Di-n-butyl phthalate promotes the neural differentiation of mouse embryonic stem cells through neurogenic differentiation 1

An understanding of the risk of gene deletion and mutation posed by endocrine-disrupting chemicals (EDCs) is necessary for the identification of etiological reagents for many human diseases. Therefore, the characterization of the genetic traits caused by developmental exposure to EDCs is an important research subject. A new regenerative approach using embryonic stem cells (ESCs) holds promise for the development of stem-cell-based therapies and the identification of novel therapeutic agents against human diseases. Here, we focused on the characterization of the genetic traits and alterations in pluripotency/stemness triggered by phthalate ester derivatives. Regarding their in vitro effects, we reported the abilities of ESCs regarding proliferation, cell-cycle control, and neural ectoderm differentiation. The expression of their stemness-related genes and their genetic changes toward neural differentiation were examined, which led to the observation that the tumor suppressor gene product p53/retinoblastoma protein 1 and its related cascades play critical functions in cell-cycle progression, cell death, and neural differentiation. In addition, the expression of neurogenic differentiation 1 was affected by exposure to di-n-butyl phthalate in the context of cell differentiation into neural lineages. The nervous system is one of the most sensitive tissues to exposure to phthalate ester derivatives. The present screening system provides a good tool for studying the mechanisms underlying the effects of EDCs on the developmental regulation of humans and rodents, especially on the neuronal development of ESCs.

Combined effect of polystyrene nanoplastic and di-n-butyl phthalate on testicular health of male Swiss albino mice: analysis of sperm-related parameters and potential toxic effects

Plastics, especially polystyrene nanoplastic particles (PSNPs), are known for their durability and absorption properties, allowing them to interact with environmental pollutants such as di-n-butyl phthalate (DBP). Previous research has highlighted the potential of these particles as carriers for various pollutants, emphasizing the need to understand their environmental impact comprehensively. This study focuses on the subchronic exposure of male Swiss albino mice to PSNP and DBP, aiming to investigate their reproductive toxicity between these pollutants in mammalian models. The primary objective of this study is to examine the reproductive toxicity resulting from simultaneous exposure to PSNP and DBP in male Swiss albino mice. The study aims to analyze sperm parameters, measure antioxidant enzyme activity, and conduct histopathological and morphometric examinations of the testis. By investigating the individual and combined effects of PSNP and DBP, the study seeks to gain insights into their impact on the reproductive profile of male mice, emphasizing potential synergistic interactions between these environmental pollutants. Male Swiss albino mice were subjected to subchronic exposure (60 days) of PSNP (0.2 mg/m, 50 nm size) and DBP (900 mg/kg bw), both individually and in combination. Various parameters, including sperm parameters, antioxidant enzyme activity, histopathological changes, and morphometric characteristics of the testis, were evaluated. The Johnsen scoring system and histomorphometric parameters were employed for a comprehensive assessment of spermatogenesis and testicular structure. The study revealed non-lethal effects within the tested doses of PSNP and DBP alone and in combination, showing reductions in body weight gain and testis weight compared to the control. Individual exposures and the combination group exhibited adverse effects on sperm parameters, with the combination exposure demonstrating more severe outcomes. Structural abnormalities, including vascular congestion, Leydig cell hyperplasia, and the extensive congestion in tunica albuginea along with both ST and Leydig cell damage, were observed in the testis, underscoring the reproductive toxicity potential of PSNP and DBP. The Johnsen scoring system and histomorphometric parameters confirmed these findings, providing interconnected results aligning with observed structural abnormalities. The study concludes that simultaneous exposure to PSNP and DBP induces reproductive toxicity in male Swiss albino mice. The combination of these environmental pollutants leads to more severe disruptions in sperm parameters, testicular structure, and antioxidant defense mechanisms compared to individual exposures. The findings emphasize the importance of understanding the interactive mechanisms between different environmental pollutants and their collective impact on male reproductive health. The use of the Johnsen scoring system and histomorphometric parameters provides a comprehensive evaluation of spermatogenesis and testicular structure, contributing valuable insights to the field of environmental toxicology.

