Metabolic Barrier against Bisphenol A in Rat Uterine Endometrium

Gestational exposure to bisphenol AF causes endocrine disorder of corpus luteum by altering ovarian SIRT-1/Nrf2/NF-kB expressions and macrophage proangiogenic function in mice

Bisphenol AF (BPAF) is extensively used in industrial production as an emerging substitute for the earlier-used bisphenol A (BPA). Studies have found that BPAF had stronger estrogenic activities than BPA. However, the effects of BPAF on the luteal function of pregnancy and its possible mechanisms are largely unknown. In this study, pregnant mice were orally administered 3.0 and 30 mg/kg/day of BPAF from gestational day (GD) 1 to 8, and samples were collected on GD 8 and GD 19. Results showed that maternal exposure to BPAF impaired embryo implantation and reduced ovarian weight, and interfered with steroid hormone secretion, and decreased the numbers and areas of corpus luteum. BPAF treatment significantly down-regulated expression levels of ovarian Star, Cyp11a, Hsd3b1, and Cyp19a1 mRNA and CYP19a1 and ERα proteins. BPAF also disrupted markers of redox/inflammation key, including silent information regulator of transcript-1 (SIRT-1), nuclear factor erythroid 2-related factor 2 (Nrf2), and nuclear factor kappa-B (NF-ĸB) expressions along with reduced ovarian antioxidant (CAT and SOD) capacity, enhanced oxidant (H2O2 and MDA) and inflammatory factor (Il6 and Tnfa) activities. Furthermore, BPAF exposure inhibited macrophages with a pro-angiogenic phenotype that specifically expressed TIE-2, accompanied by inhibition of angiogenic factors (HIF1a, VEGFA, and Angpt1) and promotion of anti-angiogenic factor Ang-2 to suppress luteal angiogenesis. In addition, BPAF administration also induced luteolysis and apoptosis by up-regulation of COX-2, BAX/BCL-2, and Cleaved-Caspase-3 protein. Collectively, our current data demonstrated that gestational exposure to BPAF caused luteal endocrine disorder by altering ovarian SIRT-1/Nrf2/NF-kB expressions and macrophage proangiogenic function in mice.

Drug delivery strategies for management of women's health issues in the upper genital tract

The female upper genital tract (UGT) hosts important reproductive organs including the cervix, uterus, fallopian tubes, and ovaries. Several pathologies affect these organ systems such as infections, reproductive issues, structural abnormalities, cancer, and inflammatory diseases that could have significant impact on women's overall health. Effective disease management is constrained by the multifaceted nature of the UGT, complex anatomy and a dynamic physiological environment. Development of drug delivery strategies that can overcome mucosal and safety barriers are needed for effective disease management. This review introduces the anatomy, physiology, and mucosal properties of the UGT and describes drug delivery barriers, advances in drug delivery technologies, and opportunities available for new technologies that target the UGT.

Menstrual blood concentrations of parabens and benzophenones and related factors in a sample of Spanish women: An exploratory study

AIM

To evaluate concentrations of parabens (PBs) and benzophenones (BzPs) in menstrual blood and explore related sociodemographic/lifestyle factors, and to compare between menstrual and peripheral blood concentrations in a subset of samples.

MATERIAL AND METHODS

Concentrations of 4 PBs [methyl- (MeP), ethyl- (EtP), propyl- (PrP) and butyl-paraben (BuP)] and 6 BzPs [BzP-1, BzP-2, BzP-3, BzP-6, BzP-8 and 4-OH-BzP] were determined in menstrual blood from 57 women and in both menstrual and peripheral blood samples from 12 women, all healthy Spanish women of reproductive age. Socio-demographic characteristics and lifestyle habits [diet and use of cosmetics and personal care products (PCPs)] were gathered using an online questionnaire. Spearman correlation analysis was performed to examine the relationship between menstrual and peripheral blood concentrations, while multivariable linear regression was used to identify potential explanatory variables for menstrual PB and BzP concentrations.

RESULTS

Globally, all menstrual blood samples had detectable levels of ≥3 compounds, and 52.6% of the samples contained ≥6 compounds. MeP, PrP, and BzP-3 were the most frequently detected compounds (detection frequencies >90.0%), with median concentrations of 1.41, 0.63, and 1.70 ng/mL of menstrual blood, respectively. Age, the use of PCPs, and consumption of some food items (meat, pasta, cheese, or dairy products) were related to the menstrual blood concentrations of some PBs/BzPs. Serum:menstrual blood ratios of PBs/BzPs ranged from 1.7 to 3.6, with no inter-matrix correlations.

CONCLUSIONS

This study reveals, to our knowledge for the first time, the widespread presence of several PBs and BzPs in intimate contact with gynecological tissues, although their concentrations in menstrual blood were not correlated with those in peripheral blood from the same women. These results shed light on the information provided by the menstrual blood as a potential matrix for characterizing exposure to PBs and BzPs, whose consequences for women's reproductive health need to be addressed.

