Cumulative and potential synergistic effects of seven different bisphenols on human granulosa cells in vitro?

Bisphenol (BP) structural analogues of BPA are widely used. Previous studies showed similar effects of BPA and BPS on reproduction in several species including human. We hypothesised that the similar effects of several bisphenols (BPs) could accumulate in granulosa cells (GCs) and affects steroidogenesis. This study investigated the effects of seven BP analogues and their equimolar cocktail on human granulosa cells (hGC) and assessed BPA, BPS, BPF and BPAF level exposures in the follicular fluid of 277 women undergoing Assisted Reproductive Technology. The hGCs were recovered after women oocyte punctures and treated with the seven BP analogues (BPS, BPA, BPAF, BPF, BPAP, BPE and BPB) or their equimolar cocktail of 7 × 1.43 or 7 × 7.14 μM for each of the seven BPs, the sum of BPs reaching 10 ("∑BPs 10 μM"), or 50 μM ("∑BPs 50 μM"), respectively. Oestradiol and progesterone secretion, cell proliferation, viability and expression of steroidogenic enzymes were investigated. Progesterone secretion was decreased by 6 BPs 10 μM and the cocktail "∑BPs 10 μM", (-17.8 to -41.3%) and by all seven BPs 50 μM and "∑BPs 50 μM" (-21.8 to -84.2%). Oestradiol secretion was decreased only by 50 μM BPAF and BPAP (-37.8% and -44%, respectively), with corresponding decreases in CYP17A1 and CYP19A1 gene expression. Cellular proliferation was decreased after treatment with 50 μM BPAF (-32.2%), BPAP (-29%), BPB (-24%) and the equimolar cocktail "∑BPs 50 μM" (-33.1%). BPB (50 μM) and the cocktail "∑BPs 50 μM" increased HSD3B2 mRNA expression. At least one BP was detected in 64 of 277 (23.1%) women follicular fluids. Similar effects of the seven BPs or their cocktail were observed on progesterone secretion and/or on cell proliferation, suggesting cumulative effects of BPs. Our results highlight the urge to consider all BPs simultaneously and to further investigate the potential additive or synergistic effects of several BPs.

Bisphenol A and bisphenol S both disrupt ovine granulosa cell steroidogenesis but through different molecular pathways

BACKGROUND

Ovarian granulosa cells (GC) are essential for the development and maturation of a proper oocyte. GC are sensitive to endocrine disruptors, including bisphenol A (BPA) and its analogue bisphenol S (BPS), plasticisers present in everyday consumer products. BPA exhibits greater binding affinity for the membrane oestrogen receptor (GPER) than for the nuclear oestrogen receptors (ERα and ERβ). Here, we analysed the effects of BPA and BPS on the steroidogenesis of ovine GC in vitro, as well as their early mechanisms of action, the ovine being a relevant model to study human reproductive impairment. Disruption of GC steroidogenesis might alter oocyte quality and consequently fertility rate. In addition, we compared the effects of a specific GPER agonist (G-1) and antagonist (G-15) to those of BPA and BPS. Ewe GC were cultured with BPA or BPS (10 or 50 µM) or G-1 (1 µM) and/or G-15 (10 µM) for 48 h to study steroidogenesis.

RESULTS

Both BPA and BPS (10 µM) altered the secretion of progesterone, however, only BPS (10 µM) affected oestradiol secretion. RNA-seq was performed on GC after 1 h of culture with BPA or BPS (50 µM) or G-1 (10 µM), followed by real-time PCR analyses of differentially expressed genes after 12, 24 and 48 h of culture. The absence of induced GPER target genes showed that BPA and BPS did not activate GPER in GC after 1 h of treatment. These molecules exhibited mainly independent early mechanisms of action. Gene ontology analysis showed that after 1 h of treatment, BPA mainly disrupted the expression of the genes involved in metabolism and transcription, while BPS had a smaller effect and impaired cellular communications. BPA had a transient effect on the expression of CHAC1 (NOTCH signalling and oxidative balance), JUN (linked to MAPK pathway), NR4A1 (oestradiol secretion inhibition), ARRDC4 (endocytose of GPCR) and KLF10 (cell growth, differentiation and apoptosis), while expression changes were maintained over time for the genes LSMEM1 (linked to MAPK pathway), TXNIP (oxidative stress) and LIF (cell cycle regulation) after 12 and 48 h, respectively.

