Heat-induced oxidative stress and inflammation involve in cadmium pollution history in the spleen of zebrafish

Evaluation of four novel non-grain protein sources completely replacing soybean meal on growth performance, serum biochemistry, amino acid transport and intestinal health of grass carp (Ctenopharyngodon idella) at different water temperatures

To investigate the effects of non-grain protein source and water temperature on growth and feed utilization differences of grass carp, the effects of different protein sources on the growth performance, serum biochemistry, digestive enzymes, amino acid transport and intestinal health of grass carp were studied at 24°C, 28°C and 32°C. In this study, a total of 1350 grass carp (5.00 ± 0.02 g) were selected, and Clostridium autoethanogenum protein (CAP), Tenebrio molitor meal (TMM), cottonseed protein concentrate (CPC) and Chlorella powder (CHP) were used as a single protein source to completely replace soybean meal for 56 days. The results showed that the final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR) and protein efficiency ratio (PER) of grass carp increased significantly with the increasing temperature (P < 0.001). The CHP and SBM groups showed no significant differences in FBW, WGR, SGR and PER (P > 0.05), which were higher than the CAP, TMM and CPC groups (P < 0.001). The alanine transaminase (ALT), aspartate aminotransferase (AST), total protein (TP) and triglyceride (TG) concentrations of grass carp at 32°C were significantly lower than those at 24°C and 28°C (P < 0.001). The acid phosphatase (ACP) activity decreased significantly with the increase of temperature (P = 0.001). The amylase (AMS) activity of the TMM, CPC and CHP groups was significantly lower than that of the SBM and CAP groups (P < 0.001), and the ACP and lipase (LPS) activities in the TMM group were significantly lower than those in the SBM group (P < 0.001). In addition, the interaction between temperatures and protein sources significantly affected the gene expression levels of amino acid transport including solute carrier family 1 member 3 (SLC1A3), solute carrier family 7 member 1 (SLC7A1), solute carrier family 7 member 5 (SLC7A5), solute carrier family 15 member 1b (SLC15A1b), solute carrier family 7 member 7 (SLC7A7), target of rapamycin (TOR), 4E binding protein 1 (4E-BP1) and ribosomal protein S6 kinase 1 (S6K1), intestinal inflammatory including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-8 (IL-8), interleukin-10 (IL-10) and tight junction proteins (occludin, claudin1, claudin3, claudin7 and claudin11) (P ≤ 0.001). Collectively, our results indicated that CHP could be a potential protein source in the case of complete replacement of soybean meal in grass carp.

Transcriptome Analysis Revealed the Early Heat Stress Response in the Brain of Chinese Tongue Sole (Cynoglossus semilaevis)

As a common influencing factor in the environment, temperature greatly influences the fish that live in the water all their life. The essential economic fish Chinese tongue sole (Cynoglossus semilaevis), a benthic fish, will experience both physiological and behavioral changes due to increases in temperature. The brain, as the central hub of fish and a crucial regulatory organ, is particularly sensitive to temperature changes and will be affected. However, previous research has mainly concentrated on the impact of temperature on the gonads of C. semilaevis. Instead, our study examines the brain using transcriptomics to investigate specific genes and pathways that can quickly respond to temperature changes. The fish were subjected to various periods of heat stress (1 h, 2 h, 3 h, and 5 h) before extracting the brain for transcriptome analysis. After conducting transcriptomic analyses, we identified distinct genes and pathways in males and females. The pathways were mainly related to cortisol synthesis and secretion, neuroactive ligand-receptor interactions, TGF beta signaling pathway, and JAK/STAT signaling pathway, while the genes included the HSP family, tshr, c-fos, c-jun, cxcr4, camk2b, and igf2. Our study offers valuable insights into the regulation mechanisms of the brain's response to temperature stress.

