Coplanar Polychlorinated Biphenyls Research Articles

Determination of the genotoxic effects of various dioxins by <em>Drosophila </em>wing spot test

Dioxins, furans and other polychlorinated biphenyls (coplanar PCBs) are three structural and toxicologically related families of compounds classified as the most toxic synthetic chemical. In this study, we investigated possible genotoxic effects of polychlorinated dibenzo-p-dioxins (PCDDs), man-made environmental contaminant, in Drosophila melanogaster by somatic mutation and recombination test (SMART). In this, we observe the chemical effects on wing phenotype of the transheterozygote flies carrying marker gene. Lethal doses of 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, 1,2,3,7,8,9-HXCDD, and 1,2,3,4,6,7,8,9-OCDD were determined. Doses of 1×10-7, 2.5×10-7, 5×10-7, and 10×10-7 μg/mL of PCDDs were used. In addition, the observed mutations were classified according to the size and the type of the mutations per wing. Results revealed no significant genotoxic effect of any of the dioxins tested. According to the mechanisms involved in the antigenotoxicity of PCDDs, it is suggested that the observed effects can be linked to the differences in the aryl hydrocarbon receptor (AHR) amino acid sequences in the gene protein of D.melanogaster

Augmentation of an Engineered Bacterial Strain Potentially Improves the Cleanup of PCB Water Pollution.

ABSTRACTPolychlorinated biphenyls (PCBs) are recalcitrant organohalide pollutants, consisting of 209 congeners. PCB cleanup in natural landscapes is expected to be achieved by the metabolic activity of microorganisms, but aerobic PCB-degrading bacteria that inhabit sites polluted by PCBs cannot degrade all PCB congeners due to the specificity of their enzymes. In this study, we investigated the degradability of PCBs when a genetically modified PCB-degrading bacterium was compounded with wild-type PCB-degrading bacteria. We used two bacterial strains, Comamonas testosteroni YAZ2 isolated from a PCB-uncontaminated natural landscape and Escherichia coli BL21(DE3) transformed with a biphenyl dioxygenase (BphA) gene from a well-known PCB degrader, Burkholderia xenovorans LB400. The enzymatic specificities of BphA were 2,3-dioxygenation in the YAZ2 and 2,3- and 3,4-dioxygenations in the recombinant E. coli. For the PCB-degrading experiment, a dedicated bioreactor capable of generating oxygen microbubbles was prototyped and used. The combined cells of the recombinant and the wild-type strains with an appropriate composite ratio degraded 40 mg/L of Kaneclor KC-300 to 0.3 ± 0.1 mg/L within 24 h. All of the health-toxic coplanar PCB congeners in KC-300 were degraded. This study suggested that the augmentation of an engineered bacterial strain could improve the cleanup of PCB water pollution. It also revealed the importance of the ratio of the strains with different PCB-degrading profiles to efficient degradation and that the application of oxygen microbubbles could rapidly accelerate the cleanup.IMPORTANCE PCB cleanup technique in a natural environment relies on the use of enzymes from microorganisms, primarily biphenyl dioxygenase and dehalogenase. Herein, we focused on biphenyl dioxygenase and created a recombinant PCB-degrading E. coli strain. Despite the development of environments for the field use of transgenic microbial strains around the world, verification of the applicability of transgenic microbial strains for PCB cleanup in the field has not yet been reported. We tentatively verified the extent to which degradability could be obtained by an augmentation model of a transgenic strain, the enzyme expression of which is easily regulated in rivers and lakes with PCB pollution. Our experiments used a dedicated bioreactor to model the natural landscape and produced results superior to those of bioremediation or biostimulation methods. The application of micro-nano bubbles, which has recently been discussed, to the cleanup of environmental pollution was also found to be useful in this study.

Lack of Offspring Nrf2 Does Not Exacerbate the Detrimental Metabolic Outcomes Caused by In Utero PCB126 Exposure.

