Apoptosis induction on human hepatoma cells Hep G2 of decabrominated diphenyl ether (PBDE-209)

Do persistent organic pollutants interact with the stress response? Individual compounds, and their mixtures, interaction with the glucocorticoid receptor

Persistent organic pollutants (POPs) are toxic substances, highly resistant to environmental degradation, which can bio-accumulate and have long-range atmospheric transport potential (UNEP, 2001). The majority of studies on endocrine disruption have focused on interferences on the sexual steroid hormones and so have overlooked disruption to glucocorticoid hormones. Here the endocrine disrupting potential of individual POPs and their mixtures has been investigated in vitro to identify any disruption to glucocorticoid nuclear receptor transcriptional activity. POP mixtures were screened for glucocorticoid receptor (GR) translocation using a GR redistribution assay (RA) on a CellInsight™ NXT high content screening (HCS) platform. A mammalian reporter gene assay (RGA) was then used to assess the individual POPs, and their mixtures, for effects on glucocorticoid nuclear receptor transactivation. POP mixtures did not induce GR translocation in the GR RA or produce an agonist response in the GR RGA. However, in the antagonist test, in the presence of cortisol, an individual POP, p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE), was found to decrease glucocorticoid nuclear receptor transcriptional activity to 72.5% (in comparison to the positive cortisol control). Enhanced nuclear transcriptional activity, in the presence of cortisol, was evident for the two lowest concentrations of perfluorodecanoic acid (PFOS) potassium salt (0.0147mg/ml and 0.0294mg/ml), the two highest concentrations of perfluorodecanoic acid (PFDA) (0.0025mg/ml and 0.005mg/ml) and the highest concentration of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) (0.0000858mg/ml). It is important to gain a better understanding of how POPs can interact with GRs as the disruption of glucocorticoid action is thought to contribute to complex diseases.

Preparation of 4-([2,2':6',2″-terpyridin]-4'-yl)-N,N-diethylaniline Ni(II) and Pt(II) complexes and exploration of their in vitro cytotoxic activities

Two metal complexes of NiLCl2 (1) and [PtLCl]Cl (2) with 4-([2,2':6',2″-terpyridin]-4'-yl)-N,N-diethylaniline (L) were synthesized and characterized. 1 and 2 exhibited selective cytotoxicity to T-24 cells more than L, compared with the normal liver cell line (HL-7702). Various experiments showed that L, 1 and 2 caused T-24 cell cycle arrest at S phase, as shown by the down-regulation of cdc25 A, cyclin A, cyclin B and CDK2 and the up-regulation of p21, p27 and p53. Furthermore, complexes 1 and 2, especially complex 2, acted as telomerase inhibitors targeting c-myc G-quadruplex DNA and triggered cell apoptosis. In addition, 1 and 2 also caused mitochondrial dysfunction. Taken together, we found that 1 and 2 exerted their cytotoxic activity mainly via inhibiting telomerase by interaction with c-myc quadruplex and disruption of mitochondrial function.

BDE-209 inhibits pluripotent genes expression and induces apoptosis in human embryonic stem cells

Decabromodiphenyl ether (BDE-209) has been detected in human serum, semen, placenta, cord blood and milk worldwide. However, little is known regarding the potential effects on the early human embryonic development of BDE-209. In this study, human embryonic stem cell lines FY-hES-10 and FY-hES-26 were used to evaluate the potential effects and explore the toxification mechanisms using low-level BDE-209 exposure. Our data showed that BDE-209 exposure (1, 10 and 100 nM) reduced the expression of pluripotent genes such as OCT4, SOX2 and NANOG and induced human embryonic stem cells (hESCs) apoptosis. The downregulation of BIRC5/BCL2 and upregulation of BAX were related to apoptosis of hESCs induced by BDE-209 exposure. A mechanism study showed that OCT4 down-regulation accompanied by OCT4 promoter hypermethylation and increasing miR-145/miR-335 levels, OCT4 inhibitors. Moreover, BDE-209 could increase the generation of intracellular reactive oxygen species (ROS) and decrease SOD2 expression. The ROS increase and OCT4 downregulation after BDE-209 exposure could be reversed partly by antioxidant N-acetylcysteine supplement. These findings showed that BDE-209 exposure could decrease pluripotent genes expression via epigenetic regulation and induce apoptosis through ROS generation in human embryonic stem cells in vitro.

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.

Cadmium and decabrominated diphenyl ether mixture: In vitro evaluation of cytotoxic, prooxidative and genotoxic effects

In order to look into the combined effects of Cd and BDE-209 in vitro, this study was aimed at examining cytotoxic and genotoxic effects using the human colon carcinoma cell line (SW 480) as a biological test system as well as to determine if ROS production was one of the possible mechanisms of their mixture action. This cell line was chosen since ingestion of contaminated food/water represents an important route of exposure to both Cd and BDE-209, which is why intestinal cells are a common target for the contaminants present in food and water. Cells were treated with single Cd in concentrations of 2.5, 7.5 or 15μg Cd/mL (corresponding to 22, 67 or 134μM), single BDE-209 in concentrations of 2.5, 5 or 10μg BDE209/mL (corresponding to 2.5, 5 or 10μM), and their mixtures (design 3×3). Mixture of Cd and BDE-209 has shown clear potential to reduce the viability of SW 480 cells, as evidenced by cytotoxicity associated with ROS generation. Factorial regression models used to identify type of interaction revealed synergism related to mixture citotoxicity and additive interaction for the effect on ROS production. The results from this introductory study could contribute to the issue of possible adverse effects associated with co-exposure and body burden with two persistent environmental pollutants, Cd and BDE-209.

Assessing reproductive and endocrine parameters in male largescale suckers (Catostomus macrocheilus) along a contaminant gradient in the lower Columbia River, USA

Persistent organochlorine pollutants such as polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p'-DDE), and polybrominated diphenyl ethers (PBDEs) are stable, bioaccumulative, and widely found in the environment, wildlife, and the human population. To explore the hypothesis that reproduction in male fish is associated with environmental exposures in the lower Columbia River (LCR), reproductive and endocrine parameters were studied in male resident, non-anadromous largescale sucker (Catostomus macrocheilus) (LSS) in the same habitats as anadromous salmonids having conservation status. Testes, thyroid tissue and plasma collected in 2010 from Longview (LV), Columbia City (CC), and Skamania (SK; reference) were studied. Sperm morphologies and thyrocyte heights were measured by light microscopy, sperm motilities by computer-assisted sperm motion analysis, sperm adenosine triphosphate (ATP) with luciferase, and plasma vitellogenin (VTG), thyroxine (T4), and triiodothyronine (T3) by immunoassay. Sperm apoptosis, viability, mitochondrial membrane potential, nuclear DNA fragmentation, and reproductive stage were measured by flow cytometry. Sperm quality parameters (except counts) and VTG were significantly different among sites, with correlations between VTG and 7 sperm parameters. Thyrocyte heights, T4, T3, gonadosomatic index and Fulton's condition factor differed among sites, but not significantly. Sperm quality was significantly lower and VTG higher where liver contaminants and water estrogen equivalents were highest (LV site). Total PCBs (specifically PCB-138, -146, -151, -170, -174, -177, -180, -183, -187, -194, and -206) and total PBDEs (specifically BDE-47, -100, -153, and -154) were negatively correlated with sperm motility. PCB-206 and BDE-154 were positively correlated with DNA fragmentation, and pentachloroanisole and VTG were positively correlated with sperm apoptosis and negatively correlated with ATP. BDE-99 was positively correlated with sperm counts and motility; T4 was negatively correlated with counts and positively correlated with motility, thus indicating possible androgenic mechanisms and thyroid endocrine disruption. Male LSS proved to be an informative model for studying reproductive and endocrine biomarkers in the LCR.

