In vitro toxicity of pirimiphos-methyl in Atlantic salmon hepatocytes

The assessment of the potential hepatotoxicity of new drugs by in vitro metabolomics

Drug hepatotoxicity assessment is a relevant issue both in the course of drug development as well as in the post marketing phase. The use of human relevant in vitro models in combination with powerful analytical methods (metabolomic analysis) is a promising approach to anticipate, as well as to understand and investigate the effects and mechanisms of drug hepatotoxicity in man. The metabolic profile analysis of biological liver models treated with hepatotoxins, as compared to that of those treated with non-hepatotoxic compounds, provides useful information for identifying disturbed cellular metabolic reactions, pathways, and networks. This can later be used to anticipate, as well to assess, the potential hepatotoxicity of new compounds. However, the applicability of the metabolomic analysis to assess the hepatotoxicity of drugs is complex and requires careful and systematic work, precise controls, wise data preprocessing and appropriate biological interpretation to make meaningful interpretations and/or predictions of drug hepatotoxicity. This review provides an updated look at recent in vitro studies which used principally mass spectrometry-based metabolomics to evaluate the hepatotoxicity of drugs. It also analyzes the principal drawbacks that still limit its general applicability in safety assessment screenings. We discuss the analytical workflow, essential factors that need to be considered and suggestions to overcome these drawbacks, as well as recent advancements made in this rapidly growing field of research.

Thermal Stress Induces Metabolic Responses in Juvenile Qingtian Paddy Field Carp Cyprinus carpio var qingtianensis

Extreme fluctuations in water temperature lead to significant economic losses for the aquaculture industry. Cyprinus carpio var qingtianensis (locally called Qingtian paddy field carp), is a local variety commonly found in Zhejiang province, China. Unlike traditional aquaculture environments, the water temperature range between day and night in the rice field environment is much larger, and the high temperature in summer may exceed the growth threshold of fish because there is no manual intervention; therefore, the study of how the Qingtian paddy field carp (PF carp) adapts to high-temperature conditions can shed light how the species adapt to the rice field environment. To investigate the molecular mechanisms of this fish under thermal stress, the liver metabolomics of Qiangtian paddy field carp (PF carp) were analyzed. In this study, metabolomics was used to examine the metabolic reaction of PF carp (102 days old, 104.69 ± 3.08 g in weight, 14.65 ± 0.46 cm in length) at water temperatures of 28 °C (control group, CG), 34 °C (experimental group (EG) 34), and 38 °C (EG38). The results show that 175 expression profile metabolites (DEMs), including 115 upregulated and 60 downregulated metabolites, were found in the CG vs. EG34. A total of 354 DEMs were inspected in CG vs. EG38, with 85 metabolites downregulated and 269 metabolites upregulated. According to the pathway enrichment study, various pathways were altered by thermal stress, including those of lipid, amino-acid, and carbohydrate metabolism. Our study presents a potential metabolic profile for PF carp under thermal stress. It also demonstrates how the host responds to thermal stress on a metabolic and molecular level.

Ecotoxicological Risk Assessment of Actellic 50 EC Insecticide on Non-Target Organisms in Parallel with the Application of Standardized Tests

This paper contributes to the ecotoxicological risk assessment of the Actellic 50 EC insecticide (with 50% pirimiphos-methyl as the active substance) tested on non-target organisms. The insecticide concentrations tested were the same for all organisms (0.1, 0.01, and 0.001 mg L^-1 of Actellic 50 EC), with an exposure of 3-5-21 days for plants and 4-5-14 days for animals. The non-target organisms tested were both plants (wheat and two ferns) and animals (the Prussian carp and marsh frog tadpoles). The tested insecticide significantly inhibited the growth of roots in wheat, a result that was also confirmed by a microbiotest application (62% root growth inhibition in sorghum and 100% germination inhibition in white mustard and garden cress). In ferns, even for the lowest concentration, the percentage of germinated spores was inhibited by 40% for Asplenium scolopendrium. The recorded toxicological effects of Actellic 50 EC upon the Prussian carp included a decrease in the respiratory rate and oxygen consumption, an increase in the number of erythrocytes and leukocytes, and an increase in blood glucose levels. The highest concentration (0.1 mg L^-1 of Actellic 50 EC) caused a 50% decrease in the survival rate of marsh frog tadpoles after 5 days of exposure, negatively affecting body volume and length. Given the high degree of toxicity of the insecticide Actellic 50 EC, we recommend continuing investigations on non-target species, including both plants and animals, as the sub-chronic effects are quite little known in the scientific literature.

