Immune defense, detoxification, and metabolic changes in juvenile Eriocheir sinensis exposed to acute ammonia

Water pollutant cadmium-induced intestinal inflammation in Eriocheir sinensis and potential therapeutic drugs

OBJECTIVE

Eriocheir sinensis is a significant crustacean in freshwater aquaculture. However, this industry is vulnerable to diseases, including intestinal inflammation. Cadmium (Cd) is a water pollutant that exacerbates intestinal inflammation in Eriocheir sinensis. This study aimed to investigate the mechanisms of Cd-induced intestinal inflammation in Eriocheir sinensis and to identify potential therapeutic agents.

METHODS

Histology, enzyme activity, and gene expression detection were combined to investigate the promoting effect of Cd on the exacerbation of intestinal inflammation in Eriocheir sinensis. Transcriptome sequencing was performed to analyze the critical signaling pathways regulating intestinal inflammation in Eriocheir sinensis.

RESULTS

Transcriptome analysis confirmed that the Toll-like receptor pathway is critical in this process. TLR4-IN-C34, a specific inhibitor of TLR4, was identified as a potential treatment for intestinal inflammation. In vivo results demonstrated that TLR4-IN-C34 effectively reduced the severity of Cd-induced intestinal inflammation in Eriocheir sinensis. The tissue morphology of the intestine, gills, and hepatopancreas of Eriocheir sinensis improved, showing a significant decrease in inflammatory factors and apoptotic genes, along with enhanced antioxidant activity.

CONCLUSIONS

In conclusion, this study indicates that the water pollutant Cd exacerbates intestinal inflammation in Eriocheir sinensis, and TLR4-IN-C34 regulates the Toll-like receptor pathway in treating intestinal inflammation. This research provides valuable insights into the management of intestinal inflammation and the sustainable cultivation of Eriocheir sinensis.

Ecological risks of high-ammonia environment with inhibited growth of Daphnia magna: Disturbed energy metabolism and oxidative stress

High ammonia pollution is a common problem in water bodies. However, research on the mechanisms underlying the toxic effects on organisms at different nutritional levels is still insufficient. Herein, based on the environmental concentration, the toxic effects of high ammonia pollution on Daphnia magna were investigated. Overall, the feeding and filtration rates of D. magna were significantly decreased by ammonia. Growth inhibition of D. magna by ammonia was confirmed by the decreased body length. After ammonia exposure, the metabolic status of D. magna changed, the correlation network weakened, and the correlations between metabolites were disrupted. Changes occurred in metabolites primarily involved in oxidative stress, fatty acid oxidation, tricarboxylic acid cycle, and protein digestion, absorption, and synthesis, which were validated through alterations in multiple biomarkers. In addition, mitochondrial function was evaluated and was found to inhibit mitochondrial activity, which was accompanied by a decreased marker of mitochondrial activity contents and ATPase activity. Thus, the results suggested that energy metabolism and oxidative stress were involved in ammonia-induced growth toxicity. This study provides new insights into the impact of ammonia on aquatic ecological health.

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

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

Mechanisms of ammonotelism, epithelium damage, cellular apoptosis, and proliferation in gill of Litopenaeus vannamei under NH4Cl exposure

