Induction of hepatic aromatase by p,p'-DDE in adult male rats

Impaired energy expenditure following exposure to either DDT or DDE in mice may be mediated by DNA methylation changes in brown adipose

The insecticide dichlorodiphenyltrichloroethane (DDT) and its persistent metabolite, dichlorodiphenyldichloroethylene (DDE), have been associated with increased adiposity and obesity in multiple generations of rodents and humans. These lipophilic pollutants accumulate in adipose tissue and appear to decrease energy expenditure through the impairment of thermogenesis in brown adipose tissue (BAT). We hypothesized that impaired thermogenesis is due to persistent epigenetic modifications of BAT. To address this, we exposed C57BL/6 J mice to DDT or DDE from gestational day (GD) 11.5 to postnatal day (PND) 5, evaluated longitudinal body temperature, and performed reduced representation bisulfite sequencing and RNA sequencing of BAT from infant and adult offspring. Exposure to DDT or DDE reduced core body temperature in adult mice, and differential methylation at the pathway and gene level was persistent from infancy to adulthood. Furthermore, thermogenesis and biological pathways essential for thermogenic function, such as oxidative phosphorylation and mechanistic target of rapamycin kinase (mTOR) signaling, were enriched with differential methylation and RNA transcription in adult mice exposed to DDT or DDE. PAZ6 human brown preadipocytes were differentiated in the presence of DDT or DDE to understand the brown adipocyte-autonomous effect of these pollutants. In vitro exposure led to limited changes in RNA expression; however, mitochondrial membrane potential was decreased in vitro with 0.1 µM and 1 µM doses of DDT or DDE. These results demonstrate that concentrations of DDT and DDE relevant to human exposure have a significant effect on thermogenesis, the transcriptome, and DNA methylome of mouse BAT and the mitochondrial function of human brown adipocytes.

POPs in long-finned pilot whales mass stranded in Iceland as a proxy for their physiological condition

Long-finned pilot whales (Globicephala melas) are the most frequently stranded cetaceans in the world; however, the predominant drivers of these events are poorly understood. In this study the levels of persistent organic pollutants from pilot whales stranded in North-east Iceland were quantified and compared to historical data and physical parameters to investigate whether contaminant load may have influenced the physiological state of stranded individuals, how these loads fluctuate with sex and age group, and if this is consistent with the literature. Historical comparison was also carried out to discern how pollutant contamination has changed throughout the past few decades. DDE, transnonachlor and PCB-153 were the top three pollutants respectively. The accumulation of POPs was greater on average in immature individuals than adults, whilst among adults, males had higher concentration than females. Moreover, despite an indication of decreasing POP loads throughout the years, knowledge of harmful thresholds remains exceedingly limited.

Effects of chronic dichlorodiphenyldichloroethylene exposure on testosterone secretion and steroidogenic pathway in the male gonad

Endocrine disrupting chemicals are present in the environment and/or in consumer products. These agents have the capacity to mimic and/or antagonize endogenous hormones and thus perturb the endocrine axis. The male reproductive tract expresses steroid hormone (androgen and estrogen) receptors at high levels and is a major target for endocrine disrupting chemicals. In this study, Long-Evans male rats were exposed to dichlorodiphenyldichloroethylene, a metabolite of dichlorodiphenyltrichloroethane and a chemical present in the environment, in drinking water at 0.1 and 10 μg/L for 4 weeks. At the end of exposure, we measured steroid hormone secretion and analyzed steroidogenic proteins, including 17β-hydroxysteroid dehydrogenase, 3β-hydroxysteroid dehydrogenase, steroidogenic acute regulatory protein, aromatase, and the LH receptor. We also analyzed Leydig cell apoptosis (poly-(ADP-ribose) polymerase) and caspase-3 in the testes. Testicular testosterone (T) and 17β-estradiol (E2) were both affected by exposure to dichlorodiphenyldichloroethylene by displaying altered steroidogenic enzyme expression. Dichlorodiphenyldichloroethylene exposure also increased the expression of enzymes mediating the pathway for programmed cell death, including caspase 3, pro-caspase 3, PARP, and cleaved PARP. Altogether, the present results demonstrate that dichlorodiphenyldichloroethylene directly and/or indirectly can target specific proteins involved in steroid hormone production in the male gonad and suggest that exposure to environmentally relevant dichlorodiphenyldichloroethylene levels has implications for male reproductive development and function.

Reproductive Health Risks Associated with Occupational and Environmental Exposure to Pesticides

A marked reduction in fertility and an increase in adverse reproductive outcomes during the last few decades have been associated with occupational and environmental chemical exposures. Exposure to different types of pesticides may increase the risks of chronic diseases, such as diabetes, cancer, and neurodegenerative disease, but also of reduced fertility and birth defects. Both occupational and environmental exposures to pesticides are important, as many are endocrine disruptors, which means that even very low-dose exposure levels may have measurable biological effects. The aim of this review was to summarize the knowledge collected between 2000 and 2020, to highlight new findings, and to further interpret the mechanisms that may associate pesticides with infertility, abnormal sexual maturation, and pregnancy complications associated with occupational, environmental and transplacental exposures. A summary of current pesticide production and usage legislation is also included in order to elucidate the potential impact on exposure profile differences between countries, which may inform prevention measures. Recommendations for the medical surveillance of occupationally exposed populations, which should be facilitated by the biomonitoring of reduced fertility, is also discussed.

Agrochemicals with estrogenic endocrine disrupting properties: Lessons Learned?

Many agrochemicals have endocrine disrupting properties. A subset of these chemicals is characterized as "estrogenic". In this review, we describe several distinct ways that chemicals used in crop production can affect estrogen signaling. Using three agrochemicals as examples (DDT, endosulfan, and atrazine), we illustrate how screening tests such as the US EPA's EDSP Tier 1 assays can be used as a first-pass approach to evaluate agrochemicals for endocrine activity. We then apply the "Key Characteristics" approach to illustrate how chemicals like DDT can be evaluated, together with the World Health Organization's definition of an endocrine disruptor, to identify data gaps. We conclude by describing important issues that must be addressed in the evaluation and regulation of hormonally active agrochemicals including mixture effects, efforts to reduce vertebrate animal use, chemical prioritization, and improvements in hazard, exposure, and risk assessments.

Examining the relationships between blubber steroid hormones and persistent organic pollutants in common bottlenose dolphins

Odontocete cetaceans bioaccumulate high concentrations of endocrine disrupting persistent organic pollutants (POPs), including dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyltrichloroethylene (DDE), and dichlorodiphenyldichloroethane (DDD) - collectively DDTs - but few studies have explored DDTs-mediated endocrine disruption in cetaceans. Herein, we use remotely collected blubber biopsies from common bottlenose dolphins (Tursiops truncatus) inhabiting a site with high localized DDTs contamination to study the relationships between DDTs exposure and steroid hormone homeostasis in cetaceans. We quantified blubber steroid hormone concentrations by liquid chromatography-tandem mass spectrometry and blubber POP concentrations by gas chromatography-mass spectrometry. We detected six steroid hormones in blubber, including progesterone (P₄), 17-hydroxyprogesterone (17OHP₄), androstenedione (AE), testosterone (T), cortisol (F), and cortisone (E). Sampled dolphins (n = 62) exhibited exposure to DDT, DDE, DDD, chlordanes (CHLDs), mirex, dieldrin, hexachlorobenzene, polychlorinated biphenyls (PCBs), and brominated diphenyl ethers (BDEs). Using principal components analysis (PCA), we determined that blubber DDTs primarily loaded to the first principal component (PC1) explaining 81.6% of the total variance in POP exposure, while the remaining POPs primarily loaded to the PC2 (10.4% of variance). PC1 scores were negatively correlated with blubber T in males and blubber F in females, suggesting that exposure to DDTs impacted androgen and corticosteroid homeostasis. These conclusions were further supported by observed negative correlations between T and o,p'-DDE, o,p'-DDD, and p,p'-DDD in males sampled in the fall, and between F and the six individual DDTs and ∑₆DDTs in females. Overall, these results suggest that POP-mediated endocrine disruption may have occurred in this stock of dolphins, which could negatively impact their health and fitness. However, this study relied on uncontrolled incidental exposures, making it impossible to establish a causal relationship between DDTs exposure and endocrine effects. Importantly, this study demonstrates that remotely collected blubber biopsies are a useful matrix for studying endocrine disruption in marine mammals.

