Alleviation of tetrabromobisphenol A toxicity in soybean seedlings by Rhodopseudomonas palustris RP1n1

This study investigated the regulatory role of Rhodopseudomonas palustris RP11 in alleviating TBBPA-induced harmful effects in soybean seedlings. In this study, the characteristics of growth promotion by strain RP11 were studied by analysing 5-aminolevulinic acid (ALA) and indole-3-acetic acid (IAA) production, as well as phosphorus-solubilizing and potassium-solubilizing ability. In the pot culture conditions, we tested whether strain RP11 improved soybean seedlings tolerance against TBBPA by measuring the root length and physiological parameters of the seedlings treated with strain RP11 and different concentration of TBBPA (0, 5, 50, 100, and 1000 mg/kg) together. The results showed that strain RP11 secreted IAA and ALA, and solubilized phosphate and potassium. In pot trials, strain RP11 increased the root length, chlorophyll content, carotenoid content, soluble sugar and protein content of soybean seedlings treated with TBBPA, in comparison with the seedlings treated only with TBBPA. Furthermore, strain RP11 induced the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), decreased the malondialdehyde (MDA) content in soybean seedlings under TBBPA stress. It was concluded that strain RP11 alleviated TBBPA-induced harmful effects in soybean seedlings by the secretion of IAA and ALA, the accumulation of carotenoid, soluble sugar and soluble protein, and the induction of SOD, CAT and POD as well as nutrient adjustment of phosphorus and potassium levels.

TBBPA regulates calcium-mediated lysosomal exocytosis and thereby promotes invasion and migration in hepatocellular carcinoma

Tetrabromobisphenol A (TBBPA) and its derivatives are the common flame-retardants that may increase the risk of development of many types of cancers, including liver cancer. However, the effects of TBBPA in the development and progression of liver cancer remains unknown. This study investigated the potential effects of TBBPA on a metastatic phenotype of hepatocellular carcinoma cell line-HepG2. Our results revealed that TBBPA significantly promoted the migration and invasion via affecting the number and distribution of lysosomes in HepG2 cells in a dose-dependent manner. Moreover, TBBPA decreased the intracellular protein levels of Beta-Hexosaminidase (HEXB), Cathepsin B (CTSB) and Cathepsin D (CTSD) while increased the extracellular CTSB and CTSD. It entailed that TBBPA exposure could promote the lysosomal exocytosis in cancer cells. The reversal results were obtained after adding lysosomal exocytosis inhibitor vacuolin-1. Docking results suggested that TBBPA could bind to TRPML1. It was consistent with the binding position of agonist ML-SA1. TRPML1 knockdown significantly decreased the invasion and migration, and the results were reversed when TBBPA was added. The results were indicated that TRPML1 was critical in lysosomal exocytosis. In addition, our results showed that TBBPA-TRPML1 complex regulated the calcium-mediated lysosomal exocytosis, thereby promoting the metastasis in liver cancer cells. It was expected that our data could provide important basis for understanding the molecular mechanism(s) of TBBPA promoting invasion and migration of hepatoma cells and give rise to profound concerns of TBBPA exposure on human health.

Toxicological assessment and underlying mechanisms of tetrabromobisphenol A exposure on the soil nematode Caenorhabditis elegans

The widespread use of tetrabromobisphenol A (TBBPA) in industries has resulted in its frequent detection in environmental matrices, and the mechanisms of its associated hazards need further investigation. In this study, the nematode Caenorhabditis elegans (C. elegans) was exposed to environmentally relevant concentrations of TBBPA (0, 0.1, 1, 10, 100, 200 μg/L) to determine its effects. At TBBPA concentrations above 1 μg/L, the number of head thrashes, as the most sensitive physiological indicator, decreased significantly. Using the Illumina HiSeq™ 2000 sequencer, differentially expressed genes (DEGs) were determined, and 52 were down regulated and 105 were up regulated in the 200 μg/L TBBPA treatment group versus the control group. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database analysis demonstrated that dorso-ventral axis formation is related to neurotoxicity; metabolism of xenobiotics by Cytochrome P450 (CYP450) and glutathione-S-transferase (GST) was found to be the vital metabolic mechanisms and were confirmed by quantitative real-time polymerase chain reaction (qRT-PCR). GST was ascribed to the augmentation because mutations in cyp-13A7 were constrained under TBBPA exposure. Additionally, oxidative stress indicators accumulated in a dose-dependent relationship. These results will help understand the molecular basis for TBBPA-induced toxicity in C. elegans and open novel avenues for facilitating the exploration of more efficient strategies against TBBPA toxicity.

