Comparative toxicological evaluation of phthalate diesters and metabolites in Sprague-Dawley male rats for risk assessment

Effects of the in-utero dicyclohexyl phthalate and di-n-hexyl phthalate administration on the oxidative stress-induced histopathological changes in the rat liver tissue correlated with serum biochemistry and hematological parameters

Phthalates are widely used as plasticizers in the industry and are found in cosmetics, food and drink packaging, drugs, toys, households, medical devices, pesticides, personal care products, and paints. Phthalates exert endocrine disrupting and peroxisome proliferator effects in humans and wildlife associated with the pathogenesis of various diseases, including diabetes, obesity, infertility, cardiovascular diseases, metabolic syndrome, and cancer. Since phthalates are metabolized in the liver, which regulates the body's energy metabolism, long or short-term exposure to the phthalates is associated with impaired glucose, lipid, and oxidative stress metabolisms contributing to liver toxicity. However, the impact of in-utero exposure to DHP and DCHP on liver metabolism has not been studied previously. Thus, in this study, we evaluated serum biochemistry parameters, hematological markers, histopathological changes, and oxidative and pentose phosphate pathway (PPP) metabolisms in the liver following in-utero DHP and DCHP administration, respectively, in male and female rats. We found increased relative and absolute liver weights and impaired triglyceride, alanine transaminase (ALT), lactate dehydrogenase (LDH), and alkaline phosphatase (ALP) levels upon dicyclohexyl phthalate (DCHP) and di-n-hexyl phthalate (DHP). Histopathological changes, including congestion, sinusoidal dilatation, inflammatory cell infiltration, cells with a pyknotic nucleus, lysis of hepatocytes, and degeneration of hepatic parenchyma have been observed in the liver samples of DHP and DCHP dose groups. Moreover, increased glutathione s-transferase (GST), glucose 6-phosphate dehydrogenase (G6PD), and glutathione reductase (GR) activities have been found in the liver samples of DHP and DCHP-treated rats associated with impaired pentose phosphate pathway (PPP) and oxidative stress metabolism. First time in the literature, we showed that in-utero exposure to DHP and DCHP causes liver damage associated with impaired oxidative stress metabolism in male and female rats. Our data may guide researchers and governments to regulate and restrict phthalates in industrial products.

Urinary phthalate metabolites and anemia: Findings from the Korean National Environmental Health Survey (2015-2017)

BACKGROUND

Several animal studies have suggested an association between phthalate exposure and decreased hemoglobin levels. To address the lack of epidemiological evidence, we evaluated the association between urinary phthalate metabolite concentrations and hematologic indices by using nationally representative data from Korea.

METHODS

Data from 3722 adults included in the third stage (2015-2017) of the Korean National Environmental Health Survey (KONEHS) were used. The association between various urinary phthalate metabolites and hematologic indices (hemoglobin, hematocrit, mean corpuscular volume [MCV], and red blood cell [RBC], white blood cell [WBC], and platelet counts) was evaluated using linear regression analysis adjusted for potential confounders. Sex-stratified analysis was performed.

RESULTS

All urinary phthalate metabolites were negatively associated with hemoglobin levels. A two-fold increase in urinary mono-(2-ethyl-5-carboxy-pentyl) phthalate (MECPP), mono-carboxyoctyl phthalate (MCOP), mono-carboxyonyl phthalate (MCNP), and mono-(3-carboxypropyl) phthalate (MCPP) levels was associated with a -0.099 g/dL (95% confidence interval (CI), -0.137 to -0.060), -0.116 g/dL (95% CI, -0.156 to -0.076), -0.111 g/dL (95% CI, -0.154 to -0.068), and -0.144 g/dL (95% CI, -0.198 to -0.089) change in hemoglobin levels, respectively. The RBC count and MCV showed negative and positive associations, respectively, with urinary phthalate metabolite concentrations. WBC counts were positively associated with MECPP, MCOP, MCNP, and MCPP levels, whereas the platelet count showed no association with urinary phthalate metabolites.

CONCLUSIONS

Urinary phthalate metabolite concentration showed a negative association with hemoglobin level. Since this was a cross-sectional study, further longitudinal and experimental studies are needed to identify a clear causal linkage and the pathological mechanism underlying phthalate exposure and anemia.

Physiologically-based toxicokinetic modeling of human dermal exposure to diethyl phthalate: Application to health risk assessment

Diethyl phthalate (DEP) has been most frequently detected in personal care products (PCPs) as a solvent followed by indoor air as one of the semi-volatile organic compounds (SVOCs). Human exposure to DEP predominantly occurs via dermal uptake. However, the available physiologically based toxicokinetics (PBTK) models are developed in rats for risk assessment of DEP exposure resulting from the oral than dermal pathway. To address this issue, DEP in simulated PCPs was dermally administrated to five adult volunteers at real population levels. Following the construction of a dermal absorption model for DEP, the dermal PBTK modeling of DEP involving PCPs and air-to-skin exposure routes in humans was developed for the first time. The data of monoethyl phthalate (MEP) in serum or urine obtained from published human studies and this study were applied to calibrate and validate the developed dermal PBTK model. Monte Carlo simulation was used to evaluate model uncertainty. The dermal absorption fraction of DEP was obtained to be 56.2% for PCPs exposure and 100% for air-to-skin exposure, respectively. Approximate 24.9% of DEP in exposed skin became absorbed into systemic circulation. Model predictions were generally within 2-fold of the observed MEP levels in human serum or urine. Uncertainty analysis showed 90% of the predicted variability (P₉₅/P₅) fell within less than one order of magnitude. Assuming human intake of 5 mg/kg bw per day, the predicted serum area under the curve at steady state of DEP from the dermal route was 1.7 (PCPs) and 2.4 (air) times of those from the peroral route, respectively. It suggested that dermal exposure to DEP would pose greater risk to human health compared with oral exposure. The application of the developed dermal PBTK model provides a valuable insight into health risk assessment of DEP in humans.