Monomethyl Phthalate Causes Early Embryo Development Delay, Apoptosis, and Energy Metabolism Disruptions Through Inducing Redox Imbalance

Phthalates are a class of environmental endocrine disrupting chemicals which can cause reproductive system damages. However, data about reproductive toxicity spectrum of phthalate metabolites among Chinese women undergoing in vitro fertilization (IVF) treatments are scarce yet. Previous studies regarding underlying embryo toxicities focused on oxidative stress and apoptosis, while energy metabolism abnormality might be another key cause for embryo developmental disruptions. Here, we found that among the measured eight phthalate metabolites, monomethyl phthalate (MMP) had the second highest urinary concentration in women receiving IVF. Compare to the lowest exposure level group, MMP in tertile 3 was associated with fewer counts of oocyte retrieved and good-quality embryos, and MMP in tertile 2 was correlated with reduced good-quality embryo rate. The direct embryo toxicities of MMP were studied using mouse 2-cell embryos. Consistent to results found in human populations, exposure to MMP induced mouse early embryo developmental delay. Furthermore, MMP exposure led to excessive reactive oxygen species production in early embryos, and antioxidant can partially rescue the early embryo development slow down. Embryo apoptosis could also be caused by oxidative stress. To be noted, elevated apoptosis level was not found in live "slow" embryos but dead embryos, which suggested that apoptosis was not related to early embryo developmental delay. Additionally, MMP exposure depleted adenosine triphosphate (ATP) synthesis of early embryos, which could be reversed by antioxidant. In conclusion, MMP, as the newly found embryonic toxicant in Chinese women, resulted in early embryo development delay, apoptosis, and energy metabolism disruptions via inducing redox imbalance.

Dysregulation of steroid metabolome in follicular fluid links phthalate exposure to diminished ovarian reserve of childbearing-age women

The widespread use of phthalates (PAEs) has drawn increasing attention due to their endocrine disruption and reproductive toxicity, while the steroid metabolome is essential for follicular development. However, the mechanism by which PAE exposure affects ovarian reserve through the steroid metabolome remains unclear. This study recruited 264 childbearing-age women in Tianjin (China) from April 2019 to August 2020 in a cross-sectional design. Target metabolome analysis of 16 steroids was performed in follicular fluid (FF) to compare diminished ovarian reserve (DOR) against normal ovarian reserve (NOR) women and differential steroids were identified using binary logistic analyses. Further analysis of eleven PAE metabolites (mPAEs) in FF was conducted, and the retrieved oocyte number (RON) representing ovarian reserve was counted. Multiple linear regression and quantile-based g-computation (qgcomp) models were used to associate individual mPAEs and mPAE mixture with the DOR-related differential steroids in FF. Mediation analysis was used to discuss the mediating effect of DOR-related steroids on the association between mPAEs and RON. Androstenedione (A4), corticosterone (CORT), cortisol (COR) and cortisone were significantly down-regulated in FF from women with DOR. Nine mPAEs with detection frequencies greater than 60% and median concentrations of 0.02-4.86 ng/mL were incorporated into statistical models. Negative associations with COR and CORT were found for mono-ethyl phthalate (mEP), mono-(2-ethyl-5-oxohexyl) phthalate (mEOHP), and mono-2-ethylhexyl phthalate (mEHP). A positive association with cortisone was found for mEOHP, mEHP, monobutyl phthalate (mBP), and mono (2-isobutyl) phthalate (miBP). The qgcomp and mediation analyses revealed that mEP and mEOHP not only significantly contributed to the decline of COR and CORT in the mixed exposure but also indirectly reduced RON through the mediating effects of COR and CORT. In conclusion, PAE exposure may decrease ovarian reserve by downregulating COR and CORT.

Glycine ameliorates MBP-induced meiotic abnormalities and apoptosis by regulating mitochondrial-endoplasmic reticulum interactions in porcine oocytes