Assessing impacts of precocious steroid exposure on thyroid physiology and gene expression patterns in the American alligator (Alligator mississippiensis)

The thyroid gland is sensitive to steroid hormone signaling, and many thyroid disrupting contaminants also disrupt steroid hormone homeostasis, presenting the possibility that thyroid disruption may occur through altered steroid hormone signaling. To examine this possibility, we studied short-term and persistent impacts of embryonic sex steroid exposure on thyroid physiology in the American alligator. Alligators from a lake contaminated with endocrine disrupting contaminants (Lake Apopka, FL, USA) have been shown to display characteristics of thyroid and steroid hormone disruption. Previous studies suggest these alterations arise during development and raise the possibility that exposure to maternally deposited contaminants might underlie persistent organizational changes in both thyroidal and reproductive function. Thus, this population provides a system to investigate contaminant-mediated organizational thyroid disruption in an environmentally-relevant context. We assess the developmental expression of genetic pathways involved in thyroid hormone biosynthesis and find that expression of these genes increases prior to hatching. Further, we show that nuclear steroid hormone receptors are also expressed during this period, indicating the developing thyroid is potentially responsive to steroid hormone signaling. We then explore functional roles of steroid signaling during development on subsequent thyroid function in juvenile alligators. We exposed alligator eggs collected from both Lake Apopka and a reference site to 17β-estradiol and a non-aromatizable androgen during embryonic development, and investigated effects of exposure on hatchling morphometrics and thyroidal gene expression profiles at 5 months of age. Steroid hormone treatment did not impact the timing of hatching or hatchling size. Furthermore, treatment with steroid hormones did not result in detectable impacts on thyroid transcriptional programs, suggesting that precocious or excess estrogen and androgen exposure does not influence immediate or long-term thyroidal physiology.

Prenatal organochlorine pesticide exposure and the disruption of steroids and reproductive hormones in cord blood: The Hokkaido study

Certain organochlorine pesticides (OCPs) are designated as persistent organic pollutants and are regulated in many countries. The effects of OCPs on pediatric endocrinology are a concern; however, only limited data exist from human studies on maternal OCP exposure and its effects on infants' hormone levels. This study was conducted as part of the Hokkaido Study Sapporo Cohort, a prospective birth cohort study in Japan. Participants included 514 women who enrolled at 23-35weeks of gestation between 2002 and 2005; maternal blood samples were collected in late pregnancy, and 29 OCPs were measured. Reproductive and steroid hormone levels in cord blood were also determined. Characteristics of mothers and their infants were obtained from self-administered questionnaires and medical records. Ultimately, 232 samples with both OCP and hormone data were analyzed. Fifteen of 29 investigated OCPs were detected in over 80% of the samples, with p,p'-dichlorodiphenyldichloroethylene showing the highest concentration (median value: 619pg/g-wet). The association between OCPs and sex hormone levels varied by sex. Linear regression models after sex stratification showed that chlordanes, cis-hexachlorobenzene, heptachlor epoxide, Mirex, and toxaphenes in maternal blood were inversely associated with testosterone, cortisol, cortisone, sex hormone-binding globin, prolactin, and androstenedione-dehydroepiandrosterone (DHEA) and testosterone-androstenediones ratios among boys. Furthermore, these OCPs were positively correlated with DHEA, follicle stimulating hormone (FSH), and adrenal androgen-glucocorticoid and FSH-inhibin B ratios among boys. In categorical quartile models, testosterone and DHEA were inversely and positively associated with OCPs, respectively. Estradiol-testosterone and adrenal androgen-glucocorticoid ratios tended to increase with increasing OCP concentrations in the higher quartile, while the testosterone-androstenedione ratio tended to decrease. Sex hormone-binding globulin and prolactin showed an inverse association with OCPs. Among girls, the linear regression model showed that only p,p'-dichlorodiphenyltrichloroethane was inversely associated with the level of DHEA and the adrenal androgen-glucocorticoid ratio, but was positively associated with cortisone levels. However, no associations were observed using the quartile categorical model. These results suggest that prenatal exposure to OCPs disrupt reproductive hormones of fetuses in utero among boys, even at relatively low levels.

2-Phenylbenzo[b]furans: Synthesis and promoting activity on estrogen biosynthesis

Estrogen biosynthesis is pivotal to many physiological processes of human. Aberrant estrogen level is closely related to a variety of diseases, including breast cancer and osteoporosis. Previously we found that 2-phenylbenzo[b]furan glycosides could promote estrogen biosynthesis. To find high active 2-phenylbenzo[b]furans, fifty-four 2-phenylbenzo[b]furans were prepared via four strategies according to corresponding substrate scopes. Biological evaluation in HEK293A cells showed that some compounds exhibited promotive activity on estrogen biosynthesis. 2-(4-Chlorophenyl)-7-methoxybenzo[b]furan possessed the highest activity with EC₅₀ value of 14.68μM. Furthermore, these compounds did not affect aromatase expression in HEK292A cells, indicating that these 2-phenylbenzo[b]furans might enhance estrogen biosynthesis via directly allosteric regulation of aromatase or indirectly via posttranslational modification.

Review of endocrine disorders associated with environmental toxicants and possible involved mechanisms

Endocrine disrupting chemicals (EDC) are released into environment from different sources. They are mainly used in packaging industries, pesticides and food constituents. Clinical evidence, experimental models, and epidemiological studies suggest that EDC have major risks for human by targeting different organs and systems in the body. Multiple mechanisms are involved in targeting the normal system, through estrogen receptors, nuclear receptors and steroidal receptors activation. In this review, different methods by which xenobiotics stimulate signaling pathways and genetic mutation or DNA methylation have been discussed. These methods help to understand the results of xenobiotic action on the endocrine system. Endocrine disturbances in the human body result in breast cancer, ovarian problems, thyroid eruptions, testicular carcinoma, Alzheimer disease, schizophrenia, nerve damage and obesity. EDC characterize a wide class of compounds such as organochlorinated pesticides, industrial wastes, plastics and plasticizers, fuels and numerous other elements that exist in the environment or are in high use during daily life. The interactions and mechanism of toxicity in relation to human general health problems, especially endocrine disturbances with particular reference to reproductive problems, diabetes, and breast, testicular and ovarian cancers should be deeply investigated. There should also be a focus on public awareness of these EDC risks and their use in routine life. Therefore, the aim of this review is to summarize all evidence regarding different physiological disruptions in the body and possible involved mechanisms, to prove the association between endocrine disruptions and human diseases.

