proteins and DNA, which is induced by the imbalance between the production of reactive oxygen species (ROS) and the biological system ability to counteract or detoxify their harmful effects. The oxidative stress damage significantly contributes to a number of diseases. Magnesium (Mg) is endowed with a novel function of removing excess ROS by releasing H₂ during the degradation. In this study, in order to explore the property of anti-oxidative damage of Mg metal, rat bone marrow mesenchymal stem cells (MSCs) oxidative damaged by ultraviolet (UV) radiation was employed to co-culture with Mg metal. The effect of Mg metal on the response of antioxidant enzymes and mitochondria in MSCs was studied. We found that Mg metal could reduce the cellular oxidative stress damage and elevate the activities of antioxidant enzymes to maintain redox homeostasis. In addition, Mg metal could reduce the risk of UV-induced cell apoptosis by increasing the ratio of Bcl-2/Bax, elevating the mitochondrial membrane potential and blocking the release of cytochrome c. This finding showed Mg metal might have the potential for treating diseases caused by oxidative stress damage. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1253-1263, 2019.

Energy metabolism and survival of the juvenile recruits of the American lobster (Homarus americanus) exposed to a gradient of elevated seawater pCO2

The transition from the last pelagic larval stage to the first benthic juvenile stage in the complex life cycle of marine invertebrates, such as the American lobster Homarus americanus, a species of high economic importance, represents a delicate phase in these species development. Under future elevated pCO₂ conditions, ocean acidification and other elevated pCO₂ events can negatively affect crustaceans. This said their effects on the benthic settlement phase are virtually unknown. This study aimed to identify the effects of elevated seawater pCO₂ on stage V American lobsters exposed to seven pCO₂ levels. The survival, development time, metabolic and feeding rates, carapace composition, and energy metabolism enzyme function were investigated. Results suggested an increase in mortality, slower development and an increase in aerobic capacity with increasing pCO₂. Our study points to potential reduction in juvenile recruitment success as seawater pCO₂ increases, thus foreshadowing important socio-economic repercussions for the lobster fisheries and industry.

Analysis of the transcriptome data in Litopenaeus vannamei reveals the immune basis and predicts the hub regulation-genes in response to high-pH stress

Soil salinization erodes the farmlands and poses a serious threat to human life, reuse of the saline-alkali lands as cultivated resources becomes increasingly prominent. Pacific white shrimp (Litopenaeus vannamei) is an important farmed aquatic species for the development and utilization of the saline-alkali areas. However, little is known about the adaptation mechanism of this species in terms of high-pH stress. In the present study, a transcriptome analysis on the gill tissues of L. vannamei in response to high-pH stress (pH 9.3 ± 0.1) was conducted. After analyzing, the cyclic nucleotide gated channel-Ca2+ (CNGC-Ca2+) and patched 1 (Ptc1) were detected as the majority annotated components in the cAMP signaling pathway (KO04024), indicating that the CNGC-Ca2+ and Ptc1 might be the candidate components for transducing and maintaining the high-pH stress signals, respectively. The immunoglobulin superfamily (IgSF), heat shock protein (HSP), glutathione s-transferase (GST), prophenoloxidase/phenoloxidase (proPO/PO), superoxide dismutase (SOD), anti-lipopolysaccharide factor (ALF) and lipoprotein were discovered as the major transcribed immune factors in response to high-pH stress. To further detect hub regulation-genes, protein-protein interaction (PPI) networks were constructed; the genes/proteins "Polymerase (RNA) II (DNA directed) polypeptide A" (POLR2A), "Histone acetyltransferase p300" (EP300) and "Heat shock 70kDa protein 8" (HSPA8) were suggested as the top three hub regulation-genes in response to acute high-pH stress; the genes/proteins "Heat shock 70kDa protein 4" (HSPA4), "FBJ murine osteosarcoma viral oncogene homolog" (FOS) and "Nucleoporin 54kDa" (NUP54) were proposed as the top three hub regulation-genes involved in adapting endurance high-pH stress; the protein-interactions of "EP300-HSPA8" and "HSPA4-NUP54" were detected as the most important biological interactions in response to the high-pH stress; and the HSP70 family genes might play essential roles in the adaptation of the high-pH stress environment in L. vannamei. These findings provide the first insight into the molecular and immune basis of L. vannamei in terms of high-pH environments, and the construction of a PPI network might improve our understanding in revealing the hub regulation-genes in response to abiotic stress in shrimp species and might be beneficial for further studies.

