Adverse effects of endocrine disruptors on the foetal testis development: focus on the phthalates

MEHP activates JNK to inhibit the migration of human foreskin fibroblasts

This study aimed to investigate the impact of mono(2-ethylhexyl) phthalate (MEHP) on the proliferation, apoptosis, and migration of human foreskin fibroblast cells (HFF-1) and the role of the JNK signaling pathway in cell migration. HFF-1 cells were randomly assigned to the control group with 0 MEHP exposure (M0) or the experimental groups with 25, 50, 100, 200, and 400 μmol/L MEHP exposure (M25, M50, M100, M200, and M400, respectively). After 24 and 48 h of MEHP exposure, the proliferation of HFF-1 cells in any group had no significant change. However, compared with the M0 group, the M200 and M400 groups presented substantially increased apoptosis of HFF-1 cells. Moreover, cell migration ability significantly decreased in all groups (p < 0.05). Additionally, the transcription and phosphorylated protein activation of JNK kinase in HFF-1 cells were substantially upregulated with the increase in MEHP exposure. Subsequently, HFF-1 cells were randomly divided into three groups: the DMSO blank control group, the 100 μM MEHP experimental group (M100), and the 100 μM MEHP plus 10 μM SP600125 (specific JNK inhibitor) experimental group (S10). The activation of JNK protein in HFF-1 cells was substantially downregulated in the S10 group. HFF-1 cells were also divided into the blank control group (M0). They were treated with 100 μM MEHP and varying concentrations of SP600125 (5, 10, and 15 μM for S5, S10, and S15, respectively). As the concentration of the antagonist increased, the migration ability of HFF-1 cells was returned to normal. Finally, the ROS in HFF-1 cells increased under MEHP exposure. This finding indicates that the regulation of cell migration by the JNK signaling pathway may be important in the occurrence of hypospadias.

Hydrothermal deconstruction of single-use personal protective equipment during the COVID-19 pandemic

To minimise the transmission of the SARS-CoV-2 virus, there has been a substantial increase in the production and usage of synthetic personal protective equipment (PPE) globally. Consequently, single-use PPE have been widely adopted without appropriate regulations for their disposal, leading to extensive environmental contamination worldwide. This study investigates the non-catalytic hydrothermal deconstruction of different PPE items, including isolation gowns, gloves, goggles, face shields, surgical masks, and filtering-facepiece respirators. The selected PPE items were subjected to hydrothermal deconstruction for 90 min in the presence of 30-bar initial oxygen pressure, at temperatures ranging between 250 °C and 350 °C. The solid content in form of total suspended solids (TSS) was reduced up to 97.6%. The total chemical oxygen demand (tCOD) and soluble chemical oxygen demand (sCOD) decreased with increasing deconstruction temperature, and at 350 °C the lowest tCOD and sCOD content of 546.6 mg/L and 470 mg/L, respectively, was achieved. Short-chained volatile fatty acids were produced after 90 min of deconstruction, predominantly acetic acid at concentrations up to 8974 mg/L. Ammonia nitrogen content (NH₃-N) of up to 542.6 mg/L was also detected. Carbon dioxide (CO₂) and unreacted oxygen (O₂) were the main gaseous by-products at up to 15.6% (w/w) and 88.7% (w/w), respectively. The findings suggest that non-catalytic hydrothermal deconstruction is a viable option to process and manage PPE waste.

State of knowledge and future research needs on microplastics in groundwater

Microplastics (MPs) are widespread in aquatic and soil environments. This study targets the issue of MPs' transfer from soil to groundwater. Scientific papers were collected and analyzed using a text-mining approach that classifies text segments. This allowed the identification of four research topics and the organization of the results into a summarizing table. Those four topics are sources of groundwater MPs, main types of MPs (physico-chemical properties, polymer units, shapes, and size), human exposure (mainly drinking water), and potential environmental and human effects. Compared to the research of MP on aquatic or soil compartments, scientific data on MP in groundwater are less substantial. Current results show a divergence due to differences in context (alluvial aquifer, fractured rock aquifer, karst aquifer, etc), collecting, sampling, and analytical methods. This divergence requires further research with standardized analytic protocols and reference materials. The associated research gaps were identified by using the same approach. The following five topics emerged: (1) the transfer of MPs from soil to underground, (2) the contribution of groundwater to drinking water microplastic pollution, (3) the interaction with other contaminants, (4) the human and environmental effects, and (5) the protective and remediation solutions.