Monobutyl phthalate (MBP) is the main metabolite of dibutyl phthalate (DBP) in vivo. MBP has a stable structure, can continuously accumulate in living organisms, and has the potentially to harm animal and human reproductive function. In the ovarian follicle microenvironment, MBP may lead to defects in follicular development and steroid production, abnormal meiotic maturation, impaired ovarian function and other reproductive deficits. In this study, SMART-seq was used to investigate the effects of MBP exposure on the in vitro maturation (IVM) and development of porcine oocytes. The results showed that differentially expressed genes after MBP exposure were enriched in the biological processes cytoskeleton, cell apoptosis, endoplasmic reticulum (ER) and mitochondria. Glycine (Gly) improved the developmental potential of porcine oocytes by regulating mitochondrial and ER function. The effect of Gly in protecting oocytes against MBP-induced damage was studied. The results showed that the addition of Gly significantly decreased the rate of MBP-induced spindle abnormalities, decreased the frequency of MBP-induced mitochondria-associated ER membrane (MAM) interactions, and downregulated the protein and gene expression of the linkage molecules Mitofusin 1 (MFN1) and Mitofusin 2 (MFN2) in the MAM. Additionally, treatment with Gly restored the distribution of the 1,4,5-triphosphate receptor 1 (IP₃R1) and voltage-dependent anion channel 1 (VDAC1), further decreasing the intracellular free calcium concentration ([Ca²⁺]_i) levels and mitochondrial Ca²⁺ ([Ca²⁺]_m) , increasing the ER Ca²⁺ ([Ca²⁺]_ER) levels, and thus significantly increasing the ER levels and mitochondrial membrane potential (ΔΨ m). Gly also decreased the levels of reactive oxygen species (ROS) and increased the levels of Glutathione (GSH), oocyte apoptosis-related indicators (Caspase-3 activity and Annexin V) and oocyte apoptosis-related genes (BAX, Caspase 3 and AIFM1). Our results suggest that Gly can ameliorate microtubule cytoskeleton abnormalities and improve oocyte maturation by reducing the defective mitochondrial-ER interactions caused by MBP exposure in vitro.

The association of serum phthalate metabolites with biomarkers of ovarian reserve in women of childbearing age

Phthalates (PAEs) are widely used plasticizers drawing increasing concern due to reproductive toxicity. However, studies on serum PAEs metabolites (mPAEs) and their associations with human ovarian function remain very scarce. In this study, from April 2019 to August 2020, a total of 297 women of childbearing age were recruited in Tianjin, China. Eleven mPAEs were analyzed in serum samples and eight mPAEs were detected at frequencies > 65% with median concentrations of 0.43-15.3 ng/mL. In multinomial logistic analysis, an increase in serum mono (2-isobutyl) phthalate (miBP) was associated with decline in antral follicle count (AFC) (OR=1.26, 95% CI: 0.99, 1.61) and 5-mono-(2-ethyl-5-hydroxyhexyl) phthalate (mEHHP) was significantly associated with AFC increase (OR=1.43, 95% CI: 1.06, 1.92), which were aligned with the associations found between mPAEs and AMH through generalized linear regression. In multiple linear regression models, per 10% increase in serum mono (2-ethylhexyl) phthalate (mEHP), mono (2-ethyl-5-oxohexyl) phthalate (mEOHP) (oxo-mEHP), and principal component 1 featured for high concentrations of mono-n-butyl phthalate (mBP), miBP and mEHP were associated with 0.15 (95% CI: -0.29, -0.02), 0.01 (95% CI: -0.01, 0.00) and 0.01 (95% CI: -0.02, 0.00) ln-unit decrease in estradiol (E2) levels, respectively, while mono-[(2-carboxymethyl) hexyl] phthalate (mCMHP) (carboxymethyl-mEHP) was positively associated with 0.05 ln-unit increase of E2 (95% CI: 0.02, 0.08). The observed negative associations between mPAEs and the Anti-Müllerian hormone (AMH) also aligned with the change in AFC. Generalized linear regression also revealed nonlinear associations between mono-ethyl phthalate (mEP), mCMHP and follicle-stimulating hormone (FSH). Overall, serum mEHP and its metabolites were negatively associated with E2. miBP was negatively associated with AFC. The nonlinear associations between mPAEs and FSH, and AMH need further study.

The selected epigenetic effects of phthalates: DBP, BBP and their metabolites: MBP, MBzP on human peripheral blood mononuclear cells (In Vitro)

Phthalates are classified as non-genotoxic carcinogens. These compounds do not cause direct DNA damage but may induce indirect DNA lesions leading to cancer development. In the presented paper we have studied the effect of di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBP), and their metabolites, such as mono-n-butyl phthalate (MBP) and monobenzyl phthalate (MBzP) on selected epigenetic parameters in human peripheral blood mononuclear cells (PBMCs). The cells were incubated with tested phthalates at 0.001, 0.01 and 0.1 μg/mL for 24 h. Next, global DNA methylation, methylation in the promoter regions of tumor suppressor genes (P16, TP53) and proto-oncogenes (BCL2, CCND1) were assessed as well as the expression profile of the indicated genes was analysed. The obtained results have revealed significant reduction of global DNA methylation level in PBMCs exposed to BBP, MBP and MBzP. Phthalates changed methylation pattern of the tested genes, decreased expression of P16 and TP53 genes and increased the expression of BCL2 and CCND1. In conclusion, our results have shown that the examined phthalates disturbed the processes of methylation and expression of tumor suppressor genes (P16, TP53) and protooncogenes (BCL2, CCND1) in human PBMCs.

