Biomonitoring of polybrominated diphenyl ether (PBDE) pollution: a field study

Tissue bioaccumulation and distribution of organic contaminants in Brazilian guitarfish Pseudobatos horkelii reveal a concerning impact of contraceptive hormones and fecal sterols

The critically endangered Brazilian guitarfish faces significant threats from environmental contamination. Assessing the impacts of such stressor is paramount from a conservational perspective. This study investigated the concentrations, distribution and accumulation patterns of organic contaminants in pregnant Brazilian guitarfish Pseudobatos horkelii. Blood, gill, gonad, liver, and muscle concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybrominated diphenyl ethers, fecal sterols, and synthetic hormones used as human contraceptives were assessed. Synthetic hormones, especially D-norgestrel, showed the highest concentrations, mainly in the liver. Together with the results of fecal sterols, this finding suggests that guitarfish are exposed to sewage discharge. OCPs, especially hexachlorobenzene, mirex, endosulfans, and drins, showed considerably high concentrations, indicating the relevance of agricultural inputs. PCBs presented significant concentrations in the muscle, indicating long-term exposure, in contrast with other analytes that were primarily concentrated in the liver. These results have conservational implications, since contaminants analyzed herein have endocrine disruptive effects.

BFRs (PBDEs and HBCDs) in freshwater species from Lake Trasimeno (Italy): The singular case of HBCDs in red swamp crayfish

Eighty-six samples belonging to five different species (crucian carp, Carassius carassius; European perch, Perca fluviatilis; tench, Tinca tinca; eel, Anguilla anguilla; red swamp crayfish, Procambarus clarkii) collected from Lake Trasimeno (Italy) were analyzed to assess polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) contamination. The Trasimeno is the largest Italian peninsular lake located in Umbria (Central Italy), in a rural area with low anthropogenic impact. All the samples were analyzed by an in-house developed analytical procedure involving a single sample preparation with dual detection: Gas- and Liquid-Chromatography coupled to tandem Mass Spectrometry (GC-MS/MS for PBDEs and LC-MS/MS for HBCDs). BFRs levels in crucian carp, tench and European perch were negligible and mostly below quantification limits (LOQs). In eel, the species with the higher fat content, PBDE sum (15 congeners) ranged from 0.269 to 0.916 ng/g w.w. BDE-47, -100 and -154 accounted for roughly 57%, 16% and 11% of the PBDE sum, respectively, while BDE-99 (usually one of the most abundant congeners in biota), only for 3%. HBCDs (sum of α-, β-, γ-isomers) were found between 0.157 and 1.14 ng/g w.w. with α- as predominant isomer (92% of the sum), followed by γ- (5%) and β- (2%). Peculiar was the contamination in red swamp crayfish characterized by negligible PBDEs and very high HBCDs levels with a singular contamination pattern. In female pools (n = 9) the mean HBCDs sum was 0.150 ng/g w.w., while in males higher concentrations were measured (mean = 2.77 ng/g w.w.). A significant correlation seems to exist between the contamination level and the seasonal cycle only in male crayfish. Interestingly, among the HBCDs, the γ-isomer was the highest (67% of the total) while α- contributes only for 20%.

Rno-miR-224-5p contributes to 2,2',4,4'-tetrabromodiphenyl ether-induced low triiodothyronine in rats by targeting deiodinases

