Reproductive and developmental toxicity of phthalates

Association Between Urinary Phthalates and Pubertal Timing in Chinese Adolescents

BACKGROUND

Phthalates are synthetic chemicals and ubiquitous environmental contaminants, with hormonal activity that may alter the course of pubertal development in children.

OBJECTIVES

To determine whether exposure to phthalate metabolites is associated with timing of pubertal development in a cross-sectional study of a school-based clustered sample of 503 children from a suburban district in Shanghai, China, who were 7-14 years of age at enrollment (2010 October to November).

METHODS

We analyzed six phthalate metabolites in urine samples by isotope-dilution liquid chromatography tandem mass spectrometry. The associations of exposures to phthalates with pubertal timing of testes, breast, and pubic hair development (represented as Tanner stages) were evaluated using an ordered logistic regression model adjusted for chronological age, body fat proportion (BF%), and parental education.

RESULTS

In boys, urinary mono-n-butyl phthalate (MBP) levels were negatively associated with testicular volume, and mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono (2-ethyl-5-oxohexyl) phthalate (MEOHP) levels were negatively associated with pubic hair stages. The odds of being in an advanced stage were decreased by 43%-51%. In girls, mono (2-ethylhexyl) phthalate (MEHP), MEHHP, and MEOHP levels, as well as the sum of these levels, were positively associated with breast stages, and the association was much stronger in girls with high BF%; the odds of being in an advanced stage were increase by 29% to 50%.

CONCLUSIONS

Phthalate metabolites investigated in this study show significant associations with pubertal timing both in boys and in girls, especially among girls with high BF%.

Carryover Effects of Acute DEHP Exposure on Ovarian Function and Oocyte Developmental Competence in Lactating Cows

We examined acute exposure of Holstein cows to di(2-ethylhexyl) phthalate (DEHP) and its carryover effects on ovarian function and oocyte developmental competence. Synchronized cows were tube-fed with water or 100 mg/kg DEHP per day for 3 days. Blood, urine and milk samples were collected before, during and after DEHP exposure to examine its clearance pattern. Ovarian follicular dynamics was monitored through an entire estrous cycle by ultrasonographic scanning. Follicular fluids were aspirated from the preovulatory follicles on days 0 and 29 of the experiment and analyzed for phthalate metabolites and estradiol concentration. The aspirated follicular fluid was used as maturation medium for in-vitro embryo production. Findings revealed that DEHP impairs the pattern of follicular development, with a prominent effect on dominant follicles. The diameter and growth rate of the first- and second-wave dominant follicles were lower (P < 0.05) in the DEHP-treated group. Estradiol concentration in the follicular fluid was lower in the DEHP-treated group than in controls, and associated with a higher number of follicular pathologies (follicle diameter >25 mm). The pattern of growth and regression of the corpus luteum differed between groups, with a lower volume in the DEHP-treated group (P < 0.05). The follicular fluid aspirated from the DEHP-treated group, but not the controls, contained 23 nM mono(2-ethylhexyl) phthalate. Culturing of cumulus oocyte complexes in the follicular fluid aspirated from DEHP-treated cows reduced the proportion of oocytes progressing to the MII stage, and the proportions of 2- to 4-cell-stage embryos (P < 0.04) and 7-day blastocysts (P < 0.06). The results describe the risk associated with acute exposure to DEHP and its deleterious carryover effects on ovarian function, nuclear maturation and oocyte developmental competence.

Occurrence and risk assessment of selected phthalates in drinking water from waterworks in China

The first nationwide survey of six phthalates (diethyl phthalate (DEP); dimethyl phthalate (DMP); di-n-butyl phthalate (DBP); butyl benzyl phthalate (BBP); bis(2-ethylhexyl) phthalate (DEHP); din-octyl phthalate (DnOP)) in drinking waters from waterworks was conducted across seven geographical zones in China. Of the six target phthalates, DBP and DEHP were the highest abundant phthalates with median (± interquartile range) values of 0.18 ± 0.47 and 0.18 ± 0.97 μg/L, respectively, but did not exceed the limit values in China's Standards for Drinking Water Quality. These phthalates in drinking water were generally higher in the northern regions of China than those in the southern and eastern regions. Based on the investigated concentrations, lifetime exposure risk assessment indicated that phthalates in drinking water did not pose carcinogenic and noncarcinogenic risks to Chinese residents, even under the conservative scenario (with 95th percentile risk). In addition, we found that DEHP contributed the greatest risk to the total exposure risk of all the selected phthalates and oral ingestion was the main exposure route for phthalates in drinking water.

Fetal and Childhood Exposure to Phthalate Diesters and Cognitive Function in Children Up to 12 Years of Age: Taiwanese Maternal and Infant Cohort Study

Few studies have examined the association between environmental phthalate exposure and children’s neurocognitive development. This longitudinal study examined cognitive function in relation to pre-and postnatal phthalate exposure in children 2–12 years old. We recruited 430 pregnant women in their third trimester in Taichung, Taiwan from 2001–2002. A total of 110, 79, 76, and 73 children were followed up at ages 2, 5, 8, and 11, respectively. We evaluated the children’s cognitive function at four different time points using the Bayley and Wechsler tests for assessing neurocognitive functions and intelligence (IQ). Urine samples were collected from mothers during pregnancy and from children at each follow-up visit. They were analyzed for seven metabolite concentrations of widely used phthalate esters. These esters included monomethyl phthalate, monoethyl phthalate, mono-butyl phthalate, mono-benzyl phthalate, and three metabolites of di(2-ethylhexyl) phthalate, namely, mono-2-ethylhexyl phthalate, mono(2-ethyl-5-hydroxyhexyl) phthalate, and mono(2-ethyl-5-oxohexyl) phthalate. We constructed a linear mixed model to examine the relationships between the phthalate metabolite concentrations and the Bayley and IQ scores. We found significant inverse associations between the children’s levels of urinary mono(2-ethyl-5-oxohexyl) phthalate and the sum of the three metabolites of di(2-ethylhexyl) phthalate and their IQ scores (β = -1.818; 95% CI: -3.061, -0.574, p = 0.004 for mono(2-ethyl-5-oxohexyl) phthalate; β = -1.575; 95% CI: -3.037, -0.113, p = 0.035 for the sum of the three metabolites) after controlling for maternal phthalate levels and potential confounders. We did not observe significant associations between maternal phthalate exposure and the children’s IQ scores. Children’s but not prenatal phthalate exposure was associated with decreased cognitive development in the young children. Large-scale prospective cohort studies are needed to confirm these findings in the future.

The effect of ventilation on indoor exposure to semivolatile organic compounds

A mechanistic model was developed to examine how natural ventilation influences residential indoor exposure to semivolatile organic compounds (SVOCs) via inhalation, dermal sorption, and dust ingestion. The effect of ventilation on indoor particle mass concentration and mass transfer at source/sink surfaces, and the enhancing effect of particles on mass transfer at source/sink surfaces are included. When air exchange rate increases from 0.6/h to 1.8/h, the steady-state SVOC (gas-phase plus particle phase with log KOA varying from 9 to 13) concentration in the idealized model decreases by about 60%. In contrast, for the same change in ventilation, the simulated indoor formaldehyde (representing volatile organic compounds) gas-phase concentration decreases by about 70%. The effect of ventilation on exposure via each pathway has a relatively insignificant association with the KOA of the SVOCs: a change of KOA from 10(9) to 10(13) results in a change of only 2-30%. Sensitivity analysis identifies the deposition rate of PM2.5 as a primary factor influencing the relationship between ventilation and exposure for SVOCs with log KOA = 13. The relationship between ventilation rate and air speed near surfaces needs to be further substantiated.

