PCB-related alteration of thyroid hormones and thyroid hormone receptor gene expression in free-ranging harbor seals (Phoca vitulina)

Blubber gene expression and cortisol concentrations reveal changing physiological stress in a Southern ocean sentinel species

The health of migratory eastern Australian humpback whales (Megaptera novaeangliae) can reflect the condition of their remote polar foraging environments. This study used gene expression (LEP, LEPR, ADIQ, AhR, TNF-α, HSP-70), blubber hormone concentrations (cortisol, testosterone), and photogrammetric body condition to assess this sentinel species during a period of unprecedented changes to anthropogenic activity and natural processes. The results revealed higher cortisol concentrations in 2020 compared to 2021, suggesting a decline in physiological stress between years. Additionally, metabolic transcripts LEPR, and AhR, which is also linked to xenobiotic metabolism, were upregulated during the 2020 southbound migration. These differences suggest that one or more environmental stressors were reduced between 2020 and 2021, with upregulated AhR possibly indicating a Southern Ocean pollutant declined between the years. This research confirms a Southern Ocean-wide decrease in whale stress during the study period and informs efforts to identify key stressors on Antarctic marine ecosystems.

Variations in thyroid hormone levels in endangered St. Lawrence Estuary belugas: Potential linkage with stress and organohalogen contaminant exposure

The St. Lawrence Estuary (SLE) beluga (Delphinapterus leucas) population is highly exposed to an array of contaminants that were identified as one of the causes to the non-recovery of this endangered and declining population. In the last decade, an increasing number of parturition-associated complications and calf mortality has been reported in this population. It was suggested that elevated exposure to organohalogens (e.g., the halogenated flame retardants polybrominated diphenyl ethers [PBDEs]) and stress could play a role in this phenomenon by perturbing thyroid hormones. The objective of this study was to investigate the impact of concentrations of organohalogen contaminants and stress (cortisol levels) on thyroid hormone variations in adult male and female SLE belugas. Because plasma could not be collected in SLE belugas for ethical reasons, skin biopsy (n = 40) was used as a less-invasive alternative matrix to determine organohalogens (PBDEs and other halogenated flame retardants, polychlorinated biphenyls, and organochlorine pesticides), cortisol, and thyroid hormones (triiodothyronine [T3] and thyroxine [T4]), and their metabolites reverse T3 and 3,5-diiodothyronine [3,5-T2]). Cortisol and thyroid hormones were analyzed by ultra-performance liquid chromatography-multiple reactions monitoring mass spectrometry (UPLC-MRM/MS). This method was compared using skin and plasma samples obtained from Arctic belugas. Comparisons of linear models showed that cortisol was a weak predictor for T4, rT3 and 3,5-T2. Specifically, there was a weak significant negative association between T4 and cortisol levels. Moreover, in male SLE belugas, a weak significant positive association was found between T3 and Σ34PBDE concentrations in skin. Our findings suggest that stress (i.e., elevated skin cortisol levels) along with organohalogen exposure (mainly PBDEs) may be associated with thyroid hormone level perturbations in skin of cetaceans.

Gene expression and trace elements in Greenlandic ringed seals (Pusa hispida)

Marine top predators such as ringed seals biomagnify environmental contaminants; and with the increasing human activities in the Arctic, ringed seals are exposed to biologically significant concentrations of trace elements resulting in reproductive impairment, immunosuppression, and neurological damages. Little is known about the molecular effects of heavy metals on these vulnerable apex predators suffering from a rapidly changing Arctic with significant loss of sea-ice. In the present study, concentrations of cadmium (Cd), mercury (Hg) and selenium (Se) were measured in liver of sixteen Greenlandic ringed seals (nine adults and seven subadults) together with molecular biomarkers involved in bio-transformation, oxidative stress, endocrine disruption and immune activity in blood and blubber. The concentrations of trace elements increased in the following order: Hg > Se > Cd with levels of mercury and selenium being highest in adults. Aryl hydrocarbon receptor nuclear translocator (ARNT), peroxisome proliferator activated receptor alpha (PPARα, estrogen receptor alpha (ESR1), thyroid hormone receptor alpha (TRα) and interleukin - 2 (IL-2) mRNA transcript levels were highest in blubber, while heat shock protein 70 (HSP70) and interleukin - 10 (IL-10) were significantly higher in blood. There were no significant correlations between the concentrations of trace elements and mRNA transcript levels suggesting that stressors other than the trace elements investigated are responsible for the changes in gene expression levels. Since Hg seems to increase in Greenlandic ringed seals, there is a need to re-enforce health monitoring of this ringed seal population.

The dynamics of persistent organic pollutant (POP) transfer from female bottlenose dolphins (Tursiops truncatus) to their calves during lactation

Persistent organic pollutants (POPs) are lipophilic compounds that can accumulate in high concentrations in the blubber of marine mammals, which are long-lived, top-level predators in their ecosystems. These compounds, which include DDTs, PCBs, PBDEs, HCHs, and CHLDs, impact mammalian health, including neurological effects, reduced immune system efficiency, and reproductive failure. POPs are transferred from females to their offspring during gestation and lactation, which have implications for the health of newborn marine mammals, particularly first-born offspring who receive higher concentrations. The dynamics of POP transfer during lactation have been studied in a few pinniped species, but there are no comparable studies on living cetaceans. Because life history strategies and behavior of lactating phocids differ from dolphins, a study on delphinid maternal transfer is warranted. To accomplish this, placenta and longitudinally collected blood and milk samples were taken concurrently from trained bottlenose dolphin, Tursiops truncatus, mother/calf pairs to assess the dynamics of maternal contaminant transfer. Initial POP levels in placenta, blood serum, and milk varied by individual and were related to the age and reproductive history of the females. Regardless of initial POP levels, maternal serum and milk concentrations decreased while calf serum POP levels increased over time. Pollutant transfer varied by POP class and by congener. Contaminant transfer efficiency to calves was most apparent for 4- to 6‑chlorine PCBs, DDT isomers p,p'-DDD, p,p'-DDT, o,p'-DDD, and o,p'-DDE, trans-nonachlor, cis-nonachlor, heptachlor epoxide, nonachlor III, and oxychlordane. By the end of the lactation period, calf serum POP levels were considerably greater than those of their mothers, particularly for compounds with fewer chlorines. POP levels were most biomagnified in the calf born to the primiparous female. These results provide critical information on one component of contaminant transfer in the marine ecosystem and for understanding potential risks of POP exposure to developing odontocete calves.

Alternative and legacy flame retardants in marine mammals from three northern ocean regions

Flame retardants are globally distributed contaminants that have been linked to negative health effects in humans and wildlife. As top predators, marine mammals bioaccumulate flame retardants and other contaminants in their tissues which is one of many human-imposed factors threatening population health. While some flame retardants, such as the polybrominated diphenyl ethers (PBDE), have been banned because of known toxicity and environmental persistence, limited data exist on the presence and distribution of current-use alternative flame retardants in marine mammals from many industrialized and remote regions of the world. Therefore, this study measured 44 legacy and alternative flame retardants in nine marine mammal species from three ocean regions: the Northwest Atlantic, the Arctic, and the Baltic allowing for regional, species, age, body condition, temporal, and tissue comparisons to help understand global patterns. PBDE concentrations were 100-1000 times higher than the alternative brominated flame retardants (altBFRs) and Dechloranes. 2,2',4,5,5'-pentabromobiphenyl (BB-101) and hexabromobenzene (HBBZ) were the predominant altBFRs, while Dechlorane-602 was the predominant Dechlorane. This manuscript also reports only the second detection of hexachlorocyclopentadienyl-dibromocyclooctane (HCDBCO) in marine mammals. The NW Atlantic had the highest PBDE concentrations followed by the Baltic and Arctic which reflects greater historical use of PBDEs in North America compared to Europe and greater industrialization of North America and Baltic countries compared to the Arctic. Regional patterns for other compounds were more complicated, and there were significant interactions among species, regions, body condition and age class. Lipid-normalized PBDE concentrations in harbor seal liver and blubber were similar, but HBBZ and many Dechloranes had higher concentrations in liver, indicating factors other than lipid dynamics affect the distribution of these compounds. The health implications of contamination by this mixture of compounds are of concern and require further research.

