Design and Synthesis of Marine Polybrominated Diphenyl Ether Derivatives as Potential Anti-Inflammatory Agents.

Natural polybrominated diphenyl ethers are generally isolated from sponges and possess a broad range of biological activities. Through screening of our marine natural product library, we discovered that polybrominated diphenyl ethers 5 and 6 exhibit considerable anti-inflammatory activity. In order to expand our repertoire of derivatives for further biological activity studies, we designed and synthesized a series of 5-related polybrominated diphenyl ethers. Importantly, compound 5a showed comparable anti-inflammatory activity while much lower cytotoxicity on lipopolysaccharide (LPS)-induced RAW264.7 cells. Additionally, western blotting analysis showed that 5a reduced the expression of phosphorylated extracellular signal-regulated kinase (p-ERK). Besides, molecular docking experiments were conducted to predict and elucidate the potential mechanisms underlying the varying anti-inflammatory activities exhibited by compounds 5a, 5, and 6.

Decarbromodiphenyl ether exposure promotes migration of triple-negative breast cancer cells through miR-221 in extracellular vesicles. / åæº´è”è‹¯é†šæš´éœ²é€šè¿‡èƒžå¤–å›Šæ³¡è£ è½½miR-221ä¿ƒè¿›ä¸‰é˜´æ€§ä¹³è ºç™Œç»†èƒžè½¬ç§».

OBJECTIVES: To investigate the effect of decarbromodiphenyl ether (BDE-209) exposure on the migration ability of triple-negative breast cancer (TNBC) cells and to explore the underlying mechanism. METHODS: Human TNBC MDA-MB-231 cells were divided into blank control group and BDE-209 exposure groups (treated with 0.02, 0.20, 2.00, 20.00 and 200.00 ng/mL BDE-209 in high glucose DMEM). Extracellular vehicles (EVs) secreted by MDA-MB-231 cells were isolated by differential ultracentrifugation. Transmission electron microscopy (SEM), nanoparticle tracking analysis (NTA) and Western blotting were performed to characterize the EVs. The effect of the EVs induced by BDE-209 exposure (EVs-BDE-209) on the migration and invasion of MDA-MB-231 cells was detected by wound-healing assay and Transwell test. qRT-PCR was used to measure the miR-221 level in EVs-BDE-209. The expression of MMP9 in MDA-MB-231 cells was determined by Western blotting. RESULTS: Compared with the blank control, BDE-209 exposure increased the tumor cell-derived EVs in dose-dependent manner. The MDA-MB-231 cells co-cultured with EVs released by 200.00 ng/mL BDE-209 exposure showed an 86% increase in cell migration rate, a 1.32-fold higher number of membrane-penetrating cells, a 2.71-fold higher expression level of miR-221, and a 1.62-fold higher expression level of MMP9 compared with the blank control group (all P<0.05). While transfection with anti-miR-221 antibody to decrease miR-221 level in EVs significantly reversed the increased invasion ability of the MDA-MB-231 cells treated with EVs-BDE-209. CONCLUSIONS: BDE-209 exposure may promote metastasis potential of MDA-MB-231 cells via EVs-BDE-209 transmitted miR-221.

BDE-47 Induces Immunotoxicity in RAW264.7 Macrophages through the Reactive Oxygen Species-Mediated Mitochondrial Apoptotic Pathway.

Polybrominated diphenyl ethers (PBDEs) are classic and emerging pollutants that are potentially harmful to the human immune system. Research on their immunotoxicity and mechanisms suggests that they play an important role in the resulting pernicious effects of PBDEs. 2,2',4,4'-Tetrabrominated biphenyl ether (BDE-47) is the most biotoxic PBDE congener, and, in this study, we evaluated its toxicity toward RAW264.7 cells of mouse macrophages. The results show that exposure to BDE-47 led to a significant decrease in cell viability and a prominent increase in apoptosis. A decrease in mitochondrial membrane potential (MMP) and an increase in cytochrome C release and caspase cascade activation thus demonstrate that cell apoptosis induced by BDE-47 occurs via the mitochondrial pathway. In addition, BDE-47 inhibits phagocytosis in RAW264.7 cells, changes the related immune factor index, and causes immune function damage. Furthermore, we discovered a significant increase in the level of cellular reactive oxygen species (ROS), and the regulation of genes linked to oxidative stress was also demonstrated using transcriptome sequencing. The degree of apoptosis and immune function impairment caused by BDE-47 could be reversed after treatment with the antioxidant NAC and, conversely, exacerbated by treatment with the ROS-inducer BSO. These findings indicate that oxidative damage caused by BDE-47 is a critical event that leads to mitochondrial apoptosis in RAW264.7 macrophages, ultimately resulting in the suppression of immune function.

