Prenatal exposure to the phytoestrogen daidzein resulted in persistent changes in ovarian surface epithelial cell height, folliculogenesis, and estrus phase length in adult Sprague-Dawley rat offspring

Next-generation risk assessment read-across case study: application of a 10-step framework to derive a safe concentration of daidzein in a body lotion

Introduction: We performed an exposure-based Next Generation Risk Assessment case read-across study using New Approach Methodologies (NAMs) to determine the highest safe concentration of daidzein in a body lotion, based on its similarities with its structural analogue, genistein. Two assumptions were: (1) daidzein is a new chemical and its dietary intake omitted; (2) only in vitro data were used for daidzein, while in vitro and legacy in vivo data for genistein were considered. Methods: The 10-step tiered approach evaluating systemic toxicity included toxicokinetics NAMs: PBPK models and in vitro biokinetics measurements in cells used for toxicogenomics and toxicodynamic NAMs: pharmacology profiling (i.e., interaction with molecular targets), toxicogenomics and EATS assays (endocrine disruption endpoints). Whole body rat and human PBPK models were used to convert external doses of genistein to plasma concentrations and in vitro Points of Departure (PoD) to external doses. The PBPK human dermal module was refined using in vitro human skin metabolism and penetration data. Results: The most relevant endpoint for daidzein was from the ERα assay (Lowest Observed Effective Concentration was 100 ± 0.0 nM), which was converted to an in vitro PoD of 33 nM. After application of a safety factor of 3.3 for intra-individual variability, the safe concentration of daidzein was estimated to be 10 nM. This was extrapolated to an external dose of 0.5 μg/cm2 for a body lotion and face cream, equating to a concentration of 0.1%. Discussion: When in vitro PoD of 33 nM for daidzein was converted to an external oral dose in rats, the value correlated with the in vivo NOAEL. This increased confidence that the rat oral PBPK model provided accurate estimates of internal and external exposure and that the in vitro PoD was relevant in the safety assessment of both chemicals. When plasma concentrations estimated from applications of 0.1% and 0.02% daidzein were used to calculate bioactivity exposure ratios, values were >1, indicating a good margin between exposure and concentrations causing adverse effects. In conclusion, this case study highlights the use of NAMs in a 10-step tiered workflow to conclude that the highest safe concentration of daidzein in a body lotion is 0.1%.

Dairy calves are exposed to isoflavones during the developmentally most sensitive period of their life

Isoflavones represent a class of phytoestrogens present in plants. In dairy cows, dietary isoflavones have been shown to negatively affect reproductive performance. To the best of our knowledge, no studies have yet been conducted to determine if calves are pre- or neonatally confronted with isoflavones and their metabolites. In the present study, we hypothesize that isoflavones are passed on from the dam to the offspring in utero. Twenty-three pregnant Holstein Friesian dams and their calves, originating from three commercial dairy farms in Belgium, were included. Heparin blood samples were collected during the first, second, and third trimester of gestation from all pregnant dams. Heparin blood and hair samples were obtained from the offspring within 24 h after parturition. Colostrum samples were collected from a subset of eight dams to determine the concentration of isoflavones and their metabolites. During the first and second trimester of gestation, the dams were fed either a youngstock (nulliparous dams) or a lactation (multiparous dams) diet. During the third trimester, both groups received a similar dry cow diet. Genistein and daidzein levels were unaffected by diet type, while their metabolite [equol, dihydrodaidzein (DHD), and o-desmethylangolensin (ODMA)] concentrations were significantly higher in the lactation group. Furthermore, metabolite concentrations decreased significantly during gestation. Isoflavones and their metabolites were detected in all colostrum samples. No correlation could be found between levels in colostrum and blood of pregnant dams or calves. Peripheral levels of isoflavones and their metabolites were significantly lower in newborn calves in comparison to their dams. Genistein and daidzein concentrations were found to be significantly higher in the calves' hair versus blood samples, suggesting prenatal exposure to isoflavones for an extended period of time. In contrast, no isoflavone metabolites were detected in the calves' hair samples. This is the first study to demonstrate that dairy calves are exposed to isoflavones during the developmentally most sensitive period of their lives. Results obtained pave the way for more extensive research to examine which effects isoflavones might have on developing organ systems like the reproductive system.

