Lead impaired immune function and tissue integrity in yellow catfish (Peltobargus fulvidraco) by mediating oxidative stress, inflammatory response and apoptosis

Toxic effects of microplastics (polyethylene) exposure on acetylcholinesterase, stress indicators and immunity in Korean Bullhead, Pseudobagrus fulvidraco

Microplastics (MPs) in aquatic environments can have toxic effects on various organisms, including fish. This study exposed Pseudobagrus fulvidraco to polyethylene MPs at 0, 10 mg/L (approximately 9.50 ×108 particles/L), 20 mg/L (approximately 1.9 ×109 particles/L), 5000 mg/L (approximately 4.75 ×1011 particles/L), and 10,000 mg/L (approximately 9.50 ×1011 particles/L) concentrations for 96 h. At relatively lower MPs concentrations (0, 10 and 20 mg/L), no significant changes were observed in acetylcholinesterase (AChE) activity, stress indicators (heat shock protein 70 and cortisol), or immune responses (lysozyme activity and immunoglobulin M levels). However, at higher MPs concentrations (5000 and 10,000 mg/L), AChE activity was significantly inhibited, stress indicators were significantly increased, and immune responses were significantly decreased. Our results indicate that acute exposure of P. fulvidraco to MPs had negligible effects at concentrations below 20 mg/L, whereas significant toxic effects such as AChE activity inhibition, stress responses, and immune suppression were observed at concentrations above 5000 mg/L. Therefore, our study highlights the risks of severe MPs pollution on aquatic ecosystems and fish health.

Lead Nitrate (Pb(NO3)2) Toxicity Effects on DNA Structure and Histopathological Damage in Gills of Common Carp (Cyprinus carpio)

The toxic impact of environmentally relevant nominal sub-lethal concentration of lead nitrate (23 mg/L) on the gills of Cyprinus carpio after 30 days of exposure was assessed. Structural alterations were analyzed through histopathology, and the DNA damage rate in peripheral erythrocytes was evaluated by alkaline comet assay. A significant deviation in the gill histoarchitecture was observed compared to the control group. Significant changes, including the curling of secondary lamellae, loss of filaments, necrosis, hyperplasia, hypertrophy of cells of primary filament, and vacuolization, were found in the fish exposed to nominal sub-lethal concentration of lead nitrate. Moreover, the comet assay showed lead nitrate-induced DNA damage, evidenced by the length of the DNA "tail" in the exposed fish. The findings of this study strongly indicated that lead nitrate, even at sub-lethal levels, could significantly alter the overall physiology of the fish. This situation could lead to severe ecological consequences.

The content and associated health risk assessment of toxic elements, micro-, and macrominerals in common carp, Wels catfish, and silver carp from the Danube River in Serbia

Three fish species (common carp, Wels catfish, and silver carp) were collected from three locations along the Danube River in Serbia, and fish meat was analyzed for the content of toxic elements, micro- and macrominerals. Silver carp had the highest lead (Pb), arsenic (As), and cadmium (Cd) content, while Wels catfish had the highest level of mercury (Hg). Moreover, metal pollution index (MPI) ranged from 0.1096 to 0.275 and among the fish, the silver carp had the highest MPI (from 0.21 to 0.28), indicating that it could be reliable bioindicator of river pollution. Maximum determined levels of As (0.1968 mg/kg of w.w.), Hg (0.175 mg/kg of w.w.), and Pb (0.0315 mg/kg of w.w.) did not exceed values prescribed by the European Commission Regulation, Codex Alimentarius Commission, Food and Agriculture Organization (FAO), and national regulations, but Cd in silver carp was at levels higher than prescribed (0.0808 mg/kg of w.w.). Furthermore, our study's results showed that the target hazard quotient (THQ) of each analyzed element and hazard index (HI) were < 1, indicating that consumers would not be exposed to adverse health effects after consuming these fish species from the Danube River. Regarding target cancer risk (TR), for Pb this was below 10-6, which was regarded as negligible, while TRs for As and Cr were between 10-4 and 10-6, which was regarded as acceptable. Moreover, since the studied fish had low values of health risk indexes, it could be concluded that fish meat did not pose a significant risk to human health.

Cross-sectional and Longitudinal Associations Between Metal Mixtures and Serum C3, C4: Result from the Manganese‑exposed Workers Healthy Cohort

