Effects of fifteen PBDE metabolites, DE71, DE79 and TBBPA on steroidogenesis in the H295R cell line

Mechanisms of Male Reproductive Toxicity of Polybrominated Diphenyl Ethers

Polybrominated diphenyl ethers (PBDE) are a group of flame retardants used in a variety of artificial materials. Despite being phased out in most industrial countries, they remain in the environment and human tissues due to their persistence, lipophilicity, and bioaccumulation. Populational and experimental studies demonstrate the male reproductive toxicity of PBDEs including increased incidence of genital malformations (hypospadias and cryptorchidism), altered weight of testes and other reproductive tissues, altered testes histology and transcriptome, decreased sperm production and sperm quality, altered epigenetic regulation of developmental genes in spermatozoa, and altered secretion of reproductive hormones. A broad range of mechanistic hypotheses of PBDE reproductive toxicity has been suggested. Among these hypotheses, oxidative stress, the disruption of estrogenic signaling, and mitochondria disruption are affected by PBDE concentrations much higher than concentrations found in human tissues, making them unlikely links between exposures and adverse reproductive outcomes in the general population. Robust evidence suggests that at environmentally relevant doses, PBDEs and their metabolites may affect male reproductive health via mechanisms including AR antagonism and the disruption of a complex network of metabolic signaling.

Review of the environmental occurrence, analytical techniques, degradation and toxicity of TBBPA and its derivatives

BFRs (brominated flame retardants) are a class of compounds that are added to or applied to polymeric materials to avoid or reduce the spread of fire. Tetrabromobisphenol A (TBBPA) is one of the known BFR used many in industries today. Due to its wide application as an additive flame retardant in commodities, TBBPA has become a common indoor contaminant. Recent researches have raised concerns about the possible hazardous effect of exposure to TBBPA and its derivatives in humans and wildlife. This review gives a thorough assessment of the literature on TBBPA and its derivatives, as well as environmental levels and human exposure. Several analytical techniques/methods have been developed for sensitive and accurate analysis of TBBPA and its derivatives in different compartments. These chemicals have been detected in practically every environmental compartment globally, making them a ubiquitous pollutant. TBBPA may be subject to adsorption, biological degradation or photolysis, photolysis after being released into the environment. Treatment of TBBPA-containing waste, as well as manufacturing and usage regulations, can limit the release of these chemicals to the environment and the health hazards associated with its exposure. Several methods have been successfully employed for the treatment of TBBPA including but not limited to adsorption, ozonation, oxidation and anaerobic degradation. Previous studies have shown that TBBPA and its derivative cause a lot of toxic effects. Diet and dust ingestion and have been identified as the main routes of TBBPA exposure in the general population, according to human exposure studies. Toddlers are more vulnerable than adults to be exposed to indoor dust through inadvertent ingestion. Furthermore, TBBP-A exposure can occur during pregnancy and through breast milk. This review will go a long way in closing up the knowledge gap on the silent and over ignored deadly effects of TBBPA and its derivatives and their attendant consequences.

Congenital Adrenal Hyperplasia-Current Insights in Pathophysiology, Diagnostics, and Management

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders affecting cortisol biosynthesis. Reduced activity of an enzyme required for cortisol production leads to chronic overstimulation of the adrenal cortex and accumulation of precursors proximal to the blocked enzymatic step. The most common form of CAH is caused by steroid 21-hydroxylase deficiency due to mutations in CYP21A2. Since the last publication summarizing CAH in Endocrine Reviews in 2000, there have been numerous new developments. These include more detailed understanding of steroidogenic pathways, refinements in neonatal screening, improved diagnostic measurements utilizing chromatography and mass spectrometry coupled with steroid profiling, and improved genotyping methods. Clinical trials of alternative medications and modes of delivery have been recently completed or are under way. Genetic and cell-based treatments are being explored. A large body of data concerning long-term outcomes in patients affected by CAH, including psychosexual well-being, has been enhanced by the establishment of disease registries. This review provides the reader with current insights in CAH with special attention to these new developments.

Adrenal Corticosteroid Perturbation by the Endocrine Disruptor BDE-47 in a Human Adrenocortical Cell Line and Male Rats

Polybrominated diphenyl ethers (PBDEs) have been previously shown to alter various endocrine biosynthetic pathways. Growing epidemiological evidence suggests that PBDEs alter cardiovascular function. The goal of this study was to examine the effects of BDE-47 on adrenal corticosteroid pathways that play vital roles in cardiovascular homeostasis and pathophysiology. The effect of BDE-47 on aldosterone and cortisol secretion was characterized in a human adrenocortical cell line. HAC15 cells were exposed to various concentrations of BDE-47 (1 nM to 100 μM). Cell viability, corticosteroid secretion, gene expression of enzymes involved in corticosteroid synthesis, and metabolic activity was examined. Additionally, Sprague Dawley male rats were orally exposed to BDE-47 (10 or 100 µg/kg), 5 days per week for 16 weeks. Organ weights and plasma corticosteroid levels were measured. In HAC15 cells, basal and stimulated aldosterone and cortisol secretion was significantly increased by BDE-47. Gene expression of several enzymes involved in corticosteroid synthesis and mitochondrial metabolism also increased. In Sprague Dawley rats, adrenal but not heart, kidney, or liver weights, were significantly increased in BDE-47 treatment groups. Plasma corticosterone levels were significantly increased in the 100 µg BDE-47/kg treatment group. No change in plasma aldosterone levels were observed with BDE-47 exposure. These data indicate that BDE-47 disrupts the regulation of corticosteroid secretion and provides further evidence that PBDEs are potential endocrine disruptors. Future studies will determine the underlying molecular mechanism of altered corticosteroid production and examine whether these alterations result in underlying cardiovascular disease in our rodent model of 16-week BDE-47 exposure.

Polybrominated Diphenylether (DE-71) Exposure Skews Phenotypic Sex Ratio, and Alters Steroid Hormone Levels and Steroidogenic Enzyme Activities in Juvenile Silurana tropicalis

The impact of the brominated flame-retardant mixture, DE-71, on gonadal steroidogenesis during sexual differentiation in Silurana tropicalis was examined. A partial lifecycle study exposing S. tropicalis to varying concentrations of DE-71 (0.0, 0.65, 1.3, 2.5, and 5.0 μg/L [nominal]) was conducted from early gastrula-stage embryo to 150 d post-metamorphosis (dpm). Exposure of S. tropicalis to DE-71 induced liver necrosis and induced abnormal ovary development characterized by previtellogenic oocyte necrosis and arrested development of vitellogenic oocytes in females in a concentration-dependent manner. Decreased mean plasma DHT and T, gonad T, and increased mean plasma E2 levels were found in 150 dpm DE-71-treated male S. tropicalis compared to controls. Plasma E2 levels in females were not significantly altered compared to control S. tropicalis, although lower plasma and gonad T were detected. Mean gonadal CYP 19 aromatase activity in both male and female S. tropicalis exposed to DE-71 was not appreciably affected. Decreased mean male 5α-reductase and CYP17 activities in both male and females were observed compared to control frogs. Overall, these studies suggested that PBDE exposure induced liver necrosis and abnormal ovary development; and reduced circulating and gonadal androgens resulting in a phenotypic skew in sex ratio toward the female sex in S. tropicalis.

