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

Effects of dietary supplementation with medicinal plant mixtures and immunostimulants on the immune response, antioxidant capacity, and hepatopancreatic health of Chinese mitten crab (Eriocheir sinensis)

Introduction

This study aimed to evaluate the efficiency of tea polyphenols (TP) and medicinal plant mixtures (Astragalus membranaceus + Lonicera japonica, Rheum officinale Bail + Scutellaria baicalensis + Platycladus orientalis) combined with astaxanthin (AST), benzoic acid (BA), and yeast complex on the health status of Eriocheir sinensis.

Method

A total of 630 crabs (male crabs: 41.51 ± 1.63 g; female crabs: 47.27 ± 0.79 g) were randomly distributed into seven groups with three replicates (male: female, 1:1). These crabs were fed as follows for 8 weeks: basal diet (M1), M2 (M1 + 100 mg/kg TP), M3 (M1 + 2.0 g/kg A. membranaceus + 20 g/kg L. japonica), M4 (M1 + 2.5 g/kg R. officinale Bail + 1.5 g/kg S. baicalensis + 1.0 g/kg P. orientalis), and M5, M6, M7 (M2, M3 and M4 with 600 mg/kg AST +1.0 g/kg BA + 20 mg/kg yeast complex added, respectively).

Results and discussion

The results showed that the activities of acid phosphatase (ACP), alkaline phosphatase (AKP), and lysosome (LZM) in the hemolymph were significantly increased in M5, M6, and M7 (P < 0.05), and the highest phagocytosis index (PI) and LZM activity were observed in M7 of female crabs. Moreover, the antioxidant indicators superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GPx), and catalase (CAT) of hepatopancreas were also significantly improved in M5, M6, and M7 (P < 0.05), while the malondialdehyde (MDA) contents showed an opposite trend. Furthermore, a morphological examination also showed the improved histological structure of hepatopancreas in M7, especially as seen in the clear lumens, no vacuolation, and integrity of the basal membrane of the hepatopancreatic tubule. Taken together, these results suggested that 2.5 g/kg R. officinale Bail, 1.5 g/kg S. baicalensis, and 1.0 g/kg P. orientalis in combination with 600 mg/kg AST, 1.0 g/kg BA, and 20 mg/kg yeast complex could improve the non-specific immunity, antioxidant capacity, and hepatopancreatic health of E. sinensis.

Effects of monoglycerides of short and medium chain fatty acids and cinnamaldehyde blend on the growth, survival, immune responses, and tolerance to hypoxic stress of Pacific white shrimp (Litopenaeus vannamei)

Free fatty acids have long been used as dietary supplements in aquaculture, but the application of monoglycerides has increased interest in more recent times. The study aimed to investigate the effects of dietary short- and medium-chain fatty acid monoglyceride and cinnamaldehyde (SMMG) on the growth performance, survival, immune responses, and tolerance to hypoxic stress of Pacific white shrimp (Litopenaeus vannamei). In Experiment 1, shrimp post-larvae were divided into 4 groups with 6 replicates and fed with diets supplemented with 0 (control), 0.3, 0.4, and 0.5% diet for 30 days. The final body weight and survival rate were determined. In Experiment 2, the juvenile shrimp from Experiment 1 were subjected to hypoxic stress conditions (dissolved oxygen level 2-2.5 mg/L) for 14 days, then the specific growth rate (SGR), survival rate, intestinal Vibrio spp. count, immune responses, and histopathological change of the hepatopancreas were analyzed. Following the 30-day feeding trial, the results revealed that the final body weight and survival of the 0.3-0.5% SMMG groups (2.81-3.06 g and 74.00-84.33%, respectively) were significantly higher than the control shrimp (1.96 g and 68.33%, respectively). In the hypoxic stress experiment, the survival rates of shrimp fed 0.4-0.5% SMMG (71.67-80.00%) were significantly higher than the control (51.67%). Although the SGR were not affected by SMMG supplementation, all immune parameters evaluated were significantly enhanced, and the intestinal Vibrio spp. counts were significantly decreased in the 0.4-0.5% SMMG-fed shrimp; the histopathological structure of the hepatopancreas was also improved in these shrimp compared to the control. Our findings indicated that SMMG as a feed additive has beneficial effects in improving shrimp health and increasing tolerance to hypoxic conditions.

The impact of co-exposure to polystyrene microplastics and norethindrone on gill histology, antioxidant capacity, reproductive system, and gut microbiota in zebrafish (Danio rerio)

In recent years, studies have focused on the combined ecological risks posed by microplastics and other organic pollutants. Although both microplastics and progestin residues are frequently detected in the aquatic environments, their ecological implications remain unknown. Adult zebrafish were exposed to polystyrene microplastics (PS, 200 nm, 200 μg/L), norethindrone (NET, 69.6 ng/L), and their mixture (200 μg/L PS + 63.1 ng/L NET) for 30 days. The results demonstrated that exposure to PS and NET resulted in gill damage. Notably, the PS and PS+NET exhibited a significant decrease in glutathione (GSH) and oxidized glutathione (GSSG) content, as well as reduced antioxidase activity in the gills. The oxidative stress in PS+NET primarily originated from PS. The PS, NET, or their mixture resulted in a decrease in testosterone (T) and estradiol (E2) levels in female. Furthermore, compared to NET, the PS+NET showed a significant reduction in E2 levels, thereby augmenting the inhibitory effect on reproductive ability mediated by NET. However, males showed an increase in 11-ketodihydrotestosterone (11-KT) content, accompanied by a significant decrease in spermatogonia (Sg) and increase in spermatocytes (Sc). Consequently, it can be inferred that PS enhances the androgenic effect of NET. In female fish brain, NET alone resulted in transcriptional down-regulation of partial hormone receptors; however, co-administration of PS effectively mitigated the interference effects. Furthermore, transcriptional downregulation of 17-alpha-hydroxylase (cyp17), hydroxysteroid 3-beta dehydrogenase (hsd3b), estrogen receptor 1 (esr1), and estrogen receptor 2a (esr2b) genes in the ovary was found to be associated with the androgenic activity induced by NET. Moreover, in comparison to PS or NET alone, PS+NET resulted in a notable decrease in Cetobacterium abundance and an increase in Aeromonas population, suggesting that the co-exposure of PS+NET may exacerbate intestinal burden. The findings highlight the importance of studying the combined toxicity of PS and NET.

Integrated transcriptome and metabolome analysis reveals the molecular responses of Pardosa pseudoannulata to hypoxic environments

Terrestrial organisms are likely to face hypoxic stress during natural disasters such as floods or landslides, which can lead to inevitable hypoxic conditions for those commonly residing within soil. Pardosa pseudoannulata often inhabits soil crevices and has been extensively studied, yet research on its response to hypoxic stress remains unclear. Therefore, we investigated the adaptive strategies of Pardosa pseudoannulata under hypoxic stress using metabolomics and transcriptomics approaches. The results indicated that under hypoxic stress, metabolites related to energy and antioxidants such as ATP, D-glucose 6-phosphate, flavin adenine dinucleotide (FAD), and reduced L-glutathione were significantly differentially expressed. Pathways such as the citric acid (TCA) cycle and oxidative phosphorylation were significantly enriched. Transcriptome analysis and related assessments also revealed a significant enrichment of pathways associated with energy metabolism, suggesting that Pardosa pseudoannulata primarily copes with hypoxic environments by modulating energy metabolism and antioxidant-related substances.

Effects of Low-Salinity Stress on Histology and Metabolomics in the Intestine of Fenneropenaeus chinensis

Metabolomics has been used extensively to identify crucial molecules and biochemical effects induced by environmental factors. To understand the effects of acute low-salinity stress on Fenneropenaeus chinensis, intestinal histological examination and untargeted metabonomic analysis of F. chinensis were performed after exposure to a salinity of 15 ppt for 3, 7, and 14 d. The histological examination revealed that acute stress resulted in most epithelial cells rupturing, leading to the dispersion of nuclei in the intestinal lumen after 14 days. Metabolomics analysis identified numerous differentially expressed metabolites (DEMs) at different time points after exposure to low-salinity stress, in which some DEMs were steadily downregulated at the early stage of stress and then gradually upregulated. We further screened 14 overlapping DEMs, in which other DEMs decreased significantly during low-salinity stress, apart from L-palmitoylcarnitine and vitamin A, with enrichments in phenylalanine, tyrosine and tryptophan biosynthesis, fatty acid and retinol metabolism, and ABC transporters. ABC transporters exhibit significant abnormalities and play a vital role in low-salinity stress. This study provides valuable insights into the molecular mechanisms underlying the responses of F. chinensis to acute salinity stress.