Study of atmospheric pressure chemical ionization of phthalates in air by ion mobility spectrometry/mass spectrometry

RATIONALE

Phthalates are widely used in consumer products in the chemical industries. Due to their abundance in the milieu, their potentially harmful effect on the environment, human and animal health there is a need for sensitive and fast methods for their detection.

METHODS

Positive polarity Corona Discharge Atmospheric Pressure Chemical Ionization (CD-APCI) in the air was applied for ionization of phthalates. The ionization method for the phthalates was studied by atmospheric pressure Ion Mobility Spectrometry (IMS) and hybrid IMS/orthogonal acceleration Time-of-Flight Mass spectrometry (IMS-oaTOF-MS).

RESULTS

CD-APCI IMS and MS spectra of selected phthalates (dimethyl phthalate, diethyl phthalate, diethyl isophthalate, diethyl terephthalate, dipropyl phthalate, diisopropyl phthalate, dibutyl phthalate, diisobutyl phthalate, and dibutyl terephthalate) were recorded. In the case of the ortho- and "iso"-isomers exclusively the protonated molecular ions [M + H]⁺ were detected. In the case of the para- and meta-isomers and regioisomers, APCI resulted in the appearance of hydrated protonated molecular ions [M + H]⁺ ·(H₂ O)_0,1,2 . The ion mobilities, collision cross-sections of these ions in air, as well as the limits of detection (LODs) for the phthalate vapors, were determined. In the case of isomeric phthalates, we have demonstrated the potential of the IMS technique for their separation.

CONCLUSIONS

The results show that CD-APCI in combination with IMS and IMS-oaTOF-MS is a suitable method for the fast and sensitive detection of phthalates with the potential to separate some isomers.

A suggested bisphenol A metabolite (MBP) interfered with reproductive organ development in the chicken embryo while a human-relevant mixture of phthalate monoesters had no such effects

Bisphenol A (BPA) and phthalate diesters are ubiquitous environmental contaminants. While these compounds have been reported as reproductive toxicants, their effects may partially be attributed to metabolites. The aim of this study was to examine reproductive organ development in chicken embryos exposed to the BPA metabolite, 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP; 100 µg/g egg) or a human-relevant mixture of 4 phthalate monoesters (85 µg/g egg). The mixture was designed within the EU project EDC-MixRisk based upon a negative association with anogenital distance in boys at 21 months of age in a Swedish pregnancy cohort. Chicken embryos were exposed in ovo from an initial stage of gonad differentiation (embryonic day 4) and dissected two days prior to anticipated hatching (embryonic day 19). No discernible effects were noted on reproductive organs in embryos exposed to the mixture. MBP-treated males exhibited retention of Müllerian ducts and feminization of the left testicle, while MBP-administered females displayed a diminished the left ovary. In the left testicle of MBP-treated males, mRNA expression of female-associated genes was upregulated while the testicular marker gene SOX9 was downregulated, corroborating a feminizing effect by MBP. Our results demonstrate that MBP, but not the phthalate monoester mixture, disrupts both male and female reproductive organ development in an avian embryo model.

The effects of di-2-ethylhexyl phthalate on testicular ultrastructure and hormone-regulated gene expression in male rats

The objective of this study is to determine testicular pathological damage and explore its molecular mechanisms after di-2-ethylhexyl phthalate (DEHP) treatment. A total of 40 healthy 5-week-old male Sprague-Dawley rats were randomly divided into four groups, which received intragastric administration of 0 mg kg^-1, 100 mg kg^-1, 500 mg kg^-1 and 1500 mg kg^-1 DEHP for six continuous weeks. After DEHP treatment, the testes wet weight and testes coefficient were calculated, the histopathological changes of the testes were examined by HE staining and the testicular ultrastructure was examined by transmission electron microscopy. The gene expression levels were analyzed by quantitative RT-PCR and the protein expression levels were analyzed by western blotting. Both 500 mg kg^-1 and 1500 mg kg^-1 DEPH treatments decreased the wet weight of the testes and testes coefficient, due to vacuoles in Sertoli cells, broken mitochondrial ridges, and degranulation. Quantitative RT-PCR showed that the relative gene expression levels of steroidogenic acute regulatory protein (StAR) and 3β-hydroxysteroid dehydrogenase (3β-HSD) increased in the 100 mg kg^-1, 500 mg kg^-1, and 1500 mg kg^-1 DEHP groups, respectively. Additionally, 17β-hydroxysteroid dehydrogenase (17β-HSD) expression levels were increased in the 1500 mg kg^-1 DEHP treatment group. Gonadotropin-releasing hormone (GnRH) expression levels were decreased with 500 mg kg^-1 and 1500 mg kg^-1 DEHP treatments. DEHP induced serious pathological damage and ultrastructure changes in rat testes, caused endocrine disorders, interfered with the synthesis of male hormones, and ultimately led to male reproductive system dysfunction.