Fitness correlates of blubber oxidative stress and cellular defences in grey seals (Halichoerus grypus): support for the life-history-oxidative stress theory from an animal model of simultaneous lactation and fasting

Life-history-oxidative stress theory predicts that elevated energy costs during reproduction reduce allocation to defences and increase cellular stress, with fitness consequences, particularly when resources are limited. As capital breeders, grey seals are a natural system in which to test this theory. We investigated oxidative damage (malondialdehyde (MDA) concentration) and cellular defences (relative mRNA abundance of heat shock proteins (Hsps) and redox enzymes (REs)) in blubber of wild female grey seals during the lactation fast (n = 17) and summer foraging (n = 13). Transcript abundance of Hsc70 increased, and Nox4, a pro-oxidant enzyme, decreased throughout lactation. Foraging females had higher mRNA abundance of some Hsps and lower RE transcript abundance and MDA concentrations, suggesting they experienced lower oxidative stress than lactating mothers, which diverted resources into pup rearing at the expense of blubber tissue damage. Lactation duration and maternal mass loss rate were both positively related to pup weaning mass. Pups whose mothers had higher blubber glutathione-S-transferase (GST) expression at early lactation gained mass more slowly. Higher glutathione peroxidase (GPx) and lower catalase (CAT) were associated with longer lactation but reduced maternal transfer efficiency and lower pup weaning mass. Cellular stress, and the ability to mount effective cellular defences, could proscribe lactation strategy in grey seal mothers and thus affect pup survival probability. These data support the life-history-oxidative stress hypothesis in a capital breeding mammal and suggest lactation is a period of heightened vulnerability to environmental factors that exacerbate cellular stress. Fitness consequences of stress may thus be accentuated during periods of rapid environmental change.

Influence of chemical dose and exposure duration on protein synthesis in green sea turtle primary cells

Understanding the impacts of chemical exposure in marine wildlife is challenging, due to practical and ethical constraints that preclude traditional toxicology research on these animals. This study addressed some of these limitations by presenting an ethical and high throughput cell-based approach to elucidate molecular-level effects of contaminants on sea turtles. The experimental design addressed basic questions of cell-based toxicology, including chemical dose and exposure time. Primary green turtle skin cells were exposed to polychlorinated biphenyl (PCB) 153 and perfluorononanoic acid (PFNA) for 24 and 48 h, at three sub-lethal, environmentally relevant concentrations (1, 10 and 100 μg/L). Sequential window acquisition of all theoretical mass spectra (SWATH-MS) identified over 1000 differentially abundant proteins within the 1% false discovery rate (FDR) threshold. The 24 h exposure resulted in a greater number of differentially abundant proteins, compared to 48 h exposure, for both contaminants. However, there were no statistically significant dose-response relationships for the number of differentially synthesised proteins, nor differences in the proportion of increased vs decreased proteins between or within exposure times. Known in vivo markers of contaminant exposure, superoxide dismutase and glutathione S-transferase, were differentially abundant following exposure to PCB153 and PFNA. SIGNIFICANCE: Cell-based (in vitro) proteomics provides an ethical and high throughput approach to understanding the impacts of chemical contamination on sea turtles. Through investigating effects of chemical dose and exposure duration on unique protein abundance in vitro, this study provides an optimised framework for conducting cell-based studies in wildlife proteomics, and highlights that proteins detected in vitro could act as biomarkers of chemical exposure and effect in vivo.

Establishment of killer whale (Orcinus orca) primary fibroblast cell cultures and their transcriptomic responses to pollutant exposure

Populations of killer whale (Orcinus orca) contain some of the most polluted animals on Earth. Yet, the knowledge on effects of chemical pollutants is limited in this species. Cell cultures and in vitro exposure experiments are pertinent tools to study effects of pollutants in free-ranging marine mammals. To investigate transcriptional responses to pollutants in killer whale cells, we collected skin biopsies of killer whales from the Northern Norwegian fjords and successfully established primary fibroblast cell cultures from the dermis of 4 out of 5 of them. Cells from the individual with the highest cell yield were exposed to three different concentrations of a mixture of persistent organic pollutants (POPs) that reflects the composition of the 10 most abundant POPs found in Norwegian killer whales (p,p'-DDE, trans-nonachlor, PCB52, 99, 101, 118, 138, 153, 180, 187). Transcriptional responses of 13 selected target genes were studied using digital droplet PCR, and whole transcriptome responses were investigated utilizing RNA sequencing. Among the target genes analysed, CYP1A1 was significantly downregulated in the cells exposed to medium (11.6 µM) and high (116 µM) concentrations of the pollutant mixture, while seven genes involved in endocrine functions showed a non-significant tendency to be upregulated at the highest exposure concentration. Bioinformatic analyses of RNA-seq data indicated that 13 and 43 genes were differentially expressed in the cells exposed to low and high concentrations of the mixture, respectively, in comparison to solvent control. Subsequent pathway and functional analyses of the differentially expressed genes indicated that the enriched pathways were mainly related to lipid metabolism, myogenesis and glucocorticoid receptor regulation. The current study results support previous correlative studies and provide cause-effect relationships, which is highly relevant for chemical and environmental management.

Persistent organic pollutant exposure and associations with gene expression in northern fur seals (Callorhinus ursinus) from St. Paul Island, Alaska

Persistent organic pollutants (POPs) are highly lipophilic compounds that accumulate at increased concentrations in high tropic level organisms like marine mammals. Marine mammals' reliance on blubber makes them susceptible to accumulating POPs at potentially toxic concentrations. In this study, we analyzed POP concentrations, (polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs), and methoxylated-BDE (MeOBDE), in the blubber of 16 subsistence harvested sub-adult, male northern fur seals as well as assessed changes in mRNA gene expression of nine relevant biomarkers including the aryl hydrocarbon receptor, thyroid receptor-α, and adiponectin. PBDE and MeOBDE concentrations were significantly lower than PCB and OCP concentrations. A negative relationship was observed between percent lipid in the blubber and contaminant concentrations, both individual and sum. Expression changes in eight biomarkers were correlated with individual and sum contaminant concentrations. This study shows that contaminant concentrations measured are correlated to changes in expression of genes from different physiological systems, metabolism and endocrine, that are important for the regulation of blubber metabolism. Northern fur seals are reliant on blubber as an energy source during times of low food intake. Potential contaminant induced changes in blubber metabolism pathways could have significant impacts on the health of individuals during critical periods.

A mammalian messenger RNA sex determination method from humpback whale (Megaptera novaeangliae) blubber biopsies

The large size of free-ranging mysticetes, such as humpback whales (Megaptera novaeangliae), make capture and release health assessments unfeasible for conservation research. However, individual energetic condition or reproductive health may be assessed from the gene expression of remotely biopsied tissue. To do this, researchers must reliably extract RNA and interpret gene expression measurements within the context of an individual's sex. Here, we outline an RNA extraction protocol from blubber tissue and describe a novel mammalian RNA sex determination method. Our method consists of a duplex reverse transcription-quantitative (real-time) polymerase chain reaction (RT-qPCR) with primer sets for a control gene (ACTB) and the X-chromosome inactivation gene (XIST). Products of each RT-qPCR had distinct melting temperature profiles based on the presence (female) or absence (male) of the XIST transcript. Using high-resolution melt analysis, reactions were sorted into one of two clusters (male/female) based on their melting profiles. We validated the XIST method by comparing results with a standard DNA-based method. With adequate quantities of RNA (minimum of approx. 9 ng µl^-1), the XIST sex determination method shows 100% agreement with traditional DNA sex determination. Using the XIST method, future cetacean health studies can interpret gene expression within the context of an individual's sex, all from a single extraction.

Relationships between gene transcription and contaminant concentrations in Baltic ringed seals: A comparison between tissue matrices

Ringed seals (Pusa hispida) are slowly recovering in the eastern and northern parts of the Baltic Sea after years of hunting pressure and contaminant exposure. Still, consequences of anthropogenic activities such as contaminant exposure and increasing temperatures are stressors that continue to have deleterious effects on their habitat and health. Transcription profiles of seven health-related genes involved in xenobiotic metabolism, endocrine disruption and stress were evaluated in blood, blubber, and liver of Baltic ringed seals in a multi-tissue approach. Selected persistent organic pollutants and total mercury concentrations were measured in blubber and liver, and muscle and liver of these animals, respectively. Concentrations of contaminants varied across tissues on a lipid weight basis but not with sex. mRNA transcript levels for all seven target genes did not vary between sexes or age classes. Transcript levels of thyroid hormone receptor alpha (TRα), retinoic acid receptor alpha (RARα) and heat shock protein 70 (HSP70) correlated with levels of persistent organic pollutants. TRα transcript levels also correlated positively with mercury concentrations in the liver. Of the three tissues assessed in this multi-tissue approach, blubber showed highest transcription levels of aryl hydrocarbon receptor nuclear translocator (ARNT), thyroid stimulating hormone receptor beta (TSHβ), oestrogen receptor alpha (ESR1) and peroxisome proliferator activated receptor alpha (PPARα). The wide range of genes expressed highlights the value of minimally invasive sampling (e.g. biopsies) for assessing health endpoints in free-ranging marine wildlife and the importance of identifying optimal matrices for targeted gene expression studies. This gene transcript profile study has provided baseline information on transcript levels of biomarkers for early on-set health effects in ringed seals and will be a useful guide to assess the impacts of environmental change in Baltic pinnipeds for conservation and management.

