Short-term tetrabromobisphenol A exposure promotes fibrosis of human uterine fibroid cells in a 3D culture system through TGF-beta signaling.

Tetrabromobisphenol A (TBBPA), a derivative of BPA, is a ubiquitous environmental contaminant with weak estrogenic properties. In women, uterine fibroids are highly prevalent estrogen-responsive tumors often with excessive accumulation of extracellular matrix (ECM) and may be the target of environmental estrogens. We have found that BPA has profibrotic effects in vitro, in addition to previous reports of the in vivo fibrotic effects of BPA in mouse uterus. However, the role of TBBPA in fibrosis is unclear. To investigate the effects of TBBPA on uterine fibrosis, we developed a 3D human uterine leiomyoma (ht-UtLM) spheroid culture model. Cell proliferation was evaluated in 3D ht-UtLM spheroids following TBBPA (10-6 -200 µM) administration at 48 h. Fibrosis was assessed using a Masson's Trichrome stain and light microscopy at 7 days of TBBPA (10-3  µM) treatment. Differential expression of ECM and fibrosis genes were determined using RT² Profiler™ PCR arrays. Network and pathway analyses were conducted using Ingenuity Pathway Analysis. The activation of pathway proteins was analyzed by a transforming growth factor-beta (TGFB) protein array. We found that TBBPA increased cell proliferation and promoted fibrosis in 3D ht-UtLM spheroids with increased deposition of collagens. TBBPA upregulated the expression of profibrotic genes and corresponding proteins associated with the TGFB pathway. TBBPA activated TGFB signaling through phosphorylation of TGFBR1 and downstream effectors-small mothers against decapentaplegic -2 and -3 proteins (SMAD2 and SMAD3). The 3D ht-UtLM spheroid model is an effective system for studying environmental agents on human uterine fibrosis. TBBPA can promote fibrosis in uterine fibroid through TGFB/SMAD signaling.

Excretion characteristics of tetrabromobisphenol-A in Wistar rats following mouth and nose inhalation exposure.

Tetrabromobisphenol-A (TBBPA), a brominated flame retardant with the largest production volume worldwide, is employed as a reactive and additive flame retardant, and also as an intermediate in the production of other retardants. The constant release of TBBPA into the environment has attracted increasing attention to its potent health effects. To date, the vast majority of health-related research on TBBPA has focused on oral exposure. This study aims to explore the excretion characteristics of TBBPA in living organisms following inhalation exposure. An inhalation exposure system was established in which the experimental animal model was exposed to inhalable particles (diameter < 10 µm) of TBBPA. The TBBPA aerosol doses used were 12.9, 54.6, 121.6, and 455.0 mg/m3 according to tuning system parameters. Following 14 d (2 h/d) of repeated inhalational exposure, the primary route of elimination was in feces for all exposed groups, and the values showed a significant positive linear relationship with exposure dose. In contrast, the elimination amount in urine was less than 0.4% of the inhaled dose. Trace levels of TBBPA (less than 0.1% of the inhaled dose) were also detected in serum, with amounts varying from 0 to 844 ng (per rat) among all groups.

A high dose mode of action for tetrabromobisphenol A-induced uterine adenocarcinomas in Wistar Han rats: A critical evaluation of key events in an adverse outcome pathway framework.

TBBPA is a non-genotoxic flame retardant used to improve fire safety in a wide variety of consumer products. Estimated human exposures to TBBPA are very low (<0.000084 mg/kg-day), relative to the doses (500 and 1000 mg/kg-day of TBBPA) administered in a recent bioassay that resulted in uterine tumors in Wistar Han rats following chronic exposure. As part of an effort to characterize the relevance of the uterine tumors to humans, data and biological knowledge relevant to the progression of events associated with TBBPA-induced uterine tumors in female rats were organized in an adverse outcome pathway (AOP) framework. Based on a review of possible MOAs for chemically induced uterine tumors and available TBBPA data sets, a plausible molecular initiating event (MIE) was the ability of TBBPA to bind to and inhibit estrogen sulfotransferases, the enzymes responsible for sulfation of estradiol. Subsequent key events in the AOP, including increased bioavailability of unconjugated estrogens in uterine tissue, would occur as a result of decreased sulfation, leading to a disruption in estrogen homeostasis, increased expression of estrogen responsive genes, cell proliferation, and hyperplasia. Available data support subsequent key events, including generation of reactive quinones from the metabolism of estrogens, followed by DNA damage that could contribute to the development of uterine tumors. Uncertainties associated with human relevance are highlighted by potential strain/species sensitivities to development of uterine tumors, as well as the characterization of a dose-dependent MIE. For the latter, it was determined that the TBBPA metabolic profile is altered at high doses (such as those used in the cancer bioassay), and thus an MIE that is only operative under repeated high dose, administration. The MIE and subsequent key events for the development of TBBPA-induced uterine tumors are not feasible in humans given differences in the kinetic and dynamic factors associated with high dose exposures in rats relative to human exposure levels to TBBPA.