Effects of Environmental Hypoxia on Serum Hematological and Biochemical Parameters, Hypoxia-Inducible Factor (hif) Gene Expression and HIF Pathway in Hybrid Sturgeon (Acipenser schrenckii ♂ × Acipenser baerii ♀)

Hypoxia is a globally pressing environmental problem in aquatic ecosystems. In the present study, a comprehensive analysis was performed to evaluate the effects of hypoxia on physiological responses (hematology, cortisol, biochemistry, hif gene expression and the HIF pathway) of hybrid sturgeons (Acipenser schrenckii ♂ × Acipenser baerii ♀). A total of 180 hybrid sturgeon adults were exposed to dissolved oxygen (DO) levels of 7.00 ± 0.2 mg/L (control, N), 3.5 ± 0.2 mg/L (moderate hypoxia, MH) or 1.00 ± 0.1 mg/L (severe hypoxia, SH) and were sampled at 1 h, 6 h and 24 h after hypoxia. The results showed that the red blood cell (RBC) counts and the hemoglobin (HGB) concentration were significantly increased 6 h and 24 h after hypoxia in the SH group. The serum cortisol concentrations gradually increased with the decrease in the DO levels. Moreover, several serum biochemical parameters (AST, AKP, HBDB, LDH, GLU, TP and T-Bil) were significantly altered at 24 h in the SH group. The HIFs are transcription activators that function as master regulators in hypoxia. In this study, a complete set of six hif genes were identified and characterized in hybrid sturgeon for the first time. After hypoxia, five out of six sturgeon hif genes were significantly differentially expressed in gills, especially hif-1α and hif-3α, with more than 20-fold changes, suggesting their important roles in adaptation to hypoxia in hybrid sturgeon. A meta-analysis indicated that the HIF pathway, a major pathway for adaptation to hypoxic environments, was activated in the liver of the hybrid sturgeon 24 h after the hypoxia challenge. Our study demonstrated that hypoxia, particularly severe hypoxia (1.00 ± 0.1 mg/L), could cause considerable stress for the hybrid sturgeon. These results shed light on their adaptive mechanisms and potential biomarkers for hypoxia tolerance, aiding in aquaculture and conservation efforts.

H2O2-Induced Oxidative Stress Responses in Eriocheir sinensis: Antioxidant Defense and Immune Gene Expression Dynamics

Eriocheir sinensis, a key species in China's freshwater aquaculture, is threatened by various diseases, which were verified to be closely associated with oxidative stress. This study aimed to investigate the response of E. sinensis to hydrogen peroxide (H2O2)-induced oxidative stress to understand the biological processes behind these diseases. Crabs were exposed to different concentrations of H2O2 and their antioxidant enzyme activities and gene expressions for defense and immunity were measured. Results showed that activities of antioxidant enzymes-specificallysuperoxide dismutase (SOD), catalase (CAT), total antioxidant capacity(T-AOC), glutathione (GSH), and glutathione peroxidase (GSH-Px)-varied with exposure concentration and duration, initially increasing then decreasing. Notably, SOD, GSH-Px, and T-AOC activities dropped below control levels at 96 h. Concurrently, oxidative damage markers, including malondialdehyde (MDA), H2O2, and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels, increased with exposure duration. The mRNA expression of SOD, CAT, and GSH-Px also showed an initial increase followed by a decrease, peaking at 72 h. The upregulation of phenoloxidaseloxidase (proPO) and peroxinectin (PX) was also detected, but proPO was suppressed under high levels of H2O2. Heat shock protein 70 (HSP70) expression gradually increased with higher H2O2 concentrations, whereas induced nitrogen monoxide synthase (iNOS) was upregulated but decreased at 96 h. These findings emphasize H2O2's significant impact on the crab's oxidative and immune responses, highlighting the importance of understanding cellular stress responses for disease prevention and therapy development.

The effect of astaxanthin on the alkalinity stress resistance of Exopalaemon carinicauda

Astaxanthin (Axn), a feed additive, can improve growth performance and enhance the environmental stress tolerance of shrimp at all growth stages. High carbonate alkalinity is considered a major stressor that affects the survival, growth, and reproduction of aquatic animals in saline-alkaline waters. In this study, a combined analysis of physiology, transcriptomics, and metabolomics was performed to explore the effected mechanism of Axn on Exopalaemon carinicauda (E. carinicauda) under alkalinity stress. The results revealed that dietary Axn can inhibit oxidative stress damage caused by alkalinity stress and maintain the normal cell structure and mitochondrial membrane potential. Transcriptomic data indicated that differentially expressed genes (DEGs) under alkalinity stress and those under alkalinity stress after Axn feeding were associated with apoptosis. The metabolic data suggested that alkalinity stress has adverse effects on ammonia metabolism, unsaturated fatty acid metabolism, and TCA cycle, and dietary Axn can improve the metabolic processes in E. carinicauda. In addition, transcriptomics and metabolomics analyses showed that Axn could help maintain the cytoskeletal structure and inhibit apoptosis under alkalinity stress; a TUNEL assay further confirmed these effects. Lastly, metabolic responses to alkalinity stress included changes in multiple amino acids and unsaturated fatty acids, and pathways related to energy metabolism were downregulated in the hepatopancreas of E. carinicauda under alkalinity stress. Collectively, all these results provide new insights into the molecular mechanisms underlying alkalinity stress tolerance in E. carinicauda after Axn feeding.

Combined toxicity of microplastics and copper on Goniopora columns

As microplastics (MP) become ubiquitous, their interactions with heavy metals threatens the coral ecosystem. This study aimed to assess the combined toxicity of MP and copper (Cu) in the environment of coral. Goniopora columna was exposed to polyethylene microplastics (PE-MP) combined with Cu2+ at 10, 20, 50, 100, and 300 μg/L for 7 days. Polyp length and adaptability were recorded daily, and coral samples were collected at 1, 3, 5, and 7 days to analyse zooxanthellae density and antioxidant activity. Tissue observations and the analysis of MP and Cu2+ accumulation were conducted on the 7th day. After 1 day of exposure, PE-MP combined with different concentrations of Cu2+ significantly decreased polyp length and adaptability compared with PE-MP alone. Simultaneously, a significant increase in malondialdehyde (MDA) content, lead to coral oxidative stress, which was a combined effect with PE-MP. After 3 days of exposure, PE-MP combined with Cu2+ at >50 μg/L significantly reduced zooxanthellae density, damaging the coral's symbiotic relationship. In antioxidant enzyme activity, superoxide dismutase (SOD) activity decreased significantly after 1 day of exposure. After 3 days of exposure, glutathione peroxidase (GPx) activity significantly increased with Cu2+ at >20 μg/L. After 5 days of exposure, PE-MP combined with different concentrations of Cu2+ significantly reduced catalase (CAT), glutathione (GSH), and glutathione transferase (GST) activity, disrupting the antioxidant enzyme system, and acting antagonistically to PE-MP alone. Tissue observations revealed that the PE-MP combined with Cu2+ at >50 μg/L caused severe mesenteric atrophy, vacuolar, and Cu2+ accumulation in the coral mesenteric compared with PE-MP alone. The results suggest that combined exposure of PE-MP and copper leads to more severe oxidative stress, disruption antioxidant enzyme system, tissue damage, and Cu2+ accumulation, resulting in a significant maladaptation of corals to the environment.

Effects of acute hypoxia and reoxygenation on histological structure, antioxidant response, and apoptosis in razor clam Sinonovacula constricta

Hypoxia is one of the major environmental problems limiting the healthy development of intensive aquaculture. Marine benthic shellfish are encountering heightened problems related to hypoxic stress as a result of ongoing human activities and aquaculture operations. Razor clam Sinonovacula constricta, a commercially valuable shellfish, has not yet been reported in studies on physiological changes caused by hypoxia and reoxygenation. To understand the negative effects of hypoxia and reoxygenation on the clams, we set up two low-oxygen concentration groups (DO 2.0 mg/L and DO 0.5 mg/L) and assessed multiple aspects of oxidative damage to their hepatopancreas and gills. After the hypoxic stress, the two tissues of the razor clam suffered varying degrees of damage, including cell degeneration and disruption of mitochondrial cristae. After reoxygenation, the 2.0 mg/L group recovered substantially, but the clams in the 0.5 mg/L group still unrecovered. The activities of antioxidant enzymes (MDA, T-AOC, SOD, GPX, and CAT) in clams were considerably altered by acute hypoxia and reoxygenation. Briefly, there was a growing and then declining trend in MDA, T-AOC, and SOD activities in the hepatopancreas, whereas GPX and CAT activities showed the converse trend. In the hepatopancreas and gills, the level of anti-apoptotic gene Bcl-2 transcripts gradually decreased with the duration of hypoxia and increased following reoxygenation. However, changes in the transcript level of the pro-apoptotic gene Bax were in contrast to that of Bcl-2. The TUNEL assay revealed that hypoxia caused apoptosis. Furthermore, at DO 0.5 mg/L, the degree of apoptosis was more significant than at DO 2.0 mg/L, and hepatopancreatic apoptosis was more severe than gill apoptosis. Collectively, our findings imply that hypoxia induces oxidative stress, histological damage, and apoptosis in razor clams in a concentration-dependent and tissue-specific manner. These consequences serve as a reminder that prolonged recovery periods may be required for razor clams to fully recover from oxidative damage resulting from hypoxia-reoxygenation episodes.

