In vivo test systems for the quantitative and qualitative analysis of the biological activity of phytoestrogens

Subchronic Exposure to Cadmium Causes Persistent Changes in the Reproductive System in Female Wistar Rats

Cadmium (Cd) is an environmental toxicant and endocrine disruptor in humans and animals, and recent studies have illustrated that the uterus is exceedingly sensitive to Cd toxicity. The aim of the study was to investigate the influence of subchronic (90 days) oral Cd exposure in daily doses of 0.09-4.5 mg/kg b.w. on the balance of sex hormones by estimating estradiol (E₂) and progesterone (P) concentrations in the uterus and plasma in comparison with the effects of 17β-E₂. Additionally, the uterine weight, histopathological changes in the uterus and ovaries, the regularity of the estrous cycle, Cd bioaccumulation in uterine tissue, and selected biochemical parameters of oxidative stress were determined. A long period of observation (three and six months following the administration period) was used to assess whether the existing effects are reversible. The lowest dose of Cd caused effects similar to 17β-E₂: an increase of E₂ concentration in the uterus, endometrial epithelium thickness, and disturbed estrous cycle with estrus phase prolongation. The obtained results suggest that Cd causes nonlinear response. Higher doses of Cd caused a significant decrease in E₂ concentration in the uterus and plasma, estrous cycle disturbances, endometrium atrophy, and structural damage in the ovaries. This dose additionally induces lipid peroxidation in the uterine tissues. It is noteworthy that a prolonged time of observation after terminating the exposure showed persistent changes in the concentration of E₂ in uterine tissue, as well as alterations in estrous cycle phases, and an increase in lipid peroxidation in the uterus. Moreover, significant positive correlations between the plasma E₂ concentration and endometrial epithelium thickness in all studied groups were found. In summary, subchronic oral Cd exposure of female rats may result in impaired fertility processes.

Fenugreek seeds estrogenic activity in ovariectomized female rats

The estrogenic activities of fenugreek seeds (Trigonella foenum-graecum L.), widely used in traditional pharmacopoeia, are reflected in the uterus of ovariectomized female rats, with a slight increase in dry and wet weight, a thickening of the stroma and the uterine epithelium and the development of the endometrial glands. In the vagina, the estrogenic action is shown through an increase in the epidermal cell number and a tendency to keratinization, leading to vaginal opening.

Furthermore, this estrogenic potential of fenugreek seeds is confirmed by the over-expression of progesterone receptors in the uterine tissues supporting possible interactions between phytoestrogens and estrogen receptors.

Therefore, Fenugreek seeds may be capable of promoting the development of reproductive tissues of immature ovariectomized rats, and its estrogenic activity may take its action by holding phystoestrogens that interact with estrogen binding sites and activate the same estradiol-mediated cell signaling pathways.

Thus, our results give added scientific support to the popular use of Fenugreek seeds as an alternative for several health problems such as fertility and menopause related disorders.

Dose-Dependent Differential Effects of In Vivo Exposure of Cadmium on Myometrial Activity in Rats: Involvement of VDCC and Ca2+-Mimicking Pathways

Present study was undertaken to study the effect of 28-days exposure of female adult rats to cadmium (Cd) in drinking water @ 3, 10 and 30 parts per million (ppm) on myometrial responsiveness to different spasmogens and unravel the possible mechanism of alterations in myometrial activity. Cadmium and Ca²⁺ levels in blood and uterus were measured by atomic absorption spectroscopy while isometric tension in myometrial strips was measured using data acquisition system-based physiograph. Dose-dependent increase in levels of cadmium was observed in both blood and uterus while calcium was increased only in the uterus as compared to those in control. Significant increase in absolute tension and mean integral tension along with non-significant increase in frequency of myometrial contraction was observed in rats of Cd-treated groups. As compared to the control, cadmium decreased and increased the effects of calcium chloride, 80 mM KCl, histamine (0.1 μM) and oxytocin (10^-2 IU/ml) in lower-dose (3 ppm) and higher-dose groups (10 and 30 ppm), respectively. Cadmium potentiated and inhibited the relaxant response to phenylephrine in myometrium of rats at lower-dose (3 ppm) and highest-dose (30 ppm) Cd-treated groups, respectively. Results of our study revealed that Cd accumulates in the myometrium of rats and alters its responsiveness to oxytocin, histamine, 80 mM KCl, calcium chloride and phenylephrine, and these effects are differentially mediated depending on levels of exposure possibly through voltage-dependent calcium channel (VDCC) and Ca²⁺-mimicking pathways.

Estrogenic Potentials of Traditional Chinese Medicine

Estrogen, a steroid hormone, is associated with several human activities, including environmental, industrial, agricultural, pharmaceutical and medical fields. In this review paper, estrogenic activity associated with traditional Chinese medicines (TCMs) is discussed first by focusing on the assays needed to detect estrogenic activity (animal test, cell assay, ligand-binding assay, protein assay, reporter-gene assay, transcription assay and yeast two-hybrid assay), and then, their sources, the nature of activities (estrogenic or anti-estrogenic, or other types), and pathways/functions, along with the assay used to detect the activity, which is followed by a summary of effective chemicals found in or associated with TCM. Applications of estrogens in TCM are then discussed by a comprehensive search of the literature, which include basic study/pathway analysis, cell functions, diseases/symptoms and medicine/supplements. Discrepancies and conflicting cases about estrogenicity of TCM among assays or between TCM and their effective chemicals, are focused on to enlarge estrogenic potentials of TCM by referring to omic knowledge such as transcriptome, proteome, glycome, chemome, cellome, ligandome, interactome and effectome.