Estimation of tetrabromobisphenol A (TBBPA) percutaneous uptake in humans using the parallelogram method.

Tetrabromobisphenol A (TBBPA) is currently the world's highest production volume brominated flame retardant. Humans are frequently exposed to TBBPA by the dermal route. In the present study, a parallelogram approach was used to make predictions of internal dose in exposed humans. Human and rat skin samples received 100 nmol of TBBPA/cm(2) skin and absorption and penetrance were determined using a flow-through in vitro system. TBBPA-derived [(14)C]-radioactivity was determined at 6h intervals in the media and at 24h post-dosing in the skin. The human skin and media contained an average of 3.4% and 0.2% of the total dose at the terminal time point, respectively, while the rat skin and media contained 9.3% and 3.5%, respectively. In the intact rat, 14% of a dermally-administered dose of ~100 nmol/cm(2) remained in the skin at the dosing site, with an additional 8% reaching systemic circulation by 24h post-dosing. Relative absorption and penetrance were less (10% total) at 24h following dermal administration of a ten-fold higher dose (~1000 nmol/cm(2)) to rats. However, by 72 h, 70% of this dose was either absorbed into the dosing-site skin or had reached systemic circulation. It is clear from these results that TBBPA can be absorbed by the skin and dermal contact with TBBPA may represent a small but important route of exposure. Together, these in vitro data in human and rat skin and in vivo data from rats may be used to predict TBBPA absorption in humans following dermal exposure. Based on this parallelogram calculation, up to 6% of dermally applied TBBPA may be bioavailable to humans exposed to TBBPA.

Neurotoxicity of FireMaster 550® in zebrafish (Danio rerio): Chronic developmental and acute adolescent exposures.

BACKGROUND: FireMaster® 550 (FM 550) is the second most commonly used flame retardant (FR) product in consumer goods and has been detected in household dust samples. However, neurobehavioral effects associated with exposure have not been characterized in detail. We investigated the behavioral effects of FM 550 in zebrafish to facilitate the integration of the cellular and molecular effects of FM 550 with its behavioral consequences. The effects of developmental FM 550 exposure on zebrafish larvae swimming shortly after the end of exposure as well as the persisting effects of this exposure on adolescent behavior were studied. In addition, the acute effects of FM 550 on behavior with exposure during adolescence in zebrafish were studied. METHODS: Developmental exposure to 0, 0.01, 0.1 or 1 mg/L of FM 550 via immersion spanned 0-5 days post fertilization, with larval testing on day 6 and adolescent testing on days 40-45. Acute adolescent (45 dpf) exposure was to 0, 1.0 or 3.0 mg/L of FM 550 via immersion, for 24 h, with testing 2 h or 1 week later. The vehicle condition was colony tank water with .0004% (developmental) or .0012% (adolescent) DMSO. Zebrafish behavior was characterized across several domains including learning, social affiliation, sensorimotor function, predator escape, and novel environment exploration. RESULTS: Persisting effects of developmental FM 550 exposure included a significant (p<0.01) reduction in social behavior among all dose groups. Acute FM 550 exposure during adolescence caused hypoactivity and reduced social behavior (p's<0.05) when the fish were tested 2 h after exposure. These effects were attenuated at the 1 week post exposure testing point DISCUSSION: Taken together, these data indicate that FM 550 may cause persisting neurobehavioral alterations to social behavior in the absence of perturbations along other behavioral domains and that developmental exposure is more costly to the organism than acute adolescent exposure.

