A study on the association of placental and maternal urinary phthalate metabolites

Gestational phthalate exposure and behavioral problems in preschool-aged children with increased likelihood of autism spectrum disorder

BACKGROUND

Experimental studies have shown associations between gestational phthalate exposure and behavioral problems among offspring; however, epidemiological evidence is still mixed. This study aims to investigate whether gestational phthalate exposure is associated with behavioral problems in preschool-aged children.

METHODS

Participants include 178 mother-child pairs from MARBLES (Markers of Autism Risk in Babies - Learning Early Signs), a cohort with high familial likelihood of autism spectrum disorder (ASD). We quantified 14 phthalate metabolites in multiple maternal urine samples collected during the 2nd and 3rd trimesters. Preschool behavior problems were assessed using the Child Behavioral Checklist (CBCL), a standardized instrument for evaluating behavior problems of children aged 1.5-5 years. To examine associations of CBCL scores with both individual phthalate biomarker concentrations and their mixture, we used negative binomial regression and weighted quantile sum regression.

RESULTS

Overall, maternal phthalate biomarker concentrations were not associated with child behavior problems. Monoisobutyl phthalate (MiBP) concentrations were inversely associated with child anxious/depressed symptoms and somatic complaints. Mono-hydroxy-isobutyl phthalate (MHiBP) and monobenzyl phthalate (MBzP) were also inversely associated with somatic complaints. When assessing trimester-specific associations, more behavior problems were associated with the 2nd trimester biomarker concentrations: mono(3-carboxypropyl) phthalate (MCPP) and monocarboxyisononyl phthalate (MCNP) were positively associated with somatic complaints. All associations became non-significant after false discovery rate correction. No association between a mixture of phthalates and CBCL scores was found.

CONCLUSIONS

Our study observed no clear evidence of gestational phthalate exposure on child behavior problems. However, our findings based on the biomonitoring assessment of multiple samples per participant could improve our understanding of gestational phthalate exposure in association with behavior problems in preschool-aged children.

Association between prenatal exposure to phthalate esters and blood pressure in children aged 3-7 years: A prospective cohort study

BACKGROUND

An increasing number of animal studies have indicated that exposure to phthalate esters (PAEs) may cause high blood pressure. However, population-based evidence is limited, particularly for pregnant women and young children.

OBJECTIVE

To examine the correlation between prenatal exposure to phthalate ester metabolites (mPAEs) and blood pressure in preschool children.

METHODS

In our cohort study, 497 pairs of mothers and children (aged 3-7 years) were enrolled at the Wuhan Maternal and Child Healthcare Hospital, Wuhan, China, between 2016 and 2017. Eight mPAEs were detected in the urine samples of pregnant women during the third trimester. Systolic (SBP) and diastolic blood pressure (DBP) were measured by physicians using an automated oscillometric sphygmomanometer and childhood hypertension was defined according to the American Academy of Pediatrics 2017 guidelines. Mixed-effects linear regression models were used to estimate the correlations between individual mPAEs and the SBP and DBP z-scores of preschoolers. Binary logistic regression models were used to examine the correlation between individual mPAEs and hypertension risk. A weighted quantile sum (WQS) regression was implemented to explore the correlation between mixed mPAEs and the SBP/DBP z-scores in children.

RESULT

Monomethyl phthalate, monobutyl phthalate (MBP), monoethyl phthalate, mono(2-ethylhexyl) phthalate, mono(2-ethyl-5-hydroxyhexyl) phthalate and mono(2-ethyl-5-oxohexyl) phthalate were significantly positively correlated with increases in the SBP and DBP z-scores, whereas MBP was significantly correlated with hypertension risk, with an odds ratio of 1.695 (95 % confidence interval: 1.322, 2.173). Moreover, the WQS regression analyses revealed that MBP increased SBP (67.7 %) and DBP (80.8 %).

CONCLUSIONS

The present study suggests that prenatal exposure to PAEs was positively correlated with increased blood pressure in pre-school children, and MBP is of particular concern because it contributed the most to the combined effect of PAE mixture on the risk of childhood hypertension.