Metabolomic Profiling Analysis of Physiological Responses to Acute Hypoxia and Reoxygenation in Juvenile Qingtian Paddy Field Carp Cyprinus Carpio Var Qingtianensis

The Qingtian paddy field carp (Cyprinus carpio var qingtianensis) is a local carp cultivated in the rice field of Qingtian county, Zhejiang province, China. The paddy field environment is distinct from the pond environment. Due to the inability to artificially increase oxygen, the dissolved oxygen greatly changes during the day. Therefore, investigating the physiological regulation to the changes of acute dissolved oxygen in Qingtian paddy field carp (PF-carp) will dramatically clarify how it adapts to the paddy breeding environment. The high tolerance of Qingtian paddy field carp to hypoxia makes it an ideal organism for studying molecular regulatory mechanisms during hypoxia process and reoxygenation following hypoxia in fish. In this study, we compared the changes of metabolites in the hepatopancreas during hypoxia stress and the following reoxygenation through comparative metabolomics. The results showed 131 differentially expressed metabolites between the hypoxic groups and control groups. Among them, 95 were up-regulated, and 36 were down-regulated. KEGG Pathway enrichment analysis showed that these differential metabolites were mainly involved in regulating lipid, protein, and purine metabolism PF-carps could require energy during hypoxia by enhancing the gluconeogenesis pathway with core glutamic acid and glutamine metabolism. A total of 63 differentially expressed metabolites were screened by a comparison between the reoxygenated groups and the hypoxic groups. Specifically, 15 were up-regulated, and 48 were down-regulated. The KEGG Pathway enrichment analysis supported that PF-carp could continue to gain energy by consuming glutamic acid and the glutamine accumulated during hypoxia and simultaneously weaken the ammonia-transferring effect of amino acids and the toxicity of ammonia. By consuming glycerophospholipids and maintaining the Prostaglandin E content, cell damage was improved, sphingosinol synthesis was reduced, and apoptosis was inhibited. Additionally, it could enhance the salvage synthesis and de novo synthesis of purine, reduce purine accumulation, promote the synthesis of nucleotide and energy carriers, and assist in recovering physiological metabolism. Overall, results explained the physiological regulation mechanism of PF-carp adapting to the acute changes of dissolved oxygen at the metabolic level and also provided novel evidence for physiological regulation of other fish in an environment with acute changes in dissolved oxygen levels.

In vitro toxicity of glyphosate in Atlantic salmon evaluated with a 3D hepatocyte-kidney co-culture model

A novel 3D Atlantic salmon co-culture model was developed using primary hepatocytes and kidney epithelial cells isolated from the same fish. Mono and co-cultures of primary hepatocytes and kidney epithelial cells were exposed for 48 h to glyphosate (5, 50 and 500 μM). For comparison, cells were also exposed to chlorpyrifos, benzo(a)pyrene and cadmium. Cell staining, cell viability assessments, RT-qPCR and global metabolomic profiling were used to examine the toxicological effects on liver and renal function and to compare responses in 3D and 2D cultures. The 3D hepatocyte cell culture was considered superior to the 2D culture due to the ATP binding cassette subfamily B member 1 (Abcb1) response and was thus used further in co-culture with kidney cells. Metabolomic analysis of co-cultured cells showed that glyphosate exposure (500 μM) altered lipid metabolism in both hepatocytes and kidney cells. Elevated levels of several types of PUFAs and long-chain fatty acids were observed in exposed hepatocytes, owing to increased uptake and phospholipid remodelling. Glyphosate suppressed the expression of estrogen receptor 1 (Esr1) and vitellogenin (Vtg) and altered histidine metabolism in exposed hepatocytes. Increased levels of cholesterol and downregulation of clusterin (Clu) suggest that glyphosate treatment affected membrane stability in Atlantic salmon kidney cells. This study demonstrates the usefulness of applying 3D co-culture models in risk assessment.