High-Content Image-Based Single-Cell Phenotypic Analysis for the Testicular Toxicity Prediction Induced by Bisphenol A and Its Analogs Bisphenol S, Bisphenol AF, and Tetrabromobisphenol A in a Three-Dimensional Testicular Cell Co-culture Model

Emerging data indicate that structural analogs of bisphenol A (BPA) such as bisphenol S (BPS), tetrabromobisphenol A (TBBPA), and bisphenol AF (BPAF) have been introduced into the market as substitutes for BPA. Our previous study compared in vitro testicular toxicity using murine C18-4 spermatogonial cells and found that BPAF and TBBPA exhibited higher spermatogonial toxicities as compared with BPA and BPS. Recently, we developed a novel in vitro three-dimensional (3D) testicular cell co-culture model, enabling the classification of reproductive toxic substances. In this study, we applied the testicular cell co-culture model and employed a high-content image (HCA)-based single-cell analysis to further compare the testicular toxicities of BPA and its analogs. We also developed a machine learning (ML)-based HCA pipeline to examine the complex phenotypic changes associated with testicular toxicities. We found dose- and time-dependent changes in a wide spectrum of adverse endpoints, including nuclear morphology, DNA synthesis, DNA damage, and cytoskeletal structure in a single-cell-based analysis. The co-cultured testicular cells were more sensitive than the C18 spermatogonial cells in response to BPA and its analogs. Unlike conventional population-averaged assays, single-cell-based assays not only showed the levels of the averaged population, but also revealed changes in the sub-population. Machine learning-based phenotypic analysis revealed that treatment of BPA and its analogs resulted in the loss of spatial cytoskeletal structure, and an accumulation of M phase cells in a dose- and time-dependent manner. Furthermore, treatment of BPAF-induced multinucleated cells, which were associated with altered DNA damage response and impaired cellular F-actin filaments. Overall, we demonstrated a new and effective means to evaluate multiple toxic endpoints in the testicular co-culture model through the combination of ML and high-content image-based single-cell analysis. This approach provided an in-depth analysis of the multi-dimensional HCA data and provided an unbiased quantitative analysis of the phenotypes of interest.

Endometriosis, endocrine disrupters, and epigenetics: an investigation into the complex interplay in women with polybrominated biphenyl exposure and endometriosis

PURPOSE

Endocrine disrupting compounds (EDCs) have been shown to affect multiple biologic processes especially steroid-hormone processes. We sought to determine differences in DNA methylation exists between women with and without endometriosis following exposure to polybrominated biphenyl (PBB).

METHODS

Cross-sectional study of 305 females in the Michigan PBB Registry. DNA was extracted, and DNA methylation was interrogated using the MethylationEPIC BeadChip (Illumina, San Diego, California). Demographic data was analyzed using Chi-squared and T tests. Linear regressions were performed for each cytosine-guanine dinucleotide (CpG) site, modeling the logit transformation of the β value as a linear function of the presence of endometriosis. Sensitivity analyses were conducted controlling for estradiol levels and menopausal status. Replication study performed evaluating for any association between CpGs reported in the literature and our findings.

RESULTS

In total, 39,877 CpGs nominally associated with endometriosis (p < 0.05) after adjusting for age and cellular heterogeneity, although none remained significant after correction for multiple comparisons (FDR < 0.05). Pathway analysis of these CpGs showed enrichment in 68 biologic pathways involved in various endocrine, immunologic, oncologic, and cell regulation processes as well as embryologic reproductive tract development and function (FoxO, Wnt, and Hedgehog signaling). We identified 42,261 CpG sites in the literature reported to be associated with endometriosis; 2012 of these CpG sites were also significant in our cohort.

CONCLUSION

We found 39,877 CpG sites that nominally associated with endometriosis (p < 0.05) after adjusting for age and cellular heterogeneity; however, none remained significant after correction for multiple comparisons (FDR < 0.05).

Tetrabromobisphenol A inhibits carboxylesterase activity of marine organisms from different trophic levels

Tetrabromobisphenol A (TBBPA), a brominated flame retardant used in synthetic polymers and electronics, is present in the aquatic environment and recent evidence suggests it can be potentially biomagnified in the marine ecosystem. However, the toxicity of TBBPA in the marine biota has not been investigated in detail. In this study we aimed to understand the role of carboxylesterases (CEs) in xenobiotic metabolism under the exposure of marine organisms to a chemical of environmental concern, TBBPA. Specifically, we tested for in vitro inhibition of CE activity in a range of marine organisms covering different ecological niches, from species from low (mussels and copepods), medium (sardines and anchovies) and high trophic levels (tuna). The results revealed that the highest inhibition of CE activity to 100 μM TBBPA was recorded in mussels (66.5% inhibition) and tunids (36.3-76.4%), whereas copepods and small pelagic fish showed comparatively lower effects (respectively, 30% and 36.5-55.6%). Our results suggest that CE-mediated detoxification and physiological processes could be compromised in TBBPA-exposed organisms and could ultimately affect humans as many of them are market species.