Predicting consequences of POP-induced disruption of blubber glucose uptake, mass gain rate and thyroid hormone levels for weaning mass in grey seal pups

Persistent organic pollutants (POPs) are endocrine disruptors that alter adipose tissue development, regulation and function. Top marine predators are particularly vulnerable because they possess large fat stores that accumulate POPs. However, links between endocrine or adipose tissue function disruption and whole animal energetics have rarely been investigated. We predicted the impact of alterations to blubber metabolic characteristics and circulating thyroid hormone (TH) levels associated with polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCPs) on suckling mass gain and weaning mass in wild grey seal pups. Glucose uptake by inner blubber was a strong predictor of whole animal mass gain rate, which in turn, resulted in heavier weaning mass. Weaning mass was predicted to increase by 3.7 ± 1.59 (sem) %, through increased mass gain rate, in the absence of the previously reported suppressive effect of dioxin-like PCB (DL-PCBs) on blubber glucose uptake. PBDEs were, conversely, associated with faster mass gain. Alleviation of this effect was predicted to reduce weaning mass by 6.02 ± 1.86% (sem). To better predict POPs effects on energy balance, it is crucial to determine if and how PBDEs promote mass gain in grey seal pups. Weaning mass was negatively related to total T3 (TT3) levels. A 20% (range = 9.3-31.7%) reduction in TT3 by DL-PCBs partially overcame the effect of DL-PCB -mediated reduction in blubber glucose uptake. Overall, DL-PCBs were thus predicted to reduce weaning mass by 1.86 ± 1.60%. Organohalogen impacts on whole-animal energy balance in grey seal pups appear to partially offset each other through opposing effects on different mechanisms. POP effects were generally minor, but the largest POP-induced reductions in weaning mass were predicted to occur in pups that were already small. Since weaning mass is positively related to first-year survival, POPs may disproportionately affect smaller individuals, and could continue to have population-level impacts even when levels are relatively low compared to historical values. Our findings show how in vitro experiments combined with measurements in vivo can help elucidate mechanisms that underpin energy balance regulation and help to quantify the magnitude of disruptive effects by contaminants and other stressors in wildlife.

Circulating concentrations of thyroid hormones and cortisol in wild and semi-natural Yangtze finless porpoise (Neophocaena asiaeorientalis)

Our understanding about how environmental and biological variables may influence circulating thyroid and adrenal hormones in free-ranging cetaceans is limited. As such, we used liquid chromatography-mass spectrometry to determine concentrations of circulating cortisol and thyroid hormones (THs; tT3, tT4) in 132 Yangtze finless porpoises (YFPs) located in Poyang Lake, (PL, n = 92) and Tian-E-Zhou Oxbow reserve (TZO, n = 40). For overall hormone comparisons, animals were partitioned by age [juvenile and adult (male and non-pregnant, non-lactating female)], sex, season (winter or spring) and geographical location. Geographically, during winter, circulating THs were significantly higher in the PL versus TZO population. Seasonally, within PL, THs were significantly higher in the winter versus spring season. Animals were further binned into groups as follows: juvenile male (JM) and juvenile female (JF), adult male (AM), non-pregnant adult female, pregnant female and non-pregnant lactating female. Intra-group comparisons between locations showed a significant increase in JM THs at PL. Significant increases in THs during winter compared to spring were detected between JM and JF groups. Mean comparisons of cortisol within and between locations for each group identified a significant increase for TZO AM versus TZO pregnant female and JM and JF. Seasonally, in PL, only JF has significantly higher cortisol in winter versus spring. Finally, we established reference values of THs and cortisol for YFPs in different geographical locations. These references are important baselines from which the effects of environmental and biological variables on THs and cortisol may be evaluated.

Long-Term Immunological Alterations in Bottlenose Dolphin a Decade after the Deepwater Horizon Oil Spill in the Northern Gulf of Mexico: Potential for Multigenerational Effects

Health assessments were conducted on bottlenose dolphins in Barataria Bay, Louisiana, USA, during 2011 to 2018, to assess potential health effects following the Deepwater Horizon oil spill, compared to the unoiled Sarasota Bay, Florida, USA, reference dolphin population. We previously reported significant increases in T-lymphocyte proliferation, as well as lower T helper 1 (Th1) cytokines, higher Th2 cytokine IL-4, and lower T regulatory (Treg) cytokine IL-10 in Barataria Bay in 2011 compared to Sarasota Bay, consistent with Deepwater Horizon oil exposure. Although values between 2013 and 2016 were more similar to those observed in Sarasota Bay, T-cell proliferation was again elevated and cytokine balance tilted toward Th2 in Barataria Bay during 2017-2018. In 2018, Barataria Bay dolphins had significantly more circulating Treg cells than Sarasota Bay dolphins. Mice experimentally exposed to oil also had significantly increased T-lymphocyte proliferation and circulating Treg cell number, including effects in their unexposed progeny. In vitro stimulation resulted in greater Th2 responsiveness in Barataria Bay compared to Sarasota Bay dolphins, and in vitro oil exposure of Sarasota Bay dolphin cells also resulted in enhanced Th2 responsiveness. Evidence points to Treg cells as a potential target for the immunomodulatory effects of oil exposure. The immunological trends observed in Barataria Bay appeared exaggerated in dolphins born after the spill, suggesting the possibility of continued oil exposure or multigenerational health consequences of exposure to oil, as observed in mice. Environ Toxicol Chem 2021;40:1308-1321. © 2021 SETAC.

Changes in thyroid hormone related proteins and gene expression induced by polychlorinated biphenyls and halogen flame retardants exposure of children in a Chinese e-waste recycling area

Polychlorinated biphenyls (PCBs) and halogen flame retardants (HFRs) are major pollutants in e-waste recycling area. High internal exposure levels of PCBs and HFRs are harmful to human thyroid hormone (TH) equilibrium. To examine their disrupting effects on TH, we conducted a study on children (n = 114) of an e-waste recycling and a control area in South China. Concentrations of PCBs, HFRs, and TH levels were determined in serum samples. TH related proteins and their corresponding gene were also monitored as markers of such disruption. Levels of these chemicals in the exposed group were much greater than those in the control group. Results of the linear regression and generalized additive model indicated the presence of close relationships between the internal exposure levels and the responses of TH related proteins, gene expression. More extensive exposure concentrations of these chemicals led to higher expression of iodothyronine deiodinase I and decreased the concentrations of thyroid-stimulating hormone, expression of TH receptor α, indicating the exertion of discrepant and even contrary influences on equilibrium of TH, and a compensation of these mechanisms may kept the homeostasis of TH. These results for children warrant further investigation on the health risks of PCBs and HFRs exposure in e-waste area.

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 L_{external structure} ∙ H_{polar 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 C_micro effect. The molecular structure L ∙ H_{polar group}^-1 for Neu5Ac is 0.080, and the L ∙ H_{polar group}^-1 interval range for the cell surface glycocalyx hydrophilicity barrier interaction is 0.101 (Saxitoxin, Stx; L_{internal structure} ∙ H_{polar group}^-1) - 0.092 (m-xylenediamine, L_{external structure} · H_{polar 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, L_ext · 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 (L_ext · 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 C_micro contraction of 0.89 and Δ C_micro 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 C_micro contraction of 0.73 and Δ C_micro expansion of 1.18 (as compared to p-dioxin). Bisphenol A exposure (L_{ext struct} ∙ H^-1: 1.08–1.12, BPA–BPE, Errγ; BPAF, L_{ext struct} ∙ H^-1: 1.23, CM Erα, β) results in increased duration at P_eff for Timm8b (P_eff 0.247) transcription and in indirect activation of the AhR/Nrf-2 hybrid pathway with decreased duration at P_eff 0.200 (Nrf1) and increased duration at P_eff 0.257 (Dffa). The Bpa/Bpaf convergent pathway C_micro contraction-expansion response increase in the lower P_eff interval is 0.040; in comparison, small molecule hormone Δ C_micro contraction-expansion response increases in the lower P_eff intervals for gene expression ≤ 0.168 (Dex· GR) ≥ 0.156 (Dht · AR), with grade of duration at P_eff (min·count) of 1.33x10⁵ (Dex/Cort) and 1.8–2.53x10⁵ (Dht/R1881) as compared to the (-) coupled (+) Δ C_microP_eff 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-C_micro determined by P_eff mapping. Study findings offer additional perspective on the basis for pressure regulated gene transcription by alterations in cell micro-compliance (Δ contraction-expansion, C_micro), and are applicable for the further predictive modeling of gene to gene transcription interactions, and small molecule modulation of cell effective pressure (P_eff) and its potential.