Designing quantitative structure activity relationships to predict specific toxic endpoints for polybrominated diphenyl ethers in mammalian cells

Polybrominated diphenyl ethers (PBDEs) are known as effective flame retardants and have vast industrial application in products like plastics, building materials and textiles. They are found to be structurally similar to thyroid hormones that are responsible for regulating metabolism in the body. Structural similarity with the hormones poses a threat to human health because, once in the system, PBDEs have the potential to affect thyroid hormone transport and metabolism. This study was aimed at designing quantitative structure-activity relationship (QSAR) models for predicting toxic endpoints, namely cell viability and apoptosis, elicited by PBDEs in mammalian cells. Cell viability was evaluated quantitatively using a general cytotoxicity bioassay using Janus Green dye and apoptosis was evaluated using a caspase assay. This study has thus modelled the overall cytotoxic influence of PBDEs at an early and a late endpoint by the Genetic Function Approximation method. This research was a twofold process including running in vitro bioassays to collect data on the toxic endpoints and modeling the evaluated endpoints using QSARs. Cell viability and apoptosis responses for Hep G2 cells exposed to PBDEs were successfully modelled with an r(2) of 0.97 and 0.94, respectively.

MSTMP, a Stilbene Derivative, Protects SH-SY5Y Cells Against Oxidative Stress

OBJECTIVE

the protective effects of a novel stilbene derivative, (e)-2-(3,4,5- trimethoxystyryl)-3,5,6-trimethylpyrazine (MStMp), on hydrogen peroxide (h2o2)-induced human derived neuroblastoma cell (Sh-Sy5y) damage and its molecular mechanisms were investigated.

METHODS

Sh-Sy5y cells were exposed to 200 μmol.l-1 h2o2 for 12 h. the effect of MStMp on cell viability and apoptosis was assessed by 3-(4,5-dimethyl- thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (Mtt) assay and flow cytometry method. the activities of lactate dehydrogenase (ldh), superoxide dismutase (Sod) and nitric oxide synthetase (noS) and the content of malondialdehyde (Mda), reduced glutathione (gSh) and nitric oxide (no) in cells were determined by commercial kits. the expressions of pro-apoptotic factor caspase-3, caspase-9 and inducible noS (inoS) were detected by Western blotting. intracellular formation of reactive oxygen species (roS) was assessed using 6-carboxy-2’,7’-dichlorofluorescin diacetate (dCfh-da) fluorescent probe.

RESULTS

MStMp increased the Sh-Sy5y cell viability by inhibition of cell apoptosis induced by h2o2. these effects were accompanied by an increase of Sod activity, gSh level, and a decrease of Mda content. Moreover, MStMp showed stronger effects on inhibition of ldh leakage, apoptotic cells, intracellular roS level and the expression of caspase-3 and caspase-9 than tMp. furthermore, MStMp induced a decrease of no level and the activity of inoS, tnoS in a time-dependent manner.

CONCLUSIONS

MStMp prevents h2o2-induced cell injury through anti-oxidation and anti-apoptosis via roS-no pathway.

Capsaicin inhibits cell proliferation by cytochrome c release in gastric cancer cells

Capsaicin (trans-8-methyl-N-vanillyl-6-nonenamide) is the principal pungent component in hot peppers. The role of capsaicin in carcinogenesis is quite controversial. Although some investigators suspect that capsaicin is a carcinogen, co-carcinogen, or tumor promoter, others have reported that it has chemopreventive and chemotherapeutic effects. The present study aimed to evaluate the cytotoxicity and chemosensitizing activities of capsaicin alone and on 5-flourouracil (5-FU)-treated gastric cancer cells. In this study, the gastric cancer cell line HGC-27 was used and capsaicin used as a chemosensitizer and 5-flourouracil (5-FU) was used as chemotherapeutic. Cytotoxicity and chemosensitizing activities were analyzed with MTT assay; supernatant levels of LDH and glucose were detected as biochemical markers of cell viability; cytochrome c and AIF were evaluated with western blot; and additionally, wound-healing assays were employed. Results suggested that capsaicin had significant anticancer abilities; such capsaicin were capable of causing multifold decreases in the half maximal inhibitory concentration IC50 value of 5-FU. The continuing controversy surrounding consumption or topical application of capsaicin clearly suggests that more well-controlled epidemiologic studies are needed to evaluate the safety and efficacy of capsaicin use. In summary, the present study demonstrated that capsaicin has the potential to be used for treating gastric carcinoma with 5-FU in vitro.

BDE-154 induces mitochondrial permeability transition and impairs mitochondrial bioenergetics

Brominated flame retardants are used in various consumer goods to make these materials difficult to burn. Polybrominated diphenyl ethers (PBDE), which are representative of this class of retardants, consist of two benzene rings linked by an oxygen atom, and contain between 1 and 10 bromine atoms in their chemical structure, with the possibility of up to 209 different congeners. Among these congeners, BDE-154 (hexa-BDE) is persistent in the environment and easy to detect in the biota, but no apparent information regarding the mechanism underlying action and toxicity is available. Mitochondria, as the main energy-producing organelles, play an important role in the maintenance of various cellular functions. Therefore, mitochondria were used in the present study as an experimental model to determine the effects of BDE-154 congener at concentrations ranging from 0.1 μM to 50 μM. Our results demonstrated that BDE-154 interacts with the mitochondrial membrane, preferably by inserting into the hydrophobic core of the mitochondrial membrane, which partially inhibits respiration, dissipates Δψ, and permeabilizes the inner mitochondrial membrane to deplete ATP. These effects are more pronounced at concentrations equal to or higher than 10 μM. Results also showed that BDE-154 did not induce reactive oxygen species (ROS) accumulation within the mitochondria, indicating the absence of oxidative stress. Therefore, BDE-154 impairs mitochondrial bioenergetics and permeabilizes the mitochondrial membrane, potentially leading to cell death but not via mechanisms involving oxidative stress.

