Dietary nano cerium oxide promotes growth, relieves ammonia nitrogen stress, and improves immunity in crab (Eriocheir sinensis)

ROS-mediated physiological activities and apoptotic effect on the survival of abalone (Haliotis discus hannai) under homoyessotoxin and ammonia stresses

Serious dinoflagellate blooms produce homoyessotoxin (homo-YTX) and ammonia (NH3-N) in eutrophic seawaters, posing threats to the healthy development of the mariculture industry. This study aimed to explore the toxicity mechanism of homo-YTX and NH3-N on the survival of abalone, which is important for the ecotoxicological research and cultivation of shellfish. The economy abalone Haliotis discus hannai was placed in homo-YTX (0, 2, 5, and 10 μg L-1) and NH3-N (0, 1.08, and 3.16 mg L-1) and a mixture of the two compounds to determine the survival rate (S), antioxidative responses, physiological activities, and apoptosis of abalone. Results show that the combination of homo-YTX and NH3-N increased the reactive oxygen species level, the malondialdehyde content, and the expression level of BCL2-associated X but decreased S; the activities of superoxide dismutase, catalase, adenosine triphosphatase, glutamic-pyruvic transaminase, xanthine oxidase, lactate dehydrogenase, and lysozyme; and the expression level of B-cell lymphoma-2. The activities of alkaline phosphatase and acid phosphatase in 10 μg L-1 of homo-YTX and 3.16 mg L-1 of NH3-N solutions and in the mixture of the two toxicants decreased. The caspase3 expression level was downregulated in 10 μg L-1 of homo-YTX. These results suggest that homo-YTX and NH3-N enhanced the oxidative stress and lipid peroxidation reactions, inhibited the energy supply, disrupted the metabolic and immune physiological functions, and activated apoptosis in the gills of abalone. ROS-mediated physiological activities and apoptosis were among the potential toxicity mechanisms of the interactive effects of homo-YTX and NH3-N on abalone.

Rhodobacter azotoformans supplementation improves defense ability of Chinese mitten crab Eriocheir sinensis against citrobacteriosis

Rhodobacter probiotics are considered as good alternatives to antibiotics for aquaculture. Yet the beneficial effects of Rhodobacter on Chinese mitten crab Eriocheir sinensis are still unclear, and more functions of Rhodobacter supplementation need to be clarified. In this study, a 60-day feeding trial was performed to investigate the protective effects of R. azotoformans against citrobacteriosis in E. sinensis by growth performance, serum immunity, hepatopancreatic antioxidant capability, intestinal flora, and resistance to Citrobacter freundii challenge assays. The results showed that R. azotoformans supplementation significantly and dose-dependently increased weight gain and specific growth rate as well as activities of serum immune and hepatopancreatic antioxidant enzymes, leading to notable improvement in the growth performance, serum immunity and hepatopancreatic antioxidant status of E. sinensis. Besides, R. azotoformans supplementation significantly enhanced intestinal microbial abundance and diversity in E. sinensis, and conferred significant protection of the crabs against C. freundii challenge with seven-day survival rates of 70.0%-100.0%. To the best of our knowledge, this is the first study to reveal the protective effects of R. azotoformans against citrobacteriosis in E. sinensis.

Comparative proteomic profiling in Chinese shrimp Fenneropenaeus chinensis under low pH stress