Diversity-oriented synthesis of marine polybrominated diphenyl ethers as potential KCNQ potassium channel activators.

Natural polybrominated diphenyl ethers, often isolated from marine sponges, have been reported to possess various biological activities, such as antibacterial, antioxidant and antidiabetic effects. Via a high throughput screening of our marine natural product library, the polybrominated diphenyl ether 3 was found to display a KCNQ potassium channel activation effect. To obtain more compound 3 related natural products and their derivatives for further bioactivity study, a diversity-oriented synthesis was conducted, leading to the successful synthesis of five polybrominated diphenyl ether natural products (1-4, 6) and 30 new derivatives. Compound 3 was found to preferentially potentiate KCNQ1 potassium channel, whereas 17h relatively activated KCNQ2 potassium channel. The structure-activity relationship was analyzed assisted by molecular docking and 17h was further conducted for its agonistic mechanism study on KCNQ2 channel. This research work may give an insight for the discovery of marine polybrominated diphenyl ether derived new drug leads.

A Multiwell-Based Assay for Screening Thyroid Hormone Signaling Disruptors Using thibz Expression as a Sensitive Endpoint in Xenopus laevis.

There is a need for rapidly screening thyroid hormone (TH) signaling disruptors in vivo considering the essential role of TH signaling in vertebrates. We aimed to establish a rapid in vivo screening assay using Xenopus laevis based on the T3-induced Xenopus metamorphosis assay we established previously, as well as the Xenopus Eleutheroembryonic Thyroid Assay (XETA). Stage 48 tadpoles were treated with a series of concentrations of T3 in 6-well plates for 24 h and the expression of six TH-response genes was analyzed for choosing a proper T3 concentration. Next, bisphenol A (BPA) and tetrabromobisphenol A (TBBPA), two known TH signaling disruptors, were tested for determining the most sensitive TH-response gene, followed by the detection of several suspected TH signaling disruptors. We determined 1 nM as the induction concentration of T3 and thibz expression as the sensitive endpoint for detecting TH signaling disruptors given its highest response to T3, BPA, and TBBPA. And we identified betamipron as a TH signaling agonist, and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) as a TH signaling antagonist. Overall, we developed a multiwell-based assay for rapidly screening TH signaling disruptors using thibz expression as a sensitive endpoint in X. laevis.

Ecological and Pharmacological Activities of Polybrominated Diphenyl Ethers (PBDEs) from the Indonesian Marine Sponge Lamellodysidea herbacea.

Two known Polybrominated Diphenyl Ethers (PBDEs), 3,4,5-tribromo-2-(2',4'-dibromophenoxy)phenol (1d) and 3,4,5,6-tetrabromo-2-(2',4'-dibromophenoxy)phenol (2b), were isolated from the Indonesian marine sponge Lamellodysidea herbacea. The structure was confirmed using 13C chemical shift average deviation and was compared to the predicted structures and recorded chemical shifts in previous studies. We found a wide range of bioactivities from the organic crude extract, such as (1) a strong deterrence against the generalist pufferfish Canthigaster solandri, (2) potent inhibition against environmental and human pathogenic bacterial and fungal strains, and (3) the inhibition of the Hepatitis C Virus (HCV). The addition of a bromine atom into the A-ring of compound 2b resulted in higher fish feeding deterrence compared to compound 1d. On the contrary, compound 2b showed only more potent inhibition against the Gram-negative bacteria Rhodotorula glutinis (MIC 2.1 µg/mL), while compound 1d showed more powerful inhibition against the other human pathogenic bacteria and fungi. The first report of a chemical defense by compounds 1d and 2b against fish feeding and environmental relevant bacteria, especially pathogenic bacteria, might be one reason for the widespread occurrence of the shallow water sponge Lamellodysidea herbacea in Indonesia and the Indo-Pacific.

40 Years of Research on Polybrominated Diphenyl Ethers (PBDEs)-A Historical Overview and Newest Data of a Promising Anticancer Drug.

