The development of methods for assessing the in vivo oestrogen-like effects of xenobiotics in CD-1 mice

Deoxynivalenol and zearalenone: Different mycotoxins with different toxic effects in donkey (Equus asinus) endometrial epithelial cells

Deoxynivalenol (DON) and zearalenone (ZEA), which are commonly found in feed products, exhibit serious negative effects on the reproductive systems of domestic animals. However, the toxicity of mycotoxins on the uterine function of donkey (Equus asinus) remains unclear. This study investigated the biological effects of DON and ZEA exposure on donkey endometrial epithelial cells (EECs). It was administered 10 μM and 30 μM DON and ZEA to cells cultured in vitro. The results showed that 10 μM DON exposure markedly changed the expression levels of pyroptosis-associated genes and that 30 μM ZEA exposure changed the expression levels of inflammation-associated genes in EECs. The mRNA expression of cancer-promoting genes was markedly upregulated in cells exposed to DON and 30 μM ZEA; in particular, 10 μM and 30 μM DON and ZEA markedly disturbed the expression of androgen and estrogen secretion-related genes. Furthermore, Q-PCR, Western blot, and immunofluorescence analyses verified the different expression patterns of related genes in DON- and ZEA-exposed EECs. Collectively, these results illustrated the impact of exposure to different toxins and concrete toxicity on the mRNA expression of EECs from donkey in vitro.

Maternal Zearalenone exposure impacted ovarian follicle formation and development of suckled offspring

Zearalenone (ZEN) is a secondary metabolite, which is mainly produced by Fusarium fungi and exists in various feeds and agricultural products. Recently, an increasing amount of data has shown that ZEN, as an estrogen-like hormone, can have harmful effects on the female reproductive system, especially on oogenesis and folliculogenesis. Breast milk is considered to be the ideal form of nutrition for infants; however, there are some records of contaminants in food, such as mycotoxins, which may be transferred from maternal blood to milk. In this study, we investigated the toxic effects of breast milk on folliculogenesis in offspring following maternal ZEN exposure. Our results showed that maternal ZEN exposure significantly inhibited the process of primordial follicle (PF) assembly and reduced the number of PFs in suckled offspring's ovaries. In addition, RNA-seq analysis showed that RIG-I-like receptor (RLRs) signaling pathways were activated after exposed to ZEN, which increased the expression levels of DNA damage (γ-H2AX, RAD51, and PARP1) and apoptosis related protein (BAX/BCL2 and Caspase-3). Finally, ZEN exposure interfered with follicular development, as evidenced by the reduced percentages of oocyte maturation and embryonic development when the offspring grew to adolescence. It is worth noting that maternal ZEN exposure disrupted the tri-methylation levels of H3K4, H3K9, and H3K27 in the offspring's oocytes. Our results indicated that maternal ZEN exposure affected ovarian development in offspring through the breast milk, which may be detrimental to their reproductive capability in adult life.

Deoxynivalenol and Zearalenone: Different Mycotoxins with Different Toxic Effects in the Sertoli Cells of Equus asinus

(1) Background: Deoxynivalenol (DON) and zearalenone (ZEA) are type B trichothecene mycotoxins that exert serious toxic effects on the reproduction of domestic animals. However, there is little information about the toxicity of mycotoxins on testis development in Equus asinus. This study investigated the biological effects of DON and ZEA exposure on Sertoli cells (SCs) of Equus asinus; (2) Methods: We administered 10 μM and 30 μM DON and ZEA to cells cultured in vitro; (3) Results: The results showed that 10 μM DON exposure remarkably changed pyroptosis-associated genes and that 30 μM ZEA exposure changed inflammation-associated genes in SCs. The mRNA expression of cancer-promoting genes was remarkably upregulated in the cells exposed to DON or 30 μM ZEA; in particular, DON and ZEA remarkably disturbed the expression of androgen and oestrogen secretion-related genes. Furthermore, quantitative RT-PCR, Western blot, and immunofluorescence analyses verified the different expression patterns of related genes in DON- and ZEA-exposed SCs; (4) Conclusions: Collectively, these results illustrated the impact of exposure to different toxins and concrete toxicity on the mRNA expression of SCs from Equus asinus in vitro.

Maternal exposure to zearalenone in masculinization window affects the fetal Leydig cell development in rat male fetus

Zearalenone is a phenolic Fusarium mycotoxin, which is ubiquitous in human and animal feedstuff and often co-occurs with other mycotoxins. ZEA has been reported to disturb Leydig cell function and even cause the apoptosis to the Leydig cells. However, the effects of gestational exposure to zearalenone on fetal Leydig cells and the underlying mechanism remain unknown. Sprague Dawley dams were daily gavaged with 0, 2.5, 5, 10, and 20 mg/kg body weight ZEA from gestational day 14-21. On gestational day 21, rats were euthanized and serum testosterone levels were measured, and testes were collected for further evaluation of Leydig cell number, cell size, gene, and protein expression. Zearalenone significantly decreased anogenital distance and its index of male fetus, serum testosterone levels, Leydig cell proteins (SCARB1, STAR, CYP11A1, CYP17A1, and INSL3), and fetal Leydig cell number at 10 and/or 20 mg/kg by delaying the commitment of stem Leydig cells into the Leydig cell lineage and proliferation. Further study found that Notch signaling (RFNG, PSEN1, NOTCH1, and NOTCH3) was up-regulated by zearalenone. In conclusion, gestational exposure to high doses of zearalenone (10 and 20 mg/kg) blocks fetal Leydig cell development, thus possibly causing the anomalies of the male reproductive tract.

Zearalenone: A Mycotoxin With Different Toxic Effect in Domestic and Laboratory Animals' Granulosa Cells

Zearalenone (ZEA), one of the most prevalent estrogenic mycotoxins, is mainly produced by Fusarium fungi and has been proven to affect the reproductive capacity of animals. Exposure of farm animals to ZEA is a global public health concern because of its toxicity and wide distribution in animal feeds. In vitro and in vivo experiments indicate that ZEA possesses estrogenic activity in mice, swine, Equus asinus and cattle. The precise mechanism of the reproductive toxicity of ZEA has not been established yet. This article reviews evidence on the deleterious effects of ZEA on mammalian folliculogenesis from early to final oogenesis stages. Such effects include impaired granulosa cell (GC) development and follicle steroidogenesis, reduced oocyte nest breakdown, damaged meiotic progression, poor fetal oocyte survival, accelerated primordial follicle activation and enhanced follicle atresia. These phenomena may result in reproductive and non-reproductive problems in domestic animals. In addition, emerging data indicates that ZEA may cause mRNA expression changes in the GCs. In general, E. asinus is more sensitive than swine to ZEA exposure. Finally, results of in vivo animal studies and in vitro tests are reported and discussed.

