Induction of oxidative stress and the transcription of genes related to apoptosis in rare minnow (Gobiocypris rarus) larvae with Aroclor 1254 exposure

Exposure of Akwesasne Mohawk women to polychlorinated biphenyls and hexachlorobenzene is associated with increased serum levels of thyroid peroxidase autoantibodies

Persistent organic pollutants (POPs) including polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), and dichlorodiphenyltrichloroethane (p,p'-DDT) were reported to influence immunological activity. As endocrine-disrupting chemicals (EDC), these pollutants may disrupt normal thyroid function and act as catalysts for development of autoimmune thyroid disease by directly and indirectly affecting levels of thyroid peroxidase antibodies (TPOAbs). Native American communities are disproportionately exposed to harmful toxicants and are at an increased risk of developing an autoimmune disease. The aim of this study was to determine the association between POPs and TPOAbs in serum obtained from Native American women. This assessment was used to measure whether increased risk of autoimmune thyroid disease occurred as a result of exposure to POPs. Data were collected from 183 Akwesasne Mohawk women, 21-38 years of age, between 2009 and 2013. Multivariate analyses were conducted to determine the association between toxicant exposure and levels of TPOAbs. In multiple logistic regression analyses, exposure to PCB congener 33 was related to elevated risk of individuals possessing above normal levels of TPOAbs. Further, HCB was associated with more than 2-fold higher risk of possessing above normal levels of TPOAbs compared to women with normal levels of TPOAbs. p,p'-DDE was not associated with TPOAb levels within this study. Exposure to PCB congener 33 and HCB was correlated with above normal levels of TPOAbs, a marker of autoimmune thyroid disease. Additional investigations are needed to establish the causes and factors surrounding autoimmune thyroid disease which are multiple and complex.

Parental cadmium exposure during the spawning period reduces cadmium sensitivity through the antioxidant system in rare minnow (Gobiocypris rarus) larvae

Cadmium (Cd) is a noxious heavy metal widely dispersed in aquatic systems. Parental Cd exposure of fish species at environmental concentrations has been shown to cause deformities and stunted growth in their offspring. However, the long-term effects and the mechanisms underlying parental Cd exposure in fish species on Cd sensitivity in their offspring remain unclear. To explore the impacts of parental Cd exposures on Cd sensitivity, rare minnow (Gobiocypris rarus) larvae whose parents were exposed to Cd at 0, 5 or 10 μg/L for 28 days were established. Results showed that parental Cd exposure in rare minnow increased the Cd content of its larvae. In terms of malformation rate, mortality rate and total length at 7 days of rare minnow larvae, parental Cd exposure at 5 or 10 μg/L reduced Cd sensitivity. Further mechanistic investigation demonstrated that parental Cd exposure significantly upregulated the expression of antioxidant gene regulated by nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-kappa B (NF-кB) in rare minnow larvae. In addition, parental Cd exposure significantly elevated the level of reactive oxygen species (ROS) and malondialdehyde (MDA), but markedly decreased catalase (CAT), superoxide dismutase (SOD) and oxidized glutathione (GST) activity. The impact of parental Cd exposure to metallothionein (MT) content and the expression of MT mRNA, a detoxifying metallothionein, showed that parental Cd exposure of rare minnow induced oxidative stress in the larvae. Meanwhile, these results indicated that parental Cd exposure in rare minnow reduced the Cd sensitivity of the larvae via activating the Nrf2-mediated antioxidant system. This project helps us to further understand the toxicological mechanism of Cd in fish species and properly assess its potential ecological risk.

Neonicotinoids caused oxidative stress and DNA damage in juvenile Chinese rare minnows (Gobiocypris rarus)

To assess the effects of neonicotinoid insecticides on fish, juvenile Chinese rare minnows (Gobiocypris rarus) were exposed to 0.1, 0.5, or 2.0 mg/L neonicotinoid insecticides (imidacloprid, nitenpyram, and dinotefuran) for 60 days. The endpoints, including oxidative stress and DNA damage, were determined. The results of oxidative stress assays showed that SOD activities were significantly increased in the 2.0 mg/L imidacloprid and 0.5 mg/L nitenpyram and dinotefuran treatments (p < 0.05). CAT activity was significantly increased with 0.1 mg/L nitenpyram (p < 0.05), whereas it was significantly decreased in the 0.1 and 2.0 mg/L dinotefuran treatment groups (p < 0.05). Moreover, MDA content was significantly decreased in all imidacloprid treatments and in the 0.5 and 2.0 mg/L dinotefuran treatments (p < 0.05); however, it was significantly increased in the 0.1 mg/L nitenpyram treatment (p < 0.05). GSH content was significantly increased at all treatments except for the 0.5 mg/L dinotefuran treatment (p < 0.05). The transcript expression results showed that gstm mRNA expression was significantly inhibited by 0.5 and 2.0 mg/L imidacloprid, and gstp1 mRNA expression was significantly inhibited by all nitenpyram treatments (p < 0.05). In addition, ugt1a mRNA expression was significantly inhibited in the 0.5 mg/L nitenpyram treatment (p < 0.05). The results of the DNA damage assay showed that tail moments were significantly increased by the 2.0 mg/L imidacloprid treatment (p < 0.01), while tail DNA was significantly increased by 0.5 and 2.0 mg/L imidacloprid, 2.0 mg/L nitenpyram and all dinotefuran treatments (p < 0.01). Moreover, olive tail moments were significantly increased by the 0.5 and 2.0 mg/L imidacloprid and 2.0 mg/L dinotefuran treatments (p < 0.01). Therefore, our oxidative stress and DNA damage findings demonstrated that imidacloprid and nitenpyram could cause adverse effects on juvenile rare minnows.