Effects of the aryl hydrocarbon receptor agonist 3-methylcholanthrene on the 17β-estradiol regulated mRNA transcriptome of the rat uterus

Polycyclic aromatic hydrocarbons (PAHs) are products of incomplete combustion of organic compounds, abundant in exhaust fumes and cigarette smoke. They act by binding to the aryl hydrocarbon receptor (AHR) which induces expression of phase 1 and phase 2 enzymes in the liver. PAH induced AHR activation may also lead to adverse effects by modulating other pathways, for example estrogen receptor (ER) signaling in the female reproductive tract. We have investigated the effects of the PAH 3-methylcholanthrene (3-MC) on 17β-estradiol (E2) dependent signaling in the uterus of ovariectomized rats to characterize the cross talk between AHR and ER on an mRNA transcriptome wide scale. A standard three day uterotrophic assay was performed in young adult Lewis rats. Treatment induced effects were analyzed using histology, immunohistochemistry and gene expression analysis by microarray and qPCR. 3-MC shows broad E2 antagonistic effects on uterine mRNA transcription of the vast majority of E2 regulated genes, significantly altering prostaglandin biosynthesis, complement activation, coagulation pathways and other inflammatory response pathways. The regulation of ER expression in the uterus, but not the regulation of E2 metabolism in the liver, was identified as a potentially important factor in mediating this general antiestrogenic effect. The regulation of prostaglandin biosynthesis by E2 is important for inflammation-like events during pregnancy including the initiation of birth. Our results suggest that adverse effects of PAHs on prostaglandin related pathways are likely caused by the interference with E2 signaling, specifically by inhibiting the E2 mediated downregulation of PGF2α. Characterization of the generalized antagonistic effect of 3-MC on E2 dependent signaling in the rat uterus thus contributes to a better understanding of molecular mechanisms of the toxicity of PAHs in female reproductive organs.

A morphological study of uterine alterations in mice due to exposure to cadmium

We investigated the morphologic and molecular effects of exposure to cadmium (Cd) for 30 and 60 days on the uteri of mice. We assessed uterine morphometric measurements, eosinophilia, mast cell numbers, endometrial apoptosis, proliferation and estrogen receptor alpha (ERα) immunoreactivity. We examined vaginal smears that reflected the hormonal alterations in the female reproductive tract. Because the female reproductive tract exhibits different morphology at each stage of the estrous cycle, we sacrificed all animals at estrus to make appropriate comparisons. Female BALB/c mice were exposed to 200 ppm Cd in their drinking water for either 30 or 60 days. Cd exposure caused significant decreases in endometrial thickness and number of glands in estrus phase uteri. The endometrial eosinophilia in the groups exposed to Cd also decreased compared to controls. Cd exposure increased the number of mast cells. Luminal and glandular epithelia were examined using the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and by immunostaining proliferating cell nuclear antigen (PCNA) and estrogen receptor α (ERα). Compared to controls, the apoptotic index increased with time in both Cd exposed groups, while the proliferation index decreased. ERα immunoreactivity was decreased in both Cd exposed groups compared to controls; the decrease was most apparent in the 30 day Cd group. We found that 60 day Cd exposure increased apoptosis in the endometrium, which may affect the receptivity of the uterus for implantation.

Effects of a glyphosate-based herbicide on the uterus of adult ovariectomized rats

Glyphosate is the active ingredient of several herbicide formulations. Different reports suggest that glyphosate-based herbicides (GBHs) may act as endocrine disruptors. We evaluated the potential estrogenic effects of a GBH formulation using the uterotrophic assay. Adult ovariectomized rats were sc injected for 3 consecutive days with: saline solution (vehicle control), 2.10-5  g E2 /kg/day (uterotrophic dose; UE2 ), 2.10-7  g E2 /kg/day (nonuterotrophic dose; NUE2 ), or 0.5, 5, or 50 mg GBH/kg/day of the. Twenty-four hours after the last injection, the uterus was removed and weighed and processed for histopathology and mRNA extraction. Epithelial cell proliferation and height and expression of estrogen-responsive genes were evaluated (estrogen receptors, ERα and ERβ; progesterone receptor, PR; complement 3, C3). Uterine weight and epithelial proliferation were not affected by GBH. However, the luminal epithelial cell height increased at GBH0.5. ERα mRNA was downregulated by all GBH doses and E2 groups, whereas PR and C3 mRNA were diminished by GBH0.5. GBH5-, GBH50-, and UE2 -treated rats showed downregulated ERα protein expression in luminal epithelial cells, while the receptor was upregulated in the stroma. GBH upregulated ERβ (GBH0.5-50) and PR (GBH5) expressions in glandular epithelial cells, similar effect to that of NUE2 group. These results indicate that, although the uterine weight was not affected, GBH modulates the expression of estrogen-sensitive genes. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1191-1201, 2017.

Phytoestrogens in Botanical Dietary Supplements: Implications for Cancer

Phytoestrogens are plant constituents that possess either estrogenic or antiestrogenic activity. Although their activities are weak as compared with human endogenous estrogens, the consumption of phytoestrogens may have clinically significant consequences. A number of botanicals, or the compounds contained therein, have been identified as putative estrogenic agents, but consensus in the biomedical community has been hampered by conflicting data from various in vitro and in vivo models of estrogenic activity. Phytoestrogens may serve as chemopreventive agents while at the same time being capable of promoting growth in estrogen receptor positive cancer cell lines. Furthermore, they may exert their estrogenic influence through receptor-dependent and/or receptor-independent mechanisms. These findings have led to speculation that phytoestrogen intake might be ill advised for patients at an increased risk for hormone-dependent cancers, cancer patients, or cancer survivors. This article will attempt to sort out discrepancies between various experimental models and establish whether certain herbs possess estrogenic activity. The review will focus on 5 popular botanical dietary supplements: Trifolium pratense (red clover), Cimicifuga racemosa (black cohosh), Humulus lupulus (hops), Angelica sinensis (dong quai), and Glycyrrhiza glabra (licorice). It will address their mechanisms of action, clinical evidence bases, and implications for use in cancer.

