Modulation of aromatase activity and mRNA by various selected pesticides in the human choriocarcinoma JEG-3 cell line

Currently used pesticides and their mixtures affect the function of sex hormone receptors and aromatase enzyme activity

The endocrine-disrupting potential of pesticides is of health concern, since they are found ubiquitously in the environment and in food items. We investigated in vitro effects on estrogen receptor (ER) and androgen receptor (AR) transactivity, and aromatase enzyme activity, of the following pesticides: 2-methyl-4-chlorophenoxyacetic acid (MCPA), terbuthylazine, iodosulfuron-methyl-sodium, mesosulfuron-methyl, metsulfuron-methyl, chlormequat chloride, bitertanol, propiconazole, prothioconazole, mancozeb, cypermethrin, tau fluvalinate, malathion and the metabolite ethylene thiourea (ETU). The pesticides were analyzed alone and in selected mixtures. Effects of the pesticides on ER and AR function were assessed in human breast carcinoma MVLN cells and hamster ovary CHO-K1 cells, respectively, using luciferase reporter gene assays. Effects on aromatase enzyme activity were analyzed in human choriocarcinoma JEG-3 cells, employing the classical [(3)H](2)O method. Five pesticides (terbuthylazine, propiconazole, prothioconazole, cypermethrin and malathion) weakly induced the ER transactivity, and three pesticides (bitertanol, propiconazole and mancozeb) antagonized the AR activity in a concentration-dependent manner. Three pesticides (terbuthylazine, propiconazole and prothioconazole) weakly induced the aromatase activity. In addition, two mixtures, consisting of three pesticides (bitertanol, propiconazole, cypermethrin) and five pesticides (terbuthylazine, bitertanol, propiconazole, cypermethrin, malathion), respectively, induced the ER transactivity and aromatase activity, and additively antagonized the AR transactivity. In conclusion, our data suggest that currently used pesticides possess endocrine-disrupting potential in vitro which can be mediated via ER, AR and aromatase activities. The observed mixture effects emphasize the importance of considering the combined action of pesticides in order to assure proper estimations of related health effect risks.

The placenta in toxicology. Part IV: Battery of toxicological test systems based on human placenta

This review summarizes the potential and also some limitations of using human placentas, or placental cells and structures for toxicology testing. The placenta contains a wide spectrum of cell types and tissues, such as trophoblast cells, immune cells, fibroblasts, stem cells, endothelial cells, vessels, glands, membranes, and many others. It may be expected that in many cases the relevance of results obtained from human placenta will be higher than those from animal models due to species specificity of metabolism and placental structure. For practical and economical reasons, we propose to apply a battery of sequential experiments for analysis of potential toxicants. This should start with using cell lines, followed by testing placenta tissue explants and isolated placenta cells, and finally by application of single and dual side ex vivo placenta perfusion. With each of these steps, the relative workload increases while the number of feasible repeats decreases. Simultaneously, the predictive power enhances by increasing similarity with in vivo human conditions. Toxic effects may be detected by performing proliferation, vitality and cell death assays, analysis of protein and hormone expression, immunohistochemistry or testing functionality of signaling pathways, gene expression, transport mechanisms, and so on. When toxic effects appear at any step, the subsequent assays may be cancelled. Such a system may be useful to reduce costs and increase specificity in testing questionable toxicants. Nonetheless, it requires further standardization and end point definitions for better comparability of results from different toxicants and to estimate the respective in vivo translatability and predictive value.

Cellular effects of metolachlor exposure on human liver (HepG2) cells

Metolachlor is one of the most commonly used herbicides in the United States. Protein synthesis is inhibited when roots and shoots of susceptible plants absorb this synthetic herbicide. While quite effective in killing weeds, several studies have shown that exposure to metolachlor results in decreased cell proliferation, growth and reproductive ability of non-target organisms. However, the mode of metolachlor action in non-target organisms has not yet been elucidated. The current study assessed effects of metolachlor exposure on immortalized human liver (HepG2) cells. Results from cell proliferation assays showed that a 72-h exposure to 50 parts per billion (ppb) metolachlor significantly inhibited growth of these cells compared to untreated controls while a decrease in the cell division rate required exposure to 500 ppb metolachlor for 48 h. Flow cytometry analysis of cell cycle distribution revealed that 500 ppb metolachlor treatment resulted in fewer HepG2 cells in G2/M phase after 72 h. Real-time PCR analysis showed a significant decrease in the abundance of the cyclin A transcripts after 12h in cells exposed to 300 ppb metolachlor. These results suggest metolachlor may affect progression through the S phase of the cell cycle and entrance into the G2 phase.