Effects of 5-Aminolevulinic Acid on Gene Expression, Immunity, and ATP Levels in Pacific White Shrimp, Litopenaeus vannamei

With the emergence of several infectious diseases in shrimp aquaculture, there is a growing interest in the use of feed additives to enhance shrimp immunity. Recently, the use of 5-aminolevulinic acid (5-ALA), a non-protein amino acid that plays a rate-limiting role in heme biosynthesis, has received attention for its positive effect on immunity in livestock animals. To evaluate the effect of 5-ALA in the Pacific white shrimp, Litopenaeus vannamei, we conducted microarray analysis, a Vibrio parahaemolyticus immersion challenge test, an ATP level assay, and gene expression analysis of some hemoproteins and genes associated with heme synthesis and degradation. Out of 15,745 L. vannamei putative genes on the microarray, 101 genes were differentially expressed by more than fourfold (p < 0.05) between 5-ALA-supplemented and control shrimp hepatopancreas. 5-ALA upregulated 99 of the 101 genes, 41 of which were immune- and defense-related genes based on sequence homology. Compared to the control, the 5-ALA-supplemented group had a higher survival rate in the challenge test, higher transcript levels of porphobilinogen synthase, ferrochelatase, catalase, nuclear receptor E75, and heme oxygenase-1 and higher levels of ATP. These findings suggest that dietary 5-ALA enhanced the immune response of L. vannamei to V. parahaemolyticus, upregulated immune- and defense-related genes, and enhanced aerobic energy metabolism, respectively. Further studies are needed to elucidate the extent of 5-ALA use in shrimp culture.

Multi-strain probiotics enhance immune responsiveness and alters metabolic profiles in the New Zealand black-footed abalone (Haliotis iris)

We assessed whether dietary administration of a multi-strain probiotic (Exiguobacterium JHEb1, Vibrio JH1 and Enterococcus JHLDc) lead to enhanced immune responsiveness in juvenile New Zealand black-footed abalone (Haliotis iris). Two groups of abalone were fed (1% body weight per day) over a four-month period with different diets. The control diet consisted of a standard commercial pellet feed (AbMax 16), whereas the treatment diet was additionally enriched with the probiotic mix. At the end of the experiment, probiotic-fed animals showed improved growth compared with control-fed abalone in length (32.3% vs 22.3%), width (31.9% vs 20.7%) and wet weight (109.6% vs 72.8%), respectively. Haemolymph sampling was conducted at the beginning of the experiment and after 2 and 4 months. Haemolymph samples were analysed for total haemocyte count (THC) and viability, presence of apoptotic cells and production of Reactive Oxygen Species (ROS). Compared with control abalone, probiotic-fed abalone had significantly higher THC (1.9 × 10⁶ vs 5.6 × 10⁵ cells), higher viability (90.8% vs 75.6%), higher percentage of ROS-positive cells (19.4% vs 0.5%) and higher numbers of non-apoptotic cells (88.0% vs 78.0%), respectively. These results indicate that the probiotic-enriched diet enhanced the immunostimulatory mechanisms, with a simultaneous low-level up-regulation of ROS production as a priming mechanism of the antibacterial defence system. Metabolomics-based profiling of foot muscle tissue additionally revealed that probiotic-fed abalone differentially expressed 17 unique metabolites, including amino acids, fatty acids and TCA cycle related compounds. These data suggest that the probiotic-supplemented diet can also alter central carbon metabolic processes, which may improve the survival, as well as the growth of abalone.

The impact of ocean acidification and cadmium on the immune responses of Pacific oyster, Crassostrea gigas

Seawater acidification (OA) and cadmium (Cd) has the potential to lead to immunosuppression effect on marine bivalves. However, the interaction between these two environmental stressors on immune system of marine bivalves has received limited attention. In order to evaluate the defense responses of oysters under the combined exposure to OA and cadmium, the oysters Crassostrea gigas were exposed to 10 μg/L Cd at three pH levels (8.1, 7.8 and 7.6) for 31 days. Results showed that OA exposure alone led to increased DNA damage, apoptosis rate and ROS production of hemocytes. However, inhibited phagocytosis rate, combined with increased DNA damage, apoptosis rate and ROS production of hemocytes were observed in oysters under exposure to Cd exposure alone or combined with OA. Significant interactive effects between OA and Cd were observed on ROS production and DNA damage of hemocytes. In addition, there is generally significant increase in the mRNA expression of genes related to immune-related TLR pathway and two immune factors (TNF and integrin beta-1B) in Cd-exposed oysters at pH 7.6. The results revealed that even though the mRNA expression of genes related to immune responses (TLR pathway and immune factors) was stimulated to counteract the immunosuppression caused by acidified seawater and Cd, depressed hemocyte function perhaps sensitized oysters to potential pathogen infection.