Oxidative and nitrosative stress in the neurotoxicity of polybrominated diphenyl ether-153: possible mechanism and potential targeted intervention

Polybrominated diphenyl ethers (PBDEs) have been known to exhibit neurotoxicity in rats; however, the underlying mechanism remains unknown and there is no available intervention. In this study, we aimed to investigate the role of oxidative and nitrosative stress in the neurotoxicity in the cerebral cortex and primary neurons in rats following the BDE-153 treatment. Compared to the untreated group, BDE-153 treatment significantly induced the neurotoxic effects in rats, as manifested by the increased lactate dehydrogenase (LDH) activities and cell apoptosis rates, and the decreased neurotrophic factor contents and cholinergic enzyme activities in rats' cerebral cortices and primary neurons. When compared to the untreated group, the oxidative and nitrosative stress had occurred in the cerebral cortex or primary neurons in rats following the BDE-153 treatment, as manifested by the increments in levels of reactive oxygenspecies (ROS), malondialdehyde (MDA), nitric oxide (NO), and neuronal nitric oxide synthase (nNOS) mRNA and protein expressions, along with the decline in levels of superoxide dismutase (SOD) activity, glutathione (GSH) content, and peroxiredoxin I (Prx I) and Prx II mRNA and protein expressions. In addition, the ROS scavenger N-acetyl-l-cysteine (NAC) or NO scavenger NG-Nitro-l-arginine (L-NNA) significantly rescued the LDH leakage and cell survival, reversed the neurotrophin contents and cholinergic enzymes, mainly via regaining balance between oxidation/nitrosation and antioxidation. Overall, our findings suggested that oxidative and nitrosative stresses are involved in the neurotoxicity induced by BDE-153, and that the antioxidation is a potential targeted intervention.

The molecular mechanism of the antagonistic activity of hydroxylated polybrominated biphenyl (OH-BB80) toward thyroid receptor β

Polybrominated biphenyls (PBBs) were widely used as additive brominated flame retardants. Their hydroxylated products (OH-PBBs) have been detected frequently in various marine mammals, causing an increased health risk. Till now, there lacks information on the potential disruption of OH-PBBs toward thyroid hormone receptor (TR) and the molecular characteristics of their interactions remain largely unknown. We herein in vitro and in silico evaluated the disrupting effect of 3,3',5,5'-tetrabromobiphenyl (BB80) and its metabolite 2,2'-dihydroxy- 3,3',5,5'-tetrabromobiphenyl (OH-BB80) toward human TR. The recombinant human TRβ two-hybrid yeast assay reveals the moderate antagonistic activity of OH-BB80 with IC₂₀ at 2 μmol/L, while BB80 shows no agonistic or antagonistic activity. OH-BB80 binds at the binding cavity of TRβ ligand binding domain (LBD) and forms one hydrogen bond with Phe272. Electrostatic interactions and hydrophobic interactions contribute much to their interactions. The binding of OH-BB80 quenches the intrinsic fluorescence of TRβ LBD at static quenching mode. Our study extends knowledge on the endocrine disrupting effect of OH-PBBs and suggests the full consideration of the biotransformation for further health risk assessment of PBBs and related structurally similar emerging contaminants.

Environmentally relevant doses of tetrabromobisphenol A (TBBPA) cause immunotoxicity in murine macrophages

TBBPA is one of the main brominated flame retardants and is ubiquitous in the environment. TBBPA can directly encounter immune cells via the bloodstream, posing potential immunotoxicity. To understand the immunomodulating effect of TBBPA on macrophages, the murine macrophages, RAW 264.7, were exposed to TBBPA at environmentally relevant concentrations (1-100 nM). The results showed that TBBPA at the selected concentrations did not alter cell viability of RAW 264.7 cells with or without LPS stimulation. TBBPA upregulated the expression of pro-inflammatory cytokines, including IL-1β, IL-6, and TNF-α, whereas it attenuated the LPS-stimulated expression of these pro-inflammatory cytokines, and the expression of anti-inflammatory cytokines, including IL-4, IL-10, and IL-13. In addition, TBBPA reduced the mRNA levels of antigen-presenting-related genes, including H2-K2, H2-Aa, Cd80, and Cd86. Moreover, TBBPA impaired the phagocytic activity of macrophages. Furthermore, exposure to TBBPA significantly elevated the protein levels of phosphorylated NF-κB p65 (p-p65), while it reduced LPS-stimulated p-p65 protein levels. DCFH-DA staining assays showed that TBBPA caused a slight but significant elevation in reactive oxygen species levels. The data obtained in the present study demonstrated that exposure to environmentally relevant concentrations of TBBPA posed immunotoxicity in macrophages and unveiled a potential health risk of TBBPA.