The detoxification effect of vitamin C on zearalenone toxicity in piglets

Zearalenone (ZEN), one of the more virulent mycotoxins occurred in various cereals and feed during recent decades and made serious health hazards to plants, animals and humans. Vitamin C (Vc) has been shown to be an effective antidote to zearalenone. In this paper, the effects of diets containing zearalenone on the growth performance, genital organ and immunoglobulin of weaning piglets and the toxicity alleviation of vitamin C were studied. Piglets were weaned at 21 days of age and 32 healthy female hybrid weaning piglets (Duroc × Landrace × Large white) with a mean weight of 12.27 ± 0.30 kg were randomly selected. The thirty-two female weaning piglets were divided into four treatment groups according to body weight: control; basal diet + vitamin C (150 mg/kg); basal diet + 1.0 mg/kg ZEN; basal diet + 1 mg/kg ZEN+vitamin C (150 mg/kg). There were eight replicates in each group. The test period was twenty-eight days. The results demonstrated that dietary zearalenone could significantly increase the length, width and area of vulva (P < 0.05), the genital organ coefficient (P < 0.05), the level of IgA, IgG and IgM (P < 0.05), the level of BUN, CRE, AST and TBIL (P < 0.05), and significantly decrease the level of E2, PROG, LH and FSH (P < 0.05). However, the addition of 150 mg/kg vitamin C to dietary zearalenone prevented deformities in the vulva, decrease in immune response capacity, changes in serum biochemical indicators and disorders in hormones level of the piglets that received the diet containing only zearalenone. In conclusion, feeding ZEN of 1.0 mg/kg can result in a deleterious effect on piglets, which was totally or partly ameliorated by dietary supplementation of vitamin C at concentrations about 150 mg/kg diet. This study systematically investigated the inhibition mechanism of vitamin C on ZEN-induced reproductive toxicity, immunotoxicity and hematological toxicity of piglets, and which provided new ideas for reducing the harm of mycotoxins to the animals through means of nutrition regulation.

Zearalenone Exposure Enhanced the Expression of Tumorigenesis Genes in Donkey Granulosa Cells via the PTEN/PI3K/AKT Signaling Pathway

Zearalenone (ZEA) is a natural contaminant existing in food and feed products that exhibits a negative effect on domestic animals’ reproduction. Donkeys possess high economic value in China and are at risk of exposure to ZEA. However, few information is available on ZEA-induced toxicity and no report on toxicity in donkeys can be found in scientific literature. We investigated the biological effects of ZEA exposure on donkey granulosa cells (dGCs) by using RNA-seq analysis. ZEA at 10 and 30 μM were administered to GCs within 72 h of in vitro culture. ZEA at 10 μM significantly altered the tumorigenesis associated genes in dGCs. Exposure to 10 and 30 μM ZEA treatment significantly reduced mRNA expression of PTEN, TGFβ, ATM, and CDK2 genes, particularly, the ZEA treatment significantly increased the expression of PI3K and AKT genes. Furthermore, immunofluorescence, RT-qPCR, and Western blot analysis verified the gene expression of ZEA-exposed GCs. Collectively, these results demonstrated the deleterious effect of ZEA exposure on the induction of ovarian cancer related genes via the PTEN/PI3K/AKT signaling pathway in dGCs in vitro.

Transcriptional profiling analysis of Zearalenone-induced inhibition proliferation on mouse thymic epithelial cell line 1

Zearalenone (ZEA) was a mycotoxin biosynthesized by a variety of Fusarium fungi via a polypeptide pathway. ZEA has significant toxic reaction on immune cells. Thymic epithelial cells (TECs) as a crucial constituent of thymic stroma can provide unique microenvironment for thymocyte maturation, but the mechanism of ZEA affecting the TECs is poorly understood. The basic data about gene expression differences for the ZEA on thymic epithelial cell line 1 (MTEC1) will help us to elucidate this mechanism. Here, cell viability and proliferation assay and transcriptome sequencing on MTEC1 treated with ZEA were performed. 4188 differentially expressed genes (DEGs) between ZEA treated and control groups were identified, confirmed and analyzed. Our results showed that 10-50μg/ml ZEA significantly inhibited MTEC1 proliferation and arrested cell cycle at G2/M phase. Gene ontology and KEGG pathway analysis revealed that Chemokine, JAK-STAT and Toll-like receptor signaling pathway, were involved in the cell cycle pathway. 16 key genes involved in the cell cycle processes were validated and the results suggested that Mitotic catastrophe (MC) may take part in ZEA inhibition of METC1 cell proliferation. These data highlighted the importance of cell cycle pathway in MTEC1 treated with ZEA, and will contribute to get the molecular mechanisms of ZEA inhibition of MTEC1 cell proliferation.

Differentiation of sow and mouse ovarian granulosa cells exposed to zearalenone in vitro using RNA-seq gene expression

Zearalenone (ZEA), a natural contaminant found in feed, has been shown to have a negative impact on domestic animal reproduction, particularly in pigs. There are species-specific differences in the ZEA-induced toxicity pattern. Here, we investigated the different biological effects of ZEA exposure on porcine and mouse granulosa cells, using RNA-seq analysis. We treated murine and porcine granulosa cells with 10 μM and 30 μM ZEA during 72 h of culturing, in vitro. The results showed that 10 μM ZEA exposure significantly altered mitosis associated genes in porcine granulosa cells, while the same treatment significantly altered the steroidogenesis associated genes in mouse granulosa cells. Exposure to 30 μM ZEA resulted in significantly up-regulated expression of inflammatory related genes in porcine granulosa cells as well as the cancer related genes in mouse granulosa cells. Similarly, 30 μM ZEA exposure significantly decreased the expression of tumor suppressor factors in the mouse granulosa cells. Furthermore, immunofluorescence, RT-qPCR as well as western-blot analysis verified the different expression of related genes in ZEA exposed porcine and mouse granulosa cells. Collectively, these results illustrate the presence of species differences with regards to ZEA effects between porcine and mouse ovarian granulosa cells, in vitro.

A novel recombinant cell fluorescence biosensor based on toxicity of pathway for rapid and simple evaluation of DON and ZEN

During an exposure, humans and animals are most often exposed to a mixture rather than individual mycotoxins. In this study, a Human Embryonic Kidney 293 cell (HEK-293) fluorescence sensor was developed to detect and evaluate mycotoxins, deoxynivalenol (DON) and zearalenone (ZEN) compounds, produced by Fusarium culmorum that are common food contaminants. TRE-copGFP (green fluorescent protein) and ERE-TagRFP (red fluorescent protein) plasmids were constructed and cotransfected into HEK-293 cells through a highly efficient, lipid-mediated, DNA-transfection procedure. Results show that fluorescence intensity was proportional to DON and ZEN concentrations, ranging from 2 to 40 ng/mL and 10 to 100 ng/mL respectively, with a detection limit of 0.75 ng/mL and 3.2 ng/mL respectively. The EC50 of DON and ZEN are 30.13 ng/mL and 76.63 ng/mL respectively. Additionally, ZEN may have a synergistic effect on enhancing AP-1 activity of the toxicity pathway of DON. These data indicate the high sensitivity and effectiveness of our biosensor system in the evaluation of the combined toxicity of ZEN, DON and their derivatives. In addition, this approach is suitable for an early warning method for the detection of ZEN and DON family mycotoxins contamination without higher-priced, conventional analytical chemistry methods.

The protective effect of resveratrol against cytotoxicity induced by mycotoxin, zearalenone

Zearalenone (ZEA), a non-steroidal estrogenic mycotoxin, is widely present in cereals and agricultural products.

Zearalenone-induced changes in biochemical parameters, oxidative stress and apoptosis in cardiac tissue

Zearalenone (ZEN) is a mycotoxin from Fusarium species commonly found in food commodities and is known to cause reproductive disorders. Several in vivo studies have shown that ZEN is haematotoxic and hepatotoxic and causes several alterations of immunological parameters. Meantime, the available information on the cardiotoxic effects of ZEN is very much limited. In the present study, we investigated the toxic effects of ZEN in heart tissues of Balb/c mice. We demonstrated that ZEN (40 mg kg−1 body weight (b.w.)) increased creatine phosphokinase, lactate dehydrogenase, aspartate transaminase, alanine transaminase, total cholesterol and triglyceride levels and induced oxidative stress as monitored by measuring the malondialdehyde level, the generation of protein carbonyls, the catalase and superoxide dismutase activity and the expression of the heat shock proteins (Hsp 70). We also demonstrated that acute administration of ZEN triggers apoptosis in cardiac tissue. Furthermore, we aimed to evaluate the safety and efficacy of crocin (CRO), a natural carotenoid, to prevent ZEN-induced cardiotoxicity in mice. In fact, combined treatment of ZEN with different doses of CRO (50, 100, and 250 mg kg−1 b.w.) showed a significant reduction of ZEN-induced toxicity for all tested markers in a dose-dependent manner. It could be concluded that CRO was effective in the protection against ZEN-induced toxicity in cardiac tissue.

