Impact of the phytoestrogen content of laboratory animal feed on the gene expression profile of the reproductive system in the immature female rat

Pregnancy and herbal medicines: An unnecessary risk for women's health-A narrative review

The indiscriminate use of herbal medicines to prevent or to heal diseases or even the use for questionable purposes such as weight loss has received both interest and scrutiny from the scientific community and general public alike. An increasing number of women put their own and the unborn child's health at risk due to a lack of knowledge about the phytochemical properties and adequate use of herbal medicine (phytomedicines or herbal supplements) and lack of communication with their healthcare provider. The purpose of this narrative review was to summarize the use of herbal medicines during pregnancy and their potential toxic effects to highlight the importance of caution when prescribing herbal medicines or supplements for women, because, in addition to suffering interactions and a great amount of information obtained in preclinical predictive studies, assessment of nephrotoxicity, neurotoxicity, hepatotoxicity, genotoxicity, and teratogenicity of traditional medicinal herbs still remains scarce in the clinical setting.

Comparison of the effects of mesquite pod and Leucaena extracts with phytoestrogens on the reproductive physiology and sexual behavior in the male rat

Mesquite (Prosopis sp.) and Leucaena leucocephala are widespread legumes, widely used to feed several livestock species and as food source for human populations in several countries. Both mesquite and Leucaena contain several phytoestrogens which might have potential estrogenic effects. Thus, the aim of this study was to evaluate the effects of mesquite pod and Leucaena extracts on several aspects of behavior and reproductive physiology of the male rat. The effects of the extracts were compared with those of estradiol (E2) and of two isoflavones: daidzein (DAI) and genistein (GEN). The following treatments were given to groups of intact male rats: vehicle; mesquite pod extract; Leucaena extract; E2; DAI; GEN. The results indicate that mesquite pod and Leucaena extracts disrupt male sexual behavior in a similar way to DAI and GEN, but less than E2. The main disruptor of sexual behavior was E2, however after 40 and 50days of administration, both extracts and phytoestrogens disrupted sexual behavior in a similar way to E2. The extracts also increased testicular germ cell apoptosis, decreased sperm quality, testicular weight, and testosterone levels, as phytoestrogens did, although these effects were less than those caused by estradiol. The number of seminiferous tubules with TUNEL-positive germ cells increased in extracts treated groups in a similar way to phytoestrogens groups, and E2 caused the greatest effect. The number of TUNEL-positive cells per tubule increased only in Leucaena extract and E2 groups, but not in mesquite- and phytoestrogens-treated groups. Spermatocytes and round spermatids were the TUNEL-positive cells observed in all experimental groups. This effect was associated with smaller testicular weights without atrophy in experimental groups compared with control. Testicular atrophy was only observed in estradiol-treated males. Testosterone decreased in males of all experimental groups, compared with control, this androgen was undetectable in E2 treated males. These results suggest that mesquite pod and Leucaena extracts cause effects similar to those of phytoestrogens in male rat reproduction, these effects were lower than those caused by E2.

Measuring the kinetics of the binding of xenoestrogens and estrogen receptor alpha by fluorescence polarization

The mechanism of endocrine disruption by environmental xenoestrogens is unclear. Bisphenol-A (BPA) is an example. Its concentration in human serum is low, and its binding with estrogen receptor (ER) is weak. Yet its effect on prostate and mammary gland development was observed. We investigated whether this effect could be explained in terms of binding kinetics. We used the method of fluorescence polarization anisotropy to measure the kinetic rate constants of the binding of ERα with 19 xenoestrogens. Relative binding affinities (RBA) were also deduced from the kinetics. We drew three observations. First, our RBAs were consistent with published values, thus establishing the validity of our results. Second, our method allowed the determination of low RBAs (∼ 10(-4)) of lipophilic ligands, such as dibutyl phthalate. They could not be measured by steady-state IC50 assays because of their low solubility. Third, we found that BPA had a surprisingly high kon > 10(4) M(-1) s(-1). While its RBA was 1500 times lower than that of 17β estradiol (E2), its kon was >1/90 that of E2. As a result, a 10 min surge of BPA from pM to nM could drive the fraction of BPA-activated ERα to a potent 0.1%. This might help to explain the observable estrogenic impacts of BPA.