Insights into Dietary Different Co-Forms of Lysine and Glutamate on Growth Performance, Muscle Development, Antioxidation and Related Gene Expressions in Juvenile Grass Carp (Ctenopharyngodon idellus)

The study aimed to compare the effects of crystalline L-lysine and L-glutamate (CAA), Lys-Glu dipeptide (KE) on the growth and muscle development of grass carp (Ctenopharyngodon idellus), and related molecular mechanisms. Five experimental diets (CR, 0.5% CAA, 1.5% CAA, 0.5% KE, 1.5% KE) containing Lys and Glu as free (Lys and Glu, CAA) dipeptide (Lys-Glu, KE) forms were prepared, respectively. A total of 450 juvenile grass carp with an initial weight of 10.69 ± 0.07 g were randomly assigned to 15 cages, and 5 treatments with 3 replicates of 30 fish each for 61 days of feeding. The results showed that the group of 0.5% KE exhibited the best growth performances according to the indicator's weight gain rate (WGR) and specific growth rate (SGR), although no statistically significant occurred among all groups; diet supplemented with 0.5% CAA significantly elevated the condition factor (CF) and viscerasomatic index (VSI) of juvenile grass carp. Diet supplemented with different Lys and Glu co-forms at different levels promoted the muscle amino acid content compared with those of CR group. Comparing with the CR group and other groups, the hardness of 0.5% CAA group significantly increased, and the springiness of 0.5% KE group excelled. Both the muscle fiber diameter and density of 0.5% KE group showed significant difference with those of the CR group, and a negative correlation between them was also observed. To uncover the related molecular mechanism of the differences caused by the different co-forms of Lys and Glu, the effect of different diets on the expressions of protein absorption, muscle quality, and antioxidation-related genes was analyzed. The results suggested that comparing with those of CR group, the dipeptide KE inhibited the expressions of genes associated with protein metabolism, such as AKT, S6K1, and FoxO1a but promoted PCNA expression, while the free style of CAA would improve the FoxO1a expression. Additionally, the muscle development-related genes (MyoD, MyOG, and Myf5) were significantly boosted in CAA co-form groups, and the expressions of fMYHCs were blocked but fMYHCs30 significantly promoted in 0.5% KE group. Finally, the effect of different co-forms of Lys and Glu on muscle antioxidant was examined. The 0.5% CAA diet was verified to increase GPX1a but obstruct Keap1 and GSTP1 expressions, resulting in enhanced SOD activity and reduced MDA levels in plasma. Collectively, the different co-forms of Lys and Glu influenced the growth of juvenile grass carp, and also the muscle development and quality through their different regulation on the protein metabolism, muscle development- and antioxidative-related genes.

Influence of Storage Time on the DNA Integrity and Viability of Spermatozoa of the Spider Crab Maja brachydactyla

Natural populations of the spider crab Maja brachydactyla constitute a fishery resource of great economic importance in many countries. As in the rest of eubrachyurans, the females of this species have ventral-type seminal receptacles where they store sperm from copulations. Sperm can be stored in these structures for months and even years before egg fertilisation, with the consequent degradation of the sperm cells during the time. In this work, we analyse the viability and the possible genetic damage in sperm accumulated in the seminal receptacles of M. brachydactyla females as a function of the storage time (from 0 to 14 months) using the comet assay technique. On one hand, we developed an algorithm for comet image analysis that improves the comet segmentation compared with the free software Open comet v1.3.1 (97% vs. 76% of detection). In addition, our software allows the manual modification of the contours wrongly delimited via the automatic tool. On the other hand, our data show a sharp decline in sperm viability and DNA integrity in the first four months of storage, which could lead to a decrease in the fecundity rate and/or viability of the embryos or larvae from the second and third clutches of the annual cycle if the repair capacity in these gametic cells is low.

Responses and modulation of the white shrimp Litopenaeus vannamei glutathione peroxidases 2 and 4 during hypoxia, reoxygenation and GPx4 knock-down

Glutathione peroxidases (GPxs) are important antioxidant enzymes that act at distinct levels of the antioxidant defense. In vertebrates, there are several glutathione peroxidase (GPx) isoforms with different cellular and tissue distribution, but little is known about their interrelationships. The shrimp Litopenaeus vannamei is the main crustacean cultivated worldwide. It is affected by environmental stressors, including hypoxia and reoxygenation that cause reactive oxygen species accumulation. Thus, the antioxidant response modulation is key for shrimp resilience. Recently, several GPx isoforms genes were identified in the L. vannamei genome sequence, but their functions are just beginning to be studied. As in vertebrates, shrimp GPx isoforms can present differences in their antioxidant responses. Also, there could be interrelationships among the isoforms that may influence their responses. We evaluated shrimp GPx2 and GPx4 expressions during hypoxia, reoxygenation, and GPx4 knock-down using RNAi for silencing, as well as the enzymatic activity of total GPx and GPx4. Also, glutathione content in hepatopancreas was evaluated. GPx2 and GPx4 presented similar expression patterns during hypoxia and reoxygenation. Their expressions decreased during hypoxia and were reestablished in reoxygenation at 6 h in non-silenced shrimp. GPx2 expression was down-regulated by GPx4 knock-down, suggesting that GPx4 affects GPx2 expression. Total GPx activity changed in hypoxia and reoxygenation at 6 h but not at 12 h, while GPx4 activity was not affected by any stressor. The GSH/GSSG ratio in hepatopancreas indicated that at early hours, the redox status remains well-modulated but at 12 h it is impaired by hypoxia and reoxygenation.

The combination of hypoxia and high temperature affects heat shock, anaerobic metabolism, and pentose phosphate pathway key components responses in the white shrimp (Litopenaeus vannamei)

Due to global warming, world water bodies have higher temperatures and lower oxygen concentrations that affect aquatic species including the white shrimp Litopenaeus vannamei. This species withstands these conditions, but the information of the physiological responses that allow them to survive are scarce. We analyzed the effects of high temperature, hypoxia, reoxygenation, and the combination of these factors on the relative expression of selected genes: HSF1, Hsp70, p53, TIGAR, HIF-1α, and VEGF1-3 in gills of L. vannamei. Additionally, glucose, lactate, NADP, and NADPH were determined. HSF1 was up-regulated in the high temperature and oxygen stress conditions, but Hsp70 was up-regulated only in reoxygenation at both temperatures. HIF-1α was also up-regulated by reoxygenation in both temperatures. Meanwhile, the VEGF genes were not altered by the stress conditions, since none of them changed expression drastically. p53 relative expression remained stable at the tested stress conditions, which prompts to the maintenance of antioxidant defenses. TIGAR expression was induced in normoxia and hypoxia at high temperature, which induced NADPH content helping to scavenge reactive oxygen species (ROS). Additionally, high temperature caused higher glucose and lactate content in normoxia and hypoxia, indicating carbohydrate mobilization and a switch to anaerobic metabolism. The results showed that HSF1, the anaerobic metabolism and the pentose phosphate pathway (PPP) are crucial for the shrimp response to these abiotic stress conditions and contribute to their survival.

Alteration of antioxidant status, glucose metabolism, and hypoxia signal pathway in Eirocheir sinensis after acute hypoxic stress and reoxygenation

Dissolved oxygen (DO) is crucial for the survival of Chinese mitten crab (Eirocheir sinensis); low DO levels adversely affect the health of these crabs. In this study, we evaluated the underlying response mechanism of E. sinensis to acute hypoxic stress by analyzing antioxidant parameters, glycolytic indicators, and hypoxia signaling factors. The crabs were exposed to hypoxia for 0, 3, 6, 12, and 24 h and reoxygenated for 1, 3, 6, 12, and 24 h. The hepatopancreas, muscle, gill, and hemolymph were sampled at different exposure times to detect the biochemical parameters and gene expression. The results showed that the activity of catalase, antioxidants, and malondialdehyde in tissues significantly increased under acute hypoxia and gradually decreased during the reoxygenation phase. Under acute hypoxic stress, glycolysis indices, including hexokinase (HK), phosphofructokinase, pyruvate kinase (PK), pyruvic acid (PA), lactate dehydrogenase (LDH), lactic acid (LA), succinate dehydrogenase (SDH), glucose, and glycogen in the hepatopancreas, hemolymph, and gills increased to varying degrees but recovered to the control levels after reoxygenation. Gene expression data showed that hypoxia signaling pathway-related genes, including hypoxia-inducible factor-1α/β (HIF1α/β), prolyl hydroxylase (PHD), factor inhibiting hypoxia-inducible factor (FIH), and glycolysis-related factors (HK and PK) were upregulated, showing that the HIF signaling pathway was activated under hypoxic conditions. In conclusion, acute hypoxic exposure activated the antioxidant defense system, glycolysis, and HIF pathway to respond to adverse conditions. These data contribute to elucidating the defense and adaptive mechanisms of crustaceans to acute hypoxic stress and reoxygenation.

Toxicity of perfluorobutanesulfonate on gill functions of marine medaka (Oryzias melastigma): A time course and hypoxia co-exposure study

Perfluorobutanesulfonate (PFBS) is found in hypoxia regions. Results of previous studies have shown that hypoxia was capable of altering the inherent toxicity of PFBS. However, regarding gill functions, hypoxic influences and time course progression of toxic effects of PFBS remain unclear. In this study, with the aim to reveal the interaction behavior between PFBS and hypoxia, adult marine medaka Oryzias melastigma were exposed for 7 days to 0 or 10 μg PFBS/L under normoxic or hypoxic conditions. Subsequently, to explore the time-course transition in gill toxicity, medaka were exposed to PFBS for 21 days. The results showed that hypoxia dramatically increased the respiratory rate of medaka gill, which was further enhanced by exposure to PFBS; although exposure to PFBS under normoxic conditions for 7 days did not alter respiration, exposure to PFBS for 21 days significantly accelerated the respiration rate of female medaka. Concurrently, both hypoxia and PFBS were potent to interrupt the gene transcriptions and Na⁺, K⁺-ATPase enzymatic activity that play pivotal roles in the osmoregulation in gills of marine medaka, consequently disrupting homeostasis of major ions in blood, such as Na⁺, Cl^-, and Ca²⁺. In addition, composition and diversity of the microbiome residing on surfaces of the gill were profiled by using amplicon sequencing. Acute exposure to hypoxia for only 7 days caused a significant decrease in diversity of the bacterial community of gill whatever the presence of PFBS, while PFBS exposure for 21 days increased the diversity of gill microbial community. Principal component analysis revealed that, compared with PFBS, hypoxia was the predominant driver of gill microbiome dysbiosis. Depending on duration of exposure, a divergence was caused in the microbial community of gill. Overall, the current findings underline the interaction between hypoxia and PFBS on gill function and demonstrate the temporal variation in PFBS toxicity.