Cytoprotective effect of propolis on heat stress induces alteration to histological, ultrastructural, and oxidative stress in catfish (Clarias gariepinus)

Our study helps to evaluate the immune response, antioxidative status, and resistance against heat stress (HS) in Clarias gariepinus treated with propolis extraction; the results will contribute to theories of fish physiology and immunity under high-temperature conditions. Forty-five fish were divided into three equal groups: the control, the HS group at 36 °C, and the HS treated with alcoholic extraction of propolis that dissolved in water for 3 weeks. The results of our study suggested that the stress response differs among tissues thymus, spleen, and liver. All the tissues showed alteration in morphological and cytological structure at the light microscope (LM) and transmission electron microscope (TEM); thymus showed edema and thymocyte destruction; the spleen detected collagen deposition, and the liver displayed endoplasmic reticulum amplification (ER). In addition, we examined oxidative stress and antioxidant defenses (lipid peroxidation, catalase, and glutathione) of the spleen and measured blood biochemical parameters (alanine transaminase and aspartic transaminase levels) after heat stress. However, this toxic effect of HS was neutralized by the propolis extraction. To conclude, propolis is recommended to cope with the impacts of heat stress on catfish (Clarias gariepinus) by improving immunity and antioxidative resistance.

Combined threats of climate change and contaminant exposure through the lens of bioenergetics

Organisms face energetic challenges of climate change in combination with suites of natural and anthropogenic stressors. In particular, chemical contaminant exposure has neurotoxic, endocrine-disrupting, and behavioral effects which may additively or interactively combine with challenges associated with climate change. We used a literature review across animal taxa and contaminant classes, but focused on Arctic endotherms and contaminants important in Arctic ecosystems, to demonstrate potential for interactive effects across five bioenergetic domains: (1) energy supply, (2) energy demand, (3) energy storage, (4) energy allocation tradeoffs, and (5) energy management strategies; and involving four climate change-sensitive environmental stressors: changes in resource availability, temperature, predation risk, and parasitism. Identified examples included relatively equal numbers of synergistic and antagonistic interactions. Synergies are often suggested to be particularly problematic, since they magnify biological effects. However, we emphasize that antagonistic effects on bioenergetic traits can be equally problematic, since they can reflect dampening of beneficial responses and result in negative synergistic effects on fitness. Our review also highlights that empirical demonstrations remain limited, especially in endotherms. Elucidating the nature of climate change-by-contaminant interactive effects on bioenergetic traits will build toward determining overall outcomes for energy balance and fitness. Progressing to determine critical species, life stages, and target areas in which transformative effects arise will aid in forecasting broad-scale bioenergetic outcomes under global change scenarios.

Luteolin, a promising quorum quencher mitigates virulence factors production in Pseudomonas aeruginosa - In vitro and in vivo approach

Pseudomonas aeruginosa (PA) is an opportunistic pathogen that causes healthcare-associated infection and high mortality in immunocompromised patients. It produces several virulence factors through quorum sensing (QS) mechanisms that is essential for subverting host immune system. Even front-line antibiotics are unable to control PA pathogenicity due to the emergence of antibiotic resistance. Luteolin is a naturally derived compound that has proven to be the effective drug to annihilate pathogens through quorum quenching mechanism. In this study, the protective effect of luteolin against the PA-mediated inflammation was demonstrated using zebrafish model. Luteolin protects zebrafish from PA infection and increases their survival rate. It was found that PA-mediated ROS, lipid peroxidation, and apoptosis were also significantly reduced in luteolin-treated zebrafish larvae. Open field test (OFT) reveals that luteolin rescued PA-infected zebrafish from retarded swimming behavior. Furthermore, luteolin increases SOD and CAT levels and decreases LDH and NO levels in PA-infected zebrafish compare to control group. Histological and gene expression analysis reveals that luteolin protects PA-infected zebrafish by decreasing gut inflammation and altering the expression of inflammatory (TNF-α, IL-1β, IL-6) and antioxidant markers (iNOS, SOD, CAT). Thus, luteolin was found to have dual effect in protecting PA-infected zebrafish by decreasing virulence factors production in PA and stimulating host immune system. This is the first study demonstrating the protective effect of luteolin using animal model. Hence, luteolin could be used as a future therapeutic drug to control multi-drug resistant PA.