Danshen enhanced the estrogenic effects of Qing E formula in ovariectomized rats

BACKGROUND

Menopause is characterized by a decrease in life quality due to the appearance of uncomfortable symptoms. Nowadays, Understanding menopause-associated pathophysiology and developing new strategies to improve the treatment of menopausal-associated symptoms is an important issue. Our study was to evaluate the synergistic effects of Danshen (salvia miltiorrhiza bunge) and the phytoestrogenic effects of 3 modified Qing E formulas, to explore a better formula for menopausal disorders.

METHODS

100 rats were randomized into 5 groups: Sham (Sham operation group), OVX (model group of ovariectomized rat), BDL (group with low concentration of Qing E Formula), BDH (group with high concentration of Qing E Formula) and BDD (group with high concentration of Qing E Formula Plus Danshen), receiving vehicle and extract of different modified Qing E formula respectively. The food intake, body weight, uterus weight, blood levels of triglycerides (TG), total cholesterol (TC) and cholesterol fractions were assessed. The mammary glands and uterus were morphologically analyzed. The bone density of tibias were measured by peripheral quantitative computed tomography (pQCT). Additionally, luciferase induction assays were performed in Hela cells with the mixtures derived from Qing E formula plus Danshen (BDD).

RESULTS

Qing E formula plus Danshen significantly increased the uterus wet weight, enhanced the thickness of uterine wall, endometrial epithelium and glandular epithelium, improved trabecular bone and total density evidently, reduced the levels of low density lipoprotein cholesterol (LDL-C) and TG, possessed notable estrogen receptor beta (ERβ) and estrogen receptor alpha (ERα) agonist activity.

CONCLUSION

Qing E formula plus Danshen exerted more evident estrogen-like effects, thus it has a potential therapeutic use to treat menopausal disorders.

Erythrina excelsa exhibits estrogenic effects in vivo and in vitro and is cytotoxic on breast and colon cancer cell lines

CONTEXT

Eythrina excelsa Baker (Fabaceae) is a medicinal plant used to treat various ailments including those of the female genital tract.

OBJECTIVE

The objective of this study is to investigate the estrogenic and cytotoxic effects of the ethanol extract of the stem bark of E. excelsa.

MATERIALS AND METHODS

Erythrina excelsa was evaluated in vitro using the yeast estrogen screen (YES). The extract was then tested in a 3-day uterotrophic assay on ovariectomised Wistar rats at doses of 50 and 100 mg/kg BW/d. Cytotoxic effects were assessed on breast (MCF-7) and colon (HT-29) cancer cell lines using the MTT cell viability assay. Additionally, a LC-PDA-ESI (+)-HRMS and HRMS/MS method was developed and applied for the identification of representative secondary metabolites scaffolds in the extract.

RESULTS

In the YES, the extract stimulated the transactivation of the estrogen receptor in a dose-dependent manner with an EC50 value of 1.8 μg/mL. In rats, E. excelsa increased uterine wet weight, uterine epithelial height, and the mRNA expression of estrogen-responsive genes in the uterus and liver at 50 whereas at 100 mg/kg BW/d anti-estrogenic effects were observed. In the MTT-assay, a dose-dependent decrease of the viability of both cell lines was observed with EC50 values of 13.6 μg/mL (MCF-7) and 27.7 μg/mL (HT-29). The phytochemical analysis revealed that the extract is rich in isoflavonoids, mainly prenylated and pyran-derivatives thereof.

CONCLUSION

Erythrina excelsa is rich in prenylated and pyran-substituted isoflavonoids, exhibits estrogenic/anti-estrogenic and cytotoxic effects and warrant sufficient interest for deeper investigations.

Botanical compounds and their regulation of nuclear receptor action: the case of traditional Chinese medicine

Nuclear receptors (NRs) are major pharmacological targets that allow an access to the mechanisms controlling gene regulation. As such, some NRs were identified as biological targets of active compounds contained in herbal remedies found in traditional medicines. We aim here to review this expanding literature by focusing on the informative articles regarding the mechanisms of action of traditional Chinese medicines (TCMs). We exemplified well-characterized TCM action mediated by NR such as steroid receptors (ER, GR, AR), metabolic receptors (PPAR, LXR, FXR, PXR, CAR) and RXR. We also provided, when possible, examples from other traditional medicines. From these, we draw a parallel between TCMs and phytoestrogens or endocrine disrupting chemicals also acting via NR. We define common principle of action and highlight the potential and limits of those compounds. TCMs, by finely tuning physiological reactions in positive and negative manners, could act, in a subtle but efficient way, on NR sensors and their transcriptional network.

Involvement of oxidative stress in the mechanism of cadmium-induced toxicity on rat uterus

The study was undertaken to explore whether cadmium bioaccumulation can induce oxidative stress in the uterus of rats. Cadmium (0.09, 0.9, 1.8 or 4.5mgCd/kg b.w.) was administered by gavage for 28 days. The animals were dissected on the first day and then after 90 days post exposure (second group of animals). The results show that cadmium accumulates in the uterus in a dose-dependent manner. The uterine Cd concentrations were almost the same in both groups, which is indicative of its long half-life in this organ. The accumulated cadmium caused significant changes in catalase (CAT) activity and lipid peroxidation (MDA) levels at concentrations from 0.09 to 0.35μgCd/g wet uterine tissue. In summary our results show that the induction of oxidative stress and lipid peroxidation in the uterus may play important roles in the mechanism of toxicity in this organ and may have a negative impact on reproductive processes.