Human environmental exposures to toxicants, such as polychlorinated biphenyls (PCBs), increase oxidative stress and disease susceptibility. Such exposures during pregnancy and/or nursing have been demonstrated to adversely affect offspring health outcomes. Nuclear factor erythroid-2-related factor 2 (Nrf2) regulates the antioxidant response and is involved in the detoxification of coplanar PCBs, like PCB126. The purpose of this study was to investigate glucose tolerance and body composition in PCB-exposed offspring expressing or lacking Nrf2. We hypothesized that offspring lacking Nrf2 expression would be more susceptible to the long-term health detriments associated with perinatal PCB exposure. During gestation, whole-body Nrf2 heterozygous (Het) and whole-body Nrf2 knockout (KO) mice were exposed to vehicle or PCB126. Shortly after birth, litters were cross-fostered to unexposed dams to prevent PCB exposure during nursing. Offspring were weaned, and their body weight, body composition, and glucose tolerance were recorded. At two months of age, PCB exposure resulted in a significant reduction in the average body weight of offspring born to Nrf2 Het dams (p < 0.001) that primarily arose from the decrease in average lean body mass in offspring (p < 0.001). There were no differences in average body weight of PCB-exposed offspring born to Nrf2 KO dams (p > 0.05), and this was because offspring of Nrf2 KO dams exposed to PCB126 during pregnancy experienced a significant elevation in fat mass (p = 0.002) that offset the significant reduction in average lean mass (p < 0.001). Regardless, the lack of Nrf2 expression in the offspring themselves did not enhance the differences observed. After an oral glucose challenge, PCB-exposed offspring exhibited significant impairments in glucose disposal and uptake (p < 0.05). Offspring born to Nrf2 Het dams exhibited these impairments at 30 min and 120 min, while offspring born to Nrf2 KO dams exhibited these impairments at zero, 15, 30, 60 and 120 min after the glucose challenge. Again, the interactions between offspring genotype and PCB exposure were not significant. These findings were largely consistent as the offspring reached four months of age and demonstrate that the lack of offspring Nrf2 expression does not worsen the metabolic derangements caused by in utero PCB exposure as we expected. Future directions will focus on understanding how the observed maternal Nrf2 genotypic differences can influence offspring metabolic responses to in utero PCB exposure.

Legacy contaminant-stable isotope-age relationships in Lake Ontario year-class Alewife (Alosa pseudoharengus)

Alewife (Alosa pseudoharengus) are the preferred prey species of the top piscivore predators in the Lake Ontario food web and are an essential constituent in the bioaccumulation of persistent organic contaminants. Year-class samples collected in 2016 represent the alewife age ranges of 2015 (Age-01) sequentially dating back to 2008 (Age-08). The most abundant contaminant measured in Lake Ontario alewife (151.5 ng/g) were total polychlorinated biphenyls (PCBs), increasing at a rate of 11.8 ng/g per year on an age-averaged concentration basis. Total mercury demonstrated the largest percent increase (240%) accumulated over alewife ages of 1–8 years. Average total concentrations of the most abundant polychlorinated dibenzo-p-dioxin isomer (2378-tetrachlorinated dibenzo-p-dioxin (TCDD), 1.3 pg/g) and polychlorinated dibenzofuran isomer (2378-tetrachlorinated dibenzofuran (2378-TCDF), 6.6 pg/g) comprised most of the overall total dioxin (2.5 pg/g) and total furan concentrations (8.7 pg/g). The vast majority (69%) of alewife total toxic equivalence (TEQ) was comprised of the non-ortho coplanar PCBs. Both mammal and avian wildlife protection values based on total TEQ were uniformly exceeded for the dioxin-like compounds measured in Lake Ontario alewife. Ontogenetic dietary influences expressed a significant impact on Age-01 alewife age-contaminant relationships and age-stable isotope concentrations and trends for legacy contaminants. Total Hg and all dioxin-like contaminants did not demonstrate the Age-01 ontogenetic dietary effects found in legacy contaminants. A prominent polychlorinated naphthalene (PCN) concentration peak measured in year-class Age-04 alewife was followed by a corresponding lake trout peak 3–4 years later illustrating a unique example of trophic-level contaminant uptake and concomitant integration delay.

The Association of the Polychlorinated Biphenyl Class of Endocrine Disruptors With Polycystic Ovary Syndrome and Thyroid Dysfunction

Introduction:. Polychlorinated biphenyls (PCBs) are a class of endocrine disruptors with a long half-life in the body that are associated with irregular menses, growth and development delay, increased cancer risk, thyroid disorders and an increased risk of diabetes. Higher levels of PCBs have been related to polycystic ovary syndrome (PCOS). PCB toxicity depends on their structure, with coplanar PCBs being most toxic (akin to dioxins); therefore, PCB subtypes were determined to see if they differed in women with PCOS compared to normal controls. Methods:. PCB levels were compared in Caucasian women with (n=29) and without (n=30) PCOS and related to metabolic features. PCBs were fractionated then analysed by high-resolution gas chromatography-unit resolution mass spectrometry. Results:. The control and PCOS groups were age and BMI matched (p=ns); insulin resistance was not different (HOMA 1.7±1.0 v 2±1.6, p=ns) but free androgen index was increased in PCOS (p<0.004). PCB-118, 138, 153 and 180 were found in all subjects, whilst fewer subjects showed PCB-28(15/59), PCB-52(4/59) or PCB-101(26/59). There was no difference for PCB-188,138,153 and 180 between controls and PCOS, but all correlated with increasing age (p<0.01) and decreasing estimated glomerular filtration rate (p<0.05); no correlations with BMI, HOMA, testosterone, TSH or T3 were found; however, PCB-118 (the only coplanar PCB detected) associated with an increased T4/T3 ratio (p<0.01). Conclusion. Despite PCBs being banned over a decade ago, PCBs were detected, but did not differ between age and BMI matched women with and without PCOS. Thyroid dysfunction may be only associated with toxic coplanar PCBs, such as PCB-118 that was associated with a higher T4/T3 ratio.