Excessive ammonia-N in coastal environment and aquaculture threatens the health of marine organisms. To explore the mechanism of gill damage induced by ammonia-N, transcriptome of Litopenaeus vannamei 's gill was carried out under 20 mg/L NH4Cl for 0, 6, and 48 h. K-means clustering analysis suggested that ammonia excretion and metabolism-related genes were elevated. GO and KEGG enrichment analysis suggested that glycosyltransferase activity and amino acid metabolism were affected by ammonia. Moreover, histological observation via three staining methods gave clues on the changes of gill after ammonia-N exposure. Increased mucus, hemocyte infiltration, and lifting of the lamellar epithelium suggested that gill epithelium was suffering damage under ammonia-N stress. Meanwhile, the composition of extracellular matrix (ECM) in connective tissue changed. Based on the findings of transcriptomic and histological analysis, we further investigated the molecular mechanism of gill damage under multiple concentrations of NH4Cl (0, 2, 10, 20 mg/L) for multiple timepoints (0, 3, 6, 12, 24, 48, 72 h). First, ammonia excretion was elevated via ion channel, transporter, and exocytosis pathways, but hemolymph ammonia still kept at a high level under 20 mg/L NH4Cl exposure. Second, we focused on glycosaminoglycan metabolism which was related to the dynamics of ECM. It turned out that the degradation and biosynthesis of chondroitin sulfate (CS) were elevated, suggesting that the structure of CS might be destructed under ammonia-N stress and CS played an important role in maintaining gill structure. It was enlightening that the destructions occurred in extracellular regions were vital to gill damage. Third, ammonia-N stress induced a series of cellular responses including enhanced apoptosis, active inflammation, and inhibited proliferation which were closely linked and jointly led to the impairment of gill. Our results provided some insights into the physiological changes induced by ammonia-N and enriched the understandings of gill damage under environmental stress.

Transcriptome analysis of Chinese mitten crabs (Eriocheir sinensis) gills in response to ammonia stress

The Chinese mitten crab (Eriocheir sinensis) is an important commercial species in China. E. sinensis is typically farmed in rice-crab symbiosis, as an important ecological farming model. However, E. sinensis is often exposed to a high ammonia environment due to the application of nitrogen fertilizers essential for rice growth. We investigated the molecular mechanisms in the gills of E. sinensis exposed to high ammonia at transcriptional and histological levels. We randomly assigned E. sinensis to two groups (control group, CG; ammonia stress group, AG), and gill samples were excised from the CG and AG groups for histopathological and transcriptome analyses. The histopathological evaluation revealed that ammonia stress damaged the gills of E. sinensis. The transcriptome analysis showed that some essential genes, including Xanthine dehydrogenase (XDH), Ubiquitin C-terminal hydrolase-L3 (UCHL3), O-linked N-acetylglucosamine transferase (OGT), Cathepsin B (CTSB), and Ubiquitin-conjugating enzyme E2 W (UBE2W) changed significantly during ammonia exposure. These genes are related to ammonia detoxification, the immune response, and apoptosis. This study demonstrated the molecular response mechanism of E. sinensis gills to ammonia stress at the transcriptional and histological levels. This study provides insight for further study on the molecular mechanism of ammonia stress in crustaceans and supplies technical support for rice crab symbiosis.

Differential Toxicity Responses between Hepatopancreas and Gills in Litopenaeus vannamei under Chronic Ammonia-N Exposure

Ammonia nitrogen is one of the main toxic substances in aquatic cultivation environments. Chronic exposure to excessive amounts of ammonia-N creates toxic consequences, retarding the growth of aquatic organisms. This study investigated the growth performance, morphological and physiological alterations, and transcriptome changes in the hepatopancreas and gills of white shrimp Litopenaeus vannamei. The results showed that there was no significant difference in the survival rate (p > 0.05), whereas growth performance was reduced significantly in the treated groups compared to the control groups (p < 0.05). Significant structural damage and vacuolation occurred in hepatopancreas and gill tissues in the treated groups. Superoxide dismutase (SOD) activity and Na+/K+-ATPase content were significantly increased by chronic ammonia-N exposure in the two tissue groups. In addition, catalase (CAT) activity and malondialdehyde (MDA) levels were significantly altered in the hepatopancreas groups (p < 0.05), whereas no differences were observed in the gill groups (p > 0.05). There were 890 and 1572 differentially expressed genes identified in the hepatopancreas (treated versus control groups) and gills (treated versus control groups), respectively, of L. vannamei under chronic ammonia-N exposure. Functional enrichment analysis revealed associations with oxidative stress, protein synthesis, lipid metabolism, and different serine proteases. The gills maintained cellular homeostasis mainly through high expression of cytoskeleton and transcription genes, whereas the hepatopancreas down-regulated related genes in the ribosome, proteasome, and spliceosome pathways. These genes and pathways are important in the biosynthesis and transformation of living organisms. In addition, both tissues maintained organismal growth primarily through lipid metabolism, which may serve as an effective strategy for ammonia-N resistance in L. vannamei. These results provided a new perspective in understanding the mechanisms of ammonia-N resistance in crustaceans.