Effect of gender, pregnancy and exposure conditions on metabolism and distribution of zearalenone in rats

The mycotoxin zearalenone (ZEA) is produced by a variety of Fusarium fungi and contaminates numerous cereals, fruits and vegetables. Interacting with the oestrogen receptors, ZEA and reduced metabolites zearalenols (ZOLs) cause hormonal effects in animals, such as abnormalities in the development of the reproductive tract and mammary gland in female offspring. Limited information is available on the pharmacokinetics of ZEA and its metabolites, particularly in pregnant females, foetuses and newborns. Our study was conducted to characterise the tissue distribution and metabolism of ZEA in male and female rats in various physiological states (virgin female, pregnant female) and exposure conditions (subcutaneous versus oral exposure, single versus repeated exposure to 1 mg/kg ZEA). Respective placental and mammary transfer to foetuses and newborns was evaluated. In all states and exposure conditions, α-ZOL and the glucuronides of ZEA and α-ZOL were the predominant metabolites, mostly concentrated in the intestine, the liver and the urine. Toxins were very low or undetectable in most of the tissues 24 h after ZEA exposure, except in foetal livers. Absorption and intestinal glucuronidation of ZEA were higher in males than females. α-ZOL concentration was significantly higher in the intestine and liver of males and pregnant females, compared to virgin females. ZEA and all its metabolites easily crossed the placental barrier and transferred into the milk. ZEA was metabolised in the foetal and neonatal stages, glucuronides being the main form detected in all organs. Metabolite elimination was slower in foetal tissues than in maternal tissues. All toxin concentrations in the foetal and neonatal tissues strongly increased in cases of repeated maternal exposure. A better knowledge of the metabolism and transfer of ZEA in foetuses and newborns will help to evaluate the health risk that such endocrine disruptors represent in these stages.

Mycotoxin zearalenone induces AIF- and ROS-mediated cell death through p53- and MAPK-dependent signaling pathways in RAW264.7 macrophages

Zearalenone (ZEN) is commonly found in many food commodities and is known to cause reproductive disorders and genotoxic effects. However, the mode of ZEN-induced cell death of macrophages and the mechanisms by which ZEN causes cytotoxicity remain unclear. The present study shows that ZEN treatment reduces viability of RAW264.7 cells in a dose-dependent manner. ZEN causes predominantly necrotic and late apoptotic cell death. ZEN treatment also results in the loss of mitochondrial membrane potential (MMP), mitochondrial changes in Bcl-2 and Bax proteins, and cytoplasmic release of cytochrome c and apoptosis-inducing factor (AIF). Pre-treatment of the cells with either z-VAD-fmk or z-IETD-fmk does not attenuate ZEN-mediated cell death, whereas catalase suppresses the ZEN-induced decrease in viability in RAW264.7 cells. Treating the cells with c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), or p53 inhibitor prevented ZEN-mediated changes, such as MMP loss, cellular reactive oxygen species (ROS) increase, and cell death. JNK or p38 MAPK inhibitor inhibited mitochondrial alterations of Bcl-2 and Bax proteins with attendant decreases in cellular ROS levels. Knockdown of AIF via siRNA transfection also diminished ZEN-induced cell death. Further, adenosine triphosphate was markedly depleted in the ZEN-exposed cells. Collectively, these results suggest that ZEN induces cytotoxicity in RAW264.7 cells via AIF- and ROS-mediated signaling, in which the activations of p53 and JNK/p38 play a key role.

Zearalenone and its metabolites as endocrine disrupting chemicals

Zearalenone (ZEA) is a macrocyclic β-resorcylic acid lactone produced by numerous species of Fusarium. It frequently contaminates corn and cereal products in many regions of the world. The biological activity of ZEA is dominated by its pronounced oestrogenicity, which is even enhanced in certain reductive metabolites. This review updates the metabolism in fungi, plants and mammalian systems, as well as the pharmacokinetics of ZEA. The present evidence for the hormonal effects of the parent mycoestrogen and some of its metabolites in vitro and in farm and experimental animals in vivo is reviewed, together with its association with endocrine-disruptive effects in humans. Possible mechanisms of the oestrogenic and carcinogenic activity of ZEA are discussed and future areas of research proposed.

Suppression of the inflammatory response in experimental arthritis is mediated via estrogen receptor alpha but not estrogen receptor beta

Introduction

The immune modulatory role of estrogens in inflammation is complex. Both pro- and anti-inflammatory effects of estrogens have been described. Estrogens bind both estrogen receptor (ER)α and β. The contribution of ERα and ERβ to ER-mediated immune modulation was studied in delayed type hypersensitivity (DTH) and in experimental arthritis

Methods

ER-mediated suppression of rat adjuvant arthritis (AA) was studied using ethinyl-estradiol (EE) and a selective ERβ agonist (ERB-79). Arthritis was followed for 2 weeks. Next, effects of ER agonists (ethinyl-estradiol, an ERα selective agonist (ERA-63) and a selective ERβ agonist (ERB-79) on the development of a tetanus toxoid (TT)-specific delayed type hypersensitivity response in wild type (WT) and in ERα - or ERβ-deficient mice were investigated. Finally, EE and ERA-63 were tested for their immune modulating potential in established collagen induced arthritis in DBA/1J mice. Arthritis was followed for three weeks. Joint pathology was examined by histology and radiology. Local synovial cytokine production was analyzed using Luminex technology. Sera were assessed for COMP as a biomarker of cartilage destruction.

Results

EE was found to suppress clinical signs and symptoms in rat AA. The selective ERβ agonist ERB-79 had no effect on arthritis symptoms in this model. In the TT-specific DTH model, EE and the selective ERα agonist ERA-63 suppressed the TT-specific swelling response in WT and ERβKO mice but not in ERαKO mice. As seen in the AA model, the selective ERβ agonist ERB-79 did not suppress inflammation. Treatment with EE or ERA-63 suppressed clinical signs in collagen induced arthritis (CIA) in WT mice. This was associated with reduced inflammatory infiltrates and decreased levels of proinflammatory cytokines in CIA joints.

Conclusions

ERα, but not ERβ, is key in ER-mediated suppression of experimental arthritis. It remains to be investigated how these findings translate to human autoimmune disease.

Comparative mechanisms of zearalenone and ochratoxin A toxicities on cultured HepG2 cells: is oxidative stress a common process?

Zearalenone (ZEN) and Ochratoxin A (OTA) are structurally diverse fungal metabolites that can contaminate feed and foodstuff and can cause serious health problems for animals as well as for humans. In this study, we get further insight of the molecular aspects of ZEN and OTA toxicities in cultured human HepG2 hepatocytes. In this context, we have monitored the effects of ZEN and OTA on (i) cell viability, (ii) heat shock protein (Hsp) 70 and Hsp 27 gene expressions as a parameter of protective and adaptive response, (iii) oxidative damage, and (iv) cell death pathways. Our results clearly showed that both ZEN and OTA inhibit cell proliferation. For ZEN, a significant induction of Hsp 70 and Hsp 27 was observed. In the same conditions, ZEN generated an important amount of reactive oxygen species (ROS). Antioxidant supplements restored the major part of cell mortality induced by ZEN. However, OTA treatment downregulated Hsp 70 and Hsp 27 protein and mRNA levels and did not induce ROS generation. Antioxidant supplements did not have a significant effect on OTA-induced cell mortality. Using another cell system (Vero monkey kidney cells), we demonstrated that OTA downregulates three members of HSP 70 family: Hsp 70, Hsp 75, and Hsp 78. Our findings showed that oxidative damage seemed to be the predominant toxic effect for ZEN, while OTA toxicity seemed to be rather because of the absence of Hsps protective response. Furthermore, the two mycotoxins induced an apoptotic cell death.