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

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

The oxidative stress and antioxidant responses of Litopenaeus vannamei to low temperature and air exposure

Low temperature and air exposure were the key attributes for waterless transportation of fish and shrimp. In order to investigate the oxidative stress and antioxidant responses of the live shrimp Litopenaeus vannamei in the mimic waterless transportation, live shrimp were cooled at 13 °C for 3 min, stored in oxygen at 15 °C for 12 h, and then revived in water at 25 °C. The survival rate of shrimp under this waterless transportation system was over 86.67%. The ultrastructure of hepatopancreas cells were observed while activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glutathione peroxidase (GSH-Px), antisuperoxide anion free radicals (ASAFR), total antioxidant capacity (TAOC), reactive oxygen species (ROS) production, content of malondialdehyde (MDA) and relative mRNA expressions of CAT and GSH-Px in the hemolymph and hepatopancreas were determined. Slight distortions of some organelles in hepatopancreas cells was reversible upon the shrimp revived from the cold shock. The activities of SOD, POD, CAT, GSH-Px, TAOC, ROS production and relative mRNA expressions of CAT and GSH-Px increased following the cold shock and reached peak levels after 3 or 6 h of storage, and then decreased gradually. There was no significant difference between the fresh and the revived shrimp in SOD, POD, GSH-Px, TAOC, ROS, MDA and relative mRNA expressions of CAT and GSH-Px. The oxidative stress and antioxidant responses were tissue-specific because hepatopancreas seemed to have a greater ability to defend against organelle damage and was more sensitive to stress than hemolymph based on the results of SOD activity, MDA content and GSH-Px mRNA expression. These results revealed that low temperature and air exposure caused significant oxidative and antioxidant responses, but did not lead to irreversible damages in this waterless system.

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

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

Homarus gammarus (Crustacea: Decapoda) larvae under an ocean acidification scenario: responses across different levels of biological organization

The present study evaluated the effects of exposure to different target pCO₂ levels: control (C: 370μatm, pH=8.15) and ocean acidification (OA: 710μatm, pH=7.85) on development and biochemical responses related with oxidative stress and energy metabolism during the crustacean Homarus gammarus (L.) larval development, integrating different levels of biological organization. After hatching in the laboratory, larvae from the same female brood were exposed to the described conditions from hatching until reaching Stage III (last larval stage - 11days). H. gammarus larvae demonstrated some susceptibility when addressing the predicted pCO₂ levels for 2100. Further analysis at the biochemical and physiological level highlighted the occurrence of oxidative stress in the OA scenario (Superoxide Dismutase reduction and higher DNA damage) that was followed by developmental effects, increased inter-moult period from SII to SIII and reduced growth. The extended exposure to these conditions may affect organisms' key life-cycle functions such as physiological resistance, growth, sexual maturation, or reproduction with implications in their future fitness and population dynamics.

Transcriptomic and morphological analyses of Litopenaeus vannamei intestinal barrier in response to Vibrio paraheamolyticus infection reveals immune response signatures and structural disruption

The white shrimp Litopenaeus vannamei has been greatly impacted by Vibrio infection. In this study, we investigated the intestinal barrier response of L vannamei following challenge with Vibrio parahaemolyticus E1, by examining morphological changes and transcriptome expression levels. A total of 16,4420 unigenes were obtained from RNAseq data after quality control and assembly, and 4646 differentially expressed genes (DEGs) were identified following Vibrio challenge, of which 2469 unigenes were significantly up-regulated and 2177 were significantly down-regulated. DEGs were determined to be involved in various physical, chemical and immunological intestinal barrier functions, including peritrophin, cytoskeleton and cell junction, pattern recognition receptors, antimicrobial peptide and immune signaling pathways, serine protease/protease inhibitor and prophenoloxidase system, apoptosis and phagocytosis, and antioxidant systems. Fifteen DEGs were randomly selected for validation by real-time quantitative PCR (RT-qPCR) and showed results consistent with the RNA-seq data. Intestinal epithelial cell morphology was also affected by Vibrio challenge, showing epithelial detachment, nuclear pyknosis, and destruction of cell junctions. These results improve our current understanding of the intestinal barrier function in the shrimp response to bacterial infection.