Hypoxia stress induces hepatic antioxidant activity and apoptosis, but stimulates immune response and immune-related gene expression in black rockfish Sebastes schlegelii

Dissolved oxygen concentrations both in the open ocean and coast have been declining due to the interaction of global climate change and human activity. Fish have evolved different adaptative strategies to cope with possibly damage induced by hypoxic environments. Black rockfish as important economic fish widely reared in the offshore sea cage, whereas related physiological response subject to hypoxia stress remained unclear. In this study, hepatic anti-oxidant enzymes (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GSH-Px]), aminotransferase (AST) and alanine aminotransferase (ALT) activities, lipid peroxidation (LPO), malondialdehyde (MDA) and glutathione (GSH) content, immunological parameters and the expression of apoptosis (bax, bcl2, p53, caspase3, xiap) and immune-related genes (c3, il-1β, ccl25, saa, hap, isg15) of black rockfish were determined during hypoxia and reoxygenation to illustrate the underlying defense response mechanisms. Results showed that hypoxia stress remarkably increased hepatic LPO and MDA content, AST and ALT activity and proportion of pyknotic nucleus. Hepatic SOD, CAT and GSH-Px activity manifested similar results, whereas GSH levels significantly decreased under hypoxia stress. The apoptosis rate of hepatocyte increased during hypoxia stress and reoxygenation. Meanwhile, p53, caspase3, bax and xiap mRNAs and bax/bcl2 rations were significantly up-regulated under hypoxia stress. However, bcl2 mRNA was significantly down-regulated. Interestingly, hypoxia stress significantly increased NBT-positive cell percent, phagocytic index, respiratory burst and ACH50 activity, and lysozyme activity. The mRNA levels of c3, ilβ, ccl25, saa, hap and isg15 were significantly up-regulated in the liver, spleen and head-kidney under hypoxia stress. The above parameters recovered to normal status after reoxygenation for 24 h Thus, hypoxia stress impairs hepatic antioxidant capacity, induces oxidative damage and apoptosis via the xiap-p53-bax-bcl2 and the caspase-dependent pathways, but enhances host immunity by regulating nonspecific immune indices and related genes expression to maintain homeostasis in black rockfish. These findings will help fully understand the hypoxia tolerance mechanisms of black rockfish and provide more data for offshore open ocean farming.

Dietary supplementation of coated sodium butyrate improves growth performance of laying ducks by regulating intestinal health and immunological performance

Introduction

This study was conducted to assess the effects of dietary supplementation of coated sodium butyrate (CSB) on the growth performance, serum antioxidant, immune performance, and intestinal microbiota of laying ducks.

Methods

A total of 120 48-week-old laying ducks were randomly divided into 2 treatment groups: the control group (group C fed a basal diet) and the CSB-treated group (group CSB fed the basal diet + 250 g/t of CSB). Each treatment consisted of 6 replicates, with 10 ducks per replicate, and the trial was conducted for 60 days.

Results

Compared with the group C, the group CSB showed a significant increase in the laying rate (p&lt;0.05) of the 53-56 week-old ducks. Additionally, the serum total antioxidant capacity, superoxide dismutase activity and immunoglobulin G level were significantly higher (p&lt;0.05), while the serum malondialdehyde content and tumor necrosis factor (TNF)-a level were significantly lower (p&lt;0.05) in the serum of the group CSB compared to the group C. Moreover, the expression of IL-1b and TNF-a in the spleen of the group CSB was significantly lower (p&lt;0.05) compared to that of the group C. In addition, compared with the group C, the expression of Occludin in the ileum and the villus height in the jejunum were significantly higher in the group CSB (p&lt;0.05). Furthermore, Chao1, Shannon, and Pielou-e indices were higher in the group CSB compared to the group C (p&lt;0.05). The abundance of Bacteroidetes in the group CSB was lower than that in the group C (p&lt;0.05), while the abundances of Firmicutes and Actinobacteria were higher in the group CSB compared to the group C (p&lt;0.05).

Conclusions

Our results suggest that the dietary supplementation of CSB can alleviate egg-laying stress in laying ducks by enhancing immunity and maintaining the intestinal health of the ducks.

Prospecting toxicity of octocrylene in Allium cepa L. and Eisenia fetida Sav

Octocrylene sunscreen is found in different environmental compartments. Unlike aquatic organisms, there are few studies evaluating the adverse effects caused by this pollutant on terrestrial plants, and no studies on soil fauna. In this study, octocrylene was evaluated at concentrations of 10, 100, and 1000 µg/L for phytotoxicity, cytogenotoxicity, and oxidative stress in Allium cepa L., and acute toxicity and oxidative stress in Eisenia fetida Sav. In A. cepa, at concentrations of 100 and 1000 µg/L, octocrylene reduced the germination potential in seeds, inhibited root elongation, and caused disturbance in cell division in roots. In E. fetida, the concentration of 1000 µg/L promoted an avoidance rate of 80%, while 10 µg/L caused a hormesis effect. The concentrations 100 and 1000 µg/L caused lipid peroxidation in A. cepa and E. fetida. Based on the results, the recurrent use of biosolids in soil fertilization, as well as the irrigation of plants with wastewater, with the presence of octocrylene can negatively impact the survival of different species that depend directly or indirectly on the soil.

Mechanism of bisphenol S exposure on color sensitivity of zebrafish larvae

Color vision, initiated from cone cells, is vitally essential for identifying environmental information in vertebrate. Although the retinotoxicity of bisphenol S (BPS) has been reported, data on the influence of BPS treatment on cone cells are scarce. In the present study, transgenic zebrafish (Danio rerio) labeling red and ultraviolet (UV) cones were exposed to BPS (0, 1, 10, and 100 μg/L) during the early stages of retinal development, to elucidate the mechanism underlying its retinal cone toxicity of BPS. The results showed that 10 and 100 μg/L BPS induced oxidative DNA damage, structural damage (decreased number of ribbon synapses), mosaic patterning disorder, and altered expression of genes involved in the phototransduction pathway in red and UV cones. Furthermore, BPS exposure also caused abnormal development of key neurons (retinal ganglion cells, optic nerve, and hypothalamus), responsible for transmitting the light-electrical signal to brain, and thereby resulted in inhibition of light-electrical signal transduction, finally diminishing the spectral sensitivity of zebrafish larvae to long- and short-type light signal at 5 day post fertilization. This study highlights the cone-toxicity of environmental relevant concentrations of BPS, and clarifies the mechanism of color vision impairment induced by BPS at the cellular level, updating the understanding of visual behavior driven by environmental factors.

Hypoxia Affects the Antioxidant Activity of Glutaredoxin 3 in Scylla paramamosain through Hypoxia Response Elements

Hypoxia is a major environmental stressor that can damage the oxidation metabolism of crustaceans. Glutaredoxin (Grx) is a key member of the thioredoxin superfamily and plays an important role in the host's defense against oxidative stress. At present, the role of Grx in response to hypoxia in crustaceans remains unclear. In this study, the full-length cDNA of Grx3 (SpGrx3) was obtained from the mud crab Scylla paramamosain, which contains a 129-bp 5' untranslated region, a 981-bp open reading frame, and a 1,183-bp 3' untranslated region. The putative SpGrx3 protein contains an N-terminal thioredoxin domain and two C-terminal Grx domains. SpGrx3 was expressed in all tissues examined, with the highest expression in the anterior gills. After hypoxia, SpGrx3 expression was significantly up-regulated in the anterior gills of mud crabs. The expression of Grx2 and glutathione S-transferases was decreased, while the expression of glutathione peroxidases was increased following hypoxia when SpGrx3 was silenced in vivo. In addition, the total antioxidant capacity of SpGrx3-interfered mud crabs was significantly decreased, and the malondialdehyde content was significantly increased during hypoxia. The subcellular localization data indicated that SpGrx3 was predominantly localized in the nucleus when expressed in Drosophila Schneider 2 (S2) cells. Moreover, overexpression of SpGrx3 reduced the content of reactive oxygen species in S2 cells during hypoxia. To further investigate the transactivation mechanism of SpGrx3 during hypoxia, the promoter region of the SpGrx3 was obtained by Genome Walking and three hypoxia response elements (HREs) were predicted. Dual-luciferase reporter assay results demonstrated that SpGrx3 was likely involved in the hypoxia-inducible factor-1 (HIF-1) pathway during hypoxia, which could be mediated through HREs. The results indicated that SpGrx3 is involved in regulating the antioxidant system of mud crabs and plays a critical role in the response to hypoxia.