The plasticizer benzyl butyl phthalate (BBP) alters the ecdysone hormone pathway, the cellular response to stress, the energy metabolism, and several detoxication mechanisms in Chironomus riparius larvae

Butyl benzyl phthalate (BBP) has been extensively used worldwide as a plasticizer in the polyvinyl chloride (PVC) industry and the manufacturing of many other products, and its presence in the aquatic environment is expected for decades. In the present study, the toxicity of BBP was investigated in Chironomus riparius aquatic larvae. The effects of acute 24-h and 48-h exposures to a wide range of BBP doses were evaluated at the molecular level by analysing changes in genes related to the stress response, the endocrine system, the energy metabolism, and detoxication pathways, as well as in the enzyme activity of glutathione S-transferase. BBP caused a dose and time-dependent toxicity in most of the selected biomarkers. 24-h exposures to high doses affected larval survival and lead to a significant response of several heat-shock genes (hsp70, hsp40, and hsp27), and to a clear endocrine disrupting effect by upregulating the ecdysone receptor gene (EcR). Longer treatments with low doses triggered a general repression of transcription and GST activity. Furthermore, delayed toxicity studies were specially relevant, since they allowed us to detect unpredictable toxic effects, not immediately manifested after contact with the phthalate. This study provides novel and interesting results on the toxic effects of BBP in C. riparius and highlights the suitability of this organism for ecotoxicological risk assessment, especially in aquatic ecosystems.

Parental occupational exposures to endocrine disruptors and the risk of simple isolated congenital heart defects

This study aims to explore the associations between parental occupational exposures to endocrine disruptors (EDs) and simple isolated congenital heart defects (CHDs). A case-control study with standardized data collection involving 761 children with isolated CHDs and 609 children without any congenital malformations was conducted in Sichuan Province of China from March in 2012 to August in 2013. An adjusted job exposure matrix was used for occupational EDs exposure assessment. Logistic regression analysis was performed to assess the associations between parental occupational EDs exposures and CHDs. Maternal age at births, maternal education level, gravity, parity, induced abortion, folic acid use, medication use, drinking capacity and area of residence periconceptionally were selected as confounding factors for mothers. For fathers, we selected the following confounding factors: paternal education level, smoking, drinking frequencies and drinking capacity periconceptionally. Maternal occupational exposures to phthalates are associated with perimembranous ventricular septal defect (PmVSD) (P = 0.001, adjusted OR 3.7, 95 % CI 1.7-8.0), patent ductus arteriosus (PDA) (P = 0.002, adjusted OR 3.8, 95 % CI 1.6-8.9), secundum atrial septal defect (s-ASD) (P = 0.008, adjusted OR 3.5, 95 % CI 1.4-8.7) and pulmonary valve stenosis (PS) (P = 0.035, adjusted OR 4.2, 95 % CI 1.1-16.0), to alkylphenolic compounds and PmVSD (P = 0.003, adjusted OR 2.2, 95 % CI 1.3-3.6), PDA (P = 0.005, adjusted OR 2.0, 95 % CI 1.1-3.5) and PS (P = 0.004, adjusted OR 3.8, 95 % CI 1.5-9.4), to heavy metals with PmVSD (P = 0.003, adjusted OR 7.3, 95 % CI 2.0-27.6) and s-ASD (P = 0.034, adjusted OR 6.5, 95 % CI 1.1-36.7). Paternal occupational exposures to phthalates are associated with PmVSD (P = 0.035, adjusted OR 1.6, 95 % CI 1.0-2.4) and PS (P = 0.026, adjusted OR 2.4, 95 % CI 1.1-5.2), to alkylphenolic compounds (P = 0.027, adjusted OR 1.5, 95 % CI 1.0-2.2) with PmVSD. In conclusion, parental occupational exposures to some specific EDs, in particular phthalates and alkylphenolic compounds, are associated with an increased risk of some CHD phenotypes. However, the findings need to be considered more circumspectly regarding a crude measure of exposure probabilities and small numbers.

Di-(2-ethylhexyl)-phthalate induces oxidative stress in human endometrial stromal cells in vitro

Di-(2-ethylhexyl)-phthalate (DEHP) accumulates in the environment, and its exposure is possibly associated with endocrine-related disease in women of reproductive age. The effects of DEHP on human endometrial cells are unknown. We treated human endometrial stromal cells with 10, 100, and 1000 pmol of DEHP and measured reactive oxygen species (ROS) generation, expression levels of antioxidant enzymes, alteration of MAPK/NF-κB signaling and hormonal receptors. DEHP increased reactive oxygen species (ROS) generation and decreased expression of superoxide dismutase (SOD), glutathione peroxidase (GPX), heme oxygenase (HO), and catalase (CAT). By DEHP exposure, p-ERK/p-p38 and NF-κB mediated transcription was increased. Additionally, DEHP induced estrogen receptor-α (ER-α) expression in a dose-dependent manner. This study shows the need for future mechanistic studies of oxidative stress, MAPK/NF-κB signaling, and ER-α as molecular mediators of DEHP-associated endometrial stromal cell alterations, which may be associated with the development of endocrine-related disease such as endometriosis.

Phthalates and neurotoxic effects on hippocampal network plasticity

Phthalates are synthetically derived chemicals used as plasticizers in a variety of common household products. They are not chemically bound to plastic polymers and over time, easily migrate out of these products and into the environment. Experimental investigations evaluating the biological impact of phthalate exposure on developing organisms are critical given that estimates of phthalate exposure are considerably higher in infants and children compared to adults. Extensive growth and re-organization of neurocircuitry occurs during development leaving the brain highly susceptible to environmental insults. This review summarizes the effects of phthalate exposure on brain structure and function with particular emphasis on developmental aspects of hippocampal structural and functional plasticity. In general, it appears that widespread disruptions in hippocampal functional and structural plasticity occur following developmental (pre-, peri- and post-natal) exposure to phthalates. Whether these changes occur as a direct neurotoxic effect of phthalates or an indirect effect through disruption of endogenous endocrine functions is not fully understood. Comprehensive investigations that simultaneously assess the neurodevelopmental, neurotoxic, neuroendocrine and behavioral correlates of phthalate exposure are needed to provide an opportunity to thoroughly evaluate the neurotoxic potential of phthalates throughout the lifespan.

Physical and chemical indices of cucumber seedling leaves under dibutyl phthalate stress

Phthalic acid ester (PAE) pollution to soil can lead to phytotoxicity in plants and potential health risks to human being. Dibutyl phthalate (DBP) as a kind of PAE has a large usage amount and large residues in soil. To analyze antioxidant responses of plants to DBP stress, effects of varying DBP concentrations on cucumber seedlings growth had been investigated. Malonaldehyde (MDA), hydrogen peroxide (H2O2), chlorophyll, proline, glutathione (GSH), and oxidized glutathione (GSSH) contents and activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD) were studied. The results showed that H2O2 content increased in cucumber seedlings with the increase of DBP concentration. The chlorophyll content in the higher DBP significantly declined compared to the control. In the present study, a disturbance of the GSH redox balance was evidenced by a marked decrease in GSH/GSSG ratio in cucumber seedlings subjected DBP stress. Our results indicated that DBP treatment not only inhibited antioxidant capacity and antioxidant enzyme activity in seedlings' leaves but might also induce chlorophyll degradation or reduce the synthesis of chlorophyll. Moreover, it could also enhance the accumulation of reactive oxygen species (ROS) which induced membrane lipid peroxidation. DBP also altered the ultrastructure of mesophyll cells, damaged membrane structure of chloroplast and mitochondrion, and increased the number and size of starch grains in chloroplasts reducing the photosynthetic capacity.