Phthalate metabolites: Characterization, toxicities, global distribution, and exposure assessment

Phthalates are plasticizers in various products and regarded as endocrine disruptors due to their anti-androgen effects. Environmental occurrence and toxicities of parent phthalates have been widely reported, while the current state of knowledge on their metabolites is rarely summarized. Based on the available literature, the present review mainly aims to 1) characterize the potential metabolites of phthalates (mPAEs) using the pharmacokinetics evidences acquired via animal or human models; 2) examine the molecular and cellular mechanism involved in toxicity for mPAEs; 3) investigate the exposure levels of mPAEs in different human specimens (e.g., urine, blood, seminal fluid, breast milk, amniotic fluid and others) across the globe; 4) discuss the models and related parameters for phthalate exposure assessment. We suggest there is subtle difference in toxic mechanisms for mPAEs compared to their parent phthalates due to their alternative chemical structures. Human monitoring studies performed in Asia, America and Europe have provided the population exposure baseline levels for typical phthalates in different regions. Urine is the preferred matrix than other specimens for phthalate exposure study. Among ten urinary mPAEs, the largest proportions of di-(2-ethylhexyl) phthalate (DEHP) metabolites (40%), monoethyl phthalate (mEP) (43%) and DEHP metabolites/mEP (both 29%) were observed in Asia, America and Europe respectively, and mono-5-carboxy-2-ethypentyl phthalate was the most abundant compounds among DEHP metabolites. Daily intakes of phthalates can be accurately calculated via urinary mPAEs if the proper exposure parameters were determined. Further work should focus on combining epidemiological and biological evidences to establish links between phthalates exposure and biological phenotypes. More accurate molar fractions (F_UE) of the urinary excreted monoester related to the ingested diesters should be collected in epidemiological or pharmacokinetic studies for different population.

Prevalence of phthalate alternatives and monoesters alongside traditional phthalates in indoor dust from a typical e-waste recycling area: Source elucidation and co-exposure risk

This study first discovered the prevalence of phthalate (PAE) alternatives and PAE monoesters alongside traditional PAEs with elevated concentrations in indoor dust from typical e-waste recycling industrial park and adjacent communities. Among nine PAEs, high-molecular-weight (HMW) PAEs dominated over low-molecular-weight (LMW) PAEs in e-waste dust, with total concentrations (∑₉PAEs) ranging from 170 to 5300 μg g^-1. The diisononyl phthalate (DiNP) was identified as the most abundant PAE in e-waste dust, with over 10 times higher median concentration than that measured in home dust. Total concentrations of three PAE alternatives ranged from 20 to 1600 μg g^-1 in e-waste dust, which were 3-10 times higher than the measured levels in home dust. A total of 13 monoesters were all identified in all samples with total concentrations of 4.7-59 μg g^-1, and biodegradation of diesters was recognized as the major source of monoesters present in indoor dust. Significant correlations between the concentrations of PAE alternatives and the HMW PAEs were observed (p < 0.05), indicating that they are being simultaneously used in electronic and electrical products. The occupationally high co-exposure of e-waste dismantling workers to multiple PAEs and PAE alternatives as well as their monoesters should be of concern.

Human Erythrocytes Exposed to Phthalates and Their Metabolites Alter Antioxidant Enzyme Activity and Hemoglobin Oxidation

Phthalates used as plasticizers have become a part of human life because of their important role in various industries. Human exposure to these compounds is unavoidable, and therefore their mechanisms of toxicity should be investigated. Due to their structure and function, human erythrocytes are increasingly used as a cell model for testing the in vitro toxicity of various xenobiotics. Therefore, the purpose of our study was to assess the effect of selected phthalates on methemoglobin (metHb), reactive oxygen species (ROS) including hydroxyl radical levels, as well as the activity of antioxidative enzymes, such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), in human erythrocytes. Erythrocytes were incubated with di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBP), and their metabolites, i.e., mono-n-butyl phthalate (MBP) and monobenzyl phthalate (MBzP), at concentrations ranging from 0.5 to 100 µg/mL for 6 or 24 h. This study shows that the analyzed phthalates disturbed the redox balance in human erythrocytes. DBP and BBP, at much lower concentrations than their metabolites, caused a statistically significant increase of metHb and ROS, including hydroxyl radical levels, and changed the activity of antioxidant enzymes. The studied phthalates disturbed the redox balance in human erythrocytes, which may contribute to the accelerated removal of these cells from the circulation.