Evaluation of estrogenic activity in animal diets using in vitro assay

A yeast estrogen bioassay (RIKILT REA) was in-house validated for feed on the 5μg 17β-estradiol-equivalents per kg level according to EC Decision 2002/657/EC. All the performance characteristics met the criteria as defined in the Decision and the REA is able to detect 17β-estradiol in animal feed at a low level of 1.15-2μgkg(-1). Subsequently, the developed and validated procedure was applied to determine the estrogenic activity in 24 feed samples intended for food producing animals, pets and laboratory animals. Two batches of rodent diet Murigran and one dog feed have been presented as a suspect, i.e. gave responses above the determined decision limit (CCα) and detection capability (CCβ). In assessing the performance of the estrogenic activity in these diets evaluated by comparison with the 17β-estradiol calibration curve, 17β-estradiol-equivalence levels of 7.07μg EEQkg(-1) and 9.54μg EEQkg(-1) in two batches of rodent diet and 5.3μg EEQkg(-1) in dog feed have been established. The activities observed in the rodent feed could be explained by chemical analysis, revealing high amounts of genistein, daidzein and trace amounts of zearalenone. In addition, the estrogenic activity in one of rodent feed was above the established CCα, but below the CCβ values established and all other samples showed no estrogenic activity with responses below the CCα value, which corresponds to levels below 2μg EEQkg(-1).

Nutritional flavonoids impact on nuclear and extranuclear estrogen receptor activities

Flavonoids are a large group of nonnutrient compounds naturally produced from plants as part of their defence mechanisms against stresses of different origins. They emerged from being considered an agricultural oddity only after it was observed that these compounds possess a potential protective function against several human degenerative diseases. This has led to recommending the consumption of food containing high concentrations of flavonoids, which at present, especially as soy isoflavones, are even available as overthecounter nutraceuticals. The increased use of flavonoids has occurred even though their mechanisms are not completely understood, in particular those involving the flavonoid impact on estrogen signals. In fact, most of the human health protective effects of flavonoids are described either as estrogenmimetic, or as antiestrogenic, while others do not involve estrogen signaling at all. Thus, the same molecule is reported as an endocrine disruptor, an estrogen mimetic or as an antioxidant without estrogenic effects. This is due in part to the complexity of the estrogen mechanism, which is conducted by different pathways and involves two different receptor isoforms. These pathways can be modulated by flavonoids and should be considered for a reliable evaluation of flavonoid, both estrogenicity and antiestrogenicity, and for a correct prediction of their effects on human health.

Mesquite pod extract modifies the reproductive physiology and behavior of the female rat

Phytoestrogens are non steroidal compounds that can bind to estrogen receptors, mimicking some effects of estradiol (E(2)). These compounds are widespread among legumes, which are used as pasture, and their importance in animal agriculture has increased. Mesquite (Prosopis sp) is a widespread legume, widely used to feed several livestock species in Mexico. The main product of mesquite is the pod, which is considered high quality food. As a legume, it could be assumed that mesquite contains some amounts of phytoestrogens which might induce potential estrogenic effects. However, to our knowledge, there are no reports regarding the possible estrogenic activity of this legume either in livestock or in animal models such as the rat. Therefore, in this study, we evaluated the potential estrogenic effects of mesquite pod extract on several aspects of behavior and reproductive physiology of the female rat. The effects of the extract were compared with those of E(2) and two isoflavones: daidzein (DAI) and genistein (GEN). The following treatments were given to groups of intact and ovariectomized (OVX) female rats: vehicle; mesquite pod extract; E(2); GEN; DAI. Compared to vehicle groups, mesquite pod extract, DAI, GEN, and E(2) increased uterine weight and induced growth in vaginal and uterine epithelia. In intact rats, mesquite pod extract, GEN and DAI altered estrous cyclicity, decreased lordotic quotient and intensity of lordosis. In OVX rats, mesquite pod extract, DAI and GEN induced vaginal estrus, increased vaginal epithelium height, and induced lordosis, although its intensity was reduced, compared with intact rats in estrus and E2-treated rats. These results suggest that mesquite pod extract could have estrogenic activity. However, the presence of phytoestrogens in this legume remains to be confirmed.