A reproductive, developmental and neurobehavioral study following oral exposure of tetrabromobisphenol A on Sprague-Dawley rats.

The objectives of these GLP US EPA OPPTS 970.3800 and 970.3700 studies were to examine the effects of tetrabromobisphenol A (TBBPA) at oral doses of 10, 100 or 1000 mg/kg BW/day over the course of 2 generations on growth as well as behavioral, neurological and neuropathologic functions in offspring. In a separate study the influence of oral TBBPA (0, 100, 300 or 1000 mg/kg BW/d) was examined on embryonic/fetal development from gestation days (GDs) 0-19. In the reproductive study, exposure to ≥ 100-mg/kg BW/d TBBPA resulted in a decrease in circulating, peripheral thyroxine (T4) levels in rats that were not accompanied by any marked alterations in triiodothyronine (T3) and thyroid stimulating hormone (TSH). These findings are explainable on the basis of induction of rat liver catabolism, a phenomenon that may be species-specific and not relevant for humans. TBBPA at up to 1000 mg/kg BW/d was not associated with any significant non-neurological effects on reproduction, growth and development. A subtle reduction, of unknown biological relevance, in the thickness of the parietal cortices of 11-day-old F2 pups in the 1000 mg/kg BW/d group was noted. This change was not accompanied by evidence of micro-anatomic changes. No estrogenic effects sufficient to affect macro and micro anatomy, fertility, reproduction, development, survival or behavior were detected in the embryofetal development study or in the multigenerational study. No other TBBPA-related effects on developmental neurotoxicity/neuropathology were detected. In the developmental study no TBBPA related change in mortality rate was observed in any of the dams. No other significant test article-related effects were noted. The no observed effect level (NOEL) for maternal and developmental toxicity was 1000 mg/kg BW/d, the highest dose evaluated.

The effects of 3,3',4,4'-tetrabromobiphenyl on rats fed diets containing a constant level of copper and varying levels of molybdenum.

Copper (Cu) metabolism is altered in rats fed diets high in molybdenum (Mo) and low in Cu. This 10-week study was carried out to examine the effects of supplemental Mo (7.5-240 µg/g diet) on male Sprague-Dawley rats fed diets adequate in Cu (5 µg/g diet) and to determine the susceptibility of Mo-treated animals to the environmental pollutant 3,3',4,4'-tetrabromobiphenyl (TBB). After 7 weeks of dietary treatment, half of the rats in each group received a single IP injection of TBB (150 µM/kg bw), while the other half received the corn oil vehicle. Rats sacrificed at 10 weeks showed no effects of Mo on growth, feed efficiency, or selected organ or tissue weights. Dose-dependent effects on plasma Mo (0-5.1 µg/mL), plasma Cu (0.95-0.20 µg/mL), and bone Cu (3.4-10 µg/g) in control through the high dose were found. Cu sequestration in the bone of Mo-treated rats is a new finding. TBB treatment resulted in dramatic weight loss and loss of absolute organ mass. Relative organ weights were increased, except for the thymus. TBB altered the concentrations of certain amino acids. Compared to control rats, this polybrominated biphenyl congener significantly decreased plasma Cu and ceruloplasmin at higher concentrations of dietary Mo and promoted the process of plasma Cu decrease by Mo, suggesting a combined effect.

Mammalian toxicology and human exposures to the flame retardant 2,2',6,6'-tetrabromo-4,4'-isopropylidenediphenol (TBBPA): implications for risk assessment.

The compound 2,2',6,6'-Tetrabromo-4,4'-isopropylidenediphenol (tetrabromobisphenol A, TBBPA) is used as a reactive and additive flame retardant. This review evaluates the mammalian toxicology of TBBPA and summarizes recent human exposure and risk assessments. TBBPA has a low potential for systemic or reproductive toxicity, and no-observed-adverse-effect-levels were greater than 1,000 mg/kg body weight (bw)/day in a 90-day oral toxicity study, a developmental toxicity study and a two-generation reproductive and developmental toxicity study. Some interactions of TBBPA with hormone-mediated pathways were noted in vitro; however, when studied in vivo, TBBPA did not produce adverse effects that might be considered to be related to disturbances in the endocrine system. Therefore, in accordance with internationally accepted definitions, TBBPA should not be considered an "endocrine disruptor." Furthermore, TBBPA is rapidly excreted in mammals and therefore does not have a potential for bioaccumulation. Measured concentrations of TBBPA in house dust, human diet and human serum samples are very low. Daily intakes of TBBPA in humans were estimated to not exceed a few ng/kg bw/day. Due to the low exposures and the low potential for toxicity, margins of exposures for TBBPA in the human population were between 6 × 10(4) (infants) to 6 × 10(7) (adults). Exposures of the general population are also well below the derived-no-effect-levels derived for endpoints of potential concern in REACH.