Mixture toxicity of chlorpyrifos-methyl, pirimiphos-methyl, and nonylphenol in Atlantic salmon (Salmo salar) hepatocytes

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Shotgun lipidomics points to combined effects on 18:0 and 18:1 lipid species.

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Combined effects seen on membrane phospholipids and TAG in salmon hepatocytes.

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Inhibited stearoyl CoA desaturase (SCD) and increased Δ6 desaturase (D6D) activity.

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Adjuvants may amend toxicity of active ingredient in pesticide formulations.

Pesticide formulations typically contain adjuvants added to enhance the performance of the active ingredient. Adjuvants may modify the bioavailability and toxicity of pesticides. In this study, the aim was to examine to which degree nonylphenol (NP) may interfere with the toxicity of two organophosphorus pesticides found in aquafeeds, chlorpyrifos-methyl (CPM) and pirimiphos-methyl (PPM). Atlantic salmon liver cells were exposed to these compounds singly or in combinations for 48 h using 3D cell cultures. Cytotoxicity, gene expression (RT-qPCR), and lipidomics endpoints were used to assess toxicity. The dose-response assessment showed that NP was the most toxic compound at equimolar concentrations (100 μM). Shotgun lipidomics pointed to a general pattern of elevated levels of saturated 18:0 fatty acids and declined levels of 18:1 monounsaturated fatty acids by the combined treatment. All three compounds had a distinct effect on membrane phospholipids, in particular on phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Lipid species patterns predicted inhibited stearoyl CoA desaturase (SCD) activity and increased Δ6 desaturase (D6D) activity in co-treated cells. While all three compounds alone mitigated increased triacylglycerol (TAG) accumulation, combined treatment resulted in lower total TAG in the cells. Multivariate analysis with PLS regression showed significant combined effects for nine genes (d5d, d6d, scd, srebf2, vtg, esr1, cyp1, ugt1a, and cat) and four lipid species (FFA 22:5, LPC 18:0, TAG52:1-FA16:0, and TAG52:1-FA18:0). In summary, this study demonstrates that the adjuvant can be the main contributor to the toxicity of a mixture of two organophosphorus pesticides with relatively low toxicity in fish cells.

Metabolic and immune responses of Chinook salmon (Oncorhynchus tshawytscha) smolts to a short-term poly (I:C) challenge

Polyinosinic:polycytidylic acid [poly (I:C)] was administered in vivo to Chinook salmon (Oncorhynchus tshawytscha) post-smolts to determine the immune responses on haematological and cellular functional parameters, including spleen (SP), head kidney (HK) and red blood cell (RBC) cytokine expression, as well as serum metabolomics. Poly (I:C) in vivo (24 h exposure) did not affect fish haematological parameters, leucocyte phagocytic activity and phagocytic index, reactive oxygen species and nitric oxide production. Gas chromatography-mass spectrometry-based metabolomics revealed that poly (I:C) significantly altered the serum biochemistry profile of 25 metabolites. Metabolites involved in the branched-chain amino acid/glutathione and transsulphuration pathways and phospholipid metabolism accumulated in poly (I:C)-treated fish, whereas those involved in the glycolytic and energy metabolism pathways were downregulated. At cytokine transcript level, poly (I:C) induced a significant upregulation of antiviral ifnγ in HK and Mx1 protein in HK, SP and RBCs. This study provides evidence for poly (I:C)-induced, immune-related biomarkers at metabolic and molecular levels in farmed O. tshawytscha in vivo. These findings provide insights into short-term effects of poly (I:C) at haematological, innate and adaptive immunity and metabolic levels, setting the stage for future studies.

Effects of Agricultural Pesticides in Aquafeeds on Wild Fish Feeding on Leftover Pellets Near Fish Farms