Proliferative and estrogenic sensitivity of the mammary gland are modulated by isoflavones during distinct periods of adolescence

Isoflavone (ISO) exposure during adolescence has been demonstrated to modulate the estrogenic and proliferative sensitivity of the adult breast tissue. In this study, we investigated whether ISO exposure restricted to the period of puberty is sufficient to result in similar effects. Female rats were divided into three groups receiving either lifelong an ISO-free diet (IDD) or an ISO-rich diet (ISD), or an ISD from postnatal day (PND) 30 to PND 60 covering the time period of puberty (pISD). Serum concentrations of ISO and metabolites were determined at PND 50 and 80. At PND 50, ISD animals had significant higher equol serum levels than pISD animals. Onset of puberty occurred significantly earlier in the pISD and ISD group compared to the animals fed IDD. Cycle length was shortest in pISD group. To determine estrogen sensitivity of the adult breast tissue, adult rats were ovariectomized and subcutaneously treated either with estradiol (E(2)) or with genistein (GEN) for 3 days (PND 77-80). Analysis of Ki-67 and proliferating cell nuclear antigen (PCNA) expression showed a reduced proliferative response of the breast to E(2) in pISD and ISD animals compared to IDD group, while the induction of progesterone receptor (PR) was higher in both IDD and pISD compared to ISD fed rats. Our results demonstrate that ISO exposure during puberty is sufficient to reduce the proliferative response of the adult mammary gland but not to reduce the response of classical E(2) sensitive genes like the PR. In summary, our results demonstrate that animals exposed during different periods of their adolescence to ISO differ in several physiological aspects. In addition, the detected differences in the serum equol levels between pISD and ISD rats and the detected differences in the estrogen sensitivity of the breast clearly underline this assumption.

Comparison of estrogenic responses in bone and uterus depending on the parity status in Lewis rats

The reproductive transition of women through peri- to postmenopause is characterized by changes in steroid hormone levels due to the cessation of the ovarian function. Beside several complaints associated with these hormonal changes, the deterioration of the trabecular bone micro-architecture and the loss of skeletal mass can cause osteoporosis. At this life stage, women often have a reproductive history of one to several pregnancies. The ovariectomized skeletally mature rat (>10 months old) is one of the most commonly used animal models for postmenopausal osteoporosis research. Despite the fact that mammals can undergo up to several reproductive cycles (primi-/pluriparous), nulliparous animals are often used and the question whether changes in the hormonal milieu subsequently affect the skeleton and influence the outcome of intervention studies is often neglected in study designs. Therefore, the aim of the present study was to compare the estrogen responsiveness of nulliparous and pluriparous rats. For this purpose, one year old virgin or retired breeder Lewis rats were either sham operated or ovariectomized, whereas half of the ovariectomized animals received subcutaneous 17β-estradiol pellets eight weeks after surgery. After another four weeks, the effects on the uterus were determined by expression analysis of estrogen-dependently regulated steroid receptor genes and well-established marker genes. Moreover, trabecular bone parameters in the tibia were analyzed by micro-computed tomography (μCT). Parity-dependency in estrogen responsiveness was observed with respect to the achieved serum E2 levels in response to similar E2 treatment. This led to differences both on the uterus wet weight and on the expression level of uterine target genes. In addition, a reversal of the ovariectomy-induced changes of the bone architecture after 17β-estradiol substitution was only observed among the nulliparous. In conclusion, the observations of this study support parity-dependent differences in the responses to estrogenic compounds in the uterus and the bone of rats. These results indicate that the parity-status has an impact on the outcome of studies aiming at the investigation of estrogenic effects of compounds potentially used in hormone replacement and thus, this should be taken into consideration for further studies and particularly for the discussion of data obtained with the preclinical ovariectomized rat animal model.

Long-term effects of the rhapontic rhubarb extract ERr 731® on estrogen-regulated targets in the uterus and on the bone in ovariectomized rats

The efficacy of ERr 731(®), a commercially available extract isolated from Rheum rhaponticum, in terms of menopausal complaints like hot flushes, depression, anxiety and vaginal dryness has been proven in a two-year clinical study. Further a recent preclinical study excluded unwanted side effects on the endometrium by showing a lack of stimulation of proliferation marker genes by ERr 731(®) or its constituents in the 3-day uterotrophic assay. The present study aimed at further substantiating the safety of ERr 731(®) in terms of endometrial hyperplasia and at the same time test for potential estrogenic effects in the bone. Therefore, ovariectomized (ovx) rats were treated in a dietary long-term administration for 90 days. Hence, the modulation of proliferation in the uterus was investigated by examining the effects on the mRNA expression of proliferation marker genes (Mki67, Pcna), on the estrogen-responsive gene C3 and on the estrogen receptors ERα and ERβ. We additionally performed densitometry analysis of the proximal tibia metaphysis using peripheral computed tomography (pQCT) and quantified bone homeostasis markers in the serum to examine potential effects on the bone. In this study design, neither an uterotrophic response nor a modulation of proliferation marker genes on mRNA level has been observed as response to the long-term application of the rhapontic extract. Furthermore, no impact of the two administered ERr 731(®) doses on the E2 deprivation-induced bone loss has been evident at the end of the study. In conclusion, the observations from previous trials regarding the endometrial safety of ERr 731(®) have been supported by our experimental findings that exclude a stimulatory activity on proliferation in the uterus in a long-term administration in the young adult rat but no effect on the bone mineral density could be observed.

Proliferative effect of whey from cows' milk obtained at two different stages of pregnancy measured in MCF-7 cells

Dietary estrogens may play a role in the etiology of hormone-dependent cancers like breast cancer. Cow's milk contains various endogenous estrogens and feed derived phytoestrogens that potentially contribute to an estrogenic effect of milk in consumers, and therefore we evaluated the effect of milk (whey) in a proliferation assay with estrogen-sensitive MCF-7 human breast cancer cells. Milk samples were obtained from 22 cows representing different stages of pregnancy (first and second half) and whey was produced from the milk. 0·1, 0·25 or 0·5% whey was included in the cell culture medium and after 6 days of treatment cell proliferation was assessed by a colorimetric method with a fluorometer. Whey induced significant (P<0·05) proliferative effects compared with control cells with no added whey at all concentrations tested. There was no difference in the proliferative effect of whey depending on the stage of pregnancy from which the milk was obtained. We did not observe anti-proliferative effects when whey was tested in the presence of 10 pm estradiol in the medium. In conclusion, these results indicate that whey, irrespective of the pregnancy stage from which the milk was obtained induced a significant proliferative response in MCF-7 cells and no anti-proliferative effect, which may be caused, at least in part, by estrogens present in milk. The implications of our findings in relation to for example breast cancer will have to be studied further in other model systems preferentially in vivo.