Hormonal effects of tetrabromobisphenol A using a combination of in vitro and in vivo assays.

The aim of this study was to investigate the hormonal effects of tetrabromobisphenol A (TBBPA) in vitro on recombinant yeasts and in vivo on mosquitofish (Gambusia affinis). The in vitro bioassays for (anti-)androgenic activities showed that TBBPA had a weak androgenic activity in vitro with recombinant yeast systems carrying human androgen receptor (hAR). In the in vivo bioassays, the gene expression patterns of vitellogenin (Vtg), estrogen receptors (ERα and ERß), and androgen receptors (ARα and ARß) in adult males and juveniles after exposure to TBBPA for 60 days were evaluated. Significant up-regulation of Vtg, ERα, and ERß mRNAs was observed in the liver after exposure to 500 nM of TBBPA. In the testis, the lowest concentration of TBBPA (50 nM) markedly induced Vtg, ERß, and ARß mRNA expression, but the same concentration significantly inhibited ARα mRNA expression. In addition, in juveniles, 100 nM of TBBPA significantly up-regulated the expression of Vtg, ERß, and ARα mRNAs. However, TBPPA did not cause histological alterations in the liver and testis of adult male mosquitofish. The results from this present study suggest that TBBPA could display low but multiple hormonal activities despite its low toxicity to mosquitofish.

Transient aberration of neuronal development in the hippocampal dentate gyrus after developmental exposure to brominated flame retardants in rats.

We immunohistochemically investigated the impact and reversibility of three brominated flame retardants (BFRs) known to be weak thyroid hormone disruptors on neuronal development in the hippocampal formation and apoptosis in the dentate subgranular zone. Pregnant Sprague-Dawley rats were exposed to 10, 100, or 1,000 ppm decabromodiphenyl ether (DBDE); 100, 1,000 or 10,000 ppm tetrabromobisphenol A (TBBPA) or 1,2,5,6,9,10-hexabromocyclododecane (HBCD) in the diet from gestational day 10 through to day 20 after delivery (weaning). On postnatal day (PND) 20, interneurons in the dentate hilus-expressing reelin increased with all chemicals, suggestive of aberration of neuronal migration. However, this increase had disappeared by PND 77. NeuN-positive mature neurons increased in the hilus on PND 77 with all chemicals. In the subgranular zone on PND 20, an increase in apoptotic bodies suggestive of impaired neurogenesis was observed after exposure to TBBPA or HBCD. The effects on neuronal development were detected at doses of ≥100 ppm DBDE; ≥1,000 ppm TBBPA; and at least at 10,000 ppm HBCD. On PND 20, the highest dose of DBDE and HBCD revealed mild fluctuations in the serum concentrations of thyroid-related hormones suggestive of weak developmental hypothyroidism, while TBBPA did not. Thus, DBDE and TBBPA may exert direct effect on neuronal development in the brain, but hypothyroidism may be operated for DBDE and HBCD at high doses. An excess of mature neurons in the hilus at later stages may be the signature of the developmental effects of BFRs. However, the effect itself was reversible.

The hormesis effect of BDE-47 in HepG2 cells and the potential molecular mechanism.

