Systematic evaluation of the evidence for identification of endocrine disrupting properties of Bisphenol F

Impact of reducing lipid content during in vitro embryo production: A systematic review and meta-analysis

There is still no consensus regarding the role of lipid modulators during in vitro embryo production. Thus, we investigated how lipid reducers during the in vitro maturation of oocytes (IVM) or in vitro culture (IVC) of embryos impact their cryotolerance. A literature search was performed using three databases, recovering 43 articles for the systematic review, comprising 75 experiments (13 performed in IVM, 62 in IVC) and testing 13 substances. In 39 % of the experiments, an increase in oocyte and/or embryo survival after cryopreservation was reported, in contrast to 48 % exhibiting no effect, 5 % causing negative effects, and 8 % influencing in a dose-dependent manner. Of the 75 experiments extracted during IVM and IVC, 41 quantified the lipid content. Of those that reduced lipid content (n = 26), 50 % increased cryotolerance, 34 % had no effect, 8 % harmed oocyte/embryo survival, and 8 % had different results depending on the concentration used. Moreover, 28 out of the 43 studies were analyzed under a meta-analytical approach at the IVC stage in cattle. There was an improvement in the cryotolerance of bovine embryos when the lipid content was reduced. Forskolin, l-carnitine, and phenazine ethosulfate positively affected cryotolerance, while conjugated linoleic acid had no effect and impaired embryonic development. Moreover, fetal bovine serum has a positive impact on cryotolerance. SOF and CR1aa IVC media improved cryotolerance, while mSOF showed no effect. In conclusion, lipid modulators did not unanimously improve cryotolerance, especially when used in IVM, but presented positive effects on cryotolerance during IVC when reaching lipid reduction.

Environmental and occupational exposure to bisphenol compounds in Finland

The aim of the study was to assess non-occupational and occupational exposure to bisphenol compounds in Finland. The participants were 151 non-occupationally exposed volunteers and 15 potentially exposed employees of a sewage-pipe relining company and a floor-coating company. The following chemicals were measured in the urine samples: bisphenol A (BPA), bisphenol F (BPF), bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE), and the metabolites of the latter two [bisphenol A (2,3-dihydroxypropyl) glycidyl ether (BADGE·H2O), bisphenol A bis(2,3-dihydroxypropyl) ether (BADGE·2 H2O), bisphenol A (3-chloro-2-hydroxypropyl) (2,3-dihydroxypropyl) ether (BADGE·HCl·H2O), bisphenol A (3-chloro-2-hydroxypropyl) glycidyl ether (BADGE·HCl), and bisphenol A bis(3-chloro-2-hydroxypropyl) ether (BADGE·2HCl) and bisphenol F bis(2,3-dihydroxypropyl) ether (BFDGE·2 H2O), and bisphenol F bis(3-chloro-2-hydroxypropyl) ether (BFDGE·2HCl)]. BADGE and BFDGE were also measured in breathing zone air samples and hand-wipe samples of the sewage-pipe relining and floor-coating workers. Non-occupational exposure to BPA has decreased in Finland. The BPF level of the non-occupationally exposed was higher than the respective levels reported in the recent literature. BPA and BPF concentrations in the workers' urine samples were in the same range as those in the corresponding concentrations of the non-occupationally exposed population. Higher concentrations of BADGE and BFDGE metabolites were found in some of the workers' urine samples. Elevated urine concentrations were also observed in the samples collected the next morning. Some of the urinary BADGE and BFDGE metabolite results correlated with the hand-wipe results. The results show that occupational exposure to BADGE and BFDGE may occur in sewage-pipe relining and floor-coating work. They also indicate that dermal contamination plays a role in total exposure. Although the measured urinary levels indicate that the absorption of these bisphenol compounds are unlikely to pose a systemic health risk, the risk of dermal sensitization remains.

Exploring a mechanism-based approach for the identification of endocrine disruptors using Adverse Outcome Pathways (AOPs) and New Approach Methodologies (NAMs) : A perfluorooctane sulfonic acid case study