Vitamin C mitigates hematological and biochemical alterations caused by di(2-ethylhexyl) phthalate toxicity in female albino mice, Mus musculus

Di(2-ethylhexyl) phthalate (DEHP) is ubiquitous environmental contaminant and identified as endocrine-disrupting chemical (EDC), present in plastics as plasticizer. Due to its versatile use, human exposure level reaches to danger limit. The main focus of our study is to see the effect of vitamin C on hematological and biochemical alterations caused by Di(2-ethylhexyl) Phthalate toxicity in female albino mice, Mus musculus. It is found to cause defects of the liver, kidney, and lungs. Its anti-androgenic nature brings the main focus on its toxicity associated with reproductive and endocrine system. In this experimental study, 18 young female Swiss albino mice, Mus musculus, were used and divided into 3 groups of 6 animals each as control (corn oil vehicle), DEHP group (100 mg/kg body weight dissolved in corn oil), and DEHP + vitamin-C group (100 mg/kg body weight each, dissolved in corn oil and double distilled water, respectively) for 90 days. In this research, serum metabolites were evaluated to study the effect of DEHP on glucose, total protein, and lipid profile along with some hematological, enzymological, and oxidative stress parameters. Simultaneously, we compared the effectiveness of vitamin-C against DEHP toxicity to mitigate the serum homeostasis disturbance. In present study, we observed, in DEHP-treated animals, glucose, triglycerides, very-low-density lipoprotein (VLDL), total protein, alkaline phosphatase (ALP), acid phosphatase (ACP), and alanine aminotransferase (ALT) levels increased remarkably, whereas total cholesterol, high-density lipoproteins (HDL), aspartate aminotransferase (AST), total RBC count, total WBC count, and hemoglobin (Hb) level significantly decreased as compared to control group. In addition, we noticed there was a decrease in superoxide dismutase (SOD) and increase in levels of lipid peroxidation (MDA) and interleukin-6 (IL-6) in DEHP treatment group as compared to control group. The results indicated vitamin C had a better improving effect against DEHP toxicity on balancing metabolic abnormalities and inflammation-related comorbidities.

Environmental Exposure to Endocrine Disrupting Chemicals Influences Genomic Imprinting, Growth, and Metabolism

Genomic imprinting is an epigenetic mechanism that results in monoallelic, parent-of-origin-specific expression of a small number of genes. Imprinted genes play a crucial role in mammalian development as their dysregulation result in an increased risk of human diseases. DNA methylation, which undergoes dynamic changes early in development, is one of the epigenetic marks regulating imprinted gene expression patterns during early development. Thus, environmental insults, including endocrine disrupting chemicals during critical periods of fetal development, can alter DNA methylation patterns, leading to inappropriate developmental gene expression and disease risk. Here, we summarize the current literature on the impacts of in utero exposure to endocrine disrupting chemicals on genomic imprinting and metabolism in humans and rodents. We evaluate how early-life environmental exposures are a potential risk factor for adult metabolic diseases. We also introduce our mouse model of phthalate exposure. Finally, we describe the potential of genomic imprinting to serve as an environmental sensor during early development and as a novel biomarker for postnatal health outcomes.

Revealing the toxicity of dimethyl phthalate (DMP) to the oxygen-carrying function of red blood cells (RBCs): The iron release mechanism

Phthalic acid esters (PAEs), as typical hormone pollutants, do harms to human health after enrichment over a long term exposure, causing the loss of oxygen-carrying function of red blood cells (RBCs). This study has investigated the mechanism for the toxicity of dimethyl phthalate (DMP) on the oxygen-carrying function of RBCs by measuring the iron release content of hemoglobin (Hb) in vivo and in vitro. The hematologic examination showed that the high dose of DMP at 1000 mg/kg significantly reduced the Hb content and increased the granulocyte content, whereas such toxicity was not relatively observed at a low (50 mg/kg) or a medium (250 mg/kg) dose of DMP. The in vitro experiments showed that DMP, incubated with RBCs, increased the iron release content as a function of DMP concentration. Interestingly, such a phenomenon was not observed when DMP was incubated with Hb alone, indicating that the release of hemoglobin iron could not directly caused by the combination of DMP and hemoglobin. The in vivo experiments indicated that DMP induced iron release and oxidative stress for rat RBCs. Moreover, vitamin C and E was found to reduce the level of iron release by recovering erythrocytes from the oxidative stress induced by DMP. This work has revealed that the oxidative stress induced by DMP, causing the release of Hb iron from RBCs, is the reason for the toxicity of DMP to the oxygen-carrying function.

Hazards of diethyl phthalate (DEP) exposure: A systematic review of animal toxicology studies

BACKGROUND

Diethyl phthalate (DEP) is widely used in many commercially available products including plastics and personal care products. DEP has generally not been found to share the antiandrogenic mode of action that is common among other types of phthalates, but there is emerging evidence that DEP may be associated with other types of health effects.

OBJECTIVE

To inform chemical risk assessment, we performed a systematic review to identify and characterize outcomes within six broad hazard categories (male reproductive, female reproductive, developmental, liver, kidney, and cancer) following exposure of nonhuman mammalian animals to DEP or its primary metabolite, monoethyl phthalate (MEP).

METHODS

A literature search was conducted in online scientific databases (PubMed, Web of Science, Toxline, Toxcenter) and Toxic Substances Control Act Submissions, augmented by review of online regulatory sources as well as forward and backward searches. Studies were selected for inclusion using PECO (Population, Exposure, Comparator, Outcome) criteria. Studies were evaluated using criteria defined a priori for reporting quality, risk of bias, and sensitivity using a domain-based approach. Evidence was synthesized by outcome and life stage of exposure, and strength of evidence was summarized into categories of robust, moderate, slight, indeterminate, or compelling evidence of no effect, using a structured framework.

RESULTS

Thirty-four experimental studies in animals were included in this analysis. Although no effects on androgen-dependent male reproductive development were observed following gestational exposure to DEP, there was evidence including effects on sperm following peripubertal and adult exposures, and the overall evidence for male reproductive effects was considered moderate. There was moderate evidence that DEP exposure can lead to developmental effects, with the major effect being reduced postnatal growth following gestational or early postnatal exposure; this generally occurred at doses associated with maternal effects, consistent with the observation that DEP is not a potent developmental toxicant. The evidence for liver effects was considered moderate based on consistent changes in relative liver weight at higher dose levels; histopathological and biochemical changes indicative of hepatic effects were also observed, but primarily in studies that had significant concerns for risk of bias and sensitivity. The evidence for female reproductive effects was considered slight based on few reports of statistically significant effects on maternal body weight gain, organ weight changes, and pregnancy outcomes. Evidence for cancer and effects on kidney were judged to be indeterminate based on limited evidence (i.e., a single two-year cancer bioassay) and inconsistent findings, respectively.