A tetramethylpyrazine piperazine derivate CXC137 prevents cell injury in SH-SY5Y cells and improves memory dysfunction of rats with vascular Dementia

We investigated the effects of CXC137, a tetramethylpyrazine piperazine derivate, on cell damage induced by N-methyl-D-aspartate (NMDA) in human derived neuroblastoma cells (SH-SY5Y) and its effect on memory dysfunction of rats with vascular dementia. It was found that the presence of CXC137 increased SH-SY5Y cells viability by inhibition of cell apoptosis induced by NMDA. These effects of CXC137 were accompanied by increases of the antioxidant superoxide dismutase activity and the level of reduced glutathione, and a decrease of lipid peroxidation product, malondialdehyde. The presence of CXC137 also showed to produce strong inhibition of cellular lactate dehydrogenase leakage, cell apoptosis and intracellular calcium overload. In a vascular dementia rat model established by bilateral common carotid arteries occlusion, treatment with CXC137 from 2 to 35 day of post-operation significantly improves the motor performance, spatial learning and memory capability of rats in both the prehensile traction test and Morris water maze test, an effect that was companied by reductions of the animal glutamic acid levels and the degree of brain mitochondrial swelling. These results suggest that CXC137 can improve the memory dysfunction in dementia and thus has important therapeutic potential for the treatment of dementia.

Plant uptake and phytotoxicity of decabromodiphenyl ether (BDE-209) in ryegrass (Lolium perenne L)

The plant uptake and phytotoxicity of decabromodiphenyl ether (BDE-209) in ryegrass (Lolium perenne L) seedlings were investigated. Results showed that ryegrass could take up BDE-209 from the contaminated soils and most of the BDE-209 in plants is located in roots, indicating that BDE-209 has low root-to-shoot translocation. Except for about 35% inhibition of root growth and about 30% decrease of the chlorophyll b and carotenoid contents of leaves, no visual toxicity symptoms were observed in seedlings grown even at a high concentration of 100 mg kg(-1). BDE-209 exposure significantly induced the generation of the superoxide radical (O2˙(-)) and malondialdehyde (MDA) in ryegrass leaves. With the increase of BDE-209 concentration, the activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione-S-transferase (GST) were significantly changed, and the ratio of reduced glutathione to oxidized glutathione (GSH/GSSG) was also significantly reduced. Results suggested that BDE-209 exposure could cause oxidative stress and damage, which may play an important role in the phytotoxicity of BDE-209 in ryegrass seedlings.

Polybrominated diphenyl ether congener (BDE-100) induces mitochondrial impairment

Brominated flame retardants are used in various consumer products to increase their resistance to fire and/or high temperatures. Polybrominated diphenyl ethers (PBDEs) are representatives of this class and among the most widely used congeners, and BDE-100 is produced on a large scale. There is a lack of toxicological data about these compounds, which has recently become a matter of concern to the scientific community. The mitochondria are recognized as the main energy-producing organelles, as well as playing a vital role in the maintenance of many cell functions. Therefore, mitochondria were used in the present work as an experimental model to evaluate the effects of the BDE-100 congeners at concentrations ranging from 0.1 μM to 50 μM. The results showed that high concentrations of BDE-100 were able to induce mitochondrial alterations. It was observed that the substance had an affinity for the hydrophilic portion of the mitochondrial membrane, as monitored by ANS, inhibiting the glutamate + malate-stimulated mitochondrial respiration and also inducing dissipation of the mitochondrial membrane potential, deregulation of calcium homoeostasis and mitochondrial swelling, the latter being insensitive to cyclosporin A (CsA) but partially inhibited by Ruthenium Red and N-ethyl maleimide. In addition, a significant reduction in mitochondrial ATP content was found, but on the other hand, no oxidative stress was observed after exposure of the mitochondria to BDE-100. These results show the key role of mitochondria in the cytotoxicity induced by BDE-100.

GdCl3 induced Hep G2 cell death through mitochondrial and external death pathways without significant elevation of ROS generation

Gadolinium (Gd) compounds have important applications as MRI contrast and potential anticancer agents. The present study investigated the mechanisms of the proapoptotic effect of gadolinium chloride (GdCl(3)) on hepatoblastoma cell line (Hep G2) tumor cells. The experimental results indicated that GdCl(3) induced apoptosis of Hep G2 at high concentration and with long time incubation; however, unlike the actions on normal cell lines, GdCl(3) did not cause any oxidative stress on tumor cells. Cytochrome c (Cyt c) and apoptosis inducing factor release, Bax translocation, collapse of mitochondria membrane potential, caspase 3 and 8 activation, and Bid cleavage were observed along with a sustained activation of extracellular signal-regulated kinase (ERK) and c-Jun NH2 terminal kinase (JNK). Addition of ERK and JNK inhibitor attenuated the effect of GdCl(3) induced apoptosis and Cyt c release. All the results suggested a novel mechanism that GdCl(3) induced Hep G2 cell death through intrinsic and external death pathways without significant elevation of reactive oxygen species generation. The present work provided new insight to understand the mechanisms of the biological effects of GdCl(3) and implications for the development of anticancer Gd agents.

2,2',4,4'-Tetrabromodiphenyl ether (BDE-47) decreases progesterone synthesis through cAMP-PKA pathway and P450scc downregulation in mouse Leydig tumor cells

Polybrominated diphenyl ethers (PBDEs) are commonly used as flame retardants in textiles, plastics and electronics and represent a group of persistent environmental contaminants. They have been found to accumulate in human and marine mammals. Previous studies have shown that PBDEs have endocrine-disrupting properties and reproductive toxicity. However, the mechanisms under the reproductive disruptions are still not well understood. In this study, we explored the effects of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) on progesterone biosynthesis and possible mechanisms in mouse Leydig tumor cells (mLTC-1). Our results showed that BDE-47 could reduce progesterone production and decrease the intracellular cAMP level induced by hCG or forskolin. These suggested that BDE-47 decreasing progesterone production in mLTC-1 cells may be associated with the decline of intracellular cAMP level. Moreover, our data also indicated that the site G protein in cAMP-PKA pathway may be involved in this process. Furthermore, the addition of cAMP analog, 8-Br-cAMP, could not reverse the decrease of progesterone biosynthesis, indicating that a post-cAMP site (or sites) might be involved into the BDE-47-decreased progesterone production. In addition, we found BDE-47 reduced the activity of P450 side chain cleavage enzyme (P450scc), which was companied with the decline of P450scc mRNA and protein level in mLTC-1 cells. Put all together, these results suggested that progesterone synthesis decrease induced by BDE-47 may be associated with attenuation of cAMP generation and reduction of P450scc activity.