WITHDRAWN: The potential contribution of endocrine disrupting chemicals to acne

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Effects of elevated dissolved carbon dioxide and perfluorooctane sulfonic acid, given singly and in combination, on steroidogenic and biotransformation pathways of Atlantic cod

In the aquatic environments, the predicted changes in water temperature, pO2 and pCO2 could result in hypercapnic and hypoxic conditions for aquatic animals. These conditions are thought to affect several basic cellular and physiological mechanisms. Yet, possible adverse effects of elevated CO2 (hypercapnia) on teleost fish, as well as combined effects with emerging and legacy environmental contaminants are poorly investigated. In this study, juvenile Atlantic cod (Gadus morhua) were divided into groups and exposed to three different water bath PFOS exposure regimes (0 (control), 100 and 200 μg L(-1)) for 5 days at 1h/day, followed by three different CO2-levels (normocapnia, moderate (0.3%) and high (0.9%)). The moderate CO2 level is the predicted near future (within year 2300) level, while 0.9% represent severe hypercapnia. Tissue samples were collected at 3, 6 and 9 days after initiated CO2 exposure. Effects on the endocrine and biotransformation systems were examined by analyzing levels of sex steroid hormones (E2, T, 11-KT) and transcript expression of estrogen responsive genes (ERα, Vtg-α, Vtg-β, ZP2 and ZP3). In addition, transcripts for genes encoding xenobiotic metabolizing enzymes (cyp1a and cyp3a) and hypoxia-inducible factor (HIF-1α) were analyzed. Hypercapnia alone produced increased levels of sex steroid hormones (E2, T, 11-KT) with concomitant mRNA level increase of estrogen responsive genes, while PFOS produced weak and time-dependent effects on E2-inducible gene transcription. Combined PFOS and hypercapnia exposure produced increased effects on sex steroid levels as compared to hypercapnia alone, with transcript expression patterns that are indicative of time-dependent interactive effects. Exposure to hypercapnia singly or in combination with PFOS produced modulations of the biotransformation and hypoxic responses that were apparently concentration- and time-dependent. Loading plots of principal component analysis (PCA) produced a significant grouping of individual scores according to the exposure scenarios at day 6 and 9. Overall, the PCA analysis produced a unique clustering of variables that signifies a positive correlation between exposure to high PFOS concentration and mRNA expression of E2 responsive genes. Notably, this pattern was not evident for individuals exposed to PFOS concentrations in combination with elevated CO2 scenarios. To our knowledge, the present study is the first of its kind, to evaluate such effects using combined exposure to a perfluoroalkyl sulfonate and elevated levels of CO2 saturation, representative of future oceanic climate change, in any fish species or lower vertebrate.

Icariin from Epimedium brevicornum Maxim promotes the biosynthesis of estrogen by aromatase (CYP19)

ETHNOPHARMACOLOGICAL RELEVANCE

Epimedium brevicornum Maxim has long been used for the treatment of osteoporosis in China and other Asian countries. However, the mechanism behind the antiosteoporotic activity of this medicinal plant is not fully understood.

AIM OF THE STUDY

The present study was designed to investigate the effects of five widely used antiosteoporotic medicinal plants (Epimedium brevicornum, Cuscuta chinensis, Rhizoma drynariae, Polygonum multiflorum, and Ligustrum lucidum) on the production of estrogen, and identify the bioactive compounds responsible for the estrogen biosynthesis-promoting effect.

MATERIALS AND METHODS

Human ovarian granulosa-like KGN cells were used to evaluate estrogen biosynthesis, and the production of 17β-estradiol was quantified by a magnetic particle-based enzyme-linked immunosorbent assay (ELISA) kit. Further, the mRNA expression of aromatase was determined by a quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR), and the protein expression of aromatase was detected by western blotting. The activity of alkaline phosphatase (ALP) in rat osteoblastic UMR-106 cells was measured using p-nitrophenyl sodium phosphate assay.

RESULTS

Among the 5 antiosteoporotic medicinal plants, the extract of Epimedium brevicornum was found to significantly promote estrogen biosynthesis in KGN cells. Icariin, the major compound in Epimedium brevicornum, was identified to be the active compound for the estrogen biosynthesis-promoting effect. Icariin promoted estrogen biosynthesis in KGN cells in a concentration- and time-dependant manner and enhanced the mRNA and protein expressions of aromatase, which is the only enzyme for the conversion of androgens to estrogens in vertebrates. Further study showed that icariin also promoted estrogen biosynthesis and ALP activity in osteoblastic UMR-106 cells.

CONCLUSIONS

These results show that the promotion of estrogen biosynthesis is a novel effect of Epimedium brevicornum, and icariin could be utilized for the prevention and treatment of osteoporosis.

Endocrine disruptors and bone metabolism

Bone microenvironment is a complex dynamic equilibrium between osteoclasts and osteoblasts and is modulated by a wide variety of hormones and osteocyte mediators secreted in response to physiological and pathological conditions. The rate of remodeling involves tight coupling and regulation of both cells population and is regulated by a wide variety of hormones and mediators such as parathyroid hormone, prostaglandins, thyroid hormone, sex steroids, etc. It is also well documented that bone formation is easily influenced by the exposure of osteoblasts and osteoclasts to chemical compounds. Currently, humans and wildlife animals are exposed to various environmental xenoestrogens typically at low doses. These compounds, known as endocrine disruptor chemicals (EDCs), can alter the systemic hormonal regulation of the bone remodeling process and the skeletal formation. This review highlights the effects of the EDCs on mammalian bone turnover and development providing a macro and molecular view of their action.

Diverse animal models to examine potential role(s) and mechanism of endocrine disrupting chemicals on the tumor progression and prevention: Do they have tumorigenic or anti-tumorigenic property?

Acting as hormone mimics or antagonists in the interaction with hormone receptors, endocrine disrupting chemicals (EDCs) have the potentials of disturbing the endocrine system in sex steroid hormone-controlled organs and tissues. These effects may lead to the disruption of major regulatory mechanisms, the onset of developmental disorders, and carcinogenesis. Especially, among diverse EDCs, xenoestrogens such as bisphenol A, dioxins, and di(2-ethylhexyl)phthalate, have been shown to activate estrogen receptors (ERs) and to modulate cellular functions induced by ERs. Furthermore, they appear to be closely related with carcinogenicity in estrogen-dependant cancers, including breast, ovary, and prostate cancers. In in vivo animal models, prenatal exposure to xenoestrogens changed the development of the mouse reproductive organs and increased the susceptibility to further carcinogenic exposure and tumor occurence in adults. Unlike EDCs, which are chemically synthesized, several phytoestrogens such as genistein and resveratrol showed chemopreventive effects on specific cancers by contending with ER binding and regulating normal ER action in target tissues of mice. These results support the notion that a diet containing high levels of phytoestrogens can have protective effects on estrogen-related diseases. In spite of the diverse evidences of EDCs and phytoestrogens on causation and prevention of estrogen-dependant cancers provided in this article, there are still disputable questions about the dose-response effect of EDCs or chemopreventive potentials of phytoestrogens. As a wide range of EDCs including phytoestrogens have been remarkably increasing in the environment with the rapid growth in our industrial society and more closely affecting human and wildlife, the potential risks of EDCs in endocrine disruption and carcinogenesis are important issues and needed to be verified in detail.