CONCLUSIONS

These results suggest that DEP exposure may induce androgen-independent male reproductive toxicity (i.e., sperm effects) as well as developmental toxicity and hepatic effects, with some evidence of female reproductive toxicity. More research is warranted to fully evaluate these outcomes and strengthen confidence in this database.

Novel toxicity of tris(1,3-dichloro-2-propyl) phosphate in adult male rats

The widespread use of tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) as a flame retardant has led to its release to the environment. Thus, the toxicological effects of TDCIPP on humans and animals are of importance. For better understanding of its potential toxicities, TDCIPP (250, 500, or 650 mg/kg/day) or vehicle control was administrated orally to adult male Wistar-Imamichi rats for 7 days. After the final administration of compounds, organ weights, histopathology, blood biochemistry, and hematology were examined. Hepatic toxicity was observed at doses ≥ 500 mg/kg/day of TDCIPP, and renal toxicity was observed at 650 mg/kg/day. The anti-androgenic activity of TDCIPP was previously confirmed in vitro and in vivo, but weights of epididymis, an androgen-dependent organ, were not affected by TDCIPP treatment in adults. Serum alkaline phosphatase activity was significantly decreased in all TDCIPP-treated rats independent of dose. Hemoglobin concentration, hematocrit, red blood cell count, and reticulocyte count were decreased in all TDCIPP-treated rats, but mean corpuscular volume, total iron-binding capacity, and serum iron were normal, suggesting that renal anemia was caused by TDCIPP. Together with previous reports on effects of anti-androgenic substances on red blood cell indices, anemia caused by TDCIPP could be due to its anti-androgenic activity. These considerations will contribute to further assessment of the toxicity of the compound.

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.

Investigation of the Potential Environmental Risks of Phthalate Derivatives Designed To Be Environmentally Friendly

Phthalate derivatives with low estrogenic activity, high infrared spectrum signals, high Raman characteristic vibration spectrum, high fluorescence intensity, and high ultraviolet sensitivity were selected as precursors from our previous studies, so that the changes in their toxicity and estrogenic activity during biological metabolism, ozone oxidation, photocatalytic degradation, photodegradation, and microbial degradation could be studied.The transformation pathways of these derivatives were simulated, and the reaction energy barriers were calculated. To determine the potential environmental risks of these phthalate derivatives, the pharmacophore models of biotoxicity and estrogen activity of phthalates were used to predict the biotoxicity and estrogen activity of the transformed products. The results showed an increase in the biotoxicity and estrogen activity of the biometabolites, ozonation products, photocatalytic degradation products, and microbial degradation products; the only products that did not follow this trend were the photodegradation products. Notably, the pathways that produced more potentially toxic compounds were the less favorable paths. Our results indicate that the transformation products of the designed environmentally friendly phthalate derivatives potentially pose environmental risks. To avoid such risks, the environmental transformation pathway of these derivatives should be simulated to screen for environmentally friendly phthalate molecules. Environ Toxicol Chem 2020;39:1138-1148. © 2020 SETAC.

Gene expression profiles for low-dose exposure to diethyl phthalate in rodents and humans: a translational study with implications for breast carcinogenesis

Phthalates are commonly included as ingredients in personal care products such as cosmetics, shampoos and perfumes. Diethyl phthalate (DEP) has been found to be anti-androgenic and linked with adverse reproductive effects on males, but effects on females are poorly understood. We designed an integrative and translational study to experimentally examine the effects of DEP exposure at a human-equivalent dose on the mammary transcriptome in rats and to subsequently examine the DEP gene signature in breast tissues (both pre-malignant and tumor) from a population study. In Sprague-Dawley rats treated orally with DEP from birth to adulthood, we identified a signature panel of 107 genes predominantly down-regulated by DEP exposure. Univariate analysis of this 107 DEP gene signature in pre-malignant breast tissues revealed that six genes (P4HA1, MPZL3, TMC4, PLEKHA6, CA8, AREG) were inversely associated with monoethyl phthalate (MEP; the urinary metabolite of DEP) concentration (p < 0.05) among postmenopausal women; all six genes loaded on to one of seven factors identified by factor analysis. Transcription factor enrichment analysis revealed that genes in this factor were enriched for androgen receptor binding sites. These six genes were also significantly down-regulated in pre-malignant adjacent tissues compared to the corresponding tumor tissues in pair-wise analyses (p < 0.05). Results from our translational study indicate that low level exposure to diethyl phthalate results in measurable genomic changes in breast tissue with implications in breast carcinogenesis.

Update of the risk assessment of di-butylphthalate (DBP), butyl-benzyl-phthalate (BBP), bis(2-ethylhexyl)phthalate (DEHP), di-isononylphthalate (DINP) and di-isodecylphthalate (DIDP) for use in food contact materials

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP Panel) was asked by the European Commission to update its 2005 risk assessments of di-butylphthalate (DBP), butyl-benzyl-phthalate (BBP), bis(2-ethylhexyl)phthalate (DEHP), di-isononylphthalate (DINP) and di-isodecylphthalate (DIDP), which are authorised for use in plastic food contact material (FCM). Dietary exposure estimates (mean and high (P95)) were obtained by combining literature occurrence data with consumption data from the EFSA Comprehensive Database. The highest exposure was found for DINP, ranging from 0.2 to 4.3 and from 0.4 to 7.0 μg/kg body weight (bw) per day for mean and high consumers, respectively. There was not enough information to draw conclusions on how much migration from plastic FCM contributes to dietary exposure to phthalates. The review of the toxicological data focused mainly on reproductive effects. The CEP Panel derived the same critical effects and individual tolerable daily intakes (TDIs) (mg/kg bw per day) as in 2005 for all the phthalates, i.e. reproductive effects for DBP (0.01), BBP (0.5), DEHP (0.05), and liver effects for DINP and DIDP (0.15 each). Based on a plausible common mechanism (i.e. reduction in fetal testosterone) underlying the reproductive effects of DEHP, DBP and BBP, the Panel considered it appropriate to establish a group-TDI for these phthalates, taking DEHP as index compound as a basis for introducing relative potency factors. The Panel noted that DINP also affected fetal testosterone levels at doses around threefold higher than liver effects and therefore considered it conservative to include it within the group-TDI which was established to be 50 μg/kg bw per day, expressed as DEHP equivalents. The aggregated dietary exposure for DBP, BBP, DEHP and DINP was estimated to be 0.9-7.2 and 1.6-11.7 μg/kg bw per day for mean and high consumers, respectively, thus contributing up to 23% of the group-TDI in the worst-case scenario. For DIDP, not included in the group-TDI, dietary exposure was estimated to be always below 0.1 μg/kg bw per day and therefore far below the TDI of 150 μg/kg bw per day. This assessment covers European consumers of any age, including the most sensitive groups. Based on the limited scope of the mandate and the uncertainties identified, the Panel considered that the current assessment of the five phthalates, individually and collectively, should be on a temporary basis.