Dose- and time-dependent changes in tissue levels of tetrabromobisphenol A (TBBPA) and its sulfate and glucuronide conjugates following repeated administration to female Wistar Han Rats

Tetrabromobisphenol A (TBBPA), a nongenotoxic flame retardant, causes uterine tumors in female rats. A proposed mode of action (MoA) for these tumors involves an increase in the bioavailability of estradiol as a result of TBBPA inhibiting estrogen sulfotransferases (ES), the enzymes responsible for inactivating and enhancing the elimination of estradiol. The objective of this study was to evaluate the effect of dose and repeated administration of TBBPA on the level of TBBPA, TBBPA-glucuronide (GA) and TBBPA-sulfate (S) conjugates in plasma, liver and uterus of female Wistar Han rats administered TBBPA (50, 100, 250, 500 or 1000 mg/kg) for 28 consecutive days. In accordance with this objective, TBBPA sulfation was used as a surrogate for evaluating the potential for estradiol sulfation to be limited at high dose levels of TBBPA. Blood samples were collected at 4 and 8 h post-dosing on study day 7, 14, and 28, while liver and uterus were collected at the same time points following 28 days of dosing. Tissue samples were analyzed for TBBPA, TBBPA-GA and TBBPA-S by LC–MS/MS. A dose-related increase in the concentration of all three analytes occurred in plasma (day 7, 14, and 28) as well as liver and uterus tissue (day 28) at both 4 and 8 h post dose. The plasma concentration of TBBPA-GA and TBBPA-S was higher in animals dosed for 28 days compared to those dosed for 7 or 14 days showing an increase in systemic circulation of these conjugates with repeated administration. The balance of these conjugates was also different in tissues with TBBPA-S > TBBPA-GA at high doses in the liver and TBBPA-GA > TBBPA-S in both plasma and uterus. In all three tissues the ratio of TBBPA-S/TBBPA-GA showed a decreasing trend with dose, suggesting that at high TBBPA dose levels sulfation of TBBPA becomes limited. This effect was most apparent in the liver and plasma at 28 days of administration. Together these data show that administration of high doses of TBBPA associated with the induction of uterine tumors, results in a disruption in the balance of conjugates reflected by a decrease in the TBBPA-S/TBBPA-GA ratio. A limitation in the sulfation of TBBPA in vivo supports in vitro data defining TBBPA as an inhibitor of ES activity, thus providing further support that the proposed MoA occurs under conditions of high dose, chronic TBBPA administration to Wistar Han rats. Given that the uterine tumors observed in rats (250–1000 mg/kg-day) only occur at very high doses that perturb homeostatic control, it is unlikely such effects would occur in humans given that current TBBPA exposure levels are approximately eight orders of magnitude lower than these doses that are associated with exceeding the capacity of conjugation pathways in animal studies.

Weak activity of UDP-glucuronosyltransferase toward Bisphenol analogs in mouse perinatal development

Bisphenol A (BPA) is a widely used industrial chemical that disrupts endocrine function. BPA is an endocrine disrupting chemical (EDC) that has been demonstrated to affect reproductive organ development, brain development, metabolic disease and post-natal behavior. Accordingly, Bisphenol analogs, Bisphenol F (BPF, bis (4-hydroxyphenyl) methane) and Bisphenol AF (BPAF, 4,4-hexafluoroisopropylidene) diphenol) are used as replacements for BPA. BPA is mainly metabolized by UDP-glucuronosyltransferase (UGT), UGT2B1, but this effective metabolizing system is weak in the fetus. In the present study, we demonstrated that hepatic UGT activity toward BPAF was very weak, in comparison with BPA and BPF, in the fetus, pups and dams. Conversely, hepatic UGT activity toward BPF was very weak in the fetus and newborn pups, and was increased to the same level as BPA post-partum. In conclusion, BPAF possibly tends to accumulate in the fetus, because of weak metabolism during the perinatal period, suggesting that the metabolism of individual Bisphenol analogs requires assessment to properly gauge their risks.