Polybrominated diphenylethers (PBDEs) act as apoptotic factors in the corpus luteum in addition to having a short-term stimulatory effect on progesterone secretion by luteal cells

To the best of our knowledge, there is a lack of data showing effect of polybrominated diphenyl ethers (PBDEs) on the corpus luteum (CL), a mini-endocrine gland responsible for a normal estrous cycle and the maintenance of pregnancy. Luteal cells obtained from corpora lutea (8-10 days after ovulation) were exposed to PBDE 47, 99, and 100 at doses of 50, 250, and 500 ng/ml for 24 and 48 hours. The progesterone (P4) level in the culture medium and caspase-3, -8, and -9 activities in the cells were estimated by ELISA. CYP11A1 and 3β-HSD protein expression were evaluated by western blot. A 2-fold increase in P4 secretion after 24 hours and no effect after 48 hours of exposure were observed. We demonstrated that the increase in P4 secretion was the result of the stimulatory action of all PBDEs on 3β-HSD protein expression and additionally, PBDE 99 alone on 3β-HSD activity (measured by the conversion of P5 into P4). In contrast, the activation of caspase-8 and -9 but not caspase-3 during 24 hours of exposure, and activation of all investigated caspases during 48 hours was observed. In conclusion, the present findings provide evidence that despite the initial stimulatory effect of PBDEs on the secretion of progesterone (due to the fact that the biochemical apparatus responsible for the conversion of cholesterol into pregnenolone remains uninterrupted). PBDEs are also a key executor of apoptosis (by activating both the extrinsic and intrinsic pathways of apoptosis after longer exposure periods) which can lead to premature dysfunction of the corpus luteum.

Effects of decabrominated diphenyl ether (PBDE-209) in regulation of growth and apoptosis of breast, ovarian, and cervical cancer cells

BACKGROUND

Polybrominated diphenyl ethers (PBDEs), commonly used in building materials, electronics, plastics, polyurethane foams, and textiles, are health hazards found in the environment.

OBJECTIVE

In this study we investigated the effects of PBDE-209, a deca-PBDE, on the regulation of growth and apoptosis of breast, ovarian, and cervical cancer cells as well as the underlying protein alterations.

METHODS

We used MCF-7 and MCF-7/ADR (multidrug-resistant MCF-7) breast cancer cell lines, the HeLa cervical cancer cell line, the OVCAR-3 ovarian cancer cell line, and the normal CHO (Chinese hamster ovary) cell line to assess the effects of PBDE-209 using cell viability, immunofluorescence, and flow cytometric assays. Western blot assays were used to detect changes in protein expression. To assess the effects of PBDE-209 on apoptosis, we used the protein kinase Cα (PKCα) inhibitor Gö 6976, the extracellular signal-regulated kinase (ERK) inhibitor PD98059, and tamoxifen.

RESULTS

Our data indicate that PBDE-209 increased viability and proliferation of the tumor cell lines and in CHO cells in a dose- and time-dependent manner. PBDE-209 also altered cell cycle distribution by inducing the S phase or G2/M phase. Furthermore, PBDE-209 partially suppressed tamoxifen-induced cell apoptosis in the breast cancer cell lines (MCF-7 and MCF-7/ADR) but suppressed Gö 6976- and PD98059-induced apoptosis in all cell lines. At the molecular level, PBDE-209 enhanced PKCα and ERK1/2 phosphorylation in the cell lines.

CONCLUSIONS

Our data demonstrate that PBDE-209 is able to promote proliferation of various cancer cells from the female reproductive system and normal ovarian CHO cells. Furthermore, it reduced tamoxifen, PKCα, and ERK inhibition-induced apoptosis. Finally, PBDE-209 up-regulated phosphorylation of PKCα and ERK1/2 proteins in tumor cells and in CHO cells.

Gestational exposure to BDE-99 produces toxicity through upregulation of CYP isoforms and ROS production in the fetal rat liver

On gestation day (GD) 6 to GD 19, pregnant Sprague Dawley rats were orally exposed to 0, 0.5, 1, and 2 mg/kg/day to one of the most prevalent polybrominated diphenyl ethers congeners found in humans, 2,2',4,4',5-pentaBDE (BDE-99). All dams were euthanized on GD 20, and live fetuses were evaluated for sex, body weight, and external, internal, and skeletal malformations and developmental variations. The liver from one fetus of each litter was excised for the evaluation of oxidative stress markers and the messenger RNA expression of multiple cytochrome P450 (CYP) isoforms. Exposure to BDE-99 during the gestational period produced delayed ossification, slight hypertrophy of the heart, and enlargement of the liver in fetuses. A transplacental effect of BDE-99, evidenced by the activation of nuclear hormones receptors that induce the upregulation of CYP1A1, CYP1A2, CYP2B1, and CYP3A2 isoforms, was also found in fetal liver. These isoforms are correlated with the activity level of the enzyme catalase and the levels of thiobarbituric acid reactive substances. However, teratogenic effects from BDE-99 exposure were not observed. Clear signs of embryo/fetal toxicity, due to a possible hormonal disruption, were evidenced by a large increase in the CYP system and the production of reactive oxygen species in fetal liver.

Protective effect of curcumin, silymarin and N-acetylcysteine on antitubercular drug-induced hepatotoxicity assessed in an in vitro model

Tuberculosis (TB) is highly endemic in India. The first-line anti-TB therapy (ATT) involving isoniazid (INH), rifampicin and pyrazinamide causes hepatotoxicity in approximately 11.5% of Indian patients. Studies have shown that ATT-induced hepatotoxicity is primarily due to oxidative stress caused by the drugs and metabolites. Herbal drugs with antioxidative properties have been tested in animal studies and clinical trials for the management of hepatotoxicity. The objective of this study was to investigate the role of curcumin (CUR), silymarin (SILY) and N-acetylcysteine (N-ACET) on hepatotoxicity by ATT drugs using an in vitro model of human hepatocellular carcinoma cell line (HepG2). HepG2 cells were treated with ATT drugs alone or along with CUR, SILY or N-ACET for a 48-h duration. The cells were monitored for viability, morphology, respiring mitochondria and cell cycle. Our results suggest that the presence of hepatoprotective drugs during treatment of HepG2 cells with ATT drugs lowers the hepatotoxic effect of the latter. This is observed in terms of (a) increased cell viability, (b) healthy-looking cell morphology as revealed by phase contrast microscopy, (c) active respiring cells as observed with confocal microscopy upon staining with a mitochondrial membrane-specific dye, MitoTracker(®) Red, and reduction in the sub-G(1) peak in cell cycle analysis by flow cytometry. Our results suggest that these hepatoprotective drugs need to be further explored as potential adjuvant therapy along with ATT drugs.

Morphological alterations of Vero cell exposed to coplanar PCB 126 and noncoplanar PCB 153

Polychlorinated biphenyls (PCBs) are widespread, persistent environmental contaminants that display a complex spectrum of toxicological properties. Exposure to PCBs has been associated with morphological anomalies in cell cultures. However, most mechanistic studies of PCBs' toxic activity have been focused on coplanar congeners. It is of importance to determine whether PCB treatment would influence cell configuration and whether these changes would depend on the structural characteristics of PCBs. In this study, we investigated cell morphological alteration in Vero cell cultures after exposure to coplanar PCB 126 and noncoplanar PCB 153. The survival of Vero cells was measured through the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test. Cytotoxicity results suggested that PCB congeners had a toxic, antiproliferative effect on Vero cells. Morphological studies described structural modifications and provided evidence that apoptosis might be the main cell death pathway in PCB 153-treated cells. The comparison between PCB 126 and PCB 153 indicated that the cell death mechanisms involved in coplanar or noncoplanar PCB congener exposure were different in Vero cells.