Ethanol extract of Psoralea corylifolia L. and its main constituent, bakuchiol, reduce bone loss in ovariectomised Sprague–Dawley rats

The aim of the present study was to investigate whether ethanol extracts of Psoralea corylifolia L. (PCE) and its active component protect against bone loss in ovariectomised rats. We screened oestrogenic activities of the main extract fractions using in vitro assays and identified bakuchiol as the most active oestrogenic component by HPLC and LC/MS, and then demonstrated that bakuchiol had strong binding affinity for oestrogen receptor (ER) α. Seventy female Sprague–Dawley rats were assigned to either a sham-operated group (n 10) or an ovariectomised group (n 60). The ovariectomised group was subdivided into six groups, each containing ten rats: vehicle group, two bakuchiol-treated groups (dose of 15 mg/kg per d or 30 mg/kg per d; ten rats for each group), two PCE-supplemented groups (0·25 % or 0·5 % extracts of diets; ten rats for each group) and a 17β-oestradiol (E2)-treated group (20 μg/kg per d). We recorded weight and feed intake every week, and killed all animals after 6 weeks. Blood was collected, and the uterus, kidneys and livers were removed. Bakuchiol has a three-fold higher binding affinity for ERα than for ERβ. Bakuchiol and PCE treatments had no uterotrophic activity even though they demonstrated oestrogenic activity in the in vitro assays. Bakuchiol and PCE treatments reduced postmenopausal bone loss by increasing alkaline phosphatase, Ca concentrations, serum E2 concentration and bone mineral density, and by decreasing the inorganic P level. The present study indicated that bakuchiol and PCE treatments could protect against bone loss.

The mycotoxin Zearalenone induces apoptosis in human hepatocytes (HepG2) via p53-dependent mitochondrial signaling pathway

Zearalenone (Zen) is a fusarial mycotoxin commonly found in several food commodities worldwide. It is frequently implicated in reproductive disorders and exerts several genotoxic effects in vivo and in vitro. In response to DNA damage, cells may undergo an intricate network of different pathways including apoptosis. Meanwhile, data regarding the induction of apoptosis after Zen exposure are limited. Thus, the aim of this study was to demonstrate whether Zen-induced DNA damage can lead to apoptosis as a stress response and which pathways are undertaken. Our results clearly show that Zen reduces cell proliferation in HepG2 cells in a dose-dependent manner as attested by the MTT assay (IC50%, 100microM). The analysis of propidum iodide uptake has shown that the amount of necrotic cells was about 6% among 55% of dead cells (at 120microM of Zen). The involvement of apoptosis as a major cause of Zen-induced cell death was further confirmed but results of caspase-3 activity showed a Zen-dose dependant increase. Furthermore, results of microarrays analysis have shown that Zen induced an upregulation of ATM and p53 genes family. ATM pathway responds primarily to DNA double-strand breaks and has been involved in the activation and stabilization of p53. The activation of p53 was accompanied by an upregulation of GADD45 to arrest the cell cycle and to allow the repair mechanisms to take place. In addition, results of genes profiling as well as western-blotting analysis showed that Zen increased the ratio of pro-apoptotic factors/anti-apoptotic factors which led to the loss of mitochondrial potential, Bax translocation and cytochrome c release. Once released, cytochome c activates caspase 9 which in turn activates caspase-3 and enhances apoptosis. In summary, these data suggested that Zen induced apoptosis in a dose-dependent manner in HepG2 cells via a p53-dependent mitochondrial pathway.

Derivation of a bisphenol A oral reference dose (RfD) and drinking-water equivalent concentration

Human exposure to bisphenol A (BPA) is due to that found in the diet, and BPA and its metabolites were detected at parts per billion (or less) concentrations in human urine, milk, saliva, serum, plasma, ovarian follicular fluid, and amniotic fluid. Adverse health effects in mice and rats may be induced after parenteral injection or after massive oral doses. Controlled ingestion trials in healthy adult volunteers with 5 mg d16-BPA were unable to detect parent BPA in plasma despite exquisitely sensitive (limit of detection = 6 nM) methods, but by 96 h 100% of the administered dose was recovered in urine as the glucuronide. The extensive BPA glucuronidation following ingestion is not seen after parenteral injection; only the parent BPA binds plasma proteins and estrogen receptors (ER). The hypothesis that BPA dose-response may be described by a J- or U-shape curve was not supported by toxicogenomic data collected in fetal rat testes and epididymes (after repeated parenteral exposure at 2-400,000 microg/kg-d), where a clear monotonic dose-response both in the numbers of genes and magnitude of individual gene expression was evident. There is no clear indication from available data that the BPA doses normally consumed by humans pose an increased risk for immunologic or neurologic disease. There is no evidence that BPA poses a genotoxic or carcinogenic risk and clinical evaluations of 205 men and women with high-performance liquid chromatography (HPLC)-verified serum or urinary BPA conjugates showed (1) no objective signs, (2) no changes in reproductive hormones or clinical chemistry parameters, and (3) no alterations in the number of children or sons:daughters ratio. Results of benchmark dose (BMD10 and BMDL10) calculations and no-observed-adverse-effect level (NOAEL) inspections of all available and reproducible rodent studies with oral BPA found BMD and NOAEL values all greater than the 5 mg/kg-d NOAELs from mouse and rat multigeneration reproduction toxicity studies. While allometric and physiologically based pharmacokinetic (PBPK) models were constructed for interspecies scaling of BPA and its interaction with ER, multigeneration feeding studies with BPA at doses spanning 5 orders of magnitude failed to identify signs of developmental toxicity or adverse changes in reproductive tract tissues; the 5-mg/kg-d NOAELs identified for systemic toxicity in rats and mice were less than the oral NOAELs for reproductive toxicity. Thus, it is the generalized systemic toxicity of ingested BPA rather than reproductive, immunologic, neurobehavioral, or genotoxic hazard that represents the point of departure. Using U.S. Environmental Protection Agency (EPA) uncertainty factor guidance and application of a threefold database uncertainty factor (to account for the fact that the carcinogenic potential of transplacental BPA exposure has yet to be fully defined and comprehensive neurobehavioral and immunotoxicologic evaluations of BPA by relevant routes and at relevant doses have yet to be completed) to the administered dose NOAEL results in an oral RfD of 0.016 mg/kg-d. Assuming the 70-kg adult consumes 2 L of water each day and adopting the default 20% U.S. EPA drinking water relative source contribution yields a 100 microg/L BPA total allowable concentration (TAC).

In vivo effects of bisphenol A in laboratory rodent studies

Concern is mounting regarding the human health and environmental effects of bisphenol A (BPA), a high-production-volume chemical used in synthesis of plastics. We have reviewed the growing literature on effects of low doses of BPA, below 50 mg/(kg day), in laboratory exposures with mammalian model organisms. Many, but not all, effects of BPA are similar to effects seen in response to the model estrogens diethylstilbestrol and ethinylestradiol. For most effects, the potency of BPA is approximately 10-1000-fold less than that of diethylstilbestrol or ethinylestradiol. Based on our review of the literature, a consensus was reached regarding our level of confidence that particular outcomes occur in response to low dose BPA exposure. We are confident that adult exposure to BPA affects the male reproductive tract, and that long lasting, organizational effects in response to developmental exposure to BPA occur in the brain, the male reproductive system, and metabolic processes. We consider it likely, but requiring further confirmation, that adult exposure to BPA affects the brain, the female reproductive system, and the immune system, and that developmental effects occur in the female reproductive system.

