Comparative analysis of distinctive transcriptome profiles with biochemical evidence in bisphenol S- and benzo[a]pyrene-exposed liver tissues of the olive flounder Paralichthys olivaceus

Multi-level assessment of the origin, feeding area and organohalogen contamination on salmon from the Baltic Sea

The Atlantic salmon (Salmo salar) population in the Baltic Sea consists of wild and hatchery-reared fish that have been released into the sea to support salmon stocks. During feeding migration, salmon migrate to different parts of the Baltic Sea and are exposed to various biotic and abiotic stressors, such as organohalogen compounds (OHCs). The effects of salmon origin (wild or hatchery-reared), feeding area (Baltic Main Basin, Bothnian Sea, and Gulf of Finland), and OHC concentration on the differences in hepatic proteome of salmon were investigated. Multi-level analysis of the OHC concentration, transcriptome, proteome, and oxidative stress biomarkers measured from the same salmon individuals were performed to find the key variables (origin, feeding area, OHC concentrations, and oxidative stress) that best account for the differences in the transcriptome and proteome between the salmon groups. When comparing wild and hatchery-reared salmon, differences were found in xenobiotic and amino acid metabolism-related pathways. When comparing salmon from different feeding areas, the amino acid and carbohydrate metabolic pathways were notably different. Several proteins found in these pathways are correlated with the concentrations of polychlorinated biphenyls (PCBs). The multi-level analysis also revealed amino acid metabolic pathways in connection with PCBs and oxidative stress variables related to glutathione metabolism. Other pathways found in the multi-level analysis included genetic information processes related to ribosomes, signaling and cellular processes related to the cytoskeleton, and the immune system, which were connected mainly to the concentrations of Polychlorinated biphenyls and Dichlorodiphenyltrichloroethane and their metabolites. These results suggest that the hepatic proteome of salmon in the Baltic Sea, together with the transcriptome, is more affected by the OHC concentrations and oxidative stress of the feeding area than the origin of the salmon.

High-quality Japanese flounder genome aids in identifying stress-related genes using gene coexpression network

The Japanese flounder is one of the most economically important marine flatfish. However, due to the increased frequency of extreme weather events and high-density industrial farming, an increasing number of environmental stresses have become severe threats to the healthy development of the Japanese flounder culture industry. Herein, we produced a high-quality chromosome-scale Japanese flounder genome using PacBio Circular Consensus Sequencing technologies. The assembled Japanese flounder genome spanned 588.22 Mb with a contig N50 size of 24.35 Mb. In total, 105.89 Mb of repetitive sequences and 22,565 protein-coding genes were identified by genome annotation. In addition, 67 candidate genes responding to distinct stresses were identified by gene coexpression network analysis based on 16 published stress-related RNA-seq datasets encompassing 198 samples. A high-quality chromosome-scale Japanese flounder genome and candidate stress-related gene set will not only serve as key resources for genomics studies and further research on the underlying stress responsive molecular mechanisms in Japanese flounder but will also advance the progress of genetic improvement and comprehensive stress-resistant molecular breeding of Japanese flounder.

Measurement(s)	genome assembly
Technology Type(s)	PacBio RS II

Bisphenol S induced dysregulations in liver; iron regulatory genes and inflammatory mediators in male Wistar rats

Bisphenol S (BPS), an analog of bisphenol A (BPA), has been frequently detected in consumer products, food wrappers, plastics, and thermal papers. Since the liver is a hub of metabolic and detoxification pathways, thus intimately related to BPS presence in the environment and body. The current study was designed to investigate the effects of BPS administration in an animal model. Twenty-five male Wistar rats weighing 175 ± 25 g were randomly divided into control and treated groups. The control group was further divided into group I (no treatment) and group II (corn oil), whereas the treatment group was divided into D-I (40 mg/kg/day), D-II (200 mg/kg/day), and D-III (400 mg/kg/day) groups, getting oral doses of BPS for 15 days. Data analysis showed a significant statistical increase in hepatic enzymes ALT (33.4%), AST (25.4%), and ALP (529.6%) in the D-III group along with the development of hypercholesterolemia and hypertriglyceridemia in all BPS groups. Aberrant mRNA expressions of some key hepatic iron regulatory genes and inflammatory mediators were evident through qRT-PCR. Bisphenol S caused congestion of central vein from mild to moderate in hepatic sections. In conclusion, our investigation insinuates BPS intoxication potential and therefore may not be a safe alternative to BPA.