Lipoxin A4 is a novel estrogen receptor modulator

Inflammation is intimately linked with naturally occurring remodeling events in the endometrium. Lipoxins comprise a group of short-lived, nonclassic eicosanoids possessing potent anti-inflammatory and proresolution properties. In the present study, we investigated the role of lipoxin A(4) (LXA(4)) in the endometrium and demonstrated that 15-LOX-2, an enzyme necessary for LX biosynthesis, is expressed in this tissue. Our results establish that LXA(4) possesses robust estrogenic activity through its capacity to alter ERE transcriptional activity, as well as expression of estrogen-regulated genes, alkaline phosphatase activity, and proliferation in human endometrial epithelial cells. Interestingly, LXA(4) also demonstrated antiestrogenic potential, significantly attenuating E2-induced activity. This estrogenic activity was directly mediated through estrogen receptors (ERs). Subsequent investigations determined that the actions of LXA(4) are exclusively mediated through ERα and closely mimic those of the potent estrogen 17β-estradiol (E2). In binding assays, LXA(4) competed with E2 for ER binding, with an IC(50) of 46 nM. Furthermore, LXA(4) exhibited estrogenic activity in vivo, increasing uterine wet weight and modulating E2-regulated gene expression. These findings reveal a previously unappreciated facet of LXA(4) bioactions, implicating this lipid mediator in novel immunoendocrine crosstalk mechanisms.

Urinary isoflavone phytoestrogens in German children and adolescents--a longitudinal examination in the DONALD cohort

SCOPE

In light of concerns about hormonally active agents, it is important to assess human exposure to such compounds, especially in children as a susceptible subgroup. Estrogenic plant constituents are present in the human diet in varying levels, in particular the isoflavones daidzein (DAI) and genistein (GEN). We aimed to examine age-dependent and secular trends in phytoestrogen exposures and to investigate equol (EQ) excretion of German children using biomarker analysis in 24-h urine samples from a longitudinally designed study.

METHODS AND RESULTS

The concentrations of DAI, its metabolite EQ and GEN were determined by GC-MS analysis in 24-h urines (510 samples) collected between 1985 and 2000 in 90 (47 boys) German children (6-18 years old), who are participants in the Dortmund Nutritional and Anthropometric Longitudinally Designed study. The results from the urinary biomarker analysis indicate isoflavone exposures at quite variable levels in German children: Analyte concentrations in over 500 urine samples cover the range reported previously in adults on typical German diet and with soy intake. EQ, the DAI metabolite produced by the gastrointestinal microflora, was detected in a high fraction of all samples, with 28/90 children (31%) excreting EQ in all their urines, and 62/90 children (68%) in at least one sample. Interestingly, when multiple urines obtained from individuals at different ages (6-18 years) were analyzed, EQ formation did not appear to be a constant trait over time. When stratified by sex, DAI, EQ and GEN concentrations (ng/mL) in urines and excretion rates (μg/day) were similar in boys and girls. Total isoflavone excretion rates (μg/day) increased during childhood (6-12 years) (p=0.02) and were constant during adolescence (13-18 years) (p=0.6). No clear trend for changes in dietary isoflavone exposure over the total study period was seen (p=0.7).

CONCLUSIONS

In conclusion, biomarkers in urine of German children and adolescents indicate a frequent, but widely variable dietary isoflavone intake and suggest no secular increase (1985-2000) in the exposure to isoflavone phytoestrogens among German children and adolescents.

Estrogen-like effects of cadmium in vivo do not appear to be mediated via the classical estrogen receptor transcriptional pathway

BACKGROUND

Cadmium (Cd), a ubiquitous food contaminant, has been proposed to be an endocrine disruptor by inducing estrogenic responses in vivo. Several in vitro studies suggested that these effects are mediated via estrogen receptors (ERs).

OBJECTIVE

We performed this study to clarify whether Cd-induced effects in vivo are mediated via classical ER signaling through estrogen responsive element (ERE)-regulated genes or if other signaling pathways are involved.

METHODS

We investigated the estrogenic effects of cadmium chloride (CdCl2) exposure in vivo by applying the Organisation for Economic Co-operation and Development (OECD) rodent uterotrophic bioassay to transgenic ERE-luciferase reporter mice. Immature female mice were injected subcutaneously with CdCl2 (5, 50, or 500 µg/kg body weight) or with 17α-ethinylestradiol (EE2) on 3 consecutive days. We examined uterine weight and histology, vaginal opening, body and organ weights, Cd tissue retention, activation of mitogen-activated protein kinase (MAPK) pathways, and ERE-dependent luciferase expression.

RESULTS

CdCl2 increased the height of the uterine luminal epithelium in a dose-dependent manner without increasing the uterine wet weight, altering the timing of vaginal opening, or affecting the luciferase activity in reproductive or nonreproductive organs. However, we observed changes in the phosphorylation of mouse double minute 2 oncoprotein (Mdm2) and extracellular signal-regulated kinase (Erk1/2) in the liver after CdCl2 exposure. As we expected, EE2 advanced vaginal opening and increased uterine epithelial height, uterine wet weight, and luciferase activity in various tissues.

CONCLUSION

Our data suggest that Cd exposure induces a limited spectrum of estrogenic responses in vivo and that, in certain targets, effects of Cd might not be mediated via classical ER signaling through ERE-regulated genes.

Treatment of menopausal symptoms by an extract from the roots of rhapontic rhubarb: the role of estrogen receptors

A dry extract from the roots of rhapontic rhubarb (extract Rheum rhaponticum (L.); ERr) has been commercially available in Germany for over two decades to treat menopausal symptoms. However, the molecular basis of its clinical effectiveness remains obscure. This article reviews the in vitro and in vivo data of its estrogenic actions, particularly those mediated by estrogen receptor-beta (ERbeta).