Selenium improved mitochondrial quality and energy supply in the liver of high-fat diet-fed grass carp (Ctenopharyngodon idella) after heat stress

This study aims to explore the effects of dietary selenium on hepatic mitochondrial quality and energy supply of grass carp (Ctenopharyngodon idella) fed with high-fat diet (HFD) after heat stress (HS). Grass carp were fed with HFD, and HFD contained 0.3 mg/kg nano-selenium for 10 weeks, thereafter exposed to HS from 26 to 34 °C, and named the HFD + HS (control) group and the HFD + Se + HS group, respectively. The results show that selenium significantly prompted the growth, increased glutathione peroxidase (GPX) activity, but reduced malondialdehyde (MDA) content in the liver and the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the serum of grass carp fed with HFD after HS. Further, selenium alleviated mitochondrial damage and increased the number of mitochondrial DNA copies in the liver of the grass carp fed with HFD after HS. And selenium also maintained mitochondrial homeostasis by upregulating the expression of mitochondrial quality control-related genes (pgc-1α, nrf1/2, tfam, opa1, mfn1/2, and drp1), mitophagy-related genes (beclin1, atg5, atg12, pink1, and parkin), and the protein expression of parkin and LC3-II/I in the liver of grass carp. Finally, selenium reduced the triglyceride (TG) level and increased the free fatty acid (FFA) level and adenosine triphosphate (ATP) production in the liver of grass carp fed with HFD after HS. In conclusion, dietary selenium alleviated liver damage and improved liver mitochondrial quality and ATP production by increasing liver antioxidant capacity and promoting liver mitochondrial quality in grass carp fed with HFD after HS, which help grass carp to resist these two stressors.

Garlic Powder Supplementation Improves Growth, Nonspecific Immunity, Antioxidant Capacity, and Intestinal Flora of Chinese Mitten Crabs (Eriocheir sinensis)

This study was conducted to survey the effects of garlic powder on growth performance, nonspecific immunity, antioxidant capacity, and intestinal flora structure of Chinese mitten crabs. Altogether, 216 crabs which originally weigh 20.71 ± 0.13 g were randomly allocated into three treatment groups with 6 replicates of 12 crabs per replicate. The control group (CN) was fed a basal diet, while the other two groups were fed the basal diet supplemented with 1000 mg/kg (GP1000) and 2000 mg/kg (GP2000) garlic powder, respectively. This trial lasted 8 weeks. The results showed that the supplementation of garlic powder improved the final body weight, weight gain rate, and specific growth rate of the crabs (P < 0.05). Meanwhile, in serum, better nonspecific immune was confirmed by the enhancement of phenoloxidase and lysozyme levels, with the improvement of phosphatase activities in GP1000 and GP2000 (P < 0.05). On the other hand, the levels of total antioxidant capacity, glutathione peroxidases, and total superoxide dismutase in serum and hepatopancreas were increased (P < 0.05) while malondialdehyde content declined (P < 0.05) as the garlic powder was added to the basal diet. And, catalase in serum also shows an increase (P < 0.05). In both GP1000 and GP2000, genes related to antioxidant and immunity, for instance, Toll-like receptor 1, glutathione peroxidase, catalase, myeloid differentiation factor 88, TuBe, Dif, relish, crustins, antilipopolysaccharide factor, lysozyme, and prophenoloxidase mRNA expression levels, were increased (P < 0.05). The abundance of Rhizobium and Rhodobacter was reduced by adding garlic powder (P < 0.05). This study indicated that dietary addition of garlic powder promoted growth, enhanced nonspecific immunity and antioxidant capacity, activated Toll pathway, IMD pathway, and proPO system, increased antimicrobial peptide expression, while simultaneously improving the intestinal flora of Chinese mitten crabs.

Transcriptome profiling reveals toxicity mechanisms following sertraline exposure in the brain of juvenile zebrafish (Danio rerio)

Sertraline (SER) is one of the most commonly detected antidepressants in the aquatic environment that can negatively affect aquatic organisms at low concentrations. Despite some knowledge on its acute toxicity to fish, the effects of chronic SER exposure remain poorly understood along with any underlying mechanisms of SER-induced toxicity. To address this knowledge gap, the effects of chronic exposure to three SER concentrations from low to high were investigated in zebrafish. Juvenile zebrafish were exposed to three concentrations of 1, 10, or 100 μg/L of SER for 28 d, after which indicators of oxidative stress and neurotoxicity in the brain were measured. Superoxide dismutase (SOD) activity was significantly enhanced by SER at 1 up to 100 μg/L, and catalase (CAT) activity was significantly induced by SER at 1 or 10 μg/L. The activity of acetylcholinesterase (AChE) was significantly induced by 10 and 100 μg/L of SER, and the serotonin (5-HT) level was significantly increased by all three concentrations of SER. To ascertain mechanisms of SER-induced toxicity, transcriptomics was conducted in the brain of zebrafish following 100 μg/L SER exposure. The molecular signaling pathways connected with circadian system and the immune system were significantly altered in the zebrafish brain. Based on transcriptomic data, the expression levels of six circadian clock genes were measured, and three genes were significantly altered in relative abundance in fish from all experimental treatments with SER, including cryptochrome circadian regulator 2 (cry2), period circadian clock 2 (per2), and period circadian clock 3 (per3). We hypothesize that the circadian system may be related to SER-induced neurotoxicity and oxidative stress in the central nervous system. This study reveals potential mechanisms and key events (i.e., oxidative stress and neurotoxicity) associated with SER-induced toxicity, and improves understanding of the molecular and biochemical pathways putatively perturbed by SER.

Physiological and muscle tissue responses in Litopenaeus vannamei under hypoxic stress via iTRAQ

White L. vannamei have become the most widely cultivated shrimp species worldwide. Cultivation of L. vannamei is one of the predominant sectors in China’s aquaculture industry. This study focused on the physiological and biochemical responses, differential protein expression, and expression characteristics of the related crucial functional protein genes under low oxygen conditions among different strains of L. vannamei. It was found that 6 h of hypoxic stress caused a significant reduction in the total hemocyte number in both strains, while the hypoxia-sensitive strain showed a stronger reduction. In contrast, the hemocyanin concentration showed only an overall upward trend. Proteomic analysis of L. vannamei muscle tissue revealed 3,417 differential proteins after 12 h of hypoxic stress. Among them, 29 differentially expressed proteins were downregulated and 244 were upregulated in the hypoxia-sensitive strain. In contrast, there were only 10 differentially expressed proteins with a downregulation pattern and 25 with an upregulation pattern in the hypoxia-tolerant strain. Five protein genes that responded significantly to hypoxic stress were selected for quantitative real-time PCR analysis, namely, hemocyanin, chitinase, heat shock protein 90 (HSP 90), programmed death protein, and glycogen phosphorylase. The results showed that the gene expression patterns were consistent with proteomic experimental data except for death protein and glycogen phosphorylase. These results can enrich the general knowledge of hypoxic stress in L. vannamei and the information provided differentially expressed proteins which may be used to assist breeding programs of L. vannamei of new strains with tolerance to hypoxia.

Hypoxia-induced oxidative stress and apoptosis in gills of scaleless carp (Gymnocypris przewalskii)

Scaleless carp (Gymnocypris przewalskii) are well adapted to low oxygen environment, but their specific adaptation mechanism to hypoxic condition remains unclear. The gill is an important respiratory organ that plays a crucial role in regulating hypoxic stress. Here, we established fish hypoxic stress model, as well as investigated oxidative stress, apoptotic responses, and relative enzyme activities in the gills of scaleless carp after exposure to various levels of hypoxic stress. The results demonstrated that gill lamellar height and basal length increased significantly under severe hypoxic stress, and interval lengths between lamellae increased significantly under hypoxic stress. Furthermore, lamellar epithelial cells underwent apoptosis, cytoplasmic contraction, and mitochondrial expansion, and the number of apoptotic cells increased significantly after exposure to severe hypoxic stress for 24 h. Subsequently, Bcl-2 and Caspase 3 mRNA levels, as well as Bcl-2/Bax expression ratio were significantly increased after exposure to severe hypoxic stress for 24 h, indicating upregulation of anti-apoptotic processes. Moreover, malondialdehyde and hydrogen peroxide levels were significantly increased after exposure to hypoxic stress for 24 h. Superoxide dismutase activity increased significantly after exposure to severe hypoxia for 8 h and then decreased, while glutathione peroxidase activity and total antioxidant capacity increased significantly under hypoxic stress. Taken together, the results indicated that scaleless carp gills respond to acute hypoxic conditions by undergoing lamellar morphology remodeling, enhanced apoptosis, and increased antioxidant enzymatic activity. The study findings provided new insight into the adaptation mechanisms of scaleless carp in response to hypoxic challenge.

Changes in metabolic profiling of whiteleg shrimp (Penaeus vannamei) under hypoxic stress

Hypoxia is a common concern in shrimp aquaculture, affecting growth and survival. Although recent studies have revealed important insights into hypoxia in shrimp and crustaceans, knowledge gaps remain regarding this stressor at the molecular level. In the present study, a gas chromatography-mass spectrometry (GC-MS)-based metabolomics approach was employed to characterize the metabolic signatures and pathways underlying responses of Pacific white shrimp (Penaeus vannamei) to hypoxia and to identify associated candidate biomarkers. We compared metabolite profiles of shrimp haemolymph before (0 h) and after exposure to hypoxia (1 & 2 h). Dissolved oxygen levels were maintained above 85 % saturation in the control and before hypoxia, and 15 % saturation in the hypoxic stress treatment. Results showed 44 metabolites in shrimp haemolymph that were significantly different between before and after hypoxia exposure. These metabolites were energy-related metabolites (e.g., intermediates of citric acid cycle, lactic acid, alanine), fatty acids and amino acids. Pathway analysis revealed 17 pathways that were significantly affected by hypoxia. The changes in metabolites and pathways indicate a shift from aerobic to anaerobic metabolism, disturbance in amino acid metabolism, osmoregulation, oxidative damage and Warburg effect-like response caused by hypoxic stress. Among the altered metabolites, lactic acid was most different between before and after hypoxia exposure and had the highest accurate value for biomarker identification. Future investigations may validate this molecule as a stress biomarker in aquaculture. This study contributes to a better understanding of hypoxia in shrimp and crustaceans at the metabolic level and provides a base for future metabolomics investigations on hypoxia.