Advances in zebrafish husbandry and management

The zebrafish has emerged over the past several decades to become a mainstream animal model. While the growth of the use of the fish in basic biomedical research has been characterized by innovation, the methods and tools for fish husbandry, management, and care have been slow to evolve beyond those conceived during the initial establishment of the model system. While these approaches and technologies have certainly served the purposes of the field, they must now be improved to better match the widening scope and scale of research being done in fish. Such advances are made possible by applying new scientific information to the development of more sophisticated approaches for fish husbandry and management, and by considering the lessons learned during the establishment of the rodent model system. This review highlights the recent progress made in various areas of fish husbandry and management and points out new directions for further improvements.

Growth and survival of zebrafish (Danio rerio) fed different commercial and laboratory diets

The need to develop standardized diets to support zebrafish (Danio rerio) research is supported by the knowledge that specific dietary ingredients, nutrients, or antinutritional factors in diets have been shown to affect development and growth of adult D. rerio and their offspring. In this study, there were seven dietary treatments consisting of five commercially available diets and two laboratory-prepared diets, three replicates per treatment. Fish were fed ad libitum twice daily for 9 weeks. At 9 weeks, both weight and length were recorded to determine condition indices. D. rerio fed one of the laboratory-prepared diets had significantly higher weights than individuals fed any of the other diets and exhibited significantly higher lengths than those fed five of the six remaining diets. Although there were significant differences in general growth demographics (length/weight) after the 9-week feeding trial, no significant differences in overall health of D. rerio were observed for the different dietary treatments as determined by statistical analysis of condition factor indices (K = [weight x 100]/length(3)). The success achieved with the laboratory-prepared diets represents the foundation for establishing an open-formulation nutritional standard to ensure that the D. rerio model for research does not generate confounding research results caused by nutritional vagaries.

An Updated Weight of the Evidence Evaluation of Reproductive and Developmental Effects of Low Doses of Bisphenol A

There is controversy over whether low doses of bisphenol A (BPA, CAS no. 80-05-7) cause reproductive and developmental effects in humans. We update the 2004 weight-of-evidence assessment of an expert panel convened by Harvard's Center for Risk Analysis by critically evaluating over 50 additional studies published between April 2002 and February 2006 that examine in vivo reproductive and developmental toxicity in mammals at doses <or=5 mg/kg-d. Our findings are consistent with the Harvard study: some statistically significant findings in rats and mice exist but they are generally countered by more numerous studies showing no effect for similar endpoints. No effect is marked or consistent across species, doses, and time points. Some mouse studies report morphological changes in testes and sperm and some non-oral mouse studies report morphological changes in female reproductive organs. Owing to lack of first-pass metabolism, results from non-oral studies are of limited relevance to oral human exposure. Human biomonitoring indicates exposures lower than the "low" doses in the reviewed animal studies. Reports of human health impact are very limited and inconsistent. Taken together, the weight of evidence does not support the hypothesis that low oral doses of BPA adversely affect human reproductive and developmental health.

Lack of effect of butylparaben and methylparaben on the reproductive system in male rats

BACKGROUND

Parabens are widely used preservatives in cosmetics and pharmaceutical products, and approved as food additives. Parabens have been considered safe for these uses for many years. Recently, adverse effects on male reproductive parameters in rats have been reported when parabens were given orally for 8 weeks starting at three weeks of age. Our studies used two representative parabens, methyl- and butylparaben, to try to replicate these studies and thereby evaluate potential reproductive effects in male Wistar rats.

METHODS

Diets containing 0, 100, 1000 or 10,000 ppm of either butyl- or methylparaben were fed to male rats for eight weeks. Rats were 22 days of age at the start of exposure. Parameters evaluated included organ weights, histopathology of reproductive tissues, sperm production, motility, morphology and reproductive hormone levels (butylparaben only).

RESULTS

None of the parameters evaluated for either paraben showed compound- or dosage-dependent adverse effects. Metabolism experiments of butylparaben indicate that it is rapidly metabolized by non-specific esterases to p-hydroxybenzoic acid and butanol, neither of which is estrogenic.