Environmental Pollutants Modulate Transcriptional Activity of Nuclear Receptors of Whales In Vitro

This study reports the transcriptional activity of fin (Balaenoptera physalus) and blue whale (Balaenoptera musculus) peroxisome proliferator-activated receptor γ (PPARG), glucocorticoid receptor (GR), and thyroid hormone receptor β (THRB), when exposed to 14 persistent organic pollutants (so-called "legacy" persistent organic pollutants (POPs)) and a synthetic mixture of POPs, using GAL4-UAS-based in vitro luciferase reporter gene assays. Polychlorinated biphenyls (PCBs) had both agonistic and antagonistic effects on PPARG and GR, and mainly antagonistic, except for PCB153, effects on THRB. 1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and its metabolites had mainly antagonistic effects on all of the receptors, except for o,p'-DDT. Given that the ligand-binding domain (LBD) of PPARG is the same in killer whales, white whales, polar bears, and humans, and that GR-LBD is identical in killer whales and minke whales and that the LBD of THRB is the same in killer whales, white whales, and humans, it is likely that the results of this study are representative for these other species as well. It is important to note that several environmental pollutants modulated the transcriptional activity of tested nuclear receptors at environmentally relevant concentrations for whales.

Disruption of thyroid hormone regulated proteins and gene expression by polychlorinated biphenyls, polybrominated diphenyl ethers and new flame retardants in residents of an e-waste region

Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and new flame retardants (NFRs) are known thyroid hormone (TH) disruptors, but their disrupting mechanisms in humans are not completely understood. In this study, we aimed to explore the disrupting mechanisms of the aforementioned chemicals via examining TH-regulated proteins and gene expression in human serum. Adult participants from an e-waste dismantling (exposed group) and a control region (control group) in South China provided blood samples for the research. Some compounds of PCBs, PBDEs, and NFRs showed strong binding affinity to the thyroid-stimulating hormone (TSH), thyroglobulin, thyroxine-binding globulin (TBG), gene expression of TH receptor α (TRα) and β, and iodothyronine deiodinase I (ID1). The highly exposed individuals had lower levels of TBG, TSH, and expression of TRα, but higher expression of ID1 than those of the control group. The disruption of TH-regulated proteins and gene expression suggested the exertion of different and, at times, even contradictory effects on TH disruption. However, no statistically significant difference was found in the TH levels between the exposed and the control group, implying that the TH disruption induced by these chemicals depends on the combined influence of multiple mechanisms. Gene expression appears to be an effective approach for investigations of TH disruption and the potential health effects.

Binding and activity of sulfated metabolites of lower-chlorinated polychlorinated biphenyls towards thyroid hormone receptor alpha

There has been long-standing evidence that the lower-chlorinated polychlorinated biphenyls (LC-PCBs) can be metabolized to hydroxylated metabolites (OH-PCBs), which play important roles in the LC-PCBs induced toxicity. Recently, multiple studies have demonstrated the further metabolic transformation of OH-PCBs to LC-PCB sulfates in vitro and in vivo. Several studies found LC-PCB sulfates could bind with thyroid hormone (TH) transport proteins in the serum, indicating the potential relevance of these metabolites in the TH system disruption effects. However, the interaction of LC-PCB sulfates with the TH nuclear receptor (TR), another kind of important functional protein in the TH system, has not been explored. Here, by using a fluorescence competitive binding assay, we demonstrated that LC-PCB sulfates could bind with TRα. Moreover, the LC-PCB sulfates had higher binding potency than their corresponding OH-PCB precursors. By using a luciferase reporter gene assay, we found the LC-PCB sulfates showed agonistic activity towards the TRα signaling pathway. Molecular docking simulation showed all the tested LC-PCB sulfates could fit into the ligand binding pocket of the TRα. The LC-PCB sulfates formed hydrogen bond interaction with arginine 228 residue of TRα by their sulfate groups, which might facilitate the TR binding and agonistic activity. The present study suggests that interaction with the TR might be another possible mechanism by which LC-PCB sulfate induce TH system disruption effects.

2,3',4,4',5-Pentachlorobiphenyl induced autophagy of the thyrocytes via DAPK2/PKD/VPS34 pathway

2,3',4,4',5-Pentachlorobiphenyl (PCB118) has been shown to cause thyroidal ultrastructure lesions, but the underlying mechanism remains elusive. This study aimed to elucidate the mechanism by which PCB118 induces the abnormalities of the thyrocytes. Wistar rats were injected intraperitoneally with PCB118 (0, 10, 100 and 1000 μg/kg/d) for 13 weeks, and FRTL-5 cells were treated with PCB118 (0, 0.25, 2.5 and 25 nM). Transmission electron microscopy showed typical autophagosomes in the thyroid of PCB118-treated rats. Immunofluorescence staining showed dose-dependent increase of autophagy in FRTL-5 cells exposed to PCB118. In vivo and vitro studies found that Tubulin beta 3 class III (Tubb3) mRNA and protein levels decreased significantly, while Death-associated protein kinase 2 (DAPK2) increased after PCB118 exposure, and the binding between Tubb3 and DAPK2 was enhanced by PCB118 in a dose-dependent manner. Moreover, PCB118 resulted in the upregulation of Protein kinase D (PKD) and downregulation of Phosphatidylinositol 3-kinase (VPS34) in mRNA levels, and the activation of PKD and VPS34 phosphorylation. Additionally, Tubb3 small interfering RNA (siTubb3) suppressed DAPK2 protein expression and PKD phosphorylation in FRTL-5 cells, while VPS34 phosphorylation was inhibited by siPKD. Furthermore, DAPK2, PKD and VPS34 were upregulated by Tubb3 overexpression following PCB118 exposure. Our results demonstrate that low concentrations of PCB118 could promote thyroid autophagy formation and cause the abnormalities in thyroidal ultrastructure, and these effects are likely to be mediated by DAPK2/PKD/VPS34 dependent pathway.

Contaminant Exposure Linked to Cellular and Endocrine Biomarkers in Southern California Bottlenose Dolphins

Cetaceans in the Southern California Bight (SCB) are exposed to high levels of halogenated organic contaminants (HOCs), which have previously been linked to impaired reproductive health and immune responses. We used a combination of molecular tools to examine the potential physiological impacts of HOC exposure in two bottlenose dolphin ( Tursiops truncatus) ecotypes in the SCB. We quantified 25 HOCs in the blubber of 22 biopsies collected from males between 2012 and 2016. We then analyzed genome-wide gene expression in skin using RNA-sequencing and measured blubber testosterone to compare HOC exposure with cellular and endocrine biomarkers. We found high levels of HOCs in both ecotypes with significantly higher total polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), tris(4-chlorophenyl)methanol (TCPMOH), and chlordane-related compounds in the coastal ecotype versus the offshore ecotype. We found evidence of PBDE bioaccumulation in both ecotypes, however, the pattern of bioaccumulation or endocrine disruption for other HOCs was different between the ecotypes, suggesting potential endocrine disruption in the coastal ecotype. We also observed correlations between HOCs and gene coexpression networks enriched for xenobiotic metabolism, hormone metabolism, and immune response that could indicate cellular effects from HOC exposure. By integrating measurements of HOC load with both transcriptome profiling and endocrine biomarkers, our approach provides insight into HOC exposure and potential impacts on wild cetacean health in southern California.

Contaminants in Atlantic walruses in Svalbard Part 2: Relationships with endocrine and immune systems

Marine mammals in the Barents Sea region have among the highest levels of contaminants recorded in the Arctic and the Atlantic walrus (Odobenus rosmarus rosmarus) is one of the most contaminated species within this region. We therefore investigated the relationships bewteen blubber concentrations of lipophilic persistent organic pollutants (POPs) and plasma concentrations of perfluoroalkyl substances (PFASs) and markers of endocrine and immune functions in adult male Atlantic walruses (n = 38) from Svalbard, Norway. To do so, we assessed plasma concentrations of five forms of thyroid hormones and transcript levels of genes related to the endocrine and immune systems as endpoints; transcript levels of seven genes in blubber and 23 genes in blood cells were studied. Results indicated that plasma total thyroxine (TT4) concentrations and ratio of TT4 and reverse triiodothyronine decreased with increasing blubber concentrations of lipophilic POPs. Blood cell transcript levels of genes involved in the function of T and B cells (FC like receptors 2 and 5, cytotoxic T-lymphocyte associated protein 4 and protein tyrosine phosphatase non-receptor type 22) were increased with plasma PFAS concentrations. These results suggest that changes in thyroid and immune systems in adult male walruses are linked to current levels of contaminant exposure.