Hypothyroidism is commonly associated with substantial adverse impacts on human health, and polybrominated diphenyl ether (PBDE), a kind of classic thyroid hormone disruptor, was speculated to be a potential environmental factor, but its effect on thyroxine metabolism has received little attention. In the present study, we investigated the role and mechanism of rno-miR-224-5p in deiodinase-mediated thyroxine metabolism in rats treated with 2,2',4,4'-tetrabromodiphenyl ether (BDE47), a predominant PBDE congener in humans. BDE47 decreased plasma triiodothyronine (T3) and thyroxine (T4) and increased reverse T3 (rT3) in the rats, and the expression of type 1 deiodinase (DIO1) and type 3 deiodinase (DIO3) increased in both the rats and H4-II-E cells. Rno-miR-224-5p was predicted to target dio1 instead of dio3, according to the TargetScan, miRmap.org and microRNA.org databases. Experiments showed that the rno-miR-224-5p level was decreased by BDE47 in a dose-dependent manner and confirmed that rno-miR-224-5p downregulated both DIO1 and DIO3 in the H4-II-E cells and in the rats, as determined using mimics and an inhibitor of rno-miR-224-5p. Furthermore, DIO1 was observed to be a direct functional target of rno-miR-224-5p, whereas DIO3 was indirectly regulated by rno-miR-224-5p via the phosphorylation of the MAPK/ERK (but not p38 or JNK) pathway. Reportedly, DIO1 and DIO3 act principally as inner-ring deiodinases and are responsible for the conversion of T4 to rT3, but not to T3, and the final clearance of thyroxine (mainly in the form of T2). Our results demonstrated that BDE47 induced low levels of T3 conversion through DIO1 and DIO3, which were regulated by rno-miR-224-5p. The findings suggest a novel additional mechanism of PBDE-induced thyroxine metabolism disorder that differs from that of PBDEs as environmental thyroid disruptors.

Seasonal variations of PCDD/Fs in fishes: inferring a hidden exposure route from Na-PCP application for schistosomiasis control

Japanese schistosomiasis was endemic in Dongting Lake, the second largest freshwater lake in China. The technical sodium pentachlorophenate (Na-PCP) was widely used during the period between the early 1960s and early 1990s to kill oncomelania, the intermediate host of Schistosomes. However, polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) also contaminated the environment of Dongting Lake due to trace impurities of Na-PCP. In this study, 13 species of freshwater fish were collected from Dongting Lake and analyzed in wet and dry seasons. Temporal (wet and dry season) variations in PCDD/Fs in fishes from Dongting Lake were observed. The concentration of PCDD/Fs was considerably higher in the wet season than in the dry season and in areas in China where Na-PCP was not applied. The higher level of PCDD/Fs in the wet season may be attributed to the use of Na-PCP in the past and to the increase in the migration of PCDD/Fs from sediments to water in the wet season. The results indicate that the risk of PCDD/Fs contamination is connected with prior consumption of fishes that live in the Na-PCP application area. However, there was no difference in the concentrations of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) between the wet and dry seasons.

Autism, Mitochondria and Polybrominated Diphenyl Ether Exposure

BACKGROUND

Autism spectrum disorders (ASD) are a growing concern with more than 1 in every 68 children affected in the United States by age 8. Limited scientific advances have been made regarding the etiology of autism, with general agreement that both genetic and environmental factors contribute to this disorder.

OBJECTIVE

To explore the link between exposure to PBDE, mitochondrial dysfunction and autism risk.

RESULTS

Perinatal exposures to PBDEs may contribute to the etiology or morbidity of ASD including mitochondrial dysfunction based on (i) their increased environmental abundance and human exposures, (ii) their activity towards implicated in neuronal development and synaptic plasticity including mitochondria, and (iii) their bioaccumulation in mitochondria.

CONCLUSION

In this review, we propose that PBDE, and possibly other environmental exposures, during child development can induce or compound mitochondrial dysfunction, which in conjunction with a dysregulated antioxidant response, increase a child's susceptibility of autism.

A mechanistic view of polybrominated diphenyl ether (PBDE) developmental neurotoxicity

Polybrominated diphenyl ethers (PBDEs), extensively used in the past few decades as flame retardants in a variety of consumer products, have become world-wide persistent environmental pollutants. Levels in North America are usually higher than those in Europe and Asia, and body burden is 3-to-9-fold higher in infants and toddlers than in adults. The latter has raised concern for potential developmental toxicity and neurotoxicity of PBDEs. Experimental studies in animals and epidemiological observations in humans suggest that PBDEs may be developmental neurotoxicants. Pre- and/or post-natal exposure to PBDEs may cause long-lasting behavioral abnormalities, particularly in the domains of motor activity and cognition. The mechanisms underlying the developmental neurotoxic effects of PBDEs are not known, though several hypotheses have been put forward. One general mode of action relates to the ability of PBDEs to impair thyroid hormone homeostasis, thus indirectly affecting the developing brain. An alternative or additional mode of action involves a direct effect of PBDEs on nervous system cells; PBDEs can cause oxidative stress-related damage (DNA damage, mitochondrial dysfunction, apoptosis), and interfere with signal transduction (particularly calcium signaling), and with neurotransmitter systems. Important issues such as bioavailability and metabolism of PBDEs, extrapolation of results to low level of exposures, and the potential effects of interactions among PBDE congeners and between PBDEs and other contaminants also need to be taken into account.