CONCLUSION

In conclusion, although they exhibited similar effects, BPA and BPS impaired different molecular pathways in GC in vitro. New investigations will be necessary to follow the temporal changes of these genes over time, as well as the biological processes involved.

Impact of food restriction on the medio-basal hypothalamus of intact ewes as revealed by a large-scale transcriptomics study

In mammals, the medio-basal hypothalamus (MBH) integrates photoperiodic and food-related cues to ensure timely phasing of physiological functions, including seasonal reproduction. The current human epidemics of obesity and associated reproductive disorders exemplifies the tight link between metabolism and reproduction. Yet, how food-related cues impact breeding at the level of the MBH remains unclear. In this respect, the sheep, which is a large diurnal mammal with a marked dual photoperiodic/metabolic control of seasonal breeding, is a relevant model. Here, we present a large-scale study in ewes (n = 120), which investigated the impact of food restriction (FRes) on the MBH transcriptome using unbiased RNAseq, followed by RT-qPCR. Few genes (~100) were impacted by FRes and the transcriptional impact was very modest (<2-fold increase or < 50% decrease for most genes). As anticipated, FRes increased expression of Npy/AgRP/LepR and decreased expression of Pomc/Cartpt, while Kiss1 expression was not impacted. Of particular interest, Eya3, Nmu and Dio2, genes involved in photoperiodic decoding within the MBH, were also affected by FRes. Finally, we also identified a handful of genes not known to be regulated by food-related cues (e.g., RNase6, HspA6, Arrdc2). In conclusion, our transcriptomics study provides insights into the impact of metabolism on the MBH in sheep, which may be relevant to human, and identifies possible molecular links between metabolism and (seasonal) reproduction.

Bisphenol S Impairs Oestradiol Secretion during In Vitro Basal Folliculogenesis in a Mono-Ovulatory Species Model

Bisphenol S (BPS) affects terminal folliculogenesis by impairing steroidogenesis in granulosa cells from different species. Nevertheless, limited data are available on its effects during basal folliculogenesis. In this study, we evaluate in vitro the effects of a long-term BPS exposure on a model of basal follicular development in a mono-ovulatory species. We cultured ovine preantral follicles (180−240 μm, n = 168) with BPS (0.1 μM (possible human exposure dose) or 10 μM (high dose)) and monitored antrum appearance and follicular survival and growth for 15 days. We measured hormonal secretions (oestradiol (at day 13 [D13]), progesterone and anti-Müllerian hormone [D15]) and expression of key follicular development and redox status genes (D15) in medium and whole follicles, respectively. BPS (0.1 µM) decreased oestradiol secretion compared with the control (−48.8%, p < 0.001), without significantly impairing antrum appearance, follicular survival and growth, anti-Müllerian hormone and progesterone secretion and target gene expression. Thus, BPS could also impair oestradiol secretion during basal folliculogenesis as it is the case during terminal folliculogenesis. It questions the use of BPS as a safe BPA substitute in the human environment. More studies are required to elucidate mechanisms of action of BPS and its effects throughout basal follicular development.

Bisphenol S Alters the Steroidome in the Preovulatory Follicle, Oviduct Fluid and Plasma in Ewes With Contrasted Metabolic Status