Associations between organohalogen exposure and thyroid- and steroid-related gene responses in St. Lawrence Estuary belugas and minke whales

Elevated concentrations of persistent organic pollutants (POPs) and emerging halogenated flame retardants (HFRs) have been reported in tissues of the endangered St. Lawrence Estuary (Canada) beluga population as well as in minke whales visiting that same feeding area. This study examined the linkages between blubber concentrations of POPs and emerging HFRs, and transcription in skin of genes involved in the regulation of thyroid and steroid axes in belugas and minke whales from the St. Lawrence Estuary. In belugas, concentrations of PCBs, OCs and hexabromobenzene (HBB) were positively correlated with the transcription of thyroid- and/or steroid-related genes, while Dec-604 CB concentrations were negatively associated with the transcription of glucocorticoid and thyroid genes. In minke whales, PBDE concentrations changed positively with Esrβ transcript levels and HBB concentrations negatively with Nr3c1 transcripts. Present results suggest that several biological functions including reproduction and energetic metabolism may represent potential targets for organohalogens in these whales.

Human cytochrome P450 enzymes 5-51 as targets of drugs and natural and environmental compounds: mechanisms, induction, and inhibition - toxic effects and benefits

Cytochrome P450 (P450, CYP) enzymes have long been of interest due to their roles in the metabolism of drugs, pesticides, pro-carcinogens, and other xenobiotic chemicals. They have also been of interest due to their very critical roles in the biosynthesis and metabolism of steroids, vitamins, and certain eicosanoids. This review covers the 22 (of the total of 57) human P450s in Families 5-51 and their substrate selectivity. Furthermore, included is information and references regarding inducibility, inhibition, and (in some cases) stimulation by chemicals. We update and discuss important aspects of each of these 22 P450s and questions that remain open.

Contaminant accumulation and biological responses in Atlantic cod (Gadus morhua) caged at a capped waste disposal site in Kollevåg, Western Norway

The aim of this study was to assess whether fish in Kollevåg, a sheltered bay on the western coast of Norway, previously utilized as a waste disposal site, could be affected by environmental contaminants leaking from the waste. Farmed, juvenile Atlantic cod (Gadus morhua) were caged for six weeks at three different locations in Kollevåg bay and at one reference location. Sediments and cod samples (bile and liver) were analyzed for polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), brominated flame retardants (BFRs), per-and polyfluoroalkyl substances (PFASs) and polycyclic aromatic hydrocarbon (PAH) metabolites, revealing a contamination gradient at the four stations. Furthermore, hepatosomatic index (HSI) and Fulton's condition factor (CF) were significantly lower in cod caged closest to the disposal site. Levels and activities of biomarker proteins, such as vitellogenin (Vtg), metallothionein (Mt), and biotransformation and oxidative stress enzymes, including cytochrome P450 1a and 3a (Cyp1a, Cyp3a), glutathione s-transferase (Gst) and catalase (Cat), were quantified in blood plasma and liver tissue. Hepatic Cat and Gst activities were significantly reduced in cod caged at the innermost stations in Kollevåg, indicating modulation of oxidative stress responses. However, these results contrasted with reduced hepatic lipid peroxidation. Significant increases in transcript levels were observed for genes involved in lipid metabolism (fasn and acly) in cod liver, while transcript levels of ovarian steroidogenic enzyme genes such as p450scc, cyp19, 3β-hsd and 20β-hsd showed significant station-dependent increases. Cyp1a and Vtg protein levels were however not significantly altered in cod caged in Kollevåg. Plasma levels of estradiol (E2) and testosterone (T) were determined by enzyme immunoassay (EIA) and showed elevated E2 levels, but only at the innermost station. We conclude that the bay of Kollevåg did not fullfill adequate environmental condition based on environmental quality standards (EQSs) for chemicals in coastal waters. Following a six weeks caging period, environmental contaminants accumulated in cod tissues and effects were observed on biomarker responses, especially those involved in reproductive processes in cod ovary.

Assessing the effects of Awba dam sediment (Nigeria) on the steroidogenesis of H295R cells using different extraction methods

In the present study, H295R human cells were used to investigate the endocrine disruptor potential of three different sediments extracts taken from a Nigerian tropical freshwater dam (Awba Dam), using three extraction methods that allowed a selective consideration of contaminants based on their binding affinity, which is mainly driven by polarity, to sediment particles. After exposure to different concentration of each extract, H295R cells were evaluated for the expression profiles of 10 steroidogenic enzyme genes and estradiol (E2) and testosterone (T) levels. Our results showed a comparable concentrated-related increase in the expression of 17β-hsd1, 3β-hsd2 and cyp21 in cells treated with the polar and non-polar extracts. The star, hmgr, cyp11b2 and 17β-hsd4 were slightly decreased, in an apparent concentration-specific manner, after treatment with the polar extract and decreased in the non-polar treatment. The cyp11a and cyp17 showed an opposite trend in the polar and non-polar treatments. E2 was significantly higher in cell treated with the non-polar extract. Elutriate exposure produced less pronounced variation in mRNA and hormones levels. Overall the extract with non-polar compounds produced the most severe effects in H295R cells. Thus, direct ingestion of detritus and mud from fishes and other benthonic organisms represent possible transfer of contaminants in the trophic web, and mainly account for alteration of the endocrine system previously observed in fish from the same study site.

Androgen receptor modulation following combination exposure to brominated flame-retardants

Endocrine disrupting compounds can interfere with androgen receptor (AR) signaling and disrupt steroidogenesis leading to reproductive failure. The brominated flame-retardant (BFR) 1, 2-dibromo-4-(1, 2-dibromoethyl) cyclohexane (TBECH), is an agonist to human, chicken and zebrafish AR. Recently another group of alternative BFRs, allyl 2, 4, 6-tribromophenyl ether (ATE), and 2, 3-dibromopropyl 2, 4, 6-tribromophenyl ether (DPTE) along with its metabolite 2-bromoallyl 2, 4, 6-tribromophenyl ether (BATE) were identified as potent human AR antagonists. These alternative BFRs are present in the environment. The aim of the present study was to determine the effect of mixed exposures to the AR agonist and the AR antagonists at environmentally relevant concentrations. In vitro reporter luciferase assay showed that the AR antagonists, when present at concentration higher than TBECH, were able to inhibit TBECH-mediated AR activity. These AR antagonists also promoted AR nuclear translocation. In vitro gene expression analysis in the non-tumorigenic human prostate epithelial cell RWPE1 showed that TBECH induced AR target genes whereas DPTE repressed these genes. Further analysis of steroidogenic genes showed that TBECH up-regulated most of the genes while DPTE down-regulated the same genes. The results indicate that when TBECH and DPTE are present together they will antagonize each other, thereby reducing their individual effects.