Combinatory effects of PBDEs and 17β-estradiol on MCF-7 cell proliferation and apoptosis

In the present work, we analyzed whether polybrominated diphenyl ethers (PBDEs) (47, 99, 100 and 209) interfere with the effect of 17β-estradiol on the proliferation and apoptosis of the MCF-7 cell line. MCF-7 cells were cultured in DMEM without phenol red; upplemented with 5% charcoal-treated fetal bovine serum for 3 days with 10 nM 17β-estradiol; with 0.1 μM, 0.5 μM or 1 μM of the tested PBDE congeners; or with both 17β-estradiol and a congener. Cell proliferation was determined by measuring BrdU incorporation, and cell apoptosis was measured by caspase-9 activity. No PBDE congener had an effect on basal cell proliferation, but they all significantly decreased basal caspase-9 activity. An additive anti-apoptotic activity and ability to induce cell proliferation was observed in the presence of 17β-estradiol.

Hydroxyl radical generation and oxidative stress in earthworms (Eisenia fetida) exposed to decabromodiphenyl ether (BDE-209)

Antioxidant responses induced by decabromodiphenyl ether (BDE-209) in the earthworms (Eisenia fetida) were studied after 7 days of exposure. Electron paramagnetic resonance (EPR) spectra indicated that hydroxyl radicals (•OH) in earthworms were significantly induced by 0.01-10 mg/kg of BDE-209. Malondialdehyde (MDA) and protein carbonyl (PCO) were stimulated at 0.5-10 mg/kg and 1-10 mg/kg, respectively. The reduced glutathione (GSH) was inhibited at 1-10 mg/kg while oxidized glutathione (GSSG) accumulated at 0.5-10 mg/kg. The GSH/GSSG ratio decreased at 0.5-10 mg/kg, and superoxide dismutase (SOD) and glutathione-S-transferase (GST) activities were induced at 0.1-1 and 0.5 mg/kg, respectively and both decreased at 10 mg/kg. Catalase (CAT) activities increased at 1-10 mg/kg. The results showed that severe oxidative stress occurred in E. fetida, and may play an important role in inducing the toxicity of BDE-209 on earthworms.

Effect of BDE-209 on glutathione system in Carassius auratus

In this study, the oxidative stress induced by deca-polybromodiphenyl ether (BDE-209) was investigated in livers of Carassius auratus. Six groups of fish were exposed to blank and 0, 0.004, 0.04, 0.4, 4 μM BDE-209 (in 0.1% DMSO) for 1, 4, 7, 10, 13 d, respectively. The following oxidative stress markers were analyzed: reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidases (GPx) and glutathione S-transferases (GSTs). No significant difference was observed in the content of GSH over the whole period of exposure (p > 0.05). Increases in hepatic GR and GPx activities were in concomitant with the decrease in GST activity. GR activity was induced after 1 d exposure, while GPx activity reached maximum at 4 d after exposure to 0.04 μM BDE-209 and GST activity was significantly inhibited at 7-13 d in all the treatment groups (0.004-4 μM group).

Genotoxicity of several polybrominated diphenyl ethers (PBDEs) and hydroxylated PBDEs, and their mechanisms of toxicity

Polybrominated diphenyl ethers (PBDEs) have been extensively utilized as flame retardants, and recently there has been concern about potential adverse effects in humans and wildlife. Their hydroxylated analogs (OH-BDEs) have received increasing attention due to their potential for endocrine and neurological toxicities. However, the potentials and mechanisms of genotoxicity of these brominated compounds have scarcely been investigated. In the present study, genotoxicity of tetra-BDEs, penta BDE, octa-BDE, deca-BDE, and tetra-OH-BDEs were investigated by use of chicken DT40 cell lines including wild-type cells and a panel of mutant cell lines deficient in DNA repair pathways. Tetra-BDEs have greater genotoxic potential than do the other BDEs tested. OH-tetra-BDEs were more genotoxic than tetra-BDEs. DT40 cells, deficient in base excision repair (Polβ(-/-)) and translesion DNA synthesis (REV3(-/-)) pathways, were hypersensitive to the genotoxic effects of tetra-BDEs and OH-tetra-BDEs. The observation of chromosomal aberrations and gamma-H2AX assay confirmed that the studied brominated compounds caused double strand breaks. Pretreatment with N-acetyl-l-cysteine (NAC) significantly rescued the Polβ(-/-) and REV3(-/-) mutants, which is consistent with the hypothesis that PBDEs and OH-BDEs cause DNA damage mediated through reactive oxygen species (ROS). Some tetra-BDEs and OH-tetra-BDEs caused base damage through ROS leading to replication blockage and subsequent chromosomal breaks.

PCB congeners induced mitochondrial dysfunction in Vero cells

Two PCB congeners were assessed for their cytotoxicity on Vero cells, in the attempt to compare their structure-activity relationship and to investigate the role of mitochondria involved in toxicity. Flow cytometry was used to monitor the changes of mitochondrial membrane potential (Δψ(m)), cell size and apoptosis rate. Treatments of Vero cell cultures with both PCB 126 and PCB 153 resulted in loss of cell viability in our experimental conditions. In ortho-substituted PCB 153 treated cells, loss of cell viability was accompanied by decreased Δψ(m) and cell shrinkage. The coplanar congener, PCB 126, had no significant effects on Δψ(m) or cell size in this time period of exposure. These studies showed that PCB 153 is more toxic than coplanar PCB 126 to Vero cells within 24h exposure. The cytotoxicity mechanism caused by coplanar or non-coplanar PCB congener was different, and apoptosis might be the main cell death pathway in PCB 153 treated cells.

Is decabromodiphenyl ether (BDE-209) a developmental neurotoxicant?

Polybrominated diphenyl ether (PBDE) flame retardants have become ubiquitous environmental pollutants. The relatively higher body burden in toddlers and children has raised concern for their potential developmental neurotoxicity, which has been suggested by animal studies, in vitro experiments, and recent human epidemiological evidence. While lower brominated PBDEs have been banned in several countries, the fully brominated decaBDE (BDE-209) is still utilized, though manufacturers will discontinue production in the U.S.A. in 2013. The recent decision by the U.S. Environmental Protection Agency to base the reference dose (RfD) for BDE-209 on a developmental neurotoxicity study has generated some controversy. Because of its bulky configuration, BDE-209 is poorly absorbed and does not easily penetrate the cell wall. Its acute and chronic toxicities are relatively low, with the liver and the thyroid as the primary targets, though there is some evidence of carcinogenicity. A few animal studies have indicated that BDE-209 may cause developmental neurotoxicity, affecting motor and cognitive domains, as seen for other PBDEs. Limited in vivo and in vitro studies have also evidenced effects of BDE-209 on thyroid hormone homeostasis and direct effects on nervous cells, again similar to what found with other lower brominated PBDEs. In contrast, a recent developmental neurotoxicity study, carried out according to international guidelines, has provided no evidence of adverse effects on neurodevelopment, and this should be considered in a future re-evaluation of BDE-209. While estimated exposure to BDE-209 in children is believed to be several orders of magnitude below the most conservative RfD proposed by the USEPA, questions remain on the extent and relevance of BDE-209 metabolism to lower brominated PBDEs in the environment and in humans.

