Evaluation of a two-generation reproduction toxicity study adding endpoints to detect endocrine disrupting activity using vinclozolin

Methodology for developing data-rich Key Event Relationships for Adverse Outcome Pathways exemplified by linking decreased androgen receptor activity with decreased anogenital distance

The Adverse Outcome Pathway (AOP) framework has gained widespread acceptance in toxicological disciplines as a tool for aiding chemical hazard assessment. Despite increased activity in AOP development, progress towards a high volume of fully endorsed AOPs has been slow, partly due to the challenging task of constructing complete AOPs according to the AOP Developer's Handbook. To facilitate greater uptake of new knowledge units onto the open-source AOP-wiki platform, a pragmatic approach was recently proposed. This approach involves considering Key Event Relationships (KERs) for individual development through systematic approaches, as they represent essential units of knowledge from which causality can be inferred; from low complexity test data to adverse outcomes in intact organisms. However, more broadly adopted harmonized methodologies for KER development would be desirable. Using the AOP Developer's Handbook as a guide, a KER linking 'decreased androgen receptor (AR) activity' with 'reduced anogenital distance (AGD)' was developed to demonstrate a methodology applicable for future developments of KERs requiring systematic literature retrieval approaches.

LIN28 Family in Testis: Control of Cell Renewal, Maturation, Fertility and Aging

Male reproductive development starts early in the embryogenesis with somatic and germ cell differentiation in the testis. The LIN28 family of RNA-binding proteins promoting pluripotency has two members—LIN28A and LIN28B. Their function in the testis has been investigated but many questions about their exact role based on the expression patterns remain unclear. LIN28 expression is detected in the gonocytes and the migrating, mitotically active germ cells of the fetal testis. Postnatal expression of LIN28 A and B showed differential expression, with LIN28A expressed in the undifferentiated spermatogonia and LIN28B in the elongating spermatids and Leydig cells. LIN28 interferes with many signaling pathways, leading to cell proliferation, and it is involved in important testicular physiological processes, such as cell renewal, maturation, fertility, and aging. In addition, aberrant LIN28 expression is associated with testicular cancer and testicular disorders, such as hypogonadotropic hypogonadism and Klinefelter’s syndrome. This comprehensive review encompasses current knowledge of the function of LIN28 paralogs in testis and other tissues and cells because many studies suggest LIN28AB as a promising target for developing novel therapeutic agents.

On the Use and Interpretation of Areola/Nipple Retention as a Biomarker for Anti-androgenic Effects in Rat Toxicity Studies

Areola/nipple retention (NR) is an established biomarker for an anti-androgenic mode of action in rat toxicity studies. It is a mandatory measurement under several OECD test guidelines and is typically assessed in combination with anogenital distance (AGD). Both NR and AGD are considered retrospective biomarkers of insufficient androgen signaling during the masculinization programming window in male fetuses. However, there are still aspects concerning NR as a biomarker for endocrine disruption that remains to be clarified. For instance, can NR be regarded a permanent adverse effect? Is it a redundant measurement if AGD is assessed in the same study? Is NR equally sensitive and specific to anti-androgenic chemical substances as a shortening of male AGD? In this review we discuss these and other aspects concerning the use of NR as a biomarker in toxicity studies. We have collected available literature from rat toxicity studies that have reported on NR and synthesized the data in order to draw a clearer picture about the sensitivity and specificity of NR as an effect biomarker for an anti-androgenic mode of action, including comparisons to AGD measurements. We carefully conclude that NR and AGD in rats for the most part display similar sensitivity and specificity, but that there are clear exceptions which support the continued assessment of both endpoints in relevant reproductive toxicity studies. Available literature also support the view that NR in infant male rats signifies a high risk for permanent nipples in adulthood. Finally, the literature suggests that the mechanisms of action leading from a chemical stressor event to either NR or short AGD in male offspring are overlapping with respect to canonical androgen signaling, yet differ with respect to other mechanisms of action.