Molecular cloning, characterization and expression analysis of caspase-3 from the oriental river prawn, Macrobrachium nipponense when exposed to acute hypoxia and reoxygenation

Caspases are present in the cytosol as inactive proenzymes but become activated when apoptosis is initiated, playing an essential role at various stages of the process. In this study, a caspase-3 (Mncaspase-3c) was cloned from gill of the oriental river prawn Macrobrachium nipponense by reverse-transcription polymerase chain reaction and rapid amplification of cDNA ends, and its properties were characterized. The 1730-bp cDNA contained an open reading frame of 1566 bp, a 123-bp 5'-untranslated region (UTR), and a 41-bp 3'-UTR containing a poly(A) tail. The molecular mass of the deduced amino acid (aa) sequence (521 aa) was 56.3 kDa with an estimated pI of 5.01. The MnCaspase-3c sequence contained a predicted caspase family p20 domain and a caspase family p10 domain at positions 236-367 and 378-468 respectively. Recombinant MnCaspase-3c protein was expressed in Escherichia coli and purified. In vitro activity assays indicated that the recombinant MnCaspase-3c hydrolyzed the substrate Ac-DEVD-pNA, suggesting a physiological role as a caspase-3. Caspase-3c gene transcripts were distributed in all M. nipponense tissues tested by quantitative RT-PCR, being especially abundant in hemocytes. Comet assays in gill tissues showed an obvious time-dependent response to hypoxia. Furthermore, Mncaspase-3c, at both the mRNA and protein levels, was demonstrated to participate in the apoptotic process in gill after stimulation by acute hypoxia. Overall, these results indicate that hypoxia triggers apoptosis in shrimp gill tissues.

Expression patterns of two carbonic anhydrase genes, Na+/K+-ATPase and V-type H+-ATPase, in the freshwater crayfish, Cherax quadricarinatus, exposed to low pH and high pH

Carbonic anhydrase (CA), Na+/K+-ATPase (NKA) and Vacuolar-type H+-ATPase (HAT) play vital roles in osmoregulation and pH balance in decapod crustaceans. As variable pH levels have a significant impact on the physiology of crustaceans, it is crucial to understand the mechanisms by which an animal maintains its internal pH. We examined expression patterns of cytoplasmic (CAc) and membrane-associated form (CAg) of CA, NKA α subunit and HAT subunit a in gills of freshwater crayfish, Cherax quadricarinatus, at three pH levels – 6.2, 7.2 (control) and 8.2 – over 24 h. Expression levels of CAc were significantly increased at low pH and decreased at high pH conditions 24 h after transfer. Expression increased at low pH after 12 h, and reached its maximum level by 24 h. CAg showed a significant increase in expression at 6 h after transfer at low pH. Expression of NKA significantly increased at 6 h after transfer to pH 6.2 and remained elevated for up to 24 h. Expression for HAT and NKA showed similar patterns, where expression significantly increased 6 h after transfer to low pH and remained significantly elevated throughout the experiment. Overall, CAc, CAg, NKA and HAT gene expression is induced at low pH conditions in freshwater crayfish.

Evaluation of ToxA and Vibrio parahaemolyticus lysate on humoral immune response and immune-related genes in Pacific red snapper

Immunogenicity of ToxA and Vibrio parahaemolyticus lysate was evaluated in a double immunostimulation scheme in Pacific red snapper after V. parahaemolyticus infection. Three groups of Pacific red snapper were intraperitonealy (i.p.) injected with phosphate-buffered saline (PBS group), ToxA of V. parahaemolyticus (ToxA-Vp group) or V. parahaemolyticus lysate (lysate-Vp group) (first injection, day 1; second injection, day 7). Fish were subsequently infected with live V. parahaemolyticus. Humoral immune parameters in skin mucus and serum were evaluated on days 1, 7, 8 and 14 days post-immunostimulation and 7 days post-infection. Moreover expression of immune-related genes was quantified by real time PCR in head-kidney leukocytes, spleen, liver, and intestine. The ToxA-Vp-treated group showed a higher anti-protease and catalase activity in skin mucus when compared with the PBS group. Measurements of SOD and CAT activities showed an increment in both activities a day after the second boost with ToxA-Vp or lysate-Vp. Interestingly, IgM levels in mucus and transcripts were enhanced followed the ToxA-Vp treatment even after challenge. Furthermore, IL-1β was strongly expressed in all analyzed cell or tissues followed ToxA-Vp or Vp-lysate treatments. Finally, SOD and CAT gene expression was up-regulated in fish immunostimulated with either treatment ToxA-Vp or lysate-Vp, mainly after infection in head-kidney leukocytes and intestine. This is the first study where the effects of ToxA from V. parahaemolyticus in the immune system of Pacific red snapper was evaluated. These results suggest that ToxA-Vp would positively affect humoral immune response and up-regulate expression of genes involved in the immune system function; and could help in the control of V. parahaemolyticus infection in Pacific red snapper Lutjanus peru, an economic important fish in Mexico.