Characterization of the estrogenic activities of zearalenone and zeranol in vivo and in vitro

In the present study, we compared the estrogenic activity of zearalenone (ZEN) and zeranol (ZOL) by determining their relative receptor binding affinities for human ERalpha and ERbeta and also by determining their uterotropic activity in ovariectomized female mice. ZOL displayed a much higher binding affinity for human ERalpha and ERbeta than ZEN did. The IC(50) values of ZEN and ZOL for binding to human ERalpha were 240.4 and 21.79nM, respectively, and the IC(50) values for binding to ERbeta were 165.7 and 42.76nM, respectively. In ovariectomized female ICR mice, s.c. administration of ZEN at doses >or=2mg/kg/day for 3 consecutive days significantly increased uterine wet weight compared with the control group, and administration of ZOL increased the uterine wet weight at lower doses (>or=0.5mg/kg/day for 3 days). Based on available X-ray crystal structures of human ERalpha and ERbeta, we have also conducted molecular modeling studies to probe the binding characteristics of ZEN and ZOL for human ERalpha and ERbeta. Our data revealed that ZEN and ZOL were able to occupy the active site of the human ERalpha and ERbeta in a strikingly similar manner as 17beta-estradiol, such that the phenolic rings of ZEN and ZOL occupied the same receptor region as occupied by the A-ring of 17beta-estradiol. The primary reason that ZOL and ZEN is less potent than 17beta-estradiol is likely because 17beta-estradiol could bind to the receptor pocket without significantly changing its conformation, while ZOL or ZEN would require considerable conformational alterations upon binding to the estrogen receptors (ERs).

Toxic effects of zearalenone and alpha-zearalenol on the regulation of steroidogenesis and testosterone production in mouse Leydig cells

Zearalenone (ZEA) and its derivative alpha-zearalenol (alpha-ZOL) are produced by fungi of the genus Fusarium and, after ingestion via contaminated cereals, may lead to animal fertility disturbances and other reproductive pathologies. The previous study demonstrated the toxic effects of ZEA and alpha-ZOL through disturbances in male fertility and other reproductive pathologies in mice. In this study, we further examined the direct biological effects of ZEA and alpha-ZOL on steroidogenesis production, primarily in Leydig cells of mice. Mature mouse Leydig cells were purified by Percoll gradient centrifugation and the cell purity was determined by 3beta-hydroxysteroid dehydrogenase (3beta-HSD) staining. To examine ZEA and alpha-ZOL-induced biological consequences, we measured testosterone secretion and transcription level of 3 key steroidogenic enzymes including 3beta-HSD-1, P450scc and StAR, in ZEA and alpha-ZOL/human chorionicgonadotropin (hCG) co-treated cells. Our results showed that ZEA and alpha-ZOL (10(-4) M, 10(-6) M and 10(-8) M) significantly suppressed hCG (10 ng/ml)-induced testosterone secretion. The suppressive effect is correlated with a decrease in the level of transcription of 3beta-HSD-1, P450scc, and StAR (P<0.05).

Induction of iron homeostasis genes during estrogen-induced uterine growth and differentiation

We have previously used genome-wide transcript profiling to investigate the relationships between changes in gene expression and physiological alterations during the response of the immature mouse uterus to estrogens. Here we describe the identification of a functionally inter-related group of estrogen-responsive genes associated with iron homeostasis, including the iron-binding protein lactotransferrin, the ferroxidase ceruloplasmin, the iron delivery protein lipocalin 2 and the iron-exporter ferroportin. Quantitative real-time PCR revealed that the expression of these genes increases with time during the uterotrophic response, reaching maximal levels in the post-proliferative phase (between 48 and 72 h). In contrast, the heme biosynthesis genes aminolevulinic acid synthase 1 and 2 were maximally induced by estrogen at 2 and 4 h, respectively, prior to increased cell proliferation. Together, these data reveal that estrogen induces the temporally coordinated expression of iron homeostasis genes in the mouse uterus, and suggest an important role for iron metabolism during sex steroid hormone-induced uterine cell growth and differentiation.

Validation study of OECD rodent uterotrophic assay for the assessment of estrogenic activity in Sprague-Dawley immature female rats

The Organization for Economic Cooperation and Development (OECD) is developing a screening and testing method to identify estrogenic/antiestrogenic compounds. Based on these demands, phase 1 study for OECD uterotrophic assay was undertaken. The OECD is in the process of validating the assay results from international participating laboratories, which carried out this study with established environmental estrogenic compounds using designed protocols. The aim of this study was to provide data for validating the OECD uterotrophic assay using Sprague-Dawley immature female rats when testing with weak or partial estrogenic compounds. Ethinyl estradiol (EE) at 0.3 or 1 microg/kg/d, a positive control used in the present study, significantly increased both uterine wet and blotted weights. In the case of weak estrogenic compounds, the uterine wet weights were significantly increased by bisphenol A (BPA) at 300 mg/kg/d, nonylphenol (NP) at 80 mg/kg/d, genistein (GN) at 35 mg/kg/d, and methoxychlor (MXC) at 500 mg/kg/d. In addition, the increase in uterine blotted weights also showed a similar pattern to that of uterine wet weights. However, both 1,1,1-trichloro-2,2-bis(p-chlorphenyl)ethane (o,p-DDT) and dibutyl phthalate (DBP) did not affect uterus (wet and blotted) weights at doses of 100 and 500 mg/kg/d. These results suggest that the increase in uterine weights should be considered useful as a sensitive endpoint for detecting weak estrogenic compounds in 3-d rodent uterotrophic assay. However, further combination studies using surrogate biomarkers may be needed to improve the sensitivity of this assay for the detection of weak estrogenic compounds, such as o,p-DDT.

Analysis of bisphenol A in natural waters by means of an optical immunosensor

This work describes a very simple, fast and sensitive method based on the use of the optical immunosensor "RIver ANAlyser" (RIANA) to the determination of bisphenol A in a waters. RIANA is based on a rapid solid-phase indirect inhibition immunoassay that takes place at an optical transducer chip chemically modified with an analyte derivative. Fluorescence produced by labelled antibodies bound to the transducer is detected by photodiodes and can be correlated with the analyte concentration. The sensor surface can be regenerated thus allowing the performance of several measurements (around 300) with the same transducer. Each test cycle, including one regeneration step, is accomplished in 15 min. The detection limit achieved in the direct determination of bisphenol A in water with this system was 0.014 microg/L. Satisfactory repeatability, with relative standard deviations (RSD) ranging between 1.48% and 6.93% were obtained. The immunosensor method developed was applied to the monitoring of bisphenol A in various types of water collected in a waterworks (from the river water source to the finished drinking water) and validated against the results obtained in the same approach by a more traditional method, based on solid-phase extraction followed by liquid chromatography-mass spectrometry. Results obtained by both techniques were in general good agreement (considering the typical overestimation bias of immunoassays), and served to prove the satisfactory removal efficiency of the overall purification process applied in the waterworks and, in particular, of the sand filtration step.