Dietary Supplementation of Chitosan Oligosaccharide–Clostridium butyricum Synbiotic Relieved Early-Weaned Stress by Improving Intestinal Health on Pigeon Squabs (Columba livia)

According to a previous study, we had found that early weaning causes harm to growth performance, intestinal morphology, activity of digestive enzymes, and antioxidant status in pigeon squabs (Columba livia). Chitosan oligosaccharides (COS) and Clostridium butyricum have been reported to have great potential to improve the growth performance and intestinal health of early-weaned animals. Therefore, the aim of this study is to explore whether dietary supplementation with COS-C. butyricum synbiotic could relieve early-weaned stress by evaluating its effects on growth performance and intestinal health in pigeon squabs. A total of 160 squabs (weaned at 7 days of age) were randomly divided into 5 groups: the control group, fed with artificial crop milk; the COS supplementation group, fed with artificial crop milk + 150 mg/kg COS; and three synbiotic supplementation groups, fed with artificial crop milk + 150 mg/kg COS + 200, 300, and 400 mg/kg C. butyricum. The results showed that a diet supplemented with COS-C. butyricum synbiotic benefitted the growth performance of early-weaned squabs; even so the differences were not significant among the five groups (p > 0.05). In addition, dietary supplementation of 150 mg/kg COS + 300~400 mg/kg C. butyricum significantly improved the intestinal morphology (especially villus surface area and the ratio of villus height to crypt depth), the activity of digestive enzymes (lipase, trypsin, and leucine aminopeptidase) in duodenum contents, and the production of total short-chain fatty acids and acetic acid in ileum content (p < 0.05). Additionally, dietary supplementation of 150 mg/kg COS + 400 mg/kg C. butyricum benefitted gut health by improving the antioxidant capacity (glutathione peroxidase and total antioxidant capacity) and cytokine status (IL-4 and IL-10) (p < 0.05), as well as by improving the intestinal microbiota diversity. In conclusion, our results revealed that dietary supplementation with synbiotic (150 mg/kg COS + 300~400 mg/kg C. butyricum) could relieve early-weaned stress by maintaining intestinal health in pigeon squabs.

Thriving in Oxygen While Preventing ROS Overproduction: No Two Systems Are Created Equal

From 2.5 to 2.0 billion years ago, atmospheric oxygen concentration [O₂] rose thousands of times, leading to the first mass extinction. Reactive Oxygen Species (ROS) produced by the non-catalyzed partial reduction of O₂ were highly toxic eliminating many species. Survivors developed different strategies to cope with ROS toxicity. At the same time, using O₂ as the final acceptor in respiratory chains increased ATP production manifold. Thus, both O₂ and ROS were strong drivers of evolution, as species optimized aerobic metabolism while developing ROS-neutralizing mechanisms. The first line of defense is preventing ROS overproduction and two mechanisms were developed in parallel: 1) Physiological uncoupling systems (PUS), which increase the rate of electron fluxes in respiratory systems. 2) Avoidance of excess [O₂]. However, it seems that as avoidance efficiency improved, PUSs became less efficient. PUS includes branched respiratory chains and proton sinks, which may be proton specific, the mitochondrial uncoupling proteins (UCPs) or unspecific, the mitochondrial permeability transition pore (PTP). High [O₂] avoidance also involved different strategies: 1) Cell association, as in biofilms or in multi-cellularity allowed gas-permeable organisms (oxyconformers) from bacterial to arthropods to exclude O_2. 2) Motility, to migrate from hypoxic niches. 3) Oxyregulator organisms: as early as in fish, and O₂-impermeable epithelium excluded all gases and only exact amounts entered through specialized respiratory systems. Here we follow the parallel evolution of PUS and O₂-avoidance, PUS became less critical and lost efficiency. In regard, to proton sinks, there is fewer evidence on their evolution, although UCPs have indeed drifted in function while in some species it is not clear whether PTPs exist.

Antioxidant, Transcriptome and the Metabolome Response to Dietary Astaxanthin in Exopalaemon carinicauda

Astaxanthin (Axn), a feed additive, is becoming increasingly important for modulating the metabolism, growth, development, and reproduction of aquatic organisms in aquaculture. In this study, Exopalaemon carinicauda (E. carinicauda) is an economically important fishery species in China that has been found to exhibit increased body weight following Axn feeding as compared to a standard diet. The antioxidant, transcriptomic, and metabolomic analyses of the response of E. carinicauda after Axn feeding were investigated. Axn could reduce the content of malondialdehyde and increase the activities of various antioxidant enzymes, which also proved that axn can improve the antioxidant capacity Transcriptomic analysis suggested that synthesis and secretion of immune proteins, cytoskeleton structure, and apoptosis signaling were altered after Axn feeding. The metabolic response to axn mainly includes the up regulation of different amino acids and the change of unsaturated fatty acids. Combined transcriptomic and metabolomic data indicated that amino acid metabolic pathways were upregulated in the muscles after Axn feeding. For good measure, energy metabolism pathways were upregulated in the muscles to improve ATP and unsaturated fatty acid production. This study provides key information to increase our understanding of the effects of Axn in shrimp.

Molecular Mechanism Based on Histopathology, Antioxidant System and Transcriptomic Profiles in Heat Stress Response in the Gills of Japanese Flounder

As an economically important flatfish in Asia, Japanese flounder is threatened by continuously rising temperatures due to global warming. To understand the molecular responses of this species to temperature stress, adult Japanese flounder individuals were treated with two kinds of heat stress—a gradual temperature rise (GTR) and an abrupt temperature rise (ATR)—in aquaria under experimental conditions. Changes in histopathology, programmed cell death levels and the oxidative stress status of gills were investigated. Histopathology showed that the damage caused by ATR stress was more serious. TUNEL signals confirmed this result, showing more programmed cell death in the ATR group. In addition, reactive oxygen species (ROS) levels and the 8-O-hDG contents of both the GTR and ATR groups increased significantly, and the total superoxide dismutase (T-SOD) activities and total antioxidant capacity (T-AOC) levels decreased in the two stressed groups, which showed damage to antioxidant systems. Meanwhile, RNA-seq was utilized to illustrate the molecular mechanisms underyling gill damage. Compared to the control group of 18 °C, 507 differentially expressed genes (DEGs) were screened in the GTR group; 341 were up-regulated and 166 were down-regulated, and pathway enrichment analysis indicated that they were involved in regulation and adaptation, including chaperone and folding catalyst pathways, the mitogen-activated protein kinase signaling (MAPK) pathway and DNA replication protein pathways. After ATR stress, 1070 DEGs were identified, 627 were up-regulated and 423 were down-regulated, and most DEGs were involved in chaperone and folding catalyst and DNA-related pathways, such as DNA replication proteins and nucleotide excision repair. The annotation of DEGs showed the great importance of heat shock proteins (HSPs) in protecting Japanese flounder from heat stress injury; 12 hsp genes were found after GTR, while 5 hsp genes were found after ATR. In summary, our study records gill dysfunction after heat stress, with different response patterns observed in the two experimental designs; chaperones were activated to defend heat stress after GTR, while replication was almost abandoned due to the severe damage consequent on ATR stress.

DNA damage and cell apoptosis induced by fungicide difenoconazole in mouse mononuclear macrophage RAW264.7

Difenoconazole (DFC) is a typical triazole fungicide. Because of its effective bactericidal activity, it has been widely used in agricultural products such as fruits and vegetables. This study revealed the cytotoxic effect of fungicide DFC on mouse monocyte macrophage RAW264.7. The results showed that the IC₅₀ value of DFC on RAW264.7 cells was 37.08 μM (24 h). DFC can significantly inhibit the viability of RAW264.7 cells, induce DNA damage and enhance apoptosis. The established cytotoxicity test showed that DFC-induced DNA double strand breaks in RAW264.7 cells. DFC-treated cells showed typical morphological changes of apoptosis, including chromatin condensation and nuclear lysis. In addition, DFC can induce the release of Cyt c, promote the collapse of mitochondrial membrane potential and increase the Bax/Bcl-2 ratio in RAW264.7 cells. Through this research, people further understand the toxicity of DFC and provide a more scientific basis for its safety application and risk management.