Lower pH gives rise to a harmful stress to crustacean. Here, we analyzed the proteomic response of Fenneropenaeus chinensis from control pH (pH value 8.2) and low pH (pH value 6.5) - treated groups by employing absolute quantitation-based quantitative proteomic (iTRAQ) analysis. Among the identified proteins, a total of 76 proteins differed in their abundance levels, including 45 upregulated and 31 downregulated proteins. The up-regulation of proteins like citrate synthase, cytochrome c oxidase, V-type proton ATPase, glyceraldehyde-3-phosphate dehydrogenase and fructose 1,6-bisphosphate-aldolase as well as the enrichment of the DEPs in multiple metabolic processes and pathways illustrated that increased energy and substrates metabolism was essential for F. chinensis to counteract low pH stress. Ion transporting related proteins, such as Na⁺/K⁺/2Cl^- cotransporter and calmodulin, participated in the homeostatic maintenance of pH in F. chinensis. There were significant downregulation expressions of lectin, lipopolysaccharide- and beta-1,3-glucan binding protein, chitinase, cathepsin L and beta-glucuronidase, which indicating the immune dysfunction of F. chinensis when exposure to low pH condition. These findings can extend our understanding on the defensive mechanisms of the low pH stress and accelerate the breeding process of low pH tolerance in F. chinensis.

The effects of ammonia-N stress on immune parameters, antioxidant capacity, digestive function, and intestinal microflora of Chinese mitten crab, Eriocheir sinensis, and the protective effect of dietary supplement of melatonin

Ammonia nitrogen pollution seriously affects the economic benefits of Chinese mitten crab (Eriocheir sinensis) farming. In this study, we first evaluated the protective effects of melatonin (MT) on immune parameters, antioxidant capacity, and digestive enzymes of E. sinensis under acute ammonia nitrogen stress. The results showed that ammonia-N stress significantly decreased the antibacterial ability of crabs, nevertheless MT could significantly improve it under ammonia-N stress (P < 0.05). Ammonia-N group hemolymph antioxidant capacity indicators (T-AOC, T-SOD, GSH-Px) were significantly decreased than control (p < 0.05), while the MT ammonia-N group hemolymph T-SOD activity significantly increased than ammonia-N group (p < 0.05). For hepatopancreas, ammonia-N group GSH-PX activity significantly decreased than control group, but MT ammonia-N group was significant increased than ammonia-N (p < 0.05). Ammonia-N stress has significantly increased the content of MDA in hemolymph and hepatopancreas (p < 0.05), but MT ammonia-N treatment significantly decreased than ammonia-N group (p < 0.05). Compared with the control group, ammonia-N significantly reduced the activities of Trypsin in the intestine and hepatopancreas (p < 0.05), while MT ammonia-N group can significantly improve the intestinal trypsin activity than ammonia-N (p < 0.05). The intestinal microbiota of E. sinensis results showed that ammonia-N stress significantly decreased the relative abundance of Bacteroidetes (p < 0.05). Ammonia-N stress significantly decreased the Dysgonomonas and Rubellimicrobium, and the Citrobacter significantly increased. In summary, melatonin has a protective effect on E. sinensis under ammonia-N stress. Acute ammonia-N stress may lead to the decrease of probiotics and the increase of pathogenic bacteria, which may be closely related to the impairment of digestive function and immune function.

Ficus hirta Vahl. promotes antioxidant enzyme activity under ammonia stress by inhibiting miR-2765 expression in Penaeus vannamei

Ficus hirta Vahl. has been reported to have hepatoprotective, antitumor, antibacterial functions, and is used to treat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Ammonia nitrogen is one of the most common environmental stress factors in aquaculture. Long-term exposure to high concentrations of ammonia nitrogen can induce oxidative stress and increase the risk of infections. However, whether Ficus hirta Vahl. has effect on ammonia nitrogen stress is unclear. In present study we report that Ficus hirta Vahl. improves the activity of total antioxidant capacity (T-AOC), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) of shrimp and decreases shrimp mortality caused by ammonia nitrogen stress. It is demonstrated that miR-2765 is negatively regulate the antioxidant capacity. We find that SOD was a direct target gene of miR-2765. MiR-2765 can bind to 3'-untranslated region (3'-UTR) of SOD to inhibit its transcription. Furthermore, Ficus hirta Vahl. down-regulates miR-2765 to activate the antioxidant capacity to alleviate the damage caused by ammonia nitrogen stress. Interestingly, overexpression of miR-2765 could attenuate the protective effect of Ficus hirta Vahl. on shrimp under ammonia nitrogen stress. These data indicate that Ficus hirta Vahl. alleviates the damage of ammonia nitrogen stress in shrimp by repressing miR-2765 and activating the antioxidant enzyme system. This study will provide a theoretical basis and a new perspective for assessing the toxicity mechanism of ammonia nitrogen in the process of farming on shrimp.