Effects of the special extract ERr 731 from Rheum rhaponticum on estrogen-regulated targets in the uterotrophy model of ovariectomized rats

A recent clinical study with a two-year application of the extract ERr 731 from Rheum rhaponticum demonstrated its efficacy and potentially suggested it safety regarding unwanted endometrial side effects. The aim of the present study is to provide experimental proof for the latter observation in a preclinical experimental animal model by assessing dose-dependent effects of ERr 731 - either alone or in combination with estradiol (E2) - on growth and proliferation in the uterus of ovariectomized (ovx) rats. ERr 731 was given in a dose corresponding to human therapeutic application and additionally in three pharmacologically relevant doses. In addition to uterine wet weight, this study examines the effects of ERr 731 on the uterine mRNA expression of the proliferation marker Ki67, proliferating cell nuclear antigen (PCNA), insulin-like growth factor-1 (IGF-1), type 1 IGF receptor (IGF-1R), the two estrogen receptor (ER) subtypes alpha and beta (ERalpha and ERbeta) and the estrogen-responsive gene complement C3 (C3). ERr 731 did neither stimulate an uterotrophic response in the uterotrophic assay with ovx rats nor stimulate or modulate the expression of genes associated with proliferation. In combination with E2, ERr 731 reduced the E2-induced uterine growth stimulation. These observations were further substantiated by the expression pattern of genes related to proliferation control, in view of the fact that the E2-induced elevation of Ki67 mRNA and PCNA protein levels in the uterus were counteracted by simultaneous treatment of the animals with ERr 731. In conclusion, the experimental findings presented here provide further evidence for the safety of ERr 731 towards unwanted uterine and endometrial proliferative events in response to ERr 731 and support observations from recent clinical trials.

Dose- and route-dependent hormonal activity of the metalloestrogen cadmium in the rat uterus

The toxic heavy metal cadmium (Cd) is regarded as a potential endocrine disruptor, since Cd exerts estrogen-like activity in vitro and can elicit some typical estrogenic responses in rodents upon intraperitoneal (i.p.) injection. But estrogenic effects have not been documented in vivo with other more relevant routes of exposure, although it is known that Cd absorption and distribution in the body is strongly affected by the application route. Therefore, we investigated its hormonal activity in ovariectomized Wistar rats after oral administration of CdCl(2) (0.05-4 mg/kg b.w. on 3 days by gavage and 0.4-9 mg/kg b.w. for 4 weeks in drinking water) in comparison with i.p. injection of CdCl(2) (0.00005-2 mg/kg b.w.). Uterus wet weight, height of uterine epithelium, and modulation of estrogen-regulated gene expression, i.e. uterine complement component 3 (C3), were determined, and also Cd-levels in uterus and liver were measured by atomic absorption spectrometry. The analysis revealed pronounced differences in Cd tissue levels and hormonal potency for the two routes of administration: a single i.p. injection of Cd increased dose-dependently uterine wet weight and thickness of the uterine epithelium. Interestingly, C3 mRNA expression in the uterus was down regulated at low doses of CdCl(2) (0.00005-0.05 mg/kg b.w.), but strongly stimulated at the highest dose of 2 mg/kg b.w. Other than i.p. injection, oral treatment with Cd, by gavage or in drinking water, did neither increase uterine wet weights nor epithelial thickness. But, both 3-day- and 4-week oral Cd administration resulted in a dose-dependent stimulation of C3 expression in the uterus, significant at and above 0.5 mg/kg b.w. In summary, our data demonstrate an estrogenic effect in the uterus upon i.p. injection of Cd, but considerably lower hormonal potency with oral administration: short and long-term oral treatment with Cd did not affect uterus weight or histology, whilst on the molecular level, an induction of estrogen sensitive uterine gene expression was observed, albeit at dose levels far exceeding those of dietary exposure in humans.

Tamoxifen-elicited uterotrophy: cross-species and cross-ligand analysis of the gene expression program

BACKGROUND

Tamoxifen (TAM) is a well characterized breast cancer drug and selective estrogen receptor modulator (SERM) which also has been associated with a small increase in risk for uterine cancers. TAM's partial agonist activation of estrogen receptor has been characterized for specific gene promoters but not at the genomic level in vivo.Furthermore, reducing uncertainties associated with cross-species extrapolations of pharmaco- and toxicogenomic data remains a formidable challenge.

RESULTS

A comparative ligand and species analysis approach was conducted to systematically assess the physiological, morphological and uterine gene expression alterations elicited across time by TAM and ethynylestradiol (EE) in immature ovariectomized Sprague-Dawley rats and C57BL/6 mice. Differential gene expression was evaluated using custom cDNA microarrays, and the data was compared to identify conserved and divergent responses. 902 genes were differentially regulated in all four studies, 398 of which exhibit identical temporal expression patterns.

CONCLUSION

Comparative analysis of EE and TAM differentially expressed gene lists suggest TAM regulates no unique uterine genes that are conserved in the rat and mouse. This demonstrates that the partial agonist activities of TAM extend to molecular targets in regulating only a subset of EE-responsive genes. Ligand-conserved, species-divergent expression of carbonic anhydrase 2 was observed in the microarray data and confirmed by real time PCR. The identification of comparable temporal phenotypic responses linked to related gene expression profiles demonstrates that systematic comparative genomic assessments can elucidate important conserved and divergent mechanisms in rodent estrogen signalling during uterine proliferation.