Genomic and Hormonal Biomarkers of Phthalate-Induced Male Rat Reproductive Developmental Toxicity Part II: A Targeted RT-qPCR Array Approach That Defines a Unique Adverse Outcome Pathway

Previously, we demonstrated that exposure to some diortho-phthalate esters during sexual differentiation disrupts male reproductive development by reducing fetal rat testis testosterone production (T Prod) and gene expression in a dose-related manner. The objectives of the current project were to expand the number of test compounds that might reduce fetal T Prod, including phthalates, phthalate alternatives, pesticides, and drugs, and to compare reductions in T Prod with altered testis mRNA expression. We found that PEs that disrupt T Prod also reduced expression of a unique "cluster" of mRNAs for about 35 genes related to sterol transport, testosterone and insulin-like hormone 3 hormone syntheses, and lipoprotein signaling and cholesterol synthesis. However, phthalates had little or no effect on mRNA expression of genes in peroxisome proliferator-activated receptor (PPAR) pathways in the fetal liver, whereas the 3 PPAR agonists induced the expression of mRNA for multiple fetal liver PPAR pathway genes without reducing testis T Prod. In summary, phthalates that disrupt T Prod act via a novel adverse outcome pathway including down regulation of mRNA for genes involved in fetal endocrine function and cholesterol synthesis and metabolism. This profile was not displayed by PEs that did not reduce T Prod, PPAR agonists or the other chemicals. Reductions in fetal testis gene expression and T Prod in utero can be used to establish relative potency factors that can be used quantitatively to predict the doses of individual PEs and mixtures of phthalates that produce adverse reproductive tract effects in male offspring.

Hypothetical roadmap towards endometriosis: prenatal endocrine-disrupting chemical pollutant exposure, anogenital distance, gut-genital microbiota and subclinical infections

BACKGROUND

Endometriosis is a gynaecological hormone-dependent disorder that is defined by histological lesions generated by the growth of endometrial-like tissue out of the uterus cavity, most commonly engrafted within the peritoneal cavity, although these lesions can also be located in distant organs. Endometriosis affects ~10% of women of reproductive age, frequently producing severe and, sometimes, incapacitating symptoms, including chronic pelvic pain, dysmenorrhea and dyspareunia, among others. Furthermore, endometriosis causes infertility in ~30% of affected women. Despite intense research on the mechanisms involved in the initial development and later progression of endometriosis, many questions remain unanswered and its aetiology remains unknown. Recent studies have demonstrated the critical role played by the relationship between the microbiome and mucosal immunology in preventing sexually transmitted diseases (HIV), infertility and several gynaecologic diseases.

OBJECTIVE AND RATIONALE

In this review, we sought to respond to the main research question related to the aetiology of endometriosis. We provide a model pointing out several risk factors that could explain the development of endometriosis. The hypothesis arises from bringing together current findings from large distinct areas, linking high prenatal exposure to environmental endocrine-disrupting chemicals with a short anogenital distance, female genital tract contamination with the faecal microbiota and the active role of genital subclinical microbial infections in the development and clinical progression of endometriosis.

SEARCH METHODS

We performed a search of the scientific literature published until 2019 in the PubMed database. The search strategy included the following keywords in various combinations: endometriosis, anogenital distance, chemical pollutants, endocrine-disrupting chemicals, prenatal exposure to endocrine-disrupting chemicals, the microbiome of the female reproductive tract, microbiota and genital tract, bacterial vaginosis, endometritis, oestrogens and microbiota and microbiota-immune system interactions.

OUTCOMES

On searching the corresponding bibliography, we found frequent associations between environmental endocrine-disrupting chemicals and endometriosis risk. Likewise, recent evidence and hypotheses have suggested the active role of genital subclinical microbial infections in the development and clinical progression of endometriosis. Hence, we can envisage a direct relationship between higher prenatal exposure to oestrogens or estrogenic endocrine-disrupting compounds (phthalates, bisphenols, organochlorine pesticides and others) and a shorter anogenital distance, which could favour frequent postnatal episodes of faecal microbiota contamination of the vulva and vagina, producing cervicovaginal microbiota dysbiosis. This relationship would disrupt local antimicrobial defences, subverting the homeostasis state and inducing a subclinical inflammatory response that could evolve into a sustained immune dysregulation, closing the vicious cycle responsible for the development of endometriosis.

WIDER IMPLICATIONS

Determining the aetiology of endometriosis is a challenging issue. Posing a new hypothesis on this subject provides the initial tool necessary to design future experimental, clinical and epidemiological research that could allow for a better understanding of the origin of this disease. Furthermore, advances in the understanding of its aetiology would allow the identification of new therapeutics and preventive actions.