TBC domain family 7-like enhances the tolerance of Penaeus vannamei to ammonia nitrogen by the up-regulation of autophagy

TBC domain family 7 (TBC1D7) is one of the subunits of tuberous sclerosis complex (TSC) and an important regulator of autophagosome biogenesis. However, the function of TBC1D7 is not fully understood in crustaceans. In the present study, TBC1D7 was identified from Penaeus vannamei. The complete coding sequence of PvTBC1D7 was of 960 bp encoding a predicted polypeptide of 319 amino acids with one conserved TBC domain, which shared high similarity with TBC1D7 of that other species. The mRNA of PvTBC1D7 was highly expressed in hemocyte and hepatopancreas, and the PvTBC1D7 protein was localized specifically in the cytoplasm of hemocyte of shrimp. Besides, PvTBC1D7 was co-localized with PvTSC1 in the cytoplasm of shrimp, indicating that there might existed a binding relationship between PvTBC1D7 and PvTSC1. During the ammonia nitrogen stress, the mRNA transcripts of PvTBC1D7 were significantly upregulated in hemocyte, hepatopancreas, and gill. Functionally, overexpression of PvTBC1D7 in vitro restored the inhibition to autophagy caused by chloroquine (CLQ) and increased the autophagy level, while the silencing of PvTBC1D7 could inhibit the autophagy. More importantly, after interfering with PvTBC1D7, the autophagy level decreased significantly both in hepatopancreas and hemocyte of P. vannamei, the mRNA expression of PvmTOR was increased remarkably with the significantly decrease of autophagy-related genes (PvATG12 and PvATG14). And the reduction of PvTBC1D7 remarkably exacerbated the damage of hepatopancreas, increased the accumulation of ROS, and reduced the survival proportion of shrimp under ammonia nitrogen stress. Altogether, these results indicated that PvTBC1D7 might positively regulate the autophagy by stabilizing the negative regulation of mTOR by TSC complex, reduce the oxidative stress damage and improve shrimp ammonia nitrogen tolerance.

cDNA Characterization and Expression of Selenium-Dependent CqGPx3 Isoforms in the Crayfish Cherax quadricarinatus under High Temperature and Hypoxia

Glutathione peroxidase 3 (GPx3) is the only extracellular selenoprotein (Sel) that enzymatically reduces H2O2 to H2O and O2. Two GPx3 (CqGPx3) cDNAs were characterized from crayfish Cherax quadricarinatus. The nerve cord CqGPx3a isoform encodes for a preprotein containing an N-terminal signal peptide of 32 amino acid residues, with the mature Sel region of 192 residues and a dispensable phosphorylation domain of 36 residues. In contrast, the pereiopods CqGPx3b codes for a precursor protein with 19 residues in the N-terminal signal peptide, then the mature 184 amino acid residues protein and finally a Pro-rich peptide of 42 residues. CqGPx3 are expressed in cerebral ganglia, pereiopods and nerve cord. CqGPx3a is expressed mainly in cerebral ganglia, antennulae and nerve cord, while CqGPx3b was detected mainly in pereiopods. CqGPx3a expression increases with high temperature and hypoxia; meanwhile, CqGPx3b is not affected. We report the presence and differential expression of GPx3 isoforms in crustacean tissues in normal conditions and under stress for high temperature and hypoxia. The two isoforms are tissue specific and condition specific, which could indicate an important role of CqGPx3a in the central nervous system and CqGPx3b in exposed tissues, both involved in different responses to environmental stressors.

Physiological and antioxidant response of Litopenaeus vannamei against Vibrio parahaemolyticus infection after feeding supplemented diets containing Dunaliella sp. flour and β-glucans

The presence of pathogen agents in shrimp farming is the main obstacle for successful aquaculture. Vibrio species are naturally part of water because they play an important role as opportunistic bacteria. Vibrio parahaemolyticus was identified as the causative agent of the Early Mortality Syndrome in 2009, causing the loss of shrimp farming worldwide. Dunaliella sp. flour has been tested against Vibrio infection proving to be an effective prophylactic method that decreases mortality and improves physiological and immune response in Litopenaeus vannamei. Juvenile shrimp were exposed to 2% Dunaliella sp. flour and commercial 1.1% β -glucan diet provided every other day for 15 days and a posterior infection with V. parahaemolyticus (1 × 10⁶ CFU/mL). To evaluate shrimp stress status, some parameters as glucose, lactate, cholesterol, triglycerides, relative superoxide dismutase (SOD) gene expression and circulating hemocytes were analyzed in hemolymph at zero and seven days before infection and at 0, 24, and 48 h post-infection. L. vannamei fed with Dunaliella sp. showed 93% and β -glucan 87% survival, compared with 79% in the infected control group. Additionally, Dunaliella sp. improved hemocyte and lipid concentrations compared to β -glucan while both immunostimulants showed an increase in SOD response against bacteria. The addition of 2% Dunaliella sp. every other day in L. vannamei diet enhanced stress response against V. parahaemolyticus infection.

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.

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.

Supplementing daidzein in diets improves the reproductive performance, endocrine hormones and antioxidant capacity of multiparous sows

Certain hormones play important roles in modulating mammalian reproductive behaviour. Daidzein is a well-known isoflavonic phytoestrogen that possesses oestrogenic activity. This study was conducted to probe the effects of daidzein supplementation in gestation diets on the reproductive performance in sows. A total of 120 multiparous sows (Landrace × Yorkshire) were randomly assigned to 2 groups (n = 60) and fed either a base diet (control) or one containing 200 mg/kg daidzein during gestation. We discovered that daidzein supplementation significantly increased the total number of piglets born per litter and number of piglets born alive per litter (P < 0.05), decreased the farrowing time (P < 0.05) and increased the serum oestrogen and progesterone concentrations (P < 0.05) at 35 d of gestation. Moreover, serum immunoglobulin G (IgG) concentration and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were higher in the daidzein-treated group than in the control group at 35 d of gestation (P < 0.05). Daidzein increased the serum SOD activity and total anti-oxidative capacity (T-AOC) at 85 d of gestation (P < 0.05). Interestingly, daidzein elevated the expression levels of the sodium-coupled neutral amino acid transporter 1 (SLC38A1) and insulin-like growth factor 1 (IGF-1) genes in the placenta (P < 0.05). These results suggest that daidzein ingestion could improve sow reproductive performance by changing serum hormones, elevating anti-oxidative capacity and up-regulating critical functional genes in the placenta.

The bifunctional 6-phosphofructokinase-2/fructose-2,6-bisphosphatase from the shrimp Litopenaeus vannamei: Molecular characterization and down-regulation of expression in response to severe hypoxia

Hypoxia is a frequent stressor in marine environments with multiple adverse effects on marine species. The white shrimp Litopenaeus vannamei withstands hypoxic conditions by activating anaerobic metabolism with tissue-specific changes in glycolytic and gluconeogenic enzymes. In animal cells, glycolytic/gluconeogenic fluxes are highly controlled by the levels of fructose-2,6-bisphosphate (F-2,6-P₂), a signal metabolite synthesized and degraded by the bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2). PFK-2/FBPase-2 has been studied in vertebrates and some invertebrates, but as far as we know, there are no reports on PFK-2/FBPase-2 from crustaceans. In the present work, we obtained cDNA nucleotide sequences corresponding to two mRNAs for PFK-2/FBPase-2 and named them PFKFBP1 (1644 bp) and PFKFBP2 (1566 bp), from the white shrimp L. vannamei. The deduced PFKFBP1 and PFKFBP2 are 547 and 521 amino acids long, respectively. Both proteins share 99.23% of identity, and only differ in 26 additional amino acids present in the kinase domain of the PFKFBP1. The kinase and phosphatase domains are highly conserved in sequence and structure between both isoforms and other proteins from diverse taxa. Total expression of PFKFBP1-2 is tissue-specific, more abundant in gills than in hepatopancreas and undetectable in muscle. Moreover, severe hypoxia (1 mg/L of DO) decreased expression of PFKFBP1-2 in gills while anaerobic glycolysis was induced, as indicated by accumulation of cellular lactate. These results suggest that negative regulation of PFKFBP1-2 at expression level is necessary to set up anaerobic glycolysis in the cells during the response to hypoxia.

c-Jun N-terminal kinase (JNK) in Procambarus clarkii: Molecular characterization and involvement in oxidative stress-induced apoptosis during molting cycle

The present study was conducted to characterize the full-length cDNA of c-Jun N-terminal kinase (JNK) in Procambarus clarkii (Pcjnk) and evaluate its potential function under different molt cycle. The full-length cDNA of Pcjnk covered 2937 bp with an open reading frame of 1320 bp, encoding 439 amino acids. A typical conserved TPY motif (118Thr-Pro-120Tyr) was found in Pcjnk. Quantitative real-time PCR (qRT-PCR) analysis revealed a constitutive expression of Pcjnk in the tested tissue, with the highest expression occurring in the hepatopancreas. Additionally, the present study initially revealed that relative mRNA expression of Pcjnk and apoptosis level were significantly higher in the premolt stage (D1/D2 and D3/D4 stage) as compared to other molt stages. In contrast to the levels of superoxide dismutase (SOD) and malondialdehyde (MDA), catalase (CAT) and glutathione peroxidase (GPX) level decreased significantly from the intermolt stage (C stage) to the premolt stage (D1/D2 and D3/D4 stage), then increased from the premolt stage to the postmolt stage (A and B stage). The results obtained in the present study indicated that molt could cause apoptosis induced by oxidative stress through the activation of JNK in Procambarus clarkii.