Endocrine-disrupting effects of thioxanthone photoinitiators

Photoinitiators used in food packaging ink, such as 2-isopropylthioxanthone (2-ITX), have been shown to migrate into food and beverages. Recently, several studies indicated that 2-ITX might be an endocrine-disrupting chemical. In this work, the effects of 2-ITX, 4-isopropylthioxanthone (4-ITX), 2,4-diethylthio xanthone (2,4-diethyl-TX), 2-chlorothioxanthone (2-chloro-TX), and 1-chloro-4-propoxythioxanthone (1-chloro-4-propoxy-TX) on steroidogenesis and androgen and estrogen receptor-mediated transcription activation have been studied using human H295R adrenocarcinoma cells and yeast hormone bioassays, respectively. None of the compounds showed androgenic or estrogenic activities, but clear antiandrogenic and antiestrogenic activities were observed for 2-ITX, 4-ITX, and 2,4-diethyl-TX, whereas 2-chloro-TX showed only antiandrogenic activity. In an adapted version of the H295R steroidogenesis assay, using gas chromatography-tandem mass spectrometry analysis of H295R media, all five compounds increased levels of 17ß-estradiol and estrone. H295R cells incubated with 2-ITX also showed significantly reduced androgen and increased pregnenolone and progesterone levels. Expression of particular steroidogenic genes, including the one encoding for aromatase (CYP19A1), was significantly upregulated after incubation of H295R cells with 2-ITX, 4-ITX, and 2,4-diethyl-TX. In line with the increased CYP19A1 mRNA expression, 2-ITX increased catalytic activity of aromatase in H295R cells as measured by cognate aromatase assays. The results indicate that thioxanthone derivatives can act as potential endocrine disruptors both at the level of nuclear receptor signaling and steroid hormone production.

The effect of triclosan on hormone secretion and viability of human choriocarcinoma JEG-3 cells

Triclosan is an antimicrobial agent frequently used in pharmaceuticals and personal care products. We analyzed triclosan for its action on placental secretion of progesterone, estradiol and human chorionic gonadotropin in vitro in the JEG-3 cells. We also investigated its action on cell viability, proliferation and apoptosis. The JEG-3 cells were cultured with increasing doses of triclosan (1×10(-9)-1×10(-4) M) for 24, 48 and 72 h. Triclosan was found to increase estradiol and progesterone secretion after short- and long-term exposure. The stimulatory effect was observed up to 10 μM after short- and long-term exposure to triclosan. In addition, triclosan caused an adverse effect on β-hCG secretion. The highest doses of triclosan (50 and 100 μM) showed a strong cytotoxic effect. Anti proliferative and pro-apoptotic effects were also observed. Overall, this study demonstrates that triclosan may indirectly disrupt steroidogenesis which may, in turn, affect placental development and consequently fetal growth.

Aromatase up-regulation, insulin and raised intracellular oestrogens in men, induce adiposity, metabolic syndrome and prostate disease, via aberrant ER-α and GPER signalling