Comparative Transcriptome Analysis of Gill Tissue in Response to Hypoxia in Silver Sillago (Sillago sihama)

Silver sillago (Sillago sihama) is a commercially important marine fish species in East Asia. In this study, we compared the transcriptome response to hypoxia stress in the gill tissue of S. sihama. The fish were divided into four groups, such as 1 h of hypoxia (hypoxia1h, DO = 1.5 ± 0.1 mg/L), 4 h of hypoxia (hypoxia4h, DO = 1.5 ± 0.1 mg/L), 4 h of reoxygen (reoxygen4h, DO = 8.0 ± 0.2 mg/L) after 4 h of hypoxia (DO = 1.5 mg/L), and normoxia or control (DO = 8.0 ± 0.2 mg/L) groups. Compared to the normoxia group, a total of 3550 genes were identified as differentially expressed genes (DEGs) (log₂foldchange > 1 and padj < 0.05), including 1103, 1451 and 996 genes in hypoxia1h, hypoxia4h and reoxygen4h groups, respectively. Only 247 DEGs were differentially co-expressed in all treatment groups. According to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, DEGs were significantly enriched in steroid biosynthesis, biosynthesis of amino acids, glutathione metabolism and metabolism of xenobiotics by cytochrome P450, ferroptosis and drug metabolism-cytochrome P450 pathways. Of these, the cytochrome P450 (CYP) and glutathione S-transferase (GST) gene families were widely expressed. Our study represents the insights into the underlying molecular mechanisms of hypoxia stress.

Health indicators and contaminant levels of a critically endangered species in the Gironde estuary, the European sturgeon

The European sturgeon, Acipenser sturio, is a highly endangered species that almost disappeared in the last decades. Thanks to yearly restocking of the population, this species is still found in the Gironde estuary (France), where juveniles grow during several years before leaving to the ocean. The aims of this study were to evaluate the pressure exerted on these fish by known organic and inorganic contaminants during their stay at the Gironde estuary, and to get information on the fish's health in this context. Monthly captures over the year 2014 provided 87 fish from the cohorts 2012 and 2013 mainly, and from cohorts 2008, 2009, and 2011, all fish born in hatchery. We report the very first analyses of contaminant levels and of biological markers measured in the blood of these fish. Low inorganic contamination was found, composed of seven metals mainly Zn (< 5 μg mL^-1), Fe (< 1.5 μg mL^-1), Cu (< 0.8 μg mL^-1), Se (< 0.8 μg mL^-1), As (< 0.25 μg mL^-1), Co (< 0.14 μg mL^-1), and Mn (< 0.03 μg mL^-1). Concerning persistent organic contaminants, the sum of seven PCBs varied from 1 to 10 ng g^-1 plasma, that of eight OCPs from 0.1 to 1 ng g^-1, and that of eight PBDEs from 10 to 100 pg g^-1. Higher levels of contaminants were measured during spring as compared to summer. The sex steroid hormone plasma levels (estradiol, testosterone, and 11-ketotestosterone) were quite low, which was predictable for juveniles. The transcription of reproduction-involved genes (EstR, AR, LHR, sox9) in blood cells was demonstrated for the first time. Some of them were correlated with organic contaminant levels PCBs and OCPs. Other gene transcriptions (sodCu and bax) were correlated with PCBs and OCPs. However, the DNA damage level measured here as comet tail DNA and micronuclei ratio in red blood cells were in the very low range of the values commonly obtained in fish from pristine areas. The data presented here can serve as a reference base for future monitoring of this population of sturgeons.