Cloning of Mn-SOD gene and its mRNA expression difference and antioxidant enzyme activities under hypoxia stress of cobia Rachycentron canadum

BACKGROUND

Environmental hypoxia affects the survival and development of organisms. It is also an important environmental factor that leads to oxidative damage. Hypoxia is a condition in which tissues are deprived of oxygen; reoxygenation is the phenomenon in which hypoxic tissues are exposed to oxygen. Hypoxia-reoxygenation is vital in pathogenesis, where the production of reactive oxygen species and antioxidant disparity significantly contribute to disease progression, and it is one of the most common physiological stressors in the aquaculture industry.

METHODS AND RESULTS

In this study, the full length of complementary DNA (cDNA) of the manganese superoxide dismutase (Mn-SOD) gene of healthy cobia Rachycentron canadum was analysed using rapid amplification of cDNA ends. The real-time quantitative Polymerase Chain Reaction was used to measure the expression levels of Mn-SOD mRNAs in various tissues (heart, muscle, brain, liver, kidney, gill, intestine, and spleen). The 2^-ΔΔCT method was used to performed the expression analysis. The experimental data were analysed using SPSS ver. 19.0 ( https://spss.software.informer.com/19.0/ ). P < 0.05 and P < 0.01 were set as significant differences. The values were articulated as mean ± standard deviation. The Mn-SOD gene cDNA sequence was 1209 bp long, including a 684 bp open reading frame, 42 bp 5'UTR and 483 bp 3'UTR, encoding 227 amino acids. Under hypoxia-reoxygen stress, the expression of Mn-SOD in brain tissue was significantly lower than in the control group after 8 h of reoxygenation and higher than the control group after 24 h. Hypoxia and subsequent reoxygenation triggered a disturbance in antioxidant homeostasis, displayed in the modification of GPx expression/activity in the liver: GPx was improved.

CONCLUSIONS

These results provide valuable information on the role of Mn-SOD regulation in oxidative stress caused by hypoxia.

Two-sided effects of prolonged hypoxia and sulfide exposure on juvenile ark shells (Anadara broughtonii)

Oxygen deficit and sulfide have been restrictive factors in mariculture zones. However, the adaptive mechanism in aquatic lives is still unclear. The commercial ark shells Anadara broughtonii were selected to test the tolerance and adaptive responses to prolonged and intermittent hypoxia with or without exogenous sulfide (mild, moderate, high) by evaluating their behavior, mortality, oxidative level, antioxidant responses, and the MAPK-mediated apoptosis in gills. The results indicated that the clams were tolerant to hypoxia and sulfide exposure but vulnerable during reoxygenation from the challenges. Even so, sulfide had remarkable effect on attenuating the accumulation of reactive oxygen species (ROS) and lipid peroxides caused by reoxygenation from prolonged hypoxia. The increase of glutathione level was probably as an early and primary protective response to prevent the expected reperfusion injury from reoxygenation. The challenges suppressed the oxidative level with a dose-dependent effect of sulfide, with an exception when exposed to mild sulfide. Synchronously, biphasic effects of exogenous sulfide on apoptotic cascade, which was induced by mild sulfide while it was inhibited by higher sulfide, were also detected in gills. The induced or inhibited apoptosis by hypoxia and sulfide kept to a typical ROS-MAPK-CASPASE cascade, desiderating further investigation.

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.

Combined hypoxia and high temperature affect differentially the response of antioxidant enzymes, glutathione and hydrogen peroxide in the white shrimp Litopenaeus vannamei

Low oxygen concentration in water (hypoxia) and high temperature are becoming more frequent due to climate change, forcing animals to endure stress or decease. Hypoxia and high temperature stress can lead to reactive oxygen species (ROS) accumulation and oxidative damage to the organisms. The shrimp Litopenaeus vannamei is the most cultivated crustacean worldwide. The aim of this study was to evaluate the expression and enzymatic activity of glutathione peroxidase (GPx), catalase (CAT) and cytosolic manganese superoxide dismutase (cMnSOD) in gills and hepatopancreas from L. vannamei in response to two combined stressors: hypoxia and reoxygenation at control and high temperature (28 vs 35 °C, respectively). In addition, glutathione and hydrogen peroxide content were analyzed. The changes were mainly tissue-specific. In gills, cMnSOD expression and enzymatic activity increased in response to the interactions between oxygen variation and thermal stress, while GPx and CAT were maintained. More changes occurred in GPx, CAT and MnSOD in hepatopancreas than in gills, mainly due to the effect of the individual stress factors of thermal stress or oxygen variations. On the other hand, the redox state of glutathione indicated that during high temperature, changes in the GSH/GSSG ratio occurred due to the fluctuations of GSSG. Hydrogen peroxide concentration was not affected by thermal stress or oxygen variations in hepatopancreas, whereas in gills, it was not detected. Altogether, these results indicate a complex pattern of antioxidant response to hypoxia, reoxygenation, high temperature and their combinations.

Nannochloropsis spp. as Feed Additive for the Pacific White Shrimp: Effect on Midgut Microbiology, Thermal Shock Resistance and Immunology

This work aimed to evaluate Nannochloropsis spp. as feed additive in the diet of Pacific white shrimp for their effect on midgut microbiology, thermal shock resistance and immunological parameters. Initially, the digestibility of the microalgae meal was assessed, and the apparent digestibility coefficient (ADC) was determined. The ADC was, in general, high in lipids (78.88%) and eicosapentaenoic fatty acid (73.86%). Then, Nannochloropsis spp. were included in diets at four levels (0, 0.5, 1 and 2% inclusion). The shrimp were reared in 500 L clear water tanks containing 20 shrimp per tank with an initial weight of 6.05 ± 0.06 g and fed four times a day. Shrimp fed with supplemented diets containing Nannochloropsis spp. (0.5 and 2%) presented higher resistance to thermal shock when compared to the non-supplemented group (control). Shrimp fed with 1 and 2% of algae inclusion had a higher production of reactive oxygen species (ROS) when compared to other treatments. No statistical difference was observed in the immunological parameters and microbiology of the intestinal tract. Thus, the inclusion of Nannochloropsis spp. in shrimp diets at 0.5 and 2% levels increases resistance to thermal shock and ROS production in shrimp.

Isochamaejasmin induces toxic effects on Helicoverpa zea via DNA damage and mitochondria-associated apoptosis

BACKGROUND

Stellera chamaejasme L. is a poisonous plant with rich resources and is thus highly valuable in terms of new pesticide development. Isochamaejasmin (ICM), one of the main ingredients in S. chamaejasme has drawn much attention owing to its antitumour properties. However, the toxicity and mode of action of ICM on insects are still not clear. In this article, the larva and neuronal cell (AW1) of Helicoverpa zea were used to clarify the insecticidal activity of ICM as well as its toxic mechanism at the cellular level.

RESULTS

The results confirmed that ICM has potential toxicity against H. zea both in vivo and in vitro via time- and dose-dependent manners. Moreover, we found that ICM caused DNA damage and increased the levels of γH2AX and OGG1 in AW1 cells. Results also showed decline in the mitochondrial membrane potential (MMP), upregulation of Bax/Bcl-2 expression resulting in the release of cytochrome c into the cytosol, activation of caspase-3/9, and cleavage of poly ADP-ribose polymerase (PARP) as a result of exposure to ICM. Additionally, a dose-dependent rise in the reactive oxygen species (ROS) levels, accumulation of a lipid peroxidation product, and inactivation of antioxidant enzymes were found in ICM-treated cells.

CONCLUSION

These findings confirmed the insecticidal activity of ICM. Furthermore, the results revealed that ICM could cause DNA damage and induce apoptosis via the mitochondrial pathway in AW1 cells. This study provides the basic information needed to understand the toxicity and mechanisms of action of ICM, which could potentially be used to develop it as a new insecticide.

Effects of cypermethrin on the hepatic transcriptome and proteome of the red claw crayfish Cherax quadricarinatus

Cypermethrin (CYP) is a synthetic pyrethroid broadly used for pest control, however, it is extremely toxic to aquatic organisms. To assess the toxicity of CYP in red claw crayfish Cherax quadricarinatus, transcriptional and proteomic approaches combining two-dimensional polyacrylamide gel electrophoresis and tandem mass spectrometry were used to compare the hepatic expression profiles. A total of 41,349 unigenes and 8839 differentially expressed genes (DEGs) were obtained, which were enriched in the process. The category of 779 (0.625 ng L^-1 CYP vs Con), 1963 (1.25 vs Con), and 2066 (1.25 vs 0.625) DEGs were screened. All findings suggested that CYP can induce antioxidant and biotransformation modulation variations in C. quadricarinatus to resist immunotoxicity and oxidative damages. The category of 196 (0.625 ng L^-1 CYP vs Con) specific proteins were differentially expressed: 24 proteins were upregulated, and 20 proteins were downregulated relative to CYP. Protein identification indicated the KEGG pathways of the human immunodeficiency virus 1 infection, insulin signaling pathway, and influenza A enriched. From the differential expression of the selected nine proteins, the increased Loc113824800, Rps19, Atp2, Rps10, Hsp40, Brafldraft_124327, and the decreased Loc117331934, Loc113213835, and Loc106806551 revealed. While for the verification of the eight genes in transcriptome and the above nine genes in proteomic, specifically, gpx5, ggt, loc106458463, chelonianin decreased in the 0.625 ng L^-1 CYP group. The transcripts of loc113816050, akr1d1 and gst, chelonianin and loc108675455 decreased and increased in the 1.25 ng L^-1 CYP group, respectively. The present study reflects the overall change in cellular structure and metabolism related to the resistance of pyrethroid insecticides.