Levels, profiles and dietary sources of hydroxylated PCBs and hydroxylated and methoxylated PBDEs in Japanese women serum samples

Human exposure to polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) may result in retention of specific congeners of hydroxylated PCBs (OH-PCBs) and hydroxylated/methoxylated PBDEs (OH-/MeO-PBDEs) in serum. However, dietary sources and biotransformation of OH-/MeO-PBDEs in humans are poorly understood. Therefore, this study was conducted to investigate the levels, profiles, and exposure sources of OH-/MeO-PBDEs along with OH-PCBs present in human serum. Twenty serum samples pooled from women of four age groups (30s/40s/50s/60s) living in four districts of Japan were analyzed for OH-/MeO-PBDEs, and their profiles were then compared with those of seafood (seaweed and fish). The major component of OH-PCBs in the phenolic fraction of serum was 4-OH-CB187 (mean: 85pgg^-1 wet weight (ww)). Total OH-PCBs accounted for about 1/20 of the total PCBs (mean; 1800pgg^-1 ww). In contrast, the predominant component of OH-PBDEs in serum was 6-OH-BDE47 (mean: 183pgg^-1 ww), which was about 20-fold higher than BDE-47 (mean; 8.7pgg^-1 ww). In the neutral fraction, 2'-MeO-BDE68 was primarily found at a similar concentration (mean 5.6pgg^-1 ww) to BDE-47. Both 4-OH-PCB187 and 2'-MeO-BDE68 were significantly correlated with woman's age (p<0.01), but not with 6-OH-BDE47 or BDE-47. The profiles of OH-PBDEs in serum were consistent with those in edible seaweeds (Sargassum fusiforme) sold for human consumption, whereas MeO-PBDEs had a similar profile as those in edible fish (Serranidae sp.) from Japanese coastal waters. These findings indicate that the profiles of OH-PBDEs and MeO-PBDEs in Japanese serum are different from those in other countries, and their sources may be specific edible seaweeds and fish, respectively. This is the first report of profiles and dietary sources of OH/MeO-PBDEs in human serum from Japan.

A Mixture Reflecting Polybrominated Diphenyl Ether (PBDE) Profiles Detected in Human Follicular Fluid Significantly Affects Steroidogenesis and Induces Oxidative Stress in a Female Human Granulosa Cell Line

Brominated flame retardants are incorporated into consumer products to prevent flame propagation. These compounds leach into the domestic environment, resulting in chronic exposure. Pregnancy failure is associated with high levels of polybrominated diphenyl ethers (PBDEs), a major class of brominated flame retardants, in human follicular fluid, raising serious questions regarding their impact on female fertility. Our goal was to elucidate the effects of a mixture of PBDEs, similar to the profile found in human follicular fluid, on an immortalized human granulosa cell line, the KGN cell line. We showed that cell viability was altered and oxidative stress was induced as reflected by increased reactive oxygen species formation at 100 μM of the PBDE mixture. Transcriptomic analysis revealed that PBDE treatments of 1, 5, and 20 μM altered the expression of several genes involved in the reactive oxygen species signaling pathway. Significant dose-dependent reductions in progesterone and estradiol levels in the culture medium were measured after PBDE treatment; in parallel, the expression of genes involved in estradiol metabolism, namely CYP1A1, was up-regulated by 5 and 20 μM of the PBDE mixture. Treatment with 20 μM PBDE also increased the expression and secretion of the proinflammatory factor, IL-6, into the KGN cell culture medium. Our results demonstrate that PBDEs can alter human granulosa cell functions by inducing oxidative stress and disrupting steroidogenesis. These results indicate that PBDEs may be detrimental to ovarian functions and thus may adversely affect female reproductive health after chronic exposure.

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.

A review on the effects of PBDEs on thyroid and reproduction systems in fish

The objective of this review was to summarize and discuss the effects of Polybrominated diphenyl ethers (PBDEs) on thyroid and reproduction systems in fish. We reviewed the evidences and mechanisms for PBDEs-induced thyroid and reproduction disruption, as well as the cross-talk between the two systems in fish. In thyroid disruption, we mainly paid attention to the effects of PBDEs on hypothalamic-pituitary-thyroid (HPT) axis, thyroid hormones (THs) transport and metabolism, thyroid receptors (TRs) and thyroid follicle histology. In reproduction disruption, we focused on the effects of PBDEs on steroid hormone production, expression of genes involved in steroidogenesis, and gonadal development. Despite that there is an interaction between thyroid and reproductive systems in fish, it is still remains unclear that PBDE-induced reproductive impairments are caused by direct effects on hypothalamic-pituitary-gonadal (HPG) functioning or by indirect action through cross-talk between the two systems. Future studies are needed to explore the relationships between reproductive toxicity and thyroid system disruption after PBDEs exposure.

Perfluorooctyl Iodide Stimulates Steroidogenesis in H295R Cells via a Cyclic Adenosine Monophosphate Signaling Pathway

Perfluorinated iodine alkanes (PFIs) are used widely in the organic fluorine industry. Increased production of PFIs has caused environmental health concerns. To evaluate the potential endocrine-disrupting effect of PFIs, we investigated the effects of perfluorooctyl iodide (PFOI) on steroidogenesis in human adrenocortical carcinoma cells (H295R). Levels of aldosterone, cortisol, 17β-estradiol, and testosterone were measured in H295R culture medium upon treatment with perfluorooctanoic acid (PFOA) and PFIs. Expression of 10 steroidogenic genes (StAR, HMGR, CYP11A1, 3βHSD2, 17βHSD, CYP17, CYP21, CYP11B1, CYP11B2, and CYP19) was measured by real-time polymerase chain reaction. Levels of cyclic adenosine monophosphate (cAMP) and adenylate cyclase (AC) activity were measured to understand the underlying mechanism of steroidogenic perturbations. Levels of production of aldosterone, cortisol, and 17β-estradiol were elevated significantly, and the level of testosterone generation decreased upon treatment with 100 μM PFOI. Similar to the effect induced by forskolin (AC activator), expression of all 10 genes involved in the synthesis of steroid hormones was upregulated significantly upon exposure to 100 μM PFOI. PFOA had no effect on steroid hormone production or steroidogenic gene expression even though it is highly structurally similar with PFOI. Therefore, the terminal -CF2I group in PFOI could be a critical factor for mediation of steroidogenesis. PFOI increased AC activity and cAMP levels in H295R cells, which implied an underlying mechanism for the disturbance of steroidogenesis. These data suggest that PFOI may act as an AC activator, thereby stimulating steroidogenesis by activating a cAMP signaling pathway.

Advances in Instrumental Analysis of Brominated Flame Retardants: Current Status and Future Perspectives

This review aims to highlight the recent advances and methodological improvements in instrumental techniques applied for the analysis of different brominated flame retardants (BFRs). The literature search strategy was based on the recent analytical reviews published on BFRs. The main selection criteria involved the successful development and application of analytical methods for determination of the target compounds in various environmental matrices. Different factors affecting chromatographic separation and mass spectrometric detection of brominated analytes were evaluated and discussed. Techniques using advanced instrumentation to achieve outstanding results in quantification of different BFRs and their metabolites/degradation products were highlighted. Finally, research gaps in the field of BFR analysis were identified and recommendations for future research were proposed.