Sex-specific behavioral effects following developmental exposure to tetrabromobisphenol A (TBBPA) in Wistar rats

Tetrabromobisphenol A (TBBPA) has become a ubiquitous indoor contaminant due to its widespread use as an additive flame retardant in consumer products. Reported evidence of endocrine disruption and accumulation of TBBPA in brain tissue has raised concerns regarding its potential effects on neurodevelopment and behavior. The goal of the present study was to examine the impact of developmental TBBPA exposure, across a wide range of doses, on sexually dimorphic non-reproductive behaviors in male and female Wistar rats. We first ran a pilot study using a single TBBPA dose hypothesized to produce behavioral effects. Wistar rat dams were orally exposed using cookie treats to 0 or 0.1 mg TBBPA/kg bw daily from gestational day (GD) 9 to postnatal day (PND) 21 to assess offspring (both sexes) activity and anxiety-related behaviors. Significant effects were evident in females, with exposure increasing activity levels. Thus, this dose was used as the lowest TBBPA dose in a subsequent, larger study conducted as part of a comprehensive assessment of TBBPA toxicity. Animals were exposed to 0, 0.1, 25, or 250 mg TBBPA/kg bw daily by oral gavage starting on GD 6 through PND 90 (dosed dams GD 6 - PND 21, dosed offspring PND 22 - PND 90). Significant behavioral findings were observed for male offspring, with increased anxiety-like behavior as the primary phenotype. These findings demonstrate that exposure to environmental contaminants, like TBBPA, can have sex-specific effects on behavior highlighting the vulnerability of the developing brain.

Degradation of tetrabromobisphenol a by ozonation: Performance, products, mechanism and toxicity

This study systematically investigated the performance of ozonation on tetrabromobisphenol A (TBBPA) degradation under different ozone dosages (5.21-83.33 μmoL/L), initial solution pH (3.0-11.0) and temperatures (10-50 °C). At the same time, the generations of inorganic products (bromide ion and bromate) under different experimental conditions were evaluated and the organic products were also identified. Then, the possible mechanism was proposed and verified by the quantum chemical calculation. In addition, variations and controlling of the toxicity were also analyzed, including acute toxicity, chronic toxicity and genotoxicity. Ozonation was proved to be an efficient and promising technology for removing TBBPA from water. TBBPA of 1.84 μmoL/L could be completely degraded within 5 min under the ozone dosage of 41.67 μmoL/L in wide ranges of pH (3.0-11.0) and temperature (10-40 °C). During the degradation of TBBPA, over 65% of the average bromine ion was detected and nine products were identified. The proposed degradation pathways verified that TBBPA might undergo addition and stepwise oxidative debromination, the hydrogen extraction, and the deprotonation. The results of toxicity testing showed that ozonation could effectively control the acute and chronic toxicity of the water samples, although the toxicity increased in the initial reaction stage due to the accumulation of more toxic intermediates.

Tetrabromobisphenol A: Disposition, kinetics and toxicity in animals and humans

Tetrabromobisphenol A (TBBPA) is a nonregulated brominated flame retardant with a high production volume, and it is applied in a wide variety of consumer products. TBBPA is ubiquitous in abiotic matrices, wildlife and humans around the world. This paper critically reviews the published scientific data concerning the disposition, metabolism or kinetics and toxicity of TBBPA in animals and humans. TBBPA is rapidly absorbed and widely distributed among tissues, and is excreted primarily in the feces. In rats, TBBPA and its metabolites have limited systemic bioavailability. TBBPA has been detected in human milk in the general population. It is available to both the developing fetus and the nursing pups following maternal exposure. It has been suggested that TBBPA causes acute toxicity, endocrine disruptor activity, immunotoxicity, neurotoxicity, nephrotoxicity, and hepatotoxicity in animals. Cell-based assays have shown that TBBPA can induce reactive oxygen species in a concentration-dependent manner, and it promotes the production of inflammatory factors such as TNF α, IL-6, and IL-8. Cells exposed to high levels of TBBPA exhibit seriously injured mitochondria and a dilated smooth endoplasmic reticulum. This review will enhance the understanding of the potential risks of TBBPA exposure to ecological and human health.

In ovo exposure to brominated flame retardants Part II: Assessment of effects of TBBPA-BDBPE and BTBPE on hatching success, morphometric and physiological endpoints in American kestrels