A review of the toxic effects of ammonia on invertebrates in aquatic environments

Aquatic invertebrates are the organisms most susceptible to ammonia toxicity. However, the toxic effects of ammonia on invertebrates are still poorly understood. This study reviews the research progress in ammonia toxicology for the period from 1986 to 2023, focusing on the effects on invertebrates. Through examining the toxic effects of ammonia at different levels of organization (community, individual, tissue and physiology, and molecular) as well as the results from omics studies, we determined that the most significant effects were on the reproductive capacity of invertebrates and the growth of offspring, although different populations show variation in their tolerance to ammonia, and tissues have varied potential to respond to ammonia stress. A multicomponent analysis is an in-depth technique employed in toxicological studies, as it can be used to explore the enrichment pathways and functional genes expressed under ammonia stress. This study comprehensively discusses ammonia toxicity from multiple aspects in order to provide new insights into the toxic effects of ammonia on aquatic invertebrates.

Divergent responses in the gut microbiome and liver metabolome to ammonia stress in three freshwater turtles

Ammonia is a common pollutant in aquaculture system, and toxic to all aquatic animals. However, different aquatic animals exhibit diverse physiological responses to high-level ammonia exposure, potentially indicating their divergent resistance to ammonia stress. In this study, juveniles of three freshwater turtles (Mauremys reevesii, Pseudemys nelsoni and Trachemys scripta elegans) were exposed to different concentrations of ammonia (0, 0.3 and 3.0 mg/L) for 30 days, and their swimming, growth performance, gut microbiota, and hepatic metabolites were measured to evaluate the interspecific difference in physiological responses to ammonia stress. Despite no differences in swimming ability, growth rate, and gut microbial diversity, observable changes in microbial community composition and hepatic metabolite profiles were shown in ammonia-exposed turtles. A relatively higher abundance of potentially pathogenic bacteria was found in M. reevesii than in the other two species. Moreover, microbial compositions and metabolic responses differed significantly among the three species. M. reevesii was, out of the three tested species, the one in which exposure to ammonia had the greatest effect on changes in bacterial genera and hepatic metabolites. Conversely, only a few metabolites were significantly changed in T. scripta elegans. Integrating these findings, we speculated that native M. reevesii should be more vulnerable to ammonia stress compared to the invasive turtle species. Our results plausibly reflected divergent potential resistance to ammonia among these turtles, in view of differential physiological responses to ammonia exposure at environmentally relevant concentrations.

Transcriptomics provides insights into toxicological effects and molecular mechanisms associated with the exposure of Chinese mitten crab, Eriocheir sinensis, to dioxin

Dioxins are stable, ubiquitous, persistent, and halogenated environmental pollutants that have recently garnered increasing attention. This study constructed a microcosmic system to simulate the real breeding conditions of the Chinese mitten crab (Eriocheir sinensis) to evaluate the impact of environmental dioxins on these aquaculture animals. Histological observation and detection of antioxidant enzyme activities revealed that dioxin exposure for different durations substantially damaged the hepatopancreas of Chinese mitten crabs, increasing the enzymatic activities of total superoxide dismutase (T-SOD) and catalase (CAT) but decreasing that of malondialdehyde (MDA). We also obtained the gene expression profiles of the hepatopancreas corresponding to different periods of dioxin exposure using RNA-seq technology. Compared with the control group, 2999 and 941 differentially expressed genes (DEGs) corresponding to different periods of dioxin exposure were identified in the hepatopancreas. Enrichment analysis indicated that some pathways, such as those governing carbohydrate metabolism, fatty acid metabolism, and immune disease, also responded to dioxin exposure. Subsequently, we selectively analyzed DEGs involved in oxidoreductase activity, carbohydrate metabolic processes, and other processes, identifying that increased expression of Hsp70, Ldh, and Trx1 and decreased expression of Lgbp, Bgal1, and Acsbg2 were potentially caused by sensitivity to environmental dioxin exposure. Therefore, we contend that, although crabs exposed to unfavorable environmental pollutants, such as dioxin, may adapt via antioxidant and immune response modulation. However, continued dioxin exposure would disrupt such homeostatic restorative capabilities. Thus, this study may provide new insights into the toxicological effects exerted by dioxin on aquatic organisms, such as E. sinensis, as well as the mechanisms underlying such toxicity.