Polybrominated diphenyl ethers (PBDEs) are a group of molecules with an ambiguous background in literature. PBDEs were first isolated from marine sponges of Dysidea species in 1981 and have been under continuous research to the present day. This article summarizes the two research aspects, (i) the marine compound chemistry research dealing with naturally produced PBDEs and (ii) the environmental toxicology research dealing with synthetically-produced brominated flame-retardant PBDEs. The different bioactivity patterns are set in relation to the structural similarities and dissimilarities between both groups. In addition, this article gives a first structure-activity relationship analysis comparing both groups of PBDEs. Moreover, we provide novel data of a promising anticancer therapeutic PBDE (i.e., 4,5,6-tribromo-2-(2',4'-dibromophenoxy)phenol; termed P01F08). It has been known since 1995 that P01F08 exhibits anticancer activity, but the detailed mechanism remains poorly understood. Only recently, Mayer and colleagues identified a therapeutic window for P01F08, specifically targeting primary malignant cells in a low µM range. To elucidate the mechanistic pathway of cell death induction, we verified and compared its cytotoxicity and apoptosis induction capacity in Ramos and Jurkat lymphoma cells. Moreover, using Jurkat cells overexpressing antiapoptotic Bcl-2, we were able to show that P01F08 induces apoptosis mainly through the intrinsic mitochondrial pathway.

Oxy-Polybrominated Diphenyl Ethers from the Indonesian Marine Sponge, Lamellodysidea herbacea: X-ray, SAR, and Computational Studies.

Polybrominated diphenyl ether (PBDE) compounds, derived from marine organisms, originate from symbiosis between marine sponges and cyanobacteria or bacteria. PBDEs have broad biological spectra; therefore, we analyzed structure and activity relationships of PBDEs to determine their potential as anticancer or antibacterial lead structures, through reactions and computational studies. Six known PBDEs (1-6) were isolated from the sponge, Lamellodysdiea herbacea; 13C NMR data for compound 6 are reported for the first time and their assignments are confirmed by their theoretical 13C NMR chemical shifts (RMSE < 4.0 ppm). Methylation and acetylation of 1 (2, 3, 4, 5-tetrabromo-6-(3', 5'-dibromo-2'-hydroxyphenoxy) phenol) at the phenol functional group gave seven molecules (7-13), of which 10, 12, and 13 were new. New crystal structures for 8 and 9 are also reported. Debromination carried out on 1 produced nine compounds (1, 2, 14, 16-18, 20, 23, and 26) of which 18 was new. Debromination product 16 showed a significant IC50 8.65 ± 1.11; 8.11 ± 1.43 µM against human embryonic kidney (HEK293T) cells. Compounds 1 and 16 exhibited antibacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Klebsiella pneumoniae with MID 0.078 µg/disk. The number of four bromine atoms and two phenol functional groups are important for antibacterial activity (S. aureus and K. pneumoniae) and cytotoxicity (HEK293T). The result was supported by analysis of frontier molecular orbitals (FMOs). We also propose possible products of acetylation and debromination using analysis of FMOs and electrostatic charges and we confirm the experimental result.

2,2',4,4',5-Pentabromodiphenyl ether induces lipid accumulation throughout differentiation in 3T3-L1 and human preadipocytes in vitro.

Flame retardants, specifically polybrominated diphenyl ethers (PBDEs), are chemical compounds widely used for industrial purposes and household materials. NHANES data indicate that nearly all Americans have trace amounts of PBDEs in serum, with even higher levels associated with occupational exposure. PBDEs are known to bioaccumulate in the environment due to their lipophilicity and stability, and more importantly, they have been detected in human adipose tissue. The present study examined whether the PBDE congener, BDE-99 (2,2',4,4',5-pentabromodiphenyl ether; 0.2-20 µM), enhances the adipogenesis of mouse and human preadipocyte cell models in vitro via induced lipid accumulation. 3T3-L1 mouse preadipocytes and human visceral preadipocytes demonstrated enhanced hormone-induced lipid accumulation upon BDE-99 treatment. In addition, BDE-99 (20 µM) induced preadipocyte differentiation and lipid development in nondifferentiated human preadipocytes. BDE-99, the second most abundant congener in human adipose tissue, increased total lipids in differentiating adipocytes and therefore showed a potential role in the regulation of adipogenesis. This warrants more research to further understand the impact of lipophilic persistent pollutants on adipose tissue homeostasis.

Synthesis and Toxicity of Halogenated Bisphenol Monosubstituted-Ethers: Establishing a Library for Potential Environmental Transformation Products of Emerging Contaminant.