Peroxisome proliferator-activated receptors, estrogenic responses and biotransformation system in the liver of salmon exposed to tributyltin and second messenger activator

The mechanisms by which organotin compounds produce modulations of the endocrine systems and other biological responses are not fully understood. In this study, juvenile salmon were force-fed diet containing TBT (0: solvent control, 0.1, 1 and 10mg/kg fish) for 72 h. Subsequently, fish exposed to solvent control and 10mg TBT were exposed to waterborne concentration (200 microg/l) of the adenylate cyclase (AC) stimulator, forskolin for 2 and 4h. The overall aim of the study was to explore whether TBT endocrine disruptive effects involve second messenger activation. Liver was sampled from individual fish (n=8) at the end of the exposures. The transcription patterns of peroxisome proliferator-activated receptor (PPAR) isotype and acyl-coenzyme A oxidase 1 (ACOX1), aromatase isoform, estrogen receptor-alpha (ER alpha), pregnane X receptor (PXR), CYP3A and glutathione S-transferase (GST) genes were measured by quantitative polymerase chain reaction (qPCR). Our data showed a consistent increase in PPAR alpha, PPAR beta and PPAR gamma mRNA and protein expression after TBT exposure that were inversely correlated with ACOX1 mRNA levels. Forskolin produced PPAR isotype-specific mRNA and protein effects that were modulated by TBT. ACOX1 expression was decreased (at 2h) and increased (at 4h) by forskolin and the presence of TBT potentiated these effects. TBT apparently increased mRNA and protein levels of cyp19a, compared to the solvent control, whereas cyp19b mRNA levels were unaffected by TBT treatment. Combined TBT and forskolin exposure produced respective decrease and increase of mRNA levels of cyp19a and cyp19b, compared with control. TBT decreased ER alpha mRNA at low dose (1mg/kg) and forskolin exposure alone produced a consistent decrease of ER alpha mRNA levels that were not affected by the presence of TBT. Interestingly, PXR and CYP3A mRNA levels were differentially affected, either decreased or increased, after exposure to TBT and forskolin, singly and also in combination. GST mRNA was increased by TBT exposure. Exposure to forskolin alone increased GST expression with time, and combined exposure with TBT potentiated these respective effects. Overall, the present study demonstrates multiple biological effects of TBT given singly or in combination with cAMP activator. There are no studies known to us that have evaluated the endocrine disruptive effects of TBT in the presence of a second messenger activator, and our data suggest that TBT may exert endocrine, biotransformation and lipid peroxidative effects through modulation of cAMP/PKA second messenger signaling with overt physiological consequences.

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.

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.

Spermatogenesis, epididymis morphology and plasma sex steroid secretion in the male lizard Podarcis sicula exposed to diuron

The present study investigates the effects of diuron, a substituted urea-based herbicide, in the male lizard Podarcis sicula utilizing quantitative and qualitative morphological features of the reproductive system and endocrinological analysis. Besides the control group, lizards were divided into three groups ([a-c]) (n=6/group) and placed for 3 weeks in terraria on polluted soil substrate sprayed with 3.75 L/ha of herbicide Toterbane 50F (50% diuron). Each terrarium was supplemented either with drinking water contaminated by herbicide (i.e. 1.08 microg/mL of diuron; group [a]), or with food contaminated by herbicide (i.e. 5.4 mg of diuron; group [b]), or with drinking water and food contaminated as described above (group [c]). None of the animals exposed to the contaminant showed any signs of general toxicity or death during the course of the experiments. Severe testicular effects are evidenced in all herbicide-treated groups, although, such effects are of a greater magnitude in lizards exposed to contaminated water (groups [a] and [c]). The main degenerative changes observed include: (1) a significant decrease in the mean gonadosomatic index of 55% in group [a] (P<0.001), 21% in group [b] (P<0.01) and 34% in group [c] (P<0.001) compared with control group; (2) a significant shrinking (P<0.001) of seminiferous tubule diameter (more than 60% of the control) in groups [a] and [c], and about 18% in group [b] (P<0.01); (3) a significant decrease in the crude numbers of spermatogonia of 92% in group [a] (P<0.001), 27% in group [b] (P<0.01) and 62% in group [c] (P<0.001) compared with control group. A complete loss of meiotic and mature germ cells in groups [a] and [c], and a reduction of primary spermatocytes, secondary spermatocytes and spermatids (more than 27% of the control) and a decrease of spermatozoa (more than 90% of the control) in group [b]; and (4) an hypertrophy of interstitial connective tissue which contains numerous lymphocytes, neutrophils and monocytes. The decrease and/or loss of germ cells seems to be related to an induction of inflammation (necrosis) rather than to apoptotic processes. Indeed, this hypothesis is supported by a TUNEL-assay, which failed to reveal any apoptotic cells either in the seminiferous epithelium or in the interstitial space in the testis of all exposed groups. Also the epididymis appears affected by diuron exposure. In particular, in experimental groups [a] and [c] it is regressed with abundant connective tissue and low epithelial cells without secretory granules, whereas in group [b] it appears partially regressed, with some secretory granules still present. At the same time, an impairment of the plasma sex-hormone levels is observed in treated lizards, as evidenced by RIA analysis. Testosterone values significantly decreased by 43% in group [a] (P<0.001), 34% in group [b] (P<0.01) and 52% in group [c] compared with control group. Instead, 17beta-estradiol plasma content is undetectable in all diuron-exposed lizards. Taken together, the results presented here indicate that diuron exposure resulted in direct male reproductive toxicity and reveal that this lizard is suitable as a laboratory reptile species for toxicological investigations.

High doses of atrazine do not disrupt activity and expression of aromatase in female gonads of juvenile goldfish (Carassius auratus L.)

Juveniles female goldfish were exposed to atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) at high doses, 100 and 1000 microg l(-1) during 56 days in order to evaluate the potential action of the herbicide as an endocrine disruptor. Plasma concentration of estradiol (E2) and 11-ketotestosterone (11-KT) as well as activity and expression of aromatase in the gonads were evaluated. These parameters were completed with morphological measures such as gonadosomatic index (GSI) and histological analyses of gonads. Morphological parameters at both 100 and 1000 microg l(-1) did not show any significant differences with the control groups. Correlated to the pathway hypothesized, no time-, dose-related effects were detected on the aromatase activity and the expression in the gonads of juvenile female goldfish. The same conclusion was attributed regarding the circulating E2 where no perceptible variation was detected. Nevertheless, a hormonal imbalance was detected for plasma concentration of the sex steroid 11-KT of fish exposed to 1000 microg l(-1) after 56 days exposure. In these particular experimental conditions, we failed to demonstrate an effect of atrazine through the induction of aromatase and hormonal imbalance associated.

Prenatal polychlorinated biphenyl exposures in eastern Slovakia modify effects of social factors on birthweight

Polychlorinated biphenyls (PCB) were widely used for industrial purposes and consumer products, but because of their toxicity, production was banned by most industrialised countries in the late 1970s. In eastern Slovakia, they were produced until 1985. During 2002-04, a birth cohort of mothers (n = 1057) residing in two Slovak districts was enrolled at delivery, and their specimens and information were collected after birth. Congeners of PCBs were measured in maternal serum by high-resolution gas chromatography with electron capture detection. In this study, we used multiple linear regression to examine the effects of prenatal PCB exposure on birthweight adjusted for gestational age, controlling for inter-pregnancy interval, and maternal smoking, age, education, ethnicity, pre-pregnancy body mass index and height. The association between total maternal serum PCB levels and birthweight was not statistically significant. However, an interaction model indicated that maternal PCB concentrations were associated with lower birthweight in Romani boys. Based on the fitted regression model, the predicted birthweight of Romani boys at the 90th percentile of maternal PCBs (12.8 ng/mL) was 133 g lower than the predicted birthweight at the 10th percentile of maternal PCBs (1.6 ng/mL). This is a similar magnitude of effect to that observed for maternal smoking and birthweight. These results suggest that higher levels of PCBs in maternal blood sera may inhibit growth in boys, particularly in those already affected by social factors related to ethnicity. This study is consistent with previous findings that boys are more susceptible than girls to growth restriction induced by in utero organochlorine exposures, and further indicates that high PCBs may magnify the influence of social disadvantage in this vulnerable group of boys.