Pressure regulated basis for gene transcription by delta-cell micro-compliance modeled in silico: Biphenyl, bisphenol and small molecule ligand models of cell contraction-expansion.

Molecular diameter, lipophilicity and hydrophilicity exclusion affinity limits exist for small molecule carrier-mediated diffusion or transport through channel pores or interaction with the cell surface glycocalyx. The molecular structure lipophilicity limit for non-specific carrier-mediated transmembrane diffusion through polarity-selective transport channels of the cell membrane is Lexternal structure ∙ Hpolar group-1 of ≥ 1.07. The cell membrane channel pore size is > 0.752 and < 0.758 nm based on a 3-D ellipsoid model (biphenyl), and within the molecular diameter size range 0.744 and 0.762 nm based on a 2-D elliptical model (alkanol). The adjusted van der Waals diameter (vdWD, adj; nm) for the subset of halogenated vapors is predictive of the required MAC for anesthetic potency at an initial (-) Δ Cmicro effect. The molecular structure L ∙ Hpolar group-1 for Neu5Ac is 0.080, and the L ∙ Hpolar group-1 interval range for the cell surface glycocalyx hydrophilicity barrier interaction is 0.101 (Saxitoxin, Stx; Linternal structure ∙ Hpolar group-1) - 0.092 (m-xylenediamine, Lexternal structure · Hpolar group). Differential predictive effective pressure mapping of gene activation or repression reveals that p-dioxin exposure results in activation of AhR-Erβ (Arnt)/Nrf-2, Pparδ, Errγ (LxRα), Dio3 (Dio2) and Trα limbs, and due to high affinity Dio2 and Dio3 (OH-TriCDD, Lext · H-1: 1.91–4.31) exothermy-antagonism (Δ contraction) with high affinity T4/rT3-TRα-mediated agonism (Δ expansion). co-planar PCB metabolite exposure (Lext · H-1: 1.95–3.91) results in activation of AhR (Erα/β)/Nrf2, Rev-Erbβ, Errα, Dio3 (Dio2) and Trα limbs with a Δ Cmicro contraction of 0.89 and Δ Cmicro expansion of 1.05 as compared to p-dioxin. co-, ortho-planar PCB metabolite exposure results in activation of Car/PxR, Pparα (Srebf1,—Lxrβ), Arnt (AhR-Erβ), AR, Dio1 (Dio2) and Trβ limbs with a Δ Cmicro contraction of 0.73 and Δ Cmicro expansion of 1.18 (as compared to p-dioxin). Bisphenol A exposure (Lext struct ∙ H-1: 1.08–1.12, BPA–BPE, Errγ; BPAF, Lext struct ∙ H-1: 1.23, CM Erα, β) results in increased duration at Peff for Timm8b (Peff 0.247) transcription and in indirect activation of the AhR/Nrf-2 hybrid pathway with decreased duration at Peff 0.200 (Nrf1) and increased duration at Peff 0.257 (Dffa). The Bpa/Bpaf convergent pathway Cmicro contraction-expansion response increase in the lower Peff interval is 0.040; in comparison, small molecule hormone Δ Cmicro contraction-expansion response increases in the lower Peff intervals for gene expression ≤ 0.168 (Dex· GR) ≥ 0.156 (Dht · AR), with grade of duration at Peff (min·count) of 1.33x105 (Dex/Cort) and 1.8–2.53x105 (Dht/R1881) as compared to the (-) coupled (+) Δ Cmicro Peff to 0.136 (Wnt5a, Esr2) with applied DES (1.86x106). The subtype of trans-differentiated cell as a result of an applied toxin or toxicant is predictable by delta-Cmicro determined by Peff mapping. Study findings offer additional perspective on the basis for pressure regulated gene transcription by alterations in cell micro-compliance (Δ contraction-expansion, Cmicro), and are applicable for the further predictive modeling of gene to gene transcription interactions, and small molecule modulation of cell effective pressure (Peff) and its potential.

A Critical Review of Polychlorinated Biphenyls Metabolism, Metabolites, and Their Correlation with Oxidative Stress.

Polychlorinated biphenyls (PCBs) are notorious persistent organic pollutants that were banned in the last century. However, PCBs still remain ubiquitous in the ecosystem due to their persistence and bioaccumulative potency against environmental and biological degradation. Albeit there is no longer the permission of commercial production of PCBs, they were continuously released into global biota via illegal disposal of e-waste or as byproducts of industrial supplies. The role of oxidative stress is often implicated in PCBs' toxicology. PCBs, especially coplanar ones, have a high affinity toward aryl hydrocarbon receptors and inducing CYP1A1, which is considered as a source of oxidative stress. Although commercial PCBs and coplanar individual PCBs, for example, PCB 77 and 126, induced oxidative stresses have been extensively investigated, PCB metabolite-induced oxidative stress has received less attention. PCBs can undergo phase I metabolism which metabolizes the parent PCBs into hydroquinone/semiquinone/quinone metabolites as a futile redox cycle, producing downstream reactive oxygen species (ROS) as byproducts. PCBs can also undergo phase II metabolism yielding methylsulfonyl metabolites that deplete glutathione and such. PCB metabolites induce oxidative stress generally via direct production of ROS or indirect scavenge antioxidant and inhibit antioxidant enzymes, disturbing cellular redox balance. This review aims to provide a critical summary of PCBs metabolism, PCBs parents, and daughter metabolite-induced oxidative stress. We especially focus on the connection between parent PCBs and downstream metabolites, to encourage research associated with PCB metabolite-induced oxidative stress.