Hepatoprotective Effect of Citrus aurantium L. Against APAP-induced Liver Injury by Regulating Liver Lipid Metabolism and Apoptosis

Acetaminophen (APAP) refers to a medication used to manage pain and fever symptoms, but it always causes liver injury when overdosed. Zhishi, dried young fruit of Citrus aurantium L., is a famous Citrus herbal medicine in Asian countries which is rich in dietary phenolic substances. In this study, the mechanism of Zhishi protected against APAP-induced liver injury was studied more deeply by metabolomic strategy and pharmacological study. The metabolomics results demonstrated that Zhishi can prevent the APAP-induced liver injury model by regulating liver metabolic disorders in glycerophospholipid metabolism, fatty acid biosynthesis and glycerolipid metabolism. Moreover, it is confirmed that Zhishi blocked apoptosis of APAP-induced BRL-3A cell by simultaneously regulating p53 up-regulated apoptosis regulator (PUMA), AMPK-SIRT1 and JNK1 signaling pathways. Our findings indicated that Zhishi exhibited a hepaprotective effect against APAP-induced liver necrosis by inhibiting the PUMA and reversing disorder of liver lipid metabolism which could assist in improving the clinical outcomes of chemical-induced liver injury.

Single and combined exposures of waterborne Cu and Cd induced oxidative stress responses and tissue injury in female rare minnow (Gobiocypris rarus)

Copper (Cu) and cadmium (Cd) are two kinds of abundant toxic metals in aquatic ecosystem. The present study evaluated the effects of waterborne Cu and Cd on oxidative stress responses and histological alterations in female rare minnow (Gobiocypris rarus). Fish were exposed for 7 days to: (i) control (no added Cu or Cd), (ii) waterborne Cu (39.2 μg L^-1), (iii) waterborne Cd (299.6 μg L^-1), and (iv) Cu and Cd in mixture (19.6 and 149.8 μg L^-1, respectively). Antioxidant enzyme activities and gene mRNA abundance in fish tissues (gills, liver, and ovaries) were induced by Cu and Cd exposures, both individually and in mixture, at day 1, but an asynchronous response was observed between most enzyme activities and gene mRNA abundance following 7 days exposure. Biochemical analysis and histological observation indicated that exposure to Cu and Cd, alone and in combination, caused evident damage to lipids and tissue structure in gills, liver and ovaries. Comparing with single Cu or Cd exposure, Cu and Cd co-exposure induced greater increase in the mRNA expression of most antioxidant genes and caused more severe lesions in fish tissues, which suggested that exposure to waterborne Cu and Cd in mixture might increase their individual toxicity. Furthermore, positive relationships between nuclear factor erythroid 2-related factor (Nrf2) expression and expression of manganese superoxide dismutase (Mn-SOD) and catalase (CAT) were also observed in the present study, which suggested that Cu or/and Cd induced expression of these antioxidant genes were might through activation of Nrf2.

Molecular cloning and characterization of two ARNT (ARNT-1 and ARNT-2) genes in Atlantic croaker and their expression during coexposure to hypoxia and PCB77

Aryl hydrocarbon receptor nuclear translocator (ARNT) is an important transcriptions factor that binds/coactivates drug-metabolizing genes in vertebrates. In this study, we report the cloning and characterization of two ARNT (ARNT-1 and ARNT-2) genes and their mRNA and protein expression in liver tissues of Atlantic croaker after co-exposure to hypoxia and 3,3',4,4'-tetrachlorobiphenyl (PCB77). The full-length croaker ARNT-1 and ARNT-2 genes encode proteins of 537 and 530 amino acids, respectively, and are highly homologous to ARNT-1 and ARNT-2 genes of other vertebrates. ARNT mRNAs are ubiquitously expressed in all tissues. Hypoxia (dissolved oxygen: 1.7 mg/L) exposure (1-4 weeks) did not affect hepatic ARNTs mRNA levels. Dietary PCB77 treatment (2 and 8 μg/g body weight/day for 4 weeks) caused marked increases in ARNTs mRNA and protein levels in normoxic fish. However, coexposure to hypoxia and PCB77 for 4 weeks significantly blunted the increase in ARNTs mRNA and protein levels in response to PCB77 exposure. These results suggest that ARNT activity and functions induced by exposure to PCB aryl hydrocarbon receptor (AhR) agonists could be compromised in croaker inhabiting hypoxic coastal regions.

Chronic brain toxicity response of juvenile Chinese rare minnows (Gobiocypris rarus) to the neonicotinoid insecticides imidacloprid and nitenpyram

Imidacloprid and nitenpyram are widely used neonicotinoid pesticides worldwide and were observed to adversely affect non-target aquatic organisms. In this study, the toxic effect of imidacloprid and nitenpyram on the brain of juvenile Chinese rare minnows (Gobiocypris rarus) was investigated by determining the oxidative stress, 8-hydroxy-2-deoxyguanosine (8-OHdG) content and acetylcholinesterase (AChE) activity. The superoxide dismutase (SOD) activities did not significantly change after long-term exposure to imidacloprid and nitenpyram. A noticeable increase of catalase (CAT) activities was observed on the brain tissues under 0.1 mg/L imidacloprid and under all nitenpyram treatments (p < 0.05). The malondialdehyde (MDA) content increased markedly under 2.0 mg/L imidacloprid and 0.1 mg/L nitenpyram treatments (p < 0.05). The glutathione (GSH) content in the brain significantly increased under 0.5 and 2.0 mg/L imidacloprid (p < 0.05). A significant decrease was observed in the mRNA levels of Cu/Zn-sod under 2.0 mg/L imidacloprid and those of cat under 0.1 and 0.5 mg/L nitenpyram (p < 0.05). The mRNA levels of gpx1 clearly decreased under 2.0 mg/L imidacloprid and under 0.1 mg/L nitenpyram (p < 0.05). The treatments of 0.1 and 0.5 mg/L nitenpyram decreased cat expression levels markedly (p < 0.05). 2.0 mg/L imidacloprid raised the 8-OHdG content. The AChE activities increased markedly under 0.5 and 2.0 mg/L imidacloprid while clearly decreasing under 2.0 mg/L nitenpyram (p < 0.05). Therefore, our results indicate that imidacloprid and nitenpyram might cause adverse effects on juvenile Chinese rare minnows brain. Notably, imidacloprid had greater impacts on juvenile rare minnows compared to nitenpyram.