Transcriptome Analysis of the Toxic Effects of Amisulbrom and Isoflucypram on Zebrafish (Danio rerio) Larvae

Fungicides are frequently detected in the water bodies, however, the adverse effects of these fungicides on aquatic lives remain limited. To better understand the adverse effects of amisulbrom (AML) and isoflucypram (ISO) on embryogenesis, zebrafish embryos were exposed to two different fungicides, 0.75 μM amisulbrom (AML) and 2.5 μM isoflucypram (ISO), for 72 h. Transcriptome sequencing was employed to identify differentially expressed genes (DEGs) after AML and ISO exposure. A total of 571 and 3471 DEGs were detected between the libraries of the two fungicides-treated groups and the control, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that PPAR signaling pathway, phototransduction, ribosome and p53 signaling pathway were significantly enriched in response to both AML and ISO stress. Moreover, a number of DEGs involved in tyrosine metabolism, phagosome pathway, cell cycle pathway, extracellular matrix (ECM) receptor interaction pathway, and arginine and proline metabolism were specially enriched after exposure to AML; a number of DEGs involved in notch signaling pathway, drug metabolism, alanine, aspartate and glutamate metabolism, amino-acyl−tRNA biosynthesis, and protein processing in endoplasmic reticulum were significantly enriched after exposure to ISO. These results provide novel insights into the toxicological mechanisms underlying fish’s responses to fungicides.

Disrupted metabolic pathways and potential human diseases induced by bisphenol S

Although the toxicity of bisphenol S has been studied in some species, the global metabolic network disrupted by bisphenol S remains unclear. To this end, published datasets related to the genes, proteins, and metabolites disturbed by bisphenol S were investigated through omics methods. The dataset revealed that bisphenol S at high concentrations tended to downregulate biomolecules, while low concentrations of bisphenol S tended to enhance metabolic reactions. The results showed that exposure to bisphenol S upregulated estrogen and downregulated androgen metabolism in humans, mice, rats, and zebrafish. Fatty acid metabolism and phospholipid metabolism in mice were upregulated. Reactions in amino acid metabolism were upregulated, with the exception of the suppressive conversion of arginine to ornithine. In zebrafish, fatty acid synthesis was promoted, while nucleotide metabolism was primarily depressed through the downregulation of pyruvate 2-o-phosphotransferase. The interference in amino acid metabolism by bisphenol S could trigger Alzheimer's disease, while its disturbance of glucose metabolism was associated with type II diabetes. Disturbed glycolipid metabolism and vitamin metabolism could induce Alzheimer's disease and diabetes. These findings based on omics data provide scientific insight into the metabolic network regulated by bisphenol S and the diseases triggered by its metabolic disruption.

Bisphenol S leads to cytotoxicity-induced antioxidant responses and oxidative stress in isolated rainbow trout (Oncorhyncus mykiss) hepatocytes

BACKGROUND

Bisphenol S (BPS) is a chemical compound that is utilized in the plastic industry as an alternative to bisphenol A (BPA). The toxic effects of BPS in fish is less known and limited. Therefore, in the present study, the influence of BPS on rainbow trout (Oncorhyncus mykiss) hepatocytes in vitro was investigated.