Insights into Aflatoxin B1 Toxicity in Cattle: An In Vitro Whole-Transcriptomic Approach.

Aflatoxins, and particularly aflatoxin B1 (AFB1), are toxic mycotoxins to humans and farm animal species, resulting in acute and chronic toxicities. At present, AFB1 is still considered a global concern with negative impacts on health, the economy, and social life. In farm animals, exposure to AFB1-contaminated feed may cause several untoward effects, liver damage being one of the most devastating ones. In the present study, we assessed in vitro the transcriptional changes caused by AFB1 in a bovine fetal hepatocyte-derived cell line (BFH12). To boost the cellular response to AFB1, cells were pre-treated with the co-planar PCB 3,3′,4,4′,5-pentachlorobiphenyl (PCB126), a known aryl hydrocarbon receptor agonist. Three experimental groups were considered: cells exposed to the vehicle only, to PCB126, and to PCB126 and AFB1. A total of nine RNA-seq libraries (three replicates/group) were constructed and sequenced. The differential expression analysis showed that PCB126 induced only small transcriptional changes. On the contrary, AFB1 deeply affected the cell transcriptome, the majority of significant genes being associated with cancer, cellular damage and apoptosis, inflammation, bioactivation, and detoxification pathways. Investigating mRNA perturbations induced by AFB1 in cattle BFH12 cells will help us to better understand AFB1 toxicodynamics in this susceptible and economically important food-producing species.

Skeletal Toxicity of Coplanar Polychlorinated Biphenyl Congener 126 in the Rat Is Aryl Hydrocarbon Receptor Dependent.

Epidemiological evidence links polychlorinated biphenyls (PCBs) to skeletal toxicity, however mechanisms whereby PCBs affect bone are poorly studied. In this study, coplanar PCB 126 (5 μmol/kg) or corn oil vehicle was administered to N = 5 and 6 male and female, wild type (WT) or AhR -/- rats via intraperitoneal injection. Animals were sacrificed after 4 weeks. Bone length was measured; bone morphology was assessed by microcomputed tomography and dynamic histomorphometry. Reduced bone length was the only genotype-specific effect and only observed in males (p < .05). WT rats exposed to PCB 126 had reduced serum calcium, and smaller bones with reduced tibial length, cortical area, and medullary area relative to vehicle controls (p < .05). Reduced bone formation rate observed in dynamic histomorphometry was consistent with inhibition of endosteal and periosteal bone growth. The effects of PCB 126 were abolished in AhR -/- rats. Gene expression in bone marrow and shaft were assessed by RNA sequencing. Approximately 75% of the PCB-regulated genes appeared AhR dependent with 89 genes significantly (p < .05) regulated by both PCB 126 and knockout of the AhR gene. Novel targets significantly induced by PCB 126 included Indian hedgehog (Ihh) and connective tissue growth factor (Ctgf/Ccn2), which regulate chondrocyte proliferation and differentiation in the bone growth plate and cell-matrix interactions. These data suggest the toxic effects of PCB 126 on bone are mediated by AhR, which has direct effects on the growth plate and indirect actions related to endocrine disruption. These studies clarify important mechanisms underlying skeletal toxicity of dioxin-like PCBs and highlight potential therapeutic targets.

Skeletal toxicity resulting from exposure of growing male rats to coplanar PCB 126 is associated with disruption of calcium homeostasis and the GH-IGF-1 axis and direct effects on bone formation.

Skeletal toxicity has been reported following exposure to polychlorinated biphenyl (PCB) mixtures. However, molecular mechanisms remain poorly understood. We exposed groups of male 4-5-week-old Sprague-Dawley rats to 3,3', 4, 4', 5-pentachlorobiphenyl (PCB 126), a dioxin-like coplanar PCB congener by a single i.p. injection of 5µmol/kg in soy oil vehicle or vehicle alone. After 4weeks, rats were euthanized. PCB exposure resulted in hypocalcemia (P < 0.05) and significant increases in serum PTH without changes in serum phosphorous. Hyperparathyroidism was accompanied by increased expression of mRNAs of vitamin D3 metabolizing cytochrome P450 enzymes CYP27B1 and CYP24 in the kidney (P < 0.05). PCB exposure also reduced body weight, serum IGF-1, and hepatic expression of mRNAs encoding the male-specific GH-pattern-regulated CYP2C11 and CYP3A2 relative to controls (P < 0.05). PCB exposure reduced long bone length, diameter, and surface area, but increased trabecular thickness and volume (P < 0.05). Serum osteocalcin (P < 0.05), a marker and a regulator of bone formation, was reduced, but PCB exposure had no effect on the bone resorption marker RatLaps. Exposure of human intestinal Caco-2 cells to 10-100nM PCB 126 in the presence of vitamin D3 resulted in inhibition of mRNAs for the calcium transporters TRPV6 and PMCA1b (P < 0.05). In addition, PCB 126 suppressed osteoblastogenesis in primary bone marrow mesenchymal stem cell cultures which was blunted by the AhR antagonist CH-223191. These data provide novel evidence that skeletal toxicity after exposure to PCB 126 is a result of disruption of calcium homeostasis and the GH-IGF-1 axis, and involves direct AhR-mediated effects on bone formation.