Environmental pollution and toxic substances: Cellular apoptosis as a key parameter in a sensible model like fish

The industrial wastes, sewage effluents, agricultural run-off and decomposition of biological waste may cause high environmental concentration of chemicals that can interfere with the cell cycle activating the programmed process of cells death (apoptosis). In order to provide a detailed understanding of environmental pollutants-induced apoptosis, here we reviewed the current knowledge on the interactions of environmental chemicals and programmed cell death. Metals (aluminum, arsenic, cadmium, chromium, cobalt, zinc, copper, mercury and silver) as well as other chemicals including bleached kraft pulp mill effluent (BKME), persistent organic pollutants (POPs), and pesticides (organo-phosphated, organo-chlorinated, carbamates, phyretroids and biopesticides) were evaluated in relation to apoptotic pathways, heat shock proteins and metallothioneins. Although research performed over the past decades has improved our understanding of processes involved in apoptosis in fish, yet there is lack of knowledge on associations between environmental pollutants and apoptosis. Thus, this review could be useful tool to study the cytotoxic/apoptotic effects of different pollutants in fish species.

Enantioselective Toxicity in Adult Zebrafish ( Danio rerio) Induced by Chiral PCB91 through Multiple Pathways

This study aimed to further investigate the toxic mechanism of chiral polychlorinated biphenyl (PCB) 91 in adult zebrafish ( Danio rerio) exposed to racemic (rac-), (+)-, or (-)-PCB91 for 63 days. The enantioselective mortalities of adult zebrafish exposed to rac-/(+)-/(-)-PCB91 were 95.86, 50.08, and 81.50%, respectively. Tubular necrosis and cellular hypertrophy occurred in the kidneys of (-)-PCB91-treated groups, whereas demyelination and immune cell infiltration occurred in brains of the rac-, (+)-, and (-)-PCB91-treated groups. Additionally, exposure to chiral PCB91 enantioselectively induced neurotoxicity, apoptosis, and inflammation in brain tissues owing to perturbations of gene expression, protein content and sphingolipid levels. The high mortality after rac-/(+)-PCB91 exposure might be due to toxic effects on brain tissue, while the high mortality after (-)-PCB91 exposure might be due to toxic effects on kidney as well as brain tissues. Thus, our findings offer an important reference for elucidating the enantioselective toxicological mechanism of chiral PCBs in aquatic organisms.

Interactive effects of hypoxia and PCB co-exposure on expression of CYP1A and its potential regulators in Atlantic croaker liver

Although marine and coastal environments which are contaminated with xenobiotic organic compounds often become hypoxic during the summer, the interactive effects of hypoxia and xenobiotic exposure on marine species such as teleost fishes remain poorly understood. The expression and activity of monooxygenase enzyme cytochrome P450-1A (CYP1A) in fishes are upregulated by exposure to polychlorinated biphenyls (PCBs), whereas they are down-regulated during hypoxia exposure. We investigated the interactive effects of hypoxia and PCB co-exposure on hepatic CYP1A expression in Atlantic croaker and on potential regulators of CYP1A. Croaker were exposed to hypoxia (1.7 mg/L dissolved oxygen), 3,3',4,4'-tetrachlorobiphenyl (PCB 77, dose: 2 and 8 µg/g body weight), and Aroclor 1254 (a common PCB mixture, dose: 0.5 and 1 µg/g body weight), alone and in combination for 4 weeks. PCB 77 exposure markedly increased hepatic CYP1A mRNA and protein expression, and ethoxyresorufin-O-deethylase (EROD, an indicator of CYP1A enzyme) activity and increased endothelial nitric oxide synthase (eNOS) protein expression. PCB 77 treatment also increased interleukin-1β (IL-1β, a cytokine) mRNA levels and protein carbonyl (PC, an indicator of reactive oxygen species, ROS) contents. These marked PCB 77- and Aroclor 1254-induced increases in CYP1A mRNA levels and EROD activity were significantly attenuated by co-exposure to hypoxia, whereas the increases in hepatic eNOS protein and IL-1β mRNA expression, and PC contents were augmented by hypoxia co-exposure. The results suggest that biotransformation of organic xenobiotics by CYP1A is reduced in fish during co-exposure to hypoxia and is accompanied by alterations in eNOS, ROS, and IL-1β levels.