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.

Risk assessment of phthalates in pharmaceuticals

Phthalates are used for industrial plasticizers to impart flexibility and durability to polyvinyl chloride. Despite widespread use of phthalates, reported endocrine-disrupting properties raise safety concerns for consumers. Since phthalates are permitted as excipients in controlled-release capsules and enteric coatings, patients taking drugs containing these chemicals may potentially be at some health risk. In this study, 102 distinct pharmaceutical products were analyzed by gas chromatography/mass spectrometry to determine phthalate content and maximal phthalate exposure rate was calculated. In 102 drug samples, di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), and diethyl phthalate (DEP) were detected in 9.8, 27.45, and 5.88% of cases, respectively. The highest level of DEP was found in extended-release (ER) capsules with concentrations ranging from 935.5 to 1535.37 ppb. The highest levels of DBP (1.32-7.07 ppb) were detected in tablets, whereas highest level (7.07 ppb) of DEHP was found in suspension preparations. The phthalate hazard index (HI) (human exposure tolerable daily intake) was calculated for each sample, but no sample exhibited an HI value exceeding 1; the minimum value taken to indicate a serious health risk. Thus, no apparent serious health risk from phthalate exposure arises from taking these medications. The low HI values suggest that phthalate contamination in pharmaceuticals may not pose an apparent significant risk to humans. However, the sources of phthalate present in pharmaceutical products still needs to be investigated and verified through on-site inspections in manufacturing processes in order to minimize human exposure. It is recommended that measures be taken to prevent phthalate contamination in pharmaceuticals.

Effects of diisononyl phthalate (DiNP) on the endocannabinoid and reproductive systems of male gilthead sea bream (Sparus aurata) during the spawning season

Diisononyl phthalate (DiNP) is a plasticizer used to improve plastic performance in a large variety of items which has been reported as an endocrine-disrupting chemical (EDC) in several organisms. The endocannabinoid system (ECS) is a cellular signaling system, whose functionality is tightly involved with reproductive function. The aim of the present study was the assessment of the effects of DiNP on the gonadal ECS and on the reproductive function of male gilthead sea bream Sparus aurata, an important marine aquacultured species in Europe, during the reproductive season. Fish were fed for 21 days with two diets contaminated with different nominal concentrations of DiNP (DiNP LOW at 15 µg DiNP kg^-1 bw day^-1 and DiNP HIGH at 1500 µg DiNP kg^-1 bw day^-1), based on the tolerable daily intake (TDI) ruled by the European Food Safety Authority for humans. The transcription of several genes related to the ECS was affected by the DiNP. Specifically, DiNP reduced the levels of endocannabinoids and endocannabinoid-like mediators, concomitant with the increase of fatty acid amide hydrolase (FAAH) activity. At the histological level, DiNP LOW induced the highest occurrence of individuals with regressed testes. Steroidogenesis was affected significantly, since plasma 11-ketotestosterone (11-KT), the main active androgen in fish, was significantly decreased by the DiNP HIGH treatment, while plasma 17β-estradiol (E₂) levels were raised, associated with an increase of the gonadosomatic index (GSI). Additionally, the level of testosterone (T) was significantly increased in the DiNP LOW group, however, the same DiNP concentration reduced the levels of 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P). The production of sperm was in general not affected, since spermiation index, sperm density, survival and the duration of forward motility did not exhibit any changes compared to controls. However, computer-assisted sperm analysis (CASA) showed that DiNP reduced the percentage of motile cells. The results clearly suggest a negative effect of DiNP via the diet on the male endocrine system of gilthead sea bream during the reproductive season.

Risk assessment of endocrine disrupting phthalates and hormonal alterations in children and adolescents

Risk assessment and hormone evaluation were carried out for di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP), endocrine disrupting chemicals (EDCs), in 302 Korean children (n = 223) and adolescents (n = 79) (< age 19). Urinary and serum concentrations of DEHP, MEHP (mono(2-ethylhexyl) phthalate), DBP, MBP (monobutyl phthalate), and PA (phthalic acid, a common final metabolite of phthalates) were detected in children and adolescents. Daily exposure levels were estimated to be 16.45 ± 36.50 μg/kg b.w./day for DEHP, which is one-third of the tolerable daily intake (TDI) value (50 μg/kg b.w./day), but 14 out of 302 participants had a hazard index (HI = intake/TDI) value >1. The mean daily exposure level of DBP was 1.23 ± 1.45 μg/kg b.w./day, which is one-eighth of the TDI value (10 μg/kg b.w./day), but 1 out of 302 participants had a HI value > 1. Positive correlations were observed between serum DBP or MEHP, and serum estradiol (E2) and/or luteinizing hormone (LH) in prepubescent children. In addition, serum MBP levels were found to be negatively correlated with serum triiodothyronine (T3) or thyroxine (T4) in male participants, and serum DEHP levels with serum thyroid stimulating hormone (TSH) in female adolescents. Low-density lipoprotein (LDL) levels were positively correlated with serum PA levels in children and adolescents. DEHP, DBP or its metabolites may be associated with altered hormone levels in children and adolescents. Data suggest that exposure levels of DEHP and DBP in Korean children need to be reduced to levels below TDI to protect them from EDC-mediated toxicities. Abbreviations: DBP: dibutyl phthalate; DEHP: di(2-ethylhexyl) phthalate; E2: estradiol; EDC: endocrine disrupting chemical; EFSA: European Food Safety Authority; FSH: follicle stimulating hormone; HDL: high density lipoprotein; HI: hazard index; LDL: low density lipoprotein; LH: luteinizing hormone; MEHP: mono(2-ethylhexyl) phthalate; MBP: monobutyl phthalate; PA: phthalic acid; PPAR: peroxisome proliferator-activated receptor gamma; PVC: polyvinyl chloride; T3: triiodothyronine; T4: thyroxine; TDI: tolerable daily intake; TG: triglyceride; TSH: thyroid stimulating hormone; UPLC/MS/MS: Ultra Performance Liquid Chromatography/Tandem Mass Spectrometry; WWF: World Wildlife Fund.