Polybrominated diphenyl ethers (PBDEs) had been used extensively in electrical and electronic products as brominated flame retardants. PBDEs are widely distributed in environment media and wildlife since they are lipophilic and persistent, resulting in bioaccumulation and bioamplification through food chains. Accumulation of PBDEs in the environment and human tissues will consequently cause potential negative effects on the ecological environment and human health. To date, some in vitro and in vivo studies have reported that PBDEs possess neurotoxicity, hepatotoxicity, immunotoxicity, reproduction toxicity, endocrine disrupting activity and carcinogenicity. BDE-47 is one of the most predominant PBDE congeners detected in human tissues. The objective of this study is to investigate whether low concentration of BDE-47 could cause hormesis effect in the human hepatoma HepG(2) cells, and to explore the possible molecular mechanism. The results showed that low concentration of BDE-47 (10(-10), 10(-9) and 10(-8) M) could promote cell proliferation and cause no obvious change in DNA damage or cell apoptosis, while the high concentration significantly inhibit cell proliferation. Meanwhile, the reactive oxygen species (ROS) in low concentration BDE-47 (10(-10), 10(-9) and 10(-8) M) treated groups significantly elevated compared with the control group. After low concentration BDE-47 treatment, the expression of proliferating cell nuclear antigen (PCNA), Cyclin D1, DNA-dependent protein kinase catalytic subunit (DNA-PKcs) and phosphorylated protein kinase B (p-Akt) in the HepG(2) cells was markedly up-regulated. However, in DNA-PKcs inhibited cells, the promotion effect on cell proliferation was significantly suppressed. Cell cycle analysis showed a significant decrease in G1 phase after exposure to low concentration of BDE-47. Moreover, pre-exposure to low concentration BDE-47 seemed alleviate the negative effects of high concentration (50 µM) exposure to cause DNA damage and apoptosis. These results suggested that BDE-47 has a hormesis effect in HepG(2) cells and DNA-PKcs/Akt pathway may be involved in regulation of cell proliferation and apoptosis.

Acute toxicity of polybrominated diphenyl ethers (PBDEs) for turbot (Psetta maxima) early life stages (ELS).

BACKGROUND, AIM AND SCOPE: The environmental presence of polybrominated diphenyl ethers (PBDEs), among which BDE-47 and BDE-99 are particularly abundant, makes toxicity data necessary to assess the hazard risk posed by PBDE to aquatic organisms. This study examines the effects of BDE-47 and BDE-99 on embryo-larval stages of the marine flatfish turbot. MATERIALS AND METHODS: The turbot embryos were exposed at nominal concentrations of BDE-47 and BDE-99 for 6 days. Selected dose levels were relevant for investigating sublethal and lethal effects. RESULTS: Both tested compounds caused lethal toxicity as well as non-lethal malformations during embryo development. We found a high toxic potency of BDE-47 compared to BDE-99 (LC50 values for embryos and larvae, respectively, BDE-47: 27.35 and 14.13 µg L⁻¹; BDE-99: 38.28 and 29.64 µg L⁻¹). DISCUSSION: The present study shows high sensitivity of fish early life stages (ELS) to PBDE compounds. Based on environmental concentrations of dissolved PBDEs from various aquatic ecosystems, waterborne BDE-47 and BDE-99 pose little risk of acute toxicity to marine fish at relevant environmental concentrations. CONCLUSIONS: Turbot fish ELS proved to be an excellent model for the study of ecotoxicity of contaminants in seawater. The results demonstrate harmful effects of PBDE on turbot ELS at concentrations in the range of parts per billion units. RECOMMENDATIONS AND PERSPECTIVES: In the perspective of risk assessment, ELS endpoints provide rapid, cost-effective and ecologically relevant information, and links should be sought between these short-term tests and effects of long-term exposures in more realistic scenarios.

Gender-specific modulation of immune system complement gene expression in marine medaka Oryzias melastigma following dietary exposure of BDE-47.