Fish as a model to assess chemical toxicity in bone

Environmental toxicology has been expanding as growing concerns on the impact of produced and released chemical compounds over the environment and human health are being demonstrated. Among the toxic effects observed in organisms exposed to pollutants, those affecting skeletal tissues (osteotoxicity) have been somehow overlooked in comparison to hepato-, immune-, neuro- and/or reproductive toxicities. Nevertheless, sub-lethal effects of toxicants on skeletal development and/or bone maintenance may result in impaired growth, reduced survival rate, increased disease susceptibility and diminished welfare. Osteotoxicity may occur by acute or chronic exposure to different environmental insults. Because of biologically and technically advantagous features - easy to breed and inexpensive to maintain, external and rapid rate of development, translucent larvae and the availability of molecular and genetic tools - the zebrafish (Danio rerio) has emerged in the last decade as a vertebrate model system of choice to evaluate osteotoxicity. Different experimental approaches in fish species and analytical tools have been applied, from in vitro to in vivo systems, from specific to high throughput methodologies. Current knowledge on osteotoxicity and underlying mechanisms gained using fish, with a special emphasis on zebrafish systems, is reviewed here. Osteotoxicants have been classified into four categories according to the pathway involved in the transduction of the osteotoxic effects: activation/inhibition of membrane and/or nuclear receptors, alteration of redox condition, mimicking of bone constituents and unknown pathways. Knowledge on these pathways is also reported here as it may provide critical insights into the development, production and release of future chemical compounds with none or low osteotoxicity, thus promoting the green/environmental friendly chemistry.

Hepatic gene expression profiles of a non-model cyprinid (Barbus plebejus) chronically exposed to river sediments

In this study, we characterized the gene expression responses of the Padanian barbel (Barbus plebejus), a native benthivorous cyprinid with a very compromised presence within the fish community of the River Po. Barbel juveniles were exposed in the laboratory to two river sediments reflecting an upstream/downstream gradient of increasing contamination and collected from one of the most anthropized tributaries of the River Po. After 7months of exposure, hepatic transcriptional changes that were diagnostic of sediment exposure were assessed. We investigated a set of 24 genes involved in xenobiotic biotransformation (cyp1a, gstα, ugt), antioxidant defense (gpx, sod, cat, hsp70), trace metal exposure (mt-I, mt-II), DNA repair (xpa, xpc), apoptosis (bax, casp3), growth (igf2), and steroid (erα, erβ1, erβ2, ar, vtg) and thyroid (dio1, dio2, trα, trβ, nis) hormone signaling pathways. In a consistent overall picture, the results showed that long-term sediment exposure mainly increased the levels of mRNAs encoding proteins involved in xenobiotic metabolism, oxidative stress defense, repair of DNA damage and activation of the apoptotic process. Transcript up-regulation of three receptor genes (erβ2, ar, trβ), likely representing compensatory responses to antagonistic/toxic effects, was also observed, confirming the exposure to disruptors of the reproductive and thyroidal axes. In contrast to expectations, a few genes showed no response (e.g., casp3) or even downregulation (vtg), further suggesting that the timing of exposure/assessment, potential compensatory effects or post-transcriptional modifications interact to modify the gene expression profiles, particularly during exposure to mixtures of contaminants.

Polychlorinated biphenyls-153 induces metabolic dysfunction through activation of ROS/NF-κB signaling via downregulation of HNF1b

Polychlorinated biphenyls (PCB) is a major type of persistent organic pollutants (POPs) that act as endocrine-disrupting chemicals. In the current study, we examined the mechanism underlying the effect of PCB-153 on glucose and lipid metabolism in vivo and in vitro. We found that PCB-153 induced per se and worsened high fat diet (HFD)-resulted increase of blood glucose level and glucose and insulin intolerance. In addition, PCB-153 induced per se and worsened HFD-resulted increase of triglyceride content and adipose mass. Moreover, PCB-153 concentration-dependently inhibited insulin-dependent glucose uptake and lipid accumulation in cultured hepatocytes and adipocytes. PCB-153 induced the expression and nuclear translocation of p65 NF-κB and the expression of its downstream inflammatory markers, and worsened HFD-resulted increase of those inflammatory markers. Inhibition of NF-κB significantly suppressed PCB-153-induced inflammation, lipid accumulation and decrease of glucose uptake. PCB-153 induced oxidative stress and decreased hepatocyte nuclear factor 1b (HNF1b) and glutathione peroxidase 1 (GPx1) expression in vivo and in vitro. Overexpression of HNF1b increased GPx1 expression, decreased ROS level, decreased Srebp1, ACC and FAS expression, and inhibited PCB-153-resulted oxidative stress, NF-κB-mediated inflammation, and final glucose/lipid metabolic disorder. Our results suggest that dysregulation of HNF1b/ROS/NF-κB plays an important role in PCB-153-induced glucose/lipid metabolic disorder.