Transcriptomic Analysis of the Liver and Brain in Grass Carp (Ctenopharyngodon idella) Under Heat Stress

Temperature is a major environmental factor that influences growth, development, metabolism, and physiological performance in fish. Grass carp (Ctenopharyngodon idella) is a highly productive fish in freshwater culture. To understand the molecular mechanism of grass carp under heat stress, we used RNA-Seq to analyze the liver and brain transcriptome of 12 libraries constructed from high-temperature (36 °C) and control (28 °C) groups. We obtained 42.49 and 42.57 GB of clean data from six liver and six brain libraries, respectively, and identified 2,534 genes that were differentially expressed in liver tissue and 1622 in brain tissue (P < 0.05). According to KEGG analysis, significant differences occurred in the expression of genes involved in metabolic and immune pathways, such as the cAMP signaling pathway, apoptosis, calcium signaling pathway, lipid metabolism, and protein processing in endoplasmic reticulum and peroxisome proliferator-activated receptor signaling pathways. This study revealed that high temperature enhanced lipid metabolism, reduced fatty acid synthesis, and disrupted the immune system of grass carp. These results investigated the molecular regulation of heat stress in grass carp and provided valuable information for the healthy culture of grass carp under high temperatures.

Exposure to heat stress causes downregulation of immune response genes and weakens the disease resistance of Micropterus salmoides

In order to understand the molecular mechanism of response to heat stress in largemouth bass (LMB) Micropterus salmoides, we performed transcriptome analysis of spleen tissue of LMB subjected to heat stress and challenged with A. veronii under heat stress. A total of 2162 DEGs were identified between the heat stressed (32 °C) and control groups (24 °C) after 7 d treatment. Gene Ontology (GO) annotation analysis revealed that these differentially expressed genes (DEGs) were mainly enriched on GO terms of biological regulation, membrane part, and binding. ELISA validation indicated that except major histocompatibility complex II (Mhc II), the protein levels of t-Sod, caspase 3 (Casp3), tumor necrosis factor-α (Tnf-α), and complement component 3 (C3) were consistent with RNA-seq results. In the experiment of A. veronii challenged under heat stress (32 °C), 2899 and 2663 DEGs were obtained from the heat stress-challenged group (H6 vs H0, H12 vs H0), while 1485 and 3501 DEGs from the control-challenged group (C6 vs C0, C12 vs C0). GO and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that immune-related categories and pathways were significantly enriched, such as immune system process, immune response and positive regulation of immune response in GO enrichment analysis, and cytokine-cytokine receptor interaction, human cytomegalovirus infection in KEGG signaling pathways. The expressions of f11, c1q and c3 in complement and coagulation pathway, as well as that of proinflammatory genes tnf-α and il-8, were deeply inhibited. Real-time quantitative PCR validation for nine DEGs showed that most of them had consistent expression trends with RNA-seq results. Our results indicated that heat stress affects the immunity and metabolism of LMB. In particular, it aggravates the inhibitory effects of A. veronii on the complement and coagulation systems while downregulating proinflammatory cytokine expression, thereby weakening the resistance of LMB to pathogen infection. Our results contribute to the elucidation of A. veronii infection pathogenic mechanisms in LMB under heat stress.

Combined effects of temperature and nutrients on the toxicity of cadmium in duckweed (Lemna aequinoctialis)

Global anthropogenic changes are altering the temperature and nutrients of the ecosystem, which might also affect the extent of cadmium (Cd) toxicity in organisms. This study aimed to investigate the combined effects of temperature and nutrient availability (here, nitrogen [N] and phosphorus [P]) on Cd toxicity in duckweed (Lemna aequinoctialis). The growth parameters, nutrient uptake, and Cd tolerance of plantlets reached their highest values for duckweed grown in medium with 28 mg/L N and 2.4 mg/L P (N:P = 11.67) at 25 °C under 1 mg/L CdCl₂ exposure. Raising the temperature (from 18 °C to 25 °C) and levels of N and P (from 0.01 N/P to 2 N/P) enhanced photosynthetic capacity and nutrient uptake, thus promoting plant growth and diluting the toxic effects of Cd. Although Cd uptake increased with increasing temperature, duckweed with relatively high biomass exhibited a lower accumulation of the toxic metal because their growth rate exceeded Cd uptake rate. Increasing N and P supply also enhanced the tolerance of duckweed to Cd by limiting Cd bioavailability. Our study therefore suggests the importance of combined effects from temperature and nutrients for Cd toxicity and provides novel insights for a comprehensive analysis of Cd toxicity associated with the environmental factors of a particular ecosystem.