Bisphenol A (BPA), a plasticizer and endocrine disruptor, has been substituted by bisphenol S (BPS), a structural analogue that had already shown adverse effects on granulosa cell steroidogenesis. The objective of this study was to assess the effect of chronic exposure to BPS, a possible endocrine disruptor, on steroid hormones in the ovary, oviduct and plasma using the ewe as a model. Given the interaction between steroidogenesis and the metabolic status, the BPS effect was tested according to two diet groups. Eighty adult ewes were allotted to restricted (R) and well-fed (WF) groups, that were further subdivided into two subgroups. Ewes were exposed to 50 µg BPS/kg/day in their diet (R50 and WF50 groups) or were unexposed controls (R0 and WF0 groups). After at least 3 months of BPS exposure, preovulatory follicular fluid, oviduct fluid and plasma were collected and steroid hormones were analyzed by gas chromatography coupled with tandem mass spectrometry (GC-MS/MS). A deleterious effect of restricted diet on the volume of oviduct fluid and numbers of pre-ovulatory follicles was observed. Exposure to BPS impaired estradiol concentrations in both follicular and oviduct fluids of well-fed ewes and progesterone, estradiol and estrone concentrations in plasma of restricted ewes. In addition, a significant interaction between metabolic status and BPS exposure was observed for seven steroids, including estradiol. In conclusion, BPS acts in ewes as an endocrine disruptor with differential actions according to metabolic status.

Chronic low BPS exposure through diet impairs in vitro embryo production parameters according to metabolic status in the ewe

Bisphenol A (BPA), an endocrine disruptor, has been replaced by structural analogues including bisphenol S (BPS). BPA and BPS exhibited similar effects regarding reproductive functions. Moreover, metabolic status and lipid metabolism are related to female fertility and could worsen BPS effects. The objective was to determine BPS in vivo effects on folliculogenesis and embryo production after chronic exposure through diet, and the influence of metabolic status in adult ewes. Sixty primiparous 2.5 year-old ewes, undergoing a restricted or well fed diet, were exposed to BPS (0, 4 or 50 µg/kg/day) for at least three months. After hormonal oestrus synchronisation and ovarian stimulation, ewes were subjected to ovum pick-up (OPU) procedures to collect immature oocytes, that underwent in vitro maturation, fertilisation and embryo production. Body weight, body condition score and plasma glucose were higher in well-fed compared to restricted ewes, while plasma NEFA was lower during the 4-5 months after the beginning of the diets. Plasma progesterone levels increased on day 5 before OPU session in well-fed compared to restricted ewes. No effect of BPS dose was observed on follicle population, plasma AMH levels and embryo production numbers and rates. However, a significant diet x BPS dose interaction was reported for cleaved embryos, > 4-cell embryos, blastocyst and early blastocyst numbers, and plasma triiodothyronine levels. Our study showed that a contrasted diet did not affect follicle population nor embryo production in adult ewes but could affect the quality and progesterone secretion of the corpus luteum. Chronic low BPS exposure had no effect on follicular population and oocyte competence. Nevertheless, the significant diet x dose interactions observed on embryo production suggest that BPS effect is modulated by metabolic status. Further studies are required to assess the risk of BPS exposure for public reproductive health.

P-180 Bisphenols are present in culture media used for ART and cell culture

Study question

Do plastic laboratory consumables and cell culture media used in human ART contain bisphenols?

Summary answer

Human embryo development media contained bisphenols close to the nanomolar concentration range while no release of bisphenols by plastic consumables was detected under routine conditions.

What is known already

The deleterious effect of the endocrine disruptor bisphenol A (BPA) on female fertility raised concerns regarding ART outcome. BPA was detected neither in media nor in the majority of plastic consumables used in ART, however it might have already been replaced by its structural analogs, including bisphenol S (BPS).

Study design, size, duration

Seventeen plastic consumables and 18 cell culture and ART media were assessed for the presence of bisphenols.

Participants/materials, setting, methods

Ten different bisphenols (bisphenol A, S, AF, AP, B, C, E, F, P, and Z) were measured using an isotopic dilution according to an on-line solid phase extraction / liquid chromatography/mass spectrometry method.

Main results and the role of chance

While all the plastic consumables of this study did contain bisphenols, none of them did release bisphenols under routine conditions. Moreover, 16 of the 18 cell culture and ART media assessed contained bisphenols, including 8 among the 10 media used in human ART. Five human ART media exhibited bisphenol concentrations higher than 0.8 nM and reached up to 3.2 nM (799 ng/L).

Limitations, reasons for caution

Further studies are required to investigate a greater number of ART media to identify less potentially harmful ones, in terms of bisphenol content.

Wider implications of the findings

As BPS has already been reported to impair oocyte quality at nanomolar concentrations, its presence in ART media, at a similar concentration range, could contribute to a decrease in the ART success rate. Thus far, there has been no regulation of these compounds in the ART context.