Male reproductive toxicity of four bisphenol antioxidants in mice and rats and their estrogenic effect

Male mice and rats were fed a diet containing four bisphenol antioxidants, 2,2'-methylenebis(4-ethyl-6-tert-butylphenol) (ME), 2,2'-methylenebis(4-methyl -6-tert-butylphenol) (MM), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol) (BM), or 4,4'-thiobis(3-methyl-6-tert-butylphenol) (TM) at levels of 0.06-0.25% for 2 months. BM and TM decreased epididymal, seminal vesicular, prostate and preputial weights, and injured seminiferous tubules in mice in a dose-dependent fashion. BM and TM also reduced sex accessory organ weights and sperm production capacity in rats, but MM and ME were more toxic to rats than BM and TM. ME and MM did not bind ERalpha up to 10(-3) M, while BM and TM competitively bound ERalpha against beta-estradiol (E2). Fifty percent inhibitory concentrations (IC50 s) of BM, TM, and bisphenol A (positive control) against E2-binding were 7.3 x 10(-6) M, 1.8 x 10(-5) M, and 1.4 x 10(-5) M, respectively. When ovariectomized (OVX) mice were sc administered TM at doses of 60 and 300 mg/kg/day for 4 days, or when OVX mice were fed BM in the diet at a level of 0.25% for 2 months, uterine weight was significantly increased. These results suggest that BM and TM are weakly toxic, possibly through an estrogenic mechanism to male reproductive organs in mice as well as rats, while MM and ME may be the direct testicular toxins in rats but not mice.

An extensive new literature concerning low-dose effects of bisphenol A shows the need for a new risk assessment

Bisphenol A (BPA) is the monomer used to manufacture polycarbonate plastic, the resin lining of cans, and other products, with global capacity in excess of 6.4 billion lb/year. Because the ester bonds in these BPA-based polymers are subject to hydrolysis, leaching of BPA has led to widespread human exposure. A recent report prepared by the Harvard Center for Risk Analysis and funded by the American Plastics Council concluded that evidence for low-dose effects of BPA is weak on the basis of a review of only 19 studies; the report was issued after a delay of 2.5 years. A current comprehensive review of the literature reveals that the opposite is true. As of December 2004, there were 115 published in vivo studies concerning low-dose effects of BPA, and 94 of these report significant effects. In 31 publications with vertebrate and invertebrate animals, significant effects occurred below the predicted "safe" or reference dose of 50 microg/kg/day BPA. An estrogenic mode of action of BPA is confirmed by in vitro experiments, which describe disruption of cell function at 10(-12) M or 0.23 ppt. Nonetheless, chemical manufacturers continue to discount these published findings because no industry-funded studies have reported significant effects of low doses of BPA, although > 90% of government-funded studies have reported significant effects. Some industry-funded studies have ignored the results of positive controls, and many studies reporting no significant effects used a strain of rat that is inappropriate for the study of estrogenic responses. We propose that a new risk assessment for BPA is needed based on a) the extensive new literature reporting adverse effects in animals at doses below the current reference dose; b) the high rate of leaching of BPA from food and beverage containers, leading to widespread human exposure; c) reports that the median BPA level in human blood and tissues, including in human fetal blood, is higher than the level that causes adverse effects in mice; and d) recent epidemiologic evidence that BPA is related to disease in women.

Estrogenic effects of zearalenone on the expression of progestin receptors and sexual behavior in female rats

Zearalenone is a resorcylic acid lactone compound that is produced by fungal infection of edible grains and is believed to influence reproduction by binding to estrogen receptors. In order to study the potential estrogenic effects of this compound in the brain, we examined the effects of zearalenone on the expression of neuronal progestin receptors and feminine sexual behavior in female rats. Ovariectomized rats were treated with zearalenone (0.2, 1.0, or 2.0 mg), estradiol benzoate, or vehicle daily for 3 days. They were then either perfused, and progestin receptors visualized by immunocytochemistry, or injected with progesterone and tested for sexual receptivity with male rats. Progestin receptor-containing cells were counted in the medial preoptic area and ventromedial hypothalamus. The two highest doses of zearalenone increased the concentration of neuronal progestin receptors, as did 10 microg of estradiol. The highest dose of zearalenone (2 mg) also induced progestin receptor staining density comparable to that of 10 microg of estradiol benzoate. In behavioral tests, ovariectomized animals treated with 2 mg of zearalenone followed by progesterone showed levels of sexual receptivity comparable to females treated daily with estradiol benzoate (2 microg) followed by progesterone. These studies suggest that, although structurally distinct and less potent than estradiol, zearalenone can act as an estrogen agonist in the rat brain.

In vivo imaging of activated estrogen receptors in utero by estrogens and bisphenol A

Environmental estrogens are of particular concern when exposure occurs during embryonic development. Although there are good models to study estrogenic activity of chemicals in adult animals, developmental exposure is much more difficult to test. The weak estrogenic activity of the environmental estrogen bisphenol A (BPA) in embryos is controversial. We have recently generated transgenic mice that carry a reporter construct with estrogen-responsive elements coupled to luciferase. We show that, using this in vivo model in combination with the IVIS imaging system, activation of estrogen receptors (ERs) by maternally applied BPA and other estrogens can be detected in living embryos in utero. Eight hours after exposure to 1 mg/kg BPA, ER transactivation could be significantly induced in the embryos. This was more potent than would be estimated from in vitro assays, although its intrinsic activity is still lower than that of diethylstilbestrol and 17beta-estradiol dipropionate. On the basis of these results, we conclude that the estrogenic potency of BPA estimated using in vitro assays might underestimate its estrogenic potential in embryos.

Bisphenol A promotes IL-4 production by Th2 cells

BACKGROUND

It has been proposed that estrogen plays an important role in modulating the Th1/Th2 cytokine balance. From this viewpoint, chemicals with estrogenic responses were expected to possess similar immunoregulatory roles which have not been defined to date. To address this, we studied the effects of one of the estrogenic chemicals, bisphenol A (BPA), on the in vitro production of Th1 and Th2 cytokines.

METHODS

Mesenteric lymph node cells from Trichinella spiralis (Ts)-infected mice were incubated with serialfold dilutions of BPA under stimulation with Ts antigen. The Th2 cytokine production in the supernatant was determined by ELISA. The Th2 cytokine production by mesenteric lymph node cells from Ts-infected mice inoculated orally with BPA was compared with that of uninoculated mice infected with Ts.

RESULTS

The antigen-stimulated interleukin (IL)-4 production by Th2-dominant mesenteric lymph node cells from Ts-infected mice increased significantly by addition of 3 microM of BPA. The IL-5 production was not affected. The production of IL-4, but not that of IL-5, by splenocytes of Th2-skewed Leishmania major-infected BALB/c mice increased at concentrations of 3 and 10 microM of BPA. However, the interferon gamma production was not affected by BPA in Th1-skewed L. major-infected C57BL/6 mice. The production of IL-4 and IL-10, but not that of IL-13, markedly increased in Ts-infected mice inoculated orally with BPA.

CONCLUSIONS

We demonstrated that the IL-4 production was increased both in vitro and in vivo by treatment with BPA. This suggests that BPA might cause allergic diseases by stimulating the IL-4 production by Th2 cells.