Use of enzymatic biomarkers of Labeo rohita to study the effect of polybrominated diphenyl ether (BDE- 209) via dietary exposure in laboratory conditions

Fishes have been widely used as a representative to estimate the health of an aquatic ecosystem. In the present study, Labeo rohita was selected for biomarker study against decabromodiphenyl ether (BDE-209), a persistent organic pollutant (POP), as it is a widely used Indian carp. The results suggested significant effects on the optimum metabolism of Labeo rohita. After 48 to 72 h of exposure, most of the biomarkers such as lactate dehydrogenase (LDH), creatine kinase (CK), serum glutamic pyruvic transaminase (SGPT), serum glutamic oxaloacetic transaminase (SGOT), and hepatosomatic index (HSI) increased drastically indicating the higher index of tissue and liver damage. On the contrary, succinic dehydrogenase (SDH), acetylcholinesterase (AChE), and alkaline phosphatase (ALP) showed a reverse trend suggesting the shifting of fish metabolism towards anaerobic respiration mode because of induced stress. Increased catalase (CAT) activity was also observed, which indicated increased abundance of reactive hydroxyl species and therefore a possible oxidative stress in fishes. It is further suggested to understand and examine the biotransformation characteristics and degradation pathways of polybrominated diphenyl ether (PBDE)s, which would be useful to comprehend their environmental fate.

Transcriptome analysis provides the first insight into the molecular basis of temperature plasticity in Banggai cardinalfish, Pterapogon kauderni

Banggai cardinalfish, Pterapogon kauderni, is a tropical fish listed as an endangered species by IUCN. Its distribution and survival condition are extremely limited, and the changes of living environment caused by global warming may seriously threaten its geographical distribution. In order to understand the survival temperature range and the potential mechanism of temperature plasticity of P. kauderni, transcriptome analysis was performed under five temperature conditions (18 °C, 22 °C, 26 °C, 30 °C and 34 °C). A total of 432,444,497 clean reads were obtained from the mix tissues of whole head, viscera (except intestine), and muscle. All clean data were spliced into 194,832 unigenes. Compared with 26 °C, 57, 107, 187 and 174 differentially expressed genes (DEGs) were obtained at 18 °C, 22 °C, 30 °C and 34 °C, respectively. Gene Ontology (GO) analysis showed the most highly enriched in the DEGs were cellular processes, binding, metabolic processes and biological regulation. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated circadian rhythm, protein processing in endoplasmic reticulum, influenza A and prion disease were significantly enriched. 47 genes that may be related to temperature stress were identified, such as Per1, MLP, IGFBP1, HSP70, HSP90α, HSPA4, DNAJB1, CALR. This is the first RNA-Seq study of P. kauderni. This information should be valuable for further targeted studies on temperature tolerance, thereby assisting the protection and development of P. kauderni.

Effects of thermal stress-induced lead (Pb) toxicity on apoptotic cell death, inflammatory response, oxidative defense, and DNA methylation in zebrafish (Danio rerio) embryos