Prenatal EDCs Impair Mate and Odor Preference and Activation of the VMN in Male and Female Rats

Environmental endocrine-disrupting chemicals (EDCs) disrupt hormone-dependent biological processes. We examined how prenatal exposure to EDCs act in a sex-specific manner to disrupt social and olfactory behaviors in adulthood and underlying neurobiological mechanisms. Pregnant rat dams were injected daily from embryonic day 8 to 18 with 1 mg/kg Aroclor 1221 (A1221), 1 mg/kg vinclozolin, or the vehicle (6% DMSO in sesame oil). A1221 is a mixture of polychlorinated biphenyls (weakly estrogenic) while vinclozolin is a fungicide (anti-androgenic). Adult male offspring exposed to A1221 or vinclozolin, and females exposed to A1221, had impaired mate preference behavior when given a choice between 2 opposite-sex rats that differed by hormone status. A similar pattern of impairment was observed in an odor preference test for urine-soaked filter paper from the same rat groups. A habituation/dishabituation test revealed that all rats had normal odor discrimination ability. Because of the importance of the ventrolateral portion of the ventromedial nucleus (VMNvl) in mate choice, expression of the immediate early gene product Fos was measured, along with its co-expression in estrogen receptor alpha (ERα) cells. A1221 females with impaired mate and odor preference behavior also had increased neuronal activation in the VMNvl, although not specific to ERα-expressing neurons. Interestingly, males exposed to EDCs had normal Fos expression in this region, suggesting that other neurons and/or brain regions mediate these effects. The high conservation of hormonal, olfactory, and behavioral traits necessary for reproductive success means that EDC contamination and its ability to alter these traits has widespread effects on wildlife and humans.

Establishment of cumulative assessment groups of pesticides for their effects on the thyroid

Cumulative assessment groups of pesticides have been established for two specific effects on the thyroid: firstly hypothyroidism, and secondly parafollicular cell (C-cell) hypertrophy, hyperplasia and neoplasia. Sources of uncertainties resulting from the methodological approach and from the limitations in available data and scientific knowledge have been identified and considered. This report supports the publication of a scientific report on cumulative risk assessment to pesticides affecting the thyroid, in which all uncertainties identified for either the exposure assessment or the establishment of the cumulative assessment groups are incorporated into a consolidated risk characterisation.

Anogenital distance as a toxicological or clinical marker for fetal androgen action and risk for reproductive disorders

Male reproductive development is intricately dependent on fetal androgen action. Consequently, disrupted androgen action during fetal life can interfere with the development of the reproductive system resulting in adverse effects on reproductive function later in life. One biomarker used to evaluate fetal androgen action is the anogenital distance (AGD), the distance between the anus and the external genitalia. A short male AGD is strongly associated with genital malformations at birth and reproductive disorders in adulthood. AGD is therefore used as an effect readout in rodent toxicity studies aimed at testing compounds for endocrine activity and anti-androgenic properties, and in human epidemiological studies to correlate fetal exposure to endocrine disrupting chemicals to feminization of new-born boys. In this review, we have synthesized current data related to intrauterine exposure to xenobiotics and AGD measurements. We discuss the utility of AGD as a retrospective marker of in utero anti-androgenicity and as a predictive marker for male reproductive disorders, both with respect to human health and rodent toxicity studies. Finally, we highlight four areas that need addressing to fully evaluate AGD as a biomarker in both a regulatory and clinical setting.

Investigations of putative reproductive toxicity of low-dose exposures to vinclozolin in Wistar rats

The current investigation examines whether the fungicide vinclozolin, which has an anti-androgenic mode of action, is capable of disrupting endocrine homeostasis at very low doses. The data generated clarify whether a non-monotonic dose-response relationship exists to enhance the current debate about the regulation of endocrine disruptors. Moreover, it is part of a series of investigations assessing the dose-response relationship of single and combined administration of anti-androgenic substances. A pre-postnatal in vivo study design was chosen which was compliant with regulatory testing protocols. The test design was improved by additional endpoints addressing hormone levels, morphology and histopathological examinations. Doses were chosen to represent an effect level (20 mg/kg bw/d), the current NOAEL (4 mg/kg bw/d), and a dose close to the "ADI" (0.005 mg/kg bw/d) for the detection of a possible non-monotonic dose-response curve. Anti-androgenic changes were observable at the effect level but not at lower exposures. Nipple/areola counts appeared to be the most sensitive measure of effect, followed by male sex organ weights at sexual maturation, and finally gross and histopathological findings. The results indicate the absence of evidence for effects at low or very low dose levels. A non-monotonic dose-response relationship was not evident.