The effects of di(2-ethylhexyl) phthalate and/or selenium on trace element levels in different organs of rats

Di(2-ethylhexyl)phthalate (DEHP), a widely used plasticizer for synthetic polymers, is known to have endocrine disruptive potential, reproductive toxicity, and induces hepatic carcinogenesis in rodents. Selenium (Se) is a component of several selenoenzymes which are essential for cellular antioxidant defense and for the functions of mammalian reproductive system. The present study was designed to investigate the effects of DEHP exposure on trace element distribution in liver, testis, and kidney tissues and plasma of Se-deficient and Se-supplemented rats. Se deficiency was produced by feeding 3-week old Sprague-Dawley rats with ≤0.05mg Se/kg diet for 5 weeks, and supplementation group were on 1mg Se/kg diet. DEHP treated groups received 1000mg/kg dose by gavage during the last 10 days of feeding period. Se, zinc (Zn), copper (Cu), iron (Fe) and manganese (Mn) levels were measured by inductively coupled plasma mass spectrometry (ICP-MS). Se supplementation caused significant increases in hepatic, renal, and testicular Se levels. With DEHP exposure, plasma Se and Zn, kidney Se, Cu and Mn levels were significantly decreased. Besides, liver Fe decreased markedly in all the DEHP-treated groups. Liver and kidney Mn levels decreased significantly in DEHP/SeD group compared to both DEHP and SeD groups. These results showed the potential of DEHP exposure and/or different Se status to modify the distribution pattern of essential trace elements in various tissues, the importance of which needs to be further evaluated.

Occurrence, Species, and Organ Differences in Bioaccumulation Patterns of Phthalate Esters in Municipal Domestic Water Supply Lakes in Ibadan, Nigeria

The occurrence of phthalate esters (PE) was examined in biota, ambient water, and sediments of two man-made lakes (Asejire and Eleyele) in southwestern Nigeria. Five fish species (Tilapia zillii, Hepsetus odoe, Parachanna obscura, Chrysichthys nigrodigitatus, and Mormyrus rume) were analyzed for PE levels and used for calculating bioconcentration factors (BCF) and biota-sediment accumulation factors (BSAF). In addition, measured PE levels were thereafter used to calculate the phthalate pollution index (PPI) in biota and the environment. At both lakes, all sampled species had k-factor > 1, showing apparently normal growth and health condition. Higher PE levels were found in sediments compared with water at both lakes, with a pattern showing that di(2-ethylhexyl) phthalate (DEHP) was predominant PE. While there were no unique patterns of PE concentrations in both lakes, differences were observed in organ concentration patterns that were evident at both lakes. For T. zillii, the BSAF was higher for dibutyl phthalate (DBP) compared to diethyl phthalate (DEP) and lowest for DEHP. The concentration pattern demonstrated that DBP concentrated more in gills (BCF: 6.7), while DEHP concentrated more in liver (BCF: 15.2) of T. zillii at Asejire. At Eleyele, T. zillii liver and gills concentrated less DEP and DEHP. The PPI value was significantly higher in sediment with respective values of 0.27 and 0.44 at Asejire and Eleyele lakes compared with water with respective values of 0.1 and 0.18 at Asejire and Eleyele lakes. Overall, our findings suggest a broader environmental and human health implication of high PE levels in these lakes, since they provide vast water volumes that are used for municipal domestic water supply. Further, these lakes support intense artisanal fisheries, representing significant sources of aquatic food resources for neighboring communities.

Phthalate esters affect maturation and function of primate testis tissue ectopically grafted in mice

Di-n-Butyl (DBP) and Di-(2-EthylHexyl) (DEHP) phthalates can leach from daily-use products resulting in environmental exposure. In male rodents, phthalate exposure results in reproductive effects. To evaluate effects on the immature primate testis, testis fragments from 6-month-old rhesus macaques were grafted subcutaneously to immune-deficient mice, which were exposed to 0, 10, or 500 mg/kg of DBP or DEHP for 14 weeks or 28 weeks (DBP only). DBP exposure reduced the expression of key steroidogenic genes, indicating that Leydig cell function was compromised. Exposure to 500 mg/kg impaired tubule formation and germ cell differentiation and reduced numbers of spermatogonia. Exposure to 10 mg/kg did not affect development, but reduced Sertoli cell number and resulted in increased expression of inhibin B. Exposure to DEHP for 14 week also affected steroidogenic genes expression. Therefore, long-term exposure to phthalate esters affected development and function of the primate testis in a time and dosage dependent manner.

Changes in epidemiologic associations with different exposure metrics: a case study of phthalate exposure associations with body mass index and waist circumference

The use of human biomonitoring data to characterize exposure to environmental contaminants in epidemiology studies has expanded greatly in recent years. Substantial variability in effect measures may arise when using different exposure metrics for a given contaminant, and it is often not clear which metric is the best surrogate for the 'causal' or 'true' exposure. Here we evaluated variability and potential bias in epidemiologic associations resulting from the use of different phthalate exposure metrics in the 2009-2010 National Health and Nutrition Examination Survey (NHANES). We examined associations between urinary phthalate metabolites and the outcomes of body mass index (BMI) and waist circumference (WC). We examined each of the following NHANES-derived exposure metrics for metabolites of individual phthalates: molar excretion rate (nmol/min), molar amount (nmol), molar concentration (nmol/mL, with and without additional model adjustment for creatinine), creatinine corrected molar concentration (nmol/g creatinine), and reconstructed daily phthalate intake (nmol/kg/day). In order to investigate potential biasing effect of each metric, we first assumed that daily intake of the parent phthalate is the causal exposure. We then constructed a simulated population based on the 2009-2010 NHANES, and randomly assigned each individual a di-2-ethylhexyl phthalate (DEHP) intake dose based on a published distribution, but independent of any other factor. Accordingly, all associations between these randomly assigned intake doses and individuals' BMI and WC should be null. Next, demographic data in the NHANES were incorporated into a pharmacokinetic model to predict urinary molar excretions of five DEHP metabolites based on the randomly assigned DEHP intake. The predicted molar excretions were then used to calculate the same exposure metrics listed above. Three exposure metrics (randomly generated intake, excretion rate, urine concentration) showed no significant associations with BMI, which supports the null hypothesis stated above. In contrast, metrics adjusted for creatinine showed a significant negative correlation, and reconstructed daily intake showed a significant positive correlation, indicating the introduction of bias away from the true (i.e., null) association. Interestingly, trends in the simulation analysis were similar to those seen in the observed NHANES data. Our findings show that, at least in this example case, the choice of exposure metric can introduce significant bias of varying magnitude and direction into the calculation of epidemiologic associations.