Nuclear receptors and endocrine disruptors in fetal and neonatal testes: a gapped landscape

During the last decades, many studies reported that male reproductive disorders are increasing among humans. It is currently acknowledged that these abnormalities can result from fetal exposure to environmental chemicals that are progressively becoming more concentrated and widespread in our environment. Among the chemicals present in the environment (air, water, food, and many consumer products), several can act as endocrine disrupting compounds (EDCs), thus interfering with the endocrine system. Phthalates, bisphenol A (BPA), and diethylstilbestrol (DES) have been largely incriminated, particularly during the fetal and neonatal period, due to their estrogenic and/or anti-androgenic properties. Indeed, many epidemiological and experimental studies have highlighted their deleterious impact on fetal and neonatal testis development. As EDCs can affect many different genomic and non-genomic pathways, the mechanisms underlying the adverse effects of EDC exposure are difficult to elucidate. Using literature data and results from our laboratory, in the present review, we discuss the role of classical nuclear receptors (genomic pathway) in the fetal and neonatal testis response to EDC exposure, particularly to phthalates, BPA, and DES. Among the nuclear receptors, we focused on some of the most likely candidates, such as peroxisome-proliferator activated receptor (PPAR), androgen receptor (AR), estrogen receptors (ERα and β), liver X receptors (LXR), and small heterodimer partner (SHP). First, we describe the expression and potential functions (based on data from studies using receptor agonists and mouse knockout models) of these nuclear receptors in the developing testis. Then, for each EDC studied, we summarize the main evidences indicating that the reprotoxic effect of each EDC under study is mediated through a specific nuclear receptor(s). We also point-out the involvement of other receptors and nuclear receptor-independent pathways.

Man is not a big rat: concerns with traditional human risk assessment of phthalates based on their anti-androgenic effects observed in the rat foetus

Phthalates provide one of the most documented example evidencing how much we must be cautious when using the traditional paradigm based on extrapolation of experimental data from rodent studies for human health risk assessment of endocrine disruptors (EDs). Since foetal testis is known as one of the most sensitive targets of EDs, phthalate risk assessment is routinely based on the capacity of such compounds to decrease testosterone production by the testis or to impair masculinization in the rat during foetal life. In this paper, the well-established inhibiting effects of phthalates of the foetal Leydig cells function in the rat are briefly reviewed. Then, data obtained in humans and other species are carefully analysed. Already in January 2009, using the organotypic culture system named Fetal Testis Assay (FeTA) that we developed, we reported that phthalates might not affect testosterone production in human foetal testes. Several recent experimental studies using xenografts confirm the absence of detectable anti-androgenic effect of phthalates in the human foetal testes. Epidemiological studies led to contradictory results. Altogether, these findings suggest that phthalates effects on foetal Leydig cells are largely species-specific. Consequently, the phthalate threshold doses that disturb foetal steroidogenesis in rat testes and that are presently used to define the acceptable daily intake levels for human health protection must be questioned. This does not mean that phthalates are safe because these compounds have many deleterious effects upon germ cell development that may be common to the different studied species including human. More generally, the identification of common molecular, cellular or/and phenotypic targets in rat and human testes should precede the choice of the toxicological endpoint in rat to accurately assess the safety threshold of any ED in humans.

Concerns about the widespread use of rodent models for human risk assessments of endocrine disruptors

Fetal testis is a major target of endocrine disruptors (EDs). During the last 20 years, we have developed an organotypic culture system that maintains the function of the different fetal testis cell types and have used this approach as a toxicological test to evaluate the effects of various compounds on gametogenesis and steroidogenesis in rat, mouse and human testes. We named this test rat, mouse and human fetal testis assay. With this approach, we compared the effects of six potential EDs ((mono-(2-ethylhexyl) phthalate (MEHP), cadmium, depleted uranium, diethylstilboestrol (DES), bisphenol A (BPA) and metformin) and one signalling molecule (retinoic acid (RA)) on the function of rat, mouse and human fetal testis at a comparable developmental stage. We found that the response is similar in humans and rodents for only one third of our analyses. For instance, RA and MEHP have similar negative effects on gametogenesis in the three species. For another third of our analyses, the threshold efficient concentrations that disturb gametogenesis and/or steroidogenesis differ as a function of the species. For instance, BPA and metformin have similar negative effects on steroidogenesis in human and rodents, but at different threshold doses. For the last third of our analyses, the qualitative response is species specific. For instance, MEHP and DES affect steroidogenesis in rodents, but not in human fetal testis. These species differences raise concerns about the extrapolation of data obtained in rodents to human health risk assessment and highlight the need of rigorous comparisons of the effects in human and rodent models, when assessing ED risk.