The Deep Correlation between Energy Metabolism and Reproduction: A View on the Effects of Nutrition for Women Fertility

In female mammals, mechanisms have been developed, throughout evolution, to integrate environmental, nutritional and hormonal cues in order to guarantee reproduction in favorable energetic conditions and to inhibit it in case of food scarcity. This metabolic strategy could be an advantage in nutritionally poor environments, but nowadays is affecting women's health. The unlimited availability of nutrients, in association with reduced energy expenditure, leads to alterations in many metabolic pathways and to impairments in the finely tuned inter-relation between energy metabolism and reproduction, thereby affecting female fertility. Many energetic states could influence female reproductive health being under- and over-weight, obesity and strenuous physical activity are all conditions that alter the profiles of specific hormones, such as insulin and adipokines, thus impairing women fertility. Furthermore, specific classes of nutrients might affect female fertility by acting on particular signaling pathways. Dietary fatty acids, carbohydrates, proteins and food-associated components (such as endocrine disruptors) have per se physiological activities and their unbalanced intake, both in quantitative and qualitative terms, might impair metabolic homeostasis and fertility in premenopausal women. Even though we are far from identifying a "fertility diet", lifestyle and dietary interventions might represent a promising and invaluable strategy to manage infertility in premenopausal women.

Exposure to endocrine disruptor induces transgenerational epigenetic deregulation of microRNAs in primordial germ cells

In mammals, germ cell differentiation is initiated in the Primordial Germ Cells (PGCs) during fetal development. Prenatal exposure to environmental toxicants such as endocrine disruptors may alter PGC differentiation, development of the male germline and induce transgenerational epigenetic disorders. The anti-androgenic compound vinclozolin represents a paradigmatic example of molecule causing transgenerational effects on germ cells. We performed prenatal exposure to vinclozolin in mice and analyzed the phenotypic and molecular changes in three successive generations. A reduction in the number of embryonic PGCs and increased rate of apoptotic cells along with decrease of fertility rate in adult males were observed in F1 to F3 generations. Blimp1 is a crucial regulator of PGC differentiation. We show that prenatal exposure to vinclozolin deregulates specific microRNAs in PGCs, such as miR-23b and miR-21, inducing disequilibrium in the Lin28/let-7/Blimp1 pathway in three successive generations of males. As determined by global maps of cytosine methylation, we found no evidence for prominent changes in DNA methylation in PGCs or mature sperm. Our data suggest that embryonic exposure to environmental endocrine disruptors induces transgenerational epigenetic deregulation of expression of microRNAs affecting key regulatory pathways of germ cells differentiation.

Estimation of in vivo dose of dermally applied chemicals leading to estrogen/androgen receptor-mediated toxicity from in vitro data--Illustration with four reproductive toxicants

We present a quantitative in vitro-in vivo extrapolation framework enabling the estimation of the external dermal exposure dose from in vitro experimental data relevant to a toxicity pathway of interest. The framework adapts elements of the biological pathway altering dose (BPAD) method [Judson et al. Chem Res Toxicol 2011;24:451] to the case of dermal exposure. Dermal doses of four toxicants equivalent to concentrations characterizing their effect on estrogen receptor α or androgen receptor activity in chemical-activated luciferase expression (CALUX) assays are estimated. The analysis shows that dermal BPADs, calculated from one in vitro concentration, can differ by up to a factor of 55, due to the impact applied dose and dermal exposure scenarios can have on skin permeation kinetics. These features should therefore be taken into account in risk assessment of dermally applied chemicals.