Trial registration number

Not applicable

P–180 Bisphenols are present in culture media used for ART and cell culture

Study question

Do plastic laboratory consumables and cell culture media used in human ART contain bisphenols?

Summary answer

Human embryo development media contained bisphenols close to the nanomolar concentration range while no release of bisphenols by plastic consumables was detected under routine conditions.

What is known already

The deleterious effect of the endocrine disruptor bisphenol A (BPA) on female fertility raised concerns regarding ART outcome. BPA was detected neither in media nor in the majority of plastic consumables used in ART, however it might have already been replaced by its structural analogs, including bisphenol S (BPS).

Study design, size, duration

Seventeen plastic consumables and 18 cell culture and ART media were assessed for the presence of bisphenols.

Participants/materials, setting, methods

Ten different bisphenols (bisphenol A, S, AF, AP, B, C, E, F, P, and Z) were measured using an isotopic dilution according to an on-line solid phase extraction / liquid chromatography/mass spectrometry method.

Main results and the role of chance

While all the plastic consumables of this study did contain bisphenols, none of them did release bisphenols under routine conditions. Moreover, 16 of the 18 cell culture and ART media assessed contained bisphenols, including 8 among the 10 media used in human ART. Five human ART media exhibited bisphenol concentrations higher than 0.8 nM and reached up to 3.2 nM (799 ng/L).

Limitations, reasons for caution

Further studies are required to investigate a greater number of ART media to identify less potentially harmful ones, in terms of bisphenol content.

Wider implications of the findings: As BPS has already been reported to impair oocyte quality at nanomolar concentrations, its presence in ART media, at a similar concentration range, could contribute to a decrease in the ART success rate. Thus far, there has been no regulation of these compounds in the ART context.

Trial registration number

Not applicable

Bisphenol S is present in culture media used for ART and cell culture

STUDY QUESTION

Do plastic laboratory consumables and cell culture media used in ART contain bisphenols?

SUMMARY ANSWER

The majority of human embryo culture media assessed contained bisphenol S close to the nanomolar concentration range, while no release of bisphenols by plastic consumables was detected under routine conditions.

WHAT IS KNOWN ALREADY

The deleterious effect of the endocrine disruptor bisphenol A (BPA) on female fertility raised concerns regarding ART outcome. BPA was detected neither in media nor in the majority of plastic consumables used in ART; however, it might have already been replaced by its structural analogs, including bisphenol S (BPS).

STUDY DESIGN, SIZE, DURATION

Seventeen plastic consumables and 18 cell culture and ART media were assessed for the presence of bisphenols.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Ten different bisphenols (bisphenol A, S, AF, AP, B, C, E, F, P and Z) were measured using an isotopic dilution according to an on-line solid phase extraction/liquid chromatography/mass spectrometry method.

MAIN RESULTS AND THE ROLE OF CHANCE

While the plastic consumables did not release bisphenols under routine conditions, 16 of the 18 cell culture and ART media assessed contained BPS. Six media exhibited BPS concentrations higher than 1 nM and reached up to 6.7 nM (1693 ng/l).

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Further studies are required to investigate a greater number of ART media to identify less potentially harmful ones, in terms of bisphenol content.

WIDER IMPLICATIONS OF THE FINDINGS

As BPS has already been reported to impair oocyte quality at nanomolar concentrations, its presence in ART media, at a similar concentration range, could contribute to a decrease in the ART success rate. Thus far, there has been no regulation of these compounds in the ART context.

STUDY FUNDING/COMPETING INTERESTS

This study was financially supported by the ‘Centre-Val de Loire’ Region (Bemol project, APR IR 2017), INRAE, BRGM, the French National Research Agency (project ANR-18-CE34-0011-01 MAMBO) and the BioMedicine Agency (Project 18AMP006 FertiPhenol). The authors declare that they have no conflict of interest that could be perceived as prejudicing the impartiality of the reported research.