Tetrabromobisphenol A bis(2,3-dibromopropyl ether) (TBBPA-BDBPE) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTPBE) are both brominated flame retardants (BFRs) that have been detected in birds; however, their potential biological effects are largely unknown. We assessed the effects of embryonic exposure to TBBPA-BDBPE and BTBPE in a model avian predator, the American kestrel (Falco sparverius). Fertile eggs from a captive population of kestrels were injected on embryonic day 5 (ED5) with a vehicle control or one of three doses within the range of concentrations that have been detected in biota (nominal concentrations of 0, 10, 50 or 100 ng/g egg; measured concentrations 0, 3.0, 13.7 or 33.5 ng TBBPA-BDBPE/g egg and 0, 5.3, 26.8 or 58.1 ng BTBPE/g egg). Eggs were artificially incubated until hatching (ED28), at which point blood and tissues were collected to measure morphological and physiological endpoints, including organ somatic indices, circulating and glandular thyroid hormone concentrations, thyroid gland histology, hepatic deiodinase activity, and markers of oxidative stress. Neither compound had any effects on embryo survival through 90% of the incubation period or on hatching success, body mass, organ size, or oxidative stress of hatchlings. There was evidence of sex-specific effects in the thyroid system responses to the BTBPE exposures, with type 2 deiodinase (D2) activity decreasing at higher doses in female, but not in male hatchlings, suggesting that females may be more sensitive to BTBPE. However, there were no effects of TBBPA-BDBPE on the thyroid system in kestrels. For the BTPBE study, a subset of high-dose eggs was collected throughout the incubation period to measure changes in BTBPE concentrations. There was no decrease in BTBPE over the incubation period, suggesting that BTBPE is slowly metabolized by kestrel embryos throughout their ∼28-d development. These two compounds, therefore, do not appear to be particularly toxic to embryos of the American kestrel.

In ovo exposure to brominated flame retardants Part I: Assessment of effects of TBBPA-BDBPE on survival, morphometric and physiological endpoints in zebra finches

Tetrabromobisphenol A bis(2,3-dibromopropyl) ether (TBBPA-BDBPE) is an additive flame retardant used in polyolefins and polymers. It has been detected in biota, including in avian eggs, yet little is known of its effects. We assessed the pattern of TBBPA-BDBPE concentrations in songbird eggs over the incubation period, and the effects of embryonic exposure to TBBPA-BDBPE in a model songbird species, the zebra finch (Taeniopygia guttata). To assess concentrations during embryo development, eggs were injected on the day they were laid with the vehicle control (safflower oil) or 100 ng TBBPA-BDBPE/g egg, and whole egg contents were collected throughout embryonic development on day 0 (unincubated), 5, 10 and 13. To evaluate effects of embryonic exposure to TBBPA-BDBPE, eggs were injected at Hamburger-Hamilton stage 18 (∼80 h after initiation of incubation) with safflower oil only, 10, 50 or 100 ng TBBPA-BDBPE/g egg (albumin injection volume 1 μl/g). Eggs were monitored for hatching success, and nestlings were monitored for growth and survival. At 15 days post-hatch, tissues were collected to assess physiological effects. TBBPA-BDBPE was incorporated into the egg as the embryo developed, and concentrations started declining in late incubation, suggesting biotransformation by the embryo. There were no effects on hatching success, nestling survival, growth, organ somatic indices, or thyroid hormone homeostasis; however, there was evidence that body condition declined in a dose-dependent manner towards the end of the rapid nestling growth phase. This decreased body condition could be a delayed effect of early developmental exposure, or it may be the result of increased exposure to biotransformation products of TBBPA-BDBPE produced over the nestling period, which are predicted to be more bioaccumulative and toxic than the parent compound.

Embryoid body-based RNA-seq analyses reveal a potential TBBPA multifaceted developmental toxicity

The frequent detection of tetrabromobisphenol A (TBBPA) in the human body, especially in umbilical cord serum and breast milk, has raised concerns about TBBPA potential effects on embryonic development. The differentiation of embryonic stem cells (ESCs) in vitro can serve as a model for the early stages of embryonic development. In this study, we differentiated mouse ESCs via 3D aggregates called embryoid bodies in presence of environment and human relevant TBPPA concentrations for 28 days. We collected samples at different time points and analyzed TBBPA-dependent global gene expression changes by RNA-seq. Our analyses revealed a potential TBBPA multifaceted developmental toxicity with effects on the nervous and cardiac/skeletal muscle systems. Mechanistically, our findings suggest TBBPA endocrine disrupting activities in part via prolactin signaling.

Environmental exposure to polybrominated biphenyl (PBB) associates with an increased rate of biological aging

Advanced age increases risk for cancer, cardiovascular disease, and all-cause mortality. However, people do not age at the same rate, and biological age (frequently measured through DNA methylation) can be older than chronological age. Environmental factors have been associated with the rate of biological aging, but it is not known whether persistent endocrine-disrupting compounds (EDCs) like polybrominated biphenyl (PBB) would associate with age acceleration. Three different epigenetic age acceleration measures (intrinsic, extrinsic, and phenotypic) were calculated from existing epigenetic data in whole blood from a population highly exposed to PBB (N=658). Association between serum PBB concentration and these measures was tested, controlling for sex, lipid levels, and estimated cell type proportions. Higher PBB levels associated with increased age acceleration (intrinsic: β=0.24, 95%CI=0.01-0.46, p = 0.03; extrinsic: β=0.39, 95%CI=0.12-0.65, p = 0.004; and phenotypic: β=0.30, 95%CI=0.05-0.54, p = 0.01). Neither age when exposed to PBB nor sex statistically interacted with PBB to predict age acceleration, but, in stratified analyses, the association between PBB and age acceleration was only in people exposed before finishing puberty and in men. This suggests that EDCs can associate with the biological aging process, and further studies are warranted to investigate other environmental pollutants' effect on aging.