Maltose promotes crucian carp survival against Aeromonas sobrial infection at high temperature

Temperature influences fish’s susceptibility to infectious disease through an immune response. However, the mechanism underlying this regulation is yet to be elucidated. In this study, we compared the susceptibility of crucian carp that were grown at 18°C and 33°C, respectively, to Aeromonas sobrial infection and found that crucian carp was more susceptible when grown at 33°C. These distinct susceptibilities of fish at different temperatures to infection may partially be explained by their differences in the metabolism as revealed by comparative metabolomics profiling: crucian carp demonstrated enhanced TCA cycle but reduced fatty acid biosynthesis; Our study also found that maltose was the most suppressed metabolite in fish grown at 33°C. Importantly, exogenous injection of maltose enhances crucian carp survival grown at 33°C by 30%. Further study showed that exogenous maltose downregulated the production of several cytokines but enhanced the lysozyme (lyz) and complement component c3, which involves the humoral innate immunity. Our results suggest that maltose promotes the survival of crucian carp likely through fine tuning the immune gene expression, and this finding provides a novel approach to manage bacterial infection.

Ingestion and effects of cerium oxide nanoparticles on Spodoptera frugiperda (Lepidoptera: Noctuidae)

The objective of this study was to evaluate the biological and nutritional characteristics of Spodoptera frugiperda (Lepidoptera: Noctuidae), an arthropod pest widely distributed in agricultural regions, after exposure to nano-CeO₂ via an artificial diet and to investigate the presence of cerium in the body of this insect through X-ray fluorescence mapping. Nano-CeO₂, micro-CeO₂, and Ce(NO₃)₃ were incorporated into the diet (0.1, 1, 10, and 100 mg of Ce L^-1). Cerium was detected in caterpillars fed with diets containing nano-CeO₂ (1, 10 and 100 mg of Ce L^-1), micro-CeO₂ and Ce(NO₃)₃, and in feces of caterpillars from the first generation fed diets with nano-CeO₂ at 100 mg of Ce L^-1 as well. The results indicate that nano-CeO₂ caused negative effects on S. frugiperda. After it was consumed by the caterpillars, the nano-CeO₂ reduced up to 4.8% of the pupal weight and 60% of egg viability. Unlike what occurred with micro-CeO₂ and Ce(NO₃)₃, nano-CeO₂ negatively affected nutritional parameters of this insect, as consumption rate two times higher, increase of up to 80.8% of relative metabolic rate, reduction of up to 42.3% efficiency of conversion of ingested and 47.2% of digested food, and increase of up to 1.7% of metabolic cost and 8.7% of apparent digestibility. Cerium caused 6.8-16.9% pupal weight reduction in second generation specimens, even without the caterpillars having contact with the cerium via artificial diet. The results show the importance of new ecotoxicological studies with nano-CeO₂ for S. frugiperda in semi-field and field conditions to confirm the toxicity.

Monitoring oxidative stress, immune response, Nrf2/NF-κB signaling molecules of Rhynchocypris lagowski living in BFT system and exposed to waterborne ammonia