Bisphenol A and S impaired ovine granulosa cell steroidogenesis

Bisphenols, plasticisers used in food containers, can transfer to food. Bisphenol A (BPA) has been described as an endocrine disruptor and consequently banned from the food industry in several countries. It was replaced by a structural analogue, Bisphenol S (BPS). BPA action on the steroidogenesis is one of the mechanisms underlying its adverse effects on the efficiency of female reproduction. This study aimed to determine whether BPS is a safe alternative to BPA regarding GC functions. Antral follicles (2–6 mm), of approximatively 1000 adult ewe ovaries, were aspired and GC purified. For 48 h, ovine GC were treated with BPA or BPS (from 1 nM to 200 µM) and the effects on cell viability, proliferation, steroid production, steroidogenic enzyme expression and signalling pathways were investigated. Dosages at and greater than 100 μM BPA and 10 µM BPS decreased progesterone secretion by 39% (P < 0.001) and 22% (P = 0.040), respectively. BPA and BPS 10 μM and previously mentioned concentrations increased oestradiol secretion two-fold (P < 0.001 and P = 0.082, respectively). Only 100 µM BPA induced a decrease (P < 0.001) in gene expression of the enzymes of steroidogenesis involved in the production of progesterone. BPA reduced MAPK3/1 phosphorylation and ESR1 and ESR2 gene expression, effects that were not observed with BPS. BPA and BPS altered steroidogenesis of ovine GC. Thus, BPS does not appear to be a safe alternative for BPA. Further investigations are required to elucidate BPA and BPS mechanisms of action.

Bisphenol S Impaired Human Granulosa Cell Steroidogenesis in Vitro

Bisphenol S (BPS) is a structural analog of the endocrine disruptor bisphenol A (BPA); it is the main BPA replacement in the plastics industry. Previous studies have shown that BPA and BPS exhibit similar effects on reproduction in fish and rodent species. BPS reportedly alters steroidogenesis in bovine granulosa cells. Luteinised granulosa cells collected from 59 women who were undergoing an in vitro fertilization procedure were cultured for 48 h in the presence or absence of BPS (10 nM, 100 nM, 1 µM, 10 µM or 50 µM). BPS exposure was investigated by assessing follicular fluids from these 59 women for their BPS content. Culture medium, cells, total messenger RNA (mRNA) and total protein extracted from the luteinised granulosa cells were examined for oestradiol and progesterone secretion, cellular proliferation, viability, gene expression, steroidogenic enzyme expression and cell signaling. BPS was measured in follicular fluids using mass spectrometry. Exposure of granulosa cells to 10 or 50 µM BPS for 48 h induced a 16% (p = 0.0059) and 64% (p < 0.0001) decrease, respectively, in progesterone secretion; 50 µM BPS decreased oestradiol secretion by 46% (p < 0.0001). Ten µM BPS also tended to reduce CYP11A1 protein expression by 37% (p = 0.0947) without affecting HSD3B1 and CYP19A1 expression. Fifty µM BPS increased ERRγ expression. Environmental levels of BPS (nanomolar range) did not induce changes in steroidogenesis in human granulosa cells. The effects of BPS were observed after only 48 h of BPS exposure. These acute effects might be similar to chronic effects of physiological BPS levels.

Bisphenol S Impaired In Vitro Ovine Early Developmental Oocyte Competence

INTRODUCTION

Bisphenol A (BPA) is a widespread compound in the plastic industry that is especially used to produce baby bottles, food packaging and metal cans. BPA, an endocrine disruptor, leads to alterations in reproductive function and therefore has been banned from the food industry. Unregulated BPA analogues, particularly Bisphenol S (BPS), have emerged and are now used in the plastic industry. Thus, this study aimed to examine the acute effects of low and environmental doses of BPS on ewe oocyte quality and developmental competence, and its mechanism of action, during in vitro maturation.

METHODS

Ewe cumulus-oocyte complexes underwent in vitro maturation in the presence or absence of BPS (1 nM, 10 nM, 100 nM, 1 µM or 10 µM). Oocytes were then subjected to in vitro fertilisation and development.