Long-term effects of dietary isoflavones on uterine gene expression profiles

Isoflavones (ISOs) are bioactive food ingredients of the traditional East Asian diet and currently discussed as alternatives to classical hormone replacement therapies and for reducing the prevalence of hormone-dependent cancers. Although there are many studies on ISOs, not much is known about their long-term effects. Therefore, we performed an animal experiment analyzing the effects of three different diets: a phytoestrogen-free diet, a diet supplemented with genistein (700 microg/g diet) and an ISO-high diet (232 microg daidzein and 240 microg genistein/g) at two distinct time points, juvenile (21 days) and adult (97 days). Exposure started prior to mating of the parents and throughout the life of the offspring. We observed a stronger increase of uterine wet weights in juvenile offspring with genistein exposure (1018+/-350 mg/kg BW) than with ISO-high diet (497+/-133 mg/kg BW). Whereas the expression of proliferation related genes (PCNA; Ki67; IGF-1; IGF-1R), analyzed by real-time-qPCR and Western blot, were significantly down-regulated in juvenile animals exposed to genistein. Additionally, genistein exposure led to estrogenic responses, observed upon increase of complement C3 and decrease of estrogen receptors gene expressions, while the exposure to ISO-high diet did not show these effects. In conclusion, both the time point on which phytoestrogen exposure starts together with the composition of the ingested phytoestrogen containing diet are of great importance for the biological response of the offspring.

Genistein decreases androgen biosynthesis in rat Leydig cells by interference with luteinizing hormone-dependent signaling

Testicular Leydig cells express estrogen receptors and are the predominant source of the male sex steroid hormone testosterone (T). Previous studies demonstrated that genistein acts through estrogen receptors in Leydig cells. In the present study, pre-treatment of Leydig cells isolated from 35 day-old male Long Evans rats with the epidermal growth factor receptor (EGFR) kinase inhibitor AG 1478 abrogated genistein inhibition of T biosynthesis. Also, incubation of Leydig cells in culture medium containing epidermal growth factor (EGF) decreased T secretion (control: 255+/-16; EGF: 190+/-17ng/10(6) cells, 24h) (P<0.05). However, T secretion by genistein-treated Leydig cells (0.1nM, 10muM; 24h) was rescued by post-treatment incubation with forskolin (control: 275+/-28 versus 325+/-35; 780+/-85; ng/10(6) cells, 3h) and dibutyryl cyclic adenosine 3'-5'-monophosphate (dbcAMP) (control: 370+/-65 versus 580+/-75; 2500+/-200; ng/10(6) cells, 3h) (P>0.05). Furthermore, post-treatment incubation with cholera toxin, an activator of G proteins, caused genistein-treated Leydig cells to produce similar T amounts as untreated control (control: 55+/-5 versus 52+/-2 and 47+/-4; ng/10(6) cells, 3h) (P>0.05). These observations imply that genistein action interferes with coupling of transmembrane luteinizing hormone receptors (LHR) with G proteins. Uncoupling of LHR from G proteins adversely affects adenylate cyclase function and impacts LH-dependent stimulation of Leydig cells. These findings have implications for testicular steroidogenesis in individuals exposed to genistein and soy-based products.

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.

Determination of the differential estrogenicity of isoflavonoids by E2-ER-ERE-dependent gene expression in recombinant yeast and MCF-7 human breast cancer cells

The use of phytoestrogens-containing natural sources as alternative hormone replacement therapy (HRT) has been a subject of debate for decades. Development of assays to characterize these phytoestrogens is required. In this study, differential estrogenicities of five isoflavonoids found in red clover and soy, including biochanin A, daidzein, formononetin, genistein and glycitein were examined in a yeast-based screen system with a classical palindromic estrogen response element (ERE)-ADE2 reporter and in a MCF-7 cell culture system with mRNA levels of ER-dependent genes compared. In a yeast-based assay, five isoflavonoids showed various extents of estrogenic potencies. A collection of primary estrogen receptor (ER)-regulated genes by estradiol (E2), including hTERT, c-MYC, BCL2 and Ha-ras (oncogenic) and quinone reductase (QR), human complement 3 (C3) and COX7RP (non-oncogenic) were selected as marker genes for a MCF-7 cell-based endogenous gene expression assay. The results indicated that the mRNA levels of these E2-ER-ERE-dependent marker genes were regulated differentially by five isoflavonoids, leading to distinct expression patterns, which are also significantly different from that of E2. Moreover, the anti-estrogenic effects of biochanin A and formononetin on E2-induced transcriptions of marker genes in MCF-7 cells were also displayed. Taken together, these results are significant for these naturally occurring isoflavonoids regarding the issues of safety and efficacy.

Inhibition of estrogen-mediated uterine gene expression responses by dioxin

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) exhibits antiestrogenic properties, including the inhibition of estrogen-induced uterine growth and proliferation. The inhibition of estrogen-mediated gene expression through ER/AhR cross-talk has been proposed as a plausible mechanism; however, only a limited number of inhibited responses have been investigated that are unlikely to fully account for the antiuterotrophic effects of TCDD. Therefore, the effects of TCDD on ethynyl estradiol (EE)-mediated uterine gene expression were investigated using cDNA microarrays with complementary physiological and histological phenotypic anchoring. Mice were gavaged with vehicle, 3 daily doses of 10 mug/kg EE, a single dose of 30 mug/kg TCDD, or a combination of EE plus TCDD and sacrificed after 4, 12, 24, and 72 h. TCDD cotreatment inhibited EE-induced uterine wet weight by 37, 23, and 45% at 12, 24, and 72 h, respectively. TCDD cotreatment also reduced EE-mediated stromal edema, hypertrophy, and hyperplasia and induced marked luminal epithelial cell apoptosis. A 2 x 2 factorial microarray design was used to identify EE- and TCDD-specific differential gene expression responses as well as their interactive effects. Only 133 of the 2753 EE-mediated differentially expressed genes were significantly modulated by TCDD cotreatment, indicating a gene-specific inhibitory response. The EE-mediated induction of many genes, including trefoil factor 1 and keratin 14, were inhibited by greater than 90% by TCDD. Functional annotation of inhibited responses was associated with cell proliferation, water and ion transport, and maintenance of cellular structure and integrity. These inhibited responses correlate with the observed histological alterations and may contribute to the antiuterotrophic effects of TCDD.