Exposure to metal mixtures compromises the immune system, with the complement system connecting innate and adaptive immunity. Herein, we sought to explore the relationships between blood cell metal mixtures and the third and fourth components of serum complement (C3, C4). A total of 538 participants were recruited in November 2017, and 289 participants were followed up in November 2021. We conducted a cross-sectional analysis at baseline and a longitudinal analysis over 4 years. Least Absolute Shrinkage and Selection Operator (LASSO) was employed to identify the primary metals related to serum C3, C4; generalized linear model (GLM) was further used to evaluate the cross-sectional associations of the selected metals and serum C3, C4. Furthermore, participants were categorized into three groups according to the percentage change in metal concentrations over 4 years. GLM was performed to assess the associations between changes in metal concentrations and changes in serum C3, C4 levels. At baseline, each 1-unit increase in log10-transformed in magnesium, manganese, copper, rubidium, and lead was significantly associated with a change in serum C3 of 0.226 (95% CI: 0.146, 0.307), 0.055 (95% CI: 0.022, 0.088), 0.113 (95% CI: 0.019, 0.206), - 0.173 (95% CI: - 0.262, - 0.083), and - 0.020 (95% CI: - 0.039, - 0.001), respectively. Longitudinally, decreased copper concentrations were negatively associated with an increment in serum C3 levels, while decreased lead concentrations were positively associated with an increment in serum C3 levels. However, no metal was found to be primarily associated with serum C4 in LASSO, so we did not further explore the relationship between them. Our research indicates that copper and lead may affect complement system homeostasis by influencing serum C3 levels. Further investigation is necessary to elucidate the underlying mechanisms.

Effects of Alkalinity Stress on Amino Acid Metabolism Profiles and Oxidative-Stress-Mediated Apoptosis/Ferroptosis in Hybrid Sturgeon (Huso dauricus ♀ × Acipenser schrenckii ♂) Livers

Alkaline water is toxic to cultured aquatic animals that frequently live in pH-neutral freshwater. Overfishing and habitat destruction have contributed to the decline in the wild sturgeon population; consequently, the domestic hybrid sturgeon has become an increasingly important commercial species in China. Hybrid sturgeons are widely cultured in alkaline water, but little is known about the effects of alkalinity stress on hybrid sturgeon liver tissues. We exposed hybrid sturgeons to four alkaline concentrations (3.14 ± 0.02 mmol/L, 7.57 ± 0.08 mmol/L, 11.78 ± 0.24 mmol/L and 15.46 ± 0.48 mmol/L). Histopathology, biochemical index assessment, gene expression level detection and metabolomics analysis were used to investigate the negative effects on liver functions following exposure to NaHCO3. Livers exposed to alkaline stress exhibited severe tissue injury and clear apoptotic characteristics. With increased exposure concentrations, the hepatic superoxide dismutase, catalase, glutathione peroxidase and alkaline phosphatase activities significantly decreased in a dose-dependent manner. NaHCO3 exposure up-regulated the transcriptional levels of apoptosis/ferroptosis-related genes in livers. Similarly, the expression trends of interleukin-1β and heat shock protein genes also increased in high-alkalinity environments. However, the expression levels of complement protein 3 significantly decreased (p < 0.05). Hepatic untargeted metabolomics revealed the alteration conditions of various metabolites associated with the antioxidant response, the ferroptosis process and amino acid metabolism (such as beta-alanine metabolism; alanine, aspartate and glutamate metabolism; and glycine, serine and threonine metabolism). These data provided evidence that NaHCO3 impaired immune functions and the integrity of hybrid sturgeon liver tissues by mediating oxidative-stress-mediated apoptosis and ferroptosis. Our results shed light on the breeding welfare of domestic hybrid sturgeons and promote the economic development of fisheries in China.

Bioaccumulation of arsenic in fish (Labeo rohita) in presence of periphyton: ameliorative effect on oxidative stress, physiological condition, immune response and risk assessment

The present study explores the use of periphyton to ameliorate toxic properties of arsenic (As) to Labeo rohita and also assesses the human food safety aspects. Fish were introduced to arsenite [As(III)] contaminated water (0.3 and 3 mg/L) along with periphyton. Biochemical, physiological and immunological parameters, including gene expression, were assessed after 30 days of exposure. Periphyton incorporation significantly improved (p < 0.05) the adverse effects of As on respiration, NH3 excretion and brain AChE activity by reducing oxidative stress and As bioaccumulation. The presence of periphyton in As(III) exposed fish (3 mg/L) increased the immune response (Immunoglobulin M and Complement C3) in the serum and the regulation of the respective immune genes in the anterior kidney was found to be similar to the control. A speciation study using LC-ICP-MS confirmed the high accumulation of As by periphyton (5.0-31.9 μg/g) as arsenate [As (V)], resulting in a lower amount of As in fish muscle. The calculated human health risk indices, Target Hazard Quotient (THQ) and Target Cancer risk (TCR) indicate that fish grown in periphyton-treated water may lower the human health risks associated with As. The study signifies the importance of periphyton-based aquaculture systems in As contaminated regions for safe fish production with enhanced yield.