Mechanistic toxicity of DEHP at environmentally relevant concentrations (ERCs) and ecological risk assessment in the Three Gorges Reservoir Area, China

Di-(2-ethylhexyl) phthalate (DEHP) associated in vitro/vivo toxicity at current environmentally relevant concentration (ERC) with attendant ecological risks in the Three Gorges Reservoir Area (TGRA) is still elusive. Responding to this challenge, a novel integrated study based on analytical and biological assays was designed to elucidate the underlying mechanisms for toxicity of DEHP and its ecological risks at ERC. In this study, GC-MS analysis showed that the highest environmental concentration of DEHP in the TGRA surface water was nearly double that of WHO and USEPA standards. Both distribution and ecological risk decreased from the upper to middle and lower reaches of the TGRA. In vitro toxicity was assessed by cell viability and DNA damage assays: DEHP exposure at ERCs (100-800 μg/L) caused significant reduction in cell viability and elevated DNA damage. Further, DEHP exposure above 400 μg/L resulted in enhanced migration behavior of cancer cells. For in vivo toxicity assessment, short term acute exposure (7 d, 400 μg/L) apparently activated the PI3K-AKT-mTOR pathway, and chronic low-level exposure (3 months, 10-33 μg/L) suppressed the hypothalamus pituitary thyroid (HPT) axis pathway in zebrafish. In addition, acute low-level exposure (5 d, 33-400 μg/L) to DEHP increased aryl hydrocarbon receptor (AhR) activity in Tg(cyp1a:gfp) zebrafish in a concentration-dependent manner. In short, DEHP at ERC has extended potential to induce diverse in vitro and in vivo toxicity at concentrations that also cause impairment of biochemical function in aquatic species of the TGRA.

Effect modification by apoptosis-related gene polymorphisms on the associations of phthalate exposure with spermatozoa apoptosis and semen quality

BACKGROUND

Human studies indicate that phthalate exposure is associated with adverse male reproductive health, and this association may be modified by genetic polymorphisms.

OBJECTIVES

We investigated whether apoptosis-related gene polymorphisms modified the associations of phthalate exposure with spermatozoa apoptosis and semen quality.

METHODS

In this Chinese population who sought for semen examination in an infertility clinic, we measured 8 phthalate metabolites in two urine samples to assess the individual's exposure levels. Apoptosis-related gene (Fas, FasL, and caspase3) polymorphisms were performed by real-time PCR. Spermatozoa apoptosis and semen quality parameters were evaluated by Annexin V/PI assay and computer-aided semen analysis, respectively.

RESULTS

We found that Fas rs2234767, FasL rs763110, and caspase3 rs12108497 gene polymorphisms significantly modified the associations between urinary phthalate metabolites and spermatozoa apoptosis. For example, urinary monobutyl phthalate (MBP) associated with an increased percentage of Annexin V⁺/PI^- spermatozoa of 25.11% (95% CI: 4.08%, 50.53%) were only observed among men with CT/TT genotype of FasL rs763110. In addition, we found that caspase3 rs12108497 gene polymorphisms significantly modified the associations of urinary mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) with decreased sperm concentration and sperm count (both p-values for interactions = 0.02).

CONCLUSION

Our results provided the first evidence that apoptosis-related gene polymorphisms might contribute to the effects of phthalate exposure on male reproductive health.

Study on the interaction between typical phthalic acid esters (PAEs) and human haemoglobin (hHb) by molecular docking

This work has evaluated the binding force between hHb and typcial PAEs (DMP, DEP, DPRP, DBP, DIBP, DHP and DPHP) using molecule docking technique. The DPHP with 3 aromatic rings has the strongest binding (-ΔG_binding: 6.0kcalmol^-1) than other PAEs (-ΔG_binding: 2.91∼4.48kcalmol^-1). The DMP with the lowest molecular weight has a high binding force (-ΔG_binding: 4.48kcalmol^-1), while the DHP with the highest molecular weight has the lowest binding force (-ΔG_binding: 2.91kcalmol^-1). When the length of side chain increases, the binding force trend to decrease, regarding the VDW forces and H-bonding. The lgK_ow-ΔG_binding plotting figure shows that a higher K_ow value is accompanied by a lower binding force. The aromatic ring existed in PAEs largely increases the binding force between the hHb and the PAEs. On the other hand, the PAEs with higher number of carbon, meaning a higher hydrophobicity, can enter into the hydrophobic space of hHb centre deeper and bond to different position. The aromatic ring decreases the depth of binding position in the hydrophobic space. This work provides basic data and a theoretical method to assess the transport and accumulation of PAEs in human body, and the cytotoxicity of PAEs to hBRCs.

Health risk assessment of exposures to a high molecular weight plasticizer present in automobile interiors

This study provides an exposure and risk assessment of diundecyl phthalate (DUP), a high molecular weight phthalate plasticizer present in automobile interiors. Total daily intake of DUP was calculated from DUP measured in wipe samples from vehicle seats from six automobiles. Four of the vehicles exhibited atypical visible surface residue on the seats. Two vehicles with no visible surface residue were sampled as a comparison. DUP was the predominant organic compound identified in each of the wipes from all seats. A risk assessment of DUP via oral, dermal, and inhalation routes resulting from contact with automobile seats was conducted. The mean, standard deviation, and maximum DUP concentrations on the seats with visible surface residue were 6983 ± 7823 μg/100 cm² and 38300 μg/100 cm², respectively. The mean and 95th percentile of the mean for daily cumulative dose of DUP for all exposure routes for the seats with no visible surface residue ranged from 7 × 10^-4 to 4 × 10^-3 mg/kg-day and from 8 × 10^-4 to 5 × 10^-3 mg/kg-day, respectively. For seats with visible surface residue, cumulative doses ranged from 2 × 10^-3 to 2 × 10^-2 mg/kg-day and from 4 × 10^-3 to 2 × 10^-2 mg/kg-day, respectively. The estimated daily intake (contact or absorbed dose) of DUP from automobile seats were far lower than the NOAELs reported in and derived from animal studies, and are well below the reported Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Derived No Effect Levels (DNELs) for the general population. Based on this analysis, using virtually any benchmark for evaluating safety, exposure to DUP via automobile seat covers did not pose a measureable increased health-risk in any population under any reasonably plausible exposure scenario.