In utero and postnatal exposure to Foeniculum vulgare and Linum usitatissimum seed extracts: modifications of key enzymes involved in epigenetic regulation and estrogen receptors expression in the offspring's ovaries of NMRI mice

BACKGROUND

Early-life exposure to exogenous estrogens such as phytoestrogens (plant-derived estrogens) could affect later health through epigenetic modifications. Foeniculum vulgare (fennel) and Linum usitatissimum (flax) are two common medicinal plants with high phytoestrogen content. Considering the developmental epigenetic programming effect of phytoestrogens, the main goal of the present study was to evaluate the perinatal exposure with life-long exposure to hydroalcoholic extracts of both plants on offspring's ovarian epigenetic changes and estrogen receptors (ESRs) expression level as signaling cascades triggers of phytoestrogens.

METHODS

Pregnant mice were randomly divided into control (CTL) that received no treatment and extract-treated groups that received 500 mg/kg/day of fennel (FV) and flaxseed (FX) alone or in combination (FV + FX) during gestation and lactation. At weaning, female offspring exposed to extracts prenatally remained on the maternal-doses diets until puberty. Then, the ovaries were collected for morphometric studies and quantitative real-time PCR analysis.

RESULTS

A reduction in mRNA transcripts of the epigenetic modifying enzymes DNMTs and HDACs as well as estrogen receptors was observed in the FV and FX groups compared to the CTL group. Interestingly, an increase in ESRα/ESRβ ratio along with HDAC2 overexpression was observed in the FV + FX group.

CONCLUSION

Our findings clearly show a positive relationship between pre and postnatal exposure to fennel and flaxseed extracts, ovarian epigenetic changes, and estrogen receptors expression, which may affect the estrogen signaling pathway. However, due to the high phytoestrogen contents of these extracts, the use of these plants in humans requires more detailed investigations.

Daidzein Activates Akt Pathway to Promote the Proliferation of Female Germline Stem Cells through Upregulating Clec11a

Female germline stem cells (FGSCs) have been successfully isolated and characterized from postnatal mammalian and human ovarian tissues. However, the effects and mechanisms of action of natural small-molecule compounds on FGSCs are largely unknown. Here, we found that daidzein promoted the viability and proliferation of FGSCs. To elucidate the mechanism underlying this, we performed RNA-Sequence in daidzein-treated FGSCs and controls. The results showed that there were 153 upregulated and 156 downregulated genes in daidzein treatment. We confirmed the expression of some genes related to cell proliferation in the sequencing results by RT-PCR, such as Type C lectin domain family 11 member a (Clec11a), Mucin1 (Muc1), Glutathione peroxidase 3 (Gpx3), and Tet methylcytosine dioxygenase 1 (Tet1). The high expression of Clec11a at the protein level after daidzein treatment was also confirmed by western blotting. Furthermore, recombinant mouse Clec11a (rmClec11a) protein was shown to promote the viability and proliferation of FGSCs. However, knockdown of Clec11a inhibited the viability and proliferation of FGSCs, which could not be rescued by the administration of daidzein. These results indicate that daidzein promoted the viability and proliferation of FGSCs through Clec11a. In addition, both daidzein and rmClec11a activated the Akt signaling pathway in FGSCs. However, Clec11a knockdown inhibited this pathway, which could not be rescued by daidzein administration. Taken together, our findings revealed that daidzein activates the Akt signaling pathway to promote cell viability and proliferation through upregulating Clec11a. This study should deepen our understanding of the developmental mechanism of FGSCs and female infertility.

The Influence of Plant Isoflavones Daidzein and Equol on Female Reproductive Processes

In this review, we explore the current literature on the influence of the plant isoflavone daidzein and its metabolite equol on animal and human physiological processes, with an emphasis on female reproduction including ovarian functions (the ovarian cycle; follicullo- and oogenesis), fundamental ovarian-cell functions (viability, proliferation, and apoptosis), the pituitary and ovarian endocrine regulators of these functions, and the possible intracellular mechanisms of daidzein action. Furthermore, we discuss the applicability of daidzein for the control of animal and human female reproductive processes, and how to make this application more efficient. The existing literature demonstrates the influence of daidzein and its metabolite equol on various nonreproductive and reproductive processes and their disorders. Daidzein and equol can both up- and downregulate the ovarian reception of gonadotropins, healthy and cancerous ovarian-cell proliferation, apoptosis, viability, ovarian growth, follicullo- and oogenesis, and follicular atresia. These effects could be mediated by daidzein and equol on hormone production and reception, reactive oxygen species, and intracellular regulators of proliferation and apoptosis. Both the stimulatory and the inhibitory effects of daidzein and equol could be useful for reproductive stimulation, the prevention and mitigation of cancer development, and the adverse effects of environmental stressors in reproductive biology and medicine.