Transcriptomics Analysis of the Toxicological Impact of Enrofloxacin in an Aquatic Environment on the Chinese Mitten Crab (Eriocheir sinensis)

Enrofloxacin is an important antimicrobial drug that is widely used in aquaculture. Enrofloxacin residues can have negative effects on aquatic environments and animals. The toxicological effects of different concentrations of enrofloxacin residues in cultured water on Chinese mitten crabs (Eriocheir sinensis) were compared. A histological analysis of the E. sinensis hepatopancreas demonstrated that the hepatopancreas was damaged by the different enrofloxacin residue concentrations. The hepatopancreas transcriptome results revealed that 1245 genes were upregulated and that 1298 genes were downregulated in the low-concentration enrofloxacin residue group. In the high-concentration enrofloxacin residue group, 380 genes were upregulated, and 529 genes were downregulated. The enrofloxacin residues led to differentially expressed genes related to the immune system and metabolic processes in the hepatopancreas of the Chinese mitten crab, such as the genes for alkaline phosphatase, NF-kappa B inhibitor alpha, alpha-amylase, and beta-galactosidase-like. The gene ontology terms "biological process" and "molecular function" were enriched in the carboxylic acid metabolic process, DNA replication, the synthesis of RNA primers, the transmembrane transporter activity, the hydrolase activity, and the oxidoreductase activity. A Kyoto Encyclopedia of Genes and Genomes pathway analysis determined that the immune and metabolic signal transduction pathways were significantly enriched. Furthermore, the nonspecific immune enzyme (alkaline phosphatase) and the metabolic enzyme system played a role in the enrofloxacin metabolism in the E. sinensis hepatopancreas. These findings helped us to further understand the basis of the toxicological effects of enrofloxacin residues on river crabs and provided valuable information for the better utilization of enrofloxacin in aquatic water environments.

Metabolomics analysis reveals the response mechanism to carbonate alkalinity toxicity in the gills of Eriocheir sinensis

Aquatic water with carbonate alkalinity presents a survival challenge to aquatic animals. As an economically important crab, large quantities of Eriocheir sinensis are cultured in carbonate-type saline-alkali ponds, while the toxic effect on E. sinensis from carbonate alkalinity is still unclear. In this study, untargeted liquid chromatography-mass spectrometry metabolomics was performed to investigate the metabolic change caused by culture alkalinity, and confirmed distinct physiological response under gradient alkalinities. There were 39 differential metabolites obtained in the low-alkalinity group (4.35 mmol/L) versus control group, and "arachidonic acid metabolism" was enriched as a core response pathway. 93 differential metabolites were identified in the high-alkalinity group (17.43 mmol/L) versus control group, and a complex response net was manifested through integrated analysis, building by "steroid hormone biosynthesis", "phenylalanine, tyrosine and tryptophan biosynthesis", "phosphonate and phosphinate metabolism", "phenylalanine metabolism", "mineral absorption", "purine metabolism" and "carbon metabolism". This indicated the mobilization of energy reserves and the suppression of protein and amino acid catabolism were manifested in E. sinensis gills to defense high alkalinity stress. In addition, the persistently regulation of key metabolites under various alkalinity, including diuretic compound "spironolactone" and the antiphlogistic compound "LXB₄", suggested anti-inflammatory action and excretion regulation were initiated to defend the stress.