Concentrations of phthalates and bisphenol A in Norwegian foods and beverages and estimated dietary exposure in adults

Phthalates and bisphenol A (BPA) are ubiquitous in our environment. These chemicals have been characterized as endocrine disruptors that can cause functional impairment of development and reproduction. Processed and packaged foods are among the major sources of human exposure to these chemicals. No previous report showing the levels of these chemicals in food items purchased in Norway is available. The aim of the present study was to determine the concentration of ten different phthalates and BPA in foods and beverages purchased on the Norwegian market and estimate the daily dietary exposure in the Norwegian adult population. Commonly consumed foods and beverages in Norway were purchased in a grocery store and analysed using gas- and liquid chromatography coupled with mass spectrometry. Daily dietary exposures to these chemicals in the Norwegian adult population were estimated using the latest National dietary survey, Norkost 3 (2010-2011). This study showed that phthalates and BPA are found in all foods and beverages that are common to consume in Norway. The detection frequency of phthalates in the food items varied from 11% for dicyclohexyl phthalate (DCHP) to 84% for di-iso-nonyl phthalate (DiNP), one of the substitutes for bis(2-ethylhexyl) phthalate (DEHP). BPA was found in 54% of the food items analysed. Among the different phthalates, the highest concentrations were found for DEHP and DiNP in the food items. Estimated dietary exposures were also equally high and dominated by DEHP and DiNP (400-500 ng/kg body weight (bw)/day), followed by di-iso-butyl phthalate (DiBP), di-n-butyl phthalate (DnBP), di-n-octyl phthalate (DnOP) and di-iso-decyl phthalate (DiDP) (30-40 ng/kg bw/day). Dimethyl phthalate (DMP), diethylphthalate (DEP) and DCHP had the lowest concentrations and the exposures were around 10-20 ng/kg bw/day. Estimated dietary exposure to BPA was 5 ng/kg bw/day. In general, levels of phthalates and BPA in foods and beverages from the Norwegian market are comparable to other countries worldwide. Grain and meat products were the major contributors of exposure to these chemicals in the Norwegian adult population. The estimated dietary exposures to these chemicals were considerably lower than their respective tolerable daily intake (TDI) values established by the European Food Safety Authority (EFSA).

Review article: the management of Crohn's disease and ulcerative colitis during pregnancy and lactation

BACKGROUND

Inflammatory bowel diseases (IBD) commonly affect young patients in the reproductive phase of their lives. The chronic and relapsing nature of IBD and the potential need for medical or surgical interventions raise concerns about family planning issues.

AIM

To review the current knowledge on IBD management in pregnant and nursing IBD patients.

METHODS

A PubMed literature search was performed using the search terms 'reproduction' and 'inflammatory bowel disease' and using the headers and main subjects of each section of this article as search terms.

RESULTS

Male and female fertility are not impaired in the majority of IBD patients. In IBD patients with quiescent disease pregnancy outcomes are not impaired in comparison to the general population, however, an increased incidence of pregnancy complications is observed in active IBD patients. As methotrexate (MTX) has been demonstrated to be teratogenic, the use of MTX is contraindicated in patients, who wish to conceive, throughout pregnancy and when nursing. However, normal pregnancies following MTX treatment at conception and later have been reported. Most of the other currently approved IBD medications are not associated with adverse pregnancy outcomes and may be used to maintain quiescent disease or to induce a rapid remission in patients with flares and active disease. Breast-feeding in IBD patients is possible and recommended.

CONCLUSIONS

The overall outcome of pregnancies in IBD patients is favourable and not different to healthy controls, thus patients with IBD should not be discouraged from having children.

Urinary phthalate metabolites are associated with decreased serum testosterone in men, women, and children from NHANES 2011-2012

CONTEXT

There is evidence of declining trends in T levels among men in recent decades, as well as trends in related conditions at multiple life stages and in both sexes. There is also animal and limited human evidence that exposure to phthalates, chemicals found in plastics and personal care products, is associated with reduced androgen levels and associated disorders.

OBJECTIVE

To explore relationships between urinary concentrations of 13 phthalate metabolites and serum total T levels among men, women, and children when adjusting for important confounders and stratifying by sex and age (6-12, 12-20, 20-40, 40-60, and 60-80 y).

DESIGN

A cross-sectional study.

SETTING

US National Health and Nutrition Examination Survey, 2011-2012.

PATIENTS OR OTHER PARTICIPANTS

US general population.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Serum total T measured by isotope dilution-liquid chromatography-tandem mass spectrometry.

RESULTS

Multiple phthalates were associated with significantly reduced T in both sexes and in differing age groups. In females, the strongest and most consistent inverse relationships were found among women ages 40-60 years. In boys 6-12 years old, an interquartile range increase in metabolites of di-2-ethylhexyl phthalate was associated with a 29% (95% confidence interval, 6, 47) reduction in T. In adult men, the only significant or suggestive inverse associations between phthalates (metabolites of di-2-ethylhexyl phthalate and dibutyl phthalate) and T were observed among men ages 40-60 years.

CONCLUSIONS

Because T plays an important role in all life stages for both sexes, future efforts should focus on better defining these relationships and their broader impacts.

Evaluation of an alternative in vitro test battery for detecting reproductive toxicants in a grouping context

Previously we showed a battery consisting of CALUX transcriptional activation assays, the ReProGlo assay, and the embryonic stem cell test, and zebrafish embryotoxicity assay as 'apical' tests to correctly predict developmental toxicity for 11 out of 12 compounds, and to explain the one false negative [7]. Here we report on applying this battery within the context of grouping and read across, put forward as a potential tool to fill data gaps and avoid animal testing, to distinguish in vivo non- or weak developmental toxicants from potent developmental toxicants within groups of structural analogs. The battery correctly distinguished 2-methylhexanoic acid, monomethyl phthalate, and monobutyltin trichloride as non- or weak developmental toxicants from structurally related developmental toxicants valproic acid, mono-ethylhexyl phthalate, and tributyltin chloride, respectively, and, therefore, holds promise as a biological verification model in grouping and read across approaches. The relevance of toxicokinetic information is indicated.

Reduced hippocampal dendritic spine density and BDNF expression following acute postnatal exposure to di(2-ethylhexyl) phthalate in male Long Evans rats

Early developmental exposure to di(2-ethylhexyl) phthalate (DEHP) has been linked to a variety of neurodevelopmental changes, particularly in rodents. The primary goal of this work was to establish whether acute postnatal exposure to a low dose of DEHP would alter hippocampal dendritic morphology and BDNF and caspase-3 mRNA expression in male and female Long Evans rats. Treatment with DEHP in male rats led to a reduction in spine density on basal and apical dendrites of neurons in the CA3 dorsal hippocampal region compared to vehicle-treated male controls. Dorsal hippocampal BDNF mRNA expression was also down-regulated in male rats exposed to DEHP. No differences in hippocampal spine density or BDNF mRNA expression were observed in female rats treated with DEHP compared to controls. DEHP treatment did not affect hippocampal caspase-3 mRNA expression in male or female rats. These results suggest a gender-specific vulnerability to early developmental DEHP exposure in male rats whereby postnatal DEHP exposure may interfere with normal synaptogenesis and connectivity in the hippocampus. Decreased expression of BDNF mRNA may represent a molecular mechanism underlying the reduction in dendritic spine density observed in hippocampal CA3 neurons. These findings provide initial evidence for a link between developmental exposure to DEHP, reduced levels of BDNF and hippocampal atrophy in male rats.