BDE-47 is one of the most widely found congeners of PBDEs in marine environments. The potential immunomodulatory effects of BDE-47 on fish complement system were studied using the marine medaka Oryzias melastigma as a model fish. Three-month-old O. melastigma were subjected to short-term (5 days) and long-term (21 days) exposure to two concentrations of BDE-47 (low dose at 290 ± 172 ng/day; high dose at 580 ± 344 ng/day) via dietary uptake of BDE-47 encapsulated in Artemia nauplii. Body burdens of BDE-47 and other metabolic products were analyzed in the exposed and control fish. Only a small amount of debrominated product, BDE-28, was detected, while other metabolic products were all under detection limit. Transcriptional expression of six major complement system genes involved in complement activation: C1r/s (classical pathway), MBL-2 (lectin pathway), CFP (alternative pathway), F2 (coagulation pathway), C3 (the central component of complement system), and C9 (cell lysis) were quantified in the liver of marine medaka. Endogenous expression of all six complement system genes was found to be higher in males than in females (p < 0.05). Upon dietary exposure of marine medaka to BDE-47, expression of all six complement genes were downregulated in males at day 5 (or longer), whereas in females, MBl-2, CFP, and F2 mRNAs expression were upregulated, but C3 and C9 remained stable with exposure time and dose. A significant negative relationship was found between BDE-47 body burden and mRNA expression of C1r/s, CFP, and C3 in male fish (r = -0.8576 to -0.9447). The above findings on changes in complement gene expression patterns indicate the complement system may be compromised in male O. melastigma upon dietary exposure to BDE-47. Distinct gender difference in expression of six major complement system genes was evident in marine medaka under resting condition and dietary BDE-47 challenge. The immunomodulatory effects of BDE-47 on transcriptional expression of these complement components in marine medaka were likely induced by the parent compound instead of biotransformed products. Our results clearly demonstrate that future direction for fish immunotoxicology and risk assessment of immunosuppressive chemicals must include parallel evaluation for both genders.

Global gene expression analysis in the livers of rat offspring perinatally exposed to low doses of 2,2',4,4'-tetrabromodiphenyl ether.

BACKGROUND: Polybrominated diphenyl ethers are a group of flame-retardant chemicals appearing increasingly in the environment. Their health effects and mechanisms of toxicity are poorly understood. OBJECTIVES: We screened for the sensitive effects and mechanisms of toxicity of 2,2 ,4,4 -tetra-bromodiphenyl ether (BDE-47) by analyzing the gene expression profile in rats exposed to doses comparable to human exposure. METHODS: Wistar dams were exposed to vehicle or BDE-47 (0.002 and 0.2 mg/kg body weight) every fifth day from gestation day 15 to postnatal day 20 by injections to caudal vein. Total RNA was extracted from the livers of pups and hybridized to the whole-genome RNA expression micro-arrays. The list of genes 2-fold differentially expressed was exported to PANTHER and Ingenuity Systems for analysis of enriched ontology groups and molecular pathways. RESULTS: Oxidoreductase and transferase protein families were enriched in exposed rats as were these biological process categories: carbohydrate metabolism; electron transport; and lipid, fatty acid, and steroid metabolism. Four signaling pathways (cascades of activation of drug-metabolizing enzymes) and 10 metabolic pathways were significantly enriched. Drug-metabolizing enzymes appear to be regulated by BDE-47 through an aryl hydrocarbon receptor-independent mechanism. Direct interaction with retinoid X receptor or its upstream cascade may be involved. The main metabolic effects consisted of activation of metabolic pathways: alpha- and omega-oxidation of fatty acids, glycolysis, and starch hydrolysis. CONCLUSIONS: Altered expression of genes involved in metabolic and signaling pathways and functions of the organism occurs after perinatal exposure of rat offspring to BDE-47 at doses relevant for the general population.

Anti-thyroid hormone activity of bisphenol A, tetrabromobisphenol A and tetrachlorobisphenol A in an improved reporter gene assay.

Previously, we transiently transfected Gal4-fused thyroid hormone receptor (TR) expressing vector and the Gal4 response reporter structure pUAS-tk-luc into HepG2 cell, developed a TR beta-1 mediated reporter gene assay to screen for compounds that acted on the TR signaling pathway. In this study, we improved the test efficiency by changing the transfected cell line into CV-1 cell. Triiodothyronine (T3) and thyroxine (T4) induced higher luciferase expression, with the median effective concentration (EC(50)) of 1.16 x 10(-8) and 1.36 x 10(-7)M, respectively. Bisphenol A (BPA) was selected as a positive antagonist, exhibiting weak anti-thyroid hormone activity with the median inhibitory concentration (IC(50)) of 1.64 x 10(-5)M. The assay showed acceptable repeatability to T3 with inter coefficient of variability (CV) of 27.5% and intra CV of 18.6%. Two flame retardants, tetrabromobisphenol A (TBBPA) and tetrachlorobisphenol A (TCBPA), were tested for their agonist and antagonist activities. As a result, we found that both of them possessed TR antagonist activity and neither of them showed agonist activity. These results suggested that TBBPA and TCBPA could act as TH antagonists. This assay provided a useful tool for the assessment of environmental chemicals as thyroid system disruptors.