Application of mass spectrometry in the analysis of polybrominated diphenyl ethers

This review summarized the applications of mass spectrometric techniques for the analysis of the important flame retardants polybrominated diphenyl ethers (PBDEs) to understand the environmental sources, fate and toxicity of PBDEs that were briefly discussed to give a general idea for the need of analytical methodologies. Specific performance of various mass spectrometers hyphenated with, for example, gas chromatograph, liquid chromatograph, and inductively coupled plasma (GC/MS, LC/MS, and ICP/MS, respectively) for the analysis of PBDEs was compared with an objective to present the information on the evolution of MS techniques for determining PBDEs in environmental and human samples. GC/electron capture negative ionization quadrupole MS (GC/NCI qMS), GC/high resolution MS (GC/HRMS) and GC ion trap MS (GC/ITMS) are most commonly used MS techniques for the determination of PBDEs. New analytical technologies such as fast tandem GC/MS and LC/MS become available to improve analyses of higher PBDEs. The development and application of the tandem MS techniques have helped to understand environmental fate and transformations of PBDEs of which abiotic and biotic degradation of decaBDE is thought to be one major source of Br(1-9)BDEs present in the environment in addition to direct loading from commercial mixtures. MS-based proteomics will offer an insight into the molecular mechanisms of toxicity and potential developmental and neurotoxicity of PBDEs.

Effects of decabrominated diphenyl ether (PBDE 209) on voltage-gated sodium channels in primary cultured rat hippocampal neurons

Polybrominated diphenyl ethers (PBDEs) are widely used as flame-retardant additives. But the application of PBDEs has been challenged due to their toxicity, especially neurotoxicity. In this study, we investigated the effects of decabrominated diphenyl ether (PBDE 209), the major PBDEs product, on voltage-gated sodium channels (VGSCs) in primary cultured rat hippocampal neurons. Employing the whole-cell patch-clamp technique, we found that PBDE 209 could irreversibly decrease voltage-gated sodium channel currents (I(Na)) in a very low dose and in a concentration-dependent manner. We had systematically explored the effects of PBDE 209 on I(Na) and found that PBDE 209 could shift the activation and inactivation of I(Na) toward hyperpolarizing direction, slow down the recovery from inactivation of I(Na), and decrease the fraction of activated sodium channels. These results suggested that PBDE 209 could affect VGSCs, which may lead to changes in electrical activities and contribute to neurotoxicological damages. We also showed that ascorbic acid, as an antioxidant, was able to mitigate the inhibitory effects of PBDE 209 on VGSCs, which suggested that PBDE 209 might inhibit I(Na) through peroxidation. Our findings provide new insights into the mechanism for the neurological symptoms caused by PBDE 209.

Distribution and fate of polybrominated diphenyl ethers in indoor environments of elementary schools

Polybrominated diphenyl ethers (PBDEs) are considered harmful to human health because of their toxicities and persistence in environments. In the current study, the distribution and fate of PBDEs in classrooms and computer rooms in 17 elementary schools in South Korea have been described. Eight congeners (brominated diphenyl ether-28, -47, -99, -100, -153, -154, -183, and -209) in air, floor dust, and product surface dust were measured. While Sigma(8)PBDEs in the air in classrooms showed considerable variations (0.659-1600 pg/m(3), arithmetic mean +/- s.d.: 377 +/- 441 pg/m(3)), those in computer rooms were somewhat similar (134-220 pg/m(3), arithmetic mean +/- s.d.: 169 +/- 40 pg/m(3)). Sigma(8)PBDEs in floor dust varied over a wide range, from 453 to 45,700 ng/g, for all rooms. Based on congener patterns, two groups were created--CL-1 that is dominated by high-brominated congeners and CL-2 primarily comprising low-brominated congeners--for both air and floor dust of classrooms. Surface dust had low concentrations, ranged from ND to 181, from ND to 128, and from ND to 256 pg/cm(2) for desk/chair sets, lockers, and playing tools, respectively. Pearson correlation coefficients were calculated individually for air, floor dust, and surface dust. The results indicate that both surface dust and floor dust may act as a secondary source of PBDEs in indoor environments after emission from facilities.

PRACTICAL IMPLICATIONS

Children have been estimated to have a higher potential exposure to PBDEs than adults. Since children spend most of their day time at school, PBDE distributions in school environments should be a matter of great concern.

Polybrominated diphenyl ethers induce developmental neurotoxicity in a human in vitro model: evidence for endocrine disruption

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are persistent and bioaccumulative flame retardants, which are found in rising concentrations in human tissues. They are of concern for human health because animal studies have shown that they possess the potential to be developmentally neurotoxic.

OBJECTIVE

Because there is little knowledge of the effects of PBDEs on human brain cells, we investigated their toxic potential for human neural development in vitro. Moreover, we studied the involvement of thyroid hormone (TH) disruption in the effects caused by PBDEs.

METHODS

We used the two PBDE congeners BDE-47 and BDE-99 (0.1-10 microM), which are most prominent in human tissues. As a model of neural development, we employed primary fetal human neural progenitor cells (hNPCs), which are cultured as neurospheres and mimic basic processes of brain development in vitro: proliferation, migration, and differentiation.

RESULTS

PBDEs do not disturb hNPC proliferation but decrease migration distance of hNPCs. Moreover, they cause a reduction of differentiation into neurons and oligodendrocytes. Simultaneous exposure with the TH receptor (THR) agonist triiodothyronine rescues these effects on migration and differentiation, whereas the THR antagonist NH-3 does not exert an additive effect.

CONCLUSION

PBDEs disturb development of hNPCs in vitro via endocrine disruption of cellular TH signaling at concentrations that might be of relevance for human exposure.

Determination of environmentally relevant exposure concentrations of polybrominated diphenyl ethers for in vitro toxicological studies

Toxicological studies at environmentally relevant concentrations are essential for understanding ecotoxic and health risks of pollutants such as polybrominated diphenyl ethers (PBDEs). However, no information is available on what exposure levels of PBDEs in vitro studies are environmentally relevant. We exposed MCF-7, HepG2, H295R and PC12 cells to BDE-47, and measured BDE-47 concentrations in the cells after exposure. We also used the percentile method to summarize literature data on environmental exposure levels of biotic tissues to PBDEs. The exposure concentration that resulted in a BDE-47 burden in cells close to the 90th percentile of PBDEs levels in tissues was assigned as the upper limit for the environmentally relevant concentration. Exposure to 1nM BDE-47 resulted in PBDEs burdens in MCF-7, HepG2 and H295R cells close to the 90th percentile but PBDEs burdens in PC12 cells were higher than the 90th percentile. In consideration of the high exposure levels in PBDE-polluted areas, we concluded that the highest environmentally relevant exposure concentration of PBDEs in culture media should be approximately 10nM for MCF-7, HepG2 and H295R cells, and<10nM for PC12 cells. These results provide an approximate reference for setting environmentally relevant exposure concentrations of PBDEs for studies in vitro.