For some years now, reduced testosterone levels have been related to obesity, insulin resistance, type 2 diabetes, heart disease, benign prostatic hypertrophy and even prostate cancer--often considered guilty more by association, than actual cause--with little attention paid to the important role of increased intracellular oestrogen, in the pathogenesis of these chronic diseases. In the final stage of the steroidogenic cascade, testosterone is metabolised to oestradiol by P450 aromatase, in the cytoplasm of adipocytes, breast cells, endothelial cells and prostate cells, to increase intracellular oestradiol concentration at the expense of testosterone. It follows therefore, that any compound that up-regulates aromatase, or any molecule that mimics oestrogen, will not only increase the activation of the mainly proliferative, classic ER-α, oestrogen receptors to induce adipogenesis and growth disorders in oestrogen-sensitive tissues, but also activate the recently identified transmembrane G protein-coupled oestrogen receptors (GPER), and deleteriously alter important intracellular signalling sequences, that promote mitogenic growth and endothelial damage. This paper simplifies how stress, xeno-oestrogens, poor dietary choices and reactive toxins up-regulate aromatase to increase intracellular oestradiol production; how oestradiol in combination with leptin and insulin cause insulin resistance and leptin resistance through aberrant serine phosphorylation; how the increased oestradiol, insulin and leptin stimulate rapid, non-genomic G protein-coupled phosphorylation cascades, to increase fat deposition and create the vasoconstrictive, dyslipidemic features of metabolic syndrome; how aberrant GPER signalling induces benign prostatic hypertrophy; and how increased intracellular oestradiol stimulates mitogenic change and tumour-cell activators, to cause prostate cancer. In essence, the up-regulation of aromatase produces increased intracellular oestradiol, increases ER-α activation and increases GPER activation, in combination with insulin, to cause aberrant downstream transduction signaling, and thus induce metabolic syndrome and mitogenic prostate growth. To understand this fact, that raised intracellular oestradiol levels in men, induce and promote obesity, gynecomastia, metabolic syndrome, type two diabetes, benign prostatic hypertrophy and prostate cancer, rather than low testosterone, represents a shift in medical thinking, a new awareness, that will reduce the rising incidence of obesity, metabolic syndrome and prostate disease, and significantly improve the health of men worldwide.

Environmental behavior of the chiral triazole fungicide fenbuconazole and its chiral metabolites: enantioselective transformation and degradation in soils

Fenbuconazole is a widely used systemic agricultural fungicide of the triazole class with one chiral center. In the present study, the enantioselective degradation of fenbuconazole and its chiral metabolites, RH-9129 and RH-9130, in two soils under aerobic and anaerobic conditions were investigated using a chiral OD-RH column on a reversed-phase liquid chromatography-tandem mass spectrometry system. Under aerobic or anaerobic conditions, the results showed the occurrence of enantioselectivity with (-)-fenbuconazole preferentially degraded in both soils. Further enantioselective analysis of converted products showed that the concentrations of four RH-9129 and RH-9130 stereoisomers were different from each other under both aerobic and anaerobic conditions. The four stereoisomer concentrations followed the order (-)-RH-9129 > (+)-RH-9129 > (-)-RH-9130 > (+)-RH-9130 in Langfang alkaline soil. However, in the case of Changsha acidic soil, different RH-9129 and RH-9130 stereoisomer patterns were produced in the order (-)-RH-9129 > (+)-RH-9129 > (+)-RH-9130 > (-)-RH-9130. The (-)-RH-9129 stereoisomer had the highest concentration formed by transformation of fenbuconazole in both soils. The degradation of RH-9129 and RH-9130 in the two soils is also stereoselective under both aerobic and anaerobic conditions, the results indicating that the (+)-RH-9130 enantiomer degraded faster than the (-)-RH-9130 enantiomer and the (+)-RH-9129 enantiomer degraded faster than the (-)-RH-9129 enantiomer. In addition, the (-)-RH-9129 isomer exhibited the slowest degradation rate in both soils. This study provides the first experimental evidence of stereoselective degradation and transformation of fenbuconazole as well as its chiral metabolites in the environment.

Herbicide metolachlor causes changes in reproductive endocrinology of male wistar rats

S-metolachlor is a chloroacetanilide herbicide widely used in the agriculture to control weeds and was demonstrated that it increases the activity of the aromatase enzyme in cell cultures, which may culminate as endocrine disruption action in vivo. To investigate this hypothesis, prepubertal Wistar male rats were exposed to metolachlor (5 or 50 mg/kg/day, NOEL for reproductive toxicity: 23.5-26.0 mg/kg/day) from PND23 (postnatal day) to PND53. During this period, the growth of the animals and the age and weight at puberty were recorded. In PND53, tissues were collected and the analysis of LH, FSH, testosterone, dihydrotestosterone (DHT), estradiol serum concentrations, morphometric evaluation of the seminiferous epithelium, and weight of the testes and the seminal vesicle (undrained and drained) was performed (Statistical difference: P < 0.05). Metolachlor caused an increase in serum concentrations of testosterone, estradiol, and FSH and a reduction in DHT but did not alter the LH. There were also observed a higher amount of fluid in the seminal vesicles, precocious puberty, and changes in morphology of the seminiferous epithelium of treated animals. We demonstrated in this paper that prepubertal exposure to S-metolachlor caused changes in reproductive endocrinology of male rats.