Molecular characterization of an adiponectin receptor homolog in the white leg shrimp, Litopenaeus vannamei

Adiponectin (AdipoQ) and its receptors (AdipoRs) are strongly related to growth and development of skeletal muscle, as well as glucose and lipid metabolism in vertebrates. Herein we report the identification of the first full-length cDNA encoding an AdipoR homolog (Liv-AdipoR) from the decapod crustacean Litopenaeus vannamei using a combination of next generation sequencing (NGS) technology and bioinformatics analysis. The full-length Liv-AdipoR (1,245 bp) encoded a protein that exhibited the canonical seven transmembrane domains (7TMs) and the inversed topology that characterize members of the progestin and adipoQ receptor (PAQR) family. Based on the obtained sequence information, only a single orthologous AdipoR gene appears to exist in arthropods, whereas two paralogs, AdipoR1 and AdipoR2, have evolved in vertebrates. Transcriptional analysis suggested that the single Liv-AdipoR gene appears to serve the functions of two mammalian AdipoRs. At 72 h after injection of 50 pmol Liv-AdipoR dsRNA (340 bp) into L. vannamei thoracic muscle and deep abdominal muscle, transcription levels of Liv-AdipoR decreased by 93% and 97%, respectively. This confirmed optimal conditions for RNAi of Liv-AdipoR. Knockdown of Liv-AdipoR resulted in significant changes in the plasma levels of ammonia, 3-methylhistine, and ornithine, but not plasma glucose, suggesting that that Liv-AdipoR is important for maintaining muscle fibers. The chronic effect of Liv-AdipoR dsRNA injection was increased mortality. Transcriptomic analysis showed that 804 contigs were upregulated and 212 contigs were downregulated by the knockdown of Liv-AdipoR in deep abdominal muscle. The significantly upregulated genes were categorized as four main functional groups: RNA-editing and transcriptional regulators, molecular chaperones, metabolic regulators, and channel proteins.

Characterization and function analysis of Hsp60 and Hsp10 under different acute stresses in black tiger shrimp, Penaeus monodon

Heat shock proteins (Hsps) are a class of highly conserved proteins produced in virtually all living organisms from bacteria to humans. Hsp60 and Hsp10, the most important mitochondrial chaperones, participate in environmental stress responses. In this study, the full-length complementary DNAs (cDNAs) of Hsp60 (PmHsp60) and Hsp10 (PmHsp10) were cloned from Penaeus monodon. Sequence analysis showed that PmHsp60 and PmHsp10 encoded polypeptides of 578 and 102 amino acids, respectively. The expression profiles of PmHsp60 and PmHsp10 were detected in the gills and hepatopancreas of the shrimps under pH challenge, osmotic stress, and heavy metal exposure, and results suggested that PmHsp60 and PmHsp10 were involved in the responses to these stimuli. ATPase and chaperone activity assay indicated that PmHsp60 could slow down protein denaturation and that Hsp60/Hsp10 may be combined to produce a chaperone complex with effective chaperone and ATPase activities. Overall, this study provides useful information to help further understand the functional mechanisms of the environmental stress responses of Hsp60 and Hsp10 in shrimp.

Oxidative stress, DNA damage and antioxidant enzyme activities in the pacific white shrimp (Litopenaeus vannamei) when exposed to hypoxia and reoxygenation

To evaluate the genotoxic and physiological effects of acute hypoxia on the pacific white shrimp (L. vannamei), shrimps were treated firstly with three dissolved oxygen levels 6.5 ppm (control), 3.0 ppm and 1.5 ppm for 24 h, respectively, and then reoxygenated (6.5 ppm) for 24 h. The changes of superoxide dismutase (SOD) activity, glutathione peroxidases (GPX) activity, malondialdehyde (MDA) concentration and DNA damage in the tissues of gill, hepatopancreas and hemolymph were examined during the period of hypoxia and reoxygenation. The results indicated SOD activity, GPX activity, MDA concentration and DNA damage all increased basically compared with the control during the period of hypoxia except for MDA concentrations in the gill at 12 h and 24 h hypoxia (3.0 ppm), and these parameters were recovered to some degree during the period of reoxygenation. Moreover, the comet assays in the tissues of gill and hepatopancreas showed an obvious time- and dose-dependent response to hypoxia, which indicated comet assay in the two tissues could be used as sensitive biomarker to detect the occurrence of hypoxia. We conclude that acute hypoxia can induce oxidative stress, DNA damage and lipid peroxidation in the tissues of gill, hepatopancreas and hemolymph of L. vannamei and the DNA damage may come from hypoxia-induced oxidative stress.