The involvement of ROS overproduction and mitochondrial dysfunction in PBDE-47-induced apoptosis on Jurkat cells

2,2',4,4'-Tetrabromodiphenyl ether (PBDE-47), as one of the congeners of polybrominated diphenyl ethers (PBDEs), is widely present and threatens the human health in many aspects. This study aims to investigate the toxic effects of PBDE-47 on cell viability, apoptosis, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) of Jurkat cells in vitro. The results showed that PBDE-47 significantly inhibited the viability of Jurkat cells in a dose-dependent manner by alamar blue assay. Significant induction of apoptosis was detected in Jurkat cells at 25-100 μM by propidium iodide staining, accompanied with overproduction of ROS and downregulation of MMP. Furthermore, N-acetyl-L-cysteine (NAC), a widely used ROS scavenger, significantly reduced the PBDE-47-induced apoptosis by decreasing ROS level and mediating recovery of the MMP. In conclusion, the results of this study suggest that PBDE-47 could induce apoptosis in Jurkat cells and ROS and mitochondrial dysfunction play important roles in the apoptotic process.

Cytotoxicity and apoptosis induction on RTG-2 cells of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and decabrominated diphenyl ether (BDE-209)

Recently, the environmental residues of polybrominated diphenyl ethers (PBDEs) have markedly increased. In particular, the levels of certain PBDE congeners in fish have raised concern regarding potential risks associated with dietary PBDEs exposures. However, little is known regarding PBDE-mediated cell injury in relevant in vitro fish cell models. In this study, the cytotoxic effects of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and decabrominated diphenyl ether (BDE-209) on RTG-2 cells were investigated. RTG-2 cells were incubated with different concentrations of BDE-47 and BDE-209 (1-100 microM) for 72 h, and a set of bioassays were conducted to measure: cell viability (evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and neutral red (NR) uptake), lactate dehydrogenase (LDH) leakage, reactive oxygen species (ROS) formation and cell apoptosis. The results showed that BDE-47 and BDE-209 inhibited the cells viability, increased LDH leakage, and induced cell apoptosis in time and concentration-dependent manner. All significant effects were observed at concentrations of 12.5 microM and above for BDE-47 and 25 microM and above for BDE-209 (P<0.05). At the concentration of 100 microM BDE-47 and BDE-209, the cell viability of the exposed cells dropped to about 40% and 50% of the control, and the apoptotic rates were 52.6% and 34.6%, respectively. After 12h exposure, a concentration-dependent increases of BDE-47 and BDE-209 (12.5-100 microM) in ROS formation were observed. Collectively, the results of cell viability, LDH leakage, cell apoptosis and ROS formation demonstrated that the toxic mechanism of PBDEs on RTG-2 might be mediated by oxidative stress.

Effects of individual polybrominated diphenyl ether (PBDE) congeners on harbour seal immune cells in vitro

Effects of polybrominated diphenyl ethers (PBDEs) on the immune system of marine mammals are poorly understood. One important innate immune function of granulocytes is the respiratory burst which generates reactive oxygen species (ROS) used to kill engulfed microorganisms. The present study investigates in vitro the effects of BDE-47, -99 and -153, on the formation of ROS, on intracellular level of thiols, on activity and efficiency of phagocytosis and on apoptosis in granulocytes of harbour seals. Compounds were tested at four different concentrations ranging from 1.5 to 12 microM. Results showed that ROS levels, thiol levels and phagocytosis were all affected when harbour seal cells were exposed to the highest concentration (12 microM) of PBDE congeners. Apoptosis was not affected by PBDEs. The observed effects were similar in adults, pups and in the 11B7501 cell line of harbour seals.

Comparative cytotoxicity and intracellular accumulation of five polybrominated diphenyl ether congeners in mouse cerebellar granule neurons

Polybrominated diphenyl ethers (PBDEs), a group of flame retardants comprising 209 congeners, have become widespread environmental pollutants. High levels of PBDEs have been detected in human tissues, particularly in North America, and body burden is especially high in infants and toddlers because of exposure through breast milk and house dust. Increasing evidence, provided by animal studies, suggests that PBDEs are developmental neurotoxicants, although the underlying mechanisms are still unknown. Various PBDEs have been reported to cause oxidative stress and to induce apoptotic cell death in several cell types. In the present study, we investigated the comparative neurotoxicity in mouse cerebellar granule neurons of five brominated diphenyl ether (BDE) congeners, chosen among the most commonly found at the highest levels in human tissues. All BDE congener tested (BDE-47, BDE-99, BDE-100, BDE-153, and BDE-209) decreased cell viability and induced apoptotic cell death, which was prevented by antioxidants. They also caused oxidative stress, as indicated by an increase in reactive oxygen species and in lipid peroxidation. For all end points measured, the potency ranking of the congeners was BDE-100 > BDE-47 > BDE-99 > BDE-153 >> BDE-209. Measurement of BDE congener levels in neurons after exposure to different concentrations showed a significant accumulation in cells, which followed the same relative ranking. The findings suggest that all BDE congeners tested exhibit the same general mode of action (induction of oxidative stress-mediated apoptosis) and that the ability of each isomer to elicit such effects is dependent upon their accumulation in neurons, particularly in the microsomal fraction and the mitochondria.

Low concentrations of the brominated flame retardants BDE-47 and BDE-99 induce synergistic oxidative stress-mediated neurotoxicity in human neuroblastoma cells

Polybrominated diphenyl ether (PBDE) flame retardants have become widespread environmental contaminants. The highest body burden has been found in toddlers and infants, due to their exposure through breast milk and house dust, and the current concern for potential adverse health effects of PBDEs relates to their developmental neurotoxicity. The mechanisms underlying the neurotoxicity of PBDEs are largely not understood, though there is evidence that PBDEs may elicit oxidative stress. In this study, two different mathematical models were used to evaluate the interaction between BDE-47 and BDE-99 on viability of neuronal cells. The combined exposure to these compounds induced synergistic effects at concentrations of BDE-47 below its threshold doses, and in a wide range of BDE-99 concentrations below its IC(50). In contrast, at concentrations of BDE-47 near its IC(50) value, and in a wide range of BDE-99 concentrations, antagonistic effects were observed. The interactions observed on cell viability were confirmed by an assessment of induction of oxidative stress. The finding that co-exposure to BDE-47 and BDE-99 could induce synergistic neurotoxic effects, in particular at low doses of BDE-47, is of much toxicological interest, as humans are exposed to mixtures of PBDEs, most notably tetra- and penta-BDE congeners.