Modulation of estradiol synthesis and aromatase activity in human choriocarcinoma JEG-3 cells exposed to tetrabromobisphenol A

The goal of the present study was to investigate the impact of tetrabromobisphenol A (TBBPA) on human choriocarcinoma-derived placental JEG-3 cells in vitro. We determined the effect of this compound on estradiol secretion, aromatase protein expression and activity in vitro in the JEG-3 cell line. We assessed the ability of TBBPA to increase intracellular levels of cAMP as well as its effect on cell viability and proliferation. Our results indicated that TBBPA, at a wide range of concentrations (1×10(-8)-5×10(-5)M), significantly induced estradiol secretion by JEG-3 cells compared to that of controls after 24, 48 or 72 h of exposure. This effect was accompanied by an increase in the aromatase protein expression in JEG-3 cells treated with 100 nM and 10 μM of TBBPA for 24 h. Additionally, in our study, we confirmed that TBBPA-induced changes in aromatase protein expression were associated w ith the up-regulation of aromatase activity and cAMP levels. No tested doses of TBBPA inhibited JEG-3 cell proliferation, except for the highest dose of 100 μM, which had a toxic effect on cell viability at all time points. The present study clearly indicates that TBBPA alters JEG-3 cells estrogen synthesis due to its action on CYP19 protein expression and thus this compound may interfere with normal placental development during early pregnancy.

Endocrine disruption and reproduction impairment in zebrafish after long-term exposure to DE-71

The objective of the present study was to investigate the impact of polybrominated diphenyl ethers (PBDEs) on fish reproduction over 2 generations. Zebrafish (Danio rerio) embryos (F0) were exposed to low concentrations (3 µg/L, 10 µg/L, and 30 µg/L) of the PBDE mixture DE-71 until they were sexually mature, and steroid hormone production, expression of genes involved in steroidogenesis, gonadal development, and gamete characteristics were examined. Exposure of female zebrafish to DE-71 resulted in lower estradiol production and downregulation of cytochrome P450 aromatase mRNA. In males, exposure to DE-71 resulted in greater testosterone production and greater cytochrome P450 c17 α-hydroxylase,17,20-lase mRNA expression. Moreover, hepatic vitellogenin mRNA and estrogenic receptor β gene transcription were downregulated in females and males. Expression of the follicle-stimulating hormone β gene in the pituitary was upregulated, and the expression of luteinizing hormone β was downregulated in both sexes. Histological examination showed inhibition of oocyte maturation in females and retarded spermiation in males. The average number of eggs (F1) produced was also reduced. Additionally, exposure of F0 embryos to DE-71 did not result in developmental toxicity, whereas delayed hatching, reduced survival, and decreased growth were observed in the F1 embryos derived from parent fish exposed to DE-71. Therefore, long-term exposure to low concentrations of PBDEs in zebrafish could cause reproductive impairment, suggesting that PBDEs might have significant adverse effects on fish population in the highly PBDEs-contaminated aquatic environment.

Effects of polychlorobiphenyls, polybromodiphenylethers, organochlorine pesticides and their metabolites on vitamin A status in lactating grey seals

Polychlorobiphenyls (PCBs), polybromodiphenylethers (PBDEs) and organochlorine pesticides (OCPs), such as dichlorodiphenyltrichloroethane (DDT) and hexachlorobenzene (HCB), are considered as endocrine disruptors in laboratory and wild animals. This study investigated whether these compounds and their hydroxylated metabolites (HO-PCBs and HO-PBDEs) may affect the homoeostasis of vitamin A, a dietary hormone, in the blubber and serum of twenty lactating grey seals sampled at early and late lactation on the Isle of May, Scotland. The effect of naturally produced compounds such as the methoxylated (MeO)-PBDEs was also examined. Vitamin A levels in inner blubber (37±9 μg/g wet weight (ww) and 92±32 μg/g ww at early and late lactation, respectively) and serum (408±143 and 390±98 ng/ml at early and late lactation, respectively) appeared to be positively related to ΣPCBs, ΣPBDEs and several individual PCB and PBDE congeners in inner blubber and serum. These findings may suggest enhanced mobilisation of hepatic retinoid stores and redistribution in the blubber, a storage site for vitamin A in marine mammals. We have also reported that serum concentrations of ΣHO-PCBs and 4-OH-CB107 tended to increase with circulating vitamin A levels. Although the direction of the relationships may sometimes differ from those reported in the literature, our results are in agreement with previous findings highlighting a disruption of vitamin A homoeostasis in the blubber and bloodstream following exposure to environmental pollutants. The fact that vitamin A and PCBs appeared to share common mechanisms of mobilisation and transfer during lactation in grey seals (Debier et al., 2004; Vanden Berghe et al., 2010) may also play a role in the different relationships observed between vitamin A and lipophilic pollutants.

Effect of chronic exposure to acetaminophen and lincomycin on Japanese medaka (Oryzias latipes) and freshwater cladocerans Daphnia magna and Moina macrocopa, and potential mechanisms of endocrine disruption

Chronic toxicity of acetaminophen and lincomycin were evaluated using freshwater organisms including two crustaceans (Daphnia magna and Moina macrocopa) and a fish (Oryzias latipes). H295R, a human adrenal cell was also used to understand the effects on steroidogenesis. In 21 d D. magna exposure, survival NOEC was found at 5.72 mg L(-1) and no reproduction related effects were noted at this level of exposure to acetaminophen, while 21 d survival or growth effects were not observed even at the highest exposure levels (153 mg L(-1)) for lincomycin. In the chronic fish toxicity test, significant reduction in juvenile survival was observed at 30 d post-hatch (dph) at 95 mg L(-1) of acetaminophen, and 0.42 mg L(-1) of lincomycin. After the exposure to both pharmaceuticals, vitellogenin levels tended to increase in male fish at 90 dph. In the eggs which were prenatally exposed to 9.5 mg L(-1) of acetaminophen, reduced hatchability was observed. The results of H295R cell assay showed that both pharmaceuticals could alter steroidogenic pathway and increase estrogenicity. Endocrine disruption potentials and their ecological implication may deserve further studies. Our observations suggest however that ecological risks of both pharmaceuticals are negligible at the concentrations currently found in the environment.

Associations between complex OHC mixtures and thyroid and cortisol hormone levels in East Greenland polar bears

The multivariate relationship between hair cortisol, whole blood thyroid hormones, and the complex mixtures of organohalogen contaminant (OHC) levels measured in subcutaneous adipose of 23 East Greenland polar bears (eight males and 15 females, all sampled between the years 1999 and 2001) was analyzed using projection to latent structure (PLS) regression modeling. In the resulting PLS model, most important variables with a negative influence on cortisol levels were particularly BDE-99, but also CB-180, -201, BDE-153, and CB-170/190. The most important variables with a positive influence on cortisol were CB-66/95, α-HCH, TT3, as well as heptachlor epoxide, dieldrin, BDE-47, p,p'-DDD. Although statistical modeling does not necessarily fully explain biological cause-effect relationships, relationships indicate that (1) the hypothalamic-pituitary-adrenal (HPA) axis in East Greenland polar bears is likely to be affected by OHC-contaminants and (2) the association between OHCs and cortisol may be linked with the hypothalamus-pituitary-thyroid (HPT) axis.