Environmental Chemical-Induced Reactive Oxygen Species Generation and Immunotoxicity: A Comprehensive Review

Significance: Reactive oxygen species (ROS), the reactive oxygen-carrying chemicals moieties, act as pleiotropic signal transducers to maintain various biological processes/functions, including immune response. Increased ROS production leads to oxidative stress, which is implicated in xenobiotic-induced adverse effects. Understanding the immunoregulatory mechanisms and immunotoxicity is of interest to developing therapeutics against xenobiotic insults. Recent Advances: While developmental studies have established the essential roles of ROS in the establishment and proper functioning of the immune system, toxicological studies have demonstrated high ROS generation as one of the potential mechanisms of immunotoxicity induced by environmental chemicals, including heavy metals, pesticides, aromatic hydrocarbons (benzene and derivatives), plastics, and nanoparticles. Mitochondrial electron transport and various signaling components, including NADH oxidase, toll-like receptors (TLRs), NF-κB, JNK, NRF2, p53, and STAT3, are involved in xenobiotic-induced ROS generation and immunotoxicity. Critical Issues: With many studies demonstrating the role of ROS and oxidative stress in xenobiotic-induced immunotoxicity, rigorous and orthogonal approaches are needed to achieve in-depth and precise understanding. The association of xenobiotic-induced immunotoxicity with disease susceptibility and progression needs more data acquisition. Furthermore, the general methodology needs to be possibly replaced with high-throughput precise techniques. Future Directions: The progression of xenobiotic-induced immunotoxicity into disease manifestation is not well documented. Immunotoxicological studies about the combination of xenobiotics, age-related sensitivity, and their involvement in human disease incidence and pathogenesis are warranted. Antioxid. Redox Signal. 40, 691-714.

Transcriptome Analysis and Identification of Cadmium-Induced Oxidative Stress Response Genes in Different Meretrix meretrix Developmental Stages

Cadmium (Cd) is one of the major pollutants in the aquatic environment, and it can easily accumulate in aquatic animals and result in toxic effects by changing the metabolism of the body, causing a serious impact on the immune system, reproductive system, and the development of offspring. The clam Meretrix meretrix is one of the commercially important species that is cultivated in large-scale aquaculture in China. To elucidate the underlying molecular mechanisms of Cd2+ in the developmental processes, fertilized eggs and larvae of M. meretrix at different developmental stages were exposed to Cd2+ (27.2 mg L-1 in natural seawater) or just natural seawater without Cd2+ (control), and high-throughput transcriptome sequencing and immunohistochemistry techniques were used to analyze the toxic effects of Cd on larvae at different early developmental stages. The results revealed 31,914 genes were differentially expressed in the different stages of M. meretrix development upon treatment with Cd2+. Ten of these genes were differentially expressed in all stages of development examined, but they comprised only six unigenes (CCO, Ndh, HPX, A2M, STF, and pro-C3), all of which were related to the oxidative stress response. Under Cd exposure, the expression levels of CCO and Ndh were significantly upregulated in D-shaped and pediveliger larvae, while pro-C3 expression was significantly upregulated in the fertilized egg, D-shaped larva, and pediveliger. Moreover, HPX, A2M, and STF expression levels in the fertilized egg and pediveliger larvae were also significantly upregulated. In contrast, CCO, Ndh, HPX, A2M, STF, and pro-C3 expression levels in the postlarva were all downregulated under Cd exposure. Besides the genes with changes in expression identified by the transcriptome, the expression of two other oxidative stress-related genes (MT and Nfr2) was also found to change significantly in the different developmental stages of M. meretrix upon Cd exposure, confirming their roles in combating oxidative stress. Overall, the findings of this study indicated that Cd would interfere with cellular respiration, ion transport, and immune response through inducing oxidative stress, and changes in the expression of oxidative stress-related genes might be an important step for M. meretrix to deal with the adverse effects of Cd at different stages of its development.

Breviscapine attenuates lead‑induced myocardial injury by activating the Nrf2 signaling pathway

The present study investigated the therapeutic potential of breviscapine (Bre) in mitigating lead (Pb)-induced myocardial injury through activation of the nuclear factor erythroid-2 related factor 2 (Nrf2) pathway. Rat cardiomyocytes (H9C2 cells) were exposed to Pb to model Pb poisoning, and various parameters, including cell viability, apoptosis and reactive oxygen species (ROS) production, were assessed using Cell Counting Kit-8, flow cytometry and 2',7'-dichlorfluoresceindiacetate assays, respectively. Additionally, a rat model of Pb poisoning was established in which blood Pb levels were measured using a graphite furnace atomic absorption spectrophotometer, and alterations in myocardial tissue, oxidative stress markers, inflammatory indicators, protein expression related to apoptosis and the Nrf2 pathway were evaluated via histopathology, ELISA and western blotting. The results showed that Bre treatment enhanced cell viability, decreased apoptosis, and reduced ROS production in Pb-exposed H9C2 cells. Moreover, Bre modulated oxidative stress markers and inflammatory factors while enhancing the expression of proteins in the Nrf2 pathway. In a rat model, Bre mitigated the lead-induced increase in blood Pb levels and myocardial injury biomarkers, and reversed the downregulation of Nrf2 pathway proteins. In conclusion, the current findings suggested that Bre mitigates Pb-induced myocardial injury by activating the Nrf2 signaling pathway, highlighting its potential as a therapeutic agent for protecting the heart from the harmful effects of Pb exposure. Further research is required to elucidate the exact mechanisms and explore the clinical applicability of Bre in mitigating Pb-induced myocardial damage.