RESULTS

1 µM BPS induced a 12.7% decrease in the cleavage rate (p = 0.004) and a 42.6% decrease in the blastocyst rate (p = 0.017) compared to control. The blastocyst rate reduction was also observed with 10 nM BPS. Furthermore, 10 µM BPS reduced the oocyte maturation rate, and 1 µM BPS decreased cumulus cell progesterone secretion. PR and AMH gene expression were reduced in cumulus cells. BPS induced a 5-fold increase in MAPK 3/1 activation (p = 0.04).

CONCLUSIONS

BPS impaired ewe oocyte developmental competence. The data suggest that BPS might not be a safe BPA analogue. Further studies are required to elucidate its detailed mechanism of action.

179 Bisphenol S affects invitro early developmental oocyte competence in ewes

In the plastics industry, bisphenol S (BPS) replaces sisphenol A reported to be an oestrogen mimetic endocrine disruptor damaging oocyte meiosis and maturation (Machtinger 2014 Reprod. Biomed. Online 29, 404). Studies on fish and rodents reported that BPS affects reproduction similarly to BPA (Uzumcu 2007 Reprod. Toxicol. 23, 337; Giulivo 2016 Environ. Res. 151, 251; Ullah 2016 Chemosphere 152, 353). Bisphenol S is detected in human urine at nanomolar concentrations (Liao 2012 Environ. Sci. Technol 46, 6860) and in some laboratory supplies (tips and tubes; unpublished data). Therefore, in this study, we assessed effects of BPS at low doses during invitro maturation (IVM) on oocyte developmental competence in ewes. Cumulus-oocyte complexes (COC) collected from ovine follicles &gt;2mm underwent 24-h IVM, in the absence or presence of BPS at 1, 10, and 100 nM and 1 and 10 µM (Sigma Chemical Co.). Nuclear oocyte maturation rate was evaluated by MII oocyte count after chromatin Hoechst staining [n=3 replicates (R), 1159 oocytes]. At 6h of IVM, BPS effects on mRNA expression of oestrogen (E2) and progesterone (P4) receptors in cumulus cells (CC) were assessed by real-time quantitative PCR. After 24h of IVM, The effect of BPS on P4 level was assessed in spent medium by enzyme-linked immunosorbent assay (n=6 R, 40 COC/condition). Transcript expression level and P4 concentration were analysed using nonparametric one-way ANOVA, with Tukey post hoc test (Rcmdr, R version 3.5.3). After 24h of IVM, matured COC underwent IVF and invitro culture (IVC) for 7 days. Cleavage and blastocyst rates were assessed on Days 2 and 7, respectively, after IVF (8 experiments, 300 COC/condition). Data were analysed using logistic regression and linear model (R version 3.5.3). Our results showed a decreased oocyte maturation rate with 10 µM BPS (76.6%, n=171; P=0.0008) compared with control (88%, n=152), with no effect on cell viability. The concentration of P4 decreased with 1 µM BPS (0.02ngmL−1 per COC) compared with control (0.034ngmL−1 per COC; P&lt;0.001). At 6h IVM, BPS had no significant effect on oestrogen receptors (ESR1, ESR2, GPER) transcripts in CC but 10 nM BPS decreased mRNA expression of P4 receptor (PR) (0.00647±0.00145; P=0,005) compared with control (0.01165±0.00196). Within fertilized COC, 1 µM BPS decreased cleavage rate (47.6%, n=152) compared with control (54.6%; P=0.004). Among cleaved embryos, blastocyst rate decreased to 14.2% and 12.5% with 10 nM and 1 µM BPS respectively (n=26, P=0.046; and n=19, P=0.017), compared with control (21.8%, n=44). Bisphenol S at a low dose during ovine IVM reduced COC P4 secretion, PR transcript in CC, and cleavage and blastocyst rates. Our data suggest that BPS at an environmental dose (10 nM) negatively affects early developmental oocyte competence. Studies are ongoing to investigate the effect of BPS on Day 6 embryo cell number and on the ERK1/2 signalling pathway in oocyte. This study was supported by INRA, Region Val-de-Loire (BEMOL) and the French National Research Agency (ANR-18-CE34-0011-01 MAMBO). We thank A. Arnould and T. Delpuech for ovine ovary collection and Endocrinology and Phenotyping laboratory for P4 assay.