Glucuronidation of hydroxylated polybrominated diphenyl ethers and their modulation of estrogen UDP-glucuronosyltransferases

Polybrominated diphenyl ethers (PBDEs) can be metabolically converted to their hydroxylated metabolites (OH-PBDEs). The estrogenic effects of PBDEs may be mediated by OH-PBDEs, but the mechanisms of which are still not understood. This study investigated the glucuronidation of 11 OH-PBDEs and their potential in modulating UDP-glucuronosyltransferases (UGTs) activity of 17β-estradiol (E2) in rat liver microsomes. The number of bromine atoms at phenolic ring was observed as the most influential factor of OH-PBDEs glucuronidation. 2'-OH-BDE-28 having one bromine atom at phenolic ring showed the fastest metabolic rates with t(1/2) value of 3.86 min, while 6-OH-BDE-137 having four bromine atoms at phenolic ring was the poorest substrate with t(1/2) value over 60 min. Regarding to the modulation of E2-UGTs activity, the phenolic hydroxyl group in OH-PBDEs played an essential role. Depending on the substitution patterns of bromine and hydroxyl group, OH-PBDEs inhibited or stimulated E2-UGTs activity. Ten of OH-PBDEs inhibited both 3-glucuronidation and 17-glucuronidation of E2 with IC(50) values varying from 3.80 to 129.38 μM, while 3'-OH-BDE-100 exhibited stimulating effects on 3-glucuronidation with EC(50) value of 35.95 μM. Kinetic analysis suggested noncompetitive inhibition mode of E2 glucuronidation by 3'-OH-BDE-7, 6-OH-BDE-47 and 2'-OH-BDE-68 with K(i) values varying from 11.95 to 67.22 μM. This study demonstrated OH-PBDEs exhibited large interindividual differences in glucuronidation and modulation of E2-UGTs activity. By inhibiting the formation of E2 glucuronidation, OH-PBDEs may increase E2 bioavailability in target tissue, thereby exerting an indirect estrogenic effect.

Characterization of polybrominated diphenyl ether toxicity in Wistar Han rats and use of liver microarray data for predicting disease susceptibilities

The toxicity of polybrominated diphenyl ethers (PBDEs), flame-retardant components, was characterized in offspring from Wistar Han dams exposed by gavage to a PBDE mixture (DE71) starting at gestation day 6 and continuing to weaning on postnatal day (PND) 21. Offspring from the dams underwent PBDE direct dosing by gavage at the same dose as their dams from PND 12 to PND 21, and then after weaning for another thirteen weeks. Liver samples were collected at PND 22 and week 13 for liver gene expression analysis (Affymetrix Rat Genome 230 2.0 Array). Treatment with PBDE induced 1,066 liver gene transcript changes in females and 1,200 transcriptional changes in males at PND 22 (false discovery rate < 0.01), but only 263 liver transcriptional changes at thirteen weeks in male rats (false discovery rate < 0.05). No significant differences in dose response were found between male and female pups. Transcript changes at PND 22 coded for proteins in xenobiotic, sterol, and lipid metabolism, and cell cycle regulation, and overlapped rodent liver transcript patterns after a high-fat diet or phenobarbital exposure. These findings, along with the observed PBDE-induced liver hypertrophy and vacuolization, suggest that long-term PBDE exposure has the potential to modify cell functions that contribute to metabolic disease and/or cancer susceptibilities.

Modulation of estrogen synthesis through activation of protein kinase A in H295R cells by extracts of estuary sediments

Sediments from two estuaries within Liaodong Bay, China, were examined for the effects on steroidogenesis using H295R human adrenocortical carcinoma cells. Total extracts (TE) isolated from sediments by Soxhlet extraction were separated into three fractions (F1, F2, and F3) using Florisil columns. After exposing H295R cells to each TE and fractions, the expressions of six steroidogenic genes (cytochrome P450 cholesterol side-chain cleavage [CYP11A], 3β-hydroxysteroid dehydrogenase type 1 [3β-HSD1], 3β-hydroxysteroid dehydrogenase type 2 [3β-HSD2], cytochrome P450 17-hydroxylase/17-20 lyase [CYP17], cytochrome P450 aromatase [CYP19], 17β-hydroxysteroid dehydrogenase [17β-HSD]), and the production of six steroid hormones (progesterone [PGT], 17-hydroxyprogesterone [17-HPT], testosterone [TTR], androstenedione [ADD], estrone [E1], and 17β-estradiol [17β-E2]) were measured. The gene expressions of CYP11A, CYP17, 3β-HSD2, and CYP19, and hormone productions of PGT, 17-HPT, TTR, ADD, E1, and 17β-E2 were significantly increased after exposure to F3 extracts from the Daliao River. In particular, greater concentrations of E1 (up to 48-fold) and 17β-E2 (up to 20-fold), as well as up-regulation of CYP19 gene expression (up to tenfold), were caused by exposure to the F3 fraction from the Daliao River, but not from the Daling River. Insight into the mechanism of action was obtained by use of principal component analysis (PCA), the results of which were consistent with unidentified constituents in F3 from the Daliao River activating the protein kinase A (PKA) pathway. This hypothesis was confirmed by reversal of the effects caused by F3 through a co-exposure of a PKA inhibitor (H89) and F3 extract. The H89 down-regulated CYP19 messenger RNA (mRNA) expression with concomitant lesser production of E1 and 17β-E2 in the co-exposure group, indicating unidentified constituents that could modulate estrogen synthesis, primarily through a mechanism of PKA activation.