Lead induced structural and functional damage and microbiota dysbiosis in the intestine of crucian carp (Carassius auratus)

Lead (Pb) is a hazardous pollutant in water environments that can cause significant damage to aquatic animals and humans. In this study, crucian carp (Carassius auratus) were exposed to waterborne Pb for 96 h; then, histopathological analysis, quantitative qPCR analysis, and 16S high-throughput sequencing were performed to explore the effects of Pb on intestinal bioaccumulation, structural damage, oxidative stress, immune response, and microbiota imbalance of C. auratus. After Pb exposure, the intestinal morphology was obviously damaged, including significantly increasing the thickness of the intestinal wall and the number of goblet cells and reducing the depth of intestinal crypts. Pb exposure reduced the mRNA expressions of Claudin-7 and villin-1 while significantly elevated the level of GST, GSH, CAT, IL-8, IL-10, IL-1, and TNF-α. Furthermore, 16S rRNA analysis showed that the Shannon and Simpson indices decreased at 48 h after Pb exposure, and the abundance of pathogenic bacteria (Erysipelotrichaceae, Weeksellaceae, and Vibrionaceae) increased after Pb exposure. In addition, the correlation network analysis found that Proteobacteria were negatively correlated with Firmicutes and positively correlated with Bacteroidetes. Functional prediction analysis of bacteria speculated that the change in intestinal microbiota led to the PPAR signaling pathway and peroxisome function of the intestine of crucian carp was increased, while the immune system and membrane transport function were decreased. Finally, canonical correlation analysis (CCA) found that there were correlations between the intestinal microbiota, morphology, antioxidant factors, and immune factors of crucian carp after Pb exposure. Taken together, our results demonstrated that intestinal flora dysbiosis, morphological disruption, oxidative stress, and immune injury are involved in the toxic damage of Pb exposure to the intestinal structure and function of crucian carp. Meanwhile, Pb exposure rapidly increased the abundance of pathogenic bacteria, leading to intestinal disorders, further aggravating the damage of Pb to intestinal structure and function. These findings provide us a basis for the link between gut microbiome changes and heavy metal toxicity, and gut microbiota can be used as biomarkers for the evaluation of heavy metal pollution in future.

Single and joint toxic effects of waterborne exposure to copper and cadmium on Coregonus ussuriensis Berg

Heavy metal contamination severely affects the aquatic environment and organisms. Copper (Cu) and cadmium (Cd) are two of the most common heavy metal contaminants that impair the survival, development, and reproduction of aquatic organisms. With the growth of agriculture and industry, there is a possibility of heavy metal pollution in Coregonus ussuriensis Berg's water source. However, there are no published studies on the toxicity to C. ussuriensis. Acute toxicity experiments in C. ussuriensis revealed the 96-h median lethal concentrations of copper and cadmium to be 0.492 mg·L-1 (95% confidence interval: 0.452-0.529) and 1.548 mg·L-1 (95% confidence interval: 1.434-1.657), respectively, and safe concentrations of 4.92 µg·L-1 and 15.48 µg·L-1, respectively. C. ussuriensis was then treated for 96 h with Cu (20% of 96 h LC50), Cd (20% of 96 h LC50), and a combination of Cu and Cd (20% of Cu 96 h LC50 + 20% of Cd 96 h LC50). The histological damage caused by the three different exposure modes to the liver and gills of C. ussuriensis was verified using hematoxylin and eosin staining. All three exposure modes caused different degrees of vacuolization, nuclear consolidation, and necrosis in the liver tissue of C. ussuriensis and edema, hyperplasia, laminar fusion, and epithelial elevation in the gill tissue compared with the reference group. The severity of the damage increased with increasing exposure time. Anti-oxidant activity in the gill and liver tissues were measured using enzyme activity assay kits to reflect oxidative stress induced by copper and cadmium exposure alone and in combination. The enzyme activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH) were substantially higher than those in the reference groups. However, the activities of the enzymes decreased with increasing exposure time. Malondialdehyde (MDA) activity significantly increased during exposure in relation to that in the reference group. Analysis of immune gene expression in C. ussuriensis gill and liver tissues was executed using real-time inverse transcript polymerase chain response (RT-PCR). The expression levels of the pro-inflammatory cytokines interleukin one beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) were positively correlated with exposure time and were significantly upregulated with increasing exposure time. Metallothionein (MT) gene expression levels were significantly upregulated in the short term after exposure compared to the reference group but decreased with increasing exposure time. Our results indicate that exposure to aqueous copper and cadmium solutions, either alone or in combination, causes histopathological damage, oxidative stress, and immunotoxicity in C. ussuriensis gill and liver tissue. This study investigated the toxic effects of copper and cadmium on C. ussuriensis to facilitate the monitoring of heavy metals in water sources for healthy aquaculture.