Organochlorine and organobromine compounds in a benthic fish (Solea solea) from Bizerte Lagoon (northern Tunisia): implications for human exposure

Information on the occurrence of persistent organic pollutants (POPs) in fish from Tunisia is scarce. In this study, thirty one persistent organic pollutants including organochlorine pesticides (OCPs) (dichlorodihenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB)), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs) were determined in solea solea muscle, from Bizerte Lagoon (northern Tunisia) and from the Mediterranean Sea (reference area) (northern Mediterranean). In the Bizerte Lagoon, contaminant concentrations generally followed this order: PCBs>DDTs>PBDEs>MeO-PBDEs>HCB>HCHs; while in the Mediterranean Sea, pollutant concentration followed this order: MeO-PBDEs>PCBs>DDTs>PBDEs>HCB>HCHs. Mean levels of organochlorine compounds were 1018 and 380 ng g(-1) lipid weight (lw) in fish from Bizerte Lagoon and the Mediterranean Sea, respectively. Mean concentrations of organobromine compounds were 279 and 301 ng g(-1) lw in sole from Bizerte Lagoon and the Mediterranean Sea, respectively. Organohalogen concentrations in fish from Bizerte Lagoon were similar or slightly lower than those reported for other marine fish species from other locations around the world. PCB, HCH, HCB and PBDE levels were negatively correlated with lipid content, while no such correlation was seen for DDTs. Assessment based on several available guidelines suggested an insignificant human health risk for dietary intake of HCB, lindane and PBDEs associated with consumption of sole. However, the estimated lifetime cancer risk from dietary exposure to DDTs and PCBs is a potential concern.

Toxicity of the flame-retardant BDE-49 on brain mitochondria and neuronal progenitor striatal cells enhanced by a PTEN-deficient background

Polybrominated diphenyl ethers (PBDEs) represent an important group of flame retardants extensively used, tonnage of which in the environment has been steadily increasing over the past 25 years. PBDEs or metabolites can induce neurotoxicity and mitochondrial dysfunction (MD) through a variety of mechanisms. Recently, PBDEs with < 5 Br substitutions (i.e., 2,2',4,4'-tetrabromodiphenyl ether [BDE-47] and 2,2',4,5'-tetrabromodiphenyl ether [BDE-49]) have gained interest because of their high bioaccumulation. In particular, congeners such as BDE-49 arise as one of the most biologically active, with concentrations typically lower than those observed for BDE-47 in biological tissues; however, its potential to cause MD at biologically relevant concentrations is unknown. To this end, the effect of BDE-49 was studied in brain mitochondria and neuronal progenitor striatal cells (NPC). BDE-49 uncoupled mitochondria at concentrations < 0.1 nM, whereas at > 1 nM, it inhibited the electron transport at Complex V (mixed type inhibition; IC(50) = 6 nM) and Complex IV (noncompetitive inhibition; IC(50) = 40 nM). These concentrations are easily achieved in plasma concentrations considering that BDE-49 (this study, 400-fold) and other PBDEs accumulate 1-3 orders of magnitude in the cells, particularly in mitochondria and microsomes. Similar effects were observed in NPC and exacerbated with PTEN (negative modulator of the PI3K/Akt pathway) deficiency, background associated with autism-like behavior, schizophrenia, and epilepsy. PBDE-mediated MD per se or enhanced by a background that confers susceptibility to this exposure may have profound implications in the energy balance of brain.