The cytotoxic effects of synthetic 6-hydroxylated and 6-methoxylated polybrominated diphenyl ether 47 (BDE47)

Polybrominated diphenyl ethers (PBDE) have been widely applied as flame retardants in plastics, polyurethane foam, paints, and synthetic fabrics. The rising PBDE level in human tissues and environment has led to concern about the health impact of exposure to PBDE. The 2,2',4,4'-tetrabromodiphenyl ether (BDE47), the dominant PBDE congener found in the environment and human tissues, has been shown to be an endocrine disruptor. It has also been reported to cause liver and neurodevelopmental toxicity. BDE47 can be metabolized to 6-OH-BDE47 and 6-MeO-BDE47. So far little has been reported on the cytotoxicity of the metabolites. In the present study, the cytotoxicity of the two metabolites was investigated by exposing human hepatoma cell line HepG2 to different doses of 6-OH-BDE47 and 6-MeO-BDE47. The cell viability, cell cycle, apoptosis, DNA damage, micronucleus levels, and oxidative stress response were studied. The results indicated that both metabolites could markedly inhibit the proliferation of HepG2 cells with 6-OH-BDE47 showing a stronger effect, and significantly increase the micronucleus level and apoptosis rate in a dose-dependant manner. Moreover, treatment with 6-OH-BDE47 (≥0.5 μM) resulted in a marked cell cycle block. The SCGE experiments revealed that both metabolites could cause DNA damage in a dose-dependant manner. Analysis of the oxidative stress response showed that 6-OH-BDE47 treatment (≥2.0 μM) significantly increased intracellular ROS levels as indicated by GSH depletion and elevation of SOD level, whereas 6-MeO-BDE47 showed a weaker effect, suggesting that oxidative stress might play a role in the cytotoxic effects. We concluded that 6-OH-BDE47 or 6-MeO-BDE47 exposure was able to induce inhibition of cell viability, increase of apoptosis rate, cell cycle block, and DNA damages, which might involve the alterated oxidative stress response due to the elevated free radicals and impaired antioxidative system.

Endocrine effects of methoxylated brominated diphenyl ethers in three in vitro models

Methoxylated brominated diphenyl ethers (MeO-BDEs) in aquatic environments have been found to be primarily of natural origin in the marine environment and not from biotransformation of synthetic PBDEs. Two of the eight MeO-PBDEs (2'-MeO-BDE-68 and 6-MeO-BDE-47) that were detected in anchovy from the Yangtze River Delta, were natural products from marine organisms. So 2'-MeO-BDE-68 and 6-MeO-BDE-47 were chosen to study the potential to modulate androgen, estrogen, or thyroid hormone receptor- (AR, ER, ThR) mediated responses by use of reporter gene assays. 2'-MeO-BDE-68 was antiandrogenic at 50 μM, estrogenic at 10 μM and antiestrogenic at 10 and 50 μM (IC50=4.88 μM). 2'-MeO-BDE-68 enhanced luciferase expression by 5 nM T3 at 50 μM. 6-MeO-BDE-47 exhibited potent antiandrogenicity at 1 μM and greater (IC50=41.8 μM) and possessed estrogenic activity at 10 μM and antiestrogenic activity at 10 and 50 μM (IC50=6.02 μM).

Endocrine disrupting chemicals: Multiple effects on testicular signaling and spermatogenesis

In the past 200 years, an enormous number of synthetic chemicals with diverse structural features have been produced for industrial, medical and domestic purposes. These chemicals, originally thought to have little or no biological toxicity, are widely used in our daily lives as well as are commonly present in foods. It was not until the first World Wildlife Federation Wingspread Conference held in 1994 were concerns about the endocrine disrupting (ED) effects of these chemicals articulated. The potential hazardous effects of endocrine disrupting chemicals (EDCs) on human health and ecological well-being are one of the global concerns that affect the health and propagation of human beings. Considerable numbers of studies indicated that endocrine disruption is linked to "the developmental basis of adult disease," highlighting the significant effects of EDC exposure on a developing organism, leading to the propensity of an individual to develop a disease or dysfunction in later life. In this review, we intend to provide environmental, epidemiological and experimental data to associate pollutant exposure with reproductive disorders, in particular on the development and function of the male reproductive system. Possible effects of pollutant exposure on the processes of embryonic development, like sex determination and masculinization are described. In addition, the effects of pollutant exposure on hypothalamus-pituitary-gonadal axis, testicular signaling, steroidogenesis and spermatogenesis are also discussed.

Neurotoxicity of brominated flame retardants: (in)direct effects of parent and hydroxylated polybrominated diphenyl ethers on the (developing) nervous system

BACKGROUND/OBJECTIVE

Polybrominated diphenyl ethers (PBDEs) and their hydroxylated (OH-) or methoxylated forms have been detected in humans. Because this raises concern about adverse effects on the developing brain, we reviewed the scientific literature on these mechanisms.

DATA SYNTHESIS

Many rodent studies reported behavioral changes after developmental, neonatal, or adult exposure to PBDEs, and other studies documented subtle structural and functional alterations in brains of PBDE-exposed animals. Functional effects have been observed on synaptic plasticity and the glutamate-nitric oxide-cyclic guanosine monophosphate pathway. In the brain, changes have been observed in the expression of genes and proteins involved in synapse and axon formation, neuronal morphology, cell migration, synaptic plasticity, ion channels, and vesicular neurotransmitter release. Cellular and molecular mechanisms include effects on neuronal viability 
(via apoptosis and oxidative stress), neuronal differentiation and migration, neurotransmitter release/uptake, neurotransmitter receptors and ion channels, calcium (Ca²⁺) homeostasis, and intracellular signaling pathways.

DISCUSSION

Bioactivation of PBDEs by hydroxylation has been observed for several endocrine end points. This has also been observed for mechanisms related to neurodevelopment, including binding to thyroid hormone receptors and transport proteins, disruption of Ca²⁺ homeostasis, and modulation of GABA and nicotinic acetylcholine receptor function.

CONCLUSIONS

The increased hazard for developmental neurotoxicity by hydroxylated (OH-)PBDEs compared with their parent congeners via direct neurotoxicity and thyroid disruption clearly warrants further investigation into a) the role of oxidative metabolism in producing active metabolites of PBDEs and their impact on brain development; b) concentrations of parent and OH-PBDEs in the brain; and c) interactions between different environmental contaminants during exposure to mixtures, which may increase neurotoxicity.

Effects of mixtures of persistent organic pollutants (POPs) derived from cod liver oil on H295R steroidogenesis

Crude cod liver oil and liver oil supplements are consumed as a source of vitamin A, D and polyunsaturated fatty acids; during winter and early pregnancy. Crude cod liver oil however constitutes a considerable source of persistent organic pollutants (POPs). This paper aimed at characterizing and quantifying the influence of POP mixtures extracted from three different steps in the cod liver oil industrial process on hormone production and the expression of steroidogenesis-related genes in H295R cells. Exposure to extracts from crude cod liver oil and from its industrial waste increased progesterone (P4), cortisol (Cort), testosterone (T) and estradiol (E2) production; and among others, the expression of MC2R, CYP11B1 and HSD3B2 genes. Observed effects after exposure to pharmaceutical cod liver oil extract were considerably lower. The type of effects on gene expression and hormone production were similar to those induced by forskolin and PCBs, the latter being the major contaminants within the extracts. Additional research is required to further unveil the mechanisms behind the observed steroidogenic effects and to assess whether the potential risk might outweigh the potential benefits of crude and processed cod liver oil consumption.

Effects of polybrominated diphenyl ethers on steroidogenesis in rat Leydig cells

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are brominated flame retardants that have been defined as major environmental pollutants. While previous studies have found that PBDEs may enhance the levels of sex-steroid hormones, their effects on testosterone secretion from rat Leydig cells are unclear. This study investigated the effects and mechanisms of PBDE-710, a mixture of tetra- and penta-PBDEs, on testosterone biosynthesis in rat Leydig cells.