Effects of ocean acidification and tralopyril on bivalve biomineralization and carbon cycling: A study of the Pacific Oyster (Crassostrea gigas)

The combined effects of emerging pollutants and ocean acidification (OA) on marine organisms and marine ecosystems have attracted increasing attention. However, the combined effects of tralopyril and OA on marine organisms and marine ecosystems remain unclear. In this study, Crassostrea gigas (C. gigas) were exposed to tralopyril (1 μg/L) and/or OA (PH = 7.7) for 21 days and a 14-day recovery acclimation. To investigate the stress response and potential molecular mechanisms of C. gigas to OA and tralopyril exposure alone or in combination, as well as the effects of OA and/or tralopyril on bivalve biomineralization and marine carbon cycling. The results showed that the combined toxicity was between that of acidification and tralopyril alone. Single or combined exposure activated the general stress defense responses of C. gigas mantle, affected energy metabolism and biomineralization of the organism and the carbon cycle of the marine ecosystem. Moreover, acidification-induced and tralopyril-induced toxicity showed potential recoverability at molecular and biochemical levels. This study provides a new perspective on the molecular mechanisms of tralopyril toxicity to bivalve shellfish and reveals the potential role of tralopyril and OA on marine carbon cycling.

Gut Microbial Composition and Liver Metabolite Changes Induced by Ammonia Stress in Juveniles of an Invasive Freshwater Turtle

As the most common pollutant in aquaculture systems, the toxic effects of ammonia have been extensively explored in cultured fish, molluscs, and crustaceans, but have rarely been considered in turtle species. In this study, juveniles of the invasive turtle, Trachemys scripta elegans, were exposed to different ammonia levels (0, 0.3, 3.0, and 20.0 mg/L) for 30 days to evaluate the physiological, gut microbiomic, and liver metabolomic responses to ammonia in this turtle species. Except for a relatively low growth rate of turtles exposed to the highest concentration, ammonia exposure had no significant impact on the locomotor ability and gut microbial diversity of turtles. However, the composition of the microbial community could be altered, with some pathogenic bacteria being increased in ammonia-exposed turtles, which might indicate the change in their health status. Furthermore, hepatic metabolite profiles via liquid chromatography-mass spectrometry revealed extensive metabolic perturbations, despite being primarily involved in amino acid biosynthesis and metabolism. Overall, our results show that ammonia exposure causes gut dysbacteriosis and disturbs various metabolic pathways in aquatic turtle species. Considering discrepant defense mechanisms, the toxic impacts of ammonia at environmentally relevant concentrations on physiological performance might be less pronounced in turtles compared with fish and other invertebrates.

Similarities and differences among the responses to three chlorinated organophosphate esters in earthworm: Evidences from biomarkers, transcriptomics and metabolomics

The wide use of chlorinated organophosphate esters (Cl-OPEs) as additive flame retardants has aroused concern about their potential risks on ecosystem and human health. However, knowledge about the toxicity of Cl-OPEs on soil organisms remains limited. In this study, earthworms, Eisenia fetida, were exposed to three representative Cl-OPEs, i.e., tris(2-chloroethyl) phosphate (TCEP), tris(2-chloro-1-methylethyl) phosphate (TCPP), and tris(1,3-dichloro-2-propyl) phosphate (TDCPP) in artificial soil. Using a combination of biochemical indicators (biomarkers), transcriptomics, and metabolomics, we compared the Cl-OPE-induced toxicity to E. fetida and provide new insight into the related molecular mechanism. All three Cl-OPEs elicited immune defense by the earthworms, as evidenced by increased acid phosphatase and alkaline phosphatase activities, and the genes involved in immune-related pathways (e.g., lysosomal and interleukin-17 signaling pathways). Furthermore, no effects on acetylcholinesterase activity were observed among the three Cl-OPEs. However, the TCPP and TDCPP treatments significantly decreased the neurotransmitter serotonin, suggesting the potential neurotoxicity of Cl-OPEs. Although TCEP affected the genes involved in carbohydrate and amino acid metabolism, the changes in the corresponding metabolites were not statistically significant. In contrast, exposure to TCPP and TDCPP induced oxidative stress, and affected xenobiotic metabolism and energy metabolism, leading to the decreased body weight in E. fetida. Based on these toxic effects, TCPP and TDCPP were more severely toxic than TCEP, despite their structural similarity. Given that the use of TCEP has been tightly regulated, our results suggest the potentially toxic effects of TCPP and TDCPP should not be ignored in future risk assessments of flame retardants.