Transcriptomic characterization of C57BL/6 mouse embryonic stem cell differentiation and its modulation by developmental toxicants

The Tox21 program calls for transforming toxicology testing from traditional in vivo tests to less expensive and higher throughput in vitro methods. In developmental toxicology, a spectrum of alternative methods including cell line based tests has been developed. In particular, embryonic stem cells (ESCs) have received widespread attention as a promising alternative model for developmental toxicity assessment. Here, we characterized gene expression changes during mouse ESC differentiation and their modulation by developmental toxicants. C57BL/6 ESCs were allowed to differentiate spontaneously and RNA of vehicle controls was collected at 0, 24, 48, 72, 96, 120 and 168 h after embryoid body (EB) formation; RNA of compound-exposed EBs were collected at 24 h. Samples were hybridized to Affymetrix Mouse Gene 2.0 ST Array; using stringent cut-off criteria of Bonferroni-adjusted p<0.05 and fold change >2.0, a total of 1996 genes were found differentially expressed among the vehicle controls at different time points. Gene ontology (GO) analysis showed these regulated genes were mostly involved in differentiation-related processes such as development, morphogenesis, metabolism, cell differentiation, cell organization and biogenesis, embryonic development, and reproduction. Biomarkers of all three germ layers or of their derivative early cell types were identified in the gene list. Principal component analysis (PCA) based on these genes showed that the unexposed vehicle controls appeared in chronological order in the PCA plot, and formed a differentiation track when connected. Cultures exposed to thalidomide, monobutyl phthalate, or valproic acid deviated significantly from the differentiation track, manifesting the capacity of the differentiation track to identify the modulating effects of diverse developmental toxicants. The differentiation track defined in this study may be further exploited as a baseline for developmental toxicity testing, with compounds causing significant deviation from the differentiation track being predicted as potential developmental toxicants.

Phthalate exposure and child development: the Polish Mother and Child Cohort Study

BACKGROUND

Widespread phthalate exposure has prompted investigations concerning their potential adverse health effects.

AIM

The objective of this study was to evaluate the impact of pre and early postnatal phthalate exposure on child psychomotor development based on the data from the prospective Polish Mother and Child Cohort Study (REPRO PL).

STUDY DESIGN, SUBJECTS AND OUTCOME MEASURES

Phthalate exposure was determined by measuring 11 phthalate metabolites (MEP, MiBP, MnBP, 3OH-MnBP, MBzP, MEHP, 5OH-MEHP, 5oxo-MEHP, OH-MiNP, oxo-MiNP, and MnOP) in the urine collected from mothers during the third trimester of pregnancy (prenatal exposure) and from their children at the 24th month of age (postnatal exposure). The analysis was performed by the HPLC-MS/MS method. Psychomotor development was assessed in children at the age of 2years by the Bayley Scales of Infant and Toddler Development.

RESULTS

Child motor development was inversely associated with natural log concentrations (μg/g creatinine) of 3OH-MnBP (β= -2.3; 95% CI -4.0 to -0.6), 5OH-MEHP (β= -1.2; 95% CI -2.2 to -0.3), 5oxo-MEHP (β= -1.8; 95% CI -3.3 to -0.2) and sum of DEHP metabolites (β= -2.2; 95% CI -3.6 to -0.8), DnBP metabolites (β= -1.9; 95% CI -3.4 to -0.4), and high molecular weight phthalates (β= -2.5; 95% CI -4.1 to -0.9) in the urine collected from mothers during pregnancy after adjustment for a variety of potential confounders. Additional adjustment for postnatal phthalate exposure did not change the results. Postnatal child exposure to phthalates was not associated with any of the measured scores of child psychomotor development.

CONCLUSIONS

The study findings add further support to the possibility that prenatal phthalate exposure may be detrimental to child neurodevelopment and underscore the importance of policies and public health interventions aiming at reduction of such exposure.

Exposure to endocrine disrupting chemicals and male reproductive health

Endocrine disrupting chemicals (EDCs) can interfere with normal hormonal balance and may exert adverse consequences on humans. The male reproductive system may be susceptible to the effects of such environmental toxicants. This review discusses the recent progress in scientific data mainly from epidemiology studies on the associations between EDCs and male reproductive health and our understanding of possible mechanisms associated with the effects of EDCs on male reproductive health. Finally, the review provides recommendations on future research to enhance our understanding of EDCs and male reproductive health. The review highlights the need for (1) well-defined longitudinal epidemiology studies, with appropriately designed exposure assessment to determine potential causal relationships; (2) chemical and biochemical approaches aimed at a better understanding of the mechanism of action of xenoestrogens with regard to low-dose effects, and assessment of identify genetic susceptibility factors associated with the risk of adverse effects following exposure to EDCs.

Co-treatment of mouse antral follicles with 17β-estradiol interferes with mono-2-ethylhexyl phthalate (MEHP)-induced atresia and altered apoptosis gene expression

Mono-2-ethyhexyl phthalate (MEHP) is a metabolite of a plasticizer found in many consumer products. MEHP inhibits mouse ovarian follicle growth by reducing 17β-estradiol (E2) production. Yet, whether MEHP causes follicle death (atresia) is unclear. We hypothesized that MEHP causes atresia by altering apoptosis gene expression, and that E2 co-treatment blocks these effects. Follicles were exposed to MEHP (0.36-36μM)±E2 for 48-96h to determine the effect of MEHP±E2 on atresia and gene expression. MEHP increased atresia, but this effect was blocked by co-treatment with E2. MEHP increased the expression of the pro-apoptotic gene Aifm1, but decreased that of the pro-apoptotic gene Bok and the anti-apoptotic gene Bcl2l10. E2 interfered with MEHP-induced changes in Aifm1 and Bcl2l10. Our findings suggest that decreased E2 levels are required for MEHP-induced follicle atresia and that Aifm1, Bok, and Bcl2l10 are involved in this process.

Intake estimates of phthalate esters for South Delhi population based on exposure media assessment

An indirect estimation method was followed to derive exposure levels of fifteen phthalate congeners in urban population of Delhi, India. The exposure media samples were collected from Jawaharlal Nehru University (JNU) campus and Okhla industrial area. GC-MS analysis of the samples indicated di(2-ethylhexyl) phthalate (DEHP) to be the most abundant congener and its estimated total daily intake level reached upto 70 μg kg(-1) d(-1). Out of the studied congeners, intake doses for di-n-butyl phthalate (DnBP) and DEHP, reached levels near or above the established exposure limit. In JNU, DEHP, dimethyl phthalate (DMP) and butyl benzyl phthalate (BBP) had 69% share in combined daily intake of Σ15 phthalates (CDI15); whereas, in Okhla, DEHP, diethyl phthalate (DEP), diisobutyl phthalate (DIBP), DnBP and DMP shared 64% of the CDI15. Food was found to be the major source of exposure contributing 67% and 74% of the estimated CDI15 at JNU and Okhla respectively.

Di-ethylhexylphthalate (DEHP) modulates cell invasion, migration and anchorage independent growth through targeting S100P in LN-229 glioblastoma cells

Glioblastoma multiforme (GBM) is the most aggressive brain cancer with a median survival of 1-2 years. The treatment of GBM includes surgical resection, radiation and chemotherapy, which minimally extends survival. This poor prognosis necessitates the identification of novel molecular targets associated with glioblastoma. S100P is associated with drug resistance, metastasis, and poor clinical outcomes in many malignancies. The functional role of S100P in glioblastoma has not been fully investigated. In this study, we examined the role of S100P mediating the effects of the environmental contaminant, DEHP, in glioblastoma cells (LN-229) by assessing cell proliferation, apoptosis, anchorage independent growth, cell migration and invasion following DEHP exposure. Silencing S100P and DEHP treatment inhibited LN-229 glioblastoma cell proliferation and induced apoptosis. Anchorage independent growth study revealed significantly decreased colony formation in shS100P cells. We also observed reduced cell migration in cells treated with DEHP following S100P knockdown. Similar results were observed in spheroid formation and expansion. This study is the first to demonstrate the effects of DEHP on glioblastoma cells, and implicates S100P as a potential therapeutic target that may be useful as a drug response biomarker.