Changes in the activities of antioxidant enzymes and reduced glutathione level in human erythrocytes exposed to selected brominated flame retardants

Currently, more and more concerns are related to oxidative stress appearing in cells as a result of xenobiotics action. It has been found that selected brominated flame retardants (BFRs) can cause reactive oxygen species (ROS) induction at environmental concentrations. Excessive ROS induction can contribute to the redox imbalance in the cell. Therefore, the aim of our work was to evaluate the effect of selected BFRs on the activity of antioxidant enzymes, i.e. superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and the level of reduced glutathione (GSH) in human erythrocytes. Erythrocytes were incubated with tetrabromobisphenol A (TBBPA), tetrabromobisphenol S (TBBPS), 2,4-dibromophenol (2,4-DBP), 2,4,6-tribromophenol (2,4,6-TBP) and pentabromophenol (PBP) in the concentration ranging from 1 to 100 μg/ml. This study has shown that the BFRs studied disturbed redox balance in human erythrocytes. TBBPA caused more significant decrease in antioxidant enzymes activities than other compounds examined. Among bromophenols studied, 2,4-DBP most strongly affected antioxidant system, which indicated that the number of bromine atoms in the molecule did not significantly affect the pro-oxidative properties of the BFRs examined.

Regulation of TBBPA-induced oxidative stress on mitochondrial apoptosis in L02 cells through the Nrf2 signaling pathway

Tetrabromobisphenol A (TBBPA) is a commonly used brominated flame retardant, which has a wide range of toxic effects on organisms. This study investigated the cytotoxic effects on human hepatocytes (L02 cells) after treated with 0, 5, 10, 20, and 40 μM of TBBPA. Results showed that TBBPA significantly increased intracellular reactive oxygen species (ROS), malondialdehyde (MDA) and the ratio of oxidized/reduced glutathione (GSSG/GSH) dose-dependently. TBBPA also decreased the cell mitochondrial membrane potential (MMP), caused the release of cytochrome C (Cyt C) to cytoplasm and promoted the expression of caspase-9 and caspase-3, and finally increased the level of apoptosis. The ROS inhibitor N-acetyl-L-cysteine (NAC) relieved the oxidative stress responses, and prevented the decrease of MMP and increase of apoptosis. In addition, TBBPA promoted the expression of antioxidant genes related to Nrf2, such as quinone oxidoreductase 1 (NQO1), catalase (CAT), and heme oxygenase 1 (HO-1). Oxidative stress initiated by TBBPA, activated mitochondrial apoptosis and Nrf2 pathway, and increased the degree of apoptosis in L02 cells.

Toxicity of BDE-47, BDE-99 and BDE-153 on swimming behavior of the unicellular marine microalgae Platymonas subcordiformis and implications for seawater quality assessment

Polybrominated diphenyl ethers (PBDEs), a class of brominated flame retardants, have been extensively applied and eventually leached into the surrounding environment. Marine microalgae are not only the dominant primary producers of marine ecosystem, but also food source for aquaculture. PBDEs have been found to remarkably inhibit growth, photosynthesis and metabolism of marine microalgae. However, whether they also affect swimming behavior of marine motile microalgae remains unknown. We chose BDE-47, BDE-99 and BDE-153 as model PBDEs, and the unicellular marine green flagellate, Platymonas subcordiformis, as test organism to figure out this issue. After two-hour exposure, motile cells proportion (MOT), swimming velocity (VCL, VAP and VSL), and swimming pattern (LIN and STR) of P. subcordiformis were measured via computer assisted cell movement tracking. Results suggest that the three PBDEs not only reduced motile cells proportion and swimming velocity, but also altered swimming pattern. BDE-47 was more toxic than BDE-99, followed by BDE-153, indicating their toxicity decreased as bromination degree increases. Swimming ability of P. subcordiformis was even completely arrested when BDE-47 and BDE-99 at 32 μg/L. The impairment of swimming ability by PBDEs might thereby hinder growth and survival of marine microalgae, and subsequently threaten marine ecosystem and aquaculture industry. More importantly, this study implies that marine microalgae swimming behavior test is more efficiency and sensitive than traditional marine microalgal bioassays, like growth and photosynthesis tests. We suggest that although future work is needed, swimming behavior analysis of P. subcordiformis with MOT, VCL and VAP as endpoints can be developed as a low-cost, convenient, fast, reliable and sensitive method for seawater quality assessment.