Study on the Mechanism of Interaction between Phthalate Acid Esters and Bovine Hemoglobin

Phthalate acid esters (PAEs) are widely used in plastic products as a series of chemical softeners. However, PAEs, which now exist in many environmental media such as the atmosphere, water, and soil, have been shown to be environmental endocrine disruptors. Hemoglobin is a functional protein that carries oxygen in the red blood cells of animals. This study aims at revealing the interactions between bovine hemoglobin (BHb) and PAEs using spectroscopic and molecular modeling methods. The results indicate that the selected representative PAEs-dimethyl phthalate (DMP), diethyl phthalate (DEP), and dibutyl phthalate (DBP)-can interact with BHb to form BHb-PAE complexes with one binding site, mainly relying on hydrophobic forces, with the affinity order DMP > DEP > DBP, opposite to the order of side-chain length. The binding of PAEs can cause conformational and micro-environmental changes in BHb, which may affect the physiological functions of Hb. Furthermore, molecular docking was applied to define the specific binding sites, the results of which show that all the three PAEs can bind into the central cavity of BHb. The study contributes to expound the toxic mechanism of PAEs in vivo from the point of hematological toxicology.

Identification of potential biomarkers of exposure to diundecyl phthalate

Diundecyl phthalate (DUP) is a high production volume chemical used as a plasticizer in polyvinyl chloride and other plastics. Specific biomarkers of DUP would be useful for human exposure assessment. To identify such biomarkers, we investigated the in vitro metabolism of DUP with human liver microsomes using online solid phase extraction coupled to HPLC-mass spectrometry. Using high resolution mass spectrometry, we conclusively confirmed the structures of four DUP specific metabolites: monoundecyl phthalate (MUP), mono-hydroxyundecyl phthalate (MHUP), mono-oxoundecyl phthalate (MOUP), and mono-carboxydecyl phthalate (MCDP). We also used high resolution mass spectrometry to isolate MCDP and MHUP from co-eluting isobaric metabolites of diisononyl phthalate (i.e., monocarboxyisononyl phthalate) and diisododecyl phthalate (i.e., monohydroxyisododecyl phthalate), respectively, that could not be separated with low resolution tandem mass spectrometry. To evaluate the potential usefulness of the newly identified DUP metabolites as exposure biomarkers, we analyzed 36 human urine samples by high resolution mass spectrometry. We detected MHUP and MCDP in >83% of the samples; median concentrations were 0.21ng/mL and 0.36ng/mL, respectively. MOUP was detected only in 14% of the samples analyzed, and MUP was not detected. All three metabolites eluted as peak clusters likely because of the presence of multiple oxidation sites and multiple isomers in DUP technical mixtures. Taken together, these findings suggest that with the appropriate mass spectrometry quantification techniques, MHUP and MCDP may serve as suitable biomarkers for assessing background exposure to DUP.

Phthalate exposure and reproductive parameters in young men from the general Swedish population

BACKGROUND

In animals, exposure to certain phthalates negatively affects the male reproductive function. Human results are conflicting and mostly based on subfertile males, in whom the association between exposure and reproductive function may differ from the general population.

OBJECTIVES

To study if levels of phthalate metabolites were associated with semen quality and reproductive hormones in general Swedish men.

METHODS

We recruited 314 young men delivering semen, urine and blood samples at the same visit. We analyzed reproductive hormones and several semen parameters including progressive motility and high DNA stainability (HDS)-a marker for sperm immaturity. In urine, we analyzed metabolites of phthalates, including diethylhexyl phthalate (DEHP). We studied associations between urinary levels of the metabolites and seminal as well as serum reproductive parameters, accounting for potential confounders.

RESULTS

DEHP metabolite levels, particularly urinary mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), were negatively associated with progressive sperm motility, which was 11 (95% CI: 5.0-17) percentage points lower in the highest quartile of MECPP than in the lowest. Further, men in the highest quartile of the DEHP metabolite monoethylhexyl phthalate had 27% (95% CI: 5.5%-53%) higher HDS than men in the lowest quartile.

CONCLUSIONS

DEHP metabolite levels seemed negatively associated with sperm motility and maturation.

Semen phthalate metabolites, spermatozoa apoptosis, and DNA damage: a cross-sectional study in China

Toxicological studies have shown that phthalates, a class of widely used chemicals, can impair male reproductive function, but epidemiological evidence is inconsistent. This study aimed to investigate the associations of semen phthalate metabolites with sperm apoptosis and DNA damage in a Chinese population. We assessed sperm apoptosis markers with Annexin V/PI analysis and sperm DNA integrity with comet assay before measuring eight phthalate metabolites in semen by high-performance liquid chromatography and tandem mass spectrometry (HPLC-MS/MS) among 463 men from Wuhan, China. We found a suggestive dose-response relationship between semen mono-(2-ethylhexyl) phthalate (MEHP) and an increased percentage of Annexin V+/PI- sperm (p for trend of <0.10). We also observed that semen monomethyl phthalate (MMP) and monoethyl phthalate (MEP) were associated with significant dose-related increases in tail length of the comet (both p for trend of <0.01). In conclusion, our data indicate that semen MEHP is associated with increased sperm apoptosis and that semen MMP and MEP are associated with increased sperm DNA damage in a Chinese population.