CONCLUSIONS

Exposure to methyl- or butylparaben in the diet for eight weeks did not affect any male reproductive organs or parameters at exposures as high as 10,000 ppm, corresponding to a mean daily dose of 1,141.1+/-58.9 or 1,087.6+/-67.8 mg/kg/day for methyl- and butylparaben, respectively. The rapid metabolism of parabens by esterases probably explains why these weakly estrogenic substances elicit no in vivo effects when administered by relevant exposure routes (i.e., topical and oral).

Key developments in endocrine disrupter research and human health

Environmental etiologies involving exposures to chemicals that mimic endogenous hormones are proposed for a number of adverse human health effects, including infertility, abnormal prenatal and childhood development, and reproductive cancers (National Research Council, 1999; World Health Organization, 2002). Endocrine disrupters represent a significant area of environmental research with important implications for human health. This article provides an overview of some of the key developments in this field that may enhance our ability to assess the human health risks posed by exposure to endocrine disrupters. Advances in methodologies of hazard identification (toxicogenomics, transcriptomics, proteomics, metabolomics, bioinformatics) are discussed, as well as epigenetics and emerging biological endpoints.

Effects of lactational exposure to soy isoflavones on reproductive system in neonatal female rats

To examine effects of lactational exposure to soy isoflavones on female reproductive system, soy isoflavones, 0 (control), 10, 50, 100, 150 or 200 mg/kg body weight, were administered to maternal rats by gavage daily during postnatal days 5-10. Ten female litters were killed on day 11. Uterine and ovary weights, serum oestradiol and progesterone concentrations, proliferating cell nuclear antigen, mRNA expressions of oestrogen receptor, androgen receptor and progesterone receptor in uterus or ovary were measured. When compared to the control group, litters in the 150 and 200 mg/kg body weight groups had significantly higher ovary and uterine weights (P < 0.05). Endometrial thickness was also significantly increased. Isoflavone-treated groups had increased proliferating cell nuclear antigen staining in comparison to the control group. Litters in the 50, 150 and 200 mg/kg body weight groups had significantly higher oestradiol concentration while lower progesterone concentrations than those in the control group (P < 0.05 or P < 0.01). All soy isoflavone-treated groups had androgen receptor mRNA expressions in ovary and uterus comparable to the control group. Progesterone receptor mRNA expression in the 150 and 200 mg/kg body weight groups was significantly lower than that in control group (P < 0.01). However, ovaries in the 150 and 200 mg/kg body weight groups had significantly higher oestrogen receptor mRNA expression while the uterus in these two treatment groups had significantly lower expressions, when compared to the control group (P < 0.05 or P < 0.01). In conclusion, lactational exposure to isoflavones could result in oestrogen-like actions on the reproductive system of neonate female rats, which mechanisms may be, at least, involved with modifications of hormone production and steroid receptor transcription in the reproductive system.

Use of traditional end points and gene dysregulation to understand mechanisms of toxicity: toxicogenomics in mechanistic toxicology

Microarray technologies can be used to generate massive amounts of gene expression information as an initial step to decipher the molecular mechanisms of toxicologic changes. Identifying genes whose expression is associated with specific toxic end points is an initial step in predicting, characterizing, and understanding toxicity. Analysis of gene function and the chronology of gene expression changes represent additional methods to generate hypotheses of the mechanisms of toxicity. Follow-up experiments are typically required to confirm or refute hypotheses derived from toxicogenomic data. Understanding the mechanism of toxicity for a compound is a critical step in forming a rational plan for developing counterscreens for toxicity and for increasing productivity of research and development while decreasing the risk of late-stage failure in pharmaceutical development.

Variations in phytoestrogen content between different mill dates of the same diet produces significant differences in the time of vaginal opening in CD-1 mice and F344 rats but not in CD Sprague-Dawley rats

BACKGROUND

The optimum test diet and rodent species/strain for evaluating endocrine-disrupting compounds (EDCs) are critical.