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.

Evaluation of the rodent Hershberger bioassay: testing of coded chemicals and supplementary molecular-biological and biochemical investigations

Under the auspices of the Organization for Economic Cooperation and Development (OECD) the Hershberger assay is being validated as an in vivo screen for compounds with (anti)androgenic potential. We participated in the final activity, the testing of coded chemicals. Test compounds included trenbolone (TREN; 1.5, 40 mg/kg), testosterone propionate (TP; 0.4 mg/kg), flutamide (FLUT; 3mg/kg), linuron (LIN; 10, 100mg/kg), 1,1-bis-(4-chlorophenyl)-2,2-dichloroethylene (p,p'-DDE; 16, 160 mg/kg), and two negative reference substances, i.e., compounds not considered to affect androgen-sensitive tissue weights (ASTWs) in the Hershberger assay, namely 4-nonylphenol (NP; 160 mg/kg) and 2,4-dinitrophenol (DNP; 10mg/kg); TREN, LIN, p,p'-DDE, NP, and DNP being used under code. Compounds were administered for 10 days by oral intubation or subcutaneous injection (TP). Additional investigations not mandatorily requested by OECD included organ gravimetry of the liver, gene expression analysis in prostate using quantitative RT PCR for prostate specific binding protein polypeptide C3 (PBPC3) and ornithine decarboxylase 1 (ODC1) and determination of testosterone metabolizing and phase II conjugating enzymes in the liver. After submission of all study reports to OECD by participants uncoding revealed the following results: (A) When assessing androgenic potential in castrated rats, administration of TREN increased the weights of ventral prostate (VP), seminal vesicles (SV), glans penis, levator ani and bulbocavernosus muscles, and Cowper's glands at the high dose. A similar or stronger (VP, SV) increase of ASTWs was observed for TP; NP and DNP were ineffective. TREN dose-dependently increased gene expression of ODC1 and PBPC3, TP induced expression of these genes even more strongly (almost) to the level of untreated intact animals, whereas NP and DNP were inactive. Liver enzyme activities depending on physiological androgen levels were lower in castrated than in intact rats and could not be restored by androgen treatment. (B) When assessing antiandrogenic potential in TP-supplemented castrated rats, administration of LIN and p,p'-DDE decreased ASTWs only at the high dose. FLUT even more effectively decreased ASTWs, NP and DNP were again without effect. Decreases in androgen-responsive gene expression in the prostate corresponding to the organ weight changes were only observed for p,p'-DDE (high dose) and flutamide (PBPC3 only). p,p'-DDE dose-dependently induced liver weights and most liver enzyme activities including androgen-dependent ones. Our study accurately reproduced ASTW changes obtained in previous studies also under code suggesting that the Hershberger assay is a robust tool to screen for an (anti)androgenic potential. Assessment of ODC1 and PBPC3 gene expression in prostate, however, may only represent a sensitive tool for the detection of an androgenic potential. Finally, p,p'-DDE may affect ASTWs by several mechanisms including enhanced testosterone metabolism.

Lindane may modulate the female reproductive development through the interaction with ER-beta: an in vivo-in vitro approach

Lindane (gamma-HCH) is a persistent environmental pollutant that may act as endocrine disrupter, affecting the nervous, immune and reproductive system, possibly through endocrine-mediated mechanisms. Since both estrogen receptors (ER-alpha and -beta) have shown to be target for endocrine disruption, we investigated the role of gamma-HCH on the development of female reproductive system. For an in vivo evaluation of gamma-HCH effects during prenatal period, pregnant CD1 mice were treated p.o. on gestational days 9-16 with 15 mg/kg bw/day of gamma-HCH and vehicle. The in vivo findings in treated F1 pups - in the absence of signs of systemic toxicity - included increase in the absolute and relative and absolute uterus weight revealed on post-natal day 22, earlier vaginal patency and reduced diameters of primary oocytes at fully sexual maturity. No effects on steroid hormone metabolism (aromatase, testosterone catabolism) were observed. Thus, gamma-HCH elicited subtle effects on female reproductive development likely mediated by ER-beta-mediated pathway(s), without a concurrent impairment of steroid hormone metabolism. Furthermore, to verify whether the endocrine interference of gamma-HCH is attributable to stimulation of ER-beta-mediated pathway(s), its effect has been evaluated in vitro on a cell line, LNCaP, expressing only functional ER-beta. In vitro treatments revealed a concentration-related effect on LNCaP cell viability and proliferation. Significantly, the contemporary addition of a pure anti-estrogen, the ER antagonist ICI 182,780, completely reversed gamma-HCH effects indicating an ER-beta-mediated action. Our findings indicate that gamma-HCH may act as endocrine disruptor during the female reproductive system development and ER-beta as a potential target for this compound and other endocrine disrupting chemicals as well.

Effects of short-term exposure to the DDT metabolite p,p'-DDE on bone tissue in male common frog (Rana temporaria)

Experimental studies as well as studies in free-ranging animals have shown that endocrine-disrupting chemicals (EDCs) impair bone tissue composition and strength. The aim of the present study was to expand our studies on bone tissue in a new group of animals by investigating whether bone tissue in frogs is an additional potential target of EDCs. Adult male European common frogs (Rana temporaria) were divided into 5 groups (n = 20) and injected (sc, single injection) with p,p'-DDE, a total dose of 0.01, 0.1, 1, or 10 mg of p,p'-DDE/kg body weight, respectively. A control group was treated with the vehicle (corn oil). Two weeks after injection the frogs were euthanized and samples taken. The diaphysis of the excised left femur was scanned using peripheral quantitative computed tomography (pQCT) and cortical variables, such as cortical bone mineral density (BMD), cortical cross-sectional area (CSA), and periosteal circumference, were determined. In addition, biomechanical three-point bending of the bones was conducted, with the load being applied to the same point as where the pQCT measurement was performed. The results from the pQCT measurements show that bone tissue in male frogs exposed to p,p'-DDE is negatively affected. A significant decrease in cortical BMD at the diaphysis was observed in frogs exposed to 1 mg p,p'-DDE. However, the biomechanical testing of the bones showed no significant differences between exposed and control group. Although this is the only study performed to date examining the possible relationships between EDCs and negative effects on frog bones, it supports both previous experimental findings in rodents and findings in free-ranging animals.