METHODS

Leydig cells from adult male rats were challenged with different concentrations of PBDE-710 (0.5-15 ng/ml) to evaluate the effects on testosterone steroidogenesis. Concentrations of testosterone and of cAMP and pregnenolone in medium were measured by radioimmunoassay (RIA) and by enzyme-linked immunosorbent assay, respectively. Nuclear translocation of protein kinase A α (PKAα) was determined by immunofluorence assay and western blot assay, and the mRNA expression of steroidogenic acute regulatory protein (StAR) was analyzed by quantitative real-time polymerase chain reaction.

RESULTS

In this in vitro study, PBDE-710 (5 or 15 ng/ml) increased basal testosterone secretion and cAMP production by 3- and 2-fold, respectively. The stimulatory effect was abolished by adenylyl cyclase inhibitor. Enzyme activity of CYP11A1, as determined by the pregnenolone concentration, was stimulated by PBDE-710 treatment. Furthermore, nuclear translocation of PKAα was increased by 20% and StAR gene expression was elevated by 4-fold after PBDE-710 treatment.

CONCLUSIONS

These results suggest that low concentrations of PBDE-710 could stimulate testosterone secretion by acting directly on Leydig cells to activate the cAMP pathway and increase expression of StAR.

Bioaccumulation and maternal transfer of PBDE 47 in the marine medaka (Oryzias melastigma) following dietary exposure

The bioaccumulation and maternal transfer of 2,2',4,4'-tetrabromodiphenyl ether (PBDE 47) were investigated in the marine medaka (Oryzias melastigma) following dietary exposure, in which PBDE 47 was bioencapsulated into brine shrimp (Artemia sp.) and fed daily to male-female pairs of medaka. In the accumulation experiment, each 2-month-old (pre-breeding) medaka were provided with dietary PBDE 47 at 1.3±0.2 μg/day for 21 days. Growth-corrected concentrations of PBDE 47 in the medaka increased over the 21 days of exposure and there were no significant differences between males and females at any of the sampling times. Final concentrations were similar for males and females after 21 days (230±30 and 250±30 μgg(-1) wet weight, respectively), accounting for 84-100% of the PBDE 47 provided in the diet. In the maternal transfer experiment, 3-month-old (breeding) medaka were provided with dietary PBDE 47 at 1.2±0.2 μg/day for 18 days, and reached body concentrations of 76±3 (males) and 61±6 (females)μgg(-1) wet weight. Female growth-corrected PBDE 47 concentrations were significantly lower than males by day 12 (P<0.05), and egg PBDE 47 concentrations were up to 25 ng/egg by day 18. Our results showed that maternal transfer is an important offloading mechanism for female fish. The fact that lipid normalized egg:female PBDE ratios did not significantly deviate from 1 further indicated that the maternal transfer of PBDE 47 is associated with lipid mobilization during egg production.

In vitro steroidogenic effects of mixtures of persistent organic pollutants (POPs) extracted from burbot (Lota lota) caught in two Norwegian lakes

This study investigated the effects of two mixtures of persistent organic pollutants (POPs) on steroidogenesis in the H295R cell line. The two mixtures were obtained from the livers of burbot (Lota lota) caught in two Norwegian lakes (Mjøsa and Losna) with different contaminant profiles. Steroid hormone levels in the cell culture medium and mRNA levels of 16 genes involved in steroidogenesis were investigated. The crude Lake Mjøsa extract had to be diluted ten times more than the Lake Losna extract in order to prevent cytotoxicity. The ten times diluted Lake Mjøsa mixture had higher levels of DDT and derivates (∑DDTs, 1.7 times) and brominated flame retardants (∑BDEs and HBCD, 15-25 times) than the Lake Losna mixture, which, on the other hand, had higher concentrations of ∑PCBs (1.5 times higher) and also of HCB, ∑HCH isomers and ∑chlordane isomers (5-20 times higher). In the cell culture media, only cortisol levels were increased at the highest exposure concentration to the Lake Mjøsa mixture, while both cortisol and estradiol levels were increased following exposure to the two highest Lake Losna mixture exposure concentrations. Testosterone levels decreased only at the highest exposure concentration of the Lake Losna mixture. Multivariate models suggested that ∑PCBs, and to a lesser extent ∑DDTs, were responsible for the cortisol responses, while estradiol and testosterone alterations were best explained by HCB and ∑PCBs, respectively. Exposure to the mixtures generally increased mRNA levels, with smaller effects exerted by the Lake Mjøsa mixture than the Lake Losna mixture. It was concluded that both mixtures affected steroidogenesis in the H295R cells. Small differences in mixture composition, rather than the high content of brominated flame retardants in the Lake Mjøsa mixture, were suggested to be the most probable reason for the apparent differences in potencies of the two mixtures.

Cryptorchidism and hypospadias as a sign of testicular dysgenesis syndrome (TDS): environmental connection

Cryptorchidism and hypospadias are common genital birth defects that affect 2-9% and 0.2-1% of male newborns, respectively. The incidence of both defects shows large geographic variation, and in several countries increasing trends have been reported. The conditions share many risk factors, and they are also interlinked to the risk of testis cancer and poor semen quality. Testicular Dysgenesis Syndrome (TDS) may underlie many cases of all these male reproductive health problems. Genetic defects in androgen production or action can cause both cryptorchidism and hypospadias, but these are not common. A monogenic reason for cryptorchidism or hypospadias has been identified only in a small proportion of all cases. Environmental effects appear to play a major role in TDS. Exposure to several persistent chemicals has been found to be associated with the risk of cryptorchidism, and exposure to anti-androgenic phthalates has been shown to be associated with hormonal changes predisposing to male reproductive problems. Despite progress in identification of endocrine-disrupting substances, we are still far from knowing all the risk factors for these birth defects, and advice for prevention must be based on precautionary principles.

Modulation of steroidogenic gene expression and hormone synthesis in H295R cells exposed to PCP and TCP

Chlorophenols (CPs) have been suspected to disrupt the endocrine system and thus affect human and wildlife reproduction but less is known about the underlying mechanism. In this study, we investigated the effects of pentachlorophenol (PCP) and 2,4,6-trichlorophenol (TCP) on human adrenocortical carcinoma cell line (H295R). The H295R cells were exposed to environmentally relevant concentration (0.0, 0.4, 1.1, 3.4μM) of PCP and TCP for 48h, and expression of specific genes involved in steroidogenesis, including cytochrome P450 (CYP11A, CYP17, CYP19), 3βHSD2, 17βHSD4 and StAR was quantitatively measured using real-time polymerase chain reaction. The selected gene expressions were significantly down-regulated compared with those in the control group. Exposure to PCP and TCP significantly decreased production of both testosterone (T) and 17β-estradiol (E2). Furthermore, a dose-dependent decrease of cellular cAMP was observed in H295R cells exposed to both PCP and TCP. A time-course study revealed that the observed selected steroidogenic gene expressions and protein abundance (StAR) are consistent with reduced cellular cAMP concentrations. The results showed that PCP and TCP may inhibit steroidogenesis by disrupting cAMP signaling. The research indicates that H295R cells can be used as an in vitro model for endocrine disruption assay for chlorophenols and the mechanism involvement of disturbing cAMP signaling.