Chiral PCB 91 and 149 Toxicity Testing in Embryo and Larvae (Danio rerio): Application of Targeted Metabolomics via UPLC-MS/MS

In this study, we aimed to investigate the dysfunction of zebrafish embryos and larvae induced by rac-/(+)-/(-)- PCB91 and rac-/(-)-/(+)- PCB149. UPLC-MS/MS (Ultra-performance liquid chromatography coupled with mass spectrometry) was employed to perform targeted metabolomics analysis, including the quantification of 22 amino acids and the semi-quantitation of 22 other metabolites. Stereoselective changes in target metabolites were observed in embryos and larvae after exposure to chiral PCB91 and PCB149, respectively. In addition, statistical analyses, including PCA and PLS-DA, combined with targeted metabolomics were conducted to identify the characteristic metabolites and the affected pathways. Most of the unique metabolites in embryos and larvae after PCB91/149 exposure were amino acids, and the affected pathways for zebrafish in the developmental stage were metabolic pathways. The stereoselective effects of PCB91/149 on the metabolic pathways of zebrafish embryos and larvae suggest that chiral PCB91/149 exposure has stereoselective toxicity on the developmental stages of zebrafish.

Stereoselective induction by 2,2',3,4',6-pentachlorobiphenyl in adult zebrafish (Danio rerio): Implication of chirality in oxidative stress and bioaccumulation

This study aimed to investigate the oxidative stress process and bioaccumulation the racemic/(-)-/(+)- 2,2',3,4',6-pentachlorobiphenyl were administered to adult zebrafish (Danio rerio) after prolonged exposure of 56-days uptake and 49-days depuration experiments. Stereoselective accumulation was observed in adult samples after racemic exposure as revealed by decreased enantiomer fractions. The two enantiomers of PCB91 accumulated at different rates with logBCFk values close to 3.7, suggesting that they were highly hazardous and persistent pollutants. Exposure to racemic/(-)-/(+)- PCB91 stereoselectively induced oxidative stress owing to changes in reactive oxygen species, malondialdehyde contents, antioxidant enzyme activities and gene expressions in brain and liver tissues. In addition, the stereoselective relationship between bioconcentration and oxidative stress were also presented in this study. Our findings might be helpful for elucidating the environmental risk of the two enantiomers of PCB91 that induce toxicity in aquatic organisms.

Exploration of Stereoselectivity in Embryo-Larvae (Danio rerio) Induced by Chiral PCB149 at the Bioconcentration and Gene Expression Levels

This paper was designed to study stereoselective enrichment and changes in gene expression when zebrafish (Danio rerio) embryo-larvae were exposed to racemic, (-)- or (+)- PCB149 (2,2’,3,4’,5’,6- hexachlorobiphenyl). Based on bioconcentration analysis, non-racemic enrichment was significantly observed after racemic exposure. No isomerization between the two isomers was found after (-)/(+)-PCB149 exposure. Furthermore, based on gene expression-data mining, CYPs genes (cyp2k6, cyp19a1b, and cyp2aa4) were differential genes after (+)-PCB149 exposure. No obvious differences of dysregulation of gene expression caused by racemic and (-)-PCB149, were observed in embryo-larvae. The above results suggested that (-)-PCB149 could be considered as the main factor causing the dysregulation of gene expression in embryo-larvae after racemic exposure; and (+)-PCB149 should be pursued apart from the racemate, when considering the toxicity of chiral PCB149. Thus, the information in our study could provide new insights to assess the environmental risk of chiral PCBs in aquatic systems.

Dioxin-like pollutants increase hepatic flavin containing monooxygenase (FMO3) expression to promote synthesis of the pro-atherogenic nutrient biomarker trimethylamine N-oxide from dietary precursors

The etiology of cardiovascular disease (CVD) is impacted by multiple modifiable and non-modifiable risk factors including dietary choices, genetic predisposition, and environmental exposures. However, mechanisms linking diet, exposure to pollutants, and CVD risk are largely unclear. Recent studies identified a strong link between plasma levels of nutrient-derived Trimethylamine N-oxide (TMAO) and coronary artery disease. Dietary precursors of TMAO include carnitine and phosphatidylcholine, which are abundant in animal-derived foods. Dioxin-like pollutants can upregulate a critical enzyme responsible for TMAO formation, hepatic flavin containing monooxygenase 3 (FMO3), but a link between dioxin-like PCBs, upregulation of FMO3, and increased TMAO has not been reported. Here, we show that mice exposed acutely to dioxin-like PCBs exhibit increased hepatic FMO3 mRNA, protein, as well as an increase in circulating levels of TMAO following oral administration of its metabolic precursors. C57BL/6 mice were exposed to 5μmol PCB 126/kg mouse weight (1.63mg/kg). At 48h post-PCB exposure, mice were subsequently given a single gavage of phosphatidylcholine dissolved in corn oil. Exposure to 5 μmole/kg PCB 126 resulted in greater than 100-fold increase in FMO3 mRNA expression, robust induction of FMO3 protein, and a 5-fold increase in TMAO levels compared with vehicle treated mice. We made similar observations in mice exposed to PCB 77 (49.6mg/kg twice); stable isotope tracer studies revealed increased formation of plasma TMAO from an orally administered precursor trimethylamine (TMA). Taken together, these observations suggest a novel diet-toxicant interaction that results in increased production of a circulating biomarker of cardiovascular disease risk.