METHODS AND RESULTS

For this purpose the fish hepatocytes were isolated, and then the cultured cells were treated with increasing concentrations of BPS (0, 15.63, 31.25, 62.50, 125, 250, and 500 µM) for 24 h. The cytotoxic impact of BPS was determined in the culture media using lactate dehydrogenase assay and then, the antioxidant defence indicators were assayed. The results showed that concentration-dependent increases were observed in the percentage of cytotoxicity. The superoxide dismutase activity was reduced, while the catalase and glutathione peroxidase activity increased with all of the BPS concentrations. The glutathione S-transferase (GST) activity significantly increased after a BPS concentration of 31.25 µM or higher, while GST Theta 1-1 activity was decreased by the same concentrations of BPS. The reduced glutathione content significantly decreased with a BPS concentration of 31.25 µM or higher, and the malondialdehyde content increased after BPS concentrations of 125, 250, and 500 µM.

CONCLUSIONS

The findings determined herein suggested that BPS causes cytotoxicity in fish hepatocytes and can lead to oxidative stress, resulting hepatotoxic in fish. Thus, the utilization of BPS instead of BPA as safe alternative in industry should be re-evaluated in the future for environmental health.

Unraveling the mechanism of long-term bisphenol S exposure disrupted ovarian lipids metabolism, oocytes maturation, and offspring development of zebrafish

Bisphenol S (BPS) acts as a xenoestrogen and disturbs the female reproductive system; however, the underlying mechanism has not been elucidated. In this study, the effect of chronic BPS exposure (1 μg/L and 100 μg/L) on ovarian lipid metabolism in zebrafish was investigated to determine its influence on adult reproductive capacity and offspring development. The results showed that long-term (240 days) exposure to BPS induced lipid accumulation in the ovaries by promoting the transport of more lipids from the circulation to the ovaries and by upregulating triacylglycerol synthesis-related genes. Significantly increased expression of cpt2, acadm, acadl, and pparα, which are involved in β-oxidation in the ovarian mitochondria, indicated that more energy was provided for oocyte maturation in exposed zebrafish ovaries. Thus, the proportion of full-grown stage oocytes in ovaries and egg reproduction were elevated at an accelerated rate, which earlier than normal reproductive cycle (8-10 days posts pawning). Moreover, the maternally BPS-exposed F1 embryos (2 h post-spawning, hpf) showed higher neutral lipid levels, impaired hatching capacity, and increased occurrence of larval deformities. All these findings demonstrated that stimulated lipid synthesis and β-oxidation in zebrafish ovaries significantly contribute to BPS-induced oocyte precociousness with subsequent effects on the development of unexposed offspring. This study provides new insight into the impact of xenoestrogens on oviparous reproduction in females and offspring development from the perspective of ovarian lipid metabolism.

Development and Evaluation of Olive Flounder cyp1a1-Luciferase Assay for Effective Detection of CYP1A-Inducing Contaminants in Coastal Sediments

Flounders have been widely used as indicator species for monitoring the benthic environment of marine coastal regions owing to their habitat and feeding preferences in or on sandy sediments. Here, a single-step, sensitive, specific, and simple luciferase assay was developed, using the olive flounder cyp1a1 gene, for effective detection of CYP1A-inducing contaminants in coastal sediments. The developed cyp1a1-luciferase assay was highly sensitive to the widely used CYP1A inducers 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), benzo[a]pyrene (B[a]P), and 3,3',4,4',5-pentachlorobiphenyl (PCB 126). In the case of TCDD, significant dose-dependent increases in luciferase activity (0.3-300 ng/L) were detected. The assay was more sensitive to PCB 126 than to B[a]P. The assay also involved the highly sensitive expression of luciferase to extracted mixtures of PCBs and polycyclic aromatic hydrocarbons (PAHs) collected from coastal sediments. PCBs were more capable of cyp1a1 induction in the assay system at small doses than PAHs in environmental samples. Using the cyp1a1-luciferase assay along with water or sediment chemistry will certainly aid in diagnosing CYP1A-inducing contaminants in coastal environments.