Associations between persistent organic pollutants and risk of breast cancer metastasis

BackgroundBreast cancer (BC) is a major public health concern with over 2 million new cases diagnosed and over 600,000 deaths in 2018 in women worldwide. When distant metastases are present at diagnosis, the 5-year survival rate is only 26%. Recent studies have suggested that persistent organic pollutants (POPs) that accumulate in adipose tissue (AT) can influence tumor phenotype and stimulate cellular processes important for metastasis such as invasion. We, therefore, tested the hypothesis that POP exposure is associated with BC metastasis. MethodsWe conducted an exploratory case-control study in which the concentrations of 49 POPs were measured in both AT and serum samples from BC patients, with or without lymph node metastasis, who underwent partial or total mastectomies, lymph node biopsies and sampling of the adipocytic tumor microenvironment. Adjusted, unconditional logistic models were used to study the associations between the POP concentrations and the risk of metastasis and other hallmarks of cancer aggressiveness. Results2.3.7.8-TCDD concentrations in AT are positively associated with the risk of metastasis in 43 patients who have BMIs equal or higher than 25 kg/m2 (odds ratio: 4.48 (1.32–20.71)). Furthermore, the concentrations of 2.3.7.8-TCDD and two coplanar PCBs (77&169) in AT also were positively associated with the risk of lymph node metastasis and the tumor size. ConclusionOur study suggests that 2.3.7.8-TCDD and some PCBs contribute to the development of tumor metastasis and other hallmarks of cancer aggressiveness. While these results should be considered with caution, this is the first study to identify such potential risk factors. Larger longitudinal studies are necessary to confirm our results.Clinical Trial Protocol Record: 2013-A00663-42.

Dioxins levels in human blood after implementation of measures against dioxin exposure in Japan

BackgroundOver the past few decades, the Japanese Ministry of the Environment has been biomonitoring dioxins in the general Japanese population and, in response to public concerns, has taken measures to reduce dioxin exposure. The objectives of this study were to assess the current dioxin dietary intake and corresponding body burden in the Japanese and compare Japanese dioxin data from 2011 to 2016 and 2002–2010 surveys. We also examined the relationship between blood dioxins and health parameters/clinical biomarkers.MethodsFrom 2011 to 2016, cross-sectional dioxin surveys were conducted on 490 Japanese (242 males and 248 females, aged 49.9 ± 7.6 years) from 15 Japanese prefectures. Blood (n = 490) and food samples (n = 90) were measured for 29 dioxin congeners including polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs) using gas chromatography coupled with high-resolution mass spectrometry. Using the 2006 World Health Organization toxic equivalence factors, the toxic equivalents (TEQs) were calculated. Clinical biomarkers and anthropometric parameters were also measured and information on lifestyle behaviours collected. Data imputations were applied to account for blood dioxins below the detection limit.ResultsThe median (95% confidence interval or CI) blood levels and dioxin dietary intake was respectively 9.4 (8.8–9.9) pg TEQ/g lipid and 0.3 (0.2–0.4) pg TEQ/kg body weight/day. The median blood dioxin level in the 2011–2016 survey was found to have decreased by 41.3% compared to the 2002–2010 surveys. Participants who were older were found to be more likely to have higher dioxin levels. Blood dioxins were also significantly associated with body mass index, triglycerides, docosahexaenoic acid, eicosapentaenoic acid, and dihomo-gamma-linoleic acid levels in blood. Furthermore, associations between blood dioxin and dietary dioxin intake were evident in the unadjusted models. However, after adjusting for confounders, blood dioxins were not found to be associated with dietary dioxin intake.ConclusionsBlood dioxin levels declined over the past decade. This study showed that the measures and actions undertaken in Japan have possibly contributed to these reductions in the body burden of dioxins in the Japanese population.