As an important branch of halogenated bisphenol compounds, the halogenated bisphenol monosubstituted-ether compounds have received a lot of attention in environmental health science because of their toxicity and variability. In this study, a synthetic method for bisphenol monosubstituted-ether byproduct libraries was developed. By using the versatile and efficient method, tetrachlorobisphenol A, tetrabromobisphenol A, and tetrabromobisphenol S monosubstituted alkyl-ether compounds were accessed in 39-82 % yield. Subsequently, the cytotoxicity of 27 compounds were screened using three different cell lines (HepG2, mouse primary astrocytes and Chang liver cells). Compound 2,6-dibromo-4-[3,5-dibromo-4-(2-hydroxyethoxy)benzene-1-sulfonyl]phenol was more toxic than other compounds in various cells, and the sensitivity of this compound to the normal hepatocytes and cancer cells was inconsistent. The compounds 2,6-dichloro-4-(2-{3,5-dichloro-4-[(prop-2-en-1-yl)oxy]phenyl}propan-2-yl)phenol and 2,6-dibromo-4-(2-{3,5-dibromo-4-[(prop-2-en-1-yl)oxy]phenyl}propan-2-yl)phenol were the most toxic to HepG2 cells, and most of the other compounds inhibited cell proliferation. Moreover, typical compounds were also reproductive and developmental toxic to zebrafish embryos at different concentrations. The synthetic byproduct libraries could be used as pure standard compounds and applied in research on environmental behavior and the transformation of halogenated flame retardants.

BDE-47 Decreases Progesterone Levels in BeWo Cells by Interfering with Mitochondrial Functions and Genes Related to Cholesterol Transport.

Polybrominated diphenyl ethers (PBDEs) have been reported to exert reproductive endocrine toxicity, but the mechanisms for this process remain unclear. Currently available studies have concentrated on the enzymatic reactions during steroidogenesis, but the results are not consistent. In this study, we explored the effects of 2,2',4,4'-tertrabromodiphenyl ether (BDE-47) on progesterone biosynthesis and the potential mechanisms in human placental choriocarcinoma cells. The results showed that BDE-47 decreased progesterone production in a dose-dependent manner but had no effect on key enzymes (Cyp11a1 and 3ß-HSD). BDE-47 exposure depolarized the mitochondrial membrane potential and downregulated adenosine triphosphate levels. The gene expression levels of Mfn2, Tspo, Atad3, Vdac1, Fis1, and Drp1, which are involved in mitochondrial dynamics and cholesterol transport, were disturbed. The demethylation of some CpG loci of mitochondrial biomarkers (Drp1, Opa1, Vdac2, and Atad3) was induced in the 1 µM BDE-47 exposure group, but no methylation change was observed with 50 µM treatment. Our findings unveiled that the reduction of progesterone synthesis induced by BDE-47 might be associated with cholesterol transportation, mitochondrial dynamics, and mitochondrial functions. These findings provide substantial data on the reproductive endocrine toxicity of PBDEs.

Brominated Diphenyl Ethers Including a New Tribromoiododiphenyl Ether from the Vietnamese Marine Sponge Arenosclera sp. and Their Antibacterial Activities.

A new tribromoiododiphenyl ether (1) and eight known brominated diphenyl ethers (2-9) were isolated from the MeOH extract of the sponge Arenosclera sp. collected in Vietnam, using repeated open column chromatography and preparative thin layer chromatography. The chemical structure of the new compound 1 was determined by analyses of spectroscopic (1D- and 2D-NMR, and MS) data and by comparison of our data with those reported in the literature. Compounds 1, 3, and 8 exhibited strong antibacterial activities against the Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus and the Gram-negative bacterium Klebsiella pneumoniae with MIC values ranging from 0.8 to 6.3 µm, while compounds 5 and 7 only displayed activities against Gram-positive bacteria with MIC values from 0.5 to 3.1 µm. Compound 2 showed activities against the four tested bacteria with MIC values ranging from 0.5 to 6.3 µm.

[The role of abnormal mitochondrial fusion and fission in PBDE-47-induced change in mitochondrial mass in PC12 cells].