Effects of decabrominated diphenyl ether (PBDE 209) exposure at different developmental periods on synaptic plasticity in the dentate gyrus of adult rats In vivo

Polybromininated diphenyl ethers (PBDEs) are widely used as flame-retardant additives. Previous studies have demonstrated that PBDEs exposure can lead to neurotoxicity. However, little is known about the effects of PBDE 209 on synaptic plasticity. This study investigated the effect of decabrominated diphenyl ether (PBDE 209), a major PBDEs product, on synaptic plasticity in the dentate gyrus of rats at different developmental periods. We examined the input/output functions, paired-pulse reactions, and the long-term potentiation of the field excitatory postsynaptic potential slope and the population spike amplitude in vivo. Rats were exposed to PBDE 209 during five different developmental periods: pregnancy, lactation via mother's milk, lactation via intragastric administration, after weaning, and prenatal to life. We found that exposed to PBDE 209 during different developmental periods could impair the synaptic plasticity of adult rats in different degrees. The results also showed that PBDE 209 might cause more serious effects on the postsynaptic cell excitability in synaptic plasticity, and the lactation period was the most sensitive time of development towards PBDE 209.

Effects of tetrabrominated diphenyl ether and hexabromocyclododecanes in single and complex exposure to hepatoma HepG2 cells

This study was designed to determine cytotoxic effects of PBDE-47 and HBCDs individually or with a mixture of both compounds exposure to Hep G2 cells. The results showed PBDE-47 and HBCDs induced increase of nitric oxide synthase (NOS) activity, release of NO, dissipation of mitochondria membrane potential and cell apoptosis. Exposure to HBCDs induced ROS formation. Moreover, preincubation with PTIO (NO scavanger) and N-acetylcysteine (ROS scavanger) partially reversed cytotoxic effects of these compounds. The possible mechanism is that PBDE-47 and HBCDs could boost generation of NO and/or ROS, impact mitochondria, and result in start-ups of apoptosis program. Cells exposed to mixture of both compounds and each of them showed non-apoptotic rate significant difference, but the combination of them caused more adverse effects on cells. These results suggest that PBDE-47 and HBCDs in single and complex exposure have the cytotoxic activity of anti-proliferation and induction of apoptosis in tumor cells in vitro.

Photodegradation of 2,2',4,4'-tetrabromodiphenyl ether in nonionic surfactant solutions

Recently, polybrominated diphenyl ethers (PBDEs) contaminated soils in electronic waste (e-waste) disposal sites of China have been reported and aroused concern. Since surfactant-aided soil washing followed by photodestruction has been suggested as a promising technology for soil remediation, the photodegradation of 2,2',4,4'-terabromodiphenyl ether (BDE-47) in nonionic surfactant solutions under UV-irradiation at 253.7 m was studied in the present work. The investigation was carried out on the effect of the type and concentration of surfactants, initial pH, and the addition of cations and acetone on BDE-47 photodecay. BDE-47 photodegradation all well followed pseudo-first-order kinetics under various conditions, and the decay rate was 0.4-1.3 times greater in the presence of surfactants than that in water alone. It was found that BDE-47 photodegradation was hardly affected through varying initial pH levels and retarded due to the presence of cations and acetone. The primary decay pathways in all surfactant micelles were shown to be reductive photodebromination, in which tri- to mono-BDEs were formed through a consecutive loss of bromine atoms. 2,4,4'-tribromodiphenyl ether (BDE-28), 4,4'-dibromodiphenyl ether (BDE-15), and 4-monobromodiphenyl ether (BDE-3) appeared sequentially as the predominant photoproducts over reaction time. Polybrominated dibenzofurans (mono- to tri-) were tentatively identified as additional intermediates for BDE-47 photodegradation in surfactant micelles.

Neurotoxicity of a polybrominated diphenyl ether mixture (DE-71) in mouse neurons and astrocytes is modulated by intracellular glutathione levels

Polybrominated diphenyl ether (PBDE) flame retardants have become widespread environmental contaminants. Body burden in the U.S. population has been shown to be higher than in other countries, and infants and toddlers have highest exposure through maternal breast milk and household dust. The primary concern for adverse health effects of PBDEs relates to their potential developmental neurotoxicity, which has been found in a number of animal studies. Information on the possible mechanisms of PBDE neurotoxicity is limited, though some studies have suggested that PBDEs may elicit oxidative stress. The present study examined the in vitro neurotoxicity of DE-71, a penta-BDE mixture, in primary neurons and astrocytes obtained from wild-type and Gclm knockout mice, which lack the modifier subunit of glutamate-cysteine ligase and, as a consequence, have very low levels of glutathione (GSH). These experiments show that neurotoxicity of DE-71 in these cells is modulated by cellular GSH levels. Cerebellar granule neurons (CGNs) from Gclm (-/-) mice displayed a higher sensitivity to DE-71 toxicity compared to CGNs from wild-type animals. DE-71 neurotoxicity in CGNs from Gclm (+/+) mice was exacerbated by GSH depletion, and in CGNs from both genotypes it was antagonized by increasing GSH levels and by antioxidants. DE-71 caused an increase in reactive oxygen species and in lipid peroxidation in CGNs, that was more pronounced in Gclm (-/-) mice. Toxicity of DE-71 was mostly due to the induction of apoptotic cell death. An analysis of DE-71-induced cytotoxicity and apoptosis in neurons and astrocytes from different brain areas (cerebellum, hippocampus, cerebral cortex) in both mouse genotypes showed a significant correlation with intracellular GSH levels. As an example, DE-71 caused cytotoxicity in hippocampal neurons with IC50s of 2.2 and 0.3 microM, depending on genotype, and apoptosis with IC50s of 2.3 and 0.4 microM, respectively. These findings suggest that the developmental neurotoxicity of PBDE may involve oxidative stress, and that individual with genetic polymorphisms leading to lower GSH levels may be more susceptible to their adverse effects.

First evidence of polybrominated diphenyl ether (flame retardants) effects in feral barbel from the Ebro River basin (NE, Spain)

Polybrominated diphenyl ethers (PBDEs) are chemicals of environmental concern due to their lipophilic, persistent and bioaccumulable characteristics as well as for their potential endocrine disrupting role. Former studies carried out in a tributary of the Cinca river (Ebro basin, NE Spain) revealed high levels of PBDEs in fish due to the discharges of effluents rich in PBDEs coming from a nearby industrial park in Barbastro. In this study, several biomarkers of pollutants exposure were measured in barbel, Barbus graellsii, before (upstream) and after (downstream) the main industrial site (Barbastro) in the Vero river. The results evidenced an enhanced hepatic phase I and II metabolism (measured as reductases, glutathione S transferase and uridinediphospho-glucuronosyltransferase), and of the antioxidant enzyme glutathione peroxidase. Conversely, fishes collected from downstream reaches had their phase I CYP1A dependent ethoxyresorufin O-deethylase, antioxidant diaphorase and brain cholinesterase activities depleted. In addition, the histological study of the liver and kidney of these fish evidenced an increase of the number and size of macrophage aggregates in most individuals collected downstream. Bivariate correlated analyses showed that the above mentioned biomarkers were correlated to measured PBDE congeners, thus indicating that the observed biological effects were unlikely to be related to other environmental factors than PBDEs. Overall, the measured biochemical and histological markers provide new evidence that in field exposed fish, PBDEs levels were associated with high activities of phase I and II metabolic enzymes, oxidative stress in liver, neurotoxicity in brain and histopathological effects in both liver and kidney.