Mouse testis development and function are differently regulated by follicle-stimulating hormone receptors signaling during fetal and prepubertal life

It is currently admitted that Follicle-Stimulating Hormone (FSH) is physiologically involved in the development and function of fetal/neonatal Sertoli cells in the rat but not the mouse. However, FSH is produced by both species from late fetal life onwards. We thus reinvestigated the role of FSH in mouse testis development at day 0 (birth) 6, 8 and 10 post-partum (dpp) by using mice that lack functional FSH receptors (FSH-R^−/−). At birth, the number and proliferative index of Sertoli cells were significantly lower in FSH-R^−/− mice than in wild type neonates. Claudin 11 mRNA expression also was significantly reduced in FSH-R^−/− testes at 0 and 8 dpp, whereas the mRNA levels of other Sertoli cell markers (Transferrin and Desert hedgehog) were comparable in FSH-R^−/− and wild type testes. Conversely, AMH mRNA and protein levels were higher at birth, comparable at 6 dpp and then significantly lower in FSH-R^−/− testes at 8–10 dpp in FSH-R^−/− mice than in controls. Although the plasma concentration of LH and the number of Leydig cells were similar in FSH-R^−/− and control (wild type), testosterone concentration and P450c17 mRNA expression were significantly increased in FSH-R^−/− testes at birth. Conversely, at 10 dpp when adult Leydig cells appear, expression of the steroidogenic genes P450scc, P450c17 and StAR was lower in FSH-R^−/− testes than in controls. In conclusion, our results show that 1) like in the rat, signaling via FSH-R controls Sertoli cell development and function during late fetal life in the mouse as well; 2) paracrine factors produced by Sertoli cells are involved in the FSH-R-dependent regulation of the functions of fetal Leydig cells in late fetal life; and 3) the role of FSH-R signaling changes during the prepubertal period.

Differential effects of bisphenol A and diethylstilbestrol on human, rat and mouse fetal leydig cell function

Endocrine disruptors (ED) have been incriminated in the current increase of male reproductive alterations. Bisphenol A (BPA) is a widely used weak estrogenic environmental ED and it is debated whether BPA concentrations within the average internal exposure are toxic. In the present study we investigated the effects of 10(-12) to 10(-5) M BPA concentrations on fetal Leydig cell function, as fetal life is a critical period of sensitivity to ED effects on male reproductive function. To this aim, fetal testes from human at 6.5-10.5 gestational weeks (GW) or from rat and mouse at a comparable critical period of development (14.5 days post-coitum (dpc) for rat and 12.5 dpc for mouse) were explanted and cultured using our validated organotypic culture system in the presence or absence of BPA for 1-3 days. BPA concentrations as low as 10(-8) M reduced testosterone secretion by human testes from day 1 of culture onwards, but not by mouse and rat testes where concentrations equal to 10(-5) M BPA were required. Similarly, 10(-8) M BPA reduced INSL3 mRNA levels only in human cultured testes. On the contrary, 10(-5) and 10(-6) M diethylstilbestrol (DES), a classical estrogenic compound, affected testosterone secretion only in rat and mouse testis cultures, but not in human testis cultures. Lastly, contrarily to the DES effect, the negative effect of BPA on testosterone produced by the mouse fetal testis was maintained after invalidation of estrogen receptor α (ERα). In conclusion, these results evidenced i) a deleterious effect of BPA on fetal Leydig cells function in human for concentrations from 10(-8) M upwards, ii) species-specific differences raising concerns about extrapolation of data from rodent studies to human risk assessment, iii) a specific signaling pathway for BPA which differs from the DES one and which does not involve ERα.