Synergic effect of retinoic acid and extremely low frequency magnetic field exposure on human neuroblastoma cell line BE(2)C

The aim of the present study was to assess whether exposure to a sinusoidal extremely low frequency magnetic field (ELF-MF; 50 Hz, 1 mT) can affect proliferation and differentiation in the human neuroblastoma cell line BE(2)C, which is representative of high risk neuroblastomas. Cells were subjected to ELF-MF exposure in the presence or absence of a neuronal differentiating agent (all-trans-retinoic acid, ATRA) for 24-72 h. In each experiment, ELF-MF-exposed samples were compared to sham-exposed samples. Cells exposed to ELF-MF combined with retinoic treatment showed a decreased cellular proliferation and an increased proportion of G(0)/G(1) phase cells compared to cells exposed to either treatment alone. Moreover, ELF-MF- and ATRA-treated cells showed more differentiated morphological traits (a higher neurite number/cell, an increased neurite length), together with a significant increase of mRNA levels of p21(WAF1/CIP1) and cdk5 genes, both involved in neuronal differentiation. In addition, the expression of cyp19 gene, which is involved both in neuronal differentiation and stress response, was evaluated; cyp19 gene expression was enhanced by ATRA treatment and significantly enhanced further by ELF-MF exposure combined with ATRA. In conclusion, our data suggest that ELF-MF exposure can strengthen ATRA effects on neuroblastoma cells.

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.

The role of oestrogen in the pathogenesis of obesity, type 2 diabetes, breast cancer and prostate disease

A detailed review of the literature was performed in a bid to identify the presence of a common link between specific hormone interactions and the increasing prevalence of global disease. The synergistic action of unopposed oestrogen and leptin, compounded by increasing insulin, cortisol and xeno-oestrogen exposure directly initiate, promote and exacerbate obesity, type 2 diabetes, uterine overgrowth, prostatic enlargement, prostate cancer and breast cancer. Furthermore these hormones significantly contribute to the incidence and intensity of anxiety and depression, Alzheimer's disease, heart disease and stroke. This review, in collaboration with hundreds of evidence-based clinical researchers, correlates the significant interactions these hormones exert upon the upregulation of p450 aromatase, oestrogen, leptin and insulin receptor function; the normal status quo of their binding globulins; and how adduct formation alters DNA sequencing to ultimately produce an array of metabolic conditions ranging from menopausal symptoms and obesity to Alzheimer's disease and breast and prostate cancer. It reveals the way that poor diet, increased stress, unopposed endogenous oestrogens, exogenous oestrogens, pesticides, xeno-oestrogens and leptin are associated with increased aromatase activity, and how its products, increased endogenous oestrogen and lowered testosterone, are associated with obesity, type 2 diabetes, Alzheimer's disease and oestrogenic disease. This controversial break-through represents a paradigm shift in medical thinking, which can prevent the raging pandemic of diabetes, obesity and cancer currently sweeping the world, and as such, it will reshape health initiatives, reduce suffering, prevent waste of government expenditure and effectively transform preventative medicine and global health care for decades.

Development of an ex vivo brown trout (Salmo trutta fario) gonad culture for assessing chemical effects on steroidogenesis

A variety of natural and synthetic environmental substances have been shown to disrupt vertebrate reproduction through mimicking or modifying the regulation of the endocrine system. Tests to screen for any such chemicals that directly interact with the steroid hormone receptors are widely available; however, few tests have been developed to identify chemicals that affect endocrine function through non-receptor mediated mechanisms. The aim of this study was, therefore, to develop an assay for the identification of substances that disrupt the activity of enzymes involved in the sex steroid biosynthesis cascade, in particular the aromatase enzyme, CYP19, that catalyses the final conversion of androgens to estrogens. A gonad ex vivo assay was developed using gonad explants harvested from juvenile brown trout and cultured in a modified Leibovitz medium. Effects on sex steroid biosynthesis were quantified through measurement of 17β-estradiol (E2) and testosterone (T) concentrations in the medium after 2 days incubation. Exposure of ovary explants to 100 ng/mL 1,4,6-androstatriene-3,17-dione (ATD), a potent pharmaceutical aromatase inhibitor, reduced E2 concentrations and elevated T concentrations confirming that CYP19 activity could be inhibited in the assay. Exposure of ovary explants to 250 ng/mL prochloraz, an imidazole fungicide, also reduced E2 concentrations but did not affect T levels, consistent with reports that in addition to inhibiting CYP19 activity, prochloraz also inhibits enzymes in the steroidogenic pathway upstream of the CYP19 enzyme. Exposure to a third chemical, tributyltin (TBT), did not affect T or E2 concentrations, further supporting previous evidence that the CYP19 modulating effects of this chemical are not mediated through direct inhibition of CYP19 activity. These results demonstrate that the gonad ex vivo assay developed here can be successfully used to identify substances that disrupt sex steroid biosynthesis and further that it has the potential to inform on their specific mode of action.