Objective: To investigate the effect of 2, 2', 4, 4'-tetrabromodiphenyl ether (PBDE-47) on the mitochondrial mass in rat adrenal pheochromocytoma (PC12) cells and the potential mechanisms. Methods: Highly differentiated PC12 cells were divided into control, 1, 10 or 20 µmol/L PBDE-47-treated groups and cultured for 24 h. Transmission electron microscopy was employed to observe the changes in mitochondrial morphology and quantity in PC12 cells. Flow cytometry was used to measure the fluorescence intensity of Nonyl Acridine Orange (NAO) , a fluorescent indicator of mitochondrial membrane cardiolipin, to reflect mitochondria mass. Western blotting was used to determine the expression levels of Mitofusion 1 (Mfn1) and Fission 1 (Fis1) proteins. To further explore the role of abnormal mitochondrial fusion and fission in PBDE-47-induced mitochondrial mass changes, PC12 cells were divided into control group, 5 µmol/L M1 treatment group, 20 µmol/L PBDE-47 treatment group and 5 µmol/L M1+20 µmol/L PBDE-47 combined treatment group and cultured for 24 h, then the fluorescence intensity of NAO and expression levels of Mfn1 and Fis1 proteins were detected. Results: The control group showed numerous mitochondria with normal morphology, while the number of mitochondria decreased after PBDE-47 treatment. Especially, the disappeared cristae, swelling and vacuoles of mitochondria and decreased fluorescence intensity of NAO (P<0.05) were observed in 10 and 20 µmol/L PBDE-47-treated groups. Meanwhile, the expression levels of Mfn1 and Fis1 proteins in the 10 and 20 µmol/L PBDE-47-treated groups were significantly decreased compared with control group (P<0.05) . However, 5 µmol/L M1 co-treatment with 20 µmol/L PBDE-47 significantly increased the levels of Mfn1 and Fis1 proteins and fluorescence intensity of NAO compared with the 20 µmol/L PBDE-47 group (P<0.05) . Conclusion: PBDE-47 can inhibit the mitochondrial fusion and fission process, thus leading to damage of mitochondria mass in PC12 cells.

Use of Phenoxyaniline Analogues To Generate Biochemical Insights into the Interactio n of Polybrominated Diphenyl Ether with CYP2B Enzymes.

Human hepatic cytochromes P450 (CYP) are integral to xenobiotic metabolism. CYP2B6 is a major catalyst of biotransformation of environmental toxicants, including polybrominated diphenyl ethers (PBDEs). CYP2B substrates tend to contain halogen atoms, but the biochemical basis for this selectivity and for species specific determinants of metabolism has not been identified. Spectral binding titrations and inhibition studies were performed to investigate interactions of rat CYP2B1, rabbit CYP2B4, and CYP2B6 with a series of phenoxyaniline (POA) congeners that are analogues of PBDEs. For most congeners, there was a <3-fold difference between the spectral binding constants (KS) and IC50 values. In contrast, large discrepancies between these values were observed for POA and 3-chloro-4-phenoxyaniline. CYP2B1 was the enzyme most sensitive to POA congeners, so the Val-363 residue from that enzyme was introduced into CYP2B4 or CYP2B6. This substitution partially altered the protein-ligand interaction profiles to make them more similar to that of CYP2B1. Addition of cytochrome P450 oxidoreductase (POR) to titrations of CYP2B6 with POA or 2'4'5'TCPOA decreased the affinity of both ligands for the enzyme. Addition of cytochrome b5 to a recombinant enzyme system containing POR and CYP2B6 increased the POA IC50 value and decreased the 2'4'5'TCPOA IC50 value. Overall, the inconsistency between KS and IC50 values for POA versus 2'4'5'TCPOA is largely due to the effects of redox partner binding. These results provide insight into the biochemical basis of binding of diphenyl ethers to human CYP2B6 and changes in CYP2B6-mediated metabolism that are dependent on POA congener and redox partner identity.

PBDEs Altered Gut Microbiome and Bile Acid Homeostasis in Male C57BL/6 Mice.