River otters (Lontra canadensis) "trapped" in a coastal environment contaminated with persistent organic pollutants: Demographic and physiological consequences

Productive coastal and estuarine habitats can be degraded by contaminants including persistent organic pollutants (POPs) such as PCBs, dioxins, and organochlorine insecticides to the extent of official designation as contaminated sites. Top-predatory wildlife may continue to use such sites as the habitat often appears suitable, and thus bioaccumulate POPs and other contaminants with potential consequences on their health and fitness. Victoria and Esquimalt harbours are located on southern Vancouver Island, British Columbia (BC) and are federally designated contaminated sites due mainly to past heavy industrial activities, such as from shipyards and sawmills. We collected scat samples from river otters (Lontra canadensis) throughout an annual cycle, and combined chemical analysis with DNA genotyping to examine whether the harbour areas constituted a contaminant-induced ecological trap for otters. We confirmed spatial habitat use by radio telemetry of a subsample of otters. Fifteen percent of otter scat contained PCB concentrations exceeding levels considered to have adverse effects on the reproduction of mink (Neovison vison), and there were significant positive correlations between concentrations of PCBs and of thyroid (T3) and sex (progesterone) hormones in fecal samples. Radio telemetry data revealed that otters did not show directional movement away from the harbours, indicating their inability to recognize the contaminated site as a degraded habitat. However, analysis and modeling of the DNA genotyping data provided no evidence that the harbour otters formed a sink population and therefore were in an ecological trap. Despite the highly POP-contaminated habitat, river otters did not appear to be adversely impacted at the population level. Our study demonstrates the value of combining chemical and biological technologies with ecological theory to investigate practical conservation problems.

Using Gene Transcription to Assess Ecological and Anthropological Stressors in Brown Bears

Increasingly, population- and ecosystem-level health assessments are performed using sophisticated molecular tools. Advances in molecular technology enable the identification of synergistic effects of multiple stressors on the individual physiology of different species. Brown bears (Ursus arctos) are an apex predator; thus, they are ideal candidates for detecting potentially ecosystem-level systemic perturbations using molecular-based tools. We used gene transcription to analyze 130 brown bear samples from three National Parks and Preserves in Alaska. Although the populations we studied are apparently stable in abundance and exist within protected and intact environments, differences in transcript profiles were noted. The most prevalent differences were among locations. The transcript patterns among groups reflect the influence of environmental factors, such as nutritional status, disease, and xenobiotic exposure. However, these profiles also likely represent baselines for each unique environment by which future measures can be made to identify early indication of population-level changes due to, for example, increasing Arctic temperatures. Some of those environmental changes are predicted to be potentially positive for brown bears, but other effects such as the manifestation of disease or indirect effects of oceanic acidification may produce negative impacts.

Utility of fur as a biomarker for persistent organic pollutants in Australian fur seals (Arctocephalus pusillus doriferus)

Persistent Organic Pollutants (POPs) can cause toxic effects in many species which include endocrine dysfunction, immunotoxicity, developmental defects and neoplasia. Species dominating the upper trophic level are vulnerable to these effects due to bioaccumulation. In Bass Strait, the Australian fur seal (Arctocephalus pusillus doriferus) is an important top order predator and sentinel species for ecosystem health. An alopecia syndrome is seen at high prevalence in juvenile, female Australian fur seals at Lady Julia Percy Island, Victoria, Australia. Previous investigations suggest causality could be due to an endocrine-like toxicant. The alopecia syndrome has significance for thermoregulation and is a likely risk factor for mortality. Fur collected from case (alopecic) and control (unaffected) seals sampled at Lady Julia Percy Island were analysed for POPs. To investigate the utility of fur for monitoring POPs concentrations in pinnipeds, a comparison of POPs concentrations in the fur and blubber of Australian fur seals stranded along the Victorian coast was undertaken. The concentration of selected POPs including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (dl-PCBs), polybrominated diphenyl ethers (PBDEs) and perfluorooctane sulfonate/perfluorooctanoic acid (PFOS/PFOA) were determined in fur using either High Resolution Gas Chromatography-Mass Spectrometry or Liquid Chromatography-Mass Spectrometry. Results indicate detectable, and in some individuals, elevated levels of dl-PCBs, PCDD/Fs and PBDEs in juvenile fur seals sampled on Lady Julia Percy Island, with significantly higher levels of dl-PCBs in case compared to control seals. Elevated levels of dl-PCBs and PCDD/Fs were found in blubber samples collected from stranded fur seals with significant correlations between blubber and fur concentrations seen, particularly for dl-PCBs. This study discusses the significance of POPs concentrations in relation to the causality of an alopecia syndrome in the Australian fur seal, and assesses the utility of fur as a non-invasive biomarker to monitor POPs exposure in this sentinel species.

Antarctic seals: Molecular biomarkers as indicators for pollutant exposure, health effects and diet

Weddell (Leptonychotes weddellii), Ross (Ommatophoca rossii) and crabeater seals (Lobodon carcinophaga) are phocid seals with a circumpolar distribution around Antarctica. As long-lived and large top predators, they bioaccumulate contaminants and are considered as sentinels of ecosystem health. Antarctic seals are increasingly exposed to climate change, pollution, shipping and fisheries. To reveal and understand possible anthropogenic impacts on their immune and health status, this study investigates sensitive biomarkers of the xenobiotic metabolism and immune system in relation to mercury (Hg) burden. Gene-transcription studies using minimally-invasive blood samples are useful to monitor physiological processes in wildlife that can be related to different stressors. Blood samples of 72 wild-caught seals (Weddell n=33; Ross n=12; crabeater n=27) in the Amundsen and Ross Seas in 2008-2011 were investigated. Copy numbers per μl mRNA transcription of xenobiotic biomarkers (aryl hydrocarbon receptor (AHR)), aryl hydrocarbon receptor nuclear translocator (ARNT) and peroxisome proliferator-activated receptor (PPARα) and immune relevant cell mediators (cytokines interleukin-2 (IL-2), interleukin-10 (IL-10) and heat-shock-protein 70 (HSP70)) were measured using reference genes Tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, zeta polypeptide (YWHAZ) and ribosomal protein L4 (RPL4) by real time RT-qPCR. Hg concentration was analysed in fur. Hg concentration increased with body weight and standard length in all species. Crabeater seals showed a lower Hg concentration than Ross and Weddell seals. Species-specific differences in gene-transcription were found between all species with highest levels of AHR, ARNT and PPARα in crabeater seals. Ross seals showed highest IL-10 and HSP70 transcription, while HSP70 was exceptionally low in crabeater seals. Between Hg and HSP70 a clear negative relationship was found in all species. The species-specific, age and sex-dependent gene-transcription probably reflect dietary habits, pollutant exposure and immune status.

Climate change-contaminant interactions in marine food webs: Toward a conceptual framework

Climate change is reshaping the way in which contaminants move through the global environment, in large part by changing the chemistry of the oceans and affecting the physiology, health, and feeding ecology of marine biota. Climate change-associated impacts on structure and function of marine food webs, with consequent changes in contaminant transport, fate, and effects, are likely to have significant repercussions to those human populations that rely on fisheries resources for food, recreation, or culture. Published studies on climate change-contaminant interactions with a focus on food web bioaccumulation were systematically reviewed to explore how climate change and ocean acidification may impact contaminant levels in marine food webs. We propose here a conceptual framework to illustrate the impacts of climate change on contaminant accumulation in marine food webs, as well as the downstream consequences for ecosystem goods and services. The potential impacts on social and economic security for coastal communities that depend on fisheries for food are discussed. Climate change-contaminant interactions may alter the bioaccumulation of two priority contaminant classes: the fat-soluble persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), as well as the protein-binding methylmercury (MeHg). These interactions include phenomena deemed to be either climate change dominant (i.e., climate change leads to an increase in contaminant exposure) or contaminant dominant (i.e., contamination leads to an increase in climate change susceptibility). We illustrate the pathways of climate change-contaminant interactions using case studies in the Northeastern Pacific Ocean. The important role of ecological and food web modeling to inform decision-making in managing ecological and human health risks of chemical pollutants contamination under climate change is also highlighted. Finally, we identify the need to develop integrated policies that manage the ecological and socioeconomic risk of greenhouse gases and marine pollutants.