The influence of dietary isoflavone on the uterotrophic response in juvenile rats

Current in vivo methods to identify and assess reproductive hazards of endocrine disrupting substances are often confounded by the presence of isoflavones (genistein, diadzein, glycitein), strongly hormonally-active substances, in the diet of laboratory rodents. However, studies that have attempted to study the influence of dietary isoflavone on qualitative and quantitative uterotrophic responses have been limited by the few doses of isoflavone tested, stress to the animals due to changing of the diet immediately prior to testing and/or comparing effects of diets of very different composition. The current study examined the effects of isoflavone on uterotrophic response by using immature female rats reared from conception on diets varying only in the amount of isoflavone concentrate (Novasoy) added to a virtually isoflavone-free soya-based diet. The effects of these diets, and a soya-free semipurified diet (AIN 93G) on uterotrophic responses to treatment with a strong (Ethinyl Estradiol, EE) or a weak (bisphenol A, BPA) estrogenic substance were examined. The pups were treated with subcutaneous injections of either EE (1 microg/kg/day), BPA (600 mg/kg/day) or corn oil (vehicle) control for 3 days starting at weaning on post natal day (PND) 21. On the morning of PND 24 pups were sacrificed and uterus weight, epithelium labeling index (Bromo deoxyuridine incorporation), uterine epithelium thickness, and peroxidase activity were determined. Diet did not influence unstimulated uterine weight, epithelial height or peroxidase activity except at the highest isoflavone diet where animals had significantly increases in all three endpoints. Uterine weight, epithelial thickness and peroxidase were all significantly increased by EE or BPA treatment. There was no evidence of diet-induced potentiation or inhibition of the stimulatory actions of either EE or BPA on either uterine weight or epithelial thickness while EE-induced increase in uterine peroxidase activity was increased synergistically by the highest dose of isoflavone. A similar response to the latter effect was seen in BPA treated animals although this response was not significantly different from that of BPA treated rats fed the isoflavone-free soy diet. The rate of endometrial epithelium labeling with BrdU was not altered by any treatment. These results indicate that dietary isoflavone content can directly influence uterine weight and other estrogen-dependent endpoints demonstrating the potential of these to reduce the active range of the uterotrophic assay. However, there is no indication that isoflavones impair or potentiate the stimulatory action of either strong (EE) or weaker (BPA) estrogen agonists on uterine weight or epithelial morphology although the data do suggest the potential for synergy between high isoflavone content and estrogen agonist in inducing uterine peroxidase.

Testicular toxicity of dietarily or parenterally administered bisphenol A in rats and mice

Male Crj:Wistar rats, HsdHot:Holtzman SD rats, Crj:CD-1(ICR) mice and C57BL/6CrSlc mice were administered bisphenol A (BPA) in the diet at a level of 0 (control) and 0.25% for 8 weeks. Daily BPA intake was about 200 and 400 mg/kg for rats and mice, respectively. No conspicuous signs of general or reproductive toxicity were observed after administration in any strain of these animals. Serum testosterone concentrations were not decreased in BPA-fed rats and mice. Successive subcutaneous administration of BPA at a dose of 200 mg/kg/day for 4 weeks significantly decreased the testis, epididymis, prostate and seminal vesicle weights, and the testicular daily sperm production in Jcl:Wistar rats. Successive intraperitoneal administration of BPA at a dose of 20 mg/kg/day for 4 weeks decreased the prostate and seminal vesicle weights but not the testis or epididymis weights. An intraperitoneal dose of 2 mg BPA/kg/day did not cause any toxicity. These results indicate that dietarily administered BPA is less toxic to most strains of rats and mice, and the maximum non-toxic dose and/or minimum toxic dose may be about 200 mg/kg/day. Subcutaneous or intraperitoneal BPA is much more toxic on male reproductive and sex accessory organs than dietary.

In vitro assay of hydrolysis and chlorohydroxy derivatives of bisphenol A diglycidyl ether for estrogenic activity

Bisphenol A diglycidyl ether (BADGE) is an epoxy resin monomer. Epoxy-based solution coatings are used in many applications as additives for a variety of plastic coatings in food packaging. It is well known that unreacted BADGE can migrate from epoxy-based packing materials into foods. Not only BADGE but also its derivatives can easily migrate into foods and it is likely that we intake BADGE and its derivatives through food or drink. Recently, endocrine disrupting chemicals (EDCs) have attracted attention because they have been shown to affect reproduction in wildlife. The estrogenic activity of BADGE derivatives has not previously been investigated. Therefore, we investigated the estrogenic activity of the BADGE derivatives, dihydrolysed BADGE (BADGE-4OH) and chlorohydroxy BADGE (BADGE-2Cl), using breast cancer cell (T47D) proliferation assay and estrogen receptor (ER) (alpha) binding assay. These chemicals exhibited T47D cell proliferation at concentrations of 10(-14)-10(-4) M. However, these chemicals did not bind to ER (alpha) in the binding assay.

Assessing estrogenic activity of phytochemicals using transcriptional activation and immature mouse uterotrophic responses

The estrogenic responses of several phytoestrogens including genistein, daidzein, coumestrol, alpha-zearalanol, zearalenone, naringenin, taxifolin and biochanin A were compared over a wide dose range using an in vitro assay that measures transcriptional activation of the estrogen receptor (ER) and an in vivo immature mouse uterotrophic assay consisting of measuring uterine wet weight increase plus sensitive morphological and biochemical endpoints in the uterus. The transcriptional activation assay showed activation of the ER by all compounds tested except taxifolin with varying magnitudes of response as compared to estradiol or diethylstilbestrol. Results from the uterotropic bioassay showed that genistein, coumestrol, zearalanol, and zearalenone caused an increase in uterine wet weight, while naringenin, taxifolin, daidzein and biochanin A failed to do so over the dose range tested. However, sensitive morphological and biochemical parameters such as uterine epithelial cell height increase, uterine gland number increase, and induction of the estrogen-responsive protein lactoferrin demonstrated that all compounds tested in this study gave some measure of estrogenicity although a wide range of estrogenic responses across compounds was shown. Use of multiple in vitro and in vivo estrogenic endpoints as described in this paper will be useful in developing estrogenic profiles for individual compounds and ultimately mixtures of compounds. Furthermore, having an estrogenic "fingerprint" for each phytochemical is an essential first step in determining potential adverse effects of exposure to phytoestrogens.

Cytotoxicity assays for mycotoxins produced by Fusarium strains: a review

Mycotoxins are naturally occurring toxic secondary metabolites of fungi that may be present in food and feed. Several of these mycotoxins have been associated with human and animal diseases. Fusarium species, found worldwide in cereals and other food types for human and animal consumption, are the most important toxigenic fungi in northern temperate regions. The overall economical loss and the detrimental health effects in humans and animals of mycotoxin contamination are enormous and therefore, rapid screening methods will form an important tool in the protection of humans and animals as well as to minimize economical losses by early detection. An overview of methods for the determination of cytotoxicity and the application of such bioassays to screen solid fungal cultures, cereals, respectively, food/feedstuffs for the presence and toxic potential of Fusarium mycotoxins is presented. Various cell lines including different endpoints of toxicity using vertebrate cells and the predictive value of the in vitro assays are reviewed. Bioassays are compared with existing chemical analytical methods and the possibilities and limitations of such systems are discussed. The review is based on 149 references.