OBJECTIVES

We conducted studies to evaluate rodent species sensitivity and the effects of diets varying in phytoestrogen content on the time of vaginal opening (VO) in CD-1 mice, Fischer 344 (F344) rats, and CD Sprague-Dawley (S-D) rats.

METHODS

Mice were weaned on postnatal day (PND) 15 and rats on PND19 and randomly assigned to control or test diets. Body weights, food consumption, and time of VO were recorded.

RESULTS

The time of VO was significantly advanced in F344 rats fed diets containing daidzein and genistein, whereas these same diets did not advance VO in S-D rats. When animals were fed the AIN-76A diet spiked with genistein, time of VO was significantly advanced at all doses in CD-1 mice, at the two highest doses in F344 rats, and at the highest dose in S-D rats. The time of VO in F344 rats was more highly correlated with the phytoestrogen content than with the total metabolizable energy (ME) of 12 diets.

CONCLUSIONS

The S-D rat is less sensitive to dietary phytoestrogens compared with the F344 rat or the CD-1 mouse, suggesting that the S-D rat is not the ideal model for evaluating estrogenic activity of EDCs. The profound effects of dietary phytoestrogens on the time of VO, an estrogen-sensitive marker, indicate that a standardized open-formula phytoestrogen-free diet containing a low ME level should be used to optimize the sensitivity of estrogenic bioassays.

The expression of Hedgehog genes (Ihh, Dhh) and Hedgehog target genes (Ptc1, Gli1, Coup-TfII) is affected by estrogenic stimuli in the uterus of immature female rats

The objective of this study was to investigate the effects of estrogen receptor (ER) agonists and an ER antagonist on the expression of Hedgehog genes (Indian hedgehog: Ihh; Desert hedgehog: Dhh) and Hedgehog target genes (Patched 1: Ptc1; glioma-associated oncogene homolog 1: Gli1; chicken ovalbumin upstream promoter transcription factor II: Coup-TfII) in the rat uterus. Immature female rats were administered once with 17alpha-ethynyl estradiol (EE, an ER agonist), propyl pyrazole triole (PPT, an ERalpha-selective agonist), diarylpropionitrile (DPN, an ERbeta-selective agonist), or ICI 182,780 (an ER antagonist). Expression of mRNA for Ihh, Dhh, and Ptc1 was dose-dependently downregulated by EE in the uterus of immature rats, mediated by ER as confirmed by coadministration of ICI 182,780. The mRNA expression levels of Ptc1, Gli1, and Coup-TfII were simultaneously downregulated during the period in which the mRNA expression levels of Ihh and Dhh were downregulated in the uterus after administration of EE. PPT downregulated the transcription of Ihh, Dhh, Ptc1, Gli1, and Coup-TfII, indicating that expression of these genes was regulated by the ERalpha-dependent pathway. DPN also downregulated the transcription of Ihh and Dhh, although the effect was weaker than that of PPT, indicating that the regulation of uterine Ihh and Dhh transcription was also affected by the ERbeta-dependent pathway. These results suggest that the expression of Hedgehog genes (Ihh, Dhh) and Hedgehog target genes (Ptc1, Gli1, Coup-TfII) is affected by estrogenic stimuli in the uterus of immature female rats.

Gene expression profiles in the liver of mice irradiated with (60)Co gamma rays and treated with soybean isoflavone

PURPOSE

To better understand the molecular mechanisms underlying the radio-protective effect of soybean isoflavone that we observed in our recent animal experiments.

MATERIALS AND METHODS

We utilized a cDNA microarray to investigate the expression profiles of 4,096 known genes in the livers of irradiated-mice with or without soybean isoflavone treatment. Dye swap approach was employed to control for gene-specific dye bias and quantitative real-time RT-PCR was performed on several genes to validate the cDNA microarray data.

RESULTS

Compared with the control group, 68 genes were up-regulated and 28 genes were down-regulated in mice treated with irradiation alone, whereas only 6 genes were down-regulated and 35 genes were up-regulated in mice treated with soybean isoflavone. Interestingly, some of the down-regulated genes in the irradiated group, such as DNA repair and stress response genes and cytoskeleton-associated genes, which are markers of cellular damage after irradiation, were maintained at close to normal expression levels after soybean isoflavone treatment.