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

Aromatase enzyme plays a central role in steroidogenesis by converting androgens to estrogens and has been proposed as an important molecular target for many environmental endocrine disrupters chemicals. In this study, we have screened 30 selected pesticides with known, unknown or supposed effects on aromatase activity, for their ability to modulate aromatase activity in the human choriocarcinoma JEG-3 cell line after both short (2 h) and long exposure (24 h). All pesticides were tested at concentrations up to 10 microM that did not cause cytotoxicity after 24h of exposure, as verified by the MTT viability assay. Four pesticides inhibited aromatase activity after 2 h of exposure: prochloraz (IC(50)<1 microM), fenbuconazole (IC(50)=1.1 microM), propiconazole (IC(50)=1.5 microM) and fenarimol (IC(50)=3.3 microM). Among them, prochloraz and fenbuconazole also exerted inhibitory effects after 24h. Toxaphen (10 microM) and heptachlor (10 microM) inhibited aromatase activity after 24h exposure only. Nine pesticides induced aromatase activity: aldrin, chlordane, cypermethrin, parathion-methyl, endosulfan, methoxychlor, oxadiazon, metolachlor and atrazine after 24 h of exposure, while tributyltin induced aromatase activity at 1 nM and 3 nM after both 2 h and 24 h of exposure, respectively. To further investigate the mechanisms of aromatase induction we measured CYP19 mRNA expression and showed that methoxychlor, aldrin, chlordane and tributyltin induced the transcription of the cyp19 gene. In addition, none of the aromatase inducers transactivated the retinoic acid receptor (RAR) in JEG-3 stably transfected with a RARE-luciferase plasmid while the RAR agonist TTNPB induced both aromatase and luciferase expression in these cells. Our results, which provide new data for fenbuconazole, as an inhibitor of human aromatase, and for eight pesticides as aromatase inducers, are discussed with regards to the regulation of aromatase expression in the JEG-3 cellular context.

Short-Term Effects of Adolescent Methylphenidate Exposure on Brain Striatal Gene Expression and Sexual/Endocrine Parameters in Male Rats

Exposure to methylphenidate (MPH) during adolescence is the elective therapy for attention deficit/hyperactivity disorder (ADHD) children, but raises major concerns for public health, due to possibly persistent neurobehavioral changes. Rats (30- to 44-days old) were administered MPH (2 mg/kg, i.p once daily) or saline (SAL). At the end of the treatment we collected plasma, testicular, liver, and brain (striatum) samples. The testes and liver were used to evaluate conventional reproductive and metabolic endpoints. Testes of MPH-exposed rats weighed more and contained an increased quantity of sperm, whereas testicular levels of testosterone (TST) were markedly decreased. The MPH treatment exerted an inductive effect on enzymatic activity of TST hydroxylases, resulting in increased hepatic TST catabolism. These findings suggest that subchronic MPH exposure in adolescent rats could have a trophic action on testis growth and a negative impact on TST metabolism. We have analyzed striatal gene expression profiles as a consequence of MPH exposure during adolescence, using microarray technology. More than 700 genes were upregulated in the striatum of MPH-treated rats (foldchange >1.5). A first group of genes were apparently involved in migration of immature neural/glial cells and/or growth of novel axons. These genes include matrix proteases (ADAM-1, MMP14), their inhibitors (TIMP-2, TIMP-3), the hyaluronan-mediated motility receptor (RHAMM), and growth factors (transforming growth factor-beta3 [TGF-beta3] and fibroblast growth factor 14 [FGF14]). A second group of genes were suggestive of active axonal myelination. These genes mediate survival of immature cells after contact with newly produced axonal matrix (laminin B1, collagens, integrin alpha 6) and stabilization of myelinating glia-axon contacts (RAB13, contactins 3 and 4). A third group indicated the appearance and/or upregulation of mature processes. The latter included genes for: K+ channels (TASK-1, TASK-5), intercellular junctions (connexin30), neurotransmitter receptors (adrenergic alpha 1B, kainate 2, serotonin 7, GABA-A), as well as major proteins responsible for their transport and/or anchoring (Homer 1, MAGUK MPP3, Shank2). All these genes were possibly involved in synaptic plasticity, namely the formation, maturation, and stabilization of new neural connections within the striatum. MPH treatment seems to potentiate synaptic plasticity, which is an age-dependent developmental phenomenon that adolescent rats are very likely to show, compared to adults. Our observations suggest that adolescent MPH exposure causes only transient changes in reproductive and hormonal parameters, and a more enduring enhancement of neurobehavioral plasticity.

Organ-specific patterns of P450arom gene isoforms are modulated by p,p'-DDE in adult male European common frog, Rana temporaria

The organ-specific gene expression patterns of P450arom isoforms have been studied in European common frog, Rana temporaria after exposure to DDE, using real-time PCR. Four groups of frogs were subcutaneously injected with DDE at 0.01, 0.1, 1 and 10 mg/kg body weight and one group, serving as the control was injected with pure corn oil. Brain, kidney, testis and liver P450aromA and P450aromB gene expressions were evaluated at day 14 after exposure. P450aromB data show that 0.1 and 10 mg DDE/kg doses caused 76% and 63% (testis) and 79% and 80% reductions, respectively, of mRNA levels. Brain P450aromB mRNA decreased 10% and 34%, respectively, after exposure to 0.01 and 0.1 mg DDE/kg. Thereafter, a 185% and 177% induction response of brain P450aromB was observed in the groups treated with 1 and 10 mg DDE/kg, respectively. In the kidney, 0.01, 0.1, 1 and 10 mg DDE/kg induced a 516%, 178%, 466% and 247% induction of P450aronB mRNA, respectively. P450aromA expression was not quantified in any of the organs. The relative abundance of P450aromB gene expression in different organs is in the order: kidney > brain > liver > testis. The present data suggest potential detrimental effect of organochlorine pesticides (OCs) and their metabolites on the European frog steroidogenic pathways. Given the high persistency in the environment and continued use in developing countries coupled with the tendency for global atmospheric transport, OCs and their metabolites such as DDE will remain a focus of concern both for scientific and societal reasons.

Steroid levels and steroid metabolism in the mussel Mytilus edulis: the modulating effect of dispersed crude oil and alkylphenols

Significant amounts of oil and alkylphenols are released into the sea by petroleum installations as a result of discharges of produced water. Some of these pollutants elicit estrogenic responses in fish, but their effects on the endocrine system of molluscs are largely unknown. In this study, mussels Mytilus edulis were exposed to North Sea oil (O) and the mixture of North Sea oil+alkylphenols (OAP), and the effects on tissue steroid levels and steroid metabolism (P450-aromatase and estradiol-sulfotransferase) were monitored. Levels of free testosterone and free estradiol were much higher in gonad tissue than in peripheral tissue, whereas esterified steroids (released after saponification) were of the same order of magnitude in both tissues. Levels of free steroids determined in gonads were not affected by exposure, but esterified steroids significantly increased in OAP exposed mussels (up to 2.4-fold). The sulfation of estradiol was investigated as a conjugation pathway, and increased activities were observed in digestive gland cytosol of both O and OAP exposure groups (up to 2.8-fold). Additionally, increased P450-aromatase activity was determined in OAP exposed mussels (up to three-fold, both in gonad and digestive gland), but not in the O group. Altogether, the results indicate that North Sea oil leads to increased sulfation of estradiol, and that in combination with alkylphenols, additional alterations are observed: increased P450-aromatase, and increased levels of esterified-steroids in gonads. Nonetheless, mussels are able to maintain gonad concentrations of free steroids unaltered, possibly via homeostatic mechanisms such as the conjugation with fatty acid or the formation of sulphate conjugates.

Pesticide exposure: the hormonal function of the female reproductive system disrupted?