Temporal transcriptome analysis in female scallop Chlamys farreri: First molecular insights into the disturbing mechanism on lipid metabolism of reproductive-stage dependence under benzo[a]pyrene exposure

Polycyclic aromatic hydrocarbons (PAHs) are one of the most widespread persistent organic pollutants (POPs) in marine environment. Benzo[a]pyrene (B[a]P), the most toxic carcinogen of PAHs, is widely studied as a representative that interferes with lipid metabolism. However, the underlying molecular mechanisms of lipid metabolism by B[a]P interference towards bivalve, one of the marine-pollution bio-indicators have not been elucidated yet, especially during gonadal development which is closely associated with lipids. In this study, female scallops Chlamys farreri were cultured with natural and 4 μg/L B[a]P exposed seawater, respectively, and a multi-stage (proliferative, growth, mature, and spawn stage) ovarian transcriptome profiling was performed to decipher the reproductive stage-dependence disturbing mechanisms on lipid metabolism caused by B[a]P in bivalves. The results revealed the potential molecular mechanism of B[a]P-induced triglycerides (TGs) accumulation, which probably resulted from the collaboration of promoting synthesis and inhibiting metabolization of TGs, notably, this mechanism also occurred at spawn stage. Correspondingly, B[a]P and TGs contents measured in ovary offered direct biochemical evidences for the interference effects and stage-dependent accumulation patterns of B[a]P. Moreover, the gene expressions of fatty acids synthesis related enzymes were down-regulated cooperatively, illustrating the molecular compensatory mechanism that reduced susceptibility from oxidative damage. And these results further emphasized the important role of prostaglandins (PGs) in immune response mediated by arachidonic acid metabolism. In addition, this study explored the underlying molecular mechanism affected by B[a]P on sterol metabolism, which possibly posed a threat to normal reproductive functions in bivalves. Taken together, our findings filled the gap of the stage-dependent interference molecular mechanisms on lipid metabolism behind bivalves, and provided a new perspective for investigating the adaptive mechanisms of bivalves under POPs stress.

Transcriptomic changes in western mosquitofish (Gambusia affinis) liver following benzo[a]pyrene exposure

Widely distributed western mosquitofish (Gambusia affinis) has been used as a new model species for hazard assessment of environmental stressors such as polycyclic aromatic hydrocarbons (PAHs). However, most of the PAH studies using G. affinis rely on targeted biomarker-based analysis, and thus may not adequately address the complexity of the toxic mechanisms of the stressors. In the present study, the whole transcriptional sequencing of G. affinis liver after exposure to a PAH model, benzo[a]pyrene (BaP) (100 μg/L), for 20 days was performed by using the HiSeq XTen sequencers. In total, 58,156,233 and 51,825,467 clean nucleotide reads were obtained in the control and BaP-exposed libraries, respectively, with average N50 lengths of 1419 bp. In addition, after G. affinis was exposed for 20 days, 169 genes were upregulated, and 176 genes were downregulated in liver. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were applied to all the genes to determine the genes' biological functions and processes. The results clearly showed that the differentially expressed genes were mainly related to immune pathways and metabolic correlation pathways. Interestingly, almost all the pathways related with the immunity were upregulated, while the metabolism pathways were downregulated. Lastly, quantitative real-time PCR (qRT-PCR) was performed to measure expressional levels of twelve genes confirmed through the DGE analysis. These results demonstrate that BaP damages immunity and enhances the consumption of all available energy storage to activate mechanisms of the detoxification in G. affinis. Up until now, the present study is the first time that a whole transcriptome sequencing analysis in the liver of G. affinis exposed to BaP has been reported.