Phthalate Exposure and Long-Term Epigenomic Consequences: A Review

Phthalates are esters of phthalic acid which are used in cosmetics and other daily personal care products. They are also used in polyvinyl chloride (PVC) plastics to increase durability and plasticity. Phthalates are not present in plastics by covalent bonds and thus can easily leach into the environment and enter the human body by dermal absorption, ingestion, or inhalation. Several in vitro and in vivo studies suggest that phthalates can act as endocrine disruptors and cause moderate reproductive and developmental toxicities. Furthermore, phthalates can pass through the placental barrier and affect the developing fetus. Thus, phthalates have ubiquitous presence in food and environment with potential adverse health effects in humans. This review focusses on studies conducted in the field of toxicogenomics of phthalates and discusses possible transgenerational and multigenerational effects caused by phthalate exposure during any point of the life-cycle.

Gestational and lactational exposition to di-n-butyl phthalate increases neurobehavioral perturbations in rats: A three generational comparative study

Di-n-butyl phthalate (DBP) cause significant deficits in cognition and memory, however the neuroanatomical basis for impairments remain poorly understood. This study evaluates neurobehavioral changes in rats for three successive generations between non-siblings by administering DBP at 500mg/kg bw dose through oral gavage from gestation day-6 to 21 and lactation (3-weeks). Weaning period evaluations and developmental deficits assessed showed variations specific to generation and the toxic potential of DBP was confounded by behavioral deficits that include changes in sensorimotor development reflex response, poor performance, low memory retention and greater latency period. The cytoarchitectural alterations witnessed in hippocampus include condensed nuclei, vacuole formation and remarkable degeneration, shrinkage of pyramidal neurons in CA1 and CA3 regions; disorganized hilar cells and hyperplasia in dentate gyrus. Comparatively, the enlisted changes were high in subsequent generations than preceding and correlates assessed between cognitive impairment(s) and endocrine function confirm a link indicating vulnerability of immature animals as target to disrupt neural and endocrine functions.

The associations of urinary phthalate metabolites with the intermediate and pregnancy outcomes of women receiving IVF/ICSI treatments: A prospective single-center study

BACKGROUND

Phthalate exposure was reported to induce defects in ovarian function, and further influence embryo development and pregnancy outcomes. However, the data about the associations of phthalates with intermediate and pregnancy outcomes of in vitro fertilization (IVF) cycles are scarce in the Chinese population.

METHODS

A total of 663 women receiving IVF/intracytoplasmic sperm injection (ICSI) treatments in our center were enrolled in this analysis. They provided one urine sample on the day of oocyte retrieval. We measured urinary concentrations of eight phthalate metabolites. Generalized linear models were used to analyze the associations of urinary phthalate metabolites with ovarian response, fertilization, early embryo development, and pregnancy outcomes.

RESULTS

Among all the phthalate metabolites, mono-n-butyl phthalate (MBP) had the highest urinary concentration with a median level of 101.51 μg/g creatinine (Cr). MBP concentration was inversely associated with normal fertilization odds (overall P-trend < 0.01). There was a significant correlation of monoethyl phthalate (MEP) with decreased odds of normal fertilization in medium-concentration group compared to low-concentration group (overall P-trend = 0.02). No significant associations of metabolite concentrations with the odds of good-quality embryos on day 3 or blastocyst formation were found. Monomethyl phthalate (MMP) and MEP in medium-concentration group reduced 22.4% (95% CI: 0.64-0.94, overall P-trend = 0.04) and 21.9% (95% CI: 0.64-0.95, overall P-trend = 0.05) of the odds to gain good-quality blastocyst compared to low-concentration group. The eight phthalate metabolites were not correlated to clinical pregnancy rate, live birth rate, or early miscarriage rate. There was no significant association of di (2-ethylhexyl) phthalate (DEHP) metabolites observed with any clinical outcomes in the total population. After excluding male infertility, mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) in medium-concentration group turned to be associated with a higher number of retrieved oocytes (overall P-trend = 0.04), whereas mono (2-ethyl-5-oxohexyl) phthalate (MEOHP) in medium-concentration group was associated with a lower odds of normal fertilization compared to low-concentration group (overall P-trend = 0.02).