Some pesticides may interfere with the female hormonal function, which may lead to negative effects on the reproductive system through disruption of the hormonal balance necessary for proper functioning. Previous studies primarily focused on interference with the estrogen and/or androgen receptor, but the hormonal function may be disrupted in many more ways through pesticide exposure. The aim of this review is to give an overview of the various ways in which pesticides may disrupt the hormonal function of the female reproductive system and in particular the ovarian cycle. Disruption can occur in all stages of hormonal regulation: 1. hormone synthesis; 2. hormone release and storage; 3. hormone transport and clearance; 4. hormone receptor recognition and binding; 5. hormone postreceptor activation; 6. the thyroid function; and 7. the central nervous system. These mechanisms are described for effects of pesticide exposure in vitro and on experimental animals in vivo. For the latter, potential effects of endocrine disrupting pesticides on the female reproductive system, i.e. modulation of hormone concentrations, ovarian cycle irregularities, and impaired fertility, are also reviewed. In epidemiological studies, exposure to pesticides has been associated with menstrual cycle disturbances, reduced fertility, prolonged time-to-pregnancy, spontaneous abortion, stillbirths, and developmental defects, which may or may not be due to disruption of the female hormonal function. Because pesticides comprise a large number of distinct substances with dissimilar structures and diverse toxicity, it is most likely that several of the above-mentioned mechanisms are involved in the pathophysiological pathways explaining the role of pesticide exposure in ovarian cycle disturbances, ultimately leading to fertility problems and other reproductive effects. In future research, information on the ways in which pesticides may disrupt the hormonal function as described in this review, can be used to generate specific hypotheses for studies on the effects of pesticides on the ovarian cycle, both in toxicological and epidemiological settings.

Endocrine-disrupting chemicals as modulators of sex steroid synthesis

Endocrine-disrupting chemicals (EDCs) are typically identified as compounds that can interact with oestrogen or androgen receptors and thus act as agonists or antagonists of endogenous hormones. Growing evidence shows that they may also modulate the activity/expression of steroidogenic enzymes. These are expressed not only in the adrenal glands and gonads but also in many tissues that have the ability to convert circulating precursors into active hormones. In this way, EDCs may impact both on sexual differentiation and development and on hormone-dependent cancers. This review summarizes the evidence for EDCs as modulators of steroidogenic enzymes, identifies the structure/activity relationship in terms of inhibiting specific enzyme activity, questions whether experimental observations can equate with natural in vivo exposure or dietary intake of EDCs, and finally looks at the mechanisms through which these chemicals may disrupt normal steroidogenesis. In summarizing the evidence, the question of whether or not the dietary intake of these endocrine disrupters could pose a threat to human sexual development and health will be addressed.

Maternal concentration of dichlorodiphenyl dichloroethylene (DDE) and initiation and duration of breast feeding

Dichlorodiphenyl dichloroethylene (DDE) has been shown to reduce the duration of breast feeding in two studies. In addition to duration, we examined whether DDE lowers the initiation of breast feeding. Between 1973 and 1991, the Michigan Department of Community Health conducted three surveys to assess polychlorinated biphenyls (PCBs) and DDE serum concentrations in Michigan anglers. Through telephone interviews with parents, we retrospectively ascertained information on breast feeding. Based on repeated maternal serum measurements between 1973 and 1991, we arrived at the level of exposure at the time of delivery by extrapolating PCB and DDE serum levels. One mother may have contributed more than one child; however, serum concentrations varied between children from the same mother. The maternal DDE and PCB serum concentrations were categorised as follows: 0 to <5 microg/L, 5 to <10 microg/L, >or=10 microg/L. Repeated measurement models and survival analyses were used to determine the relationship between DDE and PCBs and characteristics of breast feeding while controlling for cohort effects, maternal age at delivery, education, and smoking during pregnancy. We focused on 176 pregnancies of 91 mothers who had maternal exposure information and gave birth between 1969 and 1995. Initiation of breast feeding was lowered by 39.5% and duration shortened by 66.4% in children of mothers who smoked during pregnancy. In children of non-smoking mothers, the incidence ratio for breast-feeding initiation was 0.45 [95% CI 0.15, 0.94] and 0.42 [95% CI 0.10, 1.03] when maternal DDE concentrations were 5 to <10 microg/L and >or=10 microg/L respectively, compared with the lowest DDE exposure group. In these offspring (of non-smoking mothers), breast-feeding duration was shorter when DDE concentrations were higher: 13 weeks for >or=10 microg/L DDE, compared with 21.7 weeks for lower DDE. We did not detect any association between PCBs and breast feeding. In the absence of the distorting effects of maternal smoking, DDE exposure may decrease initiation and duration of breast feeding.

Health risks and benefits of bis(4-chlorophenyl)-1,1,1-trichloroethane (DDT)

DDT (bis[4-chlorophenyl]-1,1,1-trichloroethane) is a persistent insecticide that was used worldwide from the mid 1940s until its ban in the USA and other countries in the 1970s. When a global ban on DDT was proposed in 2001, several countries in sub-Saharan Africa claimed that DDT was still needed as a cheap and effective means for vector control. Although DDT is generally not toxic to human beings and was banned mainly for ecological reasons, subsequent research has shown that exposure to DDT at amounts that would be needed in malaria control might cause preterm birth and early weaning, abrogating the benefit of reducing infant mortality from malaria. Historically, DDT has had mixed success in Africa; only the countries that are able to find and devote substantial resources towards malaria control have made major advances. DDT might be useful in controlling malaria, but the evidence of its adverse effects on human health needs appropriate research on whether it achieves a favourable balance of risk versus benefit.

Effects of sub-lethal levels of dichlorodiphenyltrichloroethane and dichlorodiphenyldichloroethylene on in vitro steroid biosynthesis by ovarian follicles or steroid metabolism by embryos of rainbow trout (Oncorhynchus mykiss)

This study examined the possibility that DDT and DDE, at sub-lethal exposure levels, exert direct effects on the biotransformation of gonadal steroids by rainbow trout (Oncorhynchus mykiss) ovarian follicles and embryos. Ovarian follicles were co-incubated with DDT or DDE at 0.01 or 1 mg l-1 to examine effects of the pesticides on basal or cAMP-activated steroidogenesis. Ovarian preparations were incubated with radiolabelled [3H]pregnenolone ([3H]P5), and the tritiated metabolites of [3H]P5 metabolism were separated using high-performance liquid chromatography (HPLC). Testosterone (T) and 17beta-estradiol (E2) production were also measured using radioimmunoassay (RIA). Embryos were either exposed to the pesticides in ovo, or co-incubated in vitro with the pesticides. The effect of the pesticides on embryo steroid biotransformation was examined using a range of radioactively labelled substrates, including [3H]P5, [3H]progesterone ([3H]P4), [3H]T and [3H]E2. At the concentrations used, the pesticides had no significant effect on the relative amounts of unconjugated radiolabelled steroids formed by the biotransformation of [3H]P5 under conditions of basal or cAMP-stimulated ovarian steroidogenesis. However, DDT and DDE appeared to reduce the basal accumulation of androgen as a product of P5 biotransformation by ovarian follicles. Basal or cAMP-stimulated total estrogen production was not affected. In addition, DDT at 1 mg l-1 and DDE at 0.01 mg l-1 significantly increased and decreased cAMP-stimulated T accumulation, respectively. Also DDT at 0.01 mg l-1 and DDE at 1 mg l-1 significantly increased and decreased basal E2 accumulation, respectively. The steroid metabolites synthesized from the different substrates by embryos were essentially similar in both controls and pesticide-exposed groups, and the survival of embryos to hatch was not significantly affected by pesticide exposure, in ovo, with an approximately 90% hatchability in all treatment groups. This study suggests that although DDT and DDE may affect ovarian androgen synthesis under some conditions, under the conditions of the present study, they do not impact on overall rates of gonadal estrogen synthesis. Similarly, the pesticides do not appear to directly affect steroid biotransformation by embryos.