Prenatal and pubertal exposure to 17α-ethinylestradiol disrupts folliculogenesis and promotes morphophysiological changes in ovaries of old gerbils (Meriones unguiculatus)

17α-Ethinylestradiol is an endocrine-disrupting chemical that make up most contraceptive pills and can be found in the environment. Exposure to ethinylestradiol in different development periods may promote changes in morphophysiological parameters of reproductive and endocrine organs. Considering that the effects of low doses (15 µg/kg/day) of ethinylestradiol in ovaries from 12-month-old female gerbils (Meriones unguiculatus) were investigated. Four experimental groups used were control (without treatment), EE/PRE (treated from the 18th to the 22nd gestational day), EE/PUB (treated from the 42nd to the 49th day of life), and EE/PRE-PUB (treated in the both periods). The animals were euthanized at 12 months. Testosterone and 17β-estradiol levels were measured. The ovaries were stained with Hematoxylin and Eosin, Periodic Acid Schiff, and Gomori's Trichome. The follicles, corpus luteum, interstitial gland, lipofuscin, ovarian epithelium, and tunica albuginea were analyzed. Estradiol was higher in EE/PRE and EE/PUB groups, while testosterone was higher only in EE/PUB group. The main changes in follicle count occurred in EE/PUB and EE/PRE-PUB groups, with higher primordial follicle count and lower maturation of follicles. The corpus luteum was more evident in EE/PRE group. No differences were found in atretic follicles count. A higher area occupied by interstitial gland cells and lipofuscin deposit in these cells was noted in EE/PUB and EE/PRE-PUB groups. Higher epithelium height and thicker tunic albuginea were showed in treated groups. These results suggest that exposure to doses of EE2 in prenatal and pubertal periods of the development leads to morphological changes in senile ovaries.

The Vascular Effects of Isolated Isoflavones-A Focus on the Determinants of Blood Pressure Regulation

Isoflavones are phytoestrogen compounds with important biological activities, including improvement of cardiovascular health. This activity is most evident in populations with a high isoflavone dietary intake, essentially from soybean-based products. The major isoflavones known to display the most important cardiovascular effects are genistein, daidzein, glycitein, formononetin, and biochanin A, although the closely related metabolite equol is also relevant. Most clinical studies have been focused on the impact of dietary intake or supplementation with mixtures of compounds, with only a few addressing the effect of isolated compounds. This paper reviews the main actions of isolated isoflavones on the vasculature, with particular focus given to their effect on the determinants of blood pressure regulation. Isoflavones exert vasorelaxation due to a multitude of pathways in different vascular beds. They can act in the endothelium to potentiate the release of NO and endothelium-derived hyperpolarization factors. In the vascular smooth muscle, isoflavones modulate calcium and potassium channels, leading to hyperpolarization and relaxation. Some of these effects are influenced by the binding of isoflavones to estrogen receptors and to the inhibition of specific kinase enzymes. The vasorelaxation effects of isoflavones are mostly obtained with plasma concentrations in the micromolar range, which are only attained through supplementation. This paper highlights isolated isoflavones as potentially suitable alternatives to soy-based foodstuffs and supplements and which could enlarge the current therapeutic arsenal. Nonetheless, more studies are needed to better establish their safety profile and elect the most useful applications.

Plant polyphenols can directly affect ovarian cell functions and modify toluene effects

The influence of toluene alone and in combination with plant polyphenols apigenin, daidzein or rutin on viability, proliferation (proliferating cell nuclear antigen accumulation), apoptosis (Bax accumulation) and release of progesterone (P), testosterone (T) and estradiol (E) in cultured porcine ovarian granulosa cells was evaluated. Toluene reduced ovarian cell viability, proliferation and E release; it promoted P release, demonstrating no effect on apoptosis or T output. Apigenin alone failed to affect cell viability, proliferation, apoptosis and P and T release, but stimulated E release, promoting the inhibitory action of toluene on proliferation, preventing and even reversing the stimulatory effect of toluene on apoptosis and P. Daidzein alone reduced cell viability and promoted T release, preventing and reversing the stimulatory effect of toluene on cell proliferation. Rutin administration reduced cell viability and E output, promoting the inhibitory action of toluene on cell viability and stimulatory effect on P release, and preventing the inhibitory action of toluene on E release. Toluene reduced apigenin- and rutin-induced E release, promoting action of daidzein on cell viability. These observations suggest the action of toluene and plant polyphenols on ovarian cell functions and the functional interrelationships between these molecules in the ovary.