Risk assessment of tetrabromobisphenol A on cyclooxygenase-2 expression via MAP kinase/NF-kappaB/AP-1 signaling pathways in murine macrophages.

Tetrabromobisphenol A [2,2-bis-(3,5-dibromo-4-hydroxyphenyl)propane; TBBPA] is used worldwide as a flame retardant in numerous products. In the present study, the effects of TBBPA were examined on the expression of cyclooxygenase-2 (COX-2), inflammation-related cytokines, transcription factors, and signaling pathways responsible for transcriptional activation of the COX-2 gene in murine RAW 264.7 macrophages. Exposure to TBBPA markedly enhanced the production of prostaglandin E(2), a major COX-2 metabolite, in macrophages. TBBPA concentration-dependently increased the levels of COX-2 protein and mRNA. In addition, TBBPA increased the secretion and mRNA levels of proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-1beta. Transfection of a human COX-2 promoter construct demonstrated that TBBPA induced COX-2 promoter activity. Furthermore, transfection with pNF-kappaB-Luc and pAP-1-Luc plasmid revealed that TBBPA activated the NF-kappaB and AP-1 sites. Phosphatidylinositol 3 (PI3) kinase, its downstream signaling molecule, Akt, and mitogen-activated protein kinases (MAPK) were also significantly activated by TBBPA. Our data demonstrate TBBPA-induced COX-2 and proinflammatory cytokine expression occurs through the PI3-kinase/Akt/MAP kinase/NF-kappaB/AP-1 pathways.

Nephrotoxic potential and toxicokinetics of tetrabromobisphenol A in rat for risk assessment.

Tetrabromobisphenol A (TBBPA), one of the most widely used global brominated flame retardants, is used to improve fire safety of laminates in electrical and electronic equipment. To investigate the nephrotoxic potential of TBBPA and its toxicokinetic profile in rats, single-dose and daily 14-d repeated-dose toxicity studies at 200, 500, or 1000 mg/kg were performed. Several biochemical parameters were analyzed to evaluate nephrotoxicity of TBBPA. High-dose 1000 mg/kg TBBPA significantly elevated renal thiobarbituric acid-reactive substance (TBARS) levels, and superoxide dismutase (SOD) activity was increased at all 3 doses administered. This was associated with no change in the activity of catalase (CAT). Our results suggest that acute 1-d high-dose administration of TBBPA produced transient renal changes at 5 h. Subsequently, TBBPA in serum, urine, and kidney was determined by liquid chromatography-mass spectroscopy (LC/MS). Toxicokinetic studies indicated that TBBPA shows relatively a short half-life (7-9 h) and was eliminated almost completely in feces by 2 d. Based on the results from the 14-d repeated-dose study, TBBPA did not accumulate in the rat, and was eliminated in feces. The present results suggested that TBBPA may not be toxic to kidney, as the chemical is not bioavailable and is not present in renal tissue.

The polybrominated diphenyl ether mixture DE-71 is mildly estrogenic.

BACKGROUND: Polybrominated diphenyl ethers (PBDEs) are widely found in the environment, and they may act as endocrine disruptors. OBJECTIVE: Our goal in this study was to test the PBDE mixture DE-71 for estrogenic activity. METHODS: We used proliferation of cultured breast cancer cells (MCF-7) and trophic effects in the reproductive tracts of ovariectomized mice as estrogen bioassays. DE-71 was administered to mice by subcutaneous injection (sc) or oral gavage (po), alone or in combination with estradiol, for 3 or 34 days. Liver weights and cytochrome P450 enzyme activities were also measured. RESULTS: DE-71 increased MCF-7 cell proliferation, and this was prevented by antiestrogen. DE-71 cotreatment reduced the effect of estradiol in MCF-7 cells. In the mouse 3-day assay, DE-71 administered alone had no effect on uterine weight, uterine epithelial height (UEH), or vaginal epithelial thickness (VET); however, when DE-71 was administered as a cotreatment, it potentiated estradiol's effect on uterine weight. DE-71 administered sc to BALB/c mice for 34 days slightly increased UEH and VET, and attenuated the estradiol-induced increase in UEH; these effects were not seen in BALB/c mice treated po or in C57BL/6 mice treated sc. DE-71 increased liver weight in BALB/c, C57BL/6, and estrogen receptor-alpha knockout mice. We also found an increase in liver cytochrome P450 1A (CYP1A) and CYP2B activities when DE-71 was administered po, but only CYP2B increased after sc treatment. CONCLUSION: DE-71 behaves as a weak estrogen. In mice, the treatment route and duration determined if DE-71 was estrogenic. BALB/c mice are more susceptible to DE-71 effects in estrogen target tissues than C57BL/6 mice. DE-71 increased liver weight independently of estrogen receptor-alpha.