Bisphenol A alters β-hCG and MIF release by human placenta: an in vitro study to understand the role of endometrial cells

A proper fetomaternal immune-endocrine cross-talk in pregnancy is fundamental for reproductive success. This might be unbalanced by exposure to environmental chemicals, such as bisphenol A (BPA). As fetoplacental contamination with BPA originates from the maternal compartment, this study investigated the role of the endometrium in BPA effects on the placenta. To this end, in vitro decidualized stromal cells were exposed to BPA 1 nM, and their conditioned medium (diluted 1 : 2) was used on chorionic villous explants from human placenta. Parallel cultures of placental explants were directly exposed to 0.5 nM BPA while, control cultures were exposed to the vehicle (EtOH 0.1%). After 24–48 h, culture medium from BPA-treated and control cultures was assayed for concentration of hormone human Chorionic Gonadotropin (β-hCG) and cytokine Macrophage Migration Inhibitory Factor (MIF). The results showed that direct exposure to BPA stimulated the release of both MIF and β-hCG. These effects were abolished/diminished in placental cultures exposed to endometrial cell-conditioned medium. GM-MS analysis revealed that endometrial cells retain BPA, thus reducing the availability of this chemical for the placenta. The data obtained highlight the importance of in vitro models including the maternal component in reproducing the effects of environmental chemicals on human fetus/placenta.

Effect of gender, pregnancy and exposure conditions on metabolism and distribution of zearalenone in rats

The mycotoxin zearalenone (ZEA) is produced by a variety of Fusarium fungi and contaminates numerous cereals, fruits and vegetables. Interacting with the oestrogen receptors, ZEA and reduced metabolites zearalenols (ZOLs) cause hormonal effects in animals, such as abnormalities in the development of the reproductive tract and mammary gland in female offspring. Limited information is available on the pharmacokinetics of ZEA and its metabolites, particularly in pregnant females, foetuses and newborns. Our study was conducted to characterise the tissue distribution and metabolism of ZEA in male and female rats in various physiological states (virgin female, pregnant female) and exposure conditions (subcutaneous versus oral exposure, single versus repeated exposure to 1 mg/kg ZEA). Respective placental and mammary transfer to foetuses and newborns was evaluated. In all states and exposure conditions, α-ZOL and the glucuronides of ZEA and α-ZOL were the predominant metabolites, mostly concentrated in the intestine, the liver and the urine. Toxins were very low or undetectable in most of the tissues 24 h after ZEA exposure, except in foetal livers. Absorption and intestinal glucuronidation of ZEA were higher in males than females. α-ZOL concentration was significantly higher in the intestine and liver of males and pregnant females, compared to virgin females. ZEA and all its metabolites easily crossed the placental barrier and transferred into the milk. ZEA was metabolised in the foetal and neonatal stages, glucuronides being the main form detected in all organs. Metabolite elimination was slower in foetal tissues than in maternal tissues. All toxin concentrations in the foetal and neonatal tissues strongly increased in cases of repeated maternal exposure. A better knowledge of the metabolism and transfer of ZEA in foetuses and newborns will help to evaluate the health risk that such endocrine disruptors represent in these stages.

Distribution of bisphenol A into tissues of adult, neonatal, and fetal Sprague-Dawley rats

Bisphenol A (BPA) is an important industrial chemical used in the manufacture of polycarbonate plastic products and epoxy resin-based food can liners. The presence of BPA metabolites in urine of >90% of Americans aged 6-60 suggests ubiquitous and frequent exposure in the range of 0.02-0.2μg/kgbw/d (25th-95th percentiles). The current study used LC/MS/MS to measure placental transfer and concentrations of aglycone (receptor-active) and conjugated (inactive) BPA in tissues from Sprague-Dawley rats administered deuterated BPA (100μg/kg bw) by oral and IV routes. In adult female rat tissues, the tissue/serum concentration ratios for aglycone BPA ranged from 0.7 in liver to 5 in adipose tissue, reflecting differences in tissue perfusion, composition, and metabolic capacity. Following IV administration to dams, placental transfer was observed for aglycone BPA into fetuses at several gestational days (GD), with fetal/maternal serum ratios of 2.7 at GD 12, 1.2 at GD 16, and 0.4 at GD 20; the corresponding ratios for conjugated BPA were 0.43, 0.65, and 3.7. These ratios were within the ranges observed in adult tissues and were not indicative of preferential accumulation of aglycone BPA or hydrolysis of conjugates in fetal tissue in vivo. Concentrations of aglycone BPA in GD 20 fetal brain were higher than in liver or serum. Oral administration of the same dose did not produce measurable levels of aglycone BPA in fetal tissues. Amniotic fluid consistently contained levels of BPA at or below those in maternal serum. Concentrations of aglycone BPA in tissues of neonatal rats decreased with age in a manner consistent with the corresponding circulating levels. Phase II metabolism of BPA increased with fetal age such that near-term fetus was similar to early post-natal rats. These results show that concentrations of aglycone BPA in fetal tissues are similar to those in other maternal and neonatal tissues and that maternal Phase II metabolism, especially following oral administration, and fetal age are critical in reducing exposures to the fetus.