Transcriptomic analyses of human bronchial epithelial cells BEAS-2B exposed to brominated flame retardant (tetrabromobisphenol A)

Brominated flame retardants (BFRs) are supposed to act as disruptors of cell signaling, but the underlying mechanisms remain less clear. Human bronchial epithelial cells (BEAS-2B) were used to investigate the toxic effect and gene expression changes induced by tetrabromobisphenol A (TBBPA). By genome-wide approaches with Illumina RNA-seq, 87 genes were identified to exhibit ≥1.5-fold changes in expression after treatment by TBBPA for 48 h, among which, 79 were upregulated and 8 were downregulated. Gene ontology (GO) annotation enriched unigenes were divided into three clusters: biological process (BP), cellular component (CC) and molecular function (MF). Pathway analysis showed that NF-κB, TNF signaling, toll-like receptor, MAPK signaling and B-cell receptor were the most prominent pathways affected by TBBPA, which play key roles in regulating cell proliferation and cell differentiation, inflammatory response. Finally, for verifying the accuracy of microarray analysis, qRT-PCR was used to analyze the transcription level of key genes in the above signaling pathways, and ELISA assay confirmed the effect of TBBPA on the levels of CXCL-2, CCL-3, CCL-4, IL-1β, TNF-α, and IL-6. These findings provided important information for further exploitation of the mechanisms under-lying BFR-induced adverse health effects.

Inhibition of growth in juvenile manila clam Ruditapes philippinarum: Potential adverse outcome pathway of TBBPA

Tetrabromobisphenol A (TBBPA) is ubiquitous and its contents showing an increasing trend in the coastal environment. In order to investigate the effects of TBBPA on marine bivalves, juvenile manila clams Ruditapes phillipinarum were exposed to TBBPA for 28 days. The results showed that shell growth rate of juvenile clams after exposure to 62.5-1000 μg L^-1 TBBPA for 28 d were significantly inhibited (p < 0.05). Then in order to link the changes in filtration rate, mRNA expression of insulin-like growth factor homologue (IGF) and tissue thyroid hormone (TH) contents to growth, juvenile clams were exposed to 62.5 and 500 μg L^-1 TBBPA for 14 days. The transcriptional levels of neuroendocrine signals (NPF and insulin homologue) associated with filter feeding regulation, and genes of TH synthesis-related enzymes were also examined. The results showed that filtration rates was significantly reduced to 44.1% and 14% of controls after 14 d of exposure. In parallel, exposure to TBBPA significantly increased the expression levels of insulin which may elicit the filter feeding inhibition. TBBPA exposure caused alterations in tissue content of THs and mRNA expression of TH synthesis-related enzymes. However, the data showed increased T₃ content, T₃/T₄ ratio and mRNA expression of IGF. These data demonstrated that the most important key event of TBBPA could be linked to growth impairment in juveniles was the reduction of filtration rate. These results provide a robust framework towards revealing the underlying mechanism of the growth inhibition caused by TBBPA on bivalves and understanding the adverse outcome pathway across taxonomic phyla.

Tetrabromobisphenol A (TBBPA) Alters ABC Transport at the Blood-Brain Barrier

Tetrabromobisphenol A (TBBPA, CAS No. 79-94-7) is a brominated flame retardant used in 90% of epoxy coated circuit boards. Exposures to TBBPA can induce neurotoxicity and disrupt MAPK, estrogen, thyroid, and PPAR-associated signaling pathways. Because these pathways also regulate transporters of the central nervous system barriers, we sought to determine the effect of TBBPA on the expression and activity of 3 ATP binding cassette (ABC) transporters of the blood-brain barrier (BBB). Using a confocal based assay, we measured the ex vivo and in vivo effects of TBBPA on P-glycoprotein (P-gp), breast cancer resistant protein (BCRP), and multidrug resistance-associated protein 2 (MRP2) transport activity in rat brain capillaries. Our rationale for using a rat model was based on tissue availability, ease of handling, and availability of historical TBBPA toxicokinetic data. We found that TBBPA (1-1000 nM) exposure had no significant effect on multidrug resistance-associated protein 2 transport activity in either sex, suggesting TBBPA does not compromise the physical integrity of the BBB. However, low concentrations of TBBPA (1-100 nM) significantly decreased breast cancer resistant protein transport activity in both sexes. Additionally, TBBPA exposures (1-100 nM), elicited a sex-dependent response in P-gp transport: increasing transport activity in males and decreasing transport activity in females. All TBBPA dependent changes in transport activity were dose- and time-dependent. Inhibitors of either transcription or translation abolished the TBBPA dependent increases in male P-gp transport activity. Western blot and immunofluorescent assays confirmed the TBBPA dependent P-gp increases expression in males and decreases in females. Antagonizing PPAR-γ abolished the TBBPA dependent increases in males but not the decreases in females. However, the decreases in female P-gp transport were blocked by an ER-α antagonist. This work indicates that environmentally relevant concentrations of TBBPA (1-100 nM) alter ABC transporter function at the BBB. Moreover, permeability changes in the BBB can alter brain homeostasis, hinder central nervous system drug delivery, and increase the brain's exposure to harmful xenobiotic toxicants.