CONCLUSIONS

Comparison of gene expression profiles in the livers of irradiated-mice treated with or without soybean isoflavone suggested that soybean isoflavone may be an efficient tool to reverse irradiation damage of the liver through multiple-pathways and also provides important clues to further pursue the molecular mechanisms underlying the radio-protective activity of soybean isoflavone.

Background gene expression in rat kidney: influence of strain, gender, and diet

In order to gain better insight into factors (strain, gender, and diet) influencing background variability in kidney gene expression, we examined the transcriptomes of male and female Crl:CD(SD)IGSBR (Sprague-Dawley [SD]) and CDF(Fischer 344)/CrlBR rats maintained for 19 days on three different diets (ad libitum [AL], diet restriction-75% of AL, and casein-based phytoestrogen-free diet). Kidney RNA was analyzed using Agilent Rat oligo microarrays (approximately 20,000 genes). Principal component analysis demonstrated that strain and gender have the most impact on the variability in gene expression, while diet had a lesser effect. The majority of the affected genes differed by a magnitude of four-fold or less between strains/gender, with some previously known to be sex-hormone regulated (SLC22A7 and SLC21A1). One gene of particular interest was ornithine decarboxylase, a significant marker of cell proliferation and tumor promotion, which was expressed at an 18-fold greater level in SD rats. Further analysis revealed that the difference in expression was due to the use of an alternate polyadenylation signal resulting in the production of two different sizes of transcripts. These results demonstrate that gender and strain have significant influence on gene expression which could be a confounder when comparing results, especially when it involves predictive fingerprint/patterns.

Maternal genistein alters coat color and protects Avy mouse offspring from obesity by modifying the fetal epigenome

Genistein, the major phytoestrogen in soy, is linked to diminished female reproductive performance and to cancer chemoprevention and decreased adipose deposition. Dietary genistein may also play a role in the decreased incidence of cancer in Asians compared with Westerners, as well as increased cancer incidence in Asians immigrating to the United States. Here, we report that maternal dietary genistein supplementation of mice during gestation, at levels comparable with humans consuming high-soy diets, shifted the coat color of heterozygous viable yellow agouti (A(vy/a) offspring toward pseudoagouti. This marked phenotypic change was significantly associated with increased methylation of six cytosine-guanine sites in a retrotransposon upstream of the transcription start site of the Agouti gene. The extent of this DNA methylation was similar in endodermal, mesodermal, and ectodermal tissues, indicating that genistein acts during early embryonic development. Moreover, this genistein-induced hypermethylation persisted into adulthood, decreasing ectopic Agouti expression and protecting offspring from obesity. Thus, we provide the first evidence that in utero dietary genistein affects gene expression and alters susceptibility to obesity in adulthood by permanently altering the epigenome.

Dietary modulation of p-nonylphenol-induced polycystic kidneys in male Sprague-Dawley rats

We had previously found that p-nonylphenol (NP) at 1000-2000 ppm in a soy- and alfalfa-free diet induced severe polycystic kidney disease (PKD) in both male and female pups exposed from gestation day 7 through postnatal day (PND) 50 and hypothesized that differences in dietary components contributed to the severity of lesions relative to those reported in other studies using similar doses of NP. The present study investigated the dietary modulation of NP-induced PKD using the same exposure regimen with 2000 ppm NP in four different diets: the natural ingredient soy- and alfalfa-free diet that had been used in the earlier study, Purina 5K96; two defined diets AIN-93G, designated AIN-CAS, and a modified AIN-93G with soy protein isolate replacing casein as the protein source (AIN-SPI); and the commonly used natural ingredient diet Purina 5001 (P5001). Serum isoflavone levels were negligible in animals fed the soy-free AIN-CAS and 5K96 diets and were 2- to 18-fold higher in animals fed P5001 than in those fed AIN-SPI. Consumption of P5001 was significantly greater than consumption of the other diets, and those animals fed P5001 were generally significantly heavier than animals receiving the other diets. NP significantly reduced body weight gain in male pups regardless of the diet fed. There was no evidence of NP-induced kidney toxicity in male pups at PND 2, 14, or 21 or in the dams. In PND 50 male pups, serum blood urea nitrogen was significantly elevated by NP in all diet groups. Urine volume and urinary N-acetyl beta-glucuronidase were significantly increased by NP in the soy-free 5K96 and AIN-CAS diet groups. Relative kidney weights were increased by NP in all diet groups except P5001, with the greatest increase in AIN-CAS and 5K96 diet groups. Microscopic evaluation of kidneys from the PND 50 males showed that NP induced PKD in all diet groups but with marked variation in the severity depending on the diet. PKD was severe in 100% of the NP-treated animals in the AIN-CAS and 5K96 groups, moderate in 88% of the AIN-SPI diet group, and mild in only 40% of the P5001 diet group. Thus, diet can significantly modulate the development of PKD induced by dietary NP in rats. Soy components, as well as other complex dietary factors, may account for the level of protection afforded by the P5001 diet.