Prostate cancer risk and exposure to pesticides in British Columbia farmers

BACKGROUND

Several epidemiologic studies have reported an increased risk of prostate cancer among farmers. Our aim was to assess the risk of developing prostate cancer in relation to exposure to specific active compounds in pesticides.

METHOD

A case-control approach was used with 1,516 prostate cancer patients and 4,994 age-matched internal controls consisting of all other cancer sites excluding lung cancer and cancers of unknown primary site. Lifetime occupational history was obtained through a self-administered questionnaire and used in conjunction with a job exposure matrix to estimate the participants' lifetime cumulative exposure to approximately 180 active compounds in pesticides. Conditional logistic regression was used to assess prostate cancer risk, adjusting for potential confounding variables and effect modifiers. These include age, ethnicity, alcohol consumption, smoking, education, and proxy respondent.

RESULTS AND CONCLUSIONS

The significant association between prostate cancer risk and exposure to DDT (OR = 1.68; 95% CI: 1.04-2.70 for high exposure), simazine (OR = 1.89; 95% CI: 1.08-3.33 for high exposure), and lindane (OR = 2.02; 95% CI: 1.15-3.55 for high exposure) is in keeping with those previously reported in the literature. We also observed a significant excess risk for several active ingredients that have not been previously reported in the literature such as dichlone, dinoseb amine, malathion, endosulfan, 2,4-D, 2,4-DB, and carbaryl. Some findings in our study were not consistent with those reported in the literature, including captan, dicamba, and diazinon. It is possible that these findings showed a real association and the inconsistencies reflected differences of characteristics between study populations.

Endocrine disrupting chemicals targeting estrogen receptor signaling: identification and mechanisms of action

Many endocrine disrupting chemicals (EDCs) adversely impact estrogen signaling by interacting with two estrogen receptors (ERs): ERα and ERβ. Though the receptors have similar ligand binding and DNA binding domains, ERα and ERβ have some unique properties in terms of ligand selectivity and target gene regulation. EDCs that target ER signaling can modify genomic and nongenomic ER activity through direct interactions with ERs, indirectly through transcription factors such as the aryl hydrocarbon receptor (AhR), or through modulation of metabolic enzymes that are critical for normal estrogen synthesis and metabolism. Many EDCs act through multiple mechanisms as exemplified by chemicals that bind both AhR and ER, such as 3-methylcholanthrene. Other EDCs that target ER signaling include phytoestrogens, bisphenolics, and organochlorine pesticides, and many alter normal ER signaling through multiple mechanisms. EDCs can also display tissue-selective ER agonist and antagonist activities similar to selective estrogen receptor modulators (SERMs) designed for pharmaceutical use. Thus, biological effects of EDCs need to be carefully interpreted because EDCs can act through complex tissue-selective modulation of ERs and other signaling pathways in vivo. Current requirements by the U.S. Environmental Protection Agency require some in vitro and cell-based assays to identify EDCs that target ER signaling through direct and metabolic mechanisms. Additional assays may be useful screens for identifying EDCs that act through alternative mechanisms prior to further in vivo study.

Anti-androgenic activities of environmental pesticides in the MDA-kb2 reporter cell line

Pesticides have been suspected to act as endocrine disruptive compounds (EDCs) through several mechanisms of action, however data are still needed for a number of currently used pesticides. In the present study, 30 environmental pesticides selected from different chemical classes (azole, carbamate, dicarboximide, organochlorine, organophosphorus, oxadiazole, phenylureas, pyrazole, pyrimidine, pyrethroid and sulfonylureas) were tested for their ability to alter in vitro the transcriptional activity of the androgen receptor in the MDA-kb2 reporter cell line. The responsiveness of the system was checked by using a panel of reference ligands of androgen and glucocorticoid receptors. When tested alone at concentrations up to 10 μM, none of the studied pesticides were able to induce the reporter gene after a 18 h exposure. Conversely, co-exposure experiments with 0.1 nM dihydrotestosterone (DHT) allowed identifying 15 active pesticides with IC(50) ranging from 0.2 μM for vinclozolin to 12 μM for fenarimol. Fipronil and bupirimate were here newly described for their AR antagonistic activity.