The present study was implemented to evaluate oxidative stress, immune response, Nrf2 and NF-κB signaling molecules related genes expression of Rhynchocypris lagowski living in biofloc technology (BFT) system and exposed to waterborne ammonia. According to the differences of C:N ratios, the experiment was divided into four groups: C:N 10.8:1 (control group), C:N 15:1, C:N 20: 1 and C:N 25:1. The results demonstrated that BFT can effectively regulate water quality and promote growth, and the C:N 20:1 group has the most significant effect (P < 0.05). Besides, significant increases in immune enzymes (lysozyme, complement C3, C4, immunoglobulin M and nitric oxide synthase) and anti-inflammatory factor (IL-2) activity of R. lagowski were emerged in the treatment C:N 20:1 after the 56-d growth experiment and the challenging trial (P < 0.05). Comparing the antioxidant status of R. lagowski in liver and gut before and after ammonia stress: superoxide dismutase, total antioxidant capacity and catalase activity in treatments C:N 20:1 were significant increased (P < 0.05), while the level of malondialdehyde was marked lower than that in control. Meanwhile, treatment C:N 20:1 considerably upregulated Nrf2 signaling molecules related genes and significantly down-regulated the expression of pro-inflammatory factor gene in NF-κB signaling pathway compared with the control (P < 0.05). These results indicated that BFT could enhance growth, antioxidant and immune response and regulate Nrf2 and NF-κB related genes expression in R. lagowski, with most excellent effects in fish given C:N 20:1 group.

Effect of acute exposure to ammonia and BFT alterations on Rhynchocypris lagowski: Digestive enzyme, inflammation response, oxidative stress and immunological parameters

Biofloc technology (BFT) is a new green culture technology that is intended not merely to eradicate nitrogenous residues but also enhance immunity and antioxidant activity in aquatic animals. A 56-day feeding trial and a 96 h ammonia challenge test were implemented to evaluate the effect of acute exposure to ammonia and BFT alterations on Rhynchocypris lagowski: digestive enzyme, inflammation response, oxidative stress and immunological parameters in zero water exchange tanks. According to the differences of C/N ratios, the experiment was divided into four groups: C/N 10.8:1 (control group), C/N 15:1, C/N 20: 1 and C/N 25:1. The results provided evidence that weight gain rate (WGR), specific growth rate (SGR) and protein efficiency ratio (PER) were significantly elevated in C/N 20, while food conversion rate (FCR) was considerably decreased (P < 0.05) compared to the control. Significant increases in digestive enzyme amylase (AMS), lipase (LPS), protease (PRS) and cellulase (CES) activity; Immune enzyme complement C3, complement C4, Nitric Oxide Synthase (NOS) and immunoglobulin M (IgM) activity; Serum biochemical lysozyme (LSZ), glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT) and alkaline phosphatase (AKP) activity; Inflammation TNF-α, IL-1β, IL-2, IL-6 of R. lagowskis were found in the C/N 20 group after a 56-day feeding trial and a challenging trial (P < 0.05). Comparing the antioxidant capacity of R. lagowski in gills, brains and spleen of juveniles from the four experimental groups, the activity of superoxide dismutase (SOD), total antioxidant capacity (T-AOC), catalase (CAT) activity and glutathion reductases (GR) activity of juveniles in the C/N 20 group were significant higher (P < 0.05), and the content of malondialdehyde (MDA) was considerably lower than that in the control. Overall, these findings suggest that BFT not only can enhance R. lagowski growth performance, digestive enzyme activity, and strengthen antioxidant status but also upgrade immune response, improve the ability of resistance to ammonia stress.

Addressing Nanomaterial Immunosafety by Evaluating Innate Immunity across Living Species

The interaction of a living organism with external foreign agents is a central issue for its survival and adaptation to the environment. Nanosafety should be considered within this perspective, and it should be examined that how different organisms interact with engineered nanomaterials (NM) by either mounting a defensive response or by physiologically adapting to them. Herein, the interaction of NM with one of the major biological systems deputed to recognition of and response to foreign challenges, i.e., the immune system, is specifically addressed. The main focus is innate immunity, the only type of immunity in plants, invertebrates, and lower vertebrates, and that coexists with adaptive immunity in higher vertebrates. Because of their presence in the majority of eukaryotic living organisms, innate immune responses can be viewed in a comparative context. In the majority of cases, the interaction of NM with living organisms results in innate immune reactions that eliminate the possible danger with mechanisms that do not lead to damage. While in some cases such interaction may lead to pathological consequences, in some other cases beneficial effects can be identified.