Non-coplanar and coplanar polychlorinated biphenyls potentiate genotoxicity of aflatoxin B1 in a human hepatocyte line by enhancing CYP1A2 and CYP3A4 expression

Polychlorinated biphenyls (PCBs) are persistent organic pollutants and hazardous to human health. Aflatoxin B1 (AFB1) is a strong carcinogen dependent on activation by cytochrome P450 (CYP) 1A2 and 3A4. Humans in some regions may be exposed to both PCBs and AFB1. Since PCBs are CYP inducers, we were interested in their combined genotoxicity. In this study, the effects of non-coplanar 2,3,3′-tri- (PCB 20), 2,2′5,5′-tetra- (PCB 52), 2,3,3′,4′-tetrachlorobiphenyl (PCB 56), and coplanar 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126) on protein levels of CYP1A1, 1A2, and 3A4, and nuclear receptors AhR, CAR and PXR in a human hepatocyte (L-02) line were investigated. Moreover, the combined effects of each PCB and AFB1 for induction of micronuclei and double-strand DNA breaks (indicated by an elevation of γ-H2AX) were analyzed. The results indicated that PCBs 20, 52 and 56 reduced the expression of AhR, while elevated that of CAR and PXR, with thresholds at low micromolar concentrations. However, they were less potent than PCB 126, which was active at sub-nanomolar levels. Overexpression of human splice variant CAR 3 in the cells increased CYP1A2 and 3A4 levels, which were further enhanced by each non-coplanar PCB, suggesting a role of CAR in modulating CYPs. Pretreatment of cells with each test PCB potentiated both micronuclei formation and DNA damage induced by AFB1. This study suggests that both non-coplanar and coplanar PCBs may enhance the genotoxicity of AFB1, through acting on various nuclear receptors; the potentiation of AFB1 genotoxicity by PCBs and the potential health implications may deserve concerns and further investigation.

To freeze, or not to freeze: the impact of subzero temperature on quantifying organic contaminants in ocean sediments.

Assessing the extent of ocean bed contamination by anthropogenic organic chemicals requires collecting and preserving the native state of sediments. The latter is particularly important since most sediment analyses are performed away from the sites of samples collection. Preservation, however, is presumptuous since commonly used sediment handling practices such as freezing are structurally disruptive, the impacts of which are not well understood. In this study, the impact of freezing on quantifying the total organic carbon (TOC) contents and the extent of PAH, DDT and PCB contamination in 17 split-paired sediment samples was investigated. The samples were collected from the Santa Monica Bay, California (USA). One-half of each split-pair was frozen at -20 °C and the other half was refrigerated at 4 °C for up to 11 days. The results suggest that no significant differences exist between the frozen and the refrigerated datasets for PCBs (F1,28 = 4.01, p > 0.05), DDTs (n = 16, t-Stat < t-Critical, p > 0.05) or TOC (n = 16, t-Stat < t-Critical, p > 0.05). The results however show that less PAHs were detected in the frozen sediments (F1,24 = 8.18, p < 0.05) than in the refrigerated sediments; the larger PAHs were affected the most. Interestingly, while benzo[a]pyrene, a large PAH molecule, was affected by this apparent temperature-induced difference, its structural isomer, benzo[e]pyrene, was not. Even more interesting was the finding that while non-coplanar PCBs were affected similarly, the coplanar PCBs were not. Overall, sediment freezing within this study's timeframe appears to offer little contextual advantage over sediment refrigeration.

Contamination of organohalogen chemicals and hepatic steatosis in common kingfisher (Alcedo atthis) breeding at a nature reserve near e-waste recycling sites in South China

Severe pollution of organohalogen compounds (OHCs) including PBDEs, PCBs and DDTs is demonstrated in e-waste recycling sites and metropolis in South China, but relatively little is known of their impacts on wildlife that inhabits nature reserves in this region, especially those located at the neighborhood areas of e-waste recycling sites. In the present study, PBDEs, PCBs and DDTs as well as liver histological changes were examined in common kingfisher breeding at a nature reserve (Shimentai National Nature Reserve, SNNR) near a notorious e-waste recycling site in South China. Mean ∑PBDEs (84.9 ng/g lipid weight), ∑PCBs (397 ng/g) and ∑TEQs (total toxic equivalent of coplanar PCBs, 2.68 ng/g) concentrations in kingfishers from SNNR were approximately 2-, 5-, and 4-fold higher than those detected in a reference population, respectively; suggesting contamination of the e-waste-derived OHCs in SNNR. Mean ∑DDTs concentration (2150 ng/g) in kingfishers from SNNR was also higher (~2-fold) than that from the reference samples. While ∑DDTs dominated the composition of the OHCs at both sampling sites, ∑PCBs was also important in kingfishers from SNNR, averaging 15% of ∑OHCs. Histological examination of the liver showed steatosis occurred in 60% of the kingfishers from SNNR. Birds with hepatic steatosis had significantly (p = 0.03) higher ∑TEQs than those without steatosis. Similar trends were also found for ∑PCBs and ∑DDTs, although it is not statistically significant. It therefore seems likely that the hepatic steatosis were associated with the relatively high body-burden of OHCs, although the possibility of other factors resulting in hepatic steatosis cannot be ruled out.

Prenatal exposure to PCBs in Cyp1a2 knock-out mice interferes with F1 fertility, impairs long-term potentiation, reduces acoustic startle and impairs conditioned freezing contextual memory with minimal transgenerational effects.