Endocrine disruption in wild populations of chub (Leuciscus cephalus) in contaminated French streams

The aim of this study was to assess endocrine disruptive effects in wild population of fish in five French rivers selected to represent different pollution contexts at two seasons (summer and fall). For that purpose, a panel of biometrical parameters (length, weight, and gonado-somatic index: GSI) and biochemical (ethoxyresorufin-O-deethylase: EROD, vitellogenin: VTG, and brain aromatase) and histological biomarkers (gonads histology) were used in chub (Leuciscus cephalus), a common cyprinid fish species. In fish from the reference site, EROD activity and VTG levels were low at the two seasons. Brain aromatase activities (AAs) were similar to other species and increased with increasing GSI and gonad maturation. Among the four contaminated sites, the Jalle d'Eysines River was the most impacted site. At this site, fish were exposed to estrogenic substances as demonstrated by the VTG induction in males and the arrest of development of the gonads that led to lower brain AA compared to fish from the reference site. In fish from other contaminated sites, EROD activity was induced as compared to fish from the reference site and some males had elevated concentrations of VTG. Moreover, the presence of aromatase-inhibiting compounds was demonstrated in the sediments of three contaminated sites, even if the precise nature of contaminants is not known. This study provides new data concerning endocrine disruption in wild fish populations inhabiting French rivers and demonstrates that measurements of in vivo and in vitro aromatase could be used as biomarkers of endocrine disruption in field studies.

Sensitivity of New Zealand mudsnail Potamopyrgus antipodarum (Gray) to a specific aromatase inhibitor

The freshwater prosobranch Potamopyrgus antipodarum (Molluska, Hydrobiidea, Smith 1889) has been proposed as a suitable species to assess the impact of endocrine disrupting compounds (EDC) in aquatic ecosystems. Steroid hormone biosynthesis pathway is potentially an important target for EDC, and vertebrate-like sex steroids seem to play a functional role in the control of mollusk reproduction. To assess the response and the sensitivity of P. antipodarum to disrupters of the steroid hormone biosynthesis pathway, we have experienced the action of a specific vertebrate aromatase inhibitor, fadrozole, acting on 17beta-estradiol synthesis in two separate 28 and 42d exposures. Fadrozole had effects consistent with the expected mechanism of action. A decrease of the reproduction parameters (such as on the number of neonates and number of embryos in the brood pouch) in a dose-dependant manner was observed. The steroids levels were also impaired with the ratio 17beta-estradiol/testosterone decreased by half in exposed snails. This shift of the steroids balance was accompanied by some alteration in the gonads histology and immunohistochemistry in fadrozole-exposed snails. This study highlights the value role of P. antipodarum as a test species for assessing EDC effects in aquatic wildlife.

Induction of oxidative stress and cytotoxicity by PCB126 in JEG-3 human choriocarcinoma cells

The compound 3,3',4,4',5-pentachlorobiphenyl (PCB126) exists in various environmental media, which may have adverse effects on human health. In the present study, induction of the oxidative stress and cytotoxicity by PCB126 were investigated in the human choriocarcinoma cell line JEG-3 cells. Both the reactive oxygen species (ROS) generation and lipid peroxidation production of malondialdehyde (MDA) were obviously increased. Whereas the activity of antioxidant enzymes (superoxide dismutase [SOD] and catalase [CAT]) and glutathione (GSH) content were declined with dose-dependent manners. Furthermore, the result of the cytotoxicity assay showed a clear, dose-dependent growth inhibition effect of PCB126 in JEG-3 cells. Our present results revealed that PCB126 exhibited significant oxidative stress and cytotoxicity in human trophoblast. Given the widespread use of PCBs, a more comprehensive understanding of the significance of reproductive toxicity of PBCs is imperative for improving risk assessment and regulation of these chemicals.