De novo transcriptome assembly and RNA-Seq expression analysis in blood from beluga whales of Bristol Bay, AK

Assessing the health of marine mammal sentinel species is crucial to understanding the impacts of environmental perturbations on marine ecosystems and human health. In Arctic regions, beluga whales, Delphinapterus leucas, are upper level predators that may serve as a sentinel species, potentially forecasting impacts on human health. While gene expression profiling from blood transcriptomes has widely been used to assess health status and environmental exposures in human and veterinary medicine, its use in wildlife has been limited due to the lack of available genomes and baseline data. To this end we constructed the first beluga whale blood transcriptome de novo from samples collected during annual health assessments of the healthy Bristol Bay, AK stock during 2012-2014 to establish baseline information on the content and variation of the beluga whale blood transcriptome. The Trinity transcriptome assembly from beluga was comprised of 91,325 transcripts that represented a wide array of cellular functions and processes and was extremely similar in content to the blood transcriptome of another cetacean, the bottlenose dolphin. Expression of hemoglobin transcripts was much lower in beluga (25.6% of TPM, transcripts per million) than has been observed in many other mammals. A T12A amino acid substitution in the HBB sequence of beluga whales, but not bottlenose dolphins, was identified and may play a role in low temperature adaptation. The beluga blood transcriptome was extremely stable between sex and year, with no apparent clustering of samples by principle components analysis and <4% of genes differentially expressed (EBseq, FDR<0.05). While the impacts of season, sexual maturity, disease, and geography on the beluga blood transcriptome must be established, the presence of transcripts involved in stress, detoxification, and immune functions indicate that blood gene expression analyses may provide information on health status and exposure. This study provides a wealth of transcriptomic data on beluga whales and provides a sizeable pool of preliminary data for comparison with other studies in beluga whale.

Polychlorinated Biphenyl-Related Alterations of the Expression of Essential Genes in Harbour Seals (Phoca vitulina) from Coastal Sites in Canada and the United States

As long-lived marine mammals found throughout the temperate coastal waters of the North Pacific and Atlantic Oceans, harbour seals (Phoca vitulina) have become an invaluable sentinel of food-web contamination. Their relatively high trophic position predisposes harbour seals to the accumulation of harmful levels of persistent organic pollutants (POPs). We obtained skin/blubber biopsy samples from live-captured young harbour seals from various sites in the northeastern Pacific (British Columbia, Canada, and Washington State, USA) as well as the northwestern Atlantic (Newfoundland and Quebec, Canada). We developed harbour seal-specific primers to investigate the potential impact of POP exposure on the expression of eight important genes. We found correlations between the blubber mRNA levels of three of our eight target genes and the dominant persistent organic pollutant in seals [polychlorinated biphenyls (PCBs)] including estrogen receptor alpha (Esr1: r ² = 0.12, p = 0.038), thyroid hormone receptor alpha (Thra: r ² = 0.16; p = 0.028), and glucocorticoid receptor (Nr3c1: r ² = 0.12; p = 0.049). Age, sex, weight, and length were not confounding factors on the expression of genes. Although the population-level consequences are unclear, our results suggest that PCBs are associated with alterations of the expression of genes responsible for aspects of metabolism, growth and development, and immune function. Collectively, these results provide additional support for the use of harbour seals as indicators of coastal food-web contamination.

Indicators of Marine Pollution in the North Pacific Ocean

The complex nature of ocean pollution underscores the utility in identifying and characterizing a limited number of "indicators" that enables scientists and managers to track trends over space and time. This paper introduces a special issue on indicators of marine pollution in the North Pacific Ocean and builds on a scientific session that was held at the North Pacific Marine Science Organization. The special issue highlights studies using a variety of indicators to provide insight into the identification of legacy and emerging contaminants, the ranking of priority pollutants from various sources, and the effects of contaminants on ecosystem health in the North Pacific Ocean. Examples include the use of mussels to illustrate spatial and temporal trends of a number of contaminants following the 2011 tsunami in Japan, the use of molecular marker (linear alkylbenzenes, hopanes, and polycyclic aromatic hydrocarbons) profiles to identify pollution sources, and the use of plastic resin pellets to illustrate spatial trends of petroleum pollution around the world. Stable isotopes were used to strengthen the utility of the Glaucous-winged gull (Larus glaucescens) as an indicator of marine pollution. Examples also demonstrate the development and application of biomarker approaches, including gene transcripts, oxidative stress, estradiol, hatchability, and respiration and swimming behavior abnormalities, as a function of exposure to polychlorinated biphenyls, sulfur-diesel, Pinghu crude oil, galaxolide and antifouling biocides. We provide a brief review of indicators of marine pollution, identify research gaps, and summarize key findings from the articles published within the issue. This special issue represents the first compilation of research pertaining to marine pollution indicators in the North Pacific Ocean and provides guidance to inform mitigation and monitoring efforts of contaminants in the region.

Disruption of thyroid hormone (TH) levels and TH-regulated gene expression by polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and hydroxylated PCBs in e-waste recycling workers

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) are the primary toxicants released by electronic waste (e-waste) recycling, but their adverse effects on people working in e-waste recycling or living near e-waste sites have not been studied well. In the present study, the serum concentrations of PBDEs, PCBs, and hydroxylated PCBs, the circulating levels of thyroid hormones (THs), and the mRNA levels of seven TH-regulated genes in peripheral blood leukocytes of e-waste recycling workers were analyzed. The associations of the hormone levels and gene expression with the exposure to these contaminants were examined using multiple linear regression models. There were nearly no associations of the TH levels with PCBs and hydroxylated PCBs, whereas elevated hormone (T₄ and T₃) levels were associated with certain lower-brominated BDEs. While not statistically significant, we did observe a negative association between highly brominated PBDE congeners and thyroid-stimulating hormone (TSH) levels in the e-waste workers. The TH-regulated gene expression was more significantly associated with the organohalogen compounds (OHCs) than the TH levels in these workers. The TH-regulated gene expression was significantly associated with certain PCB and hydroxylated PCB congeners. However, the expression of most target genes was suppressed by PBDEs (mostly highly brominated congeners). This is the first evidence of alterations in TH-regulated gene expression in humans exposed to OHCs. Our findings indicated that OHCs may interfere with TH signaling and/or exert TH-like effects, leading to alterations in related gene expression in humans. Further research is needed to investigate the mechanisms of action and associated biological consequences of the gene expression disruption by OHCs.

De novo assembly of the ringed seal (Pusa hispida) blubber transcriptome: A tool that enables identification of molecular health indicators associated with PCB exposure

The ringed seal, Pusa hispida, is a keystone species in the Arctic marine ecosystem, and is proving a useful marine mammal for linking polychlorinated biphenyl (PCB) exposure to toxic injury. We report here the first de novo assembled transcriptome for the ringed seal (342,863 transcripts, of which 53% were annotated), which we then applied to a population of ringed seals exposed to a local PCB source in Arctic Labrador, Canada. We found an indication of energy metabolism imbalance in local ringed seals (n=4), and identified five significant gene transcript targets: plasminogen receptor (Plg-R(KT)), solute carrier family 25 member 43 receptor (Slc25a43), ankyrin repeat domain-containing protein 26-like receptor (Ankrd26), HIS30 (not yet annotated) and HIS16 (not yet annotated) that may represent indicators of PCB exposure and effects in marine mammals. The abundance profiles of these five gene targets were validated in blubber samples collected from 43 ringed seals using a qPCR assay. The mRNA transcript levels for all five gene targets, (Plg-R(KT), r²=0.43), (Slc25a43, r²=0.51), (Ankrd26, r²=0.43), (HIS30, r²=0.39) and (HIS16, r²=0.31) correlated with increasing levels of blubber PCBs. Results from the present study contribute to our understanding of PCB associated effects in marine mammals, and provide new tools for future molecular and toxicology work in pinnipeds.

Brain transcriptomes of harbor seals demonstrate gene expression patterns of animals undergoing a metabolic disease and a viral infection

Diseases of marine mammals can be difficult to diagnose because of their life history and protected status. Stranded marine mammals have been a particularly useful resource to discover and comprehend the diseases that plague these top predators. Additionally, advancements in high-throughput sequencing (HTS) has contributed to the discovery of novel pathogens in marine mammals. In this study, we use a combination of HTS and stranded harbor seals (Phoca vitulina) to better understand a known and unknown brain disease. To do this, we used transcriptomics to evaluate brain tissues from seven neonatal harbor seals that expired from an unknown cause of death (UCD) and compared them to four neonatal harbor seals that had confirmed phocine herpesvirus (PhV-1) infections in the brain. Comparing the two disease states we found that UCD animals showed a significant abundance of fatty acid metabolic transcripts in their brain tissue, thus we speculate that a fatty acid metabolic dysregulation contributed to the death of these animals. Furthermore, we were able to describe the response of four young harbor seals with PhV-1 infections in the brain. PhV-1 infected animals showed a significant ability to mount an innate and adaptive immune response, especially to combat viral infections. Our data also suggests that PhV-1 can hijack host pathways for DNA packaging and exocytosis. This is the first study to use transcriptomics in marine mammals to understand host and viral interactions and assess the death of stranded marine mammals with an unknown disease. Furthermore, we show the value of applying transcriptomics on stranded marine mammals for disease characterization.