Daily exposure to Di(2-ethylhexyl) phthalate alters estrous cyclicity and accelerates primordial follicle recruitment potentially via dysregulation of the phosphatidylinositol 3-kinase signaling pathway in adult mice

Humans are exposed daily to di(2-ethylhexyl) phthalate (DEHP), a plasticizer found in many consumer, medical, and building products containing polyvinyl chloride. Large doses of DEHP disrupt normal ovarian function; however, the effects of DEHP at environmentally relevant levels, the effects of DEHP on folliculogenesis, and the mechanisms by which DEHP disrupts ovarian function are unclear. The present study tested the hypothesis that relatively low levels of DEHP disrupt estrous cyclicity as well as accelerate primordial follicle recruitment by dysregulating phosphatidylinositol 3-kinase (PI3K) signaling. Adult CD-1 mice were orally dosed with DEHP (20 μg/kg/day-750 mg/kg/day) daily for 10 and 30 days. Following dosing, the effects on estrous cyclicity were examined, and follicle numbers were histologically quantified. Further, the ovarian mRNA and protein levels of PI3K signaling factors that are associated with early folliculogenesis were quantified. The data indicate that 10- and 30-day exposure to DEHP prolonged the duration of estrus and accelerated primordial follicle recruitment. Specifically, DEHP exposure decreased the percentage of primordial follicles and increased the percentage of primary follicles counted following 10-day exposure and increased the percentage of primary follicles counted following 30-day exposure. DEHP exposure, at doses that accelerate folliculogenesis, increased the levels of 3-phosphoinositide-dependent protein kinase-1, mammalian target of rapamycin complex 1, and protein kinase B and decreased the levels of phosphatase and tensin homolog, potentially driving PI3K signaling. Collectively, relatively low levels of DEHP disrupt estrous cyclicity and accelerate primordial follicle recruitment potentially via a mechanism involving dysregulation of PI3K signaling.

Associations between serum phthalates and biomarkers of reproductive function in 589 adult men

Phthalates which are widely used, are ubiquitous in the environment and in some human tissues. It is generally accepted that phthalates exert their toxic action by inhibiting Leydig cell synthesis of testosterone, but in vitro studies have also shown anti-androgenic effects at the receptor level. Some cross-sectional studies have shown inverse associations between urinary levels of phthalates and reproductive hormones, but results are conflicting and the evidence base is limited. The aim of this study was to investigate if levels of di-2-ethylhexyl phthalate (DEHP) and diisononyl phthalate (DiNP) metabolites in serum are associated with serum concentrations of male reproductive hormones and semen quality. A secondary aim was to investigate metabolic pathways of DEHP and DiNP on semen quality and reproductive hormones. A cross-sectional sample of 589 spouses of pregnant women from Greenland, Poland and Ukraine were enrolled between 2002 and 2004. The men gave semen and blood samples and were interviewed. Six phthalate metabolites of DEHP and DiNP were measured by liquid chromatography tandem mass spectrometry in serum. The metabolites were summed according to their molar weight. We observed significant inverse associations between serum levels of the metabolites, the proxies and serum testosterone. Negative associations were also discovered between some metabolites and sex hormone-binding globulin, semen volume and total sperm count. Findings are compatible with a weak anti-androgenic action of DEHP metabolites, but less so for DiNP metabolites. Metabolic pathways differed significantly between the three study sites, but without major effect on semen quality or reproductive hormones.

Di-(2-ethylhexyl) phthalate and bisphenol A exposure impairs mouse primordial follicle assembly in vitro

Bisphenol-A (BPA) and diethylhexyl phthalate (DEHP) are estrogenic compounds widely used in commercial plastic products. Previous studies have shown that exposure to such compounds have adverse effects on various aspects of mammalian reproduction including folliculogenesis. The objective of this study was to examine the effects of BPA and DEHP exposure on primordial follicle formation. We found that germ cell nest breakdown and primordial follicle assembly were significantly reduced when newborn mouse ovaries were exposed to 10 or 100 μM BPA and DEHP in vitro. Moreover, BPA and DEHP exposure increased the number of TUNEL positive oocytes and the mRNA level of the pro-apoptotic gene Bax in oocytes. These effects were associated with decreased expression of oocyte specific genes such as LIM homeobox 8 (Lhx8), factor in the germline alpha (Figla), spermatogenesis and oogenesis helix-loop-helix (Sohlh2), and newborn ovary homeobox (Nobox). Interestingly, BPA and DEHP exposure also prevented DNA demethylation of CpG sites of the Lhx8 gene in oocytes, a process normally associated with folliculogenesis. Finally, folliculogenesis was severely impaired in BPA and DEHP exposed ovaries after transplantation into the kidney capsules of immunodeficient mice. In conclusion, BPA and DEHP exposures impair mouse primordial follicle assembly in vitro.

Prenatal di-n-butyl phthalate exposure alters reproductive functions at adulthood in male rats

This study was aimed to investigate the reproductive health in adult male rats exposed to di-n-butyl phthalate (DBP) during embryonic development. Pregnant rats were injected with DBP and F1 male rats were weaned and on postnatal day 100, used for mating with normal cycling females to assess reproductive performance. After completion of cohabitation period, rats were analyzed for other reproductive end points. Transplacental exposure to DBP significantly decreased fertility in adult male rats. Prenatal exposure to DBP significantly decreased sperm density, number of motile sperms, viable sperms, and hypoosmotic swelling tail coiled sperms with an increase in morphological abnormalities in sperms. Testicular steroidogenic enzyme activity levels and serum testosterone levels were significantly decreased in rats exposed to DBP during embryonic development. In conclusion, transplacental exposure to DBP impairs male reproductive performance by decreasing steroidogenesis and spermatogenesis.

Tailoring alphabetical metamaterials in optical frequency: plasmonic coupling, dispersion, and sensing

Tailoring optical properties of artificial metamaterials, whose optical properties go beyond the limitations of conventional and naturally occurring materials, is of importance in fundamental research and has led to many important applications such as security imaging, invisible cloak, negative refraction, ultrasensitive sensing, and transformable and switchable optics. Herein, by precisely controlling the size, symmetry, and topology of alphabetical metamaterials with U, S, Y, H, U-bar, and V shapes, we have obtained highly tunable optical response covering visible-to-infrared (vis-NIR) optical frequency. In addition, we show a detailed study on the physical origin of resonance modes, plasmonic coupling, the dispersion of resonance modes, and the possibility of negative refraction. We have found that all the electronic and magnetic modes follow the dispersion of surface plasmon polaritons; thus, essentially they are electronic- and magnetic-surface-plasmon-polaritons-like (ESPP-like and MSPP-like) modes resulted from diffraction coupling between localized surface plasmon and freely propagating light. On the basis of the fill factor and formula of magnetism permeability, we predict that the alphabetical metamaterials should show the negative refraction capability in visible optical frequency. Furthermore, we have demonstrated the specific ultrasensitive surface enhanced Raman spectroscopy (SERS) sensing of monolayer molecules and femtomolar food contaminants by tuning their resonance to match the laser wavelength, or by tuning the laser wavelength to match the plasmon resonance of metamaterials. Our tunable alphabetical metamaterials provide a generic platform to study the electromagnetic properties of metamaterials and explore the novel applications in optical frequency.