Estrogenic effects of marijuana smoke condensate and cannabinoid compounds

Chronic exposure to marijuana produces adverse effects on the endocrine and reproductive systems in humans; however, the experimental evidence for this presented thus far has not been without controversy. In this study, the estrogenic effect of marijuana smoke condensate (MSC) was evaluated using in vitro bioassays, viz., the cell proliferation assay, the reporter gene assay, and the ER competitive binding assay. The results of these assays were compared with those of three major cannabinoids, i.e., THC, CBD, and CBN. The estrogenic effect of MSC was further confirmed by the immature female rat uterotrophic assay. MSC stimulated the estrogenicity related to the ER-mediated pathway, while neither THC, CBD, nor CBN did. Moreover, treatment with 10 and 25 mg/kg MSC induced significant uterine response, and 10 mg/kg MSC resulted in an obvious change in the uterine epithelial cell appearance. MSC also enhanced the IGFBP-1 gene expression in a dose-dependent manner. To identify the constituents of MSC responsible for its estrogenicity, the MSC fractionated samples were examined using another cell proliferation assay, and the estrogenic active fraction was analyzed using GC-MS. In the organic acid fraction that showed the strongest estrogenic activity among the seven fractions of MSC, phenols were identified. Our results suggest that marijuana abuse is considered an endocrine-disrupting factor. Furthermore, these results suggest that the phenolic compounds contained in MSC play a role in its estrogenic effect.

Dioxin induces an estrogen-like, estrogen receptor-dependent gene expression response in the murine uterus

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a ubiquitous environmental contaminant that elicits a broad range of toxicities in a tissue-, sex-, age-, and species-specific manner, including alterations in estrogen signaling. Many, if not all, of these effects involve changes in gene expression mediated via the activation of the aryl hydrocarbon receptor (AhR), a ligand activated transcription factor. Recent data indicate that TCDD may also elicit AhR-mediated estrogenic activity through interactions with the estrogen receptor (ER). In an effort to further characterize the estrogenic activity of TCDD, a comprehensive time-course analysis of uterine gene expression was conducted using ovariectomized C57BL/6 mice. Comparison of the temporal uterine transcriptional response to TCDD with that of ethynyl estradiol (EE) revealed a large proportion of the TCDD-mediated gene expression changes were also responsive to EE. Furthermore, pretreatment of mice with the pure ER antagonist ICI 182 780 (faslodex) inhibited gene expression responses to both EE and TCDD, providing additional evidence that these transcriptional responses involve the ER.

A cross-species analysis of the rodent uterotrophic program: elucidation of conserved responses and targets of estrogen signaling

Physiological, morphological, and transcriptional alterations elicited by ethynyl estradiol in the uteri of Sprague-Dawley rats and C57BL/6 mice were assessed using comparable study designs, microarray platforms, and analysis methods to identify conserved estrogen signaling networks. Comparative analysis identified 153 orthologous gene pairs that were positively correlated, suggesting conserved transcriptional targets important in uterine proliferation. Functional annotation for these responses were associated with angiogenesis, water and solute transport, cell cycle control, redox control, DNA replication, protein synthesis and transport, xenobiotic metabolism, cell-cell communication, energetics, and cholesterol and fatty acid regulation. The identification of conserved temporal expression patterns of these orthologs provides experimental support for the transfer of functional annotation from mouse orthologs to 44 previously unannotated rat expressed sequence tags based on their homology and co-expression patterns. The identification of comparable temporal phenotypic responses linked to related gene expression profiles demonstrates the ability of systematic comparative genomic assessments to elucidate important conserved mechanisms in rodent estrogen signaling during uterine proliferation.

The effect of increasing concentrations ofFusariumtoxins in piglet diets on histological parameters of the uterus and vagina

The effects of feeding diets containing 0.01, 0.06, 0.15, 0.22 and 0.42 mg zearalenone and 0.2, 0.8, 1.0, 1.9 and 3.9 mg deoxynivalenol per kg, originating from Fusarium toxin contaminated maize, on the uterus of 50 prepubertal piglets (10 pigs per treatment; BW 32.6+/-5.4 kg; approximately 70 days of age) were investigated. The mean weight of the uteri of animals receiving the most highly contaminated diet was significantly increased at the time of slaughtering. The histological investigation showed no marked differences between the feeding groups. Histometrical parameters of the surface epithelium of the uterus, of the uterine glands and the vaginal epithelium were not altered by the treatment.

Phytoestrogens

Collectively, plants contain several different families of natural products among which are compounds with weak estrogenic or antiestrogenic activity toward mammals. These compounds, termed phytoestrogens, include certain isoflavonoids, flavonoids, stilbenes, and lignans. The best-studied dietary phytoestrogens are the soy isoflavones and the flaxseed lignans. Their perceived health beneficial properties extend beyond hormone-dependent breast and prostate cancers and osteoporosis to include cognitive function, cardiovascular disease, immunity and inflammation, and reproduction and fertility. In the future, metabolic engineering of plants could generate novel and exquisitely controlled dietary sources with which to better assess the potential health beneficial effects of phytoestrogens.

Phytoestrogens: a review of the present state of research

Phytoestrogens are a diverse group of plant-derived compounds that structurally or functionally mimic mammalian estrogens and show potential benefits for human health. The number of articles published on phytoestrogens has risen dramatically in the past couple decades. Further research continues to demonstrate the biological complexity of phytoestrogens, which belong to several different chemical classes and act through diverse mechanisms. This paper discusses the classification of phytoestrogens, methods of identification, their proposed mechanisms of action and botanical sources for phytoestrogens. The effects of phytoestrogens on breast and prostate cancers, cardiovascular disease, menopausal symptoms and osteoporosis will also be examined including research on benefits and risks.