CONCLUSIONS

Urinary MBP concentration was much higher compared to other phthalate metabolites in this cohort of Chinese IVF/ICSI women, and also higher than it was reported by studies in other countries. MBP showed adverse impacts on fertilization. MMP and MEP could affect blastocyst quality, but not embryo quality on day 3. DEHP metabolites didn't show consistent reproductive toxicities as demonstrated in previous studies.

Beyond Phthalate Diesters: Existence of Phthalate Monoesters in South China House Dust and Implications for Human Exposure

Despite phthalate monoesters (mono-PAEs) being commonly recognized as metabolic products of phthalate diesters (di-PAEs), investigations on their environmental occurrences, particularly in indoor environments, remain limited. The present study demonstrated the presence mono-PAEs, along with a variety of di-PAEs, in house dust collected from 83 South China families. Among 15 target mono-PAEs, monobutyl phthalate (median concentration, 21.54 μg/g) dominated over other mono-PAEs in indoor dust, followed by monoethylhexyl phthalate (9.44 μg/g), monoisobutyl phthalate (5.14 μg/g), monomethyl phthalate (MMP; 2.05 μg/g), and several others. The total concentrations of detectable mono-PAEs (median, 45.40 μg/g) constituted an average of 6.7 ± 3.7% of the total concentrations of their parent diesters in the same dust. Molar concentration ratios of mono-PAEs to their respective di-PAEs varied greatly among chemicals (median, 0.001-3.1), with the highest ratios determined for the MMP/dimethyl phthalate and mono-/diisopropyl phthalate pairs (i.e., 3.1 and 1.5, respectively). In addition, no significant associations were observed between dust-associated mono- or di-PAEs and urinary mono-PAEs detected in both children (n = 48) and adult participants (n = 41). We hypothesized that mono-PAEs in dust could originate from different sources (e.g., impurities in di-PAE formulas, degradation from di-PAEs, and direct application as commercial additives), while the relative importance of various origins could differ between chemicals. Our findings demonstrate broad occurrences of mono-PAEs in indoor environments, but future studies are needed to better elucidate their sources, fate in indoor and outdoor environments, and potential human health risks.

Choline, not folate, can attenuate the teratogenic effects ofdibutyl phthalate (DBP) during early chick embryo development

Dibutyl phthalate (DBP), a persistent environmental pollutant, can induce neural tube abnormal development in animals. The possible effects of DBP exposure on human neural tube defects (NTDs) remain elusive. In this study, the distribution of DBP in the body fluid of human NTDs was detected by GC-MS. Then, chick embryos were used to investigate the effects of DBP on early embryonic development. Oxidative stress indicators in chick embryos and the body fluid of human NTDs were detected by ELISA. The cell apoptosis and total reactive oxygen species (ROS) level in chick embryos were detected by whole-mount TUNEL and oxidized DCFDA, respectively. The study found that the detection ratio of positive DBP and its metabolites in maternal urine was higher in the NTD population than that in normal controls. 8-hydroxy-2 deoxyguanosine (8-OHDG) and malondialdehyde (MDA) were evidently upregulated and superoxide dismutase (SOD) was observably downregulated in amniotic fluid and urine. Animal experiments indicated that DBP treatment induced developmental toxicity in chick embryos by enhancing the levels of oxidative stress and cell apoptosis. MDA was increased and SOD was decreased in DBP-treated embryos. Interestingly, the supplement of high-dose choline (100 μg/μL), not folic acid, could partially restore the teratogenic effects of DBP. Our data collectively suggest that the incidence of NTDs is closely associated with DBP exposure. This study may provide new insight for NTD prevention.