The influence of antenatal exposure to phthalates on subsequent female reproductive development in adolescence: a pilot study

We hypothesised that antenatal exposure to ubiquitous phthalates may lead to an earlier menarche and a lower prevalence of polycystic ovarian syndrome (PCOS) and polycystic ovarian morphology (PCO) in adolescence. The Western Australian Pregnancy Cohort (Raine) Study recruited 3000 women at 18 weeks of gestation in 1989–1991, 1377 had antenatal serum stored without thawing at −80 °C. An unselected subset was evaluated in the early follicular phase for PCO and PCOS by ultrasound and serum evaluation in adolescence. Serum was analysed for anti-Müllerian hormone (AMH), inhibin B, sex hormone binding globulin (SHBG), testosterone, androstenedione and DHEAS. Four hundred microlitres of the frozen maternal serum underwent isotope-diluted liquid chromatography–tandem mass spectrometry, with preceding enzymatic deconjugation followed by solid-phase extraction to determine phthalate exposure. Two hundred and forty four girls attended assessment and most common phthalate metabolites were detectable in the majority of the 123 samples available. Several phthalates were negatively associated with maternal SHBG, and associations with maternal androgens were less consistent. The sum of the metabolites of di-(2-ethylhexyl) phthalate was associated with a non-significant tendency towards an earlier age at menarche (P=0.069). Uterine volume was positively associated with mono-(carboxy-iso-octyl) phthalate (P=0.018). Exposure to monoethyl phthalate (MEP) and the sum of all phthalate metabolites (Σall phth.m) were protective against PCOS in adolescence (P=0.001 and P=0.005 respectively). There were negative associations of MEP with PCO (P=0.022) and of MEP with serum AMH (P=0.031). Consequently, our data suggest that antenatal exposure to environmental phthalates may be associated with oestrogenic and/or anti-androgenic reproductive effects in adolescent girls.

Di-(2-ethylhexyl)-phthalate reduces MyoD and myogenin expression and inhibits myogenic differentiation in C2C12 cells

The purpose of this study was to investigate the effects of di-(2-ethylhexyl) phthalate (DEHP) treatment on MyoD and myogenin expression and myotube formation in the murine C2C12 cells. Myogenic differentiation is principally regulated by activities of myogenic regulatory factors, such as MyoD and myogenin, leading the elongation and fusion of mononucleated myoblasts into multinucleated myotubes. In the present study, myogenic differentiation of C2C12 cells was induced by serum deprivation with medium containing vehicle or DEHP (10, 100, 1,000 μg/ml) for 5 days. Using 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assay clearly demonstrated cell viability was not affected by DEHP at any given dose. At the dose of 1,000 μg/ml DEHP, the elongation of multinucleated myotubes, and the percent of nuclei incorporated into myosin heavy chain (MyHC)-stained myotubes were markedly reduced. In addition, immunoblotting revealed expression of muscle specific marker MyHC, as well as myogenic regulatory factors MyoD and myogenin, were reduced in DEHP-treated myotubes during myogenic differentiation. Taken together, the results showed that DEHP may impair myogenic differentiation through repression of myogenic regulatory factors, such as MyoD and myogenin, resulting in a reduction of MyHC expression. This in vitro study suggests that DEHP may be an environmental risk factor for myogenesis.

Bovine induced pluripotent stem cells are more resistant to apoptosis than testicular cells in response to mono-(2-ethylhexyl) phthalate

Although the androgen receptor (AR) has been implicated in the promotion of apoptosis in testicular cells (TSCs), the molecular pathway underlying AR-mediated apoptosis and its sensitivity to environmental hormones in TSCs and induced pluripotent stem cells (iPSCs) remain unclear. We generated the iPSCs from bovine TSCs via the electroporation of OCT4. The established iPSCs were supplemented with leukemia inhibitory factor and bone morphogenetic protein 4 to maintain and stabilize the expression of stemness genes and their pluripotency. Apoptosis signaling was assessed after exposure to mono-(2-ethylhexyl) phthalate (MEHP), the active metabolite of di-(2-ethylhexyl) phthalate. Here, we report that iPSCs were more resistant to MEHP-induced apoptosis than were original TSCs. MEHP also repressed the expression of AR and inactivated WNT signaling, and then led to the commitment of cells to apoptosis via the cyclin dependent kinase inhibitor p21^CIP1. The loss of the frizzed receptor 7 and the gain of p21^CIP were responsible for the stimulatory effect of MEHP on AR-mediated apoptosis. Our results suggest that testicular iPSCs can be used to study the signaling pathways involved in the response to environmental disruptors, and to assess the toxicity of environmental endocrine disruptors in terms of the maintenance of stemness and pluripotency.

Effects of in utero di-butyl phthalate and butyl benzyl phthalate exposure on offspring development and male reproduction of rat

The study was conducted to assess the effects of in utero di-butyl phthalate (DBP) and butyl benzyl phthalate (BBP) exposure during late gestation on offspring's development and reproductive system of male rats. Pregnant rats were treated orally with DBP (2, 10, 50 mg/kg), BBP (4, 20, 100 mg/kg), and diethylstilbestrol (DES) 6 μg/kg (positive control) from GD14 to parturition. A significant reduction in dams' body weight on GD21 in DBP-, BBP-, and DES-treated groups was observed. The gestation length was considerably elevated in the treated groups. Decline in male pups' body weight was significant at PND75 in DBP- (50 mg/kg), BBP- (20,100 mg/kg), and DES-treated groups. The weight of most of the reproductive organs and sperm quality parameters was impaired significantly in DBP- (50 mg/kg) and BBP- (100 mg/kg) treated groups. Further, a non-significant decline in testicular spermatid count and daily sperm production was also monitored in treated groups. A significant reduction in serum testosterone level in BBP (100 mg/kg), whereas the testicular activity of 17β-HSD was declined non-significantly in the treated groups with respect to control. The data suggests that DBP and BBP exposure during late gestation period might have adverse effects on offspring's development, spermatogenesis, and steroidogenesis in adult rats.

Effects of di(2-ethylhexyl)phthalate on testicular oxidant/antioxidant status in selenium-deficient and selenium-supplemented rats

Di(ethylhexyl)phthalate (DEHP), the most widely used plasticizer, was investigated to determine whether an oxidative stress process was one of the underlying mechanisms for its testicular toxicity potential. To evaluate the effects of selenium (Se), status on the toxicity of DEHP was further objective of this study, as Se is known to play a critical role in testis and in the modulation of intracellular redox equilibrium. Se deficiency was produced in 3-weeks-old Sprague-Dawley rats feeding them ≤0.05 mg Se /kg diet for 5 weeks, and Se-supplementation group was on 1 mg Se/kg diet. DEHP-treated groups received 1000 mg/kg dose by gavage during the last 10 days of the feeding period. Activities of antioxidant selenoenzymes [glutathione peroxidase 1 (GPx1), glutathione peroxidase 4 (GPx4), thioredoxin reductase (TrxR)], catalase (CAT), superoxide dismutase (SOD), and glutathione S-transferase (GST); concentrations of reduced glutathione (GSH), oxidized glutathione (GSSG), and thus the GSH/GSSG redox ratio; and thiobarbituric acid reactive substance (TBARS) levels were measured. DEHP was found to induce oxidative stress in rat testis, as evidenced by significant decrease in GSH/GSSG redox ratio (>10-fold) and marked increase in TBARS levels, and its effects were more pronounced in Se-deficient rats with ∼18.5-fold decrease in GSH/GSSG redox ratio and a significant decrease in GPx4 activity, whereas Se supplementation was protective by providing substantial elevation of redox ratio and reducing the lipid peroxidation. These findings emphasized the critical role of Se as an effective redox regulator and the importance of Se status in protecting testicular tissue from the oxidant stressor activity of DEHP.