Polychlorinated biphenyls (PCBs) are toxic environmental pollutants. Humans are exposed to PCB mixtures via contaminated food or water. PCB exposure causes adverse effects in adults and after exposure in utero. PCB toxicity depends on the congener mixture and CYP1A2 gene activity. For coplanar PCBs, toxicity depends on ligand affinity for the aryl hydrocarbon receptor (AHR). Previously, we found that perinatal exposure of mice to a three-coplanar/five-noncoplanar PCB mixture induced deficits in novel object recognition and trial failures in the Morris water maze in Cyp1a2-/- ::Ahrb1 C57BL6/J mice compared with wild-type mice (Ahrb1 =high AHR affinity). Here we exposed gravid Cyp1a2-/- ::Ahrb1 mice to a PCB mixture on embryonic day 10.5 by gavage and examined the F1 and F3 offspring (not F2 ). PCB-exposed F1 mice exhibited increased open-field central time, reduced acoustic startle, greater conditioned contextual freezing and reduced CA1 hippocampal long-term potentiation with no change in spatial learning or memory. F1 mice also had inhibited growth, decreased heart rate and cardiac output, and impaired fertility. F3 mice showed few effects. Gene expression changes were primarily in F1 PCB males compared with wild-type males. There were minimal RNA and DNA methylation changes in the hippocampus from F1 to F3 with no clear relevance to the functional effects. F0 PCB exposure during a period of rapid DNA de-/remethylation in a susceptible genotype produced clear F1 effects with little evidence of transgenerational effects in the F3 generation. While PCBs show clear developmental neurotoxicity, their effects do not persist across generations for effects assessed herein.

Polychlorinated biphenyl 126 exposure in rats alters skeletal muscle mitochondrial function

In the past few years, polychlorinated biphenyls (PCBs), a class of environmental pollutants, have been associated with metabolism dysregulation. Muscle is one of the key regulators of metabolism because of its mass and its important role in terms of glucose consumption and glucose storage. It has been shown that muscle alterations, such as oxidative stress and mitochondrial dysfunction, contribute significantly to the development of metabolic diseases. No study has yet investigated the toxicological effect of PCBs on muscle mitochondrial function and oxidative stress in vivo. The aim of this study was to assess the effect of PCB126 in vivo exposure (single dose of 1.05μmol/kg) on muscle mitochondrial function and oxidative stress in rats. PCB126-treated rats showed a marked increase in Cyp1a1 mRNA levels in skeletal muscles in association with a 40% reduction in state 3 oxygen consumption rate measured with complex I substrates in permeabilized muscle fibers. Furthermore, PCB126 exposure altered the expression of some enzymes involved in ROS detoxification such as catalase and glutaredoxin 2. Our results highlight for the first time a toxic effect of coplanar PCBs on skeletal muscle mitochondrial function and oxidative stress. This suggests that acute PCB exposure, by affecting muscle metabolism, could contribute to the development of metabolic disorders. Studies are needed to determine if lower-level but longer-term PCB exposure exhibits the same effect.

Comparisons of analytical chemistry and biological activities of extracts from North Pacific gyre plastics with UV-treated and untreated plastics using in vitro and in vivo models

Plastic debris is an emerging worldwide threat to marine biota. Marine species may face unique challenges in low-flow estuarine systems with a high abundance of “macro-sized” (>4.75 mm) plastic due to the leaching of constituents and adsorbed contaminants. To simulate this leaching process, plastic samples recovered from the North Pacific Gyre along with corresponding UV-irradiated virgin plastic and non-irradiated virgin plastic counterparts were incubated in saltwater for 30 days at ambient temperatures ranging from 17 to 25 °C. Following solid-phase extraction, water samples were fractionated with sequential methanol elution from 10 to 100% and evaluated using in vitro assays assessing estrogen receptor (ER) and aryl hydrocarbon receptor (AhR) activities. In vivo responses (vitellogenin [vtg] and cytochrome p450 1A [cyp1a] mRNA) were measured following 5-day exposures in Japanese medaka (Oryzias latipes) larvae (3 days post hatch). Estrogenic plasticizers, co-planar PCBs and PAHs were quantified in the extracts using targeted GC–MS/MS and UPLC-MS/MS. In vitro estrogenicity showed highest activity in the 70% methanol fraction for all plastic leachate exposures. Whole extract in vitro estradiol equivalent (EEQ) values were 4.34 ± 2.65, 8.79 ± 2.09 and 13.78 ± 3.64 ng/L, for virgin plastic, UV-irradiated virgin plastic and North Pacific Gyre-recovered plastic, respectively (mean ± SD). Significant vtg induction was observed in medaka larvae exposed to leachate extracts from North Pacific Gyre-recovered plastic and UV-irradiated virgin plastic (9.9-fold, p = 0.039 and 10.1-fold, p = 0.042, respectively). Chemically-determined EEQ values were also localized in the 70% methanol fraction. Whole leachate extract chemical EEQ values were 0.33 ± 0.07, 1.64 ± 0.62 and 11.4 ± 2.13 ng/L, for virgin plastic, UV-irradiated virgin plastic and North Pacific Gyre-recovered plastic, respectively. In-vitro AhR activity was highest in the 70% methanol elution with greater activity in North Pacific Gyre-recovered plastic than in virgin plastic and UV-irradiated virgin plastic (toxic equivalency [TEQ] = 1.06 ± 0.54, 0.38 ± 0.07 and 0.71 ± 0.47 ng/L, respectively). CYP1A mRNA was significantly induced in larval medaka exposed to North Pacific Gyre-recovered plastic leachates (17.8-fold, p = 0.02) while exposure to virgin plastic and UV-irradiated virgin plastic leachates caused no significant change. Chemically-determined TEQ analysis for AhR indicated highest activity in the 90% methanol fraction for all leachates, with whole extract in vitro TEQs being 1.47 ± 0.87, 0.03 ± 0.05 and 0.42 ± 0.38 ng/L for North Pacific Gyre-recovered plastic, virgin plastic and UV-irradiated virgin plastic, respectively. These results indicate that weathering and UV radiation release estrogenic plasticizers and demonstrate the ability for plastics to transport adsorbed persistent organic pollutants at eco-toxicologically relevant concentrations.