Polybrominated diphenyl ethers (PBDEs) are persistent environmental contaminants with well characterized toxicities in host organs. Gut microbiome is increasingly recognized as an important regulator of xenobiotic biotransformation; however, little is known about its interactions with PBDEs. Primary bile acids (BAs) are metabolized by the gut microbiome into more lipophilic secondary BAs that may be absorbed and interact with certain host receptors. The goal of this study was to test our hypothesis that PBDEs cause dysbiosis and aberrant regulation of BA homeostasis. Nine-week-old male C57BL/6 conventional (CV) and germ-free (GF) mice were orally gavaged with corn oil (10 mg/kg), BDE-47 (100 µmol/kg), or BDE-99 (100 µmol/kg) once daily for 4 days (n = 3-5/group). Gut microbiome was characterized using 16S rRNA sequencing of the large intestinal content in CV mice. Both BDE-47 and BDE-99 profoundly decreased the alpha diversity of gut microbiome and differentially regulated 45 bacterial species. Both PBDE congeners increased Akkermansia muciniphila and Erysipelotrichaceae Allobaculum spp., which have been reported to have anti-inflammatory and antiobesity functions. Targeted metabolomics of 56 BAs was conducted in serum, liver, and small and large intestinal content of CV and GF mice. BDE-99 increased many unconjugated BAs in multiple biocompartments in a gut microbiota-dependent manner. This correlated with an increase in microbial 7α-dehydroxylation enzymes for secondary BA synthesis and increased expression of host intestinal transporters for BA absorption. Targeted proteomics showed that PBDEs downregulated host BA-synthesizing enzymes and transporters in livers of CV but not GF mice. In conclusion, there is a novel interaction between PBDEs and the endogenous BA-signaling through modification of the "gut-liver axis".

Interacting effect of diclofop-methyl on the rice rhizosphere microbiome and denitrification.

A better knowledge of the intertwined effects of herbicides on plant physiology and microbiome as well as nutrient biogeochemical cycles are needed for environmental management. Here we studied the influence of herbicide diclofop-methyl (DM) on the rice root microbiome and its relationship with N cycle. To do so, we exposed rice seedlings to 100 µg/L DM and studied rhizosphere microbiota using MiSeq-pyrosequencing, root exudation by GC-MS, and denitrification activity by 15N isotope-tracing and qRT-PCR. The richness and diversity of rhizosphere microorganisms, significantly increased after DM exposure combined with an increase in root exudation of amino acids, sugars, and fatty acids. Transcription of denitrification-related gene and denitrification rate increased significantly in the rice rhizosphere. Our results suggest that DM strongly influenced the root exudation of bacteria nutrients, which affected root microbiome community and potentially influenced N cycle in rice rhizosphere.

Weed interference with peppermint (Mentha x piperita L.) and spearmint (Mentha spicata L.) crops under different herbicide treatments: effects on biomass and essential oil yield.

BACKGROUND: 'Minor crops' such as spearmint and peppermint are high added value crops, despite the fact that their production area is comparably small worldwide. The main limiting factor in mint commercial cultivation is weed competition. Thus, field experiments were carried out to evaluate the effects of weed interference on growth, biomass and essential oil yield in peppermint and spearmint under different herbicide treatments. RESULTS: The application of pendimethalin and oxyfluorfen provided better control of annual weeds resulting in higher crop yield. Additionally, when treated with herbicides both crops were more competitive against annual weeds in the second year than in the first year. All pre-emergence herbicides increased biomass yield, since pendimethalin, linuron and oxyfluorfen reduced the density of annual weeds by 71-92%, 63-74% and 86-95%, respectively. Weed interference and herbicide application had no effect on essential oil content; however, a relatively strong impact on essential oil production per cultivated area unit was observed, mainly due to the adverse effect of weed interference on plant growth. CONCLUSION: Considering that pendimethalin and oxyfluorfen were effective against annual weeds in both spearmint and peppermint crops, these herbicides should be included in integrated weed management systems for better weed management in mint crops. © 2017 Society of Chemical Industry.

TDP-43 upregulation mediated by the NLRP3 inflammasome induces cognitive impairment in 2 2',4,4'-tetrabromodiphenyl ether (BDE-47)-treated mice.

It is now commonly known that exposure to polybrominated diphenyl ethers (PBDEs) may cause neurotoxicity and cognitive deficits in children as well as adults, but the underlying mechanisms are still not clear. In the present study, we aimed to elucidate the potential underlying mechanism of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47)-induced neurotoxicity and cognitive impairment. Our results showed that BDE-47-treated mice exhibited impaired cognition and robust upregulation of nuclear TDP-43 in the hippocampus. Hippocampus-specific TDP-43 knockdown attenuated hippocampal apoptosis, restored synaptic protein levels and thus improved cognitive dysfunction in BDE-47-treated mice. Furthermore, our data demonstrated that NLRP3 inflammasome activation played a distinct role in the upregulation of nuclear TDP-43 by downregulating Parkin in the hippocampus of BDE-47-treated mice. Knocking down NLRP3 in the hippocampus or inhibiting caspase 1 activity in BDE-47-treated mice effectively increased Parkin expression in the hippocampus, which decreased the levels of nuclear TDP-43 and ultimately abrogated TDP-43-induced neurotoxic effects. Taken together, our data indicate that TDP-43 upregulation mediated by NLRP3 inflammasome activation via Parkin downregulation in the hippocampus induces cognitive decline in BDE-47-treated mice, and suggest that inhibition of NLRP3 or TDP-43 may be a potential strategy for the prevention or treatment of cognitive impairment in BDE-47-induced neurotoxicity and brain diseases.