Non-monotonic dose-response effect of bisphenol A on rare minnow Gobiocypris rarus ovarian development

Bisphenol A (BPA) is widely spread in the environment, and can cause various reproductive disrupting effects on different organisms, including fish. Our previous published study showed that BPA has non-monotonic (inverted U-shaped) dose-response effect on rare minnow Gobiocypris rarus ovarian weight at different concentrations. To investigate the potential mechanism, we exposed female rare minnow to 1, 15 and 225 µg L(-1) BPA for 7 days in the present study. The levels of vitellogenin (Vtg), sex hormones, hydrogen peroxide (H2O2), glutathione (GSH) and triglyceride (TG) were measured. RNA-seq of ovary tissues was also performed. Result showed that Vtg, sex hormone and TG levels showed an inverted U-shaped increased response, while H2O2 and GSH levels showed a U-shaped inhibited response. RNA-seq data showed that many genes involved in lipid metabolism, oxidative stress, and proteolysis processes were altered. The change of Vtg, H2O2, GSH and TG levels was possibly related to the altered sex hormone levels. Sex hormone's direct effect, Vtg accumulation, TG accumulation and oxidative stress induced proteolysis may contribute to the change of ovary weight.

Polychlorinated biphenyls and links to cardiovascular disease

The pathology of cardiovascular disease is multi-faceted, with links to many modifiable and non-modifiable risk factors. Epidemiological evidence now implicates exposure to persistent organic pollutants, such as polychlorinated biphenyls (PCBs), with an increased risk of developing diabetes, hypertension, and obesity; all of which are clinically relevant to the onset and progression of cardiovascular disease. PCBs exert their cardiovascular toxicity either directly or indirectly via multiple mechanisms, which are highly dependent on the type and concentration of PCBs present. However, many PCBs may modulate cellular signaling pathways leading to common detrimental outcomes including induction of chronic oxidative stress, inflammation, and endocrine disruption. With the abundance of potential toxic pollutants increasing globally, it is critical to identify sensible means of decreasing associated disease risks. Emerging evidence now implicates a protective role of lifestyle modifications such as increased exercise and/or nutritional modulation via anti-inflammatory foods, which may help to decrease the vascular toxicity of PCBs. This review will outline the current state of knowledge linking coplanar and non-coplanar PCBs to cardiovascular disease and describe the possible molecular mechanism of this association.

Quercetin ameliorates polychlorinated biphenyls-induced testicular DNA damage in rats

Polychlorinated biphenyls (PCBs) are a group of environmental contaminants widely reported to cause gonadal toxicity in both humans and animals. This study investigated the amelioratory role of quercetin in PCBs-induced DNA damage in male Wistar rats. Polychlorinated biphenyls were administered intraperitoneally at a dose of 2 mg kg(-1) alone or in combination with quercetin (orally) at 50 mg kg(-1) for 25 days. Quercetin modulation of PCBs-induced gonadal toxicity was evaluated using selected oxidative stress indices, comet assay, measurement of DNA concentration and histology of the testes. Administration of PCBs alone caused a significant (P < 0.05) depletion in the total thiol level in testes of treated rats. Conversely, the levels of reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) production were markedly elevated in testes of PCBs-treated rats compared with control. Further, PCBs exposure produced statistically significant increases in DNA tail migration, degraded double-stranded DNA (dsDNA) concentration and histological alterations of testes of the treated rats compared to control. Quercetin cotreatment significantly improved the testicular antioxidant status, decreased DNA fragmentation and restored the testicular histology, thus demonstrating the protective effect of quercetin in PCBs-treated rats.

Oxidative stress and immunotoxic effects of bisphenol A on the larvae of rare minnow Gobiocypris rarus

Bisphenol A (BPA), a known endocrine disrupting chemical, is ubiquitous in the aquatic environment and can pose risk to the health of aquatic organisms. Studies on immunotoxicity of BPA in aquatic organisms are limited. In this study, rare minnow (Gobiocypris rarus) larvae were exposed to 1, 225 and 1000μg/L BPA for 7 days. Inflammatory effects of BPA exposure were assessed from the increased production of nitric oxide (NO) and reactive oxygen species (ROS), the change of iNOS mRNA and other TLRs-associated immune gene expression. Our findings provide evidences that different concentrations of BPA can induce a toxic response in fish to produce reactive free radicals which can affect the function of T lymphocytes and decrease the transcription levels of cytokine genes. The excess production of H2O2, induced oxidative stress and suppressed TLR4/NF-κB signaling, leading to immunosuppressive effects in fish larvae. The present results suggest that BPA has the potential to induce oxidative stress accompanied by immunosuppression in rare minnow larvae.