Identification of the regulatory network and potential markers for type 2 diabetes mellitus related to internal exposure to metals in Chinese adults

People intake metals from their environment. This study investigated type 2 diabetes mellitus (T2DM) related to internal exposure to metals and attempted to identify possible biomarkers. A total of 734 Chinese adults were enrolled, and urinary levels of ten metals were measured. Multinomial logistic regression model was used to assess the association between metals and impaired fasting glucose (IFG) and T2DM. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and protein-protein interaction were used to explore the pathogenesis of T2DM related to metals. After adjustment, lead (Pb) was positively associated with IFG (odds ratio [OR] 1.31, 95% confidence interval [CI] 1.06-1.61) and T2DM (OR 1.41, 95% CI 1.01-1.98), but cobalt was negatively associated with IFG (OR 0.57, 95% CI 0.34-0.95). Transcriptome analysis showed 69 target genes involved in the Pb-target network of T2DM. GO enrichment indicated that the target genes are enriched mainly in the biological process category. KEGG enrichment indicated that Pb exposure leads to non-alcoholic fatty liver disease, lipid and atherosclerosis, and insulin resistance. Moreover, there is alteration of four key pathways, and six algorithms were used to identify 12 possible genes in T2DM related to Pb. SOD2 and ICAM1 show strong similarity in expression, suggesting a functional correlation between these key genes. This study reveals that SOD2 and ICAM1 may be potential targets of Pb exposure-induced T2DM and provides novel insight into the biological effects and underlying mechanism of T2DM related to internal exposure to metals in the Chinese population.

Effects of Stocking Density on the Growth Performance, Physiological Parameters, Antioxidant Status and Lipid Metabolism of Pelteobagrus fulvidraco in the Integrated Rice-Fish Farming System

Pelteobagrus fulvidraco is a freshwater fish commonly raised in rice fields, yet the optimal stocking density for this species remains unknown. Therefore, this study aimed to investigate the appropriate stocking density of P. fulvidraco in integrated rice-fish farming systems. Three different stocking densities--low density (LD, 125 g/m2), middle density (MD, 187.5 g/m2), and high density (HD, 250 g/m2)--were set up to evaluate P. fulvidraco's growth performance, stress indices, immune function, antioxidant status, and lipid metabolism after 90 days of farming. The results indicated that HD treatment had a detrimental effect on P. fulvidraco's growth parameters. HD treatment led to an increase in cortisol (Cor) and lactate (La) levels, but a decrease in glucose (Glu) content in serum. After 90 days of farming, an immune response accompanied by the increase of complement 3 (C3), C4, and immunoglobulin M (IgM) was observed in the HD group. Meanwhile, HD treatment induced oxidative stress and altered antioxidative status evidenced by the levels of catalase (CAT), glutathione peroxidase (Gpx), glutathione (GSH), malondialdehyde (MDA), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC) in serum or liver. Additionally, the lipid metabolism-related genes including lipoprotein lipase (lpl), peroxisome proliferators-activated receptor (pparα), carnitine palmitoyltransferase-1 (cpt-1), and sterol regulatory element binding protein-1 (srebp-1) were markedly downregulated in the HD and/or MD group after 90 days of farming. In conclusion, this study contributes to a better understanding of P. fulvidraco's response to different stocking densities in integrated rice-fish farming systems. We suggest that the appropriate stocking density for P. fulvidraco in these farming systems should be below 250 g/m2, considering both fish growth and physiological responses.

Microcystin-LR-induced autophagy regulates oxidative stress, inflammation, and apoptosis in grass carp ovary cells in vitro

MC-LR is one of the cyanotoxins produced by fresh water cyanobacteria. Previous studies showed that autophagy played an important role in MC-LR-induced reproduction toxicity. However, information on the toxicological mechanism is limited. In this study, MC-LR could induce autophagy and apoptosis in GCO cells in vitro. In GCO cells that had been exposed to MC-LR, the inhibitor of 3-MA effectively decreased cell viability and damaged cell ultrastructure. Oxidative stress was significantly increased in the 3-MA + MC-LR group, accompanied by significantly increased MDA content and decreased CAT activity and GST, SOD1, GPx, and GR expression levels (P < 0.05). Inflammation was more serious in the 3-MA + MC-LR group than that of MC-LR group, which was evidenced by increasing expression levels of TNFα, IL11, MyD88, TNFR1, TRAF2, JNK, CCL4, and CCL20 (P < 0.05). Interestingly, the significant decrease of Caspase-9, Caspase-7, and Bax expression and significant increase of Bcl-2 and Bcl-2/Bax ratio in 3-MA + MC-LR group compared to MC-LR group, suggesting that extent of apoptosis were reduced. Taken together, these results indicated that MC-LR induced autophagy and apoptosis in GCO cells, however, the inhibition of autophagy decreased the extent of apoptosis, induced more serious oxidative stress and inflammation, which eventually induced cell death. Our findings provided some information for exploring the toxicity of MC-LR, however, the role of autophagy require further study in vivo.