Investigation of the interactions of lysozyme and trypsin with biphenol A using spectroscopic methods

The interaction between bisphenol A (BPA) and lysozyme (or trypsin) was investigated by UV-vis absorption, fluorescence, synchronous fluorescence, and three-dimensional fluorescence spectra techniques under physiological pH 7.40. BPA effectively quenched the intrinsic fluorescence of lysozyme and trypsin via static quenching. H-bonds and van der Waals interactions played a major role in stabilizing the BPA-proteinase complex. The distance r between donor and acceptor was obtained to be 1.65 and 2.26 nm for BPA-lysozyme and BPA-trypsin complexes, respectively. The effect of BPA on the conformation of lysozyme and trypsin was analyzed using synchronous fluorescence and three-dimensional fluorescence spectra.

Impact of acute bisphenol-A exposure upon intrauterine implantation of fertilized ova and urinary levels of progesterone and 17beta-estradiol

Bisphenol-A (BPA), a monomer used in production of polycarbonate plastics and epoxy resins, has established estrogenic properties. We assessed the impact of acute and repeated subcutaneous BPA administration upon intrauterine implantation of fertilized ova and urinary levels of 17beta-estradiol and progesterone in inseminated female mice. In Experiment 1, females received varied doses of BPA on days 1-4 of gestation. Daily doses of 6.75 and 10.125mg/animal significantly reduced the number of implantation sites. Urinary progesterone was significantly reduced by the higher dose, but no other dose had an effect on progesterone levels and no dose altered estradiol levels. In Experiment 2, inseminated females received a single dose of BPA on days 0, 1, or 2 of gestation. A single dose of 10.125mg reduced the number of implantation sites when given on day 0 or day 1, and 6.75mg on day 1 also produced fewer implantation sites, but there was no such effect of any dose when administered on day 2. These data show a lower threshold for BPA-induced pregnancy disruption than previously reported, also indicating effects of just one exposure. They confirm that this disruption is due to the actions of BPA upon implantation sites, and show that higher doses can influence systemic progesterone levels.

Derivation of a bisphenol A oral reference dose (RfD) and drinking-water equivalent concentration

Human exposure to bisphenol A (BPA) is due to that found in the diet, and BPA and its metabolites were detected at parts per billion (or less) concentrations in human urine, milk, saliva, serum, plasma, ovarian follicular fluid, and amniotic fluid. Adverse health effects in mice and rats may be induced after parenteral injection or after massive oral doses. Controlled ingestion trials in healthy adult volunteers with 5 mg d16-BPA were unable to detect parent BPA in plasma despite exquisitely sensitive (limit of detection = 6 nM) methods, but by 96 h 100% of the administered dose was recovered in urine as the glucuronide. The extensive BPA glucuronidation following ingestion is not seen after parenteral injection; only the parent BPA binds plasma proteins and estrogen receptors (ER). The hypothesis that BPA dose-response may be described by a J- or U-shape curve was not supported by toxicogenomic data collected in fetal rat testes and epididymes (after repeated parenteral exposure at 2-400,000 microg/kg-d), where a clear monotonic dose-response both in the numbers of genes and magnitude of individual gene expression was evident. There is no clear indication from available data that the BPA doses normally consumed by humans pose an increased risk for immunologic or neurologic disease. There is no evidence that BPA poses a genotoxic or carcinogenic risk and clinical evaluations of 205 men and women with high-performance liquid chromatography (HPLC)-verified serum or urinary BPA conjugates showed (1) no objective signs, (2) no changes in reproductive hormones or clinical chemistry parameters, and (3) no alterations in the number of children or sons:daughters ratio. Results of benchmark dose (BMD10 and BMDL10) calculations and no-observed-adverse-effect level (NOAEL) inspections of all available and reproducible rodent studies with oral BPA found BMD and NOAEL values all greater than the 5 mg/kg-d NOAELs from mouse and rat multigeneration reproduction toxicity studies. While allometric and physiologically based pharmacokinetic (PBPK) models were constructed for interspecies scaling of BPA and its interaction with ER, multigeneration feeding studies with BPA at doses spanning 5 orders of magnitude failed to identify signs of developmental toxicity or adverse changes in reproductive tract tissues; the 5-mg/kg-d NOAELs identified for systemic toxicity in rats and mice were less than the oral NOAELs for reproductive toxicity. Thus, it is the generalized systemic toxicity of ingested BPA rather than reproductive, immunologic, neurobehavioral, or genotoxic hazard that represents the point of departure. Using U.S. Environmental Protection Agency (EPA) uncertainty factor guidance and application of a threefold database uncertainty factor (to account for the fact that the carcinogenic potential of transplacental BPA exposure has yet to be fully defined and comprehensive neurobehavioral and immunotoxicologic evaluations of BPA by relevant routes and at relevant doses have yet to be completed) to the administered dose NOAEL results in an oral RfD of 0.016 mg/kg-d. Assuming the 70-kg adult consumes 2 L of water each day and adopting the default 20% U.S. EPA drinking water relative source contribution yields a 100 microg/L BPA total allowable concentration (TAC).