Effect of mono-(2-ethylhexyl) phthalate on human and mouse fetal testis: In vitro and in vivo approaches

The present study was conducted to determine whether exposure to the mono-(2-ethylhexyl) phthalate (MEHP) represents a genuine threat to male human reproductive function. To this aim, we investigated the effects on human male fetal germ cells of a 10⁻⁵ M exposure. This dose is slightly above the mean concentrations found in human fetal cord blood samples by biomonitoring studies. The in vitro experimental approach was further validated for phthalate toxicity assessment by comparing the effects of in vitro and in vivo exposure in mouse testes. Human fetal testes were recovered during the first trimester (7-12 weeks) of gestation and cultured in the presence or not of 10⁻⁵ M MEHP for three days. Apoptosis was quantified by measuring the percentage of Caspase-3 positive germ cells. The concentration of phthalate reaching the fetal gonads was determined by radioactivity measurements, after incubations with ¹⁴C-MEHP. A 10⁻⁵ M exposure significantly increased the rate of apoptosis in human male fetal germ cells. The intratesticular MEHP concentration measured corresponded to the concentration added in vitro to the culture medium. Furthermore, a comparable effect on germ cell apoptosis in mouse fetal testes was induced both in vitro and in vivo. This study suggests that this 10⁻⁵ M exposure is sufficient to induce changes to the in vivo development of the human fetal male germ cells.

Biomarker genes for detecting estrogenic activity of endocrine disruptors via estrogen receptors

Endocrine disruptors (EDs) are compounds used in various industrial products, drugs, and cosmetics. They can be found in the environment and disturb the endocrine and reproductive systems, resulting in adverse effects to humans and wildlife such as birth defects and developmental disorders. Since several EDs have a structure similar to that of endogenous steroid hormones such as estrogens, they intend to have an affinity for steroid hormone receptors and alter hormone-mediated metabolism by binding to these receptors. EDs are therefore a global concern and assays should be developed to efficiently determine whether these compounds are detrimental to biological systems. Diverse experimental methods may help determine the endocrine disrupting potential of EDs and evaluate the adverse effects of a single and/or combination of these reagents. Currently, biomarkers have been employed to objectively measure EDs potency and understand the underlying mechanisms. Further studies are required to develop ideal screening methods and biomarkers to determine EDs potency at environmentally relevant concentrations. In this review, we describe the biomarkers for estrogenicity of EDs identified both in vitro and in vivo, and introduce a biomarker, cabindin-D_9k (CaBP-9k), that may be used to assess estrogenic activity of EDs.

Effects of perinatal exposure to bisphenol A and di(2-ethylhexyl)-phthalate on gonadal development of male mice

PURPOSE

In this study, we investigated the effects of maternal transfer of bisphenol A (BPA) and di(2-ethylhexyl) phthalate (DEHP) during gestational and weaning periods on gonadal development of male offspring.

METHODS

Pregnant CD-1 mice were administered by gavages in corn oil with 0.1, 1, or 10 mg/kg/day of BPA and DEHP from gestational days (GD1-21) to the weaning period (postnatal days (PND) 1-21).

RESULTS

Our data indicated that the exposure significantly reduced the male-to-female sex ratio and the sizes of the gonads of male pups as recorded at PND15. The testes of the perinatally exposed male pups were developed less and the expression levels of testicular anti-mullerian hormone, androgen receptor, cyclin A, and StAR were significantly lesser than the control male pups. The less developed testes were accompanied with significant reductions in the expression levels of Gnrh and Fsh at the hypothalamic-pituitary levels. The negative effects were found to be persistent in the sexually mature pups at PND42.

CONCLUSION

Our data reveal that the maternal transfer of BPA and DEHP may impose negative influence on the development and functions of the reproductive system of male pups.

Gene expression in the fetal mouse ovary is altered by exposure to low doses of bisphenol A

Evidence from experimental studies suggests that fetal exposure to the endocrine-disrupting chemical bisphenol A (BPA) has adverse reproductive effects in both males and females. Studies from our laboratory suggest that exposure to the developing female fetus produces a unique, multigenerational effect. Specifically, maternal exposure affects the earliest stages of oogenesis in the developing fetal ovary, and the resulting subtle meiotic defects increase the likelihood that embryos produced by the exposed female in adulthood (i.e., the grandchildren) will be chromosomally abnormal. To understand the impact of BPA on the developing ovary, we conducted expression studies to characterize gene expression changes in the fetal ovary that result from BPA exposure. We first tested the validity of the approach, asking whether we could reliably detect temporal changes in expression levels of meiotic genes in controls. As anticipated, we were able to identify appropriate increases in expression in meiotic, but in few other, genes. Intriguingly, this analysis provided data on a small set of genes for which timing and expression changes suggest that they may have important and heretofore unrecognized meiotic roles. After verifying the utility of our approach, we focused our analysis on BPA-exposed animals. We found modest, but significant, changes in gene expression in the fetal ovaries from exposed fetuses. The first changes were evident within 24 h of exposure, and the most extensive changes correlated with the onset of meiosis. Furthermore, gene ontology analysis suggested that BPA acts to down-regulate mitotic cell-cycle genes, raising the possibility that fetal BPA exposure may act to limit expansion of the primordial germ cell population.