Phthalate concentrations in personal care products and the cumulative exposure to female adults and infants in Shanghai

Phthalate esters (PE) are synthetic chemicals widely used in industry, and have been detected in personal care products (PCP). Recent findings of human reports demonstrated endocrine-disrupting action associated with phthalate exposures. The aims of this study were to (1) measure levels of 11 PE in 198 PCP collected from retail markets in Shanghai and (2) assess daily dermal exposure in adult females and infants. The health risk of cumulative exposure to eight PE on reproductive system function derived from dermal PCP use was further assessed by utilizing the hazard index (HI) approach. Diethyl phthalate (DEP) was the most frequently detected compound (29.8%), followed by diisobutyl phthalate (DiBP) (6.6%). The geometric mean (GM) concentrations of daily exposure to DEP, bis(2-methoxyethyl) phthalate (DMEP), DiBP, dibutyl phthalate (DBP), diphenyl phthalate (DPP), and bis(2-ethylhexyl) phthalate (DEHP) in female adults were 0.018, 0.012, 0.002, 0.001, 0.003, and 0.002 μg/kg body weight (bw)/d, respectively. The GM daily exposure levels to PE in infants and adult females were similar except for DEHP, which was higher in infants. DEP exposure was highest in both subpopulations at either GM or maximal level. All HI of 8 PE were far less than 1, ranging from 0.0002 to 0.005, indicating no cumulative reproductive risks to these populations. DBP, DMEP, and DEHP were three major contributors to the cumulative HI. In summary, the level of phthalate in PCP from Shanghai retail markets posed no apparent cumulative risk to adult females and infants in China.

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.

Reproductive toxicity of lead, cadmium, and phthalate exposure in men

Environmental toxicants viz lead or cadmium and phthalate esters (di(2-ethylhexyl) phthalate [DEHP], dibutyl phthalate [DBP], and diethyl phthalate [DEP]) widely found in different environmental strata are linked to deteriorating male reproductive health. The objective was to assess the relationships between the seminal lead, cadmium, and phthalate (DEHP, DBP, DEP) concentrations at environmental level and serum hormone levels and semen quality in non-occupationally exposed men and specify the effect of individual and combined exposure of toxicants on semen quality. A study of 60 male partners of couples attending the Andrology Laboratory of the Reproductive Biology Department, All India Institute of Medical Sciences (AIIMS), New Delhi, India for semen analysis to assess their inability to achieve a pregnancy was selected for the study. The results of univariate and stepwise multiple regression analysis in the unadjusted model showed a significant correlation between lead or cadmium and phthalates DEHP/DBP/DEP and sperm motility, sperm concentration, and DNA damage. After adjusting for potential confounders, an association with lead or DEHP was only observed. The present data shows that lead (Pb) or cadmium (Cd) or phthalates might independently contribute to decline in semen quality and induce DNA damage. Phthalates might influence reproductive hormone testosterone. These findings are significant in light of the fact that men are exposed to a volley of chemicals; however, due to the small sample size, our finding needs to be confirmed in a larger population.

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.

Estrogenic endocrine-disrupting chemicals: molecular mechanisms of actions on putative human diseases

Endocrine-disrupting chemicals (EDC), including phthalates, bisphenol A (BPA), phytoestrogens such as genistein and daidzein, dichlorodiphenyltrichloroethane (DDT), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are associated with a variety of adverse health effects in organisms or progeny by altering the endocrine system. Environmental estrogens, including BPA, phthalates, and phytoestrogens, are the most extensively studied and are considered to mimic the actions of endogenous estrogen, 17β-estradiol (E2). Diverse modes of action of estrogen and estrogen receptors (ERα and ERβ) have been described, but the mode of action of estrogenic EDC is postulated to be more complex and needs to be more clearly elucidated. This review examines the adverse effects of estrogenic EDC on male or female reproductive systems and molecular mechanisms underlying EDC effects that modulate ER-mediated signaling. Mechanisms of action for estrogenic EDC may involve both ER-dependent and ER-independent pathways. Recent findings from systems toxicology of examining estrogenic EDC are also discussed.

Di 2-ethylhexylphtalate in the aquatic and terrestrial environment: a critical review

Phthalates are being increasingly used as softeners-plasticizers to improve the plasticity and the flexibility of materials. Amongst the different plasticizers used, more attention is paid to di (2-ethylhexylphtalate) (DEHP), one of the most representative compounds as it exhibits predominant effects on environment and human health. Meanwhile, several questions related to its sources; toxicity, distribution and fate still remain unanswered. Most of the evidence until date suggests that DEHP is an omnipresent compound found in different ecological compartments and its higher hydrophobicity and low volatility have resulted in significant adsorption to solids matrix. In fact, there are important issues to be addressed with regard to the toxicity of this compound in both animals and humans, its behavior in different ecological systems, and the transformation products generated during different biological or advanced chemical treatments. This article presents detailed review of existing treatment schemes, research gaps and future trends related to DEHP.

The effects of Di-(2-ethylhexyl)-phthalate exposure on fertilization and embryonic development in vitro and testicular genomic mutation in vivo

The present study was undertaken to determine the reproductive hazards of Di-(2-ethylhexyl)-phthalate (DEHP) on mouse spermatozoa and embryos in vitro and genomic changes in vivo. Direct low-level DEHP exposure (1 μg/ml) on spermatozoa and embryos was investigated by in vitro fertilization (IVF) process, culture of preimplanted embryos in DEHP-supplemented medium and embryo transfer to achieve full term development. Big Blue® transgenic mouse model was employed to evaluate the mutagenesis of testicular genome with in vivo exposure concentration of DEHP (500 mg/kg/day). Generally, DEHP-treated spermatozoa (1 μg/ml, 30 min) presented reduced fertilization ability (P<0.05) and the resultant embryos had decreased developmental potential compared to DMSO controls (P<0.05). Meanwhile, the transferred 2-cell stage embryos derived from treated spermatozoa also exhibited decreased birth rate than that of control (P<0.05). When fertilized oocytes or 2-cell stage embryos were recovered by in vivo fertilization (without treatment) and then exposed to DEHP, the subsequent development proceed to blastocysts was different, fertilized oocytes were significantly affected (P<0.05) whereas developmental progression of 2-cell stage embryos was similar to controls (P>0.05). Testes of the Big Blue® transgenic mice treated with DEHP for 4 weeks indicated an approximately 3-fold increase in genomic DNA mutation frequency compared with controls (P<0.05). These findings unveiled the hazardous effects of direct low-level exposure of DEHP on spermatozoa's fertilization ability as well as embryonic development, and proved that in vivo DEHP exposure posed mutagenic risks in the reproductive organ – at least in testes, are of great concern to human male reproductive health.