Assessment of Some Heavy Metals and Their Relationship with Oxidative Stress and Immunological Parameters in Aquatic Animal Species

Heavy metal accumulation changes the immune system and leads to oxidative damage in aquatic animals. The present study evaluated the correlation between heavy metal accumulation, with immunological and oxidative stress parameters, in various species in the aquatic environment of Western Iran. Fresh samples included fish (trout and carp) and shrimp obtained from Sanandaj aquaculture. After blood sampling and serum isolation for immunological study, meat sections of these animals were used to measure heavy metal concentrations to determine the oxidative stress and immunological parameters. The highest concentrations of Pb (0.82 ± 0.10), As (0.53 ± 0.18), Hg (0.47 ± 0.08), and Zn (28.77 ± 1.88) (µg/g) were found in trout, while the lowest accumulation of heavy metals except for Cd (0.24 ± 0.11) and Se (1.57 ± 0.42) (µg/g) were observed in shrimp. The antioxidant enzymes glutathione peroxidase (GPx) (1.89 ± 0.13) and superoxide dismutase (SOD) (1.96 ± 0.62) U/mg showed the highest concentrations in shrimp and lowest in the trout. Significant negative correlations were found between these enzymes with As and Pb in trout and carp. A significant positive correlation was determined between Se and Zn with GPx and a negative correlation with malondialdehyde (MDA) in shrimp. Immunological biomarkers indicated the concentrations of IL-6, TNF-α, and IFN-Ƴ were higher in fish than in shrimp, and the lowest IgM level was obtained in Shrimp. Increased Pb and Cd showed a significant relationship with increased IL-6 and TNF-α in trout compared to shrimp and carp. An increase in As and Se concentration beyound maximum permissible limits (MPL) were recorded in fish and shrimp, while a Zn level less than MPL was recorded. The target hazard quotients (THQ) and target cancer risk (TR) values of non-essential heavy metals were obtained under acceptable ranges. We suggest reducing the As and Pb content under aquaculture farms and increase in the amount of Zn through diets to keep healthy immunological and physiological conditions for aquatic species in the west of Iran.

Hepatopancreas toxicity and immunotoxicity of a fungicide, pyraclostrobin, on common carp

Pyraclostrobin (PYR), a strobilurin fungicide, has been widely used to control fungal diseases, posing potential risk to aquatic organisms. However, the toxic effects of PYR to fish remained largely unknown. In this study, common carp (Cyprinus carpio L.) was exposed to environmentally relevant levels of PYR (0, 0.5 and 5.0 μg/L) for 30 days to assess its chronic toxicity and potential toxicity mechanism. The results showed that long-term exposure to PYR induced hepatopancreas damage as evident by increased in serum transaminase activities (AST and ALT). Moreover, PYR exposure remarkably enhanced the expressions of hsp70 and hsp90, decreased the levels of antioxidant enzymes and biomarkers and promoted the reactive oxygen species (H₂O₂ and O₂^-) and MDA contents in carp hepatopancreas. PYR exposure also upregulated apoptosis-related genes (bax, apaf-1, caspase-3 and caspase-9) and reduced anti-apoptosis gene bcl-2 in fish hepatopancreas. Moreover, PYR exposure altered the expressions of inflammatory cytokines (IL-1β, IL-6, TNF-α and TGF-β) in the serum and hepatopancreas and the level of NF-κB p65 in the hepatopancreas. Further research indicated that PYR exposure markedly changed the levels of immune parameters (LYZ, C3, IgM, ACP and AKP) in the serum and/or hepatopancreas, indicating that chronic PYR exposure also has immunotoxicity on fish. Additionally, we found that PYR exposure upregulated p38 and jnk MAPK transcription levels, suggesting that MAPK may be play important role in PYR-induced apoptosis and inflammatory response in the hepatopancreas of common carp. In summary, PYR exposure induced oxidative stress, triggered apoptosis, inflammatory and immune response in common carp, which can help to elucidate the possible toxicity mechanism of PYR in fish.

Transcriptomic and proteomic analyses provide insights into the adaptive responses to the combined impact of salinity and alkalinity in Gymnocypris przewalskii