Screening has revealed that modern-day feeds used in Atlantic salmon aquaculture might contain trace amounts of agricultural pesticides. To reach slaughter size, salmon are produced in open net pens in the sea. Uneaten feed pellets and undigested feces deposited beneath the net pens represent a source of contamination for marine organisms. To examine the impacts of long-term and continuous dietary exposure to an organophosphorus pesticide found in Atlantic salmon feed, we fed juvenile Atlantic cod (Gadus morhua), an abundant species around North Atlantic fish farms, three concentrations (0.5, 4.2, and 23.2 mg/kg) of chlorpyrifos-methyl (CPM) for 30 days. Endpoints included liver and bile bioaccumulation, liver transcriptomics and metabolomics, as well as plasma cholinesterase activity, cortisol, liver 7-ethoxyresor-ufin-O-deethylase activity, and hypoxia tolerance. The results show that Atlantic cod can accumulate relatively high levels of CPM in liver after continuous exposure, which is then metabolized and excreted via the bile. All three exposure concentrations lead to significant inhibition of plasma cholinesterase activity, the primary target of CPM. Transcriptomics profiling pointed to effects on cholesterol and steroid biosynthesis. Metabolite profiling revealed that CPM induced responses reflecting detoxification by glutathione-S-transferase, inhibition of monoacylglycerol lipase, potential inhibition of carboxylesterase, and increased demand for ATP, followed by secondary inflammatory responses. A gradual hypoxia challenge test showed that all groups of exposed fish were less tolerant to low oxygen saturation than the controls. In conclusion, this study suggests that wild fish continuously feeding on leftover pellets near fish farms over time may be vulnerable to organophosphorus pesticides.

Toxicity of some aquatic pollutants to fish

Pesticide residues threaten fish that live in rivers. This study investigated the effects of Nemacur, malathion, and diuron on freshwater fish behavior, mortality, acetylcholinesterase (ACHE) activity, liver biomarkers, and residue accumulation. Fish were exposed to individual concentration of Nemacur, malathion, and diuron at 1 mg/L and to binary mixtures in glass aquarium 16 L capacity. Mortality of fish was also investigated at a range of 0.0-1 mg/L of Nemacur and malathion. The biochemical effects of the tested compounds were recorded. The results showed abnormal fish behavior at low concentration (0.1 mg/L) of malathion, high fish mortality at 0.1 mg/L of Nemacur and mixtures with Nemacur, and no mortality with diuron. Mortality increased and became more intense after 48 h rather than after 24 h. Diuron increased the effect of Nemacur and malathion at low concentration. ACHE was inhibited at different percentages in the blood serum and brain homogenate due to exposure to Nemacur, malathion, diuron, and/or a combination of these pesticides. Liver biomarker levels were higher in the blood serum of the treated fish than the control group. The interesting outcome of the study is that Nemacur is several folds more toxic than malathion and diuron. Mixtures showed synergistic effects. The pesticide residues in the fish muscles were less than those in the water. It can be concluded that low concentrations of Nemacur, malathion, and diuron are negatively affecting fish in rivers.

Metabolic signatures of bisphenol A and genistein in Atlantic salmon liver cells

Screening has revealed that aquafeeds with high inclusion of plant material may contain small amounts of endocrine disrupting agricultural pesticides. In this work, bisphenol A (BPA) and genistein (GEN) were selected as model endocrine disrupting toxicants with impact on DNA methylation in fish. Atlantic salmon hepatocytes were exposed in vitro to four concentrations of BPA and GEN (0.1, 1.0, 10 and 100 μM) for 48 h. Toxicity endpoints included cytotoxicity, global DNA methylation, targeted transcriptomics and metabolomic screening (100 μM). GEN was not cytotoxic in concentrations up to 100 μM, whereas one out of two cell viability assays indicated a cytotoxic response to 100 μM BPA. Compared to the control, significant global DNA hypomethylation was observed at 1.0 μM BPA. Both compounds upregulated cyp1a1 transcription at 100 μM, while estrogenic markers esr1 and vtg1 responded strongest at 10 μM. Dnmt3aa transcription was downregulated by both compounds at 100 μM. Metabolomic screening showed that BPA and GEN resulted in significant changes in numerous biochemical pathways consistent with alterations in carbohydrate metabolism, indicating perturbation in glucose homeostasis and energy generation, and glutamate metabolism. Pathway analysis showed that while the superpathway of methionine degradation was among the most strongly affected pathways by BPA, GEN induced changes to uridine and pyrimidine biosynthesis. In conclusion, this mechanistic study proposes metabolites associated with glucose and glutamate metabolism, glucuronidation detoxification, as well as cyp1a1, vtg1, esr1, ar, dnmt3aa, cdkn1b and insig1 as transcriptional markers for BPA and GEN exposure in fish liver cells.