BDE 49 and developmental toxicity in zebrafish

The polybrominated diphenyl ethers (PBDEs) are a group of brominated flame retardants. Human health concerns of these agents have largely centered upon their potential to elicit reproductive and developmental effects. Of the various congeners, BDE 49 (2,2',4,5'-tetrabromodiphenyl ether) has been poorly studied, despite the fact that it is often detected in the tissues of fish and wildlife species. Furthermore, we have previously shown that BDE 49 is a metabolic debromination product of BDE 99 hepatic metabolism in salmon, carp and trout, underscoring the need for a better understanding of biological effects. In the current study, we investigated the developmental toxicity of BDE 49 using the zebrafish (Danio rerio) embryo larval model. Embryo and larval zebrafish were exposed to BDE 49 at either 5 hours post fertilization (hpf) or 24 hpf and monitored for developmental and neurotoxicity. Exposure to BDE 49 at concentrations of 4iμ-32 μM caused a dose-dependent loss in survivorship at 6 days post fertilization (dpf). Morphological impairments were observed prior to the onset of mortality, the most striking of which included severe dorsal curvatures of the tail. The incidence of dorsal tail curvatures was dose and time dependent. Exposure to BDE 49 caused cardiac toxicity as evidenced by a significant reduction in zebrafish heart rates at 6 dpf but not earlier, suggesting that cardiac toxicity was non-specific and associated with physiological stress. Neurobehavioral injury from BDE 49 was evidenced by an impairment of touch-escape responses observed at 5 dpf. Our results indicate that BDE 49 is a developmental toxicant in larval zebrafish that can cause morphological abnormalities and adversely affect neurobehavior. The observed toxicities from BDE 49 were similar in scope to those previously reported for the more common tetrabrominated congener, BDE 47, and also for other lower brominated PBDEs, suggest that these compounds may share similarities in risk to aquatic species.

Polybrominated diphenyl ethers and their methoxylated analogs in mullet (Mugil cephalus) and sea bass (Dicentrarchus labrax) from Bizerte Lagoon, Tunisia

Concentrations of ten polybrominated diphenyl ethers (PBDEs) and eight methoxylated polybrominated diphenyl ethers (MeO-PBDEs) in mullet (Mugil cephalus) and sea bass (Dicentrarchus labrax) collected from the Bizerte Lagoon and the Mediterranean Sea were investigated. To the best of our knowledge, this is the first report of these compounds in marine fishes from Tunisia. The PBDE mean concentrations in fish from Bizerte Lagoon were 45.3 and 96.2 ng g(-1) lw respectively in mullet and sea bass, while the concentrations of these compounds in mullet and sea bass from Mediterranean Sea were 7.80 and 27.9 ng g(-1) lw respectively. MeO-PBDE concentrations in mullet and sea bass from Bizerte Lagoon ranged from 6.46 to 286 ng g(-1) lw and from 49.4 to 798 ng g(-1) lw respectively, while the concentrations of these compounds in mullet and sea bass from Mediterranean Sea ranged from 190 to 401 ng g(-1) lw and from 353 to 578 ng g(-1) lw respectively. The total PBDEs and total MeO-PBDEs concentration in fish from Bizerte Lagoon were similar or slightly lower than those reported for other species from other locations around the world.

Para- and ortho-substitutions are key determinants of polybrominated diphenyl ether activity toward ryanodine receptors and neurotoxicity

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are widely used flame retardants that bioaccumulate in human tissues. Their neurotoxicity involves dysregulation of calcium ion (Ca(2+))signaling; however, specific mechanisms have yet to be defined.

OBJECTIVE

We aimed to define the structure-activity relationship (SAR) for PBDEs and their metabolites toward ryanodine receptors type 1 (RyR1) and type 2 (RyR2) and to determine whether it predicts neurotoxicity.

METHODS

We analyzed [3H]ryanodine binding, microsomal Ca(2+) fluxes, cellular measurements of Ca(2+) homeostasis, and neurotoxicity to define mechanisms and specificity of PBDE-mediated Ca(2+) dysregulation.