Gymnocypris przewalskii is the only high-land endemic teleost living in Qinghai Lake, the largest saline-alkaline lake in China. Its osmoregulatory physiology remains elusive due to a lack of precise identification of the response proteins. In the present study, DIA/SWATH was used to identify differentially expressed proteins (DEPs) under alkaline (pH = 10.1, carbonate buffer), saline (12‰, sodium chloride), and saline-alkaline [carbonate buffer (pH = 10.1) plus 11‰ sodium chloride] stresses. A total of 66,056 unique peptides representing 7,150 proteins and 230 DEPs [the false discovery rate (FDR) ≤ 0.05, fold change (FC) ≥ 1.5] were identified under different stresses. Comparative analyses of the proteome and transcriptome indicated that over 86% of DEPs did not show consistent trends with mRNA. In addition to consistent enrichment results under different stresses, the specific DEPs involved in saline-alkaline adaptation were primarily enriched in functions of homeostasis, hormone synthesis and reactions of defense response, complement activation and reproductive development. Meanwhile, a protein-protein interaction (PPI) network analysis of these specific DEPs indicated that the hub genes were ITGAX, MMP9, C3, F2, CD74, BTK, ANXA1, NCKAP1L, and CASP8. This study accurately isolated the genes that respond to stress, and the results could be helpful for understanding the physiological regulation mechanisms regarding salinity, alkalinity, and salinity-alkalinity interactions.

Morphological and Functional Alterations Induced by Two Ecologically Relevant Concentrations of Lead on Danio rerio Gills

Lead (Pb), due to its high toxicity and bioaccumulation tendency, is one of the top three pollutants of concern for both humans and wildlife and occupies second place in the Priority List of Hazardous Substances. In freshwater fish, Pb is mainly absorbed through the gills, where the greatest accumulation occurs. Despite the crucial role of gills in several physiological functions such as gas exchange, water balance, and osmoregulation, no studies evaluated the effects of environmentally relevant concentrations of Pb on this organ, and existing literature only refers to high levels of exposure. Herein we investigated for the first time the molecular and morphological effects induced by two low and environmentally relevant concentrations of Pb (2.5 and 5 μg/L) on the gills of Danio rerio, a model species with a high translational value for human toxicity. It was demonstrated that Pb administration at even low doses induces osmoregulatory dysfunctions by affecting Na⁺/K⁺-ATPase and AQP3 expression. It was also shown that Pb upregulates MTs as a protective response to prevent cell damage. Modulation of SOD confirms that the production of reactive oxygen species is an important toxicity mechanism of Pb. Histological and morphometric analysis revealed conspicuous pathological changes, both dose- and time-dependent.

The multiple biotoxicity integrated study in grass carp (Ctenopharyngodon idella) caused by Ochratoxin A: Oxidative damage, apoptosis and immunosuppression

Ochratoxin A (OTA) is a common hazardous food contaminant that seriously endangers human and animal health. However, limited study is focused on aquatic animal. This research investigated the multiple biotoxicity of OTA on spleen (SP) and head kidney (HK) in grass carp and its related mechanism. Our data showed that, dietary supplemented with OTA above 1209 μg/kg caused histopathological damages by decreasing the number of lymphocytes and necrotizing renal parenchymal cells. Meanwhile, OTA caused oxidative damage and reduced the isoforms mRNAs transcripts of antioxidant enzymes (e.g., GPX1, GPX4, GSTO) partly due to suppressing NF-E2-related factor 2 (Nrf2). OTA triggered apoptosis through mitochondria and death receptor pathway potentially by p38 mitogen-activated protein kinase (p38MAPK) activation. Besides, OTA exacerbated inflammation by down-regulation of anti-inflammatory factor (e.g., IL-10, IL-4) and up-regulations of pro-inflammatory factors (e.g., TNF-α, IL-6), which could be ascribed to signaling meditation of Janus kinase / signal transducer and activator of transcription (JAK/STAT). Additionally, the safe upper limits of OTA were estimated to be 677.6 and 695.08 μg/kg based on the immune-related indexes (C3 contents in the SP and LZ activities in the HK, respectively). Our study has provided a wide insight for toxicological assessment of feed pollutant in aquatic animals.

Environmentally relevant concentrations of tris (1,3-dichloro-2-propyl) phosphate induce growth inhibition and oxidative stress in silver carp (Hypophthalmichthys molitrix) larvae

Tris (1,3-dichloro-2-propyl) phosphate (TDCIPP), widely applied as flame retardant into a variety of products, can be physically leached out to the aquatic environment. Measurable values of TDCIPP have been found in the environment and within biota. Many toxicological assessments have shown that TDCIPP could cause developmental toxicity and oxidative stress in fish. In this study, we focused on the effects of TDCIPP on the growth and oxidative stress of an important commercial fish species in China, silver carp (Hypophthalmichthys molitrix). Fish larvae was exposed to environmentally relevant concentrations (0.05, 0.5, 5 and 50 μg/L) of TDCIPP for 7, 14 and 28 days. Simultaneously, the transcription levels of genes associated with the growth hormone/insulin-like growth factor (GH/IGF) axis and the antioxidative enzymes were examined. The body length and body mass of silver carp larvae decreased significantly only under exposure to 5 and 50 μg/L of TDCIPP at 14 days compared with the control group, while differences on those paraments were observed at 0.05, 0.5, 5 and 50 μg/L when larvae were exposed for 28 days. The observation evidenced the time- and dose- dependent growth inhibitions caused by TDCIPP on silver carp larvae. Exposure to TDCIPP also decreased the contents of GH and IGF1 in fish attended by significant down-regulation of gh and igf1. Moreover, TDCIPP up-regulated the expression of cat, sod1 and gstt followed by an increase of the activities of catalase (CAT) and superoxide dismutase (SOD) and the levels of malondialdehyde (MDA) and glutathione (GSH), but the activities of glutathione peroxidase (GPX) were decreased. These results suggested that growth inhibition and oxidative stress co-occurred in silver carp larvae after exposure to environmentally relevant concentrations of TDCIPP accompanied by the abnormal expression of genes which associated with the GH/IGF axis and antioxidative enzymes.