Genomic Methods Take the Plunge: Recent Advances in High-Throughput Sequencing of Marine Mammals

The dramatic increase in the application of genomic techniques to non-model organisms (NMOs) over the past decade has yielded numerous valuable contributions to evolutionary biology and ecology, many of which would not have been possible with traditional genetic markers. We review this recent progression with a particular focus on genomic studies of marine mammals, a group of taxa that represent key macroevolutionary transitions from terrestrial to marine environments and for which available genomic resources have recently undergone notable rapid growth. Genomic studies of NMOs utilize an expanding range of approaches, including whole genome sequencing, restriction site-associated DNA sequencing, array-based sequencing of single nucleotide polymorphisms and target sequence probes (e.g., exomes), and transcriptome sequencing. These approaches generate different types and quantities of data, and many can be applied with limited or no prior genomic resources, thus overcoming one traditional limitation of research on NMOs. Within marine mammals, such studies have thus far yielded significant contributions to the fields of phylogenomics and comparative genomics, as well as enabled investigations of fitness, demography, and population structure. Here we review the primary options for generating genomic data, introduce several emerging techniques, and discuss the suitability of each approach for different applications in the study of NMOs.

Relationships between concentrations of selected organohalogen contaminants and thyroid hormones and vitamins A, E and D in Faroese pilot whales

Pilot whales (Globicephala melas) from the Faroe Islands, North-East Atlantic, have high body concentrations of organohalogenated compounds (OHCs), such as polychlorinated biphenyls (PCBs), organochlorinated pesticides (OCPs) and brominated flame retardants (BFRs). The aim of the present study was to examine if and to what extent blood plasma and liver concentrations of several groups of these OHCs are related to concentrations of relevant nutritional and hormonal biomarkers in pilot whales. Thyroid hormones (THs: total and free thyroxine and total and free triiodothyronine) and vitamin A (retinol), D (25-hydroxyvitamin D3) and E (α-tocopherol) were analysed in plasma (n=27) and vitamin A (total vitamin A, retinol and retinyl palmitate) and E (α- and γ-tocopherol) were analysed in liver (n=37) of Faroe Island pilot whales. Correlative relationships between the biomarkers and OHC concentrations previously analysed in the same tissues in these individuals were studied. The TH concentrations in plasma were significantly higher in juveniles than in adults. Vitamin D concentrations in plasma and α- and γ-tocopherol in liver were higher in adults than in juveniles. Multivariate statistical modelling showed that the age and sex influenced the relationship between biomarkers and OHCs. Some significant positive relationships were found between OHCs and thyroid hormone concentrations in the youngest juveniles (p<0.05). In plasma of juvenile whales α-tocopherol was also positively correlated with all the OHCs (p<0.05). Only few significant correlations were found between single OHCs and retinol and vitamin D in plasma within the age groups. There were significant negative relationships between hepatic PBDE concentrations and retinol (BDE-47) and γ-tocopherol (BDE-49, -47, -100, -99, -153) in liver. The relationships between OHCs and THs or vitamins suggest that in pilot whales OHCs seem to have minor effects on TH and vitamin concentrations.

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.

Enzyme induction and histopathology elucidate aryl hydrocarbon receptor-mediated versus non-aryl hydrocarbon receptor-mediated effects of Aroclor 1268 in American mink (Neovison vison)

Polychlorinated biphenyl (PCB) concentrations reported in preferred prey and blubber of bottlenose dolphins from the Turtle-Brunswick River estuary (Georgia, USA) suggest the potential for adverse effects. However, PCBs in Turtle-Brunswick River estuary dolphins are primarily derived from Aroclor 1268, and predicting toxic effects of Aroclor 1268 is uncertain because of the mixture's unique composition and associated physiochemical characteristics. These differences suggest that toxicity benchmarks for other PCB mixtures may not be relevant to dolphins exposed to Aroclor 1268. American mink (Neovison vison) were used as a surrogate model for cetaceans to characterize mechanisms of action associated with Aroclor 1268 exposure. Mink share similarities in phylogeny and life history with cetaceans and are characteristically sensitive to PCBs, making them an attractive surrogate species for marine mammals in ecotoxicity studies. Adult female mink and a subsequent F1 generation were exposed to Aroclor 1268 through diet, and effects on enzyme induction, histopathology, thyroid hormone regulation, hematology, organ weights, and body condition index were compared to a negative control and a 3,3',4,4',5-pentachlorobiphenyl (PCB 126)-positive control. Aroclor 1268 dietary exposure concentrations ranged from 1.8 µg/g wet weight to 29 µg/g wet weight. Anemia, hypothyroidism, and hepatomegaly were observed in mink exposed to Aroclor 1268 beyond various dietary thresholds. Cytochrome P450 induction and squamous epithelial proliferation jaw lesions were low in Aroclor 1268 treatments relative to the positive control. Differences in enzyme induction and the development of squamous epithelial proliferation jaw lesions between Aroclor 1268 treatments and the positive control, coupled with effects observed in Aroclor 1268 treatments not observed in the positive control, indicate that mechanisms additional to the aryl hydrocarbon receptor-mediated pathway are associated with Aroclor 1268 exposure.

Xenobiotic and Immune-Relevant Molecular Biomarkers in Harbor Seals as Proxies for Pollutant Burden and Effects

Harbor seals are exposed to increasing pressure caused by anthropogenic activities in their marine environment. Persistent organic pollutants (POPs) and trace elements are hazardous contaminants that accumulate in tissues of harbor seals. POPs and trace elements can negatively affect the immune-system and have been reported, e.g., to increase susceptibility to viral infections in seals. Biomarkers of the xenobiotic metabolism, cytokines, and heat-shock protein as cell mediators of the immune-system were established to evaluate the impact of environmental stressors on harbor seals. Harbor seals (n = 54) were captured on sandbanks in the North Sea during 2009-2012. Health assessments, including hematology, were performed, and RNAlater blood samples were taken and analyzed using quantitative polymerase chain reaction. Normalized transcript copy numbers were correlated to hematology and POP concentration in blood and trace metals in blood and fur. A significant correlation between xenobiotic markers and contaminant burden was found. Significant interrelationships between markers and POP compounds, as well as with season, weight, and hematology values, indicate that biomarkers reflect pollutant exposure and effects. A significant relationship between cortisol levels and heat-shock protein expression was observed indicating stress experienced during restraint of the seals. Interleukin-10 transcription showed significant correlations with trace elements in fur pointing toward immune regulatory effects of metal exposure. The molecular markers prove to be an important noninvasive tool that reflects contaminant exposure and the impact of anthropogenic stressors in seal species. The connection between interleukin-2, xenobiotic markers, and pollutants may indicate immune suppression in animals exposed to contaminants with subsequent susceptibility to inflammatory disease.

Organohalogen Contaminants and Vitamins in Northern Fur Seals (Callorhinus ursinus) Collected During Subsistence Hunts in Alaska

During native subsistence hunts from 1987 to 2007, blubber and liver samples from 50 subadult male northern fur seals (Callorhinus ursinus) were collected on St. Paul Island, Alaska. Samples were analyzed for legacy persistent organic pollutants (POPs), recently phased-out/current-use POPs, and vitamins. The legacy POPs measured from blubber samples included polychlorinated biphenyl congeners, DDT (and its metabolites), chlorobenzenes, chlordanes, and mirex. Recently phased-out/current-use POPs included in the blubber analysis were the flame retardants, polybrominated diphenyl ethers, and hexabromocyclododecanes. The chemical surfactants, perfluorinated alkyl acids, and vitamins A and E were assessed in the liver samples. Overall, concentrations of legacy POPs are similar to levels seen in seal samples from other areas of the North Pacific Ocean and the Bering Sea. Statistically significant correlations were seen between compounds with similar functions (pesticides, flame retardants, vitamins). With sample collection spanning two decades, the temporal trends in the concentrations of POPs and vitamins were assessed. For these animals, the concentrations of the legacy POPs tend to decrease or stay the same with sampling year; however, the concentrations of the current-use POPs increased with sampling year. Vitamin concentrations tended to stay the same across the sampling years. With the population of northern fur seals from St. Paul Island on the decline, a detailed assessment of exposure to contaminants and the correlations with vitamins fills a critical gap for identifying potential population risk factors that might be associated with health effects.