Organohalogenated pollutants in raw and UHT cow's milk from Turkey: a risk assessment of dietary intake

In this study, health risk of human exposure to organohalogenated pollutants (OHPs) through milk consumption was determined. Conventionally produced, unprocessed cow's milk samples taken from Konya District, in Turkey, and 15 different brand ultra-high-temperature (UHT) processed cow's milk samples taken from supermarkets of Turkey were analyzed for organochlorine pesticides (OCPs, α-, β-, γ-, and δ-HCHs, p,p'-DDE, p,p'-DDD, and p,p'-DDT, heptachlor, heptachlor epoxide, endosulfan I, endosulfan II, endosulfan sulfate, endrin, endrin aldehyde, endrin ketone, aldrin + dieldrin, methoxychlor), polychlorinated biphenyls (PCBs, PCB 28, 52, 101, 153, 138, and 180), and polybrominated diphenyl ethers (PBDEs, PBDE 47, 99, 100, 153, and 154 congeners). Estimated daily intake (EDI) values calculated for both adults and children consuming raw or UHT milk were determined to exceed maximum residue limits (MRLs) set for γ-HCH, ∑Heptachlor, and endrin. EDI values also exceeded admissible daily intake (ADI) values given for ∑HCH, ∑Heptachlor, ∑Endrin aldrin + dieldrin, and ∑PCBs. p,p'-DDT/p,p'-DDE ratio was 1 or higher for 66% of the milk samples, which is an indication of sustaining illegal use of DDT. A health risk is determined for dietary intake of OHPs via consumption of milk.

Tetrabromobisphenol A-induced depolarization of rat cerebellar granule cells: ex vivo and in vitro studies

The brominated flame retardant tetrabromobisphenol A (TBBPA) is toxic to cultured brain neurons, and glutamate receptors partially mediate this effect; consequently, the depolarizing effect of TBBPA on neurons is to be expected, but it is yet to be actually demonstrated. The aim of this study was to detect TBBPA-evoked depolarization and identify the underlying mechanisms. The plasma membrane potential of rat cerebellar granule cells (CGC) in cerebellar slices or in primary cultures was measured using whole-cell current clamp recordings, or the fluorescent probe oxonol VI, respectively. The contribution of NMDA and AMPA receptors, voltage-gated sodium channels and intracellular calcium mobilization was tested using their selective antagonists or inhibitors. Direct interactions of TBBPA with NMDARs were tested by measuring the specific binding of radiolabeled NMDAR ligands to isolated rat cortical membrane fraction. TBBPA (25 μM) strongly depolarized CGC in cerebellar slices, and at ≥ 7.5 μM concentration-dependently depolarized primary CGC cultures. Depolarization of the primary CGC by 25 μM TBBPA was partly reduced when MK-801 was applied alone or in combination with either TTX or CNQX, or where bastadin 12 was applied in combination with ryanodine, whereas depolarization was completely prevented when MK-801, CNQX and TTX where combined. TBBPA had no effect on the specific binding of NMDAR radio-ligands to isolated cortical membranes. These results demonstrate the depolarizing effect of TBBPA on CGC, which is mainly mediated by ionotropic glutamate receptors, while voltage-gated sodium channels are also involved. We found no evidence for the direct activation of NMDARs by TBBPA.

Metabolic perturbation, proliferation and reactive oxygen species jointly contribute to cytotoxicity of human breast cancer cell induced by tetrabromo and tetrachloro bisphenol A

Halogenated bisphenol A analogues (X-BPA) have been widely used in industrial production, such as flame retardant. Although BPA exposure was found to result in cytotoxicity, toxicity of X-BPA and molecular mechanism remain under-explored. In this study, we employed human breast cancer cell as a model to investigate the concentration-dependent toxicity and underlying mechanisms of tetrabromo bisphenol A (TBBPA) and tetrachloro bisphenol A (TCBPA). An integrated method involving molecular toxicology and mass spectrometry (MS)-based global metabolomics was applied to evaluate the toxicity of TCBPA and TBBPA on cell viability, reactive oxygen species (ROS), and metabolic alterations. The results demonstrated that low micromolar levels (0-10 μM) of TCBPA/TBBPA exposure induced cell proliferation and activated the energy metabolism of both glycolysis and amino acid. On the other hand, high micromolar levels (10-50 μM) of TCBPA/TBBPA exposure perturbed the balance between ROS and antioxidative defense process by promoting the ROS generation via the down-regulation of glutathione biosynthesis and up-regulation of nucleotide metabolism. This study, for the first time, provides evidence and mechanism for better understanding the cytotoxicity of TCBPA and TBBPA by regulating the specific metabolic pathways.