Oxidative stress as a potential mechanism linking gestational phthalates exposure to cognitive development in infancy

BACKGROUND

Gestational exposure to phthalates, endocrine disrupting chemicals widely used in consumer products, has been associated with poor recognition memory in infancy. Oxidative stress may represent one pathway linking this association. Hence, we examined whether exposure to phthalates was associated with elevated oxidative stress during pregnancy, and whether oxidative stress mediates the relationship between phthalate exposure and recognition memory.

METHODS

Our analysis included a subset of mother-child pairs enrolled in the Illinois Kids Development Study (IKIDS, N = 225, recruitment years 2013-2018). Concentrations of 12 phthalate metabolites were quantified in 2nd trimester urine samples. Four oxidative stress biomarkers (8-isoprostane-PGF2α, 2,3-dinor-5,6-dihydro-8-isoPGF2α, 2,3-dinor-8-isoPGF2α, and prostaglandin-F2α) were measured in 2nd and 3rd trimester urine. Recognition memory was evaluated at 7.5 months, with looking times to familiar and novel stimuli recorded via infrared eye-tracking. Novelty preference (proportion of time looking at a novel stimulus when paired with a familiar one) was considered a measure of recognition memory. Linear mixed effect models were used to estimate associations between monoethyl phthalate (MEP), sum of di(2-ethylhexyl) phthalate metabolites (ΣDEHP), sum of di(isononyl) phthalate metabolites (ΣDINP), and sum of anti-androgenic phthalate metabolites (ΣAA) and oxidative stress biomarkers. Mediation analysis was performed to assess whether oxidative stress biomarkers mediated the effect of gestational phthalate exposure on novelty preference.

RESULTS

The average maternal age at delivery was 31 years and approximately 50 % of participants had a graduate degree. A natural log unit increase in ΣAA, ΣDINP, and ΣDEHP was associated with a statistically significant increase in 8-isoPGF2α, 2,3-dinor-5,6-dihydro-8-isoPGF2α, and 2,3-dinor-8-isoPGF2α. The association was greatest in magnitude for ΣAA and 2,3-dinor-5,6-dihydro-8-isoPGF2α (β = 0.45, 95 % confidence interval = 0.14, 0.76). The relationship between ΣAA, ΣDINP, ΣDEHP, and novelty preference was partially mediated by 2,3-dinor-8-isoPGF2α.

CONCLUSIONS

Gestational exposure to some phthalates is positively associated with oxidative stress biomarkers, highlighting one mechanistic pathway through which these chemicals may impair early cognitive development.

Assessment of maternal phthalate exposure in urine across three trimesters and at delivery (umbilical cord blood and placenta) and its influence on birth anthropometric measures

Phthalates, commonly used in plastic manufacturing, have been linked to adverse reproductive effects. Our research from the Saudi Early Autism and Environment Study (2019-2022), involving 672 participants, focused on the impacts of maternal phthalate exposure on birth anthropometric measures. We measured urinary phthalate metabolites in 390 maternal samples collected during each of the three trimesters of pregnancy and in cord serum and placental samples obtained at delivery. We employed various statistical methods to analyze our data. Intraclass correlation coefficients were used to assess the consistency of phthalate measurements, generalized estimating equations were used to explore temporal variations across the trimesters, and linear regression models, adjusted for significant confounders and Bonferroni correction, were used for each birth outcome. Exposure to six phthalates was consistently high across trimesters, with 82 %-100 % of samples containing significant levels of all metabolites, except for mono-benzyl phthalate. We found a 3.15 %-3.73 % reduction in birth weight (BWT), 1.39 %-1.69 % reduction in head circumference (HC), and 3.63 %-5.45 % reduction in placental weight (PWT) associated with a one-unit increase in certain urinary di(2-ethylhexyl) phthalate (DEHP) metabolites during the first trimester. In the second trimester, exposure to MEP, ∑7PAE, and ∑LMW correlated with a 3.15 %-4.5 % increase in the APGAR 5-min score and increases in PWT by 8.98 % for ∑7PAE and 9.09 % for ∑LMW. Our study also highlighted the maternal-to-fetal transfer of DEHP metabolites, indicating diverse impacts on birth outcomes and potential effects on developmental processes. Our study further confirmed the transfer of DEHP metabolites from mothers to fetuses, evidenced by variable rates in the placenta and cord serum, with an inverse relationship suggesting a passive transfer mechanism. Additionally, we observed distinct phthalate profiles across these matrices, adversely impacting birth outcomes. In serum, we noticed increases associated with DEHP metabolites, with birth gestational age rising by 1.01 % to 1.11 %, HC by 2.84 % to 3.67 %, and APGAR 5-min scores by 3.77 % to 3.87 %. Conversely, placental analysis revealed a different impact: BWT decreased by 3.54 % to 4.69 %, HC reductions ranged from 2.57 % to 4.69 %, and chest circumference decreased by 7.13 %. However, the cephalization index increased by 3.67 %-5.87 %. These results highlight the complex effects of phthalates on fetal development, indicating their potential influence on crucial developmental processes like sexual maturation and brain development.