Les différentes anomalies de la reproduction masculine sont-elles en augmentation ? Faits et controverses, possibles facteurs en cause: une analyse actualisée des données de la littérature et des registres

Au cours des dernières décennies, de nombreuses observations dans la faune sauvage d’anomalies relatives à l’appareil génital et à la fonction de reproduction mâle, certaines évoquant les données de la toxicologie expérimentale, ont conduit à s’interroger sur la toxicité de facteurs environnementaux pour la reproduction de l’homme. De plus, un certain nombre d’études suggère une augmentation de la prévalence des troubles de la reproduction de l’homme adulte au cours des dernières décennies dans de nombreux pays développés. Les données les mieux documentées concernent le cancer du testicule, son rythme de croissance suggérant le rôle de facteurs environnementaux et/ou de mode de vie. Toutefois, des différences régionales et ethniques considérables dans les taux d’incidence absolue pourraient impliquer des facteurs génétiques concomitants. Parallèlement, il semble que la qualité du sperme a diminué dans de nombreux pays, à en juger aussi bien par des méta-analyses que par des analyses statistiques de données d’un seul centre. Au début des années 2000, Skakkebæk et al. à Copenhague ont formulé l’hypothèse d’une origine commune à ces différentes anomalies lors du développement du testicule durant la gestation. Existe-t-il pour ces différentes conditions des données indiquant un lien de causalité avec une exposition environnementale/professionnelle à des composés reprotoxiques ? Ne serait-ce plutôt l’exposition chronique à de très nombreux composés chimiques à faible dose qui pourrait être impliquée ? Les facteurs de style de vie jouent-ils un rôle ? L’ensemble de ces questions se fondant sur une somme d’études, dont les résultats sont loin d’être univoques, a été la source de nombreux débats aussi bien au sein de la communauté scientifique que dans les médias. Les meilleures réponses possibles à ces questions complexes sont naturellement fondamentales pour les instances en charge de l’évaluation du risque et les politiques de santé publique qu’il convient d’adopter. La présente revue donne un état des lieux actualisé de ces questions.

Cytotoxic effects and oxidative stress response of six PBDE metabolites on human L02 cells

In the present study, the cytotoxic effects and toxicological mechanism of six polybrominated diphenyl ethers (PBDEs) metabolites (3-OH-BDE47, 3-MeO-BDE47, 5-OH-BDE47, 5-MeO-BDE47, 6-OH-BDE85 and 6-MeO-BDE85) on L02 cells were explored by investigating the cell viability, apoptosis, lactic dehydrogenase (LDH) leakage, and oxidative stress response. The results showed that these metabolites could inhibit cell proliferation and induce apoptosis, among which 6-OH-BDE85 had the highest efficiency. LDH leakage test also showed that 6-OH-BDE85 had the strongest ability to cause LDH release. The reactive oxygen species (ROS) levels in 6-OH-BDE85- and 3-OH-BDE47-treated groups were significantly elevated in a dose-dependent manner. After treatment for 24 h, four BDE47 metabolites (3-OH-BDE47, 3-MeO-BDE47, 5-OH-BDE47, and 5-MeO-BDE47) induced an increase in superoxide dismutase (SOD) activity and decrease in glutathione (GSH) level, whereas 6-OH-BDE85 led to a decrease in both SOD activity and GSH level. These effects disappeared after continued culturing for another 24 h. In conclusion, these PBDE metabolites, especially 6-OH-BDE85, showed cytotoxicity on L02 cells, which was at least partially related to the oxidative stress level.

Effects of xenoestrogens on the expression of vitellogenin (vtg) and cytochrome P450 aromatase (cyp19a and b) genes in zebrafish (Danio rerio) larvae

In the present study, expression levels of vitellogenin (vtg) and cytochrome P450 aromatase genes (cyp19a and cyp19b) in zebrafish larvae during the early stages of development were investigated by quantitative real time-PCR assay. The results indicated that vtg gene transcription was induced seven days after zebrafish larvae fertilization, whereas the expression of cyp19a and cyp19b genes was detected as early as 3 and 4 days post-fertilization (dpf). Investigations into the effects of 17β-estradiol (E2) exposure on the expression of these genes showed that both vtg and cyp19b were upregulated by E2 in zebrafish larvae as early as four dpf, whereas no variation was observed in cyp19a gene expression. The estrogenic potential of pharmaceutical estrogen (DES), phenol estrogen (BPA) and the brominated flame retardants, TBBPA, DE-71 and 4-BP, were evaluated by analyzing the expression of these three genes in zebrafish larvae. The results demonstrated that natural estrogen, endocrine disrupting compounds and brominated flame retardants act as endocrine disrupters through different mechanisms. We have demonstrated for the first time that the polybrominated diphenyl ether mixture, DE-71, acts as an endocrine disrupter by upregulation of cyp19b gene expression at a relatively low concentration. These results indicate that analysis of vtg and cyp19b gene expression in zebrafish during early embryogenesis and organogenesis represents the basis of a sensitive and fast bioassay for the routine assessment of xenoestrogen effects.

Hydroxylated polybrominated diphenyl ethers and bisphenol A in pregnant women and their matching fetuses: placental transfer and potential risks

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) are suspected endocrine disruptors, which can pass through the mammalian placenta and accumulate in the human maternal-fetal-placental unit. However, little is known about mechanisms of placental transfer and the associated risk(s). Ten OH-PBDE congeners, bisphenol A (BPA), total 17beta-estradiol (E2), and total thyroxine (T4) were quantified in blood serum from 26 pregnant women and 28 matching fetuses, including three pairs of twins from South Korea. Only 6-OH-BDE-47, a naturally occurring OH-PBDE, was detected at relatively great concentrations (maternal serum: 17.5 +/- 26.3 pg/g ww, fetal cord blood serum: 30.2 +/- 27.1 pg/g ww), which suggests that exposure was related to diets among Korean women. Concentrations of 6-OH-BDE-47 in maternal and cord serum were positively correlated, with concentrations being significantly greater in cord blood serum. The placental transfer ratio between fetal and maternal blood serum for 6-OH-BDE-47 (F/M ratio: 1.4 +/- 1.1) was different than the observed placental transfer ratio of BPA and previously reported values for hydroxylated polychlorinated biphenyls (OH-PCBs). This result is possibly due to large affinities to T4 transport proteins. Lesser concentrations of E2 and T4 were detected in cord blood serum (E2: 4.7 +/- 2.2 ng/mL, T4: 8.5 +/- 1.7 microg/dL) compared to maternal blood serum (E2: 8.0 +/- 3.0 ng/mL, T4: 9.7 +/- 1.8 microg/dL). A major effect of OH-PBDE exposure might be a decrease in serum T4 concentrations. Potential risks associated with disruption of T4 transport to the developing fetus such as negative consequences for fetal neurological development should be considered in further studies.