Toward ecosystem-based sediment quality guidelines for polychlorinated biphenyls (PCBs)

To investigate whether Sediment Quality Guidelines (SQGs) for polychlorinated biphenyls (PCBs) in Canada and British Columbia achieve their objective of protecting ecosystems, we measured and compiled concentrations of PCB congeners in sediments, bivalves, crustaceans, fish, and marine mammals from 3 areas off the Pacific coast of British Columbia, Canada. The concentration data showed that whereas PCB concentrations in sediments were predominantly below the SQG of 20 µg/kg dry weight, large fractions of the PCB concentrations in fish and shellfish species exceeded the tissue residue guideline for the consumption of fish and shellfish by wildlife (i.e., 50 µg/kg wet weight [ww]) but were below the tissue residue guideline for the consumption of fish and shellfish by human populations (i.e., 2000 µg/kg ww). Also, PCB concentrations in marine mammals exceeded toxicity reference concentrations. The concentration data were used to develop species- and location-specific Biota-Sediment Accumulation Factors (BSAF = Cbiota /Csediment ), that were used to estimate PCB concentrations in wildlife species that may exist if the PCB concentration in sediments are equal to the SQGs. The results show that if the PCB concentration is equal to the SQGs, then PCB concentrations in most wildlife species can be expected to exceed the tissue residue guideline for the consumption of fish and shellfish by wildlife species and by humans, as well as toxicity reference concentrations for marine mammals. A methodology for developing SQGs for PCBs that are protective of the health of different wildlife species and human consumers of fish and shellfish from general Canadian and coastal First Nations populations was developed and applied. The proposed guidelines may provide useful guidance to establish SQGs for PCBs that can account for the ecological diversity in coastal environments and that better achieve the intent of the guidelines to protect ecosystems. The proposed methodology for guideline development may also be useful in the development of SQGs for other bioaccumulative substances.

Persistent organic pollutants (POPs) in blubber of common bottlenose dolphins (Tursiops truncatus) along the northern Gulf of Mexico coast, USA

A number of studies were initiated in response to the Deepwater Horizon (DWH) oil spill to understand potential injuries to bottlenose dolphins (Tursiops truncatus) that inhabit the northern Gulf of Mexico (NGoM) estuarine waters. As part of these studies, remote biopsy skin and blubber samples were collected from dolphins at six field sites that received varying degrees of oiling: Barataria Bay (BB), Chandeleur Sound West (CSW), Chandeleur Sound East (CSE), Mississippi Sound South (MSS), Mississippi Sound North (MSN), and St. Joseph Bay (SJ). Blubber samples from 108 male dolphins were analyzed for persistent organic pollutant (POP) concentrations, as high levels of POPs have been previously reported in other southeastern U.S. dolphins and the potential contribution of these compounds to adverse health effects in NGoM dolphins must be considered. Dolphin blubber levels of summed POPs (ΣPOPs) did not differ significantly across sites (F-test, P=0.9119) [μg/g lipid; geometric mean and 95% CI]; CSW [65.9 (51.4-84.6)], SJ [74.1 (53.0-104)], MSN [74.3 (58.7-93.9)], BB [75.3 (56.4-101)], CSE [80.5 (57.8-112)], and MSS [82.5 (65.9-103)]. Overall, POP concentrations were in the lower half of the range compared to previously reported concentrations from other southeastern U.S. sites. Increased dolphin mortalities have been ongoing in the NGoM and have been suggested to be linked with the DWH oil spill. In addition, lung disease, impaired adrenal function, and serum biochemical abnormalities have been reported in dolphins from BB, an area that was heavily oiled. The results of this study suggest that POPs are likely not a primary contributor to the poor health conditions and increased mortality observed in some populations of NGoM dolphins following the DWH oil spill.

Using cytochrome P4501A1 expression in liver and blubber to understand effects of persistent organic pollutant exposure in stranded Pacific Island cetaceans

Elevated levels of persistent organic pollutants (POPs) have been reported in tropical Pacific Island cetaceans and their environment. In addition, recent health concerns in cetacean populations have warranted investigation into potential physiological effects from POP exposure for this region. Cytochrome P450 1A1 (CYP1A1) is a candidate for examining such effects. This well-studied biomarker of exposure and effect was examined in stranded cetacean liver using immunoblot (n = 39, 16 species) and blubber using immunohistochemistry (n = 23, 10 species). Paired tissue samples allowed for CYP1A1 comparisons not only between species but also within each individual animal to examine differences between tissue types. Liver CYP1A1 expression correlated positively and significantly with blubber concentrations of all POP categories (n = 39, p < 0.050) except octachlorostyrene and pentachlorobenzene (p > 0.100). Among Stenella species, liver CYP1A1 tissue expression was correlated negatively with the sum of all blubber layer endothelial cell CYP1A1 expression (n = 14, p = 0.049). Overall, elevated expression of liver CYP1A1 confirms its use as a biomarker of POP exposure to cetaceans stranded in the tropical Pacific basin.

Seasonal variation in the skin transcriptome of common bottlenose dolphins (Tursiops truncatus) from the northern Gulf of Mexico

As long-lived predators that integrate exposures across multiple trophic levels, cetaceans are recognized as sentinels for the health of marine ecosystems. Their utility as sentinels requires the establishment of baseline health parameters. Because cetaceans are protected, measurements obtained with minimal disruption to free ranging animals are highly desirable. In this study we investigated the utility of skin gene expression profiling to monitor health and contaminant exposure in common bottlenose dolphins (Tursiops truncatus). Remote integument biopsies were collected in the northern Gulf of Mexico prior to the Deepwater Horizon oil spill (May 2010) and during summer and winter for two years following oil contamination (2010-2011). A bottlenose dolphin microarray was used to characterize the skin transcriptomes of 94 individuals from three populations: Barataria Bay, Louisiana, Chandeleur Sound, Louisiana, and Mississippi Sound, Mississippi/Alabama. Skin transcriptomes did not differ significantly between populations. In contrast, season had a profound effect on gene expression, with nearly one-third of all genes on the array differing in expression between winter and the warmer seasons (moderated T-test; p<0.01, fold-change≥1.5). Persistent organic pollutants (POPs) in blubber changed concurrently, reaching >two-fold higher concentrations in summer compared to winter, due to a seasonal decrease in blubber thickness and loss of stored lipid. However, global gene expression did not correlate strongly with seasonally changing contaminant concentrations, most likely because the refractory, lipid-stored metabolites are not substrates for phase I or II xenobiotic detoxification pathways. Rather, processes related to cell proliferation, motility, and differentiation dominated the differences in expression in winter and the warmer seasons. More subtle differences were seen between spring and summer (1.5% of genes differentially expressed). However, two presumed oil-exposed animals from spring presented gene expression profiles more similar to the summer animals (presumed exposed) than to other spring animals. Seasonal effects have not previously been considered in studies assessing gene expression in cetaceans, but clearly must be taken into account when applying transcriptomic analyses to investigate their contaminant exposure or health status.

Stress physiology in marine mammals: how well do they fit the terrestrial model?

Stressors are commonly accepted as the causal factors, either internal or external, that evoke physiological responses to mediate the impact of the stressor. The majority of research on the physiological stress response, and costs incurred to an animal, has focused on terrestrial species. This review presents current knowledge on the physiology of the stress response in a lesser studied group of mammals, the marine mammals. Marine mammals are an artificial or pseudo grouping from a taxonomical perspective, as this group represents several distinct and diverse orders of mammals. However, they all are fully or semi-aquatic animals and have experienced selective pressures that have shaped their physiology in a manner that differs from terrestrial relatives. What these differences are and how they relate to the stress response is an efflorescent topic of study. The identification of the many facets of the stress response is critical to marine mammal management and conservation efforts. Anthropogenic stressors in marine ecosystems, including ocean noise, pollution, and fisheries interactions, are increasing and the dramatic responses of some marine mammals to these stressors have elevated concerns over the impact of human-related activities on a diverse group of animals that are difficult to monitor. This review covers the physiology of the stress response in marine mammals and places it in context of what is known from research on terrestrial mammals, particularly with respect to mediator activity that diverges from generalized terrestrial models. Challenges in conducting research on stress physiology in marine mammals are discussed and ways to overcome these challenges in the future are suggested.