A high throughput screening system for predicting chemically-induced reproductive organ deformities

There is a great need for alternative testing methods for reproductive toxicants that are practical, fast, cost-effective and easy to interpret. Previously we followed a pragmatic approach using readily available tests, which was successful in predicting reproductive toxicity of chemicals [13]. This initial battery still contained apical tests and is fairly complex and low in its throughput. The current study aimed to simplify this screening battery using a mechanistic approach and a panel of high throughput CALUX reporter gene assays. A mechanistic approach was taken to validate this high throughput test battery. To this end it was challenged with two preselected sets of chemicals addressing two major apical effect classes relevant in reproductive toxicity. We found selectivity in this battery in that 82% of the compounds inducing reproductive organ deformities were predicted correctly, while for compounds inducing neural tube defects this was the case in 47% only. This is consistent with the mechanisms of toxicity covered in the battery. The most informative assays in the battery were ERalpha CALUX to measure estrogenicity and the AR-anti CALUX assay to measure androgen receptor antagonism.

Sexually dimorphic effects of ancestral exposure to vinclozolin on stress reactivity in rats

How an individual responds to the environment depends upon both personal life history as well as inherited genetic and epigenetic factors from ancestors. Using a 2-hit, 3 generations apart model, we tested how F3 descendants of rats given in utero exposure to the environmental endocrine-disrupting chemical (EDC) vinclozolin reacted to stress during adolescence in their own lives, focusing on sexually dimorphic phenotypic outcomes. In adulthood, male and female F3 vinclozolin- or vehicle-lineage rats, stressed or nonstressed, were behaviorally characterized on a battery of tests and then euthanized. Serum was used for hormone assays, and brains were used for quantitative PCR and transcriptome analyses. Results showed that the effects of ancestral exposure to vinclozolin converged with stress experienced during adolescence in a sexually dimorphic manner. Debilitating effects were seen at all levels of the phenotype, including physiology, behavior, brain metabolism, gene expression, and genome-wide transcriptome modifications in specific brain nuclei. Additionally, females were significantly more vulnerable than males to transgenerational effects of vinclozolin on anxiety but not sociality tests. This fundamental transformation occurs in a manner not predicted by the ancestral exposure or the proximate effects of stress during adolescence, an interaction we refer to as synchronicity.

Are we ready to consider transgenerational epigenetic effects in human health risk assessment?

Recently, there has been a growing concern that chemically or nutritionally mediated epigenetic changes might lead to adverse health outcomes. The natural question is whether the existing chemical safety assessment paradigm is or is not protective of epigenetic-mediated effects, and if there is a need to incorporate new endpoints to specifically address epigenetics. Of particular interest are transgenerational epigenetic effects, which can be passed on through multiple generations. To investigate these questions, a comparison was performed between OECD guideline rat toxicology studies versus several rat transgenerational epigenetic studies. This analysis focused on vinclozolin owing to the availability of a comprehensive suite of dose-response data (NOAEL, reference dose, and human exposure estimates) for both conventional and epigenetic endpoints. This analysis revealed that vinclozolin transgenerational effects were demonstrated at a dose level (100 mg/kg/day) that was: (1) ∼40-fold higher than the overall lowest-observed-adverse-effect level (LOAEL) from rat guideline studies, (2) ∼80-fold higher than the lowest NOAEL from rat guideline studies, (3) ∼80,000-fold higher than the reference dose for the molecule, and (4) ∼1.2-million fold above human exposure estimates. Through this analysis, we conclude that additional research across a spectrum of doses is necessary to elucidate the interplay between epigenetics and apical endpoints before considering epigenetics in human health risk assessment. Therefore, we recommend focusing future research toward (1) examining for potential causal relationships between epigenetic alterations and adverse apical endpoints, and (2) understanding the dose-response relationship of these causal epigenetic alterations when compared with those of the apical endpoints.