Effects of primary exposure to environmental and natural estrogens on vitellogenin production in carp (Cyprinus carpio) hepatocytes

Vitellogenin (vtg) is a precursor of the yolk proteins lipovitelline and phosvitin and is synthesized as a consequence of estrogen-dependent gene expression in female and male hepatocytes of egg-laying vertebrates. Freshly isolated carp hepatocytes of a genetically uniform strain of adult male carp (Cyprinus carpio) were used to investigate the effects of primary exposure to estrogenic compounds on the vitellogenic response to xenoestrogens. Isolated carp hepatocytes were first exposed (primary exposure) to 50 or 100 microM of either methoxychlor (MXCL) or bisphenol A (BPA), different concentrations of estrone (E1; 1 or 10 nM) or 17beta-estradiol (E2; 0.1 or 1 nM) for 2 days. Hepatocytes were exposed to xenoestrogens (secondary exposure) at both 2 and 5 days after isolation. Hepatocytes were cultured for a total period of 8 days. A competitive indirect ELISA was used to determine the level of vtg after 8 days. The concentration of chemicals used for the primary exposure induced vtg to a level that was less than 10% of the response elicited by E2 (1000 nM). A cytotoxic response, measured by MTT, was not observed after primary exposure to any of the xenoestrogens. After primary exposure to MXCL, vtg production in response to E2 was increased by 4-fold, and vitellogenesis in response to E1 treatment was doubled compared with vitellogenesis without pretreatment. No significant differences were observed between primary exposure to 50 and 100 microM MXCL. Primary exposure to 50 and 100 microM BPA increased the maximum vtg production in response to secondary E2 exposure by about 5- and 7-fold, respectively. Primary exposure to BPA (50 and 100 microM) followed by secondary exposure to E1 showed a 4- and 5-fold increase of the vtg synthesis in comparison to E1 exposure alone. Primary exposure to the endogenous estrogens had no significant influence on the vtg synthesis in response to secondary exposure to E1 or E2. Compared to hepatocytes exposed only to MXCL or BPA, primary exposure to E2 increased the vtg synthesis in hepatocytes induced by MXCL or BPA by almost a factor of 2. Primary exposure to E1 increased vitellogenesis after secondary exposure to MXCL only marginally. The present results indicate that weakly estrogenic environmental chemicals such as MXCL and BPA can increase the sensitivity of carp hepatocytes towards endogenous estrogens with respect to VTG synthesis.

Assessment of interactions of diverse ternary mixtures in an estrogen receptor-alpha reporter assay

This study used an MCF-7 cell based ER-alpha reporter gene assay to assess chemical interactions within the following ternary mixtures: (1) three synthetic pesticides, methoxychlor (MXC), o,p-DDT, and dieldrin; (2) three polyaromatic hydrocarbons, benzo[a]pyrene (BAP), 1,2-benzanthracene (BENZ), and chrysene (CHRY); and (3) an endogenous estrogen, [17beta-estradiol, (E(2))]; a phytoestrogen, genistein (GEN); and a synthetic estrogen, o,p-DDT. A full factorial design in which four concentrations of each chemical were assessed in all possible combinations (64 treatment groups) was utilized. In addition, mixtures were tested in both a low range (concentrations near the individual chemical response thresholds) and a high range ( approximately 2-10x higher) experiment. A response surface was estimated using a nonlinear mixed model, and the cumulative response in each mixture was evaluated for departure from additivity. The mixture of E(2), GEN, and DDT exhibited antagonistic interactions (p < 0.001) in both concentration ranges. However, specific interactions between E(2)/GEN and E(2)/DDT differed between the low and high range concentrations. The BAP/BENZ/CHRY mixture did not depart significantly from additivity (p = 0.66) in either concentration range, although response levels were generally low. The MXC/DDT/dieldrin mixture did not depart significantly from additivity in either the high (p = 0.065), or low dose range (p = 0.506), with generally minimal responses dominated by MXC and DDT. This methodology has allowed for a rigorous statistical evaluation of potential departures from additive interactions in endocrine active mixtures. In no case was a significantly greater-than-additive (synergistic) interaction observed.

Comparison of reporter gene assay and immature rat uterotrophic assay of twenty-three chemicals

We performed a reporter gene assay for ERalpha-mediated transcriptional activation and an immature rat uterotrophic assay of 23 chemicals, to study the relationship between these two assays and to examine the usefulness of the reporter gene assay. The chemicals analyzed in the study were as follows: benzophenone, bisphenol A, bisphenol B, bisphenol F, p-cumyl phenol, dibutyl phthalate, dicyclohexylphthalate, dihydrotestosterone, equilin, 17alpha-estradiol, estrone, ethynyl estradiol, genistein, hematoxylin, nonylphenol mixture, 4-n-nonylphenol, norethindrone, norgestrel, octachlorostyrene, 4-n-octylphenol, 4-tert-octylphenol, tributyltin-chloride and zearalenone. To perform the reporter gene assay, HeLa cells were transfected with a rat ERalpha expression construct and an estrogen-regulated luciferase reporter construct. The transcriptional activities of each chemical were tested over concentrations ranging from 10 pM to 10 microM and the EC50, PC50 and PC10 values were calculated. In the immature rat uterotrophic assay, the doses of 21 chemicals, with the exception of dibutyl phthalate and ethynyl estradiol, were 0, 2, 20 and 200 mg/kg; each group consisted of six rats. The doses of dibutyl phthalate and ethynyl estradiol were 0, 40, 200 and 1000 mg/kg per day and 0, 0.2, 2 and 20 microg/kg per day, respectively. In the reporter gene assay, the PC10 values were calculated for 15 chemicals: bisphenol A, bisphenol B, bisphenol F, p-cumyl phenol, dihydrotestosterone, equilin, 17alpha-estradiol, estrone, ethynyl estradiol, genistein, nonylphenol mixture, norethindrone, norgestrel, 4-tert-octylphenol and zearalenone. These chemicals corresponded to the chemicals that tested positive in the uterotrophic assay. The other chemicals were negative in the reporter and uterotrophic assays. Although the EC50 and PC50 values could only be calculated for five and six chemicals, respectively, the PC10 values were shown to be well correlated with the EC50 values by a correlation analysis (R(2)=0.9202). These findings demonstrate that PC10 values are preferable to EC50 and PC50 values for predicting the estrogenic activities of chemicals.

Trifolium pratense (red clover) exhibits estrogenic effects in vivo in ovariectomized Sprague-Dawley rats

Studies were conducted using an ovariectomized rat model to determine the estrogenic and antiestrogenic activity of Trifolium pratense L. (red clover) extracts. A red clover extract, standardized to contain 15% isoflavones was administered by gavage [250, 500 and 750 mg/(kg x d)] to virgin, ovariectomized 50-d-old Sprague-Dawley rats, for 21 d in the presence and absence of 17beta-estradiol [50 microg/(kg x d)]. Estrogenic effects included an increase in uterine weight, vaginal cell cornification and mammary gland duct branching. Red clover produced a dose-dependent increase in uterine weight and differentiated vaginal cells at the two higher doses, but it did not stimulate cell proliferation in the mammary glands. Neither antiestrogenic nor additive estrogenic properties were observed in any of the tissues studied. These data suggest that red clover extract is weakly estrogenic in the ovariectomized rat model.

Cell response endpoints enhance sensitivity of the immature mouse uterotropic assay

Outbred immature CD-1 mice were subcutaneously (s.c.) injected once on postnatal day 17 or on postnatal days 17, 18, and 19 with 17beta-estradiol, diethylstilbestrol, tamoxifen, 4-hydroxytamoxifen, methoxychlor, the methoxychlor metabolite HPTE, nonylphenol, o,p'-DDT, endosulfan, or kepone over a wide dose range (0.1 to 1,000,000 microg/kg). On the day following the last injection, uterine weight/body weight ratios were determined and uterine tissues processed for histologic examination. All compounds except endosulfan and kepone increased uterine wet weight compared to vehicle controls; however, the dose response curve and magnitude of response varied depending on the compound. Choosing the maximum wet weight dose for each compound, uterine tissue was evaluated for epithelial cell height, epithelial and stromal cell proliferation, endometrial gland number, and induction of estrogen-inducible proteins lactoferrin and complement C3. All compounds elicited estrogen-responsive changes in these endpoints that were individually more sensitive than uterine weight alone. We conclude that these endpoints enhance the sensitivity of the uterotropic bioassay.