Bioanalytical characterisation of multiple endocrine- and dioxin-like activities in sediments from reference and impacted small rivers

A comprehensive evaluation of organic contamination was performed in sediments sampled in two reference and three impacted small streams where endocrine disruptive (ED) effects in fish have been evidenced. The approach combined quantitative chemical analyses of more than 50 ED chemicals (EDCs) and a battery of in vitro bioassays allowing the quantification of receptor-mediated activities, namely estrogen (ER), androgen (AR), dioxin (AhR) and pregnane X (PXR) receptors. At the most impacted sites, chemical analyses showed the presence of natural estrogens, organochlorine pesticides, parabens, polycyclic aromatic hydrocarbons (16 PAHs), bisphenol A and alkylphenols, while synthetic steroids, myco-estrogens and phyto-estrogens were not detected. Determination of toxic-equivalent amounts showed that 28-96% of estrogenic activities in bioassays (0.2-6.3 ng/g 17beta-estradiol equivalents) were explained by 17beta-estradiol and estrone. PAHs were major contributors (20-60%) to the total dioxin-like activities. Interestingly, high PXR and (anti)AR activities were detected; however, the targeted analysed compounds could not explain the measured biological activities. This study highlighted the presence of multiple organic EDCs in French river sediments subjected to mixed diffuse pollution, and argues for the need to further identify AR and PXR active compounds in the aquatic environment.

P19 neuronal differentiation and retinoic acid metabolism as criteria to investigate atrazine, nitrite, and nitrate developmental toxicity

Atrazine and nitrogenous fertilizers are agrochemical contaminants frequently detected in water systems in North America. Several studies reported their ability to affect amphibian and mammalian development. Retinoids, supplied in the diet or synthesized by cells, are essential to embryogenesis. Disturbance of their homeostasis may lead to teratogenic effects. Retinoic acid (RA) is a major retinoid regulator of cell proliferation and differentiation. Previous studies reported alterations of retinoid stores in bullfrogs of Yamaska River subwatersheds (Québec, Canada), a region of intensive agricultural activities associated with atrazine, nitrate, and nitrite contaminants. These contaminants could affect RA metabolism and RA-mediated processes. Mouse P19 embryonic stem cells, which can differentiate to neurons in response to RA, were used to test this hypothesis. Cells were cultured in the absence or presence of contaminants during neuroinduction with RA and assayed by flow cytometry for expression of stage-specific embryonic antigen-1 (SSEA1) (embryonic marker) and betaIII-tubulin (neuronal marker). Cell cultures were also analyzed for RA metabolism by high performance liquid chromotagraphy (HPLC). Downregulation of SSEA1 paralleled betaIII-tubulin upregulation in an RA concentration-dependent manner. Atrazine, nitrate, and nitrite did not affect differentiation at environmentally encountered micromolar concentrations. However, low molar nitrite prevented RA-induced SSEA1 downregulation and decreased betaIII-tubulin appearance. Decreased cell viability/proliferation accompanied these differentiation effects. P19 cells metabolized RA to polar retinoids. RA metabolism was not affected at any concentration of atrazine, nitrate, or nitrite. Environmentally relevant levels of these contaminants, thus, had no gross effect on neurodifferentiation and RA catabolism of embryonic stem cells. P19 cell-based bioassays may provide valuable tools in monitoring developmental toxicity.

Why pesticides could be a common cause of prostate and breast cancers in the French Caribbean Island, Martinique. An overview on key mechanisms of pesticide-induced cancer

Prostate and breast cancers have become very frequent in Martinique. We previously conducted a multifactorial analysis in the French Caribbean Island, Martinique, in order to elucidate the aetiology of prostate cancer. Using a linear regression analysis, we found that the growth curves of incidence rates for Martinique and metropolitan France have been significantly diverging since 1983. Although a Caribbean genetic susceptibility factor may be involved in prostate carcinogenesis: this factor, because it could not have changed during the observation period, cannot per se account for the growing incidence of this cancer in the island. We therefore suggested that among possible environmental factors, the intensive and prolonged exposure to Carcinogenic, Mutagenic and/or Reprotoxic (CMR) or presumed CMR pesticides may account for the observed growing incidence of prostate cancer and thus may be involved in prostate carcinogenesis. In this study, we further attempt to show that due to their carcinogenic properties, pesticides and especially organochlorine pesticides may in fact be causally implicated in the growing incidence of prostate cancer in Martinique. Also, we suggest that CMR or presumed CMR pesticides may be causally involved in the growing incidence of breast cancer through a common endocrine disruption mechanism. We therefore propose that protective medical recommendations should be immediately set up and carried out by general practitioners, paediatricians, obstetricians, gynaecologists and urologists; and that public health measures of primary precaution and prevention should be urgently taken in close collaboration with health professionals in order to protect population, more especially pregnant women and children, with the final objective perhaps that these medical recommendations and public health measures will stop Martinique's cancer epidemic.