Lack of anti-androgenic effects of equol on reproductive neuroendocrine function in the adult male rat

Equol (EQ), a metabolite of the soy isoflavone daidzein, has well known estrogenic properties. Data from animal studies suggested that EQ may act also as an anti-androgen. However, data regarding how EQ may affect brain functions like the regulation of neuroendocrine activity and reproductive outcomes in adult male rats are still lacking. We therefore investigated the effects of EQ on sex-steroid regulated gene expression in the brain [medial preoptic area/anterior hypothalamus (MPOA/AH) and medial basal hypothalamus/median eminence (MBH/ME)], pituitary, and prostate as a reference androgen-dependent organ. Furthermore reproductive outcomes were evaluated. The anti-androgen flutamide (FLUT) served as reference compound. Male rats (n=12 per group) were treated by gavage for 5 days with either EQ (100 or 250 mg/kgBW/day), or FLUT 100 mg/kgBW/day. All vehicle- and EQ-treated males showed successful reproductive outcomes, whereas FLUT-exposed males had severe reproductive impairments resulted in infertility. FLUT decreased relative weights of prostate, seminal vesicles and epididymides, and increased serum levels of luteinizing hormone, follicle-stimulating hormone, testosterone and 5α-dihydrotestosterone without altering prolactin levels, whereas EQ exerted opposite effects. Both EQ and FLUT decreased gonadotropin releasing hormone (GnRH) expression in the MPOA/AH. Only FLUT upregulated levels of GnRH receptor expression both in the MBH/ME and pituitary. While EQ downregulated the hypothalamic ERα and ERβ expressions, but FLUT did not. In the prostate, only FLUT upregulated both ERα and AR mRNA expression levels. Taken together, our findings are the first data that EQ did not induce anti-androgenic effects on brain, prostate and male reproductive parameters, however, estrogenic neuroendocrine and reproductive effects of EQ were observed.

Pesticide exposure and endocrine dysfunction in the cotton crop agricultural workers of southern Punjab, Pakistan

This study evaluated pesticide effects on reproductive and thyroid hormones of cotton farmers of southern Punjab, Pakistan. A total of 88 cotton farmers (42 spray applicators and 46 cotton pickers) were randomly included with an equal number of age- and sex-matched controls. Sampling was done in high spraying and peak picking seasons. Serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone, prolactin, thyroid-stimulating hormone (TSH), total triiodothyroxine (TT3), and free thyroxine (fT4) were carried out by enzymatic immunoassay. Plasma cholinesterase (PChE) levels were measured by Ellman's method. Serum FSH, LH, and testosterone levels were significantly high in spray applicators (P < .01).Serum FSH and testosterone levels were significantly raised in cotton pickers (P < .01). Serum prolactin was decreased significantly in both groups (P < .01).Serum fT4 was significantly reduced in cotton pickers (P < .01). Pesticide exposure is associated with thyroid and reproductive hormone levels disturbance.

Vinclozolin--no transgenerational inheritance of anti-androgenic effects after maternal exposure during organogenesis via the intraperitoneal route

The goal of this study was to examine the potential transgenerational inheritance of anti-androgenic effects induced by Vinclozolin administered intraperitoneally to pregnant Wistar rats (Crl:WI[Han]). Dams were dosed with Vinclozolin at 0, 4 or 100mg/kg bw/d on gestation days 6-15. Male offspring of F1-F3 generations were bred with untreated females to yield F2-F4 offspring. No evident anti-androgenic effects were observed at 4mg/kg bw/d, but a case of hypospadias as well as delayed sexual maturation in F1 male offspring was observed as a sign of anti-androgenicity at 100mg/kg bw/d. However, F1-F3 males developed normally to sexual maturity and were able to mate and to generate healthy progeny. Sperm count, morphology and motility were not affected in F1-F4 generation male offspring. In conclusion, transgenerational inheritance of Vinclozolin's anti-androgenic effects was not evident in outbred Wistar rats.

In Utero and Lactational Exposure to Low-Dose Genistein-Vinclozolin Mixture Affects the Development and Growth Factor mRNA Expression of the Submandibular Salivary Gland in Immature Female Rats

It has been suggested that hormonally controlled submandibular salivary gland (SSG) development and secretions may be affected by endocrine disruptor compounds. We investigated the effects of oral gestation-lactation exposure to 1 mg/kg body weight daily dose of the estrogenic soy-isoflavone genistein and/or the anti-androgenic food contaminant vinclozolin in female rats. The SSGs of female offspring were collected at postnatal day 35 to study gland morphogenesis and mRNA expression of sex-hormone receptors and endocrine growth factors as sex-dependent biomarkers. Because of high expression in neonatal SSG, mRNA expression of transforming growth factor α was also studied. Exposure to genistein, vinclozolin, or a genistein+vinclozolin mixture resulted in significantly lower numbers of striated ducts linked to an increase in their area and lower acinar proliferation (Ki-67–positive nuclei). Exposure to the mixture had the highest significant effects, which were particularly associated with repression of epidermal growth factor, nerve growth factor, and transforming growth factor α expression. In conclusion, early exposure to low doses of genistein and vinclozolin can affect glandular structure and endocrine gene mRNA expression in prepubertal SSG in female rats, and the effects are potentialized by the genistein+vinclozolin mixture. Our study provides the first evidence that SSG are targeted by both estrogenic and anti-androgenic disrupting compounds and are more sensitive to mixtures.