Enantio-alteration of gene transcription associated with bioconcentration in adult zebrafish (Danio rerio) exposed to chiral PCB149

Enantioselective enrichment of chiral PCB149 (2,2’,3,4’,5’,6-hexachlorobiphenyl) was analysed in adult zebrafish (Danio rerio) exposed to the racemate, (−)-PCB149, and (+)-PCB149. Greater enrichment of (−)-PCB149 compared to (+) PCB149 was observed following 0.5 ng/L exposure; however, as the exposure time and concentration increased, racemic enrichment was observed in adult fish exposed to the racemate. No biotransformation between the two isomers was observed in fish exposed to single enantiomers. When zebrafish were exposed to different forms of chiral PCB149, enantioselective expression of genes associated with polychlorinated biphenyls (PCBs) was observed in brain and liver tissues and enantioselective correlations between bioconcentration and target gene expression levels were observed in brain and liver tissues. The strong positive correlations between expression levels of target genes (alox5a and alox12) and PCB149 bioconcentration suggest that prolonged exposure to the racemate of chiral PCB149 may result in inflammation-associated diseases. Prolonged exposure to (−)-PCB149 may also affect metabolic pathways such as dehydrogenation and methylation in the brain tissues of adult zebrafish. Hepatic expression levels of genes related to the antioxidant system were significantly negatively correlated with bioconcentration following exposure to (+)-PCB149.

Role of PUMA in methamphetamine-induced neuronal apoptosis

Exposure to methamphetamine (METH), a widely used illicit drug, has been shown to cause neuron apoptosis. p53 upregulated modulator of apoptosis (PUMA) is a key mediator in neuronal apoptosis. This study aimed to examine the effects of PUMA in METH-induced neuronal apoptosis. We determined PUMA protein expression in PC12 cells and SH-SY5Y cells after METH exposure using western blot. We also observed the effect of METH on neuronal apoptosis after silencing PUMA expression with siRNA using TUNEL staining and flow cytometry. Additionally, to investigate possible mechanisms of METH-induced PUMA-mediated neuronal apoptosis, we measured the protein expression of apoptotic markers, including cleaved caspase-3, cleaved PARP, Bax, B-cell leukemia/lymphoma-2 (Bcl-2) and cytochrome c (cyto c), after METH treatment with or without PUMA knockdown. Results showed that METH exposure induced cell apoptosis, increased PUMA protein levels, activated caspase-3 and PARP, elevated Bax and reduced Bcl-2 expression, as well as increased the release of cyto c from mitochondria to the cytoplasm in both PC12 and SH-SY5Y cells. All these effects were attenuated or reversed after silencing PUMA. A schematic depicting the role of PUMA in METH-induced mitochondrial apoptotic pathway was proposed. Our results suggest that PUMA plays an important role in METH-triggered apoptosis and it may be a potential target for ameliorating neuronal injury and apoptosis caused by METH.

Developmental retardation, reduced fecundity, and modulated expression of the defensome in the intertidal copepod Tigriopus japonicus exposed to BDE-47 and PFOS

2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and perfluorooctane sulfonate (PFOS) are widely dispersed persistent organic pollutants (POPs) in the marine ecosystem. However, their toxic effects on marine organisms are still poorly understood. In this study, we investigated the effects of BDE-47 and PFOS on development and reproduction at the organismal level and reactive oxygen species (ROS) production and gene expression patterns of the defensome at the cellular level in the intertidal copepod Tigriopus japonicus. In copepods exposed to BDE-47 and PFOS, we observed developmental retardation and reduced fecundity, suggesting repercussions on in vivo endpoints through alterations to the normal molting and reproduction system of T. japonicus. BDE-47 and PFOS increased levels of ROS in T. japonicus in a concentration-dependent manner, indicating that POPs can induce oxidative stress through the generation of ROS. Additionally, transcript profiles of genes related to detoxification (e.g., CYPs), antioxidant functions (e.g., GST- sigma, catalase, MnSOD), apoptosis (e.g., p53, Rb), and cellular proliferation (e.g., PCNA) were modulated over 72h in response to BDE-47 (120μg/L) and PFOS (1000μg/L). These findings indicate that BDE-47 and PFOS can induce oxidative stress-mediated DNA damage repair systems with transcriptional regulation of detoxification, antioxidant, and apoptosis-related genes, resulting in developmental retardation and reduced fecundity in the copepod T. japonicus.