Tetrabromobisphenol A (TBBPA), induces cell death in TM4 Sertoli cells by modulating Ca2+ transport proteins and causing dysregulation of Ca2+ homeostasis.

Tetrabromobisphenol A (TBBPA) is a commonly used brominated flame retardant (BFR) utilized to reduce the flammability of a variety of products. Studies have indicated that a number of BFRs are becoming widely distributed within the environment and are bio-accumulating within organisms. There has been much speculation that a variety of phenolic pollutants (including compounds chemically related to TBBPA, such as bisphenol A) may cause endocrine disruption and Ca2+ dysregulation in cells involved in spermatogenesis. In this study we therefore investigate the effects of TBBPA on mouse TM4 Sertoli cells (essential for sperm development). Results show that TBBPA increases Ca2+ within these cells in the 5-60 microM concentration range (EC50, 21 microM). TBBPA also causes cell death (LC50, 18 microM) partly via apoptosis, involving Ca2+-dependent mitochondrial depolarisation. Studies on intracellular Ca2+ transporters shows that TBBPA can inhibit sarcoplasmic/endoplasmic reticulum Ca2+-ATPases (SERCA) at low concentrations (IC50, 0.4 to 1.2 microM) and also activate the Ryanodine receptor Ca2+ channel within the 0.4-4 microM concentration range. Therefore these studies suggest that the cytotoxic effects of TBBPA on cells is partly due to dysregulation of Ca2+ signalling, by directly affecting Ca2+ transport proteins.

Exposure to tetrabromobisphenol A (TBBPA) in Wistar rats: neurobehavioral effects in offspring from a one-generation reproduction study.

Within the framework of an EU project on risk assessment of brominated flame retardants, TBBPA was studied for neurobehavioral effects in rats. To permit benchmark dose analysis, eight dose levels were chosen ranging from 0 to 3000mg/kg body weight. Exposure of parental rats started 10 and 2 weeks before mating in males and females, respectively, and was continued throughout mating, gestation and lactation. After weaning, exposure was continued in the offspring throughout life. Previous studies had indicated TBBPA-induced effects on thyroid hormones. Because of the known implication of thyroid hormones in neurodevelopment, the present experiments tested if TBBPA exposure affects thyroid-dependent neurobehavioral functions in offspring, such as auditory responses and conditioned fear. Sweet preference was included because of sex-specific effects in littermates. No statistically significant effects were found on context or cue conditioned fear or sweet preference. Auditory responses were examined with brainstem auditory evoked potentials (BAEPs) at approximately 50-110 days of age. BAEP thresholds and wave IV latency were increased in exposed female rats in the low frequency range. In male rats, thresholds were unaffected, but absolute latency of wave IV and interpeak latencies II-IV showed exposure-related increases at low frequencies. The outcome pattern suggests a predominant cochlear effect of TBBPA in females while in males neural effects are more apparent. According to benchmark analysis, the critical effect doses (CED) for prolongations of wave IV latency at 0.5kHz were in the range of 35-70mg/kg body weight with lower bounds (BMDL) of approximately 8mg/kg in males and females. The BMDL values for elevation of hearing thresholds in females were in the range of 1-40mg/kg body weight, depending on frequency. The benchmark doses for effects on the BAEP were similar to values for decreases in circulating thyroid hormones. The comparison of the exposure level at which the most sensitive effect was found with current human exposure levels yielded a margin of exposure of about 5, according to a recent risk assessment. Further investigations are needed to examine exposure pathways, fate in the body and effects of TBBPA.