Retrospective analysis of relative parameter sensitivity in multi-generation reproductive toxicity studies

Current suggestions towards amending the OECD two-generation protocol include omission of the second generation and inclusion of additional parameters. This study analysed the relative parameter sensitivity in 18 individually published multi-generation studies with substances toxic to fertility. Among parameters that most often determined the reproductive LOAEL were weight of testis, dam and pup as well as litter size. Several other parameters were found to be unaffected in all studies evaluated. Some substances affected a specific set of parameters, indicating that rarely affected parameters may prove crucial in individual situations. This argues for the inclusion of a wide spectrum of parameters to cover all possible effects. Less sensitive parameters, mechanistically related to more sensitive ones, may be omitted as they will unlikely contribute to the overall LOAEL. This study gives first insights and needs follow-up by more extensive analyses before firm conclusions on the design of the two-generation study protocol can be drawn.

Developmental and Reproductive Effects of SE5-OH: An Equol-Rich Soy-Based Ingredient

Consumption of the isoflavones daidzein, genistein, glycitein, and their structural analogues is generally considered beneficial to human health. Equol is not found in soy, but is converted from daidzein by human gut bacterial flora. Research indicates that between 30-50% of the population is capable of converting daidzein to equol; therefore, there has been recent development of a new equol-rich functional food that relies on bacterial conversion of daidzein to equol under strictly controlled conditions. Therefore, a new equol-rich soy product (SE5-OH) has been developed, based on the bacterial conversion of daidzein; and its reproductive and developmental toxicity has been evaluated in a two-generation study and a developmental toxicity study with Sprague-Dawley rats at dose levels of 200, 1000, and 2000 mg/kg/day by gavage. SE5-OH contains approximately 0.65% equol, 0.024% daidzein, 0.022% genistein, and 0.30% glycitein. From the reproductive study, the no-observed-adverse-effect-level (NOAEL) for SE5-OH determined for both male and female rats is 1000 mg/kg/day (6.5 mg equol/kg/day). In the developmental toxicity phase of the study, no effects by SE5-OH were found in the embryo-fetus at any of the doses tested. The NOAEL for developmental effects of SE5-OH is 2000 mg/kg/day (13 mg equol/kg/day).

NMR analysis of male fathead minnow urinary metabolites: a potential approach for studying impacts of chemical exposures

The potential for profiling metabolites in urine from male fathead minnows (Pimephales promelas) to assess chemical exposures was explored using nuclear magnetic resonance (NMR) spectroscopy. Both one-dimensional (1D) and two-dimensional (2D) NMR spectroscopy was used for the assignment of metabolites in urine from unexposed fish. Because fathead minnow urine is dilute, we lyophilized these samples prior to analysis. Furthermore, 1D 1H NMR spectra of unlyophilized urine from unexposed male fathead minnow and Sprague-Dawley rat were acquired to qualitatively compare rat and fish metabolite profiles and to provide an estimate of the total urinary metabolite pool concentration difference. As a small proof-of-concept study, lyophilized urine samples from male fathead minnows exposed to three different concentrations of the antiandrogen vinclozolin were analyzed by 1D 1H NMR to assess exposure-induced changes. Through a combination of principal components analysis (PCA) and measurements of 1H NMR peak intensities, several metabolites were identified as changing with statistical significance in response to exposure. Among those changes occurring in response to exposure to the highest concentration (450 microg/L) of vinclozolin were large increases in taurine, lactate, acetate, and formate. These increases coincided with a marked decrease in hippurate, a combination potentially indicative of hepatotoxicity. The results of these investigations clearly demonstrate the potential utility of an NMR-based approach for assessing chemical exposures in male fathead minnow, using urine collected from individual fish.