Lead (Pb) is a toxic environmental pollutant that is frequently present in effluents from urban, mining, and industrial sources. The combinatorial effects of heavy metal exposure and temperature in aquatic organisms have received considerable attention as heat stress occurs simultaneously in conjunction with several contaminants in a natural environment. In this study, we examined the potential effects of Pb exposure in conditions of thermal stress (34 °C) in zebrafish (Danio rerio) embryos. Thermal stress at 34 °C induced a dramatic decrease in the survival rate, although exposure to Pb at 26 °C decreased the survival rate of the embryos. Malformations, such as the curved body shape, were increased in response to exposure to a combination of Pb and heat stress. The combination of Pb and heat stress also caused a decrease in the heart rate. Moreover, Pb and high-temperature exposure induced the upregulation of SOD, CAT, TNF-α, IL-1β, p53, and BAX transcripts, and downregulation of Dnmt1 and Dnmt3b transcripts. Thermal stress enhanced transcriptional responses of eight indicator genes following Pb toxicity. The induction of cell death in response to combined exposures was also confirmed in the body of zebrafish by fluorescence intensity image analysis. These data indicated that thermal stress enhanced the poisonous effects of Pb exposure on antioxidant defense, inflammation, and apoptotic mechanisms. Transcriptional inhibition of DNA methylation-related genes might serve as a crucial factor contributing to the possibility of epigenetic adaptation by altering combined stress. We suggest that a careful evaluation of the potential effects of climate change (especially temperature) should be considered when investigating the toxic levels of metal pollution, such as Pb, in an aquatic environment.

Effects of combined stressors to cadmium and high temperature on antioxidant defense, apoptotic cell death, and DNA methylation in zebrafish (Danio rerio) embryos

Fish are frequently affected by environmental stressors, such as temperature changes and heavy metal exposure, in aquatic ecosystems. In this study, we evaluated the combined effects of cadmium (Cd) toxicity and temperature (rearing temperature of 26 °C and heat stress at 34 °C) on zebrafish (Danio rerio) embryos. The survival and heart rates of zebrafish embryos decreased at relatively high Cd concentrations of 0.07 and 0.1 mg L^-1. Abnormal morphology was induced by exposure to a combination of Cd toxicity and heat stress. The yolk sac edema size was not significantly different between the control- and Cd-treated groups. Cd exposure induced reactive oxygen species (ROS) production and cell death in the live zebrafish. High temperature (34 °C) triggered Cd-induced cell death and intracellular ROS production to a greater extent than the rearing temperature of 26 °C. Transcriptional levels of six genes-CAT, SOD, p53, BAX, Dnmt1, and Dnmt3b-were investigated. The mRNA expression of CAT and SOD, molecular indicators of oxidative stress, was increased significantly at 34 °C after Cd exposure. The mRNA expression of CAT was more sensitive to temperature than that of SOD in Cd-treated zebrafish. p53 and BAX, apoptosis-related genes, were upregulated upon combined exposure to high temperature and Cd. In addition, at 34 °C, the expression of Dnmt1 and Dnmt3b transcripts, markers of DNA methylation, was increased upon exposure of zebrafish to all concentrations of Cd. Overall, these results suggest that high temperature facilitates the potential role of Cd toxicity in the transcriptional regulation of genes involved in the antioxidant system, apoptosis, and DNA methylation.

Alterations to transcriptomic profile, histopathology, and oxidative stress in liver of pikeperch (Sander lucioperca) under heat stress

Pikeperch (Sander lucioperca) is an economically important cool-water fish. In recent years, its cultivation has become threatened by higher temperatures in summer. We previously investigated the effects of heat stress on pikeperch liver under different temperatures, but the molecular mechanism of the heat-stress response is still unknown. This study applied consistent heat stress (29 °C, 0-48 h) to pikeperch juveniles, and a transcriptomic profile of pikeperch liver under heat stress (29 °C, 0 h) was performed by RNA-Seq. The antioxidant status, changes in liver histology, and antioxidant gene expression at different time points were examined. We identified 403 differentially expressed genes (DEGs), many of which were enriched in KEGG pathways, including protein processing in endoplasmic reticulum (ER), insulin signaling, and immune-related pathways. Among these, the most significant heat-stress-related pathway was protein processing in ER, indicating that this pathway is critical for the heat-stress response. After consistent heat stress at 29 °C, the total antioxidant capacity (T-AOC), the activities of total superoxide dismutase (T-SOD) and catalase (CAT), and the mRNA expression of manganese SOD (Mn-SOD), CAT, and glutathione peroxidase 1 and 7 (GPx1 and GPx7) in the treated groups showed the same trend of first increasing and then decreasing. Levels of malondialdehyde (MDA) content did not show significant differences between samples at 0 h and 3 h, but significantly increased by 6 h, and thereafter decreased. The liver tissue was normal at 0 h (29 °C); however, it suffered histological damage with increased duration of the heat stress. Above all, heat stress at 29 °C seemed to cause oxidative damage and dysfunction in pikeperch liver between 3 h and 48 h. The present results indicate that pikeperch have the capacity to defend against heat stress and maintain relative balance of oxidation-reduction reactions mainly through activating the antioxidant system, protein processing in ER, the insulin-signaling pathway, and immune-related pathways.