Workgroup report: Implementing a national occupational reproductive research agenda--decade one and beyond

The initial goal of occupational reproductive health research is to effectively study the many toxicants, physical agents, and biomechanical and psychosocial stressors that may constitute reproductive hazards in the workplace. Although the main objective of occupational reproductive researchers and clinicians is to prevent recognized adverse reproductive outcomes, research has expanded to include a broader spectrum of chronic health outcomes potentially affected by reproductive toxicants. To aid in achieving these goals, the National Institute for Occupational Safety and Health, along with its university, federal, industry, and labor colleagues, formed the National Occupational Research Agenda (NORA) in 1996. NORA resulted in 21 research teams, including the Reproductive Health Research Team (RHRT). In this report, we describe progress made in the last decade by the RHRT and by others in this field, including prioritizing reproductive toxicants for further study; facilitating collaboration among epidemiologists, biologists, and toxicologists; promoting quality exposure assessment in field studies and surveillance; and encouraging the design and conduct of priority occupational reproductive studies. We also describe new tools for screening reproductive toxicants and for analyzing mode of action. We recommend considering outcomes such as menopause and latent adverse effects for further study, as well as including exposures such as shift work and nanomaterials. We describe a broad domain of scholarship activities where a cohesive system of organized and aligned work activities integrates 10 years of team efforts and provides guidance for future research.

Evaluation of the gene expression changes induced by 17-?-ethynyl estradiol in the immature uterus/ovaries of the rat using high density oligonucleotide arrays

BACKGROUND

In a previous study, we determined the effects of 17-alpha-ethynyl estradiol (EE) on gene expression using microarrays that represented approximately 9,000 genes, which was the state of-the-art. Higher content arrays with almost double the number of genes have since become available. In order to better determine whether common sets of gene expression changes can be predictive of estrogenic activity, we have replicated the previous experiment using the more comprehensive microarray.

METHODS

Immature 20-day-old Sprague-Dawley rats were exposed to 0.1, 1, and 10 microg EE/kg/day ( subcutaneously [s.c.]), for four days, dosing from postnatal day (PND) 20-23). Changes in a more comprehensive expression level of 15,923 rat annotated genes and expressed sequence tags were evaluated on PND 24.

RESULTS

By comparing the response of the treatment groups versus controls using various statistical parameters, we determined that the expression of 1,394 genes showed a significant change with respect to control (p< or =0.0001), to at least one of the EE dosages. The tissues from animals exposed to 0.1 microg EE/kg/day showed changes in the expression of only 33 genes, whereas when they were exposed to 1 or 10 microg EE/kg/day, the expression of 409 and 548 genes was modified, respectively. A dose-dependent analysis indicated that 592 genes showed a robust and significant response to EE exposure (increased or decreased). Our analysis confirmed the regulation of previously identified estrogen-sensitive genes, and clearly identified novel mediators of estrogen actions, both in the uterus as well as in the ovary.

CONCLUSIONS

This compendium of genes represents the largest compilation of estrogen-responsive genes that has ever been identified for the immature uterus and ovary of any species, and can be used to generate testable hypothesis to improve the understanding of the molecular pathways associated with physiological and pathophysiological responses to exposure to chemicals with estrogenic properties.