RESULTS

PBDEs possessing two ortho-bromine substituents and lacking at least one para-bromine substituent (e.g., BDE-49) activate RyR1 and RyR2 with greater efficacy than corresponding congeners with two para-bromine substitutions (e.g., BDE-47). Addition of a methoxy group in the free para position reduces the activity of parent PBDEs. The hydroxylated BDEs 6-OH-BDE-47 and 4´-OH-BDE-49 are biphasic RyR modulators. Pretreatment of HEK293 cells (derived from human embryonic kidney cells) expressing either RyR1 or RyR2 with BDE-49 (250 nM) sensitized Ca2+ flux triggered by RyR agonists, whereas BDE-47 (250 nM) had negligible activity. The divergent activity of BDE-49, BDE-47, and 6-OH-BDE-47 toward RyRs predicted neurotoxicity in cultures of cortical neurons.

CONCLUSIONS

We found that PBDEs are potent modulators of RyR1 and RyR2. A stringent SAR at the ortho and para position determined whether a congener enhanced, inhibited, or exerted nonmonotonic actions toward RyRs. These results identify a convergent molecular target of PBDEs previously identified for noncoplanar polychlorinated biphenyls (PCBs) that predicts their cellular neurotoxicity and therefore could be a useful tool in risk assessment of PBDEs and related compounds.

Absorption and translocation of polybrominated diphenyl ethers (PBDEs) by plants from contaminated sewage sludge

Polybrominated diphenyl ethers (PBDEs) are used as additive flame retardants. PBDEs are persistent, bioaccumulative and toxic compounds. They are often detected in sewage sludge which is applied on agricultural soils as fertilizer. The objective of this study was to find out whether plants are able to accumulate and translocate PBDEs. Tobacco (Nicotiana tabacum) and nightshade (Solanum nigrum) were planted in pots containing contaminated sewage sludge and uncontaminated substrate. After 6 months of plant cultivation in sewage sludge up to 15.4 ng g(-1) dw and 76.6 ng g(-1) dw of PBDE congeners--BDE 47, BDE 99 and BDE 100---were accumulated in the nightshade and tobacco tissue, respectively. Corresponding values in plants vegetated in the control garden substrate were 10 times lower. The bioconcentration factors (BCFs) of accumulated congeners were calculated. Tobacco exhibited higher BCFs values and for both plants BCFs values of BDE 47, BDE 99, BDE 100 and BDE 209 negatively correlated with their octanol-water partition coefficients (logK(ow)). The exception was decaBDE (BDE 209) which was accumulated only in tobacco tissue in the concentration of 116.8 ng g(-1) dw. The majority of PBDEs was detected in above-ground plant biomass indicating that both plants have the ability to translocate PBDEs. To our knowledge this is one of the first studies reporting the accumulation of both lower PBDEs and BDE 209 in plants. Our results suggest that absorption, accumulation and translocation of PBDEs by plants and their transfer to the food chain could represent another possible risk for human exposure.

Polybrominated diphenyl ethers in human gestational membranes from women in southeast Michigan

Polybrominated diphenyl ethers (PBDEs) have been incorporated into many consumer products as flame retardants. Due to their persistence and ability to bioaccumulate, PBDEs are ubiquitous in human blood and breast milk samples from industrialized nations. Although there exists a potential for environmental pollutants such as PBDEs to adversely impact birth outcomes and perinatal health, reports of PBDE levels in human reproductive tissues are limited. The aim of the current study is to evaluate the total levels and congener-specific profiles of PBDEs from human extraplacental gestational membranes. Gestational membranes from five term pregnancies were obtained from nonlaboring caesarian deliveries at the University of Michigan Women's Hospital Birth Center. Duplicate samples were extracted and analyzed by GC-MS for twenty-one PBDE congeners. Total PBDE loading was 17.4 +/- 3.9 pg/g tissue (5.62 +/- 1.28 ng/g lipid). Seventy-eight percent of the total measurable PBDE loading was due to BDEs 47, 49, 99, 100, and 153, with measured values of 3.63, 3.15, 3.05, 1.74, and 1.90 pg/g tissue (1170, 1018, 983, 561, and 612 pg/g lipid), respectively. The remaining 28% comprised BDEs 17, 28, 66, 71, 85, and 154. No octa-, nona-, or deca-BDEs were identified. Although previously unreported in the human gestational compartment BDE 49 comprised 17% of the total PBDE level. This work establishes baseline accumulated levels of PBDEs in gestational membranes of women in Southeast Michigan.