Effects of pollution on freshwater aquatic organisms

This paper presents the reviews of scientific papers published in 2018 issues on the effects of anthropogenic pollution on the aquatic organisms dwelling in freshwater ecosystem at global scale. The first part of the study provides the summary of relevant literature reviews followed by field and survey based studies. The second part is based on categories of different classes/sources of pollutants which affect freshwater organism. This is composed of several sections including metals and metalloids, wastewater and effluents, sediments, nutrients, pharmaceuticals, polycyclic aromatic hydrocarbons, flame retardants, persistent organic pollutants, pharmaceuticals and illicit drugs, emerging contaminants, pesticides, herbicides, and endocrine disruptors. The final part of the study highlights the reviews of published research work on new pollutants such as microplastics and engineered nanoparticles which affect the freshwater organisms. PRACTITIONER POINTS: Heavy metals concentrations should be assessed at nano-scale in aquatic environment. Air pollutants could have long-term effects on freshwater ecosystem. Future studies should focus on bioremediations of freshwater pollution.

Effects of a chronic exposure to different water temperatures and/or to an environmental cadmium concentration on the reproduction of the threespine stickleback (Gasterosteus aculeatus)

Knowledge about combined effects of chemicals and temperature on reproductive capacity of fish are rare in literature, especially when it comes to the effects of chronic low-dose chemical exposure combined to the thermal stress. The aim of the study was to evaluate the single and combined effects of temperature (16, 18, 21 °C) and an environmentally relevant concentration of waterborne cadmium (1 µg L^-1, nominal concentration) on the reproductive outputs of threespine stickleback (Gasterosteus aculeatus), and their consequences on offspring survival parameters. The high temperature (21 °C) was the only factor that affected parental parameters (gonadosomatic index "GSI", and vitellogenin "VTG" particularly). On females, 21 °C had a stimulating effect on gonadal development evaluated by an early increase, followed by a sharp decrease of GSI, probably indicating gonadal atresia. Promoting effect of temperature was corroborated by an early production of VTG. In vitro fertilization assays showed interesting results, particularly cadmium effects. As it was supposed, high temperature had a negative impact on offspring parameters (significant decrease in survival and an increase of unhatched embryos). Parental exposure to the very low concentration of cadmium had also negative consequences on mortality rate (significant increase) and hatching rate (significant decrease). Our results indicate that in a global warming context, high temperature and its combination with contaminant may impact reproductive capacity of G. aculeatus, by decreasing parental investment (low eggs and/or sperm quality).

Rapid Determination of Cadmium Contamination in Lettuce Using Laser-Induced Breakdown Spectroscopy

Quick access to cadmium (Cd) contamination in lettuce is important to supervise the leafy vegetable growth environment and market. This study aims to apply laser-induced breakdown spectroscopy (LIBS) technology for fast determination of Cd content and diagnosis of the Cd contamination degree in lettuce. Emission lines Cd II 214.44 nm, Cd II 226.50 nm, and Cd I 228.80 nm were selected to establish the univariate analysis model. Multivariate analysis including partial least squares (PLS) regression, was used to establish Cd content calibration models, and PLS model based on 22 variables selected by genetic algorithm (GA) obtained the best performance with correlation coefficient in the prediction set Rp² = 0.9716, limit of detection (LOD) = 1.7 mg/kg. K-Nearest Neighbors (KNN) and random forest (RF) were used to analyze Cd contamination degree, and RF model obtained the correct classification rate of 100% in prediction set. The preliminary results indicate LIBS coupled with chemometrics could be used as a fast, efficient and low-cost method to assess Cd contamination in the vegetable industry.