DDE-induced changes in aromatase activity in endometrial stromal cells in culture

Environmental toxicants are thought to play a role in several estrogen-dependent diseases including breast cancer and endometriosis. Toxicant-induced increased aromatase activity, an enzyme complex that catalyzes the final rate-limiting step in the conversion of androgens to estrogens, has been reported in assays using placental microsomes and cancer cells in vitro. These data suggest that environmental toxicants can increase aromatase activity and thus increase local tissue estrogen levels, which could have implications for estrogen- dependent functions in target tissues. The objective of this study was therefore to quantify the effect of the stable breakdown product of DDT, 2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE), a toxicant broadly detected in human adipose tissue, serum and follicular fluid, on aromatase activity in the endometrium, an estrogen-sensitive target tissue. Specifically, the effect of increasing log concentrations of p,p'-DDE on aromatase activity was determined in cultures of endometrial stromal cells (ESC). Relative to controls p,p'-DDE treatment significantly increased aromatase activity in ESC (135%). Moreover, ESC cells treated with p,p'-DDE were immunopositive for aromatase, whereas no aromatase staining could be demonstrated in control cultures. Our data demonstrate that p,p'-DDE treatment can increase aromatase activity in ESC in culture.

Effects of the xenoestrogen bisphenol A in diencephalic regions of the teleost fish Coris julis occur preferentially via distinct somatostatin receptor subtypes

The xenoestrogen bisphenol A, a contaminant used in the manufacturing of polymers for many consumer products, has been shown to mimic estrogenic actions. This xenoestrogen regulates secretion and expression of pituitary lactotrophs plus morphological and structural features of estrogen target tissues in rodents. Recently, ecological hazards produced by bisphenol A have drawn interests towards the effects of this environmental chemical on neurobiological functions of aquatic vertebrates of which little is known. In this study, the effects of bisphenol A on the distribution of the biologically more active somatostatin receptor subtypes in diencephalic regions of the teleost fish Coris julis were assessed using nonpeptide agonists (L-779, 976 and L-817, 818) that are highly selective for subtype(2) and subtype(5), respectively. Bisphenol A proved to be responsible for highly significant increased binding levels of subtype(2) in hypothalamic areas, while markedly decreased levels of subtype(5) were found in these diencephalic areas, as well as in the medial preglomerular nucleus. The extensive distribution of somatostatin receptor subtype(2) and subtype(5) in the teleost diencephalic areas suggests that, like in mammals, this receptor system may not only be involved in enhanced hypophysiotropic neurohormonal functions but might also promote neuroplasticity events.

Environmental and occupational factors affecting fertility and IVF success

Reproductive function has been shown to be sensitive to changes in the physical, psychosocial and chemical environments. Although reproductive effects of occupational exposure to hazardous chemicals have been well documented in the literature, the potential effects of chemical contaminants at levels representative of contemporary exposures in the general population are much less certain. Evidence for adverse effects of exposure to environmental contaminants is more conclusive among the lower animals than for humans where considerable controversy remains. In addition to potential reproductive hazards of exposure to environmental contaminants, there is also evidence for adverse reproductive effects of the physical and psychosocial environments. In this review we focus on the difficulties involved in linking exposure to putative hazardous substances in environmental and occupational settings to adverse reproductive outcomes, especially success of IVF procedures. We highlight the plausibility of adverse events through animal and cell studies and the application of these results to the interpretation of human data. We consider both the male and female partners since it is essentially their combined contributions of gametes which may be affected by chemicals, which lead to successful outcomes.

Prenatal DDT exposure in relation to anthropometric and pubertal measures in adolescent males

DDT (dichlorodiphenyltrichloroethane), a pesticide once used widely in agriculture and now limited to public health use, remains a controversial chemical because of a combination of benefits and risks. DDT or its breakdown products are ubiquitous in the environment and in humans. Compounds in the DDT family have endocrine actions and have been associated with reproductive toxicity. A previous study reported associations between prenatal exposure to p,p -DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene] and increased height and weight in adolescent boys. We examined a group with higher exposures to see whether similar associations would occur. Our study group was 304 males born in Philadelphia in the early 1960s who had participated in a previous study. Anthropometric and pubertal measures from one to six visits during their adolescent years were available, as were stored maternal serum samples from pregnancy. We measured p,p -DDE, p,p -DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)-ethane], and o,p -DDT [1,1,1-trichloro-2-(o-chlorophenyl)-2-(p-chlorophenyl)-ethane] in the maternal serum. Outcomes examined in the boys were height, ratio of sitting height to height, body mass index, triceps skinfold thickness, ratio of subscapular to the sum of triceps and subscapular skinfold thicknesses, skeletal age, serum testosterone, and serum dehydroepiandrosterone sulfate. No associations between prenatal exposure to any of the DDT compounds and any outcome measure were seen.

Steroid hormone biotransformation and xenobiotic induction of hepatic steroid metabolizing enzymes

Normal reproductive development depends on the interplay of steroid hormones with their receptors at specific tissue sites. The concentrations of hormone ligands in the circulation and at target sites are maintained through coordinated regulation on steroid biosynthesis and degradation. Changed bioavailability of steroids, through alteration of steroidogenesis or biotransformation rates, leads to changes in endocrine function. Steroid hormones lose their receptor reactivity in most cases when they are bound to binding proteins, while metabolic conversion can result in either active or inactive metabolites. Hydroxylation by cytochrome P450 (CYP) enzymes and conjugation with glucuronide and sulfate are among the major hepatic pathways of steroid inactivation. The expression of these biotransformation enzymes can be induced by many xenobiotics. The barbiturate phenobarbital and the environmental toxicant 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) are among the well characterized inducers for the CYP 2B and 3A enzymes and selected conjugation enzymes. The induction of the steroid biotransformation enzymes is partly mediated through the activation of a group of nuclear receptors including the glucocorticoid receptor, the constitutive androstane receptor (CAR), the pregnane X receptor (PXR), and the peroxisome proliferator activated receptors (PPAR). Drug or chemical-induced increases in hepatic enzyme activities are often a basis for drug-drug interactions that lead to enhanced elimination and reduced therapeutic efficacy of steroidal drugs. The effects of enzyme induction on endogenous steroid clearance, along with its possible consequence, are less well understood. While enzyme induction by xenobiotics may increase clearance of the endogenous steroid, regulatory mechanisms for steroid homeostasis may adapt and compensate for altered clearance.

A benzimidazole fungicide, benomyl, and its metabolite, carbendazim, induce aromatase activity in a human ovarian granulose-like tumor cell line (KGN)

Endocrine disruptor chemicals are known to cause a range of abnormalities in sexual differentiation and reproduction. One mechanism underlying such effects may be via alteration of aromatase activity, which is responsible for estrogen production. A good screening system for identifying endocrine disruptors has long been desired. We have recently established a human ovarian granulosa-like tumor cell line, KGN, which possesses a relatively high level of aromatase expression and is considered a useful mammalian model for investigating the in vitro effects of various chemicals on aromatase activity. In this study we screened 55 different candidate chemicals for endocrine disruptors by assaying aromatase activity. Only benomyl, known as both a benzimidazole fungicide and a microtubule-interfering agent, was found to induce aromatase activity in association with increased levels of aromatase mRNA in KGN cells. The effect of benomyl was presumed to be mediated by its metabolite carbendazim, because it produced an effect equivalent to that of benomyl. The mechanism underlying the benomyl-induced increase in aromatase activity appears independent of the cAMP-protein kinase A pathway. Treatment with taxol, another class of microtubule-interfering agents, also caused induction of aromatase in KGN cells. Both benomyl and taxol changed KGN cell morphology, including the development of cell roundness and a disorganized network of microtubules. These results indicate that benomyl is a potential endocrine disruptor that provides a novel estrogenicity and operates through a microtubule-interfering mechanism.