Hydroalcoholic extract and seed of Foeniculum vulgare improve folliculogenesis and total antioxidant capacity level in F1 female mice offspring

Background

Foeniculum vulgare (fennel) is traditionally suggested for the fertility improvement in Iranian lore due to its antioxidant and phytoestrogen compounds. The present study aimed to investigate the effects of fennel seed and its hydroalcoholic extract on the serum total antioxidant capacity (TAC) and folliculogenesis in offspring exposed to either of the treatments in utero and 56 days after birth (PND 56).

Methods

Pregnant NMRI mice were randomly divided into 5 groups of 7: extract-treated groups received 500 and 1000 mg/kg/day fennel extract (FE), seed-treated groups received 500 and 1000 mg/kg/day fennel seed (FS), and the control group (CTL) received no treatment. The treatments started from pregnancy day 1 and continued until PND 56. Body and right ovary weights and ovary dimensions were recorded. Hematoxylin and eosin stained ovary sections were prepared to calculate the proportion of different follicles. The level of TAC in the serums was also measured by fluorescence recovery after photo bleaching.

Results

A marked rise in the body and ovary weights of treated mice was observed compared to the CTL group. The mean number of primordial, primary, pre-antral, and pre-ovulatory follicles as well as corpus luteum size in the treated offspring was significantly higher compared to those of CTL offspring. The atretic follicle number was nonsignificantly lower in either of the treatment groups compared with that in the CTL. However, treatment of animals with 500 mg/kg FE showed a more pronounced effect. Animals in FS500, FE500 and FE1000 groups had a significantly higher level of serum TAC compared to the CTL group.

Conclusions

Fennel extract and seed administration in pregnancy and lactation period improve offspring’s folliculogenesis. Higher level of TAC in the serum of offspring might have positively altered the folliculogenesis milieu.

Plant isoflavones can prevent adverse effects of benzene on porcine ovarian activity: an in vitro study

We evaluated the influence of the oil-related environmental contaminant benzene (0, 10, 100, or 1000 ng/mL) alone and in combination with apigenin, daidzein, or rutin (10 μg/mL each) on viability; proliferation (accumulation of proliferating cell nuclear antigen); apoptosis (accumulation of Bax); and release of progesterone (P), testosterone (T), and estradiol (E) in cultured porcine ovarian granulosa cells. Cell viability; proliferation; apoptosis; and release of P, T, and E have been analyzed by the trypan blue test, quantitative immunocytochemistry, and ELISA, respectively. Benzene did not affect apoptosis, but reduced ovarian cell viability and P and E release, and promoted proliferation and T output. Apigenin did not affect cell viability, but stimulated proliferation and T and E release, and inhibited apoptosis and P secretion. It prevented and reversed the action of benzene on proliferation and P and T release, and induced the inhibitory action of benzene on apoptosis. Daidzein promoted cell viability, proliferation, P release, but not apoptosis and T or E release. Daidzein induced the stimulatory effect of benzene on T, without modifying other effects. Rutin administered alone reduced cell viability and apoptosis, and promoted cell proliferation. Furthermore, rutin prevented and reversed the effect of benzene on proliferation and P and E release. These observations suggest the direct action of benzene and plant polyphenols on basic ovarian cell functions, and the ability of apigenin and rutin, but not of daidzein, to prevent benzene effects on the ovary.

Isoflavones

Phytoestrogens are naturally occurring nonsteroidal phenolic plant compounds that, due to their molecular structure and size, resemble vertebrate steroids estrogens. This review is focused on plant flavonoids isoflavones, which are ranked among the most estrogenic compounds. The main dietary sources of isoflavones for humans are soybean and soybean products, which contain mainly daidzein and genistein. When they are consumed, they exert estrogenic and/or antiestrogenic effects. Isoflavones are considered chemoprotective and can be used as an alternative therapy for a wide range of hormonal disorders, including several cancer types, namely breast cancer and prostate cancer, cardiovascular diseases, osteoporosis, or menopausal symptoms. On the other hand, isoflavones may also be considered endocrine disruptors with possible negative influences on the state of health in a certain part of the population or on the environment. This review deals with isoflavone classification, structure, and occurrence, with their metabolism, biological, and health effects in humans and animals, and with their utilization and potential risks.