Characterization of AHR1 and its functional activity in Atlantic sturgeon and shortnose sturgeon

Sturgeon species are imperiled world-wide by a variety of anthropogenic stressors including chemical contaminants. Atlantic sturgeon, Acipenser oxyrinchus, and shortnose sturgeon, Acipenser brevirostrum, are largely sympatric acipenserids whose young life-stages are often exposed to high levels of benthic-borne PCBs and PCDD/Fs in large estuaries along the Atlantic Coast of North America. In previous laboratory studies, we demonstrated that both sturgeon species are sensitive to early life-stage toxicities from exposure to environmentally relevant concentrations of coplanar PCBs and TCDD. The sensitivity of young life-stages of fishes to these contaminants varies among species by three orders of magnitude and often is due to variation in the structure and function of the aryl hydrocarbon receptor (AHR) pathway. Unlike mammals, fishes have two forms of AHR (AHR1 and AHR2) with AHR2 usually being more highly expressed across tissues and functional in mediating toxicities. Based on previous studies in white sturgeon, A. transmontanus, we hypothesized that sturgeon taxa are unusually sensitive to these contaminants because of higher levels of expression and functional activity of AHR1 than in other fish taxa. To address this possibility, we characterized AHR1 in both Atlantic Coast sturgeon species, evaluated its’ in vivo expression in young life-stages and in multiple tissues of shortnose sturgeon, and tested its ability to drive reporter gene expression in AHR-deficient cells treated with graded doses of PCB126 and TCDD. Similar to white sturgeon and lake sturgeon, AHR1 amino acid sequences in Atlantic sturgeon and shortnose sturgeon were more similar to mammalian AHRs and avian AHR1s than to AHR1 in other fishes, suggesting their greater functionality in sturgeon species than in other fishes. Exposure to graded doses of coplanar PCBs and TCDD usually failed to significantly induce AHR1 expression in young life-stages or most tissues of shortnose sturgeon. However, in reporter gene assays, AHR1 drove higher levels of gene expression than AHR2 alone, but their binary combination failed to drive higher levels of expression than either AHR alone. In total, our results suggest that AHR1 may be more functional in sturgeon species than in other fishes, but probably does not explain their heightened sensitivity to these contaminants.

Examination of contaminant exposure and reproduction of ospreys (Pandion haliaetus) nesting in Delaware Bay and River in 2015

A study of ospreys (Pandion haliaetus) nesting in the coastal Inland Bays of Delaware, and the Delaware Bay and Delaware River in 2015 examined spatial and temporal trends in contaminant exposure, food web transfer and reproduction. Concentrations of organochlorine pesticides and metabolites, polychlorinated biphenyls (PCBs), coplanar PCB toxic equivalents, polybrominated diphenyl ethers (PBDEs) and other flame retardants in sample eggs were generally greatest in the Delaware River. Concentrations of legacy contaminants in 2015 Delaware Bay eggs were lower than values observed in the 1970s through early 2000s. Several alternative brominated flame retardants were rarely detected, with only TBPH [bis(2-ethylhexyl)-tetrabromophthalate)] present in 5 of 27 samples at <5 ng/g wet weight. No relation was found between p,p′-DDE, total PCBs or total PBDEs in eggs with egg hatching, eggs lost from nests, nestling loss, fledging and nest success. Osprey eggshell thickness recovered to pre-DDT era values, and productivity was adequate to sustain a stable population. Prey fish contaminant concentrations were generally less than those in osprey eggs, with detection frequencies and concentrations greatest in white perch (Morone americana) from Delaware River compared to the Bay. Biomagnification factors from fish to eggs for p,p′-DDE and total PCBs were generally similar to findings from several Chesapeake Bay tributaries. Overall, findings suggest that there have been improvements in Delaware Estuary waterbird habitat compared to the second half of the 20th century. This trend is in part associated with mitigation of some anthropogenic contaminant threats.