Silica nanoparticles are novel aqueous additive mitigating heavy metals toxicity and improving the health of African catfish, Clarias gariepinus

Silica nanoparticles (SiNPs) are among the non-toxic nanoparticles (NPs) that have magnetic capabilities. It is hypothesized that SiNPs may be able to reduce toxic effects exerted by a mixture of lead (Pb) and mercury (Hg) in African catfish Clarias gariepinus. The in vitro magnetic potential of SiNPs to absorb Pb and Hg was tested. Fish (N = 240) were divided into four groups in triplicates for 30 days. The first group served as control and the second group (SiNPs) was exposed to 1/10 of 96 h LC50 of SiNPs (14.45 mg/L). The third group (HMM) was exposed to 1/10 of 96-h LC50 of a mixture of mercury chloride (HgCl₂) and lead chloride (PbCl₂) equal to 0.04 mg/ L and 23.1 mg/L. The fourth group (SiNPs+ HMM) was exposed to a suspension composed of SiNPs, HgCl₂, and PbCl₂ at the same concentrations as the third group. Results showed that fish exposed to heavy metals revealed the following consequences; a significant decrease in hematological, immunological (complement-3 and nitric oxide), and antioxidants (total antioxidant capacity, glutathione peroxidase, superoxide dismutase, and catalase) indices, down-regulation of IL-1β, IL-8, TGF-β, NF-κβ, HSP70, and Hepcidin genes, the highest mortality rate (48.33%), higher values of alkaline phosphatase, alanine, and aspartate aminotransferases, urea, creatinine, and branchial malondialdehyde, marked up-regulation of CC chemokine and CXC chemokines, and high HMs residues levels in muscles. Extensive pathology showed degeneration with diffuse vacuolation of hepatopancreatic cells and hemorrhage in the HMM group. Interestingly, the exposed group to SiNPs and HMM demonstrated a decline of HMs concentration in fish muscles and modulated the abovementioned parameters with the regeneration of histological alterations of liver and gills. Based on the study outcomes, we highlight the importance and the safety of SiNPs as a novel aqueous additive to alleviate HMs toxicity and recommend using SiNPs for enhancing fish performance for sustaining aquaculture without adverting safety of human health by their little accumulation in muscular tissue.

Environmentally relevant concentrations of mercury inhibit the growth of juvenile silver carp (Hypophthalmichthys molitrix): Oxidative stress and GH/IGF axis

Mercury (Hg) is a global environmental contaminant, and excessive mercury levels in water can adversely affect the growth of fish. Silver carp (Hypophthalmichthys molitrix) is one of the important freshwater aquaculture fish in China, and its natural resources have been critically declining. However, the effects of Hg²⁺ exposure on the growth hormone/insulin-like growth factor (GH/IGF) axis and its toxic mechanism are still unclear. In this study, we systematically evaluated the bioaccumulation, histomorphology, antioxidant status, hormone levels, and GH/IGF axis toxicity of juvenile silver carp after exposure to environmental-related concentrations of Hg²⁺ (0, 0.05, 0.5, 5, and 50 µg/L) for 28 days. Results showed that the Hg²⁺ bioaccumulation in the liver increased with a rise in Hg²⁺ concentration and time of exposure. The body length (BL), body weight (BW), weight growth rate (WGR) and specific growth rate (SGR) all decreased after Hg²⁺ exposure. The serum levels of growth hormones (GH and IGF) and thyroid hormones (T3 and T4) were significantly decreased, and the expressions of GH/IGF axis-related genes were significantly downregulated after 7, 14, and 28 days of Hg²⁺ exposure. Correlations between the growth parameters and growth hormones or expression of genes in GH/IGF axis further suggested that environmentally relevant concentrations of Hg²⁺ could have adverse effects on growth. In addition, with increasing Hg²⁺ exposure, superoxide activities of dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST)and levels of reduced glutathione (GSH) and malondialdehyde (MDA) were significantly increased, whereas the activity of glutathione peroxidase (GPx) significantly decreased and oxidative stress-related gene significantly changed. Liver lesions were mainly characterized by inflammatory cell infiltration, hepatocyte necrosis and fat vacuolation after exposure to Hg²⁺. Taken together, the results indicate that Hg²⁺ exposure leads to growth inhibition and oxidative stress in juvenile silver.