Waterborne zinc pyrithione modulates immunity, biochemical, and antioxidant parameters in the blood of olive flounder

In this study, potential immunological and hematological effects of different concentrations (0, 1, 10, and 50 μg L^-l) of waterborne zinc pyrithione (ZnPT) were studied in the blood of the olive flounder Paralichthys olivaceus over 30 days. Reduced alternative complement activity (ACH50) and lysozyme activity were measured in fish exposed to 10 and/or 50 μg L^-l of ZnPT for 20 days. Decreased levels of total Ig were also observed in response to 10 and/or 50 μg L^-l ZnPT during the exposure period. Levels of cortisol, a marker of stress, were significantly increased by 10 and 50 μg L^-l ZnPT from day 10, and by 1 μg L^-l exposure on day 30. The levels of red blood cells (RBCs) and white blood cells (WBCs) decreased following exposure to 10 and/or 50 μg L^-l ZnPT, while no significant change was observed in hemoglobin level. Concentrations of total protein and albumin were significantly reduced with 50 μg L^-l ZnPT at day 20. Alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase activities were significantly increased following exposure to 10 and/or 50 μg L^-l ZnPT. Lipid peroxidation was induced by ZnPT, and higher concentrations (10 and 50 μg L^-l) significantly increased intracellular malondialdehyde levels during exposure. Regarding the subsequent antioxidant response, intracellular glutathione levels increased significantly in response to 10 and 50 μg L^-l ZnPT on days 20 and 30. Similarly, catalase and superoxide dismutase activity was significantly increased in response to 10 and 50 μg L^-l ZnPT after day 10. Taken together, changes in the studied parameters suggested the immunotoxicity of ZnPT, with modulations observed in hematological homeostasis and oxidative stress induction in the blood of olive flounder.

A scoping review of the health and toxicological activity of bisphenol A (BPA) structural analogues and functional alternatives

Recent studies report widespread usage or exposure to a variety of chemicals with structural or functional similarity to bisphenol A (BPA), referred to as BPA analogues or derivatives. These have been detected in foodstuffs, house dust, environmental samples, human urine or blood, and consumer products. Compared to BPA, relatively little is known about potential toxicity of these compounds. This scoping review aimed to summarize the human, animal, and mechanistic toxicity data for 24 BPA analogues of emerging interest to research and regulatory communities. PubMed was searched from March 1, 2015 to January 5, 2019 and combined with the results obtained from literature searches conducted through March 23, 2015, in The National Toxicology Program's Research Report 4 (NTP RR-04), "Biological Activity of Bisphenol A (BPA) Structural Analogues and Functional Alternatives". Study details are presented in interactive displays using Tableau Public. In total, 5748 records were screened for inclusion. One hundred sixty seven studies were included from NTP RR-04 and 175 studies were included from the updated literature search through January 2019. In total, there are 22, 117, and 221 human epidemiological, experimental animal, or in vitro studies included. The most frequently studied BPA analogues are bisphenol S (BPS), bisphenol F (4,4-BPF), and bisphenol AF (BPAF). Notable changes in the literature since 2015 include the growing body of human epidemiological studies and in vivo studies conducted in zebrafish. Numerous new endpoints were also evaluated across all three evidence streams including diabetes, obesity, and oxidative stress. However, few studies have addressed endpoints such as neurodevelopmental outcomes or impacts on the developing mammary or prostate glands, which are known to be susceptible to disruption by BPA. Further, there remains a critical need for better exposure information in order to prioritize experimental studies. Moving forward, researchers should also ensure that full dose responses are performed for all main effects in order to support hazard and risk characterization efforts. The evidence gathered here suggests that hazard and risk characterizations should expand beyond BPA in order to consider BPA structural and functional analogues.