A strategy to validate a selection of human effect biomarkers using adverse outcome pathways: Proof of concept for phthalates and reproductive effects

Human biomonitoring measures the concentrations of environmental chemicals or their metabolites in body fluids or tissues. Complementing exposure biomarkers with mechanistically based effect biomarkers may further elucidate causal pathways between chemical exposure and adverse health outcomes. We combined information on effect biomarkers previously implemented in human observational studies with mechanisms of action reported in experimental studies and with information from published Adverse Outcome Pathways (AOPs), focusing on adverse reproductive effects of phthalate exposure. Phthalates constitute a group of chemicals that are ubiquitous in consumer products and have been related to a wide range of adverse health effects. As a result of a comprehensive literature search, we present an overview of effect biomarkers for reproductive toxicity that are substantiated by mechanistic information. The activation of several receptors, such as PPARα, PPARγ, and GR, may initiate events leading to impaired male and female fertility as well as other adverse effects of phthalate exposure. Therefore, these receptors appear as promising targets for the development of novel effect biomarkers. The proposed strategy connects the fields of epidemiology and toxicology and may strengthen the weight of evidence in observational studies that link chemical exposures to health outcomes.

Changes in the uterine metabolome of the cow during the first 7 days after estrus

The uterine microenvironment during the first 7 days after ovulation accommodates and facilitates sperm transit to the oviduct and constitutes the sole source of nutrients required for the development of preimplantation embryos. Knowledge of the composition of uterine fluid is largely incomplete. Using untargeted mass spectrometry, we characterized the uterine metabolome during the first 7 days of the estrous cycle. Bovine uteri were collected on Days 0 (N = 4), 3 ( N = 4), 5 ( N = 3), and 7 ( N = 4) relative to ovulation and flushed with Dulbecco’s phosphate‐buffered saline. A total of 1,993 molecular features were detected of which 184 peaks with putative identification represent 147 unique metabolites, including amino acids, benzoic acids, lipid molecules, carbohydrates, purines, pyrimidines, vitamins, and other intermediate and secondary metabolites. Results revealed changes in the uterine metabolome as the cow transitions from ovulation to Day 7 of the estrous cycle. The majority of metabolites that changed with day reached maximum intensity on either Day 5 or 7 relative to ovulation. Moreover, several metabolites found in the uterine fluid have signaling capabilities and some have been shown to affect preimplantation embryonic development. In conclusion, the metabolome of the bovine uterus changes during early stages of the estrous cycle and is likely to participate in the regulation of preimplantation embryonic development. Data reported here will serve as the basis for future studies aiming to evaluate maternal regulation of preimplantation embryonic development and optimal conditions for the culture of embryos.

Mono-2-ethylhexyl phthalate disrupts neurulation and modifies the embryonic redox environment and gene expression

Mono-2-ethylhexl phthalate (MEHP) is the primary metabolite of di-2-ethylhexyl phthalate (DEHP), a ubiquitous contaminant in plastics. This study sought to determine how structural defects caused by MEHP in mouse whole embryo culture were related to temporal and spatial patterns of redox state and gene expression. MEHP reduced morphology scores along with increased incidence of neural tube defects. Glutathione (GSH) and cysteine (Cys) concentrations fluctuated spatially and temporally in embryo (EMB) and visceral yolk sac (VYS) across the 24h culture. Redox potentials (Eh) for GSSG/GSH were increased by MEHP in EMB (12h) but not in VYS. CySS/CyS Eh in EMB and VYS were significantly increased at 3h and 24h, respectively. Gene expression at 6h showed that MEHP induced selective alterations in EMB and VYS for oxidative phosphorylation and energy metabolism pathways. Overall, MEHP affects neurulation, alters Eh, and spatially alters the expression of metabolic genes in the early organogenesis-stage mouse conceptus.

Endoplasmic reticulum stress signaling in mammalian oocytes and embryos: life in balance

Mammalian oocytes and embryos are exquisitely sensitive to a wide range of insults related to physical stress, chemical exposure, and exposures to adverse maternal nutrition or health status. Although cells manifest specific responses to various stressors, many of these stressors intersect at the endoplasmic reticulum (ER), where disruptions in protein folding and production of reactive oxygen species initiate downstream signaling events. These signals modulate mRNA translation and gene transcription, leading to recovery, activation of autophagy, or with severe and prolonged stress, apoptosis. ER stress signaling has recently come to the fore as a major contributor to embryo demise. Accordingly, agents that modulate or inhibit ER stress signaling have yielded beneficial effects on embryo survival and long-term developmental potential. We review here the mechanisms of ER stress signaling, their connections to mammalian oocytes and embryos, and the promising indications that interventions in this pathway may provide new opportunities for improving mammalian reproduction and health.