Mono-2-ethylhexyl phthalate induced loss of mitochondrial membrane potential and activation of Caspase3 in HepG2 cells

L02 and HepG2 cells were exposed to mono-(2-ethylhexyl) phthalate (MEHP) at concentrations of 6.25-100μM. After 48h treatment, MEHP decreased HepG2 cell viability in a concentration-dependent manner and L02 cell viability in the 50 and 100μM groups (p<0.01). Furthermore, at 24 and 48h after treatment, MEHP decreased the glutathione levels of HepG2 cells in all treatment groups and in the ΔΨ(m) in L02 and HepG2 cells with MEHP≥25μM (p<0.05 or p<0.01). At 24h after treatment, MEHP induced activation of caspase3 in all treated HepG2 and L02 cells (p<0.05 or p<0.01) except the 100μM MEHP treatment group. The increase in the Bax to Bcl-2 ratio suggests that Bcl-2 family involved in the control of MEHP-induced apoptosis in these two cell types. The data suggest that MEHP could induce apoptosis of HepG2 cells through mitochondria- and caspase3-dependent pathways.

Mono-(2-ethylhexyl)-phthalate (MEHP) affects ERK-dependent GDNF signalling in mouse stem-progenitor spermatogonia

Many commercial and household products such as lubricants, cosmetics, plastics, and paint contain phthalates, in particular bis-(2-ethyhexyl)-phthalate (DEHP). As a consequence, phthalates have been found in a number of locations and foods (streambeds, household dust, bottled water and dairy products). Epidemiological and animal studies analysing phthalate exposure in males provide evidence of degradation in sperm quality, associated to an increase in the incidence of genital birth defects and testicular cancers. In the testis, spermatogenesis is maintained throughout life by a small number of spermatogonial stem cells (SSCs) that self-renew or differentiate to produce adequate numbers of spermatozoa. Disruption or alteration of SSC self-renewal induce decreased sperm count and sperm quality, or may potentially lead to testicular cancer. GDNF, or glial cell-line-derived neurotrophic factor, is a growth factor that is essential for the self-renewal of SSCs and continuous spermatogenesis. In the present study, the SSC-derived cell line C18-4 was used as a model for preliminary assessment of the effects of mono-(2-ethylhexyl)-phthalate (MEHP, main metabolite of DEHP) on spermatogonial stem cells. Our data demonstrate that MEHP disrupts one of the known GDNF signalling pathways in these cells. MEHP induced a decrease of C18-4 cell viability in a time- and dose-dependent manner, as well as a disruption of ERK1/2 activation but not of SRC signalling. As a result, we observed a decrease of expression of the transcription factor FOS, which is downstream of the GDNF/ERK1/2 axis in these cells. Taken together, our data suggest that MEHP exposure affects SSC proliferation through inhibition of specific signalling molecules.

The effects of di(2-ethylhexyl)phthalate exposure and selenium nutrition on sertoli cell vimentin structure and germ-cell apoptosis in rat testis

This study aimed to investigate the effects of di(2-ethylhexyl)phthalate (DEHP) on Sertoli-cell vimentin filaments and germ-cell apoptosis in testes of pubertal rats at different selenium (Se) status. Se deficiency was produced in 3-weeks old Sprague-Dawley rats by feeding them ≤ 0.05 Se mg/kg diet for 5 weeks, Se supplementation group was on 1 mg Se/kg diet, and DEHP was applied at 1000 mg/kg dose by gavage during the last 10 days of the feeding period. The diet with excess Se did not cause any appreciable alteration in vimentin staining and apoptosis of germ cells, but Se deficiency caused a mild decrease in the intensity of vimentin immunoreactivity and enhanced germ-cell apoptosis significantly (approximately 3-fold, p <0.0033). DEHP exposure caused disruption and collapse of vimentin filaments and significantly induced apoptotic death of germ cells (approximately 8-fold, p <0.0033). In DEHP-exposed Se-deficient animals, compared with the control, collapse of vimentin filaments was more prominent; there was serious damage to the seminiferous epithelium; and a high increment (approximately 25-fold, p <0.0033) in apoptotic germ cells was observed. Thus, Se deficiency exacerbated the toxicity of DEHP on Sertoli cells and spermatogenesis, whereas Se supplementation provided protection. These results put forward the critical role of Se in the modulation of redox status of testicular cells and emphasize the importance of Se status for reproductive health.

Phthalates and their metabolites in breast milk--results from the Bavarian Monitoring of Breast Milk (BAMBI)

Phthalates have long been used as plasticizers to soften plastic products and, thus, are ubiquitous in modern life. As part of the Bavarian Monitoring of Breast Milk (BAMBI), we aimed to characterize the exposure of infants to phthalates in Germany. Overall, 15 phthalates, including di-2-ethylhexyl phthalate (DEHP), di-n-butyl phthalate (DnBP), di-isobutyl phthalate (DiBP), di-isononyl phthalate (DiNP), three primary metabolites of DEHP [mono-(2-ethylhexyl) phthalate (MEHP), mono-isobutyl phthalate (MiBP), and mono-n-butyl phthalate (MnBP)], and two secondary metabolites of DEHP were analyzed in 78 breast milk samples. We found median concentrations of 3.9 ng/g for DEHP, 0.8 ng/g for DnBP, and 1.2 ng/g for DiBP, while other parent phthalates were found in only some or none of the samples at levels above the limit of quantitation. In infant formula (n=4) we observed mean values of 19.7 ng/g (DEHP), 3.8 ng/g (DnBP), and 3.6 ng/g (DiBP). For MEHP, MiBP, and MnBP, the median values in breast milk were 2.3 μg/l, 11.8 μg/l, and 2.1 μg/l, respectively. The secondary metabolites were not detected in any samples. Using median and 95th percentile values, we estimated an "average" and "high" daily intake for an exclusively breast-fed infant of 0.6 μg/kg body weight (b.w.) and 2.1 μg/kg b.w., respectively, for DEHP, 0.1 μg/kg b.w. and 0.5 μg/kg b.w. for DnBP, and 0.2 μg/kg b.w. and 0.7 μg/kg b.w. for DiBP. For DiNP, intake values were 3.2 μg/kg b.w. and 6.4 μg/kg b.w., respectively, if all values in milk were set half of the detection limit or the detection limit. The above-mentioned "average" and "high" intake values corresponded to only about 2% to 7%, respectively, of the recommended tolerable daily intake. Thus, it is not likely that an infant's exposure to phthalates from breast milk poses any significant health risk. Nevertheless, other sources of phthalates in this vulnerable phase have to be considered. Moreover, it should be noted that for infants nourished with formula, phthalate intake is of the same magnitude or slightly higher (DEHP) than for exclusively breast-fed infants.