Waterborne manganese modulates immunity, biochemical, and antioxidant parameters in the blood of red seabream and black rockfish

Immunotoxic effects of manganese (Mn) were investigated in the blood of the economically important marine fish, red seabream (Pagrus major) and black rockfish (Sebastes schlegelii) when exposed to different concentrations of Mn (0, 0.5, 1, and 2 mg L^-1) for 14 days. During exposure, the levels of alternative complement activity in both fish were significantly lowered at 2 mg L^-1 of Mn of exposure. Lysozyme activity was significantly decreased in black rockfish in all concentrations of Mn after 14 days, while in red seabream, the decrease was significant with concentrations of 1 and 2 mg L^-1 of Mn after 7 and 14 days of exposure. A significantly low level was observed only in the 2 mg L^-1-exposed red seabream on day 14 of exposure. The concentrations of hemoglobin, red blood cells, white blood cells, and total serum proteins were significantly decreased in both fish under exposure to 1 and 2 mg L^-1 of Mn, while cortisol, alanine transferase, aspartate transaminase, and alkaline phosphatase levels were significantly increased compared to the levels of control groups. No significant change was found in serum glucose and albumin except in red seabream exposed to 2 mg L^-1 of Mn for 14 days. The responses of the antioxidant defense system were significantly induced in both fish after exposure to 1 and 2 mg L^-1 of Mn on day 7 and 14 of exposure. Taken together, alterations of these parameters suggest the immunotoxicity of waterborne Mn produced by the modulation of hematological components and the induction of oxidative stress in the blood of these marine fish.

Long-term bisphenol S exposure induces fat accumulation in liver of adult male zebrafish (Danio rerio) and slows yolk lipid consumption in F1 offspring

Bisphenol S (BPS), as a substitute for bisphenol A, was frequently detected in human urine and blood. It has been reported that BPS could disrupt fat metabolism in vivo and vitro although mechanisms remain unclear. Additionally, there is no study that the disruptive effect of BPS on parental fat metabolism indirectly interferes with the lipid metabolism of offspring. Here, after 120-d exposure to 1, 10, 100, and 1000 μg/L BPS, the transcription level of genes involved in lipid metabolism in liver and feeding regulation of brain-gut axis, as well as the hepatic triacylglycerol (TAG) and plasma lipid levels were investigated in both male and female zebrafish. Results showed that in male liver, fatty acid synthesis and degradation were inhibited by reducing transcription levels of srebp1 and pparα, and the synthesis of TAG was significantly increased using fatty acid as a precursor by elevating agpat4 and dgat2 mRNA expression levels. As a consequence, fat accumulation and the increased TAG levels were observed in male liver, and lipid levels were also elevated in male plasma. In female liver, there was no excessive fat accumulation and BPS exposure had a non-monotonic effect on the gene expression of fasn, dagt2, and pparα. Notably, the unexposed offspring showed a large amount of yolk lipid remain at 5 days post fertilization. This study obviously demonstrated that long-term BPS exposure increases the risk of non-alcoholic fatty liver disease in male zebrafish and life-cycle exposure hazard on offspring is noteworthy.

Peptidylarginine deiminase and deiminated proteins are detected throughout early halibut ontogeny - Complement components C3 and C4 are post-translationally deiminated in halibut (Hippoglossus hippoglossus L.)

Post-translational protein deimination is mediated by peptidylarginine deiminases (PADs), which are calcium dependent enzymes conserved throughout phylogeny with physiological and pathophysiological roles. Protein deimination occurs via the conversion of protein arginine into citrulline, leading to structural and functional changes in target proteins. In a continuous series of early halibut development from 37 to 1050° d, PAD, total deiminated proteins and deiminated histone H3 showed variation in temporal and spatial detection in various organs including yolksac, muscle, skin, liver, brain, eye, spinal cord, chondrocytes, heart, intestines, kidney and pancreas throughout early ontogeny. For the first time in any species, deimination of complement components C3 and C4 is shown in halibut serum, indicating a novel mechanism of complement regulation in immune responses and homeostasis. Proteomic analysis of deiminated target proteins in halibut serum further identified complement components C5, C7, C8 C9 and C1 inhibitor, as well as various other immunogenic, metabolic, cytoskeletal and nuclear proteins. Post-translational deimination may facilitate protein moonlighting, an evolutionary conserved phenomenon, allowing one polypeptide chain to carry out various functions to meet functional requirements for diverse roles in immune defences and tissue remodelling.