Bisphenol A Exposure, Ovarian Follicle Numbers, and Female Sex Steroid Hormone Levels: Results From a CLARITY-BPA Study

Bisphenol A (BPA) is an industrial chemical found in thermal receipts and food and beverage containers. Previous studies have shown that BPA can affect the numbers and health of ovarian follicles and the production of sex steroid hormones, but they often did not include a wide range of doses of BPA, used a small sample size, focused on relatively short-term exposures to BPA, and/or did not examine the consequences of chronic BPA exposure on the ovaries or steroid levels. Thus, this study was designed to examine the effects of a wide range of doses of BPA on ovarian morphology and sex steroid hormone production. Specifically, this study tested the hypothesis that prenatal and continuous BPA exposure reduces ovarian follicle numbers and sex steroid hormone levels. To test this hypothesis, rats were dosed with vehicle, ethinyl estradiol (0.05 and 0.5 μg/kg body weight/d), or BPA (2.5, 25, 250, 2500, and 25,000 μg/kg body weight/d) from gestation day 6 until 1 year as part of the Consortium Linking Academic and Regulatory Insights on BPA Toxicity (CLARITY-BPA). Ovaries and sera were collected on postnatal days 1, 21, and 90, and at 6 months and 1 year. The ovaries were subjected to histological evaluation of follicle numbers and the sera were subjected to measurements of estradiol and progesterone. Collectively, these data indicate that BPA exposure at some doses and time points affects ovarian follicle numbers and sex steroid levels, but these effects are different than those observed with ethinyl estradiol exposure and some previous studies on BPA.

Neonatal isoflavone exposure interferes with the reproductive system of female Wistar rats

There is increasing concern about possible adverse effects of soy based infant formulas (SBIF) due to their high amount of isoflavones (ISO). The aim of the present study was to investigate effects of neonatal exposure to ISO on reproductive system of female Wistar rats. Animals were exposed to an ISO depleted diet or a diet enriched with an ISO extract (IRD; 508mg ISO/kg) during embryogenesis and adolescence. Pups of each group were fed daily by pipette with ISO-suspension (ISO+; 32mg ISO/kg bw) or placebo from postnatal day (PND) 1 until PND23 resulting in plasma concentrations similar to levels reported in infants fed SBIF. The visceral fat mass was reduced by long-term IRD. Vaginal epithelial height was increased at PND23 and vaginal opening was precocious in ISO+ groups. Later in life, more often irregular estrus cycles were observed in rats of ISO+ groups. In addition, FSH levels and uterine epithelial heights were increased at PND80 in ISO+ groups. In summary, the results indicate that neonatal ISO intake, resulting in plasma concentrations achievable through SBIF, has an estrogenic effect on prepubertal rats and influences female reproductive tract later in life.

Photoinitiator-Initiated Estrogenic Activity in Human Breast Cancer Cell Line MCF-7

A recent in vitro study reported that the photoinitiator 2-isopropylthioxanthone (2-ITX) is an endocrine-disrupting compound (EDC). However, it is not clear whether other photoinitiators such as 1-hydroxycyclohexyl phenyl ketone (1-HCHPK) and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MTMP) produce endocrine-disrupting effects. The purpose of this study was thus to assess the association between estrogenic activity and exposure to photoinitiators. For estimation of the proliferative effect of the photoinitiators, the E-screen assay was used. Six photoinitiators, 2,2-dimethoxy-2-phenylacetophenone (2,2-DMPAP), 2-ethylhexyl 4-(dimethylamino)benzoate (2-EHDAB), 1-HCHPK, 2-ITX, methyl-2-benzoylbenzoate (MBB), and MTMP, significantly increased number of MCF-7 cells, an estrogen-sensitive human breast cancer cell line. In addition, pretreatment with estrogen receptor (ER) antagonists such as clomiphene, tamoxifen, or fulvestrant, significantly reversed the proliferative effect of each photoinitiator. Data demonstrated that the six photoinitiators produced endocrine-disrupting effects and that these photoinitiators interacted with ER as agonists. Evidence indicates that the six photoinitiators demonstrated estrogenic activity via ER as agonists.