Mono(2-ethylhexyl) phthalate induces transcriptomic changes in placental cells based on concentration, fetal sex, and trophoblast cell type

Phthalates are ubiquitous plasticizer chemicals found in consumer products. Exposure to phthalates during pregnancy has been associated with adverse pregnancy and birth outcomes and differences in placental gene expression in human studies. The objective of this research was to evaluate global changes in placental gene expression via RNA sequencing in two placental cell models following exposure to the phthalate metabolite mono(2-ethylhexyl) phthalate (MEHP). HTR-8/SVneo and primary syncytiotrophoblast cells were exposed to three concentrations (1, 90, 180 µM) of MEHP for 24 h with DMSO (0.1%) as a vehicle control. mRNA and lncRNAs were quantified using paired-end RNA sequencing, followed by identification of differentially expressed genes (DEGs), significant KEGG pathways, and enriched transcription factors (TFs). MEHP caused gene expression changes across all concentrations for HTR-8/SVneo and primary syncytiotrophoblast cells. Sex-stratified analysis of primary cells identified different patterns of sensitivity in response to MEHP dose by sex, with male placentas being more responsive to MEHP exposure. Pathway analysis identified 11 KEGG pathways significantly associated with at least one concentration in both cell types. Four ligand-inducible nuclear hormone TFs (PPARG, PPARD, ESR1, AR) were enriched in at least three treatment groups. Overall, we demonstrated that MEHP differentially affects placental gene expression based on concentration, fetal sex, and trophoblast cell type. This study confirms prior studies, as enrichment of nuclear hormone receptor TFs were concordant with previously published mechanisms of phthalate disruption, and generates new hypotheses, as we identified many pathways and genes not previously linked to phthalate exposure.

Infectious and environmental placental insults: from underlying biological pathways to diagnostics and treatments

Because the placenta is bathed in maternal blood, it is exposed to infectious agents and chemicals that may be present in the mother's circulation. Such exposures, which do not necessarily equate with transmission to the fetus, may primarily cause placental injury, thereby impairing placental function. Recent research has improved our understanding of the mechanisms by which some infectious agents are transmitted to the fetus, as well as the mechanisms underlying their impact on fetal outcomes. However, less is known about the impact of placental infection on placental structure and function, or the mechanisms underlying infection-driven placental pathogenesis. Moreover, recent studies indicate that noninfectious environmental agents accumulate in the placenta, but their impacts on placental function and fetal outcomes are unknown. Critically, diagnosing placental insults during pregnancy is very difficult and currently, this is possible only through postpartum placental examination. Here, with emphasis on humans, we discuss what is known about the impact of infectious and chemical agents on placental physiology and function, particularly in the absence of maternal-fetal transmission, and highlight knowledge gaps with potential implications for diagnosis and intervention against placental pathologies.