Effects of a 5-day treatment with vinclozolin on the hypothalamo-pituitary-gonadal axis in male rats

Vinclozolin (VZ), a potent antiandrogenic fungicide, is known to interfere with male reproductive function. Little data are currently available regarding possible impacts of VZ on brain function, particularly neuroendocrine activity and regulation of the hypothalamo-pituitary-gonadal (HPG) axis. Therefore, we examined the effects of VZ on gene expression in the brain (MBH/ME, MPOA/AH, striatum, hippocampus), pituitary, prostate, seminal vesicles, and epididymis of 4-month-old male rats treated daily by gavage for 5 days with VZ (150 mg/kg body weight/day). Alterations in levels of serum hormones and gene expression were determined by RIA and qRT-PCR, respectively. Our results revealed that (i) VZ decreases epididymis weights, increases serum levels of LH and T, and decreases serum TSH and total T(4) levels; (ii) VZ affects the hypothalamic expression of both estrogen receptor (ERs) subtypes, ERalpha and ERbeta; (iii) in the extrahypothalamic brain areas, VZ alters expression of ERs and androgen receptor (AR); (iv) in the pituitary, VZ up-regulates expression of the GnRH receptor, LHbeta, alpha-subunit, and TERP-1/-2; (v) in the ventral prostate, VZ increases and decreases levels of AR and ERbeta mRNA, respectively; (vi) in the seminal vesicles, VZ increases levels of AR and ERalpha mRNA expressions; (vii) in the epididymis, VZ up-regulates AR and ERbeta mRNA expression. These results indicate that in vivo VZ is not a 'pure' antiandrogen, since it exerts mixed AR antagonistic/ERs agonistic actions observed at the levels of mRNA expression of selected androgen- and estrogen-regulated genes in the CNS, pituitary, and male accessory sex organs.

Thyroid function in Danish greenhouse workers

BACKGROUND

From animal studies it is known that currently used pesticides can disturb thyroid function.

METHODS

In the present study we investigated the thyroid function in 122 Danish greenhouse workers, to evaluate if greenhouse workers classified as highly exposed to pesticides experiences altered thyroid levels compared to greenhouse workers with lower exposure. Serum samples from the greenhouse workers were sampled both in the spring and the fall to evaluate if differences in pesticide use between seasons resulted in altered thyroid hormone levels.

RESULTS

We found a moderate reduction of free thyroxine (FT4) (10-16%) among the persons working in greenhouses with a high spraying load both in samples collected in the spring and the fall, but none of the other measured thyroid hormones differed significantly between exposure groups in the cross-sectional comparisons. However, in longitudinal analysis of the individual thyroid hormone level between the spring and the fall, more pronounced differences where found with on average 32% higher thyroid stimulating hormone (TSH) level in the spring compared to the fall and at the same time a 5-9% lower total triiodthyroxin (TT3), free triiodthyroxine (FT3) and FT4. The difference between seasons was not consistently more pronounced in the group classified as high exposure compared to the low exposure groups.

CONCLUSION

The present study indicates that pesticide exposure among Danish greenhouse workers results in only minor disturbances of thyroid hormone levels.

Developmental exposure to environmental endocrine disruptors: consequences within the ovary and on female reproductive function

Female reproductive function depends upon the exquisite control of ovarian steroidogenesis that enables folliculogenesis, ovulation, and pregnancy. These mechanisms are set during fetal and/or neonatal development and undergo phases of differentiation throughout pre- and post-pubescent life. Ovarian development and function are collectively regulated by a host of endogenous growth factors, cytokines, gonadotropins, and steroid hormones as well as exogenous factors such as nutrients and environmental agents. Endocrine disruptors represent one class of environmental agent that can impact female fertility by altering ovarian development and function, purportedly through estrogenic, anti-estrogenic, and/or anti-androgenic effects. This review discusses ovarian development and function and how these processes are affected by some of the known estrogenic and anti-androgenic endocrine disruptors. Recent information suggests not only that exposure to endocrine disruptors during the developmental period causes reproductive abnormalities in adult life but also that these abnormalities are transgenerational. This latter finding adds another level of importance for identifying and understanding the mechanisms of action of these agents.