The watershed as a conceptual framework for the study of environmental and human health

The watershed provides a physical basis for establishing linkages between aquatic contaminants, environmental health and human health. Current attempts to establish such linkages are limited by environmental and epidemiological constraints. Environmental limitations include difficulties in characterizing the temporal and spatial dynamics of agricultural runoff, in fully understanding the degradation and metabolism of these compounds in the environment, and in understanding complex mixtures. Epidemiological limitations include difficulties associated with the organization of risk factor data and uncertainty about which measurable endpoints are most appropriate for an agricultural setting. Nevertheless, it is our contention that an adoption of the watershed concept can alleviate some of these difficulties. From an environmental perspective, the watershed concept helps identify differences in land use and application of agrichemicals at a level of resolution relevant to human health outcomes. From an epidemiological perspective, the watershed concept places data into a construct with environmental relevance. In this perspectives paper, we discuss how the watershed can provide a conceptual framework for studies in environmental and human health.

Potential effects of environmental contaminants on P450 aromatase activity and DNA damage in swallows from the Rio Grande and Somerville, Texas

Cliff swallows (Petrochelidon pyrrhonota) and cave swallows (P. fulva) were sampled during the breeding season at several locations in the Rio Grande, Texas, to evaluate the potential effects of environmental contaminants on P450 aromatase activity in brain and gonads and DNA damage in blood cells. The tritiated water-release aromatase assay was used to measure aromatase activity and flow cytometry was used to measure DNA damage in nucleated blood cells. There were no significant differences in brain and gonadal aromatase activities or in estimates of DNA damage (HPCV values) among cave swallow colonies from the Lower Rio Grande Valley (LRGV) and Somerville. However, both brain and gonadal aromatase activities were significantly higher (P < 0.05) in male cliff swallows from Laredo than in those from Somerville. Also, DNA damage estimates were significantly higher (P < 0.05) in cliff swallows (males and females combined) from Laredo than in those from Somerville. Contaminants of current high use in the LRGV, such as atrazine, and some of the highly persistent organochlorines, such as toxaphene and DDE, could be potentially associated with modulation of aromatase activity in avian tissues. Previous studies have indicated possible DNA damage in cliff swallows. We did not observe any differences in aromatase activity or DNA damage in cave swallows that could be associated with contaminant exposure. Also, the differences in aromatase activity and DNA damage between male cliff swallows from Laredo and Somerville could not be explained by contaminants measured at each site in previous studies. Our study provides baseline information on brain and gonadal aromatase activity in swallows that could be useful in future studies.

DDT and its metabolite DDE alter steroid hormone secretion in human term placental explants by regulation of aromatase activity

Placental explants were used to compare the effects of two isomers of DDT (1,1,1,-trichloro-2,2-bis(p-chlorophenyl)ethane), p,p'-DDT and o,p'-DDT and their metabolites p,p'-DDE and o,p'-DDE (1,1,-dichloro-2,2-bis(p-chlorophenyl)ethylene) on steroid hormone secretion (estradiol (E2) and progesterone (P4)). Explants were treated with 1, 10, 100ng/ml or 1microg/ml of each compound for 24h. We found that all investigated compounds at all doses caused reductions of estradiol secretion. Moreover, it was shown that the inhibition of estradiol secretion was due to direct action on aromatase activity. Twenty-four-hour exposure to p,p'-DDE, o,p'-DDT or o,p'-DDE at doses of 100ng/ml or 1microg/ml increased P4 secretion, suggesting that these compounds act on P450scc. The fluorometric assay confirmed that all investigated compounds inhibited aromatase activity at a concentration of 100ng/ml. Our findings suggest that by decreasing estradiol secretion with concomitant stimulation of progesterone secretion, DDT could be a factor that influences the outcome of pregnancy.