Differences in the mechanisms of action of BDE-47 and its metabolites on OVCAR-3 and MCF-7 cell apoptosis.

Data concerning possible carcinogenic action of polybrominated diphenyl ethers (PBDEs) in hormone-dependent tissues are limited. Our earlier studies showed that 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) stimulated OVCAR-3 and MCF-7 cell proliferation, while its hydroxylated metabolites (5-OH-BDE-47 and 6-OH-BDE-47) increased estrogen receptors protein expression and extracellular signal-regulated kinase 1/2 and protein kinase Cα phosphorylation in these cell lines. In addition to cell proliferative disorder, a failure in the regulation of apoptosis can also lead to the formation and development of tumors. Therefore, in the present study, we investigated the effect of BDE-47 and its metabolites (2.5-50 ng ml-1 ) on the expression of apoptosis regulatory genes and proteins, caspase-8 and -9 activity and DNA fragmentation induced by extracellular signal-regulated kinase inhibitor (PD098059) and protein kinase Cα inhibitor (GÓ§ 6976) in ovarian (OVCAR-3) and breast (MCF-7) cancer cells. In OVCAR-3 cells, BDE-47 upregulated expression of most of the investigated genes and increased protein expression of tumor necrosis factor (TNF)-α, TNF receptor 1, caspase-6, Bcl-xl and caspase-8 activity. Whereas in MCF-7 cells, BDE-47 resulted in the downregulation of most of the investigated genes, and decreased caspase-8 and -9 activity. In both OVCAR-3 and MCF-7 cells, the expression of most of the investigated genes were downregulated by metabolites. Exposure of OVCAR-3 cells to 5-OH-BDE-47 corresponded with a decrease in the protein expression of caspase-6, caspase-9 and Bcl-xl and treatment with 6-OH-BDE-47 decreased Bcl-xl and TNF receptor 1 expression in OVCAR-3 cells and caspase-9 expression in MCF-7 cells. Hydroxylated metabolites of BDE-47 have strong inhibitory effects on apoptosis in ovarian and breast tumor cells and thus should be considered potential carcinogens in hormone-dependent cancers. Copyright © 2016 John Wiley & Sons, Ltd.

BDE-99, but not BDE-47, is a transient aryl hydrocarbon receptor agonist in zebrafish liver cells.

Polybrominated diphenyl ethers (PBDEs) are endocrine-disrupting chemicals that affect the environment and the health of humans and wildlife. In this study, the zebrafish liver (ZFL) cell line was used in vitro to investigate two major PBDE contaminants: 2, 2', 4, 4', 5-pentabromodiphenyl ether (BDE-99) and 2, 2', 4, 4'-tetrabromodiphenyl ether (BDE-47). BDE-99 was found to significantly induce cytochrome P450 (CYP1A), uridine diphosphate glucuronosyl transferase 1 family a, b (ugt1ab), 7-ethoxyresorufin-O-deethylase activity and an aryl hydrocarbon receptor (Ahr) dependent xenobiotic response element luciferase reporter system, confirming the Ahr-mediated activation of CYP1A by BDE-99. The time-course effect indicated that the role of BDE-99 in Ahr-mediated signaling is likely to be transient and highly dependent on the ability of BDE-99 to induce CYP1A and ugt1ab, and presumably its metabolism. BDE-99 also exhibited a significant dose-response effect on a developed zebrafish pregnane X receptor luciferase reporter gene system. However, the other abundant contaminant under study, BDE-47, did not exhibit the above effects. Together, these results indicated that the molecular mechanism of PBDEs induced in ZFL cells is a chemically specific process that differs between members of the PBDE family. CYP1A induction derived by BDE-99 warrants further risk assessment as the humans, wildlife and environment are exposed to a complex mixture including dioxin-like compounds and carcinogenic compounds.