Endocrine disruptors (EDs) pose a serious threat to human health and the environment and require a comprehensive evaluation to be identified. The identification of EDs require a substantial amount of data, both in vitro and in vivo, due to the current scientific criteria in the EU. At the same time, the EU strives to reduce animal testing due to concerns regarding animal welfare and sensitivity of animal studies to adequately detect adverse effects relevant for human health. Perfluorooctane sulfonic acid (PFOS) is a persistent organic pollutant that is suspected to be an ED based on academic research, however it is not identified as such from a regulatory perspective. It has previously been shown that PFOS has the potential to cause neurotoxicity as well as affect the thyroid system, and it is known that specific thyroid hormone levels are critical in the development of the brain during. In this work, the aim was to evaluate a mechanism-based approach to identify ED properties of PFOS based on the Adverse Outcome Pathway (AOP) framework and using New Approach Methods (NAMs), by comparing this approach to an ED assessment based on the currently available guidance document. An AOP network (AOPN) was generated for the thyroid modality, and AOPs leading to developmental neurotoxicity (DNT) were identified. A literature search and screening process based on the AOPN, and systematic review methodology, was performed, followed by a rigorous Weight-of-Evidence (WoE) assessment. Evidence was mapped back onto the AOPN used for the literature search, to identify possible endocrine Modes-of-Action (MoAs) for PFOS and data gaps in the two assessments. It could be concluded that PFOS fulfils the criteria for ED classification in the standard ED assessment, but not in the mechanism-based assessment. The need for quantitative information, such as quantitative AOPs, for the mechanism-based approach is discussed. The possibility of a directly neurotoxic alternative MoA was also highlighted based on available in vitro data. Opportunities and challenges with implementing AOPs and NAMs into the regulatory assessment of EDs, and assessing hazard in the Next Generation Risk Assessment, is discussed. This case study exploring the mechanism-based approach to ED identification represents an important step toward more accurate and predictive assessment of EDs based on AOPs and NAMs, and to the Next Generation Risk Assessment (NGRA) concept.

In vivo exposure to bisphenol F induces oxidative testicular toxicity: role of Erβ and p53/Bcl-2 signaling pathway

Introduction

Bisphenol F (BPF), an alternative to bisphenol A has been implicated as a gonadotoxic substance. BPF has been shown to induce hormonal imbalance and testicular oxidative damage. However, the mechanism associated with BPF-induced testicular toxicity has not been fully explored. This study was designed to explore the role of tumor protein (p53)/ B-cell lymphoma 2 (BCl-2) signaling and oestrogen receptor beta (Erβ) in BPF-induced testicular toxicity.

Methods

Male Wistar rats were randomized into control (Cntrl), BPF-treated (10, 30, and 50 mg/kg for low dose (BPF-L), medium dose (BPF-M), and high dose (BPF-H) respectively), and BPF-treated recovery (Cntrl-R, BPF-L-R, BPF-M-R, and BPF-H-R). The administration was via gavage and lasted for 28 days and the animals in the recovery groups were allowed 28-days exposure free period for recovery from BPF exposure.

Results

BPF resulted in the distortion of the testicular histoarchitecture, which was accompanied by a significant rise in testicular gamma-lutamyl transferase and lactate dehydrogenase activities but a decline in sorbitol dehydrogenase activities. Also, BPF caused a significant reduction in plasma gonadotropin-releasing hormone, luteinising hormone, follicle-stimulating hormone, and testosterone, which was associated with the downregulation of testicular 3beta-hydroxysteroid dehydrogenase and 17beta-hydroxysteroid dehydrogenase activities. Furthermore, BPF induced testicular inflammation, redox imbalance, and apoptosis, accompanied by distortion in p53/BCl-2 signaling and overexpression of Erβ. Again, the observed toxic effects of BPF were dose-dependent and not completely reversed by BPF cessation.

Discussion

Bisphenol F induced gonadotoxicity by distorting p53/BCl2 signaling and the expression of Erβ. These observed alterations were not completely reversed after the cessation of BPF exposure.

Effect of bisphenol F on sexual performance and quality of offspring in Male Wistar rats

This study investigated the effect of BPF on male sexual performance and the quality of the offspring. Eighty (80) Male Wistar rats (n = 10 per group) were randomised into normal saline-treated control and control recovery, BPF varied doses (low, medium, and high), and BPF varied doses recovery (low, medium, and high) groups. The study was terminated after 28 days of BPF oral administration. The animals were sacrificed after 24 h from the last dose, while those in the recovery groups were allowed to recover for another 28 days before being sacrificed. BPF administration was found to impair sexual performance, as shown by a significant decrease in frequencies (mount, intromission, and ejaculation frequencies) and an increase in latencies (mount, intromission, and ejaculation latencies). This was accompanied by a significant decrease in plasma LH, FSH, testosterone, dopamine, acetylcholinesterase, nitric oxide, and penile cyclic guanosine monophosphate (cGMP) level. The level of plasma oestrogen and prolactin were significantly increased following BPF administration. BPF also reduced the sperm count, morphology, viability, and motility. Furthermore, BPF reduced fertility success and index, litter size, litter weight, and offspring survival rate. These toxic effects of BPF were dose-dependent and were not reversed by withdrawal following 28 days of recovery. This study concluded that BPF disrupts sexual competence and offspring quality by suppressing the hypothalamic-pituitary-gonadal axis and mediating oestrogen-induced hyperprolactinemia. These events were associated with reduced fertility index and success, poor semen quality, and reduced offspring survival rate. The observed toxic effects of BPF were dose-dependent and not reversed by cessation of BPF exposure.