Synthesis of Aromatic Hyperbranched Polyester (HBPE) and its Use as a Nonmigrating Plasticiser

A series of aromatic hyperbranched polyesters (HBPEs) were synthesised through one-pot reaction of benzene-1,2,4-tricarboxylic anhydride, diethylene glycol, and methanol. The molecular structure of HBPEs was characterised by 1H-NMR, Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry (DSC), and thermogravimetric analysis. HBPE was used as plasticiser for poly(vinyl chloride) (PVC), and compared with traditional plasticiser bis(2-ethylhexyl) phthalate (DOP). When the plasticiser concentration in PVC was below 40 wt-%, HBPE showed better plasticisation efficiency than DOP, with enhanced impact strength and ultimate elongation. Volatility and extractability tests for PVC films indicated that there was no migration if HBPE was used as plasticiser, even under very harsh conditions, while the migration in PVC films plasticised by DOP was much greater, indicating that HBPE could be used as a substitution for DOP to lower the potential health risk from migrating phthalates during the use of PVC products.

Derivation of an oral reference dose (RfD) for the nonphthalate alternative plasticizer 1,2-cyclohexane dicarboxylic acid, di-isononyl ester (DINCH)

1,2-Cyclohexanedicarboxylic acid, 1,2-diisononylester (DINCH), a polyvinyl chloride plasticizer, has food, beverage, and medical device applications that may result in general population exposure. Although no apparent toxicity information in humans was identified, there is a substantial data set in lab animals to serve as the basis of hazard identification for DINCH. Target tissues associated with repeated dietary DINCH exposure in lab animals included liver, kidney, and thyroid and mammary glands. In contrast to some phthalate ester plasticizers, DINCH did not show evidence of hepatic peroxisomal proliferation, testicular toxicity, or liver tumors in rats. Liver and thyroid effects associated with DINCH exposure were attributed to compensatory thyroid stimulation secondary to prolonged metabolic enzyme induction. The toxicological significance of mammary fibroadenomas in female rats is unclear, given that this common benign and spontaneously occurring tumor type is unique to rats. The weight of evidence suggests DINCH is not genotoxic and the proposed mode of action (MOA) for thyroid gland lesions was considered to have a threshold. No adverse reproductive effects were seen in a two-generation study. An oral reference dose (RfD) of 0.7 mg/kg-d was derived from a human equivalent BMDL₁₀ of 21 mg/kg-d for thyroid hypertrophy/hyperplasia seen in adult F₁ rats also exposed in utero. The total uncertainty factor of 30x was comprised of intraspecies (10×) and database (3×) factors. An interspecies extrapolation factor was not applied since rodents are more sensitive than humans with respect to the proposed indirect MOA for thyroid gland lesions.

Occurrence of phthalic acid esters in source waters: a nationwide survey in China during the period of 2009-2012

The first nationwide survey of six phthalic acid esters (PAEs) (diethyl phthalate (DEP); dimethyl phthalate (DMP); di-n-butyl phthalate (DBP); butyl benzyl phthalate (BBP); bis(2-ethylhexyl) phthalate (DEHP); di-n-octyl phthalate (DnOP)) in source waters was conducted in China. The results showed these PAEs were ubiquitous in source waters. DBP and DEHP were the most frequently detected with high concentrations ranging nd-1.52 μg/L and nd-6.35 μg/L, respectively. These PAEs concentrations (except DBP) in surface water (rivers, lakes and reservoirs) were generally higher than those in groundwater; DBP had high concentrations in groundwater in Northeast China (Liao River Basin) and North China (Hai River Basin). Their concentrations in the northern regions were generally higher than those in the southern and eastern regions; particularly, in North China. Three short-chain PAEs (DMP, DEP and DBP) were detected with high concentrations in Hai River Basin, Pearl River Basin and Yellow River Basin.

Phthalate intake by infants calculated from biomonitoring data

Urine samples (n=207) of 47 infants between 1- and 5-month of age were quantitated for 12 metabolites of 7 phthalates and compared with samples collected from the mothers of the infants at different time points. Median and 95-percentile were lower for all metabolites in urine samples of infants compared to mothers. For di-2-ethylhexyl phthalate (DEHP) the 95-percentile daily intake was 23.3μg/kg b.w. for mothers and 5.4μg/kg b.w. for infants and for di-isobutyl phthalate (DiBP) 10.1μg/kg b.w. and 8.5μg/kg b.w. Some values exceeded the corresponding tolerable daily intake (TDI) for DiBP for infants and mothers and for DEHP and di-n-butyl phthalate (DnBP) only for mothers. Both, infants and mothers are able to efficiently form phase II metabolites but infants with a slightly lower degree. Therefore, a distinguished risk assessment with respect to the formed toxic metabolites of phthalates would be necessary in combination with a reduction of the most toxic phthalates.

Phthalates induce neurotoxicity affecting locomotor and thermotactic behaviors and AFD neurons through oxidative stress in Caenorhabditis elegans

Background

Phthalate esters are ubiquitous environmental contaminants and numerous organisms are thus exposed to various levels of phthalates in their natural habitat. Considering the critical, but limited, research on human neurobehavioral outcomes in association with phthalates exposure, we used the nematode Caenorhabditis elegans as an in vivo model to evaluate phthalates-induced neurotoxicity and the possible associated mechanisms.

Principal Findings

Exposure to phthalates (DEHP, DBP, and DIBP) at the examined concentrations induced behavioral defects, including changes in body bending, head thrashing, reversal frequency, and thermotaxis in C. elegans. Moreover, phthalates (DEHP, DBP, and DIBP) exposure caused toxicity, affecting the relative sizes of cell body fluorescent puncta, and relative intensities of cell bodies in AFD neurons. The mRNA levels of the majority of the genes (TTX-1, TAX-2, TAX-4, and CEH-14) that are required for the differentiation and function of AFD neurons were decreased upon DEHP exposure. Furthermore, phthalates (DEHP, DBP, and DIBP) exposure at the examined concentrations produced elevated intracellular reactive oxygen species (ROS) in C. elegans. Finally, pretreatment with the antioxidant ascorbic acid significantly lowered the intracellular ROS level, ameliorated the locomotor and thermotactic behavior defects, and protected the damage of AFD neurons by DEHP exposure.

Conclusions

Our study suggests that oxidative stress plays a critical role in the phthalate esters-induced neurotoxic effects in C. elegans.

Androgen receptor-mediated apoptosis in bovine testicular induced pluripotent stem cells in response to phthalate esters

The androgen receptor (AR) has a critical role in promoting androgen-dependent and -independent apoptosis in testicular cells. However, the molecular mechanisms that underlie the ligand-independent apoptosis, including the activity of AR in testicular stem cells, are not completely understood. In the present study, we generated induced pluripotent stem cells (iPSCs) from bovine testicular cells by electroporation of octamer-binding transcription factor 4 (OCT4). The cells were supplemented with leukemia inhibitory factor and bone morphogenetic protein 4, which maintained and stabilized the expression of stemness genes and pluripotency. The iPSCs were used to assess the apoptosis activity following exposure to phthalate esters, including di (2-ethyhexyl) phthalates, di (n-butyl) phthalate, and butyl benzyl phthalate. Phthalate esters significantly reduced the expression of AR in iPSCs and induced a higher ratio of BAX/BCL-2, thereby favoring apoptosis. Phthalate esters also increased the expression of cyclin-dependent kinase inhibitor 1 (p21^Cip1) in a p53-dependent manner and enhanced the transcriptional activity of p53. The forced expression of AR and knockdown of p21^Cip1 led to the rescue of the phthalate-mediated apoptosis. Overall, this study suggests that testicular iPSCs are a useful system for screening the toxicity of environmental disruptors and examining their effect on the maintenance of stemness and pluripotency, as well as